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Genetic basis and network studies underlying synergistic biomass accumulation of roots and shoots (SBA) are conducive for rational design of high-biomass rice breeding. In this study, association signals for root weight, shoot weight, and the ratio of root-to-shoot mass (R/S) were identified using 666 rice accessions by genome-wide association study, together with their sub-traits, root length, root thickness and shoot length. Most association signals for root weight and shoot weight did not show association with their sub-traits. Based on the results, we proposed a top-to-bottom model for SBA, i.e. root weight, shoot weight and R/S were determined by their highest priority in contributing to biomass in the regulatory pathway, followed by a lower priority pathway for their sub-traits. Owing to 37 enriched clusters with more than two association signals identified, the relationship among the six traits could be also involved in linkage and pleiotropy. Furthermore, a discrimination of pleiotropy and LD at sequencing level using the known gene OsPTR9 for root weight, R/S and root length was provided. The results of given moderate correlation between traits and their corresponding sub-traits, and moderate additive effects between a trait and the accumulation of excellent alleles corresponding to its sub-traits supported a bottom-to-top regulation model for SBA. This model depicted each lowest-order trait (root length, root thickness and shoot length) was determined by its own regulation loci, and competition among different traits, as well as the pleiotropy and LD. All above ensure the coordinated development of each trait and the accumulation of the total biomass, although the predominant genetic basis of SBA is still indistinguishable. The presentation of the above two models and evidence of this study shed light on dissecting the genetic architecture of SBA.

OBJECTIVE: To report a live birth from a patient with complete zona-free oocytes due to abnormal zona production and to reveal full time-lapse blastocyst development footage of its originating embryo. METHODS: A 34-year-old woman presented with a history of failed fertilization via standard in vitro fertilization insemination and a potential absence of zona pellucida. A total of 3 intracytoplasmic sperm injection cycles were undertaken with all oocytes collected being zona-free. Embryos created in the initial 2 cycles were cultured in the G1+/G2+ sequential media in a benchtop incubator. During the final successful cycle, the culture strategy was shifted to single step media (G-TL) in an Embryoscope+ incubator. RESULTS: The first 2 attempts led to a biochemical pregnancy or no blastocyst available for transfer. In the third cycle, 13 out of 24 collected oocytes were subjected to injection, with 4 being normally fertilized. Two blastocysts were subsequently formed, in which one was cryopreserved and the other transferred. A live baby girl (1570g) was subsequently delivered at 34 weeks of gestation by cesarean section. CONCLUSION: Live birth can be achieved for patients with zona production deficiency. Adjustment in ovarian stimulation and subsequent embryo culture strategies may have potentially contributed to the success of the 3rd cycle. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10815-021-02114-3.

Background The speciation and fast global domestication of bread wheat have made a great impact on three subgenomes of bread wheat. DNA base composition is an essential genome feature, which follows the individual-strand base equality rule and [AT]-increase pattern at the genome, chromosome, and polymorphic site levels among thousands of species. Systematic analyses on base compositions of bread wheat and its wild progenitors could facilitate further understanding of the evolutionary pattern of genome/subgenome-wide base composition of allopolyploid species and its potential causes. Results Genome/subgenome-wide base-composition patterns were investigated by using the data of polymorphic site in 93 accessions from worldwide populations of bread wheat, its diploid and tetraploid progenitors, and their corresponding reference genome sequences. Individual-strand base equality rule and [AT]-increase pattern remain in recently formed hexaploid species bread wheat at the genome, subgenome, chromosome, and polymorphic site levels. However, D subgenome showed the fastest [AT]-increase across polymorphic site from Aegilops tauschii to bread wheat than that on A and B subgenomes from wild emmer to bread wheat. The fastest [AT]-increase could be detected almost all chromosome windows on D subgenome, suggesting different mechanisms between D and other two subgenomes. Interestingly, the [AT]-increase is mainly contributed by intergenic regions at non-selective sweeps, especially the fastest [AT]-increase of D subgenome. Further transition frequency and sequence context analysis indicated that three subgenomes shared same mutation type, but D subgenome owns the highest mutation rate on high-frequency mutation type. The highest mutation rate on D subgenome was further confirmed by using a bread-wheat-private SNP set. The exploration of loci/genes related to the [AT] value of D subgenome suggests the fastest [AT]-increase of D subgenome could be involved in DNA repair systems distributed on three subgenomes of bread wheat. Conclusions The highest mutation rate is detected on D subgenome of bread wheat during domestication after allopolyploidization, leading to the fastest [AT]-increase pattern of D subgenome. The phenomenon may come from the joint action of multiple repair systems inherited from its wild progenitors.

Objective: To investigate morphokinetic characteristics of embryos displaying either reverse cleavage or direct cleavage during the first, second or third cleavage cycle. Methods: A total of 167 in vitro fertilization and/or intracytoplasmic sperm injection treatment cycles undertaken by 167 women [aged (35.0±4.6) years] were included for reverse cleavage analysis, and a total of 167 in vitro fertilization and/or intracytoplasmic sperm injection treatment cycles undertaken by 167 women [aged (33.8 ±4.3) years] were included for direct cleavage analysis in this study. Using a sibling-embryo design, morphokinetic profiles (both before and after the onset of abnormal event) of embryos displaying reverse cleavage (n=241) or direct cleavage (n=244) were compared with their unaffected siblings (the controls) in the first, second and third cell cycles (n=32, n=142, n=562; n=195, n=412, n=205, respectively), at different developmental stages up to day 3. Results: Direct cleavage embryos demonstrated significantly delayed cleavage rates prior to the event regardless of developmental stage of the occurrence, while reverse cleavage embryos showed similar cleavage rates to their unaffected siblings. Post event, direct cleavage embryos sped up cleavage rates while reverse cleavage embryos slowed down. Conclusions: Altered morphokinetic profiles are displayed by direct cleavage embryos both before and after their occurrence and reverse cleavage embryos after the occurrence, which could potentially confound morphokinetic comparisons if not separated from their unaffected sibling embryos. Further study is warranted in order to fully understand the biological mechanisms of such events.

Study question Does variation in day 5 observation timing confound embryo-morphology-based live birth prediction, and is it possible to develop a robust comprehensive numerical prediction model. Summary answer Day 5 observation timing confounds embryo-morphology-based live birth prediction. A robust comprehensive numerical prediction model can be developed after considering a number of contributing variables. What is known already Embryo development is a dynamic process, and therefore the widely used static observations potentially lead to biased prediction of live birth outcomes. So far, little is known in regard to potential confounding impact of day 5 assessment timing on the static-morphology-based live birth prediction. In addition, the inter-observer variation in morphology-based embryo assessment requires a more robust system to improve consistency of selection. Study design, size, duration This retrospective multi-center cohort study included 8866 autologous oocyte in vitro fertilisation treatment cycles performed at 14 associated clinics within the same network during 2012–2018. Only fresh cycles with single day 5 embryo transfers were included for analysis with all pregnancies followed up until birth. Repeat cycles of same patients were excluded to avoid clustering effect in statistical analysis. Participants/materials, setting, methods Dataset was randomly split into two subsets at 60:40 ratio, with one (n = 5274) used for regression analysis and model development and the other (n = 3592) used for model testing. Multiple logistic regression was performed to evaluate live birth predicting power of several potential contributors, expressed by odds ratio (OR) and 95% confidence interval (CI). A comprehensive prediction model was subsequently developed based on calculated weights of contributing factors, then tested via receiver operating characteristics (ROC) analysis. Main results and the role of chance The timings of day 5 observation of 8866 included embryos, measured by hours post insemination (HPI), distributed in a bell shape ranging from 112.0 to 120.0 h (mean±SD 115.7±1.7 h). After taking into account female age at egg collection (grouped as Limitations, reasons for caution The retrospective design does not allow for controlling of unknown confounders. HPI was based on static observations in this study so future time-lapse study may bring more insights with more accurate observation and measurement. Wider implications of the findings: The varying HPIs at day 5 observation were alarming as this could confound live birth prediction using embryology parameters. It is important to standardise the timing of embryo observations. The inclusion of HPI into a comprehensive numerical scoring system for live birth prediction may potentially improve its robustness Trial registration number Not applicable

Study question Do morphometric and morphokinetic profiles of pronuclei (PN) following intracytoplasmic sperm injection (ICSI) vary between male and female human zygotes? Summary answer Male and female zygotes displayed different PN morphometrics and morphokinetics. Additionally, variations were identified between sperm-originated (SPN) and oocyte-originated (OPN) pronuclei. What is known already Previous studies have investigated the use of PN-associated parameters via static observations as indicators of zygote viability, including size equality or juxtaposition. However, recent clinical application of time-lapse videography (TLV) provides a novel opportunity to assess these pronuclear events with greater accuracy and precision of morphometric and morphokinetic measurement. A number of recent TLV studies have also investigated potential live birth prediction by such PN associated measures, however whether or not there are gender associated differences in such measures which could in turn confound live birth prediction is unknown. Study design, size, duration: This retrospective cohort study included 94 consecutive autologous single day 5 transfer cycles (either fresh or frozen) performed between January 2019 and March 2020. Only ICSI cycles (maternal age Participants/materials, setting, methods Timings included 2nd polar body extrusion (tPb2), SPN(tSPNa)/OPN(tOPNa) appearance (differentiated by proximity to Pb2) and PN fading (tPNF). Morphometrics were evaluated at 8 (stage 1), 4 (stage 2) and 0 hour before PNF (stage 3), measuring PN area (um2), PN juxtaposition, and nucleolus precursor body (NPB) arrangement. Means ± standard deviation were compared using student t test or logistic regression as odds ratio (OR) and 95% confidence interval (CI), and proportional data by chi-squared analysis. Main results and the role of chance Logistic regression indicated that male zygotes had longer time intervals of tPb2_tSPNa than female zygotes (4.8±1.5 vs 4.2±1.0 h, OR = 1.442, 95% CI 1.009–2.061, p = 0.044), but not tPb2_tOPNa (4.7±1.8 vs 4.5±1.3 h, OR = 1.224, 95% CI 0.868–1.728, p = 0.250) and tPb2_tPNF (19.9±2.8 vs 19.1±2.3 h, OR = 1.136, 95% CI 0.957–1.347, p = 0.144). SPN increased in size from stage 1 through 2 to 3 (435.3±70.2, 506.7±77.3, and 556.3±86.4 um2, p = 0.000) and OPN did similarly (399.0±59.4, 464.3±65.2, and 513.8±63.5 um2, p = 0.000), with SPN being significantly larger than OPN at each stage (p 0.05 respectively). Limitations, reasons for caution The retrospective design does not allow for control of unknown confounders. Sample size is considered relatively small. PN area measurement may not truly represent volume as PN may not be perfectly spherical. Findings were based on women Wider implications of the findings: These findings augment and extend previous studies investigating PN parameters via static observations. The reported variations between male and female embryos may confound live birth prediction when using pronuclei morphometrics and morphokinetics. Larger scaled studies are warranted to verify these findings. Trial registration number Not applicable

The recent clinical introduction of time-lapse videography into in vitro fertilization laboratories has offered a novel opportunity for embryologists to explore improved methods for embryo selectio...

Background Colorectal cancer (CRC) poses a heavy threat to human health owing to its high incidence and mortality. Circular RNAs (circRNAs) were investigated to participate in the progression of CRC, whereas there was no revenant data on the CRC process regulated by hsa_circ_0000231. This study aimed to explore the effects of hsa_circ_0000231 on CRC progression and underneath regulatory mechanism. Methods The expression levels of hsa_circ_0000231, miR-502-5p, and Myosin VI (MYO6) mRNA were detected by quantitative real time polymerase chain reaction (qRT-PCR). Western blot was employed to determine the protein expression levels of MYO6 and proliferating cell nuclear antigen (PCNA). The effects of hsa_circ_0000231 on cell proliferation, apoptosis, migration, and invasive in CRC were determined by cell counting kit-8 proliferation (CCK-8) and colony formation assays, flow cytometry analysis, wound-healing assay, and transwell invasion assay, respectively. Glucose uptake and lactate production were severally illustrated by glucose assay kit and lactate assay kit. The relationship between miR-502-5p and hsa_circ_0000231 or MYO6 was predicted by circular RNA interactome or targetScan online databases, and identified by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. In vivo tumor formation assay was carried out to determine the effects of hsa_circ_0000231 knockdown on tumor growth in vivo. Results Hsa_circ_0000231 expression was dramatically upregulated while miR-502-5p was obviously downregulated in CRC tissues and cells compared with control groups. Hsa_circ_0000231 knockdown repressed the expression levels of MYO6 and PCNA protein. Functionally, hsa_circ_0000231 knockdown repressed cell glycolysis, proliferation, migration and invasion, and induced cell apoptosis, whereas these effects were decreased by miR-502-5p inhibitor. Mechanistically, hsa_circ_0000231 acted as a sponge of miR-502-5p and miR-502-5p bound to MYO6. Furthermore, hsa_circ_0000231 knockdown decreased tumor volume and weight of CRC in vivo. Conclusion Hsa_circ_0000231 knockdown inhibited CRC progression and glycolysis by downregulating MYO6 expression through sponging miR-502-5p, which might provide a theoretical basis in further studying circ_0000231-directed therapy in CRC.

Fungal disease meets its matchFusariumhead blight (FHB), caused by a fungus, reduces wheat crop yield and introduces toxins into the harvest. From the assembly of the genome ofThinopyrum elongatum, a wild relative of wheat used in breeding programs to improve cultivated wheat, Wanget al.cloned a gene that can address both problems (see the Perspective by Wulff and Jones). The encoded glutathioneS-transferase detoxifies the trichothecene toxin and, when expressed in wheat, confers resistance to FHB.Science, this issue p.eaba5435; see also p.822

This study investigated the efficacy of four published day 3 embryo time-lapse algorithms based on different types of datasets (known implantation data [KID] and single embryo transfer [SET]), and the confounding effect of female age and conventional embryo morphology. Four algorithms were retrospectively applied to three types of datasets generated at Fertility North between February 2013 and December 2014: (a) KID dataset (

Objective: To investigate the relationship between elevated serum progesterone levels (EP) on the day of ovulatory trigger, live birth rates, and the growth of resulting embryos. Methods: A total of 836 in vitro fertilization (IVF) cycles with 4 478 embryos in conventional culture were retrospectively analyzed, together with an additional 90 IVF cycles producing 618 embryos from culture and assessment using the Embryoscope™ time-lapse system. Results: In cycles using conventional culture, serum progesterone per follicle ≥14 mm (median 0.42 nmol/L/follicle, range 0.05-3.50 nmol/L/follicle) was a significant negative predictor of live-birth (ROC AUC = 0.395, 95% CI 0.345-0.445; P=0.000) as were progesterone/estradiol ratio (0.442, 0.391-0.494; P=0.027) and progesterone per oocyte (0.374, 0.326-0.421; P=0.000) but not progesterone alone (0.470, 0.419-0.521; P>0.05). Women with an EP/follicle (>0.42 nmol/L/follicle) had reduced live birth rates if they were ≥35 yrs (14.4% vs. 24.2%, P0.42 nmol/L/follicle) adversely affects embryo implantation in women aged ≥35 years, but not

Objective To study the performance of thawed zygotes and cleavage stage embryos transferred either on the day of thaw or after overnight culture. Methods A retrospective study of 864 frozen embryo transfer cycles. Cryosurvival rates per thawed embryo and implantation rates were analysed for embryos frozen on Day 1, Day 2 or Day 3 relative to oocyte collection (Day 0) and transferred on the day of thaw or after overnight culture, together with clinical pregnancy rates and prevalence of multiple gestations. Results Survival of Day 3 embryos was significantly lower than those frozen on Day 1 (P=0.017) or Day 2 (P=0.015). Following overnight culture, resumption of mitosis of zygotes was more frequent than Day 2 (P=0.000) which are in turn higher than Day 3 (P=0.000) embryos. The implantation rate for Day 2 embryos dividing overnight was significantly higher than those that did not divide for women Conclusions Later cleavage stage post-thaw embryos survive and resume mitosis less frequently compared to earlier stages. Embryos not resuming mitosis after culture overnight can implant, particularly Day 3 embryos, suggesting that they can further increase the cumulative pregnancy rate per oocyte collection and that discarding them is wasteful. Overnight culture is best used for logistical reasons rather than a strategy to improve pregnancy rates.

A total of 488 Day 3 human embryos with known implantation data from two independent in vitro fertilization laboratories were included for analysis, with 270 from Fertility North (FN) and 218 from Canberra Fertility Centre (CFC). Implanting embryos grew at different rates between FN and CFC as indicated in hours of the time intervals between pronuclear fading and the 4- (13.9 ± 1.1 vs. 14.9 ± 1.8), 5- (25.7 ± 1.9 vs. 28.4 ± 3.7) and 8-cell stages (29.0 ± 3.2 vs. 32.2 ± 4.6), as well as the durations of 2- (10.8 ± 0.8 vs. 11.6 ± 1.1), 3- (0.4 ± 0.5 vs. 0.9 ± 1.2), and 4-cell stages (11.8 ± 1.4 vs. 13.6 ± 2.9), all p0.05. The application of a previously published time-lapse algorithm on ICSI embryos from the two participating laboratories failed to reproduce a predictive pattern of implantation outcomes (FN: AUC=0.565, p=0.250; CFC: AUC=0.614, p=0.224). However, for the qualitative measures including poor conventional morphology, direct cleavage, reverse cleavage and6 intercellular contact points at the end of the 4-cell stage, there were similar proportions of embryos showing at least one of these biological events in either implanting (3.1% vs. 3.3%, p0.05) or non-implanting embryos (30.4% vs. 38.3%, p0.05) between FN and CFC. Furthermore, implanting embryos favored lower proportions of the above biological events compared to the non-implanting ones in both laboratories (both p0.01). To conclude, human embryo morphokinetics may vary between laboratories, therefore time-lapse algorithms emphasizing quantitative timing parameters may have reduced inter-laboratory transferability; qualitative measures are independent of cell division timings, with potentially improved inter-laboratory reproducibility.

To present a time-lapse deselection model involving both qualitative and quantitative parameters for assessing embryos on day 3.Retrospective cohort study and prospective validation.Private IVF center.A total of 270 embryos with known implantation data (KID) after day 3 transfer from 212 IVF/intracytoplasmic sperm injection (ICSI) cycles were retrospectively analyzed for building the proposed deselection model, followed by prospective validation using an additional 66 KID embryos.None.Morphological score on day 3, embryo morphokinetic parameters, abnormal cleavage patterns, and known implantation results.All included embryos were categorized either retrospectively or prospectively into 7 grades (A+, A, B, C, D, E, F). Qualitative deselection parameters included poor conventional day 3 morphology, abnormal cleavage patterns identified via time-lapse monitoring, and8 cells at 68 hours postinsemination. Quantitative parameters included time from pronuclear fading (PNF) to 5-cell stage and duration of 3-cell stage. KID implantation rates of embryos graded from A+ to F were 52.9%, 36.1%, 25.0%, 13.8%, 15.6%, 3.1%, and 0 respectively (area under the curve [AUC] = 0.762; 95% confidence interval [CI], 0.701-0.824), and a similar pattern was seen in either IVF (AUC = 0.721; 95% CI, 0.622-0.821) or ICSI embryos (AUC = 0.790; 95% CI, 0.711-0.868). Preliminary prospective validation using 66 KID embryos also showed statistically significant prediction in Medicult (AUC = 0.750; 95% CI, 0.588-0.912) and Vitrolife G-Series (AUC = 0.820; 95% CI, 0.671-0.969) suites of culture media.The proposed model involving both qualitative and quantitative deselection effectively predicts day 3 embryo implantation potential and is applicable to all IVF embryos regardless of insemination method by using PNF as the reference starting time point.

Objective To investigate the clinical significance of intercellular contact point (ICCP) in four-cell stage human embryos and the effectiveness of morphology and abnormal cleavage patterns in identifying embryos with low implantation potential. Design Retrospective cohort study. Setting Private IVF center. Patient(s) A total of 223 consecutive IVF and intracytoplasmic sperm injection treatment cycles, with all resulting embryos cultured in the Embryoscope, and a subset of 207 cycles analyzed for ICCP number where good-quality four-cell embryos were available on day 2 (n = 373 IVF and n=392 intracytoplasmic sperm injection embryos). Intervention(s) None. Main Outcome Measure(s) Morphologic score on day 3, embryo morphokinetic parameters, incidence of abnormal biological events, and known implantation results. Result(s) Of 765 good-quality four-cell embryos, 89 (11.6%) failed to achieve six ICCPs; 166 of 765 (21.7%) initially had fewer than six ICCPs but were able to establish six ICCPs before subsequent division. Embryos with fewer than six ICCPs at the end of four-cell stage had a lower implantation rate (5.0% vs. 38.5%), with lower embryology performance in both conventional and morphokinetic assessments, compared with embryos achieving six ICCPs by the end of four-cell stage. Deselecting embryos with poor morphology, direct cleavage, reverse cleavage, and fewer than six ICCPs at the four-cell stage led to a significantly improved implantation rate (33.6% vs. 22.4%). Conclusion(s) Embryos with fewer than six ICCPs at the end of the four-cell stage show compromised subsequent development and reduced implantation potential. Deselection of embryos with poor morphology and abnormal cleavage revealed via time-lapse imaging could provide the basis of a qualitative algorithm for embryo selection.

Time-lapse videography showed that human early cleavage embryos were quicker following intracytoplasmic sperm injection to reach developmental milestones compared to in vitro fertilization when using insemination as the timing start point (t0), due to differences in the time taken for embryos to reach pronuclear fading (PNF). These differences disappeared when PNF was used as t0. Using a biological rather than procedural t0 will allow a unified assessment strategy to be applied to all cycles irrespective of the insemination method.

A total of 341 fertilized and 37 unfertilized oocytes from 63 intracytoplasmic sperm injection (ICSI) treatment cycles were included for retrospective assessment using the Embryoscope time-lapse video system. The second polar body (pb2) extrusion occurred at 2.9±0.1 h (range 0.70-10.15 h) relative to sperm injection. All oocytes reduced in size following sperm injection (p0.05) with shrinkage ceasing after 2h in the unfertilized and at pb2 extrusion in the fertilized oocytes. Pb2 extrusion was significantly delayed for women aged38 years compared to those35 years (3.4±0.2 vs. 2.8±0.1, p0.01) or 35-38 years (3.4±0.2 vs. 2.8±0.1, p0.01), but timing was not related to the Day 3 morphological grades (1-4) of subsequent embryos (2.9±0.1, 2.9±0.1, 2.8±0.2 and 3.0±0.1; p0.05 respectively). A shorter time of first cleavage division relative to either sperm injection or pb2 extrusion is associated with both top grade (AUC=0.596 or 0.601, p=0.006 or 0.004) and usable embryos (AUC=0.638 or 0.632, p=0.000 respectively) on Day 3. In summary, (i) pb2 of human oocytes extrudes at various times following sperm injection, (ii) the timing of pb2 extrusion is significantly delayed when female age38 years, but not related to subsequent embryo development, (iii) all human oocytes reduce in size following sperm injection, (iv) completion of pb2 extrusion in the fertilized oocytes is a pivotal event in terminating shrinkage of the vitellus, and (v) time to first cleavage division either from sperm injection or pb2 extrusion is a significant predictive marker for embryo quality on Day 3.

BACKGROUND: Laodelphax striatellus (Fall ´ en) is a major pest of cultivated rice and is commonly controlled in China with the organophosphate insecticides. To develop a better resistance management strategy, a chlorpyrifos-resistant strain of L. striatellus was selected in the laboratory, and its cross-resistance to other insecticides and possible mechanisms of the chlorpyrifos resistance were investigated. RESULTS: After 25 generations of selection with chlorpyrifos, the selected strain of L. striatellus developed 188-fold resistance to chlorpyrifos in comparison with the susceptible strain, and showed 14- and 1.6-fold cross-resistance to dichlorvos and thiamethoxam respectively. There was no apparent cross-resistance to abamectin. Chlorpyrifos was synergised by the inhibitor triphenyl phosphate; the carboxylesterase synergistic ratio was 3.8 for the selected strain, but only 0.92 for the susceptible strain. The carboxylesterase activity of the selected strain was approximately 4 times that of the susceptible strain, whereas there was no significant change in the activities of alkaline phosphatase, acid phosphatase, glutathione S-transferase and cytochrome P450 monooxygenase between the strains. The Michaelis constant of acetylcholinesterase, maximum velocity of acetylcholinesterase and median inhibitory concentration of chlorpyrifos-oxon on acetylcholinesterase were 1.7, 2.5 and 5 times higher respectively in the selected strain. CONCLUSION: The high cross-resistance to the organophosphate dichlorvos in the chlorpyrifos-resistant strain suggests that other non-organophosphate insecticides would be necessary to counter resistance, should it arise in the field. Enhanced activities of carboxylesterase and the acetylcholinesterase insensitivity appear to be important mechanisms for chlorpyrifos resistance in L.striatellus. c � 2010 Society of Chemical Industry

Objective To investigate the prevalence and potential causes of reverse cleavage (RC) by human early-cleavage embryos and its associations with embryonic development and implantation after transfer. Design Clinical retrospective cohort study. Setting Private fertility treatment center. Patient(s) A total of 126 consecutive in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) treatment cycles, with 353 IVF and 436 ICSI embryos cultured in the Embryoscope until day 3. Intervention(s) None. Main Outcome Measure(s) Embryo assessment on day 3, incidence of abnormal division, embryo morphokinetic parameters, and fetal heart beat. Result(s) RC, referring to either blastomere fusion or failed cytokinesis, occurred up to three times per individual embryo in 27.4% of embryos during the first three cleavage cycles. A higher incidence was associated with GnRH antagonist cycles compared with agonist cycles (odds ratio [OR] 1.683), or with ICSI compared with IVF (OR 1.600). After ICSI, sperm progressive motility was associated with RC (area under the receiver operating characteristic curve: 0.573). Compared with RC-negative embryos, a lower proportion of RC-positive embryos reached 6-cell stage or beyond by day 3 (47.7% vs. 71.7%), and were more likely to have multinucleation at the 4-cell stage (10.1% vs. 5.0%). Embryos showing RC had significantly poorer performance in both conventional grading and morphokinetic parameters, and they implanted less (0/22 vs. 29/131) than those not showing RC. Conclusion(s) RC significantly compromised embryo development, culminating in poor implantation potential. For each embryo, it can occur on more than one occasion at any stage during the first 3 days of culture. It is associated with factors affecting both oocyte and sperm.