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排序方式: 共有684条查询结果,搜索用时 15 毫秒
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2.
Paola G. Andreis Piera Rebuffat Anna S. Belloni Giuliano Neri Letizia Cavallini Giuseppe Gottardo Giuseppina Mazzocchi Alberta Coi Ludwik K. Malendowicz Dr. Gastone G. Nussdorfer 《Cell and tissue research》1989,258(1):43-51
Summary The morphology and function of isolated inner (zona fasciculata/reticularis) adrenocortical cells of rats pretreated with ACTH for 3, 6, 9 or 12 days were investigated. ACTH treatment induced a notable time-dependent enhancement in the steroidogenic capacity (corticosterone production) and growth of inner cells. The volumes of cells, mitochondrial compartment, membrane space [the cellular space occupied by smooth endoplasmic reticulum (SER) membranes] and lipid-droplet compartment, as well as the surface area of mitochondrial cristae and SER tubules, were increased in relation to the duration of ACTH pretreatment, and showed a highly significant positive linear correlation with both basal and stimulated corticosterone production. The acute exposure of isolated cells to ACTH provoked a striking lipid-droplet depletion, the extent of which was linearly and positively correlated with stimulated corticosterone secretion. The hypertrophy of the mitochondrial compartment and SER are interpreted as the morphological counterpart of the enhanced steroidogenic capacity of inner adrenocortical cells, inasmuch as the enzymes of steroid synthesis are located in these two organelles, and it is well known that chronic ACTH exposure stimulates the de novo synthesis of many of them in vivo. The rise in the number of lipid droplets, in which cholesterol is stored, is interpreted as being due to the fact that, under chronic ACTH treatment, the processes leading to cholesterol accumulation in adrenocortical cells (exogenous uptake and endogenous synthesis) exceed those of its utilization in basal steroid secretion. Cholesterol accumulated in lipid droplets as a reserve material may be rapidly utilized after acute ACTH exposure to meet the needs of the enhanced steroidogenic capacity of adrenocortical cells. 相似文献
3.
Raffaella Scardigli Silvia Soddu Rita Falcioni Marco Crescenzi Letizia Cimino Ada Sacchi 《Experimental cell research》1996,227(2):223
Integrin β4subunit is present in association with α6chain on both normal and transformed epithelial cells. Recently α6β4heterodimer was found on the endothelium of medium-sized blood vessels and on immature thymocytes. In this report we show, by Northern blotting, indirect immunofluorescence, immunoprecipitation, and Western blotting, that β4subunit is expressed also on cells of mesenchymal origin such as fibroblasts, myoblasts, and myotubes. Increased expression of α6β4has been related to the aggressive metastatic phenotype of human and murine carcinomas. The transforming growth factor β1(TGF-β1) has been found to modulate the expression of several integrins and intracellular matrix proteins, as well as to stimulate cell invasion and metastatic potential. To evaluate whether α6β4expression is modulated by TGF-β1, we transfected 3T3 fibroblasts with an expression vector carrying the human TGF-β1cDNA driven by the SV40 early promoter. We observed by indirect immunofluorescence a modification in the subcellular distribution of β4subunit, which acquires a perinuclear localization. This finding suggests this integrin subunit correlates with the cytoskeletal reorganization induced by TGF-β1. 相似文献
4.
Bloom Syndrome and Maternal Uniparental Disomy for Chromosome 15 总被引:4,自引:1,他引:3
Trevor Woodage Madhuri Prasad Joanne W. Dixon Roslyn E. Selby Dennis R. Romain Letizia M. Columbano-Green David Graham Peter K. Rogan James R. Seip Arabella Smith Ronald J. Trent 《American journal of human genetics》1994,55(1):74-80
Bloom syndrome (BS) is an autosomal recessive disorder characterized by increases in the frequency of sister-chromatid exchange and in the incidence of malignancy. Chromosome-transfer studies have shown the BS locus to map to chromosome 15q. This report describes a subject with features of both BS and Prader-Willi syndrome (PWS). Molecular analysis showed maternal uniparental disomy for chromosome 15. Meiotic recombination between the two disomic chromosomes 15 has resulted in heterodisomy for proximal 15q and isodisomy for distal 15q. In this individual BS is probably due to homozygosity for a gene that is telomeric to D15S95 (15q25), rather than to genetic imprinting, the mechanism responsible for the development of PWS. This report represents the first application of disomy analysis to the regional localization of a disease gene. This strategy promises to be useful in the genetic mapping of other uncommon autosomal recessive conditions. 相似文献
5.
Carlos H. Prosperi 《Journal of phycology》1994,30(2):222-224
Nostoc cordubensis Prosperi (Cyanophyta, Nostocaceae) is characterized by its mucilaginous colonies. Much of this mucilage is produced by heterocysts. By controlling growth conditions, heterocysts with and without mucilage were obtained. Mucilaginous heterocysts retained nitrogen-fixing capability at high oxygen concentrations, whereas heterocysts lacking mucilage were unable to fix nitrogen at oxygen concentrations higher than 20%. Comparison of results obtained using tetrazolium salts as indicators of highly reduced zones showed similar results. 相似文献
6.
The influence of DNA topology on stainability with the externally binding fluorochromes Hoechst 33258 (HO) and mithramycin (MI) was investigated in HeLa nuclei in comparison with the intercalating dye propidium iodide (PI). Changes in DNA topology were induced with a mild DNAse I treatment. Stainability properties of untreated and nuclease-treated nuclei were compared with those of the supercoiled-circular and the relaxed-linear forms of the plasmid pBR322. DNAse-treated nuclei stained with HO showed a higher fluorescence intensity than control samples, independently of the dye concentration, in contrast with the findings obtained with PI. Similar behaviour was observed with the relaxed-linear form of pBR322, compared with the supercoiled-circular molecule. With MI, the stainability of HeLa nuclei did not depend on the DNA topology, whereas the stainability of the plasmid was similar to that of HO. In order to assess whether this discrepancy depended on differences in the availability of DNAse-sensitive sites to the fluorochromes, fluorescence resonance energy transfer (FRET) studies were performed in nuclei stained with HO+PI, or with HO+MI dye pairs. After DNAse I digestion, the relative FRET efficiency between donor (HO) and acceptor molecules (PI or MI) was reduced significantly only when MI was the acceptor. This result may be due to greater stainability of DNAse-sensitive sites with HO than with MI. These findings indicate that DNA stainability with base-specific fluorochromes may be affected by the topology of chromatin regions. 相似文献
7.
Guano F Bernardi R Negri C Donzelli M Prosperi E Ricotti GA Scovassi AI 《Cell death and differentiation》1994,1(2):101-107
Zinc ions exert an inhibitory effect on Ca(2+)Mg(2+)-dependent endonuclease which is supposed to be responsible for the fragmentation of DNA during apoptosis. In the experimental system we used, that is HeLa cells treated with VP-16, the protection from internucleosomal DNA degradation is modulated by Zn concentration and appears to be dependent on the time after treatment. This effect does not prevent cell death or occurrence of apoptotic parameters, suggesting that DNA ladder appearance is not a crucial event in apoptosis. The activation of poly(ADP-ribose)polymerase following the administration of VP-16, is not observed in cells in which DNA fragmentation has been abolished by zinc, supporting the hypothesis that this event is regulated by the appearance of small-sized DNA fragments. 相似文献
8.
P. Cugini C. Letizia S. Cerci L. Di Palma P. Battisti A. Coppola D. Scavo 《Chronobiology international》1993,10(2):119-122
This study deals with a chronobiological approach to the circadian rhythm of the renin-angiotensin-aldosterone system (RAAS) and the ACTH-cor-tisol axis (ACA) in patients with Addison's disease (PAD). The aim is to explore the mechanism(s) for which the circadian rhythmicity of the RAAS and ACA takes place. The study has shown that both the RAAS and ACA are devoid of a circadian rhythm in PAD. The lack of rhythmicity for renin and ACTH provides indirect evidence that their rhythmic secretion is in some way related to the circadian oscillation of aldosterone and cortisol. This implies a new concept: a positive feedback may be included among the mechanisms which chronoregulate the RAAS and ACA. 相似文献
9.
We investigated patterns of resource partitioning between two brackish crustaceans (I. baltica and G. insensibilis) on trophic mosaics of fungal species colonizing vegetal detritus. Laboratory feeding experiments were carried out to assess consumption rates and diet selection of single individuals belonging to five populations. Adults of two co-occurring population of both G. insensibilis and I. baltica and one population of G. insensibilis, occurring alone in another habitat patch, were studied. Each individual were offered both fragments of Cymodocea nodosa conditioned by 8 fungal species and sterilized fragments as sole food source for 7 days. Both species preferred "conditioned" detritus but potential resource use was greater in G. insensibilis than in I. baltica. Individual niche breadth increased and phenotypic variability reduced in the allotopic sample. Trophic similarities were lower between individuals of co-occuring populations than between I. baltica and the allotopic G. insensibilis. The results suggest that co-occurrence is an important factor contributing to the enhancement of phenotypic variability and, consequently, to a trophic generalization at population level in G. insensibilis. It emphasizes the role of fungal patchiness on detritus in regulating resource partitioning between the two species. 相似文献
10.
The circadian rhythm of serum angiotensin-converting enzyme (ACE) activity was investigated in pregnant women with normal and pre-eclamptic gestation. The chronobiological approach was able to document the occurrence of a circadian rhythm for serum ACE activity in normal pregnancy. Such a rhythm is characterized by a decreased mesor and amplitude and a shifted crest. The circadian rhythm for serum ACE activity was not detectable in pre-eclamptic pregnancy. Such an abrogation is accompanied by a negligible decrease of mesor suggesting the occurrence of a relative hyperACEemia. This disorder could play a role in pregnancy-induced hypertension. 相似文献