Electrophysiological responses to seizurogenic compounds dependent on E/I balance in human iPSC-derived cortical neural networks.

Construction of in vitro functional assay systems using human-induced pluripotent stem cells (iPSCs) as indicators for evaluating seizure liability of compounds has been anticipated. Imbalance of excitation/inhibition (E/I) inputs triggers seizure; however, the appropriate ratio of E/I neurons for evaluating seizure liability of compounds in a human iPSC-derived neural network is unknown. Here, five neural networks with varying E/I ratios (88/12, 84/16, 74/26, 58/42, and 48/52) were constructed by altering the ratios of glutamatergic (E) and GABA (I) neurons. The responsiveness of each network against six seizurogenic compounds and two GABA receptor agonists was then examined by using six representative parameters. The 52% GABA neuron network, which had the highest ratio of GABA neurons, showed the most marked response to seizurogenic compounds, however, it suggested the possibility of producing false positives. Moreover, analytical parameters were found to vary with E/I ratio and to differ for seizurogenic compounds with different mechanism of action (MoA) even at the same E/I ratio. Clustering analysis using six parameters showed the balance of 84/16, which is the closest to the biological balance, was the most suitable for detection of concentration-dependent change and classification of the MoA of seizurogenic compounds. These results suggest the importance of using a human-iPSC-derived neural network similar to the E/I balance of the living body in order to improve the prediction accuracy in the in vitro seizure liability assessment.

Detection of synchronized burst firing in cultured human induced pluripotent stem cell-derived neurons using a 4-step method.

Human induced pluripotent stem cell-derived neurons are promising for use in toxicity evaluations in nonclinical studies. The multi-electrode array (MEA) assay is used in such evaluation systems because it can measure the electrophysiological function of a neural network noninvasively and with high throughput. Synchronized burst firing (SBF) is the main analytic parameter of pharmacological effects in MEA data, but an accurate method for detecting SBFs has not been established. In this study, we present a 4-step method that accurately detects a target SBF confirmed by the researcher's interpretation of a raster plot. This method calculates one set parameter per step, in the following order: the inter-spike interval (ISI), the number of spikes in an SBF, the inter-SBF interval, and the number of spikes in an SBF again. We found that the 4-step method is advantageous over the conventional method because it determines the preferable duration of an SBF, accurately distinguishes continuous SBFs, detects weak SBFs, and avoids false detection of SBFs. We found also that pharmacological evaluations involving SBF analysis may differ depending on whether the 4-step or conventional threshold method is used. This 4-step method may contribute to improving the accuracy of drug toxicity and efficacy evaluations using human induced pluripotent stem cell-derived neurons.

Induction of long-term potentiation and depression phenomena in human induced pluripotent stem cell-derived cortical neurons.

Plasticity such as long-term potentiation (LTP) and long-term potentiation depression (LTD) in neuronal networks has been analyzed using in vitro and in vivo techniques in simple animals to understand learning, memory, and development in brain function. Human induced pluripotent stem cell (hiPSC)-derived neurons may be effectively used for understanding the plasticity mechanism in human neuronal networks, thereby elucidating disease mechanisms and drug discoveries. In this study, we attempted the induction of LTP and LTD phenomena in a cultured hiPSC-derived cerebral cortical neuronal network using multi-electrode array (MEA) systems. High-frequency stimulation (HFS) produced a potentiated and depressed transmission in a neuronal circuit for 1 h in the evoked responses by test stimulus. The cross-correlation of responses revealed that spike patterns with specific timing were generated during LTP induction and disappeared during LTD induction and that the hiPSC-derived cortical neuronal network has the potential to repeatedly express the spike pattern with a precise timing change within 0.5 ms. We also detected the phenomenon for late-phase LTP (L-LTP) like plasticity and the effects for synchronized burst firing (SBF) in spontaneous firings by HFS. In conclusion, we detected the LTP and LTD phenomena in a hiPSC-derived neuronal network as the change of spike pattern. The studies of plasticity using hiPSC-derived neurons and a MEA system may be beneficial for clarifying the functions of human neuronal circuits and for applying to drug screening.

The role performance of public health nurses as clinical instructors in Japan.

AIM: To investigate the factors associated with the role performance of public health nurses as clinical instructors in Japan. BACKGROUND: Newly graduated public health nurses in Japan have competencies that are below the minimum requirements of the Ministry of Health, Labour and Welfare because of their limited clinical experience in undergraduate clinical education. Public health nurses play crucial roles in the clinical practicum and their role performance as clinical instructors is a key to successful learning outcomes. METHODS: This study targeted public health nurses in governmental public health centres and those who had gained experience as an undergraduate clinical instructor for nursing students. A self-administered questionnaire was distributed to a national sample of 1467 public health nurses. Data were collected from July 2011 to September 2011. RESULTS: In total, 722 of 1467 questionnaires were completed (nurse age 22-64 years). Of the participants, almost half (49%) strongly disagreed (3%) or disagreed (46%) that they had confidence in their role as a clinical instructor, and preparation programmes for clinical instructors had been attended by just 262 (36.3%). Years of experience as public health nurses, previous attendance of preparation programmes, viewing their role positively, professional identity and professional competency were significantly associated with performance. Logistic regression analysis revealed that nurses with higher role performance scores had higher self-confidence, greater interests in their role and higher professional identity. CONCLUSIONS: The self-confidence and interests of public health nurses in their role as clinical instructors as well as their professional identity were found to be significant predictors of their role performance as clinical instructors. IMPLICATIONS FOR NURSING PRACTICE AND EDUCATION: The factors identified in our investigation can be used to predict effective clinical instructors and to develop preparation programmes to enhance their confidence and interests and potentially increase their role satisfaction.

Roles of neuronal nitric oxide synthase, oxidative stress, and propofol in N-methyl-D-aspartate-induced dilatation of cerebral arterioles.

BACKGROUND: It remains unclear whether N-methyl-D-aspartate (NMDA) receptors contribute to cerebral parenchymal vasodilatation, and any effects of clinically used anaesthetics on the dilatation. The present study was designed to examine whether NMDA induces neuronal nitric oxide synthase (NOS)-mediated dilatation, in the cerebral parenchymal arterioles, and whether propofol and superoxide modulate the dilatation in relation to the NMDA receptor activation. METHODS: The cerebral parenchymal arterioles within rat brain slices were monitored by a computer-assisted microscopy, and the vasodilatation in response to NMDA (10(-7) to 10(-5) M) was evaluated. Immunofluorescence analysis to neuronal and endothelial NOS and measurement of levels of superoxide and nitric oxide within the arteriole were simultaneously performed. RESULTS: Propofol, an NMDA receptor antagonist MK801, and a neuronal NOS antagonist S-methyl-l-thiocitrulline (SMTC) reduced NMDA-induced dilation, whereas a superoxide inhibitor, Tiron, and NADPH oxidase inhibitor, gp91ds-tat, augmented NMDA-induced dilatation. Immunofluorescence analysis revealed distribution of neuronal NOS in both endothelial and smooth muscle cells in addition to neuronal cells. NMDA-induced superoxide and nitric oxide within the parenchymal arterioles. The increased superoxide within the arteriole was similarly inhibited by MK801, SMTC, gp91ds-tat, propofol, and a neuronal NOS antagonist vinyl-l-NIO, whereas the level of nitric oxide was reduced by MK801, SMTC, propofol, and vinyl-l-NIO, and it was augmented by gp91ds-tat. CONCLUSIONS: NMDA dilates cerebral parenchymal arterioles possibly via neuronal NOS activation, whereas it produces superoxide via NADPH oxidase. In these arterioles, propofol reduces both the dilatation and superoxide production in response to NMDA.

Raster plots machine learning to predict the seizure liability of drugs and to identify drugs.

In vitro microelectrode array (MEA) assessment using human induced pluripotent stem cell (iPSC)-derived neurons holds promise as a method of seizure and toxicity evaluation. However, there are still issues surrounding the analysis methods used to predict seizure and toxicity liability as well as drug mechanisms of action. In the present study, we developed an artificial intelligence (AI) capable of predicting the seizure liability of drugs and identifying drugs using deep learning based on raster plots of neural network activity. The seizure liability prediction AI had a prediction accuracy of 98.4% for the drugs used to train it, classifying them correctly based on their responses as either seizure-causing compounds or seizure-free compounds. The AI also made concentration-dependent judgments of the seizure liability of drugs that it was not trained on. In addition, the drug identification AI implemented using the leave-one-sample-out scheme could distinguish among 13 seizure-causing compounds as well as seizure-free compound responses, with a mean accuracy of 99.9 ± 0.1% for all drugs. These AI prediction models are able to identify seizure liability concentration-dependence, rank the level of seizure liability based on the seizure liability probability, and identify the mechanism of the action of compounds. This holds promise for the future of in vitro MEA assessment as a powerful, high-accuracy new seizure liability prediction method.

Molecular analysis of new isolates of Tomato leaf curl Philippines virus and an associated betasatellite occurring in the Philippines.

Three new begomovirus isolates and one betasatellite were obtained from a tomato plant exhibiting leaf curl symptom in Laguna, the Philippines. Typical begomovirus DNA components representing the three isolates (PH01, PH02 and PH03) were cloned, and their full-length sequences were determined to be 2754 to 2746 nucleotides. The genome organizations of these isolates were similar to those of other Old World monopartite begomoviruses. The sequence data indicated that PH01 and PH02 were variants of strain B of the species Tomato leaf curl Philippines virus, while PH03 was a variant of strain A of the species Tomato leaf curl Philippines virus. These isolates were designated ToLCPV-B[PH:Lag1:06], ToLCPV-B[PH:Lag2:06], and ToLCPV-A[PH:Lag3:06], respectively. Phylogenetic analysis revealed that the present isolates form a separate monophyletic cluster with indigenous begomoviruses reported earlier in the Philippines. A betasatellite isolated from same sample belongs to the betasatellite species Tomato leaf curl Philippines betasatellite and designated Tomato leaf curl Philippines betasatellite-[Philippines:Laguna1:2006], ToLCPHB-[PH:Lag1:06]. When co-inoculated with this betasatellite, tomato leaf curl Philippines virus induced severe symptoms in N. benthamiana and Solanum lycopersicum plants. Using a PVX-mediated transient assay, we found that the C4 and C2 proteins of tomato leaf curl Philippines virus and the ßC1 protein of ToLCPHB-[PH:Lag1:06] function as a suppressor of RNA silencing.

Analysis of signal components < 500 Hz in brain organoids coupled to microelectrode arrays: A reliable test-bed for preclinical seizure liability assessment of drugs and screening of antiepileptic drugs.

Brain organoids with three-dimensional structure and tissue-like function are highly demanded for brain disease research and drug evaluation. However, to our knowledge, methods for measuring and analyzing brain organoid function have not been developed yet. This study focused on the frequency components of an obtained waveform below 500 Hz using planner microelectrode array (MEA) and evaluated the response to the convulsants pentylenetetrazol (PTZ) and strychnine as well as the antiepileptic drugs (AEDs) perampanel and phenytoin. Sudden and persistent seizure-like firing was observed with PTZ administration, displaying a concentration-dependent periodic activity with the frequency component enhanced even in one oscillation characteristic. On the other hand, in the administration of AEDs, the frequency of oscillation decreased in a concentration-dependent manner and the intensity of the frequency component in one oscillation also decreased. Interestingly, at low doses of phenytoin, a group of synchronized bursts was formed, which was different from the response to the perampanel. Frequency components contained information on cerebral organoid function, and MEA was proven useful in predicting the seizure liability of drugs and evaluating the effect of AEDs with a different mechanism of action. In addition, frequency component analysis of brain organoids using MEA is an important analysis method to perform in vitro to in vivo extrapolation in the future, which will help explore the function of the organoid itself, study human brain developments, and treat various brain diseases.

HIGH BACKGROUND AREA FOR RADIATION EDUCATION.

This paper describes our trial experience of the use of high radiation area for radiation education. We used environmental samples collected from the high radiation area in Fukushima prefecture and India, for the practice of radiation measurement and health risk assessment in Nagasaki University Medical School. We also carried out the field monitoring seminar for students in the existing exposure areas in Tottori prefecture and the Yamakiya observatory in Fukushima. Although the evaluation of educational effectiveness is still underway, both types of education appeared attractive for the students mostly due to the exposure from natural environment in our real life which was not achieved by using an artificial radiation source in a classroom.

E-cadherin expression in the subepithelial nevus cells of the giant congenital nevocellular nevi (GCNN) correlates with their migration ability in vitro.

BACKGROUND: Giant congenital nevocellular nevi (GCNN) are histologically characterized by the broad distribution of nevus cells in the epidermis and dermis. OBJECTIVE: To characterize E-cadherin in GCNN and define its role in nevic cell migrations. METHODS: Twenty-four cases were immunohistochemically examined and in five cases cells were isolated for primary culture for migration assays. RESULTS: The nevus cells in the superficial region showed the immunoreactivity of E-cadherin in a membranous pattern, but those in the deep part of dermis had little immunoreactivity. Ultra-structural analysis of the superficial nevus cells revealed that E-cadherin immunodeposits in the fibrillar processes around the cell body in a spotted pattern. This distribution pattern is quite different from that in the adherens junction of skin squamous epithelial cells. Boyden chamber experiments were performed using primary cultures of intradermal nevus cells. EDTA pretreatment reduced cell migration to the E-cadherin positive side when the E-cadherin positive population was relatively large in the primary cultures. CONCLUSIONS: These results indicate that E-cadherin in the nevus cells may affect nevus cell motility rather than intercellular attachment.

Toxicological evaluation of convulsant and anticonvulsant drugs in human induced pluripotent stem cell-derived cortical neuronal networks using an MEA system.

Functional evaluation assays using human induced pluripotent stem cell (hiPSC)-derived neurons can predict the convulsion toxicity of new drugs and the neurological effects of antiepileptic drugs. However, differences in responsiveness depending on convulsant type and antiepileptic drugs, and an evaluation index capable of comparing in vitro responses with in vivo responses are not well known. We observed the difference in synchronized burst patterns in the epileptiform activities induced by pentylentetrazole (PTZ) and 4-aminopryridine (4-AP) with different action mechanisms using multi-electrode arrays (MEAs); we also observed that 100 µM of the antiepileptic drug phenytoin suppressed epileptiform activities induced by PTZ, but increased those induced by 4-AP. To compare in vitro results with in vivo convulsive responses, frequency analysis of below 250 Hz, excluding the spike component, was performed. The in vivo convulsive firing enhancement of the high γ wave and ß wave component were observed remarkably in in vitro hiPSC-derived neurons with astrocytes in co-culture. MEA measurement of hiPSC-derived neurons in co-culture with astrocytes and our analysis methods, including frequency analysis, appear effective for predicting convulsion toxicity, side effects, and their mechanism of action as well as the comparison of convulsions induced in vivo.

Physiological maturation and drug responses of human induced pluripotent stem cell-derived cortical neuronal networks in long-term culture.

The functional network of human induced pluripotent stem cell (hiPSC)-derived neurons is a potentially powerful in vitro model for evaluating disease mechanisms and drug responses. However, the culture time required for the full functional maturation of individual neurons and networks is uncertain. We investigated the development of spontaneous electrophysiological activity and pharmacological responses for over 1 year in culture using multi-electrode arrays (MEAs). The complete maturation of spontaneous firing, evoked responses, and modulation of activity by glutamatergic and GABAergic receptor antagonists/agonists required 20-30 weeks. At this stage, neural networks also demonstrated epileptiform synchronized burst firing (SBF) in response to pro-convulsants and SBF suppression using clinical anti-epilepsy drugs. Our results reveal the feasibility of long-term MEA measurements from hiPSC-derived neuronal networks in vitro for mechanistic analyses and drug screening. However, developmental changes in electrophysiological and pharmacological properties indicate the necessity for the international standardization of culture and evaluation procedures.

Molecular cloning and sequencing of the cDNA for vacuolar H+-pyrophosphatase from Chara corallina1.

We have cloned a cDNA for vacuolar proton-translocating pyrophosphatase of Chara corallina that is one of the closest green algae to the land plants. The deduced protein consists of 793 amino acid residues. Its sequence is 71% identical to the H+-pyrophosphatases of land plants, and is less than 46% identical to those of marine alga and phototrophic bacterium.

Radiation streaming experiment through a labyrinth of the 12 GeV proton accelerator facility at KEK(2)--TLD REM-counter method.

The doses of radiation streaming through a labyrinth were measured using thermoluminescence dosemeters (TLDs) and neutron moderators for TLDs at the neutrino beam line of the 12 GeV proton accelerator facility of High Energy Accelerator Research Organization (KEK). The calculated doses using the Monte Carlo code, MCNPX basically agreed with the experimental results. However, unexpectedly, the calculated neutron doses were smaller than the measured ones along the upstream side of the labyrinth.

Radiation safety design for the J-PARC Project.

The High-Intensity Proton Accelerator Project, named J-PARC, is in progress, with the aim of enabling studies on the latest basic science and the advancement of nuclear technology. In the project, a high-energy proton accelerator complex with the world's highest instantaneous intensity is under construction. In order to establish a reasonable shielding design, both simplified and detailed design methods were used in the shielding design of J-PARC. This paper reviews the present status of the radiation safety design study for J-PARC.

Cytochrome P4502E1 (CYP2E1) genetic polymorphism in a case-control study of gastric cancer and liver disease.

Cytochrome P4502E1 (CYP2E1) activates carcinogenic N-nitrosamines, benzene, urethane and other low molecular weight compounds. This enzyme is also inducible by ethanol, and metabolizes alcohol. A restriction fragment length polymorphism (RFLP) using the Rsa I restriction enzyme has been identified in the CYP2E1 transcription regulatory region; recent studies suggest that this polymorphism may affect gene expression. We investigated the frequency of the Rsa I RFLP in a Japanese population in relation to gastric cancer and liver disease susceptibility. The frequency of this polymorphism was determined in 150 gastric cancer, 16 hepatocellular cancer, 48 liver cirrhosis and 203 benign gastric disease (controls) patients. This preliminary study shows no association of the specific genotype with gastric cancer in all subjects (odds ratio = 1.04, 95% CI = 0.74-3.08 for the heterozygote and 0.57, 95% CI = 0.22-1.50 for the homozygous rare allele, respectively). To further confirm this lack of association, an age and gender matched case-control study should be performed. Separately, there was no association of the Rsa I RFLP with hepatocellular carcinoma (p = 0.911), but there was a suggested difference between the non-viral associated liver cirrhosis patients and control patients. Thus, this polymorphism may be related to ethanol metabolism and consequential liver diseases in a Japanese population.

Aromatase is abundantly expressed by neonatal rat penis but downregulated in adulthood.

Although synthesis of estrogen by male gonads has been well documented for over half a century, it is only recently that the role of estrogen in male reproductive events has gained appreciation. We recently reported abundant expression of estrogen receptor (ER)-alpha and -beta in different cell types of the rat penis, whose levels diminished with advancing age. The present study, which builds on data from the ER study, was designed to determine whether the penis is capable of generating its own local estrogen by examining evidence of the expression of aromatase, a microsomal enzymatic complex which irreversibly converts androgens to estrogens, using immunohistochemistry, Western blotting, in situ hybridization and real-time PCR analyses. Secondly, the effects of sex steroid hormones on penile aromatase were examined. Discrete aromatase immunoreactive cells were localized in primordial corpus cavernosum, corpus spongiosus and os penis, blood vessels and sensory corpuscle of glans penis. In situ hybridization signals corresponded with immunohistochemical findings. Western blot, enzyme immunoassay and real-time PCR analyses of rat penile samples revealed an age-dependent expression of aromatase and estrogen, with levels at week 1 almost resembling those of the ovary, but they decreased sharply by week 8, and decreased further by week 35. This expression pattern was strikingly similar to that of ER-alpha reported previously. Testosterone and diethylstilbesterol administered prenatally upregulate levels of aromatase mRNA and protein, and estrogen postnatally. Dihydrotestosterone upregulated aromatase mRNA and protein, but not estrogen. We conclude that estrogen acts via ER in a paracrine and/or autocrine manner to regulate penile events, particularly during development, and that estrogen synthesis is regulated by estrogen and androgens.