Chemical-Shift Perturbations Reflect Bile Acid Binding to Norovirus Coat Protein: Recognition Comes in Different Flavors

Bile acids have been reported as important cofactors promoting human and murine norovirus (NoV) infections in cell culture. The underlying mechanisms are not resolved. Through the use of chemical shift perturbation (CSP) NMR experiments, we identified a low-affinity bile acid binding site of a human GII.4 NoV strain. Long-timescale MD simulations reveal the formation of a ligand-accessible binding pocket of flexible shape, allowing the formation of stable viral coat protein–bile acid complexes in agreement with experimental CSP data. CSP NMR experiments also show that this mode of bile acid binding has a minor influence on the binding of histo-blood group antigens and vice versa. STD NMR experiments probing the binding of bile acids to virus-like particles of seven different strains suggest that low-affinity bile acid binding is a common feature of human NoV and should therefore be important for understanding the role of bile acids as cofactors in NoV infection.     

Nutrient digestibility and endogenous protein losses in the foregut and small intestine of weaned dairy calves fed calf starters with conventional or enzyme-treated soybean meal

The aims of this experiment were (1) to compare the effects of a soybean meal with an enzymatic treatment (ESBM) to reduce the concentration of antinutritional factors versus a standard soybean meal (SBM) on foregut and small intestine digestion in weaned dairy calves and (2) to estimate the endogenous losses of crude protein (CP) in the small intestine. Our hypothesis was that a diet containing ESBM instead of SBM would improve ruminal and small intestine digestion and absorption of nutrients. A T-cannula was placed in the duodenum, and a second T-cannula was installed in the distal ileum of 12 Holstein calves at approximately 3 wk of age. Calves were weaned on d 42, and on d 50 they were assigned randomly to a quadruplicated 3 × 3 Latin square with 10-d periods. Digesta samples were collected on d 7 and 8 from the ileum and d 9 and 10 from the duodenum. The diets were fed for ad libitum intake and consisted of a calf starter (CS) of 20% CP with SBM as the main source of protein (CTRL), and an isonitrogenous CS with an ESBM instead of SBM (ENZT). A third diet with a low content of CP (10%) and no soy protein was fed to estimate endogenous N losses and digestibilities of test ingredients. Flows and digestibilities of nutrients were compared between CTRL and ENZT and their test ingredients (SBM vs. ESBM, respectively). Duodenal net flows of CP and total AA as well as ruminal microbial protein synthesis per kilogram of digested CP were greater, and flow of nonprotein N and CP true (corrected by endogenous and microbial flows) foregut digestibility were lower with ENZT than CTRL. The apparent small intestine digestibilities of CP and total AA were greater for ESBM than SBM, but there were no differences between the CTRL and ENZT diets. We observed no differences in digestibilities at the duodenum or ileum of starch or NDF, but true small intestine digestibilities of CP and all AA were greater with ENZT than CTRL. Total endogenous protein losses in the small intestine estimated from calves fed the low-CP with no soy protein diet were 37 ± 1.5 g of CP and 29 ± 1.4 g of AA/kg of DMI. These values may be considered the basal endogenous losses as they are similar to values obtained with the regression method, which estimates N losses when dietary N is null. Our results indicated that the inclusion of an ESBM improved the efficiency of ruminal microbial protein synthesis per digested kilogram of organic matter and CP, and increased CP and AA absorption in the small intestine despite a greater proportion of undigested dietary protein entering the duodenum.     

Measurements of single chain form factors by small-angle neutron scattering from polystyrene blends containing high concentrations of labelled molecules

A series of small angle neutron scattering measurements on blends of normal polystyrene (PSH) and labelled (deuterated) polystyrene (PSD) have been made with concentrations of PSD from 5 to 50 mol %. It is shown that the single chain form factor of the polymer in bulk can be obtained from a single concentration measurement for any concentration of labelled molecules, providing the molecular weights of the parent and labelled molecules are the same and the molecular weight distributions are narrow.     

Bladder injury model induced in rats by exposure to protamine sulfate followed by bacterial endotoxin

PURPOSE: A bladder injury model was developed using protamine sulfate (PS) and endotoxin lipopolysaccharide (LPS) administered intravesically to female Sprague-Dawley rats. MATERIALS AND METHODS: Experimental and control animals were catheterized and intravesically exposed to PS-LPS, PS, LPS, or phosphate buffered saline. After 4, 24 or 72 hours, rats were sacrificed. Urines and bladder tissues were then obtained. Bladder mucosal permeability was evaluated by measuring 14C-urea uptake 24 hours after injury. Repeated instillations of PS/LPS were also made in another group of rats over a period of 5 weeks to attempt to establish a more serious mucosal injury, possibly reflected by altered staining of the collagen IV component of the urinary basement membrane (UBM). RESULTS: Histological examination of the tissues indicated a maximal inflammatory response in the mucosa 4 hours after instillation of PS/LPS. Neutrophils and macrophages in close proximity to the UBM and intraepithelially could be demonstrated. Bladder permeability was significantly altered (26.9% 14C-urea uptake) in rats assayed 24 hours after the PS/LPS treatment, but not after exposure to PS or LPS alone (11.9 and 17.5%, respectively). Protease activity detected in urines from experimental, but not control, animals coincided with the appearance of inflammatory cells in the lamina propria. Inflammatory injury did not appear to alter the collagen IV staining of the UBM. CONCLUSIONS: This rat bladder injury model is useful for examining controversial issues regarding bladder wall structure-function alterations induced by inflammation and possibly important in the pathobiological mechanisms involved in some patients with interstitial cystitis.     

Laboratory simulation of hypervelocity debris

A series of hypervelocity damage experiments were performed on spacecraft materials in order to simulate micro-size space debris traveling at 3 to 8 km/s. Two types of impact simulations were investigated: high-power pulsed laser and laser-launched micro-flyer plate. In the first case a laser was used to generate a high-pressure shock wave which propagated into the target by means of rapid ablation of the target surface. The second case used the same laser to accelerate micro-flyer plates at a target. The laser-ablation technique and the apparatus used to propel the micro-flyer plates were compatible with a space environmental chamber equipped with instrumentation capable of analyzing the vapor ejected from the sample. Data obtained from two separate damage effects were of interest in this study: the vapor blow-off produced by the impact and the mechanical damage to the target. The value of the data obtained from both simulation methods was evaluated in terms of likeness to actual space debris damage.

Data for this work were obtained from polysulfone resin and a graphite polysulfone composite. Polysulfone was selected because it was flown on the Long Duration Exposure Facility (LDEF) satellite which spent several years in low earth orbit and experienced many space debris impacts.

The chemistry of the vapor produced by the two simulation techniques was analyzed with a time of flight mass spectrometer (TOFMS) which measured changes in the vapor chemistry as a function of time after impact, obtained a velocity measurement of the vapor, and estimated surface temperature immediately after impact using dynamic gas equations. Samples of the vapor plume were also captured and examined by transmission electron microscopy (TEM).

The mechanical damage effects caused by the simulation methods on a graphit polysulfone composite and a polysulfone resin were studied. Impact craters were examined under optical and scanning electron microscopes (SEM). Based on the two damage effect criteria the micro-flyer method proved to be a useful way to simulate hypervelocity impact of space debris. The laser-ablation method however, had shortcomings and required drastic compromises in the set criteria.     

A low emittance cw-electron injector for the ELBE accelerator

For applications in nuclear and radiation physics there is an increasing demand for electron beams with superior brightness in the medium energy range. This work presents the injector design for the superconducting accelerator ELBE [1]. The injector consists of a thermionic rf-gun, working at a frequency of 1.3 GHz in cw-mode. The superconducting section is based on the technology established at TESLA [2], modified for cw operation. The accelerator will deliver a 20 MeV beam with an rms energy spread of 10 keV and an average current of up to 1 mA. The normalised transverse emittance remains 1 π mm mrad. The arrangement and operating parameters of the accelerator components were settled by numerical optimization considering longitudinal beam dynamics. The results led to a nonlinear bunching scheme, which compensates the high longitudinal emittance from the thermionic rf-gun.     

Gain control in reflex pathways

Summary form only given. A series of experiments was undertaken to determine the gain of the stretch reflex in decerebrate cats. Stretches are applied through a servo-controlled motor that receives length and velocity feedback which are adjusted so that it behaves like a spring of a particular stiffness. As the stiffness decreases the gain of the reflex increases until the stiffness is made much less than the intrinsic muscle stiffness. Under these conditions small brief pulses can elicit shortening of 1 mm or more and reflex forces that are larger than the force produced by the stretch itself. This suggests that the gain in the reflex is 1 or more at low frequencies. It is concluded that muscle control systems are adaptive and time-varying to accomplish the various tasks required by the organism. Although under some conditions the reflex gain is on the order of one, measurement of gain is compounded by a number of nonlinearities, and the value of these nonlinearities in various tasks remains to be determined     

Machine learning in control of functional electrical stimulationsystems for locomotion

Two machine learning techniques were evaluated for automatic design of a rule-based control of functional electrical stimulation (FES) for locomotion of spinal cord injured humans. The task was to learn the invariant characteristics of the relationship between sensory information and the FES-control signal by using off-line supervised training. Sensory signals were recorded using pressure sensors installed in the insoles of a subject's shoes and goniometers attached across the joints of the affected leg. The FES-control consisted of pulses corresponding to time intervals when the subject pressed on the manual push-button to deliver the stimulation during FES-assisted ambulation. The machine learning techniques used were the adaptive logic network (ALN) and the inductive learning algorithm (IL). Results to date suggest that, given the same training data, the IL learned faster than the ALN while both performed the test rapidly. The generalization was estimated by measuring the test errors and it was better with an ALN, especially if past points were used to reflect the time dimension. Both techniques were able to predict future stimulation events. An advantage of the ALN over the IL was that ALN's can be retrained with new data without losing previously collected knowledge. The advantages of the IL over the ALN were that the IL produces small, explicit, comprehensible trees and that the relative importance of each sensory contribution can be quantified