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At least 361 records · Page 20Linked to original sources
PubMed2005

Impairment-oriented training or Bobath therapy for severe arm paresis after stroke: a single-blind, multicentre randomized controlled trial.

OBJECTIVE: To study the effects of augmented exercise therapy time for arm rehabilitation as either Bobath therapy or the impairment-oriented training (Arm BASIS training) in stroke patients with arm severe paresis. DESIGN: Single blind, multicentre randomized control trial. SETTING: Three inpatient neurorehabilitation centres. SUBJECTS: Sixty-two anterior circulation ischaemic stroke patients. INTERVENTIONS: Random assignment to three group: (A) no augmented exercise therapy time, (B) augmented exercise therapy time as Bobath therapy and (C) augmented exercise therapy time as Arm BASIS training. MAIN MEASURES MAIN OUTCOME MEASURE: Fugl-Meyer arm motor score. Secondary measure: Action Research Arm Test (ARA). Ancillary measures: Fugl-Meyer arm sensation and joint motion/pain scores and the Ashworth Scale (elbow flexors). RESULTS: An overall effect of augmented exercise therapy time on Fugl-Meyer scores after four weeks was not corroborated (mean and 95% confidence interval (CI) of change scores: no augmented exercise therapy time (n=20) 8.8, 5.2-12.3; augmented exercise therapy time (n=40) 9.9, 6.8-13.9; p = 0.2657). The group who received the augmented exercise therapy time as Arm BASIS training (n=20) had, however, higher gains than the group receiving the augmented exercise therapy time as Bobath therapy (n=20) (mean and 95% CI of change scores: Bobath 7.2, 2.6-11.8; BASIS 12.6, 8.4-16.8; p = 0.0432). Passive joint motion/pain deteriorated less in the group who received BASIS training (mean and 95% CI of change scores: Bobath -3.2, -5.2 to -1.1; BASIS 0.1, -1.8-2.0; p = 0.0090). ARA, Fugl-Meyer arm sensation, and Ashworth Scale scores were not differentially affected. CONCLUSIONS: The augmented exercise therapy time as Arm BASIS training enhanced selective motor control. Type of training was more relevant for recovery of motor control than therapeutic time spent.

Arm↗
PubMed1999

Pain in the arms induced by markedly increased intravascular pressure decreases after repeated exposures to moderately increased pressures.

It is well documented that exposure to high gravitational (G)-load in the head-to-foot direction may induce arm pain. Such G-induced arm pain is of vascular origin and caused by markedly increased pressure in the arm vessels. It has been hypothesized that the arm pain is due to pressure-induced overdistension of local blood vessels. Indeed, elevation of local intravascular pressure to levels that induce considerable arm pain results in distension of both veins and arteries. There appears to be a paucity of data regarding the effects of repeatedly increasing intravascular pressure in the arms. Accordingly, the purpose of the present study was to investigate the effect of iterative exposures to moderate pressure elevations in the arm vessels (here termed "pressure training") on the pressure distension relationships of the vessels and on pressure-induced arm pain. To experimentally induce increased transmural pressure over the vessel walls of the arms we used a modified version of a method described elsewhere; this method has also proven a useful tool for simulating G-induced arm pain.

Adaptation, Physiological↗
PubMed2001

Flow-mediated dilatation following wrist and upper arm occlusion in humans: the contribution of nitric oxide.

Flow-mediated dilatation (FMD) of the brachial artery assessed by high-resolution ultrasound is widely used to measure endothelial function. However, the technique is not standardized, with different groups using occlusion of either the wrist or the upper arm to induce increased blood flow. The validity of the test as a marker of endothelial function rests on the assumption that the dilatation observed is endothelium-dependent and mediated by nitric oxide (NO). We sought to compare the NO component of brachial artery dilatation observed following wrist or upper arm occlusion. Dilatation was assessed before and during intra-arterial infusion of the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) following occlusion of (i) the wrist (distal to ultrasound probe) and (ii) the upper arm (proximal to ultrasound probe) for 5 min in ten healthy males. Dilatation was significantly greater after upper arm occlusion (upper arm, 11.62+/-3.17%; wrist, 7.25+/-2.49%; P=0.003). During L-NMMA infusion, dilatation after wrist occlusion was abolished (from 7.25+/-2.49% to 0.16+/-2.24%; P<0.001), whereas dilatation after upper arm occlusion was only partially attenuated (from 11.62+/-3.17% to 7.51+/-2.34%; P=0.006). The peak flow stimulus was similar after wrist and upper arm occlusion. We conclude that dilatation following upper arm occlusion is greater than that observed after wrist occlusion, despite a similar peak flow stimulus. L-NMMA infusion revealed that FMD following wrist occlusion is mediated exclusively by NO, while dilatation following upper arm occlusion comprises a substantial component not mediated by NO, most probably related to tissue ischaemia around the brachial artery. FMD following wrist occlusion may be a more valid marker of endothelial function than dilatation following upper arm occlusion.

Adult↗
PubMed1992

Blood lactate, glycerol and catecholamine in arm strokes, leg kicks and whole crawl strokes.

Lactate, glycerol, and catecholamine in the venous blood were determined in 8 recreational swimmers following 60 sec of supramaximal arm strokes, kicks and the whole swim. The mean velocity of a whole stroke was higher than both arm strokes and kicks, and the mean velocity of arm strokes was higher when compared with kicks. There was a significant relationship between the mean velocity of arm strokes and the whole swim (r = 0.90; p less than 0.01). Peak blood lactate in the whole swim was higher than arm strokes (p less than 0.01) and kicks (p less than 0.01), and peak blood lactate in arm strokes was higher compared to kicks (p less than 0.01). The correlation coefficients between mean velocity and peak blood lactate in arm strokes, legs kick and whole swim were r = 0.72 (p less than 0.05); r = 0.61 (n.s.) and r = 0.35 (n.s.), respectively. These results suggest (1) that lactate in the blood during the whole crawl stroke originates predominantly from the muscle groups which work the arm and (2) that glycogen included in the muscles of the upper body which is used during arm strokes was easily convertible into the propelling force during arm swim, while additional energy from the leg muscles is not fully sufficient to increase propulsion force in a linear manner.

Adolescent↗
PubMedDate not supplied

Comparison of the effects of arm position and support on blood pressure in hypertensive and normotensive subjects.

One hundred and twenty-three hypertensive patients were compared with 120 normotensive subjects, to study the effect of arm position and arm support on blood pressure (BP). The BP tended to increase from the sitting to the standing position in both groups, except when subjects were standing with the arm held out perpendicular to the body, in which case the BP decreased. The lowest standing recordings were observed when the elbow was slightly flexed and supported at this position. The highest BP was observed in the standing position with the arm hanging at the side. Differences in the systolic BP between those with the arm hanging and when it was perpendicular to the torso, or flexed and supported at the elbow were 7.45 mmHg in hypertensives (p = 0.002) and 16.35 mmHg in normotensives (p < 0.0001). Similar figures for diastolic BP were 7.84 mmHg for hypertensives (p < 0.0001) and 9.81 mmHg for normotensives (p < 0.0001). Failure to support the arm at the elbow, even when it was positioned perpendicularly to the torso, led to an increase of 4.87/4.81 mmHg in hypertensives and 7.61/2.83 mmHg in normotensives. Arm position and arm support affect the accuracy of BP measurements. The effect of arm position is more than that of arm support, although they are additive, and more in normotensives. Healthcare providers should adhere to recommended guidelines for BP measurement.

Aged↗
PubMed2005

Estimating height from arm span measurement in Malawian children.

Arm span and standing height were measured in 289 boys and 337 girls aged 6-15 years who were free from physical deformities which can affect stature or arm span. The arm span exceeded height in all age groups of boys and in older girls. At the age of 7, 11 and 12 years girls were significantly taller than the boys and had longer arm span while at the age of 15 years, the trend was opposite. The mean difference between the two anthropometric parameters for boys was 5.45 +/- 4.21 cm (t = 3.556, p < 0.001) and for girls was 4.94 +/- 4.96 cm (t = 3.542, p < 0.001). Correlation coefficient between height and arm span measurements for Malawian boys was 0.983 and for girls was 0.986. Height, arm span and height-arm span difference increased with age of children while height to arm span ratio decreased. The gender difference in height-arm span differences was only significant at the age of 15 years. Multiple regression and cross validation were performed. Height of Malawian children of both sexes can be estimated from equation: Height (cm) = 15.756 + (0.168 x age) + (0.839 x arm span) (SEE = 0.760, R2 = 0.988).

Adolescent↗
PubMed1996

Moment arm length variations of selected muscles acting on talocrural and subtalar joints during movement: an in vitro study.

The tendon excursion method was applied to estimate the moment arm length of triceps surae, flexor hallucis longus, tibialis posterior, tibialis anterior, peroneus brevis and peroneus longus at talocrural and subtalar joints of 10 anatomical preparations. Orthogonal polynomials were fitted to the tendon excursion data and by derivation with respect to the joint angle, the instantaneous moment arm length for any joint position was evaluated. Both joints were investigated separately. Individual data, the mean moment arm together with the significant moment arm coefficients of the polynomials are presented. Considering their moment arm, the most important plantar flexor were triceps surae, flexor hallucis longus and to a much lesser extent peroneus longus, peroneus brevis and tibialis posterior. Results suggest a partially new insight into the muscle action at the subtalar joint. Although displaying a mean inversion moment arm of about -5.3 mm over the whole range of motion, triceps surae had an inversion moment arm in eversion and an eversion one in inversion. Tibialis posterior exhibited the most important inversion moment arm (-19.1 mm), whereas tibialis anterior had a very low one (-3.8 mm). For some specimens this muscle was found to have an eversion moment arm. Peronei longus and brevis had a nearly identical moment arm at the subtalar joint (21.8 and 20.5 mm).

Algorithms↗
PubMed1987

Dynein arm attachment probed with a non-hydrolyzable ATP analog. Structural evidence for patterns of activity.

The dynein arms that power ciliary motility are normally permanently attached by one end exclusively to subfiber A of each axonemal doublet (N) while the other (head) end transiently attaches to the subfiber B of the adjacent doublet (N + 1) to produce sliding of the doublets. In Tetrahymena axonemes, sliding of contiguous groups of doublets is induced by ATP suggesting that, in the absence of exogenous protease, there may be sets of potentially active and potentially inactive or refractory arms in a single axoneme. In the presence of a non-hydrolyzable analog of ATP, beta,gamma-methylene adenosine 5'-triphosphate (AMP-PCP), about half the doublets in an axonemal preparation retain all arms bound to subfiber A, but half the doublets show long regions where some arms are pulled away from subfiber A of doublet N and attached to subfiber B of doublet N + 1 by their head ends. In AMP-PCP-induced splaying, positional information regarding arm state is retained. Analysis reveals that throughout regions where B subfiber attachment is found, small groups of about four subfiber B attached arms alternate with groups of about four arms that remain attached to subfiber A. This unique pattern of attachment suggests that arms function co-operatively in groups of four. Further, the repetition of the pattern is reminiscent of metachronal activity seen at higher levels of biological organization. This suggests that in these regions we have instantaneously preserved groups of arms capable of attaching to and detaching from doublet N + 1 in rapid succession. This appearance could be used to delineate the potentially active sets of arm, primed for mechanochemical activity, within an axoneme.

Adenosine Triphosphatases↗
PubMed1996

Arm width and brightness modulation of spontaneous behaviour of two strains of mice tested in the elevated plus-maze.

Amongst the nonpharmacological variables that may influence spontaneous behaviour in the elevated plus-maze, at least two (namely, the width and brightness level of the maze arms) have not been evaluated for possible consequences on baseline activity. We therefore investigated the effect of width (5, 7, or 9 cm) and brightness level (grey vs. white) of the maze arms on the activity patterns of NMRI and C57/BL 10j mice in a plus-maze based on that described by Lister. Results indicated a clear strain difference in spontaneous behaviour in the open/closed arms with C57/BL mice making no visits on the open arms of the maze. In the NMRI strain, enlarging the arms resulted in significantly increased running in open arms but brightness level did not affect behavioural parameters. In the C57/BL mice, no significant behavioural changes were detected after increasing the arm width; however, the maze with a white floor significantly increased the latency to move and decreased ambulation. Finally, employing a maze with white closed arms and open grey arms resulted in ambulation by C57/BL mice into the open arms, a behaviour not normally observed in this strain using a uniformly bright maze. The results are discussed in terms of their putative effects in pharmacological testing.

Animals↗
PubMed1985

Validation of open:closed arm entries in an elevated plus-maze as a measure of anxiety in the rat.

A novel test for the selective identification of anxiolytic and anxiogenic drug effects in the rat is described, using an elevated + -maze consisting of two open arms and two enclosed arms. The use of this test for detecting such drug effects was validated behaviourally, physiologically, and pharmacologically. Rats made significantly fewer entries into the open arms than into the closed arms, and spent significantly less time in open arms. Confinement to the open arms was associated with the observation of significantly more anxiety-related behaviours, and of significantly greater plasma corticosterone concentrations, than confinement to the closed arms. Neither novelty nor illumination was a significant contributor to the behaviour of the rats on the + -maze. A significant increase in the percentage of time spent on the open arms and the number of entries into the open arms was observed only within clinically effective anxiolytics (chlordiazepoxide, diazepam and, less effectively, phenobarbitone). Compounds that cause anxiety in man significantly reduced the percentage of entries into, and time spent on, the open arms (yohimbine, pentylenetetrazole, caffeine, amphetamine). Neither antidepressants nor major tranquilisers had a specific effect. Exposure to a holeboard immediately before placement on the + -maze showed that behaviour on the maze was not clearly correlated either with exploratory head-dipping or spontaneous locomotor activity.

Analysis of Variance↗
PubMed1987

Coordination of arm and eye movements in tracking of sinusoidally moving targets.

Human subjects tracked sinusoidally moving visual targets with arm and eyes, in absence of visual feedback of the arm. The resulting frequency responses indicated that predictive mechanisms are involved both in arm and in eye tracking, and that the respective upper frequency limits are similar. Most importantly, substantial differences between arm and eye performance were observed: At low frequencies the gain of arm, but not of eye movement was consistently smaller than 0 dB. At higher frequencies arm, but not eye gain exhibited a marked amplitude non-linearity. The intra-trial gain and phase variability of arm movement was not correlated with the respective variability of eye movement. The reaction times to sudden changes of target parameters could be considerably different for arm and eye, and their inter-trial variability was not, or only marginally, correlated. Taken together, these findings strongly suggest that the mechanisms controlling predictive arm and eye movements in our experiment are organized to a major part in independent, parallel channels. The results are discussed with reference to a simple scheme of eye-arm coordination.

Electrooculography↗
PubMed2004

Unzipping mechanism of the double-stranded DNA unwinding by a hexameric helicase: the effect of the 3' arm and the stability of the dsDNA on the unwinding activity of the Escherichia coli DnaB helicase.

The effect of two structural elements of a replication DNA fork substrate, the length of the 3' arm of the fork and the stability of the double-stranded DNA (dsDNA) part, on the kinetics of the dsDNA unwinding by the Escherichia coli hexameric helicase DnaB protein has been examined under single turnover conditions using the rapid quench-flow technique. The length of the 3' arm of the replication fork, i.e. the number of nucleotides in the arm, is a major structural factor that controls the unwinding rate and processivity of the helicase. The data show the existence of an optimal length of the 3' arm where there is the highest unwinding rate and processivity, indicating that during the unwinding process, the helicase transiently interacts with the 3' arm at a specific distance on the arm with respect to the duplex part of the DNA. Moreover, the area on the enzyme that engages in interactions has also a discrete size. For DNA substrates with the 3' arm containing 14, or less, nucleotide residues, the DnaB helicase becomes a completely distributive enzyme. However, the 3' arm is not a "specific activating cofactor" in the unwinding reaction. Rather, the 3' arm plays a role as a mechanical fulcrum for the enzyme, necessary to provide support for the advancing large helicase molecule on the opposite strand of the DNA. Binding of ATP is necessary to engage the 3' arm with the DnaB helicase, but it does not change the initial distribution of complexes of the enzyme with the DNA fork substrate. Stability of the dsDNA has a significant effect on the unwinding rate and processivity. The unwinding rate constant is a decreasing linear function of the fractional content of GC base-pairs in the dsDNA, indicating that the activation of the unwinding step is proportional to the stability of the nucleic acid.

Adenosine Triphosphate↗
PubMed1990

Asymmetric structure of a three-arm DNA junction.

We present here experimental evidence that three-arm branched DNA molecules form an asymmetric structure in the presence of Mg2+. Electrophoretic mobility and chemical and enzymatic footprinting experiments on a three-arm branched DNA molecule formed from three 16-mer strands are described. The electrophoretic mobilities of three species of a three-arm junction in which pairs of arms are extended are found to differ in the presence of Mg2+: one combination of elongated arms migrates significantly faster than the other two. This effect is eliminated in the absence of Mg2+, leading us to suggest that the three-arm DNA junction forms an asymmetric structure due to preferential stacking of two of the arms at the junction in the presence of Mg2+. The pattern of self-protection of each 16-mer strand of the core complex exposed to Fe(II).EDTA and DNase I scission is unique, consistent with formation of an asymmetric structure in the presence of Mg2+. We conclude that three-arm junctions resemble four-arm junctions in showing preferential stacking effects at the branch site. Comparison of the scission patterns of linear duplexes and the branched trimer by the reactive probes methidiumpropyl-EDTA.Fe(II) [MPE.Fe(II)] and Cu(I)-[o-phenanthroline]2 [(OP)2CuI] further indicates that the branch point represents a site of enhanced binding for drugs, as it does in the four-arm case. Reaction with diethyl pyrocarbonate (DEPC), a purine-specific probe sensitive to conformation, is enhanced at the branch site, consistent with loosening of base pairing or unpairing at this point.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMedDate not supplied

One-pot synthesis of star-shaped macromolecules containing polyglycidol and poly(ethylene oxide) arms.

Synthesis of fully hydrophilic star-shaped macromolecules with different kinds of arms (A(x)B(y)C(z)) based on polyglycidol (PGL, A(x)) and poly(ethylene oxide) (PEO, C(z)) arms and diepoxy compounds (diglycidyl ethers of ethylene glycol (DGEG) or neopentyl glycol (DGNG) in the core, B(y)) forming the core is described. Precursors of arms were prepared by polymerization of glycidol with protected -OH groups. The first-generation stars were formed in the series of consecutive-parallel reactions of arms A(x) with diepoxy compounds (B). These first-generation stars (A(x)B(y)), having approximately O-, Mt+ groups on the cores, were used as multianionic initiators for the second generation of arms (C(z)) built by polymerization of ethylene oxide. The products with M(n) up to 10(5) and having up to approximately 40 arms were obtained. The number of arms (f) was determined by direct measurements of M(n) of the first-generation stars (M(n) of arms A(x) is known), compared with f calculated from the branching index g, determined from R(g) measured with size-exclusion chromatography (SEC) triple detection with TriSEC software. The progress of the star formation was monitored by 1H NMR and SEC. These novel water-soluble stars, having a large number of hydroxyl groups, both at the ends of PEO arms as well as within the PGL arms, can be functionalized and further used for attaching compounds of interest. This approach opens, therefore, a new way of "multiPEGylation".

Chromatography, Gel↗
PubMed1996

Effects of Side Arm Length and Structure of Para-Substituted Phenyl Derivatives on Their Binding to the Host Cyclobis(paraquat-p-phenylene).

The binding constants with the host cyclobis(paraquat-p-phenylene), 1(4+), have been determined in CH(3)CN by UV-vis spectrophotometry for a series of p-phenylene guests, symmetrically substituted with side arms of varying length and functionality. Semiempirical molecular orbital theory was employed to provide a detailed structural and energetic interpretation of the experimental binding data. In particular, the length of the side arms and the type and position of the heteroatoms on the side arms were systematically varied in order to understand the effects of external interactions on the association constants of the guests with host 1(4+). A large chelate effect involving the ethyleneoxy side arm oxygen atoms and a cooperative effect between the guest aromatic core and the side arms are significant factors which determine the binding with this host. Sequential ethyleneoxy linkages along the side arms markedly increase the binding constant with respect to a compound in which the same number of oxygens along the side arms are separated by longer aliphatic linkages. In addition, a multiplicative rather than additive effect on the binding constant is observed which demonstrates that the oxygen atoms exhibit a strong chelate effect. It was also discovered that while the side arms of these guests contribute most of the driving force for complexation, an aromatic core is necessary for the guest to reside in the cavity of the host. The binding of these guests then is dependent upon cooperation between the arms and the aromatic core. Furthermore, elongation of the central aromatic core with aliphatic side arms containing no heteroatoms leaves the association constant relatively unchanged and replacement of the oxygen atoms with sulfur markedly decreases the observed binding. These effects have been used to rationalize several observations regarding this system in the literature and may serve to improve the design of new supramolecular systems and to better understand the host/guest interaction process.

Journal Article↗
PubMed1993

A Chlamydomonas outer arm dynein mutant with a truncated beta heavy chain.

A new allele of the Chlamydomonas oda4 flagellar mutant (oda4-s7) possessing abnormal outer dynein arms was isolated. Unlike the previously described oda4 axoneme lacking all three (alpha, beta, and gamma) outer-arm dynein heavy chains, the oda4-s7 axoneme contains the alpha and gamma heavy chains and a novel peptide with a molecular mass of approximately 160 kD. The peptide reacts with a mAb (18 beta B) that recognizes an epitope on the NH2-terminal part of the beta heavy chain. These observations indicate that this mutant has a truncated beta heavy chain, and that the NH2-terminal part of the beta heavy chain is important for the stable assembly of the outer arms. In averaged electron microscopic images of outer arms from cross sections of axonemes, the mutant outer arm lacks its mid-portion, producing a forked appearance. Together with our previous finding that the mutant oda11 lacks the alpha heavy chain and the outermost portion of the arm (Sakakibara, H., D. R. Mitchell, and R. Kamiya. 1991. J. Cell Biol. 113:615-622), this result defines the approximate locations of the three outer arm heavy chains in the axonemal cross section. The swimming velocity of oda4-s7 is 65 +/- 8 microns/s, close to that of oda4 which lacks the entire outer arm (62 +/- 8 microns/s) but significantly lower than the velocities of wild type (194 +/- 23 microns/s) and oda11 (119 +/- 17 microns/s). Thus, the lack of the beta heavy chain impairs outer-arm function more seriously than does the lack of the alpha heavy chain, suggesting that the alpha and beta chains play different roles in outer arm function.

Alleles↗
PubMed1996

The sup-pf-2 mutations of Chlamydomonas alter the activity of the outer dynein arms by modification of the gamma-dynein heavy chain.

The sup-pf-2 mutation is a member of a group of dynein regulatory mutations that are capable of restoring motility to paralyzed central pair or radial spoke defective strains. Previous work has shown that the flagellar beat frequency is reduced in sup-pf-2, but little else was known about the sup-pf-2 phenotype (Huang, B., Z. Ramanis, and D.J.L. Luck. 1982. Cell. 28:115-125; Brokaw, C.J., and D.J.L. Luck. 1985. Cell Motil. 5:195-208). We have reexamined sup-pf-2 using improved biochemical and structural techniques and by the analysis of additional sup-pf-2 alleles. We have found that the sup-pf-2 mutations are associated with defects in the outer dynein arms. Biochemical analysis of sup-pf-2-1 axonemes indicates that both axonemal ATPase activity and outer arm polypeptides are reduced by 40-50% when compared with wild type. By thin-section EM, these defects correlate with an approximately 45% loss of outer dynein arm structures. Interestingly, this loss is biased toward a subset of outer doublets, resulting in a radial asymmetry that may reflect some aspect of outer arm assembly. The defects in outer arm assembly do not appear to result from defects in either the outer doublet microtubules or the outer arm docking structures, but rather appear to result from defects in outer dynein arm components. Analysis of new sup-pf-2 mutations indicates that the severity of the outer arm assembly defects varies with different alleles. Complementation tests and linkage analysis reveal that the sup-pf-2 mutations are alleles of the PF28/ODA2 locus, which is thought to encode the gamma-dynein heavy chain subunit of the outer arm. The sup-pf-2 mutations therefore appear to alter the activity of the outer dynein arms by modification of the gamma-dynein heavy chain.

Alleles↗
PubMed1978

Structural conformation of ciliary dynein arms and the generation of sliding forces in Tetrahymena cilia.

The sliding tubule model of ciliary motion requires that active sliding of microtubules occur by cyclic cross-bridging of the dynein arms. When isolated, demembranated Tetrahymena cilia are allowed to spontaneously disintegrate in the presence of ATP, the structural conformation of the dynein arms can be clearly resolved by negative contrast electron microscopy. The arms consist of three structural subunits that occur in two basic conformations with respect to the adjacent B subfiber. The inactive conformation occurs in the absence of ATP and is characterized by a uniform, 32 degrees base-directed polarity of the arms. Inactive arms are not attached to the B subfiber of adjacent doublets. The bridged conformation occurs strictly in the presence of ATP and is characterized by arms having the same polarity as inactive arms, but the terminal subunit of the arms has become attached to the B subfiber. In most instances the bridged conformation is accompanied by substantial tip-directed sliding displacement of the bridged doublets. Because the base-directed polarity of the bridged arms is opposite to the direction required for force generation in these cilia and because the bridges occur in the presence of ATP, it is suggested that the bridged conformation may represent the initial attachment phase of the dynein cross-bridge cycle. The force-generating phase of the cycle would then require a tip-directed deflection of the arm subunit attached to the B subfiber.

Animals↗