Role of ACTH on the cytomorphology of testes of the immature rat

Summary The male gametogenic development of the immature rat shows inhibitory effect by the exogenous infusion of ACTH (0.25 IU and 0.50 IU; i.p.). Seminiferous tubular degeneration, Leydig cell atrophy and Sertoli cell regression are very conspicuous in the dosage of 0.50 IU ACTH (i.p.). Cytometrical and histological evidence confirms that ACTH could be inhibited by FSH during male gametogenic development which leads to cellular degeneration of testes in the immature rat.This work is supported by CSIR, Project No. JRF 37. We thank Md. K. Doubet for photomicrography.     

Corticotropin releasing factor increases the adrenocortical responsiveness to adrenocorticotropin

Summary In the course of studying the plasma adrenocorticotropic hormone (ACTH) and corticosterone responses to synthetic corticotropin releasing factor (CRF), we noted some disparity in the responses. A higher dose (20 g compared with 5 g per rat i.a.) produced an equal plasma ACTH but greater plasma corticosterone response in adult male rats. Thus, we examined the possibility that CRF increases adrenocortical responsiveness to ACTH. CRF significantly (p<0.0005) increased the plasma corticosterone response to ACTH in rats pretreated with dexamethasone. Thus, synthetic CRF increases corticosterone secretion in rats not only by stimulating ACTH secretion, but also by increasing the adrenocortical responsiveness to ACTH.Acknowledgments. This research was supported by grant MT-5183 from the Medical Research Council of Canada and by the Department of Medicine, University of Kentucky.     

Effects of chronic treatment with ACTH on the intracellular levels of cyclic-AMP and cyclic-GMP in the rat adrenal cortex

Summary The effects of chronic ACTH treatment on the increase in the intracellular concentration of cyclic-AMP and cyclic-GMP acutely elicited by ACTH in the rat adrenal cortex were investigated. The results are consistent with the hypothesis that chronic ACTH treatment stimulates a) the de novo synthesis of adenylate- and guanylate-cyclase or b) the synthesis of new specific membrane receptors for ACTH.Part of this work was presented at the 3rd International Conference on Cyclic Nucleotides, July 1977, New Orleans, Abstr. Book, p. 79.     

Effect of ACTH on the zona reticularis of the rat adrenal cortex: an ultrastructural stereologic study.

The effects of ACTH on the rat adrenal zona reticularis were investigated by stereologic methods. It was found that the zona reticularis cell responsiveness to ACTH is similar to that of the zona fasciculata elements. This excludes that the zona reticularis of the adult rat can only function as the site of destruction of worn-out elements migrating from the adrenal outer zones.     

Manganese prolongation of pentobarbital hypnosis in the male rat

Summary Following manganese treatment, pentobarbital hypnosis was prolonged in male rats. The maximal effect occurred from 1 to 3 days following manganese treatment and the threshold dose was found to be 3 mg Mn⁺⁺/kg (i.p.).Acknowledgments. This work was supported by NIEHS Research Grant ES-02425. These data were submitted as part of a Ph.D. thesis to Purdue University, West Lafayette, Indiana, by M.J. Deimling.     

Changes in the level of ACTH in the fetal hypophysis. A study in the rat toward the end of gestation]

The isolated adrenal cell method for bioassay of ACTH was employed in order to determine the ACTH content of the hypophysis of the rat foetus, in late pregnancy. The ACTH concentration decreases between 17 days 8 h and 17 days 15 h, then it increases regularly until the term. This evolution is correlated with the change in the fluorescence intensity of the corticotrophs and with the modification of the adrenocortical activity.     

Effect of ACTH on the zona reticularis of the rat adrenal cortex: An ultrastructural stereologic study

Summary The effects of ACTH on the rat adrenalzona reticularis were investigated by stereologic methods. It was found that thezona reticularis cell responsiveness to ACTH is similar to that of thezona fasciculata elements. This excludes that thezona reticularis of the adult rat can only function as the site of destruction of worn-out elements migrating from the adrenal outer zones.Acknowledgment. We wish to thank Mr.G. Gottardo for his skilled technical assistance. This work was partly supported by a contract with the CNR No. C.T.73.00663.04.     

Comparison of the effectiveness of intramuscular and intraperitoneal ACTH in the rat

Summary Injection of 1–24 ACTH is more effective by the i.m. than i.p. route. Large doses are required to induce consistent maximal adrenal corticosterone secretion.Supported by grants from the National Institute of Arthritis, Metabolism and Digestive Diseases, National Institutes of Health, Bethesda, Maryland, USA.     

Histamine H1- and H2-receptor-mediated gastric microcirculatory effects in the aetiology of stress ulceration in the rat stomach

Stress produced severe mucosal ulcers, increased mucosal microcirculation and lowered mast cell counts in the glandular wall of rat stomachs. Mepyramine i.m. or metiamide i.p. effectively prevented both ulceration and microcirculatory changes but not stress-reduced mast cell counts.     

Effects of chronic treatment with ACTH on the intracellular levels of cyclic-AMP and cyclic-GMP in the rat adrenal cortex.

The effects of chronic ACTH treatment on the increase in the intracellular concentration of cyclic-AMP and cyclic-GMP acutely elicited by ACTH in the rat adrenal cortex were investigated. The results are consistent with the hypothesis that chronic ACTH treatment stimulates a) the de novo synthesis of adenylate- and guanylate-cyclase or b) the synthesis of new specific membrane receptors for ACTH.     

Histamine H1- and H2-receptor-mediated gastric microcirculatory effects in the aetiology of stress ulceration in the rat stomach

Summary Stress produced severe mucosal ulcers, increased mucosal microcirculation and lowered mast cell counts in the glandular wall of rat stomachs. Mepyramine i.m. or metiamide i.p. effectively prevented both ulceration and microcirculatory changes but not stress-reduced mast cell counts.Acknowledgment. The authors thank Dr W.A.M. Duncan (Smith, Kline and French Labs Ltd, England) for the generous gift of metiamide.     

Effect of thiamine hydrochloride on the blood level of 2-formyl 1-methyl pyridinium oxime chloride (2-PAM.C1) in rats.

The biological half-life of 2-PAM.C1 was found to increase in female rats pretreated with thiamine hydrochloride (10 mg/kg i.m.). No such effect was observed in the male rats.     

Activité gonadotrope d'un extrait d'urines de femmes en ménopause

Summary In agreement with earlier observations on hypophysectomized male rats, a purified extract from pooled menopausal urine has been shown to contain follicle-stimulating (FSH) as well as luteinizing (LH) activity. Its administration to immature hypophysectomized female rats increased ovarian and uterine weights and induced follicle growth and the formation of corpora lutea. If the activity of the extract is measured in standardized units by bioassay in intact female mice using the uterine weight, the dose needed for corpus luteum formation in the hypophysectomized female rat seems to be approximately ten times higher than the dose producing interstitial cell repair and complete spermatogenesis in the hypophysectomized male.

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2^e Communication: Effets sur les ovaires de rates impubères hypophysectomisées.     

Opposing effects on the cell cycle of T lymphocytes by Fbxo7 via Cdk6 and p27

G₁ phase cell cycle proteins, such as cyclin-dependent kinase 6 (Cdk6) and its activating partners, the D-type cyclins, are important regulators of T-cell development and function. An F-box protein, called F-box only protein 7 (Fbxo7), acts as a cell cycle regulator by enhancing cyclin D-Cdk6 complex formation and stabilising levels of p27, a cyclin-dependent kinase inhibitor. We generated a murine model of reduced Fbxo7 expression to test its physiological role in multiple tissues and found that these mice displayed a pronounced thymic hypoplasia. Further analysis revealed that Fbxo7 differentially affected proliferation and apoptosis of thymocytes at various stages of differentiation in the thymus and also mature T-cell function and proliferation in the periphery. Paradoxically, Fbxo7-deficient immature thymocytes failed to undergo expansion in the thymus due to a lack of Cdk6 activity, while mature T cells showed enhanced proliferative capacity upon T-cell receptor engagement due to reduced p27 levels. Our studies reveal differential cell cycle regulation by Fbxo7 at different stages in T-cell development.     

Effect of fluoride administration on renal glucose-6-phosphatase activity in rats

Renal glucose-6-phosphatase activity was found to be significantly elevated by fluoride administration (NaF 35 mg/kg, i.p.). The elevation of the enzyme activity was markedly suppressed by adrenalectomy.     

Investigations into the effects of ACTH on the half-life of mitochondrial proteins in the rat adrenal cortex

Summary ACTH elongates the half-life of the mitochondrial proteins from the rat adrenal cortex, and chloramphenicol inhibits this effect of ACTH. The hypothesis is advanced that the ACTH-provoked stabilization of the adrenocortical mitochondrial proteins requires continuous mitochondrial DNA-dependent protein synthesis.     

Investigations into the effects of ACTH on the half-life of mitochondrial proteins in the rat adrenal cortex.

ACTH elongates the half-life of the mitochondrial proteins from the rat adrenal cortex, and chloramphenicol inhibits this effect of ACTH. The hypothesis is advanced that the ACTH-provoked stabilization of the adrenocortical mitochondrial proteins requires continuous mitochondrial DNA-dependent protein synthesis.     

Immunocytological identification of two cell types in the intermediate lobe of the hypophysis of salmonids: presence of ACTH and alpha-MSH]

The lead-haematoxylin positive cells (PbH+) of the rostral pars distalis react with antibodies anti-1-24 ACTH and anti-17-39 ACTH; the pars intermedia (PI) is composed of two cell categories, but only one is revealed with cyto-immunological techniques and contains ACTH and alpha-MSH in several Salmonid species.     

Effect of fluoride administration on renal glucose-6-phosphatase activity in rats

Summary Renal glucose-6-phosphatase activity was found to be significantly elevated by fluoride administration (NaF 35 mg/kg, i.p.). The elevation of the enzyme activity was markedly suppressed by adrenalectomy.This work was supported in part by the Scientific Research Foundation (Grant 7014-267337) from the Education and Culture Ministry of Japan.     

Influence of alpha-MSH and ACTH on cortical bone remodelling in hypophysectomized rats.

Hypophysectomy increases both periosteal resorption and endosteal apposition along the femur diaphysis in rat. Administration of alpha-MSH decreased the periosteal resorption but had no effect on the endosteal apposition. ACTH had only minor effects on the endosteum. Thus, alpha-MSH and ACTH, in the doses used, have different effects on cortical bone in rat. The effect of alpha-MSH on cortical bone could be an effect of the hormone alone or by its stimulation of other factors.