Effect of complex iron on the phosphorus absorption by two freshwater algae.

Iron plays an important role in physiological processes of microalgae and also affects the absorption of other nutrients by algae cells. Therefore, iron is one of the important controlling factors for algae bloom formation. This study investigated the effect of four kinds of complex iron (EDTA-Fe, ferric humate, ferric oxalate and ferric ammonium citrate) on the phosphorus absorption by two freshwater algae (Scenedesmus quadricauda and Anabaena flos-aquae). The results showed that the species and concentration of complex iron had a significant effect on the phosphorus uptake rate of S. quadricauda, but had only a slight effect on that of A. flos-aquae. The former exhibits positive influences on phosphorus absorption and was in the following order: ferric oxalate and EDTA-Fe > ferric humate and ammonium ferric citrate, and these effects depended on whether the presence of complex iron constitutes an environmental pressure for the growth of algal cells.

Effect of different phosphorus concentrations on biodiesel production from Isochrysis zhangjiangensis under nitrogen sufficiency or deprivation condition.

The effects of two nitrogen (N) concentrations combining with three phosphorus (P) concentrations on Isochrysis zhangjiangensis growth and formation of fatty acid (FA) were investigated in this study. Biomass concentration, mass fraction, and productivity of FA in I. zhangjiangensis were low in N-deprived media. Under both N and P sufficiency conditions, the intake of P and N was 40 times and 4.7 times of the normal algal growth condition, respectively, indicating I. zhangjiangensis had the potential for removing P and N from high concentrated N and P salinity wastewater. This study also showed that P deficiency in N sufficient medium increased the FA content, however, the difference between P limitation and P deprivation was not significant (P > 0.05). In N sufficient and P limitation medium, FA productivity was the highest, with a composition suitable for biofuel, so, this condition was the optimal condition for biodiesel production from I. zhangjiangensis.

Twenty-Four-Hour Urine Phosphorus as a Biomarker of Dietary Phosphorus Intake and Absorption in CKD: A Secondary Analysis from a Controlled Diet Balance Study.

BACKGROUND AND OBJECTIVES: Twenty-four-hour urine phosphorus is commonly used as a surrogate measure for phosphorus intake and absorption in research studies, but its reliability and accuracy are unproven in health or CKD. This secondary analysis sought to determine the reliability and accuracy of 24-hour urine phosphorus as a biomarker of phosphorus intake and absorption in moderate CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Eight patients with stage 3-4 CKD participated in 2-week balance studies with tightly controlled phosphorus and calcium intakes. Thirteen 24-hour urine collections per patient were analyzed for variability and reliability of 24-hour urine phosphorus and phosphorus-to-creatinine ratio. The accuracy of 24-hour urine phosphorus to predict phosphorus intake was determined using a published equation. The relationships of 24-hour urine phosphorus with phosphorus intake, net absorption, and retention were determined. RESULTS: There was wide day-to-day variation in 24-hour urine phosphorus within and among subjects (coefficient of variation of 30% and 37%, respectively). Two 24-hour urine measures were needed to achieve ≥75% reliability. Estimating dietary phosphorus intake from a single 24-hour urine resulted in underestimation up to 98% in some patients and overestimation up to 79% in others. Twenty-four-hour urine phosphorus negatively correlated with whole-body retention but was not related to net absorption. CONCLUSIONS: From a sample of eight patients with moderate CKD on a tightly controlled dietary intake, 24-hour urine phosphorus was highly variable and did not relate to dietary phosphorus intake or absorption, rather it inversely related to phosphorus retention.

Short communication: Effect of abomasal inorganic phosphorus infusion on phosphorus absorption in large intestine, milk production, and phosphorus excretion of dairy cattle.

The objective of the study was to evaluate the effect of inorganic phosphorus (Pi) infusion on P absorption in large intestine, milk production, and phosphorus excretion. Four ruminally and ileally cannulated crossbred cows were used in a 4 × 4 Latin square with 21-d periods. Cows were fed a total mixed ration containing 0.21% P, providing 50% of the cows' P requirement. Cobalt-EDTA was used as marker to measure large intestine digesta flow. On d 13 to 21 of each period, each cow was infused daily with 0, 20.1, 40.2, or 60.3 g of Pi into the abomasum and total collection was conducted on d 18 to 21. Ileal samples were collected every 9 h on d 18 to 21. Feed, digesta, and fecal samples were analyzed for total P and Pi using the molybdovanadate yellow method and blue method, respectively. All data were analyzed using PROC GLIMMIX in SAS 9.3 (SAS Institute Inc., Cary, NC) using contrasts to evaluate linear, quadratic, and cubic effects of Pi infusion dose. Dry matter intake, apparent dry matter digestibility, milk yield, and milk total P were unaffected by Pi infusion. Ileal flow and fecal excretion of total P and Pi increased linearly with increasing infused Pi. In the large intestine, net absorption of TP and Pi was increased linearly with increasing infused Pi. The magnitude of absorption from the large intestine was greater than reflected in current models, raising questions that could be evaluated with longer infusion periods or dietary alteration.

Effects of sodium, 1,25-dihydroxyvitamin D3 and parathyroid hormone fragment on inorganic P absorption and Type IIb sodium-phosphate cotransporter expression in ligated duodenal loops of broilers.

Three experiments were conducted with 22-day-old Arbor Acres male broilers to study the effects of Na+, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and parathyroid hormone fragment [PTH (1-34)] on inorganic P absorption and Type IIb sodium-phosphate cotransporter (NaP-IIb) mRNA and protein expression levels in ligated duodenal loops. The duodenal loops were perfused with solutions (pH = 6) containing zero, 50, or 150 mmol/L of Na+ as NaCl in Exp. 1, containing zero, 30, or 300 pmol/L of 1,25-(OH)2D3 in Exp. 2, or containing zero, 65, or 650 pmol/L of PTH (1-34) in Exp. 3, respectively. Compared with the control, additions of 50 and 150 mmol/L of Na+, 30 and 300 pmol/L of 1,25-(OH)2D3, or 65 and 650 pmol/L of PTH (1-34) to the perfusates promoted (P < 0.02) the P absorption percentages and rates, respectively. Additions of the above-mentioned concentrations of Na+ or 1,25-(OH)2D3 to the perfusates increased (P < 0.003) NaP-IIb mRNA level in the duodenum of broilers, and a similar trend (P = 0.08) was observed for PTH (1-34). The Na+, 1,25-(OH)2D3, and PTH (1-34) had no effects (P > 0.15) on NaP-IIb protein level in the duodenum of broilers. The results indicate that increased P absorption due to perfusions of Na+, 1,25-(OH)2D3 or PTH (1-34) might be attributed to enhanced NaP-IIb expression in the duodenum of broilers.

The utility of the phosphate binder, ferric citrate hydrate (JTT-751), about phosphorus absorption-reducing effect in normal rats.

Hyperphosphatemia is a risk factor for arterial calcification contributing to the high-cardiovascular mortality in patients with chronic kidney disease (CKD). Ferric citrate hydrate (JTT-751) is being developed as a treatment for hyperphosphatemia with chronic renal failure and has shown a serum phosphorus-lowering effect in CKD patients. In this study, we evaluated the combination effect of JTT-751 with the phosphorus absorption-reducing effect of calcium carbonate and compared phosphorus absorption-reducing efficacy between three phosphate binders including JTT-751. Normal rats were fed a diet containing either 1% calcium carbonate, 1% JTT-751 or 1% JTT-751 with 1% calcium carbonate, for 7 days. Both 1% calcium carbonate and 1% JTT-751 alone reduced urinary phosphorus excretion, and the combined treatment reduced it more than each single-treatment, without clearly influencing calcium or iron-metabolism. Next, normal rats were fed a diet containing either 0.3, 1 and 3% lanthanum carbonate or 2.3% JTT-751, for 7 days. Either 3% lanthanum carbonate or 2.3% JTT-751 reduced urinary phosphorus excretion. Finally, we compared the reduced amount of urinary phosphorus excretion per dose of compound, of which JTT-751 is comparable to that of calcium carbonate and is greater than that of the lanthanum carbonate. In conclusion, JTT-751 showed an additive effect on the phosphorus absorption-reducing effect of calcium carbonate without influencing calcium- and iron-metabolism, and had a phosphorus absorption-reducing efficacy comparable to or greater than other existing phosphate binders.