Biomedical subjects

P Chemineau

Publications and source records attributed to P Chemineau.

At least 55 records · Page 3Linked to original sources

PubMed1993

Control of photoperiodic inhibition of luteinizing hormone secretion by dopaminergic and serotonergic systems in ovariectomized Ile-de-France ewes supplemented with oestradiol.

The role of dopaminergic and serotonergic systems on LH secretion was investigated in Ile-de-France ewes under different artificial inhibitory photoperiodic regimens. All animals were ovariectomized at the end of the breeding season, chronically treated with an oestradiol implant, and subjected to various changes in daylength for 9 months to inhibit or stimulate their LH secretion. Plasma LH concentration was assessed by taking blood samples twice a week throughout the experiment. The effects of acute intravenous injections of the dopaminergic2 receptor antagonist pimozide (0.08 mg kg-1) and the 5-hydroxytryptamine2 (5HT2) receptor antagonist cyproheptadine (3 mg kg-1) on LH pulsatility were assessed during challenges in four different situations: (1) long days (LD); (2) before short-day response (SD); (3) during refractoriness to short days (RSD); and (4) during inhibition by long days (ILD). LH in blood samples collected twice a week remained low during long days (0.59 +/- 0.03; mean +/- SEM), increased 45 +/- 1.5 days after the onset of short days and decreased 132 +/- 4.9 days later when ewes became refractory to short days, whereas ewes subjected to long days after 91 short days stopped their neuroendocrine activity 19 days earlier (113 +/- 4.7) (P < 0.01). In comparison with the pre-injection period, pimozide significantly increased the mean number of pulses in SD and RSD ewes, but not in LD and ILD ewes: SD: 0 versus 0.45 pulses in 4 h (P < 0.02); RSD: 0 versus 0.9 (P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

[Can melatonin be used in out-of-season reproduction in domestic mammals?].

Melatonin, synthetized by the pineal gland, is the chemical messenger which allows seasonal animals to perceive day length changes. The nervous message, transformed into a hormonal one, triggers pulsatile activity of the LHRH neurons. Its sites and mode of actions are not completely elucidated. The most frequent mode of distribution is the sub-cutaneous implant, which induces an advance of the cyclical ovulatory activity of ewes and goats. The date of fertilization is advanced and fecundity of females is improved. It can be used alone, or in association with other hormonal treatments, or after an artificial photoperiodic treatment. Under these conditions, it allows a quantitative and qualitative increase in out-of-season sperm production in rams and he-goats.

Animals↗

PubMed1993

[Seasonal variations in estrus behavior and ovulatory activity in Chios and Serres ewes in Greece].

Sheep are seasonal breeders, but a lower seasonality has been reported for sheep breeds from the Mediterranean countries enabling spring matings. To further substantiate this, the present study compared seasonal variation in oestrus behaviour and ovulation in two Greek breeds (Chios and Serres) maintained in the same environment. In 27 adult ewes of each breed, oestrus behaviour, the occurrence of ovulation and ovulation rate were monitored during 2 successive years by daily inspection by rams, weekly progesterone assay in circulating blood plasma and monthly ovarian laparoscopy. The periods of anoestrus (109 +/- 8 (wk) vs 178 +/- 5 d) and anovulation (63 +/- 8 vs 149 +/- 6 d) were significantly shorter (P < 0.001 and P < 0.001) and more variable in Chios than in Serres ewes. Furthermore, the percentage of ewes exhibiting oestrus at least once monthly was significantly higher from March to July in Chios than in Serres ewes. Continuous ovulation throughout the year was noted in 5 and 2 Chios ewes during year 1 and 2, respectively. Ovulation rate (3.25 +/- 0.15 vs 1.45 +/- 0.04) was higher in Chios than in Serres ewes (P < 0.001) while duration of oestrus was also longer in Chios ewes (1.8 +/- 0.05 vs 1.5 +/- 0.06 d; P = 0.002). There were significant correlations between the duration of anovulatory periods of the 2 successive years in Chios (r = 0.43) but not Serres ewes. Ovulation rate was positively related to the onset of the sexual season in Serres but not in Chios ewes. The present data suggest that: i) the efficiency of Serres but not in Chios ewes. The present data suggest that: i) the efficiency of spring mating in these breeds is suboptimal since it is a period when the percentage of ewes exhibiting oestrus and ovulation as well as ovulation rate are limited, ii) owing to the large variation in seasonality within Chios ewes and to the good between year correlation in features of seasonality, selection against seasonality in Chios ewes could be worthwhile.

Animals↗

PubMed1992

Abolition of the seasonal release of luteinizing hormone and testosterone in Alpine male goats (Capra hircus) by short photoperiodic cycles.

This study was performed to determine whether rapid alternation between long and short days abolished seasonal variations in the activity of the hypothalamo-pituitary-testis axis observed normally in Alpine and Saanen male goats during the year. Three groups of 6 males were used: group 1 remained in open sheds under the natural annual change in daylength from 16 h of light (long day) to 8 h of light (short day). Group 2 was exposed to 1 month of long days alternated with 1 month of short days; and group 3 to 2 months of long days alternated with 2 months of short days. In group 1, blood samples were taken in December, February and June; in groups 2 and 3, samples were obtained once during short and long days for the melatonin assay. For luteinizing hormone and testosterone determinations monthly samples from group 1 were obtained from September to August while, in groups 2 and 3, blood samples were taken on 4 occasions during long and short days. Weekly blood samples were taken from all groups during the whole of the experiment to measure prolactin and testosterone concentrations. Melatonin profiles indicated that secretion by the pineal gland of male goats from the treated groups adapted to rapid changes in daylength: duration of nocturnal secretion was close to that of the dark period. Treated goats were also able to transduce this signal adequately and always responded to long days by increasing their prolactin concentration (mean +/- s.e.m.; group 2: 62.4 +/- 6.8 ng/ml; group 3: 102.3 +/- 15.7 ng/ml) and to short days with a decrease in prolactin concentrations (35.0 +/- 3.6 and 46.1 +/- 9.5 ng/ml, respectively). In the treated groups, luteinizing hormone pulse frequency varied with day length. In group 2, it was higher in long days (1.1 +/- 0.3 pulses in 8 hours) than in short days (0.7 +/- 0.3) while, in group 3, this frequency was higher in short days (1.9 +/- 0.3) than in long days (0.5 +/- 0.2). Testosterone secretion also varied with daylength; in group 2, the testosterone concentrations were maximum during long days (5.8 +/- 1.4 ng/ml) while in group 3 the maximum testosterone concentrations occurred during short days (6.4 +/- 1.2 ng/ml). These results lead to the conclusion that rapid alternation of long and short days either attenuated (group 3) or prevented (group 2) seasonal changes in the activity of the hypothalamo-pituitary axis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Experimental induction of luteal cyclicity in roe deer (Capreolus capreolus).

Concentrations of progesterone and luteinizing hormone in plasma were analysed for two consecutive years in samples from nonpregnant female roe deer. Three animals were treated with monthly prostaglandin injections (325 micrograms cloprostenol) from October 1989 to April 1990 and from October 1990 to March 1991, and three were kept as controls. In control animals, a small increase in progesterone concentrations in July 1990 occurred at the same time as the commencement of the rut in other husbanded roe deer. In prostaglandin-treated animals, progesterone concentration was high at the time of the rut and remained so until late February 1990. After the next rut (August 1990), progesterone concentration remained high until March 1991. Between October and February-March, injections of prostaglandins induced dramatic, but temporary (lasting 72 h), decreases in plasma progesterone concentrations, indicating luteal regression and subsequent ovulation. We infer that roe deer can ovulate repeatedly and should therefore not be regarded as an obligate monoestrous species.

Animals↗

PubMed1991

Decrease in the seasonality of sexual behavior and sperm production in bucks by exposure to short photoperiodic cycles.

Bucks show seasonal variation in their body weight and sexual activity. Three groups of six Alpine and Saanen bucks were used over two consecutive years to investigate if rapid alternations between long and short days could abolish this seasonal variation. The control group was kept under natural annual daylength, while the experimental groups were exposed to alternations of either 1 month of 16L:8D and 1 month of 8L:16D (2-month treatment) or to 2 months of 16L:8D and 2 months of 8L:16D (4-month treatment). In the control group, body weight, sexual behavior, testicular weight and sperm production showed important seasonal variations: body weight decreased between September and January by about 7 kg; refusal to ejaculate went up to 25% in August; testicular weight varied from 103 +/- 2 g (March) to 149 +/- 7 g (October). In contrast, seasonal variations of these parameters decreased in the two experimental groups. In the 2-month treatment group, testicular weight increased from 134 +/- 7 (March) to 148 +/- 8 g (October); while in the 4-month treatment group it increased from 123 +/- 10 to 138 +/- 12 g, respectively; in the same period, the two experimental groups of bucks produced a larger total number of spermatozoa per ejaculate (6.3 +/- 0.3 x 10(9); 2-month treatment and 7.2 +/- 0.3; 4-month treatment) than in the control group (4.2 +/- 0.4). We conclude that rapid alternations between long and short days decreased seasonality in the sexual activity of bucks.

Journal Article↗

PubMed1988

Photoperiodic and melatonin treatments for the control of seasonal reproduction in sheep and goats.

The control of seasonal reproductive activity in sheep and goats in open sheds, needs extra-light (E) during the photosensitive phase (equivalent to long days, LD), followed by treatment with melatonin (equivalent to short days, SD). In autumn-born Ile-de-France or Lacaune ram lambs, 2 months of E followed by decreasing daylength for 90 days, advanced onset of the first breeding season by allowing males to reach their maximum testis volume and sperm production earlier than for untreated ram lambs. Substitution of decreasing daylength with melatonin implants allowed a transient increase in testis volume. Adult Ile-de-France rams maintained under short light rhythms with 2 month-period, demonstrated, during at least 2 consecutive years, a testis volume equivalent to that observed during the normal breeding season. These light-treated rams produced, during non-breeding season, spermatozoa in the same quantity and quality as during the normal breeding season. In anovulatory out-of-season dairy goats, E treatment was demonstrated to be necessary before melatonin treatment and melatonin to be necessary after E treatment to stimulate oestrous and ovulatory activities. Stimulation of the anovulatory females by the introduction of treated males ("male effect"), appeared to be necessary to obtain maximum stimulation of the treated females. Two months of E, followed by melatonin treatment (daily injection or drenching or subcutaneous implants) allowed cycles with ovulation to be maintained for more than 2 months. Although effective for control of out-of-season reproductive activity, melatonin slightly decreased milk production when applied soon after kidding. So, total control of reproduction in sheep and goats by manipulation of photoperiod in open sheds and melatonin treatments appears feasible in both sexes.

Animals↗

PubMed1988

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus).

In Exp. 1, the changes in pulsatile LH secretion at the onset of the breeding season were observed in 20 intact, mature Saanen does. Blood was sampled every 20 min for 6 h each week from the beginning of August until the onset of ovulatory activity, as evidenced by cycles in plasma progesterone. The first doe ovulated at the end of August and all were cycling by the end of September. As the first ovulation approached, LH pulse frequency increased by 67% and mean levels of LH increased by 47%. These changes were progressive rather than abrupt. In Exp. 2, seasonal changes in the inhibition of pulsatile LH secretion by ovarian steroids were studied in ovariectomized Saanen does. The animals were untreated (N = 4) or given subcutaneous oestradiol implants (N = 4) and blood was sampled every 10 min for 6 h, twice during the breeding season and twice during the anoestrous season. In each season, the second series of samples was taken after the animals had been treated with progesterone, administered by intravaginal implants. Season did not significantly affect LH secretion in goats not treated with oestradiol, but LH pulse frequency was 54% lower during the anoestrous season than during the breeding season in oestradiol-treated goats. Mean LH concentrations were affected in the same manner as pulse frequency, but pulse amplitude was increased by oestradiol treatment in both seasons. Progesterone had no detectable effect on LH secretion in either season. In Exp. 3, the response to repeated melatonin injections at a set time after dawn was investigated in 11 oestradiol-treated, ovariectomized goats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Ovarian capillary blood flow in seasonally anoestrous ewes induced to ovulate by treatment with GnRH.

The microsphere technique was used to obtain estimates of ovarian capillary blood flow near ovulation, in 8 seasonally anoestrous ewes, which were induced to ovulate by GnRH therapy. Plasma progesterone concentrations were monitored in jugular blood sampled between Days 4 and 7 after the onset of the preovulatory LH surge. The ewes were then slaughtered. Three of the ewes were treated with a single injection of 20 mg progesterone before GnRH therapy. In these ewes and 1 other, plasma progesterone values increased after ovulation and reached 1.0 ng/ml on Day 7 following the preovulatory LH surge (normal, functional CL), whilst in the other 4 ewes progesterone concentrations increased initially then declined to 0.5 ng/ml by Day 7 (abnormal CL). In the ewes exhibiting normal luteal function, the mean ovarian capillary blood flow was significantly greater (P less than 0.01) than that for ewes having abnormal luteal function. Irrespective of the type of CL produced, capillary blood flow was significantly greater (P less than 0.05) in ovulatory ovaries than in non-ovulatory ovaries. These findings indicate that the rate of capillary blood flow in ovaries near ovulation may be a critical factor in normal development and maturation of preovulatory follicles and function of subsequently formed CL.

Anestrus↗

PubMed1987

Ultrastructure of in vivo fertilization in the goat.

In vivo fertilization of goat eggs has been studied by electron microscopy. Eggs were recovered from superovulated or natural cyclic goats, 32 to 52 hours after the onset of oestrus; only eggs recovered between 46 and 52 hours were fertilized. Spermatozoa penetrated the zona pellucida tangentially leaving vesiculated products of the acrosome reaction at the zona surface. As sperm penetrated into the ooplasm, the second meiotic division completed and cortical granule exocytosis occurred. However a few unreacted cortical granules usually remained in the cortex of the fertilized eggs, adjacent to the plasma membrane. After swelling the two pronuclei presented similar ultrastructural morphology: they contained small, compact, agranular nucleoli and unevenly distributed chromatin. The cytoplasm in close vicinity to the apposed pronuclei contained large stacks of annulate lamellae, smooth endoplasmic reticulum, prominent Golgi complexes, as well as dense areas of unidentified material. The abundance of cytoplasmic organelles near the pronuclei might be the expression of intensive metabolic activity. Conversely, in the cortex of fertilized ova several large organelles-free cytoplasmic areas were randomly distributed.

Animals↗

PubMed1986

Production, freezing and transfer of embryos from a bluetongue-infected goat herd without bluetongue transmission.

In order to import non-seasonal Creole goats from the Carribean to Europe for an experimental purpose, thirty Creole goats were treated with 10 mg of FSH; embryos were collected at slaughter, washed and deep frozen. After rapid thawing, they were reimplanted surgically into European dairy goats. Twenty-four females ovulated but only 17 of the ovulating females had functional corpora lutea (CL) at collection. Ovulation rate (CL goat ) and recovery rate (embryo CL ) were 13.8 and 78% for females with functional CL. Of 191 embryonic structures collected, 79% were considered suitable for deep freezing: 23% were young blastocysts, 47% were expanded blastocysts, and 30% were zona-pellucida (zp)-free and zp-damaged embryos. Seventy-eight embryos were thawed and 63 were reimplanted. Sixty-eight percent of the recipient females delivered 19 kids. The percentage of kids born relative to good-quality re-implanted embryos was higher for zp-free embryos (64%) than for young and expanded blastocyts (36%). Forty-seven percent of the donor females had strong positive serological reactions for bluetongue virus antibodies against serotypes 6 and 14. However, no recipient goats or newborn kids were positive. Virus isolation attempts on the collection media and last embryo washes were negative.

Journal Article↗

PubMed1986

Induction and persistence of pituitary and ovarian activity in the out-of-season lactating dairy goat after a treatment combining a skeleton photoperiod, melatonin and the male effect.

Thirty-two out-of-season Saanen dairy goats were involved in a 2 X 2 factorial experiment using (1) extra-light treatment (equivalent to long days) from 18 January to 19 March, at the end of gestation and the onset of lactation and (2) daily melatonin injections (equivalent to short days) from 20 March to 30 June. Hence, there were 4 groups of 8 goats each: CC (control-control), EC (extra-light-control), CM (control-melatonin) and EM (extra-light-melatonin). In each group teasers (males and androgenized females) were introduced on 30 May. Serial blood samples were taken for measurement of LH pulsatility on 30 April and 30 May. Ovarian activity was followed by plasma progesterone assay and laparoscopy. Oestrous behaviour was checked daily from 30 May to 15 July. The number of LH pulses was not modified by the treatments (extra light or melatonin). Melatonin treatment increased the basal concentration of LH (Groups CC + EC = 0.30 ng/ml; Groups CM + EM = 0.38 ng/ml; P less than 0.02) and the amplitude of pulses (Groups CC + EC = 1.24; Groups CM + EM = 2.44 ng/ml; P less than 0.02); the highest amplitude was observed for females in Group EM. Melatonin-treated females ovulated earlier after introduction of teasers than did untreated goats (Groups CM + EM = 2.3 days; Groups CC + EC = 6.1 days; P less than 0.001), but treatments did not modify ovulation rate (mean 2.1) or percentage of goats experiencing a short luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

[Hourly variations in rectal temperature and prolactinemia in the creole goat kept outside in a tropical environment].

Rectal temperature and plasma prolactin level were measured hourly in "creole goats" during 27 consecutive hours in March, July and November. Simultaneously, air, "black-globe" temperature and relative humidity were measured at the height of the animals. Rectal temperature and plasma prolactin level varied according to hour and season and were always higher during the day than during the night. Plasma prolactin level increased dramatically for 3 h after dusk only in March. Rectal temperature showed a significantly higher correlation with air temperature than with "black-globe" temperature. On the contrary, plasma prolactin level was more significantly correlated with "black-globe" temperature than with air temperature. When all seasons and hours were pooled, "black-globe" temperature showed a threshold (32-34 degrees C), beyond which prolactin reached values higher than 100 ng/ml. Rectal temperature was always significantly correlated with plasma prolactin level. Plasma prolactin level as an index of thermal stress and the role of prolactin in thermoregulation have been discussed.

Animals↗

PubMed1984

[Progesterone secretion during male-induced cycle in the Creole goat in anestrus: seasonal effects].

Plasma progesterone levels during male-induced ovarian cycles were measured at three periods (March, July, November) in Creole goats. For the females experiencing a cycle of normal duration, plasma progesterone reached 2.0 ng/ml six days after male introduction. For the females experiencing a short cycle, a brief (one day) and slight (0.5 to 1.0 ng/ml) secretion of progesterone was observed during this cycle. A seasonal variation in the interval between male introduction and maximum level of progesterone during the short cycle was demonstrated (March: 4.7 days; July: 5.6 d. and November: 3.1 d.), but the maximum level reached did not vary with season (0.6; 0.9 and 0.6 ng/ml).

Animals↗

PubMed1983

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year.

The characteristics of the oestrous and ovarian cycles of local goats were studied over 2 years, on 96 females in March, 60 in July and 100 in November. After 3 weeks of separation between sexes, the females with inactive ovaries were identified and harnessed males were introduced. Detection of oestrus was undertaken daily and the date and rate of ovulation were checked at laparoscopies. The proportion of females with non-cyclic ovaries before the mating period varied according to the season and whether the females were nulliparous or suckling. Among the females with inactive ovaries before the mating period, 97% ovulated 2 . 8 days after the introduction of males; 68% of these initial ovulations were accompanied by oestrus and 76% resulted in short luteal phases (5 . 3 days) followed by a second ovulation accompanied by oestrus 89% of the time. The proportions of initial ovulations with oestrus and of initial ovulations followed by a short luteal phase were in linear relationship with the proportion of females with non-cyclic ovaries before the mating period. For the females with cyclic ovaries before the mating period, the distribution of first oestrus during the 8 days after the introduction of males was significantly different from the expected uniform distribution. A possible luteolytic action of teasing was suspected. The fertility of females in all groups was high (greater than 79%). Litter size was not different for non-cyclic and for cyclic females.

Animals↗

PubMed1982

Plasma levels of LH, FSH, prolactin, oestradiol-17beta and progesterone during natural and induced oestrus in the dairy goat.

The patterns of LH, FSH, prolactin and oestradiol-17beta, before and during natural oestrus, and of progesterone during the following cycle were studied in four French Alpine dairy goats and compared with those obtained after synchronization of oestrus in the same animals. The highest concentration of oestradiol-17beta was measured at the beginning of oestrus and was followed 3 hours later by simultaneous rises of LH, FSH and prolactin. A second FSH peak was observed 48h after the first one. On D(3) (D(0) = day of oestrus) progesterone concentration was over 1 ng/ml. The luteal phase lasted 15 days. Peak concentrations of oestradiol-17beta and progesterone were higher in animals when oestrus was induced. This was attributed to their higher ovulation rate. The second FSH peak was lower, and the interval between oestradiol-17beta peak and gonadotrophin surge longer, than at natural oestrus.

Journal Article↗

PubMedDate not supplied

Role of the uterus in early regression of corpora lutea induced by the ram effect in seasonally anoestrous Barbarine ewes.

The involvement of the uterus in early regression of corpora lutea induced by the ram effect was studied in seasonally anoestrous Barbarine ewes. In experiment 1, group I was only submitted to the male effect (control, n = 15) while group II (n = 14) was injected every 12 h with flunixin meglumine, a PGF2 alpha synthetase inhibitor (finadyne), from day 3 to day 6 (day 0: day of ram introduction). The preovulatory LH surge appeared at the same time (around 21 h after ram introduction) in both groups. Finadyne treatment significantly decreased 13-14-dihydro-15-keto-PGF2 alpha (PGFM) pulses (1.3 +/- 0.3 versus 0.4 +/- 0.2; P < 0.05), the number of short cycles (50 versus 14%, P < 0.05), and provided a single peak of oestrus, 15-16 days after the introduction of the rams, instead of between day 14 and day 23 (P < 0.01). In experiment 2, 17 hysterectomized ewes were allocated into two groups: group III (n = 8) was injected with oil and group IV (n = 9) received an intramuscular injection of 20 mg of progesterone immediately before introduction of rams. An additional group of intact ewes was used as control (group V, n = 9). Hysterectomy did not affect the ovulation response to the ram effect, but completely suppressed short cycles (0 versus 78%, P < 0.001). The preovulatory LH surge was delayed in hysterectomized females (36.0 +/- 14.1 versus 16.6 +/- 11.4 h; P < 0.004). Treatment with progesterone significantly (P < 0.01) increased the interval between introduction of rams and the preovulatory LH surge. In conclusion, suppression of short cycles by hysterectomy and an inhibitor of PGF2 alpha synthetase suggest that the uterus is essential for determining the lifespan of ram-induced corpora lutea and that premature release of PGF2 alpha is the cause of early luteal regression. The hypothesis that lower secretion of progesterone before D5 could be the initial cause of the premature induction of the luteolytic signal is discussed.

Anestrus↗

PubMedDate not supplied

Reproductive and productive performance in Chios ewes mated in spring or in autumn.

One hundred and sixty adult ewes of the Chios breed were divided randomly into two groups. One group was used for breeding in spring (S) and the other in autumn (A). In both groups oestrous behaviour was detected once a day. Ovulatory activity, 7 d after oestrus, fertility, prolificacy, embryo mortality, birth weight of lambs and milk production were recorded. The percentage of ewes which exhibited oestrous behaviour was 92 and 100% in S and A groups, respectively, while fertility of mated ewes was 98 and 100%. Ovulation rate was significantly lower in S than in A ewes (M +/- sd; 2.85 +/- 1.07 versus 3.44 +/- 1.45, respectively, P < 0.0001). However, prolificacy did not differ between the two groups (2.04 +/- 0.77 versus 2.13 +/- 0.85, for S and A ewes, respectively) as it did not increase after an ovulation rate of 4.0. There were no differences in birth weights (except for triplets) but total milk production was significantly higher in S ewes (257.5 +/- 100.7 kg versus 153.0 +/- 51.9 kg, for S and A, respectively, P < 0.001). These results suggest that despite a higher ovulation rate in autumn, higher embryonic mortality at this time of the year leads to equivalent fertility, prolificacy and birth weight in spring as in autumn.

Animals↗