Der Einfluß der Umweltfaktoren auf das Wachstum und den Häutungsrhythmus der StrandkrabbeCarcinides maenas

Zusammenfassung 1. Junge Strandkrabben von 4–16 mm Carapaxbreite wurden bis zur Geschlechtsreife unter konstanten Umweltbedingungen aufgezogen.2. Die Dauer ihrer Häutungsintervalle nimmt bei konstanter Temperatur mit der Körpergröße stetig zu.3. Die Dauer der Häutungsintervalle hängt von der Temperatur und der Ernährung ab. Von der Tageslänge scheint sie weitgehend unabhängig zu sein.4. Der relative Grösßenzuwachs bei jeder Häutung ist im gesamten untersuchten Größenbereich und bei den verschiedenen Temperaturen bei allen Häutungen gleich: Bei den Häutungen verdoppelt sich jeweils das Körpervolumen.5. Augenstielamputationen und Verlust von Extremitäten wirken auf den Häutungsrhythmus in gleicher Weise: Die Schwankungsbreite in der Dauer der Häutungsintervalle ist vermindert. Die Häutungsintervalle sind in 20° C deutlich, in 10° C nur geringfügig verkürzt.6. Durch die Anwesenheit größerer Artgenossen werden die Häutungen verzögert. Die optische Wahrnehmung spielt dabei keine Rolle.7. Aus diesen Ergebnissen wird folgendes geschlossen: Der ausschlaggebende Faktor für die Auslösung von Häutungen ist ein bestimmter Größenzuwachs. Temperatur und Ernährung beeinflussen den Häutungsrhythmus dadurch, daß sie das Tempo des Wachstums bestimmen. Die winterliche Häutungsruhe in Freilandpopulationen wird nicht durch den Kurztag bedingt, sondern durch die Kälte. Diese hemmt lediglich das Wachstum, sie verhindert nicht die Häutungen über das häutungshemmende Hormon. Dieses vermindert vielmehr die Temperaturabhängigkeit des Häutungsrhythmus, indem es die Häutungen im Warmen stärker verzögert als im Kalten. Es gestattet die Anpassung des Häutungstermins an die individuelle Lage der Tiere. Es hemmt in Anwesenheit größerer Artgenossen die Häutung. Beim Verlust mehrerer Gliedmaßen wird seine Sekretion eingestellt, so daß die nächste Häutung vorzeitig erfolgt. Das häutungshemmende Hormon bedingt dementsprechend die große individuelle Variation in der Dauer der Häutungsintervalle.

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The effect of environmental factors on growth and moulting rhythm in the shore crab,Carcinides maenas

Young crabs (carapace width 4 to 16 mm) were raised under controlled conditions in the laboratory. The time intervals between subsequent moults increase at all test temperatures with increasing body size. The length of intermoult periods varies with temperature and feeding. It is not affected by day length. Moulting takes place as soon as a certain increase in size is attained. In comparable size groups, the amount of this increase is identical in all test temperatures. Moreover, the relation of increase to initial size is constant over the whole size range investigated. The body volume doubles at each moult. Eyestalk amputations and loss of extremities have similar effects: They shorten the intermoult periods at 20° C considerably, but at 10° C they do so only slightly; furthermore, the amplitude of fluctuations is narrowed. The presence of large specimens tends to retard moulting in smaller ones; this response is independent of visual stimuli. The following assumptions are made: Low temperatures retard the moulting rhythm directly by slowing down growth. They are not acting via the moult inhibiting hormone. Loss of several extremities causes a stop of hormone delivery resulting in shortened intermoult periods. Recognition by touch of a larger specimen causes increased hormone delivery and thus retardation of the subsequent moulting process.

     

Extracellular Protease of Pseudomonas fluorescens CHA0, a Biocontrol Factor with Activity against the Root-Knot Nematode Meloidogyne incognita

In Pseudomonas fluorescens CHA0, mutation of the GacA-controlled aprA gene (encoding the major extracellular protease) or the gacA regulatory gene resulted in reduced biocontrol activity against the root-knot nematode Meloidogyne incognita during tomato and soybean infection. Culture supernatants of strain CHA0 inhibited egg hatching and induced mortality of M. incognita juveniles more strongly than did supernatants of aprA and gacA mutants, suggesting that AprA protease contributes to biocontrol.     

Carotid artery stenting: update

"Extracranial carotid artery stenosis is responsible for approximately 20-30% of ischemic strokes. Traditionally, carotid artery stenosis has been treated with carotid endarterectomy. However, the low periprocedural complication rate and the mid term durability of carotid artery stenting has made it a competitive alternative treatment strategy. This update reviews the technical aspects of carotid artery stenting, clinical data supporting carotid artery stenting-particularly in high risk patients, and the complications associated with carotid artery stenting."     

The histone deacetylase inhibitor trichostatin A mediates upregulation of 5-lipoxygenase promoter activity by recruitment of Sp1 to distinct GC-boxes

The histone deacetylase inhibitor trichostatin A (TsA) potently induces 5-lipoxygenase (5-LO) promoter activity in reporter gene assays as well as 5-LO mRNA expression. We identified two proximal Sp1/Sp3 binding sites in the 5-LO gene promoter mediating the TsA effect in both 5-LO-negative HeLa cells and in 5-LO expressing Mono Mac 6 (MM6) cells, the tandem GC-boxes, by contrast, were not important for the TsA effect. TsA neither altered the protein expression levels of Sp1/Sp3 nor of the histone deacetylases HDAC1/2, nor did it apparently change the protein complex formation by these factors. Also, treatment of cells with TsA did not change the binding affinity of Sp1/Sp3 in cell extracts, as tested by DAPA analysis using probes containing the proximal GC boxes. However, in the living cell TsA induced Sp1, Sp3 and RNA polymerase II recruitment to the 5-LO promoter without changing the acetylation status of histone protein H4. Cotransfection studies suggest that both Sp1 and Sp3 can mediate the TsA effect. This is the first report demonstrating that Sp3 is involved in the regulation of 5-LO promoter activity. In summary, we show that TsA increases 5-LO promoter activity by the enhanced recruitment of Sp1 and Sp3 to the 5-LO promoter.     

Observations below multiple lower limits of quantification: How to estimate the mean and variance

Multiple lower limits of quantification (MLOQs) result if various laboratories are involved in the analysis of concentration data and some observations are too low to be quantified. For normally distributed data under MLOQs there exists only the multiple regression method of Helsel to estimate the mean and variance. We propose a simple imputation method and two new maximum likelihood estimation methods: the multiple truncated sample method and the multiple censored sample method. A simulation study is conducted to compare the performances of the newly introduced methods to Helsel's via the criteria root mean squared error (RMSE) and bias of the parameter estimates. Two and four lower limits of quantification (LLOQs), various amounts of unquantifiable observations and two sample sizes are studied. Furthermore, the robustness is investigated under model misspecification. The methods perform with decreasing accuracy for increasing rates of unquantified observations. Increasing sample sizes lead to smaller bias. There is almost no change in the performance between two and four LLOQs. The magnitude of the variance impairs the performance of all methods. For a smaller variance, the multiple censored sample method leads to superior estimates regarding the RMSE and bias, whereas Helsel's method is superior regarding the bias for a larger variance. Under model misspecification, Helsel's method was inferior to the other methods. Estimating the mean, the multiple censored sample method performed better, whereas the multiple truncated sample method performs best in estimating the variance. Summarizing, for a large sample size and normally distributed data we recommend to use Helsel's method. Otherwise, the multiple censored sample method should be used to obtain estimates of the mean and variance of data including MLOQs.     

Growth of Zea mays L. plants with their seminal roots only. Effects on plant development, xylem transport, mineral nutrition and the flow and distribution of abscisic acid (ABA) as a possible shoot to root signal

Maize (Zea mays L.) was grown in quartz sand culture eitherwith a normal root system (controls) or with seminal roots only(‘single-rooted’). Development of adventitious rootswas prevented by using plants with an etiolated mesocotyl andthe stem base was positioned 5–8 cm above the sand. Eventhough the roots of the single-rooted plants were sufficientlysupplied with water and nutrients, the leaves experienced waterdeficits and showed decreased transpiration as trans plrationalwater flow was restricted by the constant number of xylem vesselspresent in the mesocotyl. As a consequence of this restriction,transpirational water flow velocities in the metaxylem vesselsreached mean values of 270 m h^–1 and phloem transportvelocities of 5.2 m h^–1. Despite limited xylem transportmineral nutrient concentrations in leaf tissues were not decreasedin single-rooted plants, but shoot and particularly stem developmentwas somewhat inhibited. Due to the lack of adventitious rootsthe shoot:root ratio was strongly increased in the single-rootedplants, but the seminal roots showed compensatory growth comparedto those in control plants. Consistent with decreased leaf conductance,ABA concentrations in leaves of single-rooted plants were elevatedup to 10-fold, but xylem sap ABA concentrations in these plantswere lower than in controls, in good agreement with the well-wateredconditions experienced by the seminal roots. Surprisingly, however,ABA concentrations in tissues of the seminal roots of the single-rooted plants were clearly increased compared to the controls,presumably due to increased ABA import via phloem from the water-stressedleaves. The results are discussed in relation to the role ofABA as a shoot to root signal. Key words: Zea mays, seminal roots, plant development, xylem transport, mineral nutrition, ABA, shoot-to-root signal     

MOLECULAR SYSTEMATICS OF ECTOCARPUS AND KUCKUCKIA (ECTOCARPALES, PHAEOPHYCEAE) INFERRED FROM PHYLOGENETIC ANALYSIS OF NUCLEAR- AND PIASTTD-ENCODED DNA SEQUENCES

The phylogeny of Ectocarpus and Kuckuckia strains representing widely separated populations from both hemispheres was inferred from sequence analysis of the internal transcribed spacers of the nuclear ribosomal DNA (ITS 1—5.8S-ITS 2) and the spacer region in the plastid-encoded ribulose- bis -phosphate-carboxylase (RUBISCO) cistron (partial rbc L-spacer-partial rbc S ). Both sequences resulted in matching phylogenies, with the RUBISCO spacer region being most informative at the level of genera and species and the internal transcribed spacer sequences at the level of species and populations. Three major clades were formed by strains previously described by morphology and physiology as Kuckuckia, E. fasciculatus, and E. siliculosus, confirming the validity of these taxa . Ectocarpus and Kuckuckia are regarded as sibling taxa with respect to the outgroup species Feldmannia simplex, Hincksia mitchelliae, and Pilayella littoralis. The clade formed by sexual E. siliculosus strains and most asexual Ectocarpus strains was subdivided into several clades that are consistent with geographical races within E. siliculosus. The inferred phylogeny of Ectocarpus corresponds generally with results from cross-fertilization experiments, morphology, and lipid analysis. A hypothesis on the origin and dispersal of E. siliculosus suggests several natural dispersal events during periods of global cooling as well as recent and possibly anthropogenic dispersal events .     

Two recurrent nonsense mutations and a 4 bp deletion in a quasi-symmetric element in exon 37 of the NF1 gene

We screened a total of 92 unrelated patients with neurofibromatosis type 1 (NF1) for mutations in exon 37 of the NF1 gene, by using temperature gradient gel electrophoresis. Two novel mutations were found: a 4 bp deletion in a so-called quasi-symmetric element (6789delTTAC) and a recurrent nonsense mutation, which was identified in two unrelated patients, at codon 2264 (C6792A). The independent origin of the latter mutation in two families was confirmed by haplotype analysis. The nonsense mutation and the 4 bp deletion are both predicted to lead to a truncated protein product lacking the Cterminal 20% (aproximately) of its sequence. The occurrence of three independent mutations among 92 NF1 patients at codons 2263–2264 (exon 37) suggests that a specific search for mutations in this area should be undertaken in screening programs for NF1 mutations.