Biomedical subjects

K Sakaguchi

Publications and source records attributed to K Sakaguchi.

At least 235 records · Page 13Linked to original sources

PubMed1994

Specificities and clinical significance of anti-cytoskeleton antibodies in anti-smooth muscle antibody-positive patients with chronic liver disease C.

We investigated the specificities and characteristics of anti-cytoskeleton antibodies in 13 anti-smooth muscle antibody (ASMA)-positive patients with chronic liver disease C (CLD-C), and compared them with those in 7 ASMA-positive patients with autoimmune hepatitis (AIH), and 6 ASMA-positive patients with chronic liver disease B (CLD-B). Anti-microfilaments (anti-MF) were found not only in 6/7 AIH patients (85.7%), but also in 8/13 CLD-C patients (61.5%) with a relatively high incidence, when compared with 1/6 CLD-B patients (16.7%), while, there was no significant difference in the incidence of anti-intermediate filaments (anti-IMF), especially anti-IMF IgM, among these patient groups. Among the patients with CLD-C, the mean levels of serum gammaglobulin and IgG in the anti-MF-positive patients were 2.46 +/- 1.03 g/dl and 3277 +/- 1089 mg/dl, respectively, which were higher than those in the anti-MF-negative patients (1.60 +/- 0.53 g/dl, 2245 +/- 610 mg/dl) and those in the patients with CLD-B (1.60 +/- 0.57 g/dl, 2192 +/- 339 mg/dl). Furthermore, 4 of the 8 anti-MF-positive patients with CLD-C satisfied the serological criteria for the diagnosis of AIH. These findings suggest that autoimmune mechanisms might be involved in the pathogenesis of anti-MF-positive CLD-C, and that anti-MF might be used as a marker.

Adult↗

PubMed1994

Effect of neo red cells on hemodynamics and blood gas transport in canine hemorrhagic shock and its safety for vital organs.

The purpose of this study was to evaluate the effects of liposome encapsulated hemoglobin named "Neo Red Cells (NRC)" on canine hemorrhagic shock model and its safety for the vital organs in a whole blood exchange model. HEMORRHAGIC SHOCK: Nine adult mongrel dogs were used. Under mechanical ventilation inhaling room air, blood was withdrawn via an artery at a rate of 40 ml/min in order to induce hemorrhagic shock (systolic pressure below 60 mm Hg) and then NRC was transfused. For each animal, three to five cycles of bloodletting and NRC transfusion were performed. After blood exchange, total peripheral resistance index (TPRI) decreased and cardiac index (CI) increased. These changes were more marked in the high exchange group (exchange rate over 88%; five animals) than in the low exchange group (less than 88%; four animals), indicating that the low viscosity NRC reduced the load on the circulatory system. The A-V difference in oxygen content per lg hemoglobin was greater after blood exchange, indicating that oxygen binding capacity of NRC is higher than that of red blood cells. WHOLE BLOOD EXCHANGE: Five beagles were used for the blood exchange. The blood was withdrawn from an artery at a rate of 15 ml/min and NRC was infused at the same time. A dog whose blood was exchanged with hydroxyethylstarch instead of NRC died within 15 hours after blood exchange. Three dogs whose blood was exchanged with NRC (exchange rate was from 82 to 90%) have been living over a year without any side effects. A dog sacrificed on the 15th postoperative day for autopsy, microscopically showed no side effects in vital organs. We conclude that NRC is more suitable than natural blood for treatment of hemorrhagic shock and safe for vital organs.

Animals↗

PubMed1994

Characteristics of neo red cells, their function and safety: in vivo studies.

A new type of artificial oxygen carriers, the Neo Red Cells (NRCs) have been developed and investigated for oxygen transporting efficiency and safety in experimental animals. Stroma free hemoglobin from outdated human red blood cells together with inositol hexaphosphate as an allosteric effector under sterile, pyrogen free condition were encapsulated in liposomes and then were coated with polyethylene glycol bond to hydrogenated soy phosphatidylethanolamine as a surface modifier to prevent aggregation of NRCs in plasma. The efficiency of the NRCs in tissue oxygenation was studied in rabbits which were made severely anemic by drawing 85% of their blood and immediately replacing it with NRC solution. The animals, all recovered to pre-anemic conditions within 6-8 hr and lived normally until being sacrificed, 6 months after the exchange transfusion. The circulation half-life and tissue distribution of NRCs were studied using radiolabeled NRCs. Within the circulation, the half-life of NRCs was 21 hr and extravascularly, they were distributed mainly in and metabolized by the reticuloendothelial system within 7 days. Our observations suggest that the NRCs prepared and investigated in this study are efficient oxygen carriers without causing serious adverse reactions and can be prepared free from pathogenic micro-organisms by special filtration technique before encapsulation of Hb. Currently, experiments are ongoing to control auto-oxidation of oxyHb to metHb which is higher in NRCs than in native red cells at physiological conditions.

Animals↗

PubMed1994

[Torsion of a seminoma in an intrascrotal testis. A case report].

We report a case of torsion of an intrascrotal testicular tumor. The patient was a 54-year-old man with a chief complaint of swelling and pain in the left scrotum. A testicular scan using 99mtechnetium RBC demonstrated a large cold area of isotope uptake showing loss of blood flow in his left scrotal content. Pre operative diagnosis was acute testicular torsion. A torsed testicle was delivered through an inguinal incision. The testicle appeared to be twisted 720 degrees clock wise. It was swollen and bluish in color. The blood flow did not recover after the relief of twisting. Radical orchiectomy was performed. The histology demonstrated a seminoma. He was free of disease 4 years after surgery. A torsion of testicular tumor in an undescended testis has been reported sporadically. However, the torsion of the intrascrotal testicular tumor is very rare. There have been 5 reported cases in the world literature and this case seems to be the first one in Japan.

Humans↗

PubMed1994

[A case of simultaneous bilateral spontaneous pneumothorax].

We present a case of simultaneous bilateral pneumothorax. The patient did not have any symptom and the pneumothorax was detected by health care examination. He was introduced to our hospital and two thoracic drains were inserted into both intrathoracic space as soon as possible. Four days after he was performed a bilateral partial resection of the lung through a bilateral axillary incision. Postoperative course was excellent with almost no pain. The thoracic drains were removed on second postoperative day and the patient discharged on ninth postoperative day.

Adolescent↗

PubMed1993

Direct identification of an endogenous peptide recognized by multiple HLA-A2.1-specific cytotoxic T cells.

An endogenous peptide recognized by a murine T-cell clone specific for the human class I major histocompatibility complex-encoded molecule HLA-A2.1 was identified through the use of microcapillary high-performance liquid chromatography coupled with electrospray-ionization tandem mass spectrometry. The peptide was associated with HLA-A2.1 on both normal cells and the antigen-processing-mutant cell line T2. This observation demonstrates that a processing mechanism other than that involving the transporter associated with antigen processing (TAP) proteins 1 and 2 can produce peptides that can be recognized by T cells. The peptide was also recognized by four other independently derived murine HLA-A2.1-specific murine T-cell clones. This suggests that xenogeneic responses are directed at a restricted subset of major histocompatibility complex product-associated peptides. Finally, quantitation of this peptide in cell extracts using mass spectrometry showed it to be among the most dominant HLA-A2.1 associated species on human lymphoid cells. The potential relevance of this observation to models of alloreactivity will be discussed. The methodology described should be generally useful for the identification of peptide epitopes recognized by alloreactive, tumor-specific, and autoimmune T cells.

Amino Acid Sequence↗

PubMed1993

Characteristics of endogenous peptides eluted from the class I MHC molecule HLA-B7 determined by mass spectrometry and computer modeling.

Microcapillary HPLC electrospray ionization tandem mass spectrometry was used to sequence 15 peptides eluted from HLA-B7. Sequence alignment implicated four peptide positions in specific interactions with the class I molecule, and their importance was confirmed using synthetic peptides. Because no crystal structure for HLA-B7 was available, computer-assisted modeling was used to understand novel aspects of peptide binding specificity and to accurately predict the effect of defined changes in peptide structure. The results demonstrate that mass-spectrometric sequencing coupled with computer-assisted modeling can be used in the absence of a crystal structure to make accurate predictions concerning requirements for peptide binding to class I molecules. These techniques may be valuable to predict or engineer T cell epitopes.

Amino Acid Sequence↗

PubMed1993

Two-dimensional nuclear magnetic resonance analysis of a labeled peptide bound to a class II major histocompatibility complex molecule.

The formation of peptide/major histocompatibility complex (MHC) complexes and their subsequent recognition by T cells is a pivotal event in the initiation of an immune response. While X-ray crystal structures are now available for class I MHC/peptide complexes, little detailed structural information is known about the class II MHC equivalent, and there are no solution structure data for either. A 16 amino acid residue moth cytochrome c peptide (residues 88 to 103) was 13C-labeled for two-dimensional isotope-edited NMR analysis. The peptide was labeled either selectively in the methyl groups of alanine residues or uniformly at every carbon position, and bound to unlabeled soluble mouse I-Ek class II MHC molecules. Although alpha-helical in the native cytochrome c protein and with no uniform structure in solution, the peptide is bound to the I-Ek molecule with the alpha-carbon atoms of the 11 C-terminal residues held in the binding groove. This indicates that the class II MHC peptide binding site is somewhat larger than that of class I MHC molecules (> or = 11 amino acid residues versus 8 to 10 amino acid residues), consistent with recent data on eluted peptides. Despite the large size of the complex (approximately 70 kDa), nuclear Overhauser effects are clearly detectable between peptide side-chains and the MHC molecule. Indications of the buried or exposed nature of particular side-chains within the bound peptide are derived from the NMR data and these are used together with information from previous biological studies to propose a crude model of the interaction of the peptide with the groove of the MHC molecule. We find no evidence for a conformational change in the peptide/MHC complex in the spectra at pH 5.0 versus pH 7.0, despite a 40-fold faster on-rate for the peptide at the lower pH value.

Amino Acid Sequence↗

PubMed1993

Phosphorylation at Ser-15 and Ser-392 in mutant p53 molecules from human tumors is altered compared to wild-type p53.

The product of the p53 gene suppresses cell growth and plays a critical role in suppressing development of human tumors. p53 protein binds DNA, activates transcription, and can be phosphorylated at N- and C-terminal sites. Previously, wild-type p53 was shown to be hyperphosphorylated compared to mutant p53 during p53-mediated growth arrest in vivo. Here we show that Ser-15 and Ser-9 in the N-terminal transactivation domain of wild-type human p53 are phosphorylated in vivo in cells derived from the human glioblastoma line T98G. In [Ile237]p53 and [Ala143]p53, two natural p53 mutants from human tumors that are defective for activation of transcription, phosphorylation at Ser-15 was reduced and phosphorylation at Ser-392 was increased compared to wild-type p53. No change was observed at Ser-9. [His273]p53, a third mutant, had a phosphorylation state similar to that of wild-type p53. We suggest that phosphorylation of Ser-15 may depend on the ability of p53 to adopt a wild-type conformation and may contribute to p53's ability to block cell growth.

Amino Acid Sequence↗

PubMed1993

Identification of a binding site for the human immunodeficiency virus type 1 nucleocapsid protein.

The nucleocapsid (NC) protein NCp7 of human immunodeficiency virus type 1 (HIV-1) is important for encapsidation of the virus genome, RNA dimerization, and primer tRNA annealing in vitro. Here we present evidence from gel mobility-shift experiments indicating that NCp7 binds specifically to an RNA sequence. Two complexes were identified in native gels. The more slowly migrating complex contained two RNA molecules and one peptide, while the more rapidly migrating one is composed of one RNA and one peptide. Further, mutational analysis of the RNA shows that the predicted stem and loop structure of stem-loop 1 plays a critical role. Our results show that NCp7 binds to a unique RNA structure within the psi region; in addition, this structure is necessary for RNA dimerization. We propose that NCp7 binds to the RNA via a direct interaction of one zinc-binding motif to stem-loop 1 followed by binding of the other zinc-binding motif to stem-loop 1, stem-loop 2, or the linker region of the second RNA molecule, forming a bridge between the two RNAs.

Base Sequence↗

PubMed1993

Sequence of a cDNA encoding bovine apolipoprotein H.

The nucleotide sequence of the ApoH cDNA encoding the bovine apolipoprotein H (ApoH) has been determined. The deduced protein, which contains a 19-amino-acid (aa) signal peptide and the 326-aa mature ApoH, shows 89% and 86% homology with human and rat ApoH, respectively.

Amino Acid Sequence↗

PubMed1993

The high-resolution structure of the peripheral subunit-binding domain of dihydrolipoamide acetyltransferase from the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus.

The three-dimensional structure of a 43-residue active, synthetic peptide encompassing the peripheral subunit-binding domain of dihydrolipoamide acetyltransferase from the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus has been determined by means of a multi-cooling dynamical simulated annealing protocol using restraints derived from 1H nuclear magnetic resonance spectroscopy. A total of 442 experimentally derived restraints including 13 dihedral angle (phi, chi 1) restraints were used. A final set of 35 structures was calculated with a root-mean-square deviation from the mean co-ordinates of 0.36 A for the backbone atoms and 0.96 A when side-chain heavy atoms were included for the well-defined region comprising residues Val7 to Leu39. Although assignments were made and sequential connectivities observed for the N-terminal six and C-terminal four residues, the absence of long-range NOEs suggests that the terminal regions are largely unstructured. The binding domain contains two short parallel alpha-helices (residues Val7 to Lys14 and Lys32 to Leu39), a3(10)-helix (residues Asp17 to Val21) and a structured loop made up of overlapping beta-turns (residues Gln22 to Leu31), which enclose a close-packed hydrophobic core. The loop is stabilized to a large extent by Asp34. This residue is conserved in all peripheral subunit-binding domains and its carboxylate side-chain forms a set of side-chain-main-chain hydrogen bonds with the main-chain amide protons of Gly23, Thr24, Gly25 and Leu31 and a side-chain-side-chain hydrogen bond with the hydroxyl group of Thr24. We propose that a peripheral subunit-binding site may be located in the loop region, which contains a series of highly conserved residues and provides a number of potential recognition sites. The structured region of the binding domain, comprising 33 residues, represents an exceptionally short amino acid sequence with defined tertiary structure that has no disulphide bond, ligand or cofactor to stabilize the fold. It may be approaching the lower size limit for a three-dimensional structure possessing features characteristic of larger structures, including a close-packed, non-polar interior. The organization of the side-chains in the hydrophobic core may have implications for de novo protein design.

Acetyltransferases↗

PubMed1993

Antibodies to macrophage stimulating protein (MSP): specificity, epitope interactions, and immunoassay of MSP in human serum.

Macrophage stimulating protein (MSP) is a member of a family of proteins characterized by a triple disulfide loop structure (kringle). We developed antibodies to human MSP for detection in Western blots, quantification in biological fluids, and neutralization of activity. Immunogens included native MSP, reduced and alkylated alpha and beta chains, and peptides of MSP regions with minimal sequence similarity to other kringle proteins. We found three antibody categories based on interaction with the following types of epitope: primary sequence, discontinuous (dependent on disulfide bonds), and cryptic (not exposed in native MSP). None of the antibodies reacted with related kringle proteins. A specific sandwich ELISA was developed for measuring human MSP. The mean serum concentration was 4 nM. Serum MSP did not increase over a 24-h period in response to intravenous lipopolysaccharide, indicating that MSP is not an acute phase protein. These findings are consistent with the hypothesis that regulation of MSP activity is by conversion of pro-MSP to MSP rather than by rapid changes in rates of synthesis.

Amino Acid Sequence↗

PubMed1993

A meiotic DNA polymerase from Coprinus cinereus: further purification and characterization.

A meiotic DNA polymerase that is present at a high level of activity in meiotic cells of a basidiomycete, Coprinus cinereus, was purified to near homogeneity using synthetic RNA homopolymer [poly(C)] cellulose column chromatography. This report presents the first extensive purification and characterization of any eukaryotic DNA polymerase having a role in meiosis. This enzyme is a single polypeptide with a molecular mass of 65,000. Activity in this enzyme requires magnesium ions and occurs at an optimal pH of 7.5. It is strongly inhibited by dideoxythymidine triphosphate but is relatively insensitive to aphidicolin and N-ethylmaleimide and can use poly(C)/oligo(dG)12-18 as a template-primer. Polymerase activity can be found only in cells at meiotic prophase, even though the enzyme has been identified in somatic cells in an inactive state using immunoblot analysis. Its distinctive distribution makes possible a genetic and biochemical analysis of functional role of a meiotic DNA polymerase in meiotic recombination, repair and synthesis.

Aphidicolin↗

PubMed1993

Emergency coronary angioplasty for acute myocardial infarction: predictors of early occlusion of the infarct-related artery after balloon inflation.

THE FACTORS RESPONSIBLE FOR EARLY OCCLUSION OF THE INFARCT VESSEL AFTER emergency percutaneous transluminal coronary angioplasty (PTCA) were retrospectively examined in 191 patients with acute myocardial infarction. During the 24-hour period after the initial balloon inflation, 47 patients (25%) had occlusion of the vessel (occlusion group), whereas 144 did not (nonocclusion group). The former patients immediately underwent repeat PTCA, which was successful in 37. Univariate correlates of early occlusion were a shorter time interval between the onset of symptoms and PTCA (3.5 +/- 2.2 vs 4.5 +/- 2.9 hours, p = 0.025), right coronary artery involvement (53% vs 30%, p = 0.015), prior thrombolytic therapy (49% vs 32%, p = 0.035), and undersized inflation (43% vs 17%, p < 0.001). With multivariate analysis the three independent predictors were undersized inflation (p < 0.001), right coronary artery involvement (p = 0.004), and a shorter time interval until PTCA (p = 0.011). Thus patients undergoing early PTCA and having right coronary artery involvement appear to be at greater risk of having early occlusion. Thrombolytic agents and undersized inflation may also play an important role in its development.

Aged↗

PubMed1993

Anti-platelet and anti-thrombotic effects of OP-41483.alpha-CD, a prostacyclin analogue, in experimental animals.

The effects of OP-41483.alpha-CD, 5(E)-6,9-deoxa-6,9 alpha-methylene-15-cyclopentyl-16,17,18,19,20-pentanor prostacyclin (PGI2).alpha-cyclodextrin clathrate, on platelet function and experimental thrombosis were studied. In human platelets, OP-41483 inhibited aggregation induced by adenosine diphosphate (ADP) or collagen, promoted disaggregation, and elevated cyclic adenosine monophosphate (cAMP) levels in vitro at the same order of concentrations. The equipotent antiaggregatory activity of OP-41483 to human platelets was observed in monkey platelets in vitro. Furthermore, intravenous administration of OP-41483 to monkeys, unlike PGI2, showed the antiaggregatory effect on platelets but with less effect on blood pressure, suggesting that a differential sensitivity to OP-41483 between platelet function and vascular tone exists in monkeys. In rabbits, OP-41483.alpha-CD attenuated platelet aggregation induced by ADP, collagen and platelet activating factor (PAF), decreased circulating platelet aggregates, and inhibited platelet adhesiveness to de-endothelialized blood vessels. These results suggest that the anti-thrombotic effects of OP-41483 are associated with its potent antiplatelet activities mainly because of the elevation of cAMP levels in the platelets. The potent anti-thrombotic and less hypotensive effects of this compound may be useful for various thrombotic disorders.

Adenosine Diphosphate↗

PubMed1993

Serial changes in renal function during laparoscopic cholecystectomy.

Intraoperative serial changes in systemic hemodynamic parameters and in the results of renal function tests were studied in 7 patients who underwent laparoscopic cholecystectomy (LAP) in which intra-abdominal pressure was maintained at 12 mm Hg, and in 7 patients who underwent minilaparotomy cholecystectomy (MINI). No significant changes were observed in the parameters in the MINI group during the operation. However, urine output, effective renal plasma flow and glomerular filtration rate in the LAP group were decreased 60 min after initiation of pneumoperitoneum.

Adult↗

PubMed1993

Autoimmune responses as assessed by hypergammaglobulinemia and the presence of autoantibodies in patients with chronic hepatitis C.

We investigated autoimmunity, as assessed by hypergammaglobulinemia and the presence of autoantibodies including anti-nuclear antibodies (ANA) and anti-liver membrane antibodies (LMA), in 149 patients with chronic hepatitis C, 55 patients with chronic hepatitis B and 11 patients with autoimmune hepatitis. There was no significant difference in the incidence of these autoantibodies between chronic hepatitis C and chronic hepatitis B. Nine patients with chronic hepatitis C satisfied the serological criteria of autoimmune hepatitis (ANA positive and gammaglobulin or serum IgG greater than 2500 mg/dl), but none of the patients with chronic hepatitis B met the criteria. This suggests that autoimmunity is greater in chronic hepatitis C than in chronic hepatitis B. Of the 9 patients with chronic hepatitis C, all 4 patients tested for human leukocyte antigen (HLA) phenotype had HLA-DR4, which is known to be associated with autoimmune hepatitis in Japanese patients. We believe that hepatitis C virus (HCV) infection enhances the initiation and perpetuation of autoimmunity in susceptible individuals.

Adult↗