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Biomedical subjects

K Yamauchi

Publications and source records attributed to K Yamauchi.

At least 55 records · Page 3Linked to original sources
PubMed2002

Susceptibility of Helicobacter pylori and its urease activity to the peroxidase-hydrogen peroxide-thiocyanate antimicrobial system.

The susceptibility of Helicobacter pylori to the antimicrobial system involving lactoperoxidase, hydrogen peroxide and thiocyanate was investigated. The inhibitory effect of the system on the urease activity of H. pylori, which plays a role in its colonisation of the stomach, was also investigated. Twelve H. pylori strains examined, including 10 clinical isolates, were all inhibited by the peroxidase system in brain-heart infusion broth supplemented with fetal calf serum, but to different extents. The killing effect was observed within 3 h. Although bacterial viability recovered afterwards, there was still a clear difference between cultures incubated in the presence of the complete system and control cultures incubated in the absence of lactoperoxidase, after incubation for 24 h. The urease activity and viability of H. pylori were both inactivated by this system in phosphate buffer. These effects were dependent on the concentrations of both lactoperoxidase and hydrogen peroxide and were abolished by the addition of cysteine. Furthermore, these effects were observed when bovine lactoperoxidase was replaced by recombinant human lactoperoxidase or native or recombinant human myeloperoxidase. The peroxidase system found in saliva and milk may contribute to the host defence against H. pylori infection and inhibition of transmission via the oral route.

Animals↗
PubMed2002

Bovine lactoferrin and lactoferricin derived from milk: production and applications.

Bovine lactoferrin is produced on an industrial scale from cheese whey or skim milk. The safety of purified lactoferrin has been confirmed from the results of a reverse mutation test using bacteria, a 13-week oral repeated-dose toxicity study in rats, and clinical studies. In order to apply active lactoferrin to various products, a process for its pasteurization was developed. Subsequently, lactoferrin has been used in a wide variety of products since it was first added to infant formula in 1986. A pepsin hydrolysate of lactoferrin is also used in infant formula. This hydrolysate contains a potent antimicrobial peptide named lactoferricin that is derived from the lactoferrin molecule by pepsin digestion. Semilarge-scale purification of lactoferricin can be performed by hydrophobic interaction chromatography. Lactoferricin also exhibits several biological actions and appears to be the functional domain of lactoferrin. Recent studies have demonstrated that oral administration of lactoferrin or lactoferricin exerts a host-protective effect in various animals and in humans. The results of these studies strongly suggest that the effects of oral lactoferrin are mediated by modulation of the immune system. Further elucidation of the clinical efficacy and mechanism of action of lactoferrin will increase the value of lactoferrin-containing products.

Animals↗
PubMed2002

A countermeasure to ameliorate immune dysfunction in in vitro simulated microgravity environment: role of cellularnucleotide nutrition.

Considerable evidence suggests that space travelers are immunosuppressed, presumably by microgravity environmental stresses, putting them at risk for adverse effects, such as opportunistic infections, poor wound healing, and cancer. The purpose of this study was to examine the role and mechanisms of nucleotide (NT) supplementation as a countermeasure to obviate immunosuppression during space travel. The in vitro rotary cell culture system, a bioreactor (BIO), was used to simulate the effect of microgravity and to isolate the neuroendocrine effects inherent to in vitro models. The splenocytes from normal mice were cultured in BIO and control tissue culture (TC) flasks with and without phytohemagglutinin (PHA) for mitogen assays. The culture medium was then supplemented with various concentrations of a nucleosides-nucleotides mixture (NS + NT), inosine, and uridine. Cytokines interleukin (IL)-1beta, IL-2, IL-3, tumor necrosis factor-alpha, and interferon (IFN)-gamma were measured from the supernatant by enzyme-linked immunosorbent assay. In the PHA-stimulated cultures the cellular proliferation in the BIO was significantly decreased as compared with the TC flask cells. BIO-cultured cells in the presence of NS + NT maintained mitogen responses similar to the control TC flask cells. The maintenance of the mitogen response in BIO was observed by the supplementation of uridine and not of inosine. These results are in agreement with our earlier results from unit gravity experiments that showed that pyrimidines are more effective in pleiogenic immunoprotection to hosts. Cytokines IL-1beta, IL-2, and IFN-gamma in the BIO supernatants of cells cultured in the presence of NS + NT had a significantly higher response than the control vessel. Thus, supplemental NT, especially pyrimidines, can confer immune protection and enhance cytokine responses during space travel.

Animals↗
PubMed2002

Time-dependent potentiation of the beta-cell is a Ca2+-independent phenomenon.

When isolated rat pancreatic islets are treated with 16.7 mM glucose, a time-dependent potentiation (TDP) of insulin release occurs that can be detected by subsequent treatment with 50 mM KCl. It has been thought that TDP by glucose is a Ca2+-dependent phenomenon and only occurs when exposure to glucose is carried out in the presence of Ca2+. In contrast to this, we now demonstrate TDP under stringent Ca2+-free conditions (Ca2+-free buffer containing 1 mM EGTA). In fact, under these Ca2+-free conditions glucose caused an even stronger TDP than in the presence of Ca2+. TDP induced by glucose in the absence of extracellular Ca2+ was unaffected by inhibitors of protein kinase C (PKC). However, cerulenin or tunicamycin, two inhibitors of protein acylation, eradicated TDP without affecting glucose metabolism. The TDP by glucose was not associated with an increase in the cytosolic free Ca2+ concentration ([Ca2+]i) during subsequent treatment with high K+. Exposure of islets to forskolin under Ca(2+)-free conditions did not cause TDP despite a large increase in the cellular cAMP levels. In conclusion, glucose alone induces TDP under stringent Ca2+-free conditions when [Ca2+]i was significantly lowered. Protein acylation is implicated in the underlying mechanism of TDP.

Acylation↗
PubMed2002

Association of beta-fibrinogen and factor VII polymorphism with plasma fibrinogen and factor VII levels, and no association of PAI-1 polymorphism with plasma PAI-1 levels in hemodialysis patients.

AIMS: Recent studies have stressed the roles of genetic factors on the plasma levels of hemostatic markers and on cardiovascular complications. We investigated the association of DNA polymorphisms for beta-fibrinogen, factor VII, and PAI-1 with plasma levels of these factors and with ischemic heart disease (IHD) and cerebral infarction (CI) in patients undergoing hemodialysis (HD). METHODS: beta-fibrinogen G/A-455, factor VII R353Q and PAI-1 4G/5G polymorphisms were determined by PCR-RFLP in 149 HD patients and in 100 controls. The plasma levels of fibrinogen, factor VII and PAI-1 were also measured. RESULTS: The allele frequencies and the genotype frequencies of these 3 polymorphisms were not different between HD patients and controls. In HD patients, plasma fibrinogen levels were significantly lower in the GG genotype than in the GA genotype, and plasma factor VII activity was significantly higher in the RR genotype than in the RQ genotype. Multiple regression analysis disclosed that CRP and beta-fibrinogen polymorphism were the significant determinants of fibrinogen levels. Plasma PAI-1 levels were not different among the 3 genotypes. The frequency of the A-455 allele was significantly higher in HD patients with CI than in those without CI, and the genotype distribution for beta-fibrinogen differed significantly between the 2 groups. Between the same 2 groups, however, significant differences were found neither in the frequency of the 353Q or 4G allele nor in the genotype distribution for factor VII and PAI-1. No significant differences in the frequency of the G-455, 353Q or 4G alleles, or in the genotype distribution for beta-fibrinogen, factor VII and PAI-1 were observed between patients with IHD and those without IHD. Multiple logistic regression analysis demonstrated that neither polymorphism was associated with CI or IHD. CONCLUSIONS: In HD patients, beta-fibrinogen and factor VII polymorphisms affected plasma levels of fibrinogen and factor VII, respectively. Beta-fibrinogen polymorphism was not an independent but a possible risk factor for CI in HD patients. Further study will be needed to confirm the precise role of 5-fibrinogen polymorphisms in the pathogenesis of CI in HD patients.

Adult↗
PubMed2001

Organization and expression of the Paramecium caudatum gene encoding nucleosome assembly protein 1.

The complete genomic and partial complementary DNAs encoding the ciliate Paramecium caudatum nucleosome assembly protein 1 (NAP1) have been sequenced. The nap1 gene is situated 1.2 kbp from the hemoglobin (hb) gene, with the 3' end of both genes facing each other. The nap1 gene contains no introns, and encodes a protein of 369 amino acid residues with a calculated molecular weight of 42,627. The P. caudatum NAP1 amino acid sequence shares only 23-27% identity with NAP1 amino acid sequences from other eukaryotes. Although the nap1 transcript was detected in the P. caudatum cells at both the logarithmic and stationary phases, its level increased during the stationary phase. Southern blot analysis and polymerase chain reaction amplification revealed that the P. caudatum macronucleus has a heterogeneous composition at genomic regions around the nap1 gene. The present studies indicate the nap1 and hb genes are closely arranged in the macronucleus with the intergenic region between their sequences heterogeneously composed.

Amino Acid Sequence↗
PubMed2001

Alamethicin-leucine zipper hybrid peptide: a prototype for the design of artificial receptors and ion channels.

In this report, we describe a novel concept of extramembrane control of channel peptide assembly and the eventual channel current modulation. Alamethicin is a peptide antibiotic, which usually forms ion channels in various association states. By introducing an extramembrane leucine zipper segment (Alm-LeuZ), the association number of alamethicin was effectively controlled to produce a single predominant channel open state. The assembly was estimated to be a tetramer, by comparison of the channel conductance with that of the template-assembled Alm-LeuZ tetramer, which was prepared by the conjugation of a maleimide-functionalized peptide template with cysteine-derivatized Alm-LeuZ segments. Employment of an extramembrane segment of a random conformation provided higher levels of channel conductance. The result exemplified the possibility of channel current control by a conformational switch of the extramembrane segments.

Alamethicin↗
PubMed2001

Crystallization and preliminary X-ray analysis of neural haemoglobin from the nemertean worm Cerebratulus lacteus.

The nemertean worm Cerebratulus lacteus neural tissue haemoglobin (109 amino acids, the shortest known haemoglobin) has been overexpressed in Escherichia coli, purified and crystallized. A highly redundant native data set has been collected at the Cu K(alpha) wavelength to 2.05 A resolution. The crystals belong to the orthorhombic P2(1)2(1)2(1) space group, with unit-cell parameters a = 42.5, b = 43.1, c = 60.2 A and one molecule per asymmetric unit. The anomalous difference Patterson map clearly reveals the position of the haem Fe atom, thus paving the way for MAD/SAD structure determination.

Animals↗
PubMed2001

Size-related and size-unrelated functional heterogeneity among pancreatic islets.

Functional heterogeneity of pancreatic islets was systematically analyzed for the first time using freshly isolated single rat pancreatic islets. First, 60 islets were sequentially exposed to 3, 9.4, 15.6, and 24.1 mM glucose for 30 min each in incubation experiments: 36 (60%) responded in a concentration-dependent and 19 (32%) in an all-or-none manner, and 5 (8%) islets did not respond to high glucose. As a group, the larger the islet, the higher the beta cell glucose sensitivity. However, glucose-stimulated elevation of [Ca2+]i in the beta cell. insulin/glucagon ratio in the islet, and expression of glucose transporter 2, glucokinase, and pancreatic duodenal homeobox factor-1 in the beta cell were not significantly related to islet size. Second, 50 islets were stimulated with 16.7 mM glucose in perifusion. A biphasic insulin release was found in 39 (78%), and no or little first phase response in 11 (22%) islets, irrespective of the islet size. Nevertheless, when the response was plotted as a group, it was clearly biphasic. Islet size, insulin content and the amount of insulin release were positively correlated with each other. In conclusion, there are size-related and size-unrelated functional diversity among pancreatic islets. The reason for such heterogeneity remained to be determined.

Animals↗
PubMed2001

Association of AIM, a novel apoptosis inhibitory factor, with hepatitis via supporting macrophage survival and enhancing phagocytotic function of macrophages.

A hallmark of many inflammatory diseases is the destruction of tissue cells by infiltrating hematopoietic cells including lymphocytes, neutrophils, and macrophages. The regulation of apoptosis of both target tissue cells and the infiltrating cells is one of the key events that defines the initiation and the progression of inflammation. However, the precise picture of the apoptosis regulation of the cells at the inflammatory sites is still unclear. We recently isolated a novel apoptosis inhibitory factor, termed AIM, which is secreted exclusively by tissue macrophages. In this report, we present unique characteristics of AIM associated with liver inflammation (hepatitis), identified by introducing an experimental hepatitis in both AIM-transgenic mice, which overexpress AIM in the body, and normal mice. First, endogenous AIM expression in macrophages is rapidly increased in response to inflammatory stimuli. Second, AIM appears to inhibit the death of macrophages in the inflammatory regions, judging by the remarkably increased number of macrophages observed in the liver from transgenic mice. In addition, we show that AIM also enhances the phagocytosis by macrophages, which emphasizes the multifunctional character of AIM. All these findings strongly provoke an idea that AIM may play an important role in hepatitis pathogenesis in a sequential manner; first AIM expression is up-regulated by inflammatory stimuli, and then in an autocrine fashion, AIM supports the survival of infiltrating macrophages as well as enhances phagocytosis by macrophages, which may result in an efficient clearance of dead cells and infectious or toxic reagents.

Animals↗
PubMed2001

Thiolated dermal bovine collagen as a novel support for bioactive substances--conjugation with lysozyme.

Thiol groups were introduced to dermal bovine collagen (DBC) by the reaction with gamma-thiobutyrolactone. Thiolated DBC reacted with 2-pyridyl disulfide group introduced to lysozyme to form DBC-lysozyme conjugate through disulfide bridge. The enzymatic activity of freshly prepared conjugate was almost unchanged during ten consecutive runs over one month. The DBC-lysozyme conjugate showed the maximum activity at pH 6.3, on the contrary, that of native lysozyme was pH 9.0. Thermal stability of lysozyme was enhanced by the conjugation with DBC. The present results showed that the conjugation using thiolated collagen could be one of the useful alternative approaches to modify collagen with bioactive molecules.

Animals↗
PubMed2001

Identification of novel hypocholesterolemic peptides derived from bovine milk beta-lactoglobulin.

This study was designed to clarify the mechanisms of hypocholesterolemic action of beta-lactoglobuline tryptic hydrolysate (LTH) and to identify the novel hypocholesterolemic peptide derived from LTH by screening using Caco-2 cells and animal studies. Serum and liver cholesterol levels were significantly lower in rats fed LTH than in those fed casein tryptic hydrolysate (CTH). The present study suggests that the inhibition of micellar solubility of cholesterol which causes the suppression of cholesterol absorption by a direct interaction between cholesterol mixed micelles, and LTH in the jejunal epithelia is part of the mechanism underlying the hypocholesterolemic action of LTH. Though no one could trace the hypocholesterolemic peptide to any protein origin, we identified, for the first time, a novel hypocholesterolemic peptide, Ile-Ile-Ala-Glu-Lys (IIAEK). Surprisingly, the present study provides the first direct evidence that a new hypocholesterolemic peptide derived from beta-lactoglobuline can powerfully influence serum cholesterol levels and exhibit a greater hypocholesterolemic activity in comparison with that of medicine, beta-sitosterol, in animal studies.

Administration, Oral↗
PubMed2001

Characterization of Xenopus cytosolic thyroid-hormone-binding protein (xCTBP) with aldehyde dehydrogenase activity.

Multiple cytosolic thyroid-hormone-binding proteins (CTBPs) with varying characteristics, depending on the species and tissue, have been reported. We first purified a 59-kDa CTBP from Xenopus liver (xCTBP), and found that it is responsible for major [125I]T(3)-binding activity in Xenopus liver cytosol. Amino acid sequencing of internal peptide fragments derived from xCTBP demonstrated high identity to the corresponding sequence of mammalian aldehyde dehydrogenases 1 (ALDH1). To confirm whether or not xCTBP is identical to xALDH1, we isolated cDNAs encoding xALDH1 from an adult Xenopus hepatic cDNA library. The amino acid sequences deduced from the two isolated xALDH1 cDNAs were very similar to those of mammalian ALDH1 enzymes. The recombinant xALDH1 protein exhibited both T(3)-binding activity and ALDH activity converting retinal to retinoic acid (RA), which were similar to those of xCTBP purified from liver cytosol. The T(3)-binding activity was inhibited by NAD, while the ALDH activity was inhibited by thyroid hormones. Our results demonstrate that xCTBP is identical to ALDH1 and suggest that this protein might modulate RA synthesis and intracellular concentration of free T(3). Communications between thyroid hormone and retinoid pathways are discussed.

Aldehyde Dehydrogenase↗
PubMed2001

20beta-Hydroxysteroid dehydrogenase of the Japanese eel ovary: its cellular localization and changes in the enzymatic activity during sexual maturation.

In many species of teleost, 20beta-hydroxysteroid dehydrogenase (20beta-HSD) is a key steroidogenic enzyme in the production of the oocyte maturation-inducing steroid (MIS), 17alpha, 20beta-dihydroxy-4-pregnen-3-one. In this study, 20beta-HSD in the ovary of the Japanese eel was biochemically characterized using a cell-free system. 20beta-HSD activity was located mainly in the membrane-bound fractions of the mitochondria and microsome, with lower levels detected in the cytosolic fraction. The enzymatic activity of membrane-bound 20beta-HSD was strikingly enhanced by treatment of eels with gonadotropin-rich salmon pituitary homogenate. The activity of eel ovarian mitochondrial 20beta-HSD in the presence of different solubilizing detergents was then assessed. Mitochondrial fractions solubilized by sodium deoxycholate and octhylthioglucoside retained approximately 30% of 20beta-HSD activity when compared to those of nontreated mitochondria. These results suggest that Japanese eel ovarian 20beta-HSD is composed of membrane-bound and soluble activities, and that the membrane-bound component is stimulated by gonadotropin.

Animals↗
PubMed2001

Evaluation of a multicomponent workplace health promotion program conducted in Japan for improving employees' cardiovascular disease risk factors.

BACKGROUND: The long-term effectiveness of multicomponent worksite health promotion programs targeting cardiovascular disease risk factors remains unclear in Japan. This study was conducted to evaluate the effectiveness of such a health promotion program consisting of a main program provided over 4 days and a follow-up program provided over 1 year. METHODS: The subjects of this randomized controlled trial were male employees working for a building maintenance company in Japan. The intervention group (n = 152) and the control group (n = 150) consisted of employees having abnormal findings in at least one of the following items at baseline health examination: body mass index (BMI), systolic (SBP) or diastolic blood pressure, total cholesterol, HDL cholesterol, triglycerides, and fasting blood glucose. Evaluation was conducted at 18 months after the main program. RESULTS: BMI, SBP, total cholesterol, and triglycerides improved significantly in the intervention group compared with the control group (P < 0.05). When comparisons were limited to those who showed abnormality at baseline, BMI, total cholesterol, and triglycerides improved significantly in the intervention group (P < 0.05). CONCLUSIONS: The multicomponent health promotion program provided to employees was shown to be effective in improving obesity, high blood pressure, and hyperlipidemia when evaluated 18 months after the main intervention program.

Adult↗
PubMed2001

Application of a drug delivery system in a novel rat model of chronic hyperendotoxemia.

There has not been an ideal reproducible small-animal model of chronic hyperendotoxemia to date. Our drug delivery system (DDS) is a new technology that can deliver a drug conveniently to a target organ at an optional rate. 2-Hydroxyethyl methacrylate (HEMA) was used as a carrier of lipopolysaccharide (LPS), and diethylene glycol and polyethylene glycol dimethacrylates (2G, 4G, 9G) were used as cross-linking agents. A mixed solution of HEMA and di(poly)ethylene glycol dimethacrylate was charged into a glass tube with or without LPS and polymerized by ultraviolet irradiation. This polymer was cut into DDS tablets of the same size with or without LPS. A mixture with HEMA:4G = 1:3 was the most suitable composition to release a constant concentration of LPS. We also developed a novel rat model of chronic hyperendotoxemia. Four DDS tablets, each containing 15 mg LPS, were implanted into the abdominal cavity of rats in the LPS group. The control group was implanted with four DDS tablets without LPS. Plasma levels of LPS in the study group were maintained at more than 2,000 pg/ml for 72 h after implantation. Weight gain was lower and body temperature was higher in the LPS group than in the control group. Plasma levels of inter leukin (IL)-6 in the LPS group were higher than in the control group only during the initial 12 h after implantation of DDS tablets. The white blood cell count at 24 h and platelet counts at 24, 48, and 72 h in the LPS group were lower than those in the control group. These results indicate that chronic hyperendotoxemia was maintained for 72 h by continuous release of LPS from the DDS. Moreover, the intensity of endotoxemia could be varied by varying the number of DDS tablets. It is concluded that our new rat model using LPS-DDS will be applicable and useful as a model of chronic hyperendotoxemia.

Animals↗
PubMed2001

Water drinking causes a biphasic change in blood composition in humans.

To investigate precisely the fluid shifts associated with water drinking in humans, we measured continuously blood density and plasma electrolyte concentrations using the mechanical oscillator technique and ion-selective electrodes, respectively, in healthy young volunteers before (10 min) and after (48 min) water drinking for a period of 2 min. Beat-by-beat blood pressure was also monitored throughout the experiment. Drinking 1 l tap water caused a transient increase in blood density immediately after the drinking episode (from 1051.1+/-0.5 g/l before drinking to 1051.8+/-0.5 g/l 4 min after the start of drinking, P<0.05), followed by a gradual reduction (1050.1+/-0.5 g/l at 31 min). This drinking-induced change paralleled those of haematocrit, plasma density and plasma volume. Plasma [Na+] and [Cl-] and osmolality decreased after drinking without transient increases and reached minima at about 30 min. A transient increase in mean arterial blood pressure was observed prior to the increase in blood density. These findings suggest that water drinking causes a biphasic change in plasma volume: initial haemoconcentration, probably due to sympathetic acceleration, followed by haemodilution due to the post-absorptive effect, and further suggest that the fluid shift associated with the initial haemoconcentration is isosmotic.

Adult↗