Feeding by Priapulus caudatus (Cephalorhyncha: Priapulidae): observations of the effects of seasonal temperature change and molting

The ecdysozoan Priapulus caudatus belongs to a phylum of exclusively marine worms that reigned among the most abundant benthic metazoans during the Cambrian. Usually found at great depths, this species can occasionally be found among intertidal habitats fed by exceptionally cold sea water and predominated by soft mud, as in the Lower Bay of Fundy. Live priapulids were collected there and the effects of molting and seasonally changing ambient sea water temperature on feeding were observed in the laboratory beginning in February. Feeding increased as ambient sea water temperatures increased from March through April, a relationship significantly correlated (p < 0.001). This association rapidly deteriorated once 11 °C was reached in May with no animals feeding above 13 °C. Priapulids fed until the first molt day when feeding significantly decreased (p = 0.016). This response was short-lived, and feeding slowly resumed among animals within a week post-molt. Exuvia were not consumed. The onset of molting followed color changes in cuticle appearance and was significantly correlated with increasing temperature (p < 0.001). Molting was rapid, with the exuviae clearly separated from the new cuticle within 24 h at places where the process began. Without substrate to burrow into, animals emerged from shed exuviae between 3 and 29 days, with larger animals taking longer. While the cold deep-sea is the primary habitat of P. caudatus, this species shares some of the effects of temperature and molting on feeding shown by other ecdysozoans. The observations made during this study place a limit on where P. caudatus might be found intertidally.     

An activity associated with human chromosome 21 permits nuclear colocalization of the adenovirus E1B-55K and E4orf6 proteins and promotes viral late gene expression

The adenovirus E1B-55K and E4orf6 proteins cooperate during virus infection while performing several tasks that contribute to a productive infection, including the selective nucleocytoplasmic transport of late viral mRNA. Previous studies have shown that the E4orf6 protein retains the E1B-55K protein in the nucleus of human and monkey cells, but not in those of rodents, suggesting that primate-specific cellular factors contribute to the E4orf6-mediated retention of the E1B-55K protein in the nucleus. In an effort to identify these proposed primate-specific cellular factors, the interaction of the E1B-55K and E4orf6 proteins was studied in a panel of stable human-rodent monochromosomal somatic cell hybrids. Analysis of this panel of cell lines has demonstrated the existence of an activity associated with human chromosome 21 that permits the E1B-55K and E4orf6 proteins to colocalize in the nucleus of a rodent cell. Additional hybrid cells bearing portions of human chromosome 21 were used to map this activity to a 10-megabase-pair segment of the chromosome, extending from 21q22.12 to a region near the q terminus. Strikingly, this region also facilitates the expression of adenovirus late genes in a rodent cell background while having little impact on the expression of early viral genes.     

Fluorescence in situ hybridization analysis of hindgut bacteria associated with the development of equine laminitis

Carbohydrate-induced laminitis in horses is characterized by marked changes in the composition of the hindgut microbiota, from a predominantly Gram-negative population to one dominated by Gram-positive bacteria. The objective of this study was to monitor changes in the relative abundance of selected hindgut bacteria that have previously been implicated in the pathophysiology of equine laminitis using fluorescence in situ hybridization (FISH). Caecal cannulae were surgically implanted in five Standardbred horses and laminitis induced by oral administration of a bolus dose of oligofructose. Caecal fluid and faecal specimens were collected over a 48 h period at 2 to 4 h intervals post-oligofructose administration and subjected to FISH using probes specific for nine bacterial groups to determine changes in their relative abundance compared with total bacteria hybridizing to the generic EUBMIX probe. Additionally, hoof biopsies were taken over the course of the experiment at 6 h intervals and evaluated for histopathological changes consistent with laminitis, allowing changes in hindgut microbiota to be correlated with the onset of lesions in the foot. Of the microorganisms specifically targeted, streptococci of the Streptococcus bovis/equinus complex were the only bacteria that consistently proliferated in both caecal fluid and faeces immediately before the onset of histological signs of laminitis. Furthermore, lactobacilli, Enterobacteriaceae, Allisonella histaminiformans, enterococci, Bacteroides fragilis, Mitsuokella jalaludinii and Clostridium difficile did not establish significant populations in the hindgut before the onset of equine laminitis.     

A cyclooxygenase-2/prostaglandin E2 pathway augments activation-induced cytosine deaminase expression within replicating human B cells

Within inflammatory environments, B cells encountering foreign or self-Ag can develop tertiary lymphoid tissue expressing activation-induced cytosine deaminase (AID). Recently, this DNA-modifying enzyme was detected in nonlymphoid cells within several inflamed tissues and strongly implicated in malignant transformation. This study examines whether a cyclooxygenase 2 (COX-2) pathway, often linked to inflammation, influences AID expression in activated B lymphocytes. In this paper, we report that dividing human B cells responding to surrogate C3d-coated Ag, IL-4, and BAFF express AID, as well as COX-2. A progressive increase in AID with each division was paralleled by a division-related increase in a COX-2-linked enzyme, microsomal PGE(2) synthase-1, and the PGE(2)R, EP2. Cells with the greatest expression of AID expressed the highest levels of EP2. Although COX-2 inhibitors diminished both AID expression and IgG class switching, exogenous PGE(2) and butaprost, a selective EP2 agonist, augmented AID mRNA/protein and increased the numbers of IgG(+) progeny. Despite the latter, the proportion of IgG(+) cells within viable progeny generally declined with PGE(2) supplementation. This was not due to PGE(2)-promoted differentiation to plasma cells or to greater downstream switching. Rather, because phosphorylated ataxia telangiectasia mutated levels were increased in progeny of PGE(2)-supplemented cultures, it appears more likely that PGE(2) facilitates AID-dependent DNA double-strand breaks that block B cell cycle progression or promote activation-induced cell death, or both. Taken together, the results suggest that a PGE(2) feed-forward mechanism for augmenting COX-2 pathway proteins promotes progressively increased levels of AID mRNA, protein, and function.     

The function of the yeast molecular chaperone Sse1 is mechanistically distinct from the closely related hsp70 family

The Sse1/Hsp110 molecular chaperones are a poorly understood subgroup of the Hsp70 chaperone family. Hsp70 can refold denatured polypeptides via a C-terminal peptide binding domain (PBD), which is regulated by nucleotide cycling in an N-terminal ATPase domain. However, unlike Hsp70, both Sse1 and mammalian Hsp110 bind unfolded peptide substrates but cannot refold them. To test the in vivo requirement for interdomain communication, SSE1 alleles carrying amino acid substitutions in the ATPase domain were assayed for their ability to complement sse1Delta yeast. Surprisingly, all mutants predicted to abolish ATP hydrolysis (D8N, K69Q, D174N, D203N) complemented the temperature sensitivity of sse1Delta and lethality of sse1Deltasse2Delta cells, whereas mutations in predicted ATP binding residues (G205D, G233D) were non-functional. Complementation ability correlated well with ATP binding assessed in vitro. The extreme C terminus of the Hsp70 family is required for substrate targeting and heterocomplex formation with other chaperones, but mutant Sse1 proteins with a truncation of up to 44 C-terminal residues that were not included in the PBD were active. Remarkably, the two domains of Sse1, when expressed in trans, functionally complement the sse1Delta growth phenotype and interact by coimmunoprecipitation analysis. In addition, a functional PBD was required to stabilize the Sse1 ATPase domain, and stabilization also occurred in trans. These data represent the first structure-function analysis of this abundant but ill defined chaperone, and establish several novel aspects of Sse1/Hsp110 function relative to Hsp70.     

Surface expression of Bcl-2 in chronic lymphocytic leukemia and other B-cell leukemias and lymphomas without a breakpoint t(14;18)

Since its discovery in follicular lymphoma cells at the breakpoint t(14;18), Bcl-2 has been studied extensively in many basic and clinical science settings. Bcl-2 can locate as an integral mitochondrial membrane component, where its primary role is to block apoptosis by maintaining membrane integrity. Here we show that Bcl-2 also can position on the outer cell surface membrane of B cells from patients with chronic lymphocytic leukemia (B-CLL) and certain other leukemias that do not classically possess the chromosomal breakpoint t(14;18). Although low levels of Bcl-2 can be detected on the surface membrane of apparently healthy leukemic and normal B cells, expression of Bcl-2 correlates best with spontaneous or induced apoptosis. Notably, upon induction of apoptosis, B-CLL cells were much more efficient in upregulating surface Bcl-2 than normal B cells. It is not clear if this surface membrane expression is a passive consequence of the apoptotic process or an active attempt by the B cell to abort cell death by stabilizing the plasma membrane.