Biomedical subjects

T Imada

Publications and source records attributed to T Imada.

At least 19 recordsLinked to original sources

PubMed2002

Complete, long-lasting protection against lethal infectious bursal disease virus challenge by a single vaccination with an avian herpesvirus vector expressing VP2 antigens.

Marek's disease herpesvirus is a vaccine vector of great promise for chickens; however, complete protection against foreign infectious diseases has not been achieved. In this study, two herpesvirus of turkey recombinants (rHVTs) expressing large amounts of infectious bursal disease virus (IBDV) VP2 antigen under the control of a human cytomegalovirus (CMV) promoter or CMV/beta-actin chimera promoter (Pec promoter) (rHVT-cmvVP2 and rHVT-pecVP2) were constructed. rHVT-pecVP2, which expressed the VP2 antigen approximately four times more than did rHVT-cmvVP2 in vitro, induced complete protection against a lethal IBDV challenge in chickens, whereas rHVT-cmvVP2 induced 58% protection. All of the chickens vaccinated with rHVT-pecVP2 had a protective level of antibodies to the VP2 antigen at the time of challenge, whereas only 42 and 67% of chickens vaccinated with rHVT-cmvVP2 or the conventional live IBDV vaccine, respectively, had the antibodies. The antibody level of chickens vaccinated with rHVT-pecVP2 increased for 16 weeks, and the peak antibody level persisted throughout the experiment. The serum antibody titer at 30 weeks of age was about 20 or 65 times higher than that of chickens vaccinated with rHVT-cmvVP2 or the conventional live vaccine, respectively. rHVT-pecVP2, isolated consistently for 30 weeks from the vaccinated chickens, expressed the VP2 antigen after cultivation, and neither nucleotide mutations nor deletion in the VP2 gene was found. These results demonstrate that the amount of VP2 antigen expressed in the HVT vector was correlated with the vaccine efficacy against lethal IBDV challenge, and complete protective immunity that is likely to persist for the life of the chickens was induced.

Animals↗

PubMed2002

Pancreatic necrosis and ventricular erosion in adenovirus-associated hydropericardium syndrome of broilers.

Seven 19-day-old broiler chickens affected with hydropericardium syndrome (HPS) with pancreatic necrosis and gizzard erosions were investigated pathologically and virologically. Mortality increased after 13 days of age in a flock on a broiler farm. The mortality rate of the flock reached 10% by 19 days of age. Macroscopically, the chickens had hydropericardium (the characteristic gross change of HPS), pinpoint white foci in the pancreas, and ventricular erosions. Histologically, the chickens had multifocal hepatic necrosis with intranuclear inclusions in hepatocytes, a marked increase of macrophages in the spleen and lung, mild epicardial edema, multifocal necrosis of pancreatic acinar cells with intranuclear inclusions, focal necrosis of the ventricular koilin layer, and degeneration of the ventricular glandular epithelium with intranuclear inclusions. Immunohistochemically, intranuclear inclusions in the liver, pancreas, and ventriculi were stained positively against group I avian adenovirus (GIAAV) antigens. Ultrastructurally, 67-nm diameter viral particles were present in intranuclear inclusions. Virologically, serotype 4 of GIAAV was isolated from the liver, heart, and kidney of affected chickens. The pathologic changes of the present cases differ from previous cases of HPS; therefore, the present strain of GIAAV may have different pathogenicity for chickens than the previous virus strain of HPS.

Adenoviridae Infections↗

PubMed2001

Synthesis, structure-activity relationships, and pharmacokinetic profiles of nonpeptidic alpha-keto heterocycles as novel inhibitors of human chymase.

We designed nonpeptidic chymase inhibitors based on the structure of a peptidic compound (1) and demonstrated that the combination of a pyrimidinone skeleton as a P3-P2 scaffold and heterocycles as P1 carbonyl-activating groups can function as a nonpeptidic chymase inhibitor. In particular, introduction of heterobicycles such as benzoxazole resulted in more potent chymase-inhibitory activity. Detailed structure-activity relationship studies on the benzoxazole moiety and substituents at the 2-position of the pyrimidinone ring revealed that 2r (Y-40079) had the most potent chymase-inhibitory activity (K(i) = 4.85 nM). This compound was also effective toward chymases of nonhuman origin and showed good selectivity for chymases over other proteases. Pharmacokinetic studies in rats indicated that 2r was absorbed slowly after oral administration and showed satisfactory bioavailability (BA) (T(max) = 6.0 +/- 2.3 h, BA = 19.3 +/- 6.6%, t(1/2) = 35.7 +/- 13.3 h). In conclusion, 2r is a novel, potent, and orally active chymase inhibitor which would be a useful tool in elucidating the pathophysiological roles of chymase.

Animals↗

PubMed2001

Synthesis, structure-activity relationships, and pharmacokinetic profiles of nonpeptidic difluoromethylene ketones as novel inhibitors of human chymase.

Potent human chymase inhibitors with high enzymatic selectivity and satisfactory metabolic stability were obtained by replacing the Val-Pro (P3-P2) dipeptide portion of the previously described inhibitor 1 with a nonpeptidic pyrimidinone skeleton. The potency of the novel compounds was further enhanced by the introduction of carbamoyl-substituted difluoromethylene ketone moieties. The most potent chymase inhibitor of the newly created series was 2u (Y-40018), which had a K(i) of 2.62 nM. Compound 2u possessed high selectivity for human chymase since it lacked significant activity toward other representative human proteolytic enzymes. Moreover its strict specificity for human chymase suggested that 2u strongly inhibited human and canine chymases but not rat and mouse ones. Pharmacokinetic studies in rats and dogs indicated that 2u was absorbed rapidly after oral administration and had satisfactory bioavailability in these experimental animal species (rat, 17%; dog, 32%). In conclusion, 2u is a novel, potent, and orally active chymase inhibitor which would prove very useful in revealing the precise roles of the latter in various pathophysiological processes.

Animals↗

PubMed2001

Non-peptidic inhibitors of human chymase. Synthesis, structure-activity relationships, and pharmacokinetic profiles of a series of 5-amino-6-oxo-1,6-dihydropyrimidine-containing trifluoromethyl ketones.

Chymase possesses a wide variety of actions, including promotion of angiotensin II production and histamine release from mast cells. However, due to a lack of effective inhibitors featuring both high inhibitory activity and high metabolic stability, the pathophysiological role of chymase has not been fully elucidated. We designed non-peptidic inhibitors based on the predicted binding mode of the peptidic chymase inhibitor Val-Pro-Phe-CF3 and demonstrated that the Val-Pro unit is replaceable with a (5-amino-6-oxo-2-phenyl-1,6-dihydro-1-pyrimidinyl)acetyl moiety. Structure-activity relationship studies revealed that phenyl substitution at the 2-position of the pyrimidinone ring is indispensable for high activity. The most potent compound 1h (Ki = 0.0506 microM) is superior in potency to the parent peptidic inhibitor Val-Pro-Phe-CF3 and has good selectivity for chymase over other proteases. The related analogue 1e was orally absorbed and maintained high plasma levels for at least 2h. These results suggest that the derivatives reported here could be developed as agents for treatment of chymase-induced disease.

Animals↗

PubMed2001

Rat mast cell protease-I enhances immunoglobulin E production by mouse B cells stimulated with interleukin-4.

Mast cell chymase plays important roles in inflammation and tissue remodeling. Here we show that mast cell chymase also functions as an enhancer of immunoglobulin production. In the culture of murine spleen cells stimulated with lipopolysaccharide and interleukin-4, purified rat chymase (rat mast cell protease-I; RMCP-I), at physiological concentrations, enhanced immunoglobulin E (IgE) and IgG1 syntheses but not IgG3 synthesis. The enhancement was also evident when spleen cells depleted of T cells and macrophages were employed as responding cells. Enzymatic activity of RMCP-I was required to enhance IgE and IgG1, because two inhibitors for chymotryptic enzymes, chymostatin and Y-40613, a novel chymase inhibitor, suppressed the enhanced immunoglobulin production, and phenylmethylsulphonyl fluoride, an irreversible inhibitor for serine proteases, totally abolished the enhancing effect. Furthermore, a specific inhibitor for Zn2+-dependent metalloproteases, GI 129471, could also completely inhibit the production of IgE and IgG1 that was enhanced by RMCP-I, suggesting that a metalloprotease also played an essential role in the immunoglobulin production. Our results together with others show that proteases from mast cell granules have important function not only in the efferent phase but also in the afferent phase of immune responses.

Animals↗

PubMed2001

Identification of a genetic determinant of pathogenicity in chicken anaemia virus.

The molecular basis of pathogenicity of the chicken anaemia virus (CAV) needs to be clarified in order to develop a safe, live virus vaccine. In this study, several high- and low-pathogenic infectious DNA clones were obtained from field virus samples after 12 or 38 passages in MDCC-MSB1 cells. The high-pathogenic clones induced a low haematocrit, low weight gain and high mortality. Nucleotide sequence analyses identified one amino acid, at residue 394 of the VP1 capsid protein, as a major determinant of pathogenicity. To determine the role of this amino acid in pathogenicity, chimeric infectious DNA clones and point-mutated clones were used for chicken pathogenicity tests. These analyses clearly demonstrated that residue 394 of VP1 was crucial for the pathogenicity of CAV; all of the cloned viruses with glutamine at this position were highly pathogenic, whereas those with histidine had low pathogenicity. Low-pathogenic CAV, based on an infectious DNA clone, is a candidate for a genetically homogeneous and stable CAV live vaccine.

Amino Acid Sequence↗

PubMed2001

Imported parakeets harbor H9N2 influenza A viruses that are genetically closely related to those transmitted to humans in Hong Kong.

In 1997 and 1998, H9N2 influenza A viruses were isolated from the respiratory organs of Indian ring-necked parakeets (Psittacula Krameri manillensis) that had been imported from Pakistan to Japan. The two isolates were closely related to each other (>99% as determined by nucleotide analysis of eight RNA segments), indicating that H9N2 viruses of the same lineage were maintained in these birds for at least 1 year. The hemagglutinins and neuraminidases of both isolates showed >97% nucleotide identity with those of H9N2 viruses isolated from humans in Hong Kong in 1999, while the six genes encoding internal proteins were >99% identical to the corresponding genes of H5N1 viruses recovered during the 1997 outbreak in Hong Kong. These results suggest that the H9N2 parakeet viruses originating in Pakistan share an immediate ancestor with the H9N2 human viruses. Thus, influenza A viruses with the potential to be transmitted directly to humans may be circulating in captive birds worldwide.

Amino Acid Sequence↗

PubMed2001

Laparoscopic surgery using a newly designed suction lifter.

The authors describe a simple and available abdominal wall-lift technique for endoscopic surgery that involves a new suction lifter that they designed for laparoscopic surgery. Since July 1998, the authors have used this technique successfully in eight patients with appendicitis, in one patient with a perforated duodenal ulcer, and in one patient with an adenoma of the ascending colon.

Adenoma↗

PubMed2000

Secretory production of recombinant human chymase as an active form in Pichia pastoris.

We succeeded in expressing in a Pichia pastoris (P. pastoris) host a cDNA encoding a mature human chymase (h-chymase) which was secreted directly into the culture medium. Recombinant human heart chymase (rh-chymase) was purified from the culture medium via a single one-step heparin-agarose column chromatography tracing, using succinyl-Ala-Ala-Pro-Phe-para-nitroanilide (Suc-AAPF-pNA) hydrolysing activity. On SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the rh-chymase showed a diffused protein band with molecular weight of 32-37 kDa. After deglycosylation, however, rh-chymase changed to a sharp protein band with molecular weight 28 kDa, which is equal in size to deglycosylated h-chymase. The rh-chymase had an activity to convert one of the natural substrates, angiotensin I, to angiotensin II. Double reciprocal plot analysis revealed that the K(m) value ofrh-chymase against Suc-AAPF-pNA was approximately 5.1 mM, which is close to that of purified h-chymase.

Angiotensin I↗

PubMed2000

Functional reconstitution of an active recombinant human chymase from Pichia pastoris cell lysate.

We have previously reported efficient production of mature human chymase (h-chymase) using an original system of expression in Pichia pastoris (Nakakubo et al., 2000), whereby recombinant h-chymase (rh-chymase) was secreted as a mature form with the correct N-terminal amino acid sequence and was easily purified. In the course of investigation of secretory rh-chymase, we also found large amounts of chymase to be present in insoluble form in the transformant cell. Although the cellular rh-chymase had no proteolytic activity, its chymotryptic activity was restored in a reconstitution process utilizing guanidine and glutathione. As with secretory rh-chymase, efficient purification was possible by heparin affinity chromatography. The purified cellular rh-chymase showed the same mobility as secretory rh-chymase in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) before and after deglycosylation. N-terminal amino acid sequence analysis revealed that the signal peptide had been correctly removed. K(m) value (5.93 mM), as well as pH profile and inhibition profile toward protease inhibitors of reconstituted cellular rh-chymase, indicated that the rh-chymase enzymatically closely resembles native h-chymase. Furthermore, it showed a greatly restricted proteolytic activity towards Ang I, and formed Ang II without the further cleavage which is a feature of h-chymase. It was thus found that the insoluble rh-chymase stored in the cells could be solubilized and reconstituted to give the same structure as h-chymase, not only in terms of enzyme active site but also of substrate recognition site.

Amidohydrolases↗

PubMed2000

Ileal duplication presenting as perforation: report of a case.

We describe herein the case of a 10-year-old boy in whom generalized peritonitis was caused by perforation of a tubular communicating ileal duplication cyst. Alimentary tract duplication cysts are rare congenital malformations, found primarily in children under the age of 15 years. The perforation was caused by heterotopic gastric mucosa within the duplication, giving rise to peptic ulceration in the adjacent intestinal mucosa. The presence of heterotopic gastric tissue is a primary cause of perforation that has been reported in as many as one third of patients with small intestine duplications; however, the detection of such ectopic tissue is time-consuming, and there is no readily available method of diagnosing tubular duplications. Although very few patients present with peritonitis as the initial manifestation, the possibility should be borne in mind when diagnosing and planning therapy for such emergencies, particularly in children.

Child↗

PubMed2000

Molecular modelling and conformational analysis of novel glycoprotein (Gp) IIb/IIIa antagonists. Molecular orbital calculation and the condensed heterocyclic derivatives.

A naphthalene compound was chosen as lead compound to develop a new series of fibrinogen receptor antagonists. Eight new compounds with different condensed heterocyclic parts were prepared and their in vitro activities were evaluated. 5-Amidinobenzofuran compound 2, 6-amidinobenzothiophene 7, and 5-amidinofuro[2,3-b]pyridine 8 were more active than lead compound 1. Molecular orbital calculation studies suggested the presence of a preferred spatial orientation between the amidine and the carboxylic acid.

Acetates↗

PubMed2000

Avian nephritis virus (ANV) as a new member of the family Astroviridae and construction of infectious ANV cDNA.

The complete RNA genome of the avian nephritis virus (ANV) associated with acute nephritis in chickens has been molecularly cloned and sequenced. Excluding the poly(A) tail, the genome comprises 6,927 nucleotides and contains three sequential open reading frames (ORFs). The first ORF (ORF 1a) contains a sequence encoding a serine protease motif, and the second ORF (ORF 1b) has a sequence encoding an RNA-dependent RNA polymerase. ORF 1a may be linked to the second ORF by a ribosomal frameshifting mechanism. The third ORF (ORF 2) may encode the virion structural proteins as a polyprotein precursor. Two RNAs, probably genonic and subgenonic RNA (7.5 and 3.0 kb), were detected in the cytoplasm of ANV-infected cells. ANV and human astroviruses have the same genonic organization, and both are characterized by the presence of two RNA bands. The amino acid homologies of the products of ORF 1a, 1b, and 2 were 20.3, 41.9, and 25.8% to products of the corresponding ORFs of human astrovirus serotype 1 (A/88 Newcastle strain). We have constructed a genonic-length cDNA clone of ANV to test whether the in vitro transcript is infectious. When a chicken kidney cell culture was transfected with RNA transcribed in vitro and the cDNA clone, infectious virus was produced with cytopathic effects in the absence of trypsin. These observations suggested that the ANV (G-4260 strain) is a new genus of the family Astroviridae.

Animals↗

PubMed2000

[The management of infectious mediastinitis after the open heart surgery].

Between October of 1992 and September of 1998, we performed 604 open heart operations. Among them, 12 cases (1.9%) were complicated with postoperative infectious mediastinitis. Five patients (Group A) were treated by conservative therapy which consists of open drainage and intermittent closed irrigation with dilute povidone iodine solution. Seven patients (Group B) were treated surgically in addition to the above-mentioned conservative treatment. Among those patients, one patient developed fatal complication. We have realized that mental care of the patients was also very important when long term hospitalization was necessitated. The hyperbaric oxygen therapy seemed to be also effective for postoperative mediastinitis caused by MRSA.

Aged↗

PubMed2000

[The management of aortic root replacement using the Top-Hat/Gelweave composite graft].

Composite graft replacement of the aortic root has become a routine procedure for annuloaortic ectasia (AAE) and aortic valve insufficiency (AR) with aortic dissection and the results have improved. We treated six cases of aortic root reconstruction using the Carrel patch method in 1998. The Top-Hat/Gelweave Composite graft fit together well and the procedure is technically similar to standard valve replacement. Upon measuring the valve size a Gelweave graft 1 mm larger than the valve size should be selected. There were no incidence of hemorrhage or postoperative hemolysis. Further long-term follow-up is necessary.

Aged↗

PubMed2000

[Retrograde continuous cold blood cardioplegia for combined aortic valve replacement and coronary artery bypass grafting].

Efficacy of retrograde continuous cold blood cardioplegia (RCBC) during aortic valve replacement combined with coronary bypass grafting was studied. Forty patients underwent elective aortic valve replacement, either combined with coronary bypass grafting (7 patients: group I), or isolated (33 patients: group II) using RCBC between 1996 and 1999 were analyzed retrospectively. Aortic cross clamp time was significantly prolonged in group I (150 +/- 33 min) compared to group II (109 +/- 32 min). The postoperative peak creatine kinase-MB levels were similar in both groups (73.3 +/- 23.9 versus 97.6 +/- 88.7 ng/ml). The doses of dopamine and dobutamine administered during 24 hours after surgery did not differ between the two groups (7.5 +/- 3.9 versus 6.5 +/- 5.5 mg/kg). The early (< 30-day) mortality was 0 in group I, and 3.0% in group II. These results suggest that RCBC is a safe method of myocardial protection in patients undergoing aortic valve replacement combined with coronary artery bypass grafting.

Aged↗

PubMed2000

[Combined 5-FU and CDDP in a gastric cancer patient undergoing hemodialysis--pharmacokinetics of 5-FU and CDDP].

The pharmacokinetics of 5-FU and CDDP was examined in a gastric cancer patient receiving regular hemodialysis (HD) for renal failure. The patient received combination chemotherapy of 5-FU and CDDP, then on the day of HD we measured the plasma concentration of 5-FU, total platinum, and non-protein-bound platinum of the patient. In the present case, the 5-FU concentration was kept at an almost even level during HD. Non-protein-bound platinum disappeared after being maintained in blood for a certain time when HD was started 30 minutes after the end of CDDP administration. From these findings, we conclude that combined 5-FU and low-dose CDDP therapy should be done by decreasing the dose of 5-FU, administrating CDDP only on the day the patient undergoes HD, and starting HD 30 minutes after the end of CDDP administration.

Adult↗