Validation of the Kidney Failure Risk Equation in the Colombian Population.

Introduction: Chronic kidney disease prevention programs must identify patients at risk of early progression to provide better treatment and prolong kidney replacement therapy-free survival. Risk equations have been developed and validated in cohorts outside of Colombia, so this study aims to evaluate the discrimination and calibration of the four-variable kidney failure risk equation in a Colombian population where it has yet to be validated. Methods: External validation study of a kidney failure risk equation using a historical cohort of patients with CKD stages 3, 4, and 5, adults without a history of dialysis or kidney transplantation with a two-year follow-up, belonging to the Baxter Renal Care Services Colombia network. The discriminatory capacity of the model was evaluated by the concordance index using Harrell's C statistic, and the time-dependent area under the receiver operating characteristic (ROC) curve was estimated using the nearest neighbor method, as well as the optimal cut-off point for sensitivity and specificity. Calibration was determined by the degree of agreement between the observed outcome and the probabilities predicted by the model using the Hosmer-Lemeshow statistic. Results: A total of 5,477 patients were included, with a mean age of 72 years, 36.4% diabetic, and a mean baseline eGFR of 36 ml/min/1.73 m2. The rate of dialysis initiation was three events per 100 patient-years, 95% CI (2.9-3.6). The optimal cutoff for sensitivity was 0.94, for specificity, 0.76, and the area under the ROC curve was 0.92. Harrell's C-statistic was 0.88 for the total population, 0.88 for diabetic patients, and 0.93 for those 65 years or older. The validation of the model showed good calibration. Conclusions: In this Colombian cohort, the four-variable KFRE with a two-year prediction horizon has excellent calibration and discrimination, and its use in the care of CKD Colombian patients is recommended.

Microdosimetry in low energy proton beam at therapeutic-equivalent fluence rate with silicon 3D-cylindrical microdetectors.

In this work we show the first microdosimetry measurements on a low energy proton beam with therapeutic-equivalent fluence rates by using the second generation of 3D-cylindrical microdetectors. The sensors belong to an improved version of a novel silicon-based 3D-microdetector design with electrodes etched inside silicon, which were manufactured at the National Microelectronics Centre (IMB-CNM, CSIC) in Spain. A new microtechnology has been employed using quasi-toroid electrodes of 25µm diameter and a depth of 20µm within the silicon bulk, resulting in a well-defined cylindrical radiation sensitive volume. These detectors were tested at the 18 MeV proton beamline of the cyclotron at the National Accelerator Centre (CNA, Spain). They were assembled into an in-house low-noise readout electronics to assess their performance at a therapeutic-equivalent fluence rate. Microdosimetry spectra of lineal energy were recorded at several proton energies starting from 18 MeV by adding 50µm thick tungsten foils gradually at the exit-window of the cyclotron external beamline, which corresponds to different depths along the Bragg curve. The experimentalyF¯values in silicon cover from (5.7 ± 0.9) to (8.5 ± 0.4) keV µm-1in the entrance to (27.4 ± 2.3) keV µm-1in the distal edge. Pulse height energy spectra were crosschecked with Monte Carlo simulations and an excellent agreement was obtained. This work demonstrates the capability of the second generation 3D-microdetectors to assess accurate microdosimetric distributions at fluence rates as high as those used in clinical centers in proton therapy.

New frontiers in atom probe tomography: a review of research enabled by cryo and/or vacuum transfer systems.

There has been a recent surge in the use of cryo and/or vacuum specimen preparation and transfer systems to broaden the scope of research enabled by the microscopy technique of atom probe tomography. This is driven by the fact that, as for many microscopes, the application of atom probes to air- and temperature-sensitive materials or wet biological specimens has previously been limited by transfer through air at room temperature. Here we provide an overview of areas of research that benefit from these new transfer and analysis protocols, as well as a review of current advances in transfer devices, environmental cells, and glove boxes for controlled specimen manipulation. This includes the study of catalysis and corrosion, biological samples, liquid-solid interfaces, natural aging, and the distribution of hydrogen in materials.

A method for site-specific and cryogenic specimen fabrication of liquid/solid interfaces for atom probe tomography.

A site-specific, cryogenic, focused ion beam (FIB) method is presented for the preparation of atom probe tomography (APT) specimens from a frozen liquid/solid interface. As a practical example, the interface between water and a corroded boroaluminosilicate glass has been characterized by APT for the first time. The water/glass interface is preserved throughout specimen preparation by plunge freezing the corroding glass particles with the corrosion solution into slush nitrogen. Site-specific specimen preparation is enabled through a new approach to extract and mount a small volume of material using a cryogenically cooled FIB stage and micromanipulator. The prepared APT specimens are subsequently transferred from the FIB to APT under cryogenic and high-vacuum conditions using a novel FIB/APT transfer shuttle and home-built environmental transfer hub attached to the APT system. Particular focus is given to the technical methods for specimen fabrication under cryogenic conditions. Persistent challenges are discussed in addition to future opportunities for this new specimen preparation method.

Na, K, Ca, Mg, and U-series in fossil bone and the proposal of a radial diffusion-adsorption model of uranium uptake.

Fossil bones are often the only materials available for chronological reconstruction of important archeological sites. However, since bone is an open system for uranium, it cannot be dated directly and therefore it is necessary to develop models for the U uptake. Hence, a radial diffusion-adsorption (RDA) model is described. Unlike the classic diffusion-adsorption (D-A) model, RDA uses a cylindrical geometry to describe the U uptake in fossil bones. The model was applied across a transverse section of a tibia of an extinct megamammal Macrauchenia patachonica from the La Paz Local Fauna, Montevideo State, Uruguay. Measurements of spatial distribution of Na, K, Ca, and Mg were also performed by neutron activation analysis (NAA). Gamma-ray spectrometric U-series dating was applied to determine the age of the bone sample. From U concentration profile, it was possible to observe the occurrence of a relatively slow and continuous uranium uptake under constant conditions that had not yet reached equilibrium, since the uranium distribution is a ∪-shaped closed-system. Predictions of the RDA model were obtained for a specific geochemical scenario, indicating that the effective diffusion coefficient D/R in this fossil bone is (2.4 ± 0.6)10(-12) cm(2)s(-1). Mean values of Na, K, Ca, and Mg contents along the radial line of the fossil tibia are consistent with the expected behavior for spatial distributions of these mineral elements across a modern bone section. This result indicates that the fossil tibia may have its mineral structure preserved.

Análisis de asociación de los polimorfismos -725C>G (rs1233334), -201G>A (rs1233333) y 14 bp deleción/inserción (14-pb del/ins) (rs66554220) del gen HLA-G en mujeres mexicanas con pérdida gestacional recurrente / Analysis of association of polymorphisms -725C >G ( rs1233334 ), -201G >A ( rs1233333 ) and 14 bp deletion / insert (14 - bp / ins ) ( rs66554220 ) of HLA -G gene mexican women with recurrent pregnancy loss

Antecedentes: El antígeno leucocitario humano (HLA)-G es una molécula inmunomoduladora que contribuye a la aceptación del feto semialogénico. Algunos polimorfismos de un solo nucleótido (SNP) en las regiones no codificantes del gen HLA-G inducen a la disminución de moléculas HLA-G, lo cual contribuye a complicaciones en el embarazo, tales como la preeclampsia o pérdida gestacional recurrente. Objetivo: Analizar la asociación de los polimorfismos -725C>G (rs1233334), -201G>A (rs1233333) y 14 bp deleción/inserción (14-pb del/ins) (rs66554220) del gen HLA-G en mujeres mexicanas con PGR. Métodos: Los polimorfismos -725C>G (rs1233334), -201G>A (rs1233333) y 14-pb del/ins (rs66554220) se identificaron por medio de PCR-SSOP (Polymerase Chain Reaction-sequence-specific oligonucleotide probe) y PCR (Polymerase Chain Reaction), respectivamente, en 58 mujeres con pérdida gestacional recurrente (> 2 abortos), sin factores de riesgo identificables y 56 mujeres fértiles no relacionadas (> 2 nacidos vivos). Resultados: El polimorfismo -725C>G (rs1233334) presentó diferencias significativas entre los grupos de estudio pero no se asoció con PGR (p=0,02601; OR=11,484; IC95 por ciento =0,617-213,659). Los polimorfismos -201G>A (rs1233333) y 14-pb del/ins (rs66554220) no se distribuyeron de manera diferente entre los grupos de estudio ni se asociaron con pérdida gestacional recurrente. Los polimorfismos analizados se encontraron en equilibrio de ligamiento (D'>0,3563; r²<0,1140). Conclusión. Este estudio sugiere que los polimorfismos -725C>G (rs1233334), -201G>A (rs1233333) y 14-pb del/ins (rs66554220) del gen HLA-G están en equilibrio de ligamiento y no influyen en el riesgo de pérdida gestacional recurrente en mujeres mexicanas.

Background: The human leukocyte antigen (HLA)-G is an important immunomodulatory molecule that contributes to the acceptance of the semi-allogeneic fetus. Some single nucleotide polymorphisms (SNP) in the noncoding regions of the HLA-G gene may influence the cellular levels of HLA-G, contributing to pregnancy complications such as preeclampsia or recurrent pregnancy loss. Objective: To analyze the association of -725C>G (rs1233334),-201G>A (rs1233333) and 14 bp deletion/insertion (14-bp del/ins) (rs66554220) polymorphisms in the HLA-G gene in Mexican women with RPL. Methods: -725C>G (rs1233334), -201G>A (rs1233333) and 14-bp del/ins (rs66554220) polymorphisms in the HLA-G gene were identified by PCR-SSOP (polymerase chain reaction-sequence-specific oligonucleotide probe) and PCR (polymerase chain reaction), respectively, in 58 women with recurrent pregnancy loss (> 2 miscarriages) without identifiable risk factors and 56 unrelated fertile women (> 2 live births). Results: -725C>G (rs1233334) polymorphism showed significant differences between the study groups but it was not associated with recurrent pregnancy loss (p=0.02601, OR=11.484; 95 percent CI=0.617-213.659). -201G>A (rs1233333) and 14-bp del/ins (rs66554220) polymorphisms were not distributed differently in study groups and not associated with RPL. Analyzed polymorphisms were in linkage disequilibrium (D' > 0.3563, r² < 0.1140). Conclusion: This study suggests that -725C>G (rs1233334), -201G>A (rs1233333) and 14-pb del/ins (rs66554220) in the HLA-G gene are in linkage equilibrium and do not influence the risk of recurrent pregnancy loss in Mexican women.

Mejora de la profilaxis antibiótica en cirugía colo-rectal mediante el análisis de las infecciones incisionales: estudio observacional / Improving antibiotic prophylaxis in colorectal surgery through the analysis of incisional infections: observational study

INTRODUCCIÓN. Las infecciones del sitio quirúrgico son muy frecuentes tras cirugía colo-rectal. El objetivo de este estudio es analizar cuantitativa y cualitativamente dichas infecciones en nuestro servicio. MATERIAL Y MÉTODOS. Se realizó un estudio observacional en 23 enfermos sometidos a resecciones colo-rectales programadas a los que se administró la profilaxis antibiótica habitual de nuestro servicio, gentamicina y metronidazol (G+M). Se analizó la presencia de infecciones incisionales superficiales o profundas y los gérmenes causantes. Ante los resultados, y guiados por los cultivos, se decidió cambiar la profilaxis por amoxicilina y ácido clavulánico (AMC), y continuar el estudio en 38 enfermos. RESULTADOS. Los enfermos que recibieron como profilaxis G+M tuvieron un índice de infecciones incisionales del 48%. En el 90% de esas infecciones había Escherichia coli, y en un 80% enterococos o estreptococos. En el grupo de AMC hubo un índice de infecciones incisionales del 19%, siendo la diferencia con el grupo de G+M estadísticamente significativa (p=0,021). En los cultivos de sus heridas no había enterococos ni estreptococos. DISCUSIÓN. El índice de infecciones incisionales del grupo G+M es superior al comunicado en cirugía colo-rectal programada. El predominio de Escherichia coli en estas infecciones es habitual, no así la elevada presencia de cocos positivos, especialmente enterococos. Estos resultados exigen un cambio en nuestra profilaxis antibiótica, para cubrir estreptococos y enterococos, además de bacilos negativos y anaerobios. AMC parece la opción más lógica. Nuestros resultados corroboran esta hipótesis (AU)

BACKGROUND. Surgical site infections are very common after colorectal surgery. The objective of this study is to analyze quantitatively and qualitatively such infections in our service. METHOD. An observational study was performed in 23 patients undergoing elective colorectal resections who received the usual antibiotic prophylaxis of our service, gentamicin and metronidazole (G+M). Superficial and deep incisional infections, as well as microbes that cause them, were analyzed. Given the results, and guided by the cultures, it was decided to change the prophylaxis to amoxicillin and clavulanic acid (AMC), and continue the study in 38 patients. RESULTS. Patients who were given G+M for prophylaxis had incisional infection rate of 48%. Escherichia coli was present in 90% of these infections, enterococci or streptococci were present in 80% of these infections. In the AMC group there was an incisional infection rate of 19%. The observed difference with the G+M group is statistically significant (p = 0.021). Enterococci and streptococci were not isolated in their incisions. CONCLUSION. The rate of incisional infections in the G+M group is higher than the usually reported in elective colorectal surgery. The predominance of Escherichia coli is usual in these infections, but not the high presence of positive cocci, especially enterococci. These results call for a change in our antibiotic prophylaxis to cover streptococci and enterococci, as well as gram-negative bacilli and anaerobes. AMC seems the most logical choice. Our results support this hypothesis (AU)

Terazosin-induced alterations in catalase expression and lipid peroxidation in the rat seminal vesicles.

Previous studies have shown that alpha1-adrenergic receptor antagonists may alter seminal vesicle contractility and impair fertility in male rats. This study was designed to investigate the effects of terazosin on the catalase expression in the seminal vesicles and the lipid peroxidation of the seminal fluid in normal adult rats. Wistar rats were treated with terazosin (1.2 mg kg(-1) body weight, given orally every second day) for 120 days. Catalase expression was assessed immunohistochemically in tissue sections of the seminal vesicles, and lipid peroxidation was estimated by measuring the malondialdehyde (MDA) levels in the seminal vesicles' fluid. The seminal vesicles in terazosin-treated rats were particularly distended in comparison with those of controls, and their secreting epithelium was suppressed. Cytoplasmic catalase expression in the secreting epithelial cells (% of cells) was increased in terazosin-treated specimens in comparison with controls (76.1 ± 17.1 versus 51.3 ± 25.1, P = 0.005). MDA levels (µm) were also higher in samples from treated subjects in comparison with controls (2.67 ± 1.19 versus 1.39 ± 0.19, P = 0.01). Although the direct effect of terazosin treatment on the seminal vesicles is that of impaired contractility, an indirect effect is that on fertility by increasing lipid peroxidation in the seminal fluid and/or through degrading of hydrogen peroxide that is essential for sperm capacitation.

Role of Photoexcitation and Field Ionization in the Measurement of Accurate Oxide Stoichiometry by Laser-Assisted Atom Probe Tomography.

The addition of pulsed lasers to atom probe tomography (APT) extends its high spatial and mass resolution capability to nonconducting materials, such as oxides. For a prototypical metal oxide, MgO, the measured stoichiometry depends strongly on the laser pulse energy and applied voltage. Very low laser energies (0.02 pJ) and high electric fields yield optimal stoichiometric accuracy. Correlated APT and aberration-corrected transmission electron microscopy (TEM) are used to establish the high density of corner and terrace sites on MgO sample surfaces before and after APT. For MgO, long-lifetime photoexcited holes localized at oxygen corner sites can assist in the creation of oxygen neutrals that may spontaneously desorb either as atomic O or as molecular O2. The observed trends are best explained by the relative field-dependent ionization of photodesorbed O or O2 neutrals. These results emphasize the importance of considering electronic excitations in APT analysis of oxide materials.

Highly efficient charge separation and collection across in situ doped axial VLS-grown Si nanowire p-n junctions.

VLS-grown semiconductor nanowires have emerged as a viable prospect for future solar-based energy applications. In this paper, we report highly efficient charge separation and collection across in situ doped Si p-n junction nanowires with a diameter <100 nm grown in a cold wall CVD reactor. Our photoexcitation measurements indicate an internal quantum efficiency of ~50%, whereas scanning photocurrent microscopy measurements reveal effective minority carrier diffusion lengths of ~1.0 µm for electrons and 0.66 µm for holes for as-grown Si nanowires (d(NW) ≈ 65-80 nm), which are an order of magnitude larger than those previously reported for nanowires of similar diameter. Further analysis reveals that the strong suppression of surface recombination is mainly responsible for these relatively long diffusion lengths, with surface recombination velocities (S) calculated to be 2 orders of magnitude lower than found previously for as-grown nanowires, all of which used hot wall reactors. The degree of surface passivation achieved in our as-grown nanowires is comparable to or better than that achieved for nanowires in prior studies at significantly larger diameters. We suggest that the dramatically improved surface recombination velocities may result from the reduced sidewall reactions and deposition in our cold wall CVD reactor.

Acute nateglinide administration in subjects with type 2 diabetes: effects on postprandial metabolism, coagulation, and fibrinolysis.

BACKGROUND AND AIM: Postprandial glycaemia and lipaemia are known risk factors for atherosclerosis in type 2 diabetes. Coagulation activation in the postprandial state also contributes to acceleration of atherosclerosis. Nateglinide is effective in reducing postprandial glycaemia. Its effect on glycaemia may also be beneficial in postprandial lipaemia and coagulation. The aim of this study was to examine the potential effect of a single dose of nateglinide on postprandial triglyceridaemia, coagulation, and fibrinolysis in patients with type 2 diabetes. METHODS AND RESULTS: Ten subjects with type 2 diabetes, treated with diet alone were recruited in a crossover randomized study. In the morning, after a 12- to 14-h fast, each subject received a standard mixed meal (total energy 783 kcal), preceded by one tablet of 120 mg nateglinide or placebo. Venous blood samples were drawn prior to meal consumption and 6h afterwards for the measurement of plasma glucose, insulin, and C-peptide, lipids, coagulation, and fibrinolysis factors. As expected, there was a significant reduction in postprandial glycaemia after nateglinide administration compared to placebo (P<0.001). Plasma insulin levels were significantly higher after nateglinide than after placebo (P=0.002). Nateglinide administration resulted in a lower overall postprandial reduction of tissue-plasminogen activator than placebo (-2.9+/-1.3 vs. -8.3+/-3.7 ng/ml h, P=0.003). In addition, a significant reduction of postprandial plasminogen activator inhibitor-1 was observed in comparison with the baseline values after nateglinide (P=0.001), although the overall response was not significantly different after nateglinide and placebo (P=0.31). Plasma concentrations of C-peptide, lipids and the remaining coagulation parameters studied were not different between nateglinide and placebo. CONCLUSIONS: Acute nateglinide administration improves postprandial glycaemia and fibrinolytic activity in patients with type 2 diabetes. This combined effect, if confirmed by a long-treatment study, might reduce cardiovascular risk in type 2 diabetes.

Extinction coefficients and purity of single-walled carbon nanotubes.

Single-walled carbon nanotubes (SWNTs) hold great promise for advanced applications in aerospace, electronics and medicine, yet these industries require materials with rigorous quality control. There are currently no accepted standards for quality assurance or quality control among the commercial suppliers of SWNTs. We briefly discuss the applicability of various techniques to measure SWNT purity and review, in detail, the advantages of near infrared (NIR) spectroscopy for the quantitative assessment of the bulk carbonaceous purity of SWNTs. We review the use of solution phase NIR spectroscopy for the analysis and characterization of a variety of carbon materials, emphasizing SWNTs produced by the electric arc (EA), laser oven (LO) and HiPco (HC) methods. We consider the applicability of Beer's law to carbon materials dispersed in dimethylformamide (DMF) and the effective extinction coefficients that are obtained from such dispersions. Analysis of the areal absorptivities of the second interband transition of semiconducting EA-produced SWNTs for a number of samples of differing purities has lead to an absolute molar extinction coefficient for the carbonaceous impurities in EA-produced SWNT samples. We conclude that NIR spectroscopy is the clear method of choice for the assessment of the bulk carbonaceous purity of EA-produced SWNTs, and we suggest that an absolute determination of the purity of SWNTs is within reach. Continued work in this area is expected to lead to a universal method for the assessment of the absolute bulk purity of SWNTs from all sources--such a development will be of great importance for nanotube science and for future customers for this product.

Differential effects of high-fat and high-carbohydrate isoenergetic meals on cardiac autonomic nervous system activity in lean and obese women.

Food ingestion can influence autonomic nervous system activity. This study compares the effects of 2 different isoenergetic meals on sympathetic nervous system (SNS) activity, assessed by heart rate variability (HRV) and plasma norepinephrine (NE) levels, in lean and obese women. Fifteen lean and 15 obese healthy women were examined on 2 occasions: after a carbohydrate (CHO)-rich and after a fat-rich test meal. Measurements of blood pressure, heart rate, resting energy expenditure, plasma glucose, lipids, insulin, leptin, and NE, as well as spectral analysis of the HRV, were performed at baseline and every 1 hour for 3 hours after meals. At baseline, obese women had higher SNS activity than lean controls (higher values of low-to-high frequency ratio [LF/HF], 1.52 +/- 0.31 v 0.78 +/- 0.13, P=.04; and plasma NE levels, 405.6 +/- 197.9 v 240.5 +/- 95.8 pg/mL, P<.0001). After the CHO-rich meal a greater increase in LF/HF and in plasma NE levels was observed in lean, compared to obese women (1.21 +/- 0.6 v 0.32 +/- 0.06, P=.04; and 102.9 +/- 35.4 v 38.7 +/- 12.3 pg/mL, P=.01, respectively), while no differences were observed after the fat-rich meal. Meal-induced thermogenesis was higher after the CHO-rich as compared to the fat-rich meal and was comparable between lean and obese women. Changes in HRV were not associated with the thermogenic response to the test meals. In conclusion, consumption of a CHO-rich meal causes greater cardiac SNS activation in lean than in obese women, while fat ingestion does not result in any appreciable change in either group. SNS activation does not appear to influence the thermic effect of the food in either lean or obese women.

Lack of effect of acute repaglinide administration on postprandial lipaemia in patients with type 2 diabetes mellitus.

The effect of acute repaglinide administration (2 mg) on postprandial glycaemia and lipaemia has been examined in 20 subjects with type 2 diabetes mellitus. Each subject received in the morning, after a 12 to 14 h fast, a standard mixed meal (total energy 783 kcal), preceded by one tablet of 2 mg repaglinide or placebo. Chylomicrons and chylomicron-deficient plasma were prepared by ultracentrifugation. Triglyceride levels in CM fraction (CM-triglycerides) in total plasma as well as in CM-deficient plasma (non-CM-triglycerides) were determined. A significant reduction in postprandial glycaemia was observed after repaglinide administration compared to placebo ( p < 0.001). Plasma concentrations of total triglycerides, CM-triglycerides, non-CM-triglycerides, free fatty acids and the other plasma lipids measured, were not significantly different between the two phases of the study. It is concluded that, in contrast to sulphonylureas, acute repaglinide administration does not improve postprandial lipaemia in patients with type 2 diabetes.