The hypothesis that purine nucleotides and nucleosides affect brown fat preadipocyte proliferation was tested using isolated rat interscapular brown fat preadipocytes in culture. Daily addition of 100 microM adenosine triphosphate (ATP) (n = 4) to cultures enhanced the relative DNA content by 1.5-fold compared to control cultures (P < 0.05) measured using CyQUANT-GR fluorescence. Higher concentrations of ATP inhibited growth and 500 (n = 2) or 1000 microM ATP (n = 3) almost completely inhibited growth. ATP (100 microM) did not affect while 250-1000 microM ATP decreased protein content relative to control cultures. Adenosine (100 microM; n = 3) did not affect DNA or protein content, but 500 microM and 1000 microM adenosine suppressed brown adipocyte proliferation and inhibited protein synthesis. Cultured brown adipocytes quickly removed or degraded ATP in the culture media as determined by luciferin-luciferase bioluminescence, suggesting that the inhibitory effects of high ATP concentrations may result from its breakdown to adenosine. The results support the conclusion that ATP promotes and adenosine inhibits brown adipocyte proliferation.

We have shown previously that nontumorigenic NIH 3T3 cells can be made tumorigenic and metastatic by transfection and expression of activated ras, whereas in LTA cells, which are tumorigenic but nonmetastatic, the degree of malignancy is not altered by ras. To investigate possible mechanisms of natural ras resistance, we compared the expression patterns of several genes thought to be involved in ras-induced metastatic progression in LTA (ras-resistant) and NIH 3T3 (ras-sensitive) cells, before and after constitutive expression of transfected T24-H-ras. We examined the expression of the nuclear "early-response" genes jun and fos and the "tumor-suppressor" retinoblastoma (Rb) gene, as well as genes involved in invasion (major excreted protein [MEP], tissue inhibitor of metalloproteinases [TIMP]), and cell adhesion (secreted phosphoprotein 1 [SPP1; also known as osteopontin]). We found distinct differences in both the basal and ras-induced levels of expression of most of these genes in LTA versus NIH 3T3 cells. High levels of MEP and low levels of TIMP were induced in ras-transfected NIH 3T3 cells, whereas LTA cells showed intermediate levels of MEP and high levels of TIMP that were only marginally affected by the expression of transfected ras. Similarly, SPP1 expression was strongly induced by ras in NIH 3T3 cells but was repressed by ras in LTA cells. Enzymogram assays for functional gelatinase activity showed an increase in 67-kd and 62-kd bands in NIH 3T3 cells in the presence of ras. LTA cells showed no gelatinolytic activity in the presence or absence of ras. Data from an in vitro assay for chemoinvasiveness showed a pattern as predicted from the expression of invasion-related genes; chemoinvasiveness in ras-transfected NIH 3T3 was greater than in LTA and ras-transfected LTA cells, which was greater than in NIH 3T3 cells. Differences in expression of the genes examined are believed to contribute to the ras responsiveness of NIH 3T3 cells and the ras resistance of LTA cells.

In subjects exposed to a hot environment, short-term topical pretreatment with aluminium zirconium tetrachlorhydrate delayed the onset of visible sweating although it failed to prevent the response. The delay was considered most probably to be due to the occlusive action, in the duct within the upper epidermis, of aluminium-containing conglomerates, which disappear after continuous sweating. However, microanalytical evidence indicated that ionic transport within the fundus secretory cells was also modified.

To examine the relationship between the malignant behavior of rat glioma cells and expression of the differentiation antigen glial fibrillary acidic protein (GF), we assayed the tumorigenicity and metastatic ability of P635 and its GF+ or GF- clones. We injected P635 (GF+) and clone 45 (GF-) cells intramuscularly in nude mice. Both lines formed local tumors which metastasized to lungs with equal efficiency. We then injected these lines intravenously in nude mice. Both produced experimental metastases in lungs and other organs with equal efficiency. Finally we injected P635 and several GF+ and GF- clones into the chorioallantoic membrane veins of naturally immune-deficient chick embryos and measured cell growth in embryonic liver. We again found that all clones survived and grew equally well. P635 cells are capable of extracranial growth and metastasis, two important features of the malignant phenotype. We conclude that GF in P635 is a neutral marker with respect to tumorigenicity and metastatic ability.

Light-microscopic autoradiography was used to localize the cellular sites for neutral amino acid uptake in submandibular and sublingual salivary gland epithelia. The vasculature of isolated glands was perfused for 3-5 min with either L-(3-3H)serine or L-(4-3H)phenylalanine and then fixed by perfusion with buffered glutaraldehyde. In the submandibular gland the small neutral amino acid L-serine and the aromatic amino acid L-phenylalanine were localized to central acinar cells, demilunar cells and ductal cells. In the sublingual gland silver grains associated with each of these tritiated amino acids were localized to central acinar and ductal cells. Perfusion of both submandibular and sublingual glands with unlabelled L-serine (25 mM) or L-phenylalanine (30 mM) resulted in a significant decrease in the silver grain density associated with each labelled amino acid. The absence of silver grains in the lumina of acinar and ductal cells and the presence of tight junctions near the apical surface of the epithelium strongly suggest that the initial uptake of these amino acids was mediated by basolateral plasma membrane carriers.