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Cell culture and western blotting studies revealed that aflatoxin B-1 (AFB(1)) inhibits the biosynthesis of two of the constituent polypeptides of signal recognition particle (SRP) (SRP54 and 72). SRP escorts polyribosomes carrying signal peptides from free form in the cytosol to the bound form on endoplasmic reticulum (ER) membrane during protein targeting. These effects of AFB(1) on SRP biosynthesis may inhibit the formation of functional SRP Our experiments have further shown that AFB(1) also inhibits the biosynthesis/translocation of a secretory protein, preprolactin, which fails to appear in the lumen of ER consequent to the treatment with this hepatocarcinogen. The results of the experiments presented in this article therefore enable us to infer for the first time that aflatoxin B-1 may inhibit the functioning of SRP as an escort and deplete the ER of polyribosomes for secretory protein synthesis. As these secretory proteins are important components of the plasma membrane, gap junctions and intercellular matrix, their absence from these locations could disturb cell to cell communication leading to tumorigenesis.
Question: Is there a relationship between size and death in the Iona-lived, deep-rooted tree, Acacia erioloba, in a semi-arid savanna? What is the size-class distribution of A. erioloba mortality? Does the mortality distribution differ from total tree size distribution? Does A. erioloba mortality distribution match the mortality distributions recorded thus far in other environments? Location: Dronfield Ranch, near Kimberley, Kalahari, South Africa. Methods: A combination of aerial photographs and a satellite image covering 61 year was used to provide long-term spatial data on mortality. We used aerial photographs of the study area from 1940, 1964, 1984, 1993 and a satellite image from 2001 to follow three plots covering 510 ha. We were able to identify and individually follow ca. 3000 individual trees from 1940 till 2001. Results: The total number of trees increased over time. No relationship between total number of trees and mean tree size was detected. There were no trends over time in total number of deaths per plot or in size distributions of dead trees. Kolmogorov-Smirnov tests showed no differences in size class distributions for living trees through time. The size distribution of dead trees was significantly different from the size distribution of all trees present on the plots. Overall, the number of dead trees was low in small size classes, reached a peak value when canopy area was 20 - 30 m(2), and declined in lamer size-classes. Mortality as a ratio of dead vs. total trees peaked at intermediate canopy sizes too. Conclusion: A. erioloba mortality was size-dependent, peaking at intermediate sizes. The mortality distribution differs from all other tree mortality distributions recorded thus far. We suggest that a possible mechanism for this unusual mortality distribution is intraspecific competition for water in this semi-arid environment.
Cave animals are widely recognised as model organisms to study regressive evolutionary processes like the reduction of eyes. In this paper, we report on the regressive evolution of species discrimination in the cave molly, Poecilia mexicana, which, unlike other cave fishes, still has functional eyes. This allowed us to examine the response to both visual and non-visual cues involved in species discrimination. When surface-dwelling females were given a chance to associate with either a conspecific or a swordtail (Xiphophorus hellerii) female, they strongly preferred the conspecific female both when multiple cues and when solely visual cues were available to the female. No association preference was observed when only non-visual cues were provided. In contrast, cave-dwelling females showed no preference under all testing conditions, suggesting that species recognition mechanisms have been reduced. We discuss the role of species discrimination in relation to habitat differences.
The addition of lysozyme amounting to 1000 mg/l wine does neither effect its total phenol content (Folin-Ciocalteu-Method), nor wine colour (measured by extinction at 512 nm) nor its antioxidative capacity (TEAC-Assay). No covalent binding of wine phenols to the enzyme was observed during lysozyme addition, although non-covalent interactions are possible. Lysozyme activity is not influenced by the presence of malvidin-3-glucoside and resveratrol in model experiments, whereas pH and ethanol content produce a corresponding alteration in lysozyme activity. With regard to red wine, a significant effect was noted in the presence of wine components.
Seasonal, host sex and age-related variations in helminth egg and coccidian oocyst counts were investigated in a naturally infected wild bushbuck (Tragelaphus scriptus) population in Queen Elizabeth National Park, western Uganda from April 2000 to February 2002. The prevalence and mean intensity quantified as the number of eggs and oocysts per gram of faeces were taken as a measure of parasite burdens. Host sex and age-related differences in prevalence values were not found but the overall prevalence of Eimeria sp. was significantly higher during the rainy season, and peak counts were recorded either during or soon after a peak rainfall. A similar trend was observed for Moniezia spp., although the results were marginally not significant. There were also no significant differences in mean intensity values, relative to host sex, age or season.
The AtNFXL1 gene encodes a NF-X1 type zinc finger protein required for growth under salt stress
(2006)
The human NF-X1 protein and homologous proteins in eukaryotes represent a class of transcription factors which are characterised. by NF-X1 type zinc finger motifs. The Arabidopsis genome encodes two NF-X1 homologs, which we termed AtNFXL1 and AtNFXL2. Growth and survival was impaired in atnfxl1 knock-out mutants and AtNFXL1-antisense plants under salt stress in comparison to wild-type plants. In contrast, 35S: :AtNFXL1 plants showed higher survival rates. The AtNFXL2 protein potentially plays an antagonistic role. The Arabidopsis NF-X1 type zinc finger proteins likely are part of regulatory mechanisms, which protect major processes such as photosynthesis.
Sexual dimorphism is expressed as median of the female values in percent of the median of the male values, of 4 length measurements, 3 circumferences, and 5 measurements of corpulence respectively fat. Data were obtained from a cross-sectional sample of more than 41.000 German subjects, aged from birth to age 62. The pattern of sexual dimorphism is similar in the length measurements. Girls are shorter at birth, but they increase in length at higher rates than boys and even temporarily overgrow the boys up to age 12. Thereafter, males show an obvious growth advantage leading to some 6 to 9% more length in adult males. In contrast, female circumferences are always smaller, from birth to senescence. Though, the differences between the sexes are low in circumferences, up to age 13, sexual dimorphism increases to 17% in the thoracic circumference at adulthood. Sexual dimorphism in weight and BMI is comparably with that in length measurements while subcutaneous fat and total body fat content are always higher in females. The results highlight that sexual dimorphism develops at different pace in the various components of the body and that it associates with a sex specific growth tempo.
More than one century ago, sturgeons were prevalent species in the fish communities of all major German rivers both in the North and the Baltic seas drainages. Since then, the populations declined rapidly due to river damming, overfishing and pollution. The last sturgeon catches in the Baltic drainage system occurred during the late 1960ies. Only a few individual captures have been reported during the last 30 years with the most recent records in the Lake Ladoga ( Russia), where the last confirmed catch was recorded in 1984, and a single individual caught off Estonia in 1996. Today, sturgeons are considered missing or extinct in German waters. First attempts for remediation of the species were undertaken in the mid 1990ies. Subsequently, phylogenetic and population genetic analyses of the species were carried out using mtDNA, microsatellites, and nuclear markers ( SNPs). These genetic analyses using recent and historic material have proven the existence of two different species in the Baltic Sea in what was previously considered to represent the European Atlantic sturgeon only. In the Baltic Sea, the American Atlantic sturgeon ( A. oxyrinchus) succeeded to colonize this brackish water system during the Middle Ages. In the North Sea, the European Atlantic sturgeon ( A. sturio) is considered to be the endemic species. These results led to the separation of the remediation activities in the North Sea and the Baltic Sea tributaries. Further studies on the mechanism that lead to the extinction of A. sturio in Germany and the subsequent succession of the A. oxyrinchus mtDNA haplotype are currently been carried out. Broodstock development using the northernmost populations of A. oxyrinchus is currently under way. As a further prerequisite to re-introduce this species into the Baltic, the evaluation of the status of critical habitats for the early life stages of the American Atlantic sturgeon in the River Odra has been performed in collaboration with the Institute for Inland Fisheries of Poland. Alternative fisheries techniques, based on the data of by-catch of exotic sturgeons in the fishery, are presently developed in close cooperation with the fishery to reduce fisheries related mortality in juvenile sturgeons upon release. Monitoring of habitat utilization and migration characteristics of juvenile fish upon experimental release will have to be carried out shortly, using acoustic telemetry, with the aim to follow the fate of the released fish and to determine the best time-size-release-window for future release programmes.
Female extra-pair mating, fitness and genetic diversity: Expression in socially monogamous Coal Tits
(2006)
Life on the edge: hydrogen sulfide and the fish communities of a Mexican cave and surrounding waters
(2006)
Most eucaryotic organisms classified as living in an extreme habitat are invertebrates. Here we report of a fish living in a Mexican cave (Cueva del Azufre) that is rich in highly toxic H2S. We compared the water chemistry and fish communities of the cave and several nearby surface streams. Our study revealed high concentrations of H2S in the cave and its outflow (El Azufre). The concentrations of H2S reach more than 300 mu M inside the cave, which are acutely toxic for most fishes. In both sulfidic habitats, the diversity of fishes was heavily reduced, and Poecilia mexicana was the dominant species indicating that the presence of H2S has an all-or-none effect, permitting only few species to survive in sulfidic habitats. Compared to habitats without H2S, P. mexicana from the cave and the outflow have a significantly lower body condition. Although there are microhabitats with varying concentrations of H2S within the cave, we could not find a higher fish density in areas with lower concentrations of H2S. We discuss that P. mexicana is one of the few extremophile vertebrates. Our study supports the idea that extreme habitats lead to an impoverished species diversity.
A tailor-made horseradish peroxidase (HRP) bulk composite electrode was developed on the basis of pyrolyzed cobalt tetramethoxyphenylporphyrin (CoTMPP) by modifying pore size and surface area of the porous carbon material through varying amounts of iron oxalate and sulfur prior to pyrolyzation. The materials were used to immobilize horseradish peroxidase (HRP). These electrodes were characterized in terms of their efficiency to reduce hydrogen peroxide. The heterogeneous electron transfer rate constants of different materials were determined with the rotating disk electrode method and a k(S) (401 +/- 61 s(-1)) exceeding previously reported values for native HRP was found.
Profiling of plant secondary metabolites is still a very difficult task. Liquid chromatography (LC) or capillary electrophoresis hyphenated with different kinds of detectors are methods of choice for analysis of polar, thermo labile compounds with high molecular masses. We demonstrate the applicability of LC combined with UV diode array or/and mass spectrometric detectors for the unambiguous identification and quantification of flavonoid conjugates isolated from Arahidopsis thaliana leaves of different genotypes and grown in different environmental conditions. During LC/UV/MS/MS analyses we were able to identify tetra-, tri, and di-glycosides of kaempferol, quercetin and isorhamnetin. Based on our results we can conclude that due to the co-elution of different chemical compounds in reversed phase H PLC systems the application of UV detectors does not allow to precisely profile all flavonoid conjugates existing in A. thaliana genotypes. Using MS detection it was possible to unambiguously recognize the glycosylation patterns of the aglycones. However, from the mass spectra we could not conclude neither the anomeric form of the C-1 carbon atoms of sugar moieties in glycosidic bonds between sugars or sugar and aglycone nor the position of the second carbon involved in disaccharides. The applicability of collision induced dissociation techniques (CID MS/MS) for structural analyses of the studied group of plant secondary metabolites with two types of analyzers (triple quadrupole or ion trap) was demonstrated.
In this paper on the ontogenesis and evolutionary biology of odontocete cetaceans (toothed whales), we investigate the head morphology of three perinatal pantropical spotted dolphins (Stenella attenuata) with the following methods: computer-assisted tomography, magnetic resonance imaging, conventional X-ray imaging, cryo-sectioning as well as gross dissection. Comparison of these anatomical methods reveals that for a complete structural analysis, a combination of modern imaging techniques and conventional morphological methods is needed. In addition to the perinatal dolphins, we include series of microslides of fetal odontocetes (S. attenuata, common dolphin Delphinus delphis, narwhal Monodon monoceros). In contrast to other mammals, newborn cetaceans represent an extremely precocial state of development correlated to the fact that they have to swim and surface immediately after birth. Accordingly, the morphology of the perinatal dolphin head is very similar to that of the adult. Comparison with early fetal stages of dolphins shows that the ontogenetic change from the general mammalian bauplan to cetacean organization was characterized by profound morphological transformations of the relevant organ systems and roughly seems to parallel the phylogenetic transition. from terrestrial ancestors to modern odontocetes.
Activity patterns and time budgets of bushbuck (Tragelaphus scriptus) were studied in a free-ranging population in Queen Elizabeth National Park, Uganda from August 2000 to January 2002. We investigated differences in activity patterns in relation to daytime, season, sun radiation, moonlight, age and sex. Bushbuck were found to show peak activities around sunrise and at dawn. No difference in the mean activity rates was found between the dry and wet season. Daytime activity was not predicted by differences in sun radiation, nor was nighttime activity predicted by the presence or absence of moonlight. We found the activity of adult territorial males to be strongly positively correlated with that of females, whereas the activity of young-adult non-territorial males was not significantly correlated with the activity of females. This suggests that young-adult males shift their peak activity to phases when adult territorial males are less active.
The small and large subunits of molybdopterin (MPT) synthase (MOCS2A and MOCS2B), are both encoded by the MOCS2 gene in overlapping and shifted open reading frames (ORFs), which is a highly unusual structure for eukaryotes. Theoretical analysis of genomic sequences suggested that the expression of these overlapping ORFs is facilitated by the use of alternate first exons leading to alternative transcripts. Here, we confirm the existence of these overlapping transcripts experimentally. Further, we identified a deletion in a molybdenum cofactor deficient patient, which removes the start codon for the small subunit (MOCS2A). We observed undisturbed production of both transcripts, while Western blot analysis demonstrated that MOCS2B, the large subunit, is unstable in the absence of MOCS2A. This reveals new insights into the expression of this evolutionary ancient anabolic system.
The pollination biology of three mass flowering Utricularia species of the Indian Western Ghats, U. albocaerulea, U. purpurascens, and U. reticulata, was studied for the first time by extensive observation of flower visitors, pollination experiments, and nectar analyses. The ephemerality of the Utricularia habitats on lateritic plateaus, weather conditions adverse to insects, lack of observations of flower visitors to other Utricularia spp., and the predominance of at least. facultative autogamy in the few Utricularia species studied so far suggested that an autogamous breeding system is the common case in the genus. In contrast, we showed that the studied populations are incapable of autonomous selfing, or that it is an event of negligible rarity, although P/O was similarily low as in autogamous species investigated by other authors. In all three species the spatial arrangement of the reproductive organs makes an insect vector necessary for pollen transfer between and within flowers. However, U. purpurascens and U. reticulata are highly self-compatible, which allows for visitor-mediated auto-selfing and geitonogamy on inflorescence and clone level. Floral nectar is present in extremely small volumes in all three species, but sugar concentrations are high. More than 50 species of bees, butterflies, moths, hawk moths, and clipterans were observed to visit the flowers, and flower morphology facilitated pollination by all observed visitors. The results are discussed in the context of the phenological characteristics of the studied species, especially the phenomenon of mass flowering, and the environmental conditions of their habitats.