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21.
Morphology of germ-free piglets 总被引:1,自引:0,他引:1
The postnatal ontogeny of primary (thymus) and secondary (spleen, lymph node, lingual tonsil) lymphoid tissues was studied in germ-free colostrum-deprived piglets up to age of 68 days. The thymus, which is morphologically fully developed by the end of gestation, showed no significant differences in the germ-free and conventional state. In germ-free piglets, slow development of periarteriolarly organized lymph follicles occurred in the spleen up to the end of the observation period. As distinct from the conditions in the spleen of conventional animals, the presence of a large number of pyroninophilic cells was not observed in germ-free piglets and no germinal centres were found. A similar situation was seen in the mesenteric lymph nodes, in which, in conventional piglets, cells belonging to the plasmacyte series, as well as the germinal centres, proliferate by the 13th day. Differences were also found in the organization of the follicular lymphoid tissue in the wall of the terminal ileum. In germ-free piglets, the lymph follicles increased only very slowly in size during the observation period and germinal centres were absent, while in conventional piglots germinal centres were present from the 12th day. The view is expressed that the intestinal lymphoid tissue ought rather to be classified as peripheral lymphoid tissue. 相似文献
22.
The cytoplasmic components of broad bean (Vicia faba L.) root tip cells were studied light- and electronmicroscopically. Using a light microscope, differences were revealed between cells from the cortex and from the central cylinder. For electron microscope studies the cells near the boundary between the mentioned parts of the root tip were selected at a distance of about 2 mm from the initials. The orientation of objects during embedding made possible fairly accurate localization. No peculiar, strikingly osmiophillic bodies were seen, which could be identified without doubt as osmiophillic platelets. It follows that some of the current cytoplasmic components, perhaps more or less altered were described as osmiophillic platelets. After fixation with KMnO4, in which case the electronmicrographs are most instructive, the leucoplasts show several inclusions, mostly only partially limited against the matrix; it is not clear whether the true membrane is concerned here. The origin of intravacuolar membraneous formations is discussed. 相似文献
23.
Cells ofRhodotorula gracilis form under certain conditions equatorial rings, visible in the UV-fluorescence microscope after staining with a CFW brightener.
The ultrastructural studies showed that the above rings are formed by a centripetal thickening of the cell wall. Mitochondria
with circular cristae and anomalous, ring-like mitochondria were observed in cytoplasm of the cells with developed rings.
The plates will be found at the end of the issue. 相似文献
24.
Ludvík Chvojka 《Biologia Plantarum》1961,3(1):15-28
Autor studoval v pr?běhu dvou let osmotický tlak 70 strom? 7 odr?d jabloně, ze kterých 5 odr?d plodí periodicky a 2 ka Edoro?ně. Na za?átku pokusu polovina strom? byla bez plod? a polovina s násadou plod?. Pokus byl proveden na 10 a? 121et ch stromeoh (podno? M II, M IX a M IV) v severozápadni jabloňárské oblasti ?ech (St?í?ovice, Těchobuzice). 3 a? 4krát za vegeta?ni období byly odebirány listy brachyblast? plodíoích a odpo?ívajících jabloní a stanoven osmotický tlak jejich buně?né ?távy, jako? i její elektrická vodivost. Jednou za sezónu byly odebrány terminálni pupeny brachyblast?, z kterých oby?ejně vznikaji květní pupeny, a zpraeovány stejně jako listy. Ze získaných ?daj? plyne, ?e rostouci plody jsou p?í?inou sni?ení osmotického tlaku buně?né ?távy list? jabloně 2 a? 6 atmosfér v závislosti od mno?stv? násady a období. Toto sni?ení málo závisí na po?asi a rozdíly v osmotickém tlaku buněcné ?távy jabloní plodíeích a odpo?ívajících jsou v ?ervenci vysoce pr?kazné. Osmotický tlak buně?né ?távy pupen? je sni?ován méně: 1 a? 2 atmosféry. Byla nalezena pr?kazná kladná korelace mezi hodnotou osmotického tlaku odrüdy Boskoopské ?ervené a zakládáním květnich pupen?. U ka?doro?ně plodíeích odr?d taková korelace nebyla pozorována. 相似文献
25.
InBacillus megaterium, a temperature that suppresses sporulation (43°C) only slightly exceeds both the optimum growth temperature and the temperature
still permitting sporulation (40–41°C). Here we show that, when cells grown at 35°C and transferred to a sporulation medium,
were subjected to shifts between 35°C and the sporulation suppressing temperature (SST, 43°C), their development and proteolytic
activities were deeply affected. During the reversible sporulation phase that took place at 35°C for 2–3 h (T2–T3), the cells developed forespores and their protein turnover was characterized by degradation of short-lived proteins and
proteins made accessible to the proteolytic attack because of starvation. During the following irreversible sporulation phase
refractile heat-resistant spores appeared at T4–T5. Protein turnover rate increased again after T2 and up to T8 60–70% prelabelled proteins were degraded. The SST suppressed sporulation at its beginning; at T3 no asymmetric septa were observed and the amount of heat-resistant spores at T8 was by 4–5 orders lower than at 35°C. However, the cells remained viable and were able to sporulate when transferred to a
lower temperature. Protein degradation was increased up to T3 but then its velocity sharply dropped and the amount of degraded protein at T8 corresponded to slightly more than one-half of that found at 35°C. The cytoplasmic proteolytic activity was enhanced but
the activity in the membrane fraction was decreased. When a temperature shift to SST was applied at the beginning of the irreversible
sporulation phase (T2.5), the sporulation process was impaired. A portion of forespores lyzed, the others were able to complete their development
but most spores were not heat-resistant and their coats showed defects. Protein degradation increased again because an effective
proteolytic system was developed during the reversible sporulation phase but the amount of degraded protein was slightly lower
than at 35°C. A later (T4) shift to SST had no effect on the sporulation process. 相似文献
26.
Calderobacterium hydrogenophilum is an extreme thermophilic, obligately chemoautotrophic, hydrogen-oxidizing bacterium. The cells were shown to be nonmotile straight rods of average size 0.4x2.5 m. After negative-staining of the whole cells, no flagella were observed. The multilayered cell wall was of type 1 and possessed a crystalline proteinaceous surface layer exhibiting p4 symmetry. The square unit cells had a lattice constant of approximately 11 nm. Cell division occurred by a constriction mechanism. C. hydrogenophilum differred from a similar hydrogen-oxidizing eubacterium, Hydrogenobacter thermophilus, by the absence of intracytoplasmic membrane structures in chemically fixed cells. However, an electron-dense intracytoplasmic hemispherical structure adhering to the inner membrane was frequently observed. 相似文献
27.
Vodicka P Streinz L Vávra J Koutek B Budesínský M Ondrácek J Císarrová I 《Chirality》2005,17(7):378-387
The title compounds have been prepared from the respective 3,3,3-trifluoro-2-methoxy-2-phenylpropanoic acids (MTPA) by a three-step synthesis with MTPA chloride and MTPA amide as reaction intermediates. The requested compounds were obtained in high chemical yields without any change in optical purity during the preparation. To ascertain the usefulness of this auxiliary agent in the chiral analysis, isomeric 3,3,3-trifluoro-2-phenylpropanoyl isocyanates were subjected in NMR tubes to noncatalyzed reactions with 16 different commercially available chiral alcohols. The steric arrangement of all diastereomers prepared correlated well with their NMR spectral nonequivalence data (Deltadelta), thus demonstrating the regular sign distribution of Deltadelta of particular groups according to the devised molecular model. The usefulness of the novel derivatization is discussed. 相似文献
28.
29.
This paper presents the results of the development of lymphatic and haemopoietic organs in pig fetuses of various ages. The thymus appears to be the first lymphatic organ in these fetuses as well as in other animal species so far studied. On the 77th day the thymus is fully morphologically developed. The accumulations of lymphocytes in the spleen appear on the 70th day. The development of periarteriolar formations takes place around the 84th day of gestation. Further development of lymphoid tissue in the lymph nodes, tongue (tonsilla lingualis) and intenstine is described. Lymphatic follicles were observed both in the tongue and the small intestine on the 77th day. The dynamics of haemopoietic activity in the liver and bone marrow is characterized. The germinal centers in lymphoid folicles were never observed as well as cells of the plasmatic series. 相似文献
30.