Magnetic Orientation in Solenopsis sp. Ants

It is known that magnetic fields affect ants behavior. It has been shown that Solenopsis ants are sensitive to magnetic fields but there is no experimental evidence for magnetic orientation. In this paper experiments were done to verify the magnetic orientation of Solenopsis sp. ants. The spontaneous orientation of ants in a circular arena was studied in two different magnetic conditions: in the natural geomagnetic field and under an altered magnetic field, with the horizontal geomagnetic axis shifted in 90?o. Our results show that ants consistently change their orientation direction when the magnetic field was altered. Axial circular statistics analysis showed that, in the absence of other cues, ants orient spontaneously to the horizontal geomagnetic field axis. The present paper shows for the first time magnetic orientation in Solenopsis sp. ants.     

Orientation-dependent recombination hotspot activity in bacteriophage lambda.

Promoters of genetic exchange by the Escherichia coli Rec system, Chi elements, have been analyzed in λ phages carrying bacterial EcoRI restriction fragments. Some fragments confer Chi⁺ phenotype in one orientation and Chi^? in the opposite orientation. The inactivity of Chi in one orientation explains why all active Chi elements in λ manifest a certain recombinational bias of the same sense.When these studies were undertaken, we rather expected to find two classes of Chi, one class which stimulated recombinant formation stronger to its left and one class stimulating recombinant formation more strongly to its right. The failure to find the second class is now understandable by supposing that the orientation of Chi which would have permitted it to act rightward is the orientation in which Chi has no activity at all. Several models are proposed for the orientation dependence of Chi activity.     

A regression-based 3-D shoulder rhythm

In biomechanical modeling of the shoulder, it is important to know the orientation of each bone in the shoulder girdle when estimating the loads on each musculoskeletal element. However, because of the soft tissue overlying the bones, it is difficult to accurately derive the orientation of the clavicle and scapula using surface markers during dynamic movement. The purpose of this study is to develop two regression models which predict the orientation of the clavicle and the scapula. The first regression model uses humerus orientation and individual factors such as age, gender, and anthropometry data as the predictors. The second regression model includes only the humerus orientation as the predictor. Thirty-eight participants performed 118 static postures covering the volume of the right hand reach. The orientation of the thorax, clavicle, scapula and humerus were measured with a motion tracking system. Regression analysis was performed on the Euler angles decomposed from the orientation of each bone from 26 randomly selected participants. The regression models were then validated with the remaining 12 participants. The results indicate that for the first model, the r² of the predicted orientation of the clavicle and the scapula ranged between 0.31 and 0.65, and the RMSE obtained from the validation dataset ranged from 6.92° to 10.39°. For the second model, the r² ranged between 0.19 and 0.57, and the RMSE obtained from the validation dataset ranged from 6.62° and 11.13°. The derived regression-based shoulder rhythm could be useful in future biomechanical modeling of the shoulder.     

Influence of external concentration fluctuations on leukocyte chemotactic orientation

The quantitative dependence of leukocyte chemotactic orientation on imprecision in the measurement of chemoattractant concentrations from thermal fluctuations is analyzed. First, a mathematical model relating orientation to differences in receptor occupancy across cell dimensions is developed. This is then coupled with an extension of Berg and Purcell's analysis (1) of the precision of attractant concentration measurements by means of receptor occupancy. Our results show that thermal fluctuations in external concentrations can limit the accuracy of orientation, unless the measurement noise is reduced by averaging the measurements over a period of time. Comparison of our model predictions to experimental orientation data suggests that leukocytes do overcome this limitation, and allows estimation of the time-averaging period necessary to do so. For the orientation observed in a visual bridge assay by Zigmond (2) using the attractant peptide FNLLP, we estimate that receptor occupancy measurements for spatial comparison across cell dimensions must be averaged for a few minutes. Otherwise, the fluctuations in the attractant concentration near the cell will be too great to allow the observed degree of orientation. Our analysis also suggests that the ratio of signal-to-signal noise does not adequately characterize orientation accuracy. Accurate orientation can, in some situations, occur when this ratio is substantially less than unity; in other situations, a ratio much greater than unity is required for accurate orientation.     

The Association between Cultural Orientation and Drinking Behaviors among University Students in Wuhan,China

Objectives

This study examines the association between cultural orientation and drinking behaviors among university students. Cultural orientation is the measure of how the cultural values of individuals living in their own society are influenced by cultural values introduced from the outside.

Methods

In 2011, a cross-sectional survey collected data from 1279 university students from six universities in central China. Participants used a likert scale to rank a series of statements reflecting cultural values from the previously validated Chinese Cultural Orientation Scale and answered questions about their drinking behaviors and socio-demographic characteristics.

Results

Statistically significant differences in cultural orientation were observed for gender, hometown and type of university attendance. Traditional-oriented students were more likely to be occasional drinkers or nondrinkers, while marginal-oriented students, bicultural-oriented students and western-oriented students were more likely to be regular drinkers. Bicultural orientation (OR = 1.80, P<0.05) and marginal orientation (OR = 1.64, P<0.05) increased the likelihood of the student being regular drinking, compared to students with traditional orientations. Males (OR = 4.40, P<0.05) had a higher likelihood of regular drinking than females, graduate students (OR = 2.59, P<0.05) had a higher likelihood of regular drinking than undergraduates, students from urban areas (OR = 1.79, P<0.05) had a higher likelihood of regular drinking than those from towns/rural areas, and students attending key universities (OR = 0.48, P<0.05) had a lower likelihood of regular drinking than those attending general universities.

Conclusions

Cultural orientation influences drinking behaviors. Traditional cultural orientation was associated with less drinking while western cultural orientation, marginal cultural orientation and bicultural orientation were associated with more drinking. The role of gender, hometown and university attendance is partially moderated through the influence of cultural orientation. The relationship between a traditional cultural orientation and alcohol drinking suggests that traditional Chinese cultural values should be examined for their role in possibly reducing alcohol-related risks through education and policy initiatives.     

Sun-Compass Orientation in Mediterranean Fish Larvae

Mortality is very high during the pelagic larval phase of fishes but the factors that determine recruitment success remain unclear and hard to predict. Because of their bipartite life history, larvae of coastal species have to head back to the shore at the end of their pelagic episode, to settle. These settlement-stage larvae are known to display strong sensory and motile abilities, but most work has been focused on tropical, insular environments and on the influence of coast-related cues on orientation. In this study we quantified the in situ orientation behavior of settlement-stage larvae in a temperate region, with a continuous coast and a dominant along-shore current, and inspected both coast-dependent and independent cues. We tested six species: one Pomacentridae, Chromis chromis, and five Sparidae, Boops boops, Diplodus annularis, Oblada melanura, Spicara smaris and Spondyliosoma cantharus. Over 85% of larvae were highly capable of keeping a bearing, which is comparable to the orientation abilities of tropical species. Sun-related cues influenced the precision of bearing-keeping at individual level. Three species, out of the four tested in sufficient numbers, oriented significantly relative to the sun position. These are the first in situ observations demonstrating the use of a sun compass for orientation by wild-caught settlement-stage larvae. This mechanism has potential for large-scale orientation of fish larvae globally.     

Do Cells Sense Stress or Strain? Measurement of Cellular Orientation Can Provide a Clue

We predict theoretically the steady-state orientation of cells subject to dynamical stresses that vary more quickly than the cell relaxation time. We show that the orientation is a strong function of the Poisson's ratio, ν, of the matrix when cell activity is governed by the matrix strain; if cell activity is governed by the matrix stress, the orientation depends only weakly on ν. These results can be used to differentiate systems in which the strain or the stress determine the setpoint for the mechanosensitivity of cells.     

Mutants affecting vegetative cell orientation in Volvox carteri

The vegetative cells of Volvox are highly oriented with respect to each other and to the spheroid on which they occur. Mutants have been isolated which affect this orientation either directly or indirectly. Mutants affecting flagella (flg), including a temperature-sensitive mutant, demonstrate that flagella must be present during or following embryo inversion for proper cell orientation. Other mutants (eye) which have apparently functional flagella lead to the conclusion that the presence of functional flagella is not sufficient for proper cell orientation. These mutants also demonstrate the necessity of proper cell orientation for the phototactic motion of the spheroid.     

Dynamic mechanical orientation of skeletal myofibers in vitro

Avian embryonic myoblasts respond to a continuously stretching substratum in vitro by fusing into skeletal myofibers which are oriented parallel to the direction of substratum movement. The rate of stretch is critical for optimal orientation to occur. A speed of 0.2 mm per hour gives optimal orientation and rates of stretch faster or slower than this decreases the percentage of oriented fibers. The ratio of the rate of myofiber development to the rate of substratum stretch for optimal in vitro myofiber orientation is comparable to the in vivo ratio of the rate of myofiber development to the rate of bone elongation. Thus, this in vitro system supports the idea that mechanical force may be an important element in morphogenesis of skeletal muscle.     

The transverse orientation of stomata

The orientation of cell walls co-determines development. The orientation of the slits of the stomata can be used for analyzing the factors involved. A comprehensive and annotated list is given of those plant species most of whose stomata are known to be oriented transversely to the long axis of an organ or a main rib. Included are also species showing only a trend toward transverse orientation. Transverse orientation is known from a few mosses, from Bennettitatae, fromAzolla and some other ferns, and from species of about 45 families of spermatophytes. It could be confirmed that succulent species show the trait more often than do other plants. Two thirds of the species listed belong to the Caryophyllales and Santalales, a few only to Asteraceae, but none to Rubiaceae, Cyperaceae, Poaceae, or Orchidaceae. Hence, the incidence of succulent species or of species with some succulent traits within the two orders and the lack of such species among other taxa may account in part for the distribution. On the other hand, many succulent species do not show transverse orientation whereas in, e.g.,Casuarina and Tamaricaceae transverse orientation goes together with non-succulent xeromorphy;Azolla shows no xeromorphy at all. Various factors, separately or together, may be involved. Proposed mechanisms determining the orientation of cell walls have been compiled from literature and are discussed.     

Use of a light-dependent magnetic compass for y-axis orientation in European common frog (Rana temporaria) tadpoles

We provide evidence for the use of a magnetic compass for y-axis orientation (i.e., orientation along the shore-deep water axis) by tadpoles of the European common frog (Rana temporaria). Furthermore, our study provides evidence for a wavelength-dependent effect of light on magnetic compass orientation in amphibians. Tadpoles trained and then tested under full-spectrum light displayed magnetic compass orientation that coincided with the trained shore-deep water axes of their training tanks. Conversely, tadpoles trained under long-wavelength (≥500 nm) light and tested under full-spectrum light, and tadpoles trained under full-spectrum light and tested under long-wavelength (≥500 nm) light, exhibited a 90° shift in magnetic compass orientation relative to the trained y-axis direction. Our results are consistent with earlier studies showing that the observed 90° shift in the direction of magnetic compass orientation under long-wavelength (≥500 nm) light is due to a direct effect of light on the underlying magnetoreception mechanism. These findings also show that wavelength-dependent effects of light do not compromise the function of the magnetic compass under a wide range of natural lighting conditions, presumably due to a large asymmetry in the relatively sensitivity of antagonistic short- and long-wavelength inputs to the light-dependent magnetic compass.     

Orientation mechanisms and sensory organs involved in host location in a dipteran parasitoid larva

The robber fly Mallophora ruficauda is one of the principal pests of apiculture in the Pampas region of Argentina. Larvae are solitary ectoparasitoids of third-instar scarab beetle larvae. Females of M. ruficauda do not lay eggs on or near the hosts, but on tall grasses. After hatching, larvae are dispersed by the wind and drop to the ground, where they dig and search for potential hosts. It is known that second-instar larvae of M. ruficauda exhibit active host-searching behaviour towards their preferred hosts, i.e., third-instar larvae of Cyclocephala signaticollis. Although host-location seems to be mediated by chemical cues, the mechanism of orientation and the sensory organs involved in host location remain unknown. We carried out behavioural experiments in the laboratory to address these questions. We also tested whether the orientation behaviour is exclusively based on the use of chemical cues. We found that larvae of M. ruficauda detect the chemicals with chemosensilla on the maxillary palps. Only one maxillary palp suffices for orientation, but their bilateral ablation abolishes orientation. Besides, an hexane extract of the host body was as attractive as a live host. Our results support that M. ruficauda larvae find their hosts underground by means of chemoklinotaxis.     

Assigning Membrane Binding Geometry of Cytochrome c by Polarized Light Spectroscopy

In this work we demonstrate how polarized light absorption spectroscopy (linear dichroism (LD)) analysis of the peptide ultraviolet-visible spectrum of a membrane-associated protein (cytochrome (cyt) c) allows orientation and structure to be assessed with quite high accuracy in a native membrane environment that can be systematically varied with respect to lipid composition. Cyt c binds strongly to negatively charged lipid bilayers with a distinct orientation in which its α-helical segments are on average parallel to the membrane surface. Further information is provided by the LD of the π-π^∗ transitions of the heme porphyrin and transitions of aromatic residues, mainly a single tryptophan. A good correlation with NMR data was found, and combining NMR structural data with LD angular data allowed the whole protein to be docked to the lipid membrane. When the redox state of cyt c was changed, distinct variations in the LD spectrum of the heme Soret band were seen corresponding to changes in electronic transition energies; however, no significant change in the overall protein orientation or structure was observed. Cyt c is known to interact in a specific manner with the doubly negatively charged lipid cardiolipin, and incorporation of this lipid into the membrane at physiologically relevant levels was indeed found to affect the protein orientation and its α-helical content. The detail in which cyt c binding is described in this study shows the potential of LD spectroscopy using shear-deformed lipid vesicles as a new methodology for exploring membrane protein structure and orientation.     

A method for determining the crystal orientation for any tilt position when using a transmission electron microscope double-tilt specimen holder

A method is described in this short communiction which provides a rapid and precise determination of the crystal specimen orientation in any tilt position when using a doule-tilt holder in the transmission electron microscope (TEM). It is necessary to establish three pairs of tilt angles (α_i, β_i) (i = 1, 2, 3) where three recognized directions of the crystal specimen are aligned to the electron beam direction respectively, in order to determine the crystal specimen orientation for any tilt position in a double-tilt specimen holder. In addition, the tilt position (α, β), where any orientation [ u v w] is aligned to the beam direction, can be determined with the aid of this method.A software system for computer applications of the above method has beed developed.     

Myristoylation Restricts Orientation of the GRASP Domain on Membranes and Promotes Membrane Tethering

The mammalian Golgi reassembly stacking protein (GRASP) proteins are Golgi-localized homotypic membrane tethers that organize Golgi stacks into a long, contiguous ribbon-like structure. It is unknown how GRASPs undergo trans pairing given that cis interactions between the proteins in the plane of the membrane are intrinsically favored. To test the hypothesis that myristoylation of the self-interacting GRASP domain restricts its orientation on the membrane to favor trans pairing, we established an in vitro assay that recapitulates GRASP-dependent membrane tethering and used neutron reflection under similar conditions to determine the orientation of the GRASP domain. In vivo, the membrane association of GRASP proteins is conferred by the simultaneous insertion of an N-terminal myristic acid and binding to a Golgi-associated binding partner. In our assay, the latter contact was replaced using a C-terminal hexa-His moiety, which bound to Ni²⁺-conjugated lipids incorporated into a substrate-supported bilayer lipid membrane. Nonmyristoylated protein lacked a fixed orientation on the membrane and inefficiently tethered liposomes. In contrast, myristoylated GRASP promoted tethering and exhibited a unique membrane complex. Thus, myristoylation restricts the membrane orientation of the GRASP domain favoring interactions in trans for membrane tethering.     

GEOTROPIC ORIENTATION IN ARTHROPODS : III. THE FIDDLER CRAB UCA.

On an inclined surface the fiddler crab Uca pugnax, during sidewise progression, orients upward through an angle θ on the surface. The extent of negatively geotropic orientation (θ) is a rectilinear function of sin α, where α is the inclination of the surface to the horizontal. This equation differs from that describing the geotropic orientation of various other animals. The difference is traced to the fact that from an initial position with the transverse axis of the body horizontal the crab is required to turn upward to an extent such that the vertical line from its center of gravity pierces the inclined surface within the base of support provided by the legs. This leads to the equation sec θ/tan α = const., which is obeyed within the limits of precision of the measurements. This type of control of geotropic orientation represents an extension of the "muscle tension theory," and is in no sense in conflict with this view. The assumptions underlying the analytical expression connecting θ and α are verified by the asymmetry in the orientation of male fiddlers, which is shown to be due to the presence of the enlarged chela and which disappears when the claws are removed.     

A Mathematical Model to Capture Complex Microstructure Orientation on Insect Wings

Microstructures on insect wings can promote directional drop shedding, and the local orientation of these structures is expected to facilitate drop removal. However, microstructures may exhibit very different orientations at different locations on the wing. Using the march fly Penthetria heteroptera, we propose that local orientation of small hairs (microtrichia) reflects a balance of three nonexclusive strategies: (1) preventing water from becoming stuck in intervenous grooves (microtrichia point upslope), (2) shedding water off the wing as readily as possible (microtrichia point towards the nearest edge), and, (3) shedding water away from the body (microtrichia point distally). We present evidence for all three and show that local microtrichial orientation is seldom determined by any one factor. We develop a mathematical model that employs factor-specific weighting values determined via optimization. Our predictions are tested against the orientation of microtrichia randomly sampled from a P. heteroptera specimen. Using the best-fit weighting parameters, the model displays a median residual of 20°; no residual is greater than 46°. The model also reproduces qualitative aspects of microtrichial orientation, such as bifurcation midway between veins and convergence toward peaks. This strong correspondence between modelled and observed orientation supports the role of microtrichia as directional antiwetting devices and highlights the importance of considering both function and wing geometry to explain the organization of natural microstructure arrays.     

ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. X

The inheritance of elements of geotropic performance in lines of rats (A and B) has been investigated by examining the orientation of young offspring produced in matings of F_1(AxB) with A: Previous studies had shown that the three recognizable groups of receptor elements concerned in geotropic orientation in each of these lines appeared to be inherited in such a way that B groups were dominant with respect to A groups, although this was to a minor extent complicated by influences affecting the variation of orientation as well as the exact form of the curve relating orientation angle (θ) to slope of surface. In the backcross F₁ x A, therefore, at least eight different types of curves were to be expected. These are in fact identifiable among the forty-one individuals carefully studied. Their classification is concordant with the behavior of the respective indices of variation of θ, for which an interpretation has been provided. The basic result is, therefore, that the three receptor groups of excitation units are inherited independently, and alternatively as regards the members of a homologous pair, and that rather simple dominance relations obtain between homologous groups from the two races, namely that a B effect is dominant over the homologous A effect. This interpretation has been tested in various ways, and is in principle completely consistent with the results of a similar experiment involving races A and K.     

ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. IX

Adult hybrid rats from the cross of races A x B show a total capacity to vary their geotropic performance which is identical with that of their B parents. The proportionate modifiable variability of geotropic orientation also agrees quantitatively with that for the B parents. These relationships are not disturbed by the action of adrenin, which leads to a distortion of the θ vs. α curve. Young rats of the F ₁ generation show a greater proportion of unmodifiable variation of geotropic orientation. It is pointed out that the present findings support the conclusion that the capacity of rats to exhibit variation of geotropic orientation is limited by their genetically determined composition and that the special condition in the young hybrids may be understood as due to a kind of temporary disharmony of developmental events.