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Biomedical subjects

M Hamada

Publications and source records attributed to M Hamada.

At least 397 records · Page 22Linked to original sources
PubMed1990

Enhanced DNA synthesis of cultured vascular smooth muscle cells from spontaneously hypertensive rats. Difference of response to growth factor, intracellular free calcium concentration and DNA synthesizing cell cycle.

It is widely reported that cultured vascular smooth muscle cells (CVSMCs) from spontaneously hypertensive rats (SHR) show enhanced proliferation compared with cells from Wistar-Kyoto rats (WKY). The present studies were designed to find out whether this exaggerated proliferation in SHR is determined genetically and, if so, to evaluate the mechanism on the cell cycle. (1) Incorporation of [3H]thymidine into DNA was enhanced in CVSMCs from 3- and 12-week-old SHR compared with WKY but not in CVSMCs from DOCA-salt hypertensive rats compared with the cells from sham-operated rats. (2) DNA synthesis in SHR cells was enhanced further by addition of insulin (which is considered to be a progression factor) but not by arginine-vasopressin (AVP; considered to be a competence factor) or by angiotensin II (AII). On the other hand, insulin, AVP and AII significantly augmented DNA synthesis in WKY cells. (3) Intracellular free calcium concentration was slightly, but significantly, higher in SHR cells. (4) An increase in the population of DNA-synthesizing S-phase cells and decrease in (G2 + M)-phase cells in SHR were observed by flowcytometry. These data suggest (1) that enhanced DNA synthesis in CVSMCs from SHR is determined genetically, (2) that enhanced DNA synthesis in CVSMCs from SHR is largely dependent on an increased proportion of S-phase cells and (3) that this increase in S-phase cells in CVSMCs from SHR could be due to enhanced competence gene expression in SHR cells. (4) The increased intracellular free calcium concentration is compatible with an activation of the inositol-trisphosphate pathway.

Angiotensin II↗
PubMed1990

Effect of centrifugal force and catecholamines on glycosaminoglycans synthesis of vascular smooth muscle cells in culture.

To evaluate the effect of hypertension on glycosaminoglycan (GAG) synthesis, cultured vascular smooth muscle cells (CVSMCs) from the aorta of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were exposed to centrifugal forces and catecholamines. GAG synthesis of CVSMCs was measured by the incorporation of [3H]glucosamine into GAGs which were secreted into the culture medium for 24 h. Basal level of GAG synthesis was much higher in SHR than in WKY, when expressed in terms of DNA contents. When exposed to centrifugal force, CVSMCs from rats of both strains synthesized more GAGs. GAG synthesis was enhanced by both noradrenaline (NA) and adrenaline (Ad) in WKY. The enhanced GAG synthesis in WKY by NA or Ad was prevented by pretreatment with propranolol, but not prazosin. In SHR, NA and Ad did not enhance GAG synthesis at this concentration of catecholamines. However, the effects of propranolol or prazosin on GAG synthesis in SHR, when incubated with either NA or Ad, were compatible with the phenomena observed in WKY. Adding dibutyryl cyclic AMP to the culture medium enhanced GAG synthesis in rats of both strains. These data suggest that not only the mechanical stress of high intra-arterial pressure but also beta receptor stimulation, via increasing cyclic AMP, enhance GAG synthesis of vascular smooth muscle cells in hypertension.

Animals↗
PubMed1990

Kinetic properties and isozyme composition of myosin in the mdx mutant mouse.

Skeletal muscle fibers from muscular dystrophic mice (C57BL/10-mdx) 1-4 months of age show elevated free Ca2+ concentrations both at resting and stimulated states, although contractility of adult (2-12 months old) mouse is similar to that of normal mouse. To evaluate the sensitivity of the contractile system of adult mdx mouse muscle to elevated free Ca2+ concentration, Mg2(+)-adenosine triphosphatase (ATPase) activity was examined using myosin, myosin B, and reconstituted actomyosin. Myosin Mg2(+)-ATPase activity of the mdx mouse was significantly higher than that of the normal mouse. Myosin B ATPase activity of the mdx mouse was also higher than that of normal mouse in free Ca2+ concentrations between 10(-9) and 10(-5) M, though there was no difference in the Ca2+ concentration required for half maximal activation of ATPase activity, 2 x 10(-7) M. Polymerized actin (FA) isolated from normal and mdx mice activated rabbit myosin Mg2(+)-ATPase identically, while activation of Mg2(+)-ATPase in mdx myosin by rabbit FA was significantly lower than that in normal mouse myosin. Rapid Pi liberation by Mg2(+)-ATPase in mdx mouse myosin was about half that of normal mouse myosin, being consistent with low activation of Mg2(+)-ATPase activity by rabbit FA. Polyacrylamide gel electrophoresis in the presence of pyrophosphate showed that myosin molecules of mdx and normal mice were both composed of three isozymes, although the fast migrating myosin isozyme (M1) was decreased while the slow migrating band (M3) was increased in mdx myosin. Subunit composition of myosin analyzed by polyacrylamide gel electrophoresis in the presence of SDS showed that the content of the smallest light chain (LC3) in mdx myosin was lower than that of normal mouse myosin, which agreed with findings that mdx myosin contained less M1 isozyme than normal myosin. These results indicated that the lowered response of mdx muscle fibers to elevated Ca2+ concentration can be attributed to the isozyme composition of myosin in mdx mouse.

Actomyosin↗
PubMed1990

Simultaneous determination of glucose, ethanol and lactate in alcoholic beverages and serum by amperometric flow injection analysis with immobilized enzyme reactors.

Glucose, ethanol and lactate were determined simultaneously in a flow injection system by using a parallel configuration of immobilized enzyme reactors. Hydrogen peroxide produced was monitored amperometrically at the potential of +0.65 V vs. Ag/AgCl. Linear relations between sensor responses and each species were observed in the ranges of 0.02-10 mM (glucose), 5 x 10(-4)-0.1% (v/v) (ethanol) and 0.005-1 mM (lactate) with correlation coefficients larger than 0.999 for each species. The relative standard deviations for 10 successive injections were 1.4, 0.5 and 1.1% for glucose (1 mM), ethanol (5 x 10(-3)% (v/v] and lactate (0.05 mM), respectively. Analysis of serum samples was performed with urate-eliminating reactors which were set just before each immobilized enzyme reactor. Interference of ascorbate in a serum sample was completely eliminated by using an ascorbate-eliminating reactor which was set before the sample injection valve. Application of the system to alcoholic beverages and control serum was described and the results were compared with those of free enzymatic, spectrophotometric analysis (F-kit or C-test method).

Alcoholic Beverages↗
PubMed1990

Histopathological development of equine cutaneous papillomas.

The histopathological development of equine cutaneous papillomas was studied in 78 warts naturally occurring in 50 one to 3-year-old Thoroughbred or Arab horses and in 54 warts experimentally induced in three 2-year-old Thoroughbreds. Lesions in the natural cases were categorized into three phases, growth, development and regression. Main lesions of the growing phase were marked hyperplasia of the basal cells and mild to moderate acanthosis, hyper- and parakeratosis with a few intranuclear inclusion bodies (IIB) which were positive with anti-bovine papillomavirus serum. In the developing phase, there was prominent acanthosis with cellular swelling and fusion, and marked hyper- and parakeratosis. Many IIB were also present in swollen or degenerative prickle cells and granular cells, with a high degree of parakeratosis in keratinocytes. In the regressing phase, epidermal layers were almost normal with only slight hyperplastic change. However, there was rete peg proliferation downward into the dermis with moderate proliferation of fibroblasts and collagen fibres. In addition, in 10 spontaneous and one experimental wart, the lesions were fibropapillomas and this has never been described in horses previously. It was concluded that papillomas were initiated by basal cell hyperplasia without viral antigen production, with formation of acanthosis and hyper- and parakeratosis with IIB production. These findings were confirmed by examination of the experimental cases on the basis of the gross diameter of the warts.

Animals↗
PubMed1990

Keratin expression in equine normal epidermis and cutaneous papillomas using monoclonal antibodies.

Keratin expressions in normal equine epidermis and experimentally induced equine papillomas were studied by immunohistochemical methods with three different human cytokeratin monoclonal antibodies, 34 beta B4 (directed against component 1), 34 beta E12 (directed against components 1, 5, 10, 11) and 35 beta H11 (directed against component 8). Staining patterns with 34 beta B4 and 34 beta E12 in the normal equine epidermis did not differ from those in the normal human epidermis. In the early developing papilloma, keratinocytes showed an abnormal suprabasal staining pattern and expressed an additional 56 kD keratin protein detected by 34 beta E12. In the advanced papilloma, cytolytic cells in the outer spinous and the granular layers did not stain positively with any of the three antibodies used. In both early and advanced papillomas, the expression of high molecular weight keratin proteins, as detected by 34 beta B4 and 34 beta E12, did not correlate with the degree of keratinization. By electron microscopy, keratinocytes in the advanced papilloma showed a marked decrease of tonofibrils and desmosome-tonofilament complex. These alterations may result from an abnormality in both proliferation and functional terminal differentiation of keratinocytes in the papilloma. There were obvious differences in staining patterns with 35 beta H11 between the normal human and equine epidermis; 54 kD keratin protein was expressed in suprabasal layers of the equine normal and papillomatous epidermis. Thus, this keratin protein may be regarded as a "permanent" marker for the equine epidermis.

Animals↗
PubMed1990

Ultrastructural morphology of hypomelanosis in equine cutaneous papilloma.

The morphology of hypomelanosis occurring in experimentally induced equine papillomas was investigated. Histologically, dopa-positive functioning melanocytes were decreased in number from the basal layer in the epidermis. Electron-microscopically, melanogenic organelles in the melanocytes were degenerate and melanosomes were decreased in number and size. In addition, the melanocytes had some abnormal melanosomes including melanosome complexes and giant melanosomes. Some abnormal melanosomes were also present in the keratinocytes. The hypomelanosis seemed to be related to a disturbance in melanin synthesis and melanocytic-keratinocytic interaction in the epidermal melanin unit.

Animals↗
PubMed1990

Effect of prolonged hypothermic ischaemia on myocardial sarcoplasmic reticular calcium transport.

STUDY OBJECTIVE: The aim of the study was to assess the effects of hypothermia on sarcoplasmic reticulum in myocardium subjected to prolonged ischaemia. DESIGN: Calcium regulatory activity of myocardial sarcoplasmic reticulum was measured in hearts subjected to various periods of hypothermic ischaemia in comparison with hearts subjected to normothermic ischaemia. SUBJECTS: Hearts (n = 5-9 per experiment) were obtained from male New Zealand white rabbits, 2.0-2.8 kg weight. MEASUREMENTS AND RESULTS: Calcium uptake and calcium dependent ATPase activity were measured in isolated sarcoplasmic reticulum vesicles after hypothermic ischaemia was produced by immersing hearts in saline at 4 degrees C for 3, 6, or 12 h. Normothermic hearts were immersed for 3 h at 37 degrees C. Calcium uptake and calcium dependent ATPase (Ca-ATPase) activity were markedly inhibited by normothermic ischaemia. In hypothermic ischaemia, calcium uptake was only slightly depressed after 3 h, though longer periods of ischaemia resulted in significant depression of uptake. Ca-ATPase activity was unaffected after 6 h of hypothermic ischaemia. The ratio of calcium uptake to Ca-ATPase activity decreased after 3 h of hypothermic ischaemia. The phosphoenzyme concentration in sarcoplasmic reticulum was unaffected up to 6 h. The ratio of Ca-ATPase activity to phosphoenzyme concentration was not significantly altered until 12 h. Protein composition, examined by SDS-polyacrylamide gel electrophoresis, showed a decrease in 100,000 dalton polypeptide in normothermic ischaemia and after 12 h of hypothermic ischaemia. CONCLUSIONS: These results suggest that the depression of calcium uptake activity after 6 h of hypothermic ischaemia is likely to be due to uncoupling of calcium transport from ATP hydrolysis. Depressed Ca-ATPase activity at 12 h can be attributed to a reduction in the number of active calcium pump units. Hypothermia preserves function of myocardial sarcoplasmic reticulum during ischaemia for up to 3 h.

Animals↗
PubMed1990

Clinical significance of systolic time intervals in hypertensive patients.

This paper updates the current view on clinical significance of systolic time intervals (STI) in estimating the cardiac changes associated with hypertension. The following three intervals were measured as STI: (1) electromechanical systole (QS2 interval); (2) left ventricular ejection time (LVET) and (3) pre-ejection period (PEP). Firstly, the influences of changes in heart rate, preload, afterload and myocardial contractility upon each interval were reviewed; secondly, clinical applications of STI in various types of hypertension such as essential hypertension, hypertension with angina pectoris and pheochromocytoma were studied. In patients with essential hypertension, there was a good positive correlation between PEP and left ventricular mass, and a shortening of LVET was observed only at the decompensated stage. The changes in STI in angina pectoris with or without hypertension were similar and were different from those in essential hypertensives. STI in patients with pheochromocytoma were characterized by a marked shortening of QS2 and LVET with normal PEP. These findings indicate the usefulness of STI in detecting cardiac changes in various types of hypertension.

Adrenal Gland Neoplasms↗
PubMed1990

Multiforms of mammalian adenylate kinase and its monoclonal antibody against AK1.

An attempt has been made to determine the intracellular distribution of the multiforms of the adenylate kinase (AK) isoenzymes in mammalian tissues, to shed some light on their physiological roles, especially in energy metabolism. The adenylate kinase zymograms obtained from isoelectric focusing yielded two typical isoform patterns: (1) with a pI greater than or equal to 9 and 8.6, specific for bovine skeletal muscle, heart, aorta and brain, and (2) with a pI = 7.9 and 7.1, specific for liver and kidney. Pattern (1) was attributed to the cytosolic isoenzyme (AK1) as demonstrated by immunostaining with anti-AK1. Pattern (2) was attributed to the mitochondrial isoenzyme (AK2). These results were largely confirmed by chromatofocusing experiments. The AK1 isoenzyme was partially purified from the cytosol fraction of bovine aortic smooth muscle and had an apparent Mr of 23.5 kilodaltons. Its kinetic features are discussed from a comparative standpoint. Finally, the human serum AK1 isoform was also detected by Western blotting with a monoclonal antibody directed against crystalline porcine muscle AK1. These results are to form the basis of further studies on the 'aberrant' adenylate kinase isoenzyme from the serum of Duchenne muscular dystrophics.

Adenylate Kinase↗
PubMed1990

Effects of nifedipine on left ventricular diastolic function in patients with asymptomatic or minimally symptomatic hypertrophic cardiomyopathy.

We investigated the effects of nifedipine on left ventricular diastolic function in 17 asymptomatic or minimally symptomatic patients with hypertrophic cardiomyopathy by simultaneously measuring left ventricular pressure and volume with a catheter-tipped manometer and biplane cineangiography. Studies were performed before and 20 minutes after sublingual administration of nifedipine (20 mg). Heart rates were held constant (79 +/- 12 beats/min, mean +/- SD) by right atrial pacing. Left ventricular volumes and instantaneous rates of left ventricular volume were derived from frame-by-frame (20-msec) analyses of left ventricular biplane angiograms. Left ventricular peak systolic pressure (from 122 +/- 21 to 108 +/- 13 mm Hg, p less than 0.01 vs. control) and mean aortic pressure (from 96 +/- 15 to 87 +/- 11 mm Hg, p less than 0.01) decreased significantly with nifedipine. With afterload reduction, left ventricular ejection fraction (from 0.69 +/- 0.12 to 0.74 +/- 0.08, p less than 0.01) and cardiac output (from 6.4 +/- 2.0 to 7.2 +/- 2.2 l/mm, p less than 0.05) increased significantly. However, there was a slight but significant increase in left ventricular end-diastolic pressure (from 15 +/- 8 to 18 +/- 8 mm Hg, p less than 0.05). Nifedipine did not improve left ventricular relaxation as assessed by the time constants of isovolumic pressure decay (t1/2, from 39.8 +/- 6.6 to 39.4 +/- 7.7 msec, NS; t1/e, from 53.8 +/- 9.0 to 54.4 +/- 10.7 msec, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1990

Persistent elevation of cardiac enzymes in a patient with hypertrophic cardiomyopathy--with special reference to electrocardiographic, echocardiographic and 201-thallium myocardial scintigraphic findings.

A 17-year-old female patient with hypertrophic cardiomyopathy whose serum cardiac enzymes (creatine phosphokinase = CPK, lactic dehydrogenase = LDH) showed persistent elevation was presented. Percent of CPK-MB and LDH1 in 6-year-follow-up period ranged from 3.2% to 8.5%, and 58.0% to 63.2%, respectively. This finding strongly suggests the existence of a small amount of continuous myocardial necrosis for a long time. The influence of cardiac enzyme release on the heart was assessed by serial checks of electrocardiogram, echocardiogram and 201-thallium myocardial scintigram. In serial checks of electrocardiograms, markedly decreased R wave amplitude ranging between 31% and 47% was observed in II, III, aVF and V3-6. On echocardiograms, asymmetric septal hypertrophy and a narrow left ventricular cavity were observed in all echocardiograms through the follow-up period. But, in most recent apical two-dimensional echocardiograms, hourglass appearance of the left ventricle due to a distinct cavity-formation at the apex was observed. In 201-thallium single photon emission computed tomogram, hypoperfusion area markedly extended in anterior and lateral parts. These changes in electrocardiograms, echocardiograms and 201-thallium myocardial scintigrams seemed to reflect myocardial necrosis. Our case points to a mechanism for hypertrophic cardiomyopathy to change, over time, to dilated cardiomyopathy-like features.

Adolescent↗
PubMed1990

Probestin, a new inhibitor of aminopeptidase M, produced by Streptomyces azureus MH663-2F6. I. Taxonomy, production, isolation, physico-chemical properties and biological activities.

Probestin has been isolated as part of a program designed to find microorganism-produced inhibitors of aminopeptidase M from Streptomyces azureus MH663-2F6. It was purified by use of column chromatography of Amberlite XAD-4, silica gel, YMC-gel, Toyopearl HW-40, YMC D-ODS-5 (HPLC) and then isolated as colorless powders. Probestin is competitive with the substrate, and the inhibition constant (Ki) of it was 1.9 x 10(-8) M.

Aminopeptidases↗
PubMed1990

Screening of antibiotics preferentially active against ras oncogene-expressed cells.

During the course of in vitro screening of agents which are preferentially active against ras oncogene-expressed cells, a new anthracycline (identified as 2-demethylsteffimycin D) and a heptaene (possibly a new member of partricins) were isolated from microbial fermentation broths. Among known compounds tested, 5-fluorouracil, 5-fluorodeoxyuridine and oxanosine showed high selectivity towards ras oncogene-expressed cells.

Animals↗