Substitution of lysine for arginine in the N-terminal 217th amino acid residue of the H gamma II of Staphylococcal gamma-hemolysin lowers the activity of the toxin.

The staphylococcal toxin gamma-hemolysin consists of two protein components, LukF and H gamma II. Staphylococcus aureus P83 was found to have five components, LukF, LukF-PV, LukM, LukS, and H gamma II for leukocidin or gamma-hemolysin. H gamma II of S. aureus P83 was demonstrated to be a naturally-occurring analogous molecule of H gamma II [H gamma II(P83)], in which the 217th arginine residue was replaced by lysine. The H gamma II(P83) showed about 50% of the hemolytic activity of normal H gamma II in the presence of LukF.

[The vortex cordis is never reversely directed, even in situs inversus and L-loop anomaly].

In 1926, Taussig reported on two instances of complete situs inversus of the heart and stated that "the main anatomical structure and the deep muscle bundles of the ventricles presented the mirror image of the normal, while the direction of the superficial muscle bundles remained unchanged". In an attempt to analyze whether her statement always held true, we examined the myocardial architecture of five specimens of situs inversus totalis. They were all from patients over sixty years of age and were diagnosed by postmortem examination. Every part of the heart and great vessels presented exact mirror images of the normal. However, the external muscle fibers of the ventricles ran clockwise from base to apex toward the center of the vortex, which had a striking resemblance to the normal rather than the mirror image pattern. Peeling off of the external layer revealed that the direction of fibers was first inverted and then changed into an approximate mirror image of the normal architecture within the deeper muscle layers, as illustrated by Taussig. The exception to this tendency was found at the posterior region of the morphologically left ventricle, in which there was no mirror imaging but a normal pattern throughout the depth of the wall. For the purpose of comparison, two hearts of corrected transposition (L-TGA) were examined. Their chambers were inverted but the external fibers followed the same clockwise course seen in the normal heart. Further dissection revealed that there was no mirror imaging of the architecture at any depth of the morphologically left ventricular wall. Thus there were regional differences and similarities in muscular architecture between these two kinds of ventricular inversion. It was concluded that the vortex layer was never reversely directed, even in situs inversus and L-loop anomaly, and that the deep layers within the sinus region of the left ventricle did not present a mirror image to the normal.

Functional morphology of the conduction system and the myocardium in the sheep heart as revealed by scanning and transmission electron microscopic analyses.

The pacemaker, Purkinje system and myocardium of the sheep heart were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the case of SEM, the heart tissues were subjected to chemical digestion procedures. The nodal cells in both the sinoatrial (SA) node and atrioventricular (AV) node were small in size and contained few nexuses with poor sarcoplasmic reticulum and myofibrillar development. These nodal cells were spindle-shaped and their ends often showed ramifications. In addition, the strands of nodal cells in the central part of the AV node were considerably compact and connected with neighboring strands to form a complicated three dimensional architecture. The muscle cells in the common bundle and Purkinje system were cuboidal or oval in shape and were broader and shorter than the working cardiac muscle cells. They had abundant nexuses, but exhibited poor sarcoplasmic reticulum and myofibrillar development. Three-dimensionally, the Purkinje strands formed a delicate network resembling a fishing-net. The atrial and ventricular myocardium consisted of long cylindrical muscle cells which often bifurcated and connected with neighboring cells. These cells had abundant nexuses, rich sarcoplasmic reticulum and well-developed myofibrils. This report discusses such morphological findings in correlation with their physiological properties.