Endogenous islet uncoupling protein-2 expression and loss of glucose homeostasis in ob/ob mice

We hypothesized that the loss of glucose homeostasis in ob/ob mice is associated with upregulation of islet uncoupling protein-2 (UCP2) expression, leading to impaired glucose-stimulated insulin secretion (GSIS). Changes in glucose homeostasis in lean and ob/ob mice from 5 to 16 weeks were assessed by fasting blood glucose, plasma insulin, oral glucose tolerance, and tissue insulin sensitivity. In vitro GSIS and ATP content were assayed in isolated islets, while UCP2 expression was determined by quantitative real-time PCR and immunoblotting. Short-term reduction of UCP2 expression was achieved through transfection of islets with specific small interfering RNA. Insulin resistance was detected in 5-week-old ob/ob mice, but GSIS and blood glucose levels remained normal. By 8 weeks of age, ob/ob mice displayed fasting hyperglycemia, hyperinsulinemia and glucose intolerance, and also had elevated non-esterified fatty acid concentration in plasma. In vitro, GSIS and ATP generation were impaired in ob/ob islets. Islet UCP2 expression was elevated at 5 and 8 weeks of age. Short-term knockdown of islet UCP2 increased GSIS in islets of lean mice, but had no effect in islets from ob/ob mice. Loss of glucose homeostasis and impairment of insulin secretion from isolated islets at 8 weeks in ob/ob mice is preceded by an increase in UCP2 expression in islets. Moreover, the glucolipotoxic conditions observed are predicted to increase UCP2 activity, contributing to lower islet ATP and GSIS.     

Genetic variability of human metapneumovirus infection: evidence of a shift in viral genotype without a change in illness

Human metapneumovirus (hMPV) was identified in 2001 as a cause of acute respiratory illness, but its characteristics are still being defined. We analyzed 3740 nasopharyngeal-wash specimens obtained during 2002-2004, using assays for common respiratory viruses and real-time polymerase chain reaction for hMPV. We detected hMPV in 5% of all specimens, compared with 28% for other respiratory viruses. Nucleotide sequence analysis of hMPV isolates revealed the predominant circulation of hMPV genotype A in the 2003 season but a switch to predominantly genotype B in 2004. Sequence analysis also revealed major differences in the hMPV G and SH genes but relative conservation of the F and N genes within each genotype. Phylogenetic analysis indicated a seasonal switch within hMPV genotype A subtypes as well. Despite genetic variability, we found no difference in the severity of illness caused by various hMPV isolates. These findings suggest that hMPV may vary in genetic structure, to allow for a seasonal shift in predominant genotype and the maintenance of infection rates.     

A SERCA2 pump with an increased Ca2+ affinity can lead to severe cardiac hypertrophy, stress intolerance and reduced life span

Abnormal Ca(2+) cycling in the failing heart might be corrected by enhancing the activity of the cardiac Ca(2+) pump, the sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) isoform. This can be obtained by increasing the pump's affinity for Ca(2+) by suppressing phospholamban (PLB) activity, the in vivo inhibitor of SERCA2a. In SKO mice, gene-targeted replacement of SERCA2a by SERCA2b, a pump with a higher Ca(2+) affinity, results in cardiac hypertrophy and dysfunction. The stronger PLB inhibition on cardiac morphology and performance observed in SKO was investigated here in DKO mice, which were obtained by crossing SKO with PLB(-/-) mice. The affinity for Ca(2+) of SERCA2 was found to be further increased in these DKO mice. Relative to wild-type and SKO mice, DKO mice were much less spontaneously active and showed a reduced life span. The DKO mice also displayed a severe cardiac phenotype characterized by a more pronounced concentric hypertrophy, diastolic dysfunction and increased ventricular stiffness. Strikingly, beta-adrenergic or forced exercise stress induced acute heart failure and death in DKO mice. Therefore, the increased PLB inhibition represents a compensation for the imposed high Ca(2+)-affinity of SERCA2b in the SKO heart. Limiting SERCA2's affinity for Ca(2+) is physiologically important for normal cardiac function. An improved Ca(2+) transport in the sarcoplasmic reticulum may correct Ca(2+) mishandling in heart failure, but a SERCA pump with a much higher Ca(2+) affinity may be detrimental.     

Weaning from mechanical ventilation with pressure support in patients failing a T-tube trial of spontaneous breathing

Objective Evidence that PS may facilitate weaning from mechanical ventilation (MV), although not confirmed by randomized trials, prompted us to investigate whether patients could be weaned with PS after failing a T-tube trial.Design and setting This was a prospective, non-randomized study in two French intensive care units.Patients and participants One hundred eighteen patients were enrolled and underwent a T-tube trial, after which 87 were extubated. Thirty-one underwent a further trial with PS, after which 21 were extubated.Interventions All patients under MV >24 h meeting the criteria for a weaning test underwent a 30-min T-tube trial. If this was successful, they were immediately extubated. Otherwise, a 30-min trial with +7 cm H₂O PS was initiated with an individualized pressurization slope and trigger adjustment. If all weaning criteria were met, the patients were extubated; otherwise, MV was reinstated.Measurements and Results The extubation failure rate at 48 h did not differ significantly between the groups: 11/87 (13%) versus 4/21 (19%), P=0.39. The groups were comparable with regard to endotracheal tube diameter, MV duration, the use of non-invasive ventilation (NIV) after extubation, initial severity score, age and underlying pathology, except for COPD. A significantly higher percentage of patients with COPD was extubated after the trial with PS (8/21–38%) than after a single T-tube trial (11/87–13%) (P=0.003).Conclusions Of the patients, 21/118 (18%) could be extubated after a trial with PS, despite having failed a T-tube trial. The reintubation rate was not increased. This protocol may particularly benefit patients who are most difficult to wean, notably those with COPD.     

Inhibition of multidrug resistance transporter-1 facilitates neuroprotective therapies after focal cerebral ischemia

The blood-brain barrier possesses active transporters carrying brain-permeable xenobiotics back into the blood against concentration gradients. We demonstrate that multidrug resistance transporter (Mdr)-1 is upregulated on capillary endothelium after focal cerebral ischemia; moreover, Mdr-1 deactivation by pharmacological inhibition or genetic knockout preferably enhances the accumulation and efficacy of two neuroprotectants known as Mdr-1 substrates in the ischemic brain. We predict that Mdr-1 inhibition may greatly facilitate neuroprotective therapies.     

The nicotinic acetylcholine receptor gene family of the honey bee, Apis mellifera

Nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergic synaptic transmission and play roles in many cognitive processes. They are under intense research as potential targets of drugs used to treat neurodegenerative diseases and neurological disorders such as Alzheimer's disease and schizophrenia. Invertebrate nAChRs are targets of anthelmintics as well as a major group of insecticides, the neonicotinoids. The honey bee, Apis mellifera, is one of the most beneficial insects worldwide, playing an important role in crop pollination, and is also a valuable model system for studies on social interaction, sensory processing, learning, and memory. We have used the A. mellifera genome information to characterize the complete honey bee nAChR gene family. Comparison with the fruit fly Drosophila melanogaster and the malaria mosquito Anopheles gambiae shows that the honey bee possesses the largest family of insect nAChR subunits to date (11 members). As with Drosophila and Anopheles, alternative splicing of conserved exons increases receptor diversity. Also, we show that in one honey bee nAChR subunit, six adenosine residues are targeted for RNA A-to-I editing, two of which are evolutionarily conserved in Drosophila melanogaster and Heliothis virescens orthologs, and that the extent of editing increases as the honey bee lifecycle progresses, serving to maximize receptor diversity at the adult stage. These findings on Apis mellifera enhance our understanding of nAChR functional genomics and provide a useful basis for the development of improved insecticides that spare a major beneficial insect species.     

Evolution of HIV resistance mutations in patients maintained on a stable treatment regimen after virologic failure

OBJECTIVE: We compared the rate of emergence of thymidine analogue mutations (TAMs) and major protease inhibitor mutations in adherent patients who remained on stable treatment with a thymidine analogue and/or protease inhibitor after the onset of virologic failure. DESIGN: Follow-up genotypic resistance testing was done using archived plasma obtained from patients having 0 or 1 TAM and/or 0 or 1 major protease inhibitor resistance mutation at the onset of virologic failure. RESULTS: The median duration of observed failure was 691 days. There were 41 thymidine analogue regimens and 34 protease inhibitor regimens; concomitant ritonavir was used 4 times. New major protease inhibitor mutations emerged more rapidly than did new TAMs (P = 0.0019); new TAMs emerged more rapidly in thymidine analogue regimens that did not include lamivudine (P = 0.0073). The emergence of TAMs and major protease inhibitor mutations did not differ if lamivudine was not part of the thymidine analogue regimen. The evolution of CD4 cell counts and plasma viral loads (pVLs) during virologic failure was similar regardless of whether or not a new TAM or major protease inhibitor mutations emerged or, for thymidine analogue-containing regimens, whether lamivudine was or was not used. CONCLUSIONS: Major protease inhibitor mutations arose more frequently and rapidly than did TAMs in patients with sustained virologic failure who received lamivudine.     

Examining theoretic models of adherence for validity in resource-limited settings. A heuristic approach

Mortality and morbidity for HIV-infected patients in resource-limited settings have declined markedly with increased access to combination antiretroviral therapy. One explanation for this is the high rates of adherence that patients in these settings have achieved. To help patients sustain early successes, detailed understanding of adherence processes in these locales is needed. This understanding is best arrived at using socioculturally valid theoretic models as a guide. This article introduces a heuristic schema for examining the validity of conceptual models of adherence in resource-limited settings. The schema consists of 4 analytic questions to be asked of a model being considered for use in a sociocultural context other than the one in which it was developed. To demonstrate use of the schema, an illustrative validation exercise in which the 4 questions are applied to the information-motivation-behavioral skills model of behavioral change is carried out. Examples for the illustrative exercise come from preliminary qualitative research in HIV/AIDS treatment settings in Mbarara, Uganda and Jos, Nigeria.     

Mechanical limitation during CO2 rebreathing in young patients with cystic fibrosis

The aim of the study was to determine whether a decrease in the ventilatory response to carbon dioxide (CO2) in children with cystic fibrosis (CF) is related to a mechanical limitation of the respiratory muscle capacity. The ventilatory response during CO2 rebreathing was performed in 15 patients (mean forced expiratory volume in 1 s (FEV1): 37 +/- 21% predicted, mean arterial CO2: 41+/- 5 mmHg). The slope of the minute ventilation normalised for weight per mmHg CO2 increment correlated negatively with respiratory muscle output, assessed by the oesophageal (p = 0.002), the diaphragmatic pressure time product (p = 0.01), and the tension time index (p = 0.005). In addition, this slope was correlated with dynamic lung compliance (p < 0.0001) and FEV1 (p = 0.03) but not with airway resistance and maximal transdiaphragmatic pressure. Therefore, an excessive load imposed on the respiratory muscles explains the blunting of the ventilatory response to CO2 in young patients with CF.     

The −237C→T promoter polymorphism of the SLC11A1 gene is associated with a protective effect in relation to inflammatory bowel disease in the South African population

The purpose of this study was to assess the likelihood that variation in the promoter region of the solute carrier family 11 member 1 gene (SLC11A1) contributes to inflammatory bowel disease (IBD) susceptibility in the South African population. The study cohort included 102 IBD patients, 47 with Crohn's disease (CD) and 55 with ulcerative colitis, and 192 population-matched controls. Mutation analysis revealed two novel alleles for the 5′-(GT)n repeat polymorphism, t(gt)₅ac(gt)₅ac(gt)₆ggcaga(g)₆ (allele 8) and t(gt)₅ac(gt)₅ac(gt)₈ggcaga(g)₆ (allele 9), and one previously documented point mutation −237C→T. A significantly decreased frequency of the −237C→T promoter polymorphism was observed in the patient group with IBD (p<0.001) and CD (p<0.0006) compared with the population-matched control group. These findings may be related to previous in vitro studies, which demonstrated that the point mutation at nucleotide position −237 represents a functional polymorphism that affects regulation of the upstream 5′-(GT)n repeat polymorphism differentially upon iron loading. Our findings raise the possibility that iron dysregulation mediated by allelic effects of SLC11A1 may contribute to IBD susceptibility.