Spaceflight and hind limb unloading induce similar changes in electrical impedance characteristics of mouse gastrocnemius muscle

OBJECTIVE

To assess the potential of electrical impedance myography (EIM) to serve as a marker of muscle fiber atrophy and secondarily as an indicator of bone deterioration by assessing the effects of spaceflight or hind limb unloading.

METHODS

In the first experiment, 6 mice were flown aboard the space shuttle (STS-135) for 13 days and 8 earthbound mice served as controls. In the second experiment, 14 mice underwent hind limb unloading (HLU) for 13 days; 13 additional mice served as controls. EIM measurements were made on ex vivo gastrocnemius muscle. Quantitative microscopy and areal bone mineral density (aBMD) measurements of the hindlimb were also performed.

RESULTS

Reductions in the multifrequency phase-slope parameter were observed for both the space flight and HLU cohorts compared to their respective controls. For ground control and spaceflight groups, the values were 24.7±1.3°/MHz and 14.1±1.6°/MHz, respectively (p=0.0013); for control and HLU groups, the values were 23.9±1.6°/MHz and 19.0±1.0°/MHz, respectively (p=0.014). This parameter also correlated with muscle fiber size (ρ=0.65, p=0.011) for spaceflight and hind limb aBMD (ρ=0.65, p=0.0063) for both groups.

CONCLUSIONS

These data support the concept that EIM may serve as a useful tool for assessment of muscle disuse secondary to immobilization or microgravity.

Embryonic disruption of the candidate dyslexia susceptibility gene homolog Kiaa0319-like results in neuronal migration disorders

Developmental dyslexia, the most common childhood learning disorder, is highly heritable, and recent studies have identified KIAA0319-Like (KIAA0319L) as a candidate dyslexia susceptibility gene at the 1p36-34 (DYX8) locus. In this experiment, we investigated the anatomical effects of knocking down this gene during rat corticogenesis. Cortical progenitor cells were transfected using in utero electroporation on embryonic day (E) 15.5 with plasmids encoding either: (1) Kiaa0319l small hairpin RNA (shRNA), (2) an expression construct for human KIAA0319L, (3) Kiaa0319l shRNA+KIAA0319L expression construct (rescue), or (4) controls (scrambled Kiaa0319l shRNA or empty expression vector). Mothers were injected with 5-bromo-2-deoxyuridine (BrdU) at either E13.5, E15.5, or E17.5. Disruption of Kiaa0319l function (by knockdown, overexpression, or rescue) resulted in the formation of large nodular periventricular heterotopia in approximately 25% of the rats, which can be seen as early as postnatal day 1. Only a small subset of heterotopic neurons had been transfected, indicating non-cell autonomous effects of the transfection. Most heterotopic neurons were generated in mid- to late-gestation, and laminar markers suggest that they were destined for upper cortical laminae. Finally, we found that transfected neurons in the cerebral cortex were located in their expected laminae. These results indicate that KIAA0319L is the fourth of four candidate dyslexia susceptibility genes that is involved in neuronal migration, which supports the association of abnormal neuronal migration with developmental dyslexia.

Electrical impedance alterations in the rat hind limb with unloading

OBJECTIVES

Methods are needed for quantifying muscle deconditioning due to immobilization, aging, or spaceflight. Electrical impedance myography (EIM) is one technique that may offer easy-to-follow metrics. Here, we evaluate the time course and character of the change in single- and multi-frequency EIM parameters in the hind-limb suspension model of muscle deconditioning in rats.

METHODS

Sixty-two rats were studied with EIM during a two-week period of hind limb unloading followed by a two-week recovery period. Random subsets of animals were sacrificed at one-week time intervals to measure muscle fiber size.

RESULTS

Significant alterations were observed in nearly all impedance parameters. The 50 kHz phase and multi-frequency phase-slope, created by taking the slope of a line fitted to the impedance values between 100-500 kHz, appeared most sensitive to disuse atrophy, the latter decreasing by over 33.0±6.6% (p<0.001), a change similar to the maximum reduction in muscle fiber size. Impedance alterations, however, lagged changes in muscle fiber size.

CONCLUSIONS

EIM is sensitive to disuse change in the rat, albeit with a delay relative to alterations in muscle fiber size. Given the rapidity and simplicity of EIM measurements, the technique could prove useful in providing a non-invasive approach to measuring disuse change in animal models and human subjects.

Bilateral subcortical heterotopia with partial callosal agenesis in a mouse mutant

Cognition and behavior depend on the precise placement and interconnection of complex ensembles of neurons in cerebral cortex. Mutations that disrupt migration of immature neurons from the ventricular zone to the cortical plate have provided major insight into mechanisms of brain development and disease. We have discovered a new and highly penetrant spontaneous mutation that leads to large nodular bilateral subcortical heterotopias with partial callosal agenesis. The mutant phenotype was first detected in a colony of fully inbred BXD29 mice already known to harbor a mutation in Tlr4. Neurons confined to the heterotopias are mainly born in midgestation to late gestation and would normally have migrated into layers 2-4 of overlying neocortex. Callosal cross-sectional area and fiber number are reduced up to 50% compared with coisogenic wildtype BXD29 substrain controls. Mutants have a pronounced and highly selective defect in rapid auditory processing. The segregation pattern of the mutant phenotype is most consistent with a two-locus autosomal recessive model, and selective genotyping definitively rules out the Tlr4 mutation as a cause. The discovery of a novel mutation with strong pleiotropic anatomical and behavioral effects provides an important new resource for dissecting molecular mechanisms and functional consequences of errors of neuronal migration.

Persistent spatial working memory deficits in rats following in utero RNAi of Dyx1c1

Disruptions in the development of the neocortex are associated with cognitive deficits in humans and other mammals. Several genes contribute to neocortical development, and research into the behavioral phenotype associated with specific gene manipulations is advancing rapidly. Findings include evidence that variants in the human gene DYX1C1 may be associated with an increased risk of developmental dyslexia. Concurrent research has shown that the rat homolog for this gene modulates critical parameters of early cortical development, including neuronal migration. Moreover, recent studies have shown auditory processing and spatial learning deficits in rats following in utero transfection of an RNA interference (RNAi) vector of the rat homolog Dyx1c1 gene. The current study examined the effects of in utero RNAi of Dyx1c1 on working memory performance in Sprague-Dawley rats. This task was chosen based on the evidence of short-term memory deficits in dyslexic populations, as well as more recent evidence of an association between memory deficits and DYX1C1 anomalies in humans. Working memory performance was assessed using a novel match-to-place radial water maze task that allows the evaluation of memory for a single brief (∼4-10 seconds) swim to a new goal location each day. A 10-min retention interval was used, followed by a test trial. Histology revealed migrational abnormalities and laminar disruption in Dyx1c1 RNAi-treated rats. Dyx1c1 RNAi-treated rats exhibited a subtle, but significant and persistent impairment in working memory as compared to Shams. These results provide further support for the role of Dyx1c1 in neuronal migration and working memory.

Genetic modulation of striatal volume by loci on Chrs 6 and 17 in BXD recombinant inbred mice

Natural variation in the absolute and relative size of different parts of the human brain is substantial, with a range that often exceeds a factor of 2. Much of this variation is generated by the cumulative effects of sets of unknown gene variants that modulate the proliferation, growth and death of neurons and glial cells. Discovering and testing the functions of these genes should contribute significantly to our understanding of differences in brain development, behavior and disease susceptibility. We have exploited a large population of genetically well-characterized strains of mice (BXD recombinant inbred strains) to map gene variants that influence the volume of the dorsal striatum (caudate-putamen without nucleus accumbens). We used unbiased methods to estimate volumes bilaterally in a sex-balanced sample taken from the Mouse Brain Library (www.mbl.org). We generated a matched microarray data set to efficiently evaluate candidate genes (www.genenetwork.org). As in humans, volume of the striatum is highly heritable, with greater than twofold differences among strains. We mapped a locus that modulates striatal volume on chromosome (Chr) 6 at 88 +/- 5 Mb. We also uncovered an epistatic interaction between loci on Chr 6 and Chr 17 that modulates striatal volume. Using bioinformatic tools and the corresponding expression database, we have identified positional candidates in these quantitative trait locus intervals.

Air pollution induces enhanced mitochondrial oxidative stress in cystic fibrosis airway epithelium

We studied the effects of airborne particulate matters (PM) on cystic fibrosis (CF) epithelium. We noted that PM enhanced human CF bronchial epithelial apoptosis, activated caspase-9 and PARP-1; and reduced mitochondrial membrane potential. Mitochondrial inhibitors (4,4-diisothiocyanatostilbene-2,2'disulfonic acid, rotenone and thenoyltrifluoroacetone) blocked PM-induced generation of reactive oxygen species and apoptosis. PM upregulated pro-apoptotic Bad, Bax, p53 and p21; and enhanced mitochondrial localization of Bax. The anti-apoptotic Bcl-2, Bcl-xl, Mcl-1 and Xiap remained unchanged; however, overexpression of Bcl-xl blocked PM-induced apoptosis. Accordingly, we provide the evidence that PM enhances oxidative stress and mitochondrial signaling mediated apoptosis via the modulation of Bcl family proteins in CF.

Postnatal analysis of the effect of embryonic knockdown and overexpression of candidate dyslexia susceptibility gene homolog Dcdc2 in the rat

Embryonic knockdown of candidate dyslexia susceptibility gene (CDSG) homologs in cerebral cortical progenitor cells in the rat results in acute disturbances of neocortical migration. In the current report we investigated the effects of embryonic knockdown and overexpression of the homolog of DCDC2, one of the CDSGs, on the postnatal organization of the cerebral cortex. Using a within-litter design, we transfected cells in rat embryo neocortical ventricular zone around embryonic day (E) 15 with either 1) small hairpin RNA (shRNA) vectors targeting Dcdc2, 2) a DCDC2 overexpression construct, 3) Dcdc2 shRNA along with DCDC2 overexpression construct, 4) an overexpression construct composed of the C terminal domain of DCDC2, or 5) an overexpression construct composed of the DCX terminal domain of DCDC2. RNAi of Dcdc2 resulted in pockets of heterotopic neurons in the periventricular region. Approximately 25% of the transfected brains had hippocampal pyramidal cell migration anomalies. Dcdc2 shRNA-transfected neurons migrated in a bimodal pattern, with approximately 7% of the neurons migrating a short distance from the ventricular zone, and another 30% migrating past their expected lamina. Rats transfected with Dcdc2 shRNA along with the DCDC2 overexpression construct rescued the periventricular heterotopia phenotype, but did not affect the percentage of transfected neurons that migrate past their expected laminar location. There were no malformations associated with any of the overexpression constructs, nor was there a significant laminar disruption of migration. These results support the claim that knockdown of Dcdc2 expression results in neuronal migration disorders similar to those seen in the brains of dyslexics.

Early cortical damage in rat somatosensory cortex alters acoustic feature representation in primary auditory cortex

Early postnatal freeze-lesions to the cortical plate result in malformations resembling human microgyria. Microgyria in primary somatosensory cortex (S1) of rats are associated with a reduced behavioral detection of rapid auditory transitions and the loss of large cells in the thalamic nucleus projecting to primary auditory cortex (A1). Detection of slow transitions in sound is intact in animals with S1 microgyria, suggesting dissociation between responding to slow versus rapid transitions and a possible dissociation between levels of auditory processing affected. We hypothesized that neuronal responses in primary auditory cortex (A1) would be differentially reduced for rapid sound repetitions but not for slow sound sequences in animals with S1 microgyria. We assessed layer IV cortical responses in primary auditory cortex (A1) to single pure-tones and periodic noise bursts (PNB) in rats with and without S1 microgyria. We found that responses to both types of acoustic stimuli were reduced in magnitude in animals with microgyria. Furthermore, spectral resolution was degraded in animals with microgyria. The cortical selectivity and temporal precision were then measured with conventional methods for PNB and tone-stimuli, but no significant changes were observed between microgyric and control animals. Surprisingly, the observed spike rate reduction was similar for rapid and slow temporal modulations of PNB stimuli. These results suggest that acoustic processing in A1 is indeed altered with early perturbations of neighboring cortex. However, the type of deficit does not affect the temporal dynamics of the cortical output. Instead, acoustic processing is altered via a systematic reduction in the driven spike rate output and spectral integration resolution in A1. This study suggests a novel form of plasticity, whereas early postnatal lesions of one sensory cortex can have a functional impact on processing in neighboring sensory cortex.

Quantitative trait loci linked to thalamus and cortex gray matter volumes in BXD recombinant inbred mice

To investigate whether there are separate or shared genetic influences on the development of the thalamus and cerebral cortex, we identified quantitative trait loci (QTLs) for relevant structural volumes in BXD recombinant inbred (RI) strains of mice. In 34 BXD RI strains and two parental strains (C57BL/6J and DBA/2J), we measured the volumes of the entire thalamus and cortex gray matter using point counting and Cavalieri's rule. Heritability was calculated using analysis of variance (ANOVA), and QTL analysis was carried out using WebQTL (http://www.genenetwork.org). The heritability of thalamus volume was 36%, and three suggestive QTLs for thalamus volume were identified on chromosomes 10, 11 and 16. The heritability of cortical gray matter was 43%, and four suggestive QTLs for cortex gray matter volume were identified on chromosomes 2, 8, 16 and 19. The genetic correlation between thalamus and cortex gray matter volumes was 0.64. Also, a single QTL on chromosome 16 (D16Mit100) was identified for thalamus volume, cortex gray matter volume and Morris water maze search-time preference (r=0.71). These results suggest that there are separate and shared genetic influences on the development of the thalamus and cerebral cortex.

Holo-analysis of the efficacy of Bio-Mos® in pig nutrition

This exploratory holo-analysis of the efficacy of Bio-Mos®, (BM), an outer cell wall derivative of a strain of Saccharomyces cerevisiae, is part of an empirical modelling research programme comparing the efficacies of potential replacements for veterinary prescription-free pronutrient antibiotics in pig production. The data resource was mined from 128 saccharide publications of which 31/97 on BM (1997 to 2003) provided 69 negatively controlled start-to-finish tests from 10 countries (USA 71%) using 3778 pigs(30·5 per treatment). Respective food intake, live-weight gain and food conversion responses of 0·0075 kg/day (0·99%), 0·0145 kg/day (3·58%) and −0·0526 (3·07%) have coefficients of variation of 511, 163 and 229% and beneficial gain and conversion frequencies of 73 and 68%, 54% jointly. Holo-analytical multiple regression models of BM food intake, live-weight gain and food conversion effects using conventional and less stringent probabilities contain significant independent variables for negative control performances, dosage, discontinuous dosage, test duration, year of test, non-USA test, male, grower-finisher, slatted floor, processed food, antibacterial foods, animal protein food, main vegetable protein not soya bean, added oil/fat food and factorial data, which account for 11 to 68% of variations in response. The models quantify differences in research and praxis and indicate areas for future modelling research on BM dose-response relations, effects of ration ingredient and nutrient contents, other saccharide efficacy comparisons, including lactose, and BM comparisons and interactions with other proposed antibiotic replacements.

Holo-analysis of the efficacy of Bio-Mos® in broiler nutrition

1. This first holo-analysis of the efficacy in broiler nutrition of the saccharide product, Bio-Mos(R) (BM), is part of a comprehensive empirical modelling research programme quantifying and comparing the efficacies and future research needs of the diverse candidates offered as replacements for antibiotics. 2. The data used are from 32 publications with broiler performance data from a world-wide literature collection of 124 (1997-2003) on the use of BM as a broiler feed additive. It contains the results of 82 negatively controlled feeding tests from 21 countries using a total of 85 142 broilers, averaging 401 per treatment. 3. The 82 feed intake, liveweight gain, feed conversion ratio and 44 mortality responses to BM average -12.2 g, 27.6 g, -0.0391 and 0.0311%, respectively, with coefficients of variation of 828, 227, 192 and 8392%. Respective beneficial response frequencies for gain, conversion and mortality are 65, 70 (52% jointly) and 52%. 4. Holo-analytical multiple regression models were elaborated for the effects of BM on feed intake, liveweight gain, feed conversion ratio and mortality, using conventional P<or=0.05 in/P>or=0.10 out and less stringent P<or=0.25 in/P>or=0.34 out partial regression coefficient standards, with and without>or=3xroot mean square error outliers, in order to quantify the influences of negative control performance, test duration, BM dosage, cage housing, processed feed, antibiotic feed, year of test and USA test. To date they account for only 5-36% of response variations, due primarily to 52 of the 82 tests having no reported feed formulations. 5. These exploratory models confirm beneficial responses to BM for current broiler performance levels. They also indicate a need to clarify BM dose-response relationships in order to maximise efficient use in praxis and to facilitate cogent comparisons with other pronutrients, including other saccharide products.

Holo-analysis of the efficacy of Bio-Mos® in turkey nutrition

1. This holo-analysis of the effects in turkey nutrition of Bio-Mos(R) (BM) (Alltech Inc., Nicholasville, KY) aims to elaborate comprehensive empirical models for the assessment of responses under practical conditions and for its comparison with other potential pronutrient antibiotic replacements. 2. The data bank utilised was obtained from 54 publications on BM in turkeys from a total collection of 57 papers (1995-2003) on the use of saccharide products as turkey feed additives. These yielded 33 start-to-finish negatively-controlled feed intake, liveweight gain and feed conversion and 24 mortality effects in the USA, France and Poland, using 12,723 birds with a mean of 212 birds per treatment. 3. The feed, gain, conversion and mortality responses to BM compared with the relevant negative controls average -243 g, 57.0 g, -0.0156 and 1.29% with coefficients of variation of 451, 451, 705 and 426%, respectively. Beneficial gain, conversion and mortality effects were found in 52, 52 (33% jointly) and 52% of the tests, respectively. 4. Holo-analytical multiple regression models comparing conventional P<or=0.05 in/P>or=0.10 out and less stringent P<or=0.25 in/P>or=0.34 out partial regression coefficient standards, with and without>or=1.5xroot mean square error outliers, contain significant independent variables for negative control performance, duration, year of test, not-USA test, discontinuous dosage, cage housing, mash feed, feed antibiotic, feed anticoccidial, disease condition and high control (>10%) mortality. 5. These developmental models indicate fruitful pathways for future developments with an accent on the definition of specific dose-response relationships, whilst also confirming the value and future potential for BM in turkey production in praxis.

Fibroblast growth factor-10 prevents H2O2-induced cell cycle arrest by regulation of G1 cyclins and cyclin dependent kinases

We studied the effects of fibroblast growth factor (FGF-10) on H2O2-induced alveolar epithelial cell (AEC) G1 arrest and the role of G1 cyclins. FGF-10 prevented H2O2-induced AEC G1 arrest. FGF-10 induced 2-4-fold increase in cyclin E, cyclin A and CDKs (2,4) alone and in AEC treated with H2O2. H2O2 downregulated cyclin D1; FGF-10 blocked these effects. FGF-10 prevented H2O2-induced upregulation of CDK inhibitor, p21. SiRNAp21 blocked H2O2-induced downregulation of cyclins, CDKs and AEC G1 arrest. Accordingly, we provide first evidence that FGF-10 regulates G1 cyclins and CDKs, and prevents H2O2-induced AEC G1 arrest.

DYX1C1 functions in neuronal migration in developing neocortex

Rodent homologues of two candidate dyslexia susceptibility genes, Kiaa0319 and Dcdc2, have been shown to play roles in neuronal migration in developing cerebral neocortex. This functional role is consistent with the hypothesis that dyslexia susceptibility is increased by interference with normal neural development. In this study we report that in utero RNA interference against the rat homolog of another candidate dyslexia susceptibility gene, DYX1C1, disrupts neuronal migration in developing neocortex. The disruption of migration can be rescued by concurrent overexpression of DYX1C1, indicating that the impairment is not due to off-target effects. Transfection of C- and N-terminal truncations of DYX1C1 shows that the C-terminal TPR domains determine DYX1C1 intracellular localization to cytoplasm and nucleus. RNAi rescue experiments using truncated versions of DYX1C1 further indicate that the C-terminus of DYX1C1 is necessary and sufficient to DYX1C1's function in migration. In conclusion, DYX1C1, similar to two other candidate dyslexia susceptibility genes, functions in neuronal migration in rat neocortex.

Histometric changes and cell death in the thalamus after neonatal neocortical injury in the rat

Freezing injury to the developing cortical plate results in a neocortical malformation resembling four-layered microgyria. Previous work has demonstrated that following freezing injury to the somatosensory cortex, males (but not females) have more small and fewer large cells in the medial geniculate nucleus. In the first experiment, we examined the effects of induced microgyria to the somatosensory cortex on neuronal numbers, neuronal size, and nuclear volume of three sensory nuclei: ventrobasal complex, dorsal lateral geniculate nucleus, and medial geniculate nucleus. We found that there was a decrease in neuronal number and nuclear volume in ventrobasal complex of microgyric rats when compared with shams, whereas there were no differences in these variables in the dorsal lateral geniculate nucleus or medial geniculate nucleus. We also found that there were more small and fewer large neurons in both ventrobasal complex and medial geniculate nucleus. In experiment 2, we attempted to determine the role of cell death in the thalamus on these histometric measures. We found that cell death peaked within 24 h of the freezing injury and was concentrated mostly in ventrobasal complex. In addition, there was evidence of greater cell death in males at this age. Taken together, these results support the notion that males are more severely affected by early injury to the cerebral cortex than females.

Holo-Analysis

Meta-analysis is a vague descriptor used to encompass very diverse methods of data collection analysis, ranging from simple averages to more complex statistical methods. Holo-analysis is a fully comprehensive statistical analysis of all available data and all available variables in a specified topic, with results expressed in a holistic factual empirical model. The objectives and applications of holo-analysis include software production for prediction of responses with confidence limits, translation of research conditions to praxis (field) circumstances, exposure of key missing variables, discovery of theoretically unpredictable variables and interactions, and planning future research. Holo-analyses are cited as examples of the effects on broiler feed intake and live weight gain of exogenous phytases, which account for 70% of variation in responses in terms of 20 highly significant chronological, dietary, environmental, genetic, managemental, and nutrient variables. Even better future accountancy of variation will be facilitated if and when authors of papers routinely provide key data for currently neglected variables, such as temperatures, complete feed formulations, and mortalities.

Diversity of gene expression in adenocarcinoma of the lung

The global gene expression profiles for 67 human lung tumors representing 56 patients were examined by using 24,000-element cDNA microarrays. Subdivision of the tumors based on gene expression patterns faithfully recapitulated morphological classification of the tumors into squamous, large cell, small cell, and adenocarcinoma. The gene expression patterns made possible the subclassification of adenocarcinoma into subgroups that correlated with the degree of tumor differentiation as well as patient survival. Gene expression analysis thus promises to extend and refine standard pathologic analysis.

Impaired detection of variable duration embedded tones in ectopic NZB/BINJ mice

Utilizing rodent models, prior research has demonstrated a significant association between focal neocortical malformations (i.e. induced microgyria, molecular layer ectopias), which are histologically similar to those observed in human dyslexic brains, and rate-specific auditory processing deficits as seen in language impaired populations. In the current study, we found that ectopic NZB/BINJ mice exhibit significant impairments in detecting a variable duration 5.6 kHz tone embedded in a 10.5 kHz continuous background, using both acoustic reflex modification and auditory event-related potentials (AERP). The current results add further support to the association between focal cortical malformations and impaired auditory processing, and the notion that these auditory effects may occur regardless of the cortical location of the anomaly.

Tumor necrosis factor-related apoptosis-inducing ligand and chemotherapy cooperate to induce apoptosis in mesothelioma cell lines

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in certain tumor cells. In addition, TRAIL and chemotherapy can act cooperatively, possibly as a result of chemotherapy-induced increases in expression of a TRAIL receptor, DR5. We used cell lines derived from a highly chemoresistant tumor, malignant mesothelioma, to learn whether TRAIL was effective alone or together with chemotherapy and whether cooperativity depended on increases in DR5 expression. TRAIL (codons 95-285) was expressed in a bacterial expression vector and purified by nickel affinity chromatography. TRAIL alone (25 to 500 ng/ml) had little effect on mesothelioma cells. TRAIL plus chemotherapy (doxorubicin, cis-platinum, etoposide, or gemcitabine) acted cooperatively to induce apoptosis in mesothelioma cells (M28, REN, VAMT, and MS-1). For example, in M28 cells treated for 18 h, apoptosis from TRAIL (100 ng/ml) plus doxorubicin (0.6 microg/ml; 71 +/- 11%) greatly exceeded that from TRAIL alone (21 +/- 8%) or from doxorubicin alone (6 +/- 2%) (means +/- standard deviation; P < 0.03). Mesothelioma cells treated with chemotherapy showed no change in DR5 protein by Western analysis or by immunocytochemistry. TRAIL plus chemotherapy was associated with an increase in mitochondrial cytochrome c release and mitochondrial depolarization. We conclude that TRAIL and chemotherapy act cooperatively to kill mesothelioma cell lines, not by increases in DR5 receptor but in association with mitochondrial amplification of apoptotic signals.

Unilateral induced neocortical malformation and the formation of ipsilateral and contralateral barrel fields

Freezing lesions to the developing cortical plate of rodents results in a focal malformation resembling human 4-layered microgyria, and this malformation has been shown to result in local and widespread disruptions of neuronal architecture, connectivity, and physiology. Because we had previously demonstrated that microgyria caused disruptions in callosal connections, we hypothesized that freeze lesions to the postero-medial barrel sub-field (PMBSF) in one hemisphere would affect the organization of this barrel field contralaterally. We placed freeze lesions in the presumptive PMBSF of neonatal rats and, in adulthood, assessed the architecture of the ipsilateral and contralateral barrel fields. Malformations in the PMBSF resulted in a substantial decrease in the number of barrels as identified by cytochrome oxidase activity. More importantly, we found an increase in the total area of the contralateral PMBSF, although there was no difference in individual barrel cross-sectional areas, indicating an increase in the area of inter-barrel septae. This increase in the septal area of the contralateral PMBSF is consistent with changes in callosal and/or thalamic connectivity in the contralateral hemisphere. These results are another example of both local and widespread disruption of connectional architecture following induction of focal microgyria.

PG490-88, a derivative of triptolide, blocks bleomycin-induced lung fibrosis

In this study we evaluate the antifibrotic properties of PG-490-88, a water-soluble derivative of triptolide. Triptolide is an oxygenated diterpene that is derived from a traditional Chinese herb that has potent immunosuppressive and antitumor activity. We used the intratracheal bleomycin mouse model and found that PG490-88 inhibits fibrosis in the bleomycin group when given the same day or 5 days after bleomycin. PG490-88 also markedly reduced the number of myofibroblasts in the bleomycin treatment group. An enzyme-linked immunosorbent assay of transforming growth factor (TGF)-beta in the bronchoalveolar lavage fluid showed a significant decrease in TGF-beta in the PG490-88-treated groups compared to the bleomycin-treated group. Additionally, triptolide blocked bleomycin-induced increase in TGF-beta mRNA in cultured normal human lung fibroblasts. The efficacy of PG490-88 when administered late after bleomycin installation suggests a potential role in the treatment of idiopathic pulmonary fibrosis.

Triptolide and chemotherapy cooperate in tumor cell apoptosis. A role for the p53 pathway

Triptolide (PG490), a diterpene triepoxide, is a potent immunosuppressive agent extracted from the Chinese herb Tripterygium wilfordii. We have previously shown that triptolide blocks NF-kappaB activation and sensitizes tumor necrosis factor (TNF-alpha)-resistant tumor cell lines to TNF-alpha-induced apoptosis. We show here that triptolide enhances chemotherapy-induced apoptosis. In triptolide-treated cells, the expression of p53 increased but the transcriptional function of p53 was inhibited, and we observed a down-regulation of p21(waf1/cip1), a p53-responsive gene. The increase in levels of the p53 protein was mediated by enhanced translation of the p53 protein. Additionally, triptolide induced accumulation of cells in S phase and blocked doxorubicin-mediated accumulation of cells in G(2)/M and doxorubicin-mediated induction of p21. Our data suggest that triptolide, by blocking p21-mediated growth arrest, enhances apoptosis in tumor cells.

Single cause, polymorphic neuronal migration disorders: an animal model

Injury to the developing cortical plate can result in a variety of neuronal migration disorders. The results are reported of experimental research aimed at determining whether these different types of neocortical malformations are the consequence of comparable injury of varying intensity. Freezing probes were placed on the skulls of 44 newborn rats (age equivalent to 4 to 5 months of gestation in humans) and induced either one or two freezing injuries of durations ranging from 2 to 20 seconds. A variety of cortical malformations including minor laminar dysplasias, molecular layer ectopias, microgyria, and porencephalic cysts were seen in the brains of these animals when they were examined on postnatal day (P)2, P21, and P60. The severity of the malformation was directly related to the strength (number of hits and duration) of the freezing injury. These results suggest that a single etiologic event of varying severity during neuronal migration to the neocortex can induce widely disparate malformations of the cortex.

Impaired processing of complex auditory stimuli in rats with induced cerebrocortical microgyria: An animal model of developmental language disabilities

Individuals with developmental language disabilities, including developmental dyslexia and specific language impairment (SLI), exhibit impairments in processing rapidly presented auditory stimuli. It has been hypothesized that these deficits are associated with concurrent deficits in speech perception and, in turn, impaired language development. Additionally, postmortem analyses of human dyslexic brains have revealed the presence of focal neocortical malformations such as cerebrocortical microgyria. In an initial study bridging these research domains, we found that male rats with induced microgyria were impaired in discriminating rapidly presented auditory stimuli. In order to further assess this anatomical- behavioral association, we designed two experiments using auditory-reflex modification. These studies were intended to assess whether auditory processing deficits in microgyric male rats would be seen in threshold detection of a silent gap in white noise, and in oddball detection of a two-tone stimulus of variable duration. Results showed no differences between sham and microgyric subjects on gap detection, but did show that microgyric subjects were impaired in the discrimination of two-tone stimuli presented in an oddball paradigm. This impairment was evident for stimuli with total duration of 64 msec or less, while both groups were able to discriminate stimuli with duration of 89 msec or greater. The current results further support the relationship between malformations of the cerebral cortex and deficits in rapid auditory processing. They also suggest that the parameters characterizing rapid auditory processing deficits for a specific task may be influenced by stimulus features and/or cognitive demand of that particular task.

Induced minor malformations in the neocortex of normal mice do not alter immunological functions

The interactive relationship between the CNS and the immune system is well established. Major lesions in the brain have been shown to affect immune response. However, whether minor, focal lesions (ectopias), as seen in autoimmune mice, may induce alterations in the immune system is unknown. To address this point, ectopic lesions in the neocortex were induced in neonatal DBA/2 mice (Induced minor malformations; IMM) and their immune capabilities were assessed at adulthood. Serum was collected from each animal and analyzed for the presence of autoantibodies. In addition, splenic lymphocytes and thymocytes were collected to ascertain proliferative capabilities and to assess for possible phenotypic changes in lymphocyte subsets. Mice with IMM did not manifest IgG autoantibodies against cardiolipin, dsDNA or brain membrane antigens. Total lymphocyte cellularity was not affected. The induction of cerebrocortical ectopias did not impair the ability of splenic and thymic lymphocytes to proliferate in response to anti-CD3 antibodies or Concanavalin-A (Con-A) as determined by non-radioactive (Alamar Blue) and radioactive (3H-thymidine) assays. Moreover, no difference in proliferation of unstimulated and anti-CD3-stimulated splenic lymphocytes exposed to rIL-2 or rIL-7 was observed. Flow cytomeric analysis of a variety of cell surface antigens, indicated that there was no difference in lymphocyte subsets between control and IMM groups. Therefore, we conclude that induced IMM lesions in the CNS of normal DBA/2 mice do not alter immune functions.

Impaired two-tone processing at rapid rates in male rats with induced microgyria

We previously reported that adult male rats with bilateral induced microgyria exhibit deficits in rapid auditory processing, which appear similar to auditory processing deficits seen in individuals with developmental language disabilities. The current study was designed to further elaborate that finding using an improved paradigm in which stimulus duration was uncoupled from testing experience and learning effects. Specifically, two-tone stimuli with durations of 540, 390, 332 and 249 ms were all presented within a single test session in a modified operant conditioning paradigm. Subjects were tested over a period of 12 days using this variable-stimulus format. Results confirmed microgyric male rats were impaired only in processing two-tone stimuli presented at rapid rates (i.e., 249 ms duration). Thus the current results support the previously observed link between focal malformations and deficits in rapid auditory processing.

Dendritic cells and macrophages in lung allografts: A role in chronic rejection?

Antigen presentation by lung macrophages/dendritic cells (DC) is thought to be important in obliterative bronchiolitis/bronchiolitis obliterans syndrome (OB/BOS), which severely limits survival post-lung transplantation. However, a recent study found minimal numbers of DC in lung allografts. We looked at numbers and phenotype of macrophages/DC in lung allografts using endobronchial biopsy (EBB) and transbronchial biopsy (TBB) from 22 lung transplant patients. Biopsies were stained with monoclonal markers of DC (CD1a, RFD1, and major histocompatibility complex [MHC] Class II), and "suppressor macrophages" (RFD1 and RFD7). Dendritic cells were also stained for the costimulatory molecules CD80 and CD86. Significantly greater numbers of DC/high-power field (HPF) were seen in biopsies when we defined DC using dendritic morphology and Class II MHC expression instead of CD1a expression. Dendritic cell numbers were significantly higher in eight patients with OB/BOS compared with 14 stable patients. Fifty percent of DC expressed CD86 and 20% expressed CD80. There was no difference in CD80 or CD86 expression between OB/BOS patients and stable patients. There was no correlation between DC numbers and presence or absence of acute rejection (AR), and/or cytomegalovirus (CMV) pneumonitis on current or prior biopsies. There were significantly more MHC Class II DC in EBB compared with TBB. We found minimal staining for lung macrophages capable of suppressing T-cell inflammation. We conclude that studies of lung allografts may underestimate DC numbers if relying on CD1a as the sole marker of DC. DC are increased in patients with OB/BOS compared with stable patients. EBB may be more important than TBB in looking for inflammatory changes of OB. DC expressing costimulatory molecules are present in lung allografts, and costimulatory pathway blockade may be useful in human lung allografts. Also, the absence of "suppressor" macrophages may increase susceptibility of human lung allografts to the rejection process.

Changes in efferent and afferent connectivity in rats with induced cerebrocortical microgyria

Freezing injury to the cortical plate at postnatal day (P) 1 initiates a cascade of events that ultimately result in a focal neocortical malformation resembling human 4-layered microgyria. This malformation has been associated with widespread changes in neocortical and thalamic architecture and physiology. It was hypothesized that at least some of these alterations could result from connectional reorganization following early injury. The current experiment was designed to delineate the efferent and afferent connections between the cerebral hemispheres and between the cortex and thalamus of rats with induced cerebrocortical microgyria. Microgyria were induced in the parietal cortex of rats by freezing injury on postnatal day 1. In adulthood, injections of biotinylated dextran amine were made either in the microgyric cortex, in homologous regions of the opposite hemisphere, or in ipsilateral ventrobasal complex of the thalamus. Appropriately directed connections to homotopic areas were seen in some but not all microgyric rats. In addition, heterotopic projections to frontal and secondary sensorimotor cortices were noted. Projections from homotopic regions in the hemisphere opposite to the malformation terminated most often in the medial portions of the microgyrus or avoided it entirely. There were almost no thalamocortical or corticothalamic projections between the ventrobasal complex and the microgyrus itself, although a dense plexus of thalamocortical fibers was often noted at the border between the malformed and normal cortex. These connectional changes may help explain disturbances in architecture, physiology, and behavior associated with these focal malformations.

Loss of STAT1 expression confers resistance to IFN-gamma-induced apoptosis in ME180 cells

Interferon gamma (IFN-gamma) induces apoptosis in many tumor cell lines and sensitizes tumor cells to apoptosis by tumor necrosis factor family members. IFN-gamma induces the expression of many early response genes such as interferon regulatory factor-1 (IRF-1) by activation of signal transducer and activator of transcription (STAT) factor proteins. We found that ME180 cells became resistant to IFN-gamma-induced cell death after 4-5 passages in culture. These resistant cells were characterized by a loss of STAT1 expression and a loss of inducible IRF-1 expression. We describe for the first time the emergence of a STAT1-deficient ME180 cell line.

Neuronal asymmetries in primary visual cortex of dyslexic and nondyslexic brains

Dyslexic brains exhibit histologic changes in the magnocellular (magno) cells of the lateral geniculate nucleus, and consistent with these changes, dyslexics demonstrate abnormal visually evoked potentials and brain activation to magno-specific stimuli. The current study was aimed at determining whether these findings were associated with changes in the primary visual cortex with the prediction that magno components of this cortex would be affected. We measured cross-sectional neuronal areas in primary visual cortex (area 17) in dyslexic and nondyslexic autopsy specimens. There was a significant interaction between hemispheres and diagnostic category; ie, nondyslexic brains had larger neurons in the left hemisphere, whereas dyslexic brains had no asymmetry. On the other hand, cell layers associated with magno input from the lateral geniculate nucleus did not show consistent changes in dyslexic brains. Thus, there is a neuronal size asymmetry in favor of the left primary visual cortex in nondyslexics that is absent in dyslexic brains. This is yet another example of anomalous expression of cerebral asymmetry in dyslexia similar to that of the planum temporale, which in our view reflects abnormality in circuits involved in reading.

PG490 (triptolide) cooperates with tumor necrosis factor-alpha to induce apoptosis in tumor cells

Progress in the treatment of solid tumors has been slow and sporadic. The efficacy of conventional chemotherapy in solid tumors is limited because tumors frequently have mutations in the p53 gene. Also, chemotherapy only kills rapidly dividing cells. Members of the tumor necrosis factor (TNF) family, however, induce apoptosis regardless of the p53 phenotype. Unfortunately, the cytotoxicity of TNF-alpha is limited by its activation of NF-kappaB and activation of NF-kappaB is proinflammatory. We have identified a compound called PG490, that is composed of purified triptolide, which induces apoptosis in tumor cells and sensitizes tumor cells to TNF-alpha-induced apoptosis. PG490 potently inhibited TNF-alpha-induced activation of NF-kappaB. PG490 also blocked TNF-alpha-mediated induction of c-IAP2 (hiap-1) and c-IAP1 (hiap-2), members of the inhibitor of apoptosis (IAP) family. Interestingly, PG490 did not block DNA binding of NF-kappaB, but it blocked transactivation of NF-kappaB. Our identification of a compound that blocks TNF-alpha-induced activation of NF-kappaB may enhance the cytotoxicity of TNF-alpha on tumors in vivo and limit its proinflammatory effects.

Sex differences in the effects of early neocortical injury on neuronal size distribution of the medial geniculate nucleus in the rat are mediated by perinatal gonadal steroids

Freezing injury to the cortical plate of rats induces cerebrocortical microgyria and, in males but not females, a shift toward greater numbers of small neurons in the medial geniculate nucleus (MGN). The purpose of the current study was to examine a hormonal basis for this sex difference. Cross-sectional neuronal areas of the MGN were measured in male rats, untreated female rats and female rats treated perinatally with testosterone propionate, all of which had received either neonatal cortical freezing or sham injury. Both male and androgenized female rats with microgyria had significantly smaller MGN neurons when compared to their sham-operated counterparts, whereas untreated females with microgyria did not. These differences were also reflected in MGN neuronal size distribution: both male and androgenized female rats with microgyria had more small and fewer large neurons in their MGN in comparison to shams, while there was no difference in MGN neuronal size distribution between lesioned and sham females. These findings suggest that perinatal gonadal steroids mediate the sex difference in thalamic response to induction of microgyria in the rat cortex.

Effects of neonatal freeze lesions on expression of parvalbumin in rat neocortex

Neonatal freeze lesions to the cortical plate result in focal malformations of the cerebral cortex that resemble four-layered microgyria. These malformations have been associated with local and distant changes in neuronal architecture, and have been implicated in the neocortical epileptiform discharges that can spread up to 4 mm away from the malformation itself. In an effort to assess potential changes in the development of one population of inhibitory interneurons in this malformation, we measured the density of parvalbumin-immunoreactive (ParvIR) neurons in microgyric and control cerebral cortex on postnatal days 13, 15, 21 and 64. In comparison to controls, microgyric animals exhibited a transient decrease in the expression of parvalbumin immunoreactivity in supragranular neurons, both within the malformation itself and in normal six-layered cortex up to 2 mm adjacent to it. This difference disappeared by P21. In addition, there was a permanent diminution of the density of ParvIR neurons in infragranular layers both within and immediately adjacent to the microgyrus. These results indicate that early injury to the cortical plate gives rise to both focal and more widespread changes in cortical architecture.

Proteolytic cleavage of ras GTPase-activating protein during apoptosis

p120-ras GTPase-activating protein (rasGAP) associates with Ras and negatively regulates Ras signaling by stimulating the intrinsic rate of Ras GTPase activity. rasGAP also associates with other cellular signaling proteins which suggest that rasGAP may play a role in coordinating other signal transduction pathways. Disruption of rasGAP in vivo results in extensive apoptosis. Fas-mediated apoptosis results in the activation of caspases that cleave cellular substrates which are important for maintaining cytoplasmic and nuclear integrity. We show here that rasGAP is proteolytically cleaved by caspases early in Fas-induced apoptosis of Jurkat cells. rasGAP was also cleaved by DNA-damaging chemotherapeutic agents and TNF-related apoptosis inducing ligand (TRAIL), also known as Apo2L. Based on the size of the products generated by cleavage of deletion mutants of rasGAP we predict that cleavage of rasGAP occurs in the hydrophobic region and between the SH2(2) and ras-p21 interacting domain which would leave an intact ras-p21 interacting domain. Interestingly, cleavage of rasGAP in vitro enhanced rasGAP hydrolysis activity. Our results demonstrate that diverse apoptotic stimuli cause caspase-mediated cleavage of rasGAP early in apoptosis.

MRI visualization of focal induced neocortical malformations of the rat

In an attempt to determine whether small focal malformations of the neocortex can be visualized in vivo, focal microgyria were induced in the neocortex of otherwise normal rats by freezing injury to the developing cortical plate, and in adulthood the malformation was visualized using MRI. Induced microgyria of varying size were successfully visualized with MRI, and the location and extent of the malformation was confirmed on subsequent histology. This work has potential implications for the field of experimental neuropathology by enhancing the ability to study the behavioral and connectional consequences of these malformations in animals. In addition, this work points toward future research for the in vivo visualization of these small, focal malformations in humans.

Dexamethasone inhibits lung epithelial cell apoptosis induced by IFN-gamma and Fas

Lung epithelium plays a central role in modulation of the inflammatory response and in lung repair. Airway epithelial cells are targets in asthma, viral infection, acute lung injury, and fibrotic lung disease. Activated T lymphocytes release cytokines such as interferon-gamma (IFN-gamma) that can cooperate with apoptotic signaling pathways such as the Fas-APO-1 pathway to induce apoptosis of damaged epithelial cells. We report that IFN-gamma alone and in combination with activation of the Fas pathway induced apoptosis in A549 lung epithelial cells. Interestingly, the corticosteroid dexamethasone was the most potent inhibitor of IFN-gamma- and IFN-gamma plus anti-Fas-induced apoptosis. IFN-gamma induced expression of an effector of apoptosis, the cysteine protease interleukin-1 beta-converting enzyme, in A549 cells. Dexamethasone, in contrast, induced expression of an inhibitor of apoptosis, human inhibitor of apoptosis (hIAP-1), also known as cIAP2. We suggest that the inhibition of epithelial cell apoptosis by corticosteroids may be one mechanism by which they suppress the inflammatory response.

Cleavage of focal adhesion kinase by caspases during apoptosis

Apoptotic cells undergo characteristic morphological changes that include detachment of cell attachment from the substratum and loss of cell-cell interactions. Attachment of cells to the extracellular matrix and to other cells is mediated by integrins. The interactions of integrins with the extracellular matrix activates focal adhesion kinase (FAK) and suppresses apoptosis in diverse cell types. Members of the tumor necrosis family such as Fas and Apo-2L, also known as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), induce apoptosis in both suspension and adherent cells through the activation of caspases. These caspases, when activated, cleave substrates that are important for the maintenance of nuclear and membrane integrity. In this study, we show that FAK is sequentially cleaved into two different fragments early in Apo-2L-induced apoptosis. We also demonstrate that FAK cleavage is mediated by caspases and that FAK shows unique sensitivity to different caspases. Our results suggest that disruption of FAK may contribute to the morphological changes observed in apoptotic suspension and adherent cells.

Cerebral microgyria, thalamic cell size and auditory temporal processing in male and female rats

Induction of microgyria by freezing injury to the developing somatosensory cortex of neonatal rats causes a defect in fast auditory processing in males, but not in females. It was speculated that early damage to the cortex has sexually dimorphic cascading effects on other brain regions mediating auditory processing, which can lead to the observed behavioral deficits. In the current series of experiments, bilateral microgyri were induced by placement of a freezing probe on the skulls of newborn male and female rats, and these animals were tested in adulthood for auditory temporal processing. Control animals received sham surgery. The brains from these animals were embedded in celloidin, cut in the coronal plane and the following morphometric measures assessed: microgyric volume, medial geniculate nucleus (MGN) volume, cell number, and cell size, and, as a control, dorsal lateral geniculate nucleus (dLGN) volume, cell number and cell size. There were no sex differences in the cortical pathology of lesioned animals. However, microgyric males had more small and fewer large neurons in the MGN than their sham-operated counterparts, whereas there was no difference between lesioned and sham-operated females. There was no effect on dLGN cell size distribution in either sex. Microgyric males were significantly impaired in fast auditory temporal processing when compared to control males, whereas lesioned females exhibited no behavioral deficits. These results suggest that early injury to the cerebral cortex may have different effects on specific thalamic nuclei in males and females, with corresponding differences in behavioral effects.

Effects of sex and MK-801 on auditory-processing deficits associated with developmental microgyric lesions in rats

Neonatally induced microgyric lesions produce defects in rapid auditory processing in adult male rats. Given that females across species are less susceptible to the deleterious effects of neural injury and that treatment with neuroprotective agents at the time of injury can reduce neural damage, the authors tested the effects of sex and neuroprotectant exposure on the behavioral consequences of microgyric lesions in rats. Results showed that sham but not microgyric males were able to perform the task at the fastest rate of stimulus presentation. Microgyric females, in contrast, discriminated at all stimulus conditions and did not differ from female shams. Microgyric males treated with MK-801 had reduced cortical damage and performed the discrimination at the fastest condition. Results suggest that females are less susceptible to the behavioral effects of neocortical microgyria and that MK-801 may ameliorate the behavioral consequences of these lesions in male rats.

Effects of sex and MK-801 on auditory-processing deficits associated with developmental microgyric lesions in rats

Neonatally induced microgyric lesions produce defects in rapid auditory processing in adult male rats. Given that females across species are less susceptible to the deleterious effects of neural injury and that treatment with neuroprotective agents at the time of injury can reduce neural damage, the authors tested the effects of sex and neuroprotectant exposure on the behavioral consequences of microgyric lesions in rats. Results showed that sham but not microgyric males were able to perform the task at the fastest rate of stimulus presentation. Microgyric females, in contrast, discriminated at all stimulus conditions and did not differ from female shams. Microgyric males treated with MK-801 had reduced cortical damage and performed the discrimination at the fastest condition. Results suggest that females are less susceptible to the behavioral effects of neocortical microgyria and that MK-801 may ameliorate the behavioral consequences of these lesions in male rats.

Rapamycin inhibits development of obliterative airway disease in a murine heterotopic airway transplant model

Obliterative bronchiolitis is the major cause of long-term morbidity and mortality in heart-lung and lung transplant recipients. There is presently no completely effective therapy for the treatment of obliterative bronchiolitis. We have examined the effects of rapamycin (RPM) on the development of obliterative airway disease in murine recipients of heterotopically transplanted allograft tracheas. In this model, an untreated allograft develops almost complete occlusion of the airway lumen with fibroblastic tissue and collagen scar by day 28 after transplantation. RPM administered intraperitoneally at the time of transplantation or even as late as day 14 after transplantation markedly inhibited obliteration of the airway lumen by fibroblastic tissue. Also, RPM significantly inhibited infiltration of the graft by macrophages. In the RPM-treated animals, the airway was reconstituted with an attenuated squamous epithelium rather than a normal pseudostratified epithelium. No adverse side effects were observed with RPM doses up to 12 mg/kg/ day. These findings suggest a potential role for RPM, perhaps in combination with cyclosporine, in preventing and treating obliterative bronchiolitis in heart-lung and lung allograft recipients.

Airway epithelial cells produce stem cell factor

Airway epithelial cells modulate the inflammatory response in asthmatic, allergic and fibrotic lung diseases through the secretion of cytokines that regulate the movement and activation of inflammatory cells. Mast cells play an important role in the pathogenesis of these lung diseases. In this study we report that normal airway epithelial cells express stem cell factor which is a critical mediator of mast cell growth and differentiation and that transforming growth factor-beta inhibits secretion of stem cell factor by airway epithelial cells.

Neocortical ectopias in BXSB mice: effects upon reference and working memory systems

BXSB mice have an approximately 40-60% incidence of neocortical ectopias in layer I of the prefrontal/motor cortex. Prior studies have found major behavioral differences between those with ectopias and their non-ectopic littermates. Some of these findings indicate that the two groups differ with respect to spatial reference and working memory. The purpose of this study was to measure reference and working memory in the same animals to test the hypothesis that the ectopics would have better reference memory but less effective working memory. The Lashley III maze has cul-de-sacs which must be eliminated, and T-choices where the animal has to decide whether to go left or right. Ectopic and non-ectopic mice were equally able to learn the maze and did not differ on cul-entry or T-choice errors. Then the maze was inverted and the animals were retested. Turning the maze upside down did not change the relative status of the blind alleys. Therefore, the reference memory knowledge from the prior week's training could be used to avoid entering the culs. However, inverting the maze caused a left-right mirror image reversal of the T-choices. Therefore, prior reference memory information would interfere with learning the new path through the maze, whereas working memory would enable the mouse to eliminate T-choice errors. Ectopic mice made less cul-entry errors and more T-choice errors than their non-ectopic littermates, as predicted.

Birthdates of neurons in induced microgyria

Freezing injury to the cortical plate of the newborn rat results in the formation of a focal region of cerebrocortical microdysgenesis resembling, in many ways, human 4-layered microgyria. Previous research has shown that neurons born during embryonic day (E) 20 migrate through the initial damage and take their place in the cell-dense layer of the microgyric lesion. The current study was conducted to determine: (1) whether neurons generated earlier in development would be found in microgyric cortex; and (2) whether the freezing injury would stimulate production of neurons postnatally. Rat pups from mothers who were injected with S-phase markers on E15, E17, E19, and E21 were subjected to freezing injury of the cortex to induce microgyria on postnatal day (P) 1. Other pups received a freezing lesion and then pulse or cumulative injections of S-phase markers for the next 72 h. Neurons born on E17 and E19 were found scattered throughout the cell-dense layer of the microgyric cortex. Early (E15) generated neurons were nearly absent in the microgyric cortex, and there was no evidence of postnatal induction of cortical neurogenesis. These results are considered in light of recent work demonstrating postnatal neocortical neurogenesis in response to early neocortical injury.