The carbohydrates of secretory granules and the glycocalyx in developing mucoid cells

Summary Complex carbohydrates in secretory granules and at the apical cell surface of mouse gastric mucoid cells were studied during embryogenesis and in the early postnatal period by various cytochemical methods; the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) and tannic acid-uranyl acetate (TA-UA) procedures made neutral mucosubstances (NMS) visible, whereas the hexose residues of glycoconjugates were identified using WGA-, RCA II- and ConA-ferritin. The glycocalyx was stained with ruthenium red (RR). During differentiation of the embryonic mucoid cells the number of secretory granules increased in parallel to the increase in their carbohydrate component. NMS-stainable parts in secretory granules also had binding sites for the conjugates RCA II- and WGA-ferritin, but the binding of ConA could not be identified. The increasing quantity of NMS in secretory granules was correlated with the increased amount of PA-TCH-SP and TA-UA positive substances in the apical glycocalyx only in 14- and 18-day-old embryos. The observed uniform affinity for RR and lectin conjugates in all analysed developmental stages remains to be explained.     

A mini organ culture as a model for studying the gallbladder epithelium of mouse

Summary— A mini organ culture of mouse gallbladder was developed as an alternative to primary cultures of epithelial cells of this organ. Small pieces of tissue were prepared and maintained in minimum essential Eagle medium with 10% foetal calf serum, for as long as 7 days. Qualitative and quantitative ultrastructural studies have been performed using electron microscopy. The viability of cells was evaluated by stereological quantification of endocytotic vesicles containing horseradish peroxidase and labelling of exocytotic glycoproteins with tannic acid. The morphology of tissue pieces during the 1st h of culturing and tissue isolated directly from animals exhibited no significant differences. However, after 4 h in culture degradative changes became evident in many cells. At that time, endo- and exocytosis were both dramatically reduced. After 24 h, the morphology, as well as endo- and exocytosis recovered and were comparable to the parameters of the tissue in vivo or after 1 h in culture. The endocytotic activity remained unchanged from day 1 to 7 of culturing, while the number of exocytotic vesicles gradually decreased after 2 days in culture. Our results prove that mini organ culture of gallbladder is morphologically and functionally comparable with the tissue in vivo and for studies of epithelium in culture it is more convenient than primary cultures.     

Effects of storage,mucilage presence,photoperiod, thermoperiod and salinity on germination of Farsetia aegyptia Turra (Brassicaceae) seeds: implications for restoration and seed banks in Arabian Desert

Seed viability and germination are key factors in the success of restoration efforts, especially when stored seeds are used. However, the effect of seed storage on germination of most of the native Arabian species is not well documented. We investigated the effect of storage time and role of the seed mucilage in regulating germination, dormancy, salinity tolerance and consequential survival strategy of F. aegyptia in an unpredictable arid desert setting. Effect of light and temperature during germination was studied under two photoperiods and two thermoperiods using intact and de-mucilaged seeds. Presence of mucilage and thermoperiod did not affect the germination. However, seed collection year and photoperiod had a highly significant effect on the germination. Increasing salinity levels decreased the germination of F. aegyptia but ungerminated seeds were able to germinate when salinity stress was alleviated. Seed storage at room temperature enhances the germination percentage, indicating that F. aegyptia seeds have physiological dormancy and it can be alleviated by after-ripening at dry storage. In addition, F. aegyptia seeds show ability to germinate at lower salinity concentration and remain viable even at higher saline conditions, indicating their adaptability to cope with such harsh environmental conditions.     

A study of rheological and molecular weight properties of recycled polysaccharides used as thickeners in textile printing

Polysaccharide thickeners (alginate, carboxymethylated guar gum and carboxymethylated cellulose) used for the preparation of printing pastes, were recycled from printing paste residues and from wastewater concentrates, which were separated by ultrafiltration technique from wastewater after screen printing of cotton with reactive dyes. Concentrated aqueous polysaccharide solutions were studied via rheological measurements under steady and oscillatory shear conditions. Molecular weight averages and molecular weight distribution of thickeners were determined by size exclusion chromatography.A satisfactory fitting of viscosity data is obtained with the Cross equation and mechanical spectra are described with satisfactory approximation with the Friedrich–Braun model. The obtained parameters enable a quantitative interpretation of the changes in rheological properties. Moderate changes produced by thickener recycling on the shear-thinning and viscoelastic behaviour of polymers are a direct result of changes in molecular weight averages (MWA) and molecular weight distribution (MWD).     

Tus-mediated arrest of DNA replication in Escherichia coli is modulated by DNA supercoiling

In the absence of RecA, expression of the Tus protein of Escherichia coli is lethal when ectopic Ter sites are inserted into the chromosome in an orientation that blocks completion of chromosome replication. Using this observation as a basis for genetic selection, an extragenic suppressor of Tus-mediated arrest of DNA replication was isolated with diminished ability of Tus to halt DNA replication. Resistance to tus expression mapped to a mutation in the stop codon of the topA gene (topA869), generating an elongated topoisomerase I protein with a marked reduction in activity. Other alleles of topA with mutations in the carboxyl-terminal domain of topoisomerase I, topA10 and topA66, also rendered recA strains with blocking Ter sites insensitive to tus expression. Thus, increased negative supercoiling in the DNA of these mutants reduced the ability of Tus-Ter complexes to arrest DNA replication. The increase in superhelical density did not diminish replication arrest by disrupting Tus-Ter interactions, as Tus binding to Ter sites was essentially unaffected by the topA mutations. The topA869 mutation also relieved the requirement for recombination functions other than recA to restart replication, such as recC, ruvA and ruvC, indicating that the primary effect of the increased negative supercoiling was to interfere with Tus blockage of DNA replication. Introduction of gyrB mutations in combination with the topA869 mutation restored supercoiling density to normal values and also restored replication arrest at Ter sites, suggesting that supercoiling alone modulated Tus activity. We propose that increased negative supercoiling enhances DnaB unwinding activity, thereby reducing the duration of the Tus-DnaB interaction and leading to decreased Tus activity.     

Commensalism during submerged mixed culture of Geotrichum candidum and Penicillium camembertii on glutamate and lactate

Geotrichum candidum and Penicillium camembertii were cultivated in pure and mixed cultures on glutamate- and lactate-based medium. In pure culture, P. camembertii assimilated simultaneously glutamate, as a nitrogen and carbon source for biosynthesis, and lactate as an energy source. On the contrary, G. candidum grew on glutamate alone. The mixed culture led to higher growth rates and then higher rates of substrate consumption and metabolite production than each pure culture; however, the behaviour recorded was similar to that observed during G. candidum pure culture, in particular the absence of lactate assimilation during growth, illustrating a commensalism between both species. The presence of G. candidum induced a form of “competition” and then a better assimilation by P. camembertii of the sole nitrogen source, glutamate, which was therefore used as an energy source in addition to be a carbon (and nitrogen) source. Lactate was only used for energy supply during stationary state, as also recorded during G. candidum pure culture.     

High-order SNP combinations associated with complex diseases: efficient discovery, statistical power and functional interactions

There has been increased interest in discovering combinations of single-nucleotide polymorphisms (SNPs) that are strongly associated with a phenotype even if each SNP has little individual effect. Efficient approaches have been proposed for searching two-locus combinations from genome-wide datasets. However, for high-order combinations, existing methods either adopt a brute-force search which only handles a small number of SNPs (up to few hundreds), or use heuristic search that may miss informative combinations. In addition, existing approaches lack statistical power because of the use of statistics with high degrees-of-freedom and the huge number of hypotheses tested during combinatorial search. Due to these challenges, functional interactions in high-order combinations have not been systematically explored. We leverage discriminative-pattern-mining algorithms from the data-mining community to search for high-order combinations in case-control datasets. The substantially improved efficiency and scalability demonstrated on synthetic and real datasets with several thousands of SNPs allows the study of several important mathematical and statistical properties of SNP combinations with order as high as eleven. We further explore functional interactions in high-order combinations and reveal a general connection between the increase in discriminative power of a combination over its subsets and the functional coherence among the genes comprising the combination, supported by multiple datasets. Finally, we study several significant high-order combinations discovered from a lung-cancer dataset and a kidney-transplant-rejection dataset in detail to provide novel insights on the complex diseases. Interestingly, many of these associations involve combinations of common variations that occur in small fractions of population. Thus, our approach is an alternative methodology for exploring the genetics of rare diseases for which the current focus is on individually rare variations.     

Competition during submerged mixed culture of Geotrichum candidum and Penicillium camembertii on glucose and threonine

Geotrichum candidum and Penicillium camembertii were cultivated in pure and mixed cultures on glucose and threonine. In pure cultures, G. candidum used glucose as a carbon and an energy source and threonine only as a nitrogen source, even after glucose exhaustion. Contrarily, when growing in isolation, P. camembertii used simultaneously threonine and glucose as carbon sources. A diauxic growth was recorded during the mixed culture of both species, which competed for glucose, the sole carbon source available for G. candidum growth, leading to higher glucose consumption rates than those recorded during pure cultures, while after glucose exhaustion, low growth was recorded in a second step, showing a 'competition' for threonine, the sole remaining carbon and nitrogen sources, confirmed by the increase of 1.0+/-0.1 log of the G. candidum Colony Forming Units. 'Competition' between G. candidum and P. camembertii for the limiting substrate was found to have a positive effect on growth, since it did not lead to the annihilation of one species, as usually observed, but in their coexistence, leading to a rather similar final number of the CFUs for the two populations. 'Competition' resulted in the absence of assimilation of the second available carbon substrate (lactate) as previously observed, or its use only as a nitrogen source, as was the case for threonine in this work.     

Access site complications following cardiac catheterization assessed by duplex ultrasonography

Access site complications are major source of morbidity following cardiac catheterization. Their incidence varies in the literature because of multiple definitions and methods of determining the presence of particular complication. The aim of this prospective study was to determine the incidence of access site complications following cardiac catheterization using arterial duplex ultrasonography. A total of 319 consecutive patients, who had cardiac catheterization underwent femoral artery duplex study 24 to 48 hours following manual hemostasis. Diagnostic angiogram had 232 (71.8%) while 87 (28.2%) had percutaneous coronary intervention (PCI). Femoral artery duplex ultrasound was normal in 247 (77.4%). Haematoma was found in 48 (15.1%), pseudoaneurysm in 17 (5.3%), AV fistula in 2 (0.6%) and dissection of the femoral artery in 5 (1.6%) patients. Baseline demografic characteristics were similar in group with normal duplex study and group with detected complication. Pseudoaneurysm and AV fistula were more commonly observed in patients following PCI than diagnostic angiogram (9.2% vs. 4.7%, p<0.001). Patients with documented complications more frequently had concomitant administration of antiplatelet and anticoagulant medication compared to the patients without complications (p=0.003). Hemodynamic disturbances (hypotension and bradycardia) during manual compression were more frequent in patients with complication (11% vs. 4.5%, p=0.047). Low threshold for use of duplex ultrasound should be exercised in patients following cardiac catheterization to establish the presence of access site complications. Special attention is needed in the setting of aggressive antiplatelet and anticoagulant therapy, interventional procedures and hemodynamic disturbances during manual hemostas.