Long-term selection of chickens for body weight alters muscle satellite cell behaviors.

Muscle satellite cells (SC) are resident stem-like cells that play an integral role in skeletal muscle growth and repair. Understanding how SC maintain their identities and dynamic properties is critical to animal growth. However, the genetic and environmental factors governing SC behaviors and the underpinning mechanisms remain unknown. To explore whether genetic selection influences SC behaviors, we used 2 lines of chickens selected for over 50 generations with over a 10-fold difference in body weight at 56 d of age-the Virginia high weight selection (HWS) and low weight selection (LWS) lines. To study these 2 lines, we performed both in vivo and in vitro experiments. In vivo, we studied the abundance of SC in normal physiological settings and tested their functional roles in muscle regeneration using a muscle injury model. In vitro, we isolated SC from chicken skeletal muscle and assayed their ability to proliferate and differentiate under cultured conditions. Immunohistochemical staining of breast muscle (pectoralis major) revealed that muscle fibers from HWS chickens possessed more SC than those from LWS. Further analysis showed that the SC pool from HWS muscles contained a higher percentage of activated SC compared to that of LWS. When isolated SC from HWS and LWS muscles were cultured, HWS SC exhibited greater abilities to proliferate and differentiate than those SC from LWS. To test whether the observed in vitro differences in SC properties could be confirmed in vivo, we subjected chicken breast muscle to barium chloride to induce muscle injury and regeneration. Consistent with in vitro data, breast muscle in HWS chicken experienced a faster and more robust recovery than that of LWS, as evidenced by quicker regeneration and larger muscle fiber size. Taken together, these findings suggest divergent selection for body weight not only results in correlated responses in SC number, but also changes SC growth kinetics. Further dissection of the molecular mechanism will aid the identification of the target molecules for growth intervention in chickens.

Critical nursing behaviors in care for the dying.

A beginning list of seven critical nursing behaviors in care for the dying was identified in a qualitative study. Ten experienced palliative care nurses and 10 nurse educators were asked to describe situations in which a student or graduate nurse had displayed very positive or very negative attitudes to care for the dying. Behaviors identified after content analysis of transcribed interviews were responding during death scene, providing comfort, responding to anger, enhancing personal growth, responding to colleagues, enhancing quality of life during dying, and responding to the family. Three of these behaviors were not well described in the nursing literature.