A method for linking computed image features to histological semantics in neuropathology.

In medical image analysis the image content is often represented by features computed from the pixel matrix in order to support the development of improved clinical diagnosis systems. These features need to be interpreted and understood at a clinical level of understanding Many features are of abstract nature, as for instance features derived from a wavelet transform. The interpretation and analysis of such features are difficult. This lack of coincidence between computed features and their meaning for a user in a given situation is commonly referred to as the semantic gap. In this work, we propose a method for feature analysis and interpretation based on the simultaneous visualization of feature and image domain. Histopathological images of meningiomas WHO (World Health Organization) grade I are represented by features derived from color transforms and the Discrete Wavelet Transform. The wavelet-based feature space is then visualized and explored using unsupervised machine learning methods. We show how to analyze and select features according to their relevance for the description of clinically relevant characteristics.

Maleic anhydride proton sponge as a novel MALDI matrix for the visualization of small molecules (<250 m/z) in brain tumors by routine MALDI ToF imaging mass spectrometry.

A novel vacuum stable proton sponge, 4-maleicanhydridoproton sponge (MAPS), was prepared and applied as the matrix in Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) of an aggressive brain tumor tissue (glioblastoma multiforme). Ionic maps of lactate, 2-hydroxyglutarate and chloride anions (m/z 89, 147, 35, respectively) were obtained using a routine MALDI ToF mass spectrometer.

Characterization of aromatase cytochrome P450 activity in the human temporal lobe.

Local aromatase-mediated conversion of androgens plays an important role in androgen action on the brain. To characterize estrogen formation in the human brain, we measured the microsomal aromatase activity of temporal lobe biopsies and compared it to that of human placenta using a highly sensitive 3H2O assay with [1beta-3H]androstenedione as substrate. Brain tissue was removed neurosurgically from 23 patients with epilepsy. Data of kinetic studies were analyzed with a computer-assisted, nonlinear, curve-fitting method using the Michaelis-Menten plus a nonspecific metabolism model. In contrast to data for placental aromatase activity, that for brain always had to be corrected for nonspecific tritium release. The mean K, values were 22.2 nmol/L in brain and 49.6 nmol/L in placenta. Inhibition experiments with atamestane, an inhibitor of aromatase cytochrome P450, revealed specific, dose-responsive, and competitive inhibition of both brain and placental aromatase activities. Placental aromatase activity was completely suppressible by atamestane, whereas in brain tissue there remained a residue of nonspecific tritium release. Subsequent experiments with cerebral cortex and subcortical white matter specimens of children and adults revealed a significantly higher aromatase activity in cerebral cortex than in subcortical white matter, but no sex or age differences were found.

Characterization of the 5alpha-reductase-3alpha-hydroxysteroid dehydrogenase complex in the human brain.

Although androgen metabolism in the human brain was discovered almost 30 yr ago, conclusive studies on the enzymes involved are still lacking. We therefore investigated 5alpha-reductase and colocalized 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) activity in cerebral neocortex (CX) and subcortical white matter (SC) specimens neurosurgically removed from 44 patients suffering from epilepsy. We could demonstrate the presence of the 5alpha-reductase-3alpha-HSD complex in the biopsies of all patients under investigation. Inhibition experiments with specific inhibitors for 5alpha-reductase type 1 and type 2 revealed strong evidence for the exclusive activity of the type 1 isoform. We detected a significantly higher 5alpha-reductase activity in CX than in SC (P< 0.0001), but no sex-specific differences were observed. Furthermore, we found that, in contrast to liver, only 3alpha-HSD type 2 messenger RNA is expressed in the brain and that its expression is significantly higher in SC than in CX without sex-specific differences. The present study is the first to systematically characterize the 5alpha-reductase-3alpha-HSD complex in the human brain. The lack of sex-specific differences and also the colocalization of both enzymes at all life stages suggest a more general purpose of the complex, e.g. the synthesis of neuroactive steroids or the catabolism of neurotoxic steroids, rather than control of reproductive functions.

Experimental axonal injury triggers interleukin-6 mRNA, protein synthesis and release into cerebrospinal fluid.

Diffuse axonal injury is a frequent pathologic sequel of head trauma, which, despite its devastating consequences for the patients, remains to be fully elucidated. Here we studied the release of interleukin-6 (IL-6) into CSF and serum, as well as the expression of IL-6 messenger ribonucleic acid (mRNA) and protein in a weight drop model of axonal injury in the rat. The IL-6 activity was elevated in CSF within 1 hour and peaked between 2 and 4 hours, reaching maximal values of 82,108 pg/mL, and returned to control values after 24 hours. In serum, the levels of IL-6 remained below increased CSF levels and did not exceed 393 pg/mL. In situ hybridization demonstrated augmented IL-6 mRNA expression in several regions including cortical pyramidal cells, neurons in thalamic nuclei, and macrophages in the basal subarachnoid spaces. A weak constitutive expression of IL-6 protein was shown by immunohistochemical study in control brain. After injury, IL-6 increased at 1 hour and remained elevated through the first 24 hours, returning to normal afterward. Most cells producing IL-6 were cortical, thalamic, and hippocampal neurons as confirmed by staining for the neuronal marker NeuN. These results extend our previous studies showing IL-6 production in the cerebrospinal fluid of patients with severe head trauma and demonstrate that neurons are the main source of IL-6 after experimental axonal injury.

Expression of the 17beta-hydroxysteroid dehydrogenase type 5 mRNA in the human brain.

An enzyme-mediated metabolism of androgens and estrogens including 17beta-HSD activity in the brain of vertebrates was discovered approximately 30 years ago. Mainly 5alpha-reductase and aromatase have been studied in detail. Recently we could demonstrate reductive and oxidative 17beta-HSD activity as well as considerable mRNA expression of the 17beta-HSD types 3 and 4 in the human brain. In the present study, we report on 17beta-HSD type 5 mRNA expression in brain tissue of women and men. Data analysis did not reveal sex specific differences, but we determined a significantly higher mRNA concentration in the subcortical white matter (SC) than in the cerebral cortex (CX). Investigation of reductive 17beta-HSD in vitro activity with 2 microM androstenedione as the substrate revealed no sex specific differences. Testosterone formation was significantly higher in SC than in CX. Moreover, enzyme activity was significantly higher in brain tissue of adults compared to that of children.

Intrathecal and serum interleukin-6 and the acute-phase response in patients with severe traumatic brain injuries.

Patients with severe traumatic brain injury (TBI) show a profound acute-phase response. Because interleukin-6 (IL-6) is an important mediator of these pathophysiological changes, IL-6 levels were monitored in the cerebrospinal fluid (CSF) and serum of 20 patients with severe isolated TBI. All patients received indwelling ventricular catheters for intracranial pressure monitoring and for release of CSF when intracranial pressure exceeded 15 mmHg. CSF and blood samples were drawn daily for up to 14 days. The CSF/serum albumin ratio (QA) served as a parameter of blood brain barrier dysfunction. Differential blood counts as well as the acute-phase proteins C-reactive protein, alpha 1-antitrypsin, and fibrinogen were recorded. IL-6 was detected in all CSF samples and reached values of up to 31,000 pg/mL, while serum levels remained significantly lower (alpha < or = .01) and never exceeded 1,100 pg/mL the entire study period. A correlation between CSF and serum IL-6 was found initially after the trauma and corresponded to a severe dysfunction of the blood brain barrier (r = .637, p = .001). Maximum IL-6 concentrations in serum correlated with peak levels of acute-phase proteins (C-reactive protein, alpha 1-antitrypsin, and fibrinogen). With regard to blood cell count, an initial leukocytosis combined with a borderline lymphocytopenia was observed. Thrombocytes decreased to a subnormal level during the first few days, but reached supranormal numbers by the end of the study period. Our results show that the increase of IL-6 levels in CSF and serum is followed by a profound acute-phase response in patients with TBI. Because cytokine concentrations are significantly lower in serum compared with CSF, we hypothesize that IL-6 produced in the central nervous system may play a role in initiating the acute-phase response.

Experimental diffuse axonal injury induces enhanced neuronal C5a receptor mRNA expression in rats.

Several studies suggest the involvement of the complement system in the pathophysiology of traumatic brain injury (TBI). Since the intrathecal generation of anaphylatoxin C5a has been shown to mediate inflammatory effects within the central nervous system, we sought to characterize the cellular expression of the mRNA for the C5a receptor (C5aR, CD88) in brains of rats with experimental diffuse axonal injury (DAI) by in situ hybridization. Infiltrating leukocytes expressing C5aR mRNA were seen in meninges and lateral ventricles as early as 4 h after induction of DAI. The number of infiltrating C5aR-positive cells increased gradually up to 24 h after trauma. Within the brain parenchyma, up-regulation of C5aR mRNA expression was first seen in cerebellar Purkinje cells within 8 h. At 24 h after TBI, expression of C5aR mRNA was widespread bilaterally throughout the cortex and cerebellum, the cellular expression being restricted to pyramidal neurons and Purkinje cells. The intensity of C5aR transcript signals on neurons increased further up to 96 h after trauma. Ligand binding of C5a to its receptor on neurons might mediate previously unknown functions, thus possibly leading to neurotoxicity and secondary neuronal damage after TBI.

TGF-beta is elevated in the CSF of patients with severe traumatic brain injuries and parallels blood-brain barrier function.

Traumatic brain injury (TBI) induces local and systemic immunologic changes, release of cytokines, and cell activation. Perpetuation of these cascades may contribute to secondary damage to the brain. Therefore, the ability of the antiinflammatory mediator transforming growth factor-beta (TGF-beta) to downregulate intrathecal immunoactivation may be of fundamental value for diminishing the incidence and extent of secondary insults. In this study, the release of TGF-beta into cerebrospinal fluid (CSF) and serum of 22 patients with severe TBI was analyzed with respect to the function of the blood-brain barrier (BBB) for 21 days. Levels of TGF-beta in CSF increased to their maximum on the first day (median, 1.26 ng/mL), thereafter decreasing gradually over time. Median TGF-beta values in serum always remained within the reference interval (6.5 to 71.5 ng/mL). Daily assessment of the CSF-serum albumin quotient (QA) and of the CSF-serum TGF-beta quotient (QTGF-beta) showed a strong correlation between maximal QTGF-beta and QA, indicating a passage of this cytokine from the periphery to the intrathecal compartment across the BBB. However, calculation of the TGF-beta index (QTGF-beta/Q(A)) suggested a cerebral production of TGF-beta in 9 of 22 patients. Levels of TGF-beta could not be correlated with extent of initial injury by computed tomography (CT), CD4/CD8 ratios, acute lung injury, or clinical outcome as rated by the Glasgow Outcome Scale (GOS). Although increased levels of TGF-beta in CSF seem to parallel BBB function, a partial intrathecal production is suggested, possibly modulated by elevation of interleukin-6 (IL-6). Thus, TGF-beta may function as a factor in the complex cytokine network following TBI, acting as an antiinflammatory and neuroprotective mediator.

Markers for cell-mediated immune response are elevated in cerebrospinal fluid and serum after severe traumatic brain injury in humans.

The brain is believed to be an immunologically privileged organ, sheltered from the systemic immunological defense by the blood-brain barrier (BBB). However, there is increasing evidence for a marked inflammatory response in the brain after traumatic brain injury (TBI). Markers for cellular immune activation, neopterin, beta2-microglobulin (beta2M), and soluble interleukin-2 receptor (sIL-2R), were measured for up to 3 weeks in cerebrospinal fluid (CSF) and serum of 41 patients with severe TBI in order to elucidate the time course and the origin of the cellular immune response following TBI. Neopterin gradually increased during the first posttraumatic week in both CSF and serum. Concentrations in CSF were generally higher than in serum, suggesting intrathecal release of this marker. beta2M showed similar kinetics but with higher serum than CSF concentrations. Nonetheless, intrathecal release as assessed by the beta2M index could be postulated for most of the patients. The mean levels of sIL-2R in both CSF and serum were elevated during the whole study period, serum concentrations being up to 2 x 10(4) times higher than in CSF. No significant intrathecal production of sIL-2R could be detected. The present data shows that severe TBI leads to a marked cell-mediated immune response within the brain and in the systemic circulation. In the intrathecal compartment the activated cells appear to be predominantly of the macrophage/microglia lineage, while the immune activation in the systemic circulation seems to involve mainly T-lymphocytes.

Chicken arachnoid granulations: a new model for cerebrospinal fluid absorption in man.

Cerebrospinal fluid (CSF) absorption was investigated chicken and rat using infusion tests into the cisterna magna. Data were analysed according to a mathematical model by Johnson et al. Results in rat predicted a predominant lymphatic mechanism, which was confirmed by rapid outflow of X-ray contrast media into the olfactoric mucosa. In contrast, dynamics measurements suggested CSF drainage via arachnoid granulations in chicken. CSF spaces along the optic nerve were contrasted radiographically resulting in venous drainage. Electron microscopically, villus-like structures were found at the distal optic nerve connecting the subarachnoid space with accompanying veins, resembling human arachnoid granulations. We hypothesize that CSF absorption through arachnoid villi in microsmatic chicken reflects the situation in man very well.

Interleukin-6 and its soluble receptor in serum and cerebrospinal fluid after cerebral trauma.

Interleukin-6 (IL-6) and its soluble receptor (sIL-6-R) were measured in cerebrospinal fluid (CSF) and serum of 11 severely head injured patients for up to 3 weeks following trauma. IL-6 increased immediately after injury displaying much higher concentrations in CSF than in serum (n = 11). Differently, median levels of sIL-6-R remained in the normal ranges being 10 times higher in serum than in CSF. However, increased amounts over control levels were found in CSF (n = 7) and intrathecal release of sIL-6-R was also suggested (n = 7). Although no correlation with the extent of cerebral lesion or with clinical outcome was evident, elevation of sIL-6-R in CSF supports a pivotal role for IL-6/sIL-6-R complex in the injured brain.

Cell activation and inflammatory response following traumatic axonal injury in the rat.

In a rat model of traumatic brain injury cell activation was characterized immunohistochemically from 2 h up to 2 weeks. Reactive astrocytosis became apparent perivascularly and in the grey matter within 4h after trauma. Increased OX42 immunoreactivity indicated microglial activation in cortex and hippocampus as early as 4 h, whereas up-regulation of MHC class II (OX6) was evident in white matter tracts at 24 h. Although macrophage (ED1) numbers increased in the meninges and perivascularly, brain infiltration appeared marginal. Accumulation of lymphocytes and granulocytes was not observed. Our results show that traumatic axonal injury induces a rapid and sustained glial activation in the absence of leukocyte infiltration. Thus, cell activation following diffuse trauma strongly differs from that found after focal brain damage, awaiting further functional characterization.

Telomerase activity and expression of the telomerase catalytic subunit, hTERT, in meningioma progression.

OBJECT: In recent reports, 6 to 19% of meningiomas have been classified as atypical or anaplastic/malignant. Some atypical and anaplastic meningiomas appear to arise from benign tumors by progression. Telomerase activation has recently been associated with malignant progression of human tumors. The authors have investigated a series of benign, atypical, and anaplastic/malignant meningiomas for telomerase activity and expression of the telomerase catalytic subunit human telomerase reverse transcriptase (hTERT). METHODS: A quantitative telomeric repeat amplification protocol was used to detect telomerase enzyme activity in seven (21%) of 34 benign, but in nine (75%) of 12 atypical and in seven (100%) of seven anaplastic/malignant meningiomas. Very high levels of telomerase activity were observed only in highly aggressive tumors. Messenger (m)RNA expression of the catalytic subunit hTERT was found in 11 (33%) of 33 benign, 12 (92%) of 13 atypical, and all seven anaplastic/malignant tumors. All telomerase-positive lesions were also positive for hTERT mRNA, whereas no telomerase activity was detected in six (21%) of 29 hTERT-positive tumors. This indicates that upregulation of hTERT is the rate-limiting step for telomerase activation in the majority of meningiomas. Expression of telomerase and hTERT was seen in all four tumors with gross brain invasion. All recurrent tumors or meningiomas recurring during follow up expressed hTERT. CONCLUSIONS: The results are consistent with a role for telomerase activation during the development of malignancy in meningiomas. Hence, expression of telomerase activity and hTERT might prove to be potentially useful markers for the evaluation of these tumors.

Traumatic brain injury in the developing rat pup: studies of ICP, PVI and neurological response.

Diffuse brain swelling is a common complication in young victims of a seven head injury but, there is a lack of data on relevant models of injury. We produced diffuse brain injury in 21 day old Lewis rat pups (N = 33) by modifying a recently established weight-drop-model. The trauma threshold, neurological response, histological changes, intracranial pressure (ICP), and arterial blood pressure (ABP) were determined. In addition, the pressure-volume-index (PVI) was measured 15 min before, 2 min, and 1 h after brain injury. In the 1 m/100 g group 4 of 5 rats died, whereas in the 0.5 m/100 g only 4 of 28 died. The PVI increased at 2 min after traumatic brain injury (TBI) but ICP was unchanged, except for a minor increase immediately after injury. Histological studies revealed diffuse neuronal death, predominantly involving the cortex and hippocampus. The results of the present study indicate that determination of ICP in the developing rat pup during and after diffuse brain injury is possible. A 0.5 m/100 g weight-drop-trauma results in a morphologically severe injury but with low mortality. The increase in PVI can be attributed to a decrease of cerebral perfusion pressure (CPP) after injury. However, the absence of a further increase of ICP after injury in the developing rat indicates that this may not be a primary consequence of injury in paediatric patients.

CSF dynamics in a rodent model of closed head injury.

Using ICP measurements and the bolus injection technique dynamic parameters of the cerebrospinal fluid system as there are pressure-volume-index (PVI) and resistance to CSF outflow (Rout) were investigated in a new model of diffuse closed head injury (CHI) in the rat. It was found that in the absence of brain oedema and ICP alterations an increase in PVI and Rout was present in the early (4h) period following head injury. This may be indicative for a reduction in cerebral blood flow and cerebral blood volume, both shown previously to occur after CHI. Furthermore an early impairment of CSF absorption mechanisms is evident. To answer the question, whether bolus injection techniques are advisable for clinical routine and whether results might have a predictive value, further investigations covering longer observation intervals and in the presence of secondary insults to the brain are necessary.

Intraventricular cytarabine in a case of idiopathic hypertrophic pachymeningitis.

Idiopathic hypertrophic chronic pachymeningitis (IHCP) is characterised by inflammatory fibrotic thickening of the dura mater. Long term management is controversial. A 28 year old man with craniospinal IHCP and prominent lymphocytic meningitis is reported. Cerebrospinal fluid and histological examination suggested a CD4+ T cell driven process and B cell stimulation. After surgical, tuberculostatic, and immunosuppressive treatment failed to control the progressive meningeal hypertrophy, causing severe headache and neurological disability, the disease process eventually abated with intraventricular cytarabine treatment.

Human herpes virus-8 is not associated with primary central nervous system lymphoma in HIV-negative patients.

Primary central nervous system lymphomas (PCNSL) are derived from germinal center B cells. Recent molecular studies indicate that the tumor cells or their precursors have experienced antigenic stimulation. Attractive candidates for such antigens are pathogens with the capacity to reside in the brain. The aim of the present study was to evaluate whether human herpes virus (HHV)-8 is involved in the pathogenesis of PCNSL. A series of 46 PCNSL, 31 from HIV-negative and 15 from HIV-positive patients, were analyzed using various molecular biological and immunological approaches. Nested PCR with two different protocols unequivocally demonstrated that PCNSL from HIV-negative patients did not harbor HHV-8 DNA. Among AIDS-associated PCNSL, HHV-8 DNA was found in only 1 tumor. In situ hybridization studies revealed that the lymphoma cells were HHV-8 negative in all cases. Single small mononuclear cells, most likely corresponding to bystander lymphocytes, were identified as the cellular source of HHV-8 in the HIV-positive patient with an HHV-8 PCR signal. These studies largely rule out a role for HHV-8 in the pathogenesis of PCNSL in both HIV-negative as well as HIV-positive patients.