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Biomedical subjects

D Troost

Publications and source records attributed to D Troost.

At least 19 recordsLinked to original sources
PubMed2002

"Vanishing white matter" and ovarian dysgenesis in an infant with cerebro-oculo-facio-skeletal phenotype.

We describe a girl with intrauterine growth retardation, congenital cataracts, mild dysmorphic features and joint contractures. MRI performed at 1 week and 6 months, demonstrated postnatal cerebral and cerebellar atrophy and loss of white matter. The patient died at 10 months. Post-mortem examination revealed ovarian dysgenesis. There was normal development of neuronal and axonal structures, but lack of myelination in brainstem and cerebellum. Subcortical and deep white matter of the cerebral hemispheres were largely destroyed (cavitated), with preserved, but unmyelinated axons in other brain areas. These findings are compatible with a severe leukodystrophic process of pre- or perinatal onset. The exact pathogenesis is not known.

Abnormalities, Multiple↗
PubMed2001

GOA, a novel gene encoding a ring finger B-box coiled-coil protein, is overexpressed in astrocytoma.

Serial analysis of gene expression (SAGE) was used to identify a gene named GOA (gene overexpressed in astrocytoma), which codes for a novel Ring finger B-box coiled-coil (RBCC) protein. Northern blot hybridization showed overexpression of GOA in 9 of 10 astrocytomas. Except for kidney, in which high expression was found, expression levels in normal tissues were low and comparable to normal brain. Immunohistochemistry demonstrated presence of GOA, with prominent nuclear staining, in astrocytoma tumor cells and astrocytes of fetal brain, but virtual absence in mature astrocytes. Overexpression was not due to amplification, since amplification of GOA was only found in one of 65 astrocytomas. GOA was localized to 17q24-25, a region that is frequently gained or amplified in a number of other tumor types. GOA contains two LXXLL motifs, which are thought to be important for nuclear receptor binding. Our data suggest an important role of GOA in the process of dedifferentiation that is associated with astrocytoma tumorigenesis and possibly with that of other tumor types as well.

Amino Acid Motifs↗
PubMed2001

Expression of Id proteins increases in astrocytes in the hippocampus of epileptic rats.

Reactive gliosis is a prominent morphological feature of temporal lobe epilepsy. The molecular mechanisms underlying glial cell activation remain unclear. We examined expression of Id1-3 protein, a family of helix--loop--helix proteins involved in the regulation of cell proliferation and differentiation, in glial cells after electrically induced status epilepticus (SE) in the rat. In control hippocampus, Id3 was weakly expressed in astrocytes, while Id1-2 were below detection level. After SE, Id1-3 protein expression increased markedly in reactive astrocytes within 1 day and this persisted up to 3 weeks after SE. Three months after SE when rats experience spontaneous seizures, Id expression had returned to control levels. These results support a role of the Id gene family in regulating astrocyte reactivity in epileptic tissue.

Animals↗
PubMed2001

Increased expression of neuronal nitric oxide synthase spliced variants in reactive astrocytes of amyotrophic lateral sclerosis human spinal cord.

The expression of three different neuronal nitric oxide synthase (nNOS) spliced variants, named nNOSalpha, nNOSbeta, and nNOSgamma, was investigated in the spinal cord of control and both familiar and sporadic amyotrophic lateral sclerosis (FALS and SALS) patients. Western blot analysis showed a consistent increase in nNOS expression in six SALS patients compared with controls when antibodies recognizing both nNOSalpha and nNOSbeta, or nNOSalpha, nNOSbeta, and nNOSgamma were used, whereas no change was observed when a selective anti-nNOSalpha antibody was used. Immunoreactivity signal for nNOSalpha-beta-gamma and nNOSalpha-beta was equally present in ventral horn neurons of control and ALS spinal cord but was dramatically increased in reactive astrocytes of the ventral horn and white matter in both FALS and SALS. nNOSalpha signal was equally expressed in motor neurons of normal and ALS spinal cord but was not evident in astrocytes. This finding indicates that nNOSbeta and nNOSgamma spliced variants are upregulated in reactive astrocytes in ALS. This may contribute to the peroxynitrite-mediated oxidative damage involved in the pathogenesis of both FALS and SALS.

Adult↗
PubMed2001

Expression of brain-derived neurotrophic factor and tyrosine kinase B receptor proteins in glioneuronal tumors from patients with intractable epilepsy: colocalization with N-methyl-D-aspartic acid receptor.

Recent evidence suggests that brain-derived neurotrophic factor (BDNF) and its tyrosine kinase B (TrkB) receptor, in addition to promoting neuronal survival and differentiation, modulates synaptic transmission by increasing N-methyl-D-aspartic acid receptor (NMDAR) activity. Overexpression of BDNF may, then, interfere with normal brain function, causing increased excitability. We have examined the immunohistochemical expression of BDNF, full-length TrkB receptor and the NMDAR subunit 1 and subunit 2A/B proteins (NMDAR1 and NMDAR2A/B) in glioneuronal tumors (gangliogliomas, GG, n = 40; dysembryoplastic neuroepithelial tumors, DNT, n = 15), from patients with chronic intractable epilepsy. The great majority of tumors studied were positive for all markers examined, supporting the high level of neurochemical differentiation of these lesions. BDNF and TrkB immunoreactivity (ir) was mainly observed in the neuronal component of the tumors. In GG, more than 90% of tumors contained very intense BDNF-ir ganglion cells. Double labeling confirmed the presence of BDNF-ir and TrkB-ir in neurons which contained NMDAR1. NMDAR2A/B intensely labeled abnormal neurons in both GG and DNT and co-localized with NMDAR1. The presence of BDNF and its receptor in the neuronal component of GG and DNT may suggest a role for this neurotrophin in the development of these lesions, preventing the death of abnormal neuronal cells. In addition, since these neurons contain both NMDAR1 and NMDAR2A/B subunits, the BDNF-TrkB pathway may also contribute through a modulation of glutamatergic transmission to the intrinsic epileptogenicity of glioneuronal tumors.

Adolescent↗
PubMed2001

Expression of connexin 43 and connexin 32 gap-junction proteins in epilepsy-associated brain tumors and in the perilesional epileptic cortex.

The expression of the gap-junction proteins connexin (CX) 43 and 32 was evaluated in surgical specimens of brain tumors and perilesional cortex from patients with chronic medically intractable epilepsy. In human normal brain CX32 was expressed in neurons and oligodendrocytes. CX32 immunoreactivity (IR) was observed in the neuronal component of glioneuronal tumors and in all oligodendrogliomas, 50% of which showed strong labeling, independent of the grade of differentiation. CX43, normally expressed in astrocytes, was also detected in most of the human astrocytomas and in the astroglial component of glioneuronal tumors. Whereas most of the low-grade gliomas (>60%) showed strong membranous staining, most high-grade astrocytomas exhibited a reduction of the typical plasma membrane CX43-IR and intracytoplasmic localization. Immunoblot analysis showed different CX43 isoforms in control cortex and in low-grade gliomas. However, only one single isoform (corresponding to the non-phosphorylated form of CX43) appeared to be present in most high-grade gliomas. Increased expression of CX43 protein was present in reactive astrocytes in the epileptic cortex surrounding low-grade tumors as compared to control cortex, indicating the existence of a regulatory pathway involving CX43 in the reorganization of the astrocytic syncytium in regions undergoing reactive gliosis. The high expression of connexin proteins in low-grade tumors and in the peritumoral reactive astrocytes suggests that they could contribute to tumor-related seizures.

Astrocytes↗
PubMed2001

Immunohistochemical localization of group I and II metabotropic glutamate receptors in control and amyotrophic lateral sclerosis human spinal cord: upregulation in reactive astrocytes.

Excitotoxicity, which is mediated by the excessive activation of glutamate receptors, has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). There is substantial information about the distribution and function of ionotropic glutamate receptors in the spinal cord, although the role of metabotropic glutamate receptors (mGluRs) is poorly understood in this region of the brain, particularly under pathological conditions. We used immunocytochemistry to study the general distribution of group I and group II mGluR immunoreactivity in the human spinal cord, as well as the cell-specific expression of these receptors. We also investigated whether mGluR expression was altered in the spinal cord of patients with sporadic and familial ALS. Immunocytochemical analysis of control human spinal cord demonstrated that mGluR1alpha and mGluR5 (group I mGluRs) were highly represented in neuronal cells throughout the spinal cord. mGluR1alpha showed the highest relative level of expression in ventral horn neurons (laminae VIII and IX), whereas intense mGluR5 immunoreactivity was observed within the dorsal horn (superficial laminae I and II). Group II mGluRs (mGluR2/3) immunoreactivity was mainly concentrated in the inner part of the lamina II. With respect to specific neuronal populations, mGluR2/3 and mGluR5 appeared to be most frequently expressed in calbindin-containing and calretinin-containing cells, respectively. In control spinal cord only sparse astrocytes showed a weak to moderate mGluR immunoreactivity. Regional differences in immunoreactivity were apparent in ALS compared to control. In particular, mGluR expression was increased in reactive glial cells in both gray (ventral horn) and white matter of ALS spinal cord. Upregulation of mGluRs in reactive astrocytes may represent a critical mechanism for modulation of glial function and changes in glial-neuronal communication in the course of neurodegenerative diseases.

Adult↗
PubMed2001

Glioneuronal tumors and medically intractable epilepsy: a clinical study with long-term follow-up of seizure outcome after surgery.

The present study intends to identify factors that predict postoperative clinical outcome in patients with gangliogliomas (GG) and dysembryoplastic neuroepithelial tumors (DNT). We evaluated the medical records of 45 patients with GG and 13 patients with DNT, treated surgically between 1985 and 1995. We assessed several clinical and histopathological features and analyzed the data statistically. At 5 years postoperatively, 63% of patients with GG and 58% of patients with DNT were seizure-free (Engel's class I). Younger age at surgery (P<0.01 for GG and P<0.05 for DNT), total resection (P<0.01 for GG), shorter duration of epilepsy (P<0.01), absence of generalized seizures (P<0.01 for GG; P<0.05 for DNT) and absence of epileptiform discharge in the post-operative EEG (P<0.01 for GG; P=0.01 for DNT) predicted a better postoperative seizure outcome. Tumor recurrence with malignant progression occurred in eight histologically benign GG and two anaplastic GG and was associated which older age at surgery (P=0.01) and subtotal resection of the tumor (P<0.01). Our results indicate that a prompt diagnosis, relatively soon after seizure onset, followed by complete resection of glioneuronal tumors provides the best chance for curing epilepsy and preventing their malignant transformation.

Adolescent↗
PubMed2001

High concentration of Daunorubicin and Daunorubicinol in human malignant astrocytomas after systemic administration of liposomal Daunorubicin.

The value of chemotherapy in patients with malignant astrocytoma remains controversial. In our laboratories in vitro experiments with organotypic spheroid cultures showed superior effectiveness of anthracyclines. Systemic administration did not provide in therapeutic concentrations so far. Because recent studies on Daunorubicin in liposomes in the treatment of Kaposi sarcoma have shown effectiveness with diminished systemic toxicity, we administered intravenously a single dose of Daunorubicin in liposomes in eight patients at different intervals prior to surgery (12-50 h). In samples taken from tumor, tumor-edge and where possible from adjacent brain, the levels of Daunorubicin and its active metabolite Daunorubicinol were assessed with high performance liquid chromatography. Here we report that high concentrations of Daunorubicin and Daunorubicinol were found in malignant gliomas after systemic administration of liposomal Daunorubicin.

Adult↗
PubMed2001

Ionotropic and metabotropic glutamate receptor protein expression in glioneuronal tumours from patients with intractable epilepsy.

Glioneuronal tumours are an increasingly recognized cause of chronic pharmaco-resistant epilepsy. In the present study the immunocytochemical expression of various glutamate receptor (GluR) subtypes was investigated in 41 gangliogliomas (GG) and 16 dysembryoplastic neuroepithelial tumours (DNT) from patients with intractable epilepsy. Immunocytochemistry with antibodies specific for ionotropic NR1, NR2A/B (NMDA) GluR1, GluR2 (AMPA), GluR5-7 (kainate), and metabotropic mGluR1, mGluR2-3, mGluR5, mGluR7a subtypes demonstrated in both GG and DNT the presence of an highly differentiated neuronal population, containing subunits from each receptor class. More than 50% of tumours contained a high percentage of neuronal cells immunolabelled for NMDA, AMPA and kainate receptor subunits. A high percentage of neurones showed strong expression of NR2A-B, which co-localized with NR1. Group I mGluRs (mGluR1 and mGluR5) were highly represented in the neuronal component of the tumours. Immunolabelling for several GluRs was also present in the glial component. Increased expression of mGluR2-3, mGluR5 and GluR5-7 was observed in reactive astrocytes in the perilesional zone compared to normal cortex. The neurochemical profile of glioneuronal tumours, with high expression of specific GluR subtypes, supports the central role of glutamatergic transmission in the mechanisms underlying the intrinsic and high epileptogenicity of these lesions.

Adolescent↗
PubMed2001

Induction of neonatal sodium channel II and III alpha-isoform mRNAs in neurons and microglia after status epilepticus in the rat hippocampus.

Sodium channels (NaChs) regulate neuronal excitability in both physiological and pathological conditions, including epilepsy and are therefore an important target for antiepileptic drugs. In the present study, we examined the distribution of mRNAs encoding neonatal NaChs II and III alpha-isoforms in control rat hippocampus and after electrically-induced status epilepticus (SE), using nonradioactive in situ hybridization (ISH). Only weak expression of neonatal NaCh II and III mRNAs was observed in control hippocampus. By contrast, increased expression of neonatal NaCh II and III mRNAs was observed 4 h after the induction of SE in neurons of CA1-CA3 and the dentate granule cell layer. These changes were detected only in rats in which SE was successfully induced and persisted, although less intense, for up to 3 months, when rats display spontaneous seizures. Strong expression of neonatal NaCh alpha-isoforms was observed 1 week after SE in microglial cells, as confirmed by double labelling, combining ISH with immunocytochemistry for microglia markers. The increased expression of neonatal isoforms of the NaCh in both neurons and microglial cells may represent a critical mechanism for modulation of neuronal excitability, glial function and pharmacological response to antiepileptic drugs in the course of epileptogenesis.

Animals↗
PubMed2001

Cystatin C, a cysteine protease inhibitor, is persistently up-regulated in neurons and glia in a rat model for mesial temporal lobe epilepsy.

Cystatin C (CSTC), a cysteine protease inhibitor, has been implicated in the processes of neuronal degeneration and repair of the nervous system. Using serial analysis of gene expression (SAGE), we recently identified CSTC as one of the genes that are overexpressed after electrically induced status epilepticus (SE). In the present study, Western blot analysis extended the SAGE results, showing increased CSTC protein in the hippocampus and entorhinal cortex. Immunocytochemistry revealed an increase in CSTC expression in glial cells, which was first apparent 24 h after onset of SE, and persisted for at least 3 months. Double immunolabelling confirmed that both reactive astrocytes, and activated microglia were CSTC immunopositive. Within the hippocampus, up-regulation was also observed in neuronal cells within one day after SE. Up-regulation was still present in hippocampal pyramidal cells and surviving interneurons of chronic epileptic rats (3-8 months post-SE). This study demonstrates that status epilepticus leads to a widespread and persistent up-regulation of CSTC in the hippocampus and entorhinal cortex, which may represent an intrinsic neuroprotective mechanism in the course of epileptogenesis that may counteract progression of the disease.

Animals↗
PubMed2001

Impaired RNA splicing of 5'-regulatory sequences of the astroglial glutamate transporter EAAT2 in human astrocytoma.

A loss of the glutamate transporter EAAT2 has been reported in the neoplastic transformation of astrocytic cells and astrocytoma. The RNA expression of EAAT2 and five 5'-regulatory splice variants was investigated to identify alterations of the post-transcriptional EAAT2 gene regulation in human astrocytic tumours. Three known (EAAT2, HBGTII, and HBGTIIC) and two novel (EAAT2/3 and EAAT2/31) EAAT2 transcripts originating from alternative splicing of 5'-regulatory sequences were subject to an RNA expression analysis using reverse transcription and competitive PCR. Specimens of astrocytoma World Health Organisation (WHO) grade I-IV in 14 patients and control brain tissue obtained from three normal persons were studied. The main EAAT2 RNA was found to be equally expressed in normal human brain and astrocytic tumour samples. By contrast, the expression pattern of four 5'-variants of the transporter transcript was altered in the investigated series of astrocytoma compared with normal brain. HBGTII, HBGTIIC, and EAAT2/3 were amplified from seven and four tumours and one sample, respectively. EAAT2/31 was expressed in none of the tumour specimens studied. In conclusion, in astrocytic tumours of different histopathological grades there was a substantial reduction of RNA splicing events in EAAT2. The impairment of EAAT2 splicing indicates an altered expression which is not primarily involved in the tumorigenesis but may contribute to some biological properties of astrocytoma such as oedema, necrosis, and tumour related seizures.

Alternative Splicing↗
PubMed2000

Additive cytotoxic effect of cisplatin and X-irradiation on human glioma cell cultures derived from biopsy-tissue.

PURPOSE: Investigation of the in vitro cytotoxic effect of X-rays, either alone or combined with cisplatin on early passage cell cultures derived from human glioblastoma multiforme biopsy tissue. MATERIALS AND METHODS: Fresh tumour specimens from four patients were processed to cell cultures. The U373 glioma cell line was used as a reference. Early passage cell cultures were X-irradiated (0-8 Gy) either alone or in combination with cisplatin (0.5-1 microgram/ml). Cell survival was determined by either clonogenic assay or the colorimetric MTT assay. Survival curves were generated and mathematically analysed using the linear quadratic model, to obtain the radiosensitivity parameters alpha, beta, and SF2, i.e., the Surviving Fraction after 2 Gy. RESULTS: Two patient-derived glioma cell cultures and the U373 cell line showed rather high SF2 values of 0.61-0.72 in the clonogenic assay, indicating relative high radiation resistance. Cisplatin alone (1 microgram/ml) reduced cell survival by 10-30% (n = 4). When combined with irradiation, a clear additive cytotoxic effect of cisplatin was demonstrated by the unaltered value of the alpha-parameter for reproductive cell death. CONCLUSION: Cisplatin exerted an additive rather than radiosensitising cytotoxic effect in uncharacterised patient derived glioma cell cultures.

Adult↗
PubMed2000

Microsatellite instability and promoter methylation as possible causes of NF1 gene inactivation in neurofibromas.

Neurofibromatosis type 1 (NF1) is a frequent hereditary disorder. One of the characteristic features of this disease is the development of neurofibromas. Since the NF1 gene is supposed to be a tumour suppressor gene, these neurofibromas should develop upon inactivation of both NF1 alleles. So far, mutation and deletion have been found to be involved in NF1 gene inactivation. However, these inactivating mechanisms explain the development of only a limited fraction of analysed neurofibromas. In this study, we investigated microsatellite instability (MSI) and promoter methylation as potential contributors to NF1 gene inactivation. As site-specific methylation in the NF1 promoter inhibits binding of transcription factors Sp1 and CREB, we studied the methylation status of their binding sites in particular. We analysed 20 neurofibromas and three neurofibrosarcomas, but did not find evidence for microsatellite instability or NF1 promoter methylation in any of the tumours. Thus, our data suggest that both microsatellite instability and promoter methylation are unlikely to be the major causes of NF1 gene inactivation in these tumours.

Base Sequence↗
PubMed2000

Upregulation of metabotropic glutamate receptor subtype mGluR3 and mGluR5 in reactive astrocytes in a rat model of mesial temporal lobe epilepsy.

Reactive gliosis is a prominent morphological feature of mesial temporal lobe epilepsy. Because astrocytes express glutamate receptors, we examined changes in metabotropic glutamate receptor (mGluR) 2/3, mGluR5 and transforming growth factor (TGF)-beta in glial cells of the hippocampal regions in an experimental rat model of spontaneous seizures. Rats that exhibited behavioural status epilepticus (SE) directly after 1 h of electrical angular bundle stimulation, displayed chronic spontaneous seizures after a latent period of 1-2 weeks as observed using continuous electrographic monitoring. SE resulted in hypertrophy of astrocytes and microglia activation throughout the hippocampus as revealed by immunolabelling studies. A dramatic, seizure intensity-dependent increase in vimentin immunoreactivity (a marker for reactive astrocytes) was revealed in CA3 and hilar regions where prominent neuronal loss occurs. Increased vimentin labelling was first apparent 24 h after onset of SE and persisted up to 3 months. mGluR2/3 and mGluR5 protein expression increased markedly in glial cells of CA3 and hilus by 1 week after SE, and persisted up to 3 months after SE. Double immunolabelling of brain sections with vimentin confirmed co-localization with glial fibrillary acidic protein (GFAP), mGluR2/3 and mGluR5 in reactive astrocytes. TGF-beta, a cytokine implicated in mGluR3-mediated neuroprotection, was also upregulated during the first 3 weeks after SE throughout the hippocampus. This study demonstrates seizure-induced upregulation of two mGluR subtypes in reactive astrocytes, which - together with the increased production of TGF-beta - may represent a novel mechanism for modulation of glial function and for changes in glial-neuronal communication in the course of epileptogenesis.

Animals↗
PubMed1999

Nitric oxide synthase expression and apoptotic cell death in brains of AIDS and AIDS dementia patients.

OBJECTIVES: To determine the occurrence and cellular localization of inducible nitric oxide synthase (iNOS), NOS activity and its association with cell death in brains of AIDS and AIDS dementia complex (ADC) patients. DESIGN AND METHODS: Post-mortem cerebral cortex tissue of eight AIDS patients, eight ADC patients and eight control subjects was processed for iNOS immunocytochemistry, NADPH-diaphorase activity staining as an index of NOS activity, and in situ end-labelling to detect cell death. RESULTS: iNOS-positive cells were present in the white matter of 14 out of 16 AIDS and ADC patients, whereas two out of eight control subjects showed iNOS-positive cells. iNOS immunoreactivity was exclusively localized in activated macrophages and microglial cells that both showed NADPH-diaphorase activity. In addition, NADPH-diaphorase activity, not related to iNOS immunoreactivity, was observed in astrocytes in both white and grey matter of AIDS and ADC patients. All AIDS and ADC patients, and only one control subject showed characteristic features of apoptotic cell death. CONCLUSIONS: Different forms of NOS are present in microglial cells and astrocytes of AIDS and ADC patients but are largely absent in control subjects. Although more NOS-expressing cells occur in ADC than in AIDS patients, apoptotic cell death was found in both patient groups to the same extent. We postulate that NO production in brains of AIDS patients results in cumulative cortical cell loss, which becomes neurologically evident at later stages of disease and is expressed as ADC.

AIDS Dementia Complex↗