Biomedical subjects

M Yoshii

Publications and source records attributed to M Yoshii.

At least 37 records · Page 2Linked to original sources

PubMed2000

Role of nitric oxide in the epileptogenesis of EL mice.

PURPOSE: To understand the role of nitric oxide (NO) in the regulation of seizures, we measured the extracellular levels of the NO metabolites nitrite and nitrate as indices of NO generation in the parietal cortex, hippocampus, and temporal cortex of EL mice. Furthermore, alterations of neuronal, endothelial, and inducible nitric oxide synthetase (nNOS, eNOS, and iNOS, respectively) were observed to correlate them with epileptogenesis. METHODS: EL mice of 20 weeks and 30 weeks of age (before and after the establishment of epileptogenesis, respectively) were used. Nitrite was quantified using the specific absorbancy of diazo dye. NOS isoenzymes (nNOS, iNOS, and eNOS) were also investigated in the hippocampus during development until mice were 30 weeks old. Samples (total protein, 8.33 to 8.43 microg) were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified by immunoblotting. RESULTS: EL mice that experienced repetitive seizures showed a remarkable increase in nitrite in the hippocampus at 30 weeks of age compared with EL mice that had no experience of seizures. nNOS and iNOS were major and minor components, respectively, and both increased in parallel with the development of epileptogenesis. eNOS was not detectable. CONCLUSIONS: Excess iNOS (and subsequent increase in harmful NO) and deficient eNOS (and subsequent decrease in NO identified as an endothelium-derived relaxing factor) may work together to form a focus complex.

Animals↗

PubMed2000

Histological study of masseter muscle in a mouse muscular dystrophy model (mdx mouse).

Histological changes in the masseter muscle were observed over time in mdx mice, a muscular dystrophy model. It was found that marked necrosis occurs about the time of weaning at around 4 weeks of age; then the tissue actively regenerates at 8 weeks and stabilizes as regenerated muscle with centronuclei at 15 weeks old. This study examined the centronucleus in regenerated muscle. The process from necrosis to regeneration in muscle fibers occurs a little later in the masseter muscle than in other limbic muscles. Regenerated muscles observed around 15 weeks after birth showed a moth-eaten appearance. Transmission Electron Microscope (TEM) observation of transverse sections of muscle fibers revealed that myofibrils surrounded lost regions in the area showing a moth-eaten appearance. Thus, some defensive mechanism may affect the ability of muscle fibers to maintain a function close to normal in mdx mice even though the muscle fibers develop muscular dystrophy. The function of the masseter muscle drastically changes from sucking to mastication behavior at around 4 weeks, and this was considered to influence the morphological changes in the muscle tissue. The moth-eaten appearance seen at 15 weeks may represent an appropriate myofibril reconstruction preventing invasion of the lost regions.

Aging↗

PubMed2000

[A case of familial juvenile gouty nephropathy associated with a right renal tumor].

We present a case of familial juvenile gouty nephropathy which was associated with a right renal tumor that was found incidentally. The patient was a 27-year-old woman who initially presented with acute gouty arthritis at the age of twenty years. Her mother and her sister had been attacked with acute gouty arthritis in their early twenties. Progressive deterioration in the renal function was noted in the three family members who had experienced gouty attack. Her mother was maintained on hemodialysis. As image diagnoses could not rule out malignancy in her right renal tumor, in situ non-ischemic enucleation of the right renal tumor using a microwave tissue coagulator(Microtaze) and a renal biopsy were performed. The pathological diagnosis of the renal tumor was tubulopapillary adenoma, and the renal biopsy showed minimal change in the glomeruli and tubules. The post-operative course was uneventful. The serum creatinine and creatinine clearance before and three months after the operation were 2.4 mg/dl and 2.6 mg/dl, 36.7 ml/min and 32.5 ml/min, respectively. The renal biopsy findings that glomerular and tubular changes were minimal and there was no tissue precipitation of uric acid or sodium urate, and the fact that her renal function decreased progressively despite the treatment of hyperuricemia suggested strongly that renal function might have deteriorated due to unknown factors other than hyperuricemia.

Adenoma↗

PubMed1999

A 'long-term-potentiation-like' facilitation of hippocampal synaptic transmission induced by the nootropic nefiracetam.

Nefiracetam, a nootropic agent, enhanced the slope of field excitatory postsynaptic potentials in the CA1 region of rat hippocampal slices to about 170% of basal levels, being evident still at 4-h washing-out of the drug. A similar sustained enhancement (>/=16 h after i.m. injection with nefiracetam) was observed in the population spikes recorded from the granular cell layer of the intact mouse hippocampus. Saturation of the enhancement in the synaptic strength occluded potentiation obtained with long-term potentiation (LTP) induced by high-frequency (tetanic) stimulation, and vice versa. Interestingly, the facilitatory action of nefiracetam was blocked by either the nicotinic acetylcholine (ACh) receptor antagonists, alpha-bungarotoxin and mecamylamine, or the selective protein kinase C (PKC) inhibitor, GF109203X, but in contrast, it was not affected by D-2-amino-5-phosphonovaleric acid (APV), a selective N-methyl-D-aspartate (NMDA) receptor antagonist. The results of the present study suggest that nefiracetam, whereas the action is independent of NMDA receptors, induces an 'LTP-like' facilitation of hippocampal synaptic transmission as a consequence of modulation of nicotinic ACh receptors and PKC. This may represent a likely mechanism underlying the cognition-enhancing actions of nefiracetam.

2-Amino-5-phosphonovalerate↗

PubMed1999

REP-1 gene mutations in Japanese patients with choroideremia.

BACKGROUND: Choroideremia (CHM) is an X-linked progressive dystrophy of the choroid, retinal pigment epithelium, and retina. Recently, the REP-1 gene was isolated and the causative mutations in the gene were detected in patients with CHM. In a previous study, we described a Japanese family with CHM who had a mutation in the REP-1 gene. In the present study, we performed extensive analysis of the REP-1 gene in patients with CHM from several institutions in Japan. METHODS: Twenty-six patients with CHM and 5 unaffected females from 22 independently ascertained families were examined. Exons 1-15 of the REP-1 gene were screened by single-strand conformation polymorphism. The DNA fragments suspected of any variations were directly sequenced. RESULTS: Fifteen different mutations, including one previously reported mutation, were detected in 18 families. In addition, carrier status was proven in four unaffected females found to be heterozygous for the mutant allele. CONCLUSIONS: Fifteen different mutations of the REP-1 gene were detected in 18 Japanese families. There were no hot spots for the mutations and no missense mutations. The results show that REP-1 gene defects cause CHM in Japanese patients, and the mutations in these Japanese patients differed from the mutations reported for CHM patients in Europe, Canada, and America except for R267X and 1313delTC. These findings suggest that the mutations occurred independently in the Japanese patients.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Production of radioactive endovascular stents by implantation of 133Xe ions.

A coronary stent was made radioactive by implantation of 133Xe ions for the purpose of suppressing the renarrowing of the part of blood vessel in which the stent is implanted. Electrons of relatively low energies emitted in the decay of 133Xe may give an antiproliferative effect of ionizing radiation to the intimal cells within a limited range of 1 mm. A 133Xe+ beam accelerated at 40 or 60 keV was directed to several stainless steel stents mounted on a target-holder table that could revolve and move up and down to distribute the 133Xe+ ions within a stent as well as among the stents. The radioactive stents produced contained up to 100 kBq of 133Xe and were implanted into the abdominal aortas of rabbits. Neointimal thickening was analyzed by histomorphometry for samples taken 4 weeks after stent implantation. The results indicate that the radioactive stents have a potential to suppress neointimal hyperplasia in rabbits.

Angioplasty, Balloon, Coronary↗

PubMed1998

Differential interactions of the C terminus and the cytoplasmic I-II loop of neuronal Ca2+ channels with G-protein alpha and beta gamma subunits. I. Molecular determination.

Interactions of G-protein alpha (Galpha) and beta gamma subunits (Gbeta gamma) with N- (alpha1B) and P/Q-type (alpha1A) Ca2+ channels were investigated using the Xenopus oocyte expression system. Gi3alpha was found to inhibit both N- and P/Q-type channels by receptor agonists, whereas Gbeta1 gamma2 was responsible for prepulse facilitation of N-type channels. L-type channels (alpha1C) were not regulated by Galpha or Gbeta gamma. For N-type, prepulse facilitation mediated via Gbeta gamma was impaired when the cytoplasmic I-II loop (loop 1) was deleted or replaced with the alpha1C loop 1. Galpha-mediated inhibitions were also impaired by substitution of the alpha1C loop 1, but only when the C terminus was deleted. For P/Q-type, by contrast, deletion of the C terminus alone diminished Galpha-mediated inhibition. Moreover, a chimera of L-type with the alpha1B loop 1 gained Gbeta gamma-dependent facilitation, whereas an L-type chimera with the N- or P/Q-type C terminus gained Galpha-mediated inhibition. These findings provide evidence that loop 1 of N-type channels is a regulatory site for Gbeta gamma and the C termini of P/Q- and N-types for Galpha.

Animals↗

PubMed1998

Differential interactions of the C terminus and the cytoplasmic I-II loop of neuronal Ca2+ channels with G-protein alpha and beta gamma subunits. II. Evidence for direct binding.

The present study was designed to obtain evidence for direct interactions of G-protein alpha (Galpha) and beta gamma subunits (Gbeta gamma) with N- (alpha1B) and P/Q-type (alpha1A) Ca2+ channels, using synthetic peptides and fusion proteins derived from loop 1 (cytoplasmic loop between repeat I and II) and the C terminus of these channels. For N-type, prepulse facilitation as mediated by Gbeta gamma was impaired when a synthetic loop 1 peptide was applied intracellularly. Receptor agonist-induced inhibition of N-type as mediated by Galpha was also impaired by the loop 1 peptide but only when applied in combination with a C-terminal peptide. For P/Q-type channels, by contrast, the Galpha-mediated inhibition was diminished by application of a C-terminal peptide alone. Moreover, in vitro binding analysis for N- and P/Q-type channels revealed direct interaction of Galpha with C-terminal fusion proteins as well as direct interaction of Gbeta gamma with loop 1 fusion proteins. These findings define loop 1 of N- and P/Q-type Ca2+ channels as an interaction site for Gbeta gamma and the C termini for Galpha.

Amino Acid Sequence↗

PubMed1998

Isolation of an Arabidopsis thaliana mutant in which accumulation of cucumber mosaic virus coat protein is delayed.

Cucumber mosaic virus (CMV) is known to systemically infect Arabidopsis thaliana ecotype Columbia plants. In order to identify the host factors involved in the multiplication of CMV, we isolated an A. thaliana mutant in which the accumulation of the coat protein (CP) of CMV in upper uninoculated leaves was delayed. Genetic analyses suggested that the phenotype of delayed accumulation of CMV CP in the mutant plants was caused by a single, nuclear and recessive mutation designated cum1-1, which was located on chromosome IV. The cum1-1 mutation did not affect the multiplication of tobacco mosaic virus, turnip crinkle virus or turnip yellow mosaic virus, which belong to different taxonomic groups from CMV. Accumulation of CMV CP in the inoculated leaves of cum1-1 plants was also delayed either when CMV virion or CMV virion RNA was inoculated. On the other hand, when cum1-1 and the wild-type Col-0 protoplasts were inoculated with CMV virion RNA by electroporation, the accumulations of CMV-related RNAs and the coat protein were similar. These results suggest that the cum1-1 mutation did not affect the uncoating of CMV virion and subsequent replication in an initially infected cell but affected the spreading of CMV within an infected leaf, possibly the cell-to-cell movement of CMV in a virus-specific manner.

Arabidopsis↗

PubMed1998

Nefiracetam modulates acetylcholine receptor currents via two different signal transduction pathways.

Nootropic agents are proposed to serve as cognition enhancers. The underlying mechanism, however, is largely unknown. The present study was conducted to assess the intracellular signal transduction pathways mediated by the nootropic nefiracetam in the native and mutant Torpedo californica nicotinic acetylcholine (ACh) receptors expressed in Xenopus laevis oocytes. Nefiracetam induced a short-term depression of ACh-evoked currents at submicromolar concentrations (0.01-0.1 microM) and a long-term enhancement of the currents at micromolar concentrations (1-10 microM). The depression was caused by activation of pertussis toxin-sensitive, G protein-regulated, cAMP-dependent protein kinase (PKA) with subsequent phosphorylation of the ACh receptors; in contrast, the enhancement was caused by activation of Ca(2+)-dependent protein kinase C (PKC) and the ensuing PKC phosphorylation of the receptors. Therefore, nefiracetam interacts with PKA and PKC pathways, which may explain a cellular mechanism for the action of cognition-enhancing agents.

Animals↗

PubMed1998

Isolation of an Arabidopsis thaliana mutant in which the multiplication of both cucumber mosaic virus and turnip crinkle virus is affected.

During the systemic infection of plants by viruses, host factors play an important role in supporting virus multiplication. To identify and characterize the host factors involved in this process, we isolated an Arabidopsis thaliana mutant named RB663, in which accumulation of the coat protein (CP) of cucumber mosaic virus (CMV) in upper uninoculated leaves was delayed. Genetic analyses suggested that the phenotype of delayed accumulation of CMV CP in RB663 plants was controlled by a monogenic, recessive mutation designated cum2-1, which is located on chromosome III and is distinct from the previously characterized cum1 mutation. Multiplication of CMV was delayed in inoculated leaves of RB663 plants, whereas the multiplication in RB663 protoplasts was similar to that in wild-type protoplasts. This suggests that the cum2-1 mutation affects the cell-to-cell movement of CMV rather than CMV replication within a single cell. In RB663 plants, the multiplication of turnip crinkle virus (TCV) was also delayed but that of tobacco mosaic virus was not affected. As observed with CMV, the multiplication of TCV was normal in protoplasts and delayed in inoculated leaves of RB663 plants compared to that in wild-type plants. Furthermore, the phenotype of delayed TCV multiplication cosegregated with the cum2-1 mutation as far as we examined. Therefore, the cum2-1 mutation is likely to affect the cell-to-cell movement of both CMV and TCV, implying a common aspect to the mechanisms of cell-to-cell movement in these two distinct viruses.

Arabidopsis↗

PubMed1998

Visual function in retinitis pigmentosa related to a codon 15 rhodopsin gene mutation.

To determine the phenotype of a Japanese family in which retinitis pigmentosa cosegregates with a rhodopsin gene mutation, i.e. an asparagine-to-serine change at codon 15 (Asn-15-Ser), 5 affected and 5 unaffected members of one pedigree underwent several ophthalmic examinations as well as Ganzfeld electroretinography (ERG) and multifocal ERG. Genomic DNA samples were analyzed by PCR amplification, sequencing and restriction enzyme digestion. A codon 15 rhodopsin gene mutation (Asn-15-Ser) was found in all affected members. The region of pigmentary degeneration was localized in the lower hemiretina, and visual field defects corresponded to the retinal pigmentary changes. Scotopic ERG amplitudes, rather than photopic ERG amplitudes, were reduced. Multifocal ERG revealed a low magnitude of response density, even for the upper hemiretina, which showed no bony corpuscle pigmentation. Visual function in sectorial retinitis pigmentosa associated with rhodopsin gene codon 15 mutation is on the basis of the rod-cone dystrophy, regardless of differences in phenotypic expression.

Adult↗

PubMed1998

Pattern electroretinogram elicited by a dartboard pattern.

The receptive field size of retinal ganglion cells is closely related to their eccentricity from the fovea. To elicit larger pattern-reversal electroretinograms (P-ERGs), it may be useful to stimulate the retina with patterns having elements that parallel this change in receptive field size. We describe a dartboard pattern consisting of reversal elements that enlarge gradually from the central to the peripheral stimulus field. The utility of the dartboard pattern for eliciting P-ERG was investigated by comparing it with the conventional uniform checkerboard pattern, but with the other stimulus parameters remaining unchanged (96% contrast, 35.9 cd/m2 mean luminance, 3.3 rev/s temporal frequency, 15 degrees circular field). The dartboard pattern produced a significantly larger P50 amplitude than did the checkerboard pattern, while no difference in peak latency was found when 54 min of arc was used as a standard check size for the checkerboard pattern. The dartboard pattern for eliciting P-ERG should prove clinically useful.

Adult↗

PubMed1998

Visual function and gene analysis in a family with Oguchi's disease.

A family with 1 case of retinitis pigmentosa (III-1) and 2 cases of Oguchi's disease (III-2, 3) was examined in terms of electrophysiology as well as molecular biology. The proband (III-3), a 42-year-old female, and 2 older brothers (III-1, 2, aged 52 and 45 years) and 2 unaffected members in the same family participated in this study. Corrected visual acuities of the individuals with Oguchi's disease (III-2, 3) were 1.2. On funduscopy, blood vessels stood out in relief against a metallic-appearing background and a Mizuo-Nakamura phenomenon was evident. Full-field electroretinograms (ERGs) recorded from the proband were indicative of rod dystrophy, but results of other electrophysiological examinations (multifocal ERG, pattern ERG and visual-evoked cortical potential recordings) were within normal limits. Patient III-1 had corrected visual acuities of RE 20 cm/m.m. and LE 30 cm/n.d., severe chorioretinal atrophy in both fundi, and full-field ERG revealed rod-cone dystrophy. Mutation of the arrestin gene (1147de1A) was detected in all 3 patients. Visual function in each patient coincides with that of retinitis pigmentosa or Oguchi's disease, respectively.

Adult↗

PubMed1998

Targeting of soybean-derived sterylglucoside liposomes to liver tumors in rat and mouse models.

The blood clearance, tissue uptake and antitumor efficacy against liver metastasis of M5076 reticulosarcoma in mice and against primary liver cancer in rats of doxorubicin (DOX) encapsulated in two types of liposomes, with and without a soYbean-derived sterylglucoside mixture (SG), were examined. Liposomes entrapping DOX were composed of dipalmitoylphosphatidylcholine (DPPC), SG and cholesterol (Ch) at a molar ratio of 6:1:3, (SG-liposomes) and 6:0:4 (non-SG-liposomes). Pharmacokinetic analysis of drug disposition was based on the area under the curve (AUC) for liposomes up to 24 h following i.v. injection. SG-liposomes showed lower DOX concentrations in blood and higher concentrations in liver compared with non-SG-liposomes. The highest AUC of SG-liposomes in tissue was in liver, 2.4 times higher than that of the free drug. The antitumor efficacy of SG-liposomes was compared with that of free DOX and non-SG-liposomes at a dose of 5 mg DOX/kg. SG-liposomes displayed stronger antitumor activity than the free drug and non-SG-liposomes in murine reticulosarcoma M5076 tumor models and primary liver cancer models reflecting accumulation in hepatocytes. The antitumor activity of SG-liposomes in rats with primary liver cancer was significantly higher compared with free DOX and non-SG-liposomes (ILS: 92.7%).

Animals↗

PubMed1998

[Facilitatory actions of the cognitive enhancer nefiracetam on neuronal Ca2+ channels and nicotinic ACh receptors: their intracellular signal transduction pathways].

Nootropics are proposed to serve as cognition enhancers. The underlying mechanism, however, is largely unknown. We have attempted to assess the intracellular signal transduction pathways mediating the action of nefiracetam, a nootropic agent, on neuronal Ca2+ channels and nicotinic ACh receptors. In NG108-15 cells, nefiracetam (1 microM) enhanced the activities of N/L-type Ca2+ channels without affecting T-type The nefiracetam action was mimicked by dibutyryl cAMP (1 mM), or blocked by pertussis toxin (PTX), indicating that PTX-sensitive inhibitory G-proteins and cAMP-dependent pathways mediate the drug action. Nefiracetam also exerted a dose-dependent biphasic effect on Torpedo nicotinic acetylcholine (nACh) receptors expressed in Xenopus oocytes, in which the drug induced a short-term depression of ACh-evoked currents at submicromolar concentrations (0.01-0.1 microM) and a long-term enhancement of the currents at micromolar concentrations (1-10 microM). The depression was caused by activation of PTX-sensitive G-protein-regulated cAMP-dependent protein kinase (PKA) with subsequent phosphorylation of the ACh receptors; in contrast, the enhancement was caused by activation of Ca(2+)-dependent protein kinase C (PKC) and the ensuing PKC phosphorylation of the receptors. It is concluded that nefiracetam interacts with PKA and PKC pathways, which may explain a cellular mechanism for the action of cognitive enhancers.

Animals↗

PubMed1998

[Effect of ultraviolet-filtering contact lens on rabbit eyes after exposure to ultraviolet light].

We evaluated the protective effect of a newly designed soft contact lens (SCL) on rabbit eyes. This SCL absorbs the ultraviolet B light of wavelengths between 280 nm and 320 nm. Three weeks after resecting the nictitating membrane, the rabbit corneas were covered either by the new SCL or a conventional SCL. The eyes were exposed to ultraviolet light from two 15 W lamps placed 20 cm anteriorly for 3 hours. Another three hours after the exposure, the cornea was examined first with a slitlamp biomicroscope after staining with fluorescein and then by histopathological means after enucleation. Six eyes wearing the new SCL showed moderate superficial punctate keratopathy. Six eyes wearing conventional SCL showed severe superficial keratopathy or corneal erosion. These findings were in good agreement with the histopathological findings. The new ultraviolet-filtering SCL was thus effective in protecting the rabbit cornea under our experimental conditions.

Animals↗

PubMed1998

[Successful treatment with end-to-end ureteral anastomosis for ureteral avulsion caused by abdominal blunt trauma: a case report].

Avulsion of ureter without renal injury is rarely caused by blunt trauma, only 28 cases having been reported in Japan. A 33-year-old male was admitted to our hospital 1 month after blunt abdominal trauma at work. He complained of left flank pain and macroscopic hematuria. Under the suspicion of renal or ureteral injury, drip infusion urography and abdominal computerized tomography revealed an extravasation from the left upper ureter and urinoma formation in the retroperitoneal cavity. In order to reduce the inflammation, the urinoma was drained. The retrograde pyelogram revealed complete obstruction at the left upper ureter, 20 cm from the left ureteral orifice. Urinary tract reconstruction, end-to-end ureteral anastomosis, was performed under the diagnosis of left ureteral avulsion. Drip infusion urography revealed normal ureteral healing without stricture formation at 2 years after reconstruction.

Abdominal Injuries↗