Kenneth Wing

An evaluation of the radiopacity of composite restorative materials used in Class I and Class II cavities

The radiopacity of 28 shades of 18 composite brands, recommended for use in Class I and Class II cavities, and one amalgam were tested in accordance with the instructions in the latest draft standards of ISO for resin-based filling materials. The composition of the inorganic fillers in the materials was analyzed by optical emission spectroscopy. Twelve composites showed radiopacity greater than enamel, for five the radiopacity was lower than that of dentin, and for two materials the radiopacity was between that of enamel and dentin. The optical emission spectroscopy analyses showed a large variety in the composition of the fillers. The elements added to increase radiopacity in the composite materials are barium, strontium, zinc, zirconium, and ytterbium.

A comparison of iron absorption from single meals and daily diets using radioFe (55Fe, 59Fe)

The purpose of the present study was to compare two measures of Fe absorption, one from single meals and the other from daily diets. Ten ileostomy subjects were given the same low-fibre composite diet for all three meals each day for five consecutive days. After 3 weeks the experiment was repeated with a high-fibre diet. The morning meal constituted one-seventh of the total daily diet intake, the mid-day meal two-sevenths and the evening meal four-sevenths of the total daily diet intake. On days 4 and 5 of each diet period the morning meal was labelled with 55Fe and all three meals were labelled with 59Fe. The activities retained in the subjects 19 d later showed the Fe absorption from the low-fibre diet measured from the morning meals to be almost 80% greater than the average Fe absorption measured from all meals during the same 2 d. With the high-fibre diet the absorption from the morning meals was less than 50% greater than the average for all meals but the difference was not significant. We suggest that all meals of the day should be labelled with radioFe in order to avoid inflating the measures of Fe absorption.

The effect of wheat bran on the absorption and accumulation of cadmium in rats.

1. The major purpose of the present study was to determine whether the addition of wheat bran to endosperm crisp bread in a composite diet given to rats for 6 weeks causes an increase in the accumulation of cadmium in the rats due to the Cd content in the bran, or whether binding factors in the bran, such as dietary fibre and phytic acid, reduce or prevent the accumulation of this Cd. A second purpose was to determine whether the accumulation of Cd can be estimated by measuring the absorption of 109Cd given in a single meal of the diet. 2. Three groups of eight rats were fed on one of three diets. Half of each diet consisted of a basal mixture of starch, protein, oil, minerals and vitamins. The remainder consisted of crisp breads based on refined wheat flour (endosperm group), wheat flour + bran in equal amounts (bran group) and wheat flour + Cd to give a Cd content similar to that of the bran group (endosperm + Cd group). After 41 d on the diets, the rats were deprived of food but not water for 12 h and then given a 5 g test meal of their respective diets with 109Cd added. After 3 h the remaining 109Cd-labelled diets were replaced with the unlabelled diets for 3 h before the rats were killed. 3. The total Cd contents in the wall of the proximal small intestine, including mucus, and in the liver and kidneys were highest in the endosperm + Cd group and lowest in the endosperm group.(ABSTRACT TRUNCATED AT 250 WORDS)

Cadmium accumulation from diets with and without wheat bran in rats with different iron status

Abstract The purpose of the present study was to determine to what extent the accumulation of cadmium in rats with low, marginal and high iron status is affected by the presence of bran in the diet. High iron status caused the total and fractional accumulation of cadmium from both the wheat endosperm and wheat bran diets to be decreased by almost half compared to that in the low iron status rats. The inclusion of wheat bran in the diet increased the total accumulation of cadmium in the liver by approximately the same proportion in all three iron status groups. While the results do not exclude the possibility that the availability of cadmium for absorption from wheat bran is less than that from wheat endosperm in rats with high iron status, no appreciable effect of mineral binding factors in bran on the fractional cadmium accumulation in the liver could be demonstrated in the low and marginal iron status groups. Thus, for rats with less than adequate iron status, the inclusion of wheat bran in the diet should increase the cadmium intake and its accumulation in the body by the same proportion.

Turnover of 65Zn and 85Sr in Growing Rats: A comparative investigation

Analysis of bone retention data using 2- or 3-compartment models gives nearly equal relative accretion rates for zinc and calcium (85Sr) in endochondral bone and calcifying cartilage. The rate for zinc in cortical bone is 70% of that for calcium. As the existence in cortical bone of large, slowly exchanging compartments limitating accretion is consistent with the data, the relative accretion rate for zinc may more closely reflect the relative accretion rate of cortical bone.

The importance of the body's need for zinc in determining Zn availability in food: a principle demonstrated in the rat

1. The hypothesis that the availability of zinc in a food is limited by factors in the food was tested against the hypothesis that Zn absorption is homeostatically regulated by the body according to its need for Zn. 2. The experimental model used was the short-term administration to rats of a parenteral nutrition solution with no added Zn in an attempt to increase their need for Zn in an anabolic phase. 3. The absorption and retention of 65Zn from a piece of endosperm-wheat crisp-bread in rats injected intraperitoneally with the parenteral nutrition solution was more than 40% higher than that in a control group injected with physiological saline (9 g sodium chloride/l). 4. The results indicate that the availability of Zn in the bread is not fixed but variable and dependent on the bodys need for Zn.

The availability of zinc in endosperm, whole grain and bran-enriched wheat crispbreads fed to rats on a Zn-deficient diet

The hypothesis that factors such as dietary fibre and phytate in wheat bran limit the availability of Zn was tested in growing rats fed on low-Zn diets with different wheat crispbreads as the major source of Zn. Six groups of six weanling male rats each were fed on 5 parts semi-synthetic Zn-deficient diet and 1 part wheat-endosperm crispbread for 1 week. At the beginning of the second week, the crispbread in the diet of five groups was exchanged for crispbread made using one of the following wheat flours: (1) whole grain, (2) bran-enriched whole grain, (3) endosperm with Zn added to the whole-grain level, (4) endosperm with Zn added to the bran-enriched level, (5) whole grain with Zn added to the bran-enriched level. These diets were given ad lib. together with deionized water for 2.5 weeks. The relative absorption of Zn was lowest from the three non-supplemented diets (75-82%). All the added Zn was absorbed. As appetite, body-weight increase, Zn absorption, Zn retention and the Zn concentrations in serum and bone differed only slightly among groups fed on diets with similar Zn concentrations, it is concluded that factors such as dietary fibre or phytate in wheat bran limit the availability of Zn in wheat crispbreads very little when all the Zn is needed for growth and development in rats.

A comparative study in rats of measures of the availability of dietary zinc and iron.

The purpose of this study was to compare three measures of the availability of dietary Zn and Fe in order to test their validity. Thirtysix 5-wk-old rats were fed deionized water and wheat crispbread made from endosperm flour, whole-grain flour, or endosperm flour supplemented with Zn and Fe to the whole-grain levelsad libitum for 14 d. The retention of65Zn and59Fe from test meals of the same breads after 1 wek and the sum of the excretion of endogenous Zn and Fe (injected65Zn and59Fe) with the Zn and Fe balances, respectively, were used as independent measures of Zn and Fe absorption. Measurements of Zn absorption, Zn balance, and serum Zn concentration gave quite different results with regard to the availability of Zn in the three breads, presumably because of the homeostatic regulation of the absorption and excretion of Zn when the Zn in the diet is in excess of the body’s needs. Measurements of Fe absorption, Fe balance, and Fe concentrations in liver and serum were consistent in demonstrating overloading of Fe in the group given wheat-endosperm crispbread supplemented with Zn and Fe, but there was evidence that the isotope retention method overestimated iron absorption.

The extent of coprophagy in rats with differing iron status and its effect on iron absorption.

The purpose of this study was to determine the prevalence of coprophagy in rats with differing iron status and its effect on the measurement of iron absorption from test meals with and without bran. Two experiments were performed using radioisotope-labelled microspheres added as a non-digestible marker for the ingested faeces and the diet and 59Fe added as a marker for the non-haem iron in the test meal. In this study, coprophagy occurred at group mean rates of between 5 and 22% and was independent of the iron status of the rats or the presence or absence of bran in the diet. The relative absorption of iron, measured as the retention of 59Fe from a single meal, was affected to the same extent in groups with the same iron status, if it was affected at all. Thus comparisons of iron absorption from diets with and without bran should not be affected by coprophagy.

The availability of iron, zinc and cadmium to rats from composite diets with different cereal grains

Abstract Many investigations have been reported in which the effects of varying the concentration of a single factor in grain diets on the availabilities of minerals for absorption have been studied. The purpose of this study in rats was to determine the effects on iron, zinc and cadmium availability of substituting whole grain wheat, oats, barley or rye for iron-supplemented endosperm wheat in a composite diet with one part grain flour and one part non-fat, dried milk with maize oil and vitamins. Iron concentrations varied by a factor of 3 among these diets, zinc by 1.5, cadmium by 5, and both fiber and phytate by a factor of 3.5. The absorption of 59 Fe and 65 Zn from test meals of the diets and the concentrations of iron, zinc and cadmium in selected tissues and body fluids after five weeks on the grain diets were used as independent measures of the mineral availabilities from these diets. Absorption of iron from endosperm wheat and, to a lesser extent, zinc from oats and rye appears to have been overestimated, most likely due to incomplete exchange of the radioisotopes with the supplemented or endogenous minerals in the grains. The variations in the concentrations of iron and cadmium among the diets were by far the most important factors determining the availabilities of these minerals to the rats. The fractional availabilities of iron and zinc were negatively related to the diet phytate concentration and the fractional availability of cadmium was negatively related to the iron status of the rats. The results indicate that substitution of whole grain wheat for endosperm wheat in the diet will increase cadmium accumulation considerably while substitution of oats, barley or rye should result in nearly the same or lower cadmium accumulation. Due to the low availability of iron in barley and rye, substitution of either grain for iron-supplemented endosperm wheat may compromise iron status. As the diets in this study are similar to baby formulas and breakfast cereals, porridge or a sandwich with milk, the probability that these results in rats are applicable to humans strongly suggests that studies similar to this be carried out in humans.