Temperature change rate actuated bubble mixing for homogeneous rehydration of dry pre-stored reagents in centrifugal microfluidics.

In centrifugal microfluidics, dead volumes in valves downstream of mixing chambers can hardly be avoided. These dead volumes are excluded from mixing processes and hence cause a concentration gradient. Here we present a new bubble mixing concept which avoids such dead volumes. The mixing concept employs heating to create a temperature change rate (TCR) induced overpressure in the air volume downstream of mixing chambers. The main feature is an air vent with a high fluidic resistance, representing a low pass filter with respect to pressure changes. Fast temperature increase causes rapid pressure increase in downstream structures pushing the liquid from downstream channels into the mixing chamber. As air further penetrates into the mixing chamber, bubbles form, ascend due to buoyancy and mix the liquid. Slow temperature/pressure changes equilibrate through the high fluidic resistance air vent enabling sequential heating/cooling cycles to repeat the mixing process. After mixing, a complete transfer of the reaction volume into the downstream fluidic structure is possible by a rapid cooling step triggering TCR actuated valving. The new mixing concept is applied to rehydrate reagents for loop-mediated isothermal amplification (LAMP). After mixing, the reaction mix is aliquoted into several reaction chambers for geometric multiplexing. As a measure for mixing efficiency, the mean coefficient of variation (C[combining macron]V[combining macron], n = 4 LabDisks) of the time to positivity (tp) of the LAMP reactions (n = 11 replicates per LabDisk) is taken. The C[combining macron]V[combining macron] of the tp is reduced from 18.5% (when using standard shake mode mixing) to 3.3% (when applying TCR actuated bubble mixing). The bubble mixer has been implemented in a monolithic fashion without the need for any additional actuation besides rotation and temperature control, which are needed anyhow for the assay workflow.

The histone H3 lysine 9 methyltransferase DIM-5 modifies chromatin at frequency and represses light-activated gene expression.

The transcriptional program controlling the circadian rhythm requires coordinated regulation of chromatin. Characterization of the chromodomain helicase DNA-binding enzyme CHD1 revealed DNA methylation in the promoter of the central clock gene frequency (frq) in Neurospora crassa. In this report, we show that the DNA methylation at frq is not only dependent on the DNA methyltransferase DIM-2 but also on the H3K9 methyltransferase DIM-5 and HP1. Histone H3 lysine 9 trimethylation (H3K9me3) occurs at frq and is most prominent 30 min after light-activated expression. Strains lacking dim-5 have an increase in light-induced transcription, and more White Collar-2 is found associated with the frq promoter. Consistent with the notion that DNA methylation assists in establishing the proper circadian phase, loss of H3K9 methylation results in a phase advance suggesting it delays the onset of frq expression. The dim-5 deletion strain displays an increase in circadian-regulated conidia formation on race tubes and there is a synthetic genetic interaction between dim-5 and ras-1(bd). These results indicate DIM-5 has a regulatory role in muting circadian output. Overall, the data support a model where facultative heterochromatic at frq serves to establish the appropriate phase, mute the light response, and repress circadian output.

Influence of food intake and eating habits on hypertension control among outpatients at a government health clinic in the Klang Valley, Malaysia.

INTRODUCTION: In Malaysia, hypertension prevalence has increased from 13% in 1996 to 43% in 2006 based on the Third National Health and Morbidity Survey. METHODOLOGY: Recognising the importance of hypertension control to prevent cardiovascular morbidity and mortality, a cross-sectional study was carried out to assess factors influencing blood pressure among 74 hypertensive adults (22 men, 52 women, mean age 61.1 +/- 8.8 years old) attending an outpatient clinic of a government health clinic in Klang Valley. Subjects were interviewed to obtain information on social and health, physical activity level and food intake using Diet History Questionnaire (DHQ) and Food Frequency Questionnaire (FFQ). Anthropometric measurements including weight, height, waist circumference and percentage of body fat were also conducted. RESULTS: The majority of the subjects (71.6%) had poor hypertension control as determined using blood pressure. Women aged 30-59 years old had a higher mean diastolic blood pressure (87.3 +/- 11.6 mmHg) than women aged 60 years old (78.5 +/- 9.5 mmHg) (p < 0.05). Most of the men (36.4%) achieved three out of six Medical Nutrition Therapy (MNT) for Hypertension Recommendations as outlined by the Malaysian Dietitians' Association. About one-third (30.8%) of the women achieved two out of six of the guidelines. High sodium intake (adjusted OR 3.501, 95% CI 1.116-10.985, p < 0.05), daily consumption of coffee (adjusted OR 0.302, 95% CI 0.093-0.983, p < 0.05) and less intake of milk (adjusted OR 3.328, 95% CI 1.055-10.493, p < 0.05) were associated with uncontrolled hypertension. CONCLUSION: Three quarters of the subjects had unsatisfactory hypertensive control and was related to food intake and eating habits including high salt diet, coffee consumption and inadequate milk intake were unsatisfactory. There is a need to implement a nutrition intervention programme based on MNT to achieve good hypertensive control among subjects.

Mimetics of a T cell epitope based on poly-N-acylated amine backbone structures induce T cells in vitro and in vivo.

Peptidomimetics of the major histocompatibility complex (MHC) class I-restricted ovalbumin-derived T cell epitope SIINFEKL were generated by replacing parts of the peptide backbone by a poly-N-acylated amine (PAA) backbone with aromatic, heteroaromatic, and pseudoaromatic side chains that branch off of the main chain at the amine nitrogen. The structure of the PAAs was designed to position this side chain in the central epitope anchor pocket of the MHC molecule. A number of biologically active PAAs were found that induced cytolysis by the mouse cytotoxic T cell clone 4G3. Competition experiments with independent peptides that are known to bind to the restricting MHC molecule H-2K(b) suggest that the PAAs are bound by the MHC molecules at the same site as conventional peptide epitopes. The PAAs were active also in vivo and induced primary cytotoxic T cell responses in mice.

Cutting edge: N-hydroxy peptides: a new class of TCR antagonists.

TCR antagonists are altered T cell epitopes that specifically inactivate T cells. Commonly, they are derived from agonists by amino acid side chain replacement at positions accessible to the TCR. In this paper we report for the first time that a main chain N-hydroxylation, which is not exposed at the surface of the MHC peptide complex, renders an agonist into an antagonist. These mimotopes are a new, yet undescribed class of TCR antagonists. The antagonists are about 100 times more potent than an unrelated peptide that competes for binding to the MHC molecule. The novel main chain modification enhances biostability and maintains side chain constitution and thus opens new prospects for the use of TCR antagonists in the treatment of pathological immune reactions.

Acute renal failure in Reye's syndrome.

From 1979 to 1985, 8 children with clinical and biochemical features of Reye's Syndrome developed acute renal failure. Within the same period, a total of 28 cases of Reye's Syndrome were admitted to the Paediatric Units of Singapore General Hospital. Six of them were females and 2 were males. The mean age at presentation was 28.4 months and the range was between 9 months to 47 months. Four of them died eventually. There appeared to be a correlation between the eventual outcome and severity of renal failure and neurological state of admission.