Search

Caves and rockshelters are a key component of the archaeological record but are often regarded as natural places conveniently exploited by human communities. Archaeomorphological study shows however that they are not inert spaces but have frequently been modified by human action, sometimes in ways that imply a strong symbolic significance. In this paper the concept of 'amenagement', the re-shaping of a material space or of elements within it, is applied to Chauvet Cave in France and Nawarla Gabarnmang rockshelter in Australia. Deep within Chauvet Cave, fallen blocks were moved into position to augment the natural structure known as The Cactus, while ar Nawarla Gabarnmang, blocks were removed from the ceiling and supporting pillars removed and discarded down the talus slope. These are hence not 'natural' places, but modified and socially constructed. Keywords: Chauvei Cave, Nawarla Gabarnmang, rockshelter, archaeomorphology, amenagement, geomorphological mapping, rock art, Introduction It is commonplace in archaeology to make reference to--and systematically investigate--site formation processes both natural and cultural (for a classic exposition, see Schiffer 1976). Among these investigations, it is [...]

Trans-epithelial tracer urea flux across Madin-Darby canine kidney (MDCK) cells permanently expressing the urea transporter UT-Al is stimulated by agents that activate the cAMP signaling pathway, such as vasopressin or forskolin, thus mimicking the activation of urea permeability in the inner medullary collecting duct in the presence of vasopressin. Here, we report that UT-A1-mediated urea flux is also activated two-to-threefold over background by exposing the cells to media containing LiCl. This is in contrast to reports on cortical and medullary collecting duct tubules where acute and chronic exposure to lithium (Li) suppresses the osmotic water permeability, which is also regulated by cAMP levels. The Li concentration dependence of urea flux activation was linear up to 150 mM Li. Li activated only from the basolateral side where its effect was inhibited by amiloride, presumably because Li entered the cells through a basolateral Na-H exchanger. Li and IBMX, which also weakly activated urea flux, greatly augmented each others' stimulatory effect on urea flux. However, cellular cAMP levels did not rise commensurately with urea fluxes, and even though Li augments the activation by forskolin, it greatly inhibits the forskolin-induced formation of cAMP. These results suggest that the effect of Li in this MDCK model of renal cells does not involve cAMP or at least utilizes an additional signaling pathway independent of cAMP. cyclic AMP; Madin-Darby canine kidney cells

Transepithelial [[sup.14]C]urea fluxes were measured across cultured Madin-Darby canine kidney (MDCK) cells permanently transfected to express the urea transport protein UT-A1. The urea fluxes were typically increased from a basal rate of 2 to 10 and 25 nmol x [cm.sup.-2] x [min.sup.-1] in the presence of vasopressin and forskolin, respectively. Flux activation consisted of a rapid-onset component of small amplitude that leveled off within ~ 10 min and at times even decreased again, followed by a delayed, strong increase over the next 30-40 min. Forskolin activated urea transport through activation of adenylyl cyclase; dideoxyforskolin was inactive. Vasopressin activated urea transport only from the basolateral side and was blocked by OPC-31260, indicating that its action was mediated by basolateral [V.sub.2] receptors. In the presence of the phosphodiesterase inhibitor IBMX, vasopressin activated as strongly as forskolin. By itself, IBMX caused a slow increase over 50 min to ~5 nmol x [cm.sup.-2] x [min.sup.-1] x 8-Bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP; 300 [micro]M) activated urea flux only when added basolaterally. IBMX augmented the activation by basolateral 8-BrcAMP. Urea flux activation by vasopressin and forskolin were only partially blocked by the protein kinase A inhibitor H-89. Even at concentrations >10 [micro]M, urea flux after 60 min of stimulation was reduced by urea transporter: Madin-Darby canine kidney cells