Immobilisation of phosphorus by iron-coated roots of submerged macrophytes

Hydrobiologia - To observe effects on the phosphorus retention mechanisms of a lake after re-colonisation by macrophytes, Potamogeton crispus L. and Elodea canadensis Michx. were planted in lab...     

Long-term effects of dietary isoflavones on uterine gene expression profiles

Isoflavones (ISOs) are bioactive food ingredients of the traditional East Asian diet and currently discussed as alternatives to classical hormone replacement therapies and for reducing the prevalence of hormone-dependent cancers. Although there are many studies on ISOs, not much is known about their long-term effects.Therefore, we performed an animal experiment analyzing the effects of three different diets: a phytoestrogen-free diet, a diet supplemented with genistein (700 μg/g diet) and an ISO-high diet (232 μg daidzein and 240 μg genistein/g) at two distinct time points, juvenile (21 days) and adult (97 days). Exposure started prior to mating of the parents and throughout the life of the offspring.We observed a stronger increase of uterine wet weights in juvenile offspring with genistein exposure (1018 ± 350 mg/kg BW) than with ISO-high diet (497 ± 133 mg/kg BW). Whereas the expression of proliferation related genes (PCNA; Ki67; IGF-1; IGF-1R), analyzed by real-time-qPCR and Western blot, were significantly down-regulated in juvenile animals exposed to genistein. Additionally, genistein exposure led to estrogenic responses, observed upon increase of complement C3 and decrease of estrogen receptors gene expressions, while the exposure to ISO-high diet did not show these effects.In conclusion, both the time point on which phytoestrogen exposure starts together with the composition of the ingested phytoestrogen containing diet are of great importance for the biological response of the offspring.     

Adhesion of canine and human uropathogenicEscherichia coli andProteus mirabilis strains to canine and human epithelial cells

Escherichia coli strains causing urinary tract infections in dogs produce fimbriae composed of fimbrial subunits closely related to the F12 and F13 fimbriae of human uropathogenic strains [4]. The adhesins carried by the fimbriae of human and canine isolates differ, however, as concluded from a different hemagglutination pattern and from the fact that the dog strains do not agglutinate latex beads coated with P-fimbriae receptor. This possible difference in adhesive specificity was confirmed by experiments in which the adhesion of human and dog isolates to dog kidney epithelial cells (MDCK cells) and human bladder epithelial cells (T24 cells) was compared. Dog uropathogenic strains, in contrast to human uropathogenicE. coli strains, adhere to MDCK cells but hardly to T24 cells. Adhesion to MDCK cells correlates with the presence of F12 or F13 fimbriae on the dog strains. These results suggest that homologous fimbrial subunits can carry different adhesin molecules and that these adhesin molecules can be responsible for species-specific adherence. On the contrary, adhesion of a number of dog uropathogenicProteus mirabilis strains to MDCK and T24 cells was not species specific; it depended on the mere presence of fimbriae.     

Ultrastructural immunolocalization of periodic pectin depositions in the cell wall ofNicotiana tabacum pollen tubes

Summary The monoclonal antibody (MAb) JIM5, marking acidic pectins, was used to localize ultrastructurally pectin molecules in the pollen tube wall ofNicotiana tabacum. Longitudinal sections of LR-White embedded pollen tubes were exposed to antibody treatment; accumulations of pectins were identified by counting the density of the gold particles representing the pectin epitopes along the pollen tube wall. Significant accumulations of gold grains were marked and the distances between them were measured. In many pollen tubes a more or less regular distribution of the accumulations was observed along the tube indicating a periodical deposition of pectin. The distances between the accumulations were 4–6 m. Most of the label was found in the inner part of the outer layer of the bilayered cell wall. These findings correspond to and confirm the earlier observation by our group reporting ring-shaped periodical deposits in pollen tubes after immunofluorescence labelling with the MAb JIM5 under the confocal laser scanning microscope.Abbreviations Ab antibody - MAb monoclonal antibody     

Tyrosine modification of glucose dehydrogenase from Bacillus megaterium. Effect of tetranitromethane on the enzyme in the tetrameric and monomeric state

The active tetrameric glucose dehydrogenase from Bacillus megaterium is rapidly inactivated upon reaction with tetranitromethane. The inactivation is correlated with the nitration of a single tyrosine residue/subunit. The nitration does not influence the dissociation-reassociation process of the enzyme. The inactivation is prevented by the presence of NAD, AMP, ATP. The sequence around the nitrated tyrosine residue was determined and the residue was identified as Tyr-254 in the covalent structure of the enzyme. After dissociation of the enzyme into its monomers two tyrosine residues become susceptible to nitration. The nitrated subunits are unable to reassociate to the tetramer. Isolation and sequence analysis of the peptides containing nitrotyrosine indicated that two different tyrosine residues are predominantly modified. One residue is Tyr-254 which is essential for the catalytic activity and the other one is Tyr-160 which seems to be located in the subunit binding area.     

Role of unstirred layer in intestinal absorption of phenylalanine in vivo

The appearance rate of l- and d-phenylalanine in the venous blood of rat jejunal loops in vivo is increased up to 60% if the intraluminal solution is mixed more efficiently by the simultaneous perfusion of air. The effect decreases as the luminal concentration is increased to 100 mmol/1. Thus, the apparent Michaelis constants are by 50% lower in the case of the reduced unstirred layer (26 to 17 for l- and 9 to 6 mmol/1 for d-phenylalanine).The enhancement of the absorption and the reduction of the Michaelis constants can be attributed to the reduction of the effective unstirred layer thickness by about 400–500 μm.