Control of CFTR chloride conductance by ATP levels through non-hydrolytic binding.

Site-specific mutation and membrane reconstitution experiments provide compelling evidence that the product of the gene which is at fault in the disease cystic fibrosis, termed the cystic fibrosis transmembrane conductance regulator (CFTR), is a small-conductance chloride channel activated by phosphorylation. As transport of chloride ions is passive, the predicted presence of two nucleotide-binding domains in CFTR seems as puzzling as a report that ATP hydrolysis is essential to activate the channel. We now find that in the sweat duct, which expresses high levels of CFTR and has a very high Cl- conductance, intracellular concentrations of ATP must be about normal (5 mM) for activation of this conductance, apparently by a non-hydrolytic, perhaps allosteric, mechanism. This passive dependence on ATP should mean that even a modest depletion of cell energy levels will significantly lower the energy demands of electrolyte transport by decreasing chloride conductance. We believe this direct coupling between cellular ATP levels and chloride channel activity is an adaptive mechanism to protect the tissue from damage resulting from excessive energy depletion.     

Presence of a partial urea cycle in the leech, Poecilobdella granulosa.

Ornithine carbamoyltransferase (OCT) and arginase, but not arginine synthetase (AS), were detected in the body wall and gut tissues of the leech. The activities of these enzymes were not altered by starvation. The high activity of arginase in body wall is probably due to the association of the latter with botryoidal tissue. Hirudineans, which evolved from oligochaete ancestors, appear to have lost the citrulline-arginine segment of the urea cycle due to their ammonotelic mode of nitrogen excretion.     

Application of comparative functional genomics to identify best-fit mouse models to study human cancer

Genetically modified mice have been extensively used for analyzing the molecular events that occur during tumor development. In many, if not all, cases, however, it is uncertain to what extent the mouse models reproduce features observed in the corresponding human conditions. This is due largely to lack of precise methods for direct and comprehensive comparison at the molecular level of the mouse and human tumors. Here we use global gene expression patterns of 68 hepatocellular carcinomas (HCCs) from seven different mouse models and 91 human HCCs from predefined subclasses to obtain direct comparison of the molecular features of mouse and human HCCs. Gene expression patterns in HCCs from Myc, E2f1 and Myc E2f1 transgenic mice were most similar to those of the better survival group of human HCCs, whereas the expression patterns in HCCs from Myc Tgfa transgenic mice and in diethylnitrosamine-induced mouse HCCs were most similar to those of the poorer survival group of human HCCs. Gene expression patterns in HCCs from Acox1(-/-) mice and in ciprofibrate-induced HCCs were least similar to those observed in human HCCs. We conclude that our approach can effectively identify appropriate mouse models to study human cancers.     

Presence of a partial urea cycle in the leech,Poecilobdella granulosa

Ornithine carbamoyltransferase (OCT) and arginase, but not arginine synthetase (AS), were detected in the body wall and gut tissues of the leech. The activities of these enzymes were not altered by starvation. The high activity of arginase in body wall is probably due to the association of the latter with botryoidal tissue. Hirudineans, which evolved from oligochaete ancestors, appear to have lost the citrulline-arginine segment of the urea cycle due to their ammonotelic mode of nitrogen excretion.S. N. and B. J. thank the Council of Scientific & Industrial Research and the Department of Ocean Development, Government of India, respectively for the award of research fellowships.     

An empirical relationship between the prey density and predatory efficiency ofGambusia affinis

Summary Larval density of Culex fatigans essentially influences the predatory rate of the mosquito-fish Gambusia affinis. The feeding rate of the fish gradually increases up to a maximum value at intermediate prey densities beyond which there is an asymptotic saturation in the feeding rate. The relationship is represented by an empirical equation which helps in the prediction of the ideal stocking rate of the fish in natural systems.     

A phylogenetic review of the genus Atopobathynella Schminke, 1973 (Crustacea,Malacostraca, Bathynellacea) with three new species from southeastern India

To date, the genus Atopobathynella Schminke, 1973, contains 12 Gondwanan species, including two species from India. Three new species of this genus, viz. A. indica sp. nov., A. nelloreensis sp. nov., and A. inopinata sp. nov., from southeastern India are described herein. The various characters and their states in Atopobathynella, in relation to other parabathynellid species known so far, are discussed; especially its closeness with the genus Kimberleybathynella is highlighted. A morphological phylogenetic analysis of the genus Atopobathynella,along with its closely related genus Kimberleybathynella is also done, and the inter-relationships among the 15 species of Atopobathynella and six species of Kimberleybathynella are deduced, using the software PAUP 4.0b10. This analysis, based on 39 unordered characters, has yielded 23 most parsimonious trees, with a length of 138 steps, a consistency index (CI) of 0.3768, a homoplasy index (HI) of 0.6232, a retention index (RI) of 0.6211, and a rescaled consistency index (RC) of 0.2341. The cladogram thus obtained suggests the grouping of ((A.wattsi, A. glenayleensis), (A. readi, ((((A. gascoyneensis, A. hospitalis), A. hinzeae), (((A. compagana, A. chelifera), A. valdiviana), (((A. operculata, A. paraoperculata), A. nelloreensis), (A. indica, A. inopinata)))), (A. schminkei, (((((K. gigantea, K. kimberleyensis), K. argylensis), K. pleochaeta), K. mandorana), K. hexapoda)))), outgroup). It also shows that the five Indian species are nestled between the Australian Atopobathynella and Kimberleybathynella species. The Indian species appear to be much derived as compared to their Australian counterparts. A brief note on the origin of Bathynellacea is also added at the end.

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