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Biomedical subjects

C Dong

Publications and source records attributed to C Dong.

143 records · Page 8Linked to original sources
PubMed1991

Genetic organization and diversity of the hepatitis C virus.

The nucleotide sequence of the RNA genome of the human hepatitis C virus (HCV) has been determined from overlapping cDNA clones. The sequence (9379 nucleotides) has a single large open reading frame that could encode a viral polyprotein precursor of 3011 amino acids. While there as little overall amino acid and nucleotide sequence homology with other viruses, the 5' HCV nucleotide sequence upstream of this large open reading frame has substantial similarity to the 5' termini of pestiviral genomes. The polyprotein also has significant sequence similarity to helicases encoded by animal pestiviruses, plant potyviruses, and human flaviviruses, and it contains sequence motifs widely conserved among viral replicases and trypsin-like proteases. A basic, presumed nucleocapsid domain is located at the N terminus upstream of a region containing numerous potential N-linked glycosylation sites. These HCV domains are located in the same relative position as observed in the pestiviruses and flaviviruses and the hydrophobic profiles of all three viral polyproteins are similar. These combined data indicate that HCV is an unusual virus that is most related to the pestiviruses. Significant genome diversity is apparent within the putative 5' structural gene region of different HCV isolates, suggesting the presence of closely related but distinct viral genotypes.

Amino Acid Sequence↗
PubMed1991

Cytoplasmic rheology of passive neutrophils.

The rheological properties of leukocytes are important to their effectiveness in the microcirculation. Previous studies based on in vitro data from micropipette experiments suggest that a Maxwell fluid bounded by a cortical shell with persistent tension is a realistic model for non-activated neutrophils in both the rapid and slow deformation phases. However, various viscoelastic coefficients have been obtained depending on the degree of cell deformation. In the present paper it is demonstrated that the cytoplasmic apparent viscosity and elasticity vary continuously, depending on the degree of deformation. These apparent variations are due to the inhomogeneous nature of the neutrophil internal structure. It is shown that the nucleus is much stiffer than the cytoplasm. The composite structure of the cell results in the deformation-dependent properties.

Cell Nucleus↗
PubMed1990

Passive deformations and active motions of leukocytes.

The purpose of this paper is to review the development of continuum mechanics models of single leukocytes in both passive deformations and active motions and to indicate some future directions. Models of passive deformations describe the overall rheological behavior of single leukocytes under externally applied forces and predict the average mechanical properties from experimental data. Various "apparent" viscoelastic coefficients are obtained depending on the models assumed and the types of test used. Models of spontaneous motions postulate active driving mechanisms which must be derived internally from the cell itself and probably have different bases for different kind of motions. For pseudopod protrusion on leukocytes, energy transduction from chemical potential to mechanical work associated with actin polymerization at the tip of the projection is assumed to supply the motive power. For pseudopod retraction, active contraction due to actin-myosin interaction is assumed to be the driving force. The feasibility of the hypotheses are tested via numerical examples and comparison of the theoretical results with experimental measurements.

Biomechanical Phenomena↗
PubMed1990

[Experiment research on moxibustion treating infected EHFV rat].

In this experiment, we established a rat model of EHFV infected by abdominal cavity, and observed the effect of moxibustion on the changes of antigens, antibodies, neural transmitters in blood and tissue on 60 weanling Wistar rats with EHF. The rats were divided into three groups: normal control group (N. group), EHF control group (C. group) and EHF with moxibustion group (M. group) at random. Moxibustion was given at "Shenshu" for 30 minutes daily, 7 days. The 14th day after infection of EHFV, blood and lungs of the rats were fetched. The results obtained are as follows: 1. The effect value of EHF antibodies dilution: in C. group, it is 1:267 +/- 82 (n = 8), in M.group, it is 1:336 +/- 176 (n = 10), there is a significantly different of specific antibodies between C.group and M.group. The results show that moxibustion had an effect of enhancing the function of immune system in rats with EHF. 2. The examination rate of EHFV antigens in lungs, in C.group, it is 62.5% (n = 8), in M.group, it is 49.4% (n = 16). The results show that moxibustion may enhance the immune function and the effect of eliminating virus of lymphocytes in lungs. 3. The value of BUN in serum: in N.group, it is 15.3 +/- 2.50 (n = 10), in C.group, it is 24.63 +/- 7.24 (n = 10), and in M.group, it is 16.36 +/- 4.59 (n = 26). There is a significantly different between C.group and N.group or M.group (P less than 0.001). There is no significantly different between N.group and M.group (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Influence of zhuangling agent to metabolism of lipid in aged rats].

The influence of Zhuangling Agent to the metabolism of lipid in healthy old rats has been studied. The results indicate that the agent can decrease the level of serum total cholesterol, low-density lipoprotein low-density lipoprotein cholesterol and peroxilipid and meanwhile can increase serum superoxide-dismutase and enhance the activity of acid phosphatase in some parts of the tissues. The result suggests that Zhuangling Agent possibly has an effect of anti-arteriosclerosis.

Acid Phosphatase↗
PubMed1988

Leukocyte relaxation properties.

Study of the mechanical properties of leukocytes is useful to understand their passage through narrow capillaries and interaction with other cells. Leukocytes are known to be viscoelastic and their properties have been established by micropipette aspiration techniques. Here, the recovery of leukocytes to their normal spherical form is studied after prolonged deformation in a pipette which is large enough to permit complete entry of the leukocyte. The recovery history is characterized by the time history of the major diameter (d1) and minor diameter (d2). When the cell is removed from the pipette, it shows initially a small rapid recoil followed by a slower asymptotic recovery to the spherical shape. In the presence of cell activation and formation of pseudopods, the time history for recovery is prolonged compared with passive cell recovery. If a protopod pre-existed during the holding period, the recovery only begins when the protopod starts to retract.

Cell Movement↗
PubMed1988

Passive deformation analysis of human leukocytes.

The following analysis presents an experimental and theoretical study of the passive viscoelastic behavior of human leukocytes. Individual neutrophils in EDTA were observed both during their partial aspiration into a small micropipette and after expulsion from a large micropipette where the cell had been totally aspirated and deformed into a sausage shape. To analyze the data, a passive model of leukocyte rheology has been developed consisting of a cortical shell containing a Maxwell fluid which describes the average properties of the cell cytoplasm. The cortical shell represents a crosslinked actin layer near the surface of the cell and is assumed to be under pre-stressed tension. This model can reproduce the results of experiments using micropipette for both short-time small deformation and slow recovery data after large deformation. In addition, a finite element scheme has been established for the same model which shows close agreement with the analytical solution.

Blood Viscosity↗
PubMedDate not supplied

Development of a side-view chamber for studying cell-surface adhesion under flow conditions.

Observing microscopic specimens is often useful in studies of cellular interaction with a vascular wall. We have developed an in vitro side-view flow chamber that permits observations from the side of the cell's contact with various adhesive surfaces under dynamic flow conditions. This side-view flow chamber consists of two precision rectangular glass tubes called microslides. A smaller microslide is inserted into a larger one to create a flow channel with a flat surface on which either cultured vascular endothelium can be grown or purified adhesion molecules can be coated. Two optical prisms with a 45 degrees chromium-coated surface are used along the flow channel to generate light illumination and observation pathways. The side-view images of cell-substrate contact can be obtained using a light microscope. This design allows us not only to measure the effects of flow on cell-surface adhesion strength, but also to have close observation of cell deformation and adhesive contact to various surfaces in shear flow. In addition, this chamber can readily serve for a conventional top-view flow channel, similar to the parallel-plate flow chambers used in many areas. The development of such a side-view flow chamber can be beneficial to various in vitro applications in cellular studies that require an edge view, especially for various cell interactions with cultured vascular endothelium or surfaces containing single-type adhesive molecules under flow conditions.

Animals↗
PubMedDate not supplied

Use of green fluorescent protein-conjugated beta-actin as a novel molecular marker for in vitro tumor cell chemotaxis assay.

To study the dynamics of actin cytoskeleton rearrangement in living cells, an eukaryotic expression vector expressing a beta-actin-GFP fusion protein was generated. The expression construct when transfected into NIH3T3 fibroblast, A2058 human melanoma and 293T human embryonic kidney carcinoma cell lines expressed beta-actin-GFP fusion protein, which colocalized with endogenous cellular actin as determined by histoimmunofluorescence staining. The beta-actin-GFP was also observed to be reorganized in response to treatments with the chemoattractant type IV collagen. Cells extended pseudopodial protrusions and altered the morphology of their cortical structure in response to type IV collagen stimulation. More importantly, beta-actin-GFP accumulated in areas undergoing these dynamic cytoskeleton changes, indicating that beta-actin-GFP could participate in actin polymerization. Although ectopic expression of beta-actin-GFP lead to minor side effects on cell proliferation, these studies suggest that this strategy provides an alternative to the invasive techniques currently used to study actin dynamics and permits real-time visualization of actin rearrangements in response to environmental cues.

3T3 Cells↗
PubMedDate not supplied

Mechanics of leukocyte deformation and adhesion to endothelium in shear flow.

The mechanics of leukocyte [white blood cell (WBC)] deformation and adhesion to endothelial cells (EC) in shear flow has been investigated. Experimental data on transient WBC-EC adhesion were obtained from in vivo measurements. Microscopic images of WBC-EC contact during incipient WBC rolling revealed that for a given wall shear stress, the contact area increases with time as new bonds are formed at the leading edge, and then decreases with time as the trailing edge of the WBC membrane peels away from the EC. A two-dimensional model (2D) was developed consisting of an elastic ring adhered to a surface under fluid stresses. This ring represents an actin-rich WBC cortical layer and contains an incompressible fluid as the cell interior. All molecular bonds are modeled as elastic springs distributed in the WBC-EC contact region. Variations of the proportionality between wall shear stress (tau(w)) in the vicinity of the WBC and the resulting drag force (F(s)), i.e., F(s)/tau(w), reveal its decrease with WBC deformation and increasing vessel channel height (2D). The computations also find that the peeling zone between adherent WBC and EC may account for less than 5% of the total contact interface. Computational studies describe the WBC-EC adhesion and the extent of WBC deformation during the adhesive process.

Animals↗
PubMedDate not supplied

Quantitative determination of carboxymethyl chitin in polymer-coated liposomes.

A simple turbidity method for the quantitative determination of carboxymethyl chitin (CM-chitin) in coated liposomes has been developed. Isopropanol:buffer (1:1 v/v) was selected as a good solvent system for dimyristoyl-, dipalmitoyl-, or egg phosphatidylcholines but not CM-chitin. The turbidity of CM-chitin in this solvent system was spectrophotometrically determined at 400 nm without significant interference by these phosphatidylcholines. The dependence of turbidity on the CM-chitin concentration, pH, and ionic strength were determined. It was found that analyses of the coating efficiency of dipalmitoylphosphatidylcholine liposomes by CM-chitin were reproducible within the specified ranges of formulation conditions and enabled differentiation of the effect of order of CM-chitin addition on the coating efficiency.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

Poly(4-vinylpyridine)-coated liposomes: stability studies and release of acetylsalicylic acid.

Liposomes of dimyristoylphosphatidylcholine (DMPC) and dicetylphosphate (DCP) reacted with 4-vinylpyridine (4-VP) to form a salt and, subsequently, autopolymerized for form poly(4-vinylpyridine) (poly(4-VP))-coated liposomes. The conditions for optimization of polymer coating have been determined; also, the effects of polymer coating on liposome stability, the encapsulation of ASA and its release kinetics have been measured. The coating efficiency was maximum at a DMPC:DCP 1:1 mole ratio, at pH 4.0 in acetate buffer, and a polymerization time of 40 min. The polymer-coated liposomes were stable in 2 mM sodium cholate and 4 per cent isopropanol solutions, as determined from turbidity measurements, versus a 20-25% decrease in stability of uncoated liposomes. The encapsulation efficiency of ASA reached a maximum of 9 per cent at DMPC:DCP 1:1 mole ratio. The release of ASA at 37 degrees C, pH 7.0 was characterized by an initial fast release (85 and 63 per cent in 20 min from uncoated and polymer-coated liposomes, respectively) followed by a slow, constant release rate up to 140 min. Thus, autopolymerization of a polymerizable monomer at liposome surfaces represents a potentially feasible stabilization approach for liposomes exposed to sodium cholate solutions with greater retention of solute than uncoated liposomes.

Aspirin↗