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Biomedical subjects

S Shigeta

Publications and source records attributed to S Shigeta.

At least 109 records · Page 6Linked to original sources
PubMed1996

Effective ribavirin concentration in hamster brains for antiviral chemotherapy for subacute sclerosing panencephalitis.

The ribavirin concentration in hamster brains was measured by a high-performance liquid chromatography (HPLC) system and a bioassay system. When ribavirin was administered intracranially at a dosage of 10 mg/kg of body weight per day for 10 days, a dosage which results in 100% survival of hamsters infected with subacute sclerosing panencephalitis (SSPE) virus and which inhibits the replication of SSPE virus in hamster brains, the ribavirin concentration in the brains estimated by HPLC and bioassay was kept higher than 50 micrograms/g for 10 days. The effective concentration in vivo corresponds to the concentration at which ribavirin completely inhibits the replication of SSPE virus in vitro. The maximal tolerable ribavirin concentration for hamsters was calculated to be 150 micrograms/g. Although ribavirin shows toxicity to the animals at a relatively low concentration (250 to 400 micrograms/g), intrathecal or intraventricular administration of ribavirin should be explored for potential use in the treatment of patients with SSPE, while the ribavirin concentration in cerebrospinal fluid or brain tissue should be monitored.

Animals↗
PubMed1996

Mechanism of selective inhibition of human immunodeficiency virus by ingenol triacetate.

Ingenol 3,5,20-triacetate (ITA), one of the ingenol derivatives, is a selective inhibitor of human immunodeficiency virus (HIV) replication in vitro. ITA inhibited the replication of HIV strains in MT-4 cells at concentrations of 0.051 to 0.65 microM. This concentration was approximately 10(3)-fold lower than its cytotoxic threshold. The mechanism of action of ITA is primarily attributed to the inhibition of viral adsorption to the host cells, but it is distinct from the mechanism of inhibition by other adsorption inhibitors.

Antiviral Agents↗
PubMed1996

Combination therapy of Pseudomonas aeruginosa pyelonephritis in neutropenic mice with human antilipopolysaccharide monoclonal antibody and cefsulodin.

PURPOSE: These studies were designed to determine the combined inhibitory effect of a human monoclonal antibody (MAb) and cefsulodin on Pseudomonas aeruginosa renal infection in a neutropenic condition. MATERIALS AND METHODS: Protection against the infection of mice was estimated by survival rate and bacterial numbers in the kidney and blood. Opsonophagocytic assay by human polymorphonuclear neutrophils (PMNs) and fluorescence activated cell sorter (FACS) analysis were also examined. RESULTS: Treatment of infected mice with MAb combined with a suboptimal dose of cefsulodin prevented the mice from developing pyelonephritis and bacteremia and resulted in a significantly higher survival rate than treatment with either MAb or cefsulodin alone (p < 0.01). When bacteria were preexposed to cefsulodin, a significant enhancement in opsonophagocytic killing with MAb was observed. Fluorescence activated cell sorter analysis suggested that the bacteria incubated with 1/4 minimal inhibitory concentration (MIC) of cefsulodin showed greater binding of MAb to bacteria than the control. CONCLUSION: The combination therapy with human antilipopolysaccharide MAb and cefsulodin is useful for P. aeruginosa pyelonephritis in neutropenic hosts.

Animals↗
PubMed1996

[Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1994). I. Susceptibility distribution].

The frequencies of isolation and susceptibilities to antimicrobial agents were investigated on 567 bacterial strains isolated from patients with urinary tract infections in 10 hospitals during the period of June 1994 to May 1995. Of the above total bacterial isolates, Gram-positive bacteria accounted for 26.8% and a majority of them were Enterococcus faecalis. Gram-negative bacteria accounted for 73.2% and most of them were Escherichia coli. 1. Enterococcus faecalis. Ampicillin (ABPC) and imipenem (IPM) showed the highest activities against E. faecalis isolated from patients with urinary tract infections. The MIC90s of them were 1 microgram/ml. Vancomycin (VCM) was also active with the MIC90 of 2 micrograms/ml. Piperacillin (PIPC) and biapenem (BIPM) were also active with the MIC90s of 4 micrograms/ml and 8 micrograms/ml, respectively. The others were not so active with the MIC90s of 16 micrograms/ml or above. 2. Staphylococcus aureus including MRSA. VCM showed the highest activities against S. aureus isolated from patients with urinary tract infections. Its MIC90 was 1 microgram/ml against both S. aureus and MRSA. Arbekacin (ABK) was also active with the MIC90 of 2 micrograms/ml. The others except minocycline (MINO) were not so active with the MIC90s of 64 micrograms/ml or above. 3. Staphylococcus epidermidis. MINO showed the strongest activity against S. epidermidis isolated from patients with urinary tract infections. Its MIC90 was 0.25 microgram/ml. ABK was also active with the MIC90 of 1 microgram/ml. Cephems were active with the MIC90s of 2 approximately 16 micrograms/ml, but penicillins and quinolones were not so active with the MIC90s and 64 approximately 128 micrograms/ml. 4. Citrobacter freundii. Gentamicin (GM) showed the highest activities against C. freundii isolated from patients with urinary tract infections. Its MIC90 was 1 microgram/ml. IPM was also active with the MIC90 of 2 micrograms/ml. Cefpirome (CPR) and cefozopran (CZOP) were also active with the MIC90s of 4 micrograms/ml and 8 micrograms/ml. The others were not so active with the MIC90s of 32 micrograms/ml or above. 5. Enterobacter cloacae. IPM showed the highest activities against E. cloacae. Its MIC90 was 0.5 microgram/ml. GM and amikacin (AMK), ciprofloxacin (CPFX) and tosulfloxacin (TFLX) were also active with the MIC90s of 4 micrograms/ml. Penicillins and cephems except latamoxef (LMOX), cefmenoxime (CMX), CPR and CZOP showed lower activities with the MIC90s of 256 micrograms/ml or above. 6. Escherichia coli. Most of antimicrobial agents were active against E. coli. CPR, CZOP, IPM, carumonam (CRMN), CPFX and TFLX showed the highest activities against E. coli. The MIC90s of them were 0.125 microgram/ml or below. Cefotiam (CTM), flomoxef (FMOX) CMX, ceftazidime (CAZ), and LMOX were also active with the MIC90s of 0.25 microgram/ml. Penicillins were not so active with the MIC90s of 128 micrograms/ml or above. 7. Klebsiella pneumoniae. CRMN showed the highest activities against K. pneumoniae. Its MIC90 was < or = 0.125 microgram/ml. CZOP was also active with the MIC90 of 0.25 microgram/ml. Penicillins were not so active with the MIC90s of 128 micrograms/ml or above. 8. Proteus mirabilis. P. mirabilis was susceptible to a majority of drugs. CMX, CAZ, LMOX, CRP, cefpodoxime (CPDX), CRMN, CPFX and TFLX showed the highest activities against P. mirabilis isolated from patients with urinary tract infections. The MIC90s of them were 0.125 microgram/ml or below. MINO was not so active with the MIC90 of 128 micrograms/ml. 9. Pseudomonas aeruginosa. Most of the agents were not so active against P. aeruginosa. IPM showed MIC90 of 8 micrograms/ml. The others were not so active with the MIC90s of 16 micrograms/ml or above. CPFX showed MIC50 of 0.5 microgram/ml.

Anti-Bacterial Agents↗
PubMed1996

[Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1994). II. Background of patients].

Clinical background was investigated on 628 bacterial strains isolated from patients with urinary tract infections (UTIs) in 10 hospitals during period from June, 1994 to May, 1995. 1. Distributions of sex, age and urinary tract infections Among over sixties males, the majority was taken by complicated urinary tract infections. Among females, the uncomplicated urinary tract infections was most frequent without a relation of age. As for over 40 females, the increase of complicated UTI was admitted. 2. Distribution of sex, age and pathogens isolated from UTIs In uncomplicated UTIs, Escherichia coli was most frequently isolated without a relation of age, and next Enterococcus faecalis and CNS. In complicated UTIs without indwelling catheter, E. coli, Pseudomonas aeruginosa and E. faecalis were isolated the most frequent. In complicated UTIs with indwelling catheter, P. aeruginosa was most frequently isolated, and next E. faecalis and Staphylococcus aureus. 3. Administration of antimicrobial agents and pathogens isolated from UTIs In uncomplicated UTIs, pathogens, after administration of antibiotics, isolated from patients have obviously decreased from 216 to 32 isolates. And also, pathogens of complicated UTIs without indwelling catheter, have decreased from 127 to 50 isolates. However, in complicated UTIs with indwelling catheter, pathogens after or before administration of antibiotics, were not revealed an obvious change. 4. Pathogens and UTIs with or without factor and operation In uncomplicated UTIs with or without factor and operation, E. coli was mainly detected. In complicated UTIs without indwelling catheter and with factor and operation E. faecalis was mainly detected, and next E. coli, S. aureus and P. aeruginosa. Without factor and operation, E. coli was mainly detected. In complicated UTIs with indwelling catheter and with factor and operation, P. aeruginosa, E. faecalis and S. aureus were mainly detected at 23.5%, 15.0%, 15.0%, respectively. Without factor and operation, Proteus spp. 22%, and next E. faecalis and P. aeruginosa 10% and 12%, were detected, respectively. The distribution of pathogens, in the case of Proteus spp. and P. aeruginosa has been obviously varied by the influence of factor and operation.

Adolescent↗
PubMed1996

[Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1994). III. Secular changes in susceptibility].

Susceptibilities of Enterococcus faecalis, Staphylococcus aureus, Citrobacter spp., Enterobacter spp., Escherichia coli, Klebsiella spp., Proteus mirabilis, Pseudomonas aeruginosa and Serratia spp. isolated from patients with urinary tract infections (UTIs) in 10 hospitals during June 1994 to May 1995 to various antimicrobial agents were compared with those in the same period of previous years according to a classification, uncomplicated UTIs, complicated UTIs without indwelling catheter, and complicated UTIs with indwelling catheter. No remarkable changes were found in susceptibilities of Citrobacter spp., Enterobacter spp. and Serratia spp. The susceptibilities of E. faecalis to amikacin and quinolones were better than those in 1993. As for S. aureus, susceptible strains to all drugs increased in uncomplicated UTIs. Against E. coli in 1993, the antimicrobial activities of piperacillin, cefotiam and aminoglycosides have decreased, however, in 1994, these activities have turned to the better state. As for Klebsiella spp. susceptible strains to ABPC decreased. The susceptibilities of P. mirabilis to all drugs except minocycline were good. Against P. aeruginosa in 1993, the activities of aminoglycosides have decreased, but, in 1994, these activities have turned to the better state. These data should be considered in clinical treatment of various urinary tract infections.

4-Quinolones↗
PubMed1995

Superantigen toxic shock syndrome toxin-1 (TSST-1) enhances the replication of HIV-1 in peripheral blood mononuclear cells through selective activation of CD4+ T lymphocytes.

Staphylococcus aureus has been recognized as a common cause of bacteremia of such infections in human immunodeficiency virus type 1 (HIV-1)-seropositive patients. Some staphylococcal exotoxins are recognized as superantigens. We have found that superantigen toxic shock syndrome toxin-1 (TSST-1) brings about a high level of viral production in HIV-1-infected peripheral blood mononuclear cells (PBMCs) through their activation in vitro. The p24 antigen level in the culture supernatant markedly increased in the presence of TSST-1 at a concentration of 1 pg/ml or higher. Fluorescent-activated cell sorter analysis revealed that TSST-1 specifically activated CD4+ T lymphocytes. Although significant production of tumor necrosis factor alpha (TNF-alpha) was observed in uninfected PBMCs treated with TSST-1 after 96 h of incubation, much earlier (after 12 h of incubation) production of TNF-alpha was identified in HIV-1 infected PBMCs with or without TSST-1 treatment. The addition of anti-TNF-alpha antibody to the culture medium resulted in a dramatic decrease in HIV-1 replication. These results suggest that the enhanced replication of HIV-1 by TSST-1 in PBMCs is attributable mainly to the activation of CD4+ T lymphocytes and that the induction of TNF-alpha further enhances replication. Since the enhancement of HIV-1 replication by TSST-1 occurs in a concentration range of picograms per milliliter, the superantigen TSST-1 may play an important role in the pathogenesis and clinical course of HIV-1 infections.

Antibodies↗
PubMed1995

Synthesis and antiviral activity of 6-benzyl analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) as potent and selective anti-HIV-1 agents.

Several 6-benzyl analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (1; HEPT) were synthesized and evaluated for their anti-HIV-1 activity. LDA (lithium diisopropylamide) lithiation of 5-ethyluracil derivatives 7 and 8 and subsequent reaction with an aryl aldehyde gave 6-(arylhydroxymethyl)-5-ethyluracil derivatives 9-12. 6-(Arylhydroxymethyl)-5-isopropyluracil derivatives 15-18 were prepared from the 5-isopropyl-2-thiouracil derivatives 13 and 14 by the above procedure following oxidative hydrolysis of the thione. Preparation of the target 5-alkyl-1-(alkoxymethyl)-6-benzyluracil derivatives 27-34 was carried out by acetylation of 9-14 followed by Pd-catalyzed hydrogenolysis. The 1-butyl- (37 and 39) and 1-(2-methoxyl)- (38 and 40) 5-alkyl-6-benzyluracils were synthesized by 1-alkylation of the 3-phenacyl derivatives 35 and 36 with alkyl halides followed by deprotection of the 3-phenacyl group. Compounds synthesized in this study inhibited HIV-1 replication in MT-4 cells in the submicromolar to namomolar concentration range. From this series of compounds, 6-benzyl-1-(ethoxymethyl)-5-isopropyluracil (33) was selected for clinical evaluation.

Animals↗
PubMed1995

In vitro antiviral activities of sulfated polysaccharides from a marine microalga (Cochlodinium polykrikoides) against human immunodeficiency virus and other enveloped viruses.

A marine microalga, Cochlodinium polykrikoides, produces extracellular sulfated polysaccharides. Isolation and purification of the polysaccharides were accomplished by precipitation with ethanol and Cetavlon, followed by DEAE-cellulose column chromatography (polysaccharides A1 and A2). These polysaccharides, which were homogeneous when analysed by both ultracentrifugal and electrophoretic methods, were composed of mannose, galactose, glucose and uronic acid, together with sulfate groups (S = 7-8% w/w). Both A1 and A2 inhibited the cytopathic effect of influenza virus types A and B in MDCK cells, that of respiratory syncytial virus types A and B in HEp-2 cells, that of human immunodeficiency virus type 1 in MT-4 cells; and, except A1 for herpes simplex virus type 1 and A2 for parainfluenza virus type 2 in HMV-2 cells, the cochlodinium polysaccharides showed no antiviral activity against parainfluenza virus types 2 and 3, measles virus, mumps virus or herpes simplex virus type 1 in HMV-2 cells. No cytotoxicity for host cells was observed with these polysaccharides at a concentration of 100 micrograms ml-1. Inhibitory effects on various viruses were achieved at concentrations that were not markedly inhibitory to the blood coagulation process.

Animals↗
PubMed1995

Use of lactate dehydrogenase to evaluate the anti-viral activity against influenza A virus.

The detection of lactate dehydrogenase (LDH) can be used to evaluate efficiently anti-influenza A virus agents. LDH levels in the virus-infected Madin-Darby canine kidney cell cultures were significantly higher than in controls, were in proportion to the degree of virus infection, and corresponded to a decrease in mitochondrial dehydrogenase activity as assayed using a tetrazolium colorimetric assay (MTT method). The EC50 value and cytotoxicity of ribavirin, 3-deazaguanine, pyrazofurin, and carbodine against influenza A virus as measured by the LDH detection method was equivalent to that derived by the MTT method.

Amides↗
PubMed1995

Analysis of mutations in the thymidine kinase gene of varicella zoster virus associated with resistance to 5-iodo-2'-deoxyuridine and 5-bromo-2'-deoxyuridine.

We have analyzed mutations in the thymidine kinase (TK) gene of varicella zoster virus (VZV) which showed resistance to 5-iodo-2'-deoxyuridine (IDU) and 5-bromo-2'-deoxyuridine (BrDU). Through sequencing of the TK gene, we found three amino acids were exchanged (41 Asn-->Ser, 266 Cys-->Ile, 288 Ser-->Leu). These mutations were not located at either the nucleoside- or the ATP-binding site. This result suggests that the resistance to IDU and BrDU in this particular strain is due to the change in conformation of TK rather than the replacement of amino acids in the binding sites.

Amino Acid Sequence↗
PubMed1995

Immunochemical characterization of recombinant and native tropomyosins as a new allergen from the house dust mite, Dermatophagoides farinae.

BACKGROUND: Two predominant mite species, Dermatophagoides farinae and Dermatophagoides pteronyssinus, are responsible for the immediate hypersensitivity reaction. Although a large number of antigens and allergens was detected in a whole mite culture extract, only the major allergens of Der I and II groups have been extensively studied. Much information on other important allergens remains to be accumulated. METHODS: A new allergen complementary DNA (cDNA) clone was isolated from a D. farinae protein cDNA library. The expression product of the cDNA and native tropomyosin from D. farinae were purified, characterized, and evaluated. RESULTS: An amino acid sequence deduced from the cDNA clone revealed significant homology with tropomyosins conserved in a wide range of animals. The amino acid sequences of two fragments obtained by degradation of the purified protein with cyanogen bromide coincided completely with the corresponding portions of the deduced amino acid sequence. The native tropomyosin reacted with specific IgE in the 31 sera tested at a high frequency (80.6%), comparable to that of Der f I (90.3%) and Der f II (74.2%). CONCLUSIONS: The cloned cDNA encodes tropomyosin. The high binding response of specific IgE antibodies to recombinant and native tropomyosins demonstrates that mite tropomyosin is an additional important allergen in house dust mite.

Allergens↗
PubMed1995

Anti-Tat MTT assay: a novel anti-HIV drug screening system using the viral regulatory network of replication.

Since the recognition of its pivotal role in viral replication, Tat activity has become an interesting target for chemotherapeutic intervention of HIV infection. Here, we report a sensitive and simple colorimetric assay for the screening of Tat inhibitors. We have constructed a plasmid that contains the hygromycin B phosphotransferase gene under the control of the HIV-1 long terminal repeat (LTR) and HIV-1 tat gene constitutively expressed from the cytomegalovirus promoter. This plasmid has been stably transfected to the CD4+ T cell line CEM, which is rendered resistant to hygromycin B through the action of Tat. The inhibitory activity of the anti-Tat drugs was assessed by the extent of cytotoxicity in the presence of hygromycin B as a consequence of the suppressed expression of the hygromycin B phosphotransferase gene. Spectrophotometric quantitation of cell viability was done utilizing 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) dye as the indicator. Using this assay system, we have confirmed that known anti-Tat compound Ro5-3335 and its derivative Ro24-7429 could inhibit Tat-mediated gene expression although their selectivities (anti-Tat activity versus nonselective cytotoxicity) were narrow. Since this method offers the advantage of not handling infectious particles or radioactive materials, it can offer wide applicability as a screening system for anti-Tat compounds.

Antiviral Agents↗
PubMed1995

Potent and specific inhibition of human immunodeficiency virus type 1 replication by 4-(2,6-dichlorophenyl)-1,2,5-thiadiazol-3-Y1 N,N-dialkylcarbamate derivatives.

4-(2,6-Dichlorophenyl)-1,2,5-thiadiazol-3-yl N,N-dialkylcarbamate (TDA) derivatives were found to be highly potent and specific inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in a variety of cell cultures. The most potent congener of TDA derivatives, RD4-2024, inhibited HIV-1 replication by 50% at concentrations of 12.5 and 4.8 nM in MT-4 cells and peripheral blood mononuclear cells, respectively. These concentrations were more than 2,000- and 30,000-fold lower than its 50% cytotoxic concentrations, respectively. Although the TDA derivatives were active against 3'-azido-3'-deoxythymidine-resistant HIV-1, no antiviral activities were observed against HIV-2 and nonnucleoside reverse transcriptase inhibitor-resistant mutants of HIV-1. The TDA derivatives inhibited recombinant HIV-1 reverse transcriptase activity, depending on the template-primer used for the assay. However, they did not interact with HIV-2 reverse transcriptase. Thus, the TDA derivatives belong to the family of nonnucleoside reverse transcriptase inhibitors. Because of their potent anti-HIV-1 activities in vitro and their low levels of toxicity in mice, the TDA derivatives deserve further evaluation as candidate drugs for the treatment of patients with AIDS.

Antiviral Agents↗
PubMed1995

Inhibitory effect of pyridobenzazoles on virus replication in vitro.

Twelve species of pyridobenzazoles and pyrimidobenzimidazole were examined as inhibitors of the replication of respiratory syncytial virus (RSV) in HeLa cells. From the pyridobenzazoles studied, 2-benzamido-4-cyano-1-oxo-1H,5H-pyrido[1,2-alpha]benzimidazol emerged as a potent inhibitor of the RSV. Based on its inhibitory effect on the cytopathogenicity of the RSV in HeLa cells, the 50% effective dose was found to be 0.95 micrograms/ml. The cytotoxicity of this compound for HeLa cells was examined by monitoring the incorporation of radiolabeled uridine into cellular RNA. The selectivity index was ca. 30, the same as Virazole.

Antiviral Agents↗
PubMed1995

A screening system for antiviral compounds against herpes simplex virus type 1 using the MTT method with L929 cells.

We developed the improved MTT assay system for in vitro evaluation of anti-HSV-1 agents using L929 cells derived from mouse connective tissue. This assay system provides results in 4 days using a 96-well microplate. The EC50 values of several anti-HSV agents (ACV, BVaraU, and others) were found to be similar to those obtained by the plaque reduction method using MRC-5 cells. The present MTT assay is rapid, accurate, and may be useful as an automatic screening system for evaluation of anti-HSV-1 compounds.

Animals↗
PubMed1995

A colorimetric LDH assay for the titration of infectivity and the evaluation of anti-viral activity against ortho- and paramyxoviruses.

A rapid and precise screening assay was developed for in vitro evaluation of anti-orthomyxo- and anti-paramyxovirus agents. The procedure is spectrophotometrical assessment for viability of cells via extracellular leakage of lactic dehydrogenase (LDH). HMV-II cells, a human melanoma cell line was found to be suitable for the titration of virus infectivity and screening of anti-viral agents for orthomyxo- and paramyxoviruses. Comparative titration of infectivity of stock viruses by the LDH and the MTT in site reduction of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) methods with HMV-II cells as well as plaque titration with MDCK, Vero and HeLa cells was carried out. The LDH method was comparable or more sensitive for influenza viruses (FLUV)-A, B, C, parainfluenza viruses (PFLUV)-1, 2 and less sensitive for PFLUV-3, mumps virus (MPSV), measles viruses (MLSV) and respiratory syncytial virus (RSV) than the plaque titration. The 50% effective concentration (EC50) of 1-beta-D-ribofuranosyl-1, 2, 4-triazol-3-carboxamide (ribavirin) and 5-ethynyl-1-beta-D-ribofuranosyl-imidazole-4-carboxamide (EICAR) against orthomyxo- and paramyxoviruses were examined comparatively by the LDH, MTT and plaque reduction (PR) methods. The EC50 values of FLUV-C and PFLUV-1 were able to be evaluated only by the LDH but not by the MTT and PR methods. The LDH method with HMV-II cells simplifies the assay procedure and permits the evaluation of a large number of compounds for anti-orthomyxo- and anti-paramyxoviruses activity in vitro.

Antiviral Agents↗