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PubMed1987

Ketanserin pretreatment reverses alfentanil-induced muscle rigidity.

Systemic pretreatment with ketanserin, a relatively specific type-2 serotonin receptor antagonist, significantly attenuated the muscle rigidity produced in rats by the potent short-acting opiate agonist alfentanil. Following placement of subcutaneous electrodes in each animal's left gastrocnemius muscle, rigidity was assessed by analyzing root-mean-square electromyographic activity. Intraperitoneal ketanserin administration at doses of 0.63 and 2.5 mg/kg prevented the alfentanil-induced increase in electromyographic activity compared with animals pretreated with saline. Chlordiazepoxide at doses up to 10 mg/kg failed to significantly influence the rigidity produced by alfentanil. Despite the absence of rigidity, animals that received ketanserin (greater than 0.31 mg/kg i.p.) followed by alfentanil were motionless, flaccid, and less responsive to external stimuli than were animals receiving alfentanil alone. Rats that received ketanserin and alfentanil exhibited less rearing and exploratory behavior at the end of the 60-min recording period than did animals that received ketanserin alone. These results, in combination with previous work, suggest that muscle rigidity, a clinically relevant side-effect of parenteral narcotic administration, may be partly mediated via serotonergic pathways. Pretreatment with type-2 serotonin antagonists may be clinically useful in attenuating opiate-induced rigidity, although further studies will be necessary to assess the interaction of possibly enhanced CNS, cardiovascular, and respiratory depression.

Adjuvants, Anesthesia↗

PubMed1974

A comparison of the actions of some drugs on decerebrate rigidity, muscle spindle activity and alpha-adrenoceptors.

1 The relative potencies of methotrimeprazine, (+)-methotrimeprazine, (+/-)-10-(3-dimethylamino-2-methylpropyl)-2-valeroyl phenothiazine hydrochloride (M & B 18,706) and (+)-M & B 18,706 in reducing the pressor action of noradrenaline in the spinal cat, reducing intercollicular decerebrate rigidity, and muscle spindle afferent activity have been studied.2 Methotrimeprazine was eight times as potent as (+)-methotrimeprazine in reducing the pressor action of noradrenaline and six times as potent in reducing decerebrate rigidity. M & B 18,706 was also eight times as potent as (+)-M & B 18,706 in reducing the pressor action of noradrenaline and six times as potent in reducing decerebrate rigidity.3 For the above compounds and chlorpromazine there was a significant correlation between the effective doses for the inhibition of the pressor action of noradrenaline and for the reduction of decerebrate rigidity.4 The doses which reduced decerebrate rigidity were similar to those that reduced muscle spindle afferent discharge. It is likely that these drugs reduce decerebrate rigidity by inhibiting fusimotor activity.5 Desipramine increased decerebrate rigidity and increased spindle afferent discharge.6 It is thought that the phenothiazine derivatives studied reduce decerebrate rigidity and spindle afferent discharge by inhibiting receptors for noradrenaline in the central nervous system.

Animals↗

PubMed1980

Parental factors associated with rigidity in Huntington's disease.

The discriminatory power of ten factors has been explored in relation to the presence or absence of muscular rigidity in patients with Huntington's disease. The sex and neurological sign of an affected parent were the only two significant determinants of rigidity or choreoathetosis in offspring. It was shown, using the Mantel-Haenszel method of adjusting for confounding variables that the risk of a patient displaying rigidity (and thereby having a graver prognosis) is five times as great for those with rigid parents as it is for those with non-rigid parents. Additionally, the risk of a patient displaying rigidity is more than three times as great for those with affected fathers as it is for those with affected mothers. Some implications of these findings are discussed.

Age Factors↗

PubMed1982

Pharmacological studies on 6-amino-2-fluoromethyl-3-(O-tolyl)-4(3H)-quinazolinone (afloqualone), a new centrally acting muscle relaxant. (II) Effects on the spinal reflex potential and the rigidity.

Effects of afloqualone on mono- (MSR) and poly-synaptic reflex (PSR) potentials and alpha- and gamma-rigidities were studied in experimental animals. Afloqualone dose dependently inhibited both MSR and PSR potentials in spinalized cats though afloqualone had no inhibitory effect on the patellar reflex in cats as reported in the previous paper. Afloqualone, like tolperisone, more selectively inhibited the PSR potential than MSR potential, whereas baclofen inhibited them in reverse order. However, the selectivity towards the PSR potential was higher with afloqualone than with tolperisone. In rats and cats, afloqualone dose dependently relaxed both alpha- and gamma-rigidity when administered p.o. as well as i.v. Its 50% inhibitory dose for alpha-rigidity was 1.5-2 times larger than that for gamma-rigidity. Tolperisone also relaxed both rigidities in i.v. administration, but had little effect when given p.o. Only mephenesin relaxed the post-ischaemic spinal rigidity in cats. These results suggest that afloqualone, like other well known centrally acting muscle relaxants except for baclofen, more strongly inhibits the polysynaptic pathway than the mono-synaptic pathway of the spinal cord as well as more strongly the gamma-system than the alpha-system.

Animals↗

PubMed2002

[Quantitative assessment of Parkinsonian rigidity by vessel Doppler ultrasonography].

OBJECTIVE: To investigate the value of quantitative assessment of parkinsonian rigidity by vessel Doppler ultrasonography. METHODS: The diameter of the rigid limbs, including radial artery and vein, ulnar artery and vein, brachial veins, popliteal vein, anterior tibial vein, and posterior tibial vein in twelve individuals with PD and twelve age matched controls were measured by ultrasonography in both "on" and "off" states. Meanwhile the UPDRS unified Parkinson's disease rating scale for rigidity were also recorded both in "on" and "off " states by experienced neurologists. RESULTS: The mean diameter of radial vein, ulnar vein, brachial vein, popliteal vein, anterior tibial vein and posterior tibial vein, were 1.14, 1.13, 2.47, 3.85, 1.89, and 1.33 mm respectively in "off " state (group "A"), and were 1.58, 1.54, 2.88, 4.65, 2.27, and 1.69 mm respectively in "on" states (group "B") among the PD patients. The diameters of corresponding vessels in the controls (group "C") were 2.07, 1.69, 4.15, 5.07, 2.63, and 1.99 mm respectively. The data increased from group "A" to "C" gradually. Paired samples t tested showed a significant difference between the data of group A and group B (P = 0.00 approximately 0.03) and between group A and group C (P = 0.00 approximately 0.02) and no significant difference between group B and group C (P > 0.05, except for brachial vein with P = 0.02). The data of vein diameters in rigid limbs were correspondent to the UPDRS scores for rigidity with the correlation coefficient of 0.71, 0.82, 0.91, 0.73 (all P < 0.01), 0.60 P < 0.05 , and 0.77 P < 0.01) for the above mentioned vessels respectively. CONCLUSION: The diameter of distant veins in limbs can be adopted as objective and quantitative indicators for parkinsonian rigidity and contribute to the evaluation of therapeutical effects.

Aged↗

PubMed1997

[Central motor conduction time using magnetic and vibratory stimulation in Parkinson's disease, especially in patients with rigidity].

Rigidity, tremor, akinesia and disorder of postural reflex are the main clinical features of Parkinson's disease. We presented the mechanism underlying rigidity and assessed central motor conduction time (CMCT) using magnetic, with or without vibratory, stimulations. Basal ganglia, especially, the internal pallidum, and the thalamus play major roles in the mechanism of rigidity in Parkinson's disease. Hyperexcitability of the spinal motor nucleus due to low threshold has been recognized. Magnetic stimulation is painless and is simpler than electric stimulation. Therefore, this method is used clinically for evaluating conduction disturbance of the upper motor neurons in multiple sclerosis, cerebrovascular disease and so on. CMCT measured by magnetic and/or electric stimulation may be abbreviated or normal in Parkinson's disease, according to the literature, though controversy persists in this regard. In our study, CMCT was normal in Parkinson patients. However, CMCT was reduced in patients with rigidity and tremor. Furthermore, in a portion of the patients, CMCT was further abbreviated by also applying vibratory stimulation. These observations support the hypothesis that cells in the thalamus, cortex and spinal cord and/or pathways in these portions of the central nervous system are excitable or activated in Parkinson patients with rigidity and tremor. However, elucidation of the mechanisms underlying rigidity and tremor awaits further investigation.

Humans↗

PubMed1995

Craniofacial growth in rabbits. Effects of midfacial surgical trauma and rigid plate fixation.

OBJECTIVE: To examine the effects of soft-tissue manipulation, rigid microplate fixation, and multiple osteotomies on the growing midface in rabbits. DESIGN: Randomized, controlled experiment. SUBJECTS: Forty 6-week-old male New Zealand white rabbits. INTERVENTIONS: Group 1, exposure of the left nasofrontal and midzygomatic arch regions with periosteal elevation; group 2, osteotomies at left nasofrontal suture and midzygomatic arch; group 3, rigid plate fixation of osteotomies; and group 4, rigid plate fixation alone. Animals were killed at age 20 weeks; growth was assessed by linear and spatial measurements of craniofacial regions. RESULTS: Linear data disclosed shortening of the left nasal bone (P < .05) in groups 2 through 4. Groups 3 and 4 also had shortened left zygomatic arches and orbital diameters (P < .05). Euclidean distance matrix analysis showed significant restrictive shape alterations in groups 2 through 4 (P < .05). Significant contralateral shape alterations also were found in group 3. CONCLUSION: Rigid plate fixation does not cause more severe growth disturbance than bony trauma. Use of rigid plate fixation after bony trauma does not seem to increase the restrictive effects of trauma on growth. Furthermore, removal of rigid plate fixation may not prevent growth disturbances and may induce further harmful trauma to the growing midface.

Animals↗

PubMed1997

Predicting perfectionism: applying tests of rigidity.

Adult college students (N = 108; M age = 24.3 years old) completed multidimensional measures of perfectionism (self-oriented, other-oriented, and socially-prescribed perfectionism) and behavioral rigidity (attitudinal flexibility, psychomotor speed, and motor-cognitive rigidity). Attitudinal flexibility was negatively related to all three forms of perfectionism, and motor-cognitive rigidity was positively related to self-oriented perfectionism. Multiple regression analyses indicated that attitude flexibility and motor-cognitive rigidity were significant predictors of self-oriented perfectionism, while attitude-flexibility alone was the significant predictor of socially-prescribed perfectionism. No measure of rigidity was a significant predictor of other-oriented perfectionism. Thus, dimensions of perfectionism may be predicted with different measures of cognitive-behavioral rigidity.

Adult↗

PubMed1995

Buckling of a single microtubule by optical trapping forces: direct measurement of microtubule rigidity.

As major determinants of cell shape and polarity, microtubules are required to have suitable rigidity. However, our knowledge of the mechanical properties of microtubules is far from satisfactory. We report here a new method of measuring the flexural rigidity of a single microtubule by direct buckling using the optical trapping technique. Microtubule buckling was induced by applying a small longitudinal compressing force through an optically trapped microsphere that was firmly attached to the microtubule. Three ways of estimating the flexural rigidity of a continuous slender rod, one from the observed critical load of buckling and two from deflected lengths and angles of bending, yielded values which agreed well when applied to the analysis of buckling microtubules. Unexpectedly, we found that the rigidity was not constant as expected but was dependent on microtubule length. This length dependency explains the discrepancies among reported values of microtubule flexural rigidity measured by different methods. Comparing microtubules of identical lengths, microtubules assembled with brain-derived associated proteins (4 x 10(-23) Nm2 at around 10 microns in length) were four times more rigid than those assembled from purified tubulin and stabilized with taxol (1 x 10(-23) Nm2).

Animals↗

PubMed2002

On the relation of flexible and rigid control of eating to body mass index and overeating in patients with binge eating disorder.

OBJECTIVE: To examine the relationship of flexible and rigid dimensions of restrained eating to body mass index (BMI) and overeating in outpatients with binge eating disorder (BED). METHOD: Participants were 148 consecutive outpatients who met criteria for BED. The Three-Factor Eating Questionnaire (TFEQ) was administered to assess Cognitive Restraint, Hunger, and Disinhibition. The TFEQ also contains two Cognitive Restraint subscales--Flexible Control and Rigid Control. The Eating Disorder Examination-Questionnaire version (EDE-Q) was administered to assess frequency of different forms of overeating during the past 28 days and the attitudinal features of eating disorders. RESULTS: Flexible Control and Rigid Control were significantly correlated with each other. They were both negatively correlated with BMI, but neither was significantly correlated with the frequency of binge eating or other forms of overeating. In addition, Flexible Control and Rigid Control predicted almost the same amount of variance in BMI. DISCUSSION: BED patients exhibit flexible and rigid control of eating that is related to BMI, but not to the frequency of binge eating or other forms of overeating. Results of the present study provide preliminary evidence that flexible and rigid control of eating may not be a useful distinction in BED patients. However, increased restraint, regardless of type, may prove to be of benefit with regard to weight control and may not have adverse effects on binge eating in obese BED patients.

Adult↗

PubMed1995

Rigid domains in proteins: an algorithmic approach to their identification.

A rigid domain, defined here as a tertiary structure common to two or more different protein conformations, can be identified numerically from atomic coordinates by finding sets of residues, one in each conformation, such that the distance between any two residues within the set belonging to one conformation is the same as the distance between the two structurally equivalent residues within the set belonging to any other conformation. The distance between two residues is taken to be the distance between their respective alpha carbon atoms. With the methods of this paper we have found in the deoxy and oxy conformations of the human hemoglobin alpha 1 beta 1 dimer a rigid domain closely related to that previously identified by Baldwin and Chothia (J. Mol. Biol. 129: 175-220, 1979). We provide two algorithms, both using the difference-distance matrix, with which to search for rigid domains directly from atomic coordinates. The first finds all rigid domains in a protein but has storage and processing demands that become prohibitively large with increasing protein size. The second, although not necessarily finding every rigid domain, is computationally tractable for proteins of any size. Because of its efficiency we are able to search protein conformations recursively for groups of non-intersecting domains. Different protein conformations, when aligned by superimposing their respective domain structures, can be examined for structural differences in regions complementing a rigid domain.

Algorithms↗

PubMed2002

Rigid vs. flexible dieting: association with eating disorder symptoms in nonobese women.

The correlates of rigid and flexible dieting were examined in a sample of 188 nonobese women recruited from the community and from a university. The primary aim of the study was to test the hypothesis that women who utilize rigid versus flexible dieting strategies to prevent weight gain report more eating disorder symptoms and higher body mass index (BMI) in comparison to women who utilize flexible dieting strategies. The study sample included women who were underweight (29%), normal weight (52%), and overweight (19%). None of the women were obese, as defined by BMI>30. Participants were administered a questionnaire that measures Rigid Control and Flexible Control of eating. Body weight and height were measured and measures of eating disorder symptoms and mood disturbances were administered. Our results indicated that BMI was significantly correlated with rigid dieting and flexible dieting. BMI was controlled statistically in other analyses. The study found that individuals who engage in rigid dieting strategies reported symptoms of an eating disorder, mood disturbances, and excessive concern with body size/shape. In contrast, flexible dieting strategies were not highly associated with BMI, eating disorder symptoms, mood disturbances, or concerns with body size. Since this was a cross sectional study, causality of eating disorder symptoms could not be addressed. These findings replicate and extend the findings of earlier studies. These findings suggest that rigid dieting strategies, but not flexible dieting strategies, are associated with eating disorder symptoms and higher BMI in nonobese women.

Adolescent↗

PubMed1979

Noninvasive measures of bone bending rigidity in the monkey (M. nemestrina).

The in vivo bending rigidity and bone mineral content of monkey ulnae and tibiae were measured. Bending rigidity in the anteroposterior plane was measured by an impedance probe technique. Forced vibrations of the bones were induced with an electromechanical shaker, and force and velocity at the driving point were determined. The responses over the range of 100-250 Hz were utilized to compute the bending rigidity. Bone mineral content in the cross section was determined by a photon absorption technique. Seventeen male monkeys (Macaca nemestrina) weighing 6-14 kg were evaluated. Repeatability of the rigidity measures was 4%. Bone mineral content was measured with a precision of 3.5%. Bending rigidity was correlated with the mineral content of the cross section, r = 0.899. Two monkeys were evaluated during prolonged hypodynamic restraint. Restraint produced regional losses of bone most obviously in the proximal tibia. Local bone mineral content declines 17 to 24% and the average bending rigidity declines 12 to 22%. Changes in bones leading to a reduction in mineral content and stiffness are discussed.

Animals↗

PubMed1998

Colonoscope flexural rigidity measurement.

A testing device is developed that determines the stiffness, or flexural rigidity, of an endoscope at specific locations down its length by subjecting it to a compressive axial force, a situation similar to the actual forces applied to the endoscope during a clinical procedure. The endoscope is made to deform in a similar fashion to a slender buckled column and the force causing this deformation is related to the flexural rigidity using column buckling theory. A direct relationship between the critical load needed to cause buckling and the square of column length L is demonstrated experimentally and is expected theoretically, giving confidence in the application of column buckling theory to endoscope testing. Additional confidence in the validity of the column buckling test results is obtained by their similarity to data obtained by subjecting the endoscope to a transverse load, determining deflection, and modelling the endoscope as a bent elastic beam. Several makes and models of endoscopes were tested, with flexural rigidity values typically ranging between 160 to 240 Ncm2. The effect of a metal stiffener inserted in an endoscope's accessory channel is quantified, as is the change in flexural rigidity down the insertion shaft of a graded-stiffness endoscope. Significant differences in flexural rigidity were obtained between identical endoscopes, each sharing similar usage histories, indicating the need for flexural rigidity measurements for each individual endoscope of a particular model line, though a more extensive study is required to reliably determine scope-to-scope stiffness variations for a particular model line.

Colonoscopes↗

PubMed1983

Reversal of the muscle relaxant effect of diazepam by the specific benzodiazepine antagonist Ro 15-1788: an electromyographic study in morphine model of muscular rigidity in rats.

The effects of the benzodiazepines diazepam and midazolam on the rigidity produced by systemic administration of morphine (15 mg/kg i.p.) were studied in rats. The rigidity was recorded as a tonic activity from the gastrocnemius-soleus muscle of non-anesthetized rats in the electromyogram. Both diazepam (1-5 mg/kg i.p.) and midazolam (2.5 and 5 mg/kg i.p.), when administered 45 min after morphine, temporarily antagonized the muscular rigidity. When the competitive antagonist Ro 15-1788 (ethyl-8-fluoro-5, 6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a]-[1,4]benzodiazepine-3 -carboxylate) (5 mg/kg i.p.) was administered together with diazepam (5 mg/kg i.p.), it prevented the effect of diazepam, although by itself it did not affect the morphine-induced muscular rigidity. Our results suggest that diazepam, by acting on benzodiazepine receptors, can antagonize the morphine-induced muscular rigidity. The latter phenomenon might serve as a model for some types of muscular rigidity observed in humans.

Animals↗

PubMed2005

Rigidity and bradykinesia reduce interlimb coordination in Parkinsonian gait.

OBJECTIVE: To assess the influence of rigidity and bradykinesia and the extent of dopaminergic degeneration on interlimb coordination during walking in early, drug-naive patients with Parkinsons disease (PD). DESIGN: The interlimb coordination was examined during a systematic manipulation of walking speed on a treadmill. The phase relations between arm and leg movements were related to the clinical measures of rigidity and bradykinesia as well as to the extent of dopaminergic degeneration. SETTING: Movement disorders outpatient clinic (including motion analysis laboratory) and a nuclear medicine department of a university hospital. PARTICIPANTS: Twenty-nine early and drug-naive PD patients. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The interlimb coordination during walking was evaluated by studying the (continuous) relative phase relations between movements of arms and legs. The clinical assessment of rigidity and bradykinesia was performed by using the Unified Parkinson Disease Rating Scale. The dopaminergic degeneration was expressed as striatal 2beta-carboxymethoxy-3beta-(4-iodophenyl) tropane (beta-CIT) single-photon emission computed tomography (SPECT) binding. RESULTS: The mean relative phase between arm and leg movements increased significantly with walking speed in all patients. Significant correlations were found between the rigidity and bradykinesia and the coordination measures ( P </=.007), as well as contralateral striatal [ 123 I]beta-CIT SPECT binding and coordination measures ( P <.001), in terms of asymmetry indices. CONCLUSIONS: Early, drug-naive PD patients in this sample were able to adapt their coordination patterns when walking speed was systematically manipulated. However, bradykinesia and rigidity as well as the extent of degeneration of the dopaminergic system were associated with a limited adaptive ability (flexibility) in movement coordination. The combination of a drug treatment that controls bradykinesia and rigidity and a physical therapy exercise programs possibly using external cues mechanisms are required to obtain relevant effects on gait in PD patients.

Adult↗

PubMed2006

Length-dependence of flexural rigidity as a result of anisotropic elastic properties of microtubules.

Unexplained length-dependence of flexural rigidity and Young's modulus of microtubules is studied using an orthotropic elastic shell model. It is showed that vibration frequencies and buckling load predicted by the accurate orthotropic shell model are much lower than that given by the approximate isotropic beam model for shorter microtubules, although the two models give almost identical results for sufficiently long microtubules. It is this inaccuracy of the isotropic beam model used by all previous researchers that leads to reported lower flexural rigidity and Young's modulus for shorter microtubules. In particular, much lower shear modulus and circumferential Young's modulus, which only weaken flexural rigidity of shorter microtubules, are responsible for the observed length-dependence of the flexural rigidity. These results confirm that longitudinal Young's modulus of microtubules is length-independent, and the observed length-dependence of the flexural rigidity and Young's modulus is a result of strongly anisotropic elastic properties of microtubules which have a length-dependent weakening effect on flexural rigidity of shorter microtubules.

Anisotropy↗

PubMed2004

Foldable versus rigid intraocular lenses in conjunction with pars plana vitrectomy and other vitreoretinal procedures.

PURPOSE: To compare the results of foldable acrylic intraocular lens (IOL) implantation through a clear corneal incision with those of rigid IOL implantation in eyes having pars plana vitrectomy (PPV). SETTING: Tertiary referral-based university institute. METHODS: A consecutive retrospective comparative chart review was performed in all eyes that had PPV and foldable IOL implantation between May 15, 1999, and November 1, 2000 (n = 30), and all eyes that had PPV and rigid IOL implantation between April 1, 1996, and May 14, 1999 (n = 30). Preoperative baseline data and postoperative outcome data were recorded. Pars plana vitrectomy and associated vitreoretinal procedures were performed as indicated according to individual circumstances. A minimum of 1 week of follow-up information was available for all eyes. RESULTS: Baseline characteristics in both groups of patients, including age, sex, eye involved, and phakic state, were similar. The preoperative visual acuities were also similar, ranging from 20/30 to hand motions; the mean visual acuity was 20/200. The IOL was implanted in all eyes uneventfully and did not restrict fundoscopy. The mean follow-up was significantly longer in the rigid IOL group (20 months) than in the foldable IOL group (7 months) (P<.001), probably because of the earlier case acquisition. The mean postoperative best corrected visual acuity was 20/200 in the foldable IOL group and 20/100 in the rigid IOL group. There was no difference between the 2 groups in the rate of postoperative retinal detachment, recurrent macular hole, or repeat PPV. Elevated intraocular pressure (IOP) on the first postoperative day was more common in the rigid IOL group than in the foldable IOL group (P =.078) because more patients in the rigid IOL group had surgery for diabetic ocular complications and these patients had a greater IOP rise. CONCLUSION: Acrylic IOLs can be safely implanted in conjunction with PPV in selected cases.

Acrylic Resins↗