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Biomedical subjects

A Wright

Publications and source records attributed to A Wright.

At least 361 records · Page 20Linked to original sources
PubMed1980

Value of physical signs in the diagnosis of enlarged adenoids.

In a series of children due to have surgery on their upper respiratory tracts an assessment of mouth breathing, abnormality on anterior rhinoscopy and size of the adenoid on posterior rhinoscopy was made by 3 observers. All these signs showed poor reproducibility between observers and the size of the adenoid assessed by posterior rhinoscopy showed no significant relationship to the weight of the adenoid subsequently removed.

Adenoids↗
PubMed1980

Mutations in two unlinked genes are required to produce asparagine auxotrophy in Escherichia coli.

Escherichia coli K-12 has two genes, asnA+ and asnB+, either one of which is able to satisfy the need of cells for asparagine. In order for a strain to have an auxotrophic requirement for asparagine, both genes must be mutationally inactivated. We obtained mutants with Tn5 inserted in asnB. asnB was mapped by conjugation and by three-factor P1 transductions at 15 min on the E coli K-12 linkage map, between ubiF and nagB. Specialized transducing phage lamba 781 supE was shown to carry asnB, as well as supE, ubiF, nagA, and nagB. asnA is the previously mapped ilv-linked asn locus, whiich is between uncB and rbs. E. coli C also has two asn genes, corresponding to asnA and asnB.

Aspartate-Ammonia Ligase↗
PubMed1980

The cytotoxicity of UICC and modified asbestos fibres in vitro.

Samples of asbestos were tested for their potential to damage P388D1 cells and erythrocytes. The results obtained using the two systems were generally in agreement, with the amphibole being less cytotoxic and haemolytic than the chrysotile samples. Fibre length distributions for the chrysotile samples were relatively similar, so that, for this material, cytotoxicity and fibre length could not be correlated. However, some relationship was seen with amosite samples. Although there was agreement in some cases between cytotoxicity in vitro and the numbers of mesotheliomas produced in rats during a separate study using the same dusts, this relationship was not obvious for many of the samples tested.

Animals↗
PubMed1979

Dietary fibre and blood pressure.

Ninety-four volunteers participated in a three-day weighed dietary survey and had their blood pressures measured once. They were classified according to their fibre intake. Subjects with a high-fibre intake were found to have lower mean blood pressures than those with a low-fibre intake. Forty-two of the volunteers further participated in a group of experiments. Those eating a high-fibre diet decreased their dietary fibre, and those eating a low-fibre diet increased their dietary fibre. The first group (11 subjects) showed increased mean blood pressures after four weeks of eating the experimental diet. The last group (31 subjects) showed decreased mean blood pressures after four weeks of eating the experimental diet. The 11 subjects consuming the low-fibre experimental diet showed a decrease in mean blood pressure when some of the saturated fat in their diet was replaced by polyunsaturated fat. A similar substitution carried out by 14 of the subjects consuming the high-fibre experimental diet also resulted in decreased mean blood pressure, but this was not statistically significant. Twelve more volunteers, with hypertension, were all found to have low-fibre diets. They consumed a high-fibre diet for a six-week experimental period, but their mean blood pressures did not decrease significantly; individual recordings varied substantially during this period.It is suggested that differences in the type and quantity of dietary fibre and fat may be responsible for the lower mean blood pressures of groups of vegetarians compared with similar groups of non-vegetarians.

Adolescent↗
PubMed1979

Plasmid pSC101 replication in integratively suppressed cells requires dnaA function.

Maintenance of plasmid pKC17, a derivative of plasmid pSC101, in E. coli requires a functional dnaA gene product. This was demonstrated by segregation experiments using an E. coli dnaA46 mutant, at various temperatures. Growth of this mutant at elevated temperature was allowed by the presence of a P2sig5 prophage. rpoB mutations, which suppress the temperature sensitivity of a dnaA46 mutant permit efficient maintenance of plasmid pKC17 at temperatures up to 40 degrees, conditions which normally inactivate the dnaA46 product.

DNA Replication↗
PubMed1979

Variation in the structure and bacteriophage-inactivating capacity of Salmonella anatum lipopolysaccharide as a function of growth temperature.

Growth temperature affects both the structure and the phage-inactivating capacity of Salmonella anatum A1 lipopolysaccharide. Whereas S. anatum cells normally synthesize smooth lipopolysaccharide when grown at physiological temperature (37 degrees C), a partial smooth-rough transition occurs when cells are grown at low temperature (20 to 25 degrees C). The synthesis at low growth temperature of lipopolysaccharide molecules lacking O-antigen was detected both by increased sensitivity of cells to the rough-specific bacteriophage Felix O-1 and by fractionation of oligosaccharides derived from lipopolysaccharide by mild acid hydrolysis. Growth temperature-induced changes in the structure of S. anatum A1 lipopolysaccharide also affected its ability to inactivate epsilon15, a bacteriophage that binds initially to the O-antigen portion of the molecule. Purified lipopolysaccharide prepared from cells grown at low growth temperature exhibited a higher in vitro phage-inactivating capacity than did lipopolysaccharide prepared from cells grown at physiological temperature (37 degrees C).

Chemical Phenomena↗
PubMed1978

The effect of vibration on blood flow in skeletal muscle in the rabbit.

1. The blood flow in rabbit gastrocnemius, as measured by photoelectric drop-counter, increased when the muscle was vibrated at frequencies of 22--62 Hz. 2. Blood flow increased rapidly within 1--2 s of the start of vibration, and lasted for the whole time vibration was applied. 3. The increase in blood flow was negatively correlated with the initial blood flow, being greater with lower flows. 4. The magnitude of increase was similar in both innervated and acutely denervated muscles. 5. The arterial blood pressure did not change apart from a very brief fall at the beginning of vibration. Venous pressure rose and, consequently, the perfusion pressure was lower. The increase in blood flow thus indicates a considerable dilatation in the resistance vessels of skeletal muscle.

Animals↗
PubMed1977

Multiple effects of an RNA polymerase beta' mutation on in vitro transcription.

S. tyrphimurium strain BY324 is temperature sensitive due to a mutation (rpo C32) in the gene for the RNA polymerase beta' subunit. Transcription of T7 DNA by RNA polymerase purified from this strain is temperature sensitive in vitro. The enzyme is slightly defective in template binding and RNA chain initiation, but the major defect is in RNA chain elongation. The rate of RNA chain elongation is reduced 4-5 fold relative to wild-type. RNA chain termination does not appear to be affected by the beta' mutation. While the elongation defect is suppressed by glycerol or dimethylsulfoxide, the initiation defect is not. Possible roles for the beta' subunit in enzyme function are discussed in light of these results.

DNA-Directed RNA Polymerases↗
PubMed1976

Temperature-sensitive ribonucleic acid polymerase mutant of Salmonella typhimurium with a defect in the beta' subunit.

Localized mutagenes of Salmonella typhimurium followed by a [3H]uridine enrichment procedure yielded a temperature-sensitive strain with a mutation in the rpo region of the chromosome. Ribonucleic acid (RNA) polymerase (EC 2.7.7.6; nucleoside triphosphate: RNA nucleotidyltransferase) purified from this mutant was considerably less active at the nonpermissive temperature than wild-type enzyme. Furthermore, the enzyme from this mutant, unlike RNA polymerase of previously isolated temperature-sensitive mutants, was as thermostable as wild-type enzyme when preincubated at 50 degrees C. Subunit reconstitution experiments have shown that the temperature sensitivity is caused by an alteration in the beta' subunit of the enzyme.

DNA-Directed RNA Polymerases↗
PubMed1975

Genes affecting coliphage BF23 and E colicin sensitivity in Salmonella typhimurium.

Rough strains of Salmonella typhimurium were sensitive to coliphage BF23. Spontaneous mutants resistant to BF23 (bfe) were isolated, and the trait was mapped using phage P1. The bfe gene in S. typhimurium was located between argF (66% co-transducible) and rif (61% co-transducible). The BF23-sensitive S. typhimurium strains were not sensitive to the E colicins. Cells of these rough strains absorbed colicin, as measured by loss of E2 or E3 killing units from colicin solutions and by specific adsorption of 125I-colicin E2 to bfe+ cells. Sensitivity to colicins E1, E2, and E3 was observed in a S. typhimurium strain carrying the F'8 gal+ episome. This episome complemented the tolB mutation of Escherichia coli. We conclude that the bfe+ protein satisfies requirements for adsorption of both phage BF23 and the E colicins. In addition, expression of a gene from E. coli, possibly tolB, is necessary for efficient E colicin killing of S. typhimurium.

Adsorption↗
PubMed1974

Effective treatment for paraquat poisoning in rats and its relevance to treatment of paraquat poisoning in man.

After oral administration of a lethal dose of paraquat to rats the plasma concentration remained relatively constant over four to 30 hours and was related to the paraquat content of the small intestine over the first 16 hours. During the first 30 hours the concentration of paraquat in the lung rose progressively above that of the plasma to levels which are known to cause pulmonary damage. A treatment has been devised which prevents the absorption of paraquat into the plasma and prevents accumulation of paraquat in the lung. This treatment consists of a stomach was followed by four administrations of bentonite plus purgatives at two- to three-hour intervals. Even when treatment was delayed until 10 hours after administration of paraquat 80% survival was obtained. The relevance of this treatment to paraquat poisoning in man is discussed in the light of the finding that slices of human lung accumulate paraquat in the same way as those of rat lung.

Absorption↗