A H Ritter | PubMed Health

PubMed1992

Rectal carcinoma. Long-term experience with moderately high-dose preoperative radiation and low anterior resection.

This report updated an analysis of a 14-year experience of moderately high-dose (4500 to 5000 cGy) preoperative radiation as an adjuvant to low anterior resection of 95 cases of adenocarcinoma of the rectum. The treatment was well tolerated without treatment-related mortality and with a low incidence (5.2%) of severe complications. The local recurrence rate was 4.2%, and distant failure rate was 10.5%. At 5 years, the actuarial survival rate was 66% and the disease-free survival rate was 64%. At 10 years, the actuarial survival rate and disease-free survival rate were 52%. The authors concluded that moderately high-dose (4500 to 5000 cGy) neoadjuvant radiation in clinically resectable adenocarcinoma of the rectum in which one segment of the anastomosis was in the preoperative radiation field is a safe, effective adjuvant to low anterior resection and that it offered patients excellent local control, long-term survival, and sphincter preservation. Results could be enhanced by chemotherapy, and the authors urged well-designed prospective randomized multicenter trials to determine the most appropriate drugs, dosage, and sequencing of co-adjuvant preoperative radiation therapy and chemotherapy with surgery.

Adult↗

PubMed1976

Interactions between model proteins and deoxyribonucleic acids.

Interactions between DNA and model proteins, poly(L-Lys(m)L-Ala(n)), where m + n = 100%, have been investigated using thermal denaturation and circular dichroism (CD). All complexes of DNA with these proteins precipitate in a small range of input ratios, protein to DNA, with the midpoints of all precipitation curves close to a 1:1 ratio of lysine to phosphate. The melting temperature of model protein-bound DNA regions decreases slightly as the alanine content of the model protein is increased, which can be explained as a result of insufficient charge neutralization of phosphates by lysine residues in the model proteins. In the free state, these model proteins possess varying amounts of alpha helix, random coil, or a mixture of these two, depending upon the relative lysine/alanine content. When bound to DNA, the CD of the complex shows a substantial increase in alpha-helical structure for those model proteins with 40-60% alanine, while there is no significant change in alpha-helical structure when the percent alanine is either substantially higher or lower (i.e., 81 or 19% alanine). Only those complexes formed with model proteins having 40-60% alanine undergo a drastic transition from a B-type CD to an A-type in the presence of intermediate ionic strength (0.2 M NaCl, for example). Poly(Lys19Ala81)-DNA complexes show a slight transition toward A-type CD at 0.4 M NaCl or higher. Apparently other factors, in addition to alanine and alpha-helical content, must be responsible for this B leads to A transition. At the other extreme of lysine/alanine ratio, with high lysine content, poly(Lys81Ala19) or polylysine, the presence of NaCl produces a B leads to psi transition. The possible significance of these differences in response to the binding of these model proteins is discussed.

Alanine↗