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Interactions between the embryo and its environment during the early stages of pregnancy

Khurana, Narinder Kumar (1987) Interactions between the embryo and its environment during the early stages of pregnancy. PhD thesis, Murdoch University.

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This research study tested the effects of some of the environmental factors likely to operate in vivo on the metabolism of glucose by mouse embryos. In particular, the aim of the experiments was to find an explanation for the discrepancy in glycogen content between freshly collected and in vitro cultured late preimplantation mouse embryos. These experiments originated as a result of earlier studies in which it was established that this difference in glycogen content was due to increased degradation of the polymer in vivo under the influence of ovarian steroids.

Using pulse/chase techniques, initial experiments showed that ovarian hormones, prostaglandin and F^, and other hormones regulating glucose metabolism in the adult had effects on certain aspects of glucose metabolism of embryos but did not influence the synthesis and degradation of embryonic glycogen directly. Thus, it would appear that glycogen degradation occurs as a result of changes to the uterine milieu rather than to the direct effects of hormones on embryos. Experiments were then conducted to test the effects of uterine fluid proteins at concentrations expected in vivo. Supplementing culture medium with these proteins had little influence on the metabolism of glucose, particularly the degradation of the glycogen pool. Similarly, simulation of the in vivo situation by co-culturing embryos with isolated uterine epithelial cells in medium supplemented with ovarian steroids did not help explain the dilemma of glycogen content. The final experiments in the study examined the effects of oxygen concentration on glycogen turnover and showed that low oxygen levels significantly enhanced the degradation of acid-soluble glycogen in pulse-labelled embryos without affecting their morphological development. The lower the oxygen concentration, the higher was the turnover of glycogen. In addition, the catabolic utilization of glucose was stimulated at low oxygen concentrations.

In conclusion, the results of the present investigation not only help explain the anomalous effects of in vitro culture on glycogen metabolism but also provide biochemical evidence to reinforce the view that the use of a low oxygen concentration during in vitro culture helps achieve embryonic development more closely resembling that in utero.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Wales, Ray and Costa, Nick
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