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Biomedical subjects

M Oka

Publications and source records attributed to M Oka.

At least 415 records · Page 23Linked to original sources
PubMed1993

Inactivation of peptidoleukotrienes in the isolated perfused rat lung.

Inactivation of peptidoleukotrienes by alveolar transfer and metabolism was investigated in isolated perfused rat lungs. [3H]Leukotriene (LT)C4 or [3H]LTE4 was instilled into the airways and 25 min later the distribution of tritiated metabolites in bronchoalveolar lavage fluid, lung, and perfusate was determined. Metabolism of LTC4 was found to occur in both the alveolar and vascular space in contrast to metabolism of LTE4, which occurred exclusively on the alveolar side. The alveolar transfer of leukotrienes into the perfusate was slow with only 25-29% transfer occurring during the 25-min perfusion. Only a small percentage of instilled LTC4 was transferred out of the airways unmetabolized, suggesting that this leukotriene is not the major one that is removed from the airways. In contrast, LTE4 either added directly into the airways or produced in the alveolar space from LTC4 metabolism was more readily transferred out of the lung. LTE4 was transported into alveolar cells by a nonenergy requiring, receptor-mediated mechanism inhibited by LTD4/LTE4 receptor antagonists and by probenecid. Cysteine-containing compounds (cysteine, cystine, and N-acetylcysteine) added to the perfusate caused a significant increase in LTE4/N-acetyl-LTE4 transport possibly due to a coupling of cyst(e)ine (in) and LTE4 (out) transport. Metabolism of LTC4 by gamma-glutamyltransferase appears to be the rate limiting step of peptidoleukotriene inactivation in the rat airways, being necessary for both metabolic inactivation and the formation of products which can be eliminated by transfer.

Animals↗
PubMed1993

Influence of disodium (1-hydroxythylidene) diphosphonate on bonding between glass-ceramics containing apatite and wollastonite and mature male rabbit bone.

It has been reported that bioactive glass-ceramics containing crystalline oxy- and fluoroapatite [Ca10(PO4)6(O,F2) and wollastonite (CaSiO3), chemical composition: MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF2 0.5 in weight ratio] bond to bone tissue through the formation of an apatite (a calcium and phosphorus-rich layer) on the ceramic surface. In this study, the influence of disodium (1-hydroxythylidene) diphosphonate (DHTD) on the bonding between bone and glass-ceramics containing apatite and wollastonite was investigated. Rectangular ceramic plates (15 mm x 10 mm x 2 mm, abraded with #2000 alumina powder) were implanted into the tibial bone of mature male rabbits. DHTD was administered daily by subcutaneous injection to groups 1-5: group 1-4 at doses of 20, 5.0, 1.0, and 0.1 mg/kg body wt/day for 8 weeks; and group 5 at a dose of 5 mg/kg body wt/day for 4 weeks. Group 6 was given injections of saline as a control. At 8 weeks after implantation, the rabbits were killed. The tibiae containing the ceramics were dissected out and used for a detachment test. The failure load, when an implant became detached from the bone, or when the bone itself broke, was measured. The failure loads for groups 1-6 were 0 kg, 0 kg, 8.08 +/- 2.43 kg, 7.28 +/- 2.07 kg, 5.56 +/- 1.63 kg, and 6.38 +/- 1.30 kg, respectively. Ceramic bonding to bone tissue was inhibited by a higher dose of DHTD (groups 1 and 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Natural killer activity and serum immunosuppressive acidic protein levels in esophageal and gastric cancers.

The natural killer (NK) activity of peripheral blood mononuclear cells and serum immunosuppressive acidic protein (IAP) levels were examined in patients with esophageal or gastric cancer, before and after surgery. Patients with stage IV esophageal or stage IV gastric cancer had significantly lower NK activity (39.5 +/- 14.8% and 37 +/- 11.6%, respectively), and also higher serum IAP levels (778 +/- 264 micrograms/mL and 633 +/- 156 micrograms/mL, respectively), than the corresponding control values (50 +/- 5.6% and 375 +/- 26 micrograms/mL, respectively). Patients with esophageal or gastric cancer who underwent curative resection had high NK activity (54.8 +/- 11.6% and 54.8 +/- 8.0%, respectively), and low IAP levels (471 +/- 116 micrograms/mL and 490 +/- 42 micrograms/mL, respectively), compared with those who underwent non-curative resection. Patients who underwent non-curative resection had lower NK activity and higher serum IAP levels than those who underwent curative resection, even 1 month after surgery. Mononuclear cells in the regional lymph nodes and tumor specimens showed significantly lower NK activity than those in the peripheral blood and spleen. Thus, NK activity and the IAP level reflected the immunocompetence, clinical course, and surgical curability of those patients. NK cells appeared not to have any significant antitumor activity in the regional lymph nodes or in the tumor itself, although they were still active in the peripheral blood.

Adult↗
PubMed1993

Changes in plasma dopamine-beta-hydroxylase activity during the perioperative period of cardiac surgery: an index of sympathetic nerve activity.

To evaluate the usefulness of plasma dopamine-beta-hydroxylase (DBH) activity as an index of sympathetic nerve activity during cardiac operations, we examined the serial changes in plasma DBH activity, in relation to the plasma noradrenaline (NA) level and hemodynamic parameters, in patients who underwent cardiac surgery. The plasma DBH activity decreased significantly after cardiopulmonary bypass, and remained low during dopamine (DA) infusion until 72 h after the operation. However, recovery of the hemodynamic parameters, being the mean arterial pressure, heart rate and cardiac index, was seen as early as 1-3 h postoperatively. It was therefore assumed that the plasma DBH activity takes a long time to recover after an operation. The time-course changes in the plasma NA level were quite different from the changes in DBH activity, with an apparent negative correlation being observed between them. Thus, there is a possibility that exogenously administered DA, as well as increased plasma NA, might inhibit DBH activity during cardiac surgery. Moreover, since catecholamines are often administered upon completion of cardiac surgery, measurement of the plasma catecholamine level would be inappropriate for evaluating real sympathetic nerve activity. From the results of this study, it is surmised that measurement of the plasma DBH activity could be useful for estimating the intrinsic sympathetic nerve activity of patients who have undergone cardiac surgery.

Adult↗
PubMed1993

The characterization of peritoneal and pleural exudate cells from malignant effusions.

The immune function of peripheral blood cells and cells from the pleural and abdominal effusions of patients with advanced cancer was compared to that of peripheral blood cells from controls. The parameters examined included lymphocyte subsets, natural killer (NK) cell activity, and anti-Daudi and lymphokine-activated killer (LAK) cell activity. The percentage of CD4+ pleural and peritoneal exudate cells (PEC) was significantly higher than the percentage of peripheral blood mononuclear cells (PBMC) in the patients. The percentage of CD8+CD11+ PEC and PBMC, being the suppressor T-cells, of the patients was increased compared with controls, while the percentage of CD8+CD11- PEC, being the cytotoxic T-cells, was identical to the PBMC of both patients and controls. The NK activity of PEC was significantly lower than that of PBMC in both patients and controls, and there was no correlation between the NK activity of PBMC and PEC. Although the anti-Daudi activity of PEC was markedly low, LAK cells with high activity could be induced by culture with interleukin-2 for 4 days. These results suggest that the immune function of cells in malignant effusions may be depressed due to a low population of cytotoxic T cells, low NK activity and increased suppressor T cells, while the local administration of interleukin-2 may induce LAK cells. Therefore, effective local immunotherapy for malignant effusions should not only augment effector cells, but also inhibit suppressor cells.

Adult↗
PubMed1993

Mechanisms of vancomycin-induced histamine release from rat peritoneal mast cells.

The mechanisms of vancomycin (VCM)-induced histamine release were studied with rat peritoneal mast cells. VCM (> 1 x 10(-3) M) released histamine from the isolated mast cells in a dose-dependent and noncytotoxic manner. In the absence of extracellular Ca2+, the histamine release was reduced markedly. When the intracellular Ca2+ was depleted, it was further decreased. The Fura-2-loaded single mast cells showed a biphasic increase in the intracellular Ca2+ concentration ([Ca2+]i) by VCM: the first transient and the second sustained components. In the absence of extracellular Ca2+, the transient component was unchanged, while the sustained component was eliminated completely. The IP3 content in the mast cells increased within 10 s after the application of VCM. These results suggest that VCM release histamine from rat peritoneal mast cells via an IP3 production and increase in [Ca2+]i.

Animals↗
PubMed1993

Multimodality imaging of cervicofacial actinomycosis.

Actinomycosis is an uncommon chronic disease usually caused by Actinomyces israelii. It affects the soft tissue mainly but sometimes spreads to involve salivary glands, bone, or even the skin of the face and neck. Five cases have been seen in our department. Several imaging modalities were used to assist in making the diagnosis. The cases are presented and the literature reviewed. Ultrasonography was found to be a useful diagnostic tool especially in developing the differential diagnosis.

Actinomycosis↗
PubMed1993

Stafne's bone cavity. Classification based on outline and content determined by computed tomography.

Fifteen cases (16 concavities) of the so-called "Stafne's bone cavity" were investigated with the use of computed tomography. The sizes, bony outlines, and contents were analyzed on axial images. In all cases, computed tomography clearly demonstrated the concavities on the lingual surface of the mandible. There were no empty concavities. The bony outlines and contents were divided into three types. The concavities with a portion of submandibular gland as a content were larger than those with other contents. Four of six concavities not extending to the buccal cortical plate were filled solely with fat tissue, whereas all concavities with expansion of the buccal cortical plate contained submandibular gland.

Adipose Tissue↗
PubMed1993

Treatment effect of a traditional Chinese medicine, ren-shen-yang-rong-tang (Japanese name: ninjin-youei-to), on autoimmune MRL/MP-lpr/lpr mice.

MRL/Mp-lpr/lpr (MRL/lpr) mice were treated with a traditional Chinese herbal medicine, Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NYT) intraperitoneally (i.p.) every 3 days or per os (p.o.) 6 times/week from before the onset of autoimmune disease (6 weeks of age). Fifty percent survival time was found in placebo-controlled male and female mice of 28 and 22 weeks of age, respectively. NYT-treatment markedly prolonged the survival time of MRL/lpr mice. That is, 50% survival time was 43 weeks in the i.p.-treated male mice and 30 weeks of age in the p.o.-treated female mice. Further, NYT-treatment significantly reduced occurrence of thymic atrophy and prevented the anomalous accumulation of B220+ T-cells in lymph node and spleen, both of which are characteristic in MRL/lpr mice. Moreover, grades of proteinuria were significantly reduced in both the i.p.- and p.o.-treated groups compared with the control groups. Such clinical benefit and increased survival time were interestingly not associated with the decrease in the level of autoantibodies.

Animals↗
PubMed1993

The application of titanium alloy wires for the reattachment of the greater trochanter in total hip arthroplasty.

We developed a new fixing method using titanium alloy wires in order to facilitate the attachment of the greater trochanter in total hip arthroplasty. This wire is composed of Ti-3Al-2.5V by weight. According to the fatigue test in vitro, the titanium alloy wire had better fatigue properties than Ortron 90 wire of the same diameter. In experiments in vivo, both titanium alloy wires and SUS-316L wires were used for the reattachment of the greater trochanter of dogs, and the titanium alloy wires showed better biocompatibility than the latter. Thus, titanium alloy wires seem applicable for the reattachment of the greater trochanter in human total hip arthroplasty.

Alloys↗
PubMed1993

Two types of prostacyclin receptor coupling to stimulation of adenylate cyclase and phosphatidylinositol hydrolysis in a cultured mast cell line, BNu-2cl3 cells.

Prostacyclin (PGI2)-mediated signal transduction was examined in interleukin 3 (IL-3)-dependent BNu-2cl3 mast cells. Iloprost, a stable PGI2 analogue, induced the accumulation of intracellular cAMP and IP3, and an increase in the intracellular Ca2+ concentration. Pretreatment of the cells with a protein kinase C activator, 12-O-tetradecanoyl phorbol 13-acetate, suppressed the iloprost-induced IP3 accumulation and Ca2+ mobilization, but inversely potentiated the cAMP accumulation, suggesting that neither of these signal transduction pathways of iloprosts is the result of a secondary effect of activation of the other. Removal of IL-3 from the culture medium reduced the iloprost-induced IP3 accumulation and Ca2+ mobilization, while it had no effect on the iloprost-induced cAMP accumulation at all. These results taken together suggest that BNu-2cl3 cells express two types of PGI2 receptor; one couples to stimulation of adenylate cyclase, its expression being independent of IL-3, while the other couples to phosphatidylinositol hydrolysis, its expression being dependent on IL-3.

Adenylyl Cyclases↗
PubMed1993

BQ123, an ETA receptor antagonist, attenuates endothelin-1-induced vasoconstriction in rat pulmonary circulation.

Endothelin-1 (ET-1) is a potent endogenous vasoactive peptide whose role in regulation of vascular tone is unclear. BQ123 is a recently described ETA receptor antagonist which may be useful in further investigation of the physiologic and pathophysiologic significance of ET-1. To test its efficacy in the pulmonary circulation, the vascular response to exogenous ET-1 with and without BQ123 was assessed in rat pulmonary artery (PA) rings and salt-perfused lungs. In both main and distal (250-350 microns ID) PA rings, BQ123 significantly attenuated ET-1-induced contractility, but was more effective in the larger vessels. Likewise, BQ123 significantly blunted ET-1-induced vasoconstriction in perfused lungs by > 80%. In addition, it had no effect on ET-3-mediated or U46619-mediated vasoconstriction, nor did it influence ET-1-induced vasodilation. Development of ET-1-associated hydrostatic edema was also unaffected by BQ123. We conclude that BQ123 effectively attenuates ET-1-induced vasoconstriction in both PA rings and in isolated perfused lungs. The absence of effect of BQ123 on ET-3 vasoconstriction, ET-1 vasodilation, or ET-1- and ET-3-induced hydrostatic edema formation suggests that these processes may be transduced through a non-ETA receptor.

Amino Acid Sequence↗
PubMed1993

EDRF suppresses an unidentified vasoconstrictor mechanism in hypertensive rat lungs.

To test whether endothelium-derived relaxing factor (EDRF) plays a role in regulating the hypertensive pulmonary vascular bed, we compared effects of the inhibitor of EDRF production, N omega-nitro-L-arginine (L-NNA), on resting vascular tone in lungs and conduit pulmonary arteries isolated from control and chronically hypoxic rats. In contrast to no effect on normoxic vascular tone in salt solution-perfused normotensive lungs, 100 microM L-NNA caused a marked, L-arginine-sensitive, precapillary vasoconstriction in unstimulated hypertensive lungs. Bioassay of hypertensive lung perfusate did not detect a circulating vasoconstrictor, and L-NNA vasoconstriction was not inhibited by blockers of cyclooxygenase, 5-lipoxygenase, platelet-activating factor receptors, alpha-adrenoceptors, and serotonin 5-HT2 receptors or by scavengers of superoxide anion and H2O2. Inhibitors of endothelin-1 (ET-1) production and vasoconstriction tended to blunt the response, but accumulation of perfusate ET-1 was not increased in hypertensive lungs. L-NNA vasoconstriction was blocked by Ca(2+)-free plus ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid perfusion but not by nifedipine. Quiescent, endothelium-intact hypertensive but not normotensive conduit pulmonary artery rings were markedly constricted by 200 microM L-NNA. The onset but not the peak of the response was blunted by meclofenamate. The response was reduced slightly by the ETA receptor antagonist, BQ 123. L-NNA had little effect on denuded hypertensive arteries, and treatment with dilators showed they had constricted spontaneously. Both the L-NNA and the spontaneous constrictions were readily inhibited by nifedipine. These results indicate that in rat hypertensive pulmonary arteries, the basal release of EDRF suppresses vasoconstrictor mechanisms which are not expressed in normotensive arteries.

Altitude↗
PubMed1993

NIP-121 is more effective than nifedipine in acutely reversing chronic pulmonary hypertension.

To determine if NIP-121, a new antihypertensive agent with K+ channel-opening activity, would be an effective vasodilator in pulmonary hypertension, we studied its acute hemodynamic effects under normoxic conditions in conscious chronically hypoxic pulmonary hypertensive rats and in control pulmonary normotensive rats. In contrast to no pulmonary vasodilation by NIP-121 in control rats, the K+ channel activator (10-100 mg/kg i.v.) decreased both mean pulmonary arterial pressure (from 42 +/- 2 to 33 +/- 2 mmHg; P < 0.05) and total pulmonary resistance (from 278 +/- 30 to 213 +/- 32 mmHg.l-1 x min; P < 0.05) in hypertensive rats. NIP-121 produced similar dose-related decreases in mean systemic arterial pressure and total systemic resistance in both groups of rats. Both the pulmonary and the systemic vasodilations to NIP-121 were inhibited by pretreatment with the blocker of ATP-sensitive K+ channels, glibenclamide (20 mg/kg), but not with the inhibitor of endothelium-derived relaxing factor synthesis, nitro-L-arginine (10 mg/kg). The L-type voltage-gated Ca2+ channel blocker, nifedipine (10-1,000 mg/kg i.v.), failed to cause pulmonary vasodilation in normoxic hypertensive rats, although there was dose-related systemic vasodilation. These results show that in contrast to the Ca2+ channel blocker, nifedipine, the K+ channel activator, NIP-121, is a potent vasodilator of chronic hypoxia-induced pulmonary hypertension in the rat. The mechanism of its hypotensive action in the hypertensive pulmonary vasculature might be more than simply membrane hyperpolarization and indirect inhibition of the L-type voltage-gated Ca2+ channel.

Altitude↗
PubMed1993

Cementless total hip replacement. Bio-active glass ceramic coating studied in dogs.

We studied 2 types of a cementless total hip prosthesis in dogs. Both were coated with titanium plasma-spray. In both components, the pores in the deep layer of 1 group were further coated with apatite and wollastonite containing glass-ceramic (AW glass-ceramic). 50 dogs underwent unilateral total hip replacements, and were killed at 1, 3, or 6 months postoperatively. We evaluated the femoral and the acetabular components mechanically and histologically. At 1 month, the detaching load and bone ingrowth of the AW glass-ceramic-coated femoral and acetabular components were higher than those of the control implants. At 3 and 6 months there were no differences between the 2 types of components. Thus, AW glass-ceramic enhanced the early phase of cementless implant fixation.

Animals↗
PubMed1993

New antiviral antibiotics, kistamicins A and B. II. Structure determination.

The structures of antiviral antibiotics kistamicins A and B have been determined by a combination of chemical degradation and spectral analysis. They are commonly composed of D-tyrosine, 3,5-dihydrophenylglycine, a biphenyl ether bis-amino acid, and a diphenyl substituted indole tris-amino acid, forming a tricyclic ring structure. Kistamicin B possessed a phenethylamide at the amino terminal of kistamicin A. They are structurally related to the nuclei of the vancomycin group antibiotics particularly to antibiotic complestatin.

Amino Acid Sequence↗