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Biomedical subjects

J Pelletier

Publications and source records attributed to J Pelletier.

At least 217 records · Page 12Linked to original sources
PubMed1983

[Demonstration of the influence of the photoperiod on the plasma concentration of the growth hormone in the ram].

The influence of photoperiod on GH release has been studied in Rams subjected to two different light regimes. The first group was submitted to natural daylight variations. The second group received daily the following split photoperiod: 7 L, 9 D, 1 L, 7 D, known to stimulate the release of prolactin. The experiment lasted 5 months, from January to June. In the first group, plasma GH concentrations decreased significantly from January to February (10.1 +/- 0.4 vs 8.7 +/- 0.3 ng X hr./ml; P less than 0.02), then increased from April to June (9.3 +/- 0.4 vs 10.5 +/- 0.7 ng X hr./ml; P less than 0.02). In the second group, GH concentrations were higher than in the first group in April (11.9 +/- 0.9 vs 9.3 +/- 0.4 ng X h/ml; P less than 0.05). However, it decreased between April and June (11.9 +/- 0.9 vs 9.7 +/- 0.4 ng X hr./ml; P less than 0.02) and then did not differ from that of the first group. These results show that plasma GH concentrations are affected by photoperiodic changes and suggest the existence of seasonal variations in GH plasma levels in the Ram.

Animals↗
PubMed1982

[Induced preovulatory discharge of LH during the seasonal anoestrus of the goat (author's transl)].

Preovulatory LH surges were induced and synchronized in 12 Alpine goats during the anoestrus season using a progestagen-PMSG treatment. Onsets of oestrus, plasma LH levels and numbers of ovulations were recorded. During the preovulatory surge, frequencies of blood sampling were such (1 per hour in 8 goats and 1 each 4 min. in 4 other goats) as to allow for the first time a precise description of this biological event in the goat. Results may be summarized as follows: (1) Plasma LH levels were low (less than 1 ng/ml) and constant during the hours preceding the surge, (2) the onset of LH surge preceded by 2 hrs, on the average, that of oestrus behaviour, (3) preovulatory surges presented a definite pulsatility when maximum levels were reached, (4) no positive relationship was found between the magnitude of the surge and the corresponding number of ovulation, (5) in two animals, the LH surge was definitely biphasic, each peak presenting serveral pulses of secretion.

Anestrus↗
PubMed1982

Anomalies in ovarian function of peulh ewes.

The ovarian activity of 8 Niger Peulh ewes was followed for 2 1 2 years by assaying the levels of progesterone in blood plasma sampled daily and by endoscopic observation. Although the ewes did not experience seasonal anestrus, their cycles were not regular. Most animals had persistent corpora lutea at some stage, but particularly in June. This resulted in cycles averaging 49.9+/-6.8 days in length instead of the normal 16.9+/-0.1 days. Intervals between successive luteal phases lasted 4-15 days as compared with 2.3+/-0.06 days seen in normal cycles. This occurred in most ewes at least once during the period from December to April. In these cases, the preovulatory discharge of LH was delayed until 7.5+/-1.8 days after the fall in the level of progesterone. The incidence of these anomalies suggests that the ewes had 69% of the ovulations and 56% of the behavioral estrus as compared to ewes that cycled regularly.

Journal Article↗
PubMed1982

FSH and LH variations in beef cows during the postpartum period.

To study the plasma gonadotrophin profiles of 9 cows after parturition, blood samples were obtained every 20 min for 12 hrs on three occasions between 5 and 50 days postpartum and analysed by RIA techniques. The time of the first ovulation, as judged by plasma progesterone levels, varied from 30 to more than 60 days postpartum. Variations in mean levels of FSH and LH were not significantly correlated with the postpartum interval. However, the mean levels of plasma FSH and number of LH pulses were lower in females which had not ovulated than in those which had. The cows could be classified into four groups: group 1 with less than 4 LH pulses in 12 hrs and a mean plasma FSH level less than 138 ng/ml; group 2 with more than 4 LH pulses in 12 hrs and varying plasma FSH levels; group 3 with less than 4 LH pulses in 12 hrs and a mean plasma FSH level greater than 138 ng/ml; group 4 which had ovulated. This classification indicated that the LH and FSH levels progressed significantly (2.46 to 3.56 ng/ml, P less than 0.05; 120 to 159 ng/ml, P less than 0.01, respectively) from groups 1 to 3, and that they decreased in the females which had ovulated (group 4). Since the time of the first ovulation after parturition varied, it was not possible to demonstrate any relationship between that interval and the mean plasma gonadotrophin profiles. However, when ovulation was considered as time zero there was a clear increase in plasma gonadotrophin before ovulation.

Animals↗
PubMed1982

Influence of season on mean plasma levels of prolactin, placental lactogen hormone and luteinizing hormone during the second half of gestation in the ewe.

Mean plasma levels of prolactin (PRL), placental lactogen (OCS) and luteinizing hormone (LH) have been studied in pregnant ewes at different times of the year from approximately day 60 of gestation until parturition. Three groups were constituted and inseminated at different times: September, group I; November, group II; March, group III. Blood samples were collected on two consecutive days approximately every 10 days. The results indicate that plasma PRL levels are influenced by the season. In group I, PRL concentrations were 3 and 2 times less than those of group III during the third and fifth months of gestation. OCS levels, strongly dependent on the stage of gestation, were not significantly affected by the season. LH concentrations remained low in all three groups throughout the studied period of gestation.

Animals↗
PubMed1982

Influence of 2 Br-alpha-ergocryptine (CB 154) on the secretion of prolactin, LH, FSH and testosterone and on testicular growth in rams subjected to different photoperiods.

The influence of 2-Br-alpha-ergocryptine (CB 154) on the secretion of gonadotrophins and on testicular function has been studied in rams subjected to either a normal photoperiod or an abnormal photoperiod causing hyperprolactinaemia. The CB 154 treatment significantly lowered the mean frequency of LH and testosterone pulses in hyperprolactinaemic animals as compared to solvent-treated ones. Also, only those groups subjected to an abnormal photoperiod (groups 2 and 3) exhibited a significant rise in the frequency of LH and testosterone peaks after CB 154 was withdrawn. During treatment, plasma FSH concentrations increased significantly only in group 1 which was subjected to normal photoperiodic variations. Testicular growth was delayed in CB 154-treated rams compared to solvent-treated ones only in group 3 (hyperprolactinaemic).

Animals↗
PubMed1982

Hypothalamic and pituitary cytosol receptors to 5 alpha-dihydrotestosterone and oestradiol-17 beta during the prepubertal period in the male lamb.

Hypothalamic and pituitary cytosol receptors to 5 alpha-dihydrotestosterone (DHT) and oestradiol-17 beta (E2) were measured in the male lamb from 9 to 120 days of age, 24 h after castration. Concentrations of pituitary receptors did not change with age, but the total number of receptors and the pituitary weight showed a parallel increase (P less than 0.001). Conversely, there were no marked changes in the total number of hypothalamic receptors but this number was high as early as 9 days of age, 42.4 and 80.0 fmol/hypothalamus for DHT and E2, respectively. These data suggest that the number of hypothalamic and pituitary cytosol receptors to DHT and E2, is not a critical parameter in the succession of events which precedes puberty.

Age Factors↗
PubMed1982

Seasonal variation in LH and testosterone release in rams of two breeds.

Blood was collected hourly for 24 h in December, February, April, June and September from Préalpes du sud and Ile-de-France rams. Coincidence of the LH and testosterone peaks was found for 96.4% of a total of 670 LH peaks and 647 testosterone peaks. The number of LH and testosterone peaks increased by 66% in Ile-de-France rams and 200% in Préalpes du Sud rams between December and June (P less than 0.001). Values in June and September were similar in Préalpes du Sud rams. There were no differences between breeds in December, but in June, Préalpes du Sud had significantly more peaks than did Ile-de-France rams (P less than 0.025). The numbers of LH and testosterone peaks increased significantly (P less than 0.05) in Préalpes du Sud rams between December and February or April. These results indicate that, although numbers of peaks of LH and testosterone increase when the animals pass from the non-breeding to the breeding season, the genotype influences the pattern of release through the year.

Animals↗
PubMed1982

Diurnal variation in release of LH and testosterone in the ram.

The time of appearance of plasma LH and testosterone peaks through the day determined in 75 Préalpes du Sud and 41 Ile-de-France rams in December and in 44 Préalpes du Sud and 11 Ile-de-France rams in June. The distribution of peaks throughout the day was non-random for the two hormones in the two breeds and for both times of the year (P less than 0.01 at least on each occasion; P less than 0.001 on pooled data from the two breeds). The most striking features were the occurrence of (1) a minimum of LH and testosterone peaks immediately after 'dawn' (lights on) in both months; (2) a maximum of peaks 3 h after 'dawn' in June and 4 h after 'dawn' in December. For several hours after the increase in frequency of peaks the probability of measuring peaks of LH values in December and June when adjusted for the time of 'dawn' suggest that dawn could act as a synchronizer of gonadotroph activity.

Animals↗
PubMed1981

Multiunit activity in the anterior median eminence and adjacent areas of the hypothalamus of the ewe in relation to LH secretion.

Changes in multiunit activity (MUA) in the anterior median eminence and adjacent tissues just posterior to the optic chiasma were recorded in lightly anaesthetized, ovariectomized ewes after an i.m. injection either of oil (group I) or of 50 microgram oestradiol benzoate (ODB) in oil (group II). Changes in plasma LH concentration that occurred during the recording were determined by radioimmunoassay. In both groups, when the electrodes reached the correct site, the MUA showed a bursting pattern of firing with a frequency of 0.5-1.5 bursts/s. In group I (10 ewes), the MUA showed circhoral variations at intervals of 55.1 +/- 2.8 min similar to those for LH pulses. Plasma LH levels, measured every 10 min, for 2 h in 8 ewes, showed a total of 14 pulses which were always preceded by an increase in MUA. Hormonal values and bioelectrical activity were positively correlated (p < 0.01). When cumulated hourly, the mean MUA in group I remained stable, from 10.5 to 22.5 h after oil treatment. Then, intravenous injection of 100 microgram of ODB induced a rapid increase in MUA. During the 2 h after this injection, we observed only two pulses of LH in the 8 studied ewes. In animals injected i.m. with ODB before the recording (group II, n = 16), the mean MUA (cumulated every hour) from 10.5 to 22.5 postinjection was significantly higher (p < 0.001) than in animals from group I (control). Within group II, 5 ewes discharged an obvious peak of LH, 18-24 h after ODB injection and showed a shortening of the MUA circhoral period (which varied from 10 to 20 min, at the time of initiation of the surge) followed by an increase in the mean amplitude. These 5 ewes showed a significantly higher increase (p < 0.03) in the MUA per hour (from 10.5 to 22.5 h after ODB) than the 9 which did not show an LH peak. Thus, the changes in MUA were clearly related in time to changes in LH secretion whether occurring as spontaneous pulses or as peaks induced by ODB.

Animals↗
PubMed1981

Basic neuroendocrine events before puberty in cattle, sheep and pigs.

Neuroendocrine events before puberty are compared in male and female cattle, sheep and pigs. The patterns of secretion of gonadotrophin, the age-related LH responses to castration or LH-RH administration and the effects of prolonged steroid treatment give information about the maturity of the hypothalamic-pituitary axis. It appears that in all three species the mechanisms involved in the expression of puberty are progressive rather than abrupt events. Some original contributions reported here, such as age-related changes in plasma levels and pulses of LH in the gilt, and the variations in pituitary cytosol receptors to 5 alpha-dihydrotestosterone and oestradiol-17 beta in the male lamb support this contention. Finally, this brief review of the neuroendocrine events known to occur before puberty in three domestic mammals underlines numerous missing links in our understanding of the prepubertal processes.

Aging↗
PubMed1980

Control of Sertoli and germ cell populations in the cock and sheep testes.

Sertoli cells are involved in the control of spermatogenesis. In adult animals, the Sertoli cell stocks, fixed before puberty, are highly correlated with those of the germ cells. Some factors influencing Sertoli cell stock formation have been analyzed: 1) Early hemicastration of impuberal animals showed that the proliferative activities of the Sertoli and the germ cells before puberty, rather than their initial numbers at birth, were the limiting factors of their final number in adult testis. 2) During testicular growth, LH and FSH levels were correlated to Sertoli cell stocks and to germ cell production. 3) The season of birth influenced the Sertoli cell stock formation in the ram. Daylength modified testicular development in the cockerel and the sheep. 4) Between-strain differences were more marked for the testis than for body growth in the cockerel. In the ram, Sertoli cell stocks were similar between half-brothers but significantly different between sires.

Animals↗
PubMed1980

Reassessment of LRF radioimmunoassay in the plasma and hypothalamic extracts of rats and rams.

A highly sensitive and specific radioimmunoassay for LRF was applied to the measurement of endogenous LRF in various hypothalamic extracts. Specific antiserum was obtained by injecting LRF conjugated to human serum albumin with glutaraldehyde. Thyrotropin-releasing hormone, lysine vasopressin, oxytocin, noradrenaline, LH, FSH and cortical extracts did not appear to affect the assay, and the maximum cross-reaction observed with the LRF analogs tested was 8.5 p. 100 with LRF 2-10. The best detection limit (0.4 pg/tube) was usually obtained when the labelled LRF had been purified by polyacrylamide gel electrophoresis. Within and between-assay coefficients of variation were 8.0 and 12.6 p. 100, respectively (from B/Bo = 20 to 80 p. 100). Synthetic LRF administered to rams by intravenous injection was readily detectable in the peripheral plasma. However, the direct measurement of plasma endogenous LRF may give misleading results due to non-specific interference by plasma factors. No endogenous LRF could be detected in plasma methanol or acetone extracts obtained from rats and rams in various physiological conditions. The inhibition curves parallel to the synthetic LRF curve were obtained by diluting the crude hypothalamic extracts of rams and rats, and a good correlation (r = 0.997) with the Ramirez-McCann bioassay resulted, indicating that using radioimmunoassay to determine hypothalamic LRF content may be fruitful in studying hypothalamo-pituitary gonad interactions. The LRF content of rat and ovine hypothalami ranged from 2-8 to 20-80 ng of LRF, respectively.

Animals↗
PubMed1980

[Mycotic aneurysm of bronchial artery. Apropos of a case in an infant].

The authors report the case of a 15 day old neonate presenting a beta hemolitic streptococic (group A) infection, followed by cardio-respiratory failure and radiological opacification of the left superior lobe associated with ventilatory troubles at the left lung base. Massive hemoptysis made an angiographic study mandatory with the diagnosis of a mediastinal vascular tumor placed besides the left descending aorta with compression of the left bronchovasculary pedicule. Tumor ressection was not possible during surgical exploration and a left superior lobectomy was performed. Histological examination showed pulmonary infarctus. The child died a few weeks later. Autopsy revealed mycotic arterial aneurysm of the superior bronchic artery, a very rare lesion considering its localisation and the age of the patient.

Aneurysm, Infected↗