Longitudinal analysis of cognitive performances and structural brain changes in late-life bipolar disorder.

OBJECTIVES: Cross-sectional studies in bipolar disorder (BD) suggested the presence of cognitive deficits and subtle magnetic resonance imaging (MRI) changes in limbic areas that may persist at euthymic stages. Whether or not cognitive and MRI changes represent stable attributes of BD or evolve with time is still matter of debate. To address this issue, we performed a 2-year longitudinal study including detailed neuropsychological and magnetic resonance imaging (MRI) analyses of 15 euthymic older BD patients and 15 controls. METHODS: Neuropsychological evaluation concerned working memory, episodic memory, processing speed, and executive functions. MRI analyses included voxel-based morphometry (VBM) analysis of gray matter including region of interest (ROI) analysis and tract-based spatial statistics (TBSS) analysis of white matter of diffusion tensor imaging derived fractional anisotropy (FA). RESULTS: BD patients displayed significantly lower performances in processing speed and episodic memory but not in working memory and executive functions compared to controls. However, BD patients did not differ from controls in the mean trajectory of cognitive changes during the 2 years follow-up. In the same line, longitudinal gray matter (VBM, ROI) and white matter (TBSS FA) changes did not differ between BD patients and controls. CONCLUSION: The lack of distinction between BD patients and controls in respect to the 2-year changes in cognition and MRI findings supports the notion that this disorder does not have a significant adverse impact on cognitive and brain aging. From this point of view, the present results convey a message of hope for patients suffering from BD.

Bcl-2: prolonging life in a transgenic mouse model of familial amyotrophic lateral sclerosis.

Mutations in the gene encoding copper/zinc superoxide dismutase enzyme produce an animal model of familial amyotrophic lateral sclerosis (FALS), a fatal disorder characterized by paralysis. Overexpression of the proto-oncogene bcl-2 delayed onset of motor neuron disease and prolonged survival in transgenic mice expressing the FALS-linked mutation in which glycine is substituted by alanine at position 93. It did not, however, alter the duration of the disease. Overexpression of bcl-2 also attenuated the magnitude of spinal cord motor neuron degeneration in the FALS-transgenic mice.

Cognitive impairment in late-onset depression. Limited to a decrement in information processing resources?

BACKGROUND: While cognitive dysfunction in late-onset depression (LOD) is common, the nature and determinants of this impairment are heterogeneous. It has been suggested that neuropsychological decrements in LOD patients might result from a deficit in processing resources. In order to address this issue, we analyzed processing resources in LOD to see if their decrease explains higher-level cognition (episodic memory and naming capacity) deficits. METHODS: Measures of processing speed, working memory, inhibition, episodic memory and naming capacity were administered to 14 LOD inpatients and 14 controls. RESULTS: The LOD patients performed significantly worse than the controls in all domains except for inhibition. Hierarchical regression analyses showed that naming capacity impairment was totally mediated by processing speed and working memory, whereas episodic memory dysfunction was only partially mediated by working memory. CONCLUSION: The reduction in certain processing resources (working memory, processing speed) in late-onset depressed patients appears to mediate impairments in episodic memory and naming capacity. However, episodic memory impairment cannot only be explained by processing resource decrement in LOD patients, suggesting that a primary episodic memory dysfunction is present in this condition.

Decreased infarct size after focal cerebral ischemia in mice chronically infected with Toxoplasma gondii.

To determine whether Toxoplasma gondii infection could modify biological phenomena associated with brain ischemia, we investigated the effect of permanent middle cerebral artery occlusion (MCAO) on neuronal survival, inflammation and redox state in chronically infected mice. Infected animals showed a 40% to 50% decrease of infarct size compared with non-infected littermates 1, 4 and 14 days after MCAO. The resistance of infected mice may be associated with increased basal levels of anti-inflammatory cytokines and/or a marked reduction of the MCAO-related brain induction of two pro-inflammatory cytokines, tumor necrosis factor-alpha and interferon-gamma (IFNgamma). In addition, potential anti-inflammatory/neuroprotective factors such as nerve growth factor, suppressor of cytokine signaling-3, superoxide dismutase activity, uncoupling protein-2 and glutathione (GSH) were upregulated in the brain of infected mice. Consistent with a role of GSH in central cytokine regulation, GSH depletion by diethyl maleate inhibited Toxoplasma gondii lesion resistance by increasing the proinflammatory cytokine IFNgamma brain levels. Overall, these findings indicate that chronic toxoplasmosis decisively influences both the inflammatory molecular events and outcome of cerebral ischemia.

Age-related changes in parvalbumin- and GABA-immunoreactive cells in the rat septum.

The calcium binding protein parvalbumin is present in GABAergic neurons of the medial septum-diagonal band of Broca (MS-DBB) region that project to the hippocampal formation. We examined the distribution pattern, the number, and the morphological features of the parvalbumin-containing cells (parv+) in the MS-DBB region of 2- to 3-, 8- to 9-, 15- to 16-, and 26- to 27-month-old Sprague-Dawley rats. A significant reduction in the number of parv+ cells was observed as a function of age. The mean somal area of the parv+ cells was significantly reduced in the 26- to 27-month-old rats. A significant reduction in the number of parv+ cells was also observed in the 26- to 27-month-old rats in the cingulate cortex, but not in the striatum or the hippocampal formation. No significant age-related changes were observed in the number of the GABA-immunoreactive cells in the MS-DBB region nor in the cingulate cortex. In conclusion, there is an age-related decrease in the number of parv+ cells, with no change in the number of GABA-immunoreactive cells in the MS-DBB region of the rat. Because GABA and parvalbumin are colocalized in the MS-DBB neurons, the results suggest that the level of parvalbumin is decreased, but that the cells are not lost.

Age-related changes in galanin-immunoreactive cells of the rat medial septal area.

Age-related changes in the cholinergic cells have been reported in the rat medial septal area. The neuropeptide galanin is colocalized with acetylcholine in the majority of the medial septal neurons. To assess possible age-related changes in the galanin-containing septal cells, we have examined, with immunohistochemical methods, the distribution pattern, density, and morphological features of galanin-containing cells in the rat medial septal nucleus (MS) and the nucleus of the diagonal band of Broca (DBB) in 1, 3-6, 9-12, 16-18, 24-27, and 28-30 month-old rats. A morphometric computerized analysis was also performed. In addition, the intensity of the immunolabelling was measured by densitometry. Galanin-like immunoreactivity (galanin-LI) was present in both the MS and the DBB. Our results clearly indicate a progressive age-related decrease in the number of galanin-positive cells throughout the MS-DBB complex. Our quantitative study revealed a significant loss of galanin-positive cells in the MS-DBB complex of 16-18 (50.4%), 24-27 (52.3%), and 28-30 (52.4%) month-old rats compared to 3-6 month-old animals. A non-significant reduction (28.6%) in galanin-LI cell number was observed in 3-6 month-old rats compared to 1 month-old animals. The morphometric analysis demonstrated a significant reduction (18%) in the surface of galanin-positive cells remaining in the 28-30 month-old group. Furthermore, a significant decrease in the immunolabelling intensity was consistently observed in animals of 16 month-old and older. To determine whether changes in galanin-positive cells were associated with cholinergic changes, the number of cells stained for acetylcholinesterase (AChE) was estimated in 3-6, 9-12, 16-18, and 24-27 month-old rats. There was a 43% decrease in the number of AChE-positive cells and a 71% loss of galanin-positive cells in 24-27 month-old rats compared to 3-6 month-old. The galanin-cell loss in the medial septal area was therefore associated with a parallel, although smaller, cholinergic septal cell loss.

Postnatal distribution of cpp32/caspase 3 mRNA in the mouse central nervous system: an in situ hybridization study.

Apoptotic cell death is a major feature of the developing nervous system and of certain neurodegenerative diseases. Various gene effectors and repressors of this type of cell death have been identified. Among them, bcl-xl and bax, which encode for antiapoptotic and proapoptotic proteins, respectively, play major roles during development. The gene cpp32 encodes for the caspase 3 cysteine protease and is a critical mediator of cell death during embryonic development in the mammalian brain. To gain insight into the possible implications of these cell death genes during the postnatal development, we investigated the expression of bax, bcl-xl, and cpp32 mRNAs by in situ hybridization in the mouse brain from birth to adulthood. Whereas bax and bcl-xl mRNAs were expressed widely in neonates and adult mice, our results showed that cpp32 mRNA levels were decreased strongly from 12 postnatal days. From 1 postnatal day to 12 postnatal days, cpp32 mRNA was expressed ubiquitously in all brain nuclei, including areas where neurogenesis occurred. A positive correlation between areas displaying high levels of mRNA and apoptotic nuclei also was shown. In the adult, cpp32 mRNA was restricted to the piriform and entorhinal cortices, the neocortex, and to areas where neurogenesis is observed (e.g., olfactory bulb and dentate gyrus). The same pattern of expression was observed in adult mice over-expressing the antiapoptotic protein Bcl-2. These results demonstrate that the expression of cpp32 mRNA is highly regulated during the mouse postnatal period, leading to a specific distribution in the adult central nervous system. Moreover, the prevention of cell death by Bcl-2 likely is not linked to the regulation of caspase mRNA levels.

Time course of axotomy-induced apoptotic cell death in facial motoneurons of neonatal wild type and bcl-2 transgenic mice.

In neonatal animals, axotomy of facial motoneurons induces cell death. Using the TUNEL technique, which labelled apoptotic DNA breaks in situ, the kinetics of motoneuron death were studied. Lesion of the right facial nerve were performed on two-day-old mice. Then, animals were perfused 8, 12, 16, 20, 24, 28, 32, 48, 72 and 120 h after the lesion. Our results provide direct evidence that, following an axotomy, facial motoneurons die through an apoptotic process. We showed that apoptotic neurons can be detected as early as 16 h after the lesion. Facial motoneurons die within 120 h, with a peak observed 28 h after the lesion. The kinetics of appearance of apoptotic cells were correlated with the loss of Cresyl Violet-stained motoneurons. Furthermore, labelled cells were observed in the contralateral side of the lesion, suggesting that spontaneous apoptotic cell death occurs during the postnatal period. The same study was performed on transgenic mice overexpressing the proto-oncogene bcl-2, a gene repressor of cell death. In these mice, no TUNEL-labelled cells were detected on the lesioned and unlesioned sides. In vivo, Bcl-2 may protect motoneurons from apoptotic death following axotomy and during naturally occurring cell death. These results suggest that these two types of cell death may occur via the same mechanism.

In vivo study of motoneuron death induced by nerve injury in mice deficient in the caspase 1/ interleukin-1 beta-converting enzyme.

The apoptotic cell death program is orchestrated by members of the caspase family. Among these caspases, several in vitro and in vivo reports indicate that the interleukin-1 beta-converting enzyme (or caspase 1) may be involved in neurodegenerative processes. In view of these findings, and in order to characterize the role of the interleukin-1beta-converting enzyme in mediating or modulating cell death processes in vivo, we have investigated the effects of its deletion on motoneuron survival after a facial nerve transection in newborn and adult interleukin-1 beta-converting enzyme knock-out mice. During the postnatal period of development, when facial motoneurons are highly vulnerable to axotomy, we did not observe any significant effect of the interleukin-1 beta-converting enzyme-deletion on the percentage of cell death in the lesioned nuclei. In addition, the spontaneous cell death characteristic of the postnatal period was not altered in knock-out mice. In contrast, in adult knock-out mice, a significant reduction (16%) in the number of surviving facial motoneurons was observed six weeks after axotomy. We therefore conclude that the interleukin-1 beta-converting enzyme does not appear to be critical for cell death during the postnatal period but may favor motoneuron survival during adulthood. Given the key role of caspase 3 in neuronal apoptosis during embryonic development of the central nervous system, we also investigated the role of this caspase in cell death following axotomy. Combined immunofluorescence revealed that, at least during the postnatal period, axotomized motoneurons that have apoptotic nuclear morphologies were immunopositive for the active form of caspase 3. Double-stained cells could be also observed on the unlesioned side. These results strongly suggest that caspase 3 may be involved in both the postnatal spontaneous- and axotomy-induced facial motoneuron death processes. Similar results were obtained in interleukin-1 beta-converting enzyme-deficient and wild-type mice, indicating that the interleukin-1 beta-converting enzyme may not be required for caspase 3 activation.

Early postnatal Müller cell death leads to retinal but not optic nerve degeneration in NSE-Hu-Bcl-2 transgenic mice.

Topographically localized over-expression of the human Bcl-2 protein in retinal glial Müller cells of a transgenic mice (line 71) leads to early postnatal apoptotic Müller cell death and retinal degeneration. Morphological, immunohistological and confocal laser microscopic examination of transgenic and wild-type retinas were achieved on paraffin retinal sections, postnatally. Apoptosis occurs two to three days earlier in the internal nuclear layer of transgenic retinae, than in wild-type littermates. In parallel there was a progressive disappearance of transgenic Hu-Bcl-2 over-expression, as well as of the Müller cell markers, cellular retinaldehyde-binding protein and glutamine synthetase. This phenomenon led to retinal dysplasia, photoreceptor apoptosis and then retinal degeneration and proliferation of the retinal pigment epithelium. The optic nerve, however, remains intact. Two complementary observations confirm the pro-apoptotic action of Bcl-2 over-expression in Müller cells: (i) in the peri-papillary and peripheral regions where the transgene Bcl-2 is not expressed, cellular retinaldehyde-binding protein or glutamine synthetase immunostaining persist and Müller glia do not die; and (ii) the retina conserves a normal organisation in these two regions in spite of total retinal degeneration elsewhere. We conclude that retinal dysplasia and degeneration are linked to primary Müller cell disruption. Besides its generally accepted anti-apoptotic function, over-expression of Bcl-2 also exerts a pro-apoptotic action, at least in immature Müller glia. One may suppose that Bcl-2 translocation resulting in its over-expression in retinal Müller cells could be a putative mechanism for early retinal degeneration.

cpp32 messenger RNA neosynthesis is induced by fatal axotomy and is not regulated by athanatal Bcl-2 over-expression.

In vivo, neuronal over-expression of the anti-apoptotic protein Bcl-2 prevents axotomy-induced motoneuron death and prolongs life in a mouse model of familial amyotrophic lateral sclerosis. The mechanism of these protective effects is still unknown. We have examined, in situ, the influence of Bcl-2 over-expression on the messenger RNA level of two pro-apoptotic, bax and cpp32, and one anti-apoptotic, bcl-xl, regulators of neuronal death. In neonates wild-type mice, cpp32 mRNA was increased in axotomized, dying motoneurons. No changes in bax and bcl-xl messenger RNAs expression were detected. A similar course was observed in protected axotomized neonate motoneurons of transgenic mice over-expressing Bcl-2. In adult wild-type mice no motoneuron death was detected one week after axotomy: bax and cpp32 messenger RNAs were increased and bcl-xl messenger RNA was decreased. Four weeks after the lesion, 60% of the lesioned facial motoneurons had disappeared. In the remaining motoneurons only cpp32 messenger RNA expression was superior to control level. In Bcl-2 transgenic mice, no axotomy-induced facial motoneurons death was detected but the course of the neosynthesis of cell death genes messenger RNAs was similar to wild-type mice. Bax, Bcl-x and CPP32 immunoreactivity were increased in facial motoneurons after axotomy. Thus, fatal axotomy induces cell death genes bax and cpp32 messenger RNAs neosynthesis which is not prevented by athanatal Bcl-2 over-expression. This suggests that the protective effect of Bcl-2 results from interactions with Bax and CPP32 at the post-translation level without repercussion at the messenger RNA level. Axotomy induces cell death messenger RNA neosynthesis potentially harmful at long-term despite Bcl-2 over-expression.

Acute application of an interleukin-1 beta-converting enzyme-specific inhibitor delays axotomy-induced motoneurone death.

When performed during the postnatal period, lesioning of the facial nerve induces apoptotic death of facial motoneurones. Several lines of evidence indicate that the ICE proteases family, the mammalian homologues of Ced-3, are positive effectors of this process. In order to determine whether these proteases are involved in axotomy-induced cell death in vivo, we applied a peptide inhibitor of ICE, YVAD-CHO, to the lesioned facial nerve of 2-day-old mice. The effect of YVAD-CHO on motoneurone death was tested using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling (TUNEL) method, which labels apoptotic DNA breaks in situ. Our results show that acute application of YVAD-CHO can partially delay motoneurone death since 32% fewer TUNEL-labelled motoneurones were observed in treated mice. These results indicate that ICE or ICE-like proteases may be involved in the cell death processes induced by an axotomy in vivo.

Olfactory neurons are protected from apoptosis in adult transgenic mice over-expressing the bcl-2 gene.

The olfactory system provides a useful in vivo model for studying neuronal apoptosis. The synaptic target deafferentation (olfactory bulb ablation) of the sensory epithelium induces a massive and synchronous wave of retrograde apoptosis in the large population of olfactory sensory neurons. The proto-oncogene bcl-2 is involved in the regulation of cell death and is able to block apoptosis in motoneurones. We demonstrate here that olfactory neurons over-expressing the human Bcl-2 protein in transgenic mice are long-term protected from apoptotic death following ipsilateral olfactory bulbectomy. We kinetically assessed neuronal death 32 h, 50 h and 5 days following unilateral olfactory bulbectomy, in adult C57BL6 (wild-type) and transgenic mice with olfactory neurons over-expressing the Human bcl-2 gene. Using the TUNEL method and morphometric analysis of olfactory epithelium, we confirmed the occurrence of a wave of neuronal death in wild-type mice but failed to detect a significant rate of neuronal apoptosis in the olfactory epithelium of transgenic animals. Apoptotic death of olfactory neurons probably shares common pathways with apoptotic processes occuring in other neuronal types, including motoneurons.

Vasopressin receptors in the mouse (Mus musculus) brain: sex-related expression in the medial preoptic area and hypothalamus.

We have investigated the distribution of vasopressin binding sites in the brain of male and female adult mice using a radio-iodinated ligand and film autoradiography. Vasopressin receptors were uncovered in various regions of the brain including the basal nucleus of Meynert, the substantia innominata, the hypothalamic paraventricular nucleus, the substantia nigra pars compacta and the hypoglossal nucleus. A sex-related difference in the expression of vasopressin receptors was seen in the medial preoptic area/anterior hypothalamus corresponding to the rat sexually dimorphic nucleus in the rat and in the hypothalamic mammillary nuclei. In both structures the autoradiographic labeling is more intense in females than in males. These observations confirm that vasopressin binding sites are present in the hypothalamic preoptic area of most species examined so far and that sex-related expression of neuropeptide receptors could trigger sex-related behavioral differences.

Medial septal neurons containing N-acetyl-aspartyl-glutamate-like immunoreactivity project to the hippocampal formation in the rat.

We have examined the distribution of N-acetyl-aspartyl-glutamate (NAAG)-like immunoreactive cell bodies in the medial septal nucleus and the nucleus of the diagonal band of Broca of the rat and assessed the involvement of these cells in the septo-hippocampal pathway. A series of experiments was carried out using immunohistochemistry alone or combined with the retrograde transport of a protein-gold complex injected into the dorsal hippocampal formation. A large number of NAAG-positive cells was observed in the medial septum and the diagonal band. Quantitative analysis revealed that 26% of the NAAG-like immunoreactive cells in the medial septum project to the dorsal hippocampal formation. These results demonstrate that the dipeptide NAAG is a major component of the rat septo-hippocampal pathway.

Age-related loss of galanin-immunoreactive cells in the rat septal area.

We have examined the distribution of galanin-like immunoreactive (LI) cell bodies in the medial septal nucleus (MS) and the nucleus of the diagonal band of Broca (nDBB) of young (3 months) and aged (25-30 months) rats, and assessed their respective contribution to the septohippocampal pathway. Immunohistochemical techniques were used alone or combined with the retrograde transport of a protein-gold complex injected into the dorsal hippocampus. In both groups, galanin-LI cells were observed in the MS and the nDBB. In aged rats, a significant decrease in both the staining intensity and the number of galanin-LI perikarya throughout the MS-nDBB complex was observed. Some immunoreactive cells appeared shrunken. The reduction in cell number ranged from 30 to 85%. There was also a decrease in the proportion of septohippocampal neurons containing galanin in aged rats (13% vs 20% in young animals) which however did not reach statistical significance. These results suggest that galanin-positive cells in the medial septal area undergo alterations with aging in the rat.

The mouse cpp32 mRNA transcript is early up-regulated in axotomized motoneurons following facial nerve transection.

In adult mice, axotomy of facial motoneurons induces apoptotic cell death. Cpp32, Bax and Bcl-xl are regulators of this type of cell death in the central nervous system. Using in situ hybridization, we have studied the kinetics of expression of cpp32, bax and bcl-xl mRNAs after a fatal lesion of the facial nerve in wild-type and Bcl-2 transgenic mice, where cell death is known to be prevented. In both strains of mice, cpp32 mRNA was up-regulated by 12 h following axotomy whereas changes in bax mRNA expression occurred later (from 3 days). These results provide information on the timing of molecular processes involved in cell death and could be helpful in determining a critical period during which they may be blocked.

Magnetic resonance imaging determinants of intraindividual variability in the elderly: combined analysis of grey and white matter.

Elderly individuals display a rapid age-related increase in intraindividual variability (IIV) of their performances. This phenomenon could reflect subtle changes in frontal lobe integrity. However, structural studies in this field are still missing. To address this issue, we computed an IIV index for a simple reaction time (RT) task and performed magnetic resonance imaging (MRI) including voxel based morphometry (VBM) and the tract based spatial statistics (TBSS) analysis of diffusion tensor imaging (DTI) in 61 adults aged from 22 to 88 years. The age-related IIV increase was associated with decreased fractional anisotropy (FA) as well as increased radial (RD) and mean (MD) diffusion in the main white matter (WM) fiber tracts. In contrast, axial diffusion (AD) and grey matter (GM) densities did not show any significant correlation with IIV. In multivariate models, only FA has an age-independent effect on IIV. These results revealed that WM but not GM changes partly mediated the age-related increase of IIV. They also revealed that the association between WM and IIV could not be only attributed to the damage of frontal lobe circuits but concerned the majority of interhemispheric and intrahemispheric corticocortical connections.

The contribution of aging to the understanding of the dimensionality of executive functions.

It has been reported in the literature that executive functions may be fractioned into updating, shifting, and inhibition. The present study aimed to explore whether these executive sub-components can be identified in a more age-heterogeneous sample and see if they are prone to an age-related decline. We tested the performances of 81 individuals aged from 18 to 88 years old in each executive sub-component, working memory, fluid intelligence and processing speed. Correlation analysis revealed only a slight positive relationship between the two updating measures. A linear decrement with age was observed only for two complex executive tests. Tasks indexing working memory, processing speed and fluid intelligence showed a stronger linear decline with age than executive tasks. In conclusion, our results did not replicate the executive structure known from the literature, and revealed that decrement in executive function is not an unavoidable concomitant of aging but rather concerns specific executive tasks.

[Comparative study in aged rats of behavioral deficiencies and morphometrical modifications of galanin containing neurons in the medial septal area]. / Etude comparative chez le rat âgé des déficits comportementaux et des modifications morphométriques des neurones contenant de la galanine dans la région septale médiane.

Age-related alterations in cued-training and place-training tasks were evaluated and compared to alterations in the galanin-like (GAL-LI) immunoreactive neurons in the medial septal area of the rat. Young adult (4 months) and aged (25-26 months) male Sprague-Dawley rats performed a modified version of the Morris water maze task. Immunohistochemical and morphometric techniques were used to analyse the distribution, density and morphology of GAL-LI neurons in the medial septum-diagonal band of Broca (MS-DBB) complex. A large variability in performance of the aged rats was evident, with the majority of aged rats exhibiting impaired performance on both parts of the task as compared to the young rats. In addition, there was a significant loss of GAL-LI cells in the MS-DBB complex, a significant reduction of the immunolabeling intensity of the subsisting GAL-LI cells and a non-statistically significant loss of septo-hippocampal GAL-LI neurons. There were no statistically significant correlations between the behavioral performances and the quantitative and qualitative modifications of GAL-LI cell bodies.