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Biomedical subjects

D W Slaaf

Publications and source records attributed to D W Slaaf.

At least 73 records · Page 4Linked to original sources
PubMed1991

Angiotensin II stimulates angiogenesis in the chorio-allantoic membrane of the chick embryo.

Angiotensin II was applied daily in doses of 67 or 670 ng to a section of the chick embryo chorio-allantoic membrane from day 7 to day 14 after fertilization of the eggs. During this one-week period, it caused a significant, dose-dependent increase in the vascular density index. The increase obtained with 670 ng daily was comparable to that after daily administration of 1.7 micrograms adenosine, a known stimulator of angiogenesis. The data suggest a possible role for angiotensin II as a mediator of vascular growth.

Allantoin↗
PubMed1991

Posturally induced microvascular constriction in patients with different stages of leg ischaemia: effect of local skin heating.

1. Skin microcirculation was investigated in 12 asymptomatic subjects and 76 patients, grouped according to their ankle-to-brachial systolic blood pressure index, in order to evaluate to what extent posturally induced microvascular constriction is dependent on the stage of leg ischaemia at different local skin temperatures. 2. Skin microcirculation was assessed in the supine and sitting position by using laser Doppler fluxmetry at unheated skin temperature and at 36 degrees C, and transcutaneous oximetry at 37 degrees C and 44 degrees C. 3. Skin perfusion and oxygenation diminished with decreasing ankle-to-brachial systolic blood pressure index. In healthy control subjects, perfusion and oxygenation were reduced when changing from the supine to the sitting position, but were enhanced in patients with severe leg ischaemia (ankle-to-brachial systolic blood pressure less than 30%), indicating disturbed posturally induced vasoconstriction. 4. Increasing the local skin temperature resulted in a higher perfusion and masked the posturally induced vasoconstriction in healthy subjects. In patients with severe leg ischaemia, however, perfusion was unaltered by the temperature increase, apparently because the microvessels were already maximally dilated. The induction of reactive hyperaemia produced no additional increase in perfusion or oxygenation. 5. It is concluded that posturally induced microvascular constriction in the skin is disturbed in patients with severe leg ischaemia (ankle-to-brachial systolic blood pressure index less than 30%). Disturbed microvascular constriction upon dependency was also seen in healthy subjects after local skin heating. This suggests that posturally induced vasoconstriction is mainly regulated by local mechanisms.

Adult↗
PubMed1991

Fluid dynamics and the thromboembolic reaction in mesenteric arterioles and venules.

In the mesentery of the anesthetized rabbit, the thromboembolic reaction after wall puncture lasts six times longer in arterioles than in venules, a difference that cannot be explained by fluid dynamic conditions before puncture. In the present study, it was investigated whether this difference in response between arterioles and venules results from a different degree of stenosis by the thrombus and/or a difference in velocity changes resulting in a different pressure drop over the thrombus. Arteriolar and venular mean red blood cell velocity and vessel diameter were measured before puncture and after this injury in the stenosed vessel segment and upstream. Thrombi with similar heights were formed in arterioles and venules and induced similar degrees of stenosis. A surface area reduction less than 55% induced only a small and similar decrease in volume flow (less than 10%) in arterioles and venules. Reduced velocity, a measure of wall shear rate, increased similarly in both vessel types for similar degrees of stenosis. In conclusion, changes in fluid dynamic factors, as induced by thrombus formation, cannot be held responsible for the difference in thromboembolic reaction between arterioles and venules.

Animals↗
PubMed1991

Detection of contact dermatitis in rat skin by intravital microscopy.

The sensitivity of fluorescence intravital microscopy for the detection of immunologically elicited inflammatory reactions in the skin was compared to assessment by tissue swelling measurement. Rats were immunized to the contact-sensitizing agent toluene diisocyanate (TDI) by its application to the skin and challenged by the same procedure at a different site one week thereafter. At 2, 6, or 12 hrs after challenge individual rats received a bolus of fluorescently labeled albumin intravenously. Vascular integrity was determined by estimating the surface of areas with increased vascular permeability as observed by fluorescence intravital microscopy; contact dermatitis (CD) was assessed just prior to infusion of labeled albumin determination of tissue swelling by a semi-automatic micrometer. At 12 hrs after challenge, CD was detectable by tissue swelling. Intravital fluorescence microscopy revealed massive extravasation of the fluorescent dye at the site of challenge. At 6 hrs after challenge, CD was not yet discernible by toe thickness measurements. However, by fluorescence intravital microscopy significant leakage of labeled albumin was observed. Thus, at 6 hrs after challenge fluorescence intravital microscopy was more sensitive than determination of tissue thickness increment for detection of a contact hypersensitivity reaction. At 2 hrs after challenge, CD was neither demonstrable by tissue swelling measurements, nor by fluorescence intravital microscopy. Therefore, an early component of a delayed-type hypersensitivity (DTH) reaction to a contact allergen as shown to occur in mice, remains to be demonstrated in the rat. On the other hand, fluorescence intravital microscopy revealed non-immunological skin irritation by a 5% TDI solution within 2 hrs after its application to the skin of non-immunized rats.

Animals↗
PubMed1991

Use of microphotohemolysis to distinguish differences in erythrocyte treatments.

A new microhemolytic assay was used to determine if this assay could distinguish between normal erythrocytes and those which had been experimentally altered. Solutions of erythrocytes (4% hematocrit in buffer with fluorescein isothiocyanate tagged to 150,000 MW dextran, FITC-DEX) were placed in a hemacytometer and epi-illumination with a Leitz fluorescent microscope was used to activate the fluorochrome. The resultant hemolysis that occurred only in the discrete area of activation was dependent on the total light energy used for activation (45-180 J/cm2). It was quantitated by an analysis of the amount of light transmittance through that area. The presence of glucose in the buffers decreased the rate of hemolysis and increased the time to reach 50% of the maximal response (T50). Erythrocytes treated with diamide had up to a fourfold increase in the rate of hemolysis and a 48% decrease in the T50, while chlorpromazine produced a 51% decrease in the T50 but had no effect on the rate of hemolysis. Gluteraldehyde produced a graded suppression of the hemolysis. These results demonstrate that the microphotohemolytic assay can be used with energy response curves to provide a relatively quick, quantitative determination of altered erythrocytes.

Animals↗
PubMed1991

Quantitation of erythrocyte photohemolysis by light microscopy.

In a solution of erythrocytes and a photo-active compound, light activation of the compound produces hemolysis of the cells. This study describes a new assay in which focused light through a microscope is used to induce a circumscribed hemolysis of erythrocytes that have been mixed with fluorescein isothiocyanate-dextran 150,000 (FITC-DEX) and placed in a hemacytometer. The hemolytic response was monitored by detecting transmitted light intensity in the area (1.8 x 10(-4) cm2) of activation. Only cells within the specific microscopic field of activation hemolyze. This allows for multiple sites of activation within one sample. The hemolytic response was dependent on the concentration of FITC-DEX (0.5-4 mg/ml) and on light intensity (53-210 J/cm2) but not on small changes in hematocrit (3%-5%) or on the presence of platelets and leukocytes. Rabbit erythrocytes, however, were almost twice as sensitive as those from guinea pigs. Since the photohemolytic response will depend on the composition and strength of the erythrocyte membrane and presence of oxidant defense mechanisms, we suggest that this assay could be used to detect drug- or disease-induced changes in the red blood cell membrane.

Animals↗
PubMed1991

Plasmapheresis in Raynaud's phenomenon in systemic sclerosis: a microcirculatory study.

Microcirculatory and haemorheological parameters were investigated before and after plasmapheresis in eighteen patients with secondary Raynaud's phenomenon based on progressive systemic sclerosis. After 4 plasmaphereses, once a week, all patients claimed explicit improvement of their complaints. Raynaud's phenomenon and especially the reaction upon cold provocation had disappeared and skin ulcers healed. Red blood cell (RBC) velocity increased significantly (p less than 0.001) after 4 weeks plasmapheresis. RBC aggregation and plasma viscosity were significantly lower (p less than 0.001) after the last plasmapheresis than before treatment. After 3 years four patients were still free of complaints, but in 14 patients the symptoms of Raynaud's phenomenon had reappeared after 6 to 9 months. The skin ulcers, however, did not return in these patients. RBC aggregation and plasma viscosity returned to the initial values after 9 months, while skin capillary blood flow remained significantly enhanced for 24 months. The finding that restoration of RBC aggregation and plasma viscosity to normal level is associated with enhanced skin capillary blood flow, indicates that disturbed haemorheology plays a role in the diminished skin blood flow, as observed in patients with secondary Raynaud's phenomenon. In these patients, plasmapheresis can be considered to treat severe ischemia of the digits.

Adult↗
PubMed1990

Influence of hypercapnia and hypoxia on rabbit platelet aggregation.

The influence of changes in pCO2, pH and pO2 on the aggregation of rabbit blood platelets was studied in vitro, with emphasis on hypercapnia, acidosis and hypoxia. Hypercapnia combined with acidosis caused a reduction in rabbit platelet aggregation, as induced by collagen, thrombin and ADP; the effect being most pronounced with collagen and smallest with ADP. Hypoxia reduced thrombin induced platelet aggregation, but had no effect on ADP and collagen induced aggregation. Synergistic activation of rabbit platelets, as induced by the addition of serotonin to platelet rich plasma together with collagen or ADP, seemed to be equally sensitive to changes in pCO2 and pH as activation by the individual agents, and insensitive to changes in pO2.

Adenosine Diphosphate↗
PubMed1990

Microcirculatory haemodynamics before and after vascular surgery in severe limb ischaemia--the relation to post-operative oedema formation.

To determine whether postoperative oedema could be predicted preoperatively by microcirculatory parameters, we studied nutritive capillary blood flow in 21 patients before and after limb salvage procedures. All patients had severe lower limb ischaemia and underwent femoro-popliteal or femoro-crural bypass surgery. The systolic ankle-branchial arm index and systolic toe pressure were used as macrocirculatory parameters. Intravital capillary microscopy was used to measure red blood cell (RBC) and peak RBC velocity and time to peak RBC velocity after release of a 1 min arterial occlusion in the nailfold of the toe. Transcutaneous pO2 was measured on the dorsum of the foot at rest, during oxygen inhalation and following a release of a 5 min occlusion. After surgery the mean systolic ankle-brachial index and systolic toe pressure and all transcutaneous pO2 parameters improved significantly (P less than 0.001). Mean peak RBC velocity increased from 0.156 mm/s to 0.310 mm/s (P less than 0.05), indicating that the reactive hyperaemic response in the capillary bed had improved. Eleven patients developed postoperative oedema. There were no differences in postoperative macro and microcirculatory parameters between the patients with oedema (n = 11) and those without oedema (n = 10). However, preoperatively RBC velocity and peak RBC velocity were significantly lower (P less than 0.05) and time to peak RBC velocity was significantly longer (P less than 0.01) in patients who developed oedema. These findings show that in patients with severe limb ischaemia vascular surgery improves both macro- and microcirculatory blood flow, but that these patients develop oedema after vascular surgery when microcirculatory blood flow is compromised preoperatively.

Aged↗
PubMed1990

A functional morphometric study of the cremaster muscle microcirculation in young spontaneously hypertensive rats.

Increased vascular resistance in spontaneous hypertension has been attributed to a reduced arteriolar lumen and a decrease in the number of arterioles and capillaries. In the present study, microvascular mechanisms for increased resistance were investigated in the cremaster muscle of 5-6-week-old spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY) using intravital microscopy. Vessels were classified on the basis of their location in the network relative to their branching order and function (A1-A4). In each preparation, one vessel of each category was observed for its side-branches, using bright-field microscopy. By comparing the number of side-branches seen under control conditions and after maximal vasodilatation (10(-3) mol/l adenosine, topically) we assessed their functional reserve. Capillary density was investigated using incident fluorescence microscopy. Both under control conditions and after vasodilatation, mean arterial pressure and heart rate were increased in SHR (mean arterial pressure: SHR 103 +/- 4 mmHg, WKY 89 +/- 3 mmHg, P less than 0.05; heart rate: SHR 380 +/- 16 beats/min, WKY 343 +/- 12 beats/min, P less than 0.05). Arterioles (A1-A4) of SHR and WKY were equal in diameter (SHR: 75.8 +/- 3.2, 48.7 +/- 1.1, 21.4 +/- 0.9, 10.0 +/- 0.04 microns; WKY: 71.6 +/- 2.4, 48.9 +/- 1.1, 18.5 +/- 0.9, 9.8 +/- 0.3 microns; A1-A4, respectively). After adenosine, the relative increase in diameter was similar in both groups. The number of side-branches under control conditions was similar in A1 and A2 vessels. SHR had fewer A3 vessels per A2 and fewer A4 vessels per A3 (per unit length), indicating a diminished arteriolar reserve.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Analysis of vasomotion waveform changes during pressure reduction and adenosine application.

Changes in the vasomotion waveform were studied in transverse arterioles (TAs) and their first-order side branches (FOSs) in the tenuissimus muscle of 14 young, anesthetized rabbits during stepwise arterial pressure reduction and local application of adenosine using intravital video microscopy. Pressure reduction resulted in a systematic increase in vasomotion cycle length (CL) and amplitude (A) concomitant with an increase in effective vascular diameter (Deff) and maximum diameter and a decrease in blood flow (Q). During adenosine application Deff and maximum diameter also increased, but CL and A did not change systematically. At moderate pressure reductions and during adenosine application CL changes were limited (less than 1.5 s) and nonsystematic, agreeing with an earlier study (D. W. Slaaf, G. J. Tangelder, H. C. Teirlinck, and R. S. Reneman. Microvasc. Res. 33: 71-80, 1987). In TAs these changes resulted from changes in both the dilation and the constriction phase. In FOSs, however, changes in CL were caused by prolongation of the dilation phase alone. At greatly reduced pressure levels, the CL increase was more pronounced and in both TAs and FOSs was caused by plateau formation in the dilation phase. Stretch of the arteriolar wall does not seem to play a role in control of the vasomotion waveform. Because the onsets of dilation always occur synchronously in TAs and FOSs, but the onsets of constriction do not, vasomotion seems to be a series of rhythmic dilations.

Adenosine↗
PubMed1990

Exercise-induced swelling of rat soleus muscle: its relationship with intramuscular pressure.

Exercise-induced tissue swelling and its possible consequence for tissue pressure were studied in rat soleus muscle. Rats ran for 75 min on a belt with a 10 degree positive incline. Wet weights of cryofixed soleus muscles were increased at 3 (16%), 6 (28%), 9 (16%), and 24 (16%) h after running compared with those of nonexercised controls. The transient increase in muscle wet weight correlated in time with an increase in muscle volume. Muscle fiber swelling accounted for most of the muscle swelling in absolute terms because of the large proportion (approximately 90%) of the muscle volume composed of fibers, but swelling of the interstitium was about twofold larger than fiber swelling per unit area. Muscle fiber degeneration was most frequently found at the end of the observation period, i.e., 24 h after running. The muscle swelling was not associated with an increase in intramuscular pressure. During the postexercise measuring period (18 min to 24 h after exercise), intramuscular pressures of exercised rats (1.3 +/- 0.3 mm Hg) did not differ significantly from control values (1.0 +/- 0.2 mm Hg). These findings indicate that increased intramuscular pressure is not responsible for the muscle fiber degeneration found in rat soleus muscle 24 h after endurance running.

Animals↗
PubMed1990

Recombinant human erythropoietin and its effects on macro- and microcirculation during normovolemia. A physiological study of hemodynamics, fluid status and skin microcirculation.

In 9 chronic hemodialysis patients, treated with recombinant human erythropoietin (rHuEpo), longitudinal studies were performed to investigate possible changes in macro- and microcirculatory parameters during normovolemia, as assessed echographically by determining the inferior vena cava diameter and adjusting dialysis dry weight. Hematocrit increased from 19 +/- 4 to 33 +/- 5% (p less than 0.001). Systemic vascular resistance increased from 1,020 +/- 259 to 1,283 +/- 245 dyn/s/cm-5 (p less than 0.02), while mean arterial pressure remained unchanged. Cardiac index decreased (4.9 +/- 1.4 to 3.8 +/- 0.9 liters/min/m2; p less than 0.02), caused by a decrease in heart rate (87 +/- 21 to 75 +/- 16 beats/min; p less than 0.02) and stroke index (59.9 +/- 15.2 to 51.0 +/- 10.7 ml/m2; p less than 0.02). Red blood cell volume increased (468 +/- 105 to 858 +/- 203 ml/m2; p less than 0.001) and plasma volume decreased inversely ([125I]-albumin; 2,008 +/- 338 to 1,664 +/- 225 ml/m2; p less than 0.001), whereas total blood volume remained unaltered (2,476 +/- 397 to 2,518 +/- 352 ml/m2; n.s.). Total body weight increased (57.8 +/- 12 to 62.1 +/- 12 kg; p less than 0.02), indicative of an anabolic effect of rHuEpo therapy. Skin capillary circulation as measured by transcutaneous oxymetry at 37 degrees C skin temperature impaired, reflected by the increase of the time to peak after arterial occlusion (82 +/- 21 to 121 +/- 25 s; p less than 0.02). The reactive hyperemic response following the release of occlusion showed a significant increase at high hematocrit (10.7 +/- 4.2 to 16.6 +/- 5.3 mm Hg; p less than 0.02), whereas resting transcutaneous Po2 values showed a slight but not significant increase (2.3 +/- 1.3 to 4.7 +/- 3.3 mm Hg; n.s.). The high number of pathological capillaries in hemodialyzed patients might be an additional factor for the increase in systemic vascular resistance.

Adult↗
PubMed1990

Influence of fluid removal during haemodialysis on macro- and skin microcirculation. Haemodynamic pathophysiologic study of fluid removal during haemodialysis.

Changes of macro- and microcirculation during haemodialysis and fluid removal are probably dependent on ultimate fluid status and on the efficacy of various regulation mechanisms, especially the catecholamines. This was studied in 20 chronic dialysis patients. Pre- and postdialysis stroke volume, mean arterial pressure, heart rate and systemic vascular resistance were measured. Furthermore, microcirculation was studied by Laser Doppler flow and by intravital microscopy of finger nail fold, measuring red blood cell velocity and capillary density. Pre- and postdialysis noradrenaline and adrenaline were measured. Nine patients proved to be hypovolaemic after dialysis (group I) and 11 patients proved to be normovolaemic or less hypervolaemic (group II) according to vena cava inferior parameters. There was a significant decrease of mean arterial pressure and stroke volume in group I, and an increase of heart rate, whereas in group II there was only a decrease of mean arterial pressure. Systemic vascular resistance did not change in both groups. Noradrenaline decreased although not significantly in both groups, whereas in group I adrenaline increased significantly. There was a significant decrease of skin perfusion in group I, whereas in group II there was a significant increase. Capillary density increased significantly in group II after reaching normovolaemia. Underhydration was leading to a decrease of skin microcirculation on the basis of a decrease of stroke volume and an increase of adrenaline levels. In hypervolaemic patients, who were ultrafiltrated to normovolaemia, skin microcirculation improved on the basis of a decrease of arterial and venous pressure and consequently a decrease of the myogenic response as a local autoregulatory effect.

Adult↗
PubMed1990

Foot salvage and improvement of microvascular blood flow as a result of epidural spinal cord electrical stimulation.

Epidural spinal cord electrical stimulation has been suggested as an alternative treatment in patients with limb-threatening ischemia in whom vascular reconstructive surgery is not possible anymore. We studied the effects of epidural spinal cord electrical stimulation on microcirculatory blood flow in 20 patients with ischemic rest pain and ulcers. Angiography showed occluded crural arteries technically unsuitable for reconstructive surgery. Intravital capillary microscopy was used to assess capillary density and diameter and red blood cell velocity before and after a 1-minute period of arterial occlusion. After epidural spinal cord electrical stimulation 18 patients claimed immediate pain relief, which was confirmed by intravital capillary microscopy. Capillary density increased from 10 to 19/mm2 (p less than 0.001), red blood cell velocity increased from 0.088 to 0.496 mm/sec (p less than 0.001), and peak red blood cell velocity after arterial occlusion increased from 0.092 to 0.548 mm/sec (p less than 0.001). Two patients had no immediate pain relief; they did not show improvement of microcirculatory perfusion, and amputation was necessary. During the follow-up period (3 months to 3 years, mean 27 months), six other patients had recurrent ischemic pain, and amputation was necessary. In 12 patients pain relief continued, and ischemic ulcers healed; capillary microscopy confirmed improved microcirculatory blood flow. Microcirculatory parameters were significantly higher in respondents than in nonrespondents (p less than 0.001). Life-table analysis revealed a cumulative foot salvage of 80% and 56% after 1 and 2 years, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Effects of partial plasma exchange transfusion on cerebral blood flow velocity in polycythaemic preterm, term and small for date newborn infants.

Isovolemic haemodilution with plasma was performed in 36 newborn infants with polycythaemia 3h after birth. Continuous wave Doppler ultrasonography was used to study the short and longer term influence of partial plasma exchange transfusion on cerebral blood flow velocity in both the anterior cerebral and mid cerebral arterial system up to 24h after haemodilution. The study group consisted of 11 preterm infants, 12 term infants, and 13 small for date infants. After exchange transfusion peripheral venous haemotocrit decreased from 72.5% to 59.4%. In all experimental groups cerebral blood flow velocity (CBFV) before exchange transfusion was significantly lower (18%-44%) than matched controls, and increased to control levels after exchange transfusion. CBFV improved most in preterm infants. After the transfusion the values were no different from the age-, weight-, sex- and parity-matched control groups, and they remained at this level during the next 24 h. No differences could be found between the anterior and mid-cerebral arterial system. When clinical symptoms were present, they subsided in all infants. In conclusion, partial plasma exchange transfusion has a favourable effect for at least 24 h on cerebral blood flow velocity in newborn infants with polycythaemia.

Blood Flow Velocity↗
PubMed1989

Changes in vasomotion pattern and local arteriolar resistance during stepwise pressure reduction.

Changes in vasomotion parameters and their consequences for local arteriolar resistance were studied in transverse arterioles and their first order side branches in the tenuissimus muscle of 10 young urethane anesthetized rabbits during stepwise reduction of arterial pressure, using intravital microscopy. To assess the influence of vasomotion on mean local arteriolar resistance, the effective vascular diameter, as a measure of mean flow carrying capacity, was calculated. The contribution of vasomotion to the mean local resistance is limited in transverse arterioles, but important in first order side branches, dominating the flow fluctuations in the downstream capillaries. During pressure reduction, an over-all increase in vasomotion cycle length and amplitude was found in both transverse arterioles and first order side branches, concomitant with an increase in effective arteriolar diameter and a decrease in local blood flow and reduced velocity, as a measure of wall shear rate. Flow autoregulation was observed in 70% of the arterioles. The changes in cycle length and amplitude showed only limited correlations with local blood flow, reduced velocity, arterial pressure and effective arteriolar diameter. This indicates that it is unlikely that only one of these variables is responsible for the changes in the vasomotion parameters.

Animals↗