Manganese in cell metabolism of higher plants

Manganese, a group VII element of the periodic table, plays an important role in biological systems and exists in a variety of oxidation states. The normal level of Mn in air surrounding major industrial sites is 0.03 μg/m³, in drinking water 0.05 mg/liter and in soil between 560 and 850 ppm. Manganese is an essential trace element for higher plant systems. It is absorbed mainly as divalent Mn²⁺, which competes effectively with Mg²⁺ and strongly depresses its rate of uptake. The accumulation of Mn particularly takes place in peripheral cells of the leaf petiole, petiolule and palisade and spongy parenchyma cells. Mn is involved in photosynthesis and activation of different enzyme systems. Mn deficiency may be expressed as inhibition of cell elongation and yield decrease. Mn toxicity is one of the important growth limiting factors in acid soils. Plant tops are affected to a greater extent than root systems. The toxicity symptoms are, in general, similar to the deficiency symptoms. Toxic effects of Mn on plant growth have been attributed to several physiological and biochemical pathways, although the detailed mechanism is still not very clear. Higher O₂ uptake and loss of control in Mn activated enzyme systems have been associated with Mn toxicity. Mn interferes with the uptake, transport and use of several essential elements including Ca, Fe, Cu, Al, Si, Mg, K, P and N. Excess of Mn reduces the uptake of certain elements and increases that of others. pH plays an important role in Mn uptake. Acidic pH causes a lack of substantial amount of nitrate as an alternative electron acceptor and leads to a high amount of Mn in leaves. High microbial activity, water logging and poorly structured soils cause severe Mn toxicity even in neutral soils. The molecular mechanism of Mn-tolerance is not yet clear. The level of tolerance is different in different species and seems to be controlled by more than one gene. Further information is required on the factors affecting the distribution, accumulation and membrane permeability of the metal in different plant parts and different species. Understanding of the genetic basis of Mn-tolerance is necessary to improve adaptation of crops against acid soils, water logging and other adverse soil conditions.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Role of forefinger and thumb loops in production of Ψ54 and Ψ55 in tRNAs by archaeal Pus10

Pseudouridines (Ψ) are found in structurally and functionally important regions of RNAs. Six families of Ψ synthases, TruA, TruB, TruD, RsuA, RluA, and Pus10 have been identified. Pus10 is present in Archaea and Eukarya. While most archaeal Pus10 produce both tRNA Ψ54 and Ψ55, some produce only Ψ55. Interestingly, human PUS10 has been implicated in apoptosis and Crohn’s and Celiac diseases. Homology models of archaeal Pus10 proteins based on the crystal structure of human PUS10 reveal that there are subtle structural differences in all of these Pus10 proteins. These observations suggest that structural changes in homologous proteins may lead to loss, gain, or change of their functions, warranting the need to study the structure-function relationship of these proteins. Using comparison of structural models and a series of mutations, we identified forefinger loop (reminiscent of that of RluA) and an Arg and a Tyr residue of archaeal Pus10 as critical determinants for its Ψ54, but not for its Ψ55 activity. We also found that a Leu residue, in addition to the catalytic Asp, is essential for both activities. Since forefinger loop is needed for both rRNA and tRNA Ψ synthase activities of RluA, but only for tRNA Ψ54 activity of Pus10, archaeal Pus10 proteins must use a different mechanism of recognition for Ψ55 activity. We propose that archaeal Pus10 uses two distinct mechanisms for substrate uridine recognition and binding. However, since we did not observe any mutation that affected only Ψ55 activity, both mechanisms for archaeal Pus10 activities must share some common features.     

Effect of Fatty Acids Isolated from Edible Oils Like Mustard,Linseed or Coconut on Astrocytes Maturation

The omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA, 22:6n-3) has been previously shown to facilitate some of the vital functions of astrocytes. Since some dietary oils contain alpha-linolenic acid (ALA, 18:3n-3), which is a precursor of DHA, we examined their effect on astrocyte development. Fatty acids (FAs) were isolated from commonly used oils and their compositions were determined by GLC. FAs from three oils, viz. coconut, mustard and linseed were studied for their effect on astrocyte morphology. Parallel studies were conducted with FAs from the same oils after heating for 72 h. Unlike coconut oil, FAs from mustard and linseed, both heated and raw, caused significant morphogenesis of astrocytes in culture. ss-AR binding was also substantially increased in astrocytes treated with FAs from raw mustard and linseed oils as compared to astrocytes grown in normal medium. The expression profile of the isoforms of GFAP showed that astrocyte maturation by FAs of mustard and linseed oil was associated with appearance of acidic variants of GFAP and disappearance of some neutral isoforms similar to that observed in cultures grown in serum containing medium or in the presence of DHA. Taken together, the study highlights the contribution of specific dietary oils in facilitating astrocyte development that can have potential impact on human health.     

Docosahexaenoic acid facilitates cell maturation and beta-adrenergic transmission in astrocytes

The effects of docosahexaenoic acid (DHA; 22:6 n-3), a major omega-3 PUFA in the mammalian brain, on the structure and function of astrocytes were studied using primary cultures from rat cerebra. Gas-liquid chromatography of methyl esters of FAs isolated from cultures exposed to individual FAs, namely, stearic acid, linoleic acid, arachidonic acid, and DHA, showed alterations in the lipid profiles of the membranes, with a preferential incorporation of the FA to which the cells were exposed. Immunofluorescence studies demonstrated that unlike treatment with other FAs, after which the astrocytes remained as immature radial forms, DHA-treated astrocytes showed distinct differentiation, having morphology comparable to those grown in normal serum-containing medium. Receptor binding studies to determine the concentration of various neurotransmitter receptors showed that DHA selectively increased the number of beta-adrenergic receptors (beta-ARs) compared with FA-untreated controls, suggesting a greater role of DHA on beta-AR expression in membranes. This was also reflected by an increase in downstream events of the beta-AR pathways, such as the induction of protein kinase A and glycogen turnover by isoproterenol (ISP), a beta-AR agonist in DHA-treated cells. Moreover, ISP completely transformed DHA-treated cells into mature astrocytes bearing long processes, as in cells grown under normal conditions. Together, our observations suggest that DHA plays a unique role in facilitating some of the vital functions of astrocytes in the developing brain.     

An annotated checklist of Culicoides Latreille, 1809 (Insecta: Ceratopogonidae: Diptera) with incorporation of a vector species list from India

Culicoides Latreille, 1809 (Insecta : Diptera : Ceratopogonidae) are small nematocerous biological vectors of a wide range of pathogens of veterinary and medical importance. They are distributed worldwide but prefer warm, damp, and muddy areas. Female midges require blood for egg maturation. Studies on taxonomy, proper identification keys, and distribution patterns of these flies across different geographical regions of India of these flies are limited. This article provides an updated checklist of Culicoides spp. from India collected from various scattered publications, along with their synonyms and details on their subgenera, geographical distribution, and type locality. A compiled list of different Culicoides vectors from India has also been included separately in this article, along with the type of the diseases spread.     

Peripartum Cardiomyopathy Presenting With Ventricular Tachycardia: A Rare Presentation

A 25-year-old previously asymptomatic pregnant woman at 36 weeks'' gestation was noticed to have repetitive monomorphic ventricular tachycardia. A dilated left ventricle with moderately reduced systolic function was found on echocardiographic examination. This is a very rare presentation of peripartum cardiomyopathy (PPCMP) presenting with repetitive monomorphic ventricular tachycardia.     

A recently silenced, duplicate PgiC locus in Clarkia

Previous electrophoretic analysis showed that 17 diploid species of the wildflower Clarkia (Onagraceae) have two cytosolic isozymes of phosphoglucose isomerase (PGIC; EC 5.3.1.9), whereas 15 other diploid species have a single PGIC. Molecular studies revealed that the two isozymes in the former species are encoded by duplicate genes, PgiC1 and PgiC2, whereas the single isozyme in the latter is always encoded by PgiC1. Phylogenetic analysis of the nucleotide sequences implied that PgiC2 was silenced four times independently in the genus. Here we describe a psi PgiC2 from C. mildrediae, a species in which only PgiC1 is expressed. The discovery of the psi PgiC2 is significant because it confirms a formal prediction of the phylogenetic analysis. The psi PgiC2 includes 5,039 nucleotides corresponding to 18 of the 23 exons of PgiC, as well as the intervening introns and 3' nontranslated region. The absence of an increase of nucleotide substitutions in its "exons" suggests that the gene was silenced recently. The present study appears to be the first to establish that a specific duplicate gene locus regularly expressed in a group of related plant species has been silenced in one of them. The multiple independent silencings of PgiC2 suggest that it remained functional but inessential in ancestral lineages. We discuss the possibility that PgiC2 may have been preserved in these lineages by selection against mutants causing defective PGIC1- PGIC2 heterodimers.