Insights into skeletal muscle development and applications in regenerative medicine.

Embryonic and postnatal development of skeletal muscle entails highly regulated processes whose complexity continues to be deconstructed. One key stage of development is the satellite cell, whose niche is composed of multiple cell types that eventually contribute to terminally differentiated myotubes. Understanding these developmental processes will ultimately facilitate treatments of myopathies such as Duchenne muscular dystrophy (DMD), a disease characterized by compromised cell membrane structure, resulting in severe muscle wasting. One theoretical approach is to use pluripotent stem cells in a therapeutic setting to help replace degenerated muscle tissue. This chapter discusses key myogenic developmental stages and their regulatory pathways; artificial myogenic induction in pluripotent stem cells; advantages and disadvantages of DMD animal models; and therapeutic approaches targeting DMD. Furthermore, skeletal muscle serves as an excellent paradigm for understanding general cell fate decisions throughout development.

Abnormal eye movements in hyperkinetic children with learning disability.

Eye movements were studied in 29 school children aged 6--12 years diagnosed as having Hyperactivity (HA) with Learning Disabilities (LD) and compared to an age matched control group of 32 children. The children had to track a moving target on a metronome and a canopy, to maintain eye fixation on a stationary target and to read a standard reading material. Accuracy, nystagmoid, reversal and overshoot movements were observed, as well as head movements and blinks. Persistence and deviations were monitored during fixation; duration, accuracy, number of fixations and reversals were monitored during reading. The tracking accuracy and fixation persistence were significantly inferior in the HA-LD children as compared to the control group in most items. This correlated well with the inferior performance on the reading task. This study supports the hypothesis that children with MBD and learning disabilities have primary defects in the motor control of eye movements which contribute significantly to their reading difficulties.

Microproliferation of enterochromaffin cells and the origin of carcinoid tumors of the ileum: a light microscopic and immunocytochemical study.

Using light microscopy, we studied the enterochromaffin (EC) cells in the intertumoral normal-appearing ileal mucosa in four cases of multiple ileal carcinoid tumors to investigate the mode of development of these tumors. There were 54 (39 mucosal, 15 submucosal) grossly invisible neoplastic microproliferations of cells with the attributes of EC cells, including immunocytochemical characteristics. No direct connection between these microproliferations and the intramucosal EC cells were demonstrated, nor was hyperplasia of EC cells found. Thus, we did not find a direct link between the intramucosal EC cells and carcinoid tumor.

Pyridoxine inhibition of a symbiotic streptococcus.

A symbiotic, alpha-hemolytic streptococcus that showed satellitism about a Staphylococcus aureus was recovered from blood cultures of a patient with endocarditis. Previously reported as being required for growth of symbiotic streptococci, pyridoxine hydrochloride was found to inhibit the growth of this organism.