Analysis of pVU3695, a plasmid encoding glutathione-dependent formaldehyde dehydrogenase activity and formaldehyde resistance in the Escherichia coli VU3695 clinical strain

The formaldehyde resistance of Escherichia coli VU3695 is due to the expression of glutathione-dependent formaldehyde dehydrogenase (GSH-FDH) activity, which is encoded by the adhC gene located on the plasmid pVU3695. Conjugation of this plasmid to an unrelated PolA deficient strain of E. coli indicated that it encodes its own replication initiation protein and does not confer resistance to several other antimicrobial agents tested in this work. In addition, pVU3695 has homology with replicons that belong to the IncL/M plasmid incompatibility group, which are widely distributed among the Enterobacteriaceae. Curing of pVU3695 abolished the expression of formaldehyde resistance and the presence of a 46-kDa periplasmic protein immunologically related to GSH-FDH. However, the curing of pVU3695 reduced drastically but did not abolish the expression of a protein with similar electrophoretic motility, which was associated with the expression of GSH-FDH activity still present in the cytoplasm of the plasmidless derivative. The data demonstrate that E. coli VU3695 contains a chromosomal and a plasmid copy of adhC actively expressed, with the latter being involved in resistance to exogenous formaldehyde.     

Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica

Comparing geographic variation of noncoding nuclear DNA polymorphisms, which presumably are neutral to natural selection, with geographic variation of allozymes is potentially a good way to detect the effects of selection on allozyme polymorphisms. A previous study of four anonymous nuclear markers in the American oyster, Crassostrea virginica, found dramatic differences in allele frequency between the Gulf of Mexico and the Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform in frequency between the two areas. This led to the conclusion that all of the allozyme polymorphisms were kept uniform in frequency by balancing selection. To test the robustness of this pattern, six additional anonymous nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the previously studied DNA markers, the six DNA polymorphisms examined here show geographic variation that is not significantly greater than that of allozymes. The reason for the discrepancy between the two sets of DNA polymorphisms is unclear.      

The A.M.A. Session

The use of liquid nitrogen for the removal of warts has advantages over electrocautery in certain circumstances. Although the incidence of recurrences after liquid nitrogen is higher than after cautery, it causes considerably less scarring. It is most useful in dealing with peri-ungual and multiple warts.The technique is simple and a supply of liquid nitrogen can be kept on hand in the office at relatively low cost.     

The mitogenome of Onchocerca volvulus from the Brazilian Amazonia focus

We report here the first complete mitochondria genome of Onchocerca volvulus from a focus outside of Africa. An O. volvulus mitogenome from the Brazilian Amazonia focus was obtained using a combination of high-throughput and Sanger sequencing technologies. Comparisons made between this mitochondrial genome and publicly available mitochondrial sequences identified 46 variant nucleotide positions and suggested that our Brazilian mitogenome is more closely related to Cameroon-origin mitochondria than West African-origin mitochondria. As well as providing insights into the origins of Latin American onchocerciasis, the Brazilian Amazonia focus mitogenome may also have value as an epidemiological resource.     

Long-term landscape changes in vegetation structure: fire management in the wetlands of KwaMbonambi,South Africa

In wetlands the effects of fire on vegetation dynamics are somewhat uncertain. A change detection analysis in the herbaceous wetlands of KwaMbonambi, South Africa, which were subject to frequent fires, revealed that in 1937 the study area comprised grassland (69%), herbaceous wetland (25%), indigenous swamp forest (4%) and tree plantations (1%). However, by 1970, tree plantations occupied 78% of the landscape and grasslands and herbaceous wetlands had declined to 9% and 6%, respectively, whereas indigenous swamp forest had increased to 6%. By 2009 tree plantations had been removed from the wetland areas. Despite this opportunity for herbaceous wetlands to recover their historical extent, they decreased to only 2%, mostly changing to indigenous swamp forest or to an herbaceous/fern (Stenochlaena tenuifolia)/woodland mosaic. Fire records showed suppression of fire to be an important contributing factor, particularly in wetlands that had been disturbed by tree plantations, although subsequently removed. A pilot burning experiment revealed that S. tenuifolia did not inhibit fire. It is therefore practicable to increase fire frequency to prevent the mosaic developing into forest. A conceptual model of the influence of fire regime on wetland vegetation type is presented and priorities for further research on wetlands and fire are recommended.     

Arsenic trioxide-induced transcriptional activation of stress genes and expression of related proteins in human liver carcinoma cells (HepG2).

Arsenic is a naturally occurring element, but anthropogenic activities can lead to a substantial contamination of the environment. Exposure to arsenic has been associated with a significant number of adverse health effects in humans including: cardiovascular disease, diabetes, hearing loss, developmental abnormalities, anemia, neurologic and neurobehavioral disorder, leukopenia, eosinophilia, fibrosis of the liver and the kidney and various neoplasms. However, the cellular and molecular events associated with arsenic toxicity are poorly understood. Also, the precise mechanisms by which arsenic acts as a carcinogen in humans remain to be elucidated. In the present study, we used human liver carcinoma (HepG2) cells as a model to study the molecular mechanisms of arsenic-induced toxicity and carcinogenesis. We hypothesized that arsenic-induced expression of stress genes and related proteins may play a role in the cellular and molecular events leading to toxicity and tumorigenesis in liver cells. To test this hypothesis, we performed the MTT-assay for cell viability, the CAT-Tox (L) assay for gene induction, and the Western Blot analysis to assess the expression of cellular proteins including c-fos, HMTIIA, HSP70 and p53. Data obtained from the MTT assay indicated a strong dose-response relationship with respect to arsenic trioxide toxicity. Upon 48 hr of exposure, the chemical dose required to cause 50% reduction in cell viability (LD50) was computed to be 8.55 +/- 0.58 microg/ml. The CAT-Tox (L) assay showed statistically significant inductions (p<0.05) of c-fos, HMTIIA, and HSP70. Western blot analysis also demonstrated a dose-response relationship with regard to expression of specific cellular proteins. The p53 protein was expressed in arsenic trioxide-treated cells, however, the densitometric analysis did not show any significant differences (p<0.05) between treated and control cells. The lack of a significant induction of p53 may be due to the potential mitogenic effect of arsenic at low levels of arsenic exposure.     

Disruption of an Amino Acid Transport Mutant of Neurospora crassa by KCl

A double amino acid transport-deficient mutant (Pm (-)NB) of Neurospora crassa is shown to be altered in the molecular structure of its cell wall or membrane. This alteration was revealed by a high degree of cellular disruption and cell-cell interaction following extraction by a high molar concentration of KCl.     

Alterations in Regulatory T Cell Subpopulations Seen in Preterm Infants

Regulatory T cells are a population of CD4+ T cells that play a critical role in peripheral tolerance and control of immune responses to pathogens. The purpose of this study was to measure the percentages of two different regulatory T cells subpopulations, identified by the presence or absence of CD31 (Recent thymic emigrants and peripherally induced naïve regulatory T cells), in term and preterm infant cord blood. We report the association of prenatal factors, intrauterine exposure to lipopolysaccharide and inflammation and the percentages of these regulatory T cell subpopulations in term and preterm infants. Cord blood samples were collected from both term and preterm infants and mononuclear cells isolated over a Ficoll-Hypaque cushion. Cells were then stained with fluorochrome-labeled antibodies to characterize regulatory T cell populations and analyzed with multi-color flow cytometry. Cord blood plasma C-reactive protein, and lipopolysaccharide were also measured. Placental pathology was also examined. We report a gestational age-dependent difference in the percentage of total regulatory T cells, in which preterm infants of lower gestational ages have an increased percentage of regulatory T cells. We report the presence of two populations of regulatory T cells (CD31+ and CD31-) in cord blood of term and preterm infants and their association with different maternal and fetal characteristics. Factors associated with differences in the percentage of CD31- Tregs included the use of prenatal antibiotics, steroids and magnesium sulfate. In addition, the percentage of CD31- Tregs was significantly higher in cord blood of preterm pregnancies associated with inflammation and prenatal lipopolysaccharide exposure. The peripheral Treg pool of preterm infants could be altered by prenatal exposure to inflammation and chorioamnionitis; however, the clinical implications of this finding are not yet understood.