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Biomedical subjects

R Dickstein

Publications and source records attributed to R Dickstein.

At least 19 recordsLinked to original sources
PubMed1999

Activation of selected trunk muscles during symmetric functional activities in poststroke hemiparetic and hemiplegic patients.

OBJECTIVE: To compare the EMG activity between the recti abdominii muscles and between the lumbar erector spinae muscles in hemiparetic and hemiplegic patients during functional symmetric trunk movements and to compare patients' EMG activity profiles with those of healthy controls. METHODS: EMG activity from the selected muscles was recorded during three symmetric and time controlled trunk exercises. Data analysis was based on values of cross correlations and of ratios between EMG activity of the bilateral corresponding muscles. RESULTS: In all groups, the highest cross correlations were obtained for both muscles when the muscles acted as prime movers. For the recti abdominii muscles, these values in the patients were comparable with those of the healthy subjects, whereas for the extensor muscles, the highest synchronous activity was displayed in healthy subjects and the lowest in hemiplegic patients. Laterality differences in the amount of EMG activity of the recti abdominii muscles were not biased towards one side. For the extensor muscles, in the controls, the activation levels were higher in the left erector spinae muscle than in the right one in two of the three exercises. Similarly, in the extensor muscles of the hemiparetic patients, activity on the paretic side was higher than on the non-paretic side in two exercises. CONCLUSIONS: In patients with a supratentorial poststroke hemiparesis or hemiplegia, bilateral corresponding axial trunk muscles co-contract during symmetric trunk activities. Synchronous activation is at its highest level during voluntary dynamic tasks and is greater in the recti abdominii than in the erector spinae muscles. For both muscles, EMG activation levels on the paretic side were not lower than on the non-paretic side. Thus, the assertion that the muscles on the paretic side are activated to a lesser extent than their counterparts on the non-paretic side during symmetric trunk movements was not confirmed.

Aged↗
PubMed1998

Total knee arthroplasty in the elderly: patients' self-appraisal 6 and 12 months postoperatively.

The objective of this work was to study patients' self-appraisal of total knee arthroplasty (TKA) 6 and 12 months postoperatively, and to establish which factors determine dissatisfaction from surgery. The study group consisted of 79 patients subjected to TKA who underwent rehabilitation in a specialized institution from which they were discharged home after becoming independently ambulatory and capable of independent home care. Data were collected by interviews and physical examinations which were conducted upon admission to the rehabilitation program and at the patients' homes 6 and 12 months postoperatively. Descriptive statistics and logistic regression were applied for data analysis. Results of the 1-year follow-up indicated a decrease in the prevalence of pain in the postoperated knee and improvement in ambulatory capacities. The frequency of reliance on a walking aid and the prevalence of pain in the nonoperated knee were not substantially changed, however. In 27% of the subjects pain in the nonoperated knee had worsened at 1 year. One third of the respondents expressed dissatisfaction from the operation. Outcomes of the logistic regression analysis pointed to pain in both the ipsi- and contralateral knee and to the limitations in using stairs as the variables which significantly affected the levels of dissatisfaction 1 year postoperatively. Dissatisfaction could have resulted from inappropriate expectations from either misinterpretations or limited prior knowledge of the likely results of the operation.

Aged↗
PubMed1997

Somatosensory evoked potentials of the posterior tibial nerve in hemiparetic patients: relation to stance balance and walking ability.

OBJECTIVES: To examine the association between stance ability and walking performance of poststroke hemiplegic patients and their posterior tibial nerve somatosensory evoked potentials (SEPs). DESIGN AND SETTING: Fifteen patients, residents of a geriatric rehabilitation hospital, were evaluated twice, with a 2-week interval between sessions. In each session, clinical tests of stance balance and walking ability were performed, and bilateral SEPs to stimulation of the posterior tibial nerve were recorded. Eight healthy, age-matched control subjects underwent the same tests in a single session, but SEPs were recorded unilaterally. Correlation analysis and analysis of variance (ANOVA) were used for studying the prognostic value of the initial posterior tibial nerve SEP measurements as well as the within- and between-sessions relationships between the clinical-functional tests and the SEP data. RESULTS: No significant correlations between the initial SEP values and functional improvement were established. Within each session, positive significant correlations existed between decreased latencies of several of the medium-latency SEP waves and the performance of stance and gait tasks. However, the between-sessions improvement in stance balance was not correlated with a decrease in latency of the SEP peaks or with an increase in their amplitudes. As to walking ability, in those patients whose gait significantly improved, a significant shortening of P37 and P54 latencies took place. CONCLUSIONS: The association between the initial and/or the 2-week changes in SEP of the posterior tibial nerve and improvement in stance and walking abilities is equivocal. In addition, the applicability of SEP measurements is limited by patients' physical status and cooperation. The clinical significance of posterior tibial nerve SEP testing in poststroke hemiparetic patients is therefore debatable.

Aged↗
PubMed1997

Repetitive practice of a single joint movement for enhancing elbow function in hemiparetic patients.

The primary goal of this study was to assess whether repetitive practice of flexion-extension movements of the affected elbow in hemiparetic patients enhances performance and to compare the effects of this practice mode to the effects of the physical therapy variable exercise program which is routinely applied during sessions. Subjects were 27 poststroke hemiparetic patients, residents of a rehabilitation institute, divided into an experimental (n = 15) and a control group (n = 12). The former were treated with 800 repeated elbow movements in a maximal predetermined amplitude of 80 degrees, provided in 8 equal sessions every other day. The latter received 10 min. of conventional physical therapy for the paretic upper extremity at similar time intervals. Pre- and posttreatment assessments included the bilateral measurements of kinematic variables and activation latencies of the biceps and triceps brachi muscles as well as motor and functional tests. For all criterion variables, the findings pointed to comparable improvement in both groups. It was concluded that repetitive elbow movements had no unique training effect on the kinematics of movement and on activation latencies of the primary muscles controlling elbow function in hemiparetic patients. Further, transfer of the effects of training to execution of movements towards and from the mouth was also comparable in both groups, pointing again to there being no particular advantage in using repetitive movements as a training mode for enhancement of elbow function in hemiparetic patients.

Aged↗
PubMed1996

Electromyographic and positional changes in the elbows of spastic hemiparetic patients during walking.

The displacement of the paretic elbow of hemiparetic patients into flexion during walking is an acknowledged associated reaction characteristic of upper limb spasticity. The main purpose of this study was to examine the step-dependent pattern and magnitude of the angular and electromyographic changes which take place during this flexion movement. Steps-related changes in elbow angle were measured on the paretic side of 14 hemiparetic patients during walking with a 4-point cane. The EMG activity of the ipsilateral biceps and triceps brachii muscles was concomitantly recorded. The activity of the brachioradialis muscle in 8 patients was monitored as well. In another trial, the angular and electromyographic activities were measured bilaterally in 7 patients during free walking. Flexion movement on the paretic side was characterized by a steep increase in flexion occurring during the first 4 steps, followed by a more gradual rise with successive stepping. Neither the electromyographic activity of the elbow flexor nor that of the extensor muscles was related to that flexion movement. The excursion into flexion on the non-paretic side was smaller than on the paretic side and incorporated flexion-extension fluctuations. The associated reaction at the paretic elbow during walking is a postural response which is triggered by the balance perturbation in the gait activity. It starts with a steep rise in flexion which seems to be reflexive in nature. The preservation of elbow flexion during walking may be an expression of stiffening of the elbow flexor muscles fibers.

Adult↗
PubMed1996

Somatosensory evoked potentials in aphasic patients.

The purpose of this study was to employ evoked potentials to evaluate the function of the somatosensory system in a group of right hemiplegic aphasic patients in whom conventional physical examination was inapplicable. Bilateral somatosensory evoked potentials (SEPs) in response to stimulation of the median nerve were recorded in 20 patients, and unilateral recordings were performed with 20 healthy, aged, matched controls. The major abnormality, present in 13 patients, was absence or reduction of the amplitude of the cortical components N19 and P22 in the lesioned side of the brain. Consequently, the only significant difference between the lesioned versus nonlesioned brain side in patients, and between patients and control subjects was in the amplitude of the cortical components. Since a strong correlation exists between the detected abnormality and impaired somatosensory function, it is concluded that it is highly probable that many aphasic patients suffer somatosensory deficits which, being difficult to assess, are overlooked by the medical personnel.

Aged↗
PubMed1993

[Survival and mortality in amputees with dysvascular lower limbs].

Survival and mortality in 248 cases of lower limb amputation for vascular disease, after prosthetic rehabilitation, were assessed. Mean survival time was 3.5 years, with survival in women less than in men. Survival was shorter in those with peripheral vascular disease as compared to diabetics, and also shorter in above-knee than below-knee amputations.

Aged↗
PubMed1993

Reaction and movement times in patients with hemiparesis for unilateral and bilateral elbow flexion.

BACKGROUND AND PURPOSE: This work was designed to study the effects of bilateral elbow flexion on the reaction and movement times of the impaired upper extremity of patients with hemiparesis. SUBJECTS: The subjects consisted of an experimental group of patients with hemiparesis (n = 25) and a control group of age-matched healthy volunteers (n = 26). METHODS: Each subject performed three sets of 16 elbow flexion trials. Two of these sets required unilateral movements, one for each upper extremity. The third set of movements required simultaneous elbow flexions of both upper extremities. In each trial, subjects were instructed to flex their elbows in response to an auditory signal from a supported initial position of 150 degrees through a goal orientation of 120 degrees. "Reaction time" was defined as the time between the auditory signal and movement initiation. "Movement time" was defined as the time between movement initiation and the completion of 30 degrees of elbow flexion. RESULTS: When subjects were asked to bilaterally flex their elbows, the reaction and movement times increased in both extremities. CONCLUSION AND DISCUSSION: It was speculated that in patients with hemiparesis, movement time of the nonparetic extremity in the bilateral task is limited by the rate of performance of the paretic extremity. The decrease in speed of these performance-determining variables in the bilateral task warrants consideration during physical therapy intervention for patients with hemiparesis.

Aged↗
PubMed1993

Quantitative evaluation of stance balance performance in the clinic using a novel measurement device.

This study was undertaken to test the clinical applicability of a novel device for measurement of stance balance performance. Samples were taken from hemiparetic patients (n = 27, age range 60-80) and of three groups of healthy subjects (24 subjects at ages 64-81, 13 at ages 27-50 and 24 aging 20-24 years). Stance was evaluated in six different positions incorporating two perturbing effects: visual deprivation and movements--linear and angular--of the base of support. Three variables were measured: sway and the values of the X and Y coordinates of the Center of Pressure. Concurrent validity of the system was assessed by comparing results with data of other works that tested comparable variables in similar populations and with already well established instrumentation. Repeatability of measurements was checked by performing all tests twice and comparing their results, as well as by calculating test retest reliability. The findings pointed to significant effects of vision and of movement of the base of support on sway, and to a significant difference between sway of hemiparetic patients and healthy subjects. The location of the COP in both the X and Y coordinates was not substantially influenced by the above effects. The agreement of the findings with existent knowledge indicates that the system is credible for measurement of body sway and of the location of the COP in various stance positions.

Adult↗
PubMed1992

Self-propelled weight-relieving walker for gait rehabilitation.

This paper describes a novel walking aid, the weight relieving walker (WRW), which partially relieves the body weight of an ambulating patient. The device incorporates a pneumatic weight relief mechanism, a restraint mechanism and a forward propulsion mechanism. Weight relief facilitates stance on an affected lower limb as well as the swing of that same limb. Restraint of the patient by the walker adds to trunk stability thereby facilitating walking movements of the lower extremities. A motorized, self-propelled walker neutralizes the effect of the walker's own weight on patient's locomotion. Additionally, it contributes to step symmetry. Data gathered from 26 patients with severe locomotion problems, point to a substantial contribution of the device to ambulation.

Adult↗
PubMed1991

Nodules elicited by Rhizobium meliloti heme mutants are arrested at an early stage of development.

Heme-deficient mutants of Rhizobium and Bradyrhizobium have been found to exhibit diverse phenotypes with respect to symbiotic interactions with plant hosts. We observed that R. meliloti hemA mutants elicit nodules that do not contain intracellular bacteria; the nodules contain either no infection threads ("empty" nodule phenotype) or aberrant infection threads that failed to release bacteria (Bar- phenotype). These mutant nodules expressed nodulin genes associated with nodules arrested at an early stage of development, including ENOD2, Nms-30, and four previously undescribed nodulin genes. These nodules also failed to express any of six late nodulin genes tested by hybridization, including leghemoglobin, and twelve tested by in vitro translation product analysis which are not yet correlated with specific cloned genes. We observed that R. meliloti leucine and adenosine auxotrophs induced invaded Fix- nodules that expressed late nodulin genes, suggesting that it is not auxotrophy per se that causes the hemA mutants to elicit Bar- or empty nodules. Because R. meliloti hemA mutants elicit nodules that do not contain intracellular bacteria, it is not possible to decide whether or not the Fix- phenotype of these nodules is a direct consequence of the failure of R. meliloti to supply the heme moiety of hololeghemoglobin. Our results demonstrate the importance of establishing the stage in development at which a mutant nodule is arrested before conclusions are drawn about the role of small metabolite exchange in the symbiosis.

Blotting, Northern↗
PubMed1991

Walking reeducation with partial relief of body weight in rehabilitation of patients with locomotor disabilities.

This study was undertaken to investigate the contribution of a weight-relieving system on the gait of patients with severe locomotor disabilities. Temporal parameters of gait and subjective evaluations of the effect of the system were studied in 24 patients and 6 healthy subjects. Partial weight relief was accomplished through a pneumatic system mounted in the ceiling over a conductive walkway which was placed between parallel bars. Subjects were tested in three walking trials: free walking, walking while harnessed to the system but without weight relief, and walking with relief of 20 percent of their body weight. Temporal measurements indicated a positive effect of the system on duration of the stance and swing phases. The percentage of the stance period of the involved lower limb relative to the uninvolved one increased by 148 percent; at the same time, the swing period of the involved limb relative to the sound one decreased to 68 percent of that value in free ambulation. A substantial increase in gait symmetry and velocity were also noted. Subjective information from the patients and observers also pointed to a facilitative effect of the system on the patients' ambulation. Conversely, natural gait velocity of the healthy subjects was impeded by weight relief through the system.

Adult↗
PubMed1990

Associative synaptic potentiation and depression: quantification of dissociable modifications in the hippocampal dentate gyrus favors a particular class of synaptic modification equations.

This report further characterizes associative long-term synaptic modification of the ipsilateral and contralateral synapses formed by the bilateral entorhinal cortical (EC) projection to the dentate gyrus (DG). The experimental model is the anesthetized hooded rat. The quantitative results qualify this system as a model for studying the rules of associative synaptic modification formulated in terms of individual synapses. Bilateral DG microelectrodes recorded both ipsilateral and contralateral EC-DG responses before and after brief, high-frequency EC conditioning stimulation. The weak contralateral pathway received high-frequency conditioning before, during, or after similar conditioning of the strong, converging ipsilateral pathway. Statistical analyses revealed two types of significant, dissociated synaptic modifications, which depend on the relationship of the ipsilateral and contralateral afferents. First, contralateral EC-DG responses potentiated or depressed when the converging ipsilateral responses concurrently either potentiated or remained unchanged. Second, contralateral EC-DG responses potentiated, depressed, or showed no change when the collateral ipsilateral responses concurrently either potentiated or remained unchanged. Correlation and contingency table analyses indicated that changes in the contralateral synaptic responses are not well predicted by changes at either neighboring synapses of the converging ipsilateral pathway or at synapses of the collateral ipsilateral pathway. The contingencies of associated pre- and postsynaptic activation determined by the conditioning paradigm, however, accurately predicted the altered synaptic responses of both ipsilateral and contralateral EC-DG pathways. The results imply that associative synaptic modification in the EC-DG system is specific to individual synapses and requires both appropriate presynaptic and postsynaptic activation. Because this system provides suitable controls for nonspecific effects of conditioning stimulation and because modification of neighboring synapses is dissociable, the EC-DG system can be used to study further those rules of activity-dependent associative modification that are formulated in terms of individual synapses. The discussion briefly considers published rules of synaptic modification, pointing out several rules that are not consistent with the experimental observations and one that agrees with the present results.

Animals↗
PubMed1989

Electromyographic responses of distal ankle musculature of standing hemiplegic patients to continuous anterior-posterior perturbations during imposed weight transfer over the affected leg.

This study was undertaken to evaluate the influence of weight shift over the affected leg of standing hemiplegic patients on the electromyographic responses of the medial gastrocnemius and tibialis anterior muscles during continuous anterior-posterior movements of the base of support. Recordings were taken from 10 hemiplegic subjects and from 9 healthy subjects of comparable age. Each subject was first tested standing with both feet on a level surface and then with either leg (in healthy subjects) or the unaffected leg (in hemiplegic subjects) raised on a step. The second testing position caused unloading of the elevated leg and weight shift, that is, loading of the other leg. The measured variables were modulation of muscular activity, determined by a modulation index formulated for that purpose, and the relative amount of integrated electromyographic activity in each muscle. Changes in both variables in the uneven stance position as compared with even stance, occurred primarily in the unaffected (unloaded) leg in the hemiplegic subjects. These changes were comparable to changes in the unloaded leg of the healthy subjects. Thus, imposed loading on the affected leg of the hemiplegic subjects did not significantly improve either the reduced modulation or the relatively low IEMG activity of the investigated muscles. Further studies are required to evaluate the contribution of weight shift to recovery of postural responses in the affected leg of hemiplegic patients.

Ankle Joint↗
PubMed1988

Postural responses of normal geriatric and hemiplegic patients to a continuing perturbation.

The electromyographic (EMG) activity of the gastrocnemius and tibialis anterior muscles was recorded from normal geriatric subjects and from hemiplegic patients subjected to a continuous back-and-forth movement of the platform on which they stood. The platform oscillated at a fixed frequency of 0.5 Hz. Movement amplitude was the largest each patient could withstand without support of the hands. Standing on the moving platform continued for 5 min. EMG recordings continued for 60 s, commencing 2 min after movement onset. Analysis of the EMG, in normal subjects revealed a typical pattern of reciprocal activity in the tibialis anterior and gastrocnemius, in synchrony with the back-and-forth movements of the platform. The cyclic activation of each muscle started before movement of the platform could cause its stretch. The normal movement-induced pattern of leg muscle activation was greatly disturbed or totally absent in hemiplegic patients. In such patients, various patterns of tonic activation of one or both muscles were observed in the sound as well as the afflicted leg. Occasional periodic activation of one muscle or the other was observed. However, such activation was not well synchronized with movement of the platform and did not last long. Based on the above observations, we concluded that the ability to adapt to a rhythmic platform movement by production of anticipatory phasic muscular contractions is severely disrupted in hemiplegics.

Aged↗
PubMed1988

The expression of the Escherichia coli uvrA gene in human cells.

Cells cultured from xeroderma pigmentosum (XP) patients are defective in excision repair of damaged DNA specifically at the incision step. In Escherichia coli this step is mediated by the UvrA, UvrB and UvrC gene products. Our goal is to express each of these genes in XP cells, singly or in combination, and to determine the most suitable conditions for generating faithful E. coli Uvr protein copies in functional concentrations and properly localized for the eventual repair of damaged chromosomal DNA or DNA which is introduced exogenously. The E. coli gpt gene in pSV2gpt is used as a selection marker for uvr gene transfection into XP cells. The uvr genes were cloned into composite pBR322, SV40 and gpt vectors in which each E. coli gene is flanked by individual SV40 regulatory elements. SV40-transformed XP-A cells were transfected with pSV2uvrASV2gpt, gpt+ colonies were selected, and cell lines established. Several lines were examined in detail. Cell lines 714 and 1511 contain uvrA together with flanking SV40 regulatory elements integrated intact in genomic DNA and express UvrA protein as well as a 95,000-dalton UvrA-related protein. The expression of uvrA was found to be 50-100-fold lower than the expression of gpt. Attempts were made to assay the mammalian UvrA protein for functionality, but endogenous activities interfered with assays for each of the UvrA protein's three activities. The peptide maps derived from partial proteolysis of the "mammalian" UvrA protein are identical to the E. coli UvrA protein. The sub-cellular location of UvrA protein in uvrA+ XP cells was investigated by fractionation of cell extracts in which an indirect immunofluorescence method revealed its location as being largely extra-nuclear. Two uvrA+ cell lines were examined for their UV-resistant phenotype and not unexpectedly were found not to be reverted to a state of repair proficiency.

Bacterial Proteins↗