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Biomedical subjects

A L Meyer

Publications and source records attributed to A L Meyer.

34 records · Page 2Linked to original sources
PubMed1990

Molecular dosimetry of DNA adducts in Chinese hamster ovary cells and C3H10T1/2 mouse embryo fibroblast cells treated with benzo[a]pyrene.

Chromatographic profiles of DNA adducts formed following treatment of Chinese hamster ovary (CHO) cells or C3H10T1/2 mouse embryo fibroblast cells with benzo[a]pyrene (BP), in the presence or absence of rat liver S9 fraction, have been obtained by both direct labelling ([3H]BP) and 32P-post-labelling methods. The principal adduct formed in both cell lines was (+)-N2-(7R,8S,9R-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene- 10S-yl) 2'-deoxyguanosine (detected as its 3',5'-bisphosphate by 32P-post-labelling). In both cell lines significantly higher levels of adducts were observed in the presence of S9 fraction. The results of these studies provide useful reference data on the genotoxic metabolism of BP in these widely used cell culture systems and allow comparisons with data obtained in other experimental mammalian systems. Valid comparisons of metabolism in experimental systems used as extrapolative models for man are particularly important where multiple bioactivation pathways are possible, such as in the case of polycyclic aromatic hydrocarbons.

Animals↗
PubMed1990

Genetic engineering of the pseudorabies virus genome to construct live vaccines.

Pseudorabies virus (PRV) is a herpesvirus of pigs. Homologous recombination with plasmids offers a method to engineer precise changes in the PRV genome to produce advantageous live vaccines. Safety can be ensured by using a non-reverting deletion to inactivate the thymidine kinase gene. One particularly important feature of new PRV vaccines is deletion of an antigen, so that vaccinated pigs are serologically distinguishable from infected pigs. We have constructed a live vaccine strain with deletions in the thymidine kinase gene and in the gene for a glycoprotein, gX. Molecular engineering techniques made it possible to choose deletion of gX, which has no known immunological significance, over deletion of other glycoproteins that contribute to protective immunity. Extensive experiments in pigs with isogenic virus pairs show that deletion of gX does not compromise efficacy of a vaccine as gI deletions do. Deletion of gX also suggests a site for replacement with antigens from other pathogens. In addition to molecular engineering of a live vaccine strain, research on PRV glycoproteins has led to the discovery that expression of the glycoprotein gp50 makes cells resistant to PRV infection. Perhaps this observation could be extrapolated to the level of a whole animal to allow engineering of pigs to become an alternative to engineered vaccines.

Animals↗
PubMed1989

Monoclonal antibody-based immunoaffinity chromatography for purifying corn and squash NADH: nitrate reductases. Evidence for an interchain disulfide bond in nitrate reductase.

NADH: nitrate reductase (EC 1.6.6.1) (NR) is present in small amounts in plant tissues and its polypeptide in inherently labile. Consequently, NR is difficult to purify. We have generated 20 monoclonal antibodies (McAb) for corn and squash NR and selected two for use in immunoaffinity chromatography. Squash McAb CM 15(11) and corn McAb ZM 2(69)9, which both bind corn and squash NR, were covalently coupled to Sepharose and used for purification of NR with elution of the purified enzyme by a pH 11 buffer. Although this procedure yielded highly purified NR, its activity was diminished by the pH 11 treatment. When corn leaf crude extract was applied to McAb CM 15(11)-Sepharose, NR bound and could be eluted in homogeneous form by its substrate, NADH. Corn leaf NR prepared by substrate elution retained a high level of NADH: NR activity. Immunoaffinity-purified corn and squash NR were shown to have an interchain disulfide bond as well as a reactive thiol group. These results are discussed in relation to the recently obtained sequences of NR clones and suggestions made for site-directed mutagenesis experiments to aid in identifying the cysteine residues of NR associated with these features of the enzyme.

Antibodies, Monoclonal↗
PubMed1988

The genetic toxicology of some hydrocarbon and oxygenated solvents.

Two hydrocarbon solvents (heptane and Special Boiling Point Spirit 100/140) and eight oxygenated solvents [methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, di-isobutyl ketone, isopropyl ether, hexylene glycol, secondary butyl alcohol and ME 6K (pentoxone)] have been tested for genotoxic activity. The solvents were tested in bacterial mutation assays, a yeast assay for mitotic gene conversion and in cultured mammalian cells (either rat liver or Chinese hamster ovary) for structural chromosome damage. All of the solvents gave a negative response in the bacterial mutation assays and the yeast mitotic gene conversion assay. In the rat liver chromosome assay, diacetone alcohol evoked a weak positive response, the remaining solvents gave a negative response.

Alcohols↗
PubMed1988

Reduced yield of infectious pseudorabies virus and herpes simplex virus from cell lines producing viral glycoprotein gp50.

Pseudorabies virus (PRV) glycoprotein gp50 is the homolog of herpes simplex virus (HSV) glycoprotein D. Several cell lines that constitutively synthesize gp50 were constructed. Vero cells, HeLa cells, and pig kidney (MVPK) cells that produce gp50 all gave reduced yields of PRV and HSV progeny viruses when compared with the parent cell line or the same cell line transfected to produce a different protein. The reduction in virus yield was greatest at low multiplicities of infection. The Vero and HeLa cells that produce gp50 showed an even greater reduction in HSV yield than in PRV yield. This phenomenon may be an example in a herpesvirus of the interference observed in retroviruses or cross-protection in plant virus systems.

Animals↗
PubMed1984

Molecular phenotyping of non-transformed and chemically transformed C3H10T1/2 mouse fibroblasts.

A systematic molecular phenotyping approach based on two-dimensional gel electrophoresis is being applied in an attempt to identify protein changes associated with malignant transformation. Using the C3H10T1/2 mouse cell line, two-dimensional polypeptide maps of the non-transformed cell line, several chemically transformed lines and a tumour cell line were compared. Although there is a large degree of similarity between the protein profiles of all cell lines, clear differences are evident. Initial results are consistent with the view that many of the protein changes are incidental to malignant transformation. Changes induced by 3-methylcholanthrene are retained after transplantation of the cells into nude mice.

Animals↗
PubMed1984

A framework for assessing performance problems.

How do we as managers address problems of nonperformance ? Robert Mager and Peter Pipe provide a framework for identifying the real problem, deciding whether or not there is a skill deficiency, and whether performance is punishing or whether nonperformance is rewarding. If performance really matters, are there obstacles to performing? This framework helps us to analyze performance deficiencies systematically and to move toward an appropriate solution.

Clinical Competence↗
PubMed1983

In vitro transformation assays for chemical carcinogens.

A variety of in vitro mammalian cell assays, designed specifically for the identification of carcinogenic compounds, have been in operation for more than a decade. Although no individual transformation system has won universal acceptance during this time, recent advances have led to the improved reliability and sensitivity of a number of these short-term tests. The underlying problems associated with the most widely used assays are identified and new developments in this rapidly expanding field are noted and discussed.

Animals↗
PubMed1983

Genotoxicity studies with a blend of zinc dialkyldithiophosphate lubricant additives.

The mutagenic activity of a blend of primary zinc dialkyldithiophosphate lubricant additives suspended in process oils and a blend of the process oils alone was investigated in agar layer cultures of Salmonella typhimurium TA1535, TA1537, TA1538, TA98 and TA100, both with and without the incorporation of a rat liver microsomal activation system (S9). Zinc dimethyldithiocarbamate was tested as a structurally-related model bacterial mutagen, and, in additional control experiments, the mutagenic activity of zinc dimethyldithiocarbamate and benzo[a]pyrene was investigated in combination with the blend of process oils in selected bacterial tester strains. Transformation frequencies of BHK cells were determined by colony growth in soft agar culture following treatment with a blend of the zinc dialkyldithiophosphate lubricant additives suspended in process oils, a blend of the process oils, 7,12-dimethylbenzanthracene, both in the presence and in the absence of a blend of the process oils, or zinc dimethyldithiocarbamate. All experiments incorporated a rat liver microsomal activation system (S9). Application of a blend of the zinc dialkyldithiophosphate additives or a blend of the process oils used in their manufacture did not increase the reverse mutation frequencies of Salmonella typhimurium TA1535, TA1537, TA1538, TA98 or TA100, or significantly increase the transformation frequency of BHK cells under the experimental conditions described. Zinc dimethyldithiocarbamate increased the reverse mutation frequency in some bacterial tester strains, but did not significantly increase the transformation frequency of BHK cells under the described experimental conditions. The addition of the blend of the process oils in combination with the control materials, zinc dimethyldithiocarbamate or benzo[a]pyrene had an inhibitory effect on the mutagenic activity at high doses of each in the bacterial assays, and in the BHK assay the transforming ability of 7,12-dimethylbenzanthracene was suppressed in the presence of the blend of the process oils. Thus, the additive materials showed no evidence of genotoxic activity in the bacterial mutation assays, or in the BHK transformation assay under the experimental conditions described.

Animals↗
PubMedDate not supplied

Expression of three recombinant proteins using baculovirus vectors in 23 insect cell lines.

Recombinant Autographa california baculoviruses expressing genes for pseudorabies virus glycoprotein (gp50T), human plasminogen (HPg), and beta-galactosidase (beta-gal) were used to infect 23 cell lines or strains. The objectives were to compare amounts of recombinant proteins expressed in the cell lines, compare yields from clones and parent lines, investigate the effects of long-term culture in serum-free medium on production, and determine if some lines yield gp50T with different glycosylation patterns. For HPg, IZD-MB0503 had the highest yield and four other lines (IPLB-TN-R2, IPLB-SF-1254, IPLB-LdEIta, and CM-1) had levels above that of SF-9 cells. For gp50T, four lines (IPLB-HvT1, IPLB-SF21AE, IPLB-SF21AE-15, and IPLB-SF-1254) had higher amounts than SF-9 cells. Some lines yielded gp50T with molecular mass about 1000 daltons larger than that from SF-9 cells, which suggests increased oligosaccharide processing. Equally high levels of beta-gal were expressed in three lines (SF-9, IZD-MB0503, and BCIRL-PX2-HNV3). The major conclusion is that no single cell line produced highest yields for all three recombinant proteins. Four lines were cultured in serum-free medium for 31-34 passages and then infected with the three recombinant viruses. For most cell line-recombinant combinations, the yields in serum-free medium were equal to or better than those in serum-supplemented medium. Medium composition had a much stronger effect on foreign gene expression than on susceptibility of cells to wild-type virus.

Animals↗
PubMedDate not supplied

Richmond youth against violence: a school-based program for urban adolescents.

The Richmond Youth Against Violence Project teaches middle school students in the Richmond Public Schools knowledge, attitudes, and skills for reducing their involvement in violence. These students are primarily African Americans, many of whom come from low-income, single-parent households in neighborhoods with high rates of crime and drug use. The program, "Responding in Peaceful and Positive Ways," employs a developmentally anchored health promotion model. Its goal is to promote peaceful and positive alternatives to interpersonal and situational violence, by creating environments that teach and encourage health-enhancing behaviors and intrapersonal attributes and weakening supports for health-compromising behaviors and intrapersonal attributes. The 16-session school-based program was implemented by prevention specialists with sixth graders during the 1994-1995 school year. Students are taught a seven-step problem-solving model. Program implementation was staggered to allow an intervention group to participate during the fall semester and a control group to participate during the spring semester. Outcome measures include school data and measures completed by students. There were few significant baseline differences between the intervention and control groups. A high percentage of students, particularly boys, reported exposure to community violence; more than 92% had heard gunshots. Many have also engaged in risk behaviors; 70% of the boys and 44% of the girls reported being in a fight in the preceding 30 days. The impact of the curriculum is being examined. The program has provided valuable lessons about conducting community-based research, particularly designing, implementing, and evaluating prevention programs.

Aggression↗