A mouse-adapted SARS-coronavirus causes disease and mortality in BALB/c mice

No single animal model for severe acute respiratory syndrome (SARS) reproduces all aspects of the human disease. Young inbred mice support SARS-coronavirus (SARS-CoV) replication in the respiratory tract and are available in sufficient numbers for statistical evaluation. They are relatively inexpensive and easily accessible, but their use in SARS research is limited because they do not develop illness following infection. Older (12- to 14-mo-old) BALB/c mice develop clinical illness and pneumonitis, but they can be hard to procure, and immune senescence complicates pathogenesis studies. We adapted the SARS-CoV (Urbani strain) by serial passage in the respiratory tract of young BALB/c mice. Fifteen passages resulted in a virus (MA15) that is lethal for mice following intranasal inoculation. Lethality is preceded by rapid and high titer viral replication in lungs, viremia, and dissemination of virus to extrapulmonary sites accompanied by lymphopenia, neutrophilia, and pathological changes in the lungs. Abundant viral antigen is extensively distributed in bronchial epithelial cells and alveolar pneumocytes, and necrotic cellular debris is present in airways and alveoli, with only mild and focal pneumonitis. These observations suggest that mice infected with MA15 die from an overwhelming viral infection with extensive, virally mediated destruction of pneumocytes and ciliated epithelial cells. The MA15 virus has six coding mutations associated with adaptation and increased virulence; when introduced into a recombinant SARS-CoV, these mutations result in a highly virulent and lethal virus (rMA15), duplicating the phenotype of the biologically derived MA15 virus. Intranasal inoculation with MA15 reproduces many aspects of disease seen in severe human cases of SARS. The availability of the MA15 virus will enhance the use of the mouse model for SARS because infection with MA15 causes morbidity, mortality, and pulmonary pathology. This virus will be of value as a stringent challenge in evaluation of the efficacy of vaccines and antivirals.     

Rhizodeposition shapes rhizosphere microbial community structure in organic soil

The aims of the study were to determine group specificity in microbial utilization of root-exudate compounds and whole rhizodeposition; quantify the proportions of carbon acquired by microbial groups from soil organic matter and rhizodeposition, respectively; and assess the importance of root-derived C as a driver of soil microbial community structure. Additions of 13C-labelled root-exudate compounds to organic soil and steady-state labelling of Lolium perenne, coupled to compound-specific isotope ratio mass spectrometry, were used to quantify group-specific microbial utilization of rhizodeposition. Microbial utilization of glucose and fumaric acid was widespread through the microbial community, but glycine was utilized by a narrower range of populations, as indicated by the enrichment of phospholipid fatty acid (PLFA) analysis fractions. In L. perenne rhizospheres, high rates of rhizodeposit utilization by microbial groups showed good correspondence with increased abundance of these groups in the rhizosphere. Although rhizodeposition was not the quantitatively dominant C source for microbes in L. perenne rhizospheres, relative utilization of this C source was an important driver of microbial group abundance in organic soil.     

Setting the stage for S phase

In a recent issue of Molecular Cell, Tyagi et al. (2007) show that E2F1, a positive regulator of S phase entry, recruits cofactor HCF-1 and associated hSet1/MLL histone H3 lysine 4 methyltransferase complex, facilitating the activation of genes required for proliferation.     

Zinc transporter expression profiles in the rat prostate following alterations in dietary zinc

Zinc plays important roles in numerous cellular activities and physiological functions. Intracellular zinc levels are strictly maintained by zinc homeostatic mechanisms. Zinc concentrations in the prostate are the highest of all soft tissues and could be important for prostate health. However, the mechanisms by which the prostate maintains high zinc levels are still unclear. In addition, the response of the prostate to alterations in dietary zinc is unknown. The current study explored cellular zinc levels and zinc transporter expression profiles in the lobes of the prostate during dietary marginal zinc depletion. Rats were given either zinc-adequate (ZA, 30 mg Zn/kg) or marginal zinc-deficient (MZD, 5 mg Zn/kg) diet for 9 weeks. In addition, a subgroup of the MZD rats was supplemented with phytase (1,500 unit/kg diet) to improve zinc bioavailability. We found that both zinc concentrations and ZnT2 expression in the prostate dorsolateral lobes were substantially higher than in the ventral lobes (P < 0.05). Marginal zinc depletion significantly decreased ZnT2 expression in the dorsolateral lobes (P < 0.05), and phytase supplementation had a trend to increase ZnT2 expression. In addition, of all measured zinc transporters, only ZnT2 mRNA abundance was significantly correlated to the zinc concentrations in the dorsolateral lobe. No correlations were found between zinc transporter expression and zinc concentrations in the ventral lobes. These results indicate that ZnT2 may play a significant role in the maintenance of zinc homeostasis in the prostate.     

DNA barcoding of stylommatophoran land snails: a test of existing sequences

DNA barcoding has attracted attention because it is a potentially simple and universal method for taxonomic assignment. One anticipated problem in applying the method to stylommatophoran land snails is that they frequently exhibit extreme divergence of mitochondrial DNA sequences, sometimes reaching 30% within species. We therefore trialled the utility of barcodes in identifying land snails, by analysing the stylommatophoran cytochrome oxidase subunit I sequences from GenBank. Two alignments of 381 and 228 base pairs were used to determine potential error rates among a test data set of 97 or 127 species, respectively. Identification success rates using neighbour‐joining phylogenies were 92% for the longer sequence and 82% for the shorter sequence, indicating that a high degree of mitochondrial variation may actually be an advantage when using phylogeny‐based methods for barcoding. There was, however, a large overlap between intra‐ and interspecific variation, with assignment failure (per cent of samples not placed with correct species) particularly associated with a low degree of mitochondrial variation (Kimura 2‐parameter distance < 0.05) and a small GenBank sample size (< 25 per species). Thus, while the optimum intra/interspecific threshold value was 4%, this was associated with an overall error of 32% for the longer sequences and 44% for the shorter sequences. The high error rate necessitates that barcoding of land snails is a potentially useful method to discriminate species of land snail, but only when a baseline has first been established using conventional taxonomy and sample DNA sequences. There is no evidence for a barcoding gap, ruling out species discovery based on a threshold value alone.     

Neighbourhood Factors and Depression among Adolescents in Four Caribbean Countries

Background

Past research suggests that perceived neighbourhood conditions may influence adolescents'' emotional health. Relatively little research has been conducted examining the association of perceived neighbourhood conditions with depressive symptoms among Caribbean adolescents. This project examines the association of perceived neighbourhood conditions with levels of depressive symptoms among adolescents in Jamaica, the Bahamas, St. Kitts and Nevis, and St. Vincent.

Methods

Adolescents attending grade ten of the academic year 2006/2007 in Jamaica, the Bahamas, St. Vincent, and St. Kitts and Nevis were administered the Neighbourhood Characteristics Questionnaire along with the BDI-II. Social cohesion, attachment to the neighbourhood, neighbourhood quality, neighbourhood crime, and neighbourhood disorder scales were created by summing the relevant subscales of the Neighbourhood Characteristics Questionnaire. Multiple regression analyses were used to examine the relationships of perceived neighbourhood conditions to depressive symptoms.

Results

A wide cross-section of tenth grade students in each nation was sampled (n = 1955; 278 from Jamaica, 217 from the Bahamas, 737 St. Kitts and Nevis, 716 from St. Vincent; 52.1% females, 45.6% males and 2.3% no gender reported; 12 to 19 years, mean = 15.3 yrs, sd = .95 yr). Nearly half (52.1%) of all adolescents reported mild to severe symptoms of depression with 29.1% reporting moderate to severe symptoms of depression. Overall, Jamaican adolescents perceived their neighbourhoods in a more positive manner than those in the Bahamas, St. Vincent and St. Kitts and Nevis. Results of a series of hierarchical multiple regression analyses suggested that a different pattern of neighbourhood factors for each island were associated with depressive symptoms. However, neighbourhood factors were more highly associated with depressive symptoms for Jamaican students than for students in the other three islands.

Conclusions

Neighbourhood factors appear to be partially associated with adolescents'' self-reports of depressive symptoms. However, other factors may mitigate this relationship.