Biomedical subjects

K Yoshikawa

Publications and source records attributed to K Yoshikawa.

At least 127 records · Page 7Linked to original sources

PubMed2000

Surface-induced DNA superhelicity.

Certain biopolymers, such as DNA, have a double-stranded twisted structure and frequently exhibit a supercoiled conformation. Over the past decade, extensive conformational analyses of different biopolymers have been performed using atomic force microscopy. In this technique, a necessary step in sample preparation is the adsorption of molecules on the surface, which could affect the chain conformation. Using a Monte Carlo simulation, we studied the adsorption process of circular semiflexible twisted double-stranded polymer chains on a solid surface with an emphasis on the conformational properties. We found that the conformation of an adsorbed chain strongly depends on the number of double-helical turns of the chain. Chains with weak twisting adsorbed on the surface assumes higher superhelical twisting, whereas the coiled state is seen in the bulk solution. After the adsorption, double-helical turns are accumulated in the adsorbed ("train") sections giving more conformational freedom to the nonadsorbed ("loop") sections. Chains with strong twisting show small conformational changes with adsorption. In both cases, superhelicity shows the opposite sign of writhing.

Algorithms↗

PubMed2000

Interplay between folding/unfolding and helix/coil transitions in giant DNA.

It has been well established that double-stranded DNA undergoes a melting, or helix/coil, transition into a single-stranded coil state with an increase in temperature. On the other hand, it has recently been found that, at a fixed temperature, long DNA, larger than several kilobase pairs, exhibits a discrete transition, or switching, between elongated and folded states, preserving its double-stranded structure, with the addition of various condensation agents, such as alcohol, hydrophilic polymer, multivalent cation, and cationic surfactant. In the present study, we examined the interplay between the folding/unfolding transition and the helix/coil transition in individual giant DNA molecules, by observing the conformation of single molecular chains with fluorescence microscopy. The results indicate that the helix-to-coil transition tightly cooperates with the unfolding transition in DNA.

Circular Dichroism↗

PubMed2000

Four cycloartane triterpenoids and six related saponins from Passiflora edulis.

Four cycloartane triterpenes, cyclopassifloic acids A (1), B (2), C (3), and D (4), and six related saponins, cyclopassiflosides I (5), II (6), III (7), IV (8), V (9), and VI (10), were isolated from the leaves and stems of Passiflora edulis, and their structures were elucidated on the base of extensive NMR experiments and chemical methods. Cyclopassifloic acids A-D were assigned as 22(R), 24(S)-1alpha,3beta,22,24,31-pentahydroxy-24-methylcycloartan -28-oic acid; 24(S)-1alpha,3beta,24, 31-tetrahydroxy-24-methylcycloartan-28-oic acid; 20(S),24(S)-1alpha, 3beta,21,24,31-pentahydroxy-24-methylcycloartan-28-oic acid; and 22(R)-1alpha,3beta,22-trihydroxy-24-oxocycloartan-28-oic acid, respectively. Cyclopassiflosides I-VI, in turn, were established as the 28-O-beta-D-glucopyranosides of cyclopassifloic acids A-D. Finally, cyclopassiflosides III and V were demonstrated as the 28, 31-bis-O-beta-D-glucopyranosides of cyclopassifloic acids B and C, respectively. Also obtained in this investigation were the known compounds passiflorin (11) and passifloric acid (12).

Molecular Structure↗

PubMed2000

New cycloartane triterpenoids from Passiflora edulis.

Three cycloartane triterpenes, cyclopassifloic acids E (1), F (2), and G (3), and their saponins, cyclopassiflosides VII (4), VIII (5), IX (6), X (7), and XI (8), were isolated from the leaf and stem parts of Passiflora edulis. The structures of 1-8 were elucidated on the basis of extensive NMR experiments and by chemical methods.

Magnetic Resonance Spectroscopy↗

PubMed2000

New oleanene triterpenoid saponins from Madhuca longifolia.

Four new oleanane-type triterpene glycosides, madlongisides A-D (1-4), were isolated from the seeds of Madhuca longifolia, and their structures were elucidated on the basis of extensive NMR experiments and chemical methods. Also obtained in this investigation were the known compounds mimusopside A, Mi-saponins A, B, and C, and 3-O-beta-D-glucopyranosyl protobassic acid.

Magnoliopsida↗

PubMed2000

In vitro antiinflammatory effects of neolignan woorenosides from the rhizomes of Coptis japonica.

Five dihydrobenzofuran neolignans, woorenosides I (1), II (2), III (3), IV (4), and V (5), isolated from Coptis japonica (Ranunculaceae), suppressed tumor necrosis factor (TNF)-alpha and nitric oxide (NuOmicron) production, as well as lymphocyte proliferation triggered by inflammatory signals such as various mitogens, in a dose-dependent manner. The results indicate that the woorenosides strongly inhibit the mitogenic response by activated macrophage and lymphocytes and suggest that these compounds may participate in regulating inflammatory processes.

Animals↗

PubMed2000

Oligosaccharides from Hoya carnosa.

Oligosaccharides A, B, and C (1-3, respectively) were isolated from the stem of Hoya carnosa. Their structures were established by NMR and chemical methods. Compounds 1 and 2 were 6-deoxy-3-O-methyl-beta-allopyranosyl(1-->4)-beta-cymaropyranosyl( 1-- >4)-beta-cymaropyranosyl(1-->4)-beta-cymaronic acid delta-lactone and 6-deoxy-3-O-methyl-beta-allopyranosyl(1-->4)-beta-oleandropyranosyl++ +(1 -->4)-beta-cymaropyranosyl(1-->4)-beta-cymaronic acid delta-lactone, respectively. Compound 3 was the sodium salt of 2.

Carbohydrate Conformation↗

PubMed2000

Polyhydroxylated sterols from the octocoral Dendronephthya gigantea.

Two new polyhydroxylated sterols, dendronesterols A (1) and B (2), have been isolated from the octocoral Dendronephthya gigantea. The structures of 1 and 2 were proposed on the basis of extensive NMR experiments. Compound 2 was found to be weakly cytotoxic toward L1210 cells.

Animals↗

PubMed2000

Stephanotic acid, a novel cyclic pentapeptide from the stem of Stephanotis floribunda.

The stem of Stephanotis floribunda afforded a new cyclic pentapeptide stephanotic acid (1), possessing a novel 6-(leucin-3'-yl) tryptophan skeleton. The structure of 1 was assigned on the basis of extensive NMR experiments and a chemical reaction and shown to be closely related to the bicyclic octapeptide moroidin (3), a toxin from Laportea moroides.

Madagascar↗

PubMed2000

The PEBP2beta/CBF beta-SMMHC chimeric protein is localized both in the cell membrane and nuclear subfractions of leukemic cells carrying chromosomal inversion 16.

The chromosomal inversion (16)(p13q22), which is associated with the M4-eosinophilia subtype of human acute myeloid leukemia, causes the fusion of two distinct genes. The polypeptide encoded by the chimeric gene, PEBP2p/CBFp-SMMHC, retains the ability to interact with, and dominantly interfere with the function of proteins possessing the Runt homology domain. The Runt protein homologs constitute the DNA binding subunit of the PEBP2/CBF transcription factor. We examined the subcellular localization of PEBP2beta/CBFbeta-SMMHC, as well as that of Runt protein homologs in leukemic cells carrying inversion 16 by immunoblot analysis. A significant amount of the PEBPbeta/CBFbeta-SMMHC protein was recovered from the nuclear fraction along with the Runt protein homologs. Furthermore, some of both polypeptides was retained in the DNA pellet that represents the material remaining after extraction of nuclear fraction with high salt. These observations suggest that the so-called dominant interfering effect of PEBPbeta/CBFbeta-SMMHC on PEBP2/CBF occurs inside the nucleus. In addition, we could detect PEBP2beta/CBFbeta-SMMHC in the cytoplasmic membrane fraction as well. The function of this membrane-located PEBP2beta/CBFbeta-SMMHC, if any, appears to be unrelated to that of Runt protein homologs.

Binding Sites↗

PubMed2000

Compound heterozygous group A xeroderma pigmentosum patient with a novel mutation and an inherited reciprocal translocation.

The severity of neurological abnormalities in Japanese group A xeroderma pigmentosum (XP-A) patients correlates with the sites of non-sense mutation in the XP-A gene. We describe a patient who presented with a more severe photosensitivity and neurological abnormality than those in typical Japanese XP-A patients with a splicing mutation in intron 3. The patient was compound heterozygous for the splicing mutation in intron 3, which resulted in formation of a non-sense codon in exon 4, and a novel non-sense mutation at codon 208 in exon 5, a C to T transition creating a stop codon TAG. Although the combination of these mutations might have been thought to cause only mild neurological signs, the longer truncated XP-A proteins than those of typical XP-A patients may have resulted in severe neurological symptoms. This phenomenon may be explained by a translocation of chromosome (1;10)(q25.3;q22.3) inherited from his father.

Adult↗

PubMed2000

Impaired responses of peripheral blood mononuclear cells to staphylococcal superantigen in patients with severe atopic dermatitis: a role of T cell apoptosis.

Staphylococcus aureus colonization is an almost universal feature of atopic dermatitis. In order to investigate the role of staphylococcal enterotoxin B in the pathogenesis of atopic dermatitis, we assessed the correlation between clinical disease severity and proliferative response of peripheral blood mononuclear cells to staphylococcal enterotoxin B in patients with atopic dermatitis. Peripheral blood mononuclear cells from patients with mild atopic dermatitis showed significantly increased proliferative responses to staphylococcal enterotoxin B compared to controls. In contrast, peripheral blood mononuclear cells from patients with severe atopic dermatitis showed markedly suppressed proliferative responses. Additionally, longitudinal evaluation of peripheral blood mononuclear cell samples from the same patient demonstrated that proliferative responses were suppressed only at times of severe disease exacerbation. Mixing experiments, using autologous T cells and antigen presenting cells that were isolated at different time points from the same patient, demonstrated that T cells of severe atopic dermatitis patients were dysfunctional, but their antigen presenting cell function remained intact. We found no significant differences of interleukin-2 levels in the culture supernatants between healthy controls and atopic dermatitis groups. Fluorescence-activated cell sorter analysis for APO2.7 antigen, an early apoptosis cell marker, demonstrated that approximately 60% of staphylococcal-enterotoxin-B-stimulated T cells expressed APO2.7 antigen in severe atopic dermatitis cases. By contrast, 5%-20% of T cells expressed APO2.7 after staphylococcal enterotoxin B stimulation in cases of mild atopic dermatitis and in healthy controls. Nuclear staining with Hoechst 33258 also showed approximately 40% apoptotic cells in the CD19-CD16-PBMC of severe atopic dermatitis patients, compared with only 5%-10% in the mild atopic dermatitis group and in healthy controls. Blocking monoclonal antibody to Fas ligand partially prevented the staphylococcal-enterotoxin-B-induced apoptosis detected by APO2.7 expression and Hoechst 33258 staining. Suppressed proliferation of peripheral blood mononuclear cells in severe atopic dermatitis patients may be secondary to T cell death by apoptosis. These results suggest that an infection of S. aureus producing staphylococcal enterotoxin B may play a role in aggravation of atopic dermatitis by inducing apoptosis in T cells.

Adult↗

PubMed2000

Involvement of keratinocyte activation phase in cutaneous graft healing: comparison of full-thickness and split-thickness skin grafts.

BACKGROUND: Little is known about keratinocytic activation in the graft take and healing process. OBJECTIVE: To investigate the clinical and molecular differences between pure epidermal sheet graft (PESG), split-thickness skin graft (STSG), and full-thickness skin graft (FTSG). METHODS: Three different thickness skin grafts (PESG, STSG, and FTSG) were performed onto three kinds of porcine wounds: shallow, deep, and full. Graft take, contraction, and Ki-67 and beta1 integrin expression in epidermis were studied. RESULTS: All grafts took well. As expected, full wounds covered by PESG and STSG contracted more than those covered by FTSG, whereas shallow wounds covered by FTSG contracted more than those covered by STSG. No difference in contracture was observed among deep wounds covered by PESG, STSG, and FTSG. Up-regulation of Ki-67 and beta1 integrin expression was greater in PESG and STSG, compared with little expression in FTSG. CONCLUSION: The keratinocytic activation phase may occur both in the STSG and PESG healing process, as well as serum imbibition, inosculatory, and revascularization phases.

Animals↗

PubMed2000

Retinoblastoma protein-initiated cellular growth arrest overcomes the ability of cotransfected wild-type p53 to induce apoptosis.

The retinoblastoma gene, RB, participates in the regulation of the G1/S-phase transition and in p53-mediated apoptosis. We have previously reported that stably transfected RB functions as a growth and tumour suppressor in HTB9 human bladder carcinoma cells, which carry a mutation of the p53 gene at codon 280 and lack RB expression. To elucidate the potential role of RB in the regulation of p53-mediated apoptosis, we transfected a wt p53 expression plasmid under the control of the human cytomegalovirus promoter into parental and RB-transfected HTB9 cells. The p53(+)/RB(-)cells were susceptible to apoptosis under various experimental conditions: 1) incubation in serum-free culture for 72 h, 2) short-term (6 h) or long-term (48 h) exposure to etoposide, and 3) culturing in soft agar. In contrast, p53(+)/RB(+)cells were significantly resistant to apoptosis under similar conditions and exhibited efficient growth arrest, as measured by laser scanning cytometry. Tumorigenicity in nude mice of parental HTB9 cells was lost by exogenous expression of wt p53. Likewise, none of mice injected subcutaneously with either p53(-)/RB(+)or p53(+)/RB(+)cells developed tumours, indicating that RB allows suppression of tumorigenesis, regardless of p53 status. These results suggest that the growth-inhibitory function of RB may overcome the ability of wt p53 to induce apoptosis.

Animals↗

PubMed2000

Fluorescence microscopic visualization of a DNA-cationic fullerene complex.

Cationic fullerene derivative 1, which is soluble in aqueous medium, bound to double stranded DNA. Observation of Coliphage T4 DNA in the absence and presence of 1 by fluorescence microscopy suggested that 1 bound to DNA along its groove. Upon irradiation of visible light on the DNA complex of 1, DNA was cleaved dramatically. The process of DNA photo-cleavage could be monitored continuously by fluorescence microscopy.

Bacteriophage T4↗

PubMed2000

Relationships of p40(phox) with p67(phox) in the activation and expression of the human respiratory burst NADPH oxidase.

p40(phox) of the phagocyte NADPH oxidase forms a complex with p67(phox) in cytosol, and coincidentally decreases in patients who lack p67(phox). Here we investigated the mode of translocation of p40(phox) to the membrane, its cytoskeletal localization on activation of the NADPH oxidase, and the dependency of its expression relative to that of p67(phox). When human polymorphonuclear leukocytes (PMNs) were stimulated with phorbol myristate acetate (PMA), p40(phox) was translocated to the membrane along with p67(phox), and not was released into the cytosol. Studies with resting PMNs using Triton X-100 revealed the exclusive localization of p67(phox) in the cytoskeletal fraction. Unexpectedly, however, about half of p40(phox), which is deemed to be fully associated with p67(phox), was recovered in the non-cytoskeletal fraction. Unlike p47(phox), the association of p40(phox) with cytoskeleton was not induced by the PMA-stimulation. These results indicate not only that p40(phox) associates with cytoskeleton via a molecule of p67(phox), but also that there are distinct states of p40(phox) that can be manipulated with Triton X-100. Lastly, Western-blot analysis of hematopoietic cells revealed no correlation between p40(phox) and p67(phox) in their protein expressions during cell differentiation, and also that p40(phox) can be stably present alone in cells, unless in the case of mature PMNs. In this regard, definitive proof was obtained with Epstein-Barr virus-transformed B cells of a p67(phox)-deficient patient, in which p40(phox) was normally expressed.

Down-Regulation↗

PubMed2000

Characteristics of cutaneous lymphomas in Osaka, Japan (1988-1999) based on the European Organization for Research and Treatment of Cancer classification.

Based on accumulating information, European investigators proposed a new classification for primary cutaneous lymphomas known as the European Organization for Research and Treatment of Cancer (EORTC) classification. The clinical utility of this classification in Japanese cases has not been evaluated. Material from 65 patients with cutaneous lymphomas (48 with primary disease and 17 with secondary disease) who were admitted to Osaka University Hospital during the period 1988 through 1999 was reviewed. Immunohistochemical analysis was performed in all cases. Cutaneous T-cell lymphoma (CTCL) comprised mycosis fungoides (15 cases), Sézary syndrome (1 case), lymphomatoid papulosis (5 cases), large cell CTCL (13 cases), pleomorphic small- or medium-sized CTCL (2 cases), and cutaneous natural killer /T-cell lymphoma (4 cases). B-cell lymphomas comprised 7 cases of follicle center cell lymphoma and 1 case of diffuse large B-cell lymphoma of the leg. Each category of disease in the EORTC scheme showed its characteristic features in our series. Five of 13 large cell CTCL cases were positive for CD30, and 5 were negative. The 5-year survival rate of patients with large cell CTCL CD30+ disease was 100% and that of patients with CD30- disease was 0%. (p > 0.1). Only 1 of 7 CTCL cases expressing CD30 was ALK-1+, and all 7 cases showed a favorable clinical course. The EORTC classification is effective in dealing with Japanese cases of cutaneous lymphomas.

Adolescent↗

PubMed2000

The role of dual-phase enhanced helical computed tomography in difficult intestinal bleeding.

We report a case of leiomyoma of the small bowel presenting with massive gastrointestinal (GI) bleeding that was diagnosed using dual-phase enhanced helical computed tomography (CT) in the preoperative period. A 68-year-old man was admitted to our hospital because of recurrent rectal bleeding. Gastroduodenoscopic and total colonoscopic examination results were negative; however, the patient continued to show bloody stool. Dual-phase enhanced helical CT was subsequently performed. CT revealed a hypervascular tumor, with evident extravasation of the contrast medium in the bowel lumen. We were successful in establishing the point of bleeding. Exploratory laparotomy was performed the same day. A solid round extraluminal mass was found at the proximal jejunum. Bleeding was observed over the serosal side of this tumor and segmental resection of the tumorous small intestine was performed. Pathologic examination revealed leiomyoma. Enhanced helical CT proved to be useful in localizing active GI bleeding.

Aged↗