Steric hindrance in the upper 50 kDa domain of the motor Myo2p leads to cytokinesis defects in fission yeast

Cytokinesis in many eukaryotes requires a contractile actomyosin ring that is placed at the division site. In fission yeast, which is an attractive organism for the study of cytokinesis, actomyosin ring assembly and contraction requires the myosin II heavy chain Myo2p. Although myo2-E1, a temperature-sensitive mutant defective in the upper 50 kDa domain of Myo2p, has been studied extensively, the molecular basis of the cytokinesis defect is not understood. Here, we isolate myo2-E1-Sup2, an intragenic suppressor that contains the original mutation in myo2-E1 (G345R) and a second mutation in the upper 50 kDa domain (Y297C). Unlike myo2-E1-Sup1, a previously characterized myo2-E1 suppressor, myo2-E1-Sup2 reverses actomyosin ring contraction defects in vitro and in vivo. Structural analysis of available myosin motor domain conformations suggests that a steric clash in myo2-E1, which is caused by the replacement of a glycine with a bulky arginine, is relieved in myo2-E1-Sup2 by mutation of a tyrosine to a smaller cysteine. Our work provides insight into the function of the upper 50 kDa domain of Myo2p, informs a molecular basis for the cytokinesis defect in myo2-E1, and may be relevant to the understanding of certain cardiomyopathies

A retrospective review of acute liver failure in children admitted at Red Cross War Memorial Children's Hospital

Acute liver failure (ALF) describes a clinical syndrome resulting from severe liver damage and extensive loss of functional parenchymal liver mass triggered by various factors. Early recognition and initiation of specific therapy may improve outcomes and reduce the need for liver transplantation, a treatment modality not universally available in resource constraint areas. There is paucity of data describing this syndrome in Sub-Saharan Africa in children. Objective This study aims to retrospectively review and determine the clinical presentation, aetiology, complications & outcome of ALF in children admitted at the Red Cross War Memorial Children's Hospital (RCWMCH). Methods All records of children from 0 to 13 years admitted at the RCWMCH over the period from January 2005 to December 2016 with ALF were retrospectively reviewed, after obtaining ethical approval. Patients with pre-existing evidence of chronic liver disease were excluded. Demographic variables as well as clinical presentation and investigations were captured, with determination of outcomes at 3 weeks and 6 weeks of diagnosis. Results Study included 24 children., 16 females (66.7%) and 8 males (33.3%). Median Age was 15 months, with interquartile range from 5 to 28 months. Diarrhoea, jaundice, respiratory distress, hepatomegaly and encephalopathy were common clinical features. Aetiology was infection in 37.5 % of cases (n=9, 2 of whom had autoimmune hepatitis comorbidity) and hepatitis A was most common infectious cause (n=4, 44%). Causes were indeterminate in 29.2%. Two patients had autoimmune hepatitis without co-morbidity; Reye syndrome 12.5% and 17% had miscellaneous causes. Transaminases were raised to thousands in viral causes of hepatitis, with a low C reactive protein. INR >4 and Total Bilirubin>210umol/L were associated with death outcome (p=0.04 and p=0.03 respectively. Conclusion Viral hepatitis A is the leading infective cause of acute liver failure in this study cohort and 29.2% of cases were indeterminable. INR >4 and Bilirubin > 210umol/l were predictors of poor outcome. Follow up study is recommended to better understand clinical spectrum and outcomes of children with acute liver failure in this low resource setting

Global estimates and determinants of antituberculosis drug pharmacokinetics in children and adolescents: a systematic review and individual patient data meta-analysis

BACKGROUND: Suboptimal exposure to antituberculosis drugs has been associated with unfavourable treatment outcomes. We aimed to investigate estimates and determinants of first-line antituberculosis drug pharmacokinetics in children and adolescents at a global level. METHODS: We systematically searched MEDLINE, Embase, and Web of Science (1990-2021) for pharmacokinetic studies of first-line antituberculosis drugs in children and adolescents. Individual patient data were obtained from authors of eligible studies. Summary estimates of total/extrapolated area under the plasma concentration-time curve (AUC0-24) and peak plasma concentration (Cmax) were assessed with random-effects models, normalised with current WHO-recommended paediatric doses. Determinants of AUC0-24 and Cmax were assessed with linear mixed-effects models. RESULTS: Of 55 eligible studies, individual patient data were available for 39 (71%), including 1628 participants from 12 countries. Geometric means (95% CIs) of steady-state AUC0-24 were summarised for isoniazid (18.7 [15.5-22.6] h·mg·L-1), rifampicin (34.4 [29.4-40.3] h·mg·L-1), pyrazinamide (375.0 [339.9-413.7] h·mg·L-1), and ethambutol (8.0 [6.4-10.0] h·mg·L-1). Our multivariate models indicated that younger age (especially <2 years) and HIV-positive status were associated with lower AUC0-24 for all antituberculosis drugs, while severe malnutrition was associated with lower AUC0-24 for isoniazid and pyrazinamide. N-acetyltransferase 2 rapid acetylators had lower isoniazid AUC0-24 and slow acetylators had higher isoniazid AUC0-24 than intermediate acetylators. Determinants of Cmax were generally similar to those for AUC0-24. CONCLUSION: This study provides the most comprehensive estimates of plasma exposures to first-line antituberculosis drugs in children and adolescents. Key determinants of drug exposures were identified. These may be relevant for population-specific dose adjustment or individualised therapeutic drug monitoring

Global estimates and determinants of antituberculosis drug pharmacokinetics in children and adolescents: a systematic review and individual patient data meta-analysis.

BackgroundSuboptimal exposure to antituberculosis drugs has been associated with unfavourable treatment outcomes. We aimed to investigate estimates and determinants of first-line antituberculosis drug pharmacokinetics in children and adolescents at a global level.MethodsWe systematically searched MEDLINE, Embase, and Web of Science (1990-2021) for pharmacokinetic studies of first-line antituberculosis drugs in children and adolescents. Individual patient data were obtained from authors of eligible studies. Summary estimates of total/extrapolated area under the plasma concentration-time curve (AUC0-24) and peak plasma concentration (Cmax) were assessed with random-effects models, normalised with current WHO-recommended paediatric doses. Determinants of AUC0-24 and Cmax were assessed with linear mixed-effects models.ResultsOf 55 eligible studies, individual patient data were available for 39 (71%), including 1628 participants from 12 countries. Geometric means (95% CIs) of steady-state AUC0-24 were summarised for isoniazid (18.7 [15.5-22.6] h·mg·L-1), rifampicin (34.4 [29.4-40.3] h·mg·L-1), pyrazinamide (375.0 [339.9-413.7] h·mg·L-1), and ethambutol (8.0 [6.4-10.0] h·mg·L-1). Our multivariate models indicated that younger age (especially 0-24 for all antituberculosis drugs, while severe malnutrition was associated with lower AUC0-24 for isoniazid and pyrazinamide. N-acetyltransferase 2 rapid acetylators had lower isoniazid AUC0-24 and slow acetylators had higher isoniazid AUC0-24 than intermediate acetylators. Determinants of Cmax were generally similar to those for AUC0-24.ConclusionThis study provides the most comprehensive estimates of plasma exposures to first-line antituberculosis drugs in children and adolescents. Key determinants of drug exposures were identified. These may be relevant for population-specific dose adjustment or individualised therapeutic drug monitoring