282 research outputs found
Evidence for a novel feedback loop in the Hedgehog pathway involving the seven transmembranedomain protein Smoothened and the kinase Fused.
International audienceHedgehog (HH) is a major secreted morphogen involved in development, stem cell maintenance and oncogenesis[1, 2].In Drosophila wing imaginal discs, HH produced in the posterior compartment diffuses into the anterior compartment to control target gene transcription via the transcription factor Cubitus interruptus (CI). The first steps in reception and transduction of the HH signal are mediated by its receptor Patched (PTC)[3] and the seven-transmembranedomain protein Smoothened (SMO) [4, 5]. PTC and HH control SMOby regulating its stability, trafficking and phosphorylation (for review see [6]). SMO interacts directly with the Ser-Thr protein kinase Fused (FU) and the kinesin-related protein Costal2 (COS2), which interact with each other and with CI in an intracellular âHedgehog transducing complexâ[7-9].We show here that HH induces FUtargeting to the plasma membrane in a SMO-dependent fashion and that,reciprocally,FUcontrols SMO stability and phosphorylation. FUanchorage to the membrane is sufficient to make it a potent SMO-dependent, PTC-resistant, activator of the pathway. These findings reveal a novel positive-feedback loop in HH transduction and are consistent with a model in which FU and SMO, by mutually enhancing each other's activities, sustain high levels of signalingand render the pathway robust to PTClevel fluctuations
An investigation of data compression techniques for hyperspectral core imager data
We investigate algorithms for tractable analysis of real hyperspectral image data from core samples provided by AngloGold Ashanti. In particular, we investigate feature extraction, non-linear dimension reduction using diffusion maps and wavelet approximation methods on our data
Hedgehog signal transduction proteins: contacts of the Fused kinase and Ci transcription factor with the Kinesin-related protein Costal2
BACKGROUND: Hedgehog signaling proteins play important roles in development by controlling growth and patterning in various animals including Drosophila and mammals. Hedgehog signaling triggers changes in responsive cells through a novel transduction mechanism that ultimately controls the transcription of specific target genes via the activity of zinc finger transcription factors of the Cubitus interruptus /GLI family. In flies, key Hedgehog signal transduction components have been identified including the kinesin-related protein Costal2, the serinethreonine kinase Fused, and the PEST-containing protein Suppressor of Fused. These proteins control Cubitus interruptus cleavage, nucleo-cytoplasmic localization and activation. In fly embryos, Costal2, Fused, Suppressor of Fused and Cubitus interruptus are associated in at least one cytoplasmic complex, which interacts with the microtubules in a Hedgehog-dependent manner. RESULTS: Here we identified and mapped direct interactions between Cos2, Fu, and Ci using an in vitro affinity assay and the yeast two-hybrid system. CONCLUSIONS: Our results provide new insights into the possible mechanism of the cytosolic steps of Hedgehog transduction
Unusual Presentation of Pulmonary Hydatidosis Mimicking Thoracic Malignancy in a Paediatric South African Patient
In this case report, an illustrative case of pulmonary hydatidosis in a young South African girl is presented. The acute symptomatology, rapidly worsening clinical condition and the extremely atypical appearance of the hydatid cysts on imaging were initially misleading and raised suspicion for malignant disease
Intramedullary spinal masses : a pictorial essay
CITATION: Bezuidenhout, A.F., Lipsitz, J.M., Du Plessis, A. 2014. Intramedullary spinal masses: a pictorial essay. South African Journal of Radiology, 18(1):1-7, doi: 10.4102/sajr.v18i1.602.The original publication is available at http://www.sajr.org.za/index.php/sajrThis pictorial essay provides a classification system for the most common intramedullary spinal masses and describes distinguishing imaging features that will aid the radiologist in providing a relevant differential diagnosis to guide further management.http://www.sajr.org.za/index.php/sajr/article/view/602Publisher's versio
Submesoscale Fronts in the Antarctic Marginal Ice Zone and Their Response to Wind Forcing
Submesoscale flows in the ocean are energetic motions, O(1â10 km), that influence stratification and the distributions of properties, such as heat and carbon. They are believed to play an important role in seaâiceâimpacted oceans by modulating airâseaâice fluxes and seaâice extent. The intensity of these flows and their response to wind forcing are unobserved in the seaâice regions of the Southern Ocean. We present the first submesoscaleâresolving observations in the Antarctic marginal ice zone (MIZ) collected by surface and underwater autonomous vehicles, for >3 months in austral summer. We observe salinityâdominated lateral density fronts occurring at subâkilometer scales. Surface winds are shown to modify the magnitude of the mixedâlayer density fronts, revealing strongly coupled atmosphereâocean processes. We posture that these windâfront interactions occur as a continuous interplay between front slumping and vertical mixing, which leads to the dispersion of submesoscale fronts. Such processes are expected to be ubiquitous in the Southern Ocean MIZ
Submesoscale Fronts in the Antarctic Marginal Ice Zone and Their Response to Wind Forcing
Submesoscale flows in the ocean are energetic motions, O(1â10 km), that influence stratification and the distributions of properties, such as heat and carbon. They are believed to play an important role in seaâiceâimpacted oceans by modulating airâseaâice fluxes and seaâice extent. The intensity of these flows and their response to wind forcing are unobserved in the seaâice regions of the Southern Ocean. We present the first submesoscaleâresolving observations in the Antarctic marginal ice zone (MIZ) collected by surface and underwater autonomous vehicles, for >3 months in austral summer. We observe salinityâdominated lateral density fronts occurring at subâkilometer scales. Surface winds are shown to modify the magnitude of the mixedâlayer density fronts, revealing strongly coupled atmosphereâocean processes. We posture that these windâfront interactions occur as a continuous interplay between front slumping and vertical mixing, which leads to the dispersion of submesoscale fronts. Such processes are expected to be ubiquitous in the Southern Ocean MIZ
The use of confocal microscopy in quantifying changes in membrane potential
Monitoring the plasma membrane potential and its changes can be a time consuming and challenging task especially when conventional electrophysiological techniques are used. The use of potentiometric fluorophores, namely tetramethylrhodamine methylester (TMRM), and digital imaging devices (laser scanning confocal microscopy) provides reliable and time efficient method. Two scorpion pore-forming peptides, namely PP and OP1, were used as a tool to induce depolarization of the plasma membrane potential of neuroblastoma cell line and cardiac myocytes. Alternative methods for the neuroblastoma cells and cardiac myocytes were used. Depolarization of the neuroblastoma cells was calibrated with 140 mM KCl solution with 1 ”M valinomycin, after which intensity readers were substituted in the Nernst equation for quantification. Calibration of the alternative method used of the cardiac myocytes' plasma membrane potential changes was calibrated with the use of 5, 20, 40, and 80 mM KCl solutions with 1 ”M valinomycin. A calibration curve was then constructed from which plasma membrane potential could be calculated
Meningitis-associated pneumococcal serotype 8, ST 53, strain is hypervirulent in a rat model and has non-haemolytic pneumolysin which can be attenuated by liposomes
Introduction: Streptococcus pneumoniae bacteria cause life-threatening invasive pneumococcal disease (IPD), including meningitis. Pneumococci are classified into serotypes, determined by differences in capsular polysaccharide and both serotype and pneumolysin toxin are associated with disease severity. Strains of serotype 8, ST 53, are increasing in prevalence in IPD in several countries.
Methods: Here we tested the virulence of such an isolate in a rat model of meningitis in comparison with a serotype 15B and a serotype 14 isolate. All three were isolated from meningitis patients in South Africa in 2019, where serotype 8 is currently the most common serotype in IPD.
Results and Discussion: Only the serotype 8 isolate was hypervirulent causing brain injury and a high mortality rate. It induced a greater inflammatory cytokine response than either the serotype 15B or 14 strain in the rat model and from primary mixed-glia cells isolated from mouse brains. It had the thickest capsule of the three strains and produced non-haemolytic pneumolysin. Pneumolysin-sequestering liposomes reduced the neuroinflammatory cytokine response in vitro indicating that liposomes have the potential to be an effective adjuvant therapy even for hypervirulent pneumococcal strains with non-haemolytic pneumolysin
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