A review of the recent advances for the in ovo sexing of chicken embryos using optical sensing techniques

The culling of day-old male chicks has caused ethical and economic concerns. Traditional approaches for detecting the in ovo sex of chicken embryos involve opening the eggshell and inner membrane, which are destructive, time-consuming, and inefficient. Therefore, noncontact optical sensing techniques have been examined for the in ovo sexing of chicken embryos. Compared with traditional methods, optical sensing can increase determination throughput and frequency for the rapid sexing of chicken embryos. This paper presented a comprehensive review of the different optical sensing techniques used for the in ovo sexing of chicken embryos, including visible and near-infrared (Vis-NIR) spectroscopy, hyperspectral imaging, Raman spectroscopy, fluorescence spectroscopy, and machine vision, discussing their advantages and disadvantages. In addition, the latest research regarding different detection algorithms and models for the in ovo sexing of chicken embryos was summarized. Therefore, this paper provides updated information regarding the optical sensing techniques that can be used in the poultry industry and related research.

Investigation of the Effects of Monosodium Glutamate on the Embryonic Development of the Eye in Chickens

MSG is the most ubiquitous food additive in the food industry. The aim of this report was to investigate the effects of in ovo MSG administration on embryonic chicken eye development using histological and histometric methods. A total of 410 fertilized eggs obtained from Babcock Brown laying hens (Gallus gallus domesticus) were used and divided into 5 groups: I (untreated control), II (vehicle control), III (0.12 mg/g egg MSG), IV (0.6 mg/g egg MSG), and V (1.2 mg/g egg MSG), and injections were performed via the egg yolk. At incubation day 15, 18, and 21, 6 embryos from each group were sacrificed by decapitation and pieces of eye tissue were obtained. In all MSG groups, it was determined that both corneal epithelium thickness and total corneal thickness decreased at incubation time points 15, 18, and 21 days compared with the controls (p < 0.05). The total retinal thickness, thickness of the outer nuclear layer (ONL), inner nuclear layer (INL), ganglion cell layer (GL), and nerve fibre layers (NFL), as well as the number of ganglion cells decreased significantly at incubation days 15, 18, and 21 (p < 0.05), and degenerative changes such as vacuolar degeneration and retinal pigment epithelial detachment were also observed. In conclusion, MSG in ovo administration can affect the cornea and distinct layers of retinal cells.

Effects of Induced Moisture Loss in Chicken Embryos at Embryonic Day 18 and Post-hatch Immune Response During Salmonella enteritidis Lipopolysaccharide Challenge in Broilers

Two experiments were conducted to investigate the effects of induced moisture loss on embryonic development and the immune response following an inflammatory challenge immediately post-hatch. In Experiment I, fertile leghorn eggs (n = 100) and commercial broiler eggs (n = 300) were set at 37.5°C and moisture loss was induced in one-half of the Leghorn and broiler eggs by drilling two, 1.5 mm diameter holes. The Control eggs had 0 holes. At embryonic day (ED)18, layer and broiler eggs in the 2-holes treatment had a significant (P < 0.01) increase in moisture loss compared to the control treatment (10.1% vs. 8.2%). Similarly, at ED18, the broiler eggs with 2-holes had a significant increase (P < 0.01) in moisture loss compared with control eggs (9.9% vs. 8.4%). Thymocytes from both the leghorn (104%) and broiler (62%) embryos in the 2-holes treatment had significantly increased in vitro proliferation compared with the control embryos (P ≤ 0.05). At ED18, layer and broiler embryos in the 2-holes treatment had an approximate twofold increase in the splenic CD8⁺/CD4⁺ ratio (P ≤ 0.05) and CD4⁺CD25⁺ cells percentage in both the thymus and spleen (P ≤ 0.05). At ED18, both layer and broiler embryos from the 2-holes treatment had a significant increase in splenic IL1-β, IL-6, IL-10, and TLR-4 mRNA transcription compared to the control group (P ≤ 0.05). Experiment II was repeated with 300 fertile broiler eggs. On the day of hatch, chicks were randomly distributed into one of four treatments in a 2 (0, 2 holes) × 2 (0, 500 μg lipopolysaccharide, LPS) factorial arrangement of treatments. Chicks in the LPS groups were injected intraperitoneally with 500 μg/kg BW LPS. At 24 and 48 h post-hatch, chicks hatched from eggs with 2-holes and challenged with LPS had a significant increase (P ≤ 0.05) in thymocyte proliferation at 24 h (42%) and 48 h (37%) when compared with chicks hatched from the control (0-hole; 0 μg LPS) treatment. Chicks hatched from the 2-holes treatment and challenged with the LPS had an approximately twofold higher splenic CD8⁺/CD4⁺ ratio and 1.5 fold increase in CD4⁺CD25⁺ percentage compared to control chicks (P ≤ 0.05). In chicks hatched from the 2-holes treatment, MUC2 mRNA transcription was comparable to control chicks at 24 and 48 h in response to the LPS challenge. Our data suggest that the 2-holes treatment reprograms gene transcription to facilitate cell survival via proliferation and differentiation during an LPS inflammatory challenge.

Thiacloprid Induced Developmental Neurotoxicity via ROS-Oxidative Injury and Inflammation in Chicken Embryo: The Possible Attenuating Role of Chicoric and Rosmarinic Acids

Simple Summary

The current study was designed to evaluate the negative impact of thiacloprid (TH) on the brain tissue of developing chicken embryo models and to evaluate the modulatory effects of chicoric (CA) and rosmarinic (RA) acids. The eggs were injected in ovo with different doses of TH (0.1, 1, 10, and 100 μg/egg). TH significantly increased the oxidative damage in the brain of exposed embryos in a dose-dependent manner (p < 0.001). TH significantly elevated the oxidative stress markers; protein carbonyl, malondialdehyde (MDA) content, and DNA damage (p < 0.001). Myeloperoxidase (MPO) activity and NO significantly increased with overexpression of the pro-inflammatory cytokines (IFN-γ; interferon gamma, TNF-α; tumor necrosis factor alpha, and IL-1β; interleukin-1 beta), stress-related and apoptotic genes (NF-KB, Caspase-3) in the brain tissue on both a biochemical and molecular levels (p < 0.05), while downregulating the expression of antiapoptotic Bcl-2. Co-treatment of CA and RA with TH markedly decreased the insecticide-induced toxicity with a prominent synergistic effect (p < 0.05). In conclusion, TH is suggested to be a possible neurotoxic to embryos of vertebrates and possibly humans. The study also revealed the antioxidant, anti-inflammatory, genoprotective, and antiapoptotic properties of CA and RA against TH toxicity.

Abstract

Insecticides are widely employed in agriculture to control pests and as major factors for enhancing crop productivity. Thiacloprid (TH) is one of the most-used insecticides worldwide. In this study, the negative impact of TH on the brain tissue of developing chicken embryo models and the modulatory effect of chicoric (CA) and rosmarinic (RA) acids were investigated. The eggs were injected in ovo with different doses of TH (0.1, 1, 10, and 100 μg/egg). TH significantly increased the oxidative damage in the brain of exposed embryos in a dose-dependent manner (p < 0.05). TH significantly elevated the oxidative stress markers; protein carbonyl, malondialdehyde content, and DNA damage (p < 0.05). Myeloperoxidase activity and nitric oxide significantly increased with overexpression of the pro-inflammatory cytokines (interferon gamma, tumor necrosis factor alpha, and interleukin-1 beta) and stress-related and apoptotic genes (NF-KB, Caspase-3) in the brain tissue on both biochemical and molecular levels (p < 0.05), while downregulating the expression of antiapoptotic Bcl-2. Co-treatment of CA and RA with TH markedly decreased the insecticide-induced toxicity with a prominent synergistic effect (p < 0.05). In conclusion, TH is suggested to be a possible neurotoxic to embryos of vertebrates including human. The study also revealed the antioxidant, anti-inflammatory, genoprotective, and antiapoptotic property of CA and RA against TH toxicity.

Temporal dynamics of nitric oxide wave in early vasculogenesis

Endothelium-derived nitric oxide (NO) is a mediator of angiogenesis. However, NO-mediated regulation of vasculogenesis remains largely unknown. In the present study, we show that the inhibition of NO significantly attenuated endothelial migration, ring formation, and tube formation. The contribution of nitric oxide synthase (NOS) enzymes during early vasculogenesis was assessed by evaluating endothelial NOS (eNOS) and inducible NOS (iNOS) mRNA expression during HH10-HH13 stages of chick embryo development. iNOS but not eNOS was expressed at HH12 and HH13 stages. We hypothesized that vasculogenic events are controlled by NOS-independent reduction of nitrite to NO under hypoxia during the very early phases of development. Semi-quantitative polymerase chain reaction analysis of hypoxia-inducible factor-1α (HIF-1α) showed higher expression at HH10 stage, after which a decrease was observed. This observation was in correlation with the nitrite reductase (NR) activity at HH10 stage. We observed a sodium nitrite-induced increase in NO levels at HH10, reaching a gradual decrease at HH13. The possible involvement of a HIF/NF-κB/iNOS signaling pathway in the process of early vasculogenesis is suggested by the inverse relationship observed between nitrite reduction and NOS activation between HH10 and HH13 stages. Further, we detected that NR-mediated NO production was inhibited by several NR inhibitors at the HH10 stage, whereas the inhibitors eventually became less effective at later stages. These findings suggest that the temporal dynamics of the NO source switches from NR to NOS in the extraembryonic area vasculosa, where both nitrite reduction and NOS activity are defined by hypoxia.

Antimicrobial Resistance Profiles and Genetic Typing of Salmonella Serovars from Chicken Embryos in China

Salmonella continues to be a major food and public health burden worldwide that can threaten human health via eating contaminated meats, particularly those originating from chicken. In this study, the antimicrobial resistance profiles, epidemiological characteristics of resistance genes, and pulsed field gel electrophoresis (PFGE-XbaI) typing of 120 non-Pullorum/Gallinarum Salmonella isolates recovered from chicken embryos in Henan province were determined. The antimicrobial resistant phenotypes and evaluation of the extended-spectrum beta-lactamases (ESBLs) producing strains of Salmonella were investigated by the Kirby-Bauer test and the double-disk synergy test. Additionally, 37 antimicrobial resistance genes encoding resistance to five different categories, including aminoglycosides, cephalosporins, sulphonamides, tetracyclines, and β-lactams, were examined by conventional PCR. However, genotyping analysis was conducted by macro-restriction using enzyme XbaI followed by the separation of the restricted DNA fragments by PFGE. The results of this study showed that the studied Salmonella strains were highly resistant to ampicillin (66.67%) and sulfisoxazole (66.67%), while they were all susceptible to meropenem, imipenem, colistin, and chloramphenicol. Additionally, 67.5% (81/120) of the studied strains were multidrug resistant, and 21.67% (26/120) were phenotypically confirmed as ESBLs positive. The statistical analysis showed that resistance depends on the serovars, and ESBLs positive strains showed more multi-resistance than ESBLs negative strains (p < 0.05). The genotypic antimicrobial resistance showed the detection of 14 among the 37 tested genes, and the concordance between genotypic and phenotypic antimicrobial resistance ranged from 0% to 100% depending on the serovars. However, the PFGE-XbaI typing results showed that the examined Salmonella strains were divided into 22 individual subtypes and were grouped in nine clusters, with similarity values ranging from 64.7% to 100%. From this study, we can conclude that the antimicrobial resistance of Salmonella serovars isolated from chicken embryos in Henan province was alarming, with rigorous multidrug resistance, which requires the urgent mitigation of the use of antimicrobial drugs in chicken hatcheries. Additionally, our results showed evidence of the presence of different PFGE patterns among the studied Salmonella serovars, suggesting the presence of different sources of contamination.

Prevalence and Antimicrobial Resistance of Salmonella Isolated From Dead-in-Shell Chicken Embryos in Shandong, China

The present study was designed to explore the Salmonella prevalence and antimicrobial resistance characteristics in the context of chick mortality at hatching in China. Between December 2015 and August 2017, 1,288 dead-in-shell chicken embryos were collected from four breeder chicken hatcheries in Tai'an, Rizhao, Jining, and Heze, China. Salmonella isolates were successfully recovered from 6.7% of these embryos (86/1,288) and were evaluated for serotype, antimicrobial susceptibility, Class 1 integron prevalence, antimicrobial resistance gene expression, and multilocus sequence typing (MLST). Salmonella Thompson (37.2%), and Salmonella Infantis (32.6%) were the two most prevalent isolates in these chicken embryos, and 66.3% of isolates exhibited robust ampicillin resistance, while 55.8% of isolates exhibited multi-drug resistance (MDR). The majority of isolates harbored the bla_TEM gene (74.4%), with the qnrS gene also being highly prevalent (50.0%). In contrast, just 27.9% of these isolates carried Class 1 integrons. These 86 isolates were separated into four sequence types (STs), whereby ST26 (32.2%) was the most prevalent. Overall, these results suggested that Salmonella infections may be an important cause of chicken embryo mortality in China, and that efforts to support the appropriate use of antibiotics in managing poultry populations are essential.

Susceptibility of turkeys, chickens and chicken embryos to SARS-CoV-2

The susceptibility of turkeys, chickens and chicken embryos to SARS-CoV-2 was evaluated by experimental infection. Turkeys and chickens were inoculated using a combination of intranasal, oral and ocular routes. Both turkeys and chickens did not develop clinical disease or seroconvert following inoculation. Viral RNA was not detected in oral swabs, cloacal swabs or in tissues using quantitative real-time RT-PCR. In addition, chicken embryos were inoculated by various routes including the yolk sac, intravenous, chorioallantoic membrane and allantoic cavity. In all instances, chicken embryos failed to support replication of the virus. SARS-CoV-2 does not affect turkeys or chickens in the current genetic state and does not pose any potential risk to establish an infection in both species of domestic poultry.

In vivo characterization of chick embryo mesoderm by optical coherence tomography-assisted microindentation

Embryos are growing organisms with highly heterogeneous properties in space and time. Understanding the mechanical properties is a crucial prerequisite for the investigation of morphogenesis. During the last 10 years, new techniques have been developed to evaluate the mechanical properties of biological tissues in vivo. To address this need, we employed a new instrument that, via the combination of micro‐indentation with Optical Coherence Tomography (OCT), allows us to determine both, the spatial distribution of mechanical properties of chick embryos, and the structural changes in real‐time. We report here the stiffness measurements on the live chicken embryo, from the mesenchymal tailbud to the epithelialized somites. The storage modulus of the mesoderm increases from (176 ± 18) Pa in the tail to (716 ± 117) Pa in the somitic region (mean ± SEM, n = 12). The midline has a mean storage modulus of (947 ± 111) Pa in the caudal (PSM) presomitic mesoderm (mean ± SEM, n = 12), indicating a stiff rod along the body axis, which thereby mechanically supports the surrounding tissue. The difference in stiffness between midline and presomitic mesoderm decreases as the mesoderm forms somites. This study provides an efficient method for the biomechanical characterization of soft biological tissues in vivo and shows that the mechanical properties strongly relate to different morphological features of the investigated regions.

Smartphone-Based Device for Non-Invasive Heart-Rate Measurement of Chicken Embryos

Heart rate (HR) is an important parameter in the study of the developmental physiology of chicken embryos and a crucial indicator of dead or live embryo grading in artificial incubation processes. A non-invasive HR measurement technique is required for long-term and routine HR assessment with minimal influence on embryo development. Accordingly, in this study, a non-invasive HR measurement technique of chicken embryos using a smartphone is demonstrated. The detection method of the proposed device is based on the photoplethysmography principle in which a smartphone camera is used for video recording, and the chicken embryonic HR is obtained from the recorded video images using a custom Android application. We used a smartphone to measure the embryonic HR of 60 native chicken eggs and found that it can measure the chicken embryonic HR from day 4 to day 20. The proposed smartphone HR device will be beneficial for scientific research and industrial applications. With internet connectivity, users can utilize their smartphone to measure the HR, display, share, and store the results.

(-)-Hydroxycitric Acid Influenced Fat Metabolism via Modulating of Glucose-6-phosphate Isomerase Expression in Chicken Embryos

The current research aimed to explore the impact of (-)-hydroxycitric acid (HCA) on fat metabolism and investigate whether this action of (-)-HCA was associated with modulation of glucose-6-phosphote isomerase (GPI) expression in chicken embryos. We constructed a recombinant plasmid (sh2-GPI) to inhibit GPI expression, and then embryos were treated with (-)-HCA. Results showed that (-)-HCA reduced lipid droplet accumulation, triglyceride content, and lipogenesis factors mRNA level and increased lipolysis factors mRNA expression, while this effect caused by (-)-HCA was markedly reversed when the chicken embryos were pretreated with sh2-GPI. (-)-HCA increased phospho (p)-acetyl-CoA carboxylase, enoyl-CoA hydratase short chain-1, carnitine palmitoyl transferase 1A, p-AMP-activated protein kinase, and peroxisome proliferators-activated receptor α protein expression, and this action of (-)-HCA also dispelled when the chicken embryos were pretreated with sh2-GPI. These data demonstrated that (-)-HCA decreased fat deposition via activation of the AMPK pathway, and the fat-reduction action of (-)-HCA was due to the increasing of GPI expression in chicken embryos.

Susceptibility of Chickens to Porcine Deltacoronavirus Infection

Porcine deltacoronavirus (PDCoV) is a novel swine enteropathogenic coronavirus with worldwide distribution. PDCoV belongs to the Deltacoronavirus (DCoV) genus, which mainly includes avian coronaviruses (CoVs). PDCoV has the potential to infect human and chicken cells in vitro, and also has limited infectivity in calves. However, the origin of PDCoV in pigs, the host range, and cross-species infection of PDCoV still remain unclear. To determine whether PDCoV really has the ability to infect chickens in vivo, the three lines of chicken embryos and specific pathogen free (SPF) chickens were inoculated with PDCoV HNZK-02 strain to investigate PDCoV infection in the current study. Our results indicated that PDCoV can infect chicken embryos and could be continuously passaged on them. Furthermore, we observed that PDCoV-inoculated chickens showed mild diarrhea symptoms and low fecal viral RNA shedding. PDCoV RNA could also be detected in multiple organs (lung, kidney, jejunum, cecum, and rectum) and intestinal contents of PDCoV-inoculated chickens until 17 day post-inoculation by real-time quantitative PCR (qRT-PCR). A histology analysis indicated that PDCoV caused mild lesions in the lung, kidney, and intestinal tissues. These results prove the susceptibility of chickens to PDCoV infection, which might provide more insight about the cross-species transmission of PDCoV.

Potential role of ALDH3A2 on the lipid and glucose metabolism regulated by (-)-hydroxycitric acid in chicken embryos

This study aimed to investigate the effect of (-)-hydroxycitric acid ((-)-HCA) on lipid and glucose metabolism, and further analyzed these actions whether associated with modulation of aldehyde dehydrogenase 3 family member A2 (ALDH3A2) expression in chicken embryos. Results showed that (-)-HCA decreased triglyceride content and lipid droplet counts, while these effects induced by (-)-HCA were reversed in chicken embryos pre-transfected with sh4-ALDH3A2. (-)-HCA decreased malic enzyme, acetyl-CoA carboxylase, fatty acid synthase, and sterol regulatory element binding protein-1c mRNA level, while increased carnitine palmitoyl transferase 1A (CPT1A) and peroxisome proliferators-activated receptor α (PPARα) mRNA level; and the action of (-)-HCA on lipid metabolism factors had completely eliminated in embryos pre-transfected with sh4-ALDH3A2. Chicken embryos pre-transfected with sh4-ALDH3A2 had eliminated the increasing of serum glucose and hepatic glycogen content induced by (-)-HCA. (-)-HCA decreased phosphofructokinase-1 and increased G6P, fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase (PEPCK), and pyruvate carboxylase mRNA level in chicken embryos. Similarly, the effect of (-)-HCA on these key enzyme mRNA level was reversed in embryos pre-transfected with sh4-ALDH3A2. Furthermore, (-)-HCA increased PPAR-γ-coactivator-1α (PGC-1α), PPARα, hepatic nuclear factor-4A, PEPCK, and CPT1A protein level, and these actions of (-)-HCA disappeared in embryos pre-transfected with sh4-ALDH3A2. These results indicated that (-)-HCA reduced fat accumulation and accelerated gluconeogenesis via activation of PGC-1α signaling pathway, and these effects of (-)-HCA might associate with the increasing of ALDH3A2 expression level in chicken embryos.

Turkey Hemorrhagic Enteritis Virus Can Be Titrated but Not Propagated in Chicken Embryos

This study aimed to investigate the feasibility of propagating and titrating hemorrhagic enteritis virus (HEV) in chicken embryos. A total of 308 embryonated eggs were used. At 10 days of embryonic age, eggs were inoculated via allantoic sac or chorioallantoic membrane routes with non-heat-treated (live) HEV or heat-treated (dead) HEV or served as negative controls. Allantoic fluid retrieved at 0, 1, 3, 5, and 7 days postinoculation (dpi) was tested for HEV by quantitative PCR. Inoculation with HEV did not cause visible growth impairment or lesions in the chicken embryos. Overall, there was no difference in postinoculation mortality rates among groups sham-inoculated (6/30, 20.0%) or inoculated with live (34/252, 13.4%) or dead (3/ 26, 6.9%) HEV (P = 0.58). The amount of HEV DNA detected in allantoic fluid at 7 dpi in eggs inoculated with live virus was similar to the inoculated dose, indicating that virus propagation in chicken embryos is not efficient. No HEV DNA was detected after 3 dpi in eggs inoculated with dead virus. Inoculation of chicken embryos combined with qualitative PCR can be used for titration of HEV virus stocks and presents a high correlation with in vivo titration using chickens (R² 0.98, P = 0.007). This method may be relevant in countries in which specific-pathogen-free turkeys are unavailable and in which the importation of RP19 cells, the only cell that supports effective propagation of HEV, is not permitted.

Chicken embryos share mammalian patterns of apoptosis in the posterior placodal area

In the posterior placodal area (PPA) of C57BL/6N mice and primate-related Tupaia belangeri (Scandentia), apoptosis helps to establish morphologically separated otic and epibranchial placodes. Here, we demonstrate that basically identical patterns of apoptosis pass rostrocaudally through the Pax2⁺ PPA of chicken embryos. Interplacodal apoptosis eliminates unneeded cells either between the otic anlage and the epibranchial placodes 1, 2 and/or 3, respectively (type A), or between neighbouring epibranchial placodes (type B). These observations support the idea that in chicken embryos, as in mammals, interplacodal apoptosis serves to remove vestigial lateral line placodes (Washausen & Knabe, 2018, Biol Open 7, bio031815). A special case represents the recently discovered Pax2^- /Sox2⁺ paratympanic organ (PTO) placode that has been postulated to be molecularly distinct from and developmentally independent of the ventrally adjacent first epibranchial (or 'geniculate') placode (O'Neill et al. 2012, Nat Commun 3, 1041). We show that Sox2⁺ (PTO placodal) cells seem to segregate from the Pax2⁺ geniculate placode, and that absence of Pax2 in the mature PTO placode is due to secondary loss. We further report that, between Hamburger-Hamilton (HH) stages HH14 and HH26, apoptosis in the combined anlage of the first epibranchial and PTO placodes is almost exclusively found within and/or immediately adjacent to the dorsally located PTO placode. Hence, apoptosis appears to support decision-making processes among precursor cells of the early developing PTO placode and, later, regression of the epibranchial placodes 2 and 3.

Microbiota-derived lipopolysaccharide retards chondrocyte hypertrophy in the growth plate through elevating Sox9 expression

Accumulating data show that the cytotoxicity of bacterial lipopolysaccharides (LPS) from microbiota or infection is associated with many disorders observed in the clinics. However, it is still obscure whether or not embryonic osteogenesis is affected by the LPS exposure during gestation. Using the early chicken embryo model, we could demonstrate that LPS exposure inhibits chondrogenesis of the 8-day chicken embryos by Alcian Blue-staining and osteogenesis of 17-day by Alcian Blue and Alizarin Red staining. Further analysis of the growth plates showed that the length of the proliferating zone (PZ) increases whereas that of the hypertrophic zone (HZ) decreased following LPS exposure. However there is no significant change on cell proliferation in the growth plates. Immunofluorescent staining, western blot analysis, and quantitive polymerase chain reaction revealed that Sox9 and Col2a1 are highly expressed at the messenger RNA level and their protein products are also abundant. LPS exposure causes a downregulation of Runx2 and Col10a1 expression in 8-day hindlimbs, and a suppression of Runx2, Col10a1, and Vegfa expression in 17-day phalanges. Knocking down Sox9 in ATDC5 cells by small interfering RNA transfection lead to the expression reduction of Col2a1, Runx2, and Col10a1, implying the vital role of Sox9 in the process of LPS-induced delay in the transition from proliferating chondrocytes to hypertrophic chondrocytes in the growth plate. In the presence of LPS, the antioxidant defense regulator nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is highly expressed, and the activities of superoxide dismutase 1 (SOD1), SOD2, and glutaredoxin rise in 17-day phalanges and ADTC5 cells. Simultaneously, an increase of intracellular ROS is observed. When Nrf2 expression was knocked down in ATDC5 cells, the expressions of Sox9, Col2a1, Runx2, Col10a1, and Vegfa were also going down as well. Taken together, our current data suggest that LPS exposure during gestation could restrict the chondrocytes conversion from proliferating to hypertrophic in the growth plate, in which LPS-induced Sox9 plays a crucial role to trigger the cascade of downstream genes by excessive ROS production and Nrf2 elevation.

Based serum metabolomics analysis reveals simultaneous interconnecting changes during chicken embryonic development

Metabolic disorder is a major health problem and is associated with a number of metabolic diseases. Due to native hyperglycaemia and resistance to exogenous insulin, chickens as a model had used in the studies of adipose tissue biology, metabolism and obesity. But no detailed information is available about the comprehensive changes of serum metabolites at different stages of chicken embryonic development. This study employed LC/MS-QTOF to determine the changes of major functional metabolites at incubation day 14 (E14d), 19 (E19d) and hatching day 1 (H1d), and the associated pathways of differential metabolites during chicken embryonic development were analysed using Metabolite Set Enrichment Analysis method. Results showed that 39 metabolites were significantly changed from E14d to E19d and 68 metabolites were significantly altered from E19d to H1d in chicken embryos. Protein synthesis was promoted by increasing the concentrations of L-glutamine and threonine, and gonadal development was promoted through increasing oestrone content from E14d to E19d in chicken embryos, which indicated that serum glutamine, threonine and oestrone contents may be considered as the candidate indicators for assessment of early embryonic development. 2-oxoglutaric acid mainly contributed to enhancing the citric cycle, and it plays an important role in improving the growth of chicken embryos at the late development; the decreasing of L-glutamine, L-isoleucine and L-leucine contents from E19d to H1d in chicken embryonic development implied their possible functions as the feed additive during early posthatch period of broiler chickens to satisfy the growth. These results provided insights into understand the roles of serum metabolites at different developmental stages of chicken embryos, it also provides available information for chicken as a model to study metabolic disease or human obesity.

Phenotypic developmental plasticity induced by preincubation egg storage in chicken embryos (Gallus gallus domesticus)

The developing chicken blastoderm can be temporarily maintained in dormancy below physiological zero temperature. However, prolonged preincubation egg storage impairs normal morphological and physiological development of embryos in a potential example of fetal programming (in this case, “embryonic programming”). We investigated how preincubation egg storage conditions (temperature, duration, hypoxia, and hypercapnia) affects viability, body mass, and physiological variables and functions in day 15 chicken embryos. Embryo viability was impaired in eggs stored for 2 and 3 weeks, with the effects greater at 22°C compared to 15°C. However, embryo size was reduced in eggs stored at 15°C compared with 22°C. Phenotypic change resulting from embryonic programming was evident in the fact that preincubation storage at 15°C diminished hematocrit (Hct), red blood cell concentration ([RBC]), and hemoglobin concentration ([Hb]). Storage duration at 15°C more severely affected the time course (2, 6, and 24 h) responses of Hct, [RBC], and [Hb] to progressive hypoxia and hypercapnia induced by submersion compared with storage duration at 22°C. The time‐specific regulation of acid–base balance was changed progressively with storage duration at both 22 and 15°C preincubation storages. Consequently, preincubation egg storage at 22°C resulted in poor viability compared with eggs stored at 15°C, but size and physiological functions of embryos in eggs stored for 1–2 weeks were worse in eggs stored in the cooler than stored under room conditions. Avian eggs thus prove to be useful for examining developmental consequences to physiology of altered preincubation thermal environment in very early stages of development (embryonic programming).

Insulin-like growth factor-1 (IGF-1) promotes myoblast proliferation and skeletal muscle growth of embryonic chickens via the PI3K/Akt signalling pathway

During embryonic development, IGF-1 fulfils crucial roles in skeletal myogenesis. However, the involvement of IGF-1-induced myoblast proliferation in muscle growth is still unclear. In the present study, we have characterised the role of IGF-1 in myoblast proliferation both in vitro and in vivo and have revealed novel details of how exogenous IGF-1 influences myogenic genes in chicken embryos. The results show that IGF-1 significantly induces the proliferation of cultured myoblasts in a dose-dependent manner. Additionally, the IGF-1 treatment significantly promoted myoblasts entering a new cell cycle and increasing the mRNA expression levels of cell cycle-dependent genes. However, these effects were inhibited by the PI3K inhibitor LY294002 and the Akt inhibitor KP372-1. These data indicated that the pro-proliferative effect of IGF-1 was mediated in response to the PI3K/Akt signalling pathway. Moreover, we also showed that exogenous IGF-1 stimulated myoblast proliferation in vivo. IGF-1 administration obviously promoted the incorporation of BrdU and remarkably increased the number of PAX7-positive cells in the skeletal muscle of chicken embryos. Administration of IGF-1 also significantly induced the upregulation of myogenic factors gene, the enhancement of c-Myc and the inhibition of myostatin (Mstn) expression. These findings demonstrate that IGF-1 has strong activity as a promoter of myoblast expansion and muscle fiber formation during early myogenesis. Therefore, this study offers insight into the mechanisms responsible for IGF-1-mediated stimulation of embryonic skeletal muscle development, which could have important implications for the improvement of chicken meat production.

Acute toxicity and hepatotoxicokinetic studies of Tamarindus indica extract

Tamarindus indica is widely used as a food and beverage and in traditional medicine. The apparent lack of dose standardization in herbal medicine necessitates the evaluation of the lethality T. indica on Artemia salina nauplii and chicken embryos via in vitro and in vivo techniques. Furthermore, hepatotoxicokinetics of the crude extract and fractions on Wister rats was also assessed. At concentrations of 200, 20 and 2 µg/mL, crude extract and fractions showed brine shrimp death percentages ranging from 86.70% to 3.30% and the sub-fractions showed death percentage ranges of 46.70% to 3.30%. Calculated LD₅₀ values ranged from 832 µg/mL to 5,019 µg/mL. Dosing Wister rats with 25% and 50% concentration of LD₅₀ determined for crude extract and fractions on chicken embryos showed an elevation in the ALT and AST levels in the serum. Brine shrimps and chicken embryos showed a positive correlation, with R² values of 0.541 and 0.588 (P ≤ 0.05) for fractions and subfractions, respectively, as media for the lethality assay. Dose standardization in folk herbal medicine is imperative as T. indica used as food and medicine has been shown to be toxic at high doses. Brine shrimp and chicken embryos may be comparably used as medium for toxicity assay.

T-cell development in early partially decapitated chicken embryos

We have evaluated the immunohistological and cytofluorometric changes that occur in the thymus of chicken embryos partially decapitated at 33-38 hr of incubation (DCx embryos) in an attempt to analyze possible neuroendocrinological influences on T-cell differentiation and, indirectly, the ontogeny of the so-called neuroendocrine-immune network. The thymus of DCx embryos shows important variations that profoundly and selectively affect different T-cell subsets, but not the nonlymphoid cell components of thymic stroma. These modifications include the accumulation of cell precursors, mainly DN (CD4-CD8-) cells and immature CD8lowCD4- cells, which expand but do not differentiate, resulting in an extreme decline of both DP (CD4+ CD8+) cells and TcR alpha beta-expressing cells. Accordingly, both subcapsulary and outer cortex increase in size, whereas the deep cortex and principally the thymic medulla almost disappear in DCx embryos. In contrast, other T-cell subsets of DCx embryos, largely CD8highCD4- cells and TcR gamma delta-expressing cells do not undergo significant variations throughout thymic ontogeny.