Biomedical subjects

H Chiba

Publications and source records attributed to H Chiba.

At least 19 recordsLinked to original sources

PubMed2000

Importance of the carboxy-terminal 25 amino acid residues of lung collectins in interactions with lipids and alveolar type II cells.

Surfactant proteins A and D (SP-A and SP-D) are structurally related members of the collectin family found in the alveolar compartment of the lung. SP-A binds dipalmitoylphosphatidylcholine (DPPC) and galactosylceramide (GalCer), induces liposome aggregation, and regulates the uptake and secretion of surfactant lipids by alveolar type II cells in vitro. SP-D binds phosphatidylinositol (PI) and glucosylceramide. The purpose of this study was to identify a critical stretch of primary sequence in the SP-A region Cys(204)-Phe(228) and the SP-D region Cys(331)-Phe(355) that is involved in protein-specific lipid and type II cell interactions. Chimeras ad1 and ad2 were constructed with rat SP-A/SP-D splice junctions at Cys(218)/Gly(346) and Lys(203)/Cys(331), respectively. Chimera ad1 but not ad2 retained DPPC liposome binding activity. Both chimeras retained significant binding to GalCer liposomes. Chimera ad1 did not bind to PI, whereas chimera ad2 acquired a significant PI binding. Both chimeras failed to induce liposome aggregation and to interact with alveolar type II cells. In addition, monoclonal antibody 1D6 that blocks specific SP-A functions did not recognize either chimera. From these results, we conclude that (1) the SP-A region Leu(219)-Phe(228) is required for liposome aggregation and interaction with alveolar type II cells, (2) the SP-A region Cys(204)-Cys(218) is required for DPPC binding, (3) the SP-D region Cys(331)-Phe(355) is essential for minimal PI binding, and (4) the epitope for mAb 1D6 is located at the region contiguous to the SP-A region Leu(219)-Phe(228).

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1999

Induction of tight junctions in human connexin 32 (hCx32)-transfected mouse hepatocytes: connexin 32 interacts with occludin.

Small gap junction plaques are associated with tight junction strands in some cell types including hepatocytes and it is thought that they may be closely related to tight junctions and the establishment of cell polarity. In order to examine roles of gap junctions in regulating expression and structure of tight junctions, we transfected human Cx32 cDNA into immortalized mouse hepatocytes (CHST8 cells) which lack endogenous Cx32 and Cx26. Immunocytochemistry revealed that endogenous integral tight junction protein occludin was strongly localized and was colocalized with Cx32 at cell borders in transfectants, whereas neither was detected in parental cells. In Northern blots, mRNAs encoding occludin and the other integral tight junction proteins, claudin-1 and -2, were induced in the transfectants compared to parental cells. In Western blots, occludin protein was increased in the transfectants compared to parental cells, and binding of occludin to Cx32 protein was demonstrated by immunoprecipitation. In freeze fracture of the transfectants, tight junction strands were more numerous and complex compared to parental cells, and small gap junction plaques appeared within induced tight junction strands. Nevertheless, no change in barrier function of tight junctions was observed. These results indicate that in hepatocytes, gap junction, and tight junction expression are closely coordinated, and that Cx32 may play a role in regulating occludin expression.

Animals↗

PubMed1999

IkappaB kinases phosphorylate NF-kappaB p65 subunit on serine 536 in the transactivation domain.

Recent investigations have elucidated the cytokine-induced NF-kappaB activation pathway. IkappaB kinase (IKK) phosphorylates inhibitors of NF-kappaB (IkappaBs). The phosphorylation targets them for rapid degradation through a ubiquitin-proteasome pathway, allowing the nuclear translocation of NF-kappaB. We have examined the possibility that IKK can phosphorylate the p65 NF-kappaB subunit as well as IkappaB in the cytokine-induced NF-kappaB activation. In the cytoplasm of HeLa cells, the p65 subunit was rapidly phosphorylated in response to TNF-alpha in a time dependent manner similar to IkappaB phosphorylation. In vitro phosphorylation with GST-fused p65 showed that a p65 phosphorylating activity was present in the cytoplasmic fraction and the target residue was Ser-536 in the carboxyl-terminal transactivation domain. The endogenous IKK complex, overexpressed IKKs, and recombinant IKKbeta efficiently phosphorylated the same Ser residue of p65 in vitro. The major phosphorylation site in vivo was also Ser-536. Furthermore, activation of IKKs by NF-kappaB-inducing kinase induced phosphorylation of p65 in vivo. Our finding, together with previous observations, suggests dual roles for IKK complex in the regulation of NF-kappaB.IkappaB complex.

Amino Acid Sequence↗

PubMed1999

Glial cell line-derived neurotrophic factor induces barrier function of endothelial cells forming the blood-brain barrier.

Since a deep involvement of astrocytes, a kind of glial cells, in differentiation of the blood-brain barrier (BBB) has been suggested, we examined the relation of glial cell line-derived neurotrophic factor (GDNF) to the BBB. First, immunohistochemical examination of the cerebral cortex of rats revealed that glial cell line-derived neurotrophic factor receptor (GFRalpha1) was preferentially expressed on the cell membranes of capillary endothelial cells. Second, to elucidate the effects of GDNF on the BBB, capillary endothelial cells isolated from the porcine cerebral cortex were cultured and then changes in tight junction function of the endothelial cells were examined after addition of GDNF, in terms of transendothelial electrical resistance (TER) and permeability. GDNF at concentrations of 0.1 and 1 ng/ml significantly activated the barrier function of the endothelial cells in the presence of cAMP. Since GDNF is secreted from astrocytes sheathing capillary endothelial cells in the brain cortex, our results strongly suggest that GDNF enhances the barrier function of tight junctions of the BBB on the one hand, and also supports the survival of neurons on the other hand.

Animals↗

PubMed1999

Introduction of mannose binding protein-type phosphatidylinositol recognition into pulmonary surfactant protein A.

Pulmonary surfactant protein A (SP-A) and mannose-binding protein A (MBP-A) are collectins in the C-type lectin superfamily. These collectins exhibit unique lipid binding properties. SP-A binds to dipalmitoyl phosphatidylcholine (DPPC) and galactosylceramide (GalCer) and MBP-A binds to phosphatidylinositol (PI). SP-A also interacts with alveolar type II cells. Monoclonal antibodies (mAbs PE10 and PC6) that recognize human SP-A inhibit the interactions of SP-A with lipids and alveolar type II cells. We mapped the epitopes for anti-human SP-A mAbs by a phage display peptide library. Phage selected by mAbs displayed the consensus peptide sequences that are nearly identical to 184TPVNYTNWYRG194 of human SP-A. The synthetic peptide GTPVNYTNWYRG completely blocked the binding of mAbs to human SP-A. Chimeric proteins were generated in which the rat SP-A region Thr174-Gly194 or the human SP-A region Ser174-Gly194 was replaced with the MBP-A region Thr164-Asp184 (rat ama4 or hu ama4, respectively). The mAbs failed to bind hu ama4. Rat ama4 bound to an affinity matrix on mannose-sepharose but lost all of the SP-A functions except carbohydrate binding and Ca2+-independent GalCer binding. Strikingly, the rat ama4 chimera acquired the PI binding property that MBP-A exhibits. This study demonstrates that the amino acid residues 174-194 of SP-A and the corresponding region of MBP-A are critical for SP-A-type II cell interaction and Ca2+-dependent lipid binding of collectins.

Animals↗

PubMed1999

Development and differentiation of gonadotropin hormone-releasing hormone neuronal systems and testes in the Japanese eel (Anguilla japonica).

In this study we investigated the relationship between the development of the olfactory, preoptic, and midbrain gonadotropin-releasing hormone (GnRH) neuronal systems and testicular differentiation in eels (Anguilla japonica) from embryonic stages through adulthood (5.4-50 cm body length). GnRH-synthesizing neuronal populations were first observed in the youngest fish ( approximately 5.0 cm) at the rostrobasal and caudalmost olfactory bulbs immunoreactive to a "promiscuous" (nonspecific) GnRH antiserum (635.5), and in the preoptic area and midbrain tegmentum immunoreactive to chicken GnRH II antiserum. The eel brains lacked salmon and seabream GnRH immunoreactivity. The evidence from our study suggests that the olfactory, preoptic, and midbrain GnRH populations have origins independent from those of proliferative periventricular zones within the brain. However, the olfactory GnRH neurons could have migrated out of the olfactory placodes during ages earlier than those observed in this study. Although all three GnRH neuronal populations contribute to pituitary innervation to some degree, the preoptic GnRH innervation was pronounced in the pituitary when primordial germ cells (animals approximately 5.0 cm) differentiated into male germ cells (animals 14-16 cm) and, therefore, an association can be assumed between preoptic GnRH expression and testicular differentiation in the Japanese eel.

Anguilla↗

PubMed1999

Significance of heterogeneous nuclear ribonucleoprotein B1 as a new early detection marker for oral squamous cell carcinoma.

The development of an early tumor detection marker for oral cancer is an obvious need due to the high recurrence rate and poor survival rate. Based on our previous report that overexpression of heterogeneous nuclear ribonucleoprotein (hnRNP) B1 protein was found in 100% of squamous cell carcinomas of human lung, we applied the same immunohistochemical method, using anti-hnRNP B1 antibody, to human oral squamous cell carcinoma (OSCC). Seven human tissue sections of OSCC showed strong staining with anti-hnRNP B1 antibody, and hnRNP B1 protein of 37 kDa was identified in protein fractions isolated from six of the cancerous tissue sections, while it was not found in adjacent noncancerous tissue. Moreover, three non-homogeneous (nodular) leukoplakia sections showed significant anti-hnRNP B1 staining. The results suggest that this antibody detects precancerous lesions as well as advanced lesions (stages I to IV) of OSCC. We also present positive results of cytodiagnosis for two smear specimens. All of the above results indicate that hnRNP B1 is a new and useful marker for early detection of OSCC.

Adult↗

PubMed1999

Rhodopeptins (Mer-N1033), novel cyclic tetrapeptides with antifungal activity from Rhodococcus sp. I. Taxonomy, fermentation, isolation, physico-chemical properties and biological activities.

Five novel cyclic tetrapeptides, named rhodopeptin C1, C2, C3, C4 and B5, were isolated from a strain named Rhodococcus sp. Mer-N1033. They are a novel type of cyclic tetrapeptide composed of a beta-amino acid and three usual alpha-amino acids. Rhodopeptins show high in vitro antifungal activity against Candida albicans and Cryptococcus neoformans, whereas they show no activity against bacteria.

Animals↗

PubMed1999

Rhodopeptins, novel cyclic tetrapeptides with antifungal activities from Rhodococcus sp. II. Structure elucidation.

The structures of rhodopeptins, novel antifungal peptides, were determined on the basis of physico-chemical analyses of the intact molecules and their acid hydrolysates. The structures of rhodopeptins C1, C2, C3, C4 and B5 were determined to be cyclo (-Gly-L-Orn-L-Val-3-amino-10-methyldodecanoyl-), cyclo (-Gly-L-Orn-L-Ile-3-amino-10-methyldodecanoyl-), cyclo (-Gly-L-Orn-L-Val-3-amino-12-methyltridecanoyl-), cyclo (-Gly-L-Orn-L-Val-3-amino- 12-methyltetradecanoyl-) and cyclo (-Gly-L-Lys-L-Val-3-amino-13-methyltetradecanoyl-), respectively. They are novel cyclic tetrapeptides containing a lipophilic beta-amino acid.

Amino Acid Sequence↗

PubMed1999

Rhodopeptins, novel cyclic tetrapeptides with antifungal activities from Rhodococcus sp. III. Synthetic study of rhodopeptins.

Total syntheses of cyclo (-Gly-L-Lys-L-Val-(R)-3-aminododecanoyl-); LV9nA and its diastereomer cyclo (-Gly-L-Lys-L-Val-(S)-3-aminododecanoyl-); LV9nB, congeners of rhodopeptin B5 on beta-amino acid moiety, were achieved. The beta-amino acid moiety was prepared as a racemate by the thermal Michael addition of an amine to alpha,beta-unsaturated ester. The racemic beta-amino acids were converted to their L-Valylamide derivatives and the obtained diastereomers were separated. Coupling of both diastereomers, L-Val-beta-amino acids with Gly-L-Lys gave linear tetrapeptides, and tetrapeptides were cyclized by diphenylphosphoryl azide (DPPA) method between C-terminus of beta-amino acid and N-terminus of Gly to give cyclic tetrapeptides. The deprotected cyclic tetrapeptides, LV9nA and LV9nB, both exhibited almost the same antifungal activity as the naturally obtained rhodopeptins. Furthermore, comparison of the 1H NMR spectra of two congeners and rhodopeptin B5 suggested that the stereochemistry of beta-amino acid moiety in natural rhodopeptin B5 has (R)-configuration.

Antifungal Agents↗

PubMed1998

Surfactant proteins A and D: disease markers.

The abundant and restricted expression of surfactant proteins SP-A and SP-D within the lung makes these collectins specific markers for lung diseases. The measurement of SP-A and SP-D in amniotic fluids and tracheal aspirates reflects lung maturity and the production level of the lung surfactant in infants with respiratory distress syndrome (RDS). The SP-A concentrations in bronchoalveolar lavage (BAL) fluids are significantly decreased in patients with acute respiratory distress syndrome (ARDS) and also in patients at risk to develop ARDS. The prominent increase of these proteins in BAL fluids and sputum is diagnostic for pulmonary alveolar proteinosis (PAP). The concentrations of SP-A and SP-D in BAL fluids from patients with idiopathic pulmonary fibrosis (IPF) and interstitial pneumonia with collagen vascular diseases (IPCD) are rather lower than those in healthy controls and the SP-A/phospholipid ratio may be a useful marker of survival prediction. SP-A and SP-D appear in the circulation in specific lung diseases. Their serum concentrations significantly increase in patients with PAP, IPF and IPCD. The successive monitoring of serum levels of SP-A and SP-D may predict the disease activity. The serum SP-A levels increase in patients with ARDS. SP-A is also a marker for lung adenocarcinomas and can be used to differentiate lung adenocarcinomas from other types and metastatic cancers from other origins, and to detect metastasis of lung adenocarcinomas.

Enzyme-Linked Immunosorbent Assay↗

PubMed1998

Induced potential model for muscular contraction mechanism, including two attached states of myosin head.

The model for myosin head motion along an actin filament as proposed by Mitsui & Chiba [(1996). J. theor. Biol. 182, 147-159] is here modified so that it can explain the isometric tension and isotonic velocity transients having the same parameter values as the stationary filament sliding. The modified model differs in that a myosin head forms a complex with two actin molecules in an actin filament and has two attached states in the complex instead of three. Thus an incremental step in the myosin head motion is equal to the F-actin monomer repeat (5.46 nm). Muscle properties concerning the stationary filament sliding are calculated with new parameters in a manner similar to that of Mitsui-Chiba, with the results being qualitatively similar to theirs. In studying the transient phenomena, a quantitative expression is given for the potential energy of the myosin head in the complex, and two rate constants are applied to the kinetics of the head. The time course of tension recovery after a quick length change is determined by calculating the statistical distribution of the head in the two attached states, which conforms to experimental observations by Ford et al. [(1977). J. Physiol. 269, 441-515]. The tension variations T1/T0 and T2/T0 calculated with parameters determined from the analysis of stationary filament slidings are in fairly good agreement with the experimental data by Ford et al. The model suggests that a large fluctuation exists in the relative position between the actin and myosin filaments even when the load on a muscle is kept constant. Taking this fluctuation into account explains the characteristics of the isotonic velocity transient observed by Civan & Podolsky.

Actins↗

PubMed1998

Actinin-4, a novel actin-bundling protein associated with cell motility and cancer invasion.

Regulation of the actin cytoskeleton may play a crucial role in cell motility and cancer invasion. We have produced a monoclonal antibody (NCC- Lu-632, IgM, k) reactive with an antigenic protein that is upregulated upon enhanced cell movement. The cDNA for the antigen molecule was found to encode a novel isoform of nonmuscle alpha-actinin. This isoform (designated actinin-4) was concentrated in the cytoplasm where cells were sharply extended and in cells migrating and located at the edge of cell clusters, but was absent from focal adhesion plaques or adherens junctions, where the classic isoform (actinin-1) was concentrated. Actinin-4 shifted steadily from the cytoplasm to the nucleus upon inhibition of phosphatidylinositol 3 kinase or actin depolymerization. The cytoplasmic localization of actinin-4 was closely associated with an infiltrative histological phenotype and correlated significantly with a poorer prognosis in 61 cases of breast cancer. These findings suggest that cytoplasmic actinin-4 regulates the actin cytoskeleton and increases cellular motility and that its inactivation by transfer to the nucleus abolishes the metastatic potential of human cancers.

Actinin↗

PubMed1998

Mouse P450RAI (CYP26) expression and retinoic acid-inducible retinoic acid metabolism in F9 cells are regulated by retinoic acid receptor gamma and retinoid X receptor alpha.

We have cloned a mouse cDNA homolog of P450RAI, a cytochrome P450 belonging to a new family (CYP26), which has previously been isolated from zebrafish and human cDNAs and found to encode a retinoic acid-inducible retinoic acid hydroxylase activity. The cross-species conservation of the amino acid sequence is high, particularly between the mouse and the human enzymes, in which it is over 90%. Like its human and zibrafish counterparts, the mouse P450RAI cDNA catalyzes metabolism of retinoic acid into 4-OH-retinoic acid, 4-oxo-retinoic acid, 18-OH-retinoic acid, and unidentified water-soluble metabolites when transfected into COS-1 cells. Retinoic acid-inducible retinoic acid metabolism has previously been observed in F9 murine embryonal carcinoma cells and some derivatives lacking retinoid receptors. We were interested in determining whether P450RAI could be responsible for retinoic acid metabolism in F9 cells and in studying the effect of retinoid receptor ablation on P450RAI expression. In wild-type F9 cells and derivatives lacking RAR gamma, RAR alpha, and/or RXR alpha, we observed a direct relationship between the level of retinoic acid metabolic activity and retinoic acid-induced P450RAI mRNA. These experiments, as well as others using synthetic receptor subtype-specific retinoids, suggest that the RAR gamma and RXR alpha receptors mediate the effects of retinoic acid on the expression of the P450RAI gene.

Amino Acid Sequence↗

PubMed1998

Significance of membrane glycoproteins in platelet interaction with oxidized low-density lipoprotein.

The significance of three platelet membrane glycoproteins, (CD62p, CD63, and CD36) was studied in platelet interaction with native and copper-oxidized plasma low-density lipoproteins (LDL). Native LDL acquired platelet-activating ability only after oxidation. Flow-cytometric studies showed that CD62P and CD63 were rapidly expressed on platelets at a low concentration of oxidized LDL, indicating that they are more sensitive markers than platelet aggregation for detection of platelet activation by oxidized LDL. CD36 was found to be contributing to the binding and activation of platelets with oxidized LDL, but not to the binding of platelets with native LDL. Although the presence of oxidized LDL in plasma is known, its effect on platelet function remains to be studied.

Antigens, CD↗

PubMed1998

Neonatal hyperbilirubinemia and mutation of the bilirubin uridine diphosphate-glucuronosyltransferase gene: a common missense mutation among Japanese, Koreans and Chinese.

We analyzed the bilirubin uridine diphosphate-glucuronosyltransferase (B-UGT) gene in 42 Japanese newborns with hyperbilirubinemia and determined that 21 infants were heterozygous while 3 was homozygous for Gly71Arg. Allele frequency of Gly71Arg was 0.32 in newborns with hyperbilirubinemia, which was significantly higher than 0.13 in healthy Japanese controls. This mutant allele is also prevalent among Korean and Chinese healthy controls with a frequency of 0.23 in both populations. However, this mutation was not detected in 50 healthy German controls. These data suggest that the high frequency of the Gly71Arg mutation of the B-UGT gene is associated with high incidence of neonatal hyperbilirubinemia in Japanese, Korean and Chinese populations.

Alleles↗

PubMed1998

'Alice in Wonderland' syndrome as a precursor of depressive disorder.

A 54-year-old Japanese businessman who was found to exhibit the 'Alice in Wonderland' syndrome and went on to develop a depressive disorder is described. Lengthening and shortening of time experience continued intermittently for about 3 months, and metamorphopsia, distortion of body image, and the quick-motion phenomenon (alteration in time sense) persisted for almost 2 days without interruption. There were no abnormal physical findings. The authors review studies on 'Alice in Wonderland' syndrome and suggest that depressive illness may be a causal factor.

Body Image↗

PubMed1998

Familial hypercholesterolemia with cholesteryl ester transfer protein deficiency.

A 21-year-old male was clinically diagnosed with familial hypercholesterolemia (FH) by the manifestations of hypercholesterolemia, tendon xanthoma and family history of premature coronary heart disease. Low density lipoprotein receptor gene was analyzed in attempt to determine a possible point mutation. The normal sequence was partially preserved, and the patient was genetically diagnosed as a heterozygote of FH. In addition, screening for two cholesteryl ester transfer protein (CETP) gene mutations common to Japanese revealed the patient to be a heterozygote of CETP deficiency. A complication of two influential mutations for atherosclerotic ailments was genetically ascertained.

Adult↗