Interspecific hybridization increases transposition rates of Osvaldo.

Several authors have postulated that genetic divergence between populations could result in genomic incompatibilities that would cause an increase in transposition in their hybrids, producing secondary effects such as sterility and therefore starting a speciation process. It has been demonstrated that transposition largely depends on intraspecific hybridization for P, hobo, and I elements in Drosophila melanogaster and for several elements, including long terminal repeat (LTR) and non-LTR retrotransposons, in D. virilis. However, in order to demonstrate the putative effect of transposable elements on speciation, high levels of transposition should also be induced in hybrids between species that could have been originated by this process and that are still able to interbreed. To test this hypothesis, we studied the transposition of the LTR retrotransposon Osvaldo in Drosophila buzzatii-Drosophila koepferae hybrids. We used a simple and robust experimental design, analyzing large samples of single-pair mate offspring, which allowed us to detect new insertions by in situ hybridization to polytene chromosomes. In order to compare transposition rates, we also used a stock recently obtained from the field and a highly inbred D. buzzatii strain. Our results show that the transposition rate of Osvaldo is 10(-3) transpositions per element per generation in all nonhybrid samples, very high when compared with those of other transposable elements. In hybrids, the transposition rate was always 10(-2), significantly higher than in nonhybrids. We show that inbreeding has no effect on transposition in the strains used, concluding that hybridization significantly increases the Osvaldo transposition rate.     

An exo-β-d-glucanase derived from Zea coleoptile walls with a capacity to elicit cell elongation

Cell wall proteins were extracted from maize coleoptiles, Zea mays L. B37 x MO 17, with high concentrations of LiCl. Ion-exchange, chromatofocusing and gel-filtration chromatography were employed extensively to purify exo-β-glucanase activity from the extract. The purified enzyme functioned as an exo-(1→3)-β-glucanase (E.C. 3.2.1.58) and as a glucosidase (E.C. 3.2.1.21) capable of extensive hydrolysis of the native Zea wall (1→3), (1→4)-β- d -glucan, yielding glucose as the final product. The exoglucanase also enhances elongation of maize coleoptile sections in both the presence and absence of exogenous IAA.     

Analysis of sexual differences in emotional reactions in rats

The effect of sex differences on the emotional reactivity in the rat (Rattus norvegicus) has been analyzed by means of the open field test and the acquisition of a conditioned emotional response (C.E.R.), according to Estes and Skinner technique. The combined use of C.E.R. and defecation rate techniques shows that males present a higher emotional reactivity than females. Furthermore estrous cycle affected female ambulation rates in open field.     

High sphingomyelin levels induce lysosomal damage and autophagy dysfunction in Niemann Pick disease type A

Niemann Pick disease type A (NPA), which is caused by loss of function mutations in the acid sphingomyelinase (ASM) gene, is a lysosomal storage disorder leading to neurodegeneration. Yet, lysosomal dysfunction and its consequences in the disease are poorly characterized. Here we show that undegraded molecules build up in neurons of acid sphingomyelinase knockout mice and in fibroblasts from NPA patients in which autophagolysosomes accumulate. The latter is not due to alterations in autophagy initiation or autophagosome–lysosome fusion but because of inefficient autophago–lysosomal clearance. This, in turn, can be explained by lysosomal membrane permeabilization leading to cytosolic release of Cathepsin B. High sphingomyelin (SM) levels account for these effects as they can be induced in control cells on addition of the lipid and reverted on SM-lowering strategies in ASM-deficient cells. These results unveil a relevant role for SM in autophagy modulation and characterize autophagy anomalies in NPA, opening new perspectives for therapeutic interventions.     

Chromatin insulators specifically associate with different levels of higher-order chromatin organization in Drosophila

Chromatin insulators are required for proper temporal and spatial expression of genes in metazoans. Here, we have analyzed the distribution of insulator proteins on the 56F–58A region of chromosome 2R in Drosophila polytene chromosomes to assess the role of chromatin insulators in shaping genome architecture. Data show that the suppressor of Hairy-wing protein [Su(Hw)] is found in three structures differentially associated with insulator proteins: bands, interbands, and multi-gene domains of coexpressed genes. Results show that bands are generally formed by condensation of chromatin that belongs to genes containing one or more Su(Hw) binding sites, whereas, in interbands, Su(Hw) sites appear associated with open chromatin. In addition, clusters of coexpressed genes in this region form bands characterized by the lack of CP190 and BEAF-32 insulator proteins. This pattern correlates with the distribution of specific chromatin marks and is conserved in nurse cells, suggesting that this organization may not be limited to one cell type but represents the basic organization of interphasic chromosomes.