Developing cardiac and skeletal muscle share fast-skeletal myosin heavy chain and cardiac troponin-I expression

Skeletal muscle derived stem cells (MDSCs) transplanted into injured myocardium can differentiate into fast skeletal muscle specific myosin heavy chain (sk-fMHC) and cardiac specific troponin-I (cTn-I) positive cells sustaining recipient myocardial function. We have recently found that MDSCs differentiate into a cardiomyocyte phenotype within a three-dimensional gel bioreactor. It is generally accepted that terminally differentiated myocardium or skeletal muscle only express cTn-I or sk-fMHC, respectively. Studies have shown the presence of non-cardiac muscle proteins in the developing myocardium or cardiac proteins in pathological skeletal muscle. In the current study, we tested the hypothesis that normal developing myocardium and skeletal muscle transiently share both sk-fMHC and cTn-I proteins. Immunohistochemistry, western blot, and RT-PCR analyses were carried out in embryonic day 13 (ED13) and 20 (ED20), neonatal day 0 (ND0) and 4 (ND4), postnatal day 10 (PND10), and 8 week-old adult female Lewis rat ventricular myocardium and gastrocnemius muscle. Confocal laser microscopy revealed that sk-fMHC was expressed as a typical striated muscle pattern within ED13 ventricular myocardium, and the striated sk-fMHC expression was lost by ND4 and became negative in adult myocardium. cTn-I was not expressed as a typical striated muscle pattern throughout the myocardium until PND10. Western blot and RT-PCR analyses revealed that gene and protein expression patterns of cardiac and skeletal muscle transcription factors and sk-fMHC within ventricular myocardium and skeletal muscle were similar at ED20, and the expression patterns became cardiac or skeletal muscle specific during postnatal development. These findings provide new insight into cardiac muscle development and highlight previously unknown common developmental features of cardiac and skeletal muscle. © 2012 Clause et al

Promoting Diverse Youth's Career Development through Informal Science Learning: The Role of Inclusivity and Belonging

This is the final version. Available on open access from Springer via the DOI in this recordLittle research has examined the associations between perceived inclusivity within informal science learning sites, youth program belonging and perceptions of program career preparation. This study explored relations between these factors at three timepoints (T1 = start of program, T2 = 3 months and T3 = 12 months after start). Participants were a diverse sample of 209 adolescents participating in STEM youth programs within informal science learning sites situated in the United States and United Kingdom (70% females: M age = 15.27, SD age = 1.60), with 53.1% British and 64.1% non-White. Path analysis revealed that only perceptions of inclusivity for own social identity group (i.e., gender, ethnicity) at T1 were associated with T2 STEM youth program belonging. There was a significant indirect effect of T1 perceptions of inclusivity for one's own social identity groups on T3 perceptions of program career preparation via T2 program belonging. This study highlights that, over time, perceptions of inclusivity around youth's own social identity groups (i.e., gender and ethnicity/culture) are related to a sense of youth program belonging, which in turn is later associated with perceptions of program career preparation.National Science Foundation (NSF)Wellcome TrustEconomic and Social Research Council (ESRC

Reciprocal Associations Between Science Efficacy, STEM Identity and Scientist Career Interest Among Adolescent Girls within the Context of Informal Science Learning

This is the final version. Available on open access from Springer via the DOI in this recordLimited research has explored the longitudinal pathway to youth career interests via identity and efficacy together. This study examined the longitudinal associations between science efficacy, STEM (science, technology, engineering and math) identity, and scientist career interest among girls who are historically considered as an underrepresented group among scientists. The sample included 308 girls (M age = 15.22, SD age = 1.66; 42.8% White) from six STEM youth programs, each at a different informal science learning site within the U.K. and the U.S. Longitudinal structural equation modelling demonstrated that science efficacy consistently predicted STEM identity and scientist career interest, and similarly, STEM identity consistently predicted science efficacy over a two-year period. Scientist career interest at 12 months predicted science efficacy at 24 months. The coefficients of efficacy predicting STEM identity and scientist career interest were significantly larger compared to STEM identity and scientist career interest in predicting science efficacy from 12 months to 24 months. Further mediation analysis supported a significant pathway from STEM identity at 3 months to scientist career interest at 24 months via 12-month science efficacy. The findings highlight that science efficacy and STEM identity for girls relate to their scientist career interest and these longitudinal associations are reciprocal. This study suggests that science efficacy and STEM identity mutually influence each other, and enhancing science efficacy and STEM identity is key to promoting adolescents' interest in being a scientist.Wellcome TrustNational Science Foundation (NSF)Economic and Social Research Council (ESRC

pitx2 Deficiency Results in Abnormal Ocular and Craniofacial Development in Zebrafish

Human PITX2 mutations are associated with Axenfeld-Rieger syndrome, an autosomal-dominant developmental disorder that involves ocular anterior segment defects, dental hypoplasia, craniofacial dysmorphism and umbilical abnormalities. Characterization of the PITX2 pathway and identification of the mechanisms underlying the anomalies associated with PITX2 deficiency is important for better understanding of normal development and disease; studies of pitx2 function in animal models can facilitate these analyses. A knockdown of pitx2 in zebrafish was generated using a morpholino that targeted all known alternative transcripts of the pitx2 gene; morphant embryos generated with the pitx2ex4/5 splicing-blocking oligomer produced abnormal transcripts predicted to encode truncated pitx2 proteins lacking the third (recognition) helix of the DNA-binding homeodomain. The morphological phenotype of pitx2ex4/5 morphants included small head and eyes, jaw abnormalities and pericardial edema; lethality was observed at ∼6–8-dpf. Cartilage staining revealed a reduction in size and an abnormal shape/position of the elements of the mandibular and hyoid pharyngeal arches; the ceratobranchial arches were also decreased in size. Histological and marker analyses of the misshapen eyes of the pitx2ex4/5 morphants identified anterior segment dysgenesis and disordered hyaloid vasculature. In summary, we demonstrate that pitx2 is essential for proper eye and craniofacial development in zebrafish and, therefore, that PITX2/pitx2 function is conserved in vertebrates

Reducing grid dependency in droplet collision modeling

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A new droplet collision algorithm

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Investigation of Influence of Injection Pressure on Gasoline Fuel Spray Characteristics Using Numerical Simulation

Maximum fuel injection pressure in gasoline direct injection engine is expected to increase because of its potential to reduce emissions while maintaining a high efficiency in spark ignition engine. Present gasoline injectors in the market operates in the range of 20–30\ua0MPa. Because of many positive effects of high injection pressure for the emission reduction and fuel efficiency, an interest has been developed to investigate the spray behavior at around 40\ua0MPa, 60\ua0MPa and even more higher injection pressure. A fundamental investigation of spray characteristics at high-pressure injection will help to develop the understanding of spray behavior at such elevated pressure. In the present study, a gasoline fuel spray was studied through the numerical model at an injection pressure ranging from 40 to 150\ua0MPa. A numerical simulation was performed in an optical accessible constant volume chamber. The chamber was effectively non-reacting and non-vaporizing condition since the focus was on the spray droplets. In the numerical model, gas flow was calculated by large-eddy simulation (LES) method and the liquid phase was accounted by a standard Lagrangian spray model. The fuel spray atomization was modelled using the Kelvin Helmholtz—Rayleigh Taylor (KH-RT) model, and droplet size distribution followed the Rosin-Rammler distribution function. Simulation results were validated by comparing the liquid penetration length of spray with the experimental data at different fuel injection pressures. Then, the mean droplet sizes such as arithmetic mean diameter and Sauter mean diameter of the spray droplets were compared with the measure droplet sizes as a function of pressure. The spray droplet size distribution was also shown along with measured droplet sizes. The result shows that the liquid length penetration of the spray was significantly increases together with the higher probability of smaller droplet by increasing the fuel injection pressure. Moreover, the mean droplet sizes were also reducing by increasing the fuel injection pressure, such as the droplet SMD was reduced from 13.5 to 7.5 \upmu m by injecting the fuel at pressure 150\ua0MPa instead of 40\ua0MPa