Environmentální rastrovací elektronová mikroskopie představuje jeden z posledních vývojových trendů mikroskopických metod. Umožňuje zkoumání vzorků živé či neživé přírody v podmínkách vysokého tlaku plynů - až 3000 Pa oproti tlaku pod 0.001 Pa v klasickém rastrovacím elektronovém mikroskopu., Vilém Neděla, Rudolf Autrata., and Obsahuje seznam literatury
The influence of a cytokinin, 6-benzylaminopurine (BAP), on chloroplast structure was studied using biochemical methods and electron microscopy. The average degree of thylakoid stacking was determined by digitonin fractionation and differential centrifugation of chloroplasts from tobacco plantlets after treatment with different concentrations of BAP in agar medium during cultivation in viíro. An elevated concentration of BAP in the medium induced an increase in grana stacking. This was in accordance with the lowering of the chlorophyll a/b ratio in these chloroplasts. The relative amoímt of proteins and carotenoids increased in both stromal and (to a lesser extent) granal chloroplast thylakoid fractions with the BAP concentration. The electron microscopic studies revealed nearly the same volume density of thylakoid membranes within chloroplasts of BAP treated plantlets and control ones. In the BAP treated plantlets the chloroplasts were smaller and had a profound accumulation of starch inclusions and a more flattened shape than the chloroplasts of control plantlets. The volume density of plastoglobuli in chloroplasts did not decrease under the influence of BAP,
Two types of photosystem 2-light-harvesting complex 2 (PS2-LHC2) supercomplexes with similar pigment and protein composition were isolated directly from thylakoid membranes by sucrose density gradient centrifugation. Electron microscopy and single particle image analysis revealed the first Type as single unpaired PS2-LHC2 supercomplexes, whereas the second Type was characterized as pairs of two PS2-LHC2 supercomplexes attached together by their stromal sides. Unstacking of thylakoid membranes resulted in a spontaneous disintegration of the paired supercomplexes into single unpaired particles. A model of the organisation of the pigment-protein complexes in grana region is proposed. and L. Bumba, M. Hušák, F. Vácha.
Intestinal microsporidiosis was documented by detecting abundant slightly curved spores (2.9 x 1.2 pm) in the faeces of five of twelve skinks Mabuya perrotetii Duméril et Bibron, 1839 that originated from Ghana. Clinically, the microsporidiosis was characterized by decreased appetite, diarrhea, and weight loss. Histopathological changes consisted of villous atrophy, blunting of mucosa and flattening of individual epithelial cells in the large intestine. The ultrastructure of microsporidian spores was consistent with an Encephalitozoon species. The PCR-RFLP assay and the heleroduplex mobility shift analyses were used to verify that the skink microsporidian is a species of the genus Encephalitozoon Levaditi, Nicolau et Schoen, 1923 and indicate that this microsporidian is not E. hellem, E. intestinalis or a strain of E. cuniculi. The microsporidia in African skink represent an Encephalitozoon species morphologically identical to Encephalitozoon lacerine Canning, 1981.
Chloroplasts of barley plants grown under red light (RL, 660 nm) dramatically differed from the chloroplasts of plants raised under blue light (BL, 450 nm) or control plants (white light). The chloroplasts under RL had an extensive membrane system with high stacking degree and disordered irregular shaped stacks (shaggy-formed grana). After 5 h in darkness, dynamic rearrangements of chloroplast architecture in RL- and especially BL-grown plants were restricted compared with control plants. The light spectral quality affected the content and proportions of photosynthetic pigments. The leaves of RL-grown plants had the increased ratio of low-temperature fluorescence bands, F741/F683, corresponding to emission of PSI and PSII, respectively. This increase can be related to specific architecture of chloroplasts in RL-treated plants, providing close spacing between the two photosystems, which enhances energy transfer from PSII to PSI and facilitates the movement of LHCII toward PSI., G. V. Kochetova, O. B. Belyaeva, D. S. Gorshkova, T. A. Vlasova, E. M. Bassarskaya, T. V. Zhigalova, O. V. Avercheva., and Obsahuje bibliografii
The quantitative changes of chloroplast ultrastructure and dimensions in mesophyll (MC) and bundle sheath (BSC) cells, associated with the onset of leaf senescence, were followed along the developmental leaf blade gradient of the third leaf of maize (Zea mays L.). To ascertain whether the rapidity of structural changes associated with the transition of chloroplasts from mature to senescent state is a heritable trait, the parental and the first filial generations of plants were used. The heterogeneity of leaf blade, associated with the development of maize leaf (with the oldest regions at the apex and the youngest ones at the base) was clearly discernible in the ultrastructure and dimensions of chloroplasts; however, there were differences in the actual pattern of chloroplast development between both genotypes as well as between both cell types examined. While the course of MC chloroplasts' development at the onset of leaf senescence in maize hybrid followed that of its parent rather well, this did not apply for the BSC chloroplasts. In this case, each genotype was characterized by its own distinguishable developmental pattern, particularly as regards the accumulation of starch inclusions and the associated changes of the size and shape of BSC chloroplasts. and A. Vičánková, D. Holá, J. Kutík.
Nově identifikovaná kategorie středověkých artefaktů z českých archeologických fondů představuje jeden z atributů zacházení s drahými kovy. Šest dosud evidovaných předmětů datovatelných do raného středověku pochází z různých kontextů sociálních (hrad, sídelní aglomerace, ves) i archeologických (hrob, sídlištní objekt, hradiště). Autoři zdůrazňují nezbytnost potvrzení přítomnosti stop zkoušeného kovu chemickými mikroanalýzami, a to nejen pro interpretaci artefaktu, ale i pro poznání prostředí, které manipulovalo s drahými kovy i s podvrhy, a v neposlední řadě pro upřesnění názorů na dovednosti středověkých metalurgů. and A newly identified category of medieval artefacts from Czech archaeological inventories represents one indicator of the manner in which precious metals were handled: six objects date from various social (castle, settlement agglomeration, village) and archaeological (grave, settlement feature, hillfort) early medieval contexts. The authors emphasize the necessity of confirming the presence of traces from the tested metal by chemical microanalysis, not only for interpreting the artefacts themselves, but also for understanding the environment in which both precious and spurious metals were handled.