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La migration cellulaire est une étape clé intervenant à un stade précoce de la dissémination des cellules cancéreuses dans l’organisme, et est donc responsable de la formation des métastases qui tuent environ nonante pourcent des patients atteints de cancer. De plus, ces cellules migrantes résistent à l’apoptose grâce à l’activation constitutive de voies de signalisation anti-apoptotiques, et développent donc une résistance vis-à-vis des traitements anti-cancéreux actuels qui sont généralement pro-apoptotiques. Nous avons pris pour cible ce processus de migration cellulaire dans l’espoir d’identifier des agents anti-migratoires qui permettraient de lutter contre la formation des métastases et de restaurer chez les cellules migrantes une certaine sensibilité aux traitements pro-apoptotiques.Dans la première partie de notre travail, nous avons analysé les effets anti-angiogéniques et anti-migratoires des agents anti-tubuline. Nous avons confirmé que le Taxol® présentait une action anti-angiogénique à des concentrations non-cytotoxiques. Nous avons ensuite démontré que d’autres agents anti-tubuline exerçaient la même action que le Taxol®, et que cette action leur était spécifique. Nous avons montré que certains de ces agents étaient également capables de réduire la migration de lignées cellulaires tumorales, toujours à des concentrations non-cytotoxiques, et que cette action pouvait s’exercer via une affectation du cytosquelette d’actine.Dans la deuxième partie du présent travail, nous avons démontré l’importance de la mise au point d’une approche pharmacologique originale permettant l’identification de composés à action anti-migratoire puisque l’outil utilisé par le U.S. National Cancer Institute pour le criblage de nouvelles molécules anti-cancéreuses ne permet pas de discerner l’activité anti-migratoire des molécules testées.Enfin dans la troisième partie de ce travail, après avoir souligné la raison du choix de l’actine comme cible pour inhiber la migratio, Doctorat en sciences pharmaceutiques, info:eu-repo/semantics/nonPublished

We previously showed that Trypanosoma cruzi acute infection induced infertility in a great proportion of female mice, which resulted from a defect taking place before implantation. In this study, we have analyzed every step of reproduction from mating to implantation to identify the most sensitive event. Our results show that mating, ovulation, fertilization, and first division of the zygote of infected mice take place normally compared with uninfected mice, indicating that the defect occurred after the two-cell stage. In vivo development of two-cell embryos to the blastocyst stage was indeed dramatically delayed; some embryos even arrested their development before having reached the eight-cell stage while others degenerated. The effect was less pronounced when embryos were allowed to develop in vitro, indicating that the infectious context of the mother plays a role in maintaining growth retardation. The delay of embryonic development was associated with insufficient divisions of the blastomeres and led to abnormal blastocyst outgrowth that may explain implantation failure. Inhibition of cell division was correlated with the maternal parasitemia. This work clearly shows that T. cruzi infection dramatically impedes embryonic development, offering a model for further in vivo studies of embryotrophic factors produced by the oviduct of infected females., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

La migration cellulaire est une étape clé intervenant à un stade précoce de la dissémination des cellules cancéreuses dans l’organisme, et est donc responsable de la formation des métastases qui tuent environ nonante pourcent des patients atteints de cancer. De plus, ces cellules migrantes résistent à l’apoptose grâce à l’activation constitutive de voies de signalisation anti-apoptotiques, et développent donc une résistance vis-à-vis des traitements anti-cancéreux actuels qui sont généralement pro-apoptotiques. Nous avons pris pour cible ce processus de migration cellulaire dans l’espoir d’identifier des agents anti-migratoires qui permettraient de lutter contre la formation des métastases et de restaurer chez les cellules migrantes une certaine sensibilité aux traitements pro-apoptotiques.Dans la première partie de notre travail, nous avons analysé les effets anti-angiogéniques et anti-migratoires des agents anti-tubuline. Nous avons confirmé que le Taxol® présentait une action anti-angiogénique à des concentrations non-cytotoxiques. Nous avons ensuite démontré que d’autres agents anti-tubuline exerçaient la même action que le Taxol®, et que cette action leur était spécifique. Nous avons montré que certains de ces agents étaient également capables de réduire la migration de lignées cellulaires tumorales, toujours à des concentrations non-cytotoxiques, et que cette action pouvait s’exercer via une affectation du cytosquelette d’actine.Dans la deuxième partie du présent travail, nous avons démontré l’importance de la mise au point d’une approche pharmacologique originale permettant l’identification de composés à action anti-migratoire puisque l’outil utilisé par le U.S. National Cancer Institute pour le criblage de nouvelles molécules anti-cancéreuses ne permet pas de discerner l’activité anti-migratoire des molécules testées.Enfin dans la troisième partie de ce travail, après avoir souligné la raison du choix de l’actine comme cible pour inhiber la migratio, Doctorat en sciences pharmaceutiques, info:eu-repo/semantics/nonPublished

We previously showed that Trypanosoma cruzi acute infection induced infertility in a great proportion of female mice, which resulted from a defect taking place before implantation. In this study, we have analyzed every step of reproduction from mating to implantation to identify the most sensitive event. Our results show that mating, ovulation, fertilization, and first division of the zygote of infected mice take place normally compared with uninfected mice, indicating that the defect occurred after the two-cell stage. In vivo development of two-cell embryos to the blastocyst stage was indeed dramatically delayed; some embryos even arrested their development before having reached the eight-cell stage while others degenerated. The effect was less pronounced when embryos were allowed to develop in vitro, indicating that the infectious context of the mother plays a role in maintaining growth retardation. The delay of embryonic development was associated with insufficient divisions of the blastomeres and led to abnormal blastocyst outgrowth that may explain implantation failure. Inhibition of cell division was correlated with the maternal parasitemia. This work clearly shows that T. cruzi infection dramatically impedes embryonic development, offering a model for further in vivo studies of embryotrophic factors produced by the oviduct of infected females., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

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A pulse of thimerosal (TMS), a sulfhydryl reagent, induces an instantaneous, complete and long-lasting microtubule interphasic network disassembly in mouse primary oocytes, correlated with the irreversible inhibition of meiosis reinitiation This inhibition is bypassed by dithiothreitol (DTT) while thiosalicylic acid, an analog of TMS, does induce neither microtubules depolymerisation nor inhibition of reinitiation and resumption of meiosis. This strongly suggests that the dramatic and pleiotropic inhibitory effect of TMS is specifically related to its sulfhydryl group oxidising activity of critical molecules among which tubulin. In contrast to DTT, okadaic acid (OA), known to bypass the inhibitory effect of drugs interfering with protein kinase activities, induces a late chromatin condensation and GVBD in TMS-pulsed oocytes as compared to the control situation, with no significant concomitant microtubule assembly. These cytological features are suggested to be indirectly induced by a late MAPK activation and confirm that a very early thiol oxidation induced by TMS exerts a much more dramatic effect on resumption of meiosis than any pharmacological manipulation of protein kinase activities leading to activation of MPF. Finally, taxol was shown to promote tubulin polymerisation even when microtubules were irreversibly disassembled by thiol oxidation but fails to restore the ability to undergo maturation., FLWIN, info:eu-repo/semantics/published

The effect of the sulfhydryl reagent, thimerosal (TMS) on meiosis resumption in germinal vesicle (GV)-stage denuded mouse oocytes was studied. It irreversibly inhibits both GV breakdown (GVBD) and the first polar body (pb1) extrusion in concentration- and time-dependent manners, the most striking result being the very early and narrow temporal window during which denuded primary oocytes released from their follicle are susceptible to a pulse of the drug. This inhibition is bypassed by dithiothreitol (DTT) with an efficiency declining with time, while thiosalicylic acid (TA), an analog of TMS devoid of the mercury atom, has no effect on meiosis reinitiation. These results strongly suggest that the inhibitory effect of TMS is a consequence of its sulfhydryl group oxidising activity. The molecular target(s) of this inhibitory oxidation should however be identified. In contrast to DTT, okadaic acid (OA), known to bypass the inhibitory effect of drugs interfering with protein kinase activities, only induces chromatin condensation and GVBD in TMS-pulsed oocytes with a delay of about 8 hr as compared to the control situation. This confirms that a very early thiol oxidation induced by TMS exerts a much more dramatic effect on resumption on meiosis than any pharmacological manipulation of protein kinase activities leading to activation of MPF., FLWIN, info:eu-repo/semantics/published

The alpha-fetoprotein gene (Afp) is a member of a multigenic family that comprises the related genes encoding albumin, alpha-albumin, and vitamin D binding protein. The biological role of this major embryonic serum protein is unknown although numerous speculations have been made. We have used gene targeting to show that AFP is not required for embryonic development. AFP null embryos develop normally, and individually transplanted homozygous embryos can develop in an AFP-deficient microenvironment. Whereas mutant homozygous adult males are viable and fertile, AFP null females are infertile. Our analyses of these mice indicate that the defect is caused by a dysfunction of the hypothalamic/pituitary system, leading to anovulation., info:eu-repo/semantics/published

The alpha-fetoprotein gene (Afp) is a member of a multigenic family that comprises the related genes encoding albumin, alpha-albumin, and vitamin D binding protein. The biological role of this major embryonic serum protein is unknown although numerous speculations have been made. We have used gene targeting to show that AFP is not required for embryonic development. AFP null embryos develop normally, and individually transplanted homozygous embryos can develop in an AFP-deficient microenvironment. Whereas mutant homozygous adult males are viable and fertile, AFP null females are infertile. Our analyses of these mice indicate that the defect is caused by a dysfunction of the hypothalamic/pituitary system, leading to anovulation., info:eu-repo/semantics/published

Bcl-2 mRNA expression was detected in rat blastocysts by in situ hybridization. The distribution of mRNA expression was rather heterogenous, with approximately 2% of high-expressing cells. In vitro exposure to 28 mmol/l D-glucose for 24 h resulted in a significant increase in the proportion of these cells compared with control embryos in either 6 mmol/l D-glucose or 28 mmol/l D+L-glucose. Heterogeneity in the expression of Bcl-2 was also observed at the protein level by immunocytochemistry. Exposure to 28 mmol/l D-glucose significantly increased the incidence of chromatin degradation (karyolysis) and nuclear fragmentation (karyorhexis), two nuclear markers of apoptosis in rat blastocysts. When two different antisense oligodeoxynucleotides designed to block Bcl-2 expression were added to 28 mmol/1 D-glucose, the incidence of karyolysis (but not karyorhexis) was increased compared with embryos in 28 mmol/l D-glucose alone. These data suggest that Bcl-2 is involved in the protective response against the induction of karyolysis in blastocysts on their exposure to high concentrations of D-glucose in vitro, whereas karyorhexis appears to result from the activation of an intracellular pathway that is independent of Bcl-2.

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Editorial, info:eu-repo/semantics/published

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TBBC (for Trypanosoma brucei basal body component) is a unique gene transcribed in a 4.8 kb mRNA encoding a 1,410 amino acid protein that consists almost entirely of a coiled coil structure. This protein appeared to localize in the basal body, with an accessory presence at the posterior end of the cell, the nucleus and over the flagellum. Since the two other known components of the trypanosome basal body are (gamma)-tubulin and an uncharacterized component termed BBA4 we performed double immunofluorescence experiments with anti-TBBC and either anti-BBA4 or anti-(gamma)-tubulin antibodies. These three components did not colocalize but were very closely associated, BBA4 being the most proximal to the kinetoplast DNA. Anti-TBBC antibodies detected a 170 kDa protein in western blots of total HeLa cell extracts. Moreover, these antibodies stained the centriole of HeLa and COS cells as well as the centriole of mouse spermatozoa, indicating that a TBBC-like centriolar component has been conserved during the evolution of eukaryotes., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

TBBC (for Trypanosoma brucei basal body component) is a unique gene transcribed in a 4.8 kb mRNA encoding a 1,410 amino acid protein that consists almost entirely of a coiled coil structure. This protein appeared to localize in the basal body, with an accessory presence at the posterior end of the cell, the nucleus and over the flagellum. Since the two other known components of the trypanosome basal body are (gamma)-tubulin and an uncharacterized component termed BBA4 we performed double immunofluorescence experiments with anti-TBBC and either anti-BBA4 or anti-(gamma)-tubulin antibodies. These three components did not colocalize but were very closely associated, BBA4 being the most proximal to the kinetoplast DNA. Anti-TBBC antibodies detected a 170 kDa protein in western blots of total HeLa cell extracts. Moreover, these antibodies stained the centriole of HeLa and COS cells as well as the centriole of mouse spermatozoa, indicating that a TBBC-like centriolar component has been conserved during the evolution of eukaryotes., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

Sea stars are able to make firm but temporary attachments to various substrata owing to secretions released by their podia. A duo-glandular model has been proposed in which an adhesive material is released by two types of non-ciliated secretory (NCS1 and NCS2) cells and a de-adhesive material is released by ciliated secretory (CS) cells. The chemical composition of these materials and the way in which they function have been investigated by studying the adhesive footprints left by the asteroids each time they adhere to a substratum. The footprints of Asterias rubens consist of a sponge-like material deposited as a thin layer on the substratum. Inorganic residues apart, this material is made up mainly of proteins and carbohydrates. The protein moiety contains significant amounts of both charged (especially acidic) and uncharged polar residues as well as half-cystine. The carbohydrate moiety is also acidic, comprising both uronic acids and sulphate groups. Polyclonal antibodies have been raised against footprint material and were used to locate the origin of footprint constituents in the podia. Extensive immunoreactivity was detected in the secretory granules of both NCS1 and NCS2 cells, suggesting that their secretions together make up the bulk of the adhesive material. No immunoreactivity was detected in the secretory granules of CS cells, and the only other structure strongly labelled was the outermost layer of the cuticle, the fuzzy coat. This pattern of immunoreactivity suggests that the secretions of CS cells are not incorporated into the footprints, but instead might function to jettison the fuzzy coat, thereby allowing the podium to detach., JOURNAL ARTICLE, info:eu-repo/semantics/published

Sea stars are able to make firm but temporary attachments to various substrata owing to secretions released by their podia. A duo-glandular model has been proposed in which an adhesive material is released by two types of non-ciliated secretory (NCS1 and NCS2) cells and a de-adhesive material is released by ciliated secretory (CS) cells. The chemical composition of these materials and the way in which they function have been investigated by studying the adhesive footprints left by the asteroids each time they adhere to a substratum. The footprints of Asterias rubens consist of a sponge-like material deposited as a thin layer on the substratum. Inorganic residues apart, this material is made up mainly of proteins and carbohydrates. The protein moiety contains significant amounts of both charged (especially acidic) and uncharged polar residues as well as half-cystine. The carbohydrate moiety is also acidic, comprising both uronic acids and sulphate groups. Polyclonal antibodies have been raised against footprint material and were used to locate the origin of footprint constituents in the podia. Extensive immunoreactivity was detected in the secretory granules of both NCS1 and NCS2 cells, suggesting that their secretions together make up the bulk of the adhesive material. No immunoreactivity was detected in the secretory granules of CS cells, and the only other structure strongly labelled was the outermost layer of the cuticle, the fuzzy coat. This pattern of immunoreactivity suggests that the secretions of CS cells are not incorporated into the footprints, but instead might function to jettison the fuzzy coat, thereby allowing the podium to detach., JOURNAL ARTICLE, info:eu-repo/semantics/published

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Discours de Henri Alexandre Professeur ordinaire à la Faculté de médecine, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

Taxol, a drug which promotes microtubule assembly, was used to assess the microtubule nucleating activity of pericentriolar material (PCM) in mouse oocytes prevented from undergoing germinal vesicle breakdown (GVBD), compared with oocytes allowed to proceed normally through GVBD and alsoin nucleate and anucleate oocyte fragments. Both immunofluorescence staining and ultrastructural analysis reveal that taxol induces aster formation in the cortex of oocytes undergoing GVBD, while formation of a continuous sheet of microtubule bundles parallel to the membrane is induced in metabolically GV-arrested oocytes. Since taxol also induces the formation of asters in anucleate as well as in nucleate oocyte fragments, provided they are not treated with activators of protein kinases A or C, it is concluded that microtubule nucleating activity is related to the acquisition of Maturation Promoting Factor (MPF) and does not require mixing between the nucleoplasm and cytoplasm., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

Taxol, a drug which promotes microtubule assembly, was used to assess the microtubule nucleating activity of pericentriolar material (PCM) in mouse oocytes prevented from undergoing germinal vesicle breakdown (GVBD), compared with oocytes allowed to proceed normally through GVBD and alsoin nucleate and anucleate oocyte fragments. Both immunofluorescence staining and ultrastructural analysis reveal that taxol induces aster formation in the cortex of oocytes undergoing GVBD, while formation of a continuous sheet of microtubule bundles parallel to the membrane is induced in metabolically GV-arrested oocytes. Since taxol also induces the formation of asters in anucleate as well as in nucleate oocyte fragments, provided they are not treated with activators of protein kinases A or C, it is concluded that microtubule nucleating activity is related to the acquisition of Maturation Promoting Factor (MPF) and does not require mixing between the nucleoplasm and cytoplasm., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

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Mouse morulae are known to undergo cavitation as soon as some external cells have entered the sixth cell cycle (Garbutt et al. 1987). Since the early cytological features of cavitation are still unclear, we undertook a careful ultrastructural analysis of late morulae-nascent blastocysts. In addition, since maturation of lysosomes might be involved in the first step of cavity formation, we focused our attention on these organelles by means of the cytochemical localization of trimetaphosphatase activity and by the study of the effects of chloroquine on precavitation embryos. Our results suggest that cavitation starts in a few external cells (presumably competent cells entering the sixth cell cycle), by the chloroquine-sensitive formation of degradative autophagic vacuoles engulfing lipid droplets and vacuoles containing osmiophilic material. These complex structures enlarge (as a result of lipid metabolism?) and so transform into intrablastomeric cavities which, by means of a membrane fusion process, very rapidly become extracellular cavities that coalesce. The abembryonic pole of the blastocyst is determined in this way. Moreover, we suggest that the juxtacoelic cytoplasmic processes covering the inner cell mass (ICM) cells, which are known to restrict the expression of their totipotency during early cavitation (Fleming et al. 1984), are the latest remnants of the walls of the growing intrablastomeric cavities., SCOPUS: ar.j, info:eu-repo/semantics/published

Mouse morulae are known to undergo cavitation as soon as some external cells have entered the sixth cell cycle (Garbutt et al. 1987). Since the early cytological features of cavitation are still unclear, we undertook a careful ultrastructural analysis of late morulae-nascent blastocysts. In addition, since maturation of lysosomes might be involved in the first step of cavity formation, we focused our attention on these organelles by means of the cytochemical localization of trimetaphosphatase activity and by the study of the effects of chloroquine on precavitation embryos. Our results suggest that cavitation starts in a few external cells (presumably competent cells entering the sixth cell cycle), by the chloroquine-sensitive formation of degradative autophagic vacuoles engulfing lipid droplets and vacuoles containing osmiophilic material. These complex structures enlarge (as a result of lipid metabolism?) and so transform into intrablastomeric cavities which, by means of a membrane fusion process, very rapidly become extracellular cavities that coalesce. The abembryonic pole of the blastocyst is determined in this way. Moreover, we suggest that the juxtacoelic cytoplasmic processes covering the inner cell mass (ICM) cells, which are known to restrict the expression of their totipotency during early cavitation (Fleming et al. 1984), are the latest remnants of the walls of the growing intrablastomeric cavities., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

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Full‐grown blastocysts were cultured for 707–92 h in Dulbecco's modified Eagle's medium supplemented with fetal calf serum. They were treated with (1) aphidicolin, a specific inhibitor of eucaryotic DNA polymerase α, (2) dideoxythymidine (d2Thd), the precursor of dideoxythymidine triphosphate (d2TTP), a specific inhibitor of DNA polymerase β and (3) d2TTP itself. Cytophotometric measurements of both the DNA content and the nuclear areas were performed. The results show firstly that trophectoderm differentiation into primary giant trophoblast cells is already irreversibly programmed at the blastocyst stage and does not depend on any DNA replication cycle from that stage onwards. Secondly, the typical enlargement of the trophoblastic nuclei, which occurs at the peri‐implantation period, is not related to a proportional increase in DNA content. Thirdly, the onset and progress of DNA endoreduplication in trophoblastic cells is carried out by DNA polymerase α during the first part of gestation instead of DNA polymerase β, as has previously been shown to be the case for mid‐gestation rat trophoblast cells. Copyright © 1985, Wiley Blackwell. All rights reserved, SCOPUS: ar.j, info:eu-repo/semantics/published

The inhibition of spermidine and spermine synthesis by methylglyoxal-Bis(guanylhydrazone) (MeGAG) at concentrations of 5, 10 and 20 μM, induces a reversible metabolic quiescience of mouse embryos, cultured in vitro from the 2-cell stage, at an average of 10.2, 8.5 and 6.9 cell stages respectively. In contrast, the inhibition of putrescine synthesis by α-methylornithine (α-MeOrn) at concentrations up to 10 mM fails to inhibit blastocyst formation, as shown previously. Complete reversibility of this induced arrest of development is observed for treatments up to 31 h with MeGAG at 10 μM. In agreement with the biological clock theory of Smith & MacLaren's hypothesis, the delay in cavitation is proportional to the length of treatment. However, the average cell numbers of the 'delayed nascent blastocysts' of all treated embryos (21.8-24.2) are consistently lower than that of control embryos (33.6) irrespective of the duration of treatment. It seems therefore that under some experimental conditions, DNA and chromosome replication on the one hand and cytoplasmic maturation on the other may be desynchronized. This suggests a role for a cytoplasmic factor in the induction of cavitation., SCOPUS: NotDefined.j, info:eu-repo/semantics/published

Methylglyoxal-bis (guanylhydrazone) (MG BG) is a potent inhibitor of S-adenosyl-L-methionine decarboxylase, an enzyme involved in the synthesis of the polyamines spermidine and spermine. Its effects on the fine structure of early mouse embryos developing in vitro have been studied. Cleavage is blocked at about the 8-cell stage after culture of the embryos in the presence of 10μM MG BG from the 2-cell stage onwards. The development of the quiescent embryos resumes after transfer into normal medium, but their cavitation is delayed. Moreover, these embryos have about 10 cells less than control embryos at the beginning of cavitation (Alexandre, 1979). The changes, concerning more particularly the lysosomal system, which occur in parallel in control, in embryos treated continuously with MG BG and in embryos transferred to normal medium after about 20 hr of treatment with MG BG, favour the hypothesis of a cytoplasmic 'maturation' proceeding in the absence of nuclear division in quiescent embryos. Embryos treated for 40 hr or more with MG BG show altered nucleoli, less advanced in ultrastructure, often with a reduced granular constituent, probably as the result of an impairment in RNA synthesis and maturation. The changes in the morphology of the mitochondria which occur during normal embryogenesis are not observed in MG BG-treated embryos; the metabolism of these organelles is probably affected by long treatments with the drug., SCOPUS: NotDefined.j, FLWNO, info:eu-repo/semantics/published

Journal Article, SCOPUS: NotDefined.j, info:eu-repo/semantics/published

Aphidicolin, a powerful inhibitor of nuclear DNA replication, has been used to establish the level of polyploidisation required for the realization of the late morphogenetic events (segregation, pseudogastrulation and ciliation) of differentiation without cleavage in Chaetopterus-activated eggs. A parallel has been drawn between cytophotometric estimations of the DNA content and cytoplasmic differentiation in eggs treated with aphidicolin under different experimental conditions: either pulses with aphidicolin were followed by culture in sea water or the eggs were treated with aphidicolin after development had taken place in sea water for various lengths of time. The results suggest that a 'quantal' monasterial cycle might take place 3 h after activation, corresponding presumably to the fourth or fifth replication cycle. Moreover, early DNA replication seems to be more important for morphogenesis than late DNA replication., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

The K+ ionophore valinomycin very quickly arrests cleavage in sea urchin and mouse eggs at concentrations ranging between 10 and 3 micron. Development of Axolotl and Xenopus eggs is not arrested before the blastula or gastrula stage. The motility of sea urchin sperm, blastulae and gastrulae is suppressed, within a few minutes, by 1-9 micron valinomycin., English Abstract, Journal Article, info:eu-repo/semantics/published

The development of the nucleoli and the sites of rDNA transcription have been studied by high-resolution autoradiography during the cleavage stages of mouse embryos. The appearance of fibrillar centres at the periphery of the fibrillar primary nucleoli has been observed at the 4-cell stage. Several fibrillar centres, interconnected by electron-dense fibrillar strands, form a reticulated region around the fibrillar mass at the 6- to 8-cell stage. After a 10 min pulse with [3H]uridine, only this peripheral network is labelled. At the late morula and the blastocyst stage, the fibrillar component (nucleolonema) of the reticulated nucleoli is labelled after 19 min [3H]uridine incorporation. When the embryos are reincubated for 2 h in cold medium, the label is localized mainly in the granular component. Fibrillar centres are not labelled. Autoradiograms of in vitro developed embryos pulsed for 2 h with [3H]uridine confirm that the central fibrillar core of the nucleoli of 6- to 8-cell embryos is never labelled. Thus, the fibrillar constituent of this core is not homologous to the fibrillar component of the nucleoli of later stage embryos, which is the site of active rDNA transcription. An interpretation of nucleologenesis during early mouse embryogenesis is proposed., SCOPUS: ar.j, info:eu-repo/semantics/published

Activation of unfertilized Chaetopterus eggs by treatment with an excess of KCl may lead to the production of unicellular ciliated larvae (Lillie's differentiation without cleavage). The effects of a number of inhibitors of protein (puromycin, cycloheximide, emetin), RNA (actinomycin D), and DNA (hydroxyurea) synthesis of differentiation without cleavage and on normal development have been studied in Chaetopterus. Incorporation of radioactive leucine, uridine, and thymine has been followed by biochemical methods and by autoradiography. The DNA content of the large polyploid nucleus has been estimated by cytophotometry. The initial pseudocleavage period of differentiation without cleavage is characterized by a burst in DNA and protein synthesis; the inhibitors have little or no effect on this burst and on pseudocleavage itself. Protein and DNA synthesis levels off during the following phase (segregation), but the inhibitors become more effective. RNA synthesis is almost linear for 20 h. These results are compared with those obtained on eggs from other species., Journal Article, SCOPUS: ar.j, info:eu-repo/semantics/published

The effects of aphidicolin - a powerful inhibitor of DNA polymerase alpha and of DNA replication - on normal development and on differentiation without cleavage of Chaetopterus eggs have been studied with cytological, cytochemical, and biochemical methods. The experiments show that the initial period of pseudocleavage can take place in the absence of nuclear DNA synthesis, but further development (segregation, hatching, ciliation) requires DNA synthesis. However ciliated unicellular larvae can be obtained under conditions where the DNA content of the embryos in only 40% of the controls. In fertilized eggs, aphidicolin immediately stops cleavage. The significance of these results is discussed., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

X irradiation produces a rapid and substantial decrease in DNA synthesis in cleaving eggs of Pleurodeles, as shown by thymidine incorporation experiments; this decrease is presumably due to the arresting of the cell cycle in many blastomeres. DNA replication is partly resumed at the late blastula stage after irradiation at the 2 to 4 cell stage. The present work demonstrates a high radiosensitivity of the metabolic pathway leading to the incorporation of uridine into DNA; this could be the result of the inhibition of the activity or the synthesis of such enzymes as ribonucleotide reductase, thymidylate synthetase and CTP synthetase. The radiosensitivity of this metabolic pathway becomes lower after gastrulation. Finally, irradiation strongly inhibits the synthesis of new RNA species at gastrulation, but seems to have no effect on heterodisperse RNA (mRNA) synthesis during cleavage., SCOPUS: ar.j, info:eu-repo/semantics/published

We confirm that the centrifugal migration of the chromosomes in maturing mouse oocytes depends on a microfilament-mediated process. We investigated the role of the cytoskeleton in the germinal vesicle (GV) behavior of oocytes prevented from resuming meiosis by either activators of protein kinase A or activators of protein kinase C. A time-lapse microcinematography study demonstrates that GV immobilization by isobutylmethylxanthine (IBMX) is overcome by colcemid (COL), nocodazole (NOC), and taxol and that cytochalasin D (CCD) reversibly immobilizes the GV of oocytes treated with either IBMX + COL (or NOC) or 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, known to allow a programmed GV cortical translocation. An immunofluorescence analysis shows that the disorganization of a perinuclear microtubule network is the very first cytological clue of maturation. IBMX promotes its persistence while NOC, COL, and taxol induce its immediate disappearance. It is concluded that elements of the cytoplasmic microtubular complex (CMTC) are passively involved in the control of the setting up of a 'centrifugal displacement property' (CDP) by counteracting a motive force provided by the microfilament cytoskeleton. Finally, TPA induces a clearcut reorganization instead of a total disorganization of the CMTC. This reorganization is, however, sufficient to allow the microfilaments to drive the GV displacement., SCOPUS: ar.j, info:eu-repo/semantics/published

Inhibition of cavitation by acute X-irradiation of 2-cell stage eggs was due to the early killing of the cells. Eggs in which cavitation did take place had a smaller number of cells due mainly to mitotic delay, leading to lack of inner cell mass (ICM) and its derivatives in further development. A similar effect is responsible for the inhibition of ICM formation after irradiation of morulae., SCOPUS: ar.j, info:eu-repo/semantics/published

A passive erratic movement of the germinal vesicle (GV), already visible in small incompetent oocytes, is followed by an active scalloping of the nuclear membrane soon before GV breakdown (GVBD) in cultured competent oocytes. Maturation can be inhibited by activators of protein kinase A (PK-A) and protein kinase C (PK-C). Our time-lapse cinematography analysis allowed us to describe an unexpected behaviour of the GV when PK-C, but not PK-A, is activated: GV undergoes a displacement toward the cortex according to the same biological clock which triggers the programmed translocation of the spindle in control oocytes. It is concluded that, when oocytes become committed to undergo maturation, the cytoplasm acquires a PK-A-controlled 'centrifugal displacement property' which is not restricted to the spindle., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published