ON STEREOTROPISM IN TENEBRIO LARV?

Larvæ of Tenebrio while creeping show homostrophic responses, and stereotropic orientation to lateral contacts. Homostrophic orientation is inhibited by stereotropism. Both depend upon the anterior portion of the central nervous system. Stereotropic orientation due to unilateral contact, particularly at the anterior end, persists briefly after the cessation of the contact. Equal posterior bilateral contact of the body obliterates stereotropic bending. Unequal posterior bilateral contacts lead to orientation through an angle roughly proportional to the differences in contact areas. Functional symmetry in such responses is not disturbed by asymmetrical distribution of the body "hairs." The stereotropic orientation undergoes reversal of direction, central in origin, when the stimulation is sufficiently intense. Stereotropic response, leading to maintained lateral contact with a surface or to bending when the end of such a surface has been passed, is inhibited by a definite intensity of light. These findings (1) round out the demonstration that stereotropism is truly of a tropistic character, and (2) make possible the understanding of conduct in a case involving the participation of contact stimulation, phototropism, temperature, and homostrophy.     

THE STEREOTROPISM OF THE DOGFISH (MUSTELUS CALIFORNICUS) AND ITS REVERSAL THROUGH CHANGE OF INTENSITY OF THE STIMULUS

1. The dogfish responds to certain contact stimuli by definite stereotropic reactions. These reactions can be positive or negative. 2. The sense of the stereotropic response depends on the strength of the stimulus; a "weak" stimulus, produces a positive and a "strong" stimulus, a negative response. 3. The strength of stimulus necessary to cause a reversal of the reaction depends in part on the physiological state of the animal. 4. The stereotropic reactions occur equally well in the absence of the forebrain.     

HOMOSTROPHIC REFLEX AND STEREOTROPISM IN DIPLOPODS

1. With suitable arthropods, such as the diplopods, it can be shown that body orientation following passive unilateral tension involves the homostrophic reflex. The phenomenon is exhibited when the animal is quiescent and during forward locomotion, but nothing of the sort appears in backward locomotion. 2. Receptors for the homostrophic reflex are in the body wall and are distributed throughout the length of the animal. 3. The effector nerves take their origin from the ganglia of the head alone. 4. The diplopods are stereotropic, the head turning toward the side in contact with a solid surface only as long as some part of the body maintains contact. Under suitable conditions stereotropism may mask the homostrophic reflex. 5. When a diplopod is in contact with two lateral surfaces of equal extent the path upon emergence is a straight one, conforming to the law of the parallelogram of forces.     

Emergence of layer IV barrel cytoarchitecture is delayed in somatosensory cortex of GAP-43 deficient mice following delayed development of dendritic asymmetry

The emergence of barrel cytoarchitecture in mouse somatosensory cortex is extremely well defined. However, mechanisms underlying the development of this cellular organization are not completely understood. While it is generally accepted that hollows emerge via passive displacement of cortical cells by dense thalamocortical afferent clusters in barrel centers, it is not known what causes cellular segregation of barrel sides and septa. Here, we hypothesized that the emergence of sides and septa is related to the progressive asymmetry of dendrites from the cells of the barrel side toward the barrel hollow during development. We tested this hypothesis in the barrel cortex of growth-associated protein-43 heterozygous mice (GAP43 (+/?) mice) that display a 2-day delay in retraction of septally oriented dendrites compared to (+/+) littermates. We predicted that this delayed retraction would result in a subsequent 2-day delay in the emergence of barrel sides and septa. Using cresyl violet staining of barrel cortex, we found that initial emergence of hollows was not different between GAP43 (+/?) mice and (+/+) littermate controls. However, the emergence of sides and septa was delayed by 2 days, supporting our hypothesis that the emergence of barrel sides and septa is related to, and perhaps reliant upon, the developmental step of dendritic orientation toward barrel hollows. This process, which is mechanistically distinct from the emergence of barrel hollows, is likely due to both active and passive events resulting from asymmetric cell orientation.     

Cell contacts orient some cell division axes in the Caenorhabditis elegans embryo

Cells of the early Caenorhabditis elegans embryo divide in an invariant pattern. Here I show that the division axes of some early cells (EMS and E) are controlled by specific cell-cell contacts (EMS-P2 or E-P3 contact). Altering the orientation of contact between these cells alters the axis along which the mitotic spindle is established, and hence the orientation of cell division. Contact-dependent mitotic spindle orientation appears to work by establishing a site of the type described by Hyman and White (1987. J. Cell Biol. 105:2123-2135) in the cortex of the responding cell: one centrosome moves toward the site of cell-cell contact during centrosome rotation in both intact embryos and reoriented cell pairs. The effect is especially apparent when two donor cells are placed on one side of the responding cell: both centrosomes are "captured," pulling the nucleus to one side of the cell. No centrosome rotation occurs in the absence of cell-cell contact, nor in nocodazole-treated cell pairs. The results suggest that some of the cortical sites described by Hyman and White are established cell autonomously (in P1, P2, and P3), and some are established by cell-cell contact (in EMS and E). Additional evidence presented here suggests that in the EMS cell, contact-dependent spindle orientation ensures a cleavage plane that will partition developmental information, received by induction, to one of EMS's daughter cells.     

Thermal and physiological responses of rats exposed to 2.45-GHz radiofrequency radiation: A comparison of E and H orientation

Summary Ketamine-anesthetized Sprague-Dawley rats were exposed in both E and H orientations to far-field 2.45-GHz continuous-wave radiofrequency radiation (RFR) at a power density of 60 mW/cm² (whole-body average specific absorption rate of 14 W/kg). Intermittent exposures were performed in both orientations in the same animal to repeatedly increase colonic temperature from 38.5 to 39.5° C. Tympanic, subcutaneous (sides toward and away from RFR source), and colonic temperature, ECG, arterial blood pressure, and respiratory rate were continuously recorded. The pattern of heat distribution within the animal and the physiological responses were significantly different between E-and H-orientation exposure. Irradiation in E orientation resulted in greater peripheral and tympanic heating, while irradiation in H orientation resulted in greater core heating. Heart rate and blood pressure increased significantly during irradiation and returned to baseline levels when exposure was discontinued; the increases were significantly greater in E than in H orientation. Respiratory rate increased significantly during irradiation in H, but not in E orientation. The physiological responses could have been influenced by the different levels or rates of subcutaneous and tympanic heating, or the differential between core and peripheral heating during E- and H-orientation irradiation. These results suggest that, when interpreting results of RFR exposure, animal orientation during irradiation must be considered.     

Structure of the epithelial - mesenchymal interface during early morphogenesis of the chick duodenum.

During the period of early morphogenetic folding of the intestinal epithelium, changes in the epithelial-mesenchymal interface were observed by light microscopy, scanning and transmission electron microscopy. The epithelium in cross-section, appears first as a circle, then an ellipse and finally by a triangle prior to the formation of the first three previllous ridges. The bases of all epithelial cells are flat at the circular stage. At the ellipse and triangle stages the bases of the epithelial cells occupying the sides possess lobopodia that do not penetrate the basal lamina. The immediate mesenchymal cells subjacent to those epithelial cells on the sides of the ellipse and triangle alter their orientation to being rounded-up or perpendicular to the plane of the basal lamina. Large numbers of fine mesenchymal pseudopodia in addition to many extracellular fibrils are revealed by transmission and scanning electron microscopy at the epithelial-mesenchymal interface. The fine mesenchymal pseudopodia come into close contact but do not penetrate the ruthenium red-staining basal lamina. The possible roles of close contact between epithelium and mesenchyme, the alteration in orientation of mesenchyme cells, and of the basal lamina in tissue interaction are discussed.     

Object orientation in two dimensional grasp with friction towards minimization of gripping power

This article reports an analysis of two dimensional grasp where a convex rigid object is grasped by two contact points with friction. The purpose is to find the object orientation that minimizes the norm of the contact force vector, each element of which is composed from the normal force and friction force at each contact point. The formulation of this problem requires some equality or inequality conditions. In the analysis, the solution of the equality conditions is parameterized at first. Based on the fact that the norm of the contact force vector becomes monotonic increasing function of this parameter, the minimal parameter values are calculated by means of the piecewise analysis. Using the relation between the friction coefficient and the apex angle of the friction cone effectively, the following result is obtained: the norm of the contact force, i.e, gripping power becomes locally minimal at the object orientation where the intersection point of the upper sides of two friction cones is located in opposite direction of the gravity from the center of mass of the grasped object.     

Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower

Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration.     

Evaluation of environmental and plant-associated cues for nymphal settling preference by Trioza eugeniae

Experiments were conducted to determine potential cues used by nymphs when they select the preferred abaxial side of a leaf. Nymphs most frequently settle and develop on the abaxial side of leaves. The degree of preference for the abaxial side was found to be reduced when a high density of nymphs were present, however. The orientation of leaves in a completely darkened chamber did not influence settling preference for the abaxial side, even when leaves were oriented abaxial side up. Coating both sides of a leaf with an antitranspirant compound did not prevent nymphs from preferring the abaxial side for settling. Similar results were obtained when leaves were dipped in pentane. These studies show that nymphs do not use gravity, color, light, or contact chemoreception when selecting suitable settling sites on a leaf.     

THE NERVOUS MECHANISM OF COORDINATION IN THE CRINOID,ANTEDON ROSACEUS

1. Stimulation causes Antedon to swim by means of alternate oral bending and dorsal stroke of the arms. Two arms of a given ray move alternately so that while one is executing the aboral stroke its mate is flexing ventrally. This implies reciprocal inhibition. 2. Recriprocal inhibition between the two arms of an isolated ray can be abolished by the use of either strychnine or nicotine. 3. Coordination between the rays is referable to the conducting properties of the nervous pentagon which connects the five rays. In this system an impulse loses in effectiveness as it passes from the point of origin. 4. When Antedon is made to rest oral face down on the floor of an aquarium, oral flexion of all the rays, swimming movements, and righting result. Antedon is therefore negatively stereotropic with reference to its ventral side. 5. Excitation of the dorsal cirri results in aboral bending of all the rays. Stimulation of the cirri inhibits ventral flexion to the extent of preventing righting movements while on the other hand stimulation of the ventral surface inhibits the grasp reflex of the cirri. Thus oral and aboral sides of Antedon exhibit dynamic symmetry although structurally dissimilar.     

The axis of orientation of the synlophe in the Heligmosomoidea (Nematoda, Trichostrongylina): a new approach

The definition of the axis of orientation of the synlophe is modified for the Heligmosomoidea so that one or two axes may be recognized. When two axes are present, their inclinations to the sagittal axis are different on the right and left sides, and we propose to name them right axis and left axis, respectively. During the course of evolution, starting from a single oblique axis (plesiomorphic state), an independent rotation of this axis on the right and left sides may bring about a double-axis state with a different inclination on both sides (derived state). When the rotation reaches 90 degrees for both sides, the axis becomes simple once again and is superimposed to the frontal axis (most derived state).     

A three-dimensional anatomical model of the human patello-femoral joint,for the determination of patello-femoral motions and contact characteristics

The object of this study is to develop a three-dimensional mathematical model of the patello-femoral joint, which is modelled as two rigid bodies representing a moving patella and a fixed femur. Two-point contact was assumed between the femur and patella at the medial and lateral sides and in the analysis, the femoral and patellar articular surfaces were mathematically represented using Coons' bicubic surface patches. Model equations include six equilibrium equations and eleven constraints: six contact conditions, four geometric compatibility conditions, and the condition of a rigid patellar ligament; the model required the solution of a system of 17 nonlinear equations in 17 unknowns, its response describing the six-degress-of-freedom patellar motions and the forces acting on the patella. Patellar motions are described by six motion parameters representing the translations and rotations of the patella with respect to the femur. The forces acting on the patella include the medial and lateral component of patello-femoral contact and the patellar ligament force, all of which were represented as ratios to the quadriceps tendon force. The model response also includes the locations of the medial and lateral contact points on the femur and the patella. A graphical display of its response was produced in order to visualize better the motion of the components of the extensor mechanism.Model calculations show good agreement with experimental results available from the literature. The patella was found to move distally and posteriorly on the femoral condyles as the knee was flexed from full extension. Results indicate that the relative orientation of the patellar ligament with respect to the patella remains unchanged during this motion. The model also predicts a patellar flexion which always lagged knee flexion.Our calculations show that as the angle of knee flexion increased, the lateral contact point moved distally on the femur without moving significantly either medially or laterally. The medial contact point also moved distally on the femur but moved medially from full extension to about 40° of knee flexion, then laterally as the knee flexion angle increased. The lateral contact point on the patella did not change significantly in the medial and lateral direction as the knee was flexed; however, this point moved proximally toward the basis of the patella with knee flexion. The medial contact point also moved proximally on the patella with knee flexion, and in a similar manner the medial contact point on the patella moved distally with flexion from full extension to about 40° of flexion. However, as the angle of flexion increased, the medial contact point did not move significantly in the medial-lateral direction.Model calculations also show that during the simulated knee extension exercise, the ratio of the force in the patellar ligament to the force in the quadriceps tendon remains almost unchanged for the first 30° of knee flexion, then decreases as the angle of knee flexion increases. Furthermore, model results show that the lateral component of the patello-femoral contact force is always greater than the medial component, both components increasing with knee flexion.     

A model for the interplay of receptor recycling and receptor-mediated contact in T cells

Orientation of organelles inside T cells (TC) toward antigen-presenting cells (APC) ensures that the immune response is properly directed, but the orientation mechanisms remain largely unknown. Structural dynamics of TC are coupled to dynamics of T-cell receptor (TCR), which recognizes antigen on the APC surface. Engagement of the TCR triggers its internalization followed by delayed polarized recycling to the plasma membrane through the submembrane recycling compartment (RC), which organelle shares intracellular location with the TC effector apparatus. TCR engagement also triggers TC-APC interface expansion enabling further receptor engagement. To analyze the interplay of the cell-cell contact and receptor dynamics, we constructed a new numerical model. The new model displays the experimentally observed selective stabilization of the contact initiated next to the RC, and only transient formation of contact diametrically opposed to the RC. In the general case wherein the TC-APC contact is initiated in an arbitrary orientation to the RC, the modeling predicts that the contact dynamics and receptor recycling can interact, resulting effectively in migration of the contact to the TC surface domain adjacent to the submembrane RC. Using three-dimensional live-cell confocal microscopy, we obtain data consistent with this unexpected behavior. We conclude that a TC can stabilize its contact with an APC by aligning it with the polarized intracellular traffic of TCR. The results also suggest that the orientation of TC organelles, such as the RC and the effector apparatus, toward the APC can be achieved without any intracellular translocation of the organelles.     

Qualitative determination of superoxide release at both sides of the mitochondrial inner membrane by capillary electrophoretic analysis of the oxidation products of triphenylphosphonium hydroethidine

Superoxide is released asymmetrically to both sides of the mitochondrial inner membrane. Because this membrane is impermeable to superoxide, two separate pools are formed at either side of the membrane, each with its own characteristics and potential biological effects. Here, we report an attomole-sensitive fast capillary electrophoretic method that can analyze superoxide in a single pool, either the matrix pool or that outside the mitochondria. The method uses triphenylphosphonium hydroethidine, which reacts with the superoxide in both pools. Centrifugation is used to separate the mitochondria (i.e., matrix contents) from the supernatant (i.e., products released outside the mitochondria). Each fraction is then analyzed by capillary electrophoresis with laser-induced fluorescence detection that separates and detects hydroxytriphenylphosphonium ethidium (OH-TPP-E⁺), the fluorescent superoxide-specific product. The separation takes < 3 min and the detection level is down to 3 amol OH-TPP-E⁺. The method has proved to be effective at detecting superoxide release qualitatively in the mitochondria of 143B cells, mouse liver, and rat skeletal muscle, in both the presence and the absence of inhibitors. In addition, this study confirmed that complex I releases superoxide only toward the matrix, whereas complex III releases superoxide toward both sides of the mitochondrial inner membrane. Furthermore, treatment with menadione induces superoxide release toward both sides of the mitochondrial inner membrane.     

The Function of Click Call Emission in Capybaras (Hydrochoerus hydrochaeris)

Contact calls are used to promote cohesion among individuals that live in social groups. Capybaras are very gregarious and often vocalize. This species emits a vocalization known as a click, which has been observed during aggregating and foraging behaviors, suggesting contact or monitoring call function. We carried out a playback experiment to evaluate behavioral responses to the capybara's click call and to a bird call, used as control in ten capybaras. We compared animals' latency to respond to stimuli, the time spent in behavioral patterns, alertness, head orientation toward the sound source, and approach to the sound source. All capybaras responded to the emission of the click call playback. Most of them assumed an alert position, showed head orientation toward the sound source, and approached the sound source. They promptly reacted to the first click call emission, while few reacted to the first bird call emission, used as control. All subjects showed behavioral changes after the second emission of the click call, and some responded to the third emission. Just three individuals answered after the first control emission, while none of them responded to the second and third emission of the playback. Therefore, click call playback promotes prompt behavioral changes in capybaras, including approach to the sound source. These results indicate that this vocalization functions as a contact or monitoring call in the species.     

Have attitudes toward homosexuals been shaped by natural selection?

In a series of four surveys administered either to college students or adults, reactions toward homosexuals were found to vary as a function of (1) the homosexual's likelihood of having contact with children and (2) the reproductive status (either real or imagined) of the respondent. These results are consistent with the hypothesis advanced by Gallup and Suarez (1983) that because parents have a reproductive interest in the sexual orientation of their offspring, reactions to homosexuals might be expected to vary as a function of their likelihood of having contact with children. The strong form of this hypothesis holds that the expression of homophobia should be context specific and that most people (including homosexuals) should exhibit homophobic reactions under certain conditions.     

Visual and olfactory cues for mate orientation behaviour in male white-spotted longicorn beetle, Anoplophora malasiaca

Olfactory and visual cues were shown to mediate short‐distance orientation in Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae). In a laboratory test, more than 80% (n = 42) of males walked straight upward when presented with an untreated surface with a 75° slope. When a freshly killed female was fixed at a short distance (10 cm ahead and 5 cm to left/right) from the starting point, 50% of males (n = 30) were oriented toward the female before direct contact. Similar behavioural responses were observed when female extract was directly applied to the slope or to a glass rod model fixed on the slope. When black, white, and transparent coloured rods with the extract were presented, the orientation response was significantly greater for black than to white and transparent rods, to which only a negligible response was observed.