Mapping of the vascular endothelial growth factor-producing hypoxic cells in multicellular tumor spheroids using a hypoxia-specific marker.

We have investigated the hypoxia inducibility of vascular endothelial growth factor (VEGF) in multicellular tumor spheroids of HT29 cells using a monoclonal antibody to a fluorinated bioreductive drug, EF5 [2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)aceta mide], a chemical probe for hypoxia. We have shown that VEGF expression is predominantly localized in interior spheroid cells that are sufficiently hypoxic to bioreductively activate the 2-nitroimidazole and produce immunologically detectable adducts of the EF5 compound. Northern blotting analyses demonstrated that VEGF165 is the predominant form of VEGF produced by HT29 cells and that the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate did not induce VEGF expression. This study demonstrates that VEGF expression is up-regulated in response to hypoxia and in the microenvironments found in human multicellular tumor spheroids. This investigation also illustrates the utility of the EF5 binding in multi-cellular tumor spheroids as a means of studying the expression and regulation of hypoxia-inducible genes.

Opposing effects of hypoxia on expression of the angiogenic inhibitor thrombospondin 1 and the angiogenic inducer vascular endothelial growth factor.

Tumor angiogenesis, the development of new blood vessels during malignant progression, is a regulated process that has both genetic and physiological controls. Physiologically, angiogenesis is stimulated by decreases in tissue oxygenation (i.e., hypoxia). We investigated the effect of hypoxia on the expression of two angiogenic factors reported to be genetically regulated by the p53 tumor suppressor gene: (a) the angiogenic inhibitor thrombospondin 1 (TSP-1); and (b) the angiogenic inducer vascular endothelial growth factor (VEGF). Analysis of rodent cells that differ in their p53 genotype (p53+/+ or p53-/-) indicated that in vitro exposure to hypoxia simultaneously suppressed TSP-1 and induced VEGF expression, regardless of the p53 genotype. On transformation of these cells with E1A and oncogenic H-ras, the basal level of TSP-1 expression was strongly diminished, whereas that of VEGF could still be induced by hypoxia. Consistent with these in vitro findings, sections of tumors derived from the transformed p53+/+ and p53-/- cells showed that VEGF protein overlapped with regions of hypoxia, whereas TSP-1 protein was below the limits of detection in tumor tissue. Using a panel of normal/immortalized and transformed human cells, it was found that the ability of hypoxia to inhibit TSP-1 expression depends on the cell type and/or the degree of transformation. In contrast, VEGF expression was induced by hypoxia in all of the human cell types examined. Together, these findings suggest that hypoxic and oncogenic signals could interact in the tumor microenvironment to inhibit TSP-1 and induce VEGF expression, promoting the switch to the angiogenic phenotype.

AVMA guide for veterinary medical waste management.

Lawmakers have enacted a variety of laws and regulations to ensure proper disposal of certain potentially infectious or otherwise objectionable waste. The veterinary medical profession supports scientifically based regulations that benefit public health. In 1988, Congress passed the Medical Waste Tracking Act, a federal program that mandates tracking certain regulated waste. Several types of waste generated in the typical clinical veterinary medical practice are considered regulated veterinary medical waste. Discarded needles, syringes, and other sharps; vaccines and vials that contained certain live or attenuated vaccines; cultures and stocks of infectious agents and culture plates; research animals that were exposed to agents that are infectious to human beings and their associated waste; and other animal waste that is known to be potentially harmful to human beings should be handled as regulated veterinary medical waste. Regulated veterinary medical waste should be handled with care. It should be decontaminated prior to disposal. The most popular, effective methods of decontamination are steam sterilization (autoclaving) and incineration. Chemical decontamination is appropriate for certain liquid waste. Waste should be packaged so that it does not spill. Sharps require rigid puncture- and leak-resistant containers that can be permanently sealed. Regulated veterinary medical waste that has not been decontaminated should be labeled with the universal biohazard symbol. Generators retain liability for waste throughout the entire disposal process. Therefore, it is essential to ensure that waste transporters and disposal facilities comply with state and federal requirements. Veterinary practices should maintain a written waste management program and accurate records of regulated veterinary medical waste disposal. Contingency planning and staff training are other important elements of a veterinary medical waste management program. The guide includes a model veterinary medical waste management program; however, it does not address all the variations in state and local regulations. Veterinarians should obtain copies of state and local laws and regulations and modify AVMA's model plan to create an individualized practice plan that complies with federal, state, and local laws and regulations. State and local veterinary medical organizations should monitor state and local regulation to influence decisions that affect veterinarians and to keep their members informed of changing requirements. Veterinarians and veterinary medical organizations must stay involved so that regulations do not unfairly burden the veterinary medical profession.

Safety in the veterinary medical workplace environment. Common issues and concerns.

This article addresses some of the major areas of concern related to safety in the veterinary workplace. Some practical guidance is offered for setting up programs in areas such as medical waste, hazard communication, general occupational safety and health requirements, shipments of etiologic agents, and pesticides.