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Biomedical subjects

S Kachi

Publications and source records attributed to S Kachi.

17 recordsLinked to original sources
PubMed2001

Progressive change of optical coherence tomography scans in retinal degeneration slow mice.

OBJECTIVE: To study whether optical coherence tomography (OCT) scans correlate retinal histologic findings with the progression of retinal degeneration in retinal degeneration slow (rds) mice. METHODS: Sensory retinal thickness (SRT) and outer retinal thickness (ORT), representing photoreceptor cell layer, in temporal retina at a distance 1 to 2 disc diameters from the optic disc were measured using scan profile in OCT from 6 healthy mice (16 weeks old) and 2-week-old (n = 6), 6-week-old (n = 4), and 60-week-old (n = 2) rds mice. Histologic sections were obtained from Epon-embedded retinas from the corresponding location. RESULTS: Cross-sectional OCT images correlated to the corresponding histologic sections in each mouse. Both SRT and ORT of 2-week-old rds mice (150 +/- 4 microm and 28 +/- 4 microm, respectively) lacking photoreceptor outer segments were already shorter than those of healthy mice (174 +/- 5 microm and 37 +/- 6 microm, respectively) (P<.001). In 6-week-old mice, microscopic findings revealed a decreased number of nuclei in the outer nuclear layer, and SRT and ORT (136 +/- 2 microm and 20 +/- 1 microm, respectively) were shorter than those of 2-week-old rds mice (P<.001). The SRT of 60-week-old rds mice without a photoreceptor layer was remarkably reduced (120 +/- 7 microm), and no ORT could be measured. CONCLUSION: Our findings suggest a possible relationship between SRT and ORT, as measured by OCT, and histologic change in retinal degenerative diseases. CLINICAL RELEVANCE: The quantitative analysis obtained by OCT scans may have potential to detect progressive change in degenerative retina and may be used in studying human retinal degeneration.

Animals↗
PubMed2001

Axial length and refractive error in X-linked retinoschisis.

PURPOSE: To examine the relationship between axial length and refractive error in patients with X-linked retinoschisis. DESIGN: To determine whether the hypermetropia frequently found in patients with X-linked retinoschisis is axial hypermetropia. METHODS: The axial length and refractive error were measured in 29 right eyes of 29 patients. The patients were divided into two groups: a juvenile group with ages <13 years (12 eyes) and an adult group with ages > or =13 years (17 eyes). The axial length of the right eye of 30 adult men without eye diseases whose refractive error ranged from +/- 1.0 diopter served as controls. RESULTS: In the adult patient group, the refractive error was significantly more hypermetropic and the axial length was significantly shorter than was the normal adult group (P <.001). CONCLUSION: These results strongly suggest that the hypermetropia in patients with X-linked retinoschisis is axial hypermetropia.

Adolescent↗
PubMed2001

Optical coherence tomography for the noninvasive evaluation of the cornea.

PURPOSE: To determine the optical coherence tomographic (OCT) characteristics of normal corneas and to characterize the OCT images of abnormal corneal lesions. METHODS: Eleven eyes from 10 patients were examined at the Cornea Service of the Nagoya University Hospital: 4 had corneal pathologies, 4 underwent keratoplasty, and 2 were normal controls; 1 enucleated eye was also examined. OCT (OCT 2000 Zeiss-Humphrey) was used to study the normal cornea and various corneal abnormalities. We compared the OCT images to the observations made by slit-lamp biomicroscopy. RESULTS: Fluid spaces were detected as black images. A highly reflective reflex was observed at the interface of different tissues, and intensive backscattering (reflex) was seen when the incident ray hit the laminated layers vertically. Corneal opacities were not clearly imaged when they were diffuse and mild, or when they were arranged axially in a small area, as was the scar of the graft-host junction. It was possible to obtain images from the region of the cornea that was not clearly visible by slit-lamp examination because of a corneal opacity. CONCLUSION: OCT is a noncontact and noninvasive technique that can be performed safely on diseased corneas. OCT can provide objective documentation of corneal disorders that cannot be obtained by slit-lamp examination. The use of OCT in conjunction with other conventional instruments should provide a more complete image of the cornea.

Adult↗
PubMed2001

Localization of caveolin-1 in photoreceptor synaptic ribbons.

PURPOSE: The purpose of this study is to determine whether caveolin-1 is a constituent of photoreceptor synaptic ribbons. METHODS: Immunoblot assay and electron microscopic immunocytochemistry were used to localize caveolin-1 in synaptic ribbons. RESULTS: Synaptic ribbons were localized close to the active site of presynaptic membranes and surrounded by a halo of synaptic vesicles. Immunosignals of caveolin-1 were clearly detected on the synaptic ribbons in rod and cone photoreceptors. However, the signal was seen neither on synaptic vesicles nor on presynaptic plasma membranes. CONCLUSIONS: Caveolin-1 is a component protein of synaptic ribbons and may be involved in the regulation of transmitter release.

Animals↗
PubMed2000

Phosphorylation by cyclin-dependent protein kinase 5 of the regulatory subunit of retinal cGMP phosphodiesterase. I. Identification of the kinase and its role in the turnoff of phosphodiesterase in vitro.

Cyclic GMP phosphodiesterase (PDE) is an essential component in retinal phototransduction. PDE is regulated by Pgamma, the regulatory subunit of PDE, and GTP/Talpha, the GTP-bound alpha subunit of transducin. In previous studies (Tsuboi, S., Matsumoto, H. , Jackson, K. W., Tsujimoto, K., Williamas, T., and Yamazaki, A. (1994) J. Biol. Chem. 269, 15016-15023; Tsuboi, S., Matsumoto, H., and Yamazaki, A. (1994) J. Biol. Chem. 269, 15024-15029), we showed that Pgamma is phosphorylated by a previously unknown kinase (Pgamma kinase) in a GTP-dependent manner in photoreceptor outer segment membranes. We also showed that phosphorylated Pgamma loses its ability to interact with GTP/Talpha, but gains a 10-15 times higher ability to inhibit GTP/Talpha-activated PDE than that of nonphosphorylated Pgamma. Thus, we propose that the Pgamma phosphorylation is probably involved in the recovery phase of phototransduction through shut off of GTP/Talpha-activated PDE. Here we demonstrate that all known Pgammas preserve a consensus motif for cyclin-dependent protein kinase 5 (Cdk5), a protein kinase believed to be involved in neuronal cell development, and that Pgamma kinase is Cdk5 complexed with p35, a neuronal Cdk5 activator. Mutational analysis of Pgamma indicates that all known Pgammas contain a P-X-T-P-R sequence and that this sequence is required for the Pgamma phosphorylation by Pgamma kinase. In three different column chromatographies of a cytosolic fraction of frog photoreceptor outer segments, the Pgamma kinase activity exactly coelutes with Cdk5 and p35. The Pgamma kinase activity ( approximately 85%) is also immunoprecipitated by a Cdk5-specific antibody, and the immunoprecipitate phosphorylates Pgamma. Finally, recombinant Cdk5/p35, which were expressed using clones from a bovine retina cDNA library, phosphorylates Pgamma in frog outer segment membranes in a GTP-dependent manner. These observations suggest that Cdk5 is probably involved in the recovery phase of phototransduction through phosphorylation of Pgamma complexed with GTP/Talpha in mature vertebrate retinal photoreceptors.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Phosphorylation by cyclin-dependent protein kinase 5 of the regulatory subunit of retinal cGMP phosphodiesterase. II. Its role in the turnoff of phosphodiesterase in vivo.

Retinal cGMP phosphodiesterase (PDE) is regulated by Pgamma, the regulatory subunit of PDE, and GTP/Talpha, the GTP-bound alpha subunit of transducin. In the accompanying paper (Matsuura, I., Bondarenko, V. A., Maeda, T., Kachi, S., Yamazaki, M., Usukura, J., Hayashi, F., and Yamazaki, A. (2000) J. Biol. Chem. 275, 32950-32957), we have shown that all known Pgammas contain a specific phosphorylation motif for cyclin-dependent protein kinase 5 (Cdk5) and that the unknown kinase is Cdk5 complexed with its activator. Here, using frog rod photoreceptor outer segments (ROS) isolated by a new method, we show that Cdk5 is involved in light-dependent Pgamma phosphorylation in vivo. Under dark conditions only negligible amounts of Pgamma were phosphorylated. However, under illumination that bleached less than 0.3% of the rhodopsin, approximately 4% of the total Pgamma was phosphorylated in less than 10 s. Pgamma dephosphorylation occurred in less than 1 s after the light was turned off. Analysis of the phosphorylated amino acid, inhibition of Pgamma phosphorylation by Cdk inhibitors in vivo and in vitro, and two-dimensional peptide map analysis of Pgamma phosphorylated in vivo and in vitro indicate that Cdk5 phosphorylates a Pgamma threonine in the same manner in vivo and in vitro. These observations, together with immunological data showing the presence of Cdk5 in ROS, suggest that Cdk5 is involved in light-dependent Pgamma phosphorylation in ROS and that the phosphorylation is significant and reversible. In an homogenate of frog ROS, PDE activated by light/guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) was inhibited by Pgamma alone, but not by Pgamma complexed with GDP/Talpha or GTPgammaS/Talpha. Under these conditions, Pgamma phosphorylated by Cdk5 inhibited the light/GTPgammaS-activated PDE even in the presence of GTPgammaS/Talpha. These observations suggest that phosphorylated Pgamma interacts with and inhibits light/GTPgammaS-activated PDE, but does not interact with GTPgammaS/Talpha in the homogenate. Together, our results strongly suggest that after activation of PDE by light/GTP, Pgamma is phosphorylated by Cdk5 and the phosphorylated Pgamma inhibits GTP/Talpha-activated PDE, even in the presence of GTP/Talpha in ROS.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Unusual corneal deposit after the topical use of cyclosporine as eyedrops.

PURPOSE: To report a patient who developed bilateral corneal opacities 5 days after the beginning topical cyclosporine. METHODS: Case report. A 45-year-old woman with graft-versus-host disease presented with bilateral corneal deposits. She had been treated with topical physiological saline solution, sodium hyaluronate, ofloxacin, fluorometholone, and oxybuprocaine. Cyclosporine eyedrops were added for persistent corneal epithelial defect bilaterally. Five days after cyclosporine, she complained of visual loss and dense corneal opacities were detected that covered the pupil bilaterally. RESULTS: Deposits were also observed on the punctal plugs, and infrared spectroscopy and X-ray analysis showed that these deposits had properties of cyclosporine. CONCLUSION: Topical cyclosporine, alone or in combination with other eyedrops, may cause severe corneal deposits in patients with disturbance of the corneal epithelial barrier and decreased tear clearance.

Cornea↗
PubMed2000

Structural change of bovine retinal cGMP phosphodiesterase by release of its gamma subunit: direct imaging by improved low angle rotary shadowing.

Cyclic GMP phosphodiesterase (PDE), a key enzyme for phototransduction, contains two catalytic subunits, Palpha and Pbeta, and two identical regulatory subunits, Pgammas. Neither the structure of the subunits of PDE nor their changes in structure during PDE regulation have been known. Here, improved low angle rotary shadowing was applied to depict the three-dimensional structure of bovine PDE (Palphabetagammagamma) and its changes by Pgamma release. Palphabetagammagamma and Palphabetagamma were isolated from photoreceptor membranes after treatment with a hydrolysis-resistant GTP analogue, and Palphabeta was prepared from Palphabetagammagamma tryptic digestion. Images of Palphabetagammagamma consisted of two crooked strands. These two strands faced each other to make a ring shape, but this ring structure was bent at the centre line between the two strands. In Palphabetagamma, one of these strands changed its shape toward reducing the central space of the ring structure. This ring appeared to be more bent at the centre line. In Palphabeta, both strands changed their shape such that the ring structure appeared to be a twisted quasi ring shape. These observations suggest that in Palphabetagammagamma each Pgamma is complexed with a catalytic subunit, and that the shapes of Palpha and Pbeta are drastically changed by the Pgamma release. These shape changes are no doubt crucial for various PDE regulations, such as activation of cGMP hydrolysis by Palphabeta, interaction of Palphabeta with GARP2 and a GARP2-like protein and cGMP binding to non-catalytic sites on Palphabeta.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Retinal dysfunction in basigin deficiency.

PURPOSE: To examine the retina of basigin (Bsg) knockout mice by electrophysiological and histologic methods and thereby to determine the possible function of Bsg in phototransduction and retinal development. METHODS: Scotopic and photopic electroretinograms (ERGs) were recorded from 11 wild-type, 12 heterozygous, and 8 homozygous Bsg gene knockout mice of different ages. The retinas were also examined by histologic and immunolabeling methods. RESULTS: Bsg knockout mice of 5 to 41 weeks of age showed a decrease in the amplitude of all components of both the photopic and scotopic ERGs. In contrast, the fundus and the fluorescein fundus angiography and morphology of the retina at the light microscopic level appeared to be normal until 8 weeks of age in Bsg knockout mice. Thereafter, the length of outer segment and outer nuclear layers decreased with increasing age. Immunohistochemical analysis localized Bsg protein in a variety of cells in the retina, especially in the pigment epithelium, the upper outer plexiform layer and the inner segments of photoreceptor cells. CONCLUSIONS: The results demonstrated that both rod and cone function were severely affected from an early age by the targeted disruption of the Bsg gene. In spite of abnormal ERGs, the photoreceptor cells maintained normal morphology up to 8 weeks. Thereafter, the photoreceptor cells degenerated gradually and were almost ablated by 41 weeks.

Animals↗
PubMed1999

Detailed localization of photoreceptor guanylate cyclase activating protein-1 and -2 in mammalian retinas using light and electron microscopy.

Guanylate cyclase activating proteins, GCAP-1 and GCAP-2, have a pivotal role in the activation of guanylate cyclase in phototransduction. Previous studies on the localization of GCAP-1 and GCAP-2 are contradictory. In this study, we tried to avoid possible artifacts accompanied by immunocytochemistry. Immunolabeling of a GCAP was carried out using antibodies pre-adsorbed with a different type of GCAP. In addition, immunolabeling was performed using three different animal species under different fixation and embedding. Electron microscopic immunocytochemistry was also performed to reveal subcellular localization of GCAPs as well as confirming data obtained by light microscopy. All data indicate that anti-GCAP-1 antibody binding sites were found predominantly in cone outer segments, in particular, in disk membrane regions. Sparse labeling was observed in rod outer segments, but the labeling was much lower than that seen in cone outer segments. Less labeling is also found in synaptic regions and inner segments of cones. No labeling was detected in connecting cilia and its cytoplasmic extensions. Such labeling patterns were similar among human, monkey and bovine retinas. The localization of GCAP-1 is consistent with the pattern of a recently reported human cone-specific degeneration. Anti-GCAP-2 antibody binding sites were detected in both inner and outer segments of rods and cones of all three animals although the labeling density was slightly different among species. Cryo-immuno-labeling of GCAP-2 in bovine retinas revealed that labeling sites were more concentrated in rods than those of cones, and that synaptic regions were also labeled. The different localization of GCAPs suggest that roles of GCAP-1 and GCAP-2 may be different.

Animals↗
PubMed1998

Effects of amorphous and polymorphs of PF1022A, a new antinematode drug, on Angiostrongylus costaricensis in mice.

To enhance the bioavailability of PF1022A (cyclo(D-lactyl-L-N-methylleucyl-D-3-phenyllactyl-L-N-met hylleucyl-D-lactyl-L-N-methylleucyl-D-3-phenyllactyl-L-N- methylleucyl)), a newly developed antinematode drug, we examined whether the new drug has polymorphism or not. First, four forms of PF1022A, designated as form alpha, form I, form II and form III of PF1022A, were prepared. By examining physicochemical properties of these forms by various methods including X-ray powder diffractometry and differential scanning calorimetry, it became apparent that PF1022A had one amorphous (form alpha) and three crystalline polymorphic forms, form I, form II and form III. Secondly, a dissolution study was carried out, and form alpha and form III were found to have higher solubility than form I and form II. Thirdly, anti-larval effects of the 4 forms of PF1022A on tissue-dwelling nematode, Angiostrongylus costaricensis, in mice were compared when given orally for 5 successive days at 10 or 40 mg/kg/day. Significant effects were observed in almost all parameters in host mice and worms in the groups treated with form alpha or form III, each at 40 mg/kg, but form I and form II had little effect. The present results suggest that PF1022A has polymorphism and that the form alpha and form III were more effective against tissue-dwelling nematodes than the form I and form II when given orally.

Angiostrongylus↗
PubMed1997

Influence of PF1022A on the motility of Angiostrongylus cantonensis in vitro.

Our previous in vivo studies on angiostrongyliasis showed that PF1022A had stronger killing effects against female adults than against males. No killing effects were observed against young adult worms in the central nervous system. To characterize the former in vivo action of PF1022A, in vitro effects of PF1022A on the motility of Angiostrongylus cantonensis were studied directly. Few differences in the efficacy were observed between male and female worms, but dose- and time-dependent inhibition was observed in adults treated with PF1022A at 10(-7)-10(-11) g/ml. PF1022A was slightly less effect we against young-adult worms than against adult worms. Minor effects of PF1022A were observed on the third-stage larvae. These results suggest that selectivity against adult females in vivo could be attributable to non-neuropharmacological mechanisms and that PF1022A does not pass through the blood-brain barrier in host animals.

Angiostrongylus cantonensis↗
PubMed1995

Effects of PF1022A on adult Angiostrongylus cantonensis in the pulmonary arteries and larvae migrating into the central nervous system of rats.

We examined the effects of PF1022A, newly developing in Japan, on adult Angiostrongylus cantonensis in the pulmonary arteries of rats. Following five and ten successive oral doses at 10 mg/kg per day, the first-stage larvae in rat faeces disappeared completely at 2 weeks after treatment. The treatment completely killed the female worms, but not the male worms. However, numbers of male worms were also decreased after the administration of either five successive oral doses at 10 mg/kg per day for four courses or five successive intraperitoneal doses at 0.5 mg/kg per day. Next, we examined the effects of PF1022A on larval A. cantonensis migrating into the central nervous system (CNS) of rats. Following five successive oral doses at 5 or 10 mg/kg per day and five successive intraperitoneal doses at 0.5 mg/kg per day, lesser killing effects were observed on male as well as female worms. On the basis of these results it is apparent that PF1022A will become a promising anthelmintic available as treatment for tissue-dwelling as well as intestinal nematodes.

Administration, Oral↗
PubMed1994

Effects of gabergic anthelmintics at higher concentrations on the guanidine-induced twitch responses in isolated frog rectus preparations.

Effects of various gabergic anthelmintics on the guanidine-induced twitch responses in isolated frog rectus preparations were examined. All gabergic anthelmintics such as milbemycin oxime, milbemycin D, avermectin B1a, ivermectin, and diethylcarbamazine (DEC) showed stimulatory effects on the guanidine-induced twitch responses at their higher concentrations. Only piperazine caused inhibitory effects on the twitch responses, even at higher concentrations. The stimulation of the twitch responses by the gabergic anthelmintics was antagonized with tetrodotoxin, hemicholinium-3, d-tubocurarine, and strychnine. These results suggest that all gabergic anthelmintics except piperazine stimulate the release of acetylcholine from the nerve endings and that all of them, including piperazine, have different effects on the gabergic mechanism at lower concentrations and on the cholinergic mechanism at higher concentrations.

Acetylcholine↗