Claude Desjardins

Plasma Corticosteroid, Circulating Leukocyte and Milk Somatic Cell Responses to Escherichia coli Endotoxin-Induced Mastitis

Summary A mammary quarter in each of 4 cows was infused with 0.5 mg E. coli endotoxin to determine its effect on plasma corticosteroids, circulating leukocytes and milk somatic cells. At 1.5 hr following endotoxin infusion, segmented neutrophils decreased 23%, and by 5 hr dropped 93%. A shift left in the differential circulating leukocyte count began at 2.5 hr and reached maximum proportions between 18-24 hr postendotoxin infusion. Circulating lymphocytes, monocytes and eosinophils were all depressed in response to endotoxin. Plasma corticosteroid concentrations increased (P < 0.01) 2 hr following endotoxin infusion, reached maximum concentrations at 4 hr, then returned to prein-fusion concentrations by 12 hr. The initial decrease in circulating lymphocytes at 2.5 hr was not attributed to the lytic effect of the plasma corticosteroids, since depressions in circulating lymphocytes occurred too soon (0.5 hr) after the increase in plasma corticosteroids. The high plasma corticosteroid concentration appeared to have little effect at restoring leukocyte equilibrium, since the concentration of neutrophils and total leukocytes continued to decline up to 4 hr past the initiation of the plasma corticosteroid response. Serum glucose concentrations coincided with peak plasma corticosteroid concentration and appeared to be one of the primary physiological effects mediated by elevated plasma corticosteroid concentrations. Three hours following endotoxin infusion or 1.5 hr after the noted depression in segmented neutrophils, the concentration of milk somatic cells increased from 5.7 × 104 cells/ml milk at 0 hr to 37.5 × 104 cells/ml. However swelling of infused quarters was detected as early as 2 hr postinfusion and was attributed to diapedesis and lysis of neutrophils. Total milk somatic cell concentrations reached maximum proportions at 18 hr, averaging 54 × 106 cells/ml milk. The authors thank Miss Barbara A. Becker, Mr. D. Carroll, Mr. S. T. Kirk, and Mr. A. J. Kral for their excellent technical assistance.

Social Rank in Male Mice and Adrenocortical Response to Open Field Exposure

Summary Plasma corticosterone levels were examined in socially dominant, subordinate, or unranked male mice taken directly from an undisturbed cage or following 10 min of a nonsocial neurogenic stress of exposure to an open field. There were no significant differences in plasma corticosterone levels among the social rank categories in undisturbed animals. Following open field exposure, subordinate males had the greatest levels of plasma corticosterone while dominant males had greater levels than unranked males. These data indicate that the process of social organization leads to an increase in responsiveness of male mice to a strange environment and under these circumstances the socially subordinate males are more responsive.

Testicular Metabolism in Adrenalectomized and Corticosterone Treated Rats

Summary Testicular metabolism was examined after adult rats were adrenalectom-ized and/or treated with corticosterone (0.7S, 1.5, and 3.0 mg/day) for 5 days. The weight and DNA and RNA concentrations of testes were not affected by either adrenalectomy or corticosterone replacement but corticosterone (3.0 mg) reduced (p<0.05) testis protein and prevented the loss of testis carbohydrate noted after adrenalectomy. Anaerobic glucose catabolism (cell-free preparations) increased 12% (p<0.05) after adrenalectomy and decreased 13% (p<0.05) after corticosterone (3.0 mg) therapy but neither of these treatments affected aerobic glucose catabolism. Corticosterone (3.0 mg) depressed (p<0.05) the oxidation of glucose-1-14C and glucose-6-14C to 14CO2; whereas adrenalectomy showed a tendency to increase the activity of 14CO2. Testosterone synthesis dropped (p<0.05) after corticosterone (3.0 mg) therapy but was not altered by adrenalectomy. The results suggest that adrenalectomy modifies testicular glucose ca-tabolism and that corticosterone may affect the testis by reducing glucose utilization and testosterone synthesis.

Effect of age upon the spermatogenic and steroidogenic elements of rabbit testes.

Summary Spermatozoa and testosterone production by testes of 6, 12, 24, and 36 month old rabbits were quantified. Testosterone secretion decreased significantly with age when testes were perfused with an artificial medium containing exogenous gonadotropic hormones. Total daily sperm production reached a peak at 24 months and declined significantly by 36 months of age. The fact that sperm production increases through 24 months of age indicates that testosterone secretion is adequate to maintain spermatogenesis. The decreased daily sperm production coincident with reduced testosterone secretion by perfused testes between 24 and 36 months is suggestive of a cause effect relationship.

Pituitary growth hormone and its hypothalamic releasing factor in normal and genetically diabetic mice.

Summary Pituitary GH and hypothalamic GH-RF were determined in normal and in genetically diabetic (db/db) mice during mild and severe hyperglycemia. Mildly hyperglycemic mice had above normal concentrations of GH and GH-RF (p<0.05). whereas the concentrations of GH and GH-RF were below normal in severely hyperglycemic mice (p<0.05). The results suggest that mild hyperglycemia may be stimulated by excessive GH release during the early stages of diabetes and that GH release may be inhibited by severe hyperglycemia during the latter stages of diabetes.

Nursing Duration and Suckling Intensity: Effects on Plasma Corticosterone, Circulating Leukocytes, and Mammary Nucleic Acids

Summary Lactating rats were killed after exposure to specific nursing intensities and suckling intervals to examine the effects of these factors on circulating leukocytes, plasma corticosterone, and mammary nucleic acids. Nursing durations of 0.25, 0.5, and 1 hr caused a 3-fold increase in plasma corticosterone when compared to nonnursed levels. In comparison, plasma corticosterone concentrations were similar to nonnursed control values after hours 2, 3, and 4 of nursing. In addition, exteroceptive stimuli associated with nursing provoked increases in plasma corticosterone that were comparable to values obtained from 0.25 or 0.5 hr of nursing. Circulating leukocytes decreased 24% during the first 0.5 hr of nursing with 10 pups; whereas mammary nucleic acid content increased 9%, suggesting an influx of leukocytes into mammary tissue. Histological examination of mammary glands revealed a striking increase in leukocytes within the alveolar lumina of glands within 0.5 hr after nursing. The results from this study indicate that nursing is a dynamic situation which is capable of provoking striking alterations in leukocytic and adrenocortical function.

Alteration of hypophyseal lh and fsh release by exogenous lh and fsh in orchidectomized mice.

Summary The concentration of LH and FSH in the hypophyses and plasma of ochidectomized mice was determined after injecting LH, FSH, or a control protein for 1, 3, and 6 days, respectively. Exogenous LH reduced the concentration of hypophyseal and plasma LH but FSH release was not affected in these same animals. Similarly, exogenous FSH reduced the concentration of hypophyseal and plasma FSH but LH release was not affected. This evidence suggests that exogenous LH and FSH can suppress their respective secretions specifically.