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At least 343 records · Page 19Linked to original sources
PubMed1995

Effects of ischemia on left ventricular apex rotation. An experimental study in anesthetized dogs.

BACKGROUND: Left ventricular (LV) twist has been defined as the counterclockwise rotation of the ventricular apex with respect to the base during systole. We recently showed that, since base rotation is minimal, measurement of apex rotation reflects the dynamics of LV twist. Since ischemia is known to affect endocardial and epicardial fiber force and shortening and therefore the transmural balance of torsional moments, we hypothesized that ischemia has a significant effect on apex-rotation amplitude and on untwisting during the isovolumic relaxation (IVR) period. METHODS AND RESULTS: With an optical device coupled to the LV apex, apex rotation was recorded simultaneously with LV pressure, ECG, LV segment length, and minor-axis diameters in 16 open-chest dogs. Ischemia was caused by a 1- to 2-minute snare occlusion of either the left anterior descending (LAD) or circumflex (LCx) arteries. LAD ischemia had a pronounced effect on apex rotation: an increase in apex-rotation amplitude attributed to subendocardial dysfunction at 10 seconds of ischemia; maximum apex rotation occurring later (during the IVR period) throughout the ischemia; a paradoxical relaxation pattern of initial untwisting followed by twisting and untwisting during the IVR period with ischemia; and a decrease in the amplitude of apex rotation with ischemia, possibly due to transmural dysfunction. LCx occlusion had similar effects on apex rotation, except that apex-rotation amplitude was not increased at 10 seconds of occlusion and the amplitude of apex rotation did not decrease with severe ischemia. Under control preischemic conditions, a linear relationship between apex rotation and segment length was observed during ejection and a different, steeper relationship during IVR. With regionally ischemic segments, this relationship became nonlinear for both ejection and IVR. CONCLUSIONS: Both LAD and LCx ischemia had profound effects on the dynamics of apex rotation. A paradoxical relaxation pattern occurred with ischemia. We suggest that these observations are due to changes in the dynamic transmural balance of torsional moments that determine LV twist.

Anesthesia, General↗
PubMed2004

Arthroscopic revision of failed rotator cuff repairs: technique and results.

PURPOSE: The purpose of this study was to review the results of arthroscopic revision rotator cuff repair in patients for whom a previous rotator cuff repair had failed. TYPE OF STUDY: Case series. METHODS: From October 1998 to October 2000, 14 patients with a mean age of 57.9 +/- 9.2 years underwent arthroscopic revision rotator cuff repair and were available for follow-up evaluation. The mean time from primary to revision procedure was 41.4 months (range, 8 to 240 months). Eleven patients had undergone a previous rotator cuff repair, 2 patients had undergone 2 rotator cuff repairs, and 1 patient had undergone 3 rotator cuff repairs. We found 2 medium, 1 large, and 11 massive recurrent rotator cuff tears, with a mean tear size of 4.4 x 5.5 cm. All large and massive tears required extensive arthroscopic dissection and mobilization of the rotator cuff to delineate the tear margins and repair the rotator cuff. All patients were evaluated preoperatively and postoperatively using a modified University of California Los Angeles (UCLA) scoring system. RESULTS: At a mean of 23.4 +/- 9.8 months after arthroscopic revision rotator cuff repair, 13 of 14 patients were satisfied with the procedure. The mean UCLA score increased from 13.1 +/- 2.3 preoperatively to 28.6 +/- 7.1 postoperatively (P <.00001). We noted 4 excellent, 5 good, 4 fair, and 1 poor result. The mean active forward elevation increased from 120.7 degrees +/- 48.9 degrees preoperatively to 153.6 degrees +/- 33.1 degrees postoperatively (P =.006). The mean active external rotation increased from 26.1 degrees +/- 19.3 degrees preoperatively to 44.3 degrees +/- 15.9 degrees postoperatively (P =.006). Of the 4 patients without active overhead function preoperatively, 3 gained overhead function postoperatively. One patient who did not regain overhead function had a poor result secondary to anterior deltoid detachment after the primary procedure. CONCLUSIONS: Revision arthroscopic rotator cuff repair is a technically demanding procedure. However, appropriate patient selection and careful attention to rotator cuff dissection, mobilization, and repair by arthroscopic means can lead to significant improvements in overall shoulder pain and function. LEVEL OF EVIDENCE: Level 4, case series (no or historical control group).

Aged↗
PubMedDate not supplied

The relative importance of acromial morphology and age with respect to rotator cuff pathology.

The purpose of this study was to examine the relationship between patient age, acromial morphology, and rotator cuff pathology. Data on 523 patients who had arthroscopic and/or open shoulder surgery were reviewed. Acromial morphology was classified by the system of Bigliani. All patients were categorized by postoperative diagnosis as having tendinitis of the rotator cuff, partial rotator cuff tear, complete rotator cuff tear, and non-rotator cuff-related pathology. Univariate analysis results for acromial morphology (P <.001), age (P <.001), and gender (P =.019) showed a significant association with rotator cuff pathology. Fifty percent of patients with rotator cuff tendinitis had type I acromions, and 58% of patients with full-thickness rotator cuff tears had type III acromions. Stratified univariate analysis revealed no significant association between acromial morphology and rotator cuff pathology in patients who were over 50 years old. Patients with full-thickness rotator cuff tears were significantly older than those with partial-thickness tears or tendinitis. A larger proportion of male patients than female patients had full-thickness rotator cuff tears. Multivariable logistic regression analysis identified acromial morphology, age, and gender as independent multivariate predictors of rotator cuff pathology. Age, acromial morphology, and gender all have an independent association with rotator cuff pathology.

Acromion↗
PubMedDate not supplied

The manual muscle examination for rotator cuff strength. An electromyographic investigation.

The electromyographic activity of eight muscles of the rotator cuff and shoulder girdle (supraspinatus, infraspinatus, subscapularis, pectoralis, latissimus dorsi, and the anterior, middle, and posterior deltoid) was measured from the nondominant shoulders of 11 subjects during a series of 29 isometric contractions. The contractions simulated different positions used for strength testing of the rotator cuff and involved elevation, external rotation, and internal rotation at three degrees of initial humeral rotation (-45 degrees of internal rotation, 0 degree, +45 degrees of external rotation) and scapular elevation (0 degree, 45 degrees, 90 degrees). Isolation of the supraspinatus muscle was best achieved with the test position of elevation at 90 degrees of scapular elevation and +45 degrees (external rotation) of humeral rotation. Isolation of the infraspinatus muscle was best achieved with external rotation at 0 degree of scapular elevation and -45 degrees (internal rotation) of humeral rotation. Isolation of the subscapularis muscle was best achieved with the Gerber push-off test. This study used four criteria for identifying the optimal manual muscle test for each rotator cuff muscle: 1) maximal activation of the cuff muscle, 2) minimal contribution from involved shoulder synergists, 3) minimal provocation of pain, and 4) good test-retest reliability. Based on the results of this study and known painful arcs of motion, an objective identification of the optimal tests for the manual muscle testing of the cuff was elucidated.

Adult↗
PubMed1993

Perception of horizontal head and trunk rotation: modification of neck input following loss of vestibular function.

Chronic loss of vestibular function modifies the role of neck afferents in human perception of self-motion. We characterized this change by comparing the self-motion perception of patients with chronic vestibular loss (Ps) to that of normal subjects (Ns). Stimuli consisted of sinusoidal horizontal rotations (0.025-0.4 Hz) of the trunk relative to the head (neck stimulation) and/or of the head in space (vestibular stimulation). Perception of head rotation relative to the trunk, of trunk rotation in space, or of head rotation in space was assessed in terms of gain and phase (veridical perception, G = 1 and phi = 0 degree) as well as detection threshold using a pointing procedure. (1) Perception of head rotation relative to the trunk (neck proprioception). Ps' detection threshold of head-to-trunk rotation was normal (i.e. similar to that of Ns) across all frequencies tested. Also, with peak angular velocities above 5 degrees/s, the gain of their perception was approximately normal. When peak velocity was decreased below this value, however, either by lowering stimulus frequency with peak displacement kept constant (+/- 8 degrees) or by decreasing peak displacement at constant frequency (0.05 Hz), the gain increased above unity, unlike in Ns. In contrast, the phase remained normal (approximately 0 degree). (2) Perception of trunk rotation in space. Ps perceived their trunks as stationary during neck stimulation and all vestibular-neck combinations at medium to low frequencies. At 0.4 Hz, however, Ps consistently perceived the trunk rotation, conceivably due to somatosensory self-motion cues arising from high body acceleration. In contrast, Ns perceive a trunk-in-space rotation with the neck stimulation and most of the stimulus combinations across the whole frequency range tested. Ns perceived their trunks as stationary only during head rotation on the stationary trunk (presumed to reflect a mutual cancellation of neck and vestibular signals). (3) Perception of head rotation in space. In Ps, unlike Ns, this perception always resembled that of head rotation relative to the trunk. (4) When Ps were presented with a visual or somatosensory space reference (not motion cues), their perception of trunk and head rotation in space became approximately normal. (5) We suggest that there are basically two changes in the neck-induced self-motion perception associated with chronic vestibular loss. First, neck proprioception shows a non-linear gain that overemphasizes low stimulus velocities, for unknown reasons.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1999

The role of forceps rotation in maternal and neonatal injury.

OBJECTIVE: Our purpose was to assess the impact of forceps rotation on maternal and neonatal injury. STUDY DESIGN: In this retrospective case-controlled study performed at the University of Texas Medical Branch at Galveston all forceps deliveries with a rotation of >/=90 degrees performed between July 1992 and September 1995 were identified (n = 113). For controls 167 forceps deliveries with rotations of </=45 degrees were randomly selected. Control deliveries occurred during the same time period and were matched to within 2 weeks of gestational age as well as to nulliparous versus parous status. The majority of deliveries were low; however, some midforceps deliveries were also included. RESULTS: Forceps rotations of >/=90 degrees accounted for 0.8% of all deliveries. A major fetal injury, defined as a skull fracture, subdural hematoma, brachial plexus or a sixth or seventh cranial nerve injury, occurred in 10.2% of deliveries with rotations of </=45 degrees and in 9.7% with rotations of >/=90 degrees. The only permanent injury was a brachial plexus palsy that occurred with a forceps rotation of 45 degrees. Rotations of >/=90 degrees were not associated with umbilical arterial acidemia below 7.0 or 7.1 compared with rotations of </=45 degrees. Rotations of >/=90 degrees were associated with longer maternal hospital stays (P =.009). Neither lacerations of the birth canal, third- or fourth-degree episiotomies, or fall in the maternal hematocrit correlated with the degree of forceps rotation. CONCLUSIONS: Advanced degrees of forceps rotations do not result in any clinically significant increase in infant or maternal morbidity relative to that encountered with lesser degrees of forceps rotation.

Birth Injuries↗
PubMed1995

Effect of rotational malposition of the femoral component on knee stability kinematics after total knee arthroplasty.

Excessive external rotation of the femoral component can cause an abnormally tight popliteus tendon complex, which induces loss of rotational laxity of the knee in the late phase of knee flexion after total knee arthroplasty. This study evaluated the effect of popliteus tendon release on rotational and varus-valgus laxity of implanted knees with an excessively externally rotated femoral component. Rotational and varus-valgus laxity was measured with a knee kinematics testing device before and after total knee arthroplasty. External rotational positions of the femoral component of 5 degrees and 8 degrees were compared, and the effects of popliteus tendon release on rotational and varus-valgus laxity were evaluated. To further investigate this question, the effect of a conforming articular design was compared with that of a flat tibial surface. External rotational position of 5 degrees did not change rotational or varus-valgus laxity of the knee. With an 8 degrees external rotational position, however, external rotational laxity significantly decreased in knees with a conforming surface at angles of 30 degrees, 45 degrees, 60 degrees, and 90 degrees. After popliteus tendon release, external rotational laxity significantly improved at 90 degrees flexion and was identical to that of the normal knee. Internal rotational range was similar before and after popliteus tendon release. Popliteus tendon release did not affect the varus-valgus laxity (stability) with either articular surface.

Biophysical Phenomena↗
PubMed1998

Rotational action of the supraspinatus muscle on the shoulder joint.

The shoulder joint allows three-dimensional movement. In order to analyze the function of the muscles which act on the shoulder joint, three-dimensional movements, including rotation, must be considered. Among muscles participating in the shoulder joint movement, the supraspinatus muscle is known to have abduction and stabilization effects on the shoulder joint. However, the rotational function of the supraspinatus muscle has not been identified, because few studies have been reported on it. This study investigates the rotating function of the supraspinatus muscle using electrical stimulation, magnetic resonance imaging (MRI) and anatomical examination. Electrical stimulation was applied selectively to the supraspinatus muscle of healthy subjects using percutaneous wire electrodes. The electrical stimulation was given at different positions of the shoulder joint. It was found that the electrically induced rotational movements changed their direction depending on the position of the shoulder joint. When the humerus was relatively in internal rotation, internal rotation resulted. When it was in external rotation, external rotation occurred. Regarding the abduction angle of the shoulder joint, external rotation was induced with an increase in the abduction angle, whereas internal rotation occurred when the abduction angle was decreased. By the dissection of cadavers and MRI examination, it was indicated that the relation between the running direction of the supraspinatus muscle and the center of rotation of the humeral head was dependent on the position of the shoulder joint. Those findings supported the results of electrical stimulation of the supraspinatus muscle at various shoulder positions. These results indicate that the bi-directional rotating function of the supraspinatus muscle is characterized by an anatomical relationship between the running direction of the supraspinatus muscle and the center of rotation of the humeral head.

Adult↗
PubMedDate not supplied

An electromyographic study of isokinetic axial rotation in young adults.

BACKGROUND CONTEXT: Trunk rotation is associated with over 60% of all low back injuries. However, there are gaps in the knowledge about trunk rotation. PURPOSE: To study the axial rotation torque and electromyographs (EMGs) of seven trunk muscles bilaterally in static and isokinetic modes with increasing angular velocity to determine qualitative and quantitative muscle response. STUDY DESIGN: An electromyographic study of seven trunk muscles bilaterally was carried out in 50 normal subjects during static and isokinetic axial rotation at varying angular velocity. The qualitative and quantitative force and EMG measures were made and analyzed phenomenologically and statistically. METHODS: Fifty normal young adults (27 men, 23 women) performed an isometric maximal voluntary contraction (MVC) from the neutral upright-seated posture to their right and left. Also, these subjects performed isokinetic axial rotation from neutral seated position to right and left, and from prerotated right and left "end of range posture" toward the neutral at 10, 20 and 40 degrees per second angular velocity. All experimental trials were made on axial rotation tester designed for the study. EMG was recorded from the erector spinae at L3 and T10 vertebral levels, latissimus dorsi, pectoralis major, rectus abdominis and external and internal obliques bilaterally. The torque and EMG in isokinetic condition were normalized against those of isometric condition. Descriptive statistics were calculated. Data were subjected to analysis of variance, and torque was regressed on EMG. RESULTS: The peak isokinetic torques were significantly lower than the isometric torques (p<.01), but the EMGs of the isokinetic conditions were significantly higher than those of isometric trials (p<.01). The isokinetic axial rotation torque decreased by 1 Nm to 1.5 Nm with per degree increase in velocity of rotation, with the values for 10, 20 and 40 degrees per second angular velocities being significantly different (p<.01). There was a significant increase (p<.01) in percent EMG (up to 28%) per unit torque with increasing angular velocity of rotation. The rotation torque from prerotated position to neutral was significantly higher than that of rotation away from the neutral (p<.001). The EMG magnitude increased significantly with increasing velocity (2% to 17% at 10 degrees per second), 21% to 28% at 20 degrees per second, 30% to 36% at 40 degrees per second). Regression analysis revealed poor predictability of torque based on EMG. The latter was suggested because of the role and behavior of the ligaments and joint capsules of the spine. CONCLUSION: The axial rotation is initiated and maintained by the contralateral external obliques, ipsilateral latissimus dorsi and internal oblique. The ipsilateral erector spinae likely play a stabilizer role. The isometric torque is greater than the isokinetic, which decreases with increasing velocity. Even with decreasing torque, EMG progressively increases, indicating a disproportionally higher stress in the spinal connective tissues potentiating injury. The data presented here suggest that, for safety, load and velocity of rotation should be kept low.

Abdomen↗
PubMed2002

The atlanto-axial joint: physiological range of rotation on MRI and CT.

AIMS: To measure the range of rotation and determine the instantaneous axis of rotation of the atlanto-axial joint in healthy volunteers using magnetic resonance imaging (MRI) and to highlight the appearances of the rotated atlanto-axial joint on computed tomography (CT) and MRI. MATERIALS AND METHODS: Twenty-eight healthy volunteers were examined using MRI during maximal head rotation. In addition, an anatomical specimen of the atlanto-axial joint, fixed in varying degrees of rotation, was imaged using CT. RESULTS: At the extremes of physiological rotation in healthy subjects there is striking but incomplete loss of contact between the articular surfaces of the atlas (C1) and the axis (C2). The range of rotation to the right was 20-48.5 degrees (mean 32.4 degrees ) and to the left was 13-52.75 degrees (mean 34.2 degrees ). There was no significant difference between rotation to the right and left (P = 0.455). Total rotation was 45-88.5 degrees (mean 69.25 degrees ). The instantaneous axis of rotation was located within the odontoid peg. CONCLUSION: There is a wide range of atlanto-axial rotation in normal subjects. The instantaneous axis of rotation lies within the odontoid peg. The appearances of the rotated atlanto-axial joint are striking and may be misinterpreted as subluxation.

Adolescent↗
PubMedDate not supplied

Optimized dynamic rotation with wedges.

Dynamic rotation is a computer-controlled therapy technique utilizing an automated multileaf collimator in which the radiation beam shape changes dynamically as the treatment machine rotates about the patient so that at each instant the beam shape matches the projected shape of the target volume. In simple dynamic rotation, the dose rate remains constant during rotation. For optimized dynamic rotation, the dose rate is varied as a function of gantry angle. Optimum dose rate at each gantry angle is computed by linear programming. Wedges can be included in the optimized dynamic rotation therapy by using additional rotations. Simple and optimized dynamic rotation treatment plans, with and without wedges, for a pancreatic tumor have been compared using optimization cost function values, normal tissue complication probabilities, and positive difference statistic values. For planning purposes, a continuous rotation is approximated by static beams at a number of gantry angles equally spaced about the patient. In theory, the quality of optimized treatment planning solutions should improve as the number of static beams increases. The addition of wedges should further improve dose distributions. For the case studied, no significant improvements were seen for more than 36 beam angles. Open and wedged optimized dynamic rotations were better than simple dynamic rotation, but wedged optimized dynamic rotation showed no definitive improvement over open beam optimized dynamic rotation.

Humans↗
PubMed1993

An optical device to measure the dynamics of apex rotation of the left ventricle.

Systolic counterclockwise rotation of the left ventricular apex with respect to the base has been defined as left ventricular (LV) twist or torsion. If rotation of the base during systole is small, we hypothesized that the dynamics of twist can be well characterized through the measurement of apical rotation alone. A device was designed to measure apical rotation in a simpler, more direct fashion, providing continuous high-fidelity dynamic measurements. The device consists of a light source, a position-sensitive diode, and a small rotating mirror that is coupled to the apex of the heart by a wire. As the wire rotates, apical rotation (measured in degrees) can be calculated from the position of the deflected light beam. The timing of apical rotation was compared with simultaneous recordings of electrocardiogram, LV pressure, and LV diameter measurements. An initial clockwise rotation (untwist) of 4 +/- 2 degrees (SD) occurred during isovolumic contraction followed by counterclockwise rotation (twisting) through ejection, reaching maximum apical rotation of -15 degrees just before the end of systole. Rapid untwisting during isovolumic relaxation was shown with near-complete dissipation of twist by the first one-third of the diastolic filling period. Caval occlusion caused a downward and leftward shift of the pressure-apical rotation loops, and more twist/untwist was seen to occur during the respective isovolumic contraction and relaxation periods. We conclude that this device provides precise timing and definition of rapid changes during isovolumic contraction and relaxation, confirms results obtained by more laborious methods, and provides an easy method to measure the dynamics of apical rotation continuously during interventions such as load changes.

Animals↗
PubMed2002

The effect of rotational malunion of the radius and the ulna on supination and pronation.

We have assessed the influence of isolated and combined rotational malunion of the radius and ulna on the rotation of the forearm. Osteotomies were made in both the radius and the ulna at the mid-diaphyseal level of five cadaver forearms and stabilised with intramedullary metal implants. Malunion about the axis of the respective forearm bone was produced at intervals of 10 degrees. The ranges of pronation and supination were recorded by a potentiometer under computer control. We examined rotational malunions of 10 degrees to 80 degrees of either the radius or ulna alone and combined rotational malunions of 20 degrees to 60 degrees of both the radius and ulna. Malunion of the ulna in supination had little effect on rotation of the forearm. Malunion of either the radius or of the ulna in pronation gave a moderate reduction of rotation of the forearm. By contrast, malunion of the radius in supination markedly reduced rotation of the forearm, especially with malunion greater than 60 degrees. Combined rotational malunion produced contrasting results. A combination of rotational malunion of the radius and ulna in the same direction had an effect similar to that of an isolated malunion of the radius. A combination in the opposite direction gave the largest limitation of the range of movement. Clinically, rotational malunion may be isolated or part of a complex angular/rotational deformity and rotational malunion may lead to marked impairment of rotation of the forearm. A reproducible method for assessing rotational malunion is therefore needed.

Cadaver↗
PubMedDate not supplied

Amphetamine-induced rotational behavior in rats: relationship to hypothalamic and striatal degeneration.

When lesions are placed unilaterally in the nigrostriatal system of experimental animals, rotational behavior occurs in response to peripheral administration of dopamine (DA) agonists. In spite of considerable evidence to the contrary, it is assumed that in order for this rotation to occur, an almost complete depletion of striatal DA must be achieved. To test this hypothesis further, 20 male Sprague-Dawley rats were injected unilaterally with 2 microL of 8 micrograms/microL of 6-hydroxydopamine (6-OHDA) via acute injection needles or chronically indwelling cannulae. Acute injection of 6-OHDA resulted in a rotation rate of 7.2 to 18.9 revolutions per minute in response to peripheral amphetamine injection (5 mg/Kg) while injection of 6-OHDA through chronically indwelling cannulae produced rotation ranging from 1.4 to 9.9 rotations per minute. Under the conditions of either method of injection, the animals displaying the most severe rotation still showed partial denervation of striatal DA as revealed by catecholamine fluorescence histochemistry. Conversely, numerous animals demonstrating very low rates of amphetamine-induced rotation often displayed a complete loss of striatal, accumbens, and olfactory tubercle catecholamine fluorescence. Moreover, large quantities of lateral hypothalamic amine accumulation were observed in rotating rats indicating that this neurochemical change may be of functional significance for rotational responses. The present results, when taken into consideration with previous work, indicate that the routine selection of rotating animals for pharmacological testing for potential antiParkinsonian medication or intracerebral grafting purely on the basis of their rotational behavior does not necessarily imply that complete striatal denervation has occurred. Moreover, these findings demonstrate that amine accumulation in the lateral hypothalamus of rotating animals with DA depleting lesions is an important phenomenon implicated in the expression of rotational behavior in animals and possibly in the pathophysiology of Parkinson's disease.

Amphetamine↗
PubMed1998

[Posterior position of acetabular component of a total hip prosthesis: possible cause of lower limb rotation problem].

INTRODUCTION: The authors report the case of an internal rotation of the lower limb, lately ascribed to a posterior placement of the acetabular component during total hip arthroplasty. MATERIAL AND METHOD: A 58 years old female had an irreducible internal rotation of the right hip 3 years after total hip arthroplasty for arthritis. When the hip was extended, the lower limb showed an irreducible internal rotation of 45 degrees. In flexion of the hip this rotation disappeared. AP radiograms showed femur and femoral stem in internal rotation, a healed fracture of the acetabulum, and the acetabular component seemed to be in correct position. On CT scan the acetabular component was 4 cm posterior to the anatomic location, although there was no abnormal anteversion of the stem and acetabular component. Revision, with relocation of the acetabular component, corrected lower limb rotation. DISCUSSION: Posterior position of the acetabular component has not been described as a cause of lower limb malrotation. Normally the strength of the external hip rotators muscles is three times as important as of the internal rotators. The transverse acetabular fracture led to backwards placement of the acetabular component and yelded in an automatic internal rotation of the femur, because the trochanter kept an anatomical position in the horizontal plane. The posteriorised rotation center of the hip had changed the balance of the different rotator muscles, some of them, originally external rotators, becoming internal rotators.

Acetabulum↗
PubMed2000

Cilia-driven rotational behavior in gastropod (Physa elliptica) embryos induced by serotonin and putative serotonin reuptake inhibitors (SSRIs).

We characterized the serotonin (5-hydroxytryptamine; 5-HT) receptor mediating cilia-driven rotational movement in embryos of the freshwater gastropod Physa elliptica. In addition, putative serotonin reuptake inhibitors (SSRIs), previously shown to induce other 5-HT-mediated processes in molluscs, were tested for their ability to induce rotation. As in previous studies with other freshwater gastropods, 5-HT induced a significant dose-dependent increase in rotation from 10(-6) to 10(-4) M. The 5-HT(1A) agonist 8-OH-DPAT produced a similar dose-dependent increase in rotation. However, the 5-HT(2) agonist alpha-CH3-serotonin evoked a significant rotational response only at the highest concentration of 10(-4) M. The 5-HT(2) receptor antagonist mianserin not only blocked 5-HT-induced rotation, it reduced rotation rate below that of baseline. However, two other antagonists, cyproheptadine (5-HT(2)) and propranolol (5-HT(1)), caused similar responses that consisted of an initial rotational surge followed by reduced rotation. Thus, these drugs appear to act as partial agonists. The putative SSRI fluvoxamine exhibited a significant dose-dependent increase in positive rotation as that seen with 5-HT. The SSRIs paroxetine and fluoxetine both caused an increase in rotation at 10(-6) and 10(-5) M but reduced rotation rate below that of baseline at 10(-4) M. These results agree with other studies on aquatic molluscs, suggest a 5-HT receptor with a mixed 5-HT(1)/5-HT(2) pharmacological profile and add to a now growing body of literature on the pharmacology of molluscan 5-HT receptors. In addition, all the tested putative SSRIs induced cilia-driven rotation in Physa embryos, indicating either the presence of 5-HT reuptake transporters or that these compounds act as 5-HT receptor ligands. J. Exp. Zool. 286:414-421, 2000.

Animals↗
PubMed1977

Ultrastructural changes in intersegmental cuticle during rotation of the terminal abdominal segments in a mosquito.

The terminal abdominal segments of male Aedes aegypti rotate 180 degrees within 24 hr after adult emergence, rotation occurring in the intersegmental membrane between abdominal segments VII and VIII. The ultrastructure of this rotating membrane is compared with non-rotating intersegmental membranes at different developmental stages. The deposition of cuticle in both the rotating and non-rotating intersegments appears ultrastructurally similar, and follows the sequential pattern described for the insects. Shortly after adult emergence, however, disruptive changes occur in the membrane cuticle that are more pronounced in non-rotating intersegments. This disruption occurs initially 1 hr after adult emergence and becomes maximal within 3 hr. Disruption appears to occur by the addition of fluid to the cuticle and results in a ten-fold increase in cuticle thickness in non-rotating intersegments but only a two-fold increase in thickness in the rotating intersement. While in the disrupted condition, the non-rotating intersegmental membranes become extensively folded whereas the cuticle in the rotating intersegment becomes stretched. During rotation, strain forces in the rotating intersegment result in a reorientation of microfibers in the cuticle from parabolic to parallel. This reorientation is presumably brought about by plastic flow.

Abdomen↗
PubMed1992

Visual field differences for clockwise and counterclockwise mental rotation.

Geometric line drawings were presented to normal subjects in the left visual field (LVF) or right visual field (RVF) at various degrees of rotation from a centrally presented vertical standard. The task of the subject was to indicate with a reaction time (RT) response whether the laterally presented stimulus could be rotated into the vertical standard or if it was a rotated mirror image of the standard. In Study 1, an overall right hemisphere superiority was found for RT and accuracy on match trials. Most interestingly, interactions between Visual Field and Rotation Angle for the match accuracy data and between Visual Field and Direction of Rotation (clockwise or counterclockwise) for the match RT slopes were found. These interactions suggested that clockwise rotations were more readily performed in the LVF and counterclockwise rotations in the RVF, consistent with other literature for mental rotation. The purpose of Study 2 was to replicate this finding of visual field differences for rotation direction using a design in which direction and degree of rotation were varied orthogonally. No main effect of Visual Field was found. However, significant interactions between Visual Field and Rotation Angle were found for both RT and accuracy, confirming the presence of visual field differences for rotation direction in a new sample of subjects. These differences were discussed in terms of the possibly greater relevance of medially directed stimuli and a possible hemispheric bias for rotation direction, and in terms of interhemispheric transmission factors.

Adolescent↗