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Biomedical subjects

A Kamei

Publications and source records attributed to A Kamei.

At least 37 records · Page 2Linked to original sources
PubMed1999

Variation in glycosidase activity in soluble fractions in ICR/f rat lenses with the progression of cataract formation.

The current study reports active glycosidases in the lens of ICR/f rats, which generate a hereditary cataract approximately 90 d after birth, and the variation in enzyme activity with cataract progression. Seven active glycosidases, beta-D-galactosidase, alpha-D-glucosidase, beta-D-glucosidase, beta-D-glucuronidase, beta-D-galactosaminidase, beta-D-glucosaminidase and alpha-D-mannosidase, were detected in ICR/f rat lenses. Of these, beta-D-glucuronidase and beta-D-galactosidase showed a tendency to increase in activity with the cataract progression. Furthermore, beta-D-glucosidase and alpha-D-mannosidase showed a transitory increase in activity at the time of cataract formation. This result suggests that several glycosidases in the lens may be involved in the hereditary cataract formation. The optimal pH and temperature of the seven active glycosidases in rat lenses were also measured in this study.

Animals↗
PubMed1999

Properties of partially purified beta-N-acetylglucosaminidase from bovine crystalline lens.

This paper reports that beta-N-acetylglucosaminidase from bovine lens has potent enzyme activity compared with other glycosidases in the lens. The partially purified enzyme was used to determine its physiological properties. The optimal pH and optimal temperature of this enzyme was approximately 6.3 and 40 degrees C, respectively. The apparent native molecular weight of this enzyme obtained by gel filtration chromatography was 540 kDa. Furthermore, the enzyme fraction contained 3 polypeptides with molecular weights of 28.8, 28.0 and 26.0 kDa, although it is not certain if they were one of the components of this enzyme in the current study. The Km value of this enzyme was 92.3 microM and it was inhibited strongly by HgCl2 and sodium dodecyl sulfate (SDS).

Acetylglucosaminidase↗
PubMed1998

HSP90 has neurite-promoting activity in vitro for telencephalic and spinal neurons of chick embryos.

We purified a protein from the extract of denervated chick muscle. The protein had neurite-promoting activity in vitro for the chick telencephalic neurons and spinal neurons. Partial amino acid sequencing and immunoblotting revealed that the protein was chick heat shock protein 90 (HSP90). Commercially available bovine HSP90 and recombinant chick HSP90 expressed in Escherichia coli also showed the same activity. Since HSP10 (GroES) and HSP60 (GroEL) exhibited no activity for neurite outgrowth in the same culture, this activity was specific to HSP90 among the heat shock proteins.

Amino Acid Sequence↗
PubMed1998

Intramolecular cross-linking of the extrinsic 33-kDa protein leads to loss of oxygen evolution but not its ability of binding to photosystem II and stabilization of the manganese cluster.

The extrinsic 33-kDa protein of photosystem II (PSII) was intramolecularly cross-linked by a zero-length cross-linker, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The resulting cross-linked 33-kDa protein rebound to urea/NaCl-washed PSII membranes, which stabilized the binding of manganese as effectively as the untreated 33-kDa protein. In contrast, the oxygen evolution was not restored by binding of the cross-linked protein, indicating that the binding and manganese-stabilizing capabilities of the 33-kDa protein are retained but its reactivating ability is lost by intramolecular cross-linking of the protein. From measurements of CD spectra at high temperatures, the secondary structure of the intramolecularly cross-linked 33-kDa protein was found to be stabilized against heat treatment at temperatures 20 degrees C higher than that of the untreated 33-kDa protein, suggesting that structural flexibility of the 33-kDa protein was much decreased by the intramolecular cross-linking. The rigid structure is possibly responsible for the loss of the reactivating ability of the 33-kDa protein, which implies that binding of the 33-kDa protein to PSII is accompanied by a conformational change essential for the reactivation of oxygen evolution. Peptide mapping, N-terminal sequencing, and mass spectroscopic analysis of protease-digested products of the intramolecularly cross-linked 33-kDa protein revealed that cross-linkings occurred between the amino group of Lys48 and the carboxyl group of Glu246, and between the carboxyl group of Glu10 and the amino group of Lys14. These cross-linked amino acid residues are thus closely associated with each other through electrostatic interactions.

Amino Acid Sequence↗
PubMed1998

Polyethylene glycol-modified bilirubin oxidase improves hepatic energy charge and urinary prostaglandin levels in rats with obstructive jaundice.

BACKGROUNDS/AIMS: No study has so far been conducted to clarify whether the presence of hyperbilirubinemia is detrimental to liver and renal functions. In the present study, the effects of polyethylene glycol-modified bilirubin oxidase (PEG-BOX) therapy on liver and renal function tests, hepatic energy charge and urinary prostaglandin levels were evaluated in a rat model of obstructive jaundice. METHODS: Sprague-Dawley rats were used in the experimental model of obstructive jaundice. PEG-BOX or an equivalent amount of PEG alone was intravenously injected into the animals and sampling of blood and urine, and liver harvesting were done sequentially after bile duct ligation. RESULTS: Conventional liver function tests showed no difference between PEG-BOX and control groups. However, bilirubin concentrations in the peripheral blood and liver tissue specimens markedly decreased, and the hepatic energy charge significantly increased in the PEG-BOX group as compared to controls. The blood concentration of bile acid was lower, but its urinary excretion was higher in the PEG-BOX group than in the control group. In vitro incubation of PEG-BOX with serum from rats with obstructive jaundice decreased the concentration of bilirubin but not that of bile acid. The urinary levels of prostaglandin E2 and the thromboxane B2/6-keto-prostaglandin Fla ratio were significantly lower in the PEG-BOX group than in the control group. CONCLUSIONS: The systemic reduction of bilirubin concentration may contribute to normalization of the urinary levels of prostaglandins and thromboxane B2, to decrease in serum bile acid levels, and to improvement of the hepatic energy charge in obstructive jaundice. These findings suggest that preoperative improvement of jaundice may be beneficial to patients with obstructive jaundice.

Animals↗
PubMed1998

Competitive inhibition of delta8-tetrahydrocannabinol and its active metabolites for cannabinoid receptor binding.

In vitro binding characteristics of delta8-tetrahydrocannabinol (delta8-THC) and its metabolites, 11-hydroxy-delta8-THC (11-OH-delta8-THC) and 11-oxo-delta8-THC, as well as an inactive metabolite, delta8-THC-11-oic acid, as a cannabinoid receptor site from bovine cortex were examined using the specific agonist [3H]CP-55940. 11-OH-delta8-THC and 11-oxo-delta8-THC strongly inhibited the specific binding of [3H]CP-55940. The Ki values of 11-OH-delta8-THC and 11-oxo-delta8-THC for the specific binding of [3H]CP-55940 were 52 and 143 nM, respectively, whereas that of delta8-THC-11-oic acid was 917 nM. Scatchard plot analyses indicated that 11-OH-delta8-THC and 11-oxo-delta8-THC caused a significant increase in the apparent KD value without changing the apparent Bmax. These results reveal that active metabolites of delta8-THC also competitively bind to the cannabinoid receptor as agonists.

Animals↗
PubMed1998

Partial properties of four glycosidases in normal human lens and variations in their enzyme activities during aging and with the advance of lens coloration.

This paper reports the active glycosidases in normal human lenses and their partial properties. In addition, variations in their enzyme activities during aging and with the advance of lens coloration were also examined. Five glycosidases, alpha-glucosidase, beta-D-glucuronidase, N-acetyl-beta-D-glucosaminidase, beta-D-cellobiosidase, and alpha-L-fucosidase, were detected as active glycosidases in the normal human lens. However, the activity of beta-D-cellobiosidase was considerably low as compared to the other four glycosidases. Thus, this enzyme was omitted from this study. The four glycosidases, alpha-D-glucosidase, beta-D-glucuronidase, N-acetyl-beta-D-glucosaminidase, and alpha-L-fucosidase, showed that their enzyme activities fell abruptly between the ages of 40 and 50. Furthermore, the Km values of their enzymes exhibited some variability during aging. Namely, the Km values of their enzymes indicated the lowest value between the 40 age group and 50 age group, suggesting that the substrate affinity became the strongest at these age groups. Then, variations in enzyme activity with the advance of lens coloration were examined. In each cases, the specific activity of detectable glycosidases in color lenses, white to brown, decreased. In particular, the specific activity of enzymes in the brown lens was very low, indicating that glycosidases in the brown lens may scarcely display their enzyme activities.

Adult↗
PubMed1997

Cleavage of amino acid residue(s) from the N-terminal region of alpha A- and alpha B-crystallins in human crystalline lens during aging.

The current study reports for the first time a post-translational modification at the N-terminal region of alpha A- and alpha B-crystallins in normal human lens. The post-translational modification involves a loss of amino acid residues from the N-terminal region. We found three types of losses of N-terminal amino acid(s) from alpha-crystallin. One is the loss of the N-terminal amino acid residues 1-3 from alpha A-crystallin in aged lenses of the age 70 group. The other two modifications were found in alpha B-crystallin. One is the loss of Met(1) of the N-terminus and the other is the loss of 6 amino acids from the N-terminal region. These phenomena were observed in the lenses > 40 age group. Recent studies suggest that the N-terminal region of alpha-crystallin may play a chaperone-like role at the molecular level. These losses of amino acids from the N-terminal region may affect this molecular chaperone-like activity as well as the transparent properties of the human lens.

Aging↗
PubMed1997

Identification of domains on the extrinsic 33-kDa protein possibly involved in electrostatic interaction with photosystem II complex by means of chemical modification.

The extrinsic 33-kDa protein of photosystem II (PSII) was modified with various reagents, and the resulting proteins were checked for the ability to rebind to PSII and to reactivate oxygen evolution. While modification of more than eight carboxyl groups of aspartyl and glutamyl residues with glycine methyl ester did not affect the rebinding and reactivating capabilities, modification of amino groups of lysyl residues with either N-succinimidyl propionate or 2, 4,6-trinitrobenzene sulfonic acid or modification of guanidino groups of arginyl residues with 2,3-butanedione resulted in a loss of rebinding and reactivating capabilities of the 33-kDa protein. Moreover, the number of lysyl and arginyl residues susceptible to modification was significantly decreased when the protein was bound to PSII as compared with when it was free in solution, whereas the number of carboxyl groups modified was little affected. These results suggested that positive charges are important for the electrostatic interaction between the extrinsic 33-kDa protein and PSII intrinsic proteins, whereas negative charges on the protein do not contribute to such interaction. By a combination of protease digestion and mass spectroscopic analysis, the domains of lysyl residues accessible to N-succinimidyl propionate or 2,4, 6-trinitrobenzene sulfonic acid modification only when the 33-kDa protein is free in solution were determined to be Lys4, Lys20, Lys66-Lys76, Lys101, Lys105, Lys130, Lys159, Lys186, and Lys230-Lys236. These domains include those previously reported accessible to N-hydroxysuccinimidobiotin only in solution (Frankel and Bricker (1995) Biochemistry 34, 7492-7497), and may be important for the interaction of the 33-kDa protein with PSII intrinsic proteins.

Amino Acid Sequence↗
PubMed1997

Acute disseminated demyelination due to primary human herpesvirus-6 infection.

UNLABELLED: A previously healthy 19-month-old boy developed acute encephalopathy, thrombocytopenia and hepatic dysfunction. Human herpesvirus-6 (HHV-6) DNA was found in his CSF during the acute stage of the disease by means of the polymerase chain reaction. T2-weighted MRI revealed high signal intensity in the left thalamus and left parieto-occipital deep white matter. The myelin basic protein concentration in the CSF was elevated suggesting acute demyelination. The patient is now 2.5 years old and has no sequelae. CONCLUSION: Since clinical course and neuroimaging after HHV-6 infection are similar to those in acute disseminated encephalomyelitis, clinicians must pay attention to primary HHV-6 infection in patients under 2 years old with white matter lesions.

Acute Disease↗
PubMed1996

Properties of partially purified esterase in human crystalline lens and variation in its enzyme activity during aging and with advance of senile cataract.

Two fractions of esterase were partially purified from the soluble fraction of normal human lens. The apparent molecular masses of these enzymes were approximately 200 kDa (esterase-I) and 30 kDa (esterase-II). The optimal pH of esterase-I and esterase-II was 6.0 and 7.5, and their respective optimal temperature were 43 degrees C and 46 degrees C. The K(m) values of esterase-I and esterase-II for 4-methylumbelliferyl-palmitate were 0.14 and 0.11 microM, respectively. The activity of these enzymes was inhibited by EDTA. The fraction with esterase activity also displayed lipase activity, although it is unknown whether the two enzymes are identical. Variation in the activity of these esterases was examined as a function of age for normal lens and as functions of age and coloration for senile cataractous lenses. The normal lenses maintained high enzyme activity up to the 60 age group and their enzyme activity then fell abruptly. In the senile cataractous lenses, enzyme activity was very low as compared to that of normal lenses of similar age. This shows that cataract formation may have a deleterious effect on the catalytic activity of esterase in the lens.

Aging↗
PubMed1995

Immunohistochemistry for a bifunctional protein in patients with peroxisomal disorders.

Immunohistochemical studies using antisera against bifunctional protein, a beta-oxidation enzyme, were performed on liver, kidney, and brain tissue specimens from patients with peroxisomal disorders and from controls to investigate the distribution and development of peroxisomes. Bifunctional protein-positive granules were not found in patients with Zellweger syndrome or neonatal adrenoleukodystrophy, whereas positive immunoreactivity was observed from 8 and 6 weeks gestation in the liver and kidney, respectively, and in the brain, from 23-25 weeks in the brainstem neurons and from 12-14 weeks in the white matter glia, in controls. Bifunctional protein immunoreactivity then increased with gestation in the brain. These results suggest that bifunctional protein immunohistochemistry is useful for the detection of peroxisomes, which are closely related to neuronal maturation and gliogenesis in premyelination in human brain development.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1995

Prostaglandin synthesis in human cancer cells: influence of fatty acids and butyrate.

Previous research has suggested that prostaglandins (PGs) may play a role in the development of colon cancer since tumor cells produce more PGs than normal cells. However, the exact mechanism by which PGs play a role in the development of cancer is not known. In addition, factors that influence PG synthesis are not known since they are complicated by the presence of homeostatic mechanisms. To avoid the homeostatic mechanisms, the present research was designed to examine factors that may influence PG synthesis in an in vitro system, i.e., a tissue culture. We have chosen two human colon cancer cell lines that differ in their ability to metabolize long-chain fatty acids (LCFAs), LS174T cells and HT-29 cells. We examined the effect of LCFAs on their membrane fatty acid composition, growth, and ability to release the main PGs (PGE2 and PGI). The LCFAs used were those most common in the colonic lumen [18:0, 18:2 (n-6), and 18:3 (n-3)]. In addition, we examined the effect of butyrate on the above mentioned parameters. Butyrate is produced in the colon through fermentation of dietary fibers. The data obtained suggest that although both of these tumor cell lines are of human colonic origin, they differ in their response to LCFAs and butyrate in some of the characteristics studied, such as growth, composition of membranes, and the relationship between membrane FA composition and PG synthesis. Polyunsaturated fatty acid supplementation stimulated the growth of HT-29 cells but not of LS174T cells when compared with growth in media supplemented with 18:0.(ABSTRACT TRUNCATED AT 250 WORDS)

Butyrates↗
PubMed1995

Characterization of partially purified alpha-glucosidase in the insoluble fraction of bovine crystalline lens.

Two fractions of neutral alpha-glucosidase were partially purified from the insoluble fraction of bovine lens. This is the first report of such an event to the best of our knowledge. The apparent native molecular weights of these fractions were 121 kDa (fraction-I) and 254 kDa (fraction-II). Both fractions contained three polypeptides with molecular weights of 21, 25 and 30 kDa, although the proportion of these peptides was different in both fractions. The optimal pH of fraction-I and fraction-II was pH 6.0 and 6.5, and the optimal temperature for both fractions was approximately 50 degrees C. The Km values of fractions-I and -II for 4-methylumbelliferyl-alpha-glucopyranoside were 0.086, and 0.192 mM. The activities of these enzymes were inhibited strongly by HgCl2 and slightly by D-iodoacetic acid, but not by D-turanose. From this, we suggest that the enzyme in the insoluble fraction of bovine lens may be a cytoplasmic neutral alpha-glucosidase which binds to the cell membrane.

Animals↗
PubMed1995

Variation in the glycosidase activity of human lens during aging and with advance of senile cataract.

This paper describes the glycosidases in normal lenses and the variation in their activities during aging and with the advance of cataract. In normal human lenses, four glycosidases, alpha-L-fucosidase, alpha-D-glucosidase, beta-D-glucuronidase and beta-D-galactosaminidase, exhibited strong specific activities, which fell sharply between the ages of 40 and 60. In the 50-60 age group the enzyme activities fell sharply to one-tenth and below those in the lenses of the 20-30 age group. The Km value of each enzyme also depended on age and exhibited some variability, suggesting that the substrate affinity of enzyme may be changeable. These facts show that the specific activities and Km values of some glycosidases in normal human lenses change with aging. The activities of the four glycosidases in lenses with senile cataract were also determined as a function of advanced cataract stage. The activities of the four enzymes were weak in the lenses of the younger age groups, and were undetectable in the lenses of older groups, over 60-year of age. This shows that cataract formation may have a deleterious effect on the catalytic activity of some glycosidase and inhibit them strongly.

Adult↗
PubMed1995

Direct effect of 12(S)-hydroxyeicosatetraenoic acid on rat crystalline lens is perturbation of lens normalcy.

The direct effect of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] on rat crystalline lens was investigated in this study. 12(S)-HETE lowered the glutathione (GSH) level and GSH reductase activity in the lens, while accelerating aggregation and insolubilization of lens proteins and production of thiobarbituric acid-reactive substances. The study also indicated that 12(S)-HETE insolubilized alpha-crystalline and induced opacification of the lens when the lens was incubated with 12(S)-HETE. From the results, we presumed that 12(S)-HETE may be oxidized or peroxidized easily and automatically in the air. The substances derived from 12(S)-HETE by oxidation or peroxidation may give the action disordering lens normalcy and induced cataract formation. Thus, the direct effect of 12(S)-HETE may of no benefit to the crystalline lens.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1994

Developmental immunohistochemistry of bifunctional protein in human brain.

Immunohistochemical studies of a peroxisomal enzyme, bifunctional protein, were performed on human brains (occipital cortex, cerebellum, pons) from fetus to young adult. Bifunctional protein-positive neurons appeared at 23-25 weeks of gestation in the facial nuclei of pons, at 27-28 weeks in the occipital cortex and Purkinje cells of vermis, and at 36-38 weeks in the Purkinje cells of the cerebellar hemisphere and pontine nuclei. They then increased in number with gestational age. However, bifunctional protein-positive glia appeared early in the occipital deep white matter at 17-20 weeks of gestation, their appearance shifting from the deep to the superficial white matter with increasing age. These results suggest that bifunctional protein is closely related to neuronal maturation and gliogenesis of premyelination in the human brain during development as other peroxisomal enzymes.

3-Hydroxyacyl CoA Dehydrogenases↗