Temas y problemas en Antropología Social

El presente texto tiene que ver con el programa de la materia Antropología Cultural y Social dictada en la Facultad de Psicología de nuestra Universidad de La Plata. Sus diversos capítulos cubren varios temas del curso y fueron antecedidos por otros textos temáticos menos formalizados, editados anteriormente por la Cátedra. Nos ha parecido siempre importante adaptar los conocimientos de la Antropología en el marco de las Ciencias Sociales y de la Antropología Social en particular -que constituyen el eje de la materia- con la intención de conformar un eje didáctico de materiales que sean de fácil comprensión y permitan una lectura ulterior de mayor profundidad y continuidad, según el avance en la construcción de los conocimientos por parte de alumnos. Esto es importante por cuanto la disciplina constituye, de acuerdo al nuevo perfil del Plan de Estudios, uno de los cuatro pilares de conocimiento básico de la Psicología. En este sentido, se la considera un ámbito disciplinar académico destacado que aporta a los estudiantes herramientas conceptual-metodológicas básicas para la lectura y comprensión crítica del contexto sociohistórico, cultural y político en el que desarrollan sus prácticas actuales y su futura práctica profesional. Con una perspectiva más amplia se ha pensado, al redactar los capítulos, en el posible interés que puedan tener su lectura en el ámbito general de la Universidad.Facultad de Psicologí

Untersuchung der räumlich-zeitlichen Reizkodierung im bulbus olfactorius von Xenopus laevis Larven mittels schneller konfokaler Bildgebung

Der olfaktorische Bulb (OB) ist die einzige zentrale Verarbeitungsstation des Geruchssinns. Gerüche werden im OB durch räumlich-zeitliche Aktivierungsmuster kodiert, wobei sowohl die Identität der aktivierten Neurone, als auch deren zeitliche Aktivitätsmuster reizabhängig sind. Eine angemessene Untersuchung der Duftstoffkodierung ist daher auf die gleichzeitige Beobachtung einer großen Zahl von Neuronen mit hoher zeitlicher Auflösung angewiesen. Bisher gibt es nur sehr wenige Veröffentlichungen zur Erfassung und Quantifizierung der zeitlichen Abhängigkeiten dieser neuronalen Muster. Im Rahmen dieser Arbeit wurde ein schnelles konfokales Mikroskop entwickelt, gebaut, charakterisiert und im folgenden benutzt, um zeitliche Abhängigkeiten der neuronalen Aktivitätmuster, visualisiert durch den calciumsensitiven Fluoreszenzfarbstoff Fluo-4, zu bestimmen. Im speziellen wurden die Antwortlatenzen der stimulierten Aktivität von Mitralzellensembles im OB von Xenopus Larven untersucht. Zur Quantifizierung der Ähnlichkeit von Latenzmustern wurde ein neues Maß, der Inversionsindex, eingeführt. Mit Hilfe dieses Maßes konnte gezeigt werden, dass wiederholte Reizungen mit dem gleichen Duftstoff sehr reproduzierbare Latenzmuster hervorruft. Zudem wurde gezeigt, dass die Latenzmuster sehr informativ bezüglich der Geruchsidentität sind, und nur schwach von der Konzentration abhängen. Diese Beobachtungen legen nahe, dass das Latenzmuster der Mitralzellantworten ein wichtiger geruchsspezifischer Aspekt des olfaktorischen Kodes ist, welcher im OB generiert wird. Beziehungen zu anderen Eigenschaften des Geruchssinns und potentielle Dekodierungsstrategien werden diskutiert. Für eine zweite Anwendung des schnellen Mikroskops wurde spontane Aktivität im OB in Form von Zeitserien von Bildstapeln aufgenommen. Die verschiedenen Zeitverläufe der Aktivitätsmuster wurden genutzt, um funktionelle Karten zu erstellen, auf denen der dendritische Bau einer Vielzahl von Neuronen klar zu erkennen ist. Diese Methode liefert eine mehrfarbige und kontrastreiche Visualisierung des neuronalen Netzwerkes, illustriert am Beispiel der Mitralzellen im OB von Xenopus Larven. Da diese Methode sowohl funktionelle als auch strukturelle Informationen neuronaler Populationen liefert, eröffnet sie nie da gewesene Möglichkeiten zur Untersuchung neuronaler Netzwerke

Inactivation of competitive decay channels leads to enhanced coumarin photochemistry

In the development of photolabile protecting groups, it is of high interest to selectively modify photochemical properties with structural changes as simple as possible. In this work, knowledge of fluorophore optimization was adopted and used to design new coumarin- based photocages. Photolysis efficiency was selectively modulated by inactivating competitive decay channels, such as twisted intramolecular charge transfer (TICT) or hydrogen-bonding, and the photolytic release of the neurotransmitter serotonin was demonstrated. Structural modifications inspired by the fluorophore ATTO 390 led to a significant increase in the uncaging cross section that can be further improved by the simple addition of a double bond. Ultrafast transient absorption spectroscopy gave insights into the underlying solvent-dependent photophysical dynamics. The chromophores presented here are excellently suited as new photocages in the visible wavelength range due to their simple synthesis and their superior photochemical properties

Rapid Neuromodulation of Layer 1 Interneurons in Human Neocortex

Inhibitory interneurons govern virtually all computations in neocortical circuits and are in turn controlled by neuromodulation. While a detailed understanding of the distinct marker expression, physiology, and neuromodulator responses of different interneuron types exists for rodents and recent studies have highlighted the role of specific interneurons in converting rapid neuromodulatory signals into altered sensory processing during locomotion, attention, and associative learning, it remains little understood whether similar mechanisms exist in human neocortex. Here, we use whole-cell recordings combined with agonist application, transgenic mouse lines, in situ hybridization, and unbiased clustering to directly determine these features in human layer 1 interneurons (L1-INs). Our results indicate pronounced nicotinic recruitment of all L1-INs, whereas only a small subset co-expresses the ionotropic HTR3 receptor. In addition to human specializations, we observe two comparable physiologically and genetically distinct L1-IN types in both species, together indicating conserved rapid neuromodulation of human neocortical circuits through layer 1. Inhibitory interneurons govern the function of neural circuits and are in turn controlled by neuromodulation. Here, Poorthuis et al. demonstrate that these mechanisms are conserved in layer 1 of human neocortex, where interneurons express nicotinic acetylcholine receptors that mediate fast responses and thereby enable reconfiguration of circuit function at rapid timescales

Rapid neuromodulation of ayer 1 interneurons in human neocortex

Inhibitory interneurons govern virtually all computations in neocortical circuits and are in turn controlled by neuromodulation. While a detailed understanding of the distinct marker expression, physiology, and neuromodulator responses of different interneuron types exists for rodents and recent studies have highlighted the role of specific interneurons in converting rapid neuromodulatory signals into altered sensory processing during locomotion, attention, and associative learning, it remains little understood whether similar mechanisms exist in human neocortex. Here, we use whole-cell recordings combined with agonist application, transgenic mouse lines, in situ hybridization, and unbiased clustering to directly determine these features in human layer 1 interneurons (L1-INs). Our results indicate pronounced nicotinic recruitment of all L1-INs, whereas only a small subset co-expresses the ionotropic HTR3 receptor. In addition to human specializations, we observe two comparable physiologically and genetically distinct L1-IN types in both species, together indicating conserved rapid neuromodulation of human neocortical circuits through layer 1

Adherens junction assembly of WT-N-cadherin and its mutants.

<p>(<b>A</b>) Expression pattern of WT-N-cadherin and its mutants in L cells. Confocal images of control L cells or L cell lines stably expressing the N-cadherin-Venus WT and its mutant forms. Membrane fluorescence can be seen for all mutants demonstrating plasma membrane localization and junction formation for all mutants. Top panel: Venus channel, bottom: Overlay of DIC and Venus channel. (<b>B</b>) Example images of junction assembly. Images were taken for all mutants at time 0, 1 and 2 h after imaging commenced. Established junctions can be seen for WT and R14E at 1 h and for all mutants at 2 h (arrowheads). (<b>C</b>) Quantification of junction assembly. The number of junctions formed in a field of view (FOV) was counted over time and plotted. The graph shows that the rate of junction formation for WT is fastest followed by R14E. The number of junctions for all mutants was compared to WT at 60 and 120 min. R14E was not significantly different while W2A and V81D/V174D had significantly lower number of junctions at 60 min and 120 min (n = 3 for all mutants, two-tailed unpaired t-test, P < 0.05). (<b>D</b>) Quantification of junction lifetime. The junction lifetime for junctions present in a FOV was calculated between 60 and 120 min. On average WT junctions were present for 82% of time, R14E = 75%, W2A and V81D/V174D had significantly lower average junction lifetimes of 39% and 6%, respectively, thus confirming that mutating the <i>cis</i> interface leads to highly volatile junctions (Mann-Whitney U test, P < 0.0001). Error bars indicate SD. n(WT) = 15, n(W2A) = 17, n(R14E) = 12, n(V81D/V174D) = 15 junctions. Scale bar (A) and (B) = 10 µm.</p

Influence of Ca²⁺-chelation on the individual binding interfaces of N-cadherin.

<p>(<b>A</b>) Disruption of the <i>trans</i> interaction of N-cadherin by BAPTA. Upon disruption of this interaction the fluorophores move further apart, reducing FRET. Examples for ratiometric FRET measurements of the WT (<b>B</b>), W2A (<b>C</b>), R14E (<b>D</b>) and V81D/V174D (<b>E</b>) before and after Ca²⁺-chelation are shown. After baseline recording, the Ca²⁺-chelator BAPTA (20 mM final concentration) was added. The fluorescence of the FRET acceptor Venus (yellow) and the donor Cerulean (cyan) as well as the ratio of the two (blue) are shown. (<b>F</b>) The quantification of the effect of BAPTA on all mutants is shown. While the mutants W2A and V81D/V174D showed a significantly higher decrease of the FRET signal due to Ca²⁺-chelation than the WT, no Ca²⁺-sensitivity was observed for the X-dimer mutant R14E. This confirms the hypothesis that the X-dimer is a Ca²⁺-dependent intermediate step in the formation of the strand-swapped dimer. n(WT) = 8, n(W2A) = 8, n(R14E) = 9, n(V81D/V174D) = 7 junctions. Statistics were conducted using either paired or unpaired t-test.</p

Analysis of the <i>trans</i> interaction of N-cadherin in living cells by acceptor bleach FRET experiments.

<p>(<b>A</b>) Scheme depicting the insertion of Venus (FRET acceptor) and Cerulean (FRET donor) and the interactions of cadherin molecules across a cellular junction. If the two opposing molecules interact with each other in <i>trans</i>, the donor and acceptor are within the FRET distance, resulting in an increased acceptor emission and a donor quenching (upper panel). Upon bleaching of the FRET acceptor, the FRET donor is dequenched, leading to an increase in its fluorescence (lower panel). (<b>B</b>) Example for an acceptor bleach experiment with COS7-cells expressing either N-cadherin-Venus or –Cerulean. The upper two images show the Venus-channel before and after bleaching of the Venus signal in the junction (boxed region). The Cerulean channel is depicted in the lower two images. Bleaching of the Venus fluorescence leads to a dequenching of the FRET donor Cerulean, which can be observed in the lower two images. An enlargement of the junction (boxed region) is shown next to the images. (<b>C</b>) Quantitative comparison of the acceptor bleach experiments for N-cadherin-WT and its mutants. The bars represent the mean ± SEM. The mean of the W2A (n = 32) is significantly increased compared to the WT (n = 35, p < 0.0001, Mann Whitney, ***), while the mean of the mutant R14E was significantly lower (n = 29, p=0.0001, two-tailed unpaired t-test , ***). The <i>cis</i> mutant V81D/V174D (n = 33) does not show a significant difference (p=0.1158, two-tailed unpaired t-test). Scale bar = 20 µm.</p

Junction assembly in 3D cell cultures is severely impaired for W2A mutant.

<p>(<b>A</b>) Example images of spheroid formation at various time points for N-cadherin-WT and its mutants. Scale bar = 50 µm. (<b>B</b>) Quantification of spheroid formation. Spheroid roundness was measured over time. At 3 h (inset) the roundness of all mutants was significantly lower than WT. W2A and V81D/V174D had significantly lower roundness even after 20 h and 48 h of spheroid formation (two-tailed unpaired, t-test, P < 0.05). n(WT) = 9, n(W2A) = 9, n(R14E) = 8, n(V81D/V174D) = 8 spheroids. (<b>C</b>) Ca²⁺-dependence of spheroid formation. Spheroid formation was monitored in medium with different Ca²⁺-concentrations. The roundness was measured at 20 h after spheroid formation was started. WT-N-cadherin shows a significant increase in roundness with only a slight increase in Ca²⁺-concentration (0.4 mM) and continued to gradually increase. W2A did not show any significant change in roundness regardless of the Ca²⁺-concentration indicating that W2A junctions cannot be rescued with elevated Ca²⁺-concentration. Both R14E and V81D/V174D needed twice the Ca²⁺-concentration (0.8 mM) to show a significant increase in roundness emphasizing that in 3D, loss of either X-dimer or the <i>cis</i> interface leads to a decreased Ca²⁺-sensitivity in junction assembly (n for each condition ≥ 4, Mann-Whitney U test, p < 0.05). Error bars indicate SEM. </p