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D W Slaaf

Publications and source records attributed to D W Slaaf.

At least 91 records · Page 5Linked to original sources
PubMed1989

Effect of blood gases and pH on thromboembolic reactions in rabbit mesenteric microvessels.

The influence of changes in systemic blood gas and pH values on the thromboembolic reaction following wall puncture was studied in rabbit mesenteric arterioles and venules (diameter 20-40 microns), using intravital video-microscopy. Under normal circumstances the number of emboli produced was higher in arterioles than in venules (6 and 1, respectively). The initial thrombus growth, the number of emboli produced per vessel and the total duration of the embolisation period were not significantly influenced by changes in blood gas and pH values in both arterioles and venules. Therefore, the observed difference in thromboembolic reaction between arterioles and venules cannot be explained by differences in blood gas and pH values in these microvessels. Since reduced velocity, as a measure of wall shear rate, did not correlate with the thromboembolic reaction in arterioles or venules, fluid dynamics can also not explain the difference, indicating that the thrombogenic or antithrombogenic activity of arteriolar and venular walls differs following injury. A combination of hypercapnia and hypoxia was found to result in a prolongation of the average time period needed to produce a new embolus in both vessel types. This prolongation in embolus production time was largely due to the occurrence of periods, in which the thrombus did not grow, reflecting hampering of the adhesion and aggregation of blood platelets to a growing thrombus under hypercapnic/hypoxic conditions.

Animals↗
PubMed1989

Effect of ketanserin on macrocirculatory and microcirculatory blood flow in patients with intermittent claudication. A prospective randomized study.

The effect of ketanserin on macrocirculatory and microcirculatory blood flow was investigated in a placebo-controlled, double-blind trial in 11 patients suffering from intermittent claudication using Doppler velocimetry and intravital skin capillary microscopy, respectively. After 1 year of treatment no significant change was observed either in the ketanserin or the placebo group. It appears that ketanserin has no significant effect on macrocirculatory blood flow and microcirculatory nutritional skin blood flow in patients with intermittent claudication.

Aged↗
PubMed1989

Exercise-induced focal skeletal muscle fiber degeneration and capillary morphology.

The relationship between exercise-induced focal muscle fiber degeneration and changes in capillary morphology was investigated in male Wistar rats. Untrained animals ran on a treadmill for 1 h at submaximal intensity and were killed 0, 6, or 24 h after running. Nonexercised rats served as controls. In situ perfused soleus muscles were prepared for electron microscopy. Micrographed cross sections were quantitatively analyzed for parameters indicative of capillary blood flow or transcapillary exchange. Capillary lumina were ovally rather than circularly shaped, and no indications for obstruction of blood flow at the capillary level were found. Endothelial cells and their organelles had a normal appearance in all groups. However, immediately after exercise, capillaries showed a decreased thickness of their endothelium and basal membrane, probably caused by dehydration. Six hours after exercise, muscle fibers were swollen (28% increase in cross-sectional area), resulting in a slightly increased diffusion distance. This fiber swelling was not associated with an increase in muscle water content, a finding for which no explanation could be found. Twenty-four hours after the animals ran, capillaries located near degenerated muscle fibers had an increased cross-sectional luminal area and an increased luminal circumference. This effect decreased gradually with increasing distance from the degenerated fiber area. The present morphometric results do not support the hypothesis that changes in capillary morphology primarily contribute to exercise-induced focal muscle fiber degeneration.

Animals↗
PubMed1988

Thromboembolic reaction following wall puncture in arterioles and venules of the rabbit mesentery.

The walls of rabbit mesenteric arterioles and venules (diameter 20 to 40 microns) were punctured with glass micropipets (tip diameter 6 to 8 microns). Thromboembolic reactions resulting from this standardized, small mechanical vessel wall injury could be quantified in vivo with the use of intravital video-microscopy. Following induction of the injury thrombus growth started immediately (less than 0.1 s). Bleeding times were short, on the average less than 2 s, and did not differ between arterioles and venules. The duration of the embolization process was significantly longer in arterioles than in venules (median 101 and 17 s, respectively), and more emboli were produced in arterioles than in venules (median 6 and 1, respectively). Arteriolar thrombi were more effective in plugging the punctured holes than venular thrombi. The differences in thromboembolic reaction between arterioles and venules, as found in the present study, can probably not be explained by fluid dynamic factors.

Animals↗
PubMed1988

Epidural spinal cord electrical stimulation improves microvascular blood flow in severe limb ischemia.

Epidural spinal cord electrical stimulation (ESES) was performed on 10 patients with severe limb ischemia due to atherosclerotic disease. Microcirculatory parameters were assessed before and after ESES. Bright field microscopy was used to assess capillary diameters and red blood cell (RBC) velocity in the dorsum of the foot. Fluorescein microscopy was used with intravenously injected sodium fluorescein to study capillary density and sodium fluorescein appearance time in the dorsum of the toe. The systolic ankle/arm pressure ratio and toe pressure measurements were used as macrocirculatory parameters. After ESES, clinical improvement was confirmed by intravital microscopy. Capillary density increased (p less than 0.001), RBC velocity in capillaries already perfused before ESES increased from 0.054 mm/sec to 0.762 mm/sec (p less than 0.001), and sodium fluorescein appearance time decreased from 72 to 45 seconds (p less than 0.001). Capillary diameter did not change significantly so that the increase in RBC velocity may be interpreted as enhanced volume flow. Systolic ankle/arm pressure ratios and digital arterial pressure did not change significantly. The current results show that in patients with severe occlusive arterial disease of the lower limbs, ESES recruits capillaries not perfused in the control situation and enhances skin blood flow, improvements that may explain the beneficial clinical effects of ESES.

Aged↗
PubMed1988

Microcirculatory changes in cremaster muscle during early spontaneous hypertension in the rat.

The microcirculatory control of flow was studied in the cremaster muscle of 5- to 6-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) using intravital microscopic techniques. Arterioles were classified according to a functional branching order from A1-A4 vessels. Capillary architecture was measured in a separate series of experiments. No significant differences were found in the WKY or SHR vessel diameters, with the exception of third-order arterioles, which were slightly, but significantly, larger in SHR. However, the number of A3 and A4 vessels as well as the capillary density was significantly lower in SHR than in WKY. The differences were even more pronounced during maximal vasodilation induced by local application of 10(-3) mol/l adenosine. The data show that rarefaction of small blood vessels rather than decreased arteriolar diameter is an early characteristic of spontaneous hypertension in the rat.

Age Factors↗
PubMed1988

Wall shear rate in arterioles in vivo: least estimates from platelet velocity profiles.

Velocity profiles, as determined in vivo in rabbit mesenteric arterioles with fluorescently labeled platelets as natural flow markers, were used to calculate least estimates of the actual wall shear rate in these microvessels (17-32 micron diam). The fit of the velocity data points described the profile as close to the wall as 0.5 micron. To satisfy the no-slip condition, a thin layer of fluid with a steep velocity gradient near the wall was assumed. Least estimates of wall shear rate, as calculated from the fitted platelet-velocity profiles and using the mean velocity gradient in this layer of fluid, ranged from 472 to 4,712 s-1 with a median value of 1,700 s-1. Red blood cell center-line velocities varied between 1.3 and 14.4 mm/s (median 3.4). The wall shear rates were at least 1.46-3.94 (median 2.12) times higher than expected on the basis of a parabolic velocity distribution but with the same volume flow in the vessel. Considerable spatial differences in wall shear rate might exist even within a short segment of a vessel.

Animals↗
PubMed1988

Effective diameter as a determinant of local vascular resistance in presence of vasomotion.

The mean resistance of arterioles exhibiting rhythmic changes in diameter (vasomotion) depends on the mean vascular diameter and the amplitude and shape of the vasomotion pattern. The effective diameter, defined as the diameter of a tube with constant diameter and the same vascular resistance as the vessel showing vasomotion, was calculated using Poiseuille's law. The effective diameter was used to compare the results of model calculations of square wave, sinusoidal, and triangular vasomotion patterns with those obtained from rabbit tenuissimus muscle arterioles. Due to the variability of the actual vasomotion waveforms, approximation of the effective diameter using the mean diameter, the relative vasomotion amplitude, and an assumed waveform led to erroneous results. Therefore, effective diameter should be calculated directly from the actual arteriolar diameter tracings to take into account all irregularities in the vasomotion pattern.

Animals↗
PubMed1987

Adrenergic stimulation of the rat mesenteric vascular bed: a combined micro- and macrocirculatory study.

The sympathetic nervous system is one of the primary factors controlling vascular resistance. Vascular smooth muscle contraction by sympathetic stimulation is mediated primarily by alpha-adrenoceptors. In this study, we investigated the effects of different forms of adrenergic stimulation on simultaneously measured macro- and microcirculatory dynamics in the rat mesenteric vascular bed. Macrocirculatory effects were measured by means of registration of changes in mean arterial pressure (MAP) and blood flow feeding this tissue via a miniaturized Doppler flow probe around the superior mesenteric artery. Microvascular changes were measured at the level of A2 arterioles by means of intravital microscopic registration of arteriolar diameters and red blood cell velocity (RBC vel). Topical or intra-arterial application of noradrenaline caused a dose-dependent decrease in arteriolar diameter and RBC vel at doses that did not cause significant systemic effects. On the other hand, during intravenous application of noradrenaline or other vasopressor substances an increase in MAP and decrease in organ (Doppler) blood flow was not parallelled by a decrease in arteriolar diameter or RBC vel. In contrast, RBC vel increased in a dose-related manner, whereas arteriolar diameter only secondarily decreased to a small degree. Similar results were obtained when the sympathetic nervous system was activated by means of electrical stimulation of the posterior hypothalamus. These data indicate that adrenergic stimulation can elicit different vascular responses. The ultimate microvascular effect depends upon the way of stimulation or route of drug administration.

Animals↗
PubMed1987

Arteriolar vasomotion and arterial pressure reduction in rabbit tenuissimus muscle.

Spontaneous arteriolar vasomotion and its relation to arterial pressure reduction was studied in the rabbit tenuissimus muscle using intravital microscopy. Vasomotion was observed in all transverse arterioles and their first-order side branches. Vasomotion frequency ranged from 5 to 32 cycles per minute (median: 25 cpm). The relative vasomotion amplitude in transverse arterioles varied from 0.06 to 0.44 (median: 0.22). Vasomotion was generally of the on-off type in first-order side branches. A gradual reduction in arterial pressure as achieved by aortic occlusion resulted in an abrupt disappearance of vasomotion. Vasomotion disappeared between 19 and 59 mm Hg (median: 30.4 mm Hg). No differences were found between the pressures at which vasomotion ceased in transverse arterioles and first-order side branches. With a further reduction of arterial pressure transverse arterioles attained a maximal diameter of 98-265% (median: 119%) of the maximal diameter during vasomotion. After release of occlusion vasomotion reappeared much earlier in the first-order side branches than in their feeding transverse arterioles. It is concluded that although vasomotion influences capillary perfusion, it does not play a major role in the adaptation of vascular resistance following a reduction in arterial pressure.

Animals↗
PubMed1987

Pressure regulation in muscle of unanesthetized bats.

In unanesthetized bats direct microvascular pressure measurements were made in the tensor plagiopatagii muscle without surgical intervention. Pressure recordings showed great variability due to vasomotion and other physiological stimuli, but were in the same order of magnitude as described in muscle of other species in the anesthetized state. A substantial part of the pressure gradient is dissipated at the level of the small arterioles. Arterial pressure was changed by depressurizing a box containing the body of the bat, while the muscle was under atmospheric condition. In all larger arterioles and in 12 of 19 smaller arterioles a linear relation existed between microvascular pressure and box pressure. Of 19 small arterioles, 7 exhibited a clear biphasic regulatory response to a decrease in arterial pressure. The data are discussed in relation to different models of regulation.

Anesthesia↗
PubMed1987

Does capillary recruitment exist in young rabbit skeletal muscle?

Recruitment of terminal arterioles and capillaries was studied in the tenuissimus muscle of 16 young urethane anesthetized rabbits. In one set of experiments (8 animals) intravital fluorescence microscopy was used to visualize transverse arterioles and to assess the number of their first order side branches (functionally the terminal arterioles) perfused with red blood cells before and after vasodilation (10(-4)M adenosine, applied topically). In another set of experiments (8 animals) the number of muscle capillaries perfused with red blood cells from the same parent arteriole was determined at rest and during vasodilation (reactive hyperemia), using bright field microscopy. All capillaries and first order side branches that were perfused during vasodilation were also perfused at rest. These findings indicate that in this skeletal muscle preparation no recruitment of arterioles or capillaries occurs in an anatomical sense of the word.

Animals↗
PubMed1987

A versatile incident illuminator for intravital microscopy.

A simple incident illuminator (epiilluminator) for intravital microscopy using a mirror with 50% reflectance and 50% transmittance, placed at 45 degrees to the optical axis of the microscope, in combination with a polarizer and analyzer is described. Such a system can easily be mounted in a Ploemopak incident illuminator as used for fluorescence microscopy. Images of the red blood cells contained in the microvessels appear as dark on a light background. With the use of the system, microscopic images of good quality could be obtained from human skin capillaries, and skin, pial and intestinal microvessels in rats. In muscle, however, only the superficial capillaries could be adequately visualized.

Capillaries↗
PubMed1987

A model for chronic study of vascular morphology and reactivity of physically intact rat skin microcirculation.

A non-invasive, non-traumatic model has been developed for long term study of the vascular anatomy, blood cell velocity and vascular reactivity of the cutaneous microcirculation of the rat. In the anesthetized rat, the hairless area of a toe close to the nail could be visualized by intravital video microscopy without manipulation of the skin. Good image quality of the vascular bed was obtained with the use of an incident illuminator equipped with a 50% mirror at 45 degrees to the optical axis and a polarizer-analyzer system in combination with a mercury lamp. This microscope system allows for visualization of the superficial vasculature of the skin, while microvessels can be repeatedly identified for several weeks. To test for vascular reactivity off-line analysis of blood cell velocity was performed in the control situation and during reactive hyperemia, using a video dual-window system and a cross-correlator. The mean control velocity in venules selected for testing of vascular reactivity was 70 micron/s. In these vessels a reproducible pattern of reactive hyperemia was seen with a mean peak velocity of 655 micron/s following arterial occlusion of 180 s. Possible applications of the model are discussed.

Animals↗