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Biomedical subjects

Y Kito

Publications and source records attributed to Y Kito.

At least 19 recordsLinked to original sources
PubMed2000

The quantitative analysis of three action modes of volatile anesthetics on purple membrane.

We quantitatively assessed the spectroscopic changes of purple membrane in relation to the concentrations of a volatile anesthetic. As reported previously, volatile anesthetics show three modes of action on purple membrane. By using an anesthetic for which the concentration in solution could be determined spectroscopically and by applying modified analytical methods regarding the M-intermediate lifetime, we were able to clarify the quantitative relation between anesthetic concentration and each mode of action, a relation which in the past has only been described qualitatively. We also determined through the measurement of transient pH changes with pyranine that the proton pump efficiency per photochemical cycle in an action mode induced with low concentrations of anesthetic does not change from that of the native state. Moreover, we dynamically obtained the individual M-bacteriorhodopsin difference spectrum of each state at room temperature using our flash photolysis system equipped with a wavelength-tunable dye laser. These results demonstrated again that we should clearly distinguish different action modes of anesthetics according to their concentrations.

Anesthetics↗
PubMed1999

Structural and functional differences of two forms of GTP-binding protein, Gq, in the cephalopod retina.

The major GTP-binding protein (G-protein) in the rhabdomeric photoreceptor membranes of the squid (Watasenia scintillans) has been identified as a Gq-class G-protein. Anti-Gq alpha antibodies recognized a protein not only in the photoreceptor membranes but also in soluble fractions of the retina. The 42 kD protein in the soluble fractions (soluble Gq alpha) had the same molecular mass and the same reactivities to anti-Gq antibodies as those of membrane-bound Gq alpha. The G beta subunit was scarcely detected in the soluble fractions, being found mostly in the membrane fraction, indicating soluble Gq alpha exists in monomeric form. Soluble Gq alpha had no effect on the GTPase activity of the photoreceptor membranes, suggesting that it does not interact with photoactivated rhodopsin or G beta gamma. Soluble Gq alpha would be an inactive form of Gq alpha. In the retina of Octopus fangsiao, soluble Gq alpha was scarcely detected after dark adaptation, but increased during subsequent light exposure and decreased on returning to dark adaptation. These results with Octopus suggest that functional membrane-bound Gq alpha is converted to soluble Gq alpha on exposure to light. Transformation of membrane-bound Gq alpha into the soluble form by hydroxylamine suggests that the difference between membrane-bound and soluble Gq alpha is associated with the attachment of fatty acid(s).

Aluminum Compounds↗
PubMed1999

Regulation of squid visual phospholipase C by activated G-protein alpha.

Phospholipase C (PLC) is the key enzyme in the phototransduction cascade of invertebrate rhabdomeric photoreceptors. In addition to 130 kDa PLC, a 95 kDa protein recognized by antibody against the catalytic site of PLC was found in the squid retina. The PLC-like 95 kDa protein (95 kDa PLC) was produced from 130 kDa PLC by an intrinsic protease in the presence of calcium. The 130 kDa PLC was stimulated by the active form of Gq-class G-protein alpha (Gq alpha), but the 95 kDa PLC was not, although their PLC activity was similar. A 35 kDa fragment, the counterpart of 95 kDa PLC, was not recognized by antibodies against catalytic site or N-terminal site of the 130 kDa PLC, indicating that the cleavage site is on the C-terminal side beyond the catalytic site. In the presence of a large excess of the 35 kDa fragment, 95 kDa PLC was stimulated by Gq alpha to a similar extent as intact 130 kDa PLC. These results indicate that the C-terminal polypeptide of PLC is necessary for regulation of its enzyme activity by Gq alpha. The uncoupling of PLC from Gq alpha, caused by limited proteolysis, is therefore a candidate regulatory mechanism of the phototransduction cascade in rhabdomeric photoreceptors.

Animals↗
PubMed1998

Binding of volatile anesthetics to purple membranes studied by X-ray diffraction.

Volatile anesthetics, diiodomethane and trifluoroethyl iodide, acted on the purple membrane of Halobacterium halobium in two different modes depending on the concentration. At low concentration, the absorption maximum of bacteriorhodopsin shifted from 561 to 558 nm (BR558) and the M-intermediate of the photocycle decayed faster than the native one. Higher concentration induced a species absorbing maximally at 480 nm (BR480) and the long-lived M-intermediates. The X-ray study suggested that anesthetics bound specifically to the protein-lipid interfacial region within a trimer near the surface of membrane in BR558 and entered into the hydrophobic domain of the membrane in BR480.

Anesthetics, Inhalation↗
PubMed1998

Effects of dopamine on veins in humans: comparison with noradrenaline and influence of age.

OBJECTIVE: To compare the venoconstricting effect of dopamine with that of noradrenaline and to investigate the influence of age on the responsiveness to dopamine in human subjects. METHODS: In eight young and eight elderly male subjects, increasing doses of dopamine or noradrenaline were infused into a dorsal hand vein and its diameter was measured using a linear variable differential transformer. RESULTS: There was no significant difference between the maximum venoconstriction (Emax) for dopamine and that for noradrenaline. The infusion rate to induce 50% of Emax (ED50) for dopamine in the young and elderly subjects was 363 ng x min(-1) and 352 ng min(-1), and the ED50 for noradrenaline was 40.7 ng min(-1) and 43.8 ng x min(-1), respectively. Neither in the Emax nor in the ED50 for these drugs were there significant differences between the young and elderly subjects. CONCLUSION: The venoconstricting effect of dopamine is 5-20 times less than that of noradrenaline, and aging does not influence the responsiveness to dopamine and noradrenaline in human subjects.

Adult↗
PubMed1997

A novel yeast gene, RHK1, is involved in the synthesis of the cell wall receptor for the HM-1 killer toxin that inhibits beta-1,3-glucan synthesis.

The HM-1 killer toxin from Hansenula mrakii is known to inhibit cell wall beta-1,3-glucan synthase of Saccharomyces cerevisiae and other sensitive strains of yeast. A number of mutants of Saccharomyces cerevisiae that show resistance to this toxin were isolated in order to clarify the killing mechanism of the toxin. These mutants, designated rhk (resistant to Hansenula killer), were classified into three complementation groups. A novel gene RHK1, which complements the killer-resistant phenotype of the largest complementation group rhk1, was isolated. DNA sequence analysis revealed an open reading frame that encodes a hydrophobic protein composed of 458 amino acids. Gene disruption followed by tetrad analysis showed that RHK1 is not essential and loss of RHK1 function endowed S. cerevisiae cells with complete killer resistance. A biochemical analysis suggested that RHK1 does not participate directly in the synthesis of beta-1,3-glucan but is involved in the synthesis of the receptor for the HM-1 killer toxin.

Amino Acid Sequence↗
PubMed1997

Role of glucocorticoid in the upregulation of type I interleukin-1 receptor mRNA expression in hepatocytes of endotoxin-administrated mice.

The interleukin-1 (IL-1) signal is transduced through type I IL-1 receptor (IL-1RI). We have recently reported that lipopolysaccharide (LPS) upregulated IL-1RI mRNA expression in mouse liver in vivo and that IL-1 and IL-6 directly upregulated IL-1RI mRNA expression in primary cultured mouse hepatocytes. Glucocorticoid (GC) has been reported to increase IL-1 binding to the cell surface and the expression level of IL-1R mRNA in a variety of cell types. As serum GC level is elevated in an inflammatory response, we evaluated the role of GC in LPS-induced upregulation of IL-1RI mRNA in the mouse liver. When LPS was administered to adrenalectomized (ADX) mice, IL-1RI mRNA was upregulated at a level comparable to those of untreated or sham-operated mice. A high dose of dexamethasone (Dex), however, caused upregulation of the mRNA. When primary cultured mouse hepatocytes were treated with Dex, only a weak upregulation of IL-1RI mRNA was observed. However, Dex in combination with IL-1 or IL-6 markedly enhanced the IL-1RI mRNA expression. A marked upregulation of the mRNA was also induced by treatment with a combination of IL-1 and IL-6 in the absence of Dex, reflecting the observation in ADX mice. These results suggest that the upregulation of IL-1RI mRNA in response to LPS is induced by the interaction of IL-1 and IL-6 and that GC augments their effect.

Adrenal Glands↗
PubMed1996

Molecular cloning, purification and characterization of two endo-1,4-beta-glucanases from Aspergillus oryzae KBN616.

Two endo-1,4-beta-glucanase genes, designated celA and celB, from a shoyu koji mold Aspergillus oryzae KBN616, were cloned and characterized. The celA gene comprised 877 bp with two introns. The CelA protein consisted of 239 amino acids and was assigned to the cellulase family H. The celB gene comprised 1248 bp with no introns. The CelB protein consisted of 416 amino acids and was assigned to the cellulase family C. Both genes were overexpressed under the promoter of the A. oryzae taka-amylase A gene for purification and enzymatic characterization of CelA and CelB. CelA had a molecular mass of 31 kDa, a pH optimum of 5.0 and temperature optimum of 55 degrees C, whereas CelB had a molecular mass of 53 kDa, a pH optimum of 4.0 and temperature optimum of 45 degrees C.

Amino Acid Sequence↗
PubMed1996

Ten-year experience with the Carpentier-Edwards pericardial xenograft in the tricuspid position.

We reviewed the cases of 66 patients who underwent 67 tricuspid valve replacements with Carpentier-Edwards pericardial xenografts between April 1985 and January 1994. Average patient age at time of operation was 52 years (range 8 to 71 years). Concomitant mitral or aortic valve replacements were performed in 46 patients. There were 10 operative deaths and 6 late deaths. Actuarial survival at 9 years was 75.4% +/- 5.7%. Prosthetic valve endocarditis occurred twice in one patient. Reoperations for tricuspid regurgitation and for concomitant procedures (maze operation and repair for leak of the mitral prosthesis) were performed in two patients. In both cases, examination of the explanted prostheses showed that the tricuspid regurgitation was the result of nonstructural dysfunction caused by fibrous pannus formation on the cusps of the ventricular side. Among the survivors, 47 patients (92%) were in functional class I or II. Prosthetic valve function was studied by color Doppler echocardiography. Among 38 patients, tricuspid regurgitation more than grade 3/4 or transprosthetic gradient more than 5 mm Hg was found in 11. One patient had right heart failure and the others had no symptoms. In 10 years of experience with the Carpentier-Edwards pericardial xenograft, mortality and morbidity after tricuspid valve replacement were satisfactory. Echocardiographic examination revealed subclinical prosthetic dysfunction in 35% of patients who were followed up for longer than 5 years, however, and we believe that these patients should receive careful follow-up.

Adolescent↗
PubMed1996

X-ray diffraction pattern from internal structure of bovine rhodopsin.

Pure bovine rhodopsin pellets were prepared by removal of cholic acid from rhodopsin-cholic acid complex, and X-ray diffraction patterns from the internal structure of rhodopsin were obtained for the first time using wet and dry pellet samples. The peaks at around 10 and 4.3 A spacings observed for both samples can be attributed to alpha-helices in rhodopsin molecule, providing direct evidence of the helical structure of rhodopsin. A shoulder peak at around 34 A spacing was also observed for the dry pellet, which can be explained by the first-neighbor distance between rhodopsin molecules in the sample.

Animals↗
PubMed1996

[Valvular surgery in the patients more than 70 years old].

One hundred twenty-eight valvular surgeries in patients over 70-year-old were reviewed (AVR:58, MVR:38, AVR and MVR: 11, mitral valvuloplasty (MVP): 11, AVR + MVP:11, mitral valvuloplasty (MVP): 11, AVR + MVP: 8, others: 2). Concomitant CABG was performed in 7, Maze in 6, TVR in 5 and Bentall in 3 cases. Early deaths occurred in 17 patients (13%). The early mortality was 5% in AVR, 21% MVR, 18% in AVR and MVR, 0% in MVP and 38% in AVR and MVP. Late death occurred in 16 patients. Forty-three percent of the late deaths were cardiac death. The actuarial survival at 10 years was around 50% in all groups. In the aortic position, a mechanical valve was implanted in 47 cases and a bioprosthetic valve was implanted in 33 cases. In the mitral position, the mechanical valve was implanted in 37 cases and the bioprosthetic valve was implanted in 12 cases. The event free rate after AVR at 10 years was 37% in patients with the mechanical valve (3 cerebral hemorrhage, 2 PVE, 1 thromboembolism and 1 sudden death) and 46% in patients with the bioprosthetic valve (2 PVE and 1 primary tissue failure). The event free rate after MVR at 10 years was 84% in patients with mechanical valves (1 perivalvular leak, 1 PVE and 1 sudden death) and 75% in patients with bioprosthetic valves (1 PVE and 1 sudden death). Between mechanical valve group and bioprosthesis group, no statistically significance was found in the event free curve after AVR nor MVR. There was no valve related event after MVP. Considering the better durability of bioprostheses in the aortic position than in the mitral position, the presence of atrial fibrillation and necessity of warfarin anticoagulation, we conclude that a choice of a bioprosthetic valve could be acceptable in the aortic position, but may not be recommended in the mitral position.

Aged↗
PubMed1996

Clinical experience of percutaneous cardiopulmonary support.

Recently, percutaneous cardiopulmonary support (PCPS) combined with femoro-femoral bypass without reservoir has become valued because of its quick and easy application. We developed a fully preconnected compact integrated cardiopulmonary bypass (CPB) unit (priming volume of 250 ml) with a blind pore membrane oxygenator (Kuraray Menox) for PCPS. From 1990 to 1995, PCPS was performed in 49 patients of whom 26 were weaned from support. In most cases, we applied this CICU in patients with no active bleeding (22 patients); in patients with active bleeding (n = 13), we used Medtronic's heparin-bonded close chest support pack (CCSP). Of these, PCPS was performed uneventfully for 2 h (median) in 8 elective cases; all of these patients were weaned or were switched to a left ventricular assist system (LVAS). In 8 urgent cases, such as those with low cardiac output syndrome, PCPS was performed for 4 days (median), 1 was weaned, and 2 CICU were cases switched to other procedures. In 32 cases of shock, 5 CICU patients were weaned, and 3 of them survived. Eight patients including 5 CICU patients and 1 CCSP patient were switched to operation or LVAS, and 2 CICU patients remain alive. From these data, PCPS has been shown to support the patient's circulation in the acute phase and earn time to switch to operation or LVAS; the quick and easy set-up of the CICU can improve the clinical results. The use of the Medtronic device broadened the indication for PCPS. The CCSP enlarged the indication of PCPS but could not improve the results. To improve the results, a heparin-bonded surface is desired.

Cardiopulmonary Bypass↗
PubMed1996

Aortic and mitral valve replacement with the Carpentier-Edwards pericardial bioprosthesis: 10-year results.

BACKGROUND AND AIM OF THE STUDY: This report reviews our experience with single aortic and mitral valve replacement using the Carpentier-Edwards pericardial valve in a population younger than those of other reports. METHODS: Between 1984 and 1993, 106 patients underwent single aortic or mitral valve replacement using a Carpentier-Edwards pericardial valve. There were 49 aortic and 57 mitral implants. The mean age was 56.7 +/- 14.3 years. The follow up was 100% complete; total follow up being 273.3 patient-years in the aortic (AVR) and 348.0 patient-years in the mitral valve replacement (MVR) group, with a mean of 5.6 and 6.1 years, respectively. RESULTS: The rates of thromboembolic complications for AVR and MVR were 0.37% and 0.58% per patient year respectively. There were no cases of non-structural dysfunction or anticoagulant-related hemorrhage. The incidences of prosthetic valve endocarditis for AVR and MVR were 0% and 0.86% per patient year respectively. Structural deterioration (calcification and sclerosis) occurred in one patient after AVR and in six patients after MVR, all younger than 60 years of age. Freedom from structural deterioration at five years and 10 years was 100% and 92.9% +/- 6.9% for AVR, and 100% and 76.9% +/- 8.6% for MVR. CONCLUSIONS: In conclusion, the Carpentier-Edwards aortic valve has a low incidence of valve-related complications at 10 years. Although late results of this valve in the mitral position were excellent in the elderly, leaflet degeneration is still a problem in patients under the age of 60 years.

Adult↗
PubMed1996

[Clinical study of re-do surgery after Bentall-type operation].

Among patients who underwent reconstruction of the aortic root by Bentall-type procedure using a composite graft, we investigated patients who underwent reoperation for complications related to composite graft. We employed composite graft reconstruction of the aortic root in 155 patients for 16 years prior to December 1994. Annulo-aortic ectasia was observed in 112 patients, aortic dissection in 34, and aortitis without aneurysm formation in 9. The original Bentall procedure was performed in 36, the Cabrol method in 8, the interposition method in 26, and the Carrel patch method in 85 patients. Thirteen (8.4%) of these patients required reoperation for complications related to the composite graft. Three of 4 patients with graft infection early after surgery underwent reconstruction with composite graft, but died in the hospital. The remaining patient survived after combined treatment that included the graft washing with Iodine (Isozin) solution and omentopexy. Four patients developed pseudoaneurysm formation due to sutural insufficiency and 7 has prosthetic valve failure as late complications. Three of the 4 patients with pseudoaneurysm underwent reconstruction with a second composite graft by the interposition method, while one patient with aortitis required another reoperation. In the remaining one patient, the leak was directly close along with second aortic valve replacement. All prosthetic valves used in 7 patients with prosthetic valve failure were Ionescu-Shiley biological valves. Primary tissue failure was observed in 6 and prosthetic valve endocarditis in one patient. Second cardiac valve replacement using a mechanical valve was possible. All the patients who underwent late reoperation showed favorable results. Infection of the composite graft showed the poor prognosis, and prevention of infection is important. Sutural insufficiency at the anastomosed site can be prevented by appropriate surgical procedures such as reinforcing suture, but further countermeasures for sutural insufficiency were considered necessary for aortitis in conditions, such as Behcet's diseases.

Adult↗
PubMed1995

Squid photoreceptor phospholipase C is stimulated by membrane Gq alpha but not by soluble Gq alpha.

Phospholipase C (PLC) was purified from squid retina. Soluble Gq alpha, membrane Gq alpha and G beta gamma were isolated from GTP gamma S-treated and light-illuminated photoreceptor membranes. The membrane Gq alpha stimulated phosphatidyl inositol-phospholipase C (PI-PLC) activity in a dose-dependent manner. Soluble Gq alpha and membrane G beta gamma showed no stimulating effects on PLC. GTP gamma S-binding was found exclusively in membrane fraction, with very little present in the KCl-soluble fraction which contained soluble Gq alpha. These results indicate that light-activated rhodopsin activates PLC through membrane-bound Gq alpha and suggest that the rhodopsin/Gq/PLC cascade might be the pathway of phototransduction in squid photoreceptors.

Animals↗