Biomedical subjects

David Hammond

Publications and source records attributed to David Hammond.

22 records · Page 2Linked to original sources

PubMed2002

The use of the uromodulin promoter to target production of recombinant proteins into urine of transgenic animals.

A uromodulin promoter has been isolated, sequenced, and used to generate two sets of transgenic mice for expression of the lacZ marker gene and for production of the human recombinant erythropoietin (rhEPO) in urine. We demonstrated that the 5.6-kb fragment of the uromodulin gene containing the 3.7-kb promoter area and, both the first exon and part of the second exon, were sufficient to provide kidney-specific expression of the lacZ gene. Histological analysis of the lacZ expression pattern revealed beta-galactosidase activity specifically in the thick limb of Henle's loop. However, due to random integration of the transgene, ectopic expression was detected in some transgenic lines. Analysis of the EPO-transgenic mice showed that rhEPO was secreted into the urine of founder mice (up to 6 ng/ml). We were able to breed and analyze only two sublines with a very low expression level of rhEPO (up to 260 pg/ml). All of our transgenic mice expressing rhEPO in urine developed disease symptoms similar to polycythemia in humans. These included a considerable increase in red blood cell counts, hemoglobin concentration, and hematocrit concomitant with severe thrombocytopenia, all of which were detected in the rhEPO-expressing mice. Although our model did not prove to be beneficial for commercial production of rhEPO, we concluded that the uromodulin promoter could be useful for expression of other important therapeutic proteins into the urine of transgenic animals.

Animals↗

PubMedDate not supplied

Expression of factor VIII in recombinant and transgenic systems.

Deficiency in a coagulation factor VIII (FVIII) causes a genetic disorder hemophilia A, which is treated by repeated infusions of expensive FVIII products. Recombinant FVIII (rFVIII), the culmination of years of extensive international research, is an important alternative to plasma-derived FVIII (pdFVIII) and is considered to have a higher margin of safety. Advances in biotechnology allowed production of rFVIII at industrial scale, which significantly improved treatment of hemophilia A patients. We review the contemporary methods used for FVIII expression in mammalian cell culture systems and discuss the factors responsible for insufficient recoveries of rFVIII, such as inefficient accumulation of FVIII mRNA in the cell, complexity of the mechanisms of FVIII secretion, and instability of secreted FVIII. The approaches to improve the yield of rFVIII in cell culture systems include genetic engineering of B-domain-deleted FVIII, introduction of introns into FVIII cDNA constructs for more efficient processing and accumulation of FVIII mRNA, and introduction of mutations into chaperone-binding sites of FVIII to improve its secretion. Design of FVIII with prolonged half-life in vivo is considered as another promising direction in improving rFVIII protein and efficiency of hemophilia A therapy. As an alternative to expression of rFVIII in cell culture systems, we discuss production of rFVIII in transgenic animals, where high levels of rFVIII have been successfully secreted into milk. We also pay attention to the major limitations of this approach, such as safety issues associated with potential transmission of animal pathogens. Finally, we present a brief characterization of commercial recombinant FVIII products currently available on the market for hemophilia A treatment.

Animals↗

PubMedDate not supplied

Exposure to tobacco marketing and support for tobacco control policies.

OBJECTIVES: To examine the salience of tobacco marketing on postsecondary campuses and student support for tobacco control policies. METHODS: Face-to-face surveys were conducted with 1690 students at 3 universities in southwestern Ontario. RESULTS: Virtually all (97%) students reported noticing tobacco marketing in the past year, and 35% reported noticing marketing on campus. There was strong support for smoke-free restrictions on campus, including restaurants and bars (82%), and for prohibitions on campus marketing. The presence of campus policies was associated with reduced exposure to marketing and increased policy support. CONCLUSIONS: There is strong support among students to remove tobacco marketing from campus and to introduce comprehensive smoke-free restrictions.

Adult↗

PubMedDate not supplied

The impact of cigarette warning labels and smoke-free bylaws on smoking cessation: evidence from former smokers.

BACKGROUND: To effectively address the health burden of tobacco use, tobacco control programs must find ways of motivating smokers to quit. The present study examined the extent to which former smokers' motivation to quit was influenced by two tobacco control policies recently introduced in the Waterloo Region: a local smoke-free bylaw and graphic cigarette warning labels. METHODS: A random digit-dial telephone survey was conducted with 191 former smokers in southwestern Ontario, Canada in October 2001. Former smokers who had quit in the previous three years rated the factors that influenced their decision to quit and helped them to remain abstinent. RESULTS: Thirty-six percent of former smokers cited smoke-free policies as a motivation to quit smoking. Former smokers who quit following the introduction of a total smoke-free bylaw were 3.06 (CI95 = 1.02-9.19) times more likely to cite smoking bylaws as a motivation to quit, compared to former smokers who quit prior to the bylaw. A total of 31% participants also reported that cigarette warning labels had motivated them to quit. Former smokers who quit following the introduction of the new graphic warning labels were 2.78 (CI9 = 1.20-5.94) times more likely to cite the warnings as a quitting influence than former smokers who quit prior to their introduction. Finally, 38% of all former smokers surveyed reported that smoke-free policies helped them remain abstinent and 27% reported that warning labels helped them do so. CONCLUSION: More stringent smoke-free and labelling policies were associated with a greater impact upon motivations to quit.

Adult↗