Modest Interference with Actin Dynamics in Primary T Cell Activation by Antigen Presenting Cells Preferentially Affects Lamellal Signaling

Dynamic subcellular distributions of signaling system components are critical regulators of cellular signal transduction through their control of molecular interactions. Understanding how signaling activity depends on such distributions and the cellular structures driving them is required for comprehensive insight into signal transduction. In the activation of primary murine T cells by antigen presenting cells (APC) signaling intermediates associate with various subcellular structures, prominently a transient, wide, and actin-associated lamellum extending from an interdigitated T cell:APC interface several micrometers into the T cell. While actin dynamics are well established as general regulators of cellular organization, their role in controlling signaling organization in primary T cell:APC couples and the specific cellular structures driving it is unresolved. Using modest interference with actin dynamics with a low concentration of Jasplakinolide as corroborated by costimulation blockade we show that T cell actin preferentially controls lamellal signaling localization and activity leading downstream to calcium signaling. Lamellal localization repeatedly related to efficient T cell function. This suggests that the transient lamellal actin matrix regulates T cell signaling associations that facilitate T cell activation.     

Single Session Imaging of Cerebellum at 7 Tesla: Obtaining Structure and Function of Multiple Motor Subsystems in Individual Subjects

The recent increase in the use of high field MR systems is accompanied by a demand for acquisition techniques and coil systems that can take advantage of increased power and accuracy without being susceptible to increased noise. Physical location and anatomical complexity of targeted regions must be considered when attempting to image deeper structures with small nuclei and/or complex cytoarchitechtonics (i.e. small microvasculature and deep nuclei), such as the brainstem and the cerebellum (Cb). Once these obstacles are overcome, the concomitant increase in signal strength at higher field strength should allow for faster acquisition of MR images. Here we show that it is technically feasible to quickly and accurately detect blood oxygen level dependent (BOLD) signal changes and obtain anatomical images of Cb at high spatial resolutions in individual subjects at 7 Tesla in a single one-hour session. Images were obtained using two high-density multi-element surface coils (32 channels in total) placed beneath the head at the level of Cb, two channel transmission, and three-dimensional sensitivity encoded (3D, SENSE) acquisitions to investigate sensorimotor activations in Cb. Two classic sensorimotor tasks were used to detect Cb activations. BOLD signal changes during motor activity resulted in concentrated clusters of activity within the Cb lobules associated with each task, observed consistently and independently in each subject: Oculomotor vermis (VI/VII) and CrusI/II for pro- and anti-saccades; ipsilateral hemispheres IV-VI for finger tapping; and topographical separation of eye- and hand- activations in hemispheres VI and VIIb/VIII. Though fast temporal resolution was not attempted here, these functional patches of highly specific BOLD signal changes may reflect small-scale shunting of blood in the microvasculature of Cb. The observed improvements in acquisition time and signal detection are ideal for individualized investigations such as differentiation of functional zones prior to surgery.     

Extracellular Dopamine, Norepinephrine, and Serotonin in the Nucleus Accumbens of Freely Moving Rats During Intracerebral Dialysis with Cocaine and Other Monoamine Uptake Blockers

Abstract: Monoamine-uptake blockers were applied focally (0.1–1,000 µ M ) through a dialysis probe in the nucleus accumbens of freely moving rats, and the extracellular concentrations of dopamine, norepinephrine, and serotonin were measured. The selective dopamine-uptake blocker GBR 12935 increased dopamine preferentially with only a small effect on norepinephrine, whereas the selective serotonin-uptake blocker fluoxetine increased serotonin output preferentially. In contrast, the selective norepinephrine-uptake blockers desipramine and nisoxetine enhanced not only norepinephrine, but also serotonin and dopamine appreciably. Cocaine increased all three amines with the greatest effects on dopamine and serotonin. As in our previous study on the ventral tegmental area, there was a positive association between dopamine and norepinephrine output when all blocker data were taken together. The present results suggest a contribution of the increase in norepinephrine, but not serotonin, to the enhancement of dopamine after cocaine applied focally in the nucleus accumbens.     

Asymmetric fusion between protoplasts of tomato (Lycopersicon esculentum Mill.) and gamma-irradiated protoplasts of potato (Solanum tuberosum L.): the effects of gamma irradiation

This paper describes the aggregation of nuclei in heterokaryons of tomato and unirradiated or irradiated potato protoplasts and the effects of gamma irradiation of potato and tomato protoplasts on single- and double-stranded DNA fragmentation, DNA repair and DNA synthesis as revealed by alkaline and pulsed field gel electrophoresis and an immunocytochemical technique. The prospects for obtaining highly asymmetric somatic hybrids of tomato and gamma-irradiated potato are discussed.     

Where ichthyofaunal provinces meet: the fish fauna of the Lake Edward system,East Africa

Based on literature, museum collections and three recent expeditions, an annotated species list of the Lake Edward, East Africa, drainage system is presented, excluding the endemic haplochromines. A total of 34 non-Haplochromis species belonging to 10 families and 21 genera are recorded from the system. Three of these are endemic and two others have been introduced in the region. Six species are new records for the Lake Edward system. A species accumulation curve indicates that we probably covered most of the non-Haplochromis species in the area sampled during the recent expeditions, but undetected species might still be present in the Congolese part of the system, which is poorly sampled. A comparison of the species list with those of neighbouring basins confirmed the placement of the Lake Edward system within the east-coast ichthyofaunal province.     

Identifying Optimal Models to Represent Biochemical Systems

Biochemical systems involving a high number of components with intricate interactions often lead to complex models containing a large number of parameters. Although a large model could describe in detail the mechanisms that underlie the system, its very large size may hinder us in understanding the key elements of the system. Also in terms of parameter identification, large models are often problematic. Therefore, a reduced model may be preferred to represent the system. Yet, in order to efficaciously replace the large model, the reduced model should have the same ability as the large model to produce reliable predictions for a broad set of testable experimental conditions. We present a novel method to extract an “optimal” reduced model from a large model to represent biochemical systems by combining a reduction method and a model discrimination method. The former assures that the reduced model contains only those components that are important to produce the dynamics observed in given experiments, whereas the latter ensures that the reduced model gives a good prediction for any feasible experimental conditions that are relevant to answer questions at hand. These two techniques are applied iteratively. The method reveals the biological core of a model mathematically, indicating the processes that are likely to be responsible for certain behavior. We demonstrate the algorithm on two realistic model examples. We show that in both cases the core is substantially smaller than the full model.     

Epsilonematidae (Nematoda) from a cold-water coral environment in the Porcupine Seabight, with a discussion on the status of the genus Metaglochinema Gourbault & Decraemer, 1986

Thirteen species of nematodes from the family Epsilonematidae Steiner, 1927 were found to be associated with a cold-water coral reef in the Porcupine Seabight. Among them, four species were already known from various locations such as Chile and Papua New Guinea. Three new species are described here: Glochinema trispinatumsp. n. is recognized by three dorsal thorns in the pharyngeal region. This species was also recovered from the Antarctic shelf. Epsilonema multispiralumsp. n. is characterised by a multispiral amphid consisting of 3.25 coils. Bathyepsilonema lopheliaesp. n. is characterised by its body length, the position and relative width of the amphids and the nature of the cuticular ornamentation. Within the subfamily Glochinematinae Lorenzen, 1974, the number and arrangement of ambulatory setae is considered not to be of diagnostic importance. The former species Metaglochinema strigosumGourbault & Decraemer, 1993 is therefore classified under the genus GlochinemaLorenzen, 1974. The original genus diagnosis of Metaglochinema, now a monotypic genus, is adjusted. The geographic distribution of epsilonematid nematodes is briefly discussed.     

The alkane oxidation system of Pseudomonas oleovorans: induction of the alk genes in Escherichia coli W3110(pGEc47) affects membrane biogenesis and results in overexpression of alkane hydroxylase in a distinct cytoplasmic membrane subtraction

The alkane hydroxylase system of Pseudomonas oleovorans, which catalyses the initial oxidation of aliphatic substrates, is encoded by three genes. One of the gene products, the alkane hydroxyiase AlkB, is an integral cytoplasmic membrane protein. Induction leads to the synthesis of 1.5–2% AlkB relative to the total cell protein, both in P. oleovorans and in recombinant Escherichia coli DH1. We present a study on the Induction and localization of the alkane hydroxylase in E. coli W3110, which appears to be an interesting host strain because it permits expression levels of AlkB of up to 10–15% of the total cell protein. This expression level had negative effects on cell growth. The phospholipid content of such cells was about threefold higher than that of wild-type W3110. Freeze-fracture electron microscopy showed that induction of the alk genes led to the appearance of membrane vesicles in the cytoplasm; these occurred much more frequently in cells expressing alkB than in the negative control, which contained all of the alk genes except for alkB. Isolation and separation of the membranes of cells expressing alkB by density gradient centrifugation showed the customary cytoplasmic and outer membranes, as well as a low-density membrane fraction. This additional fraction was highly enriched in AlkB, as shown both by SDS-PAGE and enzyme activity measurements. A typical cytoplasmic membrane protein, NADH oxidase, was absent from the low-density membrane fraction, alkB expression in W3110 changed the composition of the phospholipid headgroup in the membrane, as well as the fatty acid composition of the membrane. The major changes occurred in the unsaturated fatty acids: C_16:1 and C_18:1 increased at the expense of C_17:0cyc and C_19:0cyc*     

Social Network Analysis Predicts Health Behaviours and Self-Reported Health in African Villages

The provision of healthcare in rural African communities is a highly complex and largely unsolved problem. Two main difficulties are the identification of individuals that are most likely affected by disease and the prediction of responses to health interventions. Social networks have been shown to capture health outcomes in a variety of contexts. Yet, it is an open question as to what extent social network analysis can identify and distinguish among households that are most likely to report poor health and those most likely to respond to positive behavioural influences. We use data from seven highly remote, post-conflict villages in Liberia and compare two prominent network measures: in-degree and betweenness. We define in-degree as the frequency in which members from one household are named by another household as a friends. Betweenness is defined as the proportion of shortest friendship paths between any two households in a network that traverses a particular household. We find that in-degree explains the number of ill family members, whereas betweenness explains engagement in preventative health. In-degree and betweenness independently explained self-reported health and behaviour, respectively. Further, we find that betweenness predicts susceptibility to, instead of influence over, good health behaviours. The results suggest that targeting households based on network measures rather than health status may be effective for promoting the uptake of health interventions in rural poor villages.