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Biomedical subjects

T Masaki

Publications and source records attributed to T Masaki.

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

Differential distribution of subsets of myofibrillar proteins in cardiac nonstriated and striated myofibrils.

Cultured cardiac myocytes were stained with antibodies to sarcomeric alpha-actinin, troponin-I, alpha-actin, myosin heavy chain (MHC), titin, myomesin, C-protein, and vinculin. Attention was focused on the distribution of these proteins with respect to nonstriated myofibrils (NSMFs) and striated myofibrils (SMFs). In NSMFs, alpha-actinin is found as longitudinally aligned, irregular approximately 0.3-microns aggregates. Such aggregates are associated with alpha-actin, troponin-I, and titin. These I-Z-I-like complexes are also found as ectopic patches outside the domain of myofibrils in close apposition to the ventral surface of the cell. MHC is found outside of SMFs in the form of discrete fibrils. The temporal-spatial distribution and accumulation of the MHC-fibrils with respect to the I-Z-I-like complexes varies greatly along the length of the NSMFs. There are numerous instances of I-Z-I-like complexes without associated MHC-fibrils, and also cases of MHC-fibrils located many microns from I-Z-I-like complexes. The transition between the terminal approximately 1.7-microns sarcomere of any given SMF and its distal NSMF-tip is abrupt and is marked by a characteristic narrow alpha-actinin Z-band and vinculin positive adhesion plaque. A titin antibody T20, which localizes to an epitope at the Z-band in SMFs, precisely costains the 0.3-microns alpha-actinin aggregates in ectopic patches and NSMFs. Another titin antibody T1, which in SMFs localizes to an epitope at the A-I junction, typically does not stain ectopic patches and NSMFs. Where detectable, the T1-positive material is adjacent to rather than part of the 0.3-microns alpha-actinin aggregates. Myomesin and C-protein are found only in their characteristic sarcomeric locations (even in just perceptible SMFs). These A-band-associated proteins appear to be absent in ectopic patches and NSMFs.

Actinin↗
PubMed1990

Monoclonal antibodies to endothelin: application for sandwich immunoassays.

We established 16 monoclonal antibodies (MAbs) to endothelin (ET), a novel and potent vasoconstrictor. They were classified into two groups: eight of them reacted with the C-terminal portion of ET, and the other eight reacted with the non-C-terminal portion. We constructed the sandwich enzyme linked immunosorbent assays (ELISAs) using a combination of a MAb belonging to the former with that belonging to the latter, and could detect about 400 pg/ml of ET.

Animals↗
PubMed1990

Microspectrophotometric DNA analysis in ulcerative colitis with special reference to its application in diagnosis of carcinoma and dysplasia.

The deoxyribonucleic (DNA) content was measured by microspectrophotometry in 100 specimens from 60 patients with ulcerative colitis, including six patients in whom the colitis was associated with carcinoma. Some 23 of 30 (77%) specimens of dysplastic tissue showed aneuploidy or polyploidy, whereas 50 of 53 (94%) specimens of non-dysplastic tissue showed diploidy. The difference was statistically significant (p less than 0.001). Polyploidy was often observed in non-dysplastic mucosa from patients who had carcinoma or dysplasia. In the non-dysplastic patients all samples of inflamed tissue showed diploidy. Some 10% of samples without inflammation, however, also showed polyploidy. A good correlation was found between the frequency of polyploid cells and the grade of dysplasia. Microspectrophotometric measurement of DNA content proved useful in the assessment and diagnosis of dysplasia in ulcerative colitis and could be considered for screening high risk patients.

Adult↗
PubMed1990

Involvement of endothelin in the regulation of human vascular tonus. Potent vasoconstrictor effect and existence in endothelial cells.

Endothelin, a recently discovered endothelium-derived peptide, has been reported to produce potent vasoconstriction in various vessels of experimental animals. To study the involvement of endothelin in the regulation of vascular tonus in humans, isolated human mesenteric arteries were investigated by both pharmacological and immunohistochemical methods. The vasoconstrictor action of endothelin-1 was examined on ring segments of human mesenteric arteries. Endothelin-1 induced a slowly developing and sustained contraction, with an EC50 value (half-maximal effective concentration) of 2.9 x 10(-9) M, two orders of magnitude smaller than that of norepinephrine (EC50 of 3.9 x 10(-7) M), indicating that the vasoconstrictor action of endothelin-1 is about 100 times more potent than that of norepinephrine. The contractile effect of endothelin-1 was affected neither by adrenergic, cholinergic, histaminergic, nor serotonergic antagonists, nor by inhibitors of arachidonic acid metabolism. The vasoconstrictor response to endothelin-1 was effectively antagonized by nicardipine, a dihydropyridine Ca2+ channel blocker. Endothelin-1 profoundly augmented contractile response to Ca2+ in partially depolarized tissues. Immunohistochemical studies revealed for the first time that endothelin-like immunoreactivity was localized in endothelial cells of human mesenteric artery. The results of the present study indicate that endothelin-1 is one of the most potent vasoconstrictors in the human mesenteric artery and that it induces vasoconstriction via an ultimately accelerating Ca2+ influx through voltage-dependent Ca2+ channels. Since endothelin-1 can be located in human endothelial cells, it may play an important physiological or pathophysiological role.

Adult↗
PubMed1990

Endothelin receptor is coupled to phospholipase C via a pertussis toxin-insensitive guanine nucleotide-binding regulatory protein in vascular smooth muscle cells.

The mechanisms of endothelin-1 (ET) actions were investigated in cultured rat aortic vascular smooth muscle A-10 cells. The A-10 cells have a single class of high affinity binding sites for ET with an apparent Mr of 65,000-75,000 on SDS-PAGE. Stimulation of cells with ET induces mobilization of Ca2+ from both intra- and extracellular pools to produce a biphasic increase in cytoplasmic free Ca2+ concentration. ET increases cellular levels of inositol trisphosphate and 1,2-diacylglycerol, indicating activation of phospholipase C by ET. ET stimulates production of inositol phosphates in membranes prepared from A-10 cells in the presence of guanosine 5'-O-(thiotriphosphate) (GTP gamma S), but not in its absence. Further, specific binding of 125I-labeled ET to A-10 cell membranes is shown to be inhibited by GTP gamma S in a dose-dependent manner. Treatment of A-10 cells with pertussis toxin induces ADP-ribosylation of a 41,000-D membrane protein but fails to block the ET-induced increases in inositol phosphate production and Ca2+ mobilization. These results indicate that the receptor for ET is coupled to phospholipase C via a guanine nucleotide-binding regulatory protein which is distinct from the pertussis toxin substrate in A-10 cells.

Animals↗
PubMed1990

Study on the endothelin gene and its expression.

Endothelin (ET) is a potent vasoconstrictor peptide produced by vascular endothelial cells. Three distinct human endothelin genes were cloned and analysed. The results demonstrated that there were three distinct mRNAs for ET and that TPA-responsive element, mRNA stabilizing sequence, motifs for binding site of nuclear factor 1 and acute phase reactant regulatory elements were recognized in preproform ET-1 gene.

Animals↗
PubMed1990

Endocrinological studies on TAP-144-SR, a sustained-release formulation of a potent GnRH agonist (D-Leu6-[des-Gly10-NH2]-GnRH ethylamide), in male rats.

The paradoxical effects of TAP-144-SR, a biodegradable sustained-release formulation of a potent GnRH agonist (TAP-144, leuprolide acetate) were evaluated in male rats by comparing its potency with that of TAP-144 solution. A single sc injection of TAP-144-SR (equivalent to 0.1 mg/kg/day as TAP-144), prepared by encapsulating the agonist in microcapsules of copoly (DL-lactic/glycolic acid), suppressed serum levels of androgens, and the levels remained suppressed for 4 weeks. The potency of the paradoxical effects of TAP-144-SR was evaluated 4 weeks after treatment by comparing it with that of TAP-144 solution administered daily for 4 weeks. Both daily injections of TAP-144 solution and a single injection of TAP-144-SR (equivalent to 0.02, 0.2 or 2 mg/kg/day as TAP-144) decreased the weight of the testes, prostates and seminal vesicles in a dose-dependent manner in a 4-week assay in male rats. TAP-144-SR was more effective than TAP-144 solution in reducing these organ weights. Serum and pituitary concentrations of LH and FSH and serum testosterone levels were also lower in TAP-144-SR-treated than in TAP-144 solution-treated rats. These results indicate that the paradoxical effects were more extensive upon TAP-144-SR treatment, suggesting that maintaining constant serum TAP-144 levels results in more extensive desensitization of the pituitary and testes. These results also suggest advantages of TAP-144-SR over TAP-144 solution in both efficacy and convenience as an anti-prostatic tumor agent.

Androgens↗
PubMed1990

Histological studies on the therapeutic effect of sustained-release microspheres of a potent LHRH agonist (leuprorelin acetate) in an experimental endometriosis model in rats.

The therapeutic effect of sustained-release microspheres of a potent LHRH agonist (leuprorelin acetate) on experimental endometriosis in female rats was examined histologically. Endometriosis was produced in rats by autotransplantation of endometrial tissue obtained from the left uterine horn into the renal subcapsular space. In the nontreated rats, the transplants were well established and had formed large cysts containing fluid. The walls of the cysts were composed of epithelium and stroma resembling that of normal endometrium. In the rats which received the microspheres of leuprorelin acetate, growth of the transplant was markedly suppressed as evidenced by the reduced size of the cystic cavity and the flattened and pyknotic epithelium. Also, the uterine and ovarian weight decreased significantly. In the ovariectomized rats, growth of the transplant was also markedly suppressed, and the uterine weight decreased. The present results clearly indicate that a single injection of the sustained-release microspheres of leuprorelin acetate markedly suppresses growth of the transplant and produces uterine and ovarian atrophy in the rats.

Animals↗
PubMed1990

Increased maternal plasma concentration of endothelin-1 during labor pain or on delivery and the existence of a large amount of endothelin-1 in amniotic fluid.

The concentration of endothelin-1 (ET-1) in plasma and amniotic fluid from normal pregnant women was determined by a sensitive sandwich-enzyme immunoassay system, established recently. The plasma ET-1 level increased gradually during normal pregnancy as the pregnancy advanced, the levels (0.40 +/- 0.02 pmol/l, n = 45) being significantly (p less than 0.05) higher after 29 weeks of gestation than those (0.32 +/- 0.01 pmol/l, n = 30) before 28 weeks of gestation. The plasma ET-1 level during labor pain was significantly higher (0.59 +/- 0.06 pmol/l, n = 10) than that (0.40 +/- 0.02 pmol/l, n = 45) in the 3rd trimester of pregnancy without labor pain (p less than 0.02). Moreover, a high level of ET-1 (17.38 +/- 0.25 pmol/l, n = 18) was detected in amniotic fluid on term delivery. The ET-1 level in amniotic fluid was significantly higher than the levels in maternal and umbilical cord plasma (p less than 0.001 and p less than 0.001, respectively). After delivery the maternal ET-1 level decreased gradually and 2 day postpartum ET-1 levels reached the normal non-pregnant level.

Adult↗
PubMed1990

Effect of procaterol on arterial blood gas in asthmatic children.

We determined changes in arterial blood gas after the inhalation of procaterol, a highly beta 2-selective and long-acting adrenergic agonist, in 11 asthmatic children. Seven of the patients, with a maximum fall of 14 mmHg (63.6%), showed a decrease in PaO2 (mean +/- SD = -7.1 +/- 4.0 mmHg) and had poorer pulmonary function with a lower initial PaO2 than four subjects who had an increase in PaO2 after inhalation. There was a statistically significant correlation between values of the PaO2 before and after inhalation (P less than .05).

Administration, Inhalation↗
PubMed1990

Role of endothelin in mechanisms of local blood pressure control.

A potent endothelium-derived vasoconstrictive peptide, endothelin (ET), is processed from a precursor, big endothelin, by an unknown converting enzyme. It stimulates calcium channels, phospholipase C and phospholipase A2 in smooth muscle cells through activation of the receptor specific for ET. The intracellular free calcium ion concentration is increased by ET, inducing vasoconstriction. The response to ET varies according to the type of blood vessel. Mesenteric small arteries and arterioles are sensitive to ET. It is likely that various factors, including adrenaline, angiotensin II and arginine vasopressin, induce synthesis and release of ET from the endothelium. A balance among ET, endothelium-derived relaxing factor (EDRF) and atrial natriuretic peptide (ANP) may control vascular tone and regulate peripheral blood flow.

Amino Acid Sequence↗
PubMed1990

[Effects of procaterol on arterial blood gas and pulmonary function in asthmatic children].

We examined the changes in arterial blood gas, FEV1 and V50 after the inhalation of procaterol on 19 occasions in 16 asthmatic children. The initial value of PaO2 had statistically significant correlation with the initial values of %FEV1 and %V50. PaO2 fell down in 11 out of 19 (57.9%) and remarkably decreased more than 5 mmHg in 6 out of 19 (31.6%). The fall in PaO2 was most significant at 5 min after the inhalation in almost subjects. The changes in PaO2 after the inhalation had good correlation with the initial value of %FEV1 and %V50. The initial values were quite lower in the patients with decreased PaO2 more than 5 mmHg than those with increased PaO2. Severe patients showed statistically low values of the initial PaO2 and %V50 and showed a fall in PaO2 after inhalation compared with moderate patients. An increase in A-aDO2 elicited that deteriorations of V/Q ratio caused a decrease in PaO2 after inhalation. There were no significant changes in heart rates and no complaints of nausea, headache or tremor.

Administration, Inhalation↗
PubMed1990

[Endothelin].

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Amino Acid Sequence↗
PubMed1990

[A case of flexion myelopathy presenting juvenile segmental muscular atrophy of upper extremities--a successful treatment by cervical spine immobilization].

A 24-year-old man was well until 1982, when he noticed weakness and atrophy of right arm especially those of biceps muscles. These symptoms did not progress until 1988. In 1988 weakness of left elbow flexion appeared and he was admitted to our hospital. On examination, he had weakness and atrophy of both upper extremities. Fasciculation was noticed in the proximal part of right arm. When his head was bent forward, dysesthesia appeared around radial side of his arm. There were no long tract sign or objective sensory loss. EMG showed neurogenic change over both his upper extremities. In plain cervical roentgenogram there existed abnormal kyphosis of cervical vertebrae. In MRI imaged with his neck flexed, cervical cord was compressed by the posterior surface of 4th cervical vertebral body, which corresponded to the top of cervical kyphosis. Based on these signs and examinations, a diagnosis of flexion myelopathy was made. Spinal immobilization by wiring and bone graft implantation ranging from C2 to C6 was performed to limit the range of anterior nuchal flexion. After this operation, improvement of muscle strength along with the disappearance of dysesthesia on neck flexion was observed. Clinically, this case closely resembles to juvenile type of distal and segmental muscular atrophy of upper extremities (Hirayama type). From our study, pathomechanism of this case seems to be a flexion myelopathy at C4 level. This view is supported also by the good recovery after the operation. This case suggests that nonprogressive atrophy of upper extremities due to flexion myelopathy can be successfully treated by cervical spine immobilization.

Adult↗