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Mast cells release histamine and other mediators of allergy in response to stimulation of their IgE receptors. This release is generally thought to be mediated by an elevation of cytosolic \(Ca^{2+}\). Recent evidence suggests that there might be factors that modulate the coupling between \(Ca^{2+}\) levels and mediator release. The present report identifies adenosine as one such modulator. Adenosine and several of its metabolically stable analogues were shown to enhance histamine release from rat peritoneal mast cells in response to stimuli such as concanavalin A. Metabolizing endogenous adenosine with adenosine deaminase dampened the response to stimuli, whereas trapping endogenous adenosine inside mast cells with nucleoside-transport inhibitors markedly enhanced stimulated histamine release. The metabolically stable adenosine analogue 5' -(N-ethylcarboxamido)adenosine (NECA) did not affect the initial steps in the sequence from IgE-receptor activation to mediator release, which are generation of inositol trisphosphate and increase of cytosolic \(Ca^{2+}\). However, NECA did enhance the release induced in ATP-permeabilized cells by exogenous \(Ca^{2+}\), but it had no effect on the release induced by phorbol esters. These data suggest that adenosine sensitizes mediator release by a mechanism regulating stimulus-secretion coupling at a step distal to receptor activation and second-messenger generation.
No Abstract available
Zu den Wollmaßen in Nuzi
(1988)
No abstract available.
Das Martin-von-Wagner-Museum besitzt eine seit langem bekannte Sammlung bedeutender 'pontischer' Vasen, die vor kurzem durch die Erwerbung einer Oinochoe dieser Gattung sinnvoll ergänzt werden konnte (Abb. 30-34. 38. 40-45). Denn obwohl in der 'pontischen' Keramik die Oinochoen nach den Amphoren die häufigste Gefäßform sind, war gerade diese Form in der Würzburger Sammlung bisher nur durch zwei kleine, atypische Exemplare vertreten gewesen. Die neu erworbene Oinochoe kann dagegen nach ihrer Größe, ihren Formmerkmalen und ihrer Bemalung als eine typische Vertreterio dieser Form innerhalb der 'pontischen' Gattung gelten.
The effects of age, study time, and importance of text units on strategy use and memory for texts
(1988)
This study investigated study behavior and recall of a narrative text as a function of the reader's age, study time, and importance level of text units. Fifth graders, seventh graders, young- and older adults were asked to read a fairy tale, and do anything they liked to prepare for verbatim recall. Half of the subjects in each age group were assigned to an immediate recall condition; half were given additional study time. Examination of recall data showed that all subjects showed higher recall of important units in the text than unimportant units. This effect was independent of age and study time condition. Study behaviors varied significantly across age groups and study conditions: while adults underlined or took notes with equal frequency, children preferred note-taking as a study strategy. With additional study time, fifth graders, seventh graders, and older adults increased their strategic behavior; young adults did not.
Neuere Ansätze der Hochbegabtenforschung haben demonstriert, daß herausragende intellektuelle Fähigkeiten alleine noch keine kognitiven Höchstleistungen in späteren Lebensabschnitten garantieren. Insbesondere retrospektive Analysen der Daten genialer bzw. kognitiv hochproduktiver Persönlichkeiten lassen darauf schließen, daß neben Intelligenzmerkmalen auch Wissensaspekte und nichtkognitive Persönlichkeitsmerkmale entscheidend dafür verantwortlich sind, daß Höchstleistungen erzielt werden können. Im vorliegenden Beitrag wird ein Überblick über Studien gegeben, die den Einfluß bereichsspezifiscben Wissens auf kognitive Höchstleistungen darstellt, daß jedoch ab einem bestimmten Grenzwert intellektueller Fähigkeit allein das Ausmaß bereichsspezifischen Wissens in Kombination mit extremen Ausprägungen in nichtkognitiven Merkmalen wie Konzentrationsfähigkeit, Ausdauer und Erfolgsmotivation darüber entscheidet, ob intellektuelle Höchstleistungen erbracht werden können.
In neueren Untersuchungen zur Mathematikerziehung im Elementarbereich wird verstärkt auf die Bedeutung kognitiver Prozesse (Strategien) für die erfolgreiche Bewältigung von Problemlöseaufgaben hingewiesen. Im vorliegenden Beitrag wird insbesondere auf das Wissen um kognitive Prozesse und deren Steuerung, also auf Metakognitionen eingegangen. Es wird zunächst eine Einführung in traditionelle Kategorien von Metakognition gegeben und dann auf eine Weiterentwicklung eingegangen, die als "Modell des kompetenten Strategie-Anwenders" bekanntgeworden ist. Dieses Modell wird dann als Grundlage für Empfehlungen benutzt, die darauf abzielen, den Mathematikunterricht effizienter zu gestalten.
Melanoma formation in the poeciliid fish Xiphophorus is mediated primarily by a cellular oncogene, designated Tu. Elimination of Tu-specific genes releases the transforming function of Tu and leads to melanoma formation. Southern blot analyses revealed a tight linkage of a v-erb B related gene to the Tu-locus and Northern blot analyses of RNA of solid melanomas indicated a coordinated deregulation and for mutational activation of several oncogenes. In order to get a better insight into the regulation of oncogene expression in normal and transformed cells of Xiphophorus, we studied the expression of Xsrc, Xras, Xmyc, Xerb A, Xsis, and the v-erb B related gene in a melanoma derived cell line (PSM) and an embryonic cell line (A2) under conditions of low growth factor supply. Both celllines express the Xsrc, Xmyc, and Xras genes, while PSM cells in addition express the v-erb B related gene and A2 cells the Xsis gene. In PSM cells serum deprivation leads to an accumulation of most of the oncogene mRNAs analysed. This is most apparent for a 5.0 kb transcript of the v-erb B related gene, probably due to an increase in transcript stability. The levels of these mRNAs returned to normal within 2h after stimulation with 10% fetal calf serum. At the protein level we observed an initial decrease followed by an increase of the n-p60c-src kinase (the protein product of tbe Xsrc gene) activity in cells deprived of serum. Serum stimulation restored a normal pp60"-src kinase activity. In contrast serum deprivation of A2 cells reduced the transcript amounts of each of the oncogenes analysed. The same holds true for one beta-tubulin transcript, while the level of a second beta-tubulin transcript was unaffected. Serum stimulation led to a reactivation of Xras and Xsrc after a delay of approximately 48b. The pp60(c-src) kinase activity was found to be 6-10 times lower as compared to the PSM cells and did not differ between serum deprived and serum stimulated cells. Enzyme activities and isoenzyme patterns of several glycolytic enzymes were found to be not affected by serum deprivation and stimulation in both celllines.
In Xiphophorus the causative, primary cellular oncogene for melanoma formation has been assigned by classical genetics to a sex-chromosomal locus, designated Tu. Activation of Tu was proposed to be the result of the elimination of Tu-specific regulatory genes which normally suppress the transforming function in the nontumorous state. In order to understand the role which known proto-oncogenes migbt play in this process, we have analysed the expression of src, erb A, erb B, ras, abl, sis and mil related genes from Xiphophorus during embryogenesis, in non-tumorous organs and in melanoma cells. For src, ras, erb B and sis a differential expression during embryogenesis and/or in normal organs was detected, with preferential expression of src in neural tissues, a high abundance of sis transcripts in an embryonal epitheloid cellline and of erbB transcripts in the head nephros. In melanoma cells ras, src and a v-erb B related gene were found to be expressed. The src gene most likely is more involved in secondary processes during tumor progression, while the expression of the v-erb B related gene might be transformation-specific because recently such a sequence was found to map to the close vicinity of the Tu-locus.