Mikiro Mori

Differential expression of somatostatin receptors in the rat eye: SSTR4 is intensely expressed in the iris/ciliary body.

Distribution of somatostatin receptors (SSTR1-5) was determined in the rat eye. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses revealed that SSTR4 and SSTR2 are major subtypes expressed predominantly in the iris/ciliary body and retina, respectively, and that SSTR1, SSTR3 and SSTR5 are minor subtypes expressed preferentially in the posterior eye segments including the retina. In situ hybridization showed predominant SSTR4 expression in the posterior iris epithelium and ciliary body, suggesting functional roles of somatostatin in the autonomic nervous system in the anterior segments of the eye. The differential expression of SSTR1-5 may be related to distinct roles of somatostatin in the physiology of different ocular tissues.

Leukotriene A4 hydrolase, a bifunctional enzyme Distinction of leukotriene A4 hydrolase and aminopeptidase activities by site-directed mutagenesis at Glu-297

We previously obtained evidence for intrinsic aminopeptidase activity for leukotriene (LT)A4 hydrolase, an enzyme characterized to specifically catalyse the hydrolysis of LTA4 to LTB4, a chemotactic compound. From a sequence homology search between LTA4 hydrolase and several aminopeptidases, it became clear that they share a putative active site for known aminopeptidases and a zinc binding domain. Thus, Glu‐297 of LTA4 hydrolase is a candidate for the active site of its aminopeptidase activity, while His‐296, His‐300 and Glu‐319 appear to constitute a zinc binding site. To determine whether or not this putative active site is also essential to LTA4 hydrolase activity, site‐directed mutagenesis experiments were carried out. Glu‐297 was mutated into 4 different amino acids. The mutant E297Q (Glu changed to Gln) conserved LTA4 hydrolase activity but showed little aminopeptidase activity. Other mutants at Glu‐297 (E297A, E297D and E297K) showed markedly reduced amounts of both activities. It is thus proposed that either a glutamic or glutamine moiety at 297 is required for full LTA4 hydrolase activity, while the free carboxylic acid of glutamic acid is essential for aminopeptidase.

REP-1 gene mutations in Japanese patients with choroideremia

Abstract · 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.

Platelet-activating factor and somatostatin activate mitogen-activated protein kinase (MAP kinase) and arachidonate release

Platelet-activating factor (PAF) receptor and somatostatin receptor (SSTR4) were cloned, and their primary structures were identified. They are both highly expressed in the rat hippocampus. When expressed in Chinese hamster ovary cells, these receptors activated mitogen-activated protein (MAP) kinase cascade and phospholipase A2. Arachidonic acid or its derivatives, thus produced by the activation of these receptors may play some roles in synaptic transmission and synaptic plasticity.

Effect of apraclonidine on blood-aqueous barrier permeability to plasma protein in man ☆

Effect of a single instillation of 30 microliters 0.5% apraclonidine on the coefficient of protein entry (k(in)), a quantitative index of blood-aqueous barrier permeability, was determined in ten normal volunteers. Before and after administering the drug to one eye and the vehicle to the other eye of a subject, protein concentrations in the anterior chamber were measured using a laser flare-cell meter. One week later, aqueous flow rate was determined by fluorophotometry under the same experimental conditions. The k(in) was calculated from protein concentrations in the anterior chamber and the plasma and from aqueous flow rate based on a transfer equation formulating the kinetics of protein molecules in the anterior chamber. The k(in) showed a significant reduction at 3 and 4 hr after drug administration with a maximum decrease of 21 +/- 6% (mean +/- S.E., n = 10) at 3 hr, while the aqueous flow rate showed a significant reduction from 2 to 6 hr with a maximum decrease of 45 +/- 5% at 3 hr. The results indicated that topical apraclonidine reduced both blood-aqueous barrier permeability as well as aqueous flow rate in humans. This dual reduction may relate to the efficacy of this drug in suppressing the post-laser intraocular pressure rises in patients.

Clinical and functional findings in crystalline retinopathy.

Background: Crystalline retinopathy is an infrequently encountered disorder characterized by reflective retinal crystalline deposits. The clinical findings of seven patients with crystalline retinopathy are documented. Methods: Clinical features of crystalline retinopathy were studied retrospectively in seven patients, three of whom were followed up for 2 to 5 years. Results: Six patients had a similar fundus appearance, that is, the reflective yellow deposits located mainly in the deep retina with retinal pigment epithelium atrophy throughout the posterior pole and midperipheral retina and with choriocapillaris atrophy at the posterior pole. However, the results from electroretinogram responses were markedly variable. Two of the patients showed marked electroretinogram functional impairment. In addition, other sibling patients only 3 years apart in age had different degrees of disease expression. Conclusion: There is considerable variability in functional manifestations among patients with crystalline retinopathy, even in intrafamilial cases.

Energy-dependent export of leukotriene B4 in Xenopus oocytes

The export of leukotriene (LT) B4 was studied using the Xenopus oocyte system. The oocytes were microinjected intracellularly with [3H]LTB4, and the export/injection ratios were determined. The ratios decreased with increasing doses of LTB4, converging upon 4%. The export was temperature-dependent and decreased with ATP depletion, thereby suggesting that the export is energy-dependent and carrier-mediated. The LTB4 export was inhibited by 6-trans-LTB4 and its 12-epi isomer, but much less by LTD4. Neither verapamil nor quinidine significantly inhibited LTB4 export. These results suggest that oocytes have an export system specific for LTB4 and its isomers, and that the multidrug-resistant transporter is not involved in this system. By contrast, much of platelet-activating factor, another lipid mediator, was retained in oocytes at different temperatures after injection. It was thus shown that the two potent lipid mediators are exported from cells in a different manner and that oocytes are a good model for analyzing export systems for bioactive mediators.

Effect of topical phenylephrine on the permeability of the blood-aqueous barrier in man

The effects of a single instillation of 5% phenylephrine on aqueous flow and the coefficient of protein entry into the anterior chamber, an index of blood-aqueous barrier permeability, were determined in normal human eyes by measuring fluorescein concentrations with a fluorophotometer and aqueous protein concentrations with a laser flare-cell meter. Both parameters showed a concomitant biphasic change. The coefficient of protein entry showed significant increases of 31 and 66% at 1 and 2 h, and a significant decrease of 18% at 3 h. Aqueous flow showed significant increases of 81 and 125% at 1 and 2 h and a significant decrease of 20% at 4 h. It is suggested that a change in the permeability of the blood-aqueous barrier might be related to changes in aqueous flow after topical phenylephrine.

Identification of a novel VMD2 mutation in Japanese patients with Best disease

Purpose: To report a novel VMD2 gene mutation in a Japanese family with Best disease and the clinical phenotype of the patients. Patients and methods: Mutational analysis for VMD2 was performed by direct sequencing in two members of a Japanese family with Best disease. Clinical examination included visual acuity, electro-oculography (EOG), and fundus examination. Results: A T990C mutation of the VMD2 gene was found in the 20-year-old boy and his 47-year-old mother. The boy had bilateral vitelliform cyst-like lesions in both eyes and showed a pathological Arden ratio of 1.0 on EOG. The mother had a normal fundus appearance with an Arden ratio of 1.0 on EOG. Conclusion: A novel disease-causing mutation in the VMD2 gene (T990C) was found in Japanese patients with Best disease.

Localization of Platelet-Activating Factor Receptor in the Rat Brain

Platelet-activating factor (PAF) has diverse effects on various cells and tissues despite its initial characterization as an activator of platelets (Braquet et al., 1987; Izumi and Shimizu, 1995). PAF is involved in a wide variety of events in the central nervous system (CNS). This factor is related to post-ischemic neuronal injury (Panetta et al., 1989), human immuno-deficiency virus (HIV)-associated neuronal cell death (Gelbard et al., 1994), alteration of synaptic transmission (Clark et al., 1992), and induction of long-term potentiation (LTP) (Wieraszko et al., 1993; Kato et al., 1994). Also, the roles of PAF in CNS development have lately attracted attention, since a subunit of PAF acetylhydrolase is the product of the causative gene for Miller-Dieker lissencephaly (Hattori et al., 1994), a disorder due to incomplete migration of immature neurons to the cerebral cortex.