The use of Beauveria bassiana for the control of the larger grain borer, Prostephanus truncatus, in stored maize: Semi-field trials in Ghana

Laboratory research in Ghana demonstrated the effectiveness of an isolate of Beauveria bassiana (IMI 389521) from the United Kingdom against the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), a major pest of stored maize. The minimum effective concentration, following artificial infestation trials on maize, was between 109 and 1010 cfu/kg maize. Before moving out to village-level control, a major requirement was to determine if the product could effect control in artificially infested maize held under real environmental conditions in several locations in Ghana. Therefore, this study investigated the efficacy of formulated conidia of B. bassiana, IMI 389521, at two concentrations (1 × 109 and 3.16 × 109 cfu/kg maize) to control P. truncatus on stored maize kernels under semi-field conditions in Ghana. Maize ('Obatanpa' cultivar) kernels were treated with the formulated B. bassiana product and stored in polypropylene woven bags in cribs in Southern Ghana. After 24 h, one hundred adults of P. truncatus were placed into each bag containing the treated maize. Mortality and the percent of weight loss of kernels were assessed every two weeks for three months. The semi-field trials revealed the possibility of successfully controlling adult P. truncatus on maize kernels treated with B. bassiana at 3.16 × 109 cfu/kg maize. However, due to the minimal protection of kernels after four weeks, re-treating maize kernels after this period is recommended to ensure maximum protection during prolonged storage.

Geometric localization in supported elastic struts

Localized deformation patterns are a common motif in morphogenesis and are increasingly finding applications in materials science and engineering, in such instances as mechanical memories. Here, we describe the emergence of spatially localized deformations in a minimal mechanical system by exploring the impact of growth and shear on the conformation of a semi-flexible filament connected to a pliable shearable substrate. We combine numerical simulations of a discrete rod model with theoretical analysis of the differential equations recovered in the continuum limit to quantify (in the form of scaling laws) how geometry, mechanics and growth act together to give rise to such localized structures in this system. We find that spatially localized deformations along the filament emerge for intermediate shear modulus and increasing growth. Finally, we use experiments on a 3D-printed multi-material model system to demonstrate that external control of the amount of shear and growth may be used to regulate the spatial extent of the localized strain texture.

[Postcardiac arrest treatment guide]

BACKGROUND

Treatment after cardiac arrest has become more complex and interdisciplinary over the last few years. Thus, the clinically active intensive and emergency care physician not only has to carry out the immediate care and acute diagnostics, but also has to prognosticate the neurological outcome.

AIM

The different, most important steps are presented by leading experts in the area, taking into account the interdisciplinarity and the currently valid guidelines.

MATERIALS AND METHODS

Attention was paid to a concise, practice-oriented presentation.

RESULTS AND DISCUSSION

The practical guide contains all important steps from the acute care to the neurological prognosis generation that are relevant for the clinically active intensive care physician.

[Biomarkers after resuscitation : Relevance in daily clinical practice for prognosis estimation and definition of therapeutic goals]

BACKGROUND

The assessment of the neurological prognosis after cardiac arrest should be made using a multimodal approach involving clinical, physical and laboratory findings. Here, biomarkers are of high importance. The reliable prognostication has far-reaching consequences for the patient on the further course of therapy and rehabilitation.

OBJECTIVES

Which biomarkers help in prognosis estimation and therapy target definition and are currently used in daily clinical practice?

MATERIALS AND METHODS

Presentation of the multimodal approach for prognosis generation in patients after resuscitation with hypoxic-ischemic encephalopathy with special consideration and discussion of various biomarkers.

RESULTS AND CONCLUSION

Neuron-specific enolase (NSE) is the best-established predictive biomarker in patients with hypoxic-ischemic encephalopathy after cardiac arrest. In combination with other methods (clinical examination, physical testing) and considering possible interfering factors (hemolysis, tumor diseases), NSE is used after 48-72 h with a cutoff value of 90 ng/ml. Most other biomarkers have so far only been studied in smaller groups or individual studies and thus cannot currently be routinely used outside of studies.

Delivering Beauveria bassiana with electrostatic powder for the control of stored-product beetles

BACKGROUND

The efficacy of a Beauveria bassiana-based formulation (Bb38) with Entostat, an electrostatically charged powder, was investigated as a surface treatment against Cryptolestes ferrugineus, Oryzaephilus surinamensis and Sitophilus granarius adults. In lab bioassays, the efficacy of Bb38 against the aforementioned species was examined on concrete, plywood, steel and ceramic, whereas its residual efficacy against the same species was assessed on concrete and steel in the presence or absence of illumination. Finally, the efficacy of Bb38 against O. surinamensis and S. granarius adults was assessed in a commercial grain storage facility under realistic field conditions.

RESULTS

In the lab trials, O. surinamensis and C. ferrugineus were much more susceptible to Bb38 than S. granarius on all types of surfaces. Moreover, Bb38 was, at least for O. surinamensis and C. ferrugineus, as effective as the chemical standard (deltamethrin) for at least 2 months after the application, regardless of the presence or absence of illumination. Finally, in the field trial Bb38 provided a satisfactory level of control against O. surinamensis.

CONCLUSION

Bb38 is an effective surface treatment, but its efficacy varies according to the target species, the type of surface and the time post-application. This is the first published report that examines the efficacy of Bb38 as a surface treatment for wider uses in empty warehouses and related storage facilities. © 2017 Society of Chemical Industry.

Improvement of lay rescuer chest compressions with a novel audiovisual feedback device : A randomized trial

BACKGROUND

Bystander actions and skills determine among others the outcome of out-of-hospital cardiac arrest. However, the depth and rate of chest compressions (CC) are difficult to estimate for laypeople and poor CC quality may result. Our study aimed to evaluate the impact of a new feedback device on CC performance by laypeople. The percentage of CC with both correct rate and correct depth of all CC served as primary endpoint.

METHODS

Forty-eight subjects with no medical background performed 2 min of CC on a manikin with and without a novel feedback device (TrueCPR™, Physio-Control, Redmond, Wash.). The device uses a novel, non-accelerometer-based technology. Participants were randomized into two groups. Group 1 performed a 2-min CC trial first with audiovisual feedback followed by a trial with no feedback information, while group 2 performed the task in reverse order.

RESULTS

The absolute percentage of CC with correct rate and depth was significantly higher with the use of the device (59 ± 34% vs. 15 ± 21%, p < 0.0001). The longest interval without correct CC was significantly decreased (76.5 s vs. 27.5 s, p < 0.0001).

CONCLUSION

The quality of CC carried out by laypeople is significantly improved with the use of a new feedback device. The device may be useful for cardiopulmonary resuscitation (CPR) by laypeople and for educational purposes.

Biophysical model of the role of actin remodeling on dendritic spine morphology

Dendritic spines are small membranous structures that protrude from the neuronal dendrite. Each spine contains a synaptic contact site that may connect its parent dendrite to the axons of neighboring neurons. Dendritic spines are markedly distinct in shape and size, and certain types of stimulation prompt spines to evolve, in fairly predictable fashion, from thin nascent morphologies to the mushroom-like shapes associated with mature spines. It is well established that the remodeling of spines is strongly dependent upon the actin cytoskeleton inside the spine. A general framework that details the precise role of actin in directing the transitions between the various spine shapes is lacking. We address this issue, and present a quantitative, model-based scenario for spine plasticity validated using realistic and physiologically relevant parameters. Our model points to a crucial role for the actin cytoskeleton. In the early stages of spine formation, the interplay between the elastic properties of the spine membrane and the protrusive forces generated in the actin cytoskeleton propels the incipient spine. In the maturation stage, actin remodeling in the form of the combined dynamics of branched and bundled actin is required to form mature, mushroom-like spines. Importantly, our model shows that constricting the spine-neck aids in the stabilization of mature spines, thus pointing to a role in stabilization and maintenance for additional factors such as ring-like F-actin structures. Taken together, our model provides unique insights into the fundamental role of actin remodeling and polymerization forces during spine formation and maturation.

Combining electrostatic powder with an insecticide: effect on stored-product beetles and on the commodity

BACKROUND

The opportunity to reduce the amount of pirimiphos-methyl applied to grain by formulating it in an electrostatic powder was investigated. The insecticidal efficacy of pirimiphos-methyl in EC formulation or formulated using electrostatic powder (EP) as an inert carrier was investigated against Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.) and Tribolium confusum Jacquelin du Val. Furthermore, the adhesive properties of EP to rice, corn and wheat, together with the effect on bulk density and bread- and pasta-making properties, were investigated.

RESULTS

The results showed that pirimiphos-methyl formulated with EP provided better efficacy against adults when compared with EC formulation for O. surinamensis and T. confusum, but there was no difference for R. dominica. Progeny production was consistently lower in grain treated with the EP formulation than in grain treated with the EC. Tests showed that EP adhered to the kernels for longer on hard wheat than on maize or rice. In most commodities, EP did not alter the bulk density. Finally, the addition of EP did not affect flour- and bread-making properties, nor the pasta-making properties.

CONCLUSIONS

The results of the present study suggest that an EP could be used to reduce the amount of pirimiphos-methyl applied to grain for effective pest control, with no detrimental effects on grain quality. © 2016 Society of Chemical Industry.

Improving Efficacy of Beauveria bassiana against Stored Grain Beetles with a Synergistic Co-Formulant

The potential of a dry powder co-formulant, kaolin, to improve the control of storage beetles by the entomopathogenic fungus Beauveria bassiana, isolate IMI389521, was investigated. The response of Oryzaephilus surinamensis adults to the fungus when applied to wheat at 1 × 10¹⁰ conidia per kg with and without kaolin at 1.74 g per kg wheat was assessed. Addition of kaolin increased control from 46% to 88% at day 7 and from 81% to 99% at day 14 post-treatment. Following this the dose response of O. surinamensis and Tribolium confusum to both kaolin and the fungus was investigated. Synergistic effects were evident against O. surinamensis at ≥0.96 g of kaolin per kg of wheat when combined with the fungus at all concentrations tested. For T. confusum, adult mortality did not exceed 55%, however, the larvae were extremely susceptible with almost complete suppression of adult emergence at the lowest fungal rate tested even without the addition of kaolin. Finally, the dose response of Sitophilus granarius to the fungus at 15 and 25 °C, with and without kaolin at 1 g per kg of wheat, was examined. Improvements in efficacy were achieved by including kaolin at every fungal rate tested and by increasing the temperature. Kaolin by itself was not effective, only when combined with the fungus was an effect observed, indicating that kaolin was having a synergistic effect on the fungus.

Critical behaviour in the nonlinear elastic response of hydrogels

In this paper we study the elastic response of synthetic hydrogels to an applied shear stress. The hydrogels studied here have previously been shown to mimic the behaviour of biopolymer networks when they are sufficiently far above the gel point. We show that near the gel point they exhibit an elastic response that is consistent with the predicted critical behaviour of networks near or below the isostatic point of marginal stability. This point separates rigid and floppy states, distinguished by the presence or absence of finite linear elastic moduli. Recent theoretical work has also focused on the response of such networks to finite or large deformations, both near and below the isostatic point. Despite this interest, experimental evidence for the existence of criticality in such networks has been lacking. Using computer simulations, we identify critical signatures in the mechanical response of sub-isostatic networks as a function of applied shear stress. We also present experimental evidence consistent with these predictions. Furthermore, our results show the existence of two distinct critical regimes, one of which arises from the nonlinear stretch response of semi-flexible polymers.

Fluctuation-stabilized marginal networks and anomalous entropic elasticity

We study the elastic properties of thermal networks of Hookean springs. In the purely mechanical limit, such systems are known to have a vanishing rigidity when their connectivity falls below a critical, isostatic value. In this work, we show that thermal networks exhibit a nonzero shear modulus G well below the isostatic point and that this modulus exhibits an anomalous, sublinear dependence on temperature T. At the isostatic point, G increases as the square root of T, while we find G∝Tα below the isostatic point, where α≃0.8. We show that this anomalous T dependence is entropic in origin.

Escherichia coli contamination of lettuce grown in soils amended with animal slurry

A pilot study was conducted to assess the transfer of Escherichia coli from animal slurry fertilizer to lettuce, with E. coli serving as an indicator of fecal contamination and as an indicator for potential bacterial enteric pathogens. Animal slurry was applied as fertilizer to three Danish agricultural fields prior to the planting of lettuce seedlings. At harvest, leaves (25 g) of 10 lettuce heads were pooled into one sample unit (n = 147). Soil samples (100 g) were collected from one field before slurry application and four times during the growth period (n = 75). E. coli was enumerated in slurry, soil, and lettuce on 3M Petrifilm Select E. coli Count Plates containing 16 mg/liter streptomycin, 16 mg/liter ampicillin, or no antimicrobial agent. Selected E. coli isolates (n = 83) originating from the slurry, soil, and lettuce were genotyped by pulsed-field gel electrophoresis (PFGE) to determine the similarity of isolates. The slurry applied to the fields contained 3.0 to 4.5 log CFU/g E. coli. E. coli was found in 36 to 54% of the lettuce samples, streptomycin-resistant E. coli was found in 10.0 to 18.0% of the lettuce samples, and ampicillin-resistant E. coli in 0 to 2.0% of the lettuce samples (the detection limit was 1 log CFU/g). The concentration of E. coli exceeded 2 log CFU/g in 19.0% of the lettuce samples. No E. coli was detected in the soil before the slurry was applied, but after, E. coli was present until the last sampling day (harvest), when 10 of 15 soil samples contained E. coli. A relatively higher frequency of E. coli in lettuce compared with the soil samples at harvest suggests environmental sources of fecal contamination, e.g., wildlife. The higher frequency was supported by the finding of 21 different PFGE types among the E. coli isolates, with only a few common PFGE types between slurry, soil, and lettuce. The frequent finding of fecal-contaminated lettuce indicates that human pathogens such as Salmonella and Campylobacter can be present and represent food safety hazards.

Analytical expressions for the shape of axisymmetric membranes with multiple domains

Based on the Canham-Helfrich free energy, we derive analytical expressions for the shapes of axisymmetric membranes consisting of multiple domains. We give explicit equations for both closed vesicles and almost cylindrical tubes. Using these expressions, we also find the shape of a tube attached to a spherical vesicle. The resulting shapes compare well to numerical data, and our expressions can be used to easily determine membrane parameters from experimentally obtained shapes.

Iceman Survived due to Cooling Device

Although mild hypothermia treatment is part of the standard postresuscitation care today, no standard method for treatment of accidental severe hypothermia has been yet established. Different strategies including invasive and noninvasive methods have been described in the literature. We present the case of a 75-year-old man with accidental severe hypothermia (23°C) and demonstrate that using a surface cooling device with automatic controlled temperature feedback mechanism (ArcticSun2000 Medivance, Louisville, Colorado, USA) is an effective and safe method for controlled rewarming in this life-threatening setting.

Off-lattice Monte Carlo simulation of supramolecular polymer architectures

We introduce an efficient, scalable Monte Carlo algorithm to simulate cross-linked architectures of freely jointed and discrete wormlike chains. Bond movement is based on the discrete tractrix construction, which effects conformational changes that exactly preserve fixed-length constraints of all bonds. The algorithm reproduces known end-to-end distance distributions for simple, analytically tractable systems of cross-linked stiff and freely jointed polymers flawlessly, and is used to determine the effective persistence length of short bundles of semiflexible wormlike chains, cross-linked to each other. It reveals a possible regulatory mechanism in bundled networks: the effective persistence of bundles is controlled by the linker density.

Frequency-dependent stiffening of semiflexible networks: a dynamical nonaffine to affine transition

By combining the force-extension relation of single semiflexible polymers with a Langevin equation to capture the dissipative dynamics of chains moving through a viscous medium we study the dynamical response of cross-linked biopolymer materials. We find that at low frequencies the network deformations are highly nonaffine, and show a low plateau in the modulus. At higher frequencies, this nonaffinity decreases while the elastic modulus increases. With increasing frequency, more and more nonaffine network relaxation modes are suppressed, resulting in a stiffening. This effect is fundamentally different from the high-frequency stiffening due to the single-filament relaxation modes [F. Gittes and F. C. MacKintosh, Phys. Rev. E 58, R1241 (1998)], not only in terms of its mechanism but also in its resultant scaling: G'(ω) ∼ ω(α) with α > 3/4. This may determine nonlinear material properties at low, physiologically relevant frequencies.

Semiflexible filamentous composites

Inspired by the ubiquity of composite filamentous networks in nature, we investigate models of biopolymer networks that consist of interconnected floppy and stiff filaments. Numerical simulations carried out in three dimensions allow us to explore the microscopic partitioning of stresses and strains between the stiff and floppy fractions cs and cf and reveal a nontrivial relationship between the mechanical behavior and the relative fraction of stiff polymer: when there are few stiff polymers, nonpercolated stiff "inclusions" are protected from large deformations by an encompassing floppy matrix, while at higher fractions of stiff material the stiff network is independently percolated and dominates the mechanical response.

Tympanic temperature during therapeutic hypothermia

OBJECTIVE

Prehospital induction of therapeutic hypothermia after cardiac arrest may require temperature monitoring in the field. Tympanic temperature is non-invasive and frequently used in clinical practice. Nevertheless, it has not yet been evaluated in patients undergoing mild therapeutic hypothermia (MTH). Therefore, a prospective observational study was conducted comparing three different sites of temperature monitoring during therapeutic hypothermia.

METHODS

Ten consecutive patients admitted to our medical intensive care unit after out-of-hospital cardiac arrest were included in this study. During MTH, tympanic temperature was measured using a digital thermometer. Simultaneously, oesophageal and bladder temperatures were recorded in a total of 558 single measurements.

RESULTS

Compared with oesophageal temperature, bladder temperature had a bias of 0.019°C (limits of agreement ± 0.61°C (2SD)), and tympanic measurement had a bias of 0.021°C (± 0.80°C). Correlation analysis revealed a high relationship for tympanic versus oesophageal temperature (r = 0.95, p < 0.0001) and also for tympanic versus bladder temperature (r = 0.96, p < 0.0001).

CONCLUSIONS

That tympanic temperature accurately indicates both oesophageal and bladder temperatures with a very small discrepancy in patients undergoing MTH after cardiac arrest is demonstrated in this study. Although our results were obtained in the hospital setting, these findings may be relevant for the prehospital application of therapeutic hypothermia as well. In this case, tympanic temperature may provide an easy and non-invasive method for temperature monitoring.

Phase coexistence and line tension in ternary lipid systems

The ternary system consisting of cholesterol, a saturated lipid, and an unsaturated one exhibits a rich phase behavior with multiple phase coexistence regimes. Remarkably, phase separation even occurs when each of the three binary systems consisting of two of these components is a uniform mixture. We use a Flory-Huggins like model in which the phase separation of the ternary system is a consequence of an interaction between all three components to describe the system. From the associated Gibbs free energy we calculate phase diagrams, spinodals, and critical points. Moreover, we use a Van der Waals/Cahn-Hilliard like construction to derive an expression for the line tension between coexisting phases. We show how the line tension depends on the position in the phase diagram, and give an explicit expression for the concentration profile at the phase boundary.

Effective-medium approach for stiff polymer networks with flexible cross-links

Recent experiments have demonstrated that the nonlinear elasticity of in vitro networks of the biopolymer actin is dramatically altered in the presence of a flexible cross-linker such as the abundant cytoskeletal protein filamin. The basic principles of such networks remain poorly understood. Here we describe an effective-medium theory of flexibly cross-linked stiff polymer networks. We argue that the response of the cross-links can be fully attributed to entropic stiffening, while softening due to domain unfolding can be ignored. The network is modeled as a collection of randomly oriented rods connected by flexible cross-links to an elastic continuum. This effective medium is treated in a linear elastic limit as well as in a more general framework, in which the medium self-consistently represents the nonlinear network behavior. This model predicts that the nonlinear elastic response sets in at strains proportional to cross-linker length and inversely proportional to filament length. Furthermore, we find that the differential modulus scales linearly with the stress in the stiffening regime. These results are in excellent agreement with bulk rheology data.

Monte Carlo study of multiply crosslinked semiflexible polymer networks

We present a method to generate realistic, three-dimensional networks of crosslinked semiflexible polymers. The free energy of these networks is obtained from the force-extension characteristics of the individual polymers and their persistent directionality through the crosslinks. A Monte Carlo scheme is employed to obtain isotropic, homogeneous networks that minimize the free energy and for which all of the relevant parameters can be varied: the persistence length and the contour length as well as the crosslinking length may be chosen at will. We also provide an initial survey of the mechanical properties of our networks subjected to shear strains, showing them to display the expected nonlinear stiffening behavior. Also, a key role for nonaffinity and its relation to order in the network is uncovered.

Nonlinear elasticity of composite networks of stiff biopolymers with flexible linkers

Motivated by recent experiments showing nonlinear elasticity of in vitro networks of the biopolymer actin cross-linked with filamin, we present an effective medium theory of flexibly cross-linked stiff polymer networks. We model such networks by randomly oriented elastic rods connected by flexible connectors to a surrounding elastic continuum, which self-consistently represents the behavior of the rest of the network. This model yields a crossover from a linear elastic regime to a highly nonlinear elastic regime that stiffens in a way quantitatively consistent with experiment.

Immediate Recovery of Renal Function After Orthotopic Liver Transplantation in a Patient With Hepatorenal Syndrome Requiring Hemodialysis for More Than 8 Months

Severe liver dysfunction may lead to impairment of renal function without an underlying renal pathology. This phenomenon is called hepatorenal syndrome (HRS), which is associated with a poor prognosis showing a median survival of less than 2 months if renal replacement therapy is necessary. Liver transplantation is the best therapeutic option to regain renal function, but because of poor survival, these patients often die before transplantation. Herein we report a 37-year-old patient with ethyl-toxic liver cirrhosis who underwent hemodialysis due to HRS type I for more than 8 months. After living donor liver transplantation, diuresis immediately resumed, renal function soon recovered, and intermittent hemodialysis was stopped at 18 days after transplantation. Renal function was stable with a serum creatinine <2 mg/dL during the last 5 years posttransplantation. As far as we know, only a few cases of an anuric patient suffering from HRS have been reported with a survival beyond 8 months and full recovery of renal function after liver transplantation. This underlined that renal replacement therapy in HRS should be considered as a possible bridging method to liver transplantation even for longer periods.

Fission of a multiphase membrane tube

A common mechanism for intracellular transport is the use of controlled deformations of the membrane to create spherical or tubular buds. While the basic physical properties of homogeneous membranes are relatively well known, the effects of inhomogeneities within membranes are very much an active field of study. Membrane domains enriched in certain lipids, in particular, are attracting much attention, and in this Letter we investigate the effect of such domains on the shape and fate of membrane tubes. Recent experiments have demonstrated that forced lipid phase separation can trigger tube fission, and we demonstrate how this can be understood purely from the difference in elastic constants between the domains. Moreover, the proposed model predicts time scales for fission that agree well with experimental findings.

Succession in inland sand ecosystems: which factors determine the occurrence of the tall grass species Calamagrostis epigejos (L.) Roth and Stipa capillata L.?

In many successional series, grass species play an important role in mid-successional stages. Using calcareous sand ecosystems in the northern upper Rhine valley (Germany) as a model, we analyzed successional trajectories and the factors that determine their direction. A 5- to 7-year study of 23 permanent plots is presented. Polar ordination revealed that succession starts with pioneer communities (dominated by Corynephorus canescens and cryptogams) and can eventually lead to relatively stable Calamagrostis epigejos or Stipa capillata tall grass stands. At some sites, Cynodon dactylon can play a major role, but we focused on the two previously mentioned species. Gradient analyses of their ecological amplitudes by means of principal components and regression analysis were carried out in order to elucidate the factors determining the successional trajectories. Soil analyses of 71 plots established significantly positive linear relations for C. epigejos with respect to total nitrogen, extractable phosphate and potassium, as well as soil moisture indicator values. C. epigejos is not able to spread if the stress factors nutrient deficiency and dryness are combined. Lower tolerance limits are presented. In contrast, S. capillata shows negative relations to phosphate, declining strongly at P contents > 20 mg kg(-1). At a moisture indicator value of around 3.2 (indicating dry sites), S. capillata reaches its optimum. S. capillata is a model for a tall grass species which, even with low nutrient levels and dry soil conditions, can be successful in mid-successional phases; but it is displaced by C. epigejos if soil moisture increases or phosphate/potassium supply is higher. Regarding a general framework, the successional phases are characterized by processes such as replacement of species, facilitation, and inhibition.

Theory of high-force DNA stretching and overstretching

Single-molecule experiments on single- and double-stranded DNA have sparked a renewed interest in the force versus extension of polymers. The extensible freely jointed chain (FJC) model is frequently invoked to explain the observed behavior of single-stranded DNA, but this model does not satisfactorily describe recent high-force stretching data. We instead propose a model (the discrete persistent chain) that borrows features from both the FJC and the wormlike chain, and show that it resembles the data more closely. We find that most of the high-force behavior previously attributed to stretch elasticity is really a feature of the corrected entropic elasticity; the true stretch compliance of single-stranded DNA is several times smaller than that found by previous authors. Next we elaborate our model to allow coexistence of two conformational states of DNA, each with its own stretch and bend elastic constants. Our model is computationally simple and gives an excellent fit through the entire overstretching transition of nicked, double-stranded DNA. The fit gives the first value for the bend stiffness of the overstretched state. In particular, we find the effective bend stiffness for DNA in this state to be about 12 nm k(B)T, a value quite different from either the B-form or single-stranded DNA.

Improved blood cellular biocompatibility with heparin coated circuits during cardiopulmonary bypass

BACKGROUND

The clinical use of heparinized surfaces in the extracorporeal circuit was studied to find out if there was any blood cell rheologic benefit to support its use in routine low risk cardiac surgery.

METHODS

In a prospective single blind study, 39 patients were operated upon with the heart lung machine for angina pectoris by coronary bypass grafting and were randomized to a control group or a heparin group. Blood cell rheology was analysed using the St. George filtrometer where damage to the red blood cells and white blood cells was estimated by assessing deformability reductions, transit, time increases and clogging rate and clogging particle changes.

RESULTS

At the end of cardiopulmonary bypass, in the heparin group, the red cell filterability (rFR) and the white cell filterability (WFR) were 8% better than in the control group (p=0.0079 and p=0.027 respectively). The red cell transit time was 19% slower in the control group (p=0.0351). The red cell clogging rate (RCR) and clogging particles (RCP) were significantly lower in the heparin group (p=0.0212 and p=0.0409 respectively. The white cell clogging rate (WCR) and clogging particles (WCP) showed a similar pattern.

CONCLUSIONS

In spite of these significant differences the clinical outcome was similar in the groups. Thus heparin coating of the extracorporeal circuit reduces blood cell rheologic damage significantly in low risk patients undergoing routine bypass surgery for angina but this use did not lead to any clinical benefit postoperatively. Therefore the use of such circuits for routine low risk cardiac surgery cannot be recommended.

Universal algebraic relaxation of velocity and phase in pulled fronts generating periodic or chaotic states

We investigate the asymptotic relaxation of so-called pulled fronts propagating into an unstable state, and generalize the universal algebraic velocity relaxation of uniformly translating fronts to fronts that generate periodic or even chaotic states. A surprising feature is that such fronts also exhibit a universal algebraic phase relaxation. For fronts that generate a periodic state, like those in the Swift-Hohenberg equation or in a Rayleigh-Benard experiment, this implies an algebraically slow relaxation of the pattern wavelength just behind the front, which should be experimentally testable.

Heparin-coated circuits reduce occult myocardial damage during CPB: a randomized, single blind clinical trial

OBJECTIVES

Cardiopulmonary bypass is associated with a diffuse systemic inflammatory response that can cause considerable morbidity, including organ dysfunction and bleeding. Heparin-coated circuits have been shown to give a reduced inflammatory response with clinical benefits during open-heart surgery. However, the effects on lipid peroxidation, neutrophil activation and myocardial ischemic damage in the human have remained unknown.

METHODS

In a randomized single blind trial, complement activation, neutrophil counts, malondialdehyde, and cardiac enzymes were studied in 39 patients undergoing open-heart surgery. Two groups were perfused with cardiopulmonary bypass circuits with (n=20) or without heparin-coating (n=19).

RESULTS

The different complement factors (C3, C4, C3d, C3d/C3 and the C-function), neutrophil levels, MDA and the cardiac enzyme levels were comparable before CPB was started and significantly increased in both groups during bypass. There were significant intergroup differences in the neutrophil levels and MDA after reperfusion (P<0.0001). Furthermore, significant positive correlations between the lipid peroxidation, expressed as MDA levels, and the levels of neutrofils and the cardiac enzyme, CK-MB were seen within the groups.

CONCLUSIONS

Heparin coated circuits did lead to a decreased neutrophil response and MDA level. The correlations between CK-MB and neutrophil and MDA levels suggest neutrophil activation leading to lipid peroxidation that may influence myocardial damage. Heparin coating improved biocompatibility and was associated with less occult myocardial ischemic damage in patients undergoing open heart surgery.