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Biomedical subjects

M L Schmidt

Publications and source records attributed to M L Schmidt.

At least 37 records · Page 2Linked to original sources
PubMed1999

Spatial relationship of AMY protein deposits and different species of Abeta peptides in amyloid plaques of the Alzheimer disease brain.

To further define the spatial relationship of "AMY" plaques detected by antibodies to an unidentified 100 kD AMY protein and amyloid plaques in Alzheimer disease (AD) brains, double immunofluorescence studies were performed with an anti-AMY antibody and a panel of antibodies to different species of Abeta peptides. We report substantial colocalization of AMY immunoreactive plaques with amyloid plaques labeled by antibodies to species of Abeta starting at position 3 with a pyroglutamate modified glutamic acid, however AMY immunoreactive deposits colocalized to a lesser degree with amyloid plaques labeled by antibodies to other variants of the Abeta peptide. Moreover, different immunohistochemical parameters influenced the extent to which colocalization of AMY deposits and Abeta immunoreactive plaques was demonstrable. We conclude that deposits of distinct species of Abeta peptides differentially colocalize with one another and with AMY plaques in the AD brain.

Aged↗
PubMed1998

Amyloid plaques in Guam amyotrophic lateral sclerosis/parkinsonism-dementia complex contain species of A beta similar to those found in the amyloid plaques of Alzheimer's disease and pathological aging.

The Guamanian amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) is characterized by abundant neurofibrillary pathology and neuron loss. In contrast to Alzheimer's disease (AD), where extensive neurofibrillary lesions always occur with deposits of A beta in numerous amyloid plaques, A beta-rich amyloid plaques are absent or rare in most ALS/PDC patients. To characterize the amyloid plaques in the latter patients, we probed plaque-rich sections of their brains by immunohistochemistry using well-characterized antibodies to specific epitopes in the N and C termini of A beta as well as to defined epitopes in hyperphosphorylated tau (PHFtau). The results indicate that the species of A beta in the amyloid plaques of ALS/PDC patients resemble those detected in the amyloid plaques of cognitively intact subjects with pathological aging as well as patients with AD. However, the paucity of PHFtau-positive neurites in the ALS/PDC plaques suggests that they reflect pathological aging rather than AD.

Aged↗
PubMed1998

Brain trauma induces massive hippocampal neuron death linked to a surge in beta-amyloid levels in mice overexpressing mutant amyloid precursor protein.

Although brain trauma is a risk factor for Alzheimer's disease, no experimental model has been generated to explore this relationship. We developed a model of brain trauma in transgenic mice that overexpress mutant human amyloid precursor protein (PDAPP) leading to the appearance of Alzheimer's disease-like beta-amyloid (Abeta) plaques beginning at 6 months of age. We induced cortical impact brain injury in the PDAPP animals and their wild-type littermates at 4 months of age, ie, before Abeta plaque formation, and evaluated changes in posttraumatic memory function, histopathology, and regional tissue levels of the Abeta peptides Abeta1-40 and Abeta1-42. We found that noninjured PDAPP mice had impaired memory function compared to noninjured wild-type littermates (P < 0.01) and that brain-injured PDAPP mice had more profound memory dysfunction than brain-injured wild-type littermates (P < 0.001). Although no augmentation of Abeta plaque formation was observed in brain-injured PDAPP mice, a substantial exacerbation of neuron death was found in the hippocampus (P < 0.001) in association with an acute threefold increase in Abeta1-40 and sevenfold increase in Abeta1-42 levels selectively in the hippocampus (P < 0.01). These data suggest a mechanistic link between brain trauma and Abeta levels and the death of neurons.

Amyloid beta-Peptides↗
PubMed1998

Lewy bodies contain altered alpha-synuclein in brains of many familial Alzheimer's disease patients with mutations in presenilin and amyloid precursor protein genes.

Missense mutations in the alpha-synuclein gene cause familial Parkinson's disease (PD), and alpha-synuclein is a major component of Lewy bodies (LBs) in sporadic PD, dementia with LBs (DLB), and the LB variant of Alzheimer's disease (AD). To determine whether alpha-synuclein is a component of LBs in familial AD (FAD) patients with known mutations in presenilin (n = 65) or amyloid precursor protein (n = 9) genes, studies were conducted with antibodies to alpha-, beta-, and gamma-synuclein. LBs were detected with alpha- but not beta- or gamma-synuclein antibodies in 22% of FAD brains, and alpha-synuclein-positive LBs were most numerous in amygdala where some LBs co-localized with tau-positive neurofibrillary tangles. As 12 (63%) of 19 FAD amygdala samples contained alpha-synuclein-positive LBs, these inclusions may be more common in FAD brains than previously reported. Furthermore, alpha-synuclein antibodies decorated LB filaments by immunoelectron microscopy, and Western blots revealed that the solubility of alpha-synuclein was reduced compared with control brains. The presence of alpha-synuclein-positive LBs was not associated with any specific FAD mutation. These studies suggest that insoluble alpha-synuclein aggregates into filaments that form LBs in many FAD patients, and we speculate that these inclusions may compromise the function and/or viability of affected neurons in the FAD brain.

Adult↗
PubMed1998

Successful management of concurrent congenital dyserythropoietic anaemia and autoimmune haemolytic anaemia with splenectomy.

This first known case of concurrent congenital dyserythropoietic anaemia (CDA) and autoimmune haemolytic anaemia (AIHA) which occurred in a hispanic male and spanned 6 years from the age of 2. Light and electron microscopy of bone marrow erythroblasts and immunophenotyping confirmed CDA; serum/eluate warm autoantibodies and positive direct antiglobulin tests (DAT) associated with severe, episodic anaemias established AIHA. Cytogenetic analysis of bone marrow cells and peripheral blood lymphocytes ascertained sex chromosome aneuploidy (48 XY,+ Y,+ Y). Recurrent, life-threatening episodes of transfusion-dependent anaemia refractory to steroids and intravenous immune globulin, were put into stable remission at age 8 years when splenectomy successfully managed both disorders.

Anemia, Dyserythropoietic, Congenital↗
PubMed1998

The neuropathology of a chromosome 17-linked autosomal dominant parkinsonism and dementia ("pallido-ponto-nigral degeneration").

A group of similar autosomal dominant hereditary neurodegenerative disorders have been linked to chromosome 17 in thirteen kindreds. One of these disorders, known as pallido-ponto-nigral degeneration (PPND), is characterized by extensive degeneration of the globus pallidus and substantia nigra as well as accumulation of abnormally phosphorylated tau proteins. The authors now present comprehensive data on the cellular and molecular pathology of PPND, allowing its classification among chromosome 17-linked neurodegenerative disorders as well as its classification among sporadic and other familial tauopathies. First, we showed that PPND is characterized by abundant ballooned neurons in neocortical and subcortical regions as well as by tau-rich inclusions in the cytoplasm of neurons and oligodendroglia morphologically similar to those seen in corticobasal degeneration (CBD), but in a distribution pattern resembling progressive supranuclear palsy (PSP). Second, we demonstrated that antibodies to phosphorylation-independent (Alz50, 133, 304, Tau-2, T-46) as well as phosphorylation-dependent (AT8, PHF-6, 12E8, PHF-1, T3P, pS422) epitopes in human tau proteins stain these glial and neuronal inclusions as intensely as they stain CBD or PSP inclusions. Third, we probed PPND brain by Western blots using some of the same anti-tau antibodies to reveal 2 tau immunobands with molecular weights of 69 kD and 64 kD in gray and white matter extracts, as reported for both PSP and CBD. Finally, electron microscopy showed that these abnormal tau proteins formed flat twisted ribbons with a maximum diameter of 20 nanometers (nm) and a periodicity of about 200 nm, resembling those reported in CBD. Based on this, we conclude that PPND is a hereditary neurodegenerative disorder characterized by neuronal and glial tau-rich inclusions formed from aggregated filaments and hyperphosphorylated tau proteins and, hence, can be subcategorized into the tauopathy group of chromosome 17-linked neurodegenerative disorders. Further, since the morphologic and biochemical lesions of PPND overlap with those seen in sporadic CBD and PSP, we speculate that these disorders share common pathogenetic mechanisms.

Adult↗
PubMed1997

Autosomal dominant dementia with widespread neurofibrillary tangles.

Several familial dementing conditions with atypical features have been characterized, but only rarely is the neuropathology dominated solely by neurofibrillary lesions. We present a Midwestern American pedigree spanning four generations in which 15 individuals were affected by early-onset dementia with long disease duration, with an autosomal dominant inheritance pattern, and with tau-rich neurofibrillary pathology found in the brain post mortem. The average age at presentation was 55 years with gradual onset and progression of memory loss and personality change. After 30 years' disease duration, the proband's neuropathologic examination demonstrated abundant intraneuronal neurofibrillary tangles (NFTs) involving the hippocampus, pallidum, subthalamic nucleus, substantia nigra, pons, and medulla. Only sparse neocortical tangles were present and amyloid plaques were absent. The tangles were recognized by antibodies specific for phosphorylation-independent (Tau-2, T46, 133, and Alz-50) and phosphorylation-dependent epitopes (AT8, T3P, PHF-1, 12E8, AT6, AT18, AT30) in tau proteins. Electron microscopy of NFTs in the dentate gyrus and midbrain demonstrated paired helical filaments. Although the clinical phenotype resembles Alzheimer's disease, and the neuropathologic phenotype resembles progressive supranuclear palsy, an alternative consideration is that this familial disorder may be a new or distinct disease entity.

Age of Onset↗
PubMed1997

Monoclonal antibodies to purified cortical Lewy bodies recognize the mid-size neurofilament subunit.

Lewy bodies (LBs) are filamentous intraneuronal inclusions that are hallmark lesions of Parkinson's disease, and LBs have been shown, by immunohistochemistry, to contain cytoskeletal as well as other cellular proteins. Similar LBs also occur in the cortical neurons of a subset of patients with Alzheimer's disease (AD), and cortical LBs are the predominant or sole lesions in the brains of patients with an AD-like dementia known as diffuse Lewy-body disease (DLBD). To gain insight into the biochemical composition of LBs, we generated monoclonal antibodies (mAbs) to LBs purified from the brains of patients with DLBD. Here, we describe three of these new mAbs (LB48, LB202, and LB204) that stained LBs by immunohistochemistry and recognized the medium molecular mass neurofilament (NF) protein in western blots. These results support the hypothesis that NF subunits are integral components of LBs. Continued efforts to clarify the composition of LBs are likely to lead to novel strategies for the antemortem diagnosis of LB disorders as well as to insight into the role LBs play in the degeneration of affected neurons in these disorders.

Antibodies, Monoclonal↗
PubMed1997

Evidence that the MYCN oncogene regulates MRP gene expression in neuroblastoma.

We have recently shown that expression of the multidrug resistance-associated protein (MRP) gene is a powerful prognostic indicator in childhood neuroblastoma and have suggested that the MYCN oncogene may regulate MRP gene expression. To address this hypothesis, we have examined the relationship between MYCN and MRP gene expression in neuroblastoma tumours and cell lines. MYCN and MRP gene expression were highly correlated in 60 primary untreated tumours both with (P = 0.01) and without MYCN gene amplification (P < 0.0001). Like MRP, high MYCN gene expression was significantly associated with reduced survival, both in the overall study population and in older children without MYCN gene amplification (relative hazards = 13.33 and 19.61, respectively). Inhibition of MYCN, through the introduction of MYCN antisense RNA constructs into human neuroblastoma cells in vitro, resulted in decreased MRP gene expression, determined both by RNA-PCR and Western analysis. The data are consistent with MYCN influencing neuroblastoma outcome by regulating MRP gene expression.

Age Factors↗
PubMed1997

Betulinic acid induces apoptosis in human neuroblastoma cell lines.

Neuroblastoma has long been recognized to show spontaneous regression during fetal development and in the majority of stage 4s infants < 1 year of age with disseminated disease. Stage 4s disease regresses with no chemotherapy in 50% of the patients. The mechanism by which this occurs is not understood but may be programmed cell death or apoptosis. Betulinic acid (BA) has been reported to induce apoptosis in human melanoma with in vitro and in vivo model systems. Melanoma, like neuroblastoma, is derived from the neural crest cell. We hypothesised that neuroblastoma cells have the machinery for programmed cell death and that apoptosis could be induced by betulinic acid. Nine human neuroblastoma cell lines were treated in vitro with BA at concentrations of 0-20 micrograms/ml for 0-6 days. Profound morphological changes were noted within 3 days. Cells withdrew their axonic-like extensions, became non-adherent and condensed into irregular dense spheroids typical of apoptotic cell death (ED50 = 14-17 micrograms/ml). DNA fragmentation analysis showed ladder formation in the 100-1200 bp region in 3/3 neuroblastoma cell lines treated with BA for 24-72 h. Thus, apparently BA does induce AP in neuroblastoma in vitro. This model will be utilised to investigate the role of apoptosis-related genes in neuroblastoma proliferation and to determine the therapeutic efficacy of BA in neuroblastoma in vivo.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Modulation of N-myc expression alters the invasiveness of neuroblastoma.

N-myc oncogene expression plays a pivotal role in the biology of neuroblastoma, a common childhood tumor. High N-myc expression is associated with advanced disease stage, and in animal models, increased expression results in increased metastatic potential. In normal embryologic development, N-myc expression is associated with neuroblast migration out from the neural crest. To further define the relationship between N-myc and metastasis, an in vitro assay was adapted to measure tumor cell attachment, motility, and proteolytic ability in neuroblastoma cell lines. These parameters were examined in a non-amplified, uniformly N-myc overexpressing cell line and its anti-sense N-myc expressing clones. These lines have been characterized previously, and have a decrease in N-myc expression, growth rate, and tumorigenicity relative to the parent line and vector-only control transfectant. Decrease in N-myc expression resulted in a non-proportional increase of tumor cell attachment, and a proportional decrease in both tumor cell motility and proteolytic ability. In further experiments, assay of a N-myc-amplified overexpressing cell line with an intrinsic heterogeneous pattern of expression demonstrated that motile cells expressed higher amounts of N-myc relative to the general population. Together these relationships indicate that N-myc plays a causative role in the invasive phenotype, and suggest that metastasis may, in part, result from the disruption of a developmentally important normal process.

Cell Adhesion↗
PubMed1997

Monoclonal antibodies to a 100-kd protein reveal abundant A beta-negative plaques throughout gray matter of Alzheimer's disease brains.

Here we describe the initial characterization of a 100-kd protein recognized by four new monoclonal antibodies that reveal abundant and unique plaque-like lesions throughout gray matter of Alzheimer's disease brains. This 100-kd protein and these new plaque-like lesions were identified by four monoclonal antibodies raised to immunogens extracted from Alzheimer's disease neurofibrillary abnormalities. However, these antibodies did not recognize hyperphosphorylated tau in Western blots or neurofibrillary lesions by immunohistochemistry. As all of these antibodies displayed similar properties, one, AMY117, was used to characterize the new plaque-like lesions in detail. These studies demonstrated that AMY117-positive plaques were not visualized by amyloid stains and never co-localized with A beta deposits, although AMY117-positive and A beta-positive lesions frequently occurred in the same cortical and subcortical gray matter regions. Abundant AMY117-positive plaques were found in the brains of all 32 sporadic Alzheimer's disease patients and all 6 elderly Down's syndrome subjects. Although AMY117-positive plaques also were seen in the brains of nondemented patients with numerous A beta deposits. AMY117-positive plaques were rare or absent in the brains of other elderly controls and patients with other neurodegenerative or neuropsychiatric disorders. We conclude that the AMY117-positive plaques described here for the first time are major lesions of the Alzheimer's disease brain. Thus, it will be important to elucidate the role played by the 100-kd protein and the AMY117 plaques in the etiology and pathogenesis of Alzheimer's disease.

Aged↗
PubMed1997

Desmoplastic infantile astrocytoma with metastases at presentation.

A 4-month-old child presented with nystagmus and macrocephaly. He had a large tumor in the suprasellar and hypothalamic region, as well as two smaller similar masses in the posterior fossa and one in the spinal canal. A biopsy of the suprasellar mass revealed it to be a desmoplastic infantile cerebral astrocytoma. Cerebrospinal fluid obtained at surgery before tumor manipulation showed clusters of malignant cells immunopositive for glial fibrillary acidic protein. In our opinion, the smaller tumors were metastases from the large suprasellar primary astrocytoma. Review of all of the previously reported cases of desmoplastic infantile cerebral astrocytoma and of the related neoplastic entity desmoplastic infantile ganglioglioma suggested that this was a unique case, but we still recommend caution with respect to the previously accepted notion that desmoplastic infantile neuroepithelial tumors are virtually benign neoplasms.

Astrocytoma↗
PubMed1996

Convergence of Lewy bodies and neurofibrillary tangles in amygdala neurons of Alzheimer's disease and Lewy body disorders.

Amygdalae of patients with Alzheimer's disease (AD), Parkinson's disease, Down's syndrome, diffuse Lewy body disease or a combination of these diseases were probed with antibodies to neurofilament proteins as well as with Lewy body (LB)- and paired helical filament-specific antibodies. The results indicate that the amygdala is severely affected by the accumulation of both neurofibrillary tangles (NFTs) and LBs in most cases of the diseases mentioned above, and that amygdala LBs have a similar epitope composition to that of LBs in the brain stem and cerebral cortex. While large numbers of both LBs and NFTs were seen in different neurons within the amygdala, these two lesions frequently occurred together in the same neurons of the amygdala. These findings are in contrast to other sites that accumulate LBs and NFTs, but rarely both lesions in the same neuron. Thus, amygdala neurons may be selectively vulnerable to developing both LBs and NFTs, and these inclusions may play a role in the massive degeneration of these neurons in AD and LB disorders of the elderly.

Aged↗
PubMed1996

Neurofibrillary tangles in progressive supranuclear palsy contain the same tau epitopes identified in Alzheimer's disease PHFtau.

Neurofibrillary tangle (NFT)-rich brain samples from patients with progressive supranuclear palsy (PSP) or Alzheimer's disease (AD) were probed with a large panel of anti-tau antibodies to compare the species of tau present in PSP and AD NFTs by immunohistochemistry and Western blot methods. These antibodies have been shown to recognize phosphate-independent or -dependent epitopes that extend from the amino to the carboxy terminal domains of normal brain tau and the abnormal tau in the paired helical filaments (PHFs) of AD NFTs (PHFtau). The immunohistochemical studies showed that all of the tau epitopes detected in brainstem PSP NFTs also were found in hippocampal AD NFTs and vice versa. While Western blots demonstrated 2 PHFtau-like immunobands in PSP brainstem, a triplet of PHFtau proteins were seen in the AD and PSP hippocampus. Despite differences in the distribution, ultrastructure and immunoblot profile of NFTs in PSP and AD, the same constellation of tau epitopes is present in the abnormal tau proteins in PSP and AD NFTs. Thus, the generation of abnormal tau proteins in PSP (PSPtau) and AD (PHFtau) may have similar adverse biological consequences in both diseases.

Aged↗
PubMed1996

Identification of phosphorylation sites in PHF-TAU from patients with Guam amyotrophic lateral sclerosis/parkinsonism-dementia complex.

Guam Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex (Guam ALS/PDC) is a progressive neurodegenerative disorder characterized by abundant neurofibrillary tangles (NFTs) composed of aggregated paired helical filaments (PHFs). These abnormal filaments resemble the PHFs in neurofibrillary lesions of classic Alzheimer's disease (AD), and recent studies demonstrated that tau in Guam ALS/PDC is aberrantly phosphorylated and biochemically similar to the abnormal tau proteins (PHFtau) in classic AD. However, unlike PHFtau in AD, there is little information on the specific sites of phosphorylation in PHFtau from Guam ALS/PDC. Thus, to address this important issue, we examined tangle-rich Guam ALS/PDC and AD brains by Western blot, immunoelectron microscopy and immunohistochemistry using 13 antibodies to defined phosphate-dependent or -independent epitopes distributed throughout AD PHFtau. These studies identified 7 previously unknown sites of phosphorylation in PHFtau from Guam ALS/PDC (i.e. Thr181, Thr231, Ser262, Ser396, Ser404, Ser422, and the site defined by monoclonal antibody AT10), all of which also are found in AD PHFtau. Indeed, the Western blot, light and immunoelectron microscopic data suggest that NFTs, PHFs and PHFtau in Guam ALS/PDC are very similar to their counterparts in classic AD. Thus, insights into mechanisms leading to the accumulation of neurofibrillary lesions in Guam ALS/PDC may advance understanding of the pathogenesis and biological consequences of these lesions in classic AD.

Aged↗