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Biomedical subjects

M K Howett

Publications and source records attributed to M K Howett.

At least 37 records · Page 2Linked to original sources
PubMed1989

Administration of ethylnitrosourea to neonate hamsters increases growth and frequency of SV40-induced fibrosarcomas.

The in vivo interaction between the chemical carcinogen ethylnitrosourea (ENU) and the oncogenic simian virus 40 (SV40) was studied. Inbred newborn Syrian golden hamsters were injected subcutaneously with SV40 (5 x 10(6) plaque-forming units), ENU (0.5% solution, 125 or 25 mg/kg body wt), or equal mixtures of the two. Animals that received SV40 and ENU developed more tumors (100% vs 52%) within a shorter latent period (10 weeks vs 18 weeks) than animals that received SV40 alone. Animals given SV40 and ENU showed increased mortality and increased metastatic tumors (54.2% vs 30.8%) compared with those given SV40 alone. The SV40 and ENU group also exhibited multiple (greater than 10 nodules) pulmonary metastases (33.3% vs 7.7%) and metastases in multiple organs (12.5% vs 0%) compared with animals injected with SV40 alone. No difference in primary tumor size, histology, and SV40 T-antigen content was detected between SV40- and SV40/ENU-induced tumors. Four weeks after SV40 or SV40 plus ENU treatment, animals were challenged intradermally with 2.7 x 10(6) SV40-transformed hamster cells. Five weeks after challenge, 89.5% of the animals treated with SV40 and ENU and 45.4% of animals treated with SV40 developed tumors at the challenge site. Newborn animals given SV40 and ENU developed larger tumors at the challenge site (P less than 0.002) than newborns treated with SV40 alone. Thus, administration of ENU to hamsters during the neonatal stage of development produced a long-lasting systemic effect that enhanced tumor development by transplanted SV40-transformed hamster cells.

Animals↗
PubMed1987

Susceptibility of various human tissues to transformation in vivo with human papillomavirus type 11.

Human papillomaviruses (HPVs) are associated with proliferative lesions in a variety of human epithelial types. In some cases, the associations are highly specific in that a certain papillomavirus type may infect only one human epithelial cell phenotype. In other cases, one papillomavirus apparently infects several tissue types and not others. Further, HPV replication capacity varies considerably in different epithelia. Due to the lack of a suitable method, it has not been possible, until now, to define the role of the host cell phenotype in determining the outcome of infection with an HPV. We recently developed a system in which human epithelium was exposed to HPV-II and transplanted to athymic mice. Cervix and skin grafts developed into typical condylomata. We now test the hypothesis that the outcome of infection of diverse epithelial types with a single human papillomavirus is largely determined by the phenotype of the original epithelial cell. For example, skin obtained from a number of disparate sites from a single patient varied dramatically in its capacity for morphological transformation with HPV-II. Skin from penis was highly susceptible, but skin from abdomen did not transform. Vocal cord from 3 children and 2 adults responded to HPV-II infection by producing typical laryngeal papillomata. A variety of tissues were obtained from II donor infants and infected with HPV-II. Foreskin and cervical tissues of these children were transformed at a frequency of 100%. Vocal cord was transformed at an incidence of 88% and urethra at 73%. Only 37% of esophagus samples were transformed and both abdominal skin and urinary bladder from the same infants were totally resistant to morphological transformation. In a separate study, ureteral tissues from a child and an adult were completely resistant to HPV-II infection. Papillomavirus replication was readily detected as capsid antigen in foreskin, cervix, and urethra, but was poorly expressed in morphologically-transformed esophagi and vocal cords. In the last two tissues HPV-II DNA and RNA were demonstrated in cells by in situ hybridization techniques. We conclude that the epithelial cell phenotype is a major determinant of HPV-II infection, controlling both morphological transformation and viral replication.

Adolescent↗
PubMed1987

Herpes simplex virus replication and protein synthesis in a human blood-derived cell line.

Herpes simplex virus (HSV) types 1 and 2 were shown to replicate in a newly described human cell line (Meg) derived from the peripheral blood of a healthy volunteer. The cell line has both megakaryocyte-like and B cell-like properties. Upon infection with HSV-1 or -2, at a m.o.i. between 0.5 and 5, unlike B and T cells, the Meg cells were growth-arrested and this was accompanied by cytopathic effects and virus replication. The HSV proteins and glycoproteins B and D (gB and gD) made in the blood-derived Meg cells were compared to the corresponding proteins made in the non-blood-derived cell lines, Vero (African green monkey kidney cell) and HEp-2 (human epidermoid carcinoma cell). The maximum level of HSV protein synthesis occurred earlier in the Meg cells than in the Vero and HEp-2 cells. The electrophoretic pattern of HSV-1 and -2 proteins made in the Meg cell line was similar to the corresponding proteins made in the Vero and HEp-2 cell lines; however, some qualitative and quantitative differences were evident. There were no apparent differences detected in the migration pattern of gB made in all three cell lines while significant differences were observed with the gD species. However, upon hydrolysis with Staphylococcus aureus V-8 protease of the monoclonal antibody-purified gB and gD, distinct differences were observed in the electrophoretic pattern of the generated peptide fragments of both gB and gD made in the three cell lines. The results demonstrate that a human blood cell can support HSV replication and that species-specific post-translational modification of gB and gD occurs in HSV-infected Vero cells as compared to HSV-infected human cells.

Animals↗
PubMed1987

Laboratory production in vivo of infectious human papillomavirus type 11.

Human papillomaviruses (HPV) induce among patients natural lesions which produce small amounts of virus. Infection of human cell cultures does not lead to the multiplication of virus, which also does not replicate in experimental animals. We have developed a unique system for the laboratory production of HPV type 11 (HPV-11). Fragments of human neonatal foreskin were infected with an extract of naturally occurring human vulvar condylomata and grafted beneath the renal capsule of athymic mice. Later (3 to 5 months), condylomatous cysts developed from those grafts. Nuclei of koilocytotic cells contained large amounts of capsid antigen and intranuclear virions. The experimentally induced condylomata were homogenized, and the virions were extracted and used to infect another generation of human foreskin grafts in athymic mice. The HPV-11 DNA content and infectivity of the natural and experimental condylomata were similar. Extracts of experimental condylomata were subjected to differential ultracentrifugation and sedimentation in CsCl density gradients. A single, opalescent band was visible at a density of 1.34 g/ml. It contained HPV virions with HPV-11 DNA. This report is the first demonstration of the laboratory production of an HPV.

Condylomata Acuminata↗
PubMed1987

Human papillomavirus type 16 in bowenoid papulosis, intraoral papillomas, and squamous cell carcinoma of the tongue.

A 33-year-old immunosuppressed man developed bowenoid papulosis on his genitalia, velvety papules and plaques in his mouth, and invasive squamous cell carcinoma of his tongue. All three lesions were positive for human papillomavirus type 16 (HPV-16). The case provides further circumstantial evidence for a role of HPV-16 in epithelial neoplasia. The possible roles of a second HPV infection and of immunosuppression are also discussed.

Adult↗
PubMed1986

In vivo transformation of human skin with human papillomavirus type 11 from condylomata acuminata.

Human papillomaviruses (HPVs) have been implicated in the development of a number of human malignancies, but direct tests of their involvement have not been possible. We describe a system in which human skin from various sites was infected with HPV type 11 (HPV-11) extracted from vulvar condylomata and was grafted beneath the renal capsule of athymic mice. Most of the skin grafts so treated underwent morphological transformation, resulting in the development of condylomata identical to those which occur spontaneously in patients. Foreskins responded with the most vigorous proliferative response to HPV-11. The lesions produced the characteristic intranuclear group-specific antigen of papillomaviruses. Both dot blot and Southern blot analysis of DNA from the lesions revealed the presence of HPV-11 DNA in the transformed grafts. These results demonstrate the first laboratory system for the study of the interaction of human skin with an HPV. The method may be useful in understanding the mechanisms of HPV transformation and replication and is free of the ethical restraints which have impeded study. This system will allow the direct study of factors which permit neoplastic progression of HPV-induced cutaneous lesions in human tissues.

Animals↗
PubMed1984

Characterization of mRNAs that map in the BglII N fragment of the herpes simplex virus type 2 genome.

The BglII N DNA fragment (0.580 to 0.620 map units) of herpes simplex virus type 2 strain (333) is of interest because of its transforming potential. This fragment contains either partial or the complete coding sequences for nine mRNA transcripts that can be detected during a lytic infection. Subclones of the BglII N DNA fragment were generated in plasmid vectors, and the approximate locations of the mRNA transcripts were mapped by RNA blot hybridization technology. Precise 5' or 3' ends (or both) of these mRNA species were determined by S1 nuclease mapping, using the BglII N subclones as DNA probes. At least four mRNA transcripts are fully encoded in the BglII N fragment. The coding regions for all of the mRNA transcripts are densely packaged along the BglII N fragment with less than 150 base pairs between neighboring mRNA ends. Analysis of both neutral and alkaline gels failed to reveal the presence of any detectable introns. This manuscript reports a detailed transcription map for this region.

Animals↗
PubMed1983

Simian virus 40 promoters direct expression of the tetracycline gene in plasmid pACYC184.

Insertion of HindIII DNA fragments into the HindIII site of plasmid pACYC184 destroys the promoter of the plasmid tetracycline resistance gene and causes Escherichia coli cells harboring recombinant plasmids to be tetracycline sensitive and chloramphenicol resistant. The HindIII-C DNA fragment of simian virus 40 contains the two virus promoters and the virus origin of replication. We report the isolation of recombinant plasmids that contained the simian virus 40 HindIII-C DNA fragment at the HindIII site but were capable of conferring tetracycline resistance to E. coli cells. The viral promoter sequences contained in the HindIII-C fragment presumably replaced the inactivated tetracycline resistance gene promoter sequences and enabled transcription of the tetracycline resistance gene.

DNA Restriction Enzymes↗
PubMed1982

Protease inhibitors suppress fibrinolytic activity of herpesvirus-transformed cells.

Previous studies in this laboratory have quantified the fibrinolytic activity of herpesvirus-transformed cell lines and implicated the proteolytic capacity of cloned cell lines in the formation of primary and metastatic tumours. Because of the involvement of proteases in tumourigenesis in this system, we examined the effect of various protease inhibitors (alpha-1-antitrypsin, leupeptin and alpha-2-macroglobulin), as well as hamster serum containing acute phase proteins generated in response to physiological trauma, on the fibrinolytic capacity of a herpes simplex virus type 2-transformed hamster cell line. The effects of the various inhibitors on cell growth, fibrinolysis in vitro and tumourigenesis were examined. Leupeptin, alpha-1-antitrypsin, alpha-2-macroglobulin and hamster serum containing acute phase proteins were capable of inhibiting fibrinolysis in vitro, were not toxic to the cells and their action was reversible, while rejection of a mixture of protease inhibitor and transformed cells resulted in delayed tumour development.

Animals↗
PubMed1982

Detection by RNA blot hybridization of RNA sequences homologous to the BglII-N fragment of herpes simplex virus type 2 DNA.

RNA species, extracted at the time of peak synthesis of the alpha, beta, and gamma classes of herpes simplex virus polypeptides from lytically infected Vero cells, were examined for homology to the BglII-N fragment (map units 0.58 to 0.63) of herpes simplex virus type 2 DNA. By using northern blot analysis, two major and several minor polyadenylated RNA species showed homology to the BglII-N fragment at times corresponding to the maximum synthesis of the beta (7 h postinfection) and gamma (12 h postinfection) herpes simplex virus polypeptides. No alpha RNA homologous to the BglII-N fragment was detected.

Animals↗
PubMed1981

Tumorigenicity of herpesvirus-transformed cells correlates with production of plasminogen activator.

Our studies first demonstrated that established hamster cell lines transformed in vitro by herpesviruses activate plasminogen more effectively than normal hamster fibroblasts. This ability is probably due to increased levels of the enzyme plasminogen activator (PA). In the studies described here, the 333-8-9 cell line, originally transformed by herpes simplex virus type 2 strain 333, was used to derive subclonal lines that maintained stable PA phenotypes over the course of long in vitro passage. We were interested in correlating tumor formation by the subclones with their fibrinolytic capacity. Cells were, therefore, single-cell subcloned twice, and resulting cultures were tested for ability to activate plasminogen in vitro. PA activity was then quantitated by [125I]fibrin lysis assay, and high- and low-activity subclones were isolated; these retained high- or low-activity phenotypes. Syngeneic newborn hamsters were inoculated with these subclones and observed for the appearance of palpable tumors. A strong correlation between enzyme activity and tumor formation was observed in four separate trials; animals receiving high-PA subclones developed tumors more rapidly than those inoculated with the parental cell line. Tumors were also excised from test animals, and the cell lines established from the tumors were tested in vitro at different passages for their ability to activate plasminogen. These tumor cells were then reinoculated into syngeneic animals to confirm the tumorigenicity of cell lines with high fibrinolytic activity. In these experiments, the positive correlation between PA production and tumorigenicity was confirmed.

Animals↗
PubMed1980

Quantification of plasminogen activator activity associated with herpesvirus-transformed cells.

Herpesvirus-transformed cell lines were examined for plasminogen activator (PA) activity using a quantitative assay. Previous results of cold fibrin overlay assays indicated that herpesvirus-transformed hamster cell lines produce fibrinolytic activity. Quantification of this activity involved the use of an 125I-fibrin lysis assay in which medium previously incubated with transformed or normal cells was tested for its ability to lyse 125I-fibrin polymers. This assay indicated an enhanced production of plasminogen-dependent fibrinolytic activity by transformed hamster cells compared to hamster embryo fibroblasts. The kinetics of secretion failed to reveal a significant difference in plasminogen activator activity in cells transformed by either herpes simplex virus types 1 or 2 (HSV-1 or HSV-2); however, transformed cells exhibited a significant increase in activity over non-transformed cells. Further characterization of PA activity associated with cells transformed by HSV-1 or HSV-2 has revealed that the protease is secreted and can function extracellularly. Extracellular PA activity produced by HSV-transformed cells is detected more efficiently than the cell-associated enzyme. Extracellular PA can be induced in two different species of cells by infection with partially inactivated HSV-2. Lytic infection of human embryo lung cells by HSV-2 strain 333 did not enhance activity, but infection of these cells with virus inactivated by u.v. irradiation resulted in increased PA levels from the cells. Increased enzyme levels were also detected in hamster embryo fibroblasts infected with partially inactivated virus. Further investigation of this enzyme function may determine whether increased levels of protease will indicate oncogenic transformation in vitro by herpesviruses.

Animals↗
PubMed1979

Enhancement of biochemical transformation of mammalian cells by herpes simplex virus following nitrosomethylurea treatment.

A quantitative assay for the biochemical transformation of thymidine kinaseless mouse cells (N cIA cI10 cells) to an enzyme-positive phenotype by herpes simplex virus has been used to examine the effect of the carcinogen nitrosomethylurea on cell transformation. Exposure of cells to the chemical carcinogen, followed by virus infection, resulted in enhancement of transformation when compared to that seen with virus or chemical alone. Enhancement occurred after doses of nitrosomethylurea that were nontoxic to treated cells. A strong time dependence after treatment was demonstrated for enhancement which was correlated with the presence and excision-repair of alkylated DNA in treated cells.

Animals↗
PubMed1978

A nonlytic transforming mutant of herpes simplex virus type 2.

A small-plaque mutant (NO.69) of herpes simplex virus type 2 (HSV-2) strain 333 has been previously isolated and characterized in this laboratory. This mutant was shown to produce a high ratio of noninfectious to infectious particles when grown at the nonpermissive temperature in hamster embryo fibroblasts [Westmoreland D. and Rapp F. (1976). Journal of Virology [8:92--102]. In this study, we have demonstrated that it is possible to obtain noninfectious stocks of this virus which retain transforming ability in a biochemical transformation assay specific for detection of the HSV gene for thymidine kinase. This mutant contains a DNA genome that has a density identical to the DNA of wild-type virus. Virus and cell DNA synthesis after infection with the mutant at both the permissive and nonpermissive temperature are similar to that observed in cultures infected with the parental virus. Clones of mouse cells biochemically transformed by this virus contain HSV antigens and are presently being examined for oncogenicity.

Cell Line↗
PubMed1978

Production of plasminogen activator by cells transformed by herpesviruses.

Plasminogen activator is produced by hamster cells transformed by human herpesviruses. These cell lines have previously been shown to be oncogenic when injected s.c. into newborn syngeneic hamsters. Lysis of fibrin overlays by these cell lines was plasminogen dependent. Normal hamster embryo fibroblasts and a hamster cell line transformed by PARA-7 (an adenovirus-SV 40 hybrid) failed to produced lysis. In separate experiments fibrin overlay of lytically infected secondary rabbit kidney cells did not show induction of this activity during the normal course of productive infection. The human cell line TE-85 clone F-5, a clonal cell line from a human osteogenic sarcoma, failed to produce plasminogen activator, but two separate clones of these cells that were morphologically transformed after exposure to UV-inactivated herpes simplex virus type 2 produced rapid lysis of the fibrin overlay. Clonal variation was observed in herpes simplex virus types 1 and 2-transformed hamster lines and is under investigation. It is suggested that plasminogen activator detection may serve as a convenient assay system for transformation of normal cells by herpesviruses.

Animals↗
PubMed1975

Effect of hypertonic conditions on protein synthesis in cells productively infected with simian virus 40.

Hypertonic medium selectively suppressed the synthesis of most host cell polypeptides relative to the synthesis of simian virus 40 capsid polypeptides and a minority of cellular polypeptides, notably histones. Under optimal hypertonic conditions, the synthesis of the major capsid polypeptide (VP1) is enhanced about sevenfold relative to host polypeptide synthesis. Because of the small amounts of the other nonhistone capsid polypeptides (VP2) and VP3) present in cell lysates, it was difficult to quantitate the extent, if any, of their enhancement. The maintenance of the restricted pattern of protein synthesis caused by hypertonic medium was dependent on continual peptide chain initiations. The resistance of viral protein synthesis to hypertonic conditions provides a means of detecting relatively low levels of intracellular viral protein synthesis. Analysis of the specific activity of the acid-soluble [3H]lysine pool indicated that the rate of incorporation of [3H]lysine into protein was an overestimation of the actual rate of overall protein synthesis occurring in cells exposed to hypertonic as compared to isotonic conditions. Since it is likely that both cellular and viral protein synthesis draw lysine from a single pool, this change in pool specific activity does not affect the analysis of relative rates of protein synthesis at a given level of tonicity.

Cell Line↗
PubMedDate not supplied

Morphological transformation in vivo of human uterine cervix with papillomavirus from condylomata acuminata.

Carcinoma of the human uterine cervix has been associated with several infectious agents including papillomavirus. Papillomavirus group-specific antigen (GSA) and viral particles have been demonstrated in human condylomata acuminata (CA) and flat warts of the uterine cervix. Cell alterations consisting of nuclear enlargement, hyperchromasia, irregularity, binucleation and cytoplasmic clearing (koilocytosis) are often interpreted as mild to moderate dysplasia. Present evidence that human papillomavirus (HPV) is responsible for the development of these lesions relies on the association of GSA and virus particles in the affected tissue, fulfilling the first two of Koch's postulates. Direct proof of an aetiological relationship, however, requires induction of the CA change in normal, human uterine cervix after exposure to papillomavirus. Infecting human subjects with HPV is ethically unacceptable and no satisfactory alternative systems have been defined. Also, human cell cultures do not support growth or transformation by HPV. Here we report the first demonstration of the morphological transformation of human tissues with a human papillomavirus under controlled, experimental conditions. 'Transformation' is used here in its literal sense to refer to a heritable morphological alteration in the appearance of the cells. The use of this term does not indicate that the changes described are neoplastic, but they are identical to the dysplastic changes found in biopsies of uterine cervical CA. Our results demonstrate the direct involvement of CA virus in dysplastic change of human cervical tissue and indicate that the experimental system described may be useful in elucidating the contribution of human papillomaviruses to the pathogenesis of human cervical cancer.

Cell Transformation, Neoplastic↗