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Biomedical subjects

J M Davis

Publications and source records attributed to J M Davis.

At least 451 records · Page 25Linked to original sources
PubMed1987

Biogenic amine and metabolite levels in depressed patients with high versus normal hypothalamic-pituitary-adrenocortical activity.

The activity of the hypothalamic-pituitary-adrenocortical (HPA) axis is often high in depressive illness. The authors studied 132 depressed patients and 80 healthy control subjects. They report a significant direct association between HPA axis activity and adrenomedullary epinephrine secretion in depressed patients. They also found that depressed patients with high HPA activity tend to have lower CSF levels of 5-hydroxyindoleacetic acid, a serotonin metabolite, and modestly lower levels of 3-methoxy-4-hydroxyphenylglycol, a metabolite of epinephrine and norepinephrine, than patients with normal HPA activity. These findings provide potentially important leads for understanding interactions of biogenic amine systems with HPA axis function.

Biogenic Amines↗
PubMed1987

The site of action of nitrendipine in the rat kidney.

Ample evidence suggests that Ca2+ antagonists like nitrendipine are capable of inducing mild diuresis and natriuresis in states predisposing to natriuresis, although there is disagreement on common possible sites or mechanisms of action. To clarify this situation, clearance, micropuncture, and microperfusion studies were undertaken on rats to establish whether nitrendipine inhibits sodium and fluid reabsorption in strict hydropenia, and if so, in which nephron segments this occurs. The clearance studies failed to show any specific effect on glomerular filtration rate, urine flow, or sodium excretion; mean arterial blood pressure was, however, dose-dependently depressed. Single nephron filtration rate, measured in the distal tubule, was also not altered, but fractional salt and water reabsorption up to that site were modestly reduced. Since microperfusion studies failed to show any inhibition of thick ascending limb transport, this implies a proximal inhibitory action, a conclusion confirmed by proximal microperfusion studies. Thus, in strict hydropenia, nitrendipine inhibits proximal salt and water reabsorption, but the increased distal load is completely compensated by distal tubular and collecting duct mechanisms such that urinary electrolyte excretion is unaltered.

Animals↗
PubMed1987

Low residue nutritional supplementation as an adjunct to mechanical preparation for surgical treatment of the colon.

The mechanical and nutritional efficacy of a low residue nutritionally complete liquid diet was evaluated as an adjunct for colonic preparation in patients undergoing large intestinal operations. The complete liquid diet was identical to more traditional clear liquid diets in terms of cleanliness of the intestine and general profile of bacterial flora. This complete diet was well accepted by patients and was superior in its provision of energy, protein, vitamins, minerals and nitrogen. The use of this low residue supplemental diet was associated with a statistically earlier return of intestinal function and a trend toward shorter length of hospitalization. The results of this study indicate that low residue nutritionally complete liquid diets not only offer comparable mechanical cleanliness but also outstanding nutritional advantages not obtained with traditional preparatory diets.

Adult↗
PubMed1987

Response of psychotic and nonpsychotic depressed patients to tricyclic antidepressants.

The response to tricyclic antidepressants (TCAs) is studied in 75 of 121 depressed patients classified as psychotic or nonpsychotic subtypes by Research Diagnostic Criteria. Response was assessed by a clinical global evaluation scale. Of the 75 patients treated with TCAs, 40 (68%) of the nonpsychotic subtype responded in contrast to only 4 (25%) of the psychotic subtype. Adjusting for the effects of chronicity, sex, age, incapacity, agitation, retardation, endogenicity, and the unipolar-bipolar distinction as covariates, it was found that these variables failed to alter the differential response rate of the psychotic and nonpsychotic depressed groups. A literature review of 1054 patients revealed that 67% of the nonpsychotic depressed patients responded to TCAs compared with only 35% of the psychotic depressed patients.

Antidepressive Agents, Tricyclic↗
PubMed1987

Pretreatment dexamethasone suppression test as a predictor of response to phenelzine.

Twenty inpatients who met Research Diagnostic Criteria and DSM-III criteria for depression underwent a 2-week washout period before the administration of a pretreatment dexamethasone suppression test (DST); the patients then received the monoamine oxidase inhibitor (MAOI) phenelzine. The mean MAO inhibition level achieved during treatment was greater than 80%. On the basis of clinical global evaluation and changes in Hamilton Rating Scale for Depression scores, 7 of the 9 baseline DST suppressors were classified as responders, 1 as a partial responder, and 1 as a nonresponder; of the 11 baseline DST nonsuppressors, 3 were responders, 1 a partial responder, and 7 nonresponders. The Mann-Whitney U test yielded p less than .02, indicating that an abnormally high pretreatment level of cortisol in response to the DST appeared to be predictive of nonresponse to phenelzine.

Adult↗
PubMed1986

Structure of unfolded and refolded recombinant derived [Ala125]interleukin 2.

Naturally occurring interleukin 2 (IL-2) contains an odd number (three) of cysteinyl residues and thus is susceptible to the formation of a variety of intramolecular and intermolecular disulfide bonds. The cysteine at residue 125 has been replaced with an alanine residue by site-directed mutagenesis, and hence, this analogue can form only one intrachain disulfide bond. When expressed at high levels in Escherichia coli, this recombinant DNA derived IL-2 analogue is insoluble, reduced, and inactive. The protein was solubilized by denaturants and, after purification, was oxidized to form an intramolecular disulfide bond. Circular dichroism (CD) has been used to investigate the effects of various denaturants on the unfolding-refolding process of the purified, oxidized protein. A similar conformation is obtained when [Ala125]interleukin 2 [IL-2(Ala-125)] is refolded from 6 M guanidine hydrochloride, 8 M urea, or 5% acetic acid. The resultant protein, refolded from these denaturants, is monomeric and has activity comparable to or greater than that reported for naturally derived IL-2. In addition to this form, aggregates, as evidenced from gel filtration, are obtained. The specific activities of these are greatly reduced, and CD spectra indicated that they have much less helical content than the monomeric form of the protein. CD spectra also showed that the tertiary structure of IL-2(Ala-125) is entirely different in the presence of sodium dodecyl sulfate (SDS) from that of the monomeric form in the absence of SDS.

Acetates↗
PubMed1986

Cerebrospinal fluid amine metabolites. Relationships with behavioral measurements in depressed, manic, and healthy control subjects.

We studied 99 hospitalized depressed, 14 manic, and 61 healthy control subjects and evaluated relationships during a drug-free baseline period between behavioral measures (postulated to be associated with brain norepinephrine, dopamine, and serotonin function) and metabolites of these neurotransmitters sampled from lumbar cerebrospinal fluid (CSF): 3-methoxy-4-hydroxyphenylglycol (MHPG), homovanillic acid, and 5-hydroxyindoleacetic acid. Depressed subjects with increased anxiety, agitation, somatization, and sleep disturbance were found to have significantly elevated concentrations of CSF MHPG; this relationship was not found in the healthy controls. A correlation between CSF MHPG level and an anxiety/agitation dimension measured in all subjects was statistically significant but explained a modest portion of the total variance. No consistent relationships were found between CSF MHPG and depression/retardation, hostility/interpersonal sensitivity, and global severity, nor did any of these measures correlate significantly with the levels of the other monoamine metabolites, although some trends were found. Other factors did not account for the relationships between CSF MHPG and some behavioral measures, including diagnostic subgroup, motor movement, age, sex, and premenopausal or postmenopausal status in women. Suggested relationships among drug treatment modality, eventual treatment outcome, behavioral and mood state at baseline, and these metabolite levels will require further analyses.

Bipolar Disorder↗
PubMed1986

Maintenance of induced muscle tension, stimulus generalization performance, and schizophrenia.

Hand-dynamometer induced muscle tension was manipulated in the context of an experimental paradigm that included tests of discrimination and generalization with rigorously defined schizophrenic and affective patients, as well as schizotypic and normal controls (total N = 44). The experiment was designed to test predictions that derive from Broen and Storms' (1967) learning/motivational analysis of schizophrenic performance deficits. The results failed to support the theoretical predictions, but did reveal that the ability to maintain induced muscle tension within prescribed limits discriminated reliably between the groups (p less than or equal to .03) and that this discriminability increased with increasing tension demands (p less than or equal to .001). The data are discussed in terms of possible relations to basic sensory/motor (i.e., neuromuscular and/or proprioceptive) mechanisms as well as to more central psychological (i.e., attentional/cognitive) mechanisms, and directions for future research are outlined.

Adult↗
PubMed1986

The in vitro cytotoxicity of asbestos fibers: I. P388D1 cells.

In this study, the cytotoxicity of 13 fibrous samples of known fiber number and dimensions has been established in P388D1 cells. The cells were exposed in vitro to dust concentrations of 10 or 50 micrograms/ml and, after incubation for 24 or 48 hours, any changes in cellular viability, lactate dehydrogenase, and glucosaminidase levels were determined. In general, there was a close association between the reduction in cellular viability and the loss of intracellular enzymes induced by each dust, the chrysotile asbestos samples proving more cytotoxic than the amphiboles. The cytotoxicity of the fibrous dusts was shown to be related to the number of fibers greater than 8 micron in length in the samples.

Animals↗
PubMed1986

Dimensions of the Group Environment Scale.

Student teachers in yearlong mental health consultation groups completed Moos's Group Environment Scale (GES) and three semantic differential ratings of their satisfaction with the group experience. Factor analysis of the GES yielded four dimensions, the first two corresponding to Moos's hypothesized dimensions of Relationship and System Maintenance/System Change. Intercorrelations of factor composite scores with the differential ratings provided concurrent validity evidence for the factored dimensions. Results were interpreted as supporting a multidimensional rather than unidimensional structure for the GES.

Adult↗