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Biomedical subjects

S Omokawa

Publications and source records attributed to S Omokawa.

At least 37 records · Page 2Linked to original sources
PubMed1993

Evaluation of a relationship between polymer bulk hydroxyl and surface oxygen content and in vitro serum-material interaction.

To evaluate serum-material interaction for six types of minimodule and to assess the relationship between the interaction and chemical composition, notably bulk polymer hydroxyl (-OH) percent of polymer, or surface oxygen (SO) percent, polymeric membranes with varying -OH and SO percents were evaluated with normal human serum. The membrane materials (-OH percent and SO percent) evaluated included polypropylene (PP; 0% and 1.9%), polyvinyl alcohol (PVA; 23.7% and 27.3%), ethylene vinyl alcohol (EVAL 4A and D; 30.4% and 25.3%), Cuprophan (CP; 31.5% and 37.4%), and Hemophan (HP; 30.9% and 23.6%), respectively. Data from serum perfusions expressed as percent changes to sham perfusion showed that solute percent decreases were less than 10% in all materials except PVA (10-22%). PVA and CP had higher C3a, C4a, and C5a, and C3a concentration increases, and had larger suppressive effects for all three mitogen-induced mononuclear cell transformation functions (MNCTF) and concanavalin A-induced MNCTF, respectively. PVA had higher SO percent than EVAL and CP was higher than HP, despite PVA and CP having lower or comparable bulk -OH percent to EVAL or HP. The results obtained in the serum material interaction studies related more with the SO percent of the polymer rather than bulk -OH percent. The differences for C4a and PHA-induced MNCTF observed between the two EVAL membranes may be associated with significantly different pore size and therefore different surface structural properties. These results suggest that surface chemical (SO percent on the materials) and structural property analyses are important factors in biocompatibility parameter studies.

Biocompatible Materials↗
PubMed1992

An experimental study of the flow-through venous flap: investigation of the width and area of survival with one flow-through vein preserved.

A quantitative analysis was undertaken to investigate the width and area of survival of flow-through venous flaps in 20 ears of 10 rabbits. The 3.0- x 3.0-cm flap models, which included one flow-through vein, were prepared with additional circulation from the graft bed and surrounding tissue excluded, as far as possible. The flaps were divided as follows: Group A--composite grafts (n = 10), and Group B--flow-through venous flaps (n = 10). All flaps in Group A became necrotic and all those in Group B showed partial survival along the flow-through vein. The average survival width was 1.10 +/- 0.48 cm, and the survival rate was 44 +/- 19.3 percent. Microangiograms revealed patency of the flow-through vein in all flaps of Group B. Histologically, there tended to be progressively more fibrous tissue in the area further away from the flow-through vein. The model is useful to investigate the width and area of survival in flow-through venous flaps.

Angiography↗
PubMed1992

Damage and repair of hepatocyte nuclear DNA after hepatic inflow occlusion.

Recent reports emphasize that ischemic tissue damage is caused mainly by superoxide produced at the reperfusion rather than by ischemia itself. In this paper, the damage and repair of hepatocyte nuclear DNA of is investigated using rats with portasystemic shunt. Hepatic inflow was occluded for 30, 60 and two times 30 (with a 10-minute interval) minutes. Extent of DNA damage and repair were measured by nick-translation and 3H-thymidine incorporation, respectively. Superoxide, GOT and endotoxin were also measured. The results are as follows. 1. Sixty minutes of ischemia produced more serious DNA damage of the hepatocyte nucleus and a significant delay in repair as compared with 30 minutes of ischemia. 2. Intermittent ischemia for two times 30 minutes produced milder damage to DNA, and earlier recovery than a single ischemia of 60 minutes. 3. Serum and tissue peroxide increased after reperfusion in 60 minutes and intermittent ischemia, but not after 30 minutes of ischemia. Endotoxin level increased only in 60-minute ischemia. Histological change, neutrophilic cell infiltration, was most prominent in 60-minute ischemia. On the basis of these data, insofar as the duration of ischemia is not so long that cell damage becomes irreversible, damage by superoxide after reperfusion will be negligible. Therefore, intermittent short-term inflow occlusion is preferable in hepatic surgery.

Animals↗
PubMed1992

[A histopathological study on the femoral head necrosis in spontaneously hypertensive rats (SHR)].

The histopathological study was conducted in the femoral head of spontaneously hypertensive rats (SHR), which had frequently manifested osteonecrosis and a delay in the ossification at the femoral epiphysis. In order to elucidate the course of necrosis and its repair process, the bone dynamic of the femoral head was investigated with bone fluorochrome labelling technique. Femoral epiphyses in the SHR were classified into five groups, according to their histopathological changes in relation to osteonecrosis, its repair process and the delay in ossification. Changes in the growing rate of the growth plate at the femoral head and neck were measured quantitatively. As a result, the articular cartilage remained viable and overgrowing, while the epiphyseal plates were affected by the necrosis and there was early physeal maturation occurred. It is concluded that SHR appear to be a useful experimental model for Perthes' disease.

Animals↗
PubMed1991

Immunomodulating effects of serum-material interactions.

The objective of this study is to evaluate an in vitro model to assess the effects of serum-material interactions on complement activation, macromolecular adsorption, and lymphocyte response. Minifilters of clinically available materials (PVA, EVAL-4A, and EVAL-D) used in extracorporeal therapies were evaluated. The test circuit consisted of a pump, sterile tubing, collection vessels, and the minifilter. A sham circuit similar to the test circuit was constructed, but without the filter. Serum flow rates and volumes processed were scaled down to those of clinical use. Post PVA serum showed the highest degree of complement activation, macromolecular solute adsorption, and lymphocyte suppressive response when incubated with Con-A, PHA, PWM, and Candida. Post EVAL-4A sera enhanced the response of lymphocytes to Con-A and PHA, while Post EVAL-D sera showed a slight suppression to these mitogens. Blood-material interactions have been shown to cause blood cellular changes. The in vitro model employed is simple to apply and does not require an animal or patient. The membrane modules used are a mini-type of clinically available extracorporeal filters, and there is a greater direct relevancy to clinical applications than there would be using specially formulated materials. This system would provide useful preclinical information in evaluating the effect of serum-material interactions.

Blood Physiological Phenomena↗
PubMed1991

A simple experimental model of total hepatectomy, hepatic ischemia and extrahepatic portal obstruction in rats using splenic transposition.

The objective of this study was to develop an easy and simple experimental rat model of total hepatectomy, hepatic ischemia and extrahepatic portal obstruction. The first operation involved transposing the spleen with its scarified capsule in a subcutaneous pouch to produce portasystemic anastomosis. Total hepatectomy was easily performed in a lobe-by-lobe fashion 2 weeks following the first stage operation. Anhepatic rats receiving a glucose infusion survived for about 10 hours and all died of acute hepatic failure. Hepatic support systems can be accurately evaluated in this anhepatic rat model because of its uniformity. Sixty minutes of hepatic ischemia was able to be performed in rats with a transposed spleen for a portasystemic shunt and no complicated or technically involved procedure was required for the ischemic model. No rats died due to technical difficulties, suggesting the reliability and reproducibility of this ischemic model. An animal model resembling extrahepatic portal vein obstruction was also obtained by ligation of the portal vein; a simple maneuver which was able to produce collateral veins to the liver and cavernous transformation, as similarly seen in clinical patients with extrahepatic portal obstruction. Because these 3 animal models were so easily achieved in the rat, and since the changes in hepatic function and formation of the collaterals to the liver after portal vein occlusion are still poorly understood, this model should prove valuable for future study.

Animals↗
PubMed1991

Insemination of bile duct carcinoma to the liver after insertion of percutaneous biliary endoprosthesis.

Percutaneous transhepatic biliary drainage is widely used to relieve bile duct obstruction which can be caused by bile duct or pancreas carcinomas. Although the incidence is low, insemination of carcinoma along the transhepatic catheter tract is considered to be a serious complication of percutaneous transhepatic biliary drainage. The authors present a case of intrahepatic insemination of bile duct carcinoma along the catheter that subsequently underwent a curative resection consisting of pancreaticoduodenectomy and right hepatic lobectomy. It is suggested that a percutaneous biliary endoprosthesis through the tumor should be avoided in patients in whom a possible curative resection can be considered. External biliary drainage should only be performed in order to minimize the manipulation of the tumor in such patients.

Adenocarcinoma↗
PubMed1991

Hepatic hemodynamics and functions in extrahepatic portal obstruction in the rat with liver cirrhosis.

Portal vein obstruction due to a thrombus may be encountered in liver cirrhosis. However, the effect of portal vein obstruction on hepatic hemodynamics and functions, and on collateral formation has not been clear in liver cirrhosis. To rectify this, the cirrhotic rat model with portal vein ligation was evaluated. In addition to the early recovery of hepatic blood flow, the reduction in hepatic blood flow after portal vein ligation was less in the cirrhotic rat than in the normal rat. The portogram showed that, in addition to hepato-fugal collaterals, hepato-petal collaterals developed well and early in the cirrhotic rat as compared with the normal rat. Although mitochondrial functions before portal vein ligation deteriorated in the cirrhotic rat, the decrease after portal vein ligation was less, and the recovery of function was earlier in the cirrhotic than the normal rat. The influence of portal vein obstruction on hepatic hemodynamics and functions in the cirrhotic rat was less than in the normal rat, due to earlier and significant formation of hepato-petal collaterals.

Animals↗
PubMed1990

Effect of anticoagulant on biocompatibility in membrane plasmapheresis.

The effect of heparin or citrate anticoagulation on blood cellular, complement pathway and coagulation pathway was investigated in a membrane plasma exchange procedure. Two membrane plasma separators constructed of cellulose di-acetate (CA) and polyvinyl chloride (PVC) were evaluated with heparin or citrate alone for anticoagulation in a 26 year old male with myasthenia gravis. Maximum white blood cell counts decrease was 21% at 30 min for the CA with heparin while no decrease was observed for the other schemes. Platelet counts changes were comparable between heparin and citrate, while the PVC groups showed less changes than the CA groups. The CA groups, regardless of the type of anticoagulant used, indicated that complement activation occurred via the classical pathway within the module in addition to the activation via alternative pathway for the CA with heparin. In the PVC groups, complement activation was noted to occur only when heparin was used for anticoagulation. PT and PTT showed slight increases with citrate, while they were remarkably prolonged with heparin. Citrate showed less changes in cellular and humoral factors compared to heparin. CA with heparin was the most activating combination of membrane material and anticoagulant, while the PVC with citrate was the least activating combination.

Adult↗
PubMed1989

Surface area effects on efficiency and biocompatibility in experimental membrane plasmapheresis.

The effect of different surface areas on cellular, humoral, and hemodynamic changes and on plasma separation performance were investigated. Membrane plasmapheresis, consisting of plasma separation and on-line reinfusion, was carried out on dogs for 3 h with 0.6 and 0.3-m2 polyethylene (PE) and polyvinyl alcohol (PVA) modules. The plasma separation and sieving performance was comparable in both the 0.6 and 0.3-m2 modules. The initial white blood count (WBC) reductions were independent of the surface area difference, but the rebound was greater in the smaller modules. The platelet (PLT) reductions were less with the 0.3-m2 PE module in comparison to those with the larger PE module, but no differences existed between both of the PVA modules. The smaller PVA module showed less complement activation compared to the 0.6-m2 module, whereas both of the PE modules showed comparable changes. Hemodynamic responses, especially the changes in pulmonary vascular resistance, were less with the smaller modules compared to the 0.6-m2 modules. The PE modules themselves showed less blood cellular, humoral, and hemodynamic changes compared to the PVA modules. The smaller modules showed greater rebound of WBC counts, however, PLT reductions, complement activation, and changes in hemodynamic parameters were less in the smaller modules.

Animals↗
PubMed1989

Mitochondrial function of isolated rat hepatocytes from normal and cirrhotic liver.

Mitochondrial fractions were obtained from purely isolated hepatocytes of the normal and cirrhotic livers. Mitochondrial function of isolated hepatocytes was evaluated to compare between those from the normal and those from the cirrhotic livers in addition to the evaluation of the mitochondrial function of the normal and cirrhotic liver tissues. Respiratory control, ADP/O ratio and ATP synthesis were significantly lower in the cirrhotic liver tissue than those in the normal liver tissue. However, the mitochondrial function of isolated hepatocytes showed no difference between normal and cirrhotic groups. By electron microscopic examination, debris was more observed in the mitochondrial fractions from the normal and cirrhotic tissues compared to those from hepatocytes. However, no difference of the shape and size of the mitochondria was seen between the fraction from hepatocytes and that from the tissue in each group. These results suggest that as far as hepatocyte itself is concerned, the cirrhotic liver preserves the sufficient function as well as the normal liver.

Adenosine Triphosphate↗
PubMed1989

Temperature effect on bilirubin adsorption with the anion exchange resin BR-601.

Plasma perfusion with the anion exchange resin BR-601 is an effective method to treat patients with hepatic failure and hyperbilirubinemia. To assess the temperature dependency of bilirubin sorption in vitro, isotherm studies with human pathologic plasmas and an albumin-bilirubin solution were carried out. Results showed that BR-601 was more effective at 37 degrees C and 42 degrees C than at 4 degrees C and 25 degrees C for sorbing bilirubin. Therefore, plasma sorption at near physiologic temperature would be expected to be more efficient for plasma treatment than sorption at ambient temperature.

Adsorption↗