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Biomedical subjects

M S Davis

Publications and source records attributed to M S Davis.

At least 55 records · Page 3Linked to original sources
PubMed1987

Primary structure of insulin and glucagon from the flounder (Platichthys flesus).

Insulin and glucagon have been isolated from the Brockmann bodies of the flounder, a teleostean fish, and their primary structures established by automated Edman degradation. The A-chain of flounder insulin shows strong homology to the A-chains from the coho salmon (Oncorhynchus kisutch; 100%) and the anglerfish (Lophius americanus; 95%) but homologies in the B-chain region are weaker (salmon 79%, anglerfish 83%). Flounder insulin B-chain contains the novel sequence Val-Val-Pro-Pro at the NH2 terminus and the highly conserved seryl residue at position 10 (B 9 in mammals) is replaced by an alanyl residue. Flounder glucagon is identical to anglerfish glucagon II but shows four amino acid substitutions compared with salmon glucagon.

Amino Acid Sequence↗
PubMed1987

Predictive factors in repeated suicide attempts by adolescents.

A significant number of adolescents treated for attempted suicide have made previous attempts and will make subsequent attempts. These youths have a high risk of actually committing suicide. To find predictive factors of suicide risk, the authors compared 43 adolescent patients who had attempted suicide once with 38 who reported multiple attempts. The repeaters were less successful in school, displayed more hostility, reported more dysphoria, and had undergone more long-term stress. The authors believe assessing suicide risk requires evaluating the repeater's internal state of rage and dysphoria; they recommend that future studies look closely at these internal states as well as at external factors.

Achievement↗
PubMed1986

Mode of adrenergic and peptidergic inhibition of ion transport in flounder gill.

The mechanisms of inhibition of branchial ion transport by epinephrine and somatostatin were investigated in the isolated perfused gill preparation of seawater-adapted flounder Platichthys flesus. The electrogenic transepithelial potential recorded in gills perfused and bathed with identical salines was stimulated by glucagon, forskolin, or a cyclic adenosine 5' monophosphate (AMP) derivative, each administered at a concentration identified in preliminary experiments as being submaximally effective. The subsequent abilities of epinephrine and somatostatin to inhibit the stimulated potential were found to be dependent on the site of action of the stimulatory agent with respect to the formation of cyclic AMP. Thus the maximal adrenergic or peptidergic inhibition of the potential stimulated by exogenous cyclic AMP was significantly reduced compared with the maximal inhibition of the potential stimulated by either forskolin or glucagon. The data indicate dual modes of action by which epinephrine and somatostatin achieve maximal inhibition of branchial ion transport; a cyclic AMP-independent mechanism that is effective in the presence of cyclic AMP and an additional mechanism to inhibit cyclic AMP synthesis.

Animals↗
PubMed1985

Pancreatic peptides regulate Cl- secretion in the marine teleost gill.

Hormonal regulation of the ionoregulatory function of the branchial epithelium in marine teleosts has been investigated using an isolated gill preparation of the seawater-adapted flounder Platichthys flesus. Agents which are assumed to elevate the effective intracellular concentration of cyclic AMP caused a stimulation of Cl- secretion as determined by measurement of the transepithelial electrical potential difference in the isolated gill. The pancreatic endocrine glucagon may act as an endogenous regulator of ion excretion in the gill as this peptide stimulated the transepithelial potential. Another islet peptide, somatostatin, inhibited branchial electrogenic ion transport. Attempts to investigate the mode of action of these peptides by measuring cyclic AMP levels in isolated gills were unsuccessful, since it appears that the pool of cyclic nucleotide which specifies the epithelial Cl- transport rate is small compared to total cyclic AMP content. A second approach investigating the ability of somatostatin to inhibit the transepithelial potential in gills stimulated by different secretagogues suggested dual modes of action for this peptide.

Animals↗
PubMed1985

Suicidal adolescents: factors in evaluation.

Suicide attempts among adolescents are occurring more frequently and their evaluation is a difficult task. The factors related to suicide attempts in eighty-two adolescents, ages 12 to 18 were examined. They had been admitted to the adolescent unit of a large, urban general hospital for evaluation of self-destructive behavior. A systematic review of the patients' charts was performed to gather information about family structure, functioning in school, suicidal risk, degree of depression, and stressful life events. Although most were moderately depressed, a significant proportion denied having tried to harm themselves. While some repressed their anger, the majority expressed anger openly, tended to feel sad and to carry out premeditated as well as more serious suicide attempts. Most had experienced family disruption, and nearly half were functioning poorly in school. Suicide risk correlated only with current stress, while depression correlated with life-long as well as current stress. Results suggest that identification of the suicide attempt and the contributory factors, especially the degree of overt anger and depression, are crucial in deciding appropriate interventions, providing adequate treatment, and avoiding recurrence.

Adolescent↗
PubMed1984

Fibrobullous disease of the upper lobes: an extraskeletal manifestation of ankylosing spondylitis.

Fibrobullous disease of the upper lobes of the lungs is a rare extraskeletal manifestation of ankylosing spondylitis, occurring in 1.3% of patients with ankylosing spondylitis. We present a patient with this disease, and discuss this pulmonary manifestation. Because the radiographic appearance of the chest in this disease resembles that in tuberculosis, many patients are misdiagnosed and treated for tuberculosis despite negative bacteriology. Computed tomography is useful in delineating the extent of pleural thickening, bullous changes, volume loss, parenchymal fibrosis, and bronchiectasis, as well as identifying or excluding an intracavitary pulmonary mycetoma.

Adult↗
PubMed1983

Definition of the simian virus 40 early promoter region and demonstration of a host range bias in the enhancement effect of the simian virus 40 72-base-pair repeat.

The simian virus 40 (SV40) origin region includes the viral replication origin and the early and late promoters and consists of a few palindromes, a 17-base-pair (bp) A + T-rich sequence, three copies of a G + C-rich 21-bp repeat, and two copies of a 72-bp repeat. We have made sequential deletions in the SV40 origin region and determined the early promoter efficiencies of these truncated DNA segments by connecting them in the correct orientation with the coding regions of selectable marker genes and assaying the expression of the chimeric marker genes in vivo in different host cell lines. A truncated SV40 early promoter segment containing only the TATA box and the major in vivo mRNA initiation sites has essentially no promoter efficiency. We have located the major component of the SV40 early promoter within the 21-bp repeated sequences, which consist of an alternating and mutually overlapping array of two C-rich oligonucleotides having the consensus sequences Y-Y-C-C-G-C-C-C (Y = pyrimidine nucleoside) and G-C-C-C-(C)-TA-AT-A(T)-C-T. Between one and two copies of the 21-bp repeat were adequate for gene expression under conditions in which the enhancement effect of the 72-bp repeat was minimal. We also find that the SV40 72-bp repeat exhibits a pronounced host range in its enhancement of gene expression; the enhancement is only 2-fold in the nonpermissive mouse cells but amounts to 10- or 20-fold in the permissive monkey cells or the semipermissive human cells, respectively.

Animals↗
PubMed1979

Ligated chlorophyll cation radicals: Their function in photosystem II of plant photosynthesis.

Magnesium tetraphenylchlorin, a synthetic model for chlorophyll, exhibits significant variations in the unpaired spin densities of its cation radicals with concomitant changes in oxidation potentials as a function of solvent and axial ligand. Similar effects are observed for chlorophyll (Chl) a and its cation radicals. Oxidation potentials for Chl --> Chl(+.) as high as +0.9 V (against a normal hydrogen electrode) are observed in nonaqueous solvents, with linewidths of the electron spin resonance signals of monomeric Chl(+.) ranging between 9.2 and 7.8 G in solution. These changes in electronic configuration and ease of oxidation are attributed to mixing of two nearly degenerate ground states of the radicals theoretically predicted by molecular orbital calculations. Comparison of the properties of chlorophyll in vitro with the optical, redox, and magnetic characteristics attributed to P-680, the primary donor of photosystem II which mediates oxygen evolution in plant photosynthesis, leads us to suggest that P-680 may be a ligated chlorophyll monomer whose function as a phototrap is determined by interactions with its (protein?) environment.

Journal Article↗
PubMed1977

Women's liberation groups as a primary preventive mental health strategy.

As a preventive mental health worker in a community mental health center, I considered it part of my role to explore the possible therapeutic value of women's liberation groups in the community. I was particularly concerned with countering the sense of isolation and powerlessness prevalent among female adults in our suburban catchment area. Subsequent investigation and participant observation of women's groups bore out my expectation that many of the goals, premises, and methods of preventive mental health were compatible with those of women's liberation groups. These groups provided a very effective framework for personal as well as interpersonal and sociocultrual change in the direction of psychological growth.

Adaptation, Psychological↗
PubMed1975

Primary charge separation in bacterial photosynthesis: oxidized chlorophylls and reduced pheophytin.

Bacteriopheophytin, the magnesium-free base of bacteriochlorophyll, undergoes reversible one-electron reduction in organic solvents to yield an anionic free radical with characteristic optical and electron spin resonance spectra. The reduction potential of bacteriopheophytin, E1/2 approximately --0.55 V against a normal hydrogen electrode, compared to E1/2 approximately --0.85 V for bacteriochlorophyll, renders it a likely electron acceptor in the primary charge separation of photosynthesis. Comparison of these data with picosecond optical changes recently observed upon pulsed laser excitation of bacterial reaction centers leads us to propose that bacteriopheophytin is indeed a transient electron acceptor and that the primary charge separation of bacterial photosynthesis occurs between the bacteriochlorophyll complex P870 and bacteriopheophytin to yield the radicals of the oxidized chlorophyll dimer cation and reduced pheophytin anion.

Bacteriochlorophylls↗