Water Electric Field Induced Modulation of the Wetting of Hexagonal Boron Nitride: Insights from Multiscale Modeling of Many-Body Polarization

Understanding the behavior of water contacting two-dimensional materials, such as hexagonal boron nitride (hBN), is important in practical applications, including seawater desalination and energy harvesting. Water, being a polar solvent, can strongly polarize the hBN surface via the electric fields that it generates. However, there is a lack of molecular-level understanding about the role of polarization effects at the hBN/water interface, including its effect on the wetting properties of water. In this study, we develop a theoretical framework that introduces an all-atomistic polarizable force field to accurately model the interactions of water molecules with hBN surfaces. The force field is then utilized to self-consistently describe the water-induced polarization of hBN using the classical Drude oscillator model, including predicting the hBN-water binding energies which are found to be in excellent agreement with diffusion Monte Carlo (DMC) predictions. By carrying out molecular dynamics (MD) simulations, we demonstrate that the polarizable force field yields a water contact angle on multilayered hBN which is in close agreement with the recent experimentally reported values. Conversely, an implicit modeling of the hBN-water polarization energy utilizing a Lennard-Jones (LJ) potential, a commonly utilized approximation in previous MD simulation studies, leads to a considerably lower water contact angle. This difference in the predicted contact angles is attributed to the significant energy-entropy compensation resulting from the incorporation of polarization effects at the hBN-water interface. Our work highlights the importance of self-consistently modeling the hBN-water polarization energy and offers insights into the wetting-related interfacial phenomena of water on polarizable materials.

Surfactant-Aided Stabilization of Individual Carbon Nanotubes in Water around the Critical Micelle Concentration

Surfactants are widely used to disperse single-walled carbon nanotubes (SWCNTs) and other nanomaterials for liquid-phase processing and characterization. Traditional techniques, however, demand high surfactant concentrations, often in the range of 1-2 wt/v% of the solution. Here, we show that optimal dispersion efficiency can be attained at substantially lower surfactant concentrations of approximately 0.08 wt/v%, near the critical micelle concentration. This unexpected observation is achieved by introducing "bare" nanotubes into water containing the anionic surfactant sodium deoxycholate (DOC) through a superacid-surfactant exchange process that eliminates the need for ultrasonication. Among the diverse ionic surfactants and charged biopolymers explored, DOC exhibits the highest dispersion efficiency, outperforming sodium cholate, a structurally similar bile salt surfactant containing just one additional oxygen atom compared to DOC. Employing all-atomistic molecular dynamics simulations, we unravel that the greater stabilization by DOC arises from its higher binding affinity to nanotubes and a substantially larger free energy barrier that resists nanotube rebundling. Further, we find that this barrier is nonelectrostatic in nature and does not obey the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability, underscoring the important role of nonelectrostatic dispersion and hydration interactions at the nanoscale, even in the case of ionic surfactants like DOC. These molecular insights advance our understanding of surfactant chemistry at the bare nanotube limit and suggest low-energy, surfactant-efficient solution processing of SWCNTs and potentially other nanomaterials.

Fluids and Electrolytes under Confinement in Single-Digit Nanopores

Confined fluids and electrolyte solutions in nanopores exhibit rich and surprising physics and chemistry that impact the mass transport and energy efficiency in many important natural systems and industrial applications. Existing theories often fail to predict the exotic effects observed in the narrowest of such pores, called single-digit nanopores (SDNs), which have diameters or conduit widths of less than 10 nm, and have only recently become accessible for experimental measurements. What SDNs reveal has been surprising, including a rapidly increasing number of examples such as extraordinarily fast water transport, distorted fluid-phase boundaries, strong ion-correlation and quantum effects, and dielectric anomalies that are not observed in larger pores. Exploiting these effects presents myriad opportunities in both basic and applied research that stand to impact a host of new technologies at the water-energy nexus, from new membranes for precise separations and water purification to new gas permeable materials for water electrolyzers and energy-storage devices. SDNs also present unique opportunities to achieve ultrasensitive and selective chemical sensing at the single-ion and single-molecule limit. In this review article, we summarize the progress on nanofluidics of SDNs, with a focus on the confinement effects that arise in these extremely narrow nanopores. The recent development of precision model systems, transformative experimental tools, and multiscale theories that have played enabling roles in advancing this frontier are reviewed. We also identify new knowledge gaps in our understanding of nanofluidic transport and provide an outlook for the future challenges and opportunities at this rapidly advancing frontier.

Breakdown of the Nernst-Einstein relation in carbon nanotube porins

For over 100 years, the Nernst-Einstein relation has linked a charged particle's electrophoretic mobility and diffusion coefficient. Here we report experimental measurements of diffusion and electromigration of K⁺ ions in narrow 0.8-nm-diameter single-walled carbon nanotube porins (CNTPs) and demonstrate that the Nernst-Einstein relation in these channels breaks down by more than three orders of magnitude. Molecular dynamics simulations using polarizable force fields show that K⁺ ion diffusion in CNTPs in the presence of a single-file water chain is three orders of magnitude slower than bulk diffusion. Intriguingly, the simulations also reveal a disintegration of the water chain upon application of electric fields, resulting in the formation of distinct K⁺-water clusters, which then traverse the CNTP at high velocity. Finally, we show that although individual ion-water clusters still obey the Nernst-Einstein relation, the overall relation breaks down because of two distinct mechanisms for ion diffusion and electromigration.

Observation and Isochoric Thermodynamic Analysis of Partially Water-Filled 1.32 and 1.45 nm Diameter Carbon Nanotubes

Recent measurements of fluids under extreme confinement, including water within narrow carbon nanotubes, exhibit marked deviations from continuum theoretical descriptions. In this work, we generate precise carbon nanotube replicates that are filled with water, closed from external mass transfer, and studied over a wide temperature range by Raman spectroscopy. We study segments that are empty, partially filled, and completely filled with condensed water from -80 to 120 °C. Partially filled, nanodroplet states contain submicron vapor-like and liquid-like domains and are analyzed using a Clausius-Clapeyron-type model, yielding heats of condensation of water inside closed 1.32 nm diameter carbon nanotubes (3.32 ± 0.10 kJ/mol and 3.72 ± 0.11 kJ/mol) and 1.45 nm diameter carbon nanotubes (3.50 ± 0.07 kJ/mol) that are lower than the bulk enthalpy of vaporization and closer to the bulk enthalpy of fusion. Favored partial filling fractions are calculated, highlighting the effect of subnanometer changes in confining diameter on fluid properties and suggesting the promise of molecular engineering of nanoconfined liquid/vapor interfaces for water treatment or membrane distillation.

Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

Porous graphene and other atomically thin 2D materials are regarded as highly promising membrane materials for high-performance gas separations due to their atomic thickness, large-scale synthesizability, excellent mechanical strength, and chemical stability. When these atomically thin materials contain a high areal density of gas-sieving nanoscale pores, they can exhibit both high gas permeances and high selectivities, which is beneficial for reducing the cost of gas-separation processes. Here, recent modeling and experimental advances in nanoporous atomically thin membranes for gas separations is discussed. The major challenges involved, including controlling pore size distributions, scaling up the membrane area, and matching theory with experimental results, are also highlighted. Finally, important future directions are proposed for real gas-separation applications of nanoporous atomically thin membranes.

Diameter Dependence of Water Filling in Lithographically Segmented Isolated Carbon Nanotubes

Although the structure and properties of water under conditions of extreme confinement are fundamentally important for a variety of applications, they remain poorly understood, especially for dimensions less than 2 nm. This problem is confounded by the difficulty in controlling surface roughness and dimensionality in fabricated nanochannels, contributing to a dearth of experimental platforms capable of carrying out the necessary precision measurements. In this work, we utilize an experimental platform based on the interior of lithographically segmented, isolated single-walled carbon nanotubes to study water under extreme nanoscale confinement. This platform generates multiple copies of nanotubes with identical chirality, of diameters from 0.8 to 2.5 nm and lengths spanning 6 to 160 μm, that can be studied individually in real time before and after opening, exposure to water, and subsequent water filling. We demonstrate that, under controlled conditions, the diameter-dependent blue shift of the Raman radial breathing mode (RBM) between 1 and 8 cm^-1 measures an increase in the interior mechanical modulus associated with liquid water filling, with no response from exterior water exposure. The observed RBM shift with filling demonstrates a non-monotonic trend with diameter, supporting the assignment of a minimum of 1.81 ± 0.09 cm^-1 at 0.93 ± 0.08 nm with a nearly linear increase at larger diameters. We find that a simple hard-sphere model of water in the confined nanotube interior describes key features of the diameter-dependent modulus change of the carbon nanotube and supports previous observations in the literature. Longer segments of 160 μm show partial filling from their ends, consistent with pore clogging. These devices provide an opportunity to study fluid behavior under extreme confinement with high precision and repeatability.

Predicting Gas Separation through Graphene Nanopore Ensembles with Realistic Pore Size Distributions

The development of nanoporous single-layer graphene membranes for gas separation has prompted increasing theoretical investigations of gas transport through graphene nanopores. However, computer simulations and theories that predict gas permeances through individual graphene nanopores are not suitable to describe experimental results, because a realistic graphene membrane contains a large number of nanopores of diverse sizes and shapes. With this need in mind, here, we generate nanopore ensembles in silico by etching carbon atoms away from pristine graphene with different etching times, using a kinetic Monte Carlo algorithm developed by our group for the isomer cataloging problem of graphene nanopores. The permeances of H₂, CO₂, and CH₄ through each nanopore in the ensembles are predicted using transition state theory based on classical all-atomistic force fields. Our findings show that the total gas permeance through a nanopore ensemble is dominated by a small fraction of large nanopores with low energy barriers of pore crossing. We also quantitatively predict the increase of the gas permeances and the decrease of the selectivities between the gases as functions of the etching time of graphene. Furthermore, by fitting the theoretically predicted selectivities to the experimental ones reported in the literature, we show that nanopores in graphene effectively expand as the temperature of permeation measurement increases. We propose that this nanopore "expansion" is due to the desorption of contaminants that partially clog the graphene nanopores. In general, our study highlights the effects of the pore size and shape distributions of a graphene nanopore ensemble on its gas separation properties and calls into attention the potential effect of pore-clogging contamination in experiments.

Uncovering a Universal Molecular Mechanism of Salt Ion Adsorption at Solid/Water Interfaces

Solid/water interfaces, in which salt ions come in close proximity to solids, are ubiquitous in nature. Because water is a polar solvent and salt ions are charged, a long-standing puzzle involving solid/water interfaces is how do the electric fields exerted by the salt ions and the interfacial water molecules polarize the charge distribution in the solid and how does this polarization, in turn, influence ion adsorption at any solid/water interface. Here, using state-of-the-art polarizable force fields derived from quantum chemical simulations, we perform all-atomistic molecular dynamics simulations to investigate the adsorption of various ions comprising the well-known Hofmeister series at the graphene/water interface, including comparing with available experimental data. Our findings reveal that, in vacuum, the ionic electric field-induced polarization of graphene results in a significantly large graphene-ion polarization energy, which drives all salt ions to adsorb to graphene. On the contrary, in the presence of water molecules, we show that the ions and the water molecules exert waves of molecular electric fields on graphene which destructively interfere with each other. This remarkable phenomenon is shown to cause a water-mediated screening of more than 85% of the graphene-ion polarization energy. Finally, by investigating superhydrophilic and superhydrophobic model surfaces, we demonstrate that this phenomenon occurs universally at all solid/water interfaces and results in a significant weakening of the ion-solid interactions, such that ion specific effects are governed primarily by a competition between the ion-water and water-water interactions, irrespective of the nature of the solid/water interface.

Analytical Prediction of Gas Permeation through Graphene Nanopores of Varying Sizes: Understanding Transitions across Multiple Transport Regimes

Nanoporous graphene is a promising candidate material for gas separation membranes, due to its atomic thickness and low cross-membrane transport resistance. The mechanisms of gas permeation through graphene nanopores, in both the large and small pore size limits, have been reported in the literature. However, mechanistic insights into the crossover from the small pore size limit to the large pore size limit are still lacking. In this study, we develop a comprehensive theoretical framework to predict gas permeance through graphene nanopores having a wide range of diameters using analytical equations. We formulate the transport kinetics associated with the direct impingement from the bulk and with the surface diffusion from the adsorption layer on graphene and then combine them to predict the overall gas permeation rate using a reaction network model. We also utilize molecular dynamics simulations to validate and calibrate our theoretical model. We show that the rates of both the direct impingement and the surface diffusion pathways need to be corrected using different multiplicative factors, which are functions of temperature, gas kinetic diameter, and pore diameter. Further, we find a minor spillover pathway that originates from the surface adsorption layer, but is not included in our theoretical model. Finally, we utilize the corrected model to predict the permeances of CO₂, CH₄, and Ar through graphene nanopores. We show that as the pore diameter increases, gas transport through graphene nanopores can transition from being translocation dominated (pore diameter < 0.7 nm), to surface pathway dominated (pore diameter 1-2 nm), and finally to direct pathway dominated (pore diameter > 4 nm). The various gas permeation mechanisms outlined in this study will be particularly useful for the rational design of membranes made out of two-dimensional materials such as graphene for gas separation applications.

Multi-scale approach for modeling stability, aggregation, and network formation of nanoparticles suspended in aqueous solutions

Suspensions of nanoparticles (NPs) in aqueous solutions hold promise in many research fields, including energy applications, water desalination, and nanomedicine. The ability to tune NP interactions, and thereby to modulate the NP self-assembly process, holds the key to rationally synthesize NP suspensions. However, traditional models obtained by coupling the DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory of NP interactions, or suitable modifications of it, with the kinetic theory of colloidal aggregation are inadequate to precisely model NP self-assembly because they neglect hydration forces and discrete-size effects predominant at the nanoscale. By synergistically blending molecular dynamics and stochastic dynamics simulations with continuum theories, we develop a multi-scale (MS) model, which is able to accurately predict suspension stability, timescales for NP aggregation, and macroscopic properties (e.g., the thermal conductivity) of bare and surfactant-coated NP suspensions, in good agreement with the experimental data. Our results enable the formulation of design rules for engineering NP aqueous suspensions in a wide range of applications.

Mechanism and Prediction of Gas Permeation through Sub-Nanometer Graphene Pores: Comparison of Theory and Simulation

Due to its atomic thickness, porous graphene with sub-nanometer pore sizes constitutes a promising candidate for gas separation membranes that exhibit ultrahigh permeances. While graphene pores can greatly facilitate gas mixture separation, there is currently no validated analytical framework with which one can predict gas permeation through a given graphene pore. In this work, we simulate the permeation of adsorptive gases, such as CO₂ and CH₄, through sub-nanometer graphene pores using molecular dynamics simulations. We show that gas permeation can typically be decoupled into two steps: (1) adsorption of gas molecules to the pore mouth and (2) translocation of gas molecules from the pore mouth on one side of the graphene membrane to the pore mouth on the other side. We find that the translocation rate coefficient can be expressed using an Arrhenius-type equation, where the energy barrier and the pre-exponential factor can be theoretically predicted using the transition state theory for classical barrier crossing events. We propose a relation between the pre-exponential factor and the entropy penalty of a gas molecule crossing the pore. Furthermore, on the basis of the theory, we propose an efficient algorithm to calculate CO₂ and CH₄ permeances per pore for sub-nanometer graphene pores of any shape. For the CO₂/CH₄ mixture, the graphene nanopores exhibit a trade-off between the CO₂ permeance and the CO₂/CH₄ separation factor. This upper bound on a Robeson plot of selectivity versus permeance for a given pore density is predicted and described by the theory. Pores with CO₂/CH₄ separation factors higher than 10² have CO₂ permeances per pore lower than 10^-22 mol s^-1 Pa^-1, and pores with separation factors of ∼10 have CO₂ permeances per pore between 10^-22 and 10^-21 mol s^-1 Pa^-1. Finally, we show that a pore density of 10¹⁴ m^-2 is required for a porous graphene membrane to exceed the permeance-selectivity upper bound of polymeric materials. Moreover, we show that a higher pore density can potentially further boost the permeation performance of a porous graphene membrane above all existing membranes. Our findings provide insights into the potential and the limitations of porous graphene membranes for gas separation and provide an efficient methodology for screening nanopore configurations and sizes for the efficient separation of desired gas mixtures.

Electric double layer force between charged surfaces: effect of solvent polarization

In this paper, we develop a theory to delineate the consequences of finite solvent polarization in electric double layer interaction or the osmotic pressure between two similar or oppositely charged surfaces. We use previously published Langevin-Bikerman equations to calculate this electric double layer interaction force or the osmotic pressure between the charged surfaces. The osmotic pressure between oppositely charged surfaces is found to be much larger than that between similarly charged surfaces, and for either case, the influence of solvent polarization ensures a larger pressure than that predicted by the Poisson-Boltzmann (PB) model. We derive distinct scaling relationships to explain the increase of the pressure as a function of the separation between the surfaces, the solvent polarizability, and the number density of water molecules. Most importantly, we demonstrate that our theory can successfully reproduce the experimental results of interaction force between similar and oppositely charged surfaces, by accounting for the large under-prediction made by the corresponding PB model.

Phacotrabeculectomy Versus Conventional Combined Technique in Coexisting Glaucoma and Cataract

BACKGROUND

To evaluate and compare efficacy and outcome after single site phacotrabeculectomy and conventional combined surgery in cases of coexisting primary open angle glaucoma and cataract.

METHODS

This prospective study on fifty patients of concurrent primary open angle glaucoma and cataract, who had undergone combined surgery as single site phacotrabeculectomy or conventional single site trabeculectomy with extracapsular lens extraction with IOL implantation in 25 cases each. Evaluation was based on operative and postoperative complications, control of IOP and visual outcome. The follow up period ranged between twelve months to eighteen months.

RESULTS

The mean medically controlled preoperative intraocular pressure was 22 mm of Hg (Range 18 to 35 mm of Hg) by applanation method of tonometry. The range of postoperative intra-ocular pressure after one year was 11 to 22 mm of Hg in first and 14 to 26 mm Hg in second group. Failure to maintain optimum postoperative IOP without Beta-blocker was more frequent after conventional combined procedure. There was no significant difference in incidence and pattern of postoperative complications.

CONCLUSION

Phacotrabeculectomy provides effective and sustained visual recovery and adequate control of intraocular pressure as compare to conventional combined procedure.

Introduction of community-based skin-to-skin care in rural Uttar Pradesh, India

OBJECTIVE

Two-thirds of women globally give birth at home, yet little data are available on use of skin-to-skin care (STSC) in the community. We describe the acceptability of STSC in rural Uttar Pradesh, India, and measured maternal, newborn, and ambient temperature in the home in order to inform strategies for introduction of STSC in the community.

STUDY DESIGN

Community-based workers in intervention clusters implemented a community mobilization and behavior change communication program that promoted birth preparedness and essential newborn care, including adoption of STSC, with pregnant mothers, their families, and key influential community members. Acceptance of STSC was assessed through in-depth interviews and focus groups, and temperature was measured during home visits on day of life 0 or 1.

RESULTS

Incidence of hypothermia (<36.5 degrees C) was high in both low birth weight (LBW) and normal birth weight (NBW) infants (49.2%, (361/733) and 43% (418/971), respectively). Mean body temperature of newborns was lower (P<0.01) in ambient temperatures <20 degrees C (35.9+/-1.4 degrees C, n=225) compared to > or =20 degrees C (36.5+/-0.9 degrees C, n=1450). Among hypothermic newborns, 42% (331/787) of their mothers had a lower temperature (range -6.7 to 0.1 degrees C, mean difference 0.4+/-1.2 degrees C). Acceptance of STSC was nearly universal. No adverse events from STSC were reported. STSC was perceived to prevent newborn hypothermia, enhance mother's capability to protect her baby from evil spirits, and make the baby more content.

CONCLUSION

STSC was highly acceptable in rural India when introduced through appropriate cultural paradigms. STSC may be of benefit for all newborns and for many mothers as well. New approaches are needed for introduction of STSC in the community compared to the hospital.

Early postnatal cardiac changes and premature death in transgenic mice overexpressing a mutant form of serum response factor

Serum response factor (SRF) is a key regulator of a number of extracellular signal-regulated genes important for cell growth and differentiation. A form of the SRF gene with a double mutation (dmSRF) was generated. This mutation reduced the binding activity of SRF protein to the serum response element and reduced the capability of SRF to activate the atrial natriuretic factor promoter that contains the serum response element. Cardiac-specific overexpression of dmSRF attenuated the total SRF binding activity and resulted in remarkable morphologic changes in the heart of the transgenic mice. These mice had dilated atrial and ventricular chambers, and their ventricular wall thicknesses were only 1/2 to 1/3 the thickness of that of nontransgenic mice. Also these mice had smaller cardiac myocytes and had less myofibrils in their myocytes relative to nontransgenic mice. Altered gene expression and slight interstitial fibrosis were observed in the myocardium of the transgenic mice. All the transgenic mice died within the first 12 days after birth, because of the early onset of severe, dilated cardiomyopathy. These results indicate that dmSRF overexpression in the heart apparently alters cardiac gene expression and blocks normal postnatal cardiac growth and development.

Cardiomyopathy in transgenic mice with cardiac-specific overexpression of serum response factor

Serum response factor (SRF), a member of the MCM1, agamous, deficiens, SRF (MADS) family of transcriptional activators, has been implicated in the transcriptional control of a number of cardiac muscle genes, including cardiac alpha-actin, skeletal alpha-actin, alpha-myosin heavy chain (alpha-MHC), and beta-MHC. To better understand the in vivo role of SRF in regulating genes responsible for maintenance of cardiac function, we sought to test the hypothesis that increased cardiac-specific SRF expression might be associated with altered cardiac morphology and function. We generated transgenic mice with cardiac-specific overexpression of the human SRF gene. The transgenic mice developed cardiomyopathy and exhibited increased heart weight-to-body weight ratio, increased heart weight, and four-chamber dilation. Histological examination revealed cardiomyocyte hypertrophy, collagen deposition, and interstitial fibrosis. SRF overexpression altered the expression of SRF-regulated genes and resulted in cardiac muscle dysfunction. Our results demonstrate that sustained overexpression of SRF, in the absence of other stimuli, is sufficient to induce cardiac change and suggest that SRF is likely to be one of the downstream effectors of the signaling pathways involved in mediating cardiac hypertrophy.

Serum response factor-dependent regulation of the smooth muscle calponin gene

Smooth muscle calponin is a multifunctional, thin filament-associated protein whose expression is restricted to smooth muscle cell lineages in developing and postnatal tissues. Although the physiology of smooth muscle calponin has been studied extensively, the cis-elements governing its restricted pattern of expression have yet to be identified. Here we report on smooth muscle-specific enhancer activity within the first intron of smooth muscle calponin. Sequence analysis revealed a proximal consensus intronic CArG box and two distal intronic CArG-like elements, each of which bound recombinant serum response factor (SRF) as well as immunoreactive SRF from smooth muscle nuclear extracts. Site-directed mutagenesis studies suggested that the consensus CArG box mediates much of the intronic enhancer activity; mutating all three CArG elements abolished the ability of SRF to confer enhancer activity on the smooth muscle calponin promoter. Cotransfecting a dominant-negative SRF construct attenuated smooth muscle-specific enhancer activity, and transducing smooth muscle cells with adenovirus harboring the dominant-negative SRF construct selectively reduced steady-state expression of endogenous smooth muscle calponin. These results demonstrate an important role for intronic CArG boxes and the SRF protein in the transcriptional control of smooth muscle calponin in vitro.

Calcium and disease: molecular determinants of calcium crystal deposition diseases

Deposition of basic calcium phosphate (hydroxyapatite, octacalcium phosphate and tricalcium phosphate) (BCP) and crystalline calcium pyrophosphate dihydrate (CPPD) is associated with a variety of aging-related pathologies, including osteoarthritis, cartilage degeneration and pseudogout. These diseases of calcium deposition serve as some of the best-studied examples of how calcium-regulated changes in gene expression can directly lead to pathogenic consequences. Tissue damage can result when crystals stimulate cells to release matrix-degrading molecules or secrete cytokines that stimulate the release of matrix-degrading molecules. Exposure of cultured cells to crystals induces expression of cellular proto-oncogenes such as c-fos, c-myc and c-jun, by a calcium-dependent mechanism, and this response can be blocked by a potential therapeutic compound, phosphocitrate. Activation of the c-fos and c-jun genes is directly involved in expression of metalloproteinases such as collagenase and stromelysin, suggesting that crystal-mediated activation of these genes is directly involved in pathogenesis. In this review recent advances in the molecular mechanisms responsible for crystal-mediated cell activation are discussed.

Expression of the SRF gene occurs through a Ras/Sp/SRF-mediated-mechanism in response to serum growth signals

Serum Response Factor (SRF) plays a central role in the transcriptional response of mammalian cells to a variety of extracellular signals. It is a key regulator of many cellular early response genes which are believed to be involved in cell growth, differentiation, and development. The mechanism by which SRF activates transcription in response to mitogenic agents has been extensively studied, however, less is known about regulation of the SRF gene itself. Previously, we identified distinct regulatory elements in the SRF promoter that play a role in activation, including an ETS domain binding site, an overlapping Sp1/Egr-1 binding site, and two SRF binding sites. We further showed that serum induces the SRF gene by a mechanism that requires an intact SRF binding site, also termed a CArG box. In the present study we demonstrate that in response to stimulation by cells by lysophosphatidic acid (LPA) or whole serum, the SRF promoter is upregulated by a bipartite pathway that requires both an Sp1 factor binding site and the CArG motifs for maximal stimulation. The CArG box-dependent component of this pathway is targeted by Rho mediated signals, and the Sp1 binding site dependent component is targeted by Ras mediated signals.

Basic fibroblast growth factor activates serum response factor gene expression by multiple distinct signaling mechanisms

Serum response factor (SRF) plays a central role in the transcriptional response of mammalian cells to a variety of extracellular signals. It is a key regulator of many cellular early response genes which are believed to be involved in cell growth and differentiation. The mechanism by which SRF activates transcription in response to mitogenic agents has been extensively studied; however, significantly less is known about regulation of the SRF gene itself. Previously, we identified distinct regulatory elements in the SRF promoter that play a role in activation, including a consensus ETS domain binding site, a consensus overlapping Sp/Egr-1 binding site, and two SRF binding sites. We further showed that serum induces SRF by a mechanism that requires an intact SRF binding site, also termed a CArG box. In the present study we demonstrate that in response to stimulation of cells by a purified growth factor, basic fibroblast growth factor (bFGF), the SRF promoter is upregulated by a complex pathway that involves at least two independent mechanisms: a CArG box-independent mechanism that is mediated by an ETS binding site, and a novel CArG box-dependent mechanism that requires both an Sp factor binding site and the CArG motifs for maximal stimulation. Our analysis indicates that the CArG/Sp element activation mechanism is mediated by distinct signaling pathways. The CArG box-dependent component is targeted by a Rho-mediated pathway, and the Sp binding site-dependent component is targeted by a Ras-mediated pathway. Both SRF and bFGF have been implicated in playing an important role in mediating cardiogenesis during development. The implications of our findings for SRF expression during development are discussed.

Conjunctival melanoma in the black population

Melanoma of the conjunctiva is a rare, unilateral malignancy primarily affecting middle-aged whites; the annual average age-adjusted incidence rate is 0.012 per 100,000 population. Although conjunctival melanoma in the black population is extremely rare, cases have been reported. Melanoma of skin in blacks has a predilection for nonsun-exposed, nonpigmented sites such as mucous membranes, palms, and soles. Primary acquired melanosis may lead to the development of melanoma even in blacks. Primary acquired melanosis in the black population may be difficult to differentiate from racial melanosis clinically and histopathologically. Early diagnosis through awareness and education can help improve the survival of black patients with conjunctival melanoma.

Pseudomonas aeruginosa exoenzyme S ADP-ribosylates Ras at multiple sites

Pseudomonas aeruginosa exoenzyme S (ExoS) ADP-ribosylated Ras to a stoichiometry of approximately 2 molecules of ADP-ribose incorporated per molecule of Ras, which suggested that ExoS could ADP-ribosylate Ras at more than one arginine residue. SDS-polyacrylamide gel electrophoresis analysis showed that ADP-ribosylated Ras possessed a slower mobility than non-ADP-ribosylated Ras. Analysis of the ADP-ribosylation of in vitro transcribed/translated Ras by ExoS identified two electrophoretically shifted forms of Ras, which was consistent with the ADP-ribosylation of Ras at two distinct arginine residues. Analysis of ADP-ribosylated in vitro transcribed/translated Ras mutants possessing individual Arg-to-Ala substitutions showed that Arg-41 was the preferred site of ADP-ribosylation and that the second ADP-ribosylation event occurred at a slower rate than the ADP-ribosylation at Arg-41, but did not occur at a specific arginine residue. Analysis of bacterially expressed wild-type RasDeltaCAAX and RasDeltaCAAXR41K supported the conclusion that Arg-41 was the preferred site of ADP-ribosylation. Arg-41 is located adjacent to the switch 1 region of Ras, which is involved in effector interactions. Introduction of ExoS into eukaryotic cells inhibited Ras-mediated eukaryotic signal transduction since infection of PC-12 cells with an ExoS-producing strain of P. aeruginosa inhibited nerve growth factor-stimulated neurite formation. This is the first demonstration that ExoS disrupts a Ras-mediated signal transduction pathway.

Phosphocitrate inhibits a basic calcium phosphate and calcium pyrophosphate dihydrate crystal-induced mitogen-activated protein kinase cascade signal transduction pathway

Calcium deposition diseases caused by calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals are a significant source of morbidity in the elderly. We have shown previously that both types of crystals can induce mitogenesis, as well as metalloproteinase synthesis and secretion by fibroblasts and chondrocytes. These responses may promote degradation of articular tissues. We have also shown previously that both CPPD and BCP crystals activate expression of the c-fos and c-jun proto-oncogenes. Phosphocitrate (PC) can specifically block mitogenesis and proto-oncogene expression induced by either BCP or CPPD crystals in 3T3 cells and human fibroblasts, suggesting that PC may be an effective therapy for calcium deposition diseases. To understand how PC inhibits BCP and CPPD-mediated cellular effects, we have investigated the mechanism by which BCP and CPPD transduce signals to the nucleus. Here we demonstrate that BCP and CPPD crystals activate a protein kinase signal transduction pathway involving p42 and p44 mitogen-activated protein (MAP) kinases (ERK 2 and ERK 1). BCP and CPPD also cause phosphorylation of a nuclear transcription factor, cyclic AMP response element-binding protein (CREB), on serine 133, a residue essential for CREB's ability to transactivate. Treatment of cells with PC at concentrations of 10(-3) to 10(-5) M blocked both the activation of p42/p44 MAP kinases, and CREB serine 133 phosphorylation, in a dose-dependent fashion. At 10(-3) M, a PC analogue, n-sulfo-2-aminotricarballylate and citrate also modulate this signal transduction pathway. Inhibition by PC is specific for BCP- and CPPD-mediated signaling, since all three compounds had no effect on serum-induced p42/P44 or interleukin-1beta induced p38 MAP kinase activities. Treatment of cells with an inhibitor of MEK1, an upstream activator of MAPKs, significantly inhibited crystal-induced cell proliferation, suggesting that the MAPK pathway is a significant mediator of crystal-induced signals.

Expression of the serum response factor gene is regulated by serum response factor binding sites

The serum response factor (SRF) is a ubiquitous transcription factor that plays a central role in the transcriptional response of mammalian cells to a variety of extracellular signals. Notably, SRF has been found to be a key regulator of members of a class of cellular response genes termed immediate-early genes (IEGs), many of which are believed to be involved in regulating cell growth and differentiation. The mechanism by which SRF activates transcription of IEGs in response to mitogenic agents has been extensively studied. Significantly less is known about how expression of the SRF gene itself is mediated. We and others have previously shown that the SRF gene is itself transiently induced by a variety of mitogenic agents and belongs to a class of "delayed" early response genes. We have cloned the SRF promoter and in the present study have analyzed the upstream regulatory sequences involved in mediating serum responsiveness of the SRF gene. Our analysis indicates that inducible SRF expression requires both SRF binding sites located within the first 63 nucleotides upstream from the start site of transcriptional initiation and an Sp1 site located 83 nucleotides upstream from the start site. Maximal transcriptional activity of the promoter also requires two CCAATT box sites located 90 and 123 nucleotides upstream of the start site.

Observer variation in AgNOR counts in neoplastic breast lesions

OBJECTIVE

To determine interobserver and intraobserver variability of AgNOR quantitation in neoplastic lesions of the breast.

STUDY DESIGN

Forty-five cases, 20 benign and 25 malignant lesions, were included in the study. Counts were performed on one slide from each case within a pre-marked area of about 1 cm2 in a standardized manner by two observers blind to the histopathologic diagnosis and independent of each other and repeated after two weeks. Interobserver and intraobserver agreement was assessed using the Bland-Altman method.

RESULTS

Our results showed small mean interobserver and intraobserver differences but wide limits of agreement.

CONCLUSION

Observer variation in AgNOR counts is too high for the method to be of any diagnostic or prognostic relevance.

NESTED CASE - CONTROL ANALYSIS OF THE RISK FACTORS FOR HIGH ALTITUDE PULMONARY OEDEMA

A nested case-control study was undertaken on a cohort of soldiers inducted into high altitude area (11000 to 16000 feet) of Western Himalayas, with the objectives of studying the incidence of high altitude pulmonary oedema (HAPO) and its association with physical exertion and certain other predetermined risk factors. The study indicated that the cumulative incidence of HAPO was 1.42 per 1000 inductions. The association with moderate/strenuous physical exertion within 24 hours of entry into high altitude was significant (Odds ratio (OR) = 3.19; 95% confidence limits (CL) = 1.23 to 8.15); however, this association was not significant for the period 24 to 48 hours or > 48 hours. Physical exertion during first 24 hours was also significantly associated with severity of disease (OR = 14.67, 95% CL = 3.61 to 64.04), but not after 24 hours. Previous history of "high altitude sickness" was also significantly associated with HAPO (OR = 2.74, 95% CL = 1.12 to 6.77). Physical exertion during first 24 hours was found to carry an attributable risk of 2.56 per 1000 inductions and an etiologic fraction of 17.8%. No significant association of HAPO was observed with age, type of inductee (fresh/reinductee), native place, alcohol consumption and smoking.

Capnocytophaga keratitis. A clinicopathologic study of three patients, including electron microscopic observations

BACKGROUND

Histopathologic studies of this unusual keratitis caused by Capnocytophaga species have not been reported previously.

METHODS

The authors report the light microscopic and ultrastructural findings of three patients with a distinctive necrotizing keratitis caused by an anaerobic gram-negative bacillus. In three patients, ages 19, 81, and 91 years, a necrotizing stromal keratitis developed; two of these patients had a previous penetrating keratoplasty for pseudophakic bullous keratopathy. The first patient did not have ocular surgery previously and was treated initially for presumed Acanthamoeba keratitis.

RESULTS

By light microscopy, all three keratectomy specimens were strikingly similar and showed a necrotizing and/or suppurative stromal keratitis displaying myriad slender, fusiform, gram-negative bacilli located anterior to Descemet's membrane and extending into the deep corneal stroma, assuming a "picket fence" appearance. Cultures of the cornea in case 1 grew Capnocytophaga ochracea. For the remaining two patients, a diagnosis presumptively was made based on characteristic histopathologic features. Results of electron microscopic examination showed numerous bacilli that were mostly extracellular; occasional organisms were phagocytosed by macrophages.

CONCLUSION

The histopathologic features of Capnocytophaga keratitis are unique; therefore, a presumptive diagnosis can be made based on the morphology and location of the bacilli in the keratectomy specimens. To the authors' knowledge, this is the first study describing the typical histopathologic and electron microscopic findings of Capnocytophaga keratitis.

L-type voltage-sensitive calcium channel activation stimulates gene expression by a serum response factor-dependent pathway

A mechanism by which calcium-induced signals are transduced to the nucleus to activate transcription of the c-fos proto-oncogene has been characterized. The serum response element (SRE), a region of the c-fos gene which controls growth factor-induced transcription, is now shown to mediate c-fos transcription in response to activation of L-type voltage-sensitive calcium channels. Calcium-dependent transcriptional activation through the SRE is mediated by the serum response factor (SRF). Membrane depolarization induces phosphorylation of SRF at Ser-103, an event shown to enhance the ability of SRF to bind the SRE. Ca(2+)-induced SRF phosphorylation occurs via a pathway that may involve Ca2+/calmodulin-dependent kinases.

CLINICO-EPIDEMIOLOGICAL ALGORITHM FOR PREDICTING SYSTEMIC ARTERIAL HYPERTENSION AT HIGH ALTITUDE THROUGH MATHEMATICAL MODELLING

A population based hybrid design combining element of cohort and cross-sectional approach was used to develop a simple clinical algorithm to predict individual probability of developing hypertension (systolic BP > 140 mm Hg and/or diastolic BP > 90 mmHg). 3615 soldiers initially normotensive at the time of induction into high altitude, were studied by systematic random sampling. Multiple logistic regression analysis showed a high significant association between hypertension and age, body mass index (BMI), tobacco smoking and alcohol consumption. Using the constant/coefficient values obtained from the logistic model and the receiver operating characteristics (ROC) curve analysis, the following predictive rule was developed - To the age in years, add (BMIx 3.86); also add 5.53 if he is a smoker; and add 19.81 if he consumes alcohol. If the total exceeds 142, the individual is at high risk of developing hypertension. This algorithm carries a sensitivity of 68.2% and specificity of 78.5%.

A growth factor-induced kinase phosphorylates the serum response factor at a site that regulates its DNA-binding activity

A signaling pathway by which growth factors may induce transcription of the c-fos proto-oncogene has been characterized. Growth factor stimulation of quiescent fibroblasts activates a protein kinase cascade that leads to the rapid and transient phosphorylation of the serum response factor (SRF), a regulator of c-fos transcription. The in vivo kinetics of SRF phosphorylation and dephosphorylation parallel the activation and subsequent repression of c-fos transcription, suggesting that this phosphorylation event plays a critical role in the control of c-fos expression. The ribosomal S6 kinase pp90rsk, a growth factor-inducible kinase, phosphorylates SRF in vitro at serine 103, the site that becomes newly phosphorylated upon growth factor stimulation in vivo. Phosphorylation of serine 103 significantly enhances the affinity and rate with which SRF associates with its binding site, the serum response element, within the c-fos promoter. These results suggest a model in which the growth factor-induced phosphorylation of SRF at serine 103 contributes to the activation of c-fos transcription by facilitating the formation of an active transcription complex at the serum response element.

Bipolar cautery and internal thermal sclerostomy in a rabbit model

Internal thermal sclerostomy (ITS) was performed unilaterally in 35 adult New Zealand rabbits using a pinpoint bipolar cautery probe and radio-frequency power supply, with the nonoperated eyes serving as controls. Standard trabeculectomy using a limbal-based flap was also performed on 10 additional rabbits, and served as a second bench mark for comparison with the ITS technique. Intraocular pressure (IOP) was measured in all eyes preoperatively and on postoperative days 2, 4, 6, and 8. A significant (P = .005) difference between the reduction in IOP in the ITS eyes and in the control eyes was found up to postoperative day 8; on that day the reduction in IOP was 5.2 mm Hg. IOP in the eyes undergoing standard trabeculectomy was significantly (P = .05) reduced up to postoperative day 2, and gradually decreased, to 2.5 mm Hg, on postoperative day 8. The greatest reduction in IOP (2.9 mm Hg) for these eyes also occurred on postoperative day 2. Complications of ITS included iris burn (23%), peripheral corneal edema (17%), and iritis (9%). No ruptured blebs, flat anterior chambers, hyphemas, or lens damage occurred. The potential advantages of the ITS procedure using the bipolar cautery probe include a decreased risk of cataract formation because of the curved probe design. The procedure is also technically simple to perform and requires only inexpensive and readily-available equipment.

The serum response factor is extensively modified by phosphorylation following its synthesis in serum-stimulated fibroblasts

Growth factor regulation of c-fos proto-oncogene transcription is mediated by a 20-bp region of dyad symmetry, termed the serum response element. The inner core of this element binds a 67-kDa phosphoprotein, the serum response factor (SRF), that is thought to play a pivotal role in the c-fos transcriptional response. To investigate the mechanism by which SRF regulates c-fos expression, we generated polyclonal anti-SRF antibodies and used these antibodies to analyze the biochemical properties of SRF. These studies indicate that the synthesis of SRF is transient, occurring within 30 min to 4 h after serum stimulation of quiescent fibroblasts. Newly synthesized SRF is transported to the nucleus, where it is increasingly modified by phosphorylation during progression through the cell cycle. Within 2 h of serum stimulation, differentially modified forms of SRF can be distinguished on the basis of the ability to bind a synthetic serum response element. SRF protein exhibits a half-life of greater than 12 h and is predominantly nuclear, with no change occurring in its localization upon serum stimulation. We find that the induction of SRF synthesis is regulated at the transcriptional level and that cytoplasmic SRF mRNA is transiently expressed with somewhat delayed kinetics compared with c-fos mRNA expression. These features of SRF expression suggest a model whereby newly synthesized SRF functions in the shutoff of c-fos transcription.

Contact lens wear enhances adherence of Pseudomonas aeruginosa and binding of lectins to the cornea

Extended wear soft contact lenses are associated with an increased incidence of Pseudomonas aeruginosa keratitis. Because the first step in the pathogenesis of this disease is adherence of the microorganism to the corneal surface, we studied the effect of soft contact lens wear on the adherence of P. aeruginosa to the cornea. Rabbits were fitted for extended wear soft contact lenses in the left eye, and the right eye served as a control. Both eyes were then closed with a partial tarsorrhaphy. After 1-5 days of wear, the lenses were removed and the corneas of the left and right eye were removed. Differences in the number of adherent Pseudomonas and in lectin binding to lens-wearing corneas and non-lens-wearing corneas were determined. After 1, 3, and 5 days of soft contact lens wear, there was a significant increase in the number of P. aeruginosa adherent to the lens-wearing cornea. Three to eight times as many bacteria adhered to the lens-wearing eye as compared with the control eye (p less than 0.05). In addition, a soft contact lens placed in the eye followed by the immediate application of P. aeruginosa resulted in an eightfold increase in adherence of bacteria to the lens-wearing cornea (p less than 0.05). Lens wear also led to an increase in binding of concanavalin A (Con A), wheat germ agglutinin (WGA), and Maclura pomifera agglutinin (MPA) to surface epithelium covered by the lens. These corneal epithelial changes induced by extended wear soft contact lenses may provide some insight as to why soft contact lens wearers are predisposed to Pseudomonas keratitis.

Use of carbon fibers for repair of abdominal-wall defects in rats

Carbon in the form of 8-micron fibers induces growth of connective tissue. The purpose of this study was to measure and histologically characterize tissue ingrowth occurring in carbon fibers implanted for up to 12 months in abdominal-wall defects in rats, compared with polypropylene mesh. Carbon fibers induced significantly more tissue ingrowth than polypropylene mesh at 6 to 12 months postoperatively. The predominant tissues associated with carbon fibers and polypropylene mesh were dense connective tissue and fat, respectively. Fragmentation of the implants did not occur, and implant debris was not found in the regional lymph nodes. Carbon fibers are potentially useful for reinforcing abdominal-wall defects.

Aggregated platelets enhance adherence of Candida yeasts to endothelium

The adherence of Candida albicans yeasts to human umbilical vein endothelium to subendothelial extracellular matrix (ECM) was investigated. Yeasts added to confluent endothelium in citrated platelet-poor plasma adhered on the average of 1 colony forming unit (cfu) per culture well. When platelets were added as platelet-rich plasma, a significant increase of yeast adherence was not seen. However, when endothelium was contracted by treatment with 2 mM EDTA, resulting in exposure of ECM, yeast adherence was increased to 10 cfu/well. When platelets were added with these yeasts, the number of adhering yeasts was further increased to 23 cfu/well (P less than .01). This represented an increase in adherence of yeasts of 230%. When the endothelial cells were completely removed and ECM exposed, platelets were found to likewise augment yeast adherence. Platelets, when added to the ECM, formed aggregates to which the yeasts firmly adhered. Likewise, when platelets were aggregated by adenosine diphosphate and mixed with yeasts, yeasts were shown to bind avidly to aggregated platelets, whereas yeasts did not adhere to unactivated, discoid platelets. Thus, exposed subendothelial ECM induces the aggregation of platelets and yeasts bind avidly to these platelet aggregates.

Isolation of a herpes simplex virus type 2 that is retinovirulent in mice

The virulence of a herpes simplex virus type 2 (HSV-2) isolated from the urine of a patient (SL) with acquired immunodeficiency syndrome (AIDS) and bilateral acute retinal necrosis (ARN), was investigated in mice. The ratio of plaque forming units (PFU) in fibroblasts to the 50% lethal dose (LD50) of HSV-2(SL) in mice was 10 fold more than the PFU to LD50 ratio of a neurovirulent HSV-2, strain 186. Further, HSV-2(SL) caused retinitis with and without lethal encephalitis in mice inoculated intracranially (i.c.). In contrast, mice inoculated with HSV-2(186) died of encephalitis without ocular disease. HSV-2(SL) was isolated from eye and/or brain tissue 1 to 15 days post i.c. inoculation. Ocular disease progressed from an initial mild chorioretinitis on day 8 to total retinal necrosis with panuveitis by day 11 in mice given 10 PFU of HSV-2(SL) i.c. HSV antigen was detected initially in the cells of the optic nerve and spread into the ganglial cells of the nerve fiber layer, the neurosensory cells of the inner nuclear layer, and the cells of the retinal pigment epithelium (RPE) between days 8 and 10. Thus, this study supports the concept that HSV neurovirulence varies between strains and presents a HSV-2 neurotransmission animal model of ARN.

A partial-thickness epithelial defect increases the adherence of Pseudomonas aeruginosa to the cornea

Some patients with infectious keratitis have no clinically demonstrable corneal abrasion predisposing them to infection. Subtle, undetectable corneal injuries may facilitate bacterial adherence to the cornea, eventually leading to keratitis. To study this concept, we have developed a rabbit model in which a partial-thickness corneal epithelial defect was induced by filter paper impression on the cornea that removed one to two layers of corneal epithelium. Following this injury, the corneas were incubated with Pseudomonas aeruginosa, washed, and the number of bacteria adhering to the injured corneas as well as to control corneas was quantitated. Corneas treated with filter paper, either ex vivo or in vivo, allowed 20 times more bacteria to adhere than did the untreated control corneas (P less than 0.01). This superficial epithelial defect increased Pseudomonas adherence to the cornea for up to 72 hr after injury. When corneal injury was extended to the stroma, the adherence of Pseudomonas was further augmented as compared to adherence to the superficially injured cornea. Thus, we conclude that a clinically subtle, partial-thickness corneal epithelial injury can markedly facilitate the adherence of Pseudomonas aeruginosa, which may be an important predisposing factor for infectious keratitis.

The contribution of bacterial surface hydrophobicity to the process of adherence of Pseudomonas aeruginosa to hydrophilic contact lenses

Ten isolates of Pseudomonas aeruginosa obtained from the corneas of patients with Pseudomonas keratitis adhered to soft contact lenses in significantly greater numbers than did six isolates from other body sites (P less than .05). However, there was no predominant serotype among the 10 corneal isolates tested. Isolates grown statically in broth at 37 degrees C formed a pellicle and adhered two times as much to contact lenses as did isolates grown in broth while shaking which did not form a pellicle (P less than .01). The more adherent isolates (grown at 37 degrees C) were shown to be more hydrophobic than the less adherent bacteria (grown at 26 degrees C) by their propensity to accumulate at the interface between hexadecane and saline and their movement into polyethylene glycol from dextran. These corneal isolates agglutinated erythrocytes, a process that was inhibited by dilute solutions (as low as 0.01%) of three commonly used surfactants. These same surfactants inhibited the adherence of Pseudomonas aeruginosa to soft contact lens surfaces by as much as 52%. It is concluded that hydrophobic interactions may significantly contribute to the ability of Pseudomonas aeruginosa to adhere to contact lenses.

Factors influencing survival of patients with adenoid cystic carcinoma of the salivary glands

The uncertain long-term cure of adenoid cystic carcinoma of the salivary glands was determined in 30 treated patients seen between 1952 to 1984. Ten of 25 patients received elective postoperative irradiation (SEPI) after surgical extirpation of the primary/recurrent lesion; five patients had definitive radiotherapy alone. Overall, survival rates were 60%, 30%, and 7% at five, 10, and 20 years, respectively. The incidence of local recurrence was 37%, regional recurrence 3%, and distant metastasis 37%. Fewer recurrences and distant metastases were in the SEPI group than the surgery alone group. The majority of failures occurred within 10 years after initial diagnosis of primary malignancy; most of the patients died within five years after failure(s) detection. Correlations of prognosis to site of origin, and local control to total radiotherapy dose were observed. It is concluded that cure of disease can be achieved with the use of appropriate therapy.

The adherence of Pseudomonas aeruginosa to soft contact lenses

The adherence of Pseudomonas aeruginosa to extended-wear soft contact lenses (EWSCLs) may be an important initial step in the pathogenesis of EWSCL-associated infectious keratitis. P. aeruginosa tend to adhere more to worn EWSCLs than unworn EWSCLs (P less than 0.05). Normal tear components such as aqueous solutions of albumin, lysozyme, and lactoferrin all significantly enhance adherence of P. aeruginosa to unworn EWSCLs often by as much as 300%. The presence of a 1% solution of sialic acid in the bathing medium significantly reduces the adherence of P. aeruginosa to both unworn and worn lenses. Inhibition of bacterial adherence could also be achieved with the addition of mucin (which contains terminal sialic acid residues in its major sugar chains). Therefore, selective adherence by P. aeruginosa to a specific sugar (sialic acid) may be important in the initial attachment of the bacterium to soft contact lenses.

Carbohydrate deposits on the surfaces of worn extended-wear soft contact lenses

Three different commercial extended-wear soft contact lenses worn continuously by patients for at least 28 days were stained with fluorescein isothiocyanate-labeled lectins. These lectins detected the presence of alpha-linked or beta-linked D-mannose, D-glucose, D-galactose, L-fucose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and N-acetyl neuraminic acid (sialic acid) on the surfaces of the contact lenses. These saccharides are bound to other sugars that likely account for an integral part of glycoprotein and/or glycolipid deposits on lens surfaces. These tear deposits may contribute to the chemical spoilage of the lens and, furthermore, may serve as specific receptors for pathogenic microorganisms commonly implicated in extended-wear soft contact lens-associated infectious keratitis.

Malignant lymphoma of the salivary gland: case reports and review of the literature

Six cases of malignant lymphoma with unusual presentation in the salivary gland are reported here. In all subjects (except one), the lesion was located in the parotid gland. After further investigation and in accordance with the Ann Arbor staging system, patients' disease stages were I (1), II (3), III (1), and IV (1). Following the establishment of diagnosis through either tumor biopsy or resection, radiotherapy was given for early (I-II) and chemotherapy for more advanced (III-IV) stages of malignancy. With an average follow-up period of 27 months, overall 33% (2/6) survival and 67% (4/6) local control rates were observed. The literature is reviewed with consideration of clinicopathologic features and results of applied treatment.

Blastomycotic meningitis

A difficult and tragic case of central nervous system blastomycosis is presented as the basis for a review of the diagnostic criteria required to establish this diagnosis and to present a scheme for the diagnosis and therapy of chronic meningitis. The diagnosis in our case was complicated by preexisting inadequately treated tuberculosis; a prepontine mass; and a cervical intradural, extramedullary, circumferential mass. This exceptional case of chronic basilar meningitis with cervical myelopathy was caused by Blastomyces dermatitidis.

Human monoclonal antibodies to cytokeratins associated with squamous cell carcinoma

Human lymphocytes from a lymph node draining the tumor-bearing area of a patient with a large primary squamous cell carcinoma of the oral mucosa were fused with the nonproducer mouse myeloma, NS-1, to produce interspecies hybridomas. Of 95 hybridoma culture supernatants tested, 23 contained from 0.5 to 50 micrograms/ml of human IgM or IgG. Six supernatant fluids containing greater than 15 micrograms/ml of Ig were tested by indirect immunoperoxidase and immunofluorescence against sections of the autologous carcinoma. Five IgM (lambda) monoclonal antibodies stained the cytoplasm of autologous and allogeneic squamous carcinoma cells. All five monoclonal antibodies stained all layers of normal epidermis but each antibody stained the superficial keratin layer most intensely. Two of the five hybridoma antibodies were further tested. Both antibodies stained all types of normal epithelium; a network of fibers characteristic of intermediate filaments in cultured squamous carcinoma cells and cultured fibroblasts; Z lines in skeletal muscle; and axons in peripheral nerve fibers. We conclude that all five IgM monoclonal antibodies recognize cytokeratins associated with the autologous squamous cell carcinoma. Two of the five hybridoma antibodies recognize an antigenic determinant common to all types of intermediate filament proteins. These data indicate that cytokeratins released by squamous carcinoma cells induced an antibody response in this patient.

Pure intrarenal lipoma--report of a case and review of the literature

Pure intrarenal lipomas of sufficient size to be of surgical significance are among the rarest of renal tumors. A review of the literature to date revealed only 17 cases reported previously that met the histologic requirements of a pure intrarenal lipoma. We report an additional case in which the large tumor became clinically apparent following blunt trauma and rupture.

Unusual metastatic patterns of prostate adenocarcinoma

While prostatic adenocarcinoma is associated classically with osseous or lymphatic metastasis, it can present clinically with protean manifestations. We describe 4 cases that demonstrate unusual patterns of metastatic spread, including isolated supraclavicular mass, pleural effusion, suprapubic and genital skin metastasis, and priapism. Newer immunohistochemical staining techniques for prostate specific antigen and prostatic acid phosphatase can assist in localization of the metastatic adenocarcinoma to a prostatic origin.