NDVI is not reliable as a surrogate of forage abundance for a large herbivore in tropical forest habitat

Remotely sensed vegetation indices are increasingly being used in wildlife studies but field‐based support for their utility as a measure of forage availability comes largely from open‐canopy habitats. We assessed whether normalized difference vegetation index (NDVI) represents forage availability for Asian elephants in a southern Indian tropical forest. We found that the number of food species was a small percentage of all plant species. NDVI was not a good measure of food abundance in any vegetation category partly because of (a) small to moderate proportional abundances of food species relative to the total abundance of all species in that category (herbs and shrubs), (b) abundant overstory vegetation resulting in low correlations between NDVI and food abundance, despite a high proportional abundance of food species and a concordance between total abundance and food species abundance (graminoids), and (c) the relevant variables measured and important as food at the ground level (count and GBH) not being related to primary productivity (trees and recruits). NDVI had a negative relationship with the total abundance of graminoids, which represent a bulk of elephant and other herbivore diet, because of negative interaction with other vegetation and canopy cover that positively explained NDVI. Spatially interpolated total graminoid abundance modeled from field data outperformed NDVI in predicting total graminoid abundance, although interpolation models of food graminoid abundance were not satisfactory. Our results reject the utility of NDVI in mapping elephant forage abundance in tropical forests, a finding that has implications for studies of other herbivores also. Abstract in Kannada is available with online material.     

How Do Different Watering Regimes Affect the Growth,Chlorophyll Fluorescence,Phytohormone, and Phenolic Acid Content of Greenhouse-Grown Ceratotheca triloba?

We evaluated the effect of different watering regimes on the growth, chlorophyll fluorescence, phytohormones, and phenolic acids in Ceratotheca triloba (Bernh.) Hook.f., a commonly consumed African indigenous leafy vegetable. The study was conducted in the greenhouse under different watering regimes [seven (daily); three (thrice); two (twice); one (once) day(s) per week] for a period of 2 and 4-months. In each pot (7.5 cm diameter; 150 ml volume), 50 ml of water was applied per treatment. At the end of the experiment, plant growth, chlorophyll fluorescence, phytohormones, and phenolic acids were determined. A decrease in water availability resulted in a consistent decline in plant growth after a 4-month growth period. The severity of reduced water availability was more noticeable in plants watered once a week with a 1.4-fold reduction in growth and quantum efficiency of PSII (Fv/Fm) value of 0.80. The significant decline in growth and chlorophyll fluorescence was probably due to the increased production of abscisic acid (ABA) and cytokinin (CK) content together with the detected phytohormones in plants with restricted water supply. Furthermore, plants watered once a week had a trade-off between growth and phenolic acid production, with significantly higher (threefolds) concentrations of vanillic, ferulic, caffeic, and 4-coumaric acids in 4-month-old plants. Even though C. triloba grew best in well-watered soil, the plant had the potential to adapt and survive in soils with limited water supply for longer periods of growth. These findings suggest that regulation of phytohormones and phenolic acids played an important role in improving the growth of C. triloba under limited water conditions.

     

Isolation and some properties of dioxygenase and co-oxidase activities of adult human liver cytosolic lipoxygenase

The evidence presented here constitutes the first report on the occurrence of lipoxygenase (LO) activity in the adult human liver. LO activity was isolated free of hemoglobin from the whole liver cytosol by affinity chromatography using a concanavalin-A sepharose 4B column, and some properties of its dioxygenase and co-oxidase activities were examined. High-pressure liquid chromatography (HPLC) analyses of arachidonic acid metabolites suggested the presence of 5-, 12-, and 15-LO activities in the human liver. Linoleic acid was converted into 13-hydroperoxyoctadecadienoic acid. The dioxygenase activity with a V_max value of 1.74 μmoles/min/mg protein and a K_m value of 0.48 mM was noted in the presence of different concentrations of linoleic acid at pH 10. The activity was markedly stimulated by the presence of calcium, ATP, hydrogen peroxide, and KCl in the assay medium. Under optimum conditions, all the xenobiotics tested were co-oxidized by the enzyme preparations in the presence of linoleic acid. Kinetic data obtained for benzidine oxidation yielded a K_m value of 0.53 mM and a V_max value of 90.9 nmoles/min/mg protein. At present, the significance of these findings in in vivo toxicity of benzidine is unknown. The linoleic acid-dependent dioxygenase and co-oxidase activities were thermolabile and inhibited by micromolar concentrations of several classical LO inhibitors, further confirming the involvement of LO in these reactions. © 1997 John Wiley & Sons, Inc.     

Deglutarylation of glutaryl-CoA dehydrogenase by deacylating enzyme SIRT5 promotes lysine oxidation in mice

A wide range of protein acyl modifications has been identified on enzymes across various metabolic processes; however, the impact of these modifications remains poorly understood. Protein glutarylation is a recently identified modification that can be nonenzymatically driven by glutaryl-CoA. In mammalian systems, this unique metabolite is only produced in the lysine and tryptophan oxidative pathways. To better understand the biology of protein glutarylation, we studied the relationship between enzymes within the lysine/tryptophan catabolic pathways, protein glutarylation, and regulation by the deglutarylating enzyme sirtuin 5 (SIRT5). Here, we identify glutarylation on the lysine oxidation pathway enzyme glutaryl-CoA dehydrogenase (GCDH) and show increased GCDH glutarylation when glutaryl-CoA production is stimulated by lysine catabolism. Our data reveal that glutarylation of GCDH impacts its function, ultimately decreasing lysine oxidation. We also demonstrate the ability of SIRT5 to deglutarylate GCDH, restoring its enzymatic activity. Finally, metabolomic and bioinformatic analyses indicate an expanded role for SIRT5 in regulating amino acid metabolism. Together, these data support a feedback loop model within the lysine/tryptophan oxidation pathway in which glutaryl-CoA is produced, in turn inhibiting GCDH function via glutaryl modification of GCDH lysine residues and can be relieved by SIRT5 deacylation activity.     

Hydroperoxidase activity of lipoxygenase: hydrogen peroxide-dependent oxidation of xenobiotics

Since H2O2 is one of the major biologically available peroxides, its ability to support hydroperoxidase activity of highly purified soybean lipoxygenase was examined by monitoring co-oxidation of selected xenobiotics. All of the eight chemicals tested were found to be oxidized in the presence of H2O2. Tetramethylbenzidine oxidation was completely inhibited by the classical lipoxygenase inhibitor nordihydroguaiaretic acid. The reaction was enzymatic in nature and exhibited a acidic pH optimum. The data clearly indicate, for the first time, that H2O2 can efficiently replace fatty acid hydroperoxide in a xenobiotic oxidation reaction medicated by the hydroperoxidase activity of lipoxygenase.     

Distribution of the flavohaemoglobin, HMP, between periplasm and cytoplasm in Escherichia coli

Abstract The subcellular distribution of the soluble flavohaemoglobin (HMP) of Escherichia coli has been determined. Cells over-expressing HMP from the cloned hmp gene on a multicopy plasmid were fractionated by osmotic shock and lysozyme treatment. Spectral analysis of subcellular fractions showed the CO-binding haemoprotein to be cytoplasmic. However, Western blotting using antibody raised to purified HMP revealed approximately 30% of the protein to be periplasmic in the over-expressing strain. Western analysis also revealed substantial levels of periplasmic HMP in a strain expressing only chromosomally encoded protein but none in an hmp mutant. The results are discussed in relation to protein function and the similar distribution reported for Vitreoscilla globin.     

Hepatoprotective action of abhrak bhasma, an ayurvedic drug in albino rats against hepatitis induced by CCl4

Abhrak bhasma is a commonly used ayurvedic drug against many diseases including hepatitis. It is tested in albino rats using a model of hepatitis induced by a single dose of CCl4 (3 ml/kg body wt). Different doses of abhrak bhasma (10, 20, 30 and 40 mg/kg body wt) were tested to decide the dose related hepatoprotective efficacy. The centrolobular necrosis induced by single dose of CCl4 was reduced significantly by abhrak bhasma (10 mg) and liver histology was also protected by 20 mg dose. Liver acid lipase activity was lowered, while alkaline and lipoprotein lipase activities were elevated due to treatment of single dose of CCl4. Abhrak bhasma counteracted the action of CCl4 on liver lipolytic enzymes. CCl4 did not alter the kidney histologically. Activities of three lipases of rat kidney (acid, alkaline and lipoprotein lipases) were reduced by CCl4 treatment and were reversed by administration of abhrak bhasma. Acid lipase activity of rat adipose tissue was reduced by CCl4 treatment. On the contrary alkaline, lipoprotein and hormone sensitive lipases were enhanced after 24 hr of administration of CCl4. Acid lipase activity was raised by administration of different doses of abhrak bhasma concurrent with CCl4. Abhrak bhasma treatment along with CCl4 enhanced alkaline lipase activity at 10 and 20 mg dose and later it was reduced at 30 and 40 mg doses and came to normal levels. Lipoprotein and hormone sensitive lipases were reduced by the counteraction of increasing doses of abhrak bhasma.     

Characterization of high temperature-tolerant rhizobia isolated from Prosopis juliflora grown in alkaline soil

A method was developed for the fast screening and selection of high-temperature tolerant rhizobial strains from root nodules of Prosopis juliflora growing in alkaline soils. The high-temperature tolerant rhizobia were selected from 2,500 Rhizobium isolates with similar growth patterns on yeast mannitol agar plates after 72 h incubation at 30 and 45 degrees C, followed by a second screening at 47.5 degrees C. Seventeen high-temperature tolerant rhizobial strains having distinguishable protein band patterns were finally selected for further screening by subjecting them to temperature stress up to 60 degrees C in yeast mannitol broth for 6 h. The high-temperature tolerant strains were NBRI12, NBRI329, NBRI330, NBRI332, and NBRI133. Using this procedure, a large number of rhizobia from root nodules of P. juliflora were screened for high-temperature tolerance. The assimilation of several carbon sources, tolerance to high pH and salt stress, and ability to nodulate P. juliflora growing in a glasshouse and nursery of the strains were studied. All five isolates had higher plant dry weight in the range of 29.9 to 88.6% in comparison with uninoculated nursery-grown plants. It was demonstrated that it is possible to screen in nature for superior rhizobia exemplified by the isolation of temperature-tolerant strains, which established effective symbiosis with nursery-grown P. juliflora. These findings indicate a correlation between strain performance under in vitro stress in pure culture and strain behavior under symbiotic conditions. Pure culture evaluation may be a useful tool in search for Rhizobium strains better suited for soil environments where high temperature, pH, and salt stress constitutes a limitation for symbiotic biological nitrogen fixation.     

Ceramide Glycanase Activities in Human Cancer Cells

Ceramide glycanase (CGase) activities have been detected in different human tumor cells (colon, carcinoma Colo-205; neuroblastoma, IMR-32; breast cancer lines, SKBr3 and MCF7). However, the level of enzymatic activity is lower in these cells compared to that present in other mammalian tissues reported before (Basu, M., Kelly, P., Girzadas, M. A., Li, Z., and Basu, S. Methods Enzymol. (in press)). The majority of CGase activity was found in the 100,000g soluble supernatant fraction isolated from all these cell lines and tissues. Using the soluble enzyme, the requirement for optimum CGase activity was found to be consistent with previous observations found for rat and rabbit tissues (Basu, M., Dastgheib, S., Girzadas, M. A., O'Donnell, P. H., Westervelt, C. W., Li, Z., Inokuchi, J. I., and Basu, S. (1998) Acta Pol. Biochim. 42:327). The CGase activities from both Colo-205 and IMR-32 cells are optimum at a protein to detergent ratio of one. All the mammalian CGases, including human cancer cells, show an optimum pH between 5.5 and 5.8 in sodium acetate buffer. The CGase activities from cancer cells are found to be cation-independent; however, mercury, zinc, and copper ions seem to inhibit the enzyme activity substantially in both tumor cells lines. The mercury ion inhibition of CGase activities from all different sources indicates a possible structural homology in the CGase proteins.Radiolabeled substrates, labeled at the sphingosine double bond or at the 3-position of sphingosine without modifying double bond of sphingosine were used in this investigation. Both were active substrates with all enzyme preparations isolated from different cancer cells (apparent Km, 500 M for nLcOse5[³H-DT]Cer and 350 M for GgOse4[sph-3-³H]Cer with Colo-205 enzyme). Structural analogues of ceramide and sphingosine (L-PPMP, L-PDMP, alkylamines, and Tamoxifen) inhibited cancer cell CGase activities in vitro.     

Spatial and temporal activity of the dentin sialophosphoprotein gene promoter: differential regulation in odontoblasts and ameloblasts

Dentin sialoprotein and dentin phosphoprotein are non-collagenous proteins that are cleavage products of dentin sialophosphoprotein (DSPP). Although these two protein products are believed to have a crucial role in the process of tooth mineralization, their precise biological functions and the molecular mechanisms of gene regulation are not clearly understood. To understand such functions, we have developed a transgenic mouse model expressing a reporter gene (lacZ) under the control of approximately 6 kb upstream sequences of Dspp. The transgenic fusion protein was designed to reside within the cells to facilitate the precise identification of cell type and developmental stages at which the Dspp-lacZ gene is expressed. The results presented in this report demonstrate: (a) the 6 kb upstream sequences of Dspp have the necessary regulatory elements to direct the tissue specific expression of the transgene similar to endogenous Dspp, (b) both odontoblasts and ameloblasts exhibit transgene expression in a differentiation dependent manner, and (c) a differential regulation of the transgene in odontoblasts and ameloblasts occurs during tooth development and mineralization.