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Biomedical subjects

N H McKee

Publications and source records attributed to N H McKee.

At least 19 recordsLinked to original sources
PubMed1995

Recovery of synergistic skeletal muscle function following ischemia.

This study tests the hypothesis that if the fast twitch muscles in a synergistic group were more susceptible to ischemia/reperfusion injury, then the slow twitch muscle would compensate functionally during recovery. Rat hindlimb fast twitch gastrocnemius and plantaris muscles and slow twitch soleus muscle were studied. In the experimental (E) group of rats, the right hindlimbs had 2 hr of pressure-controlled (300 mmHg) tourniquet ischemia. The masses and the maximal isometric tetanic forces of the three muscles were evaluated at 1, 3, 5, and 7 weeks in E (n = 24) and a control (C) group of rats (n = 24). Gastrocnemius mass and plantaris mass were both reduced (at 1, 3, and 5 weeks and at 1 and 3 weeks, respectively), whereas there were no significant changes in the mass of the soleus. The maximal isometric tetanic forces (N) measured at 1 week of recovery were reduced to 52, 53, and 67% of C values for the gastrocnemius, plantaris, and soleus, respectively. However, at 1 week the normalized isometric tetanic forces (N/g) for all three muscles were reduced to 66-69% of the C values. By Week 3, the tetanic forces (N or N/g) of all muscles had recovered to control values. On average, the gastrocnemius, plantaris, and soleus muscles of the C groups contributed 68, 24, and 8%, respectively, of the total synergistic tetanic force. These values were unaffected by ischemia. From this experiment, it is concluded that 2 hr of tourniquet ischemia resulted in a selective decrement in mass of the fast twitch muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Fiber type morphometry and capillary geometry in free, vascularized muscle transfers.

In order to establish the relationship among intraoperative ischemia time, the recovery of contractile function, muscle fiber morphometry, and capillary geometry following free muscle transfer, 15 male dogs underwent unilateral, orthotopic free transfer of the left gracilis muscle with microneurovascular anastomosis. Intraoperative ischemia time varied from 0 to 4 hours. After a recovery period averaging 14 months, isometric contractile function was measured in the transfers and the contralateral, control muscles. Muscle fiber type composition, fiber size, and capillary geometry were quantified from histochemical sections. Transferred and control muscles had similar type I fiber percentages, type I fiber sizes, and capillary densities. Type II fiber sizes were reduced in transfers relative to controls. There was no significant effect of intraoperative ischemia on any morphometric variable. Although contractile function was generally reduced after free, vascularized transfer, there was only a weak correlation between the recovery of tetanic tension and type I fiber percentage (r = 0.53, P less than 0.05). It is concluded that free, vascularized muscle transfer results in minimal disturbance of muscle fiber type composition, fiber size, or capillary supply and that the diminished contractile function observed in this setting is still largely unexplained.

Analysis of Variance↗
PubMed1991

Perfusion parameters and pressure at zero flow in canine gracilis muscle flaps.

The perfusion parameters and pressure at zero flow were examined in island gracilis muscle flaps in dogs under sodium pentobarbital anesthesia. Complete surgical isolation of the muscle preparation was obtained. Normal blood flow in denervated muscle in situ was 8.0 +/- 0.8 ml/min/100 g tissue as measured by electromagnetic blood flowmetry. The artery supplying each flap was occluded with a microclip and the drop in pressure distal to the clip was observed. The lowest pressure obtained following occlusion was the pressure at zero flow. A positive pressure at zero flow in the vascular bed was thereby identified at a pressure of 10.3 +/- 1.2 mm Hg.

Animals↗
PubMed1990

Skeletal muscle fiber type, fiber size, and capillary supply in elite soccer players.

This study determined the fiber type composition, the fiber size, and the capillary characteristics of the vastus lateralis muscle in 11 young, elite, male soccer players and 8 sedentary male, age-matched controls. There were no significant differences (P less than 0.05) in the fiber type percentages and fiber diameter between the soccer players and controls; however, all fiber types tended to be larger in the soccer players. The soccer players possessed a greater capillary supply; this was characterized by a significantly greater mean number of capillaries surrounding each fiber (5.7 +/- 0.9 vs. 4.9 +/- 0.4), a significantly larger capillary density (282.7 +/- 42.0 vs. 220.8 +/- 38.1), and a significantly higher capillary to fiber ratio (2.2 +/- 0.6 vs 1.7 +/- 0.1). The results indicate that soccer may be an appropriate stimulus for simultaneous adaptation to endurance and high intensity exercise.

Adult↗
PubMed1989

Isometric contractile function recovery following tourniquet ischemia.

The purpose of this study was to document the recovery of isometric contractile function following tourniquet ischemia. Male Wistar rats (N = 27) were subjected to unilateral hindlimb tourniquet ischemia of 0 hr (control, N = 6), 1 hr (N = 5), 2 hr (N = 5), 3 hr (N = 5) and 4 hr (N = 3). Following a 2-week recovery period, isometric force measurements were made from both gastrocnemii of each rat with the contralateral limb acting as the control side. Each muscle was analyzed for maximal twitch (Pt, N/g), maximal rate of rise of twitch tension (DP/dt, N/sec), time to peak tension (TPT, msec), half relaxation time (RT 1/2, msec), maximal tetanus (P0, N/g, at 100 Hz), and fatigue (Burke Fatigue Protocol). Pt, P0, and DP/dt were significantly different from control values (P less than 0.05) for all hours of tourniquet ischemia. A strong negative correlation (P less than 0.001) was found for twitch (R = -0.84), tetanus (R = -0.78), and maximal rate of force development (R = -0.83) with respect to increasing hours of ischemia. The recovery of isometric twitch and tetanic function following tourniquet ischemia is inversely related to the ischemic interval. This study quantified the relationship between muscle ischemia and recovery of function following a 2-week interval and stresses the functional physiological changes which occur in skeletal muscle following tourniquet ischemia.

Animals↗
PubMed1989

Nerve fibre morphometry: a comparison of techniques.

This study compared different approaches to measuring nerve axon and fibre diameters and areas from transverse sections. A mock photomicrograph and mock tissue section, each with 100 identical, circular 'fibres' was constructed. Three measurement protocols were investigated: (A) circular approximation from minimum diameter; (B) circular approximation from the mean of orthogonal diameters; and (C) calculation of diameter and area from a digitized circumference. For each protocol, all 100 fibres on the photomicrograph were repeatedly measured using a digitizing tablet. Similarly, the fibres on the mock tissue section were measured using a digitizing tablet and microscope with camera lucida. The variance for these data was calculated. Protocols were compared on the basis of variability and the amount of digitizing time required. For diameter measurements, protocol B showed significantly lower variability than A or C (P less than 0.05), with only a modest increase in digitizing time over A. For area measurements, protocols B and C showed significantly lower variability than A (P less than 0.05), again with a modest increase in digitizing time. Measurements made using the microscope and camera lucida showed significantly lower variability than those made from the photomicrograph, but took more time. These data suggest that for diameter measurements, a mean of orthogonal diameters approach is best, and that for area measurements, a traced circumference approach is best as it is more flexible than the orthogonal diameter approach. While the microscope and camera lucida setup is more time-consuming to use, it eliminates the need for photomicrograph production.

Animals↗
PubMed1989

Functioning free muscle transplantation: making it work? What is known?

Since the early 1970s, the feasibility of transferring a muscle and having it survive and eventually function has been demonstrated both in research laboratories and clinically. Over a decade later, the factors influencing success are better understood. There have been significant contributions in concepts of muscle anatomy, muscle physiology, muscle reinnervation, and muscle's response to ischemia. Ischemia time, within reason, does not appear to be as influential as first thought. The potential for demonstrating the efficacy of postoperative exercise is but one of the areas that could benefit from further research endeavors.

Animals↗
PubMed1989

The distribution of microfilament bundles in rabbit endothelial cells in the intact aorta and during wound healing in situ.

The distribution of microfilament (MF) bundles in rabbit thoracic aortic endothelial cells (EC) fixed in situ was examined using en face preparations and the fluorescent probe 7-nitrobenz-2-oxa-1,3-diazole-phallacidin. In the normal aorta, prominent peripheral MF bundles are seen near the cell borders running the full length of each cell, parallel to the direction of blood flow, while shorter less prominent bundles are seen in the more central regions. In EC covering the flow dividers at intercostal ostia, the central MF bundles are more prominent, longer, and more numerous than in the other regions of the aorta examined. This increase in the number, size, and length of central MF bundles may result from the response of the cells to the higher shear forces present in this region of the vessel wall. Following denudation of the endothelium from a segment of the aorta with a balloon catheter, there is an initial reduction in the size of all of the MF bundles in cells near the wound edge. This is followed by an increase in the number and size of the central MF bundles. At 48 h after wounding, strongly stained central MF bundles could be detected in EC up to 0.75 mm from the wound edge. Adjacent to the wounds that had failed to reendothelialize 10 months after denudation, some regions had EC with prominent peripheral MF bundles and others, EC with prominent central MF bundles. At the very edge of the wound, the EC and their MF bundles were oriented with their long axes parallel to the wound edge and perpendicular to the direction of blood flow. The failure of the wounded vessel wall to become fully reendothelialized may be related to the orientation of EC at the wound edge. These results show that EC migration in situ is accompanied by a dramatic change in the organization of MF in which different stages can be identified. Microfilament bundles in rapidly migrating cells in vivo, 24 and 48 h after wounding, resemble stress fibers seen in EC migrating in vitro and in slowly migrating fibroblasts and epithelial cells.

Actin Cytoskeleton↗
PubMed1989

A comparative histochemical and morphometric study of canine skeletal muscle.

The purpose of this study was to determine whether there were differences in skeletal muscle properties in the hindlimb muscles of different types of dogs. Muscle samples were obtained from the gracilis, sartorius cranial head, sartorius caudal head and tibialis anterior muscles of mixed-breed and hound-type dogs and Beagles. Fiber type, fiber size and capillary morphometry determinations of each muscle from each dog were made from sections stained for myofibrillar ATPase activity. Individual animals were bilaterally symmetric for all measured variables. Fiber type, fiber size and capillary geometry varied between dogs of a given type and muscles within a given dog. There were no differences between dog types for fiber type or fiber size; significant variation in log(muscle)/log(body) mass ratios between dog types was observed for all muscles. The results indicate that for a given muscle, significant variation can occur in skeletal muscle characteristics between different types of dogs and that these differences can be independent of differences in exercise history.

Adenosine Triphosphatases↗
PubMed1988

The effect of intraoperative ischemia on the recovery of contractile function after free muscle transfer.

Isometric contractile function was studied after recovery in free, vascularized muscle transfer subjected to graded periods of intraoperative ischemia. Fifteen dogs had orthotopic replantation of their left gracilis muscles, with intraoperative ischemia times grouped as 0 (n = 3), 1 to 2 (n = 3), 2 to 3 (n = 4), or 3 to 4 (n = 5) hours. After recovery (mean 61.8 weeks), isometric twitch and tetanic tension and fatigue measurements were made in the replants and in the contralateral, control gracilis. On the average, replants were found to produce significantly less twitch (0.32 +/- 0.13 versus 0.49 +/- 0.24 N/g) and 75 Hz tetanic tension (2.2 +/- 0.9 versus 3.4 +/- 0.5 N/g) than controls. However, in several individual replants, 100% of control maximal tetanic tension was observed. Intraoperative ischemia time of up to 4 hours was not correlated with functional return. It is concluded that (1) full recovery is possible after free muscle transfer; (2) intraoperative ischemia, if less than 4 hours long, is not the primary determinant of functional recovery; and (3) factors besides intraoperative ischemia must be operative in producing the variability in recovery seen in this setting.

Animals↗
PubMed1988

Myosin light chains in regenerating rat skeletal muscle following chronic, low-frequency, electrical stimulation.

Ten days of chronic, low-frequency, electrical stimulation of regenerating rat extensor digitorum longus muscle causes an increase in the percentage of slow, phosphorylatable myosin light chains with a complementary decrease in the total fast light chain content. This altered light chain expression is similar to that observed when electrical stimulation is applied to a developing muscle in vivo.

Animals↗
PubMed1988

Fiber type, fiber size, and capillary geometric features of the semitendinosus muscle in three types of dogs.

The fiber type, fiber size, and capillary geometric features were determined from the center of the proximal half of the left and right semitendinosus muscles in 5 mixed-breed dogs, 5 hound-type dogs, and 5 Beagles. There were no significant differences between the left and right muscles of each dog. Comparisons among the 3 groups of dogs revealed that the hound-type dogs had the largest fibers (type I and type II); however, the 3 groups were similar in their fiber-type percentages and their capillary geometric features.

Animals↗