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Biomedical subjects

C Nojiri

Publications and source records attributed to C Nojiri.

At least 55 records · Page 3Linked to original sources
PubMed1983

Cloning of antibiotic-resistance genes in Streptomyces.

Antibiotic-resistance genes were shotgun cloned from antibiotic-producing Streptomyces sp. using pock-forming plasmids (pSF689 and pSF765), as cloning vectors. Streptomyces chartreusis SF1623 and S. lividans 66 were used as host strains. The ribostamycin (RSM) resistance gene was cloned from S. ribosidificus SF733 DNA (on a 2.3 Md PstI fragment) into both S. chartreusis SF1623 and S. lividans 66, using pSF689 as vector. Kanamycin (KM), novobiocin (NB), destomycin (DM) and racemomycin (RM) resistance genes were cloned from S. kanamyceticus M1164, S. spheroides M1469, S. rimofaciens M1470 and S. lavendulae A249 genomic DNA into S. lividans 66, using pSF765 as vector. Furthermore two types of KM resistance determinants derived from S. kanamyceticus M1164 were cloned using S. lividans 66, the pSF689 vector. The RSM resistance gene showed no homology to plasmid pSF733 of S. ribosidificus SF733, but hybridized to PstI or BclI digested total DNA of S. ribosidificus SF733.

Anti-Bacterial Agents↗
PubMed1983

Pock forming plasmids from antibiotic-producing Streptomyces.

Pock forming ability of fifteen plasmids isolated from antibiotic-producing Streptomyces was examined with polyethylene glycol mediated protoplast transformation. Four plasmids (pSF765, pSF689, pSF674 and pSF601) were found to have pock forming ability on Streptomyces lividans 66. Each putative transformants isolated from the center of pock regions harbored plasmids with same restriction enzyme cleavage sites as original plasmids. The plasmids from the transformants produced pock, which were morphologically identical to the original plasmids. Transformation frequency of S. lividans 66 with pSF689 from S. lividans 66 was at least 500-fold higher (5 x 10(5) transformants per 1 microgram DNA) than that with the plasmid isolated from the original strain (10(3) transformants per 1 microgram DNA). In case of pSF765 the transformation frequency was not changed (about 10(5) transformants per 1 microgram DNA) by replications in S. lividans 66. Expanded restriction enzyme maps for the four plasmids are reported.

Anti-Bacterial Agents↗
PubMedDate not supplied

In vivo protein adsorption onto polymers: a transmission electron microscopic study.

This paper reports in vivo protein adsorption onto polymers, including Biomer, PEO grafted Biomer (B-PEO-4K), heparin immobilized Biomer with PEO spacers (B-PEO-4K-HEP), and HEMA-Styrene block copolymer (H-S). Vascular grafts (6 mm ID, 7 cm in length) were fabricated with Biomer, coated on their luminal surfaces with test polymers, and implanted into the abdominal aorta of dogs. After 3 weeks-1 month, the grafts were retrieved and processed for TEM and SEM. TEM measured the thickness of adsorbed protein layers stained with a OsO4 solution, and the distribution pattern of adsorbed proteins (albumin, IgG and fibrinogen) using the immunoperoxidase technique. Retrieved grafts of Biomer and B-PEO-4K showed mural thrombi along the graft length, while thrombus formation on B-PEO-4K-HEP and H-S grafts was limited to the anastomotic sites. SEM pictures of B-PEO-4-HEP and H-S surfaces demonstrated clear morphology, with minimal platelet adhesion and activation, and microthrombi. Biomer and B-PEO-4K demonstrated a thick proteinaceous layer (1000-2000 A), whereas B-PEO-4K-HEP and H-S showed what can be described as a monolayer protein thickness (200-300 A). B-PEO-4K-HEP and H-S showed a monolayer-like adsorbed protein pattern, with high concentrations of albumin and IgG, and less fibrinogen, while Biomer and B-PEO-4K showed multilayered patterns with relatively high concentrations of fibrinogen, and less albumin. These results suggest that the surface properties of polymer may control protein adsorption pattern, and the composition of adsorbed protein is essential to in vivo long-term blood compatibility.

Adsorption↗
PubMedDate not supplied

Scanning and transmission electron microscopic evaluation of the U-100 total artificial heart blood contacting surface.

Thrombus formation, cell adhesion, mineralization, and the adsorbed protein layer have been investigated on blood contacting surfaces of the Utah-100 total artificial heart (TAH). Retrieval analysis was performed on two calves (at 7 and 97 days) and a sheep (at 21 days). Six locations on each ventricle were systematically evaluated by scanning electron microscopy. Transmission electron microscopy was used to measure the thickness and distribution of proteins (albumin, IgG, and fibrinogen) on the surface. Gross thrombus was detected only on the left atrial cuff in the 97 day calf. SEM demonstrated fairly clear surface morphology, with minimal platelet adhesion and activation, and little thrombus formation. At 97 days, calcium deposits were detected along the diaphragm-housing junction. Protein layer thickness on the diaphragm increased with implant time; dominant proteins detected on the surface were fibrinogen and IgG, rather than albumin. Improvements in design and fabrication techniques have demonstrated decreased intradevice thrombosis with the U-100 TAH. However, systemic thromboembolism still remains a problem, and further improvements in the blood contacting surface of the U-100 TAH are necessary to achieve a thrombus free TAH.

Animals↗
PubMedDate not supplied

In-storage hypothermic perfusion for heart and lung transplantation.

The authors developed a new waterproof-packed infusion device for easy and sterile in-storage hypothermic perfusion during organ transportation for heart and lung transplantation. They examined the accessibility and efficacy of this infusion device for portable heart and lung preservation in canine transplant models. Sixteen heart and bilateral lung blocks were preserved by an in-storage hypothermic perfusion technique using the infusion device with University of Wisconsin solution. Of 16 dog recipients, 5 underwent orthotopic heart transplantation with cardiopulmonary bypass, and 5 dogs received left lung transplantation; the remaining heart and lung blocks were intrathoracically transplanted into 6 dogs. Functional status and histology of 11 heart and 11 lung allografts were evaluated by post-transplant course, hemodynamic parameters, arterial blood gas measurements, microscopic examination, and so on. Eleven transplanted hearts showed good cardiac performance and maintained systemic circulation after weaning from cardiopulmonary bypass. Eleven transplanted lungs had excellent respiratory function, and all five dogs with left lung transplantation survived for 5-46 days (mean: 18.8 days). These results suggest that in-storage hypothermic perfusion with this waterproof-packed infusion device can be a useful technique for long-term organ preservation in heart and lung transplantation.

Animals↗
PubMedDate not supplied

A miniature intraventricular axial flow blood pump that is introduced through the left ventricular apex.

A new intraventricular axial flow blood pump has been designed and developed as an implantable left ventricular assist device (LVAD). The pump consists of a tube housing (10 cm in length and 14 mm in diameter), a three-vane impeller combined with a guide vane, and a DC motor. This pump is introduced into the LV cavity through the LV apex, and the outlet cannula is passed antegrade across the aortic valve. Blood is withdrawn from the LV through the inlet ports at the pump base, and discharged into the ascending aorta. A pump flow of > 8 L/min was obtained against 90 mmHg differential pressure in the mock circulatory system. In an acute dog model, this pump could produce a sufficient output of 200 ml/kg/min. In addition, the pump flow profile demonstrated a pulsatile pattern, although the rotation speed was fixed. This is mainly due to the changes in flow rate during a cardiac cycle--that is, during systole, the flow rate increases to the maximum, while the differential pressure between the LV and the aorta decreases to the minimum. Thus, this simple and compact axial flow blood pump can be a potential LVAD, with prompt accessibility and need for less invasive surgical procedures.

Animals↗
PubMedDate not supplied

In vitro studies of immobilized heparin and sulfonated polyurethane using epifluorescent video microscopy.

In situ surface modification techniques to improve the blood compatibility of blood contacting surfaces of medical devices have been developed by the authors. The techniques include heparin immobilization and sulfonated polymer grafting onto a polyurethane (PU) surface by using either ozone oxidation or photo reaction. These modified PUs were evaluated using an epifluorescent video microscope combined with a parallel plate flow cell. The epifluorescent video microscope system measured the amount of platelet coverage on the PU surfaces using whole human blood containing mepacrine labeled platelets perfused at a wall shear rate of 100 sec-1 for 20 min. Platelet activation and complement activation were also measured. Both immobilized heparin and sulfonated PUs showed significantly lower levels of platelet adhesion than the control PU. The platelet activation levels of these modified PUs also correspond to the results of the platelet adhesion. As for complement activation, heparin the immobilized surface showed the least complement activation, while sulfonated PU and the control PU showed higher levels of complement activation. In situ surface modification techniques, which use either ozone oxidation or photo reaction, are useful in a variety of medical devices even of a complex design, such as membrane oxygenators or artificial hearts.

Allylamine↗
PubMedDate not supplied

Evaluation of a new heparin bonding process in prolonged extracorporeal membrane oxygenation.

A novel heparin bonding method has been developed for in situ surface modification using ozone oxidation, and evaluated in vitro and in vivo during prolonged extracorporeal membrane oxygenation (ECMO) experiments. The ECMO system consisted of a Capiox hollow fiber membrane oxygenator (MO; Terumo Corp., Tokyo, Japan) with an integral heat exchanger, a Capiox centrifugal pump (CP), and an extracorporeal circuit. The blood contacting surfaces of the system were completely modified using the heparin bonding process, and evaluated in a chronic sheep model for extended period of time, ranging from 96 to 168 hr, under minimal systemic heparinization. The heparin bonded surface was able to maintain high levels of heparin bioactivity, and showed improved blood compatibility in in vitro epifluorescent video microscopy experiments by suppressing platelet adhesion/activation and complement activation. For the ECMO experiments, extracorporeal blood flow was maintained at 3 L/min and the activated clotting time was maintained at 150 sec. There was no significant change in the gas transfer capability or mean pressure drop across the MO over experimental times of up to 168 hr. Platelet count and other coagulation parameters remained stable within the physiologic range throughout the experiment. There were no detectable thrombi in the CP, tubing, or connectors in the test circuit. Local thrombus formation was noted in a stagnant area of the MO, although this did not interfere with its function or lead to any significant embolization. Based on these results, the heparin bonded ECMO system appears to be a safe and effective device for prolonged extracorporeal circulation under minimal systemic heparinization.

Animals↗
PubMedDate not supplied

Can heparin immobilized surfaces maintain nonthrombogenic activity during in vivo long-term implantation?

The authors previously demonstrated that heparin immobilized surfaces showed excellent nonthrombogenic properties for extracorporeal membrane oxygenation experiments as long as 168 hr. The characteristics of the heparin immobilized surfaces include high heparin bioactivity and prevention of platelet adhesion and complement activation. However, it is not known whether the heparin immobilized surfaces would be effective for in vivo long-term implantation. Heparin bioactivity may be lost because of complete degradation or blocking of binding sites on heparin by adsorbed proteins. This study attempted to elucidate the in vivo long-term fate of heparin immobilized surfaces. The blood contacting surfaces of the ventricular assist device (VAD) made from polyurethane was modified with heparin immobilization and evaluated in a long-term sheep left VAD (LVAD) model for as long as 3 months. After removal of the VAD, heparin bioactivity was measured by Factor Xa assay. The blood contacting surfaces were analyzed with a scanning electron microscope, and the adsorbed proteins on the surfaces of the diaphragm were analyzed by SDS-PAGE and Western blotting. The thickness of adsorbed proteins on the surfaces also was measured by a confocal laser microscope. For the control ventricular assist devices, thrombus formation was observed within 1 month, whereas heparin immobilized VADs were able to operate thrombus free for periods as long as 3 months. The control surfaces demonstrated a thick adsorbed protein layer on thin surfaces, whereas heparin immobilized surfaces maintained thinner adsorbed proteins on thin surfaces. Anti Factor Xa activity of the heparinized surfaces disappeared after 15 days, but the surfaces remained nonthrombogenic even after heparin bioactivity was completely lost. The protein composition analyzed by SDS-PAGE showed an albumin dominant pattern on the heparinized surfaces. The band of 110 kD corresponding to C3b was detected only on the control surfaces, which possibly activated complement, and subsequently activated platelets and coagulation. Immunoblot showed degradation products of fibronectin and vitronectin on the control surfaces, which probably were promoted by surface generated protease, whereas the heparinized surfaces showed minimal degradation throughout the experimental periods. These results suggest that the heparin moiety has an ability to control adsorbed proteins, thereby inhibiting thrombus formation during in vivo long-term implantation.

Adsorption↗