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Biomedical subjects

R R Thomas

Publications and source records attributed to R R Thomas.

8 recordsLinked to original sources
PubMed2003

Review article: colorectal cancer chemotherapy.

Colorectal cancer is a leading cause of cancer death world-wide. There have been important advances in the chemotherapeutic management of colorectal cancer as a result of a deliberate collaborative process of well-designed clinical trials. From the earlier standard of 5-fluorouracil-based therapy alone, the recent availability of newer agents, including capecitabine, irinotecan and oxaliplatin, has significantly expanded the options available for the management of patients with advanced colorectal cancer, with consequent improvements in survival. For patients with resected, high-risk, localized disease, adjuvant systemic chemotherapy improves survival. The identification of new chemotherapy regimens, the use of predictive testing and the integration of novel targeted therapies with cytotoxic chemotherapies are areas of active clinical investigation. A review of the chemotherapeutic management of colorectal cancer is presented.

Antineoplastic Agents↗
PubMed2001

A phase I and pharmacologic study of 9-aminocamptothecin administered as a 120-h infusion weekly to adult cancer patients.

PURPOSE: To define the toxicity profile and the recommended phase II doses of 9-aminocamptothecin (9-AC) administered as a weekly 120-h infusion. METHODS: 9-AC was administered over 120 h weekly to 55 adult cancer patients with solid tumors over doses ranging from 0.41 to 0.77 mg/m2 per day in a phase I and pharmacologic study. 9-AC formulated in dimethylacetamide/polyethylene glycol (DMA) was administered on a 3 of 4-week schedule, and the newer colloidal dispersion (CD) formulation was given on a 2 of 3-week schedule. RESULTS: Overall, 193 courses of therapy were administered over 122 dose levels. On the 3 of 4-week schedule, 9-AC DMA infused at > or = 0.6 mg/m2 per day for 120 h weekly produced dose-limiting neutropenia, thrombocytopenia, and diarrhea, or resulted in 1-2-week treatment delays. Shortening treatments to 2 of 3 weeks resulted in dose-limiting neutropenia and fatigue at infusion rates > 0.72 mg/m2 per day. The ratio of 9-AC lactone to total (carboxylate + lactone) drug plasma concentrations at steady-state was 0.15 +/- 0.07. Clinical toxicities and drug pharmacokinetics were not substantially different between the DMA and CD formulations. One objective response was observed in a patient with bladder cancer and minor responses were observed in patients with lung and colon cancers. Plasma area under the concentration versus time curve for 9-AC lactone modestly correlated with the degree of thrombocytopenia (r=0.51) using a sigmoid Emax pharmacodynamic model. CONCLUSION: The recommended phase II dose for the 9-AC DMA formulation is 0.48 mg/m2 per h over 120 h for 3 of 4 weeks and for the 9-AC CD formulation is 0.6 mg/m2 per day over 120 h for 2 of 3 weeks. Both regimens were well tolerated and feasible to administer.

Adult↗
PubMed1984

DNA repair kinetics in mammalian cells following split-dose irradiation.

The in situ DNA repair kinetics in intracerebral 9L tumor cells and cerebellar neurons following the second of two 1250- or 2500-rad doses separated by various times have been measured using alkaline sucrose gradients in zonal rotors. For both doses and all times employed, both cell types exhibited biphasic kinetics similar to those observed after single doses. When the two doses were separated by less than 2 hr in neurons (1 hr for tumor cells), the half-time (T1/2) of the slow phase was faster than that expected based on the amount of damage present and remained constant until the observed T1/2 coincided with the expected T1/2. When repair of the damage produced by the first dose was complete, the slow phase after the second dose exhibited the same T1/2 as after a single dose. These results suggest that the accessibility of a fraction of the chromatin is altered for a finite period during the repair process, and upon completion of repair is returned to a state indistinguishable from that existing prior to irradiation.

Animals↗
PubMed1978

Non-Hodgkin's lymphoma in children.

Until recently the prognosis of childhood non-Hodgkin's lymphoma has been poor. A program of combination chemotherapy and involved area radiotherapy was instituted in the Department of Pediatrics at Roswell Park Memorial Institute in 1971. Thirty-one biopsy proven untreated children entered this study. There were 4 Stage I, 9 Stage II, 6 Stage III, and 12 Stage IV. Initial site of presentation was neck and mediastinum in 16, abdomen in 12, and other sites in three. Nineteen were lymphocytic, seven histiocytic, three undifferentiated, and one was mixed. None had well differentiated or nodular histology. Chemotherapy consisted of vincristine and steroid induction along with intrathecal methotrexate followed by a maintenance phase consisting of daily oral 6-mercaptopurine, weekly oral methotrexate and monthly pulses of vincristine, cyclophosphamide and steroid. Because of initially poor results in Stage IV disease, the protocol was altered midway and high dose methotrexate on three occasions following induction was added. Twelve of 13 Stage I and II patients remain disease free. Four of 6 Stage III patients and 4 of 12 Stage IV patients remain disease free. Only 1/7 of the Stage IV patients prior to high dose methotrexate is disease free, whereas, 3/5 patients with high dose methotrexate are disease free. In total, 19/30 (63%) are disease free for a period ranging from 15+ to 63+ months with 19 patients being disease free for over one year and 12 for over two years.

Adolescent↗
PubMed1977

Performance characteristics of a new photometer with a moving filter tape for luminescence assay.

The performance characteristics of a new photometer that incorporated a reaction system consisting of a movable filtration tape have been studied for use with the firefly luciferase assay for adenosine 5'-triphosphate. Precision, linearity, and sensitivity are given for measuring a graded series of constant-light emitters, concentrations of adenosine 5'-triphosphate, and washed bacterial cells. Precision ranged from 1 to 10% coefficient of variation. The coefficient of correlation was 0.9985 for 7 X 10(8) to 7 X 10(3) bacteria per ml; however, the accuracy decreased at the low levels. The sample processing time was 2 min for a 1-ml sample. This instrument shows potential for many applications in quantitating small numbers of organisms, e.g., pollution, water monitoring, and clinical infection detection.

Adenosine Triphosphate↗
PubMedDate not supplied

From affirmative action to affirming diversity.

Affirmative action is based on a set of 30-year-old premises that badly need revising. White males are no longer dominant at every level of the corporation (statistically, they are merely the largest of many minorities), while decades of attack have noticeably weakened racial and gender prejudices. At the intake level, affirmative action quite effectively sets the stage for a workplace that is gender-, culture-, and color-blind. But minorities and women tend to stagnate, plateau, or quit when they fail to move up the corporate ladder, and everyone's dashed hopes lead to corporate frustration and a period of embarrassed silence, usually followed by a crisis-and more recruitment. Some companies have repeated this cycle three or four times. The problem is that our traditional image of assimilating differences-the American melting pot-is no longer valid. It's a seller's market for skills, and the people business has to attract are refusing to be melted down. So companies are faced with the task of managing unassimilated diversity and getting from it the same commitment, quality, and profit they once got from a homogeneous work force. To reach this goal, we need to work not merely toward culture- and color-blindness but also toward an openly multicultural workplace that taps the full potential of every employee without artificial programs, standards, or barriers. The author gives his own ten guidelines for learning to manage diversity by learning to understand and modify your company's culture, vision, assumptions, models, and systems.

Administrative Personnel↗