Gramicidin Lateral Distribution in Phospholipid Membranes: Fluorescence Phasor Plots and Statistical Mechanical Model.

When using small mole fraction increments to study gramicidins in phospholipid membranes, we found that the phasor dots of intrinsic fluorescence of gramicidin D and gramicidin A in dimyristoyl-sn-glycero-3-phosphocholine (DMPC) unilamellar and multilamellar vesicles exhibit a biphasic change with peptide content at 0.143 gramicidin mole fraction. To understand this phenomenon, we developed a statistical mechanical model of gramicidin/DMPC mixtures. Our model assumes a sludge-like mixture of fluid phase and aggregates of rigid clusters. In the fluid phase, gramicidin monomers are randomly distributed. A rigid cluster is formed by a gramicidin dimer and DMPC molecules that are condensed to the dimer, following particular stoichiometries (critical gramicidin mole fractions, Xcr including 0.143). Rigid clusters form aggregates in which gramicidin dimers are regularly distributed, in some cases, even to superlattices. At Xcr, the size of cluster aggregates and regular distributions reach a local maximum. Before a similar model was developed for cholesterol/DMPC mixtures (Sugar and Chong (2012) J. Am. Chem. Soc. 134, 1164⁻1171) and here the similarities and differences are discussed between these two models.

Multiscale Modeling of Complex Formation and CD80 Depletion during Immune Synapse Development.

The mechanisms that discriminate self- and foreign antigen before T cell activation are unresolved. As part of the immune system's adaptive response to specific infections or neoplasms, antigen-presenting cells (APC) and effector T cells form transcellular molecular complexes. CTLA4 expression on regulatory or effector T cells reduces T cell activation. The CTLA4 transendocytosis hypothesis proposes that CTLA4 depletes CD80 and CD86 proteins from the APC membrane, rendering the APC incapable of activating T cells. We developed a multiscale spatiotemporal model for the interaction of a T cell and APC. Formation of the immune complex between T cell and APC starts with formation of the transmembrane complexes between the major histocompatibility complex and the T cell receptor (Signal 1) and between CD80 or CD86 and CD28 (Signal 2) at the opposing membrane surfaces of the interacting cells. By 0.01 s after contact simulation, an increasing concentration gradient of the free membrane proteins develops between the opposing surfaces and spherical parts of each cell's membrane, reaching a maximum at ∼30 s. Over several hours, diffusion across the gradient equalizes the free protein concentrations. During this phase, CTLA4 surface expression and its complexation with CD80/CD86 cause internalization and degradation of CD80/CD86. The simulation results show reasonable agreement with reported experimental data and indicate that key molecular processes take place over a very broad timescale, covering five orders of magnitude. Besides the fast complexation reactions, diffusion-limited processes, especially lateral diffusion in cell membranes and geometrical constraints, considerably slow down evolution of the synapse. Our results are consistent with the CTLA4 transendocytosis hypothesis and suggest the importance of lateral diffusion of surface proteins in contributing to a gradual increase in Signal 1 and Signal 2.

[A rare case of gastric outlet syndrome: internal incarceration after removal of gastric banding]. / Teljes gyomorkimeneti elzáródás ritka esete: gyomorgyuru eltávolítását követo belso kizáródás.

The laparoscopically administrated adjustable gastric banding used to be widely practiced as treatment of extreme obesity. As lots of complaints and complications arose sooner or later after this procedure, they had to be removed quite often. Half year after such a removal we observed a 37-year-old female patient with complete gastric outlet obstruction. The patient was operated and cured completely. The cause of gastric obstruction was an internal incarceration of the pyloric region between the plication made at the time of the ring removal and the gastric body. We found no similar case of gastric outlet obstruction in the corresponding literature.

["Watermelon stomach" can be the cause of severe gastrointestinal bleeding]. / Masszív gastrointestinalis vérzést okozó "görögdinnyegyomor".

Irregular vascular dilatation in the antrum or the cardia of the stomach can be the cause of severe gastrointestinal bleeding. The first term for it - in the beginning of the 50's of the previous century - was GAVE (Gastric Antral Vascular Ectasia) since at that time no similar phenomenon had been registered before. A quarter of a century later, after publishing a few cases, a witty internist described it as "watermelon stomach" because the macroscopic picture is similarly looking as the aforesaid fruit's appearing. This rare condition occured in one of our patient with many comorbid diseases.

[Laparoscopic treatment of median arcuate ligament syndrome (MALS) -- case report]. / Truncus coeliacus compressiós szindróma laparoscopos mutéti megoldása -- Esetismertetés.

CASE REPORT: The authors report a case of a 34-year-old woman who had postprandial abdominal pain for years. During the course of her examination lactose intolerance and hiatus hernia was diagnosed. After ineffective conservative treatment CT angiography (CTA) and digital substraction angiography (DSA) was performed and showed significant celiac artery stenosis. Percutaneous transluminal angioplasty (PTA) was unsuccessful as extravasal mechanical compression was present, therefore, laparoscopic decompression and surgical division of MAL fibres were carried out. The postoperative period was characterized by a complete relief of previous symptoms and repeated CTA showed normal blood flow. DISCUSSION: The authors emphasize the importance of the measurement of peak velocity of celiac trunk with Colour Duplex abdominal ultrasonography, the examination has 100% sensitivity and 83% specificity. The Duplex ultrasonography is less expensive than the "gold standard" diagnostic methods like CT and DS angiography, and can lead us to early diagnosis. Laparoscopic surgery is safe and low expense method for celiac artery decompression, however, sometimes it is difficult to reveal the exact reason and thus setting up the proper operation plan.

[Urgent laparoscopic adrenalectomy in acute crisis caused by pheochromocytoma]. / Phaeochromocytomás krízisben végzett acut laparoscopos adrenalectomia.

CASE REPORT: Authors present the case of a 30-year-old female patient, who was admitted to the ICU because of hypertensive crisis accompanied by chest complains, cardiac decompensation, progrediating short of breath and unconsciousness. Despite the quick examinations and the prompt treatment multi-organ failure developed 3 days after admission. Investigations revealed the underlying cause, which was a left-sided suprarenal neoplasm. Hence, multidisciplinary decision was made to carry out a laparoscopic adrenalectomy urgently. The histology examination of the removed neoplasm was pheochromocytoma. In the postoperative period the condition of the patient gradually improved, her symptoms and complains settled, and finally she was discharged in a healthy condition. DISCUSSION: The diagnosis of a pheochromocytoma is a difficult task, the symptoms and complains caused by it can simulate many other illnesses. The acute crisis caused by pheochromocytoma usually can be treated conservatively, but in more severe cases with impending multi-organ failure an urgent operative treatment can be unavoidable. Though the operative risk is relatively high, the correct intra- and postoperative treatment with a quick laparoscopic procedure can be effective.

Series of concentration-induced phase transitions in cholesterol/phosphatidylcholine mixtures.

In lipid membranes, temperature-induced transition from gel-to-fluid phase increases the lateral diffusion of the lipid molecules by three orders of magnitude. In cell membranes, a similar phase change may trigger the communication between the membrane components. Here concentration-induced phase transition properties of our recently developed statistical mechanical model of cholesterol/phospholipid mixtures are investigated. A slight (<1%) decrease in the model parameter values, controlling the lateral interaction energies, reveals the existence of a series of first- or second-order phase transitions. By weakening the lateral interactions first, the proportion of the ordered (i.e., superlattice) phase (Areg) is slightly and continuously decreasing at every cholesterol mole fraction. Then sudden decreases in Areg appear at the 0.18-0.26 range of cholesterol mole fractions. We point out that the sudden changes in Areg represent first- or second-order concentration-induced phase transitions from fluid to superlattice and from superlattice to fluid phase. Sudden changes like these were detected in our previous experiments at 0.2, 0.222, and 0.25 sterol mole fractions in ergosterol/DMPC mixtures. By further decreasing the lateral interactions, the fluid phase will dominate throughout the 0.18-0.26 interval, whereas outside this interval sudden increases in Areg may appear. Lipid composition-induced phase transitions as specified here should have far more important biological implications than temperature- or pressure-induced phase transitions. This is the case because temperature and pressure in cell membranes are largely invariant under physiological conditions.

Cholesterol superlattice modulates CA4P release from liposomes and CA4P cytotoxicity on mammary cancer cells.

Liposomal drugs are a useful alternative to conventional drugs and hold great promise for targeted delivery in the treatment of many diseases. Most of the liposomal drugs on the market or under clinical trials include cholesterol as a membrane stabilizing agent. Here, we used liposomal CA4P, an antivascular drug, to demonstrate that cholesterol content can actually modulate the release and cytotoxicity of liposomal drugs in a delicate and predictable manner. We found that both the rate of the CA4P release from the interior aqueous compartment of the liposomes to the bulk aqueous phase and the extent of the drug's cytotoxicity undergo a biphasic variation, as large as 50%, with liposomal cholesterol content at the theoretically predicted C(r), e.g., 22.0, 22.2, 25.0, 33.3, 40.0, and 50.0 mol % cholesterol for maximal superlattice formation. It appears that at C(r), CA4P can be released from the liposomes more readily than at non-C(r), probably due to the increased domain boundaries between superlattice and nonsuperlattice regions, which consequently results in increased cytotoxicity. The idea that the increased domain boundaries at C(r) would facilitate the escape of molecules from membranes was further supported by the data of dehydroergosterol transfer from liposomes to MßCD. These results together show that the functional importance of sterol superlattice formation in liposomes can be propagated to distal targeted cells and reveal a new, to our knowledge, mechanism for how sterol content and membrane lateral organization can control the release of entrapped or embedded molecules in membranes.

A statistical mechanical model of cholesterol/phospholipid mixtures: linking condensed complexes, superlattices, and the phase diagram.

Despite extensive studies for nearly three decades, lateral distribution of molecules in cholesterol/phospholipid bilayers remains elusive. Here we present a statistical mechanical model of cholesterol/phospholipid mixtures that is able to rationalize almost every critical mole fraction (X(cr)) value previously reported for sterol superlattice formation as well as the observed biphasic changes in membrane properties at X(cr). This model is able to explain how cholesterol superlattices and cholesterol/phospholipid condensed complexes are interrelated. It gives a more detailed characterization of the LG(I)region (a broader region than the liquid disordered-liquid ordered mixed-phase region), which is considered to be a sludgelike mixture of fluid phase and aggregates of rigid clusters. A rigid cluster is formed by a cholesterol molecule and phospholipid molecules that are condensed to the cholesterol. Rigid clusters of similar size tend to form aggregates, in which cholesterol molecules are regularly distributed into superlattices. According to this model, the extent and type of sterol superlattices, thus the lateral distribution of the entire membrane, should vary with cholesterol mole fraction in a delicate, predictable, and nonmonotonic manner, which should have profound functional implications.

Interaction Energy between Two Separated Charged Spheres Surrounded Inside and Outside by Electrolyte.

By using the recently generalized version of Newton's shell theorem, analytical equations are derived to calculate the electric interaction energy between two separated, charged spheres surrounded outside and inside by electrolyte. This electric interaction energy is calculated as a function of the electrolyte's ion concentration, temperature, distance between the spheres and size of the spheres. At the same distance between the spheres, the absolute value of the interaction energy decreases with increasing electrolyte ion concentration and increases with increasing temperature. At zero electrolyte ion concentration, the derived analytical equation transforms into the Coulomb Equation Finally, the analytical equation is generalized to calculate the electric interaction energy of N separated, charged spheres surrounded by electrolyte.

Improved compensation in flow cytometry by multivariable optimization.

Conventional compensation of flow cytometry (FMC) data of an N-stained sample requires additional data sets, of N single-stained control samples, to estimate the spillover coefficients. Single-stained controls however are the least rigorous controls because any of the multi-stained controls are closer to the N-stained sample. In this article, a new, optimization based, compensation method has been developed that is able to use not only single- but also multi-stained controls to improve estimates of the spillover coefficients. The method is demonstrated on a data set from five-stained dentritic cells (DCs) with five single-stained and eight multi-stained controls. This approach is practical and leads to significant improvements in FCM compensation.

Misty Mountain clustering: application to fast unsupervised flow cytometry gating.

BACKGROUND: There are many important clustering questions in computational biology for which no satisfactory method exists. Automated clustering algorithms, when applied to large, multidimensional datasets, such as flow cytometry data, prove unsatisfactory in terms of speed, problems with local minima or cluster shape bias. Model-based approaches are restricted by the assumptions of the fitting functions. Furthermore, model based clustering requires serial clustering for all cluster numbers within a user defined interval. The final cluster number is then selected by various criteria. These supervised serial clustering methods are time consuming and frequently different criteria result in different optimal cluster numbers. Various unsupervised heuristic approaches that have been developed such as affinity propagation are too expensive to be applied to datasets on the order of 106 points that are often generated by high throughput experiments. RESULTS: To circumvent these limitations, we developed a new, unsupervised density contour clustering algorithm, called Misty Mountain, that is based on percolation theory and that efficiently analyzes large data sets. The approach can be envisioned as a progressive top-down removal of clouds covering a data histogram relief map to identify clusters by the appearance of statistically distinct peaks and ridges. This is a parallel clustering method that finds every cluster after analyzing only once the cross sections of the histogram. The overall run time for the composite steps of the algorithm increases linearly by the number of data points. The clustering of 106 data points in 2D data space takes place within about 15 seconds on a standard laptop PC. Comparison of the performance of this algorithm with other state of the art automated flow cytometry gating methods indicate that Misty Mountain provides substantial improvements in both run time and in the accuracy of cluster assignment. CONCLUSIONS: Misty Mountain is fast, unbiased for cluster shape, identifies stable clusters and is robust to noise. It provides a useful, general solution for multidimensional clustering problems. We demonstrate its suitability for automated gating of flow cytometry data.

[Successfully operated cases of mediastinal and retroperitoneal bronchial cysts]. / Mediastinalis és retroperitonealis bronchogen cysták sikeresen operált esetei és tanulságaik.

CASE REPORT: Two young men were operated in our department for bronchiogen cysts with unusual locations. In the first case a mediastinal cyst caused severe swallowing problems, while in the second a retroperitoneal cyst resembled to an adrenal adenoma. It was only the postoperative histology, which clarified the exact diagnosis of the removed cysts. DISCUSSION: Only a few percent of mediastinal tumours are bronchial cysts that develop due to developmental disorders. Symptomatic ones are more easily detectable. Bronchial cysts localized in the abdominal cavity or retroperitoneum are especially rare. In most of the cases the final diagnosis is made only after excision with histological examination of the cyst.

Model of autocrine/paracrine signaling in epithelial layer: geometrical regulation of intercellular communication.

An autocrine/paracrine signaling model in epithelial layers is described. The axially symmetric model of the epithelial layer explicitly considers the microvilli of the epithelial cells and the gaps between nearest neighbor microvilli. Ligand trapping site distribution functions and probability of autocrine signaling are calculated for different epithelial geometries and ligand sources by numerically solving the inhomogeneous stationary diffusion equation, the Poisson equation. In general, the global characteristics of the trapping site distribution curves are similar to the ones obtained for a planar epithelial model, and the superimposed small periodical changes of the curves reflect the details of the epithelial geometry. However, when ligands are emitted into a narrow gap between nearest neighbor microvilli the probability of local trapping is particularly high, causing a locally large deviation from the overall behavior of the trapping site distribution curves. If the microvilli of the cell are closely packed, then the probability of paracrine signaling is about 0.2. However, this probability jumps to about 0.5 if the cell is able to slightly loosen the tight packing, for example, by decreasing the diameter of the microvilli by only 2%. On the basis of our calculations, alteration of microvillus geometry represents a mechanism by which epithelial cells can efficiently regulate intercellular signaling.

[Aortoenteric fistula to the sigmoid colon complicated with entero-grafto-cutaneous fistula]. / Aortoenteralis fistula ritka formája--sigmoideo-grafto-cutan fistula.

We report a case of a 62-year-old man who presented to the emergency department with acute rectal bleeding. The patient had previous aortoiliac surgery with the utilization of an aorto-bifemoral vascular graft. Diagnosis of secondary aortoenteric fistula was made between the aortoiliac graft and sigmoid colon. This fistula had an entero-cutaneous component. After exploratory laparotomy resection of the sigma, extirpation of the entero-cutaneous fistula, excision of the graft, oversewing of the aortic stump, and extra-anatomical crossover bypass were successfully performed. This study reports a rare type of secondary aortoenteric fistula to the sigmoid colon complicated with an entero-grafto-cutaneous component and it describes an unusual and successful surgical treatment.

On the inner structure and topology of clusters in two-component lipid bilayers. Comparison of monomer and dimer Ising models.

It has been shown on model and biological systems that membrane clusters can affect in-plane membrane reactions and can control biochemical reaction cascades. Clusters of two-component phospholipid bilayers have been simulated by two Ising-type lattice models: the monomer and the dimer model. In each model the plane of one layer of the bilayer is represented by a triangular lattice, each site of which is occupied by an acyl chain of either a component 1 or a component 2 lipid molecule. The dimer model assumes that pairs of acyl chains (lipid molecules) are permanently connected, forming dimers on the lattice, while in the case of the monomer model this covalent connection between acyl chains is ignored. Phase diagrams of two-component phospholipid bilayers were successfully calculated by both models. In this work, we use Monte Carlo techniques to calculate thermodynamic averages of global and local characteristics of the largest component 2 cluster (such as outer/inner perimeter, percolation, minimal linear size, and local density) and compare the results obtained by the two models. A new method is developed to characterize the inner structure of the clusters. Each point of a cluster is classified based on its shortest distance (or depth) from the cluster's outer perimeter. Then local cluster properties, such as density, are calculated as a function of the depth. The depth analysis reveals that toward the cluster interior the average density usually decreases in midsize clusters and remains constant in very large clusters. On the basis of the simulations the following typical cluster topologies are identified at different cluster sizes and cooperativity parameter values: (i) branch-like, (ii) circular, (iii) band-like, and (iv) planar.We did not find qualitative differences between the cluster structures in the dimer and monomer model. However, at the same cluster size and cooperativity parameter value the cluster of the dimer model is more compact. The cluster properties of the dimer model are different from that of the monomer model because of the lower mixing entropy and higher formation energy of an elementary inner island.

[Plasmacytic skin infiltration in multiple myeloma]. / Myeloma multiplex kórlefolyása során megjelenô plazmasejtes bôrinfiltráció.

UNLABELLED: Authors present a case of a therapy-resistant multiple myeloma who developed plasmacytic skin infiltration in the course of the disease. AIM: To define characteristics of skin infiltrating plasma cells, which differentiate them from those cells residing in the bone marrow in order to contribute to a better understanding of the epidermoinvasion process. METHODS: Histidine decarboxylase is the only enzyme capable for histamine synthesis having significance in cell proliferation. Histidine decarboxylase was determined in skin samples and bone marrow slides by immunohistochemical procedures and in bone marrow cells using flow cytometry analysis. RESULTS: The histidine decarboxylase expression of plasma cells participating in skin invasion disappeared, while that of bone marrow plasma cells remained. CONCLUSIONS: Authors conclude that the histidine decarboxylase loss would serve as an evidence for the dedifferentiation of epidermoinvasive cells as being the result of fundamental changes in histamine metabolism. As extramedullary myeloma cells differ from those residing in the bone marrow, their therapeutical response might also be different.

[Wilkie's syndrome]. / A Wilkie-syndromáról.

Loss of retroperitoneal fatty tissue as a result of a variety of debilitating conditions and noxa is believed to be the etiologic factor of superior mesenteric artery syndrome. A case of a 35 years old female patient with severe malnutrition and weight loss is presented, who developed superior mesenteric artery syndrome. Various theories of etiology, clinical course and treatment options of this uncommon disease are discussed. In our case, conservative management was inefficient, while surgical treatment aiming to bypass the obstruction by an anastomosis between the jejunum and the proximal duodenum (duodenojejunostomy) was successful. An interdisciplinary teamwork provides the most beneficial diagnostic and therapeutic result in this often underestimated disease.