Hydrogen peroxide induces endothelial cell atypia and cytoskeleton depolymerization

Reactive oxygen intermediates induce cell injury in a variety of pathophysiological conditions. Human umbilical cord vein endothelial cell (HUVEC) cultures were exposed to 1 or 200 microM H2O2 for 15 min, and observed after 15 min, or 1, 4, 24, or 120 h. Factor VIII and the cytoskeletal proteins vimentin and tubulin were visualized immunocytochemically. Release of lactate dehydrogenase (indices of cell membrane injury) did not increase after H2O2 exposure; nor was cellular expression of factor VIII affected. 200 microM H2O2 induced cell contraction after 15 min which disappeared after 1 and 4 h, but was evident again after 24 h. Immediately after exposure, the filamentous structure of vimentin and tubulin disappeared, but normalized after 1 h. After 120 h, the cytoskeleton filaments were coarsened and disorganized, and an abundance of multinucleated giant cells were observed. Catalase (150 U/ml) abolished all effects of H2O2. One microM H2O2 did not induce any changes in HUVEC. Thus, the present concentrations of H2O2 did not induce cell necrosis or altered expression of factor VIII. Early, reversible cell contraction and depolymerization of cytoskeletal proteins were observed, followed by a delayed contraction and cell atypia after 200 microM H2O2.     

Winter climate change: Ice encapsulation at mild subfreezing temperatures kills freeze-tolerant lichens

While it has been widely proven that many lichens are extremely freeze-tolerant in the dry state, little is known about how moist lichens respond to freezing under oxic and anoxic conditions. In circumpolar areas where lichens are an important component of boreal and Arctic ecosystems, winter climate is changing, leading to increased frequency of winter thaw and ground-icing events. It is imperative to elucidate in further detail how northern vegetation responds to being encapsulated in ice. A winter icing simulation experiment was therefore undertaken, encapsulating two reindeer lichens (Cladonia stellaris and Cladonia rangiferina) and two epiphytic lichens (Parmeliopsis ambigua and Melanohalea olivacea) in ice at temperatures just below freezing for a maximum period of 98 d. Photosynthetic and chlorophyll fluorescence rates decreased strongly, clearly suggesting that the algal partner of the lichens was dying. Low but detectable respiration rates indicate that the fungal partner maintained some physiological activity. Ethanol accumulated in the lichens during ice encapsulation as a result of anaerobic respiration. The algae probably were dying from a combination of depletion of carbon reserves and toxic levels of ethanol and other stress metabolites. This experiment shows that boreal and Arctic-alpine lichens are sensitive to a warmer and more fluctuating winter climate. Increasing frequency of winter icing events may therefore have extensive and hitherto unknown effects on lichen-dominated ecosystems, their herbivores and the indigenous peoples whose livelihoods largely depend on them.     

Accuracy of body mass estimates of formalin-preserved fish – a review

This paper highlights possible effects of physical and chemical mechanisms of formalin fixation and preservation on biological tissue and reviews the consequent potential inaccuracies on estimates of body mass of small fishes fixed and preserved in formalin. Twenty-six papers including 65 independent experiments with 35 species which examine effects of formalin on body mass estimates on small fishes are included. The effect of the formalin on the specimens depends on the salinity of the water used to dilute the commercial formalin (usually 1:9 formalin: water) before being used to fixate and preserve fish. Mean wet body mass of the specimens from the studies using seawater or fresh water diluted formalin deceases by 13% and increases by 7%, respectively, from before to after being immersed in formalin. The same trend is found with condition factor in the few papers that report this parameter. Body length decreases on average by c. 2% in fixated and preserved fish regardless of whether the formalin is diluted in seawater or fresh water.     

An account of responses of spectrally opponent neurons in macaque lateral geniculate nucleus to successive contrast

Coloured surfaces in the normal environment may be brighter or dimmer than the mean adaptation level. Changes in the firing rate of cells of the parvocellular layers of macaque lateral geniculate nucleus were studied with such stimuli; chromatic mixtures briefly replaced a white adaptation field. This paradigm is therefore one of successive contrast. Families of intensity-response curves for different wavelengths were measured. When taking sections at different luminance ratios through these families of curves, strongly opponent cells displayed spectrally selective responses at low luminance ratios, while weakly opponent cells had higher chromatic thresholds and responded well to stimuli at higher luminance ratios, brighter than the adaptation field. Strength of cone opponency, defined as the weight of the inhibitory cone mechanism relative to the excitatory one, was thus related to the range of intensity in which cells appeared to operate most effectively. S-cone inputs, as tested with lights lying along tritanopic confusion lines, could either be excitatory or inhibitory. Families of curves for different wavelengths can be simulated mathematically for a given cell by a simple model by using known cone absorption spectra. Hyperbolic response functions relate cone absorption to the output signals of the three cone mechanisms, which are assumed to interact linearly. Parameters from the simulation provided estimates of strength of cone opponency and cone sensitivity which were shown to be continuously distributed. Cell activity can be related to cone excitation in a trichromatic colour space with the help of the model, to give an indication of suprathreshold coding of colour and lightness.     

Ornaments or offspring? Female sticklebacks (Gasterosteus aculeatus L.) trade off carotenoids between spines and eggs

Hypotheses and models to explain female ornaments often assume that the elaborated traits are condition dependent; nevertheless, few empirical studies have addressed this topic. We studied a population of three-spined sticklebacks (Gasterosteus aculeatus) in which the females have conspicuous, carotenoid-based red coloration to their pelvic spines. The red coloration seems not to be condition dependent, as coloration is negatively associated with age and body length and not associated with condition. Furthermore, redder females did not have a lower density of leucocytes. We found a negative association between the females' red carotenoid-based coloration in the spines and the amount of carotenoids in the female's gonads. Males choosing red-coloured females will fertilize eggs with small amounts of carotenoids and appear not to gain any benefit from their mates' phenotypic quality that could result in offspring of improved quality. These results do not support the 'direct selection hypothesis' to explain the existence of the female ornaments.     

Effective size of an Atlantic salmon (Salmo salar L.) metapopulation in Northern Spain

The genetic diversity of metapopulations is influenced not only by the effective sizes (N _e ) of individual subpopulations, but also by the total effective size of the metapopulation (meta-N _e ). We estimated meta-N _e of four neighbouring Atlantic salmon populations connected by gene flow using genetic estimates of subpopulation N _e s and migration rates derived from capture–recapture data. The meta-[^(N)]_e meta{\hbox{-}}\hat{N}_{e} was lower than the sum of [^(N)]_e \hat{N}_{e} s of the subpopulations, suggesting that genetic diversity harboured by the four river salmon metapopulation is lower than what would have been expected by viewing individual subpopulations separately. In addition, meta-[^(N)]_e meta{\hbox{-}}\hat{N}_{e} was found to be sensitive to changes in [^(N)]_e \hat{N}_{e} of the subpopulation from which net emigration rate was largest, so as that the genetic diversity of the metapopulation would be best preserved by avoiding any reductions in N _e of this subpopulation. Yet, this subpopulation is the one that has historically—and still is—experiencing the highest exploitation rate in the metapopulation system.