Search

The magnetic properties of the low-dimensional trirutile tantalates Co 1 − x Mg x Ta 2 O 6 [ x = 0.0, 0.1, 0.3, 0.5, 0.7, 1.0] are reported in this paper. CoTa 2 O 6 is an antiferromagnet with a transition temperature at T N = 6.6 K, while showing a very broad peak in the magnetic susceptibility at ≈ 12 K owing to the low dimensionality of the magnetic interactions. In our study, where Mg is introduced at the Co position, we see the disappearance of the broad transition for high values of x. For the x = 0.1 composition, three transitions are observed in the magnetization at 28 K, 6 K, and 3.3 K. Our analysis of magnetization data using the anisotropic Heisenberg and the Ising models for spin chains points out that the magnetic interactions in Co 1 − x Mg x Ta 2 O 6 are indeed low dimensional. Field-induced metamagnetic transitions are observed in the case of x = 0 and x = 0.1 compositions of Co 1 − x Mg x Ta 2 O 6 , which are evident in the magnetization isotherms at T = 2 K. Interestingly, we find that with progressive doping up to x = 0.5 and 0.7, we obtain higher magnetization pointing to the possibility of weak-ferromagnetism. This might point toward the formation of single-chain magnets, which opens up a new possibility in low dimensional oxides for spintronics applications. [ABSTRACT FROM AUTHOR]

Fundamento: La depresión en personas ancianas es un problema de salud pública dada su prevalencia y comorbilidad. Los objetivos de este trabajo son determinar el papel de los grupos de socialización como factor protector para depresión; determinar otros factores socioculturales asociados; estimar la prevalencia y determinar la concordancia de las pruebas de cribado para depresión - criterios de la Asociación Americana de Psiquiatría y el test de Hamilton. Método: Estudio descriptivo transversal. Participaron 602 personas ancianas de entre 60 y 94 años (223 varones y 379 mujeres), muestra representativa para la población residente del sur-occidente de Barranquilla, Colombia. Previo consentimiento, se aplicó una encuesta de administración directa. Se estudiaron las variables demográficas, socioeconómicas, limitación física, enfermedades degenerativas, disfunción familiar y dos tests de depresión para determinar la concordancia. Se realizó análisis bivariado entre la depresión y la pertinencia a grupos de socialización al igual que la depresión y otras variables. Se determinó análisis de cribado e índice de Kappa para la concordancia de pruebas. Resultados: La participación en grupos de socialización fue un factor protector de presentar depresión. (OR: 0,5, IC 95%: 0,34-0,73). La prevalencia de depresión fue de 29,9% (IC95%: 21,4%-39,4%), siendo en los varones 32,7%. La concordancia con el test de Kappa fue 0,63. (moderada a buena) La sensibilidad fue del 56,1%, (48,5% a 63,4%); la especificidad de 99,3%, (IC95%: 97,8%-99,8%) y el valor predictivo positivo del 97,1% ( IC95%: 97,2%-99,3%). Conclusiones: Esta investigación determina factores de riesgo para padecer depresión en ancianos potencialmente modificables. La participación en grupos de socialización es un factor protector. La disfunción familiar de tipo moderado y severo, las limitaciones sensoriales como ceguera y sordera, la soledad, ausencia de vivienda y bajos ingresos económicos se comportaron como factores de riesgo de padecer depresión. Los criterios de la Asociación Americana de Psiquiatría son específicos como prueba de cribado en la consulta medica, pero es cuestionable como tamizaje poblacional.

Extracellular and intracellular copper and zinc regulate synaptic activity and plasticity, which may impact brain functionality and human behavior. We have found that a metal coordinating molecule, Neocuproine, transiently increases free intracellular copper and zinc levels (i.e., min) in hippocampal neurons as monitored by Phen Green and FluoZin-3 fluorescence, respectively. The changes in free intracellular zinc induced by Neocuproine were abolished by the presence of a non-permeant copper chelator, Bathocuproine (BC), indicating that copper influx is needed for the action of Neocuproine on intracellular Zn levels. Moreover, Neocuproine decreased the mRNA levels of Synapsin and Dynamin, and did not affect the expression of Bassoon, tubulin or superoxide dismutase (SOD). Western blot analysis showed that protein levels of synapsin and dynamin were also down regulated in the presence of Neocuproine and that these changes were accompanied by a decrease in calcium transients and neuronal activity. Furthermore, Neocuproine decreased the number of active neurons, effect that was blocked by the presence of BC, indicating that copper influx is needed for the action of Neocuproine. We finally show that Neocuproine blocks the epileptiform-like activity induced by bicuculline in hippocampal neurons. Collectively, our data indicates that presynaptic protein configuration and function of primary hippocampal neurons is sensitive to transient changes in transition metal homeostasis. Therefore, small molecules able to coordinate transition metals and penetrate the blood-brain barrier might modify neurotransmission at the Central Nervous System (CNS). This might be useful to establish therapeutic approaches to control the neuronal hyperexcitabiltity observed in brain conditions that are associated to copper dyshomeotasis such as Alzheimer's and Menkes diseases. Our work also opens a new avenue to find novel and effective antiepilepsy drugs based in metal coordinating molecules.

The mechanism by which amyloid-β (Aβ) produces brain dysfunction in patients with Alzheimer's disease is largely unknown. According to previous studies, Aβ might share perforating properties with gramicidin, a well-accepted membrane-disrupting peptide. Therefore, we hypothesize that the key steps leading to synaptotoxicity by Aβ and gramicidin involve peptide aggregation, pore formation, and calcium dysregulation. Here, we show that Aβ and gramicidin form aggregates enriched in β-sheet structures using electron microscopy, and Thioflavin and Congo Red staining techniques. Also, we found that Aβ and gramicidin display fairly similar actions in hippocampal cell membranes, i.e. inducing Ca(2+) entry and synaptoxicity characterized by the loss of synaptic proteins and a decrease in neuronal viability. These effects were not observed in a Ca(2+) free solution, indicating that both Aβ and gramicidin induce neurotoxicity by a Ca(2+)-dependent mechanism. Using combined perforated patch clamp and imaging recordings, we found that only Aβ produced a perforation that progressed from a small (Cl(-)-selective pore) to a larger perforation that allowed the entry of fluorescent molecules. Therefore, based on these results, we propose that the perforation at the plasma membrane by Aβ is a dynamic process that is critical in producing neurotoxicity similar to that found in the brains of AD patients., (Copyright © 2014 Elsevier Inc. All rights reserved.)

With the purpose to determine the duration of serum antibodies against E. histolytica by means of the contraimmunoelectrophoresis technique, 31 patients with the diagnosis of intestinal or liver invasive amebiasis were included in this study. In 92.3% of the 13 patients subjected to transversal study, no specific antibodies were found from 10 to 24 months after the occurrence of amebic disease. In 64.7% of 17 children with liver amebiasis who were studied longitudinally, no serum antibodies were found between 4 to 10 months after the disease. The possible factors involved in the varaibility of the duration of serum antibodies against E. histolytica are discussed.

The study included 22 patients with meningoencephalitis and hypertensive cranial syndrome from cerebral edema. Mannitol was given to 13 cases and dexamethasone to 9. There were three therapeutic failures in the group given mannitol and none in that of dexamethasone (p greater than 0.05). Both drugs showed similar effect in the duration of the hypertensive cranial syndrome (39-44 hrs). Patients treated with mannitol showed hyponatremia after 48 hours. No untoward effects appeared in patients given dexamethasone.

Two cases are reported of severe type of S. aureus cellulitis which led to the production of mycotic aneurysms of the internal carotid artery. This situation has not been previously described in the literature. Analysis is made of the infectious pathogenesis of mycotic aneurysms.

A longitudinal study was carried out in 40 patients with typhoid fever, 21 with infectious hepatitis and 15 with amebic liver abscess in order to determine percentual values of lymphocytes T and B in relation with age and nutritional state as compared to a normal control group. In patients with typhoid fever, a decrease of percentual values of lymphocytes T was observed starting on the second week of evolution with intensification on the third week, predominating in patients less than seven years of age and in malnourished cases (p less than 0.001) and late recovery in the group of patients less than seven years old. In patients with acute infectious hepatitis, there was depression of lymphocytes T that persisted to the eighth week and was independent of age, but more severe in the malnourished (p less than 0.001). In cases with amebic liver abscess, depression of lymphocytes T was observed during the first six weeks of evolution without relation with age or the state of nutrition, but with increased slowliness in recovery in patients under seven years. There were no disturbances in lymphocytes B nor in cutaneous response to dinitrofluorobencene (DNFB) in the three groups of patients.

Long-term intellectual sequelae were studied in 14 children who suffered purulent meningitis during their first two years of life. A proportion of 50.0% showed an I.Q. under 90 points, but no statistical difference was found when compared with a control group made up with siblings of the patients. The main difference between both groups corresponded to a greater percentage of inadequate development in patients who had suffered meningitis. This disturbance is chiefly related with environmental factors that showed the existence of familial and social integration problems in 86% of children having an I.Q. under 90 points, against only 14% of cases showing an I.Q. above 90 points.

Fifty-one newborn infants were divided into five groups and were studied according to gestational age, hyperbilirubinemia and phototherapy. In each group, the speed of intestinal passage and content of water in feces was evaluated in terms of the variables mentioned. It was shown that neither hyperbilirubinemia nor phototherapy affect the content of water in feces, nor the speed of intestinal passage in pre-term infants. The same results were true for hyperbilirubinemia in full term infants in whom it was not possible to demonstrate the effect of phototherapy. Full term infants showed a greater content of water in feces and a higher speed of intestinal passage as compared with pre-term infants. This was possibly the result of different body weight due to a different gestational age.

Concentrations of lactate and pH were determined in the CSF of 20 normal children, 36 with viral meningitis, 16 with purulent meningitis and six with tuberculous meningitis. No differences were found between normal cases and those with viral meningitis. In patients with purulent meningitis concentration of lactate was above 30 mg/100 ml and pH below 7.3. Both determinations allowed differentiation between viral meningitis and purulent meningitis after 48 hr of treatment with antibiotics in 80% of the cases.

The concentration and activity of alpha 1-antitrypsin were studied in 20 children with the diagnosis of neonatal hepatitis. The concentration of alpha 1-AT was found normal or high in all of the patients (3.6 +/- 0.12 mg/ml). No case was found with PiZZ homozygote type alpha 1-AT deficiency. The activity of alpha l-AT was found decreased in 90% of the patients with neonatal hepatitis (control: 0.86 +/- 0.18 mg. trypsin inhibited by ml. of serum; neonatal hepatitis: 0.49 +/- 0.07 mg/ml.). The possibility that this may correspond to a disorder characteristic of neonatal hepatitis is mentioned.

The clinical histories of 97 cases admitted from 1963 to June 1977 with the diagnosis of polyradiculoneuritis were reviewed. A change in the epidemiology related with an increase in frequency of severe forms that reached up to 50.0% during the last 3 years, against 15% for the previous years, was observed. Overall lethality was 4.1%. Permanent sequelae resulted in 18.3% of the patients and the greatest contribution to this came from the group of severe forms, since 53.3% of them was definitely affected.