Meta-analysis of geographical clines in desiccation tolerance of Indian drosophilids

Tropical fruit flies (Drosophilidae) differ from temperate drosophilids in several ecophysiological traits, such as desiccation tolerance. Moreover, many species show significant differences in desiccation tolerance across geographical populations. Fruit flies from the tropical and subtropical Indian subcontinent show a clinal pattern for desiccation tolerance which is similar for more than a dozen species studied so far, suggesting adaptation to climatic differences. We performed a meta-analysis to investigate which particular climatic patterns modulate desiccation tolerance in natural populations of drosophilids. Latitude of the sampling site explained most of the variability. Seasonal thermal amplitude (fluctuations in temperature expressed as coefficient of variation) was the strongest climatic factor shaping desiccation tolerance of flies, while factors measuring humidity directly were not important. Implications for survival of flies after future climate change are suggested.     

Studies on triacylglycerol ester hydrolase from bat adipose tissue

Triacylglycerol ester hydrolase was isolated from bat adipose tissue and characterized. The partially purified enzyme had pH optimum of 8.6 and a K_m value of 0.6 mM. The enzyme was denaturated upon freezing and thawing, which was prevented by 25% glycerol. The enzyme was activated by EDTA and NaCl, while it was inhibited by serum and bovine serum albumin. Heparin, sodium fluoride and diisopropyl fluorophosphate had no effect on triacylglycerol ester hydrolase activity. It hydrolyzed triglycerides partially. Triacylglycerol ester hydrolase lost its activity during delipidation but it was reactivated by endogenous lipids and phospholipids, viz. phosphatidyl ethanolamine, phosphatidyl choline and sphingomyelin. The enzyme shows kinetic properties altogether different from lipoprotein lipase and hormone sensitive lipase     

Ion microscopic imaging of calcium during 1,25-dihydroxyvitamin D-mediated intestinal absorption

A combination of ion microscopic and conventional radionuclide techniques was employed to investigate the temporal-spatial dynamics of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃]-stimulated intestinal calcium (Ca) absorption. At varying times following the administration of a single intravenous dose of 1,25(OH)₂D₃, to vitamin D-deficient chicks, transepithelial transport and tissue retention of Ca were quantitated in vivo, using the ligated duodenal loop technique and⁴⁷Ca as the tracer. The localization of Ca in the intestinal tissue during absorption was monitored by ion microscopy, using the stable Ca isotope,⁴⁴Ca, as the absorbed species. There was little transepithelial absorption of Ca in the vitamin D-deficient animals despite a substantial tissue accumulation of luminally derived Ca, the latter localizing predominantly in the brush border region of the enterocyte, as shown by the⁴⁴Ca-ion microscopic images. The early (30 min-1 h) response to 1,25(OH)₂D₃ was an increased tissue uptake of luminal⁴⁷Ca, which also primarily associated with the brush border region, again as shown by ion microscopy. At 2–4 h after the 1,25(OH)₂)D₃ dose, there was a progressive redistribution of Ca from the brush border region throughout the cytoplasm and into the lamina propria. At 8–16 h,⁴⁷Ca absorption was maximal and⁴⁴Ca was sparsely distributed in the intestinal tissue.⁴⁷Ca absorption gradually declined and reached pre-dose levels by 72 h. At this time, tissue⁴⁴Ca was again largely limited to the brush border region. These results provide support for the multiple actions of 1,25(OH)₂D₃ on the intestinal Ca absorption