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Biomedical subjects

L C Maxwell

Publications and source records attributed to L C Maxwell.

54 records · Page 3Linked to original sources
PubMed1980

Contractile properties of transplanted extensor digitorum longus muscles of cats.

Following autologous transplantation of whole extensor digitorum longus (EDL) muscles of cats into the EDL site, we investigated the degree and time course of restoration of contractile properties of autografts toward control values. Isometric and isotonic contractile properties of 66 autografted EDL muscles were measured in situ from 40 to 440 days following transplantation. The control value for maximum tetanus tension (P0) was 27 N. The mean P0 for the autografts increased from 2% of control 40 days after transplantation to 26% 440 days after transplantation. When P0 was normalized per square centimeter of muscle fiber cross-sectional area, no significant difference was observed between the P0 of autografts (28 N/cm2) and controls. Compared to controls, autografts 40-179 days following transplantation had slower time to peak twitch tensions, half-relaxation times, and maximum velocities of shortening and smaller twitch-tetanus tension ratios. Between 180 and 440 days after transplantation, values for autografts approached control values. Autografts fatigued more than twice as rapidly as controls.

Action Potentials↗
PubMed1980

Oxidative capacity, blood flow, and capillarity of skeletal muscles.

Our purpose was to test the hypothesis that the capillarity of mammalian skeletal muscles is correlated with the oxidate capacity of muscle fibers, or with the capacity for maximum blood flow. Capillarity of skeletal muscles from several species was determined using histochemical demonstration of phosphatase activity of capillary endothelium. Serial sections were incubated for succinate dehydrogenase activity as an indicator of muscle fiber oxidative capacity, and for myofibrillar ATPase activity. three types of muscle fibers were identified. Fiber area was determined by planimetry of projected cross sections. Succinate oxidase activity of whole homogenates was determined by differential respirometry. Muscle blood flow was determined experimentally or data were obtained from the literature. No consistent relation was observed for the different fiber types in the number of adjacent capillaries. Capillary density was negatively correlated with mean fiber area. Among adult animals of several species, skeletal muscles representing a 17-fold range of oxidative capacity demonstrated no relation between capillarity and oxidative capacity or muscle blood flow at maximum oxygen uptake. We find no support for relations between oxidative capacity of muscle blood flow and the capillarity of whole muscle or individual fibers and reject the hypothesis.

Adenosine Triphosphatases↗
PubMed1979

Histochemical characteristics of the masseter and temporalis muscles of the rhesus monkey (Macaca mulatta).

The histochemical characteristics, cross-sectional area and capillary of the skeletal muscle fibers of the anterior and posterior regions of the superficial masseter and the temporalis muscles are described for juvenile and adult rhesus monkeys of both sexes. Slow twitch fatigue resistant (S), fast twitch fatigue resistant (FR) and fast twitch fatigable (FF) fibers were found in varying proportions throughout the muscles; however some fibers with an intermediate myofibrillar ATPase activity were observed in the anterior masseter. No significant differences for any of the variables were found between male and female juveniles for a specific muscle sample site. However, considerable variation was found between juvenile and adult and between adult male and female monkeys in the percentages of different fiber types and the cross-sectional area of fibers in specific regions of the superficial masseter and temporalis muscles. We conclude from these observations that significant differences in function exist both within and between the different masticatory muscles of rhesus monkeys. Functional differences may result from the pronounced sexual dimorphism evident in the dentofacial complex of the rhesus monkey.

Adenosine Triphosphatases↗
PubMed1978

Free autografting of entire limb muscles in the cat: histochemistry and biochemistry.

Fifty extensor digitorium longus muscles of 25 cats were autografted, 33 with and 17 without prior denervation. After 50 days, no significant differences were observed between predenervated and nonpredenervated autografts. Autografted muscles weighed 48% of the weight of control muscles. Few original muscle fibers survived and within 2 wk autografts contained regenerating muscle fibers. The mean cross-sectional area of muscle fibers in the autografts reached 125% of the value for control nontransplanted muscles. The mean percentage of fibers classified high oxidative in autografted muscles was 67% of values for control muscles. SDH activity of autografted muscle homogenates reached 55% of control values. Up to 60 days after surgery autografts had only fast-twitch fibers. At 170 days autografts remained 95% fast twitch in composition. Revascularization began within 4 days, but the capillary to fiber ratio of long term autografts reached only 60% of control values. Although fiber hypertrophy suggests that cats use autografted muscles, lower than control succinate dehydrogenase activity may result from altered recruitment.

Action Potentials↗
PubMed1977

The free autografting of entire limb muscles in the cat: morphology.

Normal or pre-denervated extensor digitorum longus (EDL) muscles were sucessfully grafted in place of the contralateral EDL muscles in cats. Histological preparations of 57 grafts were examined at intervals from 4 to 170 days after transplantation. The morphological sequence of events in a cat muscle graft is similar to that in the rat except that the time course of regeneration is considerably slower. Surviving original muscle fibers form a thin rim at the periphery of the graft. Beneath this rim, the original muscle fibers undergo fragmentation, starting near the periphery and progressing toward the center. Regenerating muscle fibers take the place of the degenerated muscle fibers. In pre-denervated grafts, the last of the original muscle fibers in the center of the graft have broken down by 41 days whereas in normal muscle grafts the original muscle fibers in the central region persist until 50 days. The main difference between grafts of normal and pre-denervated muscles is the rate of breakdown of the original muscle fibers. Long term grafts of both groups are morphologically very similar.

Animals↗
PubMed1977

Physiological characteristics of skeletal muscles of dogs and cats.

Our purpose was to determine if physiological characteristics of skeletal muscles of dogs and cats are related to their histochemical and biochemical characteristics. Maximum oxygen consumption (VO2max) and blood flow (Q) at VO2max were determined for in situ muscles of dogs and cats. Compared to cat muscles, dog muscles per unit mass had higher succinate oxidase activities, VO2max's, and Q's at VO2max's. There are positive relationships between Q at VO2max and VO2max and between VO2max and succinate oxidase activity. The higher VO2max's and succinate oxidase activities of dog muscles are consistent with the presence in these muscles of only slow-twitch fatique-resistant fibers and fast-twitch fatique-resistant fibers, whereas up to 50% of the fibers found in cat muscles are fast-twitch fatiqable. Capillary-to-fiber ratios are 2.40-2.97 for dog muscles compared to 2.17-2.84 for cat muscles. Thus the two- to threefold higher Q at VO2max for dog muscles compared to cat muscles is not due to a greater number of capillaries.

Animals↗
PubMedDate not supplied

Neuroanastomosis of orthotopically transplanted palmaris longus muscles.

Palmaris longus (PML) muscles of rhesus monkeys were transplanted, with or without anastomosis of the median nerve, to the nerve stump of the autograft. Because PML autografts revascularize spontaneously, vascular anastomoses were not performed. Muscle fibers regenerated in all autografts with neuroanastomosis, but in only three of eight autografts without neuroanastomosis. Five autografts without neuroanastomosis were replaced by noncontractile connective tissue. Growth and differentiation of muscle fibers into three fiber types and development of capillarity were analyzed histochemically, and succinate oxidase activity of whole-muscle homogenates was determined. None of these measures reached values for control PML muscles within 100 days of transplantation. In comparison to control muscles, autografts had slower times to peak tension and less absolute tension, but similar tension per square centimeter of muscle fiber cross-sectional area. Monkey PML autografts with neuroanastomosis were similar in structure and function to cat extensor digitorum longus autografts that had not had neuroanastomosis.

Animals↗