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Biomedical subjects

M G Lewis

Publications and source records attributed to M G Lewis.

At least 73 records · Page 4Linked to original sources
PubMed1987

Saliva as a source of feline leukemia virus antigen for diagnosis of disease.

An enzyme-linked immunosorbent assay (ELISA) for detection of feline leukemia virus (FeLV) p27 in saliva was tested for its accuracy and sensitivity in diagnosing FeLV infections. Saliva and serum samples from 564 clinical cases were tested with a 99.2% specificity. The overall accuracy of the saliva ELISA reactive to the serum ELISA was 97.9%. Experimentally, the ELISA saliva was the least sensitive in diagnosing early FeLV infections. However, the overall accuracy, ease of use, and simplicity of the test support its use as a screening procedure in clinical practice.

Animals↗
PubMed1986

Identification of calmodulin activity in purified retroviruses.

Several viruses have been shown to require calcium for their function, and to bind calcium at specific sites. However, the nature of the calcium binding molecule on viruses has not been established. One possibility is the ubiquitous calcium-binding protein calmodulin. Our studies were designed to determine whether feline leukemia virus contained calmodulin. Accordingly, we tested purified feline leukemia virus for the presence of calmodulin-like activity. The virus, like authentic calmodulin, activated cyclic AMP phosphodiesterase. The ability of the virus to activate the enzyme was blocked in the presence of the known calmodulin inhibitors trifluoperazine and W-7. This indirect evidence for the presence of calmodulin was confirmed by radioimmunoassay. Several other retroviruses were also tested using radioimmunoassay and found to contain calmodulin. Our results indicate that the calcium binding site in retroviruses may be calmodulin.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Feline leukemia vaccine: efficacy, contents and probable mechanism.

An effective subunit vaccine against feline leukemia virus infection and related diseases has been developed. The source of the vaccine immunogen is feline retrovirus persistently infected cells that continuously synthesize and shed virus polypeptides. Western blot analysis identifies FeLV-gp70, p27, p15, p12, and p10 in the subunit vaccine preparation. Cats immunized with the vaccine developed antibodies to a 70,000 MW protein of the vaccine that seems to be distinct from, but related to the FeLV-gp70 polypeptide.

Animals↗
PubMed1986

Polymorphonuclear leukocyte dysfunction associated with feline leukaemia virus infection.

The chemiluminescent characteristics of enriched (greater than 95%) peripheral blood polymorphonuclear leukocyte populations (PMN) from normal and feline leukaemia virus (FeLV)-infected cats were investigated. FeLV-infected cats demonstrated a significantly lower (P less than 0.001) PMN chemiluminescent response when compared to the response of normal age-matched controls. Normal PMN treated with FeLV-infected cat serum exhibited a depressed response in comparison to control cells. A titration of serum from infected cats supplemented with normal serum revealed a titratable suppression of chemiluminescence with increasing concentration of serum from the infected cats. However, PMN from FeLV-infected cats treated with normal serum displayed a slight increase in chemiluminescence over the same cells in autologous serum. The addition of inactivated FeLV to normal PMN caused a titratable decrease in chemiluminescence.

Animals↗
PubMed1986

Increased chemotaxis of leukocytes from mice bearing tumors.

Increased chemotaxis toward activated serum was demonstrated by leukocytes from bone marrow, spleen, and peripheral blood of tumor-bearing mice as compared with those of normal mice. Increased chemotaxis was correlated with duration of tumor growth, which, in turn, was correlated with size of tumor. Upon surgical tumor removal, chemotaxis fell to normal levels unless metastasis had occurred, in which case, the extent of chemotaxis was correlated with the volume of the metastasis. Increased chemotaxis was seen in relation to the growth of a mammary adenocarcinoma as well as that of a chemically induced fibrosarcoma. The major chemotactant in serum was shown to be complement derived, and sera from tumor-bearing and normal animals were equally effective. The presence of a tumor resulted in an increase in the percentage of polymorphonuclear cells in the bone marrow. The numbers of cells which migrated were independent of the cellular composition of the bone marrow in normal mice. In contrast, a negative correlation was found between the percentage of lymphocytes present and the number of bone marrow cells which migrated toward activated serum when the cells originated in a tumor-bearing mouse. The data suggested the increased chemotaxis was a property of the cells rather than the soluble substances in the serum.

Adenocarcinoma↗
PubMed1985

Reversal of feline retroviral suppression by indomethacin.

The immunosuppressive effect of feline leukemia virus (FeLV) and its 15,000 dalton envelope protein (p15E) were studied to determine if the mechanism of action was due to an increase in prostaglandin production. We examined the effects of exogenous PGE1 and PGE2 on the normal Con A response of feline peripheral blood lymphocytes (PBL) and found them to be inhibitory. The addition of the cyclooxygenase inhibitor indomethacin to cells incubated with FeLV or FeLV p15E and Con A completely abrogated the viral suppressive effects. This reversal was titratable and time-dependent. Other non-steroidal anti-inflammatory (NSAI) drugs were found to have similar actions. Indomethacin was also able to increase the suppressed Con A response of PBL from FeLV-infected cats. Upon measurement of PGE2 levels from PBL cultured with FeLV, we found a decrease in PGE2 accumulation associated with FeLV presence during the first 24 h of culture. These findings indicate that FeLV does not cause its immunosuppressive effects by increasing PG production and suggests that indomethacin and the other tested NSAI drugs do not produce their effect by PG inhibition.

Animals↗
PubMed1985

The reversal of feline retroviral-induced suppression of lymphocyte Con A receptor mobility by indomethacin and PGE2.

Ultraviolet light-inactivated feline leukemia virus (FeLV) and its 15,000 dalton envelope protein (p15E) inhibited concanavalin A receptor motility of feline peripheral lymphocytes (PBL). In contrast, the virus had no effect on immunoglobulin capping of feline PBL. The inhibitory action of FeLV and FeLV p15E was reversed by the addition of indomethacin. The indomethacin effect was titratable and gave significant reversal between 1 X 10(-5) and 1 X 10(-10) M. The indomethacin inhibition of the prostaglandin synthesis does not appear to be the mechanism of action in its ability to reverse FeLV suppression of Con A receptor mobility. Since the addition of prostaglandin E2 (PGE2) (1.0 microM) was also able to reverse the FeLV-induced inhibition and neither indomethacin nor PGE2 had an observable effect on Con A receptor mobility of normal PBL without FeLV present. PBL from FeLV-infected cats were sensitive to indomethacin (1.0-10.0 microM) and an indomethacin-related increase in cap formation was observed. Since both indomethacin and PGE2 were able to reverse the FeLV-induced suppression it was concluded that their mechanism of action may be through a common site. In addition, indomethacin may prove useful as an immune response modifier for therapy in FeLV-infected cats.

Animals↗
PubMed1985

Retroviral-associated eosinophilic leukemia in the cat.

Fourteen specific-pathogen-free cats were inoculated with a putative env gene recombinant feline retrovirus, PR8. An isolate of the Rickard strain of feline leukemia virus (FeLV-R), PR8, has the properties of both an exogenous (FeLV-R) and an endogenous (xenotropic) feline retrovirus (RD-114). Twelve of the PR8-inoculated cats developed viremia; 2 of the 12 cats developed eosinophilia, with 1 being diagnosed with eosinophilic leukemia and the other with extreme eosinophilic hyperplasia. Eosinophilic leukemia is rare in cats and has not previously been associated with retroviral infection. Changes in the viral envelope properties may have altered the pathogenicity of the exogenous virus to cause this rare form of leukemia.

Animals↗
PubMed1984

Inhibition of erythroid colony-forming cells by a Mr 15,000 protein of feline leukemia virus.

The effects of concentrated ultraviolet-inactivated feline leukemia virus (FeLV), the purified Mr 15,000 envelope protein (p15E) of FeLV, or the purified Mr 27,000 structural protein (p27) of FeLV on feline bone marrow mononuclear cells were studied in vitro in methylcellulose cultures. Whole virus and purified viral proteins were from the Kawakami-Theilen isolate of FeLV, which induces erythroid aplasia in cats. Bone marrow mononuclear cells from FeLV-negative young adult cats were preincubated with a medium control, ultraviolet-inactivated whole virus, or the p15E or p27 of FeLV, incubated in methylcellulose cultures for 2 days, and then observed for the formation of colony-forming units-erythroid (CFU-E) and colony-forming units-granulocyte/macrophage. The ultraviolet-inactivated Kawakami-Theilen isolate of FeLV at concentrations of 10 or 20 micrograms of viral protein/5 X 10(4) cells suppressed CFU-E to 66 to 56% of control values but had no significant effect on proliferation of colony-forming units-granulocyte/macrophage. p15E at concentrations of 0.1 to 0.2 micrograms/5 X 10(4) cells decreased CFU-E numbers to 0 to 1% of control values, whereas the same concentration of p27 did not alter CFU-E growth when compared with controls. Neither p15E nor p27 had a significant effect on growth of colony-forming units-granulocyte/macrophage. The erythrosuppressive effects of whole virus and an envelope-derived protein but not a structural core protein suggest that FeLV envelope proteins are important in the selective inhibition of erythrogenesis observed in vivo in FeLV-infected cats.

Animals↗
PubMed1981

Differences in types of prostaglandins produced by two MOCK canine kidney cell sublines.

The pattern of prostaglandins produced from arachidonic acid by two sublines of MDCK canine kidney epithelial cells was different. In one subline designated MDCK1, the most prevalent prostaglandin product was PGE2, whereas the most prevalent product in the subline designated MDCK2 was PGF2 alpha. This difference was observed when cells previously labeled with [1-14C]arachidonic acid were stimulated with either bradykinin or the calcium ionophore A23187, or when prostaglandins were produced from labeled arachidonic acid added directly to the assay medium. In the latter case, the difference was maintained over a 38-fold range of extracellular arachidonate concentrations. These findings indicate that there is a persistent difference in the distribution of prostaglandins produced by the two commonly used sublines of MDCK cells.

Animals↗
PubMed1981

Effect of essential polyunsaturated fatty acid modifications on prostaglandin production by MDCK canine kidney cells.

Supplementation of growing MDCK canine kidney tubular epithelial cultures with linoleic acid produced a 3.6- to 4.9-fold increase in bradykinin-stimulated PGE2 release as measured by radioimmunoassay. Under these conditions the cell phospholipids contained 3.9- times more linoleic acid and 5.6-times more arachidonic acid, with the inositol, ethanolamine and choline phosphoglyceride fractions becoming enriched in arachidonic acid. By contrast, supplementation with arachidonic acid did not enhance bradykinin-stimulated PGE2 release even though the arachidonic acid content of the cell phospholipids was increased 8.8-fold. The distribution of radioactive prostaglandin products was unchanged by these fatty acid enrichments, with PGE2 accounting for 55 to 68% of the total output from [1-14C]arachidonic acid. Linoleic acid supplementation also produced a 2.5-fold increase in PGE2 formation stimulated by extracellular arachidonic acid, whereas supplementation during culture with arachidonic acid caused a 55 to 80% inhibition. This difference cannot be accounted for by changes in the ability of the cells to incorporate extracellular arachidonic acid. It is suggested that at least some of the effects of linoleate supplementation on prostaglandin production are due to the resulting enrichment of the intracellular phospholipid substate pools with arachidonic acid. In addition, it appears that prolonged exposure to arachidonic acid during culture has an overriding inhibitory effect on prostaglandin production even though the total cell lipids become highly enriched in arachidonate.

Animals↗
PubMed1981

Protection against feline leukemia by vaccination with a subunit vaccine.

An effective vaccine against feline leukemia virus infection has been developed by the collection and concentration of tissue culture medium harvested from a tumor cell line. Lymphoid cells were grown to near saturation density in a normal growth medium and then transferred to a serum-free medium. The serum-free medium was collected, concentrated, and evaluated for its vaccine potential. Cats receiving the vaccine emulsified in complete Freund adjuvant developed high antiviral and antitumor titers and were protected (81%) against virus challenge. Cats receiving the vaccine without an adjuvant developed lower antibody levels and lower protection (53%) from viremia. Age-matched and litter-matched controls developed no antibody to test antigens before the challenge, and 100% became persistently viremic after the challenge. Vaccination with the soluble tumor cell antigen vaccine proved successful in preventing the induction of feline leukemia virus infection.

Adjuvants, Immunologic↗
PubMed1981

Infection of feline embryo adherent cells with feline leukemia virus: feline oncornavirus-associated cell membrane antigen expression and morphologic transformation.

Feline embryo adherent cells were infected with the Richard or Kawakami-Theilen strains of feline leukemia virus (FeLV) and examined for feline oncornavirus-associated cell membrane antigen (FOCMA), viral group-specific antigen (gsa) production, and in vitro evidence of transformation. As early as 10 days after infection, when more than half of the infected cells were gsa positive, FOCMA was detected on 5-10 percent of the cells. Transitory morphologic alterations (epithelioid appearance and rounding) were first noted in most cultures around 20-30 days post infection. At this time, approximately 50% of the cells in infected cultures expressed FOCMA. Morphologic characteristics of transformed fibroblastic cells (rounded shape, disordered alignment, and low adhesion to substratum), as well as enhanced agglutinability by plant lectins and ability to grow in agar, were demonstrated in one of four FeLV-infected, FOCMA-positive cultures. Findings showed that FOCMA may be expressed in FeLV-infected monolayer cells independent of transformation as assessed by in vitro criteria.

Agglutination Tests↗
PubMed1980

Immune complexes in transitional cell carcinoma.

Bladder cancer patients from 2 different medical centers were examined to establish whether such patients have circulating immune complexes. Four methods of analysis were used: 1) polyethylene glycol precipitation, 2) double crossed immunoelectrophoresis, 3) Raji cell and 4) Clq binding assays. In the first group of 24 patients 17 had positive results on cystoscopy for pathologically defined tumors at the time of the serum sample. Two tested positive for the presence of circulating immune complexes by all 4 techniques and an additional 1 tested positive by 3 of the 4 techniques. In the second group of 54 patients (41 of whom had pathologically definable tumors at sample date) 9 were judged possibly positive by the Raji cell assay, the polyethylene glycol and double crossed immunoelectrophoresis techniques. When tested by the Clq binding assay 8 of the 9 patients were positive, most being in the range of 260 to 320 microgram/ml. immune complex. Combining all data from the 78 patients with bladder cancer the results in 10 cases definitely were positive by all 4 techniques and an additional 2 were positive by 3 techniques. Our data indicate that a low percentage (13 to 15 per cent) of patients with bladder cancer has circulating immune complexes. Of interest is that the complexes, as judged by our assay procedures, bind Clq, contain aggregated IgG and can be dissociated into antigen and antibody. Thus, the immune complexes are similar to those found in immune complex diseases.

Aged↗
PubMed1980

Human melanoma tumor-specific antigens (II): Comparison of antigens from tumor cell plasma membranes of five melanoma patients.

Plasma membranes were purified from tumor tissue of five malignant melanoma patients. The purified membranes were solubilized by sonication in KC1 in the presence of Triton X 100. The soluble membranes that were obtained by this procedure contained human melanoma tumor-specific antigens. The antigens were separated from the other soluble plasma membrane proteins by chromatography on affinity columns made from the patients' tumor-specific pre-absorbed IgG coupled to Sepharose 4B. Specific antigens which were eluted from these affinity columns with potassium thiocyanate were determined by crossover immunoelectrophoresis. The five tumors appear to have a similar complement of melanoma tumor-specific plasma membrane-associated antigens.

Antigens, Neoplasm↗