Preface: The phylogeny, fossil record and ecological diversity of ostracod crustaceans

After more than two centuries of research, more than 65,000 living and fossil ostracod species have been described and studied, yet much remains to be learned about this ancient, widespread and diverse group of bivalved arthropods. Their higher classification and phylogeny are subjects of vigorous debate, as is their position in the broader picture of crustacean phylogeny. At the same time, major advances in our understanding of ostracod lineages and their relationships are resulting from the application of innovative approaches and techniques. This preface provides a contextual overview of the 15 contributions to this volume, which resulted from the 14th International Symposium on Ostracoda (ISO2001) held in 2001at Shizuoka, Japan. As such it provides a cross-section of topics at the forefront of research on the evolution and diversity of Ostracoda, and indicates directions for future work.     

The Structure of the Bacterial Oxidoreductase Enzyme DsbA in Complex with a Peptide Reveals a Basis for Substrate Specificity in the Catalytic Cycle of DsbA Enzymes

Oxidative protein folding in Gram-negative bacteria results in the formation of disulfide bonds between pairs of cysteine residues. This is a multistep process in which the dithiol-disulfide oxidoreductase enzyme, DsbA, plays a central role. The structure of DsbA comprises an all helical domain of unknown function and a thioredoxin domain, where active site cysteines shuttle between an oxidized, substrate-bound, reduced form and a DsbB-bound form, where DsbB is a membrane protein that reoxidizes DsbA. Most DsbA enzymes interact with a wide variety of reduced substrates and show little specificity. However, a number of DsbA enzymes have now been identified that have narrow substrate repertoires and appear to interact specifically with a smaller number of substrates. The transient nature of the DsbA-substrate complex has hampered our understanding of the factors that govern the interaction of DsbA enzymes with their substrates. Here we report the crystal structure of a complex between Escherichia coli DsbA and a peptide with a sequence derived from a substrate. The binding site identified in the DsbA-peptide complex was distinct from that observed for DsbB in the DsbA-DsbB complex. The structure revealed details of the DsbA-peptide interaction and suggested a mechanism by which DsbA can simultaneously show broad specificity for substrates yet exhibit specificity for DsbB. This mode of binding was supported by solution nuclear magnetic resonance data as well as functional data, which demonstrated that the substrate specificity of DsbA could be modified via changes at the binding interface identified in the structure of the complex.     

Living males of the 'ancient asexual' Darwinulidae (Ostracoda: Crustacea)

Three living male darwinulid ostracods of a new species of the genus Vestalenula have been found in Yakushima, Japan. This is the first report of living darwinulid males for over 100 years and their morphology casts doubt on the two previous records from the late 1800' s. The presence of male darwinulids also calls into question the hypothesis that the family Darwinulidae is an exclusively ancient asexual group, reproducing without sex for over 200 million years (Myr). Male carapaces are of similar size and shape to A-1 juvenile females of the same species, suggesting that males may have been dismissed as A-1 juveniles in other living and fossil species. The antennae and fifth limbs are sexually dimorphic: the male antennae have six segments compared with five in the female and a series of putative chemical receptors originating at the extra segment boundary, while the male fifth limbs have well-developed grasping hooks, as in males of many ostracod groups. The lack of Zenker's Organ and of complex internal structures within the hemipenis contradicts previous hypotheses of the phylogenetic position of darwinulids.     

Dual inhibition of alpha/beta-hydrolase domain 6 and fatty acid amide hydrolase increases endocannabinoid levels in neurons

Agonists at cannabinoid receptors, such as the phytocannabinoid Δ(9)-tetrahydrocannabinol, exert a remarkable array of therapeutic effects but are also associated with undesirable psychoactive side effects. Conversely, targeting enzymes that hydrolyze endocannabinoids (eCBs) allows for more precise fine-tuning of cannabinoid receptor signaling, thus providing therapeutic relief with reduced side effects. Here, we report the development and characterization of an inhibitor of eCB hydrolysis, UCM710, which augments both N-arachidonoylethanolamine and 2-arachidonoylglycerol levels in neurons. This compound displays a unique pharmacological profile in that it inhibits fatty acid amide hydrolase and α/β-hydrolase domain 6 but not monoacylglycerol lipase. Thus, UCM710 represents a novel tool to delineate the therapeutic potential of compounds that manipulate a subset of enzymes that control eCB signaling.     

Wild gregarious settlements of Ostrea edulis in a semi‐enclosed sea lough: a case study for unassisted restoration

Ostrea edulis was once prolific throughout Europe and considered as the continent's native oyster. However, O. edulis currently exists in small fragmented assemblages where natural unaided recovery is rarely encountered. This research identified the small semi‐enclosed sea Lough of Strangford on the northeast coast of Northern Ireland as one of the few locations within Europe where the native oyster displayed gregarious natural rejuvenation. On close examination, four influential parameters appeared to assist in concentrated settlement; raised topographical cultch formations, shell coverage, the number of fecund in situ adults, and site protection. If these components were to be combined and managed as part of reintroduction and restoration initiatives, high‐density settlements and self‐sustaining populations may be possible. The research also identified that unregulated harvesting of intertidal O. edulis assemblages has the potential to seriously hinder natural recoveries. Indeed, the findings suggest that a review of policy in regards to intertidal hand gathering is necessary. However, naturally occurring high‐density settlements recorded during this research should be inspirational to all involved in the restoration of the native oyster.     

Successful immunotherapy with matrix metalloproteinase-derived peptides in adjuvant arthritis depends on the timing of peptide administration

We have recently found that matrix metalloproteinases (MMPs) are targets for T-cell and B-cell reactivity in experimental arthritis. In the present article, we investigate whether modulation of MMP-specific T-cell responses could influence the course of adjuvant arthritis (AA). Lewis rats were treated nasally with MMP peptides prior to or after AA induction. Administration of the MMP-10 or the MMP-16 peptide prior to AA induction reduced the arthritic symptoms. In contrast, administration of the MMP-10 peptide after AA induction aggravated the arthritic symptoms. The present study shows the possible usefulness of MMP peptides for immunotherapy. However, a clear understanding of proper timing of peptide administration is crucial for the development of such therapies.     

A lactational study of the composition and integrity of casein micelles from the milk of the tammar wallaby (Macropus eugenii)

The amount of casein found in the milk of the tammar wallaby increases as lactation progresses. The increase is due to increasing amounts of β-casein; the α-casein remains largely constant. The α-casein is the more highly phosphorylated; the most abundant form is the 10-P, throughout lactation. The level of phosphorylation of β-casein shifts to lower average values in late lactation, possibly indicating the enzymatic reaction is overloaded by the increasing amounts of β-casein. Unlike bovine casein micelles, the wallaby micelles are not completely disrupted at pH 7.0 by sequestration of their calcium content with ethylene diamine tetraacetic acid (EDTA). Complete disruption only follows the addition of sodium dodecyl sulphate, indicating considerably greater importance for hydrophobic bonds in maintaining their integrity. This micellar behaviour indicates that, despite the evolutionary divergence of marsupials millennia ago, the caseins of wallaby milk assemble into micelles in much the same fashion as in bovine milk.