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Biomedical subjects

A M Lewis

Publications and source records attributed to A M Lewis.

At least 109 records · Page 6Linked to original sources
PubMed1979

Method for determining the extent and copy number of overlapping and nonoverlapping segments of integrated viral genomes.

We analyzed the method of exhaustive hybridization of single-stranded DNA and derived a general relationship between the fraction of the probe DNA hybridized and the sizes and copy numbers of the segments of the viral genome integrated in cellular DNA. The equations employed can be used to analyze integrated DNA comprised of overlapping and nonoverlapping segments of the viral genome. Using these equations, we analyzd the adenovirus type 2 DNA content of a series of hamster cell lines transformed by adenovirus type 2 and several adenovirus type 2-simian virus 40 hybrid viruses. We found no eividence that the integrated viral DNA is comprised of overlapsping segments. However, the number of copies of the integrated segments varies between lines cloned from the same transformed isolate, and copy numbers change during in vivo passage of transformed cells.

Adenoviruses, Human↗
PubMed1979

Age-related and thymus-dependent rejection of adenovirus 2-transformed cell tumors in the Syrian hamster.

Adenovirus type 2-transformed hamster cell-induced newborn tumor lines were usually rejected when transplanted s.c. into 21-day-old syngeneic, weanling hamsters. The tumor-inducing capacity of two of these lines (Ad2HTL3 and Ad2HTL6) was tested in intact and neonatally thymectomized hosts. After s.c. injection of suspensions prepared from these lines, none of the weaning hamsters developed tumors while 100% of the newborns and 35.2% of neonatally thymectomized, weanling hamsters developed progressively enlarging neoplasms. The susceptibility of neonatally thymectomized hamsters to tumor challenge was directly related to the degree of immunosuppression observed following thymectomy as indicated by the amplitude of the in vitro response of blood leukocytes to concanavalin A. Pretreatment of thymectomized weanlings with syngeneic adult lymphoid cells (i.p.) resulted in a significant reduction in tumor susceptibility (p = 0.03). These findings suggest that acquisition of resistance to adenovirus type 2-transformed cells during the first 21 days of life may be a thymus-dependent cellular immune process.

Adenoviridae↗
PubMed1979

Rejection of adenovirus 2-transformed cell tumors and immune responsiveness in Syrian hamsters.

Transplantation of adenovirus type 2-transformed cell-induced newborn tumor lines to different aged hamsters revealed that the cell-mediated host defenses responsible for tumor graft rejection matured early in the second week of life. When light microscopic examinations were performed during the course of tumor development, the primary histopathological difference between progressing tumors removed from newborn or thymectomized weanling hamsters and regressing lesions from normal weanlings was the lack of an early, mononuclear cell infiltrate in neoplasms from newborn and thymectomized hosts. These results suggest that the maturation of cellular immunity determines resistance to tumor transplantation in this system. This conclusion was supported by the in vitro detection of concanavalin A-responsive lymphocytes in spleens from tumor-resistant suckling but not tumor-susceptible neonatal hamsters. Although the incomplete seeding of thymus-dependent lymphocytes to the peripheral lymphoid tissues of newborn hamsters may partially explain the deficient concanavalin A responses of neonatal spleen cells, there appears to be an additional requirement for a radioresistant, adherent accessory cell population. These findings suggest that the development of a cell-mediated immune response is necessary for the rejection of adenovirus type 2-transformed cells and transformed cell-induced tumors and that this response requires the interaction of T-cells and accessory cell populations.

Adenoviridae↗
PubMed1978

Peripheral amino acid levels in patients with cancer.

Peripheral arterial and venous whole blood amino acid concentrations were determined in four groups of subjects after an overnight fast 1) normal people, 2) patients with cancer who had not lost body weight, 3) subjects with cancer who had lost more than 20% of body weight and 4) patients who had lost more than 20% of body weight from diminished intake due to cause other than cancer. Comparison of the arterial blood levels in the four groups showed that patients with cancer and weight loss had amino acid patterns different from patients who were malnourished for other reasons. Branched chain amino acids were normal in patients with malignant disease. Some gluconeogenic amino acids were reduced as in other subjects with weight loss but the characteristic rise in glycine seen with malnutrition was not present. Arterio venous differences in whole blood across the forearm showed no evidence of increase in venous excess in patients with progressive malignant disease, indicating no excessive protein catabolism in muscle tissue. The data are consistent with increased gluconeogenesis in malnourished cancer subjects, probably due to intrinsic change in hepatic metabolism.

Amino Acids↗
PubMed1978

Viral DNA sequences and gene products in hamster cells transformed by adenovirus type 2.

Complementary strand-specific adenovirus DNA of full length or from endonuclease BamHI fragments was used as a probe to estimate the fractional representation and abundance of viral sequences in five hamster cell lines (Ad2HE1-5) transformed with UV-inactivated adenovirus type 2. The fraction of the viral genome present in the five transformed cell lines varied from 44% in the Ad2HE5 cell line to 84% in the Ad2HE3 cell line. The number of viral DNA copies per diploid cell equivalent ranged from 1.8 in the Ad2HE1 line to 7.1 in the Ad2HE4 line. In vivo labeling with [35S]methionine followed by immunoprecipitation with an antiserum against adenovirus type 2 early proteins revealed virus-specific polypeptides with molecular weights of 42,000 to 58,000 in extracts from all five hamster cell lines. Several other early viral polypeptides were detected in some of the adenovirus type 2-transformed hamster cell lines.

Adenoviruses, Human↗
PubMed1976

Lymphocytic choriomeningitis virus infection in fetal, newborn, and young adult Syrian hamsters (Mesocricetus auratus).

The pathogenesis of lymphocytic choriomeningitis virus infection in fetal, newborn, and young adult hamsters was studied. Infected newborn hamsters initially developed a persistent viremia and viruria with titers often in excess of 10(4.0) mean infectious doses/0.03 ml of blood or urine. After week 12 two different patterns of infection became evident. Approximately one-half of the hamsters eventually cleared the infection, whereas the others developed a chronic progressive and ultimalely fatal disease characterized by continuous high-titered viremia and viruria and high titers of virus in their tissues. Complement-fixing antibody and, to a lesser degree, virus-neutralizing antibody coexisted with the viremia. Hamsters with persistently high levels of viremia and viruria developed chronic glomerulonephritis and widespread vasculitis, whereas hamsters that cleared their infections did not develop these lesions. Litters of hamsters born to viremic mothers were invariably infected. Litter sizes were small and breeding effectiveness was reduce; however, vertical, congenital infection was successfully passed through three generations. The course of infection in the congenitally infected hamsters was similar to that in newborn infected hamsters, with all animals producing complement-fixing antibody, some animals being capable of clearing the viremia and remaining healthy, and other animals having persistent viremia and fatal disease. Inoculated young adult hamsters did not become diseased, developed viremia and viruria which persisted up to 3 and 6 months, respectively, and developed complement-fixing antibody by 10 days after infection. The prolonged urinary excretion of large amounts of lymphocytic choriomeningitis virus by asymptomatic, chronically infected hamsters is an important public health consideration when dealing with potential human infection.

Aging↗
PubMed1976

Two adenovirus type 2-simian virus 40 hybrid populations that contain the entire SV40 genome differ in their ability to induce SV40 transplantation immunity in hamsters but not in mice.

Ad2++ HEY and Ad2++ LEY are two adenovirus 2(Ad2)-simian virus 40 (SV40) hybrids distinguished by differences in the efficiency with which they produce SV40 progeny in lytically infected African green monkey kidney cells. These virus populations are composed of nonhybrid Ad2 and hybrid virions, the majority of which contain more than 1 unit of SV40 DNA. The Ad2++ HEY and LEY populations also differ in their ability to induce SV40 transplantation immunity in rodents. Only Ad2++ HEY induces SV40 transplantation immunity in hamsters, whereas both viruses induce significant SV40 transplantation immunity in adult BALB/c mice.

Adenoviruses, Human↗
PubMed1976

Content and expression of integrated viral DNA in hamster cells transformed by nondefective adenovirus type 2- simian virus 40 hybrid viruses.

Hamster cells transformed by adenovirus 2 (Ad2) and five nondefective Ad2-simian virus 40 (SV40) hybrid viruses are all of the Ad2-transformed phenotype. All lines accumulate Ad2 RNA and Ad2 T antigen; two hybrid-transformed lines accumulate SV40 RNA, but only one contains detectable amounts of SV40 antigens. We examines selected lines from this group of transformed hamster cells for Ad2 DNA content and viral RNA expression by using hydroxyapatite chromatography and separated strands of labeled viral DNA as probes. All lines studies contain 1 to 2 Ad2 genome equivalents per haploid equivalent of cell DNA. The expression of Ad2 RNA exhibits two distinct patterns. In one pattern, transcription of the heavy strand of Ad2 DNA is less than that of the light strand, whereas in the second pattern of Ad2 RNA expression the extent of heavy-strand transcription is greatly increased. In the two lines containing SV40 RNA, the entire SV40 (-) strand is transcribed; the (+) strand is not expressed in these cells. These patterns of viral RNA expression suggest the possibility that host promoters may play a role in regulating transcription of integrated viral DNA.

Adenoviridae↗
PubMed1975

Studies of hamster cells transformed by adenovirus 2 and the nondefective Ad2-SV40 hybrids.

Adenovirus 2 does not produce tumors when injected into newborn hamsters, and this failure is not corrected by the acquisition of the portion of the SV40 genome present in any of the nondefective Ad2-SV40 hybrid viruses. However, nonhybrid Ad2 will transform hamster cells in vitro, and these transformed cells will produce tumors when injected into newborn hamsters. This finding, taken in conjunction with other studies (Graham et al., this volume; McAllister et al., 1969; McDougall et al., this volume; Williams 1973), suggests that the categorization of Ad2 and Ad5 as "nononcogenic" viruses is a reflection of host response rather than an intrinsic property of the viruses. However, transformation of hamster cells by Ad2 is inefficient, requiring 10(7)-10(8) PFU to produce a focus of transformed cells. Transformation of hamster kidney cells by the nondefective hybrids cannot be associated with portions of the SV40 genome. During the transformation process, complex interactions must occur between the hamster cell genome and the viral genome of Ad2 or the nondefective hybrids. Thus while it appears that there is very little Ad2 DNA in one nonhybrid Ad2-transformed cell line, there is a larger amount of Ad2 DNA in all of the hybrid virus-transformed cell lines. Moreover, while one Ad2+ND2-transformed line has apparently lost the SV40 portion of the viral genome, it is present and transcribed in another line transformed by the same virus. Finally, in the lines of nondefective hybrid-transformed cells examined thus far, there is extensive transcription from the Ad2 H strand. This pattern of transcription differs from transcription of the viral genome in most hybrid Ad2-transformed hamster and rat cells in which L-strand transcripion predominates.

Adenoviridae↗
PubMed1975

Simian virus 40 DNA replication, transcription, and antigen induction during infection with two adenovirus 2-SV40 hybrids that contain the entire SV40 genome.

The Ad2++hey hybrid virus population produces simian virus 40 (SV40) efficiently during lytic infection, whereas Ad2++ley does not, although both hybrids contain a complete SV40 genome. In this report, we demonstrate the synthesis of nonhydrid SV40 DNA in Ad2++HEY-infected Vero cells, but only early SV40 RNA is transcribed efficiently in Ad2++LEY-infected cells. Ad2++HEY induces SV40 U, T, and V antigens during lytic infection of African green monkey kidney cells, whereas Ad2++LEY induces only SV40 U and T antigens. These variations in the behavior of Ad2++HEY and Ad2++LEY regarding expression of SV40 functions probably reflect differences in the rate of SV40 excision from the hybrid genomes.

Adenoviridae↗
PubMed1974

A colinear map relating the simian virus 40 (SV40) DNA segments of six adenovirus-SV40 hybrids to the DNA fragments produced by restriction endonuclease cleavage of SV40 DNA.

The simian virus 40 (SV40) DNA segments present in a series of adenovirus-SV40 hybrids have been mapped with respect to the sites of cleavage of SV40 DNA by restriction endonucleases. Two approaches have been used. First, nucleic acid hybridizations were performed between equimolar quantities of the denatured DNAs of SV40 and each hybrid virus and the radiolabeled transcripts of 11 DNA fragments obtained by cleavage of SV40 DNA by restriction endonuclease from Hemophilus influenzae. Secondly, selected fragments of SV40 DNA produced by the H. influenzae or H. parainfluenzae restriction endonucleases were used to form heteroduplex DNA molecules with adenovirus and adenovirus-SV40 hybrid DNA, which were then analyzed by electron microscopy. The two sets of data were consistent and have permitted alignment of the map of the SV40 segments of the hybrid viruses with the H. influenzae and H. parainfluenzae cleavage maps of SV40. Since cells infected with some of the hybrid viruses contain one or more SV40-specific antigens, the genetic determinants of these antigens could be localized on the cleavage map.

Adenoviridae↗