Biomedical subjects

Nancy J Linford

Publications and source records attributed to Nancy J Linford.

6 recordsLinked to original sources

PubMed2006

Neuronal cell cycle re-entry mediates Alzheimer disease-type changes.

Evidence showing the ectopic re-expression of cell cycle-related proteins in specific vulnerable neuronal populations in Alzheimer disease led us to formulate the hypothesis that neurodegeneration, like cancer, is a disease of inappropriate cell cycle control. To test this notion, we used adenoviral-mediated expression of c-myc and ras oncogenes to drive postmitotic primary cortical neurons into the cell cycle. Cell cycle re-entry in neurons was associated with increased DNA content, as determined using BrdU and DAPI, and the re-expression of cyclin B1, a marker for the G2/M phase of the cell cycle. Importantly, we also found that cell cycle re-entry in primary neurons leads to tau phosphorylation and conformational changes similar to that seen in Alzheimer disease. This study establishes that the cell cycle can be instigated in normally quiescent neuronal cells and results in a phenotype that shares features of degenerative neurons in Alzheimer disease. As such, our neuronal cell model may be extremely valuable for the development of novel therapeutic strategies.

Alzheimer Disease↗

PubMed2006

Oxidative damage and aging: spotlight on mitochondria.

Whereas free radical damage has been proposed as a key component in the tissue degeneration associated with aging, there has been little evidence that free radical damage limits life span in mammals. The current research shows that overexpression of the antioxidant enzyme catalase in mitochondria can extend mouse life span. These results highlight the importance of mitochondrial damage in aging and suggest that when targeted appropriately, boosting antioxidant defenses can increase mammalian life span.

Aging↗

PubMed2006

Evaluation of methods for oligonucleotide array data via quantitative real-time PCR.

BACKGROUND: There are currently many different methods for processing and summarizing probe-level data from Affymetrix oligonucleotide arrays. It is of great interest to validate these methods and identify those that are most effective. There is no single best way to do this validation, and a variety of approaches is needed. Moreover, gene expression data are collected to answer a variety of scientific questions, and the same method may not be best for all questions. Only a handful of validation studies have been done so far, most of which rely on spike-in datasets and focus on the question of detecting differential expression. Here we seek methods that excel at estimating relative expression. We evaluate methods by identifying those that give the strongest linear association between expression measurements by array and the "gold-standard" assay. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) is generally considered the "gold-standard" assay for measuring gene expression by biologists and is often used to confirm findings from microarray data. Here we use qRT-PCR measurements to validate methods for the components of processing oligo array data: background adjustment, normalization, mismatch adjustment, and probeset summary. An advantage of our approach over spike-in studies is that methods are validated on a real dataset that was collected to address a scientific question. RESULTS: We initially identify three of six popular methods that consistently produced the best agreement between oligo array and RT-PCR data for medium- and high-intensity genes. The three methods are generally known as MAS5, gcRMA, and the dChip mismatch mode. For medium- and high-intensity genes, we identified use of data from mismatch probes (as in MAS5 and dChip mismatch) and a sequence-based method of background adjustment (as in gcRMA) as the most important factors in methods' performances. However, we found poor reliability for methods using mismatch probes for low-intensity genes, which is in agreement with previous studies. CONCLUSION: We advocate use of sequence-based background adjustment in lieu of mismatch adjustment to achieve the best results across the intensity spectrum. No method of normalization or probeset summary showed any consistent advantages.

Algorithms↗

PubMed2005

Extension of murine life span by overexpression of catalase targeted to mitochondria.

To determine the role of reactive oxygen species in mammalian longevity, we generated transgenic mice that overexpress human catalase localized to the peroxisome, the nucleus, or mitochondria (MCAT). Median and maximum life spans were maximally increased (averages of 5 months and 5.5 months, respectively) in MCAT animals. Cardiac pathology and cataract development were delayed, oxidative damage was reduced, H2O2 production and H2O2-induced aconitase inactivation were attenuated, and the development of mitochondrial deletions was reduced. These results support the free radical theory of aging and reinforce the importance of mitochondria as a source of these radicals.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2003

Chromosomal instability in pancreatic ductal cells from patients with chronic pancreatitis and pancreatic adenocarcinoma.

Pancreatic adenocarcinoma is a disease with high mortality for which chronic pancreatitis confers a markedly increased risk. We hypothesize that chromosome instability and genomic damage occur in pre-neoplastic pancreatic ductal epithelium, and that this damage may be related to oxidative stress. We used dual-color fluorescence in situ hybridization with centromere probes and locus-specific arm probes for chromosome arms 11q, 17p, and 18q to identify genomic instability in cultures of normal-appearing human pancreatic ductal epithelium from normal organ donor controls compared to patients with chronic pancreatitis or pancreatic adenocarcinoma. To examine early pancreatic tumorigenesis, we studied only normal-appearing pancreatic ductal cells adjacent to pancreatitis or carcinoma. We found that, compared to the finding in normal controls, chromosomal abnormalities are present in normal-appearing human pancreatic ductal epithelia obtained from patients with chronic pancreatitis or pancreatic adenocarcinoma. Furthermore, these chromosomal abnormalities could be induced in cultured pancreatic ductal epithelium from normal organ donors by chronic exposure to dilute hydrogen peroxide, suggesting that oxidative stress may contribute to the development of chromosomal instability in the pancreas. These results elucidate a potential mechanism linking chronic pancreatitis to pancreatic cancer and suggest that chromosomal instability may be an early event in the pathogenesis of pancreatic cancer.

Adenocarcinoma↗

PubMed2002

17beta-Estradiol and the phytoestrogen genistein attenuate neuronal apoptosis induced by the endoplasmic reticulum calcium-ATPase inhibitor thapsigargin.

Estrogenic compounds have been shown to protect neurons from a variety of toxic stimuli in vitro and in vivo and depletion of estrogen at menopause has been associated with increased risk of neurodegenerative diseases. Genistein is an isoflavone soy derivative that binds to estrogen receptors with selective estrogen receptor modulator (SERM) properties. Recent FDA recommendations of soy intake for cholesterol reduction have prompted investigation into the potentially estrogenic role of dietary soy phytochemicals in the brain. In this study, we have shown that 50nM genistein significantly reduces neuronal apoptosis in an estrogen receptor-dependent manner. The importance of apoptosis in the brain has been recognized with regard to organization of the developing brain as well as degeneration in response to disease or stroke; however, the effects of estrogenic compounds on neuronal apoptosis have not been thoroughly examined. We developed a model of apoptotic toxicity in primary cortical neurons by using the endoplasmic reticulum (ER) calcium-ATPase inhibitor, thapsigargin, to test potential anti-apoptotic effects of 17beta-estradiol and genistein. Estrogen receptor beta, but not estrogen receptor alpha, was detected in our primary neuron cultures. Thapsigargin-induced apoptosis was confirmed by loss of mitochondrial function, DNA laddering, nuclear condensation and fragmentation, and caspase activation. Both 17beta-estradiol and genistein reduced the number of apoptotic neurons and reduced the number of neurons containing active caspase-3. This effect was blocked by co-addition of ICI 182780. Our results demonstrate that genistein and 17beta-estradiol have comparable anti-apoptotic properties in primary cortical neurons and that these properties are mediated through estrogen receptors.

Animals↗