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Biomedical subjects

G Tamura

Publications and source records attributed to G Tamura.

At least 199 records · Page 11Linked to original sources
PubMed1987

Secretion of Bacillus subtilis alpha-amylase in the periplasmic space of Escherichia coli.

The Bacillus subtilis alpha-amylase structural gene (amyE) lacking its own signal peptide coding sequence was joined to the end of the Escherichia coli alkaline phosphatase (phoA) signal peptide coding sequence by using the technique of oligonucleotide-directed site-specific deletion. On induction of the phoA promoter, the B. subtilis alpha-amylase was expressed and almost all the activity was found in the periplasmic space of E. coli. The sequence of the five amino-terminal amino acids of the secreted polypeptide was Glu-Thr-Ala-Asn-Lys-, and thus the fused protein was correctly processed by the E. coli signal peptidase at the end of the phoA signal peptide.

Bacillus subtilis↗
PubMed1987

Macrophage-specific effect on lipid metabolism by an antibiotic, ascofuranone.

Ascofuranone (AF) enhanced glucose consumption of splenocytes and macrophages, while it enhanced incorporation of [14C]acetate into macrophages but not into splenocytes. When using tumor cell lines, it inhibited the incorporation of [14C]acetate into lymphoma cell lines, YAC-1 and P388, and a thymoma, L5178Y, while it stimulated that into P388D1, which is derived from P388 and has macrophage-like characteristics. Incorporation of [14C]acetate into a mammary carcinoma FM3A was also stimulated by AF. In contrast, AF stimulated uptake of methylglucose in all cell lines tested. The effect of AF was further studied using mouse myeloid leukemia, M1 cells. AF slightly stimulated the incorporation of [14C]acetate into undifferentiated M1 cells, and strongly stimulated that of hydrocortisone-differentiated M1 cells. In contrast, AF suppressed the incorporation of [14C]acetate into retinoic acid-differentiated M1 cells. Glucose consumption of these three types of M1 cells was all stimulated. From these results, we conclude that AF specifically stimulates the incorporation of [14C]acetate into macrophages while it generally stimulates glucose uptake of the cells.

Acetates↗
PubMed1987

Receptor mediated leukemogenesis: murine leukemia virus interacts with BCL1 lymphoma cell surface IgM.

Murine leukemia virus (MuLV) induced T-lymphomas bear surface receptors specific for the leukemogenic retroviruses they produce. We have proposed that such virus receptors on lymphoid tumors are the antigen-specific receptors present on their normal lymphocyte counterparts. To determine the relationship between immune receptors and virus receptors on malignant lymphocytes, a spontaneous B cell lymphoma, BCL1, was investigated. BCL1-lymphoma cells from an in vivo passaged BCL1-cell line grew in vitro only in contact with splenic stromal cells. These stromal cells produced a retrovirus, termed BCL1-V, which was lymphotropic but not leukemogenic. BCL1 cells bound BCL1-V, whereas normal spleen cells did not. Isolated BCL1-IgM bound BCL1-V, whereas three other IgM myeloma proteins, MOPC-104E, CBPC-112, and HPC-76, did not. Rat anti-BCL1-IgM monoclonal antibodies recognizing mu chain isotypic determinants and BCL1-specific idiotypic specificities, blocked BCL1-V binding to BCL1 IgM. These data support the receptor mediated leukemogenesis hypothesis, suggest a role for virus:cell surface immunoglobulin interactions in the development of B cell lymphoma, and implicate an antigen presenting cell population in the lymphomagenic process.

Animals↗
PubMed1987

[Non-invasive secretory carcinoma of the breast].

A case of non-invasive secretory carcinoma of the breast is reported. The patient was a 33-year-old Japanese woman who complained of abnormal nipple discharge from the right breast. Although physical and radiological examinations failed to find any abnormal nodular lesions in the breast, a cytological examination revealed signet-ring-like atypical cells in the smears of nipple discharge. Radical mastectomy with axillary lymph nodes dissection was performed. No nodular lesions were macroscopically observed. However, intraductal proliferation of atypical cells was microscopically found in the excised breast. Diastase-resistant PAS-positive mucus was observed in the tumor-cell-forming-lumina and in the cytoplasm of tumor cells. No metastases were observed in the axillary lymph nodes.

Adult↗
PubMed1987

[A case report of angiosarcoma of the breast].

The patient was a 24-year-old female, and had received 7-40 mg of prednisolone per day from the age of 19 because of SLE. The tumor occupied almost the entire right breast with a blue-red discoloration of the skin. Histological examination of the tumor disclosed angiosarcoma and a standard radical mastectomy was performed. No metastasis was seen in the regional lymph nodes. The patient received adjuvant chemotherapy with actinomycin D and remained well 26 months after the operation.

Adult↗
PubMed1986

Novel blockade by brefeldin A of intracellular transport of secretory proteins in cultured rat hepatocytes.

We examined the effect of brefeldin A, an antiviral antibiotic, on protein synthesis, intracellular processing, and secretion in primary culture of rat hepatocytes. The secretion was strongly blocked by the drug at 1 microgram/ml and higher concentrations, while the protein synthesis was maintained fairly well. Pulse-chase experiments with [35S]methionine demonstrated that brefeldin A completely blocked the proteolytic conversion of proalbumin to serum albumin up to 60 min of chase, although its conversion was observed as early as 20 min in the control cells. The drug also inhibited the terminal glycosylation of oligosaccharide chains of alpha 1-protease inhibitor and haptoglobin. These two modifications have been shown to occur at the trans region of the Golgi complex. The drug, however, had no effect on the proteolytic processing of the haptoglobin proform which takes place within the endoplasmic reticulum. Such an effect by brefeldin A is very similar with that induced by the carboxylic ionophore monensin. However, in contrast to evidence that monensin causes a delayed secretion of the unprocessed forms of these proteins, brefeldin A allowed the completely processed forms to be secreted after a prolonged accumulation of the unprocessed forms. Morphological observations demonstrated that the endoplasmic reticulum was markedly dilated by treatment with the drug at 10 micrograms/ml which continuously blocked the secretion. On the other hand, brefeldin A caused no inhibitory effect on the endocytic pathway as judged by cellular uptake and degradation of 125I-asialofetuin. These results indicate that brefeldin A is a unique agent which primarily impedes protein transport from the endoplasmic reticulum to the Golgi complex by a mechanism different from those considered for other secretion-blocking agents so far reported.

Adenosine Triphosphate↗
PubMed1986

Early replicative intermediates of Escherichia coli chromosome isolated from a membrane complex.

The replication origin region of the Escherichia coli chromosome was isolated from an outer membrane fraction. The chromosome was further purified by centrifugation in a cesium chloride gradient. Early replicative intermediates were enriched in the preparation when cytosine-1-beta-arabinofuranoside was added to the culture at the time of initiation of chromosome replication. DNA fragments with an eye structure having two branches of less than 400-500 bp in length were associated with components that were removed by phenol treatment. We conclude that the replication fork usually proceeds counter-clockwise toward the unc operon in the earliest period of replication.

Base Composition↗
PubMed1986

Asymmetric replication of an oriC plasmid in Escherichia coli.

Plasmid pTSO118 containing the Escherichia coli origin of replication, oriC, initiated replication simultaneously with the chromosome when temperature-sensitive host cells were synchronized by temperature shifts. Replicating intermediates of the plasmid as well as of the chromosome were isolated from the outer membrane fraction of the cell. Plasmid DNA with eye structures was enriched when cytosine-1-beta-arabinofuranoside was introduced into the culture during replication. Electron microscopy of the replicating molecules, after digestion with restriction endonucleases, showed that the replication fork proceeds exclusively counter-clockwise towards the unc operon. We conclude that the replication of the oriC plasmid is unidirectional or, if bidirectional, is highly asymmetric.

DNA Replication↗
PubMed1986

Protective effects of ketotifen on allergen-induced bronchoconstriction and skin weal.

A single-blind cross-over method was used to investigate the effects of ketotifen on the total respiratory resistance response curve to inhalation of a high concentration of allergen (1:5 w/v house dust or 1:10 w/v Japanese cedar pollen) and the weal response to intradermal injection of serially diluted allergen (1:10(3)-1:10(6) w/v). Five subjects received 2 mg of ketotifen every 12 hr for the first week and an inactive placebo in the same manner for the second week. The remaining five subjects received the placebo for the first week and ketotifen for the second week. Ketotifen did not alter base-line pulmonary function, but significantly delayed the time from the start of allergen exposure to the beginning of elevation of total respiratory resistance (P less than 0.02), and the time from the start of allergen exposure to the point at which total respiratory conductance decreased by 35% from the base-line value (P less than 0.01). Ketotifen also decreased skin test sensitivity significantly (P less than 0.01).

Adult↗
PubMed1986

Amplification and deletion of the amyE+-tmrB+ gene region in a Bacillus subtilis recombinant-phage genome by the tmrA7 mutation.

A 22.4-kilobase DNA fragment containing the tmrA7-amyR2-amyE+-tmrB+-aroI+ region of the Bacillus subtilis N7 chromosomal DNA was cloned into a recombinant B. subtilis bacteriophage, p11-AA248. The amyE+-tmrB+ gene region, approximately 12.6 kilobases, in the phage genome was amplified in a tunicamycin-resistant (Tmr) Amy+ AroI+ transductant of B. subtilis by p11-AA248. On the other hand, the amyE+-tmrB+ region in the genomes of 80 to 90% of the phage particles was deleted when the phages were induced from the Tmr Amy+ AroI+ transductants by treatment with 1.0 micrograms of mitomycin C per ml. From analyses of the physical maps and DNA nucleotide sequences in the junction region of the deleted phage genome and the parental DNA fragments, it is suggested that the deletion occurred within a direct repeat sequence composed of 18 base pairs. The endpoints of the amplified gene region seemed to be closely related to both terminal regions of the deleted DNA.

Bacillus subtilis↗
PubMed1986

Essential structure in the cloned transforming DNA that induces gene amplification of the Bacillus subtilis amyE-tmrB region.

Bacillus subtilis B7, a mutant which acquired gene amplification of the amyE-tmrB region, showed, as a result, hyperproductivity (about a 5- to 10-fold increase) of alpha-amylase and tunicamycin resistance. The mutational character was transferred to recipient cells by competence transformation. A 14-kilobase (kb) EcoRI chromosomal DNA fragment of strain B7 was found to have the transforming activity. We cloned a 6.4-kb EcoRI fragment on a phage vector lambda Charon 4A through a spontaneous deletion of 7.6 kb from the 14-kb fragment and subcloned a 1.6-kb HindIII fragment on pGR71. The cloned 6.4-kb EcoRI and 1.6-kb HindIII fragments retained the transforming activity of inducing gene amplification of the amyE-tmrB region. At the junction point (J) of the repeating units (16 kb), the tmrB gene was linked to a DNA region (M) located 4 kb upstream of amyE. The essential structure of the cloned, transforming (gene amplification-inducing) DNA was deduced to be that around J. The subcloned 1.6-kb HindIII fragment that retained the transforming activity was shown to be almost solely composed of the tmrB-J-M region. In addition, the DNA sequence around J was determined.

Bacillus subtilis↗
PubMed1986

A novel method of screening for immunomodulating substances, establishment of an assay system and its application to culture broths of microorganisms.

A novel method of screening for immunomodulating substances is developed employing lymphocytes and three mitogens. Concanavalin A (Con A) and phytohemagglutinin (PHA) are applied as T cell specific stimulants and lipopolysaccharide (LPS) as a B cell specific stimulant respectively. The lymphocytes obtained from mouse spleen are cultured with an antibiotic or a sample extract in the presence or absence of mitogen for three days and pulsed with [3H]thymidine for five hours before harvest. Differential effects of a sample compound on [3H]thymidine incorporation by the activated and quiescent lymphocytes are scored. In this procedure most of the tested antibiotics or chemical compounds with different mode of actions show non-specific effects. Cyclosporin A, a potent immunosuppressive substance, suppresses both Con A and PHA responses more extensively than LPS response and quiescent cell growth, and two cytochrome bc1 complex inhibitors, funiculosin and antimycin A3, are less suppressive to PHA response than to the others. The present system was also applied to the methanol extracts of the culture broths prepared from the type strains of Actinomycetes and Penicillium.

Adjuvants, Immunologic↗
PubMed1986

Selective suppression by prodigiosin of the mitogenic response of murine splenocytes.

In the course of screening for immunomodulating substances among microbial metabolites using a triple mitogen assay system, we detected an immunosuppressive activity which is similar to cyclosporin A. Two active components were isolated as red pigments from the fermentation broth of Streptomyces hiroshimensis and they were identified with prodigiosin 25-C and metacycloprodigiosin respectively. These compounds inhibited T lymphocyte proliferation which was induced by plant lectins, concanavalin A (Con A) and phytohemagglutinin (PHA), much more extensively than B lymphocyte proliferation which was induced by lipopolysaccharide (LPS). Prodigiosin 25-C completely inhibited induction of cytotoxic T cells in a mixed lymphocyte reaction (MLR) at 4 ng/ml.

Animals↗
PubMed1986

Activation of natural cytotoxic activity and concomitant reduction of triglyceride content of murine spleen, treated with an antitumor antibiotic, ascofuranone.

Ascofuranone (AF) elevated natural cytotoxic activity of spleen when it was administered intraperitoneally to male mice. The elevation was observed both in low and high responder mice. AF-activated splenocytes lysed NK-resistant tumor cells, FM3A, P388 and sarcoma 180 cells as well as NK-sensitive YAC-1 cells. However, AF suppressed other lymphatic functions such as mitogenic responses and interleukin 2 production. Because AF did not activate splenic NK activity in vitro, the activation is assumed to be caused by a host-mediated process. One of the possibilities is modulation of the lipid metabolism of splenocytes. Thus, we examined splenic lipid contents and revealed that AF decreased splenic triglycerides without affecting other lipids. In contrast, the antibiotic significantly increased triglyceride in muscle.

Animals↗
PubMed1986

In vitro effects of an antitumor antibiotic, ascofuranone, on the murine immune system.

Effects of an antitumor antibiotic, ascofuranone (AF) on the murine immune system were studied. Unlike lectins, AF did not induce any proliferative response of splenocytes. Furthermore, AF significantly inhibited proliferative response of splenocytes in response to lectins, such as concanavalin A, lipopolysaccharide, or phytohemagglutinin above 5 micrograms/ml. In concanavalin A-induced T-lymphocyte response, AF selectively inhibited the formation of interleukin 2 (IL-2) receptors, which was observed above 0.4 micrograms/ml. On the other hand, the inhibitory effect on the proliferative response to IL-2 of T-lymphocytes, which had already obtained IL-2 receptors, was observed above 10 micrograms/ml. IL-2 production of splenocytes in response to concanavalin A was also suppressed by AF above 2 micrograms/ml and only 3% of IL-2 was produced in the presence of AF, 10 micrograms/ml. However, AF-activated macrophages and their glycolysis was significantly stimulated. Activation of macrophages by AF was also confirmed by stimulation of interleukin 1 production and tumoricidal activity. However, natural killer activity of splenocytes was suppressed at the concentration where significant activation of tumoricidal activity of macrophages was observed. Therefore, AF had a dual effect on the immune system. Macrophages were activated to produce interleukin 1 and to kill tumor cells. On the other hand, functions of lymphocytes were suppressed.

Animals↗
PubMed1986

Bronchodilating effect of KC-404, a novel anti-asthmatic agent, and its derivatives in monkey.

The inhibitory effect of 3-isobutyryl-2-isopropylpyrazolo[1,5-alpha]pyridine (KC-404) on aerosolized methacholine- and histamine-induced increase in total respiratory resistance (Rrs) was determined in monkeys using the forced 3 Hz oscillation method and was compared with the effect of aminophylline. The effects of several derivatives of KC-404 on methacholine-induced bronchoconstriction were also determined. All of the i.v. administered pyrazolopyridine derivatives showed an inhibition of the increase in Rrs induced by aerosolized methacholine. Among these derivatives, KC-404 exerted the most potent bronchodilating effect. KC-404 also inhibited the histamine-induced increase in Rrs. These effects of KC-404 were more potent than those of aminophylline. On the other hand, the dose of KC-404 tested caused an increase in heart rate, although the degree was moderate as compared with aminophylline. From the results obtained in this study, it is considered that the pyrazolopyridine derivatives, particularly KC-404, may be promising bronchodilators for the treatment of bronchial asthma.

Airway Resistance↗
PubMed1985

Modification of fatty acid composition in adipocyte plasma membranes by an oral treatment with a new antidiabetic agent, AS-6, in genetically obese diabetic mice, db/db.

Male 12-week-old C57BL/KsJ db/db mice were treated for 1 week with a dietary admixture of an experimental antidiabetic agent, AS-6 (4-O-carboxymethylascochlorin, 0.1%). The fatty acid composition of the adipose tissue and its plasma membranes in the treated mice was compared with that in untreated db/db mice and their lean littermates. The results indicate that, when compared with the lean, the db/db adipose tissue and its plasma membrane are extremely rich in nonessential fatty acids, and AS-6 treatment modifies the fatty acyl composition only in the membranes in which 16:1 and 18:1 increase and C18 decreases.

Adipose Tissue↗