Comparative distributions of numerical and areal indices of tissue capillarity.
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Animals↗
Biomedical subjects
S Egginton
Publications and source records attributed to S Egginton.
Changes in capillary perfusion induced by different patterns of activity in rat skeletal muscle.
The proportion of "perfused" capillaries was evaluated in rat tibialis anterior at rest and during two different types of contraction after timed injection of thioflavine S. Capillary/fibre (C/F) ratio was estimated for "perfused" capillaries--those filled with fluorochrome--(Cp) from photomicrographs. Sections were subsequently stained for alkaline phosphatase and C/F ratio was estimated for all capillaries (Ct). At 7.5 sec after injection of fluorochrome, Cp:Ct at rest was 0.32 +/- 0.092 in the oxidative core and 0.43 +/- 0.058 in the glycolytic cortex (means +/- SEM). This increased to 0.83 +/- 0.045 and 0.88 +/- 0.026, respectively, during selective activation of glycolytic fibres. Activation of all fibres led to a modest further increase (0.92 +/- 0.040 in the core and 0.91 +/- 0.035 in the cortex). Blood flow (measured by radiolabelled microspheres increased to a similar extent (fivefold) in both regions of the muscle during activation of glycolytic fibres; the further increase during maximal activation was much smaller in the cortex (from 4 to 41 ml/100 g/min) than in the core (from 7 to 196 ml/100 g/min). Increased capillary perfusion during muscle contractions was thus independent of the type of activity, while muscle blood flow increased more in oxidative than in glycolytic regions during maximal activation. Thus the increase in muscle blood flow with maximal activation cannot be accounted for by further recruitment of "unperfused" capillaries and must result from a significant increase in the velocity of capillary blood flow.
Animals↗
Numerical and areal density estimates of fibre type composition in a skeletal muscle (rat extensor digitorum longus).
The composition of a mixed fast skeletal muscle (rat extensor digitorum longus) was examined to quantify the difference between the relative number of the three major fibre types in a representative muscle and their relative contribution to muscle cross-section, i.e. numerical (NN) and areal (AA) densities, respectively. These two indices clearly differ in their physiological relevance. While the former may be useful in describing hyperplasia, the latter allows for differences in size among fibre types. When estimated as NN, over 20% of fields contained 5-10% SO fibres and less than 5% had 75-80% FG fibres. In contrast, only 2% of fields had an AA of 5-10% for SO fibres while around 30% contained 75-80% FG fibres. The importance of a direct method for estimating AA is emphasised, as an indirect approach may have an error of 20-30% when used for oxidative fibre types. The use of an unbiased sampling regime to minimise error in determining both numerical and areal densities of different fibre types is illustrated.
Animals↗
PO2 histograms in various models of tissue oxygenation in skeletal muscle.
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Animals↗
Quantifying capillary distribution in four dimensions.
Analysis of spatial distribution using numerical (O-D) distribution is limited to global estimates, while linear (1-D) separation of capillaries may be used to describe unrealistic spatial patterns. Intramuscular diffusion is best viewed as an integration of all distances between surrounding capillaries, or area (2-D) of influence for individual vessels. True planar analysis also accommodates other forms of heterogeneity, and may be extrapolated to give the volume (3-D) of tissue supplied by capillaries. Temporal (4-D) heterogeneity in functional spacing may then be quantified.
Animals↗
Influence of muscle phenotype on local capillary supply.
The general method used to compute a local capillary fibre ratio for each fibre is as follows. The selected area of the section is covered by a tessellation of domains. For each fibre, the contribution of each capillary whose domain intersects the fibre is computed as the proportion of the domain area which overlaps the fibre. The sum of all the contributions from overlapping domains is taken to be the effective number of capillaries contributing to that fibre, and is called here the local capillary fibre ratio (LCFR). This parameter may be normalised by dividing by fibre area to give an index, independent of fibre size, which is capable of identifying the differential capillary supply to fibre types within a mixed muscle.
Animals↗
Thermal acclimation induces adaptive changes in subcellular structure of fish skeletal muscle.
Stereological analyses of electron micrographs were used to quantify physiologically important ultrastructures of slow-twitch oxidative (red) and fast-twitch glycolytic (white) muscle fibers from striped bass (Morone saxatilis) acclimated to 25 and 5 degrees C. The fraction of cell volume occupied by the mitochondria [volume density, Vv (mit,f)] of red fibers increases from 0.286 +/- 0.018 to 0.448 +/- 0.024 between 25 and 5 degrees C; Vv (mit,f) of white fibers increased from 0.027 +/- 0.003 and 0.040 +/- 0.004 at 25 and 5 degrees C, respectively. Because of a concomitant increase in the mass of oxidative muscle, acclimation from 25 to 5 degrees C results in an increase in total mitochondrial volume per 100 g body wt from 2.58 to 6.73 cm3 in oxidative muscle and from 2.46 to 3.40 cm3 in fast glycolytic muscle. Mitochondria of red fibers are in more clustered arrays after cold acclimation. Size and cristae surface densities of individual mitochondria are not affected markedly by acclimation, suggesting true cold-induced proliferation rather than enlargement of organelles. Harmonic means of intermitochondrial spacing in red fibers decreases from 2.64 to 1.43 micron between 25 and 5 degrees C. This reduces diffusion path lengths between sarcoplasmic and mitochondrial compartments proportionately, compensating for decreases in diffusivity of aqueous solutes. Intracellular lipid droplets of red fibers markedly increase in volume density from 0.006 +/- 0.003 at 25 degrees C to 0.079 +/- 0.014 at 5 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
Adaptation, Physiological↗
Capillary density and fine structure in rabbit papillary muscles after a high dose of norepinephrine.
Two days after an iv infusion of norepinephrine (NE) (4 micrograms.kg-1.min-1 X 60 min) in rabbits, patchy myocardial damage in frozen cross sections of right and left papillary muscles was associated with loss of staining for alkaline phosphatase (ALP), an enzyme present in normal capillary endothelium, whereas a regular pattern of staining was observed in control normal muscles. Semithin cross sections of the same muscles after resin embedment gave comparable estimates of capillary density in control muscles and undamaged regions of norepinephrine-treated muscles. In damaged regions the complete absence of ALP staining corresponded with an apparent reduction in number, but not absence, of capillaries identifiable in semithin sections with light microscopy. Electron microscopy, however, revealed capillaries present in these regions in numbers similar to control undamaged tissue. Around 90% of these capillaries exhibited marked morphological abnormalities, with an 18% increase in endothelial cell volume density and a corresponding reduction in luminal volume density. These changes are similar to those reported after ischemia in cardiac and skeletal muscle. Myocardial damage induced by a high dose of NE is therefore associated 48 hr later with loss of ALP staining and endothelial cell disruption and edema, which may impair capillary perfusion and contribute to limited working cardiac performance observed previously.
Alkaline Phosphatase↗
Differing patterns of capillary distribution in fish and mammalian skeletal muscle.
The heterogeneity of capillary supply to muscles of different metabolic capacity and fibre size was assessed in slow and fast muscles from a fish and a mammal. The area surrounding each capillary delineated by equidistant boundaries from adjacent vessels, the capillary domain, was derived from morphometric analysis of histological sections. This 2-D integration of intercapillary distances may reveal heterogeneity of supply that is hidden by a global approach, especially when compared with the more usual 0- and 1-D indices of capillarisation. Mean radii of the equivalent Kroghian tissue cylinders (R) and heterogeneity of their lognormal distribution, represented by the logarithmic standard deviation (LogSD), were calculated. In eel slow muscle there was a 35-fold greater capillary density (CD) than fast muscle (698 vs 20 mm-2) although heterogeneity of capillary spacing was similar (LogSD congruent to 0.06). The difference in CD between slow and fast muscles of rat was less pronounced, but there was significantly lower heterogeneity in the aerobic tissue (LogSD = 0.08 vs 0.10) corresponding to a range in domain area of around 350-2300 microns 2 and 400-2900 microns 2, respectively. The overall capillary to fibre ratio (C:F) is inappropriate for sparse networks where many fibres lack direct capillary contact. The cumulative fraction of individual domains overlapping a muscle fibre (local capillary to fibre ratio, LCFR) plotted against fibre area showed the best correlation of any index in all tissue and was strongest in both fish muscles (r = 0.9), indicating a functionally homologous spatial distribution of capillaries with respect to muscle fibres in tissue of widely differing oxidative capacity. These data suggest that maximal oxygen supply to, or metabolite removal from, muscle fibres is not restricted to contiguous capillaries but also involves those remote from the fibre surface.
Animals↗
Metamorphosis of the American eel, Anguilla rostrata LeSeur: III. Contractile characteristics of skeletal muscle.
Previous work has suggested a common migratory strategy among fishes may involve changes in recruitment pattern of skeletal muscle types, allowing fast muscle to function continuously. In this study no evidence was found for changes in adenine nucleotide metabolism, thought to be important in fatigued muscle, with metamorphosis from the nonmigratory yellow to migratory silver eel in either slow or fast muscle tissue. Myofibrillar ATPase activity was found to be lower than reported values for other teleosts, around 0.075 and 0.17 microM inorganic phosphate mg-1 min-1 for slow and fast muscle, respectively. No change was found in the Ca++-kinetics of the enzyme within either muscle type. Likewise, no change in the contractile performance of fast muscle was evident, arguing against changes in activity pattern. In contrast to mammalian endurance exercise training where major changes in aerobic capacity occur in fast muscle, migratory pre-adaptation in eel appears to be restricted to changes in slow muscle performance. A displacement of the slow muscle force-velocity curve to the right upon metamorphosis results in 30% increase in the tension developed at maximal power output from 2.4 to 3.2 N cm-2. The difference in migratory potential between yellow and silver eels was shown previously to involve an increased aerobic capacity. The change in contractile characteristics may further improve endurance by permitting a portion of the tissue to periodically replenish endogenous energy stores.
AMP Deaminase↗
Morphometric analysis of sparse capillary networks.
Two methods were used to assess the heterogeneity of capillary supply to muscles of widely differing metabolic capacity and fibre size. Using the method of capillary domains (DOM; Hoofd et al., 1985) and the closest-individual method (CI; Kayar et al., 1981) radii of Kroghian cylinders (R) can be calculated, and the heterogeneity of their lognormal distribution represented by the logarithmic standard deviation (Log SD). Both methods yield similar values for mean R in a tissue. DOM is more direct and quicker than CI, and may be particularly useful in the analysis of capillary oxygen supply during functional hypertrophy and in muscle regeneration where a broad distribution of fibre areas may be found. Despite a 500-fold range of capillary density, to a minimum of 20 capillaries mm-2, heterogeneity of capillary supply was similar in all muscles, indicating a functionally homologous spatial distribution. The relationship between number of fibres overlapped by a capillary domain, and domain area has zero correlation in most tissues but shows a negative trend in fish fast muscle, reflecting hyperplastic and hypertrophic growth. Capillary/fibre ratio is inappropriate for sparse networks whereas the cumulative fraction of domains vs fibre area shows a strong correlation, suggesting that maximal oxygen supply to muscle fibres is not restricted to contiguous capillaries, but also involves those remote from the fibre surface.
Animals↗
Effects of an anabolic hormone on striated muscle growth and performance.
Chronic administration of an anabolic hormone, nandrolone phenylpropionate, in sedentary female rats for 6 weeks gave a 20% increase in body weight and the same proportional increase in all muscles sampled (heart, diaphragm, soleus, TA, EHP and EDL), such that the muscle/body weight ratio was unchanged. Cardiac muscle was unresponsive to treatment. Acute stimulation of EDL via lateral popliteal nerve gave similar values for contraction time, 1/2 relaxation time and twitch:tetanus ratio in both groups suggesting no slowing of the muscle. Fatigue resistance of EDL was improved with 0.29 +/- 0.029 vs. 0.46 +/- 0.071 of maximum isometric twitch tension being developed after 10 min repetitive stimulation at 4 Hz. This improved endurance was not accompanied by any increase in strength and could not be explained on the basis of cellular hypertrophy, but appears to reflect an increased aerobic capacity of skeletal muscle. The proportion of FOG fibres in EDL increased, 38 +/- 1.1% vs. 46 +/- 1.1%, and this was paralleled in the other skeletal muscles. Specific hypertrophy of FOG and FG fibres could be conclusively demonstrated in soleus and TA, respectively.
Adenosine Triphosphatases↗
Effects of an anabolic hormone on aerobic capacity of rat striated muscle.
The effect of chronic administration for 6 weeks of an anabolic steroid, nandrolone phenylpropionate (Durabolin), was studied in three predominantly glycolytic muscles, and three oxidative muscles of sedentary female rats. Mean blood pressure and resting heart rate (HR) were lower in the anabolic-treated group, while the increase in HR during stimulation of EDL was reduced. No change was noted in the aerobic capacity of ventricular myocardium, although there was an increase in skeletal muscles due to a combination of increased capillary supply and/or TCA cycle enzyme activity. Capillary:fibre ratio (C:F) increased around 10% in glycolytic muscle with little effect on resting blood flow (BF). In EDL C:F was 1.1 +/- 0.02 vs. 1.2 +/- 0.01 and BF was 7.0 +/- 1.45 vs. 6.2 +/- 1.82 ml min-1 100 g-1 for control and Durabolin treated animals, respectively (means +/- SEM, n = 7). No increase in citrate synthase (CS) activity was evident. In soleus, where C:F was not significantly different between groups, CS activity increased from 3.9 +/- 0.34 to 5.9 +/- 0.40 microM g-1 min-1 (means +/- SEM, n = 7). Glycolytic capacity, indicated by pyruvate kinase activity, increased only in diaphragm. These data demonstrate that total oxidative metabolism of striated muscle does not necessarily increase with greater proportion of FOG fibres, nor is it always correlated with capillary supply. The positive myotrophic effect of Durabolin represents the sum of modest changes at different levels of organisation.
Aerobiosis↗
Metamorphosis of the American eel, Anguilla rostrata LeSeur: I. Changes in metabolism of skeletal muscle.
Unequivocal demarcation between immature, nonmigratory yellow eels and migratory silver eels of greater sexual maturity is possible by measuring eye diameter and retinal capillary length, which undergo a 1.5- and 2.3-fold increase during metamorphosis, respectively. Anatomical arrangement of trunk musculature is similar in the two groups except for an increased depth of slow muscle in silver eel. Histochemical analysis reveals a progressive increase in numbers of "displaced" fast fibres within slow muscle of the lateral line triangle in maturing eels, although these are unlikely to affect recruitment pattern of muscle fibre types. Previous studies have suggested greater involvement of fast muscle in locomotion of migratory eels. In contrast, estimates of enzyme activity in fast muscle suggest an inadequate aerobic capacity to fuel sustained activity. Myoglobin content is extremely low, around 0.4 nM g wet wt-1. Prolonged anaerobic metabolism is also discounted as a migratory strategy. Increased energy provision for migration is apparently derived from increased capacity for both aerobic carbohydrate metabolism and mitochondrial fatty acid oxidation within slow muscle of silver eels. Activity of hexokinase (HK) shows a 1.6-fold increase (to 0.51 microM g wet wt-1) and carnitine palmitoyltransferase (CPT) a 3.1-fold increase (to 0.22 microM g wet wt-1 min-1), suggesting a maximal flux through these pathways of 18 and 14 ATP equivalents, respectively. However, the fatty acyl transferase system of skeletal muscle mitochondria displays up to threefold greater activity with palmitoleoyl CoA (C16:1) as substrate than with the usual palmitoyl CoA (C16:0). Slow muscle of silver eel is therefore capable of deriving aerobic energy from free fatty acids and carbohydrate in the ratio 2.3:1. Differences in aerobic enzyme activities are not paralleled by myoglobin content of slow muscle, being 15 and 16 nM g wet wt-1 for yellow and silver eel, respectively. Structural reorganization of muscle fibres during metamorphosis, however, results in a twofold elevation of cytoplasmic myoglobin concentration in silver eel. It would appear that dramatic differences in metabolic capacity between life history stages of eel is required to overcome locomotory inefficiency of yellow eels and to "preadapt" silver eels for migratory activity. This increased locomotory capacity may be amplified by a subsequent training response.
Aging↗
An estimate of capillary anisotropy and determination of surface and volume densities of capillaries in skeletal muscles of the conger eel (Conger conger L.).
Fast and slow muscle fibres were isolated from the axial muscles of conger eel (Conger conger L.) and examined by electron microscopy. Volume densities of mitochondria, VV (mit, f); intracellular lipid stores, VV (lip, f); and myofibrils, VV (mf, f) were respectively 0.23, 0.18, 0.47 for slow and 0.03, 0.002, 0.79 for fast fibres. Factors affecting the representative sampling of capillary supply were investigated using semi-thin (0.5 micron) sections. An estimate of the degree of capillary anisotropy was made using the assumption of a Fisher axial distribution (Mathieu, Cruz-Orive, Hoppeler & Weibel, 1983). The capillary bed is highly anisotropic. Mean capillary cross-sectional area, determined from electron micrographs, was 25.7 and 30.5 microms2 for slow and fast muscle, respectively. The number of capillaries per unit cross-sectional fibre area, NA (c,f); volume VV (c,f); and surface density, SV (c,f) of capillaries was 615 mm-1 0.016, 135 cm-1 for slow and 21.3 mm-1 0.0007, 4.7 cm-1 for fast muscle, respectively. The relationship between the extent of the capillary bed and mitochondrial volume density is discussed in relation to the function of different muscle types.
Animals↗
Muscle fibre differentiation and vascularisation in the juvenile European eel (Anguilla anguilla L.).
The differentiation of the lateral musculature in the elver stage of the European eel (Anguilla anguilla, L.) has been studied using histochemical staining techniques. Extracellular lipid deposits constitute 12% of the body cross-sectional area. Two fibre type may be distinguished on the basis of myofibrillar ATPase activity. Fibres with an alkaline-labile (pH 10.2) ATPase occur as a two-fibre layer around the trunk circumference, with invaginations along the horizontal septum and fin insertions. These pale-yellow fibres correspond to the slow ("red") fibres of other fish and comprise around 7% of the body cross-section (mean size, 167 micrometer2). Slow fibres show a moderate staining for PAS (glycogen), but a relatively weak reaction of Sudan black (lipid) and the aerobic enzyme markers succinic dehydrogenase (SDH) and cytochrome oxidase (COX). The bulk of the trunk muscle is composed of fast fibres (68%; 328 micrometer2). These are characterised by an alkaline (pH 10.2)-stable ATPase activity, and their innervation. Each fibre is innervated by a single "en-plaque" type endplate at one myoseptal end. Fast fibres adjacent to the slow fibre layer (2-4 fibres deep) show a moderate staining for PAS and a weak reaction for SDH and COX. Deeper regions show a wide range of fibre size, with about 5% being greater than 1,400 micrometer2. Fibres greater than 200 micrometer2 show no significant staining for glycogen, lipid, SDH, or COX. Small fast fibres less than 120 micrometer2 (up to 5% of the white muscle mass) show a strong staining reaction for PAS and a slight reaction for SDH and COX activities. Parameters of vascularisation were calculated from low-magnification electron micrographs (x 1,900). The number of capillaries/fibre and % fibre perimeter in contact with capillaries were, respectively, 0.98, 6.33% (slow fibres); 0.33, 1.96% (superficial fast fibres); and 0.12, 0.71% (deep fast fibres). These values are low in comparison with other fish species. It is suggested that the low aerobic capacity of elver slow muscle reflects a relatively restricted aerobic scope for activity associated with the anguilliform mode of locomotion.
Acetylcholinesterase↗
Comparative development in captive and migratory populations of the barnacle goose.
The development of the locomotory muscles and associated skeletal structures of goslings and adults from a captive population of barnacle geese (Branta leucopsis) was compared with that from a wild migratory population. There was no significant difference between flight-muscle development of wild and captive goslings up to 7 wk of age, when the birds are first able to fly. In contrast, mass-specific citrate-synthase activity in the semimembranosus leg muscle of the captive goslings was significantly lower than that of wild goslings by 5 wk of age. During the postfledging premigratory period, captive geese showed significantly higher values for both mass and mass-specific citrate-synthase activity of the leg muscles than those of wild birds. Premigratory wild geese had significantly higher citrate-synthase activity in the pectoralis muscles and larger cardiac ventricular mass (by ca. 20%-25%) than both wild postmoulting and captive premigratory adults. Total flight-muscle mass was only slightly reduced (by ca. 10%) in long-term captive adults compared with wild premigratory adults. Most of the differences between these two populations appear primarily to reflect their relative levels of activity and/or differences in their ambient environment, rather than any intrinsic differences in developmental or adult physiology.
Animals↗
Effect of muscle ischaemia and iloprost during femorodistal reconstruction on capillary endothelial swelling.
In a placebo-controlled trial skeletal muscle biopsies were taken proximal and distal to the site of arterial stenosis, before cross-clamp and 20 min following reperfusion, in 8 well-matched critical limb ischaemia patients undergoing femorodistal bypass. Capillary endothelial swelling-a sign of reperfusion injury-was assessed following infusion with iloprost, a prostacyclin analogue, the prolonged beneficial effect of which on vascular graft flow rates has been demonstrated previously. Electron microscopy and image analysis of calf capillaries confirmed that critical limb ischemia patients had endothelial cell swelling before bypass, and that cross-clamp ischaemia caused further endothelial swelling in the placebo group. Samples from muscles proximal to the site of the bypass showed similar changes, indicating that systemic capillary damage occurs in muscle remote from the area of ischaemia. Iloprost treatment prevented endothelial swelling and increased the mean capillary lumen cross-sectional area. Iloprost, therefore, has a potentially beneficial effect on capillary function by limiting reperfusion injury during femorodistal bypass.
Aged↗