A parametric family of correlation structures for the analysis of longitudinal data.

In epidemiological settings, we are often faced with numerous short time series, and a parsimonious parametrization of the correlation structure is desired in order to optimize the efficiency of the estimation procedure. We propose a damped exponential correlation structure for modeling multivariate Gaussian outcomes. The correlation between two observations separated by s units of time is modeled as gamma s theta, where gamma is the correlation between elements separated by one s-unit, and theta is a damping parameter. For (theta = 0), (theta = 1), and theta----infinity), the correlation structures of compound symmetry, first-order autoregressive, and first-order moving average processes are obtained. Although the AR(2) dependency structure, and the combination of random effects and AR(1) errors are not special cases of the proposed parametric family, these structures can be well approximated within the family for short time series. Maximum likelihood methods for parameter estimation and interpretations of intermediate models (0 less than theta less than 1) are discussed in the context of modeling pulmonary function in an adult population in The Netherlands and T-cell subsets in homosexual men infected with human immunodeficiency virus Type I.     

Cancer incidence in Dutch Balkan veterans

Suspicion has been raised about an increased cancer risk among Balkan veterans because of alleged exposure to depleted uranium. The authors conducted a historical cohort study to examine cancer incidence among Dutch Balkan veterans. Male military personnel (n = 18,175, median follow-up 11 years) of the Army and Military Police who had been deployed to the Balkan region (1993–2001) was compared with their peers not deployed to the Balkans (n = 135,355, median follow-up 15 years) and with the general Dutch population of comparable age and sex. The incidence of all cancers and 4 main cancer subgroups was studied in the period 1993–2008. The cancer incidence rate among Balkan deployed military men was 17% lower than among non-Balkan deployed military men (hazard ratio 0.83 (95% confidence interval 0.69, 1.00)). For the 4 main cancer subgroups, hazard ratios were statistically non-significantly below 1. Also compared to the general population cancer rates were lower in Balkan deployed personnel (standardised incidence rate ratio (SIR) 0.85 (0.73, 0.99). The SIR for leukaemia was 0.63 (0.20, 1.46). The authors conclude that earlier suggestions of increased cancer risks among veterans are not supported by empirical data. The lower risk of cancer might be explained by the ‘healthy warrior effect’.     

Soluble, oligomeric, and ligand-binding extracellular domain of the human alpha7 acetylcholine receptor expressed in yeast: replacement of the hydrophobic cysteine loop by the hydrophilic loop of the ACh-binding protein enhances protein solubility

The N-terminal extracellular domain (ECD; amino acids 1-208) of the neuronal nicotinic acetylcholine receptor (AChR) alpha7 subunit, the only human AChR subunit known to assemble as a homopentamer, was expressed as a glycosylated form in the yeast Pichia pastoris in order to obtain a native-like model of the extracellular part of an intact pentameric nicotinic AChR. This molecule, alpha7-ECD, although able to bind the specific ligand alpha-bungarotoxin, existed mainly in the form of microaggregates. Substitution of Cys-116 in the alpha7-ECD with serine led to a decrease in microaggregate size. A second mutant form, alpha7-ECD(C116S,Cys-loop), was generated in which, in addition to the C116S mutation, the hydrophobic Cys-loop (Cys(128)-Cys(142)) was replaced by the corresponding hydrophilic Cys-loop from the snail glial cell acetylcholine-binding protein. This second mutant protein was water-soluble, expressed at a moderate level (0.5 +/- 0.1 mg/liter), and had a size corresponding approximately to a pentamer as judged by gel filtration and electron microscopy studies. It also bound (125)I-alpha-bungarotoxin with relatively high affinity (K(d) = 57 nm), the binding being inhibited by unlabeled alpha-bungarotoxin, d-tubocurarine, or nicotine (K(i) = 0.8 x 10(-7) m, K(i) = 1 x 10(-5) m, and K(i) = 0.9 x 10(-2) m, respectively). All three constructs were expressed as glycosylated forms, but in vitro deglycosylation reduced the heterogeneity without affecting their ligand binding properties. These results show that alpha7-ECD(C116S,Cys-loop) was expressed in P. pastoris as an oligomer (probably a pentamer) with a near native conformation and that its deglycosylated form seems to be suitable starting material for structural studies on the ligand-binding domain of a neurotransmitter receptor.     

Compound-specific isotopic fractionation patterns suggest different carbon metabolisms among Chloroflexus-like bacteria in hot-spring microbial mats

Stable carbon isotope fractionations between dissolved inorganic carbon and lipid biomarkers suggest photoautotrophy by Chloroflexus-like organisms in sulfidic and nonsulfidic Yellowstone hot springs. Where co-occurring, cyanobacteria appear to cross-feed Chloroflexus-like organisms supporting photoheterotrophy as well, although the relatively small 13C fractionation associated with cyanobacterial sugar biosynthesis may sometimes obscure this process.     

High-level expression of recombinant IgG in the human cell line per.c6

The number of therapeutic monoclonal antibodies in production is expected to rise rapidly in the next few years. As a result, there is much focus on the optimization of antibody expression platforms. Several issues are important including the speed of transition from bench to manufacturing, yield of IgG, and quality (particularly of the glycan structures present on immunoglobulins). We have characterized the human cell line PER.C6 for its ability to produce recombinant IgG. Production yields are still being optimized, but in nonfed batch culture, PER.C6 is able to grow to a cell density of 5 x 10(6) cells/mL and produce 300-500 mg/L IgG; this is likely to increase significantly in fed batch cultures. The generation of antibody-producing cell lines is fast, as rounds of amplification of inserted genes are not required for high production yields. The gene copy number of inserted genes is in the region of 1-10 copies per genome. In addition, PER.C6 is a human cell line, and so does not add glycans, which are immunogenic in humans. A core fucose molecule is essentially always present, and galactose residues are present at a physiological level (0, 1, and 2 galactose residues per glycan are present at a ratio of 1:2:1). No hybrid or high-mannose structures are seen.     

Pouchitis.

Pouchitis is a major long-term complication of the continent ileostomy as well as the ileoanal pouch anastomosis. When diagnosed on the basis of clinical, endoscopic and histologic features, this syndrome has been demonstrated almost exclusively in patients with ulcerative colitis. The clinical course, the endoscopic findings and the histologic abnormalities resemble those of ulcerative colitis. The association with extra-intestinal manifestations further supports the hypothesis that pouchitis represents ulcerative colitis in the small bowel. All ileal reservoirs show bacterial overgrowth, especially of anaerobes. As a response to this altered intraluminal environment chronic inflammation and incomplete colonic metaplasia occur. The efficiency of metronidazole does suggest that bacteriological factors play an important role in the pathogenesis of pouchitis.     

Paranormal healing and hypertension

A prospective randomised trial was carried out to see whether paranormal healing by laying on of hands might reduce blood pressure in essential hypertension and whether such an effect might be due to a paranormal, psychological, or placebo factor. Patients were randomised to three treatment groups: paranormal healing by laying on of hands (n=40), paranormal healing at a distance (n=37), and no paranormal healing (controls; n=38). Healing at a distance and no paranormal healing were investigated double blind. Systolic and diastolic blood pressures were significantly reduced in all three groups at week 15 (mean reduction (95% confidence interval) 17·1 (14·0 to 20·2)/8·3 (6·6 to 10·0) mm Hg). Only the successive reductions in diastolic blood pressures among the groups from week to week were significantly different. Each week diastolic pressure was consistently lower (average 1·9 mm Hg) after healing at a distance compared with control, but on paired comparison these differences were not significant. Probably week to week variations among the groups accounted for any differences noted.In this study no treatment was consistently better than another and the data cannot therefore be taken as evidence of a paranormal effect on blood pressure. Probably the fall in blood pressure in all three groups either was caused by the psychosocial approach or was a placebo effect of the trial itself.     

Identification of the cDNA clone which encodes the 58-kDa protein containing the amino acid sequence of rat liver non-specific lipid-transfer protein (sterol-carrier protein 2). Homology with rat peroxisomal and mitochondrial 3-oxoacyl-CoA thiolases

The relationship between the rat liver non-specific lipid-transfer protein (nsLTP) and the 58-kDa protein cross-reactive with anti-nsLTP antibodies, was investigated by cDNA analysis. A 1945-bp cDNA clone was isolated which encodes a 58.7-kDa protein. This protein is identical to the 58-kDa immunoreactive protein determined by N-terminal sequence analysis of the purified 58-kDa protein. It consists of 546 amino acid residues, of which the 123 C-terminal residues are identical to the sequence of nsLTP. The N-terminal 400 amino acid residues of the 58.7-kDa protein were found to have 23.5% identity with the sequence of both mitochondrial and peroxisomal rat 3-oxoacyl-CoA thiolases, including a hypothetical substrate-binding site. The cDNA insert hybridizes with 1.1-kb, 1.7-kb, 2.4-kb and 3.0-kb mRNA species in RNA isolated from various rat tissues and from Chinese hamster ovary (CHO) cells. Southern blot analysis suggests that these mRNA species are generated from a single gene. Mutant CHO cells, deficient in peroxisomes, lack nsLTP. We have found that the mRNA encoding nsLTP is still present in these cells, which suggests that the absence of this protein is related to the lack of peroxisomes.     

Fixed Dystonia in Complex Regional Pain Syndrome: a Descriptive and Computational Modeling Approach

Background  

Complex regional pain syndrome (CRPS) may occur after trauma, usually to one limb, and is characterized by pain and disturbed blood flow, temperature regulation and motor control. Approximately 25% of cases develop fixed dystonia. Involvement of dysfunctional GABAergic interneurons has been suggested, however the mechanisms that underpin fixed dystonia are still unknown. We hypothesized that dystonia could be the result of aberrant proprioceptive reflex strengths of position, velocity or force feedback.