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Biomedical subjects

A Ikai

Publications and source records attributed to A Ikai.

At least 55 records · Page 3Linked to original sources
PubMed1994

[Extended aortic arch anastomosis for coarctation of the aorta and interruption of the aortic arch in early infancy].

We performed extended aortic arch anastomosis, which was so called EAA procedure, for Coarctation of the Aorta (CoA) with hypoplastic aortic arch (HAA) and interruption of the aortic arch (IAA) in 17 infants under three months of age. The proximal anastomosis site was extended into ascending aorta in order that we could make non-obstructive pathway of systemic flow. During anastomosis, we employed mild systemic hypothermia and topical cooling of head and lumber lesion. Satisfactory anastomoses were performed without any neurological and renal complications except one case. Postoperative Doppler echographic evaluation revealed that the mean peak flow velocities at anastomotic site were under 2.0 m/sec at 1 and 2 years after surgery. We concluded that EAA procedure was useful for CoA with HAA and IAA in early infancy.

Anastomosis, Surgical↗
PubMed1994

[Relief of pulmonary venous obstruction for asplenia syndrome associated with total anomalous pulmonary venous connection in neonates and infants].

Five patients of asplenia syndrome with pulmonary venous obstruction underwent TAPVC repair in the period of neonates (4 patients) and infant (1 patient). They also underwent associated procedures to reconstruct or adjust pulmonary blood flow (systemic-pulmonary shunts in 2, bilateral PDA banding in 1, pulmonary artery banding in 1) in accordance with individual anatomy of the pulmonary arteries. In four of them, they required subsequent surgical procedures for reduction of pulmonary blood flow because of intractable heart failure due to increase in pulmonary blood flow mostly at the early postoperative period. The increasing pulmonary blood flow was successfully controlled by early reduction procedures (1 patient: extrathoracically adjustable PA banding, 1 patient: tightening of shunt graft) in two patients. However, one patient died in the early postoperative period because of moribund preoperative condition. The remaining one patient underwent PA banding three month after the first operation, but died in late period due to heart failure. These results suggest that the adjustment of pulmonary blood flow is critically important for management of the patients of asplenia syndrome with TAPVC after the operation, and early decision of PA band re-adjustment (or other procedures to decrease pulmonary blood flow) is mandatory to improve the results.

Abnormalities, Multiple↗
PubMed1994

[Reoperation after correction of total anomalous pulmonary venous connection: particularly for postoperative pulmonary vein stenosis].

Postoperative pulmonary vein stenosis is a major complication after the correction of the total anomalous pulmonary venous connection. Six patients developed this complication 2 to 3 months after surgery. Five underwent reoperation (3 had the third operations) with only one survivor. Risk factors for developing the stenosis were 1. small common pulmonary vein with small branches occurring in the patients with the ages at the operation below 2 days and accordingly with the infradiaphragmatic connection and 2. Y-shaped common pulmonary vein with the confluence situated far below the left atrium. Turbulence seemed the major cause of the intimal thickening occurring in the common pulmonary vein shortly distant from the orifices of the branches. Typically the anastomotic orifice was not narrowed. Relief of the stenosis was done by the excision of the hypertrophied intimal tissue frequently cutting into the branches. Severe stenosis recurred in 4 patients necessitating another operation in 3 patients which was fatal in two. Prevention is important. Creation of a large anastomosis with the incision not extending into the branches and the use of the absorbable suture materials were effective. In the infradiaphragmatic connection incorporation of the divided stump of the descending vein into the anastomosis and a T-shaped incision of the left atrium were also important.

Constriction, Pathologic↗
PubMed1993

A receptor mediated delivery of an HIV-1 derived peptide vaccine.

One way of obtaining an enhanced production of specific antibodies against given antigens is to maximize the level of antigen presentation through artificially augmented antigen uptake by antigen presenting cells (APCs). In this respect, it has been shown that the receptor mediated endocytosis of antigens can be a very effective way to achieve this purpose. Such a process should also enhance the weak immunogenicity of synthetic peptides produced as artificial vaccines with amino acid sequences resembling those of epitopic sites of pathogens. In this report we used alpha 2-macroglobulin (a2M) which has specific receptors on macrophages (MFs) as a delivery protein and were able to induce high concentrations of antibodies against an HIV-1 derived synthetic peptide in mice. a2M enhanced immunogenicity of the peptide better than Freund's adjuvant did. We should be able to develop effective peptide vaccines by further improving this system.

Animals↗
PubMed1993

Atomic force microscopy of bacteriophage T4 and its tube-baseplate complex.

Bacteriophage T4 was imaged by atomic force microscopy with the finest resolution to date with a clear image of tail fibers of an estimated diameter of 2-3 nm. T4 phages were spread on a clean surface of silicon wafer and dried under air before observation with an atomic force microscope. The head, tail and tail fibers were routinely imaged with somewhat distorted dimensions. The ease of imaging isolated phage particles with a good resolution raised our expectation for the further use of AFM in biomedical applications.

Bacteriophage T4↗
PubMed1993

Direct kinetics of bait region cleavage of alpha-2-macroglobulin by a rapid quenching method.

The rate of bait region cleavage of human alpha-2-macroglobulin by chymotrypsin was determined by a rapid quenching method under conditions where the bimolecular encounter between the two reactants was not rate-limiting. alpha 2M was first mixed with a 30 molar excess of chymotrypsin in a sequential stopped-flow apparatus and after programmed time intervals the activity of chymotrypsin was quenched with 1 N HCl. The fraction of uncleaved subunits was quantitated by SDS-PAGE under reducing conditions. The result indicated that the bait region cleavage proceeded following a two-exponential decay curve with respective rate constants of k1 = 40 s-1 and k2 = 2 s-1.

Binding Sites↗
PubMed1993

A receptor-mediated antigen delivery and incorporation system. Administration of alpha 2-macroglobulin-cytochrome c conjugate induced high concentrations of antibodies against cytochrome c in mice.

Specific receptors for alpha 2-macroglobulin (alpha 2M) are found on the plasma membrane of macrophages (M phi s), one of antigen presenting cells. So far, a receptor-mediated effective uptake by M phi of foreign antigens which were linked to alpha 2M has been shown to provoke a remarkable increase in the proliferation of T lymphocytes and in the production of antibodies in vitro. Such results encouraged us to develop a new type of vaccine using a receptor-mediated antigen delivery and incorporation system based on alpha 2M and its receptor interaction. In this report, we applied the system to experimental animals. Yeast cytochrome c was used as an antigen to see if the system worked in vivo as well as in vitro. Cytochrome c was conjugated to alpha 2M through the action of trypsin and intraperitoneally administered to mice. The titer induced in mice was measured by enzyme linked immunosorbent assay (ELISA). The production of antibodies against cytochrome c was significantly increased when the protein was given in conjugated forms with alpha 2M.

Adjuvants, Immunologic↗
PubMed1993

Isolation and characterization of a novel serine proteinase complexed with alpha 2-macroglobulin from porcine gastric mucosa.

Porcine stomach mucosa was found to contain a 740-kDa protein having endopeptidase activity toward peptide 4-methylcoumaryl-7-amide substrates and low molecular mass peptides. This protein was purified to an apparent homogeneity by a series of chromatographic steps on DEAE-cellulose, Sepharose CL-4B, hydroxylapatite, and fast protein liquid chromatography Mono Q columns. The protein was shown to be a complex of the plasma proteinase inhibitor alpha 2-macroglobulin and a 25-kDa endopeptidase. The enzyme activity was completely inhibited by diisopropyl fluorophosphate, p-amidinophenylmethanesulfonyl fluoride, leupeptin, antipain, bovine pancreatic trypsin inhibitor, soybean trypsin inhibitor, and ovomucoid, indicating that the entrapped enzyme is a serine proteinase. The proteinase could be released from alpha 2-macroglobulin by mild acid treatment and the released enzyme showed activity toward protein substrates. Substrate specificity studies using synthetic and peptide substrates indicated that the enzyme preferentially hydrolyzes Arg-X bonds and, to a much lesser extent, Lys-X bonds, and is apparently distinct from thrombin, kallikrein, plasmin, and other trypsin-like proteinases so far reported including tryptase. Thus, the present enzyme is thought to be a novel type of serine proteinase. The proteinase associated with alpha 2-macroglobulin was also found in porcine intestinal mucosa, but not in plasma.

Amino Acid Sequence↗
PubMed1993

Inhibition of cathepsin E by alpha 2-macroglobulin and the resulting structural changes in the inhibitor.

The activity of cathepsin E (M(r) approximately 80K), a dimeric aspartic proteinase with two active sites per molecule, toward a protein substrate (reduced and carboxymethylated ribonuclease A) was shown to be completely inhibited by alpha 2-macroglobulin (alpha 2M) at pH 5.5. On the other hand, the activity toward a peptide substrate (oxidized insulin B chain) was scarcely inhibited. Under these conditions, cathepsin E cleaved alpha 2M at the Phe684-Tyr685 bond in the bait region sequence, resulting in a drastic conformational change (from a doughnut to an H shape) in the inhibitor as revealed by electron microscopy, and was non-covalently trapped by alpha 2M in an approximate molar ratio (enzyme: alpha 2M) of 2:1.

Amino Acid Sequence↗
PubMed1993

Entrapment and inhibition of human immunodeficiency virus proteinase by alpha 2-macroglobulin and structural changes in the inhibitor.

The inhibitory effect of alpha 2-macroglobulin (alpha 2M), a major plasma proteinase inhibitor, on human immunodeficiency virus (HIV) proteinase was investigated. The activity of HIV proteinase toward the Moloney murine sarcoma virus-derived gag protein (a high-molecular-mass substrate) was found to be inhibited by alpha 2M at pH 5.5-7.4. On the other hand, the activity toward the B chain of oxidized insulin (a low-molecular-mass substrate) was scarcely inhibited. The complex of alpha 2M and HIV proteinase was isolated by gel filtration and the enzyme was shown to be significantly protected by the complex formation from autoinactivation under nonreducing conditions. The stoichiometry of the complex formation was found to be 2:1 (enzyme: alpha 2M, mol/mol). These results demonstrate the entrapment and concomitant inhibition of HIV proteinase by alpha 2M.

Amino Acid Sequence↗
PubMed1993

[Biomacromolecules studied by atomic force microscopy].

Recent studies of biomacromolecules by atomic force microscopy are summarized. The resolution and reproducibility of AFM when applied to soft biosamples has been gradually improved and AFM is now recognized as a most promising technology in nanometer scale observation and manipulation of biological structures.

Animals↗
PubMed1993

Structure and properties of the 26S protease complex from chick skeletal muscle.

The 26S protease complex was purified from chick skeletal muscle and shown to consist of unusually heterogeneous 21-140 kDa polypeptides, including the 21-32 kDa subunits of the 20S proteasome. Electron microscopic analysis revealed that the 26S complex may have a symmetric morphology with two large rectangular terminal domains attached to a thinner central 20S proteasome domain. The 26S complex was capable of degrading the peptide substrates of the 20S proteasome, including Suc-LLVY-AMC, N-Cbz-LLE-NA and N-Cbz-ARR-MNA. The two enzyme complexes showed similar sensitivities to various site-specific protease inhibitors, although their sensitivities to SDS were differed from each other. Immunoprecipitation with anti-26S complex antibody reduced peptide hydrolysis by the 20S proteasome. Similarly, anti-20S proteasome antibody inhibited peptide hydrolysis by the 26S complex. These results demonstrate that the 26S protease complex contains the 20S proteasome as a functional and structural component.

Amino Acid Sequence↗
PubMed1992

The active site titration of proteinases by using alpha 2-macroglobulin and high-performance liquid chromatography.

The active site titration for various proteinases relies on the development of optimal enzyme titrants for each proteinase, but these titrants are only available for a limited number of proteinases. We have described a new active site titration method applicable to various kinds of endoproteinases using small quantities of the enzymes. This method was carried out by using alpha 2-macroglobulin (alpha 2M) as a titrant and a high-performance liquid chromatography (HPLC) system. When the proteinase solution was treated with alpha 2M, the active proteinase was trapped by alpha 2M. In this reaction alpha 2M does not usually complex with inactive proteinase. After the reaction of proteinase with an excess of alpha 2M, the reaction mixture is applied to an HPLC gel column to separate the uncomplexed enzyme from the one complexed with alpha 2M. The active proteinase is complexed and eluted with alpha 2M, but the inactive proteinase is eluted at the original elution volume. The same amount of the enzyme was also applied to the column. From the decrease of the peak height at the elution position of the uncomplexed proteinase, we can estimate the ratio between enzymatically active proteinases and total proteinases. To test the usefulness of this method, we applied this method to chymotrypsin and trypsin whose activities were predetermined by conventional active site titration, and there was good agreement between both results. With this new method, we can estimate a proteinase activity with as little as 200 ng of the enzyme, a very small amount compared with those required in conventional methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗