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At least 55 records · Page 3Linked to original sources
PubMed2001

Transport and arrangement of the outer-dynein-arm docking complex in the flagella of Chlamydomonas mutants that lack outer dynein arms.

The outer dynein arms of Chlamydomonas flagella are attached to a precise site on the outer doublet microtubules and repeat at a regular interval of 24 nm. This binding is mediated by the outer dynein arm docking complex (ODA-DC), which is composed of three protein subunits. In this study, antibodies against the 83- and 62-kD subunits (DC83 and DC62) of the ODA-DC were used to analyze its state of association with outer arm components within the cytoplasm, and its localization in the axonemes of oda mutants. Immunoprecipitation indicates that DC83 and DC62 are preassembled within the cytoplasm, but that they are not associated with outer arm dynein. Both proteins are lost or greatly diminished in oda1 and oda3, mutants in the structural genes of DC62 and DC83, respectively, demonstrating that their association is necessary for their stable presence in the cytoplasm. Immunoelectron microscopy indicates that DC83 repeats at 24-nm intervals along the length of the doublet microtubules of oda6, which lacks outer arms; thus, outer arm periodicity may be determined by the ODA-DC. Flagellar regeneration and temporary dikaryon experiments indicate that the ODA-DC can be rapidly transported into the flagellum and assembled on the doublet microtubules independently of the outer arms and independently of flagellar growth. Unexpectedly, the intensity of ODA-DC labeling decreased toward the distal ends of axonemes of oda6 but not wild-type cells, suggesting that the outer arms reciprocally contribute to the assembly/stability of the ODA-DC.

Animals↗
PubMed1987

Bending patterns of Chlamydomonas flagella: IV. Mutants with defects in inner and outer dynein arms indicate differences in dynein arm function.

Mutants with outer dynein arm defects or deficiencies all show a major reduction in beat frequency to about half the normal value; some of these mutants show an additional decrease in sliding velocity associated with reduced shear amplitude and an additional reduction in beat frequency, as well as other more minor modifications of the normal forward mode bending pattern. New mutants (ida98, pf30), which appear to be deficient in a subset of inner dynein arms show a reduction in sliding velocity that is primarily associated with a reduction in shear amplitude, with only a small reduction in beat frequency. These differences in motility phenotype between inner and outer dynein arm mutants suggest that inner and outer dynein arms may have distinct functions. The relatively large decrease in sliding velocity associated with partial loss of inner arms is consistent with earlier observations on pf23, a nonmotile mutant lacking inner arms, suggesting that inner arms may have an essential function in motility. The ability to generate reverse mode bending patterns is retained in some inner or outer dynein arm mutants, but appears to be decreased in those mutants which show reduced shear amplitude for the forward mode bending pattern.

Adenosine Triphosphatases↗
PubMed1993

Role of the D arm and the anticodon arm in tRNA recognition by eubacterial and eukaryotic RNase P enzymes.

Truncated precursor tRNAs lacking the D arm or anticodon arm were studied in vitro as substrates for RNase P enzymes from Escherichia coli, Thermus thermophilus (eubacteria), and HeLa. Deletion of the D arm still allowed 5'-processing by E. coli RNase P, but strongly impaired maturation by T. thermophilus and HeLa extracts. In contrast, deletion of the anticodon arm had no influence on processing by RNase P activities from all three organisms. Inhibition kinetics and gel retardation studies showed that deletion of the D arm leads to low-affinity binding to E. coli RNase P RNA (M1 RNA). However, the E. coli enzyme appears to form sufficiently strong contacts in the region of the T arm, acceptor stem, and CCA terminus to still allow productive enzyme-substrate interaction even in the absence of the structural contribution provided by the D arm. Pb(2+)-induced hydrolysis of a tRNAGly from T. thermophilus gave identical cleavage patterns in the D arm and anticodon loop in the absence and presence of E. coli M1 RNA, whereas lead hydrolysis was strongly reduced at the CUCCAA 3'-terminus due to the presence of the enzyme.

Anticodon↗
PubMed2005

{alpha}-Syntrophin regulates ARMS localization at the neuromuscular junction and enhances EphA4 signaling in an ARMS-dependent manner.

EphA4 signaling has recently been implicated in the regulation of synapse formation and plasticity. In this study, we show that ankyrin repeat-rich membrane spanning (ARMS; also known as a kinase D-interacting substrate of 220 kD), a substrate for ephrin and neurotrophin receptors, was expressed in developing muscle and was concentrated at the neuromuscular junction (NMJ). Using yeast two-hybrid screening, we identified a PDZ (PSD-95, Dlg, ZO-1) domain protein, alpha-syntrophin, as an ARMS-interacting protein in muscle. Overexpression of alpha-syntrophin induced ARMS clustering in a PDZ domain-dependent manner. Coexpression of ARMS enhanced EphA4 signaling, which was further augmented by the presence of alpha-syntrophin. Moreover, the ephrin-A1-induced tyrosine phosphorylation of EphA4 was reduced in C2C12 myotubes after the blockade of ARMS and alpha-syntrophin expression by RNA interference. Finally, alpha-syntrophin-null mice exhibited a disrupted localization of ARMS and EphA4 at the NMJ and a reduced expression of ARMS in muscle. Altogether, our findings suggest that ARMS may play an important role in regulating postsynaptic signal transduction through the syntrophin-mediated localization of receptor tyrosine kinases such as EphA4.

Animals↗
PubMed1996

Organization of octopus arm movements: a model system for studying the control of flexible arms.

Octopus arm movements provide an extreme example of controlled movements of a flexible arm with virtually unlimited degrees of freedom. This study aims to identify general principles in the organization of these movements. Video records of the movements of Octopus vulgaris performing the task of reaching toward a target were studied. The octopus extends its arm toward the target by a wave-like propagation of a bend that travels from the base of the arm toward the tip. Similar bend propagation is seen in other octopus arm movements, such as locomotion and searching. The kinematics (position and velocity) of the midpoint of the bend in three-dimensional space were extracted using the direct linear transformation algorithm. This showed that the bend tends to move within a single linear plane in a simple, slightly curved path connecting the center of the animal's body with the target location. Approximately 70% of the reaching movements demonstrated a stereotyped tangential velocity profile. An invariant profile was observed when movements were normalized for velocity and distance. Two arms, extended together in the same behavioral context, demonstrated identical velocity profiles. The stereotyped features of the movements were also observed in spontaneous arm extensions (not toward an external target). The simple and stereotypic appearance of the bend trajectory suggests that the position of the bend in space and time is the controlled variable. We propose that this strategy reduces the immense redundancy of the octopus arm movements and hence simplifies motor control.

Animals↗
PubMed1988

Oculo-manual tracking of visual targets in monkey: role of the arm afferent information in the control of arm and eye movements.

The study was aimed at defining the role of hand (and arm) kinaesthetic information in coordination control of the visuo-oculo-manual tracking system. Baboons were trained to follow slow-moving and stepping visual targets either with the eyes alone or with the eyes and a lever moved by the forelimb about the vertical axis. A LED was attached to the lever extremity. Four oculo-manual tracking conditions were tested and compared to eye-alone tracking: Eye and hand tracking of a visual target presented on a screen, eye tracking of the hand, and eye tracking of an imaginary target actively moved by the arm. The performance of the animals evaluated in terms of latency, and velocity and position precision for both eye and hand movements was seen to be equivalent to that of humans in similar situations. After dorsal root rhizotomy (C1-T2) the animals were unable to produce slow arm motion in response to slow-moving targets. Instead, they produced successions of ballistic-like motions whose amplitude decreased as retraining proceeded. In addition, the animals could no longer respond with smooth pursuit eye movements to an imaginary target actively displaced by the animal's forelimb. It was concluded that the absence of ocular smooth pursuit after lesion results from the disruption of a signal derived from arm kinaesthetic information and addresses to the oculomotor system. This signal is likely to be used in the control of coordination between arm and eye movements during visuo-oculo-manual tracking tasks. One cause of the animal's inability to achieve slow arm movement in response to slow target motion is thought to be due to a lesion-induced alteration of the spinal common pathway dynamics which normally integrate the velocity signal descending from the arm movement command system.

Afferent Pathways↗
PubMed1997

Role of arm proprioception in calibrating the arm-eye temporal coordination.

When subjects track with the eyes an arm-attached target, eye latency is shorter than when tracking an external target. This improved synchrony could result from either a common command addressed to the two systems or from an influence of the arm command on eye motion initiation. According to the first hypothesis, the eyes should start moving long before the arm, because of the difference in dynamics. We recorded arm and eye motion together with biceps muscle activity in controls and a deafferented subject. Data support the second hypothesis. Moreover, the deafferented subject showed a lesser correlation between arm and eye motions than controls, suggesting a role for arm proprioception in the calibration of the temporal relationship between arm and eye movements.

Adult↗
PubMed2005

Evaluation of skilled arm movements in patients with stroke using a computerized motor-skill analyser for the arm.

To study the utility of a new computerized motor-skill analyser (CMSA) for evaluating visuo-motor skilled movements of the arm, we examined (1) the reproducibility of measurement with the CMSA for the arm in 13 healthy participants and 14 patients with stroke and (2) the correlation between motor skills of the affected arm evaluated with the CMSA and clinical tests for upper extremity function in 20 patients with stroke. The CMSA for the arm was used to calculate the accuracy in tracking with the hand. The inter-class correlation coefficients for lap time, geometric trajectory error, trajectory error integrated over time and the marker trajectory error integrated over time were 0.45 (NS)-0.91 (P<0.01) in healthy participants and 0.62 (P<0.05)-0.90 (P<0.01) in patients with stroke. The trajectory error integrated over time and the geometric errors of the affected arm in stroke patients were negatively correlated with the Brunnstrom stage and the simple test for evaluating hand function. The marker trajectory error integrated over time in stroke patients was negatively correlated with the simple test for evaluating hand function. These results suggest that the CMSA for the arm is useful for quantitatively evaluating delicate visuo-motor skills of the arm.

Adult↗
PubMed1988

Metabolic and heart rate responses to submaximal arm lever and arm crank ergometry.

Previous studies have shown that arm cranks and arm levers, working as propulsion mechanisms for nonambulatory individuals, may have mechanical and physiologic advantages over standard handrim wheelchairs. This study evaluated physiologic responses to arm lever and arm crank ergometry using identical workloads. An arm lever ergometer (ALE) was constructed and adapted to an arm crank ergometer (ACE) so that equal workloads could be applied with both ergometers. Fifteen able-bodied men and 15 able-bodied women exercised at a low (15 watts) and a high (45 watts) workload, with a three-minute rest interval. While exercising at each level, oxygen consumption (VO2), minute ventilation (VE), and heart rate (HR) were monitored. When low workloads with ALE and ACE were compared, no significant differences (p greater than 0.05) were demonstrated in any of the variables for men or women. For the men, at the high workload, the ALE elicited significantly lower (p less than 0.05) VO2 (by 9.8%), HR (by 6.3%), and VE (by 7.5%), than did the ACE. For the women, at the high workload, VO2 was significantly lower (p less than 0.05) (by 7.6%) with the ALE, as was VE (by 7.5%), but HR, although 3.3% lower with the ALE, was not significantly different (p greater than 0.05) from the ACE. These data suggest that the ALE is physiologically less stressful than the ACE at high workloads. Arm levers may, therefore, provide an advantage for handicapped persons when they propel themselves in wheelchairs.

Arm↗
PubMed2006

Molecular characterization of Ciona sperm outer arm dynein reveals multiple components related to outer arm docking complex protein 2.

Using proteomic and immunochemical techniques, we have identified the light and intermediate chains (IC) of outer arm dynein from sperm axonemes of the ascidian Ciona intestinalis. Ciona outer arm dynein contains six light chains (LC) including a leucine-rich repeat protein, Tctex1- and Tctex2-related proteins, a protein similar to Drosophila roadblock and two components related to Chlamydomonas LC8. No LC with thioredoxin domains is included in Ciona outer arm dynein. Among the five ICs in Ciona, three are orthologs of those in sea urchin dynein: two are WD-repeat proteins and the third one, unique to metazoan sperm flagella, contains both thioredoxin and nucleoside diphosphate kinase modules. The remaining two Ciona ICs have extensive coiled coil structure and show sequence similarity to outer arm dynein docking complex protein 2 (DC2) that was first identified in Chlamydomonas flagella. We recently identified a third DC2-like protein with coiled coil structure, Ci-Axp66.0 that is also associated in substoichiometric amounts with Ciona outer arm dynein. In addition, Oda5p, a component of an additional complex required for assembly of outer arm dynein in Chlamydomonas flagella, also groups with this family of DC2-like proteins. Thus, the assembly of outer arm dynein onto doublet microtubules involves multiple coiled-coil proteins related to DC2.

Animals↗
PubMedDate not supplied

A comparison of immediate postreduction splinting constructs for controlling initial displacement of fractures of the distal radius: a prospective randomized study of long-arm versus short-arm splinting.

PURPOSE: To compare, in a prospective, randomized manner, the sugar tong splint with a short-arm radial gutter splint in terms of patient satisfaction and the ability to maintain reduction of distal radius fractures. METHODS: A total of 118 patients with displaced distal radius fractures were enrolled; 85 patients (85 fractures) were available for follow-up evaluation and were included in the study population. There were 26 men and 59 women with a mean age of 64 years. Thirty-eight fractures were immobilized in a short-arm radial gutter splint and 47 in a sugar tong splint. Forty fractures had a stable pattern and 45 had an unstable fracture pattern. The initial patient follow-up examination occurred a mean of 8 days after splint application. RESULTS: A total of 33 fractures showed loss of fracture reduction at the initial follow-up evaluation. Sixteen of 38 fractures immobilized with the radial gutter splint displaced, whereas displacement was seen in 17 of 47 fractures immobilized with a sugar tong splint; this difference was not significant. When the splint constructs were evaluated based on fracture stability no differences were found between the splints' ability to maintain fracture reduction in both stable and unstable displaced fractures. Patients in the short-arm radial gutter splint group had significantly better Disabilities of the Arm, Shoulder, and Hand scores than those patients whose fractures were immobilized with a sugar tong splint. CONCLUSIONS: Both the sugar tong splint and the short-arm radial gutter splint had comparable performance in maintaining the initial reduction of distal radius fractures, with the short-arm splint tolerated better by patients. Based on our study we recommend the use of a short-arm radial gutter splint for initial immobilization of displaced distal radius fractures. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic, level II.

Adult↗
PubMed1995

The 78,000 M(r) intermediate chain of Chlamydomonas outer arm dynein isa WD-repeat protein required for arm assembly.

We have isolated and sequenced a full-length cDNA clone encoding the 78,000 Mr intermediate chain (IC78) of the Chlamydomonas outer arm dynein. This protein previously was shown to be located at the base of the solubilized dynein particle and to interact with alpha tubulin in situ, suggesting that it may be involved in binding the outer arm to the doublet microtubule. The sequence predicts a polypeptide of 683 amino acids having a mass of 76.5 kD. Sequence comparison indicates that IC78 is homologous to the 69,000 M(r) intermediate chain (IC69) of Chlamydomonas outer arm dynein and to the 74,000 M(r) intermediate chain (IC74) of cytoplasmic dynein. The similarity between the chains is greatest in their COOH-terminal halves; the NH(2)-terminal halves are highly divergent. The COOH-terminal half of IC78 contains six short imperfect repeats, termed WD repeats, that are thought to be involved in protein-protein interactions. Although not previously reported, these repeated elements also are present in IC69 and IC74. Using the IC78 cDNA as a probe, we screened a group of slow-swimming insertional mutants and identified one which has a large insertion in the IC78 gene and seven in which the IC78 gene is completely deleted. Electron microscopy of three of these IC78 mutants revealed that each is missing the outer arm, indicating that IC78 is essential for arm assembly or attachment to the outer doublet. Restriction fragment length polymorphism mapping places the IC78 gene on the left arm of chromosome XII/XIII, at or near the mutation oda9, which also causes loss of the outer arm. Mutants with defects in the IC78 gene do not complement the oda9 mutation in stable diploids, strongly suggesting that ODA9 is the structural gene for IC78.

Amino Acid Sequence↗
PubMedDate not supplied

Integration of olfactory information in a spatial representation enabling accurate arm choice in the radial arm maze.

The aim of the present study was to determine whether and how rats can use local olfactory cues for spatial orientation. Rats were trained in an eight-arm radial maze under different conditions as defined by the presence or absence of supplementary olfactory cues marking each arm, the availability of distant visuospatial information, and the illumination of the maze (light or darkness). The different visual conditions were designed to dissociate among the effects of light per se and those of visuospatial cues, on the use of olfactory cues for accurate arm choice. Different procedures with modifications of the arrangement of olfactory cues were used to determine if rats formed a representation of the spatial configuration of the olfactory cues and if they could rely on such a representation for accurate arm choice in the radial maze. The present study demonstrated that the use of olfactory cues to direct arm choice in the radial arm maze was critically dependent on the illumination conditions and implied two different modes of processing of olfactory information according to the presence or the absence of light. Olfactory cues were used in an explicit manner and enabled accurate arm choice only in the absence of light. Rats, however, had an implicit memory of the location of the olfactory cues and formed a representation of the spatial position of these cues, whatever the lighting conditions. They did not memorize the spatial configuration of the olfactory cues per se but needed these cues to be linked to the external spatial frame of reference.

Animals↗
PubMed2002

One-arm hop test: reliability and effects of arm dominance.

STUDY DESIGN: Test-retest reliability analysis and 2-factor ANOVA contrast of athletic group and limb dominance. OBJECTIVES: To determine the reliability of the one-arm hop test and the effects of upper-extremity dominance on test scores for 2 athletic groups. BACKGROUND: Limited information is available regarding functional performance tests of the upper extremity that involve axial loading. METHODS AND MEASURES: Thirteen male collegiate wrestlers (mean age, 20.3 +/- 1.6 years) and 13 male collegiate football players (mean age, 20.0 +/-1.7 years) without upper-extremity pathology participated in the study. Subjects were trained to perform the one-arm hop test, starting from a one-arm push-up position and then hopping as quickly as possible onto and off of a 10.2-cm platform 5 times. Subjects returned to the test site 1 to 2 days later and were timed for 2 trials of the one-arm hop test for each upper extremity. RESULTS: Within-session ICC2,1 reliability values were 0.78 for the football players and 0.81 for the wrestlers. Mean absolute differences between trials were 0.64 seconds for the football players and 0.47 seconds for the wrestlers. Trial 2 performance times were significantly faster than trial 1 times for the wrestlers. Although performance time for the nondominant side was on average 4.4% slower than that of the dominant side, performance times for the dominant side were not significantly different from those of the nondominant upper extremities. CONCLUSIONS: The results provide preliminary evidence that the one-arm hop test may be a reliable upper-extremity functional performance test with sufficient training of the subject. Uninjured upper-extremity performance for the one-arm hop test may be useful as a basis for comparing performance of an injured contralateral upper extremity.

Adult↗
PubMed1993

Magnetic stimulation: C-8 root standardization based on arm length and arm position.

Normal values for C-8 root distal latencies (DL) by magnetic stimulation (Magstim) have been reported; however, the methods of standardization have failed to consider the variables of arm length and arm position. Consequently, an artificial widening of the "normal" range occurs due to a false elevation of the standard deviation. In this study, Magstim of the C-8 nerve root was performed on 30 normal volunteers. Gender, hand temperature, age, arm length, and DL with the arm resting at the patient's side and fully abducted were recorded. DL was 13.3 +/- 1.1 ms with a side-to-side variation of 0.3 +/- 0.3 ms. The difference in DL between the arm at rest and in full abduction was 0.2 +/- 0.3 ms. Data analysis also demonstrated a direct correlation between arm length and DL. Utilizing this information a formula has been derived to more accurately describe the normal distribution of the C-8 root DL by Magstim.

Adult↗
PubMed1994

Is there an optimal arm posture? Deterioration of finger localization precision and comfort sensation in extreme arm-joint postures.

Processing of joint redundancy is one of the most important problems in motor control. For instance, gaze orientation can be obtained with an infinite number of eye and head combinations. It has been proposed that a solution to this problem might be the minimization of eye and head position-signal errors. For arm movements, where the excess of degrees of freedom is even higher, cost function was proposed as a criterion for movement selection, reflecting some comfort variable evoked from the peripheral inputs, e.g. optimal muscular energy cost or glucose consumption. However, no biological implication of comfort on motor control has yet been demonstrated. We have further investigated this approach by hypothesizing that arm posture choice also relies on a minimization of position-signal errors arising from individual joints. The prediction is that accuracy of fingertip localization by pointing made by the contralateral hand would be enhanced for comfortable postures of the target arm and degraded for uncomfortable postures using extreme joint positions. Results show an increase in pointing variability when extreme joint postures are used (wrist flexion, shoulder elevation, or both). This increase in pointing variability is proportional to the increase in subjective discomfort rating. Individual joint effects can be added arithmetically into a whole arm value for both discomfort rating and pointing variable and constant error. These results suggest that the choice of comfortable postures for the arm corresponds to an optimization of arm position-signal reliability. This new constraint might be a useful tool for further investigation on posture or trajectory formation.

Arm↗
PubMed1987

Effects of arm acceleration and behavioral conditions on the organization of postural adjustments during arm flexion.

Nine standing subjects performed unilateral arm flexion movements over an eight-fold range of speeds, under two behavioral conditions. In the visually-guided condition, a visual target informed subjects about the correct movement speed. Seven subjects also made movements of different speeds during a self-paced condition, without a visual target. Angular displacement and acceleration of the arm, and EMG activity from the hamstrings (HM), erector spinae (ES) and the anterior deltoid (AD) muscles were measured. The following results were observed. Mean rectified amplitudes of EMG activity in HM and ES were typically correlated with the average arm acceleration and presumably the disturbance to posture and/or balance. HM and ES amplitudes were correlated for only six subjects. Functions relating the ratios of HM/ES EMG amplitudes to acceleration varied between subjects. HM onset latencies were highly variable for slow movements and usually lagged movement. For movements above a threshold-like point in acceleration, HM latencies were correlated with arm acceleration and recruited before movement. ES latencies were constant for fast movements, and negatively correlated with acceleration for slower movements. The recruitment order of HM and AD was influenced by the behavioral condition but not by arm acceleration for fast movements. HM and AD were recruited coincidentally for visually-guided movements, while for self-paced movements, HM was recruited before AD. We conclude that for the arm flexion task: HM and ES are not tightly coupled; both behavioral and mechanical conditions affect the recruitment of postural muscles; and postural and focal components of the movement are probably organized by parallel processes.

Acceleration↗
PubMed2003

Modulation of cutaneous reflexes in arm muscles during walking: further evidence of similar control mechanisms for rhythmic human arm and leg movements.

Stimulation of cutaneous nerves innervating the hand evokes prominent reflexes in many arm muscles during arm cycling. We hypothesized that the mechanisms controlling reflex modulation during the rhythmic arm swing of walking would be similar to that documented during arm cycling. Thus, we expected cutaneous reflexes to be modulated by position in the walking cycle (phase dependence) and be different when walking compared to contraction while standing (task dependence). Subjects performed static postures similar to those occurring during walking and also walked on a treadmill while the superficial radial nerve was electrically stimulated pseudorandomly throughout the step cycle. EMG was recorded bilaterally from upper limb muscles and kinematic recordings were obtained from the elbow and shoulder joints. Step cycle information was obtained from force-sensing insoles. Analysis was conducted after averaging contingent upon the occurrence of stimulation in the step cycle. Phase-dependent modulation of cutaneous reflexes at early (approximately 50-80 ms) and middle (approximately 80-120 ms) latencies was observed. Coordinated bilateral reflexes were seen in posterior deltoid and triceps brachii muscles. Task dependency was seen in that reflex amplitude was only correlated with background EMG during static contraction (75% of comparisons for both early and middle latency reflexes). During walking, no significant relationship between reflex amplitude and background EMG level was found. The results show that cutaneous reflex modulation during rhythmic upper limb movement is similar to that seen during arm cycling and to that observed in leg muscles during locomotion. These results add to the evidence that, during cyclical movements of the arms and legs, similar neural mechanisms observed only during movement (e.g. central pattern generators) control reflex output.

Adolescent↗