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Biomedical subjects

J Slater

Publications and source records attributed to J Slater.

7 recordsLinked to original sources
PubMed1977

Central and peripheral norepinephrine metabolism in rat strains selectively bred for differences in response to stress.

Rats of the Maudsley nonreactive (MNRA) strain were found to contain higher levels of norepinephrine in heart, spleen, and hypothalamus than animals of the Maudsley reactive (MR) strain. Total adrenal catecholamines were also greater in nonreactive animals. There was a trend toward higher endogenous norepinephrine concentration in MR rats in brainstem and telencephalon, but this was not statistically significant. Turnover measurements calculated from the fall of norepinephrine at 1 and 4 hours after a single dose of levo-alpha-methylparatyrosine showed no significant strain differences in telencephalon or brainstem, but MNRA animals had a faster rate of norepinephrine decline in heart than had MR rats. Possibly indicative of a higher rate of norepinephrine metabolism, the percentage of 3H-non-catechol metabolites relative to total counts was higher in brainstem of MNRA rats 90 min after intraventricular injection of 3H-norepinephrine. However, the disagreement between this estimate of norepinephrine metabolism and that provided by the alpha-methyl-paratyrosine technique prevents a conclusive statement about norepinephrine metabolism in the two strains. The results are discussed in the light of the established differences in behavior between the strains as well as other work exploring relationships between catecholamine metabolism and emotionality.

Adrenal Glands↗
PubMed1977

Serum prolactin and hypothalamic dopamine in rat strains selectively bred for differences in susceptibility to stress.

Rat strains selectively bred for behavioral differences in susceptibility to mild stress exhibited differences in serum prolactin (Prl) and hypothalamic dopamine (DA). Male rats from the Maudsley Reactive (MR) strain had higher levels of serum Prl and hypothalamic DA than rats from the Maudsley Non-Reactive (MNRA) strain. MR rats also showed a greater percentage increase in serum Prl 1 h after blockade of catecholamine synthesis by administration of alpha-methylparatyrosine (alphaMpT). The correlation of basal serum Prl levels with individual susceptibility to stress constitutes further evidence that Prl may play a functional role in the organism's response to stress. Strain differences in hypothalamic DA function may play a role in the etiology of strain differences in serum Prl.

Animals↗
PubMed1976

A reevaluation of the relation between estrogen and emotionality in female rats.

It has been hypothesized that the emotionality of the female rat is reduced at estrus. In confirmation of previous research, it was found that administration of estradiol benzoate (EB;20 mug/kg) to female rats of the Maudsley Reactive (MR) strain increased open-field activity and decreased open-field defecation. In addition, ovariectomy increased open-field defecation in MR females. Supporting the generality of these findings, hormone administration reduced open-field defecation and increased open-field activity in intact females of a genetically heterogeneous background. Additional studies suggested that the decrease in open-field defecation at estrus is dependent on estrogenic suppression of food intake. Hormone replacement decreased food intake in the period preceding the open-field test, and colonic contents were also lower in rats treated with EB+P (progesterone) immediately after the completion of the open-field test. These changes were seen in both MR and genetically heterogeneous females. It was concluded that the decrease in open-field defecation at estrus may be mediated by a reduction in food intake and a consequent decrease in colonic contents and that the validity of the defecation response as a measure of emotionality may be seriously questioned under these circumstances.

Animals↗
PubMed1975

Estimation of fetal weight from ultrasonic measurement of trunk circumference.

A new method of estimating fetal weight from the circumference of the fetal trunk, measured by ultrasound, is described. Comparison of weights estimated in this way with the actual birth weights of 50 fetuses, delivered not more than 48 hours later, shows a mean error in prediction of only 75 g, and in 94 per cent the error was less than 145 g. With such accuracy, the method is of clinical value, particularly in anticipating difficult delivery and in monitoring growth of the fetus at risk.

Abdomen↗
PubMedDate not supplied

A prototype beam delivery system for the proton medical accelerator at Loma Linda.

A variable energy proton accelerator was commissioned at Fermi National Accelerator Laboratory for use in cancer treatment at the Loma Linda University Medical Center. The advantages of precise dose localization by proton therapy, while sparing nearby healthy tissue, are well documented [R. R. Wilson, Radiology 47, 487 (1946); M. Wagner, Med. Phys. 9, 749 (1982); M. Goitein and F. Chen, Med. Phys. 10, 831 (1983)]. One of the components of the proton therapy facility is a beam delivery system capable of delivering precise dose distributions to the target volume in the patient. To this end, a prototype beam delivery system was tested during the accelerator's commissioning period. The beam delivery system consisted of a beam spreading device to produce a large, uniform field, a range modulator to generate a spread out Bragg peak (SOBP), and various beam detectors to measure intensity, beam centering, and dose distributions. The beam delivery system provided a uniform proton dose distribution in a cylindrical volume of 20-cm-diam area and 9-cm depth. The dose variations throughout the target volume were found to be less than +/- 5%. Modifications in the range modulator should reduce this considerably. The central axis dose rate in the region of the SOBP was found to be 0.4 cGy/spill with an incident beam intensity of 6.7 x 10(9) protons/spill. With an accelerator repetition rate of 30 spills/min and expected intensity of 2.5 x 10(10) protons/spill for patient treatment, this system can provide 50 cGy/min for a 20-cm-diam field and 9-cm range modulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗