Transcriptional profiling of the nucleus pulposus: say yes to notochord

This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord. Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement by non-notochordal cells.     

Normal thymic cortical epithelial cells developmentally regulate the expression of a B-lineage transformation-associated antigen

Nonlymphoid, stromal cells in the mouse thymus are believed to be important in T cell maturation and have been proposed to play a central role in the acquisition of major histocompatibility complex (MHC) restriction and self-tolerance by maturing thymocytes. Both cortical and medullary epithelial cells in the thymus express high levels of class II (A) major histocompatibility antigens (MHC Ags). We show here that a specific subset of these A^– epithelial cells express a transformation-associated antigen (6C3Ag) found previously on the surfaces of Abelson murine leukemia virus-transformed pre-B cells and on those bone marrow-derived stromal cell clones which support normal and preneoplastic pre-B cell proliferation. Among solid lymphoid organs, only the thymus contains 6C3Ag¹ cells and within the thymus, this antigen is found exclusively on A^– epithelial cells in cortical regions. It is striking that the expression of the 6C3Ag on thymic epithelium is developmentally regulated, suggesting a role for this lymphostromal antigen in the maturation of the thymic microenvironment.     

In Situ and in Vitro Binding of Natriuretic Peptide Hormones in Tradescantia multiflora

Abstract: An increasing body of evidence suggests that in plants, as in vertebrates, biologically active natriuretic peptide (NP) hormones play an important role in the regulation of the osmotic and ionic balance. The evidence includes isolation and immunoaffinity purification of biologically active natriuretic peptide analogues (irPNP) from ivy that promoted stomatal opening and specifically, rapidly and transiently increased cGMP levels in root conductive tissue. In this study we demonstrate that I¹²⁵-rat atrial natriuretic peptide (rANP) binds to plasma membranes from leaf and stem tissue of Tradescantia multiflora and importantly, both unlabelled rANP and irPNP can competitively displace that binding. In addition, tissue section autoradiography reveals specific in situ binding of I¹²⁵-rANP to leaf and stem tissue. The findings are consistent with the presence of a biologically active NP system in plants and suggest that NPs signal through a dedicated receptor system.     

Phosphatidylcholine breakdown in rat liver plasma membranes. Roles of guanine nucleotides and P2-purinergic agonists

Release of P-choline and choline from purified rat plasma membrane preparations was increased by GTP and its less hydrolyzable analogues, whereas other nucleotide triphosphates had little or no effect. Stimulation by guanosine 5'-(3-O-thiol)triphosphate (GTP gamma S) was dependent upon magnesium, inhibited by guanosine 5'-(2-O-thiol)diphosphate, and independent of calcium. ATP and ADP (1-100 microM) markedly enhanced the GTP gamma S stimulation of P-choline plus choline release but had no effect alone. ADP was as effective as ATP and nonhydrolyzable ATP analogues produced a similar or greater stimulation, whereas AMP and adenosine were much less effective. Vasopressin (0.1 microM) also produced a small stimulation. Under conditions in which protein kinase C was activated, PMA also stimulated the response to GTP gamma S but was ineffective in its absence. P-choline was the initial product which was hydrolyzed to choline. Guanine nucleotide and purinergic effects were also apparent on phosphatidylcholine degradation. EGTA, at 0.5 mM, completely removed purinergic stimulation but did not affect P-choline plus choline released in response to GTP gamma S alone. Prior treatment of plasma membranes with cholera toxin or prior injection of animals with islet-activating protein did not affect the stimulation of P-choline plus choline release either by GTP gamma S alone or by GTP gamma S plus ATP. These results indicate that a phosphatidylcholine phospholipase C is coupled to purinergic receptors in rat liver plasma membranes by a GTP-binding protein. Hydrolysis of phosphatidylcholine could contribute to hepatic diacylglycerol levels and thus influence protein kinase C activity.     

Biochemical similarity among serologically distinct flagellins of Campylobacter jejuni

Abstract We describe a simplified method for obtaining highly purified flagellin, suitable for biochemical analysis using HPLC-gel permeation. Amino acid composition and N-terminal sequence analyses were performed on flagellins from serologically distinct isolates. The amino acid composition of flagellin from 10 strains was very similar. The N-terminal amino acid sequence is highly conserved. Significant sequence homology was found with flagellin of Bacillus subtilis .