Theoretical Study on Thermal Structural Fluctuation Effects of Intermolecular Configurations on Singlet Fission in Pentacene Crystal Models.

Singlet fission (SF) occurs as a result of complex excited state relaxation dynamics in molecular aggregates, where a singlet exciton (FE) state is converted into a double-triplet exciton (TT) state through the interactions with several other degrees of freedom, such as nuclear motions. In this study, we combined quantum dynamics simulation based on the quantum master equation approach with all-atom-based classical molecular mechanics/molecular dynamics to examine the thermal structural fluctuation (i.e., static disorder) effects of intermolecular configuration on SF in pentacene crystal models. In particular, we considered two types of static-disordered models, in which excited states are assumed to interact with nuclear motions of intermolecular modes in the classical mechanical/statistical manner. We found that the introduction of static disorder effects leads to a faster decay of coherence between the FE and charge transfer (CT) states in the early stage of SF, contributing to the accelerations of several FE → TT relaxation pathways. Such acceleration in these models is shown to be attributed to fluctuations in the energies and electronic coupling of the CT states based on relative relaxation factor analysis. The present study is expected to contribute to further development of bottom-up materials design for efficient SF in condensed phases where the exitonic system interacts with nuclear motions in various coupling strengths.

Theoretical study on the effect of applying an external static electric field on the singlet fission dynamics of pentacene dimer models.

We investigate the effect of applying an external static electric field on the singlet fission (SF) dynamics of pentacene dimer models using quantum chemical calculations and exciton dynamics simulations. It is found that the excitation energies of anion-cation (AC) and cation-anion (CA) pair exciton states in the SF process are significantly stabilized and destabilized, respectively, by applying an external static electric field (F) in the intermolecular direction. As a result, this change of excitation energies is found to accelerate the SF dynamics in pentacene dimer models. In particular, in the tilted- and parallel-type pentacene dimer models, SF rates at F = 0.001 a.u. are predicted to be about 2.3 and 3.0 times as large as those at F = 0.0 a.u. while keeping the TT yields large. The present result contributes to paving the way for novel physical and chemical controls, that is, an external static electric field application and donor/acceptor substitution on SF molecules, of SF dynamics.

Theoretical Study on Singlet Fission Dynamics in Slip-Stack-like Pentacene Ring-Shaped Aggregate Models.

We investigate the singlet fission (SF) dynamics of a slip-stack-like pentacene ring-shaped aggregate model, which is constructed by rotating each pentacene unit around its longitudinal axis in an H-aggregate ring. The aggregate size (N) and rotation angle (α) dependences of SF rates and double triplet (TT) yields are clarified using the quantum master equation method. It is found that there exist optimal ranges of the rotation angle α for each N, yielding efficient SF with high SF rates and TT yields. For example, in an 8-mer model, SF rates at α = 23 and 43° are 18.9 and 38.6 times as high as that at α = 30°, respectively, and the TT yields are as high as 0.871, 0.988, and 0.882 at α = 23, 30, and 43°, respectively. Analysis of the relative relaxation factors shows that the many-to-many relaxation paths from adiabatic Frenkel exciton (FE)-like states to TT-like states are opened by tuning α at relevant aggregate sizes, causing fast and high-TT-yield SF, and efficient SF occurs at α = 40° for medium N (7 ≤ N ≤ 10) or at α = 30° for large N (>10). This mechanism is interpreted by the second-order perturbation theory for electronic couplings. Namely, the inequality in the energies of charge-transfer states [CA and AC states, where the cation (C) and anion (A) are located at two neighboring sites in anticlockwise and clockwise directions, respectively] and the change in the amplitude and sign of the couplings between the FE, CT, and TT states are found to cause quantum superposition of the FE and TT states, which contribute to the high TT yield and SF rate. The present results contribute to a deeper understanding of SF dynamics in ring-shaped aggregates as well as to the development of their new design guidelines.

Theoretical Molecular Design of Phenanthrenes for Singlet Fission by Diazadibora-Substitution.

Based on the valence configuration interaction (VCI) model and quantum chemical calculations, we theoretically investigate the potential of diazadibora-substituted phenanthrenes [(BN)2-phenanthrenes] as novel singlet fission (SF) chromophores. (BN)2-substitution to phenanthrene is performed to exhibit a captodative effect, which is found to enhance both diradical character and exchange integral. These enhanced parameters induced by (BN)2-substitution are shown to bring energetically favorable SF with high triplet excitation energies. In order to reveal the relationship between diradical character and positions replaced by (BN)2, analyses based on the VCI model, odd-electron density, and resonance structures are conducted. Accordingly, a concrete design principle, which is inherent in and is understandable from the topology of (BN)2-phenanthrene, is presented. Furthermore, design strategies to fine-tuning of the diradical character are newly demonstrated based on the additional introduction of π-donor and π-acceptor. The present results provide feasible candidate molecules and novel design strategies toward the discovery of bright SF chromophores for the application to efficient organic solar cells.

Vibronic coupling density analysis and quantum dynamics simulation for singlet fission in pentacene and its halogenated derivatives.

We theoretically investigate microscopic origins of vibronic coupling (VC) contributing to singlet fission (SF) dynamics in pentacene and its halogenated derivatives. The features of VCs related to diabatic exciton states and interstate electronic couplings (Holstein and Peierls couplings, respectively) are interpreted by the VC density (VCD) analysis, which allows one to clarify the relationship between the chemical structure and VC as spatial contribution. It is found for the pentacene dimer face-to-edge configuration in a herringbone crystal that characteristic intermolecular vibrations with low frequencies exhibit strong Holstein couplings for the intermediate charge-transfer (CT) exciton states as well as Peierls couplings. From VCD analysis, the comprising density of the intermolecular CT and that of the intermolecular vibration are found to be constructively mixed in the intermolecular space, leading to the enhancement of VC. Moreover, in order to assess the chemical modification manner for controlling VC, we design several halogenated pentacene derivatives with slip-stack configurations. Our strategy to enhance VCD by halogenation is found to be rational, whereas the peaks of VC spectra for the CT states in the slip-stack packings are observed in high frequency regions. We compare their SF dynamics based on the quantum master equation explicitly including the exciton state-dependent VCs. From the analysis on relative relaxation factors between the adiabatic exciton states, their difference in the SF rate is highlighted by exciton configurations in addition to VCs. The present study is expected to be a first step toward efficient SF based on the design of VC in terms of both the chemical structure and intermolecular packing.

Quantum design for singlet-fission-induced nonlinear optical systems: Effects of π-conjugation length and molecular packing of butterfly-shaped acenes.

Theoretical molecular design of efficient nonlinear optical (NLO) systems using singlet fission (SF) is performed for butterfly-shaped acenes with/without nitrogen and sulfur substitutions using quantum chemical calculations, exciton dynamics simulations, and Marcus theory. It is found that these large systems meet the energy level matching conditions of efficient SF and exhibit superior third-order NLO properties (second hyperpolarizability γ at the molecular scale) to a typical SF molecule, pentacene. In addition, we investigate SF rates and γ in the correlated triplet pair [1(TT)] state generated by SF for various slip-stacked dimer models of these systems. For molecular packing with relatively large 1(TT) yields, a significant increase in γ/monomer in the 1(TT) state is observed, which is in good agreement with the electronic-coupling-based design guidelines obtained from our previous study. In particular, the butterfly-shaped acenes involving heteroatoms are found to exhibit a significant increase in γ/monomer as compared to the other systems. By analyzing the excitation properties in the 1(TT) state and intermolecular orbital interactions, we clarify the origin of such γ enhancement. The obtained results contribute to the construction of design guidelines for efficient SF-induced-NLO materials and demonstrate that butterfly-shaped acenes have the potential to surpass conventional NLO systems.

Theoretical Study on Third-Order Nonlinear Optical Properties for One-Hole-Doped Diradicaloids.

We investigate the relationships between open-shell character and longitudinal static second hyperpolarizabilities γ for one-hole-doped diradicaloids using the strong-correlated ab initio molecular orbital methods and simple one-dimensional (1D) three-site two-electron (3s-2e) models. As examples of one-hole-doped diradicaloids, we examine H3 +, methyl radical trimer cation ((CH3)3 +), silyl radical trimer cation ((SiH3)3 +), and 1,2,3,5-dithiadizolyl trimer cation (DTDA3 +). For H3 +, the static γ exhibits negative values and shows a monotonic increase in amplitude with an increase in the open-shell character defined by a neighbor-site interaction (y S). On the other hand, it is found for (CH3)3 +, (SiH3)3 +, and DTDA3 + that the static γ value exhibits similar behavior to that for H3 + up to an intermediate y S value, while it takes the negative maximum at a large y S value, followed by a decrease in γ amplitude, and subsequently, γ changes to positive values with a drastic increase for larger y S values. For example, in DTDA3 +, the negative/positive γ values, -69 × 105/700 × 105 au at y S = 0.75/0.87, exhibit significant enhancements in amplitude, 2.4/24 times as large as that (-29 × 105 au) at intermediate y S = 0.59 as is often the case in DTDA2. Using the 1D 3s-2e valence-bond configuration interaction model, these sign inversions and drastic increase in the amplitude of γ are found to originate in the differences in Coulomb interactions between valence electrons, between valence and core electrons, and between valence electrons and nuclei. These results contribute to pave the way for the construction of novel control guidelines for the amplitude and sign of γ for one-hole-doped diradicaloids.

Selectively crosslinked hyaluronic acid hydrogels for sustained release formulation of erythropoietin.

A novel sustained release formulation of erythropoietin (EPO) was developed using hyaluronic acid (HA) hydrogels. For the preparation of HA hydrogels, adipic acid dihydrazide grafted HA (HA-ADH) was synthesized and analyzed with (1)H NMR. The degree of HA-ADH modification was about 69%. EPO was in situ encapsulated into HA-ADH hydrogels through a selective cross-linking reaction of bis(sulfosuccinimidyl) suberate (BS(3)) to hydrazide group (pK(a) = 3.0) of HA-ADH rather than to amine group (pK(a) > 9) of EPO. The denaturation of EPO during HA-ADH hydrogel synthesis was drastically reduced with decreasing pH from 7.4 to 4.8. The specific reactivity of BS(3) to hydrazide at pH = 4.8 might be due to its low pK(a) compared with that of amine. In vitro release of EPO in phosphate buffered saline at 37 degrees C showed that EPO was released rapidly for 2 days and then slowly up to 4 days from HA-ADH hydrogels. When the hydrogels were dried at 37 degrees C for a day, however, longer release of EPO up to 3 weeks could be demonstrated. According to in vivo release test of EPO from HA-ADH hydrogels in SD rats, elevated EPO concentration higher than 0.1 ng/mL could be maintained from 7 days up to 18 days depending on the preparation methods of HA-ADH hydrogels. There was no adverse effect during and after HA-ADH hydrogel implantation.

Sustained release formulation of erythropoietin using hyaluronic acid hydrogels crosslinked by Michael addition.

A novel sustained release formulation of erythropoietin (EPO) was successfully developed using hyaluronic acid (HA) hydrogels crosslinked by Michael addition. Adipic acid dihydrazide grafted HA (HA-ADH) was prepared and then modified into methacrylated HA (HA-MA). (1)H NMR analysis showed that the degrees of HA-ADH and HA-MA modification were 69 and 29 mol%, respectively. Using the specific crosslinkers of dithiothreitol (DTT) and peptide linker, EPO was loaded during HA-MA hydrogel preparation by Michael addition chemistry between thiol and methacrylate groups. The amount of EPO recovered from both hydrogels after degradation with hyaluronidase SD (HAse SD) was about 90%. The crosslinking reaction with peptide linker (GCYKNRDCG) was faster than that with DTT. The gelation time was about 30 min for peptide linker and 180 min for DTT. In vitro release test of EPO from HA-MA hydrogel at 37 degrees C showed that EPO was released rapidly for 2 days and then slowly up to 7 days from HA-MA hydrogels. The released EPO appeared to be intact from the analysis with RP-HPLC. According to in vivo release test of EPO from HA-MA hydrogels crosslinked with the peptide linker in Sprague-Dawley (SD) rats, elevated plasma concentration of EPO was maintained up to 7 days. There was no adverse effect during and after the in vivo tests.

Morphological evaluation of microvascular networks and angiogenic factors in the selective growth of oocytes and follicles in the ovaries of mouse fetuses and newborns.

In the mammalian ovary, there is a striking difference in the distribution of blood vessels to individual follicles, suggesting that a microvascular network affects the selective growth of oocytes and follicles. In the present study the role of microvascular networks and angiogenic factors on the selective growth of oocytes and follicles was evaluated histologically in fetuses and newborns of ICR strain mice. Apparent selective growth of oocytes and follicles was observed in the ovaries of 1 day old newborns and, at this time, microvascular networks were recognized electronmicroscopically around the follicle that had completed the formation of its follicular structure and contained oocytes more than about 20 µm in diameter. In 3 day old newborns, oocytes more than 30 µm in diameter were detected where blood capillaries were well vascularized. Immunoreactivity to epidermal growth factor (EGF) and a strongly negative charged (colloidal iron-positive) substance (glycosaminoglycans; GAG), which have angiogenic activity, were detected in the ovaries of 3 day or older newborns and were identified more often around growing follicles containing oocytes more than 30 (GAG) and 40 (EGF) µm in diameter. Ovaries removed from 20 day old fetuses and cultured for 4 and 6 days in vitro showed a different distribution of growing follicles. A proportion of oocytes 20.0-24.9 µm in diameter increased during 4 and 6 days of incubation. However, the majority of oocytes did not grow further. These findings indicate that microvascular networks and angiogenic factors are deeply involved in selective oocyte growth beyond approximately 20-30 µm in diameter in mouse ovaries.

Cyotomedical therapy for insulinopenic diabetes using microencapsulated pancreatic beta cell lines.

Current therapy for type 1 diabetes mellitus involves a daily regimen of multiple subcutaneous or intramuscular injections of recombinant human insulin. To achieve long-term insulin delivery in vivo, we investigated the applicability of cytomedical therapy using beta TC6 cells or MIN6 cells, both of which are murine pancreatic beta cell lines that secrete insulin in a subphysiologically or physiologically regulated manner, respectively. We examined this therapy in the insulinopenic diabetic mice intraperitoneally injected with beta TC6 cells or MIN6 cells microencapsulated within alginate-poly(L)lysine-alginate membranes (APA-beta TC6 cells or APA-MIN6 cells). The diabetic mice treated with APA-beta TC6 cells fell into hypoglycemia, whereas those injected with APA-MIN6 cells maintained normal blood glucose concentrations for over 2 months without developing hypoglycemia. In addition, we also conducted an oral glucose tolerance test using these mice. The blood glucose concentrations of normal and of diabetic mice injected with APA-MIN6 cells similarly changed over time, although the blood insulin concentration increased later in the injected diabetic mice than in the former. These results suggest that cytomedicine utilizing microencapsulated pancreatic beta cell lines with a physiological glucose sensor may be a beneficial and safe therapy with which to treat diabetes mellitus.

Pallister-Mosaic syndrome and neuronal migration disorder.

We diagnosed Pallister-Mosaic syndrome (PMS) in a 4-month-old female infant. In addition to the presence of non-specific anomalies, involving anorectal, finger and ear anomalies, characteristic cranio-facial features and irregular skin lesions that appeared after age 2 months suggested the possibility of genetic mosaicism, PMS in particular. Fluorescence in situ hybridization technique revealed an extra copy of chromosome 12p; i (12p) in 30% of cultured skin fibroblasts. When focal skin lesions accompany neurodevelopmental disabilities in early infancy, genetic analysis for mosaicism should be considered for differential diagnosis. Significantly, we describe several phenotypic features and neuroimaging findings of the PMS in the present case, which have not been described in previous reports. The neuroimaging abnormalities we encountered, such as polymicrogyria, speculating congenital brain anomaly, may explain the severe motor and intellectual disabilities of PMS.

Availability of NMR microscopic observation of mouse embryo disorder: examination in malformations induced by maternal administration of retinoic acid.

Nuclear magnetic resonance (NMR) microscopy is a magnetic resonance imaging method with enhanced spatial resolution due to the use of a high static magnetic field and high magnetic field gradients. It is considered to be a useful tool for non-invasive and continuous investigation of tissue and organs at the histological level. In this study, we applied NMR microscopy to assessment of morphology in mouse embryos using a developmental disorder model induced by retinoic acid administration. Pregnant mice were given 50 mg/kg all-trans retinoic acid at 8.5 dpc. Embryos were collected at several time points after treatment and examined by NMR microscopy after fixation. Two-dimensional and three-dimensional spin echo sequences were used. Tissue contrast on two-dimensional images changed according to length of repetition time and echo time, and also to developmental stage of embryos. Two-dimensional and three-dimensional images nondestructively demonstrated defects in development of the skeleton and soft tissue, e.g. hypoplasia of vertebrae in the lumbar and tail regions and dysplasia of the spinal cord, in embryos exposed to retinoic acid. These morphological abnormalities were confirmed by conventional assessment after imaging. Although further improvements are required, NMR microscopy will provide a new approach for multi-parameter assessment of embryonic development under physiological and pathological conditions.

TRAIL-decoy receptor 1 plays inhibitory role in apoptosis of granulosa cells from pig ovarian follicles.

Previously, we histochemically examined the localization of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and its receptors in porcine ovarian follicles, and demonstrated a marked reduction in the expression of TRAIL-decoy receptor-1 (DcRI) in granulosa cells of atretic follicles. In the present study, to confirm the inhibitory activity of DcR1 in granulosa cells, granulosa cells prepared from healthy follicles were treated with phosphatidylinositol-specific phospholipase C (PI-PLC) to cleave glycophospholipid anchor of DcR1 and to remove DcR1 from the cell surface, and then incubated with TRAIL. PI-PLC treatment increased the number of apoptotic cells induced by TRAIL. The present finding indicated the possibility that TRAIL and its receptors were involved in induction of apoptosis in granulosa cells during atresia, and that DcR1 plays an inhibitory role in granulosa cell apoptosis.

Changes in the localization of type I, III and IV collagen mRNAs in the kidneys of hereditary nephritic (ICGN) mice with renal fibrosis.

Renal fibrotic change, extreme accumulation of extracellular matrix (ECM) components in glomeruli and tubulointerstitum, is one of the characteristic features of ICR-derived glomerulonephritis (ICGN) mice. Decreased degradation of ECMs by matrixmetalloproteinases was demonstrated in kidneys of ICGN mice. To determine the balance between production and degradation of ECMs in kidneys of ICGN mice, we examined expression of mRNAs of ECMs in those. To demonstrate the localization of type I, III and IV collagen mRNAs in kidney sections of ICGN and control ICR mice, in situ hybridization using digoxigenin-labeled oligonucleotide antisense probes for procollagen-alpha(1) (I), -alpha(1) (III) and -alpha(1) (IV) mRNAs, respectively, was performed. Negative or trace expressions of type I and III collagen mRNAs were observed in the kidneys of control mice, but stronger expressions of those were seen in glomeruli and injured renal tubules of the kidneys of ICGN mice. Moderate expression of type IV collagen mRNA was demonstrated in a part of glomeruli and renal tubules of both control and ICGN mice, and no remarkable difference was seen between them. Severe renal fibrosis, extreme accumulation of interstitial type I and III collagens is caused by increased production and decreased degradation in the kidneys of ICGN mice. Thus, the profiles of metabolism between interstitial and membranous collagens may be different in the kidneys of ICGN mice, and excessive production of interstitial collagens may be the dominant cause of renal disease in them.

Anemia with chronic renal disorder and disrupted metabolism of erythropoietin in ICR-derived glomerulonephritis (ICGN) mice.

The ICR-derived glomerulonephritis (ICGN) mouse, a new inbred mouse strain with a hereditary nephrotic syndrome, is considered to be a good model of human idiopathic nephrotic syndrome and notably exhibits proteinuria and hypoproteinemia from the neonatal stage. In chronic renal disorder (CRD), anemia is a major subsequent symptom (renal anemia). The precise cause of renal anemia remains unclear, primarily owing to the lack of appropriate spontaneous animal models for CRD. To establish adequate animal models for anemia with CRD, we examined the hematological-biochemical properties and histopathological characteristics. With the deterioration of renal function, ICGN mice developed a normochromic and normocytic anemia, and exhibited normochromic and microcytic at the terminal stage. The expression of erythropoietin (EPO) mRNA both in the kidneys and liver and the EPO leak into the urine were observed in ICGN mice, indicating a disrupted metabolism of EPO in ICGN mice. In addition, a lack of iron induced by the hemolysis in the spleen and the leak of transferrin into urine as proteinuria aggravated the anemic condition. In conclusion, the ICGN mouse is a good model for anemia with CRD.

Allometric study on the relation between the growth of preantral and antral follicles and that of oocytes in bovine ovaries.

We examined the relation between the growth of preantral and antral follicles and that of their oocytes in the ovaries of Holstein cows. We recovered follicles and oocytes (419 pairs) from the ovaries of 61 cows, and examined the relative growth relating the follicle diameter to the oocyte diameter by using six regression models for only healthy oocytes and all the oocytes including degenerated ones with and/or without zona pellucida. The best fitting model was found to be a hyperbolic regression (R(2): 0.999). The differentiated equation for the hyperbolic curve in normal oocytes with zona pellucida and the follicles was found to be y'=41.0/(x+0.253) (2): y and x are diameters of oocytes (microm) and follicles (mm), respectively. When follicles grew more than 4.0 mm in diameter, the growth rate of the oocytes calculated by the differentiation equation was found to be an asymptotic depression around zero. Thus, it is suggested that when the follicles grow more than 4.0 mm in diameter, the oocytes reach full size and cease to grow. Furthermore, it is considered that the equation can be applied to the assessment of normal growth in oocytes and follicles cultured in vitro.

Prophylactic effect of inactivated influenza vaccine on young children.

BACKGROUND: The effectiveness of inactivated influenza vaccine in healthy infants and young children has been controversial. The aim of this study was to determine the prophylactic effect of inactivated influenza vaccine in young children. METHODS: Eighty-six healthy infants and children younger than 7-years-old were immunized by a subcutaneous injection of inactivated influenza vaccine before the 1999/2000 influenza season. Ninety-four age-matched children were randomly assigned as the control. These children were followed-up from January to April, 2000. A diagnosis of influenza A virus infection was made rapidly by a positive result of the the enzyme immunoassay membrane test using enzyme-conjugated monoclonal antibodies specific for a conserved epitope of influenza A nucleoprotein. The incidence of influenza A infection was compared and statistically assessed. RESULTS: The prevalence of influenza A virus infection, diagnosed by the influenza A rapid detection test, was 5.8% in the vaccine group and 17.0% in the control group, that is significantly lower in the vaccine receiving group than the non-receiving group (P = 0.016). However, four out of five infected children in the vaccine group were younger than 2-years-old. CONCLUSION: We conclude that inactivated influenza vaccine reduces the incidence of influenza A virus infection in 2-6-year-old children.

Abnormal structural luteolysis in ovaries of the senescence accelerated mouse (SAM): expression of Fas ligand/Fas-mediated apoptosis signaling molecules in luteal cells.

Senescence accelerated mouse-prone (SAMP) mice with a shortened life span show accelerated changes in many of the signs of aging and a shorter reproductive life span than SAM-resistant (SAMR) controls. We previously showed that functional regression (progesterone dissimilation) occurs in abnormally accumulated luteal bodies (aaLBs) of SAMP mice, but structural regression of luteal cells in aaLB is inhibited. A deficiency of luteal cell apoptosis causes the abnormal accumulation of LBs in SAMP ovaries. In the present study, to show the abnormality of Fas ligand (FasL)/Fas-mediated apoptosis signal transducing factors in the aaLBs of the SAMP ovaries, we assessed the changes in the expression of FasL, Fas, caspase-8 and caspase-3 mRNAs by reverse transcription-polymerase chain reaction, and in the expression and localization of FasL, Fas and activated caspase-3 proteins by Western blotting and immunohistochemistry, respectively, during the estrus cycle/luteolysis. These mRNAs and proteins were expressed in normal LBs of both SAMP and SAMR ovaries, but not at all or only in trace amounts in aaLBs of SAMP, indicating that structural regression is inhibited by blockage of the expression of these transducing factors in luteal cells of aaLBs in SAMP mice.

Effects of in utero exposure to bisphenol A on expression of RARalpha and RXRalpha mRNAs in murine embryos.

Retinoic acid receptor (RAR) alpha and retinoid X receptor (RXR) alpha are key factors in a nuclear receptor-dependent signal. To evaluate the effects of bisphenol A (BPA), a candidate endocrine disruptor (ED), on embryonic development, we examined the mRNA levels of RARalpha and RXRalpha in murine embryos, exposed in utero to BPA (2 microg/kg/day) at 6.5-17.5 days post-coitum (dpc), by the real-time reverse transcription-polymerase chain reaction (RT-PCR) method. Higher levels of RARalpha mRNA in cerebra of male and female embryos of control groups were detected at 14.5 dpc. In utero BPA reduced the RARalpha mRNA expression. Higher levels of RXRalpha mRNA in cerebra of male and female embryos were seen at 12.5 dpc. The exposure decreased RXRalpha mRNA expression in male but not female embryos. No remarkable change in the RARalpha mRNA expression level was noted in cerebella of male or female embryos of the control group during embryonic development. Exposure to BPA increased expression levels of RARalpha mRNA in cerebella of male and female embryos at 12.5 dpc. Higher levels of RXRalpha mRNA in cerebella of male and female embryos were seen, but no remarkable changes were noted during embryonic development. BPA significantly decreased the expression levels of RXRalpha mRNA in cerebella of female embryos at 12.5, 14.5 and 18.5 dpc. RARalpha and RXRalpha mRNAs were expressed in gonads (testes and ovaries) of murine embryos from 12.5 to 18.5 dpc. In utero exposure to BPA decreased levels of RARalpha mRNA in testes of 14.5- and 18.5-dpc-embryos, levels of RXRalpha mRNA in testes of 14.5-dpc-embryos, and levels of RXRalpha mRNA in ovaries of 14.5-dpc-embryos. The present findings indicate that RARalpha and RXRalpha play crucial roles in organogenesis, and the growth and development of murine embryos, and will contribute to the assessment of the toxic effects of BPA on retinoid signals in embryogenesis.