Martin Bencsik

Artificial exosomes as tools for basic and clinical immunology.

Dendritic cell derived exosomes are able to mediate and modulate immune responses in vivo by semi-direct T cell activation. T cells can eradicate primary, metastatic, relapsed tumours and ameliorate otherwise fatal viral infections. Not surprisingly activation and expansion of T cells has become one of the main focuses for immunotherapy. Using nanotechnology, we have developed targeted and traceable in vivo artificial exosomes by coating liposomes (FDA approved) with an optimized number of MHC Class I/peptide complexes and a selected specific range of ligands for adhesion, early activation, late activation and survival T cell receptors. These targeted artificial exosomes are traceable both in vitro and in vivo via fluorescent and Magnetic Resonance Imaging and facilitate imaging of specific areas by applying localised nuclear magnetic interactions of hydrogens via super paramagnetic labels. Here we show that artificial exosomes activate and expand functional antigen specific T cells at sufficient levels. This novel system has potential basic and clinical applications in immunology where the study of membrane interactions is desired.

Electric fields induced in the human body by time-varying magnetic field gradients in MRI : numerical calculations and correlation analysis

The spatial distributions of the electric fields induced in the human body by switched magnetic field gradients in MRI have been calculated numerically using the commercial software package, MAFIA, and the three-dimensional, HUGO body model that comprises 31 different tissue types. The variation of |J|, |E| and |B| resulting from exposure of the body model to magnetic fields generated by typical whole-body x-, y- and z-gradient coils has been analysed for three different body positions (head-, heart- and hips-centred). The magnetic field varied at 1 kHz, so as to produce a rate of change of gradient of 100 T m(-1) s(-1) at the centre of each coil. A highly heterogeneous pattern of induced electric field and current density was found to result from the smoothly varying magnetic field in all cases, with the largest induced electric fields resulting from application of the y-gradient, in agreement with previous studies. By applying simple statistical analysis to electromagnetic quantities within axial planes of the body model, it is shown that the induced electric field is strongly correlated to the local value of resistivity, and the induced current density exhibits even stronger correlation with the local conductivity. The local values of the switched magnetic field are however shown to bear little relation to the local values of the induced electric field or current density.

Detection of Virgin Olive Oil Adulteration Using Low Field Unilateral NMR

The detection of adulteration in edible oils is a concern in the food industry, especially for the higher priced virgin olive oils. This article presents a low field unilateral nuclear magnetic resonance (NMR) method for the detection of the adulteration of virgin olive oil that can be performed through sealed bottles providing a non-destructive screening technique. Adulterations of an extra virgin olive oil with different percentages of sunflower oil and red palm oil were measured with a commercial unilateral instrument, the profile NMR-Mouse. The NMR signal was processed using a 2-dimensional Inverse Laplace transformation to analyze the transverse relaxation and self-diffusion behaviors of different oils. The obtained results demonstrated the feasibility of detecting adulterations of olive oil with percentages of at least 10% of sunflower and red palm oils.

Electric fields induced in a spherical volume conductor by temporally varying magnetic field gradients

A homogeneous spherical volume conductor is used as a model system for the purpose of calculating electric fields induced in the human head by externally applied time-varying magnetic fields. We present results for the case where magnetic field gradient coils, used in magnetic resonance imaging (MRI), form the magnetic field, and we use these data to put limits on the rates of gradient change with time needed to produce nerve stimulation. The electric field is calculated analytically for the case of ideal longitudinal and transverse linear field gradients. We also show results from computer calculations yielding the electric field maps in a sphere when the field gradients are generated by a real MRI gradient coil set. In addition, the effect of shifting the sphere within each gradient coil volume is investigated. Numerical analysis shows similar results when applied to a model human head.

Identifying individual wild Eastern grey wolves (Canis lupus lycaon) using fundamental frequency and amplitude of howls

The use of amplitudes to identify individuals has historically been ignored by bioacoustic researchers due to problems of attenuation. However, recent studies have shown that amplitudes encode identity in a variety of mammal species. Previously, individuality has been demonstrated in both fundamental frequency (F0) and amplitude changes of captive Eastern wolf (Canis lupus lycaon) howls with 100% accuracy where attenuation of amplitude due to distance was controlled in a captive environment. In this study, we aim to determine whether both fundamental frequency and amplitude data collected from vocalizations of wild wolves recorded over unknown distances, in variable conditions and with different recording equipment, can still encode identity. We used a bespoke code, developed in Matlab, to extract simple scalar variables from 67 high-quality solo howls from 10 wild individuals and 112 chorus howls from another 109 individuals, including lower quality howls with wind or water noise. Principal component analysis (PCA) was carried out on the fundamental frequency and normalized amplitude of harmonic 1, yielding histogram-derived PCA values on which discriminant function analysis was applied. An accuracy of 100% was achieved when assigning solo howls to individuals, and for the chorus howls a best accuracy of 97.4% was achieved. We suggest that individual recognition using our new extraction and analysis methods involving fundamental frequency and amplitudes together can identify wild wolves with high accuracy, and that this method should be applied to surveys of individuals in capture–mark–recapture and presence–absence studies of canid species.

Quantitative NMR monitoring of liquid ingress into repellent heterogeneous layered fabrics

Fabrics which are water repellent and repellent to other liquids are often constructed using multiple layers of material. Such a construction is preferable to a single layer of a liquid-repellent textile because, under the action of an applied pressure, ingress of a liquid through the first layer can be halted by the second or subsequent layers. In the quantitative investigation of this problem, current techniques provide limited information on the progress and distribution of the liquid as it ingresses into a fabric. Moreover, many techniques require that the material is delaminated prior to analysis, and cannot be conducted in real time to measure the progress of a liquid through the textile substrate. In this work we demonstrate that unilateral NMR, which allows signal to be collected from a volume of interest in a material residing above the instrument, can be a powerful tool to quantitatively monitor the ingress of a liquid through a layered sample exhibiting pronounced heterogeneities in repellency. A known volume of oil was placed on the top of a model textile sample composed of three 80 microm thick layers. Spatially resolved one dimensional vertical NMR profiles of the system were acquired as a function of the pressure vertically applied to the top of the sample. These profiles show that the absolute liquid volume present in each layer of textile can routinely be measured within 4 min with a spatial resolution of 15 microm. If each individual layer exhibits different repellency to the test liquid, the complexity of the dynamics of the ingress can be investigated in great detail. An elegant application of the unilateral instrument was obtained in which the sensitive volume matched the region of interest of the individual layers of the textile under investigation.

Robust spatially resolved pressure measurements using MRI with novel buoyant advection-free preparations of stable microbubbles in polysaccharide gels

MRI of fluids containing lipid coated microbubbles has been shown to be an effective tool for measuring the local fluid pressure. However, the intrinsically buoyant nature of these microbubbles precludes lengthy measurements due to their vertical migration under gravity and pressure-induced coalescence. A novel preparation is presented which is shown to minimize both these effects for at least 25 min. By using a 2% polysaccharide gel base with a small concentration of glycerol and 1,2-distearoyl-sn-glycero-3-phosphocholine coated gas microbubbles, MR measurements are made for pressures between 0.95 and 1.44 bar. The signal drifts due to migration and amalgamation are shown to be minimized for such an experiment whilst yielding very high NMR sensitivities up to 38% signal change per bar.

Direct measurement of porous media local hydrodynamical permeability using gas MRI

The concept of hydraulic permeability is at the core of modeling single phase or multi-phase flow in heterogeneous porous media, as it is the spatial distribution of the permeability that primarily governs the behavior of fluid flow in the medium. To date, the modeling of fluid flow in porous media has been hampered by poor estimates of local permeability. Magnetic Resonance Imaging is well known for its ability to measure non-invasively the local density and flow rate of different fluids saturating porous media [1,2]. In this paper we demonstrate the first non-invasive method for the direct measurement of a single projection of the local permeability tensor of a porous medium using gas-phase MRI. The potential for three-dimensional imaging of the medium permeability is also discussed. The limitations of the method are listed and results are presented in a model porous medium as well as in a real oil reservoir rock.

Using the vector potential in evaluating the likelihood of peripheral nerve stimulation due to switched magnetic field gradients

The time‐varying magnetic field gradients used in MRI can cause peripheral nerve stimulation (PNS) in human subjects, as a result of the electric fields induced in tissue. The local electric field, E, is given by E = −∂A/∂t − ∇ϕ where A, is the vector potential and ϕ is the scalar electric potential generated by charges accumulated at boundaries between regions of different conductivity. Difficulties in calculating ϕ have led some investigators to use −∂A/∂t alone as a predictor of the induced field. Here the spatial variation of −∂A/∂t and E is investigated for the case of a simple spherical conductor exposed to time‐varying gradients produced by two different gradient coils that generate identical internal magnetic fields, but very different vector potentials. The results indicate that the temporal derivative of A bears little relation to the induced electric field, and that consequently neglecting the effect of the scalar potential introduces significant errors in estimating the likelihood of PNS. Magn Reson Med 50:405–410, 2003.

Improving individual identification in captive Eastern grey wolves (Canis lupus lycaon) using the time course of howl amplitudes

Many bioacoustic studies have been able to identify individual mammals from variations in the fundamental frequency (F0) of their vocalizations. Other characteristics of vocalization which encode individuality, such as amplitude, are less frequently used because of problems with background noise and recording fidelity over distance. In this paper, we investigate whether the inclusion of amplitude variables improves the accuracy of individual howl identification in captive Eastern grey wolves (Canis lupus lycaon). We also explore whether the use of a bespoke code to extract the howl features, combined with histogram-derived principal component analysis (PCA) values, can improve current individual wolf howl identification accuracies. From a total of 89 solo howls from six captive individuals, where distances between wolf and observer were short, we achieved 95.5% (+9.0% improvement) individual identification accuracy of captive wolves using discriminant function analysis (DFA) to classify simple scalar variables of F0 and normalized amplitudes. Moreover, this accuracy was increased by 100% when using histogram-derived PCA values of F0 and amplitudes of the first harmonic. We suggest that individual identification accuracy can be improved by including amplitude changes for species where F0 has only been included so far. Using DFA on PCA values of both F0 and amplitude could optimize vocal identification in a range of mammal bioacoustic studies.