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S Ishida

Publications and source records attributed to S Ishida.

At least 181 records · Page 10Linked to original sources
PubMed1994

Genes involved in the dedifferentiation of plant cells.

Since the initial process of culturing tobacco mesophyll protoplasts can be considered as a model system of dedifferentiation of higher plants, the mode of expression of genes induced by auxin, a key factor in inducing dedifferentiation, has been analyzed during the regaining of meristematic activity of quiescent and differentiated tobacco mesophyll. By differential screening we have isolated three auxin-regulated genes, which we named parA, parB and parC. parA and parC, which belong to the same gene family, were supposed to play a role in transcriptional regulation upon induction by auxin, while parB encoded glutathione S-transferase. Although it was supposed that the expression of these par genes should play a pivotal role in regaining the meristematic activity of the differentiated tobacco mesophyll cells, a possibility that other less abundantly expressing genes would have been neglected in these studies has not been excluded. On the other hand, the search for genes which would be involved in maintaining cell division activity in the dedifferentiated plant cells allowed us to isolate a few genes. One of these genes, designated arcA, belonged to a beta subunit-like protein of heterotrimeric G proteins. The significance of the involvement of this gene product in maintaining the meristematic activity of plant cells cultured in vitro has been discussed.

Cell Differentiation↗
PubMed1994

Transcription from the P2 promoter of human protooncogene myc is suppressed by retinoic acid through an interaction between the E2F element and its binding proteins.

When human promyelocytic leukemia cell line HL60 was treated with retinoic acid (RA), considerable suppression of protooncogene myc expression was achieved before granulocytic differentiation became evident. From transient transfection experiments using the reporter plasmid containing exon 1 and its 2.3 kilobases upstream of the c-myc gene fused to the chloramphenicol acetyltransferase gene, it was indicated that this suppression was mainly attributable to the level of transcription initiation. Deletion down to 95 base pairs upstream of the P2 promoter did not change the suppressive effect of RA on c-myc gene expression. Mobility shift assays with respect to the P2 promoter region revealed that the 15-base pair fragment located between P1 and P2 promoters was responsive to the RA treatment. This fragment included the E2F binding site in the c-myc P2 promoter region, and a difference of shifted bands between RA-treated and untreated HL60 cells was due to complex formation of E2F and retinoblastoma protein. The present results suggest that E2F plays an important role in the process of cell differentiation by RA and that a change of the E2F binding pattern induced by RA contributes to the suppression of c-myc gene expression preceding granulocytic differentiation.

Base Sequence↗
PubMed1993

Isolation of cDNA of an auxin-regulated gene encoding a G protein beta subunit-like protein from tobacco BY-2 cells.

The addition of 2,4-dichlorophenoxyacetic acid to tobacco BY-2 cells that had been cultured in modified Linsmaier and Skoog medium deprived of auxin for 3 days induced cell division, whereas without 2,4-dichlorophenoxy-acetic acid application, no such induction of cell division was seen. When differential cDNA screening for auxin was done at 4 hr after the addition of 2,4-dichlorophenoxyacetic acid, the cDNA of an auxin-responsive gene designated arcA was isolated. The predicted gene product of arcA is a polypeptide with a M(r) of 35,825. arcA, thus, is a plant hormone-regulated gene that encodes a protein structurally related to the beta subunit of a guanine nucleotide-binding regulatory protein, which is composed of seven repetitive segments of Trp-Asp 40-aa repeats. The possibility that arcA gene products induce cell division is discussed.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Structural analysis of periplasmic carbonic anhydrase 1 of Chlamydomonas reinhardtii.

Periplasmic carbonic anhydrase 1 of the unicellular green alga Chlamydomonas reinhardtii is a heterotetrameric glycoprotein consisting of two large subunits and two small subunits [Kamo, K., Shimogawara, K., Fukuzawa, H., Muto, S. & Miyachi, S. (1990) Eur. J. Biochem. 192, 557-562]. The cDNA sequence showed that the two subunits are cotranslated as a 377-amino-acid precursor polypeptide (41.6 kDa) consisting of an N-terminal 20-amino-acid signal peptide, a large subunit (35.6 kDa) and a small subunit (4.1 kDa) [Fukuzawa, H., Fujiwara, S., Yamamoto, Y., DionisioSese, M. L. & Miyachi, S. (1990) Proc. Natl Acad. Sci. USA 87, 4383-4387]. In the present study, amino-acid-sequence analysis of the carbonic anhydrase 1 was carried out to determine the sites of disulfide bonds and N-glycosylation and the C-terminal amino acid of the large subunit. Disulfide bonds were detected between Cys21 and Cys21, Cys61 and Cys264, Cys194 and Cys198, and Cys296 and Cys351 in the amino acid sequence deduced from the cDNA. Cys21 and Cys21 link two large subunits and Cys296 and Cys351 link a large subunit to a small subunit. Thus, the holoenzyme is constructed of two disulfide-bound large subunits, each of which joins to a small subunit by a disulfide bond. The C-terminal amino acid residue of the large subunit was determined as Ala305. This indicates that the peptide consisting of 35 amino acid residues between the large and the small subunit is deleted from the precursor during maturation, since the N-terminus of the small subunit is Ala341. Three potential N-glycosylation sites in the large subunit were all glycosylated.

Amino Acid Sequence↗
PubMed1993

Determination of bovine rotavirus G and P serotypes by polymerase chain reaction.

Among bovine rotaviruses there are two major G serotypes (G6 and G10) and three P serotypes (P1, P5, and P11, each of which is defined on the basis of the VP4 antigenic specificity of NCDV, UK and KK-3, respectively). The nucleotide sequence of a P11 gene (KK-3) was determined. The predicted KK-3 VP4 contained 772 amino-acids and showed 96% amino-acid identity with B223 VP4, an American prototype of P11 bovine rotavirus. Comparative analysis of the genes determining the G and P serotypes of bovine rotaviruses allowed us to develop polymerase chain reaction (PCR)-based assays which distinguished two G serotypes and three P serotypes commonly found in bovine rotaviruses. For determination of G serotypes, a 1013 bp fragment of the VP7 gene was first reverse-transcribed and then amplified with a pair of generic primers. In a second PCR amplification, the 5' generic primer and two different typing primers (either G6- or G10-specific) were used to generate fragments whose sizes served to identify the G serotype. Similarly, for determination of P serotypes, an 864 bp fragment of the VP4 gene was first reverse-transcribed and then amplified with another pair of generic primers. In a second PCR amplification, the 5' generic primer and three different typing primers, each one specific to one of the three P serotypes, were used to generate fragments whose sizes served to identify the P serotype. These assays were able to identify the G and P serotypes of six reference bovine rotavirus strains.

Animals↗
PubMed1993

Characterization of the G serotype and genogroup of New Delhi newborn rotavirus strain 116E.

We recently reported that the culture-adapted neonatal rotavirus strain 116E represented the first P type 11 human rotavirus, based on the close relationship of its VP4 protein to that of the bovine serotype G10P11 strain B223. In this study, we demonstrated by sequence analysis and cross-neutralization studies that the VP7 protein of 116E is closely related to those of the human serotype G9 strains, F45 and WI61, but distinct from B223 and other rotaviruses. Low-level cross-neutralization was also observed between strains 116E and B223, probably because of the antigenic similarity of their VP4 proteins. We have demonstrated by RNA-RNA hybridization that strain 116E is a reassortant between strains from the Wa and bovine (KK3-like) genogroups, deriving at least seven genes from the former and at least one gene from the latter. Together with the recent identification of serotype G10P11 newborn rotavirus strains in Bangalore, India (M. Das et al., Virology, 194, 374-379, 1993), these results are consistent with the hypothesis that reassortment may be an important mechanism for generation of rotavirus strains of newborns.

Amino Acid Sequence↗
PubMed1993

Effect of metoprolol on the beta-adrenoceptor density of lymphocytes in patients with dilated cardiomyopathy.

We investigated the effect of the beta 1-selective blocker metoprolol on the beta-adrenergic receptor density of circulating lymphocytes in patients with dilated cardiomyopathy. Nine men in New York Heart Association functional classes II (six patients) and III were given metoprolol for 6 months (mean dose 45.6 +/- 18.1 mg). Their cardiac function was assessed by echocardiography. Although there was no difference in the heart rate or pressure rate products, the end-systolic and end-diastolic dimensions significantly decreased in six patients after metoprolol treatment. The ejection fraction, fractional shortening, and mean left ventricular circumferential shortening were significantly increased after the treatment. beta-Adrenoceptor densities of lymphocytes, examined by iodine 125-labeled iodocyanopindolol, were reduced in patients at entry but recovered to normal levels after the metoprolol treatment. The dissociation constants did not differ at any stage of the disease. The relationship between beta-adrenoceptor densities in lymphocytes and echocardiographic parameters showed a positive correlation with the plasma norepinephrine concentration. This study thus provides evidence that long-term metoprolol therapy for dilated cardiomyopathy is associated with beta-receptor up-regulation, and the restoration of myocardial beta-receptor density may be associated with the improved cardiac function as determined by echocardiography.

Adult↗
PubMed1993

Non-chemotactic Dictyostelium discoideum mutants with altered cGMP signal transduction.

Folic acid and cAMP are chemoattractants in Dictyostelium discoideum, which bind to different surface receptors. The signal is transduced from the receptors via different G proteins into a common pathway which includes guanylyl cyclase and acto-myosin. To investigate this common pathway, ten mutants which do not react chemotactically to both cAMP and folic acid were isolated with a simple new chemotactic assay. Genetic analysis shows that one of these mutants (KI-10) was dominant; the other nine mutants were recessive, and comprise nine complementation groups. In wild-type cells, the chemoattractants activate adenylyl cyclase, phospholipase C, and guanylyl cyclase in a transient manner. In mutant cells the formation of cAMP and IP3 were generally normal, whereas the cGMP response was altered in most of the ten mutants. Particularly, mutant KI-8 has strongly reduced basal guanylyl cyclase activity; the enzyme is present in mutant KI-10, but can not be activated by cAMP or folic acid. The cGMP response of five other mutants is altered in either magnitude, dose dependency, or kinetics. These observations suggest that the second messenger cGMP plays a key role in chemotaxis in Dictyostelium.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1993

The role of cyclic GMP in regulating myosin during chemotaxis of Dictyostelium: evidence from a mutant lacking the normal cyclic GMP response to cyclic AMP.

Evidence has previously been reported that, during chemotaxis of the cellular slime mould Dictyostelium discoideum, cyclic GMP regulates the association of myosin II with the cytoskeleton and that this regulation is effected by inhibiting myosin II heavy chain phosphorylation (Liu and Newell, J. Cell Sci., 90, 123-129, 1988; 98, 483-490, 1991). Here we provide further evidence in support of this hypothesis using a mutant (KI-10) that is defective in chemotaxis and lacks the normal cyclic AMP-induced cyclic GMP response. We found that the cyclic AMP-induced cytoskeletal actin response was similar to that of the parental strain in this mutant (although showing a slight displacement in the dose-response curve) but the cytoskeletal myosin II heavy chain response was abolished. Moreover, the mutant showed no phosphorylation of myosin II heavy chain in response to cyclic AMP. Compared to the parental strain XP55, the mutant cells contained approximately 40% more protein and their doubling time was 30% longer. These differences could be due to differences in the efficiency of cell division, a process in which the proper regulation of myosin function is essential and in which cyclic GMP may therefore play a role.

Actins↗
PubMed1993

Uptake of glycyrrhizin by isolated rat hepatocytes.

The mechanism of uptake of glycyrrhizin (GLZ) by isolated rat liver cells was studied. The uptake rate was dependent on the unbound GLZ concentration. The initial uptake rate with respect to the unbound GLZ concentration reflected the operation of both saturable and nonsaturable processes, which followed Michaelis-Menten type kinetics; the process involves a Km of 11.3 microM, Vmax of 0.112 nmol/min/10(6) cells, and a first-order rate constant (Kd) of 0.195 nmol/min/10(6) cells/mM. GLZ adsorption on the cell membrane occurs at two types of binding sites with a linear adsorption coefficient = 2.81 nmol/10(6) cells/mM and a dissociation constant = 18.3 microM and its adsorption capacity = 0.12 nmol/10(6) cells describing specific adsorption. GLZ uptake did not require the presence of Na+ in the incubation medium and was not significantly inhibited by ouabain. The Arrhenius plot of uptake of 10 microM GLZ presented a single straight line in the range of 4-37 degrees C, with an activation energy of 15.9 kcal/mol. An energy requirement was also demonstrated, as all metabolic inhibitors studied (rotenone, antimycin A, 2,4-dinitrophenol, and KCN) significantly reduced the uptake of 10 microM GLZ (p < 0.01). The uptake was competitively inhibited by glycyrrhetinic acid (GLA), taurocholate (TCA), and probenecid (PBC) with inhibition constants, Ki, of 13.7, 48.5, and 115.9 microM, respectively, and it was noncompetitively inhibited by bromosulfophthalein (Ki 9.2 microM) and indocyanine green (Ki 13.5 microM) only at low GLZ concentrations (5 and 10 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1993

Two different histamine-sensitizing activities of pertussis vaccine observed in mice on the 4th and 12th days of sensitization.

The histamine-sensitizing (HS) activities of commercial precipitated diphtheria-tetanus-purified pertussis combined vaccines (DTP) submitted to the national quality control tests during the period from 1980 to 1991 were measured in mice on days 4 (EHS) and 12 (LHS) of sensitization. Annual averages of the EHS activity of the vaccines showed continuous decline during the period, while the LHS activity stayed unchanged except for 1990 and 1991. Correlation analysis between these two HS activities revealed that the vaccines could be differentiated into two groups, those showing a significant correlation and those lacking it, depending on their source manufacturers. When the vaccine was incubated at 37 C for four weeks, both the HS activities increased for the first couple of weeks at different rates, reaching their peaks after different periods; three weeks for the EHS activity and two weeks for the LHS activity. Treating the reference pertussis vaccine (for toxicity tests) with anti-pertussis toxin horse serum neutralized completely the EHS activity but the LHS activity resisted the serum. These findings suggest a possible difference between the two HS activities in their mode of action, therefore, in their roles in possible reactogenicity of the vaccine, and a necessity for separate controls of the two activities.

Animals↗
PubMed1993

[Recent progress in analysis of arrhythmias using electrocardiography].

Recently, various novel techniques have been used in clinic to analyze arrhythmias. These include vectorcardiography, body surface ECG mapping, signal-averaged ECG, intracardiac electrogram and monophasic action potentials, and 24-hour ECG recordings. We examined 24-hour ECG recordings in patients with frequent ventricular premature contractions (VPCs), to identify VPCs possibly due to delayed afterdepolarizations (DADs). We evaluated :1) the relationship between VPC frequency and heart rate (HR); 2) the time course of changes in VPC frequency following an abrupt and sustained increase in HR; and 3) the effects of oral diltiazem on VPCs. Patients could be divided into 2 groups according to whether VPCs increased with an increase in HRs (positive correlation or P group) or not (non-positive correlation or NP group). In the P group, changes in VPCs after an abrupt and sustained increase showed 2 types: 1) delayed-ascent type, in which VPCs increased as the duration of HR increase was prolonged; and 2) non-delayed-ascent type. Diltiazem suppressed almost only the VPCs of delayed-ascent type. The VPCs of delayed-ascent type had several important feature characteristic of DADs, suggesting these VPCs may be due to DADs.

Arrhythmias, Cardiac↗