Mechanism of IL-12 mediated alterations in tumour blood vessel morphology: analysis using whole-tissue mounts

New blood vessel formation within tumours is a critical feature for tumour growth. A major limitation in understanding this complex process has been the inability to visualise and analyse vessel formation. Here, we report on the development of a whole-tissue mount technique that allows visualisation of vessel structure. Mice expressing green fluorescent protein (GFP) made it possible to easily see GFP(+) vessels within non-GFP-expressing B16 melanoma tumours. The small fragments of tumour used in this technique were also effectively stained with fluorescent probe-conjugated antibodies, allowing characterisation of the vessels based on surface marker phenotype. The vessels within tumour tissue were much more irregular and tortuous compared to those within surrounding normal muscle. B16 tumours stably transfected with the genes for IL-12 were used to assess the effects of this cytokine on tumour growth and vessel formation. The IL-12-expressing tumours grew more slowly and had much smaller blood vessels than the large, webbed vessels characteristic of the parental tumours, effects that were dependent on interferon gamma (IFN-gamma). Vessels in the parental tumours were found to express VEGFR-3, the receptor for VEGF-C and VEGF-D. Expression of this receptor by the endothelial cells of the blood vessels was lost in the cytokine expressing tumours, thus suggesting a mechanism for the antiangiogenic effects of IL-12. The combination of the whole mount technique and the GFP transgenic mice provides a powerful method for visualising tumour vasculature and characterising the effects of agents such as cytokines.

Alteration of tumour response to radiation by interleukin-2 gene transfer

We have previously shown that BALB/c-derived EMT6 mammary tumours transfected with interleukin (IL)-2 have decreased hypoxia compared to parental tumours, due to increased vascularization. Since hypoxia is a critical factor in the response of tumours to radiation treatment, we compared the radiation response of IL-2-transfected tumours to that of parental EMT6 tumours. Because the IL-2 tumours have an altered host cell composition, which could affect the interpretation of radiation sensitivity as measured by clonogenic cells, we employed flow cytometric analysis to determine the proportion of tumour cells vs host cells in each tumour type. Using this approach, we were able to correct the plating efficiency based on the number of actual tumour cells derived from tumours, making the comparison of the two types of tumours possible. We also excluded the possibility that cytotoxic T-cells present in EMT6/IL-2 tumours could influence the outcome of the clonogenic cell survival assay, by demonstrating that the plating efficiency of cells derived from EMT6/IL-2 tumours remained unchanged after depletion of Thy-1+ cells. The in vivo radiation response results demonstrated that IL-2-transfected tumours were more sensitive to radiation than parental EMT6 tumours. The hypoxic fraction of the EMT6/IL-2 tumours growing in vivo was markedly decreased relative to parental EMT6 tumours thus the increased sensitivity results from the increased vascularity we have previously observed in these tumours. These results indicate the potential therapeutic benefit of combining radiation and immunotherapy in the treatment of tumours.

Plasma ascorbic acid concentrations relate inversely to blood pressure in human subjects

This study relates antioxidant status and blood pressure (BP) in 168 healthy residents of Augusta, GA, following usual diets. BP ranges were systolic (S) 84-152, mean 112 +/- 1 mm Hg, and diastolic (D) 52-96, mean 72 +/- 1 mm Hg. Plasma concentrations of ascorbic acid (AA) were significantly inversely related to SBP (r = -0.18, P < 0.05) and DBP (r = -0.20, P < 0.01); with regression equations SBP vs AA = -0.083C + 116 and DBP = -0.077C + 76. Highest and lowest quintiles of AA differed significantly in mean SBP (108 +/- 2, 113 +/- 2 mm Hg) and DBP (69 +/- 1, 74 +/- 2), P < 0.05. Plasma AA concentrations were significantly lower in the smokers. By deleting smokers, the inverse relations of SBP and DBP with plasma AA and the slopes of the equation were enhanced. Plasma selenium, alpha-tocopherol, alpha-tocopherol:cholesterol ratio, retinol and taurine were not related to BP; whereas male gender, body mass index, body fat distribution, plasma cholesterol, low density lipoprotein cholesterol, and triglycerides correlated.

Noble metals: a toxicological appraisal of potential new environmental contaminants

The public health benefits expected by reducing known hazardous emissions from mobile sources should not be compromised by increasing levels of other potentially hazardous unregulated emissions. Catalytic converters are going to be used to meet the statutory requirements on carbon monoxide and hydrocarbon emissions from light duty motor vehicles. Platinum and palladium metals are the catalytic materials to be used in these emission control devices. Preliminary experimental evidence and analysis of the impact of these control devices on the future use and demand for platinum indicates that this metal may appear at detectable levels in the environment by the end of this decade. At the present time, platinum and palladium are not present in the public environment and represent potentially new environmental contaminants as a consequence of use of this new abatement control technology. There is relatively little information available to adequately assess the potential health hazards that may be associated with exposure to these metals and their compounds. Analysis of the environmental problems and concerns associated with possible new environmental contaminants are discussed. Limited estimates are made on community exposure by use of a meteorological dispersion model. Biodegradation potential and attention is also given to the limited toxicological information available.