Search PubMed⌕ Search

Biomedical subjects

H Matsubara

Publications and source records attributed to H Matsubara.

At least 145 records · Page 8Linked to original sources
PubMed1997

Mechanism of constant contractile efficiency under cooling inotropy of myocardium: simulation.

We have reported that, in canine hearts, cardiac cooling to 29 degrees C enhanced left ventricular contractility but changed neither the contractile efficiency of cross-bridge (CB) cycling nor the excitation-contraction coupling energy. The mechanism of this intriguing energetics remained unknown. To get insights into this mechanism, we simulated myocardial cooling mechanoenergetics using basic Ca2+ and CB kinetics. We assumed that both adenosinetriphosphatase (ATPase)-dependent sarcoplasmic reticulum (SR) Ca2+ uptake and CB detachment decelerated with cooling. We also assumed that all the ATPase-independent SR Ca2+ release, Ca2+ binding to and dissociation from troponin, and CB attachment remained unchanged. The simulated cooling shifted the CB force-free Ca2+ concentration curve to a lower Ca2+ concentration, increasing the Ca2+ responsiveness of CB force generation, and increased the maximum Ca(2+)-activated force. The simulation most importantly showed that these cooling effects combined led to a constant contractile efficiency when Ca2+ uptake and CB detachment rate constants changed appropriately. This result seems to account for our experimentally observed constant contractile efficiency under cooling inotropy.

Adenosine Triphosphatases↗
PubMed1997

Downmodulation of IL-8 receptors, type A and type B, on human lung neutrophils in vivo.

We examined the expression of interleukin (IL)-8 receptors (Rs), type A (IL-8-RA) and type B (IL-8-RB), on peripheral blood and bronchoalveolar lavage (BAL) fluid neutrophils; we also examined IL-8 and other chemoattractants in the epithelial lining fluid (ELF) of patients with chronic lower respiratory tract infection (CLI) to elucidate the in vivo regulation of IL-8Rs. Neutrophils were stained with monoclonal antibodies specific for IL-8-RA and IL-8-RB. We detected higher levels of IL-8 (81.6 +/- 25.4 ng/ml, mean +/- SE), leukotriene (LT) B4, and IL-1 beta in the ELF of the CLI patients than in their serum (P < 0.05). The expression of IL-8Rs on BAL neutrophils was significantly lower than that on peripheral blood neutrophils (P < 0.01 for both). In vitro analysis showed that low-level IL-8 (50 ng/ml) alone did not affect IL-8R expression but that it was downregulated by high-level IL-8 (500 ng/ml) alone and by low-level IL-8 in combination with LTB4 or IL-1 beta. Staurosporine reduced the downmodulation by low-level IL-8 plus LTB4 or IL-1 beta but not by high-level IL-8 alone. We speculate that pulmonary IL-8-RA and IL-8-RB may have been downmodulated by the combined effect of local chemoattractants through, in part, a protein kinase C-dependent mechanism.

Adult↗
PubMed1997

Hybrid logistic characterization of isometric twitch force-time curve of intact blood-perfused canine right ventricular papillary muscle.

We previously found that a ventricular isovolumic pressure-time curve could be well fitted by the difference between two S-shaped logistic curves for the pressure rising and falling components, and called it "hybrid logistic" function: P(t)=A/[1+exp[-(4B/A)(t-C)]]-D/[1+exp[-(4E/D)(t-F)]]+G. We reported that the parameters of this hybrid logistic function are useful to characterize left ventricular contraction and relaxation comprehensively. In this study, we investigated how well this hybrid logistic function could fit the isometric twitch force-time curves of cross-circulated right ventricular papillary muscles of 7 dogs. This function precisely fitted the isometric force curves with correlation coefficients above 0.9996, much better than another fitting function (F(t)=C(t/A)(B)exp[1-(t/A)(B)]) proposed by Nwasokwa. The present results indicate that our hybrid logistic function can also reasonably express the canine right ventricular papillary muscle isometric twitch force-time curve. We suggest the possibility that the parameters of this hybrid logistic function are also useful to comprehensively characterize right ventricular papillary muscle twitch contraction and relaxation.

Animals↗
PubMed1997

Ryanodine decreases internal Ca2+ recirculation fraction of the canine heart as studied by postextrasystolic transient alternans.

We tested our hypothesis that the O2 wasting of Ca2+ handling in the excitation-contraction (E-C) coupling in ryanodine-treated failing hearts could be reflected by a decrease in the internal Ca2+ recirculation fraction (RF). We have reported, using canine excised cross-circulated hearts, that intracoronary ryanodine (40 nmol/l blood) halved left ventricular contractility without decreasing myocardial O2 consumption for the E-C coupling. We previously suspected this mechanoenergetic state to manifest energy wasting of Ca2+ handling due to ryanodine causing leakage of Ca2+ from the sarcoplasmic reticulum. To test this hypothesis, we analyzed all the sporadic spontaneous cases of postextrasystolic potentiation (PESP) obtained during the ryanodine experiments. We calculated RF from the beat constant of the exponential decay component of not only the monotonic type but also the transient alternans type of PESP. Results showed that ryanodine significantly decreased the beat constant in both types of PESP from about 2 to 1.5 beats and hence RF from 0.6 to 0.5 on the average, supporting the hypothesis. This organ-level systems approach to Ca2+ handling using transient alternans PESP as well as monotonic PESP may help obtain better insights into the mechanoenergetics of failing hearts.

Animals↗
PubMed1997

[Reasonable lymph node dissection for T2 or T3 midthoracic esophageal cancer with cervical lymph-node metastasis].

In order to determine the reasonable lymph node dissection for T2 or T3 midthoracic esophageal cancer with cervical lymph node metastasis, a retrospective study was carried out on 106 patients receiving resection between 1983 and 1996. Metastasis to cervical lymph node was obtained in 27.4% (29/106) of patients with T2 or T3 midthoracic esophageal cancer. Within 29 patients, metastasis in cervical node only, in two fields and in three fields occupied 17.2%, 41.4% and 41.4%, respectively. And according to the histologic examination of dissected lymph nodes, metastatic sites spreaded from neck to perigastric region. Five-year survival rate of 23 patients receiving curative operation was 33.0%, and that of 13 patients excluding 3-field metastasis was 51.9%. But the main sites of nodal recurrence were cervical or superior mediastinal nodes along the bilateral recurrent laryngeal nerves, and the rate of nodal recurrence was 47.8%. These results of actual state of lymph node metastasis and prognostic benefit of aggressive dissection suggest that 3-field lymph node dissection is mandatory for T2 or T3 midthoracic esophageal cancer with cervical lymph node metastasis. And we should endeavor to upgrade the precise dissection in order to decrease the nodal recurrence.

Esophageal Neoplasms↗
PubMed1997

[Normal predicted values of CT indices reflect emphysematous alterations in the lung].

In order to obtain normal values and 95% confidence limits of various CT indices, healthy adult subjects with no history of smoking (n = 36) underwent CT scanning under a variety of conditions. By then applying the normal limits thus obtained to CT images of COPD patients (n = 45), we examined the sensitivity for detecting abnormal emphysematous changes in the lung fields. To measure emphysematous alterations, we used the average value of lung CT densities (ROI), the maximally appearing value in a CT histogram (Hist. Peak), the relative area with low CT densities below -910 HU (%LDA) and the total cross-sectional area (Area) in each lung section. Regardless of the section thickness (10 mm or 1 mm), the lung volume level at which the breath was held or the site from which CT images were taken (upper, middle or lower lung field), no significant correlation was observed between the CT indices associated with emphysematous changes and the subjects' age. This allowed us to define, independently of the subjects' age, normal values and 95% confidence limits for the CT indices. Among the CT indices surveyed, %LDA was found to be the most sensitive indicator for detecting emphysematous abnormalities. In so far as the extent of emphysema may be determined by lung CT density, classical CT images of 10-mm section thickness appear to have a sufficiently high sensitivity for the detection of emphysematous abnormalities, such that high-resolution CT may be unnecessary.

Adult↗
PubMed1996

Site-specific mutagenesis of Rhodobacter capsulatus ferredoxin I, FdxN, that functions in nitrogen fixation. Role of extra residues.

One of the two [4Fe-4S]-type clusters of the Rhodobacter capsulatus ferredoxin I, FdxN, was modified through site-specific mutagenesis of the distinctive features of the second cluster-binding motif, Cys38-X2-Cys41-X8-Cys50-X3-Cys54-X4-Cys59. First, various mutagenized products were tested to learn whether they could rescue the decreased capacity of an fdxN-null strain MSA1 to fix nitrogen: the phenotype of MSA1 was reassessed to Nifs (slow growth by nitrogen fixation) from our previous description of Nif- (Saeki, K., Suetsugu, Y., Tokuda, K., Miyatake, Y., Young, D. A., Marrs, B. L. and Matsubara, H. (1991) J. Biol. Chem. 266, 12889-12895). Substitution of Cys59 to Ser yielded an almost fully active product, while that of Cys54 did not. Gradual deletions and deletion-substitution of the 8 residues between Cys41 and Cys50 also yielded active products. Second, three of the modified FdxN proteins were subjected to purification. Only the GA protein, whose 8 residues between positions 42 and 49 were replaced by the Gly-Ala sequence, was purified. The GA protein and the authentic FdxN showed similar optical properties. The two clusters in the former had Em values of -490 and -430 mV, while those in the latter had an identical value of -490 mV, when determined by EPR analysis. It was concluded that: 1) Cys59 is not a ligand to [4Fe-4S] clusters but is important for structural integrity, 2) the residues between positions 42 and 49 may form a "loop-out" from a structure analogous to the Peptococcus aerogenes ferredoxin, and 3) the loop-out region does not have functional significance in nitrogen fixation but may be responsible for maintaining the highly negative redox potential of one of the two clusters.

Amino Acid Sequence↗
PubMed1996

Inhibition of peritoneal dissemination of colon carcinoma in syngeneic mice immunized with interleukin-2-producing cells.

We have examined the antitumor effect of murine colon carcinoma cells engineered to produce human interleukin-2 (IL-2) in syngeneic mice. Subcutaneous inoculation of retrovirally-transduced cells with IL-2 gene formed small tumors, but they became regressed spontaneously. Consequently, the inoculated mice showed prolonged survival. Histological examination of the tumors derived from IL-2-producers revealed predominant infiltration of macrophages around tumor necrotic masses. Thus, inoculation of IL-2-producing cells could protect the mice from subsequent subcutaneous or intraperitoneal challenges with wild-type cells, suggesting the induction of acquired immunity due to the effect of tumor vaccination.

Animals↗
PubMed1996

Interleukin-2 does not overcome suppression of graft rejection by cyclosporin A: effect of cyclosporin A on T cell properties in vivo.

The most evident immunosuppressive effect of cyclosporin A (CsA) on T cells is suppression of interleukin-2 (IL-2) production through the suppression of type-2B serine/threonine-specific phosphatase, calcineurin. To test whether suppression of IL-2 production is a major mechanism of CsA-mediated suppression of allograft rejection, we treated allogeneic skin-grafted mice with CsA and IL-2, and observed that IL-2 did not override the suppressive effect of CsA. Specific cytotoxic T lymphocyte (CTL) activity and natural killer (NK) activity of the spleens were increased by treatment with IL-2, and CsA significantly suppressed the killing activity. We also found that CsA-treatment decreased the expression of lck kinase of T cells and the production of IL-2 in response to concanavalin A (ConA), with minimum effect on IL-4 production. These results suggest that T cell dysfunctions other than decreased production of IL-2 are essential for suppressive effect of CsA on skin allograft rejection.

Animals↗
PubMed1996

Identification of metallothionein isoforms with capillary zone electrophoresis using a polyacrylamide-coated tube.

Metallothionein (MT) isoforms from various liver tissues were separated with capillary zone electrophoresis (CZE) using a polyacrylamide-coated tube at neutral pH. The electrophoresis was performed on MT-1 and MT-2 purified from mouse, rat, rabbit and human livers. The retention times of mouse and rat MT-1 coincided, while the retention times of rabbit and human MT-1 were longer. The retention times of MT-2 purified from the four sources were the same. MT-1 and MT-2 separated more definitely with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-Tris buffer (25 mM, pH 7.4) than with N-tris(hydroxymethyl)methyl-3-aminopropane sulfonic acid (TAPS)-Tris buffer (25 mM, pH 7.7) or with N-(2-acetamido)iminodiacetic acid (ADA)-Tris buffer (25 mM, pH 7.4). In addition, liver MT isoforms prepared from Zn- or Cd-administered mice could be separated.

Acrylic Resins↗
PubMed1996

Cloning, sequencing, and high level expression of the genes encoding adenosylcobalamin-dependent glycerol dehydrase of Klebsiella pneumoniae.

The gld genes encoding adenosylcobalamin-dependent glycerol dehydrase of Klebsiella pneumoniae were cloned by cross-hybridization with a DNA fragment of Klebsiella oxytoca diol dehydrase genes. Since the Escherichia coli clones isolated did not show appreciable enzyme activity, plasmids for high level expression of cloned genes were constructed. The enzyme expressed in E. coli was indistinguishable from the wild-type glycerol dehydrase of K. pneumoniae by the criteria of polyacrylamide gel electrophoretic, immunochemical, and catalytic properties. It was also shown that the recombinant functional enzyme consists of Mr 61,000, 22,000, and 16, 000 subunits. Sequence analysis of the genes revealed four open reading frames separated by 2-12 bases. The sequential three open reading frames from the first to the third (gldA, gldB, and gldC genes) encoded polypeptides of 555, 194, and 141 amino acid residues with predicted molecular weights of 60,659(alpha), 21,355(beta), and 16,104(gamma), respectively. High level expression of these three genes in E. coli produced more than 14-fold higher level of fully active apoenzyme than that in K. pneumoniae. It was thus concluded that these are the genes encoding the subunits of glycerol dehydrase. The deduced amino acid sequences of the three subunits were 71, 58, and 54% identical with those of the alpha, beta, and gamma subunits of diol dehydrase, respectively, but failed to show any apparent homology with other proteins.

Amino Acid Sequence↗
PubMed1996

Antitumor effect induced by the expression of granulocyte macrophage-colony stimulating factor gene in murine colon carcinoma cells.

Murine colon carcinoma cells which secrete several kinds of cytokine after retroviral transduction with corresponding genes, were examined for their antitumor effects in syngeneic mice. The mice inoculated with granulocyte macrophage-colony stimulating factor (GM-CSF) producer cells showed not only prolonged survival but also reduced tumorigenicity. The antitumor effect caused by the expression of interleukin-4 was less than that of GM-CSF, and interleukin-6 producer cells did not show any effects on the survival of the host animals. Histological examination of the GM-CSF-producing tumor revealed predominant infiltration of neutrophils and necrotic change of the tumor. The present study indicates the feasibility of cancer gene therapy with the expression of GM-CSF gene in tumor cells.

Animals↗
PubMed1996

Murine colon carcinoma cells engineered to produce human interleukin-2 induce tumor-specific anti-tumor response.

Murine colon carcinoma cells (colon 26) transduced by a retrovirus vector with the human interleukin-2 (IL-2) cDNA were studied for their tumorigenicity. Although cell growth in vitro was not affected by integration of the IL-2 gene, s.c. tumors of IL-2-producing colon 26 cells (H2) in syngeneic mice regressed spontaneously after producing small masses. Histological examination of the sites of tumor rejection revealed predominant infiltration of macrophages around the tumor necrotic mass. Subsequent challenge with parent colon 26 cells, but not with Meth A cells (fibrosarcoma of the same genetic background), did not result in tumor formation in mice which had been protected against H2 cells. Inoculation of H2 cells into syngeneic nude mice resulted in tumors with a retarded growth rate. Taken together, T cell-dependent, tumor-specific immunity is obtained by local IL-2 secretion around colon tumors, and this experimental animal model gives us a clue(s) for investigating host anti-tumor responses by cytokine production.

Animals↗
PubMed1996

Pentacoordination of the heme iron of Arthromyces ramosus peroxidase shown by a 1.8 A resolution crystallographic study at pH 4.5.

In the presence of ammonium sulfate the absorption spectra of a peroxidase from the fungus Arthromyces ramosus (ARP) showed that the low-spin component increased as the pH increased from 6.0 to 9.0, whereas in its absence ARP remained in the high-spin state in the pH range investigated. The crystal structure of ARP at pH 4.5 in the presence of ammonium sulfate at 1.8 A resolution showed that the electron density at the 6th position of the heme iron seen at pH 7.5 had disappeared and that the iron atom deviated markedly from the heme plane. These observations strongly suggest that under physiological conditions the heme of ARP is in the pentacoordinated high-spin state and that at a high pH the heme iron is able to bind ammonia, forming the low-spin state. The location of the water molecule at the distal side of the heme in peroxidases is also discussed.

Crystallography, X-Ray↗
PubMed1996

Analysis of interaction between cadmium and metallothionein isoforms by capillary zone electrophoresis.

The effects of cadmium on the peak area of metallothionein (MT) protein were studied by capillary zone electrophoresis with a polyacrylamide-coated tube at neutral pH. When cadmium was added to a commercial standard MT-1 isoform prepared from rabbit liver, the peak are of the MT-1 isoform decreased in a time- and dose-dependent manner. The MT-2 isoform also decreased with time, but the rate of decrease was lower than that of the MT-1 isoform. When ethylene glyco-bis-(beta-aminoethyl ether)-N,N,N'N'-tetraacetic acid (EGTA) was added to a solution containing cadmium and MT-1, the peak area recovered with increasing concentration of EGTA. Zinc caused a slight decrease in the peak areas of MT-1 and MT-2 compared with cadmium, while addition of sodium did not decrease the areas. Furthermore, the peak areas of MT isoforms of the crude extract prepared from zinc-treated mice also decreased with increasing concentration of cadmium. These results indicate that cadmium may changed the charge of MT, which may account for the observed differences in electrophoretic behavior.

Animals↗