Biomedical subjects

A M Scremin

Publications and source records attributed to A M Scremin.

At least 19 recordsLinked to original sources

PubMed2000

Peak and kinetic cardiorespiratory responses during arm and leg exercise in patients with spinal cord injury.

STUDY DESIGN: A paired comparison of the peak and submaximal responses of oxygen uptake and heart rate in patients with spinal cord injury (SCI) performing voluntary arm cycle exercise and functional electrical stimulation (FES) leg cycling exercise. OBJECTIVES: To test if the blunted heart rate response and slower rate of adjustment of oxygen uptake seen in patients with SCI performing FES leg cycle exercise are also characteristic of arm exercise in these patients. METHODS: Eight paraplegics performed incremental and constant work rate (CWR) exercise with the legs and arms. Mean response times (MRT) for Vo2 during exercise (on) and in recovery (off) were calculated from the breath-by-breath Vo2 profile. RESULTS: Peak heart rate was higher during incremental arm exercise, and uncorrelated with that observed during incremental FES leg cycling. For the same increase in Vo2, constant work rate arm exercise was associated with faster (and normal) Vo2 kinetics, greater increase in heart rate, and lower end-exercise blood lactate, compared to FES leg cycling. CONCLUSIONS: The consistently higher peak heart rate and Vo2, and faster Vo2 kinetics, for voluntary arm compared to FES leg cycle exercise suggest no intrinsic dysfunction of heart rate control in these paraplegics. Rather, these data suggest that during FES leg cycling the changes seen are due to some characteristic specific to the injury, such as reduced muscle mass and/or deconditioning of the remaining muscle. SPONSORSHIP: This research was supported by The Department of Veterans Affairs, Rehabilitation Research and Development Project #B603-RA. Spinal Cord (2000) 38, 340 - 345.

Adult↗

PubMed1999

Increasing muscle mass in spinal cord injured persons with a functional electrical stimulation exercise program.

OBJECTIVE: To determine the magnitude of changes in muscle mass and lower extremity body composition that could be induced with a regular regimen of functional electrical stimulation (FES)-induced lower-extremity cycling, as well as the distribution of changes in muscle mass among the thigh muscles in persons with spinal cord injury (SCI). STUDY DESIGN: Thirteen men with neurologically complete motor sensory SCI underwent a 3-phase, FES-induced, ergometry exercise program: phase 1, quadriceps strengthening: phase 2, progressive sequential stimulation to achieve a rhythmic pedaling motion (surface electrodes placed over the quadriceps, hamstrings, and gluteal muscles); phase 3, FES-induced cycling for 30 minutes. Participants moved from one phase to the next when they met the objectives for the current phase. MEASURES: Computed tomography of legs to assess muscle cross-sectional area and proportion of muscle and adipose tissue. Scans were done at baseline (before subjects started the program), at first follow-up, typically after 65.4+/-5.6 (SD) weekly sessions, and at second follow-up, typically after 98.1+/-9.1 sessions. RESULTS: Increases in cross-sectional areas were found in the following muscles: rectus femoris (31%, p<.001). sartorius (22%, p<.025), adductor magnus-hamstrings (26%, p<.001), vastus lateralis (39%, p = .001), vastus medialis-intermedius (31%, p = .025). Cross-sectional area of adductor longus and gracilis muscles did not change. The ratio of muscle to adipose tissue increased significantly in thighs and calves. There was no correlation among the total number of exercise sessions and the magnitude of muscle hypertrophy. CONCLUSIONS: Muscle cross-sectional area and the muscle to adipose tissue ratio of the lower extremities increased during a regular regimen of 2.3 FES-induced lower extremity cycling sessions weekly. The distribution of changes was related to the proximity of muscles to the stimulating electrodes.

Adipose Tissue↗

PubMed1999

Knee kinetics during functional electrical stimulation induced cycling in subjects with spinal cord injury: a preliminary study.

The purpose of this preliminary study was to describe pedal effectiveness parameters and knee-joint reaction forces generated by subjects with chronic spinal cord injury (SCI) during functional electrical stimulation (FES)-induced bicycling. Three male subjects (age 33-36 years old), who were post-traumatic SCI (ASIA-modified level A, level T4-C5) and enrolled in an FES rehabilitation program, signed informed consent forms and participated in this study. Kinematic data and pedal forces during bicycling were collected and effective force, knee-joint reaction forces, knee generalized muscle moments, and knee-joint power and work were calculated. There were three critical findings of this study: 1) pedaling effectiveness was severely compromised in this subject population as indicated by a lack of overall positive crank work; 2) knee-joint kinetics were similar in magnitude to data reported for unimpaired individuals pedaling at higher rates and workloads, suggesting excessive knee-joint loading for subjects with SCI; and 3) shear reaction forces and muscle moments were opposite in direction to data reported for unimpaired individuals, revealing an energetically unfavorable knee stabilizing mechanism. The critical findings of this study suggest that knee-joint kinetics may be large enough to produce a fracture in the compromised lower limbs of individuals with SCI.

Adult↗

PubMed1998

Functional electrical stimulation effect on skeletal muscle blood flow measured with H2(15)O positron emission tomography.

OBJECTIVE: To test the hypothesis that the limitation in muscle power development with functional electrical stimulation (FES) results from an insufficient increase in muscle blood flow (MBF) in response to activity. SUBJECTS AND METHODS: Five subjects with neurologically complete spinal cord injury (SCI) were tested to measure the MBF response to FES-induced knee extension. The MBF response to voluntary knee extension was measured in five age-matched, able-bodied controls. MBF was measured with positron emission tomography (PET) using H2(15)O as a tracer. Three scans were performed with muscle at rest (baseline), immediately after 16min of FES-induced or voluntary knee extension (activity), and 20min after the second scan (recovery). RESULTS: In SCI subjects, mean +/-SE MBF (mL/100g/min) values were: baseline = 1.85 +/- .48; post-FES = 31.9 +/- 5.65 (p = .0058 vs baseline); recovery = 6.06 +/- 1.52 (p = .0027 vs baseline). In able-bodied controls, mean +/-SE MBF values were: baseline = 8.52 +/- 3.24, post-voluntary exercise = 12.62 +/- 3.03 (p = .023 vs post-FES in SCI subjects); recovery = 10.7 +/- 6.01. CONCLUSIONS: MBF does not appear to be the limiting factor in muscle power generation with FES. The greater increase in MBF observed with FES in SCI subjects when compared with able-bodied subjects performing a similar task (unloaded knee extension against gravity) may relate to abnormal metabolism in FES-stimulated muscle.

Adult↗

PubMed1997

Physiologic responses during functional electrical stimulation leg cycling and hybrid exercise in spinal cord injured subjects.

OBJECTIVES: (1) To determine if a hybrid exercise (leg plus arm) training program performed immediately after functional electrical stimulation (FES) leg cycle exercise (LCE) training would further improve aerobic capacity when compared with FES leg cycle training alone, and (2) to compare the submaximal responses occurring during both FES-LCE alone and hybrid exercise in the same SCI subjects. DESIGN: Nonrandomized control trial whereby subjects act as their own control. SETTING: Outpatient rehabilitation in a primary care hospital. PATIENTS: A volunteer sample (n = 11) of men 20 to 50 years old with complete spinal cord injury, free from cardiovascular and metabolic disease with spasticity. INTERVENTIONS: Three phases of exercise training: phase I, progressive FES-LCE to 30 minutes of exercise (n = 11); phase II, 35.2 +/- 16.2 sessions of FES-LCE (n = 11); phase III, 41.4 +/- 17.7 30-minute sessions of hybrid exercise (n = 8). MAIN OUTCOME MEASURES: (1) Aerobic capacity-a further increase after hybrid exercise when compared with FES-LCE alone; (2) submaximal physiologic parameters (oxygen uptake [VO2], heart rate [HR], blood lactate [BLa-])-measurement of these during constant work rate exercise and a training effect. RESULTS: VO2 (the body's ability to utilize oxygen) significantly improved (p < .05) after both FES-LCE and then further after hybrid training. Hybrid exercise training resulted in significantly (p < .05) greater work rates and VO2 values than both FES-LCE at baseline and training work rates. CONCLUSION: These subjects demonstrated that hybrid exercise performed twice a week provided sufficient intensity to improve aerobic capacity and provide a medium whereby patients with SCI can burn more calories than via FES-LCE alone. This has important implications for improving the health and fitness levels of individuals with SCI and may ultimately reduce their risk of cardiovascular disease.

Adult↗

PubMed1997

Cholinesterase inhibition improves blood flow in the ischemic cerebral cortex.

The ability of central cholinesterase inhibition to improve cerebral blood flow in the ischemic brain was tested in Sprague-Dawley rats with tandem occlusion of left middle cerebral and common carotid arteries. Cerebral blood flow was measured with lodo- 14C-antipyrine autoradiography in 170 regions of cerebral cortex. The regional distribution of blood flow was characterized in normal animals by cerebral blood flow maxima in the temporal regions. After 2 h ischemia, minimum cerebral blood flow values were found in the lateral frontal and parietal areas on the left hemisphere, and a new maximum was found in the right hemisphere in an area approximately symmetrical to the ischemic focus. Heptyl-physostigmine (eptastigmine), a carbamate cholinesterase inhibitor with prolonged time of action improved cerebral blood flow in most regions, with the exception of the ischemic core. The drug also enhanced the ischemia-induced rostral shift of cerebral blood flow maxima in the right hemisphere. The effects of eptastigmine were more marked 24 h after ischemia. Discriminant analysis showed that data from only 22 regions was sufficient to achieve 100% accuracy in classifying all cases into the various experimental conditions. The redistribution of cerebral blood flow to the sensorimotor area of the right hemisphere of animals with cerebral ischemia, a phenomenon possibly related to recovery of function, was also enhanced by eptastigmine.

Animals↗

PubMed1996

Changes in gas exchange kinetics with training in patients with spinal cord injury.

We examined the ability of patients with spinal cord injury to undergo adaptations to chronic exercise training (cycle ergometry) invoked by functional electrical stimulation (FES) of the legs. Nine such patients performed incremental and constant work rate exercise before and after exercise training. Exercise sessions averaged 2.1 +/- 0.4/wk, and consisted of 30 min/session of continuous FES recumbent cycling with increasing work rate as tolerated. Peak VO2 and peak work rate significantly improved with training. Peak VO2 was significantly correlated with peak heart rate both before and after training (r = 0.97 pre and 0.85 post, P < 0.01 for both). The time course of the VO2, VCO2 and VE responses to constant-load exercise (unloaded cycling) and in recovery (mean response time MRT) were very long prior to training, and became significantly faster following training. However, there was no correlation between percentage improvement in either MRTon or MRToff for VO2 and the percentage increase in peak VO2. Exercise tolerance in these patients with spinal cord injury appears to be a direct function of the ability to increase heart rate. Further, exercise training can elicit significant improvements in both exercise tolerance and in gas exchange kinetics, even when performed only twice per week. However, these improvements may be accomplished by different mechanisms.

Adaptation, Physiological↗

PubMed1995

Gas exchange kinetics during functional electrical stimulation in subjects with spinal cord injury.

We examined the kinetics of VO2, VCO2, and VE following the onset of unloaded leg cycling, and in recovery, in six patients with spinal cord injury (SCI). Exercise was produced by functional electrical stimulation (FES) of the quadriceps, hamstrings, and gluteal muscles. End-exercise VO2 (1.03 +/- 0.16 l.min-1), VCO2 (1.20 +/- 0.22 l.min-1) and VE (41 +/- 10 l.min-1) were elevated compared to values typically seen in healthy ambulatory subjects performing similar unloaded cycling. Mean response times for the on transients (MRTon) were both long and variable across subjects for VO2 (165 +/- 62 s), VCO2 (173 +/- 58 s), and VE (202 +/- 61 s). Recovery kinetics showed much less intersubject variability, and for five of six subjects were faster than the equivalent exercise MRT for all three variables (MRToff for VO2 of 103 +/- 28 s, VCO2 136 +/- 20 s, and VE 144 +/- 34 s), but P > 0.05 for all three. Size of the O2 deficit (1.96 +/- 0.90 l) and end-exercise lactate (7.05 +/- 1.65 mmol.l-1) were similar to values reported for healthy sedentary subjects performing maximal voluntary exercise, but the end-exercise heart rate (102 +/- 16 bpm) was lower than expected for this intensity of exercise. In conclusion, FES-induced unloaded cycling leads to exaggerated responses of pulmonary gas exchange and long time constants in patients with SCI. The delayed kinetics may be due in part to a blunted increase in heart rate in addition to severe deconditioning.

Adult↗

PubMed1995

Peak and submaximal physiologic responses following electrical stimulation leg cycle ergometer training.

Eight males with spinal cord injury (SCI) participated in an exercise training program using neuromuscular electrical stimulation (NMES) leg cycle ergometry. Each subject completed a minimum of 24 (mean +/- SD = 38.1 +/- 17.2) 30-minute training sessions over a 19-week period. The initial work rate (WR) of 0 watts (W) of unloaded cycling was increased when appropriate with subjects exercising at 11.4 +/- 3.7 W (range = 6.1 W-18.3 W) at the end of the training program. Randomized block repeated measures ANOVA was used to compare pretraining and posttraining peak physiologic responses during graded NMES leg cycle tests and subpeak physiologic responses during 10 minutes of NMES leg cycle exercise at an absolute WR (0 W). A significant (P < or = 0.05) increase was observed for peak VO2; (+10%, 1.29 +/- 0.30 to 1.42 +/- 0.39 1.min-1). No other statistically significant differences were noted for any other peak variable (VCO2, VO2 ml.kg-1 min-1, VE, WR, HR, RER) pre- to posttraining. During submaximal NMES leg cycle testing, a significant decrease was noted for RER (-9.2%, 1.19 +/- 0.14 to 1.08 +/- 0.09). No other submaximal variable (VO2 1.min-1, ml.kg-1.min-1, VCO2, HR, VE) showed significant changes as a result of the training. Although the improvement in peak VO2 was not as dramatic as those reported in previous studies, it appears that NMES leg cycle training performed two times per week can significantly enhance cardiorespiratory fitness.

Adult↗

PubMed1994

Myogenic knee contracture from acute pelvic venous thrombosis.

A unique case of knee extension contracture resulting from acute pelvic venous thrombosis is presented. Magnetic resonance imaging/angiography and electrodiagnosis aided in understanding the pathogenesis and hence in designing the treatment. Neuropathies contributed to the severity of the problem. Physical treatment to ease the edema improved knee joint range of motion but did not fully restore knee flexion.

Acute Disease↗

PubMed1993

Selective vulnerability of white matter during spinal cord ischemia.

The long-term effects of spinal cord ischemia were studied in 21 rats by lesion scores (LS, n = 21), somatosensory evoked potentials (SEP, n = 16), electromyographic measurements (EMG, n = 12) and histology of the spinal cord (n = 21) 48.5 +/- 57.2 days after 10- to 12-min occlusion of the thoracic aorta and subclavian arteries. All the animals were initially paraplegic with a spastic presentation but seven recovered within 2 days (group A), demonstrating low LS (3.4 +/- 1.05) normal EMGs (n = 3) and unremarkable histology. The 14 paraplegic animals presented relevant findings of the lumbar cord consisting of white matter lesions only (group B, n = 7) or white and gray matter lesions (group C, n = 7). Group B animals showed severe deficit (LS = 11.8 +/- 2.93) without denervation on EMG (n = 5) or muscle atrophy on histology. Group C animals displayed equal impairment (LS = 14.4 +/- 0.71), denervation on EMG (n = 4), and muscle atrophy. Resting motor unit activity of groups B and C were significantly different from group A (p < 0.001), while LS of groups B and C did not differ (p = 0.083). These data underscore the nature and the extent of white matter lesions during spinal cord ischemia, a finding which has generally been eclipsed by emphasis on gray matter lesions in previous studies.

Animals↗

PubMed1993

Prolonged effects of cholinesterase inhibition with eptastigmine on the cerebral blood flow-metabolism ratio of normal rats.

The cerebrovascular and metabolic effects of the novel cholinesterase inhibitor eptastigmine were tested in conscious rats. The drug was administered by single intravenous injection, and blood flow or glucose utilization were assessed in 38 brain regions by quantitative autoradiographic techniques. A dose-dependent increase in regional cerebral blood flow (rCBF) was obtained for i.v. doses ranging from 0.5 to 3 mg kg-1. Forty minutes after the dose of 1.5 mg kg-1, average rCBF of the 38 regions studied was (mean +/- SD) 2.62 +/- 0.62 ml g-1 min-1, a value significantly higher than that of saline-injected controls (1.46 +/- 0.26; p < 0.005). In contrast, a similar dose of eptastigmine did not significantly alter regional cerebral glucose utilization (rCGU) (0.90 +/- 0.21 mumol g-1 min-1) when compared with saline-injected controls (0.99 +/- 0.08 mumol g-1 min-1). A linear correlation between rCBF and rCGU was observed both in saline (r = 0.871) and eptastigmine (r = 0.873)-injected animals but the slope of the regression line of rCBF on rCGU was significantly higher (p < 0.01) in the eptastigmine group (2.863 +/- 0.266) than in the controls that received saline (1.00 +/- 0.094). The cerebral vasodilatation induced by eptastigmine peaked at 40 min after drug administration. No toxic signs were observed at the doses used. Mean arterial blood pressure decreased after 0.5 mg kg-1 (control = 109.3 +/- 10.56 mm Hg; eptastigmine = 96.6 +/- 8.10 mm Hg) but did not differ from control at the higher doses. It is concluded that eptastigmine induces a long-lasting increase in rCBF and a significant enhancement of the rCBF:rCGU ratio in most regions. The results suggest an important role of endogenous acetylcholine in the control of cerebral perfusion.

Animals↗

PubMed1993

Effect of age on progression through temporary prostheses after below-knee amputation.

Forty six patients that underwent below knee amputation for diabetes, trauma/osteomyelitis or peripheral vascular disease were studied. Healing was estimated by the rate of progression through temporary prostheses as determined weekly by the amputee rehabilitation team (physiatrist, orthopedist, physical therapist, nurse, and prosthetist). For all groups combined, mean days +/- standard error from amputation to above knee cast with pylon and foot (AKPy) were 22.9 +/- 1.9, to below knee cast with pylon and foot (BKPy) 41.6 +/- 2.8 and to laminated temporary prostheses 66.5 +/- 4.5. A regression analysis of these variables on age (range: 29 to 84 yr) showed significant positive correlations for AKPy (r = 0.34, P = 0.0214) and BKPy (r = 0.40, P = 0.0056). An analysis of variance with contrasts (Tukey's protected t) showed significant lower values (P < 0.05) for amputation to BKPy in the trauma/osteomyelitis group when compared to diabetes or peripheral vascular disease and no difference among the last two groups. However, when variables were adjusted for age (analysis of covariance with age as a covariate), the differences among groups disappeared (covariance F(2,44) = 0.9, P > 0.4). In conclusion, age, not the cause of the amputation, correlated with healing after below knee amputation as estimated by the rate of progression through temporary prostheses.

Adult↗

PubMed1993

Isokinetic dynamometric technique for spasticity assessment.

This study was conducted to determine the feasibility of quantifying spasticity by measuring the resistance to passive movement using an isokinetic dynamometer. A quantifiable method was developed by determining the summation of the four consecutive resisting torque amplitudes during flexion and extension of the knee at specified speeds and range of motion. A more rigorous assessment was made by finding the slope of the linear regression curve of torque-velocity data. Although the values of maximum torque were higher in the spastic group than in the normal group, the difference was statistically significant only when the sum of the torque amplitudes was considered (P < 0.0028). Values of the maximum torque as well as the sum of the torque amplitudes increased in a linear fashion (r > 0.75) with increasing velocity. The slopes of the torque-velocity curves were greater in spastic subjects than in normal subjects. The sensitivity to the rate of stretch was statistically greater (P < 0.0004) for the spastic group than normals only when the sum of torque amplitudes was considered. The corresponding data obtained during the flexion and extension of the knee were not statistically different (P > 0.05). Serial summation of torque amplitudes and measurement of slope in the torque-velocity curve are sensitive and repeatable methodologies for the measurement of spasticity assessment.

Adult↗

PubMed1993

Effect of "standing" on spasticity, contracture, and osteoporosis in paralyzed males.

The effect of "standing" in a frame on spasticity (clinical assessment and H-reflex), contracture (lower extremity joint range of motion), and osteoporosis (dual photon absorptiometry) was studied in six paralyzed males (mean age 49 yr) who had been confined to wheelchairs for an average of 19 years. Standing time averaged 144 hours over a mean of 135 days. Clinical Assessment measured reflexes, tone, and clonus in the legs. Results revealed no important differences between initial and final scores for clinical assessment and joint range of motion. In three subjects for whom H-reflexes were found, latency and amplitude were not altered by "standing." Bone density was normal in the lumbar spine but significantly reduced in the femoral neck. "Standing" did not modify the bone density in any site. A follow-up interview revealed that 67% of subjects continued to "stand" and felt healthier because of it. In summary, "standing" had no ill effects, did not alter measured variables, and had a positive psychological impact.

Absorptiometry, Photon↗

PubMed1991

Role of nucleus basalis in cholinergic control of cortical blood flow.

The present investigation was designed to determine the effect of lesions localized to the nucleus basalis/substantia innominata (NB) on resting and cholinergically activated regional cerebral cortical blood flow (rCBF). Ibotenic acid (10 micrograms) was infused locally at 1 mm caudal to bregma, 3 mm lateral to the midline, and 8 mm below the cortical surface. Effectiveness of lesions was demonstrated by histological verification of lesion sites and determination of choline acetyltransferase activity in cerebral cortex homogenates. rCBF was measured with the autoradiographic iodo-14C-antipyrine technique. Resting rCBF was similar in the hemisphere that received the NB lesion and in the contralateral (intact) side in all regions examined. Physostigmine intravenous infusion (3.3 micrograms.kg-1.min-1) enhanced rCBF in frontal, parietal, occipital, and temporal cortex. The increase was symmetrical, however, indicating inability of NB lesion to affect this phenomenon. It is concluded that the cortical cholinergic afferents originating in the NB are not involved in the control of rCBF.

Acetylcholine↗

PubMed1990

Glucose utilization and reflex activity of the transected rat spinal cord.

Spinal cord glucose utilization (SCGU) of gray and white matter was studied with the quantitative autoradiography [14C]2-deoxyglucose methodology, below and above a complete low thoracic transection. One day after transection, a generalized decrease in SCGU was observed in gray matter, particularly marked in the dorsal horn of the lumbar cord. A progressive increase in SCGU was observed thereafter. Values reached levels greater than those of non-transected controls by 2 and 4 weeks after the intervention in ventral horn of the lumbar cord, and ventral and dorsal horn of the cervical cord. A similar behavior of SCGU was observed in white matter of transected animals. The development of 17 lumbar reflex modalities was quantified between days 1 and 28 after spinal transection. The delay in emergence of these reflexes was related to their complexity. Correlation of reflex scores with SCGU was significant for all lumbar cord regions but linearity of this relationship was only observed in white matter. These results uncover a close relationship between SCGU and reflex activity of the spinal cord below a complete transection, particularly striking in white matter and suggests a role of the fasciculi proprii of the spinal cord in this phenomenon.

Animals↗

PubMed1990

Brain regional distribution of physostigmine and its relation to cerebral blood flow following intravenous administration in rats.

3H-labeled physostigmine (50 micrograms.kg-1) was administered intravenously to rats, and its concentration in brain tissue and spinal cord was assessed by quantitative autoradiography. Regional cerebral blood flow (rCBF) was measured with iodo-14C-antipyrine autoradiography in control rats and in animals injected i.v. with a dose of physostigmine similar to that used for the distribution studies. Tissue concentration of 3H-physostigmine was correlated with rCBF for 37 brain regions. A high degree of correlation was found at 0.5 min after drug injection, r (correlation coefficient) = 0.87. This association decreased at later times (5 min r = 0.73, 12 min r = 0.24). Structures with high cholinesterase activity (caudate-putamen, amygdala, hippocampus) showed greater retention of physostigmine over time. The highest initial physostigmine concentrations were found in regions lacking a blood-brain barrier (pineal bland, median eminence, choroid plexus) (range = 10.4-23.8 nCi/mg) and the lowest in white matter (corpus callosum, internal capsule, hippocampus commisure, spinal cord dorsal column) (range = 1.2-2.6 nCi/mg). Initial concentrations of the drug in the areas in which physostigmine induced vasodilatation (motor, sensory, temporal and occipital cortex, claustrum, and superior collicullus) were not different from concentrations in areas of comparable basal rCBF in which no such effect was observed. Variations in drug access to brain regions, then, do not explain the topographical variations of the cerebrovascular action of physostigmine.

Animals↗