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Biomedical subjects

R G Stevens

Publications and source records attributed to R G Stevens.

At least 55 records · Page 3Linked to original sources
PubMed1990

A case-cohort study of lung cancer, ionizing radiation, and tobacco smoking among males at the Hanford Site.

Results of several epidemiological studies of workers exposed occupationally to low levels of radiation have been reported but have not included data on smoking. The authors conducted a case-cohort study of male workers at the Hanford Site with an objective of investigating the association between lung-cancer risk and occupational radiation exposure with appropriate adjustment for tobacco use. Eighty-six lung-cancer deaths for the period 1965-1980 and a stratified random sample of 445 subcohort members were included in the study. Tobacco-use data were obtained from medical records collected over each subject's period of employment. Data from this study were analyzed using methods that took into account both the case-cohort design and changes over time in the quality of the tobacco-use data collected. Tobacco use was not strongly related to the level of radiation exposure, and adjustment for tobacco use did not greatly modify results of analyses assessing the association between lung-cancer risk and cumulative dose equivalent. With or without adjustment for tobacco use, the estimated risks per unit of cumulative dose equivalent were negative, but the 95% confidence intervals were wide and included values several times those estimated from populations with high levels of irradiation.

Cohort Studies↗
PubMed1990

Iron, radiation, and cancer.

Increased iron content of cells and tissue may increase the risk of cancer. In particular, high available iron status may increase the risk of a radiation-induced cancer. There are two possible mechanisms for this effect: iron can catalyze the production of oxygen radicals, and it may be a limiting nutrient to the growth and development of a transformed cell in vivo. Given the high available iron content of the western diet and the fact that the world is changing to the western model, it is important to determine if high iron increases the risk of cancer.

Animals↗
PubMed1989

Neuroendocrine mediated effects of electromagnetic-field exposure: possible role of the pineal gland.

Reports from recent epidemiological studies have suggested a possible association between extremely low frequency (ELF; including 50- or 60-Hz) electric- and magnetic-field exposure, and increased risk of certain cancers, depression, and miscarriage. ELF field-induced pineal gland dysfunction is a possible etiological factor in these effects. Work in our laboratory and elsewhere has shown that ELF electromagnetic-field exposure can alter the normal circadian rhythm of melatonin synthesis and release in the pineal gland. Consequences of reduced or inappropriately timed melatonin release on the endocrine, neuronal, and immune systems are discussed. Laboratory data linking ELF field exposure to changes in pineal circadian rhythms in both animals and humans are reviewed. The authors suggest that the pineal gland, in addition to being a convenient locus for measuring dyschronogenic effects of ELF field exposure, may play a central role in biological response to these fields via alterations in the melatonin signal.

Animals↗
PubMed1989

Effects of xylamidine on peripheral 5-hydroxytryptamine-induced anorexia.

Rats injected peripherally with 5-hydroxytryptamine (5-HT) showed a dose-dependent decrease in food intake following overnight fasting. The peripheral 5-HT-2 antagonist xylamidine had no effect on food intake when administered alone, but antagonised 5-HT-induced anorexia. However, at the highest dose of 5-HT (5 mg/kg), both doses of xylamidine (1.0 and 2.0 mg/kg) displayed the same degree of antagonism to the anorectic effect, but failed to block it completely. The results are discussed in terms of 5-HT receptor subtypes, and it is suggested that non-5-HT-2 receptors may be partially responsible for the mediation of peripheral 5-HT-induced anorexia.

Amidines↗
PubMed1989

Acute myelocytic leukemia and prior allergies.

The relationship between prior allergies and adult acute myelocytic leukemia was investigated in a population-based case-control study. Based on data from personal interviews of 98 cases and 133 controls, a history of any type of allergy was associated with a significantly decreased risk of acute myelocytic leukemia (OR = 0.35, 95% CI = 0.20-0.60). Risk declined with the total number of specific allergies reported (p less than 0.001), and was reduced in relation to a history of prior asthma, eczema and hives. The implications of these findings in relation to natural immune surveillance against developing neoplasms are discussed.

Adult↗
PubMed1989

Relation of body size and composition to clinical biochemical and hematologic indices in US men and women.

Small but significant variations in clinical biochemical indices may be of great biological significance. Earlier studies conducted on small, chronically ill, hospitalized, anemic, and/or malnourished population samples suggested associations between body size and composition and indices of iron metabolism, serum protein, and plasma cholesterol. We studied a large, nonhospitalized probability sample of women and men in the First US Health and Nutrition Examination Survey (NHANES I) to characterize these associations. Greater weight, stature, body mass index (BMI), skinfold thickness, and lean body mass (LBM) are associated with higher hemoglobin, hematocrit, and total iron-binding capacity. LBM and body fat are weakly related to serum albumin concentrations in men and to serum total protein concentrations in women. Total cholesterol concentrations are directly associated with weight, body fat, and LBM and are more strongly associated with central than peripheral obesity. Constitutional factors may be important for clinical assessment and for interpretation of epidemiologic studies.

Adipose Tissue↗
PubMed1988

Body iron stores and the risk of cancer.

Because of evidence that increased body iron stores are associated with an increased risk of cancer, we examined iron status and cancer risk in the first National Health and Nutrition Examination Survey, a survey of more than 14,000 adults begun in 1971, with follow-up between 1981 and 1984. Among 242 men in whom cancer developed, the mean total iron-binding capacity was significantly lower (61.4 vs. 62.9 mumol per liter; P = 0.01) and transferrin saturation was significantly higher (33.1 vs. 30.7 percent; P = 0.002) than among 3113 men who remained free of cancer. The risk of cancer in men in each quartile of transferrin-saturation level relative to the lowest quartile was 1.00, 1.01, 1.10, and 1.37 (P = 0.02 for trend). The serum albumin level was significantly lower in men in whom cancer developed than in those who remained cancer-free. Among women, those in whom cancer developed did not have significantly lower total iron-binding capacity or higher transferrin saturation than those who remained cancer-free. However, a post hoc examination of 5367 women (203 with cancer) yielded a relative risk of 1.3 (95 percent confidence interval, 0.9 to 1.9) associated with a very high transferrin saturation (greater than or equal to 36.8 percent, a value in the highest quartile among men); in 5228 women with at least six years of follow-up (149 with cancer), the relative risk associated with transferrin saturation above this level was 1.5 (1.0 to 2.2). These results are consistent with the hypothesis that high body iron stores increase the risk of cancer in men. The possibility that a similar association exists in women requires further study.

Female↗
PubMed1988

The use of difference of Gaussian image filtering to assess objectively the correlation between breast vascularity and breast cancer.

The potential of thermography as a screening technique for the early detection of breast cancer was assessed by using difference of Gaussian filtering to isolate and quantify the vascular contents of breast thermograms. Forty-five patients found to have breast cancer and 49 patients who developed breast cancer within 5 years of being screened were paired with normal variants and the thermograms of each group were assessed. No statistically significant separation was resolved between either of the two paired groups implying that the vascular content of isolated thermograms is unable to provide meaningful indications of breast cancer. The processing algorithm, although developed initially for thermograms, is equally valid for other diagnostic imaging techniques and could be of use where it is required to isolate vascularity or other fine detail from larger body structures.

Breast↗
PubMed1988

Acute nonlymphocytic leukemia and residential exposure to power frequency magnetic fields.

Recent research has suggested that nonionizing radiation in the form of power-frequency magnetic fields may play some role in carcinogenesis in general and in acute nonlymphocytic leukemia in particular. Much of the epidemiologic evidence is preliminary in nature and the methods of previous studies have been criticized. In order to further evaluate this hypothesis, a population-based case-control study of adult acute nonlymphocytic leukemia and residential exposure to power-frequency magnetic fields was carried out in western Washington state. Analyses were based on 114 cases who were newly diagnosed from 1981 to 1984 and identified from a population-based cancer registry, and 133 controls who were chosen from the study area by random digit dialing. Magnetic field exposure was estimated from external electrical wiring configurations within 140 ft (42.7 m) of each subject's residence. In addition, magnetic fields were measured inside the subject's residence at the time of interview. Neither the directly measured magnetic fields nor the surrogate values based on the wiring configurations were associated with acute nonlymphocytic leukemia.

Acute Disease↗
PubMed1987

Residential magnetic and electric fields.

A magnetic flux density (MFD) and electric-field (E-field) data-acquisition system was built for characterizing extremely low-frequency fields in residences. Every 2 min during 24-h periods, MFD and E-field measurements were made in 43 homes in King, Pierce, and Snohomish counties of Washington State. The total electrical energy used in each residence during the 24-h measurement period was also recorded, and maps were drawn to scale of the distribution wiring within 43 m (140 ft) of these homes. Finally, on a separate date, field measurements were made in each home during an epidemiological interview. The results of this study can be summarized as follows: 1) 24-h-average MFD measured at two separate points in the family room were correlated, as were a 24-h-average bedroom measurement and the mean of the two family-room measurements. 2) The 24-h-average family-room MFD and E-field measurements were uncorrelated. 3) The 24-h-average total harmonic distortions of family-room MFD and E-fields were less than about 24% and 7%, respectively. 4) Residential MFD exhibited a definite 24-h (diurnal) cycle. 5) The 24-h-average and interviewer-measured MFD were correlated. 6) Residential 24-h-average MFD were correlated with the wiring code developed by Wertheimer and Leeper. 7) An improved prediction of 24-h-average residential MFD was obtained using the total number of service drops, the distance to neighboring transmission lines, and the number of primary phase conductors.

Electricity↗
PubMed1986

Iron-binding proteins and risk of cancer in Taiwan.

The relationship of serum ferritin and transferrin levels to risk of cancer was examined in a population of 21,513 Chinese male government workers in Taiwan who have been followed prospectively since 1975. On the basis of a previous study in the Solomon Islands, increased ferritin and decreased transferrin levels were predicted for those men who developed cancer. The results were consistent with the prediction. The mean serum ferritin was higher at the start of the study in 192 men who had died of cancer or who had developed primary hepatocellular carcinoma (PHC) as of July 1983, as compared to their controls. The mean serum transferrin level was lower in men who had died of cancers other than PHC. The estimate of relative risk of cancer death for a man with 200 ng ferritin/ml and 200 mg transferrin/dl, as compared to a man with levels of 20 ng/ml and 400 mg/dl, respectively, is 2.9. These serum iron-binding protein levels are at the extremes of the "normal" range. Men who subsequently died of cancer had lower hemoglobin, lower hematocrit, lower albumin, and higher globulin levels at the start of the study than did the controls. These results are consistent with the hypothesis that increased iron stores increase the risk of cancer. However, direct assessment of iron stores prior to disease was not possible, and the same constellation of findings may be consistent with other explanations.

Adult↗
PubMed1986

Serum selenium assay following serum ferritin assay.

Serum samples from 10 individuals were divided into six subsamples. Three of these were tested for ferritin by radioimmunoassay. All six samples from each subject were then tested for selenium by neutron activation assay. There was no significant difference between the selenium values that had been obtained from the sera that had been tested for ferritin and those values that had been obtained for sera not tested for ferritin.

Ferritins↗
PubMed1986

Age and risk of acute leukemia.

Previously unavailable time-depth acute leukemia incidence data were obtained from the Connecticut Tumor Registry for the years 1935-82 and for ages 0-84 years at diagnosis. Acute nonlymphocytic leukemia (ANLL) incidence has risen over the period of observation. Acute lymphocytic leukemia (ALL) incidence has risen much less dramatically. After adjustment for cohort effects, the age-incidence relationships of the acute leukemias show several remarkable features. Incidence of both ALL and ANLL is higher in males than in females in childhood but not in adulthood. Incidence of ALL is higher than incidence of ANLL in childhood, while the reverse is true in adulthood. After a fall in incidence in young adulthood, both ALL and ANLL show age-incidence curves that are similar to those of most adult carcinomas: Incidence increases as a power of age. These features of the age-risk relationship may reflect the growth characteristics of the normal hematopoietic stem cells at risk, and this growth may be influenced by exposure to infectious agents.

Acute Disease↗
PubMed1984

Age and cohort effects in primary liver cancer.

Primary liver cancer incidence data from 30 populations reported in Cancer Incidence in Five Continents were analyzed. After adjustment for time trends, log incidence increases linearly with log age. Liver cancer risk increases more rapidly with age than that of colon cancer, stomach cancer, or lung cancer in non-smokers; it increases less rapidly than that of prostatic cancer or of lung cancer in smokers. Over the past 20 years, most populations have been found to have increasing age-adjusted liver cancer incidence. There is no correlation between change in rates and magnitude of rates. Male rates are higher than female rates and the ratio of the two tends to be higher in high-risk areas.

Adenoma, Bile Duct↗