Trace metals and metalloids in Andean flamingos (Phoenicoparrus andinus) and Puna flamingos (P. jamesi) at two wetlands with different risk of exposure in the Bolivian Altiplano.

Birds are widely used as bioindicators in monitoring programs in wetlands. We compare concentrations of seven trace metals and metalloids (TMM) As, Cd, Cu, Fe, Hg, Pb, Znin both feathers and blood in two flamingo species in two high-altitude wetlands in Bolivia, with different levels of anthropogenic point source pollution. Lake Uru Uru (LUU) receives discharges from mining operations, and also effluents from the nearby city of Oruro, while Laguna Colorada (LCo) does not receive contaminants from anthropogenic sources. We sampled water and sediments at each site, as well as flamingos in three age classes in an effort to establish a benchmark for long-term monitoring. Metal concentrations in water did not differ between sites, whereas Zn and Pb concentrations of TMM in sediments were higher at LUU, and Hg higher at LCo. TMM concentrations were highly specific for all separate elements, but results point to differences between Andean flamingo (Phoenicoparrus andinus) chicks and the rest of the classes considered. As flamingo chicks did not molt before sampling, we pose that TMM concentrations in their blood and feathers may respond mainly to local conditions. Eggshells provide additional information, since adults transfer some TMM during egg development. Long-term monitoring in these species should include different age classes and sample both feathers and eggshells to monitor the environmental conditions and bioaccumulation of TMM in these species. Future studies should include sites devoid of natural sources of TMM to help distinguish sources of contamination, since some TMM (As and Pb) may be naturally in high concentrations in remote areas, like Laguna Colorada.

Epileptic seizures can be anticipated by non-linear analysis.

Epileptic seizures are a principal brain dysfunction with important public health implications, as they affect 0.8% of humans. Many of these patients (20%) are resistant to treatment with drugs. The ability to anticipate the onset of seizures in such cases would permit clinical interventions. The view of chronic focal epilepsy now is that abnormally discharging neurons act as pacemakers to recruit and entrain other normal neurons by loss of inhibition and synchronization into a critical mass. Thus, preictal changes should be detectable during the stages of recruitment. Traditional signal analyses, such as the count of focal spike density, the frequency coherence or spectral analyses are not reliable predictors. Non-linear indicators may undergo consistent changes around seizure onset. Our objective was to follow the transition into seizure by reconstructing intracranial recordings in implanted patients as trajectories in a phase space and then introduce non-linear indicators to characterize them. These indicators take into account the extended spatio-temporal nature of the epileptic recruitment processes and the corresponding physiological events governed by short-term causalities in the time series. We demonstrate that in most cases (17 of 19), seizure onset could be anticipated well in advance (between 2-6 minutes beforehand), and that all subjects seemed to share a similar 'route' towards seizure.

[Measuring Kt by ionic dialysance is a useful tool for assessing dialysis dose in critical patients]. / La determinación del Kt por dialisancia iónica es una herramienta útil para la evaluación de la dosis de diálisis en pacientes críticos.

AIM: To evaluate the Kt assessed through ionic dializance (KtOCM) in UCI patients undergoing renal replacement therapy for acute kidney injury, comparing the results with those obtained through the urea removal rate method determined by dialyzate collection (Kturea). MATERIAL AND METHODS: 18 adult UCI staying individuals suffering from renal replacement therapy requiring oliguric acute kidney injury were included in this study. RRT consisted in intermittent or extended hemodialysis performed through a Fresenius 4008E dialysis machine equipped with an on-line clearance monitor (OCM Fresenius). The KtOCM results were provided automatically. The Spearman correlation test was used to assess the relationship between the two exploratory methods and the Student s t test to compare the results obtained by the KtOCM and the Kturea. RESULTS: 35 treatments were analyzed. There were not statistically significant differences between the results form the KtOCM and the Kturea (34.9 +/- 10.69 vs 32.78 +/- 11.31, p = NS). A remarkable association was find between both methods (r = 0.87; 95CI, 0.76-0.94; p < 0.001). CONCLUSIONS: The assessment of Kt through ionic dialyzance is a simple method to estimate the dose of dialysis in critically ill patients and is and useful tool to monitor and adjust the RRT in real time according to a target dose.

The mechanism of sensory transduction in a mechanoreceptor. Functional stages in campaniform sensilla during the molting cycle.

This paper describes the ultrastructural modifications that cockroach campaniform sensilla undergo at three major stages in the molting cycle and finds that the sensilla are physiological functional at all developmental stages leading to ecdysis. Late stage animals on the verge of ecdysis have two completely separate cuticles. The campaniform sensillum sends a 220-mum extension of the sensory process through a hole in its cap in the new (inner) cuticle across a fluid-filled molting space to its functional insertion in the cap in the old (outer) cuticle. Mechanical stimulation of the old cap excites the sensillum. The ultrastructural geometry of late stage sensilla, coupled with the observation they are physiolgically functional, supports the hypotheses (a) that sensory transduction occurs at the tip of the sensory process, and (b) that cap identation causes the cap cuticle to pinch the tip of the sensory process, thereby stimulating the sensillum.

Paroxysmal events during prolonged video-video electroencephalography monitoring in refractory epilepsy. / Eventos paroxísticos durante la monitorización prolongada con videoelectroencefalografía en epilepsia refractaria.

INTRODUCTION: Given that epileptic seizures and non-epileptic paroxysmal events have similar clinical manifestations, using specific diagnostic methods is crucial, especially in patients with drug-resistant epilepsy. Prolonged video electroencephalography monitoring during epileptic seizures reveals epileptiform discharges and has become an essential procedure for epilepsy diagnosis. The main purpose of this study is to characterise paroxysmal events and compare patterns in patients with refractory epilepsy. METHODS: We conducted a retrospective analysis of medical records from 91 patients diagnosed with refractory epilepsy who underwent prolonged video electroencephalography monitoring during hospitalisation. RESULTS: During prolonged video electroencephalography monitoring, 76.9% of the patients (n=70) had paroxysmal events. The mean number of events was 3.4±2.7; the duration of these events was highly variable. Most patients (80%) experienced seizures during wakefulness. The most common events were focal seizures with altered levels of consciousness, progressive bilateral generalized seizures and psychogenic non-epileptic seizures. Regarding all paroxysmal events, no differences were observed in the number or type of events by sex, in duration by sex or age at onset, or in the number of events by type of event. Psychogenic nonepileptic seizures were predominantly registered during wakefulness, lasted longer, started at older ages, and were more frequent in women. CONCLUSIONS: Paroxysmal events recorded during prolonged video electroencephalography monitoring in patients with refractory epilepsy show similar patterns and characteristics to those reported in other latitudes.

Postnatal manganese exposure alters dopamine transporter function in adult rats: Potential impact on nonassociative and associative processes.

In the present study, we examined whether exposing rats to a high-dose regimen of manganese chloride (Mn) during the postnatal period would depress presynaptic dopamine functioning and alter nonassociative and associative behaviors. To this end, rats were given oral supplements of Mn (750 microg/day) on postnatal days (PD) 1-21. On PD 90, dopamine transporter (DAT) immunoreactivity and [3H]dopamine uptake were assayed in the striatum and nucleus accumbens, while in vivo microdialysis was used to measure dopamine efflux in the same brain regions. The effects of postnatal Mn exposure on nigrostriatal functioning were evaluated by assessing rotorod performance and amphetamine-induced stereotypy in adulthood. In terms of associative processes, both cocaine-induced conditioned place preference (CPP) and sucrose-reinforced operant responding were examined. Results showed that postnatal Mn exposure caused persistent declines in DAT protein expression and [3H]dopamine uptake in the striatum and nucleus accumbens, as well as long-term reductions in striatal dopamine efflux. Rotorod performance did not differ according to exposure condition, however Mn-exposed rats did exhibit substantially more amphetamine-induced stereotypy than vehicle controls. Mn exposure did not alter performance on any aspect of the CPP task (preference, extinction, or reinstatement testing), nor did Mn affect progressive ratio responding (a measure of motivation). Interestingly, acquisition of a fixed ratio task was impaired in Mn-exposed rats, suggesting a deficit in procedural learning. In sum, these results indicate that postnatal Mn exposure causes persistent declines in various indices of presynaptic dopaminergic functioning. Mn-induced alterations in striatal functioning may have long-term impact on associative and nonassociative behavior.

Immobilized chitosan as biosorbent for the removal of Cd(II), Cr(III) and Cr(VI) from aqueous solutions.

The generation of layer-by-layer silicate-chitosan composite biosorbent was studied. The films were evaluated on its stability regarding the polymer leakage and its capability in the removal of Cd(II), Cr(III) and Cr(VI) from an aqueous solution. SEM, EDAX and ATR-IR techniques were applied for material characterization. Silicate-chitosan films with a final layer of silicate demonstrated chitosan retention and had better sorption capacities than those without it. For metal species, such as Cd(II) and Cr(III), the greatest adsorption was obtained when the pH of the solution was 7. When Cr(VI) was evaluated, pH 4 was the optimal for its adsorption. Langmuir and Freundlich isotherms were modeled for the equilibrium data. An 80% of the adsorbed metal was recovered by HNO(3) incubation. This non-covalent immobilization method allowed chitosan surface retention and did not affect its adsorption properties. The use of a coated surface would facilitate sorbent removal from medium after adsorption.

Evaluation of Serum Symmetric Dimethylarginine Concentration as a Marker for Masked Chronic Kidney Disease in Cats With Hyperthyroidism.

BACKGROUND: Hyperthyroidism can complicate (mask) the diagnosis of chronic kidney disease (CKD) because it increases glomerular filtration rate and decreases body muscle mass, both of which can lower serum creatinine concentrations. Currently, there is no clinical test that can reliably predict which hyperthyroid cats have concurrent azotemic CKD that will become apparent after treatment of the hyperthyroidism. OBJECTIVES: To investigate serum symmetric dimethylarginine (SDMA) concentration as a potential marker of masked azotemia in untreated hyperthyroid cats. ANIMALS: Two hundred and sixty-two hyperthyroid cats and 206 aged-matched, clinically normal cats. METHODS: Prospective study. We measured creatinine, urea nitrogen, SDMA, T4 , and TSH concentrations before and 1, 3, and 6 months after treatment with radioiodine (131 I) and classified 131 I-treated cats as azotemic or nonazotemic based on persistent, post-treatment creatinine concentrations >2.1 mg/dL. Groups were compared via nonparametric tests, and diagnostic accuracy was determined by receiver operating characteristic analysis and logistic regression. RESULTS: No hyperthyroid cats were azotemic before treatment, but 42 (16%) became azotemic when rechecked at 4-8 months (median, 6 months) after 131 I treatment; of these, 14 had high SDMA concentrations before treatment. As a diagnostic test for pre-azotemic (masked) CKD in untreated hyperthyroid cats, SDMA showed a sensitivity of 33.3% and specificity of 97.7%. CONCLUSIONS AND CLINICAL IMPORTANCE: Finding a high serum SDMA concentration in a hyperthyroid cat can help predict development of azotemia after treatment. The test has high diagnostic test specificity (few false-positive results) but relatively low sensitivity (fails to predict azotemia in most hyperthyroid cats).

[Characteristics of patients with refractory epilepsy attended in a tertiary referral center in Costa Rica]. / Caracterizacion de los pacientes con epilepsia refractaria de un hospital de tercer nivel en Costa Rica.

INTRODUCTION: Thirty percent of patients with epilepsy have recurrent seizures, representing fifteen million people in the world. This population has been scarcely described. AIM: To characterize sociodemographic and clinically the patients diagnosed with refractory epilepsy in a tertiary referral hospital of the Costa Rican social security. PATIENTS AND METHODS: This study presents an analysis of all cases of refractory epilepsy evaluated at the epilepsy unit of San Juan de Dios Hospital from August, 2012 to October, 2014. RESULTS: Clinical records of 91 patients were studied; patients with psychogenic seizures were analyzed separately. The mean age of onset was 13.1 ± 11.1 years, secondary generalized seizures were the predominant type (81.3%), the most frequent etiology was mesial temporal sclerosis (48.3%) and the majority had normal neurological exams and normal or low neuropsychological assessments. Around half (48.8%) of the patients had been medicated with a range of 4-6 antiepileptic drugs, being lamotrigine, carbamazepine, valproic acid and phenytoin the most prescribed. Treatment optimization, neurosurgery, and further analysis were standard recommendations. Sociodemographic characteristics, patient management, and antiepileptic drugs used are similar to the described in other latitudes. Differences between the age of onset and gender; seizure frequency and gender; age of onset and failed treatments and time of evolution of the disease and employment were observed. The percentage and characteristics of recurrent seizures of psychogenic nature found are comparable to other refractory epilepsy studies. CONCLUSION: Sociodemographic characteristics, management of patients, antiepileptic drugs used and the differences observed are similar to those previously described.

TITLE: Caracterizacion de los pacientes con epilepsia refractaria de un hospital de tercer nivel en Costa Rica.Introduccion. El 30% de los pacientes con epilepsia presenta convulsiones recurrentes, porcentaje que representa aproximadamente a 15 millones de personas en el mundo y constituye una poblacion escasamente descrita. Objetivo. Caracterizar sociodemografica y clinicamente la poblacion de pacientes diagnosticados con epilepsia refractaria en un hospital terciario de Costa Rica. Pacientes y metodos. Se analizan los registros medicos de los pacientes con epilepsia refractaria valorados en la unidad de epilepsia del Hospital San Juan de Dios de la Caja Costarricense del Seguro Social desde agosto de 2012 a octubre de 2014. Resultados. Se incluyen los expedientes clinicos de 91 pacientes. La edad media de inicio fue de 13,1 ± 11,1 años. Las crisis secundariamente generalizadas constituyen el tipo predominante (81,3%), la etiologia mas frecuente es la esclerosis mesial temporal (48,3%) y la mayoria de los pacientes presentaba examenes neurologicos normales y valoraciones neuro­psicologicas normales o bajas. Alrededor de la mitad (48,8%) de los pacientes habia sido medicada con un rango de 4-6 farmacos antiepilepticos, y los mas prescritos fueron lamotrigina, carbamacepina, acido valproico y fenitoina. Las principales recomendaciones en estos pacientes fueron: optimizacion de tratamiento, neurocirugia y reingreso. Se observan diferencias entre la edad de inicio y el sexo, la frecuencia de las crisis y el sexo, el tiempo de evolucion de la patologia y la cantidad de tratamientos fallidos, y el tiempo de evolucion de la enfermedad y la ocupacion. Conclusiones. Las caracteristicas sociodemograficas, el manejo de los pacientes, los farmacos antiepilepticos utilizados y las diferencias encontradas son similares a las descritas en otras latitudes.

The optics of the compound eye of the honeybee (Apis mellifera).

The optical system of the compound eye of the worker honeybee, as a representative of the closed-rhabdom type of eye, was investigated and its function analyzed. Measurements of refractive indices of the elements of the optical system were made with an interference microscope. With the use of the resulting measurements, the optical system was analyzed by means of a ray-tracing procedure implemented for the IBM 7094 digital computer, and by means of the Gaussian thick lens formulae. The more detailed results of the ray-tracing technique were used for further analyses. Direct visual confirmation of the focal point was obtained. The rhabdom and the surrounding zone of lower refractive index act together as a wave guide, as demonstrated by the presence of several wave guide modes in the rhabdom. An admittance function was defined as the percentage of the rays reaching the rhabdom with respect to those entering the ommatidium. Good agreement with experimental results was found. The characterization of the visual field of an ommatidium by means of an admittance function permits the analysis of the influence of different stimuli on the eye.

Analysis of the organization and overlap of the visual fields in the compound eye of the honeybee (Apis mellifera).

Using the results of an optical analysis, a digital computer technique was developed to analyze the relative excitation produced by arbitrary figures at the rhabdom of the receptors of a compound eye. This technique was applied to several sets of figures for the honeybee (Apis mellifera) and a reasonable agreement was found with behavioral data. Similarly, the significance of a fixed cutoff angle for a visual field was investigated. It is concluded that overlap between neighboring ommatidia is highly significant for visual processing in the apposition eye, contrary to the assumptions of the mosaic theory.

Depression as a dynamical disease.

Mathematical models are helpful in the understanding of diseases through the use of dynamical indicators. A previous study has shown that brain activity can be characterized by a decrease of dynamical complexity in depressive subjects. The present paper confirms and extends these conclusions through the use of recent methodological advances: first episode and recurrent patients strongly differ in their dynamical response to therapeutic interventions. These results emphasize the need for clinical follow-ups to avoid recurrence and the necessity of specific therapeutic intervention in the case of recurrent patients.

Cytoarchitecture of the avian ventral lateral geniculate nucleus.

The avian thalamic ventral lateral geniculate nucleus (GLv) was studied by light microscopic techniques in order to understand its anatomy, neuronal composition, and the nature of its retinal and tectal afferents. The avian GLv is of considerable interest because physiological experiments show that it is the brain structure with the highest percentage of color-opponent responses (Maturana and Varela, '82). We used adult pigeons and quail for the present study. With Nissl techniques a predominance of medium-size neurons (58%) constitute the GLv. The shape, size, and orientation of the different neurons is highly variable throughout the GLv. With the Golgi methods, 5 classes of neurons are distinguished: I and IV (large), II (medium-size), III and V (small). Some class IV large neurons have bifurcated axons; no axons were distinguished on the small neurons. Optic fibers penetrating the GLv are often collateral branches of retinal axons that continue elsewhere. Fink-Heimer methods show that retinal axon terminals end around large and medium-size neurons and also reach the internal lamina of the GLv. HRP tracing shows that the large and medium-size neurons of the GLv project to the optic tectum. On the basis of comparisons between the cytoarchitecture of the GLv described here and the physiological findings previously reported (Maturana and Varela, '82; Pateromichelakis, '79), we suggest that: (1) large GLv neurons are the color-opponent units, (2) medium-size neurons are the movement-sensitive units, and (3) small neurons are either interneurons (local circuit neurons), or they might project to the area pretectalis or to some other GLv projection region not yet described.

A frequency view of colour: measuring the human sensitivity to square-wave spectral power distributions.

We have measured the chromatic threshold sensitivity to stimuli with spectral composition determined by a periodic function of energy over wavelength. This approach is analogous to frequency studies of spatial vision for the study of colour. A device was constructed permitting the synthesis of illuminants over the entire visible range (400-700 nm) in which phase, frequency and amplitude can be independently controlled. We have used 12 frequencies of square-wave functions (from 0.5 to 3.6 cycles/300 nm) and seven values of phase (between 0 degrees and 180 degrees) to obtain the contrast sensitivity function of the chromatic system in three normal trichromats. The results show maximum sensitivity around 1.5 cycles/300 nm and a high-frequency cut-off at 3.6 cycles/300 nm. These empirical values are compared with the predictions obtained from three current psychophysical models of opponent-colour process.

A dynamical analysis of oscillatory responses in the optic tectum.

Multi-unit recordings from the optic tectum of an awake pigeon displaying oscillatory behavior evoked by visual stimulus are highly non-stationary and contain a broad band of frequencies under a time-window analysis. Here we extend these observations by a non-linear dynamical analysis of these oscillatory signals (local fields potentials) in successive epochs during background activity and visual responses. Two numerical estimates have been obtained from the original data every 200 ms: (1) correlation dimension and (2) non-linear forecasting of the trajectories. Results from eight different recording sites analyzed are consistent and indicate, in the average, an increase in complexity of the signal during the oscillatory periods.

Anticipating epileptic seizures in real time by a non-linear analysis of similarity between EEG recordings.

In a previous publication we showed that non-linear analysis can extract spatio-temporal changes of brain electrical activity prior to epileptic seizures. Here we describe a new method to analyze this long-term non-stationarity in the EEG by a measure of dynamical similarity between different parts of the time series. We apply this method to the study of a group of patients with temporal lobe epilepsy recorded intracranially during transitions to seizure. We show that the method, which can be implemented on a personal computer, can track in real time spatio-temporal changes in brain dynamics several minutes prior to seizure.

Temporal patterns in human epileptic activity are modulated by perceptual discriminations.

We studied subdural recordings from a patient with an unusually focal and stable occipito-temporal epileptic discharge under four experimental conditions. The series of time intervals between successive spike discharges displayed a few (3-5) clusters of periodic values representing statistically significant short-term periodicities when tested against surrogate data. This short-term predictability was modulated during the different experimental conditions by periodicity shifts of the order of 15-30 ms. Correspondingly, there was an increased gamma-band (30-70 Hz) coherence between the epileptic focus and surrounding recording sites. We conclude that the focal epileptic activity is part of an extended network of neural activities which exert a fast modulation reflected in changes of transiently periodic activities.

Comparison of Hilbert transform and wavelet methods for the analysis of neuronal synchrony.

The quantification of phase synchrony between neuronal signals is of crucial importance for the study of large-scale interactions in the brain. Two methods have been used to date in neuroscience, based on two distinct approaches which permit a direct estimation of the instantaneous phase of a signal [Phys. Rev. Lett. 81 (1998) 3291; Human Brain Mapping 8 (1999) 194]. The phase is either estimated by using the analytic concept of Hilbert transform or, alternatively, by convolution with a complex wavelet. In both methods the stability of the instantaneous phase over a window of time requires quantification by means of various statistical dependence parameters (standard deviation, Shannon entropy or mutual information). The purpose of this paper is to conduct a direct comparison between these two methods on three signal sets: (1) neural models; (2) intracranial signals from epileptic patients; and (3) scalp EEG recordings. Levels of synchrony that can be considered as reliable are estimated by using the technique of surrogate data. Our results demonstrate that the differences between the methods are minor, and we conclude that they are fundamentally equivalent for the study of neuroelectrical signals. This offers a common language and framework that can be used for future research in the area of synchronization.

Color-opponent responses in the avian lateral geniculate: a study in the quail (Coturnix coturnix japonica).

Extracellular recordings were made from cells in the ventral lateral geniculate (GLv) of the Japanese quail (Coturnix coturnix japonica), and their responses studied with chromatic stimuli. A total of 156 units were studied, and of these, 124 were found to be optimally responsive to changes in hue, and not to changes of contrast or motion of the stimuli in their receptive fields. These chromatic responses can be characterized as follows: (1) they have large (average 15 degrees x 15 degrees) receptive fields; (2) these receptive fields are mostly located in the anterior part of the visual field; (3) the receptive fields are organized in a (rough) retinotopy in agreement with anatomical findings; (4) units exhibit a sustained response in the dark or under white illumination, which is strongly modulated by changes in hue of stimuli of equal illuminance; (4) the units have a complementary inhibitory response, thus exhibiting a color-opponent pattern of responses; (5) the inhibitory and excitatory areas of the receptive fields are uniform and superimposed; (6) there is a tendency of units of the same optimal chromatic responses to be clustered together in the Glv; (7) although units of all preference are found, the population is dominated by units with preferences in the short wavelength end of the spectrum (48%). This is the first report of a region in the avian brain where color-opponent responses are found in significant numbers, thus making it apparent that the difficulty of finding similar units in the optic tract, tectum, dorsal geniculate, or telencephalon, is not due to a lack of appropriate retinal afferents. The relationship between the present findings and other reports on the Glv's anatomy and physiology are discussed, as well as its possible roles in the generation of chromatic behavioral discrimination of birds.