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Biomedical subjects

S L Perkins

Publications and source records attributed to S L Perkins.

99 records · Page 6Linked to original sources
PubMedDate not supplied

Speciation of trace quantities of mercury using a double Magos determination.

Aqueous solutions containing zero-valent and divalent mercury may be analysed using a double-Magos determination. Results are compared with standard methodology incorporating determinations of divalent mercury, by the dithizone technique, and of total mercury. Excellent correlations of Hg2+ concentrations by the two methods were obtained; the scatter in the comparison of Hg0 determinations was interpreted in terms of the substantial error unavoidably present in the standard methodology. The new method represents a significant improvement.

Dithizone↗
PubMedDate not supplied

Expression of the c-Myc protein in childhood medulloblastoma.

PURPOSE: The purpose of this study was to determine the incidence of c-Myc protein expression in medulloblastoma/primitive neuroectodermal tumor (MB/PNET) and to identify mechanisms in addition to c-myc gene amplification that lead to increased protein expression. METHODS: We analyzed c-myc gene copy number, mRNA level and protein expression in a panel of MB/PNET cell lines. C-Myc protein levels were assessed in tumor specimens and cell lines using immunohistochemical staining with a c-Myc-specific monoclonal antibody. RESULTS: Southern analysis confirmed c-myc gene amplification in the D425 MED cell line and re-arrangement of one allele in D283 MED, which was analyzed further and appeared to represent a small deletion 3' of exon 3. C-myc transcript levels were dramatically elevated in both lines. Using a c-myc probe, fluorescence in situ hybridization (FISH) showed c-myc present in 3 tandem copies at 8q24 in D283 MED and multiple copies as double minutes in D425 MED. Immunohistochemistry showed c-Myc protein expression in 9 of 10 tumors and all cell lines, regardless of gene amplification status or level of mRNA expression. CONCLUSIONS: c-Myc protein expression is common in MB/PNET tumor specimens and cell lines. Elevated protein levels are observed in the absence of amplification, suggesting that multiple mechanisms of c-myc dysregulation may be involved in MB/PNET. These studies support a role for c-Myc in the development of this common childhood tumor.

Child↗
PubMedDate not supplied

Primary mediastinal large cell lymphoma in children: a report from the Childrens Cancer Group.

Malignant lymphomas arising in the mediastinum account for approximately 60% of all mediastinal tumors in children; two-thirds are non-Hodgkin's lymphomas and one-third represent Hodgkin's disease. In contrast to adults, in children mediastinal non-Hodgkin's lymphomas are usually synonymous with lymphoblastic lymphoma, and nonlymphoblastic lymphomas are rare. We describe nine children with primary mediastinal large cell lymphoma who were treated with the Children's Cancer Group protocol CCG-503, a randomized phase III protocol for disseminated nonlymphoblastic lymphoma. Histologic subclassification revealed three immunoblastic lymphomas, three multilobated large cell lymphomas, one with clear cell features, and two large noncleaved cell lymphomas. Sclerosis, of variable degrees, was seen in all tumors. Immunophenotyping revealed all tumors to be of B cell lineage. Thymic epithelial cells could be demonstrated, utilizing antibody to keratin, in two of nine patients, suggesting that some of the tumors are of thymic origin. None of the patients had central nervous system or bone marrow involvement. It appears that primary mediastinal nonlymphoblastic lymphomas in children, although much less common, are similar to those seen in adults. These tumors must be differentiated from lymphoblastic lymphoma and Hodgkin's disease, as the therapeutic approach may depend on histologic subtype. Primary mediastinal large cell lymphoma in children appears curable with aggressive treatment in the majority of patients.

Adolescent↗
PubMedDate not supplied

Coexpression of genes involved in apoptosis in central nervous system neoplasms.

PURPOSE: Apoptosis plays a crucial role in normal development and mediates tumor response to chemotherapy. This study investigated the pattern of apoptotic gene expression in brain tumor tissue specimens and cell lines. MATERIALS AND METHODS: BCL2, BCLXL, BCLXS, and BAX transcripts were amplified using reverse transcriptase polymerase chain reaction in 7 high-grade gliomas (HGGs), 7 ependymomas, and 6 cell lines (2 glioblastomas, 3 medulloblastomas, and 1 supratentorial-primitive neuroectodermal tumor [PNET]). Immunohistochemical staining for BCL2, BCLX, BAX, and p53 was performed in 7 pediatric low-grade gliomas (LGGs) and 7 pediatric HGGs. RESULTS: Six of seven gliomas, all ependymomas, and all glioblastoma and medulloblastoma cell lines expressed BCLXL and BAX. BCL2 expression was only detected in the supratentorial PNET line PFSK. BCLXS was absent in all tumors. By immunohistochemistry, no glial tumors stained positively for BCL2. Similar BAX and BCLX protein expression was observed in LGG and HGG. Three of five glioblastomas showed significant p53 expression. CONCLUSIONS: Coexpression of proapoptotic and antiapoptotic genes in human brain tumors supports the hypothesis that the relative expression of competing genes determines apoptotic threshold.

Apoptosis↗
PubMedDate not supplied

A Canadian tertiary care centre study of maternal and umbilical cord cotinine levels as markers of smoking during pregnancy: relationship to neonatal effects.

This study describes the prevalence of smoking among 3,220 pregnant women. Maternal and umbilical cord cotinine levels were compared with the women's self-reported cigarette consumption, infant birth weight and antepartum and perinatal complications. Of the women who reported themselves as being active smokers (23%), 76% had a partner who smoked, and 38% reported exposure to environmental smoke in the workplace. Only 15% of nonsmokers had a partner who smoked, and 13% reported workplace exposure. The mean number of cigarettes/day was 20.5 (95% CI 19.6-21.4). The relative risk of having a small-for-gestational-age infant was significantly higher in smokers for mothers of both preterm (34-36 wks, RR = 3.38, 95% CI 1.25-9.16) and term babies (> or = 37 wks, RR = 2.04, 95% CI 1.58-2.63). Mean infant birth weight was 207 g lighter in the infants of smokers (p < 0.001) and was inversely correlated to maternal serum cotinine level. Birth weight dropped by 0.99 g for every 1 ug/L increase in cotinine (r = -0.19, p < 0.01).

Adolescent↗
PubMedDate not supplied

Detection of terminal deoxynucleotidyl transferase (TdT) in nonhematopoietic small round cell tumors of children.

In the differential diagnosis of small round cell tumors (SRCTs), terminal deoxynucleotidyl transferase (TdT) is often used as a marker for lymphoblastic lymphomas and leukemias. However, the specificity of TdT using the avidin-biotin-immunoperoxidase (ABC) method is not well documented. To address this issue, we stained paraffin-embedded biopsy specimens of 64 cases of childhood SRCTs using the ABC method with anti-TdT. For any TdT-positive tumors, an additional antibody panel for lymphoid markers was applied. Two patterns of TdT positivity were observed: (1) tumor specific, consisting of strong to moderate nuclear staining, and (2) scattered positive lymphoid cells, usually in a perivascular location and expressing T-cell markers. Analysis showed that 7 of 10 medulloblastomas stained with TdT in a tumor-specific pattern (4 cases moderately to strongly positive in 75-100% of tumor cells, 3 cases weakly to moderately positive in 25-50% of cells). Also, 1 of 19 rhabdomyosarcomas and 1 of 8 Ewing's sarcomas showed moderate to strong tumor-specific TdT staining in 100 and 10% of cells, respectively. Scattered TdT-positive lymphoid cells were observed in 27% of these 64 SRCTs. These findings emphasize that TdT positivity should not be relied upon exclusively for making a diagnosis of lymphoblastic leukemia or lymphoma or ruling out other SRCTs.

Biomarkers, Tumor↗