Search PubMed⌕ Search

Biomedical subjects

R D White

Publications and source records attributed to R D White.

At least 235 records · Page 13Linked to original sources
PubMed1980

Bioactivation and covalent binding of halothane in vitro: studies with [3H]- and [14C]halothane.

To determine if the hydrogen atom of halothane (CF3CHBrCl) is retained on the reactive intermediates that covalently bind to microsomal lipids and protein, [3H]halothane and [14C]halothane were incubated with rat hepatic microsomes and a NADPH generating system. Both [3H]- and [14C]halothane were bioactivated and bound to a greater degree when incubations were performed in a N2 atmosphere rather than an O2 atmosphere. Binding of [3H]- and [14C]halothane equivalents was significanty enhanced when heaptic microsomes from phenobarbital- or Aroclor 1254-treated rats were used in the incubations. Omission of NADPH or incubation with CO was inhibitory to the binding of both [3H]- and [14C]halothane. The apparent kinetic constants for binding or halothane equivalents, Km and Vmax, indicate a significantly higher Km but lower Vmax for the formation and/or binding of 3H-binding equivalents. The results indicate tht halothane is primarily bioactivated under conditions that promote its reductive metabolism and that this reactive metabolism does not involve cleavage of the carbon-hydrogen bond of halothane. Differences in binding under N2 and O2 as well as between [3H]- and [14C]halothane suggest that multiple reactive intermediates may form during the biotransformation of halothane.

Animals↗
PubMed1979

An ultrasonic study of the thermotropic transition of dipalmitoyl phosphatidylcholine.

The acoustic absorption of sonicated and unsonicated suspensions of dipalmitoyl phosphatidylcholine has been studied as a function of temperature at frequencies between 0.6 and 4.0 MHz. The absorption at a fixed frequency passes through a maximum at a temperature which is dependent on the sample preparation and history and somewhat dependent on the frequency of observation, with sonicated vesicles exhibiting a temperature of maximum absorption 2--3 degrees C below that found for unsonicated dispersions. The temperature dependence of the absorption at fixed frequency suggests a cooperative process while the frequency dependence of the absorption at fixed temperature indicates that more than a single relaxation time is required to describe the acoustic absorption.

Liposomes↗
PubMed1979

Anesthetic considerations for aortocoronary bypass graft surgery.

Between 1964 and 1978, aortocoronary bypass graft procedures were performed in more than 300,000 patients, and the number seems to increase every year. Nevertheless, the procedure itself can result in perioperative myocardial infarction leading to death. Greater understanding of and constant attention to the myocardial oxygen (O2) supply and demand may reduce the incidence of perioperative myocardial infarction. Some of the factors influencing supply and demand can be controlled pharmacologically. Drugs such as nitroglycerin, nitroprusside, and propranolol can reduce the myocardial O2 demand. Unfortunately, there are few data to elucidate the relationship between myocardial O2 demand and supply as influenced by anesthetic drugs, especially in patients with myocardial ischemia. However, enthusiasm for aortocoronary bypass graft operations has given enormous impetus to laboratory and clinical studies of this subject. Recent developments in anesthetic management afford better means for protection of the ischemic myocardium during and after operation.

Adjuvants, Anesthesia↗
PubMed1979

[3H]gamma-Aminobutyric acid uptake into neuroglial cells of rat superior cervical sympathetic ganglia.

1. The influx of [3H]gamma-aminobutyric acid ([3H]GABA) into isolated rat superior cervical ganglia has been measured by radioassay, supplemented by autoradiography. Ganglia were incubated in oxygenated Krebs solution at 25 degrees C, containing 10 microM-amino-oxyacetic acid. Under these conditions more than 95% of accumulated tritium was unmetabolized [3H]GABA. 2. Ganglionic radioactivity increased linearly with incubation time, to yield an intracellular fluid/extracellular fluid concentration ratio (Ci/Co) of about 200 after 6 hr in 0.5 microM-external [3H]GABA. 3. Uptake showed saturation with an apparent transport constant (KT) of 6.8 microM and maximum influx velocity (Jmaxi) of 7 mumole 1. cell fluid-1- min-1. 4. The influx rate at Co = 0.5 microM was unaltered by raising intracellular GABA from 0.2 to 1 mM. 5. Influx velocity increased with temperature (5--35 degrees C) in a monotonic manner with an apparent activation energy of 14 kcal mole-1. 6. Concentrative uptake was depressed by reducing external [Na+] with ouabain, by raising [K+]o above 20 mM, or by removing external Cl-. Uptake was not particularly sensitive to Ca2+ or Mg2+ ions. 7. Utake of [3H]GABA (0.5 microM) was inhibited by beta-guanidinopropionic acid (apparent KI, 28 microM), beta-alanine (KI, 55 microM), gamma-amino-beta-hydroxybutyric acid (KI, 220 microM), beta-amino-n-butyric acid (KI, 708 microM), 3-aminopropanesulphonic acid (KI, 832 microM) and taurine (KI greater than 1 mM). Uptake was not depressed by 1 mM-glycine, alpha-alanine, leucine, serine, methionine or alpha-amino-iso-butyric acid. 8. Radioactively labelled methionine, leucine, glycine, serine, beta-alanine and taurine (concentrations less than or equal to 5 microM) were also taken up by ganglia. Of these, only uptake of beta-alanine and taurine were significantly depressed by 1 mM-GABA. 9. Autoradiographs confirmed that [3H]GABA and [3H] beta-alanine were taken up predominantly into extraneuronal sites (presumed to be neuroglial cells). Methionine, leucine, glycine and serine showed preferential accumulation in neurones. Neuronal uptake of leucine was not prevented by inhibiting protein synthesis. 10. Calculations of net fluxes from unidirectional tracer fluxes suggest that the sympathetic glial cells are capable of promoting net uptake of GABA at external concentrations above 1 microM.

Amino Acids↗
PubMed1979

Comparison of capillary ear blood and arterial blood to validate capillary sampling as an accurate assay of blood gas in swine.

Capillary sampling in swine can be performed as an accurate assay of arterial blood gases. Studies with swine provided results similar to, or slightly more favorable than, those reported for human beings, depending upon which cutaneous technique was used on human beings. On the basis of free flow or arterilization of the cutaneous sample and of the correlation between capillary and arterial pH, CO2 partial pressure (PCO2), and O2 partial pressure (PO2) values, the capillary sampling technique of complete incisement of a 2-mm section from the tip of the warmed porcine ear could be a substitution technique for arterial blood sampling. Free flow with this technique was maximized and high correlation coefficients (r) for pH (r = 0.96), PCO2 (r = 0.82), and PO2 (r = 0.90) capillary-arterial values (n = 37) were obtained.

Animals↗
PubMed1978

Staging profile of hypofertile male subjects.

Thirty-four hypofertile male subjects with either oligospermia or azoospermia underwent infertility evaluation with assay of serum follicle-stimulating hormone, luteinizing hormone, testosterone and testicular biopsy. Cytogenetic analysis of testicular tissue and peripheral leukocytes was competed on 11 patients. Fifteen male subjects underwnet bilateral contrast vasography. These studies permitted segregation of the hypofertile male population from those with post-germinal hypofertility, primary germinal hypofertility or pre-germinal hypofertility. Retrospective analysis indicates that segregation of the hypofertile male population permits optimum selection for treatment intervention.

Biopsy↗
PubMed1978

Trimethoprium-sulfamethoxazole and minocycline- hydrochloride in the treatment of culture-proved bacterial prostatitis.

Trimethoprim-sulfamethoxazole, 2 tablets twice daily for 90 days, or minocycline-hydrochloride, 100 mg. twice daily for 14 days, was given to 15 and 14 men, respectively, with culture-proved bacterial prostatitis. Given as prescribed both agents seemed equally effective in controlling symptomatic recurrence during the 12 months after cessation of therapy.

Bacterial Infections↗
PubMed1978

Discrimination between descriptive models of L-glutamate uptake by the retina using non-linear regression analysis.

1. The uptake of labelled L-glutamate by the isolated rat retina was measured over a large range of external concentrations (1 micron to 1 mM). 2. The results obtained from measurements of the initial velocity of L-glutamate uptake at different concentrations did not follow simple hyperbolic kinetics. 3. The error structure of replicate velocity measurements was examined and found to be normally distributed and heteroscedastic. 4. Descriptive models were fitted directly to data, weighted by the invariance, using non-linear regression analysis. 5. The most suitable suitable descriptive model consisted of a saturable hyperbola (Vm = 285 n-mole.(g wet wt.)-1.min-1, Km = 252 micron) and a linear term (b = 0.45 min-1).

Animals↗
PubMed1978

Arterialized capillary blood used to determine the acid-base and blood gas status of dogs.

Blood samples were collected by microhematocrit tube from posterior medial margin of the shaved, but otherwise untreated, canine ear. Acid-base and blood gas values of these samples were compared with the values of samples obtained simultaneously from the carotid artery. The arterialized nature of capillary blood from the canine ear was demonstrated under various degrees of chemical restraint and during conditions of extreme hypoxic acidosis to hyperventilatory alkalosis. Once a week determinations of acid-base and blood gas status with such arterialized capillary blood from a group of awake dogs showed within-subject variance to be significantly less (P less than 0.05) than between-subject variance; thus, uniqueness of individual dogs was reliably revealed. This technique also was used to demonstrated breed differences for acid-base and blood gas characteristics.

Acid-Base Equilibrium↗
PubMed1978

A new animal model for testing the effectiveness of chemotherapeutic agents on renal adenocarcinoma.

A renal cell endocarcinoma that arose spontaneously in a Wistar-Lewis rat has been used to screen various chemotherapeutic agents for effectiveness against this tumor. Of the agents so far tested, cyclophosphamide (Cytoxan) and vinblastine have displayed very considerable anti-tumor activity. Adriamycin was marginal, and fluorouracil (5-FU) and Cis-dichlorodiammine Platinum (II) were ineffective.

Animals↗
PubMed1977

Renal cyst puncture and abscess formation.

Percutaneous needle puncture and aspiration of suspected cystic renal masses may provide accurate diagnosis in selected cases. However, renal cyst puncture is not a totally innocuous procedure and certain complications may be encountered. Report is made of 2 cases of renal cyst puncture followed by abscess formation, necessitating surgical intervention. An improved technique involving surgical preparation of the operative area and utilization of double-needle method of cyst puncture is advocated.

Abscess↗