High molecular weight kininogen: localization in the unstimulated and activated platelet and activation by a platelet calpain(s)

High mol wt kininogen (HMWK), the major cofactor-substrate of the contact phase of coagulation, is contained within and secreted by platelets. Studies have been performed to localize platelet HMWK in both the unstimulated and activated platelet and to ascertain the effect of platelet enzymes on HMWK itself. On platelet subcellular fractionation, platelet HMWK was localized to alpha-granules, and platelets from a patient with a deficiency of these granules (gray platelet syndrome) had 28% normal platelet HMWK. Platelet HMWK, in addition to being secreted from the platelet, was also localized to the surface of the platelet when activated. Using a competitive enzyme- linked immunosorbent assay for HMWK as an indirect antibody consumption assay, the external membrane of thrombin-activated platelets as well as the releasate from these stimulated platelets had 17 ng HMWK antigen/10(8) platelets available, whereas unstimulated platelets and their supernatant had only 4.9 and 4.2 ng HMWK/10(8) platelets present, respectively. The anti-HMWK antibody consumption by activated normal platelets was specific for membrane-expressed platelet HMWK, since activated platelets from a patient with total kininogen deficiency did not adsorb the anti-HMWK antibody. Enzymes in the cytosolic fraction of platelets cleaved 125I-HMWK (mol wt 120,000) into a mol wt 100,000 polypeptide as well as smaller products at mol wt 74,000, mol wt 62,000, mol wt 47,000, and a few components below mol wt 45,000. No cleavage products were observed when DFP and leupeptin were present. The cleavage of HMWK was specifically prevented by inhibitors of calcium-activated cysteine proteases (leupeptin, N-ethylmaleimide, iodoacetamide, and EDTA) but not by inhibitors of serine proteases (DFP, benzamidine, soybean trypsin inhibitor, or aprotinin). Platelet cytosol increased the coagulant activity of exogenous purified HMWK with maximum HMWK coagulant activity (35-fold) occurring within ten minutes of exposure to platelet cytosol. Treatment of platelet cytosol with leupeptin prevented the increase in the coagulant activity of exogenous HMWK. These studies indicate that activated platelets express platelet HMWK on their external membrane and platelet enzymes can cleave and increase the coagulant activity of exogenous HMWK.     

Biophysical characteristics of skin in diabetes: a controlled study

Background  Cutaneous complications are common in diabetes. Previous assays suggest that hyperglycemia and decreased insulin signal are involved in the impairment of skin function. The aim of this study was to evaluate the biophysical characteristics of skin in patients with diabetes mellitus and compares them with healthy non-diabetic controls.
Objective  To measure biophysical characteristic of skin including transepidermal water loss (TEWL), water content, sebum and skin elasticity in patients with diabetes mellitus and compare them with healthy non-diabetic controls.
Methods  This case-control study was conducted on 38 patients with diabetes and 40 age- and sex-matched healthy people. The biophysical properties of skin including stratum corneum (SC) hydration, sebum content, TEWL and skin elasticity were measured and compared between the two groups at three different locations of the body.
Results  The measurement of SC hydration and TEWL showed no significant difference between diabetics and controls. The skin surface lipids on the forehead but not other sites were significantly lower in the diabetics than in the controls. Acoustic wave propagation speed, a measurement related to skin elasticity, was significantly lower in forearm and forehead of diabetics.
Conclusion  Diabetes affects some functional properties of epidermis and dermis that may responsible for many cutaneous manifestations of diabetes. These results suggest that patients with diabetes mellitus tend to show a normal hydration state of the SC together with decreased sebaceous gland activity and impaired skin elasticity, without any impairment of the SC barrier function.

Conflicts of interest

None declared     

ACUTE EFFECTS OF ORAL GLIBENCLAMIDE ON BLOOD PRESSURE AND FOREARM VASCULAR RESISTANCE IN DIABETICS

1. To determine the effects of an acute oral dose of glibencla-mide on blood pressure (BP), basal forearm vascular resistance (FVR) and FVR responses to the K⁺_ATP channel activating vasodilator diazoxide, a placebo-controlled, double-blind cross-over study was performed in eight male volunteers with non-insulin-dependent diabetes mellitus. 2. Changes in vascular responses to progressively increasing concentrations of diazoxide (3.75–30 mg/kg per min) and noradrenaline (25–100 ng/kg per min) were measured by venous occlusion plethysmography. 3. Glibenclamide significantly lowered plasma glucose levels compared with placebo (P < 0.02) and attenuated the decrease in FVR (P < 0.05) and the decrease in systolic BP (P < 0.05) that followed a meal. However, vasodilator responses to diazoxide were potentiated by the administration of oral glibenclamide (P < 0.01). 4. Acute administration of oral glibenclamide attenuates the normal decrease in FVR and systolic BP that follows a meal and potentiates rather than inhibits forearm vasodilator responses to intra-arterial diazoxide, probably via indirect humoral effects. These results suggest that glibenclamide has direct or indirect vasoconstrictor effects that antagonize the normal increase in forearm blood flow that follows a meal and that the inhibition of vascular K⁺ATP channels following acute oral glibenclamide administration is clinically insignificant compared with other indirect vascular effects of the drug.     

Iopamidol and meglumine diatrizoate: comparison of effects on patient discomfort during aortofemoral arteriography

Iopamidol was compared with Renografin-60 (meglumine diatrizoate, Squibb) in a controlled, randomized double-blind study of 40 patients undergoing peripheral arteriography for arteriosclerotic occlusive disease to determine which agent caused less discomfort. Each patient was evaluated for objective signs of discomfort and subjective feelings of pain and heat. Monitoring was achieved by multiple physical examinations, chemical tests, electrocardiograms, and intra-arterial pressure recordings. It is concluded that iopamidol is safe and causes significantly less patient discomfort than Renografin-60.