Detection of a heat- and acid-stable ‘progesterone’-binding protein in the rat lung

Using a modified charcoal method, we could detect a steroid-binding component in rat lung cytosol which specifically binds R5020, progesterone, and some of its natural derivatives. The concentration of binding sites is high (30–40 pmol/mg protein), the affinity is moderate, the K_d of the R5020 complex being 10⁻⁷ M. Proteolytic enzymes and sulfhydryl reagents destroyed the binding sites indicating the protein nature and the requirement for disulfide bonds. The protein sedimented in the 2 S range thus had an M_r of 10 000–15 000. Further characteristics are the extreme heat (30 min at 100°C) and acid (pH 1) stability. These properties and the fact that it was not detected in serum, distinguish this binding protein from receptors and specific serum steroid binders.     

On the role of p53 in the cellular response to aneuploidy

1. Download : Download high-res image (156KB)
2. Download : Download full-size image

     

Beta-globin gene cluster haplotype distribution in five Brazilian Indian tribes

Haplotypes derived from five polymorphic restriction sites in the beta-globin gene cluster were investigated in 139 individuals from five different Brazilian Indian tribes by the polymerase chain reaction (PCR). Eight haplotypes were identified. Haplotypes 2 (+????) and 6 (?++?+) were the most frequent and were common to all tribes. Their prevalences ranged from 60% to 93% and from 3% to 18%, respectively. Average heterozy-gosity measured by the Gini-Simpson index is markedly reduced among these Brazilian Indians when compared with Europeans (56%), but much less (8%) in relation to Asiatics, suggesting the absence of an important bottleneck effect in the early colonization of South America. The coefficient of gene differentiation (GST′) was estimated as 0.082 among six Brazilian Indian tribes, but when only three Tupi-Mondé-speaking tribes were considered, this estimate was reduced to 0.030. © 1995 Wiley-Liss, Inc.     

Theoretical analysis of lethal factors in plant populations

In this article, we are interested in the problem of the existence of a few linkage groups in which lethal infertile genes associated with yield factors are present. This hypothesis is supported by the finding of natural balanced lethal systems, which keep a short heterotic chromosome segment. It is very important to predict the number of generations that a balanced lethal system maintains in its linkage, in order to get a permanent heterozygosis without any problem with recombination. For theoretical analysis we have used the theory of absorbing Markov chains, discrete in space and time, because this is well suited to crops like barley. It results from studying some experimental data obtained by Ewald A. Favret in the CICA, INTA, Castelar, Argentina.     

Biochemical analysis of force-sensitive responses using a large-scale cell stretch device

Physical force has emerged as a key regulator of tissue homeostasis, and plays an important role in embryogenesis, tissue regeneration, and disease progression. Currently, the details of protein interactions under elevated physical stress are largely missing, therefore, preventing the fundamental, molecular understanding of mechano-transduction. This is in part due to the difficulty isolating large quantities of cell lysates exposed to force-bearing conditions for biochemical analysis. We designed a simple, easy-to-fabricate, large-scale cell stretch device for the analysis of force-sensitive cell responses. Using proximal biotinylation (BioID) analysis or phospho-specific antibodies, we detected force-sensitive biochemical changes in cells exposed to prolonged cyclic substrate stretch. For example, using promiscuous biotin ligase BirA* tagged α-catenin, the biotinylation of myosin IIA increased with stretch, suggesting the close proximity of myosin IIA to α-catenin under a force bearing condition. Furthermore, using phospho-specific antibodies, Akt phosphorylation was reduced upon stretch while Src phosphorylation was unchanged. Interestingly, phosphorylation of GSK3β, a downstream effector of Akt pathway, was also reduced with stretch, while the phosphorylation of other Akt effectors was unchanged. These data suggest that the Akt-GSK3β pathway is force-sensitive. This simple cell stretch device enables biochemical analysis of force-sensitive responses and has potential to uncover molecules underlying mechano-transduction.     

Differential Accumulation of Translatable mRNA Species During a Specific Host-pathogen Interaction Between Puccinia recondita tritici and Triticum aestivum

The time-course of mRNA induction in specific cultivar-race combinations was examined using a criss-cross interaction system consisting of nearly isogenic lines of wheat (Sinvalocho M.A. and Gamma 1R) and genetically related pathogenic races of leaf rust Puccinia recondita f. sp. tritici . Infection stimulated the differential accumulation of mRNA species, identified by in vitro translation, after only three days of inoculation with rust spores. Comparisons of different host-pathogen combinations showed polypeptide pattern changes likely to be associated with gene-for-gene relationships. At least two specific mRNAs which code for polypeptide bands of 34 and 24 kDa are associated with the compatible interaction mediated by genes A₁,/A₂ from Gamma 1R wheat line and virulence gene p_t/p₂ of rust race FO₁. Comparisons made using a mutant clone of rust, which elicits an inverse criss-cross relationship with the same wheat lines, are consistent with the proposed specificity of the detected changes.
In addition, two wheat mRNAs (coding for polypeptide bands of 20.5 and 32.5 kDa) were elicited by infection with rust race FO₁ regardless the plant genotype or reaction type. A cDNA clone involved in this kind of race specific induction has been isolated.