Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law

This paper presents a theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution. We study systems where gas molecules completely dissociate in the solvent into two parts, thus making Sievert's solubility law valid. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux is steady we obtain a differential equation on bubble radius. Bubble dynamics equation is solved analytically for the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop. We also obtain conditions of diffusion flux steadiness. The fulfillment of these conditions is studied for the case of nucleation of water vapor bubbles in magmatic melts.Comment: 22 pages, 3 figure

Minor Pilins of the Type IV Pilus System Participate in the Negative Regulation of Swarming Motility

Pseudomonas aeruginosa exhibits distinct surface-associated behaviors, including biofilm formation, flagellum-mediated swarming motility, and type IV pilus-driven twitching. Here, we report a role for the minor pilins, PilW and PilX, components of the type IV pilus assembly machinery, in the repression of swarming motility. Mutating either the pilW or pilX gene alleviates the inhibition of swarming motility observed for strains with elevated levels of the intracellular signaling molecule cyclic di-GMP (c-di-GMP) due to loss of BifA, a c-di-GMP-degrading phosphodiesterase. Blocking PilD peptidase-mediated processing of PilW and PilX renders the unprocessed proteins defective for pilus assembly but still functional in c-di-GMP-mediated swarming repression, indicating our ability to separate these functions. Strains with mutations in pilW or pilX also fail to exhibit the increase in c-di-GMP levels observed when wild-type (WT) or bifA mutant cells are grown on a surface. We also provide data showing that c-di-GMP levels are increased upon PilY1 overexpression in surface-grown cells and that this c-di-GMP increase does not occur in the absence of the SadC diguanylate cyclase. Increased levels of endogenous PilY1, PilX, and PilA are observed when cells are grown on a surface compared to liquid growth, linking surface growth and enhanced signaling via SadC. Our data support a model wherein PilW, PilX, and PilY1, in addition to their role(s) in type IV pilus biogenesis, function to repress swarming via modulation of intracellular c-di-GMP levels. By doing so, these pilus assembly proteins contribute to P. aeruginosa\u27s ability to coordinately regulate biofilm formation with its two surface motility systems

Cyclic Di-GMP-Mediated Repression of Swarming Motility by Pseudomonas aeruginosa PA14 Requires the MotAB Stator

The second messenger cyclic diguanylate (c-di-GMP) plays a critical role in the regulation of motility. In Pseudomonas aeruginosa PA14, c-di-GMP inversely controls biofilm formation and surface swarming motility, with high levels of this dinucleotide signal stimulating biofilm formation and repressing swarming. P. aeruginosa encodes two stator complexes, MotAB and MotCD, that participate in the function of its single polar flagellum. Here we show that the repression of swarming motility requires a functional MotAB stator complex. Mutating the motAB genes restores swarming motility to a strain with artificially elevated levels of c-di-GMP as well as stimulates swarming in the wild-type strain, while overexpression of MotA from a plasmid represses swarming motility. Using point mutations in MotA and the FliG rotor protein of the motor supports the conclusion that MotA-FliG interactions are critical for c-di-GMP-mediated swarming inhibition. Finally, we show that high c-di-GMP levels affect the localization of a green fluorescent protein (GFP)-MotD fusion, indicating a mechanism whereby this second messenger has an impact on MotCD function. We propose that when c-di-GMP level is high, the MotAB stator can displace MotCD from the motor, thereby affecting motor function. Our data suggest a newly identified means of c-di-GMP-mediated control of surface motility, perhaps conserved among Pseudomonas, Xanthomonas, and other organisms that encode two stator systems

ВИКОРИСТАННЯ СЦЕНАРІЇВ З ЕЛЕМЕНТАМИ КЛІНІЧНОЇ ФАРМАКОЛОГІЇ ПРИ ВИВЧЕННІ ОКРЕМИХ ТЕМ З АКУШЕРСТВА ТА ГІНЕКОЛОГІЇ

The aim of the work – to evaluate the effectiveness of training simulation trainings with the elements of clinical pharmacology in improving the quality of the educational process of students in the discipline of Obstetrics and Gynecology. The main body. A doctor of any specialty, including general practice, must know the causes, the clinic, the diagnosis of obstetric bleeding and tactics, depending on the reasons for it. Massive obstetric bleeding occupies a leading position among the causes of various types of severe obstetric disease, such as hemorrhagic shock, disseminated intravascular coagulation syndrome, etc., and the first among the causes of maternal mortality. The frequency of bleeding is from 6 to 11 % of all births. That is why it is relevant to work out the technology of the active management of the third period on the phantom of active management of the third period. In the course of our work, we concluded that training in the simulation center using modern phantoms allows students to master the basic practical skills of obstetrics, which may become necessary in future practical work of the doctor. general practice, and also provides the basis for mastering some manipulations for future specialization. Conclusions. The current development of medical science and practice necessitates making adjustments to the training of medical students with the approach of their education to international standards. That is why the quality of education in higher education institutions needs to be improved by effectively organizing and informing the educational process, by introducing advanced scientific developments into teaching practice.Мета роботи – оцінювання ефективності навчальних симуляційних тренінгів з елементами клінічної фармакології у підвищенні якості освітнього процесу студентів із дисципліни “Акушерство та гінекологія”. Основна частина. Лікар будь-якої спеціальності, в тому числі і загальної практики, повинен знати причини, клініку, діагностику акушерських кровотеч та тактику залежно від причин, що її зумовили. Масивні акушерські кровотечі займають провідне місце серед причин різних видів тяжкої акушерської патології, такої, як геморагічний шок, синдром дисемінованого внутрішньосудинного згортання крові тощо, та перше місце серед причин материнської смертності. Частота кровотеч складає від 6 до 11 % усіх пологів. Саме тому актуальним є відпрацювання на фантомі техніки активного ведення ІІІ періоду. В процесі нашої роботи ми зробили висновок, що навчання у симуляційному центрі із ви­користанням сучасних фантомів дозволяє студентам досконало оволодіти основними практичними навичками з акушерства, які можуть стати необхідними у майбутній практичній роботі лікаря загальної практики, а також закладає основу оволодіння деякими маніпуляціями для майбутньої спеціалізації. Висновки. Сучасний розвиток медичної науки й практики зумовлює необхідність вносити корективи в підготовку студентів-медиків із наближенням їхньої освіти до міжнародних стандартів. Тому якість освіти у вищих навчальних закладах необхідно покращити шляхом ефективної організації та інформатизації навчального процесу, за допомогою впровадження передових наукових розробок у практику викладання

Random-phase Approximation Treatment Of Edge Magnetoplasmons: Edge-state Screening And Nonlocality

A random-phase approximation (RPA) treatment of edge magnetoplasmons (EMP) is presented for strong magnetic fields, low temperatures, and integer filling factors \nu. It is valid for negligible dissipation and lateral confining potentials smooth on the scale of the magnetic length \ell_{0} but sufficiently steep that the Landau-level (LL) flattening can be neglected. LL coupling, screening by edge states, and nonlocal contributions to the current density are taken into account. In addition to the fundamental mode with typical dispersion relation \omega\sim q_x \ln(q_{x}), fundamental modes with {\it acoustic} dispersion relation \omega\sim q_x are obtained for \nu>2. For \nu=1,2 a {\bf dipole} mode exists, with dispersion relation \omega\sim q_x^3, that is directly related to nonlocal responses.Comment: Text 12 pages in Latex/Revtex format, 4 Postscript figure

Genes That Influence Swarming Motility and Biofilm Formation in Variovorax paradoxus EPS

Variovorax paradoxus is an aerobic soil bacterium associated with important biodegradative processes in nature. We use V. paradoxus EPS to study multicellular behaviors on surfaces.We recovered flanking sequence from 123 clones in a Tn5 mutant library, with insertions in 29 different genes, selected based on observed surface behavior phenotypes. We identified three genes, Varpa_4665, Varpa_4680, and Varpa_5900, for further examination. These genes were cloned into pBBR1MCS2 and used to complement the insertion mutants. We also analyzed expression of Varpa_4680 and Varpa_5900 under different growth conditions by qPCR.The 29 genes we identified had diverse predicted functions, many in exopolysaccharide synthesis. Varpa_4680, the most commonly recovered insertion site, encodes a putative N-acetyl-L-fucosamine transferase similar to WbuB. Expression of this gene in trans complemented the mutant fully. Several unique insertions were identified in Varpa_5900, which is one of three predicted pilY1 homologs in the EPS genome. No insertions in the two other putative pilY1 homologs present in the genome were identified. Expression of Varpa_5900 altered the structure of the wild type swarm, as did disruption of the chromosomal gene. The swarming phenotype was complemented by expression of Varpa_5900 from a plasmid, but biofilm formation was not restored. Both Varpa_4680 and Varpa_5900 transcripts were downregulated in biofilms and upregulated during swarming when compared to log phase culture. We identified a putative two component system (Varpa_4664-4665) encoding a response regulator (shkR) and a sensor histidine kinase (shkS), respectively. Biofilm formation increased and swarming was strongly delayed in the Varpa_4665 (shkS) mutant. Complementation of shkS restored the biofilm phenotype but swarming was still delayed. Expression of shkR in trans suppressed biofilm formation in either genetic background, and partially restored swarming in the mutant.The data presented here point to complex regulation of these surface behaviors

A Novel Signaling Network Essential for Regulating Pseudomonas aeruginosa Biofilm Development

The important human pathogen Pseudomonas aeruginosa has been linked to numerous biofilm-related chronic infections. Here, we demonstrate that biofilm formation following the transition to the surface attached lifestyle is regulated by three previously undescribed two-component systems: BfiSR (PA4196-4197) harboring an RpoD-like domain, an OmpR-like BfmSR (PA4101-4102), and MifSR (PA5511-5512) belonging to the family of NtrC-like transcriptional regulators. These two-component systems become sequentially phosphorylated during biofilm formation. Inactivation of bfiS, bfmR, and mifR arrested biofilm formation at the transition to the irreversible attachment, maturation-1 and -2 stages, respectively, as indicated by analyses of biofilm architecture, and protein and phosphoprotein patterns. Moreover, discontinuation of bfiS, bfmR, and mifR expression in established biofilms resulted in the collapse of biofilms to an earlier developmental stage, indicating a requirement for these regulatory systems for the development and maintenance of normal biofilm architecture. Interestingly, inactivation did not affect planktonic growth, motility, polysaccharide production, or initial attachment. Further, we demonstrate the interdependency of this two-component systems network with GacS (PA0928), which was found to play a dual role in biofilm formation. This work describes a novel signal transduction network regulating committed biofilm developmental steps following attachment, in which phosphorelays and two sigma factor-dependent response regulators appear to be key components of the regulatory machinery that coordinates gene expression during P. aeruginosa biofilm development in response to environmental cues

Aggregation of platelets, proliferation of endothelial cells and motility of cancer cells are mediated by the Bβ1(15)-42 residue of fibrin(ogen)

The fibrinogen molecule contains multiple binding motifs for different types of cellular receptors, acting as a molecular link between coagulation and cell adhesion. In this study we generated a truncated form of the fibrinogen molecule lacking the Bβ1-42 sequence by site-specific proteolysis and evaluated the role of the fragment in adhesive capabilities of platelets, endothelial and cancer cells. Fibrinogen with the removed Bβ1-42 sequence and fibrin without the Bβ15-42 fragment (desβ1-42 fibrinogen and desABβ15-42 fibrin) were obtained by proteolysis using the specific protease from the venom of Echis multisquamatis. The cleaved fragment was purified by HPLC and was identified using MALDI-TOF. ADP- and collagen-induced aggregation of washed platelets in the presence of fibrinogen desBβ1-42 was studied using an aggregometer. Proliferation of mice aortic endothelial cells (MAEC) and human umbilical vein endothelial cells (HUVEC) was studied using the fibrin desABβ15-42 as the scaffold. Cell viability was quantified by the MTT test (MAEC). Generation time was calculated for the estimation of proliferative activity of HUVEC. Lung cancer cell line Н1299 was used to evaluate cancer cell motility in vitro using the scratch assay. Direct comparison of cellular behavior in the presence of truncated vs native forms demonstrated attenuated cell adhesion in the presence of fibrinogen desBβ1-42 and fibrin desBβ15-42. The platelet aggregation rate was only slightly decreased in the presence of fibrinogen desBβ1-42 but resulted in 15-20% disaggregation of adhered platelets. We also observed the substantial decrease of generation time of HUVEC and inhibition of viability of MAEC cells grown on scaffolds of a desABβ15-42 matrix. Finally, desBβ1-42 modulated the motility of H1299 cells in vitro and suppressed the wound healing by 20% compared to the full-length fibrinogen. We postulate that fragment 1-42 of the BβN-domain of fibrinogen is not sufficient for platelet aggregation, however it may contribute to platelet clot formation in later stages. At the same time, this fragment may be important for establishing proper cell-to-cell contacts and cell viability of endothelial cells. Also, 1-42 amino acid fragment of the BβN-domain supported the migration of cancer cells suggesting that interactions of fibrinogen with cancer cells could be a target for anticancer therapy. The Bβ1-42 fragment of fibrinogen contributes to efficient intracellular interactions of different types of cells, including platelets, endothelial cells and cancer cells

Connecting Quorum Sensing, c-di-GMP, Pel Polysaccharide, and Biofilm Formation in Pseudomonas aeruginosa through Tyrosine Phosphatase TpbA (PA3885)

With the opportunistic pathogen Pseudomonas aeruginosa, quorum sensing based on homoserine lactones was found to influence biofilm formation. Here we discern a mechanism by which quorum sensing controls biofilm formation by screening 5850 transposon mutants of P. aeruginosa PA14 for altered biofilm formation. This screen identified the PA3885 mutant, which had 147-fold more biofilm than the wild-type strain. Loss of PA3885 decreased swimming, abolished swarming, and increased attachment, although this did not affect production of rhamnolipids. The PA3885 mutant also had a wrinkly colony phenotype, formed pronounced pellicles, had substantially more aggregation, and had 28-fold more exopolysaccharide production. Expression of PA3885 in trans reduced biofilm formation and abolished aggregation. Whole transcriptome analysis showed that loss of PA3885 activated expression of the pel locus, an operon that encodes for the synthesis of extracellular matrix polysaccharide. Genetic screening identified that loss of PelABDEG and the PA1120 protein (which contains a GGDEF-motif) suppressed the phenotypes of the PA3885 mutant, suggesting that the function of the PA3885 protein is to regulate 3,5-cyclic diguanylic acid (c-di-GMP) concentrations as a phosphatase since c-di-GMP enhances biofilm formation by activating PelD, and c-di-GMP inhibits swarming. Loss of PA3885 protein increased cellular c-di-GMP concentrations; hence, PA3885 protein is a negative regulator of c-di-GMP production. Purified PA3885 protein has phosphatase activity against phosphotyrosine peptides and is translocated to the periplasm. Las-mediated quorum sensing positively regulates expression of the PA3885 gene. These results show that the PA3885 protein responds to AHL signals and likely dephosphorylates PA1120, which leads to reduced c-di-GMP production. This inhibits matrix exopolysaccharide formation, which leads to reduced biofilm formation; hence, we provide a mechanism for quorum sensing control of biofilm formation through the pel locus and suggest PA3885 should be named TpbA for tyrosine phosphatase related to biofilm formation and PA1120 should be TpbB