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Biomedical subjects

R E Bryant

Publications and source records attributed to R E Bryant.

At least 19 recordsLinked to original sources
PubMed2000

Hyphal forms in the central nervous system of patients with coccidioidomycosis.

Coccidioides immitis is a dimorphic fungus that grows as a filamentous mold in soil and as a spherule at human body temperature. The hyphal or soil form is found rarely in human tissue. We report 5 cases of coccidioidomycosis in which hyphae were found in brain tissue or spinal fluid. The presence of central nervous system plastic devices appears to be associated with morphological reversion to the saprophytic form. This reversion has implications for diagnosis and therapy and may increase the risk of obstruction of the device(s).

Adult↗
PubMed1999

Meropenem pharmacokinetics in a patient with multiorgan failure from Meningococcemia undergoing continuous venovenous hemodiafiltration.

Meropenem is a carbapenem antibiotic with a broad antibacterial spectrum of activity. Its main route of elimination is through the kidneys, with 63% of the drug excreted unchanged in the urine. Meropenem clearance is diminished in renal impairment; therefore, doses need to be adjusted in patients with varying degrees of renal function. An appropriate dose of meropenem for patients undergoing continuous venovenous hemodiafiltration (CVVHDF) is unknown. We evaluated the pharmacokinetics of meropenem in a patient with fulminant meningococcemia undergoing CVVHDF. Meropenem concentrations in serial venous, arterial, and ultrafiltrate samples after a 1 g intravenous dose were measured using high-performance liquid chromatography (HPLC). Meropenem clearance was found to be 129.36 mL/min and 141.29 mL/min for every 8- and 12-hour dosing, respectively. Trough levels were above the MIC90 for Neisseria meningitidis and most anaerobic pathogens. We recommend that meropenem 1 g intravenously every 12 hours be used as the initial dose in patients undergoing CVVHDF. Differences between meropenem clearance during CVVHDF and other forms of renal replacement therapy are discussed.

Adult↗
PubMed1996

Pleural empyema.

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Adult↗
PubMed1994

Octreotide does not alter endotoxin lethality in mice or endotoxin-induced suppression of human leukocyte migration.

Octreotide, a somatostatin analog, was evaluated for its effects on long-term survival in a mouse model of endotoxemia and for its effects on endotoxin-induced suppression of human leukocyte migration. Swiss Webster mice were simultaneously rendered endotoxemic with a single intraperitoneal injection of 800 micrograms E. coli Lipopolysaccharide (LPS) and treated with one of four doses of subcutaneous (s.c.) octreotide (1.0 mg/kg in 0.4 ml saline, 0.1 mg/kg in 0.4 ml saline, 0.1 mg/kg in 0.04 ml saline, or 0.001 mg/kg in 0.04 ml saline) or saline alone (fluid-resuscitated control group: 0.4 ml saline s.c.; or non-fluid-resuscitated control group: 0.04 ml saline s.c.). Octreotide was continued with or without supplemental s.c. fluid resuscitation (0.4 ml saline) at eight hour intervals for either twenty-four or forty hours. There was no statistical significance to differences in long-term survival between comparable groups of octreotide treated vs saline treated animals during the entire fourteen day period of observation. Fluid resuscitation during the first forty hours following endotoxemia induction delayed death, but did not significantly improve long-term survival. In vitro work was conducted to determine the effect of octreotide on endotoxin-induced suppression of human leukocyte migration. Octreotide at concentrations ranging from 3.05 x 10(-5) Molar to 3.05 x 10(-11) Molar had no significant effect on leukocyte migration. In this study octreotide treatment failed to improve long-term survival in mice with endotoxemia and did not alter endotoxin-induced suppression of leukocyte migration.

Animals↗
PubMed1992

Beta-lactam enhancement of aminoglycoside activity under conditions of reduced pH and oxygen tension that may exist in infected tissues.

Aminoglycoside activity is suppressed under conditions of low pH and oxygen tension that are likely to occur in infected tissues; the suppressive effects of these conditions are additive. Under aerobic conditions, the MIC of amikacin for 10 isolates of Escherichia coli was 4.8 +/- 0.7 micrograms/ml at pH 7.2 and increased to 40.0 +/- 8.2 micrograms/ml at pH 6.0. Under anaerobic conditions, the MIC of amikacin for E. coli was 30.0 +/- 1.5 micrograms/ml at pH 7.2 and greater than 50.0 micrograms/ml at pH 6.0. In vitro and in vivo studies of amikacin activity in an acidic and hypoxic milieu containing beta-lactamase demonstrated substantially enhanced bactericidal activity when amikacin and beta-lactams were used together. Under conditions of reduced pH and oxygen tension, cefotaxime enhanced [3H]-tobramycin uptake by E. coli 14-fold and [3H]amikacin uptake 7-fold and appeared to overcome the suppressive effect of those conditions on uptake of aminoglycosides by bacteria.

Abscess↗
PubMed1989

Effect of the abscess environment on the antimicrobial activity of ciprofloxacin.

The present studies were conducted to identify factors in human purulent material that might limit or enhance the activity of ciprofloxacin against bacteria causing suppurative infection. Ciprofloxacin, imipenem, and ampicillin were tested with regard to binding or inactivation by pus. The bactericidal activity of ciprofloxacin and imipenem were tested against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, or Staphylococcus aureus in human pus with a pH of 6.0 incubated at 37 degrees C under aerobic or anaerobic conditions. The effect of single or combination drug therapy with 20 mg/kg of ciprofloxacin, imipenem, or rifampin given every 12 hours was tested against E. coli or P. aeruginosa in polymicrobic murine abscesses that had been produced by subcutaneous injection of either of those organisms mixed with Bacteroides fragilis and autoclaved human stool. Antibiotic levels and the number of bacteria surviving in pus were quantitated. Therapy of subcutaneous abscesses was delayed 72 hours to test drug efficacy against organisms in well-established infections. Levels of ampicillin, imipenem, or ciprofloxacin were reduced from 10 micrograms/ml to 3.1 +/- 4.0, 2.7 +/- 3, or 5.8 +/- 2 micrograms/ml, respectively, after incubation in eight pus specimens for 24 hours at 37 degrees C. Ampicillin levels were reduced to less than 1 microgram/ml in four pus specimens containing beta-lactamase. Imipenem levels were undetectable in two specimens and were 0.2 micrograms/ml in one specimen. Ciprofloxacin binding to pus supernate or sediment appeared to be explained by its binding to the deoxyribonucleic acid (DNA) present in pus. Activity of 5 micrograms/ml of ciprofloxacin against four E. coli or K. pneumoniae strains in pus in vitro was greater than that of twofold higher concentrations of imipenem. The bactericidal activity of ciprofloxacin and imipenem were comparable but substantially reduced against S. aureus and P. aeruginosa in pus. Ciprofloxacin alone or regimens combining ciprofloxacin with rifampin or rifampin plus imipenem reduced the number of E. coli in polymicrobic subcutaneous abscesses but had little effect on P. aeruginosa in polymicrobic abscesses. The anaerobic abscess milieu appeared to inhibit the growth of P. aeruginosa. Ciprofloxacin activity in abscess fluid did not appear to be adversely affected by acid pH, aerobic or anaerobic conditions of incubation, the abscess constituents, or the binding of ciprofloxacin to the DNA in pus. Ciprofloxacin was bound to DNA of bacterial or human origin. Binding by pus was reversible, and binding to DNA extracts of pus was blocked by pretreatment of extracts with deoxyribonuclease but not by pretreatment with ribonuclease.(ABSTRACT TRUNCATED AT 400 WORDS)

Abscess↗
PubMed1988

Chronic hyperdynamic sepsis in the rat: I. Characterization of the animal model.

We describe a new rat model of chronic hyperdynamic sepsis. After control values for weight gain, and food and water intake of each animal were obtained over a 5-day period, male Sprague-Dawley rats weighing 370-425 g were anesthetized, catheterized to allow chronic cardiac-output measurements, and a sterile subcutaneous cavity was formed over the flank area. The animals were allowed a 3-4 day postoperative recovery period. Body weight, food and water intake, and cardiac output were measured daily. Frequent blood samples were withdrawn for bacterial cultures and white cell counts (WBC). On the third and, in some cases, the fourth postoperative day, the subcutaneous cavity was inoculated with 10(9) colony-forming units of Escherichia coli and Bacteroides fragilis. The resulting sepsis was characterized by loss of body weight in spite of normal food and water intake, increased cardiac output, increased WBC, intermittent bacteremia, decreased muscle mass, and decreased cross-sectional area of skeletal muscle myofibrils. Two levels of septic response emerged--moderate and severe. Based on the above-mentioned measurements, it was possible to categorize all long-term septic animals into these two groups. Both groups exhibited cardiac-output, body-weight, and WBC data significantly different from sham controls. Repeated inoculations of the subcutaneous abscess initiated on the third postoperative day resulted in moderate sepsis with no long-term mortality, severe sepsis with 23% mortality over a 3-week period, or a 100% mortality within 4 days, depending on the virulence of the E. coli organisms used. The new model is ideally suited for pathophysiologic studies of sustained, hyperdynamic sepsis.

Animals↗
PubMed1987

Effect of abscess milieu on bactericidal activity of LY146032 against staphylococci.

The antistaphylococcal activity of LY146032 was tested in human pus in vitro and in a murine abscess model in vivo. The drug was not degraded by pus containing beta-lactamase and had equally good or better activity than nafcillin or vancomycin against Staphylococcus aureus or Staphylococcus epidermidis in vitro and in vivo. Its activity was slightly enhanced when used in combination with rifampin and tobramycin.

Abscess↗
PubMed1987

Oral ciprofloxacin in refractory gram-negative bacillary infections.

The 13 patients included in this series: had chronic Gram-negative bacillary infections that were refractory to prior antibiotic therapy; were unable or unwilling to receive intravenous antibiotics; and had altered host defenses or environmental factors that contributed to persistent infection. Five patients had chronic polymicrobic Gram-negative osteomyelitis, three had urinary tract infections caused by Pseudomonas aeruginosa, two had Pseudomonas skin infections and three had respiratory tract infections with Gram-negative bacilli. The overall bacteriological cure rate for Gram-negative bacilli was four of five osteomyelitis, all three urinary tract infections, both skin infections and one out of three respiratory infections. Secondary infections occurred in two patients with bone infections, one with prostatitis and one with deep seated cellulitis and myonecrosis. Two patients with end-stage lung disease had emergence of resistant strains during therapy. Ciprofloxacin was well tolerated and effective in most of the ambulatory patients with refractory Gram-negative bacillary infection. It appears to be especially promising for Pseudomonas infections of the bone, urinary tract and soft tissue.

Adult↗
PubMed1985

Prosthetic valve endocarditis caused by Staphylococcus epidermidis. Development of rifampin resistance during vancomycin and rifampin therapy.

Development of rifampin-resistant Staphylococcus epidermidis was documented in three patients receiving vancomycin and rifampin therapy for prosthetic valve endocarditis. The minimum inhibitory concentrations and minimum bactericidal concentrations of rifampin for the original three isolates were 0.4 micrograms/mL or less. Organisms cultured during relapse or prosthetic valve replacement had minimum inhibitory concentrations of rifampin that were 12.5, 50, and greater than 100 micrograms/mL, respectively. Surgical intervention was necessary in all patients. One died, and one required a second prosthetic valve placement. The patients were treated with vancomycin plus aminoglycoside following identification of rifampin resistance. These observations suggest that vancomycin and rifampin may not be adequate therapy for prosthetic valve endocarditis caused by S epidermidis.

Drug Resistance, Microbial↗
PubMed1983

Endotoxin contamination of enzyme conjugates used in enzyme-linked immunosorbent assays.

The specificity of the enzyme-linked immunosorbent assay(s) is thought to depend on the specificity of the antibody used in the assay system. Therefore, the association of broadly reactive antigens like endotoxin with enzyme conjugates or other enzyme-linked immunosorbent assay reagents has the potential of altering the specificity of reactions in the enzyme-linked immunosorbent assay. Using the Limulus amoebocyte lysate assay, we demonstrated that commercially prepared conjugates of goat anti-human immunoglobulin G peroxidase, goat anti-rabbit immunoglobulin G alkaline phosphatase, rabbit anti-human immunoglobulin G, and other enzyme conjugates contained endotoxin. Furthermore, the staphylococcal protein A, horseradish peroxidase, and bovine alkaline phosphatase used to prepare enzyme conjugates also contained endotoxin. Commercially obtained bovine alkaline phosphatase contained as much as 1.0 microgram of endotoxin per ml of enzyme solution. Both commercially prepared enzyme conjugates and those prepared by us contained endotoxin as determined by their absorption to immobilized monoclonal antibody to lipid A or to immobilized Limulus amoebocyte lysate. The results of this study further suggest that the endotoxin was associated with the enzyme component of the conjugate. In a competitive inhibition enzyme immunoassay, 10 micrograms of lipid A per ml inhibited binding of the enzyme conjugate to adsorbed Limulus amoebocyte lysate, thereby confirming that endotoxin mediated the binding of the conjugate in that system. The potential significance of endotoxin bound to enzyme conjugates may be far reaching because of the ubiquity of endotoxin in conjugates and the prevalence of antibodies to endotoxin in mammalian serum.

Alkaline Phosphatase↗
PubMed1982

Depletion and recovery of ATP in V79 cells with exposure to inhibitors of glycolysis and oxidative phosphorylation.

Cells of the cultured hamster cell line V79 were labeled with tritiated adenosine and incubated for up to 30 min in the presence of inhibitors of glycolysis and oxidative phosphorylation. These inhibitors were (a) 5 mM KCN plus 5 mM iodoacetate, (b) 5 mM KCN plus 5 mM KF, and (c) 15 mM KCN plus 15 mM KF. The fate of the tritium label was examined during incubation with inhibitors and also during subsequent incubation in growth medium in the absence of inhibitors. The tritiated ATP pool was found to decrease in cells incubated in the presence of any of the inhibitor combinations, but only in the presence of 15 mM KCN plus 15 mM KF was this pool decreased below the level of detection. After cells were incubated with KCN plus KF, a high level of ATP was recovered when the inhibitors were removed. Cells incubated with KCN plus iodoacetate retained depletion levels of ATP. Plating efficiency and trypan blue staining showed that KCN-KF treated cells retained viability, whereas KCN-iodoacetate treated cells did not. Cells were examined for ability to take up tritiated uridine before, during, and after depletion of ATP by incubation in the presence of 15 mM KCN plus 15 mM KF. These cells were found to have a variation in uridine uptake that was related directly to intracellular ATP level. Cells in which the ATP was very low exhibited little or no uridine uptake, whereas cells in which the ATP level was near normal exhibited normal uridine uptake.

Adenosine Triphosphate↗
PubMed1982

Chemoprophylaxis in cardiac and orthopedic surgery: comparison of cephalothin and cephapirin.

In a retrospective sequential study we determined the rate of infection occurring despite cephalothin or cephapirin chemoprophylaxis in orthopedic and cardiac surgery done from 1973 to 1977. The incidence of infection after prosthetic hip placement or open reduction of hip fracture was 3.4% and 1.0% in patients receiving cephalothin or cephapirin, respectively. The infection rate after prosthetic heart valve implantation was 3.5% in those receiving cephalothin and 1.6% in those receiving cephapirin. There was no significant difference in infection rate, duration of fever greater than or equal to 38.0 C, or length of postoperative hospitalization. The efficacy of selected antistaphylococcal antibiotics in preventing colonization of human fibrin clots by staphylococci was studied. Although cephapirin was effective at lower concentration, the activity of cephalothin and cephapirin was comparable. Cephalothin and cephapirin have equivalent chemoprophylactic activity by clinical and microbiological criteria, permitting cost to be used as a basis for choosing between these antibiotics.

Cardiac Surgical Procedures↗
PubMed1982

Isolation of a Chinese hamster cell mutant with low intracellular phosphoribosylpyrophosphate concentration.

A tritium-adenine suicide procedure was used to select for mutants with reduced uptake of adenine from a population of Chinese hamster V79 cells mutagenized with ethyl methane sulfonate. In one of the mutant lines isolated, designated KC62, the uptake of adenine, hypoxanthine, and guanine was reduced by approximately 70%. The specific activities, Km values, and Vmax values of adenine phosphoribosyltransferase and of hypoxanthine phosphoribosyltransferase were the same in extracts from KC62 and from the parental cell line. Metabolic fate studies of incorporated [3H]adenine and 3[H]hypoxanthine revealed a metabolic block at the level of phosphoribosylation. Determination of phosphoribosylpyrophosphate pool size showed that the mutant contained only 25% of the phosphoribosylpyrophosphate found in the parent. Its reduced availability in KC62 appears to result in a decreased ability to salvage adenine, hypoxanthine, and guaninine via phosphoribosylation. Phosphoribosylpyrophosphate synthetase from KC62 was shown to have an increased sensitivity to inhibition by a variety of nucleotides.

Adenine↗
PubMed1981

Isolation of hypoxanthine phosphoribosyltransferase-defective mutants in Chinese hamster V79 cells by tritium suicide.

Tritium suicide was shown to be a highly efficient method for isolating mutants defective in hypoxanthine incorporation in the Chinese hamster lung cell line V79. The tritium suicide procedure consisted of 3 kill cycles. Survivors of one kill cycle were used for the next kill cycle. The kill cycles involved incorporation of [3H]hypoxanthine for 5 or 10 min, followed by storage of 3H-labelled cells at -70 degrees C for 4-10 days. 12 clones that survived the 3rd kill cycle were tested for incorporation of [3H]hypoxanthine and all were found to be defective. At lest 6 of the clones have defective hypoxanthine phosphoribosyltransferase (HPRT) activity. One mutant, H19, chosen for further characterization, had HPRT with a 13-fold elevation in apparent Km for phosphoribosylpyrophosphate (PRPP). Thin-layer chromatography of cell extracts showed that this mutant was incapable of converting intracellular hypoxanthine to IMP or to other purine metabolites. In addition, H19 as resistant to 6-thioguanine.

Cell Line↗
PubMed1981

Acid-base changes and acetate metabolism during routine and high-efficiency hemodialysis in children.

Changes in acid-base status and plasma acetate concentrations were studied in eight children during 11 hemodialysis sessions. During dialysis, the blood bicarbonate concentration fell (20.5 +/- 0.7 to 19.6 +/- 0.8 mEq/liter), the Pco2 fell (33.4 +/- 0.8 to 27.5 +/- 1.4 mm Hg), and the pH rose (7.42 +/- 0.01 to 7.48 +/- 0.02). During the hour after dialysis, the bicarbonate concentration rose to normal (23.4 +/- 0.7 mEq/liter), the PCO2 rose (32.8 +/- 0.8 mm Hg), and the pH remained unchanged. The half-life of plasma acetate, measured after dialysis, was 8.7 min. During five "high-efficiency" dialysis sessions (urea clearance, greater than 3.0 ml/min/kg), blood bicarbonate concentration fell 3.2 mEq/liter, PCO2 fell 8.7 mm Hg, and plasma acetate rose to 7.51 mmoles/liter, whereas during six "routine efficiency" dialysis sessions (urea clearance. 1.5 to 3.0 ml/min/kg), blood bicarbonate rose 1.0 mEq/liter, PCO2 fell 36 mm Hg, and plasma acetate rose to 3.52 mmoles/liter. At 1 hour after the end of dialysis, blood bicarbonate, PCO2, and plasma acetate concentrations were similar in the two groups. Clinical problems occurred more frequently in the high-efficiency group during dialysis although the difference was not significant. The data indicate that (1) dialysis with acetate buffer effectively corrects predialysis metabolic acidosis, (2) although children have a high rate of acetate metabolism, during high-efficiency dialysis this rate is exceeded by the influx of acetate, and acid-base abnormalities occur. These abnormalities are transient but may cause clinical problems.

Acetates↗