Oxidation of a Tetrameric Nonphenolic Lignin Model Compound by Lignin Peroxidase

The present study maps the active site of lignin peroxidase in respect to substrate size using either fungal or recombinant wild type, as well as mutated, recombinant lignin peroxidases. A nonphenolic tetrameric lignin model was synthesized that contains beta-O-4 linkages. The fungal and recombinant wild type lignin peroxidase both oxidized the tetrameric model forming four products. The four products were identified by mass spectral analyses and compared with synthetic standards. They were identified as tetrameric, trimeric, dimeric, and monomeric carbonyl compounds. All four of these products were also formed from single turnover experiments. This indicates that lignin peroxidase is able to attack any of the C(alpha)-C(beta) linkages in the tetrameric compound and that the substrate-binding site is well exposed. Mutation of the recombinant lignin peroxidase (isozyme H8) in the heme access channel, which is relatively restricted and was previously proposed to be the veratryl alcohol-binding site (E146S), had little effect on the oxidation of the tetramer. In contrast, mutation of a Trp residue (W171S) in the alternate proposed substrate-binding site completely inhibited the oxidation of the tetrameric model. These results are consistent with lignin peroxidase having an exposed active site capable of directly interacting with the lignin polymer without the advent of low molecular weight mediators

Évolution postglaciaire des environnements travertineux provençaux et alpins : nouveau cadre chronologique, faciès et dynamiques morphosédimentaires

Le début du développement des systèmes travertineux holocènes du sud de la France était auparavant rattaché à la période du Préboréal, et l’accumulation carbonatée principale à « l’optimum bioclimatique atlantique ». La « mort » progressive puis le démantèlement des formations s’effectuaient entre le Néolithique et la Pax romana. De nouvelles recherches démontrent un démarrage beaucoup plus précoce de la travertinisation dès le Tardiglaciaire. L’accumulation carbonatée perdure au Néolithique et ne s’interrompt réellement qu’au Petit Age Glaciaire. De nouvelles séquences plus complètes montrent l’importance du contexte géomorphologique dans la conservation des données stratigraphiques et leur représentativité. L’organisation des différents cycles sédimentaires au sein des formations travertineuses est précisée. Une définition des faciès carbonatés au regard des différentes caractéristiques des milieux de sédimentation est proposée. Des analyses paléoécologiques soulignent le caractère sensible des ensembles travertineux en fonction des modifications du biotope. Dès le Néolithique Final, dans un contexte d’augmentation des occupations humaines, les séquences enregistrent une série de ruptures. Ces perturbations sont accompagnées de changements de faciès et d’ouvertures fortes du milieu végétal mais ne modifient pas la tendance générale à la croissance des édifices. Ce n’est qu’entre le XIIIème et le XVIIème siècle après Jésus Christ que l’on note l’interruption de l’accumulation des travertins et le démantèlement des formations. C’est également dans le même intervalle que s’instaure la dynamique majeure d’incision linéaire des talwegs encore effective aujourd’hui.The beginning of the Holocene travertine system development in Southern France was formerly attributed to the Preboreal period and the main carbonated accumulation to the « bioclimatic atlantic optimum ». The progressive decline and the dismantlement occurred between the Neolithic and the end of Roman times. New research has shown the beginning of the travertine system development in the Lateglacial period. The carbonated accumulation continued during the Neolithic and was only durably interrupted during the Little Ice Age. Newer complete stratigraphy has shown the importance of the geomorphological context in stratigraphical studies and their interpretation. The pattern of different sedimentary cycles within the travertinous formations became evident. Palaeo-ecological analyses undertaken have underlined the travertine sensitivity in accordance with biotope changes. Since the Final Neolithic, in the context of growing human occupation, ruptures in the travertine sequences have been recorded. These ruptures were accompanied by facies changing and strong vegetation opening in an ever growing travertine system. Between the XIIIth and the XVIIth century A.D., the decline and dismantlement of the travertine formations became noticeable. In the same way, the major final linear talweg incision was introduced in a morphogenic dynamic that is still happening today

You Say Bully, I Say Bullied: School Culture and Definitions of Bullying in Two Elementary Schools

Purpose This chapter examines the definitions of bullying used by students and adults in elementary schools and the effects that these definitions had within the broader school culture. Design/methodology/approach I combine interviews with 53 students and 10 adults and over 430 hours of participant observation with fifth grade students at two rural elementary schools. Findings Definitions of bullying held by those in these schools typically differed from those used by researchers. Even when individuals held definitions that were in line with those used by researchers, however, a focus on identifying bullies rather than on behaviors that fit definitions of bullying contributed to a school culture in which negative interactions were normalized and student reports of these behaviors were discouraged. Research limitations/implications This study is limited to two elementary schools in the rural Midwest and cannot be seen as representative of all schools. Support for my findings from other research combined with similar definitions and school cultures in both schools, however, suggest that these definitions and practices are part of a broader cultural context of bullying in the United States. Practical implications These findings suggest that schools might be better served by focusing less on labels like bully and more on particular behaviors that are to be taken seriously by students, teachers, staff members, and principals. Originality/value Although other researchers have studied definitions of bullying, none have combined these definitions with observational data on the broader school contexts in which those definitions are created and used

Integrated Multiscale Modeling of the Nervous System: Predicting Changes in Hippocampal Network Activity by a Positive AMPA Receptor Modulator

One of the fundamental characteristics of the brain is its hierarchical organization. Scales in both space and time that must be considered when integrating across hierarchies of the nervous system are sufficiently great as to have impeded the development of routine multilevel modeling methodologies. Complex molecular interactions at the level of receptors and channels regulate activity at the level of neurons; interactions between multiple populations of neurons ultimately give rise to complex neural systems function and behavior. This spatial complexity takes place in the context of a composite temporal integration of multiple, different events unfolding at the millisecond, second, minute, hour, and longer time scales. In this study, we present a multiscale modeling methodology that integrates synaptic models into single neuron, and multineuron, network models. We have applied this approach to the specific problem of how changes at the level of kinetic parameters of a receptor-channel model are translated into changes in the temporal firing pattern of a single neuron, and ultimately, changes in the spatiotemporal activity of a network of neurons. These results demonstrate how this powerful methodology can be applied to understand the effects of a given local process within multiple hierarchical levels of the nervous system

Simulation of Postsynaptic Glutamate Receptors Reveals Critical Features of Glutamatergic Transmission

Activation of several subtypes of glutamate receptors contributes to changes in postsynaptic calcium concentration at hippocampal synapses, resulting in various types of changes in synaptic strength. Thus, while activation of NMDA receptors has been shown to be critical for long-term potentiation (LTP) and long term depression (LTD) of synaptic transmission, activation of metabotropic glutamate receptors (mGluRs) has been linked to either LTP or LTD. While it is generally admitted that dynamic changes in postsynaptic calcium concentration represent the critical elements to determine the direction and amplitude of the changes in synaptic strength, it has been difficult to quantitatively estimate the relative contribution of the different types of glutamate receptors to these changes under different experimental conditions. Here we present a detailed model of a postsynaptic glutamatergic synapse that incorporates ionotropic and mGluR type I receptors, and we use this model to determine the role of the different receptors to the dynamics of postsynaptic calcium with different patterns of presynaptic activation. Our modeling framework includes glutamate vesicular release and diffusion in the cleft and a glutamate transporter that modulates extracellular glutamate concentration. Our results indicate that the contribution of mGluRs to changes in postsynaptic calcium concentration is minimal under basal stimulation conditions and becomes apparent only at high frequency of stimulation. Furthermore, the location of mGluRs in the postsynaptic membrane is also a critical factor, as activation of distant receptors contributes significantly less to calcium dynamics than more centrally located ones. These results confirm the important role of glutamate transporters and of the localization of mGluRs in postsynaptic sites in their signaling properties, and further strengthen the notion that mGluR activation significantly contributes to postsynaptic calcium dynamics only following high-frequency stimulation. They also provide a new tool to analyze the interactions between metabotropic and ionotropic glutamate receptors

Childhood in Sociology and Society: The US Perspective

The field of childhood studies in the US is comprised of cross-disciplinary researchers who theorize and conduct research on both children and youth. US sociologists who study childhood largely draw on the childhood literature published in English. This article focuses on American sociological contributions, but notes relevant contributions from non-American scholars published in English that have shaped and fueled American research. This article also profiles the institutional support of childhood research in the US, specifically outlining the activities of the ‘Children and Youth’ Section of the American Sociological Association (ASA), and assesses the contributions of this area of study for sociology as well as the implications for an interdisciplinary field.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Revisiting Family Leisure Research and Critical Reflections on the Future of Family-Centered Scholarship

In this special issue of Leisure Sciences, we examine the progress made and challenges ahead in research on leisure and families—20 years revisited. We consider what advancements have been made in family leisure research and potential new directions that family-centered scholars can look towards. We also consider the dominance of particular theoretical perspectives and methodological designs, and the limitations and consequences of such perspectives, to understand the complexities, diversity, and richness of the lived family experience. Emphasis is placed on the need for scholarship that explores diverse constructions of family and to provide a call to action for family-centered scholars to engage with broader global social issues