Search Results

You are looking at 1 - 10 of 10 items for

  • Author: R. L. BRINSTER x
Clear All Modify Search
Free access

R. L. BRINSTER

Summary.

The rabbit embryo is able to develop from the two-cell stage to the morula in a medium containing an amino-nitrogen source as the only metabolizable component. This amino-nitrogen source can be bovine serum albumin, oxidized glutathione, or certain single amino acids such as glutamine, proline or alanine. Although a requirement for a non-nitrogenous energy source could not be demonstrated during this period, a beneficial effect of pyruvate and lactate was shown. The optimum concentration for pyruvate was approximately 10 −4 m and for lactate was 1 to 3×10−2 m.

Free access

R. L. BRINSTER

Summary.

Carbon dioxide formed by the mouse oocyte from glucose was 0·145 pmol/hr/oocyte, which is the same as the value previously found for unfertilized mouse ova. Carbon dioxide formed by the Rhesus monkey oocyte from pyruvate and glucose was 12·77 and 0·73 pmol/hr/oocyte, respectively. Pyruvate is probably a major energy source for all early mammalian embryos.

Free access

R. L. BRINSTER

Summary.

Two-cell mouse embryos will develop into blastocysts when glutathione is the only fixed-nitrogen source in the culture medium. The optimum concentration for oxidized glutathione is 3·16×10−3 m and for reduced glutathione, 10−4 m. There was no significant difference in the number of blastocysts developing in glutathione or albumin medium.

Free access

R. L. BRINSTER

Summary.

Uptake and incorporation were determined for glutamine and asparagine as well as for nine amino acids which have been shown by culture experiments in vitro to be important in the development of the preimplantation mouse embryo. In general, there was a tenfold increase in the incorporation and a fivefold increase in uptake of the amino acids from the one-cell to the morula stage. The largest change in both incorporation and uptake occurred at about the eight-cell stage of development.

Leucine was incorporated more, and glutamine taken up in larger quantities, than the other amino acids. The rate of incorporation of leucine carbon into the embryo between the one- and two-cell stage was 0·208 and for the morula to blastocyst was 2·153 pmol/embryo/hr. The total uptake of glutamine carbon between the one- and two-cell stage was 1·768 and between the morula and blastocyst was 5·655 pmol/embryo/hr.

Fertilization of the mouse ovum did not significantly affect incorporation of leucine and had only a small effect on total uptake of leucine. This contrasts with the findings in invertebrates where fertilization results in a marked increase in all aspects of amino acid metabolism.

Free access

R. G. WALES and R. L. BRINSTER

Summary.

The accumulation of substrate carbon by mouse embryos was measured following incubation in U-14C-glucose. Following a 30-min incubation period 273 × 10-14 and 301×10-14g atoms of substrate carbon per embryo were found in 2- and 8-cell embryos respectively. By comparison, the figures for unfertilized and fertilized ova were 14 × 10 -14 and 45 × 10-14 g atoms of substrate carbon.

The intracellular concentration of substrate carbon was timedependent in both 2- and 8-cell embryos. After an 80-min incubation, substrate carbon in the 8-cell embryo was almost double that in the 2-cell embryo. Accumulation did not occur during incubations at 5° C and there was competition between glucose and galactose for uptake. The results are discussed in relation to the energy requirements of the developing zygote.

Free access

R. W. MOORE and R. L. BRINSTER

Summary.

The level of aspartate aminotransferase (AA) activity was examined in the preimplantation embryo, and there was a 29% decrease in total activity from the one-cell stage to the eight-cell stage, and a 153% increase from the eight-cell stage to the late blastocyst.

The affinity of the AA for α-ketoglutarate and aspartate was measured at the two-cell and early blastocyst stages. At the two-cell stage, the enzyme has a higher affinity for aspartate than for α-ketoglutarate while, in the early blastocyst, the affinity was the reverse. It is suggested that this result is compatible with a change from a predominance of the mitochondrial form of AA at the two-cell stage to a predominance of the cytoplasmic form at the early blastocyst stage.

There was also a steady drop (73%) in the total activity of glutamic dehydrogenase from the one-cell to the late blastocyst stage.

Free access

R. L. BRINSTER and J. D. BIGGERS

In 1959, Chang provided the first irrefutable proof of fertilization of mammalian ova in vitro. Since that time, fertilization of rabbit ova in vitro has been done by a number of workers. More recently, Yanagamachi & Chang (1963, 1964) have succeeded in fertilizing in vitro the eggs of the golden hamster. This was established microscopically and by the cleavage of some of the ova to the twocell stage. No one has yet succeeded in fertilizing mouse ova in vitro. This report describes a method for fertilizing mouse ova in vitro and obtaining the successive cleavage stages up to the blastocyst.

The unfertilized ova were obtained from random-bred Swiss mice which were superovulated by an intraperitoneal injection of 10 i.u. of pregnant mare serum gonadotrophin (Gestyl, Organon), followed 48 hr later by an intraperitoneal injection of 10 i.u. of human chorionic gonadotrophin (Pregnyl, Organon). Since ovulation occurs 11 to 14 hr

Free access

R. L. BRINSTER and JOAN THOMSON TenBROECK

Summary.

Fertilized one- and two-cell mouse embryos were transferred to the rabbit Fallopian tube. No blastocysts developed from 730 one-cell embryos transferred. A total of 141 blastocysts developed from 540 two-cell embryos transferred.

Free access

I. L. Levey, D. E. Troike and R. L. Brinster

Analysis of macromolecular synthesis by preimplantation mammalian embryos in culture has revealed that activation and expression of the embryonic genome occurs in early development. The inhibition of cleavage in mouse embryos by actinomycin D (Mintz, 1964; Skalko & Morse, 1967; Monesi, Molinaro, Spalletta & Davoli, 1970) suggests that RNA transcribed from the embryonic genome may be necessary for continued development as early as the 2-cell stage. Because actinomycin D has been reported to exert effects not clearly related to transcriptional inhibition (Manes, 1975), its role in the suppression of embryonic development should be regarded with some caution. In contrast, the mushroom toxin, α-amanitin, is a selective inhibitor of RNA polymerase II both in vitro and in vivo (Stripe & Fiume, 1967; Tata, Hamilton & Shields, 1972; Hadjiolov, Dabeva & Mackedonski, 1974). Preliminary reports have suggested that α-amanitin may inhibit cleavage of mouse embryos in culture (Golbus, Calarco & Epstein, 1973; Warner & Versteegh, 1974), although only a relatively narrow range of α-amanitin concentrations has been tested and only studies of embryos exposed at the 2-cell stage have provided sufficient data to establish statistical significance. To verify the inhibitory action of this drug and to establish dose–response relationships essential for analyses of messenger RNA metabolism, we have investigated the effects of α-amanitin upon cleavage and blastulation of mouse embryos explanted into culture at several stages of development before implantation.

Free access

E. A. Merz, R. L. Brinster, S. Brunner and H. Y. Chen

Summary. The half-lives of labelled proteins were determined for mouse preimplantation embryo stages from the germinal vesicle oocyte to the early blastocyst. While no significant differences were found among half-lives for 1-cell stages, or among half-lives for cleavage stages, a significant (P < 0·05) 28% decrease in half-life was observed between the 1-cell and the cleavage stages. Labelled protein half-lives were 18·2 and 13·1 h for the 1-cell and cleavage stages respectively. Fertilization probably initiates this increase in protein degradation rate although no significant decrease was detected until after the first cleavage.