Electron transport chain and energy transduction in Paracoccus denitrificans under autotrophic growth conditions

Cells of Paracoccus denitrificans grown autotrophically with H₂ as energy source contained a branched respiratory chain. The presence of two terminal oxidases was indicated by two cyanide sensitive sites (K _i =10^-5 M and K _i =10^-3 M). While oxidation of NADH and succinate apparently proceeded via both electron pathways as shown by the inhibition of respiration with cyanide and Antimycin A, oxidation of H₂ involved only the terminal oxidase which was less sensitive to KCN. Oxidation of H₂ was not inhibited by rotenone, and sensitive to only relatively high concentrations of Antimycin A (50 nmol/mg).Under our growth conditions, autotrophic cells contained only very small amounts of cytochrome a +a ₃ . A cytochrome b was able to bind CO (with a peak at 418 nm and a trough at 434 nm in the reduced plus CO minus reduced difference spectrum). This cytochrome b had the spectral characteristics of cytochrome o and could be the alternate oxidase. The respiratory chain contained two b cytochromes (b ₅₅₆ and b ₅₆₂ at 77°K); under steady state conditions only b ₅₅₆ was significantly reduced by NADH and succinate while both b ₅₅₆ and b ₅₆₂ were reduced by H₂.Measurement of respiration-driven proton translocation by spheroplasts showed that the oxidation of H₂ by O₂ was associated with a vectorial ejection of H⁺ (in the outward direction) with aH⁺/O value of 6 to 7.A similar result was obtained with succinate. Oxidation of endogenous substrates gave H⁺/O values corresponding to a H⁺/site ratio of 3 with 3 sites functioning in absence of inhibitors, two sites in the presence of rotenone and one site in the presence of antimycin. The H⁺/O values indicated that two energy transducing sites were involved in the oxidation of H₂ by O₂.Measurement of ATP synthesis in membrane vesicles confirmed that phosphorylation was coupled to H₂ oxidation. However, such determinations which necessitated the use of inverted vesicles, gave P/O values too low to allow any conclusions to be made on the number of coupling sites.     

Observations ultrastructurales sur la parathyroïde de souris

Résumé La parathyroïde de souris ne diffère pas essentiellement par sa structure générale de celles des autres espéces étudiées. Les cellules glandulaires se caractérisent cependant par une plus grande richesse en matériel sécrétoire figuré. La présence de ce matériel figuré dans les cavités golgiennes permet de suivre l'élaboration de granules sécrétoires typiques d'un diamètre de 160 à 200 m qui sont spécialement abondants chez la souris. Ces granules ne sont pas excrétés au pôle vasculaire des cellules; ils migrent vers les parois cellulaires apicales et latérales, fusionnent avec la membrane plasmique et semblent être excrétés sous forme soluble dans les espaces intercellulaires. Il n'existe dans la parathyroïde de souris, comme dans celle du hamster et du rat, qu'un seul type cellulaire fondamental. Les éléments clairs et sombres ne diffèrent que par leur densité hyaloplasmique; cette différence s'accuse plus ou moins selon la qualité du prélèvement.

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Summary The structure of the mouse parathyroid does not differ essentially from other species studied. However, the glandular cells are characterized through an abundance in visible secretory material. The presence of this material in the cavities of the Golgi apparatus makes it possible to observe the formation of the typical secretory granules (160–200 m in diameter) which are particularly abundant in the mouse parathyroid. These granules are not secreted directly at the vascular pole; they migrate to the apical and lateral walls, fuse with the plasma membrane, and seen to pass into the cellular space in a soluble form. In the mouse parathyroid, as in the hamster and rat, there is only one fundamental cell type. The difference between dark and clear cells lies in the density of their hyaloplasm, which, however, is a consequence of the pretreatment of the material (fixation).

     

Subcellular localization of cholesterol ester hydrolase in the human intestine

Immunocytochemistry and subcellular fractionation were used to localize the cholesterol ester hydrolase in the human small intestine. A positive immunoreaction, when using antibodies directed against pancreatic cholesterol ester hydrolase, was mainly found in endocytotic vesicles. Moreover, a label by gold particles was observed in intercellular spaces where lymphatic tissue merges. No specific immunoreactivity was obtained with the mucosa when sera directed against human pancreatic chymotrypsinogen and human pancreatic lipase were used. Conventional subcellular fractionation was performed after extensive washing of enterocytes to rule out any possible contamination by pancreatic enzymes. In these conditions a bile salt-dependent cholesterol ester hydrolase activity was detected in the soluble fraction of cells. Data agree with the concept that the intestinal cholesterol ester hydrolase may have a pancreatic origin. The absorption, if any, of this enzyme by enterocytes seems specific since other pancreatic (pro)enzymes tested (lipase, chymotrypsinogen) are not detected in these cells.     

The role of intracellular lumina in the repolarization process of a colonic adenocarcinoma cell line

When glucose is added to the culture medium, some cells of the undifferentiated HT-29 line derived from a human colonic adenocarcinoma develop spherical structures, demonstrated to be intracellular by the ruthenium red staining method, which are bordered with microvilli, contain osmiophilic substances and resemble intracellular lumina. When glucose is replaced by galactose in the culture medium, the cells differentiate apical membranes bordered with microvilli. Our observations suggest that these new apical membranes correspond to the membranes of intracellular lumina which have opened outside the cells. We suggest that intracellular lumina may represent "compensation" for loss of polarity of epithelial cells and may be an important step in the repolarizing process of the cells.     

Ultrastructure de l'endostyle de l'ascidie Microcosmus claudicans Savigny

Résumé L'endostyle de l'Ascidie Microcosmus claudicans (Savigny) contient 8 types cellulaires groupés en bandelettes longitudinales. Les cellules I sont mucipares et ciliées; les cellules III et V ciliées sont vectrices du mucus.Les cellules II et IV des bandelettes glandulaires sont très riches en ergastoplasme et renferment des grains de sécrétion apicaux d'aspect analogue. Les cellules VI également riches en ergastoplasme se distinguent des précédentes par leurs grains de sécrétion en forme de batonnet. Les cellules VII. iodophiles, sont caractérisées par leurs nombreux grains de lipopigment et leurs filaments intracytoplasmiques.Les fonctions des cellules II, IV, VI et VII sont inconnues.     

Variations in spatial and temporal distribution of Archaea in the North Sea in relation to environmental variables

The spatial and temporal distribution of pelagic Archaea was studied in the southern North Sea by rRNA hybridization, sequencing and quantification of 16S rRNA gene and membrane lipid analyses and related to physical, chemical and biological parameters to determine the factors influencing archaeal biogeography. A clear temporal variability was observed, with marine Crenarchaeota (Group I.1a) being relatively more abundant in winter and Euryarchaeota dominating the archaeal assemblage in spring and summer. Spatial differences in the lateral distribution of Crenarchaeota were also evident. In fact, their abundance was positively correlated with the copy number of the gene encoding the alpha subunit of crenarchaeotal ammonia monooxygenase (amoA) and with concentrations of ammonia, nitrate, nitrite and phosphorus. This suggests that most Crenarchaeota in the North Sea are nitrifiers and that their distribution is determined by nutrient concentrations. However, Crenarchaeota were not abundant when larger phytoplankton (>3 microm) dominated the algal population. It is hypothesized that together with nutrient concentration, phytoplankton biomass and community structure can predict crenarchaeotal abundance in the southern North Sea. Euryarchaeotal abundance was positively correlated with chlorophyll a concentrations, but not with phytoplankton community structure. Whether this is related to the potential of Euryarchaeota to perform aerobic anoxygenic phototrophy remains to be shown, but the conspicuous seasonal distribution pattern of Crenarchaeota and Euryarchaeota suggests that they occupy a different ecological niche.