Showing papers by "North Eastern Hill University published in 1988"

Aqueous extract of betel-nut of north-east India induces DNA-strand breaks and enhances rate of cell proliferation in vitro. Effects of betel-nut extract in vitro.

Abstract: An aqueous extract of betel-nut has been found to be able to induce strand breaks in DNA of mouse kidney cells in vitro. It has been also found to be able to enhance the rate of cell division at a dose of 100 μg/ml while a higher dose of 250 μg/ml was extremely toxic to the cells. Compared with arecoline (10 μg/ml), the aqueous extract of betel-nut seems to be a more potent carcinogen to mouse kidney cells in vitro.

Chromosomes and sex determination in 13 araneid spiders of North-Eastern India

Abstract: The diploid chromosome number of 13 species belonging to the family Araneidae (Araneae) ranges between 16 and 25. The ♂ sex-determining mechanism seems to be X1X2X3X4O in one species; X1X2X3O in three species and X1X2O in the remaining 9 species. The X1X2X3X4O, ♂ sex-determining mechanism is reported for the first time in spiders. All the chromosomes are with terminal centromeres. C-band preparations in 5 species suggest procentric localization of constitutive heterochromatin in all the chromosomes, though distally located C-band positive blocks are also visible in a few chromosomes. It is suggested that chromosomal evolution in this family has taken place by gradual reduction in diploid number through tandem/centric fusion followed by pericentric inversion in autosomes and nondisjunction/duplication of one X, with subsequent loss of homology in sex chromosomes.

Vegetation, biomass and productivity of seral grasslands of Cherrapunji in north-east India

Abstract: This study deals with the composition of vegetation, biomass and productivity of four different grassland types at Cherrapunji, India. Varied levels of degradation of the climax mexed evergreen forest are represented by these grasslands. Where the soil profile is deep, the grasslands are maintained through frequent fire. At each site, belowground production is more than double aboveground production. Annual turnover rates for the belowground biomass in these grasslands are more dynamical than their temperature counterparts. These grasslands are maintained under high stress conditions of thin soil cover, highly leached nutrient-deficient soils, frequent fires, and low soil moisture retention in spite of a high annual rainfall of 10372 mm.

Enzyme activities in soils: Effects of leaching, ignition, autoclaving and fumigation

Abstract: Cette etude montre qu'il y a au moins trois sites d'activite enzymatique dans le sol A l'interieur des cellules, sur la surface des colloides argilo-humiques et dans la solution du sol Les cellules representent la majeure partie des activites dehydrogenase et urease Les enzymes extracellulaires adsorbees sur les colloides argilo-humiques sont responsables de la majeure partie de l'activite de la phosphatase Les enzymes de la solution du sol representent une tres faible fraction de l'activite enzymatique totale

Effect of assam crude on photosynthesis and associated electron transport system in Anabaena doliolum.

Abstract: It has been suggested that the toxic effects of oils possibly occur either on photosystem I (PS I) or II (PS II) of the Z scheme, or perhaps but less likely, on the CO/sub 2/ fixation side of photosynthesis. The primary effect of petroleum may be through direct action on the energy yielding electron transport system. Since no information is available establishing the action of oils on PS I or II, or on the redox coupling between the two photosystems, the present study was undertaken. The influence of Assam crude on photosynthetic O/sub 2/ evolution as well as upon its electron transport system in Anabaena doliolum, a heterocystous blue-green alga (cyanobacterium), has been examined. A. doliolum and other heterocystous cyanobacteria are widely distributed in soil and aquatic ecosystems, and represent an important group of free-living, nitrogen fixing microorganisms.

Raman scattering and vibrational relaxation studies of N, N‐dimethylformamide

Abstract: The Raman band of the amide I vibrational mode of N, N-dimethylformamide was studied in the neat liquid and as a function of solvent concentration. The non-coincidence effect (anisotropy shift) is explained in terms of transition dipole-transition dipole interactions. The vibrational relaxation rate has been shown to be linearly dependent on the product of the density, viscosity and a dispersion energy-dependent term, for which a theoretical basis is outlined.

Achene germination of Parthenium hysterophorus L.: effects of light, temperature, provenance and achene size

Abstract: Summary: Resume: Zusammenfassung Ray achenes of Parthenium hysterophorus L. from widely separated localities showed a positive relationship between length and weight, and those from northern India (higher latitude) were heavier than those from the south (lower latitude). The achenes germinated well in continuous light and in the dark, but maximum germination was obtained with a 10-h photoperiod. Increasing duration of light pretreatment from 6 to 48 h resulted in greater subsequent germination in the dark. The achenes germinated over a wide range of alternating temperature regimes, but achieved maximum percentage germination at 25–30°C/15–20°C. Despite significant quantitative variation, the overall germination behaviour of achenes of different sizes was similar, although large achenes always gave higher germination than small ones. Germination was significantly influenced by seed source. The north Indian populations showed higher percentage germination than those from south India. The patterns of response of achenes of different provenances to light and alternating diurnal temperatures were slightly different. Germination des akenes de Parthenium hysterophorus L.: effets de lu lumiere, temperature et de la taille et origine des akenes Des akenes de Parthenium hysterophorus L. issus de localites tres largement eloignees ont montre une correlation positive entre la longueur et le poids; ceux du nord de l'Inde (latitude plus elevee) etaient plus lourds que ceux du sud (latitude plus basse). Les akenes ont bien germes tant en lumiere continue, qu'a l'obscurite, mais le maximum de germination a ete observe sous une photoperiode de 10 heures. Une augmentation d'une preexposition a la lumiere de 6 h a 48 h aboutit ensuite a une plus grande germination a l'obscurite. Les akenes ont germe sur un tres large eventail de regimes de temperatures alternees mais on a obtenu le maximum de pourcentage de germination a 25–30°C/15–20°C. En depit de variations quantitatives significatives, le comportement general de germination des akenes de tailles differentes a ete comparable, meme si les grands akenes germent toujours mieux que les petits. La germination est influencee de facon significative par la provenance de la graine. Les populations du nord de l'Inde expriment un pourcentage de germination plus eleve que celles du sud. Les comportements de reponse des akenes de differentes provenances a la lumiere, et aux temperatures diurnes ont ete legerement differentes. Keimung der Achanen von Parthenium hysterophorus L.: Wirkung von Licht, Temperatur und Herkunft sowie Grosse der Achanen Die Achanen von Parthenium hysterophorus L. von weit voneinander liegenden Orten zeigten ein positives Langen-Gewicht-Verhaltnis, wobei sie in Nordindien schwerer waren als im Suden. Die Achanen keimten im Dauerlicht und im Dunkeln gut, aber bei 10stundiger Lichtperiode am besten. Wenn sie zunachst einer von 6 bis auf 48 h gesteigerten Licht-Behandlung unterworfen wurden, keimten sie im Dunkeln besser. Die Achanen keimten uber eine weite Spanne wechselnder Temperatur; die maximale Keimrate wurde bei 25–30/15–20°C gefunden. Trotz signifikanter Unterschiede war die Keimung verschieden grosser Achanen im grossen und ganzen ahnlich, wenn auch die grossen immer starker als die kleinen keimten. Die Keimung war signifikant von der Herkunft beeinflusst: Die Achanen aus Nordindien hatten eine grossere Keimrate als die aus dem Suden. Das Verhalten der Achanen verschiedener Herkunft gegenuber Licht und wechselnder Tagestemperatur war wenig unterschiedlich.

Ecological implications of traditional weeding and other imposed weeding regimes under slash‐and‐burn agriculture (jhum) in northeastern India

Abstract: Summary Traditional weeding in slash-and-burn agriculture (jhum) in northeastern India involves the retention of a certain proportion of weed biomass in situ By comparing this weed management practice with total weeding and no weeding, the economic and ecological efficiency of this agroecosystem has been assessed It is concluded that traditional weeding has little effect on the yield potential of the crop mixture compared with total weeding but it could lead to conservation of soil resources by up to about 20% Indeed, harvested weed biomass put back into the system is an efficient way of recycling resources under stress Resume Implications ecologiques du desherbage traditionnel et d'autres systemes en mode de conduite avec ecobuage (Jhum) dans le Nord-Est de I'Inde Le desherbage traditionnel dans l'agriculture avec ecobuage (Jhum) dans le Nord Est de l'Inde entraine le maintien d'une certaine proportion in situ de la biomasse adventice En comparant cette methode de controle des adventices, avec le desherbage total ou le non desherbage, les efficacites economique et ecologique de cette agroecosysteme ont eteevaluees On a conclu que le desherbage traditionnel avait un petit effet sur le rendement potentiel de la culture compare au desherbage total, mais qu'il pouvait conduire a une conservation des ressources du sol jusqu'a plus de 20% En effet, la biomasse d'adventices recoltee retournant dans le systeme est un moyen efficace de recyclage des ressources Zusammenfassung Okologische Auswirkungen traditioneller und neuerer Methoden der Unkrautbekampfung bei der Brandkultur Jhum in Nordost-Indien Die herkommliche Unkrautbekampfung in der Brandkultur Jhum in Nordost-Indien fuhrt dazu, dass ein bestimmter Teil der Unkrautbiomasse auf dem Feld bleibt Im Vergleich dieser Methode zu vollstandiger oder fehlender Unkrautbekampfung wurden der okonomische Nutzen und die okologische Leistung dieses Agrookosystems mit dem Ergebnis bestimmt, dass die herkommliche Unkrautbekampfung im Gegensatz zur vollstandigen Bekampfung den Ertrag wenig steigert, aber den Nahrstoffgehalt des Bodens um bis zu 20% anheben kann, denn mit der auf dem Feld verbleibenden Unkrautbiomasse werden knappe Nahrstoffe wirksam ruckgefuhrt

Diurnal variation in renal and extra-renal excretion of ammonia-N and urea-N in a freshwater air-breathing teleost, Heteropneustes fossilis (Bloch)

Abstract: Diurnal pattern of excretion of ammonia-N and urea-N through the renal and extra-renal sources were studied in a freshwater air-breathing teleost,Heteropneustes fossilis in its aquatic medium. Ammonia-N was the major nitrogen excretory product, however, the rate of excretion of urea-N was comparatively higher than other freshwater teleosts. Almost all ammonia-N (>99%) and about 75% of urea-N were excreted through the extra-renal sources. The excretion rate of urea-N was about 10 times higher than ammonia-N through the renal and ammonia-N was 7–8 times higher than urea-N through extra-renal sources. Existence of a functional ornithine-urea cycle reported inHeteropneustes fossilis has been suggested to be the reason for this increased rate of urea excretion. Nitrogen excretion (total ammonia-N + urea-N) during the night was significantly higher than the day. A higher rate of nitrogen metabolism at night has been suggested forHeteropneustes fossilis which has been reported to be nocturnal in habit.

Crystal structure of the substituted apatites — deviation from Vegard's Law

Abstract: The substituted apatites Ca10(PO4)6(1−x)(VO4)6x(OH)2 and Pb10(PO4)6(1−x)(VO4)6x(OH)2, where x is the fraction of vanadate, were prepared in the powdered microcrystalline nature. The X-ray diffraction patterns and the infrared spectra of these substituted apatites were recorded. The analysis of the measurements established that the unit cell parameters did not vary smoothly with the degree of substitution as expected by the Vegard's Law. Two different types of linear behaviour in the two regions 0 to 50% and 50 to 100% were present. Hence, this implies the inadequacy of the Vegard's Law when applied to the whole range of substitutions.

Tracks of 18.56 MeV/u40Ar ions in lexan polycarbonate detector

Abstract: Latent damage tracks of energetic40Ar ions (18·56 MeV/u) have been recorded in Lexan polycarbonate detector. Bulk and track-etch parameters are evaluated under successive chemical etching. Our results show a linear correlation between the measured track-etch rate along the track and the corresponding total energy-loss rate and predict a threshold value of 5·0 MeV mg−1 cm2 for track registration. Maximum etchable track lengths of40Ar ions as a function of energies have also been measured and compared with three different sets of theoretical ranges.

Regulation of urea-uptake in the cyanobacterium Anabaena doliolum

Abstract: The utilization of urea was studied in the cyanobacterium Anabaena doliolum. The uptake of urea was unaltered in the presence of ammonium. The cells receiving ATP exogenously showed an induced level of urea-uptake as compared with the control cells. Urease inhibitor acetohydroxamic acid and hydroxyurea as well as glutamate analogue, MSO, did not affect the uptake of urea. These results suggest: (1) urea and ammonia have different uptake sites, (2) urea-uptake is an energy dependent process, and (3) during short-term experiments, urea uptake is not linked with the enzyme urease or the ammonium assimilating enzyme glutamine synthetase.

Copper(II) Complexes of Acyldihydrazones

Abstract: Copper(II) complexes of disalicylaldimine oxamide (H4A), malonamide (H4B), succinamide (H4C), glutaramide (H4D), adipamide (H4E), and phthalamide (H4F) have been synthesized in aqueous-alcoholic media and characterized by elemental analyses, thermoanalytical data, decomposition temperature, magnetic moments, infrared and electronic and electron spin resonance spectral studies. All the complexes were found to have the compositions Cu2(L)nH2O (where H4L = H4A, H4B, H4C, H4D, H4E, and H4F, n = 2 and 4). These complexes possess square pyramidal configuration except disalicylaldimine oxamido and phthalamido complexes which possess tetragonally distorted octahedral stereochemistry. All the complexes show sub-normal magnetic moments. The magnetic moments coupled with powder ESR spectra in the solid state at room temperature indicate strong metal-metal interaction. The infrared spectra reveal that the ligands react in the enol form as tetrabasic hexadentate ligands. On the basis of the magnitude of shift...

Toxicity of some oil constituents to Selenastrum capricornutum

Abstract: The toxicity of some oil constituents, viz., benzene, toluene, xylene, naphthalene, methylnaphthalene, dimethylnaphthalenes, trimethylnaphthalene, phenol, cresol, aniline and toluidine towards S. capricornutum was investigated. All constituents exerted detrimental effects on algal growth and toxicity depended inter alia on the number of methyl groups in the test chemicals. Aniline, toluidine and alkylnaphthalenes were most toxic to test alga and if present at a high concentration in an oil, the toxic effects of that oil would be very severe.

Metabolic changes associated with akinete germination in the cyanobacterium Anabaena doliolum

Abstract: summary The energy requirements of akinete germination in A. doliolum were met initially from aerobic oxidation of endogenously stored carbon reserve. The germination of non-photosynthetic akinetes commenced in light with new protein synthesis followed by the simultaneous development of oxygenic photosynthesis, nitrate reductase activity, glutamine synthetase activity and aspartate dehydrogenase (AsDH) activity by 24 h and heterocyst formation and nitrogenase activity by 60 h. Glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) activities were present in mature akinetes and only GPT activity increased during akinete germination. The simultaneous appearance during the course of germination of oxygenic photosynthesis, nitrate reductase activity and glutamine synthetase activity much before that of N2 fixation, implies that oxygenic photosynthesis is more closely associated developmentally with carbon dioxide and nitrate assimilation than with N2 assimilation. The activities of the transaminases (GOT and GPT) during the initial stages of germination suggest a significant role for these enzymes in amino-acid metabolism associated with germination. The appearance of nitrate reductase activity under N2-fixing conditions, in the absence of nitrate, suggests that the nitrate assimilating enzyme is not nitrate inducible.

Synthesis, characterization and structural assessment of nitrato, chloro, bromo, perchlorato, thiocyanato and sulphato mono-(benzoin thiosemicarbazonato) copper(II) complexes

Abstract: Some copper(II) complexes of the type Cu(HL)X·nH2O (where H2L = benzoin thiosemicarbazone; X=NO3; Cl, Br, SCN, ClO4 or 1/2SO4; n=O−2) have been prepared and characterized. All complexes have tetragonally distorted octahedral stereochemistry except the sulphatocomplex which is square pyramidal. The i.r. spectra reveal that HL acts as a monobasic tridentate ligand coordinating through the azine group nitrogen atom, thiocarbonyl sulphur atom and hydroxylic oxygen atom while NO3, Cl, Br and ClO4 act as terminal monodentate ligands and SCN and SO4 act as bidentate bridging ligands. The polycrystalline e.s.r. spectra suggest tetragonal symmetry for the copper(II) ion, involving a dx2−y2 ground state.