Population genetic structure of the western cherry fruit fly Rhagoletis indifferens (Diptera: Tephritidae) in British Columbia,Canada

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Molecular features of the broadly neutralizing immunoglobulin G1 b12 required for recognition of human immunodeficiency virus type 1 gp120

IgG1 b12 is a broadly neutralizing antibody against human immunodeficiency virus type 1 (HIV-1). The epitope recognized by b12 overlaps the CD4 receptor-binding site (CD4bs) on gp120 and has been a target for vaccine design. Determination of the three-dimensional structure of immunoglobulin G1 (IgG1) b12 allowed modeling of the b12-gp120 interaction in which the protruding third complementarity-determining region (CDR) of the heavy chain (H3) was crucial for antibody binding. In the present study, extensive mutational analysis of the antigen-binding site of Fab b12 was carried out to investigate the validity of the model and to identify residues important for gp120 recognition and, by inference, key to the anti-HIV-1 activity of IgG1 b12. In all, 50 mutations were tested: 40 in H3, 4 each in H2 and L1, and 2 in L3. The results suggest that the interaction of gp120 with H3 of b12 is crucially dependent not only on a Trp residue at the apex of the H3 loop but also on a number of residues at the base of the loop. The arrangement of these residues, including aromatic side chains and side chains that hydrogen bond across the base of the loop, may rigidify H3 for penetration of the recessed CD4-binding cavity. The results further emphasize the importance to gp120 binding of a Tyr residue at the apex of the H2 loop that forms a second finger-like structure and a number of Arg residues in L1 that form a positively charged, shelf-like structure. In general, the data are consistent with the b12-gp120 interaction model previously proposed. At the gene level, somatic mutation is seen to be crucial for the generation of many of the structural features described. The Fab b12 mutants were also tested against the b12 epitope-mimic peptide B2.1, and the reactivity profile had many similarities but also significant differences from that observed for gp120. The paratope map of b12 may facilitate the design of molecules that are able to elicit b12-like activities.     

Nitrogen Export from Forested Watersheds in the Oregon Coast Range: The Role of N<Subscript>2</Subscript>-fixing Red Alder

Variations in plant community composition across the landscape can influence nutrient retention and loss at the watershed scale. A striking example of plant species importance is the influence of N₂-fixing red alder (Alnus rubra) on nutrient cycling in the forests of the Pacific Northwest. To understand the influence of red alder on watershed nutrient export, we studied the chemistry of 26 small watershed streams within the Salmon River basin of the Oregon Coast Range. Nitrate and dissolved organic nitrogen (DON) concentrations were positively related to broadleaf cover (dominated by red alder: 94% of basal area), particularly when near-coastal sites were excluded (r ² = 0.65 and 0.68 for nitrate-N and DON, respectively). Nitrate and DON concentrations were more strongly related to broadleaf cover within entire watersheds than broadleaf cover within the riparian area alone, which indicates that leaching from upland alder stands plays an important role in watershed nitrogen (N) export. Nitrate dominated over DON in hydrologic export (92% of total dissolved N), and nitrate and DON concentrations were strongly correlated. Annual N export was highly variable among watersheds (2.4–30.8 kg N ha^–1 y^–1), described by a multiple linear regression combining broadleaf and mixed broadleaf–conifer cover (r² = 0.74). Base cation concentrations were positively related to nitrate concentrations, which suggests that nitrate leaching increases cation losses. Our findings provide evidence for strong control of ecosystem function by a single plant species, where leaching from N saturated red alder stands is a major control on N export from these coastal watersheds.     

Muscle activation imbalance and low-back injury in varsity athletes.

There are conflicting findings in the literature regarding erector spinae activation imbalance in people with low-back pain (LBP). Some studies have found asymmetric recruitment between muscle pairs in people with LBP, whilst other studies have not; some reported people with LBP recruit more lumbar muscles whilst other have reported greater thoracic activity. Using 242 varsity athletes, EMG activity of thoracic and lumbar erector spinae pairs was recorded during an isometric trunk extension. Activation imbalance among muscle pairs and levels was compared between athletes with and without a history of low-back injury (HxLBI). There were no group differences in the imbalance between sides, but the HxLBI group had greater activation imbalance between lumbar and thoracic levels than the No HxLBI group. Activation imbalance between levels was similar for individuals with No HxLBI and those who sustained first time injury suggesting that imbalance does not cause LBI. There was no difference between the athletes with single and multiple episode LBI, nor between short and long symptom duration suggesting that the presence of imbalance is not an impairment. Interestingly, activation imbalance occurred in both directions, meaning more thoracic activity for some, and more lumbar activity for others, which might be a functional adaptation related to pathology.     

Toxicity of polycyclic aromatic hydrocarbons. VI. Effects of 1-nitropyrene on serum enzyme levels in rats, and protection against it by beta-naphthoflavone and dimethyl sulfoxide

Male Sprague-Dawley rats were pretreated i.p. with corn oil or DMSO (1.5 ml/kg/day), or with beta-naphthoflavone (BNF, 40 mg/kg/day) in corn oil or DMSO for 3 days. 1-Nitropyrene (1-NP, 150 mg/kg) in DMSO was injected i.p. 24 hr after pretreatment. A significant increase in the levels of several serum enzymes was seen in rats pretreated with corn oil alone 24 hr after 1-NP injection. The increase in enzyme activities was significantly reduced by a 3-day pretreatment with DMSO or BNF.     

Herpes Simplex Virus DNA Packaging without Measurable DNA Synthesis

Herpes simplex virus (HSV) type 1 DNA synthesis and packaging occur within the nuclei of infected cells; however, the extent to which the two processes are coupled remains unclear. Correct packaging is thought to be dependent upon DNA debranching or other repair processes, and such events commonly involve new DNA synthesis. Furthermore, the HSV UL15 gene product, essential for packaging, nevertheless localizes to sites of active DNA replication and may link the two events. It has previously been difficult to determine whether packaging requires concomitant DNA synthesis due to the complexity of these processes and of the viral life cycle; however, we have recently described a model system which simplifies the study of HSV assembly. Cells infected with HSV strain tsProt.A accumulate unpackaged capsids at the nonpermissive temperature of 39°C. Following release of the temperature block, these capsids proceed to package viral DNA in a single, synchronous wave. Here we report that, when DNA replication was inhibited prior to release of the temperature block, DNA packaging and later events in viral assembly nevertheless occurred at near-normal levels. We conclude that, under our conditions, HSV DNA packaging does not require detectable levels of DNA synthesis.