Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors

At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10-30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of similar to 2.0-2.5 degrees C, during daily fluctuations that often exceeded 15 degrees-20 degrees C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on 'habitat-level' measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially-and temporally-explicit field observations of body temperature

Paracellular absorption is relatively low in the herbivorous Egyptian spiny-tailed lizard, Uromastyx aegyptia

Extent: 9 p.Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, mediated transport and by nonspecific, passive, paracellular transport. Although it is apparent that paracellular absorption represents a significant route for nutrient absorption in many birds and mammals, especially small, flying species, its importance in ectothermic vertebrates has not previously been explored. Therefore, we measured fractional absorption (e) and absorption rate of three paracellular probes (arabinose, L-rhamnose, cellobiose) and of 3-O-methyl D-glucose (absorbed by both mediated and paracellular pathways) by the large herbivorous lizard, Uromastyx aegyptia, to explore the relative importance of paracellular and mediated transport in an ectothermic, terrestrial vertebrate. Fractional absorption of 3-O-methyl D-glucose was high (e = 0.7360.04) and similar to other vertebrates; e of the paracellular probes was relatively low (arabinose e = 0.3160.03, Lrhamnose e = 0.1960.02, and cellobiose e = 0.1460.02), and decreased with molecular mass, a pattern consistent with other vertebrates. Paracellular absorption accounted for approximately 24% of total 3-O-methyl D-glucose uptake, indicating low reliance on this pathway for these herbivorous lizards, a pattern similar to that found in other terrestrial vertebrates, and different from small flying endotherms (both birds and bats).Todd J. McWhorter, Berry Pinshow, William H. Karasov and Christopher R. Trac

New mediators in the biology of the ductus arteriosus:Lessons from the chicken embryo

The chicken embryo is an ideal model for the study of new hypotheses on the developmental biology of ductus arteriosus (DA). A unique characteristic of chicken DA is that it is the result of the fusion of two vessels with different embryological origins, morphologies, and functionalities. The pulmonary side (PulmDA) consists almost exclusively of neural crest-derived cells, shows the structure of a muscular artery, and responds to O2 with contraction whereas the aortic part is of mesodermal origin, shows the morphology of an elastic artery and relaxes in response to O2. In addition the two parts of the DA show marked differences in responsiveness to other contractile and relaxant agents. In mammals, the most accepted model of O2-induced DA constriction involves a rise in O2 modulating the function of the mitochondrial electron transport chain (the sensor), leading to an increased production of H2O2 (the mediator) that causes the inhibition of KV channels (the effector) with Rho kinase acting as another downstream effector of the O2-sensing system in the DA. In the chicken embryo, we verified the very same pathway, proving a conserved mechanism for O2 sensing/signaling in mammalian and nonmammalian DA. Moreover, we demonstrated a developmentally regulated response to O2, which is restricted to the mature PulmDA and involves parallel maturation of the three components: sensor, mediator, and effectors. Besides O2, we used the chicken embryo model to investigate the possible ductal effects of vasoactive mediators such as ceramide, H2S, isoprostanes, or platelet-derived vasoactive mediators