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Biomedical subjects

K Perk

Publications and source records attributed to K Perk.

At least 19 recordsLinked to original sources
PubMed1999

Concealed locations of lentiviruses in caprine arthritis encephalitis system.

Ultrastructural examinations of ovine and caprine tissue culture cell lines infected with a molecular sheep lentivirus clone KV72 revealed typical cytoplasmic A type retrovirus particles and budding particles from plasma cell membrane. Blood examinations of a heavily caprine arthritis encephalitis virus-afflicted herd revealed that three goats, which on previous blood examinations had showed a high level of infection, had become negative. Two of these goats underwent a necropsy. The main findings were the presence of typical intracytoplasmic A-type particles found only in neural tissue. No budding or extracellular retrovirus particles were seen in any of the neural tissue examined or in lymph nodes, spleen, or buffy coat cell samples of these animals. This concealed location may be in some analogy with the human immunodeficiency virus system. Despite undetectable blood levels of human immunodeficiency virus in patients after potent combination therapies, they may still harbor latent viruses in different loci.

Animals↗
PubMed1995

Characteristics of ovine and caprine lentivirus infections.

A majority of ovine lentivirus (OvLv) infections seen on farms develop after long incubation and a slow progression of disease to death but in nature they may also have short latency and cause acute leukoencephalitis and/or acute arthritis and pneumonia in young kids or lambs with exceptionally high mortality. Histopathologically, OvLv diseases may be characterized by lymphoid infiltration, lymphoid hyperplasia with germinal centers and plasmocytosis in the lungs and/or in the CNS, joints and udder. Lymphoid hyperplasia in lymph nodes and spleen, as well as lymphoid infiltration in the kidneys, are almost always seen in advanced cases. In some cases, it shows similarities to lymphoproliferative diseases that are considered malignant. Alveolar epithelial hyperplasia in the lungs is generally also seen, especially in older goats with caprine arthritis encephalitis virus (CAEV), and proliferation of these epithelial cells may form acine and papillary structures and in some cases are histopathologically indistinguishable from tumor nodules seen in sheep pulmonary adenomatosis. Because of complexities in the host-lentovirus interaction, cell-associated transmission and extensive antigenic and genomic variation among infecting isolates, control of infection or prevention of spread are problematic by traditional methods and exploration of alternative control strategies employing selection and expansion of animals genetically resistant to OvLv or transgenic for certain viral genes, merits consideration. Interestingly, the pure Awassi sheep breed are susceptible to infection but do not develop the disease, as do European breeds or cross-breeds in Israel, ie they are infected but not diseased. It seems that the local Bedouin black goat breed is resistant to infection of CAEV under natural conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Isolation and preliminary characterisation of a novel retrovirus isolated from a leukaemic dog.

A novel canine retrovirus was isolated from mononuclear cells of the peripheral blood of a leukaemic dog. The main clinical and pathological findings in this dog were lethargy, anorexia, weakness, dyspnoea, severe anaemia, thrombocytopenia and a high white blood cell count, practically all of which were lymphoblasts. The virus was isolated from mononuclear cells obtained from the blood, cocultivated with indicator cells. The virus particles encode a reverse transcriptase with Mg++ preference, have a density in sucrose gradients of 1.16 g ml-1, and induce syncytia in permissive cell cultures such as Himalayan tahr ovary and canine fetal thymus lines. This agent replicates to high titres. The virus exhibits a morphogenesis and morphology typical of lentiviruses. Immunoblotting and competitive radioimmunoassays failed to detect immunological crossreactivity with other representative lentiviruses and oncoviruses of the retrovirus family.

Animals↗
PubMed1992

Propagation and characterization of novel canine lentivirus isolated from a dog.

We have recently isolated a novel canine lentivirus (canine immunodeficiency virus, [CIV]) from a leukemic dog. The virus was isolated from buffy coat cells obtained from the leukemic dog co-cultivated with indicator cells. The virus particles encode a reverse transcriptase with a preference for magnesium, have a density of 1.16 g/ml in sucrose, and induce syncytia in permissive cell lines such as Himalayan tahr ovary and canine fetal thymus. CIV replicates to high titer and highly purified virus can readily be prepared. The ultrastructure and morphogenesis of CIV is strikingly similar to that displayed by other lentiviruses, while immunoblot analysis failed to demonstrate close immunological relatedness to any other lentivirus or oncovirus. These findings suggest that this canine virus, representing the first isolation of a canine retrovirus, belongs to the lentivirus subfamily but is not closely related to other known members.

Animals↗
PubMed1990

Effect of beta-endorphin on steroidogenesis by bovine luteal cells.

To determine if opioid peptides have a local effect on the modulation of progesterone (P4) synthesis, a study was made of the effect of beta-endorphin and leu-enkephalin on P4 production by pure preparations of small luteal cells and dissociated luteal cells comprising both small and large cells from cows 2-3 months pregnant. Corpora lutea were dispersed by collagenase, and the large and small luteal cells were separated using Percoll gradients. Viable luteal cells (5 x 10(5)) were incubated in 0.5 mL of Eagle medium for 2 h at 37 degrees C, in an atmosphere of 5% CO2. Cells were treated with 8-bromoadenosine 3',5'-monophosphate (8Br-cAMP), hCG, beta-endorphin (BE) and leu-enkephalin (LE) alone or in combination. When small luteal cells were used, P4 synthesis was significantly enhanced in the presence of opioid peptides alone (P less than 0.01); there was an additive effect with 8Br-cAMP and with hCG. For dissociated luteal cells, opioid peptides alone had no effect on P4 production but the stimulation of P4 production induced by 8Br-cAMP or hCG was significantly (P less than 0.01) inhibited in the presence of opioid peptides. In contrast, dissociated luteal cells that were preincubated with PGF2 alpha (degranulation) responded to the presence of BE with increased P4 synthesis similar to that seen with the pure preparation of small luteal cells. It is concluded that opioid peptides play an auto/paracrine role in both basal and tropic hormone-induced stimulation of steroidogenesis by the bovine luteal cell.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

Presence of virus particles in neural cells of goats with caprine arthritis encephalitis.

The possible neurotropism of ungulate lentivirus was examined in clinical cases. Brain and ganglion tissue samples were examined from six female goats with caprine arthritis encephalitis and from six healthy controls. Ultrastructural examination revealed typical cytoplasmic A type retrovirus particles in the neural tissue of the diseased does. None were seen in the respective controls. Furthermore, no budding or extracellular retrovirus particles were seen in any of the neural tissue samples examined.

Animals↗
PubMed1988

Priming with low doses of methyl-CCNU reduce the toxicity of high doses of methyl-CCNU and melphalan, and increase the lifespan of mice implanted with Lewis lung carcinoma.

Pretreatment of mice with low doses of methyl-CCNU was shown to reduce the toxicity of lethal doses of methyl-CCNU or melphalan administered one or two days following the low dose. There was an increase in survival rate, body weight, thymus and kidney wet weight. Tissue morphology was less affected in the primed mice as compared to mice receiving the high dose or a high-low dose combination. In mice implanted s.c. with Lewis lung carcinoma, priming with 5 mg kg-1 methyl-CCNU 2 days before injection of a very high (35 mg kg-1) dose significantly increased the lifespan as compared to treatment with the high dose alone or with high-low dose combination. When the dose of methyl-CCNU was further increased to 40 mg kg-1 toxic death occurred, which was, however, significantly reduced by 'priming' with the low dose given. When low-high dose combination was used twice (the high dose was given on day 7 or 9, and 18 or 20 after tumour inoculation), priming with 5 mg kg-1 (but not with 10 mg kg-1) two days prior to the high dose was beneficial in reducing toxic death (in two experiments) and either increasing lifespan or not significantly increasing it. In no case was there protection of the tumour by the low-high dose combinations.

Animals↗
PubMed1988

Development of an enzyme-linked immunosorbent assay for caprine arthritis-encephalitis virus.

Because relatively few caprine arthritis-encephalitis virus (CAEV)-infected animals exhibit clinical signs of illness, efforts to control and eradicate this virus will depend heavily on a sensitive diagnostic test that can be easily carried out. The currently utilized tests are of limited usefulness because of relatively low sensitivity or because of incomplete cross-reactivity of goat sera with heterologous test antigens. An enzyme-linked immunosorbent assay (ELISA) with purified CAEV antigen and biotin-avidin amplification steps was therefore developed and compared with a radioimmunoassay (RIA) against CAEV p28. Of over 500 sera tested, there was 99% concordance between the two tests. On the other hand, 23 of 24 sera obtained from animals with clinical signs of disease that were negative by agar gel immunodiffusion test (with ovine progressive pneumonia virus antigen) were positive by ELISA and RIA. These results suggest that an ELISA with CAEV antigen is superior to the agar gel immunodiffusion test and is easier and faster than an RIA, and therefore may be the method of choice for diagnosing CAEV infection.

Animals↗
PubMed1986

Analysis of structural polypeptides of the lymphoproliferative disease virus (LPDV) of turkeys.

The polypeptide composition of the lymphoproliferative disease virus (LPDV) of turkeys was shown to comprise several polypeptides with apparent molecular weights of 76, 31, 28, 20 and 15 kDa. This polypeptide pattern is distinctly different from the protein profiles of avian leukosis viruses, reticuloendotheliosis virus, or murine leukemia viruses. Moreover, LPD virions contain 2 major structural proteins (p31 and p28), in contrast to only one major internal protein present in most other retroviruses. The 76 kDa protein was established as the major viral envelope glycoprotein. The uniqueness of the LPDV polypeptide pattern is consistent with the lack of genetic relatedness of LPDV genome to other retroviruses, establishing LPDV as a representative of a distinct group of retroviridae.

Animals↗
PubMed1985

Transforming potential of a retrovirus isolated from lung carcinoma of sheep.

A retrovirus isolated from experimentally induced sheep lung carcinoma (SPCTV) was propagated in chronically infected Himalayan tahr ovarian cells and in normal sheep lung cells. Follow-up of infection of the cells with SPCTV showed the appearance of syncytium, plaque formation, partial recovery and the establishment of a chronic infection. Virus-associated reverse transcriptase activity in the medium fluctuated but remained at a constantly high level at the stage of chronic infection. Stages of type-C virus morphogenesis were demonstrated by electron microscopy. The viral genome was detected in both the nucleus and cytoplasm by in situ hybridization. Chronically infected cells formed colonies when plated in soft agar. Following subcutaneous inoculation of chronically infected cells (of fibroblast origin) into nude mice, lymphoid tumors developed at the site of inoculation and in vital organs.

Agar↗
PubMed1985

Iron, transferrin, and acid and alkaline phosphatase in healthy turkeys and in turkeys inoculated with the lymphoproliferative disease virus.

Presented are data on iron-binding capacity determinations in the serum of turkeys infected with lymphoproliferative disease (LPD) virus and in healthy males and females (laying eggs and nonlaying) from a breeding flock. Also presented are results of serum and tissue total acid and alkaline phosphatase determinations in turkey poults infected with LPD virus and their uninfected controls and of serum enzyme levels in healthy males and females from the breeding flock. There was no significant alteration in total iron binding capacity (transferrin level) in the serum of turkeys with LPD. Turkey poults inoculated with LPD virus showed a significant decrease in serum alkaline phosphatase activity 4 and 7 weeks postinfection (pi), and a decrease in serum acid phosphatase activity 7 weeks pi. Acid and alkaline phosphatase activity determined in the spleen and pancreas (organs with pronounced tumor involvement) 7 weeks pi did not differ significantly from that of healthy controls, although there was a tendency for both enzymes to decline in the pancreas of the infected turkeys. Healthy laying female turkeys demonstrated marked elevation in serum transferrin level and in acid and alkaline phosphatase activity, as compared with males of the same age. Serum alkaline phosphatase of turkey poults was markedly higher than that of adult turkeys.

Acid Phosphatase↗
PubMed1985

Appearance of ovine progressive pneumonia virus outside the United States.

A recently isolated Israeli retrovirus from a sheep with maedi-visna was compared with other retroviruses, using cDNA-RNA hybridization in solution. The Israeli isolate was shown to have close, if not identical, genetic homologic features with the ovine progressive pneumonia virus reported in the United States, rather than with those of the maedivisna viruses of European origin.

Animals↗
PubMed1984

Isolation and characterization of a novel retrovirus from sheep affected by pulmonary carcinoma.

Sheep pulmonary carcinoma (SPC) has been shown to be associated in nature with a retrovirus, by electron microscopic, biochemical, and epidemiological criteria and by experimental transmission. In this study, a retrovirus has been isolated from SPC tumors which were experimentally induced by inoculation with a cell-free, reverse transcriptase containing fraction from a spontaneous field case of SPC, and propagated in culture. This novel virus was shown to be unrelated to murine, avian, and bovine leukemia viruses, to be exogenous to the ovine species, and to have only limited genetic relatedness to the lentiviridae (maedi-visna and caprine arthritis encephalitis virus).

Animals↗
PubMed1984

Heterotransplantation of experimentally induced sheep lung adenomatosis into nude mice.

Male ICR nude mice inoculated subcutaneously with minced tissue obtained from pulmonary adenomatosis of sheep which was induced by RNA type-C retrovirus developed a transplant which contained cysts lined by a proliferative epithelium. These cysts showed several characteristics of the epithelial tumour cells of origin, such as high glycogen content and secretion of mucin. Microinvasion of epithelial cells from the adenomatous cysts into the stroma was observed. The stromal tissue demonstrated islets of cartilage. It was concluded that virus-induced pulmonary carcinoma of sheep can be transplanted and grown in nude mice.

Animals↗
PubMed1983

Genetic control of the organ specificity of lymphoproliferative disease virus (LPDV) of turkeys.

In a previous study based on the kinetics of virus replication and tumor formation (Gazit et al., 1982), it was shown that the organotropism of lymphoproliferative disease virus (LPDV) is confined to lymphoid tissues. The present paper demonstrates that this organ specificity is controlled at the level of infection and integration, that is, the lymphoid organs, which are the only organs sustaining virus replication, and also the only organs in whose cells integrated LPDV proviruses are detectable. At the same time, the efficiency of virus replication within the various target organs is regulated both at the level of infection and integration and at the level of viral gene transcription.

Animals↗
PubMed1983

The caprine arthritis-encephalitis virus is a distinct virus within the Lentivirus group.

The genetic relatedness among viral genomes of caprine arthritis-encephalitis virus, visna virus, and progressive pneumonia virus, was determined. Whereas the genomic RNAs of two strains of visna virus are indistinguishable as reflected both by their annealing kinetics as well as by the thermal stability of the hybrids, the caprine arthritis-encephalitis virus and visna virus have only 30% of their nucleic acid sequences in common. Furthermore, within the homologous regions of the two viral genomes, there is a significant level (approximately 10%) of mismatched base pairs. This limited homology that exists between caprine arthritis-encephalitis virus and visna virus was lower than the sequence homology observed between the genomes of visna virus and progressive pneumonia virus, or between the genomes of caprine arthritis-encephalitis virus and progressive pneumonia virus. All this indicates that caprine arthritis-encephalitis virus is an additional distinct member of the Lentivirus group of the Retroviridae family.

Animals↗