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Summary. Cow oocytes and preimplantation embryos were cultured in medium containing radiolabelled methionine and the proteins synthesized were analysed by one-dimensional electrophoresis and fluorography. Marked changes in the pattern of synthesis were observed at the 8–16-cell stage of development. Quantitatively, a gradual decrease in the rate of protein synthesis occurred between the zygote and 8-cell stage and then the rate increased progressively to the blastocyst stage. Incorporation of radiolabelled uridine into RNA was first detected at the 16-cell stage. Taken together, these results suggest that protein synthesis is programmed by maternal mRNA up to the 8-cell stage but switches to mRNA derived from the zygote genome between the 8- and 16-cell stage.
Keywords: embryo; maternal mRNA; transcription; translation; cow
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The sensitive mRNA phenotyping technique of reverse transcription–polymerase chain reaction was used to demonstrate that insulin receptor mRNA is present in rat embryos during the preimplantation period. In addition, mRNA encoding insulin-like growth factor (IGF) type I and type II receptors have also been detected in rat preimplantation embryos. IGF-I mRNA was not detected in preimplantation embryos but was found in oviducts and uteri of prepubertal and early pregnant rats. IGF-II mRNA was present in both embryos and in oviducts and uteri during the preimplantation period. These findings suggest that insulin and IGF-I could influence early embryo development in endocrine or in paracrine fashions, whereas IGF-II may have an additional autocrine mode of action in affecting preimplantation embryos in rats.
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Summary. 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.
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Summary. 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.
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Summary.
The antigenicity of male bat reproductive organs was studied using agar-gel diffusion. Four precipitin lines formed with testis and anti-testis, six lines with epididymis and anti-epididymis, and six lines with ampulla and anti-ampulla sera. Tissue extracts of liver, spleen, heart and uterus cross-reacted with the three antisera to produce three lines. Ampulla, epididymis and testis possessed at least one, three and one organ-specific antigens, respectively.
Nine proteins were detected in the seminal vesicles by agar-gel electrophoresis. One of these possessed potent toxic properties when injected into rabbits and mice. The toxic protein was isolated by zonal electrophoresis and by chromatography on Sephadex G-200. It migrated electrophoretically as a pre-albumin, had a molecular weight of approximately 44,600 and an LD50 value of 162μg/kg. The relationship between this protein and the unique phenomenon of bat sperm survival is unknown.
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Summary.
The seminal vesicle of the bat (Myotis lucifugus) contained a protein toxic to mice and rabbits but not to bats. This protein was precipitated with ammonium sulphate, non-dialysable, inactivated by papain and relatively heat stable. The lethal action was caused by hypotension due to a general relaxant effect on smooth muscle. Epinephrine only momentarily elevated blood pressure. The toxin had no effect on electrical transmission along the motor-nerve axon and across the neuromuscular junction. Haematocrit values increased significantly after bat seminal vesicle was injected, while a highly significant (P> 0·01) decrease in the proportion of circulating lymphocytes and a highly significant (P>0·01) increase in proportion of circulating heterophils occurred. Isolated mouse duodenum and uterine preparations showed a diminution in contraction frequency and a decrease in muscle tone in the presence of the toxin. This was reversible by washing the toxin from the system.
The hypothesis was proposed that this seminal vesicle protein enters the female bat during copulation, blocks sperm transport, and alters the phagocytic system, thus allowing bat spermatozoa to remain in the female reproductive tract over an extended period of time.
