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Background: Calcium-fortified soy milk is growing in popularity, particularly among vegetarians, but the bioavailability of its calcium was not previously known. Additionally, the validity of isotopic labeling methods for fortified liquid products had not been established. Objectives: The objectives of this study were to compare the bioavailability of the calcium in fortified soy milk with that of calcium in cow milk and to evaluate the method of labeling soy milk for bioavailability testing. Design: A within-subject comparison of extrinsically labeled cow milk with intrinsically and extrinsically labeled soy milks was undertaken in 16 healthy men. In all tests, 300-mg Ca loads were given as a part of a light breakfast after an overnight fast. The milks were physically partitioned into liquid and solid phases to enable evaluation of tracer distribution. Results: Calcium from intrinsically labeled soy milk was absorbed at only 75% the efficiency of calcium from cow milk. Extrinsic labeling of soy milk did not produce uniform tracer distribution throughout the liquid and solid phases and resulted in a 50% overestimate of true absorbability. Conclusion: Calcium-fortified soy milk does not constitute a calcium source comparable to cow milk, and extrinsic labeling of such calcium particulate suspensions does not produce the uniform tracer distribution needed for bioavailability testing. Hence, intrinsic labeling of the fortificant is required for such liquid suspensions. Am J Clin Nutr 2000;71:1166-9. KEY WORDS Calcium, cow milk, soy milk, absorption, bioavailability, isotopic labeling, extrinsically labeled milk, intrinsically labeled milk, healthy men

Background:Calcium absorption is generally considered to be impaired under conditions of vitamin D deficiency, but the vitamin D status that fully normalizes absorption is not known for humans.Objective:To quantify calcium absorption at two levels of vitamin D repletion, using pharmacokinetic methods and commercially marketed calcium supplements.Design:Two experiments performed in the spring of the year, one year apart. In the first, in which participants were pretreated with 25-hydroxyvitamin D (25OHD), mean serum 25OHD concentration was 86.5 nmol/L; and in the other, with no pretreatment, mean serum concentration was 50.2 nmol/L. Participants received 500 mg oral calcium loads as a part of a standard low calcium breakfast. A low calcium lunch was provided at mid-day. Blood was obtained fasting and at frequent intervals for 10 to 12 hours thereafter.Methods:Relative calcium absorption at the two 25OHD concentrations was estimated from the area under the curve (AUC) for the load-induced increment in serum total calcium.Results:AUC9(± SEM), was 3.63 mg hr/dL ± 0.234 in participants pretreated with 25OHD and 2.20 ± 0.240 in those not pretreated (P< 0.001). In brief, absorption was 65% higher at serum 25OHD levels averaging 86.5 nmol/L than at levels averaging 50 nmol/L (both values within the nominal reference range for this analyte).Conclusions:Despite the fact that the mean serum 25OHD level in the experiment without supplementation was within the current reference ranges, calcium absorptive performance at 50 nmol/L was significantly reduced relative to that at a mean 25OHD level of 86 nmol/L. Thus, individuals with serum 25-hydroxyvitamin D levels at the low end of the current reference ranges may not be getting the full benefit from their calcium intake. We conclude that the lower end of the current reference range is set too low.

Background:Cost-effectiveness of calcium supplementation depends not only on the cost of the product but on the efficiency of its absorption. Published cost-benefit analyses assume equal bioavailability for all calcium sources. Some published studies have suggested that there are differences in both the bioavailability and cost of the major calcium supplements.Design:Randomized four period, three-way cross-over comparing single doses of off-the-shelf commercial calcium supplements containing either calcium carbonate or calcium citrate compared with a no-load blank and with encapsulated calcium carbonate devoid of other ingredients; subjects rendered fully vitamin D-replete with 10 μg/day 25(OH)D by mouth, starting one week prior to the first test.Subjects:24 postmenopausal womenMethods:Pharmacokinetic analysis of the increment in serum total and ionized calcium and the decrement in serum iPTH induced by an oral calcium load, based upon multiple blood samples over a 24-hour period; measurement of the rise in urine calcium excretion. Data analyzed by repeated measures ANOVA. Cost calculations based on average retail prices of marketed products used in this study from April through October, 2000.Results:All three calcium sources (marketed calcium carbonate, encapsulated calcium carbonate and marketed calcium citrate) produced identical 24-hour time courses for the increment in total serum calcium. Thus, these were equally absorbed and had equivalent bioavailability. Urine calcium rose slightly more with the citrate than with the carbonate preparations, but the difference was not significant. Serum iPTH showed the expected depression accompanying the rise in serum calcium, and there were no significant differences between products.Conclusion:Given the equivalent bioavailability of the two marketed products, the cost benefit analysis favors the less expensive carbonate product.

Abstract:: Calcium supplement use has increased and there is confusion about the relative absorbability of various sources. Absorbability of calcium from the carbonate and citrate salts was compared at 300 mg and 1000 mg calcium loads, ingested as part of a light breakfast meal. Absorption was measured at the high load both by tracer appearance in serum and by the absorptive increment in urinary calcium, and at the low load by the tracer method only. Subjects were 37 healthy adult men and women, studied as outpatients, and each tested on both salts at the same load. Mean tracer absorption (± SD) for both salts combined was 36.0% at the 300 mg load and 28.4% at the 1000 mg load. In both experiments the observed mean difference in absorption between salts was very small. By the tracer method the within-subject difference (carbonate less citrate) was +3.3%± 1.2% of the ingested dose (mean ± SEM; P <0.05) at the high load, and at the low load, 3.6%± 2.7% (NS). Combining the two experiments yielded zero difference between sources. By the urinary calcium increment method, the mean difference between salts at the 1000 mg load was 1.8 ± 4.1 mg (NS). Side-by-side comparisons of the two methods revealed that the tracer method was 3 times more sensitive than the urinary increment method. We conclude that, when taken with food, calcium from the carbonate salt is fully as absorbable as from the citrate, and that the urinary increment method is not sufficiently sensitive to be useful in comparing sources in free-living subjects.

Arctic and temperate strains of Hebeloma spp. were grown in axenic culture on glutamic acid, alanine, lysine and NH4+ as sole sources of nitrogen (N), with excess carbon (C) or deficient C (supplied as glucose). Their ability to utilize seed protein as a natural N source was also assessed. All strains tested had the capacity to assimilate amino acids and generally utilized alanine and glutamic acid more readily than NH4+. Some strains were able to utilize amino C when starved of glucose C, and could mineralize amino-N to NH3-N. Arctic strains, in particular, appeared to be pre-adapted to the utilization of seed protein N and glutamic acid N, which is often liberated in high concentrations after soil freezing. The results are discussed in relation to their possible ecological importance.

Mucin secretion by goblet cells was determined by quantifying degranulation events (DE) in isolated, superficial epithelium from canine trachea. The epithelium was isolated and explanted to a novel transparent, permeable support, and the goblet cells were visualized by video microscopy. Baseline degranulation events were quantified at 0.05 DE/min. Luminal ATP (10(-4) M, n = 10) stimulated a biphasic secretory response; a burst, maximum rate = 87.9 +/- 25.3, was followed by a plateau, rate = 1.9 +/- 0.3 DE/min. Serosal ATP elicited a complex set of responses: 9 cells failed to respond, 13 exhibited a trivial response, and 31 responded vigorously but with highly variable patterns of degranulation. Nonhydrolyzable 5'-adenylylimidodiphosphate caused degranulation from both sides of the epithelium. Luminal ADP and adenosine were ineffective. Serosal ADP and adenosine elicited a range of responses that was similar in diversity and magnitude to the ATP response. Our conclusions were as follows: 1) goblet cells in the superficial epithelium of the airway can be studied at the single-cell level in explants; 2) nucleotides stimulate goblet cells to secrete mucin; and 3) the goblet cell expresses different nucleotide receptors on its apical and basolateral membranes.

Preferred conditions for the chemical vapor deposition of thick, stoichiometric alpha-phase silicon nitride (Si3N4) plate from HSiCI3-NH3-H2 were identified by means of a designed experiment. The design included temperatures from 1300-1500°C, pressures from 0.5-2.0 Torr, and mean gas residence times from 0.01-1.0 sec. Si3N4 plates 0.05-0.5 mm thick were produced on multiple vertical substrates at rates of 5-70;μm/hr. Plates 0.5-4.0 mm thick were produced on horizontal substrates at rates of 60-1200 μm/hr. Crystallite sizes determined by X-ray line broadening range from 0.05-1.0 m. Multiple correlation analyses show that thickness variations in the deposit are reduced by decreasing gas residence time and temperature. Si3N4 plate produced under the preferred conditions exhibits theoretical density and a columnar morphology in which the >222< ctystallographic direction is oriented preferentially normal to the surface.

A modified Regula Falsi method is described which is appropriate for use when an interval bracketing of the root is known. The algorithm appears to exhibit superior asymptotic convergence properties to other modified linear methods.

The Illinois method is briefly described and the asymptotic convergence of the method investigated. Numerical examples are also given including comparisons with other similar robust methods.

The object of this paper is to describe a general method of design and analysis which has been developed for, and applied primarily to, the design of supercharger centrifugal impellers. The method has also been used as a systematic means for the analysis of such impellers as well as for the design of the corresponding diffusers and of gas-turbine compressors and turbines. The development was undertaken with the idea of obtaining, as nearly as possible, a self-sufficient and self-contained rational design method which would be influenced as little as possible by preconceived notions of what the impeller blades should look like. The method is also complete in the sense that it is not used merely as a guide to the character of the blade shape, e.g., to determine limiting curvatures. Instead, one starts from and uses the basic laws of the fluid motion to determine the required flow path and thus the complete blade shape. On the other hand, the fullest use has been made of available experience and test results as checks of the theory.

The availability of the calcium contained in a high-calcium mineral water (Sangemini), popular in Italy, was compared in 18 healthy women with the availability of milk calcium ingested at the same calcium load, using45Ca as the tracer in a randomized cross-over design. At an ingested calcium load of 2.5 mmol, absorption fraction averaged 0.433 for milk and 0.475 for Sangemini water. The mean quotient of the two (Sangemini/milk) was 1.129 (±0.056, SEM,P<0.05). The calcium of Sangemini water is thus highly bioavailable, and at least as bioavailable as milk calcium.