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Biomedical subjects

T Colton

Publications and source records attributed to T Colton.

At least 37 records · Page 2Linked to original sources
PubMed1984

Determination of carcinogenic synergism from the latent period.

We present a method for determining the presence or absence of synergism between two carcinogens A and B from the latent period of tumors. The method is applied to data consisting of the means and standard deviations of the times at which tumors become palpable and at which death from tumor occurs in animals of three groups: those given carcinogen A alone, those given B alone, and those given both A and B. Synergism was absent in the data examined.

Animals↗
PubMed1984

Evaluating a direct observation exercise in a psychiatric clerkship.

The introduction of a direct observation exercise in the psychiatric clerkship at McMaster University is presented. Preliminary investigation of the reliability, construct validity, educational effects and feasibility of the exercise is discussed. The direct observation exercise is found to measure improvement in skills, enhance the recording of student performance, be valued by the students and feasible in the clinical setting. Directions for future evaluation research with direct observation exercises are outlined.

Clinical Clerkship↗
PubMed1984

Multiple testing of hypotheses in comparing two groups.

Researchers frequently encounter studies that compare two groups on many variables. We discourage the use of multiple tests of hypotheses on individual variables, an approach that ignores the correlation among the variables and increases the chance of a type I error. Instead of examining each variable separately, we recommend using multivariate procedures that integrate all measures on a person into a unified analysis of the differences between the two groups. We describe three multivariate procedures: Hotelling's T2, discriminant analysis, and logistic regression. We also discuss the use of Bonferroni's adjustment to preserve the overall chance of a type I error in conducting individual tests on each variable after doing the multivariate procedures. We review the underlying assumptions and relative merits and disadvantages of the three multivariate methods and recommend which method to use in various circumstances.

Analysis of Variance↗
PubMed1984

Adenocarcinoma and Barrett's esophagus. An overrated risk?

The risk of developing esophageal cancer in Barrett's esophagus has been estimated at about 10%. This estimate is based primarily on data concerning the prevalence of that association in series of hospitalized patients and autopsies--a practice that tends to exaggerate the risk. We have reviewed retrospectively our experience with 115 patients whom we treated for Barrett's esophagus between September 1962 and March 1983, and have distinguished our data on the prevalence of esophageal cancer from that on incidence. For 8 patients, we found both Barrett's esophagus and esophageal adenocarcinoma during the initial evaluations for a prevalence ratio of 7%. We followed 105 patients not found to have esophageal cancer initially for a total of 350 person-years. Only 2 patients developed adenocarcinoma during that follow-up period for an incidence of 1 case per 175 person-years. This incidence, although some 40-fold greater than that of the general population, is substantially lower than previously estimated. Routine endoscopic and histologic surveillance has been recommended for patients with Barrett's esophagus because of the alleged high incidence of esophageal cancer. Inasmuch as that incidence now appears to be low, we question the value of such surveillance for these patients.

Adenocarcinoma↗
PubMed1983

Relief of continuous chronic pain by intraspinal narcotics infusion via an implanted reservoir.

Ten patients with intractable pain (five cancer and five nonmalignant) were treated with continuous intraspinal morphine delivered by an implanted continuous infusion system. Both patient groups were evaluated and compared using an identical battery of psychometric examinations administered before and 12 weeks after therapy. The cancer-pain group reported significant reduction in pain on serial visual pain analogue scales at 12 weeks compared with no change in the nonmalignant-pain group reports despite a much lower baseline report in the cancer group. Both groups of patients reduced their oral narcotic requirement significantly during continuous intraspinal morphine infusion. While the cancer patients took more oral narcotic at baseline, at 12 weeks no difference existed in oral intake between the two groups. Both groups required significant serial increases in infused morphine, indicating that spinal opiate receptor tolerance occurs. The results of this study confirm the sustained analgesic efficacy reported earlier in cancer-related pain syndromes, thus supporting further cautious expansion of this therapy within the cancer-related pain population. In contrast, a poor response was seen in the nonmalignant-pain group, consistent with the unsatisfactory responses to many potentially analgetic approaches to chronic nonmalignant pain. We are thus discouraged from further use of this therapy in the patient with chronic nonmalignant pain.

Administration, Oral↗
PubMed1982

Measurement of cancer incidence in the United States: sources and uses of data.

Since 1937, investigations have compiled a vast amount of information on cancer incidence in the United States. Three national cancer surveys were conducted in 1937, 1947, and 1969-71; each used somewhat different methods but covered populations who overlapped greatly. Concurrently, population-based tumor registries were developed that were capable of measuring cancer incidence. Since 1973, the Surveillance, Epidemiology, and End Results Program, an amalgam of such registries, had generated cancer incidence data for the United States. Available data provide a rough measure of the size of the cancer problem and may help those who direct prevention programs and those who plan studies of cancer etiology. Because the completeness and validity of existing incidence data are not known with certainty, comparisons among these incidence data are not known with certainty, comparisons among these incidence rates require cautious interpretation.

Evaluation Studies as Topic↗
PubMed1981

Thyroid function after mantle irradiation in Hodgkin's disease.

We studied the thyroid function of 64 patients with Hodgkin's disease who received mantle irradiation during the period 1966 to 1976. More than two thirds (44 of 64) had some thyroid dysfunction. Twenty had mild dysfunction manifested by an abnormal thyroid-stimulating hormone response to thyrotropin-releasing hormone. Twenty had what could be termed compensated hypothyroidism while four were overtly hypothyroid. The severity of dysfunction was not related to age, sex, or chemotherapy. We found, however, that decreased thyroid function was inversely proportional to the length of time between a diagnostic lymphangiogram and the radiation therapy. These results are consistent with the hypothesis that the iodine load of the lymphangiogram renders the thyroid gland more radiosensitive. Thyroxine suppression of the thyroid gland during the period from the lymphangiogram through the termination of radiation therapy is suggested as a means of avoiding thyroid injury.

Ethiodized Oil↗
PubMed1978

Mortality from leukaemia and cancer in shipyard nuclear workers.

A review of death certificates in New Hampshire, Maine, and Massachusetts for 1959-77 yielded a total of 1722 deaths among former workers at the Portsmouth Naval Shipyard where nuclear submarines are repaired and refuelled. Next of kin were contacted for 592. All deaths under age 80 were classified as being in former nuclear or non-nuclear workers depending on information supplied by next of kin. With U.S. age-specific proportional cancer mortality for White males as a standard, the observed/expected ratio of leukaemia deaths was 5.62 (6 observed, 1.1 expected) among the 146 former nuclear workers. For all cancer deaths, this ratio was 1.78. Among non-nuclear workers there was no statistically significant increase in proportional mortality from either leukaemia or from all cancers. The excess proportional leukaemia and cancer mortality among nuclear workers exceeds predictions based on previous data of radiation effects in man.

Aged↗
PubMed1978

Surgeons in the United States. Practice characteristics.

Data on practice characteristics were obtained as part of a national questionnaire study of surgeons in the United States. These included location and organization of surgeons' practices, use of nonphysician personnel, provision of ambulatory care, other professional activities, and variables associated with work load volume. A multivariate analysis was done to examine the relation between operative work loads and various practice characteristics. The variables associated with larger operative work loads were group or partnership practice, principal office not in a hospital, more nonphysician assistants in direct contact with patients, more hospitals in which operations were regularly done, and smaller proportions of nonsurgical patients. Group or partnership practice and nonsurgical practice were found to be most strongly related to operative work load.

Ambulatory Care↗
PubMed1978

Prevalence of senile cataract, diabetic retinopathy, senile macular degeneration, and open-angle glaucoma in the Framingham eye study.

Of the Framingham, Massachusetts Heart Study population, 2,675 individuals underwent an ophthalmologic evaluation that stressed detection of senile cataract, diabetic retinopathy, open-angle glaucoma, and senile macular degeneration. Those examined were 52 to 85 years old at the time this study was initiated. The prevalence rate of each of these ocular conditions increased with age. Prevalence of senile cataracts ranged from 4.6% for those between the ages of 52 to 64 years to 46% for those 75 to 85 years of age. Diabetic retinopathy was present in 2% of those between 52 and 64 years of age or older. Overall prevalence of senile macular degeneration was 9%, with a prevalence rate of 2% in our youngest age group and 28% in the oldest age group. Open-angle glaucoma had an overall prevalence of approximately 3%. This disease also showed a statistically significant (P less than .01) increase with age from 1.4% (52 to 64 years old) to 7.2% (75 to 85 years old).

Aged↗
PubMed1978

Comparison of luteolytic potencies of aminoglutethimide enantiomers in the rabbit and rat.

The luteolytic potency of D- and L-aminoglutethimide (D- and L-AG) was compared in in vivo assays in the rat and rabbit. By assay of plasma progesterone depletion in the rabbit, the potency of L-AG relative to D-AG was 0.21. By the plasma procedure in the rat, the relative potencies of L-AG and of the racemic mixture to D-AG were 0.04 and 0.37, respectively. By the ovarian progesterone depletion method, the L-form had very little activity and the DL-mixture was half as active as the D-isomer. Thus, in both species, almost all of the activity of the racemic mixture results from the content of D-AG. Interpretation of paradoxical data implies that in the rat, L-AG may inhibit liver degradation of progesterone at levels which do not modify secretion from the corpus luteum.

Aminoglutethimide↗
PubMed1977

Age-incidence and risk of diethylstilbestrol-related clear cell adenocarcinoma of the vagina and cervix.

This study was based on cases accessioned in the Registry of Clear Cell Adenocarcinoma of the Genital Tract in Young Females to ascertain the incidence of diethylstilbestrol (DES)-related cancers by age and year of birth. For accuracy in estimating the size of the reference population for the incidence rates, calculations were restricted to 127 white residents of the United States who were exposed prenatally to DES or other nonsteroidal synthetic estrogens. The disease is exceedingly rare prior to age 14 when the incidence rate begins to rise rapidly. The incidence peaks at age 19 (median 19.2 years) and then drops precipitately. Thus, DES-related clear cell adenocarcinoma is unusual in that nearly all cancers have been diagnosed in a narrow age range of 10 years (14 to 23 years). Women born in 1951 to 1953 have higher incidence rates than those born in the previous or subsequent three-year period. This suggests that the prevalence of pregnancy-related use of DES was at a peak in the early 1950's. The cumulative risk of this type of genital cancer, through age 24, for DES-exposed female subjects is estimated to be in the range of 0.14 to 1.4 per thousand. The wide limits are due to the fact that the number of young women exposed is not known precisly. The low risk of disease and the narrow age range of the cases, relative to the long latency period, suggest that DES is an incomplete carcinogen. Other factors, possibly related to puberty, may be involved in the causation of this disease.

Adenocarcinoma↗
PubMed1977

The Framingham Eye Study. I. Outline and major prevalence findings.

During the period 1973--1975, 2675 out of 3977 still-living members of the Framingham, Massachusetts, study population, who have been under investigation for coronary disease risk factors since 1948 and who were in 1973--1975 aged 52 to 85, were given an eye examination stressing cataract, diabetic retinopathy, macular degeneration and glaucoma. Of 2940 subjects who still lived in the local Framingham area, 2477 were examined. Local population prevalence for one or both eyes positive was: 15.5% for senile cataract, 3.1% for diabetic retinopathy, 8.8% for senile macular degeneration and 3.3% for open-angle glaucoma. The proportion of adults with poor "best" visual acuity may be much less than has been estimated by the National Health Survey and the proportion with open-angle glaucoma much more than currently suspected on the basis of foreign studies.

Age Factors↗
PubMed1977

The Framingham Eye Study. II. Association of ophthalmic pathology with single variables previously measured in the Framingham Heart Study.

Using the age-sex-specific data collected in the Framingham Heart Study 1948--1964 together with ophthalmic diagnoses made in the Framingham Eye Study in 1973--1975, the following variables were found to be associated with senile cataract: education, casual blood sugar, systemic blood pressure, height, vital capacity, serum phospholipid and hand strength; with senile macular degeneration: systemic blood pressure, height, vital capacity, left ventricular hypertrophy, hand strength and history of lung infection; with diabetic retinopathy: casual blood sugar, urine sugar and other specific elements of diabetes; with ocular hypertension: systemic blood pressure, height, casual blood sugar and pulse rate. No variables were identified as associated with open-angle glaucoma. The paper stresses the need for corroboration of these findings, which may be a mix of real and chance associations, and the need for additional analyses before any of these associations are considered evidence of factors related to risk of ophthalmic disease.

Aged↗
PubMed1977

Quality of care and unnecessary operations: a comment on The Condition of Surgery.

Issues of quality of surgical care and unnecessary operations are complex, and they will require more objective and clinically based investigations before reasonable economic judgements can be made. SOSSUS did not shy away from these questions; rather, it kept to its assigned task of describing the distribution and workloads of physicians.

Clinical Competence↗