Comparative limnology of Sambhar and Didwana lakes (Rajasthan,NW India)

Two alkaline saline inland lakes of Indian arid region were studied during 1984 and 1985, to assess functioning and interaction of various environmental and biological factors. Changes in physical and chemical variables, planktonic composition, chlorophyll content and phytoplankton primary productivity were examined.Salinity in both lakes fluctuated from almost fresh water (1.80), to hypersaline (300) and acted as the main controlling factor for almost all the biotic parameters. Maximum total alkalinities were 2162 mg l^–1 and 2090 mg l^–1, respectively in Sambhar and Didwana lakes. Dissolved oxygen ranged from completely anoxic conditions to maxima of 11.68 and 7.29 mg 1^–1, respectively in Sambhar and Didwana lakes. Nutrient enrichment in the lakes was low.The phytoplankton species composition of Sambhar lake was reduced from an earlier reported 20 genera to only 11 (Nostoc, Microcystis, Spirulina, Aphanocapsa, Oscillatoria, Merismopedia, Nitzschia, Navicula, Synedra, Cosmarium and Closterium). Phytoplankton of Didwana was composed of only 9 genera including Anabaena and Nodularia. Sambhar lake, which once contained Artemia, is now totally devoid of them. On the other hand, Artemia was the most dominant zooplankter in Didwana lake at a salinity range of 15–288. Other zooplankters such as Moina, Cyclops and Brachionus flourished at lower salinity levels in Didwana lake. The seasonal quantitative and qualitative phyto- and zooplankton changes in relation to salinity are documented.     

Effect of viscosity and dielectric constant variation on fractional fluorescence quenching analysis of coumarin dye in binary solvent mixtures

Photo physical properties of fluorescent organic compounds give an immense improved knowledge on characteristics of excited state that is beneficial to devise innovate molecules and understand their performance in particular applications. Coumarin derivatives have been extensively investigated in this regard. This article narrates steady state fluorescence quenching measurements of a coumarin derivative namely 3‐hydroxy‐3‐[2‐oxo‐2‐(3‐oxo‐3H‐benzo[f]chromen‐2‐yl)‐ethyl]‐1,3‐dihydro‐indol‐2‐one (3HBCD) in a binary mixture of acetonitrile and 1,4‐dioxane. Aniline is used as quencher. Fluorescence intensity is large in acetonitrile and decreases as the percentage of 1,4‐dioxane in the solvent mixture increases. With modest quencher concentration a deviation towards the x axis is noticed in the Stern–Volmer (S–V) plots. This downward curvature is interpreted as due to the presence of 3HBCD in different conformers in the lowest energy level. Ground state intramolecular hydrogen bonding formation is observed due to the conformational changes in the solute. Figured estimations of various quenching parameters recommend that, while dynamic quenching prompts linearity in S–V plot at lower quencher concentration, increasing quenching efficiency with increasing medium viscosity suggests that reaction is not entirely controlled by material diffusion. Stern–Volmer constant increases with decreasing medium dielectric constant.     

Mineral proximity influences mechanical response of proteins in biological mineral-protein hybrid systems

The organic phase of nacre, which is composed primarily of proteins, has an extremely high elastic modulus as compared to that of bulk proteins, and also undergoes large deformation before failure. One reason for this unusually high modulus could be the mineral-organic interactions. In this work, we elucidate the specific role of mineral proximity on the structural response of proteins in biological structural composites such as nacre through molecular modeling. The "glycine-serine" domain of a nacre protein Lustrin A has been used as a model system. It is found that the amount of work needed to unfold is significantly higher when the GS domain is pulled in the proximity of aragonite. These results indicate that the proximity of aragonite has a significant effect on the unfolding mechanisms of proteins when pulled. These results will provide very useful information in designing synthetic biocomposites, as well as further our understanding of mechanical response in structural composites in nature.     

The peripheral nervous system supports blood cell homing and survival in the Drosophila larva

Interactions of hematopoietic cells with their microenvironment control blood cell colonization, homing and hematopoiesis. Here, we introduce larval hematopoiesis as the first Drosophila model for hematopoietic colonization and the role of the peripheral nervous system (PNS) as a microenvironment in hematopoiesis. The Drosophila larval hematopoietic system is founded by differentiated hemocytes of the embryo, which colonize segmentally repeated epidermal-muscular pockets and proliferate in these locations. Importantly, we show that these resident hemocytes tightly colocalize with peripheral neurons and we demonstrate that larval hemocytes depend on the PNS as an attractive and trophic microenvironment. atonal (ato) mutant or genetically ablated larvae, which are deficient for subsets of peripheral neurons, show a progressive apoptotic decline in hemocytes and an incomplete resident hemocyte pattern, whereas supernumerary peripheral neurons induced by ectopic expression of the proneural gene scute (sc) misdirect hemocytes to these ectopic locations. This PNS-hematopoietic connection in Drosophila parallels the emerging role of the PNS in hematopoiesis and immune functions in vertebrates, and provides the basis for the systematic genetic dissection of the PNS-hematopoietic axis in the future.     

Entrainment during Ablation of Ischemic Ventricular Tachycardia. What is explanation for Post Pacing Interval shorter than the tachycardia cycle length?

Entrainment mapping of ischemic ventricular tachycardia at a site in the left ventricle where radiofrequency ablation was successful in terminating the tachycardia revealed a post-pacing interval shorter than the tachycardia cycle length. The reason for the same is explained in the current report.     

Kinetoplast morphology and segregation pattern as a marker for cell cycle progression in Leishmania donovani

Trypanosomatids are typified by uniquely configured mitochondrial DNA--the kinetoplast. The replication timing of kinetoplast DNA (kDNA) is closely linked to nuclear S phase, but nuclear and kinetoplast compartments display staggered timing of segregation, post-replication. Kinetoplast division is completed before nuclear division in Trypanosoma species while nuclear division is completed first in Crithidia species. Leishmania donovani is the causative agent of visceral leishmaniasis, a form of leishmanial infection that is often fatal. Cell cycle related studies in Leishmania are hampered by difficulties in synchronizing these cells. This report examines the replication/segregation pattern and morphology of the kinetoplast in L. donovani with the aim of determining if these traits can be used to assign cell cycle stage to individual cells. By labeling replicating cells with bromodeoxyuridine after synchronization with hydroxyurea, we find that although both nuclear and kDNA initiate replication in early S phase, nuclear division precedes kinetoplast segregation in 80% of the cells. The kinetoplast is roundish/short rod-like in G1 and in early to mid-S phase, but prominently elongated/bilobed in late S phase and early G2/M. These morphological traits and segregation pattern of the kinetoplast can be used as a marker for cell cycle stage in a population of asynchronously growing L. donovani promastigotes, in place of cell synchronization procedures or instead of using antibody staining for cell cycle stage marker proteins.     

Senescence marker protein 30 (SMP30) expression in eukaryotic cells: existence of multiple species and membrane localization

Senescence marker protein (SMP30), also known as regucalcin, is a 34 kDa cytosolic marker protein of aging which plays an important role in intracellular Ca(2+) homeostasis, ascorbic acid biosynthesis, oxidative stress, and detoxification of chemical warfare nerve agents. In our goal to investigate the activity of SMP30 for the detoxification of nerve agents, we have produced a recombinant adenovirus expressing human SMP30 as a fusion protein with a hemaglutinin tag (Ad-SMP30-HA). Ad-SMP30-HA transduced the expression of SMP30-HA and two additional forms of SMP30 with molecular sizes ～28 kDa and 24 kDa in HEK-293A and C3A liver cells in a dose and time-dependent manner. Intravenous administration of Ad-SMP30-HA in mice results in the expression of all the three forms of SMP30 in the liver and diaphragm. LC-MS/MS results confirmed that the lower molecular weight 28 kDa and 24 kDa proteins are related to the 34 kDa SMP30. The 28 kDa and 24 kDa SMP30 forms were also detected in normal rat liver and mice injected with Ad-SMP30-HA suggesting that SMP30 does exist in multiple forms under physiological conditions. Time course experiments in both cell lines suggest that the 28 kDa and 24 kDa SMP30 forms are likely generated from the 34 kDa SMP30. Interestingly, the 28 kDa and 24 kDa SMP30 forms appeared initially in the cytosol and shifted to the particulate fraction. Studies using small molecule inhibitors of proteolytic pathways revealed the potential involvement of β and γ-secretases but not calpains, lysosomal proteases, proteasome and caspases. This is the first report describing the existence of multiple forms of SMP30, their preferential distribution to membranes and their generation through proteolysis possibly mediated by secretase enzymes.