Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 541 records · Page 30Linked to original sources

PubMed1996

Measurement of intact rat osteocalcin in osteoblast (ROS17/2.8) cells and in ovariectomized rats with a sandwich enzyme immunoassay.

We developed a sandwich enzyme immunoassay system for intact rat osteocalcin to improve the region specificity for the detection of this molecule. We synthesized two peptides of N-terminal 20 residues and C-terminal 10 residues of rat osteocalcin. After conjugating these peptides with carrier protein, we obtained anti-N- and anti-C-terminal rat osteocalcin antibodies in rabbits raised against these two peptides, respectively. By using these antibodies, we measured intact rat osteocalcin levels in a two-site immunoassay manner. These antibodies did not show the cross-reactivity to human osteocalcin. The immunoreactive peak corresponding to the intact molecules was detected by our intact osteocalcin method after high-performance liquid chromatographic fractionation of osteocalcin fragments in plasma from uremic rats. Furthermore, the intact rat osteocalcin was stable over 8 hours at 25 degrees C. Intact rat osteocalcin levels extracellularly secreted from ROS 17/2.8 cells were measured by this method, showing time- and dose-dependent significant increases when administered 1,25(OH)2D3. The inhibition for the secretion of intact osteocalcin by actinomycin D was also detected quantitatively with this method. In ovariectomized rats, intact osteocalcin levels in plasma were acutely elevated after ovariectomy, and its elevation was significantly depressed by 17beta-estradiol administration. These data suggest that this sandwich method is able to measure the intact form of osteocalcin secreted by osteoblasts. As the antibodies identify the specific regions of osteocalcin molecule, this method would be useful for sensitive estimation of bone turnover for various experimental conditions in rats.

Animals↗

PubMed1996

The heparin-bound fraction of human lipoprotein-deficient serum inhibits endocytic uptake of oxidized low density lipoprotein by macrophages.

We recently demonstrated that bovine lactoferrin, a cationic whey protein from bovine milk, interacts with the negative charges of modified low density lipoproteins (modified LDL) such as acetylated LDL (acLDL) and oxidized LDL (oxLDL), which markedly interferes with their endocytic uptake by rat peritoneal macrophages (Kajikawa M, Ohta T, Takase M, Kawase K, Shimamura S, Matsuda I. Biochim Biophys Acta 1994;1213:82-90). In the present study, we examined whether human lipoprotein-deficient serum (LPDS) might contain protein(s) that could inhibit the endocytic uptake of oxLDL by mouse macrophages. We fractionated LPDS by heparin affinity chromatography and found that the cellular binding of oxLDL to mouse macrophages and subsequent endocytic uptake were inhibited by 50%-60% with the heparin-bound fraction, whereas the heparin-unbound fraction had no effect. Similar results were obtained in the experiments with acetylated LDL. Sephacryl S-300 gel-filtration chromatography of a mixture of oxLDL and the heparin-bound fraction revealed that a 150-kDa protein was associated with oxLDL. These results indicate that the electrostatic interaction of oxLDL with some component(s) of the heparin-bound fraction might interfere with the endocytic uptake of oxLDL by the macrophage scavenger receptor.

Animals↗

PubMed1996

A large thrombosed superior cerebellar artery aneurysm: a case report.

UNLABELLED: MATERIAL AND RESULT: A large thrombosed aneurysm arising from the distal superior cerebellar artery was successfully resected. DISCUSSION AND CONCLUSION: An aneurysm in this location is very rare. Accumulation of intraoperative hemodynamic data may be useful in evaluating the capacity of collateral circulation.

Adult↗

PubMed1996

Effects of moclobemide on forced-swimming stress and brain monoamine levels in mice.

Moclobemide [Ro 11-1163, p-chloro-N-(2-morpholinoethyl)benzamide, AURORIX] is known as an antidepressant and a reversible inhibitor of type A monoamine oxidase. In the present study, a forced swimming test was applied to mice to evaluate behavioral and neurochemical effects of this drug. During forced swimming posture of immobility, a typical behavioral change, was observed, and biochemical analysis of the brain revealed significant changes in the monoamine levels. The norepinephrine concentration was reduced, while that of its product was increased, indicating increase in norepinephrine turnover. The stress increased the levels of dopamine, serotonin, and their metabolites. Moclobemide significantly improved the immobility elicited by the test, and it could prevent the changes in the turnover of norepinephrine, dopamine, and serotonin induced by the stress. These results suggest that moclobemide may improve the behavioral changes induced by the forced swimming through its effects on monoamine metabolism.

Animals↗

PubMed1996

Contralateral external carotid-to-external carotid artery (half-collar) saphenous vein graft for common carotid artery occlusion.

In a patient having common carotid artery occlusion complicated with contralateral internal carotid artery stenosis, a saphenous vein bypass graft was performed from the contralateral external carotid artery to the ipsilateral external carotid artery simultaneously with contralateral carotid endarterectomy. The bypass was patent 1 year later and the patient was free from fainting spells. Among a number of the reconstructive surgical procedures, this "half-collar bypass" can be placed adequately in the subcutaneous soft tissue so that head or mandibular movement does not displace or compress the graft. Intraoperative hemodynamic measurements were considered useful in determining surgical options.

Aged↗

PubMed1996

Characteristics of cytosolic Ca2+ elevation induced by muscarinic receptor activation in single adrenal chromaffin cells of the guinea pig.

In Fura-2 loaded-single guinea pig adrenal chromaffin cells, muscarine, nicotine and KCl all caused an early peak rise in intracellular Ca concentration ([Ca2+]i) followed by a sustained rise. In Ca(2+)-free solution, muscarine, but neither nicotine nor KCl, caused a transient increase in [Ca2+]i, which was partially reduced by preceding application of caffeine or by treatment with ryanodine plus caffeine. In voltage-clamped cells at a holding potential of -60 mV, the muscarine-induced [Ca2+]i rise, especially its sustained phase, decreased in magnitude. Intracellular application of inositol 1,4,5-trisphosphate caused a transient increase in [Ca2+]i and inhibited the following [Ca2+]i response to muscarine without affecting responses to nicotine and a depolarizing pulse. Muscarine evoked membrane depolarization following brief hyperpolarization in most cells tested. There was a significant positive correlation between the amplitude of the depolarization and the magnitude of the sustained rise in [Ca2+]i. Muscarine-induced sustained [Ca2+]i rise was much greater in the current-clamp mode than that in the voltage-clamp mode. The sustained phase of [Ca2+]i rise and Mn2+ influx in response to muscarine were suppressed by a voltage-dependent Ca2+ channel blocker, methoxyverapamil. These results suggest that stimulation of muscarinic receptors causes not only extracellular Ca2+ entry, but also Ca2+ mobilization from inositol 1,4,5-trisphosphate-sensitive intracellular stores. Voltage-dependent Ca(2+)-channels may function as one of the Ca2+ entry pathways activated by muscarinic receptor in guinea pig adrenal chromaffin cells.

Adrenal Glands↗

PubMed1996

Pharmacokinetics of mycophenolate mofetil, a new immunosuppressant, in rats.

Mycophenolate mofetil (MPM), a new immunosuppressant, is the morpholinoethyl ester of mycophenolic acid (MPA). The distribution in blood and pharmacokinetics of MPA after administration of MPM were examined. The plasma to erythrocyte concentration ratio was low (0.10-0.15). MPA existed in rat plasma as the highly bound form (bound fraction was 9.79 +/- 0.57%). MPA disappeared from the systemic circulation with biexponential decay. After i.v. administration of MPM at the doses of 8.3, 16.7, and 33.3 mg/kg, the total clearance of MPA was 0.241 +/- 0.056, 0.321 +/- 0.126, and 0.317 +/- 0.092 L/h/kg, respectively. The terminal elimination half-live were 5.17 +/- 1.44, 8.89 +/- 2.76, and 7.94 +/- 2.94 h, respectively. After i.d. administration of MPM at the doses of 8.3, 16.7, 33.3, and 50.0 mg/kg, the terminal elimination half-live were 6.41 +/- 4.16, 4.49 +/- 2.20, 7.58 +/- 3.72, and 8.18 +/- 1.32 h, respectively. The mean peak times were within 30 min. The systemic availability of MPA after i.d. administration of MPM (at 8.3, 16.7, and 33.3 mg/kg) was calculated using the corresponding mean AUCiv, and the values were 84.3 +/- 35.0%, 69.9 +/- 25.7%, and 63.6 +/- 8.8%, respectively.

Animals↗

PubMed1996

Expression of 16 kDa proteolipid of vacuolar-type H(+)-ATPase in human pancreatic cancer.

Recent studies have shown that bafilomycin A1-sensitive vacuolar-type H(+)-ATPase (V-ATPase) plays important roles in cell growth and differentiation. However, there is no published study that has focused on the expression of V-ATPase in human tumour tissues. This study was designed to examine the mRNA and protein levels for the 16 kilodalton (kDa) proteolipid of V-ATPase in human pancreatic carcinoma tissues. We first investigated the mRNA level for V-ATPase in six cases of invasive pancreatic cancers and two normal pancreases, using reverse transcription-polymerase chain reaction technique. Then, we examined immunohistochemically the level of V-ATPase protein in 49 pancreatic cancers and ten benign cystic neoplasms of the pancreas, using antisera raised against the 16 kDa proteolipid. There was a notable difference in the level of V-ATPase mRNA between normal and pancreatic carcinoma tissues, with no evident difference in the expression of the beta-actin gene. Immunohistochemically, 42 out of 46 invasive ductal cancers (92%) displayed a mild to marked immunoreactivity for V-ATPase in the cytoplasm, whereas neither non-invasive ductal cancers nor benign cystic neoplasms expressed detectable immunoreactive proteins. These findings suggest that the overexpression of V-ATPase protein is characteristic of invasive pancreatic tumours. V-ATPase may play some crucial roles in tumour progression.

Adenocarcinoma↗

PubMed1996

Expression of beta-catenin in normal breast tissue and breast carcinoma: a comparative study with epithelial cadherin and alpha-catenin.

Expression of beta-catenin was investigated in normal breast tissue and 66 breast carcinomas in conjunction with expression of epithelial cadherin (E-CD) and alpha-catenin. In normal mammary ducts and acini, intense beta-catenin immunoreactivity was present at the basolateral surfaces of luminal epithelium and weak immunoreactivity was observed at the lateral borders of myoepithelial cells. No beta-catenin was revealed at the myoepithelial basal surface. The intercellular expression of beta-catenin, as well as of E-CD and alpha-catenin, was also observed in carcinoma tissues with varying staining intensity. Almost all of 10 intraductal carcinomas and approximately 70% of 41 invasive ductal carcinomas expressed the three molecules at the same level as in normal glands, whereas approximately 80% of 13 invasive lobular carcinomas showed severe deficiency of them. Two lobular carcinomas in situ showed complete absence of all of the proteins. Some of these findings were confirmed biochemically by immunoblotting analysis. In invasive ductal carcinomas, alpha-catenin was reduced more frequently in diffuse than in solid type tumours, whereas the level of expression of beta-catenin and E-CD was unchanged between them. No correlation was present between reduced expression of the adhesion molecules and lymph node metastasis.

Adult↗

PubMed1996

Histaminergic and serotonergic receptor blocking substances from the medicinal plant Garcinia mangostana.

A crude methanolic extract of the fruit hull of Mangosteen, Garcinia mangostana L. inhibited the contractions of isolated thoracic rabbit aorta induced by histamine and serotonin. The extract of the fruit hull has been fractionated by silica gel chromatography, monitoring the pharmacological activity to give alpha- and gamma-mangostin. On the basis of pharmacological data, it is suggested that alpha-mangostin and gamma-mangostin are a histaminergic and a serotonergic receptor blocking agent, respectively.

Animals↗

PubMed1996

Surgical results and the related topographic anatomy in paraclinoid internal carotid artery aneurysms.

Paraclinoid internal carotid artery aneurysms arising between the roof of the cavernous sinus and the origin of the posterior communicating artery are of considerable interest with regard to their anatomical variations and technical surgical challenges. Twenty-seven patients with 30 paraclinoid aneurysms were treated surgically through pterional intradural approach. Neck clipping was performed in 22 (73%) of the 30 aneurysms, coating in seven, and trapping in one. The surgical outcome was excellent in 24 patients (24/27, 89%), with two patients showing ipsilateral partial visual field defect (2/27, 7%). There was one death (4%) due to infarction after unintended carotid artery trapping. The characteristic topographic anatomical features which we considered to pose technical difficulties and to be responsible for the complications or failure in neck clipping were aneurysmal dome extending into the anterior clinoid process, atheroma at the neck, multiple paraclinoid aneurysms, ophthalmic artery originating at the neck, and marked supero-medial shift of the C2 segment of the carotid artery. pre-operative depiction of the topographical anatomy around the paraclinoid aneurysm is essential but not always possible on the basis of conventional angiography. Magnetic resonance or three-dimensional computerized tomographic angiography, and their axial source imaging, were useful in delineating the topography with unusual aneurysmal growth, overlap of aneurysm with the parent artery, and uncommon variations of the surrounding structures.

Adult↗

PubMed1996

Hemodynamics in an arterial union--simulation study on therapeutic unilateral vertebral artery occlusion.

Hemodynamic changes following unilateral vertebral artery (VA) occlusion were investigated in a rat model. The left carotid artery was resected and anastomosed to the right side in an end-to-side fashion to create a half-ring bypass. The distal side of the bypass was regarded as a union of VAs. Changes in the geometry, histology and hemodynamics in the union were investigated after the recipient artery was ligated. Intimal thickening was most prominently observed in the recipient arterial segment distal to the ligation site, where the lumen was obliterated. However, the portion of the lumen within 2.6 +/- 0.6 (mean +/- s.d.) mm, a distance of 2.9 +/- 0.6 times the internal diameter from the union, was not obliterated. The angle of the union was positively related to the length of this residual lumen. The results of this study explain some of the pathogenesis in unsuccessful aneurysmal thrombosis or brain stem infarction after therapeutic unilateral VA occlusion.

Animals↗

PubMed1996

IFN-gamma in combination with IL-3 accelerates platelet recovery in mice with 5-fluorouracil-induced marrow aplasia.

The effects of interferon-gamma (IFN-gamma) on platelet recovery were examined in mice with marrow aplasia induced by i.p. injection of 250 mg/kg of 5-fluorouracil (5-FU). The cytokine was administrated by microosmotic pump, with an ability to deliver a consistent intact dose of cytokine for 7 consecutive days. Administration of 250 IU/kg/day of IFN-gamma in combination with 10(3) U/kg/day of IL-3, which alone had no effect on platelet counts, diminished the nadir for platelet count and shortened the duration of thrombocytopenia. The effect was comparable to that of higher doses of IL-3 (10(5) U/kg/day). The administration of 250 IU/kg/day of IFN-gamma in combination with 10(3) U/kg/day of IL-3 also induced megakaryocyte proliferation in bone marrow cell cultures. Single administration of either 250 IU/kg/day of IFN-gamma or 10(3) U/kg/day of IL-3 had no significant effects. The effect of this combination was also comparable to that of a higher dose of IL-3 (10(5) U/kg/day). We suggest that IFN-gamma accelerates megakaryocyte development, which leads to platelet production in chemotherapy-induced marrow aplasia. The administration of IFN-gamma in combination with IL-3 might be useful for the management of marrow aplasia.

Anemia, Aplastic↗

PubMed1996

Interferon-gamma enhances megakaryocyte colony-stimulating activity in murine bone marrow cells.

We have demonstrated previously that interferon-gamma (IFN-gamma) accelerates platelet recovery in mice with 5-FU induced-marrow aplasia in vivo. However, the mechanism for the regulation of megakaryocyte development induced by IFN-gamma in bone marrow cells in vivo remains unknown. To further study the effects of IFN-gamma on megakaryocyte development, various steps during IFN-gamma-mediated accelerated differentiation of the megakaryocytes were investigated in serum-free cultures of murine bone marrow cells in vitro. IFN-gamma markedly induced acetylcholine esterase (AChE) activity, a marker of murine megakaryocytic cells, accompanied by increased colony formation of the megakaryocyte lineage. A prominent increase in megakaryocyte number was observed after IFN-gamma treatment. All of these effects were dependent on the presence of IL-3, and, therefore, these results suggest that IFN-gamma acts as a megakaryocyte potentiator (Meg-POT). However, IFN-gamma did not enhance megakaryocyte maturation with respect to increase in cell size. The effects of IFN-gamma on megakaryocyte maturation were similar to those observed after treatment with higher doses of IL-3 alone. Meg-POT is defined as a factor that induces megakaryocyte maturation. Since IFN-gamma enhanced IL-3-dependent megakaryocyte colony formation and proliferation rather than megakaryocyte maturation, the effects on megakaryocyte development, which were induced by IFN-gamma treatment, seem to be different from the effects of a Meg-POT. We, therefore, propose a new function for IFN-gamma as an enhancer of megakaryocyte colony-stimulating factor activity. The effect of IFN-gamma in vitro appears to correlate well with the acceleration of platelet recovery in vivo.

Acetylcholinesterase↗

PubMed1996

Determination of L-buthionin (SR)-sulfoximine, gamma-glutamylcysteine synthetase inhibitor in rat plasma with HPLC after prelabeling with dansyl chloride.

L-(SR)-Buthionin sulfoximine (L-(SR)-BSO) is a potent and specific inhibitor of gamma-glutamylcysteine synthetase, which catalyzes the first reaction of glutathione biosynthesis. A selective, sensitive, and simple high-performance liquid chromatographic method was developed for the determination of L-(SR)-BSO in rat plasma. After the compound was labeled with dansyl chloride (Dns-Cl) under optimal conditions, it was separated in a Zolbax-ODS column with a mobile phase that consisted of 0.01M phosphate buffer, methanol, and acetonitrile (8:1:3, v/v). The compound was detected with a fluorescence detector at an excitation wavelength of 335 nm and an emission wavelength of 525 nm using a xenon lamp. The coefficients of variation (DV) from the interassay in the low and high concentrations (10 and 500 micrograms/mL of L-(SR)-BSO in rat plasma) were 2.5 and 4.8%, respectively. The CVs from the intra-assay in the low and high concentrations were 3.2 and 5.6%, respectively. The minimum concentration of L-(SR)-BSO that could be determined was 10 micrograms/mL when 100-microL serum samples were used. The detection limit was 50 ng per injection volume. This method enables pharmacokinetic and pharmacodynamic studies in rats.

Animals↗

PubMed1996

Pore formation on proliferating yeast Saccharomyces cerevisiae cell buds by HM-1 killer toxin.

The cytocidal effect of HM-1 produced by Hansenula mrakii on yeast Saccharomyces cerevisiae cells was studied. The HM-1 strongly inhibited the growth of S. cerevisiae cells at a low concentration (IC50: 2.1 x 10(-8) M) by reducing the number of viable cells. The killer action of HM-1 was most efficient when cells were actively proliferating. Cells in a resting state were resistant, but they became HM-1-sensitive after about 90 min of culturing at 30 degrees C, concomitantly with the increment of budding index. In association with the reduction of viable cell number, ultraviolet light-absorbing cellular components were discharged from sensitive cells. HM-1 molecules appear to bind to susceptible cells rather loosely since cells incubated with HM-1 were able to proliferate after having been washed. By phase-contrast light microscopy and scanning electron microscopy, discharge of cell material was observed at the budding portions of HM-1-treated cells. Addition of sorbitol to make the culture medium isotonic partially reduced the cell death induced by HM-1. These results suggest that HM-1 acts on the budding region of proliferating yeast cells, resulting in pore formation, leakage of cell material and eventual cell death.

Cell Division↗

PubMed1996

The active site of carboxypeptidase Taq possesses the active-site motif His-Glu-X-X-His of zinc-dependent endopeptidases and aminopeptidases.

Carboxypeptidase (CPase) Taq possesses the His-Glu-X-X-His sequence, which is the consensus sequence in the active site of zinc-dependent endopeptidases and amino-peptidases, at positions 276-280. Amino acid replacement of the conserved His and Glu drastically diminished the activity of CPase Taq, and the zinc content of the enzyme was also greatly reduced when either of the two His residues was replaced with Arg or Tyr. The results indicate that this sequence actually functions as the active site in CPase Taq, showing that CPase Taq is a novel type of zinc-dependent CPase that possesses the His-Glu-X-X-His active-site motif.

Amino Acid Sequence↗

PubMed1996

Hemodynamic simulation study of cerebral arteriovenous malformations. Part 2. Effects of impaired autoregulation and induced hypotension.

The hemodynamic changes occurring during obliteration procedures for arteriovenous malformations (AVM) have not been fully elucidated. Therefore, we undertook a simulation study using a compartmental flow model to investigate the role of altered autoregulatory conditions in the development of hyperperfusion during obliteration of large high-flow AVM. Induced hypotension was also simulated to evaluate its usefulness in reducing the incidence and severity of the event. As the AVM flow was decreased during the obliteration procedures, feeder pressure increased and drainer pressure decreased, with a concomitant increase in the perfusion pressure in the brain tissue surrounding the AVM. Cerebral blood flow (CBF) remained constant at 50 ml 100 g-1 min-1 in the presence of autoregulation and increased to 67 ml 100 g-1 min-1 in its absence. When the lower limit of the autoregulatory pressure range (LAR) was shifted from 60 to 50 or 40 mm Hg, the flow volume increased markedly from 67 to 77 ml 100 g-1 min-1 or to 92 ml 100 g-1 min-1 after complete obliteration. Decrease in LAR would be a cause of the hyperperfusion. Induced systemic hypotension was found to be effective in reducing the magnitude of these hemodynamic changes, when induction was appropriately performed in a stepwise fashion. A simulation study is useful in clarifying the various hemodynamic changes that develop during the treatment of AVM.

Animals↗