The molecular epidemiology of the infectious disease caused by feline calcivirus (FCV) in Japan was investigated by analysing the phylogenetic relationship among 21 Japanese field isolates, including the F4 strain, and 30 global isolates. Parts of the capsid gene (B–F) of the isolates were amplified by RT-PCR, and the amino acid sequences were compared with those from the global isolates. Thirty-seven and 14 out of a total of 51 isolates were clustered into two distinct genogroups, I and II respectively, by UPGMA and NJ analysis. Seven of the 21 Japanese isolates (33%) fell into group I together with 30 global isolates, while the other 14 Japanese isolates (67%) belonged to group II. The bootstrap repetition analysis of groups I and II formed by the NJ method gave a value of 99.0%. The 14 latter Japanese isolates were clearly separated from the isolates in group I, and they were different from any previously known FCV, forming a new genogroup, which implies that this lineage has been confined to Japan. Comparing the amino acid sequences shared by groups I and II, the amino acid at position 377 in B region was asparagine (Asn or Asp (NH2)) in group I, while it was lysine (Lys) in all the strains in group II. Similarly, the amino acid at position 539 in the F region was alanine (Ala) or proline (Pro) in group I, while it was valine (Val) in group II; glycine (Gly) at position 557 in group I was serine (Ser) in Group II; and phenylalanine (Phe) or leucine (Leu) at position 566 in genogroup I was tyrosine (Tyr) in group II. 相似文献
Ruminal microbes harvested from a ruminally fistulated cow were incubated in simple batch and semicontinuous cultures with NH3‐N or amino‐N on nitrogen‐ or energy‐excess diets in quantity (HN and LN diets, respectively, consisting of timothy hay plus soybean meal, or corn grain), based on evaluation with the National Research Council and Cornell Net Carbohydrate and Protein System models. In a batch culture experiment, supplementation with amino‐N promoted digestion and fermentation in the course of incubation (4–24 h) on both diets, but these effects mostly disappeared when the diets were sufficiently digested (at 48 h). In a semicontinuous culture experiment using Rusitec, no effect of amino‐N was exhibited after sufficient fermentation and digestion, but significant promotion of digestion was shown in the course of incubation on the HN diet, while no such effect was detected on the LN diet. The microbial yield for 24 h did not show a significant difference between the N sources of either of the two diets. These results suggest that the stimulatory effects of amino‐N are diminished when the diets are sufficiently digested after a long retention and incubation, and also that the effectiveness of amino‐N does not require a quantitatively energy‐excess status. 相似文献
In recent years, intestinal transport processes have been studied in detail regarding both, functional and structural aspects. For monosaccharides different systems have been demonstrated for apical uptake: this includes the high-affinity SGLT1 as a distinct d-glucose system and GLUT5 for fructose. Specifically in pigs a low affinity, high-capacity system for d-glucose and d-mannose with no preference for Na+ over K+ and a very low affinity system are suggested as further uptake systems. As in other species, basolateral extrusion is mediated by GLUT2. The distributions of monosaccharide transport along the gastrointestinal axis as well as the potential role of paracellular monosaccharide absorption have not yet been clarified.
Amino acids can principally be absorbed by the paracellular and transcellular pathway whereas transcellular transport can either be mediated by facilitated diffusion or secondary active Na+-coupled transport. This includes different transport systems for neutral, anionic and cationic acids. In addition, the presence of the di-/tripeptides transport system PEPT1 which depends on an inwardly directed H+-gradient has also been confirmed for the pig small intestine, its quantitative proportion is still under debate.
Short chain fatty acids (SCFA) are the major end products of microbial carbohydrate fermentation which occurs along the gastrointestinal tract with the highest production rates in the large intestines. At least two uptake mechanisms have to be assumed, i.e., non-ionic diffusion and anionic exchange via SCFA−/HCO3−-exchange. Controversial views still exist to what extent SCFA are metabolized within the epithelial tissue.
Segmental differences between small and large intestines have been demonstrated for Na+ absorption. Whereas in the small intestines the major part of Na+ absorption is mediated by coupled nutrient transport systems, aldosterone sensitive Na+ channels and Na+/H+-exchange are the dominant mechanisms in the hindgut. For Cl− paracellular transport and anionic Cl−/HCO3−-exchange are the major absorptive mechanisms. Cl− secretion is mediated by apical channels which may be activated by toxins of different origin. Different types of Cl− channels have been identified, such as Cystic Fibrosis Transmembrane Regulator (CFTR), Ca-activated Cl− channels (CLCA) and Outwardly Rectifying Cl− Channels (ORCC). Whereas CFTR has clearly been shown for jejunal and colonic epithelial and goblet cells controversy still exists on the relevance of CLCA and ORCC in pigs.
For Ca2+ there is evidence that both recently published channels TRPV5 and TRPV6 are also expressed in pig intestinal tissues, however, this has not yet been shown on protein level. From several functional approaches it was demonstrated that phosphate uptake can be mediated by both, a Na+-dependent transcellular component and paracellularly. On a molecular basis it is uncertain whether the transport protein of transcellular mechanism belongs to the NaPi-IIb cotransporter family. 相似文献