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Biomedical subjects

R H Lenox

Publications and source records attributed to R H Lenox.

104 records · Page 6Linked to original sources
PubMed1980

Specific hormonal and neurochemical responses to different stressors.

The neuroendocrine and neurochemical responses of rats to 5 min of cold exposure versus 5 min of forced immobilization were determined and compared. We found that plasma hormones and brain neurochemical systems responded differently to the two different stressors. Plasma prolactin levels were elevated over 10-fold in the immolilized group, while rising only 2-fold in the cold stress group. Levels of corticosterone were significantly increased and growth hormone levels were decreased in both stressed groups as compared to controls. Levels of cyclic GMP were markedly elevated in 11 brain regions following cold exposure. Surprisingly, no elevation of cyclic GMP was found after forced immobilization. Cyclic AMP, norepinephrine, and dopamine levels throughout the 17 regions of brain examined showed no significant response to 5 min of either stressor. Lesions of the ventral medial tegmental area did not affect the cyclic GMP or neuroendocrine responses to cold stress. Lesion of the nucleus locus ceruleus did not affect the cyclic GMP response but significantly reduced growth hormone levels in the cold-stressed rats.

Animals↗
PubMed1979

Changes in brain levels of cyclic nucleotides and gamma-aminobutyric acid in barbiturate dependence and withdrawal.

Rats exposed to chronic intake of sodium barbital maintained high circulating levels of barbital in blood and brain and exhibited increased sensitivity ot audiogenic convulsions during the withdrawal period. Levels of gamma-aminobutyric acid (GABA), glutamate, guanosine 3',5'-monophosphate (cyclic GMP) and adenosine 3',5'-monophosphate (cyclic AMP) were measured in selected brain regions after sacrifice with high power microwave inactivation. Cyclic GMP during chronic barbital administration was significantly lower than controls in most brain regions, especially the hindbrain. During the withdrawal period cyclic GMP in the cerebellum was significantly increased, while returning at least to control levels in all other regions. GABA throughout the brain tended to be reduced during barbital dependence, while cyclic AMP and glutamate levels remained unchanged in all groups. These results indicate a possible role for cyclic GMP in the mediation of the central nervous system response during barbiturate dependence and withdrawal.

Acoustic Stimulation↗
PubMed1979

Dopamine diffusion after microwave fixation at 986 MHz.

It has been previously demonstrated by us that microwave irradiation at 2450 MHz causes diffusion of dopamine from rat brain regions of high dopamine concentration to contiguous regions low in dopamine. Because we have found that the heating pattern at 986 MHz is opposite to that seen at 2450 MHz, we attempted in the present study to eliminate DA diffusion by heating at 986 MHz. However, dopamine levels were elevated in frontal and parietal cortex, remainder of cortex, and amygdala after sacrifice by microwave irradiation at 986 MHz. Norepinephrine levels were unaffected by sacrifice method. Microwave-induced diffusion of certain substances must be considered in the interpretation of regional neurochemical data.

Animals↗
PubMed1977

Regional levels of cyclic AMP in rat brain: pitfalls of microwave inactivation.

Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to exposure configuration and output power. The rate at which metabolism was stopped was studied in various regions of the rat brain, using changes in levels of cyclic AMP and phosphodiesterase activity. Exposure times required to obtain stabilized levels of cyclic AMP varied in different brain regions, i.e., hypothalamus, cortex and cerebellum. Levels of cyclic AMP in selective regions of the brain decreased as more rapid inactivation was achieved. The authors identify important sources of variability of present microwave inactivation systems and the need for improved control of signficant microwave parameters.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Statistical characterization of the random errors in the radioimmunoassay dose--response variable.

We have developed practical methods for evaluating the magnitude of the random errors in radioimmunoassay dose--response variables, and the relationship between this error and position on the dose--response curve. This is important: to obtain appropriate weights for each point on the dose--response curve when utilizing least-squares curve-fitting methods; to evaluate whether the standards and the unknowns are subject to error of the same magnitude; for quality-control purposes; and to study the sources of errors in radioimmunoassay. Both standards and unknowns in radioimmunoassays for cAMP and cGMP were analyzed in triplicate. The same mean (Y), sample standard deviation, sy, and variance (2-y) of the response variable were calculated for each dose level. The relationship between s 2-y and y was calculated utilizing several models. Results for standards and unknowns from several assays were pooled, and a curve smoothing procedure was used to minimize random sampling errors. This pooling increased the reliability of the analysis, and confirmed the presence of the theoretically predicted nonuniformity of variance. Thus, the calculation of results from these radioimmunoassays should utilize a weighted least-squares curve-fitting program. These analyses have been computerized, and can be used as a "pre-processor" for programs for routine analysis of results of radioimmunoassay.

Analysis of Variance↗
PubMedDate not supplied

Ecto-protein kinase activity on the external surface of neural cells.

ATP is secreted in association with neurotransmitters at certain synapses and neuromuscular junctions. Extracellular ATP is known to exert potent effects on the activity of cells in the nervous system, where it can act as a neurotransmitter or as a modulator regulating the activity of other neurohormones. We have suggested that such modulation may involve the activity of extracellular protein phosphorylation systems. It is well known that intracellular protein kinases are important in the regulation of various neuronal functions, but protein kinases which use extracellular ATP to phosphorylate proteins localized at the external surface of the plasma membrane (ecto-protein kinases) have not been demonstrated in neuronal cells. Here we present direct evidence for the existence of an ecto-protein kinase and demonstrate endogenous substrates for its activity at the surface of intact neural cells. The phosphorylation of one of these surface proteins is selectively stimulated during cell depolarization. In addition, neuronal cell adhesion molecules (N-CAMs) appear to be among the substrates of ecto-protein kinase activity. These results suggest a role for surface protein phosphorylation in regulating specific functions of developing and mature neurones.

Adenosine Triphosphate↗