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Biomedical subjects

T Yoshioka

Publications and source records attributed to T Yoshioka.

At least 127 records · Page 7Linked to original sources
PubMed2000

Caspase activation and cytochrome c release during HL-60 cell apoptosis induced by a nitric oxide donor.

Nitric oxide (NO) from (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1- ium-1,2-diolate (NOC-18) induces apoptosis in human leukemia HL-60 cells. This effect was prevented by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK), thereby implicating caspase activity in the process. NOC-18 treatment resulted in the activation of several caspases including caspase-3, -6, -8, and -9(-like) activities and the degradation of several caspase substrates such as nuclear lamins and SP120 (hnRNP-U/SAF-A). Moreover, release of cytochrome c from mitochondria was also observed during NOC-18-induced apoptosis. This change was substantially prevented by Z-VAD-FMK, thereby suggesting that the released cytochrome c might function not only as an initiator but also as an amplifier of the caspase cascade. Bid, a death agonist member of the Bcl-2 family, was processed by caspases following exposure of cells to NOC-18, supporting the above notion. Thus, NO-mediated apoptosis in HL-60 cells involves a caspase/cytochrome c-dependent mechanism.

Apoptosis↗
PubMed2000

Role of the gynoecium in natural senescence of carnation (Dianthus caryophyllus L.) flowers.

Although the role of the gynoecium in natural senescence of the carnation flower has long been suggested, it has remained a matter of dispute because petal senescence in the cut carnation flower was not delayed by the removal of gynoecium. In this study, the gynoecium was snapped off by hand, in contrast to previous investigations where removal was achieved by forceps or scissors. The removal of the gynoecium by hand prevented the onset of ethylene production and prolonged the vase life of the flower, demonstrating a decisive role of the gynoecium in controlling natural senescence of the carnation flower. Abscisic acid (ABA) and indole-3-acetic acid (IAA), which induced ethylene production and accelerated petal senescence in carnation flowers, did not stimulate ethylene production in the flowers with gynoecia removed (-Gyn flowers). Application of 1-aminocyclopropane-1-carboxylate (ACC), the ethylene precursor, induced substantial ethylene production and petal wilting in the flowers with gynoecia left intact, but was less effective at stimulating ethylene production in the -Gyn flowers and negligible petal in-rolling was observed. Exogenous ethylene induced autocatalytic production of the gas and petal wilting in the -Gyn flowers. These results indicated that ethylene generated in the gynoecium triggers the onset of ethylene production in the petals of carnation during natural senescence.

Aging↗
PubMed2000

Electron microscopy analysis of the boundary layer structure of SrTiO3 semiconducting ceramic

In a boundary layer (BL) semiconducting SrTiO3-based ceramic condenser, the BL structure has been investigated using high-resolution field-emission scanning electron microscopy (FE-SEM) and field-emission (scanning) transmission electron microscopy (FE-(S)TEM). In an initial TEM observation, a double layered structure was observed at the grain boundary region. It consisted of a grain boundary (second phase) and a pair of the metal diffusion layers of up to several nanometres in width across the grain boundary where the change of the crystal lattice distance was undetected by the high-resolution TEM image. A facet structure was often observed on the grain boundaries. It was particularly formed on (020) plane of the grain crystal. High resolution SEM showed a jagged striped structure on the surface of the bulk material and on the inside grain as revealed by fracture. Using the similarity in shape and size, it can be identified to correspond to the facet boundary structure. Its formation mechanism can be explained as that during the reoxidization process when the oxide flux of the mixture of Bi2O3, PbO and CuO, painted on the bulk material, surfaces migrates into the ceramic along the grain boundary. The oxide corrodes the grain surfaces including the bulk surfaces. This corrosion particularly occurs on (020) plane of the grain so that the facet structure is produced. In this paper, by using the atomic scale high angle annular dark field STEM, it has been determined that Bi atoms preferentially replace Sr atoms on (020) in the diffusion layers. The atom position displacement was also detected at the grain surfaces and this altered atomic assignment can be determined as an origin of production of Sr2Bi4Ti5O18 at the grain boundary. Also, it was observed that the layer width of the metal diffusion layers was often different between the both grains and changed locally so that the ribbon of the diffusion layers meandered around the straight grain boundary. Its possible mechanism is also proposed.

Journal Article↗
PubMed2000

Tactile functions of mechanoreceptive afferents innervating the hand.

Four types of mechanoreceptive afferents innervate the glabrous skin of the hand. Evidence from more than three decades of combined psychophysical and neurophysiological research supports the idea that each afferent type serves a distinctly different sensory function and that these functions explain most of tactual perceptual function. The available evidence supports the following hypotheses: (1) The slowly adapting type 1 system provides the information on which form and texture perception are based. (2) The cutaneous rapidly adapting system provides information about minute skin motion and, thereby, plays a critical role in grip control. (3) The Pacinian system is responsible for the detection and perception of distant events by vibrations transmitted through objects, probes, and tools held in the hand. (4) The slowly adapting type 2 system provides information for the perception of hand conformation and for the perception of forces acting on the hand. The authors review the evidence on which these hypotheses are based. They also review the role of proprioceptive afferents in the perception of hand conformation because they appear to play a significant role along with cutaneous afferents.

Afferent Pathways↗
PubMed2000

Dentin bonding and sealing ability of a new root canal resin sealer.

The aims of this study were to find a dentin bonding system suitable for root canal treatment using a newly developed root canal resin sealer, and to examine its sealing ability. The sealer was composed of vinylidene fluoride/hexafluoropropylene copolymer, methyl methacrylate, zirconia, and tributylborane catalyst. The effects of dentin conditioners and primers on dentin bonding were studied by tensile bond strength testing and scanning electron microscopy. Apical and coronal leakage were evaluated at 1-, 4-, and 12-wk intervals by a dye penetration test using a methylene blue solution. Pulp Canal Sealer EWT and Sealapex were used as controls. Significantly high bond strength was obtained by treating dentin with EDTA, followed by application of a glutaraldehyde/2-hydroxyethyl methacrylate primer. The experimental resin sealer produced a significantly superior coronal seal at 12 wk when compared with the two control sealers (p < 0.05). Scanning electron microscopic examination revealed few gaps at the resin sealer-dentin interface.

Alkenes↗
PubMed2000

Centrosomal kinases, HsAIRK1 and HsAIRK3, are overexpressed in primary colorectal cancers.

Members of the recently identified family of Homo sapiens Aurora / Ipl1-related kinases (HsAIRKs), homologous to chromosome segregation kinases, fly Aurora and yeast Ipl1, are highly expressed during M phase, and have been suggested to regulate centrosome function, chromosome segregation, and cytokinesis. In the present study, immunohistochemical analyses were performed of HsAIRK1 and HsAIRK3 expression in 78 primary colorectal cancers and 36 colorectal adenomas as well as 15 normal colorectal specimens. In normal colon mucosa, some crypt cells showed weak positive staining in 10 and 12 out of 15 cases for HsAIRK1 and HsAIRK3, respectively, the remaining cases being negative. Elevated expression of HsAIRK1 was observed in 53 (67.9%) of the colorectal cancers, and of HsAIRK3 in 40 (51.3%). Furthermore, colorectal adenomas showed high expression of HsAIRK1 and HsAIRK3 in 11 (30.6%) and 7 (19.4%) cases, respectively, thus being intermediate between colorectal cancers and normal colorectal mucosa. Interestingly, HsAIRK1 overexpression was significantly associated with pT (primary tumor invasion) and p53 accumulation in colorectal cancers. There was no significant correlation between proliferating cell nuclear antigen-labeling index (PCNA-LI) and the levels of these proteins. The results suggest that overexpression of HsAIRK1 and HsAIRK3 might be involved in tumorigenesis and / or progression of colorectal cancers.

Adenoma↗
PubMed2000

Improved in vivo antitumor efficacy and reduced systemic toxicity of carboxymethylpullulan-peptide-doxorubicin conjugates.

The antitumor efficacy of the conjugate of doxorubicin (DXR) and carboxymethylpullulan (CMPul) with Phe-Gly spacer (CMPul-FG-DXR) was evaluated using murine tumor models and compared with that of DXR. The conjugate exhibited higher antitumor efficacy against Lewis lung carcinoma than DXR. Complete tumor regression followed by long-term tumor-free survival was frequently observed when CMPul-FG-DXR was administered i.v. three times at a dose equivalent to 10 mg / kg of DXR. The superior survival as well as anti-metastatic effect of CMPul-FG-DXR in comparison with DXR was also demonstrated with the M5076 murine reticulosarcoma model. Body weight loss in mice treated with the conjugate was less than that in the DXR-treated group, indicating lower systemic toxicity of CMPul-FG-DXR. Simply mixing CMPul with DXR did not enhance the antitumor activity of DXR, showing that the conjugation of DXR with CMPul is necessary for improved antitumor activity. However, no enhanced antitumor efficacy of the conjugates was observed against a non-solid tumor model such as P388 leukemia. In summary, improved antitumor efficacy with reduced systemic toxicity of CMPul-FG-DXR was demonstrated in the present study. CMPul-FG-DXR may be useful as a cancer chemotherapy agent against solid tumors and metastases.

Animals↗
PubMed2000

Molecular and functional characterization of HSC54, a novel variant of human heat-shock cognate protein 70.

A novel variant of human heat-shock cognate protein 70 (HSC70) transcript, named heat-shock cognate protein 54 (HSC54), was identified and characterized. The transcript encodes the protein lacking 153 amino acid residues of HSC70 in a part of the protein-binding and variable domains, resulting in a calculated molecular mass of 53.5 kDa. HSC54 mRNA was detected in all human cells and tissues examined. The protein was also detected in peripheral mononuclear cells and U937 human histiocytic lymphoma cells. Heat treatment of U937 cells up-regulated the expression of HSC54. The chaperoning activity of HSC54 was examined by luciferase renaturation assay. HSC70 recovered the luciferase activity in the presence of reticulocyte lysate as a source of cochaperones. However, HSC54 did not facilitate the recovery of denatured luciferase; besides, HSC54 significantly inhibited the HSC70-mediated chaperoning activity. In pull-down experiments, HSC54 interacted with cochaperones, p60, HSP40, and p48, as HSC70 did. The resonant mirror detection analysis showed that p60 binds to HSC54 with a higher association rate constant than HSC70 with a similar affinity constant. These results suggest that HSC54 is constitutively expressed and also inducible by stress and may function as an endogenous inhibitory regulator of HSC70 by competing the cochaperones.

Alleles↗
PubMed2000

Sapecin B alters kinetic properties of rapidly inactivating K(+) channels in rat pituitary GH(3) cells.

Sapecin B is an antibacterial protein isolated and purified from culture medium of the embryonic cell line derived from the flesh fly (Sarcophaga peregrina). It has structural similarities to the scorpion toxin charybdotoxin (CTX). We have first detailed the effects of the newly described toxin (sapecin B) on the gating kinetics of the 4-aminopyridine-sensitive, rapidly inactivating K(+) current in rat pituitary GH(3) cells in order to investigate this protein's site of action, with whole-cell voltage-clamp methods. We have found that sapecin B alters the kinetics of activation and deactivation whereas there was no effect on the inactivation process. None of the effects of sapecin B was voltage dependent. In addition, sapecin B reduced whole-cell conductance. We suggest that the toxin may be ineffective against the voltage-sensitive segment, as well as the N-terminal and C-terminal domains, and CTX and sapecin B probably may have different binding sites.

Animals↗
PubMed2000

Aortic stent-grafting with transrenal fixation: use of newly designed spiral Z-stent endograft.

PURPOSE: To evaluate the feasibility and efficacy of a newly designed stent-graft placed across the renal arteries for exclusion of abdominal aortic aneurysms (AAAs) with short or tortuous proximal necks. METHODS: Among a group of AAA patients treated with endovascular grafting, 5 had tortuous proximal necks and 13 had necks <20 mm (mean 13 mm). In these 18 cases, a 2- to 3-cm uncovered segment of the stent-graft was placed transrenally using a catheter inserted into the renal artery as a guide for graft margin positioning. A newly designed stent-graft was constructed from a custom-made spiral Z-stent covered with a thin-walled Dacron material; the endografts were deployed through 16-F (aortoaortic model) or 18-F sheaths (bifurcated devices). Renal function was assessed by preoperative and postoperative measurement of urea nitrogen and creatinine. Aneurysm exclusion and renal artery patency were evaluated during follow-up using spiral computed tomography and angiography. RESULTS: The stent-grafts were correctly placed at the intended site in all 18 patients. Renal function was not affected except transiently in 1 patient who developed bilateral renal artery stenoses 24 hours after the procedure; Palmaz stents were deployed in each renal artery to reestablish satisfactory blood flow. Of the 33 renal arteries crossed by the bare stent-graft segment, all were patent over a mean 14-month follow-up (range 7-24), including the patient with Palmaz stents implanted for postprocedural renal stenosis. Complete aneurysm exclusion was maintained in 15 (83%) of 18 patients; proximal leaks persisted in 3 patients, including 2 with severely angled proximal necks. CONCLUSIONS: Transrenal placement of the uncovered leading edge of custom-made spiral Z-stent-based endografts appears feasible and clinically effective in the treatment of AAAs with short or tortuous proximal necks.

Aged↗
PubMed2000

Local thrombus formation in the site of intravenous injection of chlorpromazine: possible colloid-osmotic lysis of the local endothelial cells.

Since amphiphilic drugs are known to interact with biomembranes, we investigated local vessel damage and thrombosis which might be brought about by intravenous dosing using chlorpromazine (CPZ) as a representative compound. CPZ-induced hemolysis was suppressed by an increase in sucrose concentration in the medium, characterizing this hemolysis to be colloid-osmotic lysis, which includes the enhancement of membrane phospholipid fluidity and consequent small pore formation in the membranes. This was supported by the observation that hemolysis by filipin, not featuring the stage of small pore formation, was not affected by sucrose. [14C]Glucose-entrapping liposomes were degraded by CPZ, and this degradation was enhanced by an increase in the intravesicle glucose concentration. These results indicated that the compound could induce colloid-osmotic lysis in erythrocytes and artificial membrane vesicles. CPZ also injured cultured porcine aortic endothelial cells (PAEC), as evidenced by lactate dehydrogenase (LDH) leakage. This injury was also suppressed by increase in sucrose concentration in the medium, suggesting that colloid-osmotic lysis again occurred. When rats were intravenously injected with CPZ, local endothelial cell (EC) injury and associated thrombus formation were observed, suggesting that CPZ's action was also evident in vivo. To our knowledge, this is the first finding which suggests that an intravenously dosed amphiphilic drug can injure local ECs based on a colloid-osmotic lysis mechanism leading to thrombosis.

Animals↗
PubMed2000

[An application of fusion fluorescent proteins in the pharmacological study of intracellular protein trafficking].

The fluorescent proteins have expanded various aspects of biological research. Proteins fused to the fluorescent proteins such as green fluorescent protein (GFP) provided researchers an opportunity to visualize the intracellular trafficking of proteins in living cells. The trafficking of proteins including that of steroid receptors involves dynamic interactions with cellular proteins such as heat shock proteins, immunophilins. Such interactions, which can be monitored by GFP fusion proteins, may be altered by pathophysiological conditions and by drugs. Thus, GFP fusion proteins may be applied to the investigations for the pharmacological manipulation of protein trafficking.

Animals↗
PubMed2000

Histochemical responses of human soleus muscle fibers to long-term bedrest with or without countermeasures.

Effects of 2- or 4-month bedrest in -6 degrees head-down tilt position with or without countermeasures on the histochemical properties of fiber phenotype and cross-sectional area (CSA) were studied in human soleus. The CSAs in slow fibers decreased approximately 32% during 4-month bedrest. This reduction was normalized after 1-month recovery. Although the reduction of percent slow fibers was not significant statistically, the percent intermediate fibers was significantly elevated 4 months after bedrest. Such shift in fiber type was not normalized following 1-month recovery. Effects of wearing an anti-g Penguin suit which has a modest, but continuous resistance at the knee and ankle (Penguin-1) or with knee resistance without loading on the ankle (Penguin-2) for 10 consecutive hours daily were also investigated during approximately 2 months of bedrest. The subjects performed knee extension and flexion for the last 15 min of each hour while in a supine position in bed. Bedrest-induced fiber atrophy was prevented in the Penguin-1 group but not the Penguin-2 group. Transformation of fiber type was not prevented in either Penguin suit group. It is suggested that long-term bedrest causes an atrophy and a shift of fiber phenotype toward fast-twitch type in human soleus. Data also indicated that loading on the muscle is an effective countermeasure for prevention of fiber atrophy but not fiber-type transformation.

Adult↗