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PubMed2000

Non-spatial water radial-arm maze learning in mice.

Recently, we published a method for examining working and reference memory in mice using a spatial version of the water radial-arm maze. Here we describe a non-spatial version of the same maze. BXSB mice were able to learn the maze as shown by the decrease in the number of working and reference memory errors over sessions. This maze was used to examine learning differences between males and females and between mice with misplaced clusters of neurons in layer I of cortex (ectopias) and those without. In a prior study using the spatial version of the water radial-arm maze, male BXSB mice had poorer working memory than females during the acquisition phase. Similarly, in this study male BXSB mice demonstrated impaired working memory during the asymptotic phase of non-spatial radial-arm maze learning. Two prior studies showed that mice with neocortical ectopias demonstrated working memory impairments compared to non-ectopic littermates in the spatial version of the water radial-arm maze. Contrary to this, in the non-spatial radial-arm maze used here, ectopic mice were not impaired in working memory and showed better memory when the working memory 'load' was the highest. Overall, both versions of the maze can be useful tools to assess spatial and non-spatial working and reference memory in mice.

Animals↗
PubMed2003

Longer moment arm results in smaller joint moment development, power and work outputs in fast motions.

Effects of moment arm length on kinetic outputs of a musculoskeletal system (muscle force development, joint moment development, joint power output and joint work output) were evaluated using computer simulation. A skeletal system of the human ankle joint was constructed: a lower leg segment and a foot segment were connected with a hinge joint. A Hill-type model of the musculus soleus (m. soleus), consisting of a contractile element and a series elastic element, was attached to the skeletal system. The model of the m. soleus was maximally activated, while the ankle joint was plantarflexed/dorsiflexed at a variation of constant angular velocities, simulating isokinetic exercises on a muscle testing machine. Profiles of the kinetic outputs (muscle force development, joint moment development, joint power output and joint work output) were obtained. Thereafter, the location of the insertion of the m. soleus was shifted toward the dorsal/ventral direction by 1cm, which had an effect of lengthening/shortening the moment arm length, respectively. The kinetic outputs of the musculoskeletal system during the simulated isokinetic exercises were evaluated with these longer/shorter moment arm lengths. It was found that longer moment arm resulted in smaller joint moment development, smaller joint power output and smaller joint work output in the larger plantarflexion angular velocity region (>120 degrees/s). This is because larger muscle shortening velocity was required with longer moment arm to achieve a certain joint angular velocity. Larger muscle shortening velocity resulted in smaller muscle force development because of the force-velocity relation of the muscle. It was suggested that this phenomenon should be taken into consideration when investigating the joint moment-joint angle and/or joint moment-joint angular velocity characteristics of experimental data.

Ankle Joint↗
PubMed1998

Comparison of two methods for computing abduction moment arms of the rotator cuff.

Biomechanical models of the shoulder mechanism require estimates of muscle moment arm magnitude. Some shoulder models have estimated muscle moment arms by assuming an idealized minimum distance path from the origin to insertion that passes around the bony geometry. Alternatively, the principle of virtual work can be used to estimate moment arms from tendon excursion and joint-angle data. The purpose of this study was to determine if these two methods give different estimates of abduction moment arms for the supraspinatus, infraspinatus, and subscapularis muscles. Muscle moment arms were estimated for these muscles on ten fresh frozen cadaver specimens. The results showed a significant difference between the two estimation methods. Average differences were 3.1 mm (10.6%), 3.9 mm (43.9%), and 7.2 mm (70.3%) for the supraspinatus, subscapularis, and infraspinatus muscles, respectively. These results suggest that shoulder models based on the origin-insertion method may give higher rotator cuff muscle force estimates than methods using the slope of the tendon excursion vs joint angle relationship.

Adult↗
PubMed1998

Increasing the moment arm of the tibialis anterior induces structural and functional adaptation: implications for tendon transfer.

Previous studies on the functional effects of tendon transfer have not examined possible muscle adaptation following transfer. The purpose of the present study was to test the hypothesis that muscle adapts to increased moment arm and excursion such that joint torque is maintained near normal levels. The moment arm and excursion of the tibialis anterior (TA) were increased by releasing the TA from its retinacular restraint at the ankle joint in growing (4-week-old) rabbits. Twelve weeks post-release, in vivo TA force during hopping was smaller in released compared with control rabbits, compensating for the increased moment arm, and thus TA torque at the ankle joint was not significantly different between groups. Physiological cross-sectional area was smaller, and the number of sarcomeres in series was larger, in the released TA compared with the control TA. These adaptations may result from chronically decreased in vivo TA force production, and chronically increased TA excursion, respectively. In addition, these adaptations were consistent with the smaller in vivo force for the released TA. Comparisons between control and sham-operated rabbits showed no significant differences for in vivo TA force, torque, or muscle architecture. Thus, muscle appears capable of adapting to increased moment arm and excursion such that joint torque is maintained near normal levels. These findings have important implications for tendon transfer procedures that increase the moment arm and/or excursion of the released muscle.

Adaptation, Physiological↗
PubMed1978

True hermaphroditism: a clinical description and a proposed function for the long arm of the Y chromosome.

True hermaphroditism is a very rare form of ambiguous genitalia characterized by the presence of both ovarian and testicular tissue in the same individual. Sixty percent of these patients have a 46,XX karyotype; however, most have H-Y antigen detectable. Since H-Y antigen is thought to be the gene product of the short arm of the Y, then the short arm must be present somewhere in the karyotype. Products of the short arm loci are thought to initiate testicular differentiation and male determination. The long arm of the Y has not been detected in true hermaphrodites. Testicular histology in true hermaphrodites is characterized by spermatogenic arrest, causing us to speculate that the long arm of the Y might be essential for germ cell maturation beyond the spermatogonia state.

Antigens↗
PubMed2001

Chlordiazepoxide specifically impairs nonspatial reference memory in the cued radial arm maze in rats.

Anxiolytic benzodiazepines, at low doses, reportedly impair the radial arm maze with nonspatial visual/tactile but not spatial cues. We replicated the former result controlling for changes in drug state and cue effectiveness. Rats learned an eight-arm radial maze with reward in only four arms. The reward varied in spatial position from trial to trial but was always cued by a piece of sandpaper at the entry to the arm. Chlordiazepoxide (5 mg/kg, ip) impaired acquisition. Rats that switched from saline during acquisition to chlordiazepoxide showed an impairment of performance that only lasted for 1 day. Removal of the cues reduced the performance of controls and switched rats to the level of the rats that received chlordiazepoxide during acquisition but did not affect the latter. These data suggest that chlordiazepoxide does indeed impair nonspatial reference memory in the radial arm maze while leaving working memory, and, possibly, spatial reference memory, intact but that the previous report of this effect was the result of a change in drug state rather than of the drug itself.

Animals↗
PubMed1986

Release from proactive interference by experimental amnesia: electroconvulsive shock improves radial-arm maze performance in rats.

Rats were trained in an eight-arm radial maze and tested using a proactive interference (PI) procedure. Each test trial consisted of forced choices of four randomly selected arms followed, after a 2-h delay, by free choices among all eight arms. Normally, rats chose correctly during the free choices by entering and retrieving food from the four arms not yet visited during the test trial. Occasionally, an interference trial preceded the test trial by 1.5 or 3 h; interference trials consisted of forced choices of another four arms and an immediate test. The presence of an interference trial lowered test-trial performance (PI). Electroconvulsive shock (ECS) administered immediately after the interference trial had no effect; i.e., PI was still observed. When ECS was administered at the midpoint of the 3-h intertrial interval, performance increased to control (no ECS, no PI) levels. Such release from PI, however, was not obtained, and test-trial performance remained inaccurate when ECS was delivered immediately after the forced choices of the test trial (either 1.5 or 3 h after the interference trial).

Amnesia↗
PubMed1987

Effects of the nicotinic receptor blocker mecamylamine on radial-arm maze performance in rats.

Lesions of cholinergic neurons have been found by many investigators to impair choice accuracy in the radial arm maze. Because muscarinic receptor blockers, such as scopolamine, have also repeatedly been found to impair choice accuracy in the radial-arm maze, it has generally been thought that the critical effect of cholinergic lesions is the deafferentation of muscarinic receptors. The possible involvement of nicotinic receptors in the cholinergic bases of cognitive performance in the radial-arm maze has not been as well investigated. The present study examined the effects of the blockade of nicotinic receptors on performance of female Sprague-Dawley rats in the radial-arm maze. Acute administration of the the nicotinic receptor blocker, mecamylamine (10 mg/kg) was found to significantly impair radial-arm maze choice accuracy. This dose also caused a significant increase in response latency in the maze. The effect on choice behavior but not locomotor speed seemed to be due to the central effects of mecamylamine, because administration of the peripheral nicotine receptor blocker, hexamethonium (20 mg/kg), did not impair choice accuracy, even though it did increase response latency to a similar degree as the 10-mg/kg dose of mecamylamine. Lower doses of mecamylamine (2.5 and 5 mg/kg) did not impair choice accuracy. These results indicate that central nicotinic as well as muscarinic cholinergic receptors are involved with cognitive functioning.

Animals↗
PubMed2002

Learning and memory in two different reward tasks in a radial arm maze in rats.

In an eight-arm radial maze, working and reference memory can be assessed simultaneously in the fixed position of reward task (FPRT) in which half of the arms are baited and their positions are fixed throughout the training trails. We characterized performance of rats in the variable position of reward task (VPRT), in which four out of eight arms were baited, but the positions were varied in every training trial. In the VPRT, the rats learned to choose all arms without any discrimination between baited and non-baited arms and the memory retention was time-dependent. The performance of rats in the FPRT was impaired by altering the spatial organization of the extramaze cues while it was not affected in the VPRT. The number of Fos-positive cells transiently increased in the cerebral cortex and hippocampus of both groups of animals during the training. Finally, bilateral lesions of the dorsal hippocampus resulted in an impairment of working memory in the FPRT and the performance of the rats in the VPRT. These results suggest that different strategies are used between the FPRT and VPRT but the hippocampus plays an important role in performance of rats trained for the VPRT as well as FPRT.

Animals↗
PubMed1997

The effects of frontal cortical lesions on remembering depend on the procedural demands of tasks performed in the radial arm maze.

We trained 24 rats to perform an eight-arm radial maze task and then assigned them with a matching procedure to one of three treatments: sham surgery or lesions of the projection areas of the mediodorsal thalamic nucleus (MDn) in the medial wall (MW) or in both the MW and rhinal sulcal (RS) areas of frontal cortex. After recovery we trained the rats to perform six tasks, beginning with the standard eight-arm task, followed by two versions of a four forced choice procedure, and then three versions of a two-choice delayed-nonmatching-to-sample (DNMTS) task. The two lesion groups performed comparably on all tasks, showing that impairments were not exacerbated by extension of the MW lesion to include all cortical areas innervated by MDn. As in previous studies, frontal animals performed the radial maze task poorly immediately after surgery but improved with subsequent training. Controlling the order of the arm entries by opening the first four gates in a random sequence had little effect on performance, although frontal animals were impaired when lengthy delays (5 or 15 min) were imposed after the last of the four forced entries. Frontal animals were not impaired on two-choice DNMTS when the arms used for training were selected at random from the eight alternatives on a trial by trial basis, even when visual cues were eliminated by darkening the room and covering the maze. Frontal animals were significantly impaired when the selection of sample and choice arms was limited to the same two alternatives on every trial. This finding may explain the reported sensitivity of DNMTS to the effects of frontal lesions when training is carried out in operant chambers.

Animals↗
PubMed1989

Differences in the induction of macrophage cytotoxicity by the specific T lymphocyte factor, specific macrophage arming factor (SMAF), and the lymphokine, macrophage activating factor (MAF).

Specific T cell factors, such as specific macrophage arming factor (SMAF), are involved in the initiation of the immune response. Induction of SMAF-producing T lymphocytes in vivo and of SMAF production by T lymphocytes in vitro is dependent on the presence of intact tumor cells, and is independent of antigen presentation by macrophages. SMAF renders peritoneal macrophages cytotoxic for tumor cells. The armed peritoneal macrophages expressed a specific cytotoxicity. However, antigen-presenting cells can trigger lymphokine-producing T lymphocytes. These T lymphocytes produce lymphokines (e.g. macrophage activating factor (MAF] that activate macrophages. The MAF-activated macrophages express a non-specific tumoricidal activity. In the present study, we investigated the difference in the induction of macrophage cytotoxicity by SMAF and MAF. The following differences were found: 1) SMAF renders peritoneal resident macrophages cytotoxic, whereas MAF could only render peritoneal exudate macrophages cytotoxic. 2) SMAF requires only a 4-h incubation with macrophages, whereas MAF activates macrophages optimally after 12 h. 3) SMAF-armed macrophages recognize only the specific target cell(s), and thus, the cytotoxicity is specific in its expression. MAF activated macrophages were non-specifically cytotoxic. 4) Lipopolysaccharide (LPS) in the culture medium did not enhance the cytotoxicity of SMAF-armed macrophages. In contrast, MAF induced tumoricidal activity was enhanced by adding LPS to the culture medium. 5) After adsorption chromatography with anti-murine interferon-gamma (IFN-gamma), the arming capacity of SMAF supernatant was not reduced, whereas the activating capacity of the MAF supernatant was significantly reduced or abrogated. After immunization of mice with allogeneic tumor cells, SMAF-producing lymphocytes were detected in the draining lymph nodes already 4 days after immunization and up to 12 days. Lymphocytes with the capacity to produce MAF were present in the draining lymph nodes 14-24 days after immunization. Our data indicate that the T cell factors SMAF and MAF can both render macrophages cytotoxic, but act in a different way and during different stages of the cellular immune response against allogeneic tumor cells.

Animals↗
PubMed2004

Effect of age on the radial arm water maze-a test of spatial learning and memory.

Aged rats show decrements in performance on cognitive tasks that require the use of spatial learning and memory. We used the 8-arm radial water maze (RAWM) to measure spatial learning as a function of age in young (6 months) and old (21 months) male F344 rats. Rats were placed in the RAWM in different start arms with the same goal arm for 3 days (five trials/day); the goal arm was changed on day 4. Old rats demonstrated spatial impairment as evidenced by increased latencies to find the hidden platform on day 4. Old rats made significantly more errors, both reference and working memory errors, than young rats on all days. It is likely that the old rats utilized non-spatial strategies to solve the task, and therefore were impaired in learning a new platform location. The RAWM is a reliable, sensitive, and powerful additional test to assess age-related spatial learning and memory deficits, combining the advantages of the Morris water maze and the radial arm maze while minimizing the disadvantages.

Aging↗
PubMed2000

Shoulder injuries in overhead athletes. The "dead arm" revisited.

The following statements summarize this article: Three distinct categories of Type 2 SLAP lesions exist: (1) anterior, (2) posterior, and (3) combined anteroposterior. Posterior Type 2 SLAP lesions have distinct clinical and anatomic features that distinguish them from anterior Type 2 SLAP lesions. Posterior and combined Type 2 SLAP lesions can be disabling to overhead-throwing athletes because of posterosuperior instability and anteroinferior pseudolaxity. The Jobe relocation test is positive with posterosuperior pain in patients with posterior or combined anterior-posterior Type 2 SLAP lesions and is negative in patients with anterior Type 2 SLAP lesions. Rotator cuff tears are frequently associated with posterior or combined anterior-posterior SLAP lesions, are lesion-location specific, and typically begin from inside the joint as undersurface tears. Repair of posterior SLAP lesions can return overhead-throwing athletes to full overhead athletic functioning. The peel-back mechanism is a likely cause of posterior Type 2 SLAP lesions. To securely repair the posterosuperior labrum to resist torsional peel-back, sulure anchors must be placed posterior to the biceps at the corner of the glenoid. The repair must be protected against external rotation past 0 degree for 3 weeks to avoid undue premature torsional stresses on the repair from the peel-back mechanism. A tight posteroinferior capsule predisposes to Type 2 SLAP lesions in overhead athletes. Shoulders at risk for the dead arm syndrome have a marked loss of internal rotation caused by contracture of the posteroinferior capsule such that less than a 180 degrees arc of rotation is achieved with the arm abducted 90 degrees (the 180 degrees rule). Type 2 SLAP lesions that cause the dead arm syndrome in overhead-throwing athletes are most likely acceleration injuries that occur in late cocking rather than deceleration injuries in follow-through. Rehabilitation of athletes with the dead arm syndrome must include the entire kinetic chain. The root cause of the dead arm syndrome is the Type 2 SLAP lesion.

Athletic Injuries↗
PubMed2003

Coactivation in arm and shoulder muscles during voluntary fixation of a single joint.

The objective of this study was to determine the organization of coactivation in the arm and shoulder muscles. Normal human subjects made alternate movements of a joint in the horizontal plane, either adduction-abduction of the second finger and shoulder, ulnar-radial deviation of the wrist, or extension-flexion of the elbow, during which they fixed a focal joint while decreasing the movement amplitude and increasing the fixation strength. They varied the fixation strength at four different levels up to the maximum. The focal-joint angle, and surface electromyograms (EMGs) from the intrinsic hand, antebrachial, upper-arm, and shoulder muscles were recorded. EMGs in the phase of fixation were quantified by integration after rectification. The degree of coactivation among the muscles was evaluated by calculating correlation coefficients across the integrated EMGs. There were correlations in the integrated EMGs among focal-joint muscles (FJMs), and also between one of the FJMs and the muscles distal and/or proximal to the FJMs: in the finger fixation between the hand and antebrachial muscles, in the wrist fixation between the antebrachial and hand/upper-arm muscles, in the elbow fixation between the upper-arm and antebrachial/shoulder muscles, and in the shoulder fixation between the shoulder and upper-arm muscles. Moderate or slight correlations were seen in muscles more distant from FJMs. Our results indicate that the longitudinal distance from FJMs in the shoulder and arm muscles is an important factor in determining levels of coactivation. This is discussed in relation to the fact that neighboring muscles share joints with FJMs.

Adolescent↗
PubMed2002

The role of vision and proprioception in the aversion of rats to the open arms of an elevated plus-maze.

The elevated plus-maze test is usually run with a short edge surrounding the open arms in order to prevent the rats from falling. The present experiment investigated the role of transparent edges differing in heights: 1 (used as control), 5, 10, 20 and 40 cm, the latter the same height as the closed arm walls. Additionally, this 40-cm high transparent edge was also studied covered by white translucent or black opaque paper. The data show that the time spent in the open arms was significantly greater when the edge height was 5, 10 or 40 cm covered by the white or black paper. However, there were no differences from the 1-cm control edge when the height was 40 cm transparent. A similar effect was observed when entries in the open arms and total entries were analyzed. The facts that there were no differences when the open arms were surrounded by 1- or 40-cm transparent edges (which allow thigmotaxis) and that the same 40-cm edge caused increases in exploratory behavior when covered by papers indicate that vision triggers aversion to open spaces.

Journal Article↗
PubMed2001

Changes in muscle moment arms following split tendon transfer of tibialis anterior and tibialis posterior.

Moment arms of tibialis anterior (TA) and tibialis posterior (TP) about the subtalar and talocrural joint axes were measured in anatomic specimens both before and after split tendon transfers. These procedures are commonly performed to correct hindfoot varus, a gait deformity that is often seen in patients with cerebral palsy, stroke, and brain injury. Split tendon transfer significantly reduced the inversion moment arms of tibialis anterior and tibialis posterior at all subtalar joint angles except for the most everted position in the case of TA. Changes in subtalar joint moment arms produced by split tendon transfer, especially those seen in TA, were variable, suggesting that the procedure may be susceptible to technical errors, especially related to balancing tensions in the medial and lateral tendon halves. Talocrural joint moment arms of both muscles were preserved following split tendon transfer. This study presents the first measurements of the moment arms of split transferred muscles. These characterizations of the mechanics of split tendon transfer will aid in the planning and assessment of these procedures.

Adult↗
PubMed2002

Rotational foot placement specifies the lever arm of the ground reaction force during the push-off phase of walking initiation.

The lever arm of the ground reaction force (GRF) about the talocrural joint axis is a functionally important indicator of the nature of foot loading. Walking initiation experiments (ten subjects; age, 23-29 years) were completed to demonstrate that rotational foot placement is a possible strategy to specify the lever arm. Externally-rotated foot placement resulted in larger lever arms during push-off. A computer simulation of push-off revealed that a decreased lever arm reduces the plantarflexion moment necessary to maintain a constant forward velocity, while increasing the required plantarflexion velocity. Shortening of the foot thus diminishes the muscular force demand but also requires high muscle fiber shortening velocities that may limit the force generating capacity of plantar flexors. Decreased plantar flexion moment and slow walking previously noted in partial-foot amputees may result from shortened lever arms in this manner.

Adult↗
PubMed2000

Comparison of C-arm CT fluoroscopy and conventional fluoroscopy for percutaneous biliary drainage procedures.

PURPOSE: To conduct a prospective randomized evaluation of C-arm computed tomography (CT) fluoroscopy for external biliary drainage procedures in comparison with conventional fluoroscopic guidance to reduce the number of transhepatic punctures as a primary endpoint. MATERIALS AND METHODS: In 18 patients with biliary obstructions, 20 external percutaneous biliary drainage procedures were prospectively performed with use of either C-arm CT fluoroscopy or conventional fluoroscopy alone. The number of hepatic punctures, procedure time, and fluoroscopy time, were analyzed separately for both methods. RESULTS: C-arm CT fluoroscopy resulted in a reduced number of transhepatic punctures, with decreased procedure and fluoroscopy times (P < .05; t test). When compared with conventional external biliary drainage procedures, a mean of 1.8+/-1 versus 4.8+/-2.8 hepatic punctures at a fluoroscopy time of 3.4+/-1.5 versus 11.4+/-7.4 minutes was required for C-arm CT fluoroscopy, while procedure times were 11+/-3.6 versus 16.2+/-9.3 minutes. CONCLUSIONS: C-arm CT fluoroscopy is associated with decreased procedure and fluoroscopy times, while fewer transhepatic punctures are required to establish external biliary drainage.

Adolescent↗