Using single-species and algal communities to determine long-term adverse effects of silver nanoparticles on freshwater phytoplankton.

The physical and chemical properties of silver nanoparticles (AgNPs) have led to their increasing use in various fields such as medicine, food, and industry. Evidence has proven that AgNPs cause adverse effects in aquatic ecosystems, especially when the release of Ag is prolonged in time. Several studies have shown short-term adverse effects of AgNPs on freshwater phytoplankton, but few studies have analysed the impact of long-term exposures on these populations. Our studies were carried out to assess the effects of AgNPs on growth rate, photosynthesis activity, and reactive oxygen species (ROS) generation on the freshwater green algae Scenedesmus armatus and the cyanobacteria Microcystis aeruginosa, and additionally on microcystin (MC-LR) generation from these cyanobacteria. The tests were conducted both in single-species cultures and in phytoplanktonic communities exposed to 1 ngL-1 AgNPs for 28 days. The results showed that cell growth rate of both single-species cultures decreased significantly at the beginning and progressively reached control-like values at 28 days post-exposure. This effect was similar for the community-cultured cyanobacteria, but not for the green algae, which maintained a sustained decrease in growth rate. While gross photosynthesis (Pg) increased in both strains exposed in single cultures, dark respiration (R) and net photosynthesis (Pn) decreased in S. armatus and M. aeruginosa, respectively. These effects were mitigated when both strains were exposed under community culture conditions. Similarly, the ROS generation shown by both strains exposed in single-species cultures was mitigated when exposure occurred in community cultures. MC-LR production and release were significantly decreased in both single-species and community exposures. These results can supply helpful information to further investigate the potential risks of AgNPs and ultimately help policymakers make better-informed decisions about their utilization for environmental restoration.

Prenatal stress exposure and multimodal assessment of amygdala-medial prefrontal cortex connectivity in infants.

Stressful experiences are linked to neurodevelopment. There is growing interest in the role of stress in the connectivity between the amygdala and medial prefrontal cortex (mPFC), a circuit that subserves automatic emotion regulation. However, the specific timing and mechanisms that underlie the association between stress and amygdala-mPFC connectivity are unclear. Many factors, including variations in fetal exposure to maternal stress, appear to affect early developing brain circuitry. However, few studies have examined the associations of stress and amygdala-mPFC connectivity in early life, when the brain is most plastic and sensitive to environmental influence. In this longitudinal pilot study, we characterized the association between prenatal stress and amygdala-mPFC connectivity in young infants (approximately age 5 weeks). A final sample of 33 women who provided data on preconception and prenatal stress during their pregnancy returned with their offspring for a magnetic resonance imaging scan session, which enabled us to characterize amygdala-mPFC structural and functional connectivity as a function of prenatal stress. Increased prenatal stress was associated with decreased functional connectivity and increased structural connectivity between the amygdala and mPFC. These results provide insight into the influence of prenatal maternal stress on the early development of this critical regulatory circuitry.

Superparamagnetic state in La0.7Sr0.3MnO3 thin films obtained by rf-sputtering.

A novel superparamagnetic state has been observed in high quality La0.7Sr0.3MnO3 (LSMO) thin films directly grown by rf-sputtering on SiOx/Si(100) substrates. The films are nanostructured without grain boundaries, constituted by locally epitaxial nanoregions grown layer-by-layer with out-of-plane (012) preferential orientation, induced by the constrain of the native silicon oxide. Low magnetic field ZFC-FC magnetization curves show a cross-over from superparamagnetic to ferromagnetic state dependent of the thickness. The thicker film (140 nm) exhibits typical ferromagnetic order. The thinner films (40 and 60 nm) exhibit superparamagnetic behavior attributed to interacting ferromagnetic monodomain nanoregions with critical size, random in-plane oriented, where the inter-monodomain boundaries with surface spin-glass structure regulate the blocking of magnetization depending on the magnetic field intensity. M(H) hysteresis loops showed noticeable coercive fields in all samples, larger than those reported for LSMO. Such properties of half-metal LSMO film foresee potential integration in new Si-technology nanodevices in Spintronics.

Accelerated DNA methylation age in adolescent girls: associations with elevated diurnal cortisol and reduced hippocampal volume.

Numerous studies have linked exposure to stress to adverse health outcomes through the effects of cortisol, a product of the stress response system, on cellular aging processes. Accelerated DNA methylation age is a promising epigenetic marker associated with stress and disease risk that may constitute a link from stress response to changes in neural structures. Specifically, elevated glucocorticoid signaling likely contributes to accelerating DNA methylation age, which may signify a maladaptive stress-related cascade that leads to hippocampal atrophy. We examined the relations among diurnal cortisol levels, DNA methylation age and hippocampal volume in a longitudinal study of 46 adolescent girls. We computed area under the curve from two daily cortisol collection periods, and calculated DNA methylation age using previously established methods based on a set of CpG sites associated with chronological age. We computed a residual score by partialling out chronological age; higher discrepancies reflect relatively accelerated DNA methylation age. We assessed hippocampal volume via T1-weighted images and automated volumetric segmentation. We found that greater diurnal cortisol production was associated with accelerated DNA methylation age, which in turn was associated with reduced left hippocampal volume. Finally, accelerated DNA methylation age significantly mediated the association between diurnal cortisol and left hippocampal volume. Thus, accelerated DNA methylation age may be an epigenetic marker linking hypothalamic-pituitary-adrenal axis dysregulation with neural structure. If these findings are replicated, the current study provides a method for advancing our understanding of mechanisms by which glucocorticoid signaling is associated with cellular aging and brain development.

[Prevalence of positive markers for hepatitis B (HBV Ags) and hepatitis C (Anti-HCV) in health personnel at the Social Security Institute of Mexico State and Municipalities]. / Prevalencia de marcadores positivos para hepatitis B (Ags-VHB) y hepatitis C (Anti-VHC) en personal de salud del ISSEMYM.

BACKGROUND: The prevalence of serum markers of viral hepatitis in health-care workers seems to be similar to that described in the general population, even though this group would appear at increased risk because exposure to potentially infectious material. There is scarce information available in Mexico in this regard. AIM: To define the prevalence of serum markers for hepatitis C (anti-HCV antibodies) and hepatitis B (hepatitis B surface antigen, HBsAg) in health-care workers at the Instituto de Seguridad Social del Estado de Mexico y Municipios (ISSEMYM) and to establish the presence of viremia in subjects with positive serum markers. METHOD: Health-care workers from ISSEMyM with unknown hepatitis serologic status participated voluntarily in this trial. They completed a written questionnaire detailing potential risk factors for viral hepatitis and provided a blood sample. RESULTS: A total of 374 health-care workers were included. Seven subjects (1.8%) were positive, 5 for anti-HCV antibodies (1.3%) and 2 for HBsAg (0.5%). None of these subjects had detectable serum HCV RNA or HBV DNA on further testing. CONCLUSIONS: The frequency of positive serum markers for viral hepatitis in this group of healthcare workers is similar to the estimated prevalence among the general population in Mexico. No case of active infection defined by positive viremia was encountered in this group of subjects.

[Dorsal osseous hemangiopericytoma: a primary or metastatic tumour?]. / Hemangiopericitoma óseo dorsal: tumor primario o metastásico?

INTRODUCTION: Hemangiopericytomas are potentially malignant vascular tumours. They are usually located in the thighs, the buttocks and the retroperitoneum. Recurrence is very common and they produce metastases that are not usually intracranial within a period of not less than 24 months. Treatment involves surgery, accompanied by radiotherapy. CASE REPORT: A 32-year-old female who had been suffering from back pain for two months. The clinical examination was normal; however, the neuroimaging studies showed a lumbar tumour that involved the L1, and the patient was therefore submitted to a surgical intervention. The histopathological analysis showed the tumour to be a hemangiopericytoma. The patient received radiotherapy, and two months later presented recurrent vomiting and headaches. Computerised tomography and magnetic resonance imaging of the head enabled us to diagnose an intracranial tumour and she underwent a new operation. A new histopathological analysis of the lesion confirmed that it was a meningeal hemangiopericytoma. CONCLUSIONS: After reviewing the literature, this is the first case of a hemangiopericytoma in which the initial symptoms were caused by metastasis and not by the primary tumour.

Hemangiopericitoma óseo dorsal: ¿tumor primario o metastásico? / Dorsal osseous hemangiopericytoma: A primari of metastatic tumour?

Introducción. Los hemangiopericitomas son tumores vasculares potencialmente malignos. Se localizan preferentemente en los muslos, los glúteos y el retroperitoneo. Recidivan con mucha frecuencia y producen metástasis que no suelen ser intracraneales en un período no menor a los 24 meses. El tratamiento es quirúrgico y acompañado de radioterapia. Caso clínico. Mujer de 32 años de edad que refería dolor dorsolumbar de dos meses de evolución. Su exploración clínica fue normal; sin embargo, los estudios neurorradiológicos le detectaron un tumor lumbar que afectaba a L1, por el que fue sometida a intervención quirúrgica. La histología demostró que se trataba de un hemangiopericitoma. La paciente recibió radioterapia, y presentó dos meses después cefalea y vómitos de repetición. Mediante tomografía computarizada y resonancia magnética de cráneo se le diagnosticó un tumor intracraneal del que fue operada. El estudio histológico de la lesión confirmó que se trataba de un hemangiopericitoma meníngeo. Conclusión. Una vez revisada la bibliografía, éste es el primer caso de un hemangiopericitoma en que los síntomas iniciales han sido ocasionados por la metástasis y no por el tumor primario (AU)

Introduction. Hemangiopericytomas are potentially malignant vascular tumours. They are usually located in the thighs, the buttocks and the retroperitoneum. Recurrence is very common and they produce metastases that are not usually intracranial within a period of not less than 24 months. Treatment involves surgery, accompanied by radiotherapy. Case report. A 32-year-old female who had been suffering from back pain for two months. The clinical examination was normal; however, the neuroimaging studies showed a lumbar tumour that involved the L1, and the patient was therefore submitted to a surgical intervention. The histopathological analysis showed the tumour to be a hemangiopericytoma. The patient received radiotherapy, and two months later presented recurrent vomiting and headaches. Computerised tomography and magnetic resonance imaging of the head enabled us to diagnose an intracranial tumour and she underwent a new operation. A new histopathological analysis of the lesion confirmed that it was a meningeal hemangiopericytoma. Conclusions. After reviewing the literature, this is the first case of a hemangiopericytoma in which the initial symptoms were caused by metastasis and not by the primary tumour (AU)