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K Okajima

Publications and source records attributed to K Okajima.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Adenosine reduces ischemia/reperfusion-induced liver injury by inhibiting leukocyte activation].

To examine whether adenosine reduces ischemia/reperfusion (I/R)-induced liver injury by inhibiting leukocyte activation via A2 receptor (A2R), we investigated the effects of adenosine and YT-146, selective A2A receptor (A2AR) agonist, on I/R-induced liver injury in rats. Adenosine and YT-146, in the range of concentrations of 10(-7)-10(-5) M, significantly inhibited the formyl-methionyl-leucyl-phenylalanine (fMLP)-induced neutrophil elastase release from isolated neutrophils by about 35% in vitro. Adenosine and YT-146, in the range of concentrations of 10(-7)-10(-5) M, significantly inhibited the endotoxin-stimulated TNF-alpha production by monocytes to less than 50% of the control. Although ZM241385, a selective A2AR antagonist, significantly enhanced the fMLP-induced neutrophil elastase release in isolated neutrophils in vitro, this agent did not affect the endotoxin-stimulated TNF-alpha production by monocytes. Male Wistar rats were subjected to complete ischemia of median and left lobes of liver for 60 min and the subsequent reperfusion. Serum levels of transaminases increased over time after hepatic I/R, peaking at 12 hrs after reperfusion. Intravenous infusion of Adenosine (1 and 10 mg/kg/hr) and YT-146 (0.1 and 1 mg/kg/hr) significantly inhibited the I/R-induced increases in serum transaminase levels 12 hrs after reperfusion. The I/R-induced decrease in hepatic tissue blood flow was significantly inhibited by adenosine and YT-146. Hepatic levels of TNF-alpha, cytokine-induced neutrophil chemoattractant (a member of interleukin-8), and myeloperoxidase were significantly increased after I/R. These increases were significantly inhibited by administration of adenosine and YT-146. However, ZM241385 did not reduce the I/R-induced liver injury and it inhibited neither the decrease in hepatic tissue blood flow, nor the indicators of leukocyte activation. These findings suggest that adenosine may reduce I/R-induced liver injury mainly by inhibiting hepatic TNF-alpha production via A2AR, thereby reducing neutrophil activation.

Adenosine↗
PubMed1999

Life-threatening bleeding in a case of autoantibody-induced factor VII deficiency.

A male patient presented with life-threatening bleeding induced by autoantibody-induced factor VII (F.VII) deficiency. This patient had macroscopic hematuria, skin ecchymosis, gastrointestinal bleeding, and a neck hematoma that was causing disturbed respiration. He developed acute renal failure and acute hepatic failure, probably due to obstruction of the ureters and the biliary tract, respectively. Although activated partial thromboplastin time was normal, prothrombin time (PT) was remarkably prolonged at 71.8 seconds compared to 14.0 seconds in a normal control. Both the immunoreactive level of F.VII antigen and the F.VII activity of the patient's plasma samples were < 1.0% of normal. Although an equal part of normal plasma was added to the patient's plasma, PT was not corrected. The patient's plasma inhibited F.VII activity. These findings suggested the presence of a plasma inhibitor for F.VII. After administration of large doses of methylprednisolone, PT was gradually shortened and plasma levels of F.VII increased over time. Bleeding, acute renal failure, and acute hepatic failure improved markedly following the steroid treatment. These observations suggest that life-threatening bleeding can be induced by autoantibody-induced F.VII deficiency and that immunosuppressive therapy using large doses of steroid can be successful in inhibiting the production of the autoantibody.

Aged↗
PubMed1999

[Antithrombin].

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Antithrombin III↗
PubMed1998

The optimal combination of hyperthermia and carbogen breathing to increase tumor oxygenation and radiation response.

PURPOSE: To determine the most effective combination of carbogen breathing with mild temperature hyperthermia (MTH) to increase the oxygenation and radiation response in murine tumors. METHODS AND MATERIALS: MTH at 41.5 degrees C for 60 min was applied by immersion of the tumor in a precisely controlled water bath. The tumor pO2 was measured with a polarographic microelectrode. The radiation response of the tumor was determined using the in vivo/in vitro assay for surviving tumor cells. RESULTS: In the FSaII fibrosarcoma the median pO2 increased from a control value of 6.5 +/- 0.5 mm Hg to 16.6 +/- 1.1 mm Hg immediately after MTH and was 10.9 +/- 1.3 mm Hg 24 h later. Carbogen breathing for 5 min increased the FSaII pO2 to 19.9 +/- 2.1 mm Hg. Carbogen breathing for 5 min beginning immediately after MTH increased the median pO2 more than 5 times to 35.4 +/- 3.8 mm Hg. This combined treatment also substantially increased the response of the tumors to a radiation exposure of 20 Gy. In another tumor model, the SCK mammary carcinoma, MTH treatment increased the median pO2 from the control level of 4.4 +/- 0.2 mm Hg to 12.6 +/- 1.2 mm Hg, and it returned to 4.3 +/- 0.3 mm Hg 24 h later. Carbogen breathing for 5 min increased the SCK tumor pO2 to 17.1 +/- 1.4 mm Hg. The median SCK pO2 was increased about 7 times to 31.2 +/- 4.2 mm Hg when MTH was followed immediately with carbogen breathing for 5 min. The radiation response was also markedly increased by this combination. When the animals breathed carbogen for 15 or 30 min, the pO2 and radiosensitivity in both tumor types either remained the same or was lower than that after 5 min of breathing. In addition, both FSaII and SCK tumors were radiosensitized 24 h after MTH treatment alone or with 5 min of carbogen breathing. CONCLUSIONS: A shorter carbogen breathing time immediately after MTH causes the most tumor radiosensitization. The results of this study also demonstrate that MTH increases radiosensitivity with and without carbogen breathing up to 24 h after the mild hyperthermia treatment.

Animals↗
PubMed1998

Role of neutrophil elastase in compression-induced spinal cord injury in rats.

We have previously demonstrated the importance of activated neutrophils in compression-induced spinal cord injury (SCI) in rats. In the present study, we investigate the action of neutrophil elastase in posttraumatic SCI, using two neutrophil elastase inhibitors (Eglin C and L658,758). SCI was induced by applying a 20-g weight to the spinal cord for 20 min at the level of T12, resulting in hindlimbs motor disturbances, which, when evaluated using a inclined-plane test, were significantly attenuated by Eglin C or L658,758. Histologic examination revealed that intramedullary hemorrhages observed 24 h after trauma were markedly attenuated in these agents. These inhibitors also significantly decreased neutrophil accumulation as shown by myeloperoxidase activity in the damaged spinal cord segment. Induction of leukocytopenia had the same effects as Eglin C or L658,758. These findings implicated neutrophil elastase in SCI. The enzyme may induce vascular damage leading to spinal cord ischemia.

Animals↗
PubMed1998

Effects of various doses of antithrombin III on endotoxin-induced endothelial cell injury and coagulation abnormalities in rats.

We previously demonstrated that antithrombin III reduced the injury to endothelial cells caused by activated leukocytes in rats administered endotoxin. This occurred via the increase of the endothelial release of prostaglandin I2, which is a potent inhibitor of leukocyte activation. We evaluated the dose of antithrombin III required to prevent such endothelial cell injury in rats administered endotoxin, by comparing the effects of various antithrombin II doses on the pulmonary vascular injury. The intravenous administration of endotoxin, 5 mg/kg, produced a transient accumulation of leukocytes in the lung, followed by pulmonary vascular injury, as indicated by an increase in the pulmonary vascular permeability, and coagulation abnormalities. The dose of 250 U/kg significantly inhibited all such effects of endotoxin. While lower doses of antithrombin III (50 and 100 U/kg) significantly inhibited such coagulation abnormalities, they failed to prevent either the pulmonary accumulation of leukocytes or the subsequent pulmonary vascular injury. Rats administered endotoxin exhibited an accumulation of neutrophils and edematous changes in the pulmonary interstitial space. Although such changes were reduced after 250 U/kg of antithrombin III, they were unaffected by lower doses of 50 and 100 U/kg. Plasma levels of 6-keto-PGF1alpha were markedly increased in rats 90 min after the administration of endotoxin, and were significantly decreased in the endotoxin-treated rats administered the lower doses of antithrombin III (50 and 100 U/kg), but not altered in those endotoxin-treated rats receiving 250 U/kg of antithrombin III. These findings suggest that a higher antithrombin III dose is necessary to prevent endothelial cell injury than is required to inhibit coagulation abnormalities in an animal model of sepsis. These observations support the notion that antithrombin III may prevent endotoxin-induced endothelial cell injury by promoting endothelial release of prostaglandin I2 and thus inhibiting leukocyte activation.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

Activated protein C reduces the severity of compression-induced spinal cord injury in rats by inhibiting activation of leukocytes.

Activated protein C (APC), an important inhibitor of the coagulation system, has recently been shown to prevent tissue injury by blocking the activation of leukocytes. To determine whether APC can also prevent post-traumatic spinal cord injury (SCI), a condition in which leukocytes play an important role, we tested the effects of APC on SCI induced in rats by compression trauma. Administration of APC, either before or after the induction of SCI, markedly reduced the motor disturbances in these animals. In contrast, neither an inactive derivative of activated factor X (DEGR-Xa), a selective inhibitor of thrombin generation, nor active site-blocked APC (DIP-APC) reduced the motor disturbances. Histological examination revealed that intramedullary hemorrhages, observed 24 hr after trauma, were significantly reduced in the animals administered APC. The increase in the tissue level of tumor necrosis factor-alpha (TNF-alpha) and the accumulation of neutrophils in the damaged segment of the spinal cord were significantly inhibited in the animals that had received APC, but these were not inhibited in those administered DIP-APC or DEGR-Xa. The induction of leukocytopenia had the same effect as APC, in that it significantly reduced motor disturbances, tissue levels of TNF-alpha, and neutrophil accumulation in the animals subjected to compressive SCI. These findings suggest that in SCI, APC reduces motor disturbances primarily by reducing the amount of TNF-alpha at the site of injury, thus inhibiting neutrophil accumulation and the resultant damage to the endothelial cells.

Animals↗
PubMed1998

Role of neutrophil elastase in stress-induced gastric mucosal injury in rats.

Activated neutrophils play an important role in tissue injury by releasing various inflammatory mediators capable of damaging endothelial cells. To investigate whether neutrophil elastase (NE) is involved in stress-induced gastric mucosal injury, we examined the effects of 2 NE inhibitors (ONO-5046 and L-658 758) as well as nitrogen mustard-induced leukocytopenia on the formation of gastric mucosal lesions, gastric mucosal blood flow, gastric mucosal microvascular permeability, and gastric neutrophil accumulation in rats subjected to water immersion-restraint stress (WIR). Gastric mucosal injury peaked 8 hours after WIR. Gastric mucosal blood flow, as measured by laser-Doppler flow cytometry, decreased to 45% of its initial level 8 hours after WIR. Gastric mucosal microvascular permeability, evaluated by Evans blue dye leakage to the gastric mucosa, showed an increase, peaking 8 hours after WIR. Gastric accumulation of neutrophils, determined by measuring gastric myeloperoxidase activity and by histologic examination, was also significantly increased 8 hours after WIR. Both of the NE inhibitors markedly prevented the formation of gastric mucosal lesions. They also decreased the reduction in gastric mucosal blood flow seen in animals subjected to WIR while preventing increases in gastric mucosal microvascular permeability. Gastric neutrophil accumulation was significantly reduced in animals given either inhibitor 8 hours after WIR. Leukocytopenia produced effects similar to those produced by the inhibitors. Taken together, these observations strongly suggest that NE promotes stress-induced gastric mucosal injury in rats by reducing gastric mucosal blood flow and increasing neutrophil accumulation.

Animals↗
PubMed1998

Spinal cord injury in the rat.

Only limited therapeutic measures are currently available for the treatment of spinal cord injury. This review describes the pathologic mechanisms of trauma-induced spinal cord injury in rats, which will contribute to new understanding of the pathologic process leading to spinal cord injury and to further development of new therapeutic strategies. Spinal cord injury induced by trauma is a consequence of an initial physical insult and a subsequent progressive injury process that involves various pathochemical events leading to tissue destruction; the latter process should therefore be a target of pharmacological treatment. Recently, activated neutrophils have been shown to be implicated in the latter process of the spinal cord injury in rats. Activated neutrophils damage the endothelial cells by releasing inflammatory mediators such as neutrophil elastase and oxygen free radicals. Adhesion of activated neutrophils to the endothelial cell could also play a role in endothelial cell injury. This endothelial cell injury could in turn induce microcirculatory disturbances leading to spinal cord ischemia. We have found that some therapeutic agents that inhibit neutrophil activation alleviate the motor disturbances observed in the rat model of spinal cord injury. Methylprednisolone (MPS) and GM1 ganglioside, which are the only two pharmacological agents currently clinically available for treatment of acute spinal cord injury, do not inhibit neutrophil activation in this rat model. Taken together, these observations raise a possibility that other pharmacological agents that inhibit neutrophil activation used in conjunction with MPS or GM1 ganglioside may have a synergistic effect in the treatment of traumatic spinal cord injury in humans.

Animals↗
PubMed1998

Two-dimensional Gabor-type receptive field as derived by mutual information maximization.

Two-dimensional receptive fields are investigated from an information theoretic viewpoint. It is known that the spatially localized and orientation- and spatial-frequency-tuned receptive fields of simple cells in the visual cortex are well described by Gabor functions. This paper shows that the Gabor functions are derived as solutions for a certain mutual-information maximization problem. This means that, in a low signal-to-noise ratio limit, the Gabor-type receptive field can extract the maximum information from input local images with regard to their categories. Accordingly, this suggests that the receptive fields of simple cells are optimally designed from an information theoretic viewpoint.

Journal Article↗
PubMed1998

The Gabor function extracts the maximum information from input local signals.

The receptive fields of simple cells in the visual cortex are well approximated by Gabor functions. This paper shows that the Gabor functions are derived as solutions for a certain mutual-information maximization problem. This means that, under rather general assumptions, the Gabor function can extract the maximum information from input local signals. This suggests that the receptive fields of simple cells are optimally designed from an information theoretic viewpoint.

Journal Article↗
PubMed1998

The anti-inflammatory properties of antithrombin III: new therapeutic implications.

Antithrombin III (AT III) supplementation has proven to be effective in the treatment of disseminated intravascular coagulation. Administration of AT III is also useful for prevention of organ failure in animals challenged with endotoxin or bacteria and it increases the survival rate of such animals. Since inhibition of coagulation abnormalities failed to prevent organ failure in animals given bacteria, AT III may exert a therapeutic effect independent of its anticoagulant effect. This therapeutic mechanism of AT III has been explored using an animal model of septicemia. AT III prevented pulmonary vascular injury by inhibiting leukocyte activation in rats given endotoxin. This effect is mediated by the promotion of endothelial release of prostacyclin which inhibits leukocyte activation. Interaction of AT III with heparin-like glycosaminoglycans (GAGs) on the endothelial cell surface appears to be important for this effect. Heparin inhibits these therapeutic effects of AT III by preventing AT III from interacting with the cell surface heparin-like GAGs. This activity of AT III may explain why AT III prevents organ failure as well as coagulation abnormalities in patients with sepsis. This antiinflammatory activity of AT III may be useful for the treatment of organ failure such as in ischemia/reperfusion-induced organ dysfunction, in which activated leukocytes play a critical role.

Animals↗
PubMed1998

Radiotherapy combined with transcatheter arterial infusion chemotherapy for locally advanced cervical cancer.

Twenty-four patients with locally advanced cervical cancer were treated with radiation therapy (RT) and transcatheter arterial infusion (TAI) chemotherapy, while 22 patients were treated with RT alone. RT consisted of a combination of external irradiation and high-dose-rate intracavitary brachytherapy. TAI therapy consisted of two sessions using cisplatin and pirarubicin, performed concurrently during the periods of external irradiation. The local-regional control rates at 1 year for the patients treated with RT plus TAI and for those treated with RT alone were 87.5% and 58.3%, respectively (p < 0.05). The 3-year cause-specific survival (CSS) rates for RT plus TAI, and RT alone were 67.1% and 55.9%, respectively (p = n.s.). The 3-year CSS rate for the 14 patients treated with RT and TAI who had well- or moderately differentiated squamous cell carcinoma without pelvic lymph node swelling was 100%, while that for the 19 patients with the same background treated with RT alone was 49% (p < 0.01). Radiation therapy combined with TAI appears to be an effective and safe treatment modality for patients with locally advanced cervical cancer.

Adult↗
PubMed1998

Tumor oxygenation after mild-temperature hyperthermia in combination with carbogen breathing: dependence on heat dose and tumor type.

We investigated the effect of hyperthermia at 40.5-42.5 degrees C as well as the combination of hyperthermia and carbogen breathing on oxygenation in the SCK murine mammary carcinoma. In addition, the important question of how long the effect of heating on tumor oxygenation lasts was addressed in both SCK and FSaII (murine fibrosarcoma) tumors. The median pO2 in control SCK tumors was 4.4 +/- 0.2 mm Hg, and it increased to a maximum of 12.6 +/- 1.2 mm Hg when the tumors were heated at 41.5 degrees C for 1 h. Carbogen breathing increased the median pO2 of SCK tumors to 17.1 +/- 1.4 mm Hg, but after heating at 41.5 degrees C, it elevated the pO2 in SCK tumors markedly to 31.3 +/- 4.2 mm Hg. The kinetics of the return to baseline oxygenation after hyperthermia was found to vary with the type of tumor and the heat dose. The pO2 of FSaII tumors remained significantly higher than that of control tumors 24 h after heating at 41.5 degrees C for 60 min. The pO2 of SCK tumors remained elevated for up to 3 h after heating at 41.5 degrees C for 30 min, but if the tumors were heated for 60 min at this temperature, the median oxygen tension declined to the control level within 1 h after heating. It was concluded that mild-temperature hyperthermia, i.e. 41.5 degrees C, alone and in combination with carbogen breathing dramatically improves the oxygenation of these murine tumors and that the tumor type influences the duration of changes in oxygenation induced by mild-temperature hyperthermia.

Animals↗
PubMed1998

[A cooperative study on concomitant with low-dose divided administration of cisplatin (CDDP) and sustained drip infusion of 5-fluorouracil (5-FU) for unresectable advanced gastric cancer. Osaka Cisplatin Gastric Cancer Study Group].

For patients with unresectable gastric cancer registered between July 1994 and September 1995, the following dosage regimen was examined: a drip infusion of cisplatin (CDDP) at 7 mg/m2/day for 5 consecutive days and 2-day withdrawal a week for 3 weeks with concomitant sustained drip infusion of 5-FU at 300 mg/m2/day for 21 days. The whole cycle was repeated again after 2-week withdrawal. The antitumor effect was seen in 39.4% among 33 cases. With respect to histological classification, there was no difference in appearance of the effect between the moderately differentiated type at 62.5% and the low-differentiated type at 42.9%. The cases which became resectable after the administration included those in which the tumor disappeared completely in the resected specimens. As adverse reactions encountered in the cases above Grade 3, anorexia, nausea and vomiting and diarrhea were seen as clinical symptoms in 10, 5.3 and 11.8%, respectively. As laboratory test values, decrease in hemoglobin, leukocytopenia and thrombocytopenia were seen in 16.7, 15.8 and 5%, respectively, while renal or liver dysfunction did not occur. This dosage regimen was considered useful for unresectable advanced gastric cancer, although myelosuppression should be watched carefully.

Adult↗
PubMed1998

Antithrombin prevents endotoxin-induced pulmonary vascular injury by inhibiting leukocyte activation.

Replacement of antithrombin has proved to be effective for treating disseminated intravascular coagulation. The administration of antithrombin is also useful for preventing organ failure in animals challenged with endotoxin or bacteria, and it increases the survival rate of such animals. Since inhibition of coagulation abnormalities by heparin failed to prevent organ failure in animals challenged with bacteria, antithrombin might exert therapeutic effects independently of its anticoagulant effect. These therapeutic mechanisms of antithrombin have been explored by using animal models of septicemia. Antithrombin prevents pulmonary vascular injury by inhibiting leukocyte activation in rats challenged with endotoxin. A higher dose of antithrombin was required to prevent pulmonary vascular injury than was required to inhibit disseminated intravascular coagulation. This preventive effect of antithrombin is mediated by the promotion of endothelial release of prostacyclin, an inhibitor of leukocyte activation. An interaction between antithrombin and heparin-like glycosaminoglycans on the endothelial cell surface appears to be important for this effect. Heparin inhibits such therapeutic effects of antithrombin by preventing it from interacting with the cell surface heparin-like glycosaminoglycans. Since activated leukocytes are of critical importance in patients with sepsis-associated organ failure, this anti-inflammatory activity of antithrombin may explain why it can prevent organ failure as well as coagulation abnormalities in patients with sepsis.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

[Changes in surgical treatment for gastric cancer].

Gastrectomy for gastric cancer was carried out successfully for the first time by Professor T. Billroth in 1881. Since then, surgical treatment for gastric cancer has come into worldwide use. In Japan, since the establishment of the Japanese Research Society for Gastric Cancer in 1962, extended radical gastrectomy, which included extended lymphadenectomy and combined resection of other organs, was the main surgical strategy to increase the radical cure rate for gastric cancer. Recently, however, as the number of cases of early gastric cancer has increased, rational surgery (type-oriented surgery) has been increasingly performed in consideration of the quality of life after surgery. Specifically, various limited operations for small early gastric cancer, and super-extended surgery for advanced gastric cancer have been carried out. To perform limited surgery for gastric cancer in which radicality is not compromised, preoperative and intraoperative diagnosis of the extent of cancerous lesions must be performed accurately, and sufficient clinicopathological knowledge of the extension of gastric cancer is indispensable. Moreover, minimally invasive surgical techniques have been developed in recent years. Every effort should be made to perform rational surgery for gastric cancer on the basis of studies in past decades.

Gastrectomy↗