Search PubMed⌕ Search

Biomedical subjects

C A Swanson

Publications and source records attributed to C A Swanson.

At least 73 records · Page 4Linked to original sources
PubMed1990

Selenium intake, age, gender, and smoking in relation to indices of selenium status of adults residing in a seleniferous area.

Duplicate meals, serum, whole blood, and toenails were collected every 3 mo for 1 y from a group of 44 free-living adults residing in high-selenium areas of South Dakota and Wyoming to assess the relation of selenium intake to indices of selenium status. The average selenium values for the group were as follows: dietary intake, 174 +/- 91 micrograms/d (mean +/- SD), 2.33 +/- 1.08 micrograms/kg body wt; serum, 2.10 +/- 0.38 mumol/L; whole blood, 3.22 +/- 0.79 mumol/L; and toenails, 15.2 +/- 3.0 nmol/g. Selenium intake (micrograms/kg body wt) was strongly correlated (all values, P less than 0.01) with selenium concentration of serum (r = 0.63), whole blood (r = 0.62), and toenails (r = 0.59). Men and women had similar mean values of serum, whole blood, and toenail selenium despite higher selenium intakes in men. Smokers had lower tissue selenium concentrations than did nonsmokers due, at least in part, to lower selenium intake. Age was not associated with tissue selenium content. Of the variables examined selenium intake was clearly the strongest predictor of tissue selenium concentration.

Adult↗
PubMed1989

Body size and breast cancer risk assessed in women participating in the Breast Cancer Detection Demonstration Project.

In a case-control study that included 2,560 breast cancer cases and 2,679 controls, the authors examined the association between body size and breast cancer with the use of measured height and weight of white US women. The subjects were women aged 26-93 years recruited between 1973 and 1975 for participation in the Breast Cancer Detection Demonstration Project, a nationwide breast cancer screening program. After controlling for the effect of potential confounders, the relative risks of breast cancer across increasing quartiles of height were 1.00, 1.07, 1.15, and 1.27 (p = 0.001, test for trend). The effect of weight independent of height was evaluated using indices of relative weight (e.g., weight/height1.5, weight/height2), and the authors identified excess weight as a risk factor for breast cancer among women who had experienced natural menopause and among women aged 50 years or older at diagnosis. Among women aged 50 years or older, for example, the relative risks of breast cancer for increasing quartiles of weight/height1.5 were 1.00, 1.04, 1.40, and 1.29 (p = 0.0006, test for trend). An inverse association between relative weight and breast cancer risk was suggested for women younger than age 50 years at diagnosis. However, the apparent protective effect of high relative weight was restricted to women with small tumors, suggesting a detection bias.

Adult↗
PubMed1989

Effect of low dietary lipid on the development of Sjögren's syndrome and haematological abnormalities in (NZB x NZW)F1 mice.

A diet low in fat was found to retard the development of autoimmune disease in (NZB x NZW)F1 mice, whereas diets high in fat content were associated with more severe disease. The ability of a reduced lipid intake to ameliorate the progression of autoimmune disease was indicated by preserved lacrimal gland secretion (measured by a modified Schirmer test), decreased infiltration of inflammatory cells into the exocrine tissue, and decreased severity of immunohaemolytic anaemia as indicated by near-normal packed cell volume and reticulocyte values. These results suggest that nutritional intervention may be of some help in reducing the severity of pathological abnormalities associated with human systemic lupus erythematosus and Sjögren's syndrome.

Anemia, Hemolytic, Autoimmune↗
PubMed1988

Breast cancer risk assessed by anthropometry in the NHANES I epidemiological follow-up study.

We examined the relation of anthropometric variables and breast cancer risk in the Epidemiological Follow-up Study of the first National Health and Nutrition Examination Survey, a cohort study based on a sample of the United States population. A total of 7149 women, 25 to 74 years of age, who were examined during the period 1971 through 1975 were included in the analysis. Stature, sitting height, elbow width, weight, and subscapular and triceps skinfold measurements were collected during the baseline interview and examination. Breast cancer cases (N = 121) were identified through hospital records or death certificates. The median follow-up period for this cohort was 10 years. Women who developed breast cancer were taller and had greater frame size (elbow width) than women who remained free of breast cancer during the follow-up period. After controlling for the effect of potential confounders, the relative risk of breast cancer was 1.9 (95% confidence interval, 1.1 to 3.1) and 2.2 (95% confidence interval, 1.3 to 3.8) among women in the fourth quartiles of stature and elbow width, respectively. Body size defined by weight, relative weight, or skinfold measurements was not associated with increased risk of breast cancer. The positive association of stature and frame size to risk of breast cancer suggests a potential role of early nutrition in cancer etiology.

Adult↗
PubMed1988

Zinc status of healthy elderly adults: response to supplementation.

The zinc status of 53 healthy elderly subjects was evaluated. The dietary Zn intake estimated by 24-h recall was 9.2 mg/d and 65% of subjects had intakes less than two-thirds of the RDA. Mean serum Zn concentration (13.0 mumol/L) and urinary Zn excretion (7.0 mumol/d) were normal. The Zn content of platelets, mononuclear cells, and polymorphonuclear cells was 5.8, 147, and 135 nmol/10(9) cells, respectively. Seventeen subjects were supplemented for 28 d with 30 mg Zn/d. The mean concentration of Zn in serum and urine increased 24% and 2.5-fold, respectively. Zn content of platelets and leukocytes did not change with Zn supplementation. The concentration of visceral proteins (ie, albumin, prealbumin, transferrin, and retinol-binding protein) and immunoglobulins (ie, IgG, IgA, and IgM) did not change with Zn supplementation. The data indicate that aging per se does not necessarily imply poor Zn status.

Aged↗
PubMed1987

Zinc and pregnancy outcome.

Total zinc needs during the last half of human pregnancy may be approximately 2.6 mg absorbed Zn/d. Adaptations in Zn utilization during pregnancy may help meet those needs. Possible adaptations include an increase in Zn absorption, reduced endogenous Zn loss, redistribution of tissue Zn, and an efficient maternal-fetal Zn transfer. A decline in circulating Zn concentration begins early in pregnancy and continues to term. The effect of gestational stage on circulating Zn should be incorporated into standards for serum Zn of pregnant women. Low maternal serum Zn levels have been associated with pregnancy-induced hypertension, abnormal parturition, and congenital anomalies. In studies done to date, Zn supplementation of 15-45 mg/d failed to improve pregnancy outcome except for a possible reduction in the incidence of a dysfunctional labor pattern. The relationship between Zn status and pregnancy outcome remains an open question.

Animals↗
PubMed1986

Dietary fat influences the expression of autoimmune disease in MRL/lpr/lpr mice.

Near-isocaloric diets with qualitative and quantitative differences in fat content have a profound influence on the manifestation and progression of the autoimmune syndrome that occurs in female MRL/lpr mice. In these animals, a high (9%) lipid intake resulted in a significantly higher mortality rate: 60% (saturated fat) and 75% (unsaturated fat) compared to 35% at 1 year for a group fed a diet low in fat. Furthermore, beginning at 7 months of age mice from both of the high fat diet groups exhibited a significantly higher incidence of proteinuria than mice in the low fat group. Immunologically, the group fed the high unsaturated fat diet had the highest incidence of anti-dsDNA autoantibodies, and the high saturated fat group had the poorest macrophage phagocytic function. The low fat diet preserved near 'normal' immune function in general, particularly IL-2 production. No significant differences were noted in either the production of rheumatoid factor or natural killer cell activity, irrespective of age or diet.

Animals↗
PubMed1983

Quantitative and qualitative aspects of selenium utilization in pregnant and nonpregnant women: an application of stable isotope methodology.

Selenium utilization of women in early and late pregnancy was compared to that of nonpregnant controls. A defined diet providing about 150 micrograms Se/day was fed for 20 days, and selenium balance was measured during the last 12 days. Net selenium retentions of the women in early and late pregnancy were 10 and 23 micrograms/day, respectively, but probably are inflated estimates of the increased selenium requirement during pregnancy. Apparent absorption of selenium was 80% for all three groups. Pregnant women tended to conserve selenium by decreasing urinary selenium excretion. Those observations were corroborated by monitoring the urinary and fecal excretion of 40 micrograms of a stable isotope of selenium (76Se) from intrinsically labeled egg. The isotope data also indicated that recent selenium intake was incorporated into a long-term selenium pool. Mean glutathione peroxidase activity was lower in plasma and higher in platelets in the pregnant women as compared to controls, but the physiological significance of those observations is unknown.

Adult↗
PubMed1983

Copper absorption and retention in pregnant women fed diets based on animal and plant proteins.

Copper absorption was determined by using 65Cu, a stable isotope of copper, in pregnant and nonpregnant women who were confined to a metabolic unit for 21 or 42 days. Absorption and retention of copper were determined from two diets. One diet was comprised primarily of animal protein sources and the other of plant protein sources. The percentage of absorbed copper from the animal protein diet was higher than from the plant protein diet. Copper absorption from the animal protein diet averaged 41.2 and 42.2% in nonpregnant and pregnant women, respectively. Copper absorption from the plant protein diet averaged 33.8% in nonpregnant women and 40.7% in pregnant women. The plant protein diet contained more copper and therefore the absolute amount absorbed was greater from the plant protein diet. The results suggest that either the level of dietary copper or a component of the diet may have an effect on copper absorption. Copper absorption from both diets tended to be higher in pregnant than in nonpregnant women, but the difference was significant only with the plant protein diet. The levels of copper fed in this study, 1.44 and 2.53 mg per day from the animal and plant protein diets, respectively, were sufficient to result in positive balance in all subjects. The amount of copper retained by pregnant women appeared adequate to provide for the increased requirements of pregnancy.

Absorption↗
PubMed1983

Effect of dietary zinc sources and pregnancy on zinc utilization in adult women fed controlled diets.

Five nonpregnant and 10 pregnant women participated in 21-day confined metabolic studies. Two diets each providing 16 mg of zinc per day were fed. In one diet 70% of the total zinc was provided by animal products and 30% was contributed by plant sources. In the second diet the proportions were reversed. Apparent absorption of zinc was determined using the balance technique. During the last 15 days of the study, zinc intake was only slightly greater than the amount of zinc excreted in feces. Mean apparent absorption values did not exceed 5% and did not vary due to diet or pregnancy. Zinc bioavailability was also assessed by measuring the apparent absorption of a stable isotope of zinc (70Zn) added to the diet. There was no significant effect of either diet or pregnancy on 70Zn absorption, which averaged about 25%. Serum zinc values were normal throughout the study and did not change significantly as a function of diet. The pregnant women, however, maintained values that were 19-27% lower than those of the nonpregnant women. In summary, the substitution of animal sources of zinc by plant products did not reduce zinc bioavailability or alter zinc utilization.

Adult↗
PubMed1983

Intrinsic labeling of chicken products with a stable isotope of selenium (76Se).

Chicken tissues were intrinsically labeled with a stable isotope of selenium (76Se) and were evaluated for use in a human feeding study. Laying hens were fed a low Se (0.06 ppm) basal diet for 39 days and then fed the basal diet supplemented with 0.3 ppm enriched 76Se (as selenite) for 35 days. Incorporation of 76Se into samples was determined by use of a double isotope dilution technique and a combined gas chromatography/mass spectrometry analysis. The 76Se content of the basal diet was increased by a factor of 9.7 with the addition of the enriched stable isotope. This maximal level of enrichment was approached in egg yolk (9.5-fold) and liver (9.0-fold). Enrichment was lower in egg white (7.2-fold) and breast meat (5.0-fold). Level of enrichment in a given tissue reflected both the turnover rate of the tissue and its natural selenium content. Selenium-depleted laying hens continuously fed 76Se at the 0.3 ppm level produced egg yolks and livers that were enriched sufficiently with the stable isotope for use in a human metabolic study.

Animals↗
PubMed1983

Reduced serum zinc concentration during pregnancy.

Serum zinc concentration and the partitioning of serum zinc between serum albumin and alpha 2-macroglobulin were measured in ten pregnant and five nonpregnant women fed controlled diets. The diet, prepared from blended foods, provided 16 mg/day of zinc. The pregnant women maintained total serum zinc concentrations which were approximately 19 to 27% lower than those of the nonpregnant controls. The decrease in serum zinc was associated with a decrease in serum albumin concentration. Although the pregnant women had lower concentrations of albumin-bound zinc and alpha 2-macroglobulin-bound zinc, the two groups maintained the same distribution of zinc in serum; approximately 75% was albumin-bound and 25% bound to alpha 2-macroglobulin. Given the expansion of maternal blood volume, a pregnant woman could have a larger circulating pool of zinc than a nonpregnant woman. The decline in serum zinc concentration with pregnancy appears to be a normal physiologic adjustment and is not necessarily indicative of inadequate zinc nutriture.

Adult↗
PubMed1982

Zinc utilization in pregnant and nonpregnant women fed controlled diets providing the zinc RDA.

Eight pregnant (P) women in their third trimester and 10 nonpregnant (NP) women participated in a 21-day confined metabolic study. The participants were fed semipurified liquid diets providing 20 mg zinc/day. Apparent zinc balance was calculated and parameters of zinc status assessed. Even though an adequate amount of a readily available form of zinc was fed, the P women consistently maintained lower mean serum zinc concentrations than the NP controls (69 micrograms/dl vs. 97 micrograms/dl). Although the dietary zinc intake was constant throughout the study, most subjects' salivary zinc levels varied greatly. In this study, salivary zinc concentrations was not a sensitive indicator of zinc intake. There were no differences in the concentrations of zinc in hair between the P and NP groups; mean values ranged from 180--220 ppm. In both groups, approximately 95% of the measured zinc output was lost in the feces and only 5% excreted in the urine. The P women tended to excrete more zinc in their urine than the NP women (900 micrograms/day vs. 650 micrograms/day), but they excreted less zinc in their feces. The P women demonstrated a greater apparent zinc retention than the NP women (1.9 +/- 0.6 vs. 0.9 +/- 0.5 mg/day). This difference, however, was not statistically significant (P greater than 0.05).

Absorption↗
PubMed1982

Sulfur dioxide inhibition of translocation in bean plants.

Exposure of the source leaf of bean (Phaseolus vulgaris L. cv. Black Valentine) for 2 hours to 2.9 microliters per liter SO(2) inhibited the net photosynthetic rate an average of 75% and, simultaneously, the translocation rate an average of 45%. Calculations indicated that the experimentally determined translocation rates from SO(2)-stressed leaves were lower than were the rates expected on the basis of the observed reductions in photosynthesis. It is inferred that, under SO(2) stress, the phloem-loading system becomes a major limiting step in controlling the translocation rate.Following removal of SO(2), photosynthesis recovered quite rapidly (to about 60% of its preexposure rate within 2 hours), but the translocation rate failed to increase during this time interval. This delayed response of translocation to removal of SO(2) does not appear to be due to an injury effect of SO(2), inasmuch as a similar effect was obtained by exposing the source leaf to a short (2-hour) interval of dark.

Journal Article↗
PubMed1980

Alterations in source-sink patterns by modifications of source strength.

Bean plants, trimmed to a simplified "double source, double sink" translocation system (the paired primary leaves serving as the double source and the paired lateral leaflets of the immature first trifoliate leaf as the double sink) were used to study the magnitude and short-term time course of change in the allocation ratio (partition ratio) of assimilates translocated from the labeled primary leaf to its respective "near" and "far leaflet" sinks in response to an increase or decrease in the source strength of the opposite primary leaf (the "control" leaf). If the rates of net photosynthesis in the two primary leaves were similar, assimilates from the labeled source leaf partitioned to the leaflet sinks in the ratio of 5:1 or higher, the dominant sink being the leaflet "nearer" to the labeled source leaf. If the rate of net photosynthesis in the control leaf was increased substantially above that of the labeled source leaf, the rate of translocation from the labeled source to either the near leaflet sink or far leaflet sink remained unaffected, despite, presumably, a higher translocation rate from the control leaf, and hence a higher phloem pressure gradient (or increased cross-sectional area) in the transport pathway from the control leaf to the leaflet sinks. If the control leaf was excised, thus reducing the source leaf area by about a half, the translocation rate from the remaining source leaf rapidly doubled, the partition ratio becoming equal to unity. If the control leaf was darkened, the partition ratio adjusted to an intermediate value. Although export rates from the labeled source leaf were increased either by excising or darkening the control leaf, the rate of net photosynthesis in the labeled leaf remained constant.

Journal Article↗
PubMed1978

Effect of light and ontogenetic stage on sink strength in bean leaves.

Light (about 3,000 foot-candles) neither increased nor decreased the sink strength of young, rapidly expanding leaves of Phaseolus vulgaris L. cv. Black Valentine, as measured by the comparative rates of import of (14)C-labeled photosynthates by sink leaves in the light versus dark in short term experiments. Although irradiated sink leaves accumulated more (14)C activity, the difference was fully accounted for by photosynthetic reabsorption of respiratory CO(2) derived from substrates translocated to the sink leaves.Maximum sink strength was attained when the sink leaf reached 7 to 8 cm(2) in area (9 to 10% of its fully expanded size). Thereafter sink strength declined rapidly and asymptotically to a near zero value at about 45% final area. During this period, however, the rapid decline in translocation was offset by a rapid rise in the photosynthetic rate of the sink leaf, maintaining a near constant relative rate of dry weight increase until the sink leaf had expanded to about 17% of its final area. Although the increasing photosynthetic capacity was associated with a decreasing import capacity, suggesting that the rate of translocation to the sink leaf was controlled by the developing capacity of the sink leaf for photosynthesis, it was not possible to vary the total (true) translocation rate to the sink leaf by varying the photosynthetic rate of the sink leaf in short term light-dark experiments. Despite a high ratio of source to sink in these experiments, no evidence accrued that translocation into young bean leaves was ever sink-limited.

Journal Article↗