Biomedical subjects

H Hoshikawa

Publications and source records attributed to H Hoshikawa.

At least 19 recordsLinked to original sources

PubMed1998

High affinity binding of oxidized LDL to mouse lectin-like oxidized LDL receptor (LOX-1).

We cloned mouse LOX-1 cDNA to take advantage of a gene-targeting technique to clarify the role of LOX-1 in vivo. Mouse LOX-1 was composed of 363 amino acids and had a C-type lectin domain type II membrane protein structure. Mouse LOX-1 had triple repeats of the sequence in the extracellular "Neck domain," which is unlike human and bovine LOX-1. LOX-1 bound oxidized LDL with two classes of binding affinity in the presence of serum. The binding component with the higher affinity showed the lowest value of Kd among the known receptors for oxidized LDL. In the absence of serum, the high affinity component disappeared, suggesting that an unknown co-factor in serum is essential for efficient uptake of oxidized LDL by endothelial cells. A low concentration of unlabeled oxidized LDL displaced 125I-labeled oxidized LDL more efficiently in the presence of serum than in the absence of serum. The co-factor in the serum may be involved in the pathophysiology of atherosclerosis in addition to the oxidation of LDL.

Amino Acid Sequence↗

PubMed1998

Ligand specificity of LOX-1, a novel endothelial receptor for oxidized low density lipoprotein.

Endothelial dysfunction, or activation, elicited by oxidized low density lipoprotein (Ox-LDL) and its lipid constituents has been shown to play a key role in the pathogenesis of atherosclerosis. We recently have identified a novel receptor for Ox-LDL-designated lectin-like Ox-LDL receptor (LOX-1) in vascular endothelial cells. To examine ligand specificity of LOX-1, we established CHO cell lines stably expressing both human and bovine LOX-1 (LOX-1-CHO). LOX-1-CHO bound and degraded 125I-labeled Ox-LDL but did not significantly degrade 125I-labeled acetylated LDL (Ac-LDL). Fucoidin and maleylated BSA (M-BSA), which inhibit 125I-Ox-LDL binding to class A scavenger receptors, did not inhibit 125I-Ox-LDL binding or degradation in LOX-1-CHO. Polyinosinic acid and carrageenan, in contrast, significantly reduced 125I-Ox-LDL binding to LOX-1-CHO by 62% and 60%, respectively. Delipidated and untreated 125I-Ox-LDL were bound and degraded equally in LOX-1-CHO; furthermore, excess amounts of unlabeled, delipidated Ox-LDL inhibited binding and degradation of untreated 125I-Ox-LDL. Taken together, LOX-1 is a receptor for Ox-LDL but not for Ac-LDL. LOX-1 recognizes protein moiety of Ox-LDL, and its ligand specificity is distinct from other receptors for Ox-LDL, including class A and B scavenger receptors.

Animals↗

PubMed1998

Effect of acetazolamide on cation concentration in the endolymph of the endolymphatic sac.

Acetazolamide (ACTZ), a carbonic anhydrase inhibitor, has been reported to decrease the endolymphatic sac (ES) DC potential (ESP) in the guinea pig. To assess the involvement of cation transport in the ESP change by ACTZ we examined the effect of ACTZ upon the K+ and Na+ activities of the ES endolymph in the guinea pig using ion-sensitive microelectrode. ACTZ (10 mg/kg), a dose that produces the ESP maximum reduction, produced a significant increase in Na+ activity of the ES endolymph with no change in K+ activity. The results suggest that Na+ transport may be directly or indirectly involved in ESP reduction by ACTZ, and that a Na(+)-H+ exchanger may be involved in Na+ influx pathway from endolymph to the ES epithelial cells.

Acetazolamide↗

PubMed1997

An endothelial receptor for oxidized low-density lipoprotein.

Endothelial dysfunction or activation elicited by oxidatively modified low-density lipoprotein (Ox-LDL) has been implicated in the pathogenesis of atherosclerosis, characterized by intimal thickening and lipid deposition in the arteries. Ox-LDL and its lipid constituents impair endothelial production of nitric oxide, and induce the endothelial expression of leukocyte adhesion molecules and smooth-muscle growth factors, which may be involved in atherogenesis. Vascular endothelial cells in culture and in vivo internalize and degrade Ox-LDL through a putative receptor-mediated pathway that does not involve macrophage scavenger receptors. Here we report the molecular cloning, using expression cloning strategy, of an Ox-LDL receptor from vascular endothelial cells. The cloned receptor is a membrane protein that belongs structurally to the C-type lectin family, and is expressed in vivo in vascular endothelium and vascular-rich organs.

Amino Acid Sequence↗

PubMed1997

Processing of proendothelin-1 at the C-terminus of big endothelin-1 is essential for proteolysis by endothelin-converting enzyme-1 in vivo.

Production of endothelin-1 is thought to be a three-step process consisting of an initial proteolytic cleavage of the proendothelin-1 precursor to big endothelin-1-Lys-Arg, C-terminal trimming by a carboxypeptidase and further processing of the big endothelin-1 peptide to endothelin-1 by endothelin-converting enzyme (ECE). To further clarify the mechanism of processing in the biosynthesis of endothelin-1, we introduced a point mutation into endothelin-1 cDNA to replace the Arg in the -4 position of the recognition motifs of furin-like convertase in human preproendothelin-1 (Arg49 or Arg89) by Gly. When mutant cDNAs were expressed in Chinese hamster ovary (CHO)-K1 cells, they failed to be processed at the mutated processing signal, suggesting that the Arg-Ser-Lys-Arg motifs of preproendothelin-1 are recognized by CHO-K1 furin-like convertase. Co-transfection with ECE-1 cDNA revealed that cleavage at Arg52 is not essential for cleavage by ECE-1, but that cleavage at Arg92 is critical. Although a high-molecular-mass form of endothelin-1 is produced by processing by ECE-1 without cleavage at Arg52, it did not evoke Ca2+ transient in endothelinA-receptor-expressing cells. In conclusion, prior cleavage at Arg92 by furin-like convertase is absolutely necessary for cleavage by ECE-1 at Trp73 to produce mature endothelin-1.

Amino Acid Sequence↗

PubMed1996

Human endothelin converting enzyme gene (ECE1) mapped to chromosomal region 1p36.1.

The chromosomal localization of the human endothelin converting enzyme gene (ECE1) has been identified. Southern blot analysis of human genomic DNA from human x mouse somatic cell hybrids demonstrated that ECE1 maps to chromosome 1. Fluorescence in situ hybridization of a digoxigenin-labeled human ECE1 probe to normal human metaphase chromosomes showed that the gene is located within chromosome band 1p36.1.

Animals↗

PubMed1994

cDNA cloning and expression of bovine endothelin converting enzyme.

We have cloned cDNA encoding bovine endothelin converting enzyme (ECE). The predicted amino acid sequence of bovine ECE consisted of 758 amino acid residues. Northern blot analysis revealed that ECE mRNA was abundantly expressed in lung. Co-expression of the cloned cDNA of bovine ECE with human preproET-1 cDNA in CHO-K1 cells resulted in the production of mature ET-1 and this production was inhibited by phosphoramidon.

Amino Acid Sequence↗

PubMed1994

Mineralocorticoid type I receptor in the rat cochlea: mRNA identification by polymerase chain reaction (PCR) and in situ hybridization.

Expression of mineralocorticoid type I receptor (MR) gene in the rat cochlea was determined using molecular biological techniques. We synthesized complementary DNA (cDNA) from rat cochlear total RNA and then amplified MR cDNA fragments by polymerase chain reaction (PCR). The amplified cDNA fragments were subcloned into an expression vector and the nucleotide sequence was analyzed to confirm the expression of mRNA encoding MR in the cochlea. We then synthesized digoxigenin-labeled riboprobes with this cloned DNA template and examined the localization of MR mRNA in the cochlea by in situ hybridization. The amino acid sequence of MR cDNA expressed in the cochlea was identical to that of the MR first cloned in the rat hippocampus. In situ hybridization showed the expression of MR mRNA in marginal cells of the stria vascularis, suggesting that aldosterone may regulate microhomeostasis of the endolymph, presumably by modulating Na, K-ATPase activity. Intense MR signal was also identified in spiral ganglion cells, the function of which remains to be determined.

Aldosterone↗

PubMed1994

Absorption activity and barrier properties in the endolymphatic sac. Ultrastructural and morphometric analysis.

A constant volume of horseradish peroxidase (HRP) was injected directly into the endolymphatic sac (ES) lumen of the guinea pig to investigate the detailed absorption activity and the barrier properties of the ES. The reaction products were analyzed using an ultrastructural and morphometric method 1 to 10 h after the injection of this tracer. The epithelial cells in the proximal portion did not absorb the intraluminal HRP at any intervals after the tracer injection. The epithelial cells of the intermediate portion were classified clearly into two types according to their absorption activity: active-absorptive, and non-active cells. Uptake in the active-absorptive cells reached its maximal rate 8 h after the injection and then decreased. The active-absorptive cells in teh intermediate portion are considered to play a major role in the macromolecular absorption in the ES epithelium. The non-active cells scarcely absorbed the intraluminal HRP, suggesting that these cells are not involved in the macromolecular absorption. The absorption activity in the distal portion was lower than that in the active-absorptive cells in the intermediate portion 1 to 8 h after the HRP injection, while higher 10 h after the injection. Not only the intermediate portion but also the distal portion may play an active role in the macromolecular absorption. In no portion of the ES did intraluminal HRP penetrate beyond the junctional complexes between epithelial cells or through the cytoplasm. It is conceivable that there is a tight barrier to the intraluminal macromolecules in the epithelial linings of the ES.

Absorption↗

PubMed1993

Ultrastructure and barrier properties of the endolymphatic duct in the guinea pig.

The ultrastructure and barrier properties of the endolymphatic duct (ED) were examined by light and electron microscopy. ED epithelial cells were classified into two types: type I and type II duct cells. The type I duct cells were cuboidal or low columnar and were characterized by a convex apical surface and a few basal processes. The type II duct cells were squamous and were characterized by a flat apical and basal membrane, many small vesicles and a number of small pits along the basal membranes. After electrophoretic horseradish peroxidase (HRP) injection into the ED lumen, no HRP uptake into ED epithelial cells of either type was observed. There was no reaction product either in the lateral intercellular spaces beyond the tight junctions between ED epithelial cells or in ED subepithelial tissues. The ED epithelial cells were considered to play no active role in apical macromolecular absorption and to be impermeable to intraluminal macromolecules.

Absorption↗

PubMed1992

Absorption of horseradish peroxidase in the endolymphatic sac: ultrastructural cytochemistry using a new electrophoretic technique.

Using a newly developed injection technique, the absorption of horseradish peroxidase (HRP) in the endolymphatic sac (ES) of the guinea pig was examined by light and electron microscopy. HRP (molecular weight: 40,000; molecular diameter: about 5-nm) was directly injected into the lumen of the ES by electrophoresis after the recording of a direct current potential in the ES lumen. Both the macrophages floating in the ES lumen and the epithelial cells in the intermediate portion of the ES absorbed intraluminal HRP. The macrophages internalized the intraluminal HRP at a higher rate than the epithelial cells, suggesting that macrophages play a major role in macromolecular absorption in the ES. It was considered that the macrophages took up intraluminal HRP by phagocytosis, while the epithelial cells of the intermediate portion took it up by pinocytosis. In contrast, the epithelial cells in the proximal portion of the ES absorbed little HRP. No penetration through the junctional complexes between epithelial cells was observed in either the intermediate or the proximal portion at any interval after the injection of HRP. This finding indicates that these junctional complexes are impermeable to intraluminal HRP.

Absorption↗

PubMed1988

Entrapment neuropathy of the palmar cutaneous branch of the median nerve by the fascia of flexor digitorum superficialis.

A case of thenar numbness, with concomitant carpal tunnel syndrome is presented. Physical findings and the result of injection of a local anesthetic into two different sites of tenderness suggested coexistence of entrapment and/or compression of the palmar cutaneous branch of the median nerve and the main trunk of the median nerve at the carpal tunnel. At operation, constriction of the palmar cutaneous branch of the median nerve by the fascia of seemingly normal flexor digitorum superficialis was observed beneath the site of maximum tenderness. After decompression of this nerve, combined with carpal tunnel release, the patient lost all pain and numbness; there was no recurrence at 5 months follow-up.

Adult↗

PubMed1985

Elastic properties of bacterial flagellar filaments. II. Determination of the modulus of rigidity.

Elongation of a helical bacterial flagellar filament subjected to fluid flow was calculated on the assumption that one end of the filament is firmly attached to a substratum. It was found that the quantity [E(d/2 pi r)2 + 2 mu] could be determined by measuring the elongation at various flow rates, where E is Young's modulus, mu the modulus of rigidity, r the radius of the helix, and d the helical pitch. Experiments were carried out to determine the above quantity for Salmonella flagellar filaments assuming a close-coil form. Because the above quantity is almost equal to 2 mu for a helical form with a large radius/pitch ratio, we were able to determine the modulus of rigidity for this kind of flagellar filament from plots of elongation vs. flow rates. The modulus of rigidity was determined to be about 1 X 10(11) dyn/cm2, i.e., 2 orders of magnitude larger than the previously estimated value.

Bacteria↗

PubMed1985

On the rotational brownian motion of a bacterial idle motor. II. Theory of fluorescence correlation spectroscopy.

The photon flux autocorrelation function of a fluorescent label attached to a bacterial motor shaft is calculated for the case in which the bacterial motor is considered to be actively but idly rotating. It is shown that even when the fluorescent label has a very short lifetime, fluorescence correlation spectroscopy should provide a useful tool for determining the rate of revolution of the bacterial motor under various solution conditions.

Bacterial Physiological Phenomena↗

PubMed1985