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Biomedical subjects

F Yan

Publications and source records attributed to F Yan.

65 records · Page 4Linked to original sources
PubMed1992

Fibrinogen adsorption on Pyrex glass tubes: a continuous kinetic study.

We present an experimental system to record continuously the adsorption kinetics of radiolabeled proteins, following an earlier study (Voegel et al., Colloids Surfaces 10 (1984) 9). We found results in accordance with the Lévêque equation at a wall shear rate of 50 s-1, for adsorption from fibrinogen solutions in Tyrode's buffer on Pyrex glass tubes. Dependence on concentration in the range 4 to 200 micrograms/mL and on distance to the tube entrance were examined. At the highest concentrations, a second slower regime appeared when coverage exceeded about 0.14 micrograms/cm2.

Adsorption↗
PubMed1992

Polymeric microballoons as ultrasound contrast agents. Physical and ultrasonic properties compared with sonicated albumin.

Air-filled polymeric microballoons were prepared with number-mean diameters of approximately 3 microns, volume-mean diameters of approximately 5 microns, and narrow particle-size distributions (standard deviation [SD] = 1.2 microns in number and SD = 2.0 microns in volume). More than 99% of the particles were below 8 microns. These particles were found to be highly echogenic for ultrasound, showing backscatter coefficients at 7.5 MHz, similar to the ones obtained with sonicated albumin microspheres. However, at 2.25 MHz, microballoons were less echogenic than albumin microspheres. These results are consistent with ultrasound attenuation measurements, which showed a maximum at 8 to 9 MHz for the microballoons compared with a reported value of 3.5 to 4.5 MHz for albumin microbubbles. Polymeric microballoons were found to be stable in plasma or under applied pressure as evidenced by unchanged particle concentration and echogenicity. Albumin microspheres were particularly unstable to applied pressure (150 mm Hg) and showed a rapid decrease in both particle counts and echogenicity.

Air↗
PubMed1992

Effect of Low Root Medium pH on Net Proton Release, Root Respiration, and Root Growth of Corn (Zea mays L.) and Broad Bean (Vicia faba L.).

The effect of low pH on net H(+) release and root growth of corn (Zea mays L.) and broad bean (Vicia faba L.) seedlings was investigated in short-term experiments at constant pH. Broad bean was more sensitive to low pH than corn: the critical values (pH values below which net H(+) release and root growth ceased) were pH 4.00 (broad bean) and pH 3.50 (corn) at 1 millimolar Ca(2+). Both proton release and root growth were progressively inhibited as the medium pH declined. Additional Ca(2+) in the root medium helped to overcome the limitations of low pH for net H(+) release and root growth. Potassium (for corn) and abscisic acid (for broad bean) increased both net H(+) release and root growth rate at the critical pH value. It is concluded that poor root growth at low pH is caused by a lack of net H(+) release that may decrease cytoplasmic pH values. Inhibited net H(+) release at high external H(+) activity is not due to a shortage of energy supply to the H(+) ATPase. Instead, a displacement of Ca(2+) by H(+) at the external side of the plasmalemma may enhance reentry of H(+) into root cells.

Journal Article↗
PubMed1992

Influence of a preadsorbed terpolymer on human platelet accumulation, fibrinogen adsorption, and ex vivo blood activation in hemodialysis hollow fibers.

Results are presented on kinetics of platelet accumulation in charged polyacrylonitrile (AN69) hollow fibers by continuous data recording under flow conditions (wall shear rate 108-1050 s-1), using suspensions of washed 111In-labeled human platelets in Tyrode's-albumin buffer, containing washed red blood cells (0-40%). Preadsorption of a terpolymer of acrylonitrile, poly(ethyleneoxide) methacrylate and trimethylaminoethyl chloride methacrylate leads to very efficient passivation with respect to platelet accumulation and fibrinogen adsorption. In human ex vivo tests, evaluation of complement peptide C3a, platelet beta-thromboglobulin, leucocyte-polymorphonuclear neutrophile elastase and fibrinopeptide A shows no detectable activation. Furthermore, preadsorption appears to result in simultaneous improvement in hemocompatibility of the blood lines leading to and from the dialysis module. This single pretreatment of dialysis membranes should allow injection of lower doses of anticoagulant to patients submitted to hemodialysis.

Acrylic Resins↗
PubMed1991

Study on induction of differentiation of a human megakaryoblastic leukemia cell line (HIMeg) by 1,25-dihydroxyvitamin D3.

It is reported that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), a physiological factor, has an inductive effect on the differentiation of a novel human megakaryoblastic leukemia cell line (HIMeg) in vitro. At the concentrations ranging from 10(-9) to 10(-6) mol/L, 1,25(OH)2D3 showed inhibition of proliferation on HIMeg cells which was demonstrated by count of survival cells and cloning efficiency. Meanwhile, using light/electron microscopy, stain of cytochemistry (including immunoenzymatic technique) and flow cytometry, we found that HIMeg cells could be further induced into more mature cells in megakaryocytic lineage confirmed by a series of evidence, including the changes of cell morphology/structure and cytochemistry, increased expression of differentiation antigens on the cell surface, and polyploidization. So, it is possible for 1,25(OH)2D3 to promote the differentiation of the cells in megakaryocytic lineage in vivo and to be used to treat acute megakaryoblastic leukemia and other diseases with malignant megakaryocytosis.

Calcitriol↗
PubMed1989

Hypocrellin-A sensitized photooxidation of bilirubin.

Hypocrellin A (HA) extracted from Hypocrellia bambusae (b.et Br.) sace, a derivative of 3,10-dihydroxy-4,9-perylenequinone, is a highly effective photosensitizer. Kinetic studies of the HA-sensitized photooxidation of bilirubin IX alpha (BR) in different solvents in the presence of various active oxygen quenchers indicate that in aprotic solvents the photooxidation goes via a Type II (1O2) mechanism, whereas in alkaline protic solvents Type I (electron transfer from an excited state of HA to the ground state of oxygen or the BR substrate). Type II and probably free radical reactions may occur simultaneously.

Bilirubin↗
PubMed1989

[Prediction of prognosis in sudden deafness].

Factors influencing the prognosis of sudden deafness were studied in 70 cases. Clinical data were analyzed and three important factors have been found: 1. Among various factors concerning the prognosis, the most important one was the presence of 8 kHz hearing. If hearing in the 8 kHz level could be obtained, prognosis would be better; 2. The time between the onset of deafness and the initial examination was found to be in close relationship with the prognosis, i.e. the sooner the patient seeks for treatment, the better would be the result; 3. The rapidity of the development of deafness was closely related to the prognosis. The faster the development of deafness, the worse would be the prognosis. An optimal regression equation for predicting prognosis has been established. According to this equation, otologists would be able to estimate the prognosis of the patients suffering from sudden deafness.

Auditory Threshold↗
PubMed1985

Allogeneic fetal liver transplantation in acute leukemia.

Three patients with acute leukemia in first complete remission were transplanted with fetal liver cells from May 1983 to June 1984. A conditioning regimen of cyclophosphamide (60-80 mg/kg) and TBI 600-700 rads (a dose rate of 5-7r per minute) was taken. The hemopoietic and immunological recovery was rapid and complete in every patient. There was proof of chimerism in case 1 as demonstrated by the existance of the XX karyotype of donor fetus in 68.7% and 75% of marrow metaphases, in 25% of peripheral blood metaphases, by the appearance of new HLA-antigens and RBC blood type antigens of donor origin. The serum alpha-fetoprotein level increased and maintained for 40 days in case 2, but definite evidence of engraftment was not observed. The allogeneic marker, the donor's HLA-antigens and RBC isoenzyme, were detected in case 3.

Adolescent↗
PubMedDate not supplied

Changes of superoxide dismutase, glutathione perioxidase and lipid peroxides in the brain of mice preconditioned by hypoxia.

We have developed an animal model of hypoxic preconditioning and assumed that oxygen radicals and their endogenous scavenging enzymes may play an important role in the preconditioning. To test this hypothesis, activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and the content of lipid peroxides (LPO) were measured during the preconditioning. Compared with unpreconditioned control animals, in animals exposed to hypoxia only once, the activities of SOD and GSH-Px in whole brain were found to be significantly decreased while the LPO content in the hippocampus significantly increased. However, those in animals exposed to 4 runs of hypoxia tended to return to control levels and were lower than those in animals exposed to 1 and 2 runs of hypoxia. Our results indicate that the oxygen radicals and their specific scavenging enzymes seem to be involved in the development of tolerance to hypoxia.

Adaptation, Physiological↗
PubMedDate not supplied

Changes in phospholipids and free fatty acids in the brains of mice preconditioned by hypoxia.

Changes in the composition and contents of phospholipids and free fatty acids were observed and compared in three groups: (A) unpreconditoned normal controls, (B) exposure to 1 run of hypoxia and (C) exposure to 4 runs of hypoxia. In group B, the content of phosphatidyl ethanolamine (PE), phosphatidyl serine (PS) and free fatty acids (FFAs) increased significantly and the content of phosphatidyl choline (PC) and sphingomyelin (SM) decreased significantly. While in group C the content of PE, PS, PC and FFAs changed significantly when compared with that of group B, all phospholipid (except SM) and FFA contents tended to decrease to the level of group A. No new FFA was seen in the brain homogenates in any of the three groups. These results suggest that the changes in the content of mouse brain phospholipids and FFAs may be adaptive and involved in the animals' tolerance to hypoxia.

Animals↗