Yuji Kira

Inhibition of rat vascular smooth muscle proliferation in vitro and in vivo by bone morphogenetic protein-2.

Vascular proliferative disorders are characterized by the proliferation of vascular smooth muscle cells (SMCs) and excessive extracellular matrix synthesis. We found that bone morphogenetic protein-2 (BMP-2) inhibited serum-stimulated increases in DNA synthesis and cell number of cultured rat arterial SMCs in a fashion quite different from that in the case of transforming growth factor-beta1 (TGF-beta1). In addition, TGF-beta1 stimulated collagen synthesis in SMCs, whereas BMP-2 did not. In an in vivo rat carotid artery balloon injury model, the adenovirus-mediated transfer of the BMP-2 gene inhibited injury-induced intimal hyperplasia. These results indicate that BMP-2 has the ability to inhibit SMC proliferation without stimulating extracellular matrix synthesis, and suggest the possibility of therapeutic application of BMP-2 for the prevention of vascular proliferative disorders.

Hypoxic induction of adrenomedullin in cultured human umbilical vein endothelial cells.

Objectives The current study evaluated the hypoxic induction of adrenomedullin gene expression and secretion, and its mechanism in cultured human umbilical vein endothelial cells (HUVEC). Methods HUVEC were exposed to hypoxia or normoxia as controls for 1 to 24 h. Using Northern blot analysis and a radioimmunoassay, we evaluated adrenomedullin expression in HUVEC. The transcriptional component of adrenomedullin gene regulation was assessed by nuclear run-off experiments, and adrenomedullin mRNA half-life was measured by actinomycin D experiments. Results We found that hypoxic conditions (1–3% oxygen) significantly increased adrenomedullin mRNA and protein in HUVEC. This increase was inversely proportional to oxygen tension and was reversible upon re-exposure to a 21% oxygen environment. Nuclear run-off experiments revealed the enhanced transcriptional rate of adrenomedullin gene. Next, actinomycin D experiments revealed the enhanced adrenomedullin mRNA stability. Conclusions These results indicate that hypoxia increases adrenomedullin gene expression and secretion in HUVEC by transcriptional and post-transcriptional mechanisms. Hypoxic induction of adrenomedullin may play a pathophysiological role in the vascular systems.

Effect of long-term cyclic mechanical load on protein synthesis and morphological changes in cultured Myocardial cells from neonatal rat

SummaryWe studied the effect of prolonged cyclic mechanical stimulation on protein synthesis and morphological changes in cultured cardiac myocytes isolated from 3-day-old neonatal rats to develop an in vitro model for cardiac hypertrophy induced by a mechanical load. Myocardial cells were cultured on deformative culture plates with M-199 culture medium in the presence or absence of fetal calf serum (FCS), and a cyclic mechanical load was applied for 2 hours up to 15 days. Mechanical stimulation for 2 hours increased the14C-phenylalanine incorporation rate of myocardial cells, both in the absence and presence of FCS or when the myocardial cells were either beating or arrested with tetrodotoxin. The incorporation rate always increased by mechanical stimulation during 15 days of cell culture as compared to cells that sustained no mechanical stress. The cell size and protein content, which increased gradually with mechanical stimulation and reached a maximum at 10 days, were even greater in the presence of FCS. Within 10 days myocardial cells had aligned in the direction of the maximal cyclic mechanical load. In these cells electron microscopy revealed an increase in the number of myofilaments associated with the development of mitochondria as recognized in the adult myocardial cells. These results indicate that long-term cyclic mechanical loading of cultured myocardial cells may be a good in vitro model for the study of cardiac hypertrophy.

Acute effects of nicotine content in cigarettes on coronary flow velocity and coronary flow reserve in men.

We investigated the acute effects of smoking on coronary flow reserve in terms of the nicotine content of cigarettes in 21 smokers. Coronary flow velocity was measured with a Doppler flow wire. Subjects smoked cigarettes containing >1 mg nicotine (n = 8, group 1) or <1 mg (n = 6, group 2). Subjects in the control group mimicked smoking without a cigarette (n = 7). Coronary flow reserve decreased after smoking in group 1, but not in group 2 or the control group. This reduction may have mediated nicotine or some other unknown substances influenced by smoking.

Effect of time interval between two balloon inflations on ischemic preconditioning during coronary angioplasty

Ischemic preconditioning, defined as a reduction in myocardial ischemia caused by repeated brief episodes of coronary occlusions, is observed during percutaneous transluminal balloon angioplasty (PTCA). To elucidate the effects of the length of the interval between consecutive balloon inflations on ischemic preconditioning during PTCA, we examined 62 patients with chronic stable angina (48 males and 14 females; mean age 62 +/- 10 yr). PTCA was performed on the left anterior descending artery lacking in collateral vessels. A 2-min balloon inflation was performed twice and the extent of ST segment elevation in the electrocardiogram and the severity of chest pain (scored from 0 to 10) for each inflation were determined and compared. Patients were divided into three groups according to the interval between the two inflations: 1 min, Group 1; 2 min, Group 2; and 5 min, Group 5. In Groups 2 and 5, ST-segment elevation was significantly decreased during the second balloon inflation, as compared with that during the first inflation (P < 0.01, P < 0.001). A significant decrease was also observed in the severity of chest pain (P < 0.05, P < 0.01). However, Group 1 showed no significant decrease in ST-segment elevation or severity of chest pain between the first and second inflations. ST-segment elevation and chest pain were reduced to a greater extent in Group 5 than in Group 2. Results suggest that an interval of more than 2 min between balloon inflations is required to achieve ischemic preconditioning during PTCA.

The effects of auricular acupuncture on weight reduction and feeding-related cytokines: a pilot study

Objective Auricular acupuncture is a common therapy used to control appetite; however, the underlying mechanism(s) of action is unclear. The present study examined changes in feeding behaviour and in the levels of several appetite-related hormones in response to auricular acupuncture, and attempted to identify the mechanism(s) by which this traditional medical treatment exerts its effects. Methods Ten healthy adult volunteers (nine female and one male) were recruited by the KOSAI Oriental Healthcare Center. The participants were randomly assigned to one of two groups (n=5 per group): an acupuncture group and a placebo group. Each received detention needle stimulus on a weekly basis for 1 month. Changes in diet, body weight, blood pressure and blood biochemistry were evaluated before treatment and at 1 week after the start of treatment. Results The difference in weight before treatment and after 1 week of treatment was significant for all participants in the acupuncture group (p=0.02). The percentage changes in active ghrelin in the acupuncture group were no significant changes observed in active ghrelin levels at 1 week after acupuncture in any individual participant (p=0.89). By contrast, the percentage changes in active ghrelin levels in the placebo group at 1 week after the start of acupuncture were significant (p=0.04). The insulin, adrenocorticotropic hormone, leptin and adiponectin levels did not change significantly in either group. Conclusions There was a statistically significant difference in the percentage change in body weight and active ghrelin levels in each individual participant in auricular acupuncture groups. This is a pilot study and the sample number is small; however, auricular acupuncture may reduce appetite by suppressing ghrelin production.

The rate of cardiac structural protein synthesis in perfused heart.

Synthesis of cardiac structural protein was studied in perfused rabbit hearts using [3H]lysine and perfluorochemical blood substitute. Relative synthesis rate was estimated in adult rabbit heart when both ventricles worked against zero pressure. The decreasing order was troponin complex, actinin complex, myosin, tropomyosin, and actin and was almost the same as that found in an in vivo study. The synthesis rates of myosin B in left and right ventricles were almost equal in hearts without left and right ventricular pressure load. In young rabbit heart with a right ventricular pressure load, an increase in the synthesis rate of right ventricular myosin B was observed along with the concomitant increase in that of left ventricle. As those increases were blocked by neither propranolol nor verapamil, it was suggested that these increases were not mediated by Ca2+ influx or beta-adrenergic receptors.

Evidence for a humoral factor mediating the effect of a pressure load on lysine incorporation in rabbit heart

Abstract Mechanisms of an increase in protein synthesis in pressure-loaded heart were studied by measuring rates of 3 H-lysine incorporation into cardiac myosin B in a perfused rabbit heart. When a pressure load had been applied to the right ventricle, a significant increase in the incorporation was found not only in the right but also in the left ventricle where pressure load was not applied. Rates of the incorporation in hearts without pressure load increased significantly in both ventricles when they were co-perfused with a heart with a pressure load on the right ventricle. These results suggest that humoral factor(s) is released from the pressure-loaded ventricle which accelerate amino acid incorporation in unloaded ventricles.

Actomyosin extracted from bovine aortic intima

Actomyosin extracted from bovine aortic intima with a KCl-ATP medium of low ionic strength, but not with a KCl medium of high ionic strength, exhibited Ca2+ sensitivity. Aortic medial actomyosin extracted with a medium of high ionic strength retained the Ca2+ sensitivity. These differences in extractability suggest that actomyosin of the aortic intima is different from that of the aortic media.