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Biomedical subjects

N Okamoto

Publications and source records attributed to N Okamoto.

At least 109 records · Page 6Linked to original sources
PubMed1999

Hyperoxia causes decreased expression of vascular endothelial growth factor and endothelial cell apoptosis in adult retina.

Mice or humans with photoreceptor degenerations experience permeability and dropout of retinal capillaries. Loss of photoreceptors results in decreased oxygen usage and thinning of the retina with increased oxygen delivery to the inner retina. To investigate the possibility that increased tissue oxygen plays a role in the vascular damage, we exposed adult mice to hyperoxia, which also increases oxygen in the retina. After 1, 2, or 3 weeks of hyperoxia, there was a statistically significant decrease in retinal vascular density that was not reversible, and endothelial cell apoptosis was demonstrated by TUNEL staining. Mice exposed to hyperoxia and mice with photoreceptor degeneration both showed decreased expression of VEGF in the retina. After complete or near-complete degeneration of photoreceptors, there was increased expression of VEGF in RPE cells, which may explain the association of photoreceptor degeneration and neovascularization in or around the RPE. Increased expression of VEGF in photoreceptors of transgenic mice failed to prevent hyperoxia-induced retinal capillary dropout. These data suggest that increased oxygen in the retina, either by increased inspired oxygen or by photoreceptor degeneration, results in endothelial cell death and dropout of capillaries. Decreased expression of VEGF may be a contributing factor, but the situation may be more complicated for mature retinal vessels than it is for immature vessels, because VEGF replacement does not rescue mature retinal vessels, suggesting that other factors may also be involved.

Animals↗
PubMed1999

A clinical and molecular study of a patient with Simpson-Golabi-Behmel syndrome.

Simpson-Golabi-Behmel syndrome (SGBS) is one of the overgrowth syndromes. Microdeletions of the glypican-3 (GPC3) gene were described by Pilia et al. (1996). Glypican-3 encodes a putative extracellular proteoglycan which is expressed in embryonic mesodermal tissues and plays an important role in embryonal growth. We report a Japanese patient with SGBS who had a single base deletion in the exon 7 of the GPC3 gene. This is the first report of a single base deletion of the GPC3 gene.

Abnormalities, Multiple↗
PubMed1999

Dramatic inhibition of retinal and choroidal neovascularization by oral administration of a kinase inhibitor.

The most common cause of new blindness in young patients is retinal neovascularization, and in the elderly is choroidal neovascularization. Therefore, there has been a great deal of attention focused on the development of new treatments for these disease processes. Previous studies have demonstrated partial inhibition of retinal neovascularization in animal models using antagonists of vascular endothelial growth factor or other signaling molecules implicated in the angiogenesis cascade. These studies have indicated potential for drug treatment, but have left many questions unanswered. Is it possible to completely inhibit retinal neovascularization using drug treatment with a mode of administration that is feasible to use in patients? Do agents that inhibit retinal neovascularization have any effect on choroidal neovascularization? In this study, we demonstrate complete inhibition of retinal neovascularization in mice with oxygen-induced ischemic retinopathy by oral administration of a partially selective kinase inhibitor that blocks several members of the protein kinase C family, along with vascular endothelial growth factor and platelet-derived growth factor receptor tyrosine kinases. The drug also blocks normal vascularization of the retina during development but has no identifiable adverse effects on mature retinal vessels. In addition, the kinase inhibitor causes dramatic inhibition of choroidal neovascularization in a laser-induced murine model. These data provide proof of concept that pharmacological treatment is a viable approach for therapy of both retinal and choroidal neovascularization.

Administration, Oral↗
PubMed1999

Evaluation of a clinic-based screening program for lung cancer with a case-control design in Kanagawa, Japan.

A case-control study was performed in Kanagawa Prefecture, Japan, which introduced lung cancer screening, by family physicians, to determine if this program was effective. The subjects were persons who died from lung cancer, restricted to those between 40 and 74 years old at death, and National Health Insurance (NHI) holders. A total of 193 lung cancer deaths meeting the criteria were selected for the case group. Three controls for each case were selected at random from living NHI holders matched by residence, gender and year of birth (+1 year). Smoking adjusted odds ratios were calculated using a multiple logistic regression model. The odds ratios of dying from lung cancer for screening participants within 12 months compared with non-participants was 0.535 which was statistically significant (95% CI, 0.337-0.850). The odds ratio in the 12-24-month period before diagnosis was 0.638 (0.302-0.967), which was also significant. The results demonstrated that screening for lung cancer by family physicians can reduce the lung cancer mortality, and that a clinic-based screening program by family physicians is effective.

Adult↗
PubMed1999

Cellular mechanisms of blood-retinal barrier dysfunction in macular edema.

PURPOSE: To determine the mechanism of blood-retinal barrier (BRB) dysfunction in human and experimental specimens using immunocytochemistry. METHODS: Extravascular albumin was localized in clinical specimens and retinas from transgenic mice that overexpress vascular endothelial growth factor (VEGF) in the photoreceptors. Transgenic mouse retinas were also labeled with Griffonia simplicifolia isolectin-B4 (GSA), a lectin that binds to endothelial cells. RESULTS: The BRB is established by the presence of tight junctions between the retinal vascular endothelial (RVE) cells and the RPE cells and by a paucity of intraendothelial cell vesicles. When BRB breakdown occurs in human ocular disorders such as diabetic retinopathy, retinitis pigmentosa, or cystoid macular edema, staining for extravascular albumin reveals leakage through the tight junctions, an upregulation of intraendothelial vesicles, and permeation of RVE or RPE cells that have undergone degenerative changes. VEGF, in addition to inducing neovascularization (NV), promotes vascular leakage. In VEGF transgenic mice, BRB failure is confined to the outer retina, the area where NV occurs. GSA binds to the luminal and abluminal surfaces of RVE cells in new and established vessels and to intraendothelial vesicles and interendothelial cell junctions in areas of vascular leakage. CONCLUSION: BRB dysfunction may be mediated by leakage through the tight junctions of RVE or RPE cells, by trans-endothelial vesicular transport, or by permeation of RVE or RPE cells that have undergone degenerative changes. GSA may be a useful marker to assist in recognizing open tight junctions and an increase in intraendothelial cell vesicles, which are indicative of BRB failure.

Animals↗
PubMed1999

Double-blind test on the efficacy of methylcobalamin on sleep-wake rhythm disorders.

The therapeutic effect of methylcobalamin (Met-12) on sleep-wake rhythm disorders was examined in a double-blind test. In the test group which was given a large dosage, a higher percentage of improvement was found compared to the control group with a small dosage, although the difference was not significant. The test group inconsistently showed significant improvement in both the sleep-wake cycle parameters and in clinical symptoms. The tendency was for the results to show a beneficial effect of Met-12 on rhythm disorders. However, because the percentage of improvement was low and significant improvement was inconsistent, Met-12 might be considered to have a low therapeutic potency and possible use as a booster for other treatment methods of the disorders.

Affect↗
PubMed1999

Association of plasma fibrinogen level and blood pressure with diabetic retinopathy, and renal complications associated with proliferative diabetic retinopathy, in Type 2 diabetes mellitus.

AIM: To clarify the association of several clinical parameters, including plasma fibrinogen level, with diabetic retinopathy in patients with Type 2 diabetes mellitus (DM). METHODS: A total of 294 Japanese patients with Type 2DM were studied; 53 patients with no diabetic retinopathy (NDR), 90 with background diabetic retinopathy (BDR), and 151 with proliferative diabetic retinopathy (PDR). Multiple logistic regression analysis was performed to assess variables independently associated with diabetic retinopathy in two settings: presence of retinopathy of any severity and presence of advanced retinopathy. RESULTS: The following parameters were identified as independent factors associated with the presence of diabetic retinopathy (NDR vs. BDR + PDR): type of therapy (P<0.0005), log-transformed plasma fibrinogen level (P < 0.05), mean blood pressure (P < 0.05), and duration of diabetes (P < 0.05). The independent variables associated with advanced retinopathy were type of therapy (P<0.00005), age (P<0.0005) and nephropathy (P<0.05). Body mass index, smoking and hypertensive status, HbA1c and total cholesterol levels were not independently associated. CONCLUSIONS: These data suggest that in patients with Type 2 DM, an increased blood viscosity due to high fibrinogen level as well as an elevated intravessel pressure play a role in the development of diabetic retinopathy, and that the progression to PDR is influenced or accompanied by the deterioration of renal status.

Aged↗
PubMed1999

Sudden death in the working population: a collaborative study in central Japan.

AIM: Few epidemiological data are available describing the sudden death of persons in their prime. This study aims to elucidate when and how sudden death occurs among employees. METHODS: A total of 196775 employees from 10 workplaces in Central Japan were surveyed for non-traumatic sudden death during 1989-1995. Demographic data and information regarding onset were collected by their workplace healthcare professionals. RESULTS: We identified 251 male and 13 female cases of sudden death. The annual incidence was 21.9 (for men) and 5.7 (for women) per 100000 population. Sudden death occurred more frequently in April when the new business year starts (risk ratio [95% confidence interval], 1.62 [0.94-2.79]) than in other months, without seasonality. Sudden death peaked on Sundays (risk ratio, 1.90 [1.20-2.99]) and Saturdays (risk ratio, 1.36 [0.83-2.21]) as compared with weekdays, and was likely to occur in the small hours (risk ratio, 1.71 [0.94-3.10] at 00-0300 h and 1.47 [0.79-2.72] at 0300-0600 h vs at 0900-1200 h. Only 17% of employees died at work, which was significantly less than expected (P<0.001). CONCLUSION: These findings differed from those of elderly people and suggest that sudden death of persons in their prime is related to occupational stress and its relief.

Adult↗
PubMed1999

Clinical features of paroxysmal positional vertigo presenting combined lesions.

Benign paroxysmal positional vertigo (BPPV) is one of the common vestibular disorders. Canalolithiasis is thought to be a likely lesion. A canalith repositioning procedure (CRP by Epley) generally yields good resolution of vertigo and nystagmus. The authors confirmed the efficacy of this procedure on typical BPPV of the posterior semicircular canal type. We designed a new procedure for BPPV of the lateral canal type, which also yielded satisfactory results. BPPV sometimes presents a nystagmus pattern, which suggests multiple lesions. We have seen eight cases of BPPV showing nystagmus that combines both the posterior and the lateral canal types. Combined CRP was performed on these cases, which again gave good clinical results. Other BPPV cases were associated with central lesions. We must be aware that BPPV may involve multiple canals and may be associated with central lesions.

Aged↗
PubMed1999

Hemolytic uremic syndrome associated with immunoglobulin A nephropathy: a case report and review of cases of hemolytic uremic syndrome with glomerular disease.

A 35-year-old man with immunoglobulin A (IgA) nephropathy who developed hemolytic uremic syndrome (HUS) presented with transient elevation of serum creatinine, thrombocytopenia, and hemolytic anemia with fragmented red cells with nephrotic syndrome. Hemolytic anemia and the temporarily deteriorated renal function were improved after hemodialysis and plasma exchange. Histological findings were consistent with HUS and IgA nephropathy. Including this case, we reviewed the cases of HUS accompanied by glomerular diseases reported from 1969 to 1996. Surprisingly, most cases showed nephrotic syndrome at the onset of HUS. Several possible relationships between HUS and nephrotic syndrome are discussed.

Adult↗
PubMed1999

Doppler echocardiographic evaluation of the hemodynamics in absent aortic valve.

Hemodynamics were estimated by Doppler echocardiography in a neonate with an absent aortic valve and absent or extremely hypoplastic mitral valve. The coronary blood flow depended on the increased end-diastolic pressure of the left ventricle. Pulmonary venous congestion, which was also due to the increased end-diastolic pressure of the left ventricle, may induce decreased oxygen saturation and, subsequently, further myocardial hypoxia, poor contraction and increased end-diastolic pressure of the left ventricle. Finally, hypoxic blood was supplied to each organ from the pulmonary artery through the ductus arteriosus, which induced severe acidosis and differential cyanosis after birth.

Aortic Valve↗
PubMed1999

Hypoxia inducible factor-1alpha is increased in ischemic retina: temporal and spatial correlation with VEGF expression.

PURPOSE: Hypoxia inducible factor-1 (HIF-1) is a transcription factor composed of HIF-1alpha and HIF-1beta subunits. HIF-1 transactivates multiple genes whose products play key roles in oxygen homeostasis, including vascular endothelial growth factor (VEGF). This study was designed to determine whether HIF-1 levels are increased in ischemic retina and whether there is a correlation with increased expression of VEGF. METHODS: C57BL/6J mice were killed at time points that span retinal vascular development (PO to adult), or on postnatal day (P) 7 they were placed in a 75% oxygen environment for 5 days and then removed to room air and killed after 0, 2, or 6, or 24 hours and 5 or 14 days. Eyes were frozen, and retinas were isolated and used for immunoblot analysis, or eyes were sectioned for immunohisto chemical staining for HIF-1alpha or HIF-1beta, or for in situ hybridization for VEGF. RESULTS: Immunoblots of retinal lysates showed low levels of HIF-1alpha at PO that were markedly increased at P4, remained high throughout the period of retinal vascular development and then decreased to an intermediate level in adults. HIF-1beta levels were relatively constant at all time points. In mice with oxygen-induced ischemic retinopathy, HIF-1alpha levels were increased in the retina. The peak of increase occurred at 2 hours, and levels returned to baseline by 24 hours. Immunohistochemistry showed increased staining for HIF-1alpha throughout the hypoxic inner retina, but not in the normoxic outer retina. There was no modulation of HIF-1beta levels. There was constitutive expression of VEGF mRNA in the inner nuclear layer that was increased 6 hours after the onset of hypoxia and remained elevated for several days. CONCLUSIONS: There are increased levels of HIF-1alpha in ischemic retina that show temporal and spatial correlation with increased expression of VEGF. These findings are consistent with the hypothesis that HIF-1 plays a role in upregulation of VEGF in ischemic retina.

Aging↗
PubMed1998

Local expression of immunoregulatory IL-12p40 gene prolonged syngeneic islet graft survival in diabetic NOD mice.

Local production of immunosuppressive cytokines will be one of the most suitable therapeutic strategies against organ-specific autoimmune diabetes. To establish such a new therapy, we constructed recombinant adenoviral vectors with inserted mIL-12p40 (Ad.IL-12p40) and mIL-10 (Ad.IL-10). Sufficient amounts of IL-12p40 and IL-10 were secreted by relevant adenovirus-transfected nonobese diabetic (NOD) islets. Shortly after transfection, 400 NOD islets transfected with Ad.IL-12p40 or Ad.IL-10 were transplanted under the renal capsule of a newly diabetic NOD mouse. NOD mice with IL-12p40-producing islet grafts kept normoglycemia in all of 14 grafted mice for over 4 wk after transplantation. In contrast, NOD mice with IL-10-producing islet grafts became diabetic in all of six grafted mice within 2 wk af-ter transplantation. Reverse transcription-PCR analysis revealed that local production of IL-12p40 led to the decrease of interferon-gamma and the augmentation of transforming growth factor-beta at the graft site. These results suggest that IL-12 plays an important role in the destruction of islet cells at the inflamed site of autoimmunity. Such a local blockade of IL-12 would be a useful gene therapy for human autoimmune diabetes.

Adenoviridae↗
PubMed1998

Site-directed mutagenesis of the conserved threonine (Thr243) of the distal helix of fungal cytochrome P450nor.

Cytochrome P450nor (P450nor) is a heme enzyme which catalyzes NO reduction in denitrifying fungi. Threonine 243 (Thr243) of P450nor, which corresponds to the conserved threonine of monooxygenase cytochrome P450s, was replaced by 18 different amino acids via site-directed mutagenesis. The mutation did not seriously affect the optical absorption and the CD spectral properties of the enzyme in several oxidation, ligation, or spin states or the association rate constant for association of NO with the ferric iron, suggesting subtle and local structural changes in the heme environment on Thr243 mutation. However, the NO reduction activity was dramatically altered by Thr243 mutation, depending on the properties of the replaced amino acids. The catalytic activity, as measured by N2O formation and NADH consumption, was considerably retained on substitution of Asn, Ser, and Gly for Thr243, while it was profoundly decreased or lost on substitution with other amino acids. Kinetic analysis of the reaction of the enzymes with NO and NADH indicated that the decrease in the enzymatic activity upon Thr243 mutation mainly results from a decrease in the rate of reduction of the ferric-NO complex with NADH. On the basis of these enzymatic, kinetic, and spectroscopic results, as well as on the basis of the crystal data for native P450nor [Park, S.-Y., et al. (1997) Nat. Struct. Biol. 4, 827-832], the role of the conserved threonine at the 243 position in the NO reduction reaction by P450nor is discussed. We also discuss structural similarities or differences in the vicinity of the conserved threonine between P450nor and other monooxygenase P450s.

Catalysis↗
PubMed1998

Cohen syndrome with high urinary excretion of hyaluronic acid.

Cohen syndrome (MIM 216550) is an autosomal recessive disorder of unknown pathogenesis. The clinical manifestations of Cohen syndrome can be explained as a connective tissue disorder. We found a remarkably high level of urinary hyaluronic acid in 3 patients with Cohen syndrome. Hyperhyaluronic aciduria is a characteristic finding in Werner syndrome and some other conditions. We suggest that the basic defect of Cohen syndrome is associated with a metabolic abnormality in the extracellular matrix.

Abnormalities, Multiple↗