The Journal of laboratory and clinical medicine
-
A plastic (Plexiglas) chamber for evaluating platelet deposition under controlled hemodynamic conditions has been developed. The perfusion chamber has been designed to retain the cylindrical shape typical of the vasculature, to be flexible enough to accept a variety of biologic and prosthetic materials, and to simulate a broad range of physiologic flow conditions in either an ex vivo or in vitro perfusion system. Three type of surfaces were exposed to blood flowing directly from the carotid artery of a heparinized pig through the perfusion chamber: de-endothelialized pig aorta, collagen strips from rabbit Achilles tendon, and an expanded polytetrafluoroethylene material (Gore-Tex). ⋯ Values of deposition on Gore-Tex obtained at similar flow conditions (105 to 425 sec-1) were reduced compared with that observed on subendothelium and showed a markedly weaker dependence on the shear rate. In contrast, deposition of platelets on collagen was more than an order of magnitude greater than on subendothelium and showed a dependence on flow only at the lowest flow rate studied (10 ml/min). The results indicate that collagen is much more reactive than subendothelium and Gore-Tex with respect to the growth and stability of platelet aggregates and moreover suggest that flow mechanisms for depositing platelets on various surface may be substantially different.
-
We examined the association of cholesterol levels in serum lipoprotein fractions, as well as of serum apolipoprotein-AI (apo-AI) and apo-AII levels, with coronary artery stenosis (CAS) and left ventricle function in a group of 43 patients with angina pectoris (33 men and 10 women) subjected to angiography. Cholesterol level in VLDL, LDL, HDL2, and HDL3 fractions was determined after separation of these fractions by density gradient ultracentrifugation. HDL-cholesterol is the sum of cholesterol in HDL2 and HDL3. ⋯ In multiple regression analysis with two or three independent variables, the relation of HDL(3)-cholesterol with CAS remained significant when other risk factors were taken into account. LVEF remained related positively with HDL(3)-cholesterol, apo-AI, or apo-AII, when either of them was tested in combination with other risk factors; of these only PMI made a significant independent contribution. Conclusions for this patient group (with low HDL-cholesterol): HDL3-cholesterol, and not HDL2-cholesterol, is informative for CAS; HDL(3)-cholesterol, apo-AI, or apo-AII, as well as CAS and PMI, are associated with LVEF.(ABSTRACT TRUNCATED AT 250 WORDS)
-
We reported previously that painful crises in patients with sickle cell anemia are accompanied by striking decreases in the percent of densest red cells (fraction 4) when studied with isopyknic Percoll-Stractan gradients. We report that an alternative to density gradients is the red cell distribution width (RDW), an estimate of red cell size variation measured with a Coulter counter. ⋯ In patients in whom serial measurements of both RDW and fraction 4 (very dense) red cells were taken during crisis, the two measurements declined in parallel. The decrease of RDW is a readily observable and objective laboratory concomitant of painful sickle crisis.
-
Furosemide stimulates urinary acidification in normal humans probably by increasing distal Na delivery and transport, thus creating a favorable electric gradient for H+ and K secretion. Therefore, furosemide should stimulate urinary acidification in patients with distal renal tubular acidosis, provided the distal nephron is capable of transporting Na and the H+ pumps can respond to the favorable electric gradient. We examined the effect of short-term furosemide administration on urinary acidification in five normal participants and 12 patients with normokalemic, hypokalemic, or hyperkalemic distal renal tubular acidosis. ⋯ The patients with voltage-dependent defect did not lower urine pH or increase net acid and K excretion. Our data demonstrate that administration of furosemide enhances urinary acidification in certain patients with distal renal tubular acidosis. We suggest that furosemide administration may be useful in the characterization of the mechanism responsible for distal renal tubular acidosis and in the treatment of distal renal tubular acidosis in selected patients.
-
The effect of changes in bicarbonate ion concentration on calcium ion concentration was examined in vitro in serum and protein-free solution. The findings in this study support the formation of a calcium-bicarbonate complex (CaHCO3+) that has a KA of 5.20 in protein-free solution. [Ca++] varied inversely with [HCO3-] in both serum and protein-free solution. This variation was independent of the known variation of [Ca++] with pH. ⋯ These findings indicate that abnormal bicarbonate concentrations should be considered when ionized calcium concentrations are estimated from total plasma calcium values in acid-base disorders. In metabolic acid-base disorders, the bicarbonate effect adds to the pH effect on calcium ion concentration. In compensated respiratory acid-base disorders, the bicarbonate effect subtracts from the pH effect on calcium ion concentration.