Genomic organization and chromosomal localization of a new repeat MS7, specific for heterochromatin of sex chromosomes in Microtus species voles of the arvalis group

The tandemly arranged MS4 repeat with monomeric units of 4.1 kb is species-specifically distributed in heterochromatin of sex chromosomes of four common vole species of genus Microtus, group arvalis [1, 2]. In this work, we studied the genomic organization of the MS4 homolog in euchromatin of the X chromosome of M. arvalis. It has been shown by analyzing the phage genomic clones that one MS4 copy makes a part of a monomeric unit exceeding 8.5 kb that also includes a new MS7 repeat and, possibly, LINE fragments. MS7 is located together with MS4 in heterochromatin of common vole sex chromosomes, but in a substantially lesser amount. Probably, as a result of an evolutionary transition of an original repeat from euchromatin of the X chromosome to heterochromatin of the Y chromosome, MS4 underwent multiple amplification, and MS7 spread throughout heterochromatin, being surrounded by the MS4 tandem arrays.     

Amino acid utilization by Chlamydomonas reinhardtii: specific study of histidine.

Phytoplankton live in fluctuating environments where many factors such as grazing pressure, sinking, light availability, nutrient uptake and turnover influence the distribution of phytoplankton in time and space. The purpose of this study was to investigate if under conditions of depletion of inorganic nitrogen, as recorded in summer in naturals waters, phytoplanktonic species have the capability of using organic nitrogen sources, including free or combined amino acids, in addition to inorganic nitrogen. The study has focussed on histidine, the degradation of which yielding potentially three nitrogen atoms for each molecule of histidine. Chlamydomonas reinhardtii (CCAP 11/32A) was cultivated axenically with two different sources of nitrogen (histidine and/or ammonium). In the presence of histidine as sole source of nitrogen, cell growth was comparable to that observed with the same concentration of nitrogen in ammonium form. In the presence of both histidine and ammonium, histidine degradation was observed only when the concentration of ammonium was depleted. Under these conditions, the first two enzymes of histidine degradation pathway, histidase (EC 4.3.1.3) and urocanase (EC 4.2.1.49) were produced and were co-ordinately regulated. Histidase activity was also controlled by succinate and glutamate as carbon sources. Histidase was purified 1018-fold and partially characterized. The molecular weight of the native enzyme was estimated to 152.4 kDa corresponding to four subunits of 38.1 kDa. The enzyme did not exhibit classical Michaelis-Menten kinetics but showed a relationship between the rate of catalysis (V) and the concentration of substrate (S), characteristic of negative allosteric behavior. A Hill coefficient of 4 was measured for histidine concentrations higher than 20.5 mM.     

Diabetogenic diet-induced insulin resistance associates with lipid droplet proteins and adipose tissue secretome,but not with sexual dimorphic adipose tissue fat accumulation in Wistar rats

The role of sexual dimorphic adipose tissue fat accumulation in the development of insulin resistance is well known. However, whether vitamin A status and/or its metabolic pathway display any sex- or depot (visceral/subcutaneous)-specific pattern and have a role in sexual dimorphic adipose tissue development and insulin resistance are not completely understood. Therefore, to assess this, 5 weeks old Wistar male and female rats of eight from each sex were provided either control or diabetogenic (high fat, high sucrose) diet for 26 weeks. At the end, consumption of diabetogenic diet increased the visceral fat depots (p < 0.001) in the males and subcutaneous depot (p < 0.05) in the female rats, compared to their sex-matched controls. On the other hand, it caused adipocyte hypertrophy (p < 0.05) of visceral depot (retroperitoneal) in the females and subcutaneous depot of the male rats. Although vitamin A levels displayed sex- and depot-specific increase due to the consumption of diabetogenic diet, the expression of most of its metabolic pathway genes in adipose depots remained unaltered. However, the mRNA levels of some of lipid droplet proteins (perilipins) and adipose tissue secretory proteins (interleukins, lipocalin-2) did display sexual dimorphism. Nonetheless, the long-term feeding of diabetogenic diet impaired the insulin sensitivity, thus affected glucose clearance rate and muscle glucose-uptake in both the sexes of rats. In conclusion, the chronic consumption of diabetogenic diet caused insulin resistance in the male and female rats, but did not corroborate with sexual dimorphic adipose tissue fat accumulation or its vitamin A status.     

New insights into the systematics of Malagasy mongoose‐like carnivorans (Carnivora,Eupleridae, Galidiinae) based on mitochondrial and nuclear DNA sequences

The Malagasy carnivorans (Eupleridae) comprise seven genera and up to ten species, depending on the authority, and, within the past decades, two new taxa have been described. The family is divided into two subfamilies, the Galidiinae, mongoose‐like animals, and the Euplerinae, with diverse body forms. To verify the taxonomic status of Galidiinae species, including recently described taxa, as well as some recognized subspecies, we studied intrageneric genetic variation and structure, using both mitochondrial and nuclear markers. Our results suggest the recognition of four species in the Galidiinae, rendering each genus monospecific. We propose to recognize three subspecies in Galidia elegans (G. e. dambrensis, G. e. elegans, and G. e. occidentalis), two subspecies in Mungotictis decemlineata (M. d. decemlineata and M. d. lineata), and two subspecies in Galidictis fasciata (G. f. fasciata and G. f. grandidieri, the latter was recently described as a distinct species). Our results indicate also that Salanoia durrelli should be treated as a junior synonym of Salanoia concolor. Low levels of intraspecific divergence revealed some geographical structure for the Galidiinae taxa, suggesting that environmental barriers have isolated certain populations in recent geological time. All taxa, whether at the species or subspecies level, need urgent conservation attention, particularly those with limited geographical distributions, as all are threatened by forest habitat degradation.     

Environmental Controls of Primary Production in Agricultural Systems of the Argentine Pampas

We studied the aboveground net primary productivity (ANPP) of wheat crops in the Argentine Pampas. Our specific objectives were to determine (a) the response of ANPP to changes in water availability (b) the regional patterns of ANPP and (c) the interannual variability and environmental controls of ANPP. We used ground and satellite data to address these questions. Wheat ANPP was calculated as the ratio between grain yield and harvest index. We developed a simple model that took into account environmental and genetic improvement effects upon harvest index. We used the normalized difference vegetational index (NDVI) as a surrogate for ANPP at the county level. Straight-line regression models were fitted to single-year and average values of ANPP and precipitation to derive temporal and spatial models for wheat. For grasslands, we used spatial and temporal models already published. At any given site, there was no difference between modeled wheat and grassland average ANPP. The response of ANPP to changes in interannual water availability decreased along the precipitation gradient when vegetation structure (for example, species composition, density, and total cover) was held constant (wheat crops). Wheat ANPP and total production variability, estimated from remotely sensed data, decreased as mean annual precipitation (MAP) increased. The percentage of soils without drainage problems was the variable that explained most of the wheat ANPP spatial variability as shown by stepwise linear regression. Precipitation variability accounted for 49% of wheat ANPP variability. Remotely sensed estimates of ANPP variability showed lower and wheat ANPP higher temporal variability than annual precipitation.     

The Indian brown mongoose,yet another invader in Fiji

A thriving population of the Indian brown mongoose (Herpestes fuscus), native to southwest India and Sri Lanka, has been discovered on the island of Viti Levu in Fiji. This is the first known introduction of this species and may derive from a pair brought from an unknown source to a private zoo in the late 1970s. They co-occur on Viti Levu with the much smaller small Indian mongoose (H. auropunctatus), and they are probably nocturnally active. No research has been conducted on their activity, diet, or impact on Fiji.     

Nucleotide affinity for a stable phosphorylated intermediate of nucleoside diphosphate kinase

Nucleoside diphosphate (NDP) kinase is transiently phosphorylated on a histidine of the active site during the catalytic cycle. In the presence of a nucleotide acceptor, the phosphohistidine bond is unstable and the phosphate is transferred to the acceptor in less than 1 msec. We describe the synthesis of an analog of the phosphoenzyme intermediate with an inactive mutant of NDP kinase in which the catalytic histidine is replaced by a cysteine. In two sequential disulfide exchange reactions, a thiophosphate group reacts with the thiol function of the cysteine that had previously reacted with dithionitrobenzoate (DTNB). The thiophosphoenzyme presents a 400,000-fold increased stability in the presence of NDPs compared with the phosphoenzyme. The binding of NDP is studied at the steady state and presteady state. Data were analyzed according to a bimolecular association model. For the first time, the true equilibrium dissociation constants of NDP for the analog of the phosphoenzyme are determined in the absence of phosphotransfer, allowing a better understanding of the catalytic mechanism of the enzyme.     

Molecular evolution of the ZFY and ZNF6 gene families

Members of the ZFY and ZNF6 gene families have been cloned from species representing different taxa and different modes of sex determination. Comparisons of these genes show the ZFY-like and ZNF6 sequences to be strongly conserved across marsupials, birds, and lepidosaurians. Sequence analyzed by neighbor-joining indicated that both gene families are monophyletic with a high bootstrap value. Pairing of sequences from males and females of nonmammalian species showed there to be no significant difference between male and female sequences from a single species, consistent with autosomal locations. The molecular distances between murine Zfy-1, Zfy-2, and other ZFY-like sequences suggested that Zfy genes have undergone a period of rapid evolutionary change not seen in human ZFY.