bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combined action of stem cell factor, leukemia inhibitory factor, and cAMP on in vitro proliferation of mouse primordial germ cells
Authors: Dolci Susanna , Pesce Maurizio , De Felici Massimo 
Published: February 2005

AbstractIn the present paper we investigated the effects of stem cell factor/mastocyte growth factor (SCF/MGF), leukemia inhibitory factor/differentiating inhibitory activity (LIF/DIA) (two growth factors known to affect primordial germ cell growth in vitro) and forskolin (FRSK) (an activator of adenylate cyclase in many cell types) alone or in combination on the survival and proliferation of primordial germ cells (PGCs) obtained from 8.5, 10.5, and 11.5 days post coitum (dpc) mouse embryos and cultured without pre‐formed cell feeder layers.The results showed that both at 1 and 3 days of culture the addition of 100 ng/ml SCF, 20 μM FRSK, or in some instances 20 ng/ml LIF alone caused a significant increase of PGC number as compared with controls. The highest effects were obtained when SCF and/or LIF were used together with FRSK. Moreover, we found that FRSK elevated cAMP levels in purified 11.5 dpc PGCs and that this compound, but not SCF and LIF, stimulated PGC proliferation, as assessed by 5‐bromo‐2′‐deoxyuridin (BrdU) incorporation.These results suggest a mechanism of combined action of cAMP with SCF and/or LIF in the control of proliferation of mouse PGCs in vitro. © 1993 Wiley‐Liss, Inc.
Glucose, pyruvate, and lactate concentrations in the blastocoel cavity of rat and mouse embryos
Authors: Brison D. R. , Hewitson L. C. , Leese H. J. 
Published: February 2005

AbstractThe concentrations of glucose, pyruvate, and lactate have been measured in the blastocoel fluid of single rat and mouse blastocysts, using the technique of micropuncture combined with an ultramicro‐fluorescence assay. When cultured in the presence of 5.55 mM glucose, 11.5–12.5 mM L‐lactate and 0.25–0.33 mM pyruvate, concentrations in the blastocoel fluid of mouse and rat were 2.30 and 2.75 mM glucose, 14.6 and 19.6 mM L‐lactate, and 0.13 and 0.50 mM pyruvate, respectively. When cultured in the presence of 1.0 mM glucose and 1.0 mM L‐lactate, concentrations in the blastocoel fluid were 0.50 and 0.59 mM glucose and 2.22 and 3.70 mM L‐lactate, respectively. These results suggest that (1) the blastocyst is capable of maintaining considerable concentration gradients of substrates across the trophectoderm, (2) the microenvironment of the blastocoel is adequately supplied with energy substrates for the development of the inner cell mass, and (3) the inner cell mass is capable of developing in both high and low glucose and lactate concentrations. © 1993 Wiley‐Liss, Inc.
Transcriptional activity and nuclear ultrastructure of 8‐cell bovine embryos developed by in vitro maturation and fertilization of oocytes from different growth categories of antral follicles
Authors: Pavlok A. , Kopečný V. , Lucas‐Hahn A. , Niemann H. 
Published: February 2005

AbstractThe normalcy of nuclear differentiation in 8‐cell bovine embryos derived by in vitro procedures from oocytes isolated from antral follicles of three different size categories was studied using autoradiographic localization of RNA synthesis and fine‐structure nuclear morphology. In the few embryos derived from the oocytes from the small category of follicles (1–2 mm) the unlabeled nuclei prevailed. In contrast, the oocytes isolated from the more progressed follicles (medium and large size: 2–8 mm) yielded embryos with only slight, if at all detectable, differences to the picture expected in in vivo developed normal embryos. The diverging features probably concerned a slower onset of gene transcription, its consecutive pattern of localization as well as less pronounced progress of chromatin condensation and nucleolar differentiation. The assessment of these morphological changes and characteristics for individual embryos was obscured by marked differences in the status of the nuclei of particular blastomeres forming an embryo. Here the differences were seen in the fragmentation of nuclei, in the degree of chromatin condensation and in the absence of the nucleolus‐associated chromatin in some of the blastomeres. It is suggested that most of the embryos from medium and large follicles have a comparable differentiation pattern of nuclear function development as embryos developing normally in vivo. © 1993 Wiley‐Liss, Inc.
Analysis of lipid peroxidation mechanisms in human spermatozoa
Authors: Aitken R. J. , Harkiss D. , Buckingham D. W. 
Published: February 2005

AbstractThe mechanisms by which ferrous ion promoters induce malondialdehyde generation by human spermatozoa have been investigated in order to provide a rational basis for the quantification and interpretation of lipid peroxidation assays. Incubation of human spermatozoa with a ferrous ion promoter in the presence of thiobarbituric acid (TBA) led to the generation of the bone fide malondialdehyde‐TBA adduct. The importance of iron in the stimulation of lipid peroxidation was emphasized by the ability of Desferal* and EDTA to suppress malondialdehyde generation. Paradoxically, when the concentration of EDTA relative to iron was equimolar or greater, the suppression of malondialdehyde formation was accompanied by the generation of hydroxyl radicals. These results suggested that the addition of promoter did not effect the first‐chain initiation of lipid peroxidation but favored an alternative mechanism involving the catalytic decomposition of pre‐existing lipid peroxides. This conclusion was reinforced by the inability of reagents that would limit the formation (superoxide dismutase and/or catalase) or availability (mannitol, formate) of hydroxyl radicals, to influence malondialdehyde generation. While hydroxyl radicals were not directly involved in Fe2+‐promoted malondialdehyde generation, the existence of significant correlations between reactive oxygen species production and the outcome of the TBA assay, suggested that Fenton chemistry might be important in the initiation of peroxidative damage. It is proposed that the impeded propagation of peroxidation initiated by Fenton or Haber Weiss reactions would lead to the accumulation of lipid peroxides in the spermatozoa and it is these peroxides that are induced to decompose during the Fe2+‐promoted TBA assay, stimulating a lipoperoxidative chain reaction and malondialdehyde formation. © 1993 Wiley‐Liss, Inc.
Sperm: Egg ratios and putative molecular signals to modulate gamete interactions in polytocous mammals
Authors: Hunter R. H. F. 
Published: February 2005

AbstractReasoning from the premises that 1) the sperm:egg ratio at the time of activation of the secondary oocyte in mammals is close to unity under conditions of spontaneous mating, 2) a majority of eggs within the cumulus oophorus of a polytocous species is fertilized in a reasonably short interval of time, and 3) spermatozoa would find it difficult to reverse their approach to the zona pellucida, it is proposed that molecular gradients exist to divert spermatozoa penetrating the cumulus mass away from eggs already activated and towards eggs as yet unfertilised. Possible sources of such molecular cues are considered, as is the event that triggers their release. © 1993 Wiley‐Liss, Inc.
The IGFs and their binding proteins in murine development
Authors: Murphy Liam J. , Barron Douglas J. 
Published: February 2005

AbstractRecent observations suggest that the diverse actions of the insulin‐like growth factors (IGFs) are the result of interactions of the various components that make up the IGF system. The components of this system include IGF‐I and ‐II and their variants, the type 1 and 2 IGF receptors and the insulin‐like growth factor binding proteins (IGFBPs). Various components of the IGF system are expressed in the developing mouse embryo and the adjacent tissues of the reproductive tract in which the embryo develops. Thus there is the potential for paracrine interactions between the maternal and fetal tissues. Transcripts for the IGF receptors, IGF‐I and IGF‐II, have been demonstrated in the periimplantation mouse embryo. While there are now data from gene ablation experiments indicating that IGF‐II is important in embryogenesis, the role of other components of the IGF system such as the IGFBPs remains unclear. The data accumulated so far are largely empirical, and there is as yet little compelling evidence that maternal IGFs derived from oviduct or uterine fluid and maternal tissues are necessary for normal fetal development. We have started to develop transgenic mice lines overexpressing IGFBPs to attempt to address the role of these binding proteins in fetal development. © 1993 Wiley‐Liss, Inc.
Transcriptional regulation of the major promoters of the human IGF‐II gene
Authors: Holthuizen P. , Van Dijk M. A. , Rodenburg R. J. T. , Koonen‐Reemst A. M. C. B. , Sussenbach J. S. 
Published: February 2005

AbstractThe human insulin‐like growth factor‐II (IGF‐II) gene constitutes a complex transcriptional unit that is controlled by four different promoters preceding multiple 5′‐untranslated exons. Expression of the IGF‐II gene is development and tissue specific and yields a family of mRNAs that all encode preproIGF‐II. We have analyzed the sequences and factors involved in the transcriptional activation of promoters P1 and P3. Detailed analysis revealed several characteristic elements and protein binding sequences. P1, which is expressed only in adult liver tissue, contains a region that can be specifically activated by the CCAAT/enhancer binding protein (C/EBP). P3 consists of a proximal promoter region that supports general transcription, whereas cell‐specific elements are located upstream. © 1993 Wiley‐Liss, Inc.
The IGF‐II receptor system: A G protein‐linked mechanism
Authors: Nishimoto Ikuo 
Published: February 2005

AbstractBased on the finding that stimulation of the IGF‐II, receptor (IGF‐IIR) is capable of activating Gi2 and calcium channels in BALB/c 3T3 fibroblasts, it was found that purified IGF‐IIR can couple directly to purified Gi2 in phospholipid vesicles. IGF‐IIR–Gi2 coupling can be characterized as follows. IGF‐IIR directly couples to Gi2 in response to IGF‐II in a stoichiometrical manner, suggesting that IGF‐IIR works as a transmembrane signaling molecule and that the seven‐transmembrane structure is not essential for receptor‐G protein coupling. The mode of IGF‐IIR–Gi2 interaction is similar to that of conventional receptor–G protein coupling, suggesting that a common G protein recognition mechanism is shared by IGF‐IIR and conventional G‐coupled receptors. The action of IGF‐IIR is specific on Gi2 among various G proteins. Finally, the activity of IGF‐IIR on Gi2 is similarly potent across the species of the proteins. These characteristics led to the discovery of a 14‐amino‐acid region in IGF‐IIR that can directly interact with and activate Gi2, and is located at residues 2410–2423 of the human receptor. Subsequent work has indicated that this region is responsible for Gi‐coupling function of intact IGF‐IIR. The most important extensions of this discovery are the following: (1) The structure–function relationship for the Gi‐activating function of this 14‐amino‐acid sequence, (2) the prediction of G protein‐coupled functions of receptors based on the results obtained from 1), and (3) clarification of the detailed mechanism whereby ligand–receptor complex recognizes G proteins. This paper reviews what we have learned from IGF‐IIR in terms of receptor–G protein interfaces and discusses future prospects. © 1993 Wiley‐Liss, Inc.
IGF‐I and the IGF‐I receptor in development of nonmammalian vertebrates
Authors: De Pablo Flora , Pérez‐Villamil Beatriz , Serna José , González‐Guerrero Pilar R. , López‐Carranza Ana , De La Rosa Enrique J. , Alemany Jorge , Caldés Trinidad 
Published: February 2005

AbstractExtracellular signals are likely to be involved in the control of growth and differentiation during embyrogenesis of vertebrates. These signals include, among others, several members of the insulin family: insulin‐like growth factor (IGF)‐I, IGF‐II, and insulin. In the chick embryo, maternal IGF‐I is stored in the yolk. In addition, the embryonic IGF‐I gene is expressed very early and in late development in multiple tissues. We have used reverse‐transcribed (RT) RNA and amplification by the polymerase chain reaction (PCR) to detect IGF‐I gene expression. IGF‐I was preferentially expressed in cephalic regions during late neurulation and early organogenesis. During late organogenesis, in some tissues, such as the eye lens, IGF‐I gene expression is compartmentalized to a subset of cells, the epithelial cells. In these lens cells, IGF‐I stimulates transcription of the δ‐crystallin gene. Competence to respond to IGF‐I exists in multiple cell types, since, based on binding studies, receptors for IGF‐I are widespread in the gastrulating and neurulating embryo. Target tissues in which an autocrine/paracrine role for IGF‐I appears more likely are the developing eye lens and retina, which are avascular organs rich in IGF‐I receptors. In late development, IGF‐I may have an additional endocrine role, with an impact on the general growth of the chick embryo. In embryos developed ex ovo, that show growth retardation after day 10 of embyrogenesis, IGF‐I serum levels are very low. By day 8, expression of IGF‐I mRNA in these embryos is markedly reduced in multiple tissues. Future studies in which IGF‐I and its receptor are overexpressed or abolished should clarify the function of this growth factor in development. © 1993 Wiley‐Liss, Inc.
Cell allocation in twin half mouse embryos bisected at the 8‐cell stage: Implications for preimplantation diagnosis
Authors: Hardy Kate , Handyside Alan H. 
Published: February 2005

AbstractPrevious work in the mouse and human has shown that removal of cells from 2‐ and 4‐cell embryos disproportionately reduces the inner cell mass (ICM), from which the fetus is derived, suggesting that preimplantation biopsy at these stages would be inadvisable. Here we have examined allocation in twin half mouse embryos produced by bisection at the 8‐cell stage. Half embryos and intact zona‐free control embryos were differentially labeled at the time of cavitation using polynucleotide‐specific fluorochromes, and the numbers of cells in the ICM and trophectoderm (TE) counted. Adding the numbers of cells in the twin halves together, the numbers of ICM cells are not significantly different from those in intact controls. In contrast, numbers of TE cells were significantly higher (P < 0.01), producing a small increase in the total cell number of half embryos. There is no concomitant decrease in ICM cell number. We propose that as the surface area of a half embryo is greater than half an intact control, TE cells in half embryos divide faster in order to reach an optimal packing density similar to that in intact control embryos. Furthermore, we suggest that preimplantation biopsy only be performed at the 8‐cell stage or later. © 1993 Wiley‐Liss, Inc.
Influence of recipient oocyte cell cycle stage on DNA synthesis, nuclear envelope breakdown, chromosome constitution, and development in nuclear transplant bovine embryos
Authors: Barnes F. L. , Collas P. , Powell R. , King W. A. , Westhusin M. , Shepherd D. 
Published: February 2005

AbstractNuclear transplantations into metaphase II (MII) and S phase oocyte cytoplasm were performed to investigate the influence of recipient cell cycle stage on nuclear function and development of bovine nuclear transplant (NT) embryos. Rate of inactivation of histone H1 kinase and duration of DNA synthesis in activated oocytes were determined. The proportion of S phase blastomeres in in vivo produced day 5.5 bovine embryos was measured. DNA synthesis was also assessed in NT embryos after transfer into MII and S phase cytoplasm. MII NT embryos were produced by fusing a blastomere into a MII oocyte; the fusion pulse served to activate the oocyte. S NT embryos were produced by fusing a blastomere into an early S phase oocyte electrically activated 4 h prior to fusion. Nuclear envelope structure, chromosome constitution, and extent of development were examined in MII and S NT embryos. Histone H1 kinase activity dropped to baseline within 2 h of electrical activation. A second electrical pulse did not alter H1 kinase activity when delivered 4 h after the first pulse. The frequency of S phase blastomeres in day 5.5 bovine embryos ranged from. 79% to 100%, depending on the duration of culture in 3H‐thymidine. Nuclear transplantation into MII cytoplasm resulted in a transient drop in DNA synthesis over 3.5 h. DNA synthesis resumed at 4.5 h post activation (hpa), concomittantly with initiation of DNA replication in activated oocytes. In contrast, DNA synthesis was not interrupted after transfer into S phase cytoplasm. DNA synthesis persisted until 13.5 hpa, as in activated oocytes. Partial or complete nuclear envelope breakdown (NEBD) occurred after transfer into MII cytoplasm, whereas the nuclear envelope remained intact in 50% of the embryos or underwent partial breakdown in S phase cytoplasm. A greater proportion of S NT embryos was diploid (50% vs. 23% MII NT embryos, P < 0.001), and a higher frequency of S NT embryos developed to the morula or blastocyst stage (22% vs. 5%, P < 0.001). The data indicate that DNA synthesis is regulated differently if the recipient oocyte is in MII or in S phase at the time of fusion. Extended DNA synthesis after transfer into MII cytoplasm suggests a re‐replication of the donor chromatin. Re‐replication, presumably, does not occur after transfer into S phase cytoplasm. Re‐replication is likely to be a consequence of permeabilization of the nuclear envelope upon NEBD in MII cytoplasm. Improved regulation of DNA synthesis after transfer into S phase cytoplasm and reduced incidence of chromosome damage in the first cell cycle may have been responsible for increased frequency of development of S NT embryos to the morula/blastocyst stage. © 1993 Wiley‐Liss, Inc.
Aspartate and glutamate transport in unfertilized pig oocytes and blastocysts
Authors: Prather R. S. , Peters M. S. , Van Winkle J. 
Published: February 2005

AbstractAmino acid transport is facilitated by specific transporters within the plasma membrane of the cell. Mediated Na+‐independent transport of L‐glutamate can be easily detected in mouse oocytes, but it is nearly undetectable in blastocyst‐stage embryos. In contrast, the Na+‐dependent transport of L‐aspartate is not detectable in oocytes, but it is detectable in eight‐cell embryos and reaches relatively high levels by the blastocyst stage. It is believed that the amino acid transporters responsible are systems x−c and X−AG, respectively. Here we report the detection of Na+‐dependent L‐aspartate transport, which increased as pig blastocysts developed, although Na+‐dependent aspartate transport was not detected in pig oocytes. Mediated Na+‐independent L‐glutamate transport was not detected in pig oocytes, in contrast to the mouse, nor in early or hatched pig blastocysts. Thus, while the developmental regulation of system X−AG is similar in both the pig and the mouse, system x−c was not detectable in pig oocytes or blastocysts. Elucidation of the molecular mechanisms controlling amino acid transport and other gene expression in early embryos should contribute to an understanding of whether and even why some aspects of developmental regulation of gene expression may need to differ among species. © 1993 Wiley‐Liss, Inc.
Competent mouse oocytes isolated from antral follicles exhibit different chromatin organization and follow different maturation dynamics
Authors: Debey Pascale , Szöllösi Maria S. , Szöllösi Daniel , Vautier Dominique , Girousse Anne , Besombes Didier 
Published: February 2005

AbstractAfter labelling DNA with the specific vital fluorophore Hoechst 33342, oocytes, isolated by puncture from antral follicles in adult mice, have two essentially different configurations of their nuclear fluorescence images. These have been called SN (where the nucleolus is not surrounded by chromatin) and NSN (where the nucleolus is not surrounded by chromatin). Intermediate configurations are also found, although with a lower frequency. The proportion of each class is on the average equal and depends neither on the presence of cumulus cells nor on the age of the mouse. Electron microscopy confirms several ultrastructural differences between these two nuclear configurations, namely, the structure of the nucleolus, which is vacuolated in NSN‐type and compact in SN‐type oocytes. Using video‐enhanced fluorescence microscopy at low level of excitation light, we could follow directly in vitro the meiotic maturation of both classes, without impairing their viability. We show that in germinal vessicle (GV) state, the chromatin does not change from one configuration into the other and that both classes are able to mature to metaphase II, although the maturation has slightly different characteristics. © 1993 Wiley‐Liss, Inc.
Mitogen‐activated protein kinase (MAP kinase) activation in Xenopus oocytes: Roles of MPF and protein synthesis
Authors: Haccard Olivier , Jessus Catherine , Rime Helene , Goris Jozef , Merlevede Wilfried , Ozon Rene 
Published: February 2005

AbstractMitogen‐activated protein kinase (MAP kinase) is a serine/threonine kinase whose enzymatic activity is thought to play a crucial role in mitogenic signal transduction and also in the progesterone‐induced meiotic maturation of Xenopus oocytes. We have purified MAP kinase from Xenopus oocytes and have shown that the protein is present in metaphase ll oocytes under two different forms: an inactive 41‐kD protein able to autoactivate and to autophosphorylate in vitro, and an active 42‐kD kinase resolved into two tyrosine phosphorylated isoforms on 2D gels.During meiotic maturation, MAP kinase becomes tyrosine phosphorylated and activated following the activation of the M‐phase promoting factor (MPF), a complex between the p34cdc2 kinase and cyclin B. In vivo, MAP kinase activity displays a different stability in metaphase l and in metaphase II: protein synthesis is required to maintain MAP kinase activity in metaphase I but not in metaphase II oocytes. Injection of either MPF or cyclin B into prophase oocytes promotes tyrosine phosphorylation of MAP kinase, indicating that its activation is a downstream event of MPF activation. In contrast, injection of okadaic acid, which induces in vivo MPF activation, promotes only a very weak tyrosine phosphorylation of MAP kinase, suggesting that effectors other than MPF are required for the MAP kinase activation. Moreover, in the absence of protein synthesis, cyclin B and MPF are unable to promote in vivo activation of MAP kinase, indicating that this activation requires the synthesis of new protein(s). © 1993 Wiley‐Liss, Inc.
Production, characterization, and immunocytochemical applications of monoclonal antibodies to human sperm protamines
Authors: Le Lannic G. , Arkhis A. , Vendrely E. , Chevaillier P. , Dadoune J. P. 
Published: February 2005

AbstractThree monoclonal antibodies against human protamines were obtained by immunization with total human basic nuclear proteins or purified protamine HP3. The specificity of antibodies was assessed by enzyme‐linked immunosorbent assay (ELISA) and Western blot. They recognized three distinct epitopes: One was specific for the protamine P1 family, another was specific for the protamine P2 family and the third was common to both families. All were specific for the human species. Antibodies were used to detect protamines in germ cells by indirect immunofluorescence and by immunoelectron microscopy. Protamines appeared in spermtid nuclei at steps 4–5 of spermiogenesis, i.e., during the chromatin condensation process, and were not accumulated in the cytoplasm before entering the nucleus. © 1993 Wiley‐Liss, Inc.