Using synoptic tracer surveys to assess runoff sources in an Andean headwater catchment in central Chile.

Headwater catchments in the Andes provide critical sources of water for downstream areas with large agricultural communities dependent upon irrigation. Data from such remote headwater catchments are sparse, and there is limited understanding of their hydrological function to guide sustainable water management. Here, we present the findings of repeat synoptic tracer surveys as rapid appraisal tools to understand dominant hydrological flow paths in the semi-arid Rio Grande basin, a 572-km2 headwater tributary of the 11,696-km2 Limarí basin in central Chile. Stable isotopes in stream water show a typical altitudinal effect, with downstream enrichment in δ2H and δ18O ratios. Seasonal signals are displayed in the isotopic composition of the springtime melting season water line with a steeper gradient, whilst evaporative effects are represented by lower seasonal gradients for autumn and summer. Concentrations of solutes indexed by electrical conductivity indicate that there are limited contributions of deeper mineralised groundwater to streamflow and that weathering rates vary in the different sub-catchments. Although simplistic, the insights gained from the study could be used to inform the structure and parameterisation of rainfall runoff models to provide seasonal discharge predictions as an evidence base for decision making in local water management.

Effects of altered gravity on the swimming behaviour of fish.

Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness-phenomena (SMS, a kinetosis). It has been argued that SMS during PAFs might not be based on microgravity alone but rather on changing accelerations from 0 g to 2 g. We test here the hypothesis that PAF-induced kinetosis is based on asymmetric statoliths (i.e., differently weighed statoliths on the right and the left side of the head), with asymmetric inputs to the brain being disclosed at microgravity. Since fish frequently reveal kinetotic behaviour during PAFs (especially so-called spinning movements and looping responses), we investigated (1) whether or not kinetotically swimming fish at microgravity would have a pronounced inner ear otolith asymmetry and (2) whether or not slow translational and continuously changing linear (vertical) acceleration on ground induced kinetosis. These latter accelerations were applied using a specially developed parabel-animal-container (PAC) to stimulate the cupular organs. The results suggest that the fish tested on ground can counter changing accelerations successfully without revealing kinetotic swimming patterns. Kinetosis could only be induced by PAFs. This finding suggests that it is indeed microgravity rather than changing accelerations, which induces kinetosis. Moreover, we demonstrate that fish swimming kinetotically during PAFs correlates with a higher otolith asymmetry in comparison to normally behaving animals in PAFs.

Increased DNA synthesis in the heart during acute allylamine cardiotoxicity.

The cardiotoxin allylamine causes acute myocellular degeneration and necrosis; in a previous ultrastructural study we observed marked mitotic activity in endothelial cells following allylamine. In the present study, we assessed proliferative activity in the heart: groups of male rats were given either a single dose (100 mg/kg) of allylamine, or two doses on successive days; all rats were killed 24 hours after the last dose. Three hours before killing, rats were given 0.37 Ci/kg (SA 6.7 mCi/mMole) H3-Thymidine, iv. Under ether anesthesia rats were killed by cardiac perfusion with formalin; the entire heart was sectioned at 4 microns for autoradiography. Multiple adjacent fields were viewed and labeled endothelial and interstitial cell nuclei were counted across the interventricular septum (IVS), right ventricular free wall (RV), and left ventricular free wall (LV). Endothelial nuclear labeling was markedly increased in IVS after 2 doses (9.7 +/- 2.2 mitoses-/mm2 vs 1.6 +/- .2 in control; P less than .05), whereas LV and RV showed their most pronounced increases at 24 hours after the first dose. Increased endothelial and interstitial cell labelling correlated with histopathologic lesions, although increased labelling after 1 dose was also seen in the absence of lesions. Prominent endothelial cell proliferation and interstitial cell activation occur rapidly in acute allylamine myocardial damage.

Studies on the mechanism of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)-induced hepatotoxicity. III. Ultrastructural characterization of bile duct injury.

The antineoplastic nitrosourea CCNU is a known hepatotoxin which has been shown to cause hyperbilirubinemia and reduction in bile flow. We studied morphological alterations in the common bile duct and interlobular bile ducts at 6, 12, and 24 h in male rats given a single oral dose (50 mg/kg) of CCNU. The portal vein was perfused with 1.0% glutaraldehyde fixative. Portal areas and the common bile duct were selectively dissected and processed using standard methods for light and transmission electron microscopy. The epithelial cells of larger common bile duct and interlobular bile ducts showed increased rough endoplasmic reticulum, markedly increased free ribosomes, and mitochondrial degeneration at 6 and 12 h after CCNU. There was also bile imbibition and loss of microvilli, which increased in severity at 12 and 24 h. The interstitium showed infiltration by acute inflammatory cells and dilated capillaries at 6 h. By 24 h, degeneration of epithelial cells was extensive; cells became necrotic and sloughed into the duct lumen. The smaller bile ductules showed no significant degenerative changes; adjacent hepatocytes were unremarkable. Early CCNU injury appears localized in the large bile ducts and reflects inflammatory edema, bile stasis, and degeneration of epithelial cells. Our studies suggest that this ductal injury may reflect metabolism of CCNU to reactive species within the bile ducts.