PubMed Health⌕ Search

Biomedical subjects

T Horii

Publications and source records attributed to T Horii.

At least 19 recordsLinked to original sources
PubMed1998

Nucleotide dependent structural and kinetic changes in Xenopus rad51.1-DNA complex stimulating the strand exchange reaction: destacking of DNA bases and restriction of their local motion.

Rad51 is a eukaryotic homologue of RecA and it catalyzes the DNA strand exchange reaction in homologous recombination. This protein, like RecA, requires ATP as a cofactor for activity. We investigated the mechanism of activation of this protein by the nucleotide cofactor by studying the effect of various nucleotides, particularly ATP, ADP and the non-hydrolyzable analog of ATP, adenosine-5'-O-(3-thiotriphosphate) (ATPgammaS) on the DNA binding of a Xenopus Rad51 protein (XRad51.1). DNA binding was studied in solution by monitoring the fluorescence changes of etheno-modified fluorescent poly(dA) or fluorescein-labeled oligo(dT) and by filter binding assay. Active nucleotides (ATP, dATP) changed the DNA binding mode of XRad51.1. In the active complex, the DNA bases were destacked and their motion was highly restricted. Dissociation of XRad51.1 from DNA was accelerated by ATP and dATP, as was dissociation of RecA from DNA. In contrast to these similarities with RecA, the XRad51.1-DNA complex was dissociated by the non-hydrolyzable analog of ATP (ATPgammaS) and this dissociation was not significantly accelerated by ADP. The effect of ATP hydrolysis on the XRad51.1-DNA complex differs from that on the RecA-DNA complex. ATP hydrolysis may not be essential for the strand exchange reaction whereas the changes in the DNA structure by ATP are important.

Animals↗
PubMed1998

Plasmodium falciparum produces prostaglandins that are pyrogenic, somnogenic, and immunosuppressive substances in humans.

Plasmodium falciparum causes the most severe form of human malaria, which kills approximately 1.5-2.7 million people every year, but the molecular mechanisms underlying the clinical symptoms and the host-parasite interaction remain unclear. We show here that P. falciparum produces prostaglandins (PGs) D2, E2, and F2alpha. After incubation with 1 mM arachidonic acid (AA), cell homogenates of P. falciparum produced PGs as determined by enzyme immunoassay and gas chromatography-selected ion monitoring. PG production in the parasite homogenate was not affected by the nonsteroidal antiinflammatory drugs aspirin and indomethacin, and was partially heat resistant, whereas PG biosynthesis by mammalian cyclooxygenase was completely inhibited by these chemicals and by heat treatment. Addition of AA to the parasite cell culture markedly increased an ability of the parasite cell homogenate to produce PGs and of parasitized red blood cells to accumulate PGs in the culture medium. PGD2 and PGE2 accumulated in the culture medium at the stages of trophozoites and schizonts more actively than at the ring stage. These findings are the first evidence of the direct involvement of a malaria parasite in the generation of substances that are pyrogenic and injurious to the host defenses. We will discuss a possible contribution of the parasite-produced PGs to pathogenesis and host-parasite interaction of P. falciparum.

Animals↗
PubMed1998

Inhibition of Escherichia coli RecA coprotease activities by DinI.

In Escherichia coli, the SOS response is induced upon DNA damage and results in the enhanced expression of a set of genes involved in DNA repair and other functions. The initial step, self-cleavage of the LexA repressor, is promoted by the RecA protein which is activated upon binding to single-stranded DNA. In this work, induction of the SOS response by the addition of mitomycin C was found to be prevented by overexpression of the dinI gene. dinI is an SOS gene which maps at 24.6 min of the E.coli chromosome and encodes a small protein of 81 amino acids. Immunoblotting analysis with anti-LexA antibodies revealed that LexA did not undergo cleavage in dinI-overexpressed cells after UV irradiation. In addition, the RecA-dependent conversion of UmuD to UmuD' (the active form for mutagenesis) was also inhibited in dinI-overexpressed cells. Conversely, a dinI-deficient mutant showed a slightly faster and more extensive processing of UmuD and hence higher mutability than the wild-type. Finally, we demonstrated, by using an in vitro reaction with purified proteins, that DinI directly inhibits the ability of RecA to mediate self-cleavage of UmuD.

Bacterial Proteins↗
PubMed1998

Complement-mediated killing of Plasmodium falciparum erythrocytic schizont with antibodies to the recombinant serine repeat antigen (SERA).

Mouse antiserum against the recombinant N-terminal domain (SE47') of serine repeat antigen (SERA) of Plasmodium falciparum inhibited the in vitro proliferation of the parasite. We purified the immunoglobulin G from mice immunized with SE47' and with Freund's or aluminum hydroxide gel, or without adjuvants. Antiserum prepared with aluminum hydroxide gel contained predominantly IgG1 subclass and was the least inhibitory to parasite proliferation. Antiserum prepared with Freund's adjuvant or without adjuvants contained SE47'-specific IgG2a, IgG2b and IgG3. These mixed IgG subclasses was more potent in growth inhibition that the IgG1. Furthermore, guinea pig complement enhanced the parasite growth inhibitory effect of the mixed SE47'-specific IgG2a, IgG2b and IgG3, but not that of the IgG1 or non-specific IgG. Heat inactivated complement could not support the enhanced growth inhibitory effect. When purified schizonts were incubated with SE47'-specific IgG2a, IgG2b and IgG3 and complement, abnormal schizonts with degenerated nuclei were observed. These data suggest that complement-mediated lysis of the schizonts by the classical pathway enhances the inhibition of the parasite cell proliferation by SE47' specific IgGs.

Adjuvants, Immunologic↗
PubMed1998

Use of the Harmonic Scalpel for harvesting arterial conduits in coronary artery bypass.

A simple and effective technique is described here for harvesting the gastroepiploic artery (GEA) and radial artery (RA) using the Harmonic Scalpel. The mean time of harvesting GEA was 9 min and that of RA was 17 min. There were no injuries or spasms of those grafts and the postoperative angiograms performed in 28 patients. This shows 100% patency of the conduits. The GEA and RA are safely harvested by using the Harmonic Scalpel and the use of arterial conduits in coronary artery bypass grafting (CABG) seems to be easily achieved.

Aged↗
PubMed1998

An in-vitro study of carbapenem-induced morphological changes and endotoxin release in clinical isolates of gram-negative bacilli.

One hundred clinical isolates, including Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris and Proteus mirabilis, were exposed to carbapenems (imipenem, panipenem, meropenem and biapenem) at 0.5 x MIC for 3 h, then their morphology was examined and endotoxin release determined. Ceftazidime, which induces filament formation, was used as a control. Scanning electron microscopy showed that these carbapenems induced formation of spherical or ovoid cells, except for P. aeruginosa treated with meropenem and biapenem; these latter cells had a 'bulge' midway along them and we have termed them 'oval-centred'. There was a relationship between morphology and the amount of endotoxin released following exposure to carbapenems or ceftazidime. Of all the species investigated, P. aeruginosa showed the most variable morphological changes. P. aeruginosa exposed to biapenem were longer oval-centred in shape, and released significantly more endotoxin than those exposed to imipenem, panipenem (spherical) or meropenem (shorter oval-centred cells) (P=0.030, 0.017 and 0.002, respectively). In all strains except P. aeruginosa, carbapenems induced significantly less endotoxin release than ceftazidime (P < 0.05).

Ceftazidime↗
PubMed1998

Carbapenem-induced endotoxin release in gram-negative bacterial sepsis rat models.

The carbapenem-induced endotoxin release was evaluated using experimental models of gram-negative bacterial sepsis in Wistar rats. Infections with Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris and Proteus mirabilis resulted in an increase of the plasma endotoxin concentration after treatment with ceftazidime and carbapenems including imipenem, panipenem, meropenem and biapenem. Except for P. aeruginosa, the plasma endotoxin concentrations after carbapenem treatment were significantly lower than those after ceftazidime treatment. It is noteworthy that treatment of P. aeruginosa sepsis with meropenem or biapenem induced significantly more endotoxin release than other carbapenems and the endotoxin concentrations induced by these carbapenems reached those of ceftazidime treatment. The plasma endotoxin concentrations appeared to correlate with the reduction of platelet counts and the elevation of both glutamic oxaloacetic transaminase and glutamic pyruvic transaminase values.

Animals↗
PubMed1998

Molecular mechanism of peptide-specific pheromone signaling in Enterococcus faecalis: functions of pheromone receptor TraA and pheromone-binding protein TraC encoded by plasmid pPD1.

Conjugative transfer of the Enterococcus faecalis plasmid pPD1 is activated by cPD1, one of several peptide sex pheromones secreted by plasmid-free recipient cells, and is blocked by a donor-produced peptide inhibitor, iPD1. Using a tritiated pheromone, [3H]cPD1, we investigated how pPD1-harboring donor cells receive these peptide signals. Donor cells rapidly incorporated [3H]cPD1. The cell extract but not the membrane fraction of the donor strain exhibited significant [3H]cPD1-binding activity. On the basis of these data and those of tracer studies, it was demonstrated that cPD1 was internalized, where it bound to a high-molecular-weight compound. The cell extract of a strain carrying the traA-bearing multicopy plasmid (pDLHH21) also exhibited high [3H]cPD1-binding activity. A recombinant TraA exhibited a dissociation constant of 0.49 +/- 0.08 nM against [3H]cPD1. iPD1 competitively inhibited [3H]cPD1 binding to TraA, whereas pheromones and inhibitors relating to other plasmid systems did not. These results show that TraA is a specific intracellular receptor for cPD1 and that iPD1 acts as an antagonist for TraA. A strain carrying the traC-bearing multicopy plasmid (pDLES23) exhibited significant [3H]cPD1-binding activity. A strain carrying traC-disrupted pPD1 (pAM351CM) exhibited lower [3H] cPD1-binding activity as well as lower sensitivity to cPD1 than a wild-type donor strain. Some of the other pheromones and inhibitors inhibited [3H]cPD1 binding to the traC transformant like cPD1 and iPD1 did. These results show that TraC, as an extracellular less-specific pheromone-binding protein, supports donor cells to receive cPD1.

Bacterial Outer Membrane Proteins↗
PubMed1998

[Early result of volume reduction left ventriculoplasty (Batista operation) for dilated cardiomyopathy].

The Batista operation is intended to improve cardiac function by reducing the diameter of the left ventricle by excising of a sizable amount of the left ventricular free wall. Candidates for this operation are patients awaiting cardiac transplantation due to end-stage dilated cardiomyopathy and those unsuitable for transplantation because of age, physical or economical reasons. We performed this operation in 10 patients between December 1996 and October 1997. The baseline indication is left ventricular diastolic dimension > or = 70 mm and New York Heart Association (NYHA) class III or IV. There were eight men and two women aged from 16 to 60 years (mean 46 years). All had non-ischemic cardiomyopathy including seven idiopathic and one each of hypertrophic, arrhythmogenic right ventricular and valvular (sarcoidosis) cardiomyopathy. Eight patients were in NYHA class IV and six needed inotropic drip therapy prior to the operation. Nine patients had significant mitral regurgitation and six had tricuspid insufficiency concomitantly. Eight patients underwent mitral valve replacement and one was treated with mitral valve plasty. Six patients also had tricuspid plasty combined with partial left ventriculectomy. Eight patients survived. Mean value of left ventricular end-diastolic diameter was reduced from 77.8 mm to 59.8 mm, left ventricular end-diastolic volume index was reduced from 189.3 to 99.2 ml/m2, ejection fraction was increased from 19.0% to 33.8% and NYHA class improved from 3.8 to 1.8. Six months later, left ventricular dilatation was not noticed in four patients examined. The Batista operation offers real hope for patients with end-stage dilated cardiomyopathy, but we still have much to learn.

Adolescent↗
PubMed1998

[Dor operation for end-stage ischemic cardiomyopathy].

Endoventricular circular patch plasty (Dor operation) was used to treat end-stage dilated ischemic cardiomyopathy in 13 patients from January to December, 1997. There were 10 men and three women aged from 57 to 78 years (mean 63 years). Single, double, triple and left main trunk coronary disease was present in one, two, eight and two patients, respectively. Mean ejection fraction was 22% (6-30%) and signs of congestive heart failure were clear in all patients [New York Heart Association (NYHA) class III in eight patients and class IV in five patients]. Angina pectoris was present in five patients. Six patients had associated significant mitral regurgitation. Coronary artery bypass grafting (mean 3.2 grafts) was used in 11 patients and mitral valve reconstruction was performed in 6 patients (4: replacement and 2: repair) combined with akinetic area exclusion by the Dor technique. All patients were successfully weaned from cardiopulmonary bypass without mechanical support and no perioperative death occurred. Three patients died in hospital at 1-2 postoperative months due to pneumonia, stroke and heart failure, respectively. Two patients died during the late period due to stroke and sudden death. Among the eight survivors, six patients were in NYHA class I-II and two patients in class III. Ejection fraction increased from 22% to 36%, end-diastolic and systolic volume indices decreased from 168 +/- 58 to 123 +/- 39 ml/m2 and from 131 +/- 60 to 81 +/- 33 ml/m2, respectively. Pulmonary capillary wedge pressure decreased from 19 +/- 10 to 14 +/- 5 mmHg. The Dor procedure is an effective surgical alternative for patients with end-stage ischemic cardiomyopathy who are considered to be candidates for cardiac transplantation.

Aged↗
PubMed1998

Two-year experience of the Batista operation for non-ischemic cardiomyopathy.

The Batista operation was performed in 30 patients (25 men and 5 women, mean age 47 years) to treat cardiac failure due to non-ischemic cardiomyopathy, mostly idiopathic dilated cardiomyopathy, from December 1996 to June 1998. Preoperative New York Heart Association (NYHA) class was IV in 21 patients including 17 receiving inotropic support, and class III in 9 patients. Seven patients required emergency surgery because of on-going shock and 23 patients were operated electively. Combined cardiac procedures were; mitral valve reconstruction in 26 patients (19 replacements, 7 repairs), tricuspid annuloplasty in 15, aortic valve replacement in 3 and one each of maze and coronary artery bypass grafting. All patients successfully weaned from cardiopulmonary bypass. Intraaortic balloon pump was used in 6 patients but no left ventricular assist device was used. Two of 23 patients (8.7%) who underwent elective operation died during hospitalization and 3 patients (13.0%) died in the late period. Six of 7 patients (85.7%) with emergency operation died in the hospital and only one survived. Sixteen of 19 survivors returned to NYHA class I-II, and 3 were in class III. Mean ejection fraction increased from 18 +/- 6% to 31 +/- 5%. Diastolic dimension decreased from 79 +/- 8 to 60 +/- 8 mm. End-diastolic and systolic volume indices decreased from 203 +/- 43 to 103 +/- 25 ml/m2 and from 164 +/- 39 to 70 +/- 25 ml/m2, respectively, at the second postoperative week. Six patients had ventriculography at one year after the operation, and no redilation was noted. Increased thickness of left ventricular wall was observed postoperatively. The Batista operation can be performed with relatively low risk and clinical improvement was obvious in elective operation, wheras risk is very high in emergency cases. Therefore, proper guidelines for patient selection and choice of procedure are critically important to achieve a successful outcome in the Batista operation.

Adolescent↗
PubMed1997

Nucleotide cofactor-dependent structural change of Xenopus laevis Rad51 protein filament detected by small-angle neutron scattering measurements in solution.

Rad51 protein, a eukaryotic homologue of RecA protein, forms a filamentous complex with DNA and catalyzes homologous recombination. We have analyzed the structure of Xenopus Rad51 protein (XRad51.1) in solution by small-angle neutron scattering (SANS). The measurements showed that XRad51.1 forms a helical filament independently of DNA. The sizes of the cross-sectional and helical pitch of the filament could be determined, respectively, from a Guinier plot and the position of the subsidiary maximum of SANS data. We observed that the helical structure is modified by nucleotide binding as in the case of RecA. Upon ATP binding under high-salt conditions (600 mM NaCl), the helical pitch of XRad51.1 filament was increased from 8 to 10 nm and the cross-sectional diameter decreased from 7 to 6 nm. The pitch sizes of XRad51.1 are similar to, though slightly larger than, those of RecA filament under corresponding conditions. A similar helical pitch size was observed by electron microscopy for budding yeast Rad51 [Ogawa, T., et al. (1993) Science 259, 1896-1899]. In contrast to the RecA filament, the structure of XRad51.1 filament with ADP is not significantly different from that with ATP. Thus, the hydrolysis of ATP to ADP does not modify the helical filament of XRad51.1. Together with our recent observation that ADP does not weaken the XRad51.1/DNA interaction, the effect of ATP hydrolysis on XRad51.1 nucleofilament should be very different from that on RecA.

Adenine Nucleotides↗
PubMed1997

Lead discovery of inhibitors of the dihydrofolate reductase domain of Plasmodium falciparum dihydrofolate reductase-thymidylate synthase.

A three-dimensional structure model of the dihydrofolate reductase (DHFR) domain of the bifunctional DHFR-thymidylate synthase of Plasmodium falciparum was used as a basis for computational screening of commercially available compounds for candidate inhibitors. Compounds which can stably dock to the model with strong ionic hydrogen bonds via protonation by an aspartic acid residue at the bottom of the active site were identified through docking simulation. Among compounds thus identified, 21 were assayed for inhibitory activity towards the recombinant DHFR domain. Two compounds, 2-amino-1,4-dihydro-4,4,7,8-tetramethyl-s-triazino(1,2-a)benzimida zole and Trp-P-2, inhibited the recombinant P. falciparum DHFR domain with Ki values of 0.54 and 8.7 microM, respectively. Kinetic analysis showed that these compounds competitively inhibited the enzyme with respect to the substrate dihydrofolate. These findings support the validity of both the modeled structure and the docking results. Furthermore, these compounds serve as leads for developing new DHFR inhibitors, since their skeletal structures are different from any of known DHFR inhibitors. This paper also reveals a new biological activity of Trp-P-2, a potent mutagen.

Animals↗
PubMed1997

Plasmodium falciparum: an epitope within a highly conserved region of the 47-kDa amino-terminal domain of the serine repeat antigen is a target of parasite-inhibitory antibodies.

Previously, the Plasmodium falciparum serine repeat antigen has been shown to be protective in primate models of malaria immunity and also to be a target of in vitro parasite-inhibitory antibodies. To further define parasite-inhibitory epitopes a series of deletions from the amino-terminal 47-kDa domain of the serine repeat antigen (SERA) were constructed as glutathione-S-transferase fusion proteins. Several GST-SERA fusion proteins were used to vaccinate mice with Freund's adjuvant and the resulting immune sera were used to assay for the inhibition of P. falciparum invasion of erythrocytes in vitro. The minimal epitope shown to be the target of invasion-blocking antibodies was SERA amino acids 17-165. Additional GST-SERA deletion constructs of the 47-kDa domain were developed and evaluated for reactivity, by Western immunoblot analysis, with a parasite-inhibitory murine monoclonal antibody (mAb 43E5), a parasite-inhibitory pooled goat polyclonal sera, and a pooled human Nigerian immune serum. The parasite-inhibitory epitope defined by mAb 43E5 was mapped to SERA amino acids 17-110 and, at least, part of the epitope was defined to include amino acids in the region of amino acids 59-72. The parasite-inhibitory epitope recognized by mAb 43E5 appears to be well conserved between diverse geographical isolates of P. falciparum. The results have relevance for malaria vaccine development and suggest that an appropriately designed recombinant SERA antigen produced from a synthetic gene in Escherichia coli may be an effective component of a candidate malaria vaccine.

Amino Acid Sequence↗
PubMed1997

Semiskeletonization of internal thoracic artery: alternative harvest technique.

A simple technique of harvesting the internal thoracic artery is described. Harvesting the internal thoracic artery as a thin pedicle without the endothoracic fascia is advantageous in terms of obtaining its maximum length, dissecting a narrow space, avoiding pleural opening, and facilitating handling of the internal thoracic artery during the coronary anastomoses. This alternative-technique requires almost the same skill and time as the conventional wide pedicle technique.

Humans↗
PubMed1997

RobA-induced multiple antibiotic resistance largely depends on the activation of the AcrAB efflux.

RobA is a member of the XylS/AraC subfamily of DNA binding proteins, and when overexpressed, it induces multiple antibiotic resistance in Escherichia coli. In this study, we introduced a multicopy robA plasmid (pMEP1) and its derivative into OmpF mutants and an AcrAB-deficient mutant. We found that a decrease in susceptibility to multiple antibiotics in these OmpF mutants when pMEP1 was introduced did not depend on OmpF porin expression. Interestingly, a delta ompF mutant (TK007) became more sensitive when pMEP1 was introduced. Moreover, no effect of RobA on the induction of multiple antibiotic resistance in an acrA1- mutant was observed. Therefore, we conclude that the multiple antibiotic resistance induced by the overexpression of RobA largely depends on the activation of the AcrAB efflux, as well as the activation of micF.

Bacterial Proteins↗
PubMed1997

Immunodiagnosis of alveolar echinococcosis by enzyme-linked immunosorbent assay using a partially purified Em18/16 enriched fraction.

An improved enzyme-linked immunosorbent assay (ELISA) system using partially purified Eml8/16 enriched fraction (PP-Em18/16) prepared by isoelectric focusing was evaluated for serodiagnosis of alveolar echinococcosis (AE). The PP-Em18/16-ELISA was compared with Em2plus-ELISA by using sera from AE and cystic echinococcosis (CE) patients in China, where both AE and CE are endemic; sera from CE patients in Australia, where only CE exists; and sera from patients with cysticercosis, paragonimiasis, or sparganosis in Korea, where no indigenous AE or CE exists. We used Em2plus-ELISA as a standard ELISA and found 24.6% (17 of 69 specimens) cross-reactivity with sera from CE. Furthermore, some of the sera from paragonimiasis, sparganosis, and cysticercosis patients were also cross-reactive in the Em2plus-ELISA. When we tested for similar cross-reactivity in the same sera from CE patients by PP-Em18/16-ELISA (23.2%, 16 of 69), it became evident that the specificity of the PP-Em18/16-ELISA was better than that of the Em2plus-ELISA, since no sera from patients with the examined parasitic diseases except CE showed cross-reactivity. Some CE patients from China showed exceptionally high levels of antibody in comparison with those of CE patients from Australia, where no AE occurs. It is speculated that these patients with strongly positive cases of CE from China may have been exposed to both species of Echinococcus.

Animals↗