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Biomedical subjects

L Wyman

Publications and source records attributed to L Wyman.

9 recordsLinked to original sources
PubMed1986

Isolation and characterization of Escherichia coli mutants defective for phenylpropionate degradation.

Mutants of Escherichia coli defective in catabolism of 3-phenylpropionate, 3-(3-hydroxyphenyl)propionate, or both were isolated after mutagenesis with ethylmethane sulfonate. Nine phenotypically distinct classes of mutants were identified, including strains lacking each of the first five enzyme activities for the degradation of these compounds and mutants pleiotropically negative for some of these activities. Characterization of these mutants was greatly facilitated by the use of indicator media in which accumulation of 3-(2,3-dihydroxyphenyl)propionate or 2-hydroxy-6-ketononadienedioic acid led to the formation of dark red or bright yellow colors, respectively, in the medium. Assays with wild-type and mutant strains indicated that 3-phenylpropionate (or its dihydrodiol), but none of the hydroxylated derivatives tested, induced the synthesis of enzymes for its conversion to 3-(2,3-dihydroxyphenyl)propionate. The remaining enzymes were induced by the 2- or 3-hydroxy or 2,3-dihydroxy derivatives of 3-phenylpropionate, with the 2-hydroxy compound acting as an apparent gratuitous inducer. Metabolism to nonaromatic intermediates appeared to be unnecessary for full induction of any pathway enzyme. One unusual class of mutants, in which 2-keto-4-pentenoate hydratase appeared to be uninducible, indicated a level of control not previously shown in meta-fission catabolic pathways.

Enzyme Induction↗
PubMed1984

Clinical evaluation of the sensitivity and specificity of a commercially available enzyme immunoassay for detection of rubella virus-specific immunoglobulin M.

A solid-phase capture antigen enzyme immunoassay (Rubazyme-M) was evaluated for sensitivity and specificity on sera from 1,200 blood donors, 51 patients with rubella, 2 infants with congenital rubella, 104 patients with other infections, and 126 patients with immunological abnormalities. The sensitivity was 100% for sera tested between days 3 and 40 after the onset of symptoms of rubella virus infection. Rubella virus-specific immunoglobulin M was detected at birth in sera from congenitally infected infants and persisted for several months. Positive Rubazyme-M responses were observed in some patients in the absence of rubella diagnosis (one blood donor, three other infections, and two immunological abnormalities), providing a test specificity of 99.6%. None of 67 patients with rubella virus-specific immunoglobulin G antibody and high levels of rheumatoid factor were positive in the test.

Adult↗
PubMed1980

Use of a teat sealer for prevention of intramammary infections in lactating cows.

An acrylic latex film that is applied like a teat dip and remains intact as a physical barrier until the next milking was developed and studied with respect to its effect on intramammary infection rates in 4 dairy herds. Rates of new infections in treated quarters were compared with the rates in control quarters on the same cows. A statistically significant reduction in the rates was observed for the following organisms: Staphylococcus aureus, 28%; S epidermidis, 33%; and coliforms, 76%. The percentage reduction for infections caused by Streptococcus agalactiae (18%) and for those caused by streptococcus other than Str agalactiae (7%) were not statistically significant. The film also was shown to be nonirritating.

Acrylates↗
PubMed1979

Bacterial output from three respiratory therapy humidifying devices.

Three devices used to humidify the air delivered to hospitalized patients were evaluated for their relative hazard as measured by the concentration of bacterial output delivered with the gas. Two of the devices were evaporative types (commonly called "humidifiers"), moisturizing with water vapor, while the third was a nebulizer, delivering water droplets in aerosol form. Reservoirs were seeded with a tracer organism Pseudomonas cepacia (approximately 10(4)/ml) in distilled water. The output gas (approximately 30 1/min) was sampled through an Andersen six-stage bacterial sampler operated at 28.3 1/min. Excess gas was bled off through a Y-tubing. Results indicate that the nebulizer produces heavily contaminated bacterial aerosols (greater than 1000 P cepacia colonies in the 3-minute sampling period) even after a 20-minute warm-up period that raised the reservoir temperature to greater than 45 degrees C. The two evaporative type devices produced virtually no viable organisms even when sampling was initiated with the reservoir at room temperature.

Cross Infection↗
PubMed1974

Studies on plasmid replication. IV. Complementation of replication-defective mutants by an incompatibility-deficient plasmid.

This paper described a complementation test system for replication-defective S. aureus pencillinase plasmids in which the incompatibility barrier has been overcome by the isolation of an incompatibility-defective (Inc-) plasmid. This plasmid appears to be stably and irreversibly integrated into the host chromosome as attempts to restore it to its original independent state have been unsuccessful. The Inc- plasmid was able to complement the thermosensitive replication defects of Seg- plasmids belonging to the same original incompatibility class but was unable to complement onels belonging to a different incompatibility class. Positive and negative phenotypic complementation tests were confirmed at the molecular level by isotopec labeling of plasmid-specific DNA molecules.

DNA Replication↗
PubMed1974

Genetic control of chromosomal and plasmid recombination in Staphylococcus aureus.

Recombination-deficient mutants of Staphylococcus aureus have been isolated and found to have properties similar to those of recombination-deficient Escherichia coli. In addition, one Rec(-) mutant was found to be defective in the restriction and modification of DNA. There is a marked reduction ( approximately 10(4)-fold) in recombination between penicillinase plasmids in the Rec(-) mutants suggesting that these elements do not encode an efficient recombination system. There is, however, a demonstrable residuum of interplasmid recombination; evidence is lacking on whether this residuum is a plasmid or host function. In the absence of the generalized host recombination system it has been possible to demonstrate that interplasmid recombination occurs during vegetative bacteriophage growth and is presumably mediated by a phage-determined recombination system.

Chromosomes, Bacterial↗