Genetic control of morphogenetic variation in the sexcombs of drosophila melanogaster

The effect of the Y-chromosome on the sexcombs in the legs ofDrosophila melanogaster has been examined in four different genotypes, viz., Oregon R+,y, sx andPc-Scx. For this purpose, various Y-chromosome-fragments (Y^L and Y^S) and one or two XO conditions have been used.The results of this investigation show that both long (Y^L) and short (Y^S) arms of the Y-chromosome tend to increase the teeth number in the sexcomb of the first legs in all genotypes excepty. The XO-1 condition, derived by the loss of one X, appears to decrease it; the XO-2, resulting from the fertilization of an X-bearing ovum by a nullo-Y sperm, appears to show an increased teeth number or no effect at all. The effect of Y-fragments is least in the case ofy and maximum insx. The various Y-fragments used also show a parallel, though inversely related, effect on the production of intermediate bristles insx.These Y-fragments show an opposite effect on the sexcombs of the second and third legs of thePc-Scx genotype. Here the mean numbers of teeth are significantly reduced in all cases as compared to those in XY;Pc-Scx/++ genotype.The different Y-fragments behave differently in their effect on sexcomb pattern. It has been suggested that secondary modifiers may be present in association with different genotypes as well as in the Y, which are required to maintain a morphodynamic equilibrium in pattern formation.This investigation has been supported by a grant from Council of Scientific and Industrial Research to the first author, Scheme No. 38 (77)/65-GAU-II.     

Effect of preceding grain legumes on growth and nitrogen uptake of dryland pearl millet

Summary In a dryland cropping systems study preceding crops either of groundnuts, cowpea or pigeon pea were found to increase the early seedling vigour, rate of plant growth and grain production of the subsequent pearl millet. No such benefit was noted from a previous crop of mung. Grown after groundnuts and cowpea the unfertilized pearl millet removed from the soil 39.9 and 32.5 kg N compared to 18.9 kg N per hectare following a pearl millet crop. At harvest the number of viable nodules was the highest in groundnuts and cowpea. Especially in groundnuts the number of viable nodules increased after flowering stage.     

Selective binding of divalent cations toward heme proteins

Potential toxicity of transition metals like Hg, Cu and Cd are well known and their affinity toward proteins is of great concern. This work explores the selective nature of interactions of Cu²⁺, Hg²⁺ and Cd²⁺ with the heme proteins leghemoglobin, myoglobin and cytochrome C. The binding profiles were analyzed using absorbance spectrum and steady-state fluorescence spectroscopy. Thermodynamic parameters like enthalpy, entropy and free energy changes were derived by isothermal calorimetry and consequent binding parameters were compared for these heme proteins. Free energy (DG) values revealed Cu²⁺ binding toward myoglobin and leghemoglobin to be specific and facile in contrast to weak binding for Hg²⁺ or Cd²⁺. Time correlated single photon counting indicated significant alteration in excited state lifetimes for metal complexed myoglobin and leghemoglobin suggesting bimolecular collisions to be involved. Interestingly, none of these cations showed significant affinity for cytochrome c pointing that, presence of conserved sequences or heme group is not the only criteria for cation binding toward heme proteins, but the microenvironment of the residues or a specific folding pattern may be responsible for these differential conjugation profile. Binding of these cations may modulate the conformation and functions of these biologically important proteins.     

Evidence for Compromised Insulin Signaling and Neuronal Vulnerability in Experimental Model of Sporadic Alzheimer’s Disease

Evidence from animal studies categorizes sporadic Alzheimer’s disease (sAD) as a metabolic syndrome with accompanying cognitive deficits. Given that glial cells act as “silent partners” to neurons by providing trophic support and defense, the present study investigated the role of glia in sAD pathology. A streptozotocin (STZ)-induced glial-neuronal co-culture model of sAD was used to study the metabolic status of the two cell types. Real time RT-PCR and Western blotting results indicated that amyloid precursor protein (APP) and β-secretase (BACE1) were highly expressed in co-cultured neurons than in monocultures. Increased amyloidogenesis was accompanied by decreased expression of mediators in insulin signaling pathway that included insulin receptor (IR), insulin receptor substrate 2 (IRS2), insulin-like growth factor 2 (IGF2), insulin-like growth factor 1 receptor (IGF1R), total-glycogen synthase kinase 3β (t-GSK3β), and phosphorylated-GSK3β^ser9 (p-GSK3β^ser9), suggesting that neuronal cells are more prone to metabolic variability when cultured in the presence of glial cells. Findings from the sAD model induced by intracerebroventricular (ICV) injection of STZ revealed that increased amyloid beta (Aβ) load in the hippocampus was potentially responsible for the hyperphosphorylation of tau at ser³⁹⁶. Furthermore, impaired cognitive functions and decreased dendritic spine density and axonal thinning in CA1 region of hippocampus were associated with decreased IR and p-GSK3β^ser9/t-GSK3β expression. Taken together, the present study provides evidence that glia mediated response and insulin signaling defects drive pathological changes in sAD and represent potential targets for delaying sAD progression.