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Biomedical subjects

N Ohta

Publications and source records attributed to N Ohta.

At least 271 records · Page 15Linked to original sources
PubMed1985

Transcriptional regulation of a periodically controlled flagellar gene operon in Caulobacter crescentus.

Temporal regulation of flagellar gene expression in Caulobacter crescentus has been examined by a detailed analysis of the flbG-flaJ-flbH-flaK hook operon. The approximate location of the promoter for this 4.4 X 10(3) base-pair transcriptional unit was determined by deletion mapping, and the flaK gene was shown by nucleotide sequencing to code for the hook protein. flaK messenger RNA was quantified by S1 nuclease mapping with an internal restriction fragment of the gene as the 5'-labeled DNA probe. The results of these assays provide the first direct evidence that periodic expression of a flagellar gene in the C. crescentus cell cycle is regulated at the transcriptional level. The effect of altering the time of gene duplication in the cell cycle was examined by subcloning the complete hook operon on a plasmid that replicates throughout the S phase. The normal periodicity of flaK transcription and translation was maintained in this merodiploid strain, which suggests that replication alone is not sufficient to initiate flagellar gene expression. We also show that the three adjacent transcriptional units III, IV and V are required in trans for transcription of the book operon, and we discuss the possible role of these genes in the hierarchical regulation of the flagellar gene expression.

Bacterial Proteins↗
PubMed1985

Synthesis of a nonacosapeptide (beta-fragment) corresponding to the N-terminal sequence 1-29 of human liver metallothionein II and its heavy metal-binding properties.

A nonacosapeptide (beta-fragment) corresponding to the N-terminal sequence 1-29 of human liver metallothionein II was synthesized by the fragment condensation method. The Cd-binding ability of the beta-fragment was much stronger than that of cysteine as thionein and synthetic alpha-fragment corresponding to the C-terminal sequence 30-61 of human liver metallothionein II. Both the alpha- and beta-fragments bound preferentially to Cu ions rather than Cd ions.

Amino Acid Sequence↗
PubMed1985

Serum levels of estrogens and testosterone in cirrhotic men with and without hepatocellular carcinoma.

Serum levels of estrogens and testosterone were measured in 25 male patients with hepatocellular carcinoma and associated cirrhosis of the liver and in another 25 male patients with cirrhosis only. The two groups were statistically comparable in terms of age distribution, duration of liver disease, incidence of alcohol abuse, incidence of hepatitis B surface antigenemia, and grade of hepatic dysfunction. Estrone was significantly elevated in both groups of patients. Estradiol concentrations were above normal in 10 patients with hepatocellular carcinoma and in 11 with cirrhosis only. All patients had normal concentrations of estriol. There were no statistical differences between the two groups in either individual or total estrogen levels (estrone 0.05 less than p less than 0.1). Eight of the patients with hepatocellular carcinoma and 5 of the cirrhotics had lower testosterone levels than normal, but this difference was not significant. However, the estrone to testosterone ratios were significantly higher in the hepatocellular carcinoma group than in the cirrhosis group (p less than 0.05). The present study seems to indicate that hyperestrogenemia commonly seen in male patients with liver cirrhosis may play some role in hepatic carcinogenesis of cirrhotic livers. Further studies are needed to determine if the estrone to testosterone ratio is implicated in hepatocarcinogenesis in cirrhotic men.

Adult↗
PubMed1985

The principal pathway from the piriform cortex to the deep amygdaloid nuclei in the cat.

Pathways relaying olfactory information to the deep amygdaloid nuclei (AMYGd) were analyzed with electrophysiological techniques in anesthetized cats. Stimulation of the piriform cortex (PC) produced orthodromic spikes in some AMYGd neurons with a mean latency of 12.2 ms and antidromic responses in other neurons with a mean latency of 9.3 ms. Stimulation of the AMYGd produced antidromic spikes in some PC neurons with a mean latency of 11.5 ms. Some neurons in the entorhinal area (EA) were activated orthodromically from the PC with a mean latency of 22 ms, and a proportion of these cells was also activated antidromically from the AMYGd. Some neurons in the agranular insular cortex were activated orthodromically from the PC, but none of them responded antidromically to AMYGd stimulation. From these observations, it is suggested that olfactory information reaches the AMYGd directly from the PC or indirectly via the EA, and that the direct path conveys the major olfactory input from the PC to the AMYGd.

Amygdala↗
PubMed1985

Analysis of human class II antigens by cloned cytolytic T cell reagents: a study using HLA loss mutant lymphoblastoid cell lines and monoclonal antibodies detecting the HLA-DP product(s).

We have utilized cloned T cell reagents and ionizing radiation-induced mutants of an HLA heterozygous lymphoblastoid cell line (LCL) to investigate the determinants detected by the cell-mediated lympholysis (CML) assay. Cells of an LCL clone, 721.501, an HLA haplotype loss mutant expressing the HLA-A2-Cw1-Bw51-DR1-Dw1-DQw1-DPw2-GLO haplotype were used as sensitizing cells for responder cells in vitro. "Cloned" reagents were generated by single-cell deposition of cells of a bulk reagent primed against 721.501 cells. Those clones were screened for cytolytic activity against HLA loss mutant targets (derived from LCL 721) of four different categories; HLA-A2 loss only, A2-Cw1-Bw51 loss, A2-Cw1-Bw51-DR1-DQw1 loss, and the entire HLA haplotype loss. Of 196 clones tested, 36 were cytolytic, including three anti-A2, five anti-Bw51/Cw1, 12 anti-DR1/DQw1, 13 anti-DP region associated with DPw2, and three of undetermined specificity, based on cytolytic patterns against the HLA loss mutant targets. Of 25 anti-HLA class II lytic clones, 23 (92%) fitted the characteristics of helper cell-independent cytolytic T cells (HITc), whereas only two of eight (25%) anti-class I clones were HITc. The 13 anti-DP region clones were divided into three subgroups defined by blocking by anti-FA and not Tü39 monoclonal antibodies (MoAb), by Tü39 and not anti-FA, and by both MoAbs.

Antibodies, Monoclonal↗
PubMed1985

[Recurrence following operative treatment of renal staghorn calculi and prophylaxis].

Residual stone and stone recurrence following operation for renal staghorn calculus were investigated in 58 kidneys of 55 patients. Residual stones were found in 12 kidneys (20.7%), but cases who underwent intraoperative radiogram using Kodak X-O mat KS film or extracorporeal renal surgery showed no residual stones. True recurrence was observed in 9 kidneys (19.6%). The rates of true recurrence after partial nephrectomy, nephrolithotomy, extended pyelolithotomy and autotransplantation with extracorporeal renal surgery were 29.2%, 8.3%, 33.3% and 0% respectively. Morphological study of renal tissue removed intraoperatively from patients with staghorn calculus suggested that calcium deposits in pelvic mucosa or collecting tube might play an important role in stone recurrence. However, despite the calcium deposits in removed specimens, no recurrences have been observed in patients who underwent extracorporeal surgery for complicated staghorn calculus. Therefore, this procedure might be useful to prevent stone recurrence.

Female↗
PubMed1984

Associations between HLA and immune responses in individuals with chronic schistosomiasis japonica.

The association of an HLA specificity with low or high immune responsiveness to Schistosoma japonicum antigen (Sj) was demonstrated among individuals who had previously been exposed to S. japonicum infection. The frequency of HLA-Aw24 specificity among low responders in the IgG antibody response determined by the enzyme-linked immunosorbent assay (ELISA) was higher than that among high responders. Significant association between HLA-B7 and high responsiveness was observed in the IgE antibody response. The frequency of HLA-Bw52-Dw12 was also found to increase among individuals with higher levels of total serum IgE. These results suggest that antibody responses to Sj are regulated by an immune response (Ir) gene(s) linked to the major histocompatibility complex (MHC), although a possibility of the presence of non-MHC-linked Ir genes is not excluded. Serum IgE levels may also be controlled by a gene(s) linked to the MHC.

Adult↗
PubMed1984

Cellular basis of anti-SB response.

Cloning of cells allosensitized in vitro against SB1, SB2, and SB3 antigens was performed by micromanipulation. One hundred and twenty-six clones were tested for both proliferative and cytolytic responses; 14 proliferative, noncytotoxic clones and one clone which demonstrated both proliferative and cytotoxic reactivity specific for SB antigens were obtained. The proliferative noncytotoxic clones tested and the clone with both cytotoxic and proliferative activity were all able to produce IL-2-like activity upon specific antigen stimulation in vitro and were positive for OKT3, OKT4 but negative for OKT8. The proliferative clones fit the characteristics of helper T cell (Th) clones while the clone with both cytotoxic and proliferative reactivities is analogous to the class of antigen-driven, helper cell-independent cytotoxic (HITc) clones. No cytolytic nonproliferative SB specific clones were detected. The prevalent induction of Th clones strongly suggests that the biological function of SB antigens is similar to other class II antigens of HLA. The existence of an SB specific HITc clone demonstrates that a determinant on an SB molecule can induce both proliferative and cytolytic responses.

Antibodies, Monoclonal↗
PubMed1984

Bredinin treatment in clinical kidney allografting.

Bredinin, a new nucleoside antibiotic isolated from Eupenicillium brefeldianum, and steroids were used as immunosuppressive agents in 31 renal transplant patients; 17 of them received grafts from living-related donors and 14 from cadavers. The one-year graft survival rates were 100% in renal recipients from living donors and 69.2% in cadaver kidney recipients. There was no serious complication from the use of these immunosuppressive agents.

Adolescent↗
PubMed1984

Physical mapping and complementation analysis of transposon Tn5 mutations in Caulobacter crescentus: organization of transcriptional units in the hook gene cluster.

Using the cloned DNA from the hook protein gene region of Caulobacter crescentus ( Ohta et al., Proc. Natl. Acad. Sci. U.S.A. 79:4863-4867, 1982), we have identified and physically mapped 19 Tn5-induced and 2 spontaneous insertion mutations to this region of the chromosome. These nonmotile mutants define a major cluster of fla genes that covers approximately 17 kilobases on the chromosome (hook gene cluster). Complementation analysis of the mutants using DNA fragments from the region subcloned in the broad host range plasmid pRK290 has shown that these fla genes are organized into at least five transcriptional units (I to V). Transcriptional unit II contains at least one gene in addition to the hook protein gene, which makes this the first operon described in C. crescentus. Expression of the hook protein gene and the genetically unlinked flagellin A and B genes by this set of mutants also furnishes additional insights into the hierarchial regulation of flagellar genes. We have found that the spontaneous insertion mutant ( SC511 ) of the hook protein gene ( flaK ) makes no flagellin A or B and that genes downstream from the hook protein gene are required in trans for expression of the hook protein operon and the flagellin A and B genes. Recombination and complementation results thus place flaK , flaJ , flaN , and flaO (R. C. Johnson and B. Ely , J. Bacteriol . 137:627-634, 1979) in the hook gene cluster, identify at least three new genes ( flbD , flbG , and flbF ), and suggest that this cluster may contain several additional, as yet unidentified, fla genes.

Bacterial Proteins↗