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Biomedical subjects

K Perk

Publications and source records attributed to K Perk.

At least 37 records · Page 2Linked to original sources
PubMed1983

Hamster endogenous retrovirus (HaER) isolated from SV-40 induced tumor cells.

A hamster cell line obtained from a secondary transplanted SV-40-induced tumor was found to spontaneously release type C virus particles. The particles possessed all biochemical features characteristic of retroviruses and induced syncytium formation in XC cells but were not oncogenic for hamsters. Nucleic acid hybridization assays demonstrated that the isolated virus was an endogenous retrovirus of hamster, lacking sequence homology with mouse and other animal species.

Animals↗
PubMed1982

Organotropism of the lymphoproliferative disease virus (LPDV) of turkeys.

Turkey poults were inoculated with lymphoproliferative disease virus (LPDV) of turkey, and the organotropism of the inoculated virus was determined from the kinetics of virus expression and tumor formation. Molecular hybridization experiments, conducted to determine the level of viral RNA expression in the various organs of infected birds, established lymphoid tissues, including bone marrow, as the target for LPDV infection. Of these, bone marrow was the first to be infected but subsequently virus replication extended to the thymus, the spleen and the bursa Of Fabricius. The low level of LPDV expression in non-target organs probably stemmed from infiltration of infected lymphatic cells. The fact that the main organs for virus replication were not invariably the ones most clinically involved suggests that the target cells for virus infection need not necessarily be the targets for virus oncogenicity. A possible mode for LP[DV infection and transformation is proposed.

Animals↗
PubMed1982

The oncostatic effect of methyl-CCNU on various experimental lymphoreticular neoplasms.

Studies on the chemotherapeutic potential of methyl-CCNU on experimental leukemias were undertaken. A number of murine transplantable in vivo lines (chemical carcinogen-induced T and B leukemias; radiation- and viral-induced T leukemias of C57BL/6, C3H/eb and SJL/J origin; radiation-induced myeloid leukemias and spontaneous reticulum cell neoplasms of SJL/J mine) were used in these studies. The optimal dose of methyl-CCNU and optimal timing of administration were extensively investigated on two sample lines of T cell leukemias of C57BL/6 mice. Leukemic cell eradication could be achieved in almost all of the different leukemias treated, irrespective of whether induction was brought about by chemical or physical means or due to a viral leukemogenic agent. Studies undertaken to elucidate the effect of methyl-CCNU on the establishment of preleukemic cells following induction of leukemia by the radiation leukemia virus (RadLV) or by total body irradiation, indicated the oncostatic effect of methyl-CCNU on early preleukemic cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Morphological and immunological comparison of caprine arthritis encephalitis and ovine progressive pneumonia viruses.

Caprine arthritis encephalitis virus (CAEV) causes a variety of pathological conditions ranging from mild to very severe and from acute to chronic, depending upon the age of initial infection and other variables. Although the virus has been reported to have properties of characteristic of retroviruses and to be related to maedi-visna virus (also called progressive pneumonia virus [PPV]), relatively little information about its morphological and immunological characteristics has been reported. We describe the morphological features of CAEV replicating in cultured caprine cells. Although the virus replicates slowly and very little virus is released from productively infected cells, it is apparent that the morphogenesis of CAEV is strikingly similar to that of maedi-visna. After the transmission of CAEV to a more permissive permanent cell line derived from Himalayan tahr ovary, it was possible to grow and purify enough virus to initiate biochemical characterization. The structural proteins of CAEV are generally very similar to those of PPV, suggesting that the two viruses are closely related but not identical. This was substantiated by showing that serum from a CAEV-infected goat immunoprecipitated both CAEV and PPV virion structural antigens from extracts of radiolabeled virus and also precipitated putative nonstructural viral antigens from extracts of both CAEV- and PPV-infected cells.

Animals↗
PubMed1980

Evidence for type-C retrovirus production by Burkitt's lymphoma-derived cell line.

Burkitt's lymphoma cell line, P3HR-I, was found to secrete virions with properties of known type-C RNA tumor viruses. The viral particles had a buoyant density of 1.16 g/ml in sucrose gradients and contained a high-molecular-weight RNA and an RNA-instructed DNA polymerase. The viral polymerase was active in an endogenous reaction requiring the presence of the four deoxyriboside triphosphates and manganese ions, and was sensitive to RNase. The DNA product of the endogenous reaction specifically hybridized to P3HR-I viral 60 to 70S RNA. Electron microscopic examination of ultrathin sections of P3HR-I cells revealed immature, mature and budding virions typical of type-C retroviridae. Nucleic acid hybridization assays showed no sequence homoblastosis virus, murine oncornaviruses, simian sarcoma virus or RD114 virus.

Burkitt Lymphoma↗
PubMed1980

Genesis, ultrastructure and cytochemical study of the cat eosinophil.

Eosinophils from cat bone marrow and peripheral blood were studied by electron microscopy and cytochemical procedures. The maturation of eosinophils and formation of typical granules were described. Contrary to the accepted opinion that the core of animal's eosinophilic specific granules have a crytal-like structure, our observations revealed that the core has a myelin-like cylindrical appearance, whose layered formation proceeds from the inside outwards. Electron microscopic observations revealed that localization of reaction product to potassium pyroantimonate and phosphotungstic acid and to acid phosphatase activity was similar to that of eosinophils of man and other animals. Antimonate deposits and acid phosphatase activity were detected between the layers of the myelin-like structure of the core. Eosinophil granules failed to yield a positive reaction for peroxidase activity. The secretory activity of the eosinophil is discussed.

Acid Phosphatase↗
PubMed1979

Biochemical characterization of the type C retrovirus associated with lymphoproliferative disease of turkeys.

Turkeys inoculated with spleen extracts from lymphoproliferative disease (LPD)-affected birds developed viremia, followed by typical LPD lesions. Electron microscopy and biochemical characterization established that the virus present in the blood of infected turkeys is a type C retrovirus. The viral particles possess a buoyant density of 1.17 g/ml in sucrose gradients; they contain high-molecular-weight RNA and an RNA-instructed DNA polymerase with efficient exogenous and endogenous activity. The LPD virus polymerase is preferentially activated by magnesium ions. Cross nucleic acid hybridization assays revealed no sequence homology between the viral genome of LPD and avian myeloblastosis virus or reticuloendotheliosis virus, thus indicating that the LPD virus belongs to a distinct group unrelated to the avian leukosis-sarcoma virus complex or to the reticuloendotheliosis virus group.

Animals↗
PubMed1979

Molecular evidence for a type C retrovirus etiology of the lymphoproliferative disease of turkeys.

Recently, we isolated from the blood of lymphoproliferative disease (LPD)-affected turkeys a type C retrovirus distinct from the avian leukosis-sarcoma virus complex and the reticuloendotheliosis virus group. We present molecular evidence for the implication of this virus in the LPD of turkeys. Using complementary DNA of LPD viral RNA, we found that the LPD viral genome is specifically and efficiently transcribed (2,500 copies per cell) in LPD tumor cells. Moreover, the LPD tumor cells contained newly inserted LPD viral information (5 to 10 copies per haploid genome), which was not present before the infection. From the absence of LPD virus-specific sequences in the normal cell genome of turkeys, it was concluded that the LPD virus is not an endogenous virus of turkeys. DNA-DNA annealing experiments revealed that the degree of sequence homology between LPD viral complementary DNA and cellular DNA of turkeys was not higher than that between LPD viral complementary DNA and cellular DNA of other species, thus indicating that the virus does not originate from turkeys.

Animals↗
PubMed1979

The effect of early treatment with methyl-CCNU on the lymphoid organs and the humoral immune response in chickens.

Presented are data upon the effect of a single or muliple administration of methyl-CCNU (a nitrosourea derivative an alkylating agent, and anticancer drug) to newly-hatched chicks. Lethal and sublethal doses of methyl-CCNU caused temporary damage to the lymphoid organs, of which the bursa was apparently the most sensitive. The decreased weight and the morphological changes observed in the bursa of treated chicks were accompanied by a parallel decrease in serum gamma-globulins level. The humoral immune response of animals treated with me-CCNU to sheep red blood cells and to killed Brucella abortus organisms was impaired in about 30% of the treated animals examined 8-10 weeks following 2 injections of 3 mg me-CCNU (given at the day of hatching and the next day). The thymus recovered rather rapidly from treatment. The time schedule of mortality and the early and late toxic manifestations of the drug as observed in chickens, in this study, are similar to previous reports obtained in mammals. Prolonged effects, however, were noted to some extent on body and spleen weight, and most dramatically, on testicular weight, morphology, and function.

Animals↗
PubMed1979

Morphologic characterization of proliferative cells and virus particles in turkeys with lymphoproliferative disease.

The tumors found in turkeys having lymphoproliferative disease (LPD) are histologically characterized by a pleomorphic population of cells of the lymphoid series. Electron microscopy has shown that, despite marked differences in shape and size, the proliferating cells share basic ultrastructural features, indicating their lymphoid origin. Virus particles morphologically and morphogenetically characteristic of type C oncorna-viruses of Retraviridae were found in different organs and plasma samples of diseased or infected turkeys with LPD. This LPD type C virus resembled members of the reticuloendotheliosis virus group but not members of the avian sarcoma virus group.

Animals↗
PubMed1978

Lack of maedi viral related RNA in pulmonary carcinoma of sheep (jaagsiekte).

Molecular hybridisation with radioactively labelled DNA complementary to the RNA of the maedi virus was used to probe for homologous RNA in the polysome fraction of pulmonary carcinomas (jaagiekte) of Awassi sheep. No sequence homology was detected, which suggests that maedi (or visna) virus is not implicated in the aetiology of pulmonary carcinoma of sheep.

Animals↗