河南新乡段卫河水对黑斑侧褶蛙早期胚胎发育的影响

研究了不同浓度新乡卫河水对黑斑侧褶蛙早期胚胎的发育毒性.结果表明:黑斑侧褶蛙胚胎在卫河水原水中不能存活;56%浓度卫河水可使胚胎畸形率和死亡率显著升高;低浓度(10%、18%、32%)卫河水能明显抑制胚胎全长的增加.在研究污染物尤其是低浓度污染物对黑斑侧褶蛙胚胎发育毒性时,生长抑制参数是比致死率和畸形率更为敏感的终点参数.卫河污染严重,存在潜在致畸变物质,应加速卫河治理.     

Effects of post-ovulatory food deprivation on the hormonal profiles, activity of the oviduct and ova transport in sows

The objective of the present study was to investigate the effect of post-ovulatory food deprivation on the hormonal profiles and consequently on the activity of the oviduct and ova transport in sows. Sows were randomly allocated to the control (C-group, n=6) or fasted (F-group, n=5) group. The F-group sows were fasted for four meals starting with the morning meal after detection of ovulation in the second oestrus after weaning. Ovulation was checked by transrectal ultrasonography. Blood was collected for the analyses of progesterone, oestradiol-17beta, prostaglandin F(2 approximately ) metabolite, insulin, free fatty acids and triglycerides. Oviductal isthmic motility was monitored on Polyview before and after ovulation until the time of slaughter. After slaughter, the isthmus opposite the side with transducer was divided into three equal segments and flushed separately and a third of the uterine horn part from the utero-tubal-junction (UTJ) was also flushed. A high proportion of ova in the F-group was found in the first and second parts of the isthmus. In the C-group, a high proportion of ova was found in the third part of the isthmus and the uterus. The mean isthmic pressure in the C-group decreased significantly (P<0.05) during the period immediately after ovulation while in the F-group mean pressure remained unchanged. The frequency of phasic pressure fluctuations were significantly (P<0.05) higher in the F- than in the C-group 13 to 24 h after ovulation. No significant differences in progesterone concentrations were seen between the two groups of sows. Prostaglandin metabolite levels were significantly (P<0.05) higher in the F-group than in the C-group. Oestradiol-17beta levels significantly (p<0.05) decreased earlier in the F- than in the C-group. Serum insulin levels were significantly (p=0.05) lower in the F- than in the C-group while free fatty acids were significantly (p<0.01) higher in the F- than in the C-group. There were no significant differences in the serum levels of triglycerides between the F- and the C-group. Therefore, it can be concluded in the present study that food deprivation is associated with changes in the hormonal profiles, activity of the oviduct and a delay of ova transport in sows.     

Effect of feeding level on progesterone concentration in early pregnant multiparous sows

The effect of three feeding regimens on progesterone level was tested during early pregnancy in multiparous sows. A total of eighteen sows in their eighth parity (8.1 +/- 2.8, mean +/- S.D.) were used. During lactation the sows were fed to appetite and after weaning they received 4 kg (52 MJ) a commercial feed per day. Following ovulation, sows were allocated to one of three treatment groups and fed 2 kg/day (low feeding, LLL) or 4 kg/day (high feeding, HHH) throughout the trial or 2 kg/day for 11 days, 4 kg/day for 10 days, and 2 kg/day for the remaining days of the study (modified feeding, LHL). Blood for progesterone and cortisol analyses was collected daily throughout the study, and for luteinizing hormone (LH) assay for 12 h at 15 min intervals on days 14 and 21 of pregnancy. An adrenocorticotropic hormone (ACTH) challenge test was performed on all sows day 28 of pregnancy. Dietary treatment did not significantly affect hormonal parameters. However, progesterone concentration tended to be lower (P = 0.08) in the HHH group than in the LLL group. In the LHL group venous progesterone concentration seemed to fluctuate. No effects of feeding were observed on progesterone concentration in allantoic fluid on day 35 of pregnancy. Venous cortisol level was significantly higher (P < 0.05) during proestrus and oestrus in all groups and there was no significant difference between groups in response to ACTH challenge. The mean amplitude of LH pulses decreased significantly (P < 0.01) from days 14 to 21 of pregnancy in all groups. In addition, an interaction was found between feeding level and baseline LH concentration and also between feeding level and mean LH concentration. Embryonic recovery was highest in the LLL (69%), lowest in the HHH (45%) and moderate in the LHL (55%) group. Neither high feeding nor modified feeding provided any benefits for reproductive performance in multiparous sows. A low feeding regimen thus appears optimal for multiparous sows in early pregnancy at least with the management regime described.     

Inductive interactions in early embryonic development.

This is an update of a previous review (Current Opinion in Cell Biology 2:969-974) in which we discussed recent work attempting to understand the sequence of inductive interactions responsible for establishing the body plan of the early embryo. As before, we concentrate on inductive interactions in amphibian embryos, where significant progress has been made in the past two years. In this update, however, we also consider recent embryological data obtained with amniote embryos such as the chick, together with complementary data provided by genetic analyses of mouse and Drosophila development.     

'Cleavage fields': hypothesis on early embryonic development

The hypothesis is put forward that events of the early embryonic development can be interpreted on the basis of a radial distribution of cytoplasmic components, i.e. of a 'cleavage field', progressively established during the growth of the oocyte. The orientations of the cleavage spindles and the corresponding furrows' positions are assumed to be correlated to the field's temporal evolution which, in turn, is determined by flows of cytoplasmic components originated by the changes in the membrane shape. From this viewpoint, a simple explanation of egg regulation is proposed, and the particular case of the sea urchin embryo is briefly discussed.     

Clinical features and hormonal profiles of cloprostenol-induced early abortions in heifers monitored by ultrasonography

Background  

The present study describes the clinical features and plasma profiles of bovine pregnancy-associated glycoprotein 1 (bPAG1), the main metabolite of prostaglandin F_2α (PG metabolite) and progesterone (P4) in heifers in which early abortions were induced.     

Retinoic acid synthesis and functions in early embryonic development

Retinoic acid (RA) is a morphogen derived from retinol (vitamin A) that plays important roles in cell growth, differentiation, and organogenesis. The production of RA from retinol requires two consecutive enzymatic reactions catalyzed by different sets of dehydrogenases. The retinol is first oxidized into retinal, which is then oxidized into RA. The RA interacts with retinoic acid receptor (RAR) and retinoic acid X receptor (RXR) which then regulate the target gene expression. In this review, we have discussed the metabolism of RA and the important components of RA signaling pathway, and highlighted current understanding of the functions of RA during early embryonic development.     

Fertilization and early embryonic development in androstenedione-immunized Merino ewes

Ewes were immunized against androstenedione (Fecundin) and assigned to be mated 14 days (179 ewes Group C) or 25 days (174 ewes Group B) after a booster immunization with Fecundin. The anti-androstenedione titres at these times were 6790 and 3240 respectively (P less than 0.01). The remaining 169 ewes were untreated controls (Group A). Ewes were mated to entire rams (12 rams to 180 ewes) at their second oestrus after synchronization of oestrus. Immunization against androstenedione caused a shortening of the time from sponge removal to mating (Day 0) and a decrease in the percentage of ewes mated by the rams. Also, ovulation rate was increased after immunization (P less than 0.01), being 1.42, 2.16 and 1.93 for Groups A, C and B respectively. Egg recovery rates on Day 2 were lower in immunized ewes and there was some indication that fertilization rates were lowered. On Day 13 after mating a higher proportion of blastocysts was recovered from ewes in Group A than from those in Groups B and C. Immunization resulted in lower fertilization rates and smaller blastocysts with lower mitotic indexes (P less than 0.01). At Days 24-32 of pregnancy fetal weight was lower in the immunized ewes. At all sampling stages, the proportion of ewes pregnant (fertility) was lowered in immunized ewes. The results of the present study show that significant reproductive wastage occurs in androstenedione-immunized Merino ewes, with lower rates of embryo recovery and delayed embryonic development being found in comparison to controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Emerging asymmetry and embryonic patterning in early mouse development

Recent studies have revealed asymmetries in the mouse zygote and preimplantation embryo, well before the establishment of anterior-posterior polarity after implantation. Whether these asymmetries are causally related to embryonic patterning or are coincidental outcomes of the topology of normal development remains uncertain.     

Effects of estradiol and progesterone on early embryonic development in aging rats

Regularly cyclic, middle-aged female rats exhibit a decreased incidence of fertility, and those females that are fertile produce small litters. These decreases in fertility and litter size are associated with reduced numbers of normal blastocysts formed and implanted, suggesting that pre- and/or peri-implantation failures may be the causes for these aging-related reproductive declines. The present study examined the relationships and influence of circulating estradiol (E2) and progesterone (P) levels on early embryonic development and implantation in middle-aged rats. Serial blood samples obtained from cannulated, middle-aged pregnant rats revealed minor decreases in plasma P and increases in E2 levels during Days 2-4 of pregnancy, compared to young pregnant rats, resulting in significantly (p less than 0.001) decreased plasma P/E2 ratios. These alterations in endogenous hormone secretion in middle-aged pregnant rats were associated with fewer normal blastocysts on Day 5 of pregnancy and reduced numbers of normally implanting embryos. Correlation analysis further revealed a significant (p less than 0.05) inverse relationship between mean circulating E2 levels and numbers of normal conceptuses on Day 12 of gestation. Moreover, s.c. administration of P implants (in Silastic) to middle-aged pregnant rats increased serum P levels by about 34-40 ng/ml, and significantly (p less than 0.05) reduced the incidence of abnormal embryos before implantation. In contrast, treatment with E2 minipumps produced a sustained rise in serum E2 (by about 7-15 pg/ml) and resulted in the complete absence of embryos in the reproductive tracts by Day 5 of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of exogenous progesterone on early embryonic development in the mare

The influence of exogenous progesterone on the development of equine oviductal embryos was determined based upon the recovery of Day-7 uterine blastocysts from treated mares (n=13) that were given 450 mg progesterone daily between Days 0 and 6 and from untreated control mares (n=13). Daily administration of 450 mg progesterone in oil significantly (P<0.02) increased serum progesterone concentrations in the treated mares. There was no significant difference in the recovery rate of Day-7 embryos between treated and control mares (8/13 versus 6/13, respectively). Embryonic development, assessed by morphologic evaluation, embryo diameter, and number of cell nuclei was not significantly different for embryos from treated and from control mares. The results of this study indicate that administration of progesterone beginning on the day of ovulation does not affect the embryo recovery rate or embryonic development, based on evaluation of uterine blastocysts recovered at Day 7 after ovulation.     

Roles of cell junctions in gametogenesis and in early embryonic development

Recent reviews of the role of cell junctions in development have focused primarily upon functions related to the relatively subtle physiological modulation of their subunits in relation to fundamental developmental processes in a wide variety of organisms. There is, however, considerable support from numerous laboratories that the more radical modulation of the presence and number of junctional subunits in many diverse tissues may play a pivotal role in a wide spectrum of developmental phenomena ranging from gametogenesis to organogenesis. Since a great deal of recent interest in this latter subject has concentrated upon vertebrate systems including mammals, this review will examine the functional significance of the modulation of gap junctions, tight junctions and desmosomes in a developing idealized mammalian system from gamete formation to tissue and organ differentiation during embryo-genesis.     

Gene expression profiles during early differentiation of mouse embryonic stem cells

Background  

Understanding the mechanisms controlling stem cell differentiation is the key to future advances in tissue and organ regeneration. Embryonic stem (ES) cell differentiation can be triggered by embryoid body (EB) formation, which involves ES cell aggregation in suspension. EB growth in the absence of leukaemia inhibitory factor (LIF) leads EBs to mimic early embryonic development, giving rise to markers representative of endoderm, mesoderm and ectoderm. Here, we have used microarrays to investigate differences in gene expression between 3 undifferentiated ES cell lines, and also between undifferentiated ES cells and Day 1–4 EBs     

Role of the transcriptional corepressor Bcor in embryonic stem cell differentiation and early embryonic development

Bcor (BCL6 corepressor) is a widely expressed gene that is mutated in patients with X-linked Oculofaciocardiodental (OFCD) syndrome. BCOR regulates gene expression in association with a complex of proteins capable of epigenetic modification of chromatin. These include Polycomb group (PcG) proteins, Skp-Cullin-F-box (SCF) ubiquitin ligase components and a Jumonji C (Jmjc) domain containing histone demethylase. To model OFCD in mice and dissect the role of Bcor in development we have characterized two loss of function Bcor alleles. We find that Bcor loss of function results in a strong parent-of-origin effect, most likely indicating a requirement for Bcor in extraembryonic development. Using Bcor loss of function embryonic stem (ES) cells and in vitro differentiation assays, we demonstrate that Bcor plays a role in the regulation of gene expression very early in the differentiation of ES cells into ectoderm, mesoderm and downstream hematopoietic lineages. Normal expression of affected genes (Oct3/4, Nanog, Fgf5, Bmp4, Brachyury and Flk1) is restored upon re-expression of Bcor. Consistent with these ES cell results, chimeric animals generated with the same loss of function Bcor alleles show a low contribution to B and T cells and erythrocytes and have kinked and shortened tails, consistent with reduced Brachyury expression. Together these results suggest that Bcor plays a role in differentiation of multiple tissue lineages during early embryonic development.     

The development of hormonal responses of cultured embryonic chick limb mesenchymal cells

Cells obtained from stage 24 chick limb buds were cultured and assayed for their ability to respond to exogenously supplied parathyroid hormone (PTH) as monitored by analysis of cellular cyclic AMP (cAMP). After 3–4 days in culture, these cells developed a striking responsiveness to the hormone; 20 -to 50-fold elevations in cAMP were routinely observed upon exposure to 10^?8, M hormone for 2 min. This response was greatest in cells initially plated at low densities (1 × 10⁶ cells/35-mm dish) and was inversely correlated to the amount of cartilage which developed in such cultures. Cells obtained from limbs of stages 23–26 embryos developed a similar responsiveness to PTH after 3–4 days in culture, but cells obtained from limbs of stage 22 embryos showed no such responsiveness even after 6 days in culture. A response to calcitonin also was noted in cultures of stage 24 limb mesenchymal cells after 4–5 days in culture, but this was of much smaller magnitude than the PTH response. Of 12 other hormones tested, only β agonists elicited any cAMP response in the cultered stage 24 limb mesenchymal cells. Although cells initially plated at a high density and grown for 8 days in culture show no response to PTH, the presence of PTH-responsive cells in such cultures could be demonstrated by sequential digestion with collagenase and replating the extracellular matrix-free cells released by this treatment. Such replated cells then exhibited a responsiveness to PTH. Thus, the responsiveness of cultured limb mesenchymal cells depends on the developmental stage of the starting limb mesenchyme, the phenotypes which develop, and physical factors such as accessibility to exogenously supplied hormone.     

Changes of glycoconjugate expression profiles during early development

A variety of glycoconjugates, including glycosphingolipids (GSLs), expressed in mammalian tissues and cells were isolated and characterized in early biochemical studies. Later studies of virus-transformed fibroblasts demonstrated the association of GSL expression profiles with cell phenotypes. Changes of GSL expression profile were observed during mammalian embryogenesis. Cell surface molecules expressed on embryos in a stage-specific manner appeared to play key roles in regulation of cell-cell interaction and cell sorting during early development. Many mAbs showing stage-specific reactivity with mouse embryos were shown to recognize carbohydrate epitopes. Among various stage-specific embryonic antigens (SSEAs), SSEA-1 was found to react with neolacto-series GSL Le^x, while SSEA-3 and SSEA-4 reacted with globo-series Gb5 and monosialyl-Gb5, respectively. GSL expression during mouse early development was shown to shift rapidly from globo-series to neolacto/lacto-series, and then to ganglio-series. We found that multivalent Le^x caused decompaction of mouse embryos, indicating a functional role of Le^x epitope in the compaction process. Autoaggregation of mouse embryonal carcinoma (EC) F9 cells provided a useful model of the compaction process. We showed that Le^x-Le^x interaction, a novel type of molecular interavction termed carbohydrate-carbohydrate interaction (CCI), was involved in cell aggregation. Similar shifting of GSL expression profiles from globo-series and neolacto/lacto-series to ganglio-series was observed during differentiation of human EC cells and embryonic stem (ES) cells, reflecting the essential role of cell surface glycoconjugates in early development.     

Salt-inducible kinase-mediated regulation of steroidogenesis at the early stage of ACTH-stimulation

Salt-inducible kinase (SIK), expressed in Y1 mouse adrenocortical tumor cells at an early stage of adrenocorticotropic hormone (ACTH)-stimulation, represses the cAMP-responsive element (CRE)-dependent gene expression of CYP11A and StAR by acting on bZIP domain of CRE-binding protein. ACTH induced the SIK’s nuclear to cytosolic translocation in a PKA-dependent manner. A mutant SIK in which the PKA-dependently phosphorylatable Ser577 had been replaced with Ala could not move out of the nucleus. The degree of CRE-reporter repression by SIK was strong as long as SIK was present in the nucleus. These indicated that intracellular translocation of SIK might be an important factor to determine the time-dependent change in the level of steroidogenic gene expression in ACTH-stimulated cells. Promoter analyses suggested that SIK repressed gene expressions not only of CYP11A and StAR but also of CYP11B1, CYP11B2 and SIK itself. We propose here that SIK is one of important molecule regulating expression of steroidogenic genes in the early phase of ACTH treatment.     

Proteomic profiles of embryonic development in the ascidian Ciona intestinalis

We report here proteomics-based protein profiles of three embryonic stages of the ascidian Ciona intestinalis. Two-dimensional gel electrophoresis revealed 416, 539, and 695 protein spots in the unfertilized eggs, 16 cell-stage embryos, and tadpole larvae, respectively. Comparative and quantitative analyses of the spot patterns identified proteins showing an increase or decrease in amount during embryonic development. Protein identification by MALDI-TOF/MS indicated not only the abundance and importance of metabolic enzymes and translation elongation factors but also the functional importance of actin-binding proteins and molecular chaperones during ascidian development. Global changes in spots for vitellogenin-like protein suggested post-translational modification or proteolytic digestion of this protein during embryogenesis. Comparison between mRNA and protein levels among unfertilized eggs, 16 cell-stage embryos and tadpole larvae indicated nonparallel expression patterns of genes and proteins. Ascidians provide an excellent system for studying gene expression and cell differentiation during development, and the present study should shed light on the associated molecular mechanism at the protein level.