bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bilateral maintenance of rabbit corpora lutea by the feto-placental unit
Authors: Nowak R. A. , Klein J. S. , Pulido D. M. , Bahr J. M. 
Published: December 2008

ABSTRACT
The present study was undertaken to determine (1) whether the rabbit feto-placental unit maintains corpora lutea systematically and/or locally and (2) the interrelationships between conceptus number, luteal weight, luteal progesterone concentrations and serum progesterone levels. Thirty-three does were divided into the following treatment groups: (I) bilaterally pregnant, two ovaries; (II) unilaterally pregnant, two ovaries; (III) bilaterally pregnant, one ovary; (IV) unilaterally pregnant, one ovary, contralateral and (V) unilaterally pregnant, one ovary, ipsilateral. Blood samples were obtained from all rabbits on days 6, 9, 12, 15, 18 and 21 post coitum. Does were killed on day 21, and the percentage of viable fetuses, fetal weights, and luteal weights recorded. Blood samples and corpora lutea were analysed for progesterone.
Serum progesterone levels were similar for all groups until day 9 post coitum. Levels in groups III, IV and V declined significantly between days 9 and 12 following removal of one ovary at day 9. Fetal viability, fetal weights and luteal progesterone concentrations did not differ among any of the groups. Luteal weights did not differ among groups I, III, IV and V, but luteal weights of animals in group II were lower than those of group I (P<0·05). Ratios of viable fetuses to number of corpora lutea ranged from 1:11–10:5. No differences were observed in serum progesterone, luteal weights or luteal progesterone concentrations among animals with two conceptuses and those with seven or more, but serum progesterone levels in does with only one conceptus were lower than those in does with more (P<0·05). These results indicate that the feto-placental unit maintains corpora lutea systemically and that the high rate of pregnancy failure by day 21 in does with only one conceptus is due to the inability of a single conceptus to maintain normal serum progesterone levels even though the corpus luteum weight is not affected.
J. Endocr. (1986) 109, 107–110
Stimulation of steroid production in isolated rat Leydig cells by unknown factors in testicular fluid differs from the effects of LH or LH-releasing hormone
Authors: Rommerts F. F. G. , Hoogerbrugge J. W. , van der Molen H. J. 
Published: December 2008

ABSTRACT
After the addition of charcoal-treated testicular fluid to Leydig cells isolated from 22-day-old rats, pregnenolone production could be increased to a maximum of tenfold within 30 min in a dose-dependent manner. Testicular fluid, but not serum, further increased pregnenolone formation threefold when pregnenolone production by Leydig cells was stimulated by the addition of LH-releasing hormone (fourfold), LH (25-fold) and 22R-hydroxycholesterol (300-fold). The effect of testicular fluid on steroid production in the presence of 22R-hydroxycholesterol was not inhibited by cycloheximide whereas cycloheximide completely inhibited the effect of LH. It appears unlikely that steroids, lipoproteins or other plasma components constitute the stimulatory agents in testicular fluid. The biologically active principles may be locally produced factors with a molecular weight > 25 000. Similar biological activities could be shown in testicular lymph from boars but not in systemic lymph from boars nor in charcoal-treated bovine follicular fluid. The presumably locally produced factor(s) may amplify the effect of LH and can thus act as a local modulator(s).
J. Endocr. (1986) 109, 111–117
Testosterone sensitivity of the seminal sacs of tree sparrows (Spizella arborea) in different reproductive states
Authors: Wilson F. E. 
Published: December 2008

ABSTRACT
Testosterone sensitivity of the seminal sacs of castrated tree sparrows from each of three reproductive states was evaluated by measuring the change in seminal-sac mass per unit change in the logarithm of replacement or plasma testosterone. Birds were exposed to exogenous testosterone for 38 days. Replacement doses less than 0·17 μmol or plasma concentrations less than about 0·7 nmol/l did not induce seminal-sac growth in photosensitive castrated birds held on short days, in photosensitive castrated birds transferred from short to long days, or in photorefractory castrated birds retained on long days. Higher replacement doses or plasma concentrations, however, stimulated log dose-dependent growth of the seminal sacs in castrated birds from all three reproductive states. The change in seminal-sac mass per unit change in the logarithm of the dose of replacement testosterone was less (P= 0·0495) in photosensitive castrated birds held on short days than in photosensitive castrated birds transferred to long days. A more critical test of sensitivity (i.e. the change in seminal-sac mass per unit change in the logarithm of mean plasma testosterone concentration) indicated, however, that sensitivity of the seminal sacs to testosterone is independent of reproductive state. That result, when considered in the context of the plasma testosterone profile of intact males during a simulated reproductive cycle, argues that the seminal sacs of sexually quiescent (photosensitive or photorefractory) tree sparrows are small not because of their insensitivity to androgens, but because of a deficiency of circulating androgens.
J. Endocr. (1986) 109, 125–131
Oxytocin release during parturition in the pelvic-neurectomized rat
Authors: Higuchi T. , Uchide K. , Honda K. , Negoro H. 
Published: December 2008

ABSTRACT
Blood levels of oxytocin during parturition in pelvic-neurectomized rats were determined by radioimmuno-assay. Four out of 29 pelvic-neurectomized rats completed parturition within 23 days of pregnancy. These rats exhibited an increase in blood levels of oxytocin during parturition similar to those of sham-operated control rats, but delivery took longer and there was a higher percentage of still-births. The rise in blood levels of oxytocin was smaller in the 16 rats in which the first fetus was expelled but where delivery did not end within day 23 of gestation than that in sham-operated controls. Levels did not increase in the other nine rats which failed to deliver the first fetus within 23 days of pregnancy. They did, however, show signs indicating delivery, such as stretch movements, vaginal bleeding and/or excretion of mucus within 23 days of gestation. Oxytocin infusion (2 mu./min) for 2–4 h increased uterine contractions in the pelvic-neurectomized rats but failed to reduce the percentage of still-births or the duration of delivery. Immuno-neutralization of circulating oxytocin by anti-oxytocin serum in intact pregnant rats resulted in a significant but much smaller prolongation of the duration of delivery compared with that observed in pelvic-neurectomized rats. The rise in blood levels of oxytocin during pregnancy may be induced, at least in part, by the Ferguson reflex via the pelvic nerve and may thus facilitate the process of delivery. A shortage of oxytocin secretion may not, however, be the main cause of the dystocia in pelvic-neurectomized rats.
J. Endocr. (1986) 109,149–154
Differential effects of passive immunization with somatostatin antiserum on adenohypophysial hormone secretions in starved rats
Authors: Hugues J. N. , Enjalbert A. , Moyse E. , Shu C. , Voirol M. J. , Sebaoun J. , Epelbaum J. 
Published: December 2008

ABSTRACT
The role of somatostatin (SRIF) on adenohypophysial hormone secretion in starved rats was reassessed by passive immunization. Because of the absence of pulsatile GH secretion in starved rats, the effects of the injection of SRIF antiserum on GH levels can be clearly demonstrated. To determine whether starvation modifies the sensitivity of the adenohypophysis to SRIF, we measured 125I-labelled iodo-N-Tyr-SRIF binding. There was no difference in the dissociation constant (Kd) nor in the maximal binding capacity (Bmax) in fed (n = 15) and starved (n = 15) animals (Kd = 0·38 ± 0·09 (s.e.m.) and 0·45 ± 0·09 nmol; Bmax = 204 ± 39 and 205 ± 30 fmol/mg protein respectively).
Administration of SRIF antiserum resulted in a dose-dependent increase in plasma concentrations of GH, TSH and prolactin. The minimal effective dose of SRIF antiserum was 50 μl for GH, 100 μl for TSH and 200 μl for prolactin.
Our results show that: (1) starvation does not modify adenohypophysial SRIF-binding sites, (2) in starved male rats endogenous SRIF exerts a negative control on prolactin secretion in vivo and (3) sensitivity to endogenous SRIF seems to be different for each hypophysial cell type.
J. Endocr. (1986) 109, 169–174
Lactogenic hormone receptors in mammary membrane preparations from prepartum and 60 and 180 day post-partum Holstein cattle
Authors: Kazmer G. W. , Barnes M. A. , Akers R. M. , Whittier W. D. 
Published: December 2008

ABSTRACT
Mammary tissue from nine Holstein cows was collected within 1 week of parturition and at 60 and at 180 days post partum. Blood samples were collected by puncture of the coccygeal vein or artery at 6-h intervals from 2 days before to 2 days after surgery. A membrane-enriched fraction of tissue homogenates was prepared by differential centrifugation. A microcomputer program (LIGAND) provided estimates of the dissociation constant (Kd) and receptor concentrations using Scatchard analysis of competition of radioiodinated human GH by bovine prolactin (NIH-bPRL-6), ovine prolactin (NIH-oPRL-15) and unlabelled human GH (NIH-hGH-I-1). Split-plot analysis of variance of hormone data indicated that mean prolactin concentrations during the periparturient period were greater than those at 60 or 180 days post partum. However, no differences were evident in prolactin content of blood samples collected immediately before biopsy. Analysis of variance of Scatchard data indicated that the Kd of the lactogenic hormone receptor did not differ at different stages of lactation, and averaged 89·7 nmol/l. Receptor concentrations were lower during the prepartum period than at 60 and 180 days post partum (0·65 vs 1·2 and 1·5 fmol/mg membrane protein respectively). The Kd of the lactogenic hormone receptor was similar when estimated with NIH-bPRL-6 or NIH-oPRL-15 competition, but 100-fold greater when estimated with NIH-hGH-I-1. It is concluded that lactogenic hormone receptor concentrations in bovine mammary tissue increase with the onset of lactation, with a pattern similar to that observed in non-ruminants.
J. Endocr. (1986) 109, 175–180
Thyroid function in newborn lambs: influence of prolactin and growth hormone
Authors: Kühn E. R. , Van Osselaer P. , Siau O. , Decuypere E. , Moreels A. 
Published: December 2008

ABSTRACT
Lambs originating from Suffolk, Milksheep and Texel crossbreeds were injected with saline, 500 μg ovine prolactin or 500 μg ovine GH within 30 min of parturition (n = 10). Birth weight was negatively correlated with plasma concentrations of reverse tri-iodothyronine (rT3) but not with thyroxine (T4), free T4 (expressed as the free thyroxine index) or cortisol. At birth, T3 and T4 plasma concentrations were high and remained high during the 3-h observation period. After 3 h a significantly lower rT3 concentration was found. The cortisol concentration at birth was also high (100–400 nmol/l) but decreased rapidly to basal values after 1 h. An injection of 500 μg prolactin after parturition did not influence the hormonal parameters studied except for rT3 where, after 2 h, lower plasma concentrations were found compared with controls.
Growth hormone raised T3 levels from 4·80 ± 0·44 (s.e.m.) nmol/l at birth to 6·74 ± 0·42 nmol/l at 1 h after birth (P < 0·01) and to 6·51 ± 0·42 nmol/l after 2 h (P < 0·05). At both times these values were significantly (P < 0·001) different from saline-injected controls. GH decreased rT3 from 6·77 ± 0·71 nmol/l at birth to 5·42 ± 0·54 nmol/l after 1 h (P < 0·05) and to 5·10 ± 0·45 nmol/l after 2 h (P < 0·01; values were also significantly different from saline controls at P < 0·05 and < 0·005 respectively). At the same time total and free T4 concentrations were increased. No influence of prolactin or GH injection on plasma cortisol concentrations was seen. It is concluded that GH may play an important role in the maturation of thyroid functions during the perinatal period of lambs by increasing T4 secretion and by increasing the conversion of T4 to T3 and decreasing the T4 to rT3 conversion rates.
J. Endocr. (1986) 109, 215–219
Prenatal stress effects over two generations in rats
Authors: Pollard I. 
Published: December 2008

ABSTRACT
Persistent effects of stress were found in second generation rats bred from females whose own mothers had been stressed during pregnancy. The second generation rats grew more slowly, with a plateau in the growth being reached at the same age as in the controls. This resulted in adult animals of both sexes being permanently smaller than their control counterparts. When these offspring were subjected to short-term stress (one session) in adulthood, the response was not significantly different to that for the controls, indicating an intact emergency response. The male offspring from the stressed group, however, had a significantly (P < 0·01) higher plasma progesterone concentration, and a significantly (P < 0·01) lower testicular enzymic 3β-hydroxysteroid dehydrogenase activity at rest, when compared with the control offspring. The fertility of the mature female from the stressed group was not affected as a third generation of litters born did not differ from the controls.
It is suggested that a changed genetic programme in the ovarian germ cells of the first generation and/or a changed uterine environment in the second generation may be implicated.
J. Endocr. (1986) 109, 239–244
Age-related changes in the concentrations of serum gonadotrophins and cholesterol in the female rabbit
Authors: YoungLai E. V. 
Published: December 2008

ABSTRACT
Peripheral serum concentrations of LH, FSH and prolactin were determined by radioimmunoassay on different days after birth in the female rabbit. Serum cholesterol concentrations were also analysed by a colorimetric method. Concentrations of serum LH and FSH showed two distinct peaks occurring on day 9 (LH, 4·05 ± 0·76 (mean ± s.e.m.) μg/l; FSH, 3·62 ± 0·67 μg/l) and either day 35 (LH, 5·90 ± 1·20 μg/l) or day 40 (FSH, 9·01 ± 1·43 μg/l). Concentrations of LH and FSH were in the adult range (LH, < 1 μg/l; FSH, < 0·6 μg/l) by day 100. Serum prolactin showed a progressive increase from day 1 (1·04 ± 0·07 μg/l) to day 100 ( 17·30 ± 2·50 μg/l) with a peak on day 40. Total serum cholesterol in another series of rabbits was high from days 1 to 22 (7·53 ± 0·64 mmol/l) and then decreased to 1·94–3·36 mmol/l by day 106. These data indicate that the two major developmental peaks in gonadotrophins may be related to ovarian function.
J. Endocr. (1986) 109, 287–290
A modulatory role for cyclic AMP in the control of thyrotrophin release: studies with forskolin and dibutyryl cyclic AMP
Authors: Davis J. R. E. , Sheppard M. C. 
Published: December 2008

ABSTRACT
We have studied the effects of cyclic AMP (cAMP) on TSH secretion by cultured rat pituitary cells, using forskolin and dibutyryl cAMP (dbcAMP) to raise the cellular cAMP content by different mechanisms. Forskolin (10 μmol/l), a stimulator of adenylate cyclase, raised the cAMP content within 10 min, but had a more delayed effect on TSH release, with no significant stimulation for at least 6 h, but a clear dose-dependent effect at 24 h. Incubation with dbcAMP likewise increased TSH release after 6–24 h. By contrast, high cellular cAMP levels induced by either forskolin or dbcAMP augmented the TSH response to TRH at an early stage, before any detectable change in unstimulated TSH release. Pretreatment of cells with forskolin led to a parallel upward shift in the subsequent TRH dose-response curve, without a significant change in median effective dose or any change in cellular TSH content.
These findings suggest that cAMP acts to increase the availability of TSH for acute release by TRH by modulation of an intracellular releasable hormone pool, and indicate synergistic interactions between the adenylate cyclase system and the phospholipid-calcium stimulus-release coupling mechanism of TRH.
J. Endocr. (1986) 109, 365–369
Effects of photoperiod on formation of oestradiol-17β in the dove brain
Authors: Hutchison J. B. , Steimer Th. , Jaggard P. 
Published: December 2008

ABSTRACT
The effects of photoperiod and castration on brain aromatase activity have been examined using an in-vitro radioassay. Formation of oestradiol-17β was lower in the preoptic area of male Barbary doves on a short daylength (6 h light: 18 h darkness) than in males on a long daylength (14 h light: 10 h darkness). This was a specific effect of photoperiod which did not influence aromatase activity in the anterior or posterior hypothalamic areas, and was not accompanied by changes in hormone-sensitive vocal behaviour. Production of 5β-dihydrotestosterone, 5β-androstane-3α,17β-diol and 5α-dihydrotestosterone by the preoptic area did not differ between birds on long or short days. Therefore, a short photoperiod does not appear to influence other pathways of androgen metabolism. In contrast to the effects of photoperiod, castration reduced oestradiol formation in both preoptic and hypothalamic areas. Intramuscular injection of testosterone propionate (TP) in intact males on short days did not restore the pattern of distribution of aromatase activity seen in males on long days. Preoptic aromatase activity was, however, restored by TP in castrated birds. We conclude that a short photoperiod influences both the activity of aromatase and the inductive effect of testosterone on enzyme activity in the preoptic area, which is known to be associated with the behavioural action of oestrogen in the dove. Photoperiod is likely to act both through changes in circulating androgen and by a direct action on preoptic cells.
J. Endocr. (1986) 109, 371–377
Relationship between human chorionic gonadotrophin-induced changes in testicular microcirculation and the formation of testicular interstitial fluid
Authors: Widmark A. , Damber J. E. , Bergh A. 
Published: December 2008

ABSTRACT
The relationship between testicular vascular permeability and testicular microcirculation as measured by laser Doppler flowmetry was studied in adult rats. In untreated control animals there was an oscillatory testicular blood-flow pattern with a frequency of 10·6 ± 0·8 pulses/min and the amount of testicular interstitial fluid (IF) collected was 61·5 ± 2·2 μl/g testis. Treatment of the rats with 25–200 i.u. human chorionic gonadotrophin (hCG) s.c. 8 h before the experiment resulted in a change in the testicular flow pattern from pulsatile to continuous and an increase in IF volume. Treatment with hCG (50 i.u., s.c.) changed the testicular blood-flow pattern from oscillatory to continuous 4, 8 and 16 h after treatment. The flow pattern returned to being pulsatile 32 h after treatment with hCG. The IF information was increased at those times when the blood-flow pattern was continuous. No effects on blood flow or IF formation were observed with 12·5 i.u. hCG s.c.
The present study shows a dose- and time-dependent covariation between the increase in testicular IF volume and the disappearance of the pulsatile flow in testicular microcirculation. It appears that a continuous flow pattern favours the transport of fluid from blood vessels to the interstitium.
J. Endocr. (1986) 109, 419–425
EVIDENCE AGAINST ANP AS A NATRIURETIC HORMONE DURING ATRIAL DISTENSION
Authors: Knapp M. F. , Hicks M. N. , Linden R. J. , Mary D.A.S.G. 
Published: December 2008

ABSTRACT
To determine whether natriuresis attributable to atrial natriuretic peptides (ANP) is obtained in response to atrial stretch after blockade of the afferent input and reflex diuresis from atrial receptors, urine flow and sodium excretion were measured in response to distension of a balloon in the left atrium with the vagi at 37 and 9°C. It is known that during such a distension ANP plasma concentration is increased by the same amount whether or not the afferent vagal fibres are intact.
In 11 chloralose anaesthetized dogs 22 distensions with the vagi at 37°C increased urine flow 117.5% and increased sodium excretion 28.7%. In 11 distensions with the vagi at 9°C, urine flow did not change but sodium excretion decreased significantly (−20.9%).
Thus natriuresis could not be demonstrated in response to atrial stretch in anaesthetised dogs after blockade of the atrial receptor reflex. These results imply that under these conditions, in which ANP is reportedly released into plasma, ANP is not acting as a hormone. The results must call into question the suggestion that ANP is released into plasma in a concentration capable of causing a natriuresis as its normal physiological function.
Steroid regulation of Na+/K+-ATPase activity in the rat kidney: effect of a new 19-nor-progestagen
Authors: Botella J. , Paris J. , Lahlou B. 
Published: December 2008

ABSTRACT
The effects of Nomegestrol acetate (17α-acetoxy-6-methyl-19-nor-4,6-pregnadiene-3,20-dione), a new 19-nor-progesterone derivative, on renal Na+/K+-ATPase activity were assessed in normal and adrenalectomized rats, and compared with the stimulatory or inhibitory actions produced by other steroids. This compound displayed an inhibitory effect which was similar to, but smaller than, that induced by progesterone and quite distinct from the stimulation produced by 19-nor-progesterone and corticosteroids. In addition, unlike progesterone, it did not antagonize the effect of aldosterone in adrenalectomized rats. This result, together with previous in-vivo and in-vitro observations on this compound indicates that additional modifications introduced in the molecular structure of 19-nor-progesterone produces a potent progestagenic substance virtually devoid of effects on renal Na+/K+-ATPase activity and sodium loss in urine.
J. Endocr. (1986) 110, 37–41
Control of leucocyte infiltration into the decidualized mouse uterus
Authors: Finn C. A. , Pope M. 
Published: December 2008

ABSTRACT
Ovariectomized mice were treated with oestrogen and progesterone on a schedule to mimic early pregnancy. Decidualization was induced with oil and uteri were examined at various times after the last progesterone injection.
The first morphological change detected in the uterus of decidualized mice following withdrawal of progesterone was infiltration of leucocytes into the stroma. This preceded overt tissue breakdown and extravasation of blood cells, and did not occur following withdrawal of progesterone without decidualization. It is suggested either that there is a release of a chemoattractant from decidual cells before any morphological changes are apparent or that the signal for attracting the leucocytes is released at the time of decidual induction, but that their migration is suppressed by progesterone.
J. Endocr. (1986) 110, 93–96