scholarly journals Preimplantation development in ungulates: a ‘ménage à quatre’ scenario

Reproduction ◽  
2020 ◽  
Vol 159 (3) ◽  
pp. R151-R172 ◽  
Author(s):  
Jérôme Artus ◽  
Isabelle Hue ◽  
Hervé Acloque
Keyword(s):  
Embryonic Development ◽  
Inner Cell Mass ◽  
Current Knowledge ◽  
Cell Mass ◽  
Extended Period ◽  
The Body ◽  
Critical Function ◽  
Embryonic Tissues ◽  
Wide Range ◽  
Implantation Period

In ungulates, early embryonic development differs dramatically from that of mice and humans and is characterized by an extended period of pre- and peri-implantation development in utero. After hatching from the zona pellucida, the ungulate blastocyst will stay free in the uterus for many days before implanting within the uterine wall. During this protracted peri-implantation period, an intimate dialog between the embryo and the uterus is established through a complex series of paracrine signals. The blastocyst elongates, leading to extreme growth of extra-embryonic tissues, and at the same time, the inner cell mass moves up into the trophoblast and evolves into the embryonic disc, which is directly exposed to molecules present in the uterine fluids. In the peri-implantation period, uterine glands secrete a wide range of molecules, including enzymes, growth factors, adhesion proteins, cytokines, hormones, and nutrients like amino and fatty acids, which are collectively referred to as histotroph. The identification, role, and effects of these secretions on the biology of the conceptus are still being described; however, the studies that have been conducted to date have demonstrated that histotroph is essential for embryonic development and serves a critical function during the pre- and peri implantation periods. Here, we present an overview of current knowledge on the molecular dialogue among embryonic, extraembryonic, and maternal tissues prior to implantation. Taken together, the body of work described here demonstrates the extent to which this dialog enables the coordination of the development of the conceptus with respect to the establishment of embryonic and extra-embryonic tissues as well as in preparation for implantation.

scholarly journals Onco-Receptors Targeting in Lung Cancer via Application of Surface-Modified and Hybrid Nanoparticles: A Cross-Disciplinary Review

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 621
Author(s):  
Fakhara Sabir ◽  
Maimoona Qindeel ◽  
Mahira Zeeshan ◽  
Qurrat Ul Ain ◽  
Abbas Rahdar ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Targeted Delivery ◽  
Current Knowledge ◽  
Folate Receptor ◽  
Delivery Systems ◽  
Chemotherapeutic Agents ◽  
The Body ◽  
Hybrid Nanoparticles ◽  
Wide Range ◽  
Surface Modified

Lung cancer is among the most prevalent and leading causes of death worldwide. The major reason for high mortality is the late diagnosis of the disease, and in most cases, lung cancer is diagnosed at fourth stage in which the cancer has metastasized to almost all vital organs. The other reason for higher mortality is the uptake of the chemotherapeutic agents by the healthy cells, which in turn increases the chances of cytotoxicity to the healthy body cells. The complex pathophysiology of lung cancer provides various pathways to target the cancerous cells. In this regard, upregulated onco-receptors on the cell surface of tumor including epidermal growth factor receptor (EGFR), integrins, transferrin receptor (TFR), folate receptor (FR), cluster of differentiation 44 (CD44) receptor, etc. could be exploited for the inhibition of pathways and tumor-specific drug targeting. Further, cancer borne immunological targets like T-lymphocytes, myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), and dendritic cells could serve as a target site to modulate tumor activity through targeting various surface-expressed receptors or interfering with immune cell-specific pathways. Hence, novel approaches are required for both the diagnosis and treatment of lung cancers. In this context, several researchers have employed various targeted delivery approaches to overcome the problems allied with the conventional diagnosis of and therapy methods used against lung cancer. Nanoparticles are cell nonspecific in biological systems, and may cause unwanted deleterious effects in the body. Therefore, nanodrug delivery systems (NDDSs) need further advancement to overcome the problem of toxicity in the treatment of lung cancer. Moreover, the route of nanomedicines’ delivery to lungs plays a vital role in localizing the drug concentration to target the lung cancer. Surface-modified nanoparticles and hybrid nanoparticles have a wide range of applications in the field of theranostics. This cross-disciplinary review summarizes the current knowledge of the pathways implicated in the different classes of lung cancer with an emphasis on the clinical implications of the increasing number of actionable molecular targets. Furthermore, it focuses specifically on the significance and emerging role of surface functionalized and hybrid nanomaterials as drug delivery systems through citing recent examples targeted at lung cancer treatment.

P–530 The use of wide thresholds for detecting intermediate chromosomal CNV up to 80% doesn’t improve PGT-A ability to discriminate true mosaic from uniformly aneuploid embryos

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
L Girardi ◽  
M Serdaroğulları ◽  
C Patassini ◽  
S Caroselli ◽  
M Costa ◽  
...  
Keyword(s):  
Inner Cell Mass ◽  
False Negative ◽  
Cell Mass ◽  
Categorical Variables ◽  
P Value ◽  
Sequencing Data ◽  
Preimplantation Genetic Testing ◽  
Exact Test ◽  
Institutional Review ◽  
Wide Range

Abstract Study question What is the effect of varying diagnostic thresholds on the accuracy of Next Generation Sequencing (NGS)-based preimplantation genetic testing for aneuploidies (PGT-A)? Summary answer When single trophectoderm biopsies are tested, the employment of 80% upper threshold increases mosaic calls and false negative aneuploidy results compared to more stringent thresholds. What is known already Trophectoderm (TE) biopsy coupled with NGS-based PGT-A technologies are able to accurately predict Inner Cell Mass’ (ICM) constitution when uniform whole chromosome aneuploidies are considered. However, minor technical and biological inconsistencies in NGS procedures and biopsy specimens can result in subtle variability in analytical results. In this context, the stringency of thresholds employed for diagnostic calls can lead to incorrect classification of uniformly aneuploid embryos into the mosaic category, ultimately affecting PGT-A accuracy. In this study, we evaluated the diagnostic predictivity of different aneuploidy classification criteria by employing blinded analysis of chromosome copy number values (CNV) in multifocal blastocyst biopsies. Study design, size, duration The accuracy of different aneuploidy diagnostic cut-offs was assessed comparing chromosomal CNV in intra-blastocysts multifocal biopsies. Enrolled embryos were donated for research between June and September 2020. The Institutional Review Board at the Near East University approved the study (project: YDU/20l9/70–849). Embryos diagnosed with uniform chromosomal alterations (single or multiple) in their clinical TE biopsy (n = 27) were disaggregated into 5 portions: the ICM and 4 TE biopsies. Overall, 135 specimens were collected and analysed. Participants/materials, setting, methods Twenty-seven donated blastocysts were warmed and disaggregated in TE biopsies and ICM (n = 135 biopsies). PGT-A analysis was performed using Ion ReproSeq PGS kit and Ion S5 sequencer (ThermoFisher). Sequencing data were blindly analysed with Ion-Reporter software. Intra-blastocyst comparison of raw NGS data was performed employing different thresholds commonly used for aneuploidy classification. CNV for each chromosome were reported as aneuploid according to 70% or 80% thresholds. Categorical variables were compared using Fisher’s exact test. Main results and the role of chance In this study, a total of 50 aneuploid patterns in 27 disaggregated embryos were explored. Single TE biopsy results were considered as true positive when they displayed the same alteration detected in the ICM at levels above the 70% or 80% thresholds. Alternatively, alterations detected in the euploid or mosaic range were considered as false negative aneuploidy results. When the 70% threshold was applied, aneuploidy findings were confirmed in 94.5% of TE biopsies analyzed (n = 189/200; 95%CI=90.37–37.22), while 5.5% showed a mosaic profile (50–70%) but uniformly abnormal ICM. Positive (PPV) and negative predictive value (NPV) per chromosome were 100.0% (n = 189/189; 95%CI=98.07–100.00) and 99.5% (n = 2192/2203; 95%CI=99.11–99.75) respectively. When the upper cut-off was experimentally placed at 80% of abnormal cells, a significant decrease (p-value=0.0097) in the percentage of confirmed aneuploid calls was observed (86.5%; n = 173/200; 95%CI=80.97–90.91), resulting in mosaicism overcalling, especially in the high range (50–80%). Less stringent thresholds led to extremely high PPV (100.0%; n = 173/173; 95%CI=97.89–100.00), while NPV decreased to 98.8% (n = 2192/2219; 95%CI=98.30–99.23). Furthermore, no additional true mosaic patterns were identified with the use of wide range thresholds for aneuploidy classification. Limitations, reasons for caution This approach involved the analysis of aneuploidy CNV thresholds at the embryo level and lacked from genotyping-based confirmation analysis. Moreover, aneuploid embryos with known meiotic partial deletion/duplication were not included. Wider implications of the findings: The use of wide thresholds for detecting intermediate chromosomal CNV up to 80% doesn’t improve PGT-A ability to discriminate true mosaic from uniformly aneuploid embryos, lowering overall diagnostic accuracy. Hence, a proportion of the embryos diagnosed as mosaic using wide calling thresholds may actually be uniformly aneuploid and inadvertently transferred. Trial registration number N/A

Changes in the properties of the developing trophoblast of preimplantation mouse embryos as revealed by aggregation studies

Development ◽  
1977 ◽  
Vol 40 (1) ◽  
pp. 143-157
Author(s):  
Paul S. Burgoyne ◽  
Thomas Ducibella
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Supporting Cell ◽  
Mouse Embryos ◽  
Mixed Cell ◽  
Time Period ◽  
Preimplantation Mouse Embryos ◽  
Wide Range ◽  
Preimplantation Mouse

Mouse embryos (8-cell to early blastocyst) were denuded with pronase, and apposed in pairs which represented a wide range of stage combinations. These pairs either formed aggregates which differentiated into double-sized blastocysts, or they failed to aggregate. The 8–16-cell stages would not envelop late morulae/early blastocysts to form layered aggregates. This must mean that as the embryo differentiates into a blastocyst, the outer surface of the trophoblast loses its capacity for supporting cell spreading. The aggregation data also demonstrate that embryos almost completely lose their potential for aggregation at a very discrete stage in development – namely, between 8 and 9 h before blastocoel formation. It is argued that this is the stage at which the zonular tight junctional seal is completed, and that it is this physical barrier which prevents aggregation. It has been argued previously that the zonular tight junctional seal allows the creation of the special microenvironment which is necessary for the determination of the inner cells as inner cell mass. The completion of this seal 8–9 h before it is required for the formation of a blastocoel would provide a suitable time period for this cell determination to occur. The results obtained also relate to the technique of chimera production. Since the aim of this technique is to generate mice with mixed cell populations, it is important that the blastocyst formed following aggregation should have both cell lines present in the inner cell mass. This can best be assured by using relatively late morula stages (75 h post-HCG injection) since these will have already segregated their inner cells, but the incomplete seal will still allow aggregation to take place.

scholarly journals Importance of Dietary Phosphorus for Bone Metabolism and Healthy Aging

Nutrients ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 3001
Author(s):  
Juan Serna ◽  
Clemens Bergwitz
Keyword(s):  
Bone Metabolism ◽  
Inorganic Phosphate ◽  
Healthy Aging ◽  
Current Knowledge ◽  
Atp Synthesis ◽  
The Body ◽  
Endocrine Regulation ◽  
Critical Function ◽  
Dietary Phosphorus ◽  
Different Tissues

Inorganic phosphate (Pi) plays a critical function in many tissues of the body: for example, as part of the hydroxyapatite in the skeleton and as a substrate for ATP synthesis. Pi is the main source of dietary phosphorus. Reduced bioavailability of Pi or excessive losses in the urine causes rickets and osteomalacia. While critical for health in normal amounts, dietary phosphorus is plentiful in the Western diet and is often added to foods as a preservative. This abundance of phosphorus may reduce longevity due to metabolic changes and tissue calcifications. In this review, we examine how dietary phosphorus is absorbed in the gut, current knowledge about Pi sensing, and endocrine regulation of Pi levels. Moreover, we also examine the roles of Pi in different tissues, the consequences of low and high dietary phosphorus in these tissues, and the implications for healthy aging.

109 EFFECTS OF LIPOLYTIC AGENTS FORSKOLIN, EPINEPHRINE AND CAFFEINE ON EMBRYONIC DEVELOPMENT AND LIPID CONTENT OF BOVINE EMBRYOS PRODUCED IN VITRO

2009 ◽  
Vol 21 (1) ◽  
pp. 154 ◽  
Author(s):  
M. Barcelo-Fimbres ◽  
G. E. Seidel
Keyword(s):  
Amino Acids ◽  
Fatty Acid ◽  
Embryonic Development ◽  
Lipid Content ◽  
Lipid Accumulation ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Nile Red ◽  
Essential Amino Acids

The objective of this experiment was to evaluate lipid accumulation and embryonic development of bovine morulae treated with different chemicals. A total of 2619 slaughterhouse oocytes from heifers and mature cows were matured in CDM medium (similar to SOF) plus 0.5% fatty acid-free BSA and hormones (M-CDM) for 23 h at 38.5°C in 5% CO2 in air. Frozen–thawed sperm were centrifuged through a Percoll gradient and co-cultured with matured oocytes for 18 h in F-CDM (CDM+heparin). Zygotes were cultured at 38.5°C in 5% CO2/5% O2/90% N2 in CDM-1 with nonessential amino acids, 10 μm EDTA, 0.5% fatty acid free BSA, and 0.5 mm fructose. After 60 h, resulting 8-cell embryos were cultured 120 h in CDM-2 (CDM-1+essential amino acids and 2 mm fructose). A factorial design was used with 7 treatments, 2 ovary sources (cows v. heifers), and 3 bulls (A, B and C) replicated twice for each bull (6 replicates). At Day 2.5 embryo cleavage and 8-cell rates were evaluated, and on Day 6 a total of 755 morulae were randomly assigned to the 7 treatments (control, 2 and 8 mm caffeine, 1 and 4 μm epinephrine, and 10 and 40 μm forskolin). To quantify lipid accumulation, Day 7 blastocysts were fixed and stained with 1 μg mL–1 Nile red dye, after which a digital photograph of the equatorial part of the embryo (including the inner cell mass) was taken at 200×, and fluorescence intensity was measured with Image Pro software from 0 to 255 shades for each pixel (0 = no lipids; 255 = greatest lipid accumulation), as previously reported (Biol. Reprod. 2007 (Suppl. 1), 87–88). Data were analyzed by ANOVA. No differences in cleavage rates (75 v. 68 ± 3.6%) or eight cell rates (61 ± v. 57 ± 2.8%) were found for heifer v. cow oocytes (P > 0.1); however, blastocyst rates per oocyte and per 8-cell embryo were greater for cows than heifers (20 v. 10 ± 2.1%, and 68 v. 35 ± 3.8%, respectively; P < 0.05). Treatments: 2 and 8 mm caffeine produced fewer blastocysts per morula than 1 and 4 μm epinephrine, 10 and 40 μm forskolin and the control (39, 5 v. 54, 49, 48, 54 and 52 ± 5.8%; respectively) (P < 0.01). More lipid content was found in whole embryos and trophoblast of heifer-derived than cow blastocysts (P < 0.05), and forskolin resulted in less lipid content than control, caffeine- and epinephrine-treated morulae in whole embryos, embryonic mass and trophoblasts (P < 0.05; Table 1). In conclusion, mature cows were a better source of oocytes than feedlot heifers for embryonic development. High doses of caffeine were detrimental to embryos, and the addition of the lypolitic agent forskolin reduced lipid content relative to control, caffeine and epinephrine-treated embryos. Table 1.Main effect treatment means of lipid content (arbitrary fluorescence units)

scholarly journals Live visualisation of electrolytes during mouse embryonic development using electrolyte indicators

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0246337
Author(s):  
Akiko Fujishima ◽  
Kazumasa Takahashi ◽  
Mayumi Goto ◽  
Takeo Hirakawa ◽  
Takuya Iwasawa ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Atpase Activity ◽  
Developmental Stage ◽  
Direct Contact ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Mouse Embryos ◽  
Cell Physiology ◽  
Intracellular Electrolyte Concentrations ◽  
Corona Green

Studies have shown that some electrolytes, including Na+ and K+, play important roles in embryonic development. However, these studies evaluated these electrolytes by using inhibitors or knockout mice, with no mention on the changes in the intracellular electrolyte concentrations during embryogenesis. In this study, we used the electrolyte indicators CoroNa Green AM and ION Potassium Green-2 AM to directly visualise intracellular concentrations of Na+ and K+, respectively, at each embryonic developmental stage in mouse embryos. We directly observed intracellular electrolyte concentrations at the morula, blastocyst, and hatching stages. Our results revealed dynamic changes in intracellular electrolyte concentrations; we found that the intracellular Na+ concentration decreased, while K+ concentration increased during blastocoel formation. The degree of change in intensity in response to ouabain, an inhibitor of Na+/K+ ATPase, was considered to correspond to the degree of Na+/K+ ATPase activity at each developmental stage. Additionally, after the blastocyst stage, trophectoderm cells in direct contact with the blastocoel showed higher K+ concentrations than in direct contact with inner cell mass, indicating that Na+/K+ ATPase activity differs depending on the location in the trophectoderm. This is the first study to use CoroNa Green AM and ION Potassium Green-2 AM in mouse embryos and visualise electrolytes during embryonic development. The changes in electrolyte concentration observed in this study were consistent with the activity of Na+/K+ ATPase reported previously, and it was possible to image more detailed electrolyte behaviour in embryo cells. This method can be used to improve the understanding of cell physiology and is useful for future embryonic development studies.

scholarly journals Stem Cell and Markers

2019 ◽  
Vol 1 (1) ◽  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Embryonic Stem Cells ◽  
Adult Stem Cells ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Stem Cell Markers ◽  
Cell Markers ◽  
Wide Range

Stem cells have the ability to go through various cell divisions and also maintain undifferentiated state. Stem cells are Embryonic (Pluripotent) and adult stem cells. Pluripotent stem cells give rise to all tissues such as ectoderm, mesoderm and endoderm. Embryonic stem cells isolated from inner cell mass of embryo blastocyst. Adult stem cells are also undifferentiated cells present in adult organisms and repair the tissue when damaged occurs but number in less. Adult stem cells are present in bone marrow, adipose tissue, blood and juvenile state umbilical cord and tissue of specific origin like liver, heart, intestine and neural tissue. Embryonic stem cells from blastocyst have the ethical problems and tumorogenecity. These can be identified by flow cytometry. There are wide range of stem cell markers which are useful in identifying them. Most of the pluripotent cell markers are common with tumor cell markers which throws a challenge for certainty.

Derivation characteristics and perspectives for mammalian pluripotential stem cells

2005 ◽  
Vol 17 (2) ◽  
pp. 135 ◽  
Author(s):  
Alan Trounson
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Cell Lines ◽  
Nuclear Transfer ◽  
Cell Mass ◽  
Embryonic Stem ◽  
The Body ◽  
Preimplantation Embryos ◽  
Specific Cell ◽  
Wide Range

Pluripotential stem cells have been derived in mice and primates from preimplantation embryos, postimplantation embryos and bone marrow stroma. Embryonic stem cells established from the inner cell mass of the mouse and human blastocyst can be maintained in an undifferentiated state for a long time by continuous passage on embryonic fibroblasts or in the presence of specific inhibitors of differentiation. Pluripotential stem cells can be induced to differentiate into all the tissues of the body and are able to colonise tissues of interest after transplantation. In mouse models of disease, there are numerous examples of improved tissue function and correction of pathological phenotype. Embryonic stem cells can be derived by nuclear transfer to establish genome-specific cell lines and, in mice, it has been shown that embryonic stem cells are more successfully reprogrammed for development by nuclear transfer than somatic cells. Pluripotential stem cells are a very valuable research resource for the analysis of differentiation pathways, functional genomics, tissue engineering and drug screening. Clinical applications may include both cell therapy and gene therapy for a wide range of tissue injury and degeneration. There is considerable interest in the development of pluripotential stem cell lines in many mammalian species for similar research interests and applications.

144 Oct-4 EXPRESSION PATTERN IN THE EQUINE EMBRYO

2007 ◽  
Vol 19 (1) ◽  
pp. 189
Author(s):  
Y. H. Choi ◽  
H. D. Harding ◽  
A. D. Obermiller ◽  
K. Hinrichs
Keyword(s):  
Embryonic Development ◽  
Expression Pattern ◽  
Embryo Development ◽  
Inner Cell Mass ◽  
Ex Vivo ◽  
Expression Patterns ◽  
Cell Mass ◽  
Population Variation ◽  
Early Embryonic Development

Oct-4 is a key transcription factor in the control of early embryonic development and maintenance of a pluripotent cell population. Variation in Oct-4 expression patterns during embryo development have been reported among species, and have been related to the time of placental development in those species. This study was conducted to investigate Oct-4 expression pattern during early embryonic development in the horse, a species with relatively delayed placentation. In vitro-produced embryos were obtained from in vitro-matured oocytes via fertilization by intracytoplasmic sperm injection. Ex vivo blastocysts were recovered from mares that had been artificially inseminated. Oct-4 status was determined by immunocytochemistry; photomicrographs were taken at 4 standardized settings to aid in qualitative comparison of the amount of fluorescence. A total of 106 oocytes and embryos were evaluated. Immature oocytes showed Oct-4 expression in the nucleus and cytoplasm, as did early-cleaved embryos (2 to 5 cells, 1 to 2 days). Oct-4 expression in embryos at 3 to 4 days (6 to 12 cells) decreased and was restricted to the cytoplasm. From 5 to 6 days (15 cells to morulae), Oct-4 intensity increased and was exclusively found in the nuclei. In vitro-produced blastocysts (7 to 8 days) expressed Oct-4 equivalently in the trophectoderm and inner cell mass nuclei; culture for 2 to 3 more days (10 to 11 days) did not alter Oct-4 expression. However, when in vitro-produced blastocysts were transferred to the uteri of mares and recovered after 2 to 3 days (IVP-ET), the embryos showed strong expression of Oct-4 within the inner cell mass and limited expression in the trophectoderm, and a similar pattern was seen for ex vivo-recovered embryos. In bigger embryos (such as a 1779-�m ex vivo embryo and a 1121-�m IVP-ET embryo), the trophectoderm lost staining completely. These results suggest that Oct-4 expression is present in both nucleus and cytoplasm in equine oocytes and early-cleaved embryos as a result of maternal mRNA accumulation. Oct-4 protein decreases over the first few days of embryonic development as these stores are used. The shift to greater expression, in the nucleus only, during further embryo development suggests embryonic genome activation. Oct-4 expression in the trophectoderm of in vitro-produced blastocysts was different from that in blastocysts that had been exposed to the uterus (both ex vivo and IVP-ET); this indicates that differentiation of the trophectoderm is dependent upon factors present in the uterine environment. The Oct-4 expression in the trophectoderm of in vitro-produced equine blastocysts thus appears to be an artifact due to in vitro culture; this finding may be applicable to the reported patterns of Oct-4 expression in embryos of other species. This work was supported by the Link Equine Research Endowment Fund, Texas A&amp;M University.

Ultrastructural observations of lethal yellow (Ay/Ay) mouse embryos

Development ◽  
1976 ◽  
Vol 35 (1) ◽  
pp. 73-80
Author(s):  
Patricia G. Calarco ◽  
Roger A. Pedersen
Keyword(s):  
Developmental Stages ◽  
Inner Cell Mass ◽  
Structural Characteristics ◽  
Cell Mass ◽  
Blastocyst Stage ◽  
Cell Organelles ◽  
Cell Stage ◽  
Wide Range ◽  
Lethal Yellow ◽  
And Control

Ay/Ay embryos were identified by the presence of large excluded blastomeres (Pedersen, 1974) and examined cytologically and ultrastructurally. Cell organelles, inclusions and junctions in the excluded blastomeres were compared with those of non-excluded cells of Ay/Ay embryos and control embryos. Excluded blastomeres always had the fine structural characteristics of earlier developmental stages and may have arrested at the 4- to 8-cell stage or slightly later. Interior cells (inner cell mass) were observed in all mutant blastocysts. Nonexcluded cells of Ay/Ay embryos were normal until degenerative changes appear in the late blastocyst stage. The mode of action of the +Ay gene was not determined, but evidence from this study and others indicates that the effects of +Ay gene action occur over a wide range of time in early cleavage and implantation.

Sign in / Sign up

Export Citation Format

Share Document