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Biomedical subjects

G D Miller

Publications and source records attributed to G D Miller.

At least 37 records · Page 2Linked to original sources
PubMed1998

Copper deficiency and arachidonic acid enhance insulin secretion in isolated pancreatic islets from lean (FaFa) Zucker rats.

Based on reports that copper deficiency can result in altered arachidonic acid (AA) metabolism and the knowledge that AA can modulate insulin secretion, we investigated the interaction of copper deficiency and AA on glucose-stimulated insulin secretion by using isolated islets. Lean male (Fa/Fa) Zucker rats were fed either a copper-adequate (Cont) or low-Cu (Cu Defic) diet (8.7 vs. 0.5 micrograms copper/g diet) for 5 weeks. Pancreatic islets were isolated and incubated in medium containing 3.3, 8.3, or 16.7 mM glucose with or without 100 microM AA. Insulin secretion was measured after either 5 (phase I) or 45 (phase II) min of incubation. In the absence of AA, islets from Cu Defic rats secreted more insulin during phase I than those from Cont rats; phase II insulin secretion was similar between the groups. Exogenous AA treatment increased insulin secretion from islets during both phases of insulin secretion, regardless of dietary copper treatment. In the presence of AA, islets from Cu Defic rats secreted more insulin in phase I than did islets from Cont rats at the 3.3 and 8.3 mM glucose levels. Similar findings were made for phase II insulin secretion. Consistent with this, Cu Defic rats tended to have higher plasma insulin levels than Cont rats (472.6 vs. 199.6 pM). In summary, Cu deficiency increases insulin release in isolated islets; this response is particularly pronounced when AA is present in the incubation medium.

Animals↗
PubMed1997

Fatty acids, not insulin, modulate alpha1-adrenergic reactivity in dorsal hand veins.

Resistance to the vasodilator action of insulin and its capacity to antagonize vascular alpha-adrenergic reactivity may contribute to the increased neurovascular tone and blood pressure in obese hypertensive subjects. We showed that nonesterified fatty acids (NEFAs) were elevated in obese hypertensive subjects and that raising NEFAs locally in dorsal hand veins of healthy normotensive subjects enhances alpha1adrenoceptor reactivity. Research by others suggests that insulin antagonizes alpha1-adrenoceptor tone in dorsal hand veins. Taken together with evidence that NEFAs antagonize several of the metabolic actions of insulin, these observations raise the possibility that NEFAs participate in resistance to the vascular effects of insulin and suggest that dorsal hand veins represent a good model for studying these interactions. Thus, we produced local hyperinsulinemia in the dorsal hand veins of six lean normal volunteers and quantified changes of venous distensibility in response to phenylephrine in the presence and absence of a local elevation of NEFAs. We confirmed that raising NEFAs locally decreased by twofold to threefold the phenylephrine ED50 (P<.01), but this alpha1-sensitizing action of NEFAs was not antagonized by insulin concentrations up to approximately 1000 microU/mL. Moreover, local hyperinsulinemia alone did not affect vascular alpha1-adrenergic sensitivity as measured by the phenylephrine ED50. To address the possibility that the absence of an insulin effect reflected a lack of nitric oxide-mediated, endothelium-dependent dilation in hand veins, responses to acetylcholine were obtained. Acetylcholine relaxed preconstricted hand veins by 60% to 80% (P<.01) in the presence and absence of indomethacin, which suggests substantial endothelium-dependent, cyclooxygenase-independent vasodilation. The results confirm that raising NEFAs locally enhances vascular alpha1-adrenoceptor sensitivity. Despite the presence of significant endothelium-dependent dilation in dorsal hand veins, insulin does not antagonize vascular alpha1-adrenoceptor sensitivity in the presence of either ambient or locally elevated fatty acids.

Acetylcholine↗
PubMed1996

Impact of fat substitutes on fat intake.

Dietary fat is the number one nutrition concern of Americans. In response to rising consumer demand for reduced-fat foods, the food industry has developed a multitude of nonfat, lowfat, and reduced-fat versions of regular food products. To generate reduced-fat or fat-free products that have the same organoleptic characteristics of the regular fat version, food manufacturers frequently employ fat substitutes in the formulation of these foods. Fat substitutes are made from either carbohydrate, protein, or fat, or a combination of these components. Researchers have questioned the impact of fat substitutes on both fat and caloric intake. The majority of research studies in which fat substitutes were either covertly or overtly substituted for dietary fat indicate that in short-term, carefully-controlled conditions, fat substitutes can decrease both dietary fat intake and percentage of calorie intake from fat. However, individuals compensate for the caloric deficit created by the fat substitutes by increasing their consumption of other macronutrients, primarily carbohydrate. The long-term effect of fat substitutes on the fat intake of free-living individuals and weight control are unknown. People tend to eat more of a food when they know that food is reduced in fat. Fat substitutes should not be considered a substitute for sound nutrition education and a healthy lifestyle which includes regular exercise.

Anticholesteremic Agents↗
PubMed1996

Copper absorption, endogenous excretion, and distribution in Sprague-Dawley and lean (Fa/Fa) Zucker rats.

We previously observed a rapid reduction in plasma ceruloplasmin activity in lean Zucker (Fa/Fa) rats fed a marginal copper (Cu)-deficient diet compared to similarly fed obese Zucker (fa/fa) and lean Sprague-Dawley rats. In an effort to understand the mechanisms underlying this response, we utilized the isotope dilution method to investigate the absorption and excretion of Cu in lean Zucker rats fed control and marginal Cu diet. Sprague-Dawley (SD) and homozygous lean Zucker rats were fed either a Cu-adequate (Cont; 7.5 micrograms Cu/g diet) or a low Cu (Low; 1.1 micrograms Cu/g diet) casein-based diet for 23 d. Two weeks following initiation of the dietary treatment, each rat was injected intramuscularly (im) with 11.2 microCi of 67Cu. Urine and feces were collected daily. On the 9th d following isotope injection, rats were killed and tissues collected. Significant dietary effects were observed in the relative absorption and endogenous fecal excretion of 67Cu. The tissue distributions of nonisotopic Cu and 67Cu activity were also different between dietary treatments. Tissues from rats fed the low-Cu diet typically had high concentrations of 67Cu and low concentrations of nonisotopic Cu compared to controls. An increase in relative 67Cu absorption was evident for rats fed the low-Cu diet (57.2 and 39.3%, for SD Low, Zucker Low, respectively, and 17.9, and 28.5% SD Cont and Zucker Cont, respectively). Rats fed the low-Cu diet also had reductions in endogenous fecal excretion of 67Cu compared to their respective controls. Although strain effects were not evident for either percent Cu absorption or endogenous fecal Cu excretion, the relative adaptive changes appeared more marked for the Sprague-Dawley rats compared to the lean Zucker rats.

Analysis of Variance↗
PubMed1996

Age considerations in nutrient needs for bone health.

Age exerts a major influence on the nutritional needs for bone health. Age influences the nutrient requirements for bone health by influencing: the growth and development of bone; the deposition of minerals leading to peak bone mass; the rate of bone loss; the levels of hormones which influence bone; the absorption and retention of nutrients required for optimal bone health, physical activity, food intake, and the level of sun exposure. Adequate calcium intake benefits bones at any age. However, dietary calcium needs vary at different ages. In June 1994, a National Institutes of Health expert panel recommended higher calcium intakes than current Recommended Dietary Allowance for several age groups. Many population groups in the United States, including young girls and women, continue to consume significantly less calcium than current recommended levels. In addition, diets low in calcium are often low in many other essential nutrients important for good bone health, including vitamin D, vitamin B6, and magnesium. Dietary recommendations for bone health should be placed in the full context of the total diet rather than a singular emphasis on calcium. To truly benefit consumers, dietary recommendations for bone health should emphasize consumption of foods high in calcium as part of a healthy diet and a healthy lifestyle.

Adult↗
PubMed1996

Calcium bioavailability from bovine milk and dairy products in premenopausal women using intrinsic and extrinsic labeling techniques.

Stable isotopes were used to compare calcium fractional absorption from intrinsically and extrinsically labeled bovine milk as well as intrinsically labeled dairy product and cheese analogue. Healthy Caucasian women were fed a controlled diet for 4 d during the follicular phase of their menstrual cycle. With breakfast on the third day, participants ingested milk containing 44Ca (intrinsic) and 42CaCl2 (extrinsic) or dairy products containing 44Ca. Total feces were collected for 2 d prior to and 10 d after isotope ingestion. Polyethylene glycol was administered to monitor completeness of fecal collections. Total calcium was determined by atomic absorption spectrophotometry, and isotopic abundance was determined by high resolution fast atom bombardment mass spectrometry. Fractional absorption was determined as the difference between the administered isotopic dose and the quantity of 44Ca or 42Ca excreted in feces. The fractional absorption of calcium from milk was not affected by the method of labeling, lactose content, fermentation or the chemical form of calcium in dairy products or cheese analogue.

Absorption↗
PubMed1995

A customized acrylic resin shell for fabricating an amalgam core on the coronally debilitated, endodontically treated posterior tooth.

This article describes a technique for fabricating a custom acrylic resin shell that will ensure a properly designed amalgam core for the coronally debilitated, endodontically treated posterior tooth. A few simple procedures result in a core foundation for root protection, an ideal crown preparation, and a more predictable final restoration.

Acrylic Resins↗
PubMed1995

Psychological correlates of reported physical activity in normal-weight and obese adults: the Reno diet-heart study.

This investigation assessed psychological correlates of reported physical activity in a sample of 381 normal-weight and obese adults who were enrolled in a 4-year, prospective, natural history study. The psychological measures included the Eating Self-Efficacy Scale, the General Well-Being Schedule, and the Center for Epidemiological Studies Depression Scale. Reported Physical Activity was defined as a composite measure of reported recreational physical activity and perceived importance of activity in health and recreation. Physical activity was correlated with a more positive psychological profile in obese subjects at both year 1 and year 5. Increases in reported physical activity over the four years were associated with improvements in depression and well-being in normal-weight subjects, and with improvements in eating self-efficacy and well-being in obese subjects.

Adult↗
PubMed1994

Rats on a macronutrient self-selection diet eat most meals from a single food cup.

Computerized meal pattern analysis was performed on female Sprague-Dawley rats (n = 10). Rats were housed for 14 days in cages adapted for macronutrient selection. Rats selected their diet from vitamin and mineral supplemented, semipurified sources of carbohydrate, fat and protein, in three individual food cups. For analysis of meal patterns, minimum meal size was > 50 mg, and mean minimum intermeal interval was 7.9 min. Daily energy intake averaged 289.0 kJ, with 75% occurring during the dark cycle. Energy intake was 28% carbohydrate, 50% fat and 22% protein. Of 12.3 daily meals, 56% were from one, 35% from two, and only 9% of the meals were from three food cups. Seventy percent of the time carbohydrate was the first meal of the dark cycle. The average number of meals per day eaten from carbohydrate, fat, and protein were not significantly different (6.9, 6.2 and 5.6, respectively, p > 0.05). Energy intake for a meal was greatest when fat was eaten (18.35 kJ), than when either carbohydrate (8.68 kJ) or protein (8.97 kJ) was eaten. Meal duration was 7.03 min for carbohydrate, 3.75 min for fat, and 7.47 min for protein. These results provide evidence that rats on a macronutrient self-selection diet eat most meals from a single macronutrient source.

Animals↗
PubMed1994

Benefits of the National Dairy Council to the dairy processing industry.

The National Dairy Council and its affiliated units have had a vital role in presenting the nutritional qualities of US dairy products to a variety of audiences. Established in 1915, National Dairy Council has been the segment of the dairy industry that initiates and administers nutrition research, implements cutting-edge educational programs, and communicates about the nutritional merits of dairy products to educators, health professionals, consumers, and other important groups. The grassroots structure of National Dairy Council allows it to communicate these important messages at both the national and local levels.

Dairy Products↗
PubMed1994

Exercise reduces fat selection in female Sprague-Dawley rats.

This study investigates the relationship between exercise and dietary macronutrient selection. Female Sprague-Dawley rats (5 months old) were placed on a macronutrient self-selection diet for 15 wk. Three food cups, each containing a separate vitamin and mineral supplemented macronutrient, i.e., fat, carbohydrate, or protein, were placed in the cage. Animals were either sedentary (Sed) or treadmill exercised (Ex) at 20 m.min-1, 60 min.d-1, for 6 d.wk-1. Cumulative daily energy and macronutrient intake were determined during this period. Energy intake was not different between Sed and Ex, 211.4 vs 213.5 kjoules.d-1, respectively. However, macronutrient intake differed with less fat eaten for Ex than Sed (81.5 kjoules and 38% for Ex; 114.0 kjoules and 47% for Sed). Carbohydrate and protein intake did not differ significantly between groups. Fifteen weeks of exercise training decreased dietary fat selection, but daily energy intake was not affected.

Animals↗
PubMed1991

Exercise decreases fat selection in female rats during weight cycling.

Weight cycling (weight loss and regain) increases fat intake in rats allowed to self-select a diet from protein, carbohydrate, and fat sources. This study reports the effects of exercise on macronutrient self-selection. Female Sprague-Dawley rats (5 mo old) self-selected their diet. After 3 wk, rats were assigned to one of the following three groups: ad libitum fed sedentary (Con), sedentary food restricted to 40% Con intake (R-Sed), or treadmill exercised (20 m/min, 1 h/day, 6 day/wk) food restricted to 40% Con intake (R-Ex). Food restriction was for 3 wk followed by 5 wk of refeeding. This was repeated for a second cycle. During restriction, body weight decreased by 30% in R-Sed and by 33% in R-Ex than in R-Sed, fat regain was greater in R-Sed. By week 3 of refeeding, total caloric consumption did not differ. However, fat selection increased in R-Sed (56% kcal) vs. R-Ex (30%) and Con (35%). Fat selection in R-Sed increased further during cycle 2 (73% kcal). Resting oxygen consumption decreased during food restriction in R-Sed and R-Ex. After refeeding, resting metabolic rate in R-Ex was significantly greater than in R-Sed. In conclusion, weight cycling increases dietary fat selection and adiposity. Exercise mitigates this effect.

Adipose Tissue↗