bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the mechanism of the selective suppression of plasma levels of follicle-stimulating hormone in the female rat after administration of steroid-free bovine follicular fluid
Authors: de Greef W. J. , de Jong F. H. , de Koning J. , Steenbergen J. , van der Vaart P. D. M. 
Published: December 2008

Steroid-free bovine follicular fluid (bFF) selectively suppresses the plasma levels of FSH in the female rat, demonstrating that bFF contains inhibin-like material. The present study was concerned with the effects of bFF on the hypothalamic release of LH releasing hormone (LH-RH) into hypophysial stalk blood and on the metabolic clearance rates of gonadotrophins.
The metabolic clearance rates of FSH, LH and prolactin were determined after a single injection of and during a constant infusion with adenohypophysial extract. Similar results were obtained with both methods, and treatment with bFF did not alter the metabolic clearance rates of FSH, LH and prolactin.
Anaesthesia with urethane, used for surgery involved in the collection of hypophysial stalk blood, did not interfere with the effect of bFF on plasma levels of FSH. The administration of bFF did not change the hypothalamic content of LH-RH, but caused a 30% decrease in the levels of LH-RH in hypophysial stalk plasma. However, a fraction isolated from bFF, which contained 20 times more inhibin-like activity per mg protein than bFF, did not alter the hypothalamic release of LH-RH into the hypophysial portal blood while this fraction was effective in specifically suppressing the plasma levels of FSH.
It was concluded that the inhibin-like activity in bFF does not suppress the plasma levels of FSH by affecting its plasma clearance or by influencing the hypothalamic release of LH-RH, but that it has a direct effect on the adenohypophysis in inhibiting the release of FSH. Besides the inhibin-like activity, bFF also contains another factor which can decrease the levels of LH-RH in hypophysial stalk plasma.
Postnatal developmental pattern of thyrotrophin releasing hormone-degrading activity in rat plasma, hypothalamus and liver: role of tri-iodothyronine
Authors: Aratan-Spire Sonia , Moilanen Kari , Czernichow Paul 
Published: December 2008

Thyrotrophin releasing hormone-degrading activity (TRH-DA) is present in plasma, hypothalamus, pituitary gland, liver and kidney of adults of several species. Each of these tissues contains more than one TRH-degrading enzyme but only one, pyroglutamate aminopeptidase, isolated from the blood, is a TRH-specific enzyme.
The aim of this study was to describe the developmental pattern of TRH-DA in the plasma, hypothalamus and liver and the role of tri-iodothyronine (T3) in the development of TRH-DA in the rat. Based on the hypothesis that thyroid hormones stimulate plasma TRH-DA in adult rats, degradation of TRH was studied in hypo- or hyperthyroid rats induced by 6-n-propyl-2-thiouracil or T3 respectively.
Tritiated TRH was incubated with plasma and homogenates of hypothalamus or liver. After separation of degradation products by thin-layer chromatography, the amount of degraded [3H]TRH (pmol/50 μl plasma or homogenate) was taken as a comparative index of TRH-DA.
Plasma TRH-DA was not detectable before day 9 while hypothalamic and hepatic TRH-DA was already active at birth. Furthermore, the maturation pattern of total TRH-DA was different in plasma compared with other tissues and T3 appeared to play a significant role in its development.
The absence of plasma TRH-DA in the neonatal period, its special thyroid-dependent developmental pattern and the presence of a specific TRH-degrading enzyme in adult blood suggest a physiological regulatory role for this activity.
Hormonal regulation of immunoglobulins and plasma cells in the mouse uterus
Authors: Canning M. B. , Billington W. D. 
Published: December 2008

Immunoperoxidase staining techniques were used to identify secreted immunoglobulin G (IgG) and IgA and the distribution of IgG- and IgA-producing cells in the uteri of mice during the oestrous cycle or after ovariectomy followed by the administration of ovarian hormones.
The most extensive staining for IgA and IgG in the myometrium and endometrium occurred during pro-oestrus and plasma cells of both isotype were concentrated around the uterine glands and lumen in high numbers at this time. Staining for IgA and IgG was least prominent during dioestrus, the stage of the oestrous cycle when plasma cells were present in the lowest numbers. After ovariectomy and hormone treatment, the highest numbers of uterine plasma cells were seen in mice injected with oestradiol alone and the lowest in those injected with progesterone alone. In mice treated with both hormones the number of plasma cells was comparable to that seen in mice treated with progesterone alone.
These results indicate that oestradiol plays a significant role in regulating uterine IgA and IgG and suggest that the increase in the numbers of plasma cells during the oestrous cycle is due to the action of oestradiol at the uterine level.
Effect of adrenalectomy on the regulation of ovarian function during lactation in the rat
Authors: de Greef W. J. , van der Schoot P. 
Published: December 2008

Corpora lutea formed after post-partum ovulation in the rat become functionally active under the influence of prolactin released as a result of suckling. During this period of luteal activity (lactational pseudopregnancy) ovulations do not occur. Despite continued suckling plasma prolactin declines gradually during lactation but this gradual decrease was not observed when adrenalectomy was performed on day 2 of lactation. The prolongation of lactational pseudopregnancy after adrenalectomy is probably associated with this observation. Daily treatment of adrenalectomized lactating rats with 5 mg corticosterone acetate, but not with 1·5 mg, reduced the duration of lactational pseudopregnancy to that of controls.
Removal of litters of five pups on day 13 of lactation was followed by resumption of ovulation 3 days later in control animals. However, in adrenalectomized rats the interval between removal of the five-pup litter and the next ovulation was prolonged to 10 or more days because of the persistence of luteal activity. This prolonged interval in adrenalectomized rats was not caused by an acute effect of the absence of adrenal hormones since it was not observed in rats which had been adrenalectomized 3 days before removal of the litter. Furthermore, the increase in the interval between removal of the five-pup litter and resumption of ovulation was also not due to the absence of the main glucocorticoid in the rat, since daily treatment with corticosterone from the day of adrenalectomy failed to prevent the occurrence of the long delay. Adrenal transplants could, however, prevent the effect induced by adrenalectomy. Since the medulla of these transplants had become necrotic, it seems that factors of adrenocortical, but not of adrenal medullary origin, are important in preventing the occurrence of the prolonged interval.
It is concluded that the adrenal glands affect the regulation of prolactin secretion during lactation and, as a consequence, are important in establishing the duration of the anovulatory state during lactation.
Thyroxine binding and cellular metabolism of thyroxine in mononuclear blood cells from patients with anorexia nervosa
Authors: Kvetny J. 
Published: December 2008

Nuclear binding of thyroxine (T4), cellular deiodination of T4 and nuclear accumulation of endogenous tri-iodothyronine (T3) were investigated in mononuclear blood cells from eight patients with anorexia nervosa.
Although the patients were euthyroid, serum T3 was depressed and serum reverse T3 increased. The nuclear maximal specific binding capacity (msbc) for T4 in cells from patients with anorexia nervosa was increased (2·4 × 10−16 mol T4/10 μg DNA, P<0·01) as compared to that of normal subjects (msbc = 1·1 × 10−16 mol T4/10 μg DNA), whereas the equilibrium association constant did not differ from that of normal subjects (Ka = 2·2 × 109 vs 3·0 × 109l/mol).
Cellular deiodination of T4 was significantly depressed (Vmax = 4·0 × 10−17 mol iodine/106 cells per min) as compared to that of normal subjects (Vmax = 2·0 × 10−16 mol iodine/106 cells per min), whereas nuclear accumulation of endogenous T3 was normal (Vmax = 3·0 10−19 mol T3/10 μg DNA per min).
Three patients started to gain weight and, concomitantly with the normalization of serum T3, the nuclear T4 capacity returned to normal. Cellular deiodination of T4 did not normalize within the observation period.
In conclusion, patients with anorexia nervosa, in which serum T3 is depressed, have an increased capacity of nuclear T4 receptors. The cellular 5' deiodinase is inhibited but nuclear accumulation of endogenous T3 is normal.
Hormonal changes in the immature rat after administration of pregnant mare serum gonadotrophin: influence of body weight
Authors: Wilson C. A. , ter Haar M. B. , Bonney R. C. , Buckingham J. , Dixson A. F. , Yeo T. 
Published: December 2008

We have shown previously that pregnant mare serum gonadotrophin (PMSG) induces ovulation only in rats weighing over 60 g on the day of injection. The under-60 g rats do not ovulate although they secrete a preovulatory surge of a pleiomorphic form of LH. Presumably this pleiomorph is inactive.
Comparisons were made of plasma hormone concentrations in rats treated with PMSG that weighed over and under 60 g. The measurements were made on samples taken between 13.00 and 22.00 h on the day of the expected preovulatory LH surge. Prolactin and corticosterone levels were lower in the lighter group compared with the heavier group. A midday pulse of GH detected in the over-60 g animals did not occur in the under-60 g group. Levels of ACTH were slightly higher in the under-60 g rats and together with the low corticosterone concentrations indicate adrenal insensitivity. Oestradiol, progesterone and TSH concentrations were the same in the two groups. Since progesterone secretion is under LH control, the 'inactive' pleiomorphic form of LH must have steroidogenic activity. There was an indication that the under-60 g rats also secreted a pleiomorphic form of FSH.
Reports in the literature indicate that prolactin, corticosterone and GH have a positive modulatory influence on natural puberty. They may also influence precocious puberty induced by PMSG, since in the unresponsive under-60 g rat plasma levels of these three hormones were low. Perhaps the release of one or more of these hormones is dependent upon the physical maturity of the animal as represented by body weight.
Androgen 5α-reductase and 3α-hydroxysteroid dehydrogenase activities in ventral prostate epithelial and stromal cells from immature and mature rats
Authors: Orlowski J. , Bird C. E. , Clark A. F. 
Published: December 2008

To study androgen-mediated differentiation in the rat ventral prostate, we separated the two principal cell types (epithelial and stromal) derived from prostates of immature and mature rats on two continuous Percoll gradients. Cells were immediately placed in culture medium. Testosterone metabolism by the two prostatic cell types was evaluated using [3H]testosterone and quantifying the formation of 5α-[3H]dihydrotestosterone (5α-DHT) and 5α-[3H]androstane-(3α or 3β), 17β-diols. In epithelial cells from both immature and mature rat prostates the major testosterone metabolites were 5α-DHT and 5α-androstane-3α, 17β-diol. Stromal cells metabolized less testosterone than did the epithelial cells. Differences in the relative levels of the various metabolites were observed for the two age groups.
To examine in more detail the changes in testosterone metabolism observed in vitro both types of cells and unfractionated cells from immature and mature rat prostates were assayed for testosterone 5α-reductase (using testosterone as substrate) and 3α-hydroxysteroid dehydrogenase (using 5α-DHT as substrate) activities (expressed as pmol substrate reduced/min per 106 cells). In immature rats both 5α-reductase and 3α-hydroxysteroid dehydrogenase activities were localized in the epithelial cell fraction (17 and 52 respectively); stromal cells showed lower 5α-reductase and 3α-hydroxysteroid dehydrogenase activity (4 and 4). Relative to epithelial cells from immature rats epithelial cells from mature rats showed a decrease in 5α-reductase (7) and an increase in 3α-hydroxysteroid dehydrogenase (160) activity while stromal 5α-reductase showed little change (3) and 3α-hydroxysteroid dehydrogenase increased to 22. Because there are more epithelial than stromal cells in the rat prostate, the former can be considered important sites for 5α-reductase and 3α-hydroxysteroid dehydrogenase activities. This contrasts with the human prostate where there is more 5α-reductase activity in the stroma than in the epithelium.
Inhibition of DNA synthesis in dermal tissue of Merino sheep treated with depilatory doses of mouse epidermal growth factor
Authors: Panaretto B. A. , Leish Z. , Moore G. P. M. , Robertson D. M. 
Published: December 2008

ABSTRACT
Two groups of three Merino wethers were infused intravenously with either 0·12 mg mouse epidermal growth factor (mEGF)/kg fleece-free body weight or 0·9% (w/v) NaCl over 24 h. Sheep treated with mEGF rejected food during treatment but feed intake was kept equal for both groups.
Wool growth and plasma concentrations of mEGF were measured during the experiment. Pieces of skin taken from the wool-growing regions of the body were incubated with radioactive thymidine in order to measure its rate of incorporation into DNA. The skin was then divided at about the level of the sebaceous glands into sections that contained the upper dermis and epidermis (E sections) and those containing the generative wool-follicle bulbs (D sections).
No mEGF was detected in the controls whereas mean levels of about 35 μg mEGF/l plasma were detected during the last 4 h of infusion in the protein-treated group. After infusion, wool growth was reduced by about 20% of the mean pretreatment level in the controls and no shedding of wool fibre was evident. In the mEGF-treated sheep, on the other hand, wool growth was depressed by 75–95% of the mean pretreatment level and the fleeces were almost completely cast in all three of the animals, leaving them nude on the wool-growing regions of the body. Wool growth was restored to its pretreatment level in this group about 1 month after infusion.
The D sections of skin contributed 50–60% of skin wet weight in controls throughout the experiment. In the mEGF group, however, E sections increased in weight by about 25% and D sections decreased by 25%, relative to pretreatment values, during the 2 weeks after infusion. Both skin sections contributed equally to skin weight thereafter.
Whereas the DNA content of E sections tended to increase after mEGF treatment there was a loss of 40%, relative to pretreatment values, in the DNA content of D sections. A significant decrease in thymidine incorporation into DNA in D sections was found, which lasted for at least 72 h after the start of infusion. Thymidine incorporation into E sections was raised during this period and again at about 10–14 days after infusion, when it was increased in both skin sections.
We have concluded that the inhibition of wool growth in the mEGF-treated animals was associated with the inhibition of DNA synthesis in the dermal skin sections which contain proliferating cells of wool follicles.
J. Endocr. (1984) 100, 25–31
Pituitary–testicular interrelationships during germinal involution in the vitamin A deficient rat
Authors: Huang H. F. S. , Zaidi P. , Nieschlag E. 
Published: December 2008

ABSTRACT
Pituitary–testicular relationships in mature male rats were investigated during the period of germinal involution after the induction of vitamin A deficiency (VAD).
Vitamin A deficiency caused a decrease in testicular weight, a gradual increase in the incidence of delayed spermiation, increased phagocytosis of spermatids and pyknosis of germ cell nuclei in rats aged 80 to 110 days. Both basal and gonadotrophin releasing hormone (GnRH)-stimulated serum FSH concentrations were increased by 100 days of age. During the same period, the per cent increment in GnRH-stimulated FSH secretion, pituitary FSH concentration and LH secretion remained unchanged. These results suggest that the increased serum FSH may mark specifically an alteration in the germinal epithelium. By 140 days of age, spermatogenic activity in the rats with VAD was limited to the spermatogonial proliferations so that only Sertoli cells, spermatogonia and preleptotene spermatocytes remained. At this time hypersecretion of FSH persisted while the per cent increment of GnRH-stimulated FSH secretion decreased. Concomitantly, basal and GnRH-stimulated LH concentrations were also increased in the presence of normal serum testosterone. These results indicate that a complete cessation of spermatogenesis beyond preleptotene spermatocytes is associated with a change in the secretion of both FSH and LH.
The relationship between serum LH and testosterone was normal until at least 110 days of age. By 140 days the ratio between basal LH and basal testosterone, and between total LH and total testosterone, after GnRH administration, increased in the rats with VAD. These changes may be caused by a hyporesponsiveness of the Leydig cells which may, in turn, be attributed to the cessation of spermatogenesis. J. Endocr. (1984) 100, 33–41
Induction of transient functional luteolysis in cyclic sheep by a 3 β-hydroxysteroid dehydrogenase inhibitor
Authors: Jenkin G. , Gemmell R. T. , Thorburn G. D. 
Published: December 2008

ABSTRACT
The mechanism by which prostaglandin F2α terminates luteal function in the sheep is unclear even though it is used extensively in animal husbandry. At the time of luteal regression, a decrease in 3β-hydroxysteroid dehydrogenase (3β-HSD) activity is apparent in the corpus luteum, but it is not known whether the decrease in enzyme activity is the primary cause of structural luteolysis. The effect of trilostane, a 3β-HSD inhibitor, on luteal function and morphology has therefore been investigated. Intravenous injection of trilostane in the mid-luteal phase of the oestrous cycle caused a decrease in ovarian tissue progesterone content. A transient decrease in peripheral and utero-ovarian vein plasma progesterone was observed but there was no significant effect on the length of the luteal phase of the cycle. There was no significant change in plasma 13,14-dihydro-15-oxo-prostaglandin F2α during the period when plasma progesterone was depressed. Morphological examination of the corpora lutea revealed a decrease in the concentration of electron-dense granules without any other features of impending luteal regression. When plasma progesterone was reduced for more than 10 h by two injections of trilostane 4 h apart, there was again no subsequent effect on the length of the oestrous cycle or on the return to oestrus. Plasma progesterone returned to preinjection levels within 24 h of injection. This evidence suggests that competitive inhibition of 3β-HSD activity, per se, is ineffective in bringing about structural luteolysis.
J. Endocr. (1984) 100, 61–66
Ovarian aromatase activity in the domestic fowl (Gallus domesticus)
Authors: Armstrong D. G. 
Published: December 2008

ABSTRACT
Fowl ovarian aromatase activity was measured by an assay based on the stereospecific elimination of tritium from [1,2-3H]testosterone. The production of tritiated water was shown to provide a valid estimate of aromatase activity under the conditions used.
The small yellow follicles and ovarian stroma contained 50% of the total ovarian aromatase activity. The activity in the thecal tissue from the rapidly growing follicles reached a maximum level in the fourth largest follicles (17% of the total ovarian activity) and thereafter declined to low levels in the largest follicle and first post-ovulatory follicle. No activity was detected in the granulosa tissue from the rapidly growing follicles.
It is proposed that the basal levels of plasma oestrogen in hens are maintained by production in the small yellow follicles and/or ovarian stroma. The variation in plasma oestrogen during the ovulatory cycle probably arises from secretion by the rapidly growing follicles.
J. Endocr. (1984) 100, 81–86
Sex differences in circadian control of LH secretion
Authors: Albers H. E. , Moline M. L. , Moore-Ede M. C. 
Published: December 2008

ABSTRACT
Sex differences in the hourly values of serum LH were examined in male and female Syrian hamsters exposed to either long photoperiods (14 h light: 10 darkness; 14L: 10D) or short photoperiods (6L: 18D). In long photoperiods, females exhibited a pro-oestrous surge of LH in response to high levels of circulating oestradiol (1047·36 ± 90·68 pmol/l), while LH values in male hamsters remained essentially constant. In females housed in short photoperiods oestradiol levels were reduced by fivefold; however, a discrete surge in serum LH, similar to that seen at pro-oestrus in females exposed to long photoperiods, was observed. Although exposure to a short photoperiod eliminates the requirement of a positive feedback of oestrogen for the expression of an afternoon surge in LH, male hamsters housed in short photoperiods showed no indication of an afternoon surge in serum LH. These observations indicate that sex differences in the neural control of LH release are not the result of sex differences in oestrogen sensitivity or responsiveness.
J. Endocr. (1984) 100, 101–105
Effect of insulin on glucose uptake by the maternal hindlimb and uterus, and by the fetus in conscious pregnant sheep
Authors: Hay W. W. , Sparks J. W. , Gilbert M. , Battaglia F. C. , Meschia G. 
Published: December 2008

ABSTRACT
Previous studies have demonstrated the presence of insulin receptors on the maternal surface of the placenta in several species and the specific binding of insulin to the placenta in sheep. However, both in-vitro and in-vivo studies have produced conflicting evidence concerning the effect of insulin on placental glucose uptake. To clarify this problem, we measured maternal hindlimb, uterine and fetal glucose and oxygen extractions and glucose/oxygen quotients in chronically catheterized, non-stressed, late-gestation pregnant sheep over 1 h at a constant concentration of arterial plasma glucose, and again during the next 2 h at the same glucose level but at a higher insulin concentration using glucose 'clamp' methodology. Insulin produced a 4·9-fold increase in glucose extraction and a 3·5-fold increase in glucose/oxygen quotient across the hindlimb; in contrast, insulin did not significantly affect uterine or fetal glucose extraction or glucose/oxygen quotient. We conclude that in contrast to other tissues of the pregnant ewe, placental glucose uptake and transfer are insensitive to variations in maternal insulin concentration.
J. Endocr. (1984) 100, 119–124