bluuebunny/crossref_metadata_2025_split huggingface dataset:
N-acetyltransferase activity in the Harderian glands of the Syrian hamster, Mesocricetus auratus, is regulated by androgens and by hormones of the pituitary-thyroid axis
Authors: Buzzell G. R. , Menendez-Pelaez A. , Hoffman R. A. , Vaughan M. K. , Reiter R. J. 
Published: December 2008

ABSTRACT
This study tested the hypothesis that activity of the enzyme N-acetyltransferase (NAT) in the Harderian gland of the Syrian hamster is regulated both by androgens and by hormones of the pituitary-thyroid axis. To test the effects of castration and hypothyroidism, intact or castrated male hamsters were given either tap water or methimazole in their drinking water for 3 weeks. Methimazole suppresses iodination of thyroglobulin, thereby decreasing circulating levels of thyroid hormones and increasing TSH levels. Hypothyroidism or castration caused elevated or depressed Harderian gland NAT activities respectively, compared with euthyroid controls. When castration and hypothyroidism were combined, the animals exhibited high NAT activity compared with castrated euthyroid males.
To test the effects of castration and hyperthyroidism, male hamsters were given daily injections of thyroxine (T4) or diluent and were either castrated or left intact for 4 weeks. Intact animals given T4 had depressed Harderian NAT activity; serum thyroid hormone levels were elevated and TSH levels were depressed compared with those of intact controls. Castrated animals had depressed NAT activity below that of intact controls; serum thyroid hormone levels were normal but TSH levels were depressed. Castrated animals given T4 injections had NAT activity similar to that of euthyroid castrated hamsters; thyroid hormone levels were elevated but TSH levels were similar to those seen in euthyroid castrated hamsters. In another experiment, both T4 and tri-iodothyronine (T3) were equally effective in decreasing NAT activity in intact males.
To determine the effects of the removal of pituitary influences, male hamsters were hypophysectomized. NAT activity in the Harderian glands of these animals was reduced compared with intact controls. Injection of T4 in hypophysectomized male hamsters did not alter NAT activity from that of hypophysectomized hamsters.
Female hamsters given methimazole for 3 weeks had elevated Harderian NAT activity compared with controls. Injection of T4 or T3 for 4 weeks led to significantly reduced Harderian gland NAT activity compared with untreated controls. This response to thyroid hormones was the same, whether T4 or T3 was used.
These results can be explained by androgens stimulating Harderian NAT activity, as has been suggested by previous published reports, and by NAT activity being inhibited by thyroid hormones or stimulated by TSH.
Journal of Endocrinology (1990) 127, 59–67
Aromatase activity in genital skin fibroblasts from normal and androgen-insensitive individuals
Authors: Stillman S. C. , Evans B. A. J. , Hughes I. A. 
Published: December 2008

ABSTRACT
Human genital skin fibroblasts were used to study aromatase activity by analysing the [3H]H2O released as [1β-3H]androstenedione is converted to oestrone. 4-Hydroxyandrostenedione was shown to be a competitive inhibitor of this aromatase activity, the concentration of inhibitor producing 50% inhibition being 1·29 nmol/l. Dexamethasone stimulated the enzyme complex in a dose-dependent manner with half-maximal stimulation at 11·5 nmol/l. A peak of induction occurred after 16 h of preincubation. Measurement of aromatase activity in normal cell strains provided a normal range for the Michaelis–Menten constant (Km) and the maximum velocity (Vmax) of 6·72±0·54 nmol/l and 215·3±33·9 fmol/mg protein per h (means ± s.e.m., n = 20) respectively. Km values obtained for partial and complete androgen insensitivity syndrome (PAIS and CAIS) patient cell strains were all within the normal range. The mean Vmax±s.e.m. in cell strains from patients with PAIS (n = 13) and CAIS (n = 11) were 127·4±19·2 and 54·8±19·3 fmol/mg protein per h respectively. Vmax values for patients with CAIS were significantly (P < 0·001) lower than normal subjects. This suggests that aromatase expression in genital skin fibroblasts is androgen-dependent.
Journal of Endocrinology (1990) 127, 177–183
Involvement of dopamine D1 receptors in the control of growth hormone secretion in the rat
Authors: Bluet-Pajot M. T. , Mounier F. , Durand D. , Kordon C. 
Published: December 2008

ABSTRACT
The effects of dopamine on GH release were investigated both in vivo in freely moving intact rats and in rats with a mediobasal hypothalamic lesion, and in vitro in a perifusion system using dispersed male rat pituitary cells kept in primary culture. In vivo, dopamine (5 mg/kg body weight) induced a rapid and very transient increase in plasma GH levels in lesioned but not in intact rats. This increase was markedly inhibited by a prior injection of the D1 antagonist SCH 23390 (0·5 mg/kg) but not of the D2 antagonist domperidone (0·5 mg/kg). The D, agonist SKF 38393 induced a dose-dependent stimulation of GH release in lesioned rats, and the effect obtained with a dose of 5 mg/kg was abolished by pretreatment with SCH 23390 (0·5 mg/kg). In vitro, dopamine (0·1 μmol/l) and SKF 38393 (0·1 μmol/l) provoked a rapid and reversible release of GH from superfused rat pituitary cells; this effect was markedly inhibited by simultaneous superfusion of SCH 23390 (1 μmol/l). These findings indicate that dopamine can stimulate basal GH release at the pituitary level and that this stimulation is mediated by D1 but not by D2 receptors. They also support the hypothesis that unidentified hypothalamic neurohormones may modulate this effect.
Journal of Endocrinology (1990) 127, 191–196
Stimulation of rat renal medullary Na+/K+-ATPase by arginine vasopressin is mediated by the V2 receptor
Authors: Charlton J. A. , Baylis P. H. 
Published: December 2008

ABSTRACT
In previous studies, we have demonstrated that 1–10 fmol arginine vasopressin (AVP)/l maximally stimulates the activity of the enzyme Na+/K+-ATPase in the rat renal medullary thick ascending limb (MTAL) of Henle's loop after 4 or 10 min of stimulation when measured using a cytochemical bioassay. We have tested the hypothesis that this stimulation is mediated by the V2 receptor in the MTAL. A cytochemical bioassay was used to investigate the effect of specific V1 and V2/V1 antagonists and a synthetic V2 agonist [1-deamino,8-d-arginine]-vasopressin (dDAVP), on the activity of Na+/K+-ATPase. There was no effect of the V1 antagonist (1 fmol-1 μmol/l) in inhibiting the activity of Na+/K+-ATPase stimulated by 1 fmol AVP/l. In contrast, 100 pmol of the V2/V1 antagonist/l significantly (P < 0·001) inhibited the stimulation of Na+/K+-ATPase activity by 1 fmol AVP/l from 55·5±4·3 (s.e.m.) to 31·9±1·6 mean integrated extinction (MIE) after 4 min of stimulation and from 67·0±3·2 to 36·9±0·7 MIE after 10 min of stimulation. Similarly, the stimulation of Na+/K+-ATPase by 10 fmol dDAVP/l was inhibited by the V2/V1 antagonist from 55·1±1·0 to 26·1±0·5 MIE after 4 min of stimulation.
We conclude that the stimulation of Na+/K+-ATPase by AVP is mediated by the V2 receptor in the rat renal MTAL.
Journal of Endocrinology (1990) 127, 213–216
Suckling-induced release of cholecystokinin into plasma in the lactating rat: effects of abdominal vagotomy and lesions of central pathways concerned with milk ejection
Authors: Linden A. , Eriksson M. , Hansen S. , Uvnäs-Moberg K. 
Published: December 2008

ABSTRACT
Plasma levels of cholecystokinin were increased in response to suckling in lactating rats. Efferent electrical stimulation of the vagal nerve increased the concentration of cholecystokinin in plasma. Abdominal vagotomy was found to block the suckling-induced release of cholecystokinin. Furthermore, lesions to the lateral midbrain, which disrupt the oxytocin-mediated milk-ejection reflex, were shown to inhibit the increase in plasma cholecystokinin. These results show that the suckling-induced release of cholecystokinin into plasma in lactating rats is dependent upon the vagal nerves and the central neural structures concerned with milk let-down.
Journal of Endocrinology (1990) 127, 257–263
Mitosis in the oesophageal epithelium of rats during chronic antithyroid treatment with carbimazole
Authors: Tuffery A. R. , Mobarak M. 
Published: December 2008

ABSTRACT
The mitotic activity of the oesophageal epithelium of male rats maintained under carefully controlled conditions was studied, using the metaphase-arrest agent, vincristine sulphate. The accumulation of metaphases was linear (r = 0·97). In untreated rats there was a clear mitotic rhythm with a peak metaphase index (expressed as a percentage) of 12·4±0·86 (s.e.m.) at 12.00–15.00 h and a trough of 1·3±0·35 at 24.00 h. The overall mean metaphase index was 5·4±0·76. The effect of treatment with the antithyroid agent, carbimazole (0·1 g/100 ml in the drinking water), for 3 weeks was to depress the higher values at 12.00–18.00 h (P <0·01), while leaving the overall index unchanged.
Carbimazole caused a significant (P <0·01), transient 40% increase in the metaphase index after 2 days; thereafter the metaphase index remained at control levels until 12 weeks of treatment when a steady decline occurred until 24 weeks.
The results are in contrast to those in previously described experiments on thyroid follicular cells which show a large increase in the first few days of treatment, followed by a steady decline towards control levels at 12 weeks. The metabolic activity of the animals is about 50% of normal at 12 weeks when both the oesophageal epithelium and the thyroid follicular cells begin to show a reduction in proliferative activity.
Journal of Endocrinology (1990) 127, 311–315
Stimulation of Na+/K+-ATPase activity by polyamines in the rat renal medullary cells of the thick ascending limb of Henle's loop
Authors: Charlton J. A. , Baylis P. H. 
Published: December 2008

ABSTRACT
Previous studies have indicated that ornithine decarboxylase (ODC) may be involved in the stimulation of Na+/K+-ATPase activity by arginine vasopressin (AVP) in the rat renal medullary thick ascending limb of Henle's loop. The present study was aimed at establishing the role of the polyamines, the conversion products of ODC activity, in the stimulation of Na+/K+-ATPase by AVP. Using cytochemical methods, we have demonstrated an increase in Na+/K+-ATPase activity after stimulation with putrescine, spermidine and spermine (each 1 mmol/l) for 2·5,2 and 1·5 min respectively. The specific inhibitors of spermidine and spermine synthase, bis-cyclohexylammonium sulphate and N-alkylated-1,3-diaminopropane respectively, inhibited the stimulation of Na+/K+-ATPase by AVP, this inhibition being reversed by spermine. These findings suggest that polyamines are involved in the stimulus-response coupling of the hormone-mediated response.
Journal of Endocrinology (1990) 127, 377–382
Insulin-like growth factor-I (IGF-I) and IGF-binding proteins both decline in the rat during late pregnancy
Authors: Gargosky S. E. , Walton P. E. , Owens P. C. , Wallace J. C. , Ballard F. J. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-I (IGF-I), IGF-II and IGF-binding proteins (IGFBP) were examined in rat serum during pregnancy and lactation. IGF-I concentrations determined after acid column chromatography of serum were low during the last third of pregnancy. IGF-II was undetectable in pregnant and non-pregnant rats. IGF-binding protein (IGFBP) concentrations, measured as high molecular mass activity in the IGF-I RIA and the IGF-II RRA of acid column fractions, paralleled the changes observed with IGF-I. Western ligand blot analysis of serum from non-pregnant rats revealed a 40–50 kDa IGFBP aligning with IGFBP-3, a smaller 28–30 kDa doublet and 24 kDa IGFBP. Serum from rats in late pregnancy lacked IGFBP-3, whereas the smaller IGFBP persisted during late pregnancy. IGFBP-3 reappeared in postpartum animals. The fall in serum IGF-I is consistent with a maternal catabolic state during late pregnancy which may maximize substrate availability for the developing fetus.
Journal of Endocrinology (1990) 127, 383–390
Stress responsiveness of hypothalamic corticotrophin-releasing factor and pituitary pro-opiomelanocortin mRNAs following high-dose glucocorticoid treatment and withdrawal in the rat
Authors: Harbuz M. S. , Nicholson S. A. , Gillham B. , Lightman S. L. 
Published: December 2008

ABSTRACT
In-situ hybridization with synthetic oligonucleotide probes was used to determine the mRNA content of corticotrophin-releasing factor (CRF) and proenkephalin A mRNA in the paraventricular nucleus, and of pro-opiomelanocortin (POMC) mRNA in the anterior pituitary gland of male rats immediately after, and during recovery from, chronic high-dose prednisolone treatment. Levels of transcripts for mRNA for both CRF and POMC were markedly reduced after the treatment, but there was a rapid return to control values for CRF mRNA within 18 h of steroid withdrawal.
In untreated animals, the stressful stimulus of i.p. hypertonic saline increased CRF and proenkephalin A mRNA within 4 h with no significant difference in response seen whether the tissues were removed at 13.00 or 20.00 h. The increase in POMC mRNA did not reach statistical significance in these animals. Although prednisolone resulted in a marked reduction of basal CRF mRNA, the stress-induced increment of CRF mRNA remained comparable with that found in untreated animals. On the day following cessation of prednisolone treatment at 09.00 h, basal and stress levels of CRF mRNA were significantly higher in rats killed at 20.00 h than at 13.00 h. Proenkephalin A mRNA transcripts were below quantifiable levels of detection in control or non-stressed prednisolone-treated animals at all the time-points studied. Stress, however, resulted in the accumulation of proenkephalin A mRNA in control animals. This response was inhibited by prednisolone treatment and only returned 18 h after withdrawal. Prednisolone treatment reduced POMC mRNA below the levels detected in untreated animals, with no detectable response to stress. However, 36 h after prednisolone withdrawal there was a significant increase in POMC mRNA in response to stress.
Prednisolone concentrations in the plasma on the morning of the day after the final administration of the steroid were very high (880 nmol/l), but these were halved by the evening of that day and had fallen to 60 nmol/l 72 h after withdrawal.
These data show that both CRF and POMC mRNA were profoundly reduced by long-term prednisolone treatment. Stress-induced accumulation of CRF mRNA, however, persisted although the proenkephalin A mRNA responses to this stress were inhibited. No increase in pituitary POMC mRNA in response to stress was apparent until 36 h after withdrawal of prednisolone.
Journal of Endocrinology (1990) 127, 407–415
Distribution of pyroglutamylpeptide amides related to thyrotrophin-releasing hormone in the central nervous system and periphery of the rat
Authors: del Rio-Garcia J. , Smyth D. G. 
Published: December 2008

ABSTRACT
A rapid and sensitive chromatographic method is presented for determining TRH and TRH-like peptides in small quantities of tissues and fluids. The procedure was applied to screen a comprehensive range of tissues from the central nervous system (CNS) and periphery of the rat. When hydrochloric acid (100 mmol/l) was used for extraction, the TRH immunoreactivity obtained was identified solely with the known tripeptide hormone. In contrast, when weakly acidic conditions were used for extraction, neutral or acidic TRH-like peptides which lacked the histidine residue at position 2 of the hormone, but reacted with TRH antibodies, were shown to be present in addition to TRH. The TRH-like peptides in the brain were located principally in the hippocampus, brain stem and dorsal colliculi. In the periphery, TRH-like peptides were shown to be present in the male reproductive system and certain endocrine tissues. In addition, the presence of TRH-like peptides was confirmed in portal blood. The results indicate that peptides with a neutral or acidic TRH-like sequence at their C-terminus are widely distributed in the CNS and periphery of the rat. These peptides appear to occur mainly or exclusively in precursor forms from which TRH immunoreactivity can be released during extraction under weakly acidic conditions.
Journal of Endocrinology (1990) 127, 445–450
Regulation of the photoperiod-induced cycle in the peripheral blood concentrations of β-endorphin and prolactin in the ram: role of dopamine and endogenous opioids
Authors: Ssewannyana E. , Lincoln G. A. 
Published: December 2008

ABSTRACT
In a group of adult Soay rams housed indoors under an artificial light cycle of alternating 16-week periods of long and short days, there was a conspicuous longterm cycle in the peripheral plasma concentrations of β-endorphin and prolactin. The levels of β-endorphin were highest under short days and lowest under long days (15-fold change), and inversely related to the changes in the plasma levels of prolactin (120-fold change). The role of dopamine in the control of β-endorphin and prolactin was investigated in a series of experiments, conducted under both long and short days, in which rams were treated with dopamine receptor agonists (dopamine and bromocriptine) and antagonists (pimozide and sulpiride). Naloxone (opioid antagonist) was also administered to assess the additional involvement of endogenous opioids.
Dopamine injected i.v. (6·6 mg/kg every 10 min) did not significantly affect the mean plasma concentrations of β-endorphin and prolactin under either long or short days. Pimozide (0·08 mg/kg i.m. every 2 h) caused a large increase in the mean plasma concentrations of β-endorphin and prolactin under long days but not short days. Naloxone (1·6 mg/kg, i.v.), administered alone or in combination with dopamine or pimozide, had no effect on the mean plasma concentrations of β-endorphin and prolactin, except under short days when, combined with pimozide, it induced an increase in the plasma concentrations of the two polypeptides.
Bromocriptine (0·06 mg/kg, s.c.) caused a significant decrease in the plasma concentrations of both β-endorphin and prolactin; this effect was most marked at the times of increased secretion (under short days for β-endorphin and under long days for prolactin). Sulpiride (0·59 mg/kg, s.c.) produced the converse effect and caused an increase in the plasma concentrations of β-endorphin and prolactin with the amplitude and duration of the effect varying with the stage of the photoperiod-induced cycle.
From these results in the Soay ram, we conclude that dopamine inhibits β-endorphin and prolactin secretion by way of D2 receptors under both long and short days. Endogenous opioids interact with dopamine, augmenting this inhibition under short days. Differences in the acute responses in the secretion of β-endorphin and prolactin, and the inverse relationship between β-endorphin and prolactin during the cycle, indicate that different regulatory systems involving dopamine influence the two pituitary polypeptides.
Journal of Endocrinology (1990) 127, 461–469
Potentiation of the growth-promoting activity of porcine growth hormone (pGH) with an antibody generated in rabbits to the peptide sequence pGH110–118
Authors: Wang B. S. , Szewczyk E. , Shieh H.-M. , Hart I. C. 
Published: December 2008

ABSTRACT
An effort was made to identify the antigenic epitope(s) of porcine GH (pGH) capable of inducing antibodies which would enhance the growth-promoting activity of the hormone. Several peptide sequences of the pGH molecule were synthesized and the antibodies to these peptides were generated in rabbits. The majority of these antibodies were found to be immunoreactive with both intact pGH and their respective peptide antigens. The biological activity of the antibodies was tested in growth-retarded hypophysectomized rats. Daily injections with pGH alone significantly increased their growth rate and treatment with a combination of pGH and antibody specific to the peptide sequence 110–118 further heightened the somatogenic effect. Administration of this antibody alone did not enhance the growth rate of hypophysectomized rats, neither did antibodies raised to intact pGH or the other peptide sequences. The present findings suggest that antibody with a particular pGH epitope specificity is able to increase the somatogenic activity of pGH and that the peptide corresponding to pGH amino acids 110–118 may prove useful in the development of growth promoting vaccines.
Journal of Endocrinology (1990) 127, 481–485
Varying dose–response characteristics of different immunoassays and an in-vitro bioassay for FSH are responsible for changing ratios of biologically active to immunologically active FSH
Authors: Jockenhövel F. , Khan S. A. , Nieschlag E. 
Published: December 2008

ABSTRACT
Serum FSH levels in fertile and infertile men were determined by applying the Sertoli cell in-vitro bioassay and six different immunoassays. Bioassay and immunoassay estimates were significantly correlated (r ranging from 0·78 to 0·86; P<0·01). On average, all immunoassays measured lower FSH concentrations in samples with low FSH levels and higher FSH concentrations in those with high FSH levels compared with the bioassay. Ratios of bioactivity to immunoreactivity (B/I) were highest in fertile men and lowest in men with severe disturbances of testicular function. Depending on which immunoassay was used these differences were either significant or only marginal. Dose–response characteristics for WHO FSH standard preparation 78/549, used in the bioassay as well as in the immunoassays, were different between immunoassays and the bioassay, suggesting that decreasing B/I ratios with increasing FSH serum levels were method-related and reflected different slopes of the dose–response characteristics of the assays, rather than being true changes in the molecular composition of FSH. The present investigation underlines the necessity of choosing the immunoassay used for comparison with the bioassay carefully and of validating the system in regard to parallelism between dose–response characteristics. B/I ratios must be interpreted with great caution and previous studies which report changing B/I ratios in various endocrine situations may have to be reevaluated.
Journal of Endocrinology (1990) 127, 523–532