Factors associated with embryo mosaicism: a systematic review and meta-analysis.

PURPOSE: Evaluate which factors are involved in the increased rate of mosaicism in embryos. METHODS: A systematic review and meta-analysis was performed. After an exhaustive search of the literature, a total of seven papers were included in the analysis. In addition, data collected from IVF cycles performed in our fertility clinic were also analysed. Day of biopsy, embryo quality, maternal and paternal age and seminal quality were the chosen factors to be studied. RESULTS: The results of the meta-analysis show that neither embryo quality nor seminal quality were related to mosaic embryo rate (OR: 1.09; 95% CI: 0.94-1.28 and OR: 1.10; 95% CI: 0.87-1.37, respectively). A positive association was observed for the variable "biopsy day" with embryos biopsied at day 6 or 7 having the highest rate of mosaicism (OR: 1.06; 95% CI: 1.01-1.11). In opposite to what happens with aneuploidy rate, which increases with maternal age, embryo mosaicism is higher in younger women (<34 years) rather than in older ones (≥34 years) (OR: 0.95; 95% CI: 0.92-0.98). However, for the "paternal age" factor, no association with mosaicism was found (OR: 1.04; 95% CI: 0.90-1.21). CONCLUSIONS: With the present study, we can conclude that the factors related to the presence of mosaicism in embryos are the embryo biopsy day and maternal age. The rest of the studied factors showed no significant relationship with mosaicism. These results are of great importance as knowing the possible causes leading to mosaicism helps to improve the clinical results of reproductive treatments.

Identification of novel candidate genes associated with meiotic aneuploidy in human embryos by whole-exome sequencing.

PURPOSE: To identify novel genetic variants responsible for meiotic embryonic aneuploidy. METHODS: A prospective observational cohort study that included 29 couples who underwent trophectoderm biopsies from 127 embryos and performed whole-exome sequencing (WES) between November 2019 and March 2022. Patients were divided into two groups according to the expected embryo aneuploidy rate based on maternal age. RESULTS: After variant filtering in the WES analysis of 58 patients/donors, five heterozygous variants were identified in female partners from the study group that had an impact on embryo aneuploidy. Additionally, a slowdown in embryo development and a decrease in the number of blastocysts available for biopsy were observed in the study group embryos. CONCLUSION: This study has identified new candidate genes and variants not previously associated with meiotic embryo aneuploidy, but which are involved in important biological processes related to cell division and chromosome segregation. WES may be an efficient tool to identify patients with a higher-than-expected risk of embryo aneuploidy based on maternal age and allow for individualized genetic counselling prior to treatment.

Identification of new variants and candidate genes in women with familial premature ovarian insufficiency using whole-exome sequencing.

PURPOSE: To identify candidate variants in genes possibly associated with premature ovarian insufficiency (POI). METHODS: Fourteen women, from 7 families, affected by idiopathic POI were included. Additionally, 98 oocyte donors of the same ethnicity were enrolled as a control group. Whole-exome sequencing (WES) was performed in 14 women with POI to identify possibly pathogenic variants in genes potentially associated with the ovarian function. The candidate genes selected in POI patients were analysed within the exome results of oocyte donors. RESULTS: After the variant filtering in the WES analysis of 7 POI families, 23 possibly damaging genetic variants were identified in 22 genes related to POI or linked to ovarian physiology. All variants were heterozygous and five of the seven families carried two or more variants in different genes. We have described genes that have never been associated to POI pathology; however, they are involved in important biological processes for ovarian function. In the 98 oocyte donors of the control group, we found no potentially pathogenic variants among the 22 candidate genes. CONCLUSION: WES has previously shown as an efficient tool to identify causative genes for ovarian failure. Although some studies have focused on it, and many genes are identified, this study proposes new candidate genes and variants, having potentially moderate/strong functional effects, associated with POI, and argues for a polygenic etiology of POI in some cases.

Capacitation and acrosome reaction changes α-tubulin immunodistribution in human spermatozoa.

Tubulin is a protein constituent of cytoskeletal microtubules, closely related to sperm motility. However, the changes in tubulin distribution following capacitation and acrosome reaction are poorly understood. This study immunolocalized and quantified the expression of α-tubulin in fresh, capacitated and acrosome-reacted samples. Immunocytochemical data showed that in capacitated and acrosome-reacted spermatozoa, α-tubulin is labelled throughout most of the flagellum (⩾66.66%). However, the mean α-tubulin-labelled area in these samples was significantly lower than in fresh samples (P<0.05). Thus, there are different sperm clusters distinguished by their α-tubulin immunoreactivity and this could be directly linked to structural changes following capacitation and acrosome reaction.

Micronized natural progesterone (Seidigestan®) vs GnRH antagonists for preventing the LH surge during controlled ovarian stimulation (PRO_NAT study): study protocol of a randomized clinical trial.

Introduction: Progesterone-primed cycles effectively suppress the pituitary LH surge during ovarian stimulation in oocyte donors and in the infertile population. Particularly in oocyte donors, the use of synthetic progesterone (progestins) has been explored in prospective clinical trials, showing mixed results. This trial was designed to determine whether the use of micronized natural progesterone is as effective as the GnRH-antagonist protocol in terms of the number of mature oocytes (MII) retrieved in oocyte donation cycles as a primary outcome, and it also aims to explore the corresponding results in recipients as a secondary outcome. Methods: We propose a prospective, open-label, non-inferiority clinical trial to compare a novel approach for oocyte donors with a control group, which follows the standard ovarian stimulation protocol used in our institution. A total of 150 donors (75 in each group) will be recruited and randomized using a computer algorithm. After obtaining informed consent, participants will be randomly assigned to one of two ovarian stimulation protocols: either the standard GnRH antagonist or the oral micronized natural progesterone protocol. Both groups will receive recombinant gonadotropins tailored to their antral follicle count and prior donation experiences, if any. The primary outcome is the number of mature metaphase II (MII) oocytes. Secondary measures include treatment duration, pregnancy outcomes in recipients, as well as the economic cost per MII oocyte obtained in each treatment regimen. Analyses for the primary outcome will be conducted in both the intention-to-treat (ITT) and per-protocol (PP) populations. Each donor can participate only once during the recruitment period. The estimated duration of the study is six months for the primary outcome and 15 months for the secondary outcomes. Discussion: The outcomes of this trial have the potential to inform evidence-based adjustments in the management of ovarian stimulation protocols for oocyte donors. Clinical trial registration: ClinicalTrials.gov, identifier, NCT05954962.

IL-6/IL-10 and IL-1ß/IL-4 ratios associated with poor ovarian response in women undergoing in-vitro fertilization.

The aim of this work was to evaluate whether serum cytokines levels are associated with ovarian response in IVF. 149 patients were included in a retrospective study. Cytokines IL-2, IL-4, IL- 6, IL-8, IL-10, VEGF, IFNγ, TNFα, IL-1α, IL-1ß, MCP-1 and EGF were measured by sandwich immunoassay previously to ovarian stimulation. Performing hierarchical cluster analysis, we observed that the antral follicle count, the total oocytes recovered and the MII recovered are grouped in the same cluster as the cytokines IL-2-4-6-10-1α-1ß, IFNγ y TNFα. Then, we found that the ratio between IL and 6 and IL-10 was higher in low responder women (2.15 versus 1.55; p = 0.035). If we establish 0.9 as a cut-off for the IL-6/IL-10, we observed that above this value the risk of having a low response to ovarian stimulation was more than 3 times greater than below this value (22.9 % versus 6.0 %; p = 0.007). Also, the ratio IL-1ß/IL-4 was higher in patients with normal or suboptimal response (0.62 versus 0.34; p = 0.034) and any patient with low response had a value greater than 0.7 (p = 0.003). As a conclusion, the IL-6/IL-10 and IL-1ß/IL-4 ratios showed differences between normoresponder women and patients with low ovarian response.

Intermediate and normal sized CGG repeat on the FMR1 gene does not negatively affect donor ovarian response.

BACKGROUND: Fragile X syndrome is associated with low ovarian reserve and poor ovarian response. The aim of this study was to investigate whether CGG repeats on the fragile X mental retardation 1 (FMR1) gene have predictive value for ovarian response to stimulation with gonadotrophins and for clinical outcome in our oocyte donation program. METHODS: Oocyte donor candidates were selected according to Instituto Bernabeu oocyte donation program requirements. Fragile X genetic screening was performed in 204 oocyte donors, defining 141 controls and 63 cases: 35-39 repeats (n = 34), 40-45 (n = 12) and >45 (n = 17). All the patients underwent ovarian stimulation using a GnRH antagonist protocol and received a GnRH agonist trigger. The main factors used to measure outcome were oocyte yields, days of stimulation, gonadotrophin dosages, biochemical pregnancy, ongoing pregnancy and miscarriage rates. RESULTS: No differences between the study group and controls were reported in oocyte yields (17.5 versus 18.9) or days of stimulation (11.40 versus 9.82). The control group used significantly more gonadotrophin (2212 versus 1850 IU) than the study group. Clinical outcome was not affected by the CGG repeats on the FMR1 gene in oocyte donors. CONCLUSIONS: No negative effect was observed for intermediate-sized CGG repeats on ovarian stimulation and clinical outcome using a non-confounding model of oocyte donation. These results disagree with previous studies performed on infertility patients. Owing to the present study, fragile X genetic screening should not be considered for prediction of response to ovarian stimulation.

Evaluation of drug seeking behavior on nicotine conditioned place preference in zebrafish.

Seeking of drugs is commonly evaluated in a specific environment for assessing drug preference. However, cognitive strategies involved in drug seeking are mostly unknown. To assess the strength of environmental cues that can be associated with nicotine in the zebrafish brain reward circuitry, we have designed herein a modified conditioned place preference (CPP) paradigm. This task was devised to identify salient environmental cues relevant for strong nicotine-environment association and drug seeking induction. During test sessions, background colors of the CPP tank chambers were shifted and preference for colors associated to nicotine was assessed. We have compared several tank designs and different compartment colors. Our findings indicated that zebrafish seeking behavior was strongly dependent on compartment color shades. Combination of red and yellow environments, which were preferred and avoided compartments, respectively, was the most effective design presenting the highest CPP-score. Interestingly, animals that stayed for longer periods in the environment conditioned to nicotine during a first testing interval were also able to follow the background color shade conditioned to nicotine to the other compartment immediately after background colors were relocated between compartments. During a second testing period, zebrafish also stayed for longer periods in the colored compartment paired to nicotine during conditioning. These findings suggest that under salient environmental conditions, zebrafish voluntarily followed a shifting visual cue previously associated with nicotine delivery. Furthermore, our findings indicate that zebrafish exhibit spatial associative learning and memory, which generates a repertoire of conspicuous locomotor behaviors induced by nicotine preference in the CPP task.

Identification of vaginal microbiome associated with IVF pregnancy.

The factors that cause a preterm birth (PTB) are not completely understood up to date. Moreover, PTB is more common in pregnancies achieved by in-vitro fertilization (IVF) than in spontaneous pregnancies. Our aim was to compare the composition of vaginal microbiome at 12 weeks of gestation between women who conceived naturally or through IVF in order to study whether IVF PTB-risk could be related to vaginal microbiome composition. We performed an observational, prospective and multicentre study among two public hospitals and a fertility private clinic in Spain. Vaginal swabs from 64 pregnant women at 12 weeks of gestation were collected to analyse the microbiome composition by sequencing the V3-V4 region of the 16S rRNA. Our results showed that the vaginal microbiome signature at 12 weeks of pregnancy was different from women who conceived naturally or through IVF. The beta diversity and the genus composition were different between both cohorts. Gardnerella, Neisseria, Prevotella, and Staphylococcus genus were enriched genus in the vaginal microbiome from the IVF group, allowing us to create a balance model to predict both cohorts. Moreover, at species level the L. iners abundance was higher and L. gasseri was lower in the IVF group. As a conclusion, our findings were consistent with a proposed framework in which IVF pregnancy are related to risk for preterm birth (PTB) suggesting vaginal microbiome could be the reason to the relation between IVF pregnancy and risk for PTB.

Characterization of the vaginal and endometrial microbiome in patients with chronic endometritis.

OBJECTIVE: To compare the endometrial and vaginal microbiome of women with and without chronic endometritis. STUDY DESIGN: A cohort study with 60 patients undergoing assisted reproductive treatment with their own or donated gametes was undertaken. Vaginal and endometrial samples were taken in the cycle prior to embryo transfer. The endometrial and vaginal microbiome was analysed by mass sequencing of the V3V4 region of 16S rRNA gene. Bioinformatics analysis was performed using QIIME2 and MicrobiomeAnalyst packages. Alpha diversity, beta diversity and taxonomic characterization were compared between samples that tested positive and negative for chronic endometritis on CD138 immunohistochemistry. RESULTS: Different bacterial communities were detected when vaginal and endometrial samples were analysed in patients with and without endometritis diagnosed using CD138 immunohistochemistry. In patients with endometritis, a higher alpha-diversity index was found in vaginal samples (p = 0.15 for the Shannon index) and significant differences were found in endometrial samples (p = 0.01 for the Shannon index). In the beta-diversity analysis, no significant differences were observed between the groups with and without endometritis. Vaginal and endometrial samples from women with endometritis showed a microbiome pattern that was not dominated by Lactobacillus spp. Relative abundance analysis identified Ralstonia and Gardnerella spp. in endometrial samples, and Streptoccoccus and Ureaplasma spp. in vaginal samples of patients diagnosed with chronic endometritis on CD138 immunohistochemistry. When comparing endometrial and vaginal samples diagnosed with endometritis on CD138 immunohistochemistry, both alpha diversity (p = 0.06 for the Shannon index and p = 0.08 for the Simpson index) and beta diversity (p < 0.001) showed significant differences. Lactobacillus spp. (p = 3.76E-4), Ralstonia spp. (p = 8.19E-4), Delftia spp. (p = 0.004) and Anaerobacillus spp. (p = 0.004) were identified in these sample groups. CONCLUSION: These results demonstrate the existence of a characteristic vaginal and endometrial microbiota in patients with chronic endometritis. Different genera and species were identified in patients with and without chronic endometritis depending on whether the sample was endometrial or vaginal. There is a clear relationship between changes in the vaginal microbiome and chronic endometritis. The microbiota is a continuum throughout the female reproductive tract, so study of the vaginal microbiota could be useful for the diagnosis of diseases of the upper reproductive tract, such as chronic endometritis.

Oligodendrogenesis in iron-deficient rats: effect of apotransferrin.

In rats, iron deficiency produces an alteration in myelin formation. However, there is limited information on the effects of this condition on oligodendroglial cell (OLGc) proliferation and maturation. In the present study, we further analyzed the hypomyelination associated with iron deficiency by studying the dynamics of oligodendrogenesis. Rats were fed control (40 mg Fe/kg) or iron-deficient (4 mg Fe/kg) diets from gestation day 5 until postnatal day 3 (P3) or 11 (P11). OLGc proliferation, migration and differentiation were investigated before and after an intracranial injection of apotransferrin at 3 days of age (P3). The proliferating cell population was evaluated at P3. Iron-deficient (ID) animals showed an increase in the oligodendrocyte precursors cell (OPC) population in comparison with controls. The overall pattern of migration of cells labeled with BrdU was investigated at P11. Iron deficiency increased the amount of BrdU(+) cells in the corpus callosum (CC) and decreased OLGc maturation and myelin formation. Changes in nerve conduction were analyzed by measuring visual evoked potentials. Latency and amplitude were significantly disturbed in ID rats compared with controls. Both parameters were substantially normalized when animals were treated with a single intracranial injection of 350 ng apotransferrin (aTf). The current results give support to the idea that iron deficiency increases the number of proliferating and undifferentiated cells in the CC compared with the control. Treatment with aTf almost completely reverted the effects of iron deficiency, both changing the migration pattern and increasing the number of mature cells in the CC and myelin formation.

Why don't consumers buy organic lamb meat? A Spanish case study.

The fall in lamb meat consumption makes it necessary to determine strategies to increase its consumption and the viability of livestock farms. Given this scenario, organic lamb meat emerges as a product with major growth potential. Using crisp-set qualitative comparative analysis (csQCA), this study analyses the profile of lamb meat consumers who decide against consuming organic lamb meat, identifying the main reasons they give for this decision. The findings reveal two majority segments of non-consumers of organic lamb meat, corresponding to 44.2% and 32.8% of conventional lamb meat consumers. In these segments, the main reasons given for non-consumption of lamb meat are, in the following order, supply, higher price and the lack of guarantees that the meat is actually organic. Thus, increasing organic lamb meat consumption necessarily involves greater efforts in the supply chain and greater promotion of information about the controls that guarantee the quality of certified organic lamb.

Sensitization-dependent nicotine place preference in the adult zebrafish.

Sensitization of motor activity is a behavioural test to evaluate the effects of psychostimulants. Conditioned place preference (CPP) is an associative learning procedure to examine the rewarding properties of drugs. We aimed to assess whether motor sensitization to drugs of abuse can make zebrafish more vulnerable to establishing drug-induced CPP. We first evaluated sensitization of locomotor activity of zebrafish to repeated administrations of nicotine and cocaine during 5 days and after 5 days of withdrawal. After withdrawal, when zebrafish were re-exposed to the same dose of nicotine or cocaine locomotor activity was increased by 103% and 166%, respectively. Different groups of zebrafish were sensitized to nicotine or cocaine and trained on a nicotine-CPP task the day after withdrawal. The nicotine dose selected for sensitization was not effective for developing CPP in naïve zebrafish whereas it elicited CPP in zebrafish that were previously sensitized to nicotine or cocaine. Levels of nicotinic acetylcholine receptor ß2, α6 and α7 subunit, Pitx3, and tyrosine hydroxylase 1 (TH1) mRNAs were increased in the brain of nicotine- and cocaine-sensitized zebrafish. Nicotine-CPP performed with drug-sensitized zebrafish provoked further enhancements in the expression of α6 and α7 subunit, Pitx3, and TH1 mRNAs suggesting that the expression of these molecules in the reward pathway is involved in both processes. Our findings indicate that repeated exposures to low doses of drugs of abuse can increase subject's sensitivity to the rewarding properties of the same or different drugs. This further suggests that casual drug intake increases the probability of becoming addict.

Evaluation of the rewarding properties of nicotine and caffeine by implementation of a five-choice conditioned place preference task in zebrafish.

The rewarding properties of drugs in zebrafish can be studied using the conditioned place preference (CPP) paradigm. Most devices that have been used for CPP consist of two-half tanks with or without a central chamber. Here we evaluated the rewarding effects of nicotine and caffeine using a tank with five arms distributed radially from a central chamber that we have denoted Fish Tank Radial Maze (FTRM). Zebrafish were trained to associate nicotine or caffeine with a coloured arm. In testing sessions to assess CPP induction, between two and five different arms were available to explore. We found that when offering the two arms, one of them associated to the drug mediating conditioning for 14 days, zebrafish showed nicotine-induced CPP but not caffeine-induced CPP. When zebrafish had the option to explore drug-paired arms together with new coloured arms as putative distractors, the nicotine-CPP strength was maintained for at least three days. The presence of novel environments induced caffeine-CPP, which was still positive after three days of testing sessions. Complementary behavioural data supported these findings. Nicotine-CPP was prevented by the histone deacetylase inhibitor phenylbutyrate administered during conditioning; however, there were no effects on caffeine-CPP. The specific acetylation of lysine 9 in histone 3 (H3-K9) was increased in nicotine-conditioned zebrafish brains. This study suggests that novel environmental cues facilitate drug-environment associations, and hence, the use of drugs of abuse.

Comprehensive mitochondrial DNA analysis and IVF outcome.

STUDY QUESTION: Do mitochondrial DNA (mtDNA) copy number and heteroplasmy in human embryos affect the ongoing pregnancy rate? SUMMARY ANSWER: Our study suggests that mtDNA copy number above a specific threshold is associated with the ongoing pregnancy rate. WHAT IS KNOWN ALREADY: Mitochondria play a vital role in cell function. Recently, there has been increasing research on mtDNA as a biomarker of embryo implantation. Although reports showed that high levels of mtDNA in the blastocyst are associated with low implantation potential, other publications were unable to confirm this. Confounding factors may influence the mtDNA copy number in euploid embryos. On the other hand it has been speculated that both mtDNA heteroplasmy and copy number contribute to mitochondrial function. Next generation sequencing (NGS) allows us to study in depth mtDNA heteroplasmy and copy number simultaneously. STUDY DESIGN SIZE DURATION: A prospective non-selection study was performed. We included 159 blastocyst biopsies from 142 couples who attended our clinic for preimplantation genetic testing for aneuploidies (PGT-A), from January 2017 to December 2017. All embryos were biopsied on Day 5 or Day 6. The aneuploid testing was performed by NGS. All blastocysts were diagnosed as euploid non-mosaic and were transferred. The mtDNA analysis was performed once the embryo diagnosis was known. PARTICIPANTS/MATERIALS SETTING METHODS: Sequencing reads mapping to the mtDNA genome were extracted from indexed bam files to identify copy number and heteroplasmy. The relative measure of mtDNA copy number was calculated by dividing the mtDNA reads by the nuclear DNA value to normalize for technical variants and the number of cells collected at the biopsy. All the results were subjected to a mathematical correction factor according to the embryo genome. Heteroplasmy was assigned by MitoSeek. MAIN RESULTS AND THE ROLE OF CHANCE: The mean average copy number and SD of mtDNA per genome was 0.0016 ± 0.0012. Regarding heteroplasmy, 40 embryos were heteroplasmy carriers (26.32%). MtDNA variants were detected in coding and non-coding regions and the highest number of variants in an embryo was eight. With respect to IVF outcome for mtDNA copy number analysis, we set a threshold of 0.003 for the following analysis. The vast majority of the embryos were below the threshold (142/159, 89.31%) and 17 embryos were classified as having higher mtDNA levels. We showed a reduction in ongoing pregnancy rate associated with elevated mtDNA copy number (42.96% versus 17.65%, P < 0.05). This result was independent of maternal age and day of the biopsy: these factors were included as confounding factors because mtDNA copy number was negatively correlated with female age (25 -30 y: 0.0017 ± 0.0011, 30 -35 y: 0.0012 ± 0.0007, 35 -40 y: 0.0016 ± 0.0009, over 40 y: 0.0024 + 0.0017, P < 0.05). Embryos biopsied on Day 5 were more likely to have higher quantities of mtDNA compared with those biopsied on Day 6 (0.0017 versus 0.0009, P < 0.001). According to IVF outcome and heteroplasmy, a lower ongoing pregnancy rate was reported for embryos that carried more than two variants. However, this did not reach statistical significance when we compared embryos with a number of variants lower or higher than two (39.15 versus 20.0, P = 0.188). Finally, a clear positive association between the mtDNA variants and copy number was reported when we compare embryos with or without heteroplasmy (0.0013 ± 0.0009 versus 0.0025 ± 0.0014, P < 0.001) and among different numbers of variants (0:0.0013 ± 0.0009, 1-2:0.0023 ± 0.0012, >2:0.0043 ± 0.0014, P < 0.05). LIMITATIONS REASONS FOR CAUTION: A limitation may be the size of the sample and the high-throughput sequencing technology that might not have detected heteroplasmy levels below 2% which requires high sequence depth A clinical randomized trial comparing the clinical outcome after the transfer of embryos selected according to mtDNA levels or only by morphological evaluation will be necessary. More research into the impact of mtDNA heteroplasmy and copy number on IVF outcome is needed. WIDER IMPLICATIONS OF THE FINDINGS: Our results demonstrate that embryos with elevated mtDNA copy number have a lower chance of producing an ongoing pregnancy. MtDNA copy number is higher in older women and is dependent upon the number of cell divisions that preceded biopsy. Moreover, our data suggest that mitochondrial activity could be a balance between functional capacity and relative mtDNA copy number. STUDY FUNDING/COMPETING INTERESTS: There are no conflicts of interest or sources of funding to declare. TRIAL REGISTRATION NUMBER: Not applicable.

Human sperm motility, capacitation and acrosome reaction are impaired by 2-arachidonoylglycerol endocannabinoid.

The endocannabinoids are cannabinoids synthesized by mammalian tissues. These compounds are closely related to the regulation of the male reproductive system. However, little is known about the effects produced by 2-arachidonoylglycerol (2AG) on in vitro human sperm functions. This study was undertaken to determine the effects produced by 2AG on fresh human sperm and in the capacitation technique. Semen samples from healthy young men were exposed to different concentrations of 2AG before and during capacitation technique. In this work, we have demonstrated that 2AG induces the spontaneous acrosome reaction and reduces progressive motility in fresh human sperm. During the capacitation technique, sperm becomes more sensitive to low concentrations of 2AG, triggering the acrosome reaction and inhibiting protein phosphorylation. In summary, 2AG affects the in vitro functionality of human sperm by reducing motility, inhibiting capacitation and triggering the acrosome reaction.

Short- and long-term effects of nicotine and the histone deacetylase inhibitor phenylbutyrate on novel object recognition in zebrafish.

RATIONALE: Zebrafish have a sophisticated color- and shape-sensitive visual system, so we examined color cue-based novel object recognition in zebrafish. We evaluated preference in the absence or presence of drugs that affect attention and memory retention in rodents: nicotine and the histone deacetylase inhibitor (HDACi) phenylbutyrate (PhB). OBJECTIVES: The objective of this study was to evaluate whether nicotine and PhB affect innate preferences of zebrafish for familiar and novel objects after short- and long-retention intervals. METHODS: We developed modified object recognition (OR) tasks using neutral novel and familiar objects in different colors. We also tested objects which differed with respect to the exploratory behavior they elicited from naïve zebrafish. RESULTS: Zebrafish showed an innate preference for exploring red or green objects rather than yellow or blue objects. Zebrafish were better at discriminating color changes than changes in object shape or size. Nicotine significantly enhanced or changed short-term innate novel object preference whereas PhB had similar effects when preference was assessed 24 h after training. Analysis of other zebrafish behaviors corroborated these results. CONCLUSIONS: Zebrafish were innately reluctant or prone to explore colored novel objects, so drug effects on innate preference for objects can be evaluated changing the color of objects with a simple geometry. Zebrafish exhibited recognition memory for novel objects with similar innate significance. Interestingly, nicotine and PhB significantly modified innate object preference.

Effects of combined nicotine and fluoxetine treatment on adult hippocampal neurogenesis and conditioned place preference.

Adult neurogenesis occurs in mammals within the dentate gyrus, a hippocampal subarea. It is known to be induced by antidepressant treatment and reduced in response to nicotine administration. We checked here whether the antidepressant fluoxetine would inverse the decrease in hippocampal neurogenesis caused by nicotine. It is shown that repeated, but not a single injection of rats with fluoxetine was able to abolish the decrease in adult dentate cell proliferation produced by nicotine treatment. We measured the expression of several biochemical parameters known to be associated with neurogenesis in the dentate gyrus. Both drugs increased the expression of p75 neurotrophin receptor, which promotes proliferation and early maturation of dentate gyrus cells. Using the conditioned place preference (CPP) paradigm, we also gave both drugs in a context in which their rewarding properties could be measured. Fluoxetine produced a significant but less robust CPP than nicotine. A single injection of fluoxetine was found to reduce nicotine-induced CPP. Moreover, the rewarding properties of nicotine were completely abolished in response to repeated fluoxetine injections. Expression of nicotine-induced CPP was accompanied by an increase of phospho-CREB (cyclic AMP-responsive element-binding protein) and HDAC2 (histone deacetylase 2) expression in the nucleus accumbens. The data suggest that fluoxetine reward, as opposed to nicotine reward, depends on dentate gyrus neurogenesis. Since fluoxetine was able to disrupt the association between nicotine and the environment, this antidepressant may be tested as a treatment for nicotine addiction using cue exposure therapy.

NMDA and AMPA/kainate glutamate receptors modulate dentate neurogenesis and CA3 synapsin-I in normal and ischemic hippocampus.

The effect of N-methyl-D-aspartate (NMDA) and 2-(aminomethyl)phenylacetic acid/kainate (AMPA/kainate) glutamate receptors on dentate cell proliferation and hippocampal synapsin-I induction was examined after global ischemia. Cell proliferation was assessed using BrdU labeling, and synaptic responses were assessed using synapsin-I expression. Systemic glutamate receptor antagonists (MK-801 and NBQX) increased BrdU-labeled cells in the dentate subgranular zone (SGZ) of control adult gerbils (30% to 90%, P < 0.05). After global ischemia (at 15 days after 10 minutes of ischemia), most CA1 pyramidal neurons died, whereas the numbers of BrdU-labeled cells in the SGZ increased dramatically (>1000%, P < 0.0001). Systemic injections of MK801 or NBQX, as well as intrahippocampal injections of either drug, when given at the time of ischemia completely blocked the birth of cells in the SGZ and the death of CA1 pyramidal neurons at 15 days after ischemia. Glutamate receptor antagonists had little effect on cell birth and death when administered 7 days after ischemia. The induction of synapsin-I protein in stratum moleculare of CA3 at 7 and 15 days after global ischemia was blocked by pretreatment with systemic or intrahippocampal MK-801 or NBQX. It is proposed that decreased dentate glutamate receptor activation--produced by glutamate receptor antagonists in normal animals and by chronic ischemic hippocampal injury--may trigger dentate neurogenesis and synaptogenesis. The synapsin-I induction in mossy fiber terminals most likely represents re-modeling of dentate granule cell neuron presynaptic elements in CA3 in response to the ischemia. The dentate neurogenesis and synaptogenesis that occur after ischemia may contribute to memory recovery after hippocampal injury caused by global ischemia.

Odor regulates the expression of the mitogen-activated protein kinase phosphatase gene hVH-5 in bilateral entorhinal cortex-lesioned rats.

Since it is known that several immediate early genes are induced by olfactory stimuli, we determined whether an olfactory stimulus also induces the expression of the mitogen-activated protein kinase (MAPK) phosphatase gene hVH-5 (homologue of vaccinia virus H1 phosphatase gene, clone 5), a member of a novel class of immediate early genes encoding dual-specificity protein phosphatases. The expression was studied by in situ hybridization in different brain structures involved in odor processing, in control and bilateral entorhinal cortex (EC) lesioned rats. EC-lesion did not significantly affect hVH-5 gene expression in the glomerular cell layer of the olfactory bulb (OB), while odor stimulation induced it in both control and EC-lesioned groups. In contrast, odor-induced expression of hVH-5 gene in mitral/granular cell layers was only evident after lesion of the EC. Similar results were obtained in the piriform cortex (PCx), a structure intimately connected to the mitral cell layer. In the CA1 hippocampal subfield, odor stimulation induced hVH-5 gene expression in both control and EC-lesioned animals, the increase being potentiated in lesioned rats. CA3 and dentate gyrus exhibited a similar pattern of gene expression, the odor stimulating gene expression in both control and lesioned groups. The amygdala (Am) displayed no significant change. It appears that through the induction of a MAPK phosphatase, the EC controls MAPK activities differently after odor stimulation in OB, PCx and hippocampus (Hip). The results illustrate the notion that odor representation in the brain requires plastic modifications at both anatomical and functional levels.