Versatile LCP surface microelectrodes for combining electrophysiology and in vivo two-photon imaging in the murine CNS

Neurons and astrocytes are highly interconnected and form a complex cellular network for signal processing in the brain. The electrical activity of neurons and astroglial Ca2+ signals are tightly coupled. Parallel recording of electrical activity and Ca2+ signals can help to identify the molecular mechanisms of neuron-glia communications. In this work, flexible liquid crystal polymer microelectrode arrays for electrical recordings and stimulations during two-photon laser-scanning microscopy (2P-LSM) were developed. The arrays were designed for standard craniotomies used for cortical 2P-LSM in vivo imaging. Being of low weight, thin and flexible, they can be easily positioned between the dura mater and the glass coverslip. Three different designs were constructed: arrays (1) with eight circular electrodes (arranged in a matrix of three by three elements, sparing the center), (2) with sixteen circular electrodes (four by four matrix) and (3) with eight rectangular electrodes (placed in four groups of 2 single sites). The initial contact sites of gold were coated with nanoporous platinum to decrease the impedance of the electrode tissue contacts and to increase the charge transfer capability. The biocompatibility of the electrodes was confirmed by immuno-histochemistry. Electrical recordings and Ca2+-imaging were performed in mice with neuronal or astroglial expression of the genetically encoded Ca2+-sensor GCaMP3. With the sixteen channel electrode arrays, an estimation of the spatially resolved electrical activity pattern within the cranial window could be described. The eight channel arrays were used in studies for simultaneous acquisition of Ca2+ (using 2P-LSM) and electrical signals. In addition, Ca2+ signals could be elicited by electrical stimulation. Using different stimulation intensities and depth of anesthesia, the change of brain activity during transition from anesthetized to awake state was investigated. In addition, the LCP technology was transferred from the cortical to a spinal cord application.Neurone und Astrozyten bilden ein komplexes interagierendes zellulares Netzwerk zur Signalverarbeitung im Gehirn. Dabei sind die elektrische Aktivitäten der Nervenzellen und die Ca2+ Signale der Astrozyten eng aneinander gekoppelt. Parallele Aufzeichnungen der elektrischen Aktivität und der Ca2+ Signale können helfen, die molekularen Mechanismen der Neuron-Glia-Kommunikation zu identifizieren. Innerhalb dieser Arbeit wurden flexible Flüssigkristall-Polymer-Mikroelektrodenarrays für elektrische Aufzeichnungen und Stimulationen für die Zwei-Photonen-Laserscan- Mikroskopie (2P-LSM) entwickelt. Die Elektrodenarrays wurden für Standard-Kraniotomien entwickelt, die für die kortikale in vivo 2P-LSM verwendet werden. Sie sind dünn, flexibel und von geringem Gewicht und können leicht auf der Dura positioniert werden. Drei verschiedene Designs wurden konstruiert: Arrays (1) mit acht runden Elektroden (angeordnet in einer drei mal drei Matrix, ohne die mittlere Elektrode), (2) mit sechzehn kreisförmigen Elektroden (vier mal vier Matrix) und (3) mit acht rechteckigen Elektroden (angeordnet in vier Gruppen von zwei einzelnen Standorten). Die ursprünglichen Elektrodenkontakte aus Gold wurden mit nanoporösem Platin beschichtet, um die Gewebekontaktimpedanz zu verringern und die Ladungsübertragungsfähigkeit zu erhöhen. Die Biokompatibilität der Elektroden immunhistochemisch getestet. Elektrische Aktivität und Ca2+ Signale wurden bei Mäusen mit neuronaler oder astroglialer Expression des Ca2+-Indikators GCaMP3 aufgezeichnet. Mit den sechzehn Kanal-Elektroden-Arrays konnten die elektrische Aktivität entlang der Kortexoberfläche innerhalb der Kraniotomie charakterisiert werden. Die achtkanaligen Arrays wurden zur gleichzeitigen Erfassung von Ca2+ (mit 2P-LSM) und elektrischen Signalen verwendet. Darüber hinaus konnten Ca2+ Signale durch elektrische Stimulation hervorgerufen werden. Mit verschiedenen Stimulationsintensitäten und der Tiefe der Anästhesie (Isofluran) wurde die Veränderung der Hirnaktivität beim Übergang von anästhesiert zu wach beobachtet. Zusätzlich konnte die Flüssigkristall-Polymer -Technologie von der kortikalen auf die spinale Anwendung übertragen werden.- European Union / EUGlia-PhD - European Union / Neurofibre

A mathematically assisted reconstruction of the initial focus of the yellow fever outbreak in Buenos Aires (1871)

We discuss the historic mortality record corresponding to the initial focus of the yellow fever epidemic outbreak registered in Buenos Aires during the year 1871 as compared to simulations of a stochastic population dynamics model. This model incorporates the biology of the urban vector of yellow fever, the mosquito Aedes aegypti, the stages of the disease in the human being as well as the spatial extension of the epidemic outbreak. After introducing the historical context and the restrictions it puts on initial conditions and ecological parameters, we discuss the general features of the simulation and the dependence on initial conditions and available sites for breeding the vector. We discuss the sensitivity, to the free parameters, of statistical estimators such as: final death toll, day of the year when the outbreak reached half the total mortality and the normalized daily mortality, showing some striking regularities. The model is precise and accurate enough to discuss the truthfulness of the presently accepted historic discussions of the epidemic causes, showing that there are more likely scenarios for the historic facts.Comment: 25 pages, 12 figure

Controle de Aedes aegypti com temefós em cemitério de Buenos Aires, Argentina

The efficacy of a larvicide, temephos, for controlling Ae. aegypti was evaluated in a cemetery in Buenos Aires, Argentina. Breeding sites decreased from 18.4% in the first study period (Nov 1998 to May 1999, without temephos) to 2.2% in the second period (Nov 1999 to May 2000, two applications), and to 0.05% in the third one (Nov 2000 to May 2001, five applications). Ovitraps with eggs decreased from 17% in the first period to 5.8% in the second period, and to 2.9% in the third one. Results suggest that, in Buenos Aires, Ae. aegypti populations are highly susceptible to temephos. It is recommended to limit the use of temephos to prevent potential epidemics rather than for routine control.Se evaluó la eficacia de un larvicida, temefós, para controlar Ae. aegypti en un cementerio de Buenos Aires, Argentina. Los criaderos descendieron de 18,4% en el primer periodo de estudio (Nov 1998 a May 1999, sin temefos) a 2,2% en el segundo (Nov 1999 a May 2000, dos aplicaciones), y a 0,05% en el tercero (Nov 2000 a May 2001, cinco aplicaciones). Las ovitrampas con huevos disminuyeron de 17% en el primer periodo a 5,8% en el segundo, y a 2,9% en el tercero. Los resultados sugieren que, en Buenos Aires, las poblaciones de Ae. aegypti son altamente susceptibles al temefós. Es recomendable limitar su uso para prevenir eventuales epidemias y no para el control rutinario.Avaliou-se a eficácia de um larvicida, temefós, para controlar Ae. aegypti em um cemitério de Buenos Aires, Argentina. Os criadouros reduziram de 18,4% no primeiro período de estudo (nov de 1998 a maio de 1999, sem temefós) para 2,2% no segundo (nov de 1999 a maio de 2000, duas aplicações), e para 0,05% no terceiro (nov de 2000 a maio de 2001, cinco aplicações). As. ovitrampas com ovos diminuíram de 17% no primeiro período para 5,8% no segundo e para 2,9% no terceiro. Os resultados sugerem que, em Buenos Aires, as populações de Ae. aegypti são altamente susceptíveis ao temefós. É recomendável seu uso para prevenir eventuais epidemias e não para o controle rotineiro

Comparative study of platinum electroplating to improve micro gold electrode arrays with LCP laminate

Decoding the cellular network interaction of neurons and glial cells are important in the development of new therapies for diseases of the central nervous system (CNS). Electrophysiological in vivo studies in mice will help to understand the highly complex network. In this paper, the optimization of epidural liquid crystal polymer (LCP) electrodes for different platinum electroplating parameters are presented and compared. Constant current and pulsed current electroplating varied in strength and duration was used to decrease the electrode impedance and to increase the charge storage capacity (CSCC). In best cases, both methods generated similar results with an impedance reduction of about 99%. However, electroplating with pulsed currents was less parameter-dependent than the electroplating with constant current. The use of ultrasound was essential to generate platinum coatings without plating defects. Electrode model parameters extracted from the electrode impedance reflected the increase in surface porosity due to the electroplating processes

Versatile Surface Electrodes for Combined Electrophysiology and Two-Photon Imaging of the Mouse Central Nervous System

Understanding and modulating CNS function in physiological as well as pathophysiological contexts remains a significant ambition in research and clinical applications. The investigation of the multifaceted CNS cell types including their interactions and contributions to neural function requires a combination of the state-ofthe-art in vivo electrophysiology and imaging techniques. We developed a novel type of liquid crystal polymer (LCP) surface micro-electrode manufactured in three customized designs with up to 16 channels for recording and stimulation of brain activity. All designs include spare central spaces for simultaneous 2P-imaging. Nanoporous platinumplated contact sites ensure a low impedance and high current transfer. The epidural implantation of the LCP micro-electrodes could be combined with standard cranial window surgery. The epidurally positioned electrodes did not only display long-term biocompatibility, but we also observed an additional stabilization of the underlying CNS tissue. We demonstrate the electrode’s versatility in combination with in vivo 2P-imaging by monitoring anesthesia-awake cycles of transgenic mice with GCaMP3 expression in neurons or astrocytes. Cortical stimulation and simultaneous 2P Ca2+ imaging in neurons or astrocytes highlighted the astrocytes’ integrative character in neuronal activity processing. Furthermore, we confirmed that spontaneous astroglial Ca2+ signals are dampened under anesthesia, while evoked signals in neurons and astrocytes showed stronger dependency on stimulation intensity rather than on various levels of anesthesia. Finally, we show that the electrodes provide recordings of the electrocorticogram (ECoG) with a high signal-to noise ratio and spatial signal differences which help to decipher brain activity states during experimental procedures. Summarizing, the novel LCP surface micro-electrode is a versatile, convenient, and reliable tool to investigate brain function in vivo

Probability of Trypanosoma cruzi transmission by Triatoma infestans (Hemiptera: Reduviidae) to the opossum Didelphis albiventris (Marsupialia: Didelphidae)

The probability of Trypanosoma cruzi transmission to opossums by independent events of predation and fecal contamination during feeding ("biting") with positive Triatoma infestans was estimated. Negative female opossums were challenged for 23 hr with 10 infected third and fourth instars of T. infestans, and tests for positivity for T. cruzi by xenodiagnosis were performed at 30, 60, and 90 days. From these data, seven probability parameters were estimated by maximum likelihood, and likelihood ratio statistics confidence intervals were calculated. Simultaneous estimation of p1 (probability that a "bite" will infect an opossum), p3 (probability that a bug that has been eaten by an opossum will infect it), and p6 (probability that the opossum will become infected if faced with an infected triatomine), resulted in p̂1 = 0.06, p̂3 = 0.075, and p̂6 = 0.059. On average, each opossum should be exposed to an average of 700 encounters with bugs during its life, resulting in about eight potentially infective contacts, to produce the 35% opossum prevalence found in the field.Facultad de Ciencias Naturales y Muse

Probability of Trypanosoma cruzi transmission by Triatoma infestans (Hemiptera: Reduviidae) to the opossum Didelphis albiventris (Marsupialia: Didelphidae)

The probability of Trypanosoma cruzi transmission to opossums by independent events of predation and fecal contamination during feeding ("biting") with positive Triatoma infestans was estimated. Negative female opossums were challenged for 23 hr with 10 infected third and fourth instars of T. infestans, and tests for positivity for T. cruzi by xenodiagnosis were performed at 30, 60, and 90 days. From these data, seven probability parameters were estimated by maximum likelihood, and likelihood ratio statistics confidence intervals were calculated. Simultaneous estimation of p1 (probability that a "bite" will infect an opossum), p3 (probability that a bug that has been eaten by an opossum will infect it), and p6 (probability that the opossum will become infected if faced with an infected triatomine), resulted in p̂1 = 0.06, p̂3 = 0.075, and p̂6 = 0.059. On average, each opossum should be exposed to an average of 700 encounters with bugs during its life, resulting in about eight potentially infective contacts, to produce the 35% opossum prevalence found in the field.Facultad de Ciencias Naturales y Muse

A mathematically assisted reconstruction of the initial focus of the yellow fever outbreak in Buenos Aires (1871)

We discuss the historic mortality record corresponding to the initial focus of the yellow fever epidemic outbreak registered in Buenos Aires during the year 1871 as compared to simulations of a stochastic population dynamics model. This model incorporates the biology of the urban vector of yellow fever, the mosquito Aedes aegypti, the stages of the disease in the human being as well as the spatial extension of the epidemic utbreak.After introducing the historical context and the restrictions it puts on  initial conditions and ecological parameters, we discuss the general features of the simulation and the dependence on initial conditions and available sites for breeding the vector. We discuss the sensitivity, to the free parameters, of statistical estimators such as: nal death toll, day of the year when the outbreak reached half the total mortality and the normalized daily mortality, showing some striking regularities. The model is precise and accurate enough to discuss the truthfulness of the  resently accepted historic discussions of the epidemic causes, showing that there are more likely scenarios for the historic facts.Fil: Fernández, María Laura. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina;Fil: Otero, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires; Argentina; Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina;Fil: Schweigmann, Nicolas Joaquin. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina;Fil: Solari, Hernan Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires; Argentina; Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina