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Biomedical subjects

F H Nielsen

Publications and source records attributed to F H Nielsen.

At least 19 recordsLinked to original sources
PubMed1992

Studies of the interaction between boron and calcium, and its modification by magnesium and potassium, in rats. Effects on growth, blood variables, and bone mineral composition.

Two experiments were performed to confirm that boron interacts with calcium, and that this interaction can be modified by dietary magnesium and potassium in the rat. Upon manipulating the dietary variables listed above, it was found that under certain conditions, boron and calcium deprivation similarly affected several variables; for example, they both could be made to elevate plasma alkaline phosphatase activity and to depress femur calcium concentration. Under some dietary conditions, both boron and calcium deprivation affected some variables related to blood or iron metabolism. However, the effects of dietary boron and calcium on spleen weight/body weight ratio, hematocrit, and femur iron concentration generally were not similar. Femur copper, magnesium, phosphorus, and zinc also were affected by an interaction between boron and calcium under some dietary conditions. The findings show that there is a relationship between boron and calcium, but they do not clearly indicate the nature of the relationship. However, the data suggest that boron and calcium act on similar systems in the rat.

Alkaline Phosphatase↗
PubMed1991

Ultratrace minerals mythical elixirs or nutrients of concern?

Demonstration of the nutritional significance of the ultratrace elements has resulted from studies indicating enhanced need in organisms exposed to various metabolic, hormonal, physiological and nutritional stresses. These studies indicate that some ultratrace elements, namely boron and silicon, will be found to be nutritionally important. The dietary lack of these elements may result in suboptimal function and composition of bone and brain.

Animals↗
PubMed1991

Nutritional requirements for boron, silicon, vanadium, nickel, and arsenic: current knowledge and speculation.

Definition of specific biochemical functions in higher animals (including humans) for the ultratrace elements boron, silicon, vanadium, nickel, and arsenic still has not been achieved although all of these elements have been described as being essential nutrients. Recently, many new findings from studies using molecular biology techniques, sophisticated equipment, unusual organisms, and newly defined enzymes have revealed possible sites of essential action for these five elements. Based on these findings and the response of animals and/or humans to low intakes of these elements, the following speculations have been presented: 1) Boron has a role that affects cell membrane characteristics and transmembrane signaling. 2) Silicon is necessary for the association between cells and one or more macromolecules such as osteonectin, which affects cartilage composition and ultimately cartilage calcification. 3) Vanadium reacts with hydrogen peroxide to form a pervanadate that is required to catalyze the oxidation of halide ions and/or stimulate the phosphorylation of receptor proteins. 4) Nickel is needed for the CO2-fixation to propionyl-CoA to form D-methylmalonyl-CoA. 5) Arsenic has an important role in the conversion of methionine to its metabolites taurine, labile methyl, and the polyamines. If any of these speculations are found to be true, the element involved will be firmly established as having a nutritional requirement because the body obviously cannot synthesize it. Based on animal findings, the dietary requirement is likely to be small; that is, expressed in micrograms per day.

Amino Acids↗
PubMed1990

Ascorbic acid: effect on ongoing iron absorption and status in iron-depleted young women.

The effect of ascorbic acid on iron retention from a diet with predicted low iron bioavailability (containing minimal meat and ascorbic acid) was investigated in iron-depleted premenopausal women. Eleven women were depleted of storage iron (indicated by serum ferritin) through a combination of diet (5.0 mg Fe/2000 kcal for 67-88 d) and phlebotomy. They then consumed a diet containing 13.7 mg Fe/2000 kcal, supplemented with placebo or ascorbic acid three times daily (1500 mg total) with meals for 5.5 wk. Ascorbic acid improved apparent iron absorption (balance method) [38 +/- 2% (means +/- SEM) vs 27 +/- 2%]. Ascorbic acid also improved hemoglobin, erythrocyte protoporphyrins, and serum iron but not hematocrit, serum ferritin, iron-binding capacity, or transferrin saturation. In iron-depleted women consuming a diet with predicted poor iron availability, ascorbic acid supplementation enhanced body iron retention for 5.5 wk.

Adult↗
PubMed1990

Effect of vanadium, iodine and their interaction on growth, blood variables, liver trace elements and thyroid status indices in rats.

A two-factor, two-by-three factorially arranged experiment was performed to ascertain whether iodine affects the response of rats to vanadium deprivation. Male weanling Wistar-Kyoto rats were fed a 16% casein 68% acid-washed ground corn diet for 8 weeks. The variables were supplemental vanadium at 0 or 1 microgram/g and supplemental iodine at 0, 0.33 or 25 micrograms/g. Vanadium deprivation increased thyroid weight and thyroid weight/body weight ratio and decreased the concentration of vanadium in liver. Vanadium and iodine interacted such that, as dietary iodine was increased, plasma glucose increased in the vanadium-deficient rats but decreased in the vanadium-supplemented rats. Also, as dietary iodine was increased, thyroid peroxidase activity decreased; the decrease was more marked in the vanadium-supplemented than the vanadium-deprived rats. The findings suggest that vanadium may have a physiological role affecting iodine metabolism and thyroid function.

Animals↗
PubMed1990

Studies on the relationship between boron and magnesium which possibly affects the formation and maintenance of bones.

Recent findings are reviewed indicating that changes in dietary boron and magnesium affect calcium, and thus bone, metabolism in animals and humans. In animals, the need for boron was found to be enhanced when they needed to respond to a nutritional stress which adversely affected calcium metabolism, including magnesium deficiency. A combined deficiency of boron and magnesium caused detrimental changes in the bones of animals. However, boron deprivation did not seem to enhance the requirement for magnesium. In two human studies, boron deprivation caused changes in variables associated with calcium metabolism in a manner that could be construed as being detrimental to bone formation and maintenance; these changes apparently were enhanced by low dietary magnesium. Changes caused by boron deprivation included depressed plasma ionized calcium and calcitonin as well as elevated plasma total calcium and urinary excretion of calcium. In one human study, magnesium deprivation depressed plasma ionized calcium and cholesterol. Because boron and/or magnesium deprivation causes changes similar to those seen in women with postmenopausal osteoporosis, these elements are apparently needed for optimal calcium metabolism and are thus needed to prevent the excessive bone loss which often occurs in postmenopausal women and older men.

Animals↗
PubMed1990

Thermogenesis and thermoregulatory function of iron-deficient women without anemia.

Physiological responses at 16 degrees C were studied in 11 women, age 28 +/- 2(mean +/- S.E.) years and 26 +/- 2% fat, after their body iron stores were depleted by diet (5.0 mg iron x 2,000 kcal-1 x d-1), phlebotomy and menstruation for about 80 d and were repleted by diet (13.7 mg iron x 2,000 kcal-1 x d-1) for about 100 d, including daily iron supplementation (50 mg of iron as ferrous sulfate) for the last 14 d of repletion. Iron depletion was characterized by a decline (p less than 0.05) in hemoglobin (12.0 +/- 0.2 g x dl-1), ferritin (5.5 +/- 0.5 ng x ml-1) and body iron balance (-9.1 +/- 2.6 mg x 6 d-1). Iron repletion, including supplementation, increased (p less than 0.05) hemoglobin (12.6 +/- 0.1 g x dl-1), ferritin (9.5 +/- 0.4 ng x ml-1) and iron balance (+67 +/- 6.7 mg x 6 d-1). Iron depletion reduced (p less than 0.05) metabolic heat production (49.6 +/- 1.1 vs 53.6 +/- 1.2 W x m-2) during acute cold exposure. The rates of cooling of the core and periphery were greater (p less than 0.05) during iron depletion than repletion. A shift in the lower core temperature threshold for shivering was paralleled by an earlier onset of shivering (p less than 0.05) in iron depletion indicating an adaptation in cold tolerance in an attempt to maintain core temperature. Iron depletion was associated with blunted post-exposure increases in plasma thyroid hormone concentrations and greater (p less than 0.05) increases in plasma norepinephrine concentrations as compared to iron repletion. In a subsample of the women, no significant effect of calcium or ascorbic acid supplementation was found on responses to cold exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1990

Response of various indices of iron status to acute iron depletion produced in menstruating women by low iron intake and phlebotomy.

We investigated response sensitivities of indices of iron status to controlled iron depletion and repletion in 11 premenopausal women. The women were depleted of storage iron (as reflected by serum ferritin) through a combination of a low-iron diet and phlebotomy. They then consumed a diet containing 13.7 mg of iron per 2000 kcal, supplemented with either ascorbic acid or placebo (for 5 1/2 weeks) and a daily 50-mg iron supplement (for the subsequent 17 days). The relative sensitivities of different indices for detecting iron depletion were as follows: ferritin greater than % transferrin saturation greater than plasma iron greater than hemoglobin greater than hematocrit greater than zinc protoporphyrin (ZnPP) and erythrocyte protoporphyrin (EP). Ascorbic acid treatment during repletion, before iron supplementation, significantly (P less than 0.05) affected changes in hemoglobin, ZnPP, ZnPP/heme, and EP/heme. Changes in heme synthesis evidently do not occur until iron stores are depleted and, conversely, during iron repletion hematopoiesis must be satisfied before iron stores, as reflected by ferritin, increase. Thus, the use of only one index of iron status is of limited value for detecting iron depletion.

Adult↗
PubMed1989

Selected ultratrace elements in total parenteral nutrition solutions.

Ultratrace elements are potentially essential (eg. boron, molybdenum, nickel, and vanadium) or toxic (eg, aluminum and cadmium) in humans. Long-term total parenteral nutrition (TPN) patients can inadvertently receive significant amounts of ultratrace elements present as contaminants in TPN solutions. We determined the intake of selected ultratrace elements from a standard TPN solution and compared it with the amount reported to be absorbed from food in normal subjects. Contamination of TPN solutions with ultratrace elements was widespread and variable. The daily intakes of Mo, Ni, V. and Cd from this contamination were comparable to the amounts reported to be absorbed through the gastrointestinal tract in normal subjects. Al intake was high; B intake was low, approximately 10% of the amount absorbed by normal subjects. Thus, TPN solutions are contaminated with significant amounts of ultratrace elements. The biological significance of the intravenous infusion of these ultratrace elements is unclear and requires further investigation, particularly in home TPN patients.

Aluminum↗
PubMed1988

Effects in rats of iron on lead deprivation.

In two fully crossed, two-factor experiments, F1 generation male rats were fed a basal diet supplemented with lead (lead acetate) at 0 or 2 micrograms/g and iron (ferric sulfate) at 50 or 250 micrograms/g (Experiment 1). Supplements in Experiment 2 were lead at 0 or 1 micrograms/g and iron at 50, 250, or 1000 micrograms/g. After 28 or 50 d in Experiment 1, and 35 d in Experiment 2, a relationship between lead and iron was found. Body weight was lower in low-lead than lead-supplemented 28-d-old rats regardless of dietary iron, whereas hematocrit and hemoglobin were lower in low-lead than lead-supplemented rats fed 50 micrograms iron/g diet. A similar finding was obtained with hematocrit and hemoglobin in 35-d-old rats. Dietary lead did not affect rats fed 250 or 1000 micrograms iron/g diet. Also, feeding low dietary lead did not affect 50-d-old rats regardless of dietary iron. Liver and bone concentrations of lead were markedly affected by dietary lead and iron. The concentration of lead in liver and bone was lower in low-lead than lead-supplemented rats. Compared to rats fed 50 micrograms iron/g diet, rats fed 250 micrograms iron/g diet exhibited a decreased lead concentration in liver and bone. This decrease was accentuated by lead supplementation. The findings suggest that lead acted pharmacologically to affect iron metabolism in rats.

Aging↗
PubMed1988

Dietary magnesium, manganese and boron affect the response of rats to high dietary aluminum.

Studies were done to ascertain whether dietary magnesium, manganese and boron affect the response of the rat to high dietary aluminum. Four factorially arranged experiments of 7 weeks duration were performed with weanling Sprague-Dawley male rats. The variables were the following supplements (microgram/g fresh diet): boron as boric acid, 0 and 3; aluminum as aluminum chloride, 0 and 1,000; and magnesium as magnesium acetate, 100 and 400 (experiments 1 and 4) or 100, 200 and 400 (experiments 2 and 3). In experiments 1 and 2, the diet was supplemented with 20 micrograms manganese/g as manganese acetate, in experiments 3 and 4 the supplement was 50 micrograms/g. High dietary aluminum seemed most toxic when dietary magnesium was low enough to cause a marked growth depression (100 micrograms/g). High dietary aluminum elevated the spleen weight/body weight and liver weight/body weight ratios in magnesium-deficient, but not in magnesium-adequate rats. High dietary aluminum depressed the concentrations of magnesium in bone more markedly in magnesium-deficient than adequate rats. On the other hand, aluminum seemed most toxic when dietary boron was not low. Aluminum more markedly depressed growth in boron-supplemented than boron-deprived rats. In the boron-deprived rats fed 400 micrograms magnesium/g of diet, high dietary aluminum (1,000 micrograms/g) apparently was beneficial, in experiments 2 and 3, hematocrit, and hemoglobin were actually normalized by high dietary aluminum. Plasma magnesium was significantly depressed by high dietary aluminum when the manganese supplement was 50 micrograms/g diet but not when it was 20 micrograms/g diet. On the other hand, growth was more markedly depressed by high dietary aluminum in boron-supplemented rats when the manganese supplement was 20 rather than 50 micrograms/g diet. The findings indicate that the response of rats to high dietary aluminum is influenced by magnesium, boron, and manganese nutriture.

Aluminum↗
PubMed1987

Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women.

A study was done to examine the effects of aluminum, magnesium, and boron on major mineral metabolism in postmenopausal women. This communication describes some of the effects of dietary boron on 12 women between the ages of 48 and 82 housed in a metabolic unit. A boron supplement of 3 mg/day markedly affected several indices of mineral metabolism of seven women consuming a low-magnesium diet and five women consuming a diet adequate in magnesium; the women had consumed a conventional diet supplying about 0.25 mg boron/day for 119 days. Boron supplementation markedly reduced the urinary excretion of calcium and magnesium; the depression seemed more marked when dietary magnesium was low. Boron supplementation depressed the urinary excretion of phosphorus by the low-magnesium, but not by the adequate-magnesium, women. Boron supplementation markedly elevated the serum concentrations of 17 beta-estradiol and testosterone; the elevation seemed more marked when dietary magnesium was low. Neither high dietary aluminum (1000 mg/day) nor an interaction between boron and aluminum affected the variables presented. The findings suggest that supplementation of a low-boron diet with an amount of boron commonly found in diets high in fruits and vegetables induces changes in postmenopausal women consistent with the prevention of calcium loss and bone demineralization.

Aged↗
PubMed1986

Hydatidiform mole: cytogenetic marker analysis in twin gestation. Report of two cases.

A hydatidiform mole associated with a fetus proved to be the result of twin gestation. On microscopic examination of the placenta the case was classified as a partial hydatidiform mole. Chromosomal markers were, however, consistent with a normal conception and a mole of diploid androgenetic origin. Chromosome analysis of a morphologic complete molar specimen yielded two cell lines, one consistent with a normal conception and one with diploid androgenesis. Twinning in molar specimens must therefore be considered, regardless of macroscopic appearance. The prenatal diagnosis of a coexisting fetus and molar placenta poses a real clinical problem; analyses must distinguish between a partial mole plus a triploid fetus and a normal fetus occurring with a partial or a complete mole. The distinction is important for decisions made during pregnancy and may be of prognostic significance after termination. The usefulness of chromosome marker analysis in distinguishing between the various origins is pointed out, and it is suggested that twin pregnancy with hydatidiform mole is more frequent than its description in the literature would suggest.

Adult↗
PubMed1985

The importance of diet composition in ultratrace element research.

This review indicates that the lack of appreciation of, information about or understanding of the importance of diet composition has had a major influence on the development of knowledge about 11 ultratrace elements in nutrition. Inappropriate trace element supplementation and inadequate or unbalanced diets probably were responsible for many of the reported inconsistent and divergent findings, and thus, for the resultant controversy regarding the essentiality of specific ultratrace elements. Vanadium and nickel are taken as examples, and evidence is presented that variations in the concentrations of dietary components can affect the response of experimental animals to the various ultratrace elements. Furthermore, there is evidence that the ultratrace elements, given in sufficient quantity, can evoke pharmacological responses in animals. Failure to recognize these phenomena probably has led to a number of incorrect or biased interpretations of experimental results. Future research on the importance of ultratrace elements in nutrition requires close attention to an often neglected experimental variable--diet composition.

Amino Acids↗
PubMed1979

Morphology of the perforating cartilage canals in the proximal tibial growth plate of the chick.

Perforating canals arise exclusively from junctional canals just above the reserve zone and they do not branch after entering the proliferative zone. They are uniformly spaced and arranged in parallel array. The cartilage canals terminate near the beginning of the zone of hypertrophic cartilage cells. Vascular components within the perforating canals consist of a central arteriole surrounded by enlarged, interconnected capillaries which are individually in contact with the adjacent cartilage matrix. TEM shows that the capillary endothelium is extremely attenuated, possesses numerous fenestrations and lacks a continuous basement membrane. The central arteriole is enlarged through the midpart of the canal and then narrows to communicate with the capillaries near the bottom of the canal. The large capillaries ascend from their point of origin and recombine near the top of the growth plate to exit as a single venule. The vascular arrangement therefore describes a system in which the outgoing blood runs in close proximity, but counter to, the incoming blood. This vascular arrangement within the perforating cartilage canal would most likely allow the zone of maturing cartilage cells to receive the highest concentration of nutrients.

Animals↗