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The intracellular mechanisms involved in the regulation of creatine phosphokinase expression in the BC3H1 muscle-like cell line have been examined under conditions of enzyme induction and repression. In the presence of low serum concentrations, BC3H1 cells cease to grow and synthesize high levels of creatine phosphokinase. When differentiated BC3H1 cultures are exposed to media containing high serum concentrations, cell division is reinitiated and further induction of creatine phosphokinase is inhibited. Accumulation of creatine phosphokinase-mRNA appears to be intimately coupled to the state of growth of BC3H1 cells. Log phase cells do not contain detectable levels of translatable creatine phosphokinase-mRNA; however, following cessation of growth, creatine phosphokinase-mRNA accumulates in approximate proportion to the increase in creatine phosphokinase activity. Reinitiation of cell division in quiescent differentiated cultures results in the arrest of further accumulation of creatine phosphokinase-mRNA but does not inhibit the translation of pre-existing creatine phosphokinase-mRNA. Under conditions of enzyme repression, however, the newly synthesized creatine phosphokinase appears to be enzymatically inactive. These results indicate that the expression of the muscle phenotype in BC3H1 cells is regulated by components present in serum and that myogenic differentiation is at least partially reversible following re-entry of quiescent cells into the cell cycle.

Disruption of the posterior pelvic ring caused by vertical shearing forces is associated with significant morbidity and mortality. We reviewed the intermediate results in 18 patients who had 20 disruptions of the posterior pelvic ring. Depending on the location of the injury, patients were treated by either skeletal traction or open reduction and internal fixation. Patients who had open reduction and internal fixation had a significantly shorter hospitalization, a shorter confinement to bed, a shorter time to full weight-bearing, and fewer early complications. In addition, on intermediate follow-up, these patients had less back and leg pain and fewer gait disturbances, and were more likely to be able to do heavy work. Further study is needed to determine whether these results will be preserved on long-term follow-up.

Human sperm contains en enzyme with diaphorase activity that appears to be unique to sperm. Electrophoretic analysis of the diaphorase activity in sperm of different individuals reveals three phenotypic patterns. This polymorphism can be explained in terms of two alleles segregating at an autosomal locus; the allele frequencies have been determined to be 0.71 and 0.29. This appears to be the first reported example of a sperm-specific genetic polymorphism in man; its existence raises a number of genetic and biochemical questions.

Protein separation has been achieved by electrical field-flow fractionation, a heretofore unrealized separation technique. Some advantages of this method relative to electrophoresis are the low voltage required, the lack of adverse heating and support effects, and the existence of the method as an elution technique. A comparison of theoretical and experimental retention shows good agreement.