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Biomedical subjects

P Naeser

Publications and source records attributed to P Naeser.

At least 37 records · Page 2Linked to original sources
PubMed1989

DNA replication in transplanted and endogenous pancreatic islets of obese-hyperglycemic mice at different stages of the syndrome.

It was the aim of the present study to examine, at different stages of the obese-hyperglycemic syndrome, rates of islet-cell DNA replication in endogenous pancreatic and grafted islets of such mice. For this purpose obese-hyperglycemic mice were given an islet transplant prepared from lean mice under the kidney capsule. Two weeks later the animals were given an IP injection of 3H-thymidine one hour before being killed. Autoradiography of pancreas and kidney sections indicated the highest labeling index (LI) for the endogenous islet cells in the youngest obese mice (6 weeks old), which was more than fivefold higher than that of lean, normoglycemic controls. The LI, however, decreased extensively with age. The transplanted islets had LI, which were higher and constant during the most intense period of the syndrome, but again there was a decrease in the oldest mice. By isolating and transplanting islets of the oldest obese mice (greater than 12 months) into younger obese mice, it was possible to revive the high cell replicatory activity of the ob/ob islets. Starvation for three days was found to markedly decrease the rate of islet cell DNA replication. Adrenalectomy of obese-hyperglycemic mice resulted in a decrease of the serum glucose and insulin concentrations; concomitantly, there was a decrease of LI of both transplanted and endogenous islets. Thus, it seems as if the attenuation of the hyperglycemia is most probably responsible for the decline of the islet cell replication with increasing age in obese-hyperglycemic mice.

Adrenalectomy↗
PubMed1989

Influence of sorbitol accumulation on growth and development of embryos cultured in elevated levels of glucose and fructose.

Day-9 rat embryos, cultured for 48 hours in 67 mmol/l D-glucose, showed impaired growth, increased malformation rate and elevated concentration of sorbitol compared to embryos cultured in medium without additional glucose supplement. Supplementing the high-glucose cultures with an aldose reductase inhibitor markedly decreased the sorbitol levels without affecting the malformations or the retarded growth of the embryos. Since embryos cultured in 6.6 mmol/l D-fructose showed normal growth and morphology despite increased accumulation of sorbitol, this study suggests a dissociation between raised sorbitol levels and glucose-induced maldevelopment in rat embryos.

Abnormalities, Drug-Induced↗
PubMed1988

Sorbitol metabolism in the retina, optic nerve, and sural nerve of diabetic rats treated with an aldose reductase inhibitor.

Sorbitol concentration has been measured in retina, optic, and sural nerve of normal, diabetic, and aldose reductase inhibitor-treated diabetic rats. The sural nerve displayed significantly higher sorbitol content than the retina and the optic nerve both in control animals and in diabetic animals. In the sural nerve the response to treatment with an aldose reductase inhibitor was more marked than in the two other tissues. The activities of aldose reductase and sorbitol dehydrogenase were not influenced by diabetes. It is suggested that aldose reductase inhibition may be of greater use for alleviating peripheral nervous system accumulation of sorbitol than for hindering CNS accumulation of the polyol.

Aldehyde Reductase↗
PubMed1988

Scleral reinforcement by a teflon graft and a tissue adhesive.

Expanded patches of polytetrafluoroetylen, teflon (Impra) together with a tissue adhesive (cyanoacrylate) have been used to reinforce the scleral wall. The material has been used in 3 different trials on animals in periods up to 8 months. The histological analysis showed that the material was well accepted. The study indicates that scleral reinforcement with teflon and cyanoacrylate is a safe procedure.

Animals↗
PubMed1988

Optic nerve involvement in a case of methanol poisoning.

The eyes and optic nerves were studied histologically in a fatal case of methanol poisoning in a 37-year-old man. The most striking findings were bilateral central necrosis of the optic nerves from behind the lamina cribrosa to the orbital apex. Proximal parts of the nerve and the tract showed no necrosis. It is suggested that the complex blood supply of the nerve may be of importance.

Adult↗
PubMed1988

Sorbitol in aortic endothelium of diabetic rats.

Sorbitol metabolism of the endothelial cells of the aorta has been studied in normal and alloxan diabetic rats by the aid of a new time- and gradient governed elution method. In the normal rats the amount of sorbitol was small whereas in the diabetic animals the content was significantly increased (p less than 0.001). The activity of sorbitol-dehydrogenase was not changed. It is possible that a metabolic injury of endothelial cells induced by a glucose overload may be mediated by formation of sorbitol.

Animals↗
PubMed1987

A new approach to the biochemical pathology of the vascular system, using time governed laminar elution and bioluminescence analyses.

Endothelial cells which cover the inner wall of blood vessels were extracted for bioluminescence analyses of nucleotides and enzymes. The contaminating blood was removed by heparinization and rinsing with ammonium chloride. The content of the endothelial cells of the rat aorta was reached by time governed laminar elution, using a saponin solution to disrupt the cell membranes. Uniformity of extraction was achieved with a Hamilton programmable pump. All the analyses of the eluted fractions showed a characteristic and reproducible peak. The activities of glucose-6-phosphate dehydrogenase and adenylate kinase were significantly higher in the diabetic animals whereas the amount of nucleotides did not differ between diabetic and control rats. The laminar elution technique combined with bioluminescence assay represents a new approach to studies of biochemical alterations in the endothelial cells. The method is also useful for extraction and analyses of other surface layers.

Adenine Nucleotides↗
PubMed1987

Quantification and gel electrophoretic analysis of proteins extracted from vascular endothelial cells.

The inner walls of tubular organs and body cavities are lined with a sheet composed of cells which control the passage through the walls and thus are of considerable physiological and biochemical interest. They are difficult to prepare but their content can be extracted and analysed, using laminar extraction and sensitive bioluminescence methods. This has been shown for the endothelial cells which line the interior of blood vessels. Although it is dealing with small amounts of material, only a minor part of it is consumed in the analyses. The bioluminescence measurements can thus be combined with other analytical procedures such as protein assay and electrophoresis. The possibilities of extending the biochemical information is of interest in the efforts to clarify the pathogenesis of vascular diseases. Laminar elution of protein from endothelial cells of the rat aorta was traced by the simultaneous efflux of adenine nucleotides. These were determined in a bioluminescence assay after conversion to ATP, while the fluorescamine reaction was used for the quantification of protein. The elution patterns obtained by these two methods showed an initial peak with a common maximum. The new possibilities of detecting relevant biochemical changes were evidenced by the finding of a marked protein loss in the fractions containing the outflux from the endothelial cells of diabetic rats. Electrophoresis of proteins eluted from endothelial cells resulted in separation into a large number of bands, but no differences were detected in the electropherograms at comparisons between normal and diabetic rats. It remains to be clarified, whether the protein depletion of the endothelial sheet is due to a concomitant loss of cells or to a cytoplasmatic loss without profound changes of the cytoplasmatic composition.

Adenine Nucleotides↗
PubMed1987

An increased number of mast cells in the sclerae of alloxan-diabetic mice.

The number of mast cells in the sclerae and retinae has been investigated in alloxan-diabetic mice, in obese-hyperglycaemic mice and in non-diabetic, lean control animals. In contrast to the alloxan-diabetic mice the obese-hyperglycaemic animals have increased circulating inulin levels. In the sclerae of alloxan-diabetic mice the number of mast cells was significantly (P less than 0.05) increased. No increase in mast cell content could be observed in the sclerae of the obese-hyperglycaemic mice. No mast cells could be observed in the retina in any of the experimental groups. It is concluded that lack of insulin may be of importance for the accumulation of mast cells in the sclerae of mice with hyperglycaemia.

Animals↗
PubMed1987

The sorbitol shunt in the retina and the optic nerve of mice with inherited and STZ-induced diabetes.

Micromethods designed for studying the sorbitol shunt permitted studies of the retina and the optic nerve from mice. A significant accumulation of sorbitol was found in the retina of 5-months-old obese-hyper-glycaemic and severely STZ diabetic mice. The latter mice also showed increased sorbitol concentrations in the optic nerve. The activities of aldose reductase were about 3 times higher in the optic nerve than in the retina. Our findings show that not only the retina but also the optic nerve accumulates sorbitol. It is suggested that this hypothetically may lead to degeneration of the optic nerve in severe diabetes as in peripheral nerves.

Animals↗
PubMed1986

Labelling of retinal capillaries in mice by repeated [3H]thymidine injections.

Injections of [3H]thymidine intraperitoneally to mice on 3 consecutive days label a small number of retinal vascular cells. A single dose of the tracer is not sufficient for adequate cell marking. Retinal capillaries from obese-hyperglycemic mice of different ages examined by this method showed no significant difference of the labelling index compared to their normal, lean controls. The present method is simple and leaves the eyes undisturbed. It may be considered well suitable for experimental studies on cell replication in the retinal capillaries.

Animals↗
PubMed1986

Cell replication in retinal vessels of streptozotocin diabetic mice.

The retinal vascular bed from streptozotocin diabetic mice was investigated with respect to cell replication. The diabetic animals showed a significantly decreased endothelial cell labelling index as compared to their normal controls. It is suggested that the low cell replication characterizes the early diabetic vascular disease and that this animal model may reflect the inducement of the simplex diabetic retinopathy.

Animals↗
PubMed1986

Increased accumulation of sorbitol in offspring of manifest diabetic rats.

The effects of maternal diabetes on somatic development and activity of the polyol pathway were investigated during early and late gestation in a rat model for diabetic pregnancy. We studied embryo-fetal growth, mortality, and malformation rate in the offspring of nondiabetic rats and in the offspring of diabetic rats either treated with an aldose reductase inhibitor during gestation or left untreated. The numbers of embryo-fetal resorptions and malformations were significantly increased in the diabetic groups compared with the controls despite maternal treatment with the aldose reductase inhibitor. The sorbitol content of embryos and membranes from the diabetic rats in early gestation was increased 3-5 times over the control values. Similarly, elevated sorbitol levels were observed in the fetal livers and placentas of the diabetic rats in late gestation. Administration of the aldose reductase inhibitor to the pregnant diabetic rats normalized the sorbitol levels in the embryos and their membranes, whereas the sorbitol contents of the fetal livers and placentas were significantly lowered but not completely corrected. Furthermore, in the diabetic groups, no differences in sorbitol levels could be demonstrated between malformed and nonmalformed offspring. The results of this study suggest that enhanced polyol metabolism leading to increased sorbitol accumulation is present in the embryos of diabetic mothers as early as organogenesis. This accumulation is apparently not a major factor in the early developmental disturbances (e.g., growth perturbations and congenital malformations) of diabetic pregnancy.

Animals↗
PubMed1983

Effects of pancreatic islet implantation on the morphology of retinal capillaries in alloxan diabetic mice.

Intrasplenic implantation of syngeneic islets normalized the hyperglycaemia of alloxan-diabetic mice irrespective of whether the implantation was performed 2 weeks or 4 months after the induction of diabetes. Islet implantation soon after the onset of diabetes prevented the development of retinal capillary disease as evidenced by a normal ratio between endothelial cells and pericytes. The increase of the cell count ratio (endothelial cells/pericytes) induced by long-term diabetes could not, however, be restored by islet implantation. The present results further underline the importance of optimal treatment for prevention of diabetic retinopathy.

Animals↗