Epithelial cell adhesion molecule (Ep-CAM) modulates cell-cell interactions mediated by classic cadherins

The contribution of noncadherin-type, Ca2+-independent cell-cell adhesion molecules to the organization of epithelial tissues is, as yet, unclear. A homophilic, epithelial Ca2+-independent adhesion molecule (Ep-CAM) is expressed in most epithelia, benign or malignant proliferative lesions, or during embryogenesis. Here we demonstrate that ectopic Ep-CAM, when expressed in cells interconnected by classic cadherins (E- or N-cadherin), induces segregation of the transfectants from the parental cell type in coaggregation assays and in cultured mixed aggregates, respectively. In the latter assay, Ep-CAM-positive transfectants behave like cells with a decreased strength of cell-cell adhesion as compared to the parental cells. Using transfectants with an inducible Ep-CAM-cDNA construct, we demonstrate that increasing expression of Ep-CAM in cadherin-positive cells leads to the gradual abrogation of adherens junctions. Overexpression of Ep-CAM has no influence on the total amount of cellular cadherin, but affects the interaction of cadherins with the cytoskeleton since a substantial decrease in the detergent-insoluble fraction of cadherin molecules was observed. Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM. While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases. As the cadherin-mediated cell-cell adhesions diminish, Ep-CAM-mediated intercellular connections become predominant. An adhesion-defective mutant of Ep-CAM lacking the cytoplasmic domain has no effect on the cadherin-mediated cell-cell adhesions. The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.     

B30.2-like domain proteins: update and new insights into a rapidly expanding family of proteins

The B30.2 domain is a conserved region of around 170 amino acids associated with several different protein domains, including the immunoglobulin folds of butyrophilin and the RING finger domain of ret finger protein. We recently reported several novel members of this family as well as previously undescribed protein families possessing the B30.2 domain. Many proteins have subsequently been found to possess this domain, including pyrin/marenostrin and the midline 1 (MID1) protein. Mutations in the B30.2 domain of pyrin/marenostrin are implicated in familial Mediterranean fever, and partial loss of the B30.2 domain of MID1 is responsible for Opitz G/BBB syndrome, characterized by developmental midline defects. In this study, we scrutinized the available sequence data bases for the identification of novel B30.2 domain proteins using highly sensitive database-searching tools. In addition, we discuss the chromosomal localization of genes in the B30.2 family, since the encoded proteins are likely to be involved in other forms of periodic fever, autoimmune, and genetic diseases.     

Auditory sustained attention is a marker of unilateral spatial neglect

The relationships between performance on a non-spatially-lateralized measure of sustained attention and spatial bias on tests sensitive to unilateral neglect were considered in a group of 44 patients with right hemisphere lesions following stroke. As predicted from earlier studies showing a strong association between unilateral spatial neglect and sustained attention, performance on a brief and monotonous tone-counting measure formed a significant predictor of spatial bias across a variety of measures of unilateral visual neglect. This study provides further evidence for a very close link between two attentional systems hitherto regarded as being quite separate, namely a spatial attention system implicated in unilateral neglect and a sustained attention system. A close connection between these two systems was predicted by Posner, who argued that the right hemisphere-dominant sustained attention system provides a strong modulatory influence on the functioning of the lateralized posterior attention system.     

Characterisation of G serotype dependent non-antibody inhibitors of rotavirus in normal mouse serum

Serotype specific (non-immunoglobulin) inhibitors of rotavirus have been identified in normal mouse serum obtained from BALB/c, CBA, and BL10 mice. Sialic acid was essential for the neutralising activity sera treated with the neuraminidase from Vibrio cholerae failed to neutralise rotavirus. G serotypes 4, 5, 7, 8, 9, and 10 were unaffected by the inhibitor(s) while G serotypes 1, 2, 6 and two G3 strains were neutralised to significant titres. Assessment of neutralisation of reassortants suggested that VP7 is the virus protein involved in the interaction although it remains possible that VP7 is influencing VP4 binding. Analysis of the sera by Western blot followed by virus overlay confirmed that binding is dependent on the presence of sialic acid. The human strain tested, Wa, bound to two (glyco) proteins (50 and 80 kDa) while the bovine strains tested, NCDV and UK bound to one (55 kDa) and two (36 and 55 kDa) proteins respectively. This indicates that while the bovine rotaviruses may bind to a common element, the human strain binds to clearly distinct proteins. We propose that these inhibitors interact with animal rotaviruses in a manner analogous to that by which they attach to target cells. The glycoprotein to which NCDV bound was purified and identified by N-terminal sequencing as murine alpha-1-anti-trypsin (MuAAT) and was confirmed to possess both neutralisation and anti-trypsin activity. Since MuAAT is known to possess only three N-linked glycans, identification and analysis of the actual virus-binding structure should now be possible.     

Inhibition of Toxoplasma gondii replication in IFN-gamma-activated human intestinal epithelial cells

A therapeutic trial, involving 130 Schistosoma mansoni-infected children, with no previous history of antischistosomal treatment, was carried out to evaluate the efficacy of two different dose regimens of praziquantel. The study was carried out because low cure rates were described in this recently established (1990) S. mansoni focus in northern Senegal, following treatment with a standard dosage of 40 mg/kg. The subjects were randomly allocated into two groups: one group (1) received 40 mg/kg in one oral dose, the other group (2) was treated with two oral doses of 30 mg/kg at a 6-hr interval. Parasitologic examination and circulating anodic antigen (CAA) detection were performed before, 10 days, three, six, and 21 weeks after chemotherapy. No significant differences in cure rates were found between the two groups. Six weeks after treatment, 34% and 44% of the individuals were found to be stool negative in group 1 and group 2, respectively. However, only 10-15% became completely negative according to the serum CAA antigen assay. Mean egg counts were reduced by 99% in both groups. Antigen detection confirmed the parasitologic results. Fewer side effects were observed in the group treated with 2 x 30 mg/kg, which may be explained by split dosage administration. Our study shows that the low cure rates observed in this area could not be improved by using a higher dosage of praziquantel.     

A computational model for blood flow through highly curved arteries with asymmetric stenoses

In this paper, we develop a three dimensional model of blood flow through curved arteries with asymmetric stenoses. Firstly, the Navier-Stokes equations representing Newtonian flow are solved using PHOENICS, a computational fluid dynamics package which utilises the Finite Volume method of solution. The severity of the stenoses considered in this study vary from about 40% to about 70%. Subsequently, the model is solved for Reynolds numbers ranging from 100 to 1200. The pressure drop results show good agreement with published results. The results also show that stenoses on a bent artery has a significant effect on blood flow characteristics.