Variations in the plasticity of functional traits indicate the differential impacts of abiotic and biotic factors on the structure and growth of trees in tropical dry forest fragments

Abiotic and biotic factors have considerable impact on the plasticity of plant functional traits, which influences forest structure and productivity; however, their inter-relationships have not been quantified for fragmented tropical dry forest (TDF) ecosystems. We asked the following questions: (1) what are the variations in the plasticity of functional traits due to soil moisture availability in TDF fragments? (2) what are the roles of soil nutrients and forest disturbances in influencing variations in the plasticity of functional traits in the TDF fragments? and (3) how do the variations in the plasticity of functional traits influence the structure and productivity of TDF fragments? Based on linear mixed-effects results, we observed significant variations among tree species for soil moisture content (SMC) under the canopy and selected functional traits across forest fragments. We categorized tree species across fragments by principal component analysis (PCA) and hierarchical clustering on principal components (HCPC) analyses into three functional types, viz., low wood density high deciduous (LWHD), high wood density medium deciduous (HWMD), and high wood density low deciduous (HWLD). Assemblage of functional traits suggested that the LWHD functional type exhibits a drought-avoiding strategy, whereas HWMD and HWLD adopt a drought-tolerant strategy. Our study showed that the variations in functional trait plasticity and the structural attributes of trees in the three functional types exhibit contrasting affinity with SMC, soil nutrients, and disturbances, although the LWHD functional type was comparatively more influenced by soil resources and disturbances compared to HWMD and HWLD along the declining SMC and edge distance gradients. Plasticity in functional traits for the LWHD functional type exhibited greater variations in traits associated with the conservation of water and resources, whereas for HWMD and HWLD, the traits exhibiting greater plasticity were linked with higher productivity and water transport. The cumulative influence of SMC, disturbances, and functional trait variations was also visible in the relative abundance of functional types in large and small sized fragments. Our analysis further revealed the critical differences in the responses of functional trait plasticity of the coexisting tree species in TDF, which suggests that important deciduous endemic species with drought-avoiding strategies might be prone to strategic exclusion under expected rises in anthropogenic disturbances, habitat fragmentation, and resource limitations.

High prevalence of asymptomatic left ventricular diastolic dysfunction and its detection among South Asian patients with Type 2 Diabetes Mellitus compared with White Europeans

Background

Heart failure (HF) is an important manifestation of Type 2 Diabetes (T2D). The development of HF in T2D may be preceded by Stage B HF. Asymptomatic left ventricular impairment, especially left ventricular diastolic dysfunction (LVDD), is a defining early feature of Stage B HF. Detection of Stage B HF is crucial as it provides an opportune target for intervention with cardio-protective therapy to prevent the development of symptomatic HF in T2D. The risk of T2DM is higher in South Asian populations resulting in increased risk of macrovascular and microvascular complications. The prevalence of Stage B HF in South Asian patients with T2DM is not known.

Purpose

(i) To compare the prevalence of Stage B HF in South Asians in India compared with White Europeans in Scotland; (ii) To test the role of NT-proBNP in identifying Stage B HF

Methods

This study involved the comparison between two independently conducted, cross-sectional studies. The patients were asymptomatic patients with T2DM with no prior history of cardiovascular disease from Chennai, India (n=246) and Tayside, Scotland (n=246). All patients underwent transthoracic echocardiogram (echo) examination to detect the presence of structural and functional echo features of Stage B HF: left atrial enlargement (LAE), left ventricular hypertrophy (LVH), LVDD and LV systolic dysfunction (LVSD). Receiver operating curves (ROC) were used to determine the predictive ability of NT-proBNP to predict LAE/LVDD/LVD/LVSD.

Results

The prevalence of Stage B HF was high in South-Asian patients with T2DM (median age of 55 [49, 62] with a high prevalence of LVDD (5% had LVH, 7.3% had LAE, 70% had LVDD and 0% had LVSD (Figure 1B). 10% of the South Asian patients had at least 2 factors contributing to Stage B HF and these patients had higher NT-proBNP titres (703.4 [500.0, 949.2] vs 423.7 [35.0, 754.2], p<0.001). ROC curves show that NT-proBNP can predict these participants with 2 or more echo features [Figure 2B, AUC: 0.7043 (0.6159, 0.7928) p<0.05]. The prevalence of Stage B HF among White Europeans (median age of 67 [61, 72].) was lower compared with South Asian patients: 15% had LVH, 13% had LAE, 19% had LVDD and 2% had LVSD (Figure 1A). 8% of White Europeans had at least 2 factors contributing to Stage B HF and these had higher NT-proBNP titres (368.9 [154.6, 1087.8] vs 186.8 [79.7, 411.5], p=0.02). ROC curves show that NT-proBNP can predict participants with 2 or more factors [Figure 2A, AUC: 0.6399 (0.5122, 0.7676) p<0.05].

Conclusion

Our study has shown that South Asian patients with T2DM have a high prevalence of Stage B HF compared with White Europeans and that the predominant Stage B HF feature is LVDD.

We also found that NTproBNP could potentially be used to detect Stage B HF and help identify at-risk patients for cardio-protective therapy such as SGLT2 inhibitor therapy that has been shown to prevent the development of future HF events.

Funding Acknowledgement

Type of funding sources: None.

DNRA: A short-circuit in biological N-cycling to conserve nitrogen in terrestrial ecosystems

This paper reviews dissimilatory nitrate reduction to ammonium (DNRA) in soils - a newly appreciated pathway of nitrogen (N) cycling in the terrestrial ecosystems. The reduction of NO₃^- occurs in two steps; in the first step, NO₃^- is reduced to NO₂^-; and in the second, unlike denitrification, NO₂^- is reduced to NH₄⁺ without intermediates. There are two sets of NO₃^-/NO₂^- reductase enzymes, i.e., Nap/Nrf and Nar/Nir; the former occurs on the periplasmic-membrane and energy conservation is respiratory via electron-transport-chain, whereas the latter is cytoplasmic and energy conservation is both respiratory and fermentative (Nir, substrate-phosphorylation). Since, Nir catalyzes both assimilatory- and dissimilatory-nitrate reduction, the nrfA gene, which transcribes the NrfA protein, is treated as a molecular-marker of DNRA; and a high nrfA/nosZ (N₂O-reductase) ratio favours DNRA. Recently, several crystal structures of NrfA have been presumed to producee N₂O as a byproduct of DNRA via the NO (nitric-oxide) pathway. Meta-analyses of about 200 publications have revealed that DNRA is regulated by oxidation state of soils and sediments, carbon (C)/N and NO₂^-/NO₃^- ratio, and concentrations of ferrous iron (Fe²⁺) and sulfide (S^2-). Under low-redox conditions, a high C/NO₃^- ratio selects for DNRA while a low ratio selects for denitrification. When the proportion of both C and NO₃^- are equal, the NO₂^-/NO₃^- ratio modulates partitioning of NO₃^-, and a high NO₂^-/NO₃^- ratio favours DNRA. A high S^2-/NO₃^- ratio also promotes DNRA in coastal-ecosystems and saline sediments. Soil pH, temperature, and fine soil particles are other factors known to influence DNRA. Since, DNRA reduces NO₃^- to NH₄⁺, it is essential for protecting NO₃^- from leaching and gaseous (N₂O) losses and enriches soils with readily available NH₄⁺-N to primary producers and heterotrophic microorganisms. Therefore, DNRA may be treated as a tool to reduce ground-water NO₃^- pollution, enhance soil health and improve environmental quality.

Invasive alien plant species: Their impact on environment, ecosystem services and human health

Ecological perturbations caused by biotic invasion have been identified as a growing threat to global sustainability. Invasive alien plants species (IAPS) are considered to be one of the major drivers of biodiversity loss and thereby altering the ecosystem services and socio-economic conditions through different mechanisms. Although the ecological impacts of IAPS are well documented, there is a dearth of studies regarding their economic quantification, livelihood considerations, biotechnological prospects (phytoremediation, bioenergy, phyto-synthesis of nanoparticles, biomedical, industrial applications etc.) and human health risk assessments of IAPS. In this context, the current panoramic review aimed to investigate the environmental, socio-ecological and health risks posed by IAPS as well as the compounded impact of IAPS with habitat fragmentation, climate and land use changes. To this end, the need of an integrated trans-disciplinary research is emphasized for the sustainable management of IAPS. The management prospects can be further strengthened through their linkage with geo-spatial technologies (remote sensing and GIS) by mapping and monitoring the IAPS spread. Further, the horizon of IAPS management is expanded to ecological indicator perspectives of IAPS, biosecurity, and risk assessment protocols with critical discussion. Moreover, positive as well as negative implications of the IAPS on environment, health, ecosystem services and socio-economy (livelihood) are listed so that a judicious policy framework could be developed for the IAPS management in order to mitigate the human health implications.

FT-IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-methyluracil (thymine)

FT-IR (400-4000 cm(-1)) and Raman spectra (200-4000 cm(-1)) of uracil and 5-methyluracil (thymine) have been recorded and analyzed. The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-methyluracil (thymine) by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, most of the B3LYP/6-311++G(∗∗) vibrational frequencies are in excellent agreement with the available experimental assignments and helped to propose in the reassignments of some missing frequencies in experimental study. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a') and non-planar (a″) for all 39 normal vibrational modes of 5-methyluracil are given by 26a'+13a″, of which 30 modes (21a'+9a″) correspond to the uracil moiety and 9 modes (5a'+4a″) to the CH3 group. Consistent assignments have been made for the internal modes of CH3 group, especially for the anti-symmetric CH3 stretching and bending modes. A possible explanation could be the planarity of pyrimidine ring and non-planarity at carbon site of methyl group which might cause the splitting of frequencies including three components due to the substitution of CH3 group at the site of C5 atom on pyrimidine ring of uracil. The three non-equivalent CH bonds of CH3 group are distinctly separated from the CH/NH ring stretching frequencies. Kekule ring stretching mode is found to be comparatively higher frequency magnitude than the mode of uracil due to the involvement of hydrogen bonding of methyl group. But, the ring breathing is found to be lower frequency magnitude compared to those for uracil which could be due to mass effect of the CH3 group in place of the hydrogen atom at the site of C5 atom on pyrimidine ring of uracil.

IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-aminouracil

Infrared (IR) and Raman spectra of uracil and 5-aminouracil have been recorded and analyzed between the region 200-4000 cm(-1). The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-aminouracil by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, the most of B3LYP/6-311++G** vibrational frequencies are in the excellent agreement with available experimental assignments and helped in the reassignments of some fundamental vibrational modes. On the basis of calculated results, the assignments of some missing frequencies in the experimental study are proposed. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a') and non-planar (a″) are given by 25a'+11a″, of which 30 modes (21a'+9a″) correspond to the uracil moiety and 6 modes (4a'+2a″) to the NH2 group. Kekule ring stretching mode is found to be comparatively higher frequency magnitude than the mode of uracil due to the involvement of hydrogen bonding of amino group. But, the ring breathing is found to be lower frequency magnitude compared to those for uracil which could be due to mass effect of the NH2 group in place of the hydrogen atom. All other bands have also been assigned different fundamentals/overtones/combinations.

FT-IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-halogenated uracils (5-X-uracils; X=F, Cl, Br, I)

Raman (200-4000 cm(-1)) and FT-IR (400-4000 cm(-1)) spectra of uracil and 5-halogenated uracils (5-X-uracils; X=F, Cl, Br, I) have been recorded and analyzed in the range 200-4000 cm(-1). The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Ab initio and DFT calculations [using Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP)] were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-halogenated uracils by employing Gaussian-03 program. Gauss View software was used to make the vibrational analysis. Raman and IR spectra have been computed theoretically for the uracil and 5-halogenated molecules. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. Quantum chemical calculations helped in the reassignments of some fundamental vibrational modes. Most of the B3LYP/6-311++G(**) vibrational frequencies are in excellent agreement with available experimental assignments. The ring breathing and kekule stretching modes are found to lower magnitudes compared to those for uracil which could be due to mass effect of halogen atom in place of the hydrogen atom. The C-X (X=F, Cl, Br, I) stretching frequency is distinctly separated from the CH/NH ring stretching frequencies on the pyrimidine ring. All other bands have also been assigned different fundamentals/overtones/combinations.

Biomass estimation of dry tropical woody species at juvenile stage

Accurate characterization of biomass in different forest components is important to estimate their contribution to total carbon stock. Due to lack of allometric equations for biomass estimation of woody species at juvenile stage, the carbon stored in this forest component is ignored. We harvested 47 woody species at juvenile stage in a dry tropical forest and developed regression models for the estimation of above-ground biomass (AGB). The models including wood-specific gravity (ρ) exhibited higher R² than those without ρ. The model consisting of ρ, stem diameter (D), and height (H) not only exhibited the highest R² value but also had the lowest standard error of estimate. We suggest that ρ-based regression model is a viable option for nondestructive estimation of biomass of forest trees at juvenile stage.

FTIR and Raman spectra and fundamental frequencies of 5-halosubstituted uracils: 5-X-uracil (X=F, Cl, Br and I)

FTIR and Raman spectra of 5-halosubstituted uracils (5-X-uracil; X=F, Cl, Br and I) were recorded in the region 200-4000cm(-1). Assuming under the C(s) point group, the distribution of normal mode of vibrations between the two species as planar (a') and non-planar (a″) are given by 21a'+9a″, of which also correspond to the 30 modes of uracil moiety and the electro negativity of halogen group substitution causes some where mixing/shifting in their modes with other modes. The ring breathing and kekule stretching modes are observed in lower magnitudes compared to those of uracil which could be due to mass effect of halogen atom in place of the hydrogen atom. The C-X (X=F, Cl, Br and I) stretching frequency is distinctly separated from the CH/NH ring stretching frequencies on the pyrimidine ring. All other bands have also been assigned different fundamentals/overtones/combinations.

Impact of post-mining subsidence on nitrogen transformation in southern tropical dry deciduous forest, India

The goal of our research was to assess the impact of post-mining land subsidence, caused due to underground coal mining operations, on fine root biomass and root tips count; plant available nutrient status, microbial biomass N (MBN) and N-mineralization rates of a Southern tropical dry deciduous forest of Singareni Coalfields of India. The changes were quantified in all the three (rainy, winter and summer) seasons, in slope and depression microsites of the subsided land and an adjacent undamaged forest microsite. Physico-chemical characteristics were found to be altered after subsidence, showing a positive impact of subsidence on soil moisture, bulk density, water holding capacity, organic carbon content, total N and total P. The increase in all the parameters was found in depression microsites, while in slope microsites, the values were lower. Fine root biomass and root tips count increased in the subsided depression microsites, as demonstrated by increases of 62% and 45%, respectively. Soil nitrate-N and phosphate-P concentrations were also found to be higher in depression microsite, showing an increase of 35.68% and 24.74%, respectively. Depression microsite has also shown the higher MBN value with an increase over control. Net nitrification, net N-mineralization and MBN were increased in depression microsite by 29.77%, 25.72% and 34%, respectively. There was a positive relation of microbial N with organic C, fine root biomass and root tips.

FTIR and raman spectra compared with ab initio calculated frequency modes for 5-aminouracil

Infrared (IR) and Raman spectra of 5-aminouracil were recorded in the region 200-4,000 cm(-1). Assuming under the C(s) point group that the distribution of the normal mode of vibrations between the two species are planar (a') and non-planar (a''), given by 25a' + 11a'' of which 30 modes (21a' + 9a'') correspond to the uracil moiety and six modes (4a' + 2a'') correspond to the NH(2) group, with a comparison of theoretically ab initio calculated frequencies, the results are in reasonably good agreement with the experimental IR and Raman spectra. Consistent assignments have been made for the internal modes of the NH(2) group, especially for the anti-symmetric NH(2) stretching and bending modes. The non-equivalence of the two NH bonds of the NH(2) group suggests a difference in the strength of the two hydrogen bonds on the pyrimidine ring. Symmetry and anti-symmetry NH stretching modes of the NH(2) group show the invalidity of the empirical relationship. These two NH(2) stretching frequencies are distinctly separated from the CH/NH ring stretching frequencies. A strong and sharp IR band that acts at 3,380 cm(-1) could be identified as the anti-symmetric NH(2) mode whereas the band at 3,290 cm(-1) smaller density could be identified as the symmetric NH(2) stretching mode.

Comparison of community composition and species diversity of understorey and overstorey tree species in a dry tropical forest of northern India

The study focuses on understorey-overstorey plant community dynamics in a dry tropical forest to facilitate appropriate management decisions. We compare community composition and species diversity of the understorey vegetation among five dry tropical forest sites in northern India. A total of 1500 quadrats distributed over 15 one-ha permanent plots in five sites differing in the degree of disturbance, were used to enumerate the understorey tree species and the results were compared with overstorey tree layer. The non-metric multidimensional scaling (NMS) ordination revealed that human disturbance intensity, as well as the overall disturbance regimes, and soil water holding capacity controlled the organisation of dry tropical forest understorey composition through effects on soil organic matter. The alpha-diversity and its components decreased with increasing human disturbance intensity, reflecting utilisation pressure and decreased soil fertility, as also revealed by the analysis of overstorey tree layer. There was a significant positive relationship between overstorey and understorey diversity. Results suggest that in the future, the existing understorey tree communities may replace the current dry tropical forest communities under prevailing environmental conditions. The study also asserts that the rate of species accumulation will be greater in more disturbed sites as well as at small spatial scale within each disturbance level.

RETRACTED: Contrasting pattern of methanotrophs in dry tropical forest soils: Effect of soil nitrogen, carbon and moisture

Population dynamics of methane-oxidizing bacteria (MOB) was measured for 2 consecutive years for four forest and one savanna sites in seasonally dry tropical regions of India. The soils were nutrient-poor and well drained. These sites differed in vegetational cover and physico-chemical features of soils. There were significant differences in MOB population size during the 2 years (mean 0.40 and 0.48 x 10(5) cells g(-1) dry soil), and at different sites (mean 0.38-0.59 x 10(5) cells g(-1) dry soil). The mean population size of MOB was higher (P<0.05) in dry seasons than in the rainy season at all the sites. There was a significant season and site interaction, indicating that the effect of different seasons differed across the sites. There was a positive relation between soil moisture and MOB population size during summer (the driest period) and a negative relation during the rest of the year. The number of MOB was consistently higher for the Kotwa hill base site than rest of the sites having higher soil organic C and total N. The results suggested that in seasonally dry tropical forests the moisture, C and N status of the soil regulates the population size of MOB (methanotrophs) in the long term.

Dynamics of viable nitrifier community, N-mineralization and nitrification in seasonally dry tropical forests and savanna

The study was conducted in Vindhyan region, to assess the N-mineralization, nitrification and size of viable community of ammonium- and nitrite-oxidizing bacteria as affected by different sites and seasons. Six different ecosystems (four forests and two savannas), which differ in terms of topography, vegetation and moisture status, were selected for the present study. The soils of the study sites differ significantly in its physico-chemical properties. The savanna site had significantly higher pH (7.2), bulk density (1.37 g cm(-3)) and silt content (67.80%) but lower water holding capacity (1.37%), total-C (16,356 microg g(-1) dry soil), N (1090 microg g(-1) dry soil) and P (213 microg g(-1) dry soil) than forest sites. The soil moisture content, N-mineralization, nitrification rates and numbers of ammonium- and nitrite-oxidizing bacteria were highest in the wet season and lowest in dry season, while the size of mineral-N (NH4(+)-N and NO3(-)-N) showed a reverse trend at the sites. The N-mineralization, nitrification and nitrifier population size differ significantly across the site and season. The numbers of free-living cells of ammonium- and nitrite-oxidizing bacteria were significantly related to each other and to N-mineralization, nitrification, soil moisture and mineral-N components. The N-mineralization, nitrification and the viable number of nitrifying cells were consistently higher for forest soils compared to savanna sites. It was concluded that soil microbial process (N-mineralization and nitrification) and nitrifier population size were dependent on site topography, vegetation cover and soil moisture status.

Cyanobacteria in Antarctica: ecology, physiology and cold adaptation

Cyanobacterial species composition of fresh water and terrestrial ecosystems and chemical environment of water in Schirmacher Oasis in Continental Antarctica was investigated. Over 35 species of cyanobacteria were recorded. Diazotrophic species both heterocystous and unicellular contributed more than half to the count except in lake ecosystem. The species composition varied among the fresh water as well as terrestrial ecosystems. The physico-chemical analyses of water revealed its poor nurient content which might have supported the growth of diazotrophic cyanobacteria in an Antarctic environment. Among the cyanobacteria Oscillatoria, Phormidium and Nostoc commune were the dominant flora in most of the habitats. The physiological characteristics of isolated cyanobacteria strains indicated that N2-fixation, nitrate uptake, nitrate-reduction, ammonium-uptake, GS-transferase activity and photosynthesis was unaffected at low temperature (5 degrees C) which indicated low temperature adaptation for Antarctic cyanobacteria. This phenomenon was not evident in different strains of tropical origin. The temperature optima for N2-fixation for the different Antarctic cyanobacterial strains was in the range of 15-25 degrees C, nearly 10 degrees C lower than their respective reference strains of tropical origin. Similar results were obtained for cyanobacteria-moss association. The low endergonic activation energy exhibited by the above metabolic activities supported the view that cyanobacteria were adapted to Antarctic ecosystem.

Medical ethnobotany of the tribals of Sonaghati of Sonbhadra district, Uttar Pradesh, India

The present ethnobotanical exploration study presents the folk medicinal uses of certain plants by tribes of the Sonbhadra district in the Uttar Pradesh state of India. One hundred and twenty five plants from 57 families, which are therapeutically used against different diseases, such as cough, cold, dysentery, diarrhoea, ulcers, diabetes, male and female weakness, snake-bite and skin disorders are covered in this report. Part of the plant used, dosage and the mode of drug administration in different ailments are described.

Effect of leaf habit and soil type on nutrient resorption and conservation in woody species of a dry tropical environment

We examined 90 dry tropical tree species growing on contrasting soil types (relatively infertile Ultisol and more fertile Inceptisol) for leaf traits such as leaf habit, specific leaf mass (SLM, leaf dry mass per leaf area), leaf chemistry (nutrient concentrations and C/N ratios), and nutrient resorption. Across the species, SLM ranged from 4.06 to 15.74 mg·cm–2 in mature leaves and from 2.60 to 15.12 mg·cm–2 in senesced leaves. Mature leaf N and P concentrations varied from 0.86% to 4.11% and 0.13% to 0.21%, respectively. Senesced leaf N concentrations varied from 0.49% to 1.90% and P from 0.04% to 0.47%. Resorption efficiencies varied from 26% to 83% (mean = 58.32% ± 1.20%) for N and from 16% to 80% (mean = 49.57% ± 1.48%) for P indicating that the woody species of dry tropical environments resorbed different nutrients in substantial amounts to support new growth. Deciduous species had greater resorbed nutrient pools and resorption efficiencies than evergreen species. Compared with the nutrient-rich environment, species from the nutrient-poor environment had a lower resorbed P pool and lower resorption efficiencies for N and P, but had similar N and P concentrations in mature leaves. Resorption efficiencies for C, N, and P were generally correlated, suggesting that the resorbed C pool acted as a vehicle for mobilizing nutrients, especially N. Species with a low or high C/N ratio in senesced leaf and a low or high N resorption efficiency occurred in both nutrient-poor and nutrient-rich environments, as well as among deciduous and evergreen leaf habits, indicating individualistic adaptations to optimize the efficiency of nutrient resource use and conservation of the dry tropical woody vegetation.Key words: leaf chemistry, leaf traits, resorption efficiency, resorbed nutrient pools, substrate-quality stability.

Overexpression of the retinoic acid-responsive gene Stra6 in human cancers and its synergistic induction by Wnt-1 and retinoic acid

Genetic defects in the Wnt-1 signaling pathway contribute to human tumor progression and are especially prevalent in colorectal cancer. We screened mouse C57MG cells to isolate mRNAs induced by Wnt-1 and identified Stra6, an mRNA known to be up-regulated by retinoic acid. Up-regulation of Stra6 mRNA was also observed in hyperplastic mammary tissue and mammary gland tumors from transgenic mice expressing Wnt-1 and in human tumors that frequently harbor defects in Wnt-1 signaling. Stimulation of C57MG cells with retinoic acid plus Wnt-1 resulted in expression of Stra6 transcript to levels greatly exceeding that observed with either stimulus alone. This synergy could be explained in part by the up-regulation of retinoic acid receptor-gamma that was observed in response to Wnt-1 signaling. Accordingly, treatment of human colorectal cancer cell lines with retinoic acid resulted in the up-regulation of Stra6 mRNA and accumulation of Stra6 protein at the cell membrane. The data support a model in which Wnt-1 signaling synergizes with retinoids to activate retinoic acid receptor-gamma-responsive genes in human cancers.

Methane consumption by soils of dryland rice agriculture: influence of varieties and N-fertilization

Growth of three rice varieties (Heera, Dhala Heera and Narendra-118) and their relationship with methane consumption was investigated under rainfed (dryland) condition. Overall methane flux rates ranged between -0.58 to 1.25 mg m(-2) h(-1) across varieties, treatments, and dates of measurements. Except for two days when soil was saturated, the soil consumed 0.05-0.58 mg CH4 m(-2) h(-1); these rates were inversely related with soil moisture. N-fertilization reduced consumption rates. Although all plant growth parameters, except for number of tillers, exhibited relationship with methane consumption in control plots, only root porosity did so in fertilized plots. Combinations of plant growth characteristics explained 74-92% variability in seasonal CH4 consumption in unfertilized plots. It was concluded that methane consumption by dryland soils was influenced by rice variety, soil moisture and nitrogen fertilization.

Tetranitromethane as a surface antiviral disinfectant

Tetranitromethane, a protein nitrating agent, was tested for its ability to disinfect surfaces from viruses. Different surfaces on commercially available pocket calculators were pretreated with either the Indiana strain of vesicular stomatitis virus or the Herts' strain of Newcastle disease virus. The calculators surfaces were then sprayed with either tetranitromethane or control solutions. The calculators were incubated for 30 min at ambient temperature, and then the surfaces were wiped with sterile swabs. The swabs were placed into test tubes containing phosphate-buffered saline. Samples of the phosphate-buffered saline were then titered on appropriate cell lines by plaque assay. The results indicated that the amount of vesicular stomatitis virus and Newcastle disease virus recovered from the tetranitromethane-treated surfaces was dramatically decreased compared to the amount of virus recovered from control-treated surfaces. These data suggest that tetranitromethane may be useful to disinfect surfaces from both enveloped and non-enveloped RNA viruses.

Essential amino acids involved in glucan-dependent aggregation of Streptococcus sobrinus

The active site of the glucan-binding lectin (or agglutinin) (GBL) of Streptococcus sobrinus was probed by specific amino acid modifying reagents. Reagents specific for carboxylates, imidazolium, phenolic, and lysyl residues inactivated the cell bound GBL, whereas agents specific for sulfhydryl, disulfide, and guanidinium groups had no effect on the lectin. A low molecular weight alpha-(1-->6)-glucan provided partial protection against the reagents which inactivated the protein, whereas an alpha-(1-->4)-glucan, incapable of complexing with the lectin, afforded no protection. A reagent specific for tryptophan, 2-hydroxy-5-nitrobenzyl bromide (HNB) did not cause a loss of GBL activity, although N-bromosuccinimide, a reagent capable of oxidizing tryptophan and less selective than HNB, was a very effective inhibitor of the glucan-dependent cellular aggregation. In the latter case, alpha-(1-->6)-glucan did not protect. Hydroxylamine partially restored the loss of lectin activity due to treatment of the cells with N-acetylimidazole (highly specific for tyrosine), glycine methyl ester plus water-soluble carbodiimide (specific for carboxylates), and diethylpyrocarbonate (specific for histidine). Because the soluble form of GBL rapidly loses activity when purified, it was necessary to perform the chemical modification of the amino acid side chains employing the cell-bound form of the lectin. Because specific ligand [alpha-(1-->6)-glucan] protected against the inactivation of the agglutinin by selected reagents and because lectin activity could be restored in some cases, it was possible to identify likely essential amino acid residues needed for glucan binding. The results, taken together, suggest that aspartic (and/or glutamic) acid, histidine, lysine, and tyrosine are critical amino acids responsible for agglutinin activity. Present efforts are directed to the design and synthesis of glucan analogues which may serve as affinity inactivating agents of the lectin. Such glucan derivatives may be of value in studies on the role of the lectin in cariogenesis.

Influence of rainfall and grazing on belowground biomass dynamics in a dry tropical savanna

Root biomass and its variation with time and soil depth were studied in ungrazed and grazed treatments, in a seasonally dry tropical savanna. A greater proportion of belowground biomass was located in the 0 – 10 cm soil depth in the rainy season compared with the summer season. In contrast, in the 10 – 50 cm soil profile, belowground biomass was greater in summer than in the rainy season. Peak belowground biomass in ungrazed savanna was not correlated to the rainfall in the early part of the rainy season, but it was correlated to total rainfall received in the later part of rainy season. Apparently the belowground component responds quickly to the rainfall events and generates growth pulses in the aboveground vegetation. Peak canopy biomass increased rapidly with the increase in peak belowground biomass and then plateaued, indicating a greater potential for accumulation of biomass belowground than aboveground. Grazing reduced belowground biomass by 41 – 55%. Maximum reduction occurred in the heavily grazed savanna. Peak belowground biomass was inversely related to grazing intensity. Key words: belowground biomass, grazing intensity, phased root growth, rainfall variability, tropical savanna.

Chelating agents inhibit activity and prevent expression of streptococcal glucan-binding lectins

Several of the cariogenic mutans streptococci produce cell wall-associated glucan-binding lectins (GBLs). The lectins bind alpha-1,6-linked glucans and have no affinity for other polysaccharides or anomeric linkages. When citrate or lactate was included in the growth medium, expression of the activities of the GBLs of Streptococcus cricetus and S. sobrinus was prevented. Furthermore, chelating agents, including citrate, lactate, EDTA, and acetylacetone, were able to reversibly inhibit glucan-induced aggregation of GBL+ streptococci. In addition, the chelating agents prevented sucrose-dependent streptococcal adhesion to glass surfaces and dispersed preformed adherent masses of the streptococci. Neither citrate nor other chelating agents modified the activities of glucosyltransferases. Expression of the lectin could only be achieved by the addition of manganous ion to the growth medium. Chloramphenicol and other metabolic inhibitors prevented synthesis of GBL in cells obtained from manganese-deficient medium and shifted to manganous ion-sufficient medium. The GBL may be a manganoprotein, the manganese of which may be perturbed, but not removed, by chelating agents. During synthesis of the GBL, manganous ion may be required in order for the protein to achieve an active conformation. Citrate or other chelating agents may have promise as anticaries agents.

Insulin-like growth factor I and II gene expression in Balb/C mouse liver during postnatal development

We studied the developmental shift from IGF-II to IGF-I mRNA synthesis in Balb/C mouse liver. IGF-I mRNA levels were low at birth, increased with age to peak at weaning, and IGF-I gene expression again increased during puberty. IGF-II expression was high during early postnatal development, but became nondetectable at weaning. Thus in early life there is a reciprocal relationship of rising IGF-I and falling IGF-II mRNA. Northern analysis revealed four IGF-I mRNA transcripts ranging from 1.1-7.0 kb, with the 1.1 kb being the most prominent. Five IGF-II transcripts ranging from 1.7-4.0 kb were found, with the 4.0 kb being the most prominent. The pattern of Serum IGF-I and IGF-II values paralleled liver IGF-I and IGF-II mRNA levels.