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Biomedical subjects

S R Simon

Publications and source records attributed to S R Simon.

At least 109 records · Page 6Linked to original sources
PubMed1983

Quantitative gait analysis after total knee arthroplasty for monarticular degenerative arthritis.

By quantitative gait analysis, we characterized the functional results of total knee arthroplasty in a group of twelve elderly patients with isolated degenerative arthritis of one knee. All patients had had a standard replacement arthroplasty performed at least two years before the study. In the gait analysis we used high-speed movie cameras synchronized with force platforms and electromyograms to provide kinetic and kinematic data. The data were compared with those obtained from an age-matched control group. In the patients most of the measurements of gait had been restored to normal levels. These measurements included: velocity; stride length; arcs of motion of the hip, knee, and ankle bilaterally; phasic muscle activity; and the amount of mechanical work performed. There were three patterns of external torque across the implants and in the control knee which were comparable in magnitude but varied in relative frequency between the two groups. As compared with the controls, the patients spent approximately 30 per cent more time in double-limb stance and had prolonged cycle times. These findings may have been the result of muscle weakness, neural impairment, or habit, but the cause could not be determined by this study.

Aged↗
PubMed1982

Quaternary-transformation-induced changes at the heme in deoxyhemoglobins.

Quaternary-structure-induced differences in both the high- and low-frequency regions of the resonance Raman spectrum of the heme have been detected in a variety of hemoglobins. These differences may be the result of (1) changes in the amino acid sequence, induced by genetic and chemical modifications, and (2) alterations in the quaternary structure. For samples in solution in low ionic strength buffers, differences in the 1357-cm-1 line (an electron-density-sensitive vibrational mode) correlate with differences in the 216-cm-1 line (the iron-histidine stretching mode). Thus, changes in the iron-histidine bond and changes in the pi-electron density of the porphyrin depend upon a common heme-globin interaction. The quaternary-structure-induced changes in the vibrational modes associated with the heme demonstrate that there is extensive communication between the heme and the globin and impact on models for the energetics of cooperativity. The local interactions of the iron-histidine mode are energetically small and destabilize the deoxy heme in the T structure with respect to the R structure. Therefore, these interactions must be larger in the ligated protein than in the deoxy protein to obtain a negative free energy of cooperativity. Additionally, our data imply that the deprotonation of the proximal histidine does not play a major role in the energetics of cooperativity. On the other hand, models for cooperativity that require conformational changes in the iron-histidine bond or direct interaction between the porphyrin and the protein are qualitatively consistent with the observed variation of heme electronic structure in concert with protein quaternary structure.

Amino Acid Sequence↗
PubMed1982

A three dimensional multi-segmental analysis of the energetics of normal and pathological human gait.

Segmental mechanical energy changes were studied in normal adults as a function of walking speed and in a group of subjects with pathologically impaired gait walking at their normal speed to determine the usefulness of this parameter in evaluating locomotor dysfunction. Of particular significance, the degree of exchange between potential and kinetic energy within and between limb segments was quantitatively evaluated. Due to the nature of most pathological gaits, no assumptions were made to impose symmetry between the right and left extremities and the translational as well as rotational kinetic energy of each of the limb segments was computed in three dimensions. Additionally, the torso was modeled as a group of segments with distributed mass in contrast to the commonly employed concentrated point mass model. In toto, a three dimensional twelve segment energetic analysis of the human body was developed and employed. In normal subjects, this analysis suggests a greater exchange between potential and kinetic energy near individually preferred walking speeds. Patterns of energy change noted in those subjects with locomotor dysfunction varied with the type of pathological disorder.

Adolescent↗
PubMed1982

High-resolution NMR studies of transmembrane cation transport: use of an aqueous shift reagent for 23Na.

23Na NMR studies of large unilamellar vesicles of egg lecithin in salt solutions are reported. A shift reagent, the dysprosium nitrilotriacetate ion Dy[N(CH2CO2)3]3-2 has been used to distinguish between 23Na+ inside and outside the vesicles. When both are present and the shift reagent is present on only one side, two clearly distinct resonances are observed. Creation of a Na+ concentration gradient and subsequent catalysis of passive transport induced by the introduction of gramicidin can be monitored easily by using the relative intensities of the two resonances. We report the observation of transport both out of and into vesicles.

Biological Transport↗
PubMed1982

Resonance Raman detection of structural dynamics at the active site in hemoglobin.

The iron-histidine stretching mode in deoxyhemoglobin displays a large change in frequency and width upon lowering the temperature from 300 to 10 K. The temperature dependence of the data indicates the presence of dynamic process. The dynamics of this mode in frozen hemoglobins can be qualitatively and quantitatively described as a vibrational dephasing via anharmonic coupling to other vibrations of the heme-imidazole system. the effect that occur at the melting transition in the low frequency modes cannot be quantitatively addressed at this point but may be indicative of the introduction of additional degrees of freedom predicated on protein influences that reflect differences in protein quaternary structure.

Heme↗
PubMed1982

Stretch reflexes of triceps surae in normal man.

In order to learn more about stretch reflex behaviour of triceps surae, normal human subjects sat in a chair with one foot on a platform attached to a torque motor that produced phasic dorsiflexion displacements on the ankle. EMG activity was recorded from triceps surae and responses were obtained for various conditions. When the subjects's foot was relaxed, stretch of triceps surae produced a single EMG component at short-latency which increased in magnitude with increasing velocity of stretch. The response was not altered if the subject was asked to plantarflex or dorsiflex the ankle voluntarily when he felt the perturbation. It was reduced by vibration of the Achilles tendon. If the triceps surae was stretched while the subject plantarflexed his ankle, the short-latency response was followed by one and sometimes two long-latency responses. Like the short-latency reflex when the foot was relaxed, none of these responses was altered by the subject's planned movement after feeling the perturbation. All of the responses were suppressed to a similar degree by vibration. The long-latency reflexes depended on long-duration of stretching and relatively slow acceleration of stretch. The reflexes persisted after anaesthesia to the foot suggesting that muscle afferents were responsible. Interactions between H-reflexes and stretch-reflexes revealed that the afferent volley producing a stretch reflex acted like the afferent volley producing a small H-reflex. Responses at an interval of 30 ms to both an electrical stimulus for an H-reflex and a stretch stimulus were possible if the electrical stimulus produced only a small H-reflex and if the subject had been plantarflexing the ankle. The short-latency reflex when the foot was relaxed or exerting a background force appears to be the monosynaptic, Ia mediated stretch reflex. The physiological properties of the long latency reflexes are similar to those of the short-latency reflex, and they may represent, at least to a certain extent, response of the motor neuron pool to successive Ia bursts.

Adult↗
PubMed1981

Structural changes at the heme induced by freezing hemoglobin.

A dramatic change occurs in the vibrational properties of the iron-histidine bond, trans to the oxygen binding site, on freezing deoxyhemoglobin. The large, quaternary structure-dependent differences in the shape and frequency of the iron-histidine mode observed in resonance Raman scattering measurements above freezing ae significantly diminished by the freezing event and the scattering intensity increases substantially. On further reduction in temperature to 10 K this broad line becomes narrow and shifts to a higher frequency. These data implicate dynamical processes and protein interaction with water as contributors to the quaternary structure dependence of the iron-histidine bond and thus reflect on the role of that bond in the energetics of cooperative ligand binding.

Allosteric Regulation↗
PubMed1980

Raman difference spectroscopy of tertiary and quaternary structure changes in methaemoglobins.

There have been several resonance Raman scattering investigations of the effect of inositol hexaphosphate (IHP) on methaemoglobins. In those studies the sensitivity for detecting frequency differences was limited to 1-2 cm-1, and consequently frequency differences were not detected although spectral intensity differences due to changes in spin equilibria were. Shelnutt et al. recently reported on the observation of frequency differences induced by changes in the quaternary structure of chemically modified deoxyhaemoglobins. An improved Raman difference spectroscopic technique with 0.1 cm-1 sensitivity allowed the detection of these differences. We report here the application of this technique to a series of methaemoglobins with and without the addition of IHP. In addition to the intensity changes resulting from changes in the spin equilibria, we have observed frequency differences. In all liganded methaemo-globins that we examined a decrease in frequency of the mode in the 1,370 cm-1 region was observed on addition of IHP. In those in which a quaternary structure change is known to occur the frequency difference is greater than 0.5 cm-1. In those in which no quaternary structure change occurs [metHbA(CN-) and methHbA(N-3)] the frequency difference is smaller (approximately 0.15 cm-1).

Hemoglobin A↗
PubMed1980

Proximal femoral osteotomy in cerebral palsy.

The purpose of this study was to examine the results of the proximal femoral osteotomy for the management of hip deformity in 32 children, aged 4 to 15 years. Twenty-two bilateral and ten unilateral procedures were performed. The indications for surgery were subluxation in 16, dislocation in two, and intoeing and femoral anteversion in 14. The average follow-up was two years and 11 months. CE angle of Wiberg, acetabular index and neck shaft angle were evaluated. The average time to regain preoperative ambulatory status was six months with intensive physical therapy. In osteotomies performed for subluxation, dislocation did not occur; roentgenographic indices showed variability in the degree of subluxation. Osteotomy performed in children older than 8 years of age produced no evidence of acetabular remodeling. THere was no recurrence with osteotomies for dislocation. In those patients with internal rotation gait, improvement resulted. Complications were few and minor. Hip dislocation in children with progressive subluxation, in spite of previous soft-tissue releases, is preventable by proximal femoral osteotomy. The inability of the roentgenographic indices to quantitate the increased stability indicates the procedure's major effect is to realign muscle forces about the hip. Treatment of the intoeing gait produced improvement of rotational deformity.

Adolescent↗
PubMed1979

Protein-heme interaction in hemoglobin: evidence from Raman difference spectroscopy.

Raman difference spectroscopy measurements on native and chemically modified human deoxyhemoglobins stabilized in either the R or the T quaternary structure revealed frequency differences in the oxidation state marker lines. The differences indicate that the R structure has an effective increase in the electron density of the antibonding pi* orbitals of the porphyrin rings. This increase is explained by a charge transfer interaction between donor orbitals and the pi* orbitals of the porphyrins. The relative amount of charge transferred, which is inferred from the Raman difference measurements, correlates with some but not all factors that influence the energetics of the quaternary structure equilibrium. In addition, the free energy of cooperativity for a variety of ligated proteins follows the same order as that of the degree of charge depletion of the pi* orbitals upon ligation as determined from the frequency of a Raman mode. The proposed electronic interaction between the protein and heme could result in energies large enough to provide a significant contribution to the energetics of hemoglobin cooperativity.

Allosteric Regulation↗
PubMed1979

Knee flexion deformities and genu recurvatum in cerebral palsy: roentgenographic findings.

Patients with cerebral palsy often have recurvatum or flexion deformities at the knee. To determine whether these are due to a bony or soft-tissue abnormality, four angles were measured on lateral roentgenograms of the knee: the femur-physis angle (angle 1); femur-Blumensaat's line angle (angle 2); tibia-plateau angle (angle 3); and tibia-physis angle (angle 4). These angles were measured for 45 patients with knee flexion deformities and for 31 with genu recurvatum. Values were also obtained from 204 normal lateral knee reoentgenograms. The age range for the whole series was from one to 22 years. Angles 2, 3 and 4 decreased from normal values with increasing age. The angulation of the proximal tibia, as measured by angle 3, is abnormal in patients with flexion deformities. Angles 2 and 3 were abnormal in cerebral-palsied patients with flexion deformities, while patients with genu recurvatum showed no significant bony abnormalities. These results suggest that treatment of flexion and recurvatum should be based on etiology.

Adolescent↗
PubMed1979

Ankle arthrodesis. Long-term follow-up with gait analysis.

A functional assessment of twelve patients after ankle arthrodesis for post-traumatic arthritis was carried out by means of an extensive clinical evaluation and gait analysis after an average follow-up of eight years. A weighted point system was developed to grade ankle function clinically. The data on gait analysis were examined to determine the effect of arthrodesis of the ankle on the over-all pattern of walking. Under conditions of normal daily living while wearing shoes, all patients functioned well after arthrodesis. The gait-analysis data obtained with the patients wearing shoes showed excellent gait characteristics, and the ankle motion that had been lost was compensated for by: (1) motion of the small joints of the ipsilateral foot; (2) altered motion of the ankle in the contralateral limb; and (3) appropriate footwear. While the patients were walking barefooted, some adverse effects of fusion of the ankle were evident. Velocity of gait was slowed and the length of stride was shortened in all twelve patients. One patient whose ankle had been fused in an equinus position had a back-knee deformity during stance phase, and another walked only on his toes when he was without shoes. The gait patterns of all patients were markedly improved when they were wearing shoes with appropriate heel heights.

Activities of Daily Living↗