Lipopolysaccharide binding protein and serum amyloid A secretion by human intestinal epithelial cells during the acute phase response.

The acute phase proteins LPS binding protein (LBP) and serum amyloid A (SAA) are produced by the liver and are present in the circulation. Both proteins have been shown to participate in the immune response to endotoxins. The intestinal mucosa forms a large surface that is continuously exposed to these microbial products. By secretion of antimicrobial and immunomodulating agents, the intestinal epithelium contributes to the defense against bacteria and their products. The aim of this study was to explore the influence of the inflammatory mediators TNF-alpha, IL-6, and IL-1beta on the release of LBP and SAA by intestinal epithelial cells (IEC). In addition, the induction of LBP and SAA release by cell lines of intestinal epithelial cells and hepatic cells was compared. The data obtained show that in addition to liver cells, IEC also expressed LBP mRNA and released bioactive LBP and SAA upon stimulation. Regulation of LBP and SAA release by IEC and hepatocytes was typical for class 1 acute phase proteins, although differences in regulation between the cell types were observed. Endotoxin did not induce LBP and SAA release. Glucocorticoids were demonstrated to strongly enhance the cytokine-induced release of LBP and SAA by IEC, corresponding to hepatocytes. The data from this study, which imply that human IEC can produce LBP and SAA, suggest a role for these proteins in the local defense mechanism of the gut to endotoxin. Furthermore, the results demonstrate that tissues other than the liver are involved in the acute phase response.     

Physical Demand but Not Dexterity Is Associated with Motor Flexibility during Rapid Reaching in Healthy Young Adults

Healthy humans are able to place light and heavy objects in small and large target locations with remarkable accuracy. Here we examine how dexterity demand and physical demand affect flexibility in joint coordination and end-effector kinematics when healthy young adults perform an upper extremity reaching task. We manipulated dexterity demand by changing target size and physical demand by increasing external resistance to reaching. Uncontrolled manifold analysis was used to decompose variability in joint coordination patterns into variability stabilizing the end-effector and variability de-stabilizing the end-effector during reaching. Our results demonstrate a proportional increase in stabilizing and de-stabilizing variability without a change in the ratio of the two variability components as physical demands increase. We interpret this finding in the context of previous studies showing that sensorimotor noise increases with increasing physical demands. We propose that the larger de-stabilizing variability as a function of physical demand originated from larger sensorimotor noise in the neuromuscular system. The larger stabilizing variability with larger physical demands is a strategy employed by the neuromuscular system to counter the de-stabilizing variability so that performance stability is maintained. Our findings have practical implications for improving the effectiveness of movement therapy in a wide range of patient groups, maintaining upper extremity function in old adults, and for maximizing athletic performance.     

Nestedness of Southern Ocean island biotas: ecological perspectives on a biogeographical conundrum

Aim To use patterns of nestedness in the indigenous and non‐indigenous biotas of the Southern Ocean islands to determine the influence of dispersal ability on biogeographical patterns, and the importance of accounting for variation in dispersal ability in their subsequent interpretation, especially in the context of the Insulantarctic and multi‐regional hypotheses proposed to explain the biogeography of these islands. Location Southern Ocean islands. Methods Nestedness was determined using a new metric, d1 (a modification of discrepancy), for the indigenous and introduced seabirds, land birds, insects and vascular plants of 26 Southern Ocean islands. To assess the possible confounding effects of spatial autocorrelation on the results, islands were assigned to 11 major island groups and each group was treated as a single island in a following analysis. In addition, nestedness of the six Southern Ocean islands comprising the South Pacific Province (New Zealand islands) was analysed. All analyses were conducted for species and genera, for each of the taxa on its own, and for the complete data sets. Results Statistically significant nestedness was found in all of the taxa examined, with nestedness declining in the order seabirds > land birds > vascular plants > insects for the indigenous species. Vagility had a marked influence on nestedness and the biogeographical patterns shown by the indigenous species. This influence was borne out by additional analyses of marine taxa and small‐sized terrestrial species, both of which were more nested than the most nested group examined here, the seabirds. Assemblages of non‐indigenous species also showed nestedness, and nestedness was generally more pronounced than in the indigenous species. Surprisingly, vagility had a significant effect on nestedness in these assemblages too. Main conclusions Nestedness analyses provide a quantitative means of comparing biogeographical patterns for groups differing in vagility. These comparisons revealed that vagility has a considerable influence on biogeographical patterns and should be taken into account in analyses. Here, investigations of more vagile taxa support hypotheses for a single origin of the Southern Ocean island biota (the Insulantarctica scenario), whilst those of less mobile taxa support the more commonly held, multi‐regional hypothesis. All biogeographical analyses across the Southern Ocean (and elsewhere) will be influenced by the effects of dispersal ability, with composite analyses dominated by sedentary groups likely to favour multi‐regional scenarios, and those dominated by mobile groups favouring single origins. Mechanisms underlying nestedness in the region range from nested physiological tolerances in more mobile groups to colonization ability and patterns of speciation in less vagile taxa. Considerable nestedness in the non‐indigenous assemblages is largely a consequence of the fact that many of these species are European weedy species.     

The affinity of the FimH fimbrial adhesin is receptor-driven and quasi-independent of Escherichia coli pathotypes

Type-1 fimbriae are important virulence factors for the establishment of Escherichia coli urinary tract infections. Bacterial adhesion to the high-mannosylated uroplakin Ia glycoprotein receptors of bladder epithelium is mediated by the FimH adhesin. Previous studies have attributed differences in mannose-sensitive adhesion phenotypes between faecal and uropathogenic E. coli to sequence variation in the FimH receptor-binding domain. We find that FimH variants from uropathogenic, faecal and enterohaemorrhagic isolates express the same specificities and affinities for high-mannose structures. The only exceptions are FimHs from O157 strains that carry a mutation (Asn135Lys) in the mannose-binding pocket that abolishes all binding. A high-mannose microarray shows that all substructures are bound by FimH and that the largest oligomannose is not necessarily the best binder. Affinity measurements demonstrate a strong preference towards oligomannosides exposing Manalpha1-3Man at their non-reducing end. Binding is further enhanced by the beta1-4-linkage to GlcNAc, where binding is 100-fold better than that of alpha-d-mannose. Manalpha1-3Manbeta1-4GlcNAc, a major oligosaccharide present in the urine of alpha-mannosidosis patients, thus constitutes a well-defined FimH epitope. Differences in affinities for high-mannose structures are at least 10-fold larger than differences in numbers of adherent bacteria between faecal and uropathogenic strains. Our results imply that the carbohydrate expression profile of targeted host tissues and of natural inhibitors in urine, such as Tamm-Horsfall protein, are stronger determinants of adhesion than FimH variation.     

Light chain diversity of murine anti-streptococcal antibodies: IgCH-linked effects on L chain expression.

L chains derived from anti-group A streptococcal carbohydrate antibodies raised in A/J, BALB/cJ, C57BL/6J, CB-20, BAB-14, and CAL-20 mice were examined by isoelectric focusing. Multiple strain-associated differences in the degree and frequency of expression of particular L chain spectrotypes were observed. Analysis of L chain-focusing patterns in allotype-congenic mice revealed that IgCH-linked genes can have profound effects on the L chain phenotypes expressed by strains with identical L chain genotypes. Lastly, the overall spectrotypic diversity of L chains from anti-GAC antibodies appears to be less extensive than the diversity of the antibodies from which these L chains derive, documented by similar techniques. These results are interpreted in light of the significance of combinatorial diversity in generating antibody heterogeneity.     

Ultrastructure of bovine embryos frozen and thawed by a two-step freezing method

An ultrastructural evaluation of a rapid tow-step freezing method, by which 6-7-day-old bovine embryos equilibrated in 1.4 M glycerol in Dulbecco's phosphate-buffered saline were frozen and thawed, was undertaken. In all non-frozen control embryos trophoblastic and embryonic cells formed a spherical structure enclosed by an intact zona pellucida. The spacial arrangement of the cells of the frozen embryos was less regular and the surrounding zona pellucida was damaged in approximately half of the cases. Some embryonic cells had increased electron density and lysosomal content showing reaction sites for acid phosphatase. In all frozen embryos, cytoplasmic defects appearing as non-membrane-bound 'empty spaces' were observed more frequently in the trophoblastic cells than in the embryonic cells. Culture of frozen embryos for 24 h revealed that cells appearing nondefective after culture may have the capability of organizing a viable embryonic structure. It was found that the most commonly used freezing method is associated with certain morphological changes. However, no additional cryoinjuries were observed in comparisons with the more complicated freezing procedures using dimethylsulfoxide as cryoprotectant.     

Relationship between morphological signs of cell injury in myocardial ischaemia.

Morphological signs of severe ischaemic injury are well known. However, we still lack knowledge about how indices of milder injuries are related on a cellular level. In a previous study we have reported on the sequence of alterations across the border zone in cat hearts subjected to 3 h of coronary occlusion. In the present study, which elaborates that study, we have examined the relationship between morphological variables in serial sections of 220 myocytes within the border zone. In cells with intact sarcolemma and no chromatin changes, the fractional volume of cytoplasm has a bimodal distribution indicating cells with and without oedema. Whereas cells with focal disruptions of the sarcolemma have a moderate oedema, usually localized submembranously, cells with extensive sarcolemmal fragmentation have an extensive oedema. A mild oedema is seen before other signs of severe cell injury, even though more extensive oedema is closely associated with sarcolemmal fragmentation. The fractional volume of mitochondria was smaller, whereas the fractional volume of lipid droplets was larger in cells with oedema than in cells without oedema.     

Problems related to infarct size measurements in the rat heart.

The feasibility of measuring the extent of hypoperfused myocardium and the infarct size was examined in rat hearts after occlusion of the left coronary artery. The extent of hypoperfused myocardium was examined by autoradiography and after perfusion with fluorescent microspheres. Both methods appeared unreliable in this model. Triphenyltetrazolium chloride (TTC) staining, however, provided a distinct demarcation line between viable myocardium, which was stained red, and the necrotic myocardium, consistent with the ultrastructural border between normal and severely damaged myocytes 5 h after coronary occlusion. TTC staining gives the best demarcation of ischemic tissues. In verapamil-treated rats, there was an apparent reduction in infarct size as compared with untreated rats; 20% reduction in infarct size 5 h after coronary occlusion and 12% reduction after 24 h. There was, however, a large postoperative mortality among the verapamil-treated rats. These problems, and the nonuniform infarct size in rats, may in part explain why infarct size limitation by verapamil has been reported from rat experiments, but not from clinical trials.