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Biomedical subjects

L E Costa

Publications and source records attributed to L E Costa.

26 records · Page 2Linked to original sources
PubMed1977

Steroid biosynthesis by gonads of rats submitted to chronic hypobaric hypoxia.

In vitro biosynthesis of steroids by testes and ovaries was studied in rats submitted to 6,000 m simulated altitude for 23 weeks and their controls at sea level atmospheric pressure. Gonads' homogenates were incubated in the presence of 4(-14) C-pregnenolone and cofactors. Extractions, partitions, paper chromatography and finally crystallizations until constant specific activity were performed. Tritium labelled internal standards were used to correct for methodological losses. In male animals, only androstenedione biosynthesis calculated per rat as well as the weight of the testes were reduced in hypoxia. Nevertheless, this reduction was accompanied by an equivalent decrease in body weight; testosterone biosynthesis was not significantly changed. On the contrary, in females, estradiol biosynthesis and the weight of the ovaries were significantly higher in hypoxic than in control animals. Macroscopic and microscopic aspect of the ovaries in hypoxic rats also indicate a hyperactivity of the steroidogenic function. Weight curves and mortality studies confirmed previous findings about the advantage of females in adaptation to hypoxia. Results show that ovaries play an active role in this process.

Altitude↗
PubMed1976

Effect of hypobaric hypoxia on erythrocytic glycolysis and 2,3 - DPG in rodents.

Glycolytic activity of red cells was determined in mice, rats and rabbits submitted to 4 700 and/or 6 000 m simulated altitude for variable periods of time and in controls at sea level. In all the species studied, glycolysis was found to be increased by the third week of exposure. 2,3-diphosphoglycerate (DPG) content was measured in rats submitted to simulated altitude for 4 to 66 days. A highly significant increase, which was higher at 4 700 than at 6 000 m, was found from the first days of exposure and throughout the whole experimental period. Our results are consistent with the hypothesis that variable DPG changes in different degrees of hypoxia are related to its ability to increase oxygen release to the tissues and negatively correlated with hematocrit increase. The data show that the increase in red cell glycolysis is only a temporary effect of relatively severe hypoxia, not related with changes in DPG concentration.

Adaptation, Physiological↗
PubMedDate not supplied

Ureteral segment replacement using a circumferential small-intestinal submucosa xenogenic graft.

We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.

Animals↗
PubMedDate not supplied

Reproductive function in female rats submitted to chronic hypobaric hypoxia.

Female rats were submitted to 5,500 m simulated altitude (50.7 kPa) for 23 weeks in a hypobaric chamber. In vitro biosynthesis of estradiol from labelled pregnenolone was studied in the ovaries of these rats and of their controls at sea level barometric pressure. The weight of the ovaries expressed as mg/rat was 63% higher (p < 0.001) and estradiol biosynthetic capacity expressed as % conversion/rat was 140% higher (p < 0.01) in hypoxic than in control rats. Estrous cycle and fertility were studied in rats submitted to 4,400 m simulated altitude (58.6 kPa) and in their controls. The percentage of estrous was significantly higher in hypoxic than in control animals. The fertility was lower in hypoxic rats. Optical microscopy showed signs of polycystic ovaries in both hypoxic groups. These results may suggest that the normal reproductive function includes oxygen dependent factors.

Animals↗
PubMedDate not supplied

An alternative to synthetic aortic grafts using jejunum.

Synthetic materials currently used for arterial grafts can provoke serious complications such as infection, rejection, and incomplete reendothelialization. Porcine small intestinal submucosa (SIS) allografts (homografts) may not share these disadvantages yet still may provide an effective graft alternative. This study was designed to provide additional information concerning the performance of this material when used as an allo-patch graft. A porcine model was selected to enable hemodynamic comparisons to the adult human physiology. Slaughterhouse small intestine was used to prepare the SIS graft material. A well-vascularized section ofjejunum was resected, rinsed, and maintained in 0.9% NaCl solution containing 10% gentamicin. The graft was prepared by removing the serosal layer, inverting the material, and discarding the mucosal surface in a similar manner. The remaining submucosa and stratum compactum constituted the graft material and was subdivided into sizes from 1.5 to 3.0 cm2 tacked to foil for manageability, and was returned to the gentamicin solution. The surgery was initiated with a femoral arterial line in the anesthetized swine, followed by isolation and preparation of the infrarenal aorta for grafting. Cross-clamps were applied and a 1.0 x 1.5-cm section of aortic wall was resected. Two sides of allograft were freed from the foil and sewn into the aorta. Then the remaining sides were removed from the foil and final graft placement was completed. The graft was harvested at postoperative day 28 and presented for microscopic examination. Results confirmed that reendothelialization with neovascularization had occurred during this interval.

Animals↗