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Biomedical subjects

I L Pike

Publications and source records attributed to I L Pike.

27 records · Page 2Linked to original sources
PubMed1984

Degradation of biochemical pools labelled with [14C]glucose during culture of 8-cell and morula--early blastocyst-stage mouse embryos in vitro and in vivo.

When 8-cell mouse embryos were chase cultured for 24 h in vitro or in vivo (in uteri of pseudopregnant mice) there was no indication of utilization of the small amount of acid-soluble glycogen synthesized during the pulse. At the morula-early blastocyst stage of development almost 50% of the label incorporated during the pulse was found in the acid-soluble glycogen fraction. The biochemical pools at this stage were relatively stable in vitro and in vivo during a short (5 h) chase period. However, marked degradation of the acid-soluble glycogen pool occurred during long periods of exposure to the uterine environment and, over 48 h in utero, almost all of the label was lost from this pool. By contrast, embryos cultured in vitro for the same period retained greater than 60% of their acid-soluble glycogen. Utilization of glucose carbon in the acid-insoluble glycogen fraction occurred during in-vitro and in-vivo chase but there was a suggestion that the change in vivo was less than that in vitro. The non-glycogen macromolecular pool was relatively stable except during extended chase culture of morulae-early blastocysts when some utilization occurred. Under these conditions utilization was less in utero than in vitro. The experiments show that the uterine environment has a marked influence on the metabolism, particularly of glycogen, of the embryo and indicate that some factor in the uterus causes net degradation of acid-soluble glycogen by the embryo at the late preimplantation stage of development.

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PubMed1982

Uptake and incorporation of glucose especially into the glycogen pools of preimplantation mouse embryos during culture in vitro.

Rate of [14C]glucose uptake by mouse embryos during in vitro culture in media containing optimal concentrations of lactate and pyruvate increased throughout preimplantation development. A reduction in the glucose concentration of the medium from 5.56 to 0.28 mM resulted in a two- to fivefold decrease in glucose metabolism, suggesting near-saturation of the membrane carrier at the lower concentration. Changes in the level of lactate and pyruvate in the medium had little effect on glucose metabolism after the third cleavage division. However, further evidence of interaction between energy substrates during the initial cleavage was obtained. Glucose was stored either as desmoglycogen during early cleavage or in a larger acid-soluble glycogen pool in the latter stages of development. The accumulation of glycogen calculated from its production by blastocysts cultured in either 5.56 or 0.28 mM glucose greatly exceeded that determined in blastocysts freshly collected from the uterus. The absence of lactate and pyruvate from the medium had only minimal effects on glycogen accumulation. Most of the glucose carbon was stored as a form of glycogen. However, considerable amounts were also found in acid-soluble material other than glycogen at all developmental stages, probably as the parent compound and its catabolites. Some was also present in lipids, nucleic acids and proteins.

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PubMed1981

Comparative studies of embryo metabolism in early pregnancy.

Embryo metabolism during early pregnancy has been investigated, mainly in the mouse and rabbit, using a variety of catabolic and anabolic parameters. The rate of metabolic activity of the conceptus continues to increase markedly with the approach of implantation. However, in species in which the embryo enters a period of delayed implantation the diapause is associated with relative metabolic quiescence. Mouse, rabbit, ovine and bovine preimplantation embryos can be cultured in a simple defined medium. Under such conditions energy substrates in the medium represent a major source of carbon for anabolism. Glucose carbon is incorporated into macromolecules during in-vitro culture of cleaving mouse embryos and implanting and diapausing mouse blastocysts. In particular, both acid-soluble glycogen and desmoglycogen are rapidly synthesized from glucose presumably to act as a source of energy at implantation. The pattern of glucose accumulation by cleaving sheep embryos and embryonic discs and early somites excised from sheep and cattle embryos between Days 14 and 18 or pregnancy is basically similar to that in the mouse except that very little glycogen is synthesized by ruminant embryos. During embryonic diapause in the tammar wallaby there is a cessation of cell division and glucose uptake appears to be relatively low. After removal of pouch young in the breeding season to reactivate embryo development, glucose accumulation by the tammar blastocyst increases. The increase is related to the start of blastocyst expansion. Furthermore, the pattern of glucose metabolism in the reactivated wallaby blastocyst is similar to that in ruminant species, approximately 30% of the glucose carbon being incorporated into macromolecules such as protein, lipid and nucleic acid but with little synthesis of glycogen.

Animals↗
PubMed1978

Albumin protection of mouse morulae and early blastocysts against the toxic effects of cuprous and cupric ions during development in vitro.

Concentrations of cuprous and cupric chloride of 50 micrometer or greater completely inhibited the development of mouse morulae and early blastocysts into blastocysts in vitro. The zona pellucida was completely dissolved at concentrations of 250 micrometer cupric and 500 micrometer cuprous ions. No significant difference in toxicity was found between the cuprous and cupric ion at 0-50 micrometer. The addition of protein, as BSA, to the culture medium partly protected the embryos against the toxic effect of both copper ions. At a concentration of 25 micrometer a significantly higher level of BSA was required to protect against the cupric than the cuprous ion. Increasing the concentration of either ion increased the level of BSA required to exert a protective effect.

Animals↗
PubMed1975

The incorporation of carbon dioxide into the major classes of RNA during culture of the preimplantation mouse embryo.

The fixation of CO2 into major classes of RNA in the mouse embryo was studied in culture. Total fixation of CO2 was low at the two-cell stage and no label was found in RNA. Between the eight-cell and morula/early blastocyst stages of development, total fixation increased markedly but decreased again at the late blastocyst stage. On a per cell basis, the level of incorporation of CO2 decreased steadily throughout the preimplantation period. A significant acceleration in the accumulation of 14CO2 into all classes of RNA occurred between eight-celled embryos and morulae/early blastocysts, and this effect was more evident when results were calculated in relation to cell number. At the late blastocyst stage, incorporation of label into RNA decreased on a per embryo and a per cell basis. Most of the label from CO2 was incorporated into the r-RNA fraction at all stages of development and incorporation into s-RNA was always less. The pattern of labelling of RNA with 14CO2 was similar to that previously obtained for the incorporation of [3H]uridine into embryonic RNA, suggesting that most of the CO2 entering the RNA pool may be incorporated into nucleotide bases. The s-RNA and r-RNA fractions were susceptible to digestion with both pancreatic ribonuclease and 0-3 M alkali. Approximately 31% of the label in the TD-RNA fraction remained after hydrolysis with ribonuclease and a similar proportion of the TD-RNA was resistant to alkali treatment. Incorporation of CO2 by morulae/early blastocysts was substantial during culture in substrate-free medium but was increased significantly in medium containing lactate plus pyruvate. Carbon dioxide fixation into RNA was decreased by preculture for 48 hr before incubation in radioactive medium. When compared with freshly collected morulae/early blastocysts, the proportion of the total label in the s-RNA fraction of precultured embryos was low, and a correspondingly greater proportion of the total label was found in the TD-RNA fraction.

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