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Biomedical subjects

M Davidson

Publications and source records attributed to M Davidson.

At least 307 records · Page 17Linked to original sources
PubMed1988

Endocrine changes in Alzheimer's disease.

In conclusion, at present, no consistent endocrine abnormalities can be detected in patients suffering from Alzheimer's disease. However, assessment of neuroendocrine function might help identify subpopulations of patients with particular neurotransmission abnormalities who are likely to benefit from a specific pharmacologic strategy. For example, patients in whom cholinomimetic drugs produce the greatest elevation in plasma cortisol concentration appear to derive the most symptomatic benefit from these drugs.

Alzheimer Disease↗
PubMed1988

Endocrine changes in Alzheimer's disease.

In conclusion, at present, no consistent endocrine abnormalities can be detected in patients suffering from Alzheimer's disease. However, assessment of neuroendocrine function might help identify subpopulations of patients with particular neurotransmission abnormalities who are likely to benefit from a specific pharmacologic strategy. For example, patients in whom cholinomimetic drugs produce the greatest elevation in plasma cortisol concentration appear to derive the most symptomatic benefit from these drugs.

Alzheimer Disease↗
PubMed1987

Effects of acetaldehyde on polymerization of microtubule proteins.

The in vitro effects of ethanol and acetaldehyde on polymerization of calf brain microtubular proteins (MTP) were examined. While ethanol up to 100 mM had no effect on the polymerization of MTP, acetaldehyde above 0.5 mM had an inhibitory effect. This effect was not dependent on the presence of microtubule-associated proteins (MAPs), since acetaldehyde had a similar effect on the polymerization of highly purified tubulin. Electron microscopy revealed that the number and the length of microtubules at equilibrium was reduced by the presence of acetaldehyde. Acetaldehyde raised the critical concentration for tubulin assembly and caused greater inhibition at lower tubulin concentrations. Acetaldehyde augmented the depolymerizing effects of Ca2+ on preassembled microtubules. In addition, acetaldehyde itself caused depolymerization of microtubules but only in the absence of MAPs. Long-term (19.5 h) incubation of MTP with acetaldehyde led to significant loss of polymerization ability which could not be reversed by removal of acetaldehyde. This loss of activity was apparently independent of the observed formation of reducible adducts between acetaldehyde and MTP.

Acetaldehyde↗
PubMed1987

Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in mouse uterine epithelial cells.

The regulation of 3-hydroxy-3-methylglutaryl-CoA reductase was studied in mouse uterine epithelium. The enzyme was rapidly inactivated during incubation with ATP/Mg2+ in vitro, and could be re-activated by incubation with partially purified rat liver phosphoprotein phosphatase. Enzyme activity was rapidly inhibited by mevalonate injection in vivo to approx. 30% of control. The percentage of total enzyme active in vivo was measured by inclusion of NaF in the isolation buffers. The percentage of enzyme active in vivo 18 h after stimulation by oestrogens remained at approx. 25% after inhibition of activity by mevalonate injection, cholesterol feeding or progesterone pretreatment. However, 9 h after oestrogen stimulation, cholesterol feeding inhibited enzyme activity to 57% of control, 94% of which was in the active form. We conclude that, although all components for a reversible phosphorylative regulation of 3-hydroxy-3-methylglutaryl-CoA reductase activity are present in uterine epithelial cells, a role in the rapid changes in epithelial enzyme activity has not been demonstrated.

Animals↗
PubMed1987

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.

Aged↗
PubMed1987

Control of exogenous factors affecting plasma homovanillic acid concentration.

Measurements of plasma homovanillic acid (pHVA) concentrations appear to be a valid research strategy in psychiatric disorders in which a central dopamine (DA) abnormality has been implicated. This study provides guidance about the control of some of the exogenous factors affecting pHVA concentrations. Fasting for 14 hours eliminates the dietary effects on pHVA in healthy human subjects. Changing position, walking for 30 minutes, or smoking two cigarettes has no effect on pHVA concentrations.

Adult↗
PubMed1987

Effects of debrisoquin and haloperidol on plasma homovanillic acid concentration in schizophrenic patients.

Plasma levels of the dopamine metabolite homovanillic acid (pHVA) may potentially reflect upon central dopamine activity. This study examines the effects of debrisoquin, haloperidol, and the two drugs combined on pHVA concentrations of schizophrenic patients. Debrisoquin is a drug that suppresses the peripheral formation of homovanillic acid without affecting the central formation. Acute haloperidol administration consistently increased pHVA concentrations in patients pretreated or not pretreated with debrisoquin, suggesting that this increment reflects haloperidol's central and not peripheral effects.

Adult↗
PubMed1987

Familial schizophrenia and treatment response.

Thirty-nine patients with chronic schizophrenia for whom hospitalization was clinically indicated received haloperidol for 4 to 6 weeks in a standardized dose schedule. Responders were compared with nonresponders for family history, baseline symptom factors, and ventricle-brain ratio (VBR). The lifetime risk for schizophrenia spectrum disorders was higher among first-degree relatives of nonresponders than among first-degree relatives of responders. Treatment responders had higher baseline scores on the factors of activation and hostile-suspiciousness, but the groups did not differ in any other baseline symptom factor or in VBR. The authors suggest that there is an association between failure to respond to drugs and genetic loading for schizophrenia spectrum disorders.

Adolescent↗
PubMed1987

Clinical correlates of platelet prostaglandin receptor subsensitivity in schizophrenia.

A diminished cAMP response to prostaglandin E1 (PGE1) in platelets from schizophrenic patients has been demonstrated previously. The authors report that among 35 actively psychotic male schizophrenic patients, the platelet cAMP response to PGE1 was negatively correlated with global symptom severity and with several indexes of positive symptom severity but not with negative symptom severity. If this subsensitivity of platelet PGE receptors extends to brain PGE receptors, schizophrenic patients may have an impairment in the ability of endogenous PGEs to inhibit dopaminergic transmission. Such impairment could have a permissive effect on the production of psychotic symptoms during exacerbations in schizophrenic patients.

Adult↗
PubMed1987

Induction of depression with oxotremorine in patients with Alzheimer's disease.

Cholinergic neurotransmission has long been implicated in the development of depression. In this study seven patients with Alzheimer's disease were given oral oxotremorine, a long-acting cholinergic agonist, to assess the drug's effects on cognitive function. There were unexpected depressive reactions in five of the seven patients; three patients dropped out of the study because of the side effects. Cardiovascular effects of the drug were negligible, but its effect on memory and cognition remains unknown because of the small number of subjects who completed the study.

Aged↗
PubMed1987

Characteristics of very poor outcome schizophrenia.

The authors compared 21 "Kraepelinian" schizophrenic patients who had been ill and dependent on others for the past 5 years with 76 chronic schizophrenic patients in remission or with exacerbations requiring hospitalization. The Kraepelinian patients met the criteria for schizophrenia by more diagnostic systems than the exacerbated patients, were less responsive to haloperidol, had more severe negative symptoms, and had similarly severe positive symptoms. They had cerebral ventricles that were more asymmetrical and a greater family history of schizophrenia spectrum disorders than the other chronic patients. These data suggest that patients with 5 years of illness and complete dependency on others may represent a subgroup of schizophrenia.

Adult↗
PubMed1987

L-dopa challenge and relapse in schizophrenia.

Neuroleptic administration has been shown to be superior to placebo in prolonging schizophrenic remission. However, individual patients are able to maintain long periods of remission in the absence of neuroleptic treatment, while others relapse soon after neuroleptic withdrawal. This study attempted to predict time to relapse in 28 schizophrenic patients withdrawn from neuroleptics and challenged with L-dopa for 7 days, then followed until relapse. Time to relapse correlated significantly with L-dopa-induced increase in BPRS score (p = .006). Five of six patients who responded to L-dopa relapsed within 4 weeks after L-dopa administration, while only four of 22 who did not respond relapsed in a comparable period.

Adult↗