463 research outputs found

    Preparation and Fractionation of Xenopus laevis Egg Extracts

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    Crude and fractionated Xenopus egg extracts can be used to provide ingredients for reconstituting cellular processes for morphological and biochemical analysis. Egg lysis and differential centrifugation are used to prepare the crude extract which in turn in used to prepare fractionated extracts and light membrane preparations

    Obtaining Eggs from Xenopus laevis Females

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    The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, collect and dejelly the eggs, and sort the eggs to remove any damaged eggs

    Feasibility of a randomized controlled trial of functional strength training for people between six months and five years after stroke: FeSTivaLS trial

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    Background: Functional Strength Training (FST) could enhance recovery late after stroke. The aim of this study was to evaluate the feasibility of a subsequent fully powered, randomized controlled trial. Methods: The study was designed as a randomized, observer-blind trial. Both interventions were provided for up to one hour a day, four days a week, for six weeks. Evaluation points were before randomization (baseline), after six weeks intervention (outcome), and six weeks thereafter (follow-up). The study took place in participants’ own homes. Participants (n = 52) were a mean of 24.4 months after stroke with a mean age of 68.3 years with 67.3% male. All had difficulty using their paretic upper (UL) and lower limb (LL). Participants were allocated to FST-UL or FST-LL by an independent randomization service. The outcome measures were recruitment rate, attrition rate, practicality of recruitment strategies, occurrence of adverse reactions, acceptability of FST, and estimation of sample size for a subsequent trial. Primary clinical efficacy outcomes were the Action Research Arm Test (ARAT) and the Functional Ambulation Categories (FAC). Analysis was conducted using descriptive statistics and thematic analysis of participants’ views of FST. A power calculation used estimates of clinical efficacy variance to estimate sample size for a subsequent trial. Results: The screening process identified 1,127 stroke survivors of whom 52 (4.6%) were recruited. The recruitment rate was higher for referral from community therapists than for systematic identification of people discharged from an acute stroke unit. The attrition rate was 15.5% at the outcome and follow-up time-points. None of the participants experienced an adverse reaction. The participants who remained in the study at outcome had received 68% of the total possible amount of therapy. Participants reported that their experience of FST provided a sense of purpose and involvement and increased their confidence in performing activities. The power calculation provides estimation that 150 participants in each group will be required for a subsequent clinical trial. Conclusions: This study found that a subsequent clinical trial was feasible with modifications to the recruitment strategy to be used

    Contemporary South African Urbanization Dynamics

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    Abstract The paper provides an overview of urbanization patterns and trends in the current era in South Africa, focusing in particular on the key dynamics and driving forces underlying migration and urbanization. It considers overall demographic trends with regard to migration and urbanization, and points to some of the difficulties with data, and with the analysis of trends and patterns. The paper explores the changing rural context and dynamics, and some of the significant processes in this context: large-scale displacement of black people off farms, the impact of land reform, and conditions in the former homeland areas. Circular migration continues to be an important way in which households in rural areas survive, but some are unable to move, and are falling out of these networks. International migration—the consequence of both conditions in the home country and the draw of the South African economy— is another significant process fuelling mainly urban growth. The paper demonstrates the importance of cities in terms of economic growth and employment, and thus their attractiveness to migrants. Continuing migration to cities is of course a challenge fo

    Dynamic DNA methylation across diverse human cell lines and tissues

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    As studies of DNA methylation increase in scope, it has become evident that methylation has a complex relationship with gene expression, plays an important role in defining cell types, and is disrupted in many diseases. We describe large-scale single-base resolution DNA methylation profiling on a diverse collection of 82 human cell lines and tissues using reduced representation bisulfite sequencing (RRBS). Analysis integrating RNA-seq and ChIP-seq data illuminates the functional role of this dynamic mark. Loci that are hypermethylated across cancer types are enriched for sites bound by NANOG in embryonic stem cells, which supports and expands the model of a stem/progenitor cell signature in cancer. CpGs that are hypomethylated across cancer types are concentrated in megabase-scale domains that occur near the telomeres and centromeres of chromosomes, are depleted of genes, and are enriched for cancer-specific EZH2 binding and H3K27me3 (repressive chromatin). In noncancer samples, there are cell-type specific methylation signatures preserved in primary cell lines and tissues as well as methylation differences induced by cell culture. The relationship between methylation and expression is context-dependent, and we find that CpG-rich enhancers bound by EP300 in the bodies of expressed genes are unmethylated despite the dense gene-body methylation surrounding them. Non-CpG cytosine methylation occurs in human somatic tissue, is particularly prevalent in brain tissue, and is reproducible across many individuals. This study provides an atlas of DNA methylation across diverse and well-characterized samples and enables new discoveries about DNA methylation and its role in gene regulation and disease

    Measuring intracellular pH in the heart using hyperpolarized carbon dioxide and bicarbonate: a 13C and 31P magnetic resonance spectroscopy study

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    AIMS: Technological limitations have restricted in vivo assessment of intracellular pH (pH(i)) in the myocardium. The aim of this study was to evaluate the potential of hyperpolarized [1-(13)C]pyruvate, coupled with (13)C magnetic resonance spectroscopy (MRS), to measure pH(i) in the healthy and diseased heart. METHODS AND RESULTS: Hyperpolarized [1-(13)C]pyruvate was infused into isolated rat hearts before and immediately after ischaemia, and the formation of (13)CO(2) and H(13)CO(3)(-) was monitored using (13)C MRS. The HCO(3)(-)/CO(2) ratio was used in the Henderson-Hasselbalch equation to estimate pH(i). We tested the validity of this approach by comparing (13)C-based pH(i) measurements with (31)P MRS measurements of pH(i). There was good agreement between the pH(i) measured using (13)C and (31)P MRS in control hearts, being 7.12 +/- 0.10 and 7.07 +/- 0.02, respectively. In reperfused hearts, (13)C and (31)P measurements of pH(i) also agreed, although (13)C equilibration limited observation of myocardial recovery from acidosis. In hearts pre-treated with the carbonic anhydrase (CA) inhibitor, 6-ethoxyzolamide, the (13)C measurement underestimated the (31)P-measured pH(i) by 0.80 pH units. Mathematical modelling predicted that the validity of measuring pH(i) from the H(13)CO(3)(-)/(13)CO(2) ratio depended on CA activity, and may give an incorrect measure of pH(i) under conditions in which CA was inhibited, such as in acidosis. Hyperpolarized [1-(13)C]pyruvate was also infused into healthy living rats, where in vivo pH(i) from the H(13)CO(3)(-)/(13)CO(2) ratio was measured to be 7.20 +/- 0.03. CONCLUSION: Metabolically generated (13)CO(2) and H(13)CO(3)(-) can be used as a marker of cardiac pH(i) in vivo, provided that CA activity is at normal levels

    BRCA2 polymorphic stop codon K3326X and the risk of breast, prostate, and ovarian cancers

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    Background: The K3326X variant in BRCA2 (BRCA2*c.9976A>T; p.Lys3326*; rs11571833) has been found to be associated with small increased risks of breast cancer. However, it is not clear to what extent linkage disequilibrium with fully pathogenic mutations might account for this association. There is scant information about the effect of K3326X in other hormone-related cancers. Methods: Using weighted logistic regression, we analyzed data from the large iCOGS study including 76 637 cancer case patients and 83 796 control patients to estimate odds ratios (ORw) and 95% confidence intervals (CIs) for K3326X variant carriers in relation to breast, ovarian, and prostate cancer risks, with weights defined as probability of not having a pathogenic BRCA2 variant. Using Cox proportional hazards modeling, we also examined the associations of K3326X with breast and ovarian cancer risks among 7183 BRCA1 variant carriers. All statistical tests were two-sided. Results: The K3326X variant was associated with breast (ORw = 1.28, 95% CI = 1.17 to 1.40, P = 5.9x10- 6) and invasive ovarian cancer (ORw = 1.26, 95% CI = 1.10 to 1.43, P = 3.8x10-3). These associations were stronger for serous ovarian cancer and for estrogen receptor–negative breast cancer (ORw = 1.46, 95% CI = 1.2 to 1.70, P = 3.4x10-5 and ORw = 1.50, 95% CI = 1.28 to 1.76, P = 4.1x10-5, respectively). For BRCA1 mutation carriers, there was a statistically significant inverse association of the K3326X variant with risk of ovarian cancer (HR = 0.43, 95% CI = 0.22 to 0.84, P = .013) but no association with breast cancer. No association with prostate cancer was observed. Conclusions: Our study provides evidence that the K3326X variant is associated with risk of developing breast and ovarian cancers independent of other pathogenic variants in BRCA2. Further studies are needed to determine the biological mechanism of action responsible for these associations
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