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Biomedical subjects

Y Nakabayashi

Publications and source records attributed to Y Nakabayashi.

At least 19 recordsLinked to original sources
PubMed2001

Ubiquitin-protein ligase activity of X-linked inhibitor of apoptosis protein promotes proteasomal degradation of caspase-3 and enhances its anti-apoptotic effect in Fas-induced cell death.

The inhibitor of apoptosis (IAP) family of anti-apoptotic proteins regulate programmed cell death and/or apoptosis. One such protein, X-linked IAP (XIAP), inhibits the activity of the cell death proteases, caspase-3, -7, and -9. In this study, using constitutively active mutants of caspase-3, we found that XIAP promotes the degradation of active-form caspase-3, but not procaspase-3, in living cells. The XIAP mutants, which cannot interact with caspase-3, had little or no activity of promoting the degradation of caspase-3. RING finger mutants of XIAP also could not promote the degradation of caspase-3. A proteasome inhibitor suppressed the degradation of caspase-3 by XIAP, suggesting the involvement of a ubiquitin-proteasome pathway in the degradation. An in vitro ubiquitination assay revealed that XIAP acts as a ubiquitin-protein ligase for caspase-3. Caspase-3 was ubiquitinated in the presence of XIAP in living cells. Both the association of XIAP with caspase-3 and the RING finger domain of XIAP were essential for ubiquitination. Finally, the RING finger mutants of XIAP were less effective than wild-type XIAP at preventing apoptosis induced by overexpression of either active-form caspase-3 or Fas. These results demonstrate that the ubiquitin-protein ligase activity of XIAP promotes the degradation of caspase-3, which enhances its anti-apoptotic effect.

Apoptosis↗
PubMed2001

X-linked inhibitor of apoptosis protein (XIAP) inhibits caspase-3 and -7 in distinct modes.

The inhibitor of apoptosis proteins (IAP) regulates cell death by inhibiting caspases. The region of X-linked (X) IAP containing the second baculovirus IAP repeat domain (BIR2) is sufficient for inhibiting caspase-3 and -7. In this study, we found that the modes of inhibition of these two caspases were different: caspase-3 is inhibited in a competitive manner whereas caspase-7 inhibition occurs through a mixed competitive and noncompetitive mechanism. Binding assays revealed that the inhibition of caspase-3 by XIAP was totally dependent on the interaction between the active site of caspase-3 and the linker region between the BIR1 and BIR2 domains of XIAP. In contrast, the active site and the NH(2)-terminal region of caspase-7 bound to the linker region and the BIR2, respectively. Moreover the BIR2 with a mutated linker region, which inhibited caspase-3 very weakly, still bound to and inhibited caspase-7. Furthermore, a chimeric caspase-7/3 comprising the NH(2)-terminal portion of caspase-7 and COOH-terminal portion of caspase-3 was inhibited by XIAP by a mixed competitive and noncompetitive mechanism. Our results suggest that the linker region between BIR1 and BIR2 domains is responsible for active site-directed, competitive inhibition of both caspase-3 and -7, whereas the BIR2 itself is involved in noncompetitive inhibition of caspase-7.

Base Sequence↗
PubMed2001

Differential elution of sodium or potassium dihydrogen- and hydrogenphosphate ions from a sephadex G-15 column with sodium or potassium chloride solution.

When a mixed solution of sodium or potassium dihydrogenphosphate and disodium or dipotassium hydrogenphosphate was eluted from a Sephadex G-15 column with either a sodium or potassium chloride solution, the elution profiles of ions showed that the hydrogenphosphate ion was eluted more rapidly than the dihydrogenphosphate ion. When the sample solutions containing potassium dihydrogenphosphate and/or dipotassium hydrogenphosphate, all of which were supplemented with phosphorus-32-labelled potassium dihydrogenphosphate, were eluted with sodium chloride solution, the elution profiles of radioactivity showed that the dihydrogenphosphate ion changed to hydrogenphosphate ion and vice versa, depending on the pH values of the sample solution and the availability of the cation of the eluent during elution for the phosphate ion to pair with.

Chromatography, Ion Exchange↗
PubMed2001

Evaluation of osmium(II) complexes as electron transfer mediators accessible for amperometric glucose sensors.

In order to lower the redox potentials of Os(III/II) complexes, the mixed ligand complexes of Os(II) were synthesized. The redox potentials of Os(III/II) complexes could be lowered by the use of 4,4'-dimethyl-2,2'-bipyridine (dmbpy), imidazole (Him) or its derivatives, and chloride ion as ligands, e.g., values of the redox (formal) potentials of 628 mV vs. Ag/AgCl for [Os(bpy)3]3+/2+ (bpy: 2,2'-bipyridine) and -6 mV for [OsCl(Him)(dmbpy)2]2+/+ were given in deaerated 0.1 mol dm-3 phosphate buffer (pH 7.0). The evaluation of Os(II) complexes as electron transfer mediators accessible for amperometric glucose sensors was examined according to the determination of the redox potentials of Os(III/II) complexes and the second-order rate constants for electron transfer between glucose oxidase (GOx) in reduced form and the Os(III) complex. Although the Os(II) complexes with lower redox potentials tended to decrease the second-order rate constants ks, the ks values for the majority of Os(II) complexes synthesized in this study were greater than that for ferrocenecarboxylic acid. Acceleration of the electron-transfer reaction is attributable to the hydrogen bonding and/or the electrostatic interaction between the Os(II) complexes and GOx. It may be consequently concluded that the mixed ligand complexes of Os(II) with bpy (dmbpy), Him (its derivatives), and Cl- can act as more efficient electron transfer mediators for the fabrication of amperometric glucose sensors.

Biosensing Techniques↗
PubMed2000

Coupling of chromatographic ion-exchange reaction with change-partner reaction. Presumed mechanism on the ion-ion interaction of inorganic ions in Sephadex G-15 columns.

A sample solution containing sodium or potassium dihydrogenphosphate or disodium or dipotassium hydrogenphosphate was eluted from a Sephadex G-15 column with either sodium or potassium chloride solution in various sample-eluent systems, and every one of the four kinds of ions employed was determined in the eluate. Then, the elution profiles showed the phenomenon that a negative peak of chloride ion coexisted in the fractions of a positive peak of phosphate ion, in all sample-eluent systems employed. This phenomenon was assumed to occur by the coupled reaction of change-partner and ion-exchange reactions including ion exclusion.

Chromatography, Ion Exchange↗
PubMed1999

DNA hybridization sensor utilizing [Os(5,6-dmphen)3]2+ by square wave voltammetry.

DNA hybridization detection utilizing [Os(5,6-dmphen)3]2+ (tris(5,6-dimethyl-phenanthroline) osmium(II/III)) as hybridization indicator was studied, because [Os(5,6-dmphen)3]2+ has the most largest association constant (K2+) and high current density in osmium methyl substituted phenanthroline complexes. As the result, target DNA could be detected selectively ranging from 6.9 x 10(-10) to 6.9 x 10(-5) g/mL using square wave voltammetry.

Base Sequence↗
PubMed1998

Regulation by an extract of embryonic chick brain of the densities of voltage-dependent Na+ and Ca2+ channels in embryonic chick skeletal muscle cells during their development in culture.

We studied the chronic effects of a brain extract (BE) prepared from chick embryonic brains on voltage-dependent Na+ channels (VDNCs) and Ca2+ channels (VDCCs) during the development of chick skeletal muscle cells in culture. The maximum rates of rise of Na+ and Ca2+ action potentials were measured electrophysiologically in an attempt to determine the effects of BE on the densities of these channels. The basic culture medium was supplemented with chick transferrin instead of whole-embryo extract and skeletal muscle cells were grown in the absence or in the presence of crude BE or fractionated BE. Long-term inclusion of BE to the culture medium increased the densities of both VDNCs and L-type VDCCs. By contrast, BE apparently decreased the density of T-type VDCCs. Our results indicate that BE contains some protein(s) that has a negative effect on the density of T-type VDCCs of skeletal muscle cells at a less differentiated stage and that this effect of BE is closely associated with subsequent regulation of the densities of VDNCs and L-type VDCCs. Possible roles of the influx of Ca2+ ions through T-type and L-type VDCCs in the control of the densities of VDNCs and L-type VDCCs are discussed.

Animals↗
PubMed1996

Single-strand conformation polymorphism (SSCP) can be explained by semistable conformation dynamics of single-stranded DNA.

The cause of separation in gel electrophoresis between highly homologous ss (single-stranded) DNAs as observed in SSCP (single-strand conformation polymorphism) was pursued. Advancing our previous explanation [J. Biochem. 99, 663-671 (1986)], the mobility difference of ssDNAs was correlated to differences in their dynamic conformation (not to differences in their most stable structure), focusing on point-substituted sites. The contribution of semistable conformation dynamics was considered to be critical. Putative factors which may influence mobility (i.e., length of ssDNAs, location of substituted sites, and types of substitutions) were experimentally examined and critically discussed. Understanding of these phenomena should yield improvements in various techniques, such as SSCP, and in evaluation of the solution structures of DNA.

Base Sequence↗
PubMed1995

Analysis of tardy ulnar nerve palsy associated with cubitus varus deformity after a supracondylar fracture of the humerus: a report of four cases.

Four cases of tardy ulnar nerve palsy associated with a cubitus varus deformity of the elbow secondary to a supracondylar fracture of the humerus are presented. All patients had surgical management of their ulnar nerve palsy. In two patients, the ulnar nerve was entrapped by scar tissue at the abnormal position and the nerve developed a sharp V-shaped kink when the elbow was flexed. In one patient, the ulnar nerve displaced anteriorly with elbow flexion and spontaneously reduced into the ulnar nerve groove with elbow extension. In one patient, the ulnar nerve remained in the ulnar nerve groove; however, it was entrapped by fibrous bands arising from the flexor carpi ulnaris. It is speculated that malunion resulting in cubitus varus deformity will alter the anatomy at the elbow and that this can have a direct effect on the position and instability of the ulnar nerve. Incongruity of the elbow joint due to cubitus varus deformity also may cause osteoarthritis changes. As a result, ulnar neuropathy may develop from irritation to the ulnar nerve from the posttraumatic osteoarthritic changes at the elbow joint.

Adolescent↗
PubMed1994

Ca2+/calmodulin-dependent regulation of the density of Na+ channels in embryonic chick skeletal muscle cells during their development in culture.

Regulation of the density of voltage-dependent Na+ channels (VDNC) was studied in chick myotubes during their development in culture. The density of VDNC was assessed quantitatively in terms of the maximum rate of rise (M.R.R.) of Na+ spikes. Chronic treatment of myotubes, whose density of VDNC had reached a plateau level after 6 days in culture, with the calmodulin (CaM) inhibitor W-7 caused a further increase in the density. A derivative of W-7, known as W-5, which has a lower affinity for CaM than does W-7, was without effect. A selective inhibitor of Ca2+/CaM-dependent protein kinase II (CaM-KII), namely, KN-62, also caused an increase in the density of VDNC when its effect was examined in mature myotubes. A structural analogue of KN-62, namely, KN-04, which is a much less effective inhibitor of CaM-KII, was without effect. These results suggest that density of VDNC in developing myotubes is regulated by Ca2+/CaM and CaM-KII. However, the role of CaM-KII in this regulation is not straightforward since it appears to decrease the density of VDNC in mature myotubes, but to increase their density in immature myotubes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Bone strength and histomorphometry of the distal femur.

The ultimate bone strength of the distal femur was measured radially, by indentation testing, around the transepicondylar line in 3 mm depth steps up to 12 mm below the subchondral bone plate. Specimens from 10 cadavers were used. This orientation of specimens was chosen as a way to provide measurement in a more physiologic orientation for load bearing and to standardize the assessment. Bone hardness declined sharply over the first 6 mm below the surface, tending to plateau at deeper levels. Within the top 6 mm layer the lateral condyle was softer than both the medial condyle and the central patellofemoral area (P < .05), but at deeper levels it maintained greater hardness. Of the histomorphometric parameters, those showing the greatest consistent correlation with hardness were bone volume fraction and trabecular separation. When the tibiofemoral and patellofemoral compartments were compared it was found that for a given value of bone volume fraction, condylar bone is marginally harder than patellofemoral bone. The data are relevant to the design of implants that match their geometric and material properties to the shape and strength of the underlying bone.

Adult↗
PubMed1994

A case of peculiar plantar warts. Human papillomavirus type 60 infection.

BACKGROUND: Various kinds of viral warts have their own typical clinical appearances and histologic properties. From each of them, a corresponding unique type of human papillomavirus (HPV) has been detected. More than 60 types of HPV have been identified from the warts and other squamous cell epithelial tumors. Human papillomavirus type 60 has been identified in an epidermal cyst on the sole. We present a case of a peculiar plantar wart infected with HPV type 60. OBSERVATIONS: A 21-year-old male student complained of yellowish hyperkeratotic slightly elevated nodules on the right plantar arch. The surface of the nodules was not papillary, but a normal ridge pattern of the sole could be traced. Histologic findings included moderate acanthosis, papillomatosis, and eosinophilic intracytoplasmic large granules with or without surrounded vacuoles. These were noted in the middle and upper epidermis, including the hypertrophic stratum corneum. Virologic findings included HPV antigen detected by anti-HPV polyclonal antibody. The DNA of HPV type 60 was detected by in situ hybridization. CONCLUSION: A new type of plantar wart infected with HPV type 60 is reported. It shows unique clinical and histologic findings that can be distinguished from those of ordinary verruca or myrmecia on the sole.

Adult↗
PubMed1992

Calcium channels in embryonic chick skeletal muscle cells after cultivation with calcium channel blocker.

The effects of chronic treatment with calcium channel blockers were studied on the expression of voltage-dependent calcium channels (VDCCs) in chick skeletal muscle cells developing in culture. Myotubes were treated after 2 days in culture with either 20 microM D600 or 10 microM nifedipine, and measurements were made of the maximum rate of rise (M.R.R.) of the two components of action potential, operated by T- and L-type VDCCs, respectively. Treatment with either blocker reduced the M.R.R. of the action potential component operated by the L-type VDCC throughout the culture period examined. The M.R.R. of the T-type VDCC component, on the other hand, was unaffected by either treatment. The reduction in the M.R.R. of the L-type component in blocker-treated cells is thought to be due to the down-regulation of the expression of L-type VDCC. Thus, it appears that the expression of L-type VDCC in the chick skeletal muscle cells can be regulated by a function of L-type VDCC, which mediate the entry of Ca2+ into the cells. The physiological significance of the L-type VDCC, which expressed prominently early in the development of skeletal muscle cells, for the differentiation of excitability is discussed.

Action Potentials↗
PubMed1992

Chronic treatment with D600 enhances development of sodium channels in cultured chick skeletal muscle cells.

We have studied the long-term effects of D600, a blocker of L-type voltage-dependent Ca channels (VDCC), on the development of voltage-dependent Na channels (VDNC) that are sensitive to tetrodotoxin (TTX), by electrophysiological measurements of the maximum rate of rise of the TTX-sensitive Na spike in cultured chick skeletal muscle cells. Chronic treatment with D600 (2-20 microM) caused a dose-dependent increase in the density of VDNC. The density of VDNC was increased by 150-250% when D600 was added to the cultures at 20 microM from the second day of culture onward. Co-treatment with an inhibitor of the transcription of RNA from DNA, alpha-amanitin, or with cycloheximide, an inhibitor of protein synthesis, prevented the up-regulation by D600. Nifedipine, a different type of blocker of L-type VDCC, was also effective in increasing the density of VDNC, and BAY K 8644, an agonist of L-type VDCC, had the opposite effect. It is suggested that the effect of D600 was mediated via a mechanism specific for L-type VDCC that involves regulation of cytosolic levels of Ca2+ and protein synthesis de novo.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Pharmacological properties of two types of calcium channel in embryonic chick skeletal muscle cells in culture.

We have studied the effects of organic and inorganic Ca channel blockers on the two-component action potentials (low- and high-threshold components) in cultured chick skeletal muscle cells, which are generated by the T- and L-type voltage-dependent Ca channels (VDCCs), respectively. Nifedipine and D600 effectively blocked the high-threshold component of the action potential, whereas omega-conotoxin and phenytoin had no effect on this component. By contrast, the low-threshold component was insensitive to all of these organic Ca channel blockers. Blocking effects of polyvalent cations were observed with the following rank order of relative potency (mean apparent dissociation constant in microM): La3+ (14.7) greater than Ni2+ (20.7) greater than Cd2+ (51.2) greater than Co2+ (912) for the low-threshold component, and Cd2+ (0.7) greater than La3+ (29.2) greater than Co2+ (431) greater than Ni2+ (1241) for the high-threshold component. Taken together, these findings suggest that the pharmacological properties of the T- and L-type VDCCs in cultured chick skeletal muscle cells may differ from those in other preparations.

Action Potentials↗