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Gutmann Markus; von Aderkas Patrick; Label Philippe; Lelu Marie-Anne 《Journal of experimental botany》1996,47(12):1905-1917
Somatic embryos of hybrid larch (Larixleptoeuropaea) whichhad been matured for 4 weeks on maturation medium, developednormally on medium supplemented with 60 µM ABA, but abnormallyon medium with no ABA. A comparative structural and histochemicalinvestigation was carried out on these two types of mature embryos.At the light microscope level, differences between both treatmentswere visible only after 23 weeks of maturation. At aroundthis time, abnormal development becomes evident macroscopically:ABA-minus embryos remain rather stubby as opposed to the morecylindrically shaped ABA-plus embryos. Whereas somatic embryosmatured with ABA consist of densely cytoplasmic cells showinga high rate of cell division, ABA-minus embryos are largelymade up of expanded and highly vacuolate cells, indicating thatgrowth in the latter is mainly due to cell expansion and notdivision. After 4 weeks of maturation, ABA-minus embryos beginto elongate in the hypocotyl region, and precocious germinationwas observed frequently. Again, these morphogenetic events werelargely due to abnormal timing of cell expansion. Histochemically,storage proteins were found only in somatic embryos maturedfor 4 weeks with ABA. This observation is in line with resultsobtained by total protein analysis, yielding significantly lowertotal protein contents in ABA-minus embryos both on a freshweight and a per embryo basis after 45 weeks of maturation.Deposition of starch grains mainly in the cortex tissue of thehypocotyl region was observed within 2 weeks of maturation invarying amounts regardless of ABA supply. Polyphenols, in particularcatechins and proanthocyanidins, were present in all embryosfrom the very onset of development. They were localized preferentiallyin the proximal suspensor cells and the basal region of theembryo. However, accumulation of polyphenols was generally muchmore pronounced in embryos matured without ABA, indicating alack of biochemical regulatory competence in those embryos. Key words: Abscisic acid, embryonal development, somatic embryo, storage protein, polyphenols 相似文献
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Presence of UDP-N-acetylmuramyl-hexapeptides and -heptapeptides in enterococci and staphylococci after treatment with ramoplanin, tunicamycin, or vancomycin. 总被引:1,自引:0,他引:1 下载免费PDF全文
D Billot-Klein D Shlaes D Bryant D Bell R Legrand L Gutmann J van Heijenoort 《Journal of bacteriology》1997,179(15):4684-4688
Analyses of the peptidoglycan nucleotide precursor contents of enterococci and staphylococci treated with ramoplanin, tunicamycin, or vancomycin were carried out by high-pressure liquid chromatography coupled with mass spectrometry (MS). In all cases, a sharp increase in the UDP-N-actetylmuramoyl-pentapeptide or -pentadepsipeptide pool was observed. Concomitantly, new peptidoglycan nucleotide peptides of higher molecular masses with hexa- or heptapeptide moieties were identified: UDP-MurNAc-pentapeptide-Asp or pentadepsipeptide-Asp in enterococci and UDP-MurNAc-pentapeptide-Gly or -Ala and UDP-MurNAc-pentapeptide-Gly-Gly or -Ala-Gly in staphylococci. These new compounds are derivatives of normal UDP-MurNAc-pentapeptide or -pentadepsipeptide precursors with the extra amino acid(s) linked to the lysine epsilon-amino group as established by various analytical procedures (MS, MS-MS fragmentation, chemical analysis, and digestion with R39 D,D carboxypeptidase). Except for tunicamycin-treated cells, it was not possible to ascertain whether these unusual nucleotides were formed by direct addition of the amino acids to UDP-MurNAc-pentapeptide (or -pentadepsipeptide) or whether they arose by reverse reactions from lipid I intermediates to which the amino acids had been added. 相似文献
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Collagen-alkaline phosphatase membranes have been prepared, and their enzymatic kinetics and in-vitro stability analyzed. Collagen-alkaline phosphatase dispersions were prepared by complexation in aqueous alkaline solution and cast into membranes by controlled dehydration. These membranes were then crosslinked in glutaraldehyde solution, washed thoroughly, and dried. Crosslinking in glutaraldehyde confers increased stability of catalytic activity to these collagen-enzyme membranes, especially when compared to uncrosslinked collagen-alkaline phosphatase membranes assayed in a similar fashion. Crosslinking in glutaraldehyde also appears to inhibit gross leaching of the soluble enzyme from the carrier matrix. Apparent intrinsic kinetic properties of the collagen-alkaline phosphatase conjugate were analyzed in membranes of various thickness in order to determine the effect of internal diffusion resistances on the kinetics of the immobilized enzyme. The apparent Michaelis constant of the immobilized enzyme decreased as a function of decreasing membrane thickness, reaching an observed apparent Michaelis constant of 1.6mM at a membrane thickness of 0.2 mm. Extrapolation of the apparent Michaelis constant to zero membrane thickness, using a linear plot of the natural logarithm of the apparent Michaelis constant versus membrane thickness, allowed estimation of the true Michaelis constant of the immobilized enzyme. The estimated value for the true Michaelis constant of the collagen-alkaline phosphatase complex was 0.7mM. This value agrees closely with reported values for several purified mammalian alkaline phosphatase. The apparent Michaelis constant for the 0.2mm collagen-enzyme membrane agrees closely with the Michaelis constant reported for an alkaline phosphate purified from chondrocyte matrix vesicles. The intrinsic maximum reaction velocity (V(m)) of the collagen-enzyme complex was estimated b plotting the observed reaction rate as a function of decreasing membrane thickness and extrapolating such plots, at various substrate concentrations, to the limiting case of zero membrane thickness. The maximum reaction velocity was obtained by the common intercept of these plots as they approached zero membrane thickness. 相似文献
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Summary Intact and denervated extensor digitorum longus (EDL) muscles of 20-day-old inbred Lewis-Wistar rats were labelled with 3H-thymidine. Ninety minutes after the injection of the isotope 4.0% of the nuclei were labelled in the intact (i.e. innervated) and 9.6% in the muscles, denervated 3 days before administration of the isotope. The labelled EDL muscles were grafted into the bed of the previously removed EDL muscles of inbred animals and these isografts were studied 30 days later.In the EDL muscles, regenerated from innervated isografts only occasionally labelled endothelial cells were found whereas in the muscles regenerated from denervated isografts also parenchymal muscle nuclei were regularly labelled. The incidence of labelled nuclei in the regenerated EDL muscles was, however, about 20 times lower than in the donor EDL muscles. The present experiments provide a direct proof of utilization of donor satellite cell nuclei for regeneration in grafted muscle tissue. With respect to the low incidence of labelled nuclei in regenerated EDL muscles, other sources of cells apparently also contribute to the regeneration process. 相似文献
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