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排序方式: 共有250条查询结果,搜索用时 31 毫秒
1.
Résumé Une méthode d'extraction physico-chimique des lipides a été appliquée à des blastospores entières de C. albicans, préalablement à leur étude en microscopie électronique à transmission. Les résultats permettent de supposer une localisation très superficielle des lipides liés à d'autres composants, en particulier peptidopolysaccharidiques, ce qui est en accord avec les données de la littérature. La méthode à également permis l'observation de structures microfibrillaires pariétales. Il s'agit surtout, d'une part, de fibrilles d'environ 50 Å de diamètre, situées dans les couches moyennes, également observables, après mise en oeuvre d'une technique d'extraction de polysaccharides sur cellules entières, et qui ont été assimilées à des fibrilles de ß 1–3 glucanes; d'autre part de fibrilles de 120 À de diamètre, situées au centre du septum de la cicatrice de bourgeonnement et qui ont été assimilées à des fibrilles de chitine.
A chemical method for lipid extraction has been applied to Candida albicans blastospores previously to their examination by transmission electron microscopy. The results led to the concept of a superficial location of lipids bounded to the peptidopolysaccharidic matrix of the cell wall. This lipid extraction also allowed us to describe cell wall microfibrillar structures. Two types of microfibrills have been particularly identified: (1) microfibrils of approximately 50 Å in diameter, involved in a network of the cell wall intermediate layers and supposed to correspond to ß 1–3 glucans; (2) fibrillar structures of 120 Å in diameter, similar to chitin microfibrils, observed in the bud scar septum.相似文献
2.
V Mitchell J C Beauvillain P Poulain M Mazzuca 《The journal of histochemistry and cytochemistry》1988,36(5):533-542
To study the relationship between the catecholamine (CA) nerve endings and the enkephalinergic cell bodies in the magnocellular dorsal nucleus (MDN) of guinea pig hypothalamus, double-labeling experiments were performed on the same tissue section at the electron microscopic level. An in vitro autoradiographic (ARG) method for [3H]-norepinephrine (NE) or [3H]-dopamine (DA) was combined with a post-embedding immunogold cytochemical technique for Met-enkephalin (Met-enk) in colchicine-treated animals. Hypothalamic slices (450 micrograms) were perfused with [3H]-NE or [3H]-DA at the fluid-gas interface, then fixed by immersion with glutaraldehyde and osmic acid. Semi-thin sections processed from the thickness of the slices showed adequate penetration of the tracers to all parts of the tissue. Frontal sections permitted visualization of some CA-uptake structures distributed around the cells. At the ultrastructural level, preservation appeared good on about 60% of the thickness of slices, and [3H]-CA structures were easily distinguished. Ultra-thin sections were successively incubated with Met-enk and colloidal gold-labeled antisera, followed by ARG processing. At the electron microscopic level, the good integrity of the tissue made possible visualization of [3H]-CA nerve terminals making synaptic contacts with enkephalinergic perikarya. These results provide morphological evidence for direct catecholaminergic control of enkephalinergic neurons of the MDN. 相似文献
3.
Lung overexpansion increases pulmonary microvascular protein permeability in young lambs 总被引:3,自引:0,他引:3
D P Carlton J J Cummings R G Scheerer F R Poulain R D Bland 《Journal of applied physiology》1990,69(2):577-583
To study the effects of inflation pressure and tidal volume (VT) on protein permeability in the neonatal pulmonary microcirculation, we measured lung vascular pressures, blood flow, lymph flow (QL), and concentrations of protein in lymph (L) and plasma (P) of 22 chronically catheterized lambs that received mechanical ventilation at various peak inflation pressures (PIP) and VT. Nine lambs were ventilated initially with a PIP of 19 +/- 1 cmH2O and a VT of 10 +/- 1 ml/kg for 2-4 h (base line), after which we overexpanded their lungs with a PIP of 58 +/- 3 cmH2O and a VT of 48 +/- 4 ml/kg for 4-8 h. QL increased from 2.1 +/- 0.4 to 13.9 +/- 5.0 ml/h. L/P did not change, but the ratio of albumin to globulin in lymph relative to the same ratio in plasma decreased, indicating altered protein sieving in the pulmonary microcirculation. Seven other lambs were mechanically ventilated for 2-4 h at a PIP of 34 +/- 1 cmH2O and a VT of 23 +/- 2 ml/kg (base line), after which their chest and abdomen were bound so that PIP increased to 54 +/- 1 cmH2O for 4-6 h without a change in VT. QL decreased on average from 2.8 +/- 0.6 to 1.9 +/- 0.3 ml/h (P = 0.08), and L/P was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
Efferent projections of the lateral septal nucleus (LS) to the preoptic area and the hypothalamus were identified in 20 female guinea pigs after iontophoretic injection of the anterograde axonal tracer Fluoro-Ruby. Tubero-infundibular (TI) neurons of the preoptic area and the hypothalamus were retrogradely labeled after intracardiac injection of Granular Blue or Fluoro-Gold. Magnocellular neurons of the supraoptic and paraventricular nuclei were also labeled. The double labeling procedure allowed an estimation of the extent of the direct relationship between LS efferents and TI neurons. Contacts between lateral septal fibers and TI cell bodies were mainly observed at the light-microscopical level in the preoptic area. A group of labeled fibers coursing along the third ventricle established sparse connections with hypothalamic periventricular TI neurons. A few appositions was observed in the infundibular (arcuate) nucleus, suggestive of a monosynaptic regulation of TI neurons by a septo-arcuate tract. Close association with labeled magnocellular neurons was also noted at the edge of the supraoptic and paraventricular nuclei. The sparse but direct connections between LS and TI neurons may be involved in the neuroendocrine functions of the LS. 相似文献
5.
Hypoproteinemia slows lung liquid clearance in young lambs 总被引:1,自引:0,他引:1
Cummings J. J.; Carlton D. P.; Poulain F. R.; Raj J. U.; Bland R. D. 《Journal of applied physiology》1993,74(1):153-160
6.
C Faille J M Wieruszeski G Lepage J C Michalski D Poulain G Strecker 《Biochemical and biophysical research communications》1991,181(3):1251-1258
Manno-oligosaccharides (DP 2 to greater than 15) were released by mild acid hydrolysis from the phosphopeptidomannan of a Candida albicans strain of A serotype (VW-32). Manno-oligosaccharides ranging from biose to heptaose were obtained in appreciable amount. Structural investigation of these oligosaccharides showed them to be of the beta-1,2-linked series. The occurrence of such compounds has already been reported in other strains of Candida albicans. We here report the assignment of the structural reporter groups of each of them, and general rules applicable for the 1H-NMR spectrum analysis of linear manno-oligosaccharide of general structure: Man(beta 1-2) [Man(beta 1-2)]nMan 相似文献
7.
The ultrastructure of T. mentagrophytes hyphal walls was studied after the use of a cytochemical reaction for polysaccharides. The sections showed a wall composed of 3 layers viz: an external, poorly reactive one with a microfibrillary structure; a medium, fairly reactive one, with a periodic structure and an internal, intensivly stained layer, not observed in old cells. Other observations suggested that the septal medium layer should be differentiated from those cited above. The results are compared with previous data and a synthetic scheme of the Trichophyton mentagrophytes hyphal wall is proposed. 相似文献
8.
Julie Jaquiéry Claude Rispe Denis Roze Fabrice Legeai Ga?l Le Trionnaire Solenn Stoeckel Lucie Mieuzet Corinne Da Silva Julie Poulain Nathalie Prunier-Leterme Béatrice Ségurens Denis Tagu Jean-Christophe Simon 《PLoS genetics》2013,9(8)
Evolutionary theory predicts that sexually antagonistic mutations accumulate differentially on the X chromosome and autosomes in species with an XY sex-determination system, with effects (masculinization or feminization of the X) depending on the dominance of mutations. Organisms with alternative modes of inheritance of sex chromosomes offer interesting opportunities for studying sexual conflicts and their resolution, because expectations for the preferred genomic location of sexually antagonistic alleles may differ from standard systems. Aphids display an XX/X0 system and combine an unusual inheritance of the X chromosome with the alternation of sexual and asexual reproduction. In this study, we first investigated theoretically the accumulation of sexually antagonistic mutations on the aphid X chromosome. Our results show that i) the X is always more favourable to the spread of male-beneficial alleles than autosomes, and should thus be enriched in sexually antagonistic alleles beneficial for males, ii) sexually antagonistic mutations beneficial for asexual females accumulate preferentially on autosomes, iii) in contrast to predictions for standard systems, these qualitative results are not affected by the dominance of mutations. Under the assumption that sex-biased gene expression evolves to solve conflicts raised by the spread of sexually antagonistic alleles, one expects that male-biased genes should be enriched on the X while asexual female-biased genes should be enriched on autosomes. Using gene expression data (RNA-Seq) in males, sexual females and asexual females of the pea aphid, we confirm these theoretical predictions. Although other mechanisms than the resolution of sexual antagonism may lead to sex-biased gene expression, we argue that they could hardly explain the observed difference between X and autosomes. On top of reporting a strong masculinization of the aphid X chromosome, our study highlights the relevance of organisms displaying an alternative mode of sex chromosome inheritance to understanding the forces shaping chromosome evolution. 相似文献
9.
10.
OLIVIER PIERRE GILBERT ENGLER JULIE HOPKINS FRÉDÉRIC BRAU ERIC BONCOMPAGNI DIDIER HÉROUART 《Plant, cell & environment》2013,36(11):2059-2070
Legumes form a symbiotic interaction with Rhizobiaceae bacteria, which differentiate into nitrogen‐fixing bacteroids within nodules. Here, we investigated in vivo the pH of the peribacteroid space (PBS) surrounding the bacteroid and pH variation throughout symbiosis. In vivo confocal microscopy investigations, using acidotropic probes, demonstrated the acidic state of the PBS. In planta analysis of nodule senescence induced by distinct biological processes drastically increased PBS pH in the N2‐fixing zone (zone III). Therefore, the PBS acidification observed in mature bacteroids can be considered as a marker of bacteroid N2 fixation. Using a pH‐sensitive ratiometric probe, PBS pH was measured in vivo during the whole symbiotic process. We showed a progressive acidification of the PBS from the bacteroid release up to the onset of N2 fixation. Genetic and pharmacological approaches were conducted and led to disruption of the PBS acidification. Altogether, our findings shed light on the role of PBS pH of mature bacteroids in nodule functioning, providing new tools to monitor in vivo bacteroid physiology. 相似文献