The transition of a muscle cell from a differentiated myotube into an adult myofiber is largely unstudied. This is primarily due to the difficulty of isolating specific developmental stimuli in vivo and the inability to maintain viable myotubes in culture for sufficient lengths of time. To address these limitations, a novel method for rapidly generating three-dimensional engineered muscles using fibrin gel casting has been developed. Myoblasts were seeded and differentiated on top of a fibrin gel. Cell-mediated contraction of the gel around artificial anchors placed 12 mm apart culminates 10 days after plating in a tubular structure of small myotubes (10-microm diameter) surrounded by a fibrin gel matrix. These tissues can be connected to a force transducer and electrically stimulated between parallel platinum electrodes to monitor physiological function. Three weeks after plating, the three-dimensional engineered muscle generated a maximum twitch force of 329 +/- 26.3 microN and a maximal tetanic force of 805.8 +/- 55 microN. The engineered muscles demonstrated normal physiological function including length-tension and force-frequency relationships. Treatment with IGF-I resulted in a 50% increase in force production, demonstrating that these muscles responded to hormonal interventions. Although the force production was maximal at 3 wk, constructs can be maintained in culture for up to 6 wk with no intervention. We conclude that fibrin-based gels provide a novel method to engineer three-dimensional functional muscle tissue and that these tissues may be used to model the development of skeletal muscle in vitro.

Stress has been shown to negatively affect learning. Academic burnout is a significant problem associated with poor academic performance. Although there has been increased attention on these two issues, literature on the relationship between students’ life stress and burnout is relatively limited. This study surveys academic burnout and life stresses among college students and further assesses whether reports of life stresses can serve as a predictor of academic burnout. The “Undergraduate Life Stress Scale” and “Learning Burnout Scale” are used as research tools, and data from 2640 students were collected. The results showed that both the level of students’ burnout and stress are in general not serious. Female students and upper year students reported higher values of life stresses. The self-identity stress, interpersonal stress, future development stress, and academic stress could jointly predict student academic burnout.

In this paper we describe the mechanical and biological features of a thermosetting polyester synthesized from glycerol and dodecanedioic acid named Poly-Glycerol-Dodecanoate (PGD). This polymer shows a glass transition temperature (Tg) around 32°C, and this accounts for its mechanical properties. At room temperature (21°) PGD behaves like a stiff elastic-plastic material, while at body temperature (37°C), it shows a compliant non-linear elastic behavior. Together with biodegradability and biocompatibility PGD has distinct shape memory features. After the polymer is cured, no matter what the final configuration is, we can recover the original shape by heating PGD to temperatures of 32°C and higher. The mechanical properties together with biocompatibility/biodegradability and shape memory features make PGD an attractive polymer for biomedical applications.

Loneliness is a common problem for many students. Research indicates that loneliness is associated with relatively poor physical health and depression among students. Burnout in students is also an important issue since it adversely affects students’ learning as well as their health and well-being. Both loneliness and learning burnout are related to negative psychological health, and there might exist a relationship between them. This study is to understand the current situation of students’ loneliness and learning burnout and further to explore the relationships between the two. The ‘Loneliness Scale’ and ‘Learning Burnout Scale’ are used as research tools, and data from 1788 students were collected. Statistical Package for the Social Sciences software was utilized to analyze the data, and the major findings shed light on whether there are differences between males and females with regard to experiencing higher loneliness and learning burnout symptoms. Results also show the relationship of the level of student loneliness and its correlation or otherwise with factors of learning burnout such as low sense of achievement and negative learning emotion.

Tissue engineered heart muscle may be able to provide a treatment modality for early stage congestive heart failure. In this study, we describe a new method to engineer functional 3-dimensional heart muscle utilizing a biodegradable fibrin gel. Primary cardiac myocytes were isolated from hearts of 2-to 3-day-old rats and processed in one of the two ways. For the first method (layering approach), the cells were plated directly on the surface of a fibrin gel-coated on polydimethylsiloxane (PDMS) surfaces. The cells were cultured in growth media and the contractile performance evaluated after formation of 3-dimensional tissue constructs. For the second method (embedding approach), the cells were suspended with thrombin and plated on 35 mm tissue culture surfaces coated with PDMS. Fibrinogen was then added to the surface. Within 7 days after initial cell plating, a 3-dimensional tissue construct of cells derived from primary heart tissue (termed bioengineered heart muscle, BEHM) resulted for both approaches.Histological evaluation showed the presence of uniformly distributed cardiac cells throughout the BEHM, both in longitudinal and cross sections. The stimulated active force of BEHMs formed using the layering approach was 835.5 6 57.2 mN (N ¼ 6) and 145.3 6 44.9 mN (N ¼ 6) using the embedding approach. The stimulated active force was dependent on the initial plating density. It was possible to maintain the contractile function of BEHM in culture for up to 2 months with daily medium changes. The BEHMs exhibited inotropy in response to external calcium and isoproterenol and could be electrically paced at frequencies of 1-7 Hz. We describe a novel method to engineer contractile 3-dimensional cardiac tissue construct with a fourfold increase specific force compared to our previous model.