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S Chastant-Maillard

Publications and source records attributed to S Chastant-Maillard.

10 recordsLinked to original sources
PubMed2006

Effects of cow age and pregnancy on Bartonella infection in a herd of dairy cattle.

Bartonella spp. are small hemotropic bacteria infecting mammals. Four Bartonella species have been recently described in cattle and wild ruminants. To date, the biology and possible pathogenic role of Bartonella species isolated from ruminants are poorly understood. Therefore, a dairy herd of 448 cows and heifers was surveyed in order to establish the prevalence of Bartonella bovis and B. chomelii infections, the level of bacteremia, and the relationship between bacteremia and age or pregnancy status. The putative impact of Bartonella infection on production performance (individual milk cell count, milk yield) and reproductive status (success of artificial insemination [AI], placental retention, embryonic death, and abortion) was also assessed. The overall mean prevalence of B. bovis bacteremia was 59%, with the highest prevalence in heifers (92.5%). No B. chomelii was isolated, and 95% (114/120) of the B. bovis strains isolated and tested by PCR-restriction fragment length polymorphism belonged to type I. The level of bacteremia was higher in pregnant cows than in nonpregnant cows (P = 0.05), and the level of bacteremia rose during the last two-thirds of gestation (P < 0.001). There was no correlation between bacteremia and milk yield, individual milk cell count, success of first AI, interval between two calvings, or incidence of abortion and embryonic death. The interval from calving to first AI was shorter and the incidence of placental retention was lower in bacteremic animals than in nonbacteremic ones (P = 0.03 and P = 0.01, respectively).

Age Factors↗
PubMed2005

In vivo meiotic resumption, fertilization and early embryonic development in the bitch.

Early development in canine species follows a very specific pattern. Oocytes are ovulated at the germinal vesicle stage and meiotic resumption occurs in the oviduct. However, because of difficulties in the accurate determination of ovulation time and in the observation of oocyte nuclear stage by light microscopy, these early events have not been fully described. Moreover, the oocyte stage at which sperm penetration occurs is still uncertain since fertilization of immature oocytes has been reported in vivo and in vitro. The aim of this study was to establish the exact timing of in vivo meiotic resumption, fertilization and early embryo development in the bitch with reference to ovulation. Ovulation was first determined by ultrasonography, artificial inseminations were performed daily and oocytes/embryos were collected between 17 and 138 h after ovulation. After fixation and DNA/tubulin staining, the nuclear stage was observed by confocal microscopy. Of the 195 oocytes/embryos collected from 50 bitches, the germinal vesicle stage was the only one present until 44 h post-ovulation, and the first metaphase II stage was observed for the first time at 54 h. Sperm penetration of immature oocytes appeared to be exceptional (three out of 112 immature oocytes). In most cases, fertilization occurred from 90 h post-ovulation in metaphase II oocytes. Embryonic development was observed up to the eight-cell stage. No significant influence of bitch breed and age on ovulation rate, maturation and developmental kinetics was observed. However, some heterogeneity in the maturation/development process was observed within the cohort of oocytes/embryos collected from one bitch. In conclusion, the most peculiar aspect of the canine species remains oocyte meiotic maturation whereas fertilization follows the same pattern as in other mammals.

Animals↗
PubMed2004

In vitro embryo production efficiency in cattle and its association with oocyte adenosine triphosphate content, quantity of mitochondrial DNA, and mitochondrial DNA haplogroup.

Mitochondria have a broad range of functions that affect reproduction, and structural as well as quantitative variation in mtDNA has been associated with gamete quality and reproductive success. To investigate the mitochondria effect on in vitro embryo production, we collected oocytes by ultrasound-guided follicular aspiration from donor cows known to differ in the developmental capacity, measured by the blastocyst formation rate, of their oocytes. To evaluate the potential effects of mtDNA and mitochondrial function on oocyte quality, the donor cows' mtDNA control region was sequenced and, after pairwise comparisons of polymorphisms, animals were grouped into two major haplogroups. The number of mtDNA molecules per oocyte was quantified by real-time PCR, and the adenosine triphosphate (ATP) content was measured in each oocyte to identify variations between haplogroups. Overall, ATP stocks in oocytes of the two haplogroups differed significantly (P < 0.05; means +/- SEM) both at the germinal vesicle and metaphase II stages (2.8 +/- 0.06 pmol vs. 2.6 +/- 0.07 pmol and 2.9 +/- 0.1 pmol vs. 2.3 +/- 0.06 pmol, respectively). The proportion of development to blastocyst was significantly different between haplogroups (22.3 +/- 2.1 % vs. 36.7 +/- 2.9 %). The number of mtDNA molecules per oocyte was highly variable (377 327 +/- 14 104, ranging from 2.0 x 10(3) to 1.2 x 10(6)) but not significantly different between the two haplogroups; significant differences were observed between animals without any apparent relationship to blastocyst production. These data suggest that mitochondria and mtDNA haplogroup affect the developmental capacity of bovine oocytes in vitro.

Adenosine Triphosphate↗
PubMed2003

Preliminary results on variability in oocyte recovery and developmental competence in cattle derived from embryonic cloning: work in progress.

To investigate female gamete developmental competence and variability in cloned cattle, we performed ovum pick-up and in vitro fertilization in four sets of cloned heifers (n = 10, two sets of triplets and two sets of twins), and four groups of non-genetically related control animals (n = 13). A total of 304 OPU were performed and 1798 oocytes were recovered. Mean oocyte production per female per OPU (+/-S.D.) was similar for clone or control animals (5.7+/-2.9 versus 6.1+/-4.5, respectively), however, in two sets of clones variance for the number of oocytes recovered differed significantly (7.1 versus 23.9 and 7.3 versus 26.7, respectively P<0.001) between clone groups and their respective controls, cloned animals being more homogenous. After in vitro maturation, fertilization with semen from the same bull, and culture, the proportion of oocytes from cloned animals that developed into blastocysts was 35.0+/-29.2% and was not significantly different from controls (29.4+/-30.9). The CV for oocyte recovery, and blastocyst rates was lower in all groups of cloned animals than in controls. Nevertheless, within each set of clones, CV values indicated some degree of variability between animals, thus confirming that cloned cattle are not the exact phenotypic copy of each other. Despite the large number of oocytes analyzed, results should be interpreted with caution due to the limited number of cloned animals.

Animals↗
PubMed2003

Consequences of transvaginal follicular puncture on well-being in cows.

The purpose of this study was to evaluate the impact of repeated follicular puncture used in the ovum pick-up technique on the welfare of cows. The evaluation relies on the physiological measurement of stress, milk production criteria, immune status, and the histological examination of ovaries. Two groups of five Holstein cows were submitted to epidural anaesthesia and genital palpation with insertion of an intravaginal ultrasound probe for transvaginal puncture (the puncture was not performed in the control group). Animals were manipulated twice a week for 8 weeks (16 manipulation sessions). The blood cortisol concentrations increased after each session; however, the concentrations were the same in both the control and the punctured groups. Two adrenocorticotrophic hormone challenge tests, performed before the first session and after the last session, showed an unchanged adrenal sensitivity through repeated puncture sessions. The transvaginal puncture did not affect milk production, or blood and milk somatic cell counts. Ovariectomies were performed on another group of four Holstein cows at various intervals (0 to 30 days) after five similar puncture sessions. Histological examination of the ovaries 4 days after puncture revealed blood-filled follicles and haemorrhagic foci in ovarian stroma, but the examination 30 days after the last puncture session demonstrated very limited, if any, fibrosis. On the basis of the criteria chosen for this study, repeated transvaginal follicular puncture on its own does not impact adversely on the welfare of cows.

Animals↗
PubMed2003

Evidence of oocyte donor cow effect over oocyte production and embryo development in vitro.

There have been few studies on a possible maternal influence on in vitro embryo production in cows. The objective of this study was to evaluate the maternal influence on oocyte production and in vitro blastocyst formation rate using repeated ovum pick-up and in vitro fertilization. Six contemporary cows raised on the same farm and with varied genetic origins were submitted to 42 weeks of ovum pick-up organized into four series. Collected oocytes were fertilized in vitro with spermatozoa from a different bull for each series. In total, 1933 oocytes were recovered from 3936 follicles with a recovery rate of 57.2% and a mean oocyte collection of 4.6+/-0.2 (mean+/-SEM) per animal per session. Animals were ranked according to their oocyte production. The best oocyte donor was the same female in all four series. No relationship was identified between oocyte production and blastocyst production rate (r=-0.08). The mean blastocyst rate was 28.8% with significant variation among animals. The best and the worst blastocyst producers were always the same animals independent of the semen used. The results of the present study support the hypothesis that in cattle, the oocyte donor influences the production of blastocysts. Furthermore, they demonstrate that oocyte and embryo production are independent factors. Further studies are necessary to identify the maternal or oocyte factors responsible for such differences.

Animals↗
PubMed2001

Induction of final maturation by sperm penetration in canine oocytes.

In contrast to oocytes of most mammals, the canine oocyte is at the germinal vesicle stage at ovulation. Moreover, the bitch is receptive to mating while immature oocytes are present in the oviducts. The aims of this study were to examine the influence of fertilization in immature oocytes on the resumption of meiosis, and the modification of both male and female chromatin in fertilized oocytes. Canine cumulus-oocyte complexes collected from routine ovariectomies were cultured in medium 199 with 20% fetal calf serum for 24 h, incubated in the same medium with fresh semen for 24 h, washed, cultured for a further 24 h and fixed. Control oocytes were cultured in the same medium but without spermatozoa for 24, 48 or 72 h. After fixation, chromatin was stained with propidium iodide and examined using laser scanning confocal microscopy. The data indicate that sperm penetration can occur in immature canine oocytes and that it induces resumption of meiosis. After 72 h of culture, the percentage of oocytes at the germinal vesicle stage was significantly lower in fertilized oocytes (40% versus 60.3% for control oocytes; P < 0.05) and the percentage of oocytes beyond metaphase I was significantly greater in fertilized oocytes (28.3% metaphase I and II, and two pronuclei versus 10.2% metaphase I and II for control oocytes; P < 0.01). Observation and measurement of the area of chromatin in fertilized oocytes showed an overall parallel condensation-decondensation of both female and male chromatin from the germinal vesicle stage to the pronuclear stage.

Animals↗
PubMed2001

In vitro maturation of bitch oocytes: effect of sperm penetration.

In contrast to most mammals, bitches ovulate immature oocytes at the germinal vesicle stage. Spermatozoa can be present in the oviduct of bitches at ovulation. The aim of this study was to investigate the influence of premature fertilization on the resumption of meiosis. In addition, the relative behaviour of male and female chromatin was observed. Canine cumulus-oocyte complexes cultured in medium 199 supplemented with 20% fetal calf serum for 24 h were incubated in vitro in the presence or absence of fresh dog semen for 24 h, and then rinsed and cultured in the same medium for a further 24 h. Chromatin was stained by propidium iodide and all oocytes were examined under laser scanning confocal microscopy. Results show that sperm penetration can occur in vitro in immature oocytes and that this induces a resumption of meiosis: at 72 h, the percentage of oocytes at the germinal vesicle stage decreased significantly and the percentage of oocytes beyond metaphase I increased. However, premature fertilization was ineffective for 40% of oocytes, which remained at the germinal vesicle stage. Measurement of chromatin areas in fertilized oocytes showed an overall parallel condensation-decondensation of both female and male chromatin from the germinal vesicle stage to the pronuclear stage, indicating that male and female chromatins are sensitive to the same cell cycle regulators.

Animals↗
PubMed2000

[Cloning and reprogramming of the nucleus in the preimplantation embryo].

In mammals, nuclear transfer (or cloning) consists of introducing the nucleus which is generally transcriptionally active into a new cytoplasmic environment, usually that of a transcriptionally inactive metaphase II oocyte. Following the transfer, intense nucleocytoplasmic exchange takes place, and is responsible for remodeling of the nuclear structure and gene reprogramming. The original development program of the donor nucleus is effaced, and the reconstructed embryo adopts that of the recipient oocyte. Both remodeling and reprogramming are regulated by maternal cytoplasmic factors. Overall transcriptional activity, splicing and translational functions as well as the specific expression of certain genes are fairly similar to corresponding activity in normal embryos. However, the development program seems to be read some hours in advance by the reconstructed embryos, and some basic information is lacking. It is particularly important to study these reprogramming abnormalities during the early stages of development in the context of specific abnormalities in fetal and neonatal development observed after transfer of somatic cells.

Animals↗