LeuX tRNA-dependent and -independent mechanisms of Escherichia coli pathogenesis in acute cystitis

Uropathogenic Escherichia coli (UPEC) contain multiple horizontally acquired pathogenicity-associated islands (PAI) implicated in the pathogenesis of urinary tract infection. In a murine model of cystitis, type 1 pili-mediated bladder epithelial invasion and intracellular proliferation are key events associated with UPEC virulence. In this study, we examined the mechanisms by which a conserved PAI contributes to UPEC pathogenesis in acute cystitis. In the human UPEC strain UTI89, spontaneous excision of PAI II(UTI89) disrupts the adjacent leuX tRNA locus. Loss of wild-type leuX-encoded tRNA(5)(Leu) significantly delayed, but did not eliminate, FimB recombinase-mediated phase variation of type 1 pili. FimX, an additional FimB-like, leuX-independent recombinase, was also found to mediate type 1 pili phase variation. However, whereas FimX activity is relatively slow in vitro, it is rapid in vivo as a non-piliated strain lacking the other fim recombinases rapidly expressed type 1 pili upon experimental infection. Finally, we found that disruption of leuX, but not loss of PAI II(UTI89) genes, reduced bladder epithelial invasion and intracellular proliferation, independent of type 1 piliation. These findings indicate that the predominant mechanism for preservation of PAI II(UTI89) during the establishment of acute cystitis is maintenance of wild-type leuX, and not PAI II(UTI89) gene content.     

Intracellular pH of frog sartorius muscle

A weak base, morpholine, has been labelled with ³H and tested for its suitability as an indicator for intracellular pH, by distribution in the tissue water of frog sartorius muscle in the species Hyla litoria. Its pK'a at 20°C in a solution of the same of ionic strength as frog Ringer was found to be 8.45 ± 0.02, which is in the range of maximal sensitivity. Morpholine equilibrated with the tissue in 17 h; it was shown that it was not bound to intracellular constituents, that it was not metabolised nor toxic in the concentrations used; it was therefore judged suitable as a pH indicator. Intracellular pH was then measured by distribution of morpholine (6.985 ± 0.08), nicotine (6.915 ± 0.03) and the weak acid 5,5′-dimethyl-2,4-oxazolidinedione (7.10 ± 0.05) and with pH-sensitive microelectrodes (5.9, the equilibrium value). It was shown that the four significantly different values could not be reconciled in terms of experimental error, heterogeneity of intracellular pH, liquid junction potential differences, or binding of indicator molecules inside the fibre. They could, however, be reconciled if the fibre water had different structure and solvent properties from the extracellular water and ions were distributed across the membrane as between two liquid phases containing different solvents. Then the H⁺ would be in equilibrium, as shown by the microelectrode measurement, but intracellular pH would be indeterminable and probably greater than 6.     

Evaluation of cDNA Libraries from Different Developmental Stages of Schistosoma mansoni for Production of Expressed Sequence Tags (ESTs)

A comparative study of the gene expression profile in differentdevelopmental stages of Schistosoma mansoni has been initiatedbased on the expressed sequence tag(EST) approach. A total of1401 ESTs were generated from seven different cDNA librariesconstructed from four distinct stages of the parasite life cycle.The libraries were first evaluated for their quality for a large-scalecDNA sequencing program. Most of them were shown to have lessthan 20% useless clones and more than 50% new genes. The redundancyof each library was also analyzed, showing that one adult wormcDNA library was composed of a small number of highly frequentgenes. When comparing ESTs from distinct libraries, we coulddetect that most genes were present only in a single library,but others were expressed in more than one developmental stageand may represent housekeeping genes in the parasite. When consideringonly once the genes present in more than one library, a totalof 466 unique genes were obtained, corresponding to 427 newS. mansoni genes. From the total of unique genes, 20.2% wereidentified based on homology with genes from other organisms,8.3% matched S. mansoni characterized genes and 71.5% representunknown genes.     

Maternal Milk Concentration of Zinc,Iron, Selenium,and Iodine and Its Relationship to Dietary Intakes

The dietary intake of zinc (Zn), iron (Fe), selenium (Se), and iodine (I) of 31 lactating Mexican–American women attending the Hidalgo County WIC program in Rio Grande Valley (RGV), Texas was estimated from 24-h dietary recall interviews. Milk samples were obtained from lactating mothers who had infants 3 months of age and younger. Milk samples were collected in two visits to assess change in breast milk composition after 1–3 months postpartum: group A—after 30–45 days and group B—75–90 days. Dietary intakes indicated that the study participants had significantly inadequate percent energy intakes than the DRI (Dietary Recommended Intakes) percent recommended kilocalorie values but protein intakes were substantially higher than the percent recommended values. The estimated percent Zn, Fe, Se, and I intakes were also significantly lower than the DRI percent recommended values. The lactating mothers consumed significantly less Zn, Se, and I when compared to the Recommended Dietary Allowances (RDA) even though Fe intake was higher than the RDA value. Breast milk concentration of Zn, Fe, and Se were in agreement within the range of representative values for Constituents of Human Milk but I has significantly less concentration than the representative value. There was no statistically significant correlation observed between dietary intake and milk concentration of Zn, Fe, Se, and I. This study compares the estimated dietary intake of zinc, iron, selenium, and iodine to the concentration of these trace elements in the maternal milk of lactating women of Mexican–American heritage who attend the Rio Grande Valley WIC clinic.     

Protective antifungal effect of neem (Azadirachta indica) extracts on mango (Mangifera indica) and rain tree (Albizia saman) wood

Neem (Azadirachta indica) extract (NE) and NE combined with copper sulfate and boric acid (NECB) were examined for their protective effect against fungal deterioration of mango (Mangifera indica) and rain tree (Albizia saman) wood. Growth of the white-rot fungus Schizophyllum commune was completely inhibited on solid medium containing 1.8% (w/w) NE or 5% (w/w) NECB. The average weight losses of NE and NECB treated wood blocks inoculated with S. commune were respectively 4.7% and 3.3% for M. indica and 4.1% and 3.0% for A. saman. These numbers were significantly lower compared to those obtained in the untreated condition. Similar observations were also noticed in the case of field tests. An average increase of life span of M. indica and A. saman due to NE treatment compared to untreated samples was about 6–7 times higher. Therefore, both NE and NECB treatments are promising preservation options for enhancing the durability of both M. indica and A. saman woods.     

Chromosome numbers and meiotic analysis in the pre-breeding of <Emphasis Type="BoldItalic">Brachiaria decumbens</Emphasis> (Poaceae)

A total of 44 accessions of Brachiaria decumbens were analysed for chromosome count and meiotic behaviour in order to identify potential progenitors for crosses. Among them, 15 accessions presented 2n = 18; 27 accessions, 2n = 36; and 2 accessions, 2n = 45 chromosomes. Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number and meiotic stability, the present study indicates the apomictic tetraploid accessions that can act as male genitor to produce interspecific hybrids with B. ruziziensis or intraspecific hybrids with recently artificially tetraploidized accessions.     

A new species of the cleptoparasitic bee genus Thyreus from northern Yemen and southwestern Saudi Arabia (Hymenoptera,Apidae)

A new species of cleptoparasitic bee of the genus Thyreus Panzer (Apinae: Melectini) is described and figured from northern Yemen and southwestern Saudi Arabia. Thyreus shebicus Engel, sp. n. is a relatively small species superficially similar to the widespread and polytypic species T. ramosus (Lepeletier de Saint Fargeau) and T. ramosellus (Cockerell) but more closely allied to various African forms on the basis of the male genitalia. The species is distinguished from its congeners on the basis of coloration pattern, male hind leg structure, and particularly male terminalia.     

Dynamics of Japanese Encephalitis Virus Transmission among Pigs in Northwest Bangladesh and the Potential Impact of Pig Vaccination

Background

Japanese encephalitis (JE) virus infection can cause severe disease in humans, resulting in death or permanent neurologic deficits among survivors. Studies indicate that the incidence of JE is high in northwestern Bangladesh. Pigs are amplifying hosts for JE virus (JEV) and a potentially important source of virus in the environment. The objectives of this study were to describe the transmission dynamics of JEV among pigs in northwestern Bangladesh and estimate the potential impact of vaccination to reduce incidence among pigs.

Methodology/Principal Findings

We conducted a comprehensive census of pigs in three JE endemic districts and tested a sample of them for evidence of previous JEV infection. We built a compartmental model to describe JEV transmission dynamics in this region and to estimate the potential impact of pig vaccination. We identified 11,364 pigs in the study area. Previous JEV infection was identified in 30% of pigs with no spatial differences in the proportion of pigs that were seropositive across the study area. We estimated that JEV infects 20% of susceptible pigs each year and the basic reproductive number among pigs was 1.2. The model suggest that vaccinating 50% of pigs each year resulted in an estimated 82% reduction in annual incidence in pigs.

Conclusions/Significance

The widespread distribution of historic JEV infection in pigs suggests they may play an important role in virus transmission in this area. Future studies are required to understand the contribution of pig infections to JE risk in humans and the potential impact of pig vaccination on human disease.