Profiles of Alexandrium catenella cysts in Puget Sound sediments and the relationship to paralytic shellfish poisoning events

The magnitude of paralytic shellfish poisoning (PSP) toxins in shellfish and the geographical scope of shellfish closures in Puget Sound have increased in recent decades. PSP, monitored by the Washington Department of Health, has spread from Sequim Bay in the 1950s into central Puget Sound in the 1970s and throughout Puget Sound by the 1990s. Alexandrium catenella, the species responsible for PSP toxins, produces a benthic resting cyst that, upon germinating, can seed blooms. This study examined whether there is a relationship between profiles of cysts in the sediment and temporal variation in PSP in shellfish and if the history of the toxin's southward expansion through Puget Sound can be seen in the cyst record. To address this question, sediment cores were collected from three Puget Sound basins, Sequim Bay, Penn Cove, and Carr Inlet, and cyst profiles were determined. Activities of ²¹⁰Pb were fitted to a depth-dependent diagenetic model to date the sediment cores and determine mixing and sediment-accumulation rates. In order to compare historical variation in PSP with cyst profiles that have been altered by bioturbation, a depth and time-dependent diagenetic model was then used to predict vertical profiles of cysts that would occur under the assumption that cyst deposition rates are proportional to PSP concentration in shellfish measured over several decades at each site. The cyst profiles predicted by the model were compared to measured cyst profiles. These comparisons suggested that Alexandrium blooms and resulting PSP concentration in shellfish are more closely linked to cyst germination and deposition at some stations than at others. Sequim Bay had relatively large numbers of cysts and it is likely that the persistent toxicity here is the result of recurrent seeding from the cyst bed. Penn Cove and Carr Inlet had few cysts despite occasional blooms, suggesting that blooms are transported into those areas, perhaps from other sites of cyst germination. Sequim Bay and Penn Cove had cysts from top to bottom of the cores so it was not possible to determine the date when cysts were first introduced into these bays, but it is likely that A. catenella has been in Penn Cove since at least 1955 or for about two decades before the WDOH PSP toxicity data would indicate. The cyst profile in Carr Inlet suggested a first appearance date of 1985 that is consistent with the first appearance of PSP in shellfish in 1988.     

Enhanced reactivity to pain in patients with rheumatoid arthritis

Introduction  

Maladaptive physiological responses to stress appear to play a role in chronic inflammatory diseases such as rheumatoid arthritis (RA). However, relatively little stress research in RA patients has involved the study of pain, the most commonly reported and most impairing stressor in RA. In the present study, we compared psychophysical and physiological responses to standardized noxious stimulation in 19 RA patients and 21 healthy controls.     

Lytic transglycosylases: concinnity in concision of the bacterial cell wall

The lytic transglycosylases (LTs) are bacterial enzymes that catalyze the non-hydrolytic cleavage of the peptidoglycan structures of the bacterial cell wall. They are not catalysts of glycan synthesis as might be surmised from their name. Notwithstanding the seemingly mundane reaction catalyzed by the LTs, their lytic reactions serve bacteria for a series of astonishingly diverse purposes. These purposes include cell-wall synthesis, remodeling, and degradation; for the detection of cell-wall-acting antibiotics; for the expression of the mechanism of cell-wall-acting antibiotics; for the insertion of secretion systems and flagellar assemblies into the cell wall; as a virulence mechanism during infection by certain Gram-negative bacteria; and in the sporulation and germination of Gram-positive spores. Significant advances in the mechanistic understanding of each of these processes have coincided with the successive discovery of new LTs structures. In this review, we provide a systematic perspective on what is known on the structure–function correlations for the LTs, while simultaneously identifying numerous opportunities for the future study of these enigmatic enzymes.