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Biomedical subjects

N Ohta

Publications and source records attributed to N Ohta.

At least 235 records · Page 13Linked to original sources
PubMed1988

Generation and functional characterization of T cell lines and clones specific for Schistosoma japonicum egg antigen in humans.

T cell lines specific for Schistosoma japonicum egg Ag were established in vitro from patients with chronic schistosomiasis japonica, and investigated their possible immunopathologic roles by testing lymphokines production and in vitro granuloma formation assay. All lines tested had surface phenotypes of CD3+ CD4+ CD8-, and showed S. japonicum soluble egg Ag (SEA)-specific proliferation requiring HLA-DR-restricted Ag presentation. Of these fractions of SEA separated by gel filtration, Fraction II (m.w. 7,000 to 18,000) and III (m.w. 7,000) induced strong proliferation of T cell lines, whereas fraction I (m.w. 18,000+) failed to induce detectable proliferation to any T cell lines tested. One of the T cell lines was cloned by micromanipulation: two of eight clones responded only to fraction II, and six to both fractions II and III. We observed that four of eight clones tested produced IL-2 in response to SEA, and three of them were able to transfer S. japonicum egg-specific granulomatous hypersensitivity in vitro to an HLA haplo-identical individual without previous schistosome infection. These immunopathologic functions of T cell clones seemed to be activated by at least two distinct epitopes of SEA. Our present observations suggest that at least two distinct CD4+ human T cells, both of which recognize epitopes expressed on SEA molecules of less than 18 kDa, might have critical roles in granulomatous hypersensitivity to eggs of S. japonicum in humans.

Adult↗
PubMed1988

Synthesis of an insulin analogue embodying a strongly fluorescent moiety, [19-tryptophan-A]insulin.

As part of our aim to study the conformation of insulin in solution by time-resolved fluorescence spectroscopy, we have synthesized the analogue [19-Tryptophan-A]insulin. In this compound, the tyrosine residue at position 19 of the A-chain of insulin, one of the most strongly conserved residues in insulins from various species, is substituted with the strongly fluorescent tryptophan residue. [19-Tryptophan-A]insulin displays 4.1 +/- 1.9% of the potency of natural insulin in binding to the insulin receptor from rat liver plasma membranes, 5.0 +/- 2.3% in stimulating lipogenesis in rat adipocytes, and 75.7 +/- 4% of the potency of insulin in radioimmunoassay. In connection with our previous work, these data indicate that an aromatic side chain at position A19 of insulin seems necessary but not sufficient for high biological activity. We further conclude that in regard to the immunogenic determinants of insulin, tryptophan in position A19 is an essentially neutral substitution for tyrosine in that position, in sharp contrast to the situation with regard to biological activity.

Adipose Tissue↗
PubMed1988

Role of the 25-, 27-, and 29-kilodalton flagellins in Caulobacter crescentus cell motility: method for construction of deletion and Tn5 insertion mutants by gene replacement.

Caulobacter crescentus incorporates two distinct, but related proteins into the polar flagellar filament: a 27-kilodalton (kDa) flagellin is assembled proximal to the hook and a 25-kDa flagellin forms the distal end of the filament. These two proteins and a third, related flagellin protein of 29 kDa are encoded by three tandem genes (alpha-flagellin cluster) in the flaEY gene cluster (S.A. Minnich and A. Newton, Proc. Natl. Acad. Sci. USA 84: 1142-1146, 1987). Since point mutations in flagellin genes had not been isolated their requirement for flagellum function and fla gene expression was not known. To address these questions, we developed a gene replacement protocol that uses cloned flagellin genes mutagenized by either Tn5 transposons in vivo or the replacement of specific DNA fragments in vitro by the antibiotic resistance omega cassette. Analysis of gene replacement mutants constructed by this procedure led to several conclusions. (i) Mutations in any of the three flagellin genes do not cause complete loss of motility. (ii) Tn5 insertions in the 27-kDa flagellin gene and a deletion mutant of this gene do not synthesize the 27-kDa flagellin, but they do synthesize wild-type levels of the 25-kDa flagellin, which implies that the 27-kDa flagellin is not required for expression and assembly of the 25-kDa flagellin; these mutants show slightly impaired motility on swarm plates. (iii) Mutant PC7810, which is deleted for the three flagellin genes in the flaEY cluster, does not synthesize the 27- or 29-kDa flagellin, and it is significantly more impaired for motility on swarm plates than mutants with defects in only the 27-kDa flagellin gene. The synthesis of essentially normal levels of 25-kDa flagellin by strain PC7810 confirms that additional copies of the 25-kDa flagellin map outside the flaEY cluster (beta-flagellin cluster) and that these flagellin genes are active. Thus, while the 29- and 27-kDa flagellins are not absolutely essential for motility in C. crescentus, their assembly into the flagellar structure is necessary for normal flagellar function.

Bacterial Proteins↗
PubMed1988

Schistosoma japonicum egg antigen-specific T cell lines in man. Induction of helper and suppressor T cell lines and clones in vitro in a patient with chronic schistosomiasis japonica.

T cell lines (TCLs) specific for Schistosoma japonicum egg antigen were established from a patient with chronic schistosomiasis japonica to investigate the regulatory mechanism of S.japonicum egg antigen-driven T cell responses in man. All five TCLs tested were CD2+, CD4+, CD8-, and were strongly proliferative only to S. japonicum egg antigen in the absence of exogenous IL-2. All but one TCL produced IL-2-like lymphokines in vitro, indicating their helper T cell functions. One TCL, SjE-3, failed to produce IL-2-like lymphokines. Moreover, this TCL suppressed the specific proliferation of autologous peripheral blood lymphocytes to S. japonicum egg antigen. This TCL produced a soluble suppressor factor(s). These functional diversities among established TCLs were also confirmed by cloned T cells. Our observations might suggest that the regulatory system through helper and suppressor T-T interactions somehow involved in T cell responses to the egg antigen in human chronic schistosomiasis japonica.

Animals↗
PubMed1988

Flexible ureterorenoscopy.

The clinical applications of flexible ureterorenoscopes have fallen behind those of their rigid counterparts. Flexible endoscopes that possess a working channel and can also be employed for treatment have at last been developed. This instrument is particularly effective in the treatment of stones in the upper urinary tract, as it can easily follow mobile upper ureteral stones and calculi in the middle or lower renal calices, which are not as accessible with a rigid endoscope. It is important to remember not to exert too much force when inserting the instrument into the ureter, renal pelvis, or renal calices, and, if one remains calm, should the visual field become temporarily obscured, there should be little danger of damaging these structures. This method will probably be increasingly employed, not only for the treatment of stones in the upper urinary tract, but also for the removal of foreign bodies and the diagnosis and treatment of small pathologic conditions or lesions such as carcinoma in situ in which the roentgenologic presentation is unclear. For this expansion of instrument use to be ensured, it is necessary to improve the resolution of the fiberoptic endoscope image and increase the instrument's angulation capabilities, increase the range of accessories that can be employed with it, and also increase familiarity with the instruments on the part of urologists.

Endoscopes↗
PubMed1987

Order of gene replication in Caulobacter crescentus; use of in vivo labeled genomic DNA as a probe.

Two methods for determining the time of gene replication in Caulobacter crescentus using a temperature sensitive DNA synthesis mutant to synchronize chromosome replication are described. Swarmer cells, blocked before DNA initiation at 37 degrees C, initiate chromosome replication within 2 min after releasing the temperature block in 32P-orthophosphate medium, as indicated by the appearance of a small number of unique genomic DNA fragments. The time at which a given chromosome segment replicates was determined by isolating genomic DNA from cells labeled for progressively longer times during the S period of the cell cycle and hybridizing the probes to cloned C. crescentus genes. The time of replication of genetically mapped Tn5 insertions was determined by preparing DNA from the Tn5 insertion mutants that had been labeled with 32P in similar experiments and hybridizing it to lambda::Tn5 DNA. These results furnish the first correlation between the order of chromosome replication and the genetic map of C. crescentus. They also show that the times of replication and expression of the hook protein and the flagellin genes, which require DNA synthesis for their transcription, both occur near mid-S phase.

Bacterial Proteins↗