Alterations in the Development of Rat Cerebellum and Impaired Behavior of Juvenile Rats after Neonatal 6-OHDA Treatment

The effects of neonatal systemic administration of the neurotoxin 6-hydroxydopamine (6-OHDA) on cerebellum development and behavior were studied in juvenile rats. The methods employed were immunohistochemistry, in situ hybridization, ligand binding, and behavioral testing. The results revealed, for the first time, that 6-OHDA treatment alters Bergmann glial cells and reduced the expression GABA_A receptor subtypes α1 and α6 especially in granule cells. The Bergmann glial cells were abnormally located and structurally different (e.g., no intimate associations with Purkinje cells). Significant microglial activation was also observed. The animals showed impairment in behavior, especially in their orientation to a novel environment. Recent data on neuron–glia interactions support the conclusion that the observed structural changes in Bergmann glia and granular neurons disrupted the normal functioning of the Purkinje cells which then in turn resulted in the impaired sensory-motor coordination at least in juvenile rats. This paper is a summary of previously published work and some recent data in this field obtained at our laboratory. Special issue dedicated to Dr. Simo S. Oja     

Retinotopic Distribution of Structural and Functional Damages following Bright Light Exposure of Juvenile Rats

In the present study, we aimed at better understanding the short (acute) and long term (chronic) degenerative processes characterizing the juvenile rat model of light-induced retinopathy. Electroretinograms, visual evoked potentials (VEP), retinal histology and western blots were obtained from juvenile albino Sprague-Dawley rats at preselected postnatal ages (from P30 to P400) following exposure to 10,000 lux from P14 to P28. Our results show that while immediately following the cessation of exposure, photoreceptor degeneration was concentrated within a well delineated area of the superior retina (i.e. the photoreceptor hole), with time, this hole continued to expand to form an almost photoreceptor-free region covering most of superior-inferior axis. By the end of the first year of life, only few photoreceptors remained in the far periphery of the superior hemiretina. Interestingly, despite a significant impairment of the outer retinal function, the retinal output (VEP) was maintained in the early phase of this retinopathy. Our findings thus suggest that postnatal exposure to a bright luminous environment triggers a degenerative process that continues to impair the retinal structure and function (mostly at the photoreceptor level) long after the cessation of the exposure regimen (more than 1 year documented herein). Given the slow degenerative process triggered following postnatal bright light exposure, we believe that our model represents an attractive alternative (to other more genetic models) to study the pathophysiology of photoreceptor-induced retinal degeneration as well as therapeutic strategies to counteract it.     

JunD的结构功能特征及其在肿瘤发展中的作用

JunD是一种属于多功能激活剂蛋白-1（activating protein-1,AP-1) 家族的转录因子,可以激活或抑制多种靶基因的表达.在生长发育过程中,在各种细胞类型中都呈现出组成性表达.近20年的临床数据及分子生物学研究表明,JunD蛋白的功能受多个复杂过程调控,包括转录控制、转录后调节、蛋白质翻译后修饰及蛋白-蛋白相互作用等.JunD基因表达的精细调控及JunD蛋白与其它蛋白之间的相互作用可调节细胞增殖、分化和凋亡等过程.JunD蛋白活性异常会导致肿瘤、代谢及病毒类疾病的发生.JunD蛋白的转录激活及抑制受1个复杂调控网络调控,在这个网络调节下,JunD蛋白在细胞的生长调控过程中发挥重要作用.本文就JunD基因表达的调控机制及其与肿瘤之间关系的最新研究进展做一综述.     

Role of Synaptic Structural Plasticity in Impairments of Spatial Learning and Memory Induced by Developmental Lead Exposure in Wistar Rats

Lead (Pb) is found to impair cognitive function. Synaptic structural plasticity is considered to be the physiological basis of synaptic functional plasticity and has been recently found to play important roles in learning and memory. To study the effect of Pb on spatial learning and memory at different developmental stages, and its relationship with alterations of synaptic structural plasticity, postnatal rats were randomly divided into three groups: Control; Pre-weaning Pb (Parents were exposed to 2 mM PbCl₂ 3 weeks before mating until weaning of pups); Post-weaning Pb (Weaned pups were exposed to 2 mM PbCl₂ for 9 weeks). The spatial learning and memory of rats was measured by Morris water maze (MWM) on PND 85–90. Rat pups in Pre-weaning Pb and Post-weaning Pb groups performed significantly worse than those in Control group (p<0.05). However, there was no significant difference in the performance of MWM between the two Pb-exposure groups. Before MWM (PND 84), the number of neurons and synapses significantly decreased in Pre-weaning Pb group, but not in Post-weaning Pb group. After MWM (PND 91), the number of synapses in Pre-weaning Pb group increased significantly, but it was still less than that of Control group (p<0.05); the number of synapses in Post-weaning Pb group was also less than that of Control group (p<0.05), although the number of synapses has no differences between Post-weaning Pb and Control groups before MWM. In both Pre-weaning Pb and Post-weaning Pb groups, synaptic structural parameters such as thickness of postsynaptic density (PSD), length of synaptic active zone and synaptic curvature increased significantly while width of synaptic cleft decreased significantly compared to Control group (p<0.05). Our data demonstrated that both early and late developmental Pb exposure impaired spatial learning and memory as well as synaptic structural plasticity in Wistar rats.     

Functional Adaptation in Female Rats: The Role of Estrogen Signaling

Background

Sex steroids have direct effects on the skeleton. Estrogen acts on the skeleton via the classical genomic estrogen receptors alpha and beta (ERα and ERβ), a membrane ER, and the non-genomic G-protein coupled estrogen receptor (GPER). GPER is distributed throughout the nervous system, but little is known about its effects on bone. In male rats, adaptation to loading is neuronally regulated, but this has not been studied in females.

Methodology/Principal Findings

We used the rat ulna end-loading model to induce an adaptive modeling response in ovariectomized (OVX) female Sprague-Dawley rats. Rats were treated with a placebo, estrogen (17β-estradiol), or G-1, a GPER-specific agonist. Fourteen days after OVX, rats underwent unilateral cyclic loading of the right ulna; half of the rats in each group had brachial plexus anesthesia (BPA) of the loaded limb before loading. Ten days after loading, serum estrogen concentrations, dorsal root ganglion (DRG) gene expression of ERα, ERβ, GPER, CGRPα, TRPV1, TRPV4 and TRPA1, and load-induced skeletal responses were quantified. We hypothesized that estrogen and G-1 treatment would influence skeletal responses to cyclic loading through a neuronal mechanism. We found that estrogen suppresses periosteal bone formation in female rats. This physiological effect is not GPER-mediated. We also found that absolute mechanosensitivity in female rats was decreased, when compared with male rats. Blocking of adaptive bone formation by BPA in Placebo OVX females was reduced.

Conclusions

Estrogen acts to decrease periosteal bone formation in female rats in vivo. This effect is not GPER-mediated. Gender differences in absolute bone mechanosensitivity exist in young Sprague-Dawley rats with reduced mechanosensitivity in females, although underlying bone formation rate associated with growth likely influences this observation. In contrast to female and male rats, central neuronal signals had a diminished effect on adaptive bone formation in estrogen-deficient female rats.     

Hematotoxicity and Genotoxicity of Mercuric Chloride Following Subchronic Exposure Through Drinking Water in Male Rats

Erythrocytes are a convenient model to understand the subsequent oxidative deterioration of biological macromolecules in metal toxicities. The present study examined the variation of hematoxic and genotoxic parameters following subchronic exposure of mercuric chloride via drinking water and their possible association with oxidative stress. Male rats were exposed to 50 ppm (HG1) and 100 ppm (HG2) of mercuric chloride daily for 90 days. A significant dose-dependent decrease was observed in red blood cell count, hemoglobin, hematocrit, and mean cell hemoglobin concentration in treated groups (HG1 and HG2) compared with controls. A significant dose-dependent increase was observed in lipid peroxidation; therefore, a significant variation was found in the antioxidant enzyme activities, such as superoxide dismutase, catalase, and glutathione peroxidase. Interestingly, mercuric chloride treatment showed a significant dose-dependent increase in frequency of total chromosomal aberration and in percentage of aberrant bone marrow metaphase of treated groups (p < 0.01). The oxidative stress induced by mercury treatment may be the major cause for chromosomal aberration as free radicals lead to DNA damage. These data will be useful in screening the antioxidant activities of natural products, which may be specific to the bone marrow tissue.     

溴氰菊酯致大鼠DNA损伤及对肝功能的影响

目的：研究溴氰菊酯（DM）对大鼠外周血淋巴细胞DNA的损伤作用及对肝脏功能的影响。方法：32只雌性Wistar大鼠随机分成4组,染毒剂量分别为0,3．125,6．250,12．500mg／kg,连续灌胃染毒10天。DNA损伤采用单细胞凝胶电泳（彗星实验）进行评价,并测定丙氨酸氨基转移酶（ALT）以反映肝功能变化。结果：染毒组大鼠外周淋巴细胞的尾DNA％（Tail DNA％）、尾矩（Tail Moment）和Olive尾矩（Olive Tail Moment）均高于对照组（P〈0．05）,差别有统计学意义。各染毒组与对照组的肝功能差异均无统计学意义。结论：DM可导致外周血淋巴细胞DNA损伤。     

Impaired Development of Rat Cerebellum Induced by Neonatal Injection of the Glycoprotein Synthesis Inhibitor, Tunicamycin

The effects of the protein glycosylation inhibitor tunicamycin on the postnatal development of the rat cerebellum were examined in vivo. Tunicamycin (0.2 micrograms) was injected intracranially into 1-day-old rats. Inhibition of glycosylation of the macromolecules in the cerebellum by tunicamycin treatment was suggested by a reduced incorporation of [3H]glucosamine into the trichloroacetic acid (TCA)-insoluble fraction. The tunicamycin treatment did not affect gain in body weight significantly. However the cerebellar weight was significantly reduced by 30-40% compared with that of the controls. Development of GABAergic and cholinergic innervations in the hypoplastic cerebellum was examined by measuring the activities of glutamate decarboxylase (GAD) and choline acetyltransferase (ChAT). The specific activity and the total activity of GAD were significantly reduced in the tunicamycin-treated cerebellum. In contrast the specific activity of ChAT was significantly increased, whereas the total activity of ChAT per cerebellum was identical with that of the controls. These results suggest that the intracranial injection of tunicamycin affects the postnatal development of rat cerebellum, such as GABAergic and cholinergic innervations.     

Galectin-1 Enhances Astrocytic BDNF Production and Improves Functional Outcome in Rats Following Ischemia

Galectin-1, an endogenous mammalian lectin, has been implicated in a variety of CNS disorders. However, its role in cerebral ischemia is still elusive. In the present study, we investigated the effect of recombinant galectin-1 on production of astrocytic brain-derived neurotrophic factor (BDNF) and functional recovery following ischemia. Endogenous galectin-1 was found to be markedly upregulated, paralleled with increased astrocytic BDNF production under ischemic conditions both in vitro and in vivo. Administration of galectin-1significantly enhanced the expression and secretion of astrocytic BDNF in dose dependent manner. Moreover, rats subjected to photochemical cerebral ischemia showed reduced neuronal apoptosis in ischemic boundary zone and improved functional recovery after brain infusion of galectin-1 (1 μg/days, 7 days). These results suggest that induction of BDNF in astrocytes by galectin-1 may be a promising intervention to attenuate brain damage after stroke.     

Functional and Structural Neural Network Characterization of Serotonin Transporter Knockout Rats

Brain serotonin homeostasis is crucially maintained by the serotonin transporter (5-HTT), and its down-regulation has been linked to increased vulnerability for anxiety- and depression-related behavior. Studies in 5-HTT knockout (5-HTT^-/-) rodents have associated inherited reduced functional expression of 5-HTT with increased sensitivity to adverse as well as rewarding environmental stimuli, and in particular cocaine hyperresponsivity. 5-HTT down-regulation may affect normal neuronal wiring of implicated corticolimbic cerebral structures. To further our understanding of its contribution to potential alterations in basal functional and structural properties of neural network configurations, we applied resting-state functional MRI (fMRI), pharmacological MRI of cocaine-induced activation, and diffusion tensor imaging (DTI) in 5-HTT^-/- rats and wild-type controls (5-HTT^+/+). We found that baseline functional connectivity values and cocaine-induced neural activity within the corticolimbic network was not significantly altered in 5-HTT^-/- versus 5-HTT^+/+ rats. Similarly, DTI revealed mostly intact white matter structural integrity, except for a reduced fractional anisotropy in the genu of the corpus callosum of 5-HTT^-/- rats. At the macroscopic level, analyses of complex graphs constructed from either functional connectivity values or structural DTI-based tractography results revealed that key properties of brain network organization were essentially similar between 5-HTT^+/+ and 5-HTT^-/- rats. The individual tests for differences between 5-HTT^+/+ and 5-HTT^-/- rats were capable of detecting significant effects ranging from 5.8% (fractional anisotropy) to 26.1% (pharmacological MRI) and 29.3% (functional connectivity). Tentatively, lower fractional anisotropy in the genu of the corpus callosum could indicate a reduced capacity for information integration across hemispheres in 5-HTT^-/- rats. Overall, the comparison of 5-HTT^-/- and wild-type rats suggests mostly limited effects of 5-HTT genotype on MRI-based measures of brain morphology and function.     

Changes in Glycoprotein Metabolism in the Cerebral Cortex Following First Exposure of Dark-reared Rats to Light

Abstract: The level of incorporation of [³H]fucose or [³H]lysine into subcel-lular fractions of the visual and motor cortices of 50-day-old dark-reared (D) and light-exposed (L) rats was determined. No differences were found between D and L rats in the incorporation of either precursor into subcellular fractions of the motor cortex, or in any fraction of the visual cortex except the synaptic-membrane fraction. After a 3-h light exposure the incorporation of [³H]fucose into the visual cortex synaptic-membrane fraction was elevated (L/D = 136%). Incorporation of [³H]lysine was elevated in the visual cortex synaptic-membrane fraction of L compared to D rats after a 1-h exposure (L/D = 118%). However, after a 3-h exposure the incorporation was depressed in this fraction (L/D = 79%). No differences could be found in the levels of activity of fucosyl transferase following first exposure to light but dark-rearing itself resulted in increased enzyme activity in the motor cortex compared to normal controls. First exposure of 20-day-old dark-reared rats to light led to an increase in the incorporation of [³H]fucose into soluble glycoproteins of both the visual and motor cortex and into particulate glycoproteins of the visual cortex only. These results are in contrast with those found with 50-day-old animals and suggest that the effects of light-exposure on [³H]fucose incorporation may be age-dependent.     

Larval Development and Vitellin-like Protein Expression in Palaemon elegans Larvae Following Xeno-oestrogen Exposure

Certain anthropogenic chemicals, most notably xeno-oestrogens,are known to have the potential to disrupt vertebrate endocrinesystems. For example, induction of the female-specific protein,vitellogenin, in male fish is a well-known effect of exposureto xeno-oestrogens and serves as a biomarker of such exposure.There have been few comparable studies of putative biomarkersof endocrine disruption in invertebrates. An exception is theupregulation of vitellin-like larval storage protein (LSP) expressionin the barnacle cypris larva following exposure to oestrogenicchemicals. The current study aimed to establish whether larvaeof the glass prawn, Palaemon elegans, are likewise susceptibleto xeno-oestrogen exposure. Using a polyclonal antiserum toP. elegans apolipovitellin, an 86 kDa polypeptide was detectedby western blotting in the larval and early postlarval stagesof this species. An indirect ELISA applied to the soluble proteinfraction of larval homogenates determined that the titre ofthis putative LSP ranged, depending on larval stage, from 0.48–0.67ng µg^–1. Exposure of P. elegans larvae to the xeno-oestrogen4-n-nonylphenol (4-NP), at 0.2–20 µg L^–1,resulted in a significant, concentration-independent increasein putative LSP levels of 5–18%. Conversely, exposureto the natural oestrogen, 17ß-oestradiol (E₂), at0.2 and 20 µg L^–1, led to a significant concentration-independentdecline (up to 11%) in LSP levels. Whether the effect of 4-NPresults from endocrine disruption is not known, however, anoestrogen receptor-mediated effect is unlikely. Other than aslight increase in larval mortality when exposed to 4-NP at2 µg L^–1, neither 4-NP nor E₂ significantly affecteddevelopment, growth or survival of P. elegans larvae.     

Structural Repair and Functional Recovery Following Cerebral Ganglion Removal in the Pulmonate Snail Melampus

SYNOPSIS. Regeneration of the nervous system of Melampus followingcerebral ganglion removal proceeds through tract, bud, and ganglionstages Each stage can represent a terminal condition in someanimals Early events of regeneration appear to include rolesfor chemotactic and growth-promoting agents and axonal guidanceby preferential adhesion to a connective tissue sheath Thislatter proposed mechanism accounts for the observed sequencein which the neural elements unite in the tract stage and forthe pattern of failures that result when the sheath is disruptedIn the tract stage of regeneration, communication through thesite of the missing ganglion is restored within the centralnervous system, and between neurons of non-excised ganglia andthe denervated periphery Some behavioral recovery results Thebud stage of regeneration is characterized by neuropil developmentand associated swelling at the site of confluence of the tractsSerotonin immunohistochemistry of bud stage preparations andretrograde dye transport via bud nerves show tracts and numeroussynaptic vancosities, but the neuron somata that are labeledare located in other ganglia Ultrastructural examination oflate bud/early ganglion stage tissue reveals the presence ofsmall undifferentiated cells By six to seven months postoperative,some snails have clearly reached a ganglion stage of regenerationcharacterized by the appearance of differentiated neurons withinthe bud The origin of these new neurons is currently under investigation.     

Trimethyltin Modulates Reelin Expression and Endogenous Neurogenesis in the Hippocampus of Developing Rats

Reelin is an extracellular matrix glycoprotein involved in the modulation of synaptic plasticity and essential for the proper radial migration of cortical neurons during development and for the integration and positioning of dentate granular cell progenitors; its expression is down-regulated as brain maturation is completed. Trimethyltin (TMT) is a potent neurotoxicant which causes selective neuronal death mainly localised in the CA1-CA3/hilus hippocampal regions. In the present study we analysed the expression of reelin and the modulation of endogenous neurogenesis in the postnatal rat hippocampus during TMT-induced neurodegeneration (TMT 6 mg/kg). Our results show that TMT administration induces changes in the physiological postnatal decrease of reelin expression in the hippocampus of developing rats. In particular, quantitative analysis of reelin-positive cells evidenced, in TMT-treated animals, a persistent reelin expression in the stratum lacunosum moleculare of Cornu Ammonis and in the molecular layer of Dentate Gyrus. In addition, a significant decrease in the number of bromodeoxyuridine (BrdU)-labeled newly-generated cells was also detectable in the subgranular zone of P21 TMT-treated rats compared with P21 control animals; no differences between P28 TMT-treated rats and age-matched control group were observed. In addition the neuronal commitment of BrdU-positive cells appeared reduced in P21 TMT-treated rats compared with P28 TMT-treated animals. Thus TMT treatment, administrated during development, induces an early reduction of endogenous neurogenesis and influences the hippocampal pattern of reelin expression in a temporally and regionally specific manner, altering the physiological decrease of this protein.     

Decreased Benzodiazepine Receptor Density in Rat Cerebellum Following Neurotoxic Doses of Phenytoin

Abstract: The effect of acute and chronic administration of phenytoin on [³H]-flunitrazepam binding was examined in the rat cerebellum. There was no significant effect of phenytoin on [³H]flunitrazepam binding in the rat cerebellum 1 and 6 h after a single i.p. injection of 200 mg/kg of phenytoin. However, after 14 days and 28 days of chronic phenytoin administration, significant de-creases in [³H]flunitrazepam receptor density were observed, with no changes in apparent affinity constants in the rat cerebellum. This effect of phenytoin was dose-dependent, as lower doses of phenytoin (100 mg/kg/day) for 14 or 28 days produced no alterations in [³H]flunitrazepam binding in the rat cerebellum. Light-microscopic examination of the rat cerebellum treated with 200 mg/kg/day of phenytoin for 14 days showed degeneration of the Purkinje cells, with edematous Bergmann astrocytes. These data provide evidence for the neuronal localization of benzodiazepine receptors on cerebellar Purkinje cells.     

A Combination Supplement of Fructo- and Xylo-Oligosaccharides Significantly Abrogates Oxidative Impairments and Neurotoxicity in Maternal/Fetal Milieu Following Gestational Exposure to Acrylamide in Rat

Neurochemical Research - Prebiotic oligosaccharides are demonstrated to confer a wide spectrum of physiological benefits during pregnancy. In view of this, focused attempts are being directed...     

Role of Sulfur Dioxide in Acute Lung Injury Following Limb Ischemia/Reperfusion in Rats

Sulfur dioxide (SO₂) is naturally synthesized by glutamate‐oxaloacetate transaminase (GOT) from l ‐cysteine in mammalian cells. We aim to investigate the role of SO₂ in inflammation in acute lung injury (ALI) following limb ischemia/reperfusion (I/R). Male Wistar rats were subjected to limb I/R and were injected with saline, GOT inhibitor hydroxamate (HDX, 0.47 mmol/kg), or the SO₂ donor Na₂SO₃/NaHSO₃ (0.54 mmol/kg/0.18 mmol/kg). Compared with the sham operation, the plasma SO₂ levels were significantly decreased by limb I/R treatment. In addition, SO₂ concentration and GOT activity in the lung tissue were also reduced in ALI. The occurrence of ALI following limb I/R can be prevented by Na₂SO₃/NaHSO₃ treatment, whereas it can be significantly aggravated by HDX. The plasma IL‐1β, IL‐6, and IL‐10 levels were consistent with myeloperoxidase activity and inflammation in lung tissue. In conclusion, our data suggest that downregulation of endogenous SO₂ production might be involved in pathogenesis of ALI following limb I/R in rats. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:389‐397, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.21492