Defining hybrid poplar (Populus deltoides × Populus trichocarpa) tolerance to ozone: identifying key parameters

This study examined whether two genotypes of hybrid poplar ( Populus deltoides  ×  Populus trichocarpa ), previously classified as ozone tolerant and ozone sensitive, had differing physiological and biochemical responses when fumigated with 120 nL L⁻¹ ozone for 6 h per day for eight consecutive days. Isoprene emission rate, ozone uptake and a number of physiological and biochemical parameters were investigated before, during and after fumigation with ozone. Previous studies have shown that isoprene protects plants against oxidative stress. Therefore, it was hypothesized that these two genotypes would differ in either their basal isoprene emission rates or in the response of isoprene to fumigation by ozone.
Our results showed that the basal emission rates of isoprene, physiological responses and ozone uptake rates were all similar. However, significant differences were found in visible damage, carotenoids, hydrogen peroxide (H₂O₂), thiobarbituric acid reactions (TBARS) and post-fumigation isoprene emission rates. It is shown that, although the classification of ozone tolerance or sensitivity had been previously clearly and carefully defined using one particular set of parameters, assessment of other key variables does not necessarily lead to the same conclusions. Thus, it may be necessary to reconsider the way in which plants are classified as ozone tolerant or sensitive.     

Population Growth and Demography of Common Loons in the Northern United States

ABSTRACT We used recent developments in theoretical population ecology to construct basic models of common loon (Gavia immer) demography and population dynamics. We parameterized these models using existing survival estimates and data from long-term monitoring of loon productivity and abundance. Our models include deterministic, 2-stage, density-independent matrix models, yielding population growth-rate estimates (λ) of 0.99 and 1.01 for intensively studied populations in our Wisconsin, USA, and New Hampshire, USA, study areas, respectively. Perturbation analysis of these models indicated that estimated growth rate is extremely sensitive to adult survival, as expected for this long-lived species. Also, we examined 20 years of count data for the 2 areas and evaluated support for a set of count-based models of population growth. We detected no temporal trend in Wisconsin, which would be consistent with fluctuation around an average equilibrium state but could also result from data limitations. For New Hampshire, the model set included varying formulations of density dependence and partitioning of stochasticity that were enabled by the annual sampling resolution. The best model for New Hampshire included density regulation of population growth and, along with the demographic analyses for both areas, provided insight into the possible importance of breeding habitat availability and the abundance of nonbreeding adults. Based on these results, we recommend that conservation organizations include nonbreeder abundance in common loon monitoring efforts and that additional emphasis be placed on identifying and managing human influences on adult loon survival.     

Localization of Phosphatases in Trypanosoma rhodesiense1

ABSTRACT. Phosphatase activity in Trypanosoma rhodesiense has been examined histochemically by light and electron microscopy and by enzymatic assay in homogenate fractions. Using a method with lead as capture ion, acid phosphatase was found in lysosome-like vesicles and in the flagellar pocket. No alkaline adenosine triphosphatase (ATPase) was detectable by this method. Direct assay of p-nitrophenylphosphatase activity in homogenate fractions showed that acid phosphatase activity was strongly membrane-bound, but that activity at pH 9 was minimal in both soluble and particulate fractions. “Endogenous” ATPase activity was localized specifically and reproducibly in the mitochondrial membranes and under the plasma membrane of the flagellum. This nonenzymic reaction product could not be eradicated by glycerol extraction or glucose depletion. Unlike the membrane staining, which was manifest only after lead treatment, heat-resistant electron-dense material was found in the matrix of lysosomal vesicles in trypanosomes fixed in glutaraldehyde only and not subjected to further treatment with heavy metal reagents. X-ray emission analysis showed the presence of calcium and phosphorus, indicating that the matrix might have a phosphate storage function.     

New prosauropod material from South Wales

New prosauropod material from a cave filling of Upper Triassic/Lower Jurassic age in Pant-y-ffynnon Quarry, South Wales, is described. The Panl-y-ffynnon fauna also includes thecodont, coelurosaur, crocodile and lepidosaur material.
Most of the prosauropod skeleton is represented. An almost complete but disarticulated skull is preserved. The skull and whole skeleton of the prosauropod are reconstructed. Evidence from the size and relative proportions of the bones, also the state of ossification, indicates that the prosauropod remains represent juveniles.
The level of the jaw articulation combined with the form of the teeth would suggest that the Pant-y-ffynnon prosauropod was omnivorous.
The Pant-y-ffynnon prosauropod resembles closely the much less complete Durdham Down (Bristol) remains of Thecodonlosaurus antiquus Morris; the Welsh material could well be juveniles of that species. Here the Pant-y-ffynnon material is ascribed to Thecodonlosaurus sp.
The mode of deposition of the fossil material is discussed, to account for the deposit containing only juveniles of the prosauropod.     

The Effects of Ribavirin on the GTP Level and the VIP Receptor Dynamic of Human IGR39 Cells

The discovery that arrestins can function as ligand-regulated signaling scaffolds has revealed a previously unappreciated level of complexity in G protein-coupled receptor (GPCR) signal transduction. Because arrestin-bound GPCRs are uncoupled from G proteins, arrestin binding can be viewed as switching receptors between two temporally and spatially distinct signaling modes. Recent work has established two factors that underscore this duality of GPCR signaling and suggest it may ultimately have therapeutic significance. The first is that signaling by receptor-arrestin “signalsomes” does not require heterotrimeric G protein activation. The second is that arrestin-dependent signals can be initiated by pathway-specific “biased agonists,” creating the potential for drugs that selectively modulate different aspects of GPCR function. Currently, however, little is known about the physiological relevance of G protein-independent signals at the cellular or whole animal levels, and additional work is needed to determine whether arrestin pathway-selective drugs will find clinical application.     

Chamber growth in ammonites inferred from colour markings and naturally etched surfaces of Cretaceous vascoceratids from Nigeria

Cretaceous Vascoceras and Jurassic Lytoceras show colour markings and etched surfaces representing original organic membranes between the septa. The main difference between the formation of ammonite and Nautilus chambers involved the continuous secretion of a gelatinous cameral liquid to support the ammonite mantle when it moved forward. The gel containing cyclically secreted membranes. here named pseudosepta, resembled the intra-cameral structures of the cuttlebone in Sepia. Pseudoscpta are attached to the shell wall in pseudosutures (Pseudoloben) which are particularly visible in the saddles of the septal suture and tend to mimic them. Their shape suggests reconstruction of posterior mantle shape during translocation. Drag-bands (Schleppstreifen) are spiral markings formed by the overlapping pseudosepta along the axial traces of the foliole folds. The chamber of ammonites was formed by a locally muscular mantle in a tripartite cycle: (1) the mantle initially remained attached to the saddles of the completed septal suture while muscular tissue within the umbilical lobes was contracted and rapidly reattached to the side of the lateral saddles; (2) the whole mantle subsequently crept forward by secreting a gelatinous matrix which contained telescoped membranes, with an adhesive function on pseudolobc flanks; (3) the mantle almost ceased to move within the sites of future lobules, but expanded and crept on before forming the mural and 'gutter' ridges of the septum. □ Ammonites, chamber growth, vascoceratids, LYTOCERAS, Nigeria.     

Rapid laying by Brown-headed Cowbirds Molothrus ater and other parasitic birds

We compared the length of time parasitic and nonparasitic female birds spent on nests while laying eggs (laying bouts) to evaluate the hypothesis that rapid laving by parasitic Brown-headed Cowbirds Molothrus ater and other parasitic birds is a specialization for brood parasitism. Brown-headed Cowbirds typically spent less than 1 min on host nests while laying (41.0 ± 4.58 [mean ± s.e.] s, n = 21). In contrast, mean laving bouts of six nonparasitic icterine species ranged from 21.5 min to 53.4 min, and laying bouts of 13 other passerine species ranged from 20.7 min to 103.7 min. By spending only a few seconds on the nest while laying, brood parasites probably increase their chances of parasitizing nests unnoticed by hosts or, if noticed, are harassed by hosts for less time. Rapid laying may be adaptive if aggression by hosts can thwart attempted parasitism by chasing away the parasite, preventing the parasite from entering the nest or injuring the parasite. Rapid laying may increase the likelihood that the parasitic egg will be accepted. We tested some of these hypotheses by recording the responses of three frequently parasitized species to a stuffed female cowbird placed on their nests for 1 min. All species attacked the model vigorously; however, the mean time for discovery of the model ranged from 3 min to 17 min, ample time for female cowbirds to parasitize the nests. We concluded that rapid laying by parasitic birds is an adaptation for parasitism and, in Brown-headed Cowbirds, reduces the chances that the parasite will be attacked by hosts.