Dementia of the Alzheimer type

Implications of neuropeptides in neurological diseases

Neuropeptides are sufficiently stable to allow valid radioimmunoassay of peptide concentrations in post-mortem human nervous tissue and in human cerebrospinal fluid. Studies have now documented abnormalities of peptide concentrations in degenerative diseases of the brain. Somatostatin concentration is reduced in the hippocampus and neocortex of patients dying with Alzheimer's type dementia. In Huntington's disease, there are reduced concentrations of substance P, met-enkephalin and cholecystokinin in the basal ganglia; in contrast the concentrations of somatostatin and TRH are increased. Immunocytochemical and experimental lesion studies are underway in an attempt to localize the peptide-containing cells affected by these disorders; and the potential role of alterations in neuropeptide function in the pathogenesis, clinical manifestations and therapy of these illnesses is of great interest. Although alterations of CSF peptide concentrations have been reported in a variety of human diseases, interpretation of these results requires knowledge of the origin and disposition of CSF peptides. Future research into the pathology of peptidergic systems will depend on the development of specific peptide antagonists to probe dynamic aspects of peptide function and on the application of the tools of molecular biology, such as specific mRNA assays, to human material.

Peptides, the limbic lobe and schizophrenia

The human brain contains several peptides with probable synaptic actions, some of which form complex neuronal networks in the limbic lobe (amygdala, hippocampus and temporal cortex). A limbic lobe abnormality has been postulated in schizophrenia on the basis of similarities between schizophrenic symptoms and symptoms in cases of known limbic pathology. Cholecystokinin (CCK), somatostatin (SRIF), neurotensin (NT), vasoactive intestinal polypeptide (VIP) and substance P (SP)-like immunoreactivities were measured by radioimmunoassay in 10 brain areas of 14 schizophrenics and 12 controls. In the schizophrenic group symptoms had been rated in life and the group was divided into Type I (n = 7) and Type II (n = 7) subgroups on the basis of the absence or presence of morbid negative symptoms. In control brains each peptide showed a characteristic distribution with high levels in cortex (CCK), limbic lobe (SOM, NT, VIP) or striatal areas (SP) and low levels of each of the peptides in thalamus. Significant (P less than 0.05) differences between groups were: reductions of CCK and SOM in hippocampus and CCK in amygdala in Type II schizophrenics, and CCK in the temporal cortex of the total schizophrenic group; and elevations of VIP in amygdala in Type I schizophrenics and of SP in the hippocampus in the total schizophrenic group. The findings could not be explained by variables such as age, delay between death and necropsy or to neuroleptic medication. These clinical-state related alterations in the peptide content of the limbic system in schizophrenia may illuminate the pathophysiological basis of the disease, particularly the distinction between Type I and II syndromes.

Neuropeptides in Alzheimer type dementia

Five neuropeptides (cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP), somatostatin (SRIF), neurotensin (NT) and substance P (SP)) were measured in 14 brain areas (4 cortical areas, hippocampus, amygdala, 3 striatal areas, 2 thalamic areas and 3 subcortical areas-- septum, substantia innominata and hypothalamus) in 12 brains with neuropathologically confirmed Alzheimer type change and in 13 control brains. Choline acetyltransferase (CAT) activity was assessed in 6 of these areas. Levels of SRIF, but not those of the other peptides, were reduced in several cortical areas in Alzheimer-type dementia (ATD). The distribution and magnitude of the reduction in SRIF were less than that of CAT activity and the temporal cortex was the only region in which there was a significant relationship between CAT and SRIF deficits. Peptide levels were unchanged in hippocampus, amygdala, thalamus, hypothalamus and striatum (except for an increase in SP in the putamen). SRIF levels were increased in substantia innominata in ATD. NT and SRIF were significantly, and VIP and SP non-significantly, reduced in the septum in ATD. Thus, apart from these alterations in the septum, SRIF was the only neuropeptide for which major changes were identified and these did not follow either the pattern of neuropathological change (e.g. in amygdala and hippocampus) or of CAT deficits (e.g. in substantia innominata).

A post-mortem comparison of the cortical cholinergic system in Alzheimer's disease and Pick's disease

Assessment of neurochemical markers in the frontal cortex indicates that choline acetyltransferase is significantly decreased in Alzheimer's and Gerstmann-Straussler dementias but not in Pick's dementia. It therefore appears that the cholinergic innervation of the cortex from the basal forebrain is intact in Pick's disease. Cortical somatostatin was decreased only in Alzheimer's disease (AD), indicating that loss of somatostatin is not a constant feature in different forms of dementia. Muscarinic binding sites were unaltered in Pick's disease and Gerstmann-Straussler syndrome but were decreased in a subpopulation of AD patients. These data suggest that in some cases of AD a significant loss of cholinoceptive neurones in the cortex is evident.

Topographic analysis of the innervation of the rat neocortex and hippocampus by the basal forebrain cholinergic system

The basal forebrain-cortex connections of the rat were topographically mapped by retrograde tracer methods; and their contribution to the cholinergic innervation of the cortex was assessed by excitotoxin lesions placed in the rostral and caudal aspects of the complex. Discrete injections of tracer into frontal cortex labeled the prominent multipolar acetylcholinesterase (AchE)-positive cells of the ventromedial globus pallidus. Injections of tracer into the parietal cortex labelled cells in the ventral globus pallidus, the underlying substantia innominata, and the lateral hypothalamus. Separate injections of Fast Blue and Nuclear Yellow in the frontal and in the parietal cortex resulted in double-labeled cells in the ventral globus pallidus, which indicates that at least some of these cells may possess collateralizing axons. The cingulate cortex is innervated predominantly by neurons in the nucleus of the horizontal limb of the diagonal band. The occipital cortex was also shown to receive a projection primarily from the nucleus of the horizontal limb of the diagonal band. The hippocampal formation is innervated primarily by cells located in the vertical limb of the diagonal band and in the medial septum. Consistent with the results of the retrograde tracing studies, excitotoxin lesions affecting the diagonal band and medial septum decreased choline acetyltransferase (CAT) activity up to 40% on the occipital cortex and by 64% in the hippocampus, but did not affect CAT activity in the rostral neocortex. In contrast, ibotenate lesions of the caudal ventral globus pallidus and substantia innominata caused decreases in CAT activity in the frontal cortex of up to 65% without affecting enzyme activity in the hippocampal formation. The results of the present study provide details on the topographic organization of the cortical projections originating in the basal forebrain complex and indicate that these neurons are the predominant source of cortical cholinergic innervation.

Cholinergic enzymes in neocortex, hippocampus and basal forebrain of non-neurological and senile dementia of Alzheimer-type patients

Choline acetyltransferase (ChAT) activity and acetylcholinesterase (AChE) staining were examined in different cortical regions, hippocampal formation and basal forebrain of non-neurological controls and of patients afflicted with senile dementia of Alzheimer type (SDAT). Both enzymes showed a clear topographical distribution in the various regions studied. In SDAT cases, ChAT activity was reduced by 0-60% in the neocortex and by up to 97% in the hippocampus depending on the area and layer examined. In the nucleus of the diagonal band of Broca (NDB) and the medial septal nucleus (MSN), the activity was decreased by 65% and 55%, respectively; no significant change was found in the lateral septal nucleus (LSN), nucleus basalis of Meynert (NBM), substantia innominata (SI) and globus pallidus (GP). Comparable changes were seen in AChE staining. The results indicate that degeneration or dysfunction of cholinergic neurons in the medial septal area and possibly neocortex is an important characteristic of SDAT.

Neurotransmitter deficits in Alzheimer's disease: criteria for significance

A series of histopathologic, morphologic, and pharmacologic criteria are proposed to establish the significance of neurochemical deficits in Alzheimer's disease. The underlying pathogenic biochemistry of a better understood neurotransmitter-deficiency syndrome, Parkinson's disease, validates these criteria. The major neurotransmitter systems are evaluated against these guidelines. Only the cholinergic system fulfills all the criteria. Noradrenergic mechanisms are also implicated. Subsequent neurochemical abnormalities found in the brains of patients with Alzheimer's disease can be evaluated against these criteria.

Mechanisms and possible causes of Alzheimer's disease

Alzheimer's disease has been found to be genetically transmitted. Structural changes in the disease include loss of neurons, specifically cholinergic and perhaps noradrenergic neurons. Functional connections among neurons are also lost. No cause has yet been determined, but slow viruses, autoimmune processes, and aluminum toxicity have been proposed.

Alzheimer's disease: a disorder of cortical cholinergic innervation

Great emphasis is being placed on identification of neurotransmitter systems involved in the symptomatic manifestations of neurological and psychiatric disorders. In the case of Alzheimer's disease, which now seems to be one of the most common causes of mental deterioration in the elderly, compelling evidence has been developed that acetylcholine-releasing neurons, whose cell bodies lie in the basal forebrain, selectively degenerate. These cholinergic neurons provide widespread innervation of the cerebral cortex and related structures and appear to play an important role in cognitive functions, especially memory. These advances reflect a close interaction between experimental and clinical neuroscientists in which information derived from basic neurobiology is rapidly utilized to analyze disorders of the human brain.

The isolation and amino acid composition of senile plaque core protein

A new method has been developed for the isolation of intact senile (neuritic) plaque cores from post-mortem brains of patients with Alzheimer's disease. The plaque cores were found to be insoluble in various protein denaturants. The amino acid composition of the plaque core protein does not resemble that of any known form of amyloid.

The failing brain

In the elderly, loss of brain wet weight and reduction in neuronal populations may be related to declining cognitive function. In some brain areas there appear to be reduced dendritic arborization. In the aging brain, neurotransmitter metabolism is affected. Catecholamine concentration appears to be especially reduced. More marked loss of cells and synapses is seen in senile dementia of the Alzheimer's type, and there is a significant reduction in choline acetyltransferase activity and in the ability of isolated biopsy tissue to synthesise acetylcholine. The significance of these findings and the possibility of drug intervention is discussed.

Lack of cholinergic deficit in the neocortex in Pick's disease

Choline acetyltransferase activity was decreased in the frontal cortex in Alzheimer's and Gerstmann-Straussler dementias but not in Pick's disease. Cortical somatostatin was only decreased in Alzheimer's dementia. Postsynaptic muscarinic binding sites appeared to be decreased in a subpopulation of Alzheimer's patients. Our data indicate that a loss of cholinergic innervation of the cortex is not common to all dementias.

Loss of neurons in the nucleus basalis of Meynert in Alzheimer's disease, paralysis agitans and Korsakoff's Disease

The nucleus basalis of Meynert, the major source of cholinergic innervation of the cerebral cortex, was morphometrically investigated in 58 cases of neuropsychiatric disorders and compared to 14 controls. The results demonstrate a loss of neurons in the nucleus basalis of Meynert in Alzheimer's disease (70%), paralysis agitans (77%), and Korsakoff's disease (47%) but no marked reduction of neurons in postencephalitic parkinsonism, Huntington's disease, chronic alcoholism without dementia, schizophrenia and infantile brain damage. Neurons of the three subdivisions of the nucleus basalis of Meynert (the nucleus septi medialis, the nucleus of the diagonal band of Broca and the nucleus basalis Meynert neurons in the substantia innominata) may be affected in a different manner in different patients within a single group homogeneous with respect to the usual clinical and neuropathological diagnostic criteria. Cell loss in the basal forebrain is restricted to the large neurons of the nucleus basalis, the immediately adjacent neurons of the globus pallidus externus not being affected. The selective degeneration of these neurons provides the morphological correlate of the cortical cholinergic deficiency in these neuropathological conditions. The degeneration of this discrete cholinergic neuronal population in several disorders of higher cortical function is probably directly related to the progressive deterioration of memory and cognitive processes in affected patients.

The responsiveness of human eccrine sweat glands to choline and carbachol. Application to the study of peripheral cholinergic functioning in Alzheimer-type dementia

The responsiveness of human eccrine sweat glands to intradermally injected choline and carbachol was studied in vivo using a plastic paint impression method. Both drugs exerted consistent dose-related effects, choline being significantly less potent than carbachol. The responses to both drugs attained a maximum level approximately 3 min after the injection, but the responses to choline had a less pronounced peak and declined more slowly than the response to carbachol. The response to choline, but not the response to carbachol, was antagonised by hemicholinium-3. Young males showed greater responsiveness to both drugs than young females, this being reflected in higher maxima of the dose-response curves obtained for the males. Smaller responses to both drugs were observed in old females than in young females, this being reflected in lower maxima of the dose-response curves obtained for the elderly group. A group of elderly female patients with clinical diagnoses of Alzheimer-type dementia showed smaller responses to both drugs than the group of non-demented elderly females. The results show that choline can stimulate eccrine sweat glands, possibly by an indirect mechanism involving active uptake and metabolic conversion to acetylcholine. The reduced responsiveness seen in the patients suffering from Alzheimer-type dementia could reflect either a loss of function of cholinergic sympathetic neurones or impaired functioning of the sweat glands themselves.

Alzheimer's disease and maternal age

Findings from several studies suggest a relationship between Alzheimer's disease and Down's syndrome. It has long been known that advanced maternal age is a risk factor for Down's syndrome, and that mothers who give birth to a child with this syndrome have characteristics consistent with accelerated aging. Little is known about risk factors for Alzheimer's disease, other than age. In this study, documentation is supplied for a hypothesis concerning a relationship between Alzheimer's disease and advanced maternal age.

CCK receptors and human neurological disease

Cholecystokinin (CCK) receptor binding was measured in postmortem brain tissue of patients with Alzheimer's dementia, Huntington's chorea, and neurologically healthy matched controls. CCK binding was significantly reduced inthe basal ganglia and cerebral cortex of Huntington's patients, but was normal in the temporal and cingulate cortex of patients with Alzheimer's disease. These findings indicate that CCK receptor loss is unique to specific neurodegenerative disease(s), and that CCK may be involved in the symptoms of Huntington's disease but is not implicated in the neuropathology of Alzheimer's dementia.

Autoradiographic localization of muscarinic cholinergic receptors in the hippocampus of patients with senile dementia

Muscarinic cholinergic receptors were localized by autoradiography in the hippocampi from 4 patients with senile dementia (S. D.) and 4 neurologically normal age-matched controls. A large number of senile plaques were observed in the hippocampi from S.D. patients, whereas they were not observed in control brains. The distribution and density of muscarinic receptors was similar in control and S.D. patients. In the hippocampus, areas rich in receptors were subiculum, strata oriens, pyramidalis and radiatum and the molecular layer of the dentate gyrus. The density of autoradiographic grains over the senile plaques was comparable to that over the surrounding neuropil, indicating that senile plaques have muscarinic receptors.

Cortical substance P-like immunoreactivity in cases of Alzheimer's disease and senile dementia of the Alzheimer type

The concentration of substance P-like immunoreactive material (SPLI) and somatostatin-like immunoreactive material (SLI) and the activity of acetyl-CoA: choline-O-acetyltransferase (ChAT; EC 2.3.1.6) were measured in eight brain regions of 13 normal patients and 12 patients with Alzheimer disease/senile dementia of the Alzheimer type (AD/SDAT). SPLI was significantly lower in five of eight regions in the patients with AD/SDAT. Younger patients with AD/SDAT had significantly lower SLI in the parietal cortex than older patients. ChAT activity and SPLI in the parietal cortex of the presenile patients with AD/SDAT were not significantly different from values found in older patients.

Philothermal response of polymorphonuclear leukocytes in dementia of the Alzheimer type

The philothermal response, i.e., the tendency of polymorphonuclear leukocytes (PMNs) to migrate along a temperature gradient toward warmer temperatures, was evaluated in 11 patients with a clinical diagnosis of dementia of the Alzheimer type (DAT) and compared to 11 age and sex-matched mentally normal individuals. While the total number of migrating PMNs did not differ significantly between these two groups, there was a significant difference in the spatial distribution of the responding cell population. The numerical parameter, R, has been introduced to provide a quantitative measure of the distribution of populations characterized by differences in motile behavior. This R value was unusually high for 10 of the DAT patients but only one of the comparison individuals. No relation between R and duration of illness, age, or sex was detected. These preliminary findings, based on a small number of clinically diagnosed DAT patients, suggest that the philothermal response may represent a biological marker with diagnostic usefulness for at least one subgroup of DAT patients.

Cholinergic projections from the basal forebrain to frontal, parietal, temporal, occipital, and cingulate cortices: a combined fluorescent tracer and acetylcholinesterase analysis

The morphologies, intercellular organization, and cortical projection patterns of putative cholinergic neurons in the basal forebrain of the rat were examined by use of fluorescent tracer histology in combination with the pharmacohistochemical regimen for acetylcholinesterase (AChE). Intensity staining AChE-containing cells projecting to frontal sensorimotor (Area 10), parietal (Area 2), and temporal (Area 4) cortices were found ipsilaterally in nucleus preopticus magnocellularis, in nucleus basalis, and in association with the substantia innominata, the ansa lenticularis, and the lateral hypothalamic area; an essentially rostrocaudal topography was observed for these projections. AChE-containing pathways to cingulate (Area 29) and visual (Area 17) cortices derived from ipsilateral somata associated with the vertical and horizontal limbs of the diagonal band, nucleus preopticus magnocellularis, rostral portions of nucleus basalis, and the substantia innominata. Neurons innervating Area 29 were generally located more rostrally than those giving rise to AChE afferents to Area 17. The vast majority of cells appeared to innervate relatively discrete areas of the cortex. Evidence for collateralization was found only in neurons projecting to visual and cingulate cortices, and these represented only 3.2% of the cells providing AChE afferents to Areas 17 and 29. The basal forebrain AChE projection cells were typically large (greater than 25 micron in maximum cell body extent), and their somata were predominantly oval, with lesser proportions being fusiform or triangular. Many were organized in clusters, particularly in nucleus basalis.

Alzheimer's disease and senile dementia of Alzheimer type. A comparative study

Clinical and neuropsychological findings, EEG, and several blood and CSF parameters were investigated in 36 patients with Alzheimer's disease (AD) and 35 patients with senile dementia of Alzheimer type (SDAT). There were more women among senile patients and more familial cases among presenile patients. The average duration of the symptoms was longer in presenile patients (6.1 years) than in senile patients (3.9 years). This could be due to the lower resistance to the disease process in the senile group. Extrapyramidal signs, especially rigidity, were found in over 60% of all patients and in practically all patients with advanced dementia. Tremor was found in three patients only. Four presenile (11%) and two senile (6%) patients had epileptic seizures. All patients had abnormal EEG recordings, mainly in form of diffuse slowing. A positive correlation was found between the EEG abnormality and the severity of dementia in AD but not in SDAT. However, the difference between the correlation coefficients in AD and SDAT was insignificant. Between EEG and the duration of the disease there was no correlation. EEG was not more abnormal in very severe dementia than in severe dementia. Other findings were similar in AD and SDAT. It is concluded that it is artificial to separate AD and SDAT at the age of 65 and that they clinically compose a single entity. This entity could well be called Alzheimer's disease.

Alzheimer's disease and senile dementia of Alzheimer type. A neuropsychological study

Neuropsychological performance was investigated in 36 presenile patients with Alzheimer's disease and 35 patients with senile dementia of Alzheimer type by using Luria's test methods. The most deteriorated performances in both groups were in memory, intellectual, higher visual and motor functions, and in orientation. The neuropsychological functions deteriorated gradually in the course of the disease process so that the shape of the performance profile was preserved. The progression of the disease seemed to be more rapid in senile patients but neuropsychologically there were no significant differences between Alzheimer's disease and senile dementia of Alzheimer type. They seemed to form a continuum of one disease. Luria's neuropsychological investigation turned out to be a useful method in the assessment of at least moderate to severe dementia.

Quantitative ultrastructural changes in rat cortical synapses during early-, mid- and late-adulthood

Quantitative ultrastructural analysis of rat parietal cortex was undertaken to determine the nature of the synaptic changes occurring in the molecular layer over a series of ages in early- (3 months), mid- (6 and 10 months) and late- (17 months) adulthood. The total number of synapses remained constant until 10 months of age, but decreased significantly by 17 months. Asymmetrical synapses on dendritic shafts were lost earlier (by 6 months) than asymmetrical synapses on dendritic spines (by 17 months). Symmetrical axodendritic synapses remained constant throughout adulthood. Analysis of synaptic terminal parameters revealed the following. Both individual and total presynaptic terminal areas decreased over the age range studied. Individual and total postsynaptic terminal areas, however, remained constant over the 3--17-month period. Positive correlations were obtained for the relationships between presynaptic terminal area and both age and synaptic vesicle number. The presynaptic terminal area was largest and contained the greatest number of vesicles at 3 months of age. This age was, in addition, characterized by the least numbers of mitochondria in the presynaptic terminal and spine apparatus in the postsynaptic terminal. The vacuolar and tubular cisternae of the presynaptic terminal were considerably reduced at 17 months. These data suggest that in the molecular layer of the cerebral cortex the period of adulthood is characterized by a diversity of synaptic changes. The 3-month age may reflect the end of the developmental phase and may be marked by changes in synaptic functional activity. The asymmetrical axodendritic synapses may constitute an intermediate form of synapse, capable of being transformed into axospinous synapses as dendritic spines continue to be formed in the adult.

Angiotensin converting enzyme in Alzheimer's disease increased activity in caudate nucleus and cortical areas

The activity of the dipeptidyl carboxypeptidase, angiotensin converting enzyme, was assayed in several brain regions of patients dying with Alzheimer's disease and compared to that of appropriately age-matched controls. Enzyme activity was found to be elevated by 44% and 41% in the medial hippocampus and parahippocampal gyrus, respectively, and by 27% and 29% in the frontal cortex (area 10 of Brodman) and caudate nucleus, respectively, in Alzheimer's disease patients. Converting enzyme activity did not differ from controls in the nucleus accumbens, substantia nigra, temporal cortex, anterior or posterior hippocampus, amydgala, and septal nuclei.

Cholinergic innervation in neuritic plaques

Although several studies of Alzheimer's disease suggest that the frequency of neuritic plaques in the cerebral cortex is correlated with the severity of dementia and with reduction in presynaptic cholinergic markers in the cortex, the relationship between cholinergic cortical innervation and the pathogenesis of plaques is unknown. The hypothesis was tested that the neurites in the plaque consist, in part, of presynaptic cholinergic axons, many of which arise from neurons in the basal forebrain. This hypothesis was tested by analyzing the character and distribution of plaques in monkeys, aged 4 to 31 years, with staining for acetylcholin-esterase and also with Congo red and silver stains. Immature and mature plaques were rich in acetylcholinesterase. As the plaques matured, the amount of amyloid increased, and the number of neurites and the activity of acetylcholinesterase decreased. End-stage amyloid-rich plaques lacked acetylcholinesterase. These observations indicate that changes in cortical cholinergic innervation are an important feature in the pathogenesis and evolution of the neuritic plaque.

Alzheimer's disease and senile dementia: loss of neurons in the basal forebrain

Recent evidence indicates that the nucleus basalis of Meynert, a distinct population of basal forebrain neurons, is a major source of cholinergic innervation of the cerebral cortex. Postmortem studies have previously demonstrated profound reduction in the presynaptic markers for cholinergic neurons in the cortex of patients with Alzheimer's disease and senile dementia of the Alzheimer's type. The results of this study show that neurons of the nucleus basalis of Meynert undergo a profound (greater than 75 percent) and selective degeneration in these patients and provide a pathological substrate of the cholinergic deficiency in their brains. Demonstration of selective degeneration of such neurons represents the first documentation of a loss of a transmitter-specific neuronal population in a major disorder of higher cortical function and, as such, points to a critical subcortical lesion in Alzheimer's patients.

Postmortem stability of dopamine-sensitive adenylate cyclase, guanylate cyclase, ATPase, and GTPase in rat striatum

The stability of dopamine-sensitive adenylate cyclase, guanylate cyclase, ATPase, and GTPase was measured in homogenates of rat striatal tissue frozen from 0 to 24 h postmortem. ATPase, GTPase, and Mg2+-dependent guanylate cyclase activities showed no significant change over this period. Mn2+-dependent guanylate cyclase activity was stable for 10 h postmortem. Basal and dopamine-stimulated adenylate cyclase activity decreased markedly during the first 5 h. However, when measured in washed membrane preparations, these adenylate cyclase activities remained stable for at least 10 h. Therefore, the postmortem loss of a soluble activator, such as GTP, may decrease the adenylate cyclase activity in homogenates. These results are not consistent with an earlier suggestion that there is a postmortem degradation of the enzyme itself. Other kinetic parameters of dopamine-sensitive adenylate cyclase can also be measured independently of postmortem changes. Thus, it is possible to investigate kinetic parameters of dopamine-sensitive adenylate cyclase, guanylate cyclase, ATPase, and GTPase in human brain obtained postmortem.

Neurochemical activities in human temporal lobe related to aging and Alzheimer-type changes

Activities relating to 3 neurotransmitter and 4 neuropeptide systems have been examined in human temporal lobe (post mortem) for their relationships with age and Alzheimer-type changes (senile plaques and cognitive function). Significant alterations with increasing age (from 61 to 92 years) in a series of non-demented cases included a reduction of the cholinergic enzyme, choline acetyltransferase, and an increase in vasoactive intestinal peptide immunoreactivity. In cases of alzheimer's disease the only neurochemical activity investigated which correlated significantly with cognitive impairment (assessed from a Mental Test Score obtained shortly before death) and with the severity of Alzheimer-type abnormalities (senile plaques density) was choline acetyltransferase. Further analyses of the data in relation to the severity of plaque formation suggest that alterations in other neurochemical activities including reductions in dopamine-beta-hydroxylase activity, cholecystokinin octapeptide (aqueous extracted) and somatostatin immunoreactivities and an increase in substance P immunoreactivity, may occur at later stages of the disease process. These comparative data suggest that biochemical changes in this brain area associated with age and earlier stages of Alzheimer's disease may be relatively selective.

Morphometric comparison of hippocampal microvasculature in ageing and demented people: diameters and densities

The diameters and densities of capillaries and arterioles in the hippocampal cortex of normal subjects and patients with Alzheimer's dementia were measured in thick celloidin sections stained for alkaline phosphatase. Microvascular diameters in general are affected more by age than by the presence of dementia of the Alzheimer type. The diameter of both capillaries and arterioles increases significantly with age. The density of capillaries decreases whereas that of the arterioles increases significantly. The capillary changes suggest that a reduced exchange potential accompanies ageing. In brains of people with Alzheimer's disease the overall capillary diameters and densities do not differ from those of age-matched controls. Regional changes may, however, be important: those hippocampal zones showing the greatest severity of or increment in nerve cell lesions do correspond to those having the highest levels of or increase in capillary density and the greatest decrease in diameter, suggesting a direct association between neuronal susceptibility to Alzheimer changes and degree of regional blood supply. Capillary surface areas, volumes and area/capillary volume ratios support the possibility of this relationship. Neurofibrillary tangles and granulovacuolar degeneration do not correlate equally with the degree of capillary "irrigation"; tangles are more closely related to these morphological vascular parameters.

A unifying hypothesis for the cause of amyotrophic lateral sclerosis, parkinsonism, and Alzheimer disease

The causes of amyotrophic lateral sclerosis, Parkinson disease, and Alzheimer disease are unknown. Furthermore, treatment for two of these conditions is almost totally lacking. The thesis is presented that each of these disorders is due to lack of a disorder-specific neurotrophic hormone. The hormone would be elaborated or stored in the target of the affected neurons. It would be released by the postsynaptic cell and then exert its effects in a retrograde fashion after being taken up by the presynaptic terminal. In the lower motor neuron syndromes of amyotrophic lateral sclerosis, failure of muscle cells to release the appropriate motor neurotrophic hormone would result in impaired function of anterior horn cells. In Parkinson disease, the neurotrophic failure would be characterized by inability of striatal cells to provide the required dopamine neurotrophic hormone with resulting impairment of substantia nigra cells. In Alzheimer disease, the abnormalities would lie in failure of the hippocampus and cortical cells to supply the relevant cholinergic neurotrophic hormone with resulting impairment of medial septal and nucleus basalis neurons. Central nervous system tissue culture provides a convenient system in which to assay these neurotrophic hormones and should permit a test of the hypothesis.

Alzheimer disease: evidence for selective loss of cholinergic neurons in the nucleus basalis

The nucleus basalis of Meynert provides diffuse cholinergic input to the neocortex. When compared with an age- and sex-matched control, the nucleus basalis from a patient with Alzheimer disease demonstrated substantial reduction of neurons. Loss of this neuronal population may represent an anatomical correlate of the well-documented cholinergic derangement in Alzheimer disease.

Postmortem stability of alpha-bungarotoxin binding sites in mouse and human brain

The postmortem stability of alpha-bungarotoxin binding sites was examined in the brains of mice handled under conditions designed to simulate the handling of human autopsy material. No significant changes in the concentration of binding sites were evident up to 24 h after death. No correlation between the number of binding sites and the delay period between death and autopsy was found in studies of frontal cortex or mid-temporal gyrus from normal humans or cases of dementia of the Alzheimer type. Samples of mid-temporal gyrus from demented patients show a significant reduction in the number of binding sites.