The surgical management of a patient with chronic renal failure and macrothrombocytopenia related to the MYH9 gene mutation: A case report.

MYH9 disease is a rare genetic disorder in which there is a mutation in the gene for the non-muscle myosin heavy chain IIA. It initially causes macrothrombocytopenia followed by other clinical manifestations. When the patient reaches adulthood, he can develop chronic kidney failure. Thus, the risk of suffering a hemorrhage, difficulty in repairing and, infections increases in individuals with this disease. In addition, the use of drugs in these patients should be carefully evaluated. An adult patient sought dental care with a complaint associated with a tooth with advanced dental caries. He had severe thrombocytopenia (7000 platelets/mm3 ), hearing loss, and chronic kidney failure. The diagnosis of MYH9 disease was confirmed through genotyping. After clinical examination, extraction was planned. Local and systemic procedures were used to prevent hemorrhage, especially postoperatively. Although the patient had an infection at the surgical wound site and no episode of postoperative bleeding, the repair process occurred normally. The purpose of this article is to report the surgical management of a patient with MYH9 disease.

Fast and slow axonal transport: A unified approach based on cargo and molecular motor coupled dynamics.

The origins of the large differences observed in the rates at which diverse particles are conveyed along axonal microtubules are still a matter of debate in the literature. There is evidence that certain neurodegenerative diseases may be triggered by disturbances in the related transport processes. Motivated by this, we employ a model to investigate mobility properties of certain cargoes whose dynamics are coupled with that of molecular motors on crowded microtubules. For certain initial and boundary conditions, we use the method of characteristics to resolve perturbatively the pair of equations of Burgers type resulting from a mean-field approach to the original microscopic stochastic model. Extensions to nonperturbative limits are explored numerically. In this context, we are able to figure out conditions under which the cargoes' average velocities may differ up to orders of magnitude just by changing the number of motors on the considered track. We then discuss possibilities to connect these theoretical predictions with available experimental data about axon transport.

Intracellular motor-driven transport of rodlike smooth organelles along microtubules.

Molecular motors are fascinating proteins that use the energy of ATP hydrolysis to drive vesicles and organelles along cytoskeleton filaments toward their final destination within the cell. Several copies of these proteins bind to the cargo and take turns transporting the cargo attaching to and detaching from the track stochastically. Despite the relevance of molecular motors to cell physiology, key aspects of their collective functioning are still unknown. In this work we propose a one-dimensional model for the transport of extensive and smooth organelles driven by molecular motors. We ran numerical simulations to study the behavior of the cargo for different motor configurations, focusing on the transport properties observable in the experiments, e.g., average speed of the organelle and variations in length. We found that active motors drive the cargo using two different mechanisms: Either they locate in front of the cargo and pull the organelle or they situate at the cargo lagging edge and push. Variations in the organelle length is in close relation with the fraction of motors in each configuration, which depends on the resisting load. The results of this model were contrasted with experimental data obtained from the tracking of rodlike mitochondria during active transport in Xenopus laevis melanophores.

Microtubule Retrograde Motors and Their Role in Retroviral Transport.

Following entry into the host cell, retroviruses generate a dsDNA copy of their genomes via reverse transcription, and this viral DNA is subsequently integrated into the chromosomal DNA of the host cell. Before integration can occur, however, retroviral DNA must be transported to the nucleus as part of a 'preintegration complex' (PIC). Transporting the PIC through the crowded environment of the cytoplasm is challenging, and retroviruses have evolved different mechanisms to accomplish this feat. Within a eukaryotic cell, microtubules act as the roads, while the microtubule-associated proteins dynein and kinesin are the vehicles that viruses exploit to achieve retrograde and anterograde trafficking. This review will examine the various mechanisms retroviruses have evolved in order to achieve retrograde trafficking, confirming that each retrovirus has its own strategy to functionally subvert microtubule associated proteins.

Lysosome motility and distribution: Relevance in health and disease.

Lysosomes are dynamic organelles, which can fuse with a variety of targets and undergo constant regeneration. They can move along microtubules in a retrograde and anterograde fashion by using motor proteins, kinesin and dynein, being main players in extracellular secretion, intracellular components degradation and recycling. Moreover, lysosomes interact with other intracellular organelles to regulate their turnover, such as ER, mitochondria and peroxisomes. The correct localization of lysosomes is relevant in several physiological processes, including appropriate antigen presentation, neurotransmission and receptors modulation in neuronal synapsis, whereas hepatic lysosomes and autophagy are master regulators of nutrient homeostasis. Alterations in lysosome function due to mutation of genes encoding lysosomal proteins, soluble hydrolases as well as membrane proteins, lead to lysosomal storage diseases (LSDs). Lysosomes containing undegraded substrates are finally stacked and therefore miss positioned inside the cell, leading to lysosomal dysfunction, which impacts a wide range of cellular functions.

A physical model of cell metabolism.

Cell metabolism is characterized by three fundamental energy demands: to sustain cell maintenance, to trigger aerobic fermentation and to achieve maximum metabolic rate. The transition to aerobic fermentation and the maximum metabolic rate are currently understood based on enzymatic cost constraints. Yet, we are lacking a theory explaining the maintenance energy demand. Here we report a physical model of cell metabolism that explains the origin of these three energy scales. Our key hypothesis is that the maintenance energy demand is rooted on the energy expended by molecular motors to fluidize the cytoplasm and counteract molecular crowding. Using this model and independent parameter estimates we make predictions for the three energy scales that are in quantitative agreement with experimental values. The model also recapitulates the dependencies of cell growth with extracellular osmolarity and temperature. This theory brings together biophysics and cell biology in a tractable model that can be applied to understand key principles of cell metabolism.

Models for microtubule cargo transport coupling the Langevin equation to stochastic stepping motor dynamics: Caring about fluctuations.

One-dimensional models coupling a Langevin equation for the cargo position to stochastic stepping dynamics for the motors constitute a relevant framework for analyzing multiple-motor microtubule transport. In this work we explore the consistence of these models focusing on the effects of the thermal noise. We study how to define consistent stepping and detachment rates for the motors as functions of the local forces acting on them in such a way that the cargo velocity and run-time match previously specified functions of the external load, which are set on the base of experimental results. We show that due to the influence of the thermal fluctuations this is not a trivial problem, even for the single-motor case. As a solution, we propose a motor stepping dynamics which considers memory on the motor force. This model leads to better results for single-motor transport than the approaches previously considered in the literature. Moreover, it gives a much better prediction for the stall force of the two-motor case, highly compatible with the experimental findings. We also analyze the fast fluctuations of the cargo position and the influence of the viscosity, comparing the proposed model to the standard one, and we show how the differences on the single-motor dynamics propagate to the multiple motor situations. Finally, we find that the one-dimensional character of the models impede an appropriate description of the fast fluctuations of the cargo position at small loads. We show how this problem can be solved by considering two-dimensional models.

Comparison of interscalene brachial plexus block and intra-articular local anesthetic administration on postoperative pain management in arthroscopic shoulder surgery / Comparação de bloqueio do plexo braquial por via interescalênica e administração de anestésico local intra-articular no manejo da dor no pós-operatório de cirurgia artroscópica do ombro / Comparación de bloqueo del plexo braquial por vía interescalénica y administración de anestésico local intraarticular en el manejo del dolor en el postoperatorio de cirugía artroscópica del hombro

BACKGROUND AND OBJECTIVES: In this study, the aim was to compare postoperative analgesia effects of the administration of ultrasound-guided interscalene brachial plexus block and intra-articular bupivacaine carried out with bupivacaine. METHODS: In the first group of patients 20 mL 0.25% bupivacaine and ultrasound-guided interscalene brachial plexus block (ISPB) were applied, while 20 mL 0.25% bupivacaine was given via intra-articular (IA) administration to the second group patients after surgery. Patients in the third group were considered the control group and no block was performed. Patient-controlled analgesia (PCA) with morphine was used in all three groups for postoperative analgesia. RESULTS: In the ISPB group, morphine consumption in the periods between 0-4, 6-12 and 12-24 postoperative hours and total consumption within 24 h was lower than in the other two groups. Morphine consumption in the IA group was lower than in the control group in the period from 0 to 6 h and the same was true for total morphine consumption in 24 h. Postoperative VASr scores in the ISPB group were lower than both of the other groups in the first 2 h and lower than the control group in the 4th and 6th hours (p < 0.05). In the IA group, VASr and VASm scores in the 2nd, 4th and 6th hours were lower than in the control group (p < 0.05). CONCLUSION: Interscalene brachial plexus block was found to be more effective than intra-articular local anesthetic injection for postoperative analgesia. .

JUSTIFICATIVA E OBJETIVOS: Comparar os efeitos na analgesia no pós-operatório da administração de bloqueio do plexo braquial por via interescalênica guiado por ultrassom e bupivacaína intra-articular, feito com bupivacaína. MÉTODOS: No primeiro grupo de pacientes, 20 mL de bupivacaína a 0,25% e bloqueio do plexo braquial por via interescalênica guiado por ultrassom (BPBI) foram administrados, enquanto 20 mL de bupivacaína a 0,25% foram administrados por via intra-articular (IA) ao segundo grupo de pacientes após a cirurgia. Os pacientes do terceiro grupo foram considerados grupo controle e nenhum bloqueio foi feito. Analgesia controlada pelo paciente (ACP) com morfina foi usada nos três grupos para analgesia pós-operatória. RESULTADOS: No grupo BPBI, o consumo de morfina nos períodos entre 0-4, 6-12 e 12-24 horas após a cirurgia e o consumo total em 24 horas foram mais baixos do que nos outros dois grupos. O consumo de morfina no grupo IA foi menor do que no grupo controle no período de 0-6 horas, como também foi menor o consumo total de morfina em 24 horas. Os escores EVAr no pós-operatório do grupo BPBI foram menores do que os escores dos dois outros grupos nas primeiras duas horas e menores do que os do grupo controle nos períodos de 4 e 6 horas (p < 0,05). No grupo IA, os escores EVAr e EVAm nos períodos de 2, 4 e 6 horas foram menores do que no grupo controle (p < 0,05). CONCLUSÃO: O bloqueio do plexo braquial por via interescalênica mostrou ser mais eficaz do que a injeção intra-articular de anestésico local para analgesia pós-operatória. .

JUSTIFICACIÓN Y OBJETIVOS: En este estudio, nuestro objetivo fue comparar en el período postoperatorio los efectos analgésicos de la administración de la bupivacaína en el bloqueo del plexo braquial por vía interescalénica guiado por ecografía y bupivacaína intraarticular. MÉTODOS: En el primer grupo de pacientes se administraron 20 mL de bupivacaína al 0,25% y se llevó a cabo el bloqueo del plexo braquial por vía interescalénica (BPBI) guiado por ecografía, mientras que al segundo grupo de pacientes se le administraron 20 mL de bupivacaína al 0,25% por vía intraarticular (IA) tras la cirugía. Los pacientes del tercer grupo fueron considerados como grupo control y en ellos no se realizó ningún bloqueo. La analgesia controlada por el paciente con morfina se usó en los 3 grupos para la analgesia postoperatoria. RESULTADOS: En el grupo BPBI, el consumo de morfina en los períodos entre 0-4, 6-12 y 12-24 h del postoperatorio y el consumo total en 24 h fueron más bajos que en los otros 2 grupos. El consumo de morfina en el grupo IA fue menor que en el grupo control en el período de 0-6 h, como también fue menor el consumo total de morfina en 24 h. Las puntuaciones EVAr en el postoperatorio del grupo BPBI fueron menores que las de los otros 2 grupos en las primeras 2 h y menores que los del grupo control en los períodos de 4 y 6 h (p < 0,05). En el grupo IA, las puntuaciones EVAr y EVAm en los períodos de 2, 4 y 6 h fueron menores que en el grupo control (p < 0,05). CONCLUSIÓN: El BPBI mostró ser más eficaz que la inyección intraarticular de anestésico local para analgesia postoperatoria. .

MYH9 gene polymorphisms may be associated with cerebrovascular blood flow in patients with type 2 diabetes.

Genetic factors play an important role in type 2 diabetes (T2D) complications. Alteration of cerebrovascular blood flow (CBF) is a direct result of cerebrovascular diseases. However, few studies have reported the role of genetics on CBF in patients with T2D. We investigated whether single-nucleotide polymorphisms (SNPs) in metabolic disease genes are associated with CBF in patients with T2D. CBF velocities of CBF were measured in 337 Han Chinese patients with T2D using transcranial Doppler sonography, with 54 cerebrovascular blood flow parameters documented. Fifty-two SNPs from 31 metabolic disease candidate genes were genotyped in patients. Quantitative allelic association and haplotype analyses were performed for candidate gene SNPs and CBF phenotypes. Spearman correlation was used to determine the relationship between CBF parameters and basic clinical characteristics, particularly, body mass index, lipids, fibrinogen, and GHbA1c. MYH9 gene SNPs (rs875726 and rs735853) may be associated with the peak velocity of the right-middle cerebral artery. SNPs rs875726, rs2009930, and rs375246 of the MYH9 gene may be associated with the mean velocity of the right-anterior and posterior cerebral artery. The haplotype G-C-A (rs2239782-rs3752462- rs2269532) of MYH9 may be associated with CBF. MYH9 gene polymorphisms may be associated with multiple CBF phenotypes in Chinese patients with T2D. However, whether MYH9 is a candidate gene for cerebrovascular diseases in Chinese patients with T2D remains unknown.

Effect of the microtubule-associated protein tau on dynamics of single-headed motor proteins KIF1A.

Intracellular transport based on molecular motors and its regulation are crucial to the functioning of cells. Filamentary tracks of the cells are abundantly decorated with nonmotile microtubule-associated proteins, such as tau. Motivated by experiments on kinesin-tau interactions [Dixit et al., Science 319, 1086 (2008)] we developed a stochastic model of interacting single-headed motor proteins KIF1A that also takes into account the interactions between motor proteins and tau molecules. Our model reproduces experimental observations and predicts significant effects of tau on bound time and run length which suggest an important role of tau in regulation of kinesin-based transport.

Influence of molecular motors on the motion of particles in viscoelastic media.

We study theoretically and by numerical simulations the motion of particles driven by molecular motors in a viscoelastic medium representing the cell cytoplasm. For this, we consider a generalized Langevin equation coupled to a stochastic stepping dynamics for the motors that takes into account the action of each motor separately. In the absence of motors, the model produces subdiffusive motion of particles characterized by a power-law scaling of the mean square displacement versus the lag time as t^{α}, with 0<α<1, similar to that observed in cells. Our results show how the action of the motors can induce a transition to a superdiffusive regime at large lag times with the characteristics of those found in experiments reported in the literature. We also show that at small lag times, the motors can act as static crosslinkers that slow down the natural subdiffusive transport. An analysis of previously reported experimental data in the relevant time scales provides evidence of this phenomenon. Finally, we study the effect of a harmonic potential representing an optical trap, and we show a way to approach to a macroscopic description of the active transport in cells. This last point stresses the relevance of the molecular motors for generating not only directed motion to specific targets, but also fast diffusivelike random motion.

MYH9 and APOL1 gene polymorphisms and the risk of CKD in patients with lupus nephritis from an admixture population.

MYH9 polymorphisms have been described to be associated with the risk of CKD in non-diabetic nephropathy, HIV nephropathy and FSGS. Predominating in black descendants, MHY9 genetic variants could partially explain the excess risk of CKD associated with African ancestry. However, recent data suggests that APOL1 gene co-segregate with MYH9, and could be the gene truly associated with CKD risk. In this study, we evaluated the role of MYH9 and APOL1 gene polymorphisms in the risk of CKD in Brazilian patients with lupus nephritis (LN). A retrospective analysis of 196 LN patients was done. MYH9 rs4821480, rs2032487, rs4821481 and rs3752462, APOL 1rs73885319, rs16996616, rs60910145, rs71785313, and APOL3 rs11089781 gene polymorphisms were determined. Genetic ancestry was ascertained both by autossomal ancestry and mitochondrial haplogroup. Primary outcome was defined as doubling of serum creatinine (DC) or end stage renal disease (ESRD). Sixty-two patients presented the PO. In our population, MYH9 and APOL1 were not in LD. None APOL polymorphism was associated with the PO, whereas rs3752462 MYH9 polymorphism showed a positive association (HR3.72, 95%CI 1.47-9.38, p = 0.005). When we analyzed the MYH9 E1 haplotype, the GCCT carriers (1 or 2 alelles present in 29.7% in the PO group vs. 18.5% in controls) showed a significant association to the risk of PO, even after adjustments for baseline estimated creatinine clearance and autossomal ancestry (HR 2.0, 95%CI 1.2-3.4, p = 0.01). Our results show that in our population MYH9, but not APOL1, gene polymorphisms confer an increased risk of CKD in LN patients, independently of race.

When size does matter: organelle size influences the properties of transport mediated by molecular motors.

BACKGROUND: Organelle transport is driven by the action of molecular motors. In this work, we studied the dynamics of organelles of different sizes with the aim of understanding the complex relation between organelle motion and microenvironment. METHODS: We used single particle tracking to obtain trajectories of melanosomes (pigmented organelles in Xenopus laevis melanophores). In response to certain hormones, melanosomes disperse in the cytoplasm or aggregate in the perinuclear region by the combined action of microtubule and actin motors. RESULTS AND CONCLUSIONS: Melanosome trajectories followed an anomalous diffusion model in which the anomalous diffusion exponent (α) provided information regarding the trajectories' topography and thus of the processes causing it. During aggregation, the directionality of big organelles was higher than that of small organelles and did not depend on the presence of either actin or intermediate filaments (IF). Depolymerization of IF significantly reduced α values of small organelles during aggregation but slightly affect their directionality during dispersion. GENERAL SIGNIFICANCE: Our results could be interpreted considering that the number of copies of active motors increases with organelle size. Transport of big organelles was not influenced by actin or IF during aggregation showing that these organelles are moved processively by the collective action of dynein motors. Also, we found that intermediate filaments enhance the directionality of small organelles suggesting that this network keeps organelles close to the tracks allowing their efficient reattachment. The higher directionality of small organelles during dispersion could be explained considering the better performance of kinesin-2 vs. dynein at the single molecule level.

Rotenone-dependent changes of anterograde motor protein expression and mitochondrial mobility in brain areas related to neurodegenerative diseases.

The presence of protein aggregates is common in neurodegenerative disorders; however, the real cause and effect of these aggregates during neurodegeneration is still a matter of investigation. We hypothesize that impairment of intracellular traffic may appear in the absence of protein inclusions and might trigger protein aggregation. In the present study, we aimed to evaluate mitochondria mobility as well as protein and messenger RNA expression of KIF1B and KIF5 that are molecular motors for neuronal anterograde traffic, in hippocampus, substantia nigra, and locus coeruleus of 10-month-old Lewis rats and cultured cells, from these same areas, following exposure to low doses of rotenone that do not lead to protein inclusions. The present study showed alteration in KIF1B and KIF5 expression, as well as in mitochondria mobility prior to protein aggregation involved in neurodegenerative disorders. These findings suggest that change in intracellular trafficking might be critical and one of the primary events for impairment of cell physiology during neurodegeneration associated with protein inclusions.

A novel component of the Rhodobacter sphaeroides Fla1 flagellum is essential for motor rotation.

Here we describe a novel component essential for flagellar rotation in Rhodobacter sphaeroides. This protein is encoded by motF (RSP_0067), the first gene of a predicted transcriptional unit which contains two hypothetical genes. Sequence analysis indicated that MotF is a bitopic membrane-spanning protein. Protease sensitivity assays and green fluorescent protein (GFP) fusions confirmed this prediction and allowed us to conclude that the C terminus of MotF is located in the periplasmic space. Wild-type cells expressing a functional GFP-MotF fusion show a single fluorescent focus per cell. The localization of this protein in different genetic backgrounds allowed us to determine that normal localization of MotF depends on the presence of FliL and MotB. Characterization of a ΔmotF pseudorevertant strain revealed that a single nucleotide change in motB suppresses the Mot(-) phenotype of the motF mutant. Additionally, we show that MotF also becomes dispensable when other mutant alleles of motB previously isolated as second-site suppressors of ΔfliL were expressed in the motF mutant strain. These results show that MotF is a new component of the Fla1 flagellum, which together with FliL is required to promote flagellar rotation, possibly through MotB.

The invasion mode of GH(3) cells is conditioned by collagen subtype, and its efficiency depends on cell-cell adhesion.

The adaptation of GH(3) cells to different microenvironments is a consequence of a partial compromise with the tumor phenotype. A collagen type IV enriched microenvironment favors an invasive phenotype and increases the substrate adhesion capacity, whereas it decreases the phosphorylation of the regulatory myosin light chain and the aggregation capacity. In contrast, the higher internal tension and increased aggregation capacity induced by collagen type I/III are factors that reduce the invasion rate. Our results show, for the first time, the importance of collagen subtypes in determining the migratory strategy: collagen I/III favors mesenchymal-like motility, whereas collagen type IV induces an ameboid-type displacement. The reciprocal modulation of the myosin light chain kinase and the Rho-kinase determines the invasive capacity through changes in tissue cohesion, extracellular matrix affinity, regulatory myosin light chain phosphorylation and spatial distribution. The collagen subtype determines which of the mechano-transduction signaling pathways will regulate the tensional homeostasis and affect the invasion ability as well as the preferred migration strategy of the cells.

Transport properties of melanosomes along microtubules interpreted by a tug-of-war model with loose mechanical coupling.

In this work, we explored theoretically the transport of organelles driven along microtubules by molecular motors of opposed polarities using a stochastic model that considers a Langevin dynamics for the cargo, independent cargo-motor linkers and stepping motion for the motors. It has been recently proposed that the stiffness of the motor plays an important role when multiple motors collectively transport a cargo. Therefore, we considered in our model the recently reported values for the stiffness of the cargo-motor linker determined in living cells (∼0.01 pN/nm,) which is significantly lower than the motor stiffness obtained in in vitro assays and used in previous studies. Our model could reproduce the multimodal velocity distributions and typical trajectory characteristics including the properties of the reversions in the overall direction of motion observed during melanosome transport along microtubules in Xenopus laevis melanophores. Moreover, we explored the contribution of the different motility states of the cargo-motor system to the different modes of the velocity distributions and could identify the microscopic mechanisms of transport leading to trajectories compatible with those observed in living cells. Finally, by changing the attachment and detachment rates, the model could reproduce the different velocity distributions observed during melanosome transport along microtubules in Xenopus laevis melanophores stimulated for aggregation and dispersion. Our analysis suggests that active tug-of-war processes with loose mechanical coupling can account for several aspects of cargo transport along microtubules in living cells.

Reconstructing the free-energy landscape associated to molecular motors processivity.

We propose a biochemical model providing the kinetic and energetic descriptions of the processivity dynamics of kinesin and dinein molecular motors. Our approach is a modified version of a well known model describing kinesin dynamics and considers the presence of a competitive inhibition reaction by ADP. We first reconstruct a continuous free-energy landscape of the cycle catalyst process that allows us to calculate the number of steps given by a single molecular motor. Then, we calculate an analytical expression associated to the translational velocity and the stopping time of the molecular motor in terms of time and ATP concentration. An energetic interpretation of motor processivity is discussed in quantitative form by using experimental data. We also predict a time duration of collective processes that agrees with experimental reports.

Currents in defective coupled ratchets.

Transport phenomena in a one-dimensional system of interacting particles is studied. This system is embedded in a periodic and left-right asymmetric potential driven by a force periodic in time and space. When the density (number of particles per site) is an integer, directional current of the particles is collective; that is, it involves the whole system since all the sites are equivalents. On the other hand, when the system has a defect, a new localized or noncollective current appears due to the migration of defects from one site to another. We show here how this "defective" (defects generated) current can be controlled by white noise.