ISSN:0094-243X    

DOI:10.1063/1.40561

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.40581

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.40590

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The ability of mammalian eggs to support freezing is shown to be related to a reversible reorganization of their cytoskeleton induced by organic compounds used as protectants. 1,2 propanediol which is very effective for the successful freezing of early embryonic stages induces the formation of a fairly homogeneous gel within the cytoplasm in which the cortical layer of highly entangled polymers is no longer apparent. In vitro, propanediol influences specifically interactions between actin and binding proteins and induces the formation of microporous and homogeneous gels able to retain a significant fraction of water within their pores. When eggs are first submitted to a partial dehydration at room temperature they become able to support rapid freezing and thawing in the presence of propanediol probably because the remaining cellular water becomes osmotically inactive. This indicates that the rheological changes of the cytoplasm that occur in the presence of propanediol make the cell able to support the physical and chemical modifications that affect their microenvironment at low temperature.

ISSN:0094-243X    

DOI:10.1063/1.40606

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Solution X‐ray scattering and osmotic pressure measurements were used to study protein interactions in concentrated solutions of either single species or mixtures of &agr;‐, &bgr;‐ and &ggr;‐crystallins from the eye lens. Different types of interactions were demonstrated in physiological conditions. &agr;‐ and &bgr;‐crystallins present repulsive interactions, well described by a repulsive coulombic electrostatic potential. The interactions between &ggr;‐crystallins are attractive. The overall repulsive interactions within the lens and account for its transparency. The interplay of repulsive and attractive interactions might account for the maintainance of a protein concentration gradient from the center to the periphery of the lens which improves the lens optical quality.

ISSN:0094-243X    

DOI:10.1063/1.40575

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Different techniques were applied to study the cytoskeleton of trophectoderm and endoderm cells of the procine blastocyst. Whole mount preparations labeled with double fluorescence for f‐actin and fibronectin and observed under a light microscope showed that f‐actin has a polarized distribution particularly evident in trophectoderm cells and that f‐actin and fibronectin are colocalized along the baso‐lateral border of trophectoderm cells. Such colocalization was not visible in endoderm cells. Microtubules stained with monoclonal antibodies to tubilin a were observed with a confocal microscope in order to reconstruct their distribution in 3‐D. Specific polarities in microtubule meshworks were observed in both cell types. Using monoclonal antibodies against cytokeratins 8 and 18 to stain intermediate filaments, we confirmed the epithelial nature of both cell layes. Stereological pictures showed that labeling with gold granules does indeed follow the individual filaments in the bundles. Although both these first two cell layers are epithelial and polarized, they differ since one belongs to the sedentary type and the other to the migratory type.

ISSN:0094-243X    

DOI:10.1063/1.40577

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have analysed the complex movements of vitally stained mitochondria in living eggs of the ascidian (prochordate) embryo soon after fertilization by time lapse confocal (Laser scanning) Microscopy. Our studies clearly show that it is possible to understand how the subcortical mitochondria rich layer contracts, tears and folds to reach its final location in the future posterior pole of the embryo that gives rise to the muscle cell lineage.

ISSN:0094-243X    

DOI:10.1063/1.40578

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have found conditions allowing direct observation of nuclei in live one‐cell mouse embryos by video enhanced fluorescence microscopy without perturbation of their development. We use the vital dye Hoechst 33342 and a high sensitivity video camera coupled to a digital image processor for registration and treatment. we can decrease by a factor 50 to 100 the dye concentration generally used and by a factor 1000 the irradiation level. Under these conditions, we have studied the structural changes of paternal chromatin just after fertilization and the progression of pronuclei during the first cell cycle with a special emphasis on the chromatin recondensation before syngamy.

ISSN:0094-243X    

DOI:10.1063/1.40579

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In order to explore the molecular nature and the regulation of dense cytomatrix which interconnects MT, NF and membranous organelles in neurons (9), the interactions between NF, MT and each of these cytoskelatal elements with brain mitochondria were investigated in vitro using biochemical and viophysical methods. From these studies, the following conclusions were drawn: 1‐ Pure NF form in vitro a highly viscous gel, dependent upon the phosphorylation state of the side arms of the NF‐H and M subunits which might participate directly to the interactions since antibodies specific of these phosphorylated sites inhibited efficiently the NF gelation. This process is modulated by both ATP hydrolysis and soluble molecules from nervous tissue and it might reflect the highly controled organization of NF bundles in axons. 2‐ In contrast with NF, low viscosity levels were detected in MT suspensions. However, the occurrence of weak interactions between MT were deduced from studies with taxol, ATP, AMP‐PNP and Mg ions, which affected the viscosity and the organization of MT in vitro, possibly through MAPs mediated interactions. 3‐ Mitochondria associated permanently in vitro to few MT through cross‐bridges involving MAPs, which bind to specific sites on the outer membrane (17). In addition, brain mitochondria (and not liver mitochondria) interact with NF in an ATP‐dependent manner, through thin cross‐bridges possibly involving the NF‐H and M subunits since these molecules, when purified, compete efficiently with MAPs for the binding to membrane sites. These results suggest the participation of structure MAPs and of NF‐H and M subunits in the spatial organization MT and NF and in anchoring mitochondria to the cytomatrix.

ISSN:0094-243X    

DOI:10.1063/1.40580

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.40591

出版商:AIP    

年代:1991

数据来源: AIP