Antemortem markers of Alzheimer's disease

Treatment of behavioural and psychiatric symptoms in dementia: implications of recent safety warnings

Atypical antipsychotics are commonly used off-label to treat behavioural and psychiatric symptoms in dementia (BPSD), particularly in elderly care homes. Much of this use is inappropriate, and trials have shown an increased likelihood of serious cerebrovascular adverse events (CVAEs) such as stroke and transient ischemic attack (TIA) in elderly patients. The aetiology of this risk is not known, but may be related to metabolic effects and excess weight gain. Based on a review of published trials with risperidone and olanzapine that shows a three-fold increase in stroke risk in elderly patients with dementia, regulators in Europe and the USA now recommend against using these agents for behavioural control, particularly in patients with a history of cerebrovascular disease. When making prescribing decisions, physicians should pay careful attention to risk versus benefit with psychotropics. Antipsychotics should be regarded only as rescue medications for acute-onset (over hours or days) or for severe chronic BPSD, or used in patients who are aggressive and/or represent a danger to themselves or others. If atypical antipsychotics are prescribed, physicians should screen for risk factors for both stroke and cardiovascular disease when initiating treatment, and regular monitoring should be undertaken if patients with chronic behavioural problems receive antipsychotic maintenance therapy. International guidelines are now required that direct prescribers in the appropriate use of alternative therapies for BPSD. Cholinesterase inhibitors (ChEIs), particularly rivastigmine, can delay the onset and reduce the severity of neuropsychiatric symptoms in dementia, and decrease the requirement for antipsychotic and other psychotropic medications. Evidence suggests that they may be more appropriate for the control of chronic (over weeks to months) mild-to-moderate BPSD.

Biological markers for the clinical diagnosis of Alzheimer's disease

There is a compelling need to develop biological marker(s) to confirm a clinical diagnosis of Alzheimer's disease (AD) during life in order to unequivocally identify AD patients for emerging therapeutic interventions. This review describes recent advances in the development of diagnostic marker(s) for AD. They include polymorphism of apolipoprotein E (ApoE) and alpha 1-antichymotrypsin as well as cerebrospinal fluid (CSF) tau and CSF-amyloid beta-protein levels, skin biopsy, and pupil dilatation assay by anti-cholinergic agent. In conclusion, ApoE genotyping should not be used as a sole diagnostic test for AD, and that monitoring of CSF-tau appeared to be most promising and reliable diagnostic aid.

Some aspects of memory disorders clearly distinguish dementia of the Alzheimer's type from depressive pseudo-dementia

Two groups of patients affected by mild dementia of the Alzheimer's type (n = 42) or by depressive pseudo-dementia (n = 26) were given a modified version of the Rey's Auditory Verbal Learning Test. The two groups were roughly matched for overall level of cognitive impairment. The main purpose of the research was to determine if some aspects of their memory disorders distinguished the two diagnostic groups. Comparison between results obtained on recall and on recognition measures was of little diagnostic usefulness in distinguishing dementia of the Alzheimer's type (DAT) from depressive pseudo-dementia (DPD). A marked prevalence of the recency over the primary effect in immediate recall, a high rate of forgetting, and the presence of many intrusion errors on delayed recall were observed more frequently in DAT than in DPD patients. None of these indices, however, was sensitive and specific enough to allow a confident diagnostic discrimination at the individual case level. The memory measure which best distinguished DAT from DPD patients was the presence of several false positive errors on delayed recognition because DAT patients adopted a very liberal response bias, endorsing many false recognition errors, whereas DPD patients adopted a conservative criterion and tended to miss real stimuli, rather than making false recognition errors.

A long-term follow-up study of cerebrospinal fluid acetylcholinesterase in delirium

Cerebrospinal fluid acetylcholinesterase (CSF AChE) was determined for elderly delirious patients during the acute stage and after a 1- and 4-year follow-up periods, and the AChE levels were compared with age-equivalent controls. The AChE levels measured during the index admission correlated with the length of life after delirium, suggesting that cholinergic dysfunction may have prognostic significance in delirious patients. Although the CSF AChE concentrations measured during the index admission were in the same range as in controls, we observed a declining trend in patients with various structural brain diseases during the follow-up period. The decreasing levels may reflect the progression of the underlying dementia in these patients.

Neurodegeneration, Alzheimer's disease, and beta-amyloid toxicity

In its majority, Alzheimer's disease is sporadic and with late onset. Therefore, age-related disturbances in cellular metabolism may come into focus with respect to the etiopathogenesis of this neurodegenerative disorder. As a possible primary abnormal event in sporadic Alzheimer's disease, a desensitization of the neuronal insulin receptor and the subsequent deficits in ATP and acetylcholine are discussed with its impact on protein processing in general and beta-amyloid formation in particular, and neurotoxicity of the latter.

Post-mortem proton magnetic resonance spectrometric measures of brain regions in patients with a pathological diagnosis of Alzheimer's disease and multi-infarct dementia

In-vitro spectrometric measures were made of spin-lattice (T1) and spin-spin (T2) relaxation times of samples of grey and white matter from the brains of 15 patients with a pathological diagnosis of Alzheimer's disease, 5 with multi-infarct dementia, and 11 non-demented subjects. Relaxation times were significantly greater in the parietal white matter and temporal white matter of patients with Alzheimer's disease compared with that of the other subjects. This was associated with an increase in tissue water content. These findings confirm measures obtained in some imaging studies.

Alzheimer's disease

Alzheimer's disease is one of the most severe and most common chronic diseases of older persons. Because occurrence of the disease is strongly related to age, its public health impact is likely to continue to increase as the population ages. As with many other diseases, a diagnosis of Alzheimer's disease is made through a combination of clinical history, physical, and neurologic examination, and laboratory evaluation. Because the dominant feature of this disease is its effect on cognition, its diagnosis requires careful evaluation of cognitive function usually with formal neuropsychological performance testing. Clinical evaluation of persons for Alzheimer's disease has four objectives: (1) to determine as accurately as possible if the person has dementia; (2) if dementia is present, to determine whether its presentation and course are consistent with a diagnosis of Alzheimer's disease; (3) to assess evidence for any alternate diagnoses, especially if the presentation and course are atypical for Alzheimer's disease; and (4) to evaluate evidence of other, coexisting, diseases that may contribute to the dementia, with strong emphasis on conditions that might respond to treatment. There is no reliable antemortem diagnostic test for Alzheimer's disease; the main purpose of laboratory testing is to identify other conditions that might cause or exacerbate dementia. Pathologically, Alzheimer's disease is characterized by the presence of two lesions on microscopic examination of the brain: neuritic plaques and neurofibrillary tangles. Both lesions can be seen in the brains of older persons without dementia. However, they are found in greater numbers in the neocortex and hippocampus with Alzheimer's disease. Caring for patients with Alzheimer's disease is demanding and requires compassion and skills that go beyond the choices among sophisticated and effective therapies that characterize much of modern medical practice. The current lack of effective pharmacotherapy for cognitive dysfunction in Alzheimer's disease should not obscure that there are many areas in which intervention can improve quality of life for both the patient and the caregiver. Achieving success in these areas typically requires that the physician work effectively with providers of many other medical and nonmedical services. Community resources, advocacy, behavior management, and experimental therapies and procedures, should be discussed with the family of each patient. In addition, persons with mild disease should be promptly informed of their diagnosis in order to obtain their wishes regarding life prolonging measures and extended care options.

Alzheimer's disease: beta-amyloid precursor protein mRNA expression in mononuclear blood cells

beta-Amyloid precursor protein (beta APP) mRNA was examined in peripheral mononuclear blood cells (PMBCs) in Alzheimer's disease, Down's syndrome and control subjects. Total RNA from PMBCs was reverse transcribed and then amplified using the polymerase chain reaction (PCR). The 3 major beta APP transcripts were expressed in PMBCs from all subjects. These results suggest that PMBCs could be a circulating source for abnormal amyloid deposition in the brain and in peripheral tissues.

Risk factors for stroke as predictors of platelet membrane fluidity in Alzheimer's disease

We have previously reported that increased platelet membrane fluidity identifies a subgroup of patients with Alzheimer's disease who have distinct clinical features including an earlier age of symptomatic onset, a more rapidly progressive cognitive decline, and a decreased prevalence of focal electroencephalographic findings. In the current study, these patients also exhibited a decreased prevalence of risk factors for stroke compared with patients who had normal platelet membrane fluidity. Our findings suggest that the platelet membrane abnormality describes a clinical subgroup of patients with Alzheimer's disease who are less likely to have coexisting cerebrovascular disease than the remaining patients who meet clinical consensus criteria for probable Alzheimer's disease.

CSF monoamine metabolites, cholinesterases and lactate in the adult hydrocephalus syndrome (normal pressure hydrocephalus) related to CSF hydrodynamic parameters

Monoamine metabolites, cholinesterases and lactic acid in lumbar cerebrospinal fluid (CSF) were investigated on patients with the adult hydrocephalus syndrome (idiopathic normal pressure syndrome; AHS, n = 15), Alzheimer's disease (AD, n = 14), multi-infarct dementia (MID, n = 13) and controls (n = 21). Patients had clinical and CSF hydrodynamic investigations. Monoamine concentrations were determined by reversed-phase liquid chromatography, cholinesterases and lactate were determined photometrically. In the AHS patients, CSF monoamine concentrations were not significantly different compared with controls, AD or MID patients. AHS and AD patients showed a similar reduction of CSF acetylcholinesterase activity compared with controls. Positive correlations were found in concentrations of CSF homovanillic acid, CSF 5-hydroxyindoleacetic acid and CSF lactic acid versus CSF outflow conductance (that is, resistance against CSF outflow) in the AHS patients. A similar pattern was observed in a subgroup of MID patients characterised by dilated ventricles and disturbed CSF hydrodynamics. These data suggest that a low CSF outflow conductance may facilitate the clearance of acidic substances from the arachnoid space at the probenecid sensitive active transport site. Alternative explanations would be that a pathologically low CSF outflow conductance is accompanied by an inverse caudorostral flow of CSF or a compromised trans-ependymal diffusion.

Platelet phospholipid synthesis in Alzheimer's disease

The rates of incorporation of [3H]choline and [3H]ethanolamine into membrane phospholipids of platelets from 22 drug-free Alzheimer's disease patients and 18 normal elderly controls were compared. No significant differences between groups were found. If alterations in lipid metabolism are involved in the pathophysiological processes underlying Alzheimer's disease, such alterations are not manifest in measures of radiolabeled base incorporation into platelet phospholipids.

Neurofibrillary changes confined to the entorhinal region and an abundance of cortical amyloid in cases of presenile and senile dementia

Cases of old-aged demented individuals exhibited abundant cortical amyloid deposits but only small numbers of neurofibrillary changes. Neuritic plaques were rare or absent. Neither Ammon's horn nor isocortex revealed sufficiently large numbers of tangles to permit the diagnosis of fully developed Alzheimer's disease. Dense accumulations of neurofibrillary tangles and neuropil threads occurred only in layer Pre-alpha (II) of the entorhinal region. This pattern of cortical destruction may represent a variant of Alzheimer's disease or an initial stage of this disorder.

Zinc and thymic hormone-dependent immunity in normal ageing and in patients with senile dementia of the Alzheimer type

Plasma zinc levels were measured in young controls, aged controls, patients with dementia of the Alzheimer type and patients with non-Alzheimer type dementia. Zinc levels decreased with age; however, no difference was found between patients with dementia and age-matched controls. Plasma levels of active or inactive thymulin, a nonapeptide produced and released by the thymus gland, were also determined in young controls, aged controls, patients with dementia of the Alzheimer type and patients with non-Alzheimer type dementia. Basal levels of active thymulin were decreased in aged controls and in patients with dementia. In vitro reactivation of thymulin after zinc addition to plasma samples was decreased in aged controls. A further impairment of thymulin reactivation was present in patients with dementia. A significant age-dependent decrease in lymphocyte proliferation after mitogen stimulation was found; however, no difference was present between aged controls and patients with dementia of the Alzheimer type. Interleukin-2-induced cell activation and its effect on mitogen-induced proliferation were also measured; once again only an age-associated decrease was found. The endocrine function of the thymus of patients with dementia appears to be more compromised than that from aged controls.

Antipsychotics in the elderly

Neuroleptics are commonly prescribed medications in the geriatric population and have a broader spectrum of indications than in younger patients. In spite of the frequent use of neuroleptics in elderly patients with organic brain syndromes, there are relatively few studies that use double-blind, placebo-controlled methodology. The results of these studies are conflicting; however, there is sufficient evidence that symptoms of agitation, behaviourial dyscontrol, and psychosis are often responsive to neuroleptic treatment. Elderly patients with schizophrenia or other psychotic disorders may also benefit from neuroleptic treatment. As there is a potential for overuse of these medications among the elderly, clear definition of checklist symptoms is imperative. Furthermore, periodic reduction of dose and possible discontinuation of the drug should be considered since many of the checklist symptoms in this age group are environmentally related and time-limited. There has so far been little evidence to support the use of one neuroleptic over another. Side-effect profiles suggest that low doses of the high potency agents are safer and better tolerated in the elderly. Both therapeutic effects and side effects should be assessed at regular intervals.

Growth properties and in vitro life span of Alzheimer disease and Down syndrome fibroblasts. A blind study

A blind study was set up to examine the in vitro growth characteristics of skin fibroblasts from 2 individuals with and 9 at risk for familial Alzheimer disease, 4 individuals with sporadic Alzheimer disease, 18 with Down syndrome as well as 5 younger and 6 older controls. Several variables (biopsy size, number of explants, medium, passage procedure) were standardized. Two growth characteristics were examined quantitatively: (i) the actual in vitro replicating life span was determined by counting the number of cells plated the previous week at 500,000 cells/flask (cumulative population doublings); and (ii) the growth potential was examined by a colony size distribution assay. A difference from the age-matched controls in the growth characteristics of skin fibroblasts was only observed for two patients with and one older individual at risk for familial Alzheimer disease. The growth properties of skin fibroblast cultures from patients with sporadic Alzheimer disease or Down syndrome were not at variance with their age-matched controls. The decrease in the growth potential observed in the familial Alzheimer disease fibroblasts is however modest and needs confirmation. It is clear that the growth properties of skin fibroblasts, as examined in this study, do not provide a good marker for any form of Alzheimer disease, nor do they provide an appropriate in vitro system to study factors which may contribute to the etiopathogenesis of Alzheimer disease or Down syndrome.

Changes in calcium homeostasis during aging and Alzheimer's disease

Several observations indirectly suggest that intracellular calcium regulation may be altered by aging and Alzheimer's disease. Thus, calcium homeostasis was examined directly in skin fibroblasts from Alzheimer's patients and compared to cells from normal young and elderly controls. Alterations in both bound and free calcium were noted; cells from Alzheimer's donors have higher levels of bound calcium but lower concentrations of free intracellular calcium when compared to cells from young and normal aged donors. These changes in calcium homeostasis may be physiologically significant, since processes that require transient elevations of intracellular free calcium, such as cell spreading, decline in the Alzheimer's cells. In summary, cultured skin fibroblasts from normal aged and Alzheimer's patients demonstrate deficits in calcium homeostasis and other metabolic processes when compared to cells from young donors.

Hypothesis: microtubules, a key to Alzheimer disease

Alzheimer disease (AD) is a clinicopathologic syndrome of unknown etiology with numerous abnormalities in neuronal and nonneuronal cells. A review of the literature suggests that a common basic intracellular defect may underlie many of the reported abnormalities. We hypothesize impairment of the microtubule (MT) system as one explanation for the pathogenesis of AD. Evidence in support of the hypothesis includes the following: MTs are ubiquitous and vital cell components, unequally distributed, with the highest concentration in the brain; various abnormalities, including the key neuropathologic lesions, can be explained by impairments of the MT system; and experiments utilizing pharmacologic agents known to disrupt MTs have reproduced certain abnormalities observed in AD. The hypothesis provides a framework for systematic investigations of MTs at the cellular and molecular levels as well as the basis for in vivo diagnostic tests for AD.

Cholinesterases in the cerebrospinal fluid, plasma, and erythrocytes of patients with Alzheimer's disease

In patients with probable Alzheimer's disease and in controls, acetyl- and butyrylcholinesterase activities were studied in cerebrospinal fluid (CSF) and plasma, and acetylcholinesterase activity of erythrocytes was determined. In addition, the molecular forms of acetylcholinesterase were measured in CSF. Severely demented patients had significantly lower acetylcholinesterase (p less than 0.01) and butyrylcholinesterase (p less than 0.05) activities in CSF than the controls had, but the activities of these enzymes in plasma and erythrocytes were within the same range in both groups. Acetylcholinesterase and butyrylcholinesterase activities in the CSF of mildly demented patients did not differ from control values. The ratio of the intermediate molecular form of acetylcholinesterase to the light molecular form of the enzyme did not differ significantly between patients with Alzheimer's disease and controls. According to our results, AChE levels were lower in the CSF of severely demented patients, but both light and intermediate molecular forms were affected.

Acetylcholine synthesis in human CSF: implications for study of central cholinergic metabolism

Investigation of neurological diseases involving central cholinergic dysfunction has led to numerous studies seeking a peripheral marker of cholinergic activity in brain. The main objective of these studies was to determine whether the ACh synthesizing activity present in human CSF was due to the presence of the enzyme choline acetyltransferase (ChAT; 68 kDa). When CSF was fractioned into low and high molecular weight (Mr) components, 80% of the ACh synthesizing activity (ACh-SA) was found to be associated with the fraction less than 10 kDa. The remaining 20% was evenly distributed among fractions in the 5-30, 30-50, 50-300, and 300 kDa fractions. Although boiling destroyed all activity greater than 10 kDa, the ChAT inhibitor NVP, at concentrations equal to or greater than that required to inhibit ChAT in human cortical tissue, did not alter the ACh-SA in either fraction. Results indicate that normal human CSF does not contain ChAT and all ACh-SA in CSF reflects non-enzymatic imidazole/histidine-like catalyzed synthesis.

Endoplasmic reticulum abnormality in Alzheimer's disease: selective alteration in platelet NADH-cytochrome c reductase activity

Previous evidence suggests that the increase in platelet membrane fluidity associated with a subgroup of patients with Alzheimer's disease results from the accumulation of internal membrane. The specific activities of enzyme markers for selective cell membrane compartments were compared in platelets from subgroups of demented patients with normal or increased fluidity as well as from normal control subjects. A statistically significant change in enzyme activity was observed only for antimycin A-insensitive NADH-cytochrome reductase, a selective marker for smooth endoplasmic reticulum (SER) in platelets. This reduction was limited to the subgroup of demented patients who had increased platelet membrane fluidity, and therefore is not a nonspecific concomitant of neurodegeneration, medication exposure, or chronic illness in general. Since the platelet membrane alteration associated with Alzheimer's disease results from the inheritance of a single major locus, these results suggest that a defect in SER function may exist in brain cells as well as peripheral cells that express this genotype.

Cognitive function and platelet membrane fluidity in Alzheimer's disease

Increased platelet membrane fluidity, as reflected by a decrease in the fluorescence anisotropy of diphenylhexatriene in labeled membranes, identifies a clinically distinct subgroup of approximately 50% of patients at our center who meet NINCDS-ADRDA clinical criteria for Alzheimer's disease. In the current study, we compared the cognitive impairments of patients in this subgroup to those observed in the residual subgroup of patients with Alzheimer's disease who had normal platelet membrane fluidity. No significant differences in the number or distribution of deficits in six cognitive domains were observed between the two subgroups. However, in the subgroup with increased platelet membrane fluidity, there were significantly more patients who exhibited dissociation of deficits on tests related to left and right parietal lobe function than in the residual subgroup. Moreover, the cases with dissociation of deficits consisted almost entirely of patients with deficits on tests reflecting left parietal lobe function and no deficit on tests of right parietal lobe function.

Longitudinal study of platelet membrane fluidity in Alzheimer's disease

Increased platelet membrane fluidity identifies a prominent subgroup of patients with Alzheimer's disease who exhibit distinct clinical features. In the current longitudinal study, the stability of this membrane characteristic was determined for 15 patients with Alzheimer's disease and 10 healthy elderly controls over a 1-year follow-up period.

Cerebral degenerations producing dementia: importance of neuropathologic confirmation of clinical diagnoses

Dementia is a major public health concern with our increasing elderly population and currently affects more than three million Americans at an annual cost of $50 billion. The marked overlap in symptomatology between Alzheimer's disease and other primary parenchymal degenerations makes antemortem diagnosis based on clinical assessment tentative at best, with error rates of 25% commonly reported. Accurate diagnosis is of vital importance in order to improve our understanding of these illnesses, evaluate potential therapies, and provide appropriate genetic counseling to family members. Direct neuropathologic examination at autopsy is currently the only reliable method for assuring accurate diagnosis, and should be undertaken in all demented patients. To illustrate the importance of these principles, we present three patients who were clinically diagnosed with Alzheimer's disease, and subsequently found to have other dementing illnesses by careful postmortem neuropathologic examination.

Cerebrospinal fluid cholinesterases in aging and in dementia of the Alzheimer type

Protein concentration and acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were assayed in the cerebrospinal fluid (CSF) of 26 healthy normal subjects (20-86 years old), 27 patients with dementia of the Alzheimer type (DAT), and 10 patients with dementia of the Alzheimer type with extrapyramidal signs (EDAT). In normal subjects, there was an age-related increase in CSF protein and AChE activity and a significant correlation (p less than 0.001) between CSF protein and BChE activity. In the DAT and EDAT groups, CSF AChE activities (mean +/- SD = 17.5 +/- 3.6 and 15.3 +/- 4.4 nmol/min/ml, respectively) were significantly lower (p less than 0.05) than in 13 age-matched control subjects (21.5 +/- 5.6 nmol/min/ml). In contrast, neither CSF protein concentration, BChE activity, nor the ratio of AChE/BChE differed significantly between groups. In patients with DAT, CSF AChE activity was significantly lower (p less than 0.05) in subjects with an early onset compared to those with a late onset (16.4 +/- 3.4 and 19.7 +/- 2.8 nmol/min/ml, respectively), and activity in the latter group did not differ significantly from control values. CSF AChE activity was not related to dementia severity and did not change significantly over an 18-month period. Although these results confirm a cholinergic deficit in patients with DAT, the considerable overlap of CSF AChE activity between groups and the nonsignificant correlation between AChE activity and dementia severity limit the usefulness of CSF AChE as a diagnostic marker of this disorder.

Monoamine metabolite concentrations and cholinesterase activities in cerebrospinal fluid of progressive dementia patients: relation to clinical parameters

Forty-five well clinically characterized patients with progressive dementia were investigated for lumbar cerebrospinal fluid (CSF) monoamine metabolites and cholinesterase activities. Monoamine concentrations were determined by reverse phase liquid chromatography with electrochemical detection and the cholinergic enzymes were measured photometrically. Firstly, all clinical and CSF parameters were studied in statistical cluster analyses to detect groups of variables which demonstrated a high correlation with respect to each other. The CSF transmitter markers were then used in multiple regression models to explain the variance of clinical variables as chosen from the cluster analyses. The degree of dementia, as assessed by global deterioration score (GDS) and activity in daily life (ADL) status, as well as the Alzheimer-related symptoms dyspraxia and dysphasia, were associated with low AChE activities in CSF. A presumed subgroup of dementia patients clinically characterized by asymmetry of neurological signs, increased unilateral tonus, stepwise progression, and high Hachinski score, showed low HVA concentrations in CSF. These data suggest a coupling of clinical/neurological parameters to different CSF transmitter profils and, thus, that CSF biochemical parameters are of use as antemortem markers in dementia conditions.

Cognitive and brain imaging measures of Alzheimer's disease

Diagnosis of Alzheimer's disease (AD) during life relies upon clinical and neurobehavioral symptoms but is presumptive without microscopic verification of neuropathology. Studies in this review observed considerable heterogeneity in AD symptoms and did not agree on how to detect the earliest symptoms. Problems exist in diagnosis. Differences in symptoms and diagnosis result from how AD is defined neurobehaviorally and on the model used for description. The studies reviewed have been considered under three basic models: A severity (staging) model; a heterogeneity (subtyping) model; and an information processing model. Differences in model intent have resulted in differences in disease description. Brain imaging measures have not invalidated models but add the neural substrate needed to examine correlation of measures within each model.

Family study of platelet membrane fluidity in Alzheimer's disease

The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene in labeled platelet membranes, an index of membrane fluidity, identifies a prominent subgroup of patients with Alzheimer's disease who manifest distinct clinical features. In a family study, the prevalence of this platelet membrane abnormality was 3.2 to 11.5 times higher in asymptomatic, first-degree relatives of probands with Alzheimer's disease than in neurologically healthy control subjects chosen without regard to family history of dementia. The pattern of the platelet membrane abnormality within families was consistent with that of a fully penetrant autosomal dominant trait. Thus, this abnormality of platelet membranes may be an inherited factor that is related to the development of Alzheimer's disease.

RS 86 in the treatment of Alzheimer's disease: cognitive and biological effects

Twelve patients who met Research Diagnostic Criteria for Alzheimer's disease (AD) completed a double-blind crossover study comparing oral RS 86, a long-acting and specific muscarinic agonist, with placebo. Cognitive and noncognitive effects were assessed with the Alzheimer's Disease Assessment Scale (ADAS). RS 86 was found to improve ADAS test scores consistently (both cognitive and noncognitive subscales) in seven patients, with a clinically obvious improvement in only two patients. RS 86 produced a significant increase in peak nocturnal cortisol levels, and this increase correlated with improvement on ADAS testing. Similarly, there was a 38% increase in amplitude of the P300 evoked potential with RS 86. The biological findings suggest that RS 86 was effective only to the extent that it enhanced central cholinergic activity.

Platelet membrane fluidity identifies a clinical subtype of Alzheimer's disease

1. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) in labeled platelet membranes, an index of membrane fluidity, identifies a prominent subgroup (approx. 50%) of patients with Alzheimer's disease who manifest distinct clinical features. 2. We review an integrated series of studies that explore both the clinical significance of this finding and the biological basis for the platelet membrane alteration.