Short-term changes in eating patterns explain the effects of condensed tannins on feed intake in heifers

Ingestion of condensed tannins decreases feed intake in ruminants. Polyethylene glycol (PEG) forms high-affinity complexes with tannins. In two experiments carried out on Holstein heifers, quebracho (Q) from the Aspidosperma quebracho served as source of condensed tannins. The aims of the study were (i) to quantify the effect of Q on feed intake and eating behaviour in cattle fed complete mixed diets (CMDs); (ii) to clarify if changes induced in ingestive behaviour and feed intake by Q in cattle can be reversed by feeding PEG; and (iii) to clarify if the decrease in feed intake is associated with short-term (astringency, post-ingestive malaise) or longer-term effects. In experiment 1, 500 g/day of Q was found to be the minimal dose that decreased feed intake in heifers. A ratio of PEG:Q equal to 1:12.5 did not fully restore feed intake. In experiment 2, four heifers received a random sequence of four rations in a Latin-square design with feeding cycles of ca. 7 days: CMD containing no supplements (C), or supplemented with 625 g/day of Q without PEG (Q), with 625 g/day of Q and 250 g/day of PEG (Q-PEG), or with 250 g/day of PEG without Q (PEG). Individual rations were continuously weighed in the trough and the behaviour of heifers was observed for 180 min after distribution of CMD. Overall, feeding Q was associated with lowered feed intake and shorter duration of eating bouts, mainly of the first eating bout, immediately after distribution of the diet. A larger portion of the diet was consumed subsequent to 180 min after distribution in Q-fed heifers. Eating rate and the water to food ratio were not affected by Q. The effects of Q on feed intake were attenuated by feeding PEG. Heifers adapted effectively to condensed tannins by increasing the number of eating bouts and the portion of diet consumed subsequent to 180 min after distribution, so that no differences in feed intake were noted on the last day of each feeding cycle. Data are interpreted to show that: (i) negative effects of Q on feed intake derive from astringency of CT and short-term post-ingestive malaise; (ii) the increased number of eating bouts and their wider partition throughout the day are means to preserve the ruminal environment in Q-fed heifers; (iii) PEG has the potential to neutralize negative effects of condensed tannins in cattle.     

Ribosomal crystallography: a flexible nucleotide anchoring tRNA translocation, facilitates peptide-bond formation, chirality discrimination and antibiotics synergism

The linkage between internal ribosomal symmetry and transfer RNA (tRNA) positioning confirmed positional catalysis of amino-acid polymerization. Peptide bonds are formed concurrently with tRNA-3' end rotatory motion, in conjunction with the overall messenger RNA (mRNA)/tRNA translocation. Accurate substrate alignment, mandatory for the processivity of protein biosynthesis, is governed by remote interactions. Inherent flexibility of a conserved nucleotide, anchoring the rotatory motion, facilitates chirality discrimination and antibiotics synergism. Potential tRNA interactions explain the universality of the tRNA CCA-end and P-site preference of initial tRNA. The interactions of protein L2 tail with the symmetry-related region periphery explain its conservation and its contributions to nascent chain elongation.     

From peptide-bond formation to cotranslational folding: dynamic, regulatory and evolutionary aspects

Ribosomes are ribozymes exerting substrate positioning and promoting substrate-mediated catalysis. Peptide-bonds are formed within a symmetrical region, thus suggesting that ribosomes evolved by gene-fusion. Remote interactions dominate substrate positioning at stereochemistry suitable for peptide-bond formation and elaborate architectural-design guides the processivity of the reaction by rotatory motion. Nascent proteins are directed into the exit tunnel at extended conformation, complying with the tunnel's narrow entrance. Tunnel dynamics facilitate its interactive participation in elongation, discrimination, cellular signaling and nascent-protein trafficking into the chaperon-aided folding site. Conformational alterations, induced by ribosomal-recycling factor, facilitate subunit dissociation. Remarkably, although antibiotics discrimination is determined by the identity of a single nucleotide, involved also in resistance, additional nucleotides dictate antibiotics effectiveness.     

Human mast cells release metalloproteinase-9 on contact with activated T cells: juxtacrine regulation by TNF-alpha

Mast cells, essential effector cells in allergic inflammation, have been found to be activated in T cell-mediated inflammatory processes in accordance with their residence in close physical proximity to T cells. We have recently reported that mast cells release granule-associated mediators and TNF-alpha upon direct contact with activated T cells. This data suggested an unrecognized activation pathway, where mast cells may be activated during T cell-mediated inflammation. Herein, we show that this cell-cell contact results in the release of matrix metalloproteinase (MMP)-9 and the MMP inhibitor tissue inhibitor of metalloproteinase 1 from HMC-1 human mast cells or from mature peripheral blood-derived human mast cells. The expression and release of these mediators, as well as of beta-hexosaminidase and several cytokines, were also induced when mast cells were incubated with cell membranes isolated from activated, but not resting, T cells. Subcellular fractionation revealed that the mature form of MMP-9 cofractionated with histamine and tryptase, indicating its localization within the secretory granules. MMP-9 release was first detected at 6 h and peaked at 22 h of incubation with activated T cell membranes, while TNF-alpha release peaked after only 6 h. Anti-TNF-alpha mAb inhibited the T cell membrane-induced MMP-9 release, indicating a possible autocrine regulation of MMP release by mast cell TNF-alpha. This cascade of events, whereby mast cells are activated by T cells to release cytokines and MMP-9, which are known to be essential for leukocyte extravasation and recruitment to affected sites, points to an important immunoregulatory function of mast cells within the context of T cell-mediated inflammatory processes.     

Ammonia transformations and abundance of ammonia oxidizers in a clay soil underlying a manure pond

Unlined manure ponds are constructed on clay soil worldwide to manage farm waste. Seepage of ammonia-rich liquor into underlying soil layers contributes to groundwater contamination by nitrate. To identify the possible processes that lead to the production of nitrate from ammonia in this oxygen-limited environment, we studied the diversity and abundance of ammonia-transforming microorganisms under an unlined manure pond. The numbers of ammonia-oxidizing bacteria and anammox bacteria were most abundant in the top of the soil profile and decreased significantly with depth (0.5 m), correlating with soil pore-water ammonia concentrations and soil ammonia concentrations, respectively. On the other hand, the numbers of ammonia-oxidizing archaea were relatively constant throughout the soil profile (10(7) amoA copies per g(soil)). Nitrite-oxidizing bacteria were detected mainly in the top 0.2 m. The results suggest that nitrate accumulation in the vadose zone under the manure pond could be the result of complete aerobic nitrification (ammonia oxidation to nitrate) and could exist as a byproduct of anammox activity. While the majority of the nitrogen was removed within the 0.5-m soil section, possibly by combined anammox and heterotrophic denitrification, a fraction of the produced nitrate leached into the groundwater.     

Purification of the gonadotropin-releasing hormone-degrading enzyme by affinity chromatography.

A crude preparation of Kallikrein inactivator, which inhibits the gonadotropin-releasing hormone (GnRH)-degrading enzyme(s) from rat hypothalamus and anterior pituitary, was fractionated by passage through an ion-exchange column. The enzyme-inhibiting fraction was coupled to Sepharose and the resin obtained was used for, affinity-chromatography purification of the GnRH-degrading enzyme. The enzyme from crude tissue preparations was retained on this column and eluted by 0.05 M phosphate buffer. A 9-12 fold increase in the specific activity of the enzyme was achieved. Bacitracin, an effective peptide inhibitor of the degradation of GnRH, was also coupled to Sepharose. Three different such Sepharose-bacitracin conjugates were synthesized, two of which inhibited the degradation of GnRH by hypothalamic and pituitary extracts. They all failed, however, to separate the active enzymic fraction from the bulk of accompanying proteins, using affinity chromatographic techniques.     

Multiplicity of affinity modification of RNAse during its alkylation with a reactive analog of 5-deoxyribonucleotide

The interaction of pancreatic RNase with 5'-deoxyribodinucleotide alkylating derivative, 4-(N-2-chloroethyl-N-methylamino)benzylamide of d(pTpA) d[(ClRCH2NH)pTpA], was studied. The unreactive oxyanalogue d[(HORCH2NH)pTpA] was shown to act as competitive inhibitor of cCMP hydrolysis by RNase. d[(ClRCH2NH)pTpA] irreversibly inactivated RNase. A protective effect was exerted by d(pTpA) and d[(HORCH2NH)pTpA]. The modification, although having an affinity character, was not accompanied by total inactivation of the enzyme. It was supposed that covalent bonding between the reagent and enzyme induced the dinucleotide displacement from the recognition site. The formation of four RNase monolabeled forms retaining the activity in the hydrolysis of cCMP and poly(U) was demonstrated.     

The interaction of PVP complexes of gossypol and its derivatives with an artificial membrane lipid matrix

In this paper, we present the results of a study on the membrane-active properties of gossypol, its derivatives and their polyvinylpyrrolidone complexes as assessed by differential scanning calorimetry and by the fluorescent probe method. The latter revealed the change in polarization of the incident radiation caused by the action of the polyphenol on the artificial membrane lipid matrix.