Pancreaticoduodenectomy with Anatomical Vascular Variant in Groove Pancreatitis-A Case Report.

Groove pancreatitis represents a chronic focal form of pancreatitis affecting the zone between the pancreatic head and the duodenal "C" loop, known as the groove area. This is a rare condition that affects the pancreatic periampullary part, including the duodenum and the common bile duct, which is usually associated with long-term alcohol and tobacco misuse, and is more frequent in men than in women. The most common clinical symptoms of groove pancreatitis include weight loss, acute abdominal pain, nausea, and jaundice. This report is about a 66-year-old woman with a history of heavy smoking, presenting with weight loss, nausea, and upper abdominal pain. Contrast-enhanced computed tomography revealed the existence of chronic pancreatitis as well as the dilatation of the main pancreatic duct, a cyst of the pancreatic head, and enlargement of the biliary tract. Conservatory treatment was initiated but with no improvement of symptoms. Since endoscopic retrograde cholangiopancreatography was not possible due to the local changes, we decided to perform pancreatoduodenectomy, as surgery appears to be the single effective treatment.

Phase-coherence classification: A new wavelet-based method to separate local field potentials into local (in)coherent and volume-conducted components.

BACKGROUND: Local field potentials (LFP) reflect the integrated electrophysiological activity of large neuron populations and may thus reflect the dynamics of spatially and functionally different networks. NEW METHOD: We introduce the wavelet-based phase-coherence classification (PCC), which separates LFP into volume-conducted, local incoherent and local coherent components. It allows to compute power spectral densities for each component associated with local or remote electrophysiological activity. RESULTS: We use synthetic time series to estimate optimal parameters for the application to LFP from within the subthalamic nucleus of eight Parkinson patients. With PCC we identify multiple local tremor clusters and quantify the relative power of local and volume-conducted components. We analyze the electrophysiological response to an apomorphine injection during rest and hold. Here we show medication-induced significant decrease of incoherent activity in the low beta band and increase of coherent activity in the high beta band. On medication significant movement-induced changes occur in the high beta band of the local coherent signal. It increases during isometric hold tasks and decreases during phasic wrist movement. COMPARISON WITH EXISTING METHODS: The power spectra of local PCC components is compared to bipolar recordings. In contrast to bipolar recordings PCC can distinguish local incoherent and coherent signals. We further compare our results with classification based on the imaginary part of coherency and the weighted phase lag index. CONCLUSIONS: The low and high beta band are more susceptible to medication- and movement-related changes reflected by incoherent and local coherent activity, respectively. PCC components may thus reflect functionally different networks.

Giardia duodenalis and Cryptosporidium spp. as contaminant protozoa of the main rivers of western Romania: genetic characterization and public health potential of the isolates.

The objective of this study was to establish the prevalence, contamination level, and public health significance of Giardia duodenalis and Cryptosporidium spp. in the primary rivers of western Romania. A total of 53 sampling points in the 24 most important western Romanian rivers in four counties (Arad, Bihor, Caraș-Severin, and Timiș) were investigated from March to September 2016. Surface water samples were collected by microfiber filtration. Cryptosporidium and Giardia (oo)cysts were isolated using immunomagnetic separation (IMS) according to the USEPA 1623 method and, after staining with fluorescently labeled (FITC) monoclonal antibodies, were identified and counted under a microscope. The Cryptosporidium and Giardia (oo)cysts were identified to species and assemblage/sub-assemblage level through the nested PCR-RFLP procedure targeting the 18S ribosomal RNA and gdh genes, respectively. PCR-based techniques were utilized for all water samples. Overall, 22 samples (41.5%) were determined to be positive for Giardia cysts (ranging from 0.05 to 300 cysts per liter), and four samples (7.5%) tested positive for Cryptosporidium oocysts (0.17-48 oocysts/l). G. duodenalis was molecularly identified in 13 water samples (24.5%), indicating the presence of the sub-assemblage A-II (n = 12) and assemblage E (n = 1). PCR-RFLP showed that two samples (3.8%) contained Cryptosporidium DNA, and the identified species were Cryptosporidium parvum and Cryptosporidium canis. All positive results were successfully confirmed by DNA sequencing. Subtyping of the zoonotic C. parvum isolate based on sequence analysis of the GP60 gene revealed the occurrence of the IIaA16G1R1 subtype. The results of this study highlight considerable contamination of river waters with pathogenic Giardia spp. and Cryptosporidium spp., suggesting a potential risk for the public and animal health. This report presents the first extended published description of the presence of Giardia spp. and Cryptosporidium spp. in the aquatic environment in Romania.

Periodic reversals in Paenibacillus dendritiformis swarming.

Bacterial swarming is a type of motility characterized by a rapid and collective migration of bacteria on surfaces. Most swarming species form densely packed dynamic clusters in the form of whirls and jets, in which hundreds of rod-shaped rigid cells move in circular and straight patterns, respectively. Recent studies have suggested that short-range steric interactions may dominate hydrodynamic interactions and that geometrical factors, such as a cell's aspect ratio, play an important role in bacterial swarming. Typically, the aspect ratio for most swarming species is only up to 5, and a detailed understanding of the role of much larger aspect ratios remains an open challenge. Here we study the dynamics of Paenibacillus dendritiformis C morphotype, a very long, hyperflagellated, straight (rigid), rod-shaped bacterium with an aspect ratio of ~20. We find that instead of swarming in whirls and jets as observed in most species, including the shorter T morphotype of P. dendritiformis, the C morphotype moves in densely packed straight but thin long lines. Within these lines, all bacteria show periodic reversals, with a typical reversal time of 20 s, which is independent of their neighbors, the initial nutrient level, agar rigidity, surfactant addition, humidity level, temperature, nutrient chemotaxis, oxygen level, illumination intensity or gradient, and cell length. The evolutionary advantage of this unique back-and-forth surface translocation remains unclear.

Discontinuities in slow finger movements in patients with Parkinson's disease.

Slow finger movements in healthy humans are characterized by discontinuous rhythmic changes in a low frequency band about 8 Hz. These pulsatile changes in velocity are thought to present the central output of an oscillatory cerebello-thalamo-cortical network in the same frequency. Hypothesizing that patients with Parkinson's disease (PD) in the dopaminergic OFF- and ON-condition show changes in the characteristics of discontinuities compared to healthy humans, we used a 3D-ultrasound device to measure slow finger movements of 16 patients with PD and 12 age-matched controls. We provide evidence that slow finger movements of patients with PD are characterized by discontinuities in acceleration, which are significantly slower in the OFF- but not in the ON-condition compared to healthy controls. Correlation analysis between clinical motor improvement after dopaminergic medication and changes of peak frequencies and peak power of discontinuities was not significant. We conclude that the oscillatory brain network of slow finger movements is affected in PD, presenting in a lower frequency in the OFF-condition. We suggest that one factor of the modulation of this network is a dopaminergic stimulation.

Modulation of local field potential power of the subthalamic nucleus during isometric force generation in patients with Parkinson's disease.

Investigations of local field potentials of the subthalamic nucleus of patients with Parkinson's disease have provided evidence for pathologically exaggerated oscillatory beta-band activity (13-30 Hz) which is amenable to physiological modulation by, e.g., voluntary movement. Previous functional magnetic resonance imaging studies in healthy controls have provided evidence for an increase of subthalamic nucleus blood-oxygenation-level-dependant signal in incremental force generation tasks. However, the modulation of neuronal activity by force generation and its relationship to peripheral feedback remain to be elucidated. We hypothesised that beta-band activity in the subthalamic nucleus is modulated by incremental force generation. Subthalamic nucleus local field potentials were recorded intraoperatively in 13 patients with Parkinson's disease (37 recording sites) during rest and five incremental isometric force generation conditions of the arm with applied loads of 0-400 g (in 100-g increments). Repeated measures analysis of variance (ANOVA) revealed a modulation of local field potential (LFP) power in the upper beta-band (in 24-30 Hz; F(3.042)=4.693, p=0.036) and the gamma-band (in 70-76 Hz; F(4)=4.116, p=0.036). Granger-causality was computed with the squared partial directed coherence and showed no significant modulation during incremental isometric force generation. Our findings indicate that the upper beta- and gamma-band power of subthalamic nucleus local field potentials are modulated by the physiological task of force generation in patients with Parkinson's disease. This modulation seems to be not an effect of a modulation of peripheral feedback.

Does increased gamma activity in patients suffering from Parkinson's disease counteract the movement inhibiting beta activity?

Akinesia and rigidity are cardinal symptoms of Parkinson's disease (PD). Previous studies analysing event-related desynchronization during movement onset associated both symptoms with pathologically increased oscillations in the beta frequency range. By focusing on the movement onset only, these studies cannot, however, shed light onto the question how oscillatory activity is changed during continuous movements. To investigate this issue, we compared the power of the local field potentials (LFP) within and above the subthalamic nucleus (STN) during rest, an isometric hold condition of the forearm, and a fist flexion and extension task in 13 patients with idiopathic PD during implantation of deep brain stimulation (DBS) electrodes. During fist flexion and extension (relative to rest), significantly increased activity in the low beta (12-18 Hz) and gamma (30-48 Hz) frequency ranges was observed within the STN, while during hold (compared to rest) no significant difference was found. For the regions above the STN the power during fist movements (compared to rest) was significantly higher, i.e. in the range of 18-30 Hz, with no significant changes in the gamma frequency range. Beta activity is claimed to inhibit movement and thereby could render fist movements more exhausting. Therefore, the observed increase in beta activity in the STN during fist movements might result in bradykinesia as experienced by many patients. We hypothesise that in order to enable repetitive fist movement despite increased beta activity, "prokinetic" gamma activity may be increased as a compensatory mechanism.

Subtype-specific statistical causalities in parkinsonian tremor.

Tremor is one of the cardinal symptoms of Parkinson's disease. Up to now, however, its pathophysiology remains poorly understood. Previously, oscillatory coupling at tremor frequency between the subthalamic nucleus und affected muscles was shown. In these studies, however, causality of coupling could not be demonstrated. Thus, we analyzed the statistical causality between intraoperatively recorded local field potentials in the subthalamic area and affected arm muscles during tremor episodes, using squared partial directed coherence, a recently developed causality measure. The analysis identified differential statistical causality patterns for Parkinson's disease patients of the akinetic-rigid subtype during tremor episodes (n=6) versus patients of the tremor-dominant subtype (n=8): for the akinetic-rigid Parkinson's disease patients significantly more cases of the subthalamic region were found to be statistically causal for electromyographic-tremor activity, a result in accordance with the standard basal ganglia model. In contrast, for the tremor-dominant patients, significantly more instances of electromyographic tremor activity turned out to be causal for activity of the subthalamic region. Furthermore, the clinical effective stimulation site coincided with the location of most input causalities from the periphery in seven out of eight tremor-dominant patients. The data suggest that, although tremor activity in tremor-dominant and akinetic-rigid Parkinson's disease patients was clinically similar, statistical causality between tremor electromyogram (EMG) and the subthalamic nucleus was fundamentally different. Therefore, we hypothesize different pathophysiological mechanisms to underlie the generation of tremor in the two subtypes of Parkinson's disease.

Surviving bacterial sibling rivalry: inducible and reversible phenotypic switching in Paenibacillus dendritiformis.

UNLABELLED: Natural habitats vary in available nutrients and room for bacteria to grow, but successful colonization can lead to overcrowding and stress. Here we show that competing sibling colonies of Paenibacillus dendritiformis bacteria survive overcrowding by switching between two distinct vegetative phenotypes, motile rods and immotile cocci. Growing colonies of the rod-shaped bacteria produce a toxic protein, Slf, which kills cells of encroaching sibling colonies. However, sublethal concentrations of Slf induce some of the rods to switch to Slf-resistant cocci, which have distinct metabolic and resistance profiles, including resistance to cell wall antibiotics. Unlike dormant spores of P. dendritiformis, the cocci replicate. If cocci encounter conditions that favor rods, they secrete a signaling molecule that induces a switch to rods. Thus, in contrast to persister cells, P. dendritiformis bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching. IMPORTANCE: In favorable environments, species may face space and nutrient limits due to overcrowding. Bacteria provide an excellent model for analyzing principles underlying overcrowding and regulation of density in nature, since their population dynamics can be easily and accurately assessed under controlled conditions. We describe a newly discovered mechanism for survival of a bacterial population during overcrowding. When competing with sibling colonies, Paenibacillus dendritiformis produces a lethal protein (Slf) that kills cells at the interface of encroaching colonies. Slf also induces a small proportion of the cells to switch from motile, rod-shaped cells to nonmotile, Slf-resistant, vegetative cocci. When crowding is reduced and nutrients are no longer limiting, the bacteria produce a signal that induces cocci to switch back to motile rods, allowing the population to spread. Genes encoding components of this phenotypic switching pathway are widespread among bacterial species, suggesting that this survival mechanism is not unique to P. dendritiformis.

Collective motion and density fluctuations in bacterial colonies.

Flocking birds, fish schools, and insect swarms are familiar examples of collective motion that plays a role in a range of problems, such as spreading of diseases. Models have provided a qualitative understanding of the collective motion, but progress has been hindered by the lack of detailed experimental data. Here we report simultaneous measurements of the positions, velocities, and orientations as a function of time for up to a thousand wild-type Bacillus subtilis bacteria in a colony. The bacteria spontaneously form closely packed dynamic clusters within which they move cooperatively. The number of bacteria in a cluster exhibits a power-law distribution truncated by an exponential tail. The probability of finding clusters with large numbers of bacteria grows markedly as the bacterial density increases. The number of bacteria per unit area exhibits fluctuations far larger than those for populations in thermal equilibrium. Such "giant number fluctuations" have been found in models and in experiments on inert systems but not observed previously in a biological system. Our results demonstrate that bacteria are an excellent system to study the general phenomenon of collective motion.

Lethal protein produced in response to competition between sibling bacterial colonies.

Sibling Paenibacillus dendritiformis bacterial colonies grown on low-nutrient agar medium mutually inhibit growth through secretion of a lethal factor. Analysis of secretions reveals the presence of subtilisin (a protease) and a 12 kDa protein, termed sibling lethal factor (Slf). Purified subtilisin promotes the growth and expansion of P. dendritiformis colonies, whereas Slf is lethal and lyses P. dendritiformis cells in culture. Slf is encoded by a gene belonging to a large family of bacterial genes of unknown function, and the gene is predicted to encode a protein of approximately 20 kDa, termed dendritiformis sibling bacteriocin. The 20 kDa recombinant protein was produced and found to be inactive, but exposure to subtilisin resulted in cleavage to the active, 12 kDa form. The experimental results, combined with mathematical modeling, show that subtilisin serves to regulate growth of the colony. Below a threshold concentration, subtilisin promotes colony growth and expansion. However, once it exceeds a threshold, as occurs at the interface between competing colonies, Slf is then secreted into the medium to rapidly reduce cell density by lysis of the bacterial cells. The presence of genes encoding homologs of dendritiformis sibling bacteriocin in other bacterial species suggests that this mechanism for self-regulation of colony growth might not be limited to P. dendritiformis.

Paenibacillus dendritiformis bacterial colony growth depends on surfactant but not on bacterial motion.

Most research on growing bacterial colonies on agar plates has concerned the effect of genetic or morphotype variation. Some studies have indicated that there is a correlation between microscopic bacterial motion and macroscopic colonial expansion, especially for swarming strains, but no measurements have been obtained for a single strain to relate the microscopic scale to the macroscopic scale. We examined here a single strain (Paenibacillus dendritiformis type T; tip splitting) to determine both the macroscopic growth of colonies and the microscopic bacterial motion within the colonies. Our multiscale measurements for a variety of growth conditions revealed that motion on the microscopic scale and colonial growth are largely independent. Instead, the growth of the colony is strongly affected by the availability of a surfactant that reduces surface tension.

Deadly competition between sibling bacterial colonies.

Bacteria can secrete a wide array of antibacterial compounds when competing with other bacteria for the same resources. Some of these compounds, such as bacteriocins, can affect bacteria of similar or closely related strains. In some cases, these secretions have been found to kill sibling cells that belong to the same colony. Here, we present experimental observations of competition between 2 sibling colonies of Paenibacillus dendritiformis grown on a low-nutrient agar gel. We find that neighboring colonies (growing from droplet inoculation) mutually inhibit growth through secretions that become lethal if the level exceeds a well-defined threshold. In contrast, within a single colony developing from a droplet inoculation, no growth inhibition is observed. However, growth inhibition and cell death are observed if material extracted from the agar between 2 growing colonies is introduced outside a growing single colony. To interpret the observations, we devised a simple mathematical model for the secretion of an antibacterial compound. Simulations of this model illustrate how secretions from neighboring colonies can be deadly, whereas secretions from a single colony growing from a droplet are not.

Method to rotate an endovascular device around the axis of a vessel using an external magnetic field.

A magnetic guidance methodology to rotate a device around the catheter axis is proposed. The specific medical application is to intracranial aneurysms. An endovascular device, the asymmetric stent, has a low porosity region that is rotated to cover the aneurysm neck so as to reduce the blood flow into and hence obliterate the aneurysm. The magnetic guidance system consists of a magnetic device attached to the asymmetric stent and an external homogeneous magnetic field of 0.1 T. This magnetic field puts a torque on the magnetic moment of the magnetic device, thereby rotating the stent for proper orientation. For the magnetic device with the required magnetic moment of 0.001 A m2, a cylindrical neodymium permanent magnet is proposed due to its favorable material characteristics while a coil electromagnet with iron core appears impractical due to demagnetizing effects.

Direct observation of nondiffusive motion of a Brownian particle.

The thermal position fluctuations of a single micron-sized sphere immersed in a fluid were recorded by optical trapping interferometry with nanometer spatial and microsecond temporal resolution. We find, in accord with the theory of Brownian motion including hydrodynamic memory effects, that the transition from ballistic to diffusive motion is delayed to significantly longer times than predicted by the standard Langevin equation. This delay is a consequence of the inertia of the fluid. On the shortest time scales investigated, the sphere's inertia has a small, but measurable, effect.

Single-beam trapping in front of reflective surfaces.

We show that the optical trapping of dielectric particles by a single focused beam in front of a weakly reflective surface is considerably affected by interference of the incident and reflected beams, which creates a standing-wave component of the total field. We use the two-photon-excited fluorescence from a trapped dyed probe to detect changes in the distance between the trapped beam focus as the focus approaches the reflective surface. This procedure enables us to determine the relative strengths of the single-beam and the standing-wave trapping forces. We demonstrate that, even for reflection from a glass-water interface, standing-wave trapping dominates, as far as 5 mum from the surface.

Sphingolipid-cholesterol rafts diffuse as small entities in the plasma membrane of mammalian cells.

To probe the dynamics and size of lipid rafts in the membrane of living cells, the local diffusion of single membrane proteins was measured. A laser trap was used to confine the motion of a bead bound to a raft protein to a small area (diam < or = 100 nm) and to measure its local diffusion by high resolution single particle tracking. Using protein constructs with identical ectodomains and different membrane regions and vice versa, we demonstrate that this method provides the viscous damping of the membrane domain in the lipid bilayer. When glycosylphosphatidylinositol (GPI) -anchored and transmembrane proteins are raft-associated, their diffusion becomes independent of the type of membrane anchor and is significantly reduced compared with that of nonraft transmembrane proteins. Cholesterol depletion accelerates the diffusion of raft-associated proteins for transmembrane raft proteins to the level of transmembrane nonraft proteins and for GPI-anchored proteins even further. Raft-associated GPI-anchored proteins were never observed to dissociate from the raft within the measurement intervals of up to 10 min. The measurements agree with lipid rafts being cholesterol-stabilized complexes of 26 +/- 13 nm in size diffusing as one entity for minutes.

Three-dimensional high-resolution particle tracking for optical tweezers by forward scattered light.

A quadrant photodiode placed in the back-focal plane of the microscope of a laser trap provides a high-resolution position sensor. We show that in addition to the lateral displacement of a trapped sphere, its axial position can be measured by the ratio of the intensity of scattered laser light to the total amount of the light reaching the detector. The addition of the axial information offers true three-dimensional position detection in solution, creating, together with a position control, a photonic force microscope with nanometer spatial and microsecond temporal resolution. The measured position signals are explained as interference of the unscattered trapping laser beam with the laser light scattered by the trapped bead. Our model explains experimental data for trapped particles in the Rayleigh regime (radius a <0.2lambda) for displacements up to the focal dimensions. The cross-talk between the signals in the three directions is explained and it is shown that this cross-talk can be neglected for lateral displacements smaller than 75 nm and axial displacements below 150 nm. The advantages of three-dimensional single-particle tracking over conventional video-tracking are shown through the example of the diffusion of the GPI-anchored membrane protein Thy1.1 on a neurite.

Photonic force microscope based on optical tweezers and two-photon excitation for biological applications.

A new scanning probe microscope, the photonic force microscope (PFM), based on optical tweezers and two-photon absorption processes for biological applications is described. Optical tweezers are used to trap a fluorescent latex bead with a diameter of 200 nm in an aqueous solution in all three dimensions. The fluorescent dye is chosen to fulfill the two-photon absorption criterion for the 1064-nm line of a Nd:YVO4 laser. The intensity of the fluorescence emission is utilized as a very sensitive position sensor along the optical axis. Two-dimensional images are formed by laterally scanning the trapped latex bead across biological samples while recording the two-photon-induced fluorescences intensity. A scanning probe image of the outer surface of a small neurite from a cultured rat hippocampal neuron is shown, which is hardly visible under differential interference contrast microscopy. The lateral resolution is given by the bead diameter; the axial resolution is 40 nm. Under the experimental conditions the maximal imaging force applied by the probe is below 5 pN.