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Biomedical subjects

K L Davis

Publications and source records attributed to K L Davis.

At least 235 records · Page 13Linked to original sources
PubMed1987

Cysteamine-induced depletion of central somatostatin-like immunoactivity: effects on behavior, learning, memory and brain neurochemistry.

The effects of a wide range of doses of systemically administered cysteamine were studied on locomotor behavior, passive avoidance memory, cortical and cerebrospinal fluid somatostatin-like immunoactivity and cortical levels of dopamine and norepinephrine. High doses of cysteamine (200 and 250 mg/kg s.c.) led to sustained locomotor activation. Doses of 150 mg/kg and above resulted in head and neck tremor and increased defecation. When cysteamine was administered immediately following the acquisition of a passive avoidance response, doses of 50 mg/kg and above resulted in significant attenuation of passive avoidance retention test performance. Cysteamine in doses of 50 mg/kg and above depleted cortical somatostatin-like immunoactivity by approximately 50%. The depletion of cortical somatostatin-like immunoactivity was accompanied by a rapid rise in somatostatin-like immunoactivity in cerebrospinal fluid. In addition to the depletion of somatostatin-like immunoactivity, high doses of cysteamine (150 mg/kg and above) produced changes in cortical levels of norepinephrine and dopamine, reminiscent of dopamine-beta-hydroxylase inhibition. The results of this series of experiments suggest that somatostatin, in addition to its effects on hormonal regulation, may play an important role in behavior and passive avoidance learning and memory. It is possible that the amnesia produced by cysteamine may have been due to the release of somatostatin into CSF from tissue stores, rather than somatostatin depletion per se. It is also possible that the catecholaminergic effects of high doses of cysteamine contribute to the behavioral deficits observed.

Animals↗
PubMed1987

Alzheimer's disease. Morbid risk among first-degree relatives approximates 50% by 90 years of age.

The morbid risk of Alzheimer's disease was studied in first-degree relatives of 50 patients who met contemporary clinical research diagnostic criteria and 45 matched controls. Relatives of patients showed a 46% cumulative incidence of probable Alzheimer's disease by 86 years of age. The risk, which was four times the control value, is consistent with other recent reports using similar, modern methods. Although not conclusive, the data suggest the operation of a relatively common, dominant autosomal gene for Alzheimer's disease, the expression of which is delayed until late old age but is largely complete by 90 years of age.

Actuarial Analysis↗
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

Platelet [3H]imipramine binding in psychiatric disorders.

The Bmax and Kd values for [3H]imipramine binding were measured in platelets from drug-free normal controls and schizophrenic and depressive patients. No differences among groups were found. Exacerbated and remitted patients with either schizophrenia or depression did not differ in platelet [3H]imipramine binding parameters. No correlations were observed between platelet [3H]imipramine binding parameters and measures of symptom severity among actively ill patients with either schizophrenia or depression.

Adult↗
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

Influence of age and relative weight on cortisol suppression in normal subjects.

The authors examined the effects of certain nonpsychiatric variables on dexamethasone suppression test (DST) results. Sixty physically healthy, nondepressed, nondemented adults participated in a standard outpatient 1-mg DST. Postdexamethasone plasma cortisol concentrations were higher in older subjects and were lower in more obese subjects. The authors conclude that age and relative weight influence cortisol suppression in healthy subjects.

Adult↗
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↗
PubMed1987

Breed differences in uterine and ovarian measurements in gestating swine.

Ovulation rate, ovary weight, corpora lutea weight and uterine length were measured at 10 or 35 d of gestation in Duroc (199) and Yorkshire gilts (114). Embryos were counted at d 35. Yorkshires had significantly more corpora lutea than Durocs (13.6 vs 12.3 at d 10; 13.9 vs 12.4 at d 35). At d 10 breeds did not differ in uterine length, but by d 35 Duroc uteri were longer (P less than .01) than Yorkshire uteri (411 vs 375 cm) despite having fewer (P greater than .05) embryos (9.9 vs 10.5). Ovary weight did not differ between breeds at 10 or 35 d. Homogeneity analyses showed that the correlation matrices were significantly different between breeds at d 35 but not at d 10. In Durocs, high positive correlations existed between total embryo number and corpora lutea number (.57), ovary weight (.53) and corpora lutea weight (.25), whereas corresponding correlations were small in Yorkshires (.21, -.02 and -.03, respectively). In Yorkshires, strong negative correlations existed between total embryo survival and corpora lutea number (-.55), ovary weight (-.30) and corpora lutea weight (-.55), but in Durocs corresponding correlations were small (-.12, .14 and -.10, respectively). These results suggest that animal scientists should consider breed differences in levels of performance and its relationships among traits when designing or interpreting experiments.

Animals↗