Nerve Cells In Mice Research Articles

Role of GABAA receptor depolarization-mediated VGCC activation in sevoflurane-induced cognitive impairment in neonatal mice.

BackgroundIn neonatal mice, anesthesia with sevoflurane depolarizes the GABA Type A receptor (GABAAR), which leads to cognitive impairment. Calcium accumulation in neurons can lead to neurotoxicity. Voltage-gated calcium channels (VGCCs) can increase intracellular calcium concentration under isoflurane and hypoxic conditions. The underlying mechanisms remain largely unknown.MethodsSix-day-old mice were anesthetized with 3% sevoflurane for 2 h/day for 3 days. The Y-Maze, new object recognition (NOR) test, the Barnes maze test, immunoassay, immunoblotting, the TUNEL test, and Golgi–Cox staining were used to assess cognition, calcium concentration, inflammatory response, GABAAR activation, VGCC expression, apoptosis, and proliferation of hippocampal nerve cells in mice and HT22 cells.ResultsCompared with the control group, mice in the sevoflurane group had impaired cognitive function. In the sevoflurane group, the expression of Gabrb3 and Cav1.2 in the hippocampal neurons increased (p < 0.01), the concentration of calcium ions increased (p < 0.01), inflammatory reaction and apoptosis of neurons increased (p < 0.01), the proliferation of neurons in the DG area decreased (p < 0.01), and dendritic spine density decreased (p < 0.05). However, the inhibition of Gabrb3 and Cav1.2 alleviated cognitive impairment and reduced neurotoxicity.ConclusionsSevoflurane activates VGCCs by inducing GABAAR depolarization, resulting in cognitive impairment. Activated VGCCs cause an increase in intracellular calcium concentration and an inflammatory response, resulting in neurotoxicity and cognitive impairment.

Chemistry that delighted us in 2021

Snakes spitting pain Most of the venomous snakes in the Liverpool School of Tropical Medicine’s collection immobilize and kill prey by injecting venom through their fangs. But some snakes protect themselves from predators by spitting venom —potentially causing pain, inflammation, and blindness. This year, a team of researchers at the school’s Centre for Snakebite Research and Interventions uncovered how the venom packs such a punch: the molecular cocktail in spitting snakes’ venom contains high levels of proteins that increase the sensation of pain ( Science 2021, DOI: 10.1126/science.abb9303 ). The team found that, while each snake’s venom had a unique concoction of toxins, all the spitting snakes had higher levels of phospholipase A 2 (PLA 2 ) enzymes in their venom than nonspitting snakes. In tests on mouse nerve cells, mixtures of venom components including PLA 2 triggered more cell activity than cocktails without it, a sign of a greater

Lactobacillus casei Strain Shirota Enhances the Ability of Geniposide to Activate SIRT1 and Decrease Inflammation and Oxidative Stress in Septic Mice.

Gardenia jasminoides Ellis is rich in geniposide, which can be transformed into the anti-oxidant and anti-inflammatory agent genipin. Genipin exhibits greater efficacy than geniposide, but it is unstable and difficult to preserve. In this study, a mouse model for sepsis was established by cecal ligation and puncture, and then we explored the effects and mechanism of Lactobacillus casei strain Shirota (LcS) on the enhancement of the ability of geniposide to reduce sepsis and decrease inflammatory and oxidative levels in mice by the regulation of sirtuin type 1 (SIRT1). The mice were evaluated and analyzed by the open field test, Morris water maze test, flow cytometry, kit assay, qPCR, and western blot. The LcS + geniposide increased the survival rate in mice with sepsis, and increased the total travel distance, number of times the mice stood up, amount of time the mice spent grooming their fur, duration in the target quadrant, and crossing area number. The testing of mouse nerve cells showed that LcS + geniposide reduced the rate of nerve cell apoptosis caused by sepsis. LcS + geniposide also decreased the amount of inflammatory-related indicators of TNF-α, IL-6, and IL-1β, and the oxidation-related levels of malondialdehyde (MDA) in the hippocampi of septic mice, and it increased the oxidase activities of superoxide dismutase (SOD) and catalase (CAT). Additionally, LcS + geniposide increased the SOD1, SOD2, and CAT mRNA expression in the hippocampi of mice with sepsis and decreased the expression of TNF-α, IL-1β, NF-κB, and p53 mRNA. LcS+geniposide also increased the SIRT1 protein expression and decreased the Ac-FOXO1, Ac-NF-κB, and Ac-p53 protein expression in the hippocampi of mice with sepsis. We also observed that LcS + geniposide decreased the inflammatory and oxidative damage in the mice with sepsis. The effect of LcS + geniposide was similar to that of the drug dexamethasone and stronger than the effect of geniposide utilized alone. LcS also enhanced the ability of geniposide to activate SIRT1 and decrease the inflammation and oxidative stress in the septic mice, and it achieved an effect same with that obtained by the use of the drug dexamethasone.

ADMSC Exo-MicroRNA-22 improve neurological function and neuroinflammation in mice with Alzheimer's disease.

The previous study by our group has found that miRNA‐22 can inhibit pyroptosis by targeting GSDMD and improve the memory and motor ability of mice with Alzheimer's disease (AD) mice by inhibiting inflammatory response. In recent years, stem cells and their exosomes have been reported to have good therapeutic effects on AD; therefore, we hypothesize that miRNA‐22 is likely to play a synergistic therapeutic effect. In this study, adipose‐derived mesenchymal stem cells (ADMSCs) were transfected into miRNA‐22 mimic to obtain miRNA‐22 loaded exosomes (Exo‐miRNA‐22), which was further used for the treatment and nerve repair of AD. In brief, 4‐month‐old APP/PS1 mice were assigned into the control group, Exo and Exo‐miRNA‐22 groups. After exosome transplantation, we observed changes in the motor and memory ability of mice. In addition, ELISA was used to detect the expression of inflammatory factors in cerebrospinal fluid and peripheral blood, Nissl staining was used to assess the survival of mouse nerve cells, immunofluorescence staining was used to determine the activation of microglia, and Western blot was utilized to detect the expression of pyroptosis‐related proteins. As a result, the nerve function and motor ability were significantly higher in mice in the Exo‐miRNA‐22 group than those in the control group and Exo group. Meanwhile, the survival level of nerve cells in mice was higher in the Exo‐miRNA‐22 group, and the expression of inflammatory factors was lower than that of the Exo group, indicating Exo‐miRNA‐22 could significantly suppress neuroinflammation. In vitro culture of PC12 cells, Aβ25‐35‐induced cell damage, detection of PC12 apoptotic level, the release of inflammatory factors and the expression of pyroptosis‐related proteins showed that Exo‐miRNA‐22 could inhibit PC12 apoptosis and significantly decrease the release of inflammatory factors. In this study, we found that miRNA‐22‐loaded ADMSC‐derived exosomes could decrease the release of inflammatory factors by inhibiting pyroptosis, thereby playing a synergetic therapeutic role with exosomes on AD, which is of great significance in AD research.

Effects of long non-coding RNA NEAT1 on sepsis-induced brain injury in mice via NF-κB.

The aim of this study was to investigate the effect of long non-coding ribonucleic acid (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) on sepsis-induced brain injury in mice through nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). The mouse model of sepsis was established by cecal ligation and puncture induction. The relative expression levels of NEAT1 and NF-κB in brain tissues of mice in healthy group and sepsis group were determined via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) and Western blotting, respectively. Subsequently, the expression of NEAT1 was silenced by transfection of small interfering RNAs (siRNAs). Meanwhile, its effect on NF-κB expression was detected. To further explore the effect of sepsis on brain injury, the content of brain water and the expression levels of apoptosis-related proteins, including B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (BAX), in mice of healthy group, sepsis group, and sepsis + si-NEAT1 group were measured. Furthermore, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were used to detect the proliferation and apoptosis of nerve cells. The relative expression levels of NEAT1 and NF-κB were significantly increased in the brain tissues of septic mice (p<0.01). Si-NEAT1 transfection significantly decreased the expressions of NEAT1 and NF-κB in brain tissues of septic mice (p<0.05). The content of brain water in mice of sepsis group was evidently increased (p<0.05). However, si-NEAT1 treatment remarkably reduced this content (p<0.05). In addition, sepsis markedly decreased the activity of nerve cells (p<0.05). However, si-NEAT1 could significantly increase the activity of nerve cells in septic mice (p<0.05). Moreover, si-NEAT1 notably decreased the expression of BAX (p<0.05), whereas it increased the expression of Bcl-2 (p<0.05). The results of apoptosis detection revealed that sepsis remarkably promoted the apoptosis of mouse nerve cells (p<0.05). In addition, si-NEAT1 transfection could evidently alleviate the apoptosis of nerve cells in septic mice (p<0.05). LncRNA NEAT1 promotes brain injury in septic mice by positively regulating NF-κB. However, si-NEAT1 transfection can reduce this injury.

Systematic Localization and Identification of SUMOylation Substrates in Knock-In Mice Expressing Affinity-Tagged SUMO1.

Protein SUMOylation is a posttranslational protein modification that is emerging as a key regulatory process in neurobiology. To date, however, SUMOylation in vivo has only been studied cursorily. Knock-in mice expressing His6-HA-SUMO1 from the Sumo1 locus allow for the highly specific localization and identification of endogenous SUMO1 substrates under physiological and pathophysiological conditions. By making use of the HA-tag and using wild-type mice for highly stringent negative control samples, SUMO1 targets can be specifically localized in and purified from cultured mouse nerve cells and mouse tissues.

A transcribed ultraconserved noncoding RNA, Uc.173, is a key molecule for the inhibition of lead-induced neuronal apoptosis.

As a common toxic metal, lead has significant neurotoxicity to brain development. Long non-coding RNAs (lncRNAs) function in multiple biological processes. However, whether lncRNAs are involved in lead-induced neurotoxicity remains unclear. Uc.173 is a lncRNA from a transcribed ultra-conservative region (T-UCR) of human, mouse and rat genomes. We established a lead-induced nerve injury mouse model. It showed the levels of Uc.173 decreased significantly in hippocampus tissue and serum of the model. We further tested the expression of Uc.173 in serum of lead-exposed children, which also showed a tendency to decrease. To explore the effects of Uc.173 on lead-induced nerve injury, we overexpressed Uc.173 in an N2a mouse nerve cell line and found Uc.173 had an inhibitory effect on lead-induced apoptosis of N2a. To investigate the molecular mechanisms of Uc.173 in apoptosis associated with lead-induced nerve injury, we predicted the target microRNAs of Uc.173 by using miRanda, TargetScan and RegRNA. After performing quantitative real-time PCR and bioinformatics analysis, we showed Uc.173 might inter-regulate with miR-291a-3p in lead-induced apoptosis and regulate apoptosis-associated genes. Our study suggests Uc.173 significantly inhibits the apoptosis of nerve cells, which may be mediated by inter-regulation with miRNAs in lead-induced nerve injury.

Nerve cells culture from lumbar spinal cord on surfaces modified by plasma pyrrole polymerization

Currently, there are several techniques for modified cell culture surfaces under research to improve cell growth and adhesion. Recently, different methods have been used for surface coating, using biomolecules that enhance cell attachment and growth of nerve cells from spinal cord, such as the use of Poly-DL-Ornithine/Laminin. Plasma-polymerized pyrrole (PPy)-treated surfaces have showed improvement on surfaces biocompatibility with the cells in culture since they do not interfere with any of the biological cell functions. In the present work, we present a novel mouse nerve cell culture technique, using PPy-treated cell culture surfaces. A comparative study of cell survival using Poly-DL-Ornithine/Laminin-treated surfaces was performed. Our results of cell survival when compared with data already reported by other investigators, show that cells cultured on the PPy-modified surface increased survival up to 21 days when compared with Poly-DL-Ornithine/Laminin-coated culture, where 8 days cell survival was obtained. There were electrical and morphological differences in the nerve cells grown in the different surfaces. By comparing the peak ion currents of Poly-DL-Ornithine/Laminin-seeded cells for 8 days with cells grown for 21 days on PPy, an increase of 516% in the Na+ current and 127% in K+ currents in cells seeded on PPy were observed. Immunofluorescence techniques showed the presence of cell synapses and culture viability after 21 days. Our results then showed that PPy-modified surfaces are an alternative culture method that increases nerve cells survival from lumbar spinal cord cell culture by preserving its electrical and morphological features.

Co-expression of activin receptor-interacting protein 1 and 2 in mouse nerve cells

Activin is a neurotrophic and neuroprotective factor in the central nervous system. Activin receptor-interacting protein 1 and 2 (ARIP1 and ARIP2) are identified as activin signal proteins in mouse brain. However, whether ARIP1 and ARIP2 are co-expressed in nerve cells and the differences of their biological activities are not well characterized. In the present study, we found that ARIP1 and ARIP2 mRNA expressions were detectable in mouse brain and their proteins were co-localized at the hypothalamus of cerebrum and granular layers in cerebellum, especially in Purkinje cells. Furthermore, ARIP1 and ARIP2 were co-expressed in mouse Neuro-2a cells, which is similar to the co-localization of ARIP1 and ARIP2 in hypothalamus neurons and Purkinje cells. Overexpression of ARIP1 in Neuro-2a cells inhibited activin signal transduction induced by activin A and Smad3, and activin A-induced voltage-gated Na+ current (INa), while ARIP2 was only a negative regulator of signal transduction induced by activin A and did not alter activin A-induced INa. Taken together, these data demonstrate that ARIP1 and ARIP2 are co-expressed in some nerve cells and their biological activities are distinct.

Spongiform pathology in mouse CNS lacking ‘neuropathy target esterase’ and cellular prion protein

Conditional inactivation of the ‘neuropathy target esterase’ (NTE) gene in mouse nerve cells was previously shown to result in CNS pathology comparable to the spongiform encephalopathy characteristic of prion diseases. To determine whether cellular prion protein (PrPc) is essential for development of this pathology we examined hippocampi of mice lacking NTE alone, PrPc alone or both NTE and PrPc. Light microscopic survey showed clear-cut spongiform changes in a majority of NTE−/− and NTE/PrP−/− double knockout mice but in only one PrP−/− mouse. EM analysis of spongiform lesions from NTE−/− and NTE/PrP−/− mice, and from the one affected PrP−/− mouse, revealed patches of branching tubular inclusions, comparable to the ‘tubulovesicular inclusions’ described previously in prion diseases. We conclude that spongiform pathology in conditional NTE knockout mice is not mediated by PrPc, and that tubulovesicular inclusions can be seen in spongiform encephalopathy of other etiologies and are not pathognomonic of prion disease.

Is Hunger a Driver of the Cognitive Development?

In their recent paper, Elman et al, 2006 nicely summarized the possible associations between food intake and reward mechanisms in patients with schizophrenia. They hypothesized that schizophrenic patients may have a predilection for excessive consumption of fast food-type nutrition owing to functionally impaired neural substrate comprising homeostatic and reward mechanisms. In our view, recent neuroendocrine findings in basic research can also help us to understand these complex mechanisms better. Diano et al, 2006 have found evidence that a hormone produced in the stomach directly stimulates the higher brain functions of spatial learning and memory development. The study showed that the hormone ghrelin, previously associated with growth hormone release and appetite, has a direct, rapid, and powerful influence on the hippocampus, a higher brain region critical for learning and memory: peripheral ghrelin can enter the hippocampus and bind to local neurons promoting alterations in connections between nerve cells in mice and rats. Ghrelin is synthesized principally in the stomachFthe first hormone found to stimulate appetite and food intake in humans, a peptide that has a role in the regulation of feeding behavior. Ghrelin also provides a peripheral signal to the hypothalamus to stimulate food intake and adiposity. This important finding can have a large impact on how we see the development of cognitive processes, especially in the light of the treatment efforts of such disabling conditions like schizophrenia. Atypical antipsychotics are widely used in the treatment of schizophrenia (Lieberman et al, 2005). Considerable evidence suggests that atypical antipsychoticassociated weight gain seems positively correlated with clinical and cognitive improvement of schizophrenic patients (Ascher-Svanum et al, 2005). During treatment with olanzapine, weight gain may be observed, frequently with an increase in appetite, but it is not clear whether or not this increase fully explains the weight gain. Antipsychoticrelated weight gain is consistent across geographies, although the extent is variable (Sussman, 2001). On the other hand, some studies found correlation between ghrelin levels and atypical antipsychotic treatment: for example, the concentration of circulating ghrelin is significantly increased during olanzapine treatment (Murashita et al, 2005). Assessment of the relationship between atypical antipsychotic use, weight gain, and glucose abnormalities is complicated by the possibility of an increased background risk of diabetes mellitus in patients with schizophrenia and the increasing incidence of diabetes mellitus in the general population. Can it be possible that the positive correlation between treatment-related weight gain and cognitive improvement is a result of the increased ghrelin production? It is possible that those antipsychotics, where treatment-emergent weight gain is observed, may have more impact on cognitive improvements of the patients as well. Polimeni and Reiss (2003) and Karagianis (2003) have commented about how schizophrenia fits with the theory of evolution. Natural selection suggests that traits are preserved and perpetuated if they offer some survival advantage. The paranoia associated with schizophrenia can actually be seen as an advantage in a hostile environment. If this weight gain–cognition relationship hypothesis is valid, it can also be explained by the evolution theory of natural selection. Simply put, those individuals who had enough food around did not need to be clever enough to seek more nutritive territories. Those who were hungry and were clever enough to survive despite this might pass on their cognitive advantages to their descendents. Furthermore, those who had to fight for food everyday had probably less effective sleep at night, which is also linked to higher ghrelin levels (Copinschi, 2005). In this aspect, besides driving other advantages, hunger was probably a driver of the evolution of the cognitive processes, and ghrelin may have been the mediator. Of course, we do not state here that overweight people are somehow smarter, because it is not the case and it is easy to explain: hunger is just increasing ghrelin level, which may boost the brain power, and the urge to find food also creates more competitive skills. However, obesity is controlled by many other factors, for example, physical activity level, Online publication: 31 May 2006 at http://www.acnp.org/citations/ Npp053106060193/default.pdf Received 23 March 2006; revised 9 May 2006; accepted 25 May 2006 *Correspondence: Dr T Treuer, Neuroscience Research, Lilly Hungaria, H-1075 Budapest, Hungary, Tel: + 36304752080, E-mail: treuert@lilly.com Neuropsychopharmacology (2006) 31, 2326–2327 & 2006 Nature Publishing Group All rights reserved 0893-133X/06 $30.00

Cellular Mechanisms of Resistance to Chronic Oxidative Stress

Oxidative stress is implicated in several pathologies such as AIDS, Alzheimer’s disease, and Parkinson’s disease, as well as in normal aging. As a model system to study the response of cells to oxidative insults, glutamate toxicity on a mouse nerve cell line, HT-22, was examined. Glutamate exposure kills HT-22 via a nonreceptor-mediated oxidative pathway by blocking cystine uptake and causing depletion of intracellular glutathione (GSH), leading to the accumulation of reactive oxygen species and, ultimately, apoptotic cell death. Several HT-22 subclones that are 10-fold resistant to exogenous glutamate were isolated and the mechanisms involved in resistance characterized. The expression levels of neither heat shock proteins nor apoptosis-related proteins are changed in the resistant cells. In contrast, the antioxidant enzyme catalase, but not glutathione peroxidase nor superoxide dismutase, is more highly expressed in the resistant than in the parental cells. In addition, the resistant cells have enhanced rates of GSH regeneration due to higher activities of the GSH metabolic enzymes γ-glutamylcysteine synthetase and GSH reductase, and GSH S-transferases activities are also elevated. As a consequence of these alterations, the glutamate resistant cells are also more resistant to organic hydroperoxides and anticancer drugs that affect these GSH enzymes. These results indicate that resistance to apoptotic oxidative stress may be acquired by coordinated changes in multiple antioxidant pathways.

Mouse adaptation determinants of poliovirus type 1 enhance viral uncoating.

Most poliovirus (PV) strains, such as PV type 1/Mahoney, cannot infect the mouse central nervous system. We previously identified two determinants of mouse adaptation of PV type 1/Mahoney at positions 22 and 31 of the viral capsid proteins VP1 and VP2, respectively (T. Couderc, J. Hogle, H. Le Blay, F. Horaud, and B. Blondel, J. Virol. 67:3808-3817, 1993). These residues are located on the interior surface of the capsid. In an attempt to understand the molecular mechanisms of adaptation of PV to mice, we investigated the effects of these two determinants on the viral multiplication cycle in a human cell line. Both determinants enhanced receptor-mediated conformational changes leading to altered particles of 135S, one of the first steps of uncoating, and viral internalization. Furthermore, the residue at position 22 of VP1 appears to facilitate RNA release. These results strongly suggest that these determinants could also facilitate conformational changes mediated by the PV murine receptor and internalization in the mouse nerve cell, thus allowing PV to overcome its host range restriction. Moreover, both mouse adaptation determinants are responsible for defects in the assembly of virions in human cells and affect the thermostability of the viral particles. Thus, these mouse adaptation determinants appear to control the balance between the viral capsid plasticity needed for the conformational changes in the early steps of infection and the structural requirements which are involved in the assembly and the stability of virions.

P3-218 - Effects of T-2 toxin on cortical nerve cells in mice.

P3-218 - Effects of T-2 toxin on cortical nerve cells in mice.

Direct visualization of the microtubule lattice seam both in vitro and in vivo.

Microtubules are constructed from alpha- and beta-tubulin heterodimers that are arranged into protofilaments. Most commonly there are 13 or 14 protofilaments. A series of structural investigations using both electron microscopy and x-ray diffraction have indicated that there are two potential lattices (A and B) in which the tubulin subunits can be arranged. Electron microscopy has shown that kinesin heads, which bind only to beta-tubulin, follow a helical path with a 12-nm pitch in which subunits repeat every 8-nm axially, implying a primarily B-type lattice. However, these helical symmetry parameters are not consistent with a closed lattice and imply that there must be a discontinuity or "seam" along the microtubule. We have used quick-freeze deep-etch electron microscopy to obtain the first direct evidence for the presence of this seam in microtubules formed either in vivo or in vitro. In addition to a conventional single seam, we have also rarely found microtubules in which there is more than one seam. Overall our data indicates that microtubules have a predominantly B lattice, but that A lattice bonds between tubulin subunits are found at the seam. The cytoplasmic microtubules in mouse nerve cells also have predominantly B lattice structure and A lattice bonds at the seam. These observations have important implications for the interaction of microtubules with MAPs and with motor proteins, and for example, suggest that kinesin motors may follow a single protofilament track.

Molecular characterization of mouse-virulent poliovirus type 1 Mahoney mutants: involvement of residues of polypeptides VP1 and VP2 located on the inner surface of the capsid protein shell.

Most poliovirus (PV) strains, including PV PV-1/Mahoney, are unable to cause paralysis in mice. Determinants for restriction of PV-1/Mahoney in mice have been identified by manipulating PV-1 cDNA and located on the viral capsid protein VP1. These determinants consist of a highly exposed amino acid sequence on the capsid surface corresponding to the B-C loop (M. Murray, J. Bradley, X. Yang, E. Wimmer, E. Moss, and V. Racaniello, Science 241:213-215, 1988; A. Martin, C. Wychowski, T. Couderc, R. Crainic, J. Hogle, and M. Girard, EMBO J. 7:2839-2847, 1988) and of residues belonging to the N-terminal sequence located on the inner surface of the protein shell (E. Moss and V. Racaniello, EMBO J. 10:1067-1074, 1991). Using an in vivo approach, we isolated two mouse-neurovirulent PV-1 mutants in the mouse central nervous system after a single passage of PV-1/Mahoney inoculated by the intracerebral route. Both mutants were subjected to two additional passages in mice, plaque purified, and subsequently characterized. The two cloned mutants, Mah-NK13 and Mah-NL32, retained phenotypic characteristics of the parental PV-1/Mahoney, including epitope map, heat lability, and temperature sensitivity. Mah-NK13 exhibited slightly smaller plaques than did the parental virus. The nucleotide sequences of the mutant genomes were determined, and mutations were identified. Mutations were independently introduced into the parental PV-1/Mahoney genome by single-site mutagenesis. Mutated PV-1/Mahoney viruses were then tested for their neurovirulence in mice. A single amino acid substitution in the capsid proteins VP1 (Thr-22-->Ile) and VP2 (Ser-31-->Thr) identified in the Mah-NK13 and Mah-NL32 genomes, respectively, conferred the mouse-virulent phenotype to the mouse-avirulent PV-1/Mahoney. Ile-22 in VP1 was responsible for the small-plaque phenotype of Mah-NK13. Both mutations arose during the first passage in the mouse central nervous system. We thus identified a new mouse adaptation determinant on capsid protein VP1, and we showed that at least one other capsid protein, VP2, could also express a mouse adaptation determinant. Both determinants are located in the inside of the three-dimensional structure of the viral capsid. They may be involved in the early steps of mouse nerve cell infection subsequent to receptor attachment.

Effect of electrical convulsions on uridine labeling and activity pattern in nerve cells in mice

Male white mice were exposed to electroshock and then injected intravenously with 5-[ 3H]uridine immediately after the shock. After 5, 30, or 60 min or 6, 12, or 24 h, the mice were killed, microautoradiographs were prepared, and grains were counted in the cortex, hippocampus, and basal ganglia. The results of the grain counts were compared with grain counts in the cortex, hippocampus, and basal ganglia of mice exposed to anoxia for 25 s and then treated in the same manner as the first groups. After electroshock the grain count decreased to 25% of that in control animals in the hippocampus and to 50% in the cortex but was normal in the basal ganglia. The counts returned to normal values within 6 h in the hippocampus, and within 1 h in the cortex. After anoxia, the grain counts were normal in the cortex and hippocampus but increased in the basal ganglia. The distribution of cells with a high or low grain count in vertical and horizontal columns of the cortex in control and convulsion animals was analyzed. There were random variations from column to column in both control and convulsion animals. In some anatomic layers there were significantly different grain counts, indicating differences in functional activity.

Ultrastructural visualization of Na +-channel associated[ 125]α-scorpion toxin binding sites on fetal mouse nerve cells in culture

Purified neurotoxin II from the scorpion Androctonus australis Hector (α-ScTx) has previously been shown to bind specifically to the voltage-sensitive Na + channels of excitable cells. Recent studies, using high specific activity 125I-labeled α-ScTx, demonstrated specific binding to neuronal cells derived from fetal mouse brains. In the present study, 125I-labeled α-ScTx was used to localize the voltage-sensitive Na + channels in cultured fetal mouse brain cells. By quantitative electron microscope autoradiography we demonstrate that specific α-ScTx binding sites are selectively located at the plasma membrane. Estimates of their density revealed that neurites at 13 days in vitro carry at least 6 × more specific α-ScTx sites than cell body membrane.

Thy-1 cell surface antigen on cloned cell lines of the rat and mouse: Stimulation by cAMP and by butyrate

The level of the Thy-1 cell surface antigen on a number of established rat and mouse nerve cell lines can be stimulated by N 6, O 2′-dibutyryl adenosine 3′:5′-cyclic monophosphoric acid (Bt 2cAMP), in some cases up to the antigen level found in whole brain. On rat cell line BN1010-3, stimulation is also produced by phosphodiesterase inhibitors, adenosine 3′:5′-cyclic monophosphoric acid (cAMP) and its 8-bromo derivative, and l-isoproterenol. Hence, antigen elevation appears to occur via cAMP-related metabolism. It is not a consequence of morphological changes brought about by cAMP elevation in these cells, and is apparently independent of the inhibition of cell division by the nucleotide. Elevations of intracellular cAMP levels for at least one hour are needed to produce Thy-1 stimulation, after which an enhanced level of Thy-1 is observable after about 12 h. Continuous stimulation is required to maintain elevated antigen levels, for upon removal of the stimulating agent, the level of Thy-1 returns to the original unstimulated value within 48 h. Potent stimulation of the antigen level is also obtained with butyrate at 1–2 mM, which appears to be acting by a cAMP independent mechanism.