Effect of dietary zinc deficiency on metallothionein concentration of epididymal luminal fluids of weanling Wistar albino rats

Metallothionein (NIT) and zinc concentrations have been estimated in luminal fluids of caput/corpus and cauda epididymis and serum of zinc deficient (ZD), pairfed (PF) and control--ad libitum fed (ZC) groups of Wistar rats. MT decreased significantly in luminal fluids of caput corpus and cauda epididymis and serum of zinc deficient rats as compared to their respective controls. However, the decrease was non-significant in luminal fluids of corpus epididymis and serum of 4-weeks zinc deficient animals as compared to their control. Zinc levels also declined significantly in luminal fluids of epididymis and serum of zinc deficient rats as compared to their respective pairfed and control groups. Thus zinc deficiency state reduces zinc and MT concentrations in luminal fluid of epididymis and serum.     

Current advances and future directions in genetic enhancement of a climate resilient food legume crop,cowpea (Vigna unguiculata L. Walp.)

Plant Cell, Tissue and Organ Culture (PCTOC) - Cowpea (Vigna unguiculata (L.) Walp.) is a warm-season legume crop which is widely grown by resource-poor small and marginal farmers of Sub-Saharan...     

Community construction

Communities are naturally constructed over time by a process of species invasion and elimination. The construction process itself, which until very recently has received little attention, may be of fundamental importance to understanding community attributes such as stability, which have received a lot of attention. So the study of community construction should become a rewarding field of mainstream ecological research.     

Genetic identity and diversity of Nigerian cacao genebank collections verified by single nucleotide polymorphisms (SNPs): a guide to field genebank management and utilization

Nigeria is the sixth largest cacao producer in the world. Field performance and quality of cacao hybrid families is largely dependent on the genetic integrity of parental clones obtained in field genebank collections. However, information on the impact of mislabeling on seed garden output in Nigeria is lacking. Using 63 single nucleotide polymorphism (SNP) markers, we analyzed 1457 cacao trees sampled from seven major field genebank plots in Nigeria to assess the genetic integrity in Nigerian cacao germplasm. The procedure of multilocus matching with known reference clones revealed up to 78% mislabeling in recently introduced international germplasm. A high rate of mislabeling was also revealed in the West African local selections and breeding lines, using Bayesian assignment test. The problem of mislabeling has been attributed to errors from the sources of introduction, pre-planting labeling errors, and rootstocks overtaking budded scions due to poor field management. The analysis of genetic diversity revealed a good representation of the available cacao germplasm groups in Nigerian field genebanks, indicating that the genetic base of Nigeria cacao germplasm has been significantly widened through germplasm introductions. However, only a small proportion of the available germplasm in the genebank have been utilized for variety development. This study proved the utility of SNP markers for cleaning up the genebanks and reducing offtypes; thereby providing a strong basis for improving the accuracy and efficiency in cacao genebank management and breeding, as well as for mobilizing improved varieties to cacao farmers in Nigeria.     

Microsatellite loci to assess genetic variation in Tor putitora

Seven polymorphic microsatellite DNA loci were identified in golden mahseer, Tor putitora, through cross‐species amplification. Thirty‐two primers developed for three cyprinid fishes were tested in the study. The genetic variation detected at each microsatellite locus in T. putitora specimens (n = 107), collected from three different rivers and one lake was assessed. The allele frequencies deviated significantly from that expected under Hardy–Weinberg equilibrium. The mean observed heterozygosity values ranged from 0.29 to 0.40. Significant genotype heterogeneity indicated that the samples were not drawn from the same gene pool. The results indicate that the identified microsatellite loci exhibit promise for use in fine scale population structure analyses of T. putitora.     

Randia retroflexa (Rubiaceae), a new species from southern Mexico

A new species of Rubiaceae,Randia retroflexa, is described and illustrated from Veracruz, Oaxaca, and Chiapas in southern Mexico. An armed canopy vine of lowland and lower montane tropical evergreen forest, it is distinguished by its paired reflexed spines and hirsute pubescence. Its distribution, habitat, and specimen citations are given and affinities are discussed.     

Insights into substrate binding at FeMo-cofactor in nitrogenase from the structure of an α-70 MoFe protein variant

The X-ray crystal structure is presented for a nitrogenase MoFe protein where the alpha subunit residue at position 70 (α-70^Val) has been substituted by the amino acid isoleucine (α-70^Ile). Substitution of α-70^Val by α-70^Ile results in a MoFe protein that is hampered in its ability to reduce a range of substrates including acetylene and N₂, yet retains normal proton reduction activity. The 2.3 Å structure of the α-70^Ile MoFe protein is compared to the α-70^Val wild-type MoFe protein, revealing that the δ methyl group of α-70^Val is positioned over Fe6 within the active site FeMo-cofactor. This work provides strong crystallographic support for the previously proposed model that substrates bind and are reduced at a single 4Fe-4S face of the FeMo-cofactor and that when α-70^Val is substituted by α-70^Ile access of substrates to Fe6 of this face is effectively blocked. Furthermore the detailed examination of the structure provides the basis for understanding the ability to trap and characterize hydrides in the variant, contributing significantly to our understanding of substrate access and substrate reduction at the FeMo-cofactor active site of nitrogenase.     

Elucidating the Population Histories and Transmission Dynamics of Papillomaviruses Using Phylogenetic Trees

Using gene genealogies constructed from gene sequence data, we show that both the mucosal and cutaneous papillomaviruses (PV)—supergroups A and B—appear to have been transmitted through susceptible populations faster than exponentially. The data and methods involved (1) examining the PV database for phylogenetic signal in an L1 open reading frame (ORF) fragment and an E1 ORF segment, (2) demonstrating that the same two fragments have evolved in a way consistent with a molecular clock, and (3) applying methods of phylogenetic tree analysis that test different scenarios for the dynamics of viral transmission within populations. The results indicate increases in PV populations of both supergroups A and B in the recent past. This form of the increases, which fit a null model of population growth with an exponent increasing in time, is compatible with the fact that human populations have grown at a faster than exponential rate, thus increasing the numbers of susceptible hosts for HPVs. There are, however, indications that the population of supergroup A has now stopped increasing in size. Received: 4 June 1996 / Accepted: 12 August 1996