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Biomedical subjects

Y Natori

Publications and source records attributed to Y Natori.

At least 19 recordsLinked to original sources
PubMed1997

Micro-anatomical study of the carotid cave.

The surgical treatment of aneurysms located in the carotid cave is often hazardous and difficult. We studied the micro-anatomy of the carotid cave and its neighbourhood by microscopic observation and histological examination using 50 sides from 25 autopsy cases. The carotid caves were found in 34 out of the 50 sides (68%) examined and were usually located in the posteromedial aspect of the carotid dural ring. They were classified into three types according to the topographic micro-anatomy: the slit-type (17/50, 34%) which showed a small, thin recess of the dura mater with fine connective tissue loosely adhered to the carotid wall; the pocket-type (12/50, 24%) which had a definite dural pouch with the apex attached to the vessel wall; and the mesh-type (5/50, 10%) which formed a slit- or pocket-type dural cave covered with a mesh-like dural roof. The remaining 16 sides (32%) showed tight dural attachment without any caval structure around the dural ring. The posteromedial portion of the carotid dural ring had no contact with any bony structure, and this distinct anatomical feature thus appear to facilitate the formation of the carotid cave. Furthermore, the availability of this potential space and the closely situated origin of the superior hypophyseal artery as well as the haemodynamic effect of the internal carotid artery may allow the development of the carotid cave aneurysm.

Adult↗
PubMed1997

Expression of monocyte chemoattractant protein-1 in experimental crescentic glomerulonephritis in rats.

Crescentic glomerulonephritis (CGN) is a rapidly progressive glomerular disease that is usually associated with a poor prognosis. Monocytes/macrophages are frequently observed in glomeruli in cases of CGN, and they are considered to play a crucial role in the pathogenesis of this disease. In this study we analyzed the glomerular expression of monocyte chemoattractant protein-1 (MCP-1), a potent chemoattractant for monocytes, in an experimental model of CGN. A model of the disease was induced in the WKY strain of rats by intravenous injection of antiserum raised against glomerular basement membranes. Accumulation of monocytes/macrophages in glomeruli was observed 4 hours after the injection of antiserum. Northern blot analysis showed that the expression of mRNA for MCP-1 was enhanced within 4 hours, peaked on day 3--when it was 60 times that in the control--and then declined. Immunostaining with MCP-1-specific antibody revealed the expression of MCP-1 protein in the diseased glomeruli but not in control glomeruli. Quantitative analysis of glomerular MCP-1 protein by enzyme-linked immunosorbent assay revealed a level 46 times that in the control in reflecting the increase in mRNA for MCP-1. These results indicate that glomeruli of rats with CGN produce MCP-1, which may play an important role in the pathogenesis of glomerular inflammation and crescent formation in CGN.

Animals↗
PubMed1997

Gene expression of CC chemokines in experimental crescentic glomerulonephritis (CGN).

CGN is a rapidly progressive glomerular disease. Monocytes/macrophages are frequently observed in glomeruli in cases of CGN and they are considered to play a crucial role in the pathogenesis of this disease. We described previously the glomerular expression of monocyte chemoattractant protein-1 (MCP-1), which is a potent chemoattractant for monocytes and a member of CC chemokine family, in an experimental model of CGN. In the present study we investigated the expression of mRNAs for other CC chemokines, namely, MCP-3, macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, RANTES and TCA3, all of which are chemotactic for monocytes, in the CGN model. First, we established a reverse transcriptase-polymerase chain reaction (RT-PCR) method by which mRNA for each of the CC chemokines could be amplified separately, and then we measured the levels of the expression of mRNAs for the chemokines in diseased glomeruli at several time points after induction of CGN. The mRNAs for all CC chemokines examined were expressed in glomeruli of rats with CGN. Moreover, induction of the gene expression of MIP-1alpha and MIP-1beta seemed to occur earlier than that of the others. CC chemokines may contribute to the recruitment and activation of monocytes in CGN, and each individual CC chemokine may play an overlapping but distinct role in the pathogenesis of this disease.

Animals↗
PubMed1997

Vitamin B6 suppresses growth and expression of albumin gene in a human hepatoma cell line HepG2.

The effect of vitamin B6 on the growth of a human hepatoma cell line HepG2 in culture was studied. The growth of HepG2 cells and protein synthesis were almost completely inhibited in medium supplemented with 5 mM pyridoxine. Pyridoxal was as effective as pyridoxine, but pyridoxamine showed no inhibitory action. The growth inhibition of HepG2 cells by pyridoxine was accompanied by a marked inhibition of secretion of plasma proteins, particularly albumin. Northern blot analysis of albumin mRNA showed that pyridoxine caused a rapid decrease in the expression of albumin gene. The electron-microscopic examination of pyridoxine-treated HepG2 cells revealed a smoothing of nuclear membrane, a decrease in the number of nucleoli, and an appearance of aggregated heterochromatin structures. These morphological features are compatible with the depressed transcriptional activity in the pyridoxine-treated cells. The mechanism by which vitamin B6 exerts its inhibitory effect was discussed in terms of our recent finding that vitamin B6 modulates expression of albumin gene by inactivating tissue-specific DNA-binding proteins. Binding of pyridoxal phosphate with tissue-specific transcription factors may reduce the capacity of these factors to interact with the regulatory region of albumin gene, resulting in the inhibition of the gene expression.

Blotting, Northern↗
PubMed1997

Effect of varying amino acid levels on protein metabolism in nephrotic rats during total parenteral nutrition.

In an attempt to determine appropriate diet in nephrotic syndrome, nephrotic rats, induced by puromycin aminonucleoside, were nourished by total parenteral nutrition fluid containing the same energy, but three different levels (1.65, 3.3, and 6.6%) of amino acids for 7 d. The fractional rate of total protein synthesis in the liver was determined by injecting a flooding dose of [3H]phenylalanine. The proportion of newly synthesized proteins retained and exported by the liver was estimated by injecting a tracer dose of [14C]leucine and then measuring the protein radioactivity remaining in the liver and present in the plasma after secretion was completed. Nephrotic animals synthesized more protein than control animals. Although the absolute synthesis rates of total protein in liver were increased with increasing amino acid administration, the absolute rates of synthesis of albumin were higher in the 3.3% group than in the other groups in nephrotic rats. However, kidney protein synthesis in nephrotic rats was higher in the 1.65% group than in the 3.3% group. Interestingly, the 3.3% group revealed the smallest urinary excretion of total protein and albumin. In addition, in the 3.3% group, plasma concentrations of total protein and albumin were higher, and plasma concentrations of total cholesterol and triglyceride were lower than in other groups. It was concluded that the 3.3% group, corresponding to a normal protein diet, has the greatest salutary effect on urinary protein excretion, followed by protein and lipid metabolism, in nephrotic rats. Not only protein intake but also the energy:protein ratio are important for diet therapy in nephrotic animals. The technique of total parenteral nutrition may be useful in defining the factors involved in glomerular permeability or permselectivity and intracellular protein metabolism.

Amino Acids↗
PubMed1997

Endocytosis of serum albumin in regenerating rat liver.

Lysosomes, isolated from rat liver after 70% partial hepatectomy (PHX), were found, by Western blotting, to contain a considerable amount of serum albumin. The level of intralysosomal serum albumin after PHX showed biphasic patterns: it increased immediately after PHX, peaked at 30 min, rapidly declined within a few hours, rose again with a peak at 15 hr, and gradually declined thereafter. At 15 hr after PHX, the content of lysosomal proteins in the liver increased to twice the level of unoperated control, and the electron-microscopic observation of the isolated lysosomes revealed numerous large membrane-delimited structures with ground substances of variable electron opacities. The increase in the intralysosomal serum albumin at 30 min and 15 hr was accompanied by changes in the buoyant densities of endosomes in Percoll density gradients. At both time points, the density profiles of endosomes isolated from hepatectomized rats shifted to the denser direction, suggesting that PHX activates fusion and/or maturation of endosomes. Formaldehyde-treated bovine serum albumin is known to be taken up by the liver by receptor-mediated endocytosis. The uptake of the modified heterologous albumin was shown to be activated as early as 30 min after PHX. Both the uptake of serum albumin into lysosomes and the shift of buoyant density profile of endosomes after PHX were inhibited by the administration of adrenergic receptor antagonists, particularly by the alpha r-antagonist prazosin. Further, the concentration of catecholamines in rat serum, particularly that of norepinephrine, was found to increase immediately after PHX, relative to that in serum from sham-operated rats. These results suggest that the elevation of serum norepinephrine levels after PHX activates endocytosis and facilitates delivery of endocytosed serum albumin to lysosomes, where albumin is digested to yield amino acids for possible use in protein synthesis during liver regeneration.

Adrenergic alpha-Antagonists↗
PubMed1996

Cloning and sequencing of cDNA encoding 4-aminobenzoate hydroxylase from Agaricus bisporus.

A cDNA clone encoding 4-aminobenzoate hydroxylase (EC 1.14.13.27) has been isolated using a probe prepared by PCR on the basis of partially determined amino acid sequences of the enzyme. The cDNA contained 1380-base pair open reading frame encoding 460 amino acid residues (M(r) 50974), 14-base pair 5'-untranslated region and 123-base pair 3'-untranslated region including a poly(A) tail of 20 nucleotides. All of the partially determined amino acid sequences were shown to be included in the deduced amino acid sequence. Homology analyses showed that the two regions on the enzyme share other flavoproteins such as salicylate hydroxylase and p-hydroxybenzoate hydroxylase.

Adenosine Diphosphate↗
PubMed1996

Detection of N-acetylgalactosaminyltransferase mRNA which determines expression of Sda blood group carbohydrate structure in human gastrointestinal mucosa and cancer.

The Sda blood group carbohydrate structure, GalNAcbeta1-4[NeuAcalpha2-3]Galbeta1-4GlcNAc-R, is expressed on glycolipid and glycoprotein in human gastrointestinal mucosa. The expression of the Sda determinant dramatically decreases in cancer tissue. The activity of the beta1,4N-acetylgalactosaminyltransferase (Sda-GalNAcT), which transfers GalNAc to NeuAcalpha2-3Galbeta1-4Glc(NAc)-R, correlates with the expression of the Sda immuno-epitope. From the total RNA fraction of human gastric mucosa, we have amplified a cDNA segment by reverse-transcription-polymerase-chain reaction (RT-PCR), using primers designed according to the cDNA sequence of a murine beta1,4GalNAcT which synthesizes the Sda determinant. An RT-PCR product of 390 bp shared 85% nucleotide identity with the murine Sda-related beta1,4GalNAcT. This RT-PCR product hybridized to a transcript in mRNA prepared from human gastric mucosa. In RT-PCR using specific primers to this PCR product, Sda-GalNAcT mRNA was detected in all samples of normal stomach and small intestine examined and the majority of normal colonic specimens. Six out of nine cases of gastric cancer, and 9 out of 13 cases of colonic cancer failed to produce the target DNA. These results correlate with the beta1,4GalNAcT activity measured in the same samples. In conclusion, a segment of the cDNA for betal,4GalNAcT which determines expression of the Sda carbohydrate structure was obtained, and reduced transcription of this beta 1,4GalNAcT resulted in the disappearance of the Sda epitope in gastrointestinal cancer.

Animals↗
PubMed1996

Vitamin B6 deficiency accelerates metabolic turnover of cystathionase in rat liver.

Although most of cystathionase was found to exist as an inactive apoenzyme in the liver of vitamin B6-deficient rats, the concentrations of the immunoreactive enzyme protein were virtually the same for control and vitamin B6-deficient livers. Under vitamin B6 deficiency, however, the rate of synthesis of cystathionase, measured by incorporation of labeled amino acid into the immunoprecipitated enzyme, was increased severalfold due to an increased level of cystathionase mRNA. Western blot analysis of lysosomal proteins showed that the amount of cystathionase in the lysosomes from the liver of vitamin B6-deficient rats was also increased severalfold. This observation suggests that lysosomes specifically recognize the apocystathionase for sequestration in preference to the holoenzyme. The present study provides the molecular basis for dual roles of vitamin B6 in controlling the metabolic turnover of cystathionase; it regulates synthesis of the enzyme by modulating the expression of cystathionase gene, and it regulates degradation of the enzyme by different susceptibilities of apo- and holoenzymes to lysosomal proteolysis.

Animals↗
PubMed1996

Jak3 expression in glomerular epithelia of IgA nephropathy (IgA-N) patients.

Jak3 is a member of the Janus kinase family which plays an important role in cytokine signal transduction. Jak3 associates the gamma(c) chain of receptors for IL-2, IL-4, IL-7, IL-9 and IL-15, and is essential for the signal transduction of these cytokines. We have isolated Jak3 kinase from renal mesangial cells and demonstrated the constitutive expression of Jak3 in glomeruli in vivo. To investigate the physiological and pathological role of Jak3 in glomeruli, we prepared anti-Jak3 antibody and analysed the localization of Jak3 in glomeruli of renal biopsy samples from various nephritis patients and normal subjects. Among 61 nephritis patients and four normal subjects investigated in the present study, Jak3 was selectively localized to glomerular epithelia of IgA-N patients (14/34 cases) and focal glomerulosclerosis patients (1/5 cases), but not detected in minimal changes (n = 6), membranous glomerulonephropathy (n = 7), crescentic glomerulonephritis (n = 4), lupus nephritis patients (n = 5), and normal subjects (n = 4). The intense immunoreactivity for Jak3 is significantly associated with the decrease in creatinine clearance (81.5 +/- 10.4 ml/min versus 104.3 +/- 29.6 ml/min; P < 0.05, Student's t-test) and the increase in level of serum creatinine (1.13 +/- 0.33 mg/dl versus 0.75 +/- 0.23 mg/dl; P < 0.01, Student's t-test) in IgA-N patients. Furthermore, gamma(c) chain was concomitantly expressed with Jak3 in glomerular epithelia in vivo and in vitro, suggesting that signal transduction via gamma(c)-Jak3 cascade may be involved in the pathogenesis of glomerular injury of IgA-N. Taken together with the recent findings that IL-4-secreting T lymphocytes in affected glomeruli injure glomerular epithelium, the responsiveness of glomerular epithelium for IL-4 may be pathologically enhanced in IgA-N.

Animals↗
PubMed1996

Cytotoxicity of sera from rats with puromycin aminonucleoside nephrosis.

Administration of puromycin aminonucleoside (PAN) to rats induces acute nephrosis with hyperlipidemia, and, in some experimental conditions, it results in chronic focal glomerulosclerosis. In this study, we examined the cytotoxicity of serum from rats with PAN-induced nephrosis, since hypercholesterolemia is considered to cause injury to vascular walls in atherosclerosis, the mechanism of which is analogous to that of glomerulosclerosis. About half of the tested sera from nephrotic rats (9 out of 17) were cytotoxic to cultured aortic endothelial cells. The toxic substance(s) was heat-stable and was extracted in the lipid fraction. Serum levels of triglyceride and cholesterol were markedly higher in the group of rats with cytotoxic serum than in the group with noncytotoxic serum. No cytotoxicity was associated with sera from control rats or the corresponding lipid fractions. Cytotoxic sera were also effective against cultured glomerular epithelial and mesangial cells. These results indicate that cytotoxic lipid is produced in rats with PAN nephrosis and the results raise the possibility that the cytotoxic lipid in nephrotic serum might contribute to lipid-mediated glomerular injury which may induce glomerulosclerosis at a subsequent stage.

Animals↗
PubMed1995

Isolation and characterization of a novel perchloric acid-soluble protein inhibiting cell-free protein synthesis.

We found a novel protein in the postmitochondria supernatant fraction of rat liver, which is soluble in 5% perchloric acid and strongly inhibits protein synthesis in a rabbit reticulocyte lysate system. The protein extracted from the supernatant fraction with 5% perchloric acid was purified by ammonium sulfate fractionation and CM-Sephadex chromatography. The protein was shown to consist of two identical subunits with a molecular mass of 14 kDa. By immunoscreening with the rabbit antisera against the protein, a cDNA encoding the protein was cloned and sequenced. The cDNA contained an open reading frame of 411 base pairs encoding a 136-amino acid protein with a molecular mass of 14,149 Da. The deduced amino acid sequence was completely identical with that constructed from all of the above peptides. Interestingly, the perchloric acid-soluble protein inhibited cell-free protein synthesis in the rabbit reticulocyte lysate system in a different manner from RNase A. The protein is likely to inhibit an initiation stage of cell-free protein synthesis. Among the rat tissues tested, the protein was located only in liver and kidney. These findings are the first report on a new inhibitor that may be involved in the regulation of protein synthesis in those tissues.

Amino Acid Sequence↗
PubMed1995

Interaction of rat liver lysosomes with basic polypeptides.

In order to gain knowledge on the interaction of lysosomes with proteins, we have assessed the equilibrium densities of the lysosomal membrane and matrix markers after in vitro incubation of rat liver lysosomes with various polypeptides. The addition of basic polypeptides, polylysine or protamine, to the suspension of lysosomes brought about a profound alteration of lysosomal membrane, causing extensive leakage of lysosomal matrix enzymes. Electron microscopic observation revealed a remarkable aggregation of lysosomes by the basic polypeptides. Polyglutamic acid, an acidic polypeptide, did not produce such effect. ATP was found to stabilize lysosomes during incubation, particularly with basic polypeptides.

Animals↗
PubMed1995

Vitamin B6 modulates expression of albumin gene by inactivating tissue-specific DNA-binding protein in rat liver.

The level of albumin mRNA in the liver of vitamin B6-deficient rats was found to be 7-fold higher than that of control rats. Since the transcriptional activity of the albumin gene, as measured by a nuclear run-on assay, was increased 5-fold in vitamin B6 deficiency, the higher concentration of albumin mRNA in the liver of vitamin-deficient rats could be attributed to the enhanced rate of transcription. The promoter proximal sequences of the albumin gene interact with a number of tissue-specific transcription factors including HNF-1 and C/EBP. We determined the binding activities of liver nuclear extracts to the HNF-1- and C/EBP-binding sites by gel mobility-shift assay and found that the activities of the extract prepared from liver of vitamin B6-deficient rats were greater than those of controls. As the concentrations of C/EBP in nuclear extracts from control and vitamin-deficient rats, estimated by Western-blot analysis, were essentially the same, the lower binding activity of the extract from control liver is probably due to inactivation of tissue-specific factors by pyridoxal phosphate and/or its analogues. We therefore examined the effect of pyridoxal phosphate and its analogues on the binding activity of nuclear extract in vitro and found that only pyridoxal phosphate effectively inhibited the binding. These observations indicate that vitamin B6 modulates albumin gene expression through a novel mechanism that involves inactivation of tissue-specific transcription factors by direct interaction with pyridoxal phosphate.

Albumins↗
PubMed1995

Detection and purification of two 14 kDa phospholipase A2 isoforms in rat kidney: their role in eicosanoid synthesis.

Phospholipase A2 (PLA2) activity in the soluble fraction of rat kidney yielded three peaks on DEAE cellulose column chromatography. From these three, we purified two PLA2 isoforms to near-homogeneity. Both had a molecular weight of approx. 14,000 on SDS-PAGE, and immunochemical and enzymological studies indicated that one is a 14 kDa type I PLA2 and the other a 14 kDa type II PLA2. RNA blot analysis confirmed that rat kidney contains both types of PLA2 and that administration of lipopolysaccharides and mercury chloride into rats increased type II PLA2 mRNA levels in kidney. When cultured rat mesangial cells were incubated with purified type I or type II PLA2 in combination with the calcium ionophore A23187 at suboptimal condition, augmentation of prostaglandin E2 production was observed. Type I and type II forms of PLA2 may play a role in arachidonate metabolism in rat kidney.

Animals↗
PubMed1995

Production of functional chick liver HMG 2a protein in Escherichia coli.

An efficient Escherichia coli system for the production of a variant form of high-mobility group-2a protein (HMG 2a), having the additional 5 amino acid residues (Ala-Pro-Thr-Leu-Glu) at the NH2-terminal, has been constructed. cDNA encoding HMG 2a was ligated with the Omp A signal peptide sequence and was inserted into an inducible bacterial expression vector pSH-L. After the plasmid introduced into E. coli was expressed by temperature shift, the recombinant product was purified by trichloacetic acid precipitation followed by Bio-Rex 70 column chromatography. The purified product showed the expected NH2-terminal sequence and the superhelical activity of circular DNA similar to the authentic HMG 2a isolated from chick liver.

Amino Acid Sequence↗
PubMed1995

Microsurgical anatomy of the superior orbital fissure.

The microsurgical anatomy of the superior orbital fissure was examined in cadaver specimens. The cavernous sinus fills the posterior margin and the orbital contents fill the anterior margin of the fissure. All of the nerves coursing in the walls of the cavernous sinus pass through the superior orbital fissure to reach the orbit. The fissure has a narrow lateral part and a larger medial part. The annular tendon from which the rectus muscles arise is situated in front of the upper half of the medial part of the fissure and is attached to the lateral margin near the junction of the lateral and medial parts. The fissure is divided into three sectors: lateral, central, and inferior. The lateral sector, which corresponds to the narrow lateral part, transmits the trochlear, frontal, and lacrimal nerves and the superior ophthalmic vein, all of which course outside the annular tendon. The central sector, which is situated behind and is aligned with the lateral part of the annular tendon, transmits the superior and inferior divisions of the oculomotor nerve, the abducens and nasociliary nerves, and the sensory and sympathetic roots of the ciliary ganglion, all of which pass through the annular tendon. The inferior sector, which is located below the annular tendon and origin of the inferior rectus muscle, is filled with a posterior extension of the orbital fat and transmits the inferior ophthalmic vein. The relationship and course of the nerves in each sector and the incisions that may be used to open and expose the contents of the fissure are reviewed.

Adult↗