Effects of a brisk walk on lipoprotein lipase activity and plasma triglyceride concentrations in the fasted and postprandial states

This study aimed to determine whether changes in plasma heparin-releasable lipoprotein lipase (LPL) activity following a brisk walk were associated with decreases in fasting and/or postprandial triglyceride (TG) concentrations. Two groups of pre-menopausal women participated. In one group (fasting study group, n=10), TG concentrations and post-heparin plasma LPL activity were measured in the fasted state on two occasions: ~18 h after a 2-h treadmill walk at 50% maximal oxygen uptake (exercise trial); and after a day of no exercise (control trial). The other group (postprandial study group, n=9) undertook two oral fat tolerance tests (blood samples taken fasting and for 6 h after a high-fat meal), with plasma LPL activity measured 6 h after meal ingestion. Pre-conditions were the same as for the fasting study group (i.e. control and prior exercise). Prior exercise reduced fasting TG concentrations by 23 (7)% (fasting study group) [mean (SEM)] and by 18 (9)% (postprandial study group) (both P<0.05), and the postprandial TG response by 23 (6)% (postprandial study group) (P<0.01). Plasma LPL activity was not significantly increased by exercise in either the fasting or postprandial study groups. However, exercise-induced changes in both fasting and postprandial LPL activity were significantly correlated with the respective exercise-induced changes in fasting TG concentration and the postprandial TG response (r=−0.70 and −0.77 respectively, P<0.05 for both). These data suggest that increased LPL activity may contribute to the hypotriglyceridaemic effect of moderate exercise, although other mechanisms are also likely to be involved. Electronic Publication     

Purification and characterization of a UDP-glucosyltransferase produced by Legionella pneumophila

Legionella pneumophila is the agent of Legionnaires' disease. It invades and replicates within eukaryotic cells, including aquatic protozoans, mammalian macrophages, and epithelial cells. The molecular mechanisms of the Legionella interaction with target cells are not fully defined. In an attempt to discover novel virulence factors of L. pneumophila, we searched for bacterial enzymes with transferase activity. Upon screening ultrasonic extracts of virulent legionellae, we identified a uridine diphospho (UDP)-glucosyltransferase activity, which was capable of modifying a 45-kDa substrate in host cells. An approximately 60-kDa UDP-glucosyltransferase was purified from L. pneumophila and subjected to microsequencing. An N-terminal amino acid sequence, as well as the sequence of an internal peptide, allowed us to identify the gene for the enzyme within the unfinished L. pneumophila genome database. The intact gene was cloned and expressed in Escherichia coli, and the recombinant protein was purified and confirmed to possess an enzymatic activity similar to that of the native UDP-glucosyltransferase. We designated this gene ugt (UDP-glucosyltransferase). The Legionella enzyme did not exhibit significant homology with any known protein, suggesting that it is novel in structure and, perhaps, in function. Based on PCR data, an enzyme assay, and an immunoblot analysis, the glucosyltransferase appeared to be conserved in L. pneumophila strains but was absent from the other Legionella species. This study represents the first identification of a UDP-glucosyltransferase in an intracellular parasite, and therefore modification of a eukaryotic target(s) by this enzyme may influence host cell function and promote L. pneumophila proliferation.     

Determining Sleep Quality in Children with Sleep Disordered Breathing: EEG Spectral Analysis Compared with Conventional Polysomnography

Study Objectives:

To identify the extent of sleep disruption in children with various severities of sleep disordered breathing (SDB) using both conventional visually scored assessment of sleep stages and arousal indices together with EEG power spectral analysis.

Design:

Sleep stages and power spectral analysis of the sleep EEG in children with varying severities of SDB with matched control subjects with no history of snoring were compared across the whole night, across sequential hours from sleep onset, and across sleep stages.

Measurements:

Overnight polysomnography was performed on 90 children (49M/41F) aged 7-12 y with SDB and 30 age-matched healthy controls (13M/17F). Sleep stages were visually scored and the EEG spectra were analyzed in 5-s epochs.

Results:

Conventional visual scoring indicated that, although sleep duration was reduced in severely affected children, sleep quality during the essential stages of SWS and REM was preserved, as evidenced by the lack of any significant decrease in their duration in SDB severity groups. This finding was supported by the lack of substantial differences in EEG spectral power between the groups over the whole night, within specific hours, and in individual sleep stages.

Conclusions:

Both conventional scoring and EEG spectral analysis indicated only minor disruptions to sleep quality in children with SDB when assessed across the night, in any specific hour of the night, or in any specific sleep stage. These results suggest that reduced daytime functioning previously reported in children with SDB may not be due to sleep disruption. We speculate that in children, in contrast to adults, a stronger sleep drive may preserve sleep quality even in severe SDB.

Citation:

Yang JSC; Nicholas CL; Nixon GM; Davey MJ; Anderson V; Walker AM; Trinder JA; Horne RSC. Determining sleep quality in children with sleep disordered breathing: EEG spectral analysis compared with conventional polysomnography. SLEEP 2010;33(9):1165-1172.     

Adenovirus genome in the placenta: association with histological chorioamnionitis and preterm birth

Adenovirus is isolated frequently from the amniotic fluid and has been implicated in severe neonatal infections. A case control study was carried out to examine the association of detection of adenovirus in placentas with preterm birth and histological chorioamnionitis. Placentas from preterm and full term deliveries were collected prospectively. Preterm cases were divided into three subgroups according to the gestational age. PCR was carried out on placental tissues for the detection of adenovirus genome. Placentas were evaluated histologically for the presence of chorioamnionitis. Chi‐square and odds ratios (OR) were used to determine if detection of adenovirus is associated with preterm birth and histological evidence of inflammation. Seventy‐one preterm and 122 full term placentas were studied. Adenovirus genome was detected in 29 (40.8%) of preterm cases and in 25 (20.5%) of the full term controls (OR = 2.6; 95% CI, 1.4–5.1; P = 0.002). Detection of adenovirus in preterm placentas was significantly higher compared to full term particularly in the lower gestational age. Detection of adenovirus in placenta followed the seasonal variation of adenovirus infections. Thirty‐seven preterm and 21 full term placentas were also selected for paraffin inclusion and histological examination. Chorioamnionitis was present more frequently in preterm adenovirus‐positive placentas compared to preterm adenovirus‐negative placentas (75% vs. 36%; P = 0.026) as well as compared to term adenovirus‐positive placentas (75% vs. 19%; P = 0.003). This study demonstrates that adenovirus infection of the placenta is associated strongly with histological chorioamnionitis and preterm birth. J. Med. Virol. 82:1379–1383, 2010. © 2010 Wiley‐Liss, Inc.     

Ammonia metabolism,the brain and fatigue; revisiting the link

This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.     

Versatile methods for the fabrication of polyvinylidene fluoride microstructures

Polyvinylidene fluoride (PVDF) microstructures are of interest for a number of BioMEMS applications both for their piezoelectric and biocompatible properties. In this work, simple soft lithography-based techniques were developed to fabricate PVDF microstructures with diverse geometries, including microarrays of pillars, lines, and wells. Four different microstructure configurations were created: freestanding, stamped discontinuous, stamped continuous and imprinted patterns. Features with lateral dimensions down to 1 μm were consistently reproduced on 2.5 cm diameter areas. Atomic force microscopy (AFM) measurements of poled PVDF microstructures confirmed a marked inverse piezoelectric behavior. The techniques presented here have a number of advantages over previously demonstrated PVDF micropatterning approaches.     

The Ghana vasectomy initiative: facilitating client-provider communication on no-scalpel vasectomy

Objective

In 2003-2004 and 2007-2008, an initiative was implemented to improve client and provider knowledge and acceptance of no-scalpel vasectomy (NSV) in Ghana.

Methods

At eight facilities, physicians were trained in NSV and staff received training in the provision of “male-friendly” services. Health promotion activities provided NSV information to prospective clients. Client-provider communication was assessed via a mystery client study (n = 6). Knowledge and acceptance of NSV among potential clients were assessed with baseline and follow-up surveys (each n = 200) in 2003-2004 and three follow-up panel surveys in 2008 (each n = 240).

Results

Trained health staff exhibited improved attitudes and knowledge regarding NSV. Mystery clients reported receiving accurate, nonjudgmental NSV counseling. Awareness of NSV among panel respondents doubled from 31% to 59% in 2003-2004 and remained high (44%) in 2008. The proportion of men who would consider NSV increased from 10% to 19% in 2007-2008. NSV procedures increased three-fold from 2003 (n = 26) to 2004 (n = 83) and 2007 (n = 18) to 2008 (n = 53).

Conclusion

Provider training in client-centered services, coupled with targeted health promotion, improved client and provider knowledge and acceptance of NSV in an African context.

Practice implications

Complementary, sustained provider training and health promotion are needed to maintain NSV service quality and acceptance.     

Testing a developmental cascade model of adolescent substance use trajectories and young adult adjustment

Developmental models highlight the impact of early risk factors on both the onset and growth of substance use, yet few studies have systematically examined the indirect effects of risk factors across several domains, and at multiple developmental time points, on trajectories of substance use and adult adjustment outcomes (e.g., educational attainment, mental health problems, criminal behavior). The current study used data from a community epidemiologically defined sample of 678 urban, primarily African American youth, followed from first grade through young adulthood (age 21) to test a developmental cascade model of substance use and young adult adjustment outcomes. Drawing upon transactional developmental theories and using growth mixture modeling procedures, we found evidence for a developmental progression from behavioral risk to adjustment problems in the peer context, culminating in a high-risk trajectory of alcohol, cigarette, and marijuana use during adolescence. Substance use trajectory membership was associated with adjustment in adulthood. These findings highlight the developmental significance of early individual and interpersonal risk factors on subsequent risk for substance use and, in turn, young adult adjustment outcomes.     

Vascularization and tissue infiltration of a biodegradable polyurethane matrix

Urethanes are frequently used in biomedical applications because of their excellent biocompatibility. However, their use has been limited to bioresistant polyurethanes. The aim of this study was to develop a nontoxic biodegradable polyurethane and to test its potential for tissue compatibility. A matrix was synthesized with pentane diisocyanate (PDI) as a hard segment and sucrose as a hydroxyl group donor to obtain a microtextured spongy urethane matrix. The matrix was biodegradable in an aqueous solution at 37 degrees C in vitro as well as in vivo. The polymer was mechanically stable at body temperatures and exhibited a glass transition temperature (Tg) of 67 degrees C. The porosity of the polymer network was between 10 and 2000 microm, with the majority of pores between 100 and 300 microm in diameter. This porosity was found to be adequate to support the adherence and proliferation of bone-marrow stromal cells (BMSC) and chondrocytes in vitro. The degradation products of the polymer were nontoxic to cells in vitro. Subdermal implants of the PDI-sucrose matrix did not exhibit toxicity in vivo and did not induce an acute inflammatory response in the host. However, some foreign-body giant cells did accumulate around the polymer and in its pores, suggesting its degradation is facilitated by hydrolysis as well as by giant cells. More important, subdermal implants of the polymer allowed marked infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants. Because of the flexibility of the mechanical strength that can be obtained in urethanes and because of the ease with which a porous microtexture can be achieved, this matrix may be useful in many tissue-engineering applications.