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81.
Summary Myogenic cells from mice homozygous for the lethal mutation motor endplate disease (med/med) were grown in culture. Like muscle cells taken from wild type (+/?) litter mates they fused to form myotubes which contracted, developed cross striations, and exposed acetylcholine receptors (AChR) on their surface. However, a decrease of 30% in the number of mononucleated cells per unit fresh weight of muscle was observed as early as 2–3 days postnatal, i.e., at least one week prior to the onset of physiological symptoms. Hence, in addition to influencing the functional maintenance of motor endplates, the med gene seems to control early events in muscle development.  相似文献   
82.
A method is described for the preparation of (1) the heavy population of bovine adrenal chromaffin granules (SH (average sedimentation coefficient) = 12 400 S in 0.25 M sucrose) essentially free from contamination with mitochondria and other organelles, and (2) a subpopulation of this heavy population which is highly enriched in noradrenalin (?95% of the total catecholamine is noradrenalin). The method is based on isopycnic gradient centrifugation using a self-generating gradient of polyvinylpyrrolidone-coated colloidal silica particles (Percoll) in 0.5 M sucrose medium.The isolated population of noradrenalin granules appeared highly electron dense in transmission electron microscopy and revealed a rather narrow size distribution. The specific content of amine and adenine nucleotides (with reference to total granule protein) was markedly higher than for the total population of heavy chromaffin granules. The molar ratio of amines to adenine nucleotides was, however, lower in the noradrenalin granules, i.e. 4.8 vs. 11.9.  相似文献   
83.
Summary The ultrastructure of atrial and ventricular myocardial cells from Acipenser stellatus is described. The cells of the atrium are more loosely connected than those of the ventricle. Cell contact is by simple intercalated discs and by desmosomes. The cells are flattened, with peripheral myofibrils and a central region of mitochondria and the nucleus. The sarcoplasmic reticulum consists of subsarcolemmal tubules, that frequently extend towards the central mitochondria. Dyads are small and positioned at any sarcomeric level. No T-tubules are present. Specific granules are restricted to the atrial cell, and are sometimes present within the SR tubules.  相似文献   
84.
25 species of lichens have been collected in semidesertic to desertic areas of Iran. On the basis of spatial relations to the substrate and anatomical features of the thallus three main groups (one with a subdivision based on colour and morphology of the thallus) can be differentiated. Selective advantages and peculiarities in connection with the desert habitat are pointed out, such as inverse thallus-structure, a dense network of skeletal hyphae in the substrate in otherwise epilithic species, proliferating areolae of the thallus, immersed pycnidia with trichogynes and brownish spores in groups with usually colourless spores. Most of the species are wide-spread in arid and often also in humid regions; only one species,Verrucaria buschirensis J. Steiner, seems to be endemic. The prevalence of cyanophilic lichens in deserts may have phylogenetic reasons, as these groups appear to date back to periods without higher vegetation and a desert-like environment.
Herrn Prof. Dr. L.Geitler zum 80. Geburtstag gewidmet.  相似文献   
85.
Harald Fuge 《Chromosoma》1978,65(3):241-246
Chromatin bridges of autosomal bivalents in anaphase I were observed in spermatocytes of Pales ferruginea. The bridges are formed without simultaneous production of akinetochoric (akinetic) fragments. A bridge consists of a single fiber up to approximately. 500 Å in diameter. Filamentous substructures of approximately 100 Å diameter can be visualized. It is suggested that these bridges represent a low order coiling of the chromatid, and may be caused by non-separation of the terminal segments of the chromatids (telomeres).  相似文献   
86.
Summary Diffusates from flower buds, flower fruits, and scape segments, and extracts of flower stalks of Narcissus pseudonarcissus contain an auxin active in the Avena geo-curvature test. The auxin behaved like indole-3-acetic acid (IAA) in thin-layer chromatography (TLC) with neutral and basic solvents on different adsorbents. After TLC, the auxin of the extracts showed chromogenic reactions identical with those of IAA; in gas-liquid chromatography on two different columns, the purified substance, after methylation, appeared at the retention time of IAA methyl ester. The auxin content of the extracts has been estimated to be equivalent to ca. 10 g IAA kg–1 fresh weight. Diffusates, collected at the basal end of excised flowering apices and of scape segments at different developmental stages, showed highest auxin activity when collected from old buds and young flowers, and from the basal, rapidly elongating scape regions. The diffusible auxin obtained from scape segments was very likely produced by the segments themselves. Thus, the shoot of Narcissus appears to possess two different sites of auxin production, namely, the apical region represented by the flower bud, the flower or the fruit, and the scape.Abbreviations IAA indole-3-acetic acid - IAA-OMe indole-3-acetic-acid methyl ester - TLC thin-layer chromatography - GLC gas-liquid chromatography  相似文献   
87.
Harald Fuge 《Chromosoma》1975,52(2):149-158
Akinetochoric chromosomal fragments in spermatocytes of mutant Pales ferruginae are transported polewards in anaphase. During migration their surfaces form radial lamellar projections between which non-kinetochoric spindle microtubules become arranged in an orderly fashion. The same morphological features had been observed earlier in intact chromosomes in late anaphase. It is assumed that the fragments are transported by some kind of poleward directed "streaming" force of the anaphase spindle, which is applied to the fragment's surface. Non-kinetochoric microtubules are thought to be engaged in the generation or, at least, in the transmission of this spindle force. Due to the morphological similarities with akinetochoric fragments, extra-kinetochoral application sites for anaphase spindle forces can be also suggested for chromosomes possessing kinetochores.  相似文献   
88.
89.
N-acylethanolamines (NAEs) are a group of lipid mediators synthesized in response to a number of physiological and pathological stimuli. Because of the low tissue concentrations of NAEs, analyses often include liquid extraction followed by solid-phase extraction and subsequent quantitation by LC/MS or GC/MS. Reported levels of NAEs vary considerably, however, and often no explanation is given for these discrepancies. Brought on by difficulties encountered during method development, the effects of using four different brands of silica-containing solid phase extraction (SPE) columns and five different brands of chloroform for sample preparation were investigated. Considerable variation in the retention and recoveries of seven NAEs and 2-arachidonoylglycerol existed between the SPE columns. Furthermore, it was found that some chloroforms contained quantifiable amounts of N-palmitoylethanolamine and N-stearoylethanolamine. Finally, it was found that use of one of the chloroforms resulted in a loss of N-oleoylethanolamine from solution due to addition of chlorine to the ω-9 bond. The identity of this reaction product was confirmed by LC-MS/MS and NMR. It is recommended that these aspects of sample preparation and analysis should be thoroughly validated during method development and the relevant information on specific brands used be reported in future communications in order to better estimate the validity of reported quantitative data.  相似文献   
90.
Acetylcholinesterases (EC 3.1.1.7, AChE) have varying amounts of carbohydrates attached to the core protein. Sequence analysis of the known primary structures gives evidence for several asparagine-linked carbohydrates. From the differences in molecular mass determined on sodium dodecyl sulfate-polyacrylamide gel before and after deglycosylation with N-glycosidase F (EC 3.2.2.18), it is seen that dimeric AChE from red cell membranes is more heavily glycosylated than the tetrameric brain enzyme. Furthermore, dimeric and tetrameric forms of bovine AChE are more heavily glycosylated than the corresponding human enzymes. Monoclonal antibodies 2E6, 1H11, and 2G8 raised against detergent-soluble AChE from electric organs of Torpedo nacline timilei as well as Elec-39 raised against AChE from Electrophorus electricus cross-reacted with AChE from bovine and human brain but not with AChE from erythrocytes. Treatment of the enzyme with N-glycosidase F abolished binding of monoclonal antibodies, suggesting that the epitope, or part of it, consists of N-linked carbohydrates. Analysis of N-acetylglucosamine sugars revealed the presence of N-acetylglucosamine in all forms of cholinesterases investigated, giving evidence for N-linked glycosylation. On the other hand, N-acetylgalactosamine was not found in AChE from human and bovine brain or in butyrylcholinesterase (EC 3.1.1.8) from human serum, indicating that these forms of cholinesterase did not contain O-linked carbohydrates. Despite the notion that within one species, the different forms of AChE arise from one gene by different splicing, our present results show that dimeric erythrocyte and tetrameric brain AChE must undergo different postsynthetic modifications leading to differences in their glycosylation patterns.  相似文献   
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