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51.
Päivi Heikkilä Arvi I. Kahri Christian Ehnholm Petri T. Kovanen 《In vitro cellular & developmental biology. Plant》1988,24(9):936-942
Summary To define the role of endogenously synthesized cholesterol in the differentiation of adrenocortical cells in primary culture,
fetal rat adrenal cells were cultured in the presence of exogenous cholesterol (serum-supplemented medium) or in the absence
of it (serum-free medium or lipoprotein-free medium). Ultrastructurally the cells had features of glomerulosa cells: mitochondria
were oval or rod shaped with lamellar inner membranes. The amount of smooth endoplasmic reticulum was small, and lipid droplets
were few. When the cells were cultured in serum-free medium some intracytoplasmic vacuoles were seen. The undifferentiated
zona glomerulosa-like cells secreted low amounts of corticosterone and 18-OH-deoxycorticosterone (18-OH-DOC) in all three
media (serum-supplemented medium, serum-free medium, and lipoprotein-free medium). Stimulation of the adrenocortical cells
with ACTH induced the ultrastructural features of differentiated zona fasciculata-like cells. Mitochondrial inner membranes
were well developed in lipoprotein-free medium, but not in serum-free medium. The amount of intracellular lipids was increased
in both media devoid of cholesterol. In the ACTH stimulated cultures the presence of exogenous cholesterol resulted in increased
secretions of corticosterone and 18-OH-DOC. In the absence of an exogenous source of cholesterol, the amounts of steroids
secreted were only half of that secreted in the presence of serum-supplemented medium. Endogenously synthesized cholesterol
is sufficient for the morphologic differentiation of fetal rat adrenocortical cells under ACTH stimulation. However, without
exogenously provided cholesterol, the steroid production accounts only for half of the maximal output achieved using serum-supplemented
medium.
This work was supported by Finnish Culture Foundation. 相似文献
52.
A unifying approach described by a random birth and death process which includes both environmental and demographic noise is introduced. It is shown that both of these noise sources play an essential role in extinction processes in general. The probability distribution of the lifetime of a population is determined and its dependence on the parameters of the model is discussed. Finally a population divided into subpopulations is modeled. The lifetime of this ensemble of subpopulations is compared to the lifetime of one large population. 相似文献
53.
54.
In liver homogenate the biosynthesis ofN-acetylneuraminic acid usingN-acetylglucosamine as precursor can be followed stepwise by applying different chromatographic procedures. In this cell-free system 16 metal ions (Zn2+, Mn2+, La3+, Co2+, Cu2+, Hg2+, VO
3
–
, Pb2+, Ce3+, Cd2+, Fe2+, Fe3+, Al3+, Sn2+, Cs+ and Li+) and the selenium compounds, selenium(IV) oxide and sodium selenite, have been checked with respect to their ability to influence a single or possible several steps of the biosynthesis ofN-acetylneuraminic acid. It could be shown that the following enzymes are sensitive to these metal ions (usually applied at a concentration of 1 mmoll–1):N-acetylglucosamine kinase (inhibited by Zn2+ and vandate), UDP-N-acetylglucosamine-2-epimerase (inhibited by zn2+, Co2+, Cu2+, Hg2+, VO
3
–
, Pb2+, Cd2+, Fe3+, Cs+, Li+, selenium(IV) oxide and selenite), andN-acetylmannosamine kinase (inhibited by Zn2+, Cu2+, Cd2+, and Co2+). Dose dependent measurements have shown that Zn2+, Cu2+ and selenite are more efficient inhibitors of UDP-N-acetylglucosamine-2-epimerase than vanadate. As for theN-acetylmannosamine kinase inhibition, a decreasing inhibitory effect exists in the following order Zn2+, Cd2+, Co2+ and Cu2+. In contrast, La3+, Al3+ and Mn2+ (1 mmoll–1) did not interfere with the biosynthesis ofN-acetylneuraminic acid. Thus, the conclusion that the inhibitory effect of the metal ions investigated cannot be regarded as simply unspecific is justified.Dedicated to Professor Theodor Günther on the occasion of his 60th birthday 相似文献
55.
Expression of polysialylated N-CAM during rat heart development 总被引:2,自引:0,他引:2
Peter M. Lackie Christian Zuber Jürgen Roth 《Differentiation; research in biological diversity》1991,47(2):85-98
Developmental patterns of immunoreactivity for the neural cell adhesion molecule (N-CAM) and alpha 2.8-linked polysialic acid (PSA) were identified in embryonic and postnatal rat heart by immunocytochemistry and immunoblotting. Polyclonal antibodies against N-CAM and a monoclonal antibody which recognises only polymers of PSA with a chain length greater than eight units were used. Gold- and alkaline-phosphatase-labelled antibodies were used for detection. The N-CAM polypeptide isoform pattern seen by immunoblotting after endoneuraminidase treatment changed as development progressed. During embryonic development a 160-kDa polypeptide isoform was predominant. Around birth, 130-, 160- and 170-kDa polypeptide isoforms were found. The expression of the 130- and 170-kDa isoforms diminished until finally, in the adult, weak immunoreactivity for bands of 120-, 130- and 160-kDa was seen. In general the extent and intensity of PSA and N-CAM immunostaining in rat heart increased until birth and declined thereafter. Early in development prominent immunostaining for PSA and N-CAM was seen in the epicardium while later in development this area was only weakly stained. Initially myocardial cells, endocardial cells and some cells in the atrioventricular cushions were immunoreactive for both PSA and N-CAM. Later in development N-CAM immunostaining was more prominent than PSA immunoreactivity, reflecting a decrease in N-CAM polysialylation, which was also seen by immunoblotting. During innervation of the heart, nerve fibres were strongly immunostained for PSA and N-CAM, and this was the only immunostaining seen in adult heart. 相似文献
56.
Pierre Trudel Danile Courchesne Christian Roy Pierre Chartrand 《Applied microbiology》1988,54(6):1550-1556
We have screened a genomic library of Trametes versicolor for genes whose expression is associated with nitrogen starvation, which has been shown to induce ligninolytic activity. Using two different approaches based on differential expression, we isolated 29 clones. These were shown by restriction mapping and cross-hybridization to code for 11 distinct differentially expressed genes. Northern analysis of the kinetics of expression of these genes revealed that at least four of them have kinetics of induction that parallel kinetics of induction of ligninolytic activity. 相似文献
57.
Behaviour of drifting insect larvae 总被引:1,自引:1,他引:0
The larval drift behaviour of 23 species representing Ephemeroptera, Plecoptera and Trichoptera was investigated in the laboratory using different current regimes. Mayfly nymphs often performed swimming, while caddis larvae were reluctant to do so. Stonefly nymphs were intermediate. In mayflies swimming seemed to be used to reach the substrate as soon as possible. In contrast most stonefly nymphs by swimming prolonged the time spent in the water column. Modes of swimming and sinking posture differed markedly between the orders. Living passively sinking animals often reached bottom faster than dead control specimens, so consequently behaviour did not always express itself in activity. Some caddis larvae spun adherent anchor lines. Differences among taxa seemed more important in explaining swimming activity compared to preferred habitats (as stream, river and lake) in each species. However, observed differences among closely related species indicated subtle differences related to microhabitat to be of profound importance in explaining the alternative behavioural strategies used. 相似文献
58.
Christian Boucher Anne Martinel Patrick Barberis Genevieve Alloing Claudine Zischek 《Molecular & general genetics : MGG》1986,205(2):270-275
Summary A class of avirulent mutants of the plant pathogenic bacterium Pseudomonas solanacearum, strain GMI1000, resistant to acridine orange (Acrr), harbour a deletion of over 85 kb in their genome. This deletion affects, a1,000 kb megaplasmid which has previously been shown to be present in most of the strains of this species. In addition at least 11 out of 13 independent Tn5 insertions, leading to loss of virulence, are located on the megaplasmid. Nine of them are present in the region which is deleted from the Acrr mutants. These results suggest that the majority of virulence genes identified so far are plasmid borne. 相似文献
59.
Daniel Chappard Christian Alexandre Sabine Palle George Riffat 《Biotechnic & histochemistry》1986,61(2):93-96
Polyester fibers are not dissolved by either glycol methacrylate or methyl methacrylate. Commercial polyester wadding is consequently an advantageous material to use in getting precise orientation of tissue specimens during embedding in methacrylate. 相似文献
60.
Daniel Chappard Christian Alexandre Sabine Palle Georges Riffat 《Biotechnic & histochemistry》1986,61(3):145-149
A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method. 相似文献