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21.
Lymphoma models for B cell activation and tolerance. VI. Reversal of anti-Ig-mediated negative signaling by T cell-derived lymphokines 总被引:1,自引:0,他引:1
D W Scott A O'Garra D Warren G G Klaus 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(12):3924-3929
We have recently described three "immature" B cell lymphomas which are exquisitely sensitive to growth inhibition by anti-Ig reagents and may serve as models for tolerance induction in normal B cells. These cells are inhibited from cell cycle progression into S after receiving a negative signal in early G1. In this paper, we demonstrate that the growth inhibition by anti-Ig can be prevented and reversed by the addition of supernatants from T cell lines. One such line, called Tova, produces factors which restore normal levels of DNA synthesis in the presence of concentrations of anti-Fab or anti-kappa immunoglobulins which cause up to a 90% inhibition of thymidine incorporation in a 2- to 3-day culture period. This factor is at least partially effective when added up to 24 hr after anti-Ig to unsynchronized lymphoma cells and it does not alter the growth of control cultures. Studies using synchronized lymphoma cells indicated that the T cell factor permitted cycle progression into S when added during the early G1 exposure to anti-kappa and was less effective when added late in G1. Preliminary characterization suggests that both B cell growth factor II (interleukin 5) and B cell stimulatory factor 1 (interleukin 4) have additive activity in this system, although another unidentified lymphokine may also be involved. The relevance of T cell reversal of Ig receptor-mediated negative signaling to neonatal B cell tolerance is emphasized. 相似文献
22.
The cytoskeleton of isolated murine primitive erythrocytes 总被引:1,自引:0,他引:1
Summary Cytoskeletons of primitive erythrocytes have been isolated from the embryos of day 12 pregnant C57/Bl mice and examined by transmission electron microscopy, immunofluorescence microscopy, and SDS-polyacrylamide gel electrophoresis. Microtubules are the most prominent cytoskeletal component. They are found either singly or organized into loose bundles just under the plasma membrane, but do not form classical marginal bands in most cells. Immunofluorescence with a polyclonal tubulin antiserum confirms this distribution and further reveals numerous mitotic figures among the cells. Rhodamine-conjugated phalloidin and heavy meromyosin labeling reveal that actin is localized in the cortex of the primitive erythrocyte in the form of 6 nm filaments. Antibody directed against avian erythrocyte alpha spectrin demonstrates that spectrin is also found in the cortex. Occasional 10-nm intermediate filaments, observed in the primitve erythrocytes by electron microscopy, are believed to be of the vimentin class based on positive reaction of the cells with vimentin-specific antiserum. In addition, a band in erythrocyte cytoskeletons comigrates in SDS-polyacrylamide gels with vimentin isolated from mouse kidney. Spectrin and actin were also found to be associated with the membrane of primitive erythrocytes when membrane ghost preparations were analyzed by SDS-polyacrylamide gel electrophoresis. 相似文献
23.
Jürgen Voigt Dieter Mergenhagen Petra Münzner Hans-Peter Vogeler Klaus Nagel 《Planta》1989,178(4):456-462
In light-dark-synchronized cultures of the unicellular green algaChlamydomonas reinhardtii, release of zoospores from the wall of the mother cell normally takes place during the second half of the dark period. The recently isolated mutant ls, however, needs light for the liberation of zoospores when grown photoautotrophically under a 12 h light-12 h dark regime. The light-induced release of zoospores was found to be prevented by addition of the photosystem-II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Furthermore, light dependence of this process was shown to be abolished when the mutant ls was grown either photoautotrophically under a 14 h light-10 h dark regime or in the presence of acetate. Our findings indicate that the light-dependency of zoospore liberation observed in cultures of this particular mutant during photoautotrophic growth under a 12 h light-12 h dark regime might be attributed to an altered energy metabolism. The light-induced release of zoospores was found to be prevented by addition of cycloheximide or chloramphenicol, antibiotics which inhibit protein biosynthesis by cytoplasmic and organellar ribosomes, respectively. Actinomycin D, an inhibitor of RNA synthesis, however, did not affect the light-induced liberation of zoospores.Sporangia accumulate in stationary cultures of the mutant ls. Release of zoospores was observed when these sporangia were collected by centrifugation and incubated in the light after resuspension in fresh culture medium. Since liberation of zoospores was not observed after dilution of the stationary cultures with fresh culture medium, we suppose that components which interfere with the action of the sporangial autolysin are accumulated in the culture medium of the mutant ls.Abbreviation DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea 相似文献
24.
25.
Klaus Rohde 《Systematic parasitology》1989,14(2):79-91
The following gill monogeneans are described, based on a survey of 240 Rastrelliger kanagurta, 12 R. faughni and 185 R. brachysoma (Scombridae) from many geographical areas: Eyelavera typica from R. kanagurta, R. faughni and R. brachysoma, Indomazocraes jagannath from R. kanagurta and R. faughni, Kuhnia sprostonae from R. kanagurta and R. brachysoma, and Kuhnia scombercolias from R. kanagurta and R. brachysoma. Eyelavera parukhini Lebedev, 1980 is synonymised with E. typica, Scomberocotyle eyela Unnithan, 1964 with Indomazocraes jagannath, Kuhnia microlepidotusi Gupta & Krishna, 1977 and K. kanagurta Mamaev & Parukhin, 1986 with K. sprostonae, K. arabica Mamaev & Parukhin, 1986 with K. scombercolias Nasir & Fuentes Zambrano, 1983. It is emphasized that populations of Monogenea from the same host species or genus in different geographical areas are likely to be conspecific, and should not be described as different species, if they differ only slightly from each other. Monogenea that differ from insufficiently described species in minor detail should not be described as new species unless material of the original species has been examined. 相似文献
26.
Wolfgang Witt Peter Hampel Klaus Böcker Angelika Mertsching 《Archives of microbiology》1989,151(2):154-158
Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 M. The inhibition by nucleotides in low concentrations is enhanced by divalent cations. 相似文献
27.
Helmut Krüger Werner Schr?der Klaus Buchner Ferdinand Hucho 《Journal of Protein Chemistry》1990,9(4):467-473
Inhibition of protein kinase C (PKC) by calmodulin is investigated and we describe the localization of inhibitory sequences within the calmodulin molecule. We present evidence that calmodulin inhibits PKC through an inhibition of the activation of PKC associated with lipid membranes: Binding of PKC to lipid vesicles is not affected, but activation is abolished. The potent calmodulin antagonist R24571 (calmidazol) did not affect the inhibition of PKC by calmodulin at concentrations up to 10–5 M. Two tryptic fragments of calmodulin were isolated which inhibited PKC. They were only slightly less potent than intact calmodulin with an IC50 of 6 µ M compared to 1 µ M of intact calmodulin. They were identified as Ser38-Arg74 and His107-Lys148. Each of the inhibiting fragments contains an intact Ca2+-binding domain with complete helix-loop-helix structure (EF hand). Other calmodulin peptides showed only weak inhibitory activity. Both fragments did not stimulate cAMP phosphodiesterase even at concentrations 100-fold higher than the calmodulin concentration needed for maximal stimulation. None of the fragments acted as a calmodulin antagonist. 相似文献
28.
Summary The ultrastructural and transmitter development of lumbar sympathetic ganglia was studied in embryonic day-6 through-18 chick embryos. At embryonic day 6, ganglia are populated by two morphologically distinct types of neuronal cells and Schwann cell precursors. The neuronal populations basically comprise a granule-containing cell and a developing principal neuron. Granule-containing cells have, an irregularly shaped or oval nucleus with small clumps of chromatin attached to the inner nuclear membrane and numerous large (up to 300 nm) membrane-limited granules. Developing principal neurons display a more rounded vesicular nucleus with evenly distributed chromatin, prominent nucleoli, more developed areas of Golgi complexes, and rough endoplasmic reticulum and large dense-core vesicles up to 120 nm in diameter. There are granule-containing cells with fewer and smaller granules which still display the nucleus typical for granule-containing cells. These granule-containing cells may develop toward developing principal neurons or the resting state of granule-containing cells found in older ganglia. Both granule-containing cells and developing principal neurons proliferate and can undergo degeneration. At embryonic day 9 there are far more developing principal neurons than granule-containing cells. Most granule-containing cells have very few granules. Mitotic figures and signs of cell degeneration are still apparent. Synapse-like terminals are found on both developing principal neurons and granule-containing cells. Ganglionic development from embryonic day 11 through 18 comprises extensive maturation of developing principal neurons and a numerical decline of granule-containing cells. Some granule-containing cells with very few and small granules still persist at embryonic day 18. The mean catecholamine content per neuron increases from 0.044 femtomol at embryonic day 7 to 0.22 femtomol at embryonic day 15. Concomitantly, there is a more than 6-fold increase in tyrosine hydroxylase activity. Adrenaline has a 14% share in total catecholamines at embryonic day 15. Somatostatin levels are relatively high at embryonic day 7 (1.82 attomol per neuron) and are 10-fold reduced by embryonic day 15. Our results suggest the presence of two morphologically distinct sympathetic neuronal precursors at embryonic day 6: one with a binary choice to become a principal neuron or to die, the other one, a granule-containing cell, which alternatively may develop into a principal neuron, acquire a resting state or die. 相似文献
29.
Reinhard Lakes Klaus Kalmring Karl-Heinz Engelhard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,166(4):553-563
Deafferentation experiments during postembryonic development show morphological and/or physiological changes of receptor fibers and of identified auditory interneurons in the CNS of the locusts Locusta migratoria and Schistocerca gregaria after unilateral ablation of one tympanic organ either in the larva or the adult animal.
相似文献
1. | In Locusta migratoria, 5 days after deafferentation, intact, contralateral receptor fibers had sprouted collaterals in the frontal acoustic neuropil of the metathoracic ganglion (Figs. 1, 2). Collateral sprouts were only rarely found in Schistocerca gregaria. |
2. | After about 20 days the deafferented auditory interneurons receive new inputs from the contralateral receptors (Figs. 3, 5, 7, 10). This largely restores their thresholds and intensity/response functions. Collaterals from the first order interneurons cross the midline to the contralateral neuropil (BSN1 neuron, Fig. 4), which is never seen in intact animals. By contrast, in the TN1 neuron no consistent morphological change due to the deafferentation could be found (Fig. 6). |
3. | Interneurons of higher order (AN1, TN3 neuron in locusts) regain their response pattern (Fig. 7) without morphological changes (Fig. 9). Bilateral recordings show that the deafferented interneurons respond more weakly to auditory stimuli than the intact neuron, but the response to vibration stimuli remains unchanged (TN3 neuron, Fig. 8). |
30.
Klaus D. Jürgens Manfred Pietschmann Kazuhiro Yamaguchi Traute Kleinschmidt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(4):469-477
Summary The oxygen binding properties of the blood of the camelid species vicuna, llama, alpaca and dromedary camel were measured and evaluated with respect to interspecific differences. The highest blood oxygen affinity, not only among camelids but of all mammals investigated so far, was found in the vicuna (P50=17.6 Torr compared to 20.3–21.6 Torr in the other species). Low hematocrits (23–34%) and small red blood cells (21–30 m3) are common features of all camelids, but the lowest values are found in theLama species. Capillary densities were determined in heart and soleus muscle of vicuna and llama. Again, the vicuna shows exceptional values (3720 cap/mm2 on average in the heart) for a mammal of this body size. Finally, heart weight as percent of body weight is higher in the vicuna (0.7–0.9%) than in the other camelids studied (0.5–0.7%). The possibility that these parameters, measured in New World tylopodes at sea level, are not likely to change considerably with transfer to high altitude, is discussed.In the vicuna, a unique combination of the following features seems to be responsible for an out-standing physical capability at high altitude: saturation of blood with oxygen in the lung is favored by a high blood oxygen affinity, oxygen supply being facilitated by low diffusion distances in the muscle tissue. Loading, as well as unloading, of oxygen is improved by a relatively high oxygen transfer conductance of the red blood cells, which is due to their small size and which compensates the negative effect of a low hematocrit on the oxygen conductance of blood. Blood oxygen transport is presumably favored by two factors: a relatively large heart mass and, as a result of low hematocrit, a low blood viscosity. Both are advantageous for achieving a high maximal cardiac output. 相似文献