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Biomedical subjects

T Greve

Publications and source records attributed to T Greve.

At least 145 records · Page 8Linked to original sources
PubMed1986

Ultrastructure of in-vitro oocyte maturation in cattle.

Cumulus-oocyte complexes were collected from cows at an abattoir by aspiration from small (1-6 mm) antral follicles. After different periods of culture the complexes were processed for electron microscopy. Cumulus expansion occurred at 12-18 h of culture and concomitantly enlargement of cumulus cell projections in the perivitelline space was seen. At 48 h the innermost cumulus cells flattened and adhered tightly to the zona pellucida. In the oocyte the following changes occurred: at 0-3 h of culture the perivitelline space developed; at 3-12 h disconnection of the junctions between cumulus cell projections and the oolemma, and the concomitant breakdown of the nucleus was observed; at 12-18 h the mitochondria moved from a peripheral location to a more even spatial distribution and the Golgi complexes decreased in size; at approximately 18 h the smooth endoplasmic reticulum formed large aggregates surrounded by mitochondria; at 18-21 h the first polar body was abstricted; at 24-40 h the cortical granules spread; at 30-40 h the polar body degenerated in some specimens; at 40-48 h the perivitelline space decreased in size; and at 48 h one oocyte was in the process of fragmentation. It is concluded that nuclear and cytoplasmic oocyte maturation is simulated in vitro. However, certain deviations were noticed compared to in-vivo maturation.

Animals↗
PubMed1985

Cryopreservation before replantation of mature teeth in monkeys. (II). Effect of preincubation, different freezing and equilibration rates and endodontic treatment upon periodontal healing.

The effect of cryopreservation in liquid nitrogen at -196 degrees C for 1 week was studied by histometric analysis of 60 mature teeth replanted in 10 green Vervet monkeys. The effect of preincubation in enriched tissue culture medium was also investigated. 2 different freezing rates were compared, and the effect of stepwise equilibration of DMSO was studied as well as the effect of root canal treatment. The histometric analysis carried out 8 weeks after replantation revealed that if the cryoprotectant was equilibrated stepwise at room temperature, 10% DMSO had an even better cryoprotecting effect than previously shown by 5% DMSO equilibrated at 0 degree C. When this procedure was combined with a slow freezing rate of 0.3 degree C/min from -4 degrees C to -35 degrees C followed by plunging in liquid nitrogen, and supplemented by endodontic treatment before replantation, the amount of normal periodontal healing was almost similar to unfrozen and immediately replanted control teeth. Furthermore, this cryoprofile induced replacement resorption equal to the replanted control teeth. Preincubation in enriched medium for 24 h did not reduce resorption activity of the periodontal ligament. Endodontic treatment reduced the inflammatory resorption, demasking, however, hereby limited amount of ankylosis, that could be reduced by the above-mentioned cryoprofile. An optimal cryoprofile for mature teeth seemed to be slow equilibration at room temperature to a final concentration of 10% DMSO, slow freezing rates (0.3 degree C/min) and plunging in liquid nitrogen at -35 degrees C combined with fast thawing after storage at -196 degrees C, and followed by endodontic treatment after thawing.

Animals↗
PubMed1984

In vitro fertilization and cleavage of in vivo matured bovine oocytes.

The effect of the interval between onset of estrus and oocyte collection on in vitro fertilization (IVF) rates has been investigated. The oocytes were surgically collected 6-18 h (Group I), 19-24 h (Group II), 25-29 h (Group III) and 30-36 h (Group IV) after the beginning of estrus. Recognizable stages of nuclear maturation were identified in 54.9% of the oocytes used for IVF (5.9% at germinal vesicle, 31.4% at metaphase I, 17.6% at metaphase II); the other 45.1% were degenerate. Considerable between- and within-cow variation in oocyte morphology, oocyte maturation and IVF results was observed. The overall fertilization and cleavage rates (to four-cell stages) were 26.5 and 6.0%, respectively. The fertilization rate increased as the interval between onset of estrus and collection increased and was optimal 30-36 h after onset. Thus, onset of estrus proved an effective means of timing oocyte collection for IVF.

Journal Article↗
PubMed1983

Endocrine profiles and egg quality in the superovulated cow.

Plasma progesterone- and LH concentrations were studied in lactating dairy cows around the superovulatory heat. The pattern of both hormones accurately reflected the donor animals' endocrine balance and could be used to evaluate and predict the subsequent potentials or quality of a given animal as embryo- and oocyte donor. It was the general impression that both PMSG- and FSH treatment caused endocrine changes in progesterone- and LH patterns that would account for improper oocyte- and embryo development.

Animals↗
PubMed1983

Heat synchronization in dairy cows.

Dairy cows were heat synchronized with two injections of cloprostenol (PG1/PG2) with an interval of 13 days and inseminated 72 hours after PG2. The total pregnancy rate obtained was 42% The probability of achieving luteal phase at PG2, the probability of undergoing luteolysis after PG2 and the probability of achieving pregnancy were all equal whether the cows were in luteal phase, follicular phase, had follicular cysts or small ovaries at PG1. Close correlations were found between the signs of heat at the insemination and the interval from calving to PG1 to the pregnancy rates.

Animals↗
PubMed1982

Endocrine profiles and embryo quality in the PMSG-PGF2alpha treated cow.

Plasma progesterone and LH concentrations around estrus were determined for both PMSG treated (experimental animals) and non-treated (control animals) dairy cows and heifers of the Holstein Friesian and Jersey breeds, and these hormone profiles were related to the embryo quality. Most experimental animals experienced an increase in progesterone concentrations following PMSG treatment and an abrupt decrease to values below 3 nmol/l after PG injection. The mean (+/-SE) intervals from prostaglandin treatment to estrus were 46.9+/-1.8 h and 64.5+/-4.8 h for experimental and control animals, respectively. At the onset of heat the progesterone concentration in experimental animals with optimal embryo quality (group I) was significantly lower (p<0.01) than in experimental animals which yielded unfertilized eggs (group II) (1.2+/-0.1 versus 3.9+/-0.8 nmol/l) and significantly higher than the level in the control group (0.6+/-0.1 nmol/l). Following estrus the progesterone profiles in all 3 groups were studied and the length of the superovulatory cycle was measured to 26.0+/-4.8 days. The preovulatory LH surge occurred sooner after prostaglandin injection in experimental (41 h) than in control animals (65 h). The LH surge in group I occurred within a narrow range and reached a higher average level than group II (24.2+/-2.2 ng/ml and 16.3+/-3.7 ng/ml, respectively). The control group attained an even higher LH surge (31.8+/-8.8 ng/ml) than did the experimental animals. The data presented in this experiment indicate that plasma levels of progesterone and LH in PMSG-PGF2alpha treated animals are related to embryo or egg quality.

Journal Article↗
PubMed1981

Two step freezing of cow embryos in 1.4 M glycerol.

Day 6 1 2 -7 1 2 cow embryos were frozen in 1.4 M glycerol in PBS, at 0.3 degrees C/min to -30 (group I), -35 (group II), and -40 degrees C (group III) before being plunged into liquid nitrogen. They were subsequently thawed by direct transfer to water at 37 degrees C. In Experiment I, embryos frozen and thawed were cultured in vitro, 12 out of 19 embryos (63%) survived and there were no significant (p > 0.05) differences in survival rates among the three freezing groups. In Experiment II, 29 embryos frozen to -30 or -35 degrees C were transferred non-surgically to heifers on day 7. Seventeen of 29 recipients (59%) were pregnant at day 60. Five embryos frozen to -35 degrees C resulted in 5 pregnancies (100%) after thawing and surgical transfer.

Journal Article↗
PubMed1981

Survival of cow blastocysts utilizing short freezing curves.

Blastocysts can survive direct transfer into liquid nitrogen after programmed freezing in 1.4 M glycerol to -29 degrees C when thawed by direct transfer into water at 37 degrees C. This observation facilitates the use of deep freezing of blastocysts in embryo transfer procedures. This makes the requirement for a special apparatus for the freezing procedure less demanding.

Animals↗
PubMed1980

Bovine egg transplantation. Superovulation, non-surgical recoveries and transfers.

Lactating dairy cows were superovulated with a pregnant mare serum gonadotrophin (PMSG)/cloprostenol (PG) regimen in their mid-luteal phase (day 10). The average interval from the PMSG injection to heat was 4.1 +/- 0.05 days. First insemination occurred 18--24 hrs after standing heat and the second insemination 12--18 hrs later. Six to eight days later (the day of recovery) the superovulatory response was assessed. The variation in number of ovulation points (corpora lutea, C.L.) was sizable, and right ovary (4.1 C.L./donor) appeared more active than left ovary (3.3 C.L./donor). The non-surgical embryo collection equipment was developed for practical use on the farms and it was possible to recover 6.0 +/- 0.6 eggs per donor (54 +/- 5% recovery rate). Approximately half of these (54.2%) were considered viable, and suitable for either direct transfer or freezing, Other eggs were retarded (5.8%), degenerated (25.7%) or unfertilized (16.3%). Several influential factors were examined and there was only little conclusive evidence for any specific effect on the superovulatory response and/or egg number and quality. The non-surgical transfer experiments with a common insemination gun was encouraging and gave rise to a pregnancy rate of 56%.

Animals↗