摘要:

During the fall last year the 6th International Congress on Spermatology was held in Siena. This Congress was subtitled: Comparative Spermatology, 20 years after.Pierre Favard and Daniel Sandoz had in fact participated in the first meeting held in Siena 20 years ago, and had disappeared since, Pierre nearly 2 years before, Daniel only a few months before the onset of the Congress.When we, at the Organizing Committee, were preparing the Congress, we had first asked Daniel Sandoz to evoke the memory of his friend and former boss, Pierre Favard. Of course he accepted this task with devotion, but alas, his illness inerrupted his life before he could do it.As they were both close friends to me, I asked for the privilege of commemorating their personalities. As they had been so close to each other — in their scientific life as well as in their editorial action of this Journal — I chose to let them united in the same praising oration.The text that follows has been pronounced in Siena, on August 30, 1

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90071-T

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—In quail oviduct epithelium, as in all metazoan and protozoan ciliated cells, cilia beat in a coordinated cycle. They are arranged in a polarized pattern oriented according to the anteroposterior axis of the oviduct and are most likely responsible for transport of the ovum and egg white proteins from the infundibulum toward the uterus. Orientation of ciliary beating is related to that of the basal bodies, indicated by the location of the lateral basal foot, which points in the direction of the active stroke of ciliary beating. This arrangement of the ciliary cortex occurs as the ultimate step in ciliogenesis and following the oviduct development. Cilia first develop in a random orientation and reorient later, simultaneously with the development of the cortical cytoskeleton. In order to know when the final orientation of basal bodies and cilia is determined in the course of oviduct development, microsurgical reversal of a segment of the immature oviduct was performed. Then, after hormone‐induced development and ciliogenesis, ciliary orientation was examined in the inverted segment and in normal parts of the ciliated epithelium. In the inverted segment, orientation was reversed, as shown by a video recording of the direction of effective flow produced by beating cilia, by the three‐dimensional bending forms of cilia immobilized during the beating cycle and screened by scanning electron microscopy, and by the position of basal body appendages as seen in thin sections by transmission electron microscopy. These results demonstrate that basal body and ciliary orientation are irreversibly determined prior to development by an endogenous signal present early in the cells of the immature oviduct, transmitted to daughter cells during the proliferative phase and expressed at the end of cilioge

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90072-U

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The synchronous cellularization of theDrosophilaembryo at the blastoderm stage provides a unique system for studying the molecular mechanisms involved in cytokinesis, using genetical and biochemical approaches. The cellularization process requires the major components of the embryonic cytoskeleton that are deposited into the egg during oogenesis. Genetical analysis indicates that it requires also the products of additional maternally‐acting genes, as well as that of a limited set of zygotically‐acting genes. The cellularization defective phenotypes associated with small deficiencies uncovering these latter loci reveal specific steps within this complex process. The molecular analysis of these genes will ultimately provide meaningful insights into the normal process of cellularization. Among them, theserendipityα gene encodes a membrane‐associated protein, which is exclusively accumulated during cellularization, and is required for the reorganization of the microfilaments as the onset of cellula

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90073-V

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90074-W

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—This review is concerned with the formation during ciliogenesis of centrioles and basal bodies, primarily in epithelial multiciliated cells from the developing vertebrate respiratory and reproductive tracts. During ciliated cell differentiation, in these as well as in other cell types, cilium formation is preceded by the formation of centrioles assembled from precursor structures having little resemblance to the mature organelle. The origin, composition and function of the centriole precursor structures in generating large numbers of centrioles in a short period of time during ciliogenesis is discussed. This review also focuses on the biochemistry of centrioles and basal bodies and on recent experimental evidence that DNA might be associated with these structure

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90075-X

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—We have isolated and characterized a cDNA which contains the entire coding sequence ofXenopus laevisraf protein. raf mRNA is identified as a member of the class of maternal RNAs. It is already relatively abundant at the beginning of oogenesis and is stable at least until the midblastula transition. The RNA is also detected later during embryogenesis in particular in gastrula, neurula, tailbud and feeding tadpole. We have also found the RNA in several adult tissues (skin, testis, stomach, intestine) at different level

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90076-Y

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Mitotin is a 125 kDa/pI 6.5 nuclear protein specific for proliferating cells and markedly increased prior to and during mitosis. This study presents evidence for the expression of this protein during dimethylsulfoxide (DMSO) induced differentiation of human promyelocytic leukemia HL 60 cells. The expression had been followed at two levels: as antigen, using a specific antimitotin monoclonal antibody and as mRNA, using a specific cDNA probe. The results from the immunofluorescent study show a gradual disappearance of mitotin in differentiating HL 60 cells starting from the fourth day after DMSO induction. On the other hand, the changes in the expression of mitotin mRNA were much more dramatic. This mRNA is expressed at a high level during the first three days of differentiation but shows a striking decrease after the fourth day. This correlates with the rapid changes in the number of blast cells in the differentiating HL 60 cell population. Therefore, the expression of mitotin mRNA can serve as a marker for the changes accompanying the termination of cell proliferation in differentiating cell

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90077-Z

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The heliozoanDimorpha mutanspossesses a complex centrosome, consisting of an axoplast which anchors radiating axopodia crossing the nucleus, two kinetosomes and different associated fibres, including striated roots. During mitosis, which is an open orthomitosis, the axoplast separates into two, then dissociates, and most of the axopodia disappear. The axoplast therefore does not transform directly into asters at the poles of the mitotic spindle, as previously suggested. The spindle poles are made up of diffuse material which appears to be linked with a pair of kinetosomes by a short striated fibre. No differentiated kinetochore was observed. At the end of telophase, some axopodial axonemes appear to be reconstituted by the juxtaposition of microtubules before the axoplast reappears. The channels followed by the axopodial axonemes crossing the nucleus were formed when the nuclear envelope reconstituted around the chromosomes. From these observations, and those on other protists, it is suggested that the centrosome results from the concentration during the cell cycle of a heterogenous group of microtubule organizing centers (MTOCs), of which the centriole might be only one of the type

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90078-2

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—In rabbit oocytes activated parthenogenetically by repetitive electric pulses, centrioles developde novoin blastocysts. Centrioles were not observed in earlier stages of development, not until the blastocoele is formed. Up to the morula stage (between 8–32 cells), a filamentous, electron‐dense material develops and aggregates with a small vesicle fraction within the well developed Golgi apparatus. A spherical to ovoid electron dense mass forms, which is comparable to the deuterosome or to the blepharoplast. The quantity of the electron dense material enlarges and it seems to give rise to the centriole “generating complex”. Centrioles arise in all three differentiated cell types of the blastocysts, the mural and polar trophoblasts and the embryonal cell mass at the same time. Some of the forming centrioles in parthenotes have a co‐linear arrangement, as in control blastocysts. It is not yet known whether the co‐linearly arranged centrioles represent a maturation phase, prior to the formation of the usual diplosome, with centrioles oriented perpendicularly to each other. Nor is it known whether the forming centrioles are functioning as the polar organizer of the mitotic spindle or if they can perform any other centri

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90079-3

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—With specific antibodies directed against non‐actin micrifilaments (NAMFs), it was possible to determine the spatial distribution of these cytoskeletal elements within the cell cortex of the ciliateClimacostomum virensby immunofluorescence. In the somatic areas, the antibodies allowed to vizualize a more or less continuous layer spanning the whole cell surface with a higher amount of filaments just beneath the ciliary rows. In the buccal region the NAMF system forms bundles running parallel to the ciliary clusters termed the membranelles. The same procedure was used on cells treated with 1 M urea, an agent which induces the release of the oral apparatus followed by a complete regeneration of this part of the cell body. Such an approach completed by an electron microscopy study allowed us to describe the dynamic of NAMFs in the region where new ciliary membranelles will organize from a few somatic kinetics. We observed that in this region, the NAMF system undergoes a desorganization‐reorganization cycle during oral apparatus regeneration. This cycle may be related to the destabilisation of the cortex which allows kinetosome proliferation and to its restabilisation which corresponds to the definitive positioning of the new kinetosomes. Consequently, regeneration ofC virens'soral apparatus seems to be a good model for studying relations between cortical NAMF cytoskeleton, positioning of kinetosomes, and cortical stabilis

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90080-7

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY