PubMed Health⌕ Search

Biomedical subjects

J Mester

Publications and source records attributed to J Mester.

At least 109 records · Page 6Linked to original sources
PubMed1984

Characterization of the estrogen receptor extracted from hen oviduct nuclei with pyridoxal phosphate.

The estrogen receptor was extracted in high yield from nuclei of laying hen oviduct with 10 mM pyridoxal-5'-phosphate (PLP). The receptor extracted under these conditions, unlike that extracted with 0.4 M KCl, displayed no tendency to aggregate on sucrose gradients in low salt. The receptor was eluted as a single peak from DEAE-Sephacel at an ionic strength of 0.13 M KCl. The receptor after DEAE chromatography had approximately half the molecular weight of that in the nuclear extract. A larger form could be reconstituted by the addition of whole nuclear extract to the DEAE eluate. These data support the notion that the nuclear estrogen receptor is a dimer composed of similar subunits.

Animals↗
PubMed1983

Effects of urea and molybdate on the chick oviduct progesterone receptor.

The chick oviduct cytosol progesterone receptor, when complexed with ligand, can be exposed to urea concentrations as high as 3 M (at 0 degrees C) without loss of steroid binding capacity. The ligand dissociation rate is increased greater than or equal to 10 fold under these conditions. The "native" 8 S form of the receptor is progressively converted to a 4 S species by urea (greater than 2 M) as seen in ultracentrifugation analysis. This conversion is inhibited by Na2MoO4 (5-50 mM) suggesting that molybdate stabilizes the 8 S molecule by direct interaction. At urea concentrations above 2 M, the ligand-free receptor looses progressively its binding capacity. The "transformed", 4 S receptor was less stable than the 8 S species, and could not be protected by molybdate.

Animals↗
PubMed1983

Protein kinase activity of purified components of the chicken oviduct progesterone receptor.

Preparations of the 90K and 110K components of the chick oviduct progesterone receptor (PR) purified to near homogeneity were tested for protein kinase activity. The 90K component was shown to incorporate radioactive phosphate from [gamma-32P]-ATP in the presence of Ca2+ but not of Mg2+ ions, while the 110K component was phosphorylated in the presence of Mg2+, but not of Ca2+. The enzymatic activity of the 90K polypeptide appeared selective, since added proteins (histones) did not become phosphorylated. However, all proteins present in the 110K preparations were phosphorylated in the presence of Mg2+. These data suggest that components of the chick oviduct PR display protein kinase activity.

Animals↗
PubMed1983

Temperature dependence of the dissociation rate constants for the nonactivated (molybdate-stabilized) and activated progesterone receptor-hormone complexes from the chick oviduct.

Both the nonactivated and activated forms of the chick oviduct cytosol progesterone receptor-hormone complexes displayed first-order dissociation kinetics at temperatures between 0 and 25 degrees C. The rate constant was always 2-3-times greater for the nonactivated than for the activated complex. The thermodynamic parameters calculated from the Eyring plot for the nonactivated and activated forms, respectively, were: delta H+ = 28.6 +/- 0.2 and 29.9 +/- 1.5 kcal/mol; -T delta S+ = 7.4 +/- 0.6 and 7.7 +/- 1.6 kcal/mol; and delta G+ = 21.3 +/- 0.5 and 22.1 +/- 0.1 kcal/mol. These values suggest that activation results in an increase in enthalpy of the ligand-receptor interaction, thus stabilizing the complex. The dissociation rate constants for the native complex obtained by two different experimental approaches, namely, isotope dilution ('chase') and dissociation against charcoal, indicated the absence of cooperativity in the receptor-ligand binding.

Animals↗
PubMed1982

Activation of the chick oviduct progesterone receptor by heparin in the presence or absence of hormone.

Activation (transformation) of the chick oviduct progesterone receptor was found to be induced at 0 degrees C by heparin free in solution as well as by chromatography on a column of heparin linked to acrylamide/agarose. The transformed molecule displayed properties of the activated form of [3H]progesterone-receptor complex obtained by heat treatment or by high ionic strength: smaller size (s20,w = 3.9 S, Stokes radius = 5.2 nm), lower rate of dissociation (t 1/2 approx. 50 h at 0 degrees C compared with approx. 20 h for the 'native' form) and increased binding to phosphocellulose. In all cases, molybdate was an effective inhibitor of transformation and stabilized a large 'native' form (s20,w = 7.9 S, Stokes radius = 7.6 nm). Transformation by neither KCl nor heparin depended on the presence of ligand bound to the receptor, and the properties of the receptor molecule produced by treatment of ligand-free receptor with high ionic strength or with heparin were identical with those of the activated progesterone-receptor complex, demonstrating that receptor activation can be obtained experimentally in the absence of hormone. Our data are compatible with a model in which activation implies separation of the 4 S units, which compose the approx. 8 S 'native' form.

Animals↗
PubMed1982

Physiologic and anthropometric aspects of vestibular regulation in rowing.

The role of the vestibular system during physical exercise has only been rarely analyzed by scientific investigations. An investigation was carried out with the purpose of obtaining information on vestibular regulation in rowers. The process of maintaining balance in the boat and the limiting factors were examined. Twenty beginners and 20 well-trained rowers participated in standardized vestibular tests in the laboratory as well as in the boat (single) on the water. The results suggest that several mechanisms in the physiologic field (torque of the body) are affected by training. The well-trained oarsmen showed a significant minor nystagmus frequency, and this criterion for general vestibular regulation also showed a relationship with the specific ability for maintaining balance in the boat.

Electronystagmography↗
PubMed1982

Progesterone receptor from chick oviduct: purification of molybdate-stabilized form and preliminary characterization.

A molydate-stabilized, 'non-activated' form of the progesterone receptor from the cytosol of oestrogen-stimulated chick oviduct has been purified to homogeneity by a three-step procedure. The first step, affinity chromatography using a N-(12-amino-dodecyl)-3-oxo-4-androsten-17 beta-carboxamide-substituted Sepharose gel, purified the receptor 1500-2700-fold with approximately equal to 50% recovery. In the second step, ion-exchange chromatography through a DEAE-cellulose column, progesterone receptor was eluted as a single peak at 0.1 M KCl. Purification after this step was greater than 6700-fold. The third step was filtration through Ultrogel AcA 34, resulting in overall purification approximately equal to 7400-fold with overall recovery approximately equal to 25% of pure receptor on the basis of 1 binding site/molecule of Mr 85000. The purified molybdate-stabilized receptor had a sedimentation coefficient approximately equal to 7.9S +/- 0.1 (n = 4) in 0.15 M or 0.4 M KCl containing sucrose 5-20% gradient and approximately equal to 8.9S +/- 0.2 (n = 6) in 0.15 M KCl containing glycerol 10-35% gradient, and its Stokes radius was 7.05 +/- 0.10 nm (n = 3) (calculated Mr between 240000 and 280000). Binding specificity of the purified receptor was the same as that found in crude cytosol. SDS-PAGE revealed a single band migrating as a polypeptide of Mr approximately equal to 85000 +/- 2300 (n = 9). PAGE under non-denaturing conditions at total acrylamide concentrations 5%, 7% and 9% showed a single [3H]ORG 2058-protein band (ORG 2058 is a high-affinity analogue more suitable than progesterone for electrophoretic studies). The data suggest that the high molecular weight molybdate-stabilized progesterone receptor purified from oestrogen-primed chick oviduct is composed of only approximately equal to 85000-Mr polypeptide chains.

Animals↗
PubMed1982

Combined effects of progesterone and tamoxifen in the chick oviduct.

Tamoxifen, an antiestrogen with no estrogenic effect on growth, differentiation, and egg white protein synthesis in the chick oviduct, has been administered together with progesterone. In estrogen differentiated, hormone-withdrawn animals, biochemical and ultrastructural data indicated that the combined treatment with progesterone plus tamoxifen increased conalbumin (+100%) and ovalbumin (+30%) more than progesterone alone and displayed estrogen-like growth-promoting properties (+50% in DNA content per oviduct). Moreover, when administered with progesterone and estradiol, tamoxifen lost part of its antiestrogenic activity. No obvious change of progesterone clearance from the blood or progesterone metabolism was recorded. The presence of progesterone in amounts similar to those resulting in optimal activity when injected alone (greater than or equal to 1 mg/kg) was necessary to obtain progesterone plus tamoxifen effects. The simultaneous presence of progesterone and tamoxifen was required in order to observe their combined effects, and it was observed that progesterone did not have to commit cells on which tamoxifen could subsequently act. In the immature "undifferentiated" oviduct, contrary to the effects of tamoxifen and progesterone alone, their combination induced cytodifferentiation of tubular gland cells which synthesized conalbumin and ovalbumin, an event never observed before in the absence of estrogen. These results support the suggestion that the hormonal milieu interferes with antiestrogen action.

Animals↗
PubMed1981

Early inhibition by progesterone of oestrogen-induced ornithine decarboxylase activity in the chick oviduct and rat uterus.

The oestradiol-induced increase of ornithine decarboxylase (ODC) activity in the 'withdrawn' chick oviduct was found to be inhibited by progesterone. In vitro (2 h at 37 degrees C), progesterone (1 mumol/l) abolished the effect of oestradiol (20 nmol/l), progesterone alone having no effect. In vivo, progesterone (3 mg/kg) inhibited approximately 70% of the augmentation of ODC activity induced in the oviduct within 2 to 6 h of treatment with oestradiol benzoate (1.5 mg/kg). Administration of progesterone alone in vivo caused an increase in the ODC activity, the maximum level measured after 6 h being similar to that obtained when the chicks were given both oestrogen and progesterone. In the rat uterus in vivo progesterone also inhibited the rise of ODC activity caused by oestradiol, approximately % inhibition being observed between 2 and 6 h after treatment. Progesterone alone had no effect on uterine ODC activity during this period.

Animals↗
PubMed1980

Steroid receptors and effects of oestradiol and progesterone on chick oviduct proteins.

After a single injection of oestradiol benzoate (1.5 mg/kg) to oestrogen-withdrawn chickens, there was an increase in magnum wet weight, DNA polymerase alpha activity, adenosine-3',5'-monophosphate-dependent protein-kinase activity and estrogen-receptor concentration, as measured over 36 h. Besides these intracellular proteins, the secretory proteins ovalbumin and conalbumin were also augmented, and detailed time-course studies were performed. Early induction kinetics for ovalbumin and conalbumin synthesis, which differed for each protein, were independent of the dose of oestradiol benzoate injected if it exceeded 0.1 mg/kg. After 6 h for ovalbumin and 2 h for conalbumin, the induction curves diverged according to the dose of hormone administered and in correlation with the persistence of elevated nuclear oestrogen-receptor concentrations, a result confirmed with 11 beta-methoxy-17 alpha-ethynyloestradiol (R 2858), a powerful synthetic oestrogen. When oestradiol benzoate (1 mg/kg) and progesterone (3 mg/kg) were injected simultaneously, the rate of conalbumin sythesis, during the first 6-8 h, was lower than that observed in animals injected with oestradiol benzoate alone. However at later times conalbumin synthesis was greater in animals receiving both hormones than with oestradiol alone. In contrast, the rate of ovalbumin synthesis after the combined injection was higher than that induced by either hormone alone throughout the entire experimental period. In order to study further the synergistic and antagonistic activities of these two hormones, a single injection of progesterone (3 mg/kg) was administered 6, 12 or 18 h after 1.5 mg/kg oestradiol benzoate. Progesterone administration resulted in a reduction in cytoplasmic, nuclear and total oestrogen receptor concentration for at least 6 h when compared with the values in birds treated with oestrogen alone. DNA polymerase and protein kinase activities were also reduced during this period. Subsequently, all parameters increased, and by 18-24 h after progesterone treatment, reached values higher than those observed in animals receiving oestrogen alone.

Animals↗
PubMed1979

[Effects of estradiol-7 alpha-butyric acid on hypothalamus cells].

When Rat uterus was incubated at 37 degrees with estradiol-7 alpha-butyric acid (OII-7 alpha-bu), no interference was observed with the intracellular estradiol receptors. In addition, OII-7 alpha-bu did not display estrogenic effect such as in vivo inhibition of LH secretion in Rat and in vitro increased activity of the enzyme ornithine-decarboxylase in the chick oviduct. Contrary to these negative findings, we have observed preoptic and septal cells in the guinea pig where micro-iontophoresis of OII-7 alpha-bu triggers changes of the electric activity within a second. We submit therefore, that this latter response is due to an interaction between the acid estrogen and the neuron membrane.

Animals↗