Biomedical subjects

Peter T Nelson

Publications and source records attributed to Peter T Nelson.

15 recordsLinked to original sources

PubMed2026

GRN rs5848 variant associates with TDP-43 pathology and cancer in opposite directions.

Epidemiologic studies have reported that cancer survivors have a relatively low risk of developing dementia, but the mechanisms underlying that inverse relationship are mostly unknown. The Granulin (GRN) gene single nucleotide variant rs5848 T allele is associated with increased risk of limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) and hippocampal sclerosis of aging (HS-Aging). The T allele is also associated with lower expression of the cognate protein progranulin (PGRN), which is a mitogen implicated in neoplasia. We examined whether the rs5848 variant associated with LATE-NC/HS-Aging pathology and cancer in the same cohort. This study leveraged genotype data from the Alzheimer's Disease Genomics Consortium (n = 8121) and the Alzheimer's Disease Sequencing Project (n = 3231), with cancer history and neuropathology data drawn from the National Alzheimer's Coordinating Center. The rs5848 T allele was associated with higher odds of LATE-NC (p < 0.001) and was also associated with lower odds of cancer (p = 0.012). Established TMEM106B, APOE, and BIN1 risk alleles for Alzheimer's disease showed no associations with cancer, implying that the GRN-related associations could not be completely explained by selection bias in the study sample. The finding of a specific allele with opposite correlative impact on cancer risk and dementia-related pathology has potential therapeutic implications.

Humans↗

PubMed2024

Limbic-predominant age-related TDP-43 encephalopathy (LATE-NC): Co-pathologies and genetic risk factors provide clues about pathogenesis.

Limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) is detectable at autopsy in more than one-third of people beyond age 85 years and is robustly associated with dementia independent of other pathologies. Although LATE-NC has a large impact on public health, there remain uncertainties about the underlying biologic mechanisms. Here, we review the literature from human studies that may shed light on pathogenetic mechanisms. It is increasingly clear that certain combinations of pathologic changes tend to coexist in aging brains. Although "pure" LATE-NC is not rare, LATE-NC often coexists in the same brains with Alzheimer disease neuropathologic change, brain arteriolosclerosis, hippocampal sclerosis of aging, and/or age-related tau astrogliopathy (ARTAG). The patterns of pathologic comorbidities provide circumstantial evidence of mechanistic interactions ("synergies") between the pathologies, and also suggest common upstream influences. As to primary mediators of vulnerability to neuropathologic changes, genetics may play key roles. Genes associated with LATE-NC include TMEM106B, GRN, APOE, SORL1, ABCC9, and others. Although the anatomic distribution of TDP-43 pathology defines the condition, important cofactors for LATE-NC may include Tau pathology, endolysosomal pathways, and blood-brain barrier dysfunction. A review of the human phenomenology offers insights into disease-driving mechanisms, and may provide clues for diagnostic and therapeutic targets.

Humans↗

PubMed2007

Cancer/testis (CT) antigens are expressed in fetal ovary.

Cancer/testis (CT) antigens are named after their expression pattern as they are typically present in various types of tumors and in the germ cells of normal adult testis. Adult ovarian tissue is usually reported to be CT antigen negative. Based on the differences in female versus male gonadal development, the ovarian counterpart of the most predominant CT antigen positive testicular germ cells are not prevalent in the adult ovary. Hence, we analyzed the protein expression of several CT antigens in fetal ovary by immunohistochemistry with various monoclonal antibodies (mAbs) previously generated by our group. The mAbs used were: MA454 (MAGE-A1), M3H67 (MAGE-A3), 57B (MAGE-A4), CT7-33 (CT7/MAGE-C1), and ES121 (NY-ESO-1). All mAbs showed some immunopositivity in fetal ovarian germ cells. The most intense staining was seen with mAbs M3H67, 57B, and CT7-33 during weeks 16-23 of gestation. The most prevalent cells stained were oogonia, with only focal staining of oocytes of the primordial follicle. We conclude that CT antigens are regularly expressed in fetal ovarian germ cells and might play an important role in male and female germ cell biology.

Antigens, Neoplasm↗

PubMed2005

RAKE and LNA-ISH reveal microRNA expression and localization in archival human brain.

microRNAs (miRNAs) are small (approximately 22 nucleotide) regulatory RNAs which play fundamental roles in many biological processes. Recent studies have shown that the expression of many miRNAs is altered in various human tumors and some miRNAs may function as oncogenes or tumor suppressor genes. However, with the exception of glioblastoma multiforme, the expression of miRNAs in brain tumors is unknown. Furthermore, methods to profile miRNAs from formalin-fixed, paraffin-embedded (FFPE) archival tissues or to study their cellular and subcellular localization in FFPE tissues have been lacking. Here we report the coordinated miRNA expression analysis from the tissue level to the subcellular level, using the RAKE (RNA-primed, array-based, Klenow Enzyme) miRNA microarray platform in conjunction with Locked Nucleic Acid (LNA)-based in situ hybridization (LNA-ISH) on archival FFPE human brains and oligodendroglial tumors. The ability to profile miRNAs from archival tissues at the tissue level, by RAKE microarrays, and at the cellular level by LNA-ISH, will accelerate studies of miRNAs in human diseases.

Brain↗

PubMed2005

Increased epitope-specific CD8+ T cells prevent murine coronavirus spread to the spinal cord and subsequent demyelination.

CD8+ T cells are important for clearance of neurotropic mouse hepatitis virus (MHV) strain A59, although their possible role in A59-induced demyelination is not well understood. We developed an adoptive-transfer model to more clearly elucidate the role of virus-specific CD8+ T cells during the acute and chronic phases of infection with A59 that is described as follows. C57BL/6 mice were infected with a recombinant A59 virus expressing the gp33 epitope, an H-2Db-restricted CD8+ T-cell epitope encoded in the glycoprotein of lymphocytic choriomeningitis virus, as a fusion with the enhanced green fluorescent protein (RA59-gfp/gp33). P14 splenocytes (transgenic for a T-cell receptor specific for the gp33 epitope) were transferred at different times pre- and postinfection (p.i.). Adoptive transfer of P14 splenocytes 1 day prior to infection with RA59-gfp/gp33, but not control virus lacking the gp33 epitope, RA59-gfp, reduced weight loss and viral replication and spread in the brain and to the spinal cord. Furthermore, demyelination was significantly reduced compared to that in nonrecipients. However, when P14 cells were transferred on day 3 or 5 p.i., no difference in acute or chronic disease was observed compared to that in nonrecipients. Protection in mice receiving P14 splenocytes prior to infection correlated with a robust gp33-specific immune response that was not observed in mice receiving the later transfers. Thus, an early robust CD8+ T-cell response was necessary to reduce virus replication and spread, specifically to the spinal cord, which protected against demyelination in the chronic phase of the disease.

Animals↗

PubMed2004

Hypoxia is important in the biology and aggression of human glial brain tumors.

We investigated whether increasing levels of tissue hypoxia, measured by the binding of EF5 [2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide] or by Eppendorf needle electrodes, were associated with tumor aggressiveness in patients with previously untreated glial brain tumors. We hypothesized that more extensive and severe hypoxia would be present in tumor cells from patients bearing more clinically aggressive tumors. Hypoxia was measured with the 2-nitroimidazole imaging agent EF5 in 18 patients with supratentorial glial neoplasms. In 12 patients, needle electrode measurements were made intraoperatively. Time to recurrence was used as an indicator of tumor aggression and was analyzed as a function of EF5 binding, electrode values and recursive partitioning analysis (RPA) classification. On the basis of EF5 binding, WHO grade 2 tumors were characterized by modest cellular hypoxia (pO2s approximately 10%) and grade 3 tumors by modest-to-moderate hypoxia (pO2s approximately 10%- 2.5%). Severe hypoxia (approximately 0.1% oxygen) was present in 5 of 12 grade 4 tumors. A correlation between more rapid tumor recurrence and hypoxia was demonstrated with EF5 binding, but this relationship was not predicted by Eppendorf measurements.

Aged↗

PubMed2004

Microarray-based, high-throughput gene expression profiling of microRNAs.

MicroRNAs (miRNAs) are small regulatory RNAs that serve fundamental biological roles across eukaryotic species. We describe a new method for high-throughput miRNA detection. The technique is termed the RNA-primed, array-based Klenow enzyme (RAKE) assay, because it involves on-slide application of the Klenow fragment of DNA polymerase I to extend unmodified miRNAs hybridized to immobilized DNA probes. We used RAKE to study human cell lines and brain tumors. We show that the RAKE assay is sensitive and specific for miRNAs and is ideally suited for rapid expression profiling of all known miRNAs. RAKE offers unique advantages for specificity over northern blots or other microarray-based expression profiling platforms. Furthermore, we demonstrate that miRNAs can be isolated and profiled from formalin-fixed paraffin-embedded tissue, which opens up new opportunities for analyses of small RNAs from archival human tissue. The RAKE assay is theoretically versatile and may be used for other applications, such as viral gene profiling.

Cell Line↗

PubMed2004

A combined computational-experimental approach predicts human microRNA targets.

A new paradigm of gene expression regulation has emerged recently with the discovery of microRNAs (miRNAs). Most, if not all, miRNAs are thought to control gene expression, mostly by base pairing with miRNA-recognition elements (MREs) found in their messenger RNA (mRNA) targets. Although a large number of human miRNAs have been reported, many of their mRNA targets remain unknown. Here we used a combined bioinformatics and experimental approach to identify important rules governing miRNA-MRE recognition that allow prediction of human miRNA targets. We describe a computational program, "DIANA-microT", that identifies mRNA targets for animal miRNAs and predicts mRNA targets, bearing single MREs, for human and mouse miRNAs.

Animals↗

PubMed2004

Comparative measurements of hypoxia in human brain tumors using needle electrodes and EF5 binding.

Hypoxia is known to be an important prognostic marker in many human cancers. We report the use of two oxygen measurement techniques in human brain tumors and compare these data with semiquantitative histological end points. Oxygenation was measured using the Eppendorf needle electrode and/or EF5 binding in 28 brain tumors. These data were compared with necrosis, mitosis, and endothelial proliferation. In some tumors, absolute EF5 binding was converted to tissue pO(2) based on in vitro calibrations. Eppendorf electrode readings could not be used to identify WHO grade 1/2 versus WHO grade 3/4 tumors, they could not differentiate grade 3 versus grade 4 glial-derived neoplasms, nor did they correlate with necrosis or endothelial proliferation scores. EF5 binding increased as the tumor grade increased and was significantly associated with necrosis and endothelial proliferation. There was no statistically significant correlation between the two hypoxia detection techniques, although both methods indicated similar absolute ranges of tissue pO(2). There was substantial inter- and intratumoral heterogeneity of EF5 binding in WHO grade 4 glial neoplasms. The majority of cells in glial-derived tumor had levels of hypoxia that were mild to moderate (defined herein as 10% to 0.5% pO(2)) rather than severe (defined as approximately 0.1% pO(2)). Immunohistochemical detection of EF5 binding tracks histological parameters in adult brain tumors, with increased binding associated with increasing necrosis and endothelial proliferation. The proportion of moderately to severely hypoxic cells is relatively low, even in the high-grade tumors. Human brain tumors are dominated by oxic to moderately hypoxic cells.

Adult↗

PubMed2004

Management of patients with schwannomatosis: report of six cases and review of the literature.

BACKGROUND: Schwannomatosis is a rare tumor syndrome characterized by the presence of multiple schwannomas without the stigmata of neurofibromatosis (NF) Type 1 or 2. To better understand the natural history and clinical management of the syndrome, a retrospective review was conducted of patients diagnosed with schwannomatosis over an 11-year period at the University of Pennsylvania Medical Center (UPMC). METHODS: Between 1990 and 2001, 131 patients underwent surgery for resection of spinal or peripheral nerve schwannomas in the Department of Neurosurgery at the University of Pennsylvania Medical Center. Among the 131 patients, there were 6 who had two or more pathologically proven schwannomas without radiographic or clinical evidence of vestibular schwannomas. The hospital charts, clinic notes, radiology films, operative reports, pathology slides, and reports from all 6 patients were retrospectively reviewed. RESULTS: The patient population consisted of 6 patients with a mean age of 48.7 (3 male: 3 female). All patients had enhanced brain magnetic resonance imaging (MRI) scans that were negative for vestibular schwannomas. Ophthalmological and general physical examinations did not reveal any findings suggestive of NF. There was no family history of NF or schwannomatosis. The locations of the schwannomas included intraspinal (multiple sites), paraspinal, brachial plexus, femoral nerve, sciatic nerve, calf, forearm, retroperitoneum, and middle cranial/infratemporal fossa region. The common presenting symptoms included paresthesias, palpable mass, pain, or weakness. All 6 patients underwent surgical resection of symptomatic lesions. CONCLUSIONS: For patients with schwannomatosis, surgery is indicated for symptomatic lesions, while asymptomatic tumors are followed conservatively. Because these patients are at increased risk for developing multiple schwannomas, we recommend regular surveillance and offer genetic counseling even though the pattern of inheritance is unknown.

Adolescent↗

PubMed2004

miRNP:mRNA association in polyribosomes in a human neuronal cell line.

MicroRNAs (miRNAs) are small regulatory RNAs that control gene expression by base-pairing with their mRNA targets. miRNAs assemble into ribonucleoprotein complexes termed miRNPs. Animal miRNAs recognize their mRNA targets via partial antisense complementarity and repress mRNA translation at a step after translation initiation. How animal miRNAs recognize their mRNA targets and how they control their translation is unknown. Here we describe that in a human neuronal cell line, the miRNP proteins eIF2C2 (a member of the Argonaute family of proteins), Gemin3, and Gemin4 along with miRNAs cosediment with polyribosomes. Furthermore, we describe a physical association between a let-7b (miRNA)-containing miRNP and its putative human mRNA target in polyribosome-containing fractions. These findings suggest that miRNP proteins may play important roles in target mRNA recognition and translational repression.

Binding Sites↗

PubMed2002

Clonal human (hNT) neuron grafts for stroke therapy: neuropathology in a patient 27 months after implantation.

Although grafted cells may be promising therapy for stroke, survival of implanted neural cells in the brains of stroke patients has never been documented. Human NT2N (hNT) neurons derived from the NTera2 (NT2) teratocarcinoma cell line were shown to remain postmitotic, retain a neuronal phenotype, survive >1 year in host rodent brains and ameliorate motor and cognitive impairments in animal models of ischemic stroke. Here we report the first postmortem brain findings of a phase I clinical stroke trial patient implanted with human hNT neurons adjacent to a lacunar infarct 27 months after surgery. Neurofilament immunoreactive neurons were identified in the graft site, fluorescent in situ hybridization revealed polyploidy in groups of cells at this site just like polyploid hNT neurons in vitro, and there was no evidence of a neoplasm. These findings indicate that implanted hNT neurons survive for >2 years in the human brain without deleterious effects.

Aged↗

PubMed2002

Optimizing gene expression analysis in archival brain tissue.

Analysis of gene expression in the brain is a valuable tool to study the function of the brain under normal and pathological conditions. Although there are many techniques used to measure gene expression the validity of any such experiment is directly related to the quality of the RNA in the samples. The most readily available source of human brain tissue is post-mortem and while frozen tissue is sometimes available, most archived tissue is fixed and paraffin-embedded. The use of fixed tissue for expression analysis introduces variables, which must be considered in the experimental design. In addition, factors associated with clinical variability of the patient and with tissue procurement can affect RNA transcript levels. In order to illustrate the effects of two common tissue fixatives, formalin and ethanol, on the quality of RNA for expression analysis we compare RNA extracted from these fixed tissues to the gold standard, flash-frozen tissue. We describe RNA extraction from fixed tissue and ways to assess the quality or intactness of the RNA using reverse transcription combined with polymerase chain reaction amplification. An advantage of using archived tissue is the ease with which single cells or subpopulations of cells can be obtained by laser microdissection. The successful isolation of RNA from microdissected cells is also presented. From our results and a review of the literature we conclude that RNA from fixed tissues is a viable source of RNA for expression analysis which should enable new experimental approaches and discoveries as long as attention is given to variables that can affect RNA at all levels of analysis.

Archives↗

PubMed2002

Microglia in diseases of the central nervous system.

Microglia (MG) are enigmatic cells of the central nervous system (CNS). MG are morphologically, antigenically and functionally flexible, and have the potential for mobility and proliferation. MG are professional antigen-presenting cells and constitute part of the local CNS innate immune system, communicating with other immune cells via chemokines, cytokines and growth factors. MG contain several antigenic and functional markers similar to macrophages and dendritic cells (DCs), but also present several differences from DCs. The exact role(s) played by MG in the normal human CNS is the topic of lively debate. MG participate in many reactive processes in the CNS and are therefore an integral part of lesions in a variety of pathologic conditions. It is thought that MG may exacerbate diverse neurological conditions, including viral encephalitis, AIDS, Multiple Sclerosis (MS) and Alzheimer's disease. A recurrent theme is the perpetuation by MG of pathological cycles of monocyte recruitment, activation and cytopathic secretions, and/or auto antigen presentation.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Primary central nervous system angiitis, amyloid angiopathy, and Alzheimer's pathology presenting with Balint's syndrome.

We report a patient who presented with Balint's syndrome as a manifestation of primary central nervous system angiitis. Clinical findings included simultanagnosia, optic ataxia, and optic apraxia. Pathologic evaluation demonstrated amyloid angiopathy and Alzheimer's plaques. The presence of primary central nervous system angiitis along with amyloid angiopathy and Alzheimer's plaques may not be coincidental. Angiitis may be a foreign body reaction to A4 amyloid deposition.

Aged↗