Biomedical subjects

P Thorner

Publications and source records attributed to P Thorner.

98 records · Page 6Linked to original sources

PubMedDate not supplied

Animal models of Alport syndrome: advancing the prospects for effective human gene therapy.

Several animal models for Alport syndrome have been described. These are available for studies on the pathogenetic mechanisms of the disease, as well as for the development of new technologies for gene therapy in this progressive hereditary kidney disease. This review summarizes current knowledge on the molecular basis of Alport syndrome, and on the animal models which all remarkably well resemble the human disease. Recent work aimed at the development of gene therapy, including hurdles and progress are discussed.

Animals↗

PubMedDate not supplied

Nodular hyperplasia in treated congenital goitrous hypothyroidism.

Two patients with congenital goitrous hypothyroidism, treated since birth, are described. Each developed progressive nodular thyroid enlargement in adolescence, possibly related to ongoing thyroid stimulation due to slight and transient elevations of thyroid stimulating hormone (TSH) levels. The incidence and degree of persistent thyroid enlargement in these patients has not been well documented. If present in a significant number of patients despite appropriate L-thyroxine replacement, our therapeutic aims in congenital goitrous hypothyroidism may need to be modified to achieve TSH suppression, rather than normalization.

Adolescent↗

PubMedDate not supplied

Hydrops fetalis and neonatal leukemia in Down syndrome.

Four newborn infants with Down syndrome and manifestations of neonatal leukemia are described. One of the four was stillborn, two died shortly after birth, and a fourth survived and all evidence of leukemia disappeared in the first month of life. Three of the four cases had hydrops fetalis, and a fourth was a macerated stillborn. Nine other similar reported cases are reviewed. We conclude that neonatal leukemia in Down syndrome is a form of leukemia that is usually transient, with spontaneous recovery, but may be fatal at or around the time of birth with manifestations of hydrops fetalis, hepatosplenomegaly, and/or progressive liver disease.

Adult↗

PubMedDate not supplied

Assessment of MYCN amplification in neuroblastoma biopsies by differential polymerase chain reaction.

Amplification of the oncogene MYCN is a genetic change frequently observed in neuroblastoma and is an indicator of poor prognosis. MYCN copy number is currently determined by Southern blot hybridization. This technique takes 2 to 3 weeks, is labor-intensive, is sensitive to DNA degradation, and requires large quantities of DNA. We have evaluated a new, semiquantitative method of estimating gene copy number that uses differential polymerase chain reaction (PCR). The procedure can be performed in 1 day, is highly reproducible, and requires only nanogram quantities of DNA. It employs a semiquantitative, nonisotopic PCR technique based on differential competition for PCR substrates. MYCN gene primers are amplified together with primers from a single-copy internal control gene. Following electrophoretic separation, the ratio of the two PCR products is determined visually and by densitometric analysis of ethidium bromide-stained agarose gels. This differential ratio is then compared to a series of ratios generated from standards of known MYCN gene copy number. We compared the results obtained by this differential PCR method with those obtained by conventional Southern blotting in 16 cases of primary neuroblastoma. All amplified tumors were detected by differential PCR, and no false positives were observed. We confirmed that differential PCR is a rapid and reliable alternative to Southern blotting for MYCN copy number assessment and is highly suited to the analysis of DNA derived from needle biopsies.

Base Sequence↗

PubMedDate not supplied

Application of a simplified comparative genomic hybridization technique to screen for gene amplification in pediatric solid tumors.

Conventional cytogenetic analysis of solid tumors is technically very demanding and requires a large number of viable cells. The technique of comparative genomic hybridization (CGH) circumvents these difficulties and has been shown to be particularly useful for identifying new gene amplifications. We have simplified the CGH technique for the detection of amplifications by utilizing a single labeling approach in which labeled tumor DNA is mixed with unlabeled normal human DNA and hybridized to normal metaphases on a slide. To examine the consistency and sensitivity of the method, initial experiments were performed using a retinoblastoma (RB) cell line and five pediatric solid tumors known to contain an amplification. The technique was easy to use and sensitive enough to detect low-level amplifications. The RB cell line showed reproducible signals at 2p24, indicative of amplified sequences, on both homologues in 95% of the metaphases (> 30) examined. Amplifications of the MYCN gene (2p24) were detected in three alveolar rhabdomyosarcomas and one medulloblastoma. CGH was then applied to six tumors in a prospective fashion, before data about specific gene amplification were available. In two, amplification of the MDM2 gene (12q13-14) was identified using CGH and later confirmed by Southern blot analysis. Four tumors negative for MDM2 and MYCN amplifications by CGH analysis were also negative by Southern blot analysis. Gene amplification as low as fourfold was detected in one tumor and the overall pattern of gene amplification detected by CGH in these tumors was not complex, involving just one amplification site for each case. Therefore, this simplified CGH technique is suitable for routine screening of pediatric solid tumors for amplifications when genetic studies are important but sample sizes are small and dividing cells are infrequent or unavailable.

Blotting, Southern↗

PubMedDate not supplied

Interstitial foam cells in renal biopsies: an aid in differentiating idiopathic membranoproliferative glomerulonephritis (type I) and membranoproliferative glomerulonephritis associated with systemic lupus erythematosus.

A patient with nephrotic syndrome whose renal biopsy showed membranoproliferative glomerulonephritis (MPGN) is described. Clinical and laboratory findings included an erythematous malar flush, proteinuria, casts in the urine and a positive antinuclear factor. Hence, it was not clear whether the MPGN was idiopathic, secondary to early systemic lupus erythematosus (SLE) or mainly a renal form of SLE. Treatment with prednisone and azathioprine was unsuccessful, and no new clinical or serological features of SLE appeared. A second renal biopsy 19 months later showed MPGN and large numbers of interstitial foam cells. The finding of foam cells prompted a review of other renal biopsies which were diagnosed as MPGN type I and diffuse proliferative lupus nephritis (DPLN), including lupus-associated MPGN. Nine of thirty-eight (24%) MPGN type I but none of 22 DPLN biopsies contained interstitial foam cells. Therefore, finding foam cells in a renal biopsy may help in differentiating MPGN type I from lupus-associated MPGN.

Adolescent↗

PubMedDate not supplied

Intra-abdominal polyphenotypic tumor.

The presence of t(11;22)(q24;q12) is often considered diagnostic of Ewing sarcoma and peripheral primitive neuroectodermal tumor (pPNET). We report a case of a polyphenotypic tumor that possessed this translocation as detected by reverse transcriptase polymerase chain reaction (RT-PCR). This tumor was positive for vimentin, desmin, low-molecular-weight keratin, neuron-specific enolase, S-100 protein, and CD57 by immunohistochemistry. Of note, the tumor was negative for MIC2. The tumor had double-minute chromosomes with > 100 copies of the MDM2 gene. Thus, the presence of the t(11;22)(q24;q12) translocation should not be considered diagnostic of Ewing sarcoma and pPNET in the absence of supporting histologic evidence such as positive staining for MIC2. The presence of this translocation in Ewing sarcoma and pPNET has been taken as evidence that these two tumors are related. Rather than extending this relationship to include some polyphenotypic tumors, other tumors may acquire this genetic change during tumor progression. Treatment regimens for tumors may be better based on phenotype rather than genotype when these two profiles are seemingly in conflict.

Abdominal Neoplasms↗

PubMedDate not supplied

Heterogeneity of MYCN amplification in a child with stroma-rich neuroblastoma (ganglioneuroblastoma).

Amplification of MYCN portends rapid tumor progression and poor prognosis in neuroblastoma. MYCN copy number has been described as homogeneous within a tumor and congruent in primary tumor and metastasis. We report a child with stage III favorable histology stroma-rich neuroblastoma (ganglioneuroblastoma) and a poor outcome with an apparent change in MYCN gene amplification by Southern blot. Initial biopsy revealed a ganglioneuroblastoma with predominance of differentiating cells designated as neuroblastoma, stroma-rich, intermixed (Shimada). Southern blot failed to demonstrate MYCN gene amplification. After front-line chemotherapy failed, a total resection was performed. In this specimen, Southern blot demonstrated MYCN amplification (15-20 copies) in the undifferentiated component and no amplification in the differentiated. Fluorescence in situ hybridization (FISH) analysis performed retrospectively on both tumor biopsies demonstrated MYCN amplification in the undifferentiated sections of both tumor specimens but not in the differentiated ones. This is the first well-documented case report of heterogeneous MYCN amplification in a child with neuroblastoma. Because key therapeutic decisions are based on the presence of MYCN amplification, physicians diagnosing and treating children with neuroblastoma need to be aware of the possibility that MYCN amplification may be heterogeneous within a tumor and may be missed using techniques based on pooled DNA such as Southern blotting. FISH may be a preferable method for determining MYCN amplification.

Blotting, Southern↗