21 results on '"Slaaf, D."'
Search Results
2. Detection of Leukocytes in Contact with the Vessel Wall from In Vivo Microscope Recordings Using a Neural Network
- Author
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Egmont-Petersen, M., Schreiner, U., Tromp, S. C., Lehmann, T. M., Slaaf, D. W., and Arts, T.
- Subjects
Leukocytes -- Research ,Microcirculation -- Research ,Image processing -- Digital techniques ,Learning models (Stochastic processes) -- Usage ,Biological sciences ,Business ,Computers ,Health care industry - Abstract
Leukocytes play an important role in the host defense as they may travel from the blood stream into the tissue in reacting to inflammatory stimuli. The leukocyte-vessel wall interactions are studied in post capillary vessels by intravital video microscopy during in vivo animal experiments. Sequences of video images are obtained and digitized with a frame grabber. A method for automatic detection and characterization of leukocytes in the video images is developed. Individual leukocytes are detected using a neural network that is trained with synthetic leukocyte images generated using a novel stochastic model. This model makes it feasible to generate images of leukocytes with different shapes and sizes under various lighting conditions. Experiments indicate that neural networks trained with the synthetic leukocyte images perform better than networks trained with images of manually detected leukocytes. The best performing neural network trained with synthetic leukocyte images resulted in an 18% larger area under the ROC curve than the best performing neural network trained with manually detected leukocytes. Index Terms--Leukocyte detection, microcirculation, model-based image processing, nonlinear filtering, object recognition, shape characterization, stochastic model.
- Published
- 2000
3. FAILURE TO CONFIRM A MICROCIRCULATORY CAUSE FOR EXERCISE INDUCED MUSCLE FIBER DEGENERATION: 481
- Author
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Binkhorst, Peeze F.M., Kuipers, H., Tangelder, G. J., Slaaf, D. W., and Frederik, P. M.
- Published
- 1989
4. DILATION OF CAPILLARIES ADJACENT TO MUSCLE FIBERS DEGENERATED DUE TO EXERCISE: 480
- Author
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Kuipers, H., Binkhorst, Peeze F.M., Tangelder, G. J., Slaaf, D. W., and Frederik, P. M.
- Published
- 1989
5. FAILURE TO CONFIRM A MICROCIRCULATORY CAUSE FOR EXERCISE INDUCED MUSCLE FIBER DEGENERATION: 481
- Author
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Binkhorst, Peeze F.M., Kuipers, H., Tangelder, G. J., Slaaf, D. W., and Frederik, P. M.
- Published
- 1980
6. DILATION OF CAPILLARIES ADJACENT TO MUSCLE FIBERS DEGENERATED DUE TO EXERCISE: 480
- Author
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Kuipers, H., Binkhorst, Peeze F.M., Tangelder, G. J., Slaaf, D. W., and Frederik, P. M.
- Published
- 1980
7. Capillary recruitment and pain relief on leg dependency in patients with severe lower limb ischemia
- Author
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Ubbink, D. T., Jacobs, M. J., Slaaf, D. W., Tangelder, G. J., Reneman, R. S., and Other departments
- Abstract
Patients suffering from severe lower limb ischemia may experience pain relief on leg dependency despite the fact that dependency normally results in arteriolar vasoconstriction. To clarify this possible paradox, skin microcirculation of the limb was investigated in 75 patients with different stages of lower limb ischemia and in 12 asymptomatic subjects. Using nailfold capillary video microscopy, red blood cell-perfused capillary density and diameter and red blood cell velocity were assessed in supine and sitting positions. Capillary density increased by changing from the supine to the sitting position, especially in patients with limb-threatening ischemia (showing a 4.5-fold increase versus a 1.5-fold increase in asymptomatic subjects). In subjects without or with mild ischemia, capillary perfusion was two to four times lower in the sitting than in the supine position. In patients with limb-threatening ischemia, perfusion was strongly reduced, being slightly higher in the sitting position. Patients with relief of pain while sitting did not always have a higher capillary perfusion but did have a higher capillary density in the sitting position. The arteriolar postural vasoconstrictive mechanism at the nutritive level is still intact in subjects without or with mild ischemia but not in patients with severe ischemia. Capillary recruitment rather than disturbed arteriolar vasoconstriction could explain why patients with severe leg ischemia prefer leg dependency
- Published
- 1992
8. In vivoinvolvement of ADP in thromboembolism through its receptors P2Y1 and P2Y12
- Author
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van Gestel, M. A., primary, Heemskerk, J. W. M., additional, Slaaf, D. W., additional, Reneman, R. S., additional, and oude Egbrink, M. G. A., additional
- Published
- 2003
- Full Text
- View/download PDF
9. Development of vasomotor responses in fetal mesenteric arteries
- Author
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Rouwet, E. V., primary, De Mey, J. G. R., additional, Slaaf, D. W., additional, Heineman, E., additional, Ramsay, G., additional, and Le Noble, F. A. C., additional
- Published
- 2000
- Full Text
- View/download PDF
10. Influence of platelet-vessel wall interactions on leukocyte rolling in vivo.
- Author
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oude Egbrink, M G, primary, Tangelder, G J, additional, Slaaf, D W, additional, and Reneman, R S, additional
- Published
- 1992
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11. Tumor angiogenesis factors reduce leukocyte adhesion in vivo.
- Author
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Tromp, S C, oude Egbrink, M G, Dings, R P, van Velzen, S, Slaaf, D W, Hillen, H F, Tangelder, G J, Reneman, R S, and Griffioen, A W
- Abstract
Leukocyte-endothelium interactions are diminished in tumors. It is reported here that, in a tumor-free in vivo model, angiogenic factors can down-regulate leukocyte adhesion to endothelium. Slow releasing pellets were loaded with either basic fibroblast growth factor (bFGF), vascular endothelial cell growth factor (VEGF) or vehicle alone and were placed in the scrotum of mice. After 3 days, a single intrascrotal injection of 1 microg/kg IL-1beta was given 4 h before vessels of the cremaster muscle were investigated for leukocyte rolling and adhesion by means of intravital microscopy. Exposure of normal tissue to either bFGF or VEGF resulted in markedly decreased levels of cytokine-induced leukocyte adhesion. Suppression of leukocyte rolling was not observed. Instead a moderate enhancement of rolling by VEGF was found. The observed differences could not be explained by differences in fluid dynamic parameters or systemic leukocyte counts. In conclusion, evidence is presented that, in vivo, angiogenic factors significantly reduce leukocyte adhesion, the final step preceding leukocyte infiltration. This observation may explain why tumors escape from immune surveillance.
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- 2000
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12. Velocity profiles of blood platelets and red blood cells flowing in arterioles of the rabbit mesentery.
- Author
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Tangelder, G J, primary, Slaaf, D W, additional, Muijtjens, A M, additional, Arts, T, additional, oude Egbrink, M G, additional, and Reneman, R S, additional
- Published
- 1986
- Full Text
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13. A rapid regional filling technique for complex binary images
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Albert, T. A. and Slaaf, D. W.
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- 1995
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14. Hypoxia induces aortic hypertrophic growth, left ventricular dysfunction, and sympathetic hyperinnervation of peripheral arteries in the chick embryo.
- Author
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Rouwet EV, Tintu AN, Schellings MW, van Bilsen M, Lutgens E, Hofstra L, Slaaf DW, Ramsay G, and Le Noble FA
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- Animals, Arteries physiopathology, Blood Pressure, Body Weight, Cell Hypoxia, Chick Embryo, Heart physiopathology, Hemodynamics, Hypertrophy, Myocardium pathology, Organ Culture Techniques, Organ Size, Ventricular Dysfunction, Left pathology, Aorta pathology, Arteries innervation, Sympathetic Nervous System physiopathology, Ventricular Dysfunction, Left physiopathology
- Abstract
Background: Low birth weight is associated with an increased incidence of cardiovascular diseases, including hypertension, later in life. This suggests that antenatal insults program for fetal adaptations of the circulatory system. In the present study, we evaluated the effects of mild hypoxia on cardiac function, blood pressure control, and arterial structure and function in near-term chick embryos., Methods and Results: Chick embryos were incubated under normoxic (21% O2) or hypoxic (15% O2) conditions and evaluated at incubation day 19 by use of histological techniques, isolated heart preparations, and in vivo measurements of sympathetic arterial tone and systemic hemodynamics. Chronic hypoxia caused a 33% increase in mortality and an 11% reduction in body weight in surviving embryos. The lumen of the ascending aorta in hypoxic embryos was 23% smaller. Left ventricular systolic pressure was 22% lower, and heart weight/body weight ratio was 14% higher. In resistance arteries of hypoxic embryos, in vivo baseline tone was 23% higher, norepinephrine sensitivity was similar, and norepinephrine release from sympathetic nerves increased 2-fold, indicating sympathetic hyperinnervation. Mean arterial pressure and heart rate were similar under resting conditions, but chronically hypoxic embryos failed to maintain blood pressure during acute stress., Conclusions: This study indicates that mild hypoxia during embryonic development induces alterations in cardiac and vascular function and structure and affects hemodynamic regulation. These findings reveal that antenatal insults have profound effects on the control and design of the circulatory system that are already established at birth and may program for hypertension and heart failure at a later age.
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- 2002
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- View/download PDF
15. Endogenous nitric oxide and prostaglandins synergistically counteract thromboembolism in arterioles but not in venules.
- Author
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Broeders MA, Tangelder GJ, Slaaf DW, Reneman RS, and Egbrink MG
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- Animals, Arterioles drug effects, Aspirin pharmacology, Blood Flow Velocity drug effects, Cyclooxygenase Inhibitors pharmacology, Female, Male, Mesentery blood supply, Nitric Oxide blood, Nitroarginine pharmacology, Prostaglandins blood, Rabbits, Thromboembolism blood, Thromboembolism enzymology, Thromboembolism physiopathology, Venules drug effects, Arterioles metabolism, Nitric Oxide physiology, Prostaglandins physiology, Thromboembolism prevention & control, Venules metabolism
- Abstract
It has been shown that NO and prostacyclin (prostaglandin I(2)) from cultured endothelium synergistically inhibit blood platelet aggregation in vitro. However, it is unknown whether this synergism is also effective in the inhibition of thromboembolism in vivo and, if it is, whether it differs between vessel types. Therefore, the effect of endogenous NO and prostacyclin, in combination or alone, on thromboembolism was studied in an in vivo model. Thromboembolism was induced by micropipette puncture of rabbit mesenteric arterioles and venules (diameter 18 to 40 micrometer). In addition, the influence of wall shear rate was analyzed. In arterioles, the combined inhibition of NO synthase (N(G)-nitro-L-arginine [L-NA] 0.1 mmol/L; local superfusion) and of cyclooxygenase (aspirin [ASA] 100 mg/kg IV) resulted in a pronounced, significant prolongation of embolization duration (median >600 seconds) compared with control (median 153 seconds) or treatment with either L-NA (234 seconds) or ASA (314 seconds). This combined effect of L-NA+ASA was greater than the sum of the individual effects of L-NA and ASA. In contrast, in venules L-NA+ASA had no additional effect on embolization duration (209 seconds) compared with the effect of L-NA alone (230 seconds); ASA alone had no effect (122 seconds; control 72 seconds). Interestingly, only in the L-NA+ASA arterioles did embolization correlate positively with wall shear rate (r(s)=0.687; P=0.028). In conclusion, this study indicates that in arterioles, but not in venules, endogenous NO and prostaglandins synergistically counteract ongoing thromboembolism after vessel wall injury and that the combination of endogenous NO and prostaglandins appears to protect against enhancement of arteriolar thromboembolism by wall shear rate.
- Published
- 2001
- Full Text
- View/download PDF
16. Development of vasomotor responses in fetal mesenteric arteries.
- Author
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Rouwet EV, De Mey JG, Slaaf DW, Heineman E, Ramsay G, and Le Noble FA
- Subjects
- Acetylcholine administration & dosage, Adrenergic alpha-Antagonists administration & dosage, Animals, Chick Embryo, Dose-Response Relationship, Drug, Hypoxia embryology, Hypoxia metabolism, Instillation, Drug, Mesenteric Arteries drug effects, Microscopy, Video, Norepinephrine administration & dosage, Phentolamine administration & dosage, Vasoconstriction drug effects, Vasoconstrictor Agents administration & dosage, Vasodilator Agents administration & dosage, Vasomotor System drug effects, Mesenteric Arteries embryology, Mesenteric Arteries physiology, Vasomotor System embryology, Vasomotor System physiology
- Abstract
Changes in mesenteric arterial diameters were studied using intravital microscopy in chick fetuses at days 13 and 17 of incubation, corresponding to 0.6 and 0.8 fetal incubation time, both during 5 min of hypoxia followed by 5 min of reoxygenation and after topical administration of increasing concentrations (10(-6)-10(-2) M) of norepinephrine (NE) and acetylcholine (ACh). Baseline diameters of second-order mesenteric arteries increased from 56 microm at 0.6 incubation to 75 microm at 0.8 incubation. Acute hypoxia induced a reduction in arterial diameter to 87 +/- 4.4% of baseline at 0.6 incubation and to 44 +/- 6.7% at 0.8 incubation (P < 0.01). During reoxygenation, mesenteric arteries dilated to 118 +/- 6.5% and 121 +/- 7.5% of baseline at 0.6 and 0.8 fetal incubation time, respectively. Phentolamine did not affect the vasoconstriction during hypoxia at 0.6 incubation, whereas this alpha-adrenergic antagonist significantly attenuated the vasoconstrictor response at 0.8 incubation (to 93 +/- 2.7% of baseline, P < 0.01). Topical NE induced maximal vasoconstriction to 71 +/- 3% of baseline at 0.6 incubation and to 35 +/- 3.8% at 0.8 incubation (P < 0.01). Maximal vasodilation to topical ACh was 113 +/- 4.4% and 122 +/- 4.8% of baseline at 0.6 and 0.8 incubation, respectively. These in vivo findings show that fetal mesenteric arteries constrict in response to acute hypoxia and that the increase in magnitude of this vasoconstrictor response from 0.6 to 0.8 of fetal development results from an increase in adrenergic constrictor capacity.
- Published
- 2000
- Full Text
- View/download PDF
17. Endogenous nitric oxide protects against thromboembolism in venules but not in arterioles.
- Author
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Broeders MA, Tangelder GJ, Slaaf DW, Reneman RS, and oude Egbrink MG
- Subjects
- Animals, Arginine pharmacology, Female, Male, Microscopy, Video, Nitroarginine pharmacology, Nitroprusside pharmacology, Rabbits, Rupture prevention & control, Arterioles injuries, Nitric Oxide physiology, Thromboembolism prevention & control, Venules injuries
- Abstract
Because nitric oxide (NO) inhibits aggregation and adhesion of blood platelets, NO may play a role in platelet-vessel wall interactions. Therefore, the purpose of this study was to investigate the involvement of endogenous NO in thromboembolic processes, as induced by wall puncture, in rabbit mesenteric arterioles and venules (diameters 20 to 43 microm). In venules, inhibition of NO synthase by superfusion of the mesentery with N omega-nitro-L-arginine (L-NA; 0.1 mmol/L) significantly increased the duration of embolization (from 50 seconds to 511 seconds) and the number of emboli produced (from 2 to 11 emboli per vessel), while the median period of time needed to produce an embolus was not influenced. On the contrary, in arterioles, L-NA had no significant effect on embolization (duration of embolization: 426 seconds in the control and 382 seconds in the L-NA group, with 20 and 12 emboli per vessel, respectively). Addition to the L-NA superfusate of L-arginine (L-ARG; 1 mmol/L), the active precursor for endogenous NO synthesis, resulted in a complete reversal of the L-NA effects in venules, while addition of the inactive D-arginine (D-ARG; 1 mmol/L) had no effect. Addition of L-ARG and D-ARG had no significant effect in arterioles. Addition to the L-NA superfusate of the exogenous NO donor sodium nitroprusside (0.1 micromol/L) also resulted in reversal of the L-NA effects in venules, while in arterioles, it slightly but significantly decreased embolization duration. The differences in effect of L-NA on embolization between arterioles and venules were not caused by differences in fluid dynamic conditions. It is concluded that the role of endogenous NO in inhibiting thromboembolic processes is more important in venules than in arterioles.
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- 1998
- Full Text
- View/download PDF
18. Capillary recruitment and pain relief on leg dependency in patients with severe lower limb ischemia.
- Author
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Ubbink DT, Jacobs MJ, Slaaf DW, Tangelder GJ, and Reneman RS
- Subjects
- Adult, Aged, Aged, 80 and over, Blood Flow Velocity, Blood Volume, Capillaries physiology, Diabetes Mellitus, Type 2, Diabetic Angiopathies physiopathology, Erythrocytes physiology, Female, Humans, Male, Microcirculation, Middle Aged, Nails blood supply, Pain, Supine Position, Toes, Ischemia physiopathology, Leg blood supply
- Abstract
Background: Patients suffering from severe lower limb ischemia may experience pain relief on leg dependency despite the fact that dependency normally results in arteriolar vasoconstriction. To clarify this possible paradox, skin microcirculation of the limb was investigated in 75 patients with different stages of lower limb ischemia and in 12 asymptomatic subjects., Methods and Results: Using nailfold capillary video microscopy, red blood cell-perfused capillary density and diameter and red blood cell velocity were assessed in supine and sitting positions. Capillary density increased by changing from the supine to the sitting position, especially in patients with limb-threatening ischemia (showing a 4.5-fold increase versus a 1.5-fold increase in asymptomatic subjects). In subjects without or with mild ischemia, capillary perfusion was two to four times lower in the sitting than in the supine position. In patients with limb-threatening ischemia, perfusion was strongly reduced, being slightly higher in the sitting position. Patients with relief of pain while sitting did not always have a higher capillary perfusion but did have a higher capillary density in the sitting position., Conclusions: The arteriolar postural vasoconstrictive mechanism at the nutritive level is still intact in subjects without or with mild ischemia but not in patients with severe ischemia. Capillary recruitment rather than disturbed arteriolar vasoconstriction could explain why patients with severe leg ischemia prefer leg dependency.
- Published
- 1992
- Full Text
- View/download PDF
19. Foot salvage and improvement of microvascular blood flow as a result of epidural spinal cord electrical stimulation.
- Author
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Jacobs MJ, Jörning PJ, Beckers RC, Ubbink DT, van Kleef M, Slaaf DW, and Reneman RS
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- Aged, Blood Flow Velocity physiology, Female, Foot blood supply, Humans, Life Tables, Male, Microcirculation, Spinal Cord, Arteriosclerosis therapy, Electric Stimulation Therapy, Foot Diseases therapy, Skin Ulcer therapy
- Abstract
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)
- Published
- 1990
20. Epidural spinal cord electrical stimulation improves microvascular blood flow in severe limb ischemia.
- Author
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Jacobs MJ, Jörning PJ, Joshi SR, Kitslaar PJ, Slaaf DW, and Reneman RS
- Subjects
- Aged, Arterial Occlusive Diseases physiopathology, Capillaries, Electrodes, Implanted, Epidural Space, Female, Fluoresceins, Humans, Male, Microcirculation, Arterial Occlusive Diseases therapy, Electric Stimulation Therapy methods, Ischemia therapy, Leg blood supply
- Abstract
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.
- Published
- 1988
- Full Text
- View/download PDF
21. Cell communication in the basal cells of the human epidermis.
- Author
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van Heukelom JS, Slaaf DW, and van der Leun JC
- Subjects
- Blister pathology, Cell Membrane physiology, Diffusion, Electrophysiology, Humans, Mathematics, Models, Biological, Skin Physiological Phenomena, Epithelial Cells, Epithelium physiology, Skin cytology
- Abstract
Electrotonic spread can be measured in the basal cells of the human epidermis. The communication between neighboring cells is high, whereas no leak to the intercellular spaces could be detected. The specific resistance of the membranes between the cells is about 10 Omegacm(2). This finding suggests that for those particles that are able to pass the cell membrane the intracellular path through the epidermis is at least as suitable as the path through the intercellular spaces.
- Published
- 1972
- Full Text
- View/download PDF
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