Seven Artemia samples from three South American countries (Chile, Brazil, Peru) were studied by starch elec-

Resistance to the extreme stresses of high temperature-desiccation and low temperature were compared among six species of the melanogaster species subgroup of Drosophila. D. melanogaster was the most resistant to all stresses. The cosmopolitan species, D. melanogaster and D. simulans, were more resistant to cold stresses than the four endemic species, D. mauritiana, D. teissieri, D. yakuba and D. erecta. D. simulans, D. mauritiana and D. teissieri showed similar resistance to heat and desiccation, while D. yakuba and especially D. erecta were sensitive to these stresses. A prerequisite for the spread of the cosmopolitan species into temperate zones thus appears to have involved a level of resistance to cold stress exceeding that of the endemics. A greater resistance to heat and desiccation stresses, such as that found in D. melanogaster, may also be necessary for the invasion of more extreme environments. All species with the exception of D. erecta and to a lesser extent D. yakuba can survive 6 h at the extreme temperature of 34�C at 95% RH, and in addition most of those flies surviving stresses of this type are fertile. This suggests that these species can survive short stress periods in a humid microhabitat in the wild.

The genetic and morphological structure of Patella candei in the Macaronesian Islands were studied by allozyme electrophoresis and multivariate analysis (canonical discriminant analysis), respectively. Sixteen enzymes, yielding 21 resolvable loci were analysed for all populations using the BIOSYS‐1 program. A disjunct distribution of genetically similar populations from the Azores and Selvagens Islands (P.c. gomesii–P.c. candei) was found, which showed two diagnostic loci with P.c. ordinaria from Madeira. Patella c. crenata from the Canaries showed an intermediate composition of 92%P.c. ordinaria and 8%P.c. gomesii–P.c. candei. Hypotheses are presented to explain the evolution of the genetic and morphological structure of P.c. candei in the Macaronesian Islands, including the interaction of natural processes and human intervention. Patella c. candei is considered to represent the ancestral form. An extinction or near extinction event may have happened in Madeira after which P.c. ordinaria arose, carrying only a small part of the diversity of the original form, which evolved in isolation. The ancestral form, P.c. candei, was depleted by human extraction from high levels of the shore in the Azores and Canaries. Patella c. gomesii, from the Azores evolved by phyletic evolution, colonizing low levels of the shore, leaving only a relict population in the Selvagens Islands, that remained almost free of human exploitation. Patella c. crenata is a hybrid with a high degree of introgression to P.c. ordinaria, which is maintained by the forces of human extraction at high‐tide levels and by intraspecific competition at low‐tide levels. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77, 341−353.

Traumatic brain injury (TBI) is a leading cause of injury-related death worldwide, yet there are no approved neuroprotective therapies that improve neurological outcome post-injury. Transient opening of the blood-brain barrier following injury provides an opportunity for passive accumulation of intravenously administered nanoparticles through an enhanced permeation and retention-like effect. However, a thorough understanding of physicochemical properties that promote optimal uptake and retention kinetics in TBI is still needed. In this study, we present a robust method for magnetic resonance imaging of nanoparticle uptake and retention kinetics following intravenous injection in a controlled cortical impact mouse model of TBI. Three contrast-enhancing nanoparticles with different hydrodynamic sizes and relaxivity properties were compared. Accumulation and retention were monitored by modelling the permeability coefficient, Ktrans, for each nanoparticle within the reproducible mouse model. Quantification of Ktrans for different nanoparticles allowed for non-invasive, multi-time point assessment of both accumulation and retention kinetics in the injured tissue. Using this method, we found that 80 nm poly(lactic-co-glycolic acid) nanoparticles had maximal Ktrans in a TBI when injected 3 hours post-injury, showing significantly higher accumulation kinetics than the small molecule, Gd-DTPA. This robust method will enable optimization of administration time and nanoparticle physicochemical properties to achieve maximum delivery.

Amphipod crustaceans have been widely used as invertebrate models in ecotoxicology due to their importance in the food chain. However, few studies have evaluated the genotoxic effects of pollutants in this model using the comet assay. The main obstacle to using amphipods in the comet assay is the difficulty in obtaining enough blood cells from a single individual. In this study, we evaluated the genotoxic effects of the water-soluble fraction (WSF) of heavy oil on the brackish/freshwater amphipod Quadrivisio aff. lutzi, which is common in the coastal lagoons of southeastern Brazil, using hemocytes obtained from single amphipods (without pooling) after optimizing hemolymph extraction. The comet assay revealed significantly higher DNA damage levels (2- to 6-fold higher) in treated amphipods compared to untreated ones with a sublethal concentration of 17.6 % of the WSF within 72 h of treatment. Two independent experiments confirmed an "up and down" pattern of DNA damage, measured as the % of DNA contained in the tail of the comets. Elevations in DNA damage levels were observed at the 6 and 48 h time points, while very low levels of DNA damage were observed at the 24 and 72 h time points. Furthermore, the comet assay revealed gender variability in the levels of DNA damage after short-term exposure.