Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Embryos”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed1993

Diagnosis of major chromosome aneuploidies in human preimplantation embryos.

A short fluorescence in-situ hybridization (FISH) procedure using fluorochrome and digoxigenin labelled DNA probes was developed for application in human preimplantation embryos in order to analyse the five chromosomes most involved in human aneuploidy (X, Y, 18, 13 and 21). The chromosomes were fluorescent-stained and detected simultaneously in 157 blastomeres from 30 human embryos. Successful FISH analysis was achieved in 93% of the blastomeres. Aberrations for these chromosomes were found in 70% of abnormally developing monospermic embryos. The majority of normally developing monospermic embryos obtained from older patients were also chromosomally abnormal. By analysing all or most of the cells from these embryos, true mosaicism was distinguished from technique failure. Mosaic embryos, polyploid embryos with ploidies as high as 8n, haploid embryos, embryos monosomic for 13/21 and for X, and embryos trisomic for 13/21 and 18, were common in abnormally developing embryos. In contrast, aneuploidy was the main chromosome abnormality found in normally developing monospermic embryos.

Adult↗
PubMed1994

The chromosome constitution of human preimplantation embryos fertilized in vitro.

The chromosome constitution of five haploid, 178 diploid and 11 triploid embryos fertilized in vitro was determined after fixation on day 2 or day 3 of development. Karyotype analysis of 178 diploid embryos revealed abnormalities in 40 (22.5%) cases: 34 (19.1%) aneuploids, four (2.2%) mosaic embryos and two (1.1%) structural anomalies were identified. The majority of aneuploid karyotypes (28/34) involved a single chromosome but six embryos had aneuploidy of two or three chromosomes. The E group was most frequently involved in aneuploid karyotypes (10/23 hyperdiploid embryos) and trisomy 16, the most common single anomaly in diploid embryos, was detected in 2.2% (4/178) of cases. Only one case of sex chromosome monosomy was identified. An excess of female karyotypes was detected in abnormal cases (sex ratio 0.48); this ratio was significantly (P < 0.05) different from that observed in normal cases (74:64, XY:XX). The incidence of aneuploidy increased with maternal age but this did not reach statistical significance. Embryo morphology and growth rate, assessed by embryo development rating (EDR), did not distinguish between normal (mean score 7.9; mean EDR 96.1) and aneuploid (mean score 8.1; mean EDR, 92.1) embryos. Numbers of hyperploid (n = 17) and hypoploid (n = 11) embryos (non-mosaic cases involving single chromosomes) were not statistically different. The relative proportions of chromosomes involved in trisomic karyotypes showed a remarkable similarity to the pattern in spontaneous abortions. Pronuclear status was an unreliable predictor of ploidy. Small numbers of karyotyped triploid embryos revealed equal proportions of XXX, XXY and XYY embryos.

Abortion, Spontaneous↗
PubMed2002

Nitric oxide synthase production and nitric oxide regulation of preimplantation embryo development.

Nitric oxide (NO) production plays an important role in regulating preimplantation embryo development. NO is produced from l-arginine by the enzyme nitric oxide synthase (NOS), which has three isoforms: endothelial (eNOS), neuronal (nNOS), and inducible (iNOS). It has been previously shown that inhibition of NO production by NG-nitro-l-arginine (l-NA) inhibits the development of two-cell embryos to the four-cell stage. However, excess NO also halts embryo development, possibly through the production of free radicals. We hypothesize that multiple NOS isoforms are expressed in order to ensure normal preimplantation embryo development and that, in this process, NO acts through the cGMP pathway. Using reverse transcription-polymerase chain reaction, mRNA for all three NOS isoforms was amplified from two-cell, four-cell, morula, and blastocyst embryos. However, blastocyst-stage embryos isolated midmorning on Day 4 of pregnancy expressed only nNOS and eNOS, whereas those isolated midafternoon again expressed all three NOS isoforms. Culture of one-cell embryos in various concentrations of Whitten (positive control), S-nitroso-N-acetylpenicillamine (SNP, a NO donor), l-NA, and/or 8-Br-cGMP demonstrated that NO is acting, at least in part, through cGMP in preimplantation embryo development. In addition, we determined that a critical concentration of NO and cGMP is required for normal embryo development and deviations from this concentration lead to developmental arrest and/or apoptosis of the embryo. This data provides support for a requirement of NO in preimplantation embryo development and one mechanism through which it regulates mitotic division in these embryos.

Animals↗
PubMed2003

Apoptosis and in vitro development of preimplantation porcine embryos derived in vitro or by nuclear transfer.

Apoptosis occurs during preimplantation development in both in vivo- and in vitro-produced embryos, and it may contribute to embryonic loss. The present study investigated the development of porcine nuclear transfer (NT) embryos reconstructed by using fetal fibroblasts as compared to embryos produced by in vitro fertilization (IVF). The onset and the frequency of apoptosis in NT and IVF embryos were examined via morphological and nuclear changes and TUNEL assay. The NT blastocysts had a similar number of nuclei as compared to IVF blastocysts and appeared to be morphologically similar. Relative to IVF embryos, the NT embryos had a lower cleavage rate (42.7% vs. 71.0%) and a lower developmental rate (11.1% vs. 28.6%) to the blastocyst stage. The earliest positive TUNEL signals were detected in the NT embryos on Day 5 of culture. The percentage of cells undergoing apoptosis in the NT embryos was higher than that of the IVF embryos and increased with time in vitro. Some of the abnormal morphological changes observed during early development related to apoptosis. Cytoplasmic fragmentation, developmental arrest, and nuclear condensation were typical characteristics of embryos undergoing apoptosis. Some mechanisms of the apoptotic pathway were triggered by changes in the NT embryos. The developmental rates of NT embryos might be improved by identifying specific apoptotic pathways and then intervening in these pathways to improve development.

Animals↗
PubMed1988

Noninvasive measurement of glucose uptake by two populations of murine embryos.

Glucose uptake was measured by a noninvasive fluorescence technique on a total of 165 morula- and blastocyst-stage murine embryos in two different culture media. Eighty-four embryos were tested in M2 medium, and the remaining 81 embryos were tested in M16. Embryos assayed in M2 took up significantly less glucose over the 4-h assay period than did embryos assayed in M16. The lower uptake of glucose by embryos in M2 corresponded with a decrease in the quality of embryos cultured overnight in M2 as judged by morphological criteria. Embryos that were judged to be degenerate or had gross abnormalities took up significantly less glucose than did normal embryos. Glucose uptake in both populations of embryos covered a wide range of values and was normally distributed. A significant effect between mothers was noted in glucose uptake for embryos assayed in both M16 and M2 media. The possible uses of noninvasive measures of glucose uptake as a test of embryo viability or for optimizing culture conditions are discussed.

Analysis of Variance↗
PubMed1990

Bovine 1-2-cell embryo development using a simple medium in three oviduct epithelial cell coculture systems.

These studies were designed to develop a coculture system using a simple medium to promote development of 1-cell bovine embryos through the 8-16-cell stage to morula and blastocyst stages. Monolayers for coculture were prepared from bovine oviduct epithelial cells (BOEC). In vivo-fertilized 1-2-cell embryos and ova (384) were surgically collected from superovulated cows. In Experiment 1, embryos cocultured in a simple glucose-free and serum-free medium (CZB) developed with superior scores of embryo quality than embryos cocultured in Ham's F-10 with serum, and a greater percentage developed past 8-16 cells than embryos cocultured in CMRL-1066 with serum (p less than 0.05). In Experiment 2, embryos cocultured with fresh BOEC monolayers averaged more (p less than 0.05) cells than did embryos in coculture with frozen-thawed BOEC monolayers or in BOEC-conditioned medium. Without glucose in the simple medium for the first 48 h of culture, more embryos blastulated (p less than 0.01) by Day 5.5 of culture (Day 6.5 of donor's estrous cycle) than embryos in the same medium with glucose present throughout. In Experiment 3, more embryos tended to hatch in BOEC coculture (p less than 0.10) than in conditioned medium. These results show that a chemically simple medium with fresh BOEC monolayers can provide a significant benefit for coculture of early bovine embryos.

Animals↗
PubMed1994

Analysis of polarity of bovine and rabbit embryos by scanning electron microscopy.

Cellular polarization during preimplantation development of the embryo is believed to be a crucial event in the transition of a zygote to a blastocyst stage embryo with morphologically and functionally differentiated cell types. While extensive studies have been done on polarity development in mouse embryos, little information is available in other species, particularly in cattle. The objective of this study was to examine the initiation of polarity by microvilli distribution on blastomeres of cattle and rabbit embryos using scanning electron microscopy (SEM). Bovine embryos were obtained by in vitro fertilization of in vitro-matured follicular oocytes. Rabbit embryos of various stages were collected from superovulated rabbits. Intact embryos and isolated blastomeres were examined in both species. Blastomeres from 1- to 8-cell embryos in both cattle and rabbits showed no polarity. The onset of transitional polarization of microvillous distribution occurred in some blastomeres of cattle embryos at the 9- to 15-cell stage; but typical, distinct polarity was not manifested until after the 16-cell stage with approximately 40% polar cells per embryo. In the rabbit blastomere polarity occurred one cell cycle later, with 46% polar cells per embryo after the 32-cell stage. The difference in cell numbers at the time polarity is evident is probably related to the different cell stages for embryo compaction and blastocyst formation in the two species.

Animals↗
PubMed2000

Oxidative phosphorylation-dependent and -independent oxygen consumption by individual preimplantation mouse embryos.

The self-referencing electrode technique was employed to noninvasively measure gradients of dissolved oxygen in the medium immediately surrounding developing mouse embryos and, thereby, characterized changes in oxygen consumption and utilization during development. A gradient of depleted oxygen surrounded each embryo and could be detected >50 microm from the embryo. Blastocysts depleted the surrounding medium of 0.6+/-0.1 microM of oxygen, whereas early cleavage stage embryos depleted the medium of only 0.3+/-0.1 microM of oxygen, suggesting a twofold increase in oxygen consumption at the blastocyst stage. Mitochondrial oxidative phosphorylation (OXPHOS) accounted for 60-70% of the oxygen consumed by blastocysts, while it accounted for only 30% of the total oxygen consumed by cleavage-stage embryos. The amount of oxygen consumed by non-OXPHOS mechanisms remained relatively constant throughout preimplantation development. By contrast, the amount of oxygen consumed by OXPHOS in blastocysts is greater than that consumed by OXPHOS in cleavage-stage embryos. The amount of oxygen consumed by one-cell embryos was modulated by the absence of pyruvate from the culture medium. Treatment of one-cell embryos and blastocysts with diamide, an agent known to induce cell death in embryos, resulted in a decline in oxygen consumption, such that the medium surrounding dying embryos was not as depleted of oxygen as that surrounding untreated control embryos. Together these results validate the self-referencing electrode technique for analyzing oxygen consumption and utilization by preimplantation embryos and demonstrate that changes in oxygen consumption accompany important physiological events, such as development, response to medium metabolites, or cell death.

Animals↗
PubMed2000

Analysis of mRNA levels for the MHC class I-like molecules CD1 and FcRn in preimplantation mouse embryos.

PROBLEM: Major histocompatibility complex (MHC) antigens expressed on preimplantation embryos are important for the control of development, reproduction, and allo-recognition of the embryo by the mother. Four types of MHC class I and MHC class I-like antigens have recently been defined: class Ia, class Ib, class Ic, and class Id, based on their similar three-dimensional protein structures. Class Ia and class Ib antigens are encoded in the MHC, whereas class Ic and class Id antigens are encoded by genes on other chromosomes. Both class Ia and class Ib MHC antigens are expressed on preimplantation mouse embryos. The function of the class Ia antigens on embryos is unknown, but the function of one class Ib antigen, Qa-2, the product of the Ped gene, has been found to control the rate of early cleavage division and subsequent embryo survival. The expression of class Ic and class Id antigens on preimplantation embryos has not yet been evaluated. In the present study, we report the analysis of mRNA expression of two class Id genes, CD1 and FcRn, in preimplantation mouse embryos. METHOD OF STUDY: A reverse transcription-polymerase chain reaction (RT-PCR) assay was performed to analyze mRNA levels for CD1 and FcRn in 1-cell, 2-cell, 8-cell, and blastocyst stage embryos from C57BL/6 mice. RESULTS: No expression of CD1 mRNA was found in any of the preimplantation embryos tested. As a by-product of this study, we found a mistake in the published sequence of the mouse CD1 gene: nucleotide 746 in the cDNA is a G not a C. This base change is in a site recognized by the restriction enzyme PstI, thereby eliminating a PstI cleavage site. Expression of mRNA for FcRn was found in all preimplantation stages tested. Higher levels of mRNA for FcRn were detectable in 2-cell and 8-cell embryos compared to 1-cell and blastocyst stage embryos. CONCLUSION: This study shows that mRNA for FcRn but not for CD1 is found in preimplantation mouse embryos.

Animals↗
PubMed1995

Increased number of cells and metabolic activity in male human preimplantation embryos following in vitro fertilization.

The number of cells and metabolic activity of male and female human preimplantation embryos were examined to determine whether male embryos are more advanced than female embryos following in vitro fertilization (IVF). The metabolic activity of embryos fertilized normally was assessed daily by non-invasive measurement of pyruvate and glucose uptake and lactate production between days 2 and 6 after insemination. On day 6, the numbers of nuclei from the trophectoderm and inner cell mass of blastocysts were counted by differential labelling and fluorescence microscopy. Nuclei were then recovered and the sex of the embryos identified using nested primers to amplify the amelogenin gene and pseudogene sequences on the X and Y chromosomes, respectively. Development of male and female embryos were then compared retrospectively. From 69 of 178 (39%) embryos that developed to the blastocyst stage, the sex of 57 was determined; 21 (37%) were male and 36 (63%) female. The number of cells in male embryos was significantly greater on day 2 (P < 0.005), and this difference was maintained up to the blastocyst stage (in both the trophectoderm and the inner cell mass), although differences were not always significant. Pyruvate uptake was significantly higher by male embryos between days 2 and 5 (P < 0.05). Glucose uptake and lactate production were significantly higher in male embryos on days 4-5 (P < 0.05); this difference was not significant on days 5-6. Extrapolation from differences in the number of cells indicates that female embryos are approximately 4.5 h delayed in their development from day 2 onwards compared with male embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Blastocyst↗
PubMed1998

Microscopic analysis of enzyme activity, mitochondrial distribution and hydrogen peroxide in two-cell rat embryos.

A developmental block is induced by phosphate in rat embryos at the late two-cell stage. The present study was designed to examine the energy metabolism of rat two-cell blocked and non-blocked embryos. Enzyme activity was measured in individual embryos by histochemical techniques. The activities of malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, pyruvate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, and phosphorylase did not differ among non-blocked and blocked embryos. However, the activity of succinate dehydrogenase was significantly decreased in blocked embryos compared with non-blocked embryos. In blocked embryos, cytochrome oxidase activity was distributed homogeneously, but was located at the perinuclear region in non-blocked embryos. Active mitochondrial organization was visualized using the fluorescent probe rhodamine 123 and laser scanning confocal microscopy. In both non-blocked and blocked embryos, mitochondria were distributed homogeneously. The concentration of H2O2 measured fluorometrically in embryos cultured without phosphate did not change significantly during the culture period, but decreased in embryos cultured with phosphate. The timing corresponded to the occurrence of the two-cell block. In summary, these results suggest that the developmental block in rat two-cell embryos is induced by disturbance of mitochondrial energy metabolism.

Animals↗
PubMed2001

Relationship between maternal endocrine environment, early embryo development and inhibition of the luteolytic mechanism in cows.

In this study, the relationship between maternal hormone environment and early embryo development in mature non-lactating Holstein-Friesian cows was investigated. Animals were inseminated at either 72 or 96 h after prostaglandin injection (n = 23) or were left as uninseminated controls (n = 10). Plasma samples were collected once a day from the first day of insemination (day 1) until day 16, when the cows underwent an oxytocin challenge, and were then slaughtered and their reproductive tracts removed. The tracts were flushed to collect embryos and the flushes were measured for interferon tau (IFN-tau) activity. Inseminated cows without an embryo on day 16 (n = 5) underwent both delayed ovulation (indicated by delayed decrease in oestradiol concentrations) and a delayed increase in progesterone concentrations after ovulation compared with cows with an embryo on day 16 (n = 15). Within the group of cows with an embryo, those with poorly developed embryos producing undetectable concentrations of IFN-tau (n = 7) had similar oestradiol profiles but underwent a delayed progesterone increase after ovulation compared with cows with well developed embryos producing measurable quantities of IFN-tau (n = 8). In the cows with an embryo, the plasma concentration of 13,14-dihydro-15-keto PGF2a, the principal metabolite of PGF2a, after injection of oxytocin was lower than that of control cows and cows without an embryo. However, when the cows with an embryo were compared on the basis of production of embryonic IFN-tau, the PGF2a response to oxytocin was attenuated completely in cows that had measurable IFN-tau activity, whereas a response of similar magnitude to that in control cows and cows without an embryo was observed in those with undetectable IFN-tau activities. In conclusion, the successful maternal recognition of pregnancy in cows depends on the presence of a sufficiently well developed embryo producing sufficient quantities of IFN-tau, which is, in turn, dependent on an appropriate pattern of maternal progesterone secretion.

Animals↗
PubMed1991

Diabetic environment and genetic predisposition as causes of congenital malformations in NOD mouse embryos.

Congenital malformations such as neural tube defects and a kinky or waved vertebral column were observed at higher incidence in embryos from nonobese diabetic (NOD) female mice with overt diabetes (NOD-D; 40.3%, P less than 0.005) or without overt diabetes (NOD-N; 8.4%, P less than 0.05) than in control Institute of Cancer Research (ICR) mouse embryos (1%) at day 13 of gestation. In vivo and in vitro preimplantation development of NOD-N, NOD-D, and ICR embryos did not differ in rate of development, size, or morphology. Embryos cultured from one-cell to early blastocyst stage were mutually transferred to uterine horns of pseudopregnant females between NOD-D and ICR mice and examined at day 13 of gestation. There were significant decreases in ratios of implantation and of viable embryos in ICR embryos transferred to NOD-D recipients (52%, P less than 0.001 and 14%, P less than 0.001, respectively) compared with those ratios in ICR embryos transferred to ICR uteri (79.2 and 56.2%) or those in NOD-D embryos transferred to ICR uteri (70.3 and 33.1%). Furthermore, 18 of 45 viable ICR embryos transferred to NOD-D dams had malformations, whereas there were no malformations in 73 viable ICR embryos transferred to ICR recipients, suggesting deleterious effects of maternal diabetic environment to embryos. On the other hand, 8 of 58 viable NOD-D embryos that were cultured in vitro and transferred to ICR uteri had malformations such as neural tube defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Effect of time of insemination on number of accessory sperm, fertilization rate, and embryo quality in nonlactating dairy cattle.

Two experiments were conducted to determine the effect of insemination time on number of accessory sperm per embryo (ovum), fertilization rate, and embryo quality. Semen was collected from three fertile Holstein bulls and cryopreserved in egg yolk-citrate-glycerol. In experiment 1, cows were continuously monitored for behavioral estrus by the HeatWatch estrous detection system and were artificially inseminated (AI) with one 0.5-ml straw (25 x 10(6) sperm) at the onset of estrus (AI 0 h), 12 h after onset (AI 12 h), or received natural service at 0 h (Nat 0 h) from one of three bulls. From 150 inseminations, 115 embryos and ova (AI 0 h: n = 39; AI 12 h: n = 39; Nat 0 h: n = 37) were recovered 6 or 7 d after insemination. Fertilization rates differed between treatments (AI 0 h: 67%; AI 12 h: 79%; Nat 0 h: 98%). Median accessory sperm per embryo (ovum) also differed (AI 0 h: 1; AI 12 h: 10; and Nat 0 h: 27) and paralleled the fertilization rate. Embryo quality was not affected by insemination time or natural service. In experiment 2, cows received AI at 0, 12, or 24 h (AI 24 h) after the onset of estrus as determined by HeatWatch. From 154 inseminations, 117 embryos and ova (AI 0 h: n = 39; AI 12 h: n = 39; AI 24 h: n = 39) were recovered 6 or 7 d after insemination. Fertilization rates did not differ in experiment 2 (AI 0 h: 66%; AI 12 h: 74%; AI 24 h: 82%); however, a trend toward a higher fertilization rate accompanied AI 24 h. Median accessory sperm values increased from AI 0 h (1) to AI 24 h (4). Embryo quality declined with AI at increasing intervals after onset of estrus, as percentages of excellent and good, fair and poor, and degenerate embryos were as follows: 77, 15, 8; 52, 38, 10; and 47, 19, 34 for the 0-, 12-, and 24-h inseminations, respectively. Results indicate AI 12 h after the onset of estrus provides a compromise between potential fertilization failure (AI 0 h) and embryo failure (AI 24 h), despite increased accessory sperm per embryo (ovum) after AI 24 h. Artificial insemination 12 h after onset of estrus should optimize fertility of dairy cattle through an acceptable fertilization rate, number of accessory sperm per embryo, and desirable embryo quality.

Animals↗
PubMed1994

Effects of time of deoxyribonucleic acid microinjection on gene detection and in vitro development of bovine embryos.

In vivo fertilized embryos were surgically collected from superovulated dairy cows to evaluate microinjection on embryo development and utilized the polymerase chain reaction technique for selection of transgenic embryos. Seventy-two percent of the embryos with visible pronuclei or nuclei were microinjected with DNA, and the remaining 28% served as uninjected controls. All embryos were cocultured with bovine oviductal epithelial cells. Mean final development scores of embryos within the same initial cell stage at collection were unaffected by microinjection. After 144 h of culture, 45% of the microinjected embryos developed to the morula or blastocyst stage. The transgene was detected in 50, 10, and 9% of demimorulae from embryos microinjected at the 1-, 2-, and 4-cell stages. Frequency of transgene detection was higher in morulae from 1-cell embryos than in morulae from 2- and 4-cell embryos. Use of in vitro coculture, embryo bisection, and polymerase chain reaction technique facilitated selection of bovine embryos that carried the transgene.

Animals↗
PubMed1990

Expression of beta-galactosidase in preimplantation ovine and porcine embryos.

Knowledge regarding the timing of embryonic expression of the mammalian genome is of relevance for the development of preimplantation diagnostic methods for human genetic diseases. For development of preimplantation diagnosis of lysosomal storage diseases, it will be necessary to know at which embryonic stage the genes for lysosomal enzymes are expressed. In previous studies by other investigators, it has been shown that lysosomal alpha- and beta-galactosidase and beta-glucuronidase in murine embryos increase 50- to 100-fold in activity between the two-cell and late blastocyst stage. We describe here expression of lysosomal beta-galactosidase in preimplantation ovine (two-cell through midblastocyst) and porcine (two-cell through late blastocyst) embryos. Expression of beta-galactosidase in ovine and porcine preimplantation embryos followed a similar rate of increase as that described for murine embryos. Activity of beta-galactosidase increased over 10-fold between the two- to four-cell and midblastocyst stages in ovine embryos, and 300-fold between the two- to four-cell and late blastocyst stages in porcine embryos. Activity expressed on a per cell basis was relatively constant in ovine embryos, as has been described in murine embryos, and increased approximately 5-fold on a per cell basis in porcine embryos. Activity of beta-galactosidase in ovine and porcine embryos initially was greater than 12-fold on a per cell or per embryo basis than in murine embryos evaluated. The knowledge of beta-galactosidase embryonic expression may provide the basis for preimplantation diagnosis of genetic beta-galactosidase deficiency in these species.

Animals↗
PubMed2001

Chronic effects of silver exposure on ion levels, survival, and silver distribution within developing rainbow trout (Oncorhynchus mykiss) embryos.

Rainbow trout embryos were chronically exposed to silver (as AgNO3) in moderately hard water (120 mg CaCO3/L, 0.70 mM Cl-, 1.3 mg/L dissolved organic matter. 12.3+/-0.1 degrees C) at nominal concentrations of 0.1, 1, and 10 microg/L (measured = 0.117+/-0.008, 1.22+/-0.16, and 13.51+/-1.58 microg/L, respectively) to investigate the effects on mortality, ionoregulation, and silver uptake and distribution of the embryo. Mortalities in the low concentrations (0.1 and 1.2 microg/L) were not significantly different from controls throughout embryonic development (days 1-32 postfertilization). Mortalities of embryos in the 13.5-microg/L treatment reached 56% by day 32 postfertilization (33% when accounting for control mortality), by which time more than 50% of surviving embryos had hatched. Accumulation of silver in whole embryos of 1.2- and 13.5-microg/L treatments reached the highest concentrations of 0.13 and 0.24 microg/g total silver, respectively, by day 32, but whole embryo silver burden was not correlated with mortality. Silver concentrations in different compartments of the whole embryo (chorion, dissected embryo, and yolk) were greatest just before hatch and were higher in the chorion for all experimental treatments. Up to 85% of total whole embryo silver content was bound to the chorion, which acts as a protective barrier during silver exposure. Whole embryo Na+ concentration in the 13.5-microg/L treatment was significantly reduced relative to controls from days 23 to 32 postfertilization, and levels in the embryo were reduced by 40% at day 32 postfertilization, indicating that silver toxicity in the whole embryo is associated with an ion regulatory disturbance that is similar to the acute effect of AgNO3 in juvenile and adult trout.

Animals↗
PubMed2006

[Tolerance of Huso dauricus embryo at its different development stages to low temperature].

This paper studied the embryo hatching rate and larva survival rate of Huso dauricus when the embryo at its different development stages was exposed to low temperature for different durations. The results showed that the embryo at its yolk plug, narrow-opening, and neural block closing stages could not survive at 2 - 8 degrees C over 24 h. When exposed to 2 - 8 degrees C for 3 days, the hatching rate of embryo at its cleavage, early blastula, and mid gastrula stages was lower than 30%. Both the embryo hatching rate and the larva survival rate were higher than 70% when the embryo at its late blastula, early blastula, optic rudiment, tail bud, heart beating, and tail touching head stages was exposed to 5 - 8 degrees C for 3 days. The death rates of embryo and larva under low temperature were increased with time. There was a negative correlation between the exposure duration at low temperature and the embryo hatching rate (r = - 0.8024) and larva survival rate (r = - 0.8468) of H. dauricus. The embryo at its late blastula, early gastrula, and optic rudiment stages had a stronger tolerance at 5 degrees C for 10 h, with the embryo hatching rate and larva survival rate being higher than 70%. It could be concluded that there was a little difference in embryo hatching rate and larva survival rate of H. dauricus when the embryo at its some development stages was preserved at low temperatures at least for 10 - 15 days and at normal temperature (16 - 17 degrees C).

Animals↗