Red-shifted light-harvesting system of freshwater eukaryotic alga Trachydiscus minutus (Eustigmatophyta,Stramenopila)

Photosynthesis Research - Survival of phototrophic organisms depends on their ability to collect and convert enough light energy to support their metabolism. Phototrophs can extend their absorption...     

Genetic dissection of testicular weight in the mouse with the BXD recombinant inbred strains

Testicular weights were studied in the mouse BXD recombinant inbred (RI) strains. These strains were derived from DBA/2J and C57BL/6J progenitors that differ significantly in their testicular weights (0.224 g ± 0.015 vs. 0.161 g ± 0.03, P < 0.0001). The heritability of testicular weights was calculated to be 0.53, and the minimum number of responsible effective factors was estimated to be 5.7. The total genome scanning of the BXD RI strains with over 1000 markers revealed a quantitative trait locus (QTL) on mouse Chromosome (Chr) 13 near the D13Mit3 marker (LOD score 6.9). This QTL region was designated Twq1 and associated with over 75% of genetic variability. Received: 23 January 1998 / Accepted: 16 March 1998     

Serogroups, K1 antigen, and antimicrobial resistance patterns of Aeromonas spp. strains isolated from different sources in Mexico

A total of 221 strains of Aeromonas species isolated in Mexico from clinical (161), environmental (40), and food (20) samples were identified using the automated system bioMérieux-Vitek. Antisera for serogroups O1 to 044 were tested using the Shimada and Sakazaki scheme. The K1 antigen was examined using as antiserum the O7:K1C of Escherichia coli. Besides, we studied the antimicrobial patterns according to Vitek AutoMicrobic system. Among the 161 clinical strains 60% were identified as A. hydrophila, 20.4% as A. caviae, and 19.25% as A. veronii biovar sobria. Only A. hydrophila and A. veronii biovar sobria were found in food (55 and 90% respectively) and environmental sources (45 and 10% respectively). Using "O" antisera, only 42.5% (94/221) of the strains were serologically identified, 55% (121/221) were non-typable, and 2.5% (6/221) were rough strains. Twenty-two different serogroups were found, O14, O16, O19, O22, and O34 represented 60% of the serotyped strains. More than 50% of Aeromonas strain examined (112/221) expressed K1 encapsulating antigen; this characteristic was predominant among Aeromonas strains of clinical origin. Resistance to ampicillin/sulbactam and cephazolin was detected in 100 and 67% of Aeromonas strain tested for their susceptibility to antibiotics. In conclusion, antibiotic-resistant Aeromonas species that possess the K1 encapsulating antigen and represent serogroups associated with clinical syndrome in man are not uncommon among Aeromonas strains isolated from clinical, food and environmental sources in Mexico.     

The effect of nutrient level on plant structure and production in a wet grassland: a field study

Since the 1950s, agricultural intensification has affected the structure and functioning of ecological systems including wet grasslands. Our study site, a wet grassland near Třeboň, Czech Republic, was historically a sedge meadow, but increased nutrient additions, a long-lasting flood in 2002 and changed mowing patterns resulted in domination by Phalaris arundinacea. The aim of the study was to determine how different nutrient conditions may affect plant structure and production in a wet grassland used for hay production. Species composition and percent cover were determined from line intercepts. Aboveground biomass was harvested six times each in 2007 and 2008 and primary production then calculated. Ingrowth core bags were used to determine belowground production. Aboveground production was two times greater in the high nutrient versus the low nutrient area in both years, while belowground production was very similar. The high nutrient area was still dominated by P. arundinacea, but Carex gracilis was now a co-dominant in the low nutrient area. However, other factors, such as water level and mowing regime, may interact with nutrient level to govern wet grassland structure and function.     

Genome-Wide Analysis of Cold Adaptation in Indigenous Siberian Populations

Following the dispersal out of Africa, where hominins evolved in warm environments for millions of years, our species has colonised different climate zones of the world, including high latitudes and cold environments. The extent to which human habitation in (sub-)Arctic regions has been enabled by cultural buffering, short-term acclimatization and genetic adaptations is not clearly understood. Present day indigenous populations of Siberia show a number of phenotypic features, such as increased basal metabolic rate, low serum lipid levels and increased blood pressure that have been attributed to adaptation to the extreme cold climate. In this study we introduce a dataset of 200 individuals from ten indigenous Siberian populations that were genotyped for 730,525 SNPs across the genome to identify genes and non-coding regions that have undergone unusually rapid allele frequency and long-range haplotype homozygosity change in the recent past. At least three distinct population clusters could be identified among the Siberians, each of which showed a number of unique signals of selection. A region on chromosome 11 (chr11:66–69 Mb) contained the largest amount of clustering of significant signals and also the strongest signals in all the different selection tests performed. We present a list of candidate cold adaption genes that showed significant signals of positive selection with our strongest signals associated with genes involved in energy regulation and metabolism (CPT1A, LRP5, THADA) and vascular smooth muscle contraction (PRKG1). By employing a new method that paints phased chromosome chunks by their ancestry we distinguish local Siberian-specific long-range haplotype signals from those introduced by admixture.     

The analogs of oxytocin and D-homoarginine vasopressin with bulky substituted phenylalanine in position 2

Solid phase technique on p-methylbenzhydrylamine resin wasused for the synthesis of eight analogs of oxytocin and 8-D-homoarginine vasopressin with the non-coded amino acids L- or D-2,3,4,5,6-pentamethylphenylalanine and L- or D-4-phenylphenylalanine in position 2. The preparation of theabove mentioned non-coded amino acids is described as well.All eight analogs were found to be potent inhibitors ofoxytocin activity in the uterotonic in vitro test in theabsence of Mg²⁺ ions. In the uterotonic test invitro in the presence of Mg²⁺ and in the test invivo, their potency is strongly decreased or completelyabolished. The substances are also weak pressor inhibitors.The L or D configuration does not seem to influence theactivity significantly.     

Secondary alcohol dehydrogenase catalyzes the reduction of exogenous acetone to 2-propanol in Trichomonas vaginalis

Secondary alcohols such as 2-propanol are readily produced by various anaerobic bacteria that possess secondary alcohol dehydrogenase (S-ADH), although production of 2-propanol is rare in eukaryotes. Specific bacterial-type S-ADH has been identified in a few unicellular eukaryotes, but its function is not known and the production of secondary alcohols has not been studied. We purified and characterized S-ADH from the human pathogen Trichomonas?vaginalis. The kinetic properties and thermostability of T.?vaginalis S-ADH were comparable with bacterial orthologues. The substantial activity of S-ADH in the parasite's cytosol was surprising, because only low amounts of ethanol and trace amounts of secondary alcohols were detected as metabolic end products. However, S-ADH provided the parasite with a high capacity to scavenge and reduce external acetone to 2-propanol. To maintain redox balance, the demand for reducing power to metabolize external acetone was compensated for by decreased cytosolic reduction of pyruvate to lactate and by hydrogenosomal metabolism of pyruvate. We speculate that hydrogen might be utilized to maintain cytosolic reducing power. The high activity of Tv-S-ADH together with the ability of T.?vaginalis to modulate the metabolic fluxes indicate efficacious metabolic responsiveness that could be advantageous for rapid adaptation of the parasite to changes in the host environment.     

An Effective Combination of Two Different Methods of Postconditioning

Ischemic tolerance based on the synthesis of protective proteins acquires its full strength by repeated exposure to stress, and "the end effector of tolerance" may paradoxically be activated by the second or lethal stress, particularly in the case of preconditioning. That happens when an additional nonspecific stressor is applied either before (preconditioning) or after (postconditioning) the period of lethal ischemia. A combination of antioxidants with pre or postconditioning prevents the acquisition of tolerance, and in the case of more severe attacks repeated stress can lead to accumulation of damage. Our attempt to weaken ischemic injury to hippocampal CA1 with antioxidants applied after lethal stress, i.e. before delayed postconditioning, was ineffective. We then tried using rapid postconditioning consisting of 30-s reperfusion alternating with 15-s ischemia repeated three times and applied immediately at the end of lethal ischemia as a tool decreasing post-ischemic production of reactive oxygen species, and combining that with delayed postconditioning consisting of an i.p. injection of Bradykinin 2?days after lethal ischemia. This approach once more confirmed the efficacy of both rapid as well as delayed postconditioning but, more importantly, it demonstrated the possibility of effectively combining these two procedures. Our findings further confirm that in cases of delayed neuronal death, which is practically pathologically-induced apoptosis, there exists a 2-day-wide therapeutic window that can be effectively exploited.     

Influence of squalene on lipid particle/droplet and membrane organization in the yeast Saccharomyces cerevisiae

In a previous study (Spanova et al., 2010, J. Biol. Chem., 285, 6127-6133) we demonstrated that squalene, an intermediate of sterol biosynthesis, accumulates in yeast strains bearing a deletion of the HEM1 gene. In such strains, the vast majority of squalene is stored in lipid particles/droplets together with triacylglycerols and steryl esters. In mutants lacking the ability to form lipid particles, however, substantial amounts of squalene accumulate in organelle membranes. In the present study, we investigated the effect of squalene on biophysical properties of lipid particles and biological membranes and compared these results to artificial membranes. Our experiments showed that squalene together with triacylglycerols forms the fluid core of lipid particles surrounded by only a few steryl ester shells which transform into a fluid phase below growth temperature. In the hem1? deletion mutant a slight disordering effect on steryl esters was observed indicated by loss of the high temperature transition. Also in biological membranes from the hem1? mutant strain the effect of squalene per se is difficult to pinpoint because multiple effects such as levels of sterols and unsaturated fatty acids contribute to physical membrane properties. Fluorescence spectroscopic studies using endoplasmic reticulum, plasma membrane and artificial membranes revealed that it is not the absolute squalene level in membranes but rather the squalene to sterol ratio which mainly affects membrane fluidity/rigidity. In a fluid membrane environment squalene induces rigidity of the membrane, whereas in rigid membranes there is almost no additive effect of squalene. In summary, our results demonstrate that squalene (i) can be well accommodated in yeast lipid particles and organelle membranes without causing deleterious effects; and (ii) although not being a typical membrane lipid may be regarded as a mild modulator of biophysical membrane properties.     

The effect of pH,bile and calcium on the adhesion ability of probiotic enterococci of animal origin to the porcine jejunal epithelial cell line IPEC-J2

Examination of adhesion ability using a quantitative assay based on radiolabelled bacteria showed that 10 Enterococcus strains exhibited adhesion ability from 2 to 4%. Enterococcus faecium EF2019 (isolate from rabbit faeces, deponed to Czech Culture of Microorganisms in Brno, CCM 7420) showed the highest adhesion ability (4.0 ± 0.4%). With regard to survival, all strains displayed good resistance towards 0.3% oxgall and HCl (pH 3.0). Pretreatment of strains with HCl (pH 3.0) significantly reduced their adhesion. Pretreatment of strains by oxgall significantly reduced the adhesion capacity of E. faecium EF2019, EF1839 and EF319 strains, while the adhesion ability of E. faecium EE3 (isolate from canine feed) slightly increased. Furthermore, addition of calcium (200 mmol/l) significantly increased (P < 0.001) the adhesion ability for all strains tested. The adhesion ability of the isolates from rabbits, EF1839 and EF529, as well as the isolate EE3 (strain from canine feed) increased from 2–3% up to 50–55% upon calcium addition. Despite, in general low adhesive properties, strains can survive passage through the gastrointestinal tract.