Platelets, endothelium, and vasospasm.
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Adenosine Diphosphate↗
Biomedical subjects
D S Houston
Publications and source records attributed to D S Houston.
Forearm vascular responses in normotensives and hypertensives after sublingual nifedipine.
Some hemodynamic variables of ten untreated hypertensives and nine normotensives were compared before and at 10, 30, and 60 min after nifedipine 10 mg sublingually. Serum nifedipine concentration was measured at each of these times, and was similar between groups. Resting forearm venous compliance did not differ between groups, and did not change after nifedipine. Nifedipine did not change mean arterial pressure significantly, but heart rate was increased in both groups. Resting forearm blood flow was significantly higher in hypertensives than normotensives and forearm vascular resistance was correspondingly lower. Forearm blood flow increased and vascular resistance fell after nifedipine in normotensives, but did not change significantly in hypertensives. Our data do not suggest any effect of nifedipine on peripheral venous compliance. We do not confirm the reported decrease in forearm venous compliance in hypertensives, but the characteristics of blood flow, vascular resistance, and lack of effect of nifedipine on blood pressure likely reflect a predominance of early hypertensives in our study population.
Administration, Oral↗
The influence of amines on various platelet responses.
Four amines, galactosamine, mannosamine, histamine and arginine were studied for their effects on platelet aggregation, platelet morphological changes, platelet protein phosphorylation and platelet secretion. Galactosamine inhibited platelet aggregation in response to arachidonic acid and ionophore A23187 but did not inhibit changes in platelet morphology, or in platelet protein phosphorylation in response to these agents and only partially inhibited platelet secretion. The results suggest that galactosamine can be used as a selective inhibitor of platelet-platelet attachment without having a significant effect on intracellular processes. Mannosamine was similar to galactosamine except that it partially suppressed phosphorylation of myosin light chain. Histamine was similar to mannosamine except that some platelet damage was seen in platelets exposed to histamine and arachidonic acid or ionophore A23187. Arginine was non-selective: it suppressed platelet aggregation, secretion and phosphorylation of myosin light chain and a 40 kDa protein (40P) in response to arachidonic acid and ionophore A23187. Arginine was also potent in suppressing platelet morphological changes. When the same four amines were evaluated for their effects on thrombin-induced aggregation; secretion was inhibited concomitantly with inhibition of aggregation. Inhibition of myosin light chain and 40P phosphorylation was evident with galactosamine, suggesting that when thrombin is used as the agonist, galactosamine is not a specific inhibitor of platelet-platelet attachment. These amines therefore have various effects on platelet responses. Under some conditions and with arachidonic acid or ionophore A23187 as agonist, one of them, galactosamine, can be used as a selective inhibitor of platelet-platelet attachment.
Arachidonic Acid↗
Charcot foot.
Charcot joint is the painless, degenerative, progressive neuropathic destruction of the bony architecture of one or more joints of the feet. Diabetes mellitus is the most common cause of Charcot joint in North America, although the exact etiology is uncertain. The classic presenting complaint involves unilateral painless swelling of the lower extremity or foot. Charcot joint is often mistaken for cellulitis or deep vein thrombosis and may result in significant foot or ankle deformities. There are several treatment options for the patient presenting with Charcot joint. Medical management often includes immobilization and maintaining nonweightbearing status. Surgical intervention, often a final attempt at managing Charcot foot, involves careful patient selection and is not recommended for all patients. The postoperative phase can be challenging for both patient, nursing staff, and the surgeon.
Arthropathy, Neurogenic↗