Contact zones between chromosome races of the common shrew Sorex araneus L. (insectivora, mammalia) at the margins of the Veps stage of the Valdai ice sheet

Cytogenetic analysis of the common shrew populations in the Valdai Hills revealed the presence of four distinct chromosome races (Western Dvina, Seliger, St. Petersburg, and Moscow). The geographic distribution of these races relative to the borders of the Late Valdai glaciation area is described and discussed. Five contact zones between chromosomal races were found, located directly on the ice-marginal formations of the Veps stage. Two races, Seliger and St. Petersburg, are located exclusively in the former ice sheet area. Attention is drawn to the fact that many of the races located in the last glacial area from the Valdai Hills through Scandinavia are characterized by endemic chromosomes (gi, gp, mo, or, etc.). It is concluded that the situation in the former glaciation area could favor the preservation of tundra or forest vegetation refuges and populations of some small mammal species.     

Mitochondrial injury by disulfiram: two different mechanisms of the mitochondrial permeability transition.

Disulfiram (Ds), a clinically employed alcohol deterrent of the thiuram disulfide (TD) class of compounds, is known to cause hepatitis and neuropathies. Although this drug has been shown to inhibit different thiol-containing enzymes, the actual mechanism of Ds toxicity is not clear. We have previously demonstrated that Ds impairs the permeability of inner mitochondrial membrane (IMM) [Arch. Biochem. Biophys. 356 (1998) 46]. In this report, the effect of Ds and its structural analogue thiram (Th) on mitochondrial functions was studied in detail. We found that mitochondria metabolize TDs in a NAD(P)H- and GSH-dependent manner. At the concentration above characteristic threshold, TDs induced irreversible oxidation of NAD(P)H and glutathione (GSH) pools, collapse of transmembrane potential, and inhibition of oxidative phosphorylation. The presence of Ca(2+) and exhaustion of mitochondrial glutathione (GSH+GSSG) decreased the threshold concentration of TDs. Swelling of the mitochondria and leakage of non-transported fluorescent dye BCECF from the matrix indicated that TDs induced the mitochondrial permeability transition (MPT). Mitochondrial permeabilization by TDs involves two, apparently distinct mechanisms. In the presence of Ca(2+), TDs produced cylosporin A-sensitive swelling of mitochondria, which was inhibited by ADP and accelerated by carboxyatractyloside (CATR) and phosphate. In contrast, the swelling produced by TDs in the absence of Ca(2+) was not sensitive to cyclosporin A (CsA), ADP and CATR but was inhibited by phosphate. Titration with N-ethylmaleimide revealed that these two mechanisms involve different SH-groups and probably different transport proteins on the IMM. Our findings indicate that at pharmacologically relevant concentrations TDs may cause an irreversible mitochondrial injury as a result of induction of the MPT.     

Correlations between the clinical course,characteristics of blast cells,and karyotype patterns in chronic myeloid leukemia

Summary Results of chromosome studies of blood and bone marrow cells from 101 patients with Ph¹ positive chronic myeloid leukemia (CML) confirm the assumption that clinical and morphologic manifestations of the disease correlate with karyotype peculiarities of leukemic cells. Several variants of the clinical course of CML may be distinguished. One is the variant with a short chronic phase and a comparatively long terminal phase. In blastic crisis the blast cells are peroxidase negative and do not possess cytoplasmic inclusions. Acute transformation occurs without any additional chromosome damage. The second, more common form is less severe because of longer chronic phase but it has a short and grave acute stage. The blast cells present definite signs of myeloid differentiation, they have basophilic or neutrophilic cytoplasmic granules and are peroxidase positive. Marker i(17q) often combined with trisomy 8 is a characteristic chromosome abnormality in the terminal stage of this variant. The third type has an extremely long chronic phase but ends in a rapidly progressing severe and resistant to therapy lymphoid blastic crisis. Blast cells have typical lymphoid morphology, they are peroxidase negative and contain granular PAS positive substance. Various additional chromosome changes appear in the terminal stage. Future studies of a larger series of patients may possibly reveal more CML variants.     

Summer distribution of Red-legged Partridges Alectoris rufa in relation to water availability on Mediterranean farmland

The suggestion that the summer distribution of Red-legged Partridges Alectoris rufa in the Mediterranean region is determined by the availability of surface water was examined on the agricultural farm, Alto Alentejo, southern Portugal. Partridge coveys were surveyed between 15 July and 15 August in 1993 and 1994. Using a vector-based Geographic Information System, we assessed, for each covey location and for the locations of a double number of random points, the distance to the nearest water point, distance to field boundaries, distance to water lines and land use classes. Univariate comparisons were made between the two groups of locations, and three multivariate logistic models were fitted through forward stepwise selection to the 1993, 1994 and pooled data sets to estimate the probability of sighting partridge coveys in the study area. Distance to water was significantly lower for partridge locations than for random points in both years and was the only variable selected for all logistic models. Apart from water availability, Red-legged Partridge locations were also affected by land use and distance to field boundaries.     

Chromosomes in acute leukemia

Summary The karyotype of leukemic cells of 78 acute leukemia patients (37 ANLL, 34ALL, and 7 of unknown type) was studied by means of G-banding. Chromsomal abnormalities were found in 50 patients (72%). Chromosomes 8, 21, 5, 7, 11, and 19 were preferentially involeved in the abnormalities, both in ANLL and in ALL. A high incidence of the characteristic rearrangement t(8,21) was noted in AML: (in 6 of 22 AML patients). An identical reciprocal translocation—t(4;11)—was seen in 4 out of 34 ALL patients.     

Zea ribosomal repeat evolution and substitution patterns

Zea and Tripsacum nuclear ribosomal internal transcribed spacer (ITS) sequences were used to evaluate patterns of concerted evolution, rates of substitutions, patterns of methylation-induced deamination, and structural constraints of the ITS. ITS pseudogenes were identified by their phylogenetic position, differences in nucleotide composition, extensive deamination at ancestral methylation sites, and substitutions resulting in low-stability secondary RNA structures. Selection was important in shaping the kinds of polymorphisms and substitutions observed in the ITS. ITS substitution rates were significantly different among the Zea taxa. Deamination of cytosines at methylation sites was a potent mutation source, but selection appeared to maintain high methylation site density throughout the ribosomal repeat except for the gene promoter. Nucleotide divergence statistics identified selectively constrained regions at the 5' ends of the ITS1 and ITS2.      

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.