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Nicholas Smith

Publications and source records attributed to Nicholas Smith.

5 recordsLinked to original sources
PubMed2006

Screening for RB1 mutations in tumor tissue using denaturing high performance liquid chromatography, multiplex ligation-dependent probe amplification, and loss of heterozygosity analysis.

Retinoblastoma is a malignant retinal neoplasm arising in infancy as a result of inactivating mutations in both alleles of the retinoblastoma susceptibility gene, RB1. Identification of the causative RB1 mutations in a patient assists in the clinical management of the affected patient and risk assessment of family members, principally on the basis of whether there is a germline mutation. In this paper, we describe our experience with molecular analysis of RB1 mutations in tumor and nontumor samples from 18 retinoblastoma patients, using multiplex ligation dependent probe amplification (MLPA) to detect large deletions or duplications, microsatellite analysis to detect loss of heterozygosity (LOH), and denaturing high performance liquid chromatography (D-HPLC) analysis to detect point mutations and small insertions or deletions. We found LOH in 71% of all cases, and 83% of these were due to acquired isodisomy rather than chromosomal deletions. Small mutations identified by D-HPLC accounted for 78% of the non-LOH mutations, and large deletions/duplications detected by MLPA accounted for the remaining 22%. We give the first report of a large, multiexon duplication in RB1 of exons 8 to 18.

Child↗
PubMed2006

Location-dependent photogeneration of calcium waves in HeLa cells.

The calcium ion (Ca(2+)) concentrations in a cell are responsible for the control of vital cellular functions and have been widely studied as a means to investigate and control cell activities. Here, we demonstrate Ca(2+) wave generation in HeLa cells by femtosecond laser irradiation and show unexpected properties of the Ca(2+) release and propagation. When the laser was focused in the cell cytoplasm, Ca(2+) release was independent of both external Ca(2+) influx and the phosphoinositide-phospholipase C (PLC) signaling pathway. The nucleus was not a susceptible target for laser-induced Ca(2+) release, whereas irradiation of the plasma membrane produced evidence of transient poration, through which the extracellular solution could enter the cell. By chelating extracellular Ca(2+), we found that laser-induced influx of ethylene glycol tetra-acetic acid (EGTA) can compete with calcium induced calcium release and significantly delay or suppress the onset of the Ca(2+) wave in the target cell. Intercellular Ca(2+) propagation was adenosine triphosphate-dependent and could be observed even when the target cell cytosolic Ca(2+) rise was suppressed by influx of EGTA. The irradiation effect on overall cell viability was also tested and found to be low (85% at 6 h after irradiation by 60 mW average power). Laser-induced Ca(2+) waves can be reliably generated by controlling the exposure and focal position and do not require the presence of caged Ca(2+). The technique has the potential to replace other methods of Ca(2+) stimulation, which either require additional caged molecules in the cell or do not have an interaction that is as well localized.

Adenosine Triphosphate↗
PubMed2005

Nested stromal epithelial tumor of the liver: six cases of a distinctive pediatric neoplasm with frequent calcifications and association with cushing syndrome.

Rare cases of nonhepatocytic mixed stromal and epithelial tumors of the liver with associated calcification and ossification have been described previously. We report 6 similar cases in children, including 2 cases associated with ectopic ACTH production. The patients were between 2 and 14 years of age at diagnosis. All tumors presented as a solitary liver mass with no extrahepatic involvement. Two adolescent females with palpable abdominal tumors presented with Cushing syndrome that abated after excision of the tumors. The other children had tumors identified incidentally on imaging studies or at laparotomy. All tumors were well circumscribed, ranging in size from 4.0 to 30.0 cm in greatest diameter. Histologically, they shared an organoid arrangement of cellular nests that were comprised of an admixture of both spindled and epithelioid cells. These cellular nests were surrounded by a band of delicate myofibroblasts and set in a dense fibrous stroma that contained slit-like to dilated blood vessels. A variable proliferation of bile ducts extended from the fibrous stroma and focally surrounded the cellular nests. One case showed a sheet-like overgrowth of the nested cells with associated necrosis. The cellular nest cells were immunoreactive for EMA, CD56, neuron specific enolase, pan-cytokeratin (4 of 6 cases), vimentin (5 of 6 cases), and WT-1 amino terminus (4 of 6 cases). Cytokeratin and EMA stained mostly epithelioid nest cells, with vimentin and WT-1 staining predominantly the spindled nest cells. The 3 cases from adolescent females showed immunoreactivity for ACTH in the nested cell population but not in the surrounding stromal cells. Immunohistochemical stains for synaptophysin and chromogranin were negative in all cases. Psammomatous calcifications were present focally in 2 cases and were extensive in 3 cases. Ossification or osteoid formation was present in 4 cases. The 1 patient whose tumor had sheet-like overgrowth of the nested cell population had a local recurrence with multiple hepatic nodules 1 year following the original resection. A 2-year-old patient has been subsequently diagnosed with nephroblastomatosis and Wilms tumor of the kidney. Follow-up information was available in an additional 3 patients with no tumor recurrence or metastatic disease at 2, 3, and 14 years.

Adolescent↗