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Biomedical subjects

J W Davis

Publications and source records attributed to J W Davis.

At least 253 records · Page 14Linked to original sources
PubMed1981

Hemorrhage of thiamine-deficient encephalopathy.

Hemorrhagic lesions of pyrithiamine-induced acute thiamine-deficient encephalopathy of the mouse (PIATDEM) consisted of petechiae, which often coalesced to form small hematomas. Electron microscopy showed the typical petechial lesion to be composed of a perivascular necrotic zone containing fibrin-platelet clot surrounded by a ring of erythrocytes. Endothelial cells were intact and tight junctions were closed. A study of permeability to horseradish peroxidase (HRP) revealed only a slight increase in the number of transport vesicles in the endothelial cells. A large amount of HRP present in the lesions seemed to have entered the brain by a hemorrhagic route which remains unclarified. Spherical latex particles, 0.23 micrometer in diameter, were injected intravenously into encephalopathic mice at a time when intracerebral hemorrhages frequently occurred. Two to 24 hours after the injection, a large number of latex particles penetrated the blood vessels at sites of hemorrhage. There were many particles in the phagosomes of the endothelial cells, which suggested transendothelial transport by the organelle. The possibility of endothelial phagocytic transport of erythrocytes as a main route of diapedesis is discussed.

Animals↗
PubMed1981

Nonselectivity of Rimler-Shotts Medium for Aeromonas hydrophila in Estuarine Environments.

Thirty presumptive Aeromonas hydrophila isolates were collected from estuarine sources using Rimler-Shotts media. Many of the isolates, especially the strains from a low-salinity site, were also identified as A. hydrophila using the API 20E system and two differential techniques devised for the identification of A. hydrophila. All of the isolates, however, had deoxyribonucleic acid base compositions with guanine-plus-cytosine ratios between 40 and 49 mol%, which excludes these strains from the genus Aeromonas.

Journal Article↗
PubMed1981

Antimicrobial susceptibility of Ureaplasma urealyticum.

An antimicrobial susceptibility test, a tow-tube broth dilution and disk elution method for Ureaplasma urealyticum, was modified to incorporate some of the standard procedures followed in traditional antimicrobial testing. The susceptibility pattern of the species was reevaluated by determining the effect of various antimicrobial agents on 21 vaginal isolates. All isolates were inhibited by tetracycline congeners (1 to 6 micrograms/ml) and killed by methenamine mandelate (0.6 mg/ml). All but one isolates were inhibited by erythromycin (0.4 to 3 micrograms/ml). Only eight isolates were inhibited by nalidixic acid (1 to 6 micrograms/ml), and seven were inhibited by nitrofurantoin (20 to 60 micrograms/ml), whereas all isolates were resistant to rifampin (1 microgram/ml) and trimethoprim-sulfamethoxazole (5 micrograms/ml). The in vitro technique described can readily be performed on individual patient isolates before the initiation of antimicrobial therapy.

Anti-Bacterial Agents↗
PubMed1981

Prevention of cigarette smoking-induced platelet aggregate formation by aspirin.

The purpose of this study was to determine whether aspirin could prevent a decrease in the platelet aggregate ratio that we previously found after cigarette smoking. Twenty healthy nonsmokers, who had not taken aspirin in the preceding seven days, smoked two tobacco cigarettes without filters during a 20-minute period. The mean platelet aggregate ratios before and after smoking were 0.91 and 0.80, respectively. When the experiments were repeated 48 hours later and seven to 18 hours after the ingestion of one tablet of aspirin (0.32 g), there was no decrease in the platelet aggregate ratio after smoking. The mean post-smoking platelet aggregate ration after aspirin (0.93) was significantly higher than before aspirin. We conclude that aspirin prevented cigarette smoking-induced platelet aggregate formation.

Adolescent↗
PubMed1980

Platelet satellitism: experimental studies.

Platelet satellitism (PS), the in vitro phenomenon of platelets rosetting about nonlymphocytic leukocytes, is an uncommon and poorly understood finding reported in the ethylenediaminetetra-acetic acid (EDTA)-anticoagulated blood of patients with a wide variety of clinical conditions. This report presents experimental studies investigating the nature of this phenomenon by utilizing the blood of patients with platelet satellitism. Wet preparation studies and electron microscopy (transmission and scanning) demonstrated the morphologic sequences involved in the phenomenon, including eventual phagocytosis of platelets by neutrophils. The results of varying conditions such as time, temperature, and anticoagulant are described. All of five patients tested were found to have cryofibrinogenemia. Certain blood components from all of three patients tested were capable of inducing PS in normal whole blood, whereas components from normal subjects usually were not. In one patient (A), the PS-inducing capability appeared to be present in both plasma and platelets. In another patient (B) the PS-inducing capability was present in platelets (in both 1966 and 1975) and also in the cryosupernate of serum and plasma; among various antisera, antifibrinogen had the greatest ability to reduce the degree of PS in patient blood; addition of moderate amounts of CaCl2 and/or MgCl2 did not diminish the phenomenon; and two sisters and two daughters demonstrated no PS. In a third patient (C) the PS-inducing capability appeared to be largely concentrated in the cryoprecipitable fraction of plasma. These studies suggest that there are different factors in the patients' blood resulting in PS. Further studies showed PS could be induced in normal blood by adding certain nonprimate antihuman antisera (anti-IgM, antialbumin or antifibrinogen) and also by adding some preparations of normal washed platelets to the same individuals's normal whole blood. This indicates that the phenomenon of PS can be produced by factors other than those specifically present in patients with PS. Antigen-antibody complexes, either formed in vivo (mixed cryoglobulinemia) or in vitro, did not result in PS when mixed with normal blood. These and other studies suggest that PS can result from the presence of several different factors, usually proteins (in conjunction with EDTA), which probably attach to the surface of platelets apparently resulting in some alteration (such as change in surface charge) causing the platelets to be attracted to and phagocytosed by neutrophils.

Blood Platelet Disorders↗
PubMed1980

Interaction of plasma fibronectin with selected cryoglobulins.

Plasma fibronectin (PFN) is associated with cryoglobulins of the polyclonal type. Cryoglobulins from two patients with essential mixed cryoglobulinaemia were analysed immunoelectrophoretically to determine a possible association between PFN and immunoglobulin complexes in the formation of cryoprecipitates. In cryoglobulins from each patient, distinctive alterations in electrophoretic migration patterns of both PFN and immunoglobulin were associated with the formation of a cryoprecipitate. The observations indicate that PFN binds to some serum component in the process of cryoglobulin formation. That component may be immunoglobulin.

Adult↗
PubMed1979

The use of sand substitution to solve the free silica problem in foundry atmospheres.

Field tests were carried out to compare the air quailty in a gray iron foundry before and after changing the molding material from the standard silica based sand to the mineral olivine. Olivine is a magnesium iron silicate (Mg, Fe) SiO4 which occurs in nature and contains little or no free silica. Data were collected using standard OSHA approved methods to determine the total dust and the respirable limit for the alpha-quartz particle loading levels. Additional samples were taken using a cascade impactor and filter tape samplers. The foundry was surveyed once before the substitution of olivine and three times after the changeover. The study demonstrates that the partial substitution of olivine can reduce the concentration of free silica to acceptable health levels. However, contamination from processes using silica sand must be controlled.

Air Pollutants↗
PubMed1979

Response to influenza A vaccine among high-risk patients.

In recent years, it has been recommended that "high-risk" patients receive influenza immunizations annually. During the 1976 National Influenza Immunization Program, a higher priority was given to these patients than to the general population. The present study was undertaken to compare the antibody response of high-risk patients with that of a group of individuals with no underlying disease after immunization with 0.5 ml of bivalent, split-virus vaccine containing 200 CCA units each of influenza A/New Jersey/76 and A/Victoria/75. Sera were obtained before and after immunization from 41 "healthy" volunteers and from 57 cariology, 31 hematology, 13 hemodialysis, and 16 renal transplant patients. The control, cardiology, and hemodialysis groups responded equally well to A/Victoria/75 antigen, but the hematology and renal transplant groups did not respond as well (P less than .05). Only the hematology patients responded at a significantly lower level (P less than .05) than the control group to A/New Jersey/76. The control and renal transplant groups had a significantly greater response to A/New Jersey/76 antigen than to A/Victoria/75 antigen (P less than .002). Although the same pattern was demonstrated by the other patient groups, the differences were not significant. Because hematology and renal transplant patients responded relatively poorly to influenza immunization, prophylactic administration of amantadine during influenza outbreaks should be considered in patients with renal function adequate to excrete this drug.

Antibodies, Viral↗
PubMed1978

Platelet aggregation. Adult-onset diabetes mellitus and coronary artery disease.

Using a turbidimetric technique, we determined 1.7 micrometer adenosine diphosphate--induced platelet aggregation and disaggregation at 37 degrees C in the platelet-rich plasmas of two groups of men with coronary artery disease. Eleven men were nondiabetic and 11 had adult-onset diabetes mellitus without retinopathy. There were no significant differences (P greater than .05) between diabetics and nondiabetics of the following variables: age, platelet count in platelet-rich plasma, first and second phases of platelet aggregation, maximum extent of aggregation, and percent disaggregation at three minutes after maximum aggregation occurred. Although the mean adenosine diphosphate--induced platelet aggregation in the platelet-rich plasmas of adult-onset diabetic men with coronary artery disease and no retinopathy was not enhanced, and the mean rate of disaggregation was not reduced, when compared with nondiabetic men with coronary artery disease or with healthy men; a slow rate of platelet disaggregation (less than 10%) occurred more frequently in the platelet-rich plasmas of men with coronary artery disease.

Adenosine Diphosphate↗
PubMed1978

Effect of aspirin on exercise-induced angina.

Suspecting that platelet thromboemboli could play a role in the pathogenesis of myocardial ischemia, we did a random-order, double-blind, crossover study of the effect of the platelet aggregation inhibitor, aspirin, on treadmill exercise-induced angina in 13 men with coronary artery disease. Although collagen-induced platelet aggregation and the second phase of adenosine diphosphate (ADP)-induced platelet aggregation were significantly decreased and the rate of disaggregation of ADP-induced platelet aggregates was significantly increased after 650 mg aspirin in buffered solution, there was no delay in onset of exercise-induced angina, change in heart rate-blood pressure product at onset of angina, or change in S-T segment depression at onset of angina. Regardless of whether the patients had received placebo or aspirin on the preceding day, treadmill exercise until angina was followed by no changes in platelet aggregation or disaggregation, platelet count in blood or platelet-rich plasma, or of the plasma concentration of nonesterified fatty acids.

Adult↗
PubMed1978

Effect of oral aspirin on "ecto-ATPase" activity of washed human platelets.

Aspirin is a potent inhibitor of the platelet release reaction and the accompanying second phase of platelet aggregation. The platelet release reaction is an active, energy-dependent process which appears to require ATP. Eight men ingested 0.32 gm of aspirin daily for 7 days. Although the second phase of 1.7 micron ADP-induced platelet aggregation was absent after aspirin ingestion, the "ecto-ATPase" activities of washed human platelet suspensions were not significantly different before and after ingestion of aspirin. This suggests that the effect of aspirin on the second phase of platelet aggregation is not mediated through inhibition of "ecto-ATPase".

Adenosine Diphosphate↗
PubMed1978

Bile acids LVIII. Bile acids and colorectal cancer.

Significant correlations have been reported by epidemiologists between the mortality from colorectal cancer in various populations and the consumption of meat or lipids by these populations. These have directed considerable attention to possible relationships between diet and the occurrence of this neoplasm. We have carried out studies of the composition of bile from rats as influenced by diets of varying lipid content. Two cannulas were surgically implanted to form an externalized bile duct through which bile was drained from the common duct and returned to the duodenum. Small aliquots were analyzed for total bile acids by enzymatic assay and for individual bile acids by high-pressure liquid chromatography, gas chromatography and gas chromatography-mass spectometry. Animals consuming diets highest in lipid content provided bile with the greatest amounts of bile acids. The primary bile acids, taurocholic, taurochenodeoxychilic, and tauro alpha- and beta-muricholic acids made up more than 99% of the 3 alph-hydroxy bile acids and were found in approximate molar ratio of 2:1:1. Either complete drainage of bile without return to the duodenum, or biliary tract obstruction had pronounced influence on the rate of secretion of bile and its composition.

Animal Feed↗