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Biomedical subjects

F F Becker

Publications and source records attributed to F F Becker.

209 records · Page 12Linked to original sources
PubMedDate not supplied

Modification of the subunit principle for reconstruction of nasal tip and dorsum defects.

This article reports our observations on, and modification of, the subunit principle with regard to reconstruction of nasal tip and dorsum defects. Forty-two patients who underwent reconstruction of a nasal tip and/or dorsum defect with a forehead flap were reviewed. These patients were categorized by how the subunit principle was used in their reconstruction and graded on the aesthetic outcome of the reconstruction. We found that the patients who had both the nasal tip and dorsum replaced obtained better results than those who had just 1 subunit replaced (P = .008). Review of postoperative photographs shows that the reason for this discrepancy in aesthetic outcomes is the line of transition between the forehead skin and remaining nasal skin if only 1 subunit is replaced. With this observation in mind, we feel that patients undergoing reconstruction of the nasal tip and/or dorsum should be evaluated for discrepancies in tissue type between the recipient nasal site and forehead donor site. If the tissues are noted to be significantly disparate, the reconstructive surgeon may consider replacing both subunits with a single forehead flap.

Esthetics↗
PubMedDate not supplied

DNA-ligase activities appear normal in the CHO mutant EM9.

The Chinese hamster ovary (CHO) mutant strain EM9 was previously shown to be hypersensitive to killing by ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS), to have a 12-fold increased baseline incidence of sister-chromatid exchanges (SCE), and to be defective in rejoining DNA strand breaks after treatment with EMS, MMS, or X-rays. A study was performed to determine if the primary biochemical defect might be a DNA ligase. DNA-ligase activities were assayed and compared after separation of the multiple forms of ligase by AcA 34 gel-filtration chromatography of total cellular extracts. In EM9 cells the levels of the presumptive replicative forms, DNA ligase Ia (480 kd) and ligase Ib (240 kd) were about 50% and 60%, respectively, of those in the parental AA8 cells, whereas DNA ligase II (80 kd) was unaltered in EM9 . In a phenotypic revertant line ( 9R1 ) ligases Ia, Ib and II levels were 35%, 37% and 100%, respectively, of those in AA8 . The reduced levels of ligases Ia and Ib in EM9 and 9R1 cells are apparently not related directly to the mutant phenotype and may be attributable to the somewhat slower growth rates of these strains compared with those of AA8 . To determine if the repair defect in EM9 might reside in the ability to induce DNA-ligase activity after treatment with a DNA-damaging agent, AA8 and EM9 cells were treated with MMS at 30 micrograms/ml for 60 min before preparing fractions for ligase assays. Under these conditions the activities of ligases Ia and Ib decreases 70-80% in both cell lines, but ligase II increased 2.0- and 2.6-fold, respectively, in AA8 and EM9 . As a further test of defective ligase activities in EM9 , assays were performed in the presence of 0.1 M NaCl or after heating the fractions for 10 min at 50 degrees C. Although all 3 forms of ligase showed altered activity under both of these conditions, there were no significant differences between EM9 and AA8 cells. These data combined with the above results provide strong evidence that the site of the primary defect in EM9 is not in either of the DNA ligases .

Animals↗
PubMedDate not supplied

Altered DNA ligase I activity in Bloom's syndrome cells.

Cells from patients with Bloom's syndrome, a rare disease associated with increased cancer frequency, exhibit cytological abnormalities. These include increased numbers of homologous chromatid interchange figures and sister-chromatid exchanges, together with abnormally slow replicon-fork progression and retarded rate of DNA-chain maturation, and suggest that the primary defect in this recessive disorder affects S-phase DNA replication. DNA ligases and DNA polymerases have long been prime candidates for abnormality in Bloom's syndrome, but various studies of DNA polymerases in Bloom's syndrome cells have disclosed no abnormalities. Evidence is presented here, as in the accompanying paper from a different laboratory, for the existence in Bloom's syndrome of an abnormality of the DNA ligase involved in semi-conservative DNA replication.

Bloom Syndrome↗
PubMedDate not supplied

The effects of tin-protoporphyrin administration on hepatic xenobiotic metabolizing enzymes in the juvenile rat.

The heme analogue tin-protoporphyrin IX (SnP) is a potent inhibitor of microsomal heme oxygenase. Administration of SnP to neonatal rats can prevent hyperbilirubinemia by blocking the postnatal increase of heme oxygenase activity. Apparently innocuous at therapeutic doses, it is of potential clinical value for chemoprevention of neonatal jaundice. We found that when 50-g male Sprague-Dawley rats were treated daily with 50 mumol of SnP/kg sc for 6 days, hepatic microsomal cytochromes b5 and P-450 were significantly diminished. Cytochrome P-450 reductase, two P-450-dependent monooxygenases, aminopyrine demethylase and benzo(a)pyrene hydroxylase, and catalase, a peroxisomal hemoprotein, were also significantly diminished. These results suggested that SnP might significantly affect the metabolism of other xenobiotics. This possibility was confirmed by the finding that hexobarbital-induced sleep lasted 4 times longer in SnP-treated rats than in controls. Inhibition of protein synthesis by SnP was ruled out as the cause of hemoprotein loss when administration of [3H]leucine to SnP-treated and control rats demonstrated that proteins of the microsomal, cytosolic, and plasma membrane fractions of the livers from both groups incorporated similar levels of leucine. When 55FeCl3 and [2-14C]glycine were administered to measure heme synthesis, heme extract from the livers of SnP-treated rats contained 4 times more label from iron and glycine than did heme from control livers. Despite the apparent increased rate of heme synthesis in SnP-treated rats, each of the three cell fractions demonstrated a significant loss of heme but contained sizable amounts of SnP. These findings suggest that SnP causes a decrease of functional hemoprotein and partial loss of enzymic activity by displacing intracellular heme.

Animals↗