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Biomedical subjects

S Sakurai

Publications and source records attributed to S Sakurai.

355 records · Page 20Linked to original sources
PubMedDate not supplied

Juvenile hormone-mediated termination of larval diapause in the bamboo borer, Omphisa fuscidentalis.

Larvae of the bamboo borer, Omphisa fuscidentalis are in diapause for more than nine months (Singtripop, T., Wanichaneewa, S., Tsuzuki, S., Sakurai, S. 1999. Larval growth and diapause in a tropical moth, Omphisa fuscidentalis Hampson. Zool. Sci. 16, 725-733). To examine the endocrine mechanisms underlying this larval diapause, we assayed the responsiveness of the diapausing larvae to 20-hydroxyecdysone (20E) and a juvenile hormone analogue (JHA: S-methoprene). 20E injection caused the larvae to halt movement, followed by deposition of a pupal cuticle. Topical application of JHA induced pupation in a dose-dependent manner. JHA also induced pupation of the larvae whose brains were removed before JHA application. In those larvae, the prothoracic glands became active and competent to respond to brain extracts within seven days after JHA treatment, and the hemolymph ecdysteroid concentration began to increase 12 days after JHA application. These results indicate that JHA stimulates the prothoracic glands of diapausing Omphisa larvae, terminating larval diapause, in contrast with previous findings that JH inhibits the brain-prothoracic gland axis and thus maintains the larval diapause. Current results therefore suggest a novel regulatory mechanism for larval diapause in this species.

Animals↗
PubMedDate not supplied

Inhibitory effects of MoAbs against a surface protein antigen in real-time adherence in vitro and recolonization in vivo of Streptococcus mutans.

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

Decreases of natural killer cells and T-lymphocyte subpopulations and increases of B lymphocytes following a 5-day occupational exposure to mixed organic solvents.

The authors examined the effects of organic solvents on lymphocyte subpopulations in blood. Natural killer and T-lymphocyte subpopulations and B (CD19+) -lymphocytes were measured with flow cytometry in 16 male rotogravure printers on a Friday and on the following Monday. Numbers of all 3 subpopulations of natural killer cells (i.e., CD57+ CD16+, CD57- CD16+, and CD57+ CD16- cells), 2 subpopulations of T lymphocytes (CD4+ CD45RA+ and total CD8+ cells), and total lymphocytes on Friday were significantly fewer than those found on the following Monday. Conversely, the number of B lymphocytes on Friday was significantly larger than the number on Monday. The number of B lymphocytes was significantly correlated with blood toluene levels on Friday. The alteration in the number of CD57+ CD16+ NK cells from Friday to the following Monday was correlated inversely with the corresponding change in exposure level of toluene on Friday. The authors suggest that the effects of mixed organic solvents (primarily toluene) are recoverable decreases of natural killer cells and T lymphocytes and increases in B lymphocytes.

Adult↗
PubMedDate not supplied

Selective decrease of the suppressor-inducer (CD4+CD45RA+) T lymphocytes in workers exposed to benzidine and beta-naphthylamine.

Previously, we reported a decrease of CD4+ T lymphocytes in workers exposed to benzidine and beta-naphthylamine, which are aromatic amines. In the present study, CD4+ T lymphocyte subpopulations (i.e., CD4+CD45RA+ and CD4+CD29+ cells), total CD4+ T lymphocytes, and CD8+ T lymphocytes were measured in 78 male dyestuff workers who had been exposed to aromatic amines. The aromatic amine workers consisted of 40 individuals who had engaged in production of aromatic amines (high-exposure group) and 38 workers who had handled only dyestuff in their job (low-exposure group). The control group consisted of 30 healthy male volunteers who were working at the same factory and who did not have a history of occupational exposure to aromatic amines or to other hazardous chemicals. The absolute and relative numbers of CD4+CD45RA+ (suppressor-inducer) T lymphocytes in the high-exposure group of aromatic amine workers were significantly lower than those in the control group, after controlling for the effects of age by the analysis of covariance. Similarly, the relative, but not absolute, number of total CD4+ T lymphocytes in the high-exposure group of aromatic amine workers was significantly lower than that found in the control group. It is suggested that the CD4+CD45RA+ T lymphocyte is a major site of the effects of aromatic amines on lymphocyte subpopulations.

2-Naphthylamine↗
PubMedDate not supplied

Increase in memory (CD4+CD29+ and CD4+CD45RO+) T and naive (CD4+CD45RA+) T-cell subpopulations in smokers.

To examine the effects of smoking on lymphocyte subpopulations, we measured the following cell subpopulations: CD4+ T-cell subpopulations (i.e., CD4+CD29+, CD4+ CD45RO+, and CD4+CD45RA+ cells); CD8+ T-cell subpopulations (i.e., CD8+CD11a+ and CD8+CD11b+ cells); and natural killer cell subpopulations (i.e., CD16+CD57-, CD16+CD57+, and CD16-CD57+ cells). We measured these subpopulations, together with total CD4+ T, total CD8+ T, total CD3+ T, B (CD19+), and total lymphocytes, in 10 male heavy smokers, 38 male light-to-moderate smokers, and 33 male nonsmokers. The mean ages were 30 y, 31 y, and 32 y, respectively, and ages did not vary significantly among the smokers. CD4+CD29+ and CD4+CD45RO+ (memory T) cells in heavy smokers were significantly more numerous than those in light-to-moderate smokers and nonsmokers. Also, these memory T-cell subpopulations were significantly more numerous in light-to-moderate smokers than in nonsmokers. The number of CD4+CD45RA+ (naive T) cells was significantly larger in heavy smokers than nonsmokers; numbers of CD4+CD45RO+ T and CD4+CD29+ T cells (memory T cells) were significantly correlated with daily cigarette consumption. Numbers of CD3+ T, CD4+ T, CD19+ B, and total lymphocytes in heavy smokers were significantly larger than in nonsmokers. There were significantly more CD3+ T, CD4+ T, and total lymphocytes in light-to-moderate smokers than in nonsmokers. The numbers of CD4+ T lymphocytes in heavy smokers were significantly larger than in light-to-moderate smokers. Perhaps CD4+ T cell subpopulations, especially memory T cells, are most susceptible to the effects of smoking on lymphocyte subpopulations.

Adult↗
PubMedDate not supplied

Effects of uncontrollable and controllable electric shocks on T lymphocyte subpopulations in the peripheral blood, spleen, and thymus of rats.

To examine the effects of uncontrollable and controllable electric shocks on the immune system in rats, the proportion of CD4+, CD8+ or CD25+ T lymphocytes to total lymphocytes was measured in the peripheral blood, spleen, and thymus. The rats were given either controllable shocks, identical uncontrollable shocks, or no shocks, and then small shocks 24 h later (reinstating shocks). The proportion of CD4+ T lymphocytes relative to total lymphocytes in both the peripheral blood and spleen of uncontrollable rats (URs) was significantly smaller than was found in no-shock rats (NRs). Similarly, the proportion of CD4+ T lymphocytes in the thymus of controllable rats (CRs) was significantly smaller than in NRs. In contrast, the proportion of CD8+ T lymphocytes in the thymus of URs was significantly larger than in NRs and CRs. The CD4+ to CD8+ T lymphocyte ratios (CD4+/CD8+ ratios) in the peripheral blood, spleen and thymus of URs were significantly smaller than in NRs; also, the ratios in the peripheral blood and spleen of URs were significantly smaller than in CRs. The white blood cell (WBC) count of URs was significantly smaller than those of NRs and CRs, and the WBC count of CRs was significantly smaller than those of NRs and CRs, and the WBC count of CRs was significantly smaller than that of NRs. These results suggest that decreases in CD4+ T lymphocytes (and/or an increase of CD8+ T lymphocytes) in the peripheral blood, spleen, and thymus are caused by uncontrollable stress followed by a reinstating stress condition, leading to the decrease of WBC in the peripheral blood and decreases in the CD4+/CD8+ ratios in these tissues.

Animals↗