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Biomedical subjects

L R Fraser

Publications and source records attributed to L R Fraser.

At least 91 records · Page 5Linked to original sources
PubMed1979

Rate of fertilization in vitro and subsequent nuclear development as a function of the post-ovulatory age of the mouse egg.

Evidence is presented to indicate that older mouse eggs are fertilized more rapidly and also develop more rapidly to the pronuclear stage than younger ones. After a low (1.5 i.u.) or a high (7.5 i.u.) dose of PMSG, female mice were killed 13 or 17 h after hCG. The eggs were mixed in vitro with preincubated spermatozoa and fixed 1--1 1/4 h later. Although fertilization levels were high in all groups, the stages of egg activation and sperm head decondensation differed significantly. The observed ranking, from most to least rapid fertilization, of eggs obtained from females treated with 7.5 i.u. and killed 17 h after hCG, 1.5 i.u. and 13 h, and 7.5 i.u. and 13 h, was consistent with the approximate length of time the eggs had resided in the oviduct, i.e. the longer that time period, the more rapid the fertilization. When eggs were fixed 4 1/4 h after mixing with spermatozoa, the majority of older eggs were fully pronuclear while only a few of the younger eggs were as advanced, indicating accelerated nuclear development in the cytoplasm of the older eggs.

Animals↗
PubMed1979

Incidence of polyspermy in mouse eggs fertilized in vivo and in vitro after administration of progesterone and oestradiol.

Female mice, induced to superovulate, were injected subcutaneously with progesterone or oestradiol near the time when hCG was given. The incidence of polyspermy in first-cleavage embryos following mating or in-vitro fertilization was then determined. There were no detectable differences in the incidence or degree of polyspermy between treated and control in either the in-vitro or in-vivo groups, although the mean incidence of polyspermy was higher in vitro than in vivo. Furthermore, there was no detectable acceleration of egg transport after administration of either hormone.

Animals↗
PubMed1979

Accelerated mouse sperm penetration in vitro in the presence of caffeine.

Evidence for accelerated mouse sperm penetration into eggs in vitro, and hence for accelerated capacitation, was obtained when the fertilizing ability of sperm suspensions was tested after preincubation, for a period of time insufficient to permit full capacitation under standard conditions, in the presence or absence of caffeine. When eggs were fixed after 1 h, the majority (76.7%) in the caffeine-containing medium were fertilized compared with only 32.1% in the caffeine-free medium. When fixation was later, after 1 h 15 min, fertilization levels were high (approximately 90%) in both groups, but significant differences in the stages of egg activation and sperm head decondensation reached were observed. In the absence of caffeine, early stages of nuclear development were predominant, while in the presence of caffeine, a significant proportion of eggs had reached terminal stages of activation. There was also some evidence for precocious sperm, but not egg, nuclear development when fertilization occurred in caffeine-containing medium.

Animals↗
PubMed1978

Murine cytomegalovirus and fertility: potential sexual transmission and the effect of this virus on fertilization in vitro.

Male mice were inoculated with murine cytomegalovirus (MCMV) to produce an acute generalized infection. Infections virus was recovered from both epididymal sperm and seminal vesicles as well as from uterine sperm collected from mated females, suggesting that MCMV might be transmitted sexually. Because the presence of virus in the ejaculate might affect the fertilization process, the effect of MCMV on the fertilization of mouse gametes and on subsequent embryonic development was studied in vitro. Although the fertilization rate was reduced when sperm were preincubated with infectious virus, this was also the case when heat-inactivated virus was used, leading to the conclusion that this effect was not due to a direct infectious interaction between virus and gametes. Subsequent embryonic development was normal, and there was no evidence of productive infection of the preimplantation embryo.

Animals↗
PubMed1978

The effect of sperm and egg genotype on the incidence of chromosomal anomalies in mouse embryos fertilized in vitro.

Analysis of the chromosomes of 1-cell mouse embryos fertilized in vitro showed that the incidence of polyploidy is independent of both sperm and egg genotype. No significant differences were detected between groups of eggs from 5 strains of mice fertilized by spermatozoa from a single strain, TO, or between groups of (C57BL/10 X CBA) F1 eggs fertilized by spermatozoa from 2 strains, CBA/H-T6 and TO, although there was significant heterogeneity between individual males in the latter set of experiments. While the majority of polyploids were triploids resulting from dispermic fertilization, some derived from diploid spermatozoa were also found.

Aneuploidy↗
PubMed1978

Maternal age and the incidence of aneuploidy in first-cleavage mouse embryos.

Eggs obtained from young virgin and aged parous female mice were fertilized in vitro to compare the incidence of aneuploidy in the resulting first-cleavage embryos. There was a significantly higher incidence of aneuploidy in the aged group (7.5% versus 3.3%) and this was due solely to a higher proportion of trisomic female chromosome complements; there was no difference in the incidence of monosomics. These results thus suggest that non-disjunction occurs more frequently in eggs from older females, leading to the production of aneuploid embryos.

Aneuploidy↗
PubMed1977

Fertilization and preimplantation development in vitro of mouse eggs obtained following stimulation with different doses of pregnant mare serum: a comparison of the responses in two strains.

Unfertilized eggs were recovered from TO and (C57BL/10 X CBA)F1 females, induced to ovulate with 0.75--10.0 IU PMS and 5.0 IU HCG/mouse, and mixed with TO sperm in vitro. Among the groups of F1 eggs, there were no significant differences in either fertilization or development to the blastocyst stage in vitro. With TO eggs, however, there was significantly lower fertility in the 0.74 and 1.5 IU PMS groups than in the higher PMS dose groups. Conversely, preimplantation development was significantly better withe low doses. To determine whether polyploidy migh affect viability in vitro, digynic polyploidy was experimentally induced in both F1 and TO eggs with cytochalasin B. Development of polyploid F1 X TO embryos to the blastocyst stage did not differ significantly form that of untreated embryos. Development of polyploid TO X TO embryos obtained from eggs stimulated with 1.5 IU PMS was still higher than that for eggs stimulated with 7.5 IU PMS. This suggests that cytoplasmic inadequacies, rather than genome imbalance, are responsible for the reduced ability of the eggs stimulated with high doses of PMS to reach the blastocyst stage in vitro.

Animals↗
PubMed1977

The effect of Mycoplasma pulmonis on fertilization and preimplantation development in vitro of mouse eggs.

The effect of Mycoplasma pulmonis suspension on mouse on mouse fertilization and preimplantation development in vitro was examined. When sperm were preincubated with M. pulmonis, fertilization of eggs occured less consistently than when untreated sperm were used. There was also a highly significant and consistent reduction in embryonic develoment in the treated group, with relatively few embryos reaching the blastocyst stage. The adverse effects were not seen with M. fermentans or with M. pulmonis organisms inactivated by heating or sonication before incubation with gametes. Likewise, preincubation of M. pulmonis in medium containing tetracycline, an antibiotic which interferes with protein synthesis, resulted in embryonic development similar to that seen in the untreated group. These results suggest that the deleterious effects obtained with viable mycoplasmas are due to some substance produced by their active metabolism. Other results indicate that the egg is susceptible to M. pulmonis for a limited time, since incubation of two-cell embryos with mycoplasmas had no effect on development to the blastocyst stage. The findings are discussed in relation to the possible association between human infertility and mycoplasma infection.

Animals↗
PubMed1977

Differing requirements for capacitation in vitro of mouse spermatozoa from two strains.

Concentrated suspensions of epididymal spermatozoa obtained from two strains of mice, TO and C57BL/10, were preincubated for 20 min, 1 h or 2 h before dilution and addition of (C57BL/10 X CBA)F1 eggs. While all 3 groups of TO spermatozoa demonstrated high fertility (greater than 90% of eggs subsequently cleaved), C57BL/10 spermatozoa preincubated for 20 min and 1 h gave significantly reduced fertilization rates compared with those in the 2 h group. Furthermore, the penetration rate of the C57BL/10 spermatozoa preincubated for 20 min was significantly slower than that for similarly treated TO spermatozoa, as demonstrated by a delay in the first cleavage. A long preincubation of C57BL/10 spermatozoa in a diluted rather than a concentrated suspension did not improve fertility, suggesting that optimal capacitation may be sperm concentration-dependent in some, if not all, strains of mice.

Animals↗
PubMed1977

The effect of PMSG dose on the incidence of chromosomal anomalies in mouse embryos fertilized in vitro.

Chromosomal analysis of first-cleavage mouse embryos obtained by fertilization of TO eggs with TO spermatozoa in vitro revealed that the incidence of polyploidy was proportional to the dose of PMSG given to the donor females. The dose-response was shown to be linear, with the level of polyploidy rising from 8-0% with a PMSG dose of 1-5 i.u./female to 20-8% with 10-0 i.u./female. A total of 64 polyploid embryos was found among the 452 examined and in all cases the polyploidy was the result of polyspermy or fertilization by diploid spermatozoa.

Aneuploidy↗
PubMed1976

Mouse sperm genotype and the rate of egg penetration in vitro.

(C57BL/10 X CBA)F1 mouse eggs were incubated in vitro with either F1 or outbred TO sperm for 15 minutes-6 hours. Upon removal from the sperm suspensions some eggs were treated with pronase to remove zonae and then cultured, while the remainder were simply cultured to allow a comparison of the fertilization rates in the two groups. Although a brief incubation was sufficient for a high rate of fertilization when the zonae remained intact, results from the zona-free eggs indicated that penetration, i.e., sperm fusion with the vitellus, had not been achieved in all eggs during the shorter incubations. Results from the latter groups of eggs indicated that a 1 hour incubation with TO sperm and a 2 hour incubation with F1 sperm were needed to obtain a mean fertilization rate of 50%. Fertilization was complete within 1.5 hours using TO sperm and 2.5 hours using F1 sperm, thus indicating that under similar environmental conditions sperm genotype can significantly affect the rate of penetration.

Animals↗
PubMed1976

Effect of removal of epididymal secretions on fertilization in vitro of mouse eggs.

The removal by centrifugation of epididymal contents from mouse spermatozoa had no deleterious effect on fertilization in vitro, and, depending on the genotype of the gametes, was frequently associated with increased levels of fertility. Washing of the spermatozoa significantly improved the fertilization rate of F1 eggs with TO spermatozoa and of BALB/c eggs with BALB/c spermatozoa, but had no significant effect of F1 spermatozoa with F1 eggs.

Animals↗
PubMed1975

The effect of ruthenium red and Concanavalin A on the vitelline surface of fertilized and unfertilized rabbit ova.

Fertilized and unfertilized rabbit ova exposed to ruthenium red with the zona intact or after mechanical removal, for the demonstration of mucopolysaccharides on the surface coat. Ova were also exposed to Concanavalin A. Ruthenium red bound strongly to elements of the zona and increased the opacity of the plasmalemma. There was no notable change in staining of the vitellus following fertilization. Although there were ruthenium red stained bodies resembling cortical granules in crypts in the plasmalemma, there was no evidence for cortical granule extrusion of mucopolysaccharides. The Concanavalin reaction was seen over both unfertilized and fertilized ova, demonstrating receptors for terminal alpha-D-mannopyranosyl, alpha-D-glycopyranosyl, beta-D-fructofuranyosyl residues. The deposit on the fertilized egg surface was enormously enhanced indicating a change in the distribution of receptor sites.

Animals↗