Biomedical subjects

S Nagata

Publications and source records attributed to S Nagata.

At least 433 records · Page 24Linked to original sources

PubMed1993

A novel protein domain required for apoptosis. Mutational analysis of human Fas antigen.

The Fas antigen is a cell surface protein that can mediate apoptosis and that belongs to the tumor necrosis factor receptor family. Murine fibroblast L929 cells or T-cell lymphoma WR19L cells expressing the human Fas antigen were killed within 4-6 h by anti-human Fas antibody in a concentration-dependent manner. Human Fas antigen cDNAs with various mutations in the cytoplasmic region were constructed and expressed in L929 cells. A deletion of 15 amino acids from the C terminus of the Fas antigen enhanced the Fas antibody-induced killing activity, whereas a further deletion abolished its activity. This suggests the presence of an inhibitory as well as a signal-transducing domain in the cytoplasmic region of the Fas antigen. A 68-amino acid portion of the signal-transducing domain significantly conserved in the Fas antigen as well as in the type I tumor necrosis factor receptor was considered to be the novel protein domain required for apoptotic signal transduction.

Amino Acid Sequence↗

PubMed1993

Lysine 87 in the beta subunit of tryptophan synthase that forms an internal aldimine with pyridoxal phosphate serves critical roles in transimination, catalysis, and product release.

This study provides valuable insights into the functions of the lysine residue that forms an internal aldimine with pyridoxal phosphate in the beta subunit of tryptophan synthase from Salmonella typhimurium. Our spectroscopic and kinetic studies demonstrate that a mutant alpha 2 beta 2 complex having beta subunit lysine 87 replaced by threonine forms external aldimines with several amino acids including L-serine, beta-chloro-1-alanine, L-tryptophan, and D-tryptophan. Because the rates of aldimine formation are very slow, we conclude that one role of lysine 87 in the wild type enzyme is to facilitate formation of external aldimines by transimination. Lysine 87 is an essential catalytic residue because the mutant alpha 2 beta 2 complex has no measurable activity in reactions catalyzed by the beta subunit and does not convert external aldimines to products. The mutant enzyme carries out two slow partial beta-elimination reactions: the conversion of beta-chloro-L-alanine and L-serine to enzyme-bound aminoacrylate. The reaction with L-serine is catalyzed by ammonia, which partially replaces the deleted epsilon-amino group. Lysine 87 is important for substrate and product release because L-serine, L-tryptophan, and aminoacrylate dissociate very slowly from the mutant alpha 2 beta 2 complex. Our ability to prepare very stable derivatives of the mutant alpha 2 beta 2 complex containing tightly bound aldimines with a substrate, a product, or a reaction intermediate provides valuable materials for ongoing x-ray crystallographic investigations and future kinetic analyses of the allosteric activation of the alpha subunit by beta subunit ligands.

Catalysis↗

PubMed1993

Left ventricular diastolic pressure-volume response immediately after successful percutaneous transvenous mitral commissurotomy.

The left ventricular (LV) diastolic pressure-volume response after percutaneous transvenous mitral commissurotomy (PTMC) was investigated to determine whether it was related to the baseline conditions of the left ventricle. Left ventriculography was performed, and the measurements of LV pressure were obtained in 32 patients before and after PTMC. Mitral valve area increased from 1.0 +/- 0.3 to 1.9 +/- 0.4 cm2 (p < 0.005) after PTMC, which caused a decrease in left atrial mean pressure (14.8 +/- 5.9 to 7.4 +/- 2.7 mm Hg; p < 0.005). LV end-diastolic pressure increased in all patients 5 minutes after PTMC. However, patients could be divided into 2 groups according to the following changes in LV end-diastolic pressure 20 minutes after PTMC: In 22 patients, LV end-diastolic pressure returned to the near-baseline level 20 minutes after PTMC (before 5.0 +/- 2.2, 5 minutes after 8.6 +/- 3.1, and 20 minutes after 6.3 +/- 2.5 mm Hg) with a significant increase in LV end-diastolic volume index (64 +/- 12 to 74 +/- 14 ml/m2; p < 0.001) and augmentation of LV stroke volume index (39 +/- 9 to 47 +/- 11 ml/m2; p < 0.001). However, in the remaining 10 patients with a larger LV volume (> 80 ml/m2) and reduced ejection fraction (< 50%) at baseline, LV end-diastolic pressure further increased 20 minutes after PTMC (before 5.5 +/- 2.8, 5 minutes after 7.8 +/- 2.7, and 20 minutes after 11.0 +/- 2.9 mm Hg) without significant changes in LV volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Aberrant transcription caused by the insertion of an early transposable element in an intron of the Fas antigen gene of lpr mice.

The mouse lpr (lymphoproliferation) mutation carries a rearrangement in the chromosomal gene for the Fas antigen, which mediates apoptosis. Isolation and characterization of mouse Fas antigen chromosomal gene from wild-type and lpr mice indicated an insertion of an early transposable element (ETn) in intron 2 of the Fas antigen gene of lpr mice. Hybrid transcripts carrying the Fas antigen and ETn sequences were expressed in the thymus and liver of the mutant. This indicated that premature termination and aberrant splicing of the Fas antigen transcript caused by the insertion of the ETn in the intron are responsible for the lymphoproliferation and autoimmune phenotype of the mutant mouse. On the other hand, an insertion of the ETn into an intron of a mammalian expression vector dramatically but not completely reduced the expression efficiency. These findings suggest that lpr mice are able to express a very low level of the Fas antigen.

Amino Acid Sequence↗

PubMed1993

Structural requirement of CRK SH2 region for binding to phosphotyrosine-containing proteins. Evidence from reactivity to monoclonal antibodies.

The SH2 region of signal-transducing proteins mediates binding to phosphotyrosine-containing proteins. We analyzed the structure-function relationship of the SH2 region of the human CRK protein by using a series of monoclonal antibodies (mAbs). Seventeen mAbs against the CRK SH2 region were classified into 5 groups according to the reactivity with mutant CRK proteins expressed in COS7 cells and in Escherichia coli and by epitope scanning with synthetic nonapeptides. Two groups of mAbs (groups A and B) were reactive only with intact SH2. Mutation(s) in either the amino-terminal B box or the carboxyl-terminal C box, which are the two subdomains of SH2, abolished the reactivity of the CRK mutants to the mAbs of groups A and B. Group A mAbs competed the binding of the CRK SH2 region to the phosphotyrosine-containing proteins. Moreover, the spectrum of the CRK mutants which were recognized by group A mAbs coincided with that of the CRK mutants which could bind phosphotyrosine-containing proteins, suggesting that group A mAbs were directed against the site of binding to phosphotyrosine-containing proteins. Group C mAbs, directed against the region between the B and C boxes, were reactive with both wild-type and mutant CRK proteins and did not affect the capacity of SH2 to bind phosphotyrosine-containing proteins. Contrary to group A and B mAbs, mAbs belonging to groups D and E, which were mapped onto the C box, did not bind well to the native CRK proteins, but bound to CRK mutants with mutation(s) in either the B or the C box. These results suggest that the B and C boxes, which are separated by a hinge region, coordinately form the functional SH2 domain that binds to the phosphotyrosine-containing proteins and to the group A mAbs.

Animals↗

PubMed1993

Rapidity of progression of aortic stenosis in patients with congenital bicuspid aortic valves.

The rapidity of progression of aortic stenosis in patients with congenital bicuspid aortic valves, and its relation to aging and valve anatomy are not well known. To elucidate these aspects, 75 patients aged 15 to 76 years were examined by echocardiography. Aortic valve sclerosis began from the second decade, the sclerotic index progressing with age (r = 0.72; p < 0.0001). Aortic valve calcium was noted from the fourth decade. Aortic valve pressure gradient increased approximately 18 mm Hg each decade, concomitant with progression of valve sclerosis (r = 0.78; p < 0.0001). Progression of cusp sclerosis was faster in patients with anteroposteriorly located cusps than in those with right-left-located cusps (p < 0.005), and was faster in those with eccentric cusps (width ratio of major and minor cusps > or = 1.2) than in those with symmetric cusps (p < 0.05). In patients with eccentric and anteroposteriorly located cusps, aortic valve pressure gradient increased 27 mm Hg per decade. In patients with congenital bicuspid aortic valves, the progression of aortic stenosis is rapid, and the rapidity depends to some extent on the position and eccentricity of the cusps.

Adolescent↗

PubMed1993

Signal transduction mediated by growth hormone receptor and its chimeric molecules with the granulocyte colony-stimulating factor receptor.

The granulocyte colony-stimulating factor receptor (G-CSF-R) and growth hormone receptor (GH-R) belong to the cytokine receptor family and have some similarity in the cytokine receptor-homologous (CRH) domain of the extracellular region. Among members of this family, the G-CSF-R and GH-R seem to function as homodimers. Previously, we showed that mouse myeloid precursor FDC-P1 cells expressing the G-CSF-R can respond to G-CSF for growth. Here we show that the GH-R can also transduce the growth signal in FDC-P1 cells in the range 10 pM-100 nM GH. At a higher concentration of GH, GH did not promote the growth of the transformant cells. A series of chimeric receptor cDNAs between the G-CSF-R and GH-R cDNAs was constructed by exon swapping and was expressed in FDC-P1 cells. A ligand-binding assay with transformants expressing chimeric receptors indicated that the entire CRH domain is necessary for specific binding of the ligand. Although the transmembrane and cytoplasmic regions of the G-CSF-R and GH-R have no apparent similarity, these regions were interchangeable, resulting in growth-signal transduction in FDC-P1 cells.

Amino Acid Sequence↗

PubMed1993

Search for functional significance of peptidylarginine deiminase in rat pituitaries: variation during pregnancy and ultrastructural localization in prolactin cells.

We have studied the expression of peptidylarginine deiminase in rat pituitaries during pregnancy. Both the enzyme protein and its mRNA decreased to low levels after the onset of gestation. Both started to increase markedly during mid pregnancy reaching their maxima on day 18 and declined thereafter. The early phase of variations were accompanied with a progressive decrease in the pituitary prolactin content, an abrupt decrease in the prolactin mRNA content, and a small but significant increase in the serum estrogen. We also performed an immunoelectron microscopic study of the enzyme, and showed its scattered localization in the cytoplasm of prolactin cells.

Animals↗

PubMed1993

Intracranial adenoid cystic carcinoma mimicking meningioma: report of two cases.

Two cases of intracranial adenoid cystic carcinoma mimicking meningioma are reported. In one, MRI showed not only a homogeneously enhancing extra-axial tumour attached to the dura mater of the posterior cranial fossa, but also surrounding dural enhancement, the "dural tail sign". In the second, CT demonstrated a well-demarcated enhancing extra-axial tumour, indistinguishable from a sphenoid ridge meningioma extending into the orbit. The neuroradiological features of intracranial adenoid cystic carcinoma may thus closely resemble those of meningioma.

Aged↗

PubMed1993

Influence of HCV infection and its subtypes on clinical course of alcoholic liver disease.

Since the assay of HCV antibody has been developed, it became clear that HCV is involved not only in patients with non-A non-B hepatitis but also in some alcoholic patients. The aim of this study is to examine the prevalence of HCV in chronic alcoholics and to elucidate the influence of HCV and its subtypes on pathogenesis and clinical feature of alcoholic liver disease. To that effect, sera from 100 alcoholics were tested for antibody against C100 of HCV by ELISA and for HCV RNA by reverse transcriptation and the PCR method. The incidence of HCV Ab/RNA was 0%/17% in patients with non specific reactive hepatitis, 0%/0% in fatty liver, 17%/17% in alcoholic hepatitis, 50%/73% in chronic hepatitis, 15%/18% in liver fibrosis and 19%/31% in liver cirrhosis. HCV Ab and RNA were positive in 21% and 31% of alcoholics, respectively. Subtypes of HCV were identified by dot blot hybridization method. Type K1, K2a and K2b were detected in 68%, 25% and 7% of 28 patients with positive HCV RNA, respectively. Type PT was not detected. In addition, serum transaminase activities were evaluated after 4 weeks abstinence. The incidence of normalization of the enzyme activity was lower in patients with positive HCV RNA than that with negative HCV RNA. Furthermore, when it was estimated in relation to HCV subtypes, the incidence of normalization in patients with type K1 was lower than that with type K2. In conclusion, the prevalence of HCV infection in alcoholic patients was much greater than general population.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Development and evaluation of a novel sterilizer with rotary vibrators.

A novel steam-air sterilizer with rotary vibrators was developed with the aim of promoting heat transfer and the effective sterilization of foods. To evaluate the effects of the sterilizer, experiments to examine heat transfer and sterilization tests were carried out. In the experiments to examine heat transfer, heat penetration factors of sterilizer with vibration, j and fh values, were 1.70 and 1.50, respectively, while those of sterilizer without vibration were 1.83 and 2.32, respectively. In the sterilization with vibration, no surviving cells were detected after 3 min, whereas 7 min were required for sterilization without vibration. The rate of the amino carbonyl reaction was repressed by heat treatment with vibration.

Amines↗

PubMed1993

Plasma atrial natriuretic peptide response to direct current cardioversion of atrial fibrillation in patients with mitral stenosis.

OBJECTIVES: The purpose of this study was to evaluate the effect of direct current cardioversion therapy on the plasma concentration of atrial natriuretic peptide and to determine the main factors that influence the change in plasma atrial natriuretic peptide levels in patients with atrial fibrillation. BACKGROUND: In atrial arrythmias, whether the fast atrial rate itself or the associated elevation of atrial pressure, or both, contributes to the increase in atrial natriuretic peptide is a subject of debate. METHODS: In 15 patients with mild mitral stenosis, plasma atrial natriuretic peptide levels were measured and transmitral flow pattern was obtained by continuous wave Doppler echocardiography immediately before cardioversion and at 5 min, 4 h, 24 h and 5 days after direct current cardioversion. Mean mitral pressure gradient and atrial filling fraction were calculated on the basis of transmitral flow. RESULTS: In three patients who did not have a successful return to sinus rhythm, plasma atrial natriuretic peptide levels remained elevated after cardioversion. In 12 patients who maintained sinus rhythm, plasma atrial natriuretic peptide levels were significantly reduced from 79 +/- 29 to 36 +/- 11 pg/ml 4 h after cardioversion to sinus rhythm. However, the mitral pressure gradient did not change significantly during the observation period. There were progressive increases in atrial filling fraction throughout the observation period. From 4 h to 5 days after direct current cardioversion, plasma atrial natriuretic peptide levels gradually increased concomitantly with the recovery of atrial mechanical function. CONCLUSION: The reduction of plasma atrial natriuretic peptide levels after direct current cardioversion might be due to recovery from the high rate of atrial firing and not to an alteration in the mitral pressure gradient. Direct current cardioversion itself does not seem to influence atrial natriuretic peptide secretion. The increase in atrial natriuretic peptide levels from 4 h to 5 days after cardioversion concomitantly with an increase in atrial filling fraction may be due to recovery of atrial mechanical function.

Adult↗

PubMed1993

Molecular cloning and tissue distribution of a receptor for pituitary adenylate cyclase-activating polypeptide.

Pituitary adenylate cyclase-activating polypeptide (PA-CAP) is a polypeptide hormone related to vasoactive intestinal polypeptide (VIP). Rat PACAP receptor cDNA was isolated from a brain cDNA library by cross-hybridization with rat VIP receptor cDNA. The recombinant PACAP receptor expressed in COS cells bound PACAP with about 1000 times higher affinity than VIP, and PACAP stimulated adenylate cyclase through the cloned PACAP receptor. The rat PACAP receptor consists of 495 amino acids, contains seven transmembrane segments, and has a significant similarity with other Gs-coupled receptors, such as VIP, glucagon, and secretin receptors. PACAP receptor mRNA was abundantly expressed in the brain, but not in the peripheral tissues except for the adrenal gland. In situ hybridization revealed a high level of expression of PACAP receptor mRNA in the hippocampal dentate gyrus, olfactory bulb, and cerebellar cortex.

Amino Acid Sequence↗

PubMed1993

Heterogeneity of hepatic acetaldehyde adducts in guinea-pigs after chronic ethanol administration: an immunohistochemical analysis with monoclonal and polyclonal antibodies against acetaldehyde-modified protein epitopes.

The formation of acetaldehyde (AcH) adducts was immunohistochemically demonstrated in the livers of experimental animals after chronic ethanol consumption. Recently, we established a hybridoma producing monoclonal antibody against the adduct. Although the polyclonal antibody obtained from a rabbit immunized with adducts had affinities for AcH adducts produced with 20 microM, 1 mM and 10 mM of AcH, the monoclonal antibody could recognize only those produced with 1 and 10 mM of AcH, suggesting that there is a difference of antigenicity between the adducts formed with a high concentration of AcH and those modified with a low concentration of AcH. AcH adducts in the liver of guinea-pigs fed ethanol for 90 days were detected by immunohistochemical staining with the polyclonal and monoclonal antibodies. The staining of liver specimens with polyclonal antibody was observed around both the portal and perivenular areas, whereas the reactions to monoclonal antibody were localized only in the perivenular area. These data suggest that AcH adducts are able to be formed around both portal and perivenular areas in the liver and that the perivenular area might be exposed to a higher concentration of AcH than the portal area after ethanol intake.

Acetaldehyde↗

PubMed1993

Purification and characterization of homospermidine synthase in Acinetobacter tartarogenes ATCC 31105.

Homospermidine synthase, catalyzing the formation of homospermidine [H2N(CH2)4NH-(CH2)4NH2] from putrescine and NAD+ with concomitant liberation of NH3, was purified 600-fold over the crude extract with a yield of about 14% to homogeneity from Acinetobacter tartarogenes ATCC 31105. The enzyme had a native molecular mass of 102 kDa, with a pI of 5.0, and was apparently composed of two identical subunits (52 kDa), suggesting that a single protein catalyzes two serial reactions, oxidation of putrescine to 4-aminobutyraldehyde and subsequent reduction of the putative Schiff base formed between this aldehyde and a second molecule of putrescine to homospermidine. The Km values for putrescine and NAD+ were 280 and 18 microM, respectively. 1,3-Diaminopropane and cadaverine were inactive as substrates, and NAD+ could not be replaced by NADP+. 1,3-Diaminopropane and NADH were potent competitive inhibitors. The enzyme had a pH optimum of 8.7, was most active at 30 degrees C, and required K+ and dithiothreitol for full activity. Putrescine and NAD+ protected the enzyme from the inhibition by thiol reagents. The NH2-terminal amino acid sequence was AQWPVYGKISGPVVI. Some of these properties were compared with those of the homospermidine synthases from a photosynthetic bacterium, Rhodopseudomonas viridis and a plant, Lathyrus sativus.

Acinetobacter↗

PubMed1993

An inducible NADP(+)-dependent D-phenylserine dehydrogenase from Pseudomonas syringae NK-15: purification and biochemical characterization.

An inducible NADP(+)-dependent D-phenylserine dehydrogenase [EC 1.1.1.-], which catalyzes the oxidation of the hydroxyl group of D-threo-beta-phenylserine, was purified to homogeneity from a crude extract of Pseudomonas syringae NK-15 isolated from soil. The enzyme consisted of two subunits identical in molecular weight (about 31,000). In addition to D-threo-beta-phenylserine, it utilized D-threo-beta-thienylserine, D-threo-beta-hydroxynorvaline, and D-threonine as substrates but was inert towards other isomers of beta-phenylserine and threonine. It showed maximal activity at pH 10.4 for the oxidation of D-threo-beta-phenylserine, and it required NADP+ as a natural coenzyme. NAD+ showed a slight coenzyme activity. The enzyme was inhibited by p-chloromercuribenzoate, HgCl2, and monoiodoacetate but not by the organic acids such as tartronate. The Michaelis constants for D-threo-beta-phenylserine and NADP+ were 0.44 mM and 29 microM, respectively. The N-terminal 27 amino acids sequence was determined. It suggested that the NADP(+)-binding site was located in the N-terminal region of the enzyme.

Alcohol Oxidoreductases↗

PubMed1993

Discrepancies between myocardial perfusion and free fatty acid metabolism in patients with hypertrophic cardiomyopathy.

To test the hypothesis that there are discrepancies between 201Tl- and 123I-beta-methylpentadecanoic acid (BMIPP) distribution in the left ventricular myocardium and to assess whether BMIPP is a useful tracer agent for the assessment of left ventricular function in hypertrophic cardiomyopathy (HCM), myocardial single photon emission computed tomography (SPECT) was performed with 201Tl and BMIPP in five normal subjects and 12 patients with asymmetric septal hypertrophy. Tracer uptake in the left ventricular myocardium was scored using a four-point grading system. A homogenous distribution of the tracer with no discrepancy between 201Tl and BMIPP uptake in the left ventricular myocardium was observed in each normal subject. In contrast, BMIPP uptake was reduced compared to 201Tl in 58 segments (40%) of the 144 myocardial segments in patients with HCM. Such discordant BMIPP uptake was observed in 15 segments (42%) of the septal segments, in 19 segments (53%) of the anterior segments, in eight segments (22%) of the lateral segments, and in 16 segments (44%) of the inferior segments. There was no significant correlation between 201Tl perfusion score and left ventricular ejection fraction, whereas there was a significant correlation between BMIPP perfusion score and left ventricular ejection fraction (r = 0.748; P < 0.01). The results indicated that there were discrepancies between 201Tl and BMIPP uptake in a significant proportion of myocardial segments, suggesting the impairment of fatty acid metabolism and that BMIPP is a useful tracer agent for the assessment of left ventricular function in hypertrophic cardiomyopathy.

Cardiomyopathy, Hypertrophic↗

PubMed1993

A new method of total reconstruction of the auricle for microtia.

This new method for total reconstruction of the auricle is a two-stage operation in which the first stage involves fabrication and grafting of a three-dimensional costal cartilage framework and the second stage is the ear elevation operation. The three-dimensional frame was designed with emphasis on the fabrication of the helical crus, intertragic notch, and antitragus and by extending the crus helicis and fixing it to the undersurface of the base frame. The reconstructed auricle will have four different floors: the cymba and cavum conchae are the bottom (fourth) level, the crus helicis is the third level, the fossa triangularis and the scapha are the second level, and the helix, anthelix, tragus, and antitragus are the top level. The skin incision was made in a W-shaped fashion to create skin flaps with ample surface area to cover the three-dimensional frame without skin grafting. Furthermore, the semilunar costal cartilage was utilized for ear elevation. Thus this new method for total reconstruction of the auricle eliminates the major problems encountered with the conventional method.

Adolescent↗