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Biomedical subjects

F F Rommerts

Publications and source records attributed to F F Rommerts.

At least 109 records · Page 6Linked to original sources
PubMed1979

Reversible interaction between androgen binding protein and testicular macromolecules causing inhibition of androgen binding activity.

Sertoli cells in culture isolated from immature rat testes secrete androgen binding protein (ABP) in the culture medium. Binding activity of ABP in concentrated medium was estimated with equilibrium dialysis against 1 nM dihydrotestosterone at 4 degrees C. The ABP protein activity was inhibited approximately 50% through addition of cytosol preparations from testis or liver, but not from brain tissue, to the concentrated culture medium; this inhibition remained constant for at least two days. The inhibitor is probably a macromolecule, because the activity could not be removed by charcoal treatment and dialysis. The percent inhibition of ABP binding activity was increased when increasing amounts of cytosol were added, it decreased in the presence of increased concentrations of androgens, but it was not influenced by variations of the concentration of ABP. Inhibition of androgen binding to ABP by cytosols in the presence of 1 nM testosterone could be reversed after dialysis in the presence of 10 nM testosterone. These results suggest a reversible competition between testosterone and the testicular macromolecule for ABP. The occurrence of this interaction between ABP and a testicular macromolecule can explain the variable results of estimated ABP binding activity in testis cytosol preparations.

Androgens↗
PubMed1979

Secretion of proteins, androgen binding protein and oestradiol by Sertoli cells in culture: effects of serum.

Effects of chicken- and foetal calf serum on secretion products of Sertoli cells have been investigated. At day 5 or 6 of culture, Sertoli cells incubated with 1% chicken serum secreted significantly more androgen binding protein (ABP) than cells cultured in media without chicken serum. This effect of chicken serum was smaller than that of chicken serum together with FSH and testosterone. Addition of 1% chicken serum or foetal calf serum stimulated the incorporation of [3H]leucine in secreted proteins by Sertoli cells. Secretion of oestradiol-17 beta (Oe2) was stimulated by addition of foetal calf serum. However, chicken serum did not stimulate the secretion of Oe2 even in the presence of extra added testosterone. The nature of the compounds in the sera responsible for these effects is unknown, but the effects cannot simply be explained by the presence of FSH or androgens. The results indicate that compounds other than FSH and androgens may influence Sertoli cell function. Evidence has been obtained that a serum component with a molecular weight of less than 5000 may be involved in the stimulation of Oe2 production.

Androgens↗
PubMed1979

Morphological characteristics of male germ cells of rats in contact with Sertoli cells in vitro.

Fragments of seminiferous epithelium were prepared from 3-week-old rats. Although the Sertoli cells formed a monolayer, germ cells (spermatogonia and early spermatocytes) remained in association with them and were of normal ultrastructural appearance. Germ cells became completely separated from Sertoli cells after 3 weeks of culture in a chemically defined medium. The contact areas between Sertoli and germ cells were characterized by desmosome-like junctions while those between germ cells appeared to be pentalaminar.

Animals↗
PubMed1977

Ribonucleic acid synthesis in vitro in primary spermatocytes isolated from rat testis.

The incorporation of [(3)H]uridine into RNA was studied quantitatively (by incorporation of [(3)H]uridine into acid-precipitable material) and qualitatively (by phenol extraction and electrophoretic separation of RNA in polyacrylamide gels) in preparations enriched in primary spermatocytes, obtained from testes of rats 26 or 32 days old. The rate of incorporation of [(3)H]uridine into RNA of isolated spermatocytes was constant during the first 8h of incubation, after which it decreased, but the decreased rate of incorporation was not reflected in a marked change in electrophoretic profiles of labelled RNA. In isolated spermatocytes, [(3)H]uridine was incorporated mainly into heterogeneous RNA with a low electrophoretic mobility. Most of this RNA was labile, as shown when further RNA synthesis was inhibited with actinomycin D. Spermatocytes in vivo also synthesized heterogeneous RNA with a low electrophoretic mobility. A low rate of incorporation of [(3)H]uridine into rRNA of isolated spermatocytes was observed. The cleavage of 32S precursor rRNA to 28S rRNA was probably retarded in spermatocytes in vitro as well as in vivo. RNA synthesis by preparations enriched in early spermatids or Sertoli cells was qualitatatively different from RNA synthesis by the spermatocyte preparations. It is concluded that isolated primary spermatocytes maintain a specific pattern of RNA synthesis, which resembles RNA synthesis in spermatocytes in vivo. Therefore isolated spermatocytes of the rat can be used for studying the possible regulation of RNA synthesis during the meiotic prophase.

Animals↗
PubMed1977

Analysis of androgen-binding protein in media from sertoli cell incubations and cytosols from rat testes.

Binding ability of androgen-binding protein (ABP) in concentrated media from Setoli cell cultures and in various preparations of cytosols from rat testicular tissue have been estimated using dialysis and polyacrylamide gel electrophoresis (PAGE). Equilibrium dialysis in the presence of 1 nM-17beta-hydroxy-5alpha-androstan-3-one appears to be the most convenient and reliable method for estimation of ABP if no other binding proteins are present. PAGE can be applied for estimation of ABP in samples which also contain other steroid-binding proteins. Estimated binding activities in culture media measured by PAGE and dialysis were essentially similar. Binding of androgens to ABP estimated with PAGE in cytosols prepared after sonication of testicular tissue was much lower than in cytosols obtained after homogenization using a Potter-Elvehjem homogenizer. When ABP was added to cytosols prepared after sonication or homogenization, approximately 50 and 90% respectively of the original binding of androgens to ABP was recovered.

Animals↗
PubMed1976

Physiological role for androgen binding protein-steroid complex in testis?

The concentration of unbound androgens in the lumen of rat testis seminiferous tubules is not dependent on the presence of the extra-cellular androgen binding protein (ABP); other parameters such as permeability properties, fluid dynamics and metabolic activities in different testicular compartments appear to have a much greater influence. It has been shown that in other target tissues the metabolic effects of steroids on cells depend on the concentration of the steroids which are not bound to extra-cellular proteins. It is therefore unlikely that the physiological function of ABP is related to the accumulation of androgens around germinal cells.

Androgens↗
PubMedDate not supplied

The regulation of the proliferation and differentiation of rat Leydig cell precursor cells after EDS administration or daily HCG treatment.

The proliferation and differentiation of possible Leydig cell precursors in adult rats were studied after destruction of the existing Leydig cells with EDS or after daily treatment with hCG. After 2 days with either treatment, a 12- to 16-fold increase in the number of [3H]thymidine-incorporating interstitial cells was found. In the case of hCG treatment, this was probably due to the high plasma hCG levels. However, after EDS treatment, LH levels start to rise between days 1 and 3, suggesting a paracrine stimulation of the proliferation of interstitial cells. After hCG treatment, a substantial increase in the numbers of Leydig cells was already found at day 2. It was concluded that hCG induced a rapid differentiation, without cell division, of existing precursor cells into recognizable Leydig cells. In rats treated with both EDS and hCG, new Leydig cells were not formed during the first 10 days. This indicates that EDS destroys not only mature Leydig cells but also those Leydig cell precursors that are able to differentiate rapidly into recognizable Leydig cells.

Animals↗
PubMedDate not supplied

Stimulation of the proliferation and differentiation of Leydig cell precursors after the destruction of existing Leydig cells with ethane dimethyl sulphonate (EDS) can take place in the absence of LH.

In hypophysectomized rats, 2 days after the administration of the cytotoxic drug ethane dimethyl sulphonate (EDS), the proliferative activity of Leydig cell precursors increased six-fold. Thus, factors other than LH act locally to stimulate the proliferation of precursor cells after EDS. Twenty-six days after EDS administration, neither cells with the morphological characteristics of Leydig cells nor histochemical enzyme activities, such as 3 beta-HSD and alpha-naphtyl esterase, could be detected in testis tissue. In hypophysectomized rats treated daily with hCG (100 iu) for 7 days, starting at 26 days after EDS, the number of Leydig cells was increased to 48 +/- 11 cells (per 1000 Sertoli cells), which is approximately 4.5% of the intact control level. 3 beta-HSD and alpha-naphtyl esterase activity could be detected, and plasma testosterone levels had increased 15-fold compared with the hypophysectomized controls. These results show that proliferation and some differentiation of precursor cells along the Leydig cell lineage can occur independent of LH, but the final stages of the differentiation process require hCG stimulation.

Animals↗