The effect of eye movement on the control of arm movement to a target

Abstract

The purpose of this study was to investigate the effect of eye movement on the control of arm movement to a target. Healthy humans flexed the elbow to a stationary target in response to a start tone. Simultaneously, the subject moved the eyes to the target (saccade eye movement), visually tracked a laser point moving with the arm (smooth pursuit eye movement), or gazed at a stationary start point at the midline of the horizontal visual angle (non-eye movement—NEM). Arm movement onset was delayed when saccade eye movement accompanied it. The onset of an electromyographic burst in the biceps muscle and the onset of saccade eye movement were almost simultaneous when both the arm and the eyes moved to the target. Arm movement duration during smooth pursuit eye movement was significantly longer than that during saccade eye movement or NEM. In spite of these findings, amplitudes of motor-evoked potential in the biceps and triceps brachii muscles were not significantly different among the eye movement conditions. These findings indicate that eye movement certainly affects the temporal control of arm movement, but may not affect corticospinal excitability in the arm muscles during arm movement.     

Investigation of saccadic eye movement effects on the fluid dynamic in the anterior chamber

The aqueous humor (AH) flow in the anterior chamber (AC) due to saccadic movements is investigated in this research. The continuity, Navier-Stokes and energy equations in 3D and unsteady forms are solved numerically and the saccadic motion was modeled by the dynamic mesh technique. Firstly, the numerical model was validated for the saccadic movement of a spherical cavity with analytic solutions and experimental data where excellent agreement was observed. Then, two types of periodic and realistic saccadic motions of the AC are simulated, whereby the flow field is computed for various saccade amplitudes and the results are reported for different times. The results show that the acting shear stress on the corneal endothelial cells from AH due to saccadic movements is much higher than that due to normal AH flow by buoyancy induced due to temperature gradient. This shear stress is higher on the central region of the cornea. The results also depict that eye saccade imposes a 3D complicated flow field in the AC consist of various vortex structures. Finally, the enchantment of heat transfer in the AC by AH mixing as a result of saccadic motion is investigated.     

Intracellular segregation of asialoglycoproteins and their receptor: a prelysosomal event subsequent to dissociation of the ligand-receptor complex

Rat hepatocytes in monolayer culture rapidly internalized asialoglycoproteins and the receptors to which they are bound. Subsequent to endocytosis, the receptor-ligand complex is dissociated within an acidic endosome (Harford, J., K. Bridges, G. Ashwell, and R. D. Klausner, 1983, J. Biol. Chem. 258:3191-3197; Harford, J., A. W. Wolkoff, G. Ashwell, and R. D. Klausner, 1983, J. Cell Biol. 96:1824- 1828). Here we show that addition of the proton ionophore monensin to the cells after dissociation has occurred results in intracellular rebinding of ligand molecules. With increasing time inside the cell, the ability of ligand to reassociate with receptor progressively decreases consistent with a segregation of receptor and ligand. The combination of colchicine and cytochalasin B appears to retard the process of segregation. In contrast, removal of sodium from the medium, while inhibiting degradation of ligand, does not affect the decrease in monensin-mediated rebinding. Nonetheless, both sodium deprivation and treatment with colchicine plus cytochalasin B result in the ligand remaining in a low density, nonlysosomal subcellular fraction. Thus, segregation, like dissociation, appears to occur in a pre-lysosomal endocytic compartment. Perturbation of the endocytic pathway by reduced temperature (18 degrees C) was also explored. Our data are consistent with two temperature-sensitive steps: receptor-ligand dissociation is inhibited and there is an independent temperature-sensitive step involved in delivery of ligand to lysosomes. This second effect was localized as being beyond the point in the pathway sensitive to sodium deprivation.     

Ciliary membrane tubulin and associated proteins: a complex stable to Triton X-114 dissociation

When either membranes from scallop gill cilia or reconstituted membranes from the same source are solubilized with Triton X-114 and the detergent is condensed by warming, no significant fraction of any major membrane protein partitions into the micellar detergent. Rather, most of the membrane lipids condense with the detergent phase, forming mixed micelles from which nearly pure lipid vesicles may be produced by adsorption of detergent with polystyrene beads. One minor membrane protein, with a molecular weight of about 20000, is associated consistently with these vesicles. The aqueous phase contains a fairly homogeneous protein-Triton X-114 micelle sedimenting at 2.6 S in the analytical ultracentrifuge. Sucrose gradient velocity analysis in a detergent-free gradient indicates moderate size polydispersity but constant polypeptide composition throughout the sedimenting protein zone. Sucrose gradient equilibrium analysis (also in a detergent-free gradient) results in a protein-detergent complex banding at a density of 1.245 g/cm³. Sedimentation of the protein-detergent complex in the ultracentrifuge, followed by fixation and normal processing for electron microscopy, reveals a fine, reticular material consisting of 5–10-nm granules. These data are consistent with previous evidence that membrane tubulin and most other membrane proteins exist together as a discrete lipid-protein complex in molluscan gill ciliary membranes.     

Ciliary membrane tubulin and associated proteins: a complex stable to Triton X-114 dissociation

When either membranes from scallop gill cilia or reconstituted membranes from the same source are solubilized with Triton X-114 and the detergent is condensed by warming, no significant fraction of any major membrane protein partitions into the micellar detergent. Rather, most of the membrane lipids condense with the detergent phase, forming mixed micelles from which nearly pure lipid vesicles may be produced by adsorption of detergent with polystyrene beads. One minor membrane protein, with a molecular weight of about 20 000, is associated consistently with these vesicles. The aqueous phase contains a fairly homogeneous protein-Triton X-114 micelle sedimenting at 2.6 S in the analytical ultracentrifuge. Sucrose gradient velocity analysis in a detergent-free gradient indicates moderate size polydispersity but constant polypeptide composition throughout the sedimenting protein zone. Sucrose gradient equilibrium analysis (also in a detergent-free gradient) results in a protein-detergent complex banding at a density of 1.245 g/cm3. Sedimentation of the protein-detergent complex in the ultracentrifuge, followed by fixation and normal processing for electron microscopy, reveals a fine, reticular material consisting of 5-10-nm granules. These data are consistent with previous evidence that membrane tubulin and most other membrane proteins exist together as a discrete lipid-protein complex in molluscan gill ciliary membranes.     

Growth of the teleost eye: novel solutions to complex constraints

Synopsis The cichlid fish, Haplochromis burtoni, is highly dependent on vision for survival in its natural habitat. As is true of most teleost fishes, the eyes continue to grow throughout life without any obvious changes in visual capability. In H. burtoni, for example, retinal area may increase by 27 × in just 6 months. During growth, there is no obvious change in the visual sensitivity, visual acuity or lens quality which must all be appropriate for the enlarging eye. This requires that during growth competing constraints be met. For example, to maintain visual acuity, the number of ganglion cells per visual angle subtended on the retina must remain the same as must the convergence ratio of the cones onto those ganglion cells. In contrast, to maintain visual sensitivity, the number of rod photoreceptors per unit retinal area must remain the same. These requirements are in conflict since a larger eye may preserve acuity with fewer cells per unit area in a larger retina. In addition, the lens properties must remain the same as the animal increases in size so that the image available is of similar quality throughout life. Experiments have been performed to reveal the adaptations during growth which allow the fish to preserve its image of the world throughout life.     

Looking beyond history: tracing the dispersal of the Malaysian complex of crops to Africa

In his 1959 book, Africa: Its Peoples and Their Culture History, George P. Murdock suggested that a Malaysian complex of crops dispersed to Africa in ancient times across the Indian Ocean along the Sabaean Lane. The Malaysian complex comprised bananas, sugarcane, taro, three yam species, rice, Polynesian arrowroot, breadfruit, coconut, areca palm, and betel leaf. Except for rice, arrowroot, and potentially taro, most of these crops were domesticated in the Island Southeast Asia-New Guinea region, from where they dispersed to Africa. Our reassessment of agronomic, archaeological, classical, genetic, and historical sources shows that we need to go beneath standard historical narratives to recover a much more ancient and complex history of crop introductions to Africa. Despite considerable uncertainty and fragmented research, we were able to conclude that the Malaysian complex of crops did not arrive in Africa as a complete assemblage at one time or along one route. Multiple lines of evidence suggest that these crops arrived in Africa at different times and followed different pathways of introduction to the continent.     

The Chitty effect: a consequence of dynamic energy allocation in a fluctuating environment

An important biological feature of cyclic populations of voles and lemmings is phase-related changes in average body mass, with adults in high-density phases being 20-30% heavier than those in low-density phases of a cycle. This observation, called the "Chitty effect," is considered to be a ubiquitous feature of cyclic populations. It has been argued that understanding the Chitty effect is fundamental to unraveling the enigma of population cycles. However, there exists no agreement among biologists regarding the causes of the Chitty effect. Here, I propose a simple hypothesis to explain the Chitty effect, based on phase-related, dynamic allocation of energy between reproductive and somatic effort. The essence of the hypothesis is that: (1) reproduction is suppressed in animals born or raised in the later part of the increase phase by environmental factors, including social influences; (2) suppression of reproduction limits the amount of energy that is diverted for reproductive effort, and forces a disproportionately greater amount of surplus power (the energy left after the energetic costs of standard and active metabolism are met) to be allocated for somatic effort; (3) the surplus energy, above and beyond what is required for routine biological activities, will allow continuous growth and deposition of additional body mass, which causes an increase in body mass; and (4) animals grow to a larger size as a population enters the peak density phase, causing an increase in the average body mass. The Chitty effect is predicted to be most pronounced at the late increase or peak phase of a population cycle. Possible causes of reproductive suppression include direct or indirect influences of the environmental factors. The Chitty effect may be a consequence, not a cause, of population cycles in small mammals.     

Glycogen-bound type-1 phosphatase: isolation and dissociation of a complex containing undegraded G-subunit

A high molecular mass type-1 phosphatase complex can be isolated from muscle glycogen particles by a fast procedure that preserves the glycogen-binding subunit of phosphatase called G from proteolysis. G can be dissociated from such complex by ion exchange chromatography on FPLC SI column, with recovery of unproteolyzed G completely separated from phosphatase catalytic subunit.     

Organization of a complex movement: fixed and variable components of the cockroach escape behavior

The escape behavior of the cockroach Periplaneta americana was studied by means of high speed filming (250 frames/s) and a computer-graphical analysis of the body and leg movements. The results are as follows: 1. The behavior begins with pure rotation of the body about the posteriorly located cerci, followed by rotation plus forward translation, and finally pure translation (Figs. 1, 2). 2. A consistent inter-leg coordination is used for the entire duration of the turn (Fig. 3A). At the start of the movement, five or all six legs execute their first stance phase (i.e. leg on the ground during locomotion) simultaneously. By the end of the turn the pattern has changed to the alternate 'tripod' coordination characteristic of insect walking. The change-over from all legs working together, to working alternately, occurs by means of a consistent pattern of delays in the stepping of certain legs. 3. The movements made by each leg during its initial stance phase are carried out using consistent movement components in the anterior-posterior (A-P) and the medial-lateral (M-L) axes (Fig. 4A). The movement at a particular joint in each middle leg is found to be diagnostic for the direction of turn. 4. The size and direction of a given leg's M-L movement in its initial stance phase depends on the same leg's prior A-P position (Fig. 5). No such feedback effects were seen among different legs. 5. Animals that are fixed to a slick surface on which they make slipping leg movements show the same inter-leg coordination (Fig. 3B), direction of initial stance movement (Fig. 4B) and dependence of the leg's initial M-L movement on its prior A-P position (Fig. 6), as did free-ranging animals. 6. Cockroaches that are walking at the moment they begin their escape reverse those ongoing leg movements that are contrary to escape movements. 7. These results are discussed in terms of the overall coordination of the complex movements, and in terms of the known properties of the neural circuitry for escape. Possibilities for neurobiological follow-up of certain of the findings presented here are also addressed.     

Purification of serine acetyltransferase,a component of a multienzyme complex,by immunoadsorption and selective dissociation of the complex

An immunoadsorbent column chromatography procedure utilizing antibody to one component of a multienzyme complex has been utilized for purification of the second component of this complex. Rabbit immunoglobulin G (IgG) specific for the O-acetylserine sulfhydrylase component of the multienzyme complex cysteine synthetase was linked to Sepharose 4B resin. A crude preparation of cysteine synthetase was bound to a column of IgG-Sepharose, other proteins were removed by washing, and the serine acetyltransferase component of the complex was eluted with 50 mmO-acetylserine, which dissociates the complex of the two enzymes. This purification step produces about a 400-fold increase in specific activity.     

The influence of natural cycles on coral reef fish movement: implications for underwater visual census (UVC) surveys

Movement patterns of some coral reef fishes change with natural cycles (e.g., tidal, lunar and seasonal), resulting in short-term shifts in fish assemblages. We reviewed the literature on temporal changes in coral reef fish assemblages derived from underwater visual census (UVC) and found that movement was rarely considered in experimental design and analysis or as cause of change in interpretation of the results. Studies of vagile species, large individuals, species forming transient spawning aggregations and studies of fishes in contiguous habitats are most likely to be affected by such movements. Ignoring predictable patterns of movement associated with such natural cycles in survey design and analysis increases “unexplained” variation, making it more difficult to detect longer-term changes in fish assemblages and reducing the effectiveness of UVC as a monitoring tool.     

Sweet potato leaf detection in a natural scene based on faster R-CNN with a visual attention mechanism and DIoU-NMS

Accurate detection of plant leaves is a meaningful and challenging task for developing smart agricultural systems. To improve the performance of detecting plant leaves in natural scenes containing severe occlusion, overlapping, or shape variation, we developed an in situ sweet potato leaf detection method based on a modified Faster R-CNN framework and visual attention mechanism. First, a convolutional block attention module was added to the backbone network to enhance and extract critical features of leaf images by fusing cross-channel information and spatial information. Subsequently, the DIoU-NMS algorithm was adopted to modify the regional proposal network by replacing the original NMS. DIoU-NMS was utilized to reduce missed and incorrect detection in scenes of densely distributed leaves by considering the targets' overlap ratio, distance, and scale. The proposed leaf detection method was tested and evaluated on sweet potato plant images collected in agricultural fields. In the datasets, sweet potato leaves were presented in various sizes and poses, and a large proportion of leaves were occluded or overlapped with each other. The experimental results showed that the proposed leaf detection method outperforms state-of-the-art object detection methods. The mean average precision of the proposed method reached 95.7%, which was 2.9% higher than that of the original Faster R-CNN and 7.0% higher than that of YOLOv5. The proposed method achieved promising performance in detecting dense leaves or occluded leaves and could provide key techniques for applications in smart agriculture and ecological monitoring, such as growth monitoring or plant phenotyping.     

High dissociation rate constant of ferrous-dioxy complex linked to the catalase-like activity in lactoperoxidase

Heme reduction of ferric lactoperoxidase (LPO) into its ferrous form initially leads to the accumulation of the unstable form of LPO-Fe(II), which spontaneously converts to a more stable species, the two of which can be identified by Soret peaks at 440 and 434 nm, respectively. Our data demonstrate that both LPO-Fe(II) species are capable of binding O(2) at a similar rate to generate the ferrous-dioxy complex. Its formation with respect to O(2) was first order and monophasic and with rate constants of k(on) = 3.8 x 10(4) m(-1) s(-1) and k(off) = 11.2 s(-1). The dissociation rate constant for the formation of LPO-Fe(II)-O(2) is relatively high, in contrast to hemoprotein model compounds. This high dissociation rate can be attributed to a combination of effects that include the positive trans effect of the proximal ligand, the heme pocket environment, and the geometry of the Fe-O(2) linkage. Our results have also shown that the decay of the LPO-Fe(II)-O(2) complex occurs by two sequential O(2)-independent steps. The first step involves formation of a short-lived intermediate that can be characterized by its Soret absorption peak at 416 nm and may be attributed to the weakening of the Fe(II)-O(2) linkage with a rate constant of 0.5 s(-1). The second step is spontaneous conversion of this intermediate to generate the native enzyme and presumably superoxide as end products with a rate constant of 0.03 s(-1). A comprehensive kinetic model that links LPO-Fe(II)-O(2) complex formation to the LPO catalase-like activity, combined with the classic catalytic cycle, is presented here.     

Beyond borders: on the influence of the creationist movement on the educational landscape in the USA and Russia

This paper provides a detailed look at how creationism originated in the United States and then explores how this evangelical trend was exported to Russia by American missionaries following the fall of the USSR. The comparison between these two countries is particularly interesting since the rivalry between the US and the USSR during the race to space caused both countries to revamp their science education. Yet, while political interests led both governments to focus on science education, creationist activities were simultaneously focused on diminishing the coverage of evolution in science classrooms. Now, decades following Sputnik’s trip to space, the urgency to strengthen scientific learning has waned, while creationists are still equally focused on removing scientific naturalism in favor of supernatural explanations for the origin of species. This paper thus offers an in-depth look at which groups are currently responsible for promoting creationist activities in the US and in Russia and which groups are working hard to keep supernatural doctrines out of science curriculum.