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DOE OSTI2022

Mineral-hydrogel composites for mitigating harmful algal bloom and supplying phosphorous for photo-biorefineries

Harmful algal blooms (HAB) are a major environmental concern in eutrophic aquatic systems. To mitigate HABs and recover the phosphorus that drives algal growth, this study developed hydrogel composites seeded with calcium phosphate and wollastonite particles, which first adsorb phosphate (P) and then precipitate it as calcium phosphate. Using a fast-growing cyanobacterium, Synechococcus elongatus 2973, as a model microalga, we found that the mineral-hydrogel composites reduced dissolved P in BG11 media from 5.1 mg/L to 0.31 mg/L, initially reducing the biomass growth rate by up to 73 % and ultimately reducing the total biomass concentration by 75 %. When applied to municipal wastewater and agricultural run-off, the composites removed 96 % and 91 % of the dissolved P, respectively. Moreover, when the recovered P-enriched composites were reused as a slow-release bio-compatible fertilizer in a photobioreactor, they effectively supported algal growth without blocking light and interfering with photosynthesis. The P-enriched composites could tune the P concentration in the culture medium and significantly promote algal lipid accumulation. Finally, this study demonstrates the mineral-hydrogel composites' potential to treat point sources of P pollution and subsequently facilitate photoautotrophic biofuel production as a nutrient, effectively recycling the captured P.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1974

Prevention of bone mineral changes induced by bed rest: Modification by static compression simulating weight bearing, combined supplementation of oral calcium and phosphate, calcitonin injections, oscillating compression, the oral diophosphonatedisodium etidronate, and lower body negative pressure

The phenomenon of calcium loss during bed rest was found to be analogous to the loss of bone material which occurs in the hypogravic environment of space flight. Ways of preventing this occurrence are investigated. A group of healthy adult males underwent 24-30 weeks of continuous bed rest. Some of them were given an exercise program designed to resemble normal ambulatory activity; another subgroup was fed supplemental potassium phosphate. The results from a 12-week period of treatment were compared with those untreated bed rest periods. The potassium phosphate supplements prevented the hypercalciuria of bed rest, but fecal calcium tended to increase. The exercise program did not diminish the negative calcium balance. Neither treatment affected the heavy loss of mineral from the calcaneus. Several additional studies are developed to examine the problem further.

Schneider, V. S.↗

DOE OSTI2025

Molecular Insights into Novel Struvite–Hydrogel Composites for Simultaneous Ammonia and Phosphate Removal

Struvite (NH 4 MgPO 4 ·6H 2 O) mineralization is an effective technique for removing ammonium and phosphate species from wastewater. However, its wider use faces obstacles because of the copresence of various pollutants in wastewater and the additional requirement for magnesium to achieve proper supersaturation conditions. To address these challenges, this study developed novel mineral–hydrogel composites that can remove ammonium and phosphate simultaneously via heterogeneous struvite and calcium phosphate (CaP) mineralization in hydrogel matrices. The composites include in situ formed struvite and CaP mineral seeds, decreasing the nucleation energy barrier of struvite and CaP formation and promoting their heterogeneous nucleation kinetics even under undersaturation conditions in bulk solution. The dual struvite and CaP seeded composites can simultaneously reduce the ammonium and total phosphate concentrations up to 60% (26.3 mg of N/g) and 91% (9.54 mg of P/g), respectively. Furthermore, the average particle sizes in composites were increased from 6.12 to 14.8 nm after wastewater treatment. Moreover, various ions commonly existing in wastewater did not significantly interfere with the removal of ammonium and phosphate. Thus, these new mineral–hydrogel composites can provide an innovative way to lower nutrient levels before discharge to streams. Moreover, encapsulating ammonium and phosphate in mineral-hydrogel composites enables their upcycling in agricultural or biorefinery applications.

Cations↗

DOE OSTI2025

Feasibility of Metal Oxide Glasses and Polymer Membranes as Sorbents for Gaseous Oxidized Mercury

Mass spectrometry methods are currently under development by the atmospheric mercury (Hg) research community to elucidate the identity of atmospheric oxidized mercury (Hg II ) compounds. Due to high instrument detection limits, materials that can quantitatively preconcentrate atmospheric Hg II without facilitating compound-altering chemical reactions are needed to support these methods. Cation exchange membranes (CEM) and nylon membranes are currently used to preconcentrate ambient Hg II for concentration measurements and Hg II compound estimation, respectively. However, CEM and nylon membranes are poor candidates for observations by mass spectrometry methods due to release of interfering compounds upon heating; glasses do not have this problem. Here, three metal oxide glasses were explored as potential alternatives for Hg II preconcentration for future use with mass spectrometry methods: calcium phosphate (CaP), iron phosphate (FeP), and calcium aluminate (CaAl). The glasses demonstrated quantitative selective capture of HgBr 2 without capture of Hg 0 . Under ambient conditions, the CaP, FeP, and CaAl sorbed 36.4 ± 12.6% of the total HgII as the CEM. However, when Hg concentrations were normalized to surface area, CaP, FeP, and CaAl sorbed more HgBr 2 in the laboratory and ambient HgII compared to CEM. The CEM and CaP retained similar concentrations of HgBr 2 when preloaded samples were deployed in the field. Additionally, a permeation tube-based calibrator was used to load sorbents with HgBr 2 for investigation of HgII retention on CEM and thermal desorption profile changes on nylon membranes during active sampling. Nylon membranes were purchased from three vendors and used to compare HgBr 2 retention; a different HgBr 2 thermal desorption profile was achieved for each vendor’s nylon membrane.

Amides↗

DOE OSTI2022

Changes in the C-terminal, N-terminal, and histidine regions of amelogenin reveal the role of oligomer quaternary structure on adsorption and hydroxyapatite mineralization

Adsorption interactions between amelogenin and calcium phosphate minerals are believed to be important to amelogenin’s function in enamel formation, however, the role of specific amino acid residues and domains within the protein in controlling adsorption is not well known. We synthesized “mechanistic probes” by systematically removing charged regions of amelogenin in order to elucidate their roles. The probes included amelogenin without the charged residues in the N-terminus (SEKR), without two, three, or eight histidines (H) in the central protein region (H2, H3, H8), or without the C-terminal residues (Delta). In-situ atomic force microscopy (AFM) adsorption studies onto hydroxyapatite (HAP) single crystals confirmed that the C-terminus was the dominant domain in promoting adsorption. We propose that subtle changes in protein-protein interactions for proteins with histidines and N-terminal residues removed resulted in changes in the oligomer quaternary size and structure that also affected protein adsorption. HAP mineralization studies revealed that the oligomer-HAP binding energy and protein layer thickness were factors in controlling the amorphous calcium phosphate (ACP) to HAP induction time. Our studies with mechanistic probes reveal the importance of the oligomer quaternary structure in controlling amelogenin adsorption and HAP mineralization.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

DPC Cement Filler Development (Progress Report)

The fillers research and development (R&D) program, mostly experimental, is part of a broader R&D program that includes new process modeling and performance assessment of criticality effects and the overall importance of criticality to repository performance (consequence screening). A literature research and consultation effort with experts by Hardin and Brady (2018) identified several potentially effective and workable filler materials including cements (primarily phosphate based), moltenmetal alloys, and low-temperature glasses. Filler attributes were defined, and the preliminary lists were compared qualitatively. Further comparative analysis will be done (e.g., cost estimates) after experimental screening has narrowed the list of alternatives. The following cement filler compositions were selected for experimental development work and accelerated testing in FY20: Aluminum phosphate cements (APCs); more specifically aluminum oxide / aluminum phosphate (Al 2 O 3 / AlPO 4 ) cements in which Al 2 O 3 serves as the filler material bound by an AlPO 4 binder formed by the reaction of Al 2 O 3 with H 3 PO 4 ; Calcium phosphate cements (CPCs); more specifically composed of pure or nearly pure hydroxyapatite or HAP (Ca 5 (PO 4 ) 3 (OH)); Wollastonite phosphate cements (WPC), specifically wollastonite and aluminum or calcium aluminum phosphates in which CaSiO 3 serves as the filler material and the phosphate serves as the binder. The FY20 effort focused on the optimization of compositions and subsequent processing of these three materials to achieve dense and well-consolidated monolithic samples with 30 to 40% porosity and permeabilities of 1 millidarcy. At the close of this progress report the aluminum phosphate cements (APCs) and the wollastonite phosphate cements (WPCs) appear to show the most promise for continued development. Less progress has been made with the calcium phosphate cements (CPCs); their slurry viscosities are high (and difficult to measure) and they exhibit relatively short cure times of 2 to 3 hours with concomitant and excessive volatile (e.g. CO 2 ) generation.

36 MATERIALS SCIENCE↗

NASA NTRS1993

Anomalous REE patterns in unequilibrated enstatite chondrites: Evidence and implications

We present here a study of Rare Earth Element (REE) microdistributions in unequilibrated enstatite chondrites (EOC's). Although the whole rock REE contents are similar in both unequilibrated and equilibrated chondrites, the host minerals of these refractory elements are different. In the least equilibrated ordinary chondrites (UOC's), the REE reside mainly in glass whereas, in their more equilibrated counterparts, the bulk of the REE is in calcium phosphate, a metamorphic mineral that formed by oxidation of phosphorous originally contained in metal. In the smaller group of enstatite (E) chondrites, calcium phosphate is absent and the phase that contains the highest REE concentrations is a minor mineral, CaS (oldhamite), which contains approximately 50 percent of the total Ca present. In E chondrites, elements typically considered to be lithophiles (such as Ca and Mn) occur in sulfides rather than silicates. This indicates formation under extremely reducing conditions, thus in a region of the solar nebula distinct from those that supplied the more abundant ordinary and carbonaceous chondrites. Previously, we observed a variety of REE patterns in the oldhamite of UEC's; they range from almost flat to some with pronounced positive Eu and Yb anomalies. Here, we searched for complementary REE patterns in other minerals from E chondrites and found them in the major mineral, enstatite. Whenever Eu and Yb anomalies are present in this mineral, they are always negative.

Crozaz, Ghislaine↗

NASA NTRS2001

E057: Renal Stone Risk Assessment During Space Flight: Assessment and Countermeasure Validation

Exposure to the microgravity environment results in many metabolic and physiological changes to humans. Body fluid volumes, electrolyte levels, and bone and muscle undergo changes as the human body adapts to the weightless environment. Changes in the urinary biochemistry occur as early as flight day 3-4 in the short duration Shuttle crewmembers. Significant decreases were observed both in fluid intake and urinary output. Other significant changes were observed in the urinary pH, calcium, potassium and uric acid levels. During Shuttle missions, the risk of calcium oxalate stone formation increased early in the flight, continued at elevated levels throughout the flight and remained in the increased risk range on landing day. The calcium phosphate risk was significantly increased early in-flight and remained significantly elevated throughout the remainder of the mission. Results from the long duration Shuttle-Mir missions followed a similar trend. Most long duration crewmembers demonstrated increased urinary calcium levels despite lower dietary calcium intake. Fluid intake and urine volumes were significantly lower during the flight than during the preflight. The calcium oxalate risk was increased relative to the preflight levels during the early in-flight period and continued in the elevated risk range for the remainder of the space flight and through two weeks postflight. Calcium phosphate risk for these long duration crewmembers increased during flight and remained in the increased risk range throughout the flight and following landing. The complexity, expense and visibility of the human space program require that every effort be made to protect the health of the crewmembers and ensure the success of the mission. Results from our early investigations clearly indicate that exposure to the microgravity environment of space significantly increases the risk of renal stone formation. The early studies have indicated specific avenues for development of countermeasures for the increased renal stone risk observed during and following space flight. Increased hydration and implementation of pharmacological countermeasures are being tested for their efficacy in mitigating the in-flight risk of renal stones. Maintaining the health and well-being of crewmembers during space flight requires a means of minimizing potential detrimental health effects of microgravity. The formation of a renal stone during flight obviously has severe consequences for the affected crewmember as well as the success of the mission.

Whitson, Peggy A.↗

DOE OSTI2022

Strategies to Recover Easily-Extractable Rare Earth Elements and Other Critical Metals from Coal Waste Streams and Adjacent Rock Strata Using Citric Acid

Maximum rare earth element (REE) extractability from a sample of Middle Kittanning coal seam underclay was previously demonstrated at ~30% of the total REE content with a citric acid solution (Montross et al., 2020). This report further refines the mechanisms of citrate application for leaching of coal seam underclays using an organic acid lixiviant and evaluates strategies to begin to scale this process to industrially relevant volumes. This study evaluates the suitability of citrate leaching solutions for downstream recovery and separation of the REEs via oxalic acid precipitation. The applicability of citric acid solutions to recover ion-adsorbed metals from clay surfaces was evaluated by leaching a prepared sample of kaolinite with known amounts of ion-adsorbed lanthanum. Citrate systematics was further defined through experiments varying the solution pH. Up-scaling investigations proceeded with percolation leaching columns and stirred tank reactors. Two embodiments were run in percolation leaching: a continuous flow-through process and a multi-stage saturated process. The results showed that in certain limited scenarios, low pH citrate solutions could be used to target REEs mineralized within secondary calcium phosphate minerals. Results from the upscaling attempts encountered difficulties in extraction efficiencies. For the percolation columns, hydrodynamic flow was insufficient to recover the extractable REE content fully. For the stirred barrels, mixing inefficiencies likely inhibited the extractability of the REEs. Oxalic acid precipitation experiments also highlighted difficulties in downstream operations. The REEs were removed from the citrate solution with high efficiency, but were accompanied by equally efficient removal of calcium in orders of magnitude of greater amounts. Overall, for citrate leaching to be effective, future studies will have to: 1) carefully consider the feedstock application (i.e., likely better suited for secondary mineralization of calcium phosphate minerals), and 2) overcome the technical barriers of large-scale processing, such as inefficient hydrodynamic regimes due to small crush sizes needed and difficulties in downstream separation and purification. Alternatively, citrate solutions may be better recommended as leaching amendments to other leaching solutions to enhance REE complexation in the solution.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2022

The Role of Process-Directing Agents on Enamel Lesion Remineralization: Fluoride Boosters

The aim of this study was to investigate the effects of two process-directing agents (polyaspartic acid and osteopontin) used in a polymer-induced liquid-precursor (PILP) process on the remineralization of bacteria-induced enamel demineralization. Enamel demineralization lesions (depths of about 180–200 µm) were created and exposed to Streptococcus mutans, cultured with a 10% sucrose solution for 21 days, and remineralized using a PILP process (pH = 7.4, 14 days) with a calcium phosphate solution containing either polyaspartic acid or osteopontin in the presence or absence of fluoride (0.5 ppm). The specimens were examined under scanning electron microscopy. The fluoride was successfully incorporated into the PILP remineralization process for both polyaspartic acid and osteopontin. When the fluoride was added to the PILP remineralization solution, there was more uniform remineralization throughout the lesion than with either polyaspartic acid or osteopontin alone. However, in the absence of these process-directing agents, fluoride alone showed less remineralization with the formation of a predominantly surface-only layer. The PILP remineralization process relies on the ability of process-directing agents to stabilize calcium phosphate ions and holds promise for enamel lesion remineralization, and these agents, in the presence of fluoride, seem to play an important role as a booster or supplement in the continuation of remineralization by reducing the mineral gains at the surface layer.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2023

A library of calcium mineral reference spectra recorded by parallel imaging using NEXAFS spectromicroscopy

Calcium minerals are ubiquitous in geology and life chemistry. Understanding the phase and chemical state of calcium minerals is important for numerous processes including materials chemistry, hard tissue biogenesis and geological processes. Photoemission spectroscopies such as near edge X-ray absorption fine structure (NEXAFS) and scanning transmission X-ray microscopy have been instrumental in identifying and characterizing calcium minerals in all these areas. In this work, we have recorded reference spectra for a range of different calcium minerals including a series of calcium carbonates, calcium oxalates and calcium phosphates. While collections of reference spectra for several calcium minerals can be found in the literature, these spectra have been reported in different contexts using a variety of instruments. We, here, report a comprehensive list of references recorded in parallel in a single experiment by imaging an array of calcium minerals using a NEXAFS microscope. We present reference NEXAFS spectra at the calcium L-, carbon K- and oxygen K-edges.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Sol-gel derived silicate-phosphate glass SiO 2 –P 2 O 5 –CaO–TiO 2 : The effect of titanium isopropoxide on porosity and thermomechanical stability

Despite of several decades lasting extensive research of bioactive and bioresorbable glasses the systematic parametrization and determination of the key factors affecting porosity and thermomechanical characteristics still remains challenging. Here, we present silica-phosphate glasses, with the composition 70SiO 2 - 20P 2 O 5 - (10-x)CaO-xTiO 2 (mol%; x = 0, 2.5, 5, and 7.5), prepared by sol -gel method and reinforced by titanium dioxide via titanium isopropoxide (TTIP) incorporation which demonstrated tunable variation of porosity from micro-to macro -region and superb mechanical integrity during the calcination process. The presence of 7.5 mol% TiO 2 promotes dimensional stability up to 1000°C as investigated by thermomechanical analysis. The XRD showed the dominant presence of silicon phosphate [Si(P 2 O 7 )], titanium phosphate [Ti(P 2 O 7 )] and calcium phosphates [β-Ca(P 2 O 6 ) and γ- Ca 2 (P 2 O 7 )]. The effect of TiO 2 doping on the multiscale morphology and porosity was investigated by means of SEM, MIP, μCT, N 2 adsorption and USAXS/SAXS. Increasing TiO 2 content leads to the formation of open porosity up to 70vol% and drives the formation of a refined interconnected macroporosity of 2-30 μm. In contrast, mesoporosity with a dominance of 3-6nm pores decreases in all samples with increasing TiO 2 content. USAXS/SAXS revealed an increase in primary particle size with increasing TiO 2 content which is in good agreement with the nitrogen physisorption analysis showing that microporosity decreases with increasing TiO2 content.

36 MATERIALS SCIENCE↗

NASA NTRS2001

Long-term measurement of bone strain in vivo: the rat tibia

Despite the importance of strain in regulating bone metabolism, knowledge of strains induced in bone in vivo during normal activities is limited to short-term studies. Biodegeneration of the bond between gauge and bone is the principle cause of this limitation. To overcome the problem of bond degeneration, a unique calcium phosphate ceramic (CPC) coating has been developed that permits long-term attachment of microminiature strain gauges to bone. Using this technique, we report the first long-term measurements of bone strain in the rat tibia. Gauges, mounted on the tibia, achieved peak or near peak bonding at 7 weeks. Measurements were made between 7-10 weeks. Using ambulation on a treadmill, the pattern and magnitude of strain measured in the tibia remained relatively constant between 7-10 weeks post implantation. That strain levels were similar at 7 and 10 weeks suggests that gauge bonding is stable. These data demonstrate that CPC-coated strain gauges can be used to accurately measure bone strain for extended periods, and provide an in vivo assessment of tibial strain levels during normal ambulation in the rat. Copyright 2001 John Wiley & Sons, Inc.

Non-programmatic↗

DOE OSTI2020

Biosorption of Uranium by Bone Meal

The treatment of aqueous solution waste containing organic compounds and radionuclides has always been a great concern since the processes available are usually expensive and unfeasible for the low volume of radioactive liquid waste recovered. In view of a more efficient and low cost treatment, biosorption-based technologies for the removal of this hazardous radionuclides, heavy metals, and organic substances from contaminated matrices have been studied as an alternative process. In this context, bone meal is the material of choice, and contains calcium phosphate in the form of hydroxyapatite. Previous studies with hydroxyapatite showed that this material is efficient in removing heavy metals from polluted soils due to its adsorbing ability. In this context, uranium biosorption capacity by using bone meal was evaluated by different experimental conditions. This study aims at analyzing the capacity of bone meal to remove uranium from aqueous solution through biosorption process, considering that this nuclide is radiotoxic and may cause serious environmental problems and risks to human life if not correctly disposed. The biosorption capacity of U by bone meal was evaluated under different experimental conditions. The results suggested that adsorption with this material can be applied in the treatment of aqueous solutions as a low-cost and highly efficient alternative to remove U. Therefore, we believe that our results are useful for other investigators dealing with similar problems. Further work is required to evaluate this material as a potential adsorbent concerning the treatment of liquid organic radioactive waste containing uranium. Next studies are crucial to ascertain the biosorption efficiency, by analyzing other variables, such as adsorbent dosage, pH and temperature.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

NASA NTRS1993

The potential role of salt abuse on the risk for kidney stone formation

The kidney stone-forming risk of a high sodium diet was evaluated by assessing the effect of such a diet on the crystallization of stone-forming salts in urine. Fourteen normal subjects participated in 2 phases of study of 10 days duration each, comprising a low sodium phase (basal metabolic diet containing 50 mmol. sodium per day) and a high sodium phase (basal diet plus 250 mmol. sodium chloride per day). The high sodium intake significantly increased urinary sodium (34 +/- 12 to 267 +/- 56 mmol. per day), calcium (2.73 +/- 1.03 to 3.93 +/- 1.51 mmol. per day) and pH (5.79 +/- 0.44 to 6.15 +/- 0.25), and significantly decreased urinary citrate (3.14 +/- 1.19 to 2.52 +/- 0.83 mmol. per day). Arterialized venous blood bicarbonate and total serum carbon dioxide concentrations decreased significantly during the high sodium diet, whereas serum chloride concentration increased. However, no change in arterialized venous pH was detected. Thus, a high sodium intake not only increased calcium excretion, but also increased urinary pH and decreased citrate excretion. The latter effects are probably due to sodium-induced bicarbonaturia and a significant decrease in serum bicarbonate concentration, respectively. Commensurate with these changes, the urinary saturation of calcium phosphate (brushite) and monosodium urate increased, and the inhibitor activity against calcium oxalate crystallization (formation product) decreased. The net effect of a high sodium diet was an increased propensity for the crystallization of calcium salts in urine.

Non-NASA Center↗

NASA NTRS1997

Renal stone risk assessment during Space Shuttle flights

PURPOSE: The metabolic and environmental factors influencing renal stone formation before, during, and after Space Shuttle flights were assessed. We established the contributing roles of dietary factors in relationship to the urinary risk factors associated with renal stone formation. MATERIALS AND METHODS: 24-hr. urine samples were collected prior to, during space flight, and following landing. Urinary and dietary factors associated with renal stone formation were analyzed and the relative urinary supersaturation of calcium oxalate, calcium phosphate (brushite), sodium urate, struvite and uric acid were calculated. RESULTS: Urinary composition changed during flight to favor the crystallization of calcium-forming salts. Factors that contributed to increased potential for stone formation during space flight were significant reductions in urinary pH and increases in urinary calcium. Urinary output and citrate, a potent inhibitor of calcium-containing stones, were slightly reduced during space flight. Dietary intakes were significantly reduced for a number of variables, including fluid, energy, protein, potassium, phosphorus and magnesium. CONCLUSIONS: This is the first in-flight characterization of the renal stone forming potential in astronauts. With the examination of urinary components and nutritional factors, it was possible to determine the factors that contributed to increased risk or protected from risk. In spite of the protective components, the negative contributions to renal stone risk predominated and resulted in a urinary environment that favored the supersaturation of stone-forming salts. Dietary and pharmacologic therapies need to be assessed to minimize the potential for renal stone formation in astronauts during/after space flight.

STS Shuttle Project↗

DOE OSTI2023

Insights into pulmonary phosphate homeostasis and osteoclastogenesis emerge from the study of pulmonary alveolar microlithiasis

Pulmonary alveolar microlithiasis is an autosomal recessive lung disease caused by a deficiency in the pulmonary epithelial Npt2b sodium-phosphate co-transporter that results in accumulation of phosphate and formation of hydroxyapatite microliths in the alveolar space. The single cell transcriptomic analysis of a pulmonary alveolar microlithiasis lung explant showing a robust osteoclast gene signature in alveolar monocytes and the finding that calcium phosphate microliths contain a rich protein and lipid matrix that includes bone resorbing osteoclast enzymes and other proteins suggested a role for osteoclast-like cells in the host response to microliths. While investigating the mechanisms of microlith clearance, we found that Npt2b modulates pulmonary phosphate homeostasis through effects on alternative phosphate transporter activity and alveolar osteoprotegerin, and that microliths induce osteoclast formation and activation in a receptor activator of nuclear factor-κB ligand and dietary phosphate dependent manner. This work reveals that Npt2b and pulmonary osteoclast-like cells play key roles in pulmonary homeostasis and suggest potential new therapeutic targets for the treatment of lung disease.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS2002

Nutrition and renal stone disease in space

There is a growing body of evidence from the National Aeronautics and Space Administration and the Russian space program showing that humans exposed to the microgravity environment of space have a greater risk for developing renal stones. Increased bone resorption and the attendant hypercalciuria and hyperphosphaturia contribute significantly to raising the urinary state of saturation with respect to the calcium salts, namely calcium oxalate and calcium phosphate. In addition, other environmental and dietary factors may adversely affect urine composition and increase stone formation risk during space flight. For example, reductions in urinary volume, pH, and citrate contribute to raising stone formation risk. In addition to raising the risk for calcium stone formation, this metabolic profile is conducive to the formation of uric acid stones. Although observations to date have suggested that there may actually be a reduced food intake during the early phase of flight, crew members on longer-duration flights may increase food intake and be at increased risk for stone formation. Taken together, these findings support the use of nutritional recommendations for crew members that would serve to reduce the stone-forming propensity of the urinary environment. Pharmacologic intervention should be directed at raising urinary volumes, diminishing bone losses, and preventing reductions in urinary pH and citrate. Success in reducing the risk for stone formation in astronauts would also be of potential major benefit to the estimated 20 million Americans with nephrolithiasis.

Review↗