永井 良三

This report is concerned with an adult presenting with stenotic bicuspid aortic valve associated with a ventricular septal defect (VSD). The association between aortic regurgitation (AR) and VSD has often been described, but that between a stenosed aortic valve and VSD has been rarely observed, although bicuspid aortic valves and ventricular septal defects are probably the two most common congenital heart defects. The development of congestive heart failure in the presented case was considered to be due to an increase in the left to right shunt through the VSD. This was attributable to a progressive elevation in left ventricular pressure as a result of the development, with age, of stenosis of the bicuspid aortic valve.

We report 4 adult patients with thyrotoxicosis accompanied by irreversible low-output heart failure. Each patient showed elevated plasma levels of thyroid hormone and prolonged low-output heart failure even after thyroid function returned to normal. Specimens of the right ventricular myocardium stained with anti-beta myosin heavy-chain MAb showed a normal staining pattern with a predominance of the beta-form. Our observations suggest that thyrotoxicosis may be one possible cause of irreversible cardiomyopathy.

We recently reported a genus-specific PCR for the mycobacterial dnaJ gene. In the present study, we have determined the nucleotide sequences of the dnaJ gene from 19 mycobacterial species (Mycobacterium tuberculosis, M. bovis, M. bovis BCG, M. africanum, M. microti, M. marinum, M. kansasii, M. gastri, M. simiae, M. scrofulaceum, M. szulgai, M. gordonae, M. avium, M. intracellulare, M. xenopi, M. fortuitum, M. chelonae, M. hemophilum, and M. paratuberculosis). On the basis of the amplified dnaJ gene nucleotide sequences, we constructed a phylogenetic tree of the mycobacterial species by using the neighbor-joining method and unweighted pairwise grouping method of arithmetic average. We found that the phylogenetic relationship inferred within the slowly growing species was in good agreement with the traditional classification, with three major branches corresponding to Runyon's groups I, II, and III. An exception was M. simiae, which was phylogenetically closer to the cluster including members of Runyon's group III than to that of Runyon's group I. On the other hand, the rapid growers, such as M. fortuitum and M. chelonae, did not form a coherent line corresponding to Runyon's group IV, indicating that our phylogenetic analysis based on the dnaJ gene reflects the phenotypic characteristics such as pigmentation but not the growth rate. Finally, we revealed the species-specific restriction sites within the amplified dnaJ gene to differentiate most of the mycobacterial DNA by a combination of PCR with restriction fragment length polymorphism analysis.

Smooth muscle myosin heavy chains (MHCs) exist in multiple isoforms. Rabbit smooth muscles contain at least three types of MHC isoforms: SM1 (204 kD), SM2 (200 kD), and SMemb (200 kD). SMI and SM2 are specific to smooth muscles, but SMemb is a nonmuscle-type MHC abundantly expressed in the embryonic aorta. We recently reported that these three MHC isoforms are differentially expressed in rabbit during normal vascular development and in experimental arteriosclerosis and atherosclerosis. The purpose of this study was to clarify whether expression of human smooth muscle MHC isoforms is regulated in developing arteries and in atherosclerotic lesions. To accomplish this, we have isolated and characterized three cDNA clones from human smooth muscle: SMHC94 (SM1), SMHC93 (SM2), and HSME6 (SMemb). The expression of SM2 mRNA in the fetal aorta was significantly lower as compared with SM1 mRNA, but the ratio of SM2 to SM1 mRNA was increased after birth. SMemb mRNA in the aorta was decreased after birth but appeared to be increased in the aged. To further examine the MHC expression at the histological level, we have developed three antibodies against human SM1, SM2, and SMemb using the isoform-specific sequences of the carboxyl terminal end. Immunohistologically, SM1 was constitutively positive from the fetal stage to adulthood in the apparently normal media of the aorta and coronary arteries, whereas SM2 was negative in fetal arteries of the early gestational stage. In human, unlike rabbit, aorta or coronary arteries, SMemb was detected even in the adult. However, smaller-sized arteries, like the vasa vasorum of the aorta or intramyocardial coronary arterioles, were negative for SMemb. Diffuse intimal thickening in the major coronary arteries was found to be composed of smooth muscles, reacting equally to three antibodies for MHC isoforms, but reactivities with anti-SM2 antibody were reduced with aging. With progression of atherosclerosis, intimal smooth muscles diminished the expression of not only SM2 but also SMI, whereas alpha-smooth muscle actin was well preserved. We conclude from these results that smooth muscle MHC isoforms are important molecular markers for studying human vascular smooth muscle cell differentiation as well as the cellular mechanisms of atherosclerosis.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a recently identified potent vascular smooth muscle cell (SMC) mitogen. We investigated the effect of shear stress on human HB-EGF mRNA levels in cultured human umbilical vein endothelial cells (HUVEC). In response to shear stress (8 dyne/cm2), HB-EGF mRNA levels in HUVEC increased rapidly, peaked at 3 h, and returned to near base line at 7 h. The shear stress-induced HB-EGF gene expression in HUVEC is completely blocked by 12-O-tetra-decanoylphorbol-13-acetate pre-treatment, suggesting the induction of HB-EGF is mediated by protein kinase C.

BACKGROUND: The closure of the ductus arteriosus (DA) is one of the most striking cardiovascular events that occur at birth. It has been attributed to oxygenation and intrinsic prostaglandins. However, selective constriction of DA suggests the presence of highly specialized contractile mechanisms in DA. We previously reported that smooth muscle myosin heavy chain isoforms, SM1 and SM2, are molecular markers for smooth muscle differentiation because of their unique expression pattern during vascular development. SM1 and SM2 are generated from a single gene through developmentally regulated alternative RNA splicing; SM1 is expressed in almost all stages of differentiation of the vascular smooth muscles, but SM2 is found only after birth. METHODS AND RESULTS: Immunohistochemistry was performed to study the expression of the different types of myosin heavy chain isoforms in DA of fetal and neonatal rabbits. Electron microscopic examinations were also carried out to demonstrate ultrastructural characteristics of ductus muscles. We found that SM2 is expressed before birth in the medial layer of DA, indicating advanced differentiation of smooth muscle cells in DA. The exact location of immunoreactivity for SM2 was in the smooth muscle cell of the medial layer of DA. Immunoreactivity for SM1, however, was not different for DA and adjacent great arteries. Transmission electron microscopy demonstrated greater amounts of myofilaments in medial smooth muscles of DA than those of aorta. CONCLUSIONS: These results indicate that smooth muscles in DA are more differentiated than those in other arteries, which may be one of the cellular mechanisms responsible for the unique closure of DA at birth.

To elucidate the mechanism(s) of myocardial reperfusion injury, we investigated the roles of cell adhesion molecules on both leukocytes and vascular endothelial cells in the reperfused myocardia. We found that within 2 hours after reperfusion leukocytes began to infiltrate into the rat myocardia subjected to 30 minutes of ischemia and clarified, for the first time, that the expression of intercellular adhesion molecule-1 was enhanced on the capillary and venous endothelial cells from 8 to 96 hours after the start of reperfusion. Furthermore, pretreatment with individual monoclonal antibodies against cell adhesion molecules (CD11a, CD11bc, CD18, and intercellular adhesion molecule-1) reduced not only the infiltration of leukocytes but also the area of infarction in the reperfused hearts. These observations suggest that cell adhesion molecules play a critical role in the pathogenesis of myocardial reperfusion injury.

The molecular mechanisms by which overloaded cardiac myocytes increase the cell size (hypertrophy) remain unknown. We have previously shown that mechanical loading increased the protein synthesis and the expression of proto-oncogene c-fos mRNA (Komuro, I., Kaida, T., Shibazaki, Y., Kurabayashi, M., Katoh, Y. Hoh, E., Takaku, F., and Yazaki, Y. (1990) J. Biol. Chem. 265, 3595-3598; Komuro, I., Katoh, Y., Kaida, T., Shibazaki, Y., Kurabayashi, M., Hoh, E., Takaku, F., and Yazaki, Y. (1991) J. Biol. Chem. 266, 1265-1268). It has been known that both mitogen-activated protein (MAP) kinase and S6 kinase can be activated by many kinds of growth factors. To clarify whether MAP kinase(s) and S6 kinase(s) are associated with the intracellular signaling of cardiac hypertrophy induced by mechanical loading, we cultured neonatal rat cardiac myocytes in deformable dishes and imposed an in vitro mechanical loading by stretching the adherent myocytes. In this study, we demonstrated that 1) myocyte stretching maximally activated a kinase activity toward myelin basic protein (MBP) at 10 min after stretching, and the kinase activity returned to the control level at 30 min after stretching; 2) kinase assays in MBP-containing gel, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealed that stretch-induced MBP kinase activity mainly migrated at 42 kDa in the immunoprecipitated fraction of anti-MAP kinase antibody, suggesting that the stretching mainly increased the 42-kDa MAP kinase activity in cardiac myocytes; 3) phosphorylation of MAP kinase was induced after stretching cardiac myocytes; 4) when protein kinase C was depleted by preincubating myocytes with 100 nM 12-O-tetradecanoyl-phorbol-13-acetate for 24 h or 2 nM staurosporine for 30 min, stretch-induced MBP kinase activity was decreased by approximately 60-70% as compared with the kinase activity in myocytes without protein kinase C depletion; 5) although the receptor tyrosine kinases were depleted by preincubating myocytes with 50 microM tyrphostin or 20 microM genistein for 30 min, there was no change in the stretch-induced MBP kinase activity; 6) stretch-induced MBP kinase activity was partially dependent on transsarcolemmal influx of Ca2+; 7) myocyte stretching also increased S6 peptide (RRLSSLRA) kinase activity in the anti-S6 kinase II antibody immunoprecipitates. From these results, we conclude that myocyte stretching increases the activities of MAP kinase and S6 peptide kinase, which may play an important role in the induction of the specific genes and the increase in the protein synthesis.

A 26-year-old man having chronic constrictive pericarditis with rare complications is described. Right ventricular inflow obstruction was caused by an intracavity giant mass which was surrounded by thick calcified pericardium. The mass consisted of old bloody fluid with some calcified tissue. The findings of auscultation closely mimicked those of tricuspid valvular stenosis.