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51.
Dr. Hermann Remmert 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1955,37(4):338-354
Zusammenfassung In einleitenden terminologischen Erwägungen wird vorgeschlagen, den Ausdruck Schlüpfrhythmus zugunsten von tageszeitlich gebundenem Schlüpfen aufzugeben. Pseudosmittia arenaria zeigt im normalen Tag-Nachtwechsel ein deutliches tageszeitlich gebundenes Schlüpfen mit einem Maximum 6–8h nach DL (Beginn der Beleuchtung).In Dauerdunkel schlüpfen keine Imagines. In Dauerlicht erscheinen die Tiere gleichmäßig über den ganzen Tag verteilt.Der ganze Bereich des sichtbaren Lichtes (geprüft von 476–641 m) ist wirksam. Auch die Lichtintensität in Licht-Dunkelbedingungen spielt im untersuchten Bereich (18–350 Lux) keine Rolle.Das Schlüpfmaximum von Ps. arenaria zeigt eine deutliche Beziehung zu DL. Es wandert bei konstanter Tageslänge um so dichter an DL heran, je kürzer die relative Länge der Lichtzeit ist.Bei kürzeren Tageslängen wandert das Maximum von DL fort, bei längeren an DL heran. Bei Tagen, die kürzer als 18h sind, liegt es in der folgenden Dunkelzeit, bei solchen, die länger als 36h sind, vor DL. Sein Weg beschreibt dabei eine kubische Parabel.Beim Eintritt des Gipfels in die folgende Dunkelzeit erscheint ein Maximum nur an jedem 2. Tag. Ein Maximum vor DL ruft ein zusätzliches Maximum in der gleichen Entfernung von LD (Beginn der Dunkelzeit) hervor. Bei extremen Tageslängen ist also dennoch ein Maximum ungefähr alle 24h zu beobachten. Dies ist exogen bedingt. Verlagert man durch schwache Beleuchtung während der Dunkelzeit das Maximum im 12h-Tag in die Lichtzeit, so erhält man ein Maximum an jedem Tag. Der Eintritt des Maximums in eine Dunkelzeit hat also das Umspringen auf einen Schlüpfgipfel an jedem 2. Tag bzw. auf 2 je Tag zur Folge.Im 12h-Tag mit absoluter Dunkelzeit während der Dunkelzeit kann man auch ein Maximum alle 12h erreichen, und zwar durch Umstimmung eines Teils der Population. Man hat dann 2 Gruppen, deren Maxima um 12h gegeneinander verschoben sind. Hemmend und fördernd auf den Einfluß des Lichtes wirken Temperatur und Substratfeuchtigkeit. Beide Faktoren können ohne Licht kein Schlüpfen hervorrufen. Beziehungen zwischen Lebensweise, Ökologie oder systematischer Stellung und tageszeitlich gebundenem Schlüpfen lassen sich bisher nicht feststellen. 相似文献
52.
Hermann Behling 《Vegetation History and Archaeobotany》1996,5(3):241-246
Palynological studies on late Quaternary lake sediments from the region of the Amazon estuary, 100 km north-east of Belém, Pará State, Brazil, enable reconstruction of lowland Amazonian rain forest during the Late-glacial and Holocene periods. Late-glacial forests included populations of Podocarpus which suggests a distinct climatic cooling. Ilex was abundant in the early Holocene. Records of the mangrove taxon, Rhizophora, indicate rapid Atlantic sea-level rise in the beginning of the Holocene. High charcoal representation may reflect the first arrival of Amerindians in the Amazon coastal area, probably about 10 800 B.P. 相似文献
53.
snRNP Sm proteins share two evolutionarily conserved sequence motifs which are involved in Sm protein-protein interactions. 总被引:3,自引:2,他引:1 下载免费PDF全文
H Hermann P Fabrizio V A Raker K Foulaki H Hornig H Brahms R Lührmann 《The EMBO journal》1995,14(9):2076-2088
The spliceosomal small nuclear ribonucleoproteins (snRNPs) U1, U2, U4/U6 and U5 share eight proteins B', B, D1, D2, D3, E, F and G which form the structural core of the snRNPs. This class of common proteins plays an essential role in the biogenesis of the snRNPs. In addition, these proteins represent the major targets for the so-called anti-Sm auto-antibodies which are diagnostic for systemic lupus erythematosus (SLE). We have characterized the proteins F and G from HeLa cells by cDNA cloning, and, thus, all human Sm protein sequences are now available for comparison. Similar to the D, B/B' and E proteins, the F and G proteins do not possess any of the known RNA binding motifs, suggesting that other types of RNA-protein interactions occur in the snRNP core. Strikingly, the eight human Sm proteins possess mutual homology in two regions, 32 and 14 amino acids long, that we term Sm motifs 1 and 2. The Sm motifs are evolutionarily highly conserved in all of the putative homologues of the human Sm proteins identified in the data base. These results suggest that the Sm proteins may have arisen from a single common ancestor. Several hypothetical proteins, mainly of plant origin, that clearly contain the conserved Sm motifs but exhibit only comparatively low overall homology to one of the human Sm proteins, were identified in the data base. This suggests that the Sm motifs may also be shared by non-spliceosomal proteins. Further, we provide experimental evidence that the Sm motifs are involved, at least in part, in Sm protein-protein interactions. Specifically, we show by co-immunoprecipitation analyses of in vitro translated B' and D3 that the Sm motifs are essential for complex formation between B' and D3. Our finding that the Sm proteins share conserved sequence motifs may help to explain the frequent occurrence in patient sera of anti-Sm antibodies that cross-react with multiple Sm proteins and may ultimately further our understanding of how the snRNPs act as auto-antigens and immunogens in SLE. 相似文献
54.
55.
Hermann Neudeck Shiao Li Oei Beate Stiemer Hartmut Hopp Renat E Graf 《The Histochemical journal》1997,29(5):419-430
Recent immunocytochemical studies have shown that placental villous trophoblasts contain the high molecular weight cytokeratin
(CK) proteins 5/6 and 17. In the case of CK 17, trophoblastic immunostaining was positive in villi covered by fibrinoid. CKs
5/6 and 17 are expressed by hyperproliferative cells. The aim of this investigation was to examine the location of these CKs
in placental infarcts, known to be demarcated by fibrinoid and hyperproliferative trophoblasts. The results were compared
with those obtained by immunostaining against Ki-67, tenascin and α1-, α6- and β1- integrins, which are involved in cell proliferation,
differentiation and regenerative processes. Furthermore, the expression of the single CKs 7, 8, 10, 13, 14, 18 and 19 was
investigated by immunocytochemistry and immunoblotting. While low and high molecular weight CKs were present in villous and
extravillous trophoblasts, only low molecular weight CKs were detected in vascular and extravascular placental smooth muscle
cells. Placental infarcts revealed different immunoreactivities in the infarct margin and centre: high molecular CKs, tenascin,
Ki-67 and oncofoetal fibronectin predominated in the infarct margin, low molecular CKs, fibrin and integrins in the centre.
The expression of tenascin and a defined change in the expression of CK 17 indicates villous repair and hyperproliferative
mechanisms in placental infarcts.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
56.
Determination of apoplastic K+ in intact leaves by ratio imaging of PBFI fluorescence 总被引:2,自引:0,他引:2
The tetraammonium salt of the K+ binding fluorescent dye benzofuranisophthalate (PBFI) was used to investigate the influence ofpotassium nutrition (0.12.1 mol m3) on apoplasticK+ inVicia faba leaves by means of ratio imaging. As a referencethe infiltration-centrifugation method was used. Both methodsreflected the influence of K+ supply on apoplastic K+ concentration.The abaxial leaf side revealed significantly higher K+ concentrations(20-25 mol m3) than the adaxial side (58 mol m3).Application of CCCP led to an immediate increase in apoplasticK+ demonstrating the reliability of the PBFI method. Key words: Vicia faba, leaf, apoplast, K+, PBFI, ratio imaging, ratiometric fluorescence microscopy 相似文献
57.
The effect of ethanol on maxi Ca2+-activated K+ channels (BK channels) in GH3 pituitary tumor cells was investigated using single-channel recordings and focusing on intracellular
signal transduction. In outside-out patches, ethanol caused a transient concentration-dependent increase of BK-channel activity.
30 mm (1.4‰) ethanol significantly increased mean channel open time and channel open probability by 26.3 ± 9% and 78.8 ± 10%, respectively;
single-channel current amplitude was not affected by ethanol. The augmenting effect of ethanol was blocked in the presence
of protein kinase C (PKC) inhibitors staurosporine, bisindolylmaleimide, and PKC (19–31) pseudosubstrate inhibitor as well
as by AMP-PNP (5′-adenylylimidodiphosphate), a nonhydrolyzable ATP-analogue, but not by the phospholipase C blocker U-73122.
Phosphatase inhibitors microcystin-LR and okadaic acid promoted the ethanol effect. The blocking effect was released at higher
concentrations of ethanol (100 mm) suggesting a second site of action or a competition between blockers and ethanol. Our results suggest that the effect of
ethanol on BK-channels is mediated by PKC stimulation and phosphorylation of the channels which increases channel activity
and hence may influence action potentials duration and hormone secretion.
Received: 24 July 1996/Revised: 27 December 1996 相似文献
58.
The fixation of trans-(NH3)2Cl2 Pt(II) to poly(I)·poly(C) at low rb (< 0.05) leads to the formation of two complexed species. The major species (ca. 82% of bound platinum) involves coordination of platinum to a single hypoxanthine base, while the other species involves coordination of two hypoxanthine bases, which are either far apart on the same strand or on separate poly(I) strands, to the platinum. These same two species are found after reaction with poly(I), as are two other species throughout the entire rb range studied (rb = 0–0.30). The latter two species are assigned to trans-Pt bound to two bases on a poly(I) strand with (a) one or (b) two free bases between the two bound bases. These two species, (a) and (b), account for ca. 35% of the bound platinum, although the 1:1 species remains dominant (ca. 55%). These two additional species are observed at high rb (>0.075) after reaction with poly(I)·poly(C) but as very minor species. They are formed by reaction with melted poly(I) loops. Also at high rb, we have observed a shifted cytidine H5 resonance arising from interaction of trans-Pt with a melted loop of poly(C). Most probably, this arises from an intramolecular poly(I) to poly(C) crosslink. Results from the reaction of trans-Pt with poly(C) are presented for comparison. 相似文献
59.
Abstract The present communication defines the conditions under which thioredoxin activates glutamine synthetase from Anabaena cylindrica . Effects are obtained at pH values around neutrality, and the activation is affected by Mg2+ in the assays. The thioredoxin systems from A. cylindrica and spinach are functionally interchangeable in the activation of glutamine synthetase. The enzyme is efficiently activated by thioredoxinm and also by thioredoxinf , but at much higher concentrations. Thioredoxinm has previously been shown to activate NADPH-dependent malate dehydrogenase and isocitrate dehydrogenase from cyanobacteria. It is speculated that thioredoxinm plays a role in the differentiation of vegetative cells to heterocysts. 相似文献
60.
Determination of betaxolol, a new beta-blocker, by gas chromatography mass spectrometry: application to pharmacokinetic studies 总被引:1,自引:0,他引:1
Betaxolol, a beta selective adrenoceptor antagonist recently approved for the treatment of hypertension, was determined by monitoring in chemical ionization mode with ammonia the [MH]+ ions of the trimethylsilyl derivatives of the drug and of its internal standard [2H5)betaxolol). Its pharmacokinetic profile obtained following administration of a 20 mg oral dose was characterized by a half-life of 22 h and a bioavailability of 85%. The main acid metabolite formed by elimination of the isopropylamino group may also be determined as the methyl TMS derivative but methylation with BF3-methanol should be used with caution since it may induce the opening of the cyclopropyl group. The routine electron capture determination procedure was compared to this mass spectrometric method and an excellent correlation was found (r = 0.9974). Both procedures have the same sensitivity (1 ng ml-1). Finally it was observed that under electron impact mode betaxolol trimethylsilyl side chain rearranged to lose TMS-O-CH=CH2; this elimination was confirmed by deuterium labelling studies. 相似文献