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Biomedical subjects

T Asakura

Publications and source records attributed to T Asakura.

At least 145 records · Page 8Linked to original sources
PubMed1995

Rice aspartic proteinase, oryzasin, expressed during seed ripening and germination, has a gene organization distinct from those of animal and microbial aspartic proteinases.

The gene organization and nucleotide sequence of an aspartic proteinase (AP) of plant origin were first disclosed by cDNA and genomic DNA cloning of a rice AP (oryzasin). The deduced amino acid sequence of oryzasin 1 was significantly similar to those of other APs (34-85%), with highest similarity (85%) to barley AP (HvAP). Oryzasin 1, as well as HvAP, is distinct from animal and microbial APs in that the plant APs contain a unique 104-amino-acid insertion in the C-terminal region. The oryzasin 1 gene spans approximately 6.6 kbp and is composed of 14 exons and 13 introns. The exon-intron organization of the oryzasin 1 gene is totally different from those of genes for animal and microbial APs such as human cathepsin D, rat renin, bovine chymosin, aspergillopepsin A of Aspergillus awamori, proteinase A of Saccharomyces cerevisiae and rhizopuspepsin of Rhizopus niveus, despite the fact that oryzasin 1 shows overall sequence similarity to these APs.

Amino Acid Sequence↗
PubMed1995

Application of 1H NMR chemical shifts to measure the quality of protein structures.

We have developed a program that can calculate proton NMR chemical shifts for proteins, using a set of co-ordinates provided for example from an X-ray or NMR structure. When applied to NMR structures, agreement between calculated and observed shifts is generally of the same quality as that for crystal structures of resolution between 2.0 and 3.0 A. There is a rather weak correlation between standard deviation (SD) and the number of NMR constraints per residue, but none with the root-mean-square deviation of one NMR structure from another. Where minimised averaged structures are present, they have about the same SD as the population from which they were taken. Refinement methods such as energy minimisation and the use of relaxation matrices and back calculation produce little or no improvement in SD. The calculation has several applications, particularly as an independent means of measuring the quality of a structure (either in the crystal or in solution), and in identifying possible assignment errors.

Crystallography, X-Ray↗
PubMed1995

Effects of a structural change in collagen upon binding to conditioned dentin studied by 13C NMR.

To develop a better adhesive functional monomer, it is imperative to understand the adhesion mechanisms of the resin to the dentin surface. Bond strength to the decalcified dentin surface pretreated with dentin primer, an aqueous ethanol solution of N-methacryloyl glycine, increases by increasing the water content in the primer. The aqueous primer could increase the thickness of the hybrid layer. The structural change of dentinal collagen with NM alpha A was studied by using a model compound for collagen,--(1Pro-2Pro-3Gly)10--, by 13C nuclear magnetic resonance (NMR). The model compound was aggregated in ethanol but dissociated in water. It was found that NM alpha A effectively dissociated the aggregated model compound in water. The dissociation of decalcified dentin was essential to create a thick hybrid layer that could afford a higher bond strength to dentin.

Adhesiveness↗
PubMed1995

Left atrial function after Cox's maze operation concomitant with mitral valve operation.

BACKGROUND: This study examined whether the atrial fibrillation that commonly occurs in patients with a mitral valve operation could be eliminated by a concomitant maze operation. METHODS: Left atrial function after Cox's maze operation performed concomitantly with a mitral valve operation was evaluated in 10 patients ranging in age from 38 to 67 years (mean age, 54 years). Seven patients who had had coronary artery bypass grafting served as the control group. Using transthoracic echocardiography, the ratio between the peak speed of the early filling wave and that of the atrial contraction wave (A/E ratio) and the atrial filling fraction (AFF) were determined from transmitral flow measurements. These two indices have been considered to represent the contribution of left atrial active contraction to ventricular filling. RESULTS: The A/E ratio and the AFF were significantly lower in the maze group (0.35 +/- 0.17 versus 0.97 +/- 0.28 [p < 0.01] and 17.6% +/- 8.8% versus 36.8% +/- 6.4% [p < 0.01], respectively). The A/E ratio and the AFF correlated inversely with age (r = -0.72, p < 0.05 and r = 0.76, p < 0.05, respectively) in the maze group. In an angiographic study, the mean left atrial maximal volume index in the maze group was approximately three times larger than that in the control group (117.5 +/- 24.3 mL/m2 versus 35.3 +/- 6.6 mL/m2 [p < 0.01]). The left atrial active emptying volume index was significantly smaller in patients in the maze group (7.2 +/- 2.5 mL/m2 versus 13.1 +/- 4.6 mL/m2 [p < 0.01]). CONCLUSIONS: After the maze procedure performed concomitantly with a mitral valve operation in patients with a dilated left atrium, left atrial contraction is detectable but incomplete in the elderly.

Adult↗
PubMed1995

Evidence for the occurrence of multiple aspartic proteinases in rice seeds.

Using reverse transcription polymerase chain reaction (RT-PCR), we identified two cDNA fragments encoding aspartic proteinases (APs). The encoded proteins, pL4 and pL5, are similar in sequence to other plant APs including barley AP and cardoon flower AP (cyprosin). The identity was 58-76% with one another. Genomic Southern blot analysis suggested that the rice AP gene constitutes a multigene family.

Amino Acid Sequence↗
PubMed1995

Effects of chronic iron deficiency anemia on brain metabolism.

The effects of chronic iron deficiency anemia on brain (cortex) metabolism were estimated by 31P-nuclear magnetic resonance spectroscopy and biochemical analyses in male Wistar rats. Iron deficiency anemia was induced by supplying diet containing either approximately 2 or approximately 6 ppm Fe. Control diet was supplemented with 100 ppm Fe as ferric citrate. After 8-9 weeks, blood hemoglobin levels were approximately 13, 5, and 3 g/100 ml in the 100 ppm, 6 ppm, and 2 ppm Fe group, respectively. The blood lactate levels at rest in these groups were approximately 3, 5, and 6 mM. The blood glucose concentration also tended to be elevated in iron-deficient rats. The high-energy phosphate contents in brain were not affected by iron deficiency. The activities of succinate dehydrogenase and cytochrome oxidase per unit protein in the 2 ppm Fe group were significantly less than in the 100 ppm Fe group, but those activities were not significantly affected by feeding diet with 6 ppm Fe. The activities of lactate dehydrogenase in iron-deficient group tended to be elevated but not significantly. The activities of non-iron containing mitochondrial enzymes, citrate synthase and beta-hydroxyacyl CoA dehydrogenase, were unchanged. It is suggested that the brain has a higher tolerance to iron deficiency than skeletal muscle in terms of the metabolic characteristics, although this may be associated with a lower level of neural activity.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1995

Changes of contractile properties of extensor digitorum longus in response to creatine-analogue administration and/or hindlimb suspension in rats.

Changes of contractile properties of extensor digitorum longus in response to hindlimb suspension and/or altered high-energy phosphate contents were studied in rats. A reduction of high-energy phosphates, especially phosphocreatine, was seen in rats fed creatine analogue beta-guanidinopropionic acid (beta-GPA), but they were elevated after 10-d supplementation of creatine. The one-half relaxation time was increased by feeding beta-GPA, but was normalized by creatine supply. The fatigue resistance of creatine-depleted muscle was significantly improved, but tended to decrease by suspension and creatine supply, although it was still better than that in the control diet group. It is indicated that the contractile properties of muscle are influenced by the high-energy phosphate content. It is also suggested that the endurance capacity may be influenced by the mitochondrial respiratory capacity, but not necessarily by the levels of high-energy phosphates.

Animals↗
PubMed1995

Functional magnetic resonance imaging of the human motor cortex.

Functional magnetic resonance (MR) imaging of the brain was performed during motor task activation in five normal subjects and a patient with meningioma using conventional fast low-angle shot sequences and a 2.0 T system. A high intensity area in the motor cortex was observed in all normal subjects. Single-slice studies showed the right-sided finger task produced an increase of 1.9-23.5% (6.67 +/- 4.36%) in the signal intensity of the left motor cortex, while the left-sided finger task increased the signal by 1.5-18.2% (6.09 +/- 3.34%) in the right motor cortex. There was no significant difference between the sides. Multiple-slice studies also showed the activated motor cortex as a high intensity area. The maximum signal intensity increase in the activated motor area was 11.0% for the left motor cortex and 8.8% for the right motor cortex. There was no significant difference between the sides. Preoperative mapping of the patient with meningioma showed that the motor cortex was displaced posteriorly by the tumor. Functional MR imaging is possible with a standard MR imaging system and conventional gradient echo sequences. Useful clinical information can be obtained by preoperative mapping of the motor cortex.

Afferent Pathways↗
PubMed1995

Aneurysm of the distal anterior inferior cerebellar artery--case report.

A 38-year-old female presented with vertigo, right hearing disturbance, and slight headache which were treated medically. However, she suddenly developed severe headache with vomiting and vertigo. Computed tomography revealed subarachnoid hemorrhage, and right vertebral angiography disclosed a rare aneurysm at the distal portion of the anterior inferior cerebellar artery. She underwent a right suboccipital craniectomy in the lateral position. The aneurysm could not be clipped because the aneurysm was tightly adhered to the brainstem, so it was trapped. Postoperatively, she showed slight VIIIth to Xth cranial nerve disturbances. Three months postoperatively, the IXth and Xth cranial nerve disturbances had disappeared, but the tinnitus and right hearing disturbance were still present. The initial symptoms were probably caused by minor bleeding from the aneurysm.

Adult↗
PubMed1995

[Ventilatory insufficiency due to upper cervical injury treated by diaphragm pacing: a case report].

A 33-year-old man suffered chronic ventilatory insufficiency with tetraplegia after an operation for atlantoaxial dislocation. He was alert and his tetraplegia gradually improved. However, continuous mechanical ventilation was necessary for him. Thirteen months after the operation, a diaphragm pacer (Avery Laboratory Inc.) was implanted on the right phrenic nerve in the cervical region. Nineteen days after the implantation of the right side pacer, a left side diaphragm pacer was also implanted. Diaphragm pacing was started two weeks after the second implantation. The pacing period was gradually prolonged and continuous pacing for 9 hours by the right side pacer and three hours by the left side pacer was able to be obtained. One year after implantation, twelve continuous hours of diaphragm pacing became possible. During diaphragm pacing, blood gas analysis was satisfactory and the patient could move sitting on a wheel chair, watch television and write letters using a word processor. We were unable to achieve total ventilatory support for him using these diaphragm pacers. We thought that the main cause of our partial failure originated from the procedure used in implanting the electrode onto the phrenic nerve. Left side pacing needs higher amplitude than that used on the right side to obtain sufficient tidal volume. The patient refused our continuing the left side pacing because of pain around the anterior chest and shoulder. Another problem to be watched is diaphragm fatigue. However, diaphragm pacing has been continued for six years and it has been useful in improving his quality of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Local chemotherapy for malignant brain tumors using methotrexate-containing fibrin glue].

Fibrin glue (FG) is an agent developed for achieving hemostasis and the adhesion of living tissue during surgical operations. Incorporation of a drug into FG may be expected to have a sustained local release. In the present study, methotrexate (MTX) included in FG (FG-MTX) was used. The release of MTX into human plasma and cerebrospinal fluid was studied by in vitro study to confirm the sustained release effect of this preparation, by in vivo study, in which the antitumor effect of FG-MTX was assessed in rats bearing 9L-gliosarcoma subcutaneously; and clinically, FG-MTX therapy was attempted in patients with malignant brain tumors. The in vitro study showed that MTX levels rapidly decreased over 1 to 3 days, but was still detected on days 7 and 14. The results showed the sustained release effect of MTX. The in vivo study showed that in the FG-MTX group, all tumors began to decrease soon after administration and disappeared in four out of five animals (80%) on about day 10. In the clinical study, sustained release for more than one week was found, and tumor decrease occurred in the case of a malignant brain tumor. Thus, FG-MTX appears to provide an effective local chemotherapy.

Animals↗
PubMed1995

Histopathological study on the effect of octreotide.

The present investigation was performed to clarify the mechanism of action of octreotide. On a quantitative study by electron microscopy showed that lysosomes were markedly increased in the patients receiving octreotide. Growth hormone (GH) was shown to be in the secretory granules by the postembedding immunogold technique, but no GH immunostaining was noted of the lysosomes. The present investigation suggests that retention of secretory granules and subsequent lysosomal increase are the mechanism of GH-lowering effect of octreotide.

Adenoma↗
PubMed1994

Partially oxygenated sickled cells: sickle-shaped red cells found in circulating blood of patients with sickle cell disease.

A previously uncharacterized type of sickled cell was found in venous blood of patients with sickle cell disease when blood was collected without exposure to air and fixed immediately with 1% glutaraldehyde solution equilibrated with 5% oxygen. These cells were either elongated, resembling irreversibly sickled cells (ISCs), or nonelongated, with a raisin-like shape. Both types assumed a normal discoidal shape upon full oxygenation. Since these cells exist only under partially oxygenated conditions, they are described as partially oxygenated sickled cells (POSCs). POSCs are morphologically distinct from partially deoxygenated sickled cells formed during deoxygenation by having rounded edges, while the latter have sharp edges. Transmission electron microscopy of POSCs revealed various amounts of misaligned Hb S polymers. Investigations in vitro demonstrated the formation of POSC-like cells by partial oxygenation of deoxygenated cells. Since POSCs contain intracellular fibers and sickle readily upon deoxygenation, they may have clinical and pathological significance.

Anemia, Sickle Cell↗
PubMed1994

Recombinant human hemoglobins designed for gene therapy of sickle cell disease.

Two human hemoglobins designed to inhibit the polymerization of sickle hemoglobin (Hb S; alpha 2 beta S2) have been produced. Mutations that disrupt the ability of Hb S to form polymers were introduced into the normal human beta-globin gene by site-specific mutagenesis. These mutations affect the axial and lateral contacts in the sickle fiber. The recombinant hemoglobin designated anti-sickling hemoglobin 1 (Hb AS1) contains the mutations beta 22 glutamic acid to alanine and beta 80 asparagine to lysine. Hb AS2 has the same beta 22 glutamic acid to alanine mutation combined with beta 87 threonine to glutamine. Human alpha- and beta AS-globin genes were separately fused downstream of beta-globin locus control region sequences and these constructs were coinjected into fertilized mouse eggs. Transgenic mouse lines that synthesize high levels of each anti-sickling hemoglobin were established and anti-sickling hemoglobins were purified from hemolysates and characterized. Both AS hemoglobins bind oxygen cooperatively and the oxygen affinities of these molecules are in the normal range. Delay time experiments demonstrate that Hb AS2 is a potent inhibitor of Hb S polymerization; therefore, locus control region beta AS2-globin gene constructs may be suitable for future gene therapy of sickle cell disease.

2,3-Diphosphoglycerate↗
PubMed1994

Activation energy for permeation of phosphonium cations through phospholipid bilayer membrane.

The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured. Phosphonium cations used were tetraphenylphosphonium (TPP+) and triphenylalkylphosphonium cations formulated as (Phe)3-P(+)-(CH2)nCH3 (n = 0-5). The conductance was dependent on voltage applied externally to the membrane in accordance with a theory developed by previous authors. Using the theory, values of beta K(i) were determined, where beta and k(i) are a linear partition coefficient and a rate constant of transmembrane ion transport, respectively. Since beta k(i) depended on the phosphonium ion concentration, values extrapolated to infinite dilution, (beta k(i))0, were determined. Temperature dependence of (beta k(i))0 allowed us to estimate the activation energy of transport, Ea. For TPP+ thermodynamic values obtained were consistent with values calculated by Flewelling and Hubbell [(1986) Biophys. J. 49, 541-552]. When (Phe)3-P(+)-(CH2)nCH3 (n = 0-5) were used, E(a) depended on the odd or even of n. This "odd and even" pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity in water, and 31P NMR chemical shift.

Biological Transport↗