Expression Profile and Distribution of Efhc1 Gene Transcript During Rodent Brain Development

One of the putative causative genes for juvenile myoclonic epilepsy (JME) is EFHC1. We report here the expression profile and distribution of Efhc1 messenger RNA (mRNA) during mouse and rat brain development. Real-time polymerase chain reaction revealed that there is no difference in the expression of Efhc1 mRNA between right and left hemispheres in both species. In addition, the highest levels of Efhc1 mRNA were found at intra-uterine stages in mouse and in adulthood in rat. In common, there was a progressive decrease in Efhc1 expression from 1-day-old neonates to 14-day-old animals in both species. In situ hybridization studies showed that rat and mouse Efhc1 mRNAs are expressed in ependymal cells of ventricle walls. Our findings suggest that Efhc1 expression is more important during initial phases of brain development and that at this stage it could be involved in key developmental mechanisms underlying JME.

Autoradiographic characterization of [3H]-5-HT-moduline binding sites in rodent brain and their relationship to 5-HT1B receptors

5-HT-moduline is an endogenous tetrapeptide [Leu-Ser-Ala-Leu (LSAL)] that was first isolated from bovine brain tissue. To understand the physiological role of this tetrapeptide, we studied the localization of 5-HT-moduline binding sites in rat and mouse brains. Quantitative data obtained with a gaseous detector of β-particles (β-imager) indicated that [3H]-5-HT-moduline bound specifically to rat brain sections with high affinity (Kd = 0.77 nM and Bmax = 0.26 dpm/mm2). Using film autoradiography in parallel, we found that 5-HT-moduline binding sites were expressed in a variety of rat and mouse brain structures. In 5-HT1B receptor knock-out mice, the specific binding of [3H]-5-HT-moduline was not different from background labeling, indicating that 5-HT-moduline targets are exclusively located on the 5-HT1B receptors. Although the distribution of 5-HT-moduline binding sites was similar to that of 5-HT1B receptors, they did not overlap totally. Differences in distribution patterns were found in regions containing either high levels of 5-HT1B receptors such as globus pallidus and subiculum that were poorly labeled or in other regions such as dentate gyrus of hippocampus and cortex where the relative density of 5-HT-moduline binding sites was higher than that of 5-HT1B receptors. In conclusion, our data, based on autoradiographic localization, indicate that 5-HT-moduline targets are located on 5-HT1B receptors present both on 5-HT afferents and postsynaptic neurons. By interacting specifically with 5-HT1B receptors, this tetrapeptide may play a pivotal role in pathological states such as stress that involves the dysfunction of 5-HT neurotransmission.

Homeobox gene Prx3 expression in rodent brain and extraneural tissues

Different cDNA clones encoding a rat homeobox gene and the mouse homologue OG-12 were cloned from adult rat brain and mouse embryo mRNA, respectively. The predicted amino acid sequences of the proteins belong to the paired-related subfamily of homeodomain proteins (Prx homeodomains). Hence, the gene was named Prx3 and the mouse and rat genes are indicated as mPrx3 and rPrx3, respectively. In the mouse as well as in the rat, the predicted Prx3 proteins share the homeodomain but have three different N termini, a 12-aa residue variation in the C terminus, and contain a 14-aa residue motif common to a subset of homeodomain proteins, termed the “aristaless domain.” Genetic mapping of Prx3 in the mouse placed this gene on chromosome 3. In situ hybridization on whole mount 12.5-day-old mouse embryos and sections of rat embryos at 14.5 and 16.5 days postcoitum revealed marked neural expression in discrete regions in the lateral and medial geniculate complex, superior and inferior colliculus, the superficial gray layer of the superior colliculus, pontine reticular formation, and inferior olive. In rat and mouse embryos, nonneuronal structures around the oral cavity and in hip and shoulder regions also expressed the Prx3 gene. In the adult rat brain, Prx3 gene expression was restricted to thalamic, tectal, and brainstem structures that include relay nuclei of the visual and auditory systems as well as other ascending systems conveying somatosensory information. Prx3 may have a role in specifying neural systems involved in processing somatosensory information, as well as in face and body structure formation.

OpenRatSLAM : an open source brain-based SLAM system

RatSLAM is a navigation system based on the neural processes underlying navigation in the rodent brain, capable of operating with low resolution monocular image data. Seminal experiments using RatSLAM include mapping an entire suburb with a web camera and a long term robot delivery trial. This paper describes OpenRatSLAM, an open-source version of RatSLAM with bindings to the Robot Operating System framework to leverage advantages such as robot and sensor abstraction, networking, data playback, and visualization. OpenRatSLAM comprises connected ROS nodes to represent RatSLAM’s pose cells, experience map, and local view cells, as well as a fourth node that provides visual odometry estimates. The nodes are described with reference to the RatSLAM model and salient details of the ROS implementation such as topics, messages, parameters, class diagrams, sequence diagrams, and parameter tuning strategies. The performance of the system is demonstrated on three publicly available open-source datasets.

Alpha-fetoprotein protects the developing female mouse brain from masculinization and defeminization by estrogens

Two clearly opposing views exist on the function of alpha-fetoprotein (AFP), a fetal plasma protein that binds estrogens with high affinity, in the sexual differentiation of the rodent brain. AFP has been proposed to either prevent the entry of estrogens or to actively transport estrogens into the developing female brain. The availability of Afp mutant mice (Afp-/-) now finally allows us to resolve this longstanding controversy concerning the role of AFP in brain sexual differentiation, and thus to determine whether prenatal estrogens contribute to the development of the female brain. Here we show that the brain and behavior of female Afp-/- mice were masculinized and defeminized. However, when estrogen production was blocked by embryonic treatment with the aromatase inhibitor 1,4,6-androstatriene-3,17- dione, the feminine phenotype of these mice was rescued. These results clearly demonstrate that prenatal estrogens masculinize and defeminize the brain and that AFP protects the female brain from these effects of estrogens. © 2006 Nature Publishing Group.

Localization of Metal Electrodes in the Intact Rat Brain Using Registration of 3D Microcomputed Tomography Images to a Magnetic Resonance Histology Atlas.

Simultaneous neural recordings taken from multiple areas of the rodent brain are garnering growing interest due to the insight they can provide about spatially distributed neural circuitry. The promise of such recordings has inspired great progress in methods for surgically implanting large numbers of metal electrodes into intact rodent brains. However, methods for localizing the precise location of these electrodes have remained severely lacking. Traditional histological techniques that require slicing and staining of physical brain tissue are cumbersome, and become increasingly impractical as the number of implanted electrodes increases. Here we solve these problems by describing a method that registers 3-D computerized tomography (CT) images of intact rat brains implanted with metal electrode bundles to a Magnetic Resonance Imaging Histology (MRH) Atlas. Our method allows accurate visualization of each electrode bundle's trajectory and location without removing the electrodes from the brain or surgically implanting external markers. In addition, unlike physical brain slices, once the 3D images of the electrode bundles and the MRH atlas are registered, it is possible to verify electrode placements from many angles by "re-slicing" the images along different planes of view. Further, our method can be fully automated and easily scaled to applications with large numbers of specimens. Our digital imaging approach to efficiently localizing metal electrodes offers a substantial addition to currently available methods, which, in turn, may help accelerate the rate at which insights are gleaned from rodent network neuroscience.

Quantitative mapping of trimethyltin injury in the rat brain using magnetic resonance histology.

The growing exposure to chemicals in our environment and the increasing concern over their impact on health have elevated the need for new methods for surveying the detrimental effects of these compounds. Today's gold standard for assessing the effects of toxicants on the brain is based on hematoxylin and eosin (H&E)-stained histology, sometimes accompanied by special stains or immunohistochemistry for neural processes and myelin. This approach is time-consuming and is usually limited to a fraction of the total brain volume. We demonstrate that magnetic resonance histology (MRH) can be used for quantitatively assessing the effects of central nervous system toxicants in rat models. We show that subtle and sparse changes to brain structure can be detected using magnetic resonance histology, and correspond to some of the locations in which lesions are found by traditional pathological examination. We report for the first time diffusion tensor image-based detection of changes in white matter regions, including fimbria and corpus callosum, in the brains of rats exposed to 8 mg/kg and 12 mg/kg trimethyltin. Besides detecting brain-wide changes, magnetic resonance histology provides a quantitative assessment of dose-dependent effects. These effects can be found in different magnetic resonance contrast mechanisms, providing multivariate biomarkers for the same spatial location. In this study, deformation-based morphometry detected areas where previous studies have detected cell loss, while voxel-wise analyses of diffusion tensor parameters revealed microstructural changes due to such things as cellular swelling, apoptosis, and inflammation. Magnetic resonance histology brings a valuable addition to pathology with the ability to generate brain-wide quantitative parametric maps for markers of toxic insults in the rodent brain.

Two functionally linked amino acids in the stem 2 region of measles virus haemagglutinin determine infectivity and virulence in the rodent central nervous system.

Rodent brain-adapted measles virus (MV) strains, such as CAM/RB and recombinant MVs based on the Edmonston strain containing the haemagglutinin (H) of CAM/RB, cause acute encephalitis after intracerebral infection of newborn rodents. We have demonstrated that rodent neurovirulence is modulated by two mutations at amino acid positions 195 and 200 in the H protein, one of these positions (200) being a potential glycosylation site. In order to analyse the effects of specific amino acids at these positions, we introduced a range of individual and combined mutations into the open reading frame of the H gene to generate a number of eukaryotic expression plasmids. The functionality of the mutant H proteins was assessed in transfected cells and by generating recombinant viruses. Interestingly, viruses caused acute encephalitis only if the amino acid Ser at position 200 was coupled with Gly at position 195, whereas viruses with single or combined mutations at these positions, including glycosylation at position 200, were attenuated. Neurovirulence was associated with virus spread and induction of neuronal apoptosis, whereas attenuated viruses failed to infect brain cells. Similar results were obtained by using primary brain-cell cultures. Our findings indicate that a structural alteration in the stem 2 region of the H protein at position 195 or 200 interferes with infectivity of rodent neurons, and suggest that the interaction of the viral attachment protein with cellular receptors on neurons is affected.

ENVIRONMENTAL TOBACCO SMOKE INDUCES OXIDATIVE STRESS IN DISTINCT BRAIN REGIONS OF INFANT MICE

Environmental tobacco smoke (ETS) leads to the death of 600,000 nonsmokers annually and is associated with disturbances in antioxidant enzyme capacity in the adult rodent brain. However, little is known regarding the influence of ETS on brain development. The aim of this study was to determine levels of malonaldehyde (MDA) and 3-nitrotyrosine (3-NT), as well as enzymatic antioxidant activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and superoxide dismutase (SOD), in distinct brain structures. BALB/c mice were exposed to ETS twice daily for 1 h from postnatal day 5 through postnatal day 18. Acute exposure was performed for 1 h on postnatal day 18. Mice were euthanized either immediately (0) or 3 h after the last exposure. Immediately after an acute exposure there were higher GR and GST activities and MDA levels in the hippocampus, higher GPx and SOD activities in the prefrontal cortex, and higher GST activity and MDA levels in the striatum and cerebellum. Three hours later there was an increase in SOD activity and MDA levels in the hippocampus and a decrease in the activity of all enzymes in the prefrontal cortex. Immediately after final repeated exposure there were elevated levels of GST and GR activity and decreased GPx activity in the hippocampus. Moreover, a rise was found in GPx and GST activities in the prefrontal cortex and increased GST and GPx activity in the striatum and cerebellum, respectively. After 3 h the prefrontal cortex showed elevated GR and GST activities, and the striatum displayed enhanced GST activity. Data showed that enzymatic antioxidant system in the central nervous system responds to ETS differently in different regions of the brain and that a form of adaptation occurs after several days of exposure.

Selective increases in regional brain glucocorticoid: a novel effect of chronic alcohol

The hypothalamo-pituitary-adrenal axis shows functional changes in alcoholics, with raised glucocorticoid release during alcohol intake and during the initial phase of alcohol withdrawal. Raised glucocorticoid concentrations are known to cause neuronal damage after withdrawal from chronic alcohol consumption and in other conditions. The hypothesis for these studies was that chronic alcohol treatment would have differential effects on corticosterone concentrations in plasma and in brain regions. Effects of chronic alcohol and withdrawal on regional brain corticosterone concentrations were examined using a range of standard chronic alcohol treatments in two strains of mice and in rats. Corticosterone was measured by radioimmunoassay and the identity of the corticosterone extracted from brain was verified by high performance liquid chromatography and mass spectrometry. Withdrawal from long term (3 weeks to 8 months) alcohol consumption induced prolonged increases in glucocorticoid concentrations in specific regions of rodent brain, while plasma concentrations remained unchanged. This effect was seen after alcohol administration via drinking fluid or by liquid diet, in both mice and rats and in both genders. Shorter alcohol treatments did not show the selective effect on brain glucocorticoid levels. During the alcohol consumption the regional brain corticosterone concentrations paralleled the plasma concentrations. Type II glucocorticoid receptor availability in prefrontal cortex was decreased after withdrawal from chronic alcohol consumption and nuclear localization of glucocorticoid receptors was increased, a pattern that would be predicted from enhanced glucocorticoid type II receptor activation. This novel observation of prolonged selective increases in brain glucocorticoid activity could explain important consequences of long term alcohol consumption, including memory loss, dependence and lack of hypothalamo-pituitary responsiveness. Local changes in brain glucocorticoid levels may also need to be considered in the genesis of other mental disorders and could form a potential new therapeutic target.

Erythropoietin crosses the blood–brain barrier to protect against experimental brain injury

Erythropoietin (EPO), recognized for its central role in erythropoiesis, also mediates neuroprotection when the recombinant form (r-Hu-EPO) is directly injected into ischemic rodent brain. We observed abundant expression of the EPO receptor at brain capillaries, which could provide a route for circulating EPO to enter the brain. In confirmation of this hypothesis, systemic administration of r-Hu-EPO before or up to 6 h after focal brain ischemia reduced injury by ≈50–75%. R-Hu-EPO also ameliorates the extent of concussive brain injury, the immune damage in experimental autoimmune encephalomyelitis, and the toxicity of kainate. Given r-Hu-EPO's excellent safety profile, clinical trials evaluating systemically administered r-Hu-EPO as a general neuroprotective treatment are warranted.

Spatial cognition for robots

The paper discusses robot navigation from biological inspiration. The authors sought to build a model of the rodent brain that is suitable for practical robot navigation. The core model, dubbed RatSLAM, has been demonstrated to have exactly the same advantages described earlier: it can build, maintain, and use maps simultaneously over extended periods of time and can construct maps of large and complex areas from very weak geometric information. The work contrasts with other efforts to embody models of rat brains in robots. The article describes the key elements of the known biology of the rat brain in relation to navigation and how the RatSLAM model captures the ideas from biology in a fashion suitable for implementation on a robotic platform. The paper then outline RatSLAM's performance in two difficult robot navigation challenges, demonstrating how a cognitive robotics approach to navigation can produce results that rival other state of the art approaches in robotics.

Hippocampal models for simultaneous localisation and mapping on an autonomous robot

To navigate successfully in a novel environment a robot needs to be able to Simultaneously Localize And Map (SLAM) its surroundings. The most successful solutions to this problem so far have involved probabilistic algorithms, but there has been much promising work involving systems based on the workings of part of the rodent brain known as the hippocampus. In this paper we present a biologically plausible system called RatSLAM that uses competitive attractor networks to carry out SLAM in a probabilistic manner. The system can effectively perform parameter self-calibration and SLAM in one dimension. Tests in two dimensional environments revealed the inability of the RatSLAM system to maintain multiple pose hypotheses in the face of ambiguous visual input. These results support recent rat experimentation that suggest current competitive attractor models are not a complete solution to the hippocampal modelling problem.