Search Results
You are looking at 1 - 5 of 5 items for
- Author: H Mulder x
- Refine by access: All content x
Search for other papers by H Mulder in
Google Scholar
PubMed
Search for other papers by B Ahrén in
Google Scholar
PubMed
Search for other papers by F Sundler in
Google Scholar
PubMed
Islet amyloid polypeptide (IAPP) is a β cell hormone, which forms islet amyloid in non-insulin-dependent diabetes mellitus and may oppose insulin action and release. Therefore, the previously observed relative overexpression of IAPP compared with insulin in streptozotocin-treated rats could be unfavourable if it occurs in diabetes. Using quantitative in situ hybridization, we examined whether insulin treatment affected IAPP and insulin gene expression and their ratio at day 8 and 20 after induction of streptozotocin diabetes (plasma glucose ∼ 30 mm). Total islet IAPP mRNA levels were less reduced than those of insulin at both time points. Differential regulation of the two hormones was further reflected by mean IAPP mRNA levels in the remaining islet cells being unaffected by streptozotocin treatment, whereas those of insulin were reduced. At both time points, insulin treatment decreased total islet levels of IAPP and insulin mRNA even more, IAPP mRNA levels being less reduced. Mean insulin mRNA levels, but not IAPP mRNA levels, in the remaining islet cells were reduced by insulin treatment. Between time points, total islet mRNA levels were higher at day 20, while mean mRNA levels in the remaining islet cells were unchanged, suggesting that regeneration of β cells had occurred. In contrast, insulin gene expression was the same at both time points in insulin-treated rats, suggesting that insulin impaired insulin expression. To summarize, we found that IAPP and insulin were differentially expressed in experimental diabetes and that insulin treatment inhibited insulin, but not IAPP, gene expression. It is therefore unlikely that insulin will protect against amyloid formation and metabolic perturbations which may arise as a consequence of IAPP overexpression.
Journal of Endocrinology (1997) 152, 495–501
Search for other papers by WILLEM DE BOER in
Google Scholar
PubMed
Search for other papers by EPPO MULDER in
Google Scholar
PubMed
Search for other papers by H. J. VAN DER MOLEN in
Google Scholar
PubMed
SUMMARY
After administration of oestradiol-17β to intact mature and immature rats, a decrease in the testicular concentration of specific oestradiol-binding sites was observed within 1 h. The binding capacity was replenished starting about 3 h after oestradiol administration and after 5 h the oestrogen receptor level had returned to control values. Exposure of intact animals to oestradiol-17β for longer periods (up to 24 h) did not result in an increase of receptor levels in testicular cytosol.
Mature animals which were hypophysectomized for periods of up to 10 days did not show a significant change in the number of specific oestradiol-binding sites in either total testicular tissue or dissected interstitial tissue. At 15 days or longer periods after hypophysectomy, an apparent increase in receptor concentrations in total testicular cytosol was observed due to a relative increase in the amount of interstitial tissue.
A specific oestradiol-binding protein is present in plasma of immature male rats aged less than 30 days. This plasma protein could also be demonstrated in the cytosol of testes of immature rats. In contrast to the cytosol receptor, which shows a moderate affinity for diethylstilboestrol (DES), the plasma protein did not bind DES. The sedimentation values of the plasma protein and the oestradiol receptor were 4 S and 8 S respectively. These differences in characteristics made it possible to demonstrate the presence of the oestradiol receptor in addition to the binding protein in testicular cytosol of rats from 14 days of age onwards. The nuclear receptor for oestradiol-17β could be demonstrated after incubation of testicular tissue of rats from 4 days of age onwards.
Search for other papers by M. A. BLANKENSTEIN in
Google Scholar
PubMed
Search for other papers by E. MULDER in
Google Scholar
PubMed
Search for other papers by J. J. BROERSE in
Google Scholar
PubMed
Search for other papers by H. J. VAN DER MOLEN in
Google Scholar
PubMed
Female Sprague–Dawley rats received a subcutaneous implant containing 2 mg oestradiol at the age of 7 weeks. One week later half of the rats treated with oestrogen and half of the rats in an untreated control group were irradiated with 2 Gy (200 rad) of X-rays. The content of oestrogen receptor of the mammary tissue and the concentration of prolactin in the plasma were studied at intervals of 2 months for a period of 14 months after this treatment. Oestrogen treatment resulted in a decrease in the content of oestrogen receptors in the mammary tissue of both irradiated and non-irradiated rats. In oestrogen-treated rats, plasma prolactin was raised 10–50 times and pituitary tumours were observed. Radiation had no additional effect on the oestrogen-receptor content of mammary tissue or the concentration of plasma prolactin. The changes in the oestrogen-receptor content of mammary tissue and the prolactin concentration of plasma preceded the development of mammary tumours. It is suggested that the synergistic action of oestrogen and radiation on rat mammary tumour development is the result of a stimulation by oestrogen and/or prolactin of the sensitivity of the mammary gland to ionizing radiation.
Search for other papers by J. C. MEIJER in
Google Scholar
PubMed
Search for other papers by G. H. MULDER in
Google Scholar
PubMed
Search for other papers by A. RIJNBERK in
Google Scholar
PubMed
Search for other papers by R. J. M. CROUGHS in
Google Scholar
PubMed
Hypothalamic corticotrophin releasing factor (CRF) activity was determined in five dogs with spontaneous hyperadrenocorticism and in three control animals (one untreated, one treated with high doses of ACTH for 2 months and one treated with high doses of cortisone for 2 months). Hypothalamic CRF activity was low or undetectable in four dogs with spontaneous pituitary-dependent hyperadrenocorticism and was reduced in one dog with Cushing's syndrome due to an adrenocortical tumour. The results are compatible with a pituitary origin for pituitary-dependent hyperadrenocorticism in the dog but are not conclusive; direct information about the rates of hypothalamic CRF secretion is required.
Search for other papers by E. MULDER in
Google Scholar
PubMed
Search for other papers by M. J. PETERS in
Google Scholar
PubMed
Search for other papers by W. M. O. VAN BEURDEN in
Google Scholar
PubMed
Search for other papers by M. GALDIERI in
Google Scholar
PubMed
Search for other papers by F. F. G. ROMMERTS in
Google Scholar
PubMed
Search for other papers by F. H. A. JANSZEN in
Google Scholar
PubMed
Search for other papers by H. J. VAN DER MOLEN in
Google Scholar
PubMed
Department of Biochemistry (Division of Chemical Endocrinology), Medical Faculty, Erasmus University Rotterdam, Rotterdam, The Netherhnds
(Received 31 March 1976)
Studies on steroid hormone receptors in testicular tissue have previously revealed the presence of specific oestradiol receptors in interstitial tissue (Brinkmann, Mulder, Lamers-Stahlhofen, Mechielsen & van der Molen, 1972) and androgen receptors in tubular tissue (Hansson, McLean, Smith, Tindall, Weddington, Nayfeh, French & Ritzen, 1974; Mulder, Peters, van Beurden & van der Molen, 1974).
Recently methods for the preparation of isolated Leydig cells (Janszen, Cooke, van Driel & van der Molen, 1976) and Sertoli cells (Fritz, Rommerts, Louis & Dorrington, 1976) have become available. In the present study, binding of testosterone and oestradiol was investigated in such Leydig cell and Sertoli cell preparations.
Leydig cells were prepared, as described by Janszen et al. (1976), from adult rats 8 days after hypophysectomy. Sertoli cells were prepared, according to Fritz et al. (1976),
