Failed Escape: Solid Surfaces Prevent Tumbling of Escherichia coli

Understanding how bacteria move close to surfaces is crucial for a broad range of microbial processes including biofilm formation, bacterial dispersion, and pathogenic infections. We used digital holographic microscopy to capture a large number (>10[superscript 3]) of three-dimensional Escherichia coli trajectories near and far from a surface. We found that within 20  μm from a surface tumbles are suppressed by 50% and reorientations are largely confined to surface-parallel directions, preventing escape of bacteria from the near-surface region. A hydrodynamic model indicates that the tumble suppression is likely due to a surface-induced reduction in the hydrodynamic force responsible for the flagellar unbundling that causes tumbling. These findings imply that tumbling does not provide an effective means to escape trapping near surfaces.National Institutes of Health (U.S.) (Grant 1-R21-EB008844-01)National Science Foundation (U.S.) (Grant OCE-0744641-CAREER)National Science Foundation (U.S.) (Grant CBET-1066566

Succeed escape: Flow shear promotes tumbling of Escherichia colinear a solid surface

Understanding how bacteria move close to a surface under various stimuli is crucial for a broad range of microbial processes including biofilm formation, bacterial transport and migration. While prior studies focus on interactions between single stimulus and bacterial suspension, we emphasize on compounding effects of flow shear and solid surfaces on bacterial motility, especially reorientation and tumble. We have applied microfluidics and digital holographic microscopy to capture a large number (>10(5)) of 3D Escherichia coli trajectories near a surface under various flow shear. We find that near-surface flow shear promotes cell reorientation and mitigates the tumble suppression and re-orientation confinement found in a quiescent flow, and consequently enhances surface normal bacterial dispersion. Conditional sampling suggests that two complimentary hydrodynamic mechanisms, Jeffrey Orbit and shear-induced flagella unbundling, are responsible for the enhancement in bacterial tumble motility. These findings imply that flow shear may mitigate cell trapping and prevent biofilm initiation

Measuring response functions of active materials from data

From flocks of birds to biomolecular assemblies, systems in which many individual components independently consume energy to perform mechanical work exhibit a wide array of striking behaviors. Methods to quantify the dynamics of these so called active systems generally aim to extract important length or time scales from experimental fields. Because such methods focus on extracting scalar values, they do not wring maximal information from experimental data. We introduce a method to overcome these limitations. We extend the framework of correlation functions by taking into account the internal headings of displacement fields. The functions we construct represent the material response to specific types of active perturbation within the system. Utilizing these response functions we query the material response of disparate active systems composed of actin filaments and myosin motors, from model fluids to living cells. We show we can extract critical length scales from the turbulent flows of an active nematic, anticipate contractility in an active gel, distinguish viscous from viscoelastic dissipation, and even differentiate modes of contractility in living cells. These examples underscore the vast utility of this method which measures response functions from experimental observations of complex active systems

Clinical evaluation of the effect of gingival thickness on increasing the width of keratinized and attached gingiva with and without preserving periosteum in an animal study

BACKGROUND AND AIM: The present study was performed in order to assess the effect of gingival thickness on amount of gingival augmentation with and without preserving periosteum. METHODS: The study was conducted on 8 ecotype dogs aged 1-5 years. At the beginning, clinical probing depth and keratinized and attached gingiva width were measured. Totally, 64 sites were operated in this study. Periosteal fenestration and denuded beds were randomly created on opposite sides of upper and lower jaws (4 sites each side). The thickness of gingiva was measured in mucogingival junction after preparation of the beds. The clinical parameters were evaluated 2 months after the surgery. The data were analyzed by Mann-Whitney U, Wilcoxon, and Pearson correlation tests. RESULTS: The results showed the average increased width of keratinized and attached gingiva was 1.8 mm and 2 mm in periosteal fenestration sites and 1.9 mm and 2.3 mm in denudation sites, respectively at 2 months post-surgery. The difference between the width of keratinized gingiva and attached gingiva before and 2 months after operation was significant in both groups (P < 0.001). However, no significant difference was shown between the two groups in terms of attached and keratinized gingival width (P = 0.100 and P = 0.720, respectively). There was no correlation between the thickness of gingiva and the amount of increased width of keratinized and attached gingiva. CONCLUSION: A gingival thickness of 0.8 to 2 mm does not affect the increment of the attached and keratinized gingival width with and without preserving periosteum. KEYWORDS: Gingiva; Denudation; Surger

Experimental observations of fractal landscape dynamics in a dense emulsion

Many soft and biological materials display so-called 'soft glassy' dynamics; their constituents undergo anomalous random motions and complex cooperative rearrangements. A recent simulation model of one soft glassy material, a coarsening foam, suggested that the random motions of its bubbles are due to the system configuration moving over a fractal energy landscape in high-dimensional space. Here we show that the salient geometrical features of such high-dimensional fractal landscapes can be explored and reliably quantified, using empirical trajectory data from many degrees of freedom, in a model-free manner. For a mayonnaise-like dense emulsion, analysis of the observed trajectories of oil droplets quantitatively reproduces the high-dimensional fractal geometry of the configuration path and its associated energy minima generated using a computational model. That geometry in turn drives the droplets' complex random motion observed in real space. Our results indicate that experimental studies can elucidate whether the similar dynamics in different soft and biological materials may also be due to fractal landscape dynamics.Comment: 10 pages, 5 figures with Appendice

Amniotic Membrane Transplantation for Persistent Epithelial Defects and Ulceration due to Pseudomonas Keratitis in a Rabbit Model

Purpose: The use of amniotic membrane has been suggested in the treatment ofinfectious keratitis for its intrinsic anti-infective properties probably mediated by its antiinflammatory effects. The aim of this study was to investigate the effect of amniotic membrane transplantation (AMT) along with ciprofloxacin to cure the primary stages of Pseudomonas keratitis. Methods: In total, 28 rabbits were selected and divided in four groups as follows: group 1 as control, group 2 with amniotic membrane, group 3 with ciprofloxacin, and group 4 with amniotic membrane combined with ciprofloxacin. About 0.05 cc suspension of Pseudomonas aeruginosa, 27853 ATCC was injected into corneal stroma. Results: The results showed groups of AMT, AMT + ciprofloxacin, and ciprofloxacin had 0% perforation while the control group had 85.6%. Average infiltration of 5.5 mm was observed in ciprofloxacin group, 5 mm in AMT + ciprofloxacin group, 24 mm in AMT group, and finally 23.75 mm for control. Amniotic membrane showed to be effective in prevention of cornea perforation as well as remission of Pseudomonas keratitis. There was no significant difference between ciprofloxacin groups in comparison with ciprofloxacin + AMT group. However, regarding the anti-inflammatory effect, the process of improvement of inflammation in ciprofloxacin + AMT group was faster. Conclusion: Transplantation of amniotic membrane in the primary stages of Pseudomonas keratitis treatment remarkably prevents the disease and it can be used to control its process

Motor crosslinking augments elasticity in active nematics

In active materials, uncoordinated internal stresses lead to emergent long-range flows. An understanding of how the behavior of active materials depends on mesoscopic (hydrodynamic) parameters is developing, but there remains a gap in knowledge concerning how hydrodynamic parameters depend on the properties of microscopic elements. In this work, we combine experiments and multiscale modeling to relate the structure and dynamics of active nematics composed of biopolymer filaments and molecular motors to their microscopic properties, in particular motor processivity, speed, and valency. We show that crosslinking of filaments by both motors and passive crosslinkers not only augments the contributions to nematic elasticity from excluded volume effects but dominates them. By altering motor kinetics we show that a competition between motor speed and crosslinking results in a nonmonotonic dependence of nematic flow on motor speed. By modulating passive filament crosslinking we show that energy transfer into nematic flow is in large part dictated by crosslinking. Thus motor proteins both generate activity and contribute to nematic elasticity. Our results provide new insights for rationally engineering active materials

Clinical Report Multiple Cutaneous Inverted Papilloma in a German shepherd Dog

Abstract Case Description-In this clinical report, occurrence of a rare case of canine cutaneous inverted papilloma was discussed. A 4-year-old, intact, male German shepherd dog was presented with multiple skin lesions, located on the inguinal region near the root of penis, which have been progressively growing since two months ago. In close examination of the lesions multiple, firm, painful, and cup-shaped nodules in different sizes with a central pore filled with keratin were observed. Treatment and Outcome-Surgical excision and histological evaluation was done. Histologically this tumor was characterized by endophytic projections of the epidermis extending into dermis.Cytopathic effects included ballooning degeneration of keratinocytes, koilocytosis, irregularity of keratohyalin granules, and margination of nuclear chromatin. Numerous eosinophilic intranuclear inclusions were present within keratinocytes of endophytic lesion. Immunohistochemically, the tumor cells were intensely positive for pancytokeratin. On the basis of histopathological and clinical findings, the tumor was diagnosed as multiple cutaneous inverted papilloma. There was no recurrence or any other complications in post operative monitoring. Clinical Relevance-Inverted papillomas are relatively uncommon in dogs; whereas, the incidence of this tumor in the inguinal region is uncommon. Treatment of inverted papilloma was completed by surgical excision in ablating the tumor masses and preventing re-growth. 92 Case Description A 4-year-old, intact, male German shepherd dog was presented for treatment of multiple skin lesions, located on the inguinal region near the root of penis. The owner declared that the masses have been growing up rapidly through two months prior to presentation. On clinical examination; all vital signs (heart Rate, respiratory rate and rectal temperature) were in the normal range. On dermatological examination, multiple, firm, painful, and cup-shaped nodules in different sizes with a central pore filled with keratin were observed and the masses had well-demarcated border Treatment and Outcome Based on the clinical examination, cutaneous neoplasia was suspected and complete surgical excision of the masses was recommended. The dog was premedicated with 0/05 mg/kg acepromazine (KELA Laboratoria) intramusculary and anesthesia intravenously was induced with 10 mg/kg thiopental sodium (Sandoz) and was maintained with halothane 2% (Halothane BP, Nicholas Piramal). An elliptical incision was made in the skin around the lesion and the masses were dissected from subcutaneous tissues. The skin was sutured with Nylon (Monofil Polyamid, Supa) USP: 2/0 in interrupted suture pattern. Postoperative care included Cefazoline (Exir Pharmaceutrical Co.) at 20 mg/kg intramuscularly, every 12 hours for 3 days. The removed masses were fixed in 10% neutral buffered formalin, processed routinely, embedded in paraffin, sectioned at 5 µm thickness, stained with hematoxylin and eosin, and studied with a routine light microscope. Immunohistochemistry of additional section was performed with Avidin-Biotin complex method by using monoclonal antibodies for pancytokeratin antibody (1/500). Microscopic examination at the nodules revealed cupshaped epidermal proliferation with centripetal papillary projections into dermi

Amniotic Membrane Transplantation for Persistent Epithelial Defects and Ulceration due to Pseudomonas Keratitis in a Rabbit Model

Purpose: The use of amniotic membrane has been suggested in the treatment of infectious keratitis for its intrinsic anti-infective properties probably mediated by its antiinflammatory effects. The aim of this study was to investigate the effect of amniotic membrane transplantation (AMT) along with ciprofloxacin to cure the primary stages of Pseudomonas keratitis. Methods: In total, 28 rabbits were selected and divided in four groups as follows: group 1 as control, group 2 with amniotic membrane, group 3 with ciprofloxacin, and group 4 with amniotic membrane combined with ciprofloxacin. About 0.05 cc suspension of Pseudomonas aeruginosa, 27853 ATCC was injected into corneal stroma. Results: The results showed groups of AMT, AMT + ciprofloxacin, and ciprofloxacin had 0% perforation while the control group had 85.6%. Average infiltration of 5.5 mm was observed in ciprofloxacin group, 5 mm in AMT + ciprofloxacin group, 24 mm in AMT group, and finally 23.75 mm for control. Amniotic membrane showed to be effective in prevention of cornea perforation as well as remission of Pseudomonas keratitis. There was no significant difference between ciprofloxacin groups in comparison with ciprofloxacin + AMT group. However, regarding the anti-inflammatory effect, the process of improvement of inflammation in ciprofloxacin + AMT group was faster. Conclusion: Transplantation of amniotic membrane in the primary stages of Pseudomonas keratitis treatment remarkably prevents the disease and it can be used to control its process. Keywords: Ciprofloxacin; Human Amniotic Membrane; Keratitis; Pseudomonas aeruginosa; Rabbi