The Relationship Between Insertive Oral and Anal Sex and Select Measures of the Composition of the Urethral Microbiota Among Men Who Have Sex With Men.

BACKGROUND: Sexual behavior may influence the composition of the male urethral microbiota, but this hypothesis has not been tested in longitudinal studies of men who have sex with men (MSM). METHODS: From December 2014 to July 2018, we enrolled MSM with nongonococcal urethritis (NGU) attending a sexual health clinic. Men attended 5 in-clinic visits at 3-week intervals, collected weekly urine specimens at home, and reported daily antibiotics and sexual activity on weekly diaries. We applied broad-range 16S rRNA gene sequencing to urine. We used generalized estimating equations to estimate the association between urethral sexual exposures in the prior 7 days (insertive oral sex [IOS] only, condomless insertive anal intercourse [CIAI] only, IOS with CIAI [IOS + CIAI], or none) and Shannon index, number of species (observed, oral indicator, and rectal indicator), and specific taxa, adjusting for recent antibiotics, age, race/ethnicity, HIV, and preexposure prophylaxis. RESULTS: Ninety-six of 108 MSM with NGU attended ≥1 follow-up visit. They contributed 1140 person-weeks of behavioral data and 1006 urine specimens. Compared with those with no urethral sexual exposures, those with IOS only had higher Shannon index ( P = 0.03 ) but similar number of species and presence of specific taxa considered, adjusting for confounders; the exception was an association with Haemophilus parainfluenzae . CIAI only was not associated with measured aspects of the urethral microbiota. IOS + CIAI was only associated with presence of H. parainfluenzae and Haemophilus . CONCLUSIONS: Among MSM after NGU, IOS and CIAI did not seem to have a substantial influence on measured aspects of the composition of the urethral microbiota.

The Incidence Rate of Sexual Behaviors Among Cisgender Men Who Have Sex with Men Attending a Sexual Health Clinic.

Although nuanced parameterization of sexual behavior may improve estimates from mathematical models of human immunodeficiency virus and sexually transmitted infection transmission, prospective estimates of the incidence of specific sexual behaviors among men who have sex with men (MSM) are limited. From December 2014 to July 2018, MSM with and without nongonococcal urethritis (NGU) completed weekly diaries over 3-12 weeks. Incidence rates of any sex, receptive anal sex, insertive anal sex, insertive oral sex, receptive rimming, and receptive hand-penile contact were 1.19, 0.28, 0.66, 0.90, 0.24, and 0.85 episodes per person-week, respectively, among 104 MSM with NGU at baseline, and 1.33, 0.54, 0.32, 0.95, 0.44, and 0.88 episodes per person-week, respectively, among 25 MSM without NGU at baseline. Most receptive anal sex (NGU + 83%, NGU - 86%) and insertive anal sex (NGU + 85%, NGU - 76%) episodes were condomless. MSM engaged in sex just over once per week, and condom use was infrequent. Insertive oral sex and receptive hand-penile contact were the most common behaviors.

Structure-Function Correlations in the Mechanism of Action of Key Antiperspirant Agents Containing Al(III) and ZAG Salts.

Aluminum hydrolysis chemistry is an important part of modern society because of the dominance of Al(III) as a highly effective antiperspirant active. However, the century-old chemistry centered on aluminum chloride (ACL) is not comprehensive enough to address all of the in vivo events associated with current commercial antiperspirants and their mechanism of action. The present study aims to address the knowledge gap among extensively studied benchmark ACL, its modified version aluminum chlorohydrate (ACH), and a more complex but less explored group of aluminum zirconium chlorohydrate glycine complexes (ZAG salts) toward understanding the mechanism of action under consumer-relevant conditions. ACH, which is the Al source used in the manufacture of ZAG salts, provides a bridge between ACL and ZAG chemistry. High viscosity and gel formation driven by pH and a specific Al(III) salt upon hydrolysis are considered the criteria for building an in vivo occlusive mass to retard or stop the flow of sweat to the skin surface, thus providing an antiperspirant effect. Rheological studies indicated that ACL and aluminum zirconium tetrachlorohydrex glycine (TETRA) were the most efficacious salt actives. Spectroscopic studies, diffraction studies, and elemental analysis suggested that small metal oxide and hydroxide species with coparticipating glycine as well as various polynuclear and oligomeric species are the key to gel formation. At a given pH, the key ingredients (NaCl, urea, bovine serum albumin, and lactic acid) in artificial sweat were found to have little influence on Al(III) salt hydrolysis. The effects of the sweat components were mostly limited to local complex formation and kinetic modification. The in vitro comparative experiments with various Al(III) and ZAG salt systems offer unprecedented insights into the chemistry of different salt types, thus paving the way for engineering more efficacious antiperspirant systems.

Incidence of Nongonococcal Urethritis in Men Who Have Sex With Women and Associated Risk Factors.

BACKGROUND: Incidence and risk factors for nongonococcal urethritis (NGU) remain poorly defined. We conducted a cohort study to estimate the incidence of NGU and identify risk factors in men who have sex with women. METHODS: We enrolled cisgender male sexually transmitted disease clinic attendees 16 years or older who reported exclusively female partners. At enrollment and 6 monthly follow-up visits, men underwent a clinical examination, provided urethral swab and urine specimens, completed a sexual behavior survey and biweekly diaries, and were tested for Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) using Aptima assays (Hologic, Inc). Nongonococcal urethritis was defined as ≥5 polymorphonuclear leukocytes per high-power field plus either urethral symptoms or visible discharge. We estimated the incidence of NGU overall, asymptomatic and symptomatic NGU, non-CT/non-MG NGU, and CT/MG-associated NGU using Poisson regression for clustered outcomes. We performed relative risk binomial regression for clustered data to identify characteristics associated with incident NGU. RESULTS: From August 2014 to July 2018, 307 participants at risk for NGU contributed 109.4 person-years. Median age was 32 years, and 52% were White. At enrollment, 107 men had NGU; of these, 88% were symptomatic, 27% had CT, and 22% had MG. Fifty men had 60 cases of incident NGU (incidence rate, 56 per 100 person-years; 95% confidence interval, 43-74). Unlike prevalent NGU at enrollment, CT/MG-associated incident NGU was rare (incidence rate, 7; 95% confidence interval [CI], 4-15), and most (78%) incident NGU was asymptomatic. Risk factors for incident NGU were ≤ high school education (adjusted rate ratio [ARR], 2.45; 95% CI, 1.19-5.00), history of CT (ARR, 2.15; 95% CI, 1.08-4.27), history of NGU (ARR, 2.67; 95% CI, 1.27-5.62), and NGU at enrollment (ARR, 2.03; 95% CI, 1.04-3.98). Neither condom use nor having a new partner was associated with incident NGU; Black race was only associated with incident symptomatic and non-CT/non-MG NGU. CONCLUSIONS: Incidence of NGU was high, predominantly non-CT/non-MG and asymptomatic. Future studies should investigate the etiology and clinical significance of asymptomatic NGU.

Urethral Microbiota in Men: Association of Haemophilus influenzae and Mycoplasma penetrans With Nongonococcal Urethritis.

BACKGROUND: Nongonococcal urethritis (NGU) is a common syndrome with no known etiology in ≤50% of cases. We estimated associations between urethral bacteria and NGU in men who have sex with men (MSM) and men who have sex with women (MSW). METHODS: Urine was collected from NGU cases (129 MSM, 121 MSW) and controls (70 MSM, 114 MSW) attending a Seattle STD clinic. Cases had ≥5 polymorphonuclear leukocytes on Gram stain plus symptoms or discharge; controls had <5 PMNs, no symptoms, no discharge. NGU was considered idiopathic when Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma genitalium, Trichomonas vaginalis, adenovirus, and herpes simplex virus were absent. The urethral microbiota was characterized using 16S rRNA gene sequencing. Compositional lasso analysis was conducted to identify associations between bacterial taxa and NGU and to select bacteria for targeted qPCR. RESULTS: Among NGU cases, 45.2% were idiopathic. Based on compositional lasso analysis, we selected Haemophilus influenzae (HI) and Mycoplasma penetrans (MP) for targeted qPCR. Compared with 182 men without NGU, the 249 men with NGU were more likely to have HI (14% vs 2%) and MP (21% vs 1%) (both P ≤ .001). In stratified analyses, detection of HI was associated with NGU among MSM (12% vs 3%, P = .036) and MSW (17% vs 1%, P < .001), but MP was associated with NGU only among MSM (13% vs 1%, P = .004). Associations were stronger in men with idiopathic NGU. CONCLUSIONS: HI and MP are potential causes of male urethritis. MP was more often detected among MSM than MSW with urethritis.

Quantifying the Deposition of Airborne Particulate Matter Pollution on Skin Using Elemental Markers.

Airborne particulate matter (PM) pollution is an environmental and health concern. The health impact of PM pollution has typically focused on the respiratory system. The impact of PM pollution on skin has been largely understudied due to the lack of a quantitative method to measure the deposition on skin. This manuscript presents a method to quantify PM pollution on skin using elemental markers as a proxy for PM. Skin tape strips were collected from forehead and buttock of 100 outdoor workers in Beijing, China. Skin samples were analyzed for 19 elemental markers using inductively coupled plasma mass spectrometry. To determine the specific elemental signature of PM for the region, air samples were collected over 7 days for PM < 2.5 µm (PM2.5) and analyzed for the same 19 elements as the skin samples. An enrichment factor was calculated for each element and the potential source was evaluated. Using the elemental markers unique to PM pollution for the region, the PM concentration deposited on skin was determined to be 0.621-2.53 µg PM2.5 /cm2. This method can be re-applied in different regions and the PM concentration on skin can inform future studies on the health impact of air pollution on skin.

Lack of Association Between the S83I ParC Mutation in Mycoplasma genitalium and Treatment Outcomes Among Men Who Have Sex With Men with Nongonococcal Urethritis.

From February 2015 to October 2017, among 20 men who have sex with men with Mycoplasma genitalium-associated nongonococcal urethritis, 15% had macrolide resistance and S83I ParC mutations. Azithromycin followed by moxifloxacin cleared Mycoplasma genitalium in 2 of 2 with and 11 of 13 without S83I mutations. Dual failures were cleared after doxycycline. S83I mutations were not associated with moxifloxacin failure.

Resolution of Symptoms and Resumption of Sex After Diagnosis of Nongonococcal Urethritis Among Men Who Have Sex With Men.

BACKGROUND: Standard counseling at nongonococcal urethritis (NGU) diagnosis includes advice to abstain from sex for at least 7 days and until symptoms resolve. METHODS: From December 2014 to July 2018, we enrolled men who have sex with men and received azithromycin (1 g) for NGU at the Public Health-Seattle and King County STD Clinic. Over 12 weeks of follow-up, participants reported daily urethral symptoms and sexual activity on web-based diaries. Nongonococcal urethritis was defined as urethral symptoms or visible urethral discharge plus 5 or greater polymorphonuclear leukocytes per high-power field. Time of symptom resolution was defined as the first of 5 consecutive asymptomatic days. RESULTS: Of 100 participants with NGU and no Chlamydia trachomatis (CT)/Mycoplasma genitalium (MG) coinfection, 36 (36%), 22 (22%), and 42 (42%) had CT-NGU, MG-NGU, and non-CT/non-MG NGU, respectively. Among men with MG-NGU, 94% had a macrolide resistance mutation. For all etiologies, median time to symptom resolution after azithromycin was 7 days (95% confidence interval [CI], 5-9); 37% had symptoms lasting longer than 7 days. For men with CT-NGU, MG-NGU, and non-CT/non-MG NGU, median time to symptom resolution was 4 days (95% CI, 2-6; 16% >7 days), undefined days (95% CI, 7 to undefined; 60% >7 days), and 7 days (95% CI, 5-11; 46% >7 days), respectively. Median time to first sexual activity (any type) was 12 days (95% CI, 11-17); it was 16 days (95% CI, 12-18) to first urethral sexual exposure. Twenty-seven percent did not avoid urethral exposure for the recommended period. CONCLUSIONS: Counseling at NGU diagnosis should educate patients that symptoms may persist more than 7 days, particularly for non-CT NGU, and emphasize the rationale for the 7-day abstinence period.

Cross-sectional study of urethral exposures at last sexual episode associated with non-gonococcal urethritis among STD clinic patients.

OBJECTIVE: Although Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) are major causes of non-gonococcal urethritis (NGU), up to 50% of cases are of unknown aetiology. We sought to identify urethral exposures at last sexual episode associated with NGU and non-CT/non-MG NGU to identify anatomical sites from which aetiologically relevant micro-organisms may be acquired. METHODS: We enrolled STD clinic patients with and without NGU assigned male sex at birth and age ≥16 into a cross-sectional study. NGU was urethral symptoms or visible discharge plus ≥5 polymorphonuclear leucocytes without Neisseria gonorrhoeae. Urine was tested for CT and MG (Aptima). We used logistic regression to estimate the association between urethral exposures at last sex and NGU separately among cisgender men and transgender women who have sex with men (MSM/TGWSM) and cisgender men who have sex with women (MSW). RESULTS: Between 8 August 2014 and 1 November 2017, we enrolled 432 patients, including 183 MSM/TGWSM (118 NGU+, 65 NGU-) and 249 MSW (126 NGU+, 123 NGU-). The mean age was 34; 59% were white. CT and MG were detected in 72 (30%) and 49 (20%) NGU+ participants, respectively. Compared with MSM/TGWSM reporting only non-urethral exposures at last sex, those reporting insertive anal intercourse (IAI) only (adjusted OR (AOR)=4.46, 95% CI 1.09 to 18.19) and IAI with insertive oral sex (IOS) (AOR=7.88, 95% CI 2.67 to 23.26) had higher odds of NGU. MSM/TGWSM reporting IOS only had no significant increased odds (AOR=1.67, 95% CI 0.58 to 4.85). Compared with MSW whose only urethral exposure at last sex was vaginal sex (VS), MSW reporting IOS and VS had similar odds of NGU (OR=0.84, 95% CI 0.50 to 1.41). The results were similar for non-CT/non-MG NGU. CONCLUSIONS: Among MSM/TGWSM, IAI may lead to transmission of yet-unidentified rectal micro-organisms that cause non-CT/non-MG NGU, in addition to transmission of known pathogens. Sites of urethral exposure appear less important for understanding NGU risk among MSW due to minimal variation in behaviour.

Long Duration of Asymptomatic Mycoplasma genitalium Infection After Syndromic Treatment for Nongonococcal Urethritis.

BACKGROUND: Although Mycoplasma genitalium (MG) is an acknowledged cause of nongonococcal urethritis (NGU), access to diagnostic testing is limited. Syndromic management is common, yet little is known about natural history. METHODS: Between August 2014 and April 2016, 13 heterosexual men aged ≥16 years with MG were identified within a cohort study of men with and without NGU attending an urban sexually transmitted diseases clinic. Men had 6-7 monthly visits. NGU was defined as ≥5 polymorphonuclear leukocytes per high-power field on urethral Gram stain plus either visible urethral discharge or urethral symptoms. Men with NGU received 1 g of azithromycin. Men with persistent NGU received moxifloxacin 400 mg for 14 days. First-void urine was retrospectively tested for MG using transcription-mediated amplification. Resistance-associated mutations were detected by polymerase chain reaction (PCR) and sequencing. Organism load was determined by quantitative PCR. RESULTS: Sixty-two percent of MG-positive men had macrolide resistance-mediating mutations (MRMM) at enrollment; 31% had parC mutations (all outside the quinolone resistance-determining region). MG persisted after azithromycin in 7 men, 6 of whom had MRMM. The median duration of persistence in the absence of curative therapy was 143 days (range, 21-228). Five men experienced symptom resolution after azithromycin, but MG persisted for another 89-186 days before moxifloxacin. Organism load was somewhat lower in MRMM than wild-type infections (P = .16). CONCLUSIONS: The high prevalence of macrolide resistance and long duration of infection after symptom resolution highlights the need for diagnostic MG testing of men with NGU to direct therapy.

Primary Syphilis in the Male Urethra: A Case Report.

We documented urethral Treponema pallidum infection in a man with nongonococcal urethritis and a negative syphilis serology using broad-range bacterial polymerase chain reaction (PCR) and sequencing, targeted PCR, and immunofluorescence microscopy. He subsequently seroconverted for syphilis. Early syphilis may present as urethritis. Urethral T. pallidum shedding can occur before seroconversion.

High dietary iron increases oxidative stress and radiosensitivity in the rat retina and vasculature after exposure to fractionated gamma radiation.

Radiation exposure in combination with other space environmental factors including microgravity, nutritional status, and deconditioning is a concern for long-duration space exploration missions. Astronauts experience altered iron homeostasis due to adaptations to microgravity and an iron-rich food system. Iron intake reaches three to six times the recommended daily allowance due to the use of fortified foods on the International Space Station. Iron is associated with certain optic neuropathies and can potentiate oxidative stress. This study examined the response of eye and vascular tissue to gamma radiation exposure (3 Gy fractionated at 37.5 cGy per day every other day for 8 fractions) in rats fed an adequate-iron diet or a high-iron diet. Twelve-week-old Sprague-Dawley rats were assigned to one of four experimental groups: adequate-iron diet/no radiation (CON), high-iron diet/no radiation (IRON), adequate-iron diet/radiation (RAD), and high-iron diet/radiation (IRON+RAD). Animals were maintained on the corresponding iron diet for 2 weeks before radiation exposure. As previously published, the high-iron diet resulted in elevated blood and liver iron levels. Dietary iron overload altered the radiation response observed in serum analytes, as evidenced by a significant increase in catalase levels and smaller decrease in glutathione peroxidase and total antioxidant capacity levels. 8-OHdG immunostaining, showed increased intensity in the retina after radiation exposure. Gene expression profiles of retinal and aortic vascular samples suggested an interaction between the response to radiation and high dietary iron. This study suggests that the combination of gamma radiation and high dietary iron has deleterious effects on retinal and vascular health and physiology.

Using natural, stable calcium isotopes of human blood to detect and monitor changes in bone mineral balance.

We are exploring variations in the Ca isotope composition of blood and urine as a new tool for early diagnosis and monitoring of changes in bone mineral balance for patients suffering from metabolic bone disease, cancers that originate in or metastasize to bone, and for astronauts who spend time in low gravity environments. Blood samples are often collected instead of, or in addition to, urine in clinical settings, so it is useful to know if variations in the Ca isotope composition of blood carry the same information as variations in urine. We found that the Ca isotope composition of blood shifts in the same direction and to the same magnitude (~2 parts per ten thousand--pptt) as that of urine in response to skeletal unloading during bed rest. However, the Ca isotope composition of blood is lighter than that of urine by 12 ± 2 pptt. This offset between blood and urine may result from Ca isotope fractionation occurring in the kidneys. This is the first study to confirm the suspected offset between the Ca isotope composition of blood and urine in humans, to directly quantify its magnitude, and to establish that either blood or urine can be used to detect and quantify bone loss.

Body mass changes during long-duration spaceflight.

BACKGROUND: During early spaceflights, many crewmembers did not meet their caloric requirements and consequently lost body mass during flight, as assessed by a decrease in postflight body mass. Maintaining body mass during spaceflight is crucial for maintaining crew health and monitoring body mass is thus important to medical operations as well as being a key component of human research. Determining body mass becomes difficult in a microgravity environment. METHODS: We report data from two mass measurement devices on the International Space Station (ISS): the Russian body mass measuring device (BMMD), which uses spring oscillation physics, and NASA's Space Linear Acceleration Mass Measurement Device (SLAMMD), which uses Newton's second law of motion (F = ma). RESULTS: For 25 crewmembers whose body mass was measured on both devices, significant body mass loss occurred compared to preflight (gravimetric scale) and averaged -4.4% as assessed by BMMD and -2.8% as assessed by SLAMMD. After an initial loss in the first 30 d of flight, body mass remained constant through the rest of the mission, as determined using either device. The mean difference between the two devices was 1.1 kg when the closest SLAMMD and BMMD measurements were compared (6.9 ± 6.2 d apart). Dietary intake during flight is approximately 80% of the World Health Organization estimated requirement and the decrease in body mass follows in-flight energy intake closely on average. CONCLUSION: Body mass monitoring is important for monitoring crew health during a mission and to help ensure that crewmembers consume adequate energy intake to mitigate the risks of spaceflight.

Sex-specific responses of bone metabolism and renal stone risk during bed rest.

The purpose of this study was to directly assess sex differences in bone loss, bone biochemistry, and renal stone risk in bed rest. Bed rest simulates some spaceflight effects on human physiology and can be used to address the potential existence of sex-specific effects on bone metabolism and renal stone risk in space. We combined data from the control subjects in five head-down-tilt bed rest studies (combined n = 50 men, 24 women) of differing durations (14-90 days). All subjects were healthy volunteers. Mean age was 35 ± 9 years for women and 33 ± 8 years for men. The main outcome measures were bone density and biochemistry, and renal stone risk chemistry. Before bed rest began, men had higher bone mineral density and content (P < 0.001), and excreted more biomarkers of bone resorption and calcium per day than did women (P < 0.05). These differences remained during bed rest. A number of urine chemistry analytes increased (e.g., calcium) or decreased (e.g., sodium, citrate, and urine volume) significantly for men and women during bed rest. These changes may predispose men to higher stone risk. Men and women do not have substantially different responses to the skeletal unloading of bed rest.

Increased dietary iron and radiation in rats promote oxidative stress, induce localized and systemic immune system responses, and alter colon mucosal environment.

Astronauts are exposed to increased body iron stores and radiation, both of which can cause oxidative damage leading to negative health effects. The purpose of this study was to investigate combined effects of high dietary iron (650 mg/kg diet) and radiation exposure (0.375 Gy cesium-137 every other day for 16 d) on markers of oxidative stress, immune system function, and colon mucosal environment in male Sprague-Dawley rats (n=8/group). Control rats consumed adequate iron (45 mg/kg diet) and were not irradiated. Combined treatments increased liver glutathione peroxidase, serum catalase, and colon myeloperoxidase while decreasing total fecal short-chain fatty acid concentrations. The high-iron diet alone increased leukocyte count. Radiation decreased the T-cell CD4:CD8 ratio. Plasma iron was negatively correlated with cytokine production in activated monocytes. Genes involved in colon microbial signaling, immune response, and injury repair were altered by radiation. Genes involved with injury repair and pathogen recognition changed with dietary iron. These data demonstrate that dietary iron and radiation, alone and combined, contribute to oxidative stress that is related to immune system alterations in circulation and the colon. The model presented may help us better understand the changes to these systems that have been identified among astronauts.

Iron status and its relations with oxidative damage and bone loss during long-duration space flight on the International Space Station.

BACKGROUND: Increases in stored iron and dietary intake of iron during space flight have raised concern about the risk of excess iron and oxidative damage, particularly in bone. OBJECTIVES: The objectives of this study were to perform a comprehensive assessment of iron status in men and women before, during, and after long-duration space flight and to quantify the association of iron status with oxidative damage and bone loss. DESIGN: Fasting blood and 24-h urine samples were collected from 23 crew members before, during, and after missions lasting 50 to 247 d to the International Space Station. RESULTS: Serum ferritin and body iron increased early in flight, and transferrin and transferrin receptors decreased later, which indicated that early increases in body iron stores occurred through the mobilization of iron to storage tissues. Acute phase proteins indicated no evidence of an inflammatory response during flight. Serum ferritin was positively correlated with the oxidative damage markers 8-hydroxy-2'-deoxyguanosine (r = 0.53, P < 0.001) and prostaglandin F2α (r = 0.26, P < 0.001), and the greater the area under the curve for ferritin during flight, the greater the decrease in bone mineral density in the total hip (P = 0.031), trochanter (P = 0.006), hip neck (P = 0.044), and pelvis (P = 0.049) after flight. CONCLUSION: Increased iron stores may be a risk factor for oxidative damage and bone resorption.

Bioavailability of nanoparticulate hematite to Arabidopsis thaliana.

The environmental effects and bioavailability of nanoparticulate iron (Fe) to plants are currently unknown. Here, plant bioavailability of synthesized hematite Fe nanoparticles was evaluated using Arabidopsis thaliana (A. thaliana) as a model. Over 56-days of growing wild-type A. thaliana, the nanoparticle-Fe and no-Fe treatments had lower plant biomass, lower chlorophyll concentrations, and lower internal Fe concentrations than the Fe-treatment. Results for the no-Fe and nanoparticle-Fe treatments were consistently similar throughout the experiment. These results suggest that nanoparticles (mean diameter 40.9 nm, range 22.3-67.0 nm) were not taken up and therefore not bioavailable to A. thaliana. Over 14-days growing wild-type and transgenic (Type I/II proton pump overexpression) A. thaliana, the Type I plant grew more than the wild-type in the nanoparticle-Fe treatment, suggesting Type I plants cope better with Fe limitation; however, the nanoparticle-Fe and no-Fe treatments had similar growth for all plant types.

Space flight calcium: implications for astronaut health, spacecraft operations, and Earth.

The space flight environment is known to induce bone loss and, subsequently, calcium loss. The longer the mission, generally the more bone and calcium are lost. This review provides a history of bone and calcium studies related to space flight and highlights issues related to calcium excretion that the space program must consider so that urine can be recycled. It also discusses a novel technique using natural stable isotopes of calcium that will be helpful in the future to determine calcium and bone balance during space flight.