Biomedical subjects
Publications and source records attributed to A Okubo.
The anti-lipolysis by ginseng polypeptide and its modified peptides was examined using porcine adipose cells. Ginseng polypeptides modified by amino acid substitution or proteolyzation reduced or lost the inhibiting activity of adrenalin-induced lipolysis. Correlation between the anti-lipolytic activity of ginseng polypeptide and its Mg(2+)- and ribose-binding activities is discussed.
The photosynthetic bacterium Rhodobacter sphaeroides f. sp. denitrificans IL106 can grow in high osmolarity. The accumulation of intracellular inorganic ions and organic solutes in cells grown in a synthetic medium containing different concentrations of NaCl was examined. Together with potassium ion, trehalose was the major organic osmoprotectant and its accumulation depended on the external salt concentration. Intracellular levels of glycine betaine and other osmoprotectants such as proline did not change when osmolarity increased.
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The nucleotide sequence of the genes encoding a pentaheme cytochrome (dmsC) and a transmembrane protein (dmsB) were determined upstream of the dmsA gene encoding dimethyl sulfoxide reductase from Rhodobacter sphaeroides f. sp. denitrificans. dmsC and dmsB encode proteins of 404 and 226 amino acid residues, which show 40% and 26% identity to the pentaheme cytochrome TorC and the transmembrane protein TorD, respectively, of the trimethylamine N-oxide reduction system in Escherichia coli.
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The substrate specificity and enantioselectivity of DMSO reductase from Rhodobacter sphaeroides f.s. denitrificans were studied on a series of alkyl aryl sulfoxides as substrate. The enzyme was found to catalyze deoxygenation of (S)-sulfoxides predominantly. (R)-Sulfoxides were recovered with a high enantiomeric excess.
PURPOSE/METHODS: A 13-year-old girl had unilateral iridocyclitis and periphlebitis. The periphlebitis exacerbated, and macular edema as well as branch retinal vein occlusion developed. The patient was treated with systemic corticosteroids. RESULTS/CONCLUSIONS: The lesions responded well to systemic corticosteroids. Histologic diagnosis of sarcoidosis was obtained by transbronchial lung biopsy. Ocular lesions in this child were similar to those seen in adult sarcoidosis. Branch retinal vein occlusion may occur as a rare vascular complication of sarcoidosis.
The gene encoding dimethyl sulfoxide (DMSO) reductase, which contains a molybdenum cofactor, of the phototrophic bacterium Rhodobacter sphaeroides f. sp. denitrificans was isolated using an oligonucleotide probe, which was synthesized based on a internal amino acid sequence of the purified enzyme. The DMSO reductase gene coded for 822 amino acids (2466 base pairs, M(r) = 89,206) as a precursor form having a signal peptide of 42 amino acids. The deduced amino acid sequence had high homology with those of some enzymes containing a molybdenum cofactor: trimethyl amine N-oxide reductase (48%), biotin sulfoxide reductase (44%), and DMSO reductase (29%) of Escherichia coli.
The inhibitory activity of angiotensin I-converting enzyme in milk increased during fermentation with the Calpis sour milk starter containing Lactobacillus helveticus and Saccharomyces cerevisiae. Two kinds of peptides inhibitory to angiotensin I-converting enzyme were purified from the sour milk by using four-step HPLC. The amino acid sequences of these inhibitors were identified as Val-Pro-Pro and Ile-Pro-Pro. The concentrations of peptides providing 50% inhibition of angiotensin I-converting enzyme were 9 and 5 microM, respectively. Most of the inhibitory activity in sour milk was attributed to these two peptides.
We studied the protective effects of midkine, a growth factor produced by a retinoic acid responsive gene, on constant light-induced retinal damage in albino BALB/C adult mice. Two days before exposure to constant light, midkine was injected into the vitreous of the left eye and a phosphate buffer saline into the right eye (control eyes). After 7 days of constant light, control eyes exhibited shortening of the photoreceptor outer segments and decreased thickness of the outer nuclear layer, whereas in midkine-treated eyes photoreceptor cells were virtually intact. Although midkine-treated eyes also showed photoreceptor damage after longer light exposure of up to 21 days, the damage was significantly less than in control eyes. Measurement of the thickness of the outer nuclear layer showed the protective effect of intravitreous midkine on the constant light-induced retinal damage. These findings suggest that midkine is a potential agent for the prevention of photoreceptor degeneration.
The binding of amaranthin, specific for Gal beta 1,3 GalNAc and sialic acid Gal beta 1,3 GalNAc sequences, to the human retina was investigated with avidin biotinylated peroxidase. Amaranthin bound to the cone and rod photoreceptors, inner plexiform layer, ganglion cells, and nerve fibers. Since peanut agglutinin, specific for Gal beta 1,3 GalNAc, selectively binds to cones, we conclude that O-glycoside-linked glycoconjugates are present on the surfaces of both cones and rods: Gal beta 1,3 GalNAc and sialic acid Gal beta 1,3 GalNAc are terminal sugars of the glycoconjugates around cones and rods, respectively.
The distribution of alpha 2,3-sialyltransferase (alpha 2,3-ST) mRNA in the rat iris and ciliary body was investigated with in situ hybridization histochemistry. Strong expression of alpha 2,3-ST mRNA was detected in the inner epithelial layer of the ciliary body and weak expression in the iris epithelium. Since the synthesis of sialoglycoconjugates is completed by terminal sialylation by the action of sialyltransferase (ST), the ST-expressed portions are considered to produce sialoglycoconjugates. Hence, the source of the sialoglycoconjugates found in the inner epithelial layer of the ciliary body in previous histochemical studies is the same epithelial cell.
Ultrastructural changes in the distribution of free ribosomes in photoreceptor inner segments in relation to photoreceptor degeneration in Purkinje cell degeneration (pcd) were studied in mutant mice reared under cyclic light and sacrificed at 30 and 120 postnatal days. On postnatal day 30, some photoreceptors appeared to be normal whereas others had degenerated to varying degrees with numerous spherules in the extracellular space surrounding degenerating inner segments. By postnatal day 120, retinal degeneration had progressed with a marked loss of photoreceptors. The distribution of free ribosomes in the mutant inner segments was random, clustered, or uniform. This was distinct from normal control retinas in which random distribution predominated. Markedly degenerated inner segments contained sparse ribosomes which coalesced in small aggregates. These changes in ribosome distribution seemed to be associated with the extent of photoreceptor degeneration. The significance of these changes in ribosome distribution, in particular clustered distribution, is discussed together with our previous findings.
Glycoconjugates, consisting of O- and N-linked types, are present on the surface of photoreceptor cells and in the interphotoreceptor matrix (IPM). This study was undertaken to facilitate understanding of the metabolic features of O-linked sialoglycoconjugates in comparison with those of N-linked glycoconjugates in the rat retina. We examined the developmental change in distribution of Gal beta 1,3GalNAc alpha 2,3-sialyltransferase mRNA in rat retinas using in situ hybridization histochemistry to detect the synthesis period of O-linked sialoglycans. Positive hybridization signal was observed in the ganglion cells throughout the postnatal days (P) examined, whereas strong signals were detected in the photoreceptor inner segments and the inner nuclear layer exclusively at P16 and P18. At P20 and older, weak or sparse signals were detected in these regions. It is likely that O-linked sialoglycoconjugates, which are detected in the mature IPM, are actively synthesized from P16 to P18 in the rat photoreceptor inner segments, suggesting that the O-linked sialoglycoconjugates in the photoreceptor layer may be stable with litter turnover in the mature retina.
Hepatocyte growth factor (HGF) is a potent mitogen for renal tubular cells, and HGF and its receptor (c-met proto-oncogene product, Met) can induce lumen formation in epithelial cells. We measured the concentration of HGF in cyst fluids from patients with renal cystic diseases. The concentration of HGF was high in proximal cyst fluid (mean 2.45 vs 0.42 ng/mL in distal cysts). Cyclic AMP concentration was higher in distal than in proximal cysts (663 vs 6.0 pmol/L). mRNA of HGF and Met were co-expressed in cyst walls from cases with polycystic kidney disease. These findings suggest that HGF is a growth factor that may mediate human renal cyst genesis.
The binding of amaranthin, specific for the Gal beta 1,3 GalNAc and NeuAc alpha 2,3 Gal beta 1,3 GalNAc sequences, to the photoreceptors of the monkey retina was investigated using the avidin-biotinylated peroxidase method. Amaranthin bound to the surfaces of both cone and rod photoreceptors. This and previous lectin histochemical studies show that O-glycoside-linked glycoconjugates are present on the surfaces of both cones and rods: Gal beta 1,3 GalNAc and NeuAc alpha 2,3 Gal beta 1,3 GalNAc are the terminal sugars of the glycoconjugates around cones and rods, respectively.
The developmental changes in the binding of Maackia amurensis lectin, specific for sialic acid alpha 2,3 galactose sequence, to the rat retina was investigated using the avidin-biotinylated peroxidase method. The lectin bound to the surfaces of photoreceptor outer segments from postnatal day 16 (P16), whereas it had bound to the other retinal layers from P14. The intense labelings of the outer segments were interspersed with unstained portions, which may correspond to cone photoreceptors. These results confirm that the sialic acid residues on the terminus of carbohydrate chains increase at P16 and mask the beta-galactose residues around rod outer segments.
We studied the distribution pattern of free ribosomes in the photoreceptor inner segments of adult mice with reference to environmental light. Eyeballs were obtained from animals at the light or dark phase of the ordinary cyclic light, and photoreceptor inner segments were examined by electron microscopy. In the light phase, free ribosomes were distributed in a random fashion, although meticulous observations revealed that they appeared to be arranged either in a spiral or linear form, or in isolation. In the dark phase, several free ribosomes were arranged in a clustered fashion. When animals were kept in continuous darkness as long as 27 hours, most of the inner segment free ribosomes showed a clustered pattern similar to that in the dark phase of the cyclic light. We discussed the light-dependent configurational changes of ribosomes with respect to their activity or inactivity in protein synthesis.