Adhesion of platelets to human artery subendothelium: effect of factor VIII-von Willebrand factor of various multimeric composition

The relationship between the multimeric size of factor VIII-von Willebrand factor (FVIII-vWF) and the support of platelet adhesion to subendothelium was studied in an annular perfusion chamber, employing human renal and umbilical arteries. Commercial factor VIII concentrates containing multimers of low molecular weight that had been shown not to correct the bleeding time upon infusion into patients with von Willebrand's disease did not support platelet adhesion in the perfusion chamber. Cryoprecipitate and two experimental FVIII-vWF concentrates containing multimers of high molecular weight supported platelet adhesion. Factor VIII-vWF purified from cryoprecipitate was subdivided into three fractions of different molecular weights (6.0-14.0, 4.0-9.0, and 3.0-7.5 X 10(6) dalton). These fractions appeared to bind equally well and to be equally effective in supporting platelet adhesion. Factor VIII-vWF with multimers of low molecular weight (0.5-1.5 X 10(6) dalton) were prepared by partial reduction. Binding of FVIII-vWF to subendothelium was not impaired, and the support of platelet adhesion appeared to be more resistant to the effect of reduction than the ristocetin cofactor activity. At high shear rate (2,500 sec-1), increased platelet adhesion was observed with partially reduced FVIII- vWF. These data indicate that the ability of FVIII-vWF preparations to correct the bleeding time is reflected in enhanced platelet adhesion to subendothelium in a perfusion chamber. These data also emphasize that multimeric size is not the only factor determining whether FVIII-vWF will support platelet adhesion.     

A Novel Neutrotrophic Property Of Glucagon-Like Peptide 1: A Promoter Of Nerve Growth Factor-Mediated Differentiation In PC12 Cells

The insulinotropic hormone glucagon-like peptide-1 (7-36)-amide (GLP-1) has potent effects on glucose-dependent insulin secretion, insulin gene expression, and pancreatic islet cell formation and is presently in clinical trials as a therapy for type 2 diabetes mellitus. We report on the effects of GLP-1 and two of its long-acting analogs, exendin-4 and exendin-4 WOT, on neuronal proliferation and differentiation, and on the metabolism of two neuronal proteins in the rat pheochromocytoma (PC12) cell line, which has been shown to express the GLP-1 receptor. We observed that GLP-1 and exendin-4 induced neurite outgrowth in a manner similar to nerve growth factor (NGF), which was reversed by coincubation with the selective GLP-1 receptor antagonist exendin (9-39). Furthermore, exendin-4 could promote NGF-initiated differentiation and may rescue degenerating cells after NGF-mediated withdrawal. These effects were induced in the absence of cellular dysfunction and toxicity as quantitatively measured by 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and lactate dehydrogenase assays, respectively. Our findings suggest that such peptides may be used in reversing or halting the neurodegenerative process observed in neurodegenerative diseases, such as the peripheral neuropathy associated with type 2 diabetes mellitus and Alzheimer's and Parkinson's diseases. Due to its novel twin action, GLP-1 and exendin-4 have therapeutic potential for the treatment of diabetic peripheral neuropathy and these central nervous system disorders.     

Influence of age on the beta 1- and beta 2-adrenergic receptors in rat liver.

The influence of maturation and aging on beta receptors in rat liver was studied. Competition binding experiments with the nonselective beta-antagonist propranolol and the subtype selective antagonists ICI 118,551 (beta 2) ICI 89,406 (beta 1), and CGP 20,712A (beta 1) revealed the presence of a mixed beta 1 and beta 2 receptor population in crude plasma membrane preparations from livers of newborn, mature, and senescent rats. The percentage of beta 1 receptors was lowest in livers from newborn rats and was increased in livers from mature and senescent rats. This increase is caused by a decrease in beta 2 receptor density on maturation, although the beta 1 receptor density is nearly constant throughout the life span of the rat. Isoproterenol-stimulated adenylate cyclase activity was inhibited in livers from senescent rats by propranolol and ICI 118,551 and to a lesser extent by ICI 89,406 and CGP 20,712A. The isoproterenol-stimulated glucose output in hepatocytes from senescent rats was inhibited concentration dependently by propranolol, ICI 118,551, ICi 89,406, and CGP 20,712A. From these results we conclude that beta 1 and beta 2 receptors are present in livers from rats of the three age groups and that the beta 1 to beta 2 receptor ratio is increased in livers from mature and senescent rats compared with newborn rats. Both beta receptor subtypes are linked to the cAMP second messenger system in newborn and senescent rats; beta 1 and beta 2 receptors are equally involved in the regulation of glycogenolysis in hepatocytes from senescent rats.     

Congenital cardiac anomalies with vein of Galen malformations in infants

Published reports and personal experience are reviewed relating to patients under 1 year of age diagnosed with a vein of Galen malformation and congenital heart disease. Including five patients from this institution, a total of 23 patients (12 neonates) with congenital heart disease and a vein of Galen malformation have been reported. Six of these had sinus venosus atrial septal defect and nine had aortic coarctation.     

Endothelin and neutral endopeptidase in the endometrium of women with menorrhagia

The mechanisms underlying excessive menstrual bleeding or menorrhagia are not understood. In view of its potent vasoconstrictor and growth factor properties, endothelin has been proposed to have a potential paracrine role in the regulation of uterine blood flow and therefore could be a factor in menorrhagia. We compared the cellular localization of endothelin and its metabolizing enzyme, neutral endopeptidase, in endometrial biopsies from women with documented menorrhagia and in those with a normal menstrual cycle. Menorrhagia was documented by measurement of menstrual blood loss, 146 +/- 141 ml (median +/- SD). Endothelin and neutral endopeptidase were localized by immunohistochemistry, and the staining intensity was graded. Their immunostaining patterns were found to differ in menorrhagia compared to the normal menstrual cycle. Endothelin was reduced in glandular epithelium in menorrhagia and did not vary cyclically, while neutral endopeptidase was increased in the glandular epithelium. In menorrhagia, stromal endothelin immunoreactivity was not different from the normal cycle and although neutral endopeptidase immunostaining in stroma was similar to the secretory phase of normal endometrium, cyclical variation was absent. The potential for increased metabolism of endothelin could be an explanation for the decreased endothelin immunostaining in the glandular epithelium.      

Glycan microheterogeneity of alpha 1-acid glycoprotein in sera and dialysates of patients on continuous ambulatory peritoneal dialysis

Total concentration and concanavalin (Con A) dependent microheterogeneity of alpha 1-acid glycoprotein (AGP) were studied in sera of eight chronic renal failure patients before the start of continuous ambulatory peritoneal dialysis (CAPD), and in sera and dialysate fluids for up to 6 months of CAPD. The glycan heterogeneity of AGP in the samples was expressed as a reactivity coefficient, i.e. the ratio of the Con A-reactive AGP components to the Con A non-reactive AGP component. Concentrations of AGP in serum and reactivity coefficients were markedly elevated in non-dialysed uraemic patients. AGP concentrations in serum increased further during the first week on CAPD, and then gradually decreased to pre-dialysis values, which were reached after 1 to 6 mth. The reactivity coefficients did not change significantly during the CAPD treatment. Dialysate AGP concentrations were low in comparison to those in serum, and there was a good correlation between the reactivity coefficients in the dialysate fluids and those in the corresponding sera. The effect of peritonitis was evaluated in a separate group of eight CAPD patients. Serum and dialysate AGP concentrations were significantly higher during than after peritonitis while the corresponding reactivity coefficients were only slightly elevated.