Histological variability in fossil and recent alligatoroid osteoderms: Systematic and functional implications

Statements about morphological variation in extinct taxa often suffer from insufficient sampling that can be remedied by taking advantage of larger sample sizes provided by related, extant taxa. This analysis quantitatively and qualitatively examines histological and morphological variation of osteoderms from extant and extinct alligatoroid specimens. Statistically significant differences were correlated with changes in osteoderm size and shape. These differences are independent of position on the body, taxonomy, or evolution. Histological variation in alligatoroid osteoderms is due to morphological constraints on the elements themselves, and not taxonomic differences. This has implications for the recognition of histological characters in the osteoderms of extinct archosaur groups that lack extant representatives. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Retroelement particles as purification, presentation and targeting vehicles.

The manipulation of retrotransposon and retroviral particles to carry biologically active molecules is becoming feasible. In addition, recent experiments suggest that it may be possible to target these engineered particles to specific cell types. This has implications for gene therapy, biological drug delivery and vaccine design.     

Avian translocations restore dual interaction networks in an island ecosystem

Many island bird species have been driven to extinction by introduced predators. Although poorly understood, these extinctions could have a 2-fold impact on bird–plant mutualisms, because island bird species can serve as both pollinators and seed dispersers. We investigated how avian translocations into a mammal-free reserve in New Zealand affected the structure of bird–flower and bird–fruit interactions. We observed bird–fruit and bird–flower interactions over a 9-year period to establish (1) the extent to which native birds are both nectivorous and frugivorous (i.e. “dual mutualists”) and (2) how avian translocations and conservation reestablished nectivory and frugivory networks. Results showed that all but one native bird species were dual mutualists. Pairwise species interaction frequencies were positively correlated between networks. However, overall levels of nectivory by each bird species were unrelated to levels of frugivory. Interaction specialization and species strength also did not differ between networks. The reintroduction of threatened and endangered bird species appeared to have restored both interaction networks, and the sequence of species recovery accelerated restorative changes. Overall results indicate that not only does the extinction of dual mutualists have a 2-fold, negative effect on mutualistic interactions with plants, they can also accelerate the recovery of ecosystem services following restoration efforts.     

The moult of Barred Warblers Sylvia nisoria in Kenya—evidence for a split wing-moult pattern initiated during the birds' first winter*

The moult of Barred Warblers Sylvia nisoria was studied during three winter seasons in southeastern Kenya at a southward passage site (Ngulia) and a wintering site (Mtito Andei). Most Barred Warblers migrating through Ngulia in November had yet to commence winter moult. These birds probably moulted subsequently in winter in northern Tanzania. In December, birds were found in heavy moult at Mtito Andei, and some of these birds were known to stay throughout the winter. By contrast, most birds reaching southeastern Kenya from late December onwards had already completed part or all of their winter moult, presumably at stopover sites in northern and eastern Kenya or in Ethiopia. Thus, winter moult in Barred Warblers takes place mainly in late November and December, either just before or soon after the final leg of autumn migration. In general, first-year birds renewed all tertials and tail feathers, about three to five secondaries per wing and commonly also the outer one to four large primaries per wing. Adults renewed all tertials and tail feathers, almost all secondaries and only occasionally an outer primary. The replacement of relatively fresh juvenile secondaries during the birds' first winter implies that the split moult pattern of this species (secondaries, tertials and tail moulted in winter; primaries and tertials in summer) is endogenously controlled.     

Effects of crowding and different food levels on growth and reproductive investment of Daphnia

The effects of daphniid crowding on juvenile growth rate, length at first reproduction, clutch size and egg size of four species of Daphnia were compared with the effects of food level. Juvenile Daphnia were grown to primipary in a flow-through system in water conditioned by different densities of the same, or another, species. At high ambient food levels, water from Daphnia that had been crowded at densities 150 l^–1 depressed growth rate and lowered body size and clutch size of D. hyalina and D. galeata; effects on the same traits of D. magna and D. pulicaria were variable (stimulation, depression, or no effect). D. hyalina and D. galeata responded to gradients of increasing daphniid density (0–300 l^–1) by altering egg mass, somatic mass and clutch size to maintain a relatively constant reproductive investment; egg mass increased with crowding and then decreased in a pattern consistent with Glazier's (1992) hypothetical model of changes in offspring size in relation to food quantity and maternal demand. Effects of crowding by conspecifics were indistinguishable from those of other species. This study, which uncouples the effect of crowding per se from ambient resource depletion, shows that chemical substances released by high densities of Daphnia can cause changes in life-history traits comparable to those that occur in response to low food levels.     

Interleukin-2 triggers a novel phosphatidylinositol 3-kinase-dependent MEK activation pathway.

Phosphatidylinositol 3-kinase (PI3-K) has been implicated as a signal-transducing component in interleukin-2 (IL-2)-induced mitogenesis. However, the function of this lipid kinase in regulating IL-2-triggered downstream events has remained obscure. Using the potent and specific PI3-K inhibitor, wortmannin, we assessed the role of PI3-K in IL-2-mediated signaling and proliferation in the murine T-cell line CTLL-2. Addition of the drug to exponentially growing cells resulted in an accumulation of cells in the G0/G1 phase of the cell cycle. Furthermore, wortmannin also partially suppressed IL-2-induced S-phase entry in G1-synchronized cells. Analysis of IL-2-triggered signaling pathways revealed that wortmannin pretreatment resulted in complete inhibition of IL-2-provoked p70 S6 kinase activation and also attenuated IL-2-induced MAP kinase activation at drug concentrations identical to those required for inhibition of PI3-K catalytic activity. Wortmannin also diminished the IL-2-triggered activation of the MAP kinase activator, MEK, but did not inhibit activation of Raf, the canonical upstream activator of MEK. These results suggest that a novel wortmannin-sensitive activation pathway regulates MEK and MAP kinase in IL-2-stimulated T lymphocytes.     

Pulmonary blood flow redistribution by increased gravitational force

This study was undertaken to assess theinfluence of gravity on the distribution of pulmonary blood flow (PBF)using increased inertial force as a perturbation. PBF was studied inunanesthetized swine exposed toG_x (dorsal-to-ventraldirection, prone position), where G is the magnitude of the force ofgravity at the surface of the Earth, on the Armstrong LaboratoryCentrifuge at Brooks Air Force Base. PBF was measured using 15-µmfluorescent microspheres, a method with markedly enhanced spatialresolution. Each animal was exposed randomly to 1, 2, and3 G_x. Pulmonary vascularpressures, cardiac output, heart rate, arterial blood gases, and PBFdistribution were measured at each G level. Heterogeneity of PBFdistribution as measured by the coefficient of variation of PBFdistribution increased from 0.38 ± 0.05 to 0.55 ± 0.11 to0.72 ± 0.16 at 1, 2, and 3G_x, respectively. At 1G_x, PBF was greatest in theventral and cranial and lowest in the dorsal and caudal regions of thelung. With increased G_x,this gradient was augmented in both directions. Extrapolation of thesevalues to 0 G predicts a slight dorsal (nondependent) region dominanceof PBF and a coefficient of variation of 0.22 in microgravity. Analysisof variance revealed that a fixed component (vascular structure)accounted for 81% and nonstructure components (including gravity)accounted for the remaining 19% of the PBF variance across the entireexperiment (all 3 gravitational levels). The results are inconsistentwith the predictions of the zone model.