The influence of pool volume and summer desiccation on the production of the resting and dispersal stage in a Daphnia metapopulation

Dispersal is a key process in metapopulations, as migrants genetically connect populations and enable the colonization of empty habitat patches. Sub-populations may differ in their numerical contribution of migrants within a metapopulation. This has strong implications on evolutionary and ecological dynamics and has led to two different hypotheses about the Daphnia metapopulation studied here: the assessment by some authors is that sub-populations contribute equally to the production of migrants, while others have postulated long-lived core populations in large "mainland” habitat patches as the dominant source of migrants. We have studied the resting and dispersal stage (ephippium) in a natural Daphnia metapopulation and in mesocosm experiments, and tested for effects of habitat size and summer desiccation. We found that a 1000-fold increase in rock pool volume resulted on average in only in a 2.8-fold increase in ephippium production. Mesocosm experiments confirmed these results: a 1000-fold increase of the mesocosms' volume resulted in a 7.2-fold increase in ephippium production. Additionally, we showed that ephippium production did not depend on the initial population size. Thus, populations in small pools may contribute only marginal fewer potential migrants in the whole metapopulation than populations in large pools. In a second mesocosm experiment we found that summer desiccation, which is a typical occurrence in small pools, is not detrimental for the populations. Daphnia hatched out of ephippia that were produced earlier within the same season and built up viable populations again. The substantial production of ephippia by populations in small pools suggests that these populations might be important for both the dynamics and global stability of metapopulation

Intraventricular catheter placement by electromagnetic navigation safely applied in a paediatric major head injury patient

Introduction: In the management of severe head injuries, the use of intraventricular catheters for intracranial pressure (ICP) monitoring and the option of cerebrospinal fluid drainage is gold standard. In children and adolescents, the insertion of a cannula in a compressed ventricle in case of elevated intracranial pressure is difficult; therefore, a pressure sensor is placed more often intraparenchymal as an alternative option. Discussion: In cases of persistent elevated ICP despite maximal brain pressure management, the use of an intraventricular monitoring device with the possibility of cerebrospinal fluid drainage is favourable. We present the method of intracranial catheter placement by means of an electromagnetic navigation techniqu

Headwaters are critical reservoirs of microbial diversity for fluvial networks

Streams and rivers form conspicuous networks on the Earth and are among nature's most effective integrators. Their dendritic structure reaches into the terrestrial landscape and accumulates water and sediment en route from abundant headwater streams to a single river mouth. The prevailing view over the last decades has been that biological diversity also accumulates downstream. Here, we show that this pattern does not hold for fluvial biofilms, which are the dominant mode of microbial life in streams and rivers and which fulfil critical ecosystem functions therein. Using 454 pyrosequencing on benthic biofilms from 114 streams, we found that microbial diversity decreased from headwaters downstream and especially at confluences. We suggest that the local environment and biotic interactions may modify the influence of metacommunity connectivity on local biofilm biodiversity throughout the network. In addition, there was a high degree of variability in species composition among headwater streams that could not be explained by geographical distance between catchments. This suggests that the dendritic nature of fluvial networks constrains the distributional patterns of microbial diversity similar to that of animals. Our observations highlight the contributions that headwaters make in the maintenance of microbial biodiversity in fluvial networks

Dispersal in dendritic networks: Ecological consequences on the spatial distribution of population densities

1. Understanding the consequences of spatial structure on ecological dynamics is a central theme in ecology. Recently, research has recognised the relevance of river and river-analogue network structures, because these systems are not only highly diverse but also rapidly changing due to habitat modifications or species invasions. 2. Much of the previous work on ecological and evolutionary dynamics in metapop- ulations and metacommunities in dendritic river networks has been either using comparative approaches or was purely theoretical. However, the use of micro- cosm experiments provides the unique opportunity to study large-scale questions in a causal and experimental framework. 3. We conducted replicated microcosm experiments, in which we manipulated the spatially explicit network configuration of a landscape and addressed how linear versus dendritic connectivity affects population dynamics, specifically the spatial distribution of population densities, and movement behaviour of the protist model organism Tetrahymena pyriformis. We tracked population densities and individual-level movement behaviour of thousands of individuals over time. 4. At the end of the experiment, we found more variable population densities between patches in dendritic networks compared to linear networks, as pre- dicted by theory. Specifically, in dendritic networks, population densities were higher at nodes that connected to headwaters compared to the headwaters themselves and to more central nodes in the network. These differences follow theoretical predictions and emerged from the different network topologies per se. These differences in population densities emerged despite weakly density- dependent movement. 5. We show that differences in network structure alone can cause characteristic spatial variation in population densities. While such differences have been postu- lated by theoretical work and are the underlying precondition for differential dis- persal evolution in heterogeneous networks, our results may be the first experimental demonstration thereof. Furthermore, these population-level dynam- ics may affect extinction risks and can upscale to previously shown metacommu- nity level diversity dynamics. Given that many species in natural river systems exhibit strong spatiotemporal patterns in population densities, our work suggests that abundance patterns should not only be addressed from a local environmental perspective, but may be the outcome of processes that are inher- ently driven by the respective habitat network structure

Conservative management of significant epidural haematomas in children

Objective: A significant epidural haematoma (EDH) is generally treated by craniotomy and evacuation. This is a report of conservative management following an EDH on computerized tomography (CT) in a paediatric population. The authors examined whether conservative treatment of radiologically significant EDH is a successful and safe therapeutic option. Methods: Retrospective data were collected from charts of patients with conservatively treated EDH in the Department of Surgery of the University Children's Hospital Zurich between September 1993 and January 2004. Included were patients without focal neurological deficits, with a Glasgow Coma Scale (GCS) of 15 and an initial CT demonstrating an EDH with a minimal thickness of 1cm. Mild clinical symptoms of raised intracranial pressure such as headache, nausea or vomiting were treated symptomatically. Follow-up included a standardized interview, a neuropaediatric examination and CT. Results: Thirteen children with EDH had successful conservative management. Only one 12-year-old female patient with a delayed diagnosed frontal EDH required surgical intervention 24h after admission and 5 days after the accident. Clinical follow-up showed patients without neurological deficits, a Glasgow Outcome Scale of 5 and no post-traumatic sequelae over an average of 4 4/12 years (range 4 months to 10 4/12 years). Follow-up CT showed complete resolution of the EDH within 2 to 3 months. Conclusions: Our results demonstrate that significant EDH can be treated non-operatively in neurologically normal children. We recommend that such treatment be performed in specialised paediatric centres under adequate neurological observation since prompt emergency operation in case of neurological deterioration should be provide

Lack of benefit of preoperative antimicrobial prophylaxis in children with acute appendicitis: a prospective cohort study

Background: Preoperative antimicrobial prophylaxis is widely used in pediatric patients undergoing appendectomy, but evidence showing a reduction of postoperative infectious complications is lacking. Methods: A prospective consecutive cohort study on changing from preoperative antimicrobial prophylaxis to no prophylaxis in children undergoing urgent appendectomy was undertaken. The impact of this change in management on postoperative infectious complications was evaluated by comparing the outcome in 100 patients receiving (group A) and a subsequent 100 patients not receiving prophylaxis (group B), which consisted of a preoperative single dose of intravenous metronidazole (10mg/kg body weight). Results: Histology confirmed acute appendicitis in 92 patients of group A and 95 patients of group B. In patients with histological simple appendicitis, postoperative infectious complications were noted in 2 (3.0%) of 69 patients from group A and in none of 70 patients from group B, and in patients with histological perforated appendicitis in 5 (22%) of 23 and 4 (16%) of 25 patients from groups A and B, respectively. Postoperative infectious complications were more frequent (p<0.05) in perforated than in simple appendicitis. These infectious complications included in simple appendicitis two wound infections in group A, and in perforated appendicitis four intraabdominal abscesses and one wound infection in group A and two intraabdominal abscesses and two wound infections in group B. Conclusion: Postoperative infectious complications were seen more often in patients with perforated appendicitis than in those with simple appendicitis. Preoperative antimicrobial prophylaxis with metronidazole did not reduce the rates of postoperative infectious complication

Third ventriculostomy in a single pediatric surgical unit

Purpose: Endoscopic third ventriculostomy (ETV) is a successful method of treatment for obstructive hydrocephalus that has become popular over the last 20years. The purpose of this paper is to study the outcome of infants with obstructive hydrocephalus treated by ETV by a single surgeon and to evaluate the safety, reliability, and efficacy of this treatment. Methods: All data were collected retrospectively. Between July 1999 and June 2005, 14 children underwent an ETV. In one child, a second ETV was performed. The age of the eight female and six male patients at the time of ETV ranged from less than 1month up to 13years and 11months. The indication for an ETV was an obstructive hydrocephalus. Median follow-up period was 5years and 9months. The need of a further operation after ETV was defined as a failure of ETV. Results: In six patients, the first ETV was successful. In the remaining eight patients, there was a need for further treatment (ventriculoperitoneal shunt). Although the follow-up shunt failed in one patient, he was successfully treated by a second ETV. Conclusion: Our study suggests that ETV can be successfully done in a small pediatric unit, but with a lower success rate because of small caseload, and therefore, lower experience and routine of the surgeon. Therefore, we propose a centralization of patients to obtain a higher number of cases. We confirm that ETV is a safe, reliable, and efficient method with a better outcome in children than infant

Der Kalte Krieg in den Schweizer Schulen: eine kulturgeschichtliche Analyse

Die gesellschaftlichen Ansprüche an die Schule sind heterogen. Während des Kalten Krieges herrschte jedoch ein bemerkenswerter Konsens darüber, dass die Institution und ihre Lehrpersonen der «Weltgefahr des Kommunismus» aktiv entgegentreten müssten. Dazu gehörten auch das Einstehen für die Geistige und die Bejahung der militärischen Landesverteidigung. Der Geschichtsunterricht und die staatsbürgerliche Erziehung galten als besonders wertvoll, um die nachwachsende Generation für «vaterländischen Werte» wie Solidarität, Freiheit, Neutralität oder Demokratie zu sensibilisieren und die Abwehrbereitschaft gegenüber dem Kommunismus zu stärken. Im geistigen Klima des Kalten Krieges wurde von den Lehrpersonen eine loyale Einstellung zum Staat erwartet. Linke, Militärdienstverweigerer oder als zu «progressiv» eingestufte Lehrkräfte konnten unter Druck geraten und sogar ihre Stelle verlieren. Die vorliegende Dissertation geht mittels einer kulturgeschichtlichen Analyse der Frage nach, wie sich Wahrnehmung und Deutung des Kalten Krieges in den Diskursen über die institutionellen Aufgaben der Schule, im Nachdenken über das Lehren und Lernen sowie in der Debatte über die Auswahl der Lehrpersonen widerspiegelten. Weiter zeigt die Studie, wie der bipolare Konflikt selbst gedeutet wurde und wie sich die Narrative, die im Unterricht vermittelt wurden, im Laufe des Kalten Krieges veränderten

Friends’ Responses to Children’s Disclosure of an Achievement-Related Success: An Observational Study

This study examined social support processes in the context of positive events. The conversations of fourth-grade through sixth-grade focal children and their friends (N = 116) were observed after focal children outperformed their friend on an achievement-related task. Changes in focal children’s performance-related positive affect from prediscussion to postdiscussion were predicted from the features of these conversations. Focal children reported more positive affect when friends engaged in relatively high levels of help seeking and relatively low levels of off-task talk. Friends’ responses were, in turn, predicted by friendship quality as rated by focal children and friends. Results are discussed in light of the changes in school adjustment and peer relationships that many children experience as they approach adolescence