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981.
Lothar Geitler 《Plant Systematics and Evolution》1966,113(3-4):273-282
Zusammenfassung Abnorme Abläufe der Formbildung während der Entwicklung der Auxosporen führen beiMeridion circulare zu einem in diesem Ausmaß bisher unbekannten Formenreichtum. Auch sehr aberrante Typen bilden in grundsätzlich normaler Weise die ersten Schalen und den Gürtel der Hypotheka, und vielfach verläuft auch die weitere Entwicklung normal. Häufig vorkommende Korrektionen bei, vor oder nach der 1. Teilung der Erstlingszelle betreffen allein die Zellform, während eine Aufregulierung abnorm kleiner Zellen zur Normalgröße nicht vorkommt. 相似文献
982.
Lothar Geitler 《Plant Systematics and Evolution》1962,109(1-2):182-183
Ohne Zusammenfassung 相似文献
983.
Thomas G. Duthy Lothar H. Staendner Paul A. Manning Michael W. Heuzenroeder 《Journal of bacteriology》1999,181(18):5847-5851
We have sequenced the entire region of DNA required for the biosynthesis of CS5 pili from enterotoxigenic Escherichia coli O115:H40 downstream of the major subunit gene, designated csfA (for coli surface factor five A). Five more open reading frames (ORFs) (csfB, csfC, csfE, csfF, and csfD) which are transcribed in the same direction as the major subunit and are flanked by a number of insertion sequence regions have been identified. T7 polymerase-mediated overexpression of the cloned csf ORFs confirmed protein sizes based on the DNA sequences that encode them. The expression of only the csf region in E. coli K-12 resulted in the hemagglutination of human erythrocytes and the cell surface expression of CS5 pili, suggesting that the cluster contains all necessary information for CS5 pilus biogenesis and function. 相似文献
984.
Steffen Lamparter Lothar Kling Michael Schrader Reinhard Ziegler Johannes Pfeilschifter 《Journal of cellular physiology》1998,175(1):89-98
Other than its known effects on the cardiovascular system, angiotensin II (Ang II) stimulates cell growth in several cell types. In this study, we examined whether it also might affect bone cell metabolism. Ang II stimulated DNA and collagen synthesis and decreased alkaline phosphatase (AP) activity in bone cell populations derived from the periosteum of fetal rat calvariae. Similar effects of Ang II were observed on human adult bone cells obtained by collagenase digestion from trabecular bone. Clonal cell analysis, autoradiographic studies, and receptor subtype analysis suggested the presence of specific Ang II receptor subtype 1 (AT1) binding sites on AP+ osteoblastic precursor cells. Ang II had no direct effects on osteoblastic cells with a mature phenotype, but paracrine effects of Ang II on mature osteoblasts could be observed upon coculture with Ang II-responsive bone cell populations. Because Ang II is known to be locally generated by endothelial cells, Ang II might play an important role in coordinating capillary cell growth and osteoblastic bone formation during bone remodeling. J. Cell. Physiol. 175:89–98, 1998. © 1998 Wiley-Liss, Inc. 相似文献
985.
Saidenbach Reservoir is situated in the Erzgebirge Hills, Saxony, in a catchment with agriculture as the principal use and a high sensitivity to soil erosion. The high elimination of total phosphorus (ca. 70%) mainly results from a) the sedimentation flux of planktonic diatoms and b) the adsorption to and sedimentation with mineral particles rich in iron. At stations with a high sulfide concentration in the 0–5 cm sediment layer (about 0.2%), the P content was likewise high (about 0.3%), probably due to the high iron concentration (more than 2.5% of dry weight). A fractionation procedure showed that the major part of the sediment phosphorus was not sensitive to reductants (dithionite) but has been found only in the following extraction step (NaOH extract). 相似文献
986.
Lothar Geitler 《Plant Systematics and Evolution》1958,105(1-3):159-166
Zusammenfassung
Spathularia flavida bildet alljährlich an dem gleichen Myzel Fruchtkörper. Die Konidienbildung erfolgt im beobachteten Fall nur an ausgeschleuderten Sporen, die sich gewöhnlich in acht Teilzellen teilen, deren jede bis zu drei Konidien bildet. Im allgemeinen ist der apikale Abschnitt der Spore gefördert. Hier kann auch eine Art von Vikariismus zwischen einer zusätzlichen Zellteilung und Konidienbildung erfolgen. Die Bildung der Konidienanlage erfolgt vor dem Ablauf der entsprechenden Mitose, die einen Tochterkern für die Konidie liefert.
Spragueola irregularis, in Osttirol festgestellt, bildet in einem gewissen niedrigen Prozentsatz reifer Asci an einem Teil der Sporen eines Ascus sukzedan und terminal kleine, kugelige Konidien an unverzweigten Sterigmen. Die maximale Zahl von Konidien, die eine Spore bildet, beträgt vier, der Inhalt der Spore ist dann verbraucht. Welche Sporen eines Ascus zur Konidienbildung übergehen, scheint keiner Regel zu unterliegen; die Konidien entstehen an einem beliebigen der beiden Pole einer Spore. Genau das gleiche Verhalten wie Exemplare aus Osttirol zeigen Exemplare aus Nordamerika und Südtirol. 相似文献
987.
This report describes the metabolic and lipidomic profiling of 97 low-molecular weight compounds from the primary metabolism and 124 lipid compounds of the diatom Thalassiosira pseudonana. The metabolic profiles were created for diatoms perturbed for 24 hours with four different treatments: (I) removal of nitrogen, (II) lower iron concentration, (III) addition of sea salt, (IV) addition of carbonate to their growth media. Our results show that as early as 24 hours after nitrogen depletion significant qualitative and quantitative change in lipid composition as well as in the primary metabolism of Thalassiosira pseudonana occurs. So we can observe the accumulation of several storage lipids, namely triacylglycerides, and TCA cycle intermediates, of which citric acid increases more than 10-fold. These changes are positively correlated with expression of TCA enzymes genes. Next to the TCA cycle intermediates and storage lipid changes, we have observed decrease in N-containing lipids and primary metabolites such as amino acids. As a measure of counteracting nitrogen starvation, we have observed elevated expression levels of nitrogen uptake and amino acid biosynthetic genes. This indicates that diatoms can fast and efficiently adapt to changing environment by altering the metabolic fluxes and metabolite abundances. Especially, the accumulation of proline and the decrease of dimethylsulfoniopropionate suggest that the proline is the main osmoprotectant for the diatom in nitrogen rich conditions. 相似文献
988.
Arjen Bogaards Abhay Varma Kai Zhang David Zach Stuart K Bisland Eduardo H Moriyama Lothar Lilge Paul J Muller Brian C Wilson 《Photochemical & photobiological sciences》2005,4(5):438-442
Fluorescence-guided resection (FGR) and photodynamic therapy (PDT) have previously been investigated separately with the objectives, respectively, of increasing the extent of brain tumour resection and of selectively destroying residual tumour post-resection. Both techniques have demonstrated trends towards improved survival, pre-clinically and clinically. We hypothesize that combining these techniques will further delay tumour re-growth. In order to demonstrate technical feasibility, we here evaluate fluorescence imaging and PDT treatment techniques in a specific intracranial tumour model. The model was the VX2 carcinoma grown by injection of tumour cells into the normal rabbit brain. An operating microscope was used for white light imaging and a custom-built fluorescence imaging system with co-axial excitation and detection was used for FGR. PDT treatment light was applied by intracranially-implanted light emitting diodes (LED). The fluorescent photosensitizer used for both FGR and PDT was ALA-induced PpIX. For PDT, ALA (100 mg kg(-1)) and low light doses (15 and 30 J) were administered over extended periods, which we refer to as metronomic PDT (mPDT). Eighteen tumour bearing rabbits were divided equally into three groups: controls (no resection); FGR; and FGR followed by mPDT. Histological whole brain sections (H&E stain) showed primary and recurrent tumours. No bacteriological infections were found by Gram staining. Selective tumour cell death through mPDT-induced apoptosis was demonstrated by TUNEL stain. These results demonstrate that the combined treatment is technically feasible and this model is a candidate to evaluate it. Further optimization of mPDT treatment parameters (drug/light dose rates) is required to improve survival. 相似文献
989.
990.
Lothar Brecker Julia Petschnigg Nicole Depiné Hansj?rg Weber Douglas W Ribbons 《European journal of biochemistry》2003,270(7):1393-1398
Only 2% of the known natural products with acetylenic bonds are alpha-alkynoates. Their polarized, conjugated triple bond is an optimal target for an enzymic hydration. Therefore they are good substrates for the enzymes involved in metabolism of acetylenic compounds, resulting in products that are suitable for bacterial growth. We isolated a Pseudomonas putida strain growing on 2-butynedioate as well as on propynoate, and determined the metabolic pathways of these two alpha-alkynoates. The triple bonds in both compounds were initially hydrated and 2-ketobutandioate as well as 3-ketopropanoate were formed. These two beta-keto acids were decarboxylated resulting in pyruvate and acetaldehyde, respectively. Pyruvate was further hydrolysed mainly to acetate and formate, whereas minor amounts were reduced to lactate. In the other biotransformation, acetaldehyde was oxidized to acetate accompanied by the reduction of 3-ketopropanoate to 3-hydroxypropanoate. Analyses of these metabolic processes were performed by in situ 1H-NMR spectroscopy in 1H2O, although the substrates, propynoate and 2-butynedioate, carried only one or even no detectable protons, respectively. However, while protons from the solvent are incorporated in the course of the pathway, the metabolites can be detected and identified. Therefore a detailed determination of the metabolic process is possible. 相似文献