Brown, Arnold L.

In two children who had multiple aneurysms in the aorta and systemic arteries, and who subsequently died, the histopathologic findings were those of giant-cell arteritis. We have designated this condition as infantile giant-cell arteritis. The etiology is unknown.

Abstract Bone marrow studies of multiple myeloma revealed, in some cases, a conspicuous proliferation of "lymphoid" cells, virtually indistinguishable by light microscopy from those seen in lympho-proliferative disorders. Electron microscopy demonstrated a variety of cells ranging from typical lymphocytes to cells with plasmocytoid features. Between these two types of elements there were cells with intermediate characteristics. In addition, in several cases of myeloma the presence of fixed reticuloendothelial cells and "reticular" plasma cells (or reticulum cells with plasmocytic features) was frequently noted. The presence of reticulum cells and lymphocytes and of cells apparently "intermediate" between these cellular elements and plasma cells, as judged from electron microscopic observations, is suggestive morphologic evidence of a phenomenon of cell transformation and evidence of a mixed cell proliferation in certain cases of multiple myeloma.

Ouabain had no effect on myofibrillar adenosine triphosphatase (ATPase) activity in normal, hypertrophic, and failing hearts with concentrations of calcium chloride varying from 0 to 5.0 mM. The quantitative effects of CaCl 2 on myofibrillar ATPase were the same in all groups studied. At necropsy it was found that myofibrillar ATPase activity of heart tissue from patients with clinical and pathologic diagnoses of failure from left ventricular volume and pressure overload was significantly lower than that of normal controls. The ATPase activity in patients with failure due to right ventricular volume and pressure overload was not significantly lower than that in normal controls. There was no difference in myofibrillar ATPase activity between normal left and normal right and between failing left and failing right ventricles. The difference demonstrated at necropsy between normal and failing hearts was not a function of age or of hypertrophy per se. Myofibrillar ATPase activity of hypertrophic nonfailing surgical pulmonary infundibular tissue was the same as that of normal postmortem ventricles. The ATPase activity of failing surgical papillary muscle in a small number of experiments was in the range of that found in failing postmortem ventricles.

Solutions of human cardiac myosin contain macromolecules which were visualized in the electron microscope by the shadow-casting technic. The dominant particle was observed to be rod-shaped, to have a globular expansion at one end, and to have a mean length of about 1500 Å. The molecule of human cardiac myosin was found to be morphologically similar to myosin molecules from canine cardiac muscle and rabbit skeletal muscle.

Muscular obstruction to left ventricular outflow is a rare but serious occurrence. Eight cases in which this disease was anatomically proved are presented. The commonest symptoms are angina, dyspnea, and palpitations. Not uncommonly a family history of heart disease may be elicited. A systolic murmur along the left sternal border is the most characteristic physical finding, but a normal aortic second sound, the presence of third and fourth heart sounds, splitting of the second sound, and the absence of a diastolic murmur are all helpful clinical guides. Withdrawal pressures from the left ventricle reveal a characteristic infundibular pressure zone. Other hemodynamic findings include an anacrotic notch on the left ventricular pressure tracing, a rapidly ascending bisferious aortic pulse and a small compensatory beat after extrasystoles. Necropsy specimens reveal a grossly thickened interventricular septum as compared with normal and hypertrophied control hearts. Microscopic alterations are minimal. The etiology remains obscure but familial and developmental factors, either or both, appear to be implicated.

The morphology of the canine cardiac myosin molecule has been investigated in the electron microscope with Hall's mica-replica technique. The molecule is an elongated rod (shaft) of nonuniform diameter with a globular expansion (head) on one end. Statistical analysis of the lengths of 1908 molecules showed that the mean length was 1610 ± 250 A; the mean length of the head was 210 ± 20 A; and the diameter of the head and that of the shaft were 35 to 40 and 15 to 20 A, respectively. About one-third of the molecules had single or multiple, fairly sharp, angulations along their shafts. Rarely, some details of the substructure of the molecule have been observed. Large, spindle-shaped aggregates, measuring 0.5 to 1 µ in length and 50 to 100 A in diameter, were produced by dilution of the myosin solutions. These aggregates were readily visualized in the electron microscope by means of Huxley's negative-staining technique. Projections often were visible along the length of the aggregates except at a central zone where they were frequently absent. The aggregates resembled the thick myofilaments of the myocardium and appeared similar to those produced by Huxley from skeletal myosin solutions.