The effects of adrenal steroids on testosterone and LH secretion and changes in serum cortisol levels in response to treatments were studied in the ram. Acute administration of synthetic ACTH (10 micrograms/kg BW) elevated (P less than 0.01) serum cortisol and transiently suppressed (P less than 0.05) serum testosterone and LH. Acute dexamethasone treatment suppressed (P less than 0.01) serum cortisol, testosterone and LH. Administration of vehicle had no effect (P greater than 0.10) on serum hormone levels. These data support the contention that adrenal steroids inhibit testicular endocrine function indirectly by acting at the hypothalamic or pituitary level because both ACTH and dexamethasone treatments suppressed serum LH. To differentiate between hypothalamic and pituitary sites of action, the pituitary and testicular responses to an LHRH challenge (100 micrograms) were examined in rams chronically treated with dexamethasone (5 mg i.m., twice daily for 5 days). This treatment regimen suppressed (P less than 0.01) serum cortisol levels. Compared with controls, basal testosterone levels were suppressed (P less than 0.05) in dexamethasone-treated rams; however, no effect (P greater than 0.10) on the magnitude of the testosterone response to LHRH or on either basal or LHRH-stimulated LH secretion was observed. Thus, although a direct testicular effect cannot be eliminated, these data suggest that, in the ram, adrenal steroids inhibit testicular endocrine function by action at the level of the hypothalamus.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Uterotropic action of estrogens in phenobarbital-treated mice.

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Animals↗

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Production of transgenic rabbits, sheep and pigs by microinjection.

Direct microinjection has been used to introduce foreign DNA into a number of terminally differentiated cell types as well as embryos of several species including sea urchin, Candida elegans, Xenopus, Drosophila and mice. Various genes have been successfully introduced into mice including constructs consisting of the mouse metallothionein-I (MT) promoter/regulator region fused to either the rat or human growth hormone (hGH) structural genes. Transgenic mice harbouring such genes commonly exhibit high, metal-inducible levels of the fusion messenger RNA in several organs, substantial quantities of the foreign growth hormone in serum and enhanced growth. In addition, the gene is stably incorporated into the germ line, making the phenotype heritable. Because of the scientific importance and potential economic value of transgenic livestock containing foreign genes, we initiated studies on large animals by microinjecting the fusion gene, MT-hGH, into the pronuclei or nuclei of eggs from superovulated rabbits, sheep and pigs. We report here integration of the gene in all three species and expression of the gene in transgenic rabbits and pigs.

Animals↗

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Two-dimensional electrophoresis and densitometric analysis of solubilized bovine sperm plasma membrane proteins detected by silver staining and radioiodination.

Bovine sperm plasma membranes were extracted with deoxycholate and subjected to two-dimensional gel electrophoresis. Proteins were visualized either by silver staining or autoradiography using 125I. When 1.5-2.0 micrograms of protein extract was applied to the first-dimension get, 250 spots could be detected by autoradiography. Thirty micrograms of protein was required to obtain spot visualization using silver strain, revealing more than 500 spots on the gel. These data establish the limit under which two-dimensional electrophoresis can be used in conjunction with flow cytometric sorting of sperm for the analysis of possible sex-specific membrane differences. The necessity of orienting sperm as they past the laser in the cell sorting system reduces throughput; thus, the number of sperm sorted within a given time is limited. It is suggested that autoradiography will allow the flow cytometer to be used in a time-efficient manner. Longer sorting times would be required to obtain sufficient sample to analyze total protein composition.

Animals↗