The influence of cell surface properties of thermophilic streptococci on attachment to stainlesssteel

The quality of milk products is threatened by the formation of biofilms of thermophilicstreptococci on the internal surfaces of plate heat exchangers used in milk processing. Althoughattachment to stainless steel surfaces is one of the first stages in the development of a biofilm, themechanisms involved in attachment have not been reported. The cell surface properties of 12strains of thermophilic streptococci were examined to determine their importance in attachment tostainless steel surfaces. Hydrophobicity, extracellular polysaccharide production and cell surfacecharge varied between the different strains but could not be related to numbers attaching. Treatingthe cells with sodium metaperiodate, lysozyme or trichloroacetic acid to disrupt cell surfacepolysaccharide had no effect on attachment. Treatment with trypsin or sodium dodecyl sulphate toremove cell surface proteins resulted in a 100-fold reduction in the number of bacteria attaching.This result suggests that the surface proteins of the thermophilic streptococci are important intheir attachment to stainless steel.     

The generation and subsequent fate of glutathionyl radicals in biological systems

Horseradish peroxidase-catalyzed oxidation of p-phenetidine in the presence of either glutathione (GSH), cysteine, or N-acetylcysteine led to the production of the appropriate thioyl radical which could be observed using EPR spectroscopy in conjunction with the spin trap 5,5-dimethyl-1-pyrroline-N-oxide. This confirms earlier work using acetaminophen (Ross, D., Albano, E., Nilsson, U., and Moldéus, P. (1984) Biochem. Biophys. Res. Commun. 125, 109-115). The further reactions of glutathionyl radicals (GS.), generated during horseradish peroxidase-catalyzed oxidation of p-phenetidine and acetaminophen in the presence of GSH, were investigated by following kinetics of oxygen uptake and oxidized glutathione (GSSG) formation. Oxygen uptake and GSSG generation were dependent on the concentration of GSH but above that which was required for maximal interaction with the primary amine or phenoxy radical generated during peroxidatic oxidation of p-phenetidine or acetaminophen, suggesting that a secondary GSH-dependent process was responsible for oxygen uptake and GSSG production. GSSG was the only product of thiol oxidation detected during peroxidatic oxidation of p-phenetidine or acetaminophen in the presence of GSH, but under nitrogen saturation conditions its production was reduced to 8 and 33% of the corresponding amounts obtained under aerobic conditions in the cases of p-phenetidine and acetaminophen, respectively. Nitrogen saturation conditions did not affect horseradish peroxidase-catalyzed metabolism. This shows that the main route of GSSG generation in such reactions is not by dimerization of GS. but via mechanism(s) involving oxygen consumption such as via GSSG-. or via GSOOH.     

Is prostaglandin E the neural mediator of the febrile response? The case against a proven obligatory role.

We have reviewed the evidence in favor of a prostaglandin mediator of the thermal responses in fever and found that PGE injected into the hypothalamus does not always cause fever, that cerebrospinal fluid concentrations of PGE are not reliable reflections of hypothalamic events, and that antipyretic drugs may act in ways other than inhibiting PGE synthesis. Fever is not blocked by prostaglandin antagonists, nor by ablation of PGE-sensitive areas of the brain. There is poor correlation between the effects of pyrogens and of PGE on cerebral neurons. There is evidence that at least one prostanoid other than prostaglandin is a mediator of fever, but the prostanoid has not been identified yet. We conclude that PGE may contribute to the neural responses in fever but is not essential.     

Extracellular potassium concentration in normal and denervated hind limb muscles of the rat

K+-sensitive electrodes with a side pore were used for measuring extracellular potassium levels in control muscles and in the gastrocnemius, extensor digitorum and soleus muscles of the rat, one, 8 and 14 days after denervation. In all cases, the extracellular potassium level was close to 5 mmol.1-1. There were no substantial differences between muscles of different functional and morphological types and between control and denervated muscles. Elevated extracellular potassium cannot therefore be the reason for increased sensory outflow of impulses observed after motor denervation.     

Molecular mechanisms of ceramide-mediated CD95 clustering.

Receptor clustering has been suggested as a crucial mechanism to initiate receptor signaling. Here we show that ceramide in sphingolipid-rich membrane rafts mediates clustering of CD95. Neutralization of surface ceramide or inhibition of its endogenous generation prevented CD95 clustering. Furthermore, application of ceramide at the cell surface triggered clustering of active but not inactive CD95. Apoptosis was inhibited by neutralization of surface ceramide or inhibition of ceramide release in vitro and in vivo. Thus, we conclude that surface ceramide mediates CD95 clustering, which is required for initiation of apoptosis, at least in some cell types.     

Interferon and cytotoxic factor (cytotoxin) released in the blood of mice infected with Mycobacterium bovis BCG. III. Interferon and cytotoxin induced by the specific antigen as compared with those induced by bacterial lipopolysaccharide

The time course of development and decline of the ability of BCG-infected mice to produce interferon in the serum in response to the intravenous infection of purified protein derivative of tuberculin (PPD) was very similar to that of their systemic hypersensitivity to PPD. A cytotoxic factor (cytotoxin) was produced in parallel with interferon in the serum of BCG-infected mice after stimulation with PPD. The duration of the period in which cytotoxin-production responsiveness to PPD was definitely detectable was much shorter than that for interferon-production responsiveness although the periods for the maximum production of interferon and cytotoxin coincided. The kinetics of release of interferon in the serum of BCG-infected mice after stimulation with PPD did not parallel that of release of cytotoxin. The four kinds of activities, interferons and cytotoxins induced by PPD and lipopolysaccharide (LPS) in the serum of BCG-infected mice, were compared for their stability to heating at 56 C and to treatment at pH 2. The kinetics of inactivation of these four activities differed significantly, when the serum was either heated at 56 C or treated at pH 2. Interferon produced in response to LPS could be neutralized by anti-L cell(NDV) interferon rabbit serum as easily as L cell (NDV) interferon, 16 times as much antiserum was required to neutralize the same amount of interferon in response to PPD, but cytotoxins induced by PPD and LPS were not neutralized at all by the antiserum. From these findings it is thought likely that interferons and cytotoxins induced by PPD and LPS in the serum of BCG-infected mice are different substances, although the antigenic relationship between cytotoxins induced by PPD and LPS remains unknown.