Pet ownership among older adults was investigated to determine whether dog owners were more likely to engage in physical activity than non-dog-pet or non–pet owners. The relationship between pet ownership and physical activity was examined using data from the Health ABC study. After age, race, education level, number of assets, family income, and site were adjusted for dog owners were more likely than non–pet owners to have engaged in non-exercise-related walking in the preceding week but did not differ from non–pet owners in walking for exercise or any physical activity. In contrast, non-dog-pet owners did not differ from non–pet owners in non-exercise-related walking in the preceding week and were less likely than non–pet owners to have engaged in walking for exercise or any physical activity in the preceding week. The activity-related benefits of pet ownership in older adults were limited to dog owners, who engaged in greater overall physical activity—non-exercise-related walking, in particular. Whether pet-related physical activity is sufficient to provide health benefits requires longitudinal investigation.
Previous reports on the slower growth of tumors in senescent mice have suggested a decrease in tumor angiogenesis in these animals, but such an observation has not yet been documented quantitatively. In this study, we report the relative amount of tumor angiogenesis and tumor volume for two different types of tumor in 11 young (8-9-wk old) versus nine older (19-mo old) male C57BL/10 mice. B16 melanoma or SP1 methylcholanthrene-induced fibrosarcoma cells were injected into the ventral skin of mice. After 3 days, the mice were killed and the injection sites were examined for angiogenesis surrounding the tumor (centrally directed tumor angiogenesis), nerve-associated angiogenesis, and tumor volume. In the older mice, there was significantly less centrally directed tumor angiogenesis for both tumors tested, and nerve-associated angiogenesis was decreased for B16 melanoma. The mean tumor volume for the B16 implants was smaller for the older animals, but the mean SP1 tumor volumes were identical for both age groups. These findings support the hypothesis that tumor growth in older animals is associated with less formation of new blood vessels, and this may explain the slower tumor growth observed in aged animals with certain experimental tumors.
In this paper we have described the binding of nanomoler concentrations of [3H]leukotriene B4 (LTB4) to human polymorphonuclear leukocytes. Because up to 80% of the total [3H]LTB4 binding was blocked by excess (greater than 100 times) [14C]LTB4, the majority of binding is specific. Stereospecificity of the LTB4 binding is demonstrated by the diminished relative abilities of the 6-trans-and 12-epi-6-trans- isomers of LTB4 to block [3H]LTB4 binding. With these two isomers 3-10-fold higher than [14C]LTB4 concentrations were needed for equivalent inhibition of [3H]LTB4 binding. This difference is quantitatively less dramatic than the differences between these isomers in many in vitro functional assays such as chemokinesis, chemotaxis, and degranulation. Binding of [3H]FMLP is not blocked at greater than 100-fold excess of LTB4. The binding of [3H]LTB4 to cells appears to be essentially irreversible at 4 degrees C, but not at 37 degrees C where initially bound LTB4 is rapidly converted to metabolites which then enter the medium. These results suggest the presence of a saturable, stereospecific site for LTB4 on PMN. The association of LTB4 binding and the initiation of pharmacological responses to LTB4 will require further studies.
The role of host-tumor interactions in tumor angiogenesis was studied in an id mouse model. Although many previous studies have described the effects of certain host factors (age, nutritional status, tumor location, etc.) on experimental tumor systems, the effects of these factors on tumor angiogenesis have not been reported. In preliminary studies we inoculated cloned tumor cells id into syngeneic mice and found positional differences in tumor growth that did not correlate with measured angiogenesis levels. In addition, while tumor growth was inhibited by radiation, tumor-induced (but not fibroblast-induced) angiogenesis was not. This id system may provide an assay not only for examining the effect of host factors on tumor angiogenesis, but also for elucidation of the mechanisms underlying neovascular induction and host response.
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