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Biomedical subjects

M Coryn

Publications and source records attributed to M Coryn.

At least 37 records · Page 2Linked to original sources
PubMed1999

Insulin resistance: the link between metabolic disorders and cystic ovarian disease in high yielding dairy cows?

A preliminary investigation was performed to examine whether insulin resistance is a factor in the pathogenesis of cystic ovarian disease (COD) in high-yielding dairy cows. In total 30 cows, of which 15 were diagnosed as suffering from COD based on the anamnesis and clinical examination, and the other 15 served as matched controls, were subjected to an intravenous glucose tolerance test (IVGTT). The aim of the study was to investigate whether insulin activity was altered in COD cows. Differences in glucose clearance between the COD cows and their controls were analyzed comparing the fractional turnover rate (k), the glucose half-time (T1/2), and the area under the curve (AUC) 60 and 120 min after infusion. Differences in insulin response were analyzed comparing the insulin increment, the insulin peak concentration, and the AUC 60 and 120 min after glucose infusion. Although insulin resistance, attended by a secondary hyperinsulinemia, is stated to directly contribute to the ovarian abnormalities that characterize the polycystic ovary syndrome (PCOS) in human medicine, this was not observed in COD cows. On the contrary, COD cows appeared to have a low insulin response following an intravenous glucose load as compared with their matched controls. This was illustrated by significantly lower insulin increments (P = 0.04) and lower insulin peak concentrations (P = 0.04). As COD cows had a significantly lower insulin response to a standard glucose load, it was concluded that insulin could be a factor in the pathogenesis of COD in dairy cows.

3-Hydroxybutyric Acid↗
PubMed1999

Immunohistochemical detection of estrogen receptors in the canine uterus and their relation to sex steroid hormone levels.

Cyclic changes in estrogen receptor expression in the uterine tissue of 60 female dogs were evaluated, using an immunohistochemical technique on formalin-fixed paraffin-embedded sections. The expression of estrogen receptors in the uterine horns, body and cervix was quantified by means of an immunohistochemical score. A negative correlation was found between staining scores in the uterine horns and serum progesterone levels. Generally, staining scores in the uterine horns were highest during proestrus, declined during estrus and were lowest during early metestrus. During anestrus high staining scores for estrogen receptors were observed, indicating sensitivity for estrogens in a sexual quiescence stage. Compared with the uterine horns, high staining scores were found in the uterine body and cervix during estrus and metestrus. No positive staining for estrogen receptors was detected in 1 pregnant uterus. Fluctuations in estrogen receptors were more pronounced in endometrial stroma cells than in epithelial cells of the uterine horns. The importance of stromal cells in the sexual cyclicity of the canine uterus should not be underestimated when studying uterine endocrinology and pathology.

Animals↗
PubMed1998

Effects of long-term treatment with bovine somatotropin on follicular dynamics and subsequent oocyte and blastocyst yield in an OPU-IVF program.

Fourteen Holstein-Friesian heifers between 15 and 22 months of age with normal reproductive tracts were used in an experimental set up to investigate the effect of a long term rBST-treatment on the follicular population prior to transvaginal ovum pick-up (OPU). The estrous cycle of the animals was synchronized by means of a double injection of 2 ml cloprostenol 11 days apart. The heifers were divided in 2 equal groups (n = 7) in which the animals had the same average body weight, one group receiving a weekly subcutaneous injection of 640 mg recombinantly derived bovine somatotropin (rBST) on Mondays (rBST-treatment group) and a control group, being injected with 10 ml of saline. Heifers in both groups were submitted to OPU twice a week on Mondays and Thursdays using a 5 Mhz transducer and a disposable, 55 mm long, 20-g short bevelled needle at a vacuum pressure corresponding to approximately 13 ml water/min. The experimental period lasted for 10 weeks (April to June), each animal receiving a total of 10 injections and being submitted to OPU for 20 times. Oocytes were subsequently matured and cultured in a separate drop per cow following conventional IVF procedures. A blood sample was taken on heparin immediately after each OPU session, for determination of blood progesterone concentrations to assess the influence of treatment and OPU procedure on the cow's estrous cycle. Although results show a significant increase in the total number of follicles and medium sized follicles in the rBST-treated group, no statistically significant different number of retrieved oocytes between the rBST-treated and nontreated group could be detected. The average number of retrieved oocytes per session per cow was comparable, being 6.4 for the treated and 6.0 for the control group. Additionally, the average number of blastocysts per cow per session did not differ significantly between groups, being 1.41 in the rBST-treated group and 1.53 in the control group. The number of cultured oocytes which developed to the blastocyst stage was 22% in the rBST-treated group, which was not significantly different from 25% in the control group. Repeated OPU appeared to induce a certain degree of acyclicity in both treated and nontreated animals.

Animals↗
PubMed1997

Timing of compaction and inner cell allocation in bovine embryos produced in vivo after superovulation.

Preimplantation development in the bovine embryo was examined by relating the occurrence of three morphogenetic processes (compaction, blastulation, and hatching) to the timing of allocation of embryonic cells to the inner cell mass (ICM) or to the trophectoderm (TE). Embryos were collected from 26 cows between Days 4 and 9 postovulation. Compaction started 5 days postovulation at the 32-cell stage. Morulae remained firmly compact until the seventh cell cycle was almost completed. Blastocyst formation started between the 64- and 128-cell stage at Days 6, 7, and 8 postovulation. Hatching was predominant at Day 9 postovulation. ICM and TE cells could successfully be distinguished by differential staining in 107 of 142 embryos (75%). Inner cells could first be detected in 20% of 16-cell embryos. Unexpectedly, it was found that inner cell allocation and compaction were independent processes, since 31% of compacted morulae displayed no ICM. Beyond the 50-cell stage, in vivo compact morulae displayed at least 10 ICM cells, whereas blastocysts with a minimum total cell number of 65 cells displayed at least 23 ICM cells. It can be concluded that the slow in vivo transition from the morula to the blastocyst stage allows sufficient time for allocation of inner cells to the ICM of the embryo.

Animals↗
PubMed1996

Post-partum anoestrus in dairy cows: a review.

In modern high-yielding dairy herds fertility is of major economic importance. In order to gain maximum profit, calving intervals should not exceed 365 days. The achievement of a 365-day calving interval requires an early resumption of ovarian activity, an excellent oestrus detection, and a high first-service conception rate. Especially the inability to detect oestrus and to mate the cows by 60 to 80 days after calving is a common problem among dairy farmers nowadays. In this article a review is given about the occurrence, causes, treatment, and prevention of post-partum anoestrus in dairy cows.

Animals↗
PubMed1990

Plasma estradiol-17 beta concentrations in the cow during induced estrus and after injection of estradiol-17 beta benzoate and estradiol-17 beta cypionate--a preliminary study.

Plasma estradiol-17 beta concentrations were investigated in cows during induced estrus and after an intramuscular injection of 10 mg of estradiol-17 beta benzoate and estradiol-17 beta cypionate to determine a withdrawal period for both preparations. After the estradiol-17 beta benzoate injection, the plasma estradiol-17 beta concentration was higher than the physiological maximum of 24 pg/ml obtained during induced estrus for a period of 114 +/- 10 h (mean +/- SEM). For estradiol-17 beta cypionate the corresponding value was 170 +/- 17 h (mean +/- SEM). A withdrawal period of 7 days for the benzoate ester and of 10 days for estradiol-17 beta cypionate is therefore proposed. These results were confirmed by biopsies taken at the injection site 8 and 15 days after the injection of estradiol-17 beta benzoate and estradiol-17 beta cypionate, respectively. In these biopsies no residues of estradiol-17 beta nor of its esters could be detected.

Animals↗
PubMed1987

Clinical and endocrine aspects of the oestrous cycle in donkeys (Equus asinus).

Oestrous behaviour and occurrence of ovulation was studied in 13 jenny asses (3-18 years) during a 15-month period. Teasing was performed daily and follicular growth, ovulation and changes of the genitalia were checked every other day by rectal palpation during dioestrus or the anovulatory season or daily during oestrus and when a follicle greater than or equal to 3 cm in diameter was present. Plasma oestrogens and progesterone levels were measured by radioimmunoassay (RIA). Of the 13 jennies, 6 showed a typical seasonal ovarian activity, 1 stopped cycling only at the end of the experiment, 2 ovulated regularly and 4 did not cycle. Mean (+/- s.d.) length of the anovulatory season in the 6 jennies with seasonal cyclic ovarian activity was 166.3 +/- 63.2 days (74-263 days). Irregular oestrous periods were detected during the anovulatory season of these jennies. Irregular signs of oestrus and follicular growth were detected in the 4 jennies which remained acyclic during the whole experiment. Mean (+/- s.d.) length of the ovulatory season was 197.8 +/- 63.4 days (102-291 days). Overall mean +/- s.d. lengths for the oestrous cycle and dioestrous and oestrous periods were 25.9 +/- 2.7 (n = 74), 18.2 +/- 2.3 (n = 70) and 7.9 +/- 2.5 (n = 79) days. Ovulatory oestrous periods tended to be longer at the start and end of the season than during the summer months. Dioestrous length was not affected by season.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Clinical, morphological and endocrinological aspects of cryptorchidism in the horse.

The authors analysed clinical, histological and hormonal data obtained from 205 cryptorchid horses. The majority of the unilaterally and bilaterally retained testes were located in the inguinal canal; however, the ratio of inguinal vs abdominal retention appeared to decrease with advancing age. In unilateral cryptorchidism, a pronounced preference was noted for left abdominal retention, whereas for inguinal cryptorchids, the retained testes occurred equally on both sides. Right inguinal retention was found to decrease with advancing age. Histology of cryptorchid testes revealed apparently normal Leydig cells and arrested spermatogenesis. Plasma testosterone concentrations were similar in normal stallions and unilateral cryptorchids, even in those which had the scrotal testis removed. Plasma oestradiol-17beta levels were lower in unilateral cryptorchids than in stallions.

Journal Article↗
PubMed1979

The mature mid-cycle follicle in the mare.

Oestrogen and progesterone concentrations in blood and follicular fluid and blood levels of LH were determined in 426 mares at different stages of the oestrous cycle. Mature follicles occur at all stages of the cycle; they ovulate readily in early metoestrus, occasionally in late metoestrus and very rarely in dioestrus. Maturation of a mid-cycle follicle is associated with intermediate levels of LH, which are less than those found during oestrus. This lower level of LH together with a high level of progesterone are probably responsible for the failure of ovulation and regression of most of the mid-cycle mature follicles found in the mare.

Animals↗
PubMed1978

Embryo transfer in cattle: an evaluation of the current situation.

A technique for the transcervical recovery of ova in cattle is described. The donors recipient pool consisted of 122 cows of different ages and 4 different breeds. Of these 102 cows were superovulated. For recovery of ova an apparatus consisting of a metal catheter glued to the inside of a 3-way Foley catheter was used. The technique used for embryo transfer was basically the same as for collecting the embryos. The 102 donors yielded at slaughter a total of 956 corpora lutea i.e. an average of 9,4 per cow. Of the ova released 294 or 30% were recovered on transcervical flushing of the uterus. 40% of the inovulated cows conceived. The future development of inovulation in cattle is discussed on the basis of the results recorded and on those previously documented.

Animals↗
PubMed1978

Clinical and endocrinological aspects of induced parturition in multiparous sows.

Intramuscular administration of PGF2alpha or its analogue ICI 80996 at 110--112 days of gestation results in grouped parturition. The decrease of progesterone levels is interrupted by a temporary increase. During expulsion rather high values are obtained compared to the control group. Unconjugated oestrogens increase, reaching maximum values just before expulsion.

Animals↗