Marine meso-herbivore consumption scales faster with temperature than seaweed primary production, supplementary material

Respiration of ectotherms is predicted to increase faster with rising environmental temperature than photosynthesis of primary producers because of the differential temperature dependent kinetics of the key enzymes involved. Accordingly, if biological processes at higher levels of complexity are constrained by underlying metabolic functions food consumption by heterotrophs should increase more rapidly with rising temperature than photo-autoptrophic primary production. We compared rates of photosynthesis and growth of the benthic seaweed Fucus vesiculosus with respiration and consumption of the isopod Idotea baltica to achieve a mechanistic understanding why warming strengthens marine plant-herbivore interactions. In laboratory experiments thallus pieces of the seaweed and individuals of the grazer were exposed to constant temperatures at a range from 10 to 20°C. Photosynthesis of F. vesiculosus did not vary with temperature indicating efficient thermal acclimation whereas growth of the algae clearly increased with temperature. Respiration and food consumption of I. baltica also increased with temperature. Grazer consumption scaled about 2.5 times faster with temperature than seaweed production. The resulting mismatch between algal production and herbivore consumption may result in a net loss of algal tissue at elevated temperatures. Our study provides an explanation for faster decomposition of seaweeds at elevated temperatures despite the positive effects of high temperatures on algal growth.

Information content: assessing meso-scale structures in complex networks

We propose a novel measure to assess the presence of meso-scale structures in complex networks. This measure is based on the identi?cation of regular patterns in the adjacency matrix of the network, and on the calculation of the quantity of information lost when pairs of nodes are iteratively merged. We show how this measure is able to quantify several meso-scale structures, like the presence of modularity, bipartite and core-periphery con?gurations, or motifs. Results corresponding to a large set of real networks are used to validate its ability to detect non-trivial topological patterns.

Electrophysiological studies on rat dorsal root ganglion neurons after peripheral axotomy: Changes in responses to neuropeptides

The effect of three peptides, galanin, sulfated cholecystokinin octapeptide, and neurotensin (NT), was studied on acutely extirpated rat dorsal root ganglia (DRGs) in vitro with intracellular recording techniques. Both normal and peripherally axotomized DRGs were analyzed, and recordings were made from C-type (small) and A-type (large) neurons. Galanin and sulfated cholecystokinin octapeptide, with one exception, had no effect on normal C- and A-type neurons but caused an inward current in both types of neurons after sciatic nerve cut. In normal rats, NT caused an outward current in C-type neurons and an inward current in A-type neurons. After sciatic nerve cut, NT only caused an inward current in both C- and A-type neurons. These results suggest that (i) normal DRG neurons express receptors on their soma for some but not all peptides studied, (ii) C- and A-type neurons can have different types of receptors, and (iii) peripheral nerve injury can change the receptor phenotype of both C- and A-type neurons and may have differential effects on these neuron types.

Pax6 is essential for establishing ventral-dorsal cell boundaries in pituitary gland development

Pax6, a highly conserved member of the paired homeodomain transcription factor family that plays essential roles in ocular, neural, and pancreatic development and effects asymmetric transient dorsal expression during pituitary development, with its expression extinguished before the ventral → dorsal appearance of specific cell types. Analysis of pituitary development in the Small eye and Pax6 −/− mouse mutants reveals that the dorsoventral axis of the pituitary gland becomes ventralized, with dorsal extension of the transcriptional determinants of ventral cell types, particularly PFrk. This ventralization is followed by a marked decrease in terminally differentiated dorsal somatotrope and lactotrope cell types and a marked increase in the expression of markers of the ventral thyrotrope cells and SF-1-expressing cells of gonadotrope lineage. We suggest that the transient dorsal expression of Pax6 is essential for establishing a sharp boundary between dorsal and ventral cell types, based on the inhibition of Shh ventral signals.

TAFII mutations disrupt Dorsal activation in the Drosophila embryo

In this study, we present evidence that the Dorsal activator interacts with limiting amounts of the TFIID complex in the Drosophila embryo. In vitro transcription reactions and protein binding assays implicate the TAFII110 and TAFII60 subunits of the TFIID complex in contributing to Dorsal-mediated activation. Mutations in TAFII110 and TAFII60 result in altered patterns of snail and twist transcription in embryos derived from dl/+ females. These results suggest that TAFIIs contribute to the activation of transcription in vivo and support the hypothesis that subunits of TFIID may serve as targets of enhancer binding proteins.