Synthesis of Antimicrobial Chitosan-Silver Nanoparticles Mediated by Reusable Chitosan Fungal Beads.

Nanoparticles, especially silver nanoparticles (Ag NPs), have gained significant attention in recent years as potential alternatives to traditional antibiotics for treating infectious diseases due to their ability to inhibit the growth of microorganisms effectively. Ag NPs can be synthesized using fungi extract, but the method is not practical for large-scale production due to time and biomass limitations. In this study, we explore the use of chitosan to encapsulate the mycelia of the white-rot fungus Stereum hirsutum and form chitosan fungal beads for use in multiple extractions and nanoparticle synthesis. The resulting nanoparticles were characterized using various techniques, including UV-vis spectrophotometry, transmission electron microscopy, dynamic light scattering, and X-ray diffraction analysis. The analysis revealed that the synthesized nanoparticles were composed of chitosan-silver nanoparticles (CS-Ag NPs) with a size of 25 nm. The chitosan fungal beads were reused in three extractions and nanoparticle synthesis before they lost their ability to produce CS-Ag NPs. The CS-Ag NPs showed potent antimicrobial activity against phytopathogenic and human pathogenic microorganisms, including Pseudomonas syringae, Escherichia coli, Staphylococcus aureus, and Candida albicans, with minimum inhibitory concentrations of 1.5, 1.6, 3.1, and 4 µg/mL, respectively. The antimicrobial activity of CS-Ag NPs was from 2- to 40-fold higher than Ag NPs synthesized using an aqueous extract of unencapsulated fungal biomass. The CS-Ag NPs were most effective at a pH of five regarding the antimicrobial activity. These results suggest that the chitosan fungal beads may be a promising alternative for the sustainable and cost-effective synthesis of CS-Ag NPs with improved antimicrobial activity.

Cardiovascular disease risk among male workers of a regional electricity distribution company in Brazil.

BACKGROUND: At energy distribution companies, office and operational employees work in different occupational environments. Cardiovascular diseases (CVD) can develop due to occupational factors and can often lead to morbidity and disability. OBJECTIVE: To evaluate the risk of CVD in workers with different occupations in an energy distribution company, using cardiometabolic indices. METHODS: Workers (men), aged between 20 and 70 years, were divided into two groups: operational (n = 78) and office (n = 106) workers. Their metabolic profiles were analyzed using anthropometric and laboratory data to obtain the atherogenic plasma index (AIP) and insulin resistance index (TyG), and to identify the hypertriglyceridemic waist (HTGW) phenotype as cardiometabolic indicators. RESULTS: There was no difference in CVD risk between the two groups. However, 82% of the test subjects presented a high risk for the development of atherosclerosis based on the AIP, and 11.4% presented the HTGW phenotype, along with the presence of dyslipidemia, insulin resistance, and being overweight as risk factors for CVD. CONCLUSIONS: Although the identified risk factors are not related to the type of occupation at work, companies in the electricity sector can invest in the implementation of measures for health promotion to protect and prevent diseases and improve labor productivity and quality.

Hygienic Behavior of Apis mellifera and Its Relationship with Varroa destructor Infestation and Honey Production in the Central Highlands of Ecuador.

The aim of this research was to analyze the relationship among hygienic behavior (HB), Varroa destructor infestation, and honey production in the central highlands of Ecuador. Overall, 75 honey bee colonies were evaluated before, during, and after production at three altitude levels (2600-2800, 2801-3000, and >3000 m.a.s.l.). The hygienic behavior percentage of the colonies was determined by the pin-killing method, and the colonies were classified into three groups: high HB (>85%), mid HB (60.1-85%), and low HB (≤60%). Varroa infestation was diagnosed as well, and honey production was evaluated only during production. HB was high and heterogeneous, averaging 80% ± 9.7%. Its highest expression was observed at lower altitudes. The infestation degree was low (3.47% ± 1.56%), although the mite was detected in all colonies upon sampling. A negative correlation was observed between HB and Varroa infestation in the first sampling (-0.49 **), suggesting that the high- and mid-altitude HB colonies underwent the lowest infestation rates, regardless of sampling. The correlations between HB and production were significant (0.26 *), indicating a positive effect of HB on production, meaning that colonies with high HB obtained the highest honey production (25.08 ± 4.82 kg/hive). The HB of bees showed an inverse relationship with altitude and it tended to reduce the effect of Varroa infestation, favoring honey production and, thus, suggesting the feasibility of selecting colonies with high HB.

Antarctic Rahnella inusitata: A Producer of Cold-Stable ß-Galactosidase Enzymes.

There has been a recent increase in the exploration of cold-active ß-galactosidases, as it offers new alternatives for the dairy industry, mainly in response to the current needs of lactose-intolerant consumers. Since extremophilic microbial compounds might have unique physical and chemical properties, this research aimed to study the capacity of Antarctic bacterial strains to produce cold-active ß-galactosidases. A screening revealed 81 out of 304 strains with ß-galactosidase activity. The strain Se8.10.12 showed the highest enzymatic activity. Morphological, biochemical, and molecular characterization based on whole-genome sequencing confirmed it as the first Rahnella inusitata isolate from the Antarctic, which retained 41-62% of its ß-galactosidase activity in the cold (4 °C-15 °C). Three ß-galactosidases genes were found in the R. inusitata genome, which belong to the glycoside hydrolase families GH2 (LacZ and EbgA) and GH42 (BglY). Based on molecular docking, some of these enzymes exhibited higher lactose predicted affinity than the commercial control enzyme from Aspergillus oryzae. Hence, this work reports a new Rahnella inusitata strain from the Antarctic continent as a prominent cold-active ß-galactosidase producer.

[Cardiac myxomas. Analysis of 78 cases]. / Mixoma cardíaco: experiencia de 28 años en resección quirúrgica.

BACKGROUND: The incidence rates of cardiac tumors are low. AIM: To report the clinical presentation of cardiac myxomas and long-term evolution after resection. MATERIAL AND METHODS: Review of a database of surgical patients undergoing surgical resection of a cardiac myxoma in a public hospital between 1990 and 2018. RESULTS: Seventy-eight patients aged 53 ± 15 years (65% females) were included. The most frequent comorbidities were arterial hypertension (40.5%), hypothyroidism (15%) and diabetes mellitus (12%). The main presenting symptoms were dyspnea (33%), neurological deficit secondary to embolism (30%) and acute pulmonary edema (5%). The most common location was the left atrium, in 87%. During surgery, cardiopulmonary bypass and aortic cross-clamp times were 50.2 ± 19.6 and 33.4 ± 15.2 min, respectively. One patient died due to severe neurological involvement. Follow-up was completed in seventy-seven patients, with a mean echocardiographic follow-up time of 10.4 ± 7.7 years. Thirty-four patients were followed for more than 10 years. Six patients (7.7%) died during the follow-up and in six patients (7%) a recurrence was identified. CONCLUSIONS: Cardiac myxoma usually has nonspecific symptoms. Surgical excision offers excellent short and long-term results. Complications and recurrence rates are low in non-hereditary myxomas but obligates to perform echocardiographic follow-up for early diagnosis of recurrence.

Avaliação da adesão ao tratamento com Tamoxifeno por mulheres com câncer de mama / Tamoxifen treatment adherence assessment by women breast cancer / Evalución de adherencia al tratamento com Tamoxifeno em mujeres com cáncer de seno

Justificativa e objetivos: A terapia antineoplásica oral apresenta vantagens comparada a outras terapias para o tratamento do câncer, por ser administrada em domicílio, de forma simples e rápida, no entanto, essa terapia aumenta a responsabilidade do paciente em relação ao seu tratamento e a adesão é fundamental para a sua eficácia. Evidenciam-se poucos estudos referente ao acompanhamento farmacoterapêutico na terapia antineoplásica oral, nesses contexto, o presente estudo busca avaliar a adesão ao tratamento com tamoxifeno em mulheres com câncer de mama, antes e após acompanhamento farmacoterapêutico. Métodos: Trata-se de um estudo clínico randomizado e quantitativo. A coleta de dados foi realizada durante seis meses. A randomização aleatória dividiu-se em Grupo Controle e Grupo Acompanhamento, sendo o acompanhamento subdividido: Antes e Após o Acompanhamento. O Grupo acompanhamento recebeu mensalmente intervenções farmacêuticas individuais. A adesão foi avaliada pelo Brief Medication Questionnair e Problemas Relacionados aos Medicamentos quanto Necessidade, Efetividade e Segurança. Resultados: Após acompanhamento farmacêutico observou-se diferença entre os grupos Grupo Acompanhamento e Grupo Controle quanto à prática de atividade física (p=0,043), adesão ao tratamento (p=0,006), redução de efeitos adversos (p=0,003) e doenças associadas (p=0,002). Os Problemas Relacionados a Medicamentos mais frequentes foram de segurança e adesão, para os quais foram realizadas 54 intervenções farmacêuticas. As reações adversas descritas pelas pacientes acometiam principalmente sistema genital e trato gastrintestinal. Conclusão: Evidenciou-se que o acompanhamento farmacoterapêutico contribuiu efetivamente na adesão ao tratamento com tamoxifeno e as intervenções farmacêuticas realizadas contribuíram para prevenção e redução dos problemas associados a farmacoterapia.(AU)

Background and objectives: Oral antineoplastic therapy has advantages compared to other therapies for the treatment of cancer, because it is administered at home, in a simple and fast, however, this therapy increases the responsibility of the patient regarding its treatment and adherence is critical to its effectiveness. There are few studies on pharmacotherapeutic monitoring in oral antineoplastic therapy. In this context, the present study aims to evaluate to adherence with tamoxifen in women with breast cancer, before and after of pharmaceutical care. Methods: It is a randomized and quantitative clinical study. Data collection was performed during six months. Random randomization was divided into Control Group and Monitoring Group. The follow-up was subdivided: Before and After Monitoring. The Monitoring Group received monthly individual pharmaceutical interventions. Adherence was assessed by the Brief Medication Questionnaire and Drug Related Problems as Need, Effectiveness, and Safety. Results: There was a significant difference between the follow-up group and control group regarding physical activity (p = 0.043), adherence to treatment (p = 0.006), reduction of adverse effects (p = 0.003) and associated diseases (p = 0.002). The most frequent drug-related problems were safety and adherence, for which 54 pharmaceutical interventions were performed. The adverse reactions described by the patients mainly affected the genital system and the gastrointestinal tract. Conclusion: It was evidence the pharmaceutical care effectively contributed to the adherence to tamoxifen treatment and the performed pharmaceutical interventions contributed to the prevention and reduction of the problems associated with phamacoterapy.(AU)

Justificación y objetivo: La terapia antineoplásica oral presenta ventajas comparadas a otras terapias para el tratamiento del cáncer, por ser administrada a domicilio, de forma simple y rápida, sin embargo, esta terapia aumenta la responsabilidad del paciente en relación a su tratamiento y la adhesión es fundamental para su eficacia. Se evidencian pocos estudios referentes al seguimiento farmacoterapéutico en la terapia antineoplásica oral, en ese contexto, el presente estudio busca evaluar la adhesión al tratamiento con tamoxifeno en mujeres con cáncer de mama, antes y después de seguimento farmacoterapéutico. Métodos: Se trata de un estudio clínico aleatorizado y cuantitativo. La recolección de datos se realizó durante seis meses. La aleatorización aleatoria se dividió en Grupo Control y Grupo Seguimiento, siendo el acompañamiento subdividido: Antes y Después del Acompañamiento. El Grupo de seguimiento recibió mensualmente intervenciones farmacéuticas individuales. La adhesión fue evaluada por el Brief Medication Questionnair y los problemas relacionados con los medicamentos como la necesidad, la eficacia y la seguridad. Resultados: Después del seguimiento farmacéutico se observó diferencia entre los grupos Grupo Acompañamiento y Grupo Control en cuanto a la práctica de actividad física (p = 0,043), adhesión al tratamiento (p = 0,006), reducción de efectos adversos (p = 0,003) y enfermidades asociadas (p = 0,003) p = 0,002). Los problemas relacionados con los medicamentos más frecuentes fueron de seguridad y adhesión, para los que se realizaron 54 intervenciones farmacéuticas. Las reacciones adversas descritas por las pacientes acometieron principalmente sistema genital y tracto gastrointestinal. Conclusión: Se evidenció que el seguimiento farmacoterapéutico contribuyó efectivamente a la adherencia al tratamiento con tamoxifeno y las intervenciones farmacéuticas realizadas contribuyeron a la prevención y reducción de los problemas asociados con la farmacoterapia.(AU)

Mixoma cardíaco: experiencia de 28 años en resección quirúrgica / Cardiac myxomas. Analysis of 78 cases

Background: The incidence rates of cardiac tumors are low. Aim: To report the clinical presentation of cardiac myxomas and long-term evolution after resection. Material and Methods: Review of a database of surgical patients undergoing surgical resection of a cardiac myxoma in a public hospital between 1990 and 2018. Results: Seventy-eight patients aged 53 ± 15 years (65% females) were included. The most frequent comorbidities were arterial hypertension (40.5%), hypothyroidism (15%) and diabetes mellitus (12%). The main presenting symptoms were dyspnea (33%), neurological deficit secondary to embolism (30%) and acute pulmonary edema (5%). The most common location was the left atrium, in 87%. During surgery, cardiopulmonary bypass and aortic cross-clamp times were 50.2 ± 19.6 and 33.4 ± 15.2 min, respectively. One patient died due to severe neurological involvement. Follow-up was completed in seventy-seven patients, with a mean echocardiographic follow-up time of 10.4 ± 7.7 years. Thirty-four patients were followed for more than 10 years. Six patients (7.7%) died during the follow-up and in six patients (7%) a recurrence was identified. Conclusions: Cardiac myxoma usually has nonspecific symptoms. Surgical excision offers excellent short and long-term results. Complications and recurrence rates are low in non-hereditary myxomas but obligates to perform echocardiographic follow-up for early diagnosis of recurrence.

High prevalence of CTX-M-1 group in ESBL-producing enterobacteriaceae infection in intensive care units in southern Chile.

Enterobacteria-producing extended-spectrum ß-lactamases (ESBL) play an important role in healthcare infections, increasing hospitalization time, morbidity and mortality rates. Among several ESBLs that emerge from these pathogens, CTX-M-type enzymes had the most successful global spread in different epidemiological settings. Latin America presents high prevalence of CTX-M-2 in ESBL-producing enterobacterial infections with local emergence of the CTX-M-1 group. However, this high prevalence of the CTX-M-1 group has not yet been reported in Chile. The aim of this study was to identify ESBLs among enterobacteria isolated from clinical samples of critically ill patients from southern Chile. One-hundred thirty seven ESBL-producing bacteria were isolated from outpatients from all critical patient units from Hernán Henríquez Aravena Hospital. Phenotype characterization was performed by antibiogram, screening of ESBL, and determination of minimum inhibitory concentration (MIC). PCR was used for genetic confirmation of resistance. Molecular typing was performed by ERIC-PCR. ESBL-producing isolates were identified as Klebsiella pneumoniae (n=115), Escherichia coli (n=18), Proteus mirabilis (n=3), and Enterobacter cloacae (n=1), presenting multidrug resistance profiles. PCR amplification showed that the strains were positive for blaSHV (n=111/81%), blaCTX-M-1 (n=116/84.7%), blaTEM (n=100/73%), blaCTX-M-2 (n=28/20.4%), blaCTX-M-9 (0.7%), blaPER-1 (0.7%), and blaGES-10 (0.7%). The multiple production of ESBL was observed in 93% of isolates, suggesting high genetic mobility independent of the clonal relationship. The high frequency of the CTX-M-1 group and a high rate of ESBL co-production are changing the epidemiology of the ESBL profile in Chilean intensive care units. This epidemiology is a constant and increasing challenge, not only in Chile, but worldwide.

High prevalence of CTX-M-1 group in ESBL-producing enterobacteriaceae infection in intensive care units in southern Chile

ABSTRACT Enterobacteria-producing extended-spectrum β-lactamases (ESBL) play an important role in healthcare infections, increasing hospitalization time, morbidity and mortality rates. Among several ESBLs that emerge from these pathogens, CTX-M-type enzymes had the most successful global spread in different epidemiological settings. Latin America presents high prevalence of CTX-M-2 in ESBL-producing enterobacterial infections with local emergence of the CTX-M-1 group. However, this high prevalence of the CTX-M-1 group has not yet been reported in Chile. The aim of this study was to identify ESBLs among enterobacteria isolated from clinical samples of critically ill patients from southern Chile. One-hundred thirty seven ESBL-producing bacteria were isolated from outpatients from all critical patient units from Hernán Henríquez Aravena Hospital. Phenotype characterization was performed by antibiogram, screening of ESBL, and determination of minimum inhibitory concentration (MIC). PCR was used for genetic confirmation of resistance. Molecular typing was performed by ERIC-PCR. ESBL-producing isolates were identified as Klebsiella pneumoniae (n = 115), Escherichia coli (n = 18), Proteus mirabilis (n = 3), and Enterobacter cloacae (n = 1), presenting multidrug resistance profiles. PCR amplification showed that the strains were positive for blaSHV (n = 111/81%), blaCTX-M-1 (n = 116/84.7%), blaTEM (n = 100/73%), blaCTX-M-2 (n = 28/20.4%), blaCTX-M-9 (0.7%), blaPER-1 (0.7%), and blaGES-10 (0.7%). The multiple production of ESBL was observed in 93% of isolates, suggesting high genetic mobility independent of the clonal relationship. The high frequency of the CTX-M-1 group and a high rate of ESBL co-production are changing the epidemiology of the ESBL profile in Chilean intensive care units. This epidemiology is a constant and increasing challenge, not only in Chile, but worldwide.

Can Triamcinolone acetonide, platelet-rich plasma, and pentosan polysulfate sodium induce oxidative stress in cultured equine chondrocytes? / Acetonido de triancinolona, plasma rico em plaquetas e pentosano polissulfato sódico podem ocasionar estresse oxidativo em cultivo de condrócitos de equinos?

ABSTRACT: Progressive deterioration and loss of articular cartilage are the final degenerative events common to osteoarthritis (OA). Reactive oxygen species (ROS) play an important role in this chondrocyte catabolic activity, leading to cell death and matrix components breakdown. Intra-articular corticosteroid injections such as triamcinolone acetonide have been used to control pain and inflammation associated with OA. New treatments for OA, platelet-rich plasma and pentosan polysulphate sodium have also been used and further investigations are necessary to determine their safety in joint cells. In this in vitro study, the use of these three substances (triamcinolone acetonide, platelet-rich plasma, and pentosan polysulphate sodium) in healthy chondrocytes did not alter the antioxidant status when compared to control groups, indicating that they could be considered safe in healthy conditions.

RESUMO: A deterioração progressiva e perda da cartilagem articular são os eventos finais da osteoartrite (OA). Espécies reativas de oxigênio (ROS) têm papel importante na atividade catabólica de condrócitos, levando a morte celular e quebra dos componentes da matriz. Injeções intra-articulares de corticosteroides, como com o acetonido de triancinolona, são usadas para controle da dor e inflamação associadas à OA. Novos tratamentos para a OA, como o plasma rico em plaquetas e o pentosano polissulfato sódico, também tem sido utilizados e necessitam de maiores investigações para determinar sua segurança para as células articulares de equinos. Neste estudo in vitro, o uso destas três substâncias (acetonido de triancinolona, pentosan polissulfato de sódio de plasma rico em plaquetas) em condrócitos saudáveis de equinos não alterou o status antioxidante quando comparado aos grupos controle, indicando que puderam ser considerados seguros em condições saudáveis.

Restoring wild-type-like CA1 network dynamics and behavior during adulthood in a mouse model of schizophrenia.

Schizophrenia is a severely debilitating neurodevelopmental disorder. Establishing a causal link between circuit dysfunction and particular behavioral traits that are relevant to schizophrenia is crucial to shed new light on the mechanisms underlying the pathology. We studied an animal model of the human 22q11 deletion syndrome, the mutation that represents the highest genetic risk of developing schizophrenia. We observed a desynchronization of hippocampal neuronal assemblies that resulted from parvalbumin interneuron hypoexcitability. Rescuing parvalbumin interneuron excitability with pharmacological or chemogenetic approaches was sufficient to restore wild-type-like CA1 network dynamics and hippocampal-dependent behavior during adulthood. In conclusion, our data provide insights into the network dysfunction underlying schizophrenia and highlight the use of reverse engineering to restore physiological and behavioral phenotypes in an animal model of neurodevelopmental disorder.

Implicancias estructurales y fisiológicas de la célula bacteriana en los mecanismos de resistencia antibiótica / Structural and physiological implications of bacterial cell in antibiotic resistance mechanisms

RESUMEN: La alta capacidad de adaptación de las bacterias a ambientes hostiles ha permitido el desarrollo de resistencia a antibacterianos, causando problemas de impacto mundial en la salud hospitalaria y de la comunidad, limitando las opciones terapéuticas lo que afecta el control de enfermedades, elevando las tasas de morbi-mortalidad. Esta capacidad de resistencia es mediada por factores estructurales y fisiológicos de las bacterias que actúan a diferentes niveles tanto extracelular como intracelular. A niveles extracelulares se destaca la capacidad de las poblaciones bacterianas en la formación de biopelículas y la regulación de señales celulares quorum sensing, permitiendo la evasión de la acción antibiótica. A nivel de envoltura celular se destaca el funcionamiento y comportamiento de la pared celular y de la membrana celular, principalmente por medio de la regulación de la expresión de canales de entrada o porinas y/ o bombas de expulsión que impiden el acceso o inducen la salida de antibióticos; otros mecanismos integran la modificación de la actividad de drogas por medio de la hidrólisis o modificación del sitio activo del fármaco. A nivel intracelular, las bacterias pueden cambiar los procesos de óxido/reducción, modificar los sitios objetivos del antibiótico e inactivar los grupos transfer, y modificar las subunidades ribosomales afectando la acción de los antibióticos que inhiben la síntesis de proteínas. A esto se añaden las modificaciones en la expresión génica y del código genético, que regula todos los anteriores, y es capaz de generar cambios adaptativos, resistencia a fármacos y desinfectantes, entre otros. La presente revisión tiene como objetivo describir las implicancias estructurales y fisiológicas de la célula bacteriana en los mecanismos de resistencia antibiótica considerando la organización estructural y fisiológica involucrada en los principales mecanismos de resistencia a antibióticos presentes en bacterias de importancia clínica que conllevan a fallas terapéuticas con alto costo en salud humana.

SUMMARY: The high adaptability of bacteria to hostile environments has favored antibacterial resistance development, impacting hospital and community healthcare worldwide. It has also affected disease control, limited therapeutic options and raised morbiditymortality rate. This resistance ability is mediated by structural and physiological factors of bacteria acting at both extracellular and cellular levels. The ability of bacterial populations in biofilm formation and regulation of cellular signal quorum sensing at the extracellular level, allows for the evasion of antibiotic action. At a cellular level, the performance and behavior of the cell wall and cell membrane is emphasized, mainly by regulating the expression of inlet channels or porins and/or expulsion pumps preventing access to, or inducing the outflow of antibiotics. Other mechanisms integrate modification of drug activity by hydrolysis or modification of the active site of the drug. Further into intracellular level, bacteria can change the oxidation/reduction processes; modify the target sites of the antibiotic and inactivate transfer groups. Bacteria can also modify the ribosomal subunits affecting the antibiotics which inhibit protein synthesis, and cause modifications of gene expression and genetic code that regulate the above mechanism. These may also generate adaptive changes and resistance to drugs and disinfectants. The aim of the present review is to describe the structural and physiological implications of bacterial cell in the mechanisms of antibiotic resistance. The study also considered the structural and physiological organization involved in the main mechanisms of antibiotic resistance in bacteria relevant to clinical healthcare.

Sorting Overlapping Spike Waveforms from Electrode and Tetrode Recordings.

One of the outstanding problems in the sorting of neuronal spike trains is the resolution of overlapping spikes. Resolving these spikes can significantly improve a range of analyses, such as response variability, correlation, and latency. In this paper, we describe a partially automated method that is capable of resolving overlapping spikes. After constructing template waveforms for well-isolated and distinct single units, we generated pair-wise combinations of those templates at all possible time shifts from each other. Subsequently, overlapping waveforms were identified by cluster analysis, and then assigned to their respective single-unit combinations. We examined the performance of this method using simulated data from an earlier study, and found that we were able to resolve an average of 83% of the overlapping waveforms across various signal-to-noise ratios, an improvement of approximately 32% over the results reported in the earlier study. When applied to additional simulated data sets generated from single-electrode and tetrode recordings, we were able to resolve 91% of the overlapping waveforms with a false positive rate of 0.19% for single-electrode data, and 95% of the overlapping waveforms with a false positive rate of 0.27% for tetrode data. We also applied our method to electrode and tetrode data recorded from the primary visual cortex, and the results obtained for these datasets suggest that our method provides an efficient means of sorting overlapping waveforms. This method can easily be added as an extra step to commonly used spike sorting methods, such as KlustaKwik and MClust software packages, and can be applied to datasets that have already been sorted using these methods.

Methods, caveats and the future of large-scale microelectrode recordings in the non-human primate.

Cognitive processes play out on massive brain-wide networks, which produce widely distributed patterns of activity. Capturing these activity patterns requires tools that are able to simultaneously measure activity from many distributed sites with high spatiotemporal resolution. Unfortunately, current techniques with adequate coverage do not provide the requisite spatiotemporal resolution. Large-scale microelectrode recording devices, with dozens to hundreds of microelectrodes capable of simultaneously recording from nearly as many cortical and subcortical areas, provide a potential way to minimize these tradeoffs. However, placing hundreds of microelectrodes into a behaving animal is a highly risky and technically challenging endeavor that has only been pursued by a few groups. Recording activity from multiple electrodes simultaneously also introduces several statistical and conceptual dilemmas, such as the multiple comparisons problem and the uncontrolled stimulus response problem. In this perspective article, we discuss some of the techniques that we, and others, have developed for collecting and analyzing large-scale data sets, and address the future of this emerging field.

Frontoparietal correlation dynamics reveal interplay between integration and segregation during visual working memory.

Working memory requires large-scale cooperation among widespread cortical and subcortical brain regions. Importantly, these processes must achieve an appropriate balance between functional integration and segregation, which are thought to be mediated by task-dependent spatiotemporal patterns of correlated activity. Here, we used cross-correlation analysis to estimate the incidence, magnitude, and relative phase angle of temporally correlated activity from simultaneous local field potential recordings in a network of prefrontal and posterior parietal cortical areas in monkeys performing an oculomotor, delayed match-to-sample task. We found long-range intraparietal and frontoparietal correlations that display a bimodal distribution of relative phase values, centered near 0° and 180°, suggesting a possible basis for functional segregation among distributed networks. Both short- and long-range correlations display striking task-dependent transitions in strength and relative phase, indicating that cognitive events are accompanied by robust changes in the pattern of temporal coordination across the frontoparietal network.

Performance evaluation of collision-reaction interface and internal standardization in quadrupole ICP-MS measurements.

The combined use of internal standardization with collision and reaction interface in an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS-CRI) was evaluated. The behavior of several elements (Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Pb, Sb, V and Zn) was studied by introducing H(2) or He through the skimmer and sampler cones of the CRI device and by using In, Rh and Sc as internal standards. Certified reference material of trace elements in water (NIST 1643e) was used to evaluate the performance of the method. A vinegar sample and mixed food diet standard reference material were directly introduced into the equipment as complex matrices for Cr and V determinations. Improvements in accuracy and precision were attained combining both strategies. The introduction of H(2) through the skimmer cone was the best way to overcome polyatomic ions formation and to improve SBR and BEC values for several elements. The use of Sc as internal standard improved the performance of ICP-QMS-CRI.

Modulation of synchrony without changes in firing rates.

It was often reported and suggested that the synchronization of spikes can occur without changes in the firing rate. However, few theoretical studies have tested its mechanistic validity. In the present study, we investigate whether changes in synaptic weights can induce an independent modulation of synchrony while the firing rate remains constant. We study this question at the level of both single neurons and neuronal populations using network simulations of conductance based integrate-and-fire neurons. The network consists of a single layer that includes local excitatory and inhibitory recurrent connections, as well as long-range excitatory projections targeting both classes of neurons. Each neuron in the network receives external input consisting of uncorrelated Poisson spike trains. We find that increasing this external input leads to a linear increase of activity in the network, as well as an increase in the peak frequency of oscillation. In contrast, balanced changes of the synaptic weight of excitatory long-range projections for both classes of postsynaptic neurons modulate the degree of synchronization without altering the firing rate. These results demonstrate that, in a simple network, synchronization and firing rate can be modulated independently, and thus, may be used as independent coding dimensions.

Directed interactions between visual areas and their role in processing image structure and expectancy.

During sensory processing, cortical areas continuously exchange information in different directions along the hierarchy. The functional role of such interactions, however, has been the subject of various proposals. Here, we investigate the role of bottom-up and top-down interactions in processing stimulus structure and their relation to expected events. Applying multivariate autoregressive methods to local field potentials recorded in alert cats, we quantify directed interactions between primary (A17/18) and higher (A21) visual areas. A trial-by-trial analysis yields the following findings. To assess the role of interareal interactions in processing stimulus structure, we recorded in naïve animals during stimulation with natural movies and pink noise stimuli. The overall interactions decrease compared with baseline for both stimuli. To investigate whether forthcoming events modulate interactions, we recorded in trained animals viewing two stimuli, one of which had been associated with a reward. Several results support such modulations. First, the interactions increase compared with baseline and this increase is not observed in a context where food was not delivered. Second, these stimuli have a differential effect on top-down and bottom-up components. This difference is emphasized during the stimulus presentation and is maximal shortly before the possible reward. Furthermore, a spectral decomposition of the interactions shows that this asymmetry is most dominant in the gamma frequency range. Concluding, these results support the notion that interareal interactions are more related to an expectancy state rather than to processing of stimulus structure.

NMDA lesions in the medial prefrontal cortex impair the ability to inhibit responses during reversal of a simple spatial discrimination.

Although lesion studies suggest that the rat medial prefrontal cortex (mPFc) is involved in the process necessary for reversal of a particular set of contingencies, the nature of lesion-induced deficits is unclear. The involvement of rat mPFc in reversal of a simple spatial discrimination was examined in the present study. Our hypothesis was that lesion-induced deficits may reflect a failure to inhibit a learned instrumental response. Lister Hooded rats were trained on a spatial discrimination task (SD), which required a correct barpress matching the cue location, then they were trained on reversal of SD (SDR), which required a correct barpress opposite to the cue location. Rats with mPFc lesions showed a slower learning rate compared to the controls. However, behavior of the lesioned rats during early and later reversal differed. During the initial SDR, the lesioned rats showed a greater number of barpresses during the intertrial interval and a slightly higher percent correct responses than that of the controls. Our data suggest that damage to mPFc may produce a lack of response inhibition, leading to an increase in nondiscriminated bapresses, thereby yielding a 'facilitation' during early reversal. mPFc lesion did not affect either open field activity or prepulse inhibition (PPI), a frequently used measure of sensorimotor gating. Disruption of reversal learning following damage to mPFc is partly due to a failure to inhibit instrumental responses, rather than to disruption of other processes involved in sensorimotor gating or general activity.