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J L Farmer

Publications and source records attributed to J L Farmer.

10 recordsLinked to original sources
PubMed1989

Analysis of cell-associated recombinant hepatitis B surface antigen by flow cytometry.

Murine L cell lines secreting recombinant hepatitis B surface antigen (rHBsAg) of either the Adw or Ayw subtype were used as a model system to develop procedures for analysis of cell-associated HBV antigens by flow cytometry. Only weak membrane immunofluorescence was observed when viable Ad or Ay cells were reacted with monoclonal antibodies (MAbs) to either subtype specific or the common group specific "a" determinant of rHBsAg. Following fixation and permeabilisation to allow access of MAbs to the intracellular compartment, specific reactivity of cells with both anti-"a" and subtype specific MAbs was readily demonstrated by flow cytometric analysis. Comparison of the fluorescence histograms produced by analysis of Ad and Ay producing cells with the anti-"a" MAb demonstrated an increased proportion of cells with high levels of intracellular rHBsAg in the Ay line. The results of these studies demonstrate that flow cytometric analysis with MAbs is a useful tool for characterizing the expression of viral antigens at the cellular level. The application of this technique to monitoring the production of native viral proteins following in vitro infection should provide valuable insights into the process of viral replication.

Animals↗
PubMed1989

Flow cytometric assays for monitoring production of recombinant HIV-1 gp160 in insect cells infected with a baculovirus expression vector.

A baculovirus expression system for the HIV-1 envelope glycoprotein gp160 has been used as a model for development of flow cytometric assays for monitoring production of cell-associated recombinant antigen. Using monoclonal antibodies to the transmembrane (gp41) or envelope (gp120) portion of gp160, gp120, but not gp41, could be reproducibly detected on the surface of insect cells 48 h after infection with the recombinant baculovirus. In contrast, fixation and permeabilization of infected cells prior to staining, to allow access of monoclonal reagents to the intracellular compartment, markedly improved the sensitivity of detection, with reactivity to both monoclonal antibodies observed at 24 h post-infection. Specificity of the intracellular immunofluorescence was verified by demonstrating that the appropriate native or recombinant HIV-1 protein blocked reactivity of monoclonal antibody with infected cells. In addition, it was observed that production of gp160 following baculovirus infection was associated with a marked increase in the 90 degrees light scatter of insect cells, as determined by flow cytometry, and that this correlated with the kinetics of cell-associated gp160 production as determined by immunofluorescence. These procedures should be of great utility for routine monitoring of recombinant proteins produced in insect cells in response to infection with recombinant baculovirus.

Animals↗
PubMed1989

In situ hybridization analysis of chromosomal homologies in Drosophila melanogaster and Drosophila virilis.

Twenty-four biotin-labeled recombinant-DNA probes which contained putative unique-sequence Drosophila melanogaster DNA were hybridized to larval salivary-gland chromosomes of D. melanogaster and Drosophila virilis. All probes hybridized to D. melanogaster chromosomes at the expected sites. However, one probe hybridized to at least 16 additional sites, and one hybridized to one additional site. Thirteen probes hybridized strongly to D. virilis chromosomes, four hybridized weakly and infrequently, and seven did not hybridize. Probes representing two multigene families (beta-tubulin and yolk-protein) hybridized as would be expected if all sites had been conserved in the two species on the same chromosomal elements. The multiple hybridization sites of a third probe which may represent a multigene family were also conserved. The results were consistent with H.J. Muller's proposal that chromosomal elements have been conserved during evolution of this genus.

Animals↗
PubMed1986

Inhibition of interleukin 2 production and expression of the interleukin 2 receptor by plasma from acquired immune deficiency syndrome patients.

Plasmas from acquired immune deficiency syndrome (AIDS) and AIDS-related complex (ARC) patients were screened for their ability to inhibit mitogen-induced proliferation of normal human lymphocytes. Plasmas from 67% of the individuals examined contained significant suppressive activity. Additional studies on the mechanism of action of the plasma inhibitor demonstrated that it functions as a nonlymphotoxic inhibitor of interleukin 2 production by stimulated human lymphocytes, and that this activity is accompanied by suppression of expression of the cell surface receptor for interleukin 2. A more detailed understanding of the action of this activity may aid in the design of therapy to minimize the contribution of this agent to the immune anergy observed in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1979

Characteristics of delta 1-pyrroline-5-carboxylate reductase from Drosophila melanogaster.

1. Biochemical properties of delta 1-pyrroline-5-carboxylate reductase from d. melanogaster have been investigated. 2. The enzyme is stable below 4 degrees C. 3. the pH optimum of the enzyme is 5.7. It is rapidly inactivated below pH 5.4. 4. The Km values for NADPH and delta 1-pyrroline-5-carboxylate are 1.6 x 10-5 and 2.5 x 10-6 M, respectively. 5. the estimated molecular weight of the enzyme is 225,000. 6. the enzyme is weakly inhibited by L-proline (Ki = 0.12 M).

Animals↗
PubMed1979

Conditional antifolate resistance in Bacillus subtilis thyA.

Resistance to antifolates in Bacillus subtilis strains results from the presence of an antifolate resistance mutation (afo). Strains which are thyA(+)afo are unconditionally resistant to antifolates. The conditional resistance of thyA afo strains is hypothesized to be due to the thyB(+) gene product (thymidylate synthetase B) having a high K(m) for the folate substrate, thus leading to thymineless death in the presence of antifolates. An alternative model for conditional antifolate resistance was shown to be incorrect by analysis of folate metabolism in methotrexate-treated cells. Genetic analysis and studies of the response of afo(+) cells to methotrexate suggested that most, if not all, B. subtilis thymine-requiring mutants are afo. Analysis of dihydrofolate reductase from afo cells did not reveal an obvious mechanism for antifolate resistance in those cells.

Bacillus subtilis↗
PubMed1977

An allele-specific suppressor of white-coral in Drosophila melanogaster.

A new allele of white-coral (wco2) was isolated from Canton S after mutagenesis. Many common laboratory stocks were found to carry a suppressor gene (Su(wco2)) which alters the phenotype of wco2 flies toward wild-type. The Su(wco2) is allele-specific (it does not suppress wco), dominant, homozygous viable, located near Su(bwV1) on the right arm of chromosome 2, and shows a simple gene-dosage effect. The degree of suppression is sensitive to the genetic background. There appears to be selection for Su(wco2) in a genotype where it does not affect eye pigmentation.

Alleles↗
PubMed1975

Identification of poly-gamma-glutamyl chain lengths in folates of Bacillus subtilis.

Bacillus subtilis strains 168 met ile leu and 23 thy contain folates which differ from one another in the number of glutamyl residues. The folate species were identified by reductive cleavage to the corresponding p-aminobenzoylglutamyl poly-gamma-glutamates and chromatography on diethylaminoethyl-cellulose. Pteroyltriglutamate is the predominant folate type, accounting for 86 to 88% of the total. Pteroyltetraglutamate is the only other type present in appreciable quantities, accounting for 5 to 6% of the total folates. Pteroyldiglutamate and pteroylpentaglutamate are present in small amounts, accounting for 1 to 3% and 1% of the total folates, respectively. Strain 168 met ile leu contains a very small amount of pteroylmonoglutamate (less than 0.5% of the total folates), but the other strain contains none.

Bacillus subtilis↗
PubMedDate not supplied

Zaprionus tuberculatus: chromosome map and gene mapping by DNA in situ hybridization.

The genus Drosophila has long been used as a model of karyotype evolution, demonstrating change by paracentric inversion and occasional centric fusion of an ancestral karyotype of five rod-shaped and one "dot" chromosome. This study shows, by mapping D. melanogaster probes hybridized to polytene chromosomes of Zaprionus tuberculatus, that this ancestral pattern extends beyond the genus Drosophila. A formal polytene chromosome map of Z. tuberculatus is presented.

Animals↗