Immunomodulatory Effects in Healthy Individuals Following a 4-Week Taoist Qigong Intervention: A Comparative Study.

BACKGROUND Qigong, an ancient health preservation technique forming part of Traditional Chinese Medicine, combines slow body movements, breathing, and meditation. While this meditative movement system has been reported to offer various physical and psychological benefits, studies on the Taoist school of qigong are sparse. This study, therefore, aimed to investigate the effects of Taoist qigong on white blood cells and other immune parameters in healthy individuals. MATERIAL AND METHODS Thirty-eight participants were recruited for the study, with 21 assigned to the experimental group and 17 to the control group. Participants in the experimental group engaged in a four-week Taoist qigong program. Blood samples for immune parameter quantification, including leukocyte count, neutrophil, eosinophil, basophil, lymphocyte, and large unstained cell (LUC) counts, as well as concentrations of IgG, IgA, IgM, C3, and C4, were collected one day before the experiment started and one day after it ended. RESULTS Post-program, the experimental group exhibited significantly lower total leukocyte counts, and reduced numbers of lymphocytes and LUCs. Additionally, a higher percentage of monocytes was noted in this group. CONCLUSIONS Taoist qigong practice induced a distinct immunomodulatory profile, characterized by decreased counts of several white blood cell parameters and increased percentages of certain agranulocytes. This outcome presents intriguing implications from a psychobiological perspective and highlights the need for further research into the immune effects of Taoist mind-body practice.

Stochastic SIR model predicts the evolution of COVID-19 epidemics from public health and wastewater data in small and medium-sized municipalities: A one year study.

The level of unpredictability of the COVID-19 pandemics poses a challenge to effectively model its dynamic evolution. In this study we incorporate the inherent stochasticity of the SARS-CoV-2 virus spread by reinterpreting the classical compartmental models of infectious diseases (SIR type) as chemical reaction systems modeled via the Chemical Master Equation and solved by Monte Carlo Methods. Our model predicts the evolution of the pandemics at the level of municipalities, incorporating for the first time (i) a variable infection rate to capture the effect of mitigation policies on the dynamic evolution of the pandemics (ii) SIR-with-jumps taking into account the possibility of multiple infections from a single infected person and (iii) data of viral load quantified by RT-qPCR from samples taken from Wastewater Treatment Plants. The model has been successfully employed for the prediction of the COVID-19 pandemics evolution in small and medium size municipalities of Galicia (Northwest of Spain).

Potential Distribution and Connectivity for Two Plethodontid Salamanders: Conservation Areas and Landscape Corridors for Two Endemic Species of México and Guatemala.

Habitat loss is one of the most important threats to biodiversity; it alters the habitat connectivity of species and is among the main causes of the global amphibian extinction crisis. Identifying the potential areas of distribution and connectivity of species is of the utmost importance so that informed decisions can be made for the conservation of vulnerable amphibian populations. In this study, we performed species distribution models and used circuit theory to model omnidirectional connectivity for two plethodontid salamanders of conservation concern distributed in the forests of Chiapas, Mexico, and Guatemala (Bolitoglossa franklini and Bolitoglossa lincolni). Potential distribution maps show an affinity for well-preserved montane forests for both species. Likewise, we found that the niches of the species are not similar. The connectivity models show that the main areas of connectivity are in the Meseta Central de Chiapas, Sierra Madre de Chiapas, and the Cordillera Volcánica Guatemalense, in this last range, important areas of connectivity were located, as well as least-cost paths and barriers to the movement of both species. We identified that important areas of climatic suitability and connectivity are not within the protected natural areas and may be threatened by the increasing influence of anthropogenic activities. The results of our study show the importance of preserving the regional forests to ensure the persistence of species with arboreal habits and high sensitivity to habitat transformation, as well as to recognize and prioritize potential areas for management and protection in both southern Mexico and Guatemala.

Immuno-priming durvalumab with bevacizumab in HER2-negative advanced breast cancer: a pilot clinical trial.

BACKGROUND: Preclinical research suggests that the efficacy of immune checkpoint inhibitors in breast cancer can be enhanced by combining them with antiangiogenics, particularly in a sequential fashion. We sought to explore the efficacy and biomarkers of combining the anti-PD-L1 durvalumab plus the antiangiogenic bevacizumab after bevacizumab monotherapy for advanced HER2-negative breast cancer. METHODS: Patients had advanced HER2-negative disease that progressed while receiving single-agent bevacizumab maintenance as a part of a previous chemotherapy plus bevacizumab regimen. Treatment consisted of bi-weekly durvalumab plus bevacizumab (10 mg/kg each i.v.). Peripheral-blood mononuclear cells (PBMCs) were obtained before the first durvalumab dose and every 4 weeks and immunophenotyped by flow-cytometry. A fresh pre-durvalumab tumor biopsy was obtained; gene-expression studies and immunohistochemical staining to assess vascular normalization and characterize the immune infiltrate were conducted. Patients were classified as "non-progressors" if they had clinical benefit (SD/PR/CR) at 4 months. The co-primary endpoints were the changes in the percentage T cell subpopulations in PBMCs in progressors versus non-progressors, and PFS/OS time. RESULTS: Twenty-six patients were accrued. Median PFS and OS were 3.5 and 11 months; a trend for a longer OS was detected for the hormone-positive subset (19.8 versus 7.4 months in triple-negatives; P = 0.11). Clinical benefit rate at 2 and 4 months was 60% and 44%, respectively, without significant differences between hormone-positive and triple-negative (P = 0.73). Non-progressors' tumors displayed vascular normalization features as a result of previous bevacizumab, compared with generally abnormal patterns observed in progressors. Non-progressors also showed increased T-effector and T-memory signatures and decreased TREG signatures in gene expression studies in baseline-post-bevacizumab-tumors compared with progressors. Notably, analysis of PBMC populations before durvalumab treatment was concordant with the findings in tumor samples and showed a decreased percentage of circulating TREGs in non-progressors. CONCLUSIONS: This study reporting on sequential bevacizumab+durvalumab in breast cancer showed encouraging activity in a heavily pre-treated cohort. The correlative studies agree with the preclinical rationale supporting an immunopriming effect exerted by antiangiogenic treatment, probably by reducing TREGs cells both systemically and in tumor tissue. The magnitude of this benefit should be addressed in a randomized setting. TRIAL REGISTRATION: (www.clinicaltrials.gov): NCT02802098 . Registered on June 16, 2020.

Predictive Model for Delivery Efficiency: Erythrocyte Membrane-Camouflaged Magnetofluorescent Nanocarriers Study.

Delivery efficiencies of theranostic nanoparticles (NPs) based on passive tumor targeting strongly depend either on their blood circulation time or on appropriate modulations of the tumor microenvironment. Therefore, predicting the NP delivery efficiency before and after a tumor microenvironment modulation is highly desirable. Here, we present a new erythrocyte membrane-camouflaged magnetofluorescent nanocarrier (MMFn) with long blood circulation time (92 h) and high delivery efficiency (10% ID for Ehrlich murine tumor model). MMFns owe their magnetic and fluorescent properties to the incorporation of manganese ferrite nanoparticles (MnFe2O4 NPs) and IR-780 (a lipophilic indocyanine fluorescent dye), respectively, to their erythrocyte membrane-derived camouflage. MMFn composition, morphology, and size, as well as optical absorption, zeta potential, and fluorescent, magnetic, and magnetothermal properties, are thoroughly examined in vitro. We then present an analytical pharmacokinetic (PK) model capable of predicting the delivery efficiency (DE) and the time of peak tumor uptake (tmax), as well as changes in DE and tmax due to modulations of the tumor microenvironment, for potentially any nanocarrier. Experimental PK data sets (blood and tumor amounts of MMFns) are simultaneously fit to the model equations using the PK modeling software Monolix. We then validate our model analytical solutions with the numerical solutions provided by Monolix. We also demonstrate how our a priori nonmechanistic model for passive targeting relates to a previously reported mechanistic model for active targeting. All in vivo PK studies, as well as in vivo and ex vivo biodistribution studies, were conducted using two noninvasive techniques, namely, fluorescence molecular tomography (FMT) and alternating current biosusceptometry (ACB). Finally, histopathology corroborates our PK and biodistribution results.

SELANSI: a toolbox for simulation of stochastic gene regulatory networks.

Motivation: Gene regulation is inherently stochastic. In many applications concerning Systems and Synthetic Biology such as the reverse engineering and the de novo design of genetic circuits, stochastic effects (yet potentially crucial) are often neglected due to the high computational cost of stochastic simulations. With advances in these fields there is an increasing need of tools providing accurate approximations of the stochastic dynamics of gene regulatory networks (GRNs) with reduced computational effort. Results: This work presents SELANSI (SEmi-LAgrangian SImulation of GRNs), a software toolbox for the simulation of stochastic multidimensional gene regulatory networks. SELANSI exploits intrinsic structural properties of gene regulatory networks to accurately approximate the corresponding Chemical Master Equation with a partial integral differential equation that is solved by a semi-lagrangian method with high efficiency. Networks under consideration might involve multiple genes with self and cross regulations, in which genes can be regulated by different transcription factors. Moreover, the validity of the method is not restricted to a particular type of kinetics. The tool offers total flexibility regarding network topology, kinetics and parameterization, as well as simulation options. Availability and implementation: SELANSI runs under the MATLAB environment, and is available under GPLv3 license at https://sites.google.com/view/selansi. Contact: antonio@iim.csic.es.

Effects of bovine serum albumin (BSA) on the excited-state properties of meso-tetrakis(sulfonatophenyl) porphyrin (TPPS4).

To infer changes in the photophysical properties of porphyrins due to complexation with albumin, a combination of Z-scan and conventional spectroscopic techniques was employed. We measured the characteristics of excited states of meso-tetrakis(sulfonatophenyl) porphyrin bound to bovine serum albumin and observed that the binding reduces the intersystem crossing quantum yield and increases the internal conversion one. A reverse saturable absorption process was observed in the nanosecond timescale. These results are important for prediction of the efficiency of this complex in medical and optical applications, because associating porphyrins to proteins enables better accumulation in tumors and improves its stability in optical devices, but at the same time, decreases its triplet quantum yield.

Photodynamic inactivation of Bovine herpesvirus type 1 (BoHV-1) by porphyrins.

In this work, the photodynamic efficiency of anionic meso-tetrakis sulfonophenyl (TPPS4), cationic meso-tetrakis methylpyridiniumyl (TMPyP) and their zinc complexes (ZnTPPS4 and ZnTMPyP) in the inactivation of Bovine herpesvirus type 1 (BoHV-1) was evaluated. At a non-cytotoxic concentration, all porphyrins showed significant antiviral activity after irradiation using a halogen lamp. The efficiency of the cationic porphyrins was higher than that of the anionic ones. Porphyrin complexation with zinc increases its lipophilicity and the number of absorbed photons, dramatically reducing the time for complete virus inactivation. The high superposition of the compound optical absorption and light source emission spectra played a key role in the virus inactivation efficiency. The results demonstrated the high effectivity of the photodynamic inactivation of BoHV-1. This method can be used as an auxiliary in the treatment of disorders attributed to BoHV-1 infection, and the porphyrins are promising photosensitizers for this application.

Current state-of-art of STR sequencing in forensic genetics.

The current state of validation and implementation strategies of massively parallel sequencing (MPS) technology for the analysis of STR markers for forensic genetics use is described, covering the topics of the current catalog of commercial MPS-STR panels, leading MPS-platforms, and MPS-STR data analysis tools. In addition, the developmental and internal validation studies carried out to date to evaluate reliability, sensitivity, mixture analysis, concordance, and the ability to analyze challenged samples are summarized. The results of various MPS-STR population studies that showed a large number of new STR sequence variants that increase the power of discrimination in several forensically relevant loci are also presented. Finally, various initiatives developed by several international projects and standardization (or guidelines) groups to facilitate application of MPS technology for STR marker analyses are discussed in regard to promoting a standard STR sequence nomenclature, performing population studies to detect sequence variants, and developing a universal system to translate sequence variants into a simple STR nomenclature (numbers and letters) compatible with national STR databases.

Toward predictive food process models: A protocol for parameter estimation.

Mathematical models, in particular, physics-based models, are essential tools to food product and process design, optimization and control. The success of mathematical models relies on their predictive capabilities. However, describing physical, chemical and biological changes in food processing requires the values of some, typically unknown, parameters. Therefore, parameter estimation from experimental data is critical to achieving desired model predictive properties. This work takes a new look into the parameter estimation (or identification) problem in food process modeling. First, we examine common pitfalls such as lack of identifiability and multimodality. Second, we present the theoretical background of a parameter identification protocol intended to deal with those challenges. And, to finish, we illustrate the performance of the proposed protocol with an example related to the thermal processing of packaged foods.

Hemolytic potential of miltefosine is dependent on cell concentration: Implications for in vitro cell cytotoxicity assays and pharmacokinetic data.

Miltefosine possesses antiparasitic, antibacterial, antifungal and antitumor activities; however, its mechanism of action is not well established. In the current work, the miltefosine concentrations required to achieve 50% hemolysis in PBS were shown to vary from 600 µM using 5×10(9) cells/mL to ~2.9 µM for ~5×10(6) cells/mL. This cell concentration-dependent hemolytic potential was described using an equation that included the membrane-water partition coefficient (K) and miltefosine concentrations in the cell membrane (cm) and aqueous medium (cw) as variables. The best-fit values for the 50% hemolysis data were log K=4.68, cm=110.8 mM, and cw=2.3 µM. Hemolysis measurements in whole blood were used to determine the erythrocyte membrane-plasma partition coefficient of miltefosine (Log KM/P=1.77). Additionally, miltefosine concentration in whole blood was found to be ~86% of that in plasma. Previously reported clinical pharmacokinetics data indicate that the plasma concentration of miltefosine peaks at ~90 µg/mL when treating visceral leishmaniasis. Using this concentration, which corresponds to ~77 µg/mL miltefosine in whole blood, we found only 2.8% hemolysis. Significant hemolysis (5.4%) was observed only after doubling the concentration to 180 µg/mL. Recently reported data indicate that miltefosine inhibitory concentrations in Leishmania are also dependent on cell concentration. The biophysical parameters assessed in the current study indicated that this type of response is associated with the accumulation of the drug in the cell membrane, which becomes damaged when critical drug concentrations are reached.

The cytotoxic activity of miltefosine against Leishmania and macrophages is associated with dynamic changes in plasma membrane proteins.

In this study, we combined electron paramagnetic resonance (EPR) spectroscopy with an analysis of biophysical cellular parameters to study the mechanisms underlying the in vitro anti-leishmanial activity of miltefosine (MT). A thiol-specific spin label attached to membrane-bound proteins of Leishmania amazonensis and peritoneal macrophages indicated that MT may bind to plasma membrane proteins in large quantities via a detergent-like action and cause structural changes associated with a marked increase in dynamics and exposure to an aqueous environment. EPR spectra of a spin-labeled stearic acid indicated strong interactions between the probe and membrane proteins and a marked increase in the membrane fluidity of MT-treated cells. The cytotoxicity of MT was found to depend on the cell concentration used in the assay. This dependence was described by an equation involving the 50% inhibitory concentrations of MT in the aqueous medium (cw50) and the cell membrane (cm50) and the membrane-aqueous medium partition coefficient of MT (K). With a cw50 of 8.7µM, macrophages were less sensitive to MT than amastigotes and promastigotes of Leishmania, which had cw50 values of 2.4-3.1µM. The estimated cm50 of MT for Leishmania was 1.8M, which appears sufficient to cause ruptures or formation of pores in the plasma membrane. Additionally, we demonstrated that the changes in the plasma membrane detected by EPR spectroscopy occurred at cytotoxic concentrations of MT, as assessed through in vitro assays.

Stochastic modeling and numerical simulation of gene regulatory networks with protein bursting.

Gene expression is inherently stochastic. Advanced single-cell microscopy techniques together with mathematical models for single gene expression led to important insights in elucidating the sources of intrinsic noise in prokaryotic and eukaryotic cells. In addition to the finite size effects due to low copy numbers, translational bursting is a dominant source of stochasticity in cell scenarios involving few short lived mRNA transcripts with high translational efficiency (as is typically the case for prokaryotes), causing protein synthesis to occur in random bursts. In the context of gene regulation cascades, the Chemical Master Equation (CME) governing gene expression has in general no closed form solution, and the accurate stochastic simulation of the dynamics of complex gene regulatory networks is a major computational challenge. The CME associated to a single gene self regulatory motif has been previously approximated by a one dimensional time dependent partial integral differential equation (PIDE). However, to the best of our knowledge, multidimensional versions for such PIDE have not been developed yet. Here we propose a multidimensional PIDE model for regulatory networks involving multiple genes with self and cross regulations (in which genes can be regulated by different transcription factors) derived as the continuous counterpart of a CME with jump process. The model offers a reliable description of systems with translational bursting. In order to provide an efficient numerical solution, we develop a semilagrangian method to discretize the differential part of the PIDE, combined with a composed trapezoidal quadrature formula to approximate the integral term. We apply the model and numerical method to study sustained stochastic oscillations and the development of competence, a particular case of transient differentiation attained by certain bacterial cells under stress conditions. We found that the resulting probability distributions are distinguishable from those characteristic of other transient differentiation processes. In this way, they can be employed as markers or signatures that identify such phenomena from bacterial population experimental data, for instance. The computational efficiency of the semilagrangian method makes it suitable for purposes like model identification and parameter estimation from experimental data or, in combination with optimization routines, the design of gene regulatory networks under molecular noise.

Transmittance and Autofluorescence of Neonatal Rat Stratum Corneum: Nerolidol Increases the Dynamics and Partitioning of Protoporphyrin IX into Intercellular Membranes.

In this work, we developed an experimental apparatus to directly measure transmittance and fluorescence in the stratum corneum (SC) ex vivo. The SC transmittance varied from ~6 to ~52 % in the wavelength range of 280-850 nm. For 260-300 nm excitation, the SC autofluorescence showed a strong emission band between 290 and 425 nm, which is associated with tryptophan, and another in the 600-670 nm range, which we attributed to a process involving resonance energy transfer to very hydrophobic keratin filaments. Weaker emission associated with less hydrophobic keratin filaments was also observed in the wavelength range of 350-480 nm. Protoporphyrin IX (PpIX) was incorporated into SC membranes, and its penetration was further increased by the addition of nerolidol to the treatment suspension. Both PpIX and the endogenous porphyrins showed fluorescence anisotropy consistent with their localization in SC membranes, and their molecular dynamics increased significantly in the presence of 1 % nerolidol. The emission and excitation spectra of PpIX and the endogenous SC porphyrins showed similar alterations during the photobleaching induced by 405-nm irradiation. This work also highlights the SC contribution to skin autofluorescence, which could be useful for fluorescence spectroscopy applications in the early diagnosis of skin diseases.

Acute Effects on the Counts of Innate and Adaptive Immune Response Cells After 1 Month of Taoist Qigong Practice.

BACKGROUND: Qigong is an ancient form of health maintenance, dating back thousands of years, which is part of Traditional Chinese Medicine. Numerous physical as well as mental benefits have been classically ascribed to this traditional mind-body method which integrates slow body movements, breathing, and meditation. Albeit we have already reported an immunomodulatory action of qigong in other investigations, measures were then assessed 1 day after the qigong program ended. PURPOSE: The aim of the present study was to assess the acute effects of Taoist qigong practice on immune cell counts in healthy subjects 1 h after training. METHOD: Forty-three healthy subjects participated in the study of whom 25 were randomly allocated to the experimental group and 18 to the control group. The experimental subjects underwent daily qigong training for 1 month. Blood samples for the quantification of immune parameters (number and percentage of monocytes, neutrophils, eosinophils, total lymphocytes, B lymphocytes, and natural killer (NK) cells) were taken the day before the experiment commenced and 1 h after the last session of the training program ended. As statistical analysis, analysis of covariance (ANCOVA) was performed. RESULTS: Statistically significant differences were found between the experimental and control groups, with the experimental group showing higher values in the number (p = 0.006) and the percentage (p = 0.04) of B lymphocytes, as well as lower values in the percentage of NK cells (p = 0.05), as compared to control. CONCLUSION: This study demonstrates that Taoist qigong is able to exert acute immunomodulatory effects on components of both innate as well as adaptive immune response.

Liposomal Entrapment of 4-Nerolidylcatechol: Impact on Phospholipid Dynamics, Drug Stability and Bioactivity.

Liposomes containing 4-nerolidylcatechol (4-NC), the major metabolite isolated from Pothomorphe umbellata, were obtained and characterized. Influence of liposomal encapsulation on chemical stability of 4-NC and on cytotoxicity profile of this drug was evaluated. Soybean phosphatidylcholine liposomes were prepared by lipid film hydration followed by extrusion. Entrapment efficiency for 4-NC was approximately 92%. Mean diameter of liposomes was 100 nm with a polydispersity index below 0.13. Liposomal 4-NC (L4-NC) and free drug (F4-NC) were submitted to forced degradation assays, monitored by HPLC. Photodegradation assay followed ICH Guidelines, using a photostability chamber equipped with both UV and white light sources. Liposomal encapsulation was able to markedly reduce 4-NC degradation rates under all the conditions tested. L4-NC showed a half-live approximately 15% higher than F4-NC under light exposure. After 72 hours, acid and base hydrolysis of F4-NC lead to 13 and 16% of degradation, respectively. However, no degradation was observed in L4-NC. EPR spectra of liposomal membrane showed that greatest changes in membrane properties were obtained when 5-doxyl stearic acid was used as the spin label, indicating a marked decrease in the fluidity of the bilayer. Following incubation with K562 cells, 4-NC showed a concentration-dependent cytotoxicity profile, while L4-NC exhibited a time and concentration-dependent profile, consistent with a controlled drug release system. F4-NC induced extensive hemolysis under isotonic conditions; conversely liposomal encapsulation protected erythrocytes from 4-NC induced lysis. Liposomal 4-NC resulted in a hemocompatibility and stable formulation, representing a viable drug delivery system to further investigate in vivo performances of 4-NC in pre clinical studies.

Long-term results of the transattical approach: an alternative technique for cochlear implantation.

Cochlear implantation through the standard posterior tympanotomy approach may sometimes be challenging. In cases with complicated anatomy or malformations, an alternative surgical technique may be chosen. The transattical approach is a simple technique based on a mastoidectomy and a transmeatal cochleostomy. The electrode is driven to the middle ear through the attic. This way it overcomes some of the standard technique's drawbacks. Our aim is to assess the value of this alternative approach in cochlear implant surgery. We conducted a comparative retrospective study; we included 74 patients operated by transattical approach and 59 patients operated with the standard technique. Auditory performance and complications at long term follow-up were compared. The consequences of the different trajectory of the electrode in the transattical approach were also studied. No significant differences were found between both groups regarding complication rates and cochlear implant performance. The electrode's integrity was not significantly affected by its different position and angles, when compared to the standard approach. We conclude that transattical approach is a safe technique for cochlear implantation. It may be considered as an alternative to the posterior tympanotomy approach for those cases where this cannot be performed.

Miltefosine increases lipid and protein dynamics in Leishmania amazonensis membranes at concentrations similar to those needed for cytotoxicity activity.

Miltefosine (MT) is a membrane-active alkylphospholipid licensed for the topical treatment of breast cancer skin metastases and the oral treatment of leishmaniasis, although its mechanism of action remains unclear. Electron paramagnetic resonance (EPR) spectroscopy of a spin-labeled lipid and a thiol-specific spin label in the plasma membrane of Leishmania promastigotes showed that MT causes dramatic increases in membrane dynamics. Although these alterations can be detected using a spin-labeled lipid, our experimental results indicated that MT interacts predominantly with the protein component of the membrane. Cell lysis was also detected by analyzing the supernatants of centrifuged samples for the presence of spin-labeled membrane fragments and cytoplasmic proteins. Using a method for the rapid incorporation of MT into the membrane, these effects were measured immediately after treatment under the same range of MT concentrations that cause cell growth inhibition. Cytotoxicity, estimated via microscopic counting of living and dead cells, indicated ∼70% cell death at the concentration of MT at which EPR spectroscopy detected a significant change in membrane dynamics. After this initial impact on the number of viable parasites, the processes of cell death and growth continued during the first 4 h of incubation. The EPR spectra of spin-labeled membrane-bound proteins were consistent with more expanded and solvent-exposed protein conformations, suggesting a detergent-like action. Thus, MT may form micelle-like structures around polypeptide chains, and proteins with a higher hydrophobicity may induce the penetration of hydrophilic groups of MT into the membrane, causing its rupture.

Modeling bacterial population growth from stochastic single-cell dynamics.

A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible.

Cell death in amastigote forms of Leishmania amazonensis induced by parthenolide.

BACKGROUND: Leishmania amazonensis infection results in diverse clinical manifestations: cutaneous, mucocutaneous or visceral leishmaniasis. The arsenal of drugs available for treating Leishmania infections is limited. Therefore, new, effective, and less toxic leishmaniasis treatments are still needed. We verified cell death in amastigote forms of Leishmania amazonensis induced by the sesquiterpene lactone parthenolide. RESULTS: The tested compound was able to concentration-dependently affect axenic and intracellular amastigotes, with IC50 values of 1.3 µM and 2.9 µM, respectively after 72 h incubation. No genotoxic effects were observed in a micronucleus test in mice. Parthenolide induced morphological and ultrastructural changes in axenic amastigotes, including a loss of membrane integrity, swelling of the mitochondrion, cytoplasmic vacuoles, and intense exocytic activity in the region of the flagellar pocket. These results led us to investigate the occurrence of autophagic vacuoles with monodansylcadaverine and the integrity of the plasma membrane and mitochondrial membrane potential using flow cytometry. In all of the tests, parthenolide had positive results. CONCLUSIONS: Our results indicate that the antileishmanial action of parthenolide is associated with autophagic vacuole appearance, a reduction of fluidity, a loss of membrane integrity, and mitochondrial dysfunction. Considering the limited repertoire of existing antileishmanial compounds, the products derived from medicinal plants has been one the greatest advances to help develop new chemotherapeutic approaches.