bluuebunny/crossref_metadata_2025_split huggingface dataset:
MATURATION OF THE INHIBITORY FEEDBACK ACTION OF OESTROGEN ON FOLLICLE-STIMULATING HORMONE SECRETION IN THE IMMATURE FEMALE RAT: A ROLE FOR ALPHA-FOETOPROTEIN
Authors: MEIJS-ROELOFS H. M. A. , KRAMER P. 
Published: December 2008

The maturation of the inhibitory feedback action of oestrogen on FSH secretion in the immature female rat was studied from 5 days of age until after the first ovulation. To study the role of the oestrogen binding alpha-foetoprotein (AFP) which is present in the blood of young animals, the effects of various doses of oestradiol and of the synthetic oestrogen R2858 (11β-methoxy-17-ethynyl-oestradiol), which is not bound by AFP, were compared in ovariectomized rats.
A rise in the serum concentration of FSH within 2 days of ovariectomy was first observed in rats ovariectomized at 8 days of age. Between 8 and 28 days of age the rise in FSH after ovariectomy could be prevented by oestrogen injections in such a way that the resulting FSH concentration amounted to 50% of that in ovariectomized control rats. This was achieved with a constant dose of 0·00015 μg R2858/100 g body weight, whereas the dose of oestradiol needed decreased from 0·05 to 0·01 μg/100 g body weight indicating an increased sensitivity to the feedback action of oestradiol. After day 28, sensitivity to the feedback action of both R2858 and oestradiol decreased progressively up to the time of the first ovulation.
In contrast to results at earlier ages, none of the doses of either oestrogen was capable of maintaining near-physiological concentrations of FSH after 20 days of age.
It is concluded that the apparent increase in sensitivity to the feedback action of oestradiol occurring before 28 days of age reflects the disappearance of AFP from the blood, whereas the subsequent decrease in sensitivity is independent of AFP. Moreover, it is concluded that up to about 20 days of age oestradiol could be, though not necessarily is, the sole ovarian factor involved in regulating FSH secretion, whereas at later ages additional steroids and/or factors must be involved.
PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE, FOLLICLE-STIMULATING HORMONE AND PROGESTERONE DURING THE BREEDING SEASON IN EWES IMMUNIZED AGAINST ANDROSTENEDIONE OR TESTOSTERONE
Authors: MARTENSZ N. D. , SCARAMUZZI R. J. 
Published: December 2008

Levels of plasma LH, FSH and progesterone during the breeding season were measured by radioimmunoassay in control ewes and ewes actively immunized against androstenedione-11α-hemisuccinyl–bovine serum albumin or testosterone-3(O-carboxymethyl)oxime–bovine serum albumin. Immunization against androstenedione resulted in normal oestrous cycles with raised plasma LH and progesterone levels and a reduction in the concentration of FSH during the luteal phase. It is tentatively suggested that androstenedione, or its metabolites, could modify the oestrogenic control of LH secretion and facilitate the release of FSH in the ewe.
Immunization against testosterone prevented oestrus and resulted in markedly increased levels of LH without alteration of the FSH concentration. Since evidence of increased binding of oestradiol-17β was found in the ewes immunized against testosterone, these results cannot be attributed solely to a reduction in the biologically active fraction of testosterone.
PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE DURING ANOESTRUS IN EWES ACTIVELY IMMUNIZED AGAINST OESTRADIOL-17β, OESTRONE OR TESTOSTERONE
Authors: MARTENSZ N. D. , SCARAMUZZI R. J. , VAN LOOK P. F. A. 
Published: December 2008

The concentrations of LH and FSH in jugular venous plasma were measured during anoestrus in control ewes and ewes actively immunized against 17β-oestradiol-6-(O-carboxymethyl)oxime–bovine serum albumin, oestrone-6-(O-carboxymethyl)oxime–bovine serum albumin or testosterone-3-(O-carboxymethyl)oxime–bovine serum albumin. During a 12 h sampling period, the basal level of LH and the frequency of LH pulses were significantly increased in all the immunized animals. The plasma FSH concentration was increased in two out of five oestradiol-immunized ewes and two out of three oestrone-immunized animals. The plasma FSH concentration in the testosterone-immunized animals was similar to the control values.
Significant titres of antibodies to oestradiol-17β were found in all the immunized animals. It is suggested that binding of oestradiol-17β in the circulation by antibodies reduced the negative feedback action normally exerted by this steroid on LH secretion and, to a lesser extent, on FSH secretion. However, since the oestradiol antibody titres in the testosterone-immunized and oestrone-immunized ewes were considerably lower than those found in the oestradiol-immunized animals, it is possible that testosterone and oestrone, perhaps by acting as prehormones, could influence the negative feedback control by oestradiol-17β of gonadotrophin secretion in the anoestrous ewe.
HYPERALDOSTERONISM IN THE SODIUM-DEPLETED RAT: MODE OF ALDOSTERONE-STIMULATING ACTION OF FRUSEMIDE
Authors: SPÄT A. , TARJÁN ÉVA , TÓTH G. 
Published: December 2008

SUMMARY
The mechanism of diuretic-induced hyperaldosteronism was examined in dexamethasone-pretreated rats. The diuretic drug frusemide brought about a rapid increase in plasma renin activity and aldosterone concentration in serum. Half an hour after the administration of frusemide the mean concentration of aldosterone was 25 times higher than in vehicle-treated control animals. Administration of SQ 20,881, an inhibitor of angiotensin converting enzyme, prevented the adrenal response to frusemide. The response of aldosterone was completely blocked by indomethacin. This drug reduced renin release and probably also inhibited the effect on the adrenal glands of angiotensin, released in response to frusemide. Our results indicate that the effects of diuretics on the adrenal glomerulosa cells are mediated by the renin–angiotensin system also in the rat. Hyperaldosteronism is dependent on the maintenance of prostaglandin synthesis. ACTH has no essential role in this response.
INHIBITORY ACTION OF FOLLICULAR FLUID ON PROGESTERONE AND PROSTAGLANDIN SYNTHESIS IN BOVINE FOLLICLES
Authors: SHEMESH MORDECHAI 
Published: December 2008

SUMMARY
The present studies examined the inhibitory effect of mid-cycle and preovulatory bovine follicular fluid (bFF) on the secretion of progesterone and prostaglandin F2α (PGF2α) by bovine theca and granulosa cells cultured in tissue culture Medium 199. The inhibitory effect of bFF on the secretion of PGF2α by incubated and cultured hemipituitary glands of male rats was also studied. Addition of 5, 10 or 20% charcoal-extracted, mid-cycle bFF to the culture medium caused a twofold decrease in the accumulation of both progesterone and PGF2α by the cultured granulosa cells (P < 0·01). In contrast, when preovulatory bFF was used, there was no inhibitory effect on secretion of progesterone and PGF2α. The addition of 10% mid-cycle bFF to the culture medium caused a two- to fourfold decrease in the accumulation of both PGF2α and progesterone by the cultured theca (P < 0·008). However, in the presence of 1 μg LH/ml, the inhibitory effect of mid-cycle bFF on progesterone and PGF2α secretion was abolished. The secretion of PGF2α was significantly (P < 0·03) decreased in male rat hemipituitary glands after 5 h of incubation or 18 h of culture. These findings suggest that bFF from mid-cycle follicles inhibits prostaglandin synthetase as well as luteinization. The inhibition disappeared with bFF from preovulatory follicles.
DISTRIBUTION AND DEGRADATION OF TWO TRITIUM-LABELLED CORTICOTROPHIN ANALOGUES IN THE RAT
Authors: BENNETT H. P. J. , McMARTIN COLIN 
Published: December 2008

SUMMARY
The distribution and degradation of corticotrophin-(1–24)-tetracosapeptide specifically labelled with tritium at Tyr2, Phe7 or Tyr23 and [d-Ser1, Lys17, Lys18]-corticotrophin-(1–18)-octadecapeptide amide labelled at Tyr2 were studied at various times after intravenous injection into rats. By characterizing the radioactivity in plasma and various tissues, an overall picture of the metabolic handling of the two peptides emerged. The peptides left the circulation rapidly, entering mainly muscle and skin where they were extensively degraded. The d-Ser1-containing analogue was less rapidly degraded and intact peptide persisted in muscle and skin for up to 1 h. This peptide probably returned to the circulation giving rise to the sustained plasma levels observed after injection of the d-Ser1-substituted octadecapeptide but not after injection of the tetracosapeptide. Although initially the kidneys did not clear such large amounts of peptide as did muscle and skin they played an important role by continuously and, on the basis of existing evidence, irreversibly clearing the peptides and peptide fragments from the circulation and degrading them.
LARGE-SCALE PREPARATION OF HIGHLY PURIFIED PYROGEN-FREE HUMAN GROWTH HORMONE FOR CLINICAL USE
Authors: JONES R. LUMLEY , BENKER G. , SALACINSKI P. R. , LLOYD T. J. , LOWRY P. J. 
Published: December 2008

SUMMARY
A method is described for the large-scale isolation of highly purified human growth hormone for therapeutic use. The hormone was extracted from frozen pituitary glands under mildly alkaline conditions. Purification was effected by gel filtration and ion-exchange chromatography. The final product was pyrogen-free and had a potency of 2·5 i.u./mg measured by bioassay against the current international standard. The yield of growth hormone/gland was approximately 5 mg.
OESTROGENIC EFFECTS OF CATECHOL OESTROGENS ON SECRETION OF PROLACTIN BY THE PITUITARY GLAND AND SYNTHESIS OF DNA BY THE MAMMARY GLAND IN OVARIECTOMIZED RATS
Authors: YANAI REIKO , NAGASAWA HIROSHI 
Published: December 2008

SUMMARY
The effects of 2-hydroxyoestradiol-17β and 2-hydroxyoestriol (2OH-OE3) on levels of serum prolactin, DNA synthesis by the mammary gland and the weight of the uterus were examined in ovariectomized Sprague–Dawley rats.
2-Hydroxyoestradiol-17β had a potent oestrogenic activity in stimulating the secretion of prolactin by the pituitary gland, the synthesis of DNA by the mammary gland and in increasing the weight of the uterus. On the other hand, 2OH-OE3 increased the weight of the uterus only.
BLOOD LEVELS OF SYNTHETIC GLUCOCORTICOIDS AFTER ADMINISTRATION BY VARIOUS ROUTES
Authors: MIYACHI YUKITAKA , YOTSUMOTO HIDEKI , KANO TAKASHI , MIZUCHI AKIRA , MUTO TETSUICHIRO , YANAGIBASHI KAZUYUKI 
Published: December 2008

SUMMARY
Using reliable radioimmunoassay methods, the concentrations of prednisolone, prednisolone-hemisuccinate, betamethasone and betamethasone-17-benzoate were determined after administration by various routes. Serum prednisolone and betamethasone concentrations increased to peak levels 2 h after oral administration and then decreased gradually. The half-times of disappearance of prednisolone and betamethasone from blood, after a single oral dose, were both approximately 180–220 min. Five to fifteen minutes after intramuscular injections of 20 mg prednisolone-hemisuccinate the peak serum concentration was 63·7 ± 7·4 μg/ 100 ml and 30 min later plasma unesterified prednisolone reached its highest level (28·8 ± 2·6 μg/100 ml). The administration of steroids through the rectum induced gradual increases in the levels of serum steroids, reaching a maximum of 25% of the peak serum concentrations observed after oral administration. Plasma betamethasone-17-benzoate levels of 300 ng/ 100 ml were observed after topical application of betamethasone-17-benzoate gel to the skin.
In patients with liver disease, the clearance of betamethasone was very slow compared with that in normal control subjects and significant amounts were retained in the blood 24 h after oral administration, showing that the liver is the most important organ for the metabolism of synthetic glucocorticoid. The concentrations of prednisolone and prednisolone-hemisuccinate in the cerebrospinal fluid were very low after the intramuscular injection of prednisolone-hemisuccinate, confirming the relative impermeability of the blood–brain barrier to polar steroids.
METABOLISM OF TESTOSTERONE AND 5α-REDUCED ANDROGENS BY THE RABBIT PROSTATE AND EPIDIDYMIS: STUDIES IN VITRO AND IN VIVO
Authors: BOOTH W. D. , JONES R. 
Published: December 2008

SUMMARY
The metabolism of radioactively labelled testosterone, 5α-dihydrotestosterone, 5α-androstane-3α,17β-diol and 5α-androstane-3β,17β-diol by the rabbit epididymis and prostate has been investigated in vitro and in vivo. In vitro, the rate of conversion of testosterone to 5α-reduced androgens was low in both glands. Varying the nature of the tissue preparation, age of animal or incubation medium did not improve the situation substantially. However, the rabbit prostate and epididymis metabolized 5α-reduced androgens readily. The prostate was particularly efficient at interconverting 5α-androstane-3α,17β-diol and 5α-dihydrotestosterone, whereas the capacity of the epididymis to carry out this step was much lower. Small amounts of 5α-androstane-3,17-dione and androsterone were also identified. Both glands interconverted 5α-dihydrotestosterone and 5α-androstane-3β,17β-diol to a comparable degree.
Following the intravenous injection of 3H-labelled testosterone, significant levels of 3H-labelled 5α-dihydrotestosterone were found in the prostate and epididymis within 30 min. Furthermore, 5α-androstane-3α,17β-diol was detected in both glands. In blood plasma, the ratio of radioactively labelled testosterone: 5α-dihydrotestosterone was 2: 1, i.e. similar to that for endogenous steroids. The intravenous injection of 3H-labelled 5α-androstane-3α-17β-diol gave rise to much higher amounts of 5α-dihydrotestosterone in the prostate than in the epididymis, whereas the reverse was found for the levels of unmetabolized diol.
The results indicate that the prostate and epididymis of the adult rabbit differ in their capacity to metabolize 5α-reduced androgens and that both glands depend to a large extent on the relatively high levels of 5α-dihydrotestosterone and 5α-androstanediols present in the peripheral circulation, rather than the metabolism of testosterone in situ.
A SENSITIVE AND SPECIFIC ASSAY FOR 5-METHOXYTRYPTOPHOL IN PLASMA
Authors: LEONE R. M. , SILMAN R. E. , HOOPER R. J. L. , FINNIE M. D. A. , CARTER S. J. , EDWARDS R. , SMITH I. , TOWELL P. , MULLEN P. E. 
Published: December 2008

SUMMARY
5-Methoxytryptophol (ML) is found in the pineal gland and is known to have biological activity especially as an antigonadotrophic agent, but methods have been lacking for its measurement in the circulation. A gas chromatography–mass spectrometry assay using a trimethylsilyl derivative has been developed for the routine measurement of ML in plasma. The assay is of great specificity and has a sensitivity of 20 pmol/l. Studies on the levels of pineal indoles in the circulation, however, have been hampered by the possibility that extraneous compounds are being cross-measured. Thus the specificity of the routine assay has been further validated by comparing it with an alternative assay system where all the major parameters were changed, i.e. derivatizing reagent, internal standard and mass number. Results that were obtained using both assay systems were closely comparable.
CHANGES IN THE CONCENTRATION OF 5-METHOXYTRYPTOPHOL IN THE CIRCULATION AT DIFFERENT PHASES OF THE HUMAN MENSTRUAL CYCLE
Authors: HOOPER R. J. L. , SILMAN R. E. , LEONE R. M. , FINNIE M. D. A. , CARTER S. J. , GRUDZINSKAS J. G. , GORDON Y. B. , HOLLAND DIANE T. , CHARD T. , MULLEN P. E. , SMITH I. 
Published: December 2008

SUMMARY
The pineal indole 5-methoxytryptophol (ML) has been shown to have an antigonadal activity when administered to experimental animals, but data on its normal pattern of secretion have been lacking. Using a new gas chromatography–mass spectrometry assay, the concentration of ML at various phases of the human menstrual cycle has been studied. Daily samples were obtained throughout the month from five women with a normal cycle and two women taking an oral contraceptive. In women with a normal cycle levels of ML were found to be significantly lower in the last third of their cycle; this change was not seen in women taking an oral contraceptive who had low levels throughout the month. The changes in concentration of ML did not correlate with the changes in concentration of gonadotrophins.
EFFECTS OF PROSTAGLANDIN E2 AND DIBUTYRYL CYCLIC AMP ON THE HISTAMINE-INDUCED PRODUCTION OF CORTISOL AND CORTICOSTERONE IN ISOLATED CANINE ADRENAL CELLS
Authors: HIROSE T. , MATSUMOTO I. , AIKAWA T. 
Published: December 2008

SUMMARY
The steroidogenic effect of histamine in isolated adrenocortical cells of the dog was investigated in the presence of prostaglandin E2 (PGE2) and/or dibutyryl cyclic AMP (dbcAMP) in the medium. The effect of histamine, in combination with PGE2, was less than their total individual effects in the production of cortisol, but not of corticosterone. With dbcAMP the effect was just equal to them. However, the combination of histamine, PGE2 and dbcAMP showed an increase twice that of their total individual effects in the production of both steroids. These results indicate that, in the dog, histamine, PGE2 and dbcAMP may act synergistically in the adrenocortical cells.
EPITESTOSTERONE IN THE PLASMA OF THE GOAT DURING PREGNANCY AND AT PARTURITION
Authors: FLINT A. P. F. , BURROW P. V. 
Published: December 2008

SUMMARY
Epitestosterone, a product of the metabolism of androstenedione by the caprine placenta in vitro, is present in the plasma of the pregnant goat. The maternal concentrations of both epitestosterone and unconjugated oestrogens (mostly oestradiol-17α) in the blood increased before parturition and dropped post partum. Measurement of arteriovenous differences at term indicated that epitestosterone was secreted by the uterus; its production was not dependent on the presence of corpora lutea. It is suggested that the concentration of epitestosterone (+ androstenedione + oestrogens) in maternal plasma may be used as an indicator of placental C-17,20 lyase activity; the slight rise in the concentration of these compounds prepartum suggests a relatively small increase in flow through this enzyme.
INFLUENCE OF ANDROGENS ON THE WEIGHTS OF THE MALE ACCESSORY REPRODUCTIVE ORGANS AND ON THE ACTIVITIES OF MITOCHONDRIAL ENZYMES IN THE EPIDIDYMIS OF THE RAT
Authors: BROOKS D. E. 
Published: December 2008

SUMMARY
The influence of androgens on the male accessory glands of the rat was assessed in terms of changes in weight and of the specific activity of the mitochondrial enzymes, succinate dehydrogenase, glycerolphosphate dehydrogenase and pyruvate carboxylase, in the epididymis. In some instances, the activity of the cytoplasmic enzymes, hexokinase and phosphofructokinase, was also measured and the influence of androgens on these enzymes was found to be similar to that on the mitochondrial enzymes. After the administration of androgen to castrated rats the specific activity of enzymes reached a new steady state sooner than did epididymal weight. The time taken for the specific activity of the enzymes to reach a new steady state after the removal of androgen was variable, depending on the enzyme and the region of the epididymis. This time was generally longer, however, than the time taken for induction, and in the case of glycerolphosphate dehydrogenase, the decline of activity was slower in the cauda than in the caput. In castrated animals, about 100 times as much androgen was required to attain maximum tissue weight as was required to attain maximum enzyme activity. The epididymis, prostate and seminal vesicles responded similarly to androgen in terms of the dose–response pattern and the time taken for tissue weight to attain a new steady-state value, although the gain in weight of the epididymis relative to its weight in unstimulated control animals was less than the relative gain of the other accessory glands. Enzymes in the cauda epididymidis required lower amounts of androgen to elicit maximum activity than were required by those in the caput. The rate of change in the accessory glands in attaining new steady-state levels of tissue weight and enzyme activity was independent of the dose of androgen except during the first few days of hormone administration. Androgens were the most effective steroids in stimulating an increase of tissue weight and enzyme activity, although some changes were induced by oestradiol-3-benzoate and progesterone.
FAILURE OF MELATONIN TO INCREASE SERUM PROLACTIN LEVELS IN OVARIECTOMIZED RATS SUBJECTED TO SUPERIOR CERVICAL GANGLIONECTOMY OR PINEALECTOMY
Authors: CARDINALI D. P. , FAIGÓN MARÍA R. , SCACCHI P. , MOGUILEVSKY J. 
Published: December 2008

SUMMARY
The effects of melatonin on serum prolactin levels were examined in ovariectomized rats primed with oestradiol and progesterone, and subjected to bilateral superior cervical ganglionectomy or pinealectomy.
Ganglionectomy resulted in a significant depression of the serum prolactin concentration, as well as in impairment of the prolactin release evoked by administration of steroid. Treatment with melatonin increased serum prolactin in control but not in ganglionectomized rats. Injection of melatonin potentiated the steroid-induced release of prolactin in control rats; this effect of melatonin was not detected in ganglionectomized rats. Pinealectomy did not affect basal prolactin levels, nor impair the release of prolactin evoked by steroid treatment; however, it was effective in blocking the melatonin-induced release of prolactin in vehicletreated rats, as well as the potentiation of steroid-induced prolactin release by melatonin. Intracranial surgery by itself increased prolactin release. These results suggest that systemically administered melatonin needs an intact pineal gland to augment serum prolactin levels.
EFFECT OF CHRONIC PARATHYROIDECTOMY ON CALCIUM METABOLISM IN THE LACTATING RAT
Authors: FRY J. M. , CURNOW D. H. , GUTTERIDGE D. H. , RETALLACK R. W. 
Published: December 2008

This study examined the effect of chronic parathyroidectomy (PTX) in rats on calcium homeostasis in milk and serum and on litter growth rate throughout lactation.
Parathyroidectomy was carried out by excision 8 weeks before mating and any animals with evidence of parathyroid regeneration over this time were discarded. Maternal serum and milk samples were collected at days 6, 12 and 20 of lactation and serum samples from the pups were obtained at day 20. Litter growth was measured by weighing the pups daily.
Significantly lower concentrations of ionized and total calcium and significantly higher concentrations of phosphate in the serum were found in the PTX animals compared with the sham-operated controls (P< 0·001). The ratio of ionized to total calcium in serum was significantly lower in the PTX group. The mean total calcium concentration in milk was significantly higher at day 6 in the PTX group (P< 0·05) but was not different from the sham-operated group at days 12 and 20. The ratio of milk calcium to percentage milk solids was the same in both groups of animals at all three sampling periods. Litter growth rate was not significantly different in the two groups up to day 5 or from days 12 to 20. It was lower in the PTX group (P< 0·001) between days 5 and 12. The total concentration of calcium in serum from the young was not significantly different in the two groups.
It was concluded that parathyroid hormone (PTH) is required for normal maternal calcium homeostasis in serum during lactation and therefore its absence may affect milk homeostasis indirectly for part of lactation. In contrast the concentration of calcium in milk and litter growth rate can be maintained at normal levels in late lactation suggesting that PTH is not an essential hormone in the regulation of calcium levels in milk.