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Biomedical subjects

A Burny

Publications and source records attributed to A Burny.

At least 181 records · Page 10Linked to original sources
PubMed1989

Synthetic peptides approach to identification of epitopes on bovine leukemia virus envelope glycoprotein gp51.

Peptides corresponding to residues 21-28, 39-48, 57-67, 59-69, 78-92, 144-155, 144-157, 195-205, 255-268, and 260-268 of envelope glycoprotein gp51 of bovine leukemia virus (BLV) were chemically synthesized and coupled to keyhole limpet hemocyanin or tetanus toxoid. All peptides were immunogenic in rabbits and induced production of antipeptide antibodies. Enzyme-linked immunosorbent assays using Tween 80-purified gp51 or BLV particles showed that antibodies against peptides 78-92, 255-268, and to a lesser extent 39-48 and 144-157 were able to react with the parent glycoprotein, purified or as an integer part of BLV particles. Antisera against peptides 39-48, 78-92, and 144-157 neutralized VSV (BLV) pseudotypes in vitro, the highest neutralization titer being obtained with the 78-92 cyclized peptide. These observations confirm that the NH2 moiety of gp51 carries epitopes involved in virus infectivity.

Animals↗
PubMed1989

Synthesis of functional bovine leukemia virus (BLV) p34tax protein by recombinant baculoviruses.

The bovine leukemia virus (BLV) p34tax (also called tat, p34, XLOR gene product) is a 34-kDa polypeptide encoded in the 3'-terminal region of the virus. This protein is responsible for positive transcriptional trans-activation of promoter elements located within the BLV long-terminal repeat. We introduced the protein-coding region of BLV p34tax into the genome of the baculovirus Autographa californica nuclear polyhedrosis virus. After infection of the insect Spodoptera frugiperda (SF9) cell line, this recombinant strain of baculovirus produced approximately 100 to 150 mg of p34tax per 2 X 10(9) cells. This protein, when introduced into mammalian fibroblasts by using a cell-to-cell fusion technique, functionally trans-activated the BLV long-terminal repeat. Analysis of 32P-labeled proteins of SF9 cells expressing BLV tax by two-dimensional gel electrophoresis indicated that the BLV p34tax was phosphorylated.

Animals↗
PubMed1989

Structural and functional characterization of mutants of the bovine leukemia virus transactivator protein p34.

Mutants of the bovine leukemia virus (BLV) transactivator protein (tat, tax, p34, the XLOR gene product) were constructed by site-directed deletions, in-phase linker insertions, or fragment replacements (swapping) among BLV variants. The mutant constructs were transfected into cos cells and transiently expressed. Western blot analysis using a mixture of monoclonal antibodies to wild-type p34 revealed the presence of mutated XLOR gene products in all the mutants tested. The transactivating activity of 11 tax mutants containing site-directed deletions and in-phase linker insertions was completely abolished. Only the swapping mutant tested, a hybrid between two BLV variants, transactivated LTR-directed gene expression at wild-type levels. These data illustrate the narrow range of structural variations that allow full activity of the BLV tax product and suggest that the present molecular structure of the transactivator protein results from heavy evolutionary constraints.

Blotting, Western↗
PubMed1989

Expression of the bovine leukemia virus transactivator protein p34 by a recombinant vaccinia virus.

In order to characterize the bovine leukemia virus transactivator protein, a recombinant vaccinia virus (v-LOR) containing the BLV post-envelope long open reading frame was constructed. v-LOR was shown to encode a functional protein able to transactivate the BLV long terminal repeat-directed gene expression in the infected cells. The encountered level of transactivation was about one third of that measured in BLV-infected fetal lamb kidney cell lysates.

Animals↗
PubMed1989

Use of two monoclonal antibodies in an ELISA test for the detection of antibodies to bovine leukaemia virus envelope protein gp51.

A competition ELISA technique involving two monoclonal anti-gp51 antibodies has been developed for the detection of bovine leukaemia virus (BLV) antibodies. Precoated gp51 antigen-microtitre plates were obtained by incubation of plastic adsorbed monoclonal antibody with a non-purified BLV preparation. Samples to be tested were incubated in the wells of the gp51-coated plates; the presence of anti-gp51 antibodies was indicated by competition for antigen binding with an enzyme linked monoclonal antibody directed to an important epitope on gp51. This test is as sensitive as a routinely used indirect ELISA test; it is highly specific, reliable and easy to perform.

Animals↗
PubMed1989

Bovine leukaemia virus ISCOMs: biochemical characterization.

The glycoprotein gp51 of bovine leukaemia virus (BLV) has been included in an immunostimulating complex (ISCOM). The ISCOM was characterized biochemically in SDS-polyacrylamide gel electrophoresis showing the presence of proteins of estimated molecular weights of 50 and 30 kDa. Immunoblotting showed that gp51 was present in the ISCOM. The BLV-ISCOM had a S-value of 19 S and the electronmicrograph showed the cage-like structure as previously reported for other ISCOMs. About 17% of the total amount of gp51 in the cell culture fluid was recovered in the ISCOMs. The largest loss of gp51 was encountered during the sedimentation of the virus. An ELISA, utilizing monoclonal antibodies to defined epitopes for capture was developed to control the antigenicity of epitopes, e.g. those known to induce neutralizing antibodies. Using this device as a quality control for epitopes the following could be stated. First, ISCOMs prepared from virus solubilized with the non-ionic detergents Triton X-100 or MEGA did not react with neutralizing monoclonal antibodies. In contrast, ISCOMs prepared from virus solubilized with the non-ionic detergents Tween-20, Tween-80 or octyl glucoside did react with the neutralizing antibodies. Second, the neutralizing epitopes were better exposed in ISCOMs than the other epitopes of gp51. In a preliminary experiment it was shown that gp51 in ISCOMs was highly immunogenic.

Adjuvants, Immunologic↗
PubMed1989

Mutations located on both F1 and F2 subunits of the Newcastle disease virus fusion protein confer resistance to neutralization with monoclonal antibodies.

The fusion gene sequence of six Newcastle disease virus escape mutants revealed that residues important for the integrity of antigenic site 1 and antigenic site 2 were located, respectively, on the F2 subunit and within the cysteine-rich domain of the F1 subunit. We further report the antibody-binding capacity of these mutants.

Amino Acid Sequence↗
PubMed1989

Effect of pituitary somatotropin injections on plasma insulin-like growth factor I and somatotropin profiles in growing heifers.

Effects of daily injections of pituitary-derived bovine somatotropin (bST) for 6 wk were evaluated in 10 growing heifers and compared to 9 placebo-treated control animals. Bovine somatotropin was injected at 50 micrograms/kg BW each day. Body weight and growth, plasma concentrations of insulin-like growth factor I (IGF-I) and somatotropin (ST) were assessed. To measure plasma concentrations of IGF-I, we validated a RIA in which bovine plasma samples were extracted with acid-ethanol, a method that resulted in greater than 90% recovery of IGF-I. Average daily gain was similar during the first 4 wk of the experiment in both control and bST-treated groups; however, at the end of the experimental period (wk 4 and 6) ADG was greater (P less than .05) in bST-treated heifers (1.24 +/- .21 kg/d vs .75 +/- .25 kg/d). Plasma IGF-I from wk 2 to wk 6 were increased in bST-treated animals (452 +/- 97 ng/ml at wk 2; 683 +/- 106 ng/ml at wk 6) compared with controls (293 +/- 62 ng/ml at wk 2 (P less than .01) and 293 +/- 115 ng/ml at wk 6 (P less than .001). Moreover, ADG over the 6-wk experimental period was correlated with mean IGF-I concentrations determined over the same period (r = .55; P less than .01). As expected, mean plasma ST concentrations were increased in bST-injected animals from wk 1 to 6. Gel chromatographic profiles of bovine plasma exhibit a 150,000 molecular weight ST-dependent binding protein-IGF-I complex and a 30,000 molecular weight non-ST-dependent complex. This study validates a method for measuring IGF-I in cattle, and shows a positive relationship among IGF-I and ADG after ST treatment. No correlation, however, was found between plasma ST and growth performance.

Animals↗
PubMed1988

The neurotrophic factor neuroleukin is 90% homologous with phosphohexose isomerase.

Neuroleukin (NLK) is a protein of relative molecular mass (Mr) 56,000 (56K) secreted by denervated rat muscle and found in large amounts in muscle, brain, heart and kidneys. The protein is a neurotrophic factor for spinal and sensory neurons and a lymphokine product of lectin-stimulated T-cells. It also induces immunoglobulin secretion by human mononuclear cells. Molecular clones of NLK have been expressed in monkey COS cells and the product was shown to have the same biological and biochemical properties as the extracted protein. NLK is abundant in muscle, brain and kidney, but is active at concentrations of 10(-9) to 10(-11) M, similar to those for other polypeptide factors. We have cloned the gene for pig muscle phosphohexose isomerase (PHI) (EC 5.3.1.9) which catalyses the conversion of glucose-6-phosphate to fructose-6-phosphate, an obligatory step in glycolysis, and determined its amino-acid sequence. Surprisingly, it is 90% homologous to the sequence of mouse neuroleukin.

Amino Acid Sequence↗
PubMed1988

The mode of insertion of the paramyxovirus F1 N-terminus into lipid matrix, an initial step in host cell/virus fusion.

A protein sequence of the viral envelope is responsible for the fusion of the viral membrane with the cell membrane. It has been hypothesized that this fusion protein acts by inserting its hydrophobic moiety into the target membrane. The paper reports on the mode of insertion of the Newcastle disease virus (NDV) fusion protein N-terminus peptide into a lipid membrane using infrared spectroscopy and conformational analysis. The peptide was shown to adopt an oblique orientation with respect to the lipid acyl chains. This unusual orientation is expected to induce the disorganization of the surrounding lipids, which had been suggested as one of the initial events in the virus/cell fusion.

Amino Acid Sequence↗
PubMed1988

Fusion (F) protein gene of Newcastle disease virus: sequence and hydrophobicity comparative analysis between virulent and avirulent strains.

The nucleotide and predicted amino acid sequences have been obtained for the fusion (F) protein gene of the avirulent strain La Sota of Newcastle disease virus (NDV). The F1 N-terminus begins with the tripeptide Leu-Ileu-Gly instead of Phe-X-Gly as usually observed in fusion peptide. It was found that the cleavage-activation domain of the avirulent La Sota strain contained single (but no pairs of) basic residues in the sequence Gly-Arg-Gln-Gly-Arg. Hydrophobicity analysis suggested that the cleavage-activation domain became more hydrophobic and could be less accessible for host-specific protease(s); dibasic residues next to the F1 N-terminus were shown to be important for keeping the cleavage-activation site in exposed positioning, suitable for F protein activation. Comparative sequence analysis of the NDV F proteins revealed a striking homology between lentogenic La Sota and mesogenic Beaudette C strains. Furthermore, 58 variable positions were recorded in the NDV F protein, excluding signal sequence; some of these mutations, in the cysteine-clustered region, were surmised to alter virulence.

Amino Acid Sequence↗
PubMed1988

Effects of an anabolic treatment before puberty with trenbolone acetate-oestradiol or oestradiol alone on growth rate, testicular development and luteinizing hormone and testosterone plasma concentrations.

Scrotal circumference, growth and hormonal status after prepubertal anabolic treatments were studied in 18 conventional Belgian White Blue bulls from 3 to 13 mo of age. Young bulls were assigned into three groups: six untreated (control) bulls, six bulls implanted with 140 mg trenbolone acetate + 20 mg oestradiol (Revalor; TBA-E2) and six bulls treated with 45 mg oestradiol (Compudose; E2). Mean scrotal circumference was similar in the three groups at Day O (between 13.0 +/- 0.3 cm to 13.4 +/- 0.7 cm). From Days O to 230, scrotal circumference was strongly inhibited in implanted bulls, 23.2 +/- 1.4, 21.7 +/- 1.0 cm, respectively, for TBA-E2 and E2 at Day 210, as compared with 29.5 +/- 2.2 cm in control bulls (P < 0.001). Afterwards, differences lessened gradually and no significant divergence was observed between the three groups from Day 310. Average plasma luteinizing hormone (LH) concentrations were similar in the three groups throughout the assay. Mean testosterone levels remained extremely low upto Day 150 in TBA-E2 and E2 groups (0.6 +/- 0.6, 1.2 +/- 0.7 ng/ml, respectively) before they increased abruptly and reached values observed in control bulls at Day 180 (4.0 +/- 1.9 ng/ml). The pulsatil character of LH and testosterone profiles was abolished by the anabolic treatments. Luteinizing hormone-releasing hormone (LHRH) injection was followed by an immediate and sharp increase in plasma LH concentrations in all groups at Day 0. Anabolic treatments strongly reduced LH and testosterone responses to LHRH in treated groups.

Journal Article↗
PubMed1988

Detection of B and T cells, with lectins or antibodies, in healthy and bovine leukemia virus-infected cattle.

Lectins, polyclonal antibodies and monoclonal antibodies (MAbs) were evaluated as markers for bovine lymphocytes obtained from healthy animals and from cattle infected with bovine leukemia virus (BLV). In the blood from healthy cattle the proportion of cells identified as T lymphocytes with the lectin Helix pomatia (HP) (67.8 +/- 6.2%) using the indirect immunofluorescence technique was similar to the proportion of cells identified by the MAbs P5 (66.1 +/- 3.8%) and BLT-1 (59.8 +/- 7.1%). The proportion of B cells in blood from healthy animals identified with a polyclonal antibody to bovine IgM (18.0%) was similar to that identified with a MAb to bovine IgM (16.2%). However, greater variation between individual values was detected with the MAb (SD = 8.2) than with the polyclonal antibody (SD = 4.0). In the blood from BLV-infected cattle with persistent lymphocytosis, both the polyclonal and the MAb revealed a threefold increase of B cells. A proportion of the B cells had an increased amount of immunoglobulin molecules in their plasma membrane as indicated by flow cytometry. The proportion of T lymphocytes, identified by the MAb P5, was reduced to one-third of that in non-infected cattle. The indirect HP labelling gave inconsistent results and seems not to detect solely T lymphocytes among blood lymphocytes from BLV-infected cattle.

Animals↗
PubMed1988

Bovine leukaemia: facts and hypotheses derived from the study of an infectious cancer.

Bovine leukaemia virus (BLV) is the etiological agent of chronic lymphatic leukaemia/lymphoma in cows, sheep and goats. Infection without neoplastic transformation was also obtained in pigs, rhesus monkeys, chimpanzees, rabbits and observed in capybaras and water-buffaloes. Structurally and functionally, BLV is a relative of human T lymphotropic viruses 1 and 2 (HTLV-I and HTLV-II) In humans, HTLV-I induces a T-cell leukaemia and its type 2 counterpart has been found in dermatopathic lymphadenopathy, hairy T-cell leukaemia and prolymphocytic leukaemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. Bovine leukaemia virus, HTLV-I and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably the absence of chronic viraemia, a long latency period and lack of preferred proviral integration sites in tumours, is similar to that of adult T-cell leukaemia/lymphoma induced by HTLV-I. The most striking feature of these three naturally transmitted leukaemia viruses is the X region located between the env gene and the long terminal repeat (LTR) sequence. The X region contains several overlapping long open reading frames. One of them, designated XBL-I, encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably is involved in "genetic instability" of BLV-infected cells of the B cell lineage. The "genetic instability" renders the infected cell susceptible to move, along a number of stages, towards full malignancy. Little is known about these events and their causes; we present some theoretical possibilities. Bovine leukaemia virus infection has a worldwide distribution. In temperate climates, the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by haematophagous insects, there are indications of insect-borne propagation of the virus.

Animals↗
PubMed1988

Bovine leukemia: facts and hypotheses derived from the study of an infectious cancer.

Bovine leukemia virus is the etiological agent of a chronic lymphatic leukemia/lymphoma in cows, sheep, and goats. Infection without neoplastic transformation also was obtained in pigs, rhesus monkeys, chimpanzees, and rabbits, and was observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of the human T lymphotropic viruses (HTLV-I and HTLV-II). HTLV-I induces in humans a T cell leukemia, and its type II counterpart has been found in dermatopathic lymphadenopathy, hairy T cell leukemia and prolymphocytic leukemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. BLV, HTLV-I, and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably, the absence of chronic viremia, a long latency period, and a lack of preferred proviral integration sites in tumors, is similar to that of adult T cell leukemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukemia viruses is the X region located between the env gene and the LTR sequence. The X region contains several overlapping long open reading frames. One of them designated XBL-I encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably involved in "genetic instability" of BLV-infected cells of the B cell lineage. The genetic instability puts the cell into a context of fragility and ready to move along a number of stages towards full malignancy. Little is known about these events and their causes; we have presented some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by hematophageous insects, there are indications of insect-born propagation of the virus.

Animals↗
PubMed1988

Even transcriptionally competent proviruses are silent in bovine leukemia virus-induced sheep tumor cells.

To investigate the role of proviral integration and expression in cellular transformation induced by bovine leukemia virus (BLV), three BLV-induced tumors harboring a single proviral copy were selected upon restriction and hybridization analysis. Tumors 344 and 395 were shown to contain a full-size proviral copy, whereas in tumor 1345 the provirus appeared to be heavily deleted. RNA gel blot hybridization with an antisense RNA probe showed no transcription of the viral sequences in the fresh tumors or in sheep tumor cells growing in vitro. The proviruses were cloned and transfected in mammalian cell lines. Transient-expression experiments revealed that the complete proviruses were still able to express the trans-activating protein (Tat) as well as structural proteins, demonstrating that the nonexpression of a provirus in a tumor cell does not necessarily imply a structural alteration of the viral information. In contrast, sequence analysis of the provirus with a large deletion and transient-expression assays proved that this truncated provirus, isolated from a tumor, was unable to code for viral proteins. These data indicate that expression of viral genes, including tat, is not required for the maintenance of the transformed state.

Animals↗