Biological response and developmental toxicity of zebrafish embryo and larvae exposed to multi-walled carbon nanotubes with different dimension.

The development and use of nanomaterials are increasing significantly. Among nanomaterials, carbon nanotubes are of particular interest due to its distinctive physicochemical properties. This material composed of sheets of graphite has very high thermal conductivity, metallic-type electrical conductivity, stiffness, toughness and unique ability to bond to itself in an extended network with extraordinary strength. Its application in the industry is continuously growing, which could lead to the accumulation in the environment and a consequent impact on both humans and ecosystems. Considering that environmental systems are dynamic, it is difficult to predict the risks associated with the release of nanomaterials to the environment. Bioindicators are useful tools as primary signals of environmental risk, and their responses reveal the organism and ecosystem health. In the present study, we evaluated the impact of multi-walled carbon nanotubes with different dimensions and agglomeration pattern on zebrafish embryo and larvae; mainly, studies were focused on physiological and behavioral responses. In embryos, measurements were hatching rate, morphology changes, and viability. In larvae, locomotor activity, heart rate, innate inflammatory response, general and tissue-specific morphology were measured. MWCNT-S (short, wide and mostly dispersed) caused depression of the locomotor activity of larvae, indicating an alteration of the central nervous system, and depression of neutrophil migration activity. MWCNT-L (long, thin and agglomerated) caused malformations during larval development, a decrease of neutrophil migration and alteration of cardiac rhythm. Results obtained for both carbon nanotubes were different, highlighting the importance of dimensions of the same nanomaterial, and also the kind of agglomeration and shape adopted, for the toxic effects on organisms.

In vivo study of teratogenic and anticonvulsant effects of antiepileptics drugs in zebrafish embryo and larvae.

Epilepsy is a neurological disorder treated with antiepileptic drugs (AEDs). Since AEDs are administered in women in childbearing age, it is critical to study if drugs are capable of inducing developmental toxicity. Along the bibliography available, there is no research comparing teratogenicity and anticonvulsant effect within the same study. In the present study, we evaluated the teratogenic and anticonvulsant effects of six different AEDs: carbamazepine, levetiracetam, lamotrigine, phenobarbital, phenytoin and valproic acid. Zebrafish was the selected animal model because of its small size, rapid external development and similar neurophysiology to mammals. Zebrafish embryo and larvae were exposed to AEDs. Embryo development was monitored by their hatching and morphology. In larvae, locomotor activity was measured as a parameter of neurotoxicity. Finally, anticonvulsant effect was determined after exposure to AEDs in zebrafish larvae treated with the proconvulsant drug pentylenetetrazole. Our results suggest that lamotrigine and phenytoin could be suitable non-teratogenic and efficient anticonvulsant options for epilepsy treatment.

Relation between biophysical properties of nanostructures and their toxicity on zebrafish.

In recent years, the use of commercial nanoparticles in different industry and health fields has increased exponentially. However, the uncontrolled application of nanoparticles might present a potential risk to the environment and health. Toxicity of these nanoparticles is usually evaluated by a fast screening assay in zebrafish (Danio rerio). The use of this vertebrate animal model has grown due to its small size, great adaptability, high fertilization rate and fast external development of transparent embryos. In this review, we describe the toxicity of different micro- and nanoparticles (carbon nanotubes, dendrimers, emulsions, liposomes, metal nanoparticles, and solid lipid nanoparticles) associated to their biophysical properties using this model. The main biophysical properties studied are size, charge and surface potential due to their impact on the environment and health effects. The review also discusses the correlation of the effects of the different nanoparticles on zebrafish. Special focus is made on morphological abnormalities, altered development and abnormal behavior. The last part of the review debates changes that should be made in future directions in order to improve the use of the zebrafish model to assess nanotoxicity.

Symptomatic BK Virus Infection Is Associated With Kidney Function Decline and Poor Overall Survival in Allogeneic Hematopoietic Stem Cell Recipients.

Nephropathy due to BK virus (BKV) infection is an evolving challenge in patients undergoing hematopoietic stem cell transplantation (HSCT). We hypothesized that BKV infection was a marker of kidney function decline and a poor prognostic factor in HSCT recipients who experience this complication. In this retrospective study, we analyzed all patients who underwent their first allogeneic HSCT at our institution between 2004 and 2012. We evaluated the incidence of persistent kidney function decline, which was defined as a confirmed reduction in estimated glomerular filtration rate of at least 25% from baseline using the Chronic Kidney Disease Epidemiology equation. Cox proportional hazard regression was used to model the cause-specific hazard of kidney function decline, and the Fine-Gray method was used to account for the competing risks of death. Among 2477 recipients of a first allogeneic HSCT, BK viruria was detected in 25% (n = 629) and kidney function decline in 944 (38.1%). On multivariate analysis, after adjusting for age, sex, acute graft-versus-host disease (GVHD), chronic GVHD, preparative conditioning regimen, and graft source, BK viruria remained a significant risk factor for kidney function decline (p < 0.001). In addition, patients with BKV infection and kidney function decline experienced worse overall survival. After allogeneic HSCT, BKV infection was strongly and independently associated with subsequent kidney function decline and worse patient survival after HSCT.

Prolonged exposure to GH impairs insulin signaling in the heart.

Acromegaly is associated with cardiac hypertrophy, which is believed to be a direct consequence of chronically elevated GH and IGF1. Given that insulin is important for cardiac growth and function, and considering that GH excess induces hyperinsulinemia, insulin resistance, and cardiac alterations, it is of interest to study insulin sensitivity in this tissue under chronic conditions of elevated GH. Transgenic mice overexpressing GH present cardiomegaly and perivascular and interstitial fibrosis in the heart. Mice received an insulin injection, the heart was removed after 2  min, and immunoblotting assays of tissue extracts were performed to evaluate the activation and abundance of insulin-signaling mediators. Insulin-induced tyrosine phosphorylation of the insulin receptor (IR) was conserved in transgenic mice, but the phosphorylation of IR substrate 1 (IRS1), its association with the regulatory subunit of the phosphatidylinositol 3-kinase (PI3K), and the phosphorylation of AKT were decreased. In addition, total content of the glucose transporter GLUT4 was reduced in transgenic mice. Insulin failed to induce the phosphorylation of the mammalian target of rapamycin (mTOR). However, transgenic mice displayed increased basal activation of the IR/IRS1/PI3K/AKT/mTOR and p38 signaling pathways along with higher serine phosphorylation of IRS1, which is recognized as an inhibitory modification. We conclude that GH-overexpressing mice exhibit basal activation of insulin signaling but decreased sensitivity to acute insulin stimulation at several signaling steps downstream of the IR in the heart. These alterations may be associated with the cardiac pathology observed in these animals.

Partial intercalation with DNA of peptides containing two aromatic amino acids.

The interactions with DNA of tetrapeptide amides containing lysine at the N-terminal position and aromatic amino acids at the second and fourth positions (Ala at position three), 1-6, have been investigated by nmr, CD, and viscometric methods. Tetrapeptides with N-terminal lysine and a single aromatic amino acid, 7-10, were investigated as controls. Significant decreases in DNA viscosity occurred on addition of 7, with the aromatic group at the second position, but not with any of the other single aromatic amino acid peptides. All of the tetrapeptides with two aromatic groups caused DNA viscosity decreases which were two to three times larger than with 7. Peptides with p-nitrophenylalanine (p-NO2Phe) as the aromatic group were synthesized for nmr studies because of its simpler aromatic nmr spectrum relative to Phe. Large upfield shifts of the aromatic proton signals were obtained when the amino acid in the second position was L-p-NO2Phe, and the fourth position contained either p-NO2Phe or Phe. Such peptides also caused the largest DNA viscosity decreases on complex formation. Smaller upfield shifts of the aromatic signals were obtained when the amino acid in the second position was L-Phe or a D isomer of Phe or p-NO2Phe. With all peptides, larger upfield nmr shifts were obtained with heat-denatured, recooled DNA than with native DNA under the same conditions. As with nmr, CD results are quite different for the peptides with L and D amino acids at the second position. All of the results can be interpreted in terms of a model in which lysine interacts stereospecifically with the backbone in a DNA double helix and the aromatic group at the second position stacks strongly with the base pairs when the amino acid is an L isomer. The aromatic group at the fourth position can also interact with the base pairs, but primarily through a sideways stacking of the aromatic group with base pairs for either L or D isomers. Because of covalent constraints on the separation distance for the two aromatic groups in the tetrapeptides, they must stack on opposite sides of the same base pair in violation of the neighbor exclusion principle observed with classical intercalators. This stacking at the same base pair no doubt accounts for the larger viscosity decreases in DNA with the peptides containing two aromatic groups relative to those with a single aromatic group.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical synthesis of an artificial antigen containing the trisaccharide hapten of Mycobacterium leprae.

The trisaccharide allyl O-(3,4-di-O-methyl-beta-D-glucopyranosyl)-(1----4)-O-(2,3-di-O-methyl-al pha-L- rhamnopyranosyl)-(1----2)-3-O-methyl-alpha-L-rhamnopyranoside was synthesized from partially methylated monosaccharide derivatives. Condensation of 1,4-di-O-acetyl-2,3-di-O-methyl-alpha-L-rhamnopyranose promoted by boron trifluoride etherate with the appropriate alcohol proceeded stereoselectively and with very high yields. Selective deacetylation and glycosylation with 2,4-di-O-acetyl-3,6-di-O-methyl-alpha-D-glucopyranosyl bromide led to a trisaccharide. The acrylamide copolymers of mono-, di-, and tri-saccharide were compared in their ability to specifically bind antibodies from leprosy patients.