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K Tyml

Publications and source records attributed to K Tyml.

49 records · Page 3Linked to original sources
PubMed1987

Red cell perfusion in skeletal muscle at rest and after mild and severe contractions.

The aim of this study was to evaluate the distribution of red cell perfusion in sartorius muscle of anesthetized frogs by analyzing simultaneously red cell velocity (VRBC), number of cells per unit capillary length (NRBC), and density of perfused capillaries (CD) in a 2.07 X 2.71-mm region of the muscle visualized microscopically at very low magnification. In the 16 muscles studied, a severe 1-min electrical stimulation induced statistically significant increases in the mean values, VRBC, NRBC, and CD, as well as significant decreases in heterogeneities (SD/mean) of these three parameters when going from rest to postcontraction hyperemia. A mild 3-s stimulation caused significant increases only in VRBC and NRBC. Red cell perfusion, computed as a product of the three parameters divided by the mean capillary length, increased significantly from 87.4 +/- 81.9 to 417.9 +/- 118.2 (SD) and from 96.9 +/- 75.7 to 192.5 +/- 190.2 (SD) cells X s-1 X mm-3, respectively. In both stimulations, the postcontraction increase of red cell supply to the muscle, expressed in cells per second per cubic millimeter, was larger than any individual increase in the three parameters. Based on pooled data from all muscles, both NRBC and CD were determined to be dependent on VRBC. The present study supports the view that VRBC, NRBC, CD, and heterogeneity of red cell distribution depend on vascular tone and demonstrates for the first time that these four dependencies can operate both concurrently and synergistically to increase O2 supply to muscle after contraction.

Animals↗
PubMed1986

Capillary recruitment and heterogeneity of microvascular flow in skeletal muscle before and after contraction.

The two objectives of this study were to evaluate the spatial distribution of velocities measured simultaneously in a population of capillaries at the surface of a sartorius muscle in anesthetized frogs, and to estimate the cross-sectional density of capillaries perfused with red cells in this muscle at rest and after supramaximal stimulation. In each of 10 muscles studied, the mean velocity associated with this distribution increased significantly after the stimulation (overall increase from 0.12 mm/sec in control to 0.46 mm/sec at the peak of hyperemia). The coefficient of variation (i.e., ratio of standard deviation to mean velocity), however, decreased, indicating that the individual velocities became relatively more homogeneous and that microvascular adjustments occurred at the capillary level. Additionally, the proportion of capillaries with zero or very low velocities (0-0.1 mm/sec) was reduced practically in all muscles suggesting an improved oxygen exchange after every stimulation. In contrast to these consistent velocity responses in all muscles, capillary recruitment was detected only in 5 out of 10 muscles (overall density increase from 104 to 134 cap/mm2). This partial occurrence of recruitment (range, 23-149%) was associated with control mean velocities less than 0.1 mm/sec. Since, in light of the velocity data, the absence of recruitment in the 5 remaining muscles did not necessarily signify the lack of microvascular adjustments at the capillary level, it is proposed that more sensitive indexes, such as the reduction in the proportion of low flow capillaries and the increase in relative homogeneity, be used in addition to or instead of recruitment, to describe more completely the microvascular response to stimulation.

Animals↗
PubMed1985

Are endothelial cells rich in filaments involved in the phenomenon of electrically induced stoppages of flow in frog capillaries?

The aim of this study was to determine the frequency of occurrence of the phenomenon in skin and muscle capillaries in both young and mature frogs and to examine the ultrastructure of endothelial cells found in these capillaries. Using microelectrode techniques, trains of pulses of durations up to 90 s, amplitudes -0.2 to -2.0 V, frequencies 10 to 64 Hz and pulse widths 5 to 50 msec were applied to microscopically visualized capillaries situated either in skin (knee region) or at the surface of a sartorius muscle in metamorphosed, intermediately aged or mature frogs. Reproducible flow stoppages induced by these trains of pulses occurred in 2.3%, 1.4% and 6.7% of all tested muscle capillaries and in 11.1%, 82.5% and 68.6% of all skin capillaries in the three age groups, respectively. Examinations of electron micrographs of very thin sections of both skin and muscle capillaries revealed that only 13 out of 47 (27.7%) and 4 out of 45 (8.9%) endothelial cells in these two tissues contained filament bundles. In light of these ultrastructural findings, the dramatically high occurrence of the phenomenon of electrically induced stoppages of flow in skin capillaries (in both intermediately aged and mature frogs) cannot be explained in terms of the hypothesis involving endothelial cells rich in filaments. It is concluded that caution must be exercised when interpreting this phenomenon in terms of the several microvascular responses which the electrical stimulation can elicit.

Age Factors↗
PubMed1985

Simultaneous assessment of red cell perfusion in skeletal muscle by laser Doppler flowmetry and video microscopy.

The objective of this study was to compare temporal and spatial variations of the laser Doppler flowmeter output (V) with the corresponding variations of perfusion (cells/mm3 X mm/s) evaluated by video microscopy. The flowmetry and video microscopy sampled 2 mm3 (approx.) and 0.84 mm3 surface volumes of the sartorius muscle in anesthetized frogs, respectively. The overall ranges of the output and perfusion measurements were from 0.01 to 0.72 V and from 45 to 1404 cells/mm3 X mm/s. Within these ranges, temporal variations induced by muscle contraction correlated well (overall r = 0.91), but the spatial variations associated with the resting state correlated poorly (overall r = 0.45). When the penetration of the laser light was limited to 0.3-0.4 mm (to make the volumes sampled by both techniques more comparable) the overall r of the spatial comparison increased to 0.86. It is concluded that the flowmeter (1) is affected by red cell perfusion below the tissue depth of 0.3-0.4 mm, and (2) can follow both the temporal and spatial variations of red cell perfusion in the tissue examined.

Capillaries↗
PubMed1984

Occurrence of the "capillary contractility" phenomenon and its significance in the distribution of microvascular flow in frog skeletal muscle.

The phenomenon of "capillary contractility" was first described more than 100 years ago. Recent reports on this phenomenon in the frog mesentery have been based on the observation of dramatic reductions of luminal diameter and blood flow during electrical stimulation of the capillary wall. The aim of this study was to establish the presence and the occurrence of this phenomenon in the frog sartorius muscle and to evaluate its contribution to the distribution of flow. Eight 1.3 X 1.7-mm areas of the muscle surface in eight anesthetized frogs were visualized by means of a microscope and also video-recorded during stimulation experiments. Microelectrodes and semitransparent surface electrodes introduced constant currents (0.1 to 1.0 microA) or pulse trains (5-msec pulse width, 1 to 64 Hz frequency, -0.2 to -5.4 V amplitude) either to individual capillaries or to whole populations of capillaries situated in these areas. Caution was exercised that stimuli did not cause muscle twitching. Red cell velocity in capillaries was measured from video recordings by the flying spot technique. Microelectrode stimulations caused flow stoppages in 4 out of 60 individual stimulated capillaries. Surface electrode stimulations had practically no effect on the mean red cell velocity in any of these populations but an appreciable effect on individual velocities in 7.5% of all capillaries in these populations. It is concluded that the phenomenon of electrically induced reductions of flow exists in the frog sartorius muscle, but it is scarce. It seems unlikely, therefore, that it represents a major mechanism of flow distribution in this tissue.

Acetylcholine↗
PubMed1983

Heterogeneity of capillary diameters in skeletal muscle of the frog.

Capillary diameters in sartorius muscle of frogs were measured in vivo by means of a new computer video method, based on the passage of red blood cells (RBCs) through the capillary (C. Ellis, R. Sanfranyos, and A. Groom (1983), Microvasc. Res. 26, 139-150). The distribution of capillary diameters from 21 frogs was represented by a histogram with a mean +/- SD of 16.7 +/- 4.4 microns (N = 83). The measured dimensions (mean +/- SD) of frog RBCs, which have a flattened ellipsoidal shape, were: major axis = 24.1 +/- 2.6 microns (N = 149); minor axis = 16.5 +/- 1.5 microns (N = 158); thickness at center = 5.4 +/- 0.8 microns (N = 32). Frog RBCs travel through capillaries with their major axes predominantly parallel to the direction of flow; therefore, RBCs pass through capillaries without deformation provided that the diameter of the capillary is larger than the minor axis of the cell. By standardizing the measured values of capillary diameter in terms of mean minor dimension of the RBCs (ratio of means for frog being 1.0, approx), we were able to compare the diameter distribution in an amphibian with that in a mammal (rat). If RBC size alone mattered, both standardized distributions should superimpose; however, that for frog was shifted to the right of that for rat, indicating that frog RBCs are less deformable than RBCs of rat. This highlights the necessity, in the microcirculation, for matching capillary diameter to both size and deformability of the red cell.

Animals↗
PubMed1982

Evaluation of the flying spot technique as a television method for measuring red cell velocity in microvessels.

The success of measuring red cell velocity in microvessels by television methods based on cross-correlation depends to a considerable extent on the optical contrast between red cells and plasma gaps passing through these vessels. Poor optical contrast, such as under conditions of low magnification, may result in deteriorated cross-correlograms and, consequently, in completely erroneous velocity values. The success of measuring velocity by the flying spot technique, however, depends only on the operator's ability (1) to discern the moving red cells, and (2) to match the speed of the spot to that of these cells. We have implemented this technique as a television method and estimated the subjective error involved in this velocity matching. Under a total magnification of 112 X, the estimated relative errors among four observers in the velocity range from 0.10 to 0.57 mm/s varied between 4.4 and 14.9%, while the overall error was 8.7%. It was concluded that this technique can provide, in the range from 0 up to possibly 1-2 mm/s, quick and reliable velocity measurements with a reasonable accuracy. Also, since no sophisticated equipment is required for the implementation, this method, at present, is much less expensive than the other conventional television methods for measuring velocity.

Animals↗
PubMedDate not supplied

Effect of superoxide dismutase and 21-aminosteroids (lazaroids) on microvascular perfusion following ischemia-reperfusion in skeletal muscle.

Intravital video microscopy was used to test superoxide dismutase and a lazaroid analogue, U-74389F, as a pretreatment for ischemia-reperfusion-induced microvascular dysfunction in skeletal muscle. Twenty-two male Wistar rats (350-400 g), anesthetized with sodium pentobarbital (65 mg/kg i.p.), were divided into groups to test the lazaroid analogue U-74389F (3 mg/kg; n = 8), a citric acid/citrate mixture (CS-4; n = 4) used as the vehicle for the lazaroid analogue, superoxide dismutase (SOD, 10 mg/kg; n = 5), and saline (n = 5). Normothermic ischemia of the extensor digitorum longus muscle was induced for 3 h by tightening a tourniquet placed around the limb above the muscle. Measurements of the number of perfused capillaries (CDper; mm-1) and capillary red blood cell velocity (VRBC; mm/s) were made after 30, 60 and 90 min of reperfusion. Thirty minutes following release of the tourniquet, all test groups showed a significant drop in CDper. The extent of this reduction was maximal in SOD treated muscles, while it was minimized in the lazaroid-treated muscles following 90 min reperfusion. Hyperemia occurred only in muscles treated with saline or lazaroid. The hyperemia was of limited duration in saline-treated muscles, but lasted the entire reperfusion period following lazaroid treatment. An index of microvascular flow, estimated from the product of VRBC and CDper, indicated that flow was significantly greater in muscles treated with lazaroids as compared with all other groups following the 90-min reperfusion. We conclude that whereas SOD was detrimental, the lazaroid analogue U-74389F improved microvascular perfusion following 3 h of no-flow ischemia and 90 min reperfusion.

Animals↗
PubMedDate not supplied

Capillary ultrastructure and functional capillary density.

We briefly summarize our findings on alterations in capillary structure in skeletal muscle and heart in response to up to 30 min of ischemia. In frog sartorius muscle, reactive hyperemia was absent in atrophy. Increased spatial heterogeneity of red cell velocity in individual capillaries was observed, as were increases in the percentage of capillaries with damaged endothelium and white cell volume density in capillaries. Examination of the effect of aging on the response of the vascular bed to 30 min ischemia in extensor digitorum longus muscle of Fisher 344 rats suggested that the lack of postischemic hyperemia and structural alterations in frog muscle were related to disuse rather than aging per se. However, the specific study of disuse in rat extensor digitorum longus muscle after chronic application of tetrodotoxin revealed both capillary damage and a postischemic hyperemic response. It suggested an effect of the degree of tissue deterioration on the hyperemic response after short-term disuse in rat muscle, compared to longer-term atrophy in frog. Morphometric data in isolated rabbit heart suggested a link between microvascular compression as a result of tissue edema and decreased perfusion after 30 min total ischemia.

Aging↗