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Biomedical subjects

K S Chang

Publications and source records attributed to K S Chang.

At least 163 records · Page 9Linked to original sources
PubMed1979

Enzyme immunoassay for feline oncornavirus-associated cell membrane antigen (FOCMA) and detection of FOCMA in cell extract by enzyme immunoassay inhibition test.

An enzyme immunoassay (EIA) for FOCMA has been developed. The assay uses alkaline phosphatase-conjugated rabbit anti-cat IgG as the second antibody and p-nitrophenyl phosphate as the substrate for the enzyme to detect cat FOCMA antibody bound to the target cells. In comparison with the indirect immunofluorescence (IIF) test, which was originally used for FOCMA assay, our results showed a good correlation between the two methods. The EIA gives a more objective measure of FOCMA reactivity than does IIF. FOCMA was successfully extracted from FOCMA-positive cell membranes by 0.5% Triton X-100 and further fractionated by ammonium sulfate. The FOCMA activity was assayed by IIF and EIA inhibition test. Most of the FOCMA activity was found in the fractions precipitated by 30% and 50% ammonium sulfate saturation.

Animals↗
PubMed1978

Immune reactivity of RBL-3, a nonproducer leukemia induced by Rauscher murine leukemia virus in C57BL/6 mice.

A cultured line of RBL-3 leukemia, induced by Rauscher murine leukemia virus (R-MuLV) in C57BL/6 mice, was found to be a virus nonproducer. An NB tropic virus indistinguishable from R-MuLV, however, was recovered after treatment with 5-iodo-2'-deoxyuridine (optimal concentration, 200 microgram/ml). Dexamethasone treatment slightly boosted the production of the activated virus but did not by itself activate the virus. RBL-3 cells were found to have Fc receptors but no surface immunoglobulin or Thy 1.2 antigen. RBL-3 cells exhibited the Friend-Moloney-Rauscher virus-specific transplantation antigen as shown by its immunosensitivity and immunogenicity in tumor rejection experiments. Crude membrane and crude soluble antigen preparations obtained from RBL-3 cell membranes retained the capacity to induce tumor rejection.

Animals↗
PubMed1977

Reverse transcriptase of foamy virus. Purification of the enzymes and immunological identification.

Reverse transcriptase from foamy virus, strain H4188 was estimated and purified. The enzyme has the following characteristics: 1. The reaction utilized preferentially oligo (dT) poly (rA) as a primer-template; however, the synthetic primer-template oligo (dT) poly (dA) could also be used to some extent. 2. The reaction utilized oligo (dG) poly (rC) as a primer-template with very low efficiency. 3. The crude virus preparation had a detectable endogenous reaction using the four deoxyribonucleotides for DNA polymerization. 4. The cation requirement for the enzyme reaction was much more biased for Mn++ than for Mg++ ions. 5. The molecular weight of the partially-purified enzyme was estimated to be about 80,000. Aggregates of 240,000 daltons were also seen. The activity of this enzyme was not inhibited by antisera against the reverse transcriptases of various type C RNA viruses, namely, feline endogenous leukemia virus, RD 114, Woolly simian sarcoma virus (SSV-1) and avian myeloblastosis virus (AMV). Antiserum against Rauscher leukemia virus (RLV) enzyme was marginally active against foamy virus enzyme, perhaps indicating a slight cross-reaction. The biochemical characteristics of foamy virus reverse transcriptase seemed to be very close to those of the type C RNA viruses, but the immunological reaction proved that the foamy virus reverse transcriptase was distinct from the others.

Epitopes↗
PubMed1977

Properties of RBL-5 leukemia cells cultivated in vitro.

RBL-5 leukemia induced by Rauscher murine leukemia virus (R-MuLV) carried in the ascites form in C57BL/6 mice was cultivated in vitro and passaged continuously. Both low- and high-passage cells released the same level of murine leukemia virus, as detected by the XC plaque assay. Membrane antigens of the cultivated cells were also detected by the indirect immunofluorescence assay. Both low- and high-passage cells showed the same activity of antigen detectable by anti-R-MuLV serum, whereas only the high-passage cells reacted strongly against a syngeneic antiserum to RBL-5 crude membrane (CM). The oncogenicity of the low and high passages of the cultivated cells was compared with the ascites cells. The results indicated that the oncogenic potential of the cells gradually decreased during in vitro passage. The accumulation or retention of CM antigen on the membrane of the high-passage cells suggested that their decreased oncogenic potential might be due to increased immunogenicity and/or immunosensitivity. This strengthened the hypothesis that the cellular transplantation antigens are not identical to type C viral antigens, since the R-MuLV antigens were not altered during passage in vitro.

Animals↗
PubMed1976

Immunogenic properties of a nonproducer malignant tumor induced by murine sarcoma virus.

A cloned cell line H-11 (HP) derived from an MSV-induced neoplasm (a hemangiosarcoma) was found to possess virus-specific tumor rejection antigen(s). The specific nature of the immune response was established through the use of a polyoma virus-induced neoplasm no. 89 both in cross immunization and cross challenge experiments. Virus antigens or surface antigens associated with virus production are not responsible for tumor rejection since virus production could not be detected, nor were any viral fingerprints of MSV found by the several assays used.

Animals↗
PubMed1976

Susceptibility of xeroderma pigmentosum cells to transformation by murine and feline sarcoma viruses.

Among various strains of skin fibroblasts tested, two strains derived from xeroderma pigmentosum (XP) patients (ages 19 and 25) with neurological complications and two strains obtained from heterozygotes (ages 54 and 18) showed relatively higher susceptibility than normal age-matched controls to transformation by feline sarcoma virus (FSV). Only one strain from a normal individual also showed a high susceptibility. Generally, there was a parallelism in susceptibilities to FSV and Kirsten murine sarcoma virus (KiMsv). However, cells from normal individuals of 46 years or older exhibited high ratios of FSV:KiMSV titers which were due to their lower susceptibility to KiMSV. Cells from two XP patients (ages 25 and 22) and a heterozygote (age 18), who were in a younger age group, manifested such a differential susceptibility to FSV and KiMSV. There was a correlation between the relative sensitivity of XP cells to the cytotoxic effect of 4-nitroquinoline 1-oxide and killing effect of UV light. Pretreatment of fibroblasts from three XP patients by a subtoxic dose of 4-nitroquinoline 1-oxide 24 hr before viral infection facilitated transformation by KiMSV and FSV, whereas no such effect was observed with three normal cells strains similarly treated.

4-Nitroquinoline-1-oxide↗
PubMed1975

Distinction between tumor-specific transplantation antigen and virion antigens in solubilized products from membranes of virus-induced leukemic cells.

A membrane antigen from RBL-5 leukemic cells that was solubilized and partially purified is further characterized in this study. This soluble antigen is capable of immunizating syngeneic hosts to reject neoplastic cells and thus resembles TSTA. It also induces cytotoxic antibody in syngeneic hosts capable of specifically lysing RBL-5 cells in vitro. RBL-5, however, releases infectious virus (RLV); it was necessary therefore to rule out virus or structural virion antigens as the effective immunogen. Infectious virus was not detectable in our initial crude membrane (CM) material, nor in the papain-solubilized CS or the G-150 Sephadex-chromatographed fraction. Virus-neutralizing antibody was not detected, under stringent assay conditions, in the syngeneic anti-CM sera. Antigen preparations CM, CS and the chromatographeal fractions F1, F2 and F3 were assayed in a complement-fixation test against brood-reacting antisera capable of detecting virus envelope antigen and gs antigen and against syngeneic antisera. Although our antigen preparations were positive for virion antigens, CS and F2 contained an antigen that reacted only with syngeneic antiserum. These same fractions were those reactive as immunogens. On the basis of these data, it is postulated that a cellular membrane component, other than viral, functions as TSTA.

Animals↗
PubMed1975

Studies of polyoma virus DNA: cleavage map of the polyoma virus genome.

A small-plaque polyoma virus, MPC-1, was isolated from a mouse plasmacytoma. The DNA of this polyoma virus was cleaved with a restriction enzyme from Haemophilus influenzae (Hin d), and the molecular weights of the limit products were analyzed by electrophoresis and electron microscopy. The fragments produced by this enzyme have been ordered by analysis of partial digest products. A physical map of the polyoma virus genome was then constructed.

Animals↗
PubMed1975

Isolation of a B-tropic type-C virus from reticulum cell neoplasms induced in BALB/c mice by SJL/J type-C virus.

D1-murine leukemia virus (MuLV), an N-tropic type-C virus isolated from a spontaneous reticulum cell neoplasm, type B (RCN-B) of an SJL/J mouse was propagated in NIH Swiss mouse embryo cell cultures. When injected into BALB/c mice 1 day after neonatal thymectomy, 30% of the inoculated mice developed RCN-B in 5 months, whereas none of the uninoculated controls did. From the spleen and lymph node extracts of all RCN-B-bearing mice tested, B-tropic type-C viruses (designated E1-MuLV) were isolated in high titers (10-5 minus 10-6 XC plaque-forming units/ml). Only low titers (10-1 minus 10-2 XC plaque-forming units/ml) of N- or B-tropic viruses were isolated from those thymectomized mice, inoculated but nontumorous, whereas only N-tropic viruses were detected in the uninoculated thymectomized mice. No virus was isolated from the nonthymectomized, untreated controls. Antigenically, the viral envelope antigen (VEA) of E1-MuLV was distinct from those of DU-MuLV, xVEA, or Gross-VEA, but some cross reaction with AKR-MuLV-VEA was observed. The relationship of D1-MuLV to E1-MuVL with respect to oncogenesis and viral genome activation was discussed.

AKR murine leukemia virus↗
PubMed1975

Radiation-enhanced murine sarcoma virus genome rescue activity.

Although the doses of X-ray (312-2,500 R) used for irradiation of cells caused impairment of DNA synthesis and cell replication, co-cultivation of X-irradiated MuLV- carrier cells with un-irradiated nonproducer cells of MSV-induced tumour resulted in as much as 20-fold increase in MSV retrieval compared with the un-irradiated control. The enhancement was apparent also as a 3-fold increase in the number of cells producing MSV (infectious centers) in the co-cultivation plate. This suggested that the MSV genome rescue efficiency in terms of MSV per cell, as well as the number of cells producing MSV, increased markedly. By uridine-3H-labeling and focus assay experiments, evidence was presented which suggested that an increase in MSV/MuLV ratio in the culture fluid of co-cultivation plates was obtained when the MuLV-carrier cells were pre-irradiated. By contrast, X-irradiation of the nonproducer cells prior to co-cultivation caused only reductions of MSV genome rescue efficiency. However, use of X-irradiated MuLV-carrier cells for co-cultivation with X-irradiated nonproducer cells restored this efficiency to some extent. The dose-survival curve of the nonproducer cells was not much different from those of the MuLV-carrier cells after X-irradiation. It was suggested that the viability of nonproducer cells was required for replication of MuLV transferred from the carrier cells and for subsequent MSV genome rescue.

Cell Line↗