摘要:

An intraperitoneal injection of leucine-enkephalin into rats stimulates gonadotropin and prolactin release. To elucidate the mechanism of this releasing property of leucine-enkephalin, rat hemipituitaries were incubated with either enkephalin alone or enkephalin in combination with LHRH. Enkephalin alone had no effect on LH or prolactin release in vitro but potentiated the LH response to LHRH. Neither leucine-enkephalin nor LHRH alone had an effect on GH release; however, when combined, a GH response to LHRH occurred. These results suggest that leucine-enkephalin can modify the pituitary responsiveness to certain hypothalamic releasing hormones by a direct pituitary action.

ISSN:1663-2818    

DOI:10.1159/000178989

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

In order to investigate the role of prolactin in the control of the circadian rhythm of plasma aldosterone (PA), plasma renin activity (PRA), cortisol (PC), aldosterone and prolactin (PRL) levels were determined in samples at 4-hour intervals from 5 normal supine men over a period of 24 h under basal conditions and subsequently over a period of 24 h during suppression of prolactin release by bromocriptine (CB-154). After suppression of prolactin, statistically significant circadian rhythms in PC and PA have been detected with a moderate decrease of PA concentration, while the PC level remained unalterated. PRA rhythmicity persisted with a significant shift of acrophase and remarkable reduction of plasma levels. Moreover, during CB administration a significant correlation was obtained between PA and PC, while no correlation was detected between PA and PRA. These data are consistent with the following concepts: (a) the prolactin does not play a significant role in the regulation of circadian rhythm and concentration of plasma aldosterone in normal supine men, and (b) bromocriptine induces a remarkable reduction of PRA and a variable decrease in plasma aldosterone, but it does not influence the secretion of cortisol in normal subjects.

ISSN:1663-2818    

DOI:10.1159/000178990

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The effect of administration of thiourea (5 g/kg in diet) alone or simultaneously with thyroxine (1 mg/l in drinking water) on the frequency of hyperplastic benign osteoma of the skull was studied in AkR mice. Animals treated with both thiourea and thyroxine were in hyperthyroidism: the thyroxine dose received was higher than that required to prevent thiourea-induced thyroid gland hypertrophy. A significant increase of the intracranial bone tumour (IBT) frequency was observed both in mice treated with thiourea alone and those which received thiourea and thyroxine simultaneously. Increase of IBT frequency was not due to the antithyroid effect of thiourea but seems due to a direct toxic action of thiourea on the pituitary.

ISSN:1663-2818    

DOI:10.1159/000178991

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Arginine vasotocin (AVT) has previously been proposed to be a pineal hormone which reduces reproductive competency in mammals. The effects of AVT on the growth of immature reproductive organs of the mouse have been studied using blind study techniques. Evidence is presented which fails to support the proposed role of AVT as a mammalian antigonadotrophin.

ISSN:1663-2818    

DOI:10.1159/000178992

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

In vitro adrenal accumulation of cyclic 3´5´-adenosine monophosphate (cyclic AMP) and release of corticosterone in response to adrenocorticotropic hormone (ACTH), cyclic AMP or theophylline was assessed in 60- and 340-day-old male rats. Adrenal tissue from mature animals secreted significantly smaller quantities of corticosterone in response to ACTH, theophylline or cyclic AMP. Additionally, mature tissue accumulated significantly less cyclic AMP after treatment with ACTH or a combination of ACTH and theophylline. The data suggest an age-related refractoriness of adrenal cortical tissue to ACTH which may in part be related to decreased availability of and/or sensitivity to cyclic AM

ISSN:1663-2818    

DOI:10.1159/000178993

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Fresh and stored preparations of human pituitary somatotropin examined by different polyacrylamide gel electrophoresis techniques and by gel exclusion chromatography (Ultrogel) clearly demonstrated that the hormone undergoes a structural alteration during storage for 3 years. The formed aggregates were readily quantitated from the gel filtration profile and from polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate (SDS-PAGE). According to gel filtration the amount of aggregates in fresh and stored hormone was determined to be 2 and 10%, respectively, while SDS-PAGE indicated 6 and 14%.

ISSN:1663-2818    

DOI:10.1159/000178994

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Female rats in constant illumination (LL) fail to show the facilitation of LH release following steroid administration that is characteristic of animals in normal lighting. To determine whether this effect is mediated through changes in ovarian function, rats were spayed either at the time of placement into different lighting schedules (LL or a 14:10 light-dark (LD) schedule) or 10 weeks later, and their plasma LH responses to steroids were compared after an additional 3-week exposure to the experimental lighting conditions. To test the LH response, estradiol benzoate (EB) was injected at 12.00 h and followed 72 h later by injection of progesterone (P) or a second injection of EB. Neither steroid regime revealed differences in LH release between animals ovariectomized at the time of placement into LL and those spayed 10 weeks later. The duration of castration in animals in LD affected the LH response to a priming dose of EB, but not to a second dose of EB or to P. It is concluded that altered ovarian activity is not the factor which mediates the loss of a facilitatory response of LH release following administration of gonadal steroids to rats under constant illumination.

ISSN:1663-2818    

DOI:10.1159/000178995

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The patterns of oestrous cycles were examined in new strains of mice exhibiting a high (SHN) and a low (SLN) mammary tumour incidence. These mice originated from the same stock of Swiss albino mice. At the age of 3–4 months, SHN mice showed much longer cycles with continual dioestrous periods than SLN mice. The average lengths of cycles and dioestrous periods were, respectively, 8.3 ± 0.3 and 6.0 ± 0.4 days in SHN mice and 4.6 ± 0.1 and 2.5 ± 0.1 days in SLN mice. Furthermore, the distinct alteration in the patterns of cycles from SHN to SLN type was associated with complete reduction in mammary tumour incidence in highly inbred C3H/He female mice maintained by brother X sister mating with no selection for mammary tumourigenesis. The relation between the pattern of oestrous cycles and mammary tumourigenesis is discussed from the viewpoint of the endogenous hormonal milieu and the responsiveness of target o

ISSN:1663-2818    

DOI:10.1159/000178996

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Surgical adrenalectomy or the administration of aminoglutethimide, corticosterone (B), and androstenedione (Δ4) to the immature female rat had no effect on the timing of vaginal membrane opening. Dehydroepiandrosterone (DHA) and estrone (E1) significantly hastened vaginal patency. Aminoglutethimide increased pituitary LH content while FSH content was decreased. An anti-17β-E2 antibody increased pituitary LH content and plasma concentration suggesting enhanced synthesis and release of LH. Pituitary FSH content was unaltered while plasma FSH decreased. Aminoglutethimide increased adrenal and ovarian but not pituitary weight while the antibody had no effect. Since little DHA is present in rat plasma and adrenal and since only estrogens have any effect on the onset of puberty, it is likely that the adrenal is not directly involved in pubertal development in the female ra

ISSN:1663-2818    

DOI:10.1159/000178997

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The role of neurotransmitters in the release of prolactin (PRL) is reviewed. Special attention is paid to dopamine (DA) as the possible prolactin-inhibiting factor (PIF). Among other agents, estrogens alone can act directly on the pituitary galactotropes without involving hypothalamic factors. Peripherally, in addition to its stimulatory action on mammary tissue, PRL exerts a permissive role on ovarian steroidogenesis. A possible physiological action of this hormone on the regulation of adrenal function remains uncertain. The secretory rhythms of PRL are described and the mechanisms involved are discussed. A number of drugs can modify the secreting pattern of PRL mainly by acting on the dopaminergic control mechanisms. The usefulness of such agents in the clinical evaluation of galactotrope cell function is reviewed.

ISSN:1663-2818    

DOI:10.1159/000178998

出版商:S. Karger AG    

年代:1979

数据来源: Karger