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Biomedical subjects

M Takiguchi

Publications and source records attributed to M Takiguchi.

At least 91 records · Page 5Linked to original sources
PubMed1999

Development of a new catheter-tip pressure transducer.

Two major disadvantages of the conventional catheter-tip transducer have been incapability to calibrate baseline pressure and to adjust sensitivity after insertion. A vast majority of conventional catheter-tip transducers are classified as gauge type. Due to their structure they are inherently incapable of recalibrating after insertion. We have overcome this problem by developing a new differential type catheter-tip transducer equipped with a lumen that connects a small chamber at the backside of the transducer to another external port. This lumen is capable of pressure passage. The output of this type depends on the difference between the two imposed pressures. This passage makes a baseline standard possible, when the end of the lumen is exposed to atmospheric pressure. When pneumatic pressure is imposed to the end of the lumen using a syringe, for example, the transducer output shifts up and down in accordance to that pressure, enabling baseline pressure recalibration and verifying the degree of sensitivity after insertion. By obtaining the following data, we confirmed the stability and availability of this transducer: Baseline drift less than 0.04 mmHg/8 hour, frequency characteristics flat up to 60 Hz, and common mode rejection ratio more than 46 dB.

Catheterization, Peripheral↗
PubMed1998

Hypoglycemia-associated hyperammonemia caused by impaired expression of ornithine cycle enzyme genes in C/EBPalpha knockout mice.

Ammonia produced by amino acid metabolism is detoxified through conversion into urea by the ornithine cycle in the liver, whereas carbon skeletons of amino acids are converted to glucose by gluconeogenic enzymes. Promoter and enhancer sequences of several genes for ornithine cycle enzymes interact with members of the CCAAT/enhancer-binding protein (C/EBP) transcription factor family. Disruption of the C/EBPalpha gene in mice causes hypoglycemia associated with the impaired expression of gluconeogenic enzymes. Here we examined the expression of ornithine cycle enzyme genes in the livers of C/EBPalpha-deficient mice. mRNA levels for the first, third, fourth, and fifth enzymes of five enzymes in the cycle were decreased in C/EBPalpha-deficient mice. Protein levels for the first, second, fourth, and fifth enzymes were also decreased. In situ hybridization analysis revealed that the enzyme mRNAs were distributed normally in the periportal region but were disordered in C/EBPalpha-deficient mice with relatively higher mRNA levels in the midlobular region. Blood ammonia concentrations in the mutant mice were severalfold higher than in wild-type mice. Thus, C/EBPalpha is crucial for ammonia detoxification by ornithine cycle enzymes and for coordination of gluconeogenesis and urea synthesis.

Ammonia↗
PubMed1998

Mechanisms of transcription in eosinophils: GATA-1, but not GATA-2, transactivates the promoter of the eosinophil granule major basic protein gene.

Granule major basic protein (MBP) is expressed exclusively in eosinophils, basophils, and placental trophoblasts. To identify the cis-elements and transcription factors involved in regulating MBP expression, we subcloned 3.2 kb of sequence upstream of the exon 9 transcriptional start site (P2 promoter) and serial 5' deletions into the pXP2 luciferase reporter vector. An 80% decrement in promoter activity was obtained when MBP sequences between bp -117 to -67 were deleted. To identify transcription factors that bind to and transactivate through the bp -117 to -67 region, we first compared the upstream genomic sequences of human and murine MBP; a potential GATA binding consensus site was conserved in the 50-bp region between the two genes. To determine which GATA proteins bind this consensus site, we performed electrophoretic mobility shift assays (EMSAs), which showed that both GATA-1 and GATA-2 can bind to this consensus site. To determine the functionality of this site, we tested whether GATA-1 and GATA-2, either individually or in combination, can transactivate the MBP promoter in the Jurkat T cell line. Cotransfection with a GATA-1 expression vector produced 20-fold augmentation of MBP promoter activity, whereas GATA-2 had no activity. In contrast, combined cotransfection of GATA-1 and GATA-2 decreased the ability of GATA-1 to transactivate the MBP promoter by approximately 50%. Our results provide the first evidence for a GATA-1 target gene in eosinophils, a negative regulatory role for GATA-2 in MBP expression, and possibly eosinophil gene transcription in general during myelopoiesis.

Binding Sites↗
PubMed1998

Crucial role of N-terminal residue of binding peptides in recognition of the monoclonal antibody specific for the peptide-HLA-B5, -B35 complex.

The monoclonal antibody (mAb) 4D12 specific for the HLA-B5, -B35 cross-reacting group (CREG) bound to a fraction of HLA-B*3501 and HLA-B*5101 molecules carrying self-peptides. Analysis of the binding of mAb 4D12 to HLA-B*3501 and -B*5101 molecules pulsed with chemically synthesized peptides revealed that this mAb recognizes a restricted number of peptides and that P1 of the bound peptides critically influences its binding. The 4D12 mAb bound only to HLA-B*3501 molecules carrying peptides with Asn, Asp, Glu, Ser, and Val at P1. Analysis using an HLA-B*3501 crystallographic model suggested that 4D12 may recognize the side chain of the P1 residue that is pointing to the solvent. On the other hand, 4D12 bound only to HLA-B*5101 molecules carrying peptides with Asn or Asp at P1, suggesting that the 4D12 epitope formed by Glu, Ser, or Val at P1 and the A-pocket was changed by the substitution of His for Tyr at residue 171 of HLA-B*3501 molecules. This was confirmed by testing the binding of mAb 4D12 to HLA-B*3501 mutant molecules at residue 171 carrying these peptides. These results together suggest that the conformation of the A-pocket and its hydrogen bound network with the P1 residue is also critical for the binding of mAb 4D12. The present study shows the molecular basis of the specificity of 4D12 for the peptide-HLA class I complex.

Amino Acid Sequence↗
PubMed1998

Residue 116 determines the C-terminal anchor residue of HLA-B*3501 and -B*5101 binding peptides but does not explain the general affinity difference.

HLA-B*3501 and -B*5101 molecules, which belong to the HLA-B5 cross-reactive group, bind peptides carrying similar anchor residues at P2 and the C-terminus, but differences are observed in the preference for a Tyr residue at the C-terminus and the affinity of peptides. A recent study of HLA-B*3501 crystal structure suggested that residue 116 on the floor of the F-pocket determines a preference for anchor residues at the C-terminus. In order to evaluate the role of the residue 116 in the peptide binding to both HLA-B*3501 and HLA-B*5101 molecules, we generated HLA-B*3501 mutant molecules carrying Tyr at residue 116 (B*3501-116Y) and tested the binding of a panel of nonamer peptides to the B*3501-116Y molecules by a stabilization assay with RMA-S transfectants expressing the mutant molecules. The substitution of Tyr for Ser at residue 116 markedly reduced the affinity of nonamer peptides carrying Tyr at P9, while it enhanced that of nonamer peptides carrying Ile and Leu at P9. On the other hand, the affinity of peptides carrying aliphatic hydrophobic residues at P9 to B*3501-116Y molecules was much higher than that to HLA-B*3501 and HLA-B*5101 molecules. These results indicate that residue 116 is critical for the structural difference of the F-pocket between HLA-B*3501 and HLA-B*5101 which determines the C-terminal anchor residues, while leaving other residues which differ between HLA-B*3501 and HLA-B*5101 may be responsible for the low peptide binding property of the latter.

Binding Sites↗
PubMed1998

Primary aortoenteric fistula with a chronic isolated abdominal aortic dissection: report of a case.

A 47-year-old woman on long-term hemodialysis due to a chronic isolated abdominal aortic dissection was admitted to our department with severe abdominal pain. She had not suffered any hematemesis or melena. An emergency laparotomy revealed an abdominal aortic aneurysm with a diameter of 60mm, densely adhered to the ileum. An aortoenteric fistula manifesting as intramural rupture into the ileum was found after infrarenal abdominal aortic and bilateral common iliac cross-clamping. The fistula on the ileac side was nontransmural, but that on the aortic side communicated with the pseudolumen of the abdominal aorta, and contained mural thrombus. The infrarenal abdominal aorta and bilateral common iliac arteries were replaced with a collagen-sealed woven Dacron bifurcated graft. Histological examination of the ileum in this portion showed intramural bleeding and xanthomatous granulation with foam cell infiltration in the thickened subserosa. While it is difficult to diagnose nonpenetrating aortoenteric fistula preoperatively, such a fistula must be considered in a patient with severe abdominal pain, for whom previous abdominal aortic surgery has been performed or when an abdominal aneurysm is observed. To our knowledge, no other case of an aortoenteric fistula presenting as an intramural rupture into the ileum in an isolated abdominal aortic dissection has ever been reported.

Adult↗
PubMed1998

Precise distribution of neuronal nitric oxide synthase mRNA in the rat brain revealed by non-radioisotopic in situ hybridization.

Regional distribution of neurons expressing neuronal nitric oxide synthase mRNA in the rat brain was examined by non-radioisotopic in situ hybridization, using digoxigenin-labeled complementary RNA probes. Clustering of intensely positive neurons was observed in discrete areas including the main and accessory olfactory bulbs, the islands of Calleja, the amygdala, the paraventricular nucleus of the thalamus, several hypothalamic nuclei, the lateral geniculate nucleus, the magnocellular nucleus of the posterior commissure, the superior and inferior colliculi, the laterodorsal and pedunculopontine tegmental nuclei, the nucleus of the trapezoid body, the nucleus of the solitary tract and the cerebellum. Strongly-stained isolated neurons were scattered mainly in the cerebral cortex, the basal ganglia and the brain stem, especially the medulla reticular formation. In the hippocampus, an almost uniform distribution of moderately stained neurons was observed in the granular cell layer of the dentate gyrus and in the pyramidal cell layer of the Ammon's horn, while more intensely stained isolated neurons were scattered over the entire hippocampal region. These observations can serve as a good basis for studies on function and gene regulation of neuronal nitric oxide synthase.

Animals↗
PubMed1998

T cells expressing killer cell inhibitory receptors do not carry TCR for alloantigens.

The role of T cells carrying the killer cell inhibitory receptor (KIR) is unknown. Here we investigate the allo-response of KIR+ CD3+ cells (KIR+ T cells). KIR+ T cells was found in 4.6-14.7% of the T cells from the PBMC of healthy individuals. Flow cytometry analysis showed that the percentage of KIR+ T cells in T cells from three individuals was decreased after stimulation with allogeneic PBMC. These findings suggest that KIR+ T cells do not respond to alloantigens. Furthermore, the analyses using purified KIR+ T cells also confirmed that KIR+ T cells do not respond to alloantigens.

Antibodies, Monoclonal↗
PubMed1998

Immunohistochemical localization of arginase II and other enzymes of arginine metabolism in rat kidney and liver.

Arginine is a precursor for the synthesis of urea, polyamines, creatine phosphate, nitric oxide and proteins. It is synthesized from ornithine by argininosuccinate synthetase and argininosuccinate lyase and is degraded by arginase, which consists of a liver-type (arginase I) and a non-hepatic type (arginase II). Recently, cDNAs for human and rat arginase II have been isolated. In this study, immunocytochemical analysis showed that human arginase II expressed in COS-7 cells was localized in the mitochondria. Arginase II mRNA was abundant in the rat small intestine and kidney. In the kidney, argininosuccinate synthetase and lyase were immunostained in the cortex, intensely in proximal tubules and much less intensely in distal tubules. In contrast, arginase II was stained intensely in the outer stripes of the outer medulla, presumably in the proximal straight tubules, and in a subpopulation of the proximal tubules in the cortex. Immunostaining of serial sections of the kidney showed that argininosuccinate synthetase and arginase II were colocalized in a subpopulation of proximal tubules in the cortex, whereas only the synthetase, but not arginase II, was present in another subpopulation of proximal tubules. In the liver, all the enzymes of the urea cycle, i.e. carbamylphosphate synthetase I, ornithine transcarbamylase, argininosuccinate synthetase and lyase and arginase I, showed similar zonation patterns with staining more intense in periportal hepatocytes than in pericentral hepatocytes, although zonation of ornithine transcarbamylase was much less prominent. The implications of these results are discussed.

Animals↗
PubMed1998

Regulation of the urea cycle enzyme genes in nitric oxide synthesis.

Nitric oxide (NO) is synthesized from arginine by nitric-oxide synthase (NOS), and citrulline that is generated can be recycled to arginine by argininosuccinate synthase (AS) and argininosuccinate lyase (AL). Rats were injected with bacterial lipopolysaccharide (LPS) and expression of the inducible isoform of NOS (iNOS), AS and AL was analysed. In RNA blot analysis, iNOS mRNA was induced by LPS in the lung, heart, liver and spleen, and less strongly in the skeletal muscle and testis. AS and AL mRNAs were induced in the lung and spleen. Kinetic studies showed that iNOS mRNA increased rapidly in both spleen and lung, reached a maximum 2-5 h after the treatment, and decreased thereafter. On the other hand, AS mRNA increased more slowly and reached a maximum in 6-12 h (by about 10-fold in the spleen and 2-fold in the lung). AL mRNA in the spleen and lung increased slowly and remained high up to 24 h. In immunohistochemical analysis, macrophages in the spleen that were negative for iNOS and AS before LPS treatment were strongly positive for both iNOS and AS after this treatment. As iNOS, AS and AL were co-induced in rat tissues and cells, citrulline-arginine recycling seems to be important in NO synthesis under the conditions of stimulation. Arginine is a common substrate of NOS and arginase. Rat peritoneal macrophages were cultured in the presence of LPS and expression of iNOS and livertype arginase (arginase I) was analysed. mRNAs for iNOS and arginase I were induced by LPS in a dose-dependent manner. iNOS mRNA appeared 2 h after LPS treatment and increased up to a near-maximum at 8-12 h. On the other hand, arginase I mRNA began to increase after 4 h with a lag time and reached a maximum at 12 h. Immunoblot analysis showed that iNOS and arginase I proteins were also induced. Induction of iNOS and arginase I mRNAs were also observed in LPS-injected rats in vivo. Thus, arginase I appears to have an important role in downregulating NO synthesis in murine macrophages by decreasing the availability of arginine. A cDNA for human arginase II, an arginase isozyme, was isolated. A polypeptide of 354 amino acid residues including the putative NH2-terminal presequence for mitochondrial import was predicted. It was 59% identical with arginase I. mRNA for human arginase II was present in the kidney and other tissues but was not detected in the liver. Arginase II mRNA was co-induced with iNOS mRNA in murine macrophage-like RAW 264.7 cells by LPS. This induction was enhanced by dexamethasone and dibutyrul cAMP, and was prevented by interferon-gamma. These results indicate that NO synthesis is regulated by arginine-synthesizing and -degrading enzymes in a complicated manner.

Amino Acid Sequence↗
PubMed1998

The C/EBP family of transcription factors in the liver and other organs.

Members of the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors are pivotal regulators of liver functions such as nutrient metabolism and its control by hormones, acute-phase response and liver regeneration. Recent progress in clarification of regulatory mechanisms for the C/EBP family members gives insight into understanding the liver functions at the molecular level.

Animals↗
PubMed1998

Ultrasonographic and serologic studies of experimental cysticercosis in rats infected with Taenia taeniaeformis.

Rats experimentally infected with Taenia taeniaeformis were followed-up until 14 weeks post inoculation with eggs (PIE) by hepatic ultrasonographic (US) image and serum antibody response analyses. Parasitic cysts could be imaged as small (2 mm in diameter) anechoic areas with or without a parenthesis-like echogenic small line from two weeks PIE. Immunoblot analysis using antigens from oncospheres (TtO), 30-day-old (TtM-30) and 300-day-old metacestodes (TtM-300) revealed that: (1) these three different developmental stages showed their own unique patterns suggesting the presence of stage-specific antigens; (2) faint IgM antibody responses to some components of TtO and TtM-30 or TtM-300 could be detected from one and two weeks PIE, respectively, and (3) IgG responses to some major components of both TtO and TtM-300, and TtM-30 were easily detected from four and five weeks PIE onwards, respectively. Both TtO and TtM (especially TtM-300) appeared to be highly useful for detection of antibody responses in experimentally infected rats. Due to the easiness in preparation of antigens, fully developed metacestodes may be the best candidate antigens for serodiagnosis. These results strongly suggest that both US image and antibody analyses using antigens from fully developed metacestodes are useful for detection of the early stage of cysticercosis in laboratory animal model.

Animals↗
PubMed1998

Comparison of attenuation and liver-kidney contrast of liver ultrasonographs with histology and biochemistry in dogs with experimentally induced steroid hepatopathy.

Digital analysis of liver ultrasound images (USGs) was compared to histological and serum enzyme activity results in dogs with steroid-induced hepatopathy. Steroid hepatopathy was used as a model for diffuse liver diseases. Prednisolone administration resulted in increased acoustic backscatter (hyperechogenicity) of the liver with reference to the kidney and significant depth attenuation (hyper-attenuation). Absolute changes were determined by histogram analysis of echo means (Ems) of area samples (1 x 1 cm) of liver and kidney at the depth of 2 cm (liver-kidney contrast) and at 2 cms and 4 cm (depth attenuation). Liver-kidney contrast histograms correlated well with histology but were more sensitive than serum enzyme activity and subjective visual interpretation. Depth attenuation was the earliest detectable acoustic change. These results suggested that depth attenuation is an early and sensitive indicator of steroid hepatopathy. Liver-kidney contrast correlates well with histology and may complement biopsy examination during follow-up studies.

Alanine Transaminase↗
PubMed1998

Endoscopic and transcutaneous ultrasonographic findings and grey-scale histogram analysis in dogs with caerulein-induced pancreatitis.

Endoscopic ultrasonography (EUS), grey-scale histogram analysis of EUS images, and transcutaneous ultrasonography (TUS) were done in four dogs with caerulein-induced pancreatitis. One other dog was subjected to laparotomy and biopsy specimens were collected for histopathology. By EUS, the pancreatic lesions were first detected at 60 minutes after the start of caerulein infusion. They were detected after 120 to 150 minutes when using TUS. EUS findings included swelling, a more distinct lobular pattern, subcapsular hypoechoic areas, and anechoic stripes through the pancreatic tissue. No marked changes in the histogram analysis was seen until 30 minutes. From 30 to 60 minutes, a decrease in the mean brightness of the pancreatic tissue was observed. These changes in mean brightness reflected histopathological findings showing vacuolization of acinar cells and interstitial oedema of the pancreas. These findings indicated that EUS can detect slight and diffuse changes in pancreatic tissue. Furthermore, grey-scale histogram analysis detects histopathological changes more sensitively than endoscopic ultrasound images.

Animals↗
PubMed1998

Fas-independent apoptosis of T cells via killer cell inhibitory receptors.

Killer cell inhibitory receptor (KIR) is expressed on NK cells and T cells, and negatively regulates the recognition of these cells via its binding to HLA class I molecules. Here we show the evidence that KIR is involved in apoptosis of T cells. The triggering of NKB1 molecules using DX9 anti-NKB1 mAb induced apoptosis of the cytotoxic T lymphocyte (CTL) clone expressing NKB1. Moreover, the cross-linking of NKB1 molecules together with CD3 molecules enhanced the apoptosis. The CTL clone carries Fas molecules, but failed to express Fas ligand (FasL) even after the cross-linking of both NKB1 and CD3 molecules. The apoptosis of the CTL clone induced by the cross-linking of both NKB1 and CD3 molecules was inhibited by IL-1beta-converting enzyme (ICE) inhibitor. These results together indicate that the apoptosis of CTL induced by the triggering of NKB1 molecules is not Fas-mediated but is linked to other signaling pathways using the ICE-like protease cascade.

Animals↗