Biomedical subjects

Toru Nakazawa

Publications and source records attributed to Toru Nakazawa.

32 records · Page 2Linked to original sources

PubMed2004

[Two cases of orbital myositis with monoclonal gammopathy of undetermined significance].

PURPOSE: We report two cases of idiopathic orbital myositis with monoclonal gammopathy. CASE: Case one was a 47-year-old man, who had bilateral swelling of the extraocular muscles and impairment of the left optic nerve. Case two was a 27-year-old woman, who had bilateral proptosis. An immunological test showed that both patients had monoclonal gammopathy, and they were diagnosed as having monoclonal gammopathy of undetermined significance(MGUS). RESULTS: In case one, the patient achieved remission with steroid pulse therapy followed by administration of high doses of a steroid. In case two, because of repeated recurrence, the patient was treated with steroid pulse therapy and then radiation therapy to achieve final remission. CONCLUSION: We need to pay attention in the diagnosis of orbital myositis to distinguish MGUS. Such patients have an atypical clinical course and are resistant to ordinary steroid therapy.

Adult↗

PubMed2003

VLDL induces adipocyte differentiation in ApoE-dependent manner.

OBJECTIVE: To clarify the role of very low density lipoprotein (VLDL) and apolipoprotein E (apoE) in adipogenesis, we studied newly developed hyperlipidemic obese (ob/ob;apoE-/-) mice. Because hydrolysis of VLDL is believed to be the major source of adipogenic free fatty acids, a higher plasma level of VLDL in these mice should exaggerate obesity. METHODS AND RESULTS: When fed a high-fat, high-cholesterol diet, ob/ob;apoE-/- mice did not show increased body weight or an increased amount of adipose tissue in spite of increased plasma VLDL levels, whereas ob/ob mice showed an increased body weight and amount of adipose tissue, suggesting that there is a novel apoE-dependent pathway for adipogenesis. In vitro experiments using bone marrow stromal cells and 3T3-L1 cells confirmed this notion. ApoE-deficient VLDL did not induce adipogenesis, whereas normal VLDL induced adipogenesis in these cells. The incubation of apoE-deficient VLDL with recombinant human apoE restored its adipogenic activity. Tetrahydrolipstatin, a lipoprotein lipase inhibitor, did not affect the adipogenic activity of VLDL, suggesting that hydrolysis of VLDL did not play a major role in its effects. In fact, lipid components of VLDL or free fatty acids induced only partial adipogenesis. CONCLUSIONS: Our findings indicate that VLDL induces adipogenesis in an apoE-dependent manner both in vitro and in vivo.

Adipocytes↗

PubMed2003

Quantifying alterations of macular thickness before and after panretinal photocoagulation in patients with severe diabetic retinopathy and good vision.

PURPOSE: To investigate the alterations of macular thickness during and after panretinal photocoagulation (PRP) in patients with severe diabetic retinopathy and good vision, and to compare the outcomes of weekly and biweekly treatments. DESIGN: Prospective, comparative interventional case series. PARTICIPANTS: Thirty-six patients with severe nonproliferative diabetic retinopathy or non-high-risk proliferative diabetic retinopathy whose visual acuity was 20/20 or better before PRP. METHODS: Seventy-two eyes of 36 patients underwent scatter PRP in 4 sessions. The macular thickness was measured by optical coherence tomography. The photocoagulation sessions were performed weekly to one eye and biweekly to the other eye. Each eye was selected at random. MAIN OUTCOME MEASURES: Best-corrected visual acuity and macular thickness. RESULTS: Visual acuities were maintained in 89% of eyes with weekly treatments and 92% of eyes with biweekly treatments. Macular thickness was increased transiently in the central macula in both eyes, more in the weekly treated eyes, and then decreased to control levels in eyes treated biweekly but remained thickened in eyes treated weekly. CONCLUSION: For eyes with severe diabetic retinopathy and good vision, PRP with either weekly or biweekly treatment did not affect postoperative visual acuity. However, biweekly treatments allowed faster recovery of macular thickening after PRP than weekly treatments.

Adult↗

PubMed2003

Intrinsic activation of PI3K/Akt signaling pathway and its neuroprotective effect against retinal injury.

PURPOSE: The aim of this study was to determine whether the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway can function as a neuroprotective pathway following induced retinal injury. METHODS: The activation of Akt was assessed by immunoblot analysis, and the role of PI3K/Akt pathway was evaluated by TUNEL staining and counting the number of retrogradely-labeled retinal ganglion cells (RGCs) in the whole retina at 168 h after injury with or without PI3K specific inhibitor, LY294002. RESULTS: Akt was induced within one hr and reached a maximum 6 hrs after optic nerve clamping. The activation was observed in the RGC layer including RGCs, the inner plexiform layer, inner nuclear layer, and in the photoreceptor outer segments. The number of surviving RGCs was decreased significantly 168 hrs after injury. LY294002 partially inhibited the activation of Akt, and significantly decreased the number of surviving RGCs as compared with that of injury alone. CONCLUSIONS: These results indicate that the PI3K/Akt signaling pathway is activated intrinsically and has a neuroprotective effect on injured RGCs.

Animals↗

PubMed2003

Expression and functional properties of unique inward rectifier K+ channel Kir7.1 in the porcine iris and retinal pigment epithelium.

PURPOSE: To investigate the membrane functional properties of porcine iris pigment epithelial cells (IPE), and compare the characters of inward rectifier potassium (Kir) channel in the IPE with those in the retinal pigment epithelial cells (RPE). METHODS: IPE and RPE were acutely dissociated from porcine eyes. Functional properties of Kir channels were characterized using whole cell patch clamp recording techniques. Expression of Kir7.1 mRNA in both cells was detected by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Whole cell current in the IPE exhibited a mild inward K+ rectification, and showed little dependence on [K+]o. Unusual high (7.04 +/- 1.7) Rb+ to K+ inward conductance ratio indicated that Kir7.1 subunit was expressed in the IPE as the same as RPE cells. Also, Kir7.1 mRNA was detected in both porcine IPE and RPE by RT-PCR. However, functional expression of Kir conductance in IPE cells (21.7 S/F) was much smaller than that in RPE cells (205.6 S/F). CONCLUSIONS: The Kir7.1 subunit was predominantly expressed in the acutely dissociated porcine IPE and its functional properties are similar to those in the RPE. However, the current density seems too small to fulfill the task of the Kir function of RPE.

Animals↗

PubMed2002

Presence of mitogen-activated protein kinase in retinal Müller cells and its neuroprotective effect ischemia-reperfusion injury.

The purpose of this study was to determine whether the mitogen-activated protein kinase (MAPK) signaling pathway in the retina plays a neuroprotective role against ischemia- reperfusion injury. Western blot analysis showed that the MAPK activity was markedly increased within an hour after ischemia-reperfusion and subsequently decreased. Immunohistochemical studies revealed that MAPK was expressed mainly in the retinal Müller cells (RMCs). Pre-ischemic intravitreal administration of a MAPK inhibitor, U0126, increased the number of ganglion cell deaths induced by ischemia-reperfusion injury. We conclude that the MAPK activated in the RMCs protects ganglion cells against the ischemia-reperfusion injury through glia-neuronal interaction.

Animals↗

PubMed2002

Nipradilol inhibits apoptosis by preventing the activation of caspase-3 via S-nitrosylation and the cGMP-dependent pathway.

To study whether nipradilol, which is used as an ophthalmic solution for the treatment of glaucoma, has a cytoprotective effect, we investigated its effect on the apoptosis induced by serum withdrawal in PC12 cells. Nipradilol has alpha1- and beta-adrenoceptor-blocking and nitric oxide (NO)-donating properties. We also investigated the effects of timolol, prazosin and S-nitroso-N-acetylpenicillamine (SNAP) on PC12 cell death. Serum withdrawal from PC12 cells resulted in apoptosis, and the survival rate was decreased in a time-dependent manner. The addition of nipradilol to the medium showed a cytoprotective effect on PC12 cell death in a dose-dependent manner, but timolol and prazosin did not. We measured caspase-3 activity to clarify the mechanism of the inhibition of apoptosis in the presence or absence of dithiothreitol (DTT). The caspase-3 activity could be reactivated by DTT. In addition, to investigate the relationship of the cGMP-dependent pathway to the nipradilol-induced cytoprotective effect, we tested the effect of the protein kinase G inhibitor KT5823. KT5823 partially reversed the nipradilol-mediated cytoprotective effect. These results indicate that the cytoprotective effect of nipradilol in PC12 cell death was due to the caspase-3 inhibition mediated by NO-related S-nitrosylation and activation of protein kinase G.

Animals↗

PubMed2002

Comparative expression profiles of Trk receptors and Shc-related phosphotyrosine adapters during retinal development: potential roles of N-Shc/ShcC in brain-derived neurotrophic factor signal transduction and modulation.

Neurotrophins (NTs) have multiple roles in retinal development and survival, which are mediated through their specific receptors and signaling molecules. An emerging family of adapter protein, Shc (Src homology and collagen)-related molecules, i.e., Shc/ShcA, Sck/ShcB, and N-Shc/ShcC, has been implicated in various phosphotyrosine signal transduction mechanisms, including that for NTs. To explore the potential role(s) of Shc-related adapters in NT signaling in the retina, we compared the developmental changes of the mRNA expression of TrkA -B, and -C in the rat retina, on one hand and, on the other hand, studied which members of the Shc family were activated after brain-derived neurotrophic factor (BDNF) application in axotomized rat retinas. Early in development, both TrkA and ShcA were highly expressed, whereas, in late development to adulthood, TrkB/C and ShcB/C were highly expressed. In the mature retinal ganglion cell layer, the expression of ShcB/C and TrkB/C was evident. Immunoreactivity of ShcC was located in the retinal ganglion cells, amacrine cells, and inner plexiform layer. The response of ShcC following retinal axotomy was most profound with the administration of BDNF, and there was some response with neurotrophin-3. These results indicate that ShcC could be a potential phosphotyrosine adapter among the Shc family members for BDNF signaling and function during retinal development and regeneration in vivo.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Neuroprotective effect of nipradilol on axotomized rat retinal ganglion cells.

PURPOSE: To determine whether nipradilol, a new anti-glaucoma drug, can protect retinal ganglion cells (RGCs) from secondary cell death caused by transection of the optic nerve (ON). METHODS: The ON was transected 0.7 mm from its exit from the eye in Sprague Dawley rats. Nipradilol (1 x 10(-8) - 10(-3) M), timolol, prazosin, or sodium nitroprusside (SNP) (1 x 10(-6) - 10(-4) M) was injected intravitreally fifteen-minutes before the ON transection. Control eyes received the same amount of phosphate buffered (PB). The RGCs were labeled retrogradely by placing gelfoam soaked in fluoro-gold (FG) on the stump of ON. RGCs density was determined by counting the FG-labeled RGCs in flat-mounted retinas 3 to 14 days post-transection. To determine whether the neuroprotective action of nipradilol was due to its NO-donor property, carboxy-PTIO, a NO-scavenger, or KT5832, a protein kinase G inhibitor, was injected with the nipradilol. RESULTS: After ON transection, the number of surviving RGCs after intravitreal injection of 1 x 10(-4) M nipradilol was significantly higher than that following PB injection. This protective activity was dose-dependent. Neither timolol nor prazosin had a neuroprotective effect but SNP protected RGCs in a dose-dependent manner. Carboxy-PTIO and KT5832 decreased the neuroprotective effect of nipradilol. CONCLUSIONS: These results indicate that nipradilol has a possibility of neuroprotective effect on axotomized RGCs, and the effect depended mainly on its NO-donor property.

Adrenergic Antagonists↗

PubMed2002

Brain-derived neurotrophic factor prevents axotomized retinal ganglion cell death through MAPK and PI3K signaling pathways.

PURPOSE: Brain-derived neurotrophic factor (BDNF) has a potential neuroprotective effect on axotomized retinal ganglion cells (RGCs); however, the mechanism, in regard to intracellular signaling, of BDNF-induced neuroprotection of RGCs is largely unknown. Intracellular signaling was investigated, by using axotomized RGCs and the relative contribution of the two major downstream signaling routes of TrkB determined--that is, mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K)-Akt routes, mediated by BDNF. METHODS: Neuroprotective effects of BDNF were determined by quantifying the surviving RGCs after axotomy, by retrograde labeling. The MAPK and Akt levels were determined by Western blot analysis and activity assays. Quantification of the relative contribution of the two signaling pathways was performed by use of specific inhibitors for MAPK and PI3K (i.e., U0126 and LY294002, respectively). RESULTS: Intravitreous administration of BDNF had the most profound neuroprotective effects on axotomized RGCs among the neurotrophins. Burst phosphorylation of MAPK and Akt was induced by BDNF within 1 hour and was sustained over 2 weeks in the whole retina. Immunohistochemistry revealed that phosphorylated MAPK was detected in the RGCs and retinal Müller cells, and Akt was in the RGCs. BDNF-induced phosphorylation of MAPK and Akt was suppressed by their specific inhibitors. Moreover, administration of U0126 and LY294002 decreased significantly, but only partially, the neuroprotective effect of BDNF on the axotomized RGCs. CONCLUSIONS: BDNF-mediated signaling involves activation of both MAPK and Akt on the axotomized adult rat retina, and the collaboration of both MAPK and PI3K-Akt pathways seems to be necessary in neuroprotective signaling in axotomized RGCs.

Animals↗

PubMedDate not supplied

A method for evaluating drug effects on intermittent claudication using a treadmill in rats with unilateral hindlimb artery occlusion.

INTRODUCTION: We have developed an in vivo experimental model for evaluating peripheral arterial insufficiency and predicting the efficacy of drugs on intermittent claudication (IC). We found that rats that had been running normally on a treadmill developed a gait disturbance when a hindlimb artery was unilaterally occluded. We hypothesized that the distance run before gait disturbance developed (DGD) in rats with occlusion of a hindlimb artery might be an appropriate index of the severity of peripheral insufficiency, and that the model might serve as a test bed for evaluating drug efficacy. To prove this hypothesis, we examined whether DGD was determined by severity of hindlimb ischemia. Furthermore, we also examined whether cilostazol, which has been proved to have ameliorative effects in patients with IC, increased DGD. METHODS: To vary the severity of ischemia, either the superficial femoral artery, the distal portion of the iliac artery, or the proximal portion of iliac artery was unilaterally occluded. After a recovery period, these rats were subjected to a treadmill test (15 m/min and 15% incline) to determine DGD and examine the effect of cilostazol on DGD. RESULTS: DGD was the longest and shortest in rats with superficial femoral artery and proximal portion of iliac artery occlusion, respectively. Intermediate DGD was observed in rats with distal portion of iliac artery occlusion. These data suggest that DGD is correlated with the severity of hindlimb ischemia. Two weeks or longer administration of cilostazol 30 and 100 mg/kg twice a day evoked a significant increase in DGD. DISCUSSION: Peripheral arterial insufficiency and its modulation by drugs can be evaluated in rats with unilateral hindlimb artery occlusion, on a treadmill, by measuring DGD.

Animals↗

PubMedDate not supplied

Mitogen-activated protein kinase inhibitor, PD98059, inhibits rat retinal pigment epithelial cell replication by cell cycle arrest.

PURPOSE: To investigate the effect of PD98059, a mitogen-activated protein kinase (MAPK) inhibitor, on the replication of rat cultured retinal pigment epithelial (RPE) cells. METHODS: Growth-phase rat RPE cells were exposed to various concentrations of PD98059 in serum-free F12 medium containing 0.1% dimethyl sulfoxide. Cell proliferation was assessed by cell counts using a hemocytometer. Cell viability was tested by CellTiter 96 AQueous Non-Radioactive Cell Proliferation Assay at 24 hours after PD98059 application. Hoechst 33552 and propidium iodide staining were used to assess nuclear morphology. Immunostaining with Ki67 antibody was used for cell cycle analysis because the staining patterns produced on cells are characteristic depending on their position within the cell cycle. RESULTS: PD98059 inhibited cellular proliferation of cultured rat RPE cells in a dose-dependent manner but did not induce cell death. Twenty-four hours after the application of PD98059, cultured RPE cells were not immunopositive for Ki67, indicating that their cell cycle was arrested in the G0/G1 phase. CONCLUSION: These results demonstrated that MAPK inhibition arrested cell cycle progression of rat cultured RPE cells at the G0/G1 phase. The pharmacological induction of cell cycle arrest could be a new approach to inhibit cellular proliferation in such conditions as proliferative vitreoretinopathy.

Animals↗

PubMedDate not supplied

Clinical features of bilateral acute idiopathic maculopathy.

PURPOSE: To describe the clinical course of bilateral acute idiopathic maculopathy (BAIM), and to analyze its pathophysiology. CASE: A 33-year-old Japanese woman presented with a sudden, severe, bilateral visual disturbance following a flu-like illness. She was examined by fluorescein angiography (FA), indocyanine green angiography (IA), scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and multifocal electroretinography (mfERG). OBSERVATIONS: A diagnosis of BAIM was made in this patient based on typical ophthalmoscopic features, which included a pathognomonic yellowish-white foveal lesion. FA demonstrated a breakdown of the outer blood-retinal barrier, with the size and location corresponding to the white lesion, and IA disclosed a choroidal circulatory disturbance. SLO demonstrated that the deep retinal and choroidal layers were disorganized, and OCT showed retinal edema. Electrophysiological dysfunction was detected by mfERGs. After steroid therapy, the patient's visual acuity recovered to normal. The pooling of fluorescein dye and the OCT-determined retinal edema were resolved. However, the physiological dysfunction detected by mfERGs remained. CONCLUSIONS: We conclude that the major abnormality in BAIM is an alteration of the retinal pigment epithelium causing severe edema.

Acute Disease↗

PubMedDate not supplied

Effective treatment of diffuse diabetic macular edema by temporal grid pattern photocoagulation.

BACKGROUND AND OBJECTIVE: To determine the effectiveness of laser grid pattern photocoagulation to the macula but not the papillomacular bundle for the treatment of diffuse diabetic macular edema. PATIENTS AND METHODS: Thirty-five eyes of 23 patients with diffuse diabetic macular edema underwent laser grid photocoagulation excluding the papillomacular bundle area. Best-corrected visual acuity by Snellen chart, foveal thickness using a retinal mapping program by optical coherence tomography (OCT), and mean deviation sensitivity by Humphrey automated central perimetry were investigated before and 1, 3, and 6 months after the treatment. RESULTS: Six months after treatment, the visual acuity was improved by 2 or more lines in 16 eyes (43%) and the foveal thickness decreased in 32 eyes (91%). The mean deviation worsened in 34 eyes (97%). There was a significant correlation between the improvement of visual acuity and the initial mean deviation, suggesting that a better visual acuity would be expected with a preoperative mean deviation of approximately -20 dB. CONCLUSION: Grid pattern photocoagulation without treatment to the papillomacular bundle area was effective in treating diffuse diabetic macular edema, especially in eyes with an initial mean deviation showing moderate dysfunction.

Aged↗