Trilobites Calmoniidae de l'Ordovicien supérieur du Maroc et les origines de la Province Malvino-Cafre

A re-examination of the trilobite Baniaspis globosa Destombes (Phacopina) from the Ashgill of the Anti-Atlas (Morocco) shows that it has several derived characters which allow us to classify it in the family Calmoniidae. Calmoniids were characteristic members of the Malvino-Kaffric province during the Lower Devonian. Hence we regard the origins of this palaeogeographic province as located on the northern Gondwanan margin as early as Ashgill, or even Caradoc, times. We agree with those authors who have suggested that the trilobite associations present in the Anti-Atlas, the Montagne Noire (France) and Bohemia during the earlier Ordovician argue against the existence of a 'proto-Tethys' ocean.     

Replacement of potassium ions by ammonium ions in different micro-organisms grown in potassium-limited chemostat culture

The biomass concentration extant in potassiumlimited cultures of either Klebsiella pneumoniae or Bacillus stearothermophilus (when growing at a fixed temperature and dilution rate in a glucose/ammonium salts medium) increased progressively as the medium pH value was raised step-wise from 7.0 to 8.5. Because the macromolecular composition of the organisms did not vary significantly, this increase in biomass could not be attributed to an accumulation of storage-type polymers but appeared to reflect a pH-dependent decrease in the cells' minimum K⁺ requirement. Significantly, this effect of pH was not eviden with cultures in which no ammonium salts were present and in which either glutamate or nitrate was added as the sole nitrogen source; however, it was again manifest when various concentrations of NH₄Cl were added to the glutamate-containing medium. This suggested a functional replacement of K⁺ by NH ₄ ⁺ , a proposition consistent with the close similarity of the ionic radii of the potassium ion (1.33 Å) and the ammonium ion (1.43 Å). At pH 8.0, and with a medium containing both glutamate (30 mM) and NH₄Cl (100 mM), cultures of B. stearothermophilus would grow without added potassium at a maximum rate of 0.7 h^-1. Under these conditions the cells contained maximally 0.1% (w/w) potassium (derived from contaminating amounts of this element in the medium constituents), a value which should be compared with one of 1.4% (w/w) for cells growing in a potassiumlimited medium containing initially 0.5 mM K⁺. Qualitatively similar findings were made with cultures of K. pneumoniae; and whereas one may not conclude that NH ₄ ⁺ can totally replace K⁺ in the growth of these bacteria, it can clearly do so very extensively.     

Cyclosporin A inhibits IL 2-driven proliferation of human alloactivated T cells

The influence of cyclosporin A (CsA) on the interleukin 2 (IL 2)-driven proliferation of allo-activated human T lymphocytes has been studied. CsA (50, 100, and 250 ng/ml) appeared to affect the IL 2-driven proliferation. The impaired proliferation could not be reversed with exogenous interferon-gamma. The doubling time of the cell populations appeared to increase with higher CsA doses. The cytotoxic capacity of the cells was also strongly inhibited by CsA. The cells regained proliferative and cytotoxic properties after CsA has been removed and cells were additionally cultured in normal medium. The data strongly suggest that CsA has an inhibitory influence on essential basic processes in T cells.     

Un biofacies à Trilobites Homalonotidae dans I'Ordovicien de la marge nord-gondwanienne: implications paléobiologiques et paléogéographiques

During the Llandeilo, the sandy lithological units which develop locally in the Armorican Massif, Spain and Morocco, are all characterized by similar trilobite associations in which endobenthic homalonotids. well adapted to shallow water and sandy substrate, are predominant. During the Llandeilo, on the northern Gondwanan margin, the wide geographical distribution of most of the trilobites, controlled by environmental factors, shows that the existence of a 'Proto-Tethys' ocean is unlikely. □ North Gondwana, Trilobita, Homalonotidae, Ordovician, Llandeilo. palaeoenvironment.     

Interleukin-6 administration has no acute hemodynamic or hematologic effect in the dog

To investigate the possible hemodynamic effects of interleukin-6 (IL-6), a single dose of 15 mcg/kg of recombinant IL-6 isolated from Escherichia coli was injected intravenously in six pentobarbital-anesthetized dogs. After 30 min, saline infusion was performed to maintain the pulmonary artery balloon-occluded pressure at baseline level. The animals were observed for up to 5 hours. No other hemodynamic alteration was observed than a gradual decline in cardiac output attributed to anesthesia. Hematologic variables, blood glucose, and total serum proteins were also constant. IL-6 levels were markedly elevated in the blood, but no tumor necrosis factor activity was detected. Thus a primary role for IL-6 in the early cardiovascular alterations associated with septic shock seems unlikely.     

Functional involvement of calcium in the homologous up-regulation of the 1,25-dihydroxyvitamin D3 receptor in osteoblast-like cells

In several cell types 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) causes up-regulation of its receptor. The present study demonstrates that in the osteoblast-like cell line UMR 106 this up-regulation is inhibited by two different calcium channel blockers (nitrendipine, verapamil). Also with chelating extracellular calcium (EGTA) and by inhibition of calcium release from intracellular stores (TMB-8) comparable results were obtained. These findings indicate that calcium is functionally involved in this cellular response to the steroid hormone 1,25(OH)₂D₃. Moreover, data obtained with EGTA show that the 1,25(OH)₂D₃ receptor level is closely regulated by the extracellular calcium concentration.     

Lipopolysaccharide-binding protein is vectorially secreted and transported by cultured intestinal epithelial cells and is present in the intestinal mucus of mice

Lipopolysaccharide-binding protein (LBP) is an important modulator of the host's response to endotoxin. In a previous study, we found evidence for the synthesis of LBP by intestinal epithelial cells. In this study, we explored the polarity of LBP secretion by these cells. Polarized monolayers of Caco-2 cells were used as intestinal mucosa model. Cells were stimulated apically or basally with cytokines, and LBP secretion was analyzed. Furthermore, the presence of LBP in intestinal mucus of healthy and endotoxemic mice was studied using a mucus-sampling technique. The constitutive unipolar LBP secretion from the apical cell surface was markedly enhanced when cells were exposed to cytokines at their apical surface. However, bioactive LBP was secreted from both cell surfaces after basolateral stimulation of cells. Cytokines also influenced the secretion of the acute phase proteins serum amyloid A, apoA-I, and apoB from both surfaces of Caco-2 cells. Furthermore, transport of exogenous LBP from the basolateral to the apical cell surface was demonstrated. In line with these in vitro data, the presence of LBP in intestinal mucus was strongly enhanced in mice after a challenge with endotoxin. The results indicate that LBP is present at the mucosal surface of the intestine, a phenomenon for which secretion and transport of LBP by intestinal epithelial cells may be responsible.     

Cutting edge: cationic antimicrobial peptides block the binding of lipopolysaccharide (LPS) to LPS binding protein

We investigated the mechanism by which cationic antimicrobial peptides block the activation of macrophages by LPS. The initial step in LPS signaling is the transfer of LPS to CD14 by LPS binding protein (LBP). Because many cationic antimicrobial peptides bind LPS, we asked whether these peptides block the binding of LPS to LBP. Using an assay that measures the binding of LPS to immobilized LBP, we show for the first time that a variety of structurally diverse cationic antimicrobial peptides block the interaction of LPS with LBP. The relative ability of different cationic peptides to block the binding of LPS to LBP correlated with their ability to block LPS-induced TNF-alpha production by the RAW 264.7 macrophage cell line.     

Regulation of lipopolysaccharide-induced NO synthase expression in the major organs in a mouse model. The roles of endogenous interferon-gamma, tumor necrosis factor-alpha and interleukin-10

Elevated NO production mediated by activation of the enzyme iNOS is thought to play a central role in the development of tissue damage observed during septic shock. IFN-gamma, TNF-alpha and IL-10 have been shown to be involved in the regulation of LPS-induced serum levels of the NO-oxidation products nitrate and nitrite. Therefore, in the present study, we investigated the role of endogenous IFN-gamma, TNF-alpha and IL-10 in the regulation of LPS-induced tissue iNOS expression in the major organs. To this end, mice were pre-treated with anti-IFN-gamma, anti-TNF-alpha, anti-IL-10 monoclonal antibodies, or combinations of these, two hours before intraperitoneal LPS-challenge. Immunohistochemical staining for iNOS and determination of iNOS activity indicated that iNOS expression was mainly upregulated in the small intestine, lung and heart, and that IFN-gamma, TNF-alpha as well as IL-10 are involved in the regulation of iNOS expression and enzyme activity. Whereas blocking either IFN-gamma or TNF-alpha did not affect iNOS expression, iNOS enzymatic activity seems to be inhibited. In contrast, blocking both mediators nearly completely prevents iNOS expression after LPS challenge, suggesting that the presence of either IFN-gamma or TNF-alpha is essential for LPS-induced iNOS expression in these organs. Combined treatment of these monoclonal antibodies revealed that whereas on the one hand IL-10 inhibits LPS-induced iNOS expression, on the other hand IL-10 or an IL-10 inducible factor is also involved in the upregulation of iNOS expression after LPS challenge.