Habitat utilization by sympatric European mink<Emphasis Type="Italic">Mustela lutreola</Emphasis> and polecats<Emphasis Type="Italic">Mustela putorius</Emphasis> in south-western France

The European minkMustela lutreola Linnaeus, 1761 and the European polecatMustela putorius Linnaeus, 1758 are related species sympatric in southwestern France. The European mink is rapidly disappearing whereas the polecat maintains good populations. Seasonal habitat use of both species was compared in the Landes de Gascogne region to identify if some vulnerability factors of the European mink were associated with habitats occupied by this mustelid. Potential habitats were mapped using a satellite picture and 12 main types of habitats were defined. Animal locations were recorded by radiotracking 9 European mink and 14 polecats from March 1996 to August 1999. Resting animals were located by triangulation, and, when possible, resting places were described. Animals in activity were tracked by continuous monitoring. Data collected revealed a strong preference of European mink for flooded habitats, particularly open marshes, flooded woodlands and moorlands. They seldom left the corridor of the riparian forest and their resting places were mainly in flooded environments, above ground (under herbs or bushes) or in cavities between tree roots. European polecats were less tightly linked to wetlands. Most of their locations were in the pine forests outside the valleys and their resting places were mainly in burrows. The strong specialisation of European mink in aquatic habitats is probably one of the main reasons for its decline because wetlands suffer drastic damages throughout all of its range. Maintaining adequate water levels is crucial for satisfying habitat requirements of mink.     

Inhibiting catalase activity sensitizes 36B10 rat glioma cells to oxidative stress

Gliomas are extremely resistant to anticancer therapies resulting in poor patient survival, due, in part, to altered expression of antioxidant enzymes. The primary antioxidant enzyme, catalase, is elevated constitutively in gliomas compared to normal astrocytes. We hypothesized that downregulating catalase in glioma cells would sensitize these cells to oxidative stress. To test this hypothesis, we implemented two approaches. The first, a pharmacological approach, used 3-amino-1,2,4-triazole, an irreversible inhibitor that reduced catalase enzymatic activity by 75%. Pharmacological inhibition of catalase was not associated with a reduction in rat 36B10 glioma cell viability until the cells were challenged with additional oxidative stress, i.e., ionizing radiation or hydrogen peroxide (H(2)O(2)). In the second molecular approach, we generated 36B10 glioma cells stably expressing catalase shRNA; a stable cell line displayed a 75% reduction in catalase immunoreactive protein and enzymatic activity. This was accompanied by an increase in intracellular reactive oxygen species and extracellular H(2)O(2). These cells exhibited increased sensitivity to radiation and H(2)O(2), which was rescued by the antioxidant, N-acetylcysteine. These results support the hypothesis that catalase is a major participant in the defense of 36B10 glioma cells against oxidative stress mediated by anticancer agents capable of increasing steady-state levels of H(2)O(2).     

Improving model construction of profile HMMs for remote homology detection through structural alignment

Background  

Remote homology detection is a challenging problem in Bioinformatics. Arguably, profile Hidden Markov Models (pHMMs) are one of the most successful approaches in addressing this important problem. pHMM packages present a relatively small computational cost, and perform particularly well at recognizing remote homologies. This raises the question of whether structural alignments could impact the performance of pHMMs trained from proteins in the Twilight Zone, as structural alignments are often more accurate than sequence alignments at identifying motifs and functional residues. Next, we assess the impact of using structural alignments in pHMM performance.     

Complex segregation analysis reveals a multigene model for lung cancer

Lung cancer risk is largely attributed to tobacco exposure, but genetic predisposition also plays an etiologic role. Several studies have investigated the involvement of genetic predisposition in lung cancer aggregation in affected families, although with inconsistent results. Some studies have provided evidence for Mendelian inheritance, whereas others have suggested that environmental models are most appropriate for lung cancer aggregation in families. To examine the genetic basis of lung cancer, we performed segregation analysis on 14,378 individuals from 1,561 lung cancer case families, allowing for the effects of smoking, sex, and age. Both a Mendelian decreasing model and a Mendelian codominant model were found to be the best fitting models for susceptibility. However, when we modeled age-of-onset, all Mendelian models and the environmental model were rejected suggesting that multiple genetic factors (possibly multiple genetic loci and interactions) contribute to the age-of-onset of lung cancer. The results provide evidence that multiple genetic factors contribute to lung cancer and may act as a guide in further studies to localize susceptibility genes in lung cancer.     

Aging reduces responsiveness to BSO- and heat stress-induced perturbations of glutathione and antioxidant enzymes

Aging alters cellular responses to both heat and oxidative stress. Thiol-mediated metabolism of reactive oxygen species (ROS) is believed to be important in aging. To begin to determine the role of thiols in aging and heat stress, we depleted liver glutathione (GSH) by administering l-buthionine sulfoximine (BSO) in young (6 mo) and old (24 mo) Fisher 344 rats before heat stress. Animals were given BSO (4 mmol/kg ip) or saline (1 ml ip) 2 h before heat stress and subsequently heated to a core temperature of 41 degrees C over a 90-min period. Liver tissue was collected before and 0, 30, and 60 min after heat stress. BSO inhibited glutamate cysteine ligase (GCL, the rate-limiting enzyme in GSH synthesis) catalytic activity and resulted in a decline in liver GSH and GSSG that was more pronounced in young compared with old animals. Catalase activity did not change between groups until 60 min after heat stress in young BSO-treated rats. Young animals experienced a substantial and persistent reduction in Cu,Zn-SOD activity with BSO treatment. Mn-SOD activity increased with BSO but declined after heat stress. The differences in thiol depletion observed between young and old animals with BSO treatment may be indicative of age-related differences in GSH compartmentalization that could have an impact on maintenance of redox homeostasis and antioxidant balance immediately after a physiologically relevant stress. The significant changes in antioxidant enzyme activity after GSH depletion suggest that thiol status can influence the regulation of other antioxidant enzymes.     

An association between a NQO1 genetic polymorphism and risk of lung cancer

NAD(P)H:quinone oxidoreductase (NQO1) is a detoxification enzyme that protects against the regeneration of reactive oxygen species chemically induced by oxidative stress, cytotoxicity, mutagenicity, and carcinogenicity. The protection conferred by NQO1 protein reduces certain environmental carcinogens, such as nitroaromatic compounds, heterocyclic amines, and possible cigarette smoke condensate. The gene coding for NQO1 has a genetic polymorphism (C-->T) at nucleotide position 609 (i.e. amino acid codon 187) of the NQO1 cDNA. This polymorphism was shown to reduce NQO1 enzyme activity, thereby diminishing the protection provided by NQO1. Therefore, we hypothesized that individuals with the variant NQO1 genotype are at higher risk for lung cancer. Using a case-control study, we genotyped the NQO1 variants successfully by PCR-RFLP in 826 lung cancer patients and 826 healthy control subjects matched for age, sex, ethnicity, and smoking status. The frequency of the NQO1 T-allele was statistically significantly different among three ethnic groups (p<0.001). In further analysis of Caucasians, the variant NQO1 genotypes (CT and TT) were associated with a marginally increased lung cancer risk (OR=1.19; 95% CI: 0.95-1.50). The elevated lung cancer risk was only evident in younger individuals (age <62 years old) (OR=1.46; 95% CI: 1.04-2.05), women (OR=1.89; 95% CI: 1.33-2.68), and never smokers (OR=1.80; 95% CI: 1.03-3.13). Furthermore, we found a statistically significant trend in the development of lung cancer at an early age in women with increasing copies of the variant allele (p=0.03). These results suggest that the NQO1 variant genotype may modulate lung cancer risk, especially in younger individuals (age<62), women, and never smokers.     

DNA double-strand breaks induce deletion of CTG.CAG repeats in an orientation-dependent manner in Escherichia coli

The influences of double-strand breaks (DSBs) within a triplet repeat sequence on its genetic instabilities (expansions and deletions) related to hereditary neurological diseases was investigated. Plasmids containing 43 or 70 CTG.CAG repeats or 43 CGG.CCG repeats were linearized in vitro near the center of the repeats and were transformed into parental, RecA-dependent homologous recombination-deficient, or RecBC exonuclease-deficient Escherichia coli. The resulting repair process considerably increased deletion of the repeating sequence compared to the circular DNA controls. Unexpectedly, the orientation of the insert relative to the unidirectional ColE1 origin of replication affected the amount of instability generated during the repair of the DSB. When the CTG strand was the template for lagging-strand synthesis, instability was increased, most markedly in the recA- strain. Results indicated that RecA and/or RecBC might play a role in DSB repair within the triplet repeat. Altering the length, orientation, and sequence composition of the triplet repeat suggested an important role of DNA secondary structures during repair intermediates. Hence, we hypothesize that ColE1 origin-dependent replication was involved during the repair of the DSB. A model is presented to explain the mechanisms of the observed genetic instabilities.     

Adaptive responses to low-dose/low-dose-rate gamma rays in normal human fibroblasts: the role of growth architecture and oxidative metabolism

To investigate low-dose/low-dose-rate effects of low-linear energy transfer (LET) ionizing radiation, we used gamma-irradiated cells adapted to grow in a three-dimensional architecture that mimics cell growth in vivo. We determined the cellular, molecular and biochemical changes in these cells. Quiescent normal human fibroblasts were irradiated with single acute or chronic doses (1-10 cGy) of (137)Cs gamma rays. Whereas exposure to an acute dose of 10 cGy increased micronucleus formation, protraction of the dose over 48 h reduced micronucleus frequency to a level similar to or lower than what occurs spontaneously. The protracted treatment also up-regulated the cellular content of the antioxidant glutathione. These changes correlated with modulation of phospho-TP53 (serine 15), a stress marker that was regulated by doses as low as 1 cGy. The DNA damage that occurred after exposure to an acute dose of 10 cGy was protected against in two ways: (1) up-regulation of cellular antioxidant enzyme activity by ectopic overexpression of MnSOD, catalase or glutathione peroxidase, and (2) inhibition of superoxide anion generation by flavin-containing oxidases. These results support a significant role for oxidative metabolism in mediating low-dose radiation effects and demonstrate that cell culture in three dimensions is ideal to investigate radiation-induced adaptive responses. Expression of connexin 43, a constitutive protein of gap junctions, and the G(1) checkpoint were more sensitive to regulation by gamma rays in cells maintained in a three-dimensional than in a two-dimensional configuration.     

Manipulation of cellular redox parameters for improving therapeutic responses in B-cell lymphoma and multiple myeloma

Developing novel combined-modality therapeutic approaches based on understanding of the involvement of redox biology in apoptosis of malignant cells is a promising approach for improving clinical responses in B-cell lymphoma and multiple myeloma. Therapeutic modalities that generate reactive oxygen species (i.e., radiation, photodynamic therapy, and specific chemotherapeutic drugs) have been shown to be selectively cytotoxic to malignant B-cells. In this review, we will discuss agents that induce apoptosis in B-cell tumors by oxidative stress. Subsequently, a novel biochemical rationale (based on fundamental differences in cancer vs. normal cell oxidative metabolism) for combining oxidative stressors with radiotherapy and chemotherapy, that may lead to designing of more effective treatment strategies for B-cell malignancies, will be discussed. Besides providing potential curative benefit, such novel therapies could also selectively target and inhibit the emergence of drug-resistance in tumor cells, which is a major determinant of treatment failure in many B-cell malignancies.