Estrogen Induction Of Biotin-Binding Protein In Immature Chicks - Kinetics, Hormonal Specificity And Modulation

Employing a specific radioimmunoassay for quantification, the kinetics of estrogen-induced elevation in the plasma concentration of biotin-binding protein (BBP) in immature male chicks was investigated. A single injection of the steroid hormone enhanced the plasma BBP content several-fold at 6 h, reaching peak levels around 48 h and declining thereafter. A 2-fold amplification of the response was evident during secondary stimulation with the hormone. The magnitude of the response was hormonal dose-dependent while the initial lag phase and the time of peak protein accumulation were unaltered within the hormonal doses tested. The circulatory half-life of the specific protein in normal and estrogenized birds was 10 h. Hyperthyroidism markedly decreased the hormonal response while the opposite effect was seen during hypothyroidism. The antiestrogens E- and Z-clomiphene citrate effectively blocked the protein induction whereas progesterone, either alone or in combination with estrogen, was ineffective in modulating the induction. Cycloheximide administration drastically inhibited the inductive response. The above observations clearly suggest that the genes corresponding to the two isofunctional proteins of chicken egg, viz. BBP and avidin, are differentially regulated.

Hormonal induction of riboflavin carrier protein in the chicken oviduct and liver: a comparison of kinetics and modulation

Estrogen (E) induction of riboflavin carrier protein (RCP) in the chicken oviduct and liver was investigated to compare and contrast the kinetics, hormonal specificity and modulation of its elaboration in the 2 steroid-responsive tissues. During primary stimulation, continued daily E administration to immature female chicks elicited, after an initial lag, rapid growth and RCP content of the oviduct; neither progesterone (P) nor testosterone (T) could substitute for E in this respect. Furthermore, P given along with E curtailed tissue growth and its RCP content, whereas E + T had a synergistic effect on tissue growth only. During secondary stimulation, E administration steeply enhanced both tissue weight and RCP content without any lag. Interestingly, P (but not T) could substitute for E in augmenting magnum RCP concentration to a comparable extent while a concomitant effect on tissue growth was less marked. In contrast, hepatic induction of RCP was absolutely E-specific during both primary and secondary stimulations. Secondary stimulation with either E or P of E-primed birds enhanced the rates of RCP synthesis in the oviduct relative to that of total protein, whereas in the liver only E was effective in this regard. The absolute rate of E-induced RCP synthesis in both the steroid-stimulated tissues was significantly higher than that of general protein elaboration.

Induction of riboflavin-carrier protein in the immature male rat by estrogen: kinetic and hormonal specificity

The kinetics of estrogen-induced accumulation of riboflavin-carrier protein in the plasma was investigated in immature male rats using a specific and sensitive homologous radio-immunoassay procedure developed for this purpose. Following a single injection of the steroid hormone, plasma riboflavin-carrier protein levels increased markedly after an initial lag period of approximately 24 h, reaching peak levels around 96 h and declining thereafter. A 1.5 fold amplification of the inductive response was evident on secondary stimulation with the hormone. The magnitude of the response was dependent on hormonal dose, whereas the initial lag phase and the time of peak riboflavin-carrier protein induction were unaltered within the range of the steroid doses (0.1–10 mg/ kg body wt.) tested. Simultaneous administration of progesterone did not affect either the kinetics or the maximum level of the protein induced. The hormonal specificity of this induction was further adduced by the effect of administration of antiestrogens viz., En and Zu chlomiphene citrates, which effectively curtailed hormonal induction of the protein. That the induction involvedde novo-protein synthesis was evident from the complete inhibition obtained upon administration of cycloheximide. Passive immunoneutralization of endogenous riboflavin-carrier protein with antiserum to the homologous protein terminated pregnancy in rats confirming the earlier results with antiserum to chicken riboflavin-carrier protein.

Estrogen-induced synthesis of riboflavin-binding protein in immature chicks kinetics and hormonal specificity

The kinetics of estrogen-induced elevation in the plasma concentration of riboflavin-binding protein, a minor yolk constituent, was investigated in immature male chicks, using a specific and sensitive radioimmunoassay proceudre. Following a single injection of the hormone, the plasma riboflavin-binding protein content was enhanced several-fold at 6 h. reaching peak levels around 48 h and declining thereafter. A two-fold amplication of the response was evident on secondary stimulation with the hormone. A 4-h lag phase prior to onset of induction was noticed during both primary and secondary stimulat ions with the steroid hormone. The magnitude of the response was dependent on the hormonal dose whereas the initial lag phase and the time of peak riboflavin-binding protein accumulation were unaltered within the range of hormonal doses tested. The half-life of riboflavin-binding protein in the circulation was 10 h, as calculated from measurement of the rate of disappearance of exogenously administered 125I-labelled protein. Simultaneous administration of progestrone did bot affect the kinetics of riboflavin-binding protein production. On the other hand, the antiestrogens, cis- and trans-clomiphene citrates, given 30 min prior to estrogen and cycloheximide, effectively countered the hormone-induced riboflavin-binding protein elaboration. Both progesterone and the anti-esterogens per se were completely ineffective in substituting for estrogen in the inductive ptrocess.

Oestrogen-induced synthesis of thiamin-binding protein in immature chicks. Kinetics of induction, hormonal specificity and modulation

A specific radioimmunoassay procedure was developed to monitor the plasma concentrations of thiamin-binding protein, a minor yolk constituent of the chicken egg. By using this sensitive assay, the kinetics of oestrogen-induced elaboration of this specific protein in immature chicks was investigated. After a single injection of the steroid hormone, with an initial lag period of 4–5h the thiamin-binding protein rapidly accumulated in the plasma, attaining peak concentrations around 75h and declining thereafter. A 4-fold amplification of the response was noticed during the secondary stimulation, and this increased to 9-fold during the tertiary stimulation with the steroid hormone. The magnitude of the response was dependent on the hormone dose, and the initial latent period and the duration of the ascending phase of induction were unchanged for the hormonal doses tested during both the primary and secondary stimulations. The circulatory half-life of the protein was 6h as calculated from the measurement of the rate of disappearance of the exogenously administered 125I-labelled protein. Simultaneous administration of progesterone, dihydrotestosterone or corticosterone did not alter the pattern of induction. On the other hand, hyperthyroidism markedly decreased the oestrogenic response, whereas propylthiouracil-induced hypothyroidism had the opposite effect. The anti-oestrogen E- and Z-clomiphene citrates, administered 30min before oestrogen, effectively blocked the hormonal induction. α-Amanitin and cycloheximide administered along with or shortly after the sex steroid severely curtailed the protein elaboration. A comparison of the kinetics of induction of thiamin- and riboflavin-binding proteins by oestrogen revealed that, beneath an apparent similarity, a clear-cut difference exists between the two vitamin-binding proteins, particularly with regard to hormonal dose-dependent sensitivity of induction and the half-life in circulation. The steroid-mediated elaboration of the two yolk proteins thus appears to be not strictly co-ordinated, despite several common regulatory features underlying their induction.

Hormonal modulation of riboflavin carrier protein secretion by immature rat Sertoli cells in culture

We report here that a protein species with biochemical and immunological similarity with chicken egg riboflavin carrier protein (RCP) is synthesized and secreted by immature rat Sertoli cells in culture. When quantitated by a specific heterologous radioimmunoassay, optimal concentrations of FSH (25 ng/ml) brought about 3-fold stimulation of RCP secretion. FSH, in the presence of testosterone (10−6 M) brought about 6-fold stimulation of secretion of RCP over the control cultures which were maintained in the absence of these two factors. The aromatase inhibitor (1,4,6-androstatrien-3,17-dione) curtailed 85% of the enhanced secretion of RCP, suggesting that the hormonal stimulation is mediated through in situ synthesized estrogen and this could be confirmed with exogenous estradiol-17 β which brought about 3 — fold enhancement of secretion of RCP at a concentration of 10−6 M. When tamoxifen (10 μM) was added along with FSH and testosterone, there was 75% decrease in the enhanced secretion of RCP. Addition of this anti-estrogen together with exogenous estradiol resulted in 55% decrease in elevated levels of RCP. Cholera toxin (1 μg/ml) and 8-bromo-cyclic AMP (0.5 mM) mimicked the action of FSH on the secretion of RCP thus suggesting that FSH stimulation of RCP production may be mediated through cyclic AMP. These findings suggest that estrogen mediates RCP induction in hormonally stimulated sertoli cells presumably to function as the carrier of riboflavin to the developing germ cells through blood-testis barrier in rodents.

Voltage gated Na+ channels contribute to membrane voltage fluctuation in \alpha T3-1 pituitary gonadotroph cells

\alpha T3-1 cells showed a slope resistance of 1.8 G\omega. The cell membrane surface was not smooth and a scanning electron micrograph showed a complex structure with blebs and microvilli like projections. The cells showed spontaneous fluctuations at zero current resting membrane potential and hyperpolarization increased the amplitude of membrane potential fluctuations. The amplitude of membrane potential fluctuations at hyperpolarized membrane potential was attenuated on application of TTX to the bath solution. The potential at which half steady state inactivation of isolated sodium current occurred, was at a very hyperpolarized potential (-95.4 mV). The study presented in this paper shows that the voltage gated sodium channels contribute to the increase in the amplitude of electrical noise with hyperpolarization in \alpha T3-1 cells.

An immunochemical study of ovine pituitary follicle-stimulating hormone (FSH)

An immunochemical study of ovine follicle-stimulating hormone and its antibody carried out by using precipitin, agglutinating and complement-fixation systems, has suggested that the follicle-stimulating hormone, possibly by virtue of it being a univalent antigen, forms a soluble complex with its specific antibody. This antiserum is species nonspecific in that it is able to neutralize the follicle-stimulating activity of rat, mouse, hamster, guinea pig pituitary extracts, and pregnant mare serum gonadotropin. Human chorionic gonadotropin, however, has been shown not to form a complex with the follicle-stimulating hormone specific antibody.

Effect of calcium deficiency on the mechanical properties of hydroxyapatite crystals

The deterioration of the mechanical properties of bone with age is related to several factors including the structure, organization and chemistry of the constituent phases; however, the relative contribution of each of these factors is not well understood. In this study, we have investigated the effect of chemistry (calcium deficiency) on the mechanical properties of single crystals of hydroxyapatite. Single crystals of stoichiometric crystals grown by the flux method and calcium-deficient platelet crystals grown using wet chemical methods were used as model systems. Using nanoindentation, we show that calcium deficiency leads to an 80% reduction in the hardness and elastic modulus and at least a 75% reduction in toughness in plate-shaped hydroxyapatite crystals. Measurement of local mechanical properties using nanoindentation and nanoscale chemistry through elemental mapping in a transmission electron microscope points to a direct correlation between the observed spatial variation in composition and the large scatter in the measured hardness and modulus values. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The ability of prolactin to change the sensitivity of the pituitary of the lactating rat to luteinising hormone releasing hormonein vitro

The ability of prolactin to influence the responsiveness of the lactating rat pituitary to luteinising hormone releasing hormone has been examinedin vitro. The pituitary responsivenessin vivo to luteinising hormone releasing hormone decreased as a function of increase in the lactational stimulus. Prolactin inhibited the spontaneousin vitro release of luteinising hormone and follicle stimulating hormone to a small extent, from the pituitary of lactating rats with the suckling stimulus. However, it significantly inhibited the release of these two hormones from luteinising hormone releasing hormone-stimulated pituitaries. The responsiveness of pituitaries of rats deprived of their litter 24 h earlier, to luteinising hormone releasing hormone was also inhibited by prolactin, although minimal. It was concluded that prolactin could be influencing the functioning of the pituitary of the lactating rat by (a) partially suppressing the spontaneous release of gonadotropin and (b) inhibiting the responsiveness of the pituitary to luteinising hormone releasing hormone.

H I deficiency in cluster spiral galaxies - Dependence on galaxy size

From the available H I data on spiral galaxies in three rich Abell clusters and the Virgo Cluster, it is shown that galaxies with medium to large optical sizes tend to be more severely deficient in atomic hydrogen than the small galaxies. This is so both in terms of the fractional number of galaxies that are deficient and the amount of gas lost by a galaxy. The fraction of H I-deficient galaxies increases with size over most of the size range, saturating or dropping only for the largest galaxies. A comparative study is made of various currently accepted gas removal mechanisms, namely those which are a result of galaxy-intracluster medium interactions, e.g., ram pressure stripping, as well as those due to galaxy-galaxy interactions, i.e., collisions and tidal interactions. It is shown that, with the exception of tidal interactions, all of these mechanisms would produce a size dependence in H I deficiency that is the opposite of that observed. That is, the gas in the largest galaxies would be the least affected by these mechanisms. However, if there is significant mass segregation, these processes may give the trends observed in the size dependence of H I deficiency.

Oestrogen-induced synthesis of thiamin-binding protein in immature chicks. Kinetics of induction, hormonal specificity and modulation

A specific radioimmunoassay procedure was developed to monitor the plasma concentrations of thiamin-binding protein, a minor yolk constituent of the chicken egg. By using this sensitive assay, the kinetics of oestrogen-induced elaboration of this specific protein in immature chicks was investigated. After a single injection of the steroid hormone, with an initial lag period of 4–5h the thiamin-binding protein rapidly accumulated in the plasma, attaining peak concentrations around 75h and declining thereafter. A 4-fold amplification of the response was noticed during the secondary stimulation, and this increased to 9-fold during the tertiary stimulation with the steroid hormone. The magnitude of the response was dependent on the hormone dose, and the initial latent period and the duration of the ascending phase of induction were unchanged for the hormonal doses tested during both the primary and secondary stimulations. The circulatory half-life of the protein was 6h as calculated from the measurement of the rate of disappearance of the exogenously administered 125I-labelled protein. Simultaneous administration of progesterone, dihydrotestosterone or corticosterone did not alter the pattern of induction. On the other hand, hyperthyroidism markedly decreased the oestrogenic response, whereas propylthiouracil-induced hypothyroidism had the opposite effect. The anti-oestrogen E- and Z-clomiphene citrates, administered 30min before oestrogen, effectively blocked the hormonal induction. a-Amanitin and cycloheximide administered along with or shortly after the sex steroid severely curtailed the protein elaboration. A comparison of the kinetics of induction of thiamin- and riboflavin-binding proteins by oestrogen revealed that, beneath an apparent similarity, a clear-cut difference exists between the two vitamin-binding proteins, particularly with regard to hormonal dose-dependent sensitivity of induction and the half-life in circulation. The steroid-mediated elaboration of the two yolk proteins thus appears to be not strictly co-ordinated, despite several common regulatory features underlying their induction.

Hemiorchidectomy leads to dramatic and immediate alterations in pituitary follicle-stimulating hormone secretion and the functional activity of the remaining testis in the adult male bonnet monkey (Macaca radiata)

The aim of the present study was to examine the effect of hemiorchidectomy (HO) on serum FSH, LH, testosterone (T), and inhibin (INH) concentrations as well as on the testicular volume (TV) and on changes in the kinetics of germ cell turnovers in the remaining testis of adult male bonnet monkeys. Blood samples collected at 2200 h at various times before and after HO and testicular biopsies obtained at different periods were subjected to hormone analysis and DNA flow cytometry. Though serum T levels were lowered (p < 0.05) at 12 h after HO, T levels rapidly returned to intact control concentrations by Day 5. While serum LH remained unaltered, serum FSH increased markedly within 2 days of HO and remained significantly (p < 0.05) elevated over the next 90 days. Though serum INH showed a significant decrease (p < 0.05) by 15 min of HO, it returned to approximately 80% of intact levels within one week. The TV of the remaining testis showed maximal increment by Day 30 (p < 0.05) of HO. DNA flow cytometric analysis 24 days after HO showed increases (p < 0.05) in spermatogonia (2C) and primary spermatocytes (4C). These cell types by Day 45 had transformed to round (1C) and elongate (HC) (by 38%, p < 0.001) spermatids. Overall spermatogenesis (conversion of 2C to 1C and HC) showed significant enhancement at Days 110 and 175, suggesting that the spurt in spermatogenic activity is not confined to a single spermatogenic cycle.