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Yoshio Akagi

Publications and source records attributed to Yoshio Akagi.

18 recordsLinked to original sources
PubMed2006

Aqueous flow in galactose-fed dogs.

Dogs fed galactose develop diabetes-like ocular complications that include keratopathy, cataracts, and retinopathy. The purpose of this study was to investigate whether galactosemic dogs display reduced aqueous flow similar to that observed in patients with insulin-dependent diabetes mellitus. Twelve male beagles at 9 months of age were divided into three groups of four. The Galactose group was fed diet containing 30% galactose for 97 months and the Reversal group was fed the galactose diet for an initial 38 months then standard dog diet for the remaining period. The Control group was fed standard dog diet for 97 months. Aqueous flow was determined by fluorophotometry in one eye per dog at 96 and 97 months after the initiation of galactose feeding. Intraocular pressure (IOP) was measured once in the morning by pneumatonometry. Anterior chamber depth was measured by A-scan. At the end of the experiment, eyes were enucleated and processed for histological examination. Dogs fed galactose diet for 97 months had significantly (p<0.05) increased body weights but similar IOP and anterior chamber depth compared to the other groups, and significantly (p=0.05) reduced aqueous flow compared to the control group (4.4+/-2.2 vs. 6.8+/-2.4 microl/min, mean+/-standard deviation, respectively). Additionally, aqueous flow decreased in the Reversal group to 3.1+/-1.3 microl/min (p=0.002). This decrease correlated with morphological changes of the ciliary processes. Like patients with insulin-dependent diabetes mellitus, galactose-fed dogs demonstrate reduced aqueous flow. This reduction was irreversible and independent of the retinopathy present. This animal model may be useful for the study of aqueous humor dynamics in diabetes.

Animals↗
PubMed2006

Identification of the nuclear export signal in the helix-loop-helix inhibitor Id1.

Id proteins play important roles in cellular differentiation and proliferation by negatively regulating basic helix-loop-helix transcription factors. Although their intracellular localization may change depending on the biological situation, little is known about the molecular determinants underlying such changes. Here we report the identification of a nuclear export signal (NES) in Id1. The identified NES was different from that of Id2, but had the ability to confine heterologous green fluorescent protein to the cytoplasm. Thus, our results indicate that the intracellular localization of Id1 is regulated differently from that of Id2.

Amino Acid Sequence↗
PubMed2006

Development- and age-associated expression pattern of peroxiredoxin 6, and its regulation in murine ocular lens.

Peroxiredoxin (PRDX) 6 is a unique member of the PRDX family. Its antioxidant and signaling properties are related to its expression level in cells. We studied development- and age-associated changes in PRDX6 expression in the murine lens. We also investigated the effects of dexamethasone (Dex), transforming growth factor-beta1 (TGF-beta1) and tumor necrosis factor-alfa (TNF-alpha) on PRDX6 expression. Expression levels of PRDX6 mRNA in whole lenses isolated from postnatal day (PD) 1- to 18-month-old mice, and the effects of Dex, TGF-beta1 and TNF-alpha on the expression of PRDX6 in lens epithelial cells (LECs), were monitored using real-time reverse transcriptase-polymerase chain reaction (PCR) or Western blot. Localization of PRDX6 was studied using in situ hybridization and immunohistochemistry. PRDX6 expression gradually increased in the lenses of 4-week- to 6-month-old mice and declined thereafter. In situ hybridization and immunohistochemistry revealed that PRDX6 was localized in the cytoplasm of LECs and in lens fibers. Intense PRDX6 staining was present in the whole lens on gestational days 14 and 18. The lenses of PD1 mice showed diminished nuclear fiber staining, while those of 4-week-old mice revealed lack of nuclear fiber staining but intense staining of the germinative zone. LECs treated with TNF-alpha or Dex showed higher PRDX6 expression, while TGF-beta1 down regulated expression. Thus, our results provide a topographic basis for understanding the role of PRDX6 in the lens.

Aging↗
PubMed2006

Correlation between adult diabetic cataracts and red blood cell aldose reductase levels.

PURPOSE: To investigate the correlation between adult diabetic cataracts and levels of aldose reductase (AR) in red blood cells (RBCs). METHODS: The study involved 337 eyes of 337 patients with diabetes. The extent and severity of lens opacity was assessed according to the Lens Opacities Classification System III (LOCS III). The AR levels within RBCs were determined with an ELISA. The relationship between the AR level in RBCs and the prevalence of nuclear cataract, cortical cataract, and posterior subcapsular cataract in patients with diabetes was examined. RESULTS: There were no significant alterations in AR level in RBCs in patients with a diabetes duration of < or = 10 years and patients < 60 years of age. In each subgroup, a higher amount of AR levels in RBCs significantly correlated with the prevalence of posterior subcapsular cataracts. A significant association between cortical cataract and AR level in RBCs was also seen in a subgroup of patients younger than 60 years. CONCLUSIONS: AR emerges as an important factor affecting the onset of posterior subcapsular cataracts at the early stages of diabetes mellitus. This raises the possibility that AR inhibitors could play a useful role in treatment of adult diabetic cataract through its inhibition of AR activities.

Adult↗
PubMed2005

Characteristics of acid extrusion from Chinese hamster ovary cells expressing different prostaglandin EP receptors.

Acid extrusion responses to prostaglandin E2 were investigated in Chinese hamster ovary (CHO) cells heterologously expressing human EP1, EP2, and EP3I receptors (hEP1, hEP2 and hEP3I) by using a microphysiometer that detected small pH changes in the extracellular microenvironment. In the cells expressing hEP1, which is known to increase intracellular Ca2+, prostaglandin E2 (1 and 10 nM) slowly accelerated acid extrusion, but at higher concentrations an initial transient phase (approximately 5 times greater than the basal acidification) overlapped the slowly developing phase. In contrast, the cells expressing hEP2, which evokes cAMP production, showed dual responses to prostaglandin E2: an initial reduction followed by an acceleration of acid extrusion. In the cells expressing hEP3I, which is known to produce both a decrease in cAMP and a modest increase in intracellular Ca2+, acid extrusion was gradually accelerated by prostaglandin E2 and reached a plateau at around 2 min. Elimination of extracellular Ca2+ diminished the responses to prostaglandin E2 in hEP1 cells, but had little effect on the responses in hEP2 and hEP3I cells. Forskolin mimicked the dual effects of prostaglandin E2 observed in the hEP2 cells. Pretreatment with pertussis toxin inhibited the response to prostaglandin E2 in hEP3I cells, but the responses in hEP1 and hEP2 cells were not affected. Na+/H+ exchanger (NHE) inhibitors (EIPA and HOE642) suppressed all the responses induced by prostaglandin E2 in hEP1, hEP2, and hEP3I cells. These results suggest that EP receptor subtypes regulate acid extrusion mainly via NHE-1 through distinct signal transduction pathways in CHO cells.

Animals↗
PubMed2005

Vlgr1 knockout mice show audiogenic seizure susceptibility.

Susceptibility to audiogenic seizures, which are reflex seizures provoked by loud noise, can be induced in rodents by acoustic priming (exposing animals to strong auditory stimuli at an early developmental stage). Some strains of mice and rats are susceptible to audiogenic seizures without priming and these have been used as good experimental models with which to study epilepsies. Here we identified Vlgr1d and Vlgr1e, novel alternatively-spliced variants of Vlgr1b/MGR1, which, upon sequence analysis, were shown to be transcripts from a locus previously characterized as mass1. Vlgr1 (Vlgr1b, Vlgr1d and Vlgr1e) mRNA is expressed predominantly in the neuroepithelium of the developing mouse brain. Our protein-tagged experiment suggested that Vlgr1d and Vlgr1e are secretory molecules, while Vlgr1b is a receptor. Knockout mice lacking exons 2-4 of Vlgr1 were susceptible to audiogenic seizures without priming, although there were no apparent histological abnormalities in their brains. Ninety-five percent of these knockout mice exhibited wild running, a feature typical of the preconvulsive phase of audiogenic seizures triggered by loud noise (11 kHz, 105 dB), and 68% exhibited tonic convulsions at 3 weeks after birth. Our monogenic mice, which have a unique genetic background, serve as a useful tool for further studies on seizures.

Acoustic Stimulation↗
PubMed2004

Corneal changes after small-incision cataract surgery in patients with diabetes mellitus.

OBJECTIVE: To evaluate functional impairment in the corneal endothelium of eyes in patients with diabetes mellitus, after small-incision cataract surgery. METHODS: Evaluation was performed in 93 eyes in patients with type 2 diabetes mellitus (diabetic group) and 93 eyes in patients without diabetic mellitus (nondiabetic group) who underwent cataract surgery. Using a topography system, the corneal thickness in the central area was measured before surgery and 1 day, 1 week, and 1 month after surgery. Corneal endothelial cells were counted using a noncontact specular microscope. RESULTS: No significant differences in any preoperative measures were observed between the diabetic and nondiabetic groups. The increase in corneal thickness 1 month after surgery was significantly higher in the diabetic group than in the nondiabetic group (P =.03). The corneal endothelial cell losses 1 day and 1 week after surgery were significantly higher in the diabetic group than in the nondiabetic group (after 1 day, P =.03; and after 1 week, P =.04). CONCLUSION: Compared with nondiabetic eyes, eyes of patients with diabetes mellitus showed more damage in corneal endothelial cells due to cataract surgery and a delay in the postoperative recovery of corneal edema.

Aged↗
PubMed2004

DeltaFosB expression and cataract.

DeltaFosB is a truncated form of a FosB transcription factor, which is created by alternative splicing. Previous work has shown that transgenic mice expressing DeltaFosB both in the retina and in the lens developed a posterior subcapsular cataract resulting from the misalignment of the fibres in the suture region. In the previous study, it was not clear whether DeltaFosB expression was required in both tissues to produce the cataract. Therefore, DeltaFosB expression targeted to either the lens or the retina was undertaken in order to clarify the contribution of each tissue to cataract development. For lens expression, the R2betaB1DeltaFosB construct was synthesized (R2, an enhancer; betaB1, a chicken betaB1 crystallin gene promoter fragment). For the retina, RhoDeltaFosB was prepared. As a promoter, the bovine rhodopsin upstream region was used. DeltaFosB expression in heterozygote animals was monitored by Western blotting. Cataract development in heterozygotes of R2betaB1DeltaFosB transgenics and in both heterozygotes and homozygotes of RhoDeltaFosB transgenics was followed by slitlamp examination. The transgenic mice prepared with RhoDeltaFosB expressed DeltaFosB only in the retina and showed no sign of lens opacity. One line of the R2betaB1DeltaFosB transgenic was found to have expression only in the lens and developed posterior subcapsular cataract. We concluded that retinal expression of DeltaFosB is not sufficient to cause cataract while expression exclusively in the lens produces posterior subcapsular cataract.

Animals↗
PubMed2004

LEDGF regulation of alcohol and aldehyde dehydrogenases in lens epithelial cells: stimulation of retinoic acid production and protection from ethanol toxicity.

Retinoic acid (RA) is required for the normal growth and maintenance of many cell types, including lens epithelial cells (LECs). Alcohol (ADH) and aldehyde (ALDH) dehydrogenases are implicated in cellular detoxification and conversion of vitamin A to RA. Lens epithelium-derived growth factor (LEDGF) provides cellular protection against stress by transactivating stress-associated genes. Here we show evidence that LEDGF binds and transactivates heat shock (nGAAn) and stress response (A/TGGGGA/T) elements in the promoters of ADH1, ADH4, and retinaldehyde 2 (RALDH2) genes. Electrophoretic mobility and supershift assays disclosed specific binding of LEDGF to nGAAn and A/TGGGGA/T elements in these gene promoters. Transfection experiments in LECs with promoters linked to a chloramphenicol acetyltransferase (CAT) reporter gene along with LEDGF cDNA revealed higher CAT activity. RT-PCR results confirmed that LECs overexpressing LEDGF contained increased levels of ADH1, ADH4, and RALDH2 mRNA. Notably, LECs displayed higher LEDGF mRNA and protein expression during ethanol stress. Cells overexpressing LEDGF typically exhibited elevated RA levels and survived well during ethanol stress. The present findings indicate that LEDGF is one of the transcriptional activators of these genes that facilitates cellular protection against ethanol stress and plays a role in RA production.

Alcohol Dehydrogenase↗
PubMed2003

Apoptotic cell death in the lens epithelium of rat sugar cataract.

Apoptosis of lens epithelial cells (LECs) is implicated in the pathogenesis of several types of cataract formation. The high intracellular levels of polyol induce histological change in the LECs, which is considered the earliest event in sugar cataractogenesis. This study was designed to investigate whether high galactose exposure induces apoptosis in LECs during the development of sugar cataract. The effect of an aldose reductase inhibitor, SNK-860, was also examined. We induced sugar cataract in Sprague-Dawley rats by feeding them a 50% galactose-containing diet with or without SNK-860. The percentage of LECs undergoing apoptosis was measured by the terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling (TUNEL) method, and DNA fragmentation analyses were performed. Galactitol levels in the lens epithelium were quantified by gas chromatography. The number of TUNEL-positive cells gradually increased throughout the period of galactose exposure, up to 5 days. DNA fragmentation analysis in LECs of rats fed a galactose-rich diet demonstrated an apparent ladder pattern. SNK-860 reduced the percentage of TUNEL-positive cells, the amount of intracellular galactitol, and the levels of DNA laddering. To explore the mechanism of the apoptotic process, the expression of p53, a potent mediator of apoptosis, was examined. Based on Western blot and real-time reverse transcription-polymerase chain reaction results, the amount of p53-expression increased at both the protein and mRNA levels after galactose exposure, and the increase in p53-expression was inhibited by SNK-860. Based on these results, we concluded that apoptosis occurs in rat lens epithelial cells following galactose exposure. Furthermore, the reduction of apoptosis by aldose reductase inhibitor suggests that this apoptosis is associated with the accumulation of sugar alcohols. It is probable that the mechanism of apoptosis during sugar cataract formation involves the increased expression of p53.

Aldehyde Reductase↗
PubMed2003

[The inhibitory effect of aldose reductase inhibitor for proliferation in the lens epithelial cells of rat sugar cataract].

PURPOSE: To evaluate the inhibitory effect of aldose reductase inhibitor (ARI) for the accumulation of sugar alcohol and the enhanced proliferation of lens epithelial cells of rats fed a galactose diet. METHODS: Sprague-Dawley rats were fed a diet containing 50% galactose with or without ARI (SNK-860). Histological changes in the lenses were observed by light microscopy, and the amount of galactitol accumulated in the lens epithelium was measured by liquid-gas chromatography. Immuno-histochemical staining of proliferating cell nuclear antigen (PCNA) in whole-mount preparations was performed to assay the proliferative ability of the lens epithelial cells. RESULTS: The amount of galactitol in the lens epithelium and the number of PCNA positive cells in rats administered ARI were less than in rats fed the galactose diet. Multi-layered epithelium was observed in advanced cataract of rats fed the galactose diet, but not in the rats given ARI. CONCLUSION: The administration of ARI can prevent cataractous changes and aberrant proliferation of lens epithelial cells.

Aldehyde Reductase↗
PubMed2002

Two-phase response of acid extrusion triggered by purinoceptor in Chinese hamster ovary cells.

The functional characteristics of purinoceptors in Chinese hamster ovary (CHO) cells were investigated using a microphysiometer which detects small metabolic changes to living cells in real-time as variations of pH in the extracellular microenvironment. Uridine 5'-triphosphate (UTP) increased the extracellular acidification rate biphasically, namely a transient and a steady response were observed. The transient phase reached a peak (four- to fivefold the basal extracellular acidification rate in amplitude) within 20 s and was followed by the steady phase which was sustained for more than 1 min at an amplitude less than twofold the basal extracellular acidification rate. Both phases showed a concentration-dependent increase in response to UTP. However, there was a significant difference in the pEC(50) value for UTP between the transient (4.8) and steady phases (6.1). Like UTP, ATP increased the extracellular acidification rate, but alpha,beta-methyleneATP (alpha,beta-MeATP), 2-methylthioATP (2-MeSATP), ADP, UDP and adenosine did not. This result suggests that the acid is extruded through a P2Y(2) or P2Y(2)-like purinoceptor. 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and 4-isopropyl-3-methylsulphonylbenzoyl-guanidine methanesulphonate (HOE642) suppressed both phases of the UTP-stimulated extracellular acidification rate response with high affinity (pIC(50): approximately 7.0). This result suggests that the Na(+)/H(+) exchanger 1 (NHE-1) predominantly mediates the UTP-induced acid extrusion response in CHO cells. Elimination of extracellular Ca(2+) or treatment with thapsigargin diminished both phases of the UTP-stimulated extracellular acidification rate. In addition, N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide hydrochloride (W-7) also abrogated the two phases. These results are consistent with the involvement of NHE-1 which is activated via Ca(2+)/calmodulin. Persistent exposure to UTP reduced both extracellular acidification rate phases, causing desensitization of the P2Y purinoceptor. This desensitization did not affect the acid extrusion response mediated by the alpha(1)-adrenoceptor.

Animals↗
PubMed2002

Increased expression of p21(WAF-1/CIP-1) in the lens epithelium of rat sugar cataract.

It has been demonstrated that exquisite regulation of the cell cycle between the activation and inhibition is crucial to maintain the transparency of the ocular lens. While it is generally recognized that the sugar cataract is accompanied by the enhanced proliferation of lens epithelial cells (LECs), it is unclear whether or not an inhibitory mechanism against the lens proliferation is involved, except for TGF-beta. In this study, the authors demonstrated the enhanced expression of p21(WAF-1/CIP-1), a potent inhibitor against cell cycle progression, and its specific temporal and regional expression profiles in the LECs during the development of sugar cataract. Sugar cataract was induced in 6-week-old male Sprague-Dawley rats by feeding them on a 50% galactose-rich diet, and then the expression patterns of p21(WAF-1/CIP-1) mRNA and protein with the advance of the sugar cataract were studied. Western blot analyses showed that p21(WAF-1/CIP-1) expression increased throughout the period of galactose exposure, up to 21 days. Also, a gradual increase in the number of p21(WAF-1/CIP-1) positive cells was observed immunohistochemically in the course of the galactose exposure. Interestingly, p21(WAF-1/CIP-1) was significantly expressed in the multi-layered epithelium, which was observed typically in the advanced cataract. Proliferating cell nuclear antigen (PCNA), an indicator of cell proliferation, was also positive in the most multi-layered epithelial cells. In addition, transient expression of PCNA mRNA and its protein was noticed throughout the lens epithelium in the course of the sugar cataract development. Prior to the elevation of p21(WAF-1/CIP-1) mRNA expression, PCNA mRNA expression increased greatly and reached a peak according to the semiquantitative analyses using either the real time reverse transcription-polymerase chain reaction (RT-PCR) or the Southern blot analyses. Based on these observations, it is possible that p21(WAF-1/CIP-1) is elevated and exerts its inhibitory action against the proliferating epithelial cells during the development of the sugar cataract.

Animals↗
PubMed2002

Distribution of alpha-1 adrenoceptor subtypes in RNA and protein in rabbit eyes.

We investigated subtypes of alpha-1 adrenoceptor (AR) in rabbit ocular tissues using reverse transcription-polymerase chain reaction (RT - PCR), in situ hybridization (ISH) and binding studies. Competitive RT - PCR assays specific for the subtypes of alpha-1 AR revealed that the mRNA expression of alpha-1a AR was dominant, and that of each alpha-1b and alpha-1d was less than 10% and 0.5% of total alpha-1 ARs mRNA, respectively, in the iris, ciliary body, choroid and retina. In alpha-1a AR splice isoform-specific RT - PCR assays, we found a distinct proportion of each isoform mRNA in the iris, ciliary body and choroid. The results of the ISH assays for alpha-1a AR subtype showed that hybridization signals were clearly observed in the iris dilator muscle and in the epithelium of the ciliary processes. In binding studies, alpha-1A AR was a dominant subtype in the iris, choroid and retina in contrast to the ciliary body that had more alpha-1B than alpha-1A AR subtype at protein level.

Adrenergic alpha-Antagonists↗
PubMed2002

Effect of galactose diet removal on the progression of retinal vessel changes in galactose-fed dogs.

PURPOSE: Feeding dogs a diet containing 30% galactose induces experimental galactosemia and results in the formation of diabetes-like microvascular lesions of the retina. The appearance and progression of these retinal lesions can be arrested in a dose-dependent manner by treating these dogs with aldose reductase inhibitors from the onset of galactosemia. To determine whether the elimination of galactosemia can also reduce the progression of retinal lesions, the galactose diet was removed from the galactosemic dogs after either the appearance of pericyte ghosts or formation of microaneurysms. METHODS: Ten control dogs were fed a normal diet, and 50 dogs were fed a diet containing 30% galactose. The galactose diet was removed from 15 dogs after 24 months, the time at which pericyte ghosts had previously been observed to develop, and from another 15 dogs after 31 months, when microaneurysms had previously been observed to develop. Eighteen dogs were continued on a galactose diet. Beginning at 24 months, eyes from each group were enucleated at approximately 6-month intervals. Changes in retinal lesions were quantified by computer image analyses. RESULTS: Significant (P < 0.05-0.01) increases in the endothelium-pericyte (E-P) ratio and decreases in pericyte density were observed with increased duration of galactose feeding. Although no reversal of retinal lesions occurred, differences in the progression of retinal lesions between the galactose-fed and galactose-deprived groups became evident after 12 to 24 months. CONCLUSIONS: Discontinuation of galactose in the diet at the initial stages of background retinopathy beneficially delays the progression of retinal lesions.

Animals↗