Southern analysis of BT-R 1, the Manduca sexta gene encoding the receptor for the Cry1Ab toxin of Bacillus thuringiensis

Various subspecies of the gram-positive bacterium Bacillus thuringiensis are known to produce a wide array of insecticidal crystal proteins (ICPs) upon sporulation. These ICPs act primarily on the brush border of midgut epithelial cells of susceptible larvae. Recently, a protein of 210?kDa, isolated from the midgut of Manduca sexta, has been demonstrated to bind the Cry1Ab toxin produced by B. thuringiensis subsp. berliner and is therefore postulated to be involved in mediating the toxicity of Cry1Ab. The cDNA encoding the 210?kDa protein, termed BT-R₁ (Bacillus thuringiensis receptor-1), was recently cloned, and shows limited homology to the cadherin superfamily of proteins. Quite naturally, there is a great deal of interest in the characterization of BT-R ₁ , the gene encoding the 210?kDa Cry1Ab binding protein. The studies presented here involve the use of various restriction fragments prepared from the cDNA encoding BT-R₁ as probes of Southern blots bearing M. sexta genomic DNA cleaved with a variety of restriction endonucleases. These Southern blot data reveal that there are two discrete regions within the M. sexta genome which encode sequences homologous to BT-R₁. On the basis of the signal intensities seen on Southern blots, it appears that only one of these genes encodes BT-R₁, whereas the other is a closely related homologue.     

A simple and novel interpretation of the three-dimensional structure of globular proteins based on quantum-mechanical computations on small model molecules. I

It is suggested that the three-dimensional structure of globular proteins is partly determined by a framework of strengthened hydrogen bonds that involves both ionic side chains and water molecules in addition to the polypeptide backbone. This conclusion follows from a combination of the results of ab initio molecular-orbital computations on small model molecules and high-accuracy x-ray data on the rubredoxin molecule. The computations yield the idea of hydrogen-bonded bridges that are built from tens of atoms, and the experimental information yields the idea that the bridges are assembled into clusters, each of which is built from hundreds of atoms. Some 10 such clusters then form a globular protein.     

Cellular response to oxidative stress at sulfhydryl group receptor sites on the erythrocyte membrane

Ellman's reagent was used to induce an oxidative stimulus on the exofacial membrane sulfhydryl groups of the human erythrocyte. Thiol-disulfide exchange occurring extracellularly was monitored using resonance Raman spectroscopy, and intracellular changes were observed by 1H spin echo nuclear magnetic resonance spectroscopy of the intact cell. The stimulus caused oxidation and depletion of the glutathione pool, which was followed at higher concentrations of Ellman's reagent by a depletion of intracellular ergothioneine levels. Larger changes are induced intracellularly than would be expected from the stoichiometry of the reaction at the exofacial surface. A mechanism is proposed which links exofacial sulfhydryl receptor sites via the transport proteins to spectrin and glutathione. The consequences for the cellular redox balance of an extracellular stimulus of this type are discussed.     

New data on small mammals in the Kazakh Uplands

Small mammals were studied in the Kazakh Uplands in the spring and fall of 2008. The trapping studies revealed 10 species. Abundances of the animals were low in the four main distinct characteristic biotopes of Bayanaul National Park, but those of biotope dominants were high. In the Kazakh Uplands, rodents and insectivores are clearly restricted to certain biotopes. Biodiversity indices for small mammal communities are low, indicating that the community structure is disturbed.     

Influence of development rate on pharyngeal teeth formula in <Emphasis Type="Italic">Abramis brama</Emphasis> (L.) bream: Experimental cata

An experiment on acceleration and retardation of ontogeny with thyroid manipulation has revealed direct changes in definitive dentition of pharyngeal bones in Abramis brama bream. As development rate accelerates, the number of teeth reduces to the formula 5-4. When development rate is retarded, this number increases to the formula 6-5. Moreover, an additional minor row of teeth (1.6–5.1, 2.6–5.2) is formed. The observed changes in tooth numbers exceed the known variability in natural populations of bream. It is assumed that heterochronies lead to the changes in the number of teeth.