Pulsed Magnetic Field Therapy…
By Dr. D. C. Laycock, Ph.D. Med. Eng. MBES, MIPEM
All living cells within the body possess potentials between the inner
and outer membrane of the cell, which, under normal healthy circumstances,
are fixed. Different cells, e.g. Muscle cells and Nerve cells, have different
potentials of about -70 mV respectively. When cells are damaged, these
potentials change such that the balance across the membrane changes,
causing the attraction of positive sodium ions into the cell and negative
trace elements and proteins out of the cell. The net result is that liquid
is attracted into the interstitial area and swelling or edema ensues.
The application of pulsed magnetic fields has, through research findings,
been shown to help the body to restore normal potentials at an accelerated
rate, thus aiding the healing of most wounds and reducing swelling faster.
The most effective frequencies found by researchers so far, are very
low frequency pulses of a 50Hz base. These, if gradually increased to
25 pulses per second for time periods of 600 seconds (10 minutes), condition
the damaged tissue to aid the natural healing process.
PAIN REDUCTION is another area in which pulsed electromagnetic therapy
has been shown to be very effective. Pain signals are transmitted along
nerve cells to pre-synaptic terminals. At these terminals, channels in
the cell alter due to a movement of ions. The membrane potential changes,
causing the release of a chemical transmitter from a synaptic vesicle
contained within the membrane. The pain signal is chemically transferred
across the synaptic gap to chemical receptors on the post synaptic nerve
cell. This all happens in about 1/2000th of a second, as the synaptic
gap is only 20 to 50 n.-meter wide. As the pain signal, in chemical form,
approaches the post synaptic cell, the membrane changes and the signal
is transferred. If we look at the voltages across the synaptic membrane
then, under no pain conditions, the level is about -70 mV. When the pain
signal approaches, the membrane potential increases to approximately
+30 mV, allowing a sodium flow. This in turn triggers the synaptic vesicle
to release the chemical transmitter and so transfer the pain signal across
the synaptic gap or cleft. After the transmission, the voltage reduces
back to its normal quiescent level until the next pain signal arrives.
The application of pulsed magnetism to painful sites causes the membrane
to be lowered to a hyper-polarization level of about -90 mV. When a pain
signal is detected, the voltage must now be raised to a relatively higher
level in order to fire the synaptic vesicles.
Since the average change of potential required to reach the trigger
voltage of nearly +30 mV is +100 mV, the required change is too great
and only +10 mV is attained. This voltage is generally too low to cause
the synaptic vesicle to release the chemical transmitter and hence the
pain signal is blocked. The most effective frequencies that have been
observed from research in order to cause the above changes to membrane
potentials, are a base frequency of 200Hz and pulse rate settings of
between 5 and 25Hz.
Source: Lecture abstract of 28-01-1995, Dr. D. C. Laycock, Ph.D. Med.
Eng. MBES, MIPEM, B.Ed. (Hons Phys. Sc.). Consultant Clinical Engineer,
Westville Associates and Consultants (UK).
--------------------------------------------------------------------------------
Beneficial Effects of Pulsed Electromagnetic Fields
Bassett CA.
Bioelectric Research Center, Columbia University, Riverdale, New York
10463.
Selective control of cell function by applying specifically configured,
weak, time-varying magnetic fields has added a new, exciting dimension
to biology and medicine. Field parameters for therapeutic, pulsed electromagnetic
field (PEMFs) were designed to induce voltages similar to those produced,
normally, during dynamic mechanical deformation of connective tissues.
As a result, a wide variety of challenging musculoskeletal disorders
have been treated successfully over the past two decades. More than a
quarter million patients with chronically ununited fractures have benefitted,
worldwide, from this surgically non-invasive method, without risk, discomfort,
or the high costs of operative repair. Many of the athermal bioresponses,
at the cellular and subcellular levels, have been identified and found
appropriate to correct or modify the pathologic processes for which PEMFs
have been used. Not only is efficacy supported by these basic studies
but by a number of double-blind trials. As understanding of mechanisms
expands, specific requirements for field energetics are being defined
and the range of treatable ills broadened. These include nerve regeneration,
wound healing, graft behavior, diabetes, and myocardial and cerebral
ischemia (heart attack and stroke), among other conditions. Preliminary
data even suggest possible benefits in controlling malignancy.
Source: J Cell Biochem 1993 Apr;51(4):387-93
Alzheimer's Disease
After applying external electromagnetic fields ranging 5 to 8 Hz, large
improvements were detected in Alzheimer's patients. These included
improved visual memory, drawing performance, spatial orientation, mood,
short-term memory and social interactions. Ref R. Sandyk, "Alzheimer's
Disease: Improvement of Visual Memory and Visuoconstructive Performance
Treatment with Picotesla Range Magnetic Fields," International
Journal of Neurosci.
Alzheimer's Disease
R. Sandyk et al.: 'Age-Related Disruption of Circadian Rhythms: Possible
Relationship to Memory Impairment and Implications for Therapy with Magnetic
Fields, 'International Journal of Neuroscience, 59 (4), August 1991,
pp. 259-262. - The circadian rhythm seems to be causally related to memory
loss in the elderly and possibly also to Alzheimer's disease. PEMF can
probably improve memory performance in elderly patients by resetting
the biological clock.
R. Sandyk: 'Alzheimer's Disease: Improvement of Visual Memory and Visuoconstructive
Performance by Treatment with low intensity PEMF in Picotesla intensity
' International Journal of Neuroscience, 76 (3-4), June 1994, pp. 185ff.
- Two Alzheimer's patients showed a definite improvement after treatment
with PEMF, especially in the visual memory and their drawing abilities.
There were also improvements in other cognitive functions, in the ability
of these patients to orient themselves in space, their mental/emotional
condition, their ability to make social contact and their short-term
memory.
Neuropsychologia. 2003;41(8):952-67. Related Articles, Links
Spelling via semantics and phonology: exploring the effects of age,
Alzheimer's disease, and primary semantic impairment.
Cortese MJ, Balota DA, Sergent-Marshall SD, Buckner RL.
Department of Psychology, Morehead State University, 601 Ginger Hall,
Morehead, KY 40351, USA.
Spelling performance across a common set of stimuli was examined in young
adults, healthy older adults, individuals with early stage dementia of
the Alzheimer's type (DAT), and four individuals with a primary semantic
impairment (PSI). The stimuli included homophones and low-frequency sound-to-spelling
consistent (i.e. words with more predictable spellings) and inconsistent
words (i.e. words with less predictable spellings). The results indicate
that when spelling homophonic words (spelling/pleIn/ as plane versus
plain), younger adults and to a greater extent individuals with PSI placed
relatively more emphasis on phonological information (i.e. spell the
word based on sound-to-spelling principles) whereas healthy older adults
and individuals with DAT placed relatively more emphasis on semantic
information (i.e. spell the word based on the dominant usage). For non-homophonic
words, large consistency effects (spelling plaid as plad) were observed
for both individuals with DAT and individuals with PSI. It is proposed
that the decrease in accuracy for inconsistent words has different bases
in DAT and PSI. We propose that deficits in attentional control (i.e.
selection) underlie performance in DAT whereas disruption of semantic
representations underlies performance in PSI.
PMID: 12667531 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
Hippocampus. 2003;13(1):67-80. Related Articles, Links
Encoding of novel picture pairs activates the perirhinal cortex: an
fMRI study.
Pihlajamaki M, Tanila H, Hanninen T, Kononen M, Mikkonen M, Jalkanen
V, Partanen K, Aronen HJ, Soininen H.
Department of Neuroscience and Neurology, University of Kuopio, Kuopio,
Finland.
It is well established in nonhuman primates that the medial temporal
lobe (MTL) structures, the hippocampus and the entorhinal and perirhinal
cortices, are necessary for declarative memory encoding. In humans, the
neuropathological and neuropsychological changes in early Alzheimer's
disease (AD) further support a role for the rhinal cortex in the consolidation
of new events into long-term memory. Little is known, however, regarding
the function of the rhinal cortex in humans in vivo. To examine the participation
of the interconnected MTL structures as well as the whole-brain network
of activated brain areas in visual associative long-term memory, functional
magnetic resonance imaging (fMRI) was used to determine the brain regions
that are activated during encoding and retrieval of paired pictures in
12 young control subjects. The most striking finding in the MTL activation
pattern was the consistent activation of the perirhinal cortex in the
encoding-baseline and encoding-retrieval comparisons with a strict statistical
threshold (P < 0.00001). In contrast, no perirhinal cortex activation
was detected in the retrieval-baseline or retrieval-encoding comparisons
even with a low statistical threshold (P < 0.05). The location of
the perirhinal activation area was in the transentorhinal part of the
perirhinal cortex, in the medial bank of the collateral sulcus. The hippocampus
and the more posterior parahippocampal gyrus were activated in both encoding
and retrieval conditions. During the encoding processing, MTL activations
were more consistent and the hippocampal activation area located more
anteriorly than during retrieval. The frontal, parietal, temporal, and
occipital association cortices were also activated in the encoding-baseline
and retrieval-baseline comparisons. The data suggest that encoding, but
not retrieval, of novel picture pairs activates the perirhinal cortex.
To our knowledge, this is the first fMRI study reporting encoding activation
in this transentorhinal part of the perirhinal cortex, the site of the
very earliest neuropathological changes in AD.
PMID: 12625459 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
Methods Find Exp Clin Pharmacol. 2002;24 Suppl D:17-20. Related Articles,
Links
Simultaneous ERP and event-related fMRI: focus on the time course of
brain activity in target detection.
Mulert C, Jager L, Pogarell O, Bussfeld P, Schmitt R, Juckel G, Hegerl
U.
Laboratory for Clinical Neurophysiology, Department of Psychiatry, LMU,
Munich, Germany.
The event-related P300 potential has been widely used in neurophysiological
research. It is usually evoked with an oddball paradigm. One main reason
for its broad application in neurophysiological research is the fact
that in several brain/mental diseases, such as Alzheimer's disease or
schizophrenia, attenuations of the P300 amplitude and latency have been
described. However, a precise correlation of the scalp data to the underlying
brain regions was not possible, as the correct localization of the generators
of scalp-measured electroencephalogram (EEG) data was limited, due to
the low spatial resolution of EEG-data. With the availability of modern
imaging technologies, functional Magnetic Resonance Imaging (fMRI) in
particular, the underlying brain activations could be detected using
an oddball task. Although the spatial resolution of fMRI is excellent,
the time resolution is restricted. For a comprehensive understanding
of the brain activity underlying the P300 paradigm, we have used a combination
of EEG and fMRI to get a precise localization and a high-time resolution
of the underlying brain activity.
PMID: 12575464 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
5: Ann Neurol. 2003 Jan;53(1):102-8. Related Articles, Links
Motor cortex excitability in Alzheimer's disease: A transcranial magnetic
stimulation study.
Ferreri F, Pauri F, Pasqualetti P, Fini R, Dal Forno G, Rossini PM.
Department of Neurology, University Campus Biomedico.
Motor deficits affect patients with Alzheimer's disease only at later
stages. Recent studies demonstrate that the primary motor cortex is affected
by neuronal degeneration accompanied by the formation of amyloid plaques
and neurofibrillary tangles. It is conceivable that neuronal loss is
compensated by reorganization of the neural circuitries occurring along
the natural course of the disease, thereby maintaining motor performances
in daily living. Cortical motor output to upper limbs was tested via
motor-evoked potentials from forearm and hand muscles elicited by transcranial
magnetic stimulation of motor cortex in 16 patients with mild Alzheimer's
disease without motor deficits. Motor cortex excitability was increased,
and the center of gravity of motor cortical output, as represented by
excitable scalp sites, showed a frontal and medial shift, without correlated
changes in the site of maximal excitability (hot-spot). This may indicate
functional reorganization, possibly after the neuronal loss in motor
areas. Hyperexcitability might be caused by a dysregulation of the intracortical
GABAergic inhibitory circuitries and selective alteration of glutamatergic
neurotransmission. Such findings suggest that motor cortex hyperexcitability
and reorganization allows prolonged preservation of motor function during
the clinical course of Alzheimer's disease.
PMID: 12509853 [PubMed - in process]
------------------------------------------------------------------------
6: Brain Res Cogn Brain Res. 2002 Nov;14(3):347-56. Related Articles,
Links
Functional magnetic resonance imaging of brain activity in the visual
oddball task.
Ardekani BA, Choi SJ, Hossein-Zadeh GA, Porjesz B, Tanabe JL, Lim KO,
Bilder R, Helpern JA, Begleiter H.
Center for Advanced Brain Imaging, Nathan Kline Institute for Psychiatric
Research, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA.
Abnormalities in the P300 ERP, elicited by the oddball task and measured
using EEG, have been found in a number of central nervous system disorders
including schizophrenia, Alzheimer's disease, and alcohol dependence.
While electrophysiological studies provide high temporal resolution,
localizing the P300 deficit has been particularly difficult because the
measurements are collected from the scalp. Knowing which brain regions
are involved in this process would elucidate the behavioral correlates
of P300. The aim of this study was to determine the brain regions involved
in a visual oddball task using fMRI. In this study, functional and high-resolution
anatomical MR images were collected from seven normal volunteers. The
data were analyzed using a randomization-based statistical method that
accounts for multiple comparisons, requires no assumptions about the
noise structure of the data, and does not require spatial or temporal
smoothing. Activations were detected (P<0.01) bilaterally in the supramarginal
gyrus (SMG; BA 40), superior parietal lobule (BA 7), the posterior cingulate
gyrus, thalamus, inferior occipitotemporal cortex (BA 19/37), insula,
dorsolateral prefrontal cortex (BA 9), anterior cingulate cortex (ACC),
medial frontal gyrus (BA 6), premotor area, and cuneus (BA 17). Our results
are consistent with previous studies that have observed activation in
ACC and SMG. Activation of thalamus, insula, and the occipitotemporal
cortex has been reported less consistently. The present study lends further
support to the involvement of these structures in visual target detection.
PMID: 12421658 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
7: Neuroimage. 2002 Nov;17(3):1403-14. Related Articles, Links
Functional imaging of visuospatial processing in Alzheimer's disease.
Prvulovic D, Hubl D, Sack AT, Melillo L, Maurer K, Frolich L, Lanfermann
H, Zanella FE, Goebel R, Linden DE, Dierks T.
Department of Psychiatry, University of Frankfurt, Frankfurt, Germany.
Alzheimer's disease (AD) is known to cause a variety of disturbances
of higher visual functions that are closely related to the neuropathological
changes. Visual association areas are more affected than primary visual
cortex. Additionally, there is evidence from neuropsychological and imaging
studies during rest or passive visual stimulation that the occipitotemporal
pathway is less affected than the parietal pathway. Our goal was to investigate
functional activation patterns during active visuospatial processing
in AD patients and the impact of local cerebral atrophy on the strength
of functional activation. Fourteen AD patients and fourteen age-matched
controls were measured with functional magnetic resonance imaging (fMRI)
while they performed an angle discrimination task. Both groups revealed
overlapping networks engaged in angle discrimination including the superior
parietal lobule (SPL), frontal and occipitotemporal (OTC) cortical regions,
primary visual cortex, basal ganglia, and thalamus. The most pronounced
differences between the two groups were found in the SPL (more activity
in controls) and OTC (more activity in patients). The differences in
functional activation between the AD patients and controls were partly
explained by the differences in individual SPL atrophy. These results
indicate that parietal dysfunction in mild to moderate AD is compensated
by recruitment of the ventral visual pathway. We furthermore suggest
that local cerebral atrophy should be considered as a covariate in functional
imaging studies of neurodegenerative disorders.
PMID: 12414280 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
8: Hum Brain Mapp. 2002 Dec;17(4):230-6. Related Articles, Links
Novelty detection and repetition suppression in a passive picture viewing
task: a possible approach for the evaluation of neuropsychiatric disorders.
Jessen F, Manka C, Scheef L, Granath DO, Schild HH, Heun R.
Department of Psychiatry, University of Bonn, Bonn, Germany.
The applicability of functional magnetic resonance imaging (fMRI) in
patients with Alzheimer's disease (AD) or schizophrenia is frequently
limited by cognitive impairment, which prevents the adequate execution
of complex tasks. An experimental design that puts only minor demands
on the patients' cognitive ability but engages disease-relevant brain
structures would be of benefit. Novelty detection and repetition suppression
are two basic components of memory that might be used to investigate
specific brain areas under these conditions. Novelty detection has been
related to hippocampal activation increases. Stimulus repetition related
activation decreases (suppression) have been observed in the extrastriate
cortex and have been related to perceptual priming. Both processes have
been examined primarily in neuroimaging studies with complex cognitive
tasks. We used event-related fMRI to investigate novelty- and repetition-related
effects in an attended but passive picture-viewing task in healthy subjects.
The differential activation, detected in the novel vs. repeated contrast,
was located in the bilateral anterior hippocampus and in bilateral occipital
and inferior-temporal areas. The hippocampal activation is of interest
because medial temporal lobe lesions are key features in AD and schizophrenia.
The repetition-related activation decreases in the extrastriate areas
are of potential value in investigating the conflicting results regarding
perceptual priming impairment in both disorders. Our results indicate
that activation of disease-relevant brain regions under passive task
conditions is possible. This might increase the utility of functional
imaging in cognitively impaired patients. Copyright 2002 Wiley-Liss,
Inc.
PMID: 12395390 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
9: Neurosci Lett. 2002 Sep 6;329(3):293-6. Related Articles, Links
Motor cortex excitability in Alzheimer disease: one year follow-up study.
Pennisi G, Alagona G, Ferri R, Greco S, Santonocito D, Pappalardo A,
Bella R.
Department of Neurological Sciences, University of Catania, Azienda Policlinico
dell' Universita, Via S. Sofia, 78, 95123 Catania, Italy.
Seventeen patients affected by Alzheimer disease (AD) underwent two transcranial
magnetic stimulation (TMS) studies separated by an interval of 12 months,
in order to monitor possible changes in motor cortex excitability. After
the first examination, all patients were treated with cholinesterase
inhibitor drugs. Motor threshold (MT), amplitude of motor evoked potentials
and central motor conduction time were considered. After one year, the
mean MT values showed a decrease significantly correlated with the severity
of cognitive involvement, evaluated by means of the Mini Mental State
Examination (MMSE). The difference in MT between the two recording sessions
showed no significant correlation with the difference in MMSE score.
One year of treatment with cholinesterase inhibitor drugs did not stop
the progressive increase in motor cortex excitability. Serial analysis
of TMS might represent a method to monitor the rate of change in motor
cortex excitability in patients with AD.
PMID: 12183034 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
10: Neurology. 2002 Aug 13;59(3):392-7. Related Articles, Links
Noninvasive in vivo assessment of cholinergic cortical circuits in AD
using transcranial magnetic stimulation.
Di Lazzaro V, Oliviero A, Tonali PA, Marra C, Daniele A, Profice P, Saturno
E, Pilato F, Masullo C, Rothwell JC.
Institute of Neurology, Catholic University, Largo A. Gemelli 8, 00168
Rome, Italy.
BACKGROUND: A recently devised test of motor cortex excitability (short
latency afferent inhibition) was shown to be sensitive to the blockade
of muscarinic acetylcholine receptors in healthy subjects. The authors
used this test to assess cholinergic transmission in the motor cortex
of patients with AD. METHODS: The authors evaluated short latency afferent
inhibition in 15 patients with AD and compared the data with those of
12 age-matched healthy controls. RESULTS: Afferent inhibition was reduced
in the patients (mean responses +/- SD reduced to 85.7% +/- 15.8% of
the test size) compared with controls (mean responses +/- SD reduced
to 45.3% +/- 16.2% of the test size; p < 0.001, unpaired t-test).
Administration of a single oral dose of rivastigmine improved afferent
inhibition in a subgroup of six patients. CONCLUSIONS: The findings suggest
that this method can be used as a noninvasive test of cholinergic pathways
in AD. Future studies are required to evaluate whether short latency
afferent inhibition measurements have any consistent clinical correlates.
PMID: 12177373 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
11: J Neurosci. 2002 Aug 15;22(16):7218-24. Related Articles, Links
Compromised hemodynamic response in amyloid precursor protein transgenic
mice.
Mueggler T, Sturchler-Pierrat C, Baumann D, Rausch M, Staufenbiel M,
Rudin M.
Central Technologies, Novartis Pharma, AG, CH-4002 Basel, Switzerland.
APP23 transgenic mice overexpressing amyloid precursor protein (APP751)
reproduce neuropathological changes associated with Alzheimer's disease
such as high levels of amyloid plaques, cerebral amyloid angiopathy,
and associated vascular pathologies. Functional magnetic resonance imaging
(fMRI) was applied to characterize brain functionality in these mice
through global pharmacological stimulation. The cerebral hemodynamic
response to infusion of the GABA(A) antagonist bicuculline was significantly
reduced in aged APP23 mice compared with age-matched wild-type littermates.
This is in part attributable to a compromised cerebrovascular reactivity,
as revealed by the reduced responsiveness to vasodilatory stimulation
by acetazolamide. The study shows that fMRI is a sensitive tool to phenotype
genetically engineered animals modeling neuropathologies.
PMID: 12177216 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
12: Ann Neurol. 2002 Apr;51(4):491-8. Related Articles, Links
Subjective memory complaints: objective neural markers in patients with
Alzheimer's disease and major depressive disorder.
Gron G, Bittner D, Schmitz B, Wunderlich AP, Riepe MW.
Memory Clinic, University of Ulm, Germany.
Patients with probable Alzheimer's disease and depressive patients frequently
present with subjective memory complaints. Objective distinction of underlying
neuronal substrate malfunction and early cross-sectional differential
diagnosis have been elusive thus far. We used repetitive learning and
free recall of abstract geometric patterns during functional magnetic
resonance imaging to assess episodic memory in older subjects (ages 56-64
years) who sought first-time medical attention with subjective memory
complaints and were diagnosed with probable Alzheimer's disease (NINCDS-ADRDA
criteria; ages 51-67 years) or major depressive disorder (DSM-IV; ages
50-65 years). Contrasting healthy seniors or depressive patients with
Alzheimer's disease patients revealed superiority of hippocampal activation.
Contrasting Alzheimer's disease patients with seniors showed bilateral
prefrontal activity as a correlate of futile compensation of episodic
memory failure. Contrasting patients who had major depressive disorder
with seniors or patients who had Alzheimer's disease showed bilateral
activation of the orbitofrontal cortex and the anterior cingulate. Subjective
memory complaints may be classified objectively and very early with functional
magnetic resonance imaging of episodic memory in groups of patients with
Alzheimer's disease and depressive syndrome. This may facilitate drug
trials with evaluation of specific treatments, but further studies will
be needed to establish the differential diagnosis for the individual
patient.
PMID: 11921055 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
13: Neurosci Lett. 2001 Nov 13;314(1-2):57-60. Related Articles, Links
Transcranial magnetic stimulation in Alzheimer disease: motor cortex
excitability and cognitive severity.
Alagona G, Bella R, Ferri R, Carnemolla A, Pappalardo A, Costanzo E,
Pennisi G.
Department of Neurological Sciences, University of, Catania, Italy
To study the possible changes of cortical excitability in the Alzheimer
disease (AD) by transcranial magnetic stimulation (TMS) and to evaluate
their eventual correlation with its stage twenty-one AD patients and
18 normal controls underwent TMS. Motor threshold, amplitudes of motor
evoked potentials (MEPs), central motor conduction time (CMCT) and silent
period (SP) were considered. The motor threshold in AD patients was lower
than in normal subjects with a significant correlation between the stage
of cognitive severity. The amplitude of MEPs was increased and the SP
duration was reduced in AD patients. No significant differences were
obtained for CMCT. These findings could suggest a correlation between
increased motor cortical excitability and cognitive severity. Moreover,
the increased cortical excitability could represent a key to understand
the mechanism of AD and may have implication for novel treatment strategies.
PMID: 11698146 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
14: Neurology. 2001 Sep 11;57(5):812-6. Related Articles, Links
Dissociation of regional activation in mild AD during visual encoding:
a functional MRI study.
Kato T, Knopman D, Liu H.
Center for Magnetic Resonance Research, Department of Radiology, University
of Minnesota, Minneapolis, USA.
OBJECTIVE: The authors studied mild patients with AD with a visual learning
paradigm to determine whether activations of medial temporal regions
on fMRI differ in AD compared to nondemented individuals. BACKGROUND:
Changes in activation patterns of medial temporal lobe regions may serve
as a biologic marker of altered brain function early in the course of
AD. METHODS: The authors studied eight healthy young subjects, eight
late middle-age nondemented volunteers, and seven patients with mild
AD. All subjects underwent fMRI scanning in which they viewed a set of
geometric designs for 45 seconds. Changes in blood flow were analyzed
by comparing the prestimulus fMRI signal with that present during the
stimulus presentation. RESULTS: Patients with AD, who had very poor recall
of the geometric designs subsequently, showed increased blood flow (activation)
during stimulus presentation only in a visual association area. Both
the young and older nondemented subjects, all of whom had good recall
of the designs, showed activations during stimulus presentation of the
right entorhinal cortex, right supramarginal gyrus, right prefrontal
regions, and left anterior-inferior temporal lobe. The younger and older
nondemented subjects did not differ in fMRI activation patterns. CONCLUSIONS:
Failure of activation in AD of either temporal lobe or prefrontal regions
is consistent with established clinical-pathologic correlations in AD.
fMRI may be useful in confirming a memory disorder diagnosis and also
may be useful in detecting individuals with incipient dysfunction in
learning as a result of disorders such as AD.
PMID: 11552009 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
15: J Cogn Neurosci. 2000;12 Suppl 2:24-34. Related Articles, Links
Functional brain imaging of young, nondemented, and demented older adults.
Buckner RL, Snyder AZ, Sanders AL, Raichle ME, Morris JC.
Howard Hughes Medical Institute and Department of Psychology, Washington
University, St. Louis, MO 63130, USA.
Brain imaging based on functional MRI (fMRI) provides a powerful tool
for characterizing age-related changes in functional anatomy. However,
between-population comparisons confront potential differences in measurement
properties. The present experiment explores the feasibility of conducting
fMRI studies in nondemented and demented older adults by measuring hemodynamic
response properties in an event-related design. A paradigm involving
repeated presentation of sensory-motor response trials was administered
to 41 participants (14 young adults, 14 nondemented older adults, and
13 demented older adults). For half of the trials a single sensory-motor
event was presented in isolation and in the other half in pairs. Hemodynamic
response characteristics to the isolated events allowed basic response
properties (e.g., amplitude and variance) between subject groups to be
contrasted. The paired events further allowed the summation properties
of the hemodynamic response to be characterized. Robust and qualitatively
similar activation maps were produced for all subject groups. Quantitative
results showed that for certain regions, such as in the visual cortex,
there were marked reductions in the amplitude of the hemodynamic response
in older adults. In other regions, such as in the motor cortex, relatively
intact response characteristics were observed. These results suggest
caution should be exhibited in interpreting simple main effects in response
amplitude between subject groups. However, across all regions examined,
the summation of the hemodynamic response over trials was highly similar
between groups. This latter finding suggests that, even if absolute measurement
differences do exist between subject groups, relative activation change should be preserved. Designs that rely on group interactions between
task conditions, parametric manipulations, or group interactions between
regions should provide valuable data for making inferences about functional-anatomic
changes between different populations.
PMID: 11506645 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
16: Clin Neurophysiol. 2001 Aug;112(8):1436-41. Related Articles, Links
Motor cortex disinhibition in Alzheimer's disease.
Liepert J, Bar KJ, Meske U, Weiller C.
Department of Neurology, Friedrich Schiller University, Jena, Germany.
OBJECTIVES: To explore subclinical disturbances in the motor cortex of
patients with Alzheimer's disease (AD). METHODS: We used transcranial
magnetic stimulation in a paired pulse technique to test intracortical
inhibition (ICI) and intracortical facilitation in mildly to moderately
demented AD patients with a normal neurological examination. Patients
were studied before and during treatment with the cholinesterase inhibitor
donepezil. RESULTS: AD patients had a reduced ICI compared to an age-matched
control group. The amount of disinhibition correlated with the severity
of dementia. Treatment with 10 mg donepezil daily was associated with
an increase of ICI. CONCLUSIONS: The subclinical motor cortex disinhibition
in AD patients indicates a functional disturbance, and is probably associated
with a cholinergic deficit.
PMID: 11459683 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
17: Neuroscience. 2001;104(3):667-76. Related Articles, Links
Remembering familiar people: the posterior cingulate cortex and autobiographical
memory retrieval.
Maddock RJ, Garrett AS, Buonocore MH.
Depaartment of Psychiatry, University of California Davis, Sacramento
65817, USA.
Most functional imaging studies of memory retrieval investigate memory
for standardized laboratory stimuli. However, naturally acquired autobiographical
memories differ from memories of standardized stimuli in important ways.
Neuroimaging studies of natural memories may reveal distinctive patterns
of brain activation and may have particular value in assessing clinical
disorders of memory. This study used functional magnetic resonance imaging
to investigate brain activation during successful retrieval of autobiographical
memories elicited by name-cued recall of family members and friends.
The caudal part of the left posterior cingulate cortex was the most strongly
activated region and was significantly activated in all eight subjects
studied. Most subjects also showed significant activation of the left
anterior orbitomedial, anterior middle frontal, precuneus, cuneus, and
posterior inferior parietal cortices, and the right posterior cingulate
and motor cortices.Our findings are consistent with prior studies showing
posterior cingulate cortex activation during autobiographical memory
retrieval. This region is also consistently activated during retrieval
of standardized memory stimuli when experimental designs emphasizing
successful retrieval are employed. Our results support the hypothesis
that the posterior cingulate cortex plays an important role in successful
memory retrieval. The posterior cingulate cortex has strong reciprocal
connections with entorhinal and parahippocampal cortices. Studies of
early Alzheimer's disease, temporal lobectomy, and hypoxic amnesia show
that hypometabolism of the posterior cingulate cortex is an early and
prominent indicator of pathology in these patients. Our findings suggest
that autobiographical memory retrieval tasks could be used to probe the
functional status of the posterior cingulate cortex in patients with
early Alzheimer's disease or at risk for that condition.
PMID: 11440800 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
18: Neuroreport. 2001 Jun 13;12(8):1649-52. Related Articles, Links
Preserved stimulus deviance detection in Alzheimer's disease.
Pekkonen E, Jaaskelainen LP, Erkinjuntti T, Hietanen M, Huotilainen M,
Ilmoniemi RJ, Naatanen R.
Department of Neurology, University of Helsinki, and Medical Engineering
Centre, Helsinki University Central Hospital, Finland.
Aging attenuates automatic auditory discrimination to duration change,
whereas frequency change detection is relatively unimpaired in aging
and in Alzheimer's disease (AD). Here we studied with a whole-head magnetometer
whether cortical auditory discrimination to duration change as shown
by magnetic mismatch negativity (MMNm) response is impaired in AD. Twenty
AD patients with mild to moderate cognitive impairment and 18 age-matched
healthy subjects were monaurally presented a sequence of frequent standard
tones embedded with occasional deviants with shorter duration. MMNm was
significantly delayed in the left hemisphere ipsilaterally to the ear
stimulated in the patient group, whereas the MMNm amplitudes over both
hemispheres were quite similar in both groups. This suggests that although
MMNm is delayed in the left hemisphere, the automatic discrimination
to duration change in the auditory cortex is not attenuated in the early
stages of AD.
PMID: 11409733 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
19: Brain. 2001 Jun;124(Pt 6):1131-7. Related Articles, Links
Examination of motor output pathways in patients with corticobasal ganglionic
degeneration using transcranial magnetic stimulation.
Valls-Sole J, Tolosa E, Marti MJ, Valldeoriola F, Revilla M, Pastor P,
Blesa R.
Unitat d'EMG, Neurology Service, Hospital Clinic, Universitat de Barcelona,
Villarroel, 170 Barcelona 08036, Spain.
The alien hand sign (AHS) is often encountered in patients with corticobasal
ganglionic degeneration (CBGD), revealing a unilateral dysfunction of
the motor system of unknown pathophysiology. We examined the possibility
of an abnormal cortical representation of hand muscles in 10 patients
with probable CBGD and a prominent AHS. Cortical maps were obtained from
the responses to magnetic stimuli applied with a figure of eight coil
at an intensity of 110% above motor threshold. For comparison, the same
study was carried out in 10 normal volunteers, eight patients with Parkinson's
disease and eight patients with Alzheimer's disease. AHS patients had
a larger extension of the cortical map to stimulation of the hemisphere
contralateral to the AHS in comparison with the ipsilateral hemisphere.
Furthermore, in six patients, focal stimulation of the hemisphere ipsilateral
to the AHS gave rise to ipsilateral responses, delayed by a mean of 7.7
+/- 2.2 ms with respect to those recorded in the same muscle to contralateral
stimulation. None of the other patients or control subjects had ipsilateral
responses. Our results indicate an enhanced excitability, or reduced
inhibition, of the motor area of the hemisphere contralateral to the
AHS. The delay of the ipsilateral responses is compatible with a disinhibited
transcallosal input.
PMID: 11353729 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
20: Hum Brain Mapp. 2000 Aug;10(4):195-6. Related Articles, Links
Comment on:
* Hum Brain Mapp. 2000 Aug;10(4):197-203.
Perceptual priming and extrastriate cortex: consensus and controversy.
Nyberg L.
Department of Psychology, Umea University, Sweden.
Publication Types:
* Comment
PMID: 10949056 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
21: AJNR Am J Neuroradiol. 2000 Mar;21(3):524-31. Related Articles,
Links
Functional MR imaging using a visually guided saccade paradigm for comparing
activation patterns in patients with probable Alzheimer's disease and
in cognitively able elderly volunteers.
Thulborn KR, Martin C, Voyvodic JT.
Department of Radiology, MR Research Center, University of Pittsburgh
Medical Center, PA, USA.
BACKGROUND AND PURPOSE: Alzheimer's disease is associated with progressive
visuospatial dysfunction. This study used functional MR (fMR) imaging
with an eye movement paradigm to investigate differences in visuospatial
cognition between patients with probable Alzheimer's disease (pAD) and
cognitively able elderly volunteers. METHODS: Using established, although
imperfect, clinical criteria, patients with pAD (n = 18) and cognitively
able elderly volunteers (n = 10) were selected for study. All patients
underwent echo-planar fMR imaging at 1.5 T. The visually guided saccade
paradigm consisted of alternating periods (30 s) of central fixation
and visually guided saccades to a target appearing randomly along the
horizontal meridian. Activation maps were derived using a voxelwise t
test, comparing the signal intensities between the two steady-state conditions.
The activation patterns were characterized by Talairach coordinates,
activation volumes, and laterality ratios (LRs). RESULTS: Statistically
significant differences existed between the activation patterns of the
patients with pAD and those of the volunteers. In contrast to the control
group, a left-dominant parietal activation pattern and enhanced prefrontal
cortical activation were observed in most patients with pAD. CONCLUSION:
Within the limitations of the imperfect clinical standard of reference,
the reduction in right parietal activation producing the left-dominant
LR for the intraparietal sulcus may reflect the progressive dysfunction
in spatial attention associated with Alzheimer's disease, considering
the known parietal lobe involvement in this function and the disease.
The high specificity of a positive intraparietal sulcal LR measured by
fMR imaging may have a role in detecting and monitoring Alzheimer's disease.
PMID: 10730646 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
22: Dtsch Med Wochenschr. 1999 Dec 23;124(51-52):1577-81. Related Articles,
Links
[Neurology. Therapeutic advances through systems research and molecular
biology]
[Article in German]
Hohlfeld R, Brandt T.
Institut fur Klinische Neuroimmunologie, Klinikum Grosshadern, Ludwig
Maximilians Universitat, Munchen.
PMID: 10664661 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
23: Brain Res. 1999 Dec 11;850(1-2):179-88. Related Articles, Links
Regulation of GTPase and adenylate cyclase activity by amyloid beta-peptide
and its fragments in rat brain tissue.
Soomets U, Mahlapuu R, Tehranian R, Jarvet J, Karelson E, Zilmer M, Iverfeldt
K, Zorko M, Graslund A, Langel U.
Department of Neurochemistry and Neurotoxicology, Arrhenius Laboratories,
Stockholm University, Sweden.
Modulation of GTPase and adenylate cyclase (ATP pyrophosphate-lyase,
EC 4.6.1.1) activity by Alzheimer's disease related amyloid beta-peptide,
A beta (1-42), and its shorter fragments, A beta (12-28), A beta (25-35),
were studied in isolated membranes from rat ventral hippocampus and frontal
cortex. In both tissues, the activity of GTPase and adenylate cyclase
was upregulated by A beta (25-35), whereas A beta (12-28) did not have
any significant effect on the GTPase activity and only weakly influenced
adenylate cyclase. A beta (1-42), similar to A beta (25-35), stimulated
the GTPase activity in both tissues and adenylate cyclase activity in
ventral hippocampal membranes. Surprisingly, A beta (1-42) did not have
a significant effect on adenylate cyclase activity in the cortical membranes.
At high concentrations of A beta (25-35) and A beta (1-42), decreased
or no activation of adenylate cyclase was observed. The activation of
GTPase at high concentrations of A beta (25-35) was pertussis toxin sensitive,
suggesting that this effect is mediated by Gi/G(o) proteins. Addition
of glutathione and N-acetyl-L-cysteine, two well-known antioxidants,
at 1.5 and 0.5 mM, respectively, decreased A beta (25-35) stimulated
adenylate cyclase activity in both tissues. Lys-A beta (16-20), a hexapeptide
shown previously to bind to the same sequence in A beta-peptide, and
prevent fibril formation, decreased stimulation of adenylate cyclase
activity by A beta (25-35), however, NMR diffusion measurements with
the two peptides showed that this effect was not due to interactions
between the two and that A beta (25-35) was active in a monomeric form.
Our data strongly suggest that A beta and its fragments may affect G-protein
coupled signal transduction systems, although the mechanism of this interaction
is not fully understood.
PMID: 10629763 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
24: J Neurol Sci. 1999 Nov 30;170(2):119-23. Related Articles, Links
Motor cortex inhibition is not impaired in patients with Alzheimer's
disease: evidence from paired transcranial magnetic stimulation.
Pepin JL, Bogacz D, de Pasqua V, Delwaide PJ.
University Department of Neurology, CHR Citadelle, Bd du XIIeme de Ligne,
1, 4000, Liege, Belgium.
Motor cortex excitability was studied by transcranial magnetic stimulation
(TMS) in 17 patients with Alzheimer's disease (AD). Resting and active
thresholds for TMS were significantly reduced in AD patients compared
to young and aged healthy subjects. The maximum amplitude of the motor
response evoked by TMS was also significantly increased in AD patients.
We have tested if these changes are related to a modification of the
short-lasting intracortical inhibition of the motor cortex by paired
conditioning-test TMS. We found no significant differences between AD
patients and aged healthy subjects even if there is a slight but significant
difference between aged and young normal subjects. We conclude that the
modification of excitability of the motor cortex does not result from
an impaired intracortical inhibition.
PMID: 10561527 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
25: J Int Neuropsychol Soc. 1999 Jul;5(5):377-92. Related Articles,
Links
Neuroanatomic substrates of semantic memory impairment in Alzheimer's
disease: patterns of functional MRI activation.
Saykin AJ, Flashman LA, Frutiger SA, Johnson SC, Mamourian AC, Moritz
CH, O'Jile JR, Riordan HJ, Santulli RB, Smith CA, Weaver JB.
Department of Psychiatry, Dartmouth Medical School, Lebanon, NH 03756,
USA.
Impairment in semantic processing occurs early in Alzheimer's disease
(AD) and differential impact on subtypes of semantic relations have been
reported, yet there is little data on the neuroanatomic basis of these
deficits. Patients with mild AD and healthy controls underwent 3 functional
MRI auditory stimulation tasks requiring semantic or phonological decisions
(match-mismatch) about word pairs (category-exemplar, category-function,
pseudoword). Patients showed a significant performance deficit only on
the exemplar task. On voxel-based fMRI activation analyses, controls
showed a clear activation focus in the left superior temporal gyrus for
the phonological task; patients showed additional foci in the left dorsolateral
prefrontal and bilateral cingulate areas. On the semantic tasks, predominant
activation foci were seen in the inferior and middle frontal gyrus (left
greater than right) in both groups but patients showed additional activation
suggesting compensatory recruitment of locally expanded foci and remote
regions, for example, right frontal activation during the exemplar task.
Covariance analyses indicated that exemplar task performance was strongly
related to signal increase in bilateral medial prefrontal cortex. The
authors conclude that fMRI can reveal similarities and differences in
functional neuroanatomical processing of semantic and phonological information
in mild AD compared to healthy elderly, and can help to bridge cognitive
and neural investigations of the integrity of semantic networks in AD.
PMID: 10439584 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
26: J Neurol. 1997 May;244(5):304-7. Related Articles, Links
Magnetic stimulation in Alzheimer's disease.
de Carvalho M, de Mendonca A, Miranda PC, Garcia C, Luis ML.
Department of Neurology, Hospital de Santa Maria, Lisbon, Portugal.
Alzheimer's disease (AD) is a common cause of dementia in which some
clinical motor abnormalities have been described. We used transcranial
magnetic stimulation in order to test the hypothesis that the change
in the motor cortex might cause modifications in motor excitability.
Fourteen mildly to moderately affected AD patients were compared with
11 controls matched for age, height and sex. The motor evoked potential
threshold value for the relaxed abductor digiti minimi was lower in the
AD patients than in the control group for both left and right hemispheres
(P < 0.05). No statistically significant difference was found comparing
the left and the right hemispheres thresholds in each population. The
mean interside threshold differences were small and not significantly
different between patients and controls. The spinal motor neuron excitability,
as evaluated by F/M and H/M waves amplitude ratios, showed no difference
between the groups, reinforcing the motor cortex increased excitability
hypothesis to explain this difference. Degeneration of inhibitory gabaergic
terminals might be the basis for the increased cortical excitability
in the motor cortex of the Alzheimer patients; postsynaptic changes in
the GABAA receptors might also affect inhibitory gabaergic transmission.
The increased excitability found by transcranial magnetic stimulation
in the motor cortex is important for understanding the emergence of seizures
and myoclonus in this disease.
PMID: 9178155 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
27: Neuroreport. 1996 May 31;7(8):1365-8. Related Articles, Links
Alzheimer's disease affects parallel processing between the auditory
cortices.
Pekkonen E, Huotilainen M, Virtanen J, Naatanen R, Ilmoniemi RJ, Erkinjuntti
T.
Department of Psychology, University of Helsinki, Finland.
Auditory evoked magnetic fields (AEFs) were recorded from 11 patients
with Alzheimer's disease (AD) and 11 age-matched controls using the 122-channel
whole-head magnetometer. Auditory stimuli were monaurally presented with
interstimulus intervals (ISI) of 0.5 and 2.5 s in different blocks. The
peak latencies of P50m and N100m responses were significantly longer
in AD patients than in controls over the ipsilateral but not over the
contralateral auditory cortex with respect to the ear stimulated. This
finding suggests that parallel auditory processing is impaired between
the auditory cortices in AD patients. The present MEG measurement might
provide an objective index to evaluate auditory dysfunction in AD.
PMID: 8856676 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
28: J Neurol Sci. 1996 Jan;135(1):31-7. Related Articles, Links
Evaluation of the motor cortex by magnetic stimulation in patients with
Alzheimer disease.
Perretti A, Grossi D, Fragassi N, Lanzillo B, Nolano M, Pisacreta AI,
Caruso G, Santoro L.
Department of Clinical Neurophysiology, University of Naples, Italy.
Motor evoked potentials (MEPs) from abductor pollicis brevis (APB) and
tibialis anterior (TA) muscles elicited by transcranial magnetic stimulation
of the motor cortex were studied in 15 patients with Alzheimer disease
(AD). An abnormally higher MEP threshold in APB, frequently associated
with absence of the MEP in relaxed TA muscles, was found in 40% of patients,
almost all of them in the more severe stage of the disease. The MEP amplitude
and averaged MEP/MAP ratio were reduced respectively by 20% and 26% in
the APB muscle, and by 46.7% and 53.3% in the TA muscle. The less frequent
prolongation of the central conduction time (CCT) (20%) might reflect
preservation of the impulse propagation along the surviving pyramidal
fibers. In 63.6% of the patients the central silent period (cSP) duration
in the APB muscle was shortened; the mean value was significantly different
between patients and controls. The results of this study suggest that
loss and/or dysfunction of motor cortex neurones, including pyramidal
cells and inhibitory interneurones may occur in AD patients before clinical
signs become apparent.
PMID: 8926493 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
29: J Med Chem. 1995 Apr 28;38(9):1558-70. Related Articles, Links
In vitro muscarinic activity of spiromuscarones and related analogs.
Wu ES, Griffith RC, Loch JT 3rd, Kover A, Murray RJ, Mullen GB, Blosser
JC, Machulskis AC, McCreedy SA.
Department of Chemistry and Biology, Fisons Pharmaceuticals, Rochester,
New York 14623, USA.
The cholinergic hypothesis of Alzheimer's disease suggests that cholinergic
agonists may have therapeutic potential for treating the attendant memory
deficits of the disease. As part of a program aimed at preparing metabolically
stable, nonquaternary analogs of muscarone, 1-oxa-2,8-dimethyl-8-azaspiro[4.5]decan-3-one,
2a, and related analogs have been synthesized and their in vitro muscarinic
activity evaluated. The synthetic strategy in the formation of the 1-spiro[4.5]decan-3-one
ring system of 2a involved cyclization of the diol 4 in the presence
of Nafion-Hg. The spiromuscarone 2a was found to displace [3H]Oxo-M binding
with a Ki value of 7 nM. Affinities of the oxime and hydrazone analogs
of 2a were lower than 2a. The compounds in these series were partial
muscarinic agonists as demonstrated by stimulation of phosphatidyl inositol
hydrolysis assay, with 2a showing the highest intrinsic intrinsic activity
(60% as compared with carbachol). The results from this study indicate
that an exo double bond at the C-3 position is essential for the receptor
binding.
PMID: 7739014 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
30: West J Med. 1994 Sep;161(3):273-8. Related Articles, Links
Mapping human brain activity in vivo.
Mazziotta JC.
Department of Neurology, Reed Neurological Research Center, Los Angeles,
CA.
A wide range of structural and functional techniques now exists to map
the human brain in health and disease. These approaches span the gamut
from external tomographic imaging devices (positron-emission tomography,
single photon-emission computed tomography, magnetic resonance imaging,
computed tomography), to surface detectors (electroencephalography, magnetoencephalography,
transcranial magnetic stimulation), to measurements made directly on
the brain's surface or beneath it (intrinsic signal imaging, electrocorticography).
The noninvasive methods have been combined to provide unique and previously
unavailable insights into the macroscopic organization of the functional
neuroanatomy of human vision, sensation, hearing, movement, language,
learning, and memory. All methods have been applied to patients with
neurologic, neurosurgical, and psychiatric disease and have provided
a rapidly expanding knowledge of the pathophysiology of diseases such
as epilepsy, cerebrovascular disease, neoplasms, neurodegenerative diseases,
mental illness, and addiction states. In addition, these new methods
have become a mainstay of preoperative surgical planning and the monitoring
of pharmacologic or surgical (transplantation) interventions. Most recently,
the ability to observe the reorganization of the human nervous system
after acute injury, such as occurs with cerebral infarction or head trauma,
or in the course of a progressive degenerative process such as Alzheimer's
or Parkinson's disease, may provide new insights and methods in the rapidly
expanding field of neurorehabilitation. Our newfound ability to generate
maps and databases of human brain development, maturation, skill acquisition,
aging, and disease states is both an exciting and formidable task.
Publication Types:
* Review
* Review, Tutorial
PMID: 7975566 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
31: J Med Chem. 1994 Aug 19;37(17):2774-82. Related Articles, Links
Design, synthesis, and neurochemical evaluation of 2-amino-5-(alkoxycarbonyl)-3,4,5,6-tetrahydropyridines
and 2-amino-5-(alkoxycarbonyl)-1,4,5,6-tetrahydropyrimidines as M1 muscarinic
receptor agonists.
Dunbar PG, Durant GJ, Rho T, Ojo B, Huzl JJ 3rd, Smith DA, el-Assadi
AA, Sbeih S, Ngur DO, Periyasamy S, et al.
Department of Medicinal and Biological Chemistry, College of Pharmacy,
University of Toledo, Ohio 43606.
Four regioisomers of 2-amino-(methoxycarbonyl)-3,4,5,6-tetrahydropyridine
(2a-5a) were synthesized as the racemates to evaluate the utility of
exocyclic amidines in the development of novel agonists for M1 muscarinic
receptors. Of the four regioisomers, only racemic 2-amino-5-(methoxycarbonyl)-3,4,5,6-tetrahydropyridine
(4a; CDD-0075-A) displayed high affinity (IC50 = 10 +/- 3.0 microM) and
activity at muscarinic receptors coupled to PI metabolism in the rat
cortex (260 +/- 4.5% stimulation above basal levels at 100 microM). A
series of 2-amino-5-(alkoxycarbonyl)-3,4,5,6-tetrahydropyridines then
was synthesized for further evaluation as M1 agonists. Only the propargyl
derivative (4d) retained substantial agonist activity (120 +/- 14% at
100 microM) in this series. On the basis of the activity of the 5-(alkoxycarbonyl)-1,4,5,6-
tetrahydropyrimidines (1a and 1d) and the 2-amino-5-(alkoxycarbonyl)-3,4,5,6-tetrahydropyridines,
the corresponding cyclic guanidine derivatives were synthesized and tested.
2-Amino-5-(methoxycarbonyl)-1,4,5,6-tetrahydropyrimidine (7a) displayed
a modest affinity for muscarinic receptors in the CNS (22 +/- 5.3 microM)
and an ability to stimulate PI turnover in rat cerebral cortex (81 +/-
16% at 100 microM). The propargyl derivative (7d) also had modest binding
affinity (31 +/- 15 microM) and high activity (150 +/- 8.5% at 100 microM),
as expected based on the activity of propargyl esters of 1,4,5,6-tetrahydropyrimidine
and 2-amino-3,4,5,6-tetrahydropyridine. Computational chemical studies
revealed five distinct minimum-energy conformations for 1a, (R)-4a, and
7a, and three for 1d, (R)-4d, and 7d, each with a unique orientation
of the ester moiety. Each of the five conformations for 1a could be superimposed upon a unique conformer of (R)-4a and 7a, suggesting that the compounds
interact with muscarinic receptors in a similar fashion. Taken together,
the data indicate the general utility of amidine systems as suitable
replacements for the ammonium group of acetylcholine in developing ligands
with activity at M1 muscarinic receptors in the central nervous system.
Such compounds might be useful in the treatment of patients with Alzheimer's
disease.
PMID: 8064804 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
32: Cerebrovasc Brain Metab Rev. 1992 Spring;4(1):1-27. Related Articles,
Links
PET correlates of normal and impaired memory functions.
Heiss WD, Pawlik G, Holthoff V, Kessler J, Szelies B.
Max-Planck-Institut fur neurologische Forschung, Koln, Germany.
To date, positron emission tomography (PET) has been the only technology
for the quantitative imaging of the changes of regional cerebral glucose
(rCMRGl) or oxygen metabolism and blood flow (rCBF) associated with psychophysical
stimulation and with the performance of mental tasks. So far, the majority
of studies performed in healthy subjects demonstrated activation patterns
involving not only certain limbic structures, most of all hippocampus,
amygdala, parahippocampus, and cingulate, but also temporal, parietal,
and occipital association cortex, depending on the applied paradigm.
Indeed, the closest correlation between regional metabolism and memory
test scores was found in mesiotemporal structures during the performance
of memory tasks. Metabolic or CBF studies also seem to indicate that
memorizing strategies may differ among individuals. PET was repeatedly
used to investigate metabolic and/or blood flow abnormalities in patients
with various amnestic syndromes. In cases with uni- or bilateral lesions
of mesiotemporal structures, caused by surgery, herpes simplex encephalitis,
or permanent ischemic, anoxic, or toxic damage, disturbances of metabolism
and blood flow typically extended far beyond the morphological defects
detected by computed tomography or magnetic resonance. In acute transient
global amnesia, CBF and metabolism were decreased bilaterally in the
mesiotemporal lobes, where hypometabolism persisted for some time, while
higher values were observed in thalamus and some cortical areas. Diencephalic
lesions causing Korsakoff's syndrome were associated with decreased rCMRGl
in the hippocampal formation, upper brainstem, cingulate, and thalamus.
Discrete thalamic infarcts caused amnesia and metabolic depression in the morphologically intact ipsilateral thalamus and in various projection
areas of the infarcted nuclei. In ischemic forebrain lesions, amnestic
deficits could be related to involvement of the anterior cingulate and
of basal cholinergic nuclei. A large number of pathologies are diffusely
spread out in the brain and affect partially or predominantly structures
in memory processing. This holds true especially in the various dementias
where memory disturbances are a consistent and often leading feature.
Notably, Alzheimer's disease can be distinguished from other dementias
by its characteristic pattern of metabolic dysfunction, with the most
prominent changes occurring in parietotemporal and frontal association
cortex whose residual metabolism is related to the severity of the disease.
Therefore, activation studies using paradigms involving memory functions
enhance that typical pattern. Only in the activated state is metabolism
of mesiotemporal structures significantly correlated with the performance
in memory tests. Other dementias also affect some of the distributed
memory networks, with Huntington's disease suggesting a role of the striatum
in memory processing.(ABSTRACT TRUNCATED AT 400 WORDS)
Publication Types:
* Review
* Review, Academic
PMID: 1562450 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
33: Acupunct Electrother Res. 1992;17(2):107-48. Related Articles, Links
Common factors contributing to intractable pain and medical problems
with insufficient drug uptake in areas to be treated, and their pathogenesis
and treatment: Part I. Combined use of medication with acupuncture, (+)
Qi gong energy-stored material, soft laser or electrical stimulation.
Omura Y, Losco BM, Omura AK, Takeshige C, Hisamitsu T, Shimotsuura Y,
Yamamoto S, Ishikawa H, Muteki T, Nakajima H, et al.
Heart Disease Research Foundation, New York.
Most frequently encountered causes of intractable pain and intractable
medical problems, including headache, post-herpetic neuralgia, tinnitus
with hearing difficulty, brachial essential hypertension, cephalic hypertension
and hypotension, arrhythmia, stroke, osteo-arthritis, Minamata disease,
Alzheimer's disease and neuromuscular problems, such as Amyotrophic Lateral
Sclerosis, and cancer are often found to be due to co-existence of 1)
viral or bacterial infection, 2) localized microcirculatory disturbances,
3) localized deposits of heavy metals, such as lead or mercury, in affected
areas of the body, 4) with or without additional harmful environmental
electro-magnetic or electric fields from household electrical devices
in close vicinity, which create microcirculatory disturbances and reduced
acetylcholine. The main reason why medications known to be effective
prove ineffective with intractable medical problems, the authors found,
is that even effective medications often cannot reach these affected
areas in sufficient therapeutic doses, even though the medications can
reach the normal parts of the body and result in side effects when doses
are excessive. These conditions are often difficult to treat or may be
considered incurable in both Western and Oriental medicine. As solutions
to these problems, the authors found some of the following methods can
improve circulation and selectively enhance drug uptake: 1) Acupuncture,
2) Low pulse repetition rate electrical stimulation (1-2 pulses/second),
3) (+) Qi Gong energy, 4) Soft lasers using Ga-As diode laser or He-Ne
gas laser, 5) Certain electro-magnetic fields or rapidly changing or
moving electric or magnetic fields, 6) Heat or moxibustion, 7) Individually
selected Calcium Channel Blockers, 8) Individually selected Oriental
herb medicines known to reduce or eliminate circulatory disturbances.
Each method has advantages and limitations and therefore the individually
optimal method has to be selected. Applications of (+) Qi Gong energy
stored paper or cloth every 4 hours, along with effective medications,
were often found to be effective, as Qigongnized materials can often
be used repeatedly, as long as they are not exposed to rapidly changing
electric, magnetic or electro-magnetic fields. Application of (+) Qi
Gong energy-stored paper or cloth, soft laser or changing electric field
for 30-60 seconds on the area above the medulla oblongata, vertebral
arteries or endocrine representation area at the tail of pancreas reduced
or eliminated microcirculatory disturbances and enhanced drug uptake.(ABSTRACT
TRUNCATED AT 400 WORDS)
Publication Types:
* Clinical Trial
PMID: 1353650 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
34: J Neurol Neurosurg Psychiatry. 1991 May;54(5):443-8. Related Articles,
Links
Posterior cortical dementia with alexia: neurobehavioural, MRI, and
PET findings.
Freedman L, Selchen DH, Black SE, Kaplan R, Garnett ES, Nahmias C.
Department of Psychology, Mississauga Hospital, Ontario, Canada.
A progressive disorder of relatively focal but asymmetric biposterior
dysfunction is described in a 54 year old right handed male. Initial
clinical features included letter-by-letter alexia, visual anomia, acalculia,
mild agraphia, constructional apraxia, and visuospatial compromise. Serial
testing demonstrated relentless deterioration with additional development
of transcortical sensory aphasia, Gerstmann's tetrad, and severe visuoperceptual
impairment. Amnesia was not an early clinical feature. Judgment, personality,
insight, and awareness remained preserved throughout most of the clinical
course. Extinction in the right visual field to bilateral stimulation
was the sole neurological abnormality. Early CT was normal and late MRI
showed asymmetrical bioccipitoparietal atrophy with greater involvement
of the left hemisphere. Results from positron emission tomography (PET)
showed bilaterally asymmetric (left greater than right) occipitotemporoparietal
hypometabolism. The metabolic decrement was strikingly asymmetric with
a 50% reduction in glucose consumption confined to the left occipital
cortex. The picture of occipitotemporoparietal compromise verified by
MRI, PET, and neurobehavioural testing would be unusual for such degenerative
dementias as Alzheimer's (AD) and Pick's disease, although atypical AD
with predominant occipital lobe involvement cannot be excluded. This
case supports the concepts of posterior cortical dementia (PCD) as a
clinically distinct entity and for the first time documents its corresponding
metabolic deficit using PET.
PMID: 1865209 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
35: Eur Neurol. 1991;31(4):259-69. Related Articles, Links
Mapping of event-related potentials to auditory and visual odd-ball
paradigms in patients affected by different forms of dementia.
Onofrj M, Gambi D, Del Re ML, Fulgente T, Bazzano S, Colamartino P, Malatesta
G.
Istituto di Clinica Neurologica, Universita G. D'Annunzio, Chieti, Italia.
The paper reports the results of recordings and maps of event-related
potentials (ERPs) in patients with Alzheimer's disease (AD), progressive
supranuclear palsy (PSP) and in subjects affected by dementia in multiple
sclerosis (MS). ERPs were recorded from 19 scalp electrode derivations
using both visual and acoustic paradigms. In 43% of AD patients, ERPs
were normal; in 20%, although present, ERP components were delayed, while
in the other 37% none of the N2 and P3 peaks could be recorded, because
of abnormal topography of potentials on the scalp. In patients with PSP,
the normal ERP sequence was not identified. In patients with MS delayed
ERPs (50%), abnormal topography of ERPs (30%) and absence of ERPs (20%)
were observed. The follow-up of AD patients showed a progressive alteration
of ERPs. ERP topography alterations were observed in AD, PSP and MS patients
with poorest cognitive performances.
PMID: 1868869 [PubMed - indexed for MEDLINE] |