Search PubMed⌕ Search

Biomedical subjects

K Aoyama

Publications and source records attributed to K Aoyama.

At least 37 records · Page 2Linked to original sources
PubMed2001

Chemical structure and biological activity of a lipid A component from Helicobacter pylori strain 206.

The chemical structure of a lipid A, which was obtained as a minor component from lipopolysaccharide of Helicobacter pylori strain 206-1, was determined to be a glucosamine beta-(1 -6) disaccharide 1-(2-aminoethyl)phosphate acylated by (R)-3-hydroxyoctadecanoic acid, (R)-3- hydroxyhexadecanoic acid, and (R)-3-(octadecanoyloxy)octadecanoic acid at the 2-, 3- and 2'-positions, respectively. Compared with the other major lipid A from the same strain, which was previously reported [Suda Y, Ogawa T, Kashihara W et al. Chemical structure of lipid A from Helicobacter pylori strain 206-1 lipopolysaccharide. J Biochem 1997; 121: 1129--1133], the structure was very similar with one exception. An (R)-3-hydroxyhexadecanoic acid was present at the 3-position of the novel lipid A component. The structure is apparently identical to one of the proposals by Moran et al. [Moran AP, Lindner B, Walsh EJ. Structural characterization of the lipid A component of Helicobacter pylori rough- and smooth-form lipopolysaccharides. J Bacteriol 1997; 179: 6453--6463], who concluded the same structure as the so-called major lipid A from the H. pylori strain NCTC 11637 but without isolating a homogeneous component. The endotoxic properties and pro-inflammatory cytokine-inducing activities of this novel tetra-acyl type lipid A were lower than those of previously reported major tri-acyl type lipid A.

Animals↗
PubMed2000

Cytokine-inducing macromolecular glycolipids from Enterococcus hirae: improved method for separation and analysis of its effects on cellular activation.

Previously, we showed that several minor macromolecular glycolipids accounting for less than 5% of the lipoteichoic acid (LTA) fraction from Enterococcus hirae ATCC 9790 possess cytokine-inducing activity, whereas the purified LTA does not. In other words, the immunobiological activity of the LTA fraction reported in the 1980s was not attributable to LTA itself, but to other glycolipids coexisting in the fraction. In the present study, we improved the procedure of separation of the active glycolipids and evaluated their effects on cellular activation. The immunobiologically active glycolipids were separated from the crude glycolipid fraction obtained by hot phenol-water extraction of the cells. The total yield of active glycolipids was about fivefold higher than that separated by the previous method. Interleukin-6-inducing activities of the active glycolipids from 1,25-dihydroxy vitamin D(3)-differentiated human monocytic leukemia cells, THP-1, were inhibited by anti-CD14 mAbs in a dose-dependent manner. Macrophages from Toll-like receptor (TLR)-2-deficient or -4-deficient mice completely lacked the ability to produce tumor necrosis factor-alpha on stimulation with active glycolipids. These observations indicated that the cellular activation by the active glycolipids from E. hirae is mediated by CD14 and by both TLR2 and TLR4.

Animals↗
PubMed2000

N-methylation ability for azaheterocyclic amines is higher in Parkinson's disease: nicotinamide loading test.

The discovery of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) leads to the hypothesis that Parkinson's disease (PD) is may be initiated or precipitated by endogenous toxins by the mechanism similar to that of MPTP in genetically-predisposed individuals. The higher cerebrospinal fluid levels of N-methylated azaheterocyclic amines, such as beta-carboline and tetrahydroisoquinoline, have been found in parkinsonian patients compared with age-matched controls. To estimate the N-methylation ability for azaheterocyclic amines in parkinsonian patient, nicotinamide was dosed with 100 mg to 26 parkinsonians and 20 controls consisted of 16 other neurogenic disease patients and 4 healthy volunteers. The urine was collected for 4 h, and then analyzed urinary its metabolites by an improved HPLC method. Nicotinamide has a pyridine ring in its structure and may be metabolized through the pathways similar to those for the endogenous neurotoxins. The urinary excretions of nicotinamide metabolites were significantly affected by aging. The excretion of N1-methylnicotinamide decreased along with aging both in PD patients and controls. In younger (65 years old or younger) PD patients, the excretion amount of N1-methylnicotinamide was significantly higher than that in younger controls. The decline rate of N1-methylnicotinamide excretion in parkinsonians was significantly greater than that in controls; the rate is more than 2-fold higher in parkinsonian patients. The age-associated decrease in 1-methyl-2-pyridone-5-carboxyamide excretion was observed only in parkinsonian patients, but not in controls. The total excreted amount of N-methylated metabolites (N1-methylnicotinamide plus 1-methyl-2-pyridone-5-carboxyamide) was also observed the age-related decline in both groups. The urinary excretions of nicotinamide and nicotinamide-N-oxide were not influenced by aging. These results would indicate that the excess N-methylation ability for azaheterocyclic amines before the onset had been implicated in PD. On the other hand, the present results suggested that the contribution of aberrant cytochrome P450 or aldehyde oxidase activity acting on the pyridine ring, that could act as detoxification routes of endogenous neurotoxins, would be small in the etiology of PD.

Aged↗
PubMed2000

Limitin: An interferon-like cytokine that preferentially influences B-lymphocyte precursors.

We have identified an interferon-like cytokine, limitin, on the basis of its ability to arrest the growth of or kill lympho-hematopoietic cells. Limitin strongly inhibited B lymphopoiesis in vitro and in vivo but had little influence on either myelopoiesis or erythropoiesis. Because limitin uses the interferon alpha/beta receptors and induces interferon regulatory factor-1, it may represent a previously unknown type I interferon prototype. However, preferential B-lineage growth inhibition and activation of Janus kinase 2 in a myelomonocytic leukemia line have not been described for previously known interferons.

Amino Acid Sequence↗
PubMed2000

A new method of predicting pulmonary capillary wedge pressure: the arterial pressure ratio.

The response of arterial blood pressure to an increase in intrathoracic pressure has been shown to be predictive of pulmonary capillary wedge pressure. We devised a new method, which we termed the arterial pressure ratio. We defined arterial pressure ratio as the ratio of systolic blood pressure of the final beat during the strain phase of the Valsalva manoeuvre to that during apnoea before the manoeuvre, and tested the accuracy of arterial pressure ratio in predicting pulmonary capillary wedge pressure. In 30 patients scheduled for elective abdominal aortic reconstruction, following induction of general anaesthesia and tracheal intubation, a 20-G catheter and pulmonary artery catheter were inserted through the radial artery and right internal jugular vein, respectively. Pulmonary capillary wedge pressure was then measured during a brief period of apnoea and the Valsalva manoeuvre was performed by application of pressure to the reservoir bag. Airway pressure was maintained at 30 cmH2O for 10 s and then released. Radial arterial pressure and airway pressure were recorded simultaneously, and arterial pressure ratio was calculated. There was a close linear correlation between arterial pressure ratio and pulmonary capillary wedge pressure (r = 0.88, p < 0.0001).

Aged↗
PubMed2000

Spy1, a histidine-containing phosphotransfer signaling protein, regulates the fission yeast cell cycle through the Mcs4 response regulator.

Common histidine-to-aspartate (His-to-Asp) phosphorelay signaling systems involve three types of signaling components: a sensor His kinase, a response regulator, and a histidine-containing phosphotransfer (HPt) protein. In the fission yeast Schizosaccharomyces pombe, two response regulators, Mcs4 and Prr1, have been identified recently, and it was shown that they are involved in the signal transduction implicated in stress responses. Furthermore, Mcs4 appears to be involved in mitotic cell-cycle control. However, neither the HPt phosphotransmitter nor His kinase has been characterized in S. pombe. In this study, we identified a gene encoding an HPt phosphotransmitter, named Spy1 (S. pombe YPD1-like protein). The spy1(+) gene showed an ability to complement a mutational lesion of the Saccharomyces cerevisiae YPD1 gene, which is involved in an osmosensing signal transduction. The result from yeast two-hybrid analysis indicated that Spy1 interacts with Mcs4. To gain insight into the function of Spy1, a series of genetic analyses were conducted. The results provided evidence that Spy1, together with Mcs4, plays a role in regulation of the G(2)/M cell cycle progression. Spy1-deficient cells appear to be precocious in the entry to M phase. In the proposed model, Spy1 modulates Mcs4 in a negative manner, presumably through a direct His-to-Asp phosphorelay, operating upstream of the Sty1 mitogen-activated protein kinase cascade.

Amino Acid Sequence↗
PubMed2000

Identification and characterization of a novel gene, hos3+, the function of which is necessary for growth under high osmotic stress in fission yeast.

hos3 mutants of the fission yeast Schizosaccharomyces pombe showed the phenotype of high osmolarity sensitivity for growth. An S. pombe strain carrying the hos3-M26 allele cannot form colonies on agar plates containing 2 M glucose, but the parental strain can do so very well, as demonstrated previously. The hos3+ gene was cloned and identified as one that encodes a small protein of 94 amino acids, which shows no sequence similarity to any other proteins in the current databases. A hos3delta strain, which we then constructed, had the phenotype of high osmolarity sensitivity, as in the case of the original hos3-M26 mutant. More interestingly, when these hos- cells were grown in the non-permissive growth condition in the presence of 2 M glucose, we found that unusually many septated cells were accumulated after a prolonged incubation. A multicopy suppressor gene for hos- mutations was also isolated and identified as the dsk1+ gene encoding a protein kinase, which was previously suggested to be implicated in a process of the mitotic regulation of S. pombe. The function of the hos3+ gene is discussed from these results.

Cloning, Molecular↗
PubMed2000

Stromal cell CD9 and the differentiation of hematopoietic stem/progenitor cells.

CD9 belongs to the tetraspan family of proteins that facilitates the regulation of cell proliferation, motility, and adhesion. In mouse hematopoietic organs, CD9 is expressed by myeloid and stromal cells. Although the precise mechanisms are not clear, antibody ligation of CD9 on stromal cells regulates the adhesion between stromal cells and hematopoietic stem cells, the production of myeloid cells in long term bone marrow cultures and the differentiation of hematopoietic stem cells. A 100 kD protein co-precipitated with CD9 is distinct from several previously reported CD9-associated molecules with respect to size and distribution. Identification and analysis of this interesting protein may clarify the molecular mechanisms through which CD9 bearing stromal cells control the differentiation of hematopoietic stem cells and/or allow them to maintain their vital self-renewal capacity.

Animals↗
PubMed2000

Nitration of manganese superoxide dismutase in cerebrospinal fluids is a marker for peroxynitrite-mediated oxidative stress in neurodegenerative diseases.

Peroxynitrite can nitrate tyrosine residues of proteins. We examined nitrotyrosine-containing proteins in cerebrospinal fluid of 66 patients with neurogenic disease by immunoblot analysis. Nitrated tyrosine residue-containing protein was observed in the cerebrospinal fluid and was concluded to be manganese superoxide dismutase (Mn-SOD). The nitrated Mn-SOD level was strikingly elevated in amyotrophic lateral sclerosis patients and was slightly increased in Alzheimer's and Parkinson's disease patients, whereas an elevated Mn-SOD level was observed only in progressive supranuclear palsy group.

Adult↗