A reduced CP level without medicinal zinc oxide does not alter the intestinal morphology in weaned pigs 24 days post-weaning.

The use of medicinal zinc oxide (ZnO) to prevent diarrhoea post-weaning will be banned in the EU from 2022. Therefore, new alternatives are needed to avoid an increase in diarrhoea and higher antibiotic use. A low dietary CP level has shown to lower the frequency of diarrhoea in pigs, due to lower microbial protein fermentation in the colon as well as improved conditions in the small intestine after weaning. The objective of this study was to examine the effect of decreased CP levels post-weaning as an alternative to medicinal ZnO on gut morphology and histopathology. Five hundred and sixty pigs were randomly assigned into one of six groups receiving a two-phase diet from 5.5 to 15 kg: positive control group (PC) with medicinal ZnO and standard levels of protein (19.1-18.4% CP), negative control group (NC) without medicinal ZnO and standard levels of protein (19.1-18.4% CP). The remaining four low protein groups were a low-standard (LS) CP level (16.6-18.4% CP), a low-low (LL) CP level (16.6-16.2% CP), a very low-high (VLH) CP level (14-19.3% CP) and a very low-medium (VLM) CP level (14-17.4% CP). Individual BW was recorded at day 0, 10 and 24 post-weaning, and all antibiotic treatments were recorded. Tissue samples from the small intestine (mid-jejunum) for morphological and histopathologic analysis, organ weights, blood and urine samples were collected at day 10 and 24 post-weaning from a total of 90 sacrificed weaners. The results demonstrated no differences in intestinal morphology between groups, but the histopathology showed a damaged brush border score in VLM and VLH pigs . In addition, a lower blood urea nitrogen in VLM pigs at 24 days was found. The LL and VLM pigs had a significantly decreased average daily gain in the overall trial period compared to PC and NC pigs. Conclusively, intestinal brush border was damaged by the very low protein diet at 24 days post-weaning, but intestinal morphology was unaffected by dietary strategy.

Calcium ion binding to clinically relevant chemical modifications of human serum albumin.

Calcium binding to glycated, penicilloylated, acetylated, and normal defatted human serum albumin as well as to mercapt- and nonmercaptalbumin was studied by equilibrium dialysis of radioactive Ca2+. Binding was quantified by five Scatchard constants [ni = 1, (i = 1-4) and n5 = 10]. Glycation resulted in increased k1- and k2-values and unchanged k3-k5-values, whereas penicilloylation increased all five association constants. The increments were greater the more pronounced the modification, and the enhancements caused by penicilloylation were, for the same degree of modification, greater than those produced by glycation. In contrast, acetylation by acetylsalicylate did not affect calcium binding. Likewise, binding to mercapt- and nonmercaptalbumin was the same, a finding showing that the thiol group of cysteine 34 is not important for calcium binding. D-Glucose and penicillin G are known to react with lysine residues of albumin, and the enhancement of binding resulting from glycation or penicilloylation is probably brought about by unspecific electrostatic effects, possibly supplemented by conformational changes of the protein molecule. The relative importance of the three domains of human serum albumin for calcium binding is discussed.

Myristic acid binding to human serum albumin investigated by dialytic exchange rate.

Dialysis rate determinations of several fatty acids in the absence of albumin revealed that the myristate anion, like that of laurate, in aqueous solution, pH 7.5, is present as a monomer anion when the concentration is below 25 microM. Palmitate and oleate solutions, on the other hand, show a tendency to aggregation even at concentrations below 0.5 microM. Multiple binding of myristate to human serum albumin in phosphate buffer, at pH 7.5, 37 degrees C, was investigated by exchange of 14C-labeled myristate across a dialysis membrane under conditions of binding equilibrium. A binding isotherm was established by least squares fitting of the stoichiometric binding constants in the stepwise binding equation to the experimental data. The best-fit solution was supplemented with 30 acceptable solutions within a probability limit of 0.95. A concept of one or two distinct high-affinity sites for binding of fatty acids could not be verified; the observations allow a variety of binding mechanisms ranging from cooperativity of the first two myristates to a model with four equal and independent sites.

Photooxidation of human serum albumin and its complex with bilirubin.

Irradiation with visible light of human serum albumin in aqueous solution at pH 8, in the presence of catalytic amounts of rose bengal or methylene blue, resulted in random oxidation of the histidine residues in the protein under consumption of one mole O2, and release of somewhat less than one proton, per histidine residue degraded. An increase of light absorption at 250 nm was proportional to the amount of oxygen consumed. Bilirubin bound to the oxidized protein showed an increased light absorption at its maximum, 460 nm, and a decreased binding affinity, indicating a conformational change of the protein on oxidation of histidine residues. This change also resulted in a slight perturbation of tyrosine light absorption, corresponding to a shift of the chromophore to more polar surroundings. Further, a sensitized oligomerization of albumin was observed, independent of oxidation of the histidine residues, and not consuming oxygen. Irradiation of a complex of human serum albumin with one molecule of bound bilirubin, in the absence of a sensitizing dye, resulted in a fast, non-oxygen consuming process whereby the light absorption maximum of the pigment was shifted 4 nm towards longer wavelength and part of the bilirubin was converted to a more polar pigment, bound less firmly to the protein. This was followed by a relatively slow oxidation of the pigment under uptake of one mole O2. Parallel photooxidation of the protein carrier could not be detected. It is considered possible that the fast, anaerobic process is operative in phototherapy of hyperbilirubinemia in the newborn. Serum albumin is probably not oxidized during this treatment.