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Biomedical subjects

M Akimoto

Publications and source records attributed to M Akimoto.

At least 19 recordsLinked to original sources
PubMed2006

Retinal repair by transplantation of photoreceptor precursors.

Photoreceptor loss causes irreversible blindness in many retinal diseases. Repair of such damage by cell transplantation is one of the most feasible types of central nervous system repair; photoreceptor degeneration initially leaves the inner retinal circuitry intact and new photoreceptors need only make single, short synaptic connections to contribute to the retinotopic map. So far, brain- and retina-derived stem cells transplanted into adult retina have shown little evidence of being able to integrate into the outer nuclear layer and differentiate into new photoreceptors. Furthermore, there has been no demonstration that transplanted cells form functional synaptic connections with other neurons in the recipient retina or restore visual function. This might be because the mature mammalian retina lacks the ability to accept and incorporate stem cells or to promote photoreceptor differentiation. We hypothesized that committed progenitor or precursor cells at later ontogenetic stages might have a higher probability of success upon transplantation. Here we show that donor cells can integrate into the adult or degenerating retina if they are taken from the developing retina at a time coincident with the peak of rod genesis. These transplanted cells integrate, differentiate into rod photoreceptors, form synaptic connections and improve visual function. Furthermore, we use genetically tagged post-mitotic rod precursors expressing the transcription factor Nrl (ref. 6) (neural retina leucine zipper) to show that successfully integrated rod photoreceptors are derived only from immature post-mitotic rod precursors and not from proliferating progenitor or stem cells. These findings define the ontogenetic stage of donor cells for successful rod photoreceptor transplantation.

Animals↗
PubMed2004

Hepatocyte growth factor as an enhancer of nmda currents and synaptic plasticity in the hippocampus.

Hepatocyte growth factor (HGF) promotes the survival and migration of immature neurons, but its role in the mature brain has remained elusive. In the hippocampus of juvenile rats, we found that the HGF receptor c-Met was expressed in neurons. Furthermore, it was highly Tyr-phosphorylated, more so than in the liver under normal conditions, suggesting that the receptor is activated and that HGF may act continuously in the intact brain. Exogenously applied HGF enhanced synaptic long-term potentiation (LTP) in the CA1 region of hippocampus, but did not affect long-term depression. We further found that HGF augmented N-methyl-D-aspartate receptor-mediated currents in both slices and dissociated neurons. This augmentation is likely to underlie the enhancement of LTP. Considering that the expression of both HGF and c-Met are known to be induced by ischemic stimuli, this modulation would provide a novel understanding of a neuronal regulatory systems shared with pathogenic ischemic states.

Animals↗
PubMed2004

Cyclooxygenase-2 expression and relationship to tumour progression in human renal cell carcinoma.

AIMS: Cyclooxygenase (COX), which catalyses the synthesis of prostaglandins from arachidonic acid, has two isoforms; COX-1 and COX-2. There is ample evidence to suggest an important role for COX-2 in cancer. The aim of this study was to evaluate the clinical significance of COX-2 expression and its localization in the development and progression of human renal cell carcinoma (RCC). METHODS AND RESULTS: The expression and localization of COX-2 were evaluated in human RCC tissues from 75 patients by immunohistochemistry. Immunoreactive COX-2 protein was observed in all cases of RCC, and the levels of COX-2 expression were correlated with tumour grade and pathological stage. Expression of COX-2 was higher in the granular cell subtype than in the clear cell subtype of RCC. Immunoelectron microscopy revealed that COX-2 was expressed in the nuclear membrane, rough endoplasmic reticulum, Golgi complex and mitochondrial membrane of RCC cells. CONCLUSION: COX-2 overexpression within these intracellular organelles in RCC may be associated with renal cell carcinogenesis and COX-2 may be a useful biomarker in RCC.

Adult↗
PubMed2003

S-oxidation of S-methyl-esonarimod by flavin-containing monooxygenases in human liver microsomes.

1. Studies using human liver microsomes and recombinant human cytochrome P450 (CYP) and flavin-containing monooxygenase (FMO) were performed to identify the enzymes responsible for the metabolism of S-methyl-esonarimod (M2), an active metabolite of esonarimod (KE-298, a novel antirheumatic drug). 2. S-oxidative activities of M2 significantly correlated with those of methyl p-tolyl sulfide, a specific substrate of FMOs, as tested using 10 different human liver microsomes (r(2) = 0.539, p<0.05). Thermal treatment of microsomes reduced the S-oxidative activity in the absence of the NADPH-generating system at 45 degrees C for 5 min. However, methimazole, a known competitive substrate of FMOs, was a weak inhibitor of the S-oxidation in liver microsomes. 3. Recombinant human FMO1 and FMO5 produced M3 in greater quantities than recombinant human FMO3. The S-oxidation of M2 by recombinant human FMO5 was not appreciably inhibited in the presence of methimazole. In contrast, methimazole was effective in suppressing the catalytic activity of recombinant human FMO1 and FMO3. 4. The apparent K(m) (K(m app)) for the S-oxidation of M2 in human recombinant FMO5 (2.71 microM) was similar to that obtained using human liver microsomes (2.43 microM). 5. The present results suggest that the S-oxidation of S-methyl esonarimod reflects FMO5 activity in the human liver because the recombinant FMO5 data match well with the human liver microsomal experiments.

Cytochrome P-450 Enzyme System↗
PubMed2002

A new delivery system for 5-fluorouracil using prodrug and converting enzyme.

AIMS: To evaluate a new delivery system of 5-fluorouracil (5-FU) using 5-fluorocytosine (5-FC) as a prodrug and cytosine deaminase induced in vitro and in vivo. METHODS: Fibroblastic cells from rabbit Tenon's capsule were cultured. The cells were exposed to 5-FU and 5-FC with or without cytosine deaminase induced by recombinant adenovirus. In the in vitro study, cell proliferation and DNA synthesis were assessed by MTS, BrdU assay. The effect of 5-FC removal after the treatment of 5-FC and cytosine deaminase induction was also assayed. In the in vivo study cells with or without cytosine deaminase induction were transplanted into the subconjunctival space of mice, followed by eye drops of 1000 microg/ml of 5-FC three times a day. The mice were sacrificed at days 1, 5, and 10, then the cells transplanted were evaluated. RESULTS: Cell proliferation was inhibited by exposure to 5-FU in a dose dependent manner; however, up to 1000 microg/ml of 5-FC did not affect cell proliferation. Cell proliferation was inhibited by exposure to 5-FC in a time dependent manner with induction of cytosine deaminase following infection of recombinant adenovirus. When 5-FC was removed 3 or 6 days after the treatment, the cells grew again. The effect was reproduced in the in vivo model of subconjunctival cellular proliferation although 5-FC was administrated as eye drops. There were no cases with corneal erosion. CONCLUSION: Cell proliferation was inhibited by co-exposure of 5-FC and cytosine deaminase. This new delivery system may merit controlled delivery of 5-FU after filtering surgery.

Animals↗
PubMed2002

Pharmacokinetic and pharmacodynamic analysis of TS-943, a selective non-peptide platelet glycoprotein-IIb/IIIa (GPIIb/IIIa) receptor antagonist, using a nonlinear mixed effect model in dogs.

A simultaneous analysis of the pharmacokinetics and pharmacodynamics of TS-943, a selective nonpeptide platelet glycoprotein-IIb/IIIa (GPIIb/IIIa) receptor antagonist, was made in dogs using a nonlinear mixed effect model. Plasma concentrations of TS-943 were determined after bolus intravenous injection, constant infusion and bolus plus constant infusion. Pharmacokinetic/pharmacodynamic data were fitted using NONMEM software. The pharmacokinetics of TS-943 fitted a two-compartment open model with first-order elimination. The pharmacodynamic model that best fitted platelet aggregation was an inhibitory sigmoid Emax model. The final estimates for E0 (baseline effect), Emax (maximum effect), IC50 (50% inhibitory concentration) and gamma (Hill coefficient) were 66.3%, 64.3%, 104 ng mL(-1) and 1.37, respectively. Correlations between TS-943 plasma concentration and extension of template bleeding time were examined by fitting with an exponential model. The TS-943 plasma concentration necessary to double bleeding time (C2-BTE) was approximately 209 ng mL(-1). The model estimated that the C2-BTE/IC50 (inhibition of platelet aggregation) ratio was approximately 2.0-fold in dogs. Our results suggest that the ratio values for dogs and man are comparable. A nonlinear mixed effect model was a useful tool for exploring the concentration-effect relationship for both efficacy and safety of TS-943 in dogs and man. In this study, the dog was found to be a useful model for screening of efficacy and safety of TS-943 in man.

Amidines↗
PubMed2001

Lack of association of mutations of the bestrophin gene with age-related macular degeneration in non-familial Japanese patients.

BACKGROUND: Heterozygous mutations of the bestrophin gene are associated with Best macular dystrophy (BMD). The bestrophin gene is specifically expressed in the retinal pigment epithelium. BMD is a hereditary form of macular degeneration that may develop subretinal neovascularisation similar to the wet type of age-related macular degeneration (AMD). PURPOSE: To study whether mutations of the bestrophin gene occur in non-familial Japanese AMD patients. METHODS: A total of 85 non-familial AMD patients (average age 67.5 years; 71 male, 14 female) diagnosed by indocyanine green angiography were screened. Among them, 69 patients (81 %) were classified as having wet type AMD. Genomic DNA was purified from the total blood and used as the template for polymerase chain reaction (PCR). All the exons of bestrophin gene were amplified by PCR. Mutation analysis was performed by SSCP using the ABI Prism 310 Genetic Analyzer (Perkin Elmer). Nucleotide sequence was determined by direct sequencing of the PCR amplicons. As the control, 105 non-AMD patients (average age 62.0 years; 52 male, 53 female) were screened by the same method. RESULTS: Only one AMD patient had a specific polymorphism in exon 2, but no mutations leading to amino acid substitutions were found. In exon 2 and 3, two further polymorphisms were detected in all AMD patients as well as normal controls. CONCLUSION: No mutations were found in the bestrophin gene in nonfamilial Japanese patients with AMD or in normal controls.

Aged↗
PubMed2001

Definition of a 1-Mb homozygous deletion at 9q32-q33 in a human bladder-cancer cell line.

We performed detailed molecular analyses of a suspected homozygous deletion on chromosome 9q32-q33 in a bladder-cancer cell line (KYBTDS) derived from a superficial papillary transitional cell carcinoma (TCC). We examined 13 sequence-tagged site (STS) markers mapped along 9q32-q33 by polymerase chain reaction (PCR), and used 13 bacterial artificial chromosome (BAC)/bacteriophage P1-derived artificial chromosome (PAC) genomic clone probes representing these STS markers as probes for dual-color fluorescence in situ hybridization (FISH) analyses to define the deleted region cytogenetically and at the molecular level. Southern blotting confirmed the findings. This combination of techniques revealed that the homozygous deletion in the KYBTDS cell line involved less than 1 megabase of DNA, flanked by markers A003P42 and SGC33380. This interval overlaps part of a common region of deletion observed in a number of primary bladder cancers; moreover, the DNA sequence within the 1-Mb segment corresponds to part of a YAC genomic clone that encompasses a putative tumor suppressor gene, DBCCR1.

Blotting, Southern↗
PubMed2001

Evaluation of the retinal nerve fiber layer thickness in eyes with idiopathic macular holes.

PURPOSE: To compare the retinal nerve fiber layer thickness in eyes with idiopathic macular holes and age-matched normal controls using scanning laser polarimeter. METHODS: The retinal nerve fiber layer thickness was measured in 40 eyes of 40 consecutive patients with idiopathic macular hole (stage 1, 10 eyes; stage 2, eight eyes; stage 3, 15 eyes; stage 4, seven eyes) and 40 eyes of 40 age-matched normal controls with a scanning laser polarimeter. The retinal nerve fiber layer thickness within a 10-pixel-wide ellipse located concentrically with the disk and located 1.5-disk diameters from the center of the disk was measured. The mean overall retinal nerve fiber layer thickness of the peripapillary retina, four 90-degree quadrants, and 16 equal sectors of every 22.5 degrees was calculated for both groups. The retinal nerve fiber layer thickness in the two groups was statistically compared. RESULTS: The mean retinal nerve fiber layer thickness measurement for the overall peripapillary retina and for three of the four 90-degree quadrants was not significantly different between the two groups. However, the temporal 90-degree quadrant was significantly thinner in the macular hole group (47.2 versus 54.6 microm, P =.026). For the 16 sectors of 22.5 degrees, the lower three sectors of the four sectors in the temporal quadrant were thinner in the macular hole group (P <.05). CONCLUSIONS: The retinal nerve fiber layer thickness of the papillomacular area is thinner in eyes with idiopathic macular hole than that in normal eyes. The progressive thinning of the retinal nerve fiber layer thickness as the stage of the macular hole advances may suggest that surgery should be done at the earliest stage.

Aged↗
PubMed2001

Preferential gene transfer to BBN-induced rat bladder tumor by simple instillation of adenoviral vector.

OBJECTIVES: We examined the efficacy and safety of intravesical instillation of adenoviral vectors to develop gene therapy protocols for bladder cancer. In this study, an adenoviral vector containing the beta-galactosidase gene was instilled into the rat bladder with N-butyl-N-(4-hydroxybutyl) nitrosamine-induced tumors. We evaluated the effect of the glycosaminoglycan (GAG) layer on adenoviral transduction of bladder urothelium. In addition, we determined the systemic distribution of the adenoviral vector after instillation. METHODS: An adenoviral vector containing either the beta-galactosidase or the herpes simplex virus thymidine kinase gene was transurethrally instilled into the bladder, after which efficacy of gene transfer was evaluated by staining with 5-bromo-4-chloro-3-indolyl-beta-D-galactopyraminoside, and the distribution of the gene was examined by reverse transcriptase-polymerase chain reaction. To determine the extent to which the GAG layer may have inhibited gene transfer by the adenoviral vector, prior to instillation of adenoviral vector, normal bladders were pretreated with either phosphate-buffered saline or HCl, which would destroy the mucosal GAG layer. RESULTS: We found that intravesical instillation of an adenoviral vector caused preferential gene transfer to the tumor cells and that expression of the transferred gene occurred exclusively in the bladder. Removing the GAG layer rendered the normal bladder highly susceptible to adenoviral gene transfer, indicating that GAG on normal mucosa prevented adenoviral gene transfer. CONCLUSIONS: BBN-induced bladder tumors were preferentially transduced by instillation of adenoviral vectors probably due to the lack of GAG layers on their surface. Intravesical instillation of adenoviral vectors does not result in systemic infection. These results encourage the consideration of gene therapy in the treatment of human bladder cancer.

Adenoviridae↗
PubMed2001

Adenovirus-mediated ex vivo gene transfer of basic fibroblast growth factor promotes collateral development in a rabbit model of hind limb ischemia.

Adenovirus-mediated ex vivo gene transfer of basic fibroblast growth factor (bFGF), a new strategy for the treatment of chronic vascular occlusive disease, was examined in a rabbit model of hind limb ischemia. The left femoral artery was completely excised to induce an ischemic state in the hind limb of male rabbits. Simultaneously, a skin section was resected from the wound, and host fibroblasts were cultured. The cultured fibroblasts were infected with adenovirus vector containing modified human bFGF cDNA with the secretory signal sequence (AxCAMAssbFGF) or LacZ cDNA (AxCALacZ). At 21 days after femoral artery excision, the gene-transduced fibroblasts were administered through the left internal iliac artery. The fibroblasts significantly accumulated in the ischemic hind limb, and the AxCAMAssbFGF-treated cells secreted bFGF for less than 14 days without elevation of systemic bFGF level. At 28 days after cell administration, calf blood pressure ratio, angiographic score, capillary density of muscle tissue and blood flow of the left internal iliac artery were determined, and animals with AxCAMAssbFGF-treated cells showed significantly greater development of collateral vessels, as compared with those with AxCALacZ-treated cells. These findings suggest that adenovirus-mediated ex vivo gene transfer of bFGF was effective for improvement of chronic limb ischemia.

Adenoviridae↗
PubMed2001

Repair of a fistula between the bladder and the perineal skin by femoral gracilis flap interposition.

The successful repair of a fistula between the bladder and the perineal skin using a femoral gracilis flap is reported. A 70-year-old woman, who 10 years previously had undergone a total hysterectomy for uterine cancer, developed a fistula between the bladder and the perineal skin after she underwent Mile's operation for rectal cancer. Initially, an attempt was made to repair the fistula by the transabdominal approach. This failed, probably because of the lack of supporting tissue between the bladder and the perineal skin. The second repair was performed with plastic surgeons. A secure three-layer bladder closure was accomplished. A right femoral gracilis flap was developed and rotated 180 degrees to fill the defect in the skin and subcutaneous tissue. Four weeks after surgery, cystography revealed no fistula or urinary leakage and the drainage catheter was removed. Femoral gracilis flap interposition was successful for repair of a fistula between the bladder and the perineal skin when there was no supporting tissue due to extensive exenteration in the surgical removal of rectal cancer and after other repair procedures had been unsuccessful.

Aged↗
PubMed2001

Urothelial mucosal concentration of levofloxacin administered before transurethral resection: Is the mucosal concentration predictable?

BACKGROUND: Although it is an established surgical technique, transurethral resection (TUR) is associated with a certain incidence of postoperative bacteriuria. Assessment was made whether the urothelial mucosal concentration of an antibiotic administered before TUR was high enough to decrease the incidence of urinary tract infection (UTI). Also investigated were factors predicting the organ concentration. METHODS: Forty-nine patients (45 men and four women aged 51-79 years with a median age of 70 years) who underwent TUR between August 1996 and September 1997 were enrolled in the study. Each patient received 200 mg of levofloxacin (LVFX) about two hours before surgery. Blood and bladder urine were collected and urothelial mucosa was harvested at the time of TUR. Then the LVFX concentration in these samples was measured using high-performance liquid chromatography. The association between drug levels, or the ratio to the serum concentration, and factors likely to affect the vascular system that delivers the drug (age, bodyweight, blood pressure, pulse rate, total cholesterol and diabetes mellitus) were investigated. RESULTS: The mean serum drug level was 2.4 microg/mL, and it was 206.4 microg/mL in the urine and 5.7 microg/mL in the urothelial mucosa. The mean ratio of the mucosal to serum concentrations was 2.6. The urinary drug concentration showed no association with any of the factors assessed, while the serum concentration decreased with increasing bodyweight (P = 0.03). As the diastolic blood pressure increased, both the mucosal drug concentration and the mucosa/serum ratio decreased (P < 0.01). When the relationship between the serum and mucosal concentrations was investigated, no correlation was found. However, the mucosa/serum ratio (indicating the transfer of LVFX from the blood) was positively correlated with the mucosal concentration. CONCLUSION: Preoperative administration of LVFX was demonstrated to have potential value for the prophylaxis of UTI after TUR. Both the mucosal concentration and the mucosa/serum ratio were correlated with the diastolic blood pressure. As the diastolic blood pressure seems to be an indicator of the tissue concentration of LVFX, it may be possible to set the optimum dose based on the diastolic pressure.

Aged↗
PubMed2001

Scrotal reconstruction with a thinned flap based on both inferior epigastric arteries. Case report.

A 62-year-old man presented with an extensive defect of the scrotum caused by Fournier's gangrene. We reconstructed the scrotum using a thinned flap based on both inferior epigastric arteries one month after the first debridement. This method has the advantage of achieving adequate mobility of the reconstructed scrotum. The results were satisfactory both functionally and cosmetically, although we had to repair a hernia at the donor site a year later.

Debridement↗
PubMed2001

Suicide gene therapy for chemically induced rat bladder tumor entailing instillation of adenoviral vectors.

The efficacy of an in vivo gene therapy protocol making use of an adenoviral vector in the treatment of bladder cancer was examined. Bladder tumors were induced in rats by oral administration of BBN (N-butyl-N-(4-hydroxybutyl)nitrosamine). Histologically, such tumors resemble those seen in human bladder cancer, and the cells can be selectively transduced using adenoviral vectors. The therapeutic protocol thus entailed instillation of an adenoviral vector containing the HSV-tk suicide gene into rat bladder followed by a regimen of intraperitoneal ganciclovir (GCV) injections. Histological examination after a short-term GCV regimen (3 days) revealed marked vacuolization of the tumor cells. Moreover, TUNEL assays showed that the cytotoxic reaction was mediated by apoptosis. Following a long-term GCV regimen (14 days), tumor growth was significantly inhibited and glandular metaplasia was observed. This is the first report demonstrating the efficacy of in vivo suicide gene therapy in a chemically induced transitional cell carcinoma like that seen in most human bladder cancer. Intravesical instillation is already a well established clinical technique. Our findings indicate that now there is a strong potential for its incorporation into new and useful gene therapies aimed at the treatment of human bladder cancer.

Adenoviridae↗
PubMed2001

Electromyography of male rat perineal musculature during copulatory behavior.

Electromyogram (EMG) recordings were made from the bulbospongiosus (BS) and ischiocavernosus (IC) muscles of the awake male rat in order to evaluate the roles played by these muscles in the implementation of penile intromission during a copulatory encounter. Male rats with bipolar wire electrodes implanted chronically in the BS and IC muscles were mated with sexually receptive females. Concurrent videotape recordings established a relationship between EMG and components of male rat copulatory behavior, i.e. mount, intromission and ejaculation. On EMGs recorded from the IC muscle, the initial low-amplitude phase at the initiation of each behavioral component was distinguished from the late high-amplitude phase whenever the male accomplished mounting or intromission. In the BS muscle, the late high-amplitude phase was observed only when the male accomplished intromission. Power spectrum analysis by fast Fourier transformation revealed that in the IC muscle the two phases differed at an overall range of 100-1,000 Hz. In the BS muscle, however, the spectra of the two phases differed at a specific range of 400-600 Hz. Recruitment of additional motor units would culminate in such a characteristic rise in the power spectrum. The results suggest that somatosensory inputs contingent on the intromission cause such recruitment in the BS to regulate penile cups and other movements.

Animals↗