ISSN:1663-2818    

DOI:10.1159/000181460

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000181461

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000181462

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The field of chronobiology, the study of the rhythms in plants and animals, was restricted to botanists for centuries. Only recently during the last decades could research be broadened to include animals and later even human beings. Rhythms have been documented and related to the alternation of day and night and to the succession of the seasons. Nowadays, chronobiology has developed into a multidisciplinary field in which scientists are involved in basic research as well as in applied topics. This paper gives an introduction to the field, especially dealing with the aspect of rhythm development, and the way in which the different 24-hour rhythms in children become apparent.

ISSN:1663-2818    

DOI:10.1159/000181463

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000181486

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Epidermal growth factor (EGF) is the most important member of a family of growth factors which exert their effects via a single 170,000 Mr plasma membrane receptor. Other members include transforming growth factor-α (TGF-α), amphiregulin and several viral growth factors. The receptor is widely distributed in fetal and postnatal tissues. The predominant family member in the fetus appears to be TGF-α. EGF production in tissues matures in the perinatal period. Activation of the receptor in the fetal and neonatal periods in rodents evokes important growth and development actions. Tissue EGF and EGF receptor concentrations are modulated by thyroid hormones, estrogen, testosterone and growth hormone, suggesting that selected growth and developmental actions of thyroid and steroid hormones may be mediated by

ISSN:1663-2818    

DOI:10.1159/000181487

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The neurohormone gonadotropin-releasing hormone (GnRH) is a decapeptide which is synthesized in the hypothalamus and released into the hypophysial portal system in a pulsatile manner. GnRH exerts its effect on the anterior pituitary gonadotrophs where it regulates the secretion and synthesis of gonadotropins (luteinizing hormone and follicle-stimulating hormone) through receptor-mediated actions. The GnRH receptor has been characterized and shown to be coupled to the formation of ‘second messengers’ which participate in signal transduction mechanisms. GnRH stimulation of luteinizing hormone release is a Ca2+-dependent process. G protein, phosphoinositide hydrolysis, protein kinase C as well as arachidonic acid and some of its metabolites were identified as possible mediators in the proc

ISSN:1663-2818    

DOI:10.1159/000181488

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

We have characterized intracellularly the androgen-receptor (A-R) complexes formed by genital skin fibroblasts from 2 unrelated males with qualitative defects of the androgen receptor: one has a small nonhypospadic penis as part of a syndrome of mild androgen resistance; the other was born with ambiguous external genitalia. The dissociation rate constants of testosterone, methyltrienolone (MT), dihydrotestosterone (DHT) and mibolerone (MB) from normal androgen receptors were determined at various temperatures: when plotted by the method of Arrhenius, they yielded a linear hierarchy of dissociation states with energies of state IV > III > II > I, respectively. Relative to this hierarchy, patient A-R complexes were displaced to higher, androgen-inappropriate energies in a mutant-distinctive pattern. MB- or MT-R complexes of both patients were thermolabile; however, both up-regulated normally in response to prolonged incubation with either hormone. Apparent equilibrium affinity constants (Kd) of the DHT- and MB-R complexes formed by both patients were normal; however, the binding capacity (Bmax) for MB in 1 case was subnormal. The distinctive biochemical phenotypes of A-R complexes in these 2 patients with androgen resistance will facilitate the definition of structure-function relations in the androgen receptor, a classical DNA-binding, transcription-regulating protein.

ISSN:1663-2818    

DOI:10.1159/000181489

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

During the past years there has been an improvement in our understanding of the molecular mechanism of action of the progesterone receptor (PR). This was due to the obtention of monoclonal antibodies against PR which allowed the first structural analyses and led to the cloning of the genes.

ISSN:1663-2818    

DOI:10.1159/000181490

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

It is now widely accepted that insulin stimulates glucose metabolism in its target tissues via recruitment of transporters from a large intracellular pool to the plasma membrane. Recent studies, however, suggest a two-step model for insulin action, of transporter translocation and transporter activation. Data confirming this hypothesis for the first time are presented. It is shown that insulin significantly enhances the intrinsic activity of glucose transporters in human and rat adipose cells, in physiological as well as in diabetic state. The functional activity of transporters is impaired in the diabetic state, but surprisingly, ‘diabetic’ transporters exhibit normal or even enhanced intrinsic activity. In both noninsulin-dependent diabetes mellitus and streptozotocin-diabetic rats, insulin resistance is associated with 50% transporter depletion in the intracellular pool, thus leading to a decreased number of transporters appearing in the plasma membrane in response to insulin. It is concluded that impaired glucose transport in diabetes is secondary (1) to intracellular transporter depletion, and (2) to the presence of inhibitory factors interfering with the full expression of glucose transporters at the plasma membrane, thus contributing to postreceptor insulin resista

ISSN:1663-2818    

DOI:10.1159/000181491

出版商:S. Karger AG    

年代:1990

数据来源: Karger