Structural and functional roles of KCC2 in developing cortex

Cation chloride cotransporters (CCCs) are critical for controlling intracellular chloride homeostasis. The CCC family is composed of four isoforms of K-Cl cotransporters (KCC1-4), two isoforms of Na-K-2Cl cotransporters (NKCC1-2), one Na-Cl cotransporter (NCC) and two the structurally related proteins with unknown function, CCC8 also known as cation-chloride cotransporter interaction protein, CIP, and CCC9. KCC2 is a neuron-specific isoform, which plays a prominent role in controlling the intracellular Cl- concentration in neurons and is responsible for producing the negative shift of GABAA responses from depolarizing to hyperpolarizing during neuronal maturation. In the present studies we first used in situ hybridization to examine the developmental expression patterns of the cation-chloride cotransporters KCC1-4 and NKCC1. We found that they display complementary expression patterns during embryonic brain development. Most interestingly, KCC2 expression in the embryonic central nervous system strictly follows neuronal maturation. In vitro data obtained from primary and organotypic neuronal cultures support this finding and revealed a temporal correlation between the expression of KCC2 and synaptogenesis. We found that KCC2 is highly expressed in filopodia and mature spines as well as dendritic shaft and investigated the role of KCC2 in spine formation by analyzing KCC2-/- neurons in vitro. Our studies revealed that KCC2 is a key factor in the maturation of dendritic spines. Interestingly, the effect of KCC2 in spine formation is not due to Cl- transport activity, but mediated through the interaction between KCC2 C-terminal and intracellular protein associated with cytoskeleton. The interacting protein we found is protein 4.1N by immunoprecipitation. Our results indicate a structural role for KCC2 in the development of functional glutamatergic synapses and suggest KCC2 as a synchronizer for the functional development of glutamatergic and GABAergic synapses in neuronal network. Studies on the regulatory mechanisms of KCC2 expression during development and plasticity revealed that synaptic activity of both the glutamatergic and GABAergic system is not required for up-regulation of KCC2 during development, whereas in acute mature hippocampal slices which undergo continuous synchronous activity induced by the absence of Mg2+ solution, KCC2 mRNA and protein expression were down-regulated in CA1 pyramidal neurons subsequently leading to a reduced capacity for neuronal Cl- extrusion. This effect is mediated by endogenous BDNF-TrkB down-stream cascades involving both Shc/FRS-2 and PLCγ-CREB signaling. BDNF mediated changes in KCC2 expression indicate that KCC2 is significantly involved in the complex mechanisms of neuronal plasticity during development and pathophysiological conditions.

Children and adolescents in full-time special education : an epidemiological and magnetic resonance imaging study

The need for special education (SE) is increasing. The majority of those whose problems are due to neurodevelopmental disorders have no specific aetiology. The aim of this study was to evaluate the contribution of prenatal and perinatal factors and factors associated with growth and development to later need for full-time SE and to assess joint structural and volumetric brain alterations among subjects with unexplained, familial need for SE. A random sample of 900 subjects in full-time SE allocated into three levels of neurodevelopmental problems and 301 controls in mainstream education (ME) provided data on socioeconomic factors, pregnancy, delivery, growth, and development. Of those, 119 subjects belonging to a sibling-pair in full-time SE with unexplained aetiology and 43 controls in ME underwent brain magnetic resonance imaging (MRI). Analyses of structural brain alterations and midsagittal area and diameter measurements were made. Voxel-based morphometry (VBM) analysis provided detailed information on regional grey matter, white matter, and cerebrospinal fluid (CSF) volume differences. Father’s age ≥ 40 years, low birth weight, male sex, and lower socio-economic status all increased the probability of SE placement. At age 1 year, one standard deviation score decrease in height raised the probability of SE placement by 40% and in head circumference by 28%. At infancy, the gross motor milestones differentiated the children. From age 18 months, the fine motor milestones and those related to speech and social skills became more important. Brain MRI revealed no specific aetiology for subjects in SE. However, they had more often ≥ 3 abnormal findings in MRIs (thin corpus callosum and enlarged cerebral and cerebellar CSF spaces). In VBM, subjects in full-time SE had smaller global white matter, CSF, and total brain volumes than controls. Compared with controls, subjects with intellectual disabilities had regional volume alterations (greater grey matter volumes in the anterior cingulate cortex bilaterally, smaller grey matter volume in left thalamus and left cerebellar hemisphere, greater white matter volume in the left fronto-parietal region, and smaller white matter volumes bilaterally in the posterior limbs of the internal capsules). In conclusion, the epidemiological studies emphasized several factors that increased the probability of SE placement, useful as a framework for interventional studies. The global and regional brain MRI findings provide an interesting basis for future investigations of learning-related brain structures in young subjects with cognitive impairments or intellectual disabilities of unexplained, familial aetiology.

The Pathobiology of the Saccular Cerebral Artery Aneurysm Rupture and Repair : A Clinicopathological and Experimental Approach

Backround and Purpose The often fatal (in 50-35%) subarachnoid hemorrhage (SAH) caused by saccular cerebral artery aneurysm (SCAA) rupture affects mainly the working aged population. The incidence of SAH is 10-11 / 100 000 in Western countries and twice as high in Finland and Japan. The estimated prevalence of SCAAs is around 2%. Many of those never rupture. Currently there are, however, no diagnostic methods to identify rupture-prone SCAAs from quiescent, (dormant) ones. Finding diagnostic markers for rupture-prone SCAAs is of primary importance since a SCAA rupture has such a sinister outcome, and all current treatment modalities are associated with morbidity and mortality. Also the therapies that prevent SCAA rupture need to be developed to as minimally invasive as possible. Although the clinical risk factors for SCAA rupture have been extensively studied and documented in large patient series, the cellular and molecular mechanisms how these risk factors lead to SCAA wall rupture remain incompletely known. Elucidation of the molecular and cellular pathobiology of the SCAA wall is needed in order to develop i) novel diagnostic tools that could identify rupture-prone SCAAs or patients at risk of SAH, and to ii) develop novel biological therapies that prevent SCAA wall rupture. Materials and Methods In this study, histological samples from unruptured and ruptured SCAAs and plasma samples from SCAA carriers were compared in order to identify structural changes, cell populations, growth factor receptors, or other molecular markers that would associate with SCAA wall rupture. In addition, experimental saccular aneurysm models and experimental models of mechanical vascular injury were used to study the cellular mechanisms of scar formation in the arterial wall, and the adaptation of the arterial wall to increased mechanical stress. Results and Interpretation Inflammation and degeneration of the SCAA wall, namely loss of mural cells and degradation of the wall matrix, were found to associate with rupture. Unruptured SCAA walls had structural resemblance with pads of myointimal hyperplasia or so called neointima that characterizes early atherosclerotic lesions, and is the repair and adaptation mechanism of the arterial wall after injury or increased mechanical stress. As in pads of myointimal hyperplasia elsewhere in the vasculature, oxidated LDL was found in the SCAA walls. Immunity against OxLDL was demonstrated in SAH patients with detection of circulating anti-oxidized LDL antibodies, which were significantly associated with the risk of rupture in patients with solitary SCAAs. Growth factor receptors associated with arterial wall remodeling and angiogenesis were more expressed in ruptured SCAA walls. In experimental saccular aneurysm models, capillary growth, arterial wall remodeling and neointima formation were found. The neointimal cells were shown to originate from the experimental aneurysm wall with minor contribution from the adjacent artery, and a negligible contribution of bone marrow-derived neointimal cells. Since loss of mural cells characterizes ruptured human SCAAs and likely impairs the adaptation and repair mechanism of ruptured or rupture-prone SCAAs, we investigated also the hypothesis that bone marrow-derived or circulating neointimal precursor cells could be used to enhance neointima formation and compensate the impaired repair capacity in ruptured SCAA walls. However, significant contribution of bone marrow cells or circulating mononuclear cells to neointima formation was not found.

Comparison and integration of MEG and fMRI

MEG directly measures the neuronal events and has greater temporal resolution than fMRI, which has limited temporal resolution mainly due to the larger timescale of the hemodynamic response. On the other hand fMRI has advantages in spatial resolution, while the localization results with MEG can be ambiguous due to the non-uniqueness of the electromagnetic inverse problem. Thus, these methods could provide complementary information and could be used to create both spatially and temporally accurate models of brain function. We investigated the degree of overlap, revealed by the two imaging methods, in areas involved in sensory or motor processing in healthy subjects and neurosurgical patients. Furthermore, we used the spatial information from fMRI to construct a spatiotemporal model of the MEG data in order to investigate the sensorimotor system and to create a spatiotemporal model of its function. We compared the localization results from the MEG and fMRI with invasive electrophysiological cortical mapping. We used a recently introduced method, contextual clustering, for hypothesis testing of fMRI data and assessed the the effect of neighbourhood information use on the reproducibility of fMRI results. Using MEG, we identified the ipsilateral primary sensorimotor cortex (SMI) as a novel source area contributing to the somatosensory evoked fields (SEF) to median nerve stimulation. Using combined MEG and fMRI measurements we found that two separate areas in the lateral fissure may be the generators for the SEF responses from the secondary somatosensory cortex region. The two imaging methods indicated activation in corresponding locations. By using complementary information from MEG and fMRI we established a spatiotemporal model of somatosensory cortical processing. This spatiotemporal model of cerebral activity was in good agreement with results from several studies using invasive electrophysiological measurements and with anatomical studies in monkey and man concerning the connections between somatosensory areas. In neurosurgical patients, the MEG dipole model turned out to be more reliable than fMRI in the identification of the central sulcus. This was due to prominent activation in non-primary areas in fMRI, which in some cases led to erroneous or ambiguous localization of the central sulcus.

Effects of Metabolic Risk Factors and Type 1 Diabetes on Brain Glucose and Brain Metabolites

The metabolic syndrome and type 1 diabetes are associated with brain alterations such as cognitive decline brain infarctions, atrophy, and white matter lesions. Despite the importance of these alterations, their pathomechanism is still poorly understood. This study was conducted to investigate brain glucose and metabolites in healthy individuals with an increased cardiovascular risk and in patients with type 1 diabetes in order to discover more information on the nature of the known brain alterations. We studied 43 20- to 45-year-old men. Study I compared two groups of non-diabetic men, one with an accumulation of cardiovascular risk factors and another without. Studies II to IV compared men with type 1 diabetes (duration of diabetes 6.7 ± 5.2 years, no microvascular complications) with non-diabetic men. Brain glucose, N-acetylaspartate (NAA), total creatine (tCr), choline, and myo-inositol (mI) were quantified with proton magnetic resonance spectroscopy in three cerebral regions: frontal cortex, frontal white matter, thalamus, and in cerebellar white matter. Data collection was performed for all participants during fasting glycemia and in a subgroup (Studies III and IV), also during a hyperglycemic clamp that increased plasma glucose concentration by 12 mmol/l. In non-diabetic men, the brain glucose concentration correlated linearly with plasma glucose concentration. The cardiovascular risk group (Study I) had a 13% higher plasma glucose concentration than the control group, but no difference in thalamic glucose content. The risk group thus had lower thalamic glucose content than expected. They also had 17% increased tCr (marker of oxidative metabolism). In the control group, tCr correlated with thalamic glucose content, but in the risk group, tCr correlated instead with fasting plasma glucose and 2-h plasma glucose concentration in the oral glucose tolerance test. Risk factors of the metabolic syndrome, most importantly insulin resistance, may thus influence brain metabolism. During fasting glycemia (Study II), regional variation in the cerebral glucose levels appeared in the non-diabetic subjects but not in those with diabetes. In diabetic patients, excess glucose had accumulated predominantly in the white matter where the metabolite alterations were also the most pronounced. Compared to the controls values, the white matter NAA (marker of neuronal metabolism) was 6% lower and mI (glia cell marker) 20% higher. Hyperglycemia is therefore a potent risk factor for diabetic brain disease and the metabolic brain alterations may appear even before any peripheral microvascular complications are detectable. During acute hyperglycemia (Study III), the increase in cerebral glucose content in the patients with type 1 diabetes was, dependent on brain region, between 1.1 and 2.0 mmol/l. An every-day hyperglycemic episode in a diabetic patient may therefore as much as double brain glucose concentration. While chronic hyperglycemia had led to accumulation of glucose in the white matter, acute hyperglycemia burdened predominantly the gray matter. Acute hyperglycemia also revealed that chronic fluctuation in blood glucose may be associated with alterations in glucose uptake or in metabolism in the thalamus. The cerebellar white matter appeared very differently from the cerebral (Study IV). In the non-diabetic men it contained twice as much glucose as the cerebrum. Diabetes had altered neither its glucose content nor the brain metabolites. The cerebellum seems therefore more resistant to the effects of hyperglycemia than is the cerebrum.

Distal anterior cerebral artery aneurysms

Objective: Distal anterior cerebral artery (DACA) aneurysms represent about 6% of all intracranial aneurysms. So far, only small series on treatment of these aneurysms have been published. Our aim is to evaluate the anatomic features, microneurosurgical techniques, treatment results, and long-term outcome in patients treated for DACA aneurysms. Patients and methods: We analyzed the clinical and radiological data on 517 consecutive patients diagnosed with DACA aneurysm at two neurosurgical centers serving solely the Southern (Helsinki) and Eastern (Kuopio) Finland in 1936–2007, and used a defined subgroup of the whole study population in each part of the study. Detailed anatomic analysis was performed in 101 consecutive patients from 1998 to 2007. Treatment results were analyzed in 427 patients treated between 1980 to 2005, the era of CT imaging and microneurosurgery. Long-term treatment outcome of ruptured DACA aneurysm(s) was evaluated in 280 patients with a median follow-up of 10 years; no patients were lost to follow-up. Results: DACA aneurysms, found most often (83%) at the A3 segment of the anterior cerebral artery (ACA), were smaller (median 6 mm vs. 8 mm), more frequently associated with multiple aneurysms (35% vs. 18%), and presented more often with intracerebral hematomas (ICHs) (53% vs. 26%) than ruptured aneurysms in general. They were associated with anomalies of the ACA in 23% of the patients. Microsurgical treatment showed similar complication rates (treatment morbidity 15%, treatment mortality 0.4%) as for other ruptured aneurysms. At one year after subarachnoid hemorrhage (SAH), DACA aneurysms had equally favorable outcome (GOS≥4) as other ruptured aneurysms (74% vs. 69%) but their mortality was lower (13% vs. 24%). Factors predicting unfavorable outcome for ruptured DACA aneurysms were advanced age, Hunt&Hess≥3, rebleeding before treatment, ICH, intraventricular hemorrhage, and severe preoperative hydrocephalus. The cumulative relative survival ratio showed 16% excess mortality in patients with ruptured DACA aneurysm during the first three years after SAH compared to the matched general population. From the fourth year onwards, there was no excess mortality during the follow-up. There were four episodes of recurrent SAH, only one due to treated DACA aneurysm, with a 10-year cumulative risk of 1.4%. Conclusions: The special neurovascular features and frequent association with anterior cerebral artery anomalies must be taken into account when planning occlusive treatment of DACA aneurysms. Clipping of DACA aneurysms provides a long-lasting result, with very small rates of rebleeding. After surviving three years from rupture of DACA aneurysm, the long-term survival of these patients becomes similar to that of the matched general population.

Task-dependent activations of human auditory cortex during pitch discrimination and pitch memory tasks

"The functional organization of auditory cortex (AC) is still poorly understood. Previous studies suggest segregation of auditory processing streams for spatial and nonspatial information located in the posterior and anterior AC, respectively (Rauschecker and Tian, 2000; Arnott et al., 2004; Lomber and Malhotra, 2008). Furthermore, previous studies have shown that active listening tasks strongly modulate AC activations (Petkov et al., 2004; Fritz et al., 2005; Polley et al., 2006). However, the task dependence of AC activations has not been systematically investigated. In the present study, we applied high-resolution functional magnetic resonance imaging of the AC and adjacent areas to compare activations during pitch discrimination and n-back pitch memory tasks that were varied parametrically in difficulty. We found that anterior AC activations were increased during discrimination but not during memory tasks, while activations in the inferior parietal lobule posterior to the AC were enhanced during memory tasks but not during discrimination. We also found that wide areas of the anterior AC and anterior insula were strongly deactivated during the pitch memory tasks. While these results are consistent with the proposition that the anterior and posterior AC belong to functionally separate auditory processing streams, our results show that this division is present also between tasks using spatially invariant sounds. Together, our results indicate that activations of human AC are strongly dependent on the characteristics of the behavioral task."

Poststroke survival and ischemic stroke recurrence : the cerebral small-vessel disease perspective

The aim of the present study was to investigate the influence of different manifestations of cerebral SVD on poststroke survival and ischemic stroke recurrence in long-term follow-up. The core imaging features of small-vessel disease (SVD) are confluent and extensive white matter changes (WMC) and lacunar infarcts. These are associated with minor motor deficits but a major negative influence on cognition, mood, and functioning in daily life, resulting from small-vessel lesions in the fronto-subcortical brain network. These sub-studies were conducted as part of the Helsinki Stroke Aging Memory (SAM) study. The SAM cohort consisted of 486 consecutive patients aged 55 to 85 years who were admitted to Helsinki University Central Hospital with acute ischemic stroke. The study included comprehensive clinical, neuropsychological, psychiatric and radiological assessment three months poststroke. The patients were followed up up for 12 years using extensive national registers. The effect of different manifestations of cerebral SVD on poststroke survival and stroke recurrence was analyzed controlling for factors such as age, education, and cardiovascular risk factors. Poststroke dementia and cognitive impairment relate to poor long-term survival. In particular, deficits in executive functions as well as visuospatial and constructional abilities predict poor outcome. The predictive value of cognitive deficits is further underlined by the finding that depression-executive dysfunction syndrome (DES), but not depression in itself, is associated with poor poststroke survival. Delirium is not independently associated with increased risk for long-term poststroke mortality, although it is associated with poststroke dementia. Furthermore, acute index stroke attributable to SVD is associated with poorer long-term survival and a higher risk for cardiac death than other stroke subtypes. Severe WMC, a surrogate of SVD, is independently related to an increased risk of stroke recurrence at five years. In summary, cognitive poststroke outcomes reflecting changes in the executive network brain, and the presence of cerebral SVD are important determinants of poststroke mortality and ischemic stroke recurrence, regardless of whether SVD is the cause of the index stroke or a condition concurrent to some other etiology.

Neuroprotective activity of Wedelia calendulacea on cerebral ischemia/reperfusion induced oxidative stress in rats

Objective: This study was undertaken to evaluate the neuroprotective activity of Wedelia calendulacea against cerebral ischemia/reperfusion induced oxidative stress in the rats. Materials and Methods: The global cerebral ischemia was induced in male albino Wistar rats by occluding the bilateral carotid arteries for 30 min followed by 1 h and 4 h reperfusion. At various times of reperfusion, the histopathological changes and the levels of malondialdehyde (MDA), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-s-transferase (GST), and hydrogen peroxide (H(2)O(2)) activity and brain water content were measured. Results: The ischemic changes were preceded by increase in concentration of MDA, hydrogen peroxide and followed by decreased GPx, GR, and GST activity. Treatment with W. calendulacea significantly attenuated ischemia-induced oxidative stress. W. calendulacea administration markedly reversed and restored to near normal level in the groups pre-treated with methanolic extract (250 and 500 mg/kg, given orally in single and double dose/day for 10 days) in dose-dependent way. Similarly, W. calendulacea reversed the brain water content in the ischemia reperfusion animals. The neurodegenaration also conformed by the histopathological changes in the cerebral-ischemic animals. Conclusion: The findings from the present investigation reveal that W. calendulacea protects neurons from global cerebral-ischemic injury in rat by attenuating oxidative stress.

Cerebroprotective activity of Wedelia calendulacea on global cerebral ischemia in rats

The present study was to investigate the effect of W. calendulacea on ischemia and reperfusion-induced cerebral injury. Cerebral ischemia was induced by occluding right and left common carotid arteries (global cerebral ischemia) for 30 min followed by reperfusion for 1 h and 4 h individually. Various biochemical alterations, produced subsequent to the application of bilateral carotid artery occlusion (BCAO) followed by reperfusion viz. increase in lipid peroxidation (LPO), hydrogen peroxide (H(2)O(2)), and decrease in reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD), level in the brain tissue, Western blot analysis (Cu-Zn-SOD and CAT) and assessment of cerebral infarct size were measured. All those enzymes are markedly reversed and restored to near normal level in the groups pre-treated with W. calendulacea (250 and 500 mg/kg given orally in single and double dose/day for 10 days) in dose-dependent way. The effect of W. calendulacea had increased significantly the protein expression of copper/zinc superoxide dismutase (Cu-Zn-SOD) and CAT in cerebral ischemia. W. claendulacea was markedly decrease cerebral infarct damages but results are not statistically significant. It can be concluded that W. calendulacea possesses a neuroprotective activity against cerebral ischemia in rat.