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PubMed1987

Kinetics of red blood cell passage through interendothelial slits into venous sinuses in rat spleen, analyzed by in vivo microscopy.

Sequential photomicrographs of RBCs passing through interendothelial slits (IES) in walls of venous sinuses in rat spleen were obtained by video recording in vivo microscopic views. Kinetics of RBC passage were analyzed by slow-motion playback of recordings. An inverted microscope and oblique lighting from a water-cooled fiber optic light source were key elements in obtaining images of sufficient quality for analysis. The direction of RBC passage through IES was, invariably, from reticular spaces of the red pulp into venous sinuses. RBC flow through an individual IES occurred as brief discontinuous bursts, separated by periods of zero, or near zero, flow. Mean rates of RBC flow through six IES analyzed in normal relaxed spleen ranged from 1.4 to 9.1 cells/15 sec, the total RBCs studied being 1523 and the total combined period of observation 98 min. The maximum instantaneous rate was 10 RBCs/sec. RBC transit times ranged from 0.02 to 60.5 sec, even for a single IES; the distribution was highly skewed: median 0.23 sec, mean 1.7 sec. Analysis of RBC flow through two closely adjacent IES simultaneously, for 30 min, showed that most bursts were asynchronous. The results indicate that changes in caliber of IES are primarily responsible for the observed pattern of flow. It was estimated that only 19% of the total IES present anatomically actually allowed passage of RBCs during any 5-min period.

Animals↗

PubMed1987

The kinetics of drug-membrane interactions in human erythrocytes.

The time course of the shape transformations and vesicle release in human erythrocytes caused by lysophosphatidylcholine and chlorpromazine was monitored using a light microscope-video recording technique. The time required for the erythrocytes to reach a stage I echinocytic shape decreased from 4.0 to 2.0 s, when the concentration of the lysophosphatidylcholine solution injected was increased from 1 to 25 microM. The time required to reach stage II decreased from 8.3 to 3.5 s and that required for vesicle release and the formation of stage IV spherocytes decreased from 78.0 to 11.6 s. Correspondingly, the time needed for the formation of stage I stomatocytes decreased from 2.3 to 1.0 s and that for stage II stomatocytes from 3.1 to 2.0 s, when the ambient chlorpromazine concentration was increased from 50 to 200 microM. The kinetics of the shape transformations of the erythrocytes were dependent on the ambient drug concentration. The rate of shape transformations could be predicted from a formula derived for the kinetics of the incorporation of the detergent into the cell membrane, providing that the affinity coefficient and mass transfer coefficient for drugs changed as a function of the free drug concentration. The results give a time scale for the drug-membrane interactions, i.e., the formation of stages I and II for drug-lipid bilayer interactions and the release of vesicles for drug-cytoskeleton interactions.

Chlorpromazine↗

PubMedDate not supplied

The effects of induced acute hyperglycemia in the cat on the retinal capillary blood flow.

PURPOSE: To study the effect of acute hyperglycemia on the erythrocyte flow in specific retinal capillary paths. METHODS: A technique for fluorescent labeling of a known fraction of the erythrocyte moiety of systemic blood was combined with fluorescence viewing of the retinal capillary network in live cats. This technique was developed to enable visualization of the erythrocyte flow in the retinal capillary network and used to acquire video recording of the retinal capillary erythrocyte flow in normal feline eyes. The pattern of capillary erythrocyte flow under normal blood glucose levels and normal systemic blood pressure served as baseline. Acute hyperglycemia was induced by intravenous injection of glucose while monitoring the systemic blood pressure. Two subsets of functional capillary pathways previously defined as S (simple) and C (complex) were identified in the recorded data. The relationship between erythrocyte flux in random selections of these two pathways and the level of hyperglycemia and systemic blood pressure was determined. RESULTS: Induction of acute hyperglycemia led to acute elevation of the systemic blood pressure that returned to baseline levels within few minutes, while blood glucose remained high. The capillary erythrocyte flux in S paths was significantly higher than in C paths at all values of systemic blood pressure. The capillary erythrocyte flux in the S paths was directly proportional to the systemic blood pressure whereas the flux in C paths was minimally affected by acute hyperglycemia for the systemic blood pressure range between 110 and 160 mm Hg. CONCLUSIONS: The erythrocyte flux in S paths is affected by the changes of the systemic blood pressure and these paths act as 'shunt vessels' when acute elevation of the systemic blood pressure occurs. C paths maintain stable perfusion under changing conditions, most probably in an effort to minimally alter the basic metabolic needs of the retinal tissue. Hyperglycemia per se was not responsible for changes of the cell flux in these capillary paths.

Acute Disease↗

PubMed1997

Monitoring and analysis of occupational exposure to chain saw exhausts.

The extent of inhalation exposure to loggers from two-stroke chain saws was measured and evaluated under various conditions. Carbon monoxide, measured by personal air monitoring and determination of carboxyhemoglobin levels of the loggers, was used as an indicator of exhaust exposure. Video recordings were made to analyze the influence of varying working conditions and the individual handling of the chain saw on the amount of pollutants inhaled. The American Conference of Governmental Industrial Hygienists biological exposure index (BEI) for carboxyhemoglobin (3.5%) was exceeded during logging in heavy timber stands. When workers were paid on a piecework basis, carboxyhemoglobinemia increased to its maximum level in the first 2-3 hours of the shift and then declined. After 8 hours carboxyhemoglobin levels were 20-30% lower compared with the maximum. Increased exhaust inhalation with short-term exposures to carbon monoxide up to 400 ppm was observed in the following conditions: (1) felling operations, (2) other operations performed in a leaning of squatting position, (3) limbing in thick tops of coniferous trees, (4) working at low wind velocity, and (5) working in thick forest stands. Maximum allowable blood concentrations for carboxyhemoglobin are exceeded in chain saw operators in logging operations. Blood sampling at the end of the workday is not always suitable for determining the highest carboxyhemoglobin levels in loggers during the shift. The exposure of chain saw operators to exhaust increases under certain conditions.

Adult↗

PubMedDate not supplied

An assessment of player error as an injury causation factor in international football.

OBJECTIVE: To quantify the frequency of injury in football as a function of tackle parameters. METHOD: Video recordings of 123 international matches in three Federation Internationale de Football Association tournaments were used to analyze tackle parameters, and team physicians provided reports of postmatch medical attention to players. RESULTS: A total of 8572 tackles were assessed, of which 3464 (40.4%) were fouls. There were 299 incidents of on-pitch medical attention, of which 131 (44%) resulted from foul tackles, and 200 postmatch team physicians' reports, of which 96 (48%) resulted from foul tackles. The cases of on-pitch medical attention resulted in 76 (25%) postmatch physicians' reports, but 124 (62%) of the postmatch physicians' reports were not associated with on-pitch medical attention. Tackled players received 74% of the postmatch medical reports. Tackle types with the greatest probability of requiring medical attention were from the side in terms of tackle direction, jumping vertically in terms of tackle mode, and a clash of heads in terms of tackle action. CONCLUSION: Human error on the part of players during the process of tackling and inadequacies in the laws of football and/or their application by match referees were equally responsible for the high levels of injury observed.

Adolescent↗

PubMed1995

[Interobserver concordance of echographic semiology in liver cirrhosis].

OBJECTIVES: The aim of this study was to evaluate the interobserver agreement of cirrhosis symptomatology. METHODS: Eight patients with cirrhosis (without ascites) and 23 patients with chronic liver disease without cirrhosis were included. Four observers (2 juniors and 2 seniors, with 1 specialist and 1 general radiologist in each group) independently evaluated video recordings. Agreement of 18 variables was calculated by using kappa index (k), intraclass correlation coefficient (r) and agreement proportion. Observer bias and poorly trained observers were also investigated. RESULTS: Liver: surface: k = 0.68, homogeneity: k = 0.25, span: r = 0.87, caudate lobe: r = 0.4 to 0.57 according to 3 dimensions, right lobe length: k = 0.33. Veins: portal diameter: r = 0.73, splenic diameter: r = 0.75; umbilical vein: presence: k = 0.19, diameter: r = 0.5; left gastric vein: presence: k = 0, diameter: r = 0.18; spleno-renal shunt: k = 0.41. Spleen length: r = 0.93. Presence of cirrhosis: k = 0.53. The mean agreement for the 18 variables was not significantly different between juniors (0.53 +/- 0.32) and seniors (0.40 +/- 0.38) but was significantly better in specialists (0.61 +/- 0.22) than in general radiologists (0.43 +/- 0.40; P < 0.05). CONCLUSIONS: Interobserver agreement of ultrasonography is good to excellent for the main characteristics of the liver, the main splanchnic veins and spleen but poor to fair for collateral vessels and the caudate lobe. Agreement for diagnosis of cirrhosis is good but should be improved by only selecting reliable signs or experienced echographists.

Adult↗

PubMed1997

The qualitative assessment of general movements in preterm, term and young infants--review of the methodology.

We describe the state of the art of Prechtl's method for the qualitative assessment of general movements as a diagnostic tool for early detection of brain dysfunction. After discussing the optimal technique for video recording general movements in preterm, term and young infants, attention is focused on the proper analysis of this spontaneous motor pattern. Recently, a group of active researchers in the field reached consensus on the various qualities of normal and abnormal general movements. These definitions are reported here in full. Since it is a newly introduced method careful investigation into its reliability is required. Various groups of investigators have obtained data which demonstrate the robust character of the method (interscorer agreement: 78-98%). Finally, we discuss the validity of this early assessment method on the basis of the reports published so far. While the method's sensitivity is similar in all age groups studied (preterm, term, first month, second month, and third month age epochs), and averages 94.5%, the specificity of the method is age-dependent. It is low during the early ages, increases gradually and reaches 82 to 100% at 3 months post-term. This phenomenon is explained by spontaneous recovery of early dysfunction. In contrast, consistent abnormalities of general movements are linked to neurological deficits found at the 2 year follow-up.

Brain Diseases↗

PubMed2005

Odor-modulated orientation in walking male cockroaches Periplaneta americana, and the effects of odor plumes of different structure.

The location of distant resources using odor information usually also requires information on the flow of air (or water) through the environment together with the expression of internally programmed steering responses. The orientation responses of virgin male Periplaneta americana L. to wind and the female sex-pheromone component (-)-periplanone-B were video-recorded in a laboratory wind tunnel and quantified. P. americana males showed no preferred walking orientation when released in zero wind in the absence of pheromone. When introduced into 25 cm s(-1) wind in the absence of pheromone, 79% of males walked downwind. Upon introduction to a plume of (-)-periplanone-B in wind, 100% of males walked upwind in the pheromone plume to the source. Males were then challenged with wind-borne plumes of (-)-periplanone-B of four different temporal/spatial structures. In nearly all cases, the only statistically significant changes in behavioral parameters measured from their walking tracks were observed from males tracking the treatment consisting of the most turbulent plume. The plume-tracking performances of males challenged with the other three less turbulent plumes were visually and quantitatively similar, regardless of the width. Males tracking all four plumes showed evidence of turns resulting from multiple mechanisms. Some of the observed maneuvers were temporally regular counterturns, suggesting steering according to an ongoing internal program, while others could have been triggered by encountering the change in odor concentration between pheromone and clean air at the lateral boundary of the plume or chemotactically upon the detection of changes in odor concentration.

Analysis of Variance↗

PubMed2003

Bimodal locomotion elicited by electrical stimulation of the midbrain in the salamander Notophthalmus viridescens.

The present experiments were designed to identify the mesencephalic locomotor region (MLR) in the salamander. An in vitro semi-intact preparation from a decerebrate adult salamander (Notophthalmus viridescens) was developed in which the locomotor activities were monitored from electromyographic and video recordings. The results show that the two locomotor modes exhibited by salamanders (i.e., stepping and swimming) were evoked by electrical microstimulation (5-15 Hz; 0.1-10 microA; 2 msec pulses) of a circumscribed region in the caudal mesencephalon. At threshold current strength (0.5-3.5 microA at 15 Hz), rhythmic limb movements and intersegmental coordination, such as during stepping, were induced. As the stimulation strength was subsequently increased, the frequency of stepping became more rapid, and, at 2.0-5.5 microA, the limbs were held back against the body wall and swimming movements of the trunk were induced. An additional increase of the stimulation strength induced an increase of the frequency and amplitude of the swimming movements. Anatomical studies conducted in parallel revealed the presence of choline acetyltransferase immunoreactive cells in the functionally identified MLR region. Together, the present results indicate that the MLR is present in salamanders and that its level of activation determines the mode of locomotion. Walking is induced at low activation levels, and swimming, which constitutes a faster mode of locomotion, requires stronger stimulation of the MLR. Furthermore, as in other vertebrates, the MLR contains cholinergic cells.

Animals↗

PubMed2003

The ontogenetic scaling of hydrodynamics and swimming performance in jellyfish (Aurelia aurita).

It is not well understood how ontogenetic changes in the motion and morphology of aquatic animals influence the performance of swimming. The goals of the present study were to understand how changes in size, shape and behavior affect the hydrodynamics of jet propulsion in the jellyfish Aurelia aurita and to explore how such changes affect the ontogenetic scaling of swimming speed and cost of transport. We measured the kinematics of jellyfish swimming from video recordings and simulated the hydrodynamics of swimming with two computational models that calculated thrust generation by paddle and jet mechanisms. Our results suggest that thrust is generated primarily by jetting and that there is negligible thrust generation by paddling. We examined how fluid forces scaled with body mass using the jet model. Despite an ontogenetic increase in the range of motion by the bell diameter and a decrease in the height-to-diameter ratio, we found that thrust and acceleration reaction scaled with body mass as predicted by kinematic similarity. However, jellyfish decreased their pulse frequency with growth, and speed consequently scaled at a lower exponential rate than predicted by kinematic similarity. Model simulations suggest that the allometric growth in Aurelia results in swimming that is slower, but more energetically economical, than isometric growth with a prolate bell shape. The decrease in pulse frequency over ontogeny allows large Aurelia medusae to avoid a high cost of transport but generates slower swimming than if they maintained a high pulse frequency. Our findings suggest that ontogenetic change in the height-to-diameter ratio and pulse frequency of Aurelia results in swimming that is relatively moderate in speed but is energetically economical.

Acceleration↗

PubMed1988

Semi-automated analysis of manually reconstructed tracks of progressively motile human spermatozoa.

Several alternative algorithms for computer-assisted derivation of measurements of movement characteristics from manually reconstructed tracks of progressively motile human spermatozoa were compared. Fifty tracks were reconstructed at 30 Hz from video recordings and analysed using traditional manual methods and by four combinations of computer algorithms. The best algorithm set was identified ('Videomot.mdpt') and the values for the curvilinear, average path and linear velocities (VCVL, VAVE and VLIN respectively), the amplitude of lateral displacement of the sperm head about the axis of progression (AH) and the number of times the sperm head crossed the average path (the 'beat/cross frequency', BXF) obtained using it were compared to those obtained by manual analysis. There was a considerable time saving when the computer-assisted method was used and the values it gave for the various movement characteristics showed good correspondence with those obtained manually. In addition, repeated data entry and analysis was found to be highly reproducible. When the tracks were re-plotted at 6 Hz (as used by the multiple-exposure photomicrography method for sperm motility analysis) insufficient information remained in the tracks for reliable determination of anything other than VLIN. We conclude that the Videomot.mdpt program provides reliable values for the movement characteristics of progressively motile human spermatozoa, and believe it will be of great value in the validation of commercial systems providing automated sperm movement analysis and in laboratories which do not have access to such costly equipment.

Algorithms↗

PubMed1994

Video-imaging of lumen narrowing; muscle shortening and flow responsiveness in isolated bronchial segments of the pig.

The amount of smooth muscle shortening required to cause narrowing of the bronchial lumen and to significantly alter airflow in an airway has not not been measured. Accordingly, in this study, the lumens of isolated fluid-filled bronchial segments from pigs were directly visualized using a fibreoptic endoscope and video-recording. The extent of lumen narrowing was related to smooth muscle contraction, determined morphometrically, and to bronchial lumen flow. Narrowing was produced by electrical field stimulation (EFS), (70 V, 20 Hz, 2-3 ms) and acetylcholine (ACh), (10(-5)-10(-2) M). The diameter of the relaxed bronchial lumen and the reduction in diameter produced by maximum electrical field stimulation were both greater when the transmural pressure was increased (from -8 to 20 cmH2O). The percentage change in diameter produced by electrical field stimulation was not, however, significantly different over this pressure range. Electrical field stimulation caused the bronchial lumen to narrow by 28.5 +/- 3.3% in diameter, and by 45.7 +/- 3.8% in cross-sectional area, at zero transmural pressure. Maximum doses of acetylcholine (10(-2) M) reduced the lumen diameter by 48.3 +/- 3.3%, and the area by 70.3 +/- 4.8%. In separate experiments, maximum doses of ACh stopped the flow of Krebs solution perfused through the lumen of bronchial segments. Morphometric measurements indicated that smooth muscle shortened by a maximum of 32.5 +/- 2.8% to acetylcholine 10(2) M, relative to fully-relaxed dimensions. Simultaneous imaging of the lumen and adventitia of bronchi showed that the luminal margin narrowed more than the adventitia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed2006

Problems with technical equipment during laparoscopic surgery. An observational study.

BACKGROUND: This study was designed to investigate the incidence of technical equipment problems during laparoscopic procedures. METHODS: A video-capturing system was used, consisting of an analog video recorder with three camera image inputs and a microphone. Problems with all technical equipment used by the surgical team, such as the insufflator, diathermy apparatus, monitors, light source, camera and camera unit, endoscope, suction devices, and instruments, were registered. RESULTS: In total, 30 procedures were randomly videotaped. In 87% (26/30) of the procedures, one or more incidents with technical equipment (49 incidents) or instruments (9 incidents) occurred. In 22 of those incidents (45%) the technical equipment was not correctly positioned or not present at all; in the other 27 (55%), the equipment malfunctioned as a result of a faulty connection (9), a defect (5), or the wrong setting of the equipment (3). In 10 (20%) cases the exact cause of equipment malfunctioning was unclear. CONCLUSIONS: The incidence of problems with laparoscopic technical equipment is high. To prevent such problems, improvement and standardization of equipment is needed, combined with the incorporation of checklist use before the start of a surgical procedure. Future research should be aimed at development, implementation, and evaluation of these measures into the operating room.

Adult↗

PubMed1997

Usefulness of pallidotomy in advanced Parkinson's disease.

OBJECTIVE: The combined effect of posteroventral pallidotomy and optimal medical treatment was assessed in 22 patients with levodopa sensitive Parkinson's disease. METHODS: Timed motor tests, video recordings, and computer assisted optoelectronic movement analysis were used for serial hourly assessments performed preoperatively and four and 12 months after operation. Tests were made while patients were on optimal medical therapy. RESULTS: There were no serious adverse events of surgery. Two of the 22 patients could not complete all the tests after operation. The proportion of dyskinesia periods decreased in the 20 patients and there was a proportional increase in normal or fairly normal occasions. "Off" periods were not significantly affected. In 12 of 13 patients with limb dyskinesia this symptom was completely abolished in the contralateral limbs. There was also some degree of improvement axially and ipsilaterally. Tremor was moderately improved contralaterally. Bradykinesia remained unchanged. Results at 12 months follow up were similar to those at four months. CONCLUSION: Pallidotomy produced a pronounced positive effect on dyskinesia and a moderate effect on tremor. Bradykinesia was not affected. Posteroventral pallidotomy may be useful in patients with Parkinson's disease who have severe motor fluctuations and may allow an increase in levodopa dose to alleviate bradykinesia in "off" states.

Adult↗

PubMed2006

Impacts of chronic stress and social status on various physiological and performance measures in pigs of different breeds.

Pigs typically experience various environmental stressors, which can negatively affect performance. Cortisol concentrations and various immune and performance measures are influenced by breed, but few data exist describing the impact of breed on stress responsiveness in pigs. The objective of this experiment was to determine if certain physiological responses to chronic stressors differed among 3 breeds and 2 commercial lines of pigs. The pigs were Landrace (n = 36), Meishan (n = 30), Yorkshire (n = 32), or 1 of 2 commercial lines (Line-A and Line-B; both n = 36). All pigs were weaned at 17 to 21 d and kept in a common nursery. At 49 d of age, pigs were assigned to 1 of 2 treatments: stress (heat, crowding, and mixing) or control (no stress treatment). Pigs were allocated to groups of 3 pigs per pen of the same sex. Control pigs were kept with their littermates. At the onset of the experiment, stressed pigs were mixed with 2 unfamiliar pigs once, and heat and crowding stressors were implemented simultaneously for 14 d. Pigs allocated to the stress treatment were video-recorded for 24 h following initiation of mixing to determine social status: dominant, intermediate, or submissive. Blood samples were taken at d 0 (baseline), 1, 7, and 14 to assess cortisol concentrations and immune measures. Breed and treatment affected cortisol, immune, and performance measures, but no significant breed x treatment interactions were found. In general, pigs subjected to the chronic stressor had lower (P < 0.001) BW and ADG (P < 0.001) than did control pigs. Plasma cortisol was lower (P < 0.001) among stressed pigs at d 7 and 14. Regardless of breed, lipopolysaccharide-induced proliferation (P < 0.01) and natural killer (NK; P < 0.005) cytotoxicity were greater in stressed pigs compared with controls. Furthermore, among stressed pigs, dominant pigs had a greater total white blood cell count (P < 0.005), NK (P < 0.05), and phagocytosis (P < 0.05) than the subordinate pigs. The results indicate that pig breed did not influence the physiological responses to the chronic concurrent stressors imposed for 14 d in this study, but social status did influence the immune responsiveness of these pigs to heat, crowding, and mixing.

Animals↗

PubMed1999

Effects of high-impact exercise on ultrasonic and biochemical indices of skeletal status: A prospective study in young male gymnasts.

Physical activity has been proposed as one strategy to enhance bone mineral acquisition during growth. The aim of this study was to determine whether frequent impact loading associated with gymnastics training confers a skeletal benefit on pre- and peripubertal male gymnasts. We measured broadband ultrasonic attenuation (BUA, dB/MHz) at the calcaneus (CBUA); ultrasound velocity (m/s) at the calcaneus (CVOS), distal radius (RVOS) and phalanx (PVOS); serum osteocalcin (OC); total alkaline phosphatase (ALP) and insulin-like growth factor-I (IGF-I) every 3-4 months over an 18-month period in elite male gymnasts and matched normoactive controls (pubertal stage </=2). Ground reaction forces of common gymnastics maneuvers were determined using a force platform and loading histories of the upper and lower extremities approximated from video recordings. Ultrasound results were expressed as a standardized score (Z score) adjusted for age, height, and weight. At baseline, no differences were detected between the gymnasts (n = 31) and controls (n = 50) for CBUA, although ultrasound velocity at each site was higher in the gymnasts (0.6-1.5 SD) than the predicted mean in controls (p </= 0. 001). Over 18 months, CBUA Z scores increased significantly in the gymnasts from baseline (0.3 vs. 1.0, p < 0.05, n = 18). In contrast, ultrasound velocity did not increase in either group, although CVOS and RVOS remained significantly higher in gymnasts compared with controls (range p < 0.01 and < 0.001). No differences between groups were found for OC, ALP, or IGF-I at any time. Gymnastics training was associated with on average 102 and 217 impacts per session on the upper and lower extremities, respectively, with peak magnitudes of 3.6 and 10.4 times body weight. These results suggest that frequent high-impact, weight-bearing exercise during the pre and peripubertal period may enhance the mechanical competence of the skeleton, perhaps offering an important strategy for osteoporosis prevention if the benefits are maintained.

Body Constitution↗

PubMed2000

Preimplant measures of preverbal communicative behavior as predictors of cochlear implant outcomes in children.

OBJECTIVE: Comparison of preverbal communication behavior in young children before receiving cochlear implants with outcomes 3 yr after implantation on speech identification and speech production tasks, to assess whether outcomes can be predicted from characteristics inherent to the child before implantation. DESIGN: Video recordings of preverbal communicative behavior were examined before use of the implant to quantify turn-taking and demonstration of autonomy by the child. Speech identification ability was measured 3 yr after implantation based on the Iowa Closed-Set Speech Perception Sentence Test, continuous discourse tracking, and an observational measure of telephone use. Speech production ability was measured 3 yr after implantation by the Edinburgh Articulation Test. Associations between the preimplant measures and the 3-yr outcomes were assessed by correlation analysis of data from 33 children. RESULTS: The 3-yr performance measures of speech identification were correlated with the preimplant measure of autonomy. Telephone use and speech production ability were not significantly associated with the preimplant measures. CONCLUSIONS: Up to a fourth of the variance in speech identification performance 3 yr after cochlear implantation of young children may be predicted from characteristics that are inherent to the child before implantation. Those characteristics are represented by the demonstration of autonomy in preverbal communicative interactions, whether by means of vocalization or by gesture. If those characteristics are acquired during infancy, outcomes in children with auditory prostheses including cochlear implants may be enhanced by activities that encourage autonomy in early years.

Child Behavior↗

PubMed1990

Visual tracking of moving targets by freely flying honeybees.

The ability of freely-flying honeybees to track moving targets was examined by training them to collect a reward on a target, and then videotaping their approach to the target while it was in motion. Training experiments were carried out with several groups of bees, using various colors for the target and the background. Computer-aided frame-by-frame analysis of video recordings was used to plot the instantaneous positions of the target, as well as the position and orientation of the approaching bee in three dimensions. The results show that bees are perfectly capable of tracking moving targets and landing on them. When the distance of the target is greater than 15 cm, approaching bees correct for angular deviations of the target from the midline, both in the horizontal and in the vertical plane. In either plane, the input variables that are important to the tracking system seem to be (1) the angular bearing of the target with respect to the midline, and (2) the angular velocity of the target with respect to the eye. The tracking control system tends to orient the bee such that the target is located frontally, at an angle of ca. 35 deg below the bee's long axis. The chromatic properties of tracking behavior were investigated by employing combinations of colors for the target and background such that the boundary between the target and the background presented a contrast that was visible either only to the green-sensitive receptors of the bee's eye, or only to the blue-sensitive receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗