Segregation,viral phenotype,and proviral structure of 23 avian leukosis virus inserts in the germ line of chickens

Summary We have artificially introduced 23 avian leukosis virus (ALV) proviral inserts into the chicken germ line by injection of wild-type and recombinant subgroup A ALV near the blastoderm of fertile eggs just before incubation. Eight viremic males were identified as germline mosaics because they transmitted proviral DNA to their generation 1 (G-1) progeny at a low frequency. Eleven female and 9 male G-1 progeny carried 23 distinct proviruses that had typical major clonal proviral-host DNA junction fragments detectable after digestion of their DNA with SacI, Southern blotting and hybridization with a probe representing the complete ALV genome. These proviruses, identified by their typical proviral-host DNA junction fragments, were transmitted to approximately 50% of their G-2 progeny after mating the G-1 parents to a line of chickens lacking endogenous ALV proviral inserts. One G-1 female carried 2 proviruses and another 3. The proviruses appeared to be scattered throughout the genome. One of the 14 proviruses carried by females was on the sex (Z) chromosome. Two of the 3 proviruses carried by a single G-1 female were linked with a recombination frequency of about 0.20. Twenty-one of the proviruses coded for infectious ALV. Two proviruses coded for envelope glycoprotein, and cell cultures carrying them were relatively resistant to subgroup A sarcoma virus, but failed to produce infectious ALV. One of these proviruses coded for internal gag proteins, had a deletion in pol, but produced non-infectious virus particles. The other failed to code for gag proteins and had no detectable internal deletions nor did it produce virus particles. Thus, we have shown that replication-competent ALV can artificially infect germ-line cells and that spontaneous defects in the inherited proviruses occur at a rather low rate.     

Sequence variation in ZFX introns in human populations

DNA variation in human populations was studied by examining the last intron of the ZFX gene (about 1, 151 bp) with a worldwide sample of 29 individuals. Only one polymorphic site was found, which is located in an Alu sequence. This polymorphism is present at an intermediate frequency in all populations studied, and could be a shared polymorphism or due to migration among populations in Asia, Europe, and Africa. The nucleotide diversity is 0.04%, supporting the view that the level of nucleotide variation in nuclear DNA is very low in humans. From the sequence data, the age (T) of the most recent common ancestor of the sampled sequences is estimated: the mode of T is about 306,000 years, and the 95% confidence interval of T is 162,000-952,000 years. This mode estimate is considerably older than the estimates from Y- linked sequences.      

Influence of blood glucose on convulsive seizures from hyperbaric oxygen

Previous evidence suggests a causal relationship between blood glucose levels and the development of generalized epileptiform seizures. In the present study rats were pretreated with glucose, alloxan, or insulin prior to exposure to 6 atmospheres absolute (ATA) oxygen in a hyperbaric chamber. The results showed that the administration of glucose prior to oxygen exposure increased the time-to-seizure by 90% and alloxan by 110%, whereas in contrast insulin decreased the time-to-seizure by 55%. Blood glucose levels were consistently elevated in rats following oxygen exposure. A trend towards reduced lung damage by glucose and alloxan pretreatment was suggested by the data, although no changes were significant. Our results showed that prior administration of glucose or alloxan offered partial protection from oxygen toxicity in rats, whereas insulin generally augumented the reaction.     

Ev 2, a genetic locus containing structural genes for endogenous virus, codes for Rous-associated virus type 0 produced by line 72 chickens.

ev 2 is one of seven recently described genetic loci of chickens which contain structural genes for endogenous virus. ev 2 is present exclusively in line 72 chickens, an inbred strain of white Leghorns which is homozygous for the capacity to produce Rous-associated virus type 0 (RAV-0), a subgroup E virus. This phenotype is known as V+ and has been assigned a genetic allele designated V-E7. The segregation of ev 2 was followed in a genetic cross in which the V-E7+ phenotype was also segregating. The progeny of the cross were analyzed for endogenous viral loci by cleavage of embryo DNA with restriction endonuclease SstI, electrophoretic separation of the resulting fragments, and identification of bands containing viral sequences by hybridization of the DNA to radiolabeled viral RNA. Four endogenous viral loci, ev 1, ev 2, ev 4, and ev 5, were identified in the progeny of the cross. One of the progeny contained no detectable endogenous viral sequences. ev 1, ev 4, and ev 5 were present in progeny of both the V-E7+ and V-E7- phenotypes. ev 2 was present exclusively in progeny of the V-E7+ phenotype, and all V-E7+ progeny contained ev 2. In addition, one of the V-E7+ progeny contained only ev 2. FRom these data, we conclude that ev 2 codes for RAV-0 virus produced by the cells of line 72 chickens.     

Growth and nitrogen relations in the mat-forming lichens Stereocaulon paschale and Cladonia stellaris

BACKGROUND AND AIMS: Mat-forming lichens in the genera Stereocaulon and Cladonia have ecosystem-level effects in northern boreal forests. Yet the factors affecting the productivity of mat-forming lichens are not known. The aim of the presented work was to investigate whether mat-forming lichens adapted to low N availability employ N-conserving mechanisms similar to those of vascular plants in nutrient-poor ecosystems. Specifically, the following questions were asked: (a) Do lichens translocate N from basal areas to apical growth areas? (b) Are the quantities of N translocated of ecological significance. (c) Is lichen growth dependent on tissue N concentration [N]. METHODS: Two different, but complementary, field experiments were conducted using the mat-forming N2-fixing Stereocaulon paschale and non-fixing Cladonia stellaris as model species. First, N translocation was investigated by feeding lichens with Na(15)NO3 either directly to the apex (theoretical sink) or to the basal part (theoretical source) and observing the redistribution of (15)N after a growth period. Secondly, growth and variation in [N] in thalli of different lengths was measured after a growth period. KEY RESULTS: (15)N fed to lower parts of lichen was translocated towards the growing top, but not vice versa, indicating physiologically dependent translocation that follows a sink-source relationship. In the growth experiment where thalli were cut to different lengths, the significant decrease in [N] in apices of short vs. longer thalli after a growth period is consistent with internal relocation as an ecologically important source of N. CONCLUSIONS: The presented results demonstrate that internal recycling of N occurs in both species investigated and may be ecologically important in these mat-forming lichens under field conditions. The higher nitrogen use efficiency and relative growth rate in C. stellaris in comparison with S. paschale probably enable C. stellaris to dominate the ground cover vegetation in dry boreal coniferous forests under undisturbed conditions.     

Pathology-specific experimental antivenoms for haemotoxic snakebite: The impact of immunogen diversity on the in vitro cross-reactivity and in vivo neutralisation of geographically diverse snake venoms

BackgroundSnakebite is a neglected tropical disease that causes high global rates of mortality and morbidity. Although snakebite can cause a variety of pathologies in victims, haemotoxic effects are particularly common and are typically characterised by haemorrhage and/or venom-induced consumption coagulopathy. Antivenoms are the mainstay therapeutic for treating the toxic effects of snakebite, but despite saving thousands of lives annually, these therapies are associated with limited cross-snake species efficacy due to venom variation, which ultimately restricts their therapeutic utility to particular geographical regions.Methodology/Principal findingsIn this study we explored the feasibility of generating globally effective pathology-specific antivenoms to counteract the haemotoxic signs of snakebite envenoming. Two different immunogen mixtures, consisting of seven and twelve haemotoxic venoms sourced from geographically diverse and/or medically important snakes, were used to raise ovine polyclonal antibodies, prior to characterisation of their immunological binding characteristics and in vitro neutralisation profiles against each of the venoms. Despite variability of the immunogen mixtures, both experimental antivenoms exhibited broadly comparable in vitro venom binding and neutralisation profiles against the individual venom immunogens in immunological and functional assays. However, in vivo assessments using a murine preclinical model of antivenom efficacy revealed substantial differences in venom neutralisation. The experimental antivenom generated from the seven venom immunogen mixture outperformed the comparator, by providing protective effects against venom lethality caused by seven of the eight geographically diverse venoms tested, including three distinct venoms that were not used as immunogens to generate this antivenom. These findings suggest that a core set of venom immunogens may be sufficient to stimulate antibodies capable of broadly neutralising a geographically diverse array of haemotoxic snake venoms, and that adding additional venom immunogens may impact negatively on the dose efficacy of the resulting antivenom.Conclusions/SignificanceAlthough selection of appropriate immunogens that encapsulate venom toxin diversity without diluting antivenom potency remains challenging and further optimisation is required, the findings from this pilot study suggest that the generation of pathology-specific antivenoms with global utility is likely to feasible, thereby highlighting their promise as future modular treatments for the world’s tropical snakebite victims.     

Genetic variation in South Indian castes: evidence from Y-chromosome, mitochondrial, and autosomal polymorphisms

Background

Major population movements, social structure, and caste endogamy have influenced the genetic structure of Indian populations. An understanding of these influences is increasingly important as gene mapping and case-control studies are initiated in South Indian populations.

Results

We report new data on 155 individuals from four Tamil caste populations of South India and perform comparative analyses with caste populations from the neighboring state of Andhra Pradesh. Genetic differentiation among Tamil castes is low (R_ST = 0.96% for 45 autosomal short tandem repeat (STR) markers), reflecting a largely common origin. Nonetheless, caste- and continent-specific patterns are evident. For 32 lineage-defining Y-chromosome SNPs, Tamil castes show higher affinity to Europeans than to eastern Asians, and genetic distance estimates to the Europeans are ordered by caste rank. For 32 lineage-defining mitochondrial SNPs and hypervariable sequence (HVS) 1, Tamil castes have higher affinity to eastern Asians than to Europeans. For 45 autosomal STRs, upper and middle rank castes show higher affinity to Europeans than do lower rank castes from either Tamil Nadu or Andhra Pradesh. Local between-caste variation (Tamil Nadu R_ST = 0.96%, Andhra Pradesh R_ST = 0.77%) exceeds the estimate of variation between these geographically separated groups (R_ST = 0.12%). Low, but statistically significant, correlations between caste rank distance and genetic distance are demonstrated for Tamil castes using Y-chromosome, mtDNA, and autosomal data.

Conclusion

Genetic data from Y-chromosome, mtDNA, and autosomal STRs are in accord with historical accounts of northwest to southeast population movements in India. The influence of ancient and historical population movements and caste social structure can be detected and replicated in South Indian caste populations from two different geographic regions.     

Cell damage unmasks 15-lipoxygenase activity in human neutrophils

Metabolism of arachidonic acid (10 microM) into 15(S)-hydroxyl-5,8,11-cis-13-trans-eicosatetraenoic acid (15-HETE) was proportional to lactate dehydrogenase release from human neutrophils incubated with supratherapeutic concentrations of non-steroidal anti-inflammatory agents. In contrast to others (Vanderhoek, J., and Bailey, J. (1984) J. Biol. Chem. 259, 6752-6756), we report that increased 15-HETE formation was not uniquely attributable to 5 mM ibuprofen, and it did not originate from enzymatic activation. For instance, ibuprofen (1-5 mM) did not affect the isolated 15-lipoxygenase enzyme in the 100,000 X g supernatant from neutrophil lysates, and dose-dependent increases in 15-HETE biosynthesis, proportional to lactate dehydrogenase release, were evident with benoxaprofen, naproxen, flurbiprofen, or etodolac. At similar supratherapeutic concentrations (1-5 mM), aspirin and phenylbutazone did not influence lactate dehydrogenase release or 15-HETE production. In further contrast, neutrophils did not tolerate 1-5 mM ibuprofen. Biochemical, morphological, flow cytometric, and fluorochromatic analyses each indicated cytological damage. A correlation between lactate dehydrogenase release and increased 15-HETE formation was a dose-dependent property also exhibited by arachidonic acid alone (10-100 microM). We conclude that cytological damage, facilitating access of arachidonic acid to 15-lipoxygenase in a cytosolic compartment, accounts for this phenomenon.