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Biomedical subjects

T H Chang

Publications and source records attributed to T H Chang.

At least 91 records · Page 5Linked to original sources
PubMed1986

Monoclonal antibodies against Trichomonas vaginalis.

Spleen lymphocytes obtained from mice immunized with Trichomonas vaginalis ATCC 30001 were fused with P3-X63-Ag8-653 mouse myeloma in order to produce hybridoma-secreting antibodies against T. vaginalis associated antigens. Six hybridoma cloned cell lines were established; three produced IgG1, two produced IgG2a, and one produced IgM monoclonal antibody. These six monoclonal antibodies showed binding to seven isolated strains of T. vaginalis but did not bind to Giardia lamblia. Three of those monoclonal antibodies did not bind to Tritrichomonas foetus. These anti-trichomonal monoclonal antibodies should prove to be of great value as diagnostic and research reagents.

Animals↗
PubMed1983

An application of immunocytology to the analysis of the cell kinetics of upper respiratory and digestive tract squamous carcinoma.

An antinucleoside immunofluorescence technique (ANIF) facilitated evaluation of labeling index (LI) from frozen sections of 36 upper respiratory and digestive tract squamous cancers (URDTS) from a group of 35 patients. There were 35 URDTS of the larynx, oral cavity, or pharynx and the LIs of this population ranged from 0-39.4%, (mean, 14.7%); 6% of URDTS (2 of 36) were not assessable by ANIF. The administration of nontherapeutic radioactive materials, the establishment of cell cultures, and perturbations in cell growth implicit in the removal of tumor from host prior to assessment are unnecessary in the application of this technique.

Carcinoma, Squamous Cell↗
PubMed1983

Two Ustilago maydis viral dsRNAs of different size code for the same product.

UmV is a double-stranded RNA (dsRNA) virus of the corn fungus Ustilago maydis. There are three viral subtypes, P1, P4 and P6, which differ in the specificity of their secreted killer toxins. Each has three size classes of dsRNAs: H (heavy), M (medium), and L (light). We find that, unique among dsRNA viruses, two segments of different size code for the same product--the toxin resistance factor. The smaller dsRNA (L) is homologous to one end of the larger (M), and may have arisen by replication and packaging of a sub-genomic mRNA. We have also compared all the UmV dsRNAs with each other and with the dsRNAs of the similar yeast virus (ScV) by Northern gel and by 3' sequence analysis. Like those of ScV, many of the UmV dsRNAs have one 3' terminus with the sequence UUUUUCAOH or UUUUUCGOH. The H and L dsRNAs of similar size in different viral subtypes are generally related in sequence. The UmV H dsRNAs of different size are not detectably related in sequence.

Base Sequence↗
PubMed1983

Cocarcinogenic action of aspirin on gastric tumors induced by N-nitroso-N-methylnitroguanidine in rats.

Albino rats (noninbred) were divided into 4 groups: 1) 56 control rats, 2) 40 rats fed 1 ml aspirin suspension (40 mg/ml) twice a week, 3) 20 rats given N-nitroso-N-methylnitroguanidine (MNNG) solution (250 micrograms/ml) to drink ad libitum, and 4) 40 rats given both aspirin and MNNG. In 18 months, there were no gastrointestinal tumors in groups 1 and 2, 8 cases of gastric tumors in group 3, and 37 cases of gastric tumors in group 4. Adenocarcinomas of the glandular stomach were found in 21 of 40 rats in group 4 but in only 4 of the 20 rats in group 3; the difference in incidence was significant. Histologic and electron microscopic examination of the epidermoid carcinomas and adenocarcinomas in group 4 showed no difference from such tumors induced by MNNG only. Hyperplasia of the forestomach mucosa and hyperplasia of the pyloric gland region of the glandular stomach in group 4 were more severe.

Adenocarcinoma↗
PubMed1982

Human anti-tetanus toxoid monoclonal antibody secreted by EBV-transformed human B cells fused with murine myeloma.

An Epstein-Barr virus (EBV)-transformed human B cell line (B6) producing anti-tetanus toxoid (TT) antibody was fused with a nonimmunoglobulin (Ig)-producing murine myeloma and selected in hypoxanthine-aminopterin-thymidine (HAT) medium containing 10(-5) M ouabain. Surviving cells were cloned by limiting dilution and confirmed as hybrids by karyotype analysis and G-11 staining. Hybridomas were stable and secreted 10-fold more anti-TT antibody (IgM kappa) than the human parental cell line. In addition, the hybridomas exhibited a markedly reduced growth requirement for serum (1% fetal calf serum). Since EBV can be used to expand rare antigen-specific B cells in the human, the technique described here may be at present the method of choice for producing human monoclonal antibodies.

Animals↗
PubMed1981

Detection of monoclonal antibody-defined colorectal carcinoma antigen by solid-phase binding inhibition radioimmunoassay.

We have established a solid-phase binding inhibition radioimmunoassay for the detection of colorectal carcinoma-specific antigens in tissue culture supernatants of human colorectal carcinoma cell lines and in serum and urine of colorectal carcinoma patients. Using the [3H]glucosamine-labeled cell membrane glycolipid antigen and colorectal carcinoma-specific monoclonal antibodies in this assay, we have been able to detect several human colorectal carcinoma membrane-specific antigens that are released from the cell membrane into tissue culture supernatants, and an antigen detected by antibodies 1116-NS-19-9 and 1116-NS-52a that is found only in the serum and urine of cancer patients.

Antibodies, Monoclonal↗
PubMed1981

Release of monoclonal antibody-defined antigens by human colorectal carcinoma and melanoma cells.

Many but not all of the cell surface antigens studied were released into tissue culture medium of human colorectal carcinoma and melanoma cells maintained in vitro. Two groups of monoclonal antibody-defined antigens are described. One group is composed of molecules that are released easily and in large quantitites into the tissue culture milieu. In this group, four glycolipid antigens of colon carcinoma, including a monosialoganglioside, and five glycoproteins of melanoma were detected in tissue culture supernatants. Antigens of the second group could not be detected in tissue culture supernatants. This group included one colorectal carcinoma antigen, the nature of which is unknown, and a glycoprotein of melanoma cells.

Antibodies, Neoplasm↗
PubMed1980

The percentage of cells in DNA synthesis in epidermoid carcinomas of the head and neck: a preliminary report.

The in vivo study of cell kinetics of squamous carcinomas of the head and neck is in its infancy. One cell kinetic parameter, the labelling index (LI), the percentage of cells actively replicating DNA, was estimated in carcinomas of the oral cavity (10), larynx (6) and pharynx(5) by an histochemical immunoglobulin technique developed recently in our laboratory: the antinucleoside antibody technique (ANIP-LI). Data from earlier experiments using autoradiography (3H-thymidine) have established that the enzyme-antibody and isotopic techniques are equivalent. The LI ranged from 1 to 30 with a mean of 13 in this group of tumors. The LI could not be evaluated for 14% (3/21) of the specimens. The 3 patients with tumors not suitable for ANIP-LI had received a full course of radiotherapy and/or chemotherapy before they had entered our study. The higher the LI of the tumor, the greater the likelihood that the surgical stage would be higher than the clinical stage, most often as a result of clinically unrecognized lymph node metastasis. However, the number of tumors sampled was inadequate for a statistical trend to be identified. The potential for the LI to be useful in the formulation of improved therapeutic strategies awaits the accumulation of more data from studies currently in progress.

Carcinoma, Squamous Cell↗
PubMed1980

Production of monoclonal antibodies in serum free medium.

We have succeeded in growing several established hybridoma cell lines (1116NS-19; 116NS-33a; 1116NS-52a; 1083-17-1A; 691-19-19) in a serum free medium supplemented with physiological concentrations of insulin (5 microgram/ml) and transferrin (5 microgram/ml). The hybridoma cells replicate in this medium and will secrete monoclonal antibodies in quantities comparable to those produced in the presence of serum. Adapted hybridoma cultures have been secreting antibodies in the supplemented serum free (SSF) medium for more than 3 months. Parental mouse myeloma P3x63Ag8 cells and non-secreting subclone 653 cells cannot survive longer than 6 days under the same conditions. Both insulin and transferrin are necessary for hybridoma cells to grow in serum free medium and omission of either one will not permit cell multiplication.

Antibody-Producing Cells↗
PubMed1980

Antibody-directed cytotoxic agents: use of monoclonal antibody to direct the action of toxin A chains to colorectal carcinoma cells.

We have constructed cell-specific cytotoxic agens by covalently coupling the A chain from diphtheria toxin or ricin toxin to monoclonal antibody directed against a colorectal carcinoma tumor-associated antigen. Antibody 1083-17-1A was modified by attachment of 3-(2-pyridyldithio)propionyl or cystaminyl groups and then treated with reduced A chain to give disulfide-linked conjugates that retained the original binding specificity of the antibody moiety. the conjugates showed cytotoxic activity for colorectal carcinoma cells in culture, but were not toxic in the same concentration range for a variety of cell lines that lacked the antigen. Under defined conditions virtually 100% of antigen-bearing cultured cells were killed, whereas cells that lacked the antigen were not affected. Conjugates containing toxin A chains coupled to monoclonal antibodies may be useful in studying functions of various cell surface components and, possibly, as tumor-specific therapeutic agents.

Animals↗
PubMed1978

Differentiation of 3T3-L1 fibroblasts to adipocytes. Effect of insulin and indomethacin on the levels of insulin receptors.

Differentiating (3T3-L1) and nondifferentiating (3T3-C2) fibroblastic cell lines possess two classes of insulin receptors, high affinity (KD = 1.0 to 3.7 X 10(-9) M) and low affinity (KD = 2.0 to 3.6 X 10(-8) M). Confluent cultures of 3T3-L1 cells induced to differentiate by insulin (1.74 x 10(-6) M) or indomethacin (1.25 x 10(-4) M) exhibit a 3-fold increase in the number of high affinity and low affinity receptors per cell or a 1.5- to 1.8-fold increase in the number of receptors per micron2 of surface area. In contrast, nondifferentiating 3T3-C2 cells treated with insulin or indomethacin lose almost completely the high affinity insulin receptors while retaining the same levels of low affinity receptors. The loss of high affinity receptors of the 3T3-C2 cells is accompanied by the disappearance of the stimulatory effect of insulin on the production of CO2 from glucose and on the uptake of aminoisobutyrate. The levels of high affinity insulin receptors appear to be regulated by different mechanisms in the differentiating (3T3-L1) and nondifferentiating (3T3-C2) cell lines. The mode of this regulation may have a bearing on the ability of a particular cell line to differentiate.

Adipose Tissue↗