Accumulation and detoxification of cadmium in <Emphasis Type="Italic">Brassica pekinensis</Emphasis> and <Emphasis Type="Italic">B. chinensis</Emphasis>

The effect of excessive Cd on the growth and metal uptake by leafy vegetables Brassica chinensis L. (cv. Wuyueman) and Brassica pekinensis (Lour.) Rupr. (cv. Qingyan 87-114) were studied in hydroponic solution culture. The Cd concentration higher than 10 μM significantly decreased the root elongation and leaf chlorophyll contents of both plant species. The shoots of B. pekinensis had significantly higher concentrations of total and water-soluble Cd than B. chinensis. The roots of both species accumulated more Cd than the shoots in all the Cd treatments. Most of the Cd in the roots was found in the cell walls. The shoot/root ratio of Cd concentrations in B. pekinensis was always greater than that in B. chinensis. But, the concentration and proportion of Cd in the cell walls in B. chinensis were higher than that in B. pekinensis. Cadmium treatments also increased the concentrations of total non-protein thiols (NPT) in the shoots of the both species. A significant correlation was found between the concentrations of soluble Cd and NPT in plant shoots.     

Observational visuospatial encoding of the cache locations of others by western scrub-jays (<Emphasis Type="Italic">Aphelocoma californica</Emphasis>)

Western scrub-jays (Aphelocoma californica) hide food and rely on spatial memory to recover their caches at a later date. They also rely on observational spatial memory to steal caches made by other individuals. Successful pilfering may require an understanding of allocentric space because the observer will often be in a different position from the demonstrator when the caching event occurs. We compared cache recovery accuracy of pairs of observers that watched a demonstrator cache food. The pattern of recovery searches showed that observers were more accurate when they had observed the caching event from the same viewing direction as the demonstrator than when they had watched from the opposite direction. Search accuracy was not affected by whether or not the tray-specific local cues provided left–right landmark information (i.e. heterogeneous vs. homogeneous local cues), or whether or not the caching tray location was rotated. Taken together, these results suggest that observers have excellent spatial memory and that they have little difficulty with mental rotation.     

Recent decrease in chinstrap penguin (<Emphasis Type="Italic">Pygoscelis antarctica</Emphasis>) populations at two of Admiralty Bay’s islets on King George Island,South Shetland Islands,Antarctica

We examined the breeding populations of chinstrap penguins (Pygoscelis antarctica) on Chabrier Rock and Shag Island within Admiralty Bay, King George Island, South Shetland Islands, Antarctica from 2002 to 2004. When comparing our results to historic data from 1979, we found an overall decline of 57% in the last 25 years, mirroring the population trend of this species in other regions of the Antarctic Peninsula. Our results are discussed in relation to factors hypothesized to be driving the declines found at other sites, as well as the importance of consistent annual censuses to accurately determine population trends.     

Competition between Hardwood Hammocks and Mangroves

A bstract The boundaries between mangroves and freshwater hammocks in coastal ecotones of South Florida are sharp. Further, previous studies indicate that there is a discontinuity in plant predawn water potentials, with woody plants either showing predawn water potentials reflecting exposure to saline water or exposure to freshwater. This abrupt concurrent change in community type and plant water status suggests that there might be feedback dynamics between vegetation and salinity. A model examining the salinity of the aerated zone of soil overlying a saline body of water, known as the vadose layer, as a function of precipitation, evaporation and plant water uptake is presented here. The model predicts that mixtures of saline and freshwater vegetative species represent unstable states. Depending on the initial vegetation composition, subsequent vegetative change will lead either to patches of mangrove coverage having a high salinity vadose zone or to freshwater hammock coverage having a low salinity vadose zone. Complete or nearly complete coverage by either freshwater or saltwater vegetation represents two stable steady-state points. This model can explain many of the previous observations of vegetation patterns in coastal South Florida as well as observations on the dynamics of vegetation shifts caused by sea level rise and climate change.     

Metabolism of mono- and dihalogenated C1 and C2 compounds by <Emphasis Type="Italic">Xanthobacter autotrophicus</Emphasis> growing on 1,2-dichloroethane

The conversion of and toxic effects exerted by several mono- and dihalogenated C1 and C2 compounds on cultures of Xanthobacter autotrophicus GJ10 growing on 1,2-dichloroethane were investigated. Bromochloromethane, dibromomethane and 1-bromo-2-chloroethane were utilized by strain GJ10 in batch culture as a cosubstrate and sole carbon source. The rate of degradation of dihalomethanes by whole cells was lower than that of 1,2-dichloroethane, but a significant increase of the rate of dihalomethane biodegradation was observed when methanol or ethanol were added as a cosubstrate. Products of the degradation of several tested compounds by haloalkane dehalogenase were analyzed and a new metabolic pathway based on hydrolytic conversion to formaldehyde was proposed for the dihalomethanes. Strain GJ10 growing on 1,2-dichloroethane converted 2-fluoroethanol and 1-chloro-2-fluoroethane to 2-fluoroacetate, which was tolerated up to a concentration of 2.5 mM. On the basis of the results from batch cultures an inert (dichloromethane), a growth-supporting (dibromomethane) and a toxic (1,2-dibromoethane) compound were selected for testing their effects on a continuous culture of strain GJ10 growing on 1,2-dichloroethane. The compounds were added as pulses to a steady-state chemostat and the response of the culture was followed. The effects varied from a temporary decrease in cell density for dibromomethane to severe toxicity and culture washout with 1,2-dibromoethane. Our results extend the spectrum of halogenated C1 and C2 compounds that are known to be degraded by strain GJ10 and provide information on toxic effects and transformation of compounds not serving as a carbon source for this bacterium.     

<Emphasis Type="Italic">Slc11a1</Emphasis> (<Emphasis Type="Italic">Nramp1</Emphasis>) alleles interact with acute inflammation loci to modulate wound-healing traits in mice

Lines of mice were obtained by selective breeding for maximum (AIRmax) or minimum (AIRmin) acute inflammation. They present distinct neutrophil influx and show frequency disequilibrium of the solute carrier family 11a member 1 (Slc11a1) alleles. This gene is involved in ion transport at the endosomes within macrophages and neutrophils, interfering in their activation. Homozygous AIRmax and AIRmin sublines for the Slc11a1 gene were produced to examine the interaction of this gene with the acute inflammatory loci. The present work investigated wound-healing traits in AIRmax and AIRmin mice, in F₁ and F₂ intercrosses, and in Slc11a1 sublines. Two-millimeter ear punches were made in the mice and hole closure was measured during 40 days. AIRmax mice demonstrated significant tissue repair while AIRmin mice did not. Significant differences between the responses of male and female mice were also observed. Wound-healing traits demonstrated a correlation with neutrophil influx in F₂ populations. AIRmax ^SS showed higher ear-wound closure than AIRmax ^RR mice, suggesting that the Slc11a1 S allele favored ear tissue repair. QTL analysis has detected two inflammatory loci modulating ear wound healing on chromosomes 1 and 14. These results suggest the involvement of the acute inflammation modifier QTL in the wound-healing phenotype.     

Erythrocyte surface sialic acid levels of clinically healthy mongrel and exotic (alsatian and terrier) breeds of dogs

The erythrocyte surface sialic acid concentration of clinically healthy mongrel and exotic (Alsatian i.e. German shepherd and Terrier) breeds of dogs was analyzed in order to determine their role in the genetic resistance of these breeds of dogs to diseases that cause anaemia. The mean erythrocyte surface sialic acid (ESA) concentration was 57.08 ± 1.67, 34.50 ± 2.30 and 20.20 ± 3.54 mg/dl for Mongrel, Alsatian (German shepherd) and Terrier breeds of dogs, respectively, on acid hydrolysis. The mean values of ESA obtained following enzymic hydrolysis of haemoglobin-free erythrocyte membranes using Clostridium chauvoei (Jakari strain) sialidase were 49.08 ± 0.41, 30.97 ± 1.82 and 18.64 ± 0.75 mg/dl for Mongrel, Alsatian (German shepherd) and Terrier dogs respectively. When Trypanosoma vivax sialidase was used the ESA values obtained were 50.81 ± 0.37, 41.70 ±  0.94 and 19.65 + 0.65 mg/dl for Mongrel, Alsatian (German shepherd) and Terrier breeds of dogs respectively. This represents a statistically significant difference (P < 0.001) between the mean ESA concentration of all the breeds of dogs investigated in this study. The higher mean ESA concentration in Mongrel dogs, compared to the exotic breeds may be responsible for their resistance to disease conditions, whose aetiologic agents produce neuraminidase and also cause anaemia.     

The extent and significance of petroleum hydrocarbon contamination in Crater Lake,Oregon

In order to evaluate hydrocarbon inputs to Crater Lake from anthropogenic and natural sources, samples of water, aerosol, surface slick and sediment were collected and analyzed by gas chromatography-mass spectrometry (GC-MS) for determination of their aliphatic and aromatic hydrocarbon concentrations and compositions. Results show that hydrocarbons originate from both natural (terrestrial plant waxes and algae) and anthropogenic (petroleum use) sources and are entering the lake through direct input and atmospheric transport. The concentrations of petroleum hydrocarbons range from low to undetectable. The distributions and abundances of n-alkanes, polycyclic aromatic hydrocarbons (PAH) and unresolved complex mixture (UCM) from petroleum are similar for all surface slick sampling sites. The estimated levels of PAH in surface slicks range from 7–9 ng/m² which are low. Transport of petroleum-derived hydrocarbons from the lake surface has resulted in their presence in some sediments, particularly near the boat operations mooring (total petroleum HC = 1440 μg/kg, dry wt. compared to naturally derived n-alkanes, 240 μg/kg, dry wt.). The presence of biomarkers such as the tricyclic terpanes, hopanes and steranes in shallow sediments further confirms petroleum input from boat traffic. In the deep lake sediments, petroleum hydrocarbon concentrations were very low (16 μg/kg, dry wt.). Very low concentrations of PAH were detected in shallow sediments (17–40 μg/kg at 5 m depth near the boat operations) and deep sediments (3–15 μg/kg at 580 m depth). The individual PAH concentrations in sediments (μg/kg or ppb range) are at least three orders of magnitude less than reported threshold effects levels (mg/kg or ppm range, test amphipod Hyalella azteca). Therefore, no adverse effects are expected to occur in benthic biota exposed to these sediments. Boating activities are leaving a detectable level of petroleum in surface waters and lake sediments but these concentrations are very low.