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Biomedical subjects

Z C Chen

Publications and source records attributed to Z C Chen.

At least 37 records · Page 2Linked to original sources
PubMed1991

Isolation and characterization of a cDNA clone encoding the anti-viral protein from Phytolacca americana.

Phytolacca anti-viral protein (PAP) was purified from Phytolacca leaves and the N-terminal was sequenced. A cDNA library was made from mRNAs isolated from Phytolacca leaves and cDNA clones for PAP were identified using oligonucleotide probes derived from the N-terminal amino acid sequence. The PAP-cDNA clone was sequenced from both directions. The predicted amino acid sequence of PAP was compared with the amino acid sequences of other ribosome-inactivating proteins. The identities of these proteins to PAP ranged from 29 to 38%, and a region was found in each with a sequence similar to the PAP sequence (AIQMVSEAARFKYI). Southern blot analysis indicates that PAP is encoded by a multi-gene family.

Amino Acid Sequence↗
PubMed1991

A genetic study of human interferon-alpha-induced repair of DNA damage in hepatitis B patients.

In vitro treatment with human interferon-alpha (HuIFN-alpha) of hepatitis B virus-infected peripheral lymphocytes from 17 hepatitis B patients induced a decrease in the frequency of sister-chromatid exchanges (SCE). There was a significant difference in mean SCE frequencies between the HuIFN-alpha-treated patients and the control group, but not between acute and chronic hepatitis B patients treated with HuIFN-alpha.

Adult↗
PubMed1991

Chemical transformation of human embryonic nasopharyngeal epithelial cells in vitro.

The association of Epstein-Barr virus (EBV) with poorly differentiated carcinoma of the nasopharynx is well known; however, certain environmental factors, such as nitrosamines, are also important for the development of this cancer (Ho, 1975). N,N'-Dinitrosopiperazine (DNPZ) can induce nasopharyngeal carcinoma in rats and increased sister chromatid exchange frequency in human embryonic nasopharyngeal epithelial (HENE) cells. We have now demonstrated the transformation by DNPZ of HENE cells, which had a prolonged life span, anchorage-independent growth, chromosomal aberrations, tumorigenicity and morphological and ultrastructural alterations. These transformed cells might derive from the columnar epithelium of the nasopharynx, as indicated by the positive histochemical reaction with CAM 5.2 antikeratin antibody. Negative results in an immunofluorescence test for EBV nuclear antigen and Southern hybridization for EBV DNA rule out the participation of this virus in the neoplastic transformation of HENE cells by DNPZ.

Animals↗
PubMed1991

Biological functions of recombinant human interleukin-2.

Recombinant interleukin-2 (rIL-2) is able to maintain the growth and multiplication of T-lymphocytes and IL-2 dependent CTLL-2 cells up to 28 days with the multiplication of T-lymphocytes as high as about 1000 fold. When rIL-2 and its monoclonal antibody were added together, the above functions of rIL-2 were specially blocked, showing that these biological functions were exerted specifically by rIL-2. The rIL-2 is also able to increase the natural killer (NK) activity up to 46-96%, while higher concentrations of rIL-2 might exhibit inhibitory effect. The cytotoxicity of lymphokine activated killer (LAK) cells induced by rIL-2 for killing HL-60 cell line and solid tumour (human lung carcinoma) reached 54.84% and 37.96%, respectively. All these results indicate that the biological functions of rIL-2 were quite similar to that of the natural one.

Antibodies, Monoclonal↗
PubMed1990

Effect of tumor-derived immunosuppressive factor(s) on interleukin 2 and on expression of interleukin 2 receptor.

In this paper, we have described the effects of tumor-derived immunosuppressive factor(s) (TDSF) on interleukin 2 (IL-2) production, on IL-2 responsiveness and on the expression of IL-2 receptors. The results showed that TDSF was able to markedly inhibit the production of IL-2 from PHA-stimulated lymphocytes and IL-2-dependent proliferation of activated lymphocytes, and to partially inhibit the expression of IL-2 receptor. These results suggest that inhibiting IL-2 production and responsiveness may be a major mechanism by which TDSF inhibit T lymphocyte proliferation and other immune responses. That TDSF exerted a very potent inhibiting action on IL-2 responsiveness is especially noticeable if we consider using IL-2 as an immunotherapeutic agent. This may be an important reason why treatment of tumor with IL-2 did not yield satisfactory results so far.

Glycoproteins↗
PubMed1990

Effect of immunosuppressive factor produced by human lung cancer cell line A549 on the production and action of interleukin 1.

A549, a human lung cancer cell line, spontaneously produces a tumor-derived immunosuppressive factor (TDSF) which inhibits the production and action of interleukin 1 (IL-1). After exposure of macrophages to TDSF for 5 h, the production of IL-1 by macrophages was significantly inhibited. The inhibition was much stronger if TDSF existed continuously in macrophage culture. The response of thymocytes treated with nylon wool to exogenous IL-1 was significantly suppressed in the presence of TDSF, suggesting that TDSF can inhibit the action of IL-1. The thymocytes untreated with nylon wool could proliferate after being stimulated with Con A. The proliferation was significantly suppressed by TDSF in a dose-dependent manner. These results suggest that the inhibitory action of TDSF on T cell activation is associated with IL-1, and that TDSF might exert an inhibitory action on other reactions mediated by IL-1. Furthermore, TDSF can reduce the supplementation of new T cells by inhibiting the proliferation of thymocytes.

Animals↗
PubMed1989

Biologic characteristics of an immunosuppressive factor derived from a human lung cancer cell line.

A 549, a human lung cancer cell line, spontaneously produces a tumor-derived immunosuppressive factor (TDSF) which inhibited PHA-stimulated T lymphocyte proliferation via a noncytotoxic mechanism. The inhibition increased in a dose-dependent pattern. The factor also markedly suppressed production of interleukin (IL-2) by PHA-stimulated lymphocytes and IL 2-dependent proliferation of activated lymphocytes. The fact that TDSF possessed very potent inhibitive action on IL-2 is especially noteworthy if we consider the use of IL-2 as immunotherapeutic agent. The synthesis of the factor was inhibited by mitomycin C, actinomycin D and cycloheximide, indicating that the factor is a genic product of A 549 cells. The factor is chemically a protein with a molecular weight greater than 150 KD and sensitive to extremes of pH, heating to 60 degrees C and trypsin treatment.

Glycoproteins↗
PubMed1989

Investigation on the inhibitory effect of tumor-derived immunosuppressive factor(s) on T lymphocyte proliferation.

Using five tumor cell lines, the effect of tumor-derived immunosuppressive factor(s) (TDSF) on T lymphocyte proliferation and its mechanism have been investigated. It was found that TDSF markedly inhibited PHA-stimulated T lymphocyte proliferation via a noncytotoxic mechanism. The inhibition increased in dose-dependent manner and the maximum inhibition was achieved when the factor was added at the initiation of the culture. When PBMC were preincubated with supernatants of tumor cells for 24 h, washed extensively and then cocultured with freshly prepared PBMC, similar suppressive effects were observed. The above results indicated that the activation of any suppressor cell subgroup may be one of the mechanisms of immunosuppressive action of TDSF.

Glycoproteins↗
PubMed1989

[Neoplastic transformation of human embryonic/nasopharyngeal epithelial cells induced by N N'-dinitrosopiperazine (DNP) in vitro].

This is the first report on N N'-dinitrosopiperazine (DNP)-induced malignant transformation of human embryonic nasopharyngeal cells. The transformed cells possessed a prolonged life span, anchorage of independent growth, chromosome aberration, tumorigenicity and altered cell morphology. Under electron microscope, these cells were identical to cells of poorly differentiated carcinoma. The results demonstrated that DNP was able to induce not only nasopharyngeal carcinoma of rats in vivo, but also neoplastic transformation of human embryonic nasopharyngeal epithelial cells in vitro.

Animals↗
PubMed1989

Effect of insulin on the production of interleukin 2 by T lymphocytes.

The effect of insulin on interleukin 2 (IL-2) production was investigated. The results showed that insulin alone did not stimulate the resting T lymphocytes to produce IL-2, but enhanced the production of IL-2 by T lymphocytes and interleukin 1 (IL-1) by macrophages in the presence of lectin. Insulin augmented the response of T lymphocytes to IL-1 in the presence of Con A. The peak time of IL-2 production was not affected by insulin.

Animals↗
PubMed1988

Wounding properties of steel pellets with different velocities and quality on soft tissue of dogs.

The characteristics of the soft-tissue wounds of the hind legs of 155 dogs produced by stainless steel spheres with four different masses and at various impact velocities were observed. It was found that when the mass of the spheres was identical, the velocity became the main factor to determine the severity of the damage; when the mass of the spheres was different but their kinetic energy was similar, then a smaller but faster sphere produced more severe damage than a larger but slower one. Shallow but wide and severe wounds usually resulted. The rate of disability of extremities with such wounds was very high. These wounding properties of steel spheres have caused some new problems in the treatment of war injuries.

Animals↗