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Abstract Aim We addressed four objectives: (1) Determine the regional responses of species, size classes and a vegetation type to climate and parent material predictors, including their distributions in environmental space and the relative contributions of the predictors to explained variation. (2) Determine whether size classes of a species respond similarly to climate and parent material. (3) Assess the extent to which the predicted regional distribution of a vegetation type can be approximated by the distribution of its diagnostic species and vice versa . The establishment of a consistent relationship between the distribution of a vegetation type and its diagnostic species would facilitate change detection, management and conservation planning by allowing the use of one distribution to generate the other when data availability is limited. (4) Examine landscape-scale environmental variability in predicted species and vegetation type distributions. Location South-western USA (Arizona, New Mexico and southern Colorado). Methods Ecological response surface models were developed using a data base of 1409 vegetation plots to analyse biotic–environmental relationships of (1) Pinus ponderosa P. & C. Lawson and Abies concolor (Gord. & Glend.) Lindl. Ex Hildebr. size classes, (2) P. ponderosa, A. concolor and Quercus gambelii Nutt. combined size classes, and (3) a P. ponderosa forest type widely distributed in the south-western USA. Results and main conclusions Pinus ponderosa and A. concolor models generally were judged to be successful. Quercus gambelii models were judged unsuccessful, which may result from the influence of variables not modelled, such as soil moisture, disturbance, biotic factors and other site limiting factors. Size classes differed in the range of environmental conditions associated with high occurrence probabilities within and between species, reflecting differences in the effects of climate variability and anthropogenic changes, such as... [ABSTRACT FROM AUTHOR]

Congenital myasthenic syndromes (CMSs) are a group of rare genetic disorders of the neuromuscular junction resulting in structural or functional causes of fatigable weakness that usually begins early in life. Mutations in pre-synaptic, synaptic and post-synaptic proteins have been demonstrated in human cases, with more than half involving aberrations in nicotinic acetylcholine receptor (AChR) subunits. CMS was first recognized in dogs in 1974 as an autosomal recessive trait in Jack Russell Terriers (JRTs). A deficiency of junctional AChRs was demonstrated. Here we characterize a CMS in 2 contemporary cases of JRT littermates with classic clinical and electromyographic findings, and immunochemical confirmation of an approximately 90% reduction in AChR protein content. Loci encoding the 5 AChR subunits were evaluated using microsatellite markers, and CHRNB1 and CHRNE were identified as candidate genes. Sequences of the splice sites and exons of both genes revealed a single base insertion in exon 7 of CHRNE that predicts a frameshift mutation and a premature stop codon. We further demonstrated this pathogenic mutation in CHRNE in archival tissues from unrelated JRTs studied 34 years ago. [ABSTRACT FROM AUTHOR]

Objectives The aim of this study was to evaluate the HIV-1 RNA pooled nucleic acid amplification testing (NAAT) strategy to screen pregnant women in the 'window period' of acute HIV infection (AHI) in rural South Africa. Methods In 2007 and 2008, 750 consecutive pregnant women on their first antenatal care visit to a primary health care clinic were tested anonymously for HIV infection. HIV-1 RNA pooled NAAT was performed on HIV antibody-negative samples. All positive pools were tested individually and positive samples were classified as incident cases to calculate HIV incidence. Results The overall HIV prevalence was 37.3% [95% confidence interval (CI) 34.3-41.3]. Of the 467 HIV antibody-negative samples, four (0.9%) were HIV-1 RNA-positive. The mean viral load in the four samples was 386 260 HIV-1 RNA copies/mL (range 64 200-1 228130). The HIV incidence was 11.2% per year (95% CI 0.3-22.1) and all women with AHI were ≤21 years of age. Conclusions Identifying AHI in pregnancy is important for health interventions to reduce perinatal and heterosexual transmission of HIV, and to estimate HIV incidence for epidemiological surveillance. [ABSTRACT FROM AUTHOR]