Life cycle of Cyclops vicinus in relation to food availability, predation, diapause and temperature

The seasonal cycle of Cyclops vicinus was studied during a 5year period in the shallow and hypertrophic Lake Søbygård.The annual number of generations varied between three and sixand sometimes included midsummer generations. Naupliar and copepoditedensity was extremely high, the maximum recorded being 1313and 745 1^–1 respectively. The seasonal fluctuation inthe abundance of C.vicinus was related to the concentrationof edible phytoplankton (EDP): when diatoms and cryptomonadswere abundant, nauplii and copepodites were also abundant, whereaswhen greens such as Scenedesmus spp. were dominant, no cohortswere observed. The maximum density of copepodites in the separatecohorts and the amount of EDP, expressed as carbon content,were found to be significantly correlated. The development ofthe second cohort also seemed to depend on the occurrence ofa peak in rotifer density. High number of eggs per female generallycoincided with high biovolume of EDP, suggesting that algaeconstituted a major part of the diet of adult C. vicinus. Theduration of the naupliar stage was inversely related to temperatureand is one of the shortest times that have been recorded inthe literature. The short duration is probably attributableto the abundance of food. Fish composition and the calculatedsex ratio of C.vicinus indicate low predation pressure fromplanktivorous fish. The high density of C.vicinus during thesummer, when the whole population would be expected to haveentered diapause, is probably attributable to the concurrenceof low predation and the abundance of food.     

Histochemische Untersuchungen zum Energie- und Pentosephosphatstoffwechsel bei der epithelialen Wundheilung

Zusammenfassung Im Verlauf des epithelialen Wundverschlusses können zwei Phasen unterschieden werden. In der ersten Phase (0–48 Std) kommt es zur Glykogeneinlagerung in das Epithel des Wundrandes; bei hohen Aktivitäten der Enzyme SDH, LDH, G-6-P-DH und 6-P-G-DH steigt der RNS-Gehalt in den basalen Zellen an. Im Verlauf der zweiten Phase (60–114 Std) nehmen sowohl der Glykogengehalt als auch die Aktivitäten von LDH, G-6-P-DH und 6-P-G-DH ab. Im gleichen Zeitraum bildet sich eine Epithelschicht in der Wundmitte, deren anfänglicher Glykogenreichtum gegen Ende der Wundheilung wieder verschwindet. Hier ist bei hohen Aktivitäten der LDH, G-6-P-DH und 6-P-G-DH ebenfalls ein Anstieg der RNS-Konzentration nachweisbar. Die Befunde zeigen, daß bei der Wundheilung ein Teil der verfügbaren Glucose über den Pentosephosphat-Zyklus für die Nucleinsäuresynthese verwendet wird.

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Histochemical studies of energy and pentosephosphate metabolism during epithelial wound healing

Summary During epithelial wound healing two periods can be distinguished. In the first period (0–48 h) glycogen is accumulated in the epithelium of the peripheral wound zone, and increasing activities of SDH, LDH, G-6-P-DH and RNA concentrations especially in the basal cells can be detected. In the second period (60–114 h) the glycogen content as well as the activities of LDH, G-6-P-DH and 6-P-G-DH decrease. At the same time an epithelial layer is built up in the central wound zone, the glycogen content of which disappears till the end of wound healing. In this layer high activities of LDH, G-6-P-DH and 6-P-G-DH and an increase of RNA concentration can be demonstrated. The findings illustrate, that during wound healing the available glucose partially is metabolized by the pentose-phosphateshunt and is used for the synthesis of nucleic acids.

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Herrn Professor Dr. Dr. F. Timm zum 75. Geburtstag zugeeignet.

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Wesentliche Teile dieser Untersuchung werden von Herrn R. Schroll dem Fachbereich Theoretische Medizin der Universität Tübingen als Inauguraldissertation vorgelegt.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Fibrin Clot Structure and Platelet Aggregation in Patients with Aspirin Treatment Failure

Background

Aspirin is a cornerstone in prevention of cardiovascular events and modulates both platelet aggregation and fibrin clot formation. Some patients experience cardiovascular events whilst on aspirin, often termed aspirin treatment failure (ATF). This study evaluated both platelet aggregation and fibrin clot structure in patients with ATF.

Methods

We included 177 stable coronary artery disease patients on aspirin monotherapy. Among these, 116 (66%) had ATF defined as myocardial infarction (MI) whilst on aspirin. Platelet aggregation was assessed by Multiplate® aggregometry and VerifyNow®, whereas turbidimetric assays and scanning electron microscopy were employed to study fibrin clot characteristics.

Results

Enhanced platelet aggregation was observed in patients with ATF compared with non-MI patients following stimulation with arachidonic acid 1.0 mM (median 161 (IQR 95; 222) vs. 97 (60; 1776) AU*min, p = 0.005) and collagen 1.0 µg/mL (293 (198; 427) vs. 220 (165; 370) AU*min, p = 0.03). Similarly, clot maximum absorbance, a measure of fibrin network density, was increased in patients with ATF (0.48 (0.41; 0.52) vs. 0.42 (0.38; 0.50), p = 0.02), and this was associated with thinner fibres (mean ± SD: 119.7±27.5 vs. 127.8±31.1 nm, p = 0.003) and prolonged lysis time (552 (498; 756) vs. 519 (468; 633) seconds; p = 0.02). Patients with ATF also had increased levels of C-reactive protein (CRP) (1.34 (0.48; 2.94) and 0.88 (0.32; 1.77) mg/L, p = 0.01) compared with the non-MI group. Clot maximum absorbance correlated with platelet aggregation (r = 0.31–0.35, p-values<0.001) and CRP levels (r = 0.60, p<0.001).

Conclusions

Patients with aspirin treatment failure showed increased platelet aggregation and altered clot structure with impaired fibrinolysis compared with stable CAD patients without previous MI. These findings suggest that an increased risk of aspirin treatment failure may be identified by measuring both platelet function and fibrin clot structure.     

Conversion of solvent evaporation residues from the AB- (acetone - butanol) bioprocess into bacterial cells accumulating thermoplastic polyesters

In a bioconversion study based on utilisation of by-products from the AB- (acetone - butanol) bioprocess a new isolated gram-negative solvent tolerant bacterium was used to convert the AB process residue after removal of the major part of the solvents. The bacterium identified as a representative of the genus Alcaligenes (designated as Alcaligenes sp. G) was capable of growth up to optical densities ranging from 8 to 20 and simultaneously of polyhydroxyalkanoate-(PHA-)accumulation up to 40% per dry weight. A standardised medium based on AB by-products containing 7 g/l of butyrate and 5 g/l of acetate at pH 7.5 was used in our studies for bioconversion into PHAs. Concentrations of 1-butanol, which is known for its membrane damaging properties in microorganisms, were tolerated in the AB by-products medium up to 4 g/l without significant inhibition of cellular growth. No inhibition of growth was observed, when the medium was adjusted to 40 g/l butyrate. Due to the toxicity of the remaining 1-butanol maintenance of sterility is of no high priority during the process. The use of acetate and butyrate from an AB process is expected to provide a higher return-on-investment than the combustion of biogas to help meet energy demands.     

TNF-alpha, leptin, and lymphocyte function in human aging

Aging is associated with increased inflammatory activity and concomitant decreased T cell mediated immune responses. Leptin may provide a link between inflammation and T cell function in aging. The aim of the study was to investigate if plasma levels of tumor necrosis factor (TNF)-alpha were associated with leptin, circulating interleukin-2 receptors (sIL-2R), and phytohaemagglutinin (PHA) induced IL-2 production in whole blood in elderly humans. Circulating levels of TNF-alpha and sIL-2R were higher in elderly humans (N=42) compared to a young control group (N=37) whereas there was no difference with regard to IL-2 production. Furthermore, there were no age-related differences in serum levels of leptin. However, women had higher levels than men. In the elderly people, serum levels of leptin were correlated with TNF-alpha in univariate regression analysis and in a multiple linear regression analysis adjusting for the effect of gender and body mass index. Furthermore, TNF-alpha, but not leptin, was positively correlated to sIL-2R and negatively correlated to IL-2 production. In conclusion, increased plasma levels of TNF-alpha in aging is associated with poor IL-2 production ex vivo and lymphocyte activation in vivo. These associations do not seem to involve leptin.     

Effects of azathioprine and its metabolites on repair mechanisms of the intestinal epithelium in vitro

Erosions and ulcerations of the intestinal epithelium are hallmarks of inflammatory bowel diseases (IBD). Intestinal epithelial cell migration (restitution) and proliferation are pivotal mechanisms for healing of epithelial defects after mucosal injury. In addition, the rate of apoptosis of epithelial cells may modulate intestinal wound healing. The purine antagonists azathioprine (AZA) and 6-mercaptopurine (6-MP) are widely used drugs in the treatment of IBD. In the present study, the hitherto unknown effects of AZA as well as its metabolites 6-MP and 6-thioguanine (6-TG) on repair mechanisms and apoptosis of intestinal epithelia were analysed. Intestinal epithelial cell lines (human Caco-2, T-84 and HT-29 cells, rat IEC-6 cells) were incubated with AZA, 6-MP or 6-TG for 24 h (final concentrations 0.1-10 microM). Migration of Caco-2 and IEC-6 cells was analysed by in vitro restitution assays. Caco-2 and IEC-6 cell proliferation was evaluated by measurement of [3H]thymidine incorporation into DNA. Apoptosis of Caco-2, T-84, HT-29 and IEC-6 cells was assessed by histone ELISA, 4'6'diamidino-2'phenylindole-dihydrochloride staining as well as flow cytometric analysis of Annexin V/propidium iodide (PI)-stained cells. Cell cycle progression was evaluated by PI staining and flow cytometry. Epithelial restitution was not significantly affected by any of the substances tested. However, proliferation of intestinal epithelial cells was inhibited in a dose-dependent manner (maximal effect 92%) by AZA, 6-MP as well as 6-TG. In HT-29 cells, purine antagonist-effected inhibition of cell proliferation was explained by a cell cycle arrest in the G2 phase. In contrast, AZA, 6-MP and 6-TG induced no cell cycle arrest in Caco-2, T-84 and IEC-6 cells. AZA, 6-MP as well as 6-TG induced apoptosis in the non-transformed IEC-6 cell line but not in human Caco-2, T-84 and HT-29 cells. In summary, AZA and its metabolites exert no significant effect on intestinal epithelial restitution. However, they profoundly inhibit intestinal epithelial cell growth via various mechanisms: they cause a G2 cell cycle arrest in HT-29 cells, induce apoptosis in IEC-6 cells and dose-dependently inhibit intestinal epithelial proliferation.     

BGX: a fully Bayesian integrated approach to the analysis of Affymetrix GeneChip data

We present Bayesian hierarchical models for the analysis of Affymetrix GeneChip data. The approach we take differs from other available approaches in two fundamental aspects. Firstly, we aim to integrate all processing steps of the raw data in a common statistically coherent framework, allowing all components and thus associated errors to be considered simultaneously. Secondly, inference is based on the full posterior distribution of gene expression indices and derived quantities, such as fold changes or ranks, rather than on single point estimates. Measures of uncertainty on these quantities are thus available. The models presented represent the first building block for integrated Bayesian Analysis of Affymetrix GeneChip data: the models take into account additive as well as multiplicative error, gene expression levels are estimated using perfect match and a fraction of mismatch probes and are modeled on the log scale. Background correction is incorporated by modeling true signal and cross-hybridization explicitly, and a need for further normalization is considerably reduced by allowing for array-specific distributions of nonspecific hybridization. When replicate arrays are available for a condition, posterior distributions of condition-specific gene expression indices are estimated directly, by a simultaneous consideration of replicate probe sets, avoiding averaging over estimates obtained from individual replicate arrays. The performance of the Bayesian model is compared to that of standard available point estimate methods on subsets of the well known GeneLogic and Affymetrix spike-in data. The Bayesian model is found to perform well and the integrated procedure presented appears to hold considerable promise for further development.     

The use of 2,2′‐dithiobis(5‐nitropyridine) (DTNP) for deprotection and diselenide formation in protected selenocysteine‐containing peptides

In contrast to the large number of sidechain protecting groups available for cysteine derivatives in solid phase peptide synthesis, there is a striking paucity of analogous selenocysteine Se‐protecting groups in the literature. However, the growing interest in selenocysteine‐containing peptides and proteins requires a corresponding increase in availability of synthetic routes into these target molecules. It therefore becomes important to design new sidechain protection strategies for selenocysteine as well as multiple and novel deprotection chemistry for their removal. In this paper, we outline the synthesis of two new Fmoc selenocysteine derivatives [Fmoc‐Sec(Meb) and Fmoc‐Sec(Bzl)] to accompany the commercially available Fmoc‐Sec(Mob) derivative and incorporate them into two model peptides. Sec‐deprotection assays were carried out on these peptides using 2,2′‐dithiobis(5‐nitropyridine) (DTNP) conditions previously described by our group. The deprotective methodology was further evaluated as to its suitability towards mediating concurrent diselenide formation in oxytocin‐templated target peptides. Sec(Mob) and Sec(Meb) were found to be extremely labile to the DTNP conditions whether in the presence or absence of thioanisole, whereas Sec(Bzl) was robust to DTNP in the absence of thioanisole but quite labile in its presence. In multiple Sec‐containing model peptides, it was shown that bis‐Sec(Mob)‐containing systems spontaneously cyclize to the diselenide using 1 eq DTNP, whereas bis‐Sec(Meb) and Sec(Bzl) models required additional manipulation to induce cyclization. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Gut evacuation rates and ingestion rates of Eudiaptomus graciloides measured by means of the gut fluorescence method

Diel variation in feeding rates of Eudiaptomus graciloides wasmeasured in situ with the gut fluorescence method during Mayand June in the eutrophic Frederiksborg Slotss Pronounced dielperiodicity occurred in both periods with highest feeding ratesduring the night. The food concentration as well as the periodicitywas almost constant with depth, indicating that the feedingactivity represents a behavioral periodicity. The gut evacuationmeasured in the laboratory on field-collected copepods was exponentialand temperature-dependent. The exponential decline in gut contentwas found for both copepods feeding continuously and when feedinghad ceased. Considering spatial and temporal variation in feedingactivity, daily ratios were 61–68 body carbon per day,and higher than if calculated from existing laboratory dataof short-term feeding dates.