Biomedical subjects

K Yanagi

Publications and source records attributed to K Yanagi.

171 records · Page 10Linked to original sources

PubMedDate not supplied

Synthesis of fusion proteins of Epstein-Barr virus nuclear antigens in E. coli and their antigenicity.

Expression and yield in E. coli of a panel of fusion proteins containing various domains of Epstein-Barr virus nuclear antigens, EBNA-1, EBNA-2, EBNA-3, EBNA-4 and EBNA-6, were scrutinized. The antigenicity of the EBNA fusion proteins against human sera was examined. Monospecific antisera to the different EBNA domains were produced by immunizing guinea pigs and rabbits. An EBNA-6 fusion polypeptide was useful for separating anti-EBNA-6 antibody from human sera by immunoaffinity purification. The applications of the fusion proteins to clinical diagnosis are discussed.

Animals↗

PubMedDate not supplied

Performance of a new hybrid artificial liver support system using hepatocytes entrapped within a hydrogel.

To develop a hybrid artificial liver support system (ALSS), the authors constructed a rotating-disk type ALSS using hepatocytes entrapped within a calcium alginate hydrogel. This module was designed in imitation of the gas-liquid contactor that uses the same principle. Forty disks with film-shaped hydrogel were mounted to a horizontal rotating axis and were kept in contact with blood. The concentration of hepatocytes in the gel varied from 1.9 X 10(9) to 1.7 X 10(10) cells/L gel. Entrapping hepatocytes within hydrogel kept the hepatocytes viable, and results of in vitro experiments showed ammonium metabolism and urea synthesis. The results of ex vivo perfusion experiments using cats with acute hepatic insufficiency indicated that this module had the ability to replace liver function in vivo.

Ammonia↗

PubMedDate not supplied

Improvement of metabolic performance of hepatocytes cultured in vitro in a packed-bed reactor for use as a bioartificial liver.

A packed-bed reactor using reticulated polyvinyl formal (PVF) resin as a support material is a useful configuration to achieve high density culture of hepatocytes for use as a bioartificial liver. The authors investigated the effects of oxygen concentrations of the culture medium on the metabolic performance of hepatocytes cultured in the reactor. A packed-bed reactor loaded with 250 PVF resin cubes (2 x 2 x 2 mm) was used. Hepatocytes obtained from male Wistar rats were inoculated into the reactor. Culture medium was perfused from the reservoir into the reactor through an oxygenator using a roller pump. Concentration of the dissolved oxygen in the medium was controlled by changing the gas mixture ratio supplied to the oxygenator. Hepatocytes cultured in the packed-bed reactor (cell density: 8.6 x 10(6) cells/cm3 PVF) under conditions of high dissolved oxygen concentrations ranging from 260 to 460 micromol/L showed 30% higher ammonium metabolic activity and 85% higher albumin secretion activity compared with those from the monolayer culture in the earlier culture stage (up to 2 days). However, low oxygen concentrations in the medium (<100 micromol/L) impaired activities of cultured hepatocytes.

Animals↗

PubMedDate not supplied

Effects of shear stress on metabolic function of the co-culture system of hepatocyte/nonparenchymal cells for a bioartificial liver.

To improve the culture conditions of hepatocytes for use as a bioartificial liver, the effects of shear flow on the co-culture system of hepatocytes/nonparenchymal cells (NPC) were investigated. A flow chamber with a collagen coated rectangular glass plate, where hepatocytes (5 x 10(4) cell/cm2) and NPC (2 x 10(5) cell/cm2) were seeded, was used to attain a shear stress of 4.7 dyne/cm2. Concentrations of ammonia and urea in the medium were measured daily during the 2 week experiment. The metabolic activity of hepatocytes in the homotypic culture were lower than those of the co-culture, especially when the cultivation time exceeded 1 week. In addition, the applied shear flow promoted activity of the co-culture system. An enhancement in the rates of ammonium removal and urea synthesis was obtained in the perfusion systems. Morphologic observation revealed that aggregates of hepatocytes formed abundantly in the perfusion system and hepatocytes developed a cuboid shape. This suggested that perfusion affected the function and morphology of hepatocytes in the co-culture system. Shear flow could induce cell-cell interactions and secretion of extracellular matrix through the activation of NPC.

Animals↗

PubMedDate not supplied

Operating point control system for a continuous flow artificial heart: in vitro study.

We proposed and developed a practical and effective servo control system for rotary blood pumps. A rotary blood pump for assisting the failing natural heart should be operated only in physiologically acceptable conditions. The operation of a rotary blood pump is based on the rotational speed of the impeller and pressure head. If the pump flow and the pressure head are set within an acceptable range, the driving condition is deemed normal condition, and this control system maintains the preset operating point by applying proportional and detective control (PD control). If the pump flow or pressure head is outside the acceptable range, the driving condition is determined to be abnormal condition, and this system operates the pump in a recovery fashion. If the driving condition is kept under abnormal conditions of sudden decrease of the flow, the condition is termed a suction condition. The controller releases the pump from the suction condition and later returns it to the normal condition. In this study, we evaluated these servo control modes of the centrifugal pump and confirmed whether the performance of this proposed operating point control system was practical.

Algorithms↗

PubMedDate not supplied

Blood flow and leukocyte adhesiveness are reduced in the microcirculation of a peritoneal disseminated colon carcinoma.

Dynamic behavior of leukocytes in the microcirculation of solid tumor tissue was visualized using a fluorescent labeling technique combined with the use of a real-time confocal laser-scanning microscope (CLSM) system. Colon tumor cells (RCN-9) were inoculated into the peritoneal cavity of male Fischer 344 rats. Tumor-free rats were similarly injected with physiological saline (intraperitoneally). Ten days after tumor inoculation, the mesentery was exteriorized and subjected to vital microscopic observation under the CLSM system. Leukocytes were labeled with rhodamine 6G (100 microg kg(-1), intravenously), and their behavior within the microvessels (10-30 microm in diameter) was analyzed both in the solid tumor tissues and the normal mesentery. Wall shear rate was calculated from the measured values of vessel diameter and erythrocyte flow velocity. In tumor microvasculature of tumor-bearing rats, the centerline erythrocyte velocity (0.73 +/- 0.58 mm s(-1), mean +/- standard deviation) and wall shear rate (210 +/- 151 s(-1)) were significantly lower than those of the tumor-free rats (1.27 +/- 0.83 mm s(-1), 344 +/- 236 s(-1), respectively). Despite such reduced flow conditions, flux of the rolling leukocytes as well as density of the adhered leukocytes both decreased significantly in tumor microvasculature as compared with normal controls. The methods developed in this work show promise in improving our understanding of tumor biology and pathophysiology.

Adhesiveness↗

PubMedDate not supplied

Insulin increases blood flow rate in the microvasculature of cremaster muscle of the anesthetized rats.

The hemodynamic actions of insulin in skeletal muscle microvasculature are not yet well elucidated. In the present study, we investigated the effects of systemic insulin injection on arteriole and capillary diameter and blood flow rate in rat cremaster muscle, using intravital real-time confocal laser-scanning microscope system in combination with selective fluorescent labeling. Subcutaneous insulin injecbon (1 U/kg) significantly increased serum insulin levels at 15 minutes as compared with saline injection. At 15 and 30 minutes after insulin injection, blood glucose levels were significantly lower compared to saline injected controls. Arteriolar diameter was significantly increased at 15 and 30 minutes by insulin. Arteriolar erythrocyte flow velocity was significantly increased at 15 and 30 minutes. In addition, capillary erythrocyte flow velocity was increased at 15 and 30 minutes. These results demonstrated that calculated blood flow rates in capillary and arteriole increased after insulin injection.

Anesthesia↗

PubMedDate not supplied

Effects of intra-arterial administration of prostaglandin E1 on rat cremaster muscle microcirculation.

In plastic and reconstructive surgery, postoperative drug therapy with prostaglandin E1 (PGE1) has been widely used to prevent flap necrosis and to extend flap surviving area. In the present study, we assessed the effects of intra-arterial administration of PGE1 on microcirculation. The left cremaster muscle of male Wistar rats were used to measure microcirculatory hemodynamic parameters. The values of internal vessel diameter and erythrocyte velocity were measured by using the confocal laser-scanning microscope (CLSM) system and fluorescent dyes. The blood flow rate was calculated from measured internal vessel diameter and erythrocyte velocity. Internal vessel diameter and flowing erythrocytes were satisfactorily visualized by using the CLSM system. The blood flow rate of arteriole, venule and capillary were dose dependently increased by the intra-arterial administration of PGE1 from the minimum dose of 0.01 ng/kg/min. It is suggested that the intra-arterial administration of PGE1 is a more effective way of postoperative drug therapy than intravenous injection for flap surgery.

Alprostadil↗

PubMedDate not supplied

A high density culture of hepatocytes using a reticulated polyvinyl formol resin.

To enable high density culture of hepatocytes to be used as a hybrid artificial liver support or bioreactor system, collagen coated reticulated polyvinyl formal (PVF) resin (a filter material with a porosity of more than 80%) was used for the primary culture of hepatocytes. Stationary and perfusion culture experiments using PVF resin and monolayer culture were performed as control experiments. Due to the porous structure of the substrate material, hepatocytes were able to penetrate the reticulated pores of the PVF resin, and adhere to and spread on its surface. The densities of hepatocytes attained with PVF were about 10 times as high as those in the monolayer culture using conventional collagen coated Petri dishes. Hepatocytes immobilized in the PVF resin showed viability, as assessed by glutamic pyruvic transaminase (GPT) activity in the medium. Perfusion culture with PVF resin showed stable, high level metabolism, ammonium removal, and urea secretion comparable to the monolayer culture. It is concluded that perfusion culture with PVF resin is useful in attaining a high density culture of hepatocytes.

Animals↗