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.

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.

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.

Galanin-like peptide (GALP) is a target for regulation by leptin in the hypothalamus of the rat.

Galanin-like peptide (GALP), which was recently isolated from the porcine hypothalamus, shares sequence homology with galanin and binds with high affinity to galanin receptors. To study the distribution and regulation of GALP-expressing cells in the brain, we cloned a 120 base-pair cDNA fragment of rat GALP and produced an antisense riboprobe. In situ hybridization for GALP mRNA was then performed on tissue sections throughout the forebrain of adult ovariectomized female rats. We found GALP mRNA-containing cells in the arcuate nucleus (Arc), caudal dorsomedial nucleus, median eminence and the pituitary. Because GALP mRNA in the Arc appeared to overlap with the known distribution of leptin receptor mRNA, we tested the hypothesis that GALP expression is regulated by leptin. Using in situ hybridization, we compared the number of GALP mRNA-containing cells among groups of rats that were fed ad lib or fasted for 48 h and treated with either leptin or vehicle. Fasting reduced the number of identifiable cells containing GALP mRNA in the Arc, whereas the treatment of fasted animals with leptin produced a 4-fold increase in the number of cells expressing GALP message. The presence of GALP mRNA in the hypothalamus and pituitary and its regulation by leptin suggests that GALP may have important neuroendocrine functions, including the physiological regulation of feeding, metabolism, and reproduction.

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability.

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis -acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.

Supporting families after sudden infant death.

Parents consistently report that supportive contacts with their health care providers make a difference in their overall adjustment to their baby's death. Parents require continuing validation that the baby's death is no one's fault, that it was not caused by anything they did or did not do. In supporting bereaved families, our goal is to assist parents to incorporate the baby's death into their lives in a way that allows them to continue to function and to recognize life as worth living and happiness as possible.

Multiplicity reactivation of reovirus particles after exposure to ultraviolet light.

McClain, Mary E. (California State Department of Public Health, Berkeley), and Rex S. Spendlove. Multiplicity reactivation of reovirus particles after exposure to ultraviolet light. J. Bacteriol. 92:1422-1429. 1966.-Exposure of reovirus suspensions to moderate doses of ultraviolet light results in essentially exponential inactivation of infectivity to survivals of 10(-2) to 10(-3). With suspensions of sufficiently high particle concentration, larger doses of ultraviolet light (6 to 12 min) are associated with multiplicity reactivation (MR) which is demonstrable both by immunofluorescent-cell count and by plaque assay in FL human amnion cells. Similar effects are produced by photodynamic inactivation in the presence of proflavine, but not by thermal inactivation at 50 C. All three reovirus types exhibit MR under appropriate conditions, and all three interact in mixed ultraviolet suspensions with high efficiency. Progeny from FL cells infected under conditions of MR were as infectious as those of unirradiated inocula, with yields per cell ranging from 10(4) to 4 x 10(4) infective units.