Population genetic structure and conservation of Asian elephants (Elephas maximus) across India

This study examines the population genetic structure of Asian elephants (Elephas maximus) across India, which harbours over half the world's population of this endangered species. Mitochondrial DNA control region sequences and allele frequencies at six nuclear DNA microsatellite markers obtained from the dung of free-ranging elephants reveal low mtDNA and typical microsatellite diversity. Both known divergent clades of mtDNA haplotypes in the Asian elephant are present in India, with southern and central India exhibiting exclusively the β clade of Fernando et al. (2000), northern India exhibiting exclusively the α clade and northeastern India exhibiting both, but predominantly the α clade. A nested clade analysis revealed isolation by distance as the principal mechanism responsible for the observed haplotype distributions within the α and β clades. Analyses of molecular variance and pairwise population FST tests based on both mitochondrial and microsatellite DNA suggest that northern-northeastern India, central India, Nilgiris (in southern India) and Anamalai-Periyar (in southern India) are four demographically autonomous population units and should be managed separately. In addition, evidence for female philopatry, male-mediated gene flow and two possible historical biogeographical barriers is described.

Rapid divergence of ecotypes of an invasive plant

Invasive species demonstrate rapid evolution within a very short period of time allowing one to understand the underlying mechanism(s). Lantana camara, a highly invasive plant of the tropics and subtropics, has expanded its range and successfully established itself almost throughout India. In order to uncover the processes governing the invasion dynamics, 218 individuals from various locations across India were characterized with six microsatellites. By integrating genetic data with niche modelling, we examined the effect of drift and environmental selection on genetic divergence. We found multiple genetic clusters that were non-randomly distributed across space. Spatial autocorrelation revealed a strong fine-scale structure, i.e. isolation by distance. In addition, we obtained evidence of inhibitory effects of selection on gene flow, i.e. isolation by environmental distance. Perhaps, local adaptation in response to selection is offsetting gene flow and causing the populations to diverge. Niche models suggested that temperature and precipitation play a major role in the observed spatial distribution of this plant. Based on a non-random distribution of clusters, unequal gene flow among them and different bioclimatic niche requirements, we concluded that the emergence of ecotypes represented by two genetic clusters is underway. They may be locally adapted to specific climatic conditions, and perhaps at the very early stages of ecological divergence.

Differences in host species relationships and biogeographic influences produce contrasting patterns of prevalence, community composition and genetic structure in two genera of avian malaria parasites in southern Melanesia

1. Host-parasite interactions have the potential to influence broadscale ecological and evolutionary processes, levels of endemism, divergence patterns and distributions in host populations. Understanding the mechanisms involved requires identification of the factors that shape parasite distribution and prevalence. 2. A lack of comparative information on community-level host-parasite associations limits our understanding of the role of parasites in host population divergence processes. Avian malaria (haemosporidian) parasites in bird communities offer a tractable model system to examine the potential for pathogens to influence evolutionary processes in natural host populations. 3. Using cytochrome b variation, we characterized phylogenetic diversity and prevalence of two genera of avian haemosporidian parasites, Plasmodium and Haemoproteus, and analysed biogeographic patterns of lineages across islands and avian hosts, in southern Melanesian bird communities to identify factors that explain patterns of infection. 4. Plasmodium spp. displayed isolation-by-distance effects, a significant amount of genetic variation distributed among islands but insignificant amounts among host species and families, and strong local island effects with respect to prevalence. Haemoproteus spp. did not display isolation-by-distance patterns, showed marked structuring of genetic variation among avian host species and families, and significant host species prevalence patterns. 5. These differences suggest that Plasmodium spp. infection patterns were shaped by geography and the abiotic environment, whereas Haemoproteus spp. infection patterns were shaped predominantly by host associations. Heterogeneity in the complement and prevalence of parasite lineages infecting local bird communities likely exposes host species to a mosaic of spatially divergent disease selection pressures across their naturally fragmented distributions in southern Melanesia. Host associations for Haemoproteus spp. indicate a capacity for the formation of locally co-adapted host-parasite relationships, a feature that may limit intraspecific gene flow or range expansions of closely related host species.

Genetic analysis of Indian tasar silkmoth (Antheraea mylitta) populations

Indian tasar silkmoth, Antheraea mylitta is an economically important wild silkmoth species distributed across India. A number of morphologically and ethologically well-defined ecotypes are known for this species that differ in their primary food plant specificity. Most of these ecotypes do not interbreed in nature, but are able to produce offspring under captive conditions. Microsatellite markers were developed for A. mylitta, and out of these, ten well-behaved microsatellite loci were used to analyze the population structure of different ecoraces. A total of 154 individual moths belonging to eight different ecoraces, were screened at each locus. Hierarchical analysis of population structure using Analysis of MOlecular VAriance (AMOVA) revealed significant structuring (F-ST = 0.154) and considerable inbreeding (F-IS = 0.505). A significant isolation by distance was also observed. The number of possible population clusters was investigated using distance method, Bayesian algorithm and self organization maps (SOM). The first two methods revealed two distinct clusters, whereas the SOM showed the different ecoraces not to be clearly differentiated. These results suggest that although there is a large degree of phenotypic variation among the different ecoraces of A. mylitta, genetically they are not very different, and the phenotypic differences may largely be a result of their respective ecology.

Isolation of hen's egg yolk very low density lipoproteins by DEAE-cellulose chromatography

A procedure has been developed for the isolation of very low density lipoproteins from hen's egg yolk plasma using DEAE-cellulose chromatography. This procedure is rapid and does not require ultracentrifugation and should, therefore, serve as a useful procedure for use in laboratories where this facility does not exist.

Limiting the Extent of the RDN1 Heterochromatin Domain by a Silencing Barrier and Sir2 Protein Levels in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, transcriptional silencing occurs at the cryptic mating-type loci (HML and HMR), telomeres, and ribosomal DNA ( rDNA; RDN1). Silencing in the rDNA is unusual in that polymerase II (Pol II) promoters within RDN1 are repressed by Sir2 but not Sir3 or Sir4. rDNA silencing unidirectionally spreads leftward, but the mechanism of limiting its spreading is unclear. We searched for silencing barriers flanking the left end of RDN1 by using an established assay for detecting barriers to HMR silencing. Unexpectedly, the unique sequence immediately adjacent to RDN1, which overlaps a prominent cohesin binding site (CARL2), did not have appreciable barrier activity. Instead, a fragment located 2.4 kb to the left, containing a tRNA(Gln) gene and the Ty1 long terminal repeat, had robust barrier activity. The barrier activity was dependent on Pol III transcription of tRNA(Gln), the cohesin protein Smc1, and the SAS1 and Gcn5 histone acetyltransferases. The location of the barrier correlates with the detectable limit of rDNA silencing when SIR2 is overexpressed, where it blocks the spreading of rDNA heterochromatin. We propose a model in which normal Sir2 activity results in termination of silencing near the physical rDNA boundary, while tRNA(Gln) blocks silencing from spreading too far when nucleolar Sir2 pools become elevated.

A Note on Diffraction of Water Waves by a Nearly Vertical Barrier

A simplified perturbational analysis is employed, together with the application of Green's theorem, to determine the first-order corrections to the reflection and transmission coefficients in the problem of diffraction of surface water waves by a nearly vertical barrier in two basically important cases: (i) when the barrier is partially immersed and (ii) when the barrier is completely submerged. The present analysis produces the desired results fairly easily and relatively quickly as compared with the known integral equation approach to this class of diffraction problems.

Solution of a Boundary-Value Problem associated with Diffraction of Water Waves by a Nearly Vertical Barrier

An exact solution is derived for a boundary-value problem for Laplace's equation which is a generalization of the one occurring in the course of solution of the problem of diffraction of surface water waves by a nearly vertical submerged barrier. The method of solution involves the use of complex function theory, the Schwarz reflection principle, and reduction to a system of two uncoupled Riemann-Hilbert problems. Known results, representing the reflection and transmission coefficients of the water wave problem involving a nearly vertical barrier, are derived in terms of the shape function.

Synthesis and Isolation of 5,6-Dihydro-4H-1,3-Oxazine Hydrobromides by Autocyclization of N-(3-Bromopropyl)amides

5,6-Dihydro-4H-1,3-oxazine hydrobromides have been synthesized by the nucleophilic autocyclo-O-alkylation of N-(3-bromopropyl)amides under neutral conditions in chloroform. It is found that electron-donating amide alpha-substituents influence the autocyclization efficiency.

Barrier crossing in one and three dimensions by a long chain

We consider the Kramers problem for a long chain polymer trapped in a biased double-well potential. Initially the polymer is in the less stable well and it can escape from this well to the other well by the motion of its N beads across the barrier to attain the configuration having lower free energy. In one dimension we simulate the crossing and show that the results are in agreement with the kink mechanism suggested earlier. In three dimensions, it has not been possible to get an analytical `kink solution' for an arbitrary potential; however, one can assume the form of the solution of the nonlinear equation as a kink solution and then find a double-well potential in three dimensions. To verify the kink mechanism, simulations of the dynamics of a discrete Rouse polymer model in a double well in three dimensions are carried out. We find that the time of crossing is proportional to the chain length, which is in agreement with the results for the kink mechanism. The shape of the kink solution is also in agreement with the analytical solution in both one and three dimensions.

Reactions of palladium chloride with amino spirocyclic cyclotriphosphazenes: Isolation and Crystal Structures of Novel Mono- and Bimetallic Complexes Formed by the Hydrolysis of a .lambda.5-Diazaphospholane Ring

The reaction of the amino spirocyclic cyclotriphosphazene N3P3(NMe2)4(NHCH2CH2CH2NH) (2) with palladium chloride gives the stable chelate complex [PdCl2.2] (4). An X-ray crystallographic study reveals that one of the nitrogen atoms of the diaminoalkane moiety and an adjacent phosphazene ring nitrogen atom are bonded to the metal. An analogous reaction with the phosphazene N3P3(NMe2)4(NHCH2CH2NH) (1) gives initially a similar complex which undergoes facile hydrolysis to give the novel monometallic and bimetallic complexes [PdCl2.HN3P3(O)(NMe2)4(NHCH2CH2NH2)] (5) and [PdCl{N3P3(NMe2)4(NCH2CH2NH2)}]2(O) (6), which have been structurally characterized; in the former, an (oxophosphazadienyl)ethylenediamine is chelated to the metal whereas, in the latter, an oxobridged bis(cyclotriphosphazene) acts as a hexadentate nitrogen donor ligand in its dianionic form. Crystal data for 4 : a = 14.137(1) angstrom, b = 8.3332(5) angstrom, c = 19.205(2) angstrom, beta = 96.108(7)degrees, P2(1)/c, Z = 4, R = 0.027 with 3090 reflections (F > 5sigma(F)). Crystal data for 5 : a = 8.368(2) angstrom, b = 16.841(4) A, c = 16.092(5) angstrom, beta = 98.31(2)degrees, P2(1)/n, Z = 4, R = 0.049 with 3519 reflections (F > 5sigma(F)). Crystal data for 6 : a = 22.455(6) angstrom, b = 14.882(3) angstrom, c = 13.026(5) angstrom, 6 = 98.55(2)degrees, C2/c, Z = 4, R = 0.038 with 3023 reflections (F > 5sigma(F)).

Surface barrier effects in non-resonant microwave absorption by superconducting thin films of YBa2Cu3O7??

We present an unusual temperature dependence of hysteresis in the Lion resonant microwave absorption (NRMA) signals from superconducting thin films of YBa2Cu3O7-delta. We observe that the hysteresis increases with increase in temperature till T-c which we interpret as evidence for the presence of Bean-Livingston surface barriers (BLSB) in the single crystalline films.

Isolation of transforming growth factor-beta 2 cDNA from a fish, Cyprinus carpio by RT-PCR

Transforming Growth Factors-beta (TGF-beta s) have been described in many vertebrate species of amphibians, aves and mammals. In this report we demonstrate the presence of TGF-beta 2 in pisces. TGF-beta 2 has been cloned from a fish, Cyrinus carpio, by RT-PCR using degenerate oligonucleotide primers. Sequence analysis of the amplified product and alignment of the deduced amino acid sequence with the human TGF-beta 2 amino acid sequence revealed 81% and 93% identity in the precursor and the mature regions, respectively. The northern blot analysis of fish heart RNA shows a major messenger RNA species of about 8.0 kb and two messages of very low abundance of about 5.0 kb and 4.0 kb. The identification of TGF-beta 2 isoform in Pisces and it's high degree of homology with the mammalian isoform suggests that among all TGF-beta isoforms, TGF-beta 2 is the most conserved during evolution. (C) 1997 Elsevier Science B.V.