CF2 Represses Actin 88F Gene Expression and Maintains Filament Balance during Indirect Flight Muscle Development in Drosophila

The zinc finger protein CF2 is a characterized activator of muscle structural genes in the body wall muscles of the Drosophila larva. To investigate the function of CF2 in the indirect flight muscle (IFM), we examined the phenotypes of flies bearing five homozygous viable mutations. The gross structure of the IFM was not affected, but the stronger hypomorphic alleles caused an increase of up to 1.5X in the diameter of the myofibrils. This size increase did not cause any disruption of the hexameric arrangement of thick and thin filaments. RT-PCR analysis revealed an increase in the transcription of several structural genes. Ectopic overexpression of CF2 in the developing IFM disrupts muscle formation. While our results indicate a role for CF2 as a direct negative regulator of the thin filament protein gene Actin 88F (Act88F), effects on levels of transcripts of myosin heavy chain (mhc) appear to be indirect. This role is in direct contrast to that described in the larval muscles, where CF2 activates structural gene expression. The variation in myofibril phenotypes of CF2 mutants suggest the CF2 may have separate functions in fine-tuning expression of structural genes to insure proper filament stoichiometry, and monitoring and/or controlling the final myofibril size

Axial and Radial Forces of Cross-Bridges Depend on Lattice Spacing

Nearly all mechanochemical models of the cross-bridge treat myosin as a simple linear spring arranged parallel to the contractile filaments. These single-spring models cannot account for the radial force that muscle generates (orthogonal to the long axis of the myofilaments) or the effects of changes in filament lattice spacing. We describe a more complex myosin cross-bridge model that uses multiple springs to replicate myosin's force-generating power stroke and account for the effects of lattice spacing and radial force. The four springs which comprise this model (the 4sXB) correspond to the mechanically relevant portions of myosin's structure. As occurs in vivo, the 4sXB's state-transition kinetics and force-production dynamics vary with lattice spacing. Additionally, we describe a simpler two-spring cross-bridge (2sXB) model which produces results similar to those of the 4sXB model. Unlike the 4sXB model, the 2sXB model requires no iterative techniques, making it more computationally efficient. The rate at which both multi-spring cross-bridges bind and generate force decreases as lattice spacing grows. The axial force generated by each cross-bridge as it undergoes a power stroke increases as lattice spacing grows. The radial force that a cross-bridge produces as it undergoes a power stroke varies from expansive to compressive as lattice spacing increases. Importantly, these results mirror those for intact, contracting muscle force production

DAAM is required for thin filament formation and Sarcomerogenesis during muscle development in Drosophila.

During muscle development, myosin and actin containing filaments assemble into the highly organized sarcomeric structure critical for muscle function. Although sarcomerogenesis clearly involves the de novo formation of actin filaments, this process remained poorly understood. Here we show that mouse and Drosophila members of the DAAM formin family are sarcomere-associated actin assembly factors enriched at the Z-disc and M-band. Analysis of dDAAM mutants revealed a pivotal role in myofibrillogenesis of larval somatic muscles, indirect flight muscles and the heart. We found that loss of dDAAM function results in multiple defects in sarcomere development including thin and thick filament disorganization, Z-disc and M-band formation, and a near complete absence of the myofibrillar lattice. Collectively, our data suggest that dDAAM is required for the initial assembly of thin filaments, and subsequently it promotes filament elongation by assembling short actin polymers that anneal to the pointed end of the growing filaments, and by antagonizing the capping protein Tropomodulin

Diet quality is positively associated with 100% fruit juice consumption in children and adults in the United States: NHANES 2003-2006

<p>Abstract</p> <p>Background</p> <p>One hundred percent fruit juice (100% FJ) has been viewed by some as a sweetened beverage with concerns about its effect on weight. Little regard has been given to the contribution of 100% FJ to diet quality.</p> <p>Methods</p> <p>In this study data from the 2003-2006 National Health and Nutrition Examination Survey were used to examine the association of 100% FJ consumption with diet quality in participants 2-5 years of age (y) (n = 1665), 6-12 y (n = 2446), 13-18 y (n = 3139), and 19+y (n = 8861). Two 24-hour dietary recalls were used to determine usual intake using the National Cancer Institute method. Usual intake, standard errors, and regression analyses (juice independent variable and Healthy Eating Index-2005 [HEI-2005] components were dependent variables), using appropriate covariates, were determined using sample weights.</p> <p>Results</p> <p>The percentage of participants 2-5 y, 6-12 y, 13-18 y, and 19+y that consumed 100% FJ was 71%, 57%, 45%, and 62%, respectively. Usual intake of 100% FJ (ounce [oz]/day) among the four age groups was: 5.8 ± 0.6, 2.6 ± 0.4, 3.7 ± 0.4, and 2.4 ± 0.2 for those in age groups 2-5 y, 6-12 y, 13-18 y, and 19+y, respectively. Consumption of 100% FJ was associated with higher energy intake in 6-12 y, 13-18 y, and 19+y; and higher total, saturated, and discretionary fats in 13-18 y participants. Consumption of 100% FJ was associated with higher total HEI-2005 scores in all age groups (< 0.0001). In 100% FJ consumers, total and whole fruit consumption was higher and intake of added sugars was lower in all age groups.</p> <p>Conclusions</p> <p>Usual intake of 100% FJ consumption exceeded MyPyramid recommendations for children 2-5 y, but was associated with better diet quality in all age groups and should be encouraged in moderation as part of a healthy diet.</p

Identification of Antifungal Compounds Active against Candida albicans Using an Improved High-Throughput Caenorhabditis elegans Assay

Candida albicans, the most common human pathogenic fungus, can establish a persistent lethal infection in the intestine of the microscopic nematode Caenorhabditis elegans. The C. elegans–C. albicans infection model was previously adapted to screen for antifungal compounds. Modifications to this screen have been made to facilitate a high-throughput assay including co-inoculation of nematodes with C. albicans and instrumentation allowing precise dispensing of worms into assay wells, eliminating two labor-intensive steps. This high-throughput method was utilized to screen a library of 3,228 compounds represented by 1,948 bioactive compounds and 1,280 small molecules derived via diversity-oriented synthesis. Nineteen compounds were identified that conferred an increase in C. elegans survival, including most known antifungal compounds within the chemical library. In addition to seven clinically used antifungal compounds, twelve compounds were identified which are not primarily used as antifungal agents, including three immunosuppressive drugs. This assay also allowed the assessment of the relative minimal inhibitory concentration, the effective concentration in vivo, and the toxicity of the compound in a single assay