Altered distribution of some surface glycosaminoglycans and glycoconjugates on human blood platelets in diabetes mellitus.

The distribution of some proteoglycan anionic sites and carbohydrate moieties on the diabetic platelet surface has been investigated by cytochemical methods. Human blood platelets obtained from either diabetic patients (serum glycaemia 9.6-19.

Enhanced prothrombin and intrinsic factor X activation on blood platelets from diabetic patients.

The present work was conducted to bring information about the enhanced procoagulant activity of blood platelets in diabetes mellitus, as compared to normal control platelets. The inquiry was performed on platelets from either human patients or hamsters with streptozotocin-induced diabetes. The experiments comprised functional assays of factor Xa and thrombin generation in the presence of normal or diabetic platelets, using saturating amounts of coagulation factors.

Some Major Plasmalemma Proteins of Human Diabetic Platelets are Involved in the Enhanced Platelet Adhesion to Cultured Valvular Endothelial Cells.

To extend our investigations on the interaction between diabetic platelets and endothelium, we tried to identify the molecular components involved in the increased adhesiveness of diabetic platelets to cultured valvular endothelial cells (VEC). Platelets from diabetic patients were radiolabeled with ((3)H]-adenine, incubated for 30 min at 37°C with confluent VEC grown in medium containing 4.5 g/L glucose, and the monolayer-associated radioactivity was used to calculate the adhesion index.

Increased adhesion of human diabetic platelets to cultured valvular endothelial cells.

Diabetes is accompanied by impaired platelet function and accelerated vascular disease. To find out whether a correlation exists between these two complications, and if modifications occurring in diabetic platelets influence their relationship with endothelium, we have studied the interaction between platelets isolated from plasma of diabetic patients and bovine valvular endothelial cells (VEC), in culture. For quantitative analysis, normal and diabetic [3H]-adenine-labeled platelets were incubated with confluent VEC grown in Dulbecco's modified Eagle medium, containing 4.

Changes in the platelet surface charge in rabbits with experimental hypercholesterolemia.

The effect of hypercholesterolemia on the platelet surface charge was examined in rabbits fed a lipid-rich diet (0.5% cholesterol and 5% butter). The strong anionic sites were detected with cationized ferritin (CF) pI 8.

Alterations of phospholipid asymmetry in the membrane of spontaneously aggregated platelets in diabetes.

The changes of asymmetric distribution of anionic phospholipids of human platelets in diabetic patients were studied by fluorescent and freeze fracture cytochemistry, using merocyanine 540 (MC 540) and polymyxin B (PxB) as specific markers. The membrane anionic phospholipids were detected with PxB, a membrane nonpermeant probe, used either in native form for freeze fracture electron microscopy or as dansylated or iodinated derivative for fluorescence microscopy or gamma counting, respectively. MC 540 is a naturally fluorescent probe which reportedly inserts into less packed bilayer domains.

Study of the endogenous lectins of the human platelet plasma membrane.

Plasma membranes isolated from human blood platelets and human intact platelets, either fresh or previously fixed, were investigated for their possible content in intrinsic sugar-binding proteins (lectins) which can specifically bind monosaccharides such as fucose, mannose, and galactose. Light and heavy fractions of platelet plasma membrane and intact platelets fixed with 2% formaldehyde and suspended in Tyrode's buffer pH 7.0 were incubated with either L-(1-3H)-fucose, D-(1-3H)-mannose or D-(1-3H)-galactose.

Changes in the organization of membrane lipids during human platelet activation. Study by fluorescent and freeze-fracture cytochemistry.

Modifications in the membrane lipid organization of human platelets activated with different agents (adenosine 5'-diphosphate, thrombin, collagen type I, and monosaccharides such as fucose, mannose, and galactose) were analyzed in vitro by using three lipid markers. Cholesterol was detected upon interaction with filipin, the anionic phospholipids were reacted with polymyxin B, and alterations in the degree of lipid packing were evaluated with the lipophilic fluorescent probe merocyanine 540, which reportedly inserts into bilayer domains whose lipids are more disordered. Filipin-sterol complexes and polymyxin B-anionic phospholipid complexes form characteristic membrane deformations which were examined in freeze-fracture preparations, whereas the merocyanine 540 binding to platelet membrane was recorded by fluorescent microscopy.

Reversal by arginine-vasotocin of the effects of pinealectomy on the amount of 5-hydroxytryptamine in the hypothalamus and the concentrations of luteinizing hormone and follicle-stimulating hormone in the plasma of immature male rats.

Pinealectomy in immature (25-day-old) male Wistar rats significantly decreased the content of 5-hydroxytryptamine (5-HT) in the hypothalamus and increased concentrations of plasma LH and FSH 3 days after surgery. Extremely small amounts (10(-4) pg) of arginine-vasotocin (AVT) injected into the third ventricle (pineal recess) 5 min after pinealectomy completely prevented the decrease in the hypothalamic content of 5-HT and the increase in the concentration of LH and FSH in the plasma. It is suggested that AVT prevented the increase of plasma levels of LH and FSH after pinealectomy by increasing levels of 5-HT at postsynaptic receptor sites.

Pineal vasotocin: release into cat cerebrospinal fluid by melanocyte-stimulating hormone release-inhibiting factor.

The intracarotid injection of both synthetic melanocyte-stimulating hormone release-inhibiting factor (MIF) and purified MIF prepared from bovine hypothalami induces arginine vasotocin release into cerebrospinal fluid of cats and significantly decreases the pineal arginine vasotocin content at 5 minutes after the injection. The present results demonstrate an extrapituitary endocrine effect of synthetic and purified bovine MIF.

Pineal vasotocin: release into cat cerebrospinal fluid by melanocyte-stimulating hormone release-inhibiting factor.

The intracarotid injection of both synthetic melanocyte-stimulating hormone release-inhibiting factor (MIF) and purified MIF prepared from bovine hypothalami induces arginine vasotocin release into cerebrospinal fluid of cats and significantly decreases the pineal arginine vasotocin content at 5 minutes after the injection. The present results demonstrate an extrapituitary endocrine effect of synthetic and purified bovine MIF.

Diurnal rhythm of vasotocin in the pineal of the male rat.

The pineal content of arginine vasotocin in the male rat is subject to diurnal changes, having a high value around noon and a low value around midnight. Since in rats exposed to 24 h constant light the pineal content in arginine vasotocin decreases, and in the rats exposed to 24 h constant darkness the pineal content in arginine vasotocin increases, it appears that during the night both the synthesis and release of arginine vasotocin is enhanced.

Chromatographic evidence for vasotocin biosynthesis by cultured pineal ependymal cells from rat fetuses.

Cultured pineal ependymal cells from rat fetuses aged 17 to 19 days post-coitum release into their media a substance that has hydroosmotic, antidiuretic and rat uterine activities. Paper chromatography of concentrates from culture media demonstrates that the substance possessing all the above activities was eluted from a slow moving region (Rf 0.15-0.

Reversal by vasotocin of pinealectomy and constant light effects on the pituitary melanocyte-stimulating hormone (MSH) content in the mouse.

A single injection of 1 pg synthetic arginine vasotocin (AVT) into the third ventricle of the mouse completely prevented the pituitary MSH increase which occurs seven days after pinealectomy or 24 h after exposure to constant light. The same concentration of AVT injected into the third ventricle of normal mice markedly decreased the pituitary MSH content at 20 min following the injection. The present results suggest that AVT injected into the third ventricle of the mouse inhibits synthesis and/or release of MSH-release inhibiting factor (MIF).