Biomedical subjects

J L Beard

Publications and source records attributed to J L Beard.

At least 55 records · Page 3Linked to original sources

PubMed1996

Iron nutrition in rural home bound elderly persons.

The objective of this study was to describe the iron status of a sample of rural elderly home-delivered meals recipients as determined by a relatively non-invasive capillary blood sampling system. Fifty-six persons were assessed in their homes. The incidence of iron deficiency was considerable and was similar to incidences reported in other elderly populations. Females were at higher risk for iron deficiency than males despite a similar low dietary iron intake of 10-11 mg/day in both genders. Data were collected on drug use, general health conditions and other variables that may alter iron status in the elderly but they had no significant statistical effects in this study. We interpret this data on a high prevalence of iron deficiency in females as suggestive that they are at considerable risk of iron deficiency due to a lifelong poorer iron status than men.

Activities of Daily Living↗

PubMed1995

Iron deficiency and anemia of chronic disease in elderly women: a discriminant-analysis approach for differentiation.

To differentiate iron-deficiency anemia and anemia associated with chronic inflammatory diseases in elderly women, subsets of laboratory, dietary, and functional assessment variables were obtained by using discriminant analysis. Fifty-one subjects (70-79 y of age) were classified into one of four groups on the basis of the presence of iron deficiency and chronic inflammatory disease. Iron deficiency was defined on the basis of a significant response in hemoglobin concentration after iron supplementation. The discriminating subset of laboratory tests consisted of measures for serum ferritin, plasma transferrin receptors, and erythrocyte sedimentation rate. The discriminant function classified subjects into iron-deficient, anemia of chronic disease, or a category in which the two coexist, with an error rate of 18.6%. The addition of other variables (dietary iron and functional assessment information) did not appreciably improve the classification. The results of these three key laboratory tests may help to identify functional iron deficiency in the presence of chronic inflammation.

Aged↗

PubMed1995

Classical selenium-dependent glutathione peroxidase expression is decreased secondary to iron deficiency in rats.

While there are reports that classical selenium-dependent glutathione peroxidase (Se-GPX1) activity is decreased during iron deficiency, the relationship between tissue iron status and Se-GPX1 activity remains speculative. This study was undertaken to investigate the mechanism for the decrease in Se-GPX1 activity during iron deficiency. Male weanling Sprague-Dawley rats were given free access to either an iron-deficient or an iron-adequate diet for eight weeks, after which blood, livers, kidneys, hearts, brains and testes were surgically excised. During iron deficiency, Se-GPX1 mRNA levels in liver tissue were decreased by approximately 55%. Similarly, the concentration of immunoreactive Se-GPX1 protein and total selenium-dependent glutathione peroxidase (Se-GPX) activity were decreased by 55% and 60%, respectively. In kidney, heart and brain total Se-GPX activities were depressed as much as 33%. Selenium concentration in liver was reduced by 42%, whereas the decrease in Se concentrations in kidney, heart, and brain ranged from 17 to 25%. Concentrations of plasma Se also were reduced by 18%, but testes showed little change in either Se-GPX activity or Se concentration during iron deficiency. Results suggest that the synthesis of Se-GPX1 protein is decreased during iron deficiency possibly due to pretranslational regulation.

Anemia, Iron-Deficiency↗

PubMed1995

Brain iron, transferrin and ferritin concentrations are altered in developing iron-deficient rats.

To study the iron, transferrin, and ferritin distribution at subcellular levels in response to acute dietary iron deficiency, we tested the hypothesis that early post-weaning iron deficiency can change iron and iron regulatory protein concentrations in rat brain. Male Sprague-Dawley rats were fed diets containing either 2 or 35 micrograms iron/g for 2, 3 or 4 wk starting at 21 d of age. Brain iron, transferrin and ferritin concentrations in cytosolic and microsomal fractions of either whole brain or pons and cerebellum were then determined. After 14 d of dietary iron restriction, brain iron concentrations were 50% lower in the microsomal fraction and 30% lower in cytosol compared with controls. Brain cytosolic transferrin concentration almost doubled in the same animals. Brain ferritin concentration in fractions from rats fed the iron-deficient diet for 14 d was lower than in controls, but then remained fairly constant. Absolute brain weight and total brain protein contents were unaffected by iron restriction. This study extends previous research by demonstrating that the brain responds to changes in body iron status with a change in transferrin concentration. If the dietary restriction is quite severe, this adaptation is insufficient. This study also notes that brain ferritin decreases with decreasing body iron status, though it was less responsive than nonheme iron in liver. The concept that iron enters the brain through a highly regulated endocytotic process at the blood brain barrier, that undoubtedly involves the regulation of transferrin receptors in capillary endothelial cell, is supported by our observation of elevated transferrin concentrations in brain of iron-deficient rats.

Anemia, Iron-Deficiency↗

PubMed1995

Sensory acceptability of meat and dairy products and dietary fat in male collegiate swimmers.

This study was undertaken to determine whether high-level training alters food choice behavior with regard to meat and dairy products because of their high fat content. Twenty male collegiate swimmers were compared to 20 male sedentary students for dietary fat intake, nutrition knowledge, and liking of meat and dairy products. There was no significant difference between the two groups for restraint, energy intake, dietary fat intake, and energy derived from fat. Nutrition knowledge, energy derived from saturated fat, and cholesterol intake, however, were significantly higher in the athletes. The two groups did not differ in their hedonic ratings of flavor or in their overall degree of liking of the meat and dairy products, and the athletes actually liked the appearance and texture of the products significantly more than did the sedentary students. This study shows that the sensory appeal of fat-containing animal products is not affected in male swimmers by a high level of exercise.

Adult↗

PubMed1995

Effect of thyroid hormone replacement in iron-deficient rats.

To determine if the previously observed alterations in norepinephrine (NE) metabolism and resting metabolic rate in iron-deficient (ID) rats result from hypothyroidism, exogenous thyroxine (T4) and 3,5,3'-triiodothyronine (T3) were administered to ID rats in doses sufficient to normalize the plasma concentrations of these hormones, whereas other ID and control (CN) rats received placebo treatment. Resting oxygen consumption was approximately 25% higher in ID than CN rats; T4 but not T3 treatment alleviated this elevated oxygen uptake. The NE content of interscapular brown adipose tissue (IBAT), liver, and heart was 70-80% lower in ID than CN rats, and NE turnover in the same tissues was likewise 40-60% lower in ID than CN rats, with no systematic effect of either T3 or T4 treatment. Liver T(4)5'-deiodinase activity was 70% lower in ID than CN rats and increased with T4 but not T3 treatment. These experiments show that iron deficiency alters NE and energy metabolism in a way that is mostly independent of its effects on thyroid hormone metabolism.

Adipose Tissue, Brown↗

PubMed1995

Growth in iron-deficient rats.

Poor growth in iron deficiency is commonly observed in animal studies. Previous studies from our laboratory showed that iron-deficient rats are metabolically inefficient and have less body fat than controls and proposed that iron deficiency was related to increased metabolic rates and heat loss. To examine these points more completely, we examined growth and metabolic rate of iron-deficient rats at two environmental temperatures, 25 degrees C and 32 degrees C, and feed efficiency in separate groups of rats during a period of rapid growth. Iron deficiency (hemoglobin [Hb] approximately 60 g/liter) was associated with a systematic elevation of metabolic rate over the 24-hr day with animals at 25 degrees C. This did not occur in animals living in thermoneutrality. Iron deficiency affected growth of animals at 25 degrees C but not at 32 degrees C. Feed efficiency (kcal retained/kcal absorbed) was 25 +/- 4.2 and 31 +/- 4.9 kcal (P < 0.0001), respectively, in iron deficient rats and animals were not anorexic. Use of food-restricted animals allowed the direct calculation that iron deficiency was associated with a 10%-15% increase requirement for growth. We conclude that iron deficiency anemia is associated with a poor feed efficiency and that it is attenuated when nonshivering thermogenesis is minimized by a thermoneutral environment.

Anemia, Iron-Deficiency↗

PubMed1995

Effects of long-term moderate exercise on iron status in young women.

The impact of long-term (6-month) moderate exercise on the iron status of previously sedentary women was determined by randomly assigning 62 college-age women into one of the following four groups: 1) 50 mg.d-1 iron supplement, low iron diet (N = 16); 2) Placebo, free choice diet (N = 13); 3) Meat supplement to achieve 15 mg.d-1 iron intake (N = 13); and 4) Control, free choice diet (N = 20). All groups except the Control group exercised 3 d.wk-1 at 60%-75% of their heart rate reserve. VO2max was measured at baseline and week 24. Blood was sampled at baseline and every 4 wk thereafter for 24 wk to measure iron status and to elucidate the causes for alterations in iron status. Subjects had depleted iron stores throughout the study as indicated by their serum ferritin levels (< 15 ng.ml-1). Serum iron, total iron binding capacity and transferrin saturation were not compromised with exercise. Mean hemoglobin level in the Placebo/Ex group was significantly (P < 0.05) lower than the 50 Fe/Ex and the Meat/Ex groups by week 24. However, changes in serum albumin, haptoglobin, and erythropoietin data from the study cannot explain these changes.

Adult↗

PubMed1994

Altered monamine metabolism in caudate-putamen of iron-deficient rats.

The effect of iron deficiency on brain monoamine metabolism using in vivo microdialysis techniques has not been previously reported. We, therefore, examined the monoamines, dopamine and norepinephrine, and their metabolites at steady state by in vivo microdialysis in rat brain caudate-putamen in 11-week-old iron-deficient anemic (hemoglobin < 7 g/dl) and control rats (Hb > 14 g/dl). Caudate-putamen dopamine (DA), dihydroxyphenyl acetic acid (DOPAC), and homovanillic acid (HVA) concentrations were increased by 53%, 57%, and 30% (p < 0.001), respectively, in iron-deficient rats in samples collected over a 4-h period. While diminished numbers of D2 receptors have been previously reported, the present findings suggest an additional defect in monoamine uptake and catabolism.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1994

Iron deficiency: assessment during pregnancy and its importance in pregnant adolescents.

The assessment of iron deficiency in pregnancy requires the accurate determination of indicators that have significant within-subject variability. For instance, serum ferritin concentrations may vary by as much as 25% from one day to the next. Added to this uncertainty about biological variability is the influence of plasma volume expansion on concentration-dependent indexes such as ferritin, plasma iron, and hemoglobin. Multiple measurements of iron status are suggested, and, if this is not possible, within-subject variability needs to be included in the confidence of assigning individuals to iron-status groups. An example of this former approach is shown for a group of pregnant adolescents with a very high prevalence of iron deficiency. Although the assessment of iron status in human populations is advanced compared with that of other nutrients, there is still a large uncertainty about absolute diagnosis during pregnancy.

Adolescent↗

PubMed1993

Day-to-day variation in iron-status indexes in elderly women.

Day-to-day variability in biochemical indicators of iron status in well-hydrated and healthy women 70-79 y old (n = 10) was determined. Venous blood was collected on 4 nonconsecutive days during a 2-wk period. Analytical (sigma 2 rep) and biological (sigma 2 fd) variance components were computed based on a previously established scheme in younger adults. These two variance components were summed to obtain the total day-to-day variability (sigma 2 fd). Our results indicate that biological variation contributed most to the intraindividual variation. We calculated that sampling once for most iron indexes and twice for plasma transferrin receptors in elderly individuals is adequate to accurately determine these indexes whereas serum iron and transferrin saturation, indexes with high CVfd, require seven and eight measurements, respectively. These data, compared with previously published data in younger adults, demonstrate that aging is associated with a decreased variation in some indexes of iron status such as serum ferritin.

Aged↗

PubMed1993

Are we at risk for heart disease because of normal iron status?

A recent prospective three-year follow-up study of 1931 men in Finland demonstrated a significant 2.2-fold greater risk of acute myocardial infarct in 42- to 60-year-old men who had serum ferritin concentrations above 200 micrograms/dL. However, the mean plasma ferritin concentration in this population was high and the prevalence of hemochromatosis was unknown; these issues mitigate the suggestion that high-normal iron stores leads to heart disease.

Adult↗

PubMed1993

Iron in the brain.

The location and function of iron in the central nervous system are reviewed with particular emphasis on human biology. Iron is distributed to different cell types in the brain in a heterogeneous fashion through the action of transferrin, transferrin receptors, and the metabolic needs of those cells. The function of this iron and its storage is documented in states of growth and development as well as during pathological states associated with aging. The information relating this biology to current observations of attention deficits in iron-deficient humans is also reviewed.

Adult↗

PubMed1993

Hepatic glucose production and insulin sensitivity and responsiveness in iron-deficient anemic rats.

We performed euglycemic hyperinsulinemic glucose clamps at insulin infusion rates of 1.9, 4.0, 9.3, and 19.3 mU.kg-1 x min-1 in rats with varying severities of iron deficiency anemia (IDA; mean hemoglobin concentrations of 59, 79, 107, and 137 g/l) to assess the effect of IDA on insulin sensitivity and responsiveness. Glucose appearance and disappearance (Rd) rates were determined using a primed continuous infusion of [3-3H]glucose. Basal plasma glucose and insulin concentrations were similar between the IDA and control rats. Basal hepatic glucose production was significantly (P = 0.0001) elevated in the two most anemic groups (13.6 +/- 2.4 and 12.6 +/- 3.1 vs. 10.6 +/- 2.2 and 10.2 +/- 2.0 mg.kg-1 x min-1). A significant upward shift in the insulin dose-response curves for Rd indicated an increase in peripheral insulin responsiveness in the two most anemic groups while a slight leftward shift was suggestive of an increase in insulin sensitivity in all three anemic groups. Hepatic insulin sensitivity and responsiveness were unaffected by IDA. We conclude that increased glucose utilization rates in IDA rats are due primarily to an increase in peripheral insulin responsiveness.

Anemia, Hypochromic↗

PubMed1993

Exercise training alters feed efficiency and body composition in iron deficient rats.

Studies of body composition and feed efficiency were conducted on 80 male Sprague-Dawley rats to determine how exercise training alters growth and development in iron deficient animals. Animals were assigned to iron deficient (ID) or control (CN) diets (AIN-76, w/o cellulose), and sedentary (SD) or exercised groups [EX, treadmill running, 4 d.wk-1, 90 min.d-1, 65% maximal oxygen consumption (VO2max), maintained for 6 or 12 wk. The ID diet caused a sustained moderate iron deficiency (Hb 7.2 +/- 0.2 g.dl-1). Iron deficient animals failed to increase maximal oxygen consumption despite the rigorous training program, through training resulted in 25% or 35% higher VO2max in 6- or 12-wk CN rats. At 6 wk, IDEX animals had significantly (33%) lower growth rates than did IDSD animals, which in turn were 22% less than CNs. Overall, exercise did not alter relative amounts of protein in the carcass (% total mass); however, a significant interaction between diet and treatment duration was evident in IDEX animals at 12 wk, who had lower % protein than CNEX-12 or IDSD-6 rats. Training decreased fat 11% in CN at 6 wk but not 12 wk, and 20% in IDs at 12 wk but not 6 wk. Feed efficiency and energy intake were 28% and 12% lower in IDEX animals than CNEX at 6 wk. Training increased caloric intake in CNEX animals but not IDEX animals at 6 and 12 wk. Thus, exercise training exacerbates the poor growth associated with ID through alterations in both food intake and feed efficiency in early phases of training, but adaptation is apparent.

Animals↗

PubMed1992

Regional distribution of iron and iron-regulatory proteins in the brain in aging and Alzheimer's disease.

It is well established that iron, which is of considerable importance for normal neurological function, is highly regulated in all organ systems. However, until recently, iron regulation in the nervous system has received little attention. This study quantitatively compares the levels of the major iron-regulatory proteins, transferrin and ferritin, and iron itself in three cerebral cortical regions of the human brain from material collected at autopsy. Three groups were studied: 1) normal adult (under 65 yr of age), 2) aged (greater than 65), and 3) Alzheimer's disease. Normally, transferrin is more abundant in white matter than in gray matter. Ferritin is approximately 10x more abundant than transferrin throughout the brain regions examined and is evenly distributed, as is iron, in the gray and white matter. In Alzheimer's disease transferrin is consistently decreased particularly in the white matter of the various cerebral cortical regions examined whereas the iron and ferritin changes are inconsistent. The observations in this study are consistent with our general hypothesis that iron homeostasis is disrupted in the aging brain and the alterations in iron-regulatory proteins are exacerbated in Alzheimer's disease. The decrease in transferrin levels could indicate a decreased mobility and subsequent utilization of iron in the brain. Such a decrease in iron availability could play a significant role in neuronal degeneration and increased peroxidative damage known to occur in Alzheimer's disease.

Adult↗

PubMed1992

The relationship of serum and salivary cortisol in a sample of healthy elderly.

The purpose of this study was to assess the validity of salivary cortisol as an index of adrenocortical activity in older adults. Serum and salivary cortisol samples were collected in a sample of 36 healthy older adults (mean age = 66.64). The relationship of serum and salivary cortisol levels was assessed using correlation and regression analyses. In addition, the stability of serum and salivary levels over repeated samplings was assessed. The findings indicate that salivary measures of cortisol covary with serum levels, and both measures remain stable over repeated samplings. The utility of salivary cortisol as a marker of physiological reactivity is discussed. Future research is recommended to explore the emotional correlates of physiological reactivity in older adults.

Aged↗

PubMed1991

Day-to-day variation in iron-status indices in healthy men and women.

We evaluated the day-to-day variation of four iron-status indices: hemoglobin (Hb), hematocrit (Hct), plasma ferritin (PF), and plasma iron (PI). Finger-prick blood samples were collected for 31 consecutive days in 20 healthy men and women. Replicate (sigma 2rep) and day-to-day (sigma 2day) variance components were estimated. Day-to-day variation in the iron-status measures was similar between men and women except for PF, for which the variation was greater in women. The CVs for a single future determination for Hb, Hct, PF, and PI were 4.6%, 3.0%, 15.2%, and 26.7% for males and 4.4%, 3.2%, 26.8%, and 29.0% for females, respectively. Three to 10 independent measurements are required to accurately determine PF and PI whereas one is adequate for Hb and Hct. Thus, day-to-day biological variation is a major component of the variability in these iron-status indicators and must be considered when assessing iron status.

Adult↗