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Biomedical subjects

P L Kaye

Publications and source records attributed to P L Kaye.

52 records · Page 3Linked to original sources
PubMed1988

Insulin stimulates protein synthesis in compacted mouse embryos.

Preliminary work suggested that insulin affects preimplantation mouse embryos. We investigated the effects of insulin on incorporation of [3H]-leucine by embryos cultured for long (greater than 24 h) or short (4 h) terms with insulin. Insulin stimulated incorporation by compacted 8-cell embryos, blastocysts and expanded blastocysts. The stimulation in blastocysts had an EC50 of 0.5 pM in the presence of 1 g/L BSA and was blocked by anti-human insulin anti-serum. Inclusion of insulin in the medium elevated the levels of incorporation towards those of embryos developing in vivo. The stimulation was not observed in uncompacted 8-cell embryos. The ontogeny of stimulation at compaction coincides with a switch in energy dependence from lactate and pyruvate to glucose and an increase in protein synthetic activity.

Animals↗
PubMed1986

Glycine and Na+ transport in preimplantation mouse embryos.

The dependence of glycine uptake on glycine and Na+ concentrations was determined and compared in 2-cell embryos and blastocysts. In both, uptake was by a combination of a Na+-independent non-saturable route and a Na+-dependent saturable system with Km values of 62 microM and 274 microM for 2-cell embryos and blastocysts respectively. Na+-dependent saturable uptake by embryos of both stages had a Hill coefficient of 2 for Na+, indicating co-transport of 2 Na+ with each glycine molecule. These results suggest that glycine enters 2-cell embryos by the gly-system, and blastocysts by a similarly Na+-dependent system with characteristics resembling the A-system.

Animals↗
PubMed1986

Whole protein uptake and metabolism by mouse blastocysts.

Preimplantation mouse embryos take up whole 125I-labelled BSA from their environment. In blastocysts this uptake was temperature-sensitive and reversibly inhibited by trypan blue: properties consistent with an endocytotic mechanism. The uptake kinetics indicate that a saturable component predominates at low protein concentrations, but a non-saturable component is the major uptake route at higher concentrations. This suggests that BSA is pinocytosed probably bound to the membrane and dissolved in the bulk solvent phase. The rate of uptake, equivalent to about 5 pl/min/blastocyst was similar to that reported for non-saturable glycine uptake. In blastocysts the protein is degraded to acid-soluble products. At reported genital tract fluid protein concentrations this would represent a significant contribution to the embryonic pool of fixed nitrogen.

Animals↗
PubMed1985

Glycine transport in mouse eggs and preimplantation embryos.

In pre-compaction embryos glycine was taken up by the glycine-specific gly-system, which is concentrative, weakly exchangeable and dependent on Na+. After compaction glycine uptake increased, apparently due to the expression of the A-transport system and its reactivity with glycine. Studies of the metabolic fate of carbon from glycine indicated conversion to serine and alanine. These changes are interpreted to show that glycine could provide carbon for intermediary energy metabolism, resulting in CO2, as well as for macromolecular synthesis.

Alanine↗
PubMed1983

Uncoordinated synthesis of histones and DNA by mouse eggs and preimplantation embryos.

The temporal coordination of histone and DNA synthesis in mouse eggs and preimplantation embryos were examined. In unfertilized mouse eggs arrested at metaphase II, histone synthesis was observed, but at lower rates than previously reported for fertilized zygotes. Cytosine arabinoside, an inhibitor of DNA synthesis, was used to study the relationship between DNA and histone synthesis during cleavage stages of mouse development. Cytosine arabinoside (50 microM) inhibited by 90% the incorporation of [3H]thymidine into DNA by two-cell embryos and blastocysts. At this concentration, cytosine arabinoside inhibited incorporation of [3H]lysine into blastocyst histones by only 30% and had no effect at the two-cell stage. These results are interpreted to show that DNA synthesis and histone synthesis are not coordinated temporally during early development of the mouse, but may become more so as development proceeds.

Animals↗
PubMed1982

Amino acid transport and exchange in preimplantation mouse embryos.

Between the 1-cell zygote and the early blastocyst stage of mouse embryos the net rate of uptake of methionine increased, the internal pool became progressively more expanded and less easily reached steady state, and the specificity of competitor amino acids changed. Sodium-dependent transport was first detected in compacted morulae (16--32-cell stage). Uptake of [14C]methylaminoisobutyric acid was detectable in blastocysts but not in unfertilized eggs. Efflux of methionine by an exchange transport system was detectable at all stages, but in intact blastocysts much higher external concentrations were required to activate exchange transport. An exchange system with properties similar to that operating at cleavage stages was exposed when blastocysts were collapsed with cytochalasin D. Since this exchange system was not detectable in isolated inner cell masses, it may be confined to the juxtacoelic surface of trophectoderm cells.

Amino Acids↗
PubMed1981

Histone synthesis in preimplantation mouse embryos.

The synthesis of histones by preimplantation mouse embryos was examined by electrophoresis of [3H]-lysine-labeled acid extracts of cleavage stage embryos. Histones were synthesized by fertilized zygotes, two-cell, eight-cell, and morula stage embryos. Their identity was confirmed by coextraction and coelectrophoresis in a number of systems and differential labeling with [3H]-tryptophan. There was evidence of post-translational modifications of the embryonic histones. The estimated histone synthetic rate was sufficient to provide the chromatin requirements of cleavage division as related to DNA synthesis. The results are discussed in relation to coordination of histone and DNA synthesis in the preimplantation embryo.

Animals↗
PubMed1981

Endogenous amino acid pool sizes in mouse eggs and preimplantation embryos.

The endogenous pool sizes of 17 amino acids were measured directly in samples of mouse eggs, 8-cell embryos and blastocysts by estimation of the fluorescent product of the reaction of o-phthalaldehyde and primary amines. Taurine, glycine, alanine, glutamate and aspartate were detected at high levels. During the transition to the blastocyst, most amino acid pools increased 2-3-fold, but the taurine and glycine pools decreased to about 50 and 10%, respectively, of the egg value. The amino acid distribution in cumulus masses was similar to that of the egg and embryo samples but different from that of serum.

Amino Acids↗