Biomedical subjects

J H Britton

Publications and source records attributed to J H Britton.

8 recordsLinked to original sources

PubMed1999

Field assessment of Beauveria bassiana (Balsamo) vuillemin and potential synergism with diflubenzuron for control of savanna grasshopper complex (Orthoptera) in Mali.

In large-scale field trials in Mali, formulated conidia of Beauveria bassiana (Balsamo) Vuillemin strain GHA were tested against unconfined grasshopper populations in field plots of 10 ha each. The trials compared B. bassiana conidia formulated in a mineral oil carrier, formulated diflubenzuron, a combination of B. bassiana plus formulated diflubenzuron, and fenitrothion. A total of 30 different species of grasshoppers occurred in the experimental plots, of which 3 were dominant in all plots, namely, Cryptocatantops haemorrhoidalis (Krauss), Acrotylus blondeli (Saussure), and Hieroglyphus daganensis (Krauss). The density of grasshopper populations in the plots was determined by the number of grasshoppers counted in 0.1-m2 rings laid out in repeated transects. All treatments significantly reduced the grasshopper densities in the experimental plots compared to the untreated controls. After 14 days posttreatment the grasshopper populations decreased by 38.1% in plots treated with B. bassiana alone, 29.4% in plots treated with diflubenzuron alone, and 55.6% in plots treated with the B. bassiana plus diflubenzuron. Effects of the diflubenzuron-B. bassiana mixture were additive and not synergistic. In the fenitrothion plots, after a drop of 95.5% within the first 48 h after the treatment, the grasshopper population steadily increased at a rate of 12.4% per day for the remainder of the 14-day period, whereas densities in the other treated plots continued to decrease. These trials suggest that B. bassiana, with or without a diflubenzuron additive, exerts a continuous effect over a prolonged period.

Animals↗

PubMed1990

Growth and development of the axr1 mutants of Arabidopsis.

We have recovered eight new auxin-resistant lines of Arabidopsis that carry mutations in the AXR1 gene. These eight lines, together with the 12 lines described in a previous report, define at least five different axr1 alleles. All of the mutant lines have a similar phenotype. Defects include decreases in plant height, root gravitropism, hypocotyl elongation, and fertility. Mutant line axr1-3 is less resistant to auxin than the other mutant lines and has less severe morphological abnormalities. This correlation suggests that the morphological defects are a consequence of a defect in auxin action. To determine whether the altered morphology of mutant plants is associated with changes in cell size or tissue organization, tissue sections were examined using scanning electron microscopy. No clear differences in cell size were observed between wild-type and mutant tissues. However, the vascular bundles of mutant stems were found to be less well differentiated than those in wild-type stems. The auxin sensitivity of rosette-stage plants was determined by spraying plants with auxin solutions. Mutant rosettes were found to be significantly less sensitive to exogenously applied auxin than wild-type rosettes, indicating that the AXR1 gene functions in aerial portions of the plant. Our studies suggest that the AXR1 gene is required for auxin action in most, if not all, tissues of the plant and plays an important role in plant development. Linkage studies indicate that the gene is located on chromosome 1 approximately 2 centiMorgans from the closest restriction fragment length polymorphism.

Drug Resistance↗

PubMed1988

The mitochondrial uncoupling protein gene. Correlation of exon structure to transmembrane domains.

The mitochondrial uncoupling protein, a protein essential for the thermogenic properties of brown fat in mammals, is inserted in the inner mitochondrial membrane by means of six alpha-helical hydrophobic transmembrane domains. We have sequenced a complete cDNA and parts of the gene to determine that the mitochondrial uncoupling protein gene is composed of six exons, each of which encodes a transmembrane domain. We also show that transcription of the uncoupling protein gene is from a single start site; however, the use of alternative poly(A) addition signal sequences results in two mRNAs, the major species of 1221 nucleotides, not including the poly(A) tail, and a minor species of about 1600 nucleotides. The 5'-untranslated region of the mRNA is composed of 231 nucleotides, and the 3'-untranslated region contains 81 nucleotides prior to addition of the poly(A) tail.

Adipose Tissue, Brown↗

PubMed1986