Showing papers by "North Eastern Hill University published in 1992"

Soil microbial population numbers and enzyme activities in relation to altitude and forest degradation

Abstract: Microbial population numbers and their enzyme activities in terms of different enzymes, namely dehydrogenase, urease and phosphatase, were estimated in four forest stands (two at low and two at higher altitudes). The two forest stands at each altitude were at different stages of regeneration. At both altitudes, fungal and bacterial population numbers were higher in the less degraded forests than in the more degraded ones. Consequently, the different enzyme activities were also greater in the less degraded forest soils. A correlation coefficient was calculated between fungal population numbers, bacterial population numbers, soil moisture, organic C and the various enzymes activities. Dehydrogenase activity showed a positive correlation with fungal population numbers in all of the forest stands. However, the bacterial population numbers only showed a significant correlation (r = 0.639, P < 0.05) with dehydrogenase enzyme in the less degraded forest at the lower altitude. A significant positive correlation was established between urease activity and fungal and bacterial population numbers at the lower altitude, but only with the fungal population numbers at the higher altitude. At the higher altitude no significant correlation could be established with phosphatase and any of these traits. At the lower altitude, however, phosphatase showed a positive correlation with organic C and fungal population numbers. These enzymes showed a marked seasonality. The results of the investigation indicated that disturbance of soil and vegetation has an adverse effect on microbial population numbers and microbial enzyme activities.

Microenvironmental variability and species diversity in treefall gaps in a sub-tropical broadleaved forest

Abstract: Microenvironmental variability and species diversity in gaps and forest understorey were studied to assess the role of treefall gaps in maintaining composition and patchy distribution in a broad-leaved sub-tropical climax forest, Mawphlang, Meghalaya, India Photon flux density was higher in gaps than in the surrounding understorey Relative humidity was low and the litter layer was relatively thin in gaps throughout the year Soil moisture and photon flux density in the gaps significantly varied between seasons and gaps of different sizes Relative humidity significantly varied between seasons but difference among gaps was insignificant Among-gap and among-season variations in soil and air temperature were insignificant The number of tree species in the gaps was positively correlated with gap area, and tree species abundance showed higher equitability in larger than in smaller gaps In gaps, α-diversity was highest for herbs and lowest for shrubs β-diversity was highest for shrubs and lowest for tree seedlings α-diversity of tree seedlings was higher in the gaps than in the forest understorey Conversely, β-diversity was higher in the understorey than in the gaps Low species similarity for tree seedlings among the gaps could be an effect of patchy distribution of parent tree species in the forest Thus a significant change in light and moisture regimes along the gap size gradient played an important role in influencing the composition and abundance of shade tolerant and intolerant tree species in gaps on one hand, and affected the overall species diversity of the forest, on the other

Ecology of soil microflora and mycorrhizal symbionts in degraded forests at two altitudes

Abstract: Microbial populations were estimated in four different forest stands at different regenerational stages, two each at higher and lower altitudes. The fungal and bacterial populations showed marked seasonal variations at both altitudes. Quantitatively, the bacterial population was higher than the fungal population. Although 25 fungal species were isolated at the lower altitude, only 15 were obtained at the higher altitude. Penicillium chrysogenum and Trichoderma viride were dominant at the lower and higher altitudes, respectively. In the more degraded forest stand at the lower altitude both the fungal and the bacterial population showed a significant positive correlation with organic C (r=0.658 and 0.735, respectively), whereas in the less degraded forest stand there was a significant correlation only between the fungal population and organic C (r=0.835). At the higher altitude, however, a highly significant correlation (P<0.05) was observed between the fungal population, soil moisture and organic C in both the forest stands. Disturbance to the soil and vegetation adversely affected the microbial population, and also affected endogonaceous spores. At the lower altitude, plants in the more degraded forest stand were more mycotrophic compared to those in the less degraded stand. The level of mycorrhizal infection showed a highly positive correlation with soil moisture, organic C, total N, and available P. The spore population, however, was correlated negatively with these parameters. Three different endogonaceous genera, Glomus, Gigaspora, and Acaulospora, were identified during the course of investigation. Glomus, however, was dominant.

Study of unscheduled DNA synthesis following exposure of human cells to arecoline and extracts of betel nut in vitro

Abstract: Aqueous, acetic acid, hydrochloric acid and ethanol extracts of betel nut (Areca catechu L.) have been found to induce unscheduled DNA synthesis in Hep 2 cells obtained from human larynx carcinoma, in vitro. Different concentrations of extracts of betel nut induced dose-dependent unscheduled DNA synthesis in Hep 2 cells. Together with the viability of the Hep 2 cells, our results indicate that the aqueous and acetic acid extracts of betel nut induce relatively more unscheduled DNA synthesis than the hydrochloric acid and ethanol extracts and arecoline. The carcinogenic potency of raw and unprocessed betel nut of North-East India used in this study is discussed.

Enzyme activities related to litter decomposition in forests of different age and altitude in North East India

Abstract: Cellulase, amylase and invertase activities were studied in extracts of different leaf litters selected from four different forest stands, two of each from low and higher altitudes. Enzyme activities were generally considerably higher in litter at the lower altitude than at the higher altitude. The age of the forest from which the litter was taken had no consistent effect on these enzyme activities. Cellulase and amylase activities showed a marked seasonal variation at both altitudes. Invertase activity was higher at the beginning of litter decomposition, whereas cellulase and amylase activities increased during litter decomposition. At the lower altitude, invertase activity was higher in herbaceous litter than tree litter. At the higher altitude, all activities were higher in angiosperm litter than in coniferous litter. Invertase activity correlated positively with soluble sugars in all of the litters, whereas cellulase activity had no significant relationship with cellulose content. Cellulase and amylase activities, but not invertase activity, were generally correlated significantly with numbers of fungi and bacteria.

Simultaneous determination of trace heavy metals in waters by atomic absorption spectrometry after preconcentration by solvent extraction

Abstract: A simple and rapid method for the simultaneous extraction of heavy metals using a new reagent 5-(2′-carbomethoxyphenyl; azo-8-quinolinol(R) into methyl isobutyl. ketone (MIBK) and their subsequent determination by flame atomic absorption spectrometry is described. The method has been applied to the determination of Cu. Pb, Ni, Fe, Cr, Co and Mo in drinking and bore well waters. The extraction has been carried out with an aqueous to organic phase ratio to achieve around 30 fold preconcentration of metals. Extraction parameters and the influence of diverse ions have been studied. The detection limits (36) for Cu, Pb, Ni, Fe, Cr, Co and Mo are 0.07, 0.23, 0.15, 0.09, 0.22, 0.17, 0.38 μg/l, respectively. Higher preconcentration factors can be achieved by using a higher aqueous to organic phase ratio and lower concentration of metals can be determined.

Somatic embryogenesis and high frequency plantlet regeneration in callus cultures of Thevetia peruviana

Abstract: Plantlet regeneration through somatic embryogenesis has been achieved in the apocynaceous medicinal treeThevetia peruviana L. Calluses obtained by culturing young leaf discs on MS medium containing 9 μM 2,4-dichlorophenoxyacetic acid and 4.6 μM kinetin, when subjected to reduced levels of the growth regulators followed by higher cytokinin treatment, produced numerous somatic embryos. Somatic embryos developed into complete plantlets on a medium devoid of growth regulators. An average of 40–50 plantlets were obtained from 50 mg of embryogenic callus. Survival of transplants was 60% under glasshouse conditions.

Design of liposome to improve encapsulation efficiency of gelonin and its effect on immunoreactivity and ribosome inactivating property

Abstract: Gelonin, purified from the seeds of Gelonium multiflorum, using cation-exchange and gel-filtration chromatography was characterised for its purity, homogeneity and molecular weight by reverse-phase HPLC (RP-HPLC) and SDS-PAGE analysis. The HPLC purified gelonin was used for entrapment studies in the liposomes. Liposomes were prepared by reverse phase evaporation (REV) technique using three different types of lipid composition in the same molar ratio. The method resulted in 75–80% entrapment efficiency of gelonin in the liposomes. Entrapped and unentrapped gelonin was characterized for physico-chemical, immunochemical and biological properties. The immunoreactivity of entrapped gelonin was fully preserved but the ribosome-inactivating property was slightly inhibited. The method involved mild conditions, highly reproducible and the liposomes produced appeared to be stable for several months. It has important implications in the development of cell type specific cytotoxic agents where a chemical cross-linking is involved which significantly inhibits both immunoreactivity and ribosome-inactivating ability of the toxin.

Diversity, distribution, and seasonal abundance of Ephemeroptera in streams of Meghalaya State, India

Abstract: Diversity, distribution, seasonal changes in density and relative abundance of Ephemeroptera nymphs were studied in five stations on three streams in and around Shillong, Meghalaya state, North-eastern India. Seventeen species belonging to eight genera and five families were recorded. Diversity (Shannon's index) was governed by the heterogeneity of the substratum which in turn was influenced by catchment disturbances (quarrying, logging, and entry of sewage). Seasonal changes in density were governed by the spate-frequency regime of the streams. Relative abundance showed dominance of one or two species at impacted stations, while in less disturbed ones, a more equitable distribution of species was observed.

Use of subtherapeutical dose of cisplatin and vitamin C against murine Dalton's lymphoma.

Abstract: The antitumor activity of subtherapeutical dose of cisplatin and vitamin C combinations was studied against murine Dalton's lymphoma in vivo. The sequence-dependent synergistic antitumor effect of vitamin C and cisplatin was shown to lead to the regression of the tumor resulting in a significant increase in the host survivals with tumor free hosts. Decrease in tumor pH noted in the treated tumor bearing mice and involvement of host's immune system could be an important step in this sequence-dependent antitumor activity of vitamin C and cisplatin.

Regeneration of plantlets from hypocotyl-derived callus of Coptis teeta

Abstract: Callus cultures of Coptis teeta were established from hypocotyl segments (excised from aseptically germinating seeds) on Murashige and Skoog (MS) medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin. Microshoots were produced within 6–7 weeks of subculturing this callus in 1/2 MS nutrient medium supplemented with kinetin alone. Excised microshoots were rooted in 1/2 MS nutrient medium containing indolebutyric acid (IBA). The complete plantlets were hardened and established.

Properties of a ribosome-inactivating protein, gelonin, purified using three different methods.

Abstract: Ribosome-inactivating protein, gelonin, isolated from an Indian plant Gelonium multiflorum of Euphorbiaceae family has been used to design and synthesize immunotoxins and hormonotoxins for selective targeting purposes. Since gelonin isolated by aqueous extraction, cation-exchange chromatography and gel-filtration chromatography (Method I), contains non-proteinous material absorbing at 280 nm, the ammonium sulphate precipitation method (Method II) and Cibacron blue affinity chromatography method. (Method III) have been used to purify gelonin from the dry seeds. Three batches of gelonin purified by each method were prepared and subjected to extensive physico-chemical and immunochemical characterization. The molecular weight was determined by gel-filtration chromatography on a pre-calibrated Sephadex G-100, TSK-G4000 TW on HPLC or Superose-12 on fast protein liquid chromatography. In all cases, the molecular weight was approximately 30,000Da. The SDS-PAGE also revealed a homogeneous protein of 30kDa molecular weight. In Method II, the non-proteinous material which binds to CMC-gel in association of gelonin was substantially removed during ammonium sulphate fractionation. A careful analysis clearly revealed that Method II, although yielded low protein, gave gelonin devoid of the non-proteinous material. The SPDP modification of epsilon-NH2 groups of gelonin obtained from Methods I, II, and III was also carried out and its effect on immunoreactivity was studied.

Weak luminescence from the frozen-thawed root tips of Cicer arietinum. L.

Abstract: We observed a weak luminescence (the intensity of which is about 30–40 times that of the control level) emanating from the root tips of Cicer arietinum. L when subjected to sudden freezing followed by fast thawing. The pattern of the variation of the intensity of photon emission with time after the treatment shows a shoulder and then a peak after which the intensity gradually reduces to background level. The intensity of light emission was found to be oxygen-dependent and could be suppressed by the addition of a radical chain terminator (phenol). The spectral distribution of the emitted photons could also be determined.

Age-specific development of malate-aspartate shuttle in the liver and kidney of mice.

Abstract: The activities of malate-aspartate shuttle enzymes were measured in the liver and kidney of 15-, 30-, and 60-day old mice. The results indicate that the activities (U/mg protein) of both isoenzymes (cytosolic and mitochondrial) of both malate dehydrogenase and aspartate aminotransferase are significantly higher in the liver of 15-day old mice than in the liver of 30- and 60-day old animals. However, the shuttle enzymes showed a peak value in the kidney of 30-day old mice. In vitro reconstitution of malate-aspartate shuttle showed a similar pattern of activity in the tissues studied. These findings suggest that the activity of malate-aspartate shuttle is expressed differentially in these tissues of mice at different postnatal ages.

Effect of inorganic fertilizers on the development of foot rot disease of soybean caused by Sclerotium rolfsii

Abstract: The effect of soil amendments with chemical fertilizers on the rhizosphere micro flora and on the development of foot rot disease of soybean was studied in-vivo. The fertilizers significantly increased bacteria but reduced fungi (excepting rock phosphate at 0.10 and 0.25%) and actinomycete in soybean rhizosphere. Rock phosphate (0.25%) and urea (0.5%) increased Aspergilli while Znso 4 (0.10 and 0.25%) increased Penicillia in the rhizosphere. Soil amendments initially increased Sclerotium rolfsii population in soil resulting in increased pre-ernergence seed rot. Seedlings which escaped seed rot, delayed symptom expression. Higher concentration (0.5%) of most of the fertilizers used were found to be toxic to the growth and yield of soybean. In field, urea (80 kg/ha) and Znso 4 (10 kg/ha) initially increased S. rolfsii population which decreased slightly at a later stage. A significant reduction in the disease .was recorded with all the fertilizers used, of which Znso 4 produced the best result. Urea (80 kg/ha) and ZnS0 4 (10 kg/ha) stimulated plant growth, which was reflected on the increased plant height and yield as compared to others.

Light-induced biophotonic emission from plant tissues

Abstract: The emission of biophotons in the visible range, following a delay time of 2-200 seconds after exposure to light, has been measured in germinating seeds, roots, flowers, leaves, and cells. It was found that the biophotonic signals are reproducible and light-induced. The observed signals from germinating seeds of Phaseolus aures and decaying leaves of Eucalyptus are presented to show that the signals have characteristic kinetics and intensity. The kinetics of the signal was found to be independent of the stage of growth or decay, though its intensity varied with biological factors. The kinetics in the first minute is characterized by a single exponential decay term while that in the region t less than or equal to 200 s is characterized by two exponentials. The variation in the intensity of the signal with mass, state of hydration, and growth, and the effect of inhibitors in various systems (e.g. leaves, lichen, Chlorella) are reported.

Nitrite metabolism in the cyanobacterium Anabaena cycadeae: Regulation of nitrite uptake and nitrite reductase by ammonia

Abstract: Nitrogen regulation of nitrite uptake and nitrite reductase was studied in the cyanobacterium Anabaena cycadeae and its glutamine-auxotrophic mutant. The development of the nitrite-uptake system preceded, and was independent of, the development of nitrate reductase. The levels of both of the systems were higher in the glutamine auxotroph lacking glutamine synthetase (GS) than in the wild-type strain having normal GS activity. The nitrite-uptake system was found to be constitutive and ammonia-repressible whereas the nitrite-reductase system was ammonia-repressible and nitrite-inducible. Ammonia did not inhibit the nitrite-uptake and nitrite reductase activities in the glutamine auxotroph whereas glutamine did so, suggesting that repression of nitrite-uptake and nitrite reductase systems by ammonia requires the operation of GS and probably involves the participation of some organic nitrogen metabolites like glutamine.