Author Correction: Mapping the world's free-flowing rivers.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Humans reshape wetlands: Unveiling the last 100 years of morphological changes of the Mara Wetland, Tanzania.

The Lower Mara River and Wetland, Tanzania, is an important ecosystem and unique water resource for a vast semi-arid area. The river, an affluent of Lake Victoria, and the wetland are experiencing morphological and vegetation changes resulting in channel avulsions and wetland expansion. This study analyses the changes over the last 100 years and investigates natural and anthropogenic behaviors to explain the increase of the Mara Wetland area. We collated historical topographic maps and satellite images. We conducted two field surveys in low and high flow condition with an unmanned aerial vehicle, a sonar and an ADCP. We mapped selected areas as well as the bed topography in some stretches of the river, measured discharges, and collected river bed and suspended sediment samples. The analysis of the sediments shows that the wetland system, dominated by papyrus sp., is very efficient in trapping sediment, releasing clear water to the Lake Victoria. The historical reconstruction using topographic maps, satellite images and a multivariable analysis including hydrology and land cover, shows that 4 major avulsions occurred in the last 70 years due to a combination of natural behaviors, hydrological fluctuations and anthropogenic factors such as basin deforestation, farming and grazing along the river banks and in the wetland. Each avulsion led to substantial expansion of the wetland. Combined, they increased the wetland area by a factor of 3.6. Describing the Lower Mara River dynamic behavior, this work provides relevant information for sustainable future water and sediment management in order to preserve wetland habitats and natural resources.

Mapping the world's free-flowing rivers.

Free-flowing rivers (FFRs) support diverse, complex and dynamic ecosystems globally, providing important societal and economic services. Infrastructure development threatens the ecosystem processes, biodiversity and services that these rivers support. Here we assess the connectivity status of 12 million kilometres of rivers globally and identify those that remain free-flowing in their entire length. Only 37 per cent of rivers longer than 1,000 kilometres remain free-flowing over their entire length and 23 per cent flow uninterrupted to the ocean. Very long FFRs are largely restricted to remote regions of the Arctic and of the Amazon and Congo basins. In densely populated areas only few very long rivers remain free-flowing, such as the Irrawaddy and Salween. Dams and reservoirs and their up- and downstream propagation of fragmentation and flow regulation are the leading contributors to the loss of river connectivity. By applying a new method to quantify riverine connectivity and map FFRs, we provide a foundation for concerted global and national strategies to maintain or restore them.

Differential evolution of peripheral cytokine levels in symptomatic and asymptomatic responses to experimental influenza virus challenge.

Exposure to influenza virus triggers a complex cascade of events in the human host. In order to understand more clearly the evolution of this intricate response over time, human volunteers were inoculated with influenza A/Wisconsin/67/2005 (H3N2), and then had serial peripheral blood samples drawn and tested for the presence of 25 major human cytokines. Nine of 17 (53%) inoculated subjects developed symptomatic influenza infection. Individuals who will go on to become symptomatic demonstrate increased circulating levels of interleukin (IL)-6, IL-8, IL-15, monocyte chemotactic protein (MCP)-1 and interferon (IFN) gamma-induced protein (IP)-10 as early as 12-29 h post-inoculation (during the presymptomatic phase), whereas challenged patients who remain asymptomatic do not. Overall, the immunological pathways of leucocyte recruitment, Toll-like receptor (TLR)-signalling, innate anti-viral immunity and fever production are all over-represented in symptomatic individuals very early in disease, but are also dynamic and evolve continuously over time. Comparison with simultaneous peripheral blood genomics demonstrates that some inflammatory mediators (MCP-1, IP-10, IL-15) are being expressed actively in circulating cells, while others (IL-6, IL-8, IFN-α and IFN-γ) are probable effectors produced locally at the site of infection. Interestingly, asymptomatic exposed subjects are not quiescent either immunologically or genomically, but instead exhibit early and persistent down-regulation of important inflammatory mediators in the periphery. The host inflammatory response to influenza infection is variable but robust, and evolves over time. These results offer critical insight into pathways driving influenza-related symptomatology and offer the potential to contribute to early detection and differentiation of infected hosts.

Hydroxychloroquine sulfate treatment is associated with later onset of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a clinically diverse, complex autoimmune disease which may present with coincident onset of many criteria or slow, gradual symptom accrual. Early intervention has been postulated to delay or prevent the development of more serious sequelae. One option for treatment in this setting is hydroxychloroquine. Using 130 US military personnel who later met ACR SLE criteria, a retrospective study of onset, development and progression of SLE with and without pre-classification hydroxychloroquine (n = 26) use was performed. Patients treated with hydroxychloroquine prior to diagnosis had a longer (Wilcoxon signed rank test, P = 0.018) time between the onset of the first clinical symptom and SLE classification (median: 1.08 versus 0.29 years). Patients treated with prednisone before diagnosis also more slowly satisfied the classification criteria (Wilcoxon signed rank test, P = 0.011). The difference in median times between patients who received NSAIDs before diagnosis, as opposed to those who did not, was not different (P = 0.19). Patients treated with hydroxychloroquine also had a lower rate of autoantibody accumulation and a decreased number of autoantibody specificities at and after diagnosis. These findings are consistent with early hydroxychloroquine use being associated with delayed SLE onset. A prospective, blinded trial testing the capacity of hydroxychloroquine to delay or prevent SLE in high risk populations is warranted.

The reference range and within-person variability of thyroid stimulating hormone during the first and second trimesters of pregnancy.

OBJECTIVE: To further explore first and second trimester reference ranges for thyroid stimulating hormone (TSH) and examine within-person variability of TSH and thyroid peroxidase (TPO) antibody. SETTING: Women coming for routine prenatal care in early pregnancy agreed to participate in a trial of integrated serum screening for Down's syndrome. Two serum samples were obtained from each woman, one each in the first and second trimesters. These samples were also available for TSH and TPO measurements in the present study. METHODS: TSH and TPO antibody measurements were performed in 1126 women with ultrasound-dated pregnancies who provided serum samples in both trimesters. TSH reference ranges were established for the entire cohort and for the antibody-negative subgroup. Within-person variability of TSH measurements between trimesters was examined. RESULTS: Median TSH values are lower in the first trimester than in the second (1.00 versus 1.29 mIU/l), but 98th centile values are higher (5.20 versus 4.18 mIU/l). High correlation exists between individual women's first and second trimester TSH measurements (r=0.75, r2=0.56, p<0.001). Among 23 women with TSH values above the 98th centile in the second trimester, 17 (74%) were over the 95th centile in the first trimester. TPO antibody measurements are also highly correlated between trimesters (r=0.97, r)=0.94). CONCLUSION: Proper interpretation of TSH measurements during pregnancy requires that laboratories establish and monitor appropriate reference ranges. TSH levels show high within-person consistency between trimesters.

Hereditary haemochromatosis and hepatocellular carcinoma in males: a strategy for estimating the potential for primary prevention.

OBJECTIVES: Homozygosity for the C282Y mutation of the HFE gene is the main cause of iron overload in hereditary haemochromatosis. This study calculated the number of hepatocellular carcinoma cases among a cohort of white males that could be attributed to C282Y homozygosity. A better understanding of the extent of potentially preventable mortality arising from this cancer might help with decision making about the feasibility of population screening. METHODS: We combined information from published life tables, age-specific cancer rates and DNA studies of archived liver biopsy specimens to calculate the number of cases of hepatocellular carcinoma that might occur during the lifetime of a cohort of 1,000,000 men, including a subgroup of 5000 C282Y homozygotes. RESULTS: Hepatocellular carcinoma was estimated to occur in 2673 men in the cohort (1:374); 267 of these cases were in the subgroup of 5000 C282Y homozygotes (1:17). If these 267 cases were prevented, the remaining lifetime risk among all males would be 1:416. The relative risk for this cancer in C282Y homozygotes is 23. CONCLUSIONS: There continues to be uncertainty about the efficacy of screening for haemochromatosis. Hepatocellular carcinoma is the most readily quantifiable serious health problem attributable to this source. Further confirmatory DNA (C282Y) studies would be helpful in larger, unbiased sets of archived biopsy specimens, as a way to confirm the present estimate. Any strategy designed to prevent attributable liver cancer is likely to prevent other serious problems from haemochromatasis as well.

Rapid clinical progression to diagnosis among African-American men with systemic lupus erythematosus.

The initial clinical course of systemic lupus erythematosus (SLE) is variable, ranging from relatively minor manifestations progressing over years to rapid onset of fulminate disease. We sought to identify factors associated with the rapid manifestation of SLE. Chart review of military medical records was used to identify 130 patients who met the American College of Rheumatology classification criteria for SLE. Demographics, clinical criteria date of occurrence, and the date of SLE classification (at least four clinical criteria) met were documented. Prospectively stored serum samples prior to the diagnosis were evaluated for SLE autoantibodies. Median time from the first recorded criteria to diagnosis was significantly shorter in African-American (AA) males compared with AA females and European American (EA) females and males combined. AA males were more likely to have nephritis as their first clinical symptom. Also, less time transpired between the first clinical criterion and SLE diagnosis in AA males with nephritis than in other groups presenting with nephritis. Even when cases presenting with nephritis were excluded, a diagnosis of SLE was made more rapidly in AA males. African-American men progress from initial clinical manifestations to SLE diagnosis more rapidly than other ethnic or gender groups.

Selective small antigenic structures are capable of inducing widespread autoimmunity which closely mimics the humoral fine specificity of human SLE.

Recent data have suggested that autoantibodies in lupus can progress from simple immunity against a few antigenic structures to a complex response against multiple autoantigens. Our aim was to determine whether these diverse epitope patterns can indeed be generated by antigenic challenge with a single, small structure. Rabbits were immunized with either a 60 kDa Ro peptide commonly antigenic in human systemic lupus erythematosus (SLE) (Ro 274-289) or one which is rarely a humoral target (Ro 500-515). Rabbits immunized with the antigenic peptide (Ro 274-289) not only developed antibodies to multiple epitopes of 60 kDa Ro and La, as has been described, but also produced non-cross-reactive antibodies to the common spliceosomal proteins Sm B' and D1, and nRNP A and C. Rabbits immunized with the Ro 274-289 peptide also mount a progressive, diversified immune response to the sequential antigenic regions of these proteins (60 kDa Ro, Sm B' and D1, nRNP A and C), which is nearly identical to that seen in human SLE. Animals immunized with the nonantigenic peptide Ro 500-515 develop antibodies only to 60 kDa Ro. These results demonstrate that loss of tolerance to select single, small antigenic structures can begin a cascade which virtually recreates, at the epitope level, the humoral autoimmune specificity seen in human SLE.

Flow cytometry of Escherichia coli on microfluidic devices.

Flow cytometry of the bacterium Escherichia coli was demonstrated on a microfabricated fluidic device (microchip). The channels were coated with poly(dimethylacrylamide) to prevent cell adhesion, and the cells were transported electrophoretically by applying potentials to the fluid reservoirs. The cells were electrophoretically focused at the channel cross and detected by coincident light scattering and fluorescence. The E. coli were labeled with a membrane-permeable nucleic acid stain (Syto15), a membrane-impermeable nucleic acid stain (propidium iodide), or a fluorescein-labeled antibody and counted at rates from 30 to 85 Hz. The observed labeling efficiencies for the dyes and antibody were greater than 94%.

The role of Epstein-Barr virus in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a devastating autoimmune disease with no known cure. Lupus patients suffer from a myriad of clinical symptoms which variably include arthritis, pleuritis, pericarditis, vasculitis, and nephritis. The underlying mechanisms behind these clinical findings and the etiologic events preceding and causing disease onset, however, remain largely unknown. For many years, investigators have suspected that Epstein-Barr virus might somehow be involved in the etiology and/or pathogenesis of systemic lupus. Numerous studies have examined this possibility from various angles and have arrived at different conclusions. This work reviews these historical papers in the context of new results and presents a hypothetical role for this virus as an etiological environmental trigger for SLE.

A 12-amino-acid segment, present in type s2 but not type s1 Helicobacter pylori VacA proteins, abolishes cytotoxin activity and alters membrane channel formation.

Helicobacter pylori, a gram-negative bacterium associated with gastritis, peptic ulceration, and gastric adenocarcinoma in humans, secretes a protein toxin, VacA, that causes vacuolar degeneration of epithelial cells. Several different families of H. pylori vacA alleles can be distinguished based on sequence diversity in the "middle" region (i.e., m1 and m2) and in the 5' end of the gene (i.e., s1 and s2). Type s2 VacA toxins contain a 12-amino-acid amino-terminal hydrophilic segment, which is absent from type s1 toxins. To examine the functional properties of VacA toxins containing this 12-amino-acid segment, we analyzed a wild-type s1/m1 VacA and a chimeric s2/m1 VacA protein. Purified s1/m1 VacA from H. pylori strain 60190 induced vacuolation in HeLa and Vero cells, whereas the chimeric s2/m1 toxin (in which the s1 sequence of VacA from strain 60190 was replaced with the s2 sequence from strain Tx30a) lacked detectable cytotoxic activity. Type s1/m1 VacA from strain 60190 formed membrane channels in a planar lipid bilayer assay at a significantly higher rate than did s2/m1 VacA. However, membrane channels formed by type s1 VacA and type s2 VacA proteins exhibited similar anion selectivities (permeability ratio, P(Cl)/P(Na) = 5). When an equimolar mixture of the chimeric s2/m1 toxin and the wild-type s1/m1 toxin was added to HeLa cells, the chimeric toxin completely inhibited the activity of the s1/m1 toxin. Thus, the s2/m1 toxin exhibited a dominant-negative phenotype similar to that of a previously described mutant toxin, VacA-(Delta6-27). Immunoprecipitation experiments indicated that both s2/m1 VacA and VacA-(Delta6-27) could physically interact with a c-myc epitope-tagged s1/m1 VacA, which suggests that the dominant-negative phenotype results from the formation of heterooligomeric VacA complexes with defective functional activity. Despite detectable differences in the channel-forming activities and cytotoxic properties of type s1 and type s2 VacA proteins, the conservation of type s2 sequences in many H. pylori isolates suggests that type s2 VacA proteins retain an important biological activity.

Lupus autoantibodies recognize the product of an alternative open reading frame of SmB/B'.

An unusual feature of the gene for the spliceosomal protein SmB/B' is the presence of an unusually long alternative open reading frame (aORF) which could encode 220 amino acids. We cloned and expressed this aORF protein and used immunological assays to determine its antigenicity in patients with systemic lupus. Sera from 10 of 22 (46%) anti-Sm positive lupus patients showed significant binding to the SmB' aORF protein by ELISA while neither the normal controls nor anti-Sm negative lupus patient controls showed significant reactivity. Antigenicity of the SmB' aORF protein was further localized to the C-terminus using a deletion construct. This is the first known example in which the product of an alternative open reading frame acts as an autoantigen in human disease. These results are consistent with the possibility that generation of anti-Sm autoantibodies in a subset of lupus patients is due to abnormal processing and expression of an aORF SmB/B' message, by an as yet unidentified mechanism.

Genomic organization, chromosome location, and expression analysis of mouse beta-synuclein, a candidate for involvement in neurodegeneration.

The synuclein family of proteins is a group of primarily brain-expressed polypeptides that show a high degree of amino acid conservation. alpha-Synuclein is the best known of the synuclein family, as it is a major component of the Lewy body, a cytoplasmic inclusion characteristic of Parkinson's disease as well as a variety of related neurodegenerative disorders. With the discovery that mutations in alpha-synuclein can cause Parkinson's disease, a potential role for the other synuclein family members in neurodegenerative disease is being considered. beta-Synuclein in particular may deserve special attention, as it is co-expressed with alpha-synuclein at presynaptic nerve terminals, is subject to phosphorylation by Ca(2+) calmodulin protein kinase II, appears important for neural plasticity, and forms aggregates in the brains of patients with Parkinson's disease and a related disorder. To facilitate study of beta-synuclein, we have cloned the mouse beta-synuclein gene (Sncb) and determined its genomic organization, size, and intron-exon structure. Using an interspecific backcross mapping panel from The Jackson Laboratory, we were then able to localize Sncb to chromosome 13 at the MGD 35.0 cM position. Like the human beta-synuclein gene, Sncb appears to consist of six exons separated by five introns. Unlike the human beta-synuclein gene, the mouse ortholog possesses a variant GC 5' splice donor sequence at the exon 4 - intron 4 boundary in a highly conserved splice junction consensus. Northern blot analysis and Western blot analysis both indicate that Sncb is highly expressed in the brain. Knowledge of the genomic organization and expression pattern of Sncb will allow functional studies of its potential role in neurodegeneration to commence in the mouse.

Antigenic diversity among Helicobacter pylori vacuolating toxins.

Helicobacter pylori vacuolating cytotoxin (VacA) is a secreted protein that induces vacuolation of epithelial cells. To study VacA structure and function, we immunized mice with purified type s1-m1 VacA from H. pylori strain 60190 and generated a panel of 10 immunoglobulin G1kappa anti-VacA monoclonal antibodies. All of the antibodies reacted with purified native VacA but not with denatured VacA, suggesting that these antibodies react with conformational epitopes. Seven of the antibodies reacted with both native and acid-treated VacA, which suggests that epitopes present on both oligomeric and monomeric forms of the toxin were recognized. Two monoclonal antibodies, both reactive with epitopes formed by amino acids in the carboxy-terminal portion of VacA (amino acids 685 to 821), neutralized the cytotoxic activity of type s1-m1 VacA when toxin and antibody were mixed prior to cell contact but failed to neutralize the cytotoxic activity of type s1-m2 VacA. Only 3 of the 10 antibodies consistently recognized type s1-m1 VacA toxins from multiple H. pylori strains, and none of the antibodies recognized type s2-m2 VacA toxins. These results indicate that there is considerable antigenic diversity among VacA toxins produced by different H. pylori strains.

Amino-terminal hydrophobic region of Helicobacter pylori vacuolating cytotoxin (VacA) mediates transmembrane protein dimerization.

Helicobacter pylori VacA is a secreted protein toxin that forms channels in lipid bilayers and induces multiple structural and functional alterations in eukaryotic cells. A unique hydrophobic segment at the amino terminus of VacA contains three tandem repeats of a GxxxG motif that is characteristic of transmembrane dimerization sequences. To examine functional properties of this region, we expressed and analyzed ToxR-VacA-maltose binding protein fusions using the TOXCAT system, which was recently developed by W. P. Russ and D. M. Engelman (Proc. Natl. Acad. Sci. USA 96:863-868, 1999) to study transmembrane helix-helix associations in a natural membrane environment. A wild-type VacA hydrophobic region mediated insertion of the fusion protein into the inner membrane of Escherichia coli and mediated protein dimerization. A fusion protein containing a mutant VacA hydrophobic region (in which glycine 14 of VacA was replaced by alanine) also inserted into the inner membrane but dimerized significantly less efficiently than the fusion protein containing the wild-type VacA sequence. Based on these results, we speculate that the wild-type VacA amino-terminal hydrophobic region contributes to oligomerization of the toxin within membranes of eukaryotic cells.

Biomedical research leaders: report on needs, opportunities, difficulties, education and training, and evaluation.

The National Association of Physicians for the Environment (NAPE) has assumed a leadership role in protecting environmental health in recent years. The Committee of Biomedical Research Leaders was convened at the recent NAPE Leadership Conference: Biomedical Research and the Environment held on 1--2 November 1999, at the National Institutes of Health, Bethesda, Maryland. This report summarizes the discussion of the committee and its recommendations. The charge to the committee was to raise and address issues that will promote and sustain environmental health, safety, and energy efficiency within the biomedical community. Leaders from every important research sector (industry laboratories, academic health centers and institutes, hospitals and care facilities, Federal laboratories, and community-based research facilities) were gathered in this committee to discuss issues relevant to promoting environmental health. The conference and this report focus on the themes of environmental stewardship, sustainable development and "best greening practices." Environmental stewardship, an emerging theme within and outside the biomedical community, symbolizes the effort to provide an integrated, synthesized, and concerted effort to protect the health of the environment in both the present and the future. The primary goal established by the committee is to promote environmentally responsible leadership in the biomedical research community. Key outcomes of the committee's discussion and deliberation were a) the need for a central organization to evaluate, promote, and oversee efforts in environmental stewardship; and b) immediate need to facilitate efficient information transfer relevant to protecting the global environment through a database/clearinghouse. Means to fulfill these needs are discussed in this report.

Pancreatic pseudotumor in an 11-year-old child: imaging findings.

BACKGROUND: An inflammatory pseudotumor is a benign, solid lesion of unclear etiology. Some authors believe it is a true neoplasm, while others consider it a post-infectious or post-traumatic process. It is most commonly found in the lung; an inflammatory pseudotumor of the pancreas is rare. This case report is the sixth of a pancreatic pseudotumor in a child. PATIENTS AND METHODS: An 11-year-old girl presented with obstructive jaundice due to a mass in the head of the pancreas. The mass was identified by sonography. This was confirmed by MRI and CT. The mass enhanced with gadolinium, but its enhancement at CT was similar to the remainder of the pancreas. RESULTS: At operation, a pancreatic inflammatory pseudotumor was totally resected.

Acid activation of Helicobacter pylori vacuolating cytotoxin (VacA) results in toxin internalization by eukaryotic cells.

Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either acidic or alkaline pH ('activation') results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of acid-activated [125I]-VacA to cells at 4 degrees C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS-PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37 degrees C but not at 4 degrees C. Furthermore, internalization of the intact toxin was detected only if VacA was acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-D-glucose. These results indicate that acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.

Late-onset SCA2: 33 CAG repeats are sufficient to cause disease.

SCA-2 is an autosomal dominant inherited disorder characterized by ataxia, slow saccades, and hyporeflexia. The authors evaluated a patient with a mild balance problem with a SCA-2 allele sized at 33 CAG repeats. The authors then ascertained her 91 year-old mother, who showed disease onset at age 86 with an SCA-2 allele of identical size. Their study indicates that 33 CAG repeats can be pathogenic at the SCA-2 locus, though such an allele may produce an extremely late onset and gradual rate of disease progression.