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Biomedical subjects

A T Davis

Publications and source records attributed to A T Davis.

At least 109 records · Page 6Linked to original sources
PubMed1982

Threonine metabolism of chicks fed threonine-imbalanced diets.

Experiments were conducted to determine the metabolic fate of threonine in chicks fed threonine-imbalanced diets. Threonine imbalance was produced by the addition of 3% serine to a threonine-limited diet, and prevented by the addition of 0.2% threonine to the diet. Serine decreased plasma and liver free threonine concentrations, and increased hepatic threonine dehydrogenase and threonine aldolase activities. All changes, including reduced food intake, appeared to occur within 1 day of feeding the imbalanced diet. Despite the decrease in free threonine concentrations and the increase in threonine aldolase and threonine dehydrogenase activities, net threonine catabolism was not markedly increased. This was evidenced by similar amounts of 14CO2 exhaled by chicks fed control and imbalanced diets containing L-[U-14C] threonine, and by similar growth of chicks that were forced-fed both diets to maintain equivalent food intake. It is possible that increases in threonine catabolism contribute to depressions of plasma and tissue threonine concentrations. However, the growth depression caused by serine-induced threonine imbalance is due to depressed food intake.

Alcohol Oxidoreductases↗
PubMed1982

Threonine-degrading enzymes in the chicken.

Threonine dehydratase, threonine aldolase, and threonine dehydrogenase activities of liver, kidney, skeletal muscle, duodenum, heart, whole brain, and pancreas of the chick (Gallus domesticus) were determined. The highest activities of threonine dehydratase and threonine aldolase were found in liver and muscle and the highest threonine dehydrogenase in the pancreas. Threonine aldolase was more active than threonine dehydratase in all tissues except kidney and intestine, both of which had low activities of these enzymes. Chick liver threonine dehydratase and threonine dehydrogenase, but not threonine aldolase, activities varied significantly during a 24-hr period.

Alcohol Oxidoreductases↗
PubMed1980

Cell-directed inhibition of polymorphonuclear leukocyte chemotaxis in a patient with mucocutaneous candidiasis.

A patient with mucocutaneous candidiasis and impaired polymorphonuclear leukocyte (PMN) chemotaxis is described. The patient's PMN chemotaxis was markedly decreased in the presence of autologous plasma but normal in control plasma. Cell-directed inhibitory activity was found in whole patient plasma as well as the 40% ammonium sulfate precipitate fraction of both the patient's and the control plasma. The inhibitor was heat stable, reversible, nondialyzable, eluted from DEAE cellulose with 0.005 M sodium phosphate buffer, and migrated with IgG on immunoelectrophoresis. The supernate from 40% ammonium sulfate-fractionated patient and control plasma contained a cell-directed enhancer of PMN chemotaxis that antagonized the cell-directed inhibitor activity. It is possible that the patient's chemotactic defect may be caused by imbalance between plasma factors that regulate chemotaxis.

Ammonium Sulfate↗
PubMed1980

Synergistic action of ampicillin and nafcillin against ampicillin-resistant Haemophilus influenzae.

Six strains of ampicillin-resistant Haemophilus influenzae type b were studied in vitro for synergy between ampicillin and nafcillin. The minimal inhibitory concentrations for these strains with 10(4) colony-forming units per ml were 6.25 to 12.5 microgram of ampicillin per ml and 6.25 to 25 microgram of nafcillin per ml. Studies with these agents demonstrated synergism against all six strains of H. influenzae type b. Most strains were inhibited by 0.78 microgram of nafcillin plus 0.78 microgram of ampicillin per ml. A child with osteomyelitis caused by H. influenzae type b was successfully treated with a combination of ampicillin and nafcillin. These data suggest that further studies assessing the synergistic effect of this drug combination against H. influenzae type b are warranted.

Ampicillin↗
PubMed1980

Neurosurgical shunt infections. A review.

Shunt infections occur in 6-25% of hydrocephalic patients with shunts. Although Staphylococcus epidermidis and Staphylococcus aureus cause the majority of such infections, enteric bacteria account for at least 10-15%. The clinical presentation in most patients is nonspecific. Most investigators agree that the entire infected shunt should be removed before antibiotic therapy is initiated. The choice of an antibiotic should be guided by in vitro susceptibility of the etiologic agent, and the ability of the drug to pass the blood-brain barrier. The efficacy of prophylactic antibiotics in reducing shunt infections is controversial.

Bacterial Infections↗
PubMed1980

An explosive outbreak of Mycoplasma pneumoniae infection in a summer camp.

An outbreak of Mycoplasma pneumoniae infection occurred in the summer of 1978 in a boys' camp in northern Wisconsin and affected 139 of 196 persons (71%); 115 (59%) had laboratory evidence of infection. In 77% of the cases, onset of disease occurred within three weeks after arrival at camp, in contrast to the usually indolent spread of the disease. Attack rates decreased with increasing age. The sensitivity of serology for detecting M pneumoniae disease may have been as low as 79%. There was shorter duration of cough in those treated with erythromycin within four days after onset of symptoms.

Adolescent↗
PubMed1979

The effect of some protease substrates and inhibitors on chemotaxis and protease activity of human polymorphonuclear leukocytes.

Both low- and high-molecular-weight inhibitors of serine proteases were found to inhibit chemotaxis by human polymorphonuclear leukocytes totally at widely varying concentrations. Synthetic low-molecular-weight substrates with trypsin-like or chymotrypsin-like specificity were also shown to be potent inhibitors of chemotaxis. Chemotactic inhibition was reversible except with a titrant for the active site of a serine protease. N-acetyl-L-tyrosine ethyl ester was found to be a suitable substrate for measuring protease activity of polymorphonuclear leukocyte. Concentrations of the various protease inhibitors that caused 100% chemotactic inhibition caused 80%-100% inhibition of protease activity of polymorphonuclear leukocytes.

Benzamidines↗
PubMed1978

Effect of TMP-SMX on nasopharyngeal carriage of ampicillin-sensitive and ampicillin-resistant hemophilus influenzae type B.

The carriage rate of ampicillin-resistant Hemophilus influenzae type B in a chronic care facility was investigated. Up to 48% of the children carried this strain. Of interest was the finding of simulaneous carriage of ampicillin-resistant and ampicillin-sensitive HITB, a phenomenon which was detected by using both chocolate agar and chocolate agar containing 2 microgram/ml of ampicillin. A trial of sulfamethoxazole-trimethoprin successfully eradicated the ampicillin-sensitive HITB, but had no effect on the ampicillin-resistant HITB.

Ampicillin↗
PubMed1978

Chemotaxis of Salmonella typhimurium to amino acids and some sugars.

Patterns of chemotaxis by Salmonella typhimurium strain LT-2 to l-amino acids and to several sugars were quantitated by the Adler capillary procedure. Competition experiments indicated that LT-2 possesses three predominant receptors, or interacting sets of receptors, for amino acids. These were termed the aspartate, serine, and alanine classes, respectively. Studies with strains carrying point and deletion mutations affecting components of the phosphoenolpyruvate: glycose phosphotransferase system (PTS) made unlikely a role in primary reception of d-glucose by the three soluble PTS components, namely HPr, enzyme I, and factor III. A ptsG mutant defective in membrane-bound enzyme IIB' of the high-affinity glucose transport system was shown to exhibit normal chemotaxis providing pleiotropic effects of the mutation were eliminated by its genotypic combination with other pts mutations or, phenotypically, by addition of cyclic AMP and substrate. A correlation was demonstrated between chemotaxis to glucose and activity of the low-affinity glucose transport complex, membrane-bound enzymes IIB:IIA, and an enzyme IIB:IIA mutant was shown to have a preponderant defect in chemotaxis to glucose and mannose. Of four systems capable of galactose transport, only the beta-methylgalactoside transport system was implicated in chemotaxis to galactose. Some properties of a mutant possibly defective in processing of signals for chemotaxis to sugars is described.

Amino Acids↗
PubMed1978

Enterobacter aerogenes primary bacteremia in pediatric patients.

Enterobacter aerogenes bacteremia associated with the infusion of contaminated admixed intravenous (IV) fluid occurred in seven patients in a pediatric hospital over a five-day period. Clinical illness was characterized by spiking fever in all patients. The temporal clustering of cases allowed for rapid recognition of the problem. The primary control measure was the prompt replacement of the IV fluids, although IV antibiotics were also administered. Hospital pharmacy practices for admixing IV solutions should follow published recommendations to minimize this source of potential contamination of fluids.

Child↗
PubMed1977

PMN chemotactic inhibition associated with a cryoglobulin.

A child with recurrent pyogenic infections, eczema, markedly elevated serum concentrations IgA, and totally absent PMN chemotactic acticity is described. The chemotactic defect was characterized as a humoral inhibitor present in serumand plasma, directed toward autologous as well as homologous PMN's. Immunochemical studies revealed the purified inhibitor to be a cryoglobulin composed of an IgM-IgA complex. Incubation of the cryoglobulin complex with PMN's resulted in a quantitative dose-response curve.

Antibody Specificity↗