Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 37 records · Page 2Linked to original sources

PubMed2000

Presynaptic inhibitory actions of lignocaine in canine isolated, blood-perfused atrial preparations.

1. Cardiac effects of lignocaine on sinoatrial nodal pacemaker activity and atrial contractility were investigated in five canine isolated, blood-perfused right atria that were perfused with heparinized blood from support dogs. The effects of lignocaine on responses to intracardiac nerve stimulation and administered acetylcholine and noradrenaline were also examined. 2. Lignocaine was injected into the support dog intravenously or administered selectively to the sinus node artery of the isolated atrium. At doses that did not produce significant depressor action (0.3, 1.0 and 3.0 mg/kg), lignocaine produced no significant changes in heart rate. A large dose of 10 mg/kg lignocaine caused significant depressor effects and slight bradycardia. Direct administration of lignocaine (0.3, 1.0, 3.0, 10.0 and 30.0 mumol) into the sinus node artery of the isolated atrium consistently caused slight negative chronotropic and rather marked negative inotropic effects. 3. After treatment with a relatively large dose of lignocaine, electrical stimulation-induced negative chronotropic and inotropic responses were significantly inhibited in a dose-related manner, but positive chronotropic and inotropic responses were slightly depressed only at an extremely high dose of lignocaine (10.0 mumol). 4. Noradrenaline-induced positive chronotropic and inotropic effects were not modified by any doses of lignocaine used (0.3, 1.0, 3.0 and 10.0 mumol). Acetylcholine-induced negative chronotropic and inotropic effects were slightly, but significantly, depressed by 10 mumol lignocaine. 5. These results suggest that a relatively large dose of lignocaine has a dominant presynaptic inhibitory action, particularly on the parasympathetic component.

Anesthetics, Local↗

PubMed2000

Effect of vitamin K2 on osteoblast apoptosis: vitamin K2 inhibits apoptotic cell death of human osteoblasts induced by Fas, proteasome inhibitor, etoposide, and staurosporine.

Vitamin K2 is used for the treatment of osteoporosis, but the precise mode of action is still not clear. We investigated the effects of vitamin K2 on apoptosis of human osteoblasts. Human osteoblastic cell line MG63 cells and human primary osteoblast-like cells obtained from bone fragments in corrective surgery were used as human osteoblasts. Cells were cultured with or without various concentrations of vitamin K2 and tumor necrosis factor-alpha (TNF-alpha). We then determined the proliferative response, expression of Fas and Bcl-2-related proteins, and Fas-mediated apoptosis of these cells induced by anti-Fas immunoglobulin M (IgM). In addition, the effect of vitamin K2 in osteoblast apoptosis induced by Z-Leu-Leu-Leu-aldehyde (LLL-CHO), etoposide, or staurosporine was also examined. Human osteoblasts did not show spontaneous apoptosis in culture, even in the presence of vitamin K2 or TNF-alpha. Furthermore, proliferation of the cells was not influenced by vitamin K2 or TNF-alpha. Fas was functionally expressed on human osteoblasts, and the treatment with TNF-alpha significantly enhanced both Fas expression and Fas-mediated apoptosis of osteoblasts. The addition of vitamin K2 to the culture resulted in a dose-dependent inhibition of functional Fas expression on osteoblasts, in the presence or absence of TNF-alpha. Treatment of human osteoblasts with vitamin K2 clearly suppressed Bax expression of the cells, although the expression of Bcl-2 was not influenced by vitamin K2. Fas ligand (FasL) cDNA transformants were cytotoxic against osteoblasts, and the cytotoxicity was increased when osteoblasts were treated with TNF-alpha. The addition of vitamin K2 to osteoblasts significantly decreased the cytotoxic effects of FasL cDNA transformants. Furthermore, apoptosis of human osteoblasts induced by LLL-CHO, etoposide, or staurosporine was also clearly suppressed in vitamin K2-treated osteoblasts. Our results suggest that vitamin K2 inhibits apoptotic cell death of osteoblasts and maintains the number of osteoblasts. These actions may explain the therapeutic efficacy of vitamin K2 in osteoporosis.

Apoptosis↗

PubMed2000

Inotropic, chronotropic, and dromotropic effects mediated via parasympathetic ganglia in the dog heart.

Some parasympathetic ganglionic cells are located in the epicardial fat pad between the medial superior vena cava and the aortic root (SVC-Ao fat pad) of the dog. We investigated whether the ganglionic cells in the SVC-Ao fat pad control the right atrial contractile force, sinus cycle length (SCL), and atrioventricular (AV) conduction in the autonomically decentralized heart of the anesthetized dog. Stimulation of both sides of the cervical vagal complexes (CVS) decreased right atrial contractile force, increased SCL, and prolonged AV interval. Stimulation of the rate-related parasympathetic nerves to the sinoatrial (SA) node (SAPS) increased SCL and decreased atrial contractile force. Stimulation of the AV conduction-related parasympathetic nerves to the AV node prolonged AV interval. Trimethaphan, a ganglionic nicotinic receptor blocker, injected into the SVC-Ao fat pad attenuated the negative inotropic, chronotropic, and dromotropic responses to CVS by 33 approximately 37%. On the other hand, lidocaine, a sodium channel blocker, injected into the SVC-Ao fat pad almost totally inhibited the inotropic and chronotropic responses to CVS and partly inhibited the dromotropic one. Lidocaine or trimethaphan injected into the SAPS locus abolished the inotropic responses to SAPS, but it partly attenuated those to CVS, although these treatments abolished the chronotropic responses to SAPS or CVS. These results suggest that parasympathetic ganglionic cells in the SVC-Ao fat pad, differing from those in SA and AV fat pads, nonselectively control the atrial contractile force, SCL, and AV conduction partially in the dog heart.

Animals↗

PubMed2000

A Na+/Ca2+ exchanger inhibitor, KB-R7943, caused negative inotropic responses and negative followed by positive chronotropic responses in isolated, blood-perfused dog heart preparations.

Effects of a Na+/Ca2+ exchanger inhibitor, KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl] isothiourea methanesulfonate), on the sinoatrial nodal pacemaker activity, atrial contractility and ventricular contractility were investigated in the isolated and blood-perfused right atrium and left ventricle of the dog. KB-R7943 (0.03- 3 micromol) induced negative inotropic effects and negative followed by positive chronotropic effects in the right atrium and negative inotropic effects in the left ventricle. Neither atropine nor hexamethonium affected the cardiac responses to KB-R7943. Propranolol attenuated the positive chronotropic response to KB-R7943 but imipramine did not. Tetrodotoxin potentiated the positive chronotropic response to KB-R7943 in 6 of 11 isolated atria. When NaCl infusion increased atrial contractile force and atrial rate, KB-R7943-induced negative inotropic and chronotropic responses were attenuated in a dose-dependent manner. CaCl2 infusion potentiated the negative chronotropic response to KB-R7943 but did not affect the inotropic response significantly. On the other hand, ouabain (17 nmol) attenuated the negative inotropic response, but not chronotropic response, to KB-R7943. These results suggest that KB-R7943-induced cardiac effects relate to the Na+ activity, probably mediated through the Na+/Ca2+ exchanger, and the Na+/Ca2+ exchanger modifies the pacemaker activity and myocardial contractility in the dog heart.

Animals↗

PubMed2000

Acute desensitization of adenosine by adenosine infusion in isolated dog atria.

We investigated the effects of a continuous infusion of adenosine on responses of sinus rate and developed tension to bolus injections of adenosine and acetylcholine in isolated, blood-perfused canine right atria. Each drug was directly injected into the sinus node artery of the isolated atrium. During adenosine infusions, the negative chronotropic and inotropic responses to bolus injections of adenosine were significantly inhibited in a dose-related manner, while the negative responses to administered acetylcholine were consistently potentiated. These results indicate that adenosine infusion has an acute desensitizing action on subsequent bolus adenosine, although the cholinergic action is enhanced by a continuous infusion of adenosine.

Acetylcholine↗

PubMed2000

[Bronchofiberscopy].

New diagnostic modalities have been used in conjunction with endoscopy for early detection of lung cancer. Videoendoscope is routinely used instead of fiberoptic bronchoscope. Fluorescence diagnosis has been proved to be useful in detecting subtle lesions which might be invisible by conventional endoscopy in central airway. Also, a number of small peripheral lesions has increased by the helical CT. CT guided transbronchial lung as well as needle cytology are indicated for definitive diagnosis of such lesions. Endobronchial Ultrasonography is employed to evaluate the depth of cancer invasion of the bronchus and lymph node swelling around the bronchus. It should be helpful in staging of lung cancer and selecting therapy.

Bronchoscopy↗

PubMed1999

Inhibition of caspase cascade by HTLV-I tax through induction of NF-kappaB nuclear translocation.

NF-kappaB is required for prevention of apoptosis. We examined the importance of human T-cell leukemia virus-I (HTLV-I) Tax protein to stimulate NF-kappaB nuclear translocation, thus preventing apoptosis. Jurkat cells and JPX-9 cells in which the inducible Tax expression plasmid vector was stably transfected were used in the present study. Both Jurkat and Tax(-) JPX-9 cells had small amounts of basal nuclear NF-kappaB activity. The addition of NF-kappaB inhibitors suppressed NF-kappaB nuclear translocation of the cells, thus inducing apoptosis. Sequential activation of caspases from caspase-8 to caspase-3 was shown during this process. NF-kappaB nuclear translocation in JPX-9 cells was stimulated through Tax expression, and both the activation of caspases and apoptosis induced by NF-kappaB inhibitors were significantly suppressed in the Tax(+) JPX-9 cells. The expression of Bcl-2, Bax, and Bcl-x was not changed among Jurkat, Tax(-) JPX-9, and Tax(+) JPX-9 cells in the presence or absence of NF-kappaB inhibitors. X-chromosome-linked inhibitor of apoptosis (XIAP) protein expression in Tax(-) JPX-9 cells was significantly suppressed by NF-kappaB inhibitors, however, its expression in Tax(+) JPX-9 cells was maintained even by the addition of NF-kappaB inhibitors. Our results suggest that the activation of NF-kappaB via Tax protein in HTLV-I infected cells renders the cells resistant to apoptosis. The expression of anti-apoptotic gene products such as XIAP to suppress caspase cascade, results in an increase of cytokine production and cell proliferation; one of the proposed mechanisms that promotes autoimmune disorders such as Sjögren's syndrome and rheumatoid arthritis found in HTLV-I seropositive subjects.

Apoptosis↗

PubMed1999

Polarizing microscopy of eyespot of Chlamydomonas: in situ observation of its location, orientation, and multiplication.

The eyespot in the cell of Chlamydomonas reinhardtii has been found to appear as a bright spot under the cross polar setting of a polarizing microscope. This was confirmed by isolating the eyespot from a homogenate of wall-deficient mutant cw-15, and by observing it under a polarizing microscope. Thus, the eyespot was proved to be a strongly birefringent body. Next, gametes (mt+ and mt-) of 137c strain were prepared by cultivating it in a low-nitrogen (NH4Cl) medium. Here, every cell shows only one (and never more than one) birefringent spot. The birefringent eyespot was located always near the surface on the "equator," that is, at the farthest point from the "meridionial" cell-axis that is defined as the bisector of the two flagella projected out from the cell surface. It was shown, in addition, that the optic axis of this birefringent eyespot is oriented in the cell always along the parallel direction of the cell axis defined above. Thus, the polarizing microscopy has been shown to provide a powerful method for in vivo, in situ pursuit of the eyespot of Chlamydomonas.

Animals↗

PubMed1999

Effects of lidocaine on isolated, blood-perfused ventricular contractility in the dog.

Direct inotropic effects of lidocaine on ventricular muscle were investigated in isolated canine left ventricular preparations which were perfused with a donor dog's arterial blood. Intravenous administration of lidocaine in doses of less than 1 mg/kg did not cause any significant hemodynamic or cardiac changes in the donor dog and in the isolated ventricular preparation. A large dose of 10mg/kg of lidocaine produced a marked depressor response in the donor and a negative inotropic effect in the isolated ventricle. Direct injection of lidocaine (1-30 micromol) to the isolated preparation induced a dose-related decrease in the ventricular contractile force. Infusion of lidocaine (3 micromol/ml per min) did not influence norepinephrine- or calcium chloride-induced positive inotropic effects. In the frequency-force relationship, lidocaine generally depressed the contractility, exhibiting the positive staircase phenomenon. On the other hand, a calcium entry inhibitor, diltiazem, readily caused the negative staircase. From these results, it is concluded that (1) a large amount of lidocaine has a cardiac depressant property, (2) lidocaine has no antiadrenergic properties, and (3) the action of lidocaine may probably be due to the effect of intracellular calcium movement but not to a modification of Ca inward currents.

Adrenergic alpha-Agonists↗

PubMed1999

The autonomously replicating sequence (ARS) of the yeast Saccharomyces exiguus Yp74L-3.

Fragments containing ARSes were cloned from the genomic DNA of the yeast Saccharomyces exiguus Yp74L-3, and the essential regions for ARSes were restricted for these fragments. Mapping studies of ARS-acting sequences in one of these fragments suggested that S. exiguus recognizes a sequence as an ARS that is different from that recognized by Saccharomyces cerevisiae. Two ARS essential regions of S. exiguus were sequenced, and an ARS core consensus sequence of S. exiguus was deduced to be MATTAMWAWWTK. This sequence differs significantly from that of S. cerevisiae in two positions, suggesting that these nucleotide substitutions cause the difference in the ARS-recognition modes between S. exiguus and S. cerevisiae.

Base Sequence↗

PubMed1999

Inhibitory effect of a new anti-rheumatic drug T-614 on costimulatory molecule expression, cytokine production, and antigen presentation by synovial cells.

The present study was undertaken to investigate the immunoregulatory effects of T-614 (3-formylamino-7-methylsulfonylamino-6-phenoxy-4H-1-benzopyran-4-o ne) on synovial cells in vitro. Synovial cells were cultured with T-614 in the presence or absence of various cytokines. After incubation, the costimulatory molecule expression on synovial cells and cytokine production in culture supernatants were analyzed by an indirect immunofluorescence method and enzyme-linked immunosorbent assay, respectively. We also examined the effect of T-614 on the function of synovial cells as antigen-presenting cells (APCs). The costimulatory molecules including CD54, CD58, and CD106 were constitutionally expressed on the surface of synovial cells. However, neither CD80 nor CD86 nor CD102 was found on the surface, and these costimulatory molecules could not be induced by any cytokines. T-614 itself did not affect the costimulatory molecule expression and cytokine production of unstimulated synovial cells. The stimulation of synovial cells with interferon-gamma (IFN-gamma), interleukin-1beta, or 12-O-tetradecanoyl phorbol 13-acetate enhanced the expression of costimulatory molecules and the proinflammatory cytokine production of these cells. Both the up-regulated expression of these costimulatory molecules and the enhanced production of proinflammatory cytokines were significantly inhibited by T-614. Autologous T cell proliferation in response to purified protein derivative by IFN-gamma-treated synovial cells was significantly suppressed by T-614. T-614 has considerable immunosuppressive effects on synovial cells by inhibiting the costimulatory molecule expression and cytokine production of these cells and the antigen-specific T cell proliferation mediated by the synovial cells. These results suggest that T-614 plays an important immunoregulatory role in rheumatoid synovial tissues.

Adjuvants, Immunologic↗

PubMed1999

Tumor necrosis factor-alpha and interleukin-1beta increase the Fas-mediated apoptosis of human osteoblasts.

Our recent work demonstrated functional Fas expression on human osteoblasts, and the histologic examination of the periarticular osteoporosis region in patients with rheumatoid arthritis (RA) showed apoptosis in osteoblasts. High concentrations of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6--which are thought to increase bone resorption--have been determined in RA synovium. We investigated the effect of these cytokines on the Fas-mediated apoptosis of human osteoblasts. The human osteoblastic cell line MG63 and human primary osteoblast-like cells from bone biopsy specimens were used as human osteoblasts. Fas expression on these cells was examined by flow cytometry, and Fas-mediated apoptosis induced by anti-Fas immunoglobulin M (IgM) was determined by a chromium 51 release assay, the presence of cells with hypodiploid DNA, staining with Hoechst 33258 dye, and the detection of DNA fragmentation on agarose gel electrophoresis. The proliferation of osteoblasts was analyzed by a tritiated thymidine incorporation assay. Spontaneous apoptosis was not found on cultured osteoblasts. The apoptosis of human osteoblasts was not induced by TNF-alpha, IL-1beta, or IL-6 alone in the absence of anti-Fas IgM. In addition, proliferation of the cells was not affected by these cytokines. Fas was constitutively expressed on unstimulated osteoblasts, and treatment of these cells with IL-1beta or TNF-alpha significantly augmented Fas expression. Human osteoblasts were committed to apoptosis with anti-Fas IgM, and the treatment of both IL-1beta and TNF-alpha markedly increased Fas-mediated apoptosis. TNF-alpha augmented both Fas expression and Fas-mediated apoptosis more efficiently than did IL-1beta. In addition, an additive effect on both Fas expression and Fas-mediated apoptosis was demonstrated when TNF-alpha and IL-1beta were added to osteoblasts. IL-6 influenced neither Fas expression nor the Fas-mediated apoptosis of osteoblasts. Furthermore, no synergistic effect of IL-6 with IL-1beta or TNF-alpha was observed. IL-1beta, TNF-alpha, or IL-6 did not change Bcl-2 expression. Our results suggest that IL-1beta and TNF-alpha regulate osteoblast cell number by up-regulating the Fas-mediated apoptosis of osteoblasts, one of the putative mechanisms inducing periarticular osteoporosis in patients with RA.

Apoptosis↗

PubMed1999

DNA sequence of the beta-isopropylmalate dehydrogenase gene and phylogenetic analysis of the yeast Saccharomyces exiguus Yp74L-3.

The beta-isopropylmalate dehydrogenase (LEU2) gene from a homothallic wild-type yeast, Saccharomyces exiguus Yp74L-3, was analyzed to estimate the phylogenetic position of this strain in yeasts. The beta-isopropylmalate dehydrogenase gene of Yp74L-3 was first isolated as a clone complementing the leu2 mutation of Saccharomyces cerevisiae, and then confirmed to complement the haploid leu2 mutant derived from strain Yp74L-3 through genetic transformation. The nucleotide sequence of the cloned DNA revealed an open reading frame (ORF) encoding the beta-isopropylmalate dehydrogenase composed of 365 amino acids. The beta-isopropylmalate dehydrogenase coding sequence from the Yp74L-3 strain displayed 76.7% similarity to that of S. cerevisiae. Candidates for a UAS and a TATA-box in the 5'-upstream region and for a poly-A attachment site in the 3'-downstream region were found. A phylogenetic tree constructed from the nucleotide sequences of the beta-isopropylmalate dehydrogenase coding regions revealed that Yp74L-3 is located between S. cerevisiae and the Kluyveromyces yeasts. The LEU2 gene cloned from Yp74L-3 will serve as an effective genetic marker for constructing the transformation system in S. exiguus Yp74L-3.

Journal Article↗

PubMed1999

Effects of amlodipine on native cardiac Na+ channels and cloned alpha-subunits of cardiac Na+ channels.

The inhibitory effects of amlodipine besilate (CAS 11470-99-6) on the native Na+ current (INa) and cloned human cardiac Na+ channel alpha subunit (hH1) were studied by whole cell patch clamp techniques. Amlodipine produced tonic block of INa in a concentration- and holding potential (HP)-dependent manner with hyperpolarization of H infinity. Amlodipine produced phasic blockade of INa, which was dependent on HP and pulse duration. Amlodipine produced tonic blockade of hH1 in a concentration-dependent manner with 1 : 1 stoichiometry, and phasic blockade of hH1 which was dependent on the pulse duration. Amlodipine blocked INa in a voltage- and frequency-dependent manner via affinity to the resting as well as inactivated conformations of the alpha subunit.

Algorithms↗

PubMed1999

How and how much can Hoechst 33258 cause unwinding in a DNA duplex?

The effect of Hoechst 33258 binding on the geometry of a DNA duplex (plasmid pBR322) has been examined using topoisomerase II relaxation followed by gel electrophoresis. Of this drug-DNA system, fluorescence, optical absorption, and calorimetric measurements were also made at various drug and DNA concentrations and in the same buffer as that for the topoisomerase reaction. It has been confirmed that there are two modes of drug-DNA interaction. When the drug concentration is much lower than the DNA base pair concentration, the Hoechst 33258 molecule binds in the minor groove of the DNA duplex and occupies a site formed of five continuous base pair sequences that contain no G.C pair. Here, the equilibrium constant K1 is 1.8 x 10(7) M-1 (at 37 degrees C), and the enthalpy of binding delta H1 is -865 cal/mol. When the drug concentration is much higher, on the other hand, it shows another binding mode which is much weaker, so that K2 = 2.25 x 10(4) M-1 and delta H2 is -464 cal/mol, which gives fluorescence quenching, which has no base pair preference, and which causes an unwinding of the duplex by 1 degree.

Bisbenzimidazole↗

PubMed1999

Construction of an effective host-vector system for the yeast Saccharomyces exiguus Yp74L-3.

An effective host-vector system specific to the yeast Saccharomyces exiguus Yp74L-3 was constructed to promote the molecular genetic analyses for the yeast. To obtain a stable reversionless host strain, we constructed an S. exiguus strain carrying leu2::ScURA3 by disrupting the S. exiguus LEU2 gene with the S. cerevisiae URA3 gene. A vector plasmid unique to S. exiguus was subsequently developed by inserting both the LEU2 gene and an ARS cloned from S. exiguus into an Escherichia coli phagemid, pUC119. The vector constructed, pTH119 was able to transform the S. exiguus leu2::ScURA3 strain to Leu+ efficiently. The stability of the vector in the S. exiguus host cells resembled that of a YRp-type vector in S. cerevisiae.

Fungal Proteins↗

PubMed1999

Successful treatment of adult-onset Henoch-Schönlein purpura nephritis with high-dose immunoglobulins.

A 26-year-old woman was admitted for the evaluation of edema and massive proteinuria. She had a history of purpura of the lower extremities, abdominal pain and melena. Laboratory investigations showed hypoalbuminemia, hypercholesterolemia and proteinuria of over 10 g/day. Renal biopsy showed moderate proliferative glomerulonephritis with mesangial immunoglobulin A (IgA) deposition. She was diagnosed as having Henoch-Schonlein purpura nephritis. Oral prednisolone, dipyridamole and intravenous heparin treatment were not effective. Steroid pulse therapy induced a partial improvement of proteinuria to 2-3 g/day. High-dose intravenous immunoglobulin (i.v.-IG) treatment was introduced and a dramatic improvement of proteinuria was noted. I.v.-IG should be fully considered in patients with steroid-resistant Henoch-Schonlein purpura nephritis.

Adult↗

PubMed1999

[A case of ectopic pituitary adenoma localized in the sphenoid sinus].

Intrasphenoidal pituitary adenoma is relatively rare. Only 13 cases have been reported in the literature. We present a case of intrasphenoidal pituitary adenoma in a 74-year-old man. He had no endocrinological abnormalities. Skull tomograms revealed sellar floor erosion but showed no enlargement of the pituitary fossa. Computed tomographic (CT) scan revealed an isodense mass showing no contrast enhancement in the sphenoid sinus. The intrasphenoidal tumor appeared slightly hypointense compared with normal brain on T1-weighted image, and showed less contrast enhancement after intravenous injection of Gd-DTPA on magnetic resonance imaging (MRI). Transsphenoidal pituitary microsurgery was performed, and all of the intrasphenoidal tumor was removed with the mucosa. The sellar floor was thin and easily breakable in parts. After removal of the sellar floor the dura was opened, but no evidence of a pituitary tumor was shown. No connection between the pituitary gland and the sphenoidal tissue was found. Microscopic examination of sections showed tumor cell nests in the sphenoidal mucosa. We think this ectopic pituitary adenoma occurred through the migration of Rathke's pouch in the sphenoid sinus.

Adenoma↗