Effects of light on respiration and oxygen isotope fractionation in soybean cotyledons

Light effects on electron flow through the cyanide-resistant respiratory pathway, oxygen isotope fractionation and total respiration were studied in soybean (Glycine max L.) cotyledons. During the first 12 h of illumination there was an increase in both electron partitioning through the alternative pathway and oxygen isotope fractionation by the alternative oxidase. The latter probably indicates a change in the properties of the alternative oxidase. There was no engagement of the alternative oxidase in darkness and its fractionation was 27‰. In green cotyledons 60% of the respiration flux was through the alternative pathway and the alternative oxidase fractionation was 32‰. Exposing previously illuminated tissue to continuous darkness induced a decrease in the electron partitioning through the alternative pathway. However, this decrease was not directly linked with the low cellular sugar concentration resulting from the lack of light because 5 min of light every 12 h was sufficient to keep the alternative pathway engaged to the same extent as plants grown under control conditions.     

An arctic community of symbiotic fungi assembled by long‐distance dispersers: phylogenetic diversity of ectomycorrhizal basidiomycetes in Svalbard based on soil and sporocarp DNA

Aim Current evidence from temperate studies suggests that ectomycorrhizal (ECM) fungi require overland routes for migration because of their obligate symbiotic associations with woody plants. Despite their key roles in arctic ecosystems, the phylogenetic diversity and phylogeography of arctic ECM fungi remains little known. Here we assess the phylogenetic diversity of ECM communities in an isolated, formerly glaciated, high arctic archipelago, and provide explanations for their phylogeographic origins. Location Svalbard. Methods We generated and analysed internal transcribed spacer (ITS) nuclear ribosomal DNA sequences from both curated sporocarp collections (from Svalbard) and soil polymerase chain reaction (PCR) clone libraries (from Svalbard and the North American Arctic), compared these with publicly available sequences in GenBank, and estimated the phylogenetic diversity of ECM fungi in Svalbard. In addition, we conducted coalescent analyses to estimate migration rates in selected species. Results Despite Svalbard’s geographic isolation and arctic climate, its ECM fungi are surprisingly diverse, with at least 72 non‐singleton operational taxonomic units (soil) and 109 phylogroups (soil + sporocarp). The most species‐rich genera are Thelephora/Tomentella, Cortinarius and Inocybe, followed by Hebeloma, Russula, Lactarius, Entoloma, Sebacina, Clavulina, Laccaria, Leccinum and Alnicola. Despite the scarcity of available reference data from other arctic regions, the majority of the phylogroups (73.4%) were also found outside Svalbard. At the same time, all putative Svalbard ‘endemics’ were newly sequenced taxa from diverse genera with massive undocumented diversity. Overall, our results support long‐distance dispersal more strongly than vicariance and glacial survival. However, because of the high variation in nucleotide substitution rates among fungi, allopatric persistence since the Pliocene, although unlikely, cannot be statistically rejected. Results from the coalescent analyses suggest recent gene flow among different arctic areas. Main conclusions Our results indicate numerous recent colonization events and suggest that long‐distance, transoceanic dispersal is widespread in arctic ECM fungi, which differs markedly from the currently prevailing view on the dispersal capabilities of ECM fungi. Our molecular evidence indicates that long‐distance dispersal has probably played a major role in the phylogeographic history of some ECM fungi in the Northern Hemisphere. Our results may have implications for studies on the biodiversity, ecology and conservation of arctic fungi in general.     

Social class differences in secular trends in established coronary risk factors over 20 years: a cohort study of British men from 1978-80 to 1998-2000

Background

Coronary heart disease (CHD) mortality in the UK since the late 1970s has declined more markedly among higher socioeconomic groups. However, little is known about changes in coronary risk factors in different socioeconomic groups. This study examined whether changes in established coronary risk factors in Britain over 20 years between 1978–80 and 1998–2000 differed between socioeconomic groups.

Methods and Findings

A socioeconomically representative cohort of 7735 British men aged 40–59 years was followed-up from 1978–80 to 1998–2000; data on blood pressure (BP), cholesterol, body mass index (BMI) and cigarette smoking were collected at both points in 4252 survivors. Social class was based on longest-held occupation in middle-age. Compared with men in non-manual occupations, men in manual occupations experienced a greater increase in BMI (mean difference = 0.33 kg/m²; 95%CI 0.14–0.53; p for interaction = 0.001), a smaller decline in non-HDL cholesterol (difference in mean change = 0.18 mmol/l; 95%CI 0.11–0.25, p for interaction≤0.0001) and a smaller increase in HDL cholesterol (difference in mean change = 0.04 mmol/l; 95%CI 0.02–0.06, p for interaction≤0.0001). However, mean systolic BP declined more in manual than non-manual groups (difference in mean change = 3.6; 95%CI 2.1–5.1, p for interaction≤0.0001). The odds of being a current smoker in 1978–80 and 1998–2000 did not differ between non-manual and manual social classes (p for interaction = 0.51).

Conclusion

Several key risk factors for CHD and type 2 diabetes showed less favourable changes in men in manual occupations. Continuing priority is needed to improve adverse cardiovascular risk profiles in socially disadvantaged groups in the UK.     

Synthesis of an antigenic site of native acetylcholine receptor peptide 159-169 of Torpedo acetylcholine receptor alpha-chain.

A region of the alpha-subunit of the nicotinic acetylcholine receptor (AChR) of the Torpedo electric organ, containing residues 161-166, has been proposed to be a major antigenic site in the native AChR protein. We report the synthesis of a peptide corresponding to residues 159-169, which contains the proposed antigenic region. In quantitative radiometric titrations, radiolabelled anti-(native AChR) antibodies from three different species, rabbit, rat and dog, exhibited considerable binding (approx. 15% relative to native AChR) to Sepharose-immobilized peptide 159-169, but did not bind significantly to Sepharose-immobilized unrelated proteins or peptides. Specificity was further confirmed by the finding that no rabbit anti-AChR antibodies bound to the peptide after absorption with native AChR. These data indicate that the region 159-169 contains an antigenic site that is readily accessible in solubilized native Torpedo AChR.     

Mouse T lymphocyte response to acetylcholine receptor determined by T cell receptor for antigen V beta gene products recognizing Mls-1a.

Mice of strain B6, but not AKR/J, respond to immunization with Torpedo acetylcholine receptor (AChR) by manifesting in vitro an Ag-specific T lymphocyte proliferative response. Our analysis of (AKR x B6)F1 mice reveals that the T cell unresponsiveness of AKR/J is inherited as a dominant trait, possibly associated with expression of the Mls-1a allele. Mice derived from backcrossing (AKR x B6)F1 x B6 were selected for H-2b homozygosity and were classified as Mls-1a or Mls-1b according to the relative numbers of peripheral blood T cells that expressed the TCR V beta 6 gene product. After challenge by injection with AChR in CFA, lymph node cells from mice classified as having less than 2% of V beta 6+ peripheral T cells had low responsiveness to AChR, whereas mice with greater than 7% V beta 6+ peripheral T cells had high T cell responsiveness to AChR. These results are consistent with the notion that regulation of the T cell repertoire by Mls loci may be a determinant of susceptibility to autoimmunity.     

Spatiotemporal scaling of plant species richness and functional diversity in a temperate semi‐natural grassland

The accumulation of biodiversity in space and time has been modelled extensively using the species–area relationship and the species–time relationship, respectively. Recently, these models have been combined into time–area curves in order to investigate spatiotemporal scaling of species richness. This study expands on previous research by applying these spatiotemporal models to functional diversity. Understanding spatiotemporal dynamics of ecological traits is important due to their crucial role in ecosystem functioning and mediating species responses to environmental change. We present a new function based on the semi‐logarithmic species–area relationship, which was applied with a power function to vegetation survey data from Scottish machair grassland for both species richness and two measures of functional diversity. When taking a whole‐study approach using non‐linear mixed effects models, the semi‐logarithmic function used here shows a positive time–area interaction for species richness, contrasting with the negative interaction of the power law found in previous investigations. Although there was a negative time–area interaction for functional diversity measures at the whole‐study scale, parameter estimates were inconsistent at the individual site level. Overall, the results reveal differing spatiotemporal dynamics of species and their traits and suggest that the appropriate scale for space‐for‐time substitutions depends on the aspect of biodiversity being investigated. The new model developed in this study, and the novel application to functional diversity, opens up future possible research into spatiotemporal dynamics of biodiversity.     

Neuronal autoantibody titers in the course of small-cell lung carcinoma and platinum-associated neuropathy

The aims of this study were to investigate, in patients with newly diagnosed small-cell lung carcinoma (SCLC), whether or not there may be a relationship between the presence, type or titer of circulating neuronal autoantibodies and (i) the extent of SCLC dissemination at presentation, (ii) the development of peripheral neuropathy during platinum chemotherapy, (iii) survival time. We studied stored serum from 58 patients with uncomplicated SCLC who had participated in two trials conducted by the North Central Cancer Treatment Group (NCCTG); 29 had extensive disease and 29 had limited disease. No patient had neuropathy or other neurological or paraneoplastic problems at the time of enrollment but each group included 14 or 15 patients respectively who developed peripheral neuropathy in the course of chemotherapy. We tested five consecutive serum specimens from each patient in blinded fashion by (i) an indirect immunofluorescence assay optimized to detect neuron-restricted nuclear and cytoplasmic antibodies (triple substrate of mouse cerebellum, gut and kidney), and (ii) immunoprecipitation assays to detect neuronal Ca²⁺-channel-binding antibodies (N-type and P/Q-type). Sera that were positive by immunofluorescence were analyzed further by Western blotting. Neuronal autoantibodies were significantly more frequent in patients who had limited SCLC at presentation (12/29 or 41% positive) than in those with extensive SCLC (5/29 or 17% positive, P = 0.02). Neuronal autoantibodies of nuclear or cytoplasmic specificity were found in 50% of the seropositive patients with limited SCLC (21% of the total group), but in no patient with extensive SCLC (P = 0.01). The frequency of neuronal autoantibodies did not differ significantly among patients who did and did not develop peripheral neuropathy. Titers fell progressively during chemotherapy and did not rise again when peripheral neuropathy became clinically evident. This argues against a synergism between drug toxicity and neuronal autoimmunity as the mechanism of platinum-associated peripheral neuropathy. Seropositivity for neuronal autoantibodies did not affect the survival of patients with either limited or extensive SCLC. It is conceivable that the immunosuppression attendant on combined cisplatin/etoposide therapy cancels a pre-existing protective antitumor immune response (presumably cytotoxic-T-cell-mediated) for which the nuclear and cytoplasmic paraneoplastic IgG autoantibodies serve as a surrogate marker. Testing of this hypothesis would require the survival of seropositive and seronegative patients to be compared in a larger trial, using a therapeutic modality that does not compromise immunocompetence. Received: 20 November 1998 / Accepted: 6 January 1999     

Recombinant human acetylcholine receptor alpha-subunit induces chronic experimental autoimmune myasthenia gravis

A synthetic gene encoding the 210 N-terminal residues of the alpha-subunit of the nicotinic acetylcholine receptor (AChR) of human skeletal muscle was cloned into an inducible expression plasmid to produce a fusion protein in high yield in Escherichia coli. Like native human AChR, the recombinant human alpha 1-210 protein induced AChR-binding, AChR-modulating, and AChR-blocking autoantibodies in rats when injected once intradermally as an emulsion in CFA, with Bordetella pertussis vaccine as supplementary adjuvant. The minimum dose of recombinant protein required to induce biochemical signs of experimental autoimmune myasthenia gravis (EAMG) with 100% incidence was 2.2 micrograms. With 6.6 to 22 micrograms, serum levels of autoantibodies were persistent, and clinically apparent EAMG lasted more than a month. Clinical, electrophysiological, and biochemical indices of EAMG induced by doses of 66 micrograms or more were more uniformly severe and persistent, with 33% fatality. Rats receiving a control extract of E. coli containing plasmid without the alpha 1-210 codon insert, with adjuvants, did not develop autoantibodies or signs of EAMG. This highly reproducible new model of EAMG induced by a recombinant human autoantigen should be valuable for testing Ag-specific immunotherapeutic strategies that might be applicable to treating acquired myasthenia gravis in humans.     

Identification and functional analysis of three distinct mutations in the human galactose-1-phosphate uridyltransferase gene associated with galactosemia in a single family.

We have identified three mutations associated with transferase-deficiency galactosemia in a three-generation family including affected members in two generations and have modeled all three mutations in a yeast-expression system. A sequence of pedigree, biochemical, and molecular analyses of the galactose-1-phosphate uridyltransferase (GALT) enzyme and genetic locus in both affected and carrier individuals revealed three distinct base substitutions in this family, two (Q188R and S135L) that had been reported previously and one (V151A) that was novel. Biochemical analyses of red-blood-cell lysates from the relevant family members suggested that each of these mutations was associated with dramatic impairment of GALT activity in these cells. While this observation was consistent with our previous findings concerning the Q188R mutation expressed both in humans and in a yeast-model system, it was at odds with a report by Reichardt and colleagues, indicating that in their COS cell-expression system the S135L substitution behaved as a neural polymorphism. To address this apparent paradox, as well as to investigate the functional significance of the newly identified V151A substitution, all three mutations were recreated by site-directed mutagenesis of the otherwise wild-type human GALT sequence and were expressed both individually and in the appropriate allelic combinations in a GALT-deficient strain of the yeast Saccharomyces cerevisiae.(ABSTRACT TRUNCATED AT 250 WORDS)