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Biomedical subjects

A M Dharmarajan

Publications and source records attributed to A M Dharmarajan.

60 records · Page 4Linked to original sources
PubMed1988

Effect of the exposure of intrafollicular oocytes to clomiphene citrate on pregnancy outcome in the rabbit.

This study was designed to determine if exposure of rabbit intrafollicular oocytes to clomiphene citrate (CC) affects pregnancy outcome after in vitro ovulation, in vitro fertilization (IVF), and embryo transfer (ET). Ovaries were perfused in the presence or absence of CC (10(-5) M) and estradiol (E2, 100 ng/ml). Human chorionic gonadotropin (hCG, 50 IU) was added to the perfusate of all ovaries. In vitro ovulated ova were retrieved, inseminated, and transferred to host rabbits. Neither CC nor CC + E2 significantly affected hCG-induced ovulation or fertilization. CC significantly reduced (P less than 0.025) percentage of ovulated ova resulting in offspring. Addition of E2 significantly (P less than 0.05) reversed the reduction in offspring associated with CC alone. These results may be due to the antiestrogenic effects of CC on the intrafollicular oocyte, which compromises postfertilization development.

Animals↗
PubMed1986

Comparison of flow rates and composition of ovarian lymph and blood in the day-16 pregnant rat.

Rats (5) at Day 16 of pregnancy were anaesthetized and a modification of a venous outflow technique was used to collect ovarian venous blood and lymph for 2 h. Both fluids were analysed for progesterone, 20 alpha-dihydroprogesterone, total protein, transferrin and albumin concentrations. In addition SDS gel electrophoresis was carried out to obtain an initial indication of permeability of capillaries to the various protein fractions. The concentrations of progesterone and 20 alpha-dihydroprogesterone in ovarian lymph were only 37% and 48% respectively of the corresponding concentrations in the venous plasma. Total protein concentration in the lymph was 53% of the venous plasma. The albumin and transferrin concentrations were similarly lower in lymph than plasma but the difference was only significant for transferrin. This study confirms that the rate of lymph flow, per unit mass of tissue, is high for the ovary and represents about 1.1% of plasma flow. It shows also that of the total progestagens secreted only around 0.5% leave by the lymphatic route. The finding of relatively low progestagen concentrations in lymph questions the view that progestagens are transported by simple diffusion from the luteal cell to blood and raises the possibility of a counter-current flow between fluid in the interstitial space and blood.

20-alpha-Dihydroprogesterone↗
PubMed1985

Quantitative ultrastructural characteristics relating to transport between luteal cell cytoplasm and blood in the corpus luteum of the pregnant rat.

The synthesis and secretion of progesterone by the corpus luteum (CL) may be limited or controlled by transport mechanisms operating between circulating blood and luteal cell cytoplasm. To examine this possibility, the structural features involved in transport, including membrane surface areas and diffusion distances, were quantitated in the CL of 16-day pregnant rats. One ovary from each of eight rats was fixed by perfusion via a cannula inserted into the parametrial artery, and two CL from each ovary were processed for electron microscopy and examined with standard morphometric techniques. For comparison, one CL from each of a further eight ovaries was diced into small cubes, fixed by immersion, and analyzed similarly. In perfusion-fixed CL, there was a substantial volume of vascular space (20% of the total) and interstitial space (5%) and an extensive surface area of capillaries (441 mm2 per CL). The luteal-cell membrane had numerous projections which increased its surface area by a factor of 3.08. Almost 60% of the luteal-cell surface directly faced a capillary, and a further 37% faced interstitial space which probably extended to a capillary surface. Only 3% was in direct contact with a neighboring luteal cell. Despite the extensive interstitial space the harmonic mean thickness, an estimate of likely effective diffusion distance between luteal cell cytoplasm and blood, was only 0.42 micron. This was less than half of the calculated arithmetic mean thickness owing to the presence of surface projections and an uneven capillary endothelium. Results from immersion-fixed CL were qualitatively similar; but the proportion of interstitial space was only 59% of that in perfusion-fixed CL, and the contribution of surface projections to the total area of luteal-cell membranes was significantly reduced. Collectively, these results suggest that membranes and spaces between blood and luteal-cell cytoplasm are structured so as to minimize transport distances.

Animals↗
PubMed1984

Rate of blood flow and growth of the corpora lutea of pregnancy and of previous cycles throughout pregnancy in the rat.

The rate and distribution of ovarian blood flow was measured with radioactive microspheres in nulliparous rats at Days 4, 7, 10, 13, 16 and 22 of gestation; term is Day 23. Ovaries were dissected into large corpora lutea (or CL of pregnancy), small CL, assumed to be those of previous cycles, and the ovarian stroma which included follicles and additional small CL. Total ovarian blood flow was similar over Days 4-10, but then increased progressively to reach 916 +/- 69 microliter/min at Day 22. The main cause of this increase was a 786% rise in blood flow to the large CL over Days 10-22. Weight of the CL of previous cycles increased by 289% over Days 10-16 and their rate of blood flow and histological appearance were similar to those of the large CL. These results indicate that neither reduced blood flow nor vascular degeneration, as determined by light microscopic examination, initiates the reported fall in progesterone secretion near term. At least some of the CL of previous cycles are maintained and indeed grow during gestation and have a blood circulation and histological appearance characteristic of steroidogenic tissue.

Animals↗
PubMed1983

Morphometric analysis of the corpus luteum of 16-day pregnant rats: the effect of preparative procedures on volume of luteal cells, interstitial, and vascular compartments.

The volumes of the major tissue compartments, vascular space, interstitial space, and luteal cells, in the corpus luteum (CL) of 16-day pregnant rats were determined morphometrically after different fixation procedures. Ovaries were fixed by perfusion at physiologic pressures (PF), by immersion directly in fixative (IF), by immersion after clamping blood vessels to prevent escape of blood (IFC), or by immersion after administration of heparin to prevent blood clotting (IFH). Three CL in each of eight ovaries were examined for each fixation method. Total volumes were significantly larger in CL fixed by PF and IFC, and approximated physiologic volumes as assessed from frozen ovaries. Perfusion-fixed CL had significantly larger vascular and interstitial spaces and smaller cell volumes than immersion-fixed CL. Capillary surface area varied significantly between the four groups in accordance with absolute volume of vascular space. Estimated numbers of endothelial cells and amounts of connective tissue differed significantly, presumably due to difficulties in identifying these components in immersion-fixed CL with collapsed vessels. The fixation methods used caused substantial fluid shifts between the three major compartments. A theoretical approach for considering these shifts and the likely physiologic situation was developed.

Animals↗