The genetics of coat colors in the mongolian gerbil (Meriones unguiculatus)

Genetic studies demonstrated three loci controlling coat colors in the Mongolian gerbil. F1 hybrids of white gerbils with red eyes and agouti gerbils with wild coat color had the agouti coat color. The segregating ratio of agouti and white in the F2 generation was 3:1. In the backcross (BC) generation (white x F1), the ratio of the agouti and white coat colors was 1:1. Next, inheritance of the agouti coat color was investigated. Matings between agouti and non-agouti (black) gerbils produced only agouti gerbils. In the F2 generation, the ratio of agouti to non-agouti (black) was 3:1. There was no distortion in the sex ratios within each coat color in the F1, F2 and BC generations. This indicated that the white coat color of gerbils is governed by an autosomal recessive gene which should be named the c allele of the c (albino) locus controlling pigmentation, and the agouti coat color is controlled by an autosomal dominant gene which might be named the A allele of the A (agouti) locus controlling pigmentation patterns in the hair. The occurrence of the black gerbil demonstrated clearly the existence of the b (brown) locus, and it clearly indicated that the coat colors of gerbils can basically be explained by a, b, and c loci as in mice and rats.     

Characterization of Seizure-Induced Cysteinyl-Leukotriene Formation in Brain Tissue of Convulsion-Prone Gerbils

Tonic-clonic seizures elicited in convulsion-prone gerbils resulted in a large increase in immunoreactive prostaglandin (PG) F2 alpha and in a smaller increase in immunoreactive leukotriene (LT) C4-like material in brain tissue. Brain tissue contents of both eicosanoids were found to reach a maximum at 6 min after the onset of seizures and were still elevated at 54 min after the beginning of convulsions. By reversed phase HPLC the immunoreactive LTC4-like material was identified as LTC4 and LTD4 at 6 min after the onset of convulsions, whereas at 54 min after the onset, transformation of LTD4 to LTE4 could be detected as well. In gerbils showing only weak seizure activity a small increase in PGF2 alpha but no increase in immunoreactive LTC4-like material could be detected at 6 min after the onset of convulsions. Pretreatment with indomethacin abolished the formation of PGF2 alpha but significantly enhanced the biosynthesis of immunoreactive LTC4-like material at 18 min after the beginning of seizures. The results demonstrate formation of cysteinyl-LT following tonic-clonic convulsions in spontaneously convulsing gerbils which could be enhanced by inhibition of the cyclooxygenase pathway of arachidonic acid metabolism. Since cysteinyl-LT have potent biological actions in various organs this finding warrants further investigations on the potential role of cysteinyl-LT in the CNS.     

Anticonvulsants for soman-induced seizure activity

This report describes studies of anticonvulsants for the organophosphorus (OP) nerve agent soman: a basic research effort to understand how different pharmacological classes of compounds influence the expression of seizure produced by soman in rats, and a drug screening effort to determine whether clinically useful antiepileptics can modulate soman-induced seizures in rats. Electroencephalographic (EEG) recordings were used in these studies. Basic studies were conducted in rats pretreated with HI-6 and challenged with 1.6×LD₅₀ soman. Antimuscarinic compounds were extremely effective in blocking (pretreatment) or terminating soman seizures when given 5 min after seizure onset. However, significantly higher doses were required when treatment was delayed for more than 10 min, and some antimuscarinic compounds lost anticonvulsant efficacy when treatment was delayed for more than 40 min. Diazepam blocked seizure onset, yet seizures could recur after an initial period of anticonvulsant effect at doses 2.5 mg/kg. Diazepam could terminate ongoing seizures when given 5 min after seizure onset, but doses up to 20 mg/kg were ineffective when treatment was delayed for 40 min. The GABA uptake inhibitor, tiagabine, was ineffective in blocking or terminating soman motor convulsions or seizures. The glutamate receptor antagonists, NBQX, GYKI 52466, and memantine, had weak or minimal antiseizure activity, even at doses that virtually eliminated signs of motor convulsions. The antinicotinic, mecamylamine, was ineffective in blocking or stopping seizure activity. Pretreatment with a narrow range of doses of ₂-adrenergic agonist, clonidine, produced variable protection (40–60%) against seizure onset; treatment after seizure onset with clonidine was not effective. Screening studies in rats, using HI-6 pretreatment, showed that benzodiazepines (diazepam, midazolam and lorazepam) were quite effective when given 5 min after seizure onset, but lost their efficacy when given 40 min after onset. The barbiturate, pentobarbital, was modestly effective in terminating seizures when given 5 or 40 min after seizure onset, while other clinically effective antiepileptic drugs, trimethadione and valproic acid, were only slightly effective when given 5 min after onset. In contrast, phenytoin, carbamazepine, ethosuximide, magnesium sulfate, lamotrigine, primidone, felbamate, acetazolamide, and ketamine were ineffective.The animals used in studies performed in, or sponsored by, this Institute were handled in accordance with the principles stated in the Guide for the Care and Use of Laboratory Animals, proposed by the Committee to Revise the Care and Use of Laboratory Animals of the Institute of Laboratory Animal Resources, National Research Council, and published by National Academy Press, 1996, and the Animal Welfare Act of 1966, as amended. The opinions or assertions contained herein are the private views of the authors, and are not to be construed as reflecting the views of the Department of the Army or the Department of Defense.     

Stimulus-induced behavior in F1 hybrids of seizure-sensitive and seizure-resistant gerbils

We previously established two strains of Mongolian gerbil: a seizure-sensitive strain, established by selective inbreeding for motor seizures elicited by a stimulus called the S method and a seizure-resistant strain that does not exhibit inducible seizures. The behavior of the seizure-sensitive strain is characterized by a progressive increase in responsiveness to weekly application of the S method, from repetitive backward ear movements appearing after postnatal day 40, to a full-blown seizure, while the seizure-resistant strain is apparently unaffected by the stimulation. The difference between these two strains is presumably genetic. To determine the genetic factors underlying this difference, we first examined developmental changes in the stimulus-induced behavior of the F1 hybrids. When the S method was applied, most F1 hybrids had repetitive movements of the ears (and head) similar to the seizure-sensitive gerbils, but generalized seizures emerged considerably later than in seizure-sensitive gerbils. These results suggest that a half dose of the gene products involved renders most gerbils susceptible to the stimulus but is insufficient for the rapid accumulation of an as yet undefined change needed to spread the abnormal electrophysiologic activity to elicit generalized seizures.     

13例SCN2A 基因突变相关儿童神经系统疾病表型分析

摘要 目的：总结并分析SCN2A基因突变引起的儿童神经系统疾病相关表型谱特点。方法：采用回顾性研究,收集2018年6月至2021年6月在上海交通大学医学院附属上海儿童医学中心神经内科诊治的患儿,并经二代基因测序检测,纳入SCN2A基因突变者,研究并总结患儿神经系统临床表型特点。结果：共纳入13例SCN2A突变患儿,包括新生突变9例和遗传性突变4例。其中11例患儿伴有癫痫发作,发作年龄为1日龄~1岁11月龄,4例在新生儿期起病 （36%）,1~3 月龄起病2例（18%）,4~12月龄起病2例（18%）,1岁后起病3例（27%）;发作类型中强直阵挛发作、痉挛发作、局灶性发作均各有4例（36%）,阵挛发作1例（9%）。另有2例无癫痫发作的患儿,1例表现为全面性发育迟缓,另一例表现为发育迟缓合并孤独症谱系疾病。11例癫痫患儿中,丛集性发作患儿10例。遗传性突变4例患儿中2例智力、运动发育正常;9例新生突变的患儿中8例伴有运动、智力发育落后,1例发育正常。11例癫痫患儿表型中良性家族性新生儿癫痫1例,新生儿惊厥2例,婴儿痉挛症2例,不能分类的早发性癫痫性脑病3例,儿童期起病的癫痫性脑病2例,热厥附加症1例。结论：SCN2A基因突变引起的儿童神经系统疾病以癫痫表现居多、癫痫表型谱广,少数表现为不伴癫痫发作的发育迟缓和孤独症谱系疾病。     

Anticonvulsant effects of thymoquinone, the major constituent of Nigella sativa seeds, in mice.

The anticonvulsant effects of thymoquinone, the major constituent of Nigella sativa seeds, were investigated using pentylenetetrazole (PTZ)- and maximal electroshock (MES)-induced seizure models. We also studied the effect of thymoquinone on pentobarbital-induced hypnosis, locomotor activity, and motor coordination. In PTZ-induced seizure, the intraperitoneally injection of thymoquinone with doses of 40 and 80 mg/kg, prolonged the onset of seizures and reduced the duration of myoclonic seizures. The protective effect of thymoquinone against mortality was 71.4% and 100% in the mentioned doses, respectively. In MES model, thymoquinone failed to reduce the duration of seizure, whereas exhibited a complete protection against mortality. In PTZ model, flumazenil (10 mg/kg, i.p.), an antagonist of benzodiazepine (BZD) site in the GABAA-BZD receptor complex, inhibited the prolongation of seizure latency, but did not show any effect on the duration of myoclonic seizures. Also, pretreatment with naloxone (0.1 and 03 mg/kg, i.p.) inhibited the prolongation of myoclonic seizure latency and antagonized the reduction of myoclonic seizure duration induced by thymoquinone (40 and 80 mg/kg) in the PTZ model. Moreover, thymoquinone (40 and 80 mg/kg) did not have any hypnosis effect in the pentobarbital-induced hypnosis, but impaired the motor coordination and reduced the locomotor activity. These results indicate that thymoquinone may have anticonvulsant activity in the petit mal epilepsy probably through an opioid receptor-mediated increase in GABAergic tone.     

Ontogeny of susceptibility to the convulsant, Ro 5-4864, and its relationship to audiogenic seizure susceptibility in inbred mice

The postnatal development of susceptibility to the convulsant effects of Ro5-4864 (4'-chlorodiazepam) was characterized in two inbred mouse strains (DBA/2J and BALB/c ByJ) which as adults differ markedly in their response to this convulsant. Onset of susceptibility to a dose of Ro5-4864 which caused a high frequency of clonic seizures in adults was observed at 10 days of age in DBA/2 mice, but not until 35 days in BALB/c By mice. At 14 days of age an abrupt increase in susceptibility to Ro5-4864-induced tonic seizures was found in DBA/2 but not BALB/c By mice. Both the peak of tonic seizure susceptibility (21 days) and the time course of its subsequent age-dependent decline closely paralleled the change in audiogenic seizure susceptibility in the DBA/2 strain. PK11195 (40 mg/kg) blocked Ro5-4864 (25 mg/kg)-induced, age-dependent tonic seizures but had no effect on clonic seizure induction in the same mice. These observations establish that both the susceptibility to Ro5-4864 in adult mice and the postnatal time course for development of susceptibility to this convulsant are inherently different in these two strains of mice. The lack of coincidence between the developmental onset of susceptibility to Ro5-4864-induced seizures and the onset of supersensitivity to Ro5-4864-induced tonic seizures during the period of peak audiogenic seizure susceptibility in DBA/2 mice implies that more than one neurochemical mechanism is involved in the ability of Ro5-4864 to induce seizures in this strain. However, the blockade of Ro5-4864-induced tonic seizures by PK11195 suggests that peripheral type benzodiazepine receptors may mediate this effect.     

Epilepsy and electromagnetic fields: effects of simulated atmospherics and 100-Hz magnetic fields on audiogenic seizure in rats

In order to study the possible association between epileptic seizures and natural electromagnetic fields, 32 female audiogenic seizure (AGS)-susceptible rats were exposed to simulated 10 kHz and 28 kHz atmospherics and to a sinusoidally oscillating magnetic field with a frequency of 100 Hz and field strength of 1 A/m. After the electromagnetic exposure, seizures were induced in the rats with a sound stimulus. The severity of the seizure was determined on an ordinal scale, the audiogenic response score (ARS). The time from the beginning of the sound stimulus to the onset of the seizure (seizure latency) and the duration of the convulsion was measured. No differences from the control experiments were found in the experiments with simulated atmospherics, but the 100 Hz magnetic field increased the seizure latency by about 13% (P<0.02). The results do not support the hypothesis that natural atmospheric electromagnetic signals could affect the onset of epileptic seizures, but they suggest that AGS-susceptible rats may be a useful model for studying the biological effects of electromagnetic fields.     

Modulation of spontaneous seizures in the mongolian gerbil: effects of beta-endorphin

Intraventricular injection of beta-endorphin (0.1-3 micrograms) into gerbils from the UCLA seizure sensitive strain reduced the incidence and severity of spontaneous epileptiform seizures, both the motor manifestations and the preceding high voltage focal spiking and accompanying seizure activity in the cortical EEG. This "'anticonvulsant" effect of beta-endorphin was prevented by prior administration of naloxone (1 mg . kg-1 IP). These findings suggest that the endogenous opioid peptide may be involved in the normal suppression of the epileptic diathesis in these animals during the interictal periods.     

Scalp EEG for the diagnosis of epilepsy and photosensitivity in the baboon

Spontaneous seizures have been observed in several baboon species housed at the Southwest National Primate Research Center (SNPRC), including Papio hamadryas anubis and cynocephalus/anubis, hamadryas/anubis, and papio/anubis hybrids. The goal of this study was to establish a noninvasive, reliable electroencephalographic technique to characterize epilepsy phenotypes and assess photosensitivity in these subspecies. Thirty baboons with witnessed seizures, and 15 asymptomatic baboons underwent scalp electroencephalograms (EEGs) with photic stimulation (PS). The sensitivity and specificity of surface EEG for identifying interictal epileptic discharges (IEDs) in baboons with witnessed seizures were examined. The morphology of IEDs, electroclinical features of seizures and responses to PS, reproducibility of EEG findings, and intrarater reliability were also evaluated. Twenty-three seizure baboons (77%) demonstrated IEDs, predominantly with frequencies of 4-6 Hz in 18 baboons and 2-3 Hz in six baboons. Two seizure animals had a mixture of 2-3-Hz and 4-6-Hz IEDs. All animals with 2-3-Hz IEDs were 3 years old or younger. Myoclonic seizures (MS) and generalized tonic-clonic seizures (GTCS) were recorded in 13 baboons (43%). PS activated IEDs in 15 baboons (50%) and seizures in nine baboons. The presence of IEDs or seizures was not associated with a particular gender or species (Fisher exact test, alpha=0.05). Seizures were more common in animals >3 years old, while PS-induced IEDs and seizures were more prevalent in P.h. anubis/cynocephalus crosses compared to P.h. anubis. In the asymptomatic controls, IEDs were recorded in five baboons (33%), and photoparoxysmal responses were observed in two (13%). Surface EEG is a sensitive and reliable instrument for characterizing the epilepsy encountered in Papio species. Electroclinically, the seizure animals had generalized epilepsy with photosensitivity. The variation in IED morphology may be age-related or it may reflect different epileptic phenotypes. Ketamine provoked IEDs and seizures in most seizure animals and only in a few asymptomatic baboons; therefore, it may enhance the sensitivity of surface EEG for detecting a predisposition to epilepsy.     

Changes inγ-aminobutyric acid during different stages of picrotoxin-induced seizure,and the effect of pretreatment withγ-acetylenic GABA and phenobarbital

Changes in GABA content of various brain areas during different stages of picrotoxin-induced seizures and following pretreatment with the anti-convulsants phenobarbital andγ-acetylenic GABA were studied. Picrotoxin (6mg/kg) produced clonic/tonic convulsions associated with a 34% reduction in GABA content of the sensory motor cortex. A reduction of 24% was observed 1 min before the onset of seizure and the reduction in GABA content was reversible 20 min after the convulsion. No significant changes were observed in the cerebellum or spinal cord/medulla oblongata. Pretreatment with phenobarbital (100mg/kg) delayed the onset of convulsion and decreased the mortality rate without causing any change in GABA content at the pre-convulsive, convulsive or post-convulsive stages.γ-Acetylenic GABA (100mg/kg) has elevated GABA levels in different areas of the brain by 2–3-fold after 60 min treatment. This increase was reduced by 44% during the onset of picrotoxin-induced seizures. Picrotoxin convulsion can occur in the presence of normal, reduced or even elevated brain GABA content. The only consistent factor is a one-third reduction in GABA content before the onset of seizure.     

Unidirectional distribution of mosaicism in chimeric rats.

Experimental rat chimeras were produced by aggregation of eight-cell embryos from two inbred strains, ACI/Hkm and WKAH/Hkm, which differ from each other in their major histocompatibility complexes and coat colors, and their mosaicism was analyzed. The existence of the isozyme Es-1, a serum cholinesterase specifically produced by WKAH-derived cells, and the agouti coat color due to ACI cells, indicated that all of the rats analyzed were unequivocal chimeras. The proportion of ACI cells in the red blood cell populations of the chimeras varied from 45% to 98%, as determined with a fluorescence-activated cell sorter and a monoclonal antibody against class I (RT1) antigen. Digital analysis of the coat color revealed that the proportion of the ACI type of coat color ranged from 72% to 98% in these chimeric rats. Each phenotype expressed in the coat color was complex and varied in size. The ratios of red blood cells and the coat color inclined toward the ACI type of cell population. Conversely, the rate of the WKAH-cell-type population was less than 50%. A breeding test disclosed chimerism of germ cells in two chimeric rats, and there were more pups with agouti coats than with albino coats. Taken together, it was shown in most of the phenotypes analyzed that the ACI type of cells was predominant in all of the chimeric rats. We discuss the possible causes for this unbalanced distribution in the rats.     

Thermoregulatory, behavioral and seizure modulatory effects of AVP in the gerbil

Recent reports suggest that arginine vasopressin (AVP) may be an endogenous antipyretic peptide and a mediator of febrile convulsions [10,12]. The spontaneously seizing Mongolian gerbil was used to investigate the thermoregulatory, behavioral and seizure modulatory effects of AVP. Injection of AVP (1.0 and 5.0 μg IV and 0.01–1.0 mg/kg SC) caused dose-related falls in body temperature. Stereotypic scratching, terminated by a body shake, was observed after AVP (1.0–5.0 μg IV). However, such behavior was not observed after subcutaneous injection of AVP. AVP did not potentiate seizure induction in the gerbils but rather reduced the seizure incidence. The data demonstrate that AVP can reduce body temperature and cause specific behaviors, but it does not appear to play a role in the pathogenesis of seizures in the seizure sensitive strain of Mongolian gerbil.     

Genetics of Ustilago violacea. XXXII. Genetic evidence for transposable elements

Crosses between Ustilago violacea mutant strains with different color phenotypes that were derived from the 1.A1 and 2.A2 laboratory strains yielded, as expected, bisectored teliospore colonies with the parental colors as well as the a-1 and the a-2 mating-types. Generally, wild teliospore collections usually produced sporidia of both mating-types, providing two-mating-type (TMT) strains. Occasionally, however, sporidia with only one mating-type allele, a-1 or a-2, were obtained from teliospores, providing one-mating-type (OMT) strains. Crosses between OMT and laboratory strains with different color phenotypes gave (1) bisectored teliospore colonies with the parental colors or colonies with a parental color and a nonparental color and (2) nonsectored colonies with the nonparental color or with the parental color. The frequencies for the occurrence of non-parental color ranged from 41% to 93%, depending on the strain. The yield of teliospore colonies was usually reduced for these crosses. In many of these teliospore colonies, morphologically-altered sporidia (MAS phenotype) were observed. The morphology and the size of the sporidia with the MAS phenotype differed from those of teliospore colonies of the crosses between the laboratory strains. In addition, these sporidia did not form conjugants. A cross involving the TMT strains C449 yielded the MAS phenotype as well as a high incidence of tetrad colonies with a nonparental color. The high degree of instability of the parental color phenotypes, and the high frequency of the appearance of nonparental color phenotypes as well as the appearance of the MAS phenotype, are in accord with the presence of active and inactive transposable elements in the OMT strains, TMT strains, and laboratory strains.     

Identification of QTLs Involved in the Development of Amygdala Kindling in the Rat

Amygdala kindling is useful for modeling human epilepsy development. It has been known that genetic factors are involved in the development of amygdala kindling. The purpose of this study was to identify the loci that are responsible for the development of amygdala kindling. To achieve this, rat strains from a LEXF/FXLE recombinant inbred (RI) strain panel were used. The phenotypes of amygdala kindling-related parameters for seven RI strains and parental LE/Stm and F344/Stm strains were determined. They included the afterdischarge threshold (ADT), the afterdischarge duration (ADD), and the kindling rate, an incidence of development of kindling. Quantitative trait loci (QTL) analysis was performed to identify linkage relationships between these phenotypes and 1,033 SNP markers. Although no significant differences in pre-kindling ADT and ADD were observed, a significant difference in the kindling rate was found for the LEXF/FXLE RI strain. Two QTLs for the amygdala kindling rate (Agkr1 and Agkr2) were identified on rat chromosome 2. These findings clearly prove the existence of genetic influences that are involved in kindling development and suggest that substantial genetic components contribute to the progression of partial seizures into generalized seizures.     

Lack of correlation of central nervous system inflammation and neuropathology with the development of seizures following acute virus infection

Infection of C57BL/6 mice by the intracerebral route with the Daniels (DA) strain of Theiler's murine encephalomyelitis virus (TMEV) resulted in acute behavioral seizures in approximately 50% of the mice. By titration, the viral dose correlated with the percentage of mice developing seizures; however, neuropathological changes were similar over the dose range, and viral clearance from the brains occurred uniformly by day 14 postinfection (p.i.). Other TMEV strains and mutants (GDVII, WW, BeAn 8386 [BeAn], DApBL2M, H101) induced seizures in C57BL/6 mice to various degrees. The BeAn strain and DApBL2M mutant were similar to the DA strain in the percentages of mice developing seizures and neuropathological changes and in the extent of infected cells. The GDVII and WW strains caused 100% mortality by days 5 and 6 p.i., respectively, at which time neuropathological changes and neuronal infection were extensive. The H101 mutant induced seizures and caused 100% mortality by day 7 p.i.; however, only minor neuropathological changes and few infected cells were observed. Thus, in H101 mutant infections, it appears that elevated levels of cytokines, rather than neuronal cell death, play the dominant role in seizure induction.     

Variation of the melanocortin 1 receptor gene in the macaques

Melanocortin 1 receptor (MC1R), a G-coupled seven-transmembrane receptor protein, plays a key role in the regulation of melanin synthesis in mammals. Sequence variation of the MC1R gene (MC1R) has been associated with pigmentation phenotypes in humans and in several animal species. The macaques (genus Macaca) are known to show a marked inter-specific variation in coat color although the causative genetic variation remains unclear. We investigated nucleotide sequences of the MC1R in 67 individuals of 18 macaque species with different coat color phenotypes including black and agouti. Twenty-eight amino acid replacements were identified in the macaques, but none of these amino acid replacements could explain the black coat color of Macaca silenus and the Sulawesi macaque species. Our molecular evolutionary analysis has revealed that nonsynonymous substitution/synonymous substitution (dN/dS) ratio of the MC1R has not been uniform in the macaque groups and, moreover, their coat color and dN/dS ratio were not related. These results suggest that the MC1R is unlikely to be responsible for the coat color variation of the macaques and functions of MC1R other than pigmentation might be associated with the different selective pressures on the MC1R in macaques.