According to the cross-bridge model of muscle contraction, an interaction of myosin heads with interdigitating actin filaments produces tension. Although X-ray equatorial diffraction patterns of active (contracting) muscle show that the heads are in the vicinity of the actin filaments, structural proof of actual attachment of heads to actin during contraction has been elusive. We show here that during contraction of frog skeletal muscle, the 5.9-nm layer line arising from the genetic helix of actin is intensified by as much as 56% of the change which occurs when muscle enters rigor, using a two-dimensional X-ray detector. This provides strong structural evidence that myosin heads do in fact attach during contraction.

Actins↗

PubMedDate not supplied

Genetic and environmental effects on urinary kallikrein, catecholamines, sodium, potassium, urea nitrogen and inorganic sulfate sulfur levels in school-age twins.

A genetic analysis of twins at school was undertaken using as variables urinary concentrations of kallikrein, catecholamines, sodium and potassium which have been demonstrated to be associated with blood pressure levels. In addition to these variables, urinary concentrations of urea nitrogen and inorganic sulfate sulfur which are indices of protein intake were investigated. 35 pairs of monozygotic twins and 19 pairs of dizygotic twins aged from 6 to 14 years were examined. Variance and correlation tests for genetic analysis indicated that in school children, hereditary factors play a role in the control of urinary potassium, sodium and kallikrein excretion. However, with regard to the urinary excretion of catecholamines, urea nitrogen and inorganic sulfate sulfur, hereditary control is not so apparent.

Adolescent↗

PubMedDate not supplied

Blunt liver trauma: a new concept for classification of liver trauma based on vessel injury.

We reviewed a consecutive 143 cases of blunt liver trauma, 43 children and 100 adults, to clarify the pathosis of liver trauma and to reasonably select treatment, non-operative or operative management. The primary determinant in the prognosis of liver trauma was clearly hemorrhage due to vessel injuries and its main treatment method was hemostasis. We developed a new concept for the classification of blunt liver trauma based on vessel injuries: I = subcapsular Glissonian vessel injuries, II = transcapsular Glissonian vessel injuries and III = in-/out-flow vessel injuries and 3 basic types were divided into 2 subtypes, respectively. Distribution of liver trauma according to the present classification was as follows: type I = 23% in child cases and 22% in adult cases, type II = 65% and 64% and type III = 12% and 14%, respectively. The main management was non-operative for type I, minor or major surgery for type II, and extended surgery for type III. The analysis of dead cases showed the following: I = 0% in child cases and 6% in adult, II = 60% and 55%; III = 40% and 39%, respectively. The first direct cause was hemorrhage: 60% in child cases and 49% in adult. The present classification was applicable for both child and adult patients, and presented a selection of management for liver trauma, suggesting the prognosis.

Adult↗