The in vitro antitumor effectiveness of murine lymphokine-activated killer (LAK) cells induced by recombinant IL-2

We have studied the in vitro antitumor effectiveness of murine lymphokine-activated killer (LAK) cells induced by recombinant IL-2 (rIL-2). LAK cells were generated by placing 5 X 10(7) fresh C 57 BL/6 splenocytes (erythrocytes were lysed osmotically) in 10-cm (diameter) dishes (Falcon) containing 10 ml of complete medium (CM). The CM consisted of RPMI 1640 with 0.1 mM non-essential amino acids, 1 microM sodium pyruvate, 5 X 10(-5)M 2-mercaptoethanol, 50 micrograms/ml gentamicin sulfate, 0.03% glutamine, 10% heat-inactivated fetal calf serum (FCS) and 10 units/ml of rIL-2 (TGP-3, provided by TAKEDA Chemical Industries, Ltd). The dishes were incubated horizontally at 37 degrees C in a 5% CO2 atmosphere for 72-96 hr. The LAK cells were then harvested, washed three times, and resuspended in RPMI 1640 with 5% heat-inactivated FCS for the in vitro cytotoxicity assay. The antitumor cytotoxic activity of LAK cells was estimated in triplicate by 4 hr 51Cr release assays. The cytotoxic activity of LAK cells against syngeneic 203 glioma and normal syngeneic glioblasts was approximately 50% and a few %, respectively. The in vitro cytotoxicity of LAK cells against syngeneic EL-4 thymoma, allogeneic YAC-1 lymphoma and P-815 mastocytoma was 72%, 87% and 43%, respectively. Thus LAK cells have apparent tumor specificity in vitro and are easily generated. Fresh splenocytes of CBA/J mice were markedly lytic for natural killer (NK)-sensitive YAC-1 cells, but not for 203-glioma cells or NK-resistant P-815 cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of anticonvulsants on cellular immunity

The effects of anticonvulsants on cellular immunity were examined in murine models. Fresh splenocytes were obtained from mice which had been intraperitoneally given 1 mg of phenytoin, 2 mg of phenobarbital, or 20mg of valproate for 28 days. The serum concentration of phenytoin, phenobarbital and valproate in these animals were 10-20 micrograms/ml, 30-40 micrograms/ml and 50-70 micrograms/ml, respectively. The proliferative response of splenocytes to mitogens was assessed by 3H-thymidine incorporation. The cytotoxic activities of cells such as natural killer (NK) cells, cytotoxic T lymphocytes (CTL), and lymphokine-activated killer (LAK) cells were estimated by a 4 hr-51Cr release assay. Phenytoin suppressed lymphocyte proliferation, NK activity, and CTL activity, but never LAK activity. Phenobarbital suppressed proliferative response to rIL-2 and CTL activity, but did not suppress NK activity nor LAK activity. In turn sodium pyruvate never suppressed any activity on cellular immunity.     

In vivo and in vitro glycogenic effects of methionine sulfoximine are different in two inbred strains of mice

We investigated the relationship between brain glycogen anabolism and methionine sulfoximine (MSO)-induced seizures in two inbred mouse strains that presented differential susceptibility to the convulsant. CBA/J was considered a MSO-high-reactive strain and C57BL/6J a MSO-low-reactive strain. Accordingly, the dose of MSO needed to induce seizures in CBA/J mice is lower than that in C57BL/6J mice, and CBA/J mice which had seizures, died during the first convulsion. In addition, the time--course of the MSO effect is faster in CBA/J mice than that in C57BL/6J mice. Analyses were performed in C57BL/6J and CBA/J mice after administration of 75 (subconvulsive dose) and 40 mg/kg of MSO (subconvulsive dose, not lethal dose), respectively. In the preconvulsive period, MSO induced an increase in the brain glycogen content of C57BL/6J mice only. Twenty-four hours after MSO administration, the brain glycogen content increased in both strains. The activity and expression of fructose-1,6-bisphosphatase, the last key enzyme of the gluconeogenic pathway, were increased in MSO-treated C57BL/6J mice as compared to control mice, at all experimental time points, whereas they were increased in CBA/J mice only 24 h after MSO administration. These latter results correspond to CBA/J mice that did not have seizures. Interestingly, the differences observed in vivo were consistent with results in primary cultured astrocytes from the two strains. This data suggests that the metabolism impairment, which was not a consequence of seizures, could be related to the difference in seizure susceptibility between the two strains, depending on their genetic background.     

Genotypic influences on striatal dopaminergic regulation in mice

Genotypic influences on dopaminergic-induced behaviors and striatal dopaminergic receptors were evaluated in CBA/J, C57BL/6J and BALB/cJ male mice. CBA/J mice were less behaviorally sensitive to apomorphine (stereotypic behavior), but more sensitive to haloperidol (catalepsy) than C57BL/6J and BALB/cJ mice. Striatal dopaminergic receptors, assayed by binding of [³H]spiroperidol (antagonist) and [³H]ADTN (agonist), were 50% fewer in CBA/J compared to BALB/cJ mice; C57BL/6J mice had low to intermediate numbers of receptors.

Striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations were similar in all strains. However, a 20% higher DOPAC/dopamine ratio in CBA/J mice suggests greater dopamine turnover. Median eminence dopamine was similar in all strains, but norepinephrine was 30% higher in BALB/cJ mice.

CBA/J mice failed to show antagonist-induced supersensitivity-type responses to chronic haloperidol treatment: enhanced stereotypic response to apomorphine and a 30% increase of dopaminergic receptors occurred in C57BL/6J and BALB/cJ mice, but not in CBA/J mice. These data suggest that CBA/J mice either cannot respond to chronic haloperidol treatment or have an elevated threshold for induction of supersensitivity response.

Chronic treatment with the dopamine agonist bromocriptine (7d) depressed apomorphine-induced stereotypic behavior in C57BL/6J mice and eliminated stereotypy in BALB/cJ mice, but caused no change in stereotypic behavior in CBA/J mice. Dopaminergic receptors were 15% lower after bromocriptine treatment in all strains.

These results suggest that some striatal dopaminergic functions are impaired in CBA/J mice relative to BALB/cJ and C57BL/6J mice. The impaired haloperidol-induced supersensitivity responses in the CBA/J mouse may be a useful model for analyzing similar impairments of supersensitivity responses in old rodents.     

Genotypic variation in striatal calmodulin content

CBA/J and BALB/cJ mice have quantitative differences in the nigrostriatal projection. The number of nigral tyrosine hydroxylase reactive neurons, nigral and striatal tyrosine hydroxylase activity and the density of striatal D-2 dopamine receptors are all less in the CBA/J compared to the BALB/cJ mouse. An unrelated strain, the C57BL/6J, has a striatal D-2 dopamine receptor density that is intermediate to that of CBA/J and BALB/cJ mice. CBA/J mice also show deficits in the ability of brain monoaminergic receptor systems to develop supersensitivity. Calmodulin may participate in several striatal dopaminergic receptor mechanisms. Thus, striatal calmodulin was examined in CBA/J, C57BL/6J and BALB/cJ mice. Striatal calmodulin was greater in CBA/J mice than in C57BL/6J or BALB/cJ. In all three strains, cerebral cortical calmodulin was similar. The percent distribution of total striatal calmodulin between soluble and particulate fractions was similar in the three strains. Calcium redistributed soluble striatal calmodulin into the particulate fraction and EGTA shifted calmodulin from the particulate into the soluble fraction. The percent of total striatal calmodulin redistributed by either treatment was similar in all three strains. Gel filtration chromatography of heat-treated soluble extracts from CBA/J and BALB/cJ striatum was similar in elution pattern, although more calmodulin was observed in extracts from the CBA/J. Possible mechanisms for the strain differences in calmodulin are discussed along with their relationship to strain differences in striatal dopamine receptor subtypes.     

Congenital Defects Among the Offspring of Epileptic Fathers: Role of the Genotype and Phenytoin Therapy in a Mouse Model

The progeny of coisogenic C57BL/6J mice homozygous for either the tottering (tg/tg) or wildtype (+/+) allele were examined to determine the role of parental seizure disorders and paternal anticonvulsant drug therapy on the incidence of congenital malformations. Pregnancy outcomes in which one, both, or neither of the parents had an epileptic genotype were compared for various maternal and fetal reproductive parameters. In addition, the progeny from phenytoin-treated male tottering (tg/tg) mice with a spontaneous seizure disorder and from control untreated (+/+) male mice were similarly examined for evidence of congenital defects. The results of these experiments suggest that neither the parental genotype with respect to seizure disorders nor paternal anticonvulsant treatment with phenytoin is responsible for an increased incidence of congenital malformations.     

Resistance to diet-induced obesity is associated with increased proopiomelanocortin mRNA and decreased neuropeptide Y mRNA in the hypothalamus

Mechanisms mediating genetic susceptibility to diet-induced obesity have not been completely elucidated. Elevated hypothalamic neuropeptide Y (NPY) and decreased hypothalamic proopiomelanocortin (POMC) are thought to promote the development and maintenance of obesity. To assess the potential role of hypothalamic neuropeptide gene expression in diet-induced obesity, the present study examined effects of a high-fat diet on hypothalamic NPY and POMC mRNA in three strains of mice that differ in susceptibility to develop diet-induced obesity. C57BL/6J, CBA, and A/J mice were fed either normal rodent chow or a high-fat diet for 14 weeks after which hypothalamic gene expression was measured. On the high-fat diet, C57BL/6J mice gained the most weight, whereas A/J mice gained the least weight. On the high-fat diet, NPY mRNA significantly decreased as body weight increased in CBA and A/J mice, but not in C57BL/6J mice. In addition, POMC mRNA significantly increased as body weight increased in A/J mice, but not in CBA and C57BL/6J mice. Since decreased NPY mRNA and increased POMC mRNA would presumably attenuate weight gain, these results suggest that a high-fat diet produces compensatory changes in hypothalamic gene expression in mice resistant to diet-induced obesity but not in mice susceptible to diet-induced obesity.     

Morphology of the dorsal cochlear nucleus in C57BL/6J and CBA/J mice across the life span.

The morphology of the dorsal cochlear nucleus (DCN) was evaluated across the life span in inbred C57BL/6J (C57) and CBA/J (CBA) mice using 5 age groups (young adult to very old). C57 mice exhibit progressive cochlear sensorineural pathology and hearing loss during middle age; CBA mice have only modest sensorineural pathology late in life. DCN layers I, II, and III were evaluated histologically with serial sections stained for Nissl and fibers. DCN volume decreased with age in C57 mice, but the change began earliest and was most pronounced in layer III. In CBA mice, volume increased during the first year of life and decreased only in the oldest mice. All major DCN cell types were found in both strains at all ages. There was an age-related decrease in the mean size of neurons in C57 mice that was first observed in layer III. In CBA mice, only a nonsignificant trend toward smaller neurons was observed in the oldest mice. An age-related decline in the number of neurons in layer III (but not in layers I and II) occurred in C57 mice. Aged CBA mice exhibited no significant loss of DCN neurons. Thus, age-related changes in the DCN were much more pronounced in C57 mice than in CBA mice, and the changes in C57 mice were most pronounced in layer III. Because layer III receives most of the DCN's primary auditory input, it would be directly affected by age-related hearing loss and degeneration of spiral ganglion cells in C57 mice. This suggests that the age-related changes observed in DCN layer III of C57 mice are affected by progressive peripheral degenerative changes; when peripheral loss is minimal (CBA mice), less substantial age-related changes are observed.     

Genotypic influences on pituitary responsiveness to haloperidol in mice

Previous studies from this laboratory demonstrated that CBA/J mice have impaired striatal dopaminergic supersensitivity in response to subchronic haloperidol administration. Others have speculated that the peripheral hyperprolactinemia produced by haloperidol is necessary for the striatal dopamine receptor supersensitization produced by dopamine antagonists. In the present experiments, we tested the hypothesis that the impaired supersensitization response to haloperidol in CBA/J mice was secondary to an impaired hyperprolactinemic response by comparing the CBA/J mice with other mice that show normal supersensitization responses: the BALB/cJ and C57BL/6J strains. Acute haloperidol treatments increased serum prolactin levels 60 min later in all three strains, with the greatest response in CBA/J mice. After longer haloperidol treatment (2 or 21 days), serum prolactin remained elevated in CBA/J and, to a lesser extent, in C57BL/6J mice; levels remained low throughout treatment in BALB/cJ mice. Although, the basal density of pituitary dopamine receptors [( 3H]spiperone or D-2 binding sites) was greater in CBA/J than BALB/cJ mice, only BALB/cJ mice showed increased pituitary D-2 binding sites following chronic haloperidol administration. Taken together with previous studies of dopamine and noradrenaline receptors in these mouse strains, we conclude that CBA/J mice have a generalized impairment in their supersensitization responses to pharmacologic blockade of receptors. These data do not support the involvement of prolactin in haloperidol-induced dopamine receptor up-regulation.     

Astrocytes are not susceptible to lysis by natural killer cells

A cell population from the central nervous system, of mainly astrocytes, was prepared and their susceptibility to natural killer cell lysis was compared to YAC-1 cells and L929 cells. Two populations of natural killer cells were used: the splenocytes of mice immunized with Semliki Forest virus 3 days previously and day 5 inflammatory cells from West Nile virus-infected CBA/H mouse brain. Both cell populations showed high lytic activity on YAC-1 cells and the effector cells possessed conventional natural killer cell markers, i.e., Thy1 +/-, L3T4-, Lyt2-, GM1+. The results revealed that astrocytes are not susceptible to lysis by natural killer cells and hence argue against the hypothesis that the absolute concentration of MHC antigens on the cell surface determines the susceptibility to natural killer cell lysis.     

Neurospecific S-100 protein content in brains of different mouse strains

Total whole brain concentrations of S-100 protein and of its water-soluble fraction were determined in 11 inbred mouse straine: DBA/2J, AKR/J, CBA/Lac, C57BL/6J, C57BL/6J-Ay, C3H/He, C3H/f, DD, A/He, BALB/cLac, CC57BR/Mv, and in cerebral cortex, cerebellum and hippocampus in DBA/2J, AKR/J and CBA/Lac strains. Highly significant differences in the concentrations of the water-soluble S-100 protein were found between some strains. Slight differences were found in total S-100 protein content in whole brains between the strains (0.01 less that P less than 0.05). The DBA/2J mice had the highest brain S-100 protein content, and were characterized by a higher learning rate in shuttle-box as compared to CBA/Lac and AKR/J mice, who had a low content of this neurospecific protein.     

Glycine immunoreactivity and receptor binding in the cochlear nucleus of C57BL/6J and CBA/CaJ mice: Effects of cochlear impairment and aging

Glycinergic neurons in the cochlear nucleus (CN) of C57BL/6J (C57) and CBA/CaJ (CBA) mice were studied by using immunocytochemical and receptor-binding techniques. Adult C57 mice exhibit progressive cochlear pathology as they age, whereas aging CBA mice retain good hearing. In the CN of old C57 mice (18 months) with severe hearing loss, the number of glycine-immunoreactive neurons decreased significantly. The number (B_max) of strychnine-sensitive glycine receptors (GlyR) decreased significantly in the dorsal CN of old C57 mice. Significant effects were not observed in the CN of middle-aged C57 mice (with less-severe hearing loss) or in very old CBA mice (which do not exhibit severe hearing loss). The data suggest that the combination of severe hearing loss and old age results in deficits in one or more inhibitory glycinergic circuits in the CN. J. Comp. Neurol. 385:405–414, 1997. © 1997 Wiley-Liss, Inc.     

Immunochemical studies of brain glutamate decarboxylase and GABA-transaminase of six inbred strains of mice

Six different inbred strains of mice (C57BL/6J, CBA/CaJ, CE/J, DBA/2J, LP/J and RF/J) were compared in terms of specific activities and immunochemical properties of brain L-glutamate decarboxylase (GAD) and gamma-aminobutyrate transaminase (GABA-T), the enzymes responsible for the synthesis and degradation of GABA, respectively. GAD from the brains of the different strains was indistinguishable on the basis of specific activities, double diffusion tests, immunoelectrophoresis and inhibition by antibody. However, microcomplement fixation tests showed GAD from DBA and C57BL mice to be most distinctly different from GAD extracted from the Swiss mouse, from which the original antigen was prepared and that the enzyme from the CE, LP and RF also differed. Similar fixation curves were obtained for the GAD from CBA and Swiss mice. GABA-T from the different strains was indistinguishable on the basis of all the tests employed.     

Genetic variance contributes to naltrexone-induced inhibition of sucrose intake in inbred and outbred mouse strains

The study of genetic variance in opioid receptor antagonism of sucrose and other forms of sweet intake has been limited to reductions in sweet intake in mice that are opioid receptor-deficient or lacking either pre-pro-enkephalin or beta-endorphin. Marked genetic variance in inbred mouse strains has been observed for sucrose intake across a wide array of concentrations in terms of sensitivity, magnitude, percentages of kilocalories consumed as sucrose and compensatory chow intake. The present study examined potential genetic variance in systemic naltrexone's dose-dependent (0.01-5 mg/kg) and time-dependent (5-120 min) ability to decrease sucrose (10%) intake in eleven inbred (A/J, AKR/J, BALB/cJ, CBA/J, C3H/HeJ, C57BL/6J, C57BL/10J, DBA/2J, SJL/J, SWR/J, 129P3/J) and one outbred (CD-1) mouse strains. A minimum criterion sucrose intake (1 ml) under vehicle treatment, designed to avoid "floor effects" of antagonist treatment was not achieved in three (A/J, AKR/J, CBA/J) inbred mouse strains. Marked genetic variance in naltrexone's ability to inhibit sucrose intake was observed in the remaining strains with the greatest sensitivity observed in the C57BL/10J and C57BL/6J strains, intermediate sensitivity in BALB/cJ, C3H/HeJ, CD-1 and DBA/2J mice, and the least sensitivity in 129P3/J, SWR/J and SJL/J strains with a 7.5-36.5 fold range of greater effects in the ID(50) of naltrexone-induced inhibition in C57BL/10J relative to the three less-sensitive strains across the time course. Naltrexone primarily affected the maintenance, rather than the initiation of intake in BALB/cJ, CD-1, C3H/HeJ, DBA/2J and SJL/J mice, but significantly reduced sucrose intake at higher doses across the time course in C57BL/6J, C57BL/10J and 129P3/J mice. Whereas SWR/J mice failed to display any significant reduction in sucrose intake at any time point following any of the naltrexone doses, naltrexone's maximal magnitude of inhibitory effects was small (35-40%) in 129P3/J and SJL/J mice, moderate ( approximately 50%) in BALB/cJ, C3H/HeJ, CD-1 and DBA2/J mice, and profound (70-80%) in C57BL/6J and C57BL/10J mice. Indeed, the latter two strains displayed significantly greater percentages of naltrexone-induced inhibition of sucrose intake than virtually all other strains. These data indicate the importance of genetic variability in opioid modulation of sucrose intake.     

Mouse brain IgG-like immunoreactivity: strain-specific occurrence in microglia and biochemical identification of IgG

Unlike the brains of most mammals, the mouse brain appears unique in the massive appearance of cells showing IgG-like immunoreactivity, which has repeatedly been shown via immunohistochemistry. In the present study, we first examined possible species differences in IgG-like immunohistochemical staining in the brains of various rodents, including mice. In four of six mouse strains examined (ICR, Balb/c, C57BL/6, and AKR/J), antibodies against mouse IgG revealed positive staining in many brain microglia. However, no such positive staining was detected in brains of the rat, hamster, guinea pig, or two other mouse strains (CBA/N and CBA/J). We purified IgG-like-immunoreactive molecule(s) biochemically from brain of the ICR mouse as a representative mouse strain. Our amino-acid-sequence analysis proved that the purified protein was identical to serum IgG. The possibility of IgG synthesis by brain microglia in the ICR mouse was denied by our RT-PCR experiments and in situ hybridization histochemistry. In addition, Fcgamma-receptor-deficient double-knockout mice of the C57BL/6 genetic background contained no IgG-immunoreactive microglia in the brain. These results clearly indicate that microglial IgG staining is due to the uptake of serum IgG through Fcgamma receptors. However, the strain-specific mechanisms resulting in microglial IgG uptake remain to be elucidated, in that Fcgamma receptors are omnipresent in microglia of all rodents examined here.     

FOS and FOSB expression in the medial preoptic nucleus pars compacta of maternally active C57BL/6J and DBA/2J mice

C57BL/6J and DBA/2J inbred mice differ in aspects of maternal behavior and in the morphology of the medial preoptic nucleus (MPO), suggesting a possible association. DBA/2J mice have a compact subnucleus in the MPO, the MPOpc, that is sexually dimorphic and absent in C57BL/6J mice. To determine whether MPOpc cells are activated by maternal behavior, FOS and FOSB immunohistochemistry was performed on brain sections of C57BL/6J and DBA/2J mothers following the return of their pups after a separation of 2 days. In both light and dark phases of the daily cycle, stimulation of DBA/2J mothers evoked an increase in FOS- and FOSB-immunoreactivity in the MPOpc. Stimulated C57BL/6J mice, which lack the MPOpc, did not show an increase in cellular activity in the corresponding MPO region. Cells immediately lateral to the MPOpc were activated by pup stimulation, in both strains. These results suggest that MPOpc cells are active during maternal behavior, and that strain differences in maternal behavior are related to anatomical differences in the MPO.     

Nervous system antigen-5, an antigenic cell surface component of neuroectodermal origin.

The antigenic cell surface component NS-5 (nervous system antigen-5) is recognized by antiserum raised in C3H.SW/Sn mice against cerebellum of 4-day-old C57BL/6J mice. When analyzed in the cytotoxicity test the antiserum detects a cell surface antigen or set of antigens present not only an cerebellum but also other parts of the central nervous system, including retina, as well as on mature spermatozoa and to a lesser degree on kidney. All other non-neural tissues tested, liver, splee, thymocytes, muscle, testis, adrenal gland and epidermis do not express detectable amounts of the antigen. Among seven murine tumors of the nervous system, medulloepithelioma shows high levels of NS-5 expression, whereas neuroblastoma Cl300, glioma G26, glioblastome, ependymoblastoma, ependymoblastoma EPA and glioblastoma G26l do not carry detectable NS-5. All mouse strains tested (C57BL/6J, C3H.SW/Sn, C3H/HeDiSn, A/J, AKR/J, BALB/cJ and DBA/2) express similar levels of NS-5. The antigen is demonstrable not only on postnatal day 4 neural tissue, but also in lower amounts on adult nervous system. On embryonic day 9, the earliest stage tested, and at all subsequent stages during embryonic development, NS-K is already present in brain and spinal cord, but not in gut.     

Morphology of the octopus cell area of the cochlear nucleus in young and aging C57BL/6J and CBA/J mice

The influence of aging and age-related cochlear impairment on the ventral cochlear nucleus was evaluated by measuring morphological properties of the octopus cell area (OCA) in five age groups of inbred C57BL/6J and CBA/J mice (young adult to very old). The former strain demonstrates progressive cochlear sensorineural pathology and hearing loss during middle age; the latter has only modest sensorineural pathology late in life. Histological sections of the OCA were evaluated with serial sections and several strains for neurons, glia, and fibers, and Golgi impregnations were also used. Aging was associated with a decrease in volume of the OCA, a loss of neurons, slight decrease in neuron size, increased packing density of glial cells, and changes in dendrites ranging from minor to total loss of primary branches. The greatest changes occurred in extreme old age, beyond the median lifespan. Age-related changes were not exacerbated by sensorineural pathology in aging C57BL/6J mice. Individual octopus cells varied greatly in the extent of age-related abnormality.     

Degeneration of granule cells following chronic phenytoin administration: an electron microscopic investigation of the mouse cerebellum

Fifteen male mice (C57/Bl6J) were fed the liquid diet "Stardit" supplemented with vitamins together with phenytoin for 8 weeks; experimental animals and controls were pair-fed. After 8 weeks of treatment, the anesthetized animals were perfused with 3.5% glutaraldehyde. Tissue samples of the cerebral cortex (area 3), cerebellum (vermis), thalamus, hypothalamus, and liver were embedded in Araldite. All phenytoin-treated animals displayed a hepatomegaly. Semithin sections and ultrastructural investigations of the cerebellar vermis showed pyknoses of granule cells and an enlargement and swelling of parallel fibers in presynaptic areas in the molecular layer. The swollen axons showed an accumulation of tubular structures which represented proliferated smooth endoplasmic reticulum. Similar tubular structures were observed in hepatocytes of experimental animals. It is proposed that phenytoin caused an induction of the microsomal system of hepatocytes and granule cells which led to a proliferation of the smooth endoplasmic reticulum. The transport of these organelles to the axon terminals of parallel fibers via the axoplasmic flow is assumed to cause a swelling of the presynaptic area. A dying-back process may then lead to pyknosis of granule cells. Chronic phenytoin administration to mice is a new experimental model of neuroaxonal dystrophy.     

Comparison of seizure phenotype and neurodegeneration induced by systemic kainic acid in inbred, outbred, and hybrid mouse strains

We assessed inbred, outbred and hybrid mouse strains for susceptibility to seizures and neurodegeneration induced by systemic administration of kainic acid (KA). Each strain showed a unique pattern of susceptibility to seizures as assessed by the dose necessary to induce continuous tonic clonic seizures, progression through six seizure levels, the number of mice that failed to satisfy seizure criteria, and seizure-induced mortality. In general, the C57BL/6, ICR, FVB/N, and BALB/c strains were resistant to seizures while the C57BL/10, DBA/2 J, and F1 C57BL/6*CBA/J strains were vulnerable. Neuronal cell death was quantified in four subfields of the hippocampus: CA3, the hilus of the dentate gyrus, CA1, and the dentate granule cell layer. Neurodegeneration was also semiquantitatively assessed in other brain regions including the neocortex, striatum, thalamus, hypothalamus and amygdala. Although there was variability in the extent of cell death within strains, there were significant differences in the amount of hippocampal cell death between strains and also different patterns of neurodegeneration in affected brain areas. In general, the C57BL/6, C57BL/10, and F1 C57BL/6*CBA/J strains were resistant to neurodegeneration while the FVB/N, ICR and DBA/2 J strains were vulnerable. The BALB/c strain was unique in that neurodegeneration was confined to the hippocampus. Consistent with previous findings, the resistant neurodegeneration phenotype was dominant in an F1 cross of resistant and vulnerable inbred strains. Our results, using a large number of mouse strains, definitively demonstrate that a mouse strain's seizure phenotype is not related to its neurodegeneration phenotype.