Molecular genotyping of a large, multicentric collection of tubercle bacilli indicates geographical partitioning of strain variation and has implications for global epidemiology of Mycobacterium tuberculosis

Tuberculosis continues to be a major killer disease, despite an all-out effort launched against it in the postgenomic era. We describe here the population structure of Mycobacterium tuberculosis strains, as revealed by a chromosome-wide scan of fluorescent amplified fragment length polymorphisms (FAFLPs), for more than 1,100 independent isolates from 11 different countries. The bacterial strains were genotyped based on a total of 136 +/- 1 different FAFLP markers at the genome sequence interface, with details on IS6110 profiles, drug resistance status, clinicopathological observations, and host status integrated into the analysis process. The strains were found to cluster with possible geographic affinities, including the parameters of host species type, IS6110 profile, and drug susceptibility status. Of the five most commonly amplified fragment sets (or amplitypes), type A predominated in strains of mixed origin, deposited in The Netherlands; type B was exclusively observed for Indian isolates; type C was found mainly in strains from Peru and Australia; and types D and E predominated in European strains from France and Italy. The amplitypes were independent of certain large sequence polymorphisms representing two important deletions, TbD1 and Rd9. It appears that M. tuberculosis has a high genomic diversity with a possible geographic evolution. This may have occurred due to specific genomic deletions and synonymous substitutions selected rigorously against host defenses and environmental stresses on an evolutionary timescale. The genotypic data reported here are additionally significant for genotype-phenotype correlations and for determining whether pathogen diversity is a reflection f the host population diversity.     

Contribution of variants in the small heterodimer partner gene to birthweight,adiposity, and insulin levels: mutational analysis and association studies in multiple populations

Loss of function mutations in the small heterodimer partner (SHP) gene have been reported to cause obesity and increased birth weight. We examined the relation between genetic variation in SHP and birth weight, adiposity, and insulin levels in three independent populations. The coding regions and 562 bases of the SHP promoter were screened for mutations in 329 subjects with severe early-onset obesity. Two novel missense mutations, R34G and R36C, were identified; these were not found in control subjects and did not cosegregate with obesity in family studies. Two common polymorphisms, G171A and -195CTGAdel, were found in 12 and 16% of subjects, respectively. Within the obese cohort, G171A and -195CTGAdel carriers had higher and lower birth weights, respectively, than wild-type subjects, the rare homozygotes for G171A being particularly large at birth. In a U.K. population-based cohort of 1,079 children, the 171A allele was associated with higher BMI (P < 0.05) and waist circumference (P = 0.001). Children carrying the G171A variant had higher 30-min insulin responses to a glucose load (P = 0.03). In conclusion, although mutations in SHP are not a common cause of severe human obesity, genetic variation in the SHP locus may influence birth weight and have effects on BMI, possibly through effects on insulin secretion.     

Association of polymorphisms in GPR10, the gene encoding the prolactin-releasing peptide receptor with blood pressure,but not obesity,in a U.K. Caucasian population

Prolactin-releasing peptide (PrRP) and its G-protein-coupled receptor, GPR10, have been implicated in the central control of appetite and blood pressure. To determine whether mutations in these genes might contribute to morbid obesity, we screened both genes in 94 subjects with severe early-onset obesity. Four rare silent variants in PrRP and eight polymorphisms in GPR10 were found, two of which (V283I and P305L) altered amino acid sequence but were also found in U.K. Caucasian control subjects. Cells expressing the P305L variant receptor generated less intracellular calcium in response to PrRP than cells expressing the wild-type receptor. To examine whether genetic variation of the GPR10 locus might be associated with phenotypes relevant to obesity and/or blood pressure, the most common noncoding (G-62A) and coding (C914T [P305L]) polymorphisms were typed in 1,084 U.K. Caucasians. While no association was found with BMI, carriers of the P305L allelic variant had significantly lower systolic (123.95 vs. 128.55 mmHg, P < 0.05) and diastolic (74.90 vs. 78.20 mmHg, P < 0.01) blood pressure than wild-type subjects. In conclusion, we have conducted the first genetic study of GPR10 and its ligand PrRP in relation to metabolic phenotypes and have identified an association between GPR10 polymorphisms and diastolic and systolic blood pressure. The alteration in signaling properties of the receptor produced by P305L may provide a functional basis for this association.     

Time dependence of the frequency and amplitude of the local nanomechanical motion of yeast

We report the time dependence of the local nanomechanical motion of the Saccharomyces cerevisiae (yeast) cell wall. The motion was measured under physiological conditions with an atomic force microscope over relatively extended periods of 15 seconds. The cell wall motion displayed a distinct 2-state amplitude behavior as revealed by Fourier analysis, while the frequency followed a normal Gaussian distribution centered at approximately 1.61 kHz. There was no apparent temporal relationship between either characteristic. Local motion of the bud scar on the same cell contained multiple frequencies different from that of the cell wall. Each frequency component displayed normal Gaussian fluctuations, while 1 component displayed slight 2-state amplitude behavior. The motion of the cell wall and bud scar was dependent on cellular metabolism, as confirmed by treatment with a metabolic inhibitor. The variability in frequency and amplitude of the motion provides a characteristic basis for further analysis of factors that affect the motion.     

Leptin predicts a worsening of the features of the metabolic syndrome independently of obesity

OBJECTIVE: The term metabolic syndrome (MS) describes a cluster of cardiovascular risk factors including dyslipidemia, glucose intolerance, insulin resistance, and hypertension. Obesity increases the risk of MS, but as obesity is neither necessary nor sufficient to cause the syndrome, there is considerable interest in identifying obesity-independent pathways. One such pathway may involve the actions of the adipokine leptin, which is associated cross-sectionally with MS and prospectively with coronary heart disease and stroke, independently of obesity. Our goal was to test the hypothesis that leptin predicts the development of the features of MS independently of obesity. RESEARCH METHODS AND PROCEDURES: This study used a prospective population-based cohort of 748 middle-aged whites in whom baseline measures of leptin and repeated measurement of the subcomponents of the MS at 5 and 10 years were available. The features of the MS were characterized as five factors (obesity, dyslipidemia, elevated blood pressure, glucose intolerance, and insulin resistance), which were combined to create an MS summary score. RESULTS: Baseline leptin significantly predicted the development of obesity (p = 0.001) and, after adjustment for BMI, development of glucose intolerance (p = 0.016) and insulin resistance (p < 0.0001). Leptin levels did not independently predict a change in lipids or blood pressure. Leptin levels significantly predicted the development of the MS (p = 0.036), independently of baseline BMI. DISCUSSION: Leptin predicts the development of the MS independently of baseline obesity. This association is specifically related to the development of glucose intolerance and insulin resistance. The extent to which these relationships are explained through residual confounding by obesity remains to be determined.     

Evaluation of Prader-Willi Syndrome gene MAGEL2 in severe childhood-onset obesity

MAGEL2 is one of the five genes inactivated in Prader-Willi Syndrome, a neurodevelopmental chromosome microdeletion disorder modified by genomic imprinting. By early childhood, individuals with Prader-Willi Syndrome exhibit hypothalamic dysfunction, including hyperphagia, and become obese in the absence of behavioral intervention. Murine Magel2 is highly expressed in the hypothalamus during development. We screened the MAGEL2 open reading frame for mutations in genomic DNA samples from hyperphagic but non-dysmorphic individuals with severe childhood-onset obesity. Although no mutations likely to affect gene function were identified, we identified three variant alleles. We conclude that severe childhood-onset obesity is not commonly caused by MAGEL2 mutations.     

Aqueous ring-opening metathesis polymerisation of 7-oxanorbornene derivatives with oxygen-containing functionalities

A number of 7-oxanorbornene derivatives with hydroxymethyl, methoxymethyl and acetoxymethyl functionalities were synthesised and investigated as monomers in ring-opening metathesis polymerisation (ROMP) catalysed by commercial ruthenium trichloride in aqueous ethanolic solvents. Comparison was made with related polymerisations of 7-oxanorbornene derivatives with anhydride, methoxymethyl and carboxylic acid functionalities. The structures of the polymers were investigated by ¹H and ¹³C NMR and their molar masses and molar mass distributions by gel-permeation chromatography.     

Pleomorphic adenoma of the submandibular gland: an evolving change in practice following review of a personal case series

We reviewed patients with submandibular gland pleomorphic adenoma treated at a tertiary referral centre in the United Kingdom (1988–2004). Thirty-seven patients were identified, 32 newly diagnosed cases and 5 cases of recurrent disease previously treated elsewhere. The exact pre-operative diagnosis was “unknown” in 76% of the new cases. All cases were surgically excised (41% with extracapsular gland excision and 59% by selective level Ib, IIa and III neck dissection). Temporary marginal mandibular nerve neuropraxia was documented in 25% of cases. All 32 new cases remain clinically tumour free at the time of writing. In patients with recurrent disease, complete microscopic tumour clearance was achieved in three of the five cases, however all remain clinically tumour free. Pleomorphic adenomas of the submandibular gland are uncommon, with good prognosis following complete tumour excision. Recurrent tumours, however, are frequently multi-focal and difficult to excise completely. The adequacy of primary surgery is crucial and supports an approach for a more radical excision primarily by a selective level lb, IIa and III neck dissection; ensuring complete disease clearance for pleomorphic adenoma, avoiding the risks of tumour spillage associated with a limited excision and tumour handling; and removing the primary echelon of lymph nodes at risk of metastasis if the pathology turns out to be malignant.     

Living donor liver paired exchange: A North American first

Paired organ exchange can be used to circumvent living donor-recipient ABO incompatibilities. Herein, we present the first case of successful liver paired exchange in North America. This 2-way swap required 4 simultaneous operations: 2 living donor hepatectomies and 2 living donor liver transplants. A nondirected anonymous living donor gift initiated this domino exchange, alleviating an ABO incompatibility in the other donor-recipient pair. With careful attention to ethical and logistical issues, paired liver exchange is a feasible option to expand the donor pool for incompatible living liver donor-recipient pairs.