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Biomedical subjects

M Muraki

Publications and source records attributed to M Muraki.

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

[Evaluation of low-flow sevoflurane anesthesia].

Six of twelve ASA 1 or 2 patients were allocated to the low-flow sevoflurane anesthesia group (LFA) and the other 6 to the high-flow sevoflurane anesthesia group (HFA). Sevoflurane consumption of LFA was 1-7th of that of HFA. Soda lime temperature was maintained below 40.0 degrees C and there was no danger of toxic sevoflurane degradation products. The serum inorganic fluoride concentration increased with the rise in % hours (the amount of inhaled sevoflurane in percent multiplied by the length of time under anesthesia in hours), but did not reach the nephrotoxic level of 50 microM in any patient. We conclude that low-flow sevoflurane anesthesia is a safe and clinically useful anesthetic method.

Adult↗
PubMed1993

Role of Arg115 in the catalytic action of human lysozyme. X-ray structure of His115 and Glu115 mutants.

The structure of modified human lysozymes (HLs), in which Arg115 is replaced by His or Glu, has been investigated by X-ray analysis at 1.77 A resolution. The mutation of the 115th residue by His does not affect the backbone structure as indicated by a root-mean-square deviation (r.m.s.d) of 0.14 A for the superposition of equivalent C alpha atoms between His115 HL and wild-type HL. In contrast, the corresponding r.m.s.d. value for Glu115 HL is 0.38 A which is twice as large as the estimated co-ordinate error of 0.2 A. Movement of the backbone structure is observed in the region of residues 100 to 130, which give an r.m.s.d. value of 0.61 A and a maximum deviation of 1.46 A for Arg119. A significant movement is also observed in the region of residues 45 to 50, which are located at the opposite side of the region of residues 100 to 120 with respect to the active site cleft. As a result, the active site cleft of Glu115 HL is narrower than the cleft of His115 HL or wild-type HL. This structural change is considered to be responsible for the low catalytic activity of Glu115 HL and the change of the catalytic property found in the hydrolysis of oligosaccharides. The replacement of Arg115 by Glu changes the charge distribution in the molecule, and the change in the electrostatic field may affect polar interactions among residues. The side-chain group of His115 and Glu115 is almost parallel to the indole moiety of Trp34, but the carboxyl group of Glu115 is laterally shifted to avoid overlapping with the indole moiety. The carboxylate anion of Glu115, which does not favor the face-to-face contact with aromatic groups, may provide a driving force for the structural change. The prominent structural change caused by the single mutation suggests that Arg115 is a key residue in maintaining the structure of the active site cleft.

Arginine↗
PubMed1992

Expression and secretion of wheat germ agglutinin by Saccharomyces cerevisiae.

Genes encoding pre-protein and prepro-protein of wheat germ agglutinin isolectin 2 (WGA2) were chemically synthesized and expressed in the yeast Saccharomyces cerevisiae under the control of the ENO1 promoter. Yeast harboring either a pre-WGA2 or a prepro-WGA2 gene expression plasmid secreted a mature form of WGA2 into the culture medium. The amount of WGA2 secreted by the strain KS58-2Ddel, which has a ssl1 mutation causing a supersecretion of human lysozyme [Suzuki, K., Ichikawa, K. & Jigami, Y. (1989) Mol. Gen. Genet. 219, 58-64], was 20-fold greater than that secreted by the wild-type strain KK4. The recombinant WGA2 from the cells containing the prepro-WGA2 gene expression plasmid was purified to homogeneity by a three-step ion-exchange chromatography scheme. As in wheat, the N-terminal signal peptide of recombinant WGA2 purified from yeast culture was processed to form an N-terminal 5-oxoprolyl (pyroglutamyl) residue. Likewise, we found that the C-terminal pro-region of recombinant WGA2 had also been processed in yeast. Using electrospray ionization mass spectrometry, we found the processed C-terminus to be heterogeneous in both recombinant WGA2 purified from yeast and in authentic WGA2. The major component of the recombinant WGA2 contained two additional amino acids at its C-terminus compared to that of authentic WGA2. In spite of this difference in the C-terminus, the recombinant WGA2 exhibited a sugar binding activity that was indistinguishable from that of authentic WGA2.

Amino Acid Sequence↗
PubMed1992

Dissection of the functional role of structural elements of tyrosine-63 in the catalytic action of human lysozyme.

The functional role of tyrosine-63 in the catalytic action of human lysozyme (EC 3.2.1.17) has been probed by site-directed mutagenesis. In order to identify the role of Tyr63 in the interaction with substrate, both the three-dimensional structures and the enzymatic functions of the mutants, in which Tyr63 was converted to phenylalanine, tryptophan, leucine, or alanine, have been characterized in comparison with those of the wild-type enzyme. X-ray crystallographical analysis of the mutant enzyme at not less than 1.77-A resolution indicated no remarkable change in tertiary structure except the side chain of 63rd residue. The conversion of Tyr63 to Phe or Trp did not change the enzymatic properties against the noncharged substrate (or substrate analogs) largely, while the conversion to Leu or Ala markedly reduced the catalytic activity to a few percent of wild-type enzyme. Kinetic analysis using p-nitrophenyl penta-N-acetyl-beta-(1----4)-chitopentaoside (PNP-(GlcNAc)5) as a substrate revealed that the reduction of activity should mainly be attributed to the reduction of affinity between enzyme and substrate. The apparent contribution of the phenolic hydroxyl group and the phenol group in the side chain of Tyr63 was estimated to 0.4 +/- 0.4 and 2.5 +/- 0.8 kcal mol-1, respectively. The result suggested that the direct contact between the planar side-chain group of Tyr63 and the sugar residue at subsite B is a major determinant of binding specificity toward a electrostatically neutral substrate in the catalytic action of human lysozyme.

Acetylglucosamine↗
PubMed1992

X-ray structural evidence for a local helix-loop transition in alpha-lactalbumin.

The three-dimensional structure of human alpha-lactalbumin for two crystal forms has been determined by x-ray analysis. One crystal (the form LT) was obtained at pH 4.2 and room temperature, while the other crystal (the form HT) was grown at pH 6.5 and 37 degrees C. The backbone structure for Lys1-Ile95 residues is almost conserved between the two structures as indicated by the root mean square difference of 0.30 A for the superposition of equivalent C alpha atoms. The calcium ion is surrounded by seven oxygen atoms of three carboxyl groups, two carbonyl groups, and two water molecules, which form a distorted pentagonal bipyramid in both structures. A large difference in polypeptide folding is found in the region of Leu96-Leu123 residues. Especially in the region of Trp104-Cys111 residues, a distorted alpha-helix is observed in the form HT while a loop structure is formed in the other crystal. The fact that the crystals of both forms appeared in the same batch at pH 6.5 and room temperature indicates that the human alpha-lactalbumin structure is highly fluctuated in solution and the folding and unfolding of the alpha-helix of Trp104-Cys111 residues are in equilibrium. Since the crystal of the form HT exclusively appeared around the physiological temperature, the structure of this form can be considered as the native structure. The partially unfolded structure in the form LT indicates that the local denaturation occurs even at room temperature.

Amino Acid Sequence↗
PubMed1992

X-ray structure of Glu 53 human lysozyme.

The three-dimensional structure of a modified human lysozyme (HL), Glu 53 HL, in which Asp 53 was replaced by Glu, has been determined at 1.77 A resolution by X-ray analysis. The backbone structure of Glu 53 HL is essentially the same as the structure of wild-type HL. The root mean square difference for the superposition of equivalent C alpha atoms is 0.141 A. Except for the Glu 53 residue, the structure of the active site region is largely conserved between Glu 53 HL and wild-type HL. However, the hydrogen bond network differs because of the small shift or rotation of side chain groups. The carboxyl group of Glu 53 points to the carboxyl group of Glu 35 with a distance of 4.7 A between the nearest carboxyl oxygen atoms. A water molecule links these carboxyl groups by a hydrogen bond bridge. The active site structure explains well the fact that the binding ability for substrates does not significantly differ between Glu 53 HL and wild-type HL. On the other hand, the positional and orientational change of the carboxyl group of the residue 53 caused by the mutation is considered to be responsible for the low catalytic activity (ca. 1%) of Glu 53 HL. The requirement of precise positioning for the carboxyl group suggests the possibility that the Glu 53 residue contributes more than a simple electrostatic stabilization of the intermediate in the catalysis reaction.

Amino Acid Sequence↗
PubMed1992

[A case of interstitial pneumonitis associated with polymyositis complicated by renal cell carcinoma].

A 55-year-old woman was referred to the department of urology in our hospital with left renal tumor, discovered during examinations at another hospital for fever and dyspnea on exertion. Because surgery was difficult due to severe hypoxemia, pulmonary function impairment (restrictive) and bilateral diffuse interstitial shadows on chest X-ray film, the patient was referred to our department. Interstitial pneumonitis was found on transbronchial lung biopsy, and serum GOT, LDH and CPK values were elevated. These symptoms and abnormalities of laboratory data were improved by administration of prednisolone 60 mg/day, and left nephrectomy was performed without any complications. Pathological examination of the surgical specimen showed clear cell carcinoma (Grawitz). Steroid therapy was tapered off and her clinical course was good. Six months after surgery, the patient developed a recurrence of fever, which was not responsive to antibiotics. Polymyositis was diagnosed on the basis of elevated serum GOT, LDH and CPK, electromyogram and muscle biopsy findings and positive anti-Jo-1 antibody. Polymyositis/dermatomyositis is sometimes associated with interstitial pneumonitis or malignant neoplasms, but rarely with both simultaneously. Moreover, renal cell carcinoma is very rare among the malignant neoplasms associated with polymyositis/dermatomyositis, and we therefore report this unusual case.

Antibodies, Antinuclear↗
PubMed1991

The importance of precise positioning of negatively charged carboxylate in the catalytic action of human lysozyme.

The role of aspartic acid 53 of human lysozyme (peptidoglycan N-acetylmuramoylhydrolase, EC 3.2.1.17) has been investigated by a site-directed mutagenesis. In order to clarify the importance of precise positioning of the negatively charged carboxylate group in the active site geometry, both the three-dimensional structure and the enzymatic function of glutamic acid 53 human lysozyme (Glu-53 human lysozyme) have been characterized in comparison with those of wild type enzyme. Glu-53 human lysozyme was crystallized and analysed by X-ray crystallography. No remarkable difference in the conformation of whole molecule except the side chain of 53rd residue was observed. In spite of full retention of the binding activities against either beta-1,4-linked trisaccharide of N-acetylglucosamine ((GlcNAc)3) or the corresponding hexasaccharide ((GlcNAc)6), the conversion of Asp-53 to Glu reduced the enzymatic activities against both bacterial cell substrate and p-nitrophenyl penta-N-acetyl-beta(1----4)-chitopentaoside (p-NO2-(GlcNAc)5) to a few percent of the activities of wild type enzyme. Calculation of electrostatic potential around the reaction center predicted that no significant change in pKa of Glu-35 was caused by the mutation. These results indicate that the precise positioning of the negatively charged carboxylate in the geometry of reaction center is essential for the rate enhancement in the catalytic action of lysozyme, and suggest that Asp-53 of human lysozyme participates in the catalytic action not simply in an electrostatical manner but partly in a nucleophilical manner.

Aspartic Acid↗
PubMed1991

[Study of prognostic factors of survival in patients with unresectable non-small cell lung cancer].

We studied prognostic factors of survival in 121 patients unresectable non-small cell lung cancer treated between March 1983 and November 1988 at forth department of internal medicine, Kinki university school of medicine, about histology, clinical stage, age, sex, performance status, Brinkman Index, hemoglobin, serum TP, serum Alb, serum LDH, pulmonary function and chemotherapy. The prognostic factors were studied using survival rate by Kaplan-Meier method, univariate analysis by Log-rank test and generalized Wilcoxon test and multivariate analysis by proportional hazard model of Cox. The prognostic factors of pretreatment were age, serum Alb, serum LDH, pulmonary dysfunction of mixed type and performance status. In the classified study according to histology, age and pulmonary dysfunction of mixed type were prognostic importance in patients with squamous cell lung cancer. Hemoglobin in patients with squamous cell lung cancer was important, too. The chemotherapy given good response improved patient's prognosis.

Adenocarcinoma↗
PubMed1991

[A case of hydrocephalus with hypacusis due to hemangioblastoma].

A case of a brain stem hemangioblastoma with recurrent episodes of hypacusis due to progression of hydrocephalus is reported. The patient was a 25-year-old female, admitted to the department of otorhinolaryngology with complaints of hearing difficulty, headache and blurred vision. Neuroradiological studies showed a tumor from the medulla oblongata, obliterating the IVth ventricle, and a secondary hydrocephalus. Hearing loss fluctuated as hydrocephalus progressed. Multiple V-P shunting procedures relieved episodic hypacusis. The patient remains asymptomatic at present and has resumed normal activity. The mechanism of episodic hearing loss due to hydrocephalus is though to be due to the fact that through the ductus perilymphaticus and the ductus endolymphaticus, especially the former, increased intracranial pressure is transmitted to the inner ear. Through the ductus perilymphaticus there is communication between the perilymphatic space and the intracranial subarachnoid space. Through the ductus endolymphaticus there is communication with the subdural space. Increased ICP effects the inner ear. It is suspected that, in this particular case, the progression of hydrocephalus effected the patient's hearing.

Adult↗
PubMed1989

A structural requirement in the subsite F of lysozyme. The role of arginine 115 in human lysozyme revealed by site-directed mutagenesis.

Arginine 115 in the subsite F of human lysozyme (peptidoglycan N-acetylmuramoylhydrolase, EC 3.2.1.17) was replaced with lysine, histidine, glutamine or glutamine acid by site-directed mutagenesis. The conversions which conserve positive charge, Arg115 to Lys or His (at acidic pH), have little affected on either the kinetic parameters for Micrococcus lysodeikticus cells or the activity against glycol chitin, nor on the cleavage patterns of hexa(N-acetylglucosamine) [(GlcNAc)6] and penta(N-acetylglucosamine) [(GlcNAc)5]. On the other hand, the conversions which cause loss of the positive charge, Arg115 to His (neutral and alkaline pH), Gln or Glu, not only reduced the activity against glycol chitin but also changed the cleavage patterns for (GlcNAc)6 and (GlcNAc)5. These results suggest that Arg115 is structurally required not for the specific hydrogen bonding interaction with a sugar residue but for the positively charged character in the construction of subsite F in human lysozyme.

Arginine↗
PubMed1989

[Group infection of tuberculosis in a private extra-school tutoring institute].

1) Two students of different high-schools were found to have pulmonary tuberculosis by school medical examination. These two students learned in the same private extra-school tutoring institute when they were junior high-school students. Assuming this event as a group infection of tuberculosis in the extra-school tutoring institute, we performed an extraordinary examination on the teachers working there. 2) In the extraordinary examination, a patient who could be judged as the source of infection was found. 3) As a result of extraordinary examination on students learning in the institute, a bimodal distribution was noted in the size of tuberculin test, compared with the results of tuberculin test at the first grade of junior high-school, the reaction was amplified. Twenty four students were subjected to chemoprophylaxis. 4) One case of pleurisy occurred from a student recommended chemoprophylaxis by the ad hoc committee on epidemic of tuberculosis, and the recommendation was neglected by an attending physician.

Adolescent↗
PubMed1988

Engineering of human lysozyme as a polyelectrolyte by the alteration of molecular surface charge.

The surface positive charges of human lysozyme were either increased or decreased to alter the electrostatic interaction between enzyme and substrate in the lytic action of human lysozyme using site-directed mutagenesis. The amino acid substitutions accompanying either the addition or the removal of two units of positive charge have shifted the optimal ionic strength (NaCl concentration in 10 mM Mes buffer, pH 6.2) for the lysis of Micrococcus lysodeikticus cell from 0.04 M to 0.1 M and from 0.04 M to 0.02 M respectively. In addition to the change in ionic strength-activity profile, the pH-activity profile and the effect of a polycationic electrolyte, poly-L-Lys-HCl, on the lytic activity were significantly changed. Owing to the shifts in both ionic strength profiles and pH profiles the Arg74/Arg126 mutant has become a better catalyst than wild-type enzyme under the conditions of high ionic strength and high pH, and the Gln41/Ser101 mutant has become a better catalyst under the conditions of low ionic strength and low pH.

Amino Acid Sequence↗
PubMed1987

The roles of conserved aromatic amino-acid residues in the active site of human lysozyme: a site-specific mutagenesis study.

In order to probe the roles of Tyr-63, Trp-64 and Trp-109 in the active site of human lysozyme (peptidoglycan N-acetylmuramoylhydrolase, EC 3.2.1.17), six human lysozymes containing a mutation, Tyr-63 to Leu, Trp-64 to Phe or Tyr, Trp-109 to Phe or Tyr, and Glu-35 to Asp, were newly synthesized and their immunological and enzymatical activities were examined in comparison with the native enzyme. Enzymatic characterization indicated: (i) that the existences of an aromatic residue at position 63 and a tryptophan residue at position 64 are essential for the effective hydrolysis of glycol chitin substrate, but not for the lysis of bacterial substrate; (ii) that the conversion of Trp-109 to Phe or Tyr reduces the maximal velocity of the lytic reaction to 25% of the wild-type enzyme; however, the apparent affinity constant is not affected. Further, the difference between the activity against the charged substrate and that against the non-charged substrate was discussed from a viewpoint of the electrostatic interaction between enzyme and substrate.

Amino Acid Sequence↗
PubMed1987

Engineering of the active site of human lysozyme: conversion of aspartic acid 53 to glutamic acid and tyrosine 63 to tryptophan or phenylalanine.

Three human lysozymes containing a mutation either at Asp-53 to Glu or at Tyr-63 to Trp or Phe were synthesized and examined for their immunological and enzymatical activities in comparison with the native one. All mutants were immunologically indistinguishable from native human lysozyme. The [Trp63] and [Phe63] mutants catalysed the hydrolysis of Micrococcus lysodeikticus cell wall and glycol chitin effectively, while the [Glu53] mutant displayed very low activity toward M. lysodeikticus cells and no detectable activity toward glycol chitin.

Amino Acid Sequence↗
PubMed1986

Expression of synthetic human-lysozyme gene in Saccharomyces cerevisiae: use of a synthetic chicken-lysozyme signal sequence for secretion and processing.

A multicopy plasmid was constructed to direct the synthesis and secretion of human lysozyme (HLY) in Saccharomyces cerevisiae. This plasmid contains a synthetic chicken-lysozyme signal sequence (SIG) and a synthetic HLY structural gene, both inserted between the yeast GAL10 promoter and 2 mu plasmid FLP (flip-flop recombination gene) terminator. The resulting plasmid directed the expression of the hybrid pre-lysozyme, with most of the HLY activity secreted into the culture medium and extracellular periplasmic space. The HLY activity in the culture medium increased with cell growth. The yeast accurately processed the hybrid precursor at the junction between the chicken SIG and the coding sequence downstream, yielding mature HLY. HLY purified from the culture medium was homogeneous and displayed specific activity identical to that of authentic HLY.

Animals↗
PubMed1986

CT classification of small thalamic hemorrhages and their clinical implications.

Thirty-seven small thalamic hemorrhages (less than 2 cm) were classified into four types depending on topographic location. Patients with posterolateral lesions had severe sensory and motor disability as well as the worst prognosis. Anterolateral lesions resulted in mild prefrontal signs with milder sensory and motor impairment. Medial hematomas disturbed consciousness in the acute stage, followed by impaired prefrontal signs of long duration. Dorsal hematomas were associated with ipsilateral parieto-occipital signs (aphasia on the left and topographic memory disturbance on the right).

Aged↗