A surface protein antigen (PAc) of Streptococcus mutans, particularly the A-region of the molecule, has been reported to interact with salivary components on the tooth surface. It might be a candidate antigen inducing the production of antibodies against the adherence of S. mutans to the tooth surface. We investigated the effects of monoclonal antibodies (MoAbs) obtained by immunization of synthetic PAc peptides that completely correspond to the amino acid sequence of part of the A-region. These MoAbs recognize several core B-cell epitopes in the sequence. Two (KH5 and SH2) of these antibodies reacted with both S. mutans and Streptococcus sobrinus, but not with Streptococcus sanguis, Streptococcus salivarius, Porphyromonas gingivalis or Lactobacillus casei. They clearly inhibited the real-time adherence of S. mutans to salivary components in a biosensor. KH5, which showed a real-time inhibition (71%), also significantly prevented the recolonization of S. mutans on the tooth surface in rats. These results suggested that the core B-cell epitope (-Y---L--Y----) recognized by KH5 was the essential sequence in the antigenic epitopes of PAc protein recognized specifically by the inhibitory antibody. Therefore, the amino acid residues were found to be important in the initial attachment of S. mutans to the tooth surface. These results provide for the mechanism of PAc molecule in the initial attachment of S. mutans on the tooth surface and more effective designs for the removal of S. mutans and S. sobrinus from the oral cavity.

Adhesins, Bacterial↗

PubMedDate not supplied

High-sensitivity antitumor drug sensitivity testing.

For antitumor drug sensitivity testing we have been performing the succinic dehydrogenase inhibition test using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). A new tetrazolium salt 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl-amino) carbonyl]-2H-tetrazolium hydroxide (XTT) has been synthesized recently, and we have been conducting basic studies using it. We were able to obtain a high degree of sensitivity by adding phenazine methosulfate as a promoter in this assay. In these assays, there was a positive correlation between absorbance and cell count and XTT assay was more sensitive than MTT assay. In XTT assay, the production of formazan increases with reaction time over a protracted period of time, we assessed the possibility of performing assays with fewer cells than MTT was used. The results using cancer cell lines showed that when reacted for a longer time (6 h), it was possible to perform adequate assays using this method with 5,000 cells per well, and it will be useful when the amount of biopsy specimen is limited. We also evaluated the inhibition index of each of the drugs, comparing it with the MTT assay.

Cell Count↗

PubMedDate not supplied

Cancer risk in space due to radiation assessed by determining cell lethality and mutation frequencies of prokaryotes and a plasmid during the Second International Microgravity Laboratory (IML-2) Space Shuttle experiment.

We participated in a space experiment conducted during the 2nd International Microgravity Laboratory Mission (IML-2) project. The aim of our study was to investigate the effects of space radiation, i.e., high-LET (linear energy transfer) cosmic radiation, on living organisms in the 'Realtime Radiation Monitoring Device (RRMD)'. The biological samples, dried E. coli DNA repair-deficient mutant cells and shuttle vector plasmid pZl89 DNA, were prepared and placed in a biospecimen box sandwiched between 'Harzlas' plastic radiation detectors. This box was then loaded into the RRMD sensor unit in the Space Shuttle 'Columbia' and an identical box was left in the NASA John F. Kennedy Space Center (KSC) as a control. 'Columbia' (flight No. STS-65) was launched from KSC in Florida, USA on July 8, 1994. The mission duration was 14.75 days and after 'Columbia' returned to earth, we studied (i) the lethal and mutagenic effects of high-LET cosmic radiation on E. coli mutants and (ii) the relationship between high-LET cosmic radiation and the mutation frequency of pZ189 DNA. There were virtually no differences between the cell viabilities of the space and control samples of Escherichia coli KMBL3835 (wild-type), KY383 (lexA-), KY385 (recA-) and KY386 (uvrA-), nor between the mutation frequency ratios of the space and control E. coli mutant samples. Furthermore, the survival and mutation frequency of the supF gene of pZ189 DNA space samples did not differ from those of the control samples. We concluded there was no cancer risk during this Space Shuttle flight.

Cosmic Radiation↗

PubMedDate not supplied

Comparison of effects of doxorubicin and radiation on p53-dependent apoptosis in vivo.

The effects of doxorubicin and radiation on apoptosis, p53 expression, and tumor growth in human tumor xenografts were investigated. Human ependymoblastoma (NNE), primitive neuroectodermal tumor (YKP), glioblastoma (KYG) and small cell lung carcinoma (GLS) that are all transplantable to nude mice were treated with doxorubicin (8 mg/kg) or radiation (1 Gy). The histological study was performed by using TUNEL and p53 staining. Cytotoxic effects of doxorubicin and radiation were compared with no-treatment group by the growth curves and apoptotic index of tumor to each treatment. In NNE with wild-type p53, doxorubicin induced growth delay of tumors (tumor volume doubling time; 13.7+/-3.3 days in control group vs 30.4+/-1.5 days in doxorubicin group), but no growth delay of tumors in KYG and GLS with mutant type p53. While radiation-induced apoptosis appeared most frequently at 6 h after irradiation, doxorubicin-induced apoptosis had a tendency to appear later. Furthermore, although the frequency of doxorubicin-induced apoptosis was lower than that of apoptosis by 1 Gy irradiation, apoptotic cells appeared for many hours after the treatment. Doxorubicin-induced apoptosis may be correlated with p53 phenotype because apoptosis was induced only in tumor with wild-type p53, but it appeared less frequently and later than radiation-induced apoptosis.

Animals↗