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Biomedical subjects

D F Johnson

Publications and source records attributed to D F Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1978

Spontaneous cytotoxicity of cultured human cell lines mediated by normal peripheral blood lymphocytes. III. Kinetic parameters.

The mechanism of spontaneous cell-mediated cytotoxicity (SCMC) of cultured cell lines has been investigated and compared with antibody-dependent cell-mediated cytotoxicity (ADCMC) by detailed kinetic analysis. The mechanism of SCMC resembles that of an enzyme, as does ADCMC where effector cells are analogous to an enzyme and the 51Cr-labeled target cells are analogous to the substrate. Temporal kinetic studies revealed an induction period of about 1 hr before significant 51Cr release for SCMC, but not for ADCMC. This induction period is not due to differences in effector-target affinity between SCMC and ADCMC. On the basis of kinetic analysis it was shown that SCMC approaches simple Michaelis-Menten enzyme kinetics, allowing determination of a Michaelis constant, Km, and maximal velocity, Vmax, for the interaction between a given effector and target cell. The Km values thus determined were found to be identical for the lysis of several target cell lines of varying SCMC susceptibility to effector cells from a given donor, whereas Vmax values for lysis of different target cells varied considerably. However, effector cells isolated from the peripheral blood of different donors exhibited different Km values for the target cells tested. Moreover, the Km value obtained for ADCMC effected by a given donor's lymphocytes was found equal to the Km value obtained for SCMC by that donor.

Adult↗
PubMed1976

Hormonal control of female sexual attractiveness proceptivity, and receptivity in rhesus monkeys.

The sexual behavior of 18 female and 11 male rhesus monkeys was observed in pair tests, in two experiments. In one experiment the females controlled the occurrence of pair tests. The females were ovariectomized and treated with estradiol, two dosages of testosterone, estradiol plus testosterone, estradiol plus dexamethasone, or no hormone; and the effects of the treatment on female attractiveness, proceptivity, and receptivity were examined. Sexual attractiveness of females to males (the effectiveness of the female as a sexual stimulus) was affected by estrogen and androgen. Estrogen enhanced attractiveness, but the effect of androgen depended on the dose. Female sexual proceptivity (the extent to which the female seeks out the male and elicits sexual behavior) was heightened by estrogen and androgen. Female sexual receptivity (willingness to receive a male in copulation was somewhat stimulated by estradiol, but not by testosterone. Both estradiol and testosterone had a greater effect on attractiveness and proceptivity than on receptivity. The hypothesis that testosterone is the "libidinal hormone" in female primates was not supported.

Animals↗
PubMed1976

Possible role of dopamine in diethylstilbestrol-elicited accumulation of cyclic AMP in incubated male rat hypothalamus.

Pimozide and haloperidol, the dopaminergic antagonists, have been shown to effectively block diethylstilbestrol (DES)-elicited [3H] adenosine 3', 5'-monophosphate (cAMP) accumulation in incubated hypothalami from immature male rats. Several noradrenergic antagonists (i.e. propranolol, MJ-1999 and phenoxybenzamine) failed to reduce [3H]cAMP levels significantly. Pimozide was found to be more specific than haloperidol as it did not effect norepinephrine (NE)-elicited formation of [3H]cAMP, while the latter blocker caused a 48% reduction of the stimulation by NE. Pimozide was also more potent than haloperidol in inhibiting DES-stimulated [3H]cAMP formation. It can be inferred from these data that as a result of DES-receptor interaction dopamine (DA) is released and in turn activates DA-sensitive adenylate cyclase in the hypothalamus.

Animals↗