Effect of legume-based cropping systems on nitrogen mineralization potential of Vertisol

The quantity and patterns of net mineralization of soil nitrogen (N) were studied in Vertisols under different cropping systems in the semi-arid tropical areas. Eight cropping systems were selected; three contained pigeonpea (PP), one contained PP and cowpea (COP), and two contained chickpea (CP) as legume component crops, one included sequence cropping with nonlegumes during the rainy and postrainy seasons, and one system was kept fallow (F) during the rainy season and sown to sorghum (S) during the postrainy season. Cropping systems with PP as a component crop increased mineralizable N(N _o ) content two-fold in the soil compared with fallow + sorghum (F+S)–F+S system. The N mineralization rate constant (k) was not significantly affected by previous cropping history of the soil; however, a numerically higher rate constant was observed in the COP/PP intercrop, followed by sequential S+safflower (SF) system as compared to the other soils. Mineral N accumulation curves for six soils were more accurately described by the exponential model than the linear model. The active N fraction (N _o /N_tot %) varied between 8 and 16% for different systems and a direct relationship was observed between N _o /N_tot and total N for the soils under diverse cropping systems.ICRISAT JA (1638)     

Caspase-dependent and -independent cell death induced by 3-nitropropionic acid in rat cortical neurons

Mitochondria play a critical role in cell death by releasing apoptogenic factors, such as cytochrome c and apoptosis-inducing factor (AIF), from the intermembrane space into the cytoplasm. Because mitochondrial dysfunction has been shown to be involved in several neurodegenerative diseases, mitochondrial toxins are largely used to model these disorders. These include 3-nitropropionic acid (3-NP), an irreversible inhibitor of succinate dehydrogenase, which has been used to model Huntington's disease and was previously reported by us to induce apoptotic cell death through caspase activation. In the present study, we evaluated the involvement of caspase-independent neuronal cell death induced by 3-NP (1 mM) and the effect of z-VDVAD-fmk, an inhibitor of caspase-2, using cortical neurons in culture. Our results highly suggest that 3-NP induces both caspase-dependent and -independent cell death. We showed that z-VDVAD-fmk prevented both caspase-2 and -3-like activities evoked by 3-NP, but only partly prevented chromatin fragmentation/condensation. However, z-VDVAD-fmk did not avoid 3-NP-induced release of cytochrome c or AIF from mitochondria nor did it affect the levels of mitochondrial Bax. Furthermore, 3-NP-mediated decrease in plasma membrane integrity was not affected by z-VDVAD-fmk. Under these conditions, the inhibitor prevented the caspase-dependent cell death.     

Landscape effects on large scale abundance patterns of turtle doves Streptopelia turtur in Portugal

The European turtle dove is both a highly valued game species and a species of conservation concern, which is declining due probably to a combination of habitat degradation and unsustainable hunting. Although declines seem to be less severe in the Mediterranean region, it remains uncertain the extent to which ongoing land use changes will negatively affect this species. This study examined this issue, by estimating the effects of landscape composition on the broad scale abundance pattern of breeding turtle doves in continental Portugal. Turtle doves were surveyed in the breeding seasons of 2002 and 2003, from 3160 point counts spaced at about 1-km intervals along 158 transects of about 20 km, evenly covering the country. The frequency of occurrence of turtle doves at each transect was used as a proxy of species abundance, and related using GAM modelling to 21 variables describing land cover and woody linear features (e.g., hedgerows and riparian galleries). Turtle doves were most abundant in north- and central-eastern Portugal, with high abundances also recorded in the regions around Lisbon and along the Guadiana valley. Abundances were positively related to forest cover, particularly by broadleaved forests and by pine stands without woody understory, to cover by permanent crops, and to the density of woody linear habitats. Results suggest that conservation of Mediterranean turtle doves requires policies and management strategies reversing the pervasive trends of forest management neglect and agricultural abandonment, while preserving hedgerows and riparian galleries in more intensive agricultural landscapes.     

Isolation,characterization and analysis of the agglutinative activity of a lectin from <Emphasis Type="Italic">Crotalaria spectabilis</Emphasis>

Lectins are proteins with ability to recognize specific carbohydrates. These are present in virtually all organisms and have increasing applications in biotechnology. Here, our aim was to purify lectins from seeds of Crotalaria spectabilis Roth and determine their agglutinative ability. In this study, 45 g of seeds were milled, their proteins were precipitated by acetone or ammonium sulfate and purified by exclusion and ion-exchange chromatography. An isolated lectin was submitted to tests for hemagglutination and inhibition of hemagglutinating activity by carbohydrates as well as tests for its response to chelating and reducing agents. Our results show that the apparent molecular weight (as determined by SDS-PAGE) of the lectin is 30 kDa, and the tests for inhibition of erythrocytes’ agglutinative activity by sugars were positive for d-galactose and N-acetyl-d-galactosamine. Data obtained with the chelating agent EDTA demonstrated the presence of divalent cations in the protein structure. However, the reducing agent 2-mercaptoethanol was unable to inhibit the protein’s bioactivity. The lectin agglutinated the blood groups A, B, AB and O, as well as bacterial lineages from the species Leptospira interrogans and Leptospira biflexa, indicating a prospective application in the diagnosis and treatment of leptospirosis.     

Robustness of the approximate likelihood of the protracted speciation model

The protracted speciation model presents a realistic and parsimonious explanation for the observed slowdown in lineage accumulation through time, by accounting for the fact that speciation takes time. A method to compute the likelihood for this model given a phylogeny is available and allows estimation of its parameters (rate of initiation of speciation, rate of completion of speciation and extinction rate) and statistical comparison of this model to other proposed models of diversification. However, this likelihood computation method makes an approximation of the protracted speciation model to be mathematically tractable: it sometimes counts fewer species than one would do from a biological perspective. This approximation may have large consequences for likelihood‐based inferences: it may render any conclusions based on this method completely irrelevant. Here, we study to what extent this approximation affects parameter estimations. We simulated phylogenies from which we reconstructed the tree of extant species according to the original, biologically meaningful protracted speciation model and according to the approximation. We then compared the resulting parameter estimates. We found that the differences were larger for high values of extinction rates and small values of speciation‐completion rates. Indeed, a long speciation‐completion time and a high extinction rate promote the appearance of cases to which the approximation applies. However, surprisingly, the deviation introduced is largely negligible over the parameter space explored, suggesting that this approximate likelihood can be applied reliably in practice to estimate biologically relevant parameters under the original protracted speciation model.     

Water cytotoxicity and dioxins bioaccumulation in an Egyptian delta wetland ecosystem

Manzala Lake, as one of the main Egyptian wetland ecosystems, is facing risks of pollution. An in vitro cytotoxicity test using a mammalian cell line was employed to determine the toxicity of multiple pollutants in the water and Tilapia zillii fish sampled from the lake. The concentrations of seven polychlorinated dibenzo-p-dioxins and ten polychlorinated dibenzofurans were investigated in water and muscle of the fish in 2014. Cytotoxicity testing showed that the percentage inhibition of cell viability in the studied sites ranged between 56.16% and 83.22%. Dioxin analysis indicated that the average concentrations of 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,4,6,7,8,9-octachlorodibenzofuran were higher than the toxic equivalence quotients (TEQs) set by the World Health Organization (WHO) in all water and fish muscle samples; however, the average concentration of 2,3,7,8-tetrachlorodibenzofuran was higher only in fish muscle samples. The bioaccumulation factor (BAF) ranged dramatically between 2 and 58.5 for the detected dioxins. Adverse human health effects through the consumption of fish are not expected, because dioxin levels in fish muscle are deemed safe for human consumption. Implementation of a strategic multidisciplinary action plan is strongly recommended to sustain this delta wetland ecosystem.     

études sur les phénomenes électrocapillaires

Sans résuméI. Analyse électrocapillaire des matières colorantes. Rev. gén. Mat. Col. 1926 Vol. 30 pp 34–45II. Phénomènes électrocapillaires et le problème du cancer. Arch. Med. Exper. 1926 Vol. I p 381III. Phénomènes électrocapillaires et l'antagonismes microbiens. Bol. Istituto Sier. Milano 1927 Vol. VI p 313.     

Analysis of higher-primate phylogeny from transversion differences in nuclear and mitochondrial DNA by Lake's methods of evolutionary parsimony and operator metrics

In the companion paper (Holmquist et al. 1988), we concluded that there is no agreement on either the correct branching order or differential rates of evolution among the higher primates, and we examined in depth why this uncertainty in the evolutionary understanding of our closest living relatives persists. Recently, Lake developed two novel methods, based on group properties of transition and transversion operators, that (a) permit, in principle, objective resolution of problems of the above type and (b) attach a statistical significance level to the conclusions drawn. In the present paper, we develop formulas for using these two methods in tandem and apply them to study transversion differences in (1) nuclear DNA for a 7-kb segment of the psi eta-globin locus and a 3-kb intergenic region between the psi beta- and delta- globin loci and (2) mitochondrial DNA for the 896-bp fragment of Brown et al. Although each of these nucleotide sequence regions has its characteristic tempo and mode of evolution, the nuclear and mitochondrial data together, comprising a total of 10,939 base positions, support a Homo/Pan clade at the 97% confidence level. If we calibrate the divergence point for humans and chimpanzees at 5 Myr, consideration of the transversion branch lengths for the combined nuclear data indicates that the gorilla lineage branched off 600,000- 900,000 years prior to that, although the 2 sigma sampling errors do not preclude either a temporal trifurcation for the three species or a considerably more ancient branch point for the gorilla. To resolve the length of this central branch to a relative accuracy of 25% and 30% will require a factor of 16 and nine times more data, respectively-- i.e., in excess of 100,000 homologous nucleotides for each of the four primates. For the nuclear genes, heterogeneity in evolutionary rates between different parts of the genome is mostly restricted to the human lineage for these two segments. The lineage leading to chimpanzees has evolved 0.4 (3-kb fragment) to 3.5 (7-kb segment) times as rapidly as the lineage leading to humans, and that leading to the gorilla has evolved approximately one-fifth to one-half as rapidly as that leading to chimpanzees. Thus, even local molecular clocks can "tick" badly. As significant is the fact that virtually contiguous parts of the genome tick at markedly different rates.(ABSTRACT TRUNCATED AT 400 WORDS)