A monoclonal antibody detects a difference in the cellular composition of developing and regenerating limbs of newts

We have previously described a monoclonal antibody (called 22/18) that reacts with the early blastemal cells of the regenerating limb of the newt (Notophthalmus viridescens). In embryos of two newt species the antibody reacts with the epidermis, glial cells in the neural tube, the lens and cells in a restricted region of the aorta. In the developing limb bud less than 1% of the mesenchymal cells were reactive with 22/18, although most cells stained brightly with an antibody to another cytoskeletal component. When limbs were amputated prior to the arrival of nerves (axons and Schwann cells) at the amputation plane there was no extra reactivity with 22/18 as compared to the contralateral unamputated control, even though the amputated buds regenerated satisfactorily. Limbs amputated after nerves are present at the plane of amputation respond by forming a 22/18-positive blastema. The appearance of the 22/18 responses is a function of the stage of limb development as shown by amputation of forelimb and hindlimb buds at a larval stage where development of the forelimb is greatly advanced relative to the hindlimb. The distribution of the 22/18-positive cells in larval blastemas showed them to be closely associated with axons as detected by double staining with an antiserum to a neurofilament subunit. The clear antigenic difference between development and regeneration may be related to the relationship between embryonic regulation and epimorphic regeneration, and also to the acquisition of nerve-dependent proliferation of blastemal cells.     

Development of oxidative stress tolerance resulted in reduced ability to undergo morphologic transitions and decreased pathogenicity in a t-butylhydroperoxide-tolerant mutant of Candida albicans

We tested the hypothesis that adaptation of Candida albicans to chronic oxidative stress inhibits the formation of hyphae and reduces pathogenicity. Candida albicans cells were exposed to increasing concentrations of t-butylhydroperoxide (tBOOH), a lipid peroxidation-accelerating agent, and mutants with heritable tBOOH tolerance were isolated. Hypha formation by the mutants was negligible on Spider agar, indicating that the development of oxidative stress tolerance prevented Candida cells from undergoing dimorphic switches. One of the mutants, C. albicans AF06, was five times less pathogenic in mice than its parental strain, due to its reduced germ tube-, pseudohypha- and hypha-forming capability, and decreased phospholipase secretion. An increased oxidative stress tolerance may therefore be disadvantageous when this pathogen leaves blood vessels and invades deep organs. The AF06 mutant was characterized by high intracellular concentrations of endogenous oxidants, reduced monounsaturated and polyunsaturated fatty acid contents, the continuous induction of the antioxidative defense system, decreased cytochrome c-dependent respiration, and increased alternative respiration. The mutation did not influence growth rate, cell size, cell surface, cellular ultrastructures, including mitochondria, or recognition by human polymorphonuclear leukocytes. The selection of oxidative stress-tolerant respiratory Candida mutants may also occur in vivo, when reduced respiration helps the fungus to cope with antimycotic agents.     

Endotoxins do not influence transplacental transmission of lymphotropic human herpesviruses and human papillomaviruses into amniotic fluid taken from healthy mothers before parturition in Hungary

Pregnant women were examined following healthy pregnancies at term. Amniotic fluids were sampled before arteficial rupture of membranes using closed vacutainer system. Blood samples were also taken from the pregnants simultaneously. Endotoxin concentrations of amniotic fluids were tested by the semiquantitative Limulus amebocyte lysate. Both amniotic fluids and blood samples were tested for the presence of DNA of lymphotropic human herpesviruses. The DNA of human papillomaviruses were tested only in the amniotic fluid samples. One-third of the amniotic fluids tested were found to contain measurable amounts of endotoxin. Lymphotropic herpesvirus DNA was deteced in every fourth amniotic fluid sample and in every 8th blood sample. The prevalence of papillomaviruses was 7 of 96 samples. No significant correlation was found between the presence of endotoxin and viruses in the amniotic fluids. Epstein-Barr virus, human cytomegalovirus and human herpesvirus type 7 were found more frequently in the amniotic fluids than in blood samples (7 to 1). The prevalence of human herpesvirus 6 and 8 was higher in the blood samples than that in the amniotic fluids. The mean weight of the neonates were not impaired significantly by the presence of either viruses or endotoxin. Possible post partum consequences, i.e. partial immunotolerance to viruses is discussed.     

Conditional QTL mapping of protein content in wheat with respect to grain yield and its components

Grain protein content in wheat (Triticum aestivum L.) is generally considered a highly heritable character that is negatively correlated with grain yield and yield-related traits. Quantitative trait loci (QTL) for protein content was mapped using data on protein content and protein content conditioned on the putatively interrelated traits to evaluate possible genetic interrelationships between protein content and yield, as well as yield-related traits. Phenotypic data were evaluated in a recombinant inbred line population with 302 lines derived from a cross between the Chinese cultivar Weimai 8 and Luohan 2. Inclusive composite interval mapping using IciMapping 3.0 was employed for mapping unconditional and conditional QTL with additives. A strong genetic relationship was found between protein content and grain yield, and yield-related traits. Unconditional QTL mapping analysis detected seven additive QTL for protein content, with additive effects ranging in absolute size from 0.1898% to 0.3407% protein content, jointly accounting for 43.45% of the trait variance. Conditional QTL mapping analysis indicated two QTL independent from yield, which can be used in marker-assisted selection for increasing yield without affecting grain protein content. Three additional QTL with minor effects were identified in the conditional mapping. Of the three QTLs, two were identified when protein content was conditioned on yield, which had pleiotropic effects on those two traits. Conditional QTL mapping can be used to dissect the genetic interrelationship between two traits at the individual QTL level for closely correlated traits. Further, conditional QTL mapping can reveal additional QTL with minor effects that are undetectable in unconditional mapping.     

Preparation of the pentasaccharide hapten of the GPL of Mycobacterium avium serovar 19 by achieving the glycosylation of a tertiary hydroxyl group

The chemical synthesis of the glycopeptidolipid-type pentasaccharide hapten of Mycobacterium avium serovar 19 with a trifluoroacetamido spacer at the reducing end is described. The spacer-armed pentasaccharide 31, when conjugated to an immunogenic protein, can be applied to the serodiagnosis of mycobacterial infections. The questionable structure of the penultimate monosaccharide unit was clarified as 6-deoxy-3-C-methyl-2,4-di-O-methyl-L-mannopyranose. The occurrence of the 6-deoxy-3-C-methyl-2,4-di-O-methyl-L-talopyranose could be excluded by the presence of the large H-1'-H-2' coupling constant, which proves the 4C1 (L) conformation as the favoured one.     

Separate Na,K-ATPase genes are required for otolith formation and semicircular canal development in zebrafish

We have investigated the role of Na,K-ATPase genes in zebrafish ear development. Six Na,K-ATPase genes are differentially expressed in the developing zebrafish inner ear. Antisense morpholino knockdown of Na,K-ATPase alpha1a.1 expression blocked formation of otoliths. This effect was phenocopied by treatment of embryos with ouabain, an inhibitor of Na,K-ATPase activity. The otolith defect produced by morpholinos was rescued by microinjection of zebrafish alpha1a.1 or rat alpha1 mRNA, while the ouabain-induced defect was rescued by expression of ouabain-resistant zebrafish alpha1a.1 or rat alpha1 mRNA. Knockdown of a second zebrafish alpha subunit, alpha1a.2, disrupted development of the semicircular canals. Knockdown of Na,K-ATPase beta2b expression also caused an otolith defect, suggesting that the beta2b subunit partners with the alpha1a.1 subunit to form a Na,K-ATPase required for otolith formation. These results reveal novel roles for Na,K-ATPase genes in vestibular system development and indicate that different isoforms play distinct functional roles in formation of inner ear structures. Our results highlight zebrafish gene knockdown-mRNA rescue as an approach that can be used to dissect the functional properties of zebrafish and mammalian Na,K-ATPase genes.     

Segregation of the replication terminus of the two Vibrio cholerae chromosomes

Genome duplication and segregation normally are completed before cell division in all organisms. The temporal relation of duplication and segregation, however, can vary in bacteria. Chromosomal regions can segregate towards opposite poles as they are replicated or can stay cohered for a considerable period before segregation. The bacterium Vibrio cholerae has two differently sized circular chromosomes, chromosome I (chrI) and chrII, of about 3 and 1 Mbp, respectively. The two chromosomes initiate replication synchronously, and the shorter chrII is expected to complete replication earlier than the longer chrI. A question arises as to whether the segregation of chrII also is completed before that of chrI. We fluorescently labeled the terminus regions of chrI and chrII and followed their movements during the bacterial cell cycle. The chrI terminus behaved similarly to that of the Escherichia coli chromosome in that it segregated at the very end of the cell division cycle: cells showed a single fluorescent focus even when the division septum was nearly complete. In contrast, the single focus representing the chrII terminus could divide at the midcell position well before cell septation was conspicuous. There were also cells where the single focus for chrII lingered at midcell until the end of a division cycle, like the terminus of chrI. The single focus in these cells overlapped with the terminus focus for chrI in all cases. It appears that there could be coordination between the two chromosomes through the replication and/or segregation of the terminus region to ensure their segregation to daughter cells.     

Impacts of hunting on mammals in African tropical moist forests: a review and synthesis

• 1 Available information on the consumption of wild meat in West and Central Africa is reviewed. We show that mammals are the prime source of bushmeat, and that ungulates and rodents make up the highest proportion of biomass extracted.
• 2 We present data on current knowledge of extraction patterns of wild mammals in West and Central Africa, and evidence that at current off‐take levels, within the range states, mammals as bushmeat are being depleted on an unprecedented scale. Extraction rates are orders of magnitude higher there than in comparable ecosystems like the Amazon, and much less likely to be sustainable.
• 3 However, basic knowledge of the biology of harvestable tropical moist forest mammals, and the consequences of hunting on mammalian communities, which permits accurate estimation of maximal production rate (the excess of growth over replacement rate), is largely unavailable, and this hinders estimation of hunting quotas and sustainability. Comparisons are made with the existing information available on Amazon basin mammals and hunting patterns reported there.