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Biomedical subjects

H Lassmann

Publications and source records attributed to H Lassmann.

At least 163 records · Page 9Linked to original sources
PubMed1994

The cyclooxygenase and lipoxygenase inhibitor BW755C protects rats against kainic acid-induced seizures and neurotoxicity.

In this study the effect of the anti-inflammatory drugs indomethacin, ibuprofen, ebselen (PZ 51, 2-phenyl-1,2-benzoisoselenazol-3(2H)-one), and BW755C (3-amino-1-(m-(trifluoromethyl-phenyl)-2-pyrazoline) on kainic acid (KA)-induced behavioral and neurochemical changes in rats was investigated. Rats injected with KA (10 mg/kg s.c.) developed seizure activity with a 20% mortality within the first 4 h and neuronal degeneration in the limbic system after 3 days. Pretreatment with the cyclooxygenase inhibitor indomethacin (10 mg/kg i.p.) augmented KA-induced epileptic activity and increased the mortality in status epilepticus to 80%. Another cyclooxygenase inhibitor, ibuprofen (20 mg/kg i.p.), and the lipoxygenase inhibitor ebselen (20 mg/kg i.p.) showed no effect on KA-induced symptoms and neurochemical changes. Application of the cyclooxygenase/lipoxygenase inhibitor BW755C (40 mg/kg i.p.) reduced the severity of seizures and protected significantly from irreversible brain lesions induced by KA. The marked reduction of glutamate decarboxylase (GAD; 53.3 +/- 12.2% of control) and choline acetyltransferase (ChAT; 60.9 +/- 9.1% of control) activities in amygdala/pyriform cortex and GAD activity in hippocampus (69.4 +/- 5.6% of control) observed 3 days after KA injection was abolished by BW755C treatment. Histopathological analyses of brain tissue showed that treatment with BW755C prevented the KA-induced nerve cell degeneration, edema, hemorrhages, and tissue necrosis in amygdala/pyriform cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1994

Oligodendrocytes in the early course of multiple sclerosis.

The neuropathology of demyelinating lesions in multiple sclerosis was studied in specimens obtained by diagnostic needle biopsy during early stages of the disease. The lesions were characterized by a chronic inflammatory reaction dominated by lymphocytes and macrophages, plaque-like demyelination, and astroglial sclerosis. Oligodendrocytes within the lesions were studied by immunocytochemistry using antibodies against various myelin and oligodendroglia components. The expression of messenger RNA for proteolipid protein was determined by in situ hybridization. Our studies revealed that myelin-oligodendrocyte glycoprotein is a sensitive and reliable marker for identification of oligodendrocytes in demyelinated plaques. The results suggest that in the early course of the disease in some patients, oligodendrocytes may largely be preserved, whereas in others oligodendroglial loss is pronounced. Loss of oligodendrocytes was only marginally related to the stage of demyelinating activity within the lesions. These findings indicate that the pathogenesis of demyelination may vary within different multiple sclerosis patients.

Adolescent↗
PubMed1994

Histopathology and the blood-cerebrospinal fluid barrier in multiple sclerosis.

Histopathology of multiple sclerosis is defined by a chronic inflammatory process and the presence of large confluent plaques of demyelination. Ongoing disease activity is due to an active inflammatory process, mainly mediated by T lymphocytes and macrophages, and is associated with blood-brain-barrier damage. B lymphocytes and plasma cells are present especially in the lesions that occur during the late chronic stage of the disease. Although all plaques are characterized by demyelination, the patterns of oligodendroglia destruction and of damage to other tissue elements, such as axons and astrocytes, are variable in different cases. Oligodendrocytes are less affected by plaques that develop during the first bouts of the disease than by those plaques arising after several years of disease duration. Our data indicate that mechanisms of plaque formation may vary in different multiple sclerosis patients and in different stages of the disease process.

Acute Disease↗
PubMed1994

Animal models.

Different models of experimental autoimmune encephalomyelitis (EAE) have been successfully applied to investigate and manifold aspects of the autoimmune pathogenesis of multiple sclerosis. Studies using myelin-specific T-cell lines that transfer EAE to naive recipient animals established that only activated lymphocytes are able to cross the endothelial blood-brain barrier and cause autoimmune disease within the local parenchyma. All encephalitogenic T cells are CD4+ Th1-type lymphocytes that recognize autoantigenic peptides in the context of MHC class II molecules. In the case of myelin basic protein (MBP) specific EAE in the Lewis rat, the T-cell response is directed against one strongly dominant peptide epitope. The encephalitogenic T cells preferentially use one particular set of T-cell receptor genes. Although MBP is a strong encephalitogen in many species, a number of other brain protein are now known to induce EAE. These include mainly myelin components (PLP, MAG, and MOG), but also, the astroglial S-100 beta protein. Encephalitogenic T cells produce only inflammatory changes in the central nervous system, without extensive primary demyelination. Destruction of myelin and oligodendrocytes in these models requires additional effector mechanisms such as auto-antibodies binding to myelin surface antigens such as the myelin-oligodendrocyte glycoprotein.

Animals↗
PubMed1994

Expression and developmental regulation of Ehk-1, a neuronal Elk-like receptor tyrosine kinase in brain.

Protein tyrosine kinases are pivotal in central nervous tissue development and maintenance. Here we focus on the expression of Ehk-1, a novel Elk-related receptor tyrosine kinase. Ehk-1 gene expression is observed in the developing and adult central nervous system and is highly regulated throughout development at both the messenger RNA and protein levels. Three messenger RNA transcripts of 8.5, 5.9 and 5.1 kb are detectable in the rat brain and a variety of splice possibilities have been identified. However, a major protein species of around M(r) 120,000 predominates throughout development. Ehk-1 messenger RNA and protein levels are highest in the first postnatal week. By in situ messenger RNA hybridization the gene is expressed by all neurons of the adult brain, but mostly in the hippocampus, cerebral cortex and large neurons of the deep cerebellar nuclei, as well as the Purkinje and granular cells of the cerebellum. At earlier stages of development, transcripts are most prominent in the periventricular germinal layers of the brain. Immunohistochemistry reveals a pronounced membrane associated protein expression in immature neurons. In the adult animal, peak reactivity was found in the neuropil with sparing of most perikarya. The spatial and temporal pattern of ehk-1 gene expression suggests a role in both the development and maintenance of differentiated neurons of the central nervous system.

Amino Acid Sequence↗
PubMed1994

Patterns of oligodendroglia pathology in multiple sclerosis.

Patterns of inflammation, demyelination and oligodendrocyte pathology were studied in acute multiple sclerosis and during early and late exacerbations of chronic multiple sclerosis. Cells within lesions were identified by immunocytochemistry with markers for T lymphocytes, macrophages, oligodendrocytes and astrocytes. In addition, in situ hybridization for proteolipid protein mRNA was used to identify myelinating and myelin supporting oligodendrocytes. Degenerating cells in the lesions were detected by DNA fragmentation in cell nuclei. The inflammatory reaction in all three types of multiple sclerosis lesions was shown to be dominated by T lymphocytes and macrophages. In late chronic multiple sclerosis lesions, a significant increase in the number of immunoglobulin producing plasma cells was found in infiltrates as compared with acute and early multiple sclerosis lesions. In all three types of multiple sclerosis, confluent plaques of demyelination were found to be present. In acute multiple sclerosis, demyelination was found to be associated with extensive destruction of other tissue elements, including oligodendrocytes, astrocytes and axons, but even in these destructive lesions a considerable number of oligodendrocytes was preserved and at disposal therefore, for rapid remyelination. During early exacerbations of chronic multiple sclerosis, selective demyelination was associated with almost complete preservation of oligodendrocytes in the majority of cases. Correspondingly, a high number of remyelinating lesions was present at that stage of disease. In lesions developing late after onset of multiple sclerosis, demyelination generally accompanied extensive destruction and loss of oligodendrocytes. In these lesions, remyelination was sparse and restricted to lesional borders. The observed patterns of cell death suggest that in some cases oligodendrocytes, in others myelin sheaths are the primary target of the destructive process. Our data indicate that the type and amount of inflammation, de- and remyelination, and of tissue damage vary between different forms of multiple sclerosis and between different stages of the disease, possibly reflecting different pathogenic mechanisms in a disease spectrum.

Adult↗
PubMed1994

Differential expression of ICAM-1, VCAM-1 and their ligands LFA-1, Mac-1, CD43, VLA-4, and MHC class II antigens in murine Toxoplasma encephalitis: a light microscopic and ultrastructural immunohistochemical study.

Light microscopic and ultrastructural immunohistochemistry of cell adhesion molecules (CAMs) and major histocompatibility class II antigens (Ia) expression in experimental murine Toxoplasma encephalitis (TE) revealed a prominent upregulation of the intercellular cell adhesion molecule-1 (ICAM-1) and of Ia on cerebral endothelia, microglia, ependyma, and choroid plexus epithelium during acute and chronic TE. Microglia also expressed Mac-1 and leukocyte function-associated antigen-1 (LFA-1), which are both ligands of ICAM-1, as well as CD45. The prominent simultaneous expression of a multitude of these molecules on microglia is indicative of a central immunologic function of this cell type in TE. Additionally, occasional astrocytic processes slightly expressed Ia in full-blown TE. The vascular cell adhesion molecule-1 (VCAM-1) was restricted to endothelia of cerebral blood vessels, which frequently showed perivascular cuffing of inflammatory cells, ependyma, and choroid plexus epithelium. Upregulation of Ia, CAMs and their ligands correlated with disease activity. Immunohistochemical analysis of the functional state of infiltrating T cells showed a preferential recruitment of CD44+ memory and activated interleukin-2R+ T cells in TE.

Animals↗
PubMed1994

Contra: evidence against a primary lesion in the target organ in autoimmune disease.

We discuss evidence suggesting that autoreactive T cell clones are components of the normal immune repertoire. Since these lymphocytes reach the brain only in the activated state, activation must take place outside of the target tissue. Within the brain, most of the autoimmune T cells undergo apoptosis rather than further proliferation.

Animals↗
PubMed1994

Distribution of immunoglobulins in squamous cell carcinoma of the head and neck.

The immune response with respect to immunoglobulin production in the tumor was investigated in 23 patients with advanced squamous cell carcinomas of the head and neck. Immunohistochemical staining with monoclonal antibodies against IgG, IgM, IgA, IgD and IgE in the tumor was compared to normal hypopharyngeal mucosa. For IgG, IgA and IgM no significant differences between tumor and control tissues could be found. In contrast, a high number of IgE-positive cells was counted in most squamous cell carcinomas compared to normal mucosa. Most of these cells appeared as plasma cells. Regarding IgD the differences between tumor and control tissues, were less pronounced but also significant.

Carcinoma, Squamous Cell↗
PubMed1994

Differentiation between cellular apoptosis and necrosis by the combined use of in situ tailing and nick translation techniques.

BACKGROUND: A number of enzymatic techniques have recently been developed to detect DNA fragmentation in apoptosis at the cellular level. However, since DNA fragmentation also occurs in cellular necrosis, we studied to which extent the use of DNA polymerase (nick translation) or terminal transferase (tailing) allows the differentiation between internucleosomal DNA degradation, typical for apoptosis, and the more random DNA destruction in necrosis. EXPERIMENTAL DESIGN: We compared these techniques on in vitro and in vivo models for apoptotic or necrotic cell death. Apoptosis of thymocytes in vitro was induced by gamma-irradiation, necrosis by the cytotoxic action of antibody and complement. Cell death in vivo was examined on paraffin-embedded tissue material from animals with autoimmune encephalomyelitis that served as a model for apoptosis, or in kainic acid-induced nerve cell degeneration as a model for necrosis. RESULTS: DNA fragmentation was visualized by the incorporation of labeled nucleotides into the nuclei of affected cells utilizing tailing or nick translation techniques. In the early stages of cell degeneration in vitro, cells undergoing apoptosis were preferentially labeled by tailing, whereas necrotic cells were identified by nick translation. Similarly, early stages of necrosis in vivo were preferentially detected by nick translation, whereas tailing was slightly more sensitive for the detection of apoptosis. Results obtained with these enzymatic techniques were in accord with the assessment of cell death by morphologic criteria. Both techniques could be applied in tissue samples even after prolonged fixation in paraformaldehyde if the sections were pretreated with proteinase K digestion. CONCLUSIONS: Our studies show that both in situ nick translation and in situ tailing are useful in detecting DNA fragmentation in cell suspensions and tissue sections. These techniques may help to define the molecular mechanisms leading to cell death in experimental conditions and eventually in human tissue.

Animals↗
PubMed1993

Synaptic pathology of Alzheimer's disease.

Prospective clinico-pathological studies on dementia in Alzheimer's disease (AD), performed during the past decades, revealed a relatively poor correlation between the degree of clinical deficit and the severity of the typical neuropathological lesions of AD, the amyloid plaques and the neurofibrillary tangles. More recent data, obtained by electron microscopy, immunocytochemical as well as immunochemical techniques indicate that synaptic loss may be a better structural correlate of dementia than other brain lesions. Synaptic pathology is reflected by a loss of all major components of small synaptic vesicles and most peptides, stored in large dense cored vesicles. The significant increase of chromogranin A proprotein, a major component of large dense cored vesicles, may rather represent a defect of protein processing than preservation of a specific synaptic subpopulation. Within the brain of AD patients, the degree of synaptic loss is uneven. Most prominent reduction of synapses is found in the outer parts of the dentate gyrus molecular layer, possibly reflecting the destruction of neurons, located in the layer 2 of the entorhinal cortex. However, within the neocortex, no preferential loss of synapses in any of the cortical layers has been found. Cerebral amyloid deposition in diffuse plaques has little effect on synapse density and structure. However, within the dense amyloid core of a classical plaque, synapses are completely lost. In the surrounding neuritic portion of the plaques, synaptophysin reactivity is frequently increased, due to enlargement of synaptic boutons and to accumulation of synaptophysin in dystrophic axons. Although the reason for synapse loss in AD is yet unknown, most results suggest that it may reflect degeneration of neurons, projecting into the respective cortical areas.

Alzheimer Disease↗
PubMed1993

Inhibition of experimental autoimmune encephalomyelitis by an antibody to the intercellular adhesion molecule ICAM-1.

Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by active immunization with myelin from guinea pig spinal cord by the encephalitogenic myelin basic protein or by adoptive transfer using myelin basic protein-specific CD4-positive T cells. Treatment with purified monoclonal antibody (1A-29) to the intercellular adhesion molecule-1 and its F(ab')2 fragments efficiently suppressed active EAE. Control treatment with an irrelevant antibody or saline did not alter the course of the disease. Histological sections of the central nervous system showed a pronounced reduction of inflammatory infiltrates during treatment with antibody to intercellular adhesion molecule-1. In the adoptive transfer model of EAE, 1A-29 had only a minor effect. Proliferation assays on lymph node cells ex vivo from 1A-29- and saline-treated animals were performed. Administration of 1A-29 suppressed antigen-specific T-cell proliferation. The differential effects in EAE versus adoptive transfer EAE suggest that 1A-29 acts predominantly on the induction phase of the immune response and, to a lesser extent, on the transendothelial migration of T cells. We conclude that intercellular adhesion molecule-1-dependent pathways are critically involved in the pathogenesis of EAE and that antibodies to leukocyte adhesion molecules could be a novel therapeutic approach to autoimmune disease of the central nervous system.

Animals↗
PubMed1993

T cells specific for the myelin oligodendrocyte glycoprotein mediate an unusual autoimmune inflammatory response in the central nervous system.

Myelin oligodendrocyte glycoprotein (MOG)-specific T cells mediate an autoimmune inflammatory response in the central nervous system (CNS) that differs radically from conventional models of T cell-mediated experimental allergic encephalomyelitis (EAE). Using synthetic peptides an encephalitogenic T cell epitope of MOG for the Lewis rat was identified within the extracellular IgG V-like domain of the protein, amino acids 44-53 (FSRVVHLYRN). The adoptive transfer of CD4+ T cells specific for this epitope induce an intense, dose-dependent inflammatory response in the CNS of naive syngeneic recipients. However, unlike the inflammatory response induced by myelin basic protein (MBP)-specific T cell lines, inflammation mediated by the MOG peptide-specific T cells failed to induce a gross neurological deficit. This unexpected observation was not due to a reduction in the overall inflammatory response in the CNS, but was specifically associated with a decrease in the extent of parenchymal (as opposed to perivascular) inflammation, a selective decrease in the number of ED1+ macrophages infiltrating the CNS, and a total lack of peripheral nerve inflammation. The decreased recruitment of macrophages into the CNS could not be ascribed to deficiencies in the synthesis of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-6 or IL-2 by the T cell line. Moreover, this sub-clinical inflammatory response induced severe blood-brain barrier dysfunction as demonstrated by the induction of severe clinical disease following intravenous injection of a demyelinating MOG-specific monoclonal antibody. The neurological deficit in EAE thus exhibits an unexpected dependence on the identity of the target autoantigen, which determines the extent and nature of the local inflammatory response and ultimately the extent of the neurological deficit.

Amino Acid Sequence↗
PubMed1993

Bone marrow derived elements and resident microglia in brain inflammation.

Infection of the central nervous (CNS) system by the human immunodeficiency virus (HIV) depends on the migration of infected hematogenous cells into the brain. We thus used quantitative light and electron microscopic immunocytochemistry to study the homing and turnover of bone marrow derived cells in the CNS in radiation bone marrow chimeras under normal conditions and in experimental autoimmune encephalomyelitis (EAE) as an experimental model of brain inflammation. Our studies suggest the following conclusions. First, the central nervous system is continuously patrolled by a small number of T-lymphocytes and monocytes. Meningeal and perivascular monocytes are slowly replaced by hematogenous cells under normal conditions, and this turnover is accelerated in the course of inflammation. In contrast, resident microglia represent a very stable cell pool, which in adult animals is only exceptionally replaced by hematogenous cells, even after recovery from severe brain inflammation. Second, although in bone-marrow-chimeric animals resident microglia, astrocytes, and ependymal cells are not able to present antigen to Lewis T-lymphocytes, the inflammatory reaction in EAE is qualitatively and quantitatively similar in these animals compared to fully histocompatible Lewis rats. Finally, resident microglia express the macrophage activation antigen ED1. Thus, microglia cells appear to function as effector cells in EAE lesions.

Animals↗
PubMed1993

Uncommon types of polyglucosan bodies in the human brain: distribution and relation to disease.

The significance of the development of polyglucosan bodies (PBs) in the CNS is incompletely understood. We present the clinicopathological features of three autopsy cases with numerous PBs other than the common corpora amylacea or Lafora bodies. The first patient had pleomorphic PBs in the neuronal processes of pallidum and substantia nigra which, thus, are consistent with Bielschowsky bodies. Bielschowsky bodies involved also the hypothalamus and tegmentum of midbrain and medulla. The present case was the first not associated with any clinical symptoms. The second patient also had incidental Bielschowsky bodies in the external pallidum, substantia nigra, and pallidothalamic, pallidonigral and nigrostriatal tracts. Additionally, unique clusters of small PBs appeared in the cerebral cortex, putamen, pallidum, and caudate nucleus. Immunostaining suggested that these small clustered PBs were located in the cytoplasm and processes of astrocytes. Ultrastructurally, these clustered PBs were in agreement with previous descriptions of PBs. The third patient had adult polyglucosan body disease. Most PBs in the white matter were corpora amylacea situated in astrocytic processes or axons. In the gray matter, many pleomorphic PBs resembling Bielschowsky bodies occurred in neuronal processes. In the peripheral nervous system, a few PBs were seen in myelinated axons.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Magnetic resonance imaging investigation of blood-brain barrier damage in adoptive transfer experimental autoimmune encephalomyelitis.

Recent advances in fast magnetic resonance imaging (MRI) techniques have allowed quantification of parameters such as T1 relaxation time, which can be modified by changes in the water content of a tissue. We have used this new method to study the evolution of blood-brain barrier (BBB) changes after adoptive transfer of MBP-specific (AT-EAE) and ovalbumin-specific T cell lines in Lewis rats. Measurable changes in T1 relaxation time suggesting widespread increase in BBB permeability were found, starting on day 3 post inoculation (p.i.), in the midbrain and brainstem of AT-EAE rats. In addition, we noted a significant decrease in T1 relaxation time before injection of a paramagnetic agent, in the cisternal cerebrospinal fluid (CSF) of diseased animals, starting on day 5 p.i. In vitro measurement of T1 in CSF containing various concentrations of albumin, IgM and glucose showed that, at physiological concentrations, a T1 decrease is mainly associated with an increase in albumin concentration. A moderate increase in BBB and blood-CSF barrier permeability was found as early as 4-8 h p.i., in rats injected with MBP-specific as in animals injected with ovalbumin-specific T cell lines, suggesting a non-specific mechanism. Experimental MRI may become a powerful tool to sequentially analyse changes in barrier dynamics, for example following pharmacological intervention.

Animals↗
PubMed1993

Detection of DNA fragmentation in apoptosis: application of in situ nick translation to cell culture systems and tissue sections.

Since DNA fragmentation is a key feature of programmed cell death (PCD) and also occurs in certain stages of necrosis, we have adapted the methodology of in situ nick-translation (ISNT) to detect DNA fragmentation on a single-cell level. We first established the technique for cell preparations. Apoptosis was induced by gamma-irradiation on freshly isolated rat thymocytes. After fixation procedures, ISNT was performed by overnight incubation either with fluorescein-12-dUTP or with digoxigenin-labeled 11-dUTP and DNA polymerase I. The enzymatic incorporation of labeled nucleotides at sites of DNA fragmentation was detected by flow cytometry either directly or indirectly with fluorescein-conjugated anti-digoxigenin. The quantitative results demonstrated close correlation with morphological essays for apoptosis, DNA gel electrophoresis, and ISNT. Proliferating cells determined by bromodeoxyuridine immunofluorescence were not labeled by ISNT. Immunocytochemistry for cell surface antigens in combination with ISNT allowed the identification of specific cell types undergoing PCD. Furthermore, the simultaneous application of photolabeling techniques with ethidium monoazide and ISNT led to the identification of DNA fragmentation in cells with still intact membranes. Extending ISNT to tissue sections of paraformaldehyde-fixed, paraffin-embedded material reliably revealed labeling of cells with typical morphological features of apoptosis. However, this technique was not useful in detecting early stages of necrotic cell death.

Animals↗