Effects of cross-sectional area on human bite studied with raw carrot and surimi gel

The effects of the cross-sectional area of food samples on bite force with molar teeth were investigated using raw carrots and surimi gels. We evaluated human bite force for food samples with different sizes between the upper and lower molars using a multiple-point sheet sensor and electromyography (EMG). The bite force curve and EMG clearly showed textural characteristics of the carrot and gel. In particular, the first peak in the bite curves corresponded to breaking point in the compression test. With increasing cross-sectional area of both foodstuffs, the bite force and contact area increased and the average stress to which the specimen was subjected (mean stress) tended to decrease, while the stress produced between the teeth and the specimen (active stress) did not change. Chewing rhythm and EMG activities were not greatly influenced by sample size. These findings suggest that higher bite force might cause difficulty in biting food with a larger cross-sectional area.     

Equilibrium gel permeation: a single-photon counting spectrophotometer for studies of protein interaction.

When a small column or flow cell packed with gel particles is completely saturated with a solution containing molecular species of interest, the average cross-sectional area occupied by the solute (partition cross section) is conveniently and precisely determined by direct optical scanning. For a mixture of interacting solutes this equilibrium gel permeation measurement yields the weight average of the species partition cross sections and the variation of this quantity with solute concentration permits determination of the solute interaction parameters (stoichiometry, equilibrium constants). We have developed a computer-controlled single-photon counting spectrophotometer for these measurements. The instrument exhibits high precision over a wide range of optical density. With counting times in the range of 10-1000 s the standard deviations on optical densities of protein solutions measured at 220 nm are typically 0.0006 at 1 OD, 0.002 at 2 OD, 0.005 at 4 OD. Beer's law tests show that deviations from linearity are less than these precision limits. Partition cross-section measurements for proteins can be made with an accuracy of better than 0.001 and information can be obtained with protein solutions at least as low as 1 mug/ml.     

Active stress during compression testing of various foods measured using a multiple-point sheet sensor

Using a multiple-point sheet sensor (MSS), load and contact area were directly measured for compression of four different foods. The MSS provided temporal and spatial changes in stress applied on the sample surface during the testing. The sum of load value detected by the MSS corresponded to the load measured by a universal testing machine during the compression. The contact area between a flat probe and food surface varied with the variety of foods even though under a small strain, and increased as compression strain increased. The active stress, that is, the load divided by the contact area, was different from conventional stress, that is, the load divided by the initial cross-sectional area. The value of active stress provided a better explanation of textural characteristics of food, because texture is often sensed under a large deformation and mixed assessment of mechanical and geometrical properties.     

Respiratory cross-sectional area-flux measurements of the human chest wall

A new device that utilizes the voltages induced in separate coils encircling the rib cage and abdomen by a magnetic field is described for measurement of cross-sectional areas of the human chest wall (rib cage and abdomen) and their variation during breathing. A uniform magnetic field (1.4 X 10(-7) Tesla at 100 kHz) is produced by generating an alternating current at 100 kHz in two square coils, 1.98 m on each side, parallel to the planes of the areas to be measured and placed symmetrically cephalad and caudad to these planes at a mean distance of 0.53 m. We demonstrated that the accuracy of the device on well-defined surfaces (squares, circles, rectangles, ellipses) was within 1% in all cases. Observed errors are due primarily to small inhomogeneities of the magnetic field and variation of the orientation of the coil relative to the field. Using a second magnetic field (80 kHz) perpendicular to the first, we measured the errors due to nonparallel orientation during quiet breathing and inspiratory capacity maneuvers. In 10 normal subjects, orientation effects were less than 2% for the rib cage and less than 0.7% for the abdomen. In five of these subjects, orientation effects at functional residual capacity in lateral and seated postures were generally less than or equal to 5%, but estimated tidal volume during spontaneous breathing was comparable to measurements in the supine posture. In five curarized patients, we assessed the linearity of volume-motion relationships of the rib cage and abdomen, comparing cross-sectional area and circumference measurements. Departures from linearity using cross-sectional areas were only one-third of those using circumferences. In seven normal subjects we compared cross-sectional area measurements with respiratory inductive plethysmography (RIP) and found comparable estimates of lung volume change over a wide range of relative rib cage contributions to tidal volume (-5 to 105%), with slightly higher standard deviations for the RIP (SD = 10% for RIP; SD = 4% for cross-sectional area).     

The effect of specimen geometry on the mechanical behaviour of trabecular bone specimens.

The effect of specimen geometry on the mechanical behaviour of trabecular bone specimens was studied by non-destructive uniaxial compression to 0.4% strain using cylindrical specimens with different sizes and length-to-diameter ratios, and by comparing cubic and cylindrical specimens with the same cross-sectional area. Both the length and the cross-sectional area of the specimen had a highly significant influence on the mechanical behaviour (p less than 0.0001). Within the actual range of length (2.75-11.0 mm) the normalized stiffness (Young's modulus) was related nearly linearly to the specimen length. This dependency on specimen length is suggested to be caused mainly by structural disintegrity of the trabecular specimens near the surface. The normalized stiffness (Young's modulus) was also positively correlated to the cross-sectional area. This dependency on cross-sectional area is probably due to friction-induced stress inhomogeneity at the platen-specimen interface. A cube with side length 6.5 mm or a cylindrical specimen with 7.5 mm diameter and 6.5 mm length are suggested as standard specimens for comparative studies on trabecular bone mechanics.     

Preparative Gel Electrophoresis at High Sample Load. The Effect of Some Experimental Variables on Separation Performance

The separation of model protein pairs (hemoglobin/ albumin, trypsin/chymotrypsin, hemoglobin A/hemoglobin F) was studied in an apparatus for preparative gel electrophoresis at loads up to 40 mg/cm ²of the cross-sectional area of the gel bed. Separation was favored by higher ionic strength and by longer migration path. Under the conditions used and within the load range studied, increasing total protein load had no adverse effect but increased voltage gradient, temperature, or gel strength were all unfavorable.     

Responding to a Variable Environment: Home Range, Foraging Behavior, and Nest Relocation in the Costa Rican Rainforest Ant Aphaenogaster araneoides

We studied how the tropical wet forest ant Aphaenogaster araneoides adjusted its home range and foraging behavior in response to changes in the leaf litter and food environments. We decoupled litter abundance and food availability by creating a factorial treatment design including litter removal and food supplementation. Leaf litter removal caused a decrease in the number of foraging trips but an increase in their duration. Over a 2-week experimental period, about half of the colonies relocated their nests. We found a strong effect of nearest neighbor distance upon the home range areas of colonies after they relocated their nests. In summary, short-term manipulations of resources resulted in changes in home range area and foraging behaviors that differed depending upon nest relocation and the competitive environment.     

Bilayer dimensions and hydration of glycolipids

X-ray diffraction measurements are available on a wide range of glycolipid multilamellar assemblies in excess water, but not at the defined water contents that are needed to derive bilayer dimensions. For lamellar crystalline phases and gel phases with untilted chains, or where the tilt angle is known, the cross-sectional area per chain from wide-angle diffraction can be used to determine the area per lipid molecule at the bilayer surface. Using the lipid molecular volume from densitometry, it is then possible to obtain the bilayer thickness and hence, from the lamellar repeat spacing, the water layer thickness and degree of hydration of the lipid polar groups. This is done here by using the available data for bilayer-forming diacyl and dialkyl glycosylglycerols, and for certain glycosphingolipids. The lamellar crystalline phases of these glycolipids are largely anhydrous, and the degree of hydration of the lamellar gel phases is much lower than that of the corresponding phosphoglycerolipid gel phases. A point of current uncertainty is whether the chains in the gel phases of diacyl glycoglycerolipids are appreciably tilted, unlike their dialkyl counterparts.     

Promotion of apple tree growth and fruit production by the EBW-4 strain of Bacillus subtilis in apple replant disease soil.

A field trial was conducted near Kelowna, British Columbia, to determine the effect of biological treatments alone and in combination with formalin fumigation in apple replant disease soil. The response was measured by the increase in cross-sectional trunk area, total shoot growth, and fruit yield of McIntosh apple trees on M.26 rootstock. The postplanting drench application of strain EBW-4 of Bacillus subtilis alone was consistently effective in increasing cross-sectional trunk area for 5 years, total shoot growth for 4 years, and fruit yield for 3 years. The biological agent EBW-4 of B. subtilis in combination with formalin fumigation was also effective in promoting total shoot growth and cross-sectional trunk area. The application of formalin fumigation alone was effective in increasing shoot growth for 2 years and cross-sectional trunk area for 1 year only. This treatment did not increase fruit yield for 3 years. The consistent performance of strain EBW-4 of B. subtilis during 1986-1991 indicates that this bacterium has the potential for biological control of replant disease under orchard conditions in the Okanagan Valley of British Columbia.     

A new molecular model for collagen elasticity based on synchrotron X-ray scattering evidence.

Collagen is the most abundant structural protein in vertebrates. The specific shape of its stress-strain curve is crucial for the function of a number of organs. Although the macroscopic mechanical behavior of collagen is well known, there is still no explanation of the elastic process at the supramolecular level. We have performed in situ synchrotron x-ray scattering experiments, which show that the amount of lateral molecular order increases upon stretching of collagen fibers. In strain cycling experiments the relation between strain and diffuse equatorial scattering was found to be linear in the "heel" region of the stress-strain curve. A new molecular model for collagen elasticity is proposed, which, based on the existence of thermally activated molecular kinks, reproduces this linearity and gives a simple explanation for the form of the stress-strain curve of collagen.     

Giant lipid vesicles filled with a gel: shape instability induced by osmotic shrinkage

We report the properties of giant lipid vesicles enclosing an agarose gel. In this system, the lipid bilayer retains some basic properties of biological membranes and the internal fluid exhibits viscoelastic properties, thus permitting us to address the question of the deformation of a cell membrane in relation to the mechanical properties of its cytoskeleton. The agarose gel (concentration c0gel = 0.07%, 0.18%, 0.36%, and 1% w/w), likely not anchored to the membrane, confers to the internal volume elastic moduli in the range of 10-10(4) Pa. Shapes and kinetics of de-swelling of gel-filled and aqueous solution-filled vesicles are compared upon either a progressive or a fast osmotic shrinkage. Both systems exhibit similar kinetics. Shapes of solution-filled vesicles are well described using the area difference elasticity model, whereas gel-filled vesicles present original patterns: facets, bumps, spikes (c0gel < 0.36%), or wrinkles (c0gel > or = 0.36%). These shapes partially vanish upon re-swelling, and some of them are reminiscent of echinocytic shapes of erythrocytes. Their characteristic size (microns) decreases upon increasing c0gel. A possible origin of these patterns, relying on the formation of a dense impermeable gel layer at the vesicle surface and associated with a transition toward a collapsed gel phase, is advanced.     

Behavioral and physiological resistance of the German cockroach to gel baits (Blattodea: Blattellidae)

A gel bait-resistant German cockroach, Blattella germanica (L.), strain Cincy was collected in Cincinnati, OH. This strain exhibited a high level of behavioral resistance to Avert (0.05% abamectin) and Maxforce FC (0.01% fipronil) gel baits. Topical application assays indicated moderate levels of physiological resistance of the Cincy strain to abamectin and fipronil. Resistance ratios (based on LD50 values from topical applications) to abamectin and fipronil were 2.5 and 8.7, respectively. The Cincy strain of had a significantly lower LD50 value to abamectin than a nonaverse field strain (Dorie) and similar LD50 values to fipronil as the Dorie strain. The aversion behavior (avoidance of gel baits) was therefore caused by food ingredients in the gel baits. The Cincy strain showed avoidance of agar containing fructose, glucose, maltose, and sucrose, which are phagostimulants to the laboratory strain. Modifications of the inert ingredients in the Maxforce FC gel bait significantly improved the efficacy against the Cincy strain. The Cincy strain produced significantly smaller oothecae and lower numbers of eggs in each egg capsule than the nonaverse Jwax and Dorie strains of cockroaches, suggesting fitness costs are associated with resistance.     

Development of a Listeria monocytogenes EGDe partial proteome reference map and comparison with the protein profiles of food isolates

A partially annotated proteome reference map of the food pathogen Listeria monocytogenes was developed for exponentially growing cells under standardized, optimal conditions by using the sequenced strain EGDe (serotype 1/2a) as a model organism. The map was developed by using a reproducible total protein extraction and two-dimensional (2-D) polyacrylamide gel electrophoresis analysis procedure, and it contained 33 identified proteins representing the four main protein functional classes. In order to facilitate analysis of membrane proteins, a protein compartmentalization procedure was assessed. The method used provided partial fractionation of membrane and cytosolic proteins. The total protein 2-D profiles of three serotype 1/2a strains and one serotype 1/2b strain isolated from food were compared to the L. monocytogenes EGDe proteome. An average of 13% of the major protein spots in the food strain proteomes were not matched in the strain EGDe proteome. The variation was greater for the less intense spots, and on average 28% of these spots were not matched. Two of the proteins identified in L. monocytogenes EGDe were missing in one or more of the food isolates. These two proteins were proteins involved in the main glycolytic pathway and in metabolism of coenzymes and prosthetic groups. The two corresponding genes were found by PCR amplification to be present in the four food isolates. Our results show that the L. monocytogenes EGDe reference map is a valuable starting point for analyses of strains having various origins and could be useful for analyzing the proteomes of different isolates of this pathogen.     

Hydrostatic pressure induces hydrocarbon chain interdigitation in single-component phospholipid bilayers

By use of neutron diffraction for structural analysis, the temperature-pressure phase diagrams of several fully hydrated single-component phospholipid bilayers have been explored up to hydrostatic pressures of 2 kbars. The gel to liquid-crystalline phase transition temperature Tm increases linearly with pressure over a 10(-3)-2 kbar range in accordance with the Clausius-Clapeyron relationship giving dTm/dP values of 23.0 degrees C/kbar for 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 28.0 degrees C/kbar for 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC). The so-called pretransition was not observed in the isothermal pressure experiments, suggesting that no appreciable volume change occurs at this transition. These results are in good agreement with those reported using other techniques. In addition, at pressures higher than the isothermal liquid-crystalline to gel transition pressure, a new pressure-induced phase transition was observed for DPPC and DSPC in which the hydrocarbon chains from apposing monolayers become interdigitated with the chains occupying a cross-sectional area approximately equal to 5% less than in the gel phase. The temperature-pressure phase diagrams show the gel-interdigitated phase boundaries to be highly curved and the minimum pressure at which interdigitation occurs to decrease with increasing hydrocarbon chain length.     

Chip-based gel electrophoresis method for the quantification of half-antibody species in IgG4 and their by- and degradation products

The inter-heavy-chain disulfide bonds of the IgG4 subclass can be described as being at equilibrium with the intra-chain disulfide bonds. This means that a fraction of IgG4 has noncovalently linked heavy chains (half-antibody). The percentage of half-antibodies produced depends upon the expression system used. Nondenaturing assays fail to separate the half-antibodies from the native form because two half-molecules are held together by noncovalent forces. The pharmaceutical industry needs a reliable denaturing assay for checking batch-to-batch consistency. Until now sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) has been the standard method used to detect the presence of half-antibodies. However, this technique is laborious and cannot be automated. Furthermore, cumbersome densitometric measurements are necessary for quantification. To overcome these disadvantages a chip-based gel electrophoresis method was investigated. In the nonreduced format the separation profile is compared with that from SDS-PAGE. The limit of quantification as a percentage of the amount applied, repeatability, reproducibility, and linearity are compared with those of SDS-PAGE. The amounts of half-antibody and of by- and degradation products were determined for several batches by using area percentage and by external calibration with IgG4 as a reference standard. Both methods allow avoidance of error introduction for the quantification as is the case by application of myosin as reference concentration. Both sets of results are compared with each other and with the results from SDS-PAGE. In the reduced format it is noted that the reduction of the inter-heavy-chain disulfide bridges proceeds faster than the reduction of the heavy-light-chain bonds. Therefore optimized conditions are necessary to obtain a complete reduction.     

Mutagenicity assay for nitroarenes of air pollutants held in leaves of woody plants.

A new method was developed for the detection of mutagenic nitroarenes held in the leaves of woody plants using a small amount of leaves. This method consists of extraction of mutagen from fresh leaves (15-30 g) by ultrasonication with ethyl acetate and purification by elution with benzene on a silica gel column to remove such inhibitory components for mutagenesis as chlorophyll. The mutation assay uses the new Salmonella typhimurium strains YG1021 (a nitroreductase-overproducing strain of TA98) and YG1024 (an O-acetyltransferase-overproducing strain of TA98), which are very sensitive to some nitroarenes in the absence of S9, and standard strain YG1020 (TA98 containing pBR322-Aps) for comparison. This method was applied to woody plants growing on various sites in the Tokyo metropolitan area and the suburbs. It was shown that the leaves of all woody plants tested contained different amounts of mutagens, probably mutagenic nitroarenes, depending upon their growing sites.     

Predicting long bone loading from cross-sectional geometry

Long bone loading histories are commonly evaluated using a beam model by calculating cross-sectional second moments of areas (SMAs). Without in vivo strain data, SMA analyses commonly make two explicit or implicit assumptions. First, while it has long been known that axial compression superimposed on bending shifts neutral axes away from cross-sectional area centroids, most analyses assume that cross-sectional properties calculated through the area centroid approximate cross-sectional strength. Second, the orientation of maximum bending rigidity is often assumed to reflect the orientation of peak or habitual bending forces the bone experiences. These assumptions are tested in sheep in which rosette strain gauges mounted at three locations around the tibia and metatarsal midshafts measured in vivo strains during treadmill running at 1.5 m/sec. Calculated normal strain distributions confirm that the neutral axis of bending does not run through the midshaft centroid. In these animals, orientations of the principal centroidal axes around which maximum SMAs (Imax) are calculated are not in the same planes in which the bones experienced bending. Cross-sectional properties calculated using centroidal axes have substantial differences in magnitude (up to 55%) but high correlations in pattern compared to cross-sectional properties calculated around experimentally determined neutral axes. Thus interindividual comparisons of cross-sectional properties calculated from centroidal axes may be useful in terms of pattern, but are subject to high errors in terms of absolute values. In addition, cross-sectional properties do not necessarily provide reliable data on the orientations of loads to which bones are subjected.     

Architectural and histochemical diversity within the quadriceps femoris of the brown lemur (Lemur fulvus)

Physiologically related features of muscle morphology are considered with regard to functional adaptation for locomotor and postural behavior in the brown lemur (Lemur fulvus). Reduced physiological cross-sectional area, estimated maximum excursion of the tendon of insertion, length of tendon per muscle fasciculus, and areal fiber type composition were examined in the quadriceps femoris in order to assess the extent of a "division of labor" among four apparent synergists. Each of these four muscles in this prosimian primate displays a distinguishing constellation of morphological features that implies functional specialization during posture and normal locomotion (walk/run, galloping, leaping). Vastus medialis is best suited for rapid whole muscle recruitment and may be reserved for relatively vigorous activities such as galloping and leaping (e.g., small cross-sectional area per mass, long excursion, predominance of fast-low oxidative fibers, relatively little tendon per fasciculus). In theory, rectus femoris could be employed isometrically in order to store elastic strain energy during all phasic activities (e.g., large cross-sectional area per mass, short excursion, predominance of fast-high oxidative fibers, large amount of tendon per fasciculus). Vastus intermedius exhibits an overall morphology indicative of a typical postural muscle (e.g., substantial cross-sectional area, short excursion, predominance of slow-high oxidative fibers, large amount of tendon per fasciculus). The construction of vastus lateralis reflects an adaptation for high force, relatively high velocity, and resistance to fatigue (e.g., large cross-sectional area, long excursion, most heterogeneous distribution of fiber types, large amount of tendon per fasciculus); this muscle is probably the primary contributor to a wide range of locomotor behaviors in lemurs. Marked dramatic architectural disparity among the four bellies, coupled with relative overall fiber type heterogeneity, suggests the potential for exceptional flexibility in muscle recruitment within this mass. One interpretation of this relatively complex neuromuscular organization in the brown lemur is that it represents an adaptation for the exploitation of a three-dimensional arboreal environment by rapid quadrupedalism and leaping among irregular and spatially disordered substrates.     

Characterization and purification of a new bacteriocin with a broad inhibitory spectrum produced by Lactobacillus plantarum lp 31 strain isolated from dry-fermented sausage

Aims:  Characterization and purification of a new bacteriocin produced by Lactobacillus plantarum LP 31 strain, isolated from Argentinian dry-fermented sausage.
Methods and Results:  Lactobacillus plantarum LP 31 strain produces an antimicrobial compound that inhibits the growth of food-borne pathogenic bacteria. It was inactivated by proteolytic enzymes, was stable to heat and catalase and exhibited maximum activity in the pH range from 5·0 to 6·0. Consequently, it was characterized as a bacteriocin. It was purified by RP (reverse-phase) solid-phase extraction, gel filtration chromatography and RP-HPLC. Plantaricin produced by Lact. plantarum LP 31 is a peptide with a molecular weight of 1558·85 Da as determined by Maldi-Tof mass spectrometry and contains 14 amino acid residues. It was shown to have a bactericidal effect against Pseudomonas sp., Staphylococcus aureus , Bacillus cereus and Listeria monocytogenes.
Conclusions:  The bacteriocin produced by Lact. plantarum LP 31 may be considered as a new plantaricin according to its low molecular weight and particular amino acid composition.
Significance and Impact of the Study:  In view of the interesting inhibitory spectrum of this bacteriocin and because of its good technological properties (resistance to heat and activity at acidic pH), this bacteriocin has potential applications as a biopreservative to prevent the growth of food-borne pathogens and food spoilage bacteria in certain food products.     

Purification and characterization of an antimicrobial peptide produced by <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain 4B

An antimicrobial peptide produced by a bacterium isolated from the effluent pond of a bovine abattoir was purified and characterized. The strain was characterized by biochemical profiling and 16S rDNA sequencing as Pseudomonas sp. The antimicrobial peptide was purified by ammonium sulfate precipitation, gel filtration, and ion exchange chromatography. Direct activity on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was observed. A major band on SDS-PAGE suggested that the antimicrobial peptide has a molecular mass of about 30 kDa. The substance was inhibitory to a broad range of indicator strains, including pathogenic and food spoilage bacteria such as Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, among other. The partially purified antimicrobial substance remained active over a wide temperature range and was resistant to all proteases tested. This substance showed different properties than other antimicrobials from Pseudomonas species, suggesting a novel antimicrobial peptide was characterized.