Antifreeze Proteins in the Arctic Shorthorn Sculpin (Myoxocephalus scorpius)

The plasma of shorthorn sculpin caught at Grise Fiord (Southern Ellesmere Island, arctic Canada) during late August contained antifreeze proteins which were essentially identical, with respect to molecular weight, number of components and amino acid composition, to the antifreeze proteins found in Newfoundland populations of shorthorn sculpin. The concentration of antifreeze protein in the plasma of the arctic sculpins during the summer was similar to that observed in the plasma of Newfoundland sculpin during the winter. The results suggest that unlike their Newfoundland counterparts, the plasma of sculpin residing in the High Arctic contains high concentrations of antifreeze protein all year round.Key words: shorthorn sculpin, Myoxocephalus scorpius, antifreeze protein

In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail

Magnetic reconnection is one of the most important processes in astrophysical, space and laboratory plasmas. Identifying the structure around the point at which the magnetic field lines break and subsequently reform, known as the magnetic null point, is crucial to improving our understanding reconnection. But owing to the inherently three-dimensional nature of this process, magnetic nulls are only detectable through measurements obtained simultaneously from at least four points in space. Using data collected by the four spacecraft of the Cluster constellation as they traversed a diffusion region in the Earth's magnetotail on 15 September, 2001, we report here the first in situ evidence for the structure of an isolated magnetic null. The results indicate that it has a positive-spiral structure whose spatial extent is of the same order as the local ion inertial length scale, suggesting that the Hall effect could play an important role in 3D reconnection dynamics.Comment: 14 pages, 4 figure

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Antifreeze Proteins in the Arctic Shorthorn Sculpin (Myoxocephalus scorpius)

The plasma of shorthorn sculpin caught at Grise Fiord (Southern Ellesmere Island, arctic Canada) during late August contained antifreeze proteins which were essentially identical, with respect to molecular weight, number of components and amino acid composition, to the antifreeze proteins found in Newfoundland populations of shorthorn sculpin. The concentration of antifreeze protein in the plasma of the arctic sculpins during the summer was similar to that observed in the plasma of Newfoundland sculpin during the winter. The results suggest that unlike their Newfoundland counterparts, the plasma of sculpin residing in the High Arctic contains high concentrations of antifreeze protein all year round.Key words: shorthorn sculpin, Myoxocephalus scorpius, antifreeze protein

Antifreeze protein dispersion in eelpouts and related fishes reveals migration and climate alteration within the last 20 Ma.

Antifreeze proteins inhibit ice growth and are crucial for the survival of supercooled fish living in icy seawater. Of the four antifreeze protein types found in fishes, the globular type III from eelpouts is the one restricted to a single infraorder (Zoarcales), which is the only clade know to have antifreeze protein-producing species at both poles. Our analysis of over 60 unique antifreeze protein gene sequences from several Zoarcales species indicates this gene family arose around 18 Ma ago, in the Northern Hemisphere, supporting recent data suggesting that the Arctic Seas were ice-laden earlier than originally thought. The Antarctic was subject to widespread glaciation over 30 Ma and the Notothenioid fishes that produce an unrelated antifreeze glycoprotein extensively exploited the adjoining seas. We show that species from one Zoarcales family only encroached on this niche in the last few Ma, entering an environment already dominated by ice-resistant fishes, long after the onset of glaciation. As eelpouts are one of the dominant benthic fish groups of the deep ocean, they likely migrated from the north to Antarctica via the cold depths, losing all but the fully active isoform gene along the way. In contrast, northern species have retained both the fully active (QAE) and partially active (SP) isoforms for at least 15 Ma, which suggests that the combination of isoforms is functionally advantageous

Helical Antifreeze Proteins Have Independently Evolved in Fishes on Four Occasions

<div><p>Alanine-rich α-helical (type I) antifreeze proteins (AFPs) are produced by a variety of fish species from three different orders to protect against freezing in icy seawater. Interspersed amongst and within these orders are fishes making AFPs that are completely different in both sequence and structure. The origin of this variety of types I, II, III and antifreeze glycoproteins (AFGPs) has been attributed to adaptation following sea-level glaciations that occurred after the divergence of most of the extant families of fish. The presence of similar types of AFPs in distantly related fishes has been ascribed to lateral gene transfer in the case of the structurally complex globular type II lectin-like AFPs and to convergent evolution for the AFGPs, which consist of a well-conserved tripeptide repeat. In this paper, we examine the genesis of the type I AFPs, which are intermediate in complexity. These predominantly α-helical peptides share many features, such as putative capping structures, Ala-richness and amphipathic character. We have added to the type I repertoire by cloning additional sequences from sculpin and have found that the similarities between the type I AFPs of the four distinct groups of fishes are not borne out at the nucleotide level. Both the non-coding sequences and the codon usage patterns are strikingly different. We propose that these AFPs arose via convergence from different progenitor helices with a weak affinity for ice and that their similarity is dictated by the propensity of specific amino acids to form helices and to align water on one side of the helix into an ice-like pattern.</p></div

Dot matrix comparisons of type I cDNAs from the four different groups of fishes.

<p>A line indicates a match of at least 9 out of 12 bases with red indicating a sense/antisense match. The blue bars denote the coding region (signal peptides excluded). These sequences correspond to those shown in Fig. 3.</p