PubMed Health⌕ Search

Biomedical subjects

J C O'Brien

Publications and source records attributed to J C O'Brien.

28 records · Page 2Linked to original sources
PubMed1980

Tyrosine aminotransferase sensitivity to bromodeoxyuridine during restricted intervals of S phase in hepatoma cells.

Synchronized hepatoma tissue culture (HTC) cells, accumulated at the G1/S boundary with aminopterin, were released into S phase with either thymidine or 5-bromodeoxyuridine (BUdR). Tyrosine aminotransferase (TAT) activity was found to be unaffected by BUdR over the initial 3 h of S phase, but then to rapidly decline to a new basal level of 40% of control by 9 h. There was no corresponding response in the activities of alcohol dehydrogenase, malate dehydrogenase, acid phosphatase, and alkaline phosphatase, or in the rate of protein and RNA synthesis. If BUdR incorporation was restricted to limited periods of S phase, TAT was found to be maximally suppressed by incorporation into the initial 40% of the DNA. Incorporation of the analogue into the latter 60% of DNA synthesized during S phase had no effect on TAT. This is the first report that the effect of BUdR on TAT in HTC cells is associated with incorporation of the analog into DNA synthesized during a specific interval of S phase.

Animals↗
PubMed1977

Acetylcholine receptor metabolism in a nonfusing muscle cell line.

The development and turnover of acetylcholine receptors in a nonfusing muscle cell line has been investigated using iodinated alpha-bungarotoxin as a probe for acetylcholine receptor. logarithmically growing cells do not bind toxin, while cells that have ceased cell division bind toxin at a site which has the pharmacological characteristics of an acetylcholine receptor. These binding sites are removed from the cell surface at a rate equal to 8.9 +/- 0.5% of the total surface binding sites/h and appear at a rate equal to 8.3 +/- 1.5% of the total surface binding sites/h. Appearance of new binding sites can occur for a period of 1 1/2 h in the presence of cycloheximide, during which time 15% of the surface receptors can be replaced. There is a hidden population of receptors which is not accessible to toxin without disrupting the cell. This population amounts to 35% of the Triton-extractable receptors in the cell and is composed of two classes. One class, termed a precursor receptor, appears to move from the hidden population to the cell surface, and composes about 40% of the total hidden receptor population. The second class of hidden receptors does not appear to function as a surface precursor and is neither depleted nor enriched by any of the procedures we employed. Surface receptors and hidden receptors are distinguishable on the basis of their sedimentation coefficient about 0.5 to 0.6 S lower than surface receptors. We were unable to distinguish between precursor and non-precursor hidden receptors on the basis of cursor and nonprecursor hidden receptors on the basis of their sedimentation coefficients.

Acetylcholine↗
PubMed1977

Semisynthetic cytochrome c.

Horse heart cytochrome c can be split with cyanogen bromide into a heme peptide (residues 1-65) and a nonheme peptide (residues 66-104). In a process involving (i) complex formation between the two fragments and (ii) restoration of the severed peptide linkage, a fully active cytochrome c preparation can be re-formed. Use has been made of this process to couple the heme peptide to peptide 66-104 synthesized by the Merrifield solid-phase procedure. The semisynthetic product formed in this manner is indistinguishable from reconstituted cytochrome c prepared with nonsynthetic peptide 66-104.

Amino Acids↗
PubMedDate not supplied

Surgical management of thyroid cancer invading the airway.

BACKGROUND: Locally advanced thyroid cancer invading the tracheal cartilage represents a difficult treatment dilemma during thyroidectomy. METHODS: A retrospective chart review was performed to determine the results of laryngotracheal resection or tracheal cartilage shave with adjuvant radiotherapy in patients with locally advanced thyroid cancer invading the upper airway. RESULTS: Of 597 patients undergoing thyroidectomy for thyroid cancer, 40 were found to have laryngotracheal invasion. Thirty-five patients with superficial invasion underwent cartilage shave procedures with adjuvant radiotherapy; five with full-thickness invasion underwent radical resection, including tracheal sleeve resection (n = 3) or total laryngectomy (n = 2). Histologic subtypes included papillary (n = 32), follicular (n = 2), Hurthle cell (n = 1), medullary (n = 3), and anaplastic (n = 2). Of the cartilage shave group, 25 are currently alive with no evidence of disease at a mean follow-up of 81 months (range 1-290). Six developed isolated local/regional recurrence and were managed with total laryngectomy (n = 1), tracheal resection (n = 1), cervical lymphadenectomy (n = 1), or repeat radiotherapy (n = 3). All six patients remain free of disease at a mean follow-up of 5 years. Of those who underwent initial laryngotracheal resection, four remain free of disease at a mean follow-up of 5 years. The rates of 10-year disease-free survival and overall survival for all patients were 47.9% (95% confidence interval [CI] 24.8, 71.0) and 83.9% (95% CI 70.3, 97.5), respectively. CONCLUSIONS: These data suggest that adequate management of thyroid cancer with laryngotracheal invasion can be achieved with a more conservative surgical approach and adjuvant radiotherapy, reserving more radical resections for extensive primary lesions or locally recurrent disease.

Adolescent↗