Downward myocardial creep during stress PET imaging is inversely associated with mortality

PURPOSE

The myocardial creep is a phenomenon in which the heart moves from its original position during stress-dynamic PET myocardial perfusion imaging (MPI) that can confound myocardial blood flow measurements. Therefore, myocardial motion correction is important to obtain reliable myocardial flow quantification. However, the clinical importance of the magnitude of myocardial creep has not been explored. We aimed to explore the prognostic value of myocardial creep quantified by an automated motion correction algorithm beyond traditional PET-MPI imaging variables.

METHODS

Consecutive patients undergoing regadenoson rest-stress [82Rb]Cl PET-MPI were included. A newly developed 3D motion correction algorithm quantified myocardial creep, the maximum motion at stress during the first pass (60 s), in each direction. All-cause mortality (ACM) served as the primary endpoint.

RESULTS

A total of 4,276 patients (median age 71 years; 60% male) were analyzed, and 1,007 ACM events were documented during a 5-year median follow-up. Processing time for automatic motion correction was < 12 s per patient. Myocardial creep in the superior to inferior (downward) direction was greater than the other directions (median, 4.2 mm vs. 1.3-1.7 mm). Annual mortality rates adjusted for age and sex were reduced with a larger downward creep, with a 4.2-fold ratio between the first (0 mm motion) and 10th decile (11 mm motion) (mortality, 7.9% vs. 1.9%/year). Downward creep was associated with lower ACM after full adjustment for clinical and imaging parameters (adjusted hazard ratio, 0.93; 95%CI, 0.91-0.95; p < 0.001). Adding downward creep to the standard PET-MPI imaging model significantly improved ACM prediction (area under the receiver operating characteristics curve, 0.790 vs. 0.775; p < 0.001), but other directions did not (p > 0.5).

CONCLUSIONS

Downward myocardial creep during regadenoson stress carries additional information for the prediction of ACM beyond conventional flow and perfusion PET-MPI. This novel imaging biomarker is quantified automatically and rapidly from stress dynamic PET-MPI.

Trace elements dyshomeostasis in liver and brain of weanling mice under altered dietary selenium conditions

BACKGROUND

A balanced diet containing selenium (Se) and other trace elements is essential for normal development and growth. Se has been recognized as an essential trace element; however, its interaction with other elements has not been fully investigated. In the present study, sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), Se and rubidium (Rb), were analysed in liver and brain regions under altered dietary Se intake in weanling mice to identify major discriminatory elements.

METHODS

The study investigated the effects of different levels of Se intake on the elemental composition in liver and brain tissues of weaned mice. After 24 weeks of feeding with Se adequate, deficient, and excess diets, elemental analysis was performed on the harvested tissues using Inductively coupled plasma mass spectrometry (ICP-MS). Statistical analysis that included analysis of covariance (ANCOVA), correlation coefficient analysis, principal component analysis, and partial least squares discriminant analysis were performed.

RESULTS

The ANCOVA showed statistically significant changes and correlations among the analysed elements under altered dietary Se status. The multivariate analysis showed differential changes in elements in liver and brain regions. The results suggest that long-term dietary Se alternations lead to dyshomeostasis in trace elements that are required in higher concentrations compared to Se. It was observed that changes in the Fe, Co, and Rb levels were similar in all the tissues studied, whereas the changes in Mg, Cr, and Mn levels were different among the tissues under altered dietary Se status. Additionally, the changes in Rb levels correlated with the dietary Se intake but had no relation with the tissue Se levels.

CONCLUSIONS

The findings suggest interactions between Mg, Cr, Mn, Fe, Co, and Se under altered Se status may impact cellular functions during postnatal development. However, the possible biological significance of alterations in Rb levels under different dietary Se paradigms needs to be further explored.

Relationship of multiple metals mixture and osteoporosis in older Chinese women: An aging and longevity study

Osteoporosis has become a major health problem in older women. Previous studies have linked individual metals exposure with osteoporosis, but combined effects remain inconclusive. We aimed to explore the individual and combined association between multiple metals mixture and osteoporosis risk in older Chinese women. A total of 2297 older women (aged ≥60) from the Hongshuihe region of Guangxi, southern China included. We measured 22 blood metal levels through inductively coupled plasma mass spectrometry. And osteoporosis was defined as a T score ≤ -2.5. The least absolute shrinkage and selection operator (LASSO) penalized regression, and Bayesian kernel machine regression (BKMR) models were performed to explore the association between blood metals and osteoporosis risk. Of 2297 older women, there were 829 osteoporosis and 1468 non-osteoporosis participants. The median age was 71 and 68 years old in the osteoporosis and the non-osteoporosis group, respectively. In the single-metal model, rubidium and vanadium were negatively associated with osteoporosis (P for trend = 0.02 and 0.002, respectively), and lead presented the reverse trend (P for trend = 0.01). The LASSO penalized regression model selected nine metals (calcium, cadmium, cobalt, lead, magnesium, rubidium, strontium, vanadium and zinc), which were included in the subsequent analysis. And the multiple-metal model presented a consistent trend with the single-metal model using the selected metals. Furthermore, we performed BKMR to explore the combined effect, and found an overall negative effect between metals mixture and osteoporosis risk when all the metals were fixed at 50th, and rubidium and vanadium were the main contributors. In addition, blood Rb and V were significantly negatively related to OP risk with other metals at different levels (25th, 50th and 75th percentiles). The study suggests metal mixture exposure and osteoporosis risk in older Chinese women, and further studies need to be conducted.

Multiple metals exposure and blood mitochondrial DNA copy number: A cross-sectional study from the Dongfeng-Tongji cohort

OBJECTIVE

Mitochondria are essential organelles that execute fundamental biological processes, while mitochondrial DNA is vulnerable to environmental insults. The aim of this study was to investigate the individual and mixture effect of plasma metals on blood mitochondria DNA copy number (mtDNAcn).

METHODS

This study involved 1399 randomly selected subcohort participants from the Dongfeng-Tongji cohort. The blood mtDNAcn and plasma levels of 23 metals were determined by using quantitative real-time polymerase chain reaction (qPCR) and inductively coupled plasma mass spectrometer (ICP-MS), respectively. The multiple linear regression was used to explore the association between each metal and mtDNAcn, and the LASSO penalized regression was performed to select the most significant metals. We also used the quantile g-computation analysis to assess the mixture effect of multiple metals.

RESULTS

Based on multiple linear regression models, each 1% increase in plasma concentration of copper (Cu), rubidium (Rb), and titanium (Ti) was associated with a separate 0.16% [β(95% CI) = 0.158 (0.066, 0.249), P = 0.001], 0.20% [β(95% CI) = 0.196 (0.073, 0.318), P = 0.002], and 0.25% [β(95% CI) = 0.245 (0.081, 0.409), P = 0.003] increase in blood mtDNAcn. The LASSO regression also confirmed Cu, Rb, and Ti as significant predictors for mtDNAcn. There was a significant mixture effect of multiple metals on increasing mtDNAcn among the elder participants (aged ≥65), with an approximately 11% increase in mtDNAcn for each quartile increase in all metal concentrations [β(95% CI) = 0.146 (0.048, 0.243), P = 0.004].

CONCLUSIONS

Our results show that plasma Cu, Rb and Ti were associated with increased blood mtDNA, and we further revealed a significant mixture effect of all metals on mtDNAcn among elder population. These findings may provide a novel perspective on the effect of metals on mitochondrial dysfunction.

First record of trace element accumulation in a freshwater ectoparasite, Paradiplozoon ichthyoxanthon (Monogenea; Diplozoidae), infecting the gills of two yellowfish species, Labeobarbus aeneus and Labeobarbus kimberleyensis

BACKGROUND

Elevated levels of trace elements in the aquatic environment poses risks to the health of biota and humans. Parasites are important components in ecosystems; responding to changes in the health of aquatic ecosystems and can accumulate trace elements in their tissues to higher levels than their hosts. Monogeneans are an important group of fish ectoparasites being directly exposed to the aquatic environment.

METHODS

In this study concentrations of Ti, Fe, Cu, Zn, Rb, Sr and Ag were analysed in the monogenean parasite, Paradiplozoon ichthyoxanthon (by total reflection x-ray fluorescence spectrometry and graphite furnace atomic absorption spectrometry), and the muscle, liver and gills of two host fish species, Labeobarbus aeneus and Labeobarbus kimberleyensis (by inductively coupled plasma -- mass spectrometry).

RESULTS

Most striking was the accumulation pattern for Zn in parasites; mean levels of Zn were as high as 1448 and 1652 mg kg^-1 dw, respectively, with no significant difference between the two host-parasite groups, leading to bioconcentration factors of approximately 93 (parasite/fish muscle) and 15 (parasite/fish liver). In addition, Fe was accumulated in the parasite to a higher degree compared to the fish hosts' tissues. Cu levels were higher in P. ichthyoxanthon than in the muscle tissue of both host fishes, but lower than liver tissue.

CONCLUSION

These findings demonstrate the usefulness of this parasite species as a sentinel organism in aquatic ecosystems it inhabits for Fe and Zn. Other trace elements under investigation were not accumulated higher in the parasite compared to its fish host. Lower Rb levels in the parasite compared to its hosts indicate no biomagnification of this metal. Further investigations are required to determine if similar trends in trace element accumulation occur in other monogeneans.

DATA AVAILABILITY

All data generated in the analysis of host and parasite tissues are presented in the manuscript.

Mycorrhiza-mediated potassium transport in Medicago truncatula can be evaluated by using rubidium as a proxy

Arbuscular mycorrhizal (AM) fungi considerably improve plant nutrient acquisition, particularly phosphorus and nitrogen. Despite the physiological importance of potassium (K⁺) in plants, there is increasing interest in the mycorrhizal contribution to plant K⁺ nutrition. Yet, methods to track K⁺ transport are often costly and limiting evaluation opportunities. Rubidium (Rb⁺) is known to be transported through same pathways as K⁺. As such our research efforts attempt to evaluate if Rb⁺ could serve as a viable proxy for evaluating K⁺ transport in AM symbiosis. Therefore, we examined the transport of K⁺ in Medicago truncatula colonized by the AM fungus Rhizophagus irregularis isolate 09 having access to various concentrations of Rb⁺ in custom-made two-compartment systems. Plant biomass, fungal root colonization, and shoot nutrient concentrations were recorded under sufficient and limited K⁺ regimes. We report that AM plants displayed higher shoot Rb⁺ and K⁺ concentrations and a greater K⁺:Na⁺ ratio relative to non-colonized plants in both sufficient and limited K⁺ conditions. Consequently, our results indicate that Rb⁺ can be used as a proxy to assess the movement of K⁺ in AM symbiosis, and suggest the existence of a mycorrhizal uptake pathway for K⁺ nutrition in M. truncatula.

Association of urinary rubidium concentrations with hypertension risk and blood pressure levels: A cross-sectional study in China

BACHGROUND

Rubidium resembles potassium. We hypothesized that rubidium might play a role in blood pressure control.

METHODS

We measured urinary rubidium concentrations and blood pressure levels using validated techniques and methods in 2002 eligible participants. Multivariable logistic and linear regression models were applied to explore the associations. The restricted cubic spline model was utilized to investigate the dose-response relationship. Furthermore, we explored the associations of rubidium with risk factors (glomerular filtration rate, uric acid, and homocysteine) for hypertension and relevant biochemical indexes.

RESULTS

After adjustment for potential confounders and urinary potassium and sodium levels, doubling of urinary rubidium concentrations was significantly associated with decreased hypertension risk [odds ratio (OR), 0.76; 95% confidence interval (CI), 0.61, 0.93] and reduced systolic blood pressure (SBP) levels of 2.92 (95% CI: 1.56, 4.26) mm Hg. Each 1.00 mg/L increase in rubidium concentrations was associated with a 1.25 mm Hg decreased SBP levels, which was at least 200 times more effective than potassium. Furthermore, urinary rubidium concentrations were negatively associated with the risk factors for hypertension.

CONCLUSIONS

Rubidium might have more prominent effects on lowering blood pressure levels than potassium. Prospective studies and experimental research focusing on our findings are needed.

Sex-specific associations of exposure to metal mixtures with telomere length change: Results from an 8-year longitudinal study

Studies on the relationships between exposure to metal mixtures and telomere length (TL) are limited, particularly longitudinal studies. Few studies are available on the potential sex-specific associations between metal exposures and TL change. We examined blood metal concentrations and TL at baseline (August 2012) and follow-up (June 2020) among 316 participants in a ferro-manganese refinery. The least absolute shrinkage and selection operator (LASSO) followed by the generalized linear model (GLM) was applied to evaluate the associations between multiple-metal exposures and TL change (TL in 2012 minus TL in 2020). Bayesian kernel machine regression (BKMR) was applied to cope with metal mixtures and evaluate their joint effects on TL change. Among men, three statistical methods consistently showed rubidium was negatively associated with TL change (β [95% CI] = -2.755 [-5.119, -0.391] in the GLM) and dominated the negative overall effects of 10 metal mixtures (magnesium, manganese, iron, cobalt, copper, zinc, selenium, rubidium, cadmium, and lead) on TL change (posterior inclusion probabilities = 0.816). Among women, the GLM (β [95% CI] = 4.463 [0.943, 7.983]) and LASSO (β = 4.289) showed rubidium was positively associated with TL change. Interestingly, no significant association was observed between exposure to metal mixtures and TL change in overall participants (P > 0.05). Furthermore, stratified analysis showed significant relationships between rubidium and TL change in men (β = -2.744), women (β = 3.624), and current smokers (β = -3.266) (both P interaction <0.05). In summary, our findings underlined the steady and negative association between rubidium and TL change among men with potential sex-dependent heterogeneities. Further experimental studies are required to expound the underlying mechanisms.

Benefits provided by four ectomycorrhizal fungi to Pinus taeda under different external potassium availabilities

Ectomycorrhizal fungi contribute to the nutrition of many woody plants, including those in the Pinaceae family. Loblolly pine (Pinus taeda L.), a native species of the Southeastern USA, can be colonized by multiple species of ectomycorrhizal fungi. The role of these symbionts in P. taeda potassium (K⁺) nutrition has not been previously investigated. Here, we assessed the contribution of four ectomycorrhizal fungi, Hebeloma cylindrosporum, Paxillus ammoniavirescens, Laccaria bicolor, and Suillus cothurnatus, in P. taeda K⁺ acquisition under different external K⁺ availabilities. Using a custom-made two-compartment system, P. taeda seedlings were inoculated with one of the four fungi, or kept non-colonized, and grown under K⁺-limited or -sufficient conditions for 8 weeks. Only the fungi had access to separate compartments in which rubidium, an analog tracer for K⁺, was supplied before harvest. Resulting effects of the fungi were recorded, including root colonization, biomass, and nutrient concentrations. We also analyzed the fungal performance in axenic conditions under varying supply of K⁺ and sodium. Our study revealed that these four ectomycorrhizal fungi are differentially affected by external K⁺ and sodium variations, that they are not able to provide similar benefits to the host P. taeda in our growing conditions, and that rubidium may be used with some limitations to estimate K⁺ transport from ectomycorrhizal fungi to colonized plants.

Potential synergy between PSMA uptake and tumour blood flow for prediction of human prostate cancer aggressiveness

Background

Both prostate-specific membrane antigen (PSMA) uptake and tumour blood flow (TBF) correlate with International Society of Urological Pathology (ISUP) Grade Group (GG) and hence prostate cancer (PCa) aggressiveness. The aim of the present study was to evaluate the potential synergistic benefit of combining the two physiologic parameters for separating significant PCa from insignificant findings.

Methods

From previous studies of [⁸²Rb]Rb positron emission tomography (PET) TBF in PCa, the 43 patients that underwent clinical [⁶⁸Ga]Ga-PSMA-11 PET were selected for this retrospective study. Tumours were delineated on [⁶⁸Ga]Ga-PSMA-11 PET or magnetic resonance imaging. ISUP GG was recorded from 52 lesions.

Results

[⁶⁸Ga]Ga-PSMA-11 maximum standardized uptake value (SUVmax) and [⁸²Rb]Rb SUVmax correlated moderately with ISUP GG (rho = 0.59 and rho = 0.56, both p < 0.001) and with each other (r = 0.65, p < 0.001). A combined model of [⁶⁸Ga]Ga-PSMA-11 and [⁸²Rb]Rb SUVmax separated ISUP GG > 2 from ISUP GG 1–2 and benign with an area-under-the-curve of 0.85, 96% sensitivity, 74% specificity, and 95% negative predictive value. The combined model performed significantly better than either tracer alone did (p < 0.001), primarily by reducing false negatives from five or six to one (p ≤ 0.025).

Conclusion

PSMA uptake and TBF provide complementary information about tumour aggressiveness. We suggest that a combined analysis of PSMA uptake and TBF could significantly improve the negative predictive value and allow non-invasive separation of significant from insignificant PCa.

Amelioration of imiquimod-induced psoriasis-like dermatitis in mice by DSW therapy inspired hydrogel

Psoriasis is a long-lasting and recurrent autoimmune disease which is incurable so far. Dead Sea water (DSW) therapy is an effective approach to help control the symptoms of psoriasis due to the abundant mineral ions in DSW, which inspired the material formulation in this study. Rubidium-Sodium alginate/Polyacrylamide hydrogels (Rb-SA/PAAm gels) composed of sodium alginate and polyacrylamide interpenetrating network structure with different concentrations of rubidium and certain magnesium and zinc content were prepared for the treatment of psoriasis. The obtained results suggest the good mechanical properties of the Rb-SA/PAAm gels including toughness and swelling performance. In terms of in vitro tests, the Rb-SA/PAAm gels not only show nontoxicity to human keratinocyte cell line (Hacats) but also inhibits the activity against inflammatory NF-κβ signaling pathway. Meanwhile, they can release Rb+ which enable the Rb-SA/PAAm gels have better antibacterial ability to Streptococcus and Escherichia coli. The results obtained from in vivo tests indicate that these hydrogels could alleviate the symptoms of psoriasis caused by Imiquimod (IMQ) in mice by reducing the inflammatory factor in STAT3 pathway and therefore reduce the immune stimulation of the spleen. In conclusion, the 100Rb-SA/PAAm gel has demonstrated great potential to be a topical wettable dressing for psoriasis treatment.

3D PET/CT 82Rb PET myocardial blood flow quantification: comparison of half-dose and full-dose protocols

PURPOSE

Quantification of myocardial blood flow (MBF) has become central in the clinical application of Rubidium-82 (⁸²Rb) PET myocardial perfusion scans. Current recommendations suggest injections of 1100-1500 MBq of ⁸²Rb in bolus form, which poses a potential risk of PET system saturation on most 3D PET/CT systems currently being used. We aimed to evaluate the frequency and impact of PET system saturation and to test the potential use of a half-dose acquisition protocol.

METHODS

This study comprised 20 patients who underwent repeated rest scans in a single imaging session, one employing a full-dose (FD), and the other scan a half-dose (HfD) protocol. Datasets were evaluated for saturation based on visual assessments of input functions and sinograms. We compared FD and HfD MBF measurements using Bland-Altman plots, coefficients of variation (CV), and paired t tests. A correction factor permitting serial analyses using FD/HfD imaging protocols was obtained using only the datasets without saturation.

RESULTS

A dose reduction of 47% was reported for the HfD protocol (FD, 1247 ± 196 MBq; HfD, 662 ± 115 MBq). Saturation effects were observed in 4/20 (20%) FD scans, with none observed in the 20 HfD scans. Assessment of MBFs for FD and HfD protocols revealed bias in the MBF assessments of 0.09 ml/g/min (global MBF, FD = 1.03 ± 0.29 vs HfD = 0.94 ± 0.22 ml/g/min (p = 0.001)). Exclusion of patients with visually identified saturation effects (N = 4) reduced the bias to 0.05 ml/g/min (global MBF, FD = 0.97 ± 0.28 vs HfD = 0.92 ± 0.23 ml/g/min (p = 0.02)). From the datasets without saturation effect, it was possible to generate a bias-correction: Corrected MBF_HfD = 1.09*MBF_HfD-0.03 ml/g/min. MBF_FD and MBF_HfD did not differ following the bias correction (MBF_FD = 0.97 ± 0.28, MBF_{HfD,corrected} = 0.98 ± 0.25 ml/g/min, p = 0.77).

CONCLUSION

Saturation effects can be problematic in ⁸²Rb MBF studies using the recommended FD protocols for 3D PET/CT scanners. The use of HfD protocol eliminates the risks of saturation and should be used instead of clinical protocols to avoid erroneous results.

Rubidium-containing mesoporous bioactive glass scaffolds support angiogenesis, osteogenesis and antibacterial activity

In this study, rubidium-containing mesoporous bioglass (Rb-MBG) scaffolds were formed with the investigation of the influence of Rb addition on angiogenic and osteogenic differentiation abilities of hBMSC. The phase composition, microstructure, pore size distribution, ion release, biological activity, drug loading rate, and release rate of Rb-MBG were characterized. The proliferation and differentiation of hBMSC, the markers of bone formation (ALP, COL-1) and angiogenesis (VEGF, HIF-1α), and wnt/β-catenin related-signaling pathway gene were studied by cell culture. Rb-MBG loaded with antibacterial agents enoxacin (ENX), coliforms and Staphylococcus aureus were cultured together to study the antibacterial effects. The results indicate that the samples have a 350-550 μm large pore structure and 4.5-5.5 nm mesoporous size. Adding Rb can increase the activity of ALP, the secretion of VEGF and COLI, and the expression of HIF-1α of hBMSCs. Rb containing MBG is likely to enhance the proliferation and differentiation of hBMSCs through the influence of Wnt/ß-catenin signal path. Rb-MBG scaffold can load effectively and release Rb ions and ENX continuously to damage the bacterial cell membrane with the synergistic effect, and therefore achieve antibacterial results. In conclusion, adding Rb to MBG supports angiogenesis and osteogenesis of hBMSCs, as well as antibacterial activity.

Nitric oxide and glutamate are contributors of anti-seizure activity of rubidium chloride: A comparison with lithium

The neuro-protective effects of rubidium and lithium as alkali metals have been reported for different central nervous system dysfunctions including mania and depression. The aim of this study was evaluating as well as comparing the effects of rubidium chloride (RbCl) and lithium chloride (LiCl) on different seizures paradigms in mice and determining the involvement of NMDA receptors and nitrergic pathway. To assess the seizures threshold, animals received intravenous pentylenetetrazole (PTZ, 0.5%; 1 mL/min). Male NMRI mice (6-8 weeks) received intraperitoneal (i.p.) injections of different doses of RbCl and LiCl. Doses greater than 10 mg/kg of RbCl showed a significant anticonvulsant activity 60 min after administration; the anticonvulsant effects of LiCl was observed at the doses more than 5 mg/kg and after 30 min in PTZ-induced seizure threshold. But, RbCl (10, 20 mg/kg, i.p) or LiCl (5, 10 mg/kg, i.p) injection did not induce protection against maximal electroshock (MES) or intraperitoneal injection of PTZ lethal dose (80 mg/kg)-induced seizure models. Pre-treatment with L-NAME (non-selective nitric oxide synthase (NOS) inhibitor, 10 mg/kg; i.p.) and 7-nitroindazole (selective neuronal NOS inhibitor, 30 mg/kg; i.p.) enhanced the anticonvulsive effects of both RbCl (5 mg/kg, i.p.) and LiCl (1 mg/kg, i.p.) in PTZ-induced seizure threshold model. Injection of MK-801 (NMDA receptor antagonist, 0.05 mg/kg; i.p.) before RbCl (5 mg/kg, i.p.; P < 0.001) and LiCl (1 mg/kg, i.p.; P < 0.001) administration increased the anti-seizure activity. But, treatment with L-arginine (precursor of nitric oxide, 100 mg/kg; i.p.) decreased the seizure threshold of both RbCl (20 mg/kg, i.p.; P < 0.001) and LiCl (10 mg/kg, i.p.; P < 0.001). Measurement of nitrite levels in hippocampus of animals revealed a remarkable reduction after treatment with RbCl (20 mg/kg, i.p; P < 0.05) and LiCl (10 mg/kg, i.p; P < 0.01). To conclude, rubidium may protect central nervous system against seizures in PTZ-induced seizures threshold model through NMDA/nitrergic pathways with a similarity to lithium effects in mice.

Serum Cesium, Rhenium, and Rubidium in Rheumatoid Arthritis Patients

A considerable attention has been focused on the possible association between ultra-trace elements (UTEs) status and pathogenesis of many diseases including rheumatoid arthritis (RA). UTEs have important roles in numerous metabolic processes. Serum Cs, Rb, and Re levels in RA are not studied previously. The correlation of serum Cs, Rb, and Re levels with the well-known serological parameters, anticyclic citrullinated protein antibody (ACPA), C-reactive protein (CRP), ESR, and rheumatoid factor (RF) is also not studied previously. The present study aimed to measure the level and the correlation between serum UTEs with various blood tests results in RA patients. Serum Cs, Rb, Re, ACPA, CRP, RF, and ESR were measured in Iraqi RA patients who have a positive ACPA (ACPA > 25 U/ml) and compared with healthy individuals. There were significant elevations (p < 0.05) in serum levels of all the measured parameters as compared with those of the healthy control group except Rb and uric acid which have not been changed. Subgrouping of patients according to the results of CRP and RF leads to different results. In the low-CRP group, the high-RF subgroup showed an elevation of ACPA, Cs, and ESR in comparison with the low-RF patients. In the high-CRP group, the patients with high RF showed an increase in the levels of Cs, Rb, ESR, and ACPA. The patient group with high RF and high CRP showed more significant correlations between serum UTEs and serological tests. Serum levels of UTEs were significantly altered in RA patients. The variations in the serum levels of the measured parameters in RA need more investigation to explore the possible association between these UTEs and RA. RA subgroups, according to the results of CRP and CPA, produce more and various information than taking RA as a whole group in the estimation of UTEs.

Accumulation of U, Th, Pb, V, Rb, and Ag in wild mushrooms Macrolepiota procera (Scop.) Singer from Goč, Serbia

In this study, the content of U, Th, Pb, V, Rb, and Ag in 19 soil samples from unpolluted Goč Mountain area (Serbia) was determined. The same elements were determined in 19 Macrolepiota procera samples, separately for caps and stipes. Soil samples were subjected to the BCR sequential extraction procedure. Element contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). Obtained soil values for U were in the range from 0.30 to 0.86 mg/kg and for Th from 1.7 to 13.2 mg/kg. These values are the first for background levels at unpolluted Goč area, and they are lower than the corresponding values for European unpolluted soil. The mean values in soil for Pb, V, Rb, and Ag were 27.6, 57.4, 15.8, and 0.76 mg/kg, respectively. PCA was applied to establish criteria for translocation of the analyzed elements between two parts of the mushroom. Efficient translocation for all elements except Ag as the main amount of the elements was found in caps. The mean content in the caps for U and Th was 4.3 and 63 μg/kg, respectively. Bioconcentration factors were much higher than 1 only for Rb and Ag. M. procera only weakly accumulates U and Th from soil in unpolluted areas. These findings indicate limited role of M. procera in the mycoremediation of the mentioned actinides.

On the rubidium and lithium content and availability in the sub-arid south-eastern Mediterranean: potential health implications

Rubidium and lithium are rather rare elements in environmental research, despite their affiliation with a group of chemically active metals and the abundance of Rb in the environment. A growing body of evidence, although controversial, has indicated that both elements possess unique essential and neurophysiological characteristics in biota and humans. Both elements may concentrate in soil and vegetation of sub-arid environments. We investigated the content and (potential) availability of Rb and Li in the soils and natural waters of Galilee, the Coastal Plain, and the northern Negev of Israel. A newly developed chromatographic technique for the separation of truly dissolved Rb and Li compounds has been applied. High concentrations of Rb, together with high values of the potentially vital Rb-to-K ratio, were found in the soils, the soil solutions, rainwater, throughfall water, and the plant litter leachates, but not in the surface and spring waters. This may indicate a sequestration of Rb in the local soils and a semi-closed Rb turnover in the soil-plant system with a major input from sea aerosols. Low Li bulk and available concentrations were determined in all the natural compartments. Possible implications of such specific environmental features on the local population health were discussed.

Rubidium extraction from seawater brine by an integrated membrane distillation-selective sorption system

The ultimate goal of seawater reverse osmosis (SWRO) brine management is to achieve minimal liquid discharge while recovering valuable resources. The suitability of an integrated system of membrane distillation (MD) with sorption for the recovery of rubidium (Rb⁺) and simultaneous SWRO brine volume reduction has been evaluated for the first time. Polymer encapsulated potassium copper hexacyanoferrate (KCuFC(PAN)) sorbent exhibited a good selectivity for Rb⁺ sorption with 10-15% increment at 55 °C (Langmuir Q_max = 125.11 ± 0.20 mg/g) compared to at 25 °C (Langmuir Q_max = 108.71 ± 0.20 mg/g). The integrated MD-KCuFC(PAN) system with periodic membrane cleaning, enabled concentration of SWRO brine to a volume concentration factor (VCF) of 2.9 (65% water recovery). A stable MD permeate flux was achieved with good quality permeate (conductivity of 15-20 μS/cm). Repeated cycles of MD-KCuFC(PAN) sorption with SWRO brine enabled the extraction of 2.26 mg Rb⁺ from 12 L of brine (equivalent to 1.9 kg of Rb/day, or 0.7 tonne/yr from a plant producing 10,000 m³/day brine). KCuFC(PAN) showed a high regeneration and reuse capacity. NH₄Cl air stripping followed by resorcinol formaldehyde (RF) resin filtration enabled to recover Rb⁺ from the desorbed solution.

Quantification of rubidium as a trace element in beef using laser induced breakdown spectroscopy

This study evaluates the potential of laser induced breakdown spectroscopy (LIBS) coupled with chemometrics to develop a quantification model for rubidium (Rb) in minced beef. A LIBSCAN 150 system was used to collect LIBS spectra of minced beef samples. Beef liver was used to spike the Rb levels in minced beef. All samples were dried, powdered and pelleted using a hydraulic press. Measurements were conducted by scanning 100 different locations with an automated XYZ sample chamber. Partial least squares regression (PLSR) was used to develop the calibration model, yielding a calibration coefficient of determination (R_c²) of 0.99 and a root mean square error of calibration (RMSEC) of 0.05ppm. The model also showed good results with leave-one-out cross validation, yielding a cross-validation coefficient of determination (R_cv²) of 0.90 and a root mean square error of cross-validation (RMSECV) of 0.22ppm. The current study shows the potential of LIBS as a rapid analysis tool for the meat processing industry.

Investigation of the RbCa molecule: Experiment and theory

We present a thorough theoretical and experimental study of the electronic structure of RbCa. The mixed alkali-alkaline earth molecule RbCa was formed on superfluid helium nanodroplets. Excited states of the molecule in the range of 13 000-23 000 cm^-1 were recorded by resonance enhanced multi-photon ionization time-of-flight spectroscopy. The experiment is accompanied by high level ab initio calculations of ground and excited state properties, utilizing a multireference configuration interaction method based on multiconfigurational self consistent field calculations. With this approach the potential energy curves and permanent electric dipole moments of 24 electronic states were calculated. In addition we computed the transition dipole moments for transitions from the ground into excited states. The combination of experiment and theory allowed the assignment of features in the recorded spectrum to the excited [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] states, where the experiment allowed to benchmark the calculation. This is the first experimental work giving insight into the previously unknown RbCa molecule, which offers great prospects in ultracold molecular physics due to its magnetic and electronic dipole moment in the [Formula: see text] ground state.

Breast milk concentration of rubidium in lactating mothers by instrumental neutron activation analysis method

OBJECTIVE

Relatively little is known about the trace elements content of human milk from different countries. This has not been fully investigated especially among Iranian women. This study aimed to assess the concentration of Rubidium (Rb) as a poisonous trace element in transitional breast milk of lactating mothers living in Mashhad.

METHODS

Forty nursing mothers in early lactation 3 days to 15 days postpartum, free from any medical disorder and/or medication were randomly selected. We have applied Instrumental Neutron Activation Analysis (INAA) to assess the long-lived isotope trace element Rb in transitional milk of these economically moderate 18-39 year old Iranian women.

FINDINGS

The average concentration level of Rb was 32.176 ppm dry weight (min 8.660, max 107.210 ppm). No significant correlation was observed between Rb concentration and maternal weight and age (P=0.06, P=0.05 respectively) and newborns' weight, age and sex (P=0.07, P=0.2, P=0.2 respectively).

CONCLUSION

Although the Rubidium concentration found in this study is among the highest reported in the literature, it could not be compared to other studies because of differences in analytical performance, state of lactation, and unavailable reference ranges, so this finding needs further investigations.