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D. P. Boshier

Department of Anatomy, University of Auckland, Private Bag, Auckland, New Zealand

The close anatomical and physiological relationship between the implanting blastocyst and the associated uterine epithelium was early indicated when Alden (1947) observed that lipid droplets became scarce or wanting in the apical regions of the maternal epithelial cells in the immediate neighbourhood of the rat blastocyst. However, neither Krehbiel (1937) nor Enders & Schlafke (1967) found significant changes in the uterine epithelial lipids, and Potts (1969) stated that at the time of implantation the lipid spread from the basal part of the cell to the supranuclear zone.

After biochemical analyses of whole uterine homogenates, Beall & Werthessen (1971) concluded that triglycerides, accumulated in the uterine tissues before implantation, were depleted from implantation sites by Day 7. Triglycerides are the principal components of neutral lipids, and these compounds vary in quantity and intracellular distribution within the rat uterine epithelium during

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D. P. BOSHIER

The Pontamine Blue reaction (Finn & McLaren, 1967) reflects the increased vascular permeability at the site of blastocyst attachment (Psychoyos, 1960) which presages cellular changes in the uterus associated with implantation of the embryo (Finn & McLaren, 1967; Boshier, 1968, 1969). Leakage of this macromolecular dye, therefore, precedes any modifications in uterine histology that can be associated with attachment of the embryo. The increase in vascular permeability has been considered a sine qua non for decidua formation (Psychoyos, 1961). In this study, the Pontamine Blue reaction was used (1) as confirmation of earlier observations (Boshier, 1968) that implantation in sheep occurs on the 16th day of pregnancy, and (2) to determine whether this reaction is present in sheep, a species in which there is no evidence of decidual cell formation preceding the uterine epithelial changes which occur at the implantation site (Boshier, 1968, 1969). New Zealand Romney ewes of different ages were killed 15 min after an intravenous injection, lasting over 60 sec, of that volume of a 0·5% solution of Pontamine Sky Blue 5BX in normal saline which was equivalent to 10% of the recipient's blood volume [calculated as (lb body wt×0·07 litres)/2·2]. Uteri containing extra-embryonic membranes were examined under cold normal saline, and the caruncular and inter-caruncular areas were compared for difference in colouration. Only those uteri in which there was a differentially
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D. P. BOSHIER

Summary.

Histological examination of sheep extra-embryonic membranes obtained 18 days post coitum permitted more precise assessment of embryonic viability than did reliance on the macroscopic appearance of the embryo. Thirteen of twenty-seven sets of membranes examined had contained embryos which, although within the normal development range, were of doubtful viability. These thirteen sets of serosal membranes were found histologically to fall into one of two groups. Seven specimens were similar to seven sets of membranes in which a living embryo had been found, while six sets paralleled the remaining degenerating membranes in which there was no recognizable embryo. Histological features of the normal and degenerating serosal membranes are described.

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D. P. BOSHIER

Summary.

Reproductive performance before parturition has been investigated in laboratory mice of two breeding systems, each of two highly inbred strains and their F1 progeny. More corpora lutea of pregnancy were found in the BUB and I/Fn strains than in the C57BL/10J and A/Fn strains respectively, or in the F1s derived from the pairs contrasted.

BUB and I/Fn females had more pre-implantation and fewer postimplantation losses than females of the C57BL/10J and A/Fn strains, while F 1 females lost proportionately fewest potential young both before and after implantation. The number of conceptuses lost at different times during pregnancy differed proportionately in the populations examined and the BUB females differed from all others in not having a marked rise in embryonic mortality at about the 10th day of gestation. The significance of this departure from the norm is discussed.

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D. P. BOSHIER

Summary.

Embryo attachment and implantation in the ewe have been examined with a view to (a) elucidating the interrelationships of the trophoblast and the uterine epithelium, and (b) defining accurately the time relationships of the various phenomena. Embryonic attachment occurred during the 15th day of pregnancy and cytological changes within the uterine caruncular epithelium that appeared on the following day and were completed within a week, resulted in the formation of plaques of multinucleate symplasm and the death of some maternal epithelial cells.

High levels of acid phosphatase activity, considered to demonstrate the release of lysosomal hydrolases, were associated with the modification of the maternal epithelium and with the later trophoblastic invasion of the uterine stroma. Alkaline phosphatase activity present in the apical cell membranes of the opposing trophoblast and uterine epithelium is considered to be associated with carbohydrate metabolism and the production of trophoblastic fibrinoid.

No evidence was obtained to support proposals that trophoblastic binucleate giant cells have a major role in modifying the uterine epithelium through their phagocytic activity or as a source of the cryptal epithelium. The cryptal epithelium during the first 6 weeks of pregnancy appears to be derived from the symplasmic plaques of maternal epithelium.

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D. P. BOSHIER and K. M. MORIARTY

Summary.

One half of the forty-eight New Zealand Romney ewes to be mated with either a Romney or Southdown ram were immunologically sensitized to the ram 2 weeks before tupping. After 12 to 13 weeks of pregnancy, the ewes were slaughtered and each reproductive tract and conceptus examined. Sensitization to the sire had no effect on fecundity, fertility, placental weight or foetal size.

However, the number of placentomes per foetus tended to be larger in sensitized than in control ewes and was significantly greater in inter-breed than in intra-breed matings. It is suggested that the increased number of placentomes is due to heightened sensitivity of the maternal and foetal tissues at implantation, resulting from their antigenic differences.

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D. P. Boshier and June M. Katz

Summary.

Fructose-1,6-diphosphate (FDP) hydrolysis, which was measured in tissue extracts from mature rat endometrium, was maximal during late dioestrus and early pro-oestrus and reflected the variations in the plasma levels of ovarian steroids. Treatment of ovariectomized animals with oestradiol or medroxyprogesterone acetate increased FDP hydrolysis when compared with control animals, although oestradiol was the more effective. FDP hydrolysis was greater in extracts of endometrial tissue from uterine horns containing a silk IUD or of deciduomal tissue from pseudopregnant rats, in which the peak was on Day 9, than in extracts of endometrium from the control contralateral horn. These findings are interpreted as linking glycogen metabolism in normal endometrium, IUD-containing horns, and decidual tissue to the role of FDP in gluconeogenesis and the promotion of glycogen storage.

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D. P. Boshier, Hilary Holloway and Ngaire M. Millener

Summary. Specific histochemical techniques showed triacylglycerols to be the predominant neutral lipid in intracellular lipid droplets of uterine epithelial cells. After their extraction from pure samples of uterine epithelial cells, triacylglycerols were in lower concentration (μg/μg DNA) during pro-oestrus (0·4) than at any other stage of the oestrous cycle (0·73–0·86), decreased during Days 3 (0·5), 4 (0·25) and 5 (0·24) of pregnancy, and were lower in ovariectomized females receiving oestradiol (0·18) than in those receiving medroxyprogesterone acetate (0·93). It is suggested that these triacylglycerols could be used by the blastocysts and their contiguous endometrium as a readily available energy and metabolite source during implantation.

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D. P. Boshier, R. J. Fairclough and H. Holloway

Summary. Neutral lipids in the maternal uterine caruncular epithelium were studied by histochemical localization with Oil Red O. Results using a scoring system of 1 (negligible lipid) to 5 (maximal lipid) showed that intraepithelial lipid stores were minimal until Days 7–8 of the oestrous cycle and then increased to have a mean score of 4·4 on Days 14–15. In early pregnancy, although relatively high with a mean score of 3·2 at Day 15–16, such neutral lipids were significantly lower than those present at a comparable stage in the oestrous cycle. Thereafter, levels declined to a mean score of 1 on Days 21–23 of pregnancy. Such neutral lipid loss appears to be one of the first signs of the maternal response to the implanting embryo and precedes morphological evidence of transformation of either maternal or fetal tissues.

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S. C. Riley, D. P. Boshier, V. Luu-The, F. Labrie and J. R. G. Challis

Summary. Immunoreactive 3β-hydroxysteroid dehydrogenase/Δ54-isomerase (3β-HSD) was localized in adrenal glands of sheep fetuses in cortical-type cells, but not in medullary-type cells, from day 43 of gestation to term and in 2–4-day-old neonates. From day 54 of gestation, the formation of distinct zones within the adrenal cortex was apparent and immunoreactive 3β-HSD was found in cortical cells in the zona fasciculata and in groups and cords of cortical cells within the developing medulla, with weak positive staining in the zona glomerulosa. At this stage, most medullary cells were positive for immunoreactive tyrosine hydroxylase, and some of these cells with a juxta-cortical distribution also stained positively for immunoreactive phenylethanolamine N-methyl transferase (PNMT). Between days 65 and 130, the adrenal medulla increased in size with little change in the width of the cortex. Organization and zonation of immunoreactive 3β-HSD staining cells were evident in the zona fasciculata and in groups of cells in the medulla. Between day 130 and term, uniform immunoreactive 3β-HSD staining was found throughout the zona fasciculata, and there was also staining in single cells and small clusters of cells throughout the medulla. At this stage, immunoreactive tyrosine hydroxylase was distributed in most cells throughout the medulla, but in two distinct patterns: cells staining intensely for immunoreactive tyrosine hydroxylase in the central region of the medulla, and cells exhibiting weaker staining for immunoreactive tyrosine hydroxylase localized in a juxta-cortical position. These juxta-cortical cells were also positive for immunoreactive PNMT. Similar patterns of immunoreactive 3β-HSD, tyrosine hydroxylase and PNMT staining were found in 2–4-day-old neonates. We conclude that immunoreactive 3β-HSD is present in adrenal glands of sheep fetuses throughout gestation and in neonates, that progressive organization of cells containing 3β-HSD to form the fetal adrenal cortex occurs during gestation, and that immunoreactive 3β-HSD-positive cells may be closely associated with catecholamine biosynthesizing medullary cells during fetal life.

Keywords: adrenal gland; 3β-hydroxysteroid isomerase; fetus; sheep