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Biomedical subjects

G Schwartz

Publications and source records attributed to G Schwartz.

At least 181 records · Page 10Linked to original sources
PubMed1981

Quantitation of changes in cell surface determinants during skeletal muscle cell differentiation using monospecific antibody.

The differentiation of skeletal muscle is characterized by recognition, alignment, and subsequent fusion of myoblast cells at their surfaces to form large, multinucleated myotubes. Monoclonal antibodies were used to investigate antigenic changes in the cell surface membrane specific for various stages of myogenesis. Chick embryonic skeletal muscle cells were cultured in vitro to the desired stage of differentiation and then injected into BALB/c mice. Spleen cells from the immunized mice were hybridized with NS-1 or P3 8653 mouse myeloma cells. Hybrid cell clones were selected in HAT medium and screened using an indirect radioimmunoassay for the production of monoclonal antibodies specific to myogenic cell surfaces. Target cells for the radioimmunoassay included three stages of myogenesis (myoblasts, midfusion, myoblasts, and myotubes) and chick lung cells as a control for polymorphic antigens. Sixty-one clones were obtained which produced antibodies specific for myogenic cells. Thirty-five of these clones were generated from mice immunized with midfusion myoblast stages of myogenesis and 26 were obtained from mice immunized with the later myotube stage of myogenesis. Quantitative measurements by RIA of myogenic determinants per cell surface area on each target cell type revealed that most of the determinants decrease during myogenesis when midfusion myoblasts are used as the immunogen. When myotube stages are used as the immunogen, more determinants increase with cell differentiation. Therefore, the most common pattern of determinant change is for them to be present at all stages of myogenesis but to vary quantitatively through development. There are determinants unique to each stage of myogenesis and marked quantitative differences within a cell stage for each determinant.

Animals↗
PubMed1981

Effect of choline on central dopaminergic function in normal subjects.

Oral administration of choline (10 g) had no effect on basal serum growth hormone or prolactin concentrations in normal subjects (N = 5). Choline significantly enhanced the increase in growth hormone secretion induced by apomorphine HCl (0.5 mg s.c.). These data suggest that cholinergic mechanisms may enhance hypothalamic-pituitary dopaminergic function in man in contrast to their inhibitory effect on dopaminergic function in the basal ganglia.

Adult↗
PubMed1981

Effect of sleep deprivation on dopamine receptor function in normal subjects.

Twenty-four hours sleep deprivation significantly decreased the growth hormone response to the dopamine receptor agonist, apomorphine HCl, in five normal men (0.5 mg s.c.) and one woman (0.75 mg s.c.) but had no effect on basal or post-apomorphine prolactin concentrations. These results suggest that sleep deprivation decreases the sensitivity of certain central dopamine receptors. The relevance of this finding to the antidepressant effect of sleep deprivation is unclear.

Adult↗
PubMed1979

Myocardial infarction in the differential diagnosis of dementias in the elderly.

The incidence of cerebral lesions in relation to myocardial infarction (MI) was evaluated on the basis of data obtained from medical records and autopsy reports on 269 psychogeriatric patients, in a 13-year retrospective study. Among 84 demented patients with MI, brain infarcts and hemorrhages were found in 42 percent, and Alzheimer's disease in 17 percent; (combination in 8 percent). In contrast, among 70 demented patients without MI, brain infarcts and hemorrhages were found in 11 percent, and Alzheimer's disease in 43 percent; (combination in 6 percent). Therefore, when it is difficult to differentiate senile dementia (Alzheimer's disease) from dementia due to cerebrovascular impairment, data on the presence or absence of myocardial infarction may prove useful.

Aged↗
PubMed1979

Plasma magnesium in chronic schizophrenia. A preliminary report.

A group of 36 subjects, 20 chronic schizophrenic patients and 16 nonpsychotic mentally retarded patients were chosen at random from the chronic care wards of the Douglas Hospital to assess levels of magnesium, calcium and phosphorus. No significant differences were found between the two groups in calcium and phosphorus. However, the magnesium level was significantly lower (p less than 0.01) in the schizophrenic group than in the mentally retarded group. This difference reached a level of 0.001 significance when chronic female schizophrenic patients were compared to the female mentally retarded group. Hospitalization, diet and medication were excluded as possible etiological factors.

Adult↗
PubMed1979

Quantitation of lymphocyte response to PHA by flow cytofluorometry. III. Heterogeneity of induction period.

Early events in phytohaemagglutinin (PHA) stimulation of mouse splenocytes have been quantitated by using flow cytometry and supravital staining with acridine orange (AO). Increasing percentages of single cells with increased metachromatic (red) AO staining were demonstrated in cultures stimulated by PHA for up to 24 hr. These differences in staining could be eliminated by fixation with 1:1 ethanol/acetone before staining. Stimulated cells showed an increase in nonspecific esterase activity as measured by flow cytometry after supravital staining with fluorescein diacetate (FDA). The data reported show a heterogeneity in the per cell response of mouse splenocytes to PHA. The relationship between these data and the mechanism of mitogen stimulation is discussed.

Acridine Orange↗
PubMed1978

Synthesis of des(tetrapeptide B(1-4)) and des(pentapeptide B(1-5)) human insulins. Two biologically active analogues.

Two analogues of human insulin, des(tetrapeptide B(1-4))-and des (pentapeptide B(1-5))-insulin, which differ from the parent molecule in that the N-terminal tetrapeptide and pentapeptide sequences, respectively, have been eliminated, have been synthesized. The des(tetrapeptide B(1-4))-insulin shows potencies of 13 IU/mg by the mouse convulsion assay method and 7.6 IU/mg by the radioimmunoassay method. The des(pentapeptide B(1-5))-insulin possesses a potency of 1.2 IU/mg when assayed by the glucose-oxidation method in isolated fat cells and 3.7 IU/mg by the radioimmunoassay technique. The natural hormone has a potency of 23--25 IU/mg by both assay methods.

Adipose Tissue↗
PubMed1978

Electroencephalograms and autopsy findings in geropsychiatry.

The relationships between post-mortem findings and electroencephalographic tests obtained during the 12 mo before death were investigated for 100 psychogeriatric subjects. The results, which due to methodological limitations are only tentative, suggest a fairly close correlation between the two sets of data, which can, however, be obscured by a number of factors, notably the presence of severe physical illness (cerebral and systemic, including severe drug effects) of a nonstructural type at the time of the EEG. In their absence, diffuse EEG slowing strongly suggests senile-Alzheimer's brain disease (it is associated with plaque and tangle formation, ventricular dilatation, and cortical atrophy); and intermittent lateralized slow waves strongly suggest hemodynamic problems due to sclerosis of cerebral arteries. Brain lesions produce EEG changes mostly if large and close to the cortex. If the necessary precuations in EEG interpretation are taken (i.e., mainly consideration of present clinical state), the EEG is diagnostically quite helpful in this group of subjects.

Age Factors↗
PubMed1978

Bromocriptine: effect on serum prolactin and growth hormone in psychogeriatric hospital patients.

Serum prolactin (PRL) and human growth hormone (HGH) were assessed before, and three hours after oral administration of 2.5 mg of bromocriptine in 39 hospitalized geriatric patients with organic brain syndrome. Serum PRL concentrations decreased significantly irrespective of initial values (also in the 7 geriatric control subjects), but HGH levels were low in all patients and did not change during the three hours after administration of bromocriptine. Closer scrutiny of the HGH responses to bromocriptine in 5 patients and 5 controls showed that the serum HGH response was more variable among the patients than among the controls. The findings are discussed in relation to neuroendocrine changes associated with aging, institutional living, and mental disease.

Aged↗
PubMed1978

Peptidase-deficient mutants of Escherichia coli.

Mutant derivatives of Escherichia coli K-12 deficient in several peptidases have been obtained. Mutants lacking a naphthylamidase, peptidase N, were isolated by screening for colonies unable to hydrolyze L-alanine beta-naphthylamide. Other mutants were isolated using positive selections for resistance to valine peptides. Mutants lacking peptidase A, a broad-specificity aminopeptidase, were obtained by selection for resistance to L-valyl-L-leucine amide. Mutants lacking a dipeptidase, peptidase D, were isolated from a pepN pepA strain by selection for resistance to L-valyl-glycine. Starting with a pepN pepA pepD strain, selection for resistance to L-valyl-glycyl-glycine or several other valine peptides produced mutants deficient in another aminopeptidase, peptidase B. Mutants resistant to L-valyl-L-proline lack peptidase Q, an activity capable of rapid hydrolysis of X-proline dipeptides. Using these selection procedures, a strain (CM89) lacking five different peptidases has been isolated. Although still sensitive to valine, this strain is resistant to a variety of valine di- and tripeptides. The ability of this strain to use peptides as sources of amino acids is much more restricted than that of wild-type E. coli strains. Strains containing only one of the five peptidases missing in CM89 have been constructed by transduction. The peptide utilization profiles of these strains show that each of the five peptidases can function during growth in the catabolism of peptides.

Alleles↗