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Biomedical subjects

P T Allen

Publications and source records attributed to P T Allen.

36 records · Page 2Linked to original sources
PubMed1975

Transformation of cells in human bone tumor cultures.

Two cell lines from tumors of 16 patients with osteosarcoma and two cell lines from 5 patients with giant cell tumor of bone showed conversion of cell type after 2 to 13 months in culture. Transformed cells of epithelial like morphology appeared in small focal areas and rapidly overgrew nontransformed cells. These cells were characterized by rapid growth, loss of contact inhibition, and growth in soft agar. Attempts to demonstrate virus(es) by electron microscopy, treatment with chemicals, or by inoculation of human cell lines were thus far unsuccessful. Antigens not present in parental cultures were observed in the transformed cells by fixed immunofluorescence test with sera of 13 and 20 osteosarcoma patients and 3 of 8 patients with giant cell tumor of bone. Absorption of positive sera with transformed cells of either osteosarcoma or giant cell tumor removed the reaction but not with absorption with heterophile material or mycoplasma. Presence of group-specific-like antigen (gs-3) in the transformed cells (but not in parent cultures) was shown by immunofluorescence. Fluids of transformed cultures contained heavy RNA similar to that of oncornaviruses. These findings suggest the presence of viral information in some human bone tumors.

Antigens, Neoplasm↗
PubMed1975

Virus retrieval studies in human neoplasia.

Short- and long-term co-cultures of 49 cases of human osteosarcoma cells with bone marrow or peripheral blood cells of patients with different types of leukemia were studied. Morphological changes were observed in 7 of 13 long-term co-cultures resembling those induced by RNA tumor viruses. The changes were accompanied by appearance of cytoplasmic antigen as shown by fixed immunofluorescence test with sera from patients with osteosarcoma, leukemia, and of some apparently normal blood donors. Absorption with Forssman-like substances, whole human embryo cells or osteosarcoma cells demonstrated the reaction to be due to tumor antigen(s) in co-culture cells showing morphological changes. Electron microscopy showed a few type C virus particles in one co-culture. Cell-free filtrates of fluid from the transformed co-cultures induced morphological changes in 1 of 4 human embryo cultures. Uninoculated embryo cultures or those inoculated with filtrates from parental sarcoma or leukemia cultures showed no morphological changes. Human embryo cell cultures treated with fluid from parental leukemic bone marrow but not from parental sarcoma cultures showed appearance of cytoplasmic antigen by immunofluorescence test with sera of osteosarcoma and leukemia patients and of some apparently normal blood donors. Transformed human co-cultures showed the cytoplasmic antigen with 28 of 48 sera of osteosarcoma and leukemia patients tested, after absorption with Forssman-like material, human embryo, and mycoplasma suspensions. Fourteen of 49 sera of normal donors were also positive with the transformed co-cultures. Similar results were obtained in an earlier series of experiments with human embryonic cultures transformed by fluid from different osteosarcoma-leukemia co-cultures when examined by fixed immunofluorescence tests with sera of patients with osteosarcoma and leukemia. In 2 whole human embryo cell cultures showing morphological changes high molecular weight RNA was found, similar to that of RNA animal tumor viruses and in one of the cultures transient reverse transcriptase was detected.

Antigens, Viral↗
PubMed1975

Alteration of the syncytium-forming property of XC cells by productive Moloney leukemia virus infection.

The effect of productive murine leukemia virus (MuLV) infection of the syncytium-forming property of XC cells was studied MuLV-Moloney-infected XC cells, designated XC(M), initially went through a period of spontaneous syncytium formation. The syncytia then disappeared, and XC(M) cells continued to propagate and produce both infectious MuLV and MuLV group-specific antigens. However, XC(M) cells became refractory to syncytium formation that was induced by Kirsten, Friend, Rauscher, and Moloney strains of murine oncornaviruses. These data suggest that XC(M) cells lost their syncytium-forming ability as a result of productive MuLV infection.

Animals↗
PubMed1973

Further studies on the influence of steroids on viral infection in mice.

Certain steroids have been reported to enhance experimental viral infections, whereas others have little or no effect. Interference with the interferon system has been suggested as a possible mechanism for the viral infection-enhancing (VIE) activity of hormones. In the present study, steroids (prednisolone, progesterone, testosterone) which had no effect on MM virus infection demonstrated VIE activity against Mayaro virus infection. It is suggested that the VIE activity of a hormone may be dependent on the viral agent used for challenge. Data are also presented which suggest that, in addition to interference with the interferon system, the VIE activity of steroid hormones may be the result of at least two other actions: (i) alteration of cell membranes; (ii) stimulation of initial viral replication.

Animals↗
PubMed1973

Structural rearrangement and subunit composition of RNA from released Soehner-Dmochowski murine sarcoma virions.

Two types of genomic, high-molecular-weight RNA species were found in Soehner-Dmochowski murine sarcoma virions released from virus-induced rat tumor cells grown in tissue culture. The type of RNA species observed depended on the length of exposure of the tumor cells to radioactive precursor. Early RNA of virions labeled up to 4 h with radioactive uridine had a sedimentation coefficient of 50S, and late RNA of virions labeled for 24 h had a sedimentation coefficient of 58S. Thermal transitions of early and late RNA indicated a difference in the configuration or structure of these two types of RNA. The late RNA may represent either a different configurational state of the early RNA or an aggregate molecule of two early RNA components joined together. Heat dissociation revealed that the major subunit of both RNA types was a 28S species, which was not susceptible to degradation by the addition of micrococcal nuclease to virions. A transitional, intermediate RNA species with a sedimentation coefficient of 37 to 40S was detected when early RNA was dissociated by dimethyl sulfoxide or heat at temperatures suboptimal for complete conversion. No free RNA subunit components were detected in virions harvested at intervals as short as 30 s or 5 min. A model for the assembly of genomic RNA from 28S RNA subunits is proposed.

Animals↗
PubMed1973

Strandedness and complementarity of DNA from long-term RNA-dependent DNA polymerase reactions of Soehner-Dmochowski murine sarcoma virus.

The DNA product of the endogenously instructed RNA-dependent DNA polymerase reaction of murine sarcoma virus continued to be synthesized for as long as 64 h in the presence of 0.008% Triton X-100. Higher detergent concentrations and actinomycin D inhibited DNA product synthesis. The DNA product from long-term polymerase reactions consisted of small DNA fragments as shown by sedimentation in alkaline sucrose gradients. The enzymatic DNA product was separated into a slow sedimenting fraction and a fast sedimenting fraction by rate-zonal centrifugation. Fast sedimenting DNA was the predominant fraction made in viral polymerase reactions containing 262 mM NaCl. By using a combination of S-1 nuclease and pancreatic RNase A, the amount of single-stranded DNA, double-stranded DNA, and DNA-RNA hybrid present in the slow-sedimenting and fast-sedimenting fractions was determined. Under standard polymerase conditions of 70 mM NaCl, single-stranded DNA was the major form of DNA found in both fractions. In contrast, the prevalent form of DNA made in the presence of 262 mM NaCl was DNA-RNA hybrid. Hybridization studies in which either S-1 nuclease or pancreatic RNase A was used to measure hybrid formation demonstrated not only that the DNA product was complementary in base sequence to the RNA genome, but also that at least 79 to 84% of the RNA genome was transcribed into complementary DNA.

Animals↗
PubMed1973

Structural characteristics and nucleotide sequence analysis of genomic RNA from RD-114 virus and feline RNA tumor viruses.

The results of molecular hybridization experiments have demonstrated that the RNA genome of RD-114 virus has extensive nucleotide sequence homology with the RNA genome of Crandell virus, an endogenous type C virus of cats, but only limited homology with the RNA genomes of feline sarcoma virus and feline leukemia virus. The genomic RNAs of RD-114 virus and Crandell virus also had identical sedimentation coefficients of 50S. A structural rearrangement of genomic RNA did not exist within released RD-114 virions, whereas a structural rearrangement of genomic RNA did occur within feline sarcoma virions and feline leukemia virions after release from virus-producing cells.

Animals↗
PubMed1971

Interferon-inducing characteristics of MM virus.

Interferon induction by MM virus in mice and in L cells was studied. In mice the virus readily induced interferon. The time of appearance was dose-dependent. A large virus dose induced interferon by 4 hr, whereas a small dose resulted in interferon production which paralleled virus replication 24 hr after infection. In L cells the interferon-inducing capacity of the virus was rapidly destroyed by ultraviolet light irradiation. Heating (56 C) of the virus, on the other hand, greatly increased its ability to induce interferon. Interferon production could also be increased by prior treatment of the cells with homologous interferon (priming). The increase in interferon production after priming was dependent on the concentration of interferon used for priming, the length of interferon treatment, and the multiplicity of infection. It is suggested that MM virus might be useful for the further study of the mechanisms involved in the production and action of interferon.

Animals↗
PubMed1971

Inhibition by estrone of the antiviral protection and interferon elicited by interferon inducers in mice.

The susceptibility of mice to infection with MM virus is markedly increased after treatment with the sex hormone estrone. Studies were undertaken to determine if either suppression of production or interference with the action of interferon was involved in this phenomenon. The protection of mice against MM virus infection by several interferon-inducing agents was partially impeded by estrone treatment either 24 hr before or 24 hr after the administration of the inducing agent. The titers of circulating interferon induced by each of the agents were lower in estrone-pretreated animals than in untreated controls. The protection of mice by exogenous L cell interferon was blocked only when the hormone was given prior to the interferon. It is concluded that the adverse activity of estrone is related to its ability to interfere with the action of interferon.

Journal Article↗
PubMed1970

Rapid sensitive assay for interferons based on the inhibition of MM virus nucleic acid synthesis.

A method for assaying mouse interferon based on the inhibition of viral ribonucleic acid (RNA) synthesis was devised. The amount of MM virus and RNA synthesized in interferon-treated L-cell cultures was determined by measuring the amount of (3)H-uridine converted into a trichloroacetic acid-insoluble form after treatment of the infected cultures with 2.5 mug of actinomycin D per ml. The amount of RNA synthesized was inversely related to the concentration of interferon used for treatment. A linear dose-response regression curve was obtained by plotting the log of the amount of RNA made, expressed as a percentage of the control, versus the log of the reciprocal of the interferon dilution. A unit of interferon was defined as that concentration which inhibited nucleic acid synthesis by 50% (INAS(50)). The concentration of mouse interferon could be determined within 24 hr. This assay method, on the average, was approximately half as sensitive as the method which measured the 50% reduction of MM virus plaque number (PDD(50)-MM method), but was, on the average, almost 1.7 times as sensitive as the PDD(50)-VSV method. It averaged approximately 20 times the sensitivity of the methods which used as end points the 70% reduction in yield of MM virus or the complete inhibition of cytopathic effect by MM virus. The reproducibility of the INAS(50) technique was tested in two ways. (i) Four independent assays of an interferon specimen were performed with replicate cultures. The standard deviation was 11.2% of the mean titer. (ii) On different dates, one interferon specimen was assayed seven times and another was assayed four times. The standard deviations were 21.5 and 26.6% of the respective mean titers.

Animals↗
PubMed1970

Effect of Estrogen and Other Steroids on MM Virus Infection in Mice.

The effect of several steroid hormones on the susceptibility of mice to infection with MM virus was studied. Estrone, cortisone, and hydrocortisone increased mortality, whereas progesterone, prednisolone, and testosterone had no effect. The viral infection-enhancing (VIE) activity of estrone was maximal when the hormone was given 24 to 72 hr prior to viral inoculation. Less VIE activity was seen when the estrone was administered at the same time as the virus, and hormone treatment 24 hr after inoculation had no significant effect on mortality. Virus was found in the blood 24 hr before it appeared in the brain, regardless of estrone treatment. However, viremia was demonstrated in estrone-treated mice 48 hr before it occurred in control animals. There was no significant difference in the respective titers reached in the sera or the brains of the two groups.

Journal Article↗
PubMed1968

Replication of Western equine encephalomyelitis virus. II. Cytoplasmic structure involved in the synthesis and development of the virions.

Analysis of the cytoplasmic fraction of chick embryo cells during the exponential phase of Western equine encephalomyelitis (WEE) virus growth showed that the viral ribonucleic acid (RNA) labeled by a short pulse with (3)H-uridine was associated with a structure which sedimented in sucrose density gradients with a coefficient of 65S. The RNA extracted from this structure sedimented in sucrose density gradients at 26S. After a longer period of exposure to (3)H-uridine, the radio-active viral RNA was associated with a structure which sedimented in sucrose density gradients as would materials with coefficients of about 140S. The 140S structure contained viral RNA and viral protein. It was shown that the 140S structures are not virus-induced polysomes. The 140S structure contained predominantly the 40S type of viral RNA and some 26S type. Electrophoretic analysis of the disrupted virion revealed that at least two proteins (types I and II) were present in the purified virion. Only type II protein was present in the 140S structure. Unlike the virion, the 140S structure did not contain any lipid which could be detected by the incorporation of (14)C-choline. These data suggest that the 140S structure represents the internal nucleoprotein part of the virion. The rate of appearance of labeled virus lags behind that of the formation of the 140S structure in infected cells. Pulse-chase experiments with (3)H-leucine suggest that the 140S structure may represent a precursor to the virus particle. The results are discussed in terms of the maturation of WEE virus in the infected cells.

Acrylates↗