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Biomedical subjects

L H Byrd

Publications and source records attributed to L H Byrd.

9 recordsLinked to original sources
PubMed1994

Blood pressure inversely correlates with thrombin-evoked calcium rise in platelets.

Earlier investigations showed a positive correlation between basal cytosolic free calcium in human platelets and blood pressure; however, recent studies have failed to show this relation. We undertook the present work to examine which platelet cytosolic calcium parameters (namely, cytosolic calcium in resting or stimulated states in calcium-containing and calcium-free media) present the least variability and best correlation with blood pressure. We studied 17 healthy white men on three different occasions separated by 1- and 4-week intervals. Their manual and ambulatory automated 24-hour blood pressure measurements were correlated with cytosolic calcium in resting and stimulated (thrombin-treated) fura 2-loaded platelets. The following cytosolic calcium parameters were measured in 1 mmol/L calcium and calcium-free media: basal cytosolic calcium, peak thrombin-evoked cytosolic calcium, and post-transient cytosolic calcium 5 minutes after thrombin treatment. The highest and lowest coefficients of variation were respectively shown by the basal cytosolic calcium (22.8%) and peak thrombin-evoked cytosolic calcium (10.1%) in calcium medium. Basal cytosolic calcium did not correlate with any of the blood pressure parameters. Of the cytosolic calcium parameters, peak thrombin-evoked cytosolic calcium in calcium medium demonstrated consistent (negative) correlations with blood pressure, with better correlations shown with diastolic than systolic blood pressure of both automated and manual blood pressure readings. Peak thrombin-evoked cytosolic calcium in calcium medium showed similar correlations with nighttime and daytime automated blood pressure measurements. There were no correlations between peak thrombin-evoked cytosolic calcium in calcium-free medium and blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Kinetics of Ca2(+)-ATPase activation in platelet membranes of essential hypertensives and normotensives.

To explore the etiology of altered Ca metabolism in essential hypertension, we studied parameters, i.e., maximal initial reaction velocity (Vmax) and Michaelis constant (Km), of Ca activation kinetics of Ca2(+)-ATPase in membrane fractions (isolated by a sucrose gradient) from platelets of blacks and whites, 27 of whom were essential hypertensives, 17 of whom were normotensives with a family history of essential hypertension, and 10 of whom were normotensives without a family history of the disease. The Vmax of hypertensives was significantly lower than in normotensives without a family history of essential hypertension (hypertensives, 14.99 +/- 1.71 nmol Pi.mg protein-1.min-1; normotensives, positive family history, 22.67 +/- 3.17 nmol Pi.mg protein-1.min-1; normotensives, negative family history, 27.54 +/- 4.37 nmol Pi.mg protein-1.min-1; overall, P = 0.0078). The Km was lower in both hypertensives and normotensives with a positive family history of essential hypertension as compared with normotensives with a negative family history of the disease (hypertensives, 1.70 +/- 0.23 microM; normotensives, positive family history, 1.38 +/- 0.2 microM; normotensives, negative family history, 2.79 +/- 0.58 microM; overall, P = 0.0251). Furthermore, the Km in whites was inversely related to plasma renin activity (r = 0.50; P less than 0.005). We propose that a lower Vmax for Ca2(+)-ATPase may play a role in the higher level of free Ca in platelets of essential hypertensives and that a higher affinity of the enzyme to Ca may reflect a process compensating for the lower Vmax. We also suggest that a higher Km for Ca2(+)-ATPase in juxtaglomerular cells of whites would result in blunting the release of renin.

Adult↗
PubMed1990

Variations in the apparent pH set point for activation of platelet Na-H antiport.

To explore the role of the Na-H antiport in essential hypertension, we studied the kinetics of cytosolic pH and external sodium activation of this transport system in platelets from 65 normotensive and essential hypertensive subjects on and off antihypertensive medications. Subjects included both blacks and whites, as well as men and women. The fluorescent dye 2'7-bis(carboxyethyl)-5,6-carboxyfluorescein was used to monitor the cytosolic pH in these cells. Platelets from black (hypertensive and normotensive) men and hypertensive white men demonstrated a highly significant alkaline shift in the apparent cytosolic pH set point for activation of the Na-H antiport. For the hypertensive subgroups, the cytosolic pH set point values (mean +/- SEM) were: white men, 7.45 +/- 0.052; white women, 7.04 +/- 0.089; black men, 7.66 +/- 0.148; and black women, 7.20 +/- 0.082. For the normotensive subgroups, the cytosolic pH set point values were: white men, 7.13 +/- 0.034; white women, 7.05 +/- 0.036; black men, 7.50 +/- 0.110; and black women, 7.20 +/- 0.176 (p = 0.0016 for race and p = 0.0001 for gender, using a three-way analysis of variance by race, gender, and hypertension). There were no race-, gender-, or blood pressure-related differences among the various cohorts in the kinetics of sodium activation of the Na-H antiport, the cellular buffering power, and basal pH. These results suggest that at basal pH the Na-H antiport is quiescent in platelets from both black and white women and normotensive white men.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1981

Bordetella bronchiseptica peritonitis associated with continuous ambulatory peritoneal dialysis.

Bordetella bronchiseptica has rarely been reported as an opportunistic pathogen in humans. This is the first documented report of peritonitis due to B. bronchiseptica. The organism was seen on a Gram strain of peritoneal fluid and was isolated from a culture of the fluid. It was thought that the source of infection was related to the close contact of the patient with his dog. The patient was successfully treated with chloramphenicol administered intraperitoneally and intravenously.

Anti-Bacterial Agents↗
PubMed1978

Association between Streptococcus faecalis urinary infections and graft rejection in kidney transplantation.

In the first month after transplantation 50% of 193 consecutive renal transplant recipients had bacteriuria. The most common organisms isolated were Streptococcus faecalis (34), Escherichia coli (28), Pseudomonas spp. (11), and staphylococcus (9). There was a significant correlation between infection with Str. faecalis and graft failure at one, three, and twelve months. This observation suggests that urinary infection with Str. faecalis may be associated with graft failure which is probably the result of immunological factors.

Adult↗
PubMed1978

Successful coronary artery bypass in hemodialysis patients.

Cardiovascular disease is the major casue of death in maintenance hemodialysis patients. We report two chronic hemodialysis patients with unstable, disabling angina in association with severe coronary artery disease involving all three major vessels. Both successfully underwent coronary artery bypass surgery and subsequently experienced dramatic clinical improvement. Principles of management are discussed and it is suggested that hemodialysis patients should not be arbitrarily denied consideration of coronary artery bypass surgery when it is otherwise indicated.

Adult↗
PubMed1976

Treponemal antigen in immunopathogenesis of syphilitic glomerulonephritis.

A patient with syphilitic glomerulonephritis had a renal biopsy and was treated for secondary syphilis. Light, electron, and immunofluorescence microscopic studies revealed an acute proliferative glomerulonephritis with subepithelial, intramembranous, and subendothelial immune complex deposits containing IgG, IgA, IgM, C4, and C3. Similar local deposits containing predominantly IgM were noted in areas of mesangial proliferation. Indirect fluorescent antibody studies employing rabbit treponemal antibody and sheep antirabbit globulin conjugate revealed the presence of treponemal antigen in the glomerular deposits. This finding provides strong evidence for the immunopathogenesis of the glomerular lesion as well as a causal link with Treponema pallidum.

Adult↗