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Biomedical subjects

C R Liu

Publications and source records attributed to C R Liu.

30 records · Page 2Linked to original sources
PubMed1985

Antibody responses to two Epstein-Barr virus nuclear antigens defined by gene transfer.

By transfecting small fragments of Epstein-Barr virus (EBV) DNA into cells, we defined two nuclear antigens, termed M and K, and examined serum from 258 subjects for antibodies against these antigens. We hoped to learn whether such single-antigen systems would clarify the association of EBV with various diseases. Although reactivity to M antigen was found in only 14 per cent of healthy EBV-seropositive subjects, 90 per cent of Chinese and North African patients with nasopharyngeal carcinoma had antibody to M. Nearly all persons (96 per cent) who were EBV seropositive, as judged by their serologic reaction to a nuclear antigen encoded by the complete virus (EBNA), had a reaction to K antigen. However, serum samples from three patients with chronic active EBV infection did not react to K, even though the serum contained anti-M titers above 1:1000. Lymphoid cells from one such patient carried a normal gene for K and made K protein of correct size. Therefore, in this patient the absence of antibody to K had not resulted from a viral mutation that destroyed the K protein. These serologic studies show that some patients with chronic active EBV infection have an abnormal immune response to a specific viral gene product.

Adult↗
PubMed1982

Stable expression in mouse cells of nuclear neoantigen after transfer of a 3.4-megadalton cloned fragment of Epstein-Barr virus DNA.

All cells that harbor the Epstein-Barr virus (EBV) genome contain a neoantigen in the nucleus (EBNA). By transfection we located a segment of the genome that encodes or induces an antigen serologically related to EBNA. The responsible genes are found in the 3.4-megaldalton BamHI fragment K of EBV DNA, specifically in the left 1.9 megadaltons represented by HindIII fragment I1. Mouse LTK- cells were cotransformed with recombinant plasmids, containing the herpes simplex virus thymidine kinase gene and either EcoRI fragment B or BamHI fragment of K of EBV DNA. The TK+ cells surviving in selective medium were cloned. About 50% of the clones expressed the neoantigen in every nucleus. These mouse cells were used as antigens in immunofluorescence tests. Antibody to the nuclear antigen was found in 30 human sera known to contain antibody to EBNA; it was not detected in 18 sera that did not have antibody to EBNA. Mouse cells expressing EBNA as the result of acquisition of cloned EBV DNA fragments should prove useful in the characterization of the structure of this antigen and as reagents for the diagnosis of EBV infections.

Animals↗
PubMed1976

Relationship of nuclease activity and synthesis to senescence of corn (Zea mays L.) stalk pith, cob parenchyma and first developed leaf tissues.

An increase in total RNase activity was associated with three patterns of cell senescence in corn (Zea mays L.) (cv. WF9 X 38-11) cob parenchyma during the first two weeks following silking, stalk pith tissue after internode elongation and the first developed leaf of seedlings. Stalk pith tissue had two RNase activities, one inhibited by EDTA and one not. Both remained in approximately equal amounts in young to old pith tissue. In the first developed leaf of seedlings, the activity not inhibited by EDTA remained at a constant low level during the period studied, while the other activity varied. No inhibition by EDTA was found in cob parenchyma tissue. Incubation of sections of cob parenchyma and stalk pith tissues suggested that the total RNase activity of cob parenchyma is very stable and that of stalk pith tissue is relatively stable. An age-related increase in DNase activity was found in stalk pith tissue and in the first developed leaf of seedlings, but not in cob parenchyma tissue.

Cell Survival↗
PubMedDate not supplied

Modified thermal clearance technique for determination of blood flow during local hyperthermia.

The thermal clearance method utilizes the rate of temperature decay after the applied power is turned off to estimate the local blood flow. A limitation of this method has been its inability to account for the contribution of thermal conduction to the rate of temperature decay. As a result, the blood flow is generally overestimated. A modification of the thermal clearance method is described in this paper which enables the conduction component to be determined. Profiles of the tissue temperature are obtained in three mutually orthogonal directions about the point where thermal clearance is measured. The Laplacian of the temperature is evaluated from these profiles by the method of finite differences. The tissue thermal conductivity is estimated from literature values. The greatest source of error is the uncertainty in the location of the washout point in each catheter. Strict thermometry requirements must be adopted to reduce the localization error to +/- 0.25 cm. The thermometry catheters should be orthogonal to within +/- 10 degrees and all three catheters should be in contact at the washout point. The methodology was tested in a phantom, studied by use of a computer model, and implemented in the clinic. The experimental error in the conduction component is typically 50%. The resulting error in the blood flow depends on the relative rates of energy removal by blood flow and thermal conduction. When perfusion is the dominant mode of energy removal, the resulting uncertainty in the blood flow is typically in the range 20-30%.

Blood Flow Velocity↗