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Biomedical subjects

R R Roy

Publications and source records attributed to R R Roy.

At least 199 records · Page 11Linked to original sources
PubMed1987

Fiber-type composition of selected hindlimb muscles of a primate (cynomolgus monkey).

The distribution of fiber types in selected leg and thigh muscles of three male Cynomolgus monkeys were determined. Almost all fibers could be classified as fast-glycolytic (FG), fast-oxidative glycolytic (FOG), or slow-oxidative (SO) according to the qualitative histochemical staining scheme described by Peter et al. (1972). Most muscles showed regional variations in fiber-type distributions, i.e., the percent SO was higher and the percent FG was lower in the deep, compared to the superficial, regions of the muscle. Exceptions were the soleus and plantaris muscles, which contained similar distributions of fiber types throughout their cross sections. In the extensor compartment of the leg, a layering of fiber types from deep to superficial were evident in the triceps surae and plantaris complex with the deepest muscle, the soleus, having primarily SO fibers. A similar layering arrangement was observed in the extensor compartment of the thigh, with the deepest muscle, the vastus intermedius, having a much larger proportion of SO fibers than the other muscles in the quadriceps complex. These results indicate that Cynomolgus monkey hindlimb muscles, unlike human leg muscles (Saltin and Gollnick: Handbook of Physiology, L.D. Peachey, ed. American Physiological Society, MD, pp. 55-631, 1983) have a regional distribution of fiber types similar to that observed in many subprimate mammals. Further, the presence of compartmentalization of fiber types within the cross section of several of the muscles studied is suggestive of structure-function interrelationships related to motor control.

Animals↗
PubMed1987

Electromyography of rat soleus, medial gastrocnemius, and tibialis anterior during hind limb suspension.

Hind limb suspension is a model frequently utilized to study muscle plasticity. One reason for its frequent use is that it is thought to mimic in many respects the conditions imposed on some muscles during spaceflight. Changes in muscle properties that follow hind limb suspension generally have been attributed to reductions in the recruitment of these muscles. To determine the validity of this assumption, the electromyographic (EMG) activity of three hind limb muscles, the soleus, a slow extensor, the medial gastrocnemius, a fast extensor, and the tibialis anterior, a fast flexor, was studied. The EMG was recorded in each rat for 25 min of each hour for 24 consecutive hours, 7 and 3 days prior, on the day of, and 3, 7, 14, 21, and 28 days after hind limb suspension. Control rats were treated similarly and their EMG recorded on corresponding days. Compared with presuspension, soleus activity was reduced significantly to 91% on the first day of suspension, but had recovered to 81% of its normal activity by the seventh day. Similarly, there was a significant reduction to 54% in activity of the medial gastrocnemius on the day of hind limb suspension which recovered to 98% of its presuspension values by day 7. In contrast, the tibialis anterior showed a significant increase in activity relative to presuspension values within 3 days of the initiation of suspension. These data indicate that hind limb suspension produced only a relatively short-term reduction in the activity of both the soleus and medial gastrocnemius and results in an increased activity in the tibialis anterior. Collaborative studies showed that significant alterations in muscle mass and metabolic and mechanical properties occurred and persisted in spite of the recovery of activation in the soleus and medial gastrocnemius. In addition, no alterations in mass and mechanical properties were evident in the tibialis anterior during a 4-week suspension even though the EMG increased after hind limb suspension. Together, these data indicate that the adaptations in muscle properties following hind limb suspension are not closely related to changes in the total amount of muscle EMG activity per day.

Adaptation, Physiological↗
PubMed1987

Mechanical properties of rat skeletal muscle after hind limb suspension.

It is clear that there are events which occur in response to neuromuscular activity that are essential to maintain normal muscle properties. Two factors though to influence muscle contractile properties are tension and electrical activity. To study these variables the hind limbs of 10 postpubertal female Sprague-Dawley rats were prevented from supporting the weight of the body for 4 weeks, then in situ isometric properties were determined and compared with 10 age-matched control rats. The soleus (slow plantarflexor), the medial gastrocnemius (fast plantarflexor), and the tibialis anterior (fast dorsiflexor) were studied. The suspended soleus wet weight was 42% lower and the maximum isometric twitch (Pt) and tetanic (P0) tensions were 62 and 69% lower respectively, than in the control rats. The suspended medial gastrocnemius was 18% lower in wet weight and 14 and 9% lower in P0 and Pt than the controls. No differences in wet weight, P0 or Pt were observed in tibialis anterior. Mean contraction time was 22% shorter in the soleus, 9% in the medial gastrocnemius, and unchanged in the tibialis anterior following suspension. Further, the percent of P0 attained during a 330-ms tetanus at 20 Hz was 15% lower in the suspended soleus and unchanged in the other two muscles. The fatigue index (ratio of tension after 2 min of stimulation at 40 Hz for 330 ms once per second to the maximum tension developed during the test) was unaffected by suspension in the soleus and tibialis anterior but was reduced from 49% to 36% in the medial gastrocnemius. The maximum rate of shortening of all three muscles was unaffected by suspension. These results indicate that suspension of the hind limbs selectively affects the mass and force-generating capabilities of the plantarflexors, particularly the predominantly slow soleus. In contrast, the fatigability of only the fast plantarflexor was increased whereas the slow plantarflexor was unaffected. These results, considered in light of collaborative studies, suggest that the chronic force-time levels in a muscle have an important influence on tension- and speed-related properties but not necessarily the fatigability of that muscle. Further, a marked difference in the sensitivity of the contractile elements of slow and fast muscle to this influence was evident.

Animals↗
PubMed1987

Size and metabolic properties of single muscle fibers in rat soleus after hindlimb suspension.

The effects of 28 days of hindlimb suspension (HS) and HS plus 10 daily forceful lengthening contractions on rat soleus muscle fibers were studied. Compared with age-matched controls (CON), soleus wet weights of suspended rats were significantly decreased (approximately 49%). In HS rats, the light adenosinetriphosphatase (ATPase) fibers (staining lightly for myosin ATPase, pH = 8.8) atrophied more than the dark ATPase fibers (staining darkly for myosin ATPase, pH = 8.8). Single-fiber alpha-glycerophosphate dehydrogenase (GPD) and succinate dehydrogenase (SDH) activities and the proportion of dark ATPase fibers were higher in HS than CON rats. Daily forceful lengthening contractions did not prevent the suspension-induced changes. These results considered in conjunction with a collaborative study on the mechanical properties of HS rats (Roy et al., accompanying paper) suggest a shift in the contractile potential of the muscle following HS without a deficit in SDH, a metabolic property commonly associated with resistance to fatigue. The results support the view that soleus muscle fibers can change from a slow-twitch oxidative to a fast-twitch oxidative-glycolytic profile, but rarely to a fast-twitch glycolytic one, and that SDH and GPD activity per volume of tissue can be maintained or increased even when there are severe losses of contractile proteins.

Adenosine Triphosphatases↗
PubMed1987

Size and metabolic properties of fibers in rat fast-twitch muscles after hindlimb suspension.

Hindlimb suspension (HS) results in whole muscle atrophic and metabolic changes that vary in magnitude in different hindlimb muscles. The present study was designed to investigate these effects in single fibers. Fiber type and size and the activities of two metabolic marker enzymes were determined in a deep (close to the bone) and a superficial (away from the bone) region of the medial gastrocnemius (MG) and the tibialis anterior (TA) of control (CON) and 28-day HS adult female rats. Fibers were classified as dark or light adenosinetriphosphatase (ATPase) based on their qualitative staining reaction for myosin ATPase following alkaline preincubation. Fiber area and succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) activities were determined in tissue sections by use of an image analysis system. After 28 days of HS, the mean body weights of the CON and HS were similar. MG atrophied 28%, whereas TA weight was maintained in the HS. Both dark and light ATPase fibers in the deep region of the MG had smaller cross-sectional areas following HS, with the atrophic response being approximately twice as great in the light ATPase fibers. No significant changes in fiber type composition in either muscle or in fiber sizes in the superficial region of the MG or in either region of the TA were observed. Mean SDH activities of both fiber types were significantly lower in the MG and TA following HS. In contrast, mean GPD activities were either increased or maintained in light and dark ATPase fibers of both muscles in HS. Changes in SDH and GPD activity could not be directly linked to changes in fiber cross-sectional area. In summary, these data suggest an independence of the mechanisms determining muscle fiber size and metabolic adaptations associated with HS.

Adenosine Triphosphatases↗
PubMed1987

Maximal force as a function of anatomical features of motor units in the cat tibialis anterior.

In 11 tibialis anterior muscles of the cat, a single motor unit was characterized physiologically and subsequently depleted of its glycogen through repetitive stimulation of an isolated ventral root filament. Muscle cross sections were stained for glycogen using a periodic acid-Schiff reaction, and single-fiber optical densities were determined to identify those fibers belonging to the stimulated motor unit. Innervation ratios were determined by counting the total number of muscle fibers in a motor unit in sections taken through several levels of the muscle. The average innervation ratios for the fast, fatigueable (FF) and fast, fatigue-resistant (FR) units were similar. However, the slow units (S) contained 61% fewer fibers than the fast units (FF and FR). Muscle fibers belonging to S and FR units were similar in cross-sectional area, whereas fibers belonging to FF units were significantly larger than fibers belonging to either S or FR units. Additionally, muscle fibers innervated by a single motoneuron varied by two- to eightfold in cross-sectional area. Specific tensions, based on total cross-sectional area determined by summing the areas of all muscle fibers of each unit, showed a modest difference between fast and slow units, the means being 23.5 and 17.2 N X cm-2, respectively. Variations in maximum tension among units could be explained principally by innervation ratio, although fiber cross-sectional area and specific tension did contribute to differences between unit types.

Animals↗
PubMed1986

Fiber type and fiber size of cat ankle, knee, and hip extensors and flexors following low thoracic spinal cord transection at an early age.

Effects of low thoracic spinal transection on muscle weights, fiber type distributions, and fiber cross-sectional areas (CSAs) of selected cat hind limb mixed-fast flexors and extensors and slow extensors were studied. Cats were spinalized at T12 at 2 weeks of age and maintained for 6 to 12 months. In general spinalization resulted in a decrease in muscle weights of extensors, while the weights of those muscles that function as either flexors or as both flexors and extensors were maintained. The percentages of fast-twitch [fast glycolytic (FG) and fast oxidative-glycolytic (FOG)] fibers increased and slow oxidative (SO) fibers decreased as a result of spinalization. However, FG fibers had a smaller CSA after spinal transection in both extensors and flexors. The total relative CSA of FG fibers per whole muscle was similar in spinalized and control cats. The relative muscle CSA occupied by SO fibers decreased in extensors and flexors as a result of a lower proportion of SO fibers and/or smaller SO fibers in spinalized cats. These findings suggest that muscles become more "fast-like" histochemically while little change occurs in the oxidative staining properties in either extensors or flexors in 6- to 12-month-old cats transected at 2 weeks of age. Further, these data suggest that the amount of muscle atrophy that occurs as a result of spinal transection is not closely related to the percentage reduction in SO fibers.

Animals↗
PubMed1986

Effects of training on the recovery of full-weight-bearing stepping in the adult spinal cat.

The effects of ambulatory training on the extent and time course of recovery of weight-bearing-stepping in cats spinalized (T12-T13) as adults were investigated. One month after spinal cord transection, 14 of 16 cats were capable of bearing the full weight of their hindquarters with their hind limbs during stepping on a motor-driven treadmill if the tail was pinched or crimped. Of those 14 cats 8 were assigned to a trained and 6 to an untrained group. Trained cats were subjected to 30 min/day of treadmill exercise, 5 days/week. Training was initiated 1 month posttransection and continued until 5 to 7 months posttransection. Daily records were kept on the treadmill speeds used, the time at each speed, and the number of steps that were not full weight bearing. The number of full-weight-bearing steps times treadmill speed was used as a measure of performance. The tail was crimped whenever necessary, but was required less and less as training progressed. Performance plateaus were reached between 25 and 85 days after initiating training (mean = 48 +/- 22 days). Maximum treadmill speeds increased in untrained cats from 0.075 +/- 0.042 m/s 1 month posttransection to 0.240 +/- 0.042 m/s 5 to 7 months posttransection and those of trained cats increased from 0.079 +/- 0.045 m/s to 0.619 +/- 0.133 m/s during this same period. We conclude that a much larger proportion of adult spinal cats are capable of full-weight-bearing stepping than reported, and that training which emphasizes early tail crimping and complete weight bearing at all times results in marked improvements in the locomotor capacity of the hind limbs.

Animals↗
PubMed1986

Fiber type and fiber size changes in selected thigh muscles six months after low thoracic spinal cord transection in adult cats: exercise effects.

The effects of low thoracic spinal cord transection on muscle weights, fiber type compositions and, fiber cross-sectional areas of selected hind limb muscles were studied. Adult cats were spinalized at T12 and maintained for approximately 6 months. Some spinalized cats were exercised on a treadmill 30 min/day, 5 days/week to determine the role of weight support in maintaining the muscle properties. Spinalization resulted in a significant decrease in the weights of most extensors, whereas the flexors or those that act as both flexors and extensors were maintained near control values. All muscles showed a significant increase in the percentage of fast-twitch fibers and decrease in slow oxidative fibers following spinalization. In addition, the predominant fast fiber type in each muscle tended to have the largest decrease in cross-sectional area in the spinalized cats. The atrophic and fiber type adaptations were less pronounced in the exercised cats. In contrast, the relative cross-sectional area of high oxidative fibers generally was similar among the three groups. These results demonstrated that the muscles below the level of the lesion became more "fast-like" histochemically following spinal cord transection, whereas the oxidative properties were relatively unaffected. Further, daily exercise involving weight support appeared to be an important deterrent to these atrophic responses, particularly in the muscles that normally have a postural function (i.e., the slow extensors).

Animals↗
PubMed1986

Multiple-section radionuclide tomography of the kidney: a clinical evaluation.

The clinical utility of radionuclide emission tomography of the kidney in comparison with conventional gamma-camera imaging has been assessed from scans of 60 patients suspected of having space-occupying lesions of the kidney. Nineteen patients had renal tumour, 17 had cysts and seven had renal pseudotumours; the remainder had no lesion. Objective trials using four observers showed only a slight, statistically insignificant advantage from the addition of tomographic sections to conventional images. However, in several individual cases tomography had aided diagnosis, particularly in obese patients, when an alternative non-invasive investigation (ultrasonography) was inconclusive. In seven patients a positive diagnosis of renal pseudotumour was made possible by tomography; definite identification of ectopic functioning cortical tissue at the location of a mass suspected after urography was considered to be a distinct diagnostic advantage gained from emission tomography of the kidney.

Adenocarcinoma↗
PubMed1985

Recruitment patterns in the rat hindlimb muscle during swimming.

Cycle periods and electromyographic (EMG) burst durations of selected extensors and flexors are shorter during swimming than during running at 27 m/min, while the relative ON-OFF timing of these interrelationships are similar. The mean EMG activities of the tibialis anterior and adductor longus were higher and the soleus and medial gastrocnemius were lower during swimming than during running. Both fast and slow extensors are activated during both forms of locomotion, thus demonstrating that there is not a selective recruitment of fast or selective inhibition of slow ankle extensors during swimming as measures of muscle blood flow have suggested.

Animals↗
PubMed1985

Biochemical and physiological changes in overloaded rat fast- and slow-twitch ankle extensors.

The rat soleus (SOL) or medial gastrocnemius (MG) were chronically overloaded by removing their major synergists bilaterally. After 12-14 wks the overloaded SOL (OS) and overloaded MG (OMG) muscles had approximately 50% greater cross-sectional areas (CSA) than the controls. Maximum twitch (Pt) and tetanic (Po) tensions were approximately 46% larger in the OS compared with the normal SOL. The OMG produced 10 and 37% higher Pt and Po, respectively. Specific tension (Po/CSA) was not altered in either group (P greater than 0.05). Contraction times and half-relaxation times were unchanged. Myofibrillar and myosin ATPase specific activities indicated a shift toward that resembling a slower muscle in both the OS and the red portion but not the white portion of the OMG. Generally, markers of glycogen metabolism were reduced (P less than 0.05) in the same muscle areas that showed reduced ATPase activity. These biochemical results were consistent with the apparent histochemical conversion of fibers from fast-twitch, glycolytic----fast-twitch, oxidative-glycolytic----slow-twitch, oxidative types in these muscle areas. These results suggest that overloading either a fast- or slow-twitch plantarflexor results in an increase in muscle mass and maximum tension and in metabolic shifts that generally resemble those observed in a slower muscle. Further, the degree of adaptation appears to be related to the initial fiber type composition of the muscle and/or of the muscle region.

Adenosine Triphosphatases↗
PubMed1985

How flexible is the neural control of muscle properties?

The issue addressed in this paper is to what extent are selected physiological properties and associated protein systems of muscle fibres controlled or regulated by neuronal systems. One extreme position would be that all muscle proteins are controlled completely by the neural system that innervates the muscle. The opposite position would be that none of the muscle proteins are under neural influence. Although the concept that there is complete neural control of all proteins has generally received more support, it is more likely that there is only partial neural control of some proteins. Identical physiological, morphological and metabolic properties of all muscle fibres within a motor unit would suggest a complete neural control of all protein systems in muscle fibres. However, evidence against this idea is provided by the marked heterogeneity in the activities of two enzymes, alpha glycerophosphate dehydrogenase and succinic dehydrogenase (SDH), and in the wide variations in muscle fibre cross-sectional areas among fibres of the same motor unit in the cat soleus and tibialis anterior.

Animals↗
PubMed1984

Architectural design and fiber-type distribution of the major elbow flexors and extensors of the monkey (cynomolgus).

Because the architectural and biochemical properties of skeletal muscle dictate its force, velocity, and displacement properties, the major extensors (triceps brachii) and flexors (biceps brachii, brachialis, and brachioradialis) of the elbow in a primate (cynomolgus, monkey) were studied. Functional cross-sectional areas (CSA) were calculated from muscle mass, mean fiber length (normalized to a 2.20 microns sarcomere length), and angle of fiber pinnation measurements from each muscle. Fiber-type distributions were determined and used as a gross index of the biochemical capacities of the muscle. The extensor group had a shorter mean fiber length (31 vs. 47 mm), a larger CSA (13 vs. 8 cm2), and a higher overall percentage of slow-twitch fibers (47 vs. 26%). Consequently, the elbow extensors had a relatively greater potential for force production and force maintenance than the flexors. In contrast, the flexors were designed to optimize their length-velocity potentials; i.e., they had relatively long fibers and a higher fast-twitch fiber composition than the extensors. These morphologic differences between antagonistic muscle groups should be considered when evaluating the motor control mechanisms regulating reciprocal movements about the elbow.

Animals↗
PubMed1984

Architectural and histochemical analysis of the semitendinosus muscle in mice, rats, guinea pigs, and rabbits.

The architectural and histochemical properties of the anatomically distinct compartments of the semitendinosus muscle (ST) of mice, rats, guinea pigs, and rabbits show that the ST is composed of two separate compartments aligned in series--a distal compartment (STd) and a proximal one (STp). The STp is further subdivided into a ventral head (STpv) and a dorsal head (STpd). The muscle fibers were arranged in parallel to the line of muscle pull within each compartment. The STd has the longest and the STpv the shortest fibers in all species. The physiological cross-sectional area and the estimated tetanic tension was greatest in the STd. Based on the staining pattern for myosin ATPase (alkaline preincubation) and an oxidative indicator (NADH or SDH), the STpv has the highest percentage of slow-oxidative (SO) or SO plus fast-oxidative-glycolytic (FOG) fibers of any portion of the muscle. The differences in fiber-type distributions and architectural designs of the separate compartments suggest a specialization of function of the individual compartments.

Animals↗
PubMed1984

A technique for estimating mechanical work of individual muscles in the cat during treadmill locomotion.

Mechanical work, the product of force and length change, was assessed in selected hindlimb extensors of two adult cats during three different speeds of unrestrained treadmill locomotion. Forces were measured using implanted transducers placed on the soleus (SOL) and medial gastrocnemius (MG) tendons. A three dimensional technique of muscle length estimation using high speed cinematography was found preferable to either two dimensional or trigonometric measurements derived from anatomical and kinematic parameters. Length excursions increased in both muscles as treadmill speed increased. However, at all speeds of locomotion, the uniarticular SOL exhibited a greater range of motion than the biarticular MG. Increases in treadmill speed resulted in higher peak forces in the MG and constant or slightly lower peak forces in the SOL. These speed-dependent changes in length and force resulted in higher total positive work, lower total negative work, and higher net work for both muscles with increasing speeds. These data illustrate the importance of three-dimensional kinematics in determining changes in muscle length and describe the relative force and work changes in a slow and fast ankle extensor with changes in speed of locomotion.

Animals↗
PubMed1984

Interrelationships of contraction time, Vmax, and myosin ATPase after spinal transection.

Interrelationships of selected mechanical and biochemical properties of hindlimb extensor muscles following low thoracic cord transection were studied. Kittens were spinalized (Sp) at 2 wk and maintained for 6-12 mo. Some Sp animals were exercised (Sp-E) on a treadmill 25-30 min/day, 5 days/wk. In situ contractile properties of the slow-twitch soleus (SOL) and fast-twitch medical gastrocnemius (MG) muscles of normal (N), Sp, and Sp-E cats were determined. Exercise did not affect most parameters; thus Sp and Sp-E groups are considered collectively. The cross-sectional areas (CSA) of the SOL and MG decreased by 43 and 32%, respectively. Specific tension (tension/CSA) was maintained in the SOL but decreased (P less than 0.05) in the MG. Contraction time (CT) and half-relaxation time were significantly shorter in the SOL but unchanged in the MG. Maximum shortening velocity (Vmax) and myosin ATPase (mumol X mg-1 X min-1) increased (P less than 0.05) in the SOL of both groups and the MG of Sp. Frequency-tension responses of both muscles shifted toward that resembling a "faster" muscle. These results substantiate the existence of relatively independent regulatory mechanisms for Vmax and CT and show that myosin ATPase levels are more closely related to Vmax than CT. Although the changes in the SOL were consistent with the hypothesis that slow fibers are converted to fast, the elevated Vmax and myosin ATPase of the MG suggest that significant changes also occur within a "fast" fiber-type category.

Adenosine Triphosphatases↗