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H Ozeki

Publications and source records attributed to H Ozeki.

At least 37 records · Page 2Linked to original sources
PubMed1997

Chemical characterization of pheomelanogenesis starting from dihydroxyphenylalanine or tyrosine and cysteine. Effects of tyrosinase and cysteine concentrations and reaction time.

Two types of melanin pigment are produced in mammals; the brown-to-black eumelanins and the yellow-to-reddish-brown pheomelanins. The switch from one type of melanin to the other appears to be regulated by the levels of tyrosinase and thiols, such as cysteine and glutathione. This study examines the process of pheomelanin formation starting from dihydroxyphenylalanine (dopa) or tyrosine and cysteine. We prepared pheomelanins by tyrosinase oxidation of dopa or tyrosine in the presence of cysteine. Experimental variables were reaction time, tyrosinase concentration, and dopa or tyrosine to cysteine ratio. Following the reactions, we measured concentrations of tyrosine, dopa, cysteine and cysteinyldopas, amounts of total melanin (TM) by Soluene-350 solubilization and aminohydroxyphenylalanine (AHP), a specific indicator of pheomelanin, formed by hydriodic acid hydrolysis, and absorbance ratio, A650/A500. It was found that (1) mixed melanogenesis is a heterogeneous process in which pheomelanogenesis proceeds first, followed by eumelanogenesis, as shown by changes in the tyrosine and cysteinyldopa concentrations, the AHP/TM ratio, and the A650/A500 ratio during the course of melanogenesis and (2) lower tyrosinase concentration favors pheomelanogenesis even when the availability of cysteine is limited, as shown by AHP/TM ratios that were higher than the corresponding tyrosine to cysteine ratios. These results indicate that the switch from eumelanogenesis to pheomelanogenesis can be achieved by lowering the tyrosinase activity, which conforms to our proposal that tyrosinase activity is the major factor controlling the course of melanogenesis.

Cysteine↗
PubMed1997

Chemical characterization of eumelanins with special emphasis on 5,6-dihydroxyindole-2-carboxylic acid content and molecular size.

Mammalian melanins exist in two chemically distinct forms; the brown to black eumelanins and the yellow to reddish pheomelanins. Eumelanins are derived from copolymerization of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Eumelanins can be quantified by HPLC analysis of the oxidation product pyrrole-2,3,5-tricarboxylic acid (PTCA) and by our spectrophotometric method (Sp.EM). We also developed a spectrophotometric method for assaying the total amount of eu- and pheomelanins by dissolving them in Soluene-350 (TM). In addition, we previously showed that Sp.EM/TM and PTCA/TM ratios are significant parameters in characterizing eumelanins produced in follicular melanocytes. The objectives of this study were (1) to clarify the significance of Sp.EM/TM and PTCA/TM ratios in synthetic eumelanins and (2) to apply these methods to characterizing natural eumelanins with various DHI/ DHICA ratios and molecular sizes. The results obtained show that (1) the Sp.EM/TM ratio of synthetic eumelanins increases as polymerization proceeds, (2) the Sp.EM/TM and PTCA/TM ratios in copolymers of DHI and DHICA correlate to the percentage content of DHICA-derived units, and (3) combination of the Sp.EM/TM and PTCA/TM ratios serves to estimate the DHICA content and the degree of polymerization in natural eumelanins.

Animals↗
PubMed1997

Dihydro-1,4-benzothiazine-6,7-dione, the ultimate toxic metabolite of 4-S-cysteaminylphenol and 4-S-cysteaminylcatechol.

4-S-Cysteaminylphenol (4-S-CAP) and the corresponding catechol 4-S-cysteaminylcatechol (4-S-CAC) have been evaluated for melanocytotoxicity. It was shown recently that tyrosinase oxidation of these substrates produces a violet pigment, dihydro-1,4-benzothiazine-6,7-dione (BQ). In this study we examined whether BQ is the ultimate toxic metabolite produced in melanoma cells from 4-S-CAP/4-S-CAC. Biochemical experiments showed that (1) BQ was formed by autoxidation of 4-S-CAC as well as by tyrosinase oxidation of 4-S-CAP/4-S-CAC, (2) BQ reacted rapidly with thiols such as reduced glutathione (GSH), and (3) BQ inhibited the activity of alcohol dehydrogenase, an SH enzyme. In vitro experiments showed that (1) the cytotoxicity of 4-S-CAC was mostly prevented by catalase and superoxide dismutase, (2) BQ was highly cytotoxic to B16 melanoma cells (IC50 being 3.9 microM as compared with 507 microM for 4-S-CAP), (3) BQ was metabolized rapidly to a GSH adduct in melanoma cells, and (4) the same GSH adduct was also formed upon incubation of melanoma cells with 4-S-CAP, the reaction being tyrosinase dependent. In vivo experiments showed that intratumoral administration of BQ (0.5 micromol) inhibited the subcutaneous growth of B16 melanoma nearly as effectively as 4-S-CAP/4-S-CAC (20 micromol). These results indicate that BQ is the ultimate toxic metabolite produced by tyrosinase oxidation of 4-S-CAP/4-S-CAC. BQ deprives melanoma cells of GSH and may inactivate SH enzymes essential for DNA synthesis and cell proliferation by covalent binding through their cysteine residues, thereby exerting melanocytotoxicity. Cytotoxicity of 4-S-CAC depends mostly on autoxidation producing BQ and active oxygens.

Animals↗
PubMed1997

[Developmental eye abnormalities in mouse fetuses induced by retinoic acid].

To clarify the relationship between neural crest cells and ocular anomalies, pregnant mice were treated intraperitoneally with 12.5 mg/kg retinoic acid suspended in corn oil on day 7 of pregnancy (RA group). Control mice were given an equal volume of corn oil (control group). Each group consisted of 5 mother mice, and the offsprings were removed on day 18 of gestation. The fetal mortality was 46.3% in the RA group and 2.2% in the control group. Twenty-two live fetuses of the RA group and 45 of the control group were grossly observed, and the eyes were examined histologically. In the RA group, gross malformations such as microphthalmos (95.5%), cleft lip and palate (36.4%), and central nervous system anomalies (31.8%) were observed, and in the control group, malformations such as microphthalmos (6.7%), central nervous system anomalies (2.2%), and low set ears (2.2%) were seen. Histological examination revealed microphthalmos (47.7%), anophthalmos (38.6%), faulty closure of the embryonic fissure (36.4%), developmental abnormalities of the vitreous (34.1%), aphakia (22.7%), goniodysgenesis (18.2%), and faulty separation of the lens vesicle (15.9%) in the RA group. These anomalies arose from abnormal neural crest cell migration induced by retinoic acid. They were detected in only 3.3, 1.1, 3.3, 8.9, 1.1, 2.2 and 2.2%, respectively of the control group.

Animals↗
PubMed1997

[Four cases of persistent hyperplastic primary vitreous].

We evaluated four cases of persistent hyperplastic primary vitreous (PHPV) encountered at Nagoya City University Hospital in 1995. PHPV was seen unilaterally in three cases and bilaterally in one. The series comprised two males and two females, ranging in age from three to eight months, with an average of 4.8 months. Case 1 had a white strand running from the optic disc to the posterior surface of the lens in the left eye. Case 2 showed leukocoria in the right eye and central corneal opacity in the left. Magnetic resonance imaging (MRI) revealed total retinal detachment in both eyes. Case 3 exhibited retinal folds running from the optic disc to the posterior surface of the lens in the left eye. Case 4 showed elongation of the ciliary processes and leukocoria in the right eye. Ipsilateral total retinal detachment was seen in MRI. Three eyes of two cases were microphthalmic. Associated ocular anomalies included, posterior embryotoxon, sclerocornea, hypoplasia of the iris stroma and peripapillary staphyloma. There were accompanying systemic anomalies such as arachnoidal cyst, syndactyly, microcephalus, heart anomalies, pulmonary atresia and asplenia. Patients with PHPV should be carefully examined for the possible presence of other ocular and systemic anomalies caused by neural crest disorders.

Abnormalities, Multiple↗
PubMed1996

Chemical characterization of melanins in sheep wool and human hair.

The color of hair and wool in mammals and feathers in birds is mostly determined by the quantity and quality of melanins that are synthesized in follicular melanocytes and transferred to keratinocytes. These are two chemically distinct types of melanin pigments: the black to brown eumelanins and the yellow to reddish pheomelanins. Melanins in sheep wool and human hair of various colors were characterized by HPLC methods to estimate 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-derived units in eumelanins and benzothiazine units in pheomelanins. Melanins were also characterized by spectrophotometric methods after differential solubilization in alkalies. It was demonstrated that 1) black wool in Asiatic sheep contains eumelanin with the DHICA content similar to black mouse melanin, while black to brown melanins from human hair contain much lower ratios of DHICA-derived units, comparable to the slaty mutation in mice, 2) dark brown to brown hair in human contains eumelanin whose chemical properties are indistinguishable from those of black hair; 3) dark red wool and red human hair contain pheomelanic pigments whose chemical properties are rather different from those of yellow pheomelanins in mice, and 4) light brown, blonde, and red hairs in human can be differentiated from each other with this methodology.

Animals↗
PubMed1996

Spectrophotometric characterization of eumelanin and pheomelanin in hair.

Mammalian melanins exist in two chemically distinct forms: the brown to black eumelanins and the yellow to reddish-brown pheomelanins. They can be quantified by HPLC analysis of pyrrole-2,3,5-tricarboxylic acid (PTCA) and aminohydroxyphenylalanine (AHP). We recently developed a spectrophotometric method for assaying the total amount of eu- and pheomelanins by dissolving melanins in Soluene-350 plus water. In this study, we examined whether absorbance at 500 nm (A500) of the Soluene-350 solution reflects the total amount of melanins obtained by the HPLC methods, and whether the ratio of absorbances between 650 and 500 nm reflects the eumelanin/total melanin ratio in mouse hair, sheep wool, and human hair. Our findings were as follows: (1) Total melanin levels calculated from A500 values correlate well with those obtained from PTCA and AHP values by multiplying with the following factors: for mice, PTCA x 45 + AHP x 2.5; for sheep, PTCA x 40 + AHP x 15; and for humans, PTCA x 160 + AHP x 10. (2) The A650/ A500 ratios were higher (0.25-0.33) in black to brown hair while they were significantly lower (0.10-0.14) in yellow to red hair. These results indicate that (1) the A500 value can be used to quantify the total combined amount of eu- and pheomelanins, and (2) the A650/A500 ratio can serve as a parameter to estimate the eumelanin/total melanin ratio. The present method provides a convenient way to qualitatively characterize eu- and pheomelanins in melanins produced in follicular melanocytes.

Animals↗
PubMed1996

[The study on the mechanism of brain damage due to high flow and pressure during selective cerebral perfusion].

It has been reported that the high flow and pressure perfusion produced the brain damage during selective cerebral perfusion. This time we studied the mechanism of this brain damage with mock circulation. We made the mock circulation system of brain with the hard shell reservoir as cranium, and with the triple soft bags as brain tissue, involving into reservoir. We designed the control group that intracranial pressure (ICP) was 0 mmHg at pump off, and the increasing intracranial pressure (IICP) group that ICP was 10 mmHg at pump off. We measured the flow-pressure relationship in the control and IICP group, and then stenosis in outflow. In results, the flow and pressure in both the inflow and outflow side increased significantly (p < 0.001) in control groups, as pump flow increased. The changes of the flow and pressure in IICP group showed a same tendency to the control group. Moreover, both the inflow volume into bag and the outflow volume from bag decreased as pump flow increased stepwisely. The pressure in both inflow and outflow side increased significantly and the volume of the inflow side in IICP group showed a tendency to decrease, compared with the control. The stenosis in the outflow side produced the significant increase in the pressure of both inflow and outflow side, and intracranium, with the same pump flow as the control without stenosis. In conclusion, the high flow perfusion produced the increase of the several pressure in intracranial and extracranial vessels. Moreover, the high flow perfusion produced the decrease of the intracranial blood volume cerebral blood flow. The high flow perfusion does not necessarily contribute to the cerebral tissue perfusion. The stenosis at the side of venous return produced relative high perfusion. This result suggests that the venous return should be taken care of during the selective cerebral perfusion.

Blood Pressure↗
PubMed1996

[Histochemical studies on two cases of Peters' anomaly].

We examined glycosaminoglycan molecular species in the corneal stroma and the sclera histochemically in two cases of Peters' anomaly. Paraffin-embedded sections were stained with either hematoxylin-eosin or sensitized high iron diamine combined with enzyme digestion and then examined with a light microscope. In the center of the cornea, the histological specimens revealed defects of the corneal endothelium and Descemet's membrane, together with a local defect of the corneal stroma. Disorganized lens materials were detected in the corneal stroma. In the peripheral cornea, the undifferentiated iris adhered to the corneal posterior surface. Based upon the findings mentioned above, these two cases were diagnosed as having Peters' anomaly caused by faulty separation of the lens vesicle. The sclera showed normal structures in the specimen stained with hematoxylin-eosin. In both cases, the corneal stroma involved nearly equal amounts of chondroitin sulfate A/C and B. The sclera, on the other hand, contained a large amount of chondroitin sulfate A/C and a relatively small amount of chondroitin sulfate B. Keratan sulfate was never detected in either the cornea or the sclera. Thus, disorders of glycosaminoglycan molecular species were detected in the sclera as well as in the corneal stroma.

Corneal Opacity↗
PubMed1996

[A case of nonrhegmatogenous retinal detachment in Dandy-Walker Syndrome].

A 2-month-old female presented with nonrhegmatogenous retinal detachment in Dandy-Walker syndrome. At the fist examination, coloboma involving the optic disc in both eyes was detected. The left eye showed microphthalmos with sclerocornea, persistent pupillary membrane, hypoplasia of the iris stroma, and bullous retinal detachment near the optic disc. Chromosomal analysis revealed a mosaic pattern: 46, XX/47, XXX. Increased intracranial pressure associated with Dandy-Walker syndrome was detected by a neurosurgeon at the age of 3 months. The patient was followed for several weeks, and then nonrhegmatogenous retinal detachment appeared in the right eye. Subretinal fluid alternately increased and decreased in both eyes. A ventriculo-peritoneal shunt was performed at the age of 6 months, and the retinal detachment was remarkably reduced in both eyes after lowering of intracranial pressure. Coloboma involving the optic disc, sclerocornea, persistent pupillary membrane, hypoplasia of iris stroma, and Dandy-Walker syndrome were thought to be caused by the abnormal development of neural crest cells. We surmised that the retinal detachment in this case might have resulted from a communicating pathway between the subarachnoid space and the subretinal space. We concluded that the etiology of retinal detachment associated with optic disc anomaly should be investigated to determine adequate treatment.

Coloboma↗
PubMed1995

Antimelanoma effect of 4-S-cysteaminylcatechol, an activated form of 4-S-cysteaminylphenol.

Rational chemotherapy of malignant melanoma could be developed by taking advantage of the presence of melanogenic enzymes in melanoma cells. 4-S-Cysteaminylphenol (4-S-CAP) has been evaluated for melanocytotoxicity and antimelanoma effect. Although 4-S-CAP is selectively toxic to pigmented melanoma cells, it is not potent enough when applied as a single agent. To increase the efficacy of 4-S-CAP, we synthesized 4-S-cysteaminylcatechol (4-S-CAC), an activated form of 4-S-CAP, and compared its biochemical properties and antimelanoma effects with those of the isomers 3-S-cysteaminylcatechol (3-S-CAC) and 2-S-cysteaminyl-hydroquinone (2-S-CAH). 4-S-CAC was found to be a better substrate for melanoma tyrosinase than was L-3,4-dihydroxyphenylalanine, the natural catecholic substrate. 3-S-CAC was a poor substrate, whereas 2-S-CAH was not a substrate. 4-S-CAC was the most cytotoxic to three lines of melanoma cells in vitro, followed by 2-S-CAH and 3-S-CAC. When applied i.p. for 9 days at a dose of 100 mg/kg, 4-S-CAC.HCl, increased by 46-52% the life span of C57BL/6 mice inoculated i.p. with B16 melanoma; this effect was comparable to that of a 50 mg/kg dose of 5-(3,3-dimethyltriazenyl)-1H-imidazole-4-carboxamide. 3-S-CAC was marginally effective, whereas 2-S-CAH was toxic to the host. This systemic toxicity of 2-S-CAH reflected its susceptibility to autoxidation. Growth of B16 melanoma cells inoculated s.c. was significantly inhibited by i.p. administration of 4-S-CAC.HCl (200 mg/kg) for 5 days (P < 0.05). These results suggest that 4-S-CAC is a potent antimelanoma agent, the effect of which is mostly mediated through tyrosinase oxidation.

Animals↗
PubMed1995

Chemical characterization of hair melanins in various coat-color mutants of mice.

Mammalian melanins exist in two chemically distinct forms: the brown to black eumelanins and the yellow to reddish pheomelanins. Melanogenesis is influenced by a number of genes, the levels of whose products determine the quantity and quality of the melanins produced. To examine the effects of various coat-color genes on the chemical properties of melanins synthesized in the follicular melanocytes of mice, we have introduced new methods to solubilize differentially pheomelanins and brown-type eumelanins. We applied these and previously developed high-performance liquid chromatography and spectrophotometric methods for assaying eu- and pheomelanins to characterize melanins in various mutant mice: black, lethal yellow, viable yellow, agouti, brown, light, albino, dilute, recessive yellow, pink-eyed dilution, slaty, and silver. It was demonstrated that 1) complete solubilization of melanins in Soluene-350 is a convenient method to estimate the total amount of eu- and pheomelanins, 2) lethal yellow, viable yellow, and recessive yellow hairs contain almost pure pheomelanins, and 3) melanins from brown, light, silver, and pink-eyed black hairs share chemical properties in common that are characterized by partial solubility in strong alkali. We suggest that 1) the brown-type eumelanins have lower degrees of polymerization than the black-type eumelanins, and 2) slaty hair melanin contains a greatly reduced ratio of 5,6-dihydroxyindole-2-carboxylic acid-derived units as compared with black and other eumelanic hair melanins. These results indicate that our methodology, high-performance liquid chromatography and spectrophotometric methods combined, may be useful in chemically characterizing melanin pigments produced in follicular melanocytes.

Animals↗
PubMed1994

[The protective effect and problem of retrograde cerebral perfusion].

In order to study the protective effect and problem of retrograde perfusion (RCP), cerebral hemodynamics and cerebral metabolism were evaluated in fourteen pigs weighing 25-30 kg. Intracranial pressure, carotid arterial flow and pressure, and internal jugular venous pressure as cerebral hemodynamics; pyruvate, lactate, and oxygen consumption as cerebral metabolism; and brain temperature were measured. The animal was cooled to electrical cerebral silence on electroencephalogram under cardiopulmonary bypass. Then, animals were divided into three groups: group I (n = 4); circulatory arrest; group II (n = 3); RCP through superior vena cava (SVC); group III (n = 7); RCP through bilateral internal jugular vein (IJV). Retrograde perfusion flow was regulated to maintain the SVC pressure or IJV pressure of 30 mmHg, for 90 minutes. The variations in brain temperature were least in group III. As perfusion flow increased, intracranial pressure, and inferior vena cava (IVC) pressure increased. But, cerebral perfusion pressure, which was calculated from the difference of intracranial arteriovenous pressure, did not increase and, SVC pressure and returned blood flow through the aorta did not increase in group III. In group II, there was no significant relation between pump flow, SVC pressure, and intracranial pressure, but SVC pressure had a positive correlation with the pressure gradient of SVC-IJV. The uptake of cerebral lactate, cerebral pyruvate, and lactate-pyruvate ratio, and cerebral oxygen consumption were superior in group III than other groups. In conclusion, RCP through IJV was advantageous to maintain hypothermia and aerobic metabolism of the brain during systemic hypothermic circulatory arrest.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[The study on cerebral hemodynamics during selective cerebral perfusion].

This study was undertaken to clarify characterization on cerebral hemodynamics during deep hypothermic selective perfusion (SCP) in 18 pigs. Besides, the changes on cerebral hemodynamics were investigated with obstruction to venous drainage due to the clamp of superior vena cava (SVC) cannula. For SCP, blood was infused into aortic arch with the clamp of descending aorta, during 90 minutes at 20 degrees C. We measured regional cerebral blood flow (CBF), intracranial pressure (ICP), and carotid arterial flow (CAF), and carotid arterial pressure. The carotid arterial pressure as perfusion pressure was not significantly correlated with CAF, CBF and ICP. Although CAF increased as pump flow rate increased, the relationship between pump flow and CBF was not significant. Moreover, SVC pressure showed a tendency to increase, as CAF increased. Both ICP and internal jugular vein pressure (IJVP) were significantly (p < 0.01) increase, and CAF was significantly (p < 0.05) decrease with the clamp of SVC cannula. On the other hand, both ICP and IJVP were significantly decrease, and both CAF and CBF were increase, without unclamp of SVC cannula. The results suggest that cerebral autoregulation is intact during deep hypothermic SCP, and hyperperfusion cause the increase of shunt flow in extracranial area, and besides, the increase of ICP with obstruction to venous drainage cause decrease in cerebral blood flow.

Animals↗
PubMed1993

Spectrophotometric assay of eumelanin in tissue samples.

Most of the natural melanin pigments consist of not only indolic eumelanin but also sulfur-containing pheomelanin. Previous methods for spectrophotometric assay of melanins use solubilization in alkaline media; a major disadvantage of these procedures is that they do not distinguish between eumelanin and pheomelanin. A spectrophotometric method for assaying eumelanin in tissue samples is described. Sepia melanin serves as a standard. Hair and melanoma samples were hydrolyzed in hot hydriodic acid, and insoluble eumelanic pigments were solubilized in hot sodium hydroxide in the presence of hydrogen peroxide and analyzed for absorbance at 350 nm (A350). The detection limit of eumelanin was ca. 2 micrograms. Eumelanins prepared from dopa, 5,6-dihydroxyindole and its carboxy derivative gave similar A350 values. Mixed-type melanins prepared from dopa and various ratios of cysteine gave A350 values inversely proportional to their sulfur contents. Excellent correlations were observed between A350 values and contents of pyrrole-2,3,5-tricarboxylic acid, an oxidation product specific for eumelanin, in hair samples from sheep and humans of various colors and in melanomas and eyes from mice. The present method provides a specific and direct measurement of eumelanin contents in tissue samples.

Acids↗
PubMed1992

Hydroxamamide as a chelating moiety for the preparation of 99Tcm radiopharmaceuticals (I).

Hydroxamamides contain a nitrogen and an oxygen as donor atoms, and can be synthesized by the simple reaction of nitriles with hydroxylamine. Benzohydroxamamide (BHam) was investigated as a new ligand for 99Tcm. The yield of the 99Tcm-BHam complex was determined by thin-layer chromatography using cellulose strips. A high yield of the complex was obtained at room temperature over a wide pH range, even at BHam concentrations as low as 5 x 10(-7) M. Cellulose acetate electrophoresis indicated that the complex was uncharged. When the 99Tcm-BHam complex was injected into mice, it was cleared gradually from the blood by means of the hepatobiliary system with low urinary excretion. Uptake by the stomach and the spleen was low. These results demonstrate the high affinity of BHam for 99Tcm and the high stability of the 99Tcm-BHam complex. The hydroxamamide group may be a promising chelating moiety for designing new 99Tcm radiopharmaceuticals.

Animals↗
PubMed1990

Functional expression of the mutants of the chloroplast tRNA(Lys) gene from the liverwort, Marchantia polymorpha, in Escherichia coli.

The anticodon of the tRNA(Lys) gene (trnK) in the liverwort, Marchantia polymorpha, was artificially converted to an amber anticodon. This mutant tRNA(Lys) (CTA) gene carrying either the intron of the C27-C43 mismatch at the anticodon-stem is not functional in Escherichia coli, but without both of them, it does work as a tRNA(Lys) amber suppressor.

Base Composition↗