Julio Landero

Lead, mercury, and cadmium exposure and attention deficit hyperactivity disorder in children

BACKGROUND There is limited research examining the relationship between lead (Pb) exposure and medically diagnosed attention deficit hyperactivity disorder (ADHD) in children. The role of mercury (Hg) and cadmium (Cd) exposures in ADHD development is even less clear. OBJECTIVES To examine the relationship between Pb, Hg, and Cd and ADHD in children living inside and outside a Lead Investigation Area (LIA) of a former lead refinery in Omaha, NE. METHODS We carried out a case-control study with 71 currently medically diagnosed ADHD cases and 58 controls from a psychiatric clinic and a pediatric clinic inside and outside of the LIA. The participants were matched on age group (5-8, 9-12 years), sex, race (African American or Caucasians and others), and location (inside or outside LIA). We measured whole blood Pb, total Hg, and Cd using inductively coupled plasma mass spectrometry. RESULTS Inside the LIA, the 27 cases had blood Pb geometric mean (GM) 1.89 µg/dL and the 41 controls had 1.51 µg/dL. Outside the LIA, the 44 cases had blood Pb GM 1.02 µg/dL while the 17 controls had 0.97 µg/dL. After adjustment for matching variables and maternal smoking, socioeconomic status, and environmental tobacco exposure, each natural log unit blood Pb had an odds ratio of 2.52 with 95% confidence interval of 1.07-5.92. Stratification by the LIA indicated similar point estimate but wider CIs. No associations were observed for Hg or Cd. CONCLUSIONS Postnatal Pb exposure may be associated with higher risk of clinical ADHD, but not the postnatal exposure to Hg or Cd.

Development and application of a selenium speciation method in cattle feed and beef samples using HPLC-ICP-MS: evaluating the selenium metabolic process in cattle

Selenium (Se) is an essential element for mammals with diet being the major source of intake. For this work cattle feed was enriched with combinations of selenium enriched yeast, canola oil, and/or vitamin E in order to evaluate the accumulation and metabolism of selenium in beef cattle. A method to identify and/or quantify the selenium species: selenocystine (SeCys2), selenomethionine (SeMet), selenomethionine-Se-oxide (SeOMet), and inorganic selenium species, selenate (Se(VI)) and selenite (Se(IV)), was developed and applied to cattle feed and beef samples.

Development of Chitosan and Polylactic Acid Based Methotrexate Intravitreal Micro-Implants to Treat Primary Intraocular Lymphoma: An In Vitro Study

Primary intraocular lymphoma (PIOL) is an uncommon but clinically and pathologically distinct form of non-Hodgkins lymphoma. It provides a therapeutic challenge because of its diverse clinical presentations and variable clinical course. Currently available treatments for PIOL include intravenous multiple drug chemotherapy, external beam radiation therapy, and intravitreal methotrexate (MTX) injection. Each intravitreal injection of MTX is associated with potentially toxic peaks and subtherapeutic troughs of intraocular MTX concentration. Repetitive injections are required to maintain therapeutic levels of MTX in the eye. A sustained release drug delivery system is desired for optimized therapeutic release (0.2-2.0 μg/day) of MTX for over a period of 1 month to achieve effective treatment of PIOL. This study reports development of a unique intravitreal micro-implant, which administers therapeutic release of MTX over a period of 1 month. Chitosan (CS) and polylactic acid (PLA) based micro-implants are fabricated for different MTX loadings (10%, 25%, and 40% w/w). First, CS and MTX mixtures are prepared for different drug loadings, and lyophilized in Tygon® tubing to obtain CS-MTX fibers. The fibers are then cut into desired micro-implant lengths and dip coated in PLA for a hydrophobic surface coating. The micro-implant is characterized using optical microscopy, scanning electron microscopy (SEM), time of flight-secondary ion mass spectroscopy (ToF-SIMS), and differential scanning calorimetry (DSC) techniques. The release rate studies are carried out using a UV-visible spectrophotometer. The total release durations for 10%, 25%, and 40% w/w uncoated CS-MTX micro-implants are only 19, 29, and 32 h, respectively. However, the therapeutic release durations for 10%, 25%, and 40% w/w PLA coated CS-MTX micro-implants significantly improved to 58, 74, and 66 days, respectively. Thus, the PLA coated CS-MTX micro-implants are able to administer therapeutic release of MTX for more than 50 days. The release kinetics of MTX from the coated micro-implants is explained by (a) the Korsmeyer-Peppas and zero order model fit (R2 ∼ 0.9) of the first 60% of the drug release, which indicates the swelling of polymer and initial burst release of the drug; and (b) the first order and Higuchi model fit (R2 ∼ 0.9) from the tenth day to the end of drug release, implying MTX release in the therapeutic window depends on its concentration and follows diffusion kinetics. The PLA coated CS-MTX micro-implants are able to administer therapeutic release of MTX for a period of more than 1 month. The proposed methodology could be used for improved treatment of PIOL.

Coupling transmission electron microscopy with synchrotron radiation X-ray fluorescence microscopy to image vascular copper

Recently, using synchrotron radiation X-ray fluorescence microscopy (SRXRF), the copper accumulation in rat aortic elastin and copper topography in human THP-1 cell monolayer have been described. However, it is necessary to locate more accurately cellular copper in the vascular cells and tissues. In the current study, SRXRF coupling with transmission electron microscopy (TEM) was used to image copper in sections of human THP-1 cells and mouse aorta. The results showed that sections of 1 µm thickness are required for SRXRF producing a correlative image with TEM between copper topography and cellular ultrastructure. As compared with SRXRF alone, coupling TEM with SRXRF can clearly identify the location of copper in the nucleus and nucleolus in non-dividing THP-1 cell sections, and can differentiate the copper location at elastic laminae from collagen in mouse aortic sections. Thus, these results revealed new information about the copper topography in vascular cells and tissues and highlighted the potential of TEM-SRXRF to investigate the role of copper in macrophage and aortic homeostasis.

Multiple liquid chromatography separations and nanoESI-ion trap detection of plasma proteins in search of stroke biomarkers: A pilot study

Stroke is the most common cause of morbidity and death in the Western world, following ischemic heart disease and cancer. Stroke can be of two types, ischemic or hemorrhagic, with ischemic stroke accounting for approximately 85% of the total number of strokes. Well-recognized environmental risk factors for stroke include hypertension, smoking, diabetes mellitus, atrial fibrillation, and atherosclerosis. Computed tomography (CT) scanning is used to diagnose hemorrhagic stroke but is relatively ineffective and may remain normal in patients with mild ischemic strokes. Magnetic Resonance Imaging (MRI) is more sensitive in detecting ischemia than CT, especially in the diagnosis of mild stroke but it is still not 100% sensitive or precise. A simple and low-cost, rapid blood test to confirm a clinical and imaging diagnosis of ischemic stroke would be extremely useful. Based on this, the central idea of this paper is to develop a method that would be applicable to a statistically viable sample set to provide candidate biomarkers for distinguishing stroke types. In search of these candidate biomarkers, different analytical separation techniques have been used to screen for major differences in the proteomes of patients plasma samples with proteomics for identification.

A Transgenic Drosophila Model for Arsenic Methylation Suggests a Metabolic Rationale for Differential Dose-Dependent Toxicity Endpoints

The mechanisms by which exposure to arsenic induces its myriad pathological effects are undoubtedly complex, while individual susceptibility to their type and severity is likely to be strongly influenced by genetic factors. Human metabolism of arsenic into methylated derivatives, once presumed to result in detoxification, may actually produce species with significantly greater pathological potential. We introduce a transgenic Drosophila model of arsenic methylation, allowing its consequences to be studied in a higher eukaryote exhibiting conservation of many genes and pathways with those of human cells while providing an important opportunity to uncover mechanistic details via the sophisticated genetic analysis for which the system is particularly well suited. The gene for the human enzyme, arsenic (+3 oxidation state) methyltransferase, was introduced into nonmethylating Drosophila under inducible control. Transgenic flies were characterized for enzyme inducibility, production of methylated arsenic species, and the dose-dependent consequences for chromosomal integrity and organismal longevity. Upon enzyme induction, transgenic flies processed arsenite into mono and dimethylated derivatives identical to those found in human urine. When induced flies were exposed to 9 ppm arsenite, chromosomal stability was clearly reduced, whereas at much higher doses, adult life span was significantly increased, a seemingly paradoxical pair of outcomes. Measurement of arsenic body burden in the presence or absence of methylation suggested that enhanced clearance of methylated species might explain this greater longevity under acutely toxic conditions. Our study clearly demonstrates both the hazards and the benefits of arsenic methylation in vivo and suggests a resolution based on evolutionary grounds.

Arsenic speciation in seafood by LC-ICP-MS/MS: method development and influence of culinary treatment

Arsenic speciation in seafood after several culinary treatments was performed and AsB, As(III), DMA, MMA and As(V) species were determined by liquid chromatography hyphenated to triple-quadrupole inductively coupled plasma mass spectrometry (LC-ICP-MS/MS) using O2 as the reaction gas for the conversion of 75As to 75As16O. The influence of culinary treatments (boiling, frying and sauteing) with or without the addition of spices (salt, lemon juice and garlic) on the As species in blacktip shark and Asian tiger shrimp was investigated. Arsenic species were extracted by using a 30 mmol L−1 HNO3 solution. Ammonium phosphate (10 mmol L−1) was used as the mobile phase. The influence of pH and the addition of 1% (v/v) methanol were investigated. Oil, water, butter and the spices used during cooking were analysed to perform a close mass balance of the total As. The speciation method was also employed for a certified reference material (CRM, DORM-3), and the accuracy was evaluated by statistical comparison between the certified value and the total As concentration determined by ICP-MS after acid digestion and also by a comparison of the sum of As species with the total As. It was demonstrated that the culinary treatments practically did not influence the stability of As species in uncooked seafood. On the other hand, significant analyte losses (from 15 up to 45%) were observed for boiled seafood. The speciation analysis method presented accuracy and robustness for both raw seafood and seafood after the culinary treatments. The limits of quantification were 4, 21, 4, 9 and 18 ng g−1 for AsB, As(III), DMA, MMA and As(V), respectively. This study allowed the determination of As species in seafood after culinary treatments, thus offering additional information about the behaviour of species during cooking.

A feasible method for As speciation in several types of seafood by LC-ICP-MS/MS

A method for arsenic speciation in shark, shrimp, squid, oyster and scallop using liquid chromatography coupled to inductively coupled plasma triple quadrupole mass spectrometry (LC-ICP-MS/MS) was proposed. Suitable sensitivity and selectivity by LC-ICP-MS/MS were obtained using 10 mmol L-1 (NH4)2HPO4 diluted in 1% methanol (pH 8.65) as mobile phase. Recoveries from 90 to 104% for arsenobetaine (AsB), arsenite [As(III)], dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate [As(V)] were obtained for all samples. A certificated reference material was also analyzed and the sum of As species was in agreement with the total As concentration. Limits of quantification (LOQ) for AsB, As(III), DMA, MMA, and As(V) were 6, 30, 6, 12 and 26 ng g-1, respectively. Higher concentration of AsB was found in all seafood, while As(III) and DMA were found only in oyster. Arsenate was found in squid and scallops, and MMA was below the LOQ in all samples.

Investigation of the Elemental Profile of Petroleum Jelly-Based Personal Care Products by ICP-MS

ABSTRACT Hair-relaxing kits are used by many women, a high percentage of whom are African American, to transform curly hair to straight hair. Almost all varieties consist of extremely caustic solutions that demonstrate pH values in the range of 10–14. Because of the harshness of this alkaline reagent, petroleum jelly (petrolatum) is often times incorporated into the composition to protect the scalp. Petrolatum, a highly organic byproduct of crude oil, is widely used in cosmetics and topical pharmaceuticals as well. This article reports the elemental composition of various brands of hair-relaxing creams. Several sample preparation techniques were investigated for the digestion of this very organic, viscous matrix. Inductively coupled plasma-mass spectrometry was used for its multi-element capability and high sensitivity. Internal standard calibration was used in the quantitation of a select group of metals, transition metals, and metalloids (Ti, V, Cr, Co, Ni, Ga, Ge, As, Se, Rb, Sr, Zr, Nb, Mo, Ag, Cd, Cs, Ba, W, Re, Tl, Pb, U) and the established method was applied to various brands of hair-relaxing kits. Major elemental constituents were Ti, Sr, and Ba, and these were found at low µg g−1 in all brands considered.

INFLUENCE OF HYDROPHOBIC SURFACE MODIFICATION OF CHITOSAN BASED METHOTREXATE (MTX) MICRO IMPLANTS TO TREAT INTRAOCULAR LYMPHOMA

Primary intraocular lymphoma (PIOL) is a rare form of lymphoma which is encountered in ocular oncology practice. Most preferred treatment has been intravitreal MTX injections which do not have a long lasting chemotherapeutic effect due to rapid elimination of the drug. In this study, chitosan (CS) and polylactic acid (PLA) based intraocular implants are fabricated for different MTX loadings (10%, 25% and 40% w/w). The implants administer a therapeutic dosage of 0.2–2.0 μg/day of MTX over a period of a month. PLA coated CS-MTX implants can be used for sustained release of MTX, thereby improving the treatment of PIOL.Copyright