Intracellular transformation and disposal mechanisms of magnetosomes in macrophages and cancer cells

Magnetosomes are magnetite nanoparticles biosynthesized by magnetotactic bacteria. Given their potential clinical applications for the diagnosis and treatment of cancer, it is essential to understand what becomes of them once they are within the body. With this aim, here we have followed the intracellular long-term fate of magnetosomes in two cell types: cancer cells (A549 cell line), because they are the actual target for the therapeutic activity of the magnetosomes, and macrophages (RAW 264.7 cell line), because of their role at capturing foreign agents. It is shown that cells dispose of magnetosomes using three mechanisms: splitting them into daughter cells, excreting them to the surrounding environment, and degrading them yielding less or non-magnetic iron products. A deeper insight into the degradation mechanisms by means of time-resolved X-ray absorption near-edge structure (XANES) spectroscopy has allowed us to follow the intracellular biotransformation of magnetosomes by identifying and quantifying the iron species occurring during the process. In both cell types there is a first oxidation of magnetite to maghemite and then, earlier in macrophages than in cancer cells, ferrihydrite starts to appear. Given that ferrihydrite is the iron mineral phase stored in the cores of ferritin proteins, this suggests that cells use the iron released from the degradation of magnetosomes to load ferritin. Comparison of both cellular types evidences that macrophages are more efficient at disposing of magnetosomes than cancer cells, attributed to their role in degrading external debris and in iron homeostasis.

Expanded hemodialysis: what's up, Doc?

In recent years there has been an increasing interest in expanded hemodialysis (HDx), an emerging renal replacement therapy based on the use of medium cut-off membranes (MCO). Thanks to the internal architecture of these types of membranes, with a higher pore size and smaller fiber inner diameter to favor internal filtration rate, they can increase the removal of larger middle molecules in conventional hemodialysis. Secondarily, several reports suggest that this therapy potentially improve the outcomes for end-stage renal disease patients. However, HDx has not been defined yet and the characteristics of MCO membranes are not well stablished. The aim of this narrative review is to define HDx and summarize the dialyzers that have been used so far to perform this therapy, collect the evidence available on its efficacy and clinical outcomes compared with other hemodialysis techniques and settle the bases for its optimal prescription.

Incorporation of Tb and Gd improves the diagnostic functionality of magnetotactic bacteria

Magnetotactic bacteria are envisaged as potential theranostic agents. Their internal magnetic compass, chemical environment specificity and natural motility enable these microorganisms to behave as nanorobots, as they can be tracked and guided towards specific regions in the body and activated to generate a therapeutic response. Here we provide additional diagnostic functionalities to magnetotactic bacteria Magnetospirillum gryphiswaldense MSR-1 while retaining their intrinsic capabilities. These additional functionalities are achieved by incorporating Tb or Gd in the bacteria by culturing them in Tb/Gd supplemented media. The incorporation of Tb provides luminescence properties, enabling potential applications of bacteria as biomarkers. The incorporation of Gd turns bacteria into dual contrast agents for magnetic resonance imaging, since Gd adds T₁ contrast to the existing T₂ contrast of unmodified bacteria. Given their potential clinical applications, the diagnostic ability of the modified MSR-1 has been successfully tested in vitro in two cell models, confirming their suitability as fluorescent markers (Tb-MSR-1) and dual contrast agents for MRI (Gd-MSR-1).

Obesity, chronic kidney disease progression and the role of the adipokine C1q/TNF related protein-3

INTRODUCTION AND AIMS

Obesity is a risk factor for incident chronic kidney disease (CKD). C1q/TNF related protein 3 (CTRP3) is an adipokine with multiple effects and may modulate the association between obesity and vascular diseases. The aim of the study is to explore potential links between obesity, CTRP3 levels and CKD progression.

METHODS

Patients with stage 3 and 4 CKD without previous cardiovascular events were enrolled and divided into groups according to body mass index (BMI) and sex. Demographic, clinical, analytical data and CTRP3 levels were collected at baseline. During follow-up, renal events (defined as dialysis initiation, serum creatinine doubling or a 50% decrease in estimated glomerular filtration rate were registered).

RESULTS

81 patients were enrolled. 27 were obese and 54 non-obese. Baseline CTRP3 was similar between both groups (90.1±23.8 vs 84.5±6.2; p=0.28). Of the sum, 54 were men and 27 women, with higher CTRP3 in women (81.4±24.7 vs 106±24.7;p<0.01). During a mean follow-up of 68 months, 15 patients had a renal event. Patients in the higher CTRP3 tertile had less events but without statistical significance (p=0.07). Obese patients in the higher CTRP3 tertile significantly had less renal events (p=0.049). By multiple regression analysis CTRP3 levels could not predict renal events (HR 0.98; CI95% 0.96-1.06).

CONCLUSIONS

CTRP3 levels are higher in woman than men in patients with CKD, with similar levels between obese and non obese. Higher CTRP3 levels at baseline were associated with better renal outcomes in obese patients.

Magnetic Anisotropy of Individual Nanomagnets Embedded in Biological Systems Determined by Axi-asymmetric X-ray Transmission Microscopy

Over the past few years, the use of nanomagnets in biomedical applications has increased. Among others, magnetic nanostructures can be used as diagnostic and therapeutic agents in cardiovascular diseases, to locally destroy cancer cells, to deliver drugs at specific positions, and to guide (and track) stem cells to damaged body locations in regenerative medicine and tissue engineering. All these applications rely on the magnetic properties of the nanomagnets which are mostly determined by their magnetic anisotropy. Despite its importance, the magnetic anisotropy of the individual magnetic nanostructures is unknown. Currently available magnetic sensitive microscopic methods are either limited in spatial resolution or in magnetic field strength or, more relevant, do not allow one to measure magnetic signals of nanomagnets embedded in biological systems. Hence, the use of nanomagnets in biomedical applications must rely on mean values obtained after averaging samples containing thousands of dissimilar entities. Here we present a hybrid experimental/theoretical method capable of working out the magnetic anisotropy constant and the magnetic easy axis of individual magnetic nanostructures embedded in biological systems. The method combines scanning transmission X-ray microscopy using an axi-asymmetric magnetic field with theoretical simulations based on the Stoner-Wohlfarth model. The validity of the method is demonstrated by determining the magnetic anisotropy constant and magnetic easy axis direction of 15 intracellular magnetite nanoparticles (50 nm in size) biosynthesized inside a magnetotactic bacterium.

Mortalidad y función renal a largo plazo en pacientes ingresados en UCI por Covid-19 con fracaso renal agudo, terapia continua de reemplazo renal y ventilación mecánica invasiva

Introducción La interacción

de COVID-19, ventilación mecánica invasiva (VMI) y fracaso renal agudo (FRA) con necesidad de terapia continua de reemplazo renal (TCRR) es conocida, pero hay pocos datos publicados sobre el pronóstico a largo plazo de este tipo de FRA.

Métodos

Este estudio analiza los resultados a largo plazo de 30 pacientes ingresados en la UCI por neumonía por COVID-19, con VMI y FRA con TCRR en el pico de máxima incidencia. Comparamos las características basales, la evolución clínica y bioquímica y los diferentes filtros usados en la TCRR para identificar los factores de riesgo asociados a la muerte intrahospitalaria. Se analizaron el filtrado glomerular estimado (FGe), la proteinuria y la hematuria a los 6 meses de seguimiento de los supervivientes.

Resultados

De los 30 pacientes, 19 fallecieron y 11 fueron dados de alta. Los pacientes con peor función renal tuvieron mayor mortalidad (p = 0,009). Los filtros usados con capacidad adsortiva no ofrecieron beneficios en cuanto a la supervivencia. De los 11 supervivientes, ninguno requirió terapia renal sustitutiva (TRS) una vez superada la infección, pero tuvieron una pérdida importante y mantenida en el tiempo de función renal (FGe de 44 ml/min/1,73 m²).

Conclusión

La mortalidad en pacientes con neumonía por COVID-19 que requieren VMI y TCRR es extremadamente elevada (63%). Los filtros con capacidad adsortiva no modificaron la supervivencia. La función renal basal fue un factor predictor de mortalidad. En este tipo de FRA el deterioro de la función renal no se recupera, objetivándose una reducción importante del FGe a los 6 meses.

Exploring the Different Degrees of Magnetic Disorder in TbxR1-xCu2 Nanoparticle Alloys

Recently, potential technological interest has been revealed for the production of magnetocaloric alloys using Rare-Earth intermetallics. In this work, three series of TbxR1-xCu2 (R ≡ Gd, La, Y) alloys have been produced in bulk and nanoparticle sizes via arc melting and high energy ball milling. Rietveld refinements of the X-ray and Neutron diffraction patterns indicate that the crystalline structure in all alloys is consistent with TbCu2 orthorhombic Imma bulk crystalline structure. The analyses of the DC-magnetisation (MDC) and AC-susceptibility (χAC) show that three distinct degrees of disorder have been achieved by the combination of both the Tb3+ replacement (dilution) and the nanoscaling. These disordered states are characterised by transitions which are evident to MDC, χAC and specific heat. There exists an evolution from the most ordered Superantiferromagnetic arrangement of the Tb0.5La0.5Cu2 NPs with Néel temperature, TN∼ 27 K, and freezing temperature, Tf∼ 7 K, to the less ordered weakly interacting Superparamagnetism of the Tb0.1Y0.9Cu2 nanoparticles (TN absent, and TB∼ 3 K). The Super Spin Glass Tb0.5Gd0.5Cu2 nanoparticles (TN absent, and Tf∼ 20 K) are considered an intermediate disposition in between those two extremes, according to their enhanced random-bond contribution to frustration.

Magnetosomes could be protective shields against metal stress in magnetotactic bacteria

Magnetotactic bacteria are aquatic microorganisms with the ability to biomineralise membrane-enclosed magnetic nanoparticles, called magnetosomes. These magnetosomes are arranged into a chain that behaves as a magnetic compass, allowing the bacteria to align in and navigate along the Earth’s magnetic field lines. According to the magneto-aerotactic hypothesis, the purpose of producing magnetosomes is to provide the bacteria with a more efficient movement within the stratified water column, in search of the optimal positions that satisfy their nutritional requirements. However, magnetosomes could have other physiological roles, as proposed in this work. Here we analyse the role of magnetosomes in the tolerance of Magnetospirillum gryphiswaldense MSR-1 to transition metals (Co, Mn, Ni, Zn, Cu). By exposing bacterial populations with and without magnetosomes to increasing concentrations of metals in the growth medium, we observe that the tolerance is significantly higher when bacteria have magnetosomes. The resistance mechanisms triggered in magnetosome-bearing bacteria under metal stress have been investigated by means of x-ray absorption near edge spectroscopy (XANES). XANES experiments were performed both on magnetosomes isolated from the bacteria and on the whole bacteria, aimed to assess whether bacteria use magnetosomes as metal storages, or whether they incorporate the excess metal in other cell compartments. Our findings reveal that the tolerance mechanisms are metal-specific: Mn, Zn and Cu are incorporated in both the magnetosomes and other cell compartments; Co is only incorporated in the magnetosomes, and Ni is incorporated in other cell compartments. In the case of Co, Zn and Mn, the metal is integrated in the magnetosome magnetite mineral core.

Investigating the Size and Microstrain Influence in the Magnetic Order/Disorder State of GdCu2 Nanoparticles

A series of GdCu 2 nanoparticles with controlled sizes ranging from 7 nm to 40 nm has been produced via high-energy inert-gas ball milling. Rietveld refinements on the X-ray diffraction measurements ensure that the bulk crystalline I m m a structure is retained within the nanoparticles, thanks to the employed low milling times ranging from t = 0.5 to t = 5 h. The analysis of the magnetic measurements shows a crossover from Superantiferromagnetism (SAF) to a Super Spin Glass state as the size decreases at NP size of 〈 D 〉 ≈ 18 nm. The microstrain contribution, which is always kept below 1%, together with the increasing surface-to-core ratio of the magnetic moments, trigger the magnetic disorder. Additionally, an extra contribution to the magnetic disorder is revealed within the SAF state, as the oscillating RKKY indirect exchange achieves to couple with the aforementioned contribution that emerges from the size reduction. The combination of both sources of disorder leads to a maximised frustration for 〈 D 〉 ≈ 25 nm sized NPs.

P1180EVOLUTION OF SERUM B2MICROGLOBULIN LEVELS IN INCIDENT PERITONEAL DIALYSIS PATIENTS

Background and Aims

Retention of ß2microglobulin (ß2M), an uremic toxin in the middle molecular range, has been associated with cardiovascular morbidity and mortality in dialysis patients. Although ß2M levels are usually measured in hemodialysis patients, this practice is not common among peritoneal dialysis (PD) patients. The aim of this study is to evaluate the evolution of serum ß2M levels in incident PD patients.

Method

Prospective, observational study including incident PD patients in our hospital from January 2015 to October 2019. Patients with cardiorrenal syndrome or patients coming from hemodialysis were excluded. Serum ß2M levels were collected before starting PD and during follow up. Weekly KtV, residual renal function and cardiovascular events were also collected during follow up.

Results

We included 30 patients with a mean age of 57 +/- 17 years. 56.3% were male and 15.6% were diabetic. Mean follow up was 19.8 +/- 16.9 months. 18 patients were on continous ambulatory PD and 12 in automated PD. Mean serum ß2M levels before starting PD were 12.8 +/- 6.6 mg/l and they remained stable during follow up (12.9 +/- 5.2 mg/l, 15 +/- 4.2 mg/l, 14.3 +/- 6.9 mg/l, 10.2+/- 4.5 mg/l at month 6, 12, 24 and 36, respectively; p NS). No differences in serum ß2M levels were observed between continous ambulatory PD and automated PD. Serum ß2M levels were inversely and significantly correlated with weekly KtV (r= -0.943; p 0.009) and residual renal function (r= -0.829; p 0.042). One cardiovascular event was recorded during follow up.

Conclusion

Serum ß2M levels remain stable during follow up in our cohort of incident PD patients and is significantly and inversely correlated with weekly KtV and residual renal function. Serum ß2M levels monitoring could be helpful in these patients and would yield important information in this population.

Persistent pruritus as a rare and potentially serious manifestation of liver involvement in autosomal dominant polycystic kidney disease

Polycystic liver disease (PCLD) is the most frequent extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD), usually asymptomatic. We present a patient with ADPKD who developed cholestatic pruritus due to bile duct compression of multiple liver cysts. Because of severity of pruritus she received treatment with lanreotide to reduce liver volume and she was studied to be included in the liver transplant waiting list. She evolved favourably with medical treatment and she is now asymptomatic. In conclusion, persistent pruritus is a rare but potentially serious manifestation of PCLD, so it should be taken into account in patients with ADPKD.

The new marker YKL-40, a molecule related to inflammation, is associated with cardiovascular events in stable haemodialysis patients

Background

YKL-40 is a glycoprotein associated with inflammatory conditions, including atherosclerosis and endothelial dysfunction. The objective was to analyse serum YKL-40 levels in a haemodialysis population and explore their association with dialysis dosing measures, inflammation, body composition and development of cardiovascular (CV) events.

Methods

We performed a prospective study of 78 chronic haemodialysis patients enrolled in 2013 and followed up until 2018. At baseline, serum YKL-40, inflammatory and nutrition markers and body composition were assessed. During a median follow-up of 43 (interquartile range 24–66) months, CV events were recorded.

Results

The mean age of patients was 62 ± 16 years and 66% were men. The mean YKL-40 was 207 ± 106 ng/dL. Higher YKL-40 levels were associated with lower Kt/V_urea, convective volume, serum albumin and prealbumin and with higher troponin T. During follow-up, 50% developed CV events. Cox analysis showed an association between CV events and YKL-40, diabetes, hypertension, C-reactive protein, lower prealbumin, β₂-microglobulin, glycosylated haemoglobin and troponin T values. The multivariate Cox analysis confirmed an independent association between CV events and YKL-40 {hazard ratio [HR] 1.067 [95% confidence interval (CI) 1.009–1.211]; P: 0.042}, troponin T [HR 1.037 (95% CI 1.009–1.683); P: 0.007], lower prealbumin [HR 0.827 (95% CI 0.224–0.988); P: 0.009] and diabetes [HR 2.103 (95% CI 1.554–3.172); P: 0.008]. Kaplan–Meier confirmed the association between CV events and YKL-40 (log rank 7.28; P = 0.007).

Conclusions

YKL-40 is associated with CV events in haemodialysis patients. Higher dialysis dose and convective volume are associated with lower serum YKL-40 levels.

Impact of anticoagulation and platelet antiaggregation on anaemia and haemorragic events in patients with chronic kidney disease stages 3 and 4

BACKGROUND AND OBJECTIVE

There is controversy concerning the risk/benefit of anticoagulation/antiaggregation in chronic kidney disease (CKD) patients. We analysed the impact of anticoagulation/antiaggregation on anaemia and haemorrhagic events in CKD patients.

PATIENTS AND METHODS

A total of 232 CKD patients stages 3 and 4 were followed during a mean follow-up time of 36.7 ± 11.6 months: 81 patients did not receive any anticoagulation or antiaggregation treatment, 91 received anticoagulation treatment and 60 patients received platelet antiaggregation. Haemorrhagic and cardiovascular events were recorded.

RESULTS

Haemoglobin and ferritine levels were significantly higher in patients who did not receive anticoagulation or antiaggregation (Hb 13.7 ± 1.6, 13.3 ± 1.8 and 12.7±1.9g/dl, p=0.004; ferritine 170 ± 145, 140 ± 138, 105 ± 99μg/l, p=0.023). During follow up, 36 haemorrhagic events were registered: 4in the control group, 23 in the anticoagulation group and 9in the antiaggregation group (log rank 12.5; p=0.002). In a Cox model adjusted by age, renal function and haemoglobin levels, the anticoagulation increased the risk of bleeding by 4times (HR 4.180, 1.955-8.937); p=0,001) and antiaggregation by almost 3times (HR 2.780, 1.257-6.149, p=0.012). A total of 64 cardiovascular events were registered, 21 of which were classified as atherosclerotic events: 10 in the antiaggregation group, 8in the control group and 3in the anticoagulation group (log rank: 8.351; p=0.015). Anticoagulation treatment showed a reduction in the risk of atherosclerotic events (HR 0.136, 0.033-0.551, p=0.005) while platelet antiaggregation did not modified this risk (HR 1,566, 0.569-4.308).

CONCLUSIONS

Anticoagulation and antiaggregation increase haemorrhagic risk in patients with CKD and worsen anaemia. Anticoagulation reduces atherosclerotic events by more than 85% while platelet antiaggregation does not modify this risk.

High convective volumes are associated with improvement in metabolic profile in diabetic patients on online haemodiafiltration

BACKGROUND AND OBJECTIVE

Online haemodiafiltration (OL-HDF) with high convective transport volumes improves patient survival in haemodialysis. Limiting the amount of convective volume has been proposed in patients with diabetes mellitus due to glucose load that is administered with replacement fluid. The objective of the study was to analyse the influence of substitution volume on the evolution of the metabolic profile and body composition of incident diabetic patients on OL-HDF.

MATERIAL AND METHODS

Prospective observational study in 29 incident diabetic patients on postdilution OL-HDF. Baseline data included clinical and demographic data, laboratory parameters (metabolic, nutritional and inflammatory profile) and body composition with bioimpedance spectroscopy (BIS). Laboratory parameters and mean substitution volume per session were collected every 4 months, and in 23 patients a further BIS was performed after a minimum of one year. Variations in glycosylated haemoglobin (HbA1c), triglycerides, total cholesterol, LDL-c, HDL-c, albumin, prealbumin and C reactive protein (CRP) were calculated at one year, 2 years, 3 years, and at the end of follow-up. Quarterly and annual variations were calculated as independent periods, and changes in body composition were analysed.

RESULTS

Age at baseline was 69.7±13.6 years, 62.1% were male, 72.3±13.9kg, 1.78±0.16m², with 48 (35.5-76) months on dialysis. Approximately 81.5% received insulin, 7.4% antidiabetic drugs and 51.9% statins. Mean substitution volume was 26.9±2.9L/session and follow-up period (time on OL-HDF) was 40.4±26 months. A significant correlation was observed between mean substitution volume and the increase in HDL-c (r=0.385, p=0.039) and prealbumin levels (r=0.404, p=0.003) throughout follow-up. Moreover, substitution volume was correlated with a reduction in CRP levels at one year (r=-0.531, p=0.005), 2 years (r=-0.463, p=0.046), and at the end of follow-up (r=-0.498, p=0.007). Patients with mean substitution volume >26.9L/session had a higher reduction in triglycerides and CRP, and an increase in HDL-c levels. These patients with >26.9L/session finished the study with higher HDL-c (48.1±9.4mg/dL vs. 41.2±11.6mg/dL, p=0.025) and lower CRP levels (0.21 [0.1-2.22] mg/dL vs. 1.01 [0.15-6.96] mg/dL, p=0.001), with no differences at baseline. Quarterly comparisons between substitution volume and laboratory changes [n=271] showed a significant correlation with a reduction in HbA1c (r=-0.146, p=0.021). Similar findings were obtained with annual comparisons [n=72] (r=-0.237, p=0.045). An annual mean substitution volume over 26.6L/session (29.3±1.7L/session vs. 23.9±1.9L/session) was associated with a reduction in HbA1c (-0.51±1.24% vs. 0.01±0.88%, p=0.043). No correlation was observed between substitution volume and changes in weight, body mass index or BIS parameters.

CONCLUSION

There is not enough evidence to restrict convective transport in diabetic patients on OL-HDF due to the glucose content of the replacement fluid.

Obesity and chronic kidney disease progression-the role of a new adipocytokine: C1q/tumour necrosis factor-related protein-1

Background

Obesity is a risk factor for incident chronic kidney disease (CKD) in the general population. C1q/tumour necrosis factor-related protein 1 (CTRP1) is a new adipokine with multiple vascular and metabolic effects and may modulate the association between obesity and vascular diseases. The aim of the study is to explore potential links between obesity, CTRP1 levels and CKD progression.

Methods

Patients with Stages 3 and 4 CKD without previous cardiovascular events were enrolled and divided into two groups according to body mass index (BMI). Demographic, clinical and analytical data and CTRP1 levels were collected at baseline. During follow-up, renal events [defined as dialysis initiation, serum creatinine doubling or a 50% decrease in estimated glomerular filtration rate (Modification of Diet in Renal Disease)] were registered.

Results

A total of 71 patients with CKD were divided into two groups: 25 obese (BMI >30 kg/m²) and 46 non-obese. CTRP1 in plasma at baseline was higher in obese patients [median (interquartile range) 360 (148) versus 288 (188) ng/mL, P = 0.041]. No significant association was found between CTRP1 levels and CKD stage, presence of diabetes, aldosterone and renin levels, or blood pressure. Obese patients had higher systolic blood pressure (P = 0.018) and higher high-sensitivity C-reactive protein (P = 0.019) and uric acid (P = 0.003) levels, without significant differences in the percentage of diabetic patients or albuminuria. During a mean follow-up of 65 months, 14 patients had a renal event. Patients with CTRP1 in the lowest tertile had more renal events, both in the overall sample (log rank: 5.810, P = 0.016) and among obese patients (log rank: 5.405, P = 0.020). Higher CTRP1 levels were associated with slower renal progression (hazard ratio 0.992, 95% confidence interval 0.986–0.998; P = 0.001) in a model adjusted for obesity, aspirin, albuminuria and renal function.

Conclusions

CTRP1 levels are higher in obese than in non-obese patients with CKD. High CTRP1 levels may have a renal protective role since they were associated with slower kidney disease progression. Interventional studies are needed to explore this hypothesis.

Evaluation of the efficacy of a medium cut-off dialyser and comparison with other high-flux dialysers in conventional haemodialysis and online haemodiafiltration

BACKGROUND

Online haemodiafiltration (OL-HDF) has been shown to reduce all-cause mortality versus conventional haemodialysis (HD); however, it is not always available. In these situations, a novel class of membranes with a higher pore size, medium cut-off (MCO) dialysers, could be promising. The aim of this study is to evaluate the efficacy of an MCO dialyser in the removal of small and medium-size molecules and compare it with standard high-flux (HF) dialysers in HD and OL-HDF.

METHODS

In this crossover study, 18 prevalent HD patients were studied in three single mid-week dialysis treatments during three consecutive weeks as follows: first week with OL-HDF with a standard HF dialyser, second week with conventional HD with a standard HF dialyser and third week with conventional HD with an MCO dialyser. Reduction ratios (RRs) of different-sized molecules and albumin losses were collected for the different dialysers.

RESULTS

MCO HD provided a greater reduction of middle and larger middle molecules compared with standard HF HD [rate reduction (RR) β2-microglobulin 74.7% versus 69.7%, P=0.01; RR myoglobin 62.5% versus 34.3%, P=0.001; RR prolactin 60% versus 32.8%, P=0.001; RR α1-glycoprotein 2.8% versus -0.1%, P=0.01]. We found no difference in the clearance of small and larger middle molecules comparing MCO HD with OL-HDF. Albumin losses were 0.03  g/session with MCO HD and 3.1  g/session with OL-HDF (P=0.001).

CONCLUSION

MCO HD is superior to standard HF HD in the removal of middle and larger middle molecules and it is not inferior to OL-HDF in the clearance of small and larger middle molecules. Thus it could be an alternative in patients in which it is not possible to perform OL-HDF.

Mixed cryoglobulinaemia vasculitis after sustained hepatitis C virological response with direct-acting antivirals

Mixed cryoglobulinaemia (MCG) is one of the most severe extrahepatic hepatitis C virus (HCV)-associated complications, and could involve several organs, including the kidney. MCG prognosis relies on HCV response to antiviral treatment and has changed over the last years, especially after the introduction of new direct acting antivirals (DAA). MCG persistence despite sustained virological response (SVR) is uncommon and has a poorly known meaning and prognosis. We report a case of a patient with chronic HCV infection treated with DAA who developed MCG vasculitis despite the SVR.

Configuration of the magnetosome chain: a natural magnetic nanoarchitecture

Magnetospirillum gryphiswaldense is a microorganism with the ability to biomineralize magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Rather than straight lines, magnetosome chains are slightly bent, as evidenced by electron cryotomography. Our experimental and theoretical results suggest that due to the competition between the magnetocrystalline and shape anisotropies, the effective magnetic moment of individual magnetosomes is tilted out of the [111] crystallographic easy axis of magnetite. This tilt does not affect the direction of the chain net magnetic moment, which remains along the [111] axis, but explains the arrangement of magnetosomes in helical-like shaped chains. Indeed, we demonstrate that the chain shape can be reproduced by considering an interplay between the magnetic dipolar interactions between magnetosomes, ruled by the orientation of the magnetosome magnetic moment, and a lipid/protein-based mechanism, modeled as an elastic recovery force exerted on the magnetosomes.

Any grade of relative overhydration is associated with long-term mortality in patients with Stages 4 and 5 non-dialysis chronic kidney disease

Background

Overhydration (OH) is associated with mortality in chronic kidney disease (CKD). A relative overhydration adjusted for extracellular water (OH/ECW) measured by bioimpedance >15% has shown an increased mortality risk in haemodialysis but few studies have been developed in advanced CKD. Our objective was to evaluate the effect of OH on mortality in patients with Stage 4 or 5 non-dialysis CKD.

Methods

We performed a prospective study of 356 patients enrolled in 2011 and followed up until 2016. At baseline we collected general characteristics, serum inflammatory and nutrition markers, cardiovascular events (CVEs) and body composition using bioimpedance spectroscopy. During a median follow-up of 50 (24–66) months we collected mortality data.

Results

The mean creatinine was 3.5 ± 1.3 mg/dL, median proteinuria was 0.5 [interquartile range (IQR) 0.2–1.5] g/24 h, median OH was 0.6 (IQR −0.4–1.5) L and mean relative OH (OH/ECW) was 2.3 ± 0.8%. We found that 32% of patients died. The univariate Cox analysis showed an association between mortality and age, diabetes, previous CVEs, Charlson comorbidity index, low albumin and pre-albumin, high C-reactive protein (CRP), low lean tissue and high OH/ECW. Multivariate Cox analysis confirmed an association between mortality and age {exp(B) 1.1 [95% confidence interval (CI) 1.0–1.3]; P = 0.001}, Charlson comorbidity index [exp(B) 1.1 (95% CI 1.0–1.2); P = 0.01], CRP [exp(B) 1.1 (95% CI 1.0–1.2); P = 0.04], OH/ECW [exp(B) 3.18 (95% CI 2.09–4.97); P = 0.031] and low lean tissue [exp(B) 0.82 (95% CI 0.69–0.98); P = 0.002]. Kaplan–Meier analysis confirmed higher mortality in patients with OH/ECW >0% (log rank 11.1; P = 0.001).

Conclusion

Any grade of relative OH measured by OH/ECW >0% is associated with long-term mortality in patients with Stage 4 or 5 non-dialysis CKD.

Influence of the bacterial growth phase on the magnetic properties of magnetosomes synthesized by Magnetospirillum gryphiswaldense

BACKGROUND

The magnetosome biosynthesis is a genetically controlled process but the physical properties of the magnetosomes can be slightly tuned by modifying the bacterial growth conditions.

METHODS

We designed two time-resolved experiments in which iron-starved bacteria at the mid-logarithmic phase are transferred to Fe-supplemented medium to induce the magnetosomes biogenesis along the exponential growth or at the stationary phase. We used flow cytometry to determine the cell concentration, transmission electron microscopy to image the magnetosomes, DC and AC magnetometry methods for the magnetic characterization, and X-ray absorption spectroscopy to analyze the magnetosome structure.

RESULTS

When the magnetosomes synthesis occurs during the exponential growth phase, they reach larger sizes and higher monodispersity, displaying a stoichiometric magnetite structure, as fingerprinted by the well defined Verwey temperature. On the contrary, the magnetosomes synthesized at the stationary phase reach smaller sizes and display a smeared Verwey transition, that suggests that these magnetosomes may deviate slightly from the perfect stoichiometry.

CONCLUSIONS

Magnetosomes magnetically closer to stoichiometric magnetite are obtained when bacteria start synthesizing them at the exponential growth phase rather than at the stationary phase.

GENERAL SIGNIFICANCE

The growth conditions influence the final properties of the biosynthesized magnetosomes. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editors: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Asymptomatic Intradialytic Supraventricular Arrhythmias and Adverse Outcomes in Patients on Hemodialysis

BACKGROUND AND OBJECTIVES

Supraventricular arrhythmias are associated with high morbidity and mortality. Nevertheless, this condition has received little attention in patients on hemodialysis. The objective of this study was to analyze the incidence of intradialysis supraventricular arrhythmia and its long-term prognostic value.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We designed an observational and prospective study in a cohort of patients on hemodialysis with a 10-year follow-up period. All patients were recruited for study participation and were not recruited for clinical indications. The study population comprised 77 patients (42 men and 35 women; mean age =58±15 years old) with sinus rhythm monitored using a Holter electrocardiogram over six consecutive hemodialysis sessions at recruitment.

RESULTS

Hypertension was present in 68.8% of patients, and diabetes was present in 29.9% of patients. Supraventricular arrhythmias were recorded in 38 patients (49.3%); all of these were short, asymptomatic, and self-limiting. Age (hazard ratio, 1.04 per year; 95% confidence interval, 1.00 to 1.08) and right atrial enlargement (hazard ratio, 4.29; 95% confidence interval, 1.30 to 14.09) were associated with supraventricular arrhythmia in the multivariate analysis. During a median follow-up of 40 months, 57 patients died, and cardiovascular disease was the main cause of death (52.6%). The variables associated with all-cause mortality in the Cox model were age (hazard ratio, 1.04 per year; 95% confidence interval, 1.00 to 1.08), C-reactive protein (hazard ratio, 1.04 per 1 mg/L; 95% confidence interval, 1.00 to 1.08), and supraventricular arrhythmia (hazard ratio, 3.21; 95% confidence interval, 1.29 to 7.96). Patients with supraventricular arrhythmia also had a higher risk of nonfatal cardiovascular events (hazard ratio, 4.32; 95% confidence interval, 2.11 to 8.83) and symptomatic atrial fibrillation during follow-up (hazard ratio, 17.19; 95% confidence interval, 2.03 to 145.15).

CONCLUSIONS

The incidence of intradialysis supraventricular arrhythmia was high in our hemodialysis study population. Supraventricular arrhythmias were short, asymptomatic, and self-limiting, and although silent, these arrhythmias were independently associated with mortality and cardiovascular events.

On the mineral core of ferritin-like proteins: structural and magnetic characterization

It is generally accepted that the mineral core synthesized by ferritin-like proteins consists of a ferric oxy-hydroxide mineral similar to ferrihydrite in the case of horse spleen ferritin (HoSF) and an oxy-hydroxide-phosphate phase in plant and prokaryotic ferritins. The structure reflects a dynamic process of deposition and dissolution, influenced by different biological, chemical and physical variables. In this work we shed light on this matter by combining a structural (High Resolution Transmission Electron Microscopy (HRTEM) and Fe K-edge X-ray Absorption Spectroscopy (XAS)) and a magnetic study of the mineral core biomineralized by horse spleen ferritin (HoSF) and three prokaryotic ferritin-like proteins: bacterial ferritin (FtnA) and bacterioferritin (Bfr) from Escherichia coli and archaeal ferritin (PfFtn) from Pyrococcus furiosus. The prokaryotic ferritin-like proteins have been studied under native conditions and inside the cells for the sake of preserving their natural attributes. They share with HoSF a nanocrystalline structure rather than an amorphous one as has been frequently reported. However, the presence of phosphorus changes drastically the short-range order and magnetic response of the prokaryotic cores with respect to HoSF. The superparamagnetism observed in HoSF is absent in the prokaryotic proteins, which show a pure atomic-like paramagnetic behaviour attributed to phosphorus breaking the Fe-Fe exchange interaction.

Breakdown of magnetism in sub-nanometric Ni clusters embedded in Ag

Downsizing to the nanoscale has opened up a spectrum of new magnetic phenomena yet to be discovered. In this context, we investigate the magnetic properties of Ni clusters embedded in a metallic Ag matrix. Unlike in Ni free-standing clusters, where the magnetic moment increases towards the atomic value when decreasing the cluster size, we show, by tuning the Ni cluster size down to the sub-nanoscale, that there is a size limit below which the clusters become non-magnetic when embedded in Ag. To this end, we have fabricated by DC-sputtering a system composed of sub-nanometer sized and non interacting Ni clusters embedded into a Ag matrix. A thorough experimental characterization by means of structural techniques (x-ray diffraction, x-ray absorption spectroscopy) and DC-magnetization confirms that the cluster size is in the sub-nanometric range and shows that the magnetization of the system is dramatically reduced, reaching only 38% of the bulk value. The experimental system has been reproduced by density functional theory calculations on Ni m clusters (m = 1-6, 10 and 13) embedded in Ag. The combination of the experimental and theoretical analysis points out that there is a breakdown of magnetism occurring below a cluster size of six atoms. According to our results, the loss of magnetic moment is not due to Ag-Ni hybridization but to charge transfer between the Ni sp and d orbitals, and the reduced magnetization observed experimentally is explained on the basis of the presence of a narrow cluster size-distribution where magnetic and non-magnetic clusters coexist.

Magnetite biomineralization in Magnetospirillum gryphiswaldense: time-resolved magnetic and structural studies

Magnetotactic bacteria biosynthesize magnetite nanoparticles of high structural and chemical purity that allow them to orientate in the geomagnetic field. In this work we have followed the process of biomineralization of these magnetite nanoparticles. We have performed a time-resolved study on magnetotactic bacteria Magnetospirillum gryphiswaldense strain MSR-1. From the combination of magnetic and structural studies by means of Fe K-edge X-ray absorption near edge structure (XANES) and high-resolution transmission electron microscopy we have identified and quantified two phases of Fe (ferrihydrite and magnetite) involved in the biomineralization process, confirming the role of ferrihydrite as the source of Fe ions for magnetite biomineralization in M. gryphiswaldense. We have distinguished two steps in the biomineralization process: the first, in which Fe is accumulated in the form of ferrihydrite, and the second, in which the magnetite is rapidly biomineralized from ferrihydrite. Finally, the XANES analysis suggests that the origin of the ferrihydrite could be at bacterial ferritin cores, characterized by a poorly crystalline structure and high phosphorus content.

Ni doped Fe3O4 magnetic nanoparticles

In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.