Biomedical subjects

J Stambouly

Publications and source records attributed to J Stambouly.

3 recordsLinked to original sources

PubMed1986

Host and phage-coded functions required for coliphage N4 DNA replication.

Escherichia coli strains containing mutations in various deoxyribonucleic acid synthesis cistrons have been tested for their ability to support bacteriophage N4 growth and, specifically, N4 DNA synthesis. N4 DNA synthesis is independent of the activity of the products of the E. coli dnaA, dnaB, dnaC, dnaE, dnaG, and rep genes. In contrast, N4 DNA replication requires the products of the dnaF, (ribonucleotide reductase) and lig (DNA ligase) genes of E. coli. N4 DNA replication, specifically processing of short DNA fragments requires the 5'-3' exonuclease activity of the polA gene product. However, its DNA polymerizing activity is not required. In addition, the sensitivity of N4 DNA synthesis to inhibitors or temperature-sensitive mutants of E. coli DNA gyrase suggests that this activity is required for N4 DNA synthesis. To date, we have found five N4 gene products required for N4 DNA replication: dbp (a single-stranded DNA binding protein), dnp (a DNA polymerase), dns (unknown function), vRNAp (the N4 virion-associated, DNA-dependent RNA polymerase) and exo (a 5'-3' exonuclease).

Coliphages↗

PubMed1981

Short communication: neurofibromatosis fibroblasts: slow growth and abnormal morphology.

We hypothesized that skin fibroblasts from patients with neurofibromatosis (NF) may have abnormalities of growth in tissue culture to correlate with the clinical abnormalities of overgrowth and malignancy seen in this disease. Using five lines of NF cells, age- and passage-matched to normal controls, we found that NF fibroblasts grew more slowly and stopped growing at a lower population density than normal cells (P less than 0.0005). The same cells also incorporated [3H]thymidine at a lower rate than normal skin fibroblasts (9,330 +/- 3,240 versus 42,100 +/- 6,840; P less than 0.01). The addition of epidermal growth factor to the medium stimulated the growth of both the normal and the NF fibroblasts; however, the stimulation of the NF fibroblasts was inadequate to fully correct the slow growth rate (P less than 0.025). NF cells (N = 5) were found to be morphologically different from normal skin fibroblasts (N = 5) in culture by light microscopy. NF cells were larger (approximately 9 X 10(4) X 2 X 10(4) versus 2 X 10(4) X 2 X 10(4) A), pleomorphic, and failed to form confluent monolayers when growth ceased. Speculation These data indicate that there may be an underlying abnormality of growth regulation in neurofibromatosis. The slow growth of neurofibromatosis fibroblasts, and their diminished response to epidermal growth factor, provides a means for studying the growth abnormality of neurofibromatosis in tissue culture. In addition, the expression of this abnormality may serve as a marker for the disease.

Culture Techniques↗

PubMed1980

Diminished epidermal growth factor binding by neurofibromatosis fibroblasts.

Neurofibromatosis (NF) is an autosomal dominant disease characterized by growth abnormalities of epithelial, mesothelial, and endothelial elements. We recently reported abnormal growth and morphology of NF fibroblasts in tissue culture. Because epidermal growth factor (EGF) is known to stimulate the growth of fibroblasts in tissue culture, we studied the binding of commercial iodine 125-labeled EGF to age- and passage-matched confluent NF (N = 6) and normal (N = 4) fibroblasts. Fibroblasts were maintained at 37 degrees C for 2, 30, 60, 120, and 240 minutes in a medium in which the cells grow slowly (Dulbecco's Eagle medium) and one in which they grow normally (Ham's F-12 medium). Binding assays were done in both serum-free media according to accepted procedures. The EGF binding did not differ in the two media, and pooled data are presented. These data demonstrate no significant differences in the early binding of EGF to normal and NF fibroblasts (4,682 +/- 1,092 versus 3,441 +/- 826 cpm/10(6) cells; 20,000 cpm/ng; p > 0.15 at 30 minutes). At one hour, however, differences suggestive of abnormal EGF binding become apparent (12,495 +/- 1,989 versus 3,172 +/- 853 cpm/10(6) cells; 20,000 cpm/ng; p < 0.0025). We conclude that there may be a membrane defect in NF which is reflected by diminished EGF binding.

Cells, Cultured↗