Glucocorticoids promote structural and functional maturation of foetal cardiomyocytes: a role for PGC-1α.

Glucocorticoid levels rise dramatically in late gestation to mature foetal organs in readiness for postnatal life. Immature heart function may compromise survival. Cardiomyocyte glucocorticoid receptor (GR) is required for the structural and functional maturation of the foetal heart in vivo, yet the molecular mechanisms are largely unknown. Here we asked if GR activation in foetal cardiomyocytes in vitro elicits similar maturational changes. We show that physiologically relevant glucocorticoid levels improve contractility of primary-mouse-foetal cardiomyocytes, promote Z-disc assembly and the appearance of mature myofibrils, and increase mitochondrial activity. Genes induced in vitro mimic those induced in vivo and include PGC-1α, a critical regulator of cardiac mitochondrial capacity. SiRNA-mediated abrogation of the glucocorticoid induction of PGC-1α in vitro abolished the effect of glucocorticoid on myofibril structure and mitochondrial oxygen consumption. Using RNA sequencing we identified a number of transcriptional regulators, including PGC-1α, induced as primary targets of GR in foetal cardiomyocytes. These data demonstrate that PGC-1α is a key mediator of glucocorticoid-induced maturation of foetal cardiomyocyte structure and identify other candidate transcriptional regulators that may play critical roles in the transition of the foetal to neonatal heart.

K201 modulates excitation-contraction coupling and spontaneous Ca2+ release in normal adult rabbit ventricular cardiomyocytes.

OBJECTIVES: The drug K201 (JTV-519) increases inotropy and suppresses arrhythmias in failing hearts, but the effects of K201 on normal hearts is unknown. METHODS: The effect of K201 on excitation-contraction (E-C) coupling in normal myocardium was studied by using voltage-clamp and intracellular Ca(2+) measurements in intact cells. Sarcoplasmic reticulum (SR) function was assessed using permeabilised cardiomyocytes. RESULTS: Acute application of <1 micromol/L K201 had no significant effect on E-C coupling. K201 at 1 micromol/L decreased Ca(2+) transient amplitude (to 83+/-7%) without affecting I(Ca,L) or the SR Ca(2+) content. At 3 micromol/L K201 caused a larger reduction of Ca(2+) transient amplitude (to 60+/-7%) with accompanying reductions in I(Ca,L) amplitude (to 66+/-8%) and SR Ca(2+) content (74+/-9%). Spontaneous SR Ca(2+) release during diastole was induced by increasing intracellular [Ca(2+)]. At 1 micromol/L K201 reduced the frequency of spontaneous Ca(2+) release. The effect of K201 on SR-mediated Ca(2+) waves and Ca(2+) sparks was examined in beta-escin-permeabilised cardiomyocytes by confocal microscopy. K201 (1 micromol/L) reduced the frequency and velocity of SR Ca(2+) waves despite no change in SR Ca(2+) content. At 3 micromol/L K201 completely abolished Ca(2+) waves and reduced the SR Ca(2+) content (to approximately 73%). K201 at 1 micromol/L reduced Ca(2+) spark amplitude and frequency. Assays specific to SR Ca(2+)-ATPase and RyR2 activity indicated that K201 inhibited both SR Ca(2+) uptake and release. CONCLUSIONS: K201 modifies E-C coupling in normal cardiomyocytes. A dual inhibitory action on SERCA and RyR2 explains the ability of K201 to suppress spontaneous diastolic Ca(2+) release during Ca(2+) overload without significantly affecting Ca(2+) transient amplitude.

The effect of femoral prosthesis design on cement strain in cemented total hip arthroplasty.

Finite element studies show that the highest cement stresses are located at the most proximal and distal ends of the prosthesis. In vitro biomechanical and histologic analyses of autopsy-retrieved cemented femoral components show these areas to be associated with cement-prosthesis debonding. In this study, cement strains were measured in 2 geometrically different femoral stems in paired cadaver femora: A straight, collared, moderately tapered stem (Centralign) was compared with an anatomically curved, collarless, dramatically tapered stem (Scientific Hip Prosthesis [SHP]). Results showed that the maximum strain and the overall strain profile differed between the 2 stems. The Centralign had peak strains located at the most proximal gauge positions, whereas the peak strains of the SHP were located around the middle of the femoral stem. Minimization of cement strain, especially at the crucial proximal and distal areas of the stem, by altering component design may be able to reduce cement-prosthesis debonding and improve clinical results.

Resting energy expenditure in asymptomatic HIV-infected females.

The purpose of this study was to investigate whether resting energy expenditure (REE) is elevated in early, asymptomatic human immunodeficiency virus (HIV)-infected females and to study the contribution of a cytokine, tumor necrosis factor-alpha (TNF-alpha), to hypermetabolism. Cross-sectional comparison of REE in asymptomatic HIV+ females and a control group matched for age, body mass index (BMI), and fat-free mass (FFM). Twenty-six females aged 35 +/- 7 years (10 HIV+ [mean CD4+ T cell count 636/mm3] and 16 healthy controls) participated in this study. REE was measured by indirect calorimeter using a Deltatrac ventilated hood with a continuous rate of 40 L/min for 30 minutes after a 40-minute equilibrium period. All tests were performed after a 12-hour overnight fast. Twenty-four-hour urinary nitrogen was calculated to correct for respiratory quotient. Body composition was measured by bioelectrical impedance (BioAnalogics, Beaverton, OR). TNF-alpha was measured by ELISA (R & D Systems, Minneapolis, MN). Absolute REE was 17% higher (1755 kcal/kg +/- 410 versus 1497 kcal/kg +/- 197) in the HIV+ group compared with the control group (p < 0.05). REE remained significantly higher in the HIV+ group when REE was adjusted for body composition differences (p = 0.04). Results revealed a 23% higher level of TNF-alpha in the HIV+ subjects (p < 0.01); however, only a weak correlation existed between TNF-alpha and REE (r = .352). This study documented that hypermetabolism and elevated TNF-alpha exist in HIV+ females in the early stages of disease.

A biomechanical analysis of internal fixation of complex tibial plateau fractures.

OBJECTIVE: To compare the mechanical stability of fixation of an unstable bicondylar tibial plateau fracture with several different fixation techniques in a cadaveric model. DESIGN: Randomized laboratory investigation using a simulated bicondylar tibial plateau fracture with metaphyseal-diaphyseal dissociation. SETTING: Complex tibial plateau fractures were instrumented and tested under ramp and cyclic loading conditions on a servohydraulic materials testing machine. INTERVENTION: Each tibia was instrumented sequentially with a lateral buttress plate, a lateral and a medial buttress plate, and a lateral buttress and an anteromedial antiglide plate for ramp load testing. For cyclic testing, one of the three constructs was used on each specimen. MAIN OUTCOME MEASUREMENTS: Vertical subsidence of the medial tibial plateau was measured in both ramp and cyclic loading in order to evaluate the three internal fixation techniques. RESULTS: No significant difference was measurable between the dual buttress construct and the lateral buttress/anteromedial antiglide construct. However, the lateral buttress plate alone provided significantly less stability. CONCLUSIONS: A lateral buttress plate with an anteromedial antiglide plate may provide equally effective fixation as compared with the dual buttress plating technique in complex tibial plateau fractures. This less invasive technique may also be associated with fewer complications due to the lack of soft tissue stripping that is required for its application.

HLA-DQA1 genotyping by bi-directional sequencing of PCR-amplified DNA spanning exon 2.

We describe a simple, reliable technique for HLA-DQA1 genotyping based on direct DNA sequencing of PCR amplified fragments from genomic DNA. The alleles of DQA1 can be divided into two subsets, with one subset demonstrating a 3 base deletion in exon 2 relative to the other. Typing heterozygous individuals who possess one allele from each sub-group can be difficult using a direct sequencing approach, since the two overlapping DNA sequences move out of phase by 3 nucleotides once the point of deletion is reached. The complete sequence is obtained by performing two separate sequencing reactions with fluorescent dye primers, coming from either end of the template. This allows all heterozygous positions in exon 2 to be unambiguously assigned.

Implementing a continuous renal replacement therapies program.

Initiating and maintaining a continuous renal replacement therapy (CRRT) program presented more challenges than first anticipated; however, problems remained within the health care team's ability to solve. Here a multidisciplinary group reflects on what was done, should have been done, and remains to be done to offer effective CRRT at this university medical center. All participating members have come to realize that communication and collaboration are necessary to accomplish implementation of a complex program such as CRRT.

The incidence of exercise-induced bronchospasm in competitive figure skaters.

Pediatric commitment to competitive sports is on the rise. Previous reports of the incidence of exercise-induced bronchospasm (EIB) have investigated high school, college, and Olympic athletes in traditional sports. The purpose of this study was to investigate the incidence of EIB in competitive figure skating, a high-intensity, cold-weather sport performed by young athletes. To investigate the incidence of EIB in skaters, 100 competitive skaters from five Mid-Atlantic rinks completed rinkside pulmonary function tests. Results showed an overall incidence of 30%, signaling the need for education and screening for EIB in youth participating in physically demanding, cold-weather sports.

Transient diplegia in children who fail to thrive.

We describe a group of eight children seen over a 4-year period. After a few months of apparently normal health and development, the children developed feeding difficulty, failed to thrive and had mild diplegia. No other underlying pathology was demonstrated. After a period of careful attention to feeding in the stimulating environment of a child development centre, the feeding difficulty, developmental delay and diplegia all disappeared, but, by school age, the children showed learning or behavioural difficulty. It is suggested that these children suffered a subtle neurological insult during the intra-uterine period and that this predisposed them to the neurological difficulty and failure to thrive. It is important to distinguish this small group of children from those in whom non-organic failure to thrive is found and parental neglect is suspected.

Changes in mallard (Anas platyrhynchos) serum chemistry due to age, sex, and reproductive condition.

Selected serum constituents were analyzed from 50 adult mallards (Anas platyrhynchos) of both sexes during several stages of reproduction: pre-egg laying, egg laying, incubating, molting, and postreproductive. Similar assays were conducted on sera from ducklings aged 5 to 58 days. Values for total protein (TPR), albumin (ALB), glucose (GLU), gamma-glutamyl transferase (GGT), calcium (CA), phosphorus (PHOS) and magnesium (MG) differed by sex. When all data were combined and analyzed for sex-related differences within each reproductive condition separately, all assays except lactate dehydrogenase (LD-L), cholinesterase (CHE), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CRN) and direct bilirubin (BIDI) differed between sexes during one or more reproductive periods. Each assay showed differences among the various reproductive conditions regardless of gender. The pattern of change differed between sexes. All assays except ALB, GLU, CA and MG showed age-related changes. Lipemia in the sample interfered with all chemistries except TPR, LD-L and CA. Results indicate that when using clinical chemistry as a diagnostic tool in the mallard, age and reproductive condition should be determined in order to compare the data to appropriate control values.