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PubMed1983

Reserpine-induced rigidity in rats: drug effects on muscle tone from corpus striatum and nucleus accumbens.

A study of the pathophysiological mechanisms of reserpine rigidity with the aid of a mechanographic method for the quantification of muscle tone. Apomorphine was used as a test substance to reduce reserpine rigidity by stimulation of dopamine receptors. Some experiments were made with additional drug treatment in an attempt to ascertain the dopaminergic specificity of the test. Apomorphine injected bilaterally to the corpus striatum has been shown to counteract the rigidity [6]. Microinjections of reserpine to corpus striatum induced rigidity with dominance in the hindleg ipsilateral to the side of injection. This rigidity was reduced by subcutaneous apomorphine. The effect of subcutaneous apomorphine on the rigidity was blocked by prior microinjection of trifluoperazine to the corpus striatum. Injections to nucleus accumbens were ineffective in all these respects. It is concluded that reserpine induces rigidity mainly by interference with the dopamine transmission in the corpus striatum.

5-Hydroxytryptophan↗
PubMed1987

Reversal of opioid-induced muscular rigidity in rats: evidence for alpha-2 adrenergic involvement.

Compounds from several different pharmacological classes were tested for their ability to reverse the muscular rigidity induced by an intravenous dose of fentanyl that also caused loss of the righting reflex (LOR). Opioid antagonists reversed the entire syndrome--LOR and rigidity but, generally, rigidity could be reversed nonspecifically by doses of compounds that caused LOR by themselves (e.g., CNS depressants). Muscle relaxants and agonists of histamine, which appeared to be acting peripherally, were also effective. On the other hand, serotonergic drugs and dopamine agonists were not. However, dopaminergic antagonists with adrenolytic activity (i.e., chlorpromazine, haloperidol) reversed rigidity, whereas sulpiride did not. Moreover, rigidity reversed by neuroleptics could be restored by piperoxane, an alpha-2 adrenergic antagonist. In addition, clonidine and other alpha-2 agonists selectively reversed only rigidity following systemic or central administration at doses several orders of magnitude lower than other compounds tested. It is proposed that opioid-induced rigidity is reversed by inhibition of sympathoadrenal outflow which can be accomplished selectively, centrally, by alpha-2 agonists.

Adrenergic alpha-Agonists↗
PubMed1993

Automated method for the measurement of fentanyl-induced muscular rigidity.

An automated method is described that can accurately and reliably measure weight displacement resulting from hindlimb extension due to muscular rigidity following opioid administration in rats. IV administration of fentanyl (0.035 mg/kg) immediately induced rigidity. Rigidity was dose dependently reversed by the alpha 2-agonist clonidine with an ED50 value equal to 0.011 mg/kg IV. Second, rigidity was restored following administration of the alpha 2-antagonist idazoxan (0.3 mg/kg, IV) thereby confirming an alpha 2-mediated mechanism of action. Previously, reversal of fentanyl-induced muscular rigidity was measured by subjective rating criteria not suitable for quantitative potency comparisons. The new automated rigidity model provides a simple yet precise measurement of the ability of alpha 2-agonists to attenuate opioid-induced muscular rigidity in rats.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1994

Atipamezole, an alpha 2 antagonist, augments opiate-induced muscle rigidity in the rat.

Atipamezole is a new, highly selective alpha2-adrenoceptor antagonist currently undergoing clinical trials as an antagonist for dexmedetomidine, a potent alpha2 agonist with sedative and analgesic properties. It has previously been demonstrated that dexmedetomidine, acting at central alpha2 adrenoceptors, antagonizes opiate-induced muscle rigidity. However, the role of endogenous alpha2-adrenergic systems in opiate-induced rigidity remains to be elucidated. The present study was designed to assess the effects of atipamezole on basal muscle tone and on alfentanil-induced muscle rigidity in the rat. Muscle tone was measured using gastrocnemius electromyography (EMG). After a 15-min baseline, saline or atipamezole (0.3 or 1.0 mg/kg) was administered, and 10 min later, saline or alfentanil (50, 150, or 300 micrograms/kg) was injected subcutaneously. Data were collected for an additional 60 min. Atipamezole (1.0 mg/kg) pretreatment (in the absence of alfentanil) produced a small increase in tonic EMG activity when compared with saline pretreatment. After saline pretreatment, significant muscle rigidity occurred in the two highest alfentanil dose groups. Atipamezole (0.3 and 1.0 mg/kg) augmented alfentanil-induced muscle rigidity. The ability of the alpha2 antagonist to potentiate both basal muscle tone and alfentanil-induced rigidity suggests that endogenous adrenergic activity and/or direct alpha2-adrenoceptor interaction with opioid receptors mediate opiate-induced muscle rigidity. These findings may be of clinical as well as basic neuropharmacological interest.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1993

Stretch reflexes of individual parkinsonian patients studied during changes in clinical rigidity following medication.

Stretch reflexes were elicited in flexor carpi radialis (FCR) of healthy subjects and patients with Parkinson's disease by forcible ramp and hold extensions of the wrist joint. Individual patients were studied off treatment when rigidity was detected clinically at the joint and throughout the clinical response to anti-parkinsonian medication that abolished or reduced their rigidity. In this way the possible effects of inter-subject variability upon the relationship between reflex behaviour and rigidity were eliminated. The long-latency (M2) stretch reflexes of the patient group were increased on average compared to those of healthy subjects. However, in the large majority of individual patients there were no significant correlations between the amplitudes of their M2 or total (short-latency (M1) + M2) reflex activities, recorded off and on treatment, and the accompanying changes in clinically assessed rigidity. These results suggest that parkinsonian rigidity cannot be uniquely attributed to the increased reflex responsiveness measured by the present laboratory techniques. However, the techniques used to test reflex function in our study differed in several respects (e.g., background activity, stretching wave form) from those employed during clinical assessment of rigidity so that the balance of reflex mechanisms may have varied in the two situations. Therefore, these results cannot be taken as definitive evidence against a reflex origin of rigidity.

Aged↗
PubMed1987

Rigidity in rats due to radio frequency decerebration and effects of chlorpromazine and mephenesin.

Bilateral radio frequency (RF) lesions of the midbrain were produced in an attempt to establish a non-bleeding method of producing decerebrate rigidity in rats. Marked extensor rigidity occurred with a high reproducibility in hindlimbs without the appearance of voluntary movement. Stretch reflex tension induced by repetitive dorsiflexion of the hindfeet was employed as a measure of the intensity of rigidity. Chlorpromazine-HCl (0.1-1 mg/kg, i.v.) and mephenesin (10-50 mg/kg, i.v.) which depress intercollicular decerebrate rigidity, reduced the RF decerebrate rigidity. These results suggest that RF decerebrate rigidity can be used instead of intercollicular transection rigidity in the pharmacological and physiological studies.

Animals↗
PubMed2000

Inhibition by neuropeptide Y of fentanyl-induced muscular rigidity at the locus coeruleus in rats.

The aim of this study was to evaluate the effects of centrally administered neuropeptide Y (NPY) on muscular rigidity induced by fentanyl in Sprague-Dawley rats. They were anesthetized with ketamine (120 mg/kg, i.p.) and their lungs were mechanically ventilated. Intravenous administration of fentanyl (100 microg/kg) consistently evoked a significant increase in the electromyographic activity (EMG) recorded from the sacrococcygeus dorsalis lateralis muscle. This implied muscular rigidity was appreciably attenuated by intracerebroventricular administration of NPY (4 nmol/2.5 microl). Microinjection of NPY (40 or 160 pmol/50 nl) into the bilateral locus coeruleus (LC) elicited an inhibition of the EMG activation induced by fentanyl in a dose-dependent manner. Microinjection of 160 pmol NPY plus antiserum against NPY (NPY(Ab), 1:20) into the LC failed to suppress fentanyl-induced muscular rigidity. However, this implied muscular rigidity was not affected by NPY plus normal rabbit serum (NRS, 1:20). In addition, NPY(Ab) or NRS per se had no substantial effect on the rigidity. Microinjection of NPY (160 pmol) into the areas adjacent to the LC did not attenuate the rigidity. Our results suggest that the centrally administered NPY attenuated fentanyl-induced muscular rigidity by acting at the LC, but endogenous NPY may not be involved in this process.

Animals↗
PubMed1973

Dynamic spindle reflexes and the rigidity of Parkinsonism.

The effects of stimulating the reflex arc from dynamic spindle endings were examined in patients with the rigidity of Parkinsonism and in control subjects. The arc was activated phasically by a tendon tap and by electrical stimulation in 15 patients. The effect of reinforcement by Jendrassik's manoeuvre was observed. The response to phasic activation indicated central facilitation of the reflex loop in the patients with Parkinsonism, with a concurrent decrease in fusimotor drive to dynamic spindles. These abnormalities could not be correlated with the severity of the patients' rigidity, and they did not alter when the rigidity was reduced by levodopa. The effect of activating dynamic spindle endings tonically by vibration at 50 Hz was also examined. The reflex contraction of the biceps and triceps muscles in response to vibration was found to be increased in 24 patients with rigidity compared with 24 control subjects. Patients with severe rigidity developed a more powerful contraction in response to vibration than patients with mild rigidity. The response to vibration was reduced by treatment with levodopa but the amount of this reduction could not be correlated with changes in the patients' rigidity.

Adult↗
PubMed1993

Antagonist effects of beta-funaltrexamine and naloxonazine on alfentanil-induced antinociception and muscle rigidity in the rat.

Alfentanil is a potent and short-acting mu opioid agonist that produces both antinociceptive effects and muscle rigidity. In the present study, the susceptibility of alfentanil-induced antinociception and rigidity to antagonism by the selective mu antagonist beta-funaltrexamine and the selective mu-1 antagonist naloxonazine was examined. Alfentanil (37.7-150.0 micrograms/kg) produced a dose-dependent increase both in antinociception as measured by the warm-water tail-dip assay and in rigidity as measured by electromyographic recording of the gastrocnemius muscle. Both beta-funaltrexamine (10.0 and 20.0 mg/kg) and naloxonazine (7.5 and 15.0 mg/kg) produced dose-dependent and parallel rightward shifts in the alfentanil dose-effect curves for both antinociception and rigidity. Furthermore, the alfentanil dose-effect curves for antinociception and rigidity were shifted to the right to a similar degree by any given pretreatment. These results suggest that alfentanil-induced antinociception in the warm-water tail-dip test and rigidity are mediated by pharmacologically similar populations of opioid receptors. More specifically, these results suggest that mu-1 opioid receptors mediate both alfentanil-induced antinociception and rigidity.

Alfentanil↗
PubMed1996

Direct measurement of the torsional rigidity of single actin filaments.

Flexural and torsional rigidities of actin filaments are important factors in cell motility and muscle contraction, where actin filaments serve as mechanical elements. The flexural rigidity has already been determined by directly observing the bending of individual filaments under a microscope, but measurement of the torsional rigidity has been relatively scarce and indirect, because torsion of an actin filament is difficult to visualize. This paper shows that the torsional rigidity can be measured directly by visualizing the torsional Brownian motion of a single actin filament with a novel methodology based on an optical trapping technique. Actin filaments (F-actin) were prepared by polymerizing actin monomers binding Ca2+ ion or Mg2+ ion at the high affinity site. The torsional rigidity of F-Ca(2+)-actin ((8.5(+/- 1.3)) x 10(-26) N m2) was about three times as large as that of F-Mg(2+)-actin ((2.8(+/- 0.3)) x 10(-26) N m2), whereas the flexural rigidity ((6.0(+/- 0.2)) x 10(-26) N m2) was almost independent of the kind of the bound cation. The dynamic structure of F-actin is regulated by the bound metal in an anisotropic manner. The torsional rigidities above, whether of F-Ca(2+)-actin or F-Mg(2+)-actin, are one to two orders of magnitude greater than previous experimental estimates.

Actins↗
PubMed1998

X-ray diffuse scattering and rigid-body motion in crystalline lysozyme probed by molecular dynamics simulation.

Rigid-body motions are determined from a 1 ns molecular dynamics simulation of the unit cell of orthorhombic hen egg-white lysozyme and their contribution to X-ray diffuse scattering intensities are examined. Using a dynamical cluster technique, groups of backbone atoms that move as approximately rigid bodies are derived from the intramolecular interatomic fluctuation matrix. These groups tend to be local in the sequence or connected by disulphide bonds, and contain on average five residues each, X-ray diffuse scattering patterns, which are sensitive to collective motions, are calculated from the full simulation trajectory (including all the protein degrees of freedom). The results reproduce the main features of the experimental scattering. Diffuse scattering is also calculated from fitted trajectories of the rigid bodies. The full simulation diffuse scattering and atomic displacements are found to be well reproduced by a model in which the backbone atoms form the rigid groups determined using the dynamical cluster technique and the individual side-chains behave as separate rigid bodies: the resulting R-factor with the full simulation scattering is 5%. Quantitatively poorer agreement is obtained from trajectories in which the secondary structural elements of the protein are considered rigid. Rigid whole-molecule and domain motions make only minor contributions to the protein atom displacements. Finally, correlations in the interatomic fluctuations are examined directly using a canonical method.

Computer Simulation↗
PubMed1977

Failure of L-dopa to relieve activated rigidity in Parkinson's disease.

Rigidity in Parkinson patients can be easily quantitated by determining net work required to passively flex and extend the forearm through an arc of 100 degrees. Rigidity thus measured can be subdivided into two very distinct types, resting and activated. Resting rigidity, measured while the patient is relaxed, responds to all effective therapeutic agents and correlates closely to degree of clinical improvement. Activated rigidity, measured during voluntary activity, is not relieved by any presently available medical treatment. It remains unchanged at pre-therapy levels even in patients who may temporarily appear to have dramatic improvement in clinical symptomatology. Longitudinal measurements made in hundreds of parkinson patients over intervals ranging from 5 to 15 years show continuing high levels of activated rigidity through the entire period of study. In marked contrast to our wide experience with parkinson patients is a single, well documented case of Wilson's disease who appears to have recovered completely both by clinical examination and by all of our machine measurements. This patient had high levels of extrapyramidal deficit, repeatedly measured over a period of four months when penicillamine therapy was being investigated. He then suddenly reverted to normal and returned to full time employment. High values of resting rigidity activated rigidity, akinesia and resting tremor all reverted to normal and have remained normal for the past 6 years. The implication of this study is that L-dopa and related treatments only mask the symptomatology of Parkinson's disease and are not retarding the underlying pathological process. Penicillamine, on the other hand, probably does relieve the destructive process in Wilson's disease and may in early cases, permanently relieve the extrapyramidal dysfunction.

Adult↗
PubMed2001

[Complication profiles of posterior chamber intraocular lenses IOL). An analysis of 586 foldable and 2077 rigid explanted intraocular lenses].

BACKGROUND: Foldable intraocular lenses (IOL) have become increasingly preferred choice for IOL implantation after cataract removal. However, both foldable as well as rigid IOLs are not yet complication-free and may need explanation. MATERIAL AND METHODS: A total of 2663 explanted posterior chamber IOLs (PCIOLs) were accessioned at the Center for Research on Ocular Therapeutics and Biodevices between January 1988 and September 2000. The lenses were examined grossly using a Leitz/Wild M-8-Zoom stereomicroscope. The clinical reasons for explanation were documented for foldable as well as for rigid lenses. RESULTS: Of a total of 2663 explanted PCIOLs, 586 were foldable lenses and 2077 were rigid PMMA lenses The most frequent reason for explantation of all 2663 IOLs studied was decentration/dislocation. Optic and haptic damage and posterior capsule rupture were significantly more often a reason for explantation in several foldable designs compared to rigid PCIOLs. Whereas rigid designs lead more often to corneal decompensation. The percentage of explanted IOLs because of inflammatory reactions decreased significantly from 1994 to 2000. CONCLUSIONS: The complication profiles of rigid and foldable IOLs revealed some apparent differences due to the nature of the IOL biomaterials and designs. IOL optic/haptic damage was a common complication for foldable IOLs, whereas it was only discovered in single digits for rigid PMMA IOLs. The possible explanation for this is, that the soft and flexible biomaterials, from which all the foldable IOLs were manufactured, are easier to be damaged during folding, unfolding and insertion procedure. In our opinion this relative disadvantage of foldable IOLs is by far outweighed by the numerous advantages of the small incision cataract surgery. The decreasing inflammatory reactions can be explained by advances in surgical techniques, especially the secure in-the-bag fixation of IOLs.

Humans↗
PubMed1998

Effects of nail rigidity on fracture healing. Strength and mineralisation in rat femoral bone.

The present study was undertaken to assess the effects of the rigidity of nails on the healing of fractures as evaluated by mechanical strength and rate of bone mineralisation. Ten rats supplied biomechanical data at the start of the experiment and another 100 rats were randomly assigned to 5 groups. In 20 rats no intervention was performed, and they served as a reference group of normal values. Thus, 80 rats underwent a standardised partial osteotomy in the left femur diaphysis prior to manual fracture, reaming and intramedullary nailing. One group received rigid steel nails (group 1) and another, cannulated steel nails (group 2). Group 3 received semi-rigid titanium nails and group 4, soft polyethylene nails. Ten rats in each group were evaluated at 6 and 12 weeks after fracture, and radiographs and callus diameter measurements were performed. Dual-energy X-ray absorptiometry (DEXA) of the bones was performed, and the degree of mineralisation in the callus segment, distal diaphysis and total femur was calculated by the scanner. Subsequently, the bones were tested mechanically by a three-point bending test in a Mini Bionix (MTS) testing system. Radiographs revealed clearly visible fractures at 6 weeks in the intervention groups. At 12 weeks there were no signs of bridging callus in group 4, while the other groups presented scarcely visible osteotomies. The callus area in group 4 was significantly larger at both 6 and 12 weeks than in groups 1-3. In these groups there was a significant decrease in callus area between 6 and 12 weeks. Both maximum bending load, bending rigidity and fracture energy increased significantly in groups 1-3 between 6 and 12 weeks, while bending load and fracture energy increased in group 4. At 6 weeks no significant differences were detected between groups 1-3 in mechanical strength. Group 4 had a significantly reduced maximum bending load and fracture energy at 6 and 12 weeks as well as bending rigidity at 12 weeks. At 12 weeks group 3 had a significantly increased maximum bending load and fracture energy compared with groups 1 and 2. Bone mineral count (BMC) in the callus region in group 4 was significantly reduced at both 6 and 12 weeks. BMC in the callus showed no significant differences between groups 1-3, either at 6 or at 12 weeks. BMC in the distal diaphysis was significantly reduced in groups 1 and 4 compared with group 2 at 12 weeks. Bone mineral density (BMD) in the callus region revealed no significant differences between groups 1-3 at 6 weeks, while at 12 weeks BMD was higher in group 3 than in group 1. BMD in the callus region and total femur in group 4 was significantly reduced at 6 weeks. This study demonstrates that diaphyseal fractures treated with titanium nails with a bending rigidity similar to the intact femur have a higher maximum bending load and fracture energy at 12 weeks than both rigidly or softly nailed fractures. BMD in the callus region was also highest after titanium nailing at 12 weeks. BMD in the distal diaphysis and total femur indicates that the degree of stiffness of the nails have little influence on total bone mineralisation at 12 weeks.

Absorptiometry, Photon↗
PubMed2006

Preoperative assessment in patients with postintubation tracheal stenosis : Rigid and flexible bronchoscopy versus spiral CT scan with multiplanar reconstructions.

BACKGROUND: Postintubation stenosis remains the most frequent indication for tracheal surgery. Rigid bronchoscopy has traditionally been considered the technique of choice for the preoperative diagnostic assessment. However, this technique is not routinely available, and new techniques such as flexible videobronchoscopy and spiral computed tomography (CT) scan with multiplanar reconstructions have been proposed as alternatives to rigid bronchoscopy. The aim of this study was to compare these techniques in the diagnostic assessment of patients with tracheal stenosis submitted to surgical treatment. METHODS: Twelve patients who underwent airway resection and reconstruction for postintubation tracheal and laryngotracheal stenosis were preoperatively evaluated with rigid and flexible bronchoscopy and with spiral CT scan with multiplanar reconstructions. The following parameters were examined: involvement of subglottic larynx, length of the stenosis, and associated lesions. The results were compared with the intraoperative findings. RESULTS: The accuracy of rigid bronchoscopy, flexible bronchoscopy, and CT scan in the evaluation of the involvement of subglottic larynx was, respectively, 92%, 83%, and 83%. The evaluation of the length of the stenosis was correct in 83%, 92%, and 25% of the patients, respectively, with rigid bronchoscopy, flexible bronchoscopy, and CT scan. A significant correlation was observed between the length of the stenosis measured intraoperatively and preoperatively with rigid (p < 0.001) and flexible bronchoscopy (p < 0.05) but not with CT scan (p = 0.08). The three techniques correctly showed the presence of an associated tracheoesophageal fistula in two patients, but CT scan did not correctly show the exact location of the fistula in relation to the airway. Flexible bronchoscopy was the only effective technique in the assessment of laryngeal function. CONCLUSIONS: Rigid bronchoscopy remains the procedure of choice in the evaluation of candidates for tracheal resection and reconstruction for postintubation stenosis, and it should be available in centers that perform surgery of the airway. Flexible bronchoscopy and CT scan have to be considered complementary techniques in the evaluation of laryngeal function and during follow-up.

Adult↗
PubMed2007

Comparison of the effects of bilateral posterior dynamic and rigid fixation devices on the loads in the lumbar spine: a finite element analysis.

A bilateral dynamic stabilization device is assumed to alter favorable the movement and load transmission of a spinal segment without the intention of fusion of that segment. Little is known about the effect of a posterior dynamic fixation device on the mechanical behavior of the lumbar spine. Muscle forces were disregarded in the few biomechanical studies published. The aim of this study was to determine how the spinal loads are affected by a bilateral posterior dynamic implant compared to a rigid fixator which does not claim to maintain mobility. A paired monosegmental posterior dynamic implant was inserted at level L3/L4 in a validated finite element model of the lumbar spine. Both a healthy and a slightly degenerated disc were assumed at implant level. Distraction of the bridged segment was also simulated. For comparison, a monosegmental rigid fixation device as well as the effect of implant stiffness on intersegmental rotation were studied. The model was loaded with the upper body weight and muscle forces to simulate the four loading cases standing, 30 degrees flexion, 20 degrees extension, and 10 degrees axial rotation. Intersegmental rotations, intradiscal pressure and facet joint forces were calculated at implant level and at the adjacent level above the implant. Implant forces were also determined. Compared to an intact spine, a dynamic implant reduces intersegmental rotation at implant level, decreases intradiscal pressure in a healthy disc for extension and standing, and decreases facet joint forces at implant level. With a rigid implant, these effects are more pronounced. With a slightly degenerated disc intersegmental rotation at implant level is mildly increased for extension and axial rotation and intradiscal pressure is strongly reduced for extension. After distraction, intradiscal pressure values are markedly reduced only for the rigid implant. At the adjacent level L2/L3, a posterior implant has only a minor effect on intradiscal pressure. However, it increases facet joint forces at this level for axial rotation and extension. Posterior implants are mostly loaded in compression. Forces in the implant are generally higher in a rigid fixator than in a dynamic implant. Distraction strongly increases both axial and shear forces in the implant. A stiffness of the implant greater than 1,000 N/mm has only a minor effect on intersegmental rotation. The mechanical effects of a dynamic implant are similar to those of a rigid fixation device, except after distraction, when intradiscal pressure is considerably lower for rigid than for dynamic implants. Thus, the results of this study demonstrate that a dynamic implant does not necessarily reduce axial spinal loads compared to an un-instrumented spine.

Biomechanical Phenomena↗
PubMed2006

Retrograde proximal rigid ureteroscopy and pyeloscopy in prepubertal children: safe and effective.

PURPOSE: Traditionally, rigid ureteroscopy in adults has been reserved for distal ureteral procedures, due to the risk of injury associated with proximal ureteroscopy. However, the safety of proximal rigid ureteroscopy in prepubertal children is not well established. MATERIALS AND METHODS: We retrospectively evaluated all prepubertal children (12 years old and younger) who underwent attempted rigid proximal ureteroscopy and pyeloscopy. The indications for ureteroscopy were treatment of ureteral and/or renal pelvic calculi, and evaluation of hematuria. All patients were evaluated postoperatively with renal and bladder ultrasonography and abdominal radiography (if stone was visible before treatment). RESULTS: A total of 24 consecutive children 3.4 to 12 years old underwent 24 ureteropyeloscopic procedures. Of these children 20 (83%) successfully underwent 20 rigid ureteroscopic and pyeloscopic procedures. However, 4 procedures (17%) were converted from rigid to flexible endoscopy to perform 4 successful ureteropyeloscopies. The indications for ureteroscopy were treatment of ureteral and/or renal pelvic calculi in 22 patients and evaluation of hematuria in 2. Followup was 0.6 to 3.6 years (mean 1.9) for the patients undergoing rigid ureteropyeloscopy. All children with calculi were rendered stone-free based on direct visualization by complete ureteroscopy and pyeloscopy of the affected system. No complications occurred during any of the procedures. CONCLUSIONS: Proximal rigid ureteroscopy and pyeloscopy can be safely applied toward treatment of proximal ureteral and renal pelvic calculi as well as diagnostic ureteropyeloscopy in prepubertal children. The technique has several advantages compared to flexible ureteroscopy.

Age Factors↗
PubMed2005

Polyrigid and polyaffine transformations: a novel geometrical tool to deal with non-rigid deformations - application to the registration of histological slices.

We describe in this paper a novel kind of geometrical transformations, named polyrigid and polyaffine. These transformations efficiently code for locally rigid or affine deformations with a small number of intuitive parameters. They can describe compactly large rigid or affine movements, unlike most free-form deformation classes. Very flexible, this tool can be readily adapted to a large variety of situations, simply by tuning the number of rigid or affine components and the number of parameters describing their regions of influence. The displacement of each spatial position is defined by a continuous trajectory that follows a differential equation which averages the influence of each rigid or affine component. We show that the resulting transformations are diffeomorphisms, smooth with respect to their parameters. We devise a new and flexible numerical scheme to allow a trade-off between computational efficiency and closeness to the ideal diffeomorphism. Our algorithms are implemented within the Insight Toolkit, whose generic programming style offers rich facilities for prototyping. In this context, we derive an effective optimization strategy of the transformations which demonstrates that this new tool is highly suitable for inference. The whole framework is exemplified successfully with the registration of histological slices. This choice is challenging, because these data often present locally rigid deformations added during their acquisition, and can also present a loss of matter, which makes their registration even more difficult. Powerful and flexible, this new tool opens up large perspectives, in non-rigid 3D rigid registration as well as in shape statistics.

Algorithms↗