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Karel Rakusan - One of the best experts on this subject based on the ideXlab platform.
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early and late effect of neonatal hypo and hyperthyroidism on coronary Capillary Geometry and long term heart function in rat
Cardiovascular Research, 1997Co-Authors: Marcia I Heron, Frantisek Kolar, Frantisek Papousek, Karel RakusanAbstract:Objective: The aim of the present study was two-fold: (1) to examine the effect of hyper- and hypothyroidism on the developing coronary Capillary network in neonatal rats, and (2) to determine in adult rats that had re-established euthyroid status whether long-term changes in Capillary Geometry or cardiac function had been induced by either neonatal thyroid condition. Method: Two-day-old rats were treated every other day for 12 or 28 days with either 3,3′,5-triiodo- l -thyronine or 0.05% 6- n -propylthiouracil. After this time, treatment was stopped and in two-thirds of the rats morphometric examination of Capillary Geometry and immunohistochemical detection of proliferating cell nuclear antigen (PCNA) expression in endothelial cell nuclei were conducted. Remaining rats were weaned and grew to 80 days of age, at which time persistent changes in Capillary Geometry, PCNA expression, and cardiac function were assessed. Results: Neonatal hyperthyroidism induced cardiomegaly ( P < 0.01), whereas neonatal hypothyroidism attenuated cardiac growth ( P < 0.01). Capillary numerical density, Capillary segment lengths, and PCNA-labelling analysis indicated marked Capillary growth in hyperthyroid rats ( P < 0.05), but attenuated Capillary growth in hypothyroid rats. The elicited Capillary growth response appeared to be more dependent on altered tissue maturation than on cardiac growth rate. After discontinuing treatment both neonatal thyroid conditions induced a deficit in left ventricular growth ( P < 0.01). Furthermore, neonatal hyperthyroidism appeared to inhibit subsequent Capillary growth in distal regions of the Capillary bed in addition to inducing lasting positive chronotropic and inotropic effects on cardiac function ( P < 0.05). Neonatal hypothyroidism did not produce any lasting changes in capillarization or in cardiac function. Conclusions: Results suggest that neonatal thyroid status influences early growth and development of the coronary Capillary network, possibly by regulating tissue maturation, as well as inducing lasting effects on subsequent cardiac and Capillary growth and heart function.
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effect of nifedipine on coronary Capillary Geometry in normotensive and hypertensive rats
Hypertension, 1994Co-Authors: Karel Rakusan, Nicholas Cicutti, Stanislav Kazda, Z TurekAbstract:The aim of this study was to describe quantitatively changes in the coronary Capillary network resulting from hypertrophy in spontaneously hypertensive rats (SHR) and a potential effect of long-term treatment of these animals with nifedipine. Age-matched male SHR and Wistar-Kyoto (WKY) rats were treated for 27 weeks. Four experimental groups were analyzed: (1) untreated SHR, (2) nifedipine-treated SHR, (3) untreated control WKY rats, and (4) nifedipine-treated WKY rats. Treatment significantly decreased systolic blood pressure in SHR, although normotensive pressures were not reached. SHR had significantly higher cardiac weight, which decreased in nifedipine-treated rats, but values remained above those in control animals. Morphometric evaluation revealed lower Capillary density and larger Capillary domain area in hearts from SHR, which were partially attenuated by treatment with nifedipine. Capillary domain area was also significantly larger at arteriolar portions compared with domains supplied at venular portions. Capillary segment length was consistently shorter on the venular than arteriolar portion of the Capillary, whereas no differences were observed between hearts from WKY rats and SHR. Treatment with nifedipine resulted in a prolongation of segment length. Reconstruction of the three-dimensional Capillary supply unit (Capillary domain area times Capillary segment length) revealed significant differences between the amount of tissue supplied by a Capillary at its arteriolar portion than more distally, which was detectable in all experimental groups. In hypertrophic hearts from SHR this tissue volume is increased mainly because of longer interCapillary distances and larger domains, especially on arteriolar portions.(ABSTRACT TRUNCATED AT 250 WORDS)
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Geometry of Capillary networks in volume overloaded rat heart
Microvascular Research, 1991Co-Authors: Sanjay Batra, Karel RakusanAbstract:Volume overload cardiac hypertrophy was induced in male Sprague-Dawley rats by experimental aortocaval fistula. This procedure resulted in considerable increases in left ventricular mass (70%) by 21–23 days. Our objective was to study the effect of volume overload on the Geometry of coronary capillaries in the left ventricular midmyocardium. Tissue sections were stained according to a protocol that distinguished arteriolar (AC) and venular (VC) Capillary regions by color. Morphometric data were then collected and compared between AC and VC regions. In sham-operated controls (CON; n = 8), the tissue area (Capillary domain) supplied by a single Capillary decreased from AC to VC regions (AC = 505 ± 5 μm2; VC = 452 ± 7 μm2; P < 0.01; mean ± SE). In volume overloaded hearts (VOL; n = 8), only VC domain areas were reduced from control values (P < 0.01) and the differences between AC and VC regions were preserved (AC = 480 ± 5 μm2; VC = 395 ± 6 μm2; P < 0.01). Minimal Capillary length was significantly longer in volume overloaded hearts (VOL = 723 ± 18; CON = 581 ± 20 μm; P < 0.01). In the control group, AC segment length was longer than VC segment length (AC = 93 ± 2 μm; VC = 74 ± 2 μm; P < 0.01). In volume overload, AC segment length was also longer than VC segment length, but the divergence between AC and VC regions was increased (AC = 108 ± 3 μm; VC = 71 ± 2 μm; P < 0.01). These changes in Capillary Geometry may be secondary to specific changes in the arrangement and dimension of myocytes in the left ventricular wall following volume overload hypertrophy.
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Geometry of Capillary networks in hypertrophied rat heart
Microvascular Research, 1991Co-Authors: Sanjay Batra, Karel Rakusan, Scott E CampbellAbstract:Capillary Geometry was examined in normal and hypertrophic myocardium. Hypertrophy was induced by aortic constriction in neonatal rats. Morphometric data were obtained from tissue sections exposed to a staining technique that distinguished the arteriolar and venular portions of capillaries by color. In sham-operated controls, the theoretical tissue region supplied by a single Capillary decreased from the arteriolar to venular side (499 +/- 3 microns 2 and 456 +/- 5 microns 2, P less than 0.05; mean +/- SE) of capillaries. In hypertrophy, only arteriolar Capillary tissue regions increased in size, thus enlarging the difference between arteriolar and venular ends (547 +/- 6 microns 2 and 464 +/- 5 microns 2, P less than 0.01). InterCapillary distances, measured at various levels along the Capillary path length, decreased in a stepwise manner in both normal and hypertrophic hearts. In hypertrophic hearts, mean Capillary path length was significantly longer than in controls, but the total length of the individual Capillary nets was reduced. In both groups, arteriolar Capillary segment length was longer (P less than 0.01) than venular Capillary segment length. Given that PO2 values are lower on the venular side of capillaries, this spatially distinctive Geometry in normal myocardium: smaller domains, shorter interCapillary distances and segment lengths, would provide favorable geometric conditions for oxygen diffusion. In hypertrophy, average interCapillary distance increased, and the distinction between arteriolar and venular portions of capillaries was further exacerbated.
Timothy I Musch - One of the best experts on this subject based on the ideXlab platform.
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effects of aging on Capillary Geometry and hemodynamics in rat spinotrapezius muscle
American Journal of Physiology-heart and Circulatory Physiology, 2003Co-Authors: John A Russell, David C Poole, Casey A Kindig, Brad J Behnke, Timothy I MuschAbstract:The effects of aging on muscle microvascular structure and function may play a key role in performance deficits and impairment of O2 exchange within skeletal muscle of senescent individuals. To det...
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effect of heart failure on muscle Capillary Geometry implications for 02 exchange
Medicine and Science in Sports and Exercise, 1998Co-Authors: David C Poole, Timothy I MuschAbstract:UNLABELLED There is strong evidence that chronic heart chronic heart failure (CHF) impairs skeletal muscle function independent of blood flow and bulk O2 delivery. PURPOSE This investigation sought to determine whether alterations in muscle Capillary Geometry and surface area that are thought to be primary determinants of the efficacy for blood-tissue 02 exchange might be altered in CHF and contribute to these changes. METHODS Plantaris (fast twitch) and soleus (slow twitch) muscles from control (C) and 6- to 7-wk post myocardial infarcted (CHF) rates were perfusion-fixed in situ. These muscles were analyzed using morphometric techniques that facilitated determination of muscle sarcomere length fiber cross-sectional area, Capillary tortuosity and branching coefficient (c(K,0)), Capillary length, volume, and surface area. RESULTS Normalized to a sarcomere length of 2.1 microns, plantaris fiber cross-sectional area decreased by 21% (P < 0.05), and Capillary-to-fiber ratio decreased from 2.05 +2- 0.07 in C to 1.79 +2- 0.04 (P < 0.05) in CHF, but these variables were unchanged in soleus. These was no change in c(K,0) or Capillary diameter in either muscle, and thus Capillary length and surface area per fiber volume remained unchanged. From the measured fiber atrophy and Capillary involution in plantaris reductions of total muscle Capillary length, volume, and surface area of 11%, 9% and 17%, respectively, are estimated. CONCLUSION These changes, coupled with reduced blood flow may impair the effective matching of muscle fiber 02 delivery to 02 requirement during repeated muscle contractions (i.e. exercise). The scenario is expected to reduce intramyocyte 02 partial pressure and thereby contribute to the greater fatigability characteristic of the CHF condition.
Sanjay Batra - One of the best experts on this subject based on the ideXlab platform.
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a novel method to demonstrate Capillary Geometry and perfusion patterns in rat brain from the same histological section
Advances in Experimental Medicine and Biology, 1996Co-Authors: Sanjay Batra, Martin F KonigAbstract:The Geometry of the microvascular bed as well as its perfusion pattern are important determinants of oxygen transport to tissues. In the present study, we analyzed Capillary Geometry in the rat parietal cortex using discriminative morphometric methods. Specifically, we labeled arteriolar Capillary (i.e. the proximal portion of the Capillary bed, AC) and venular Capillary (i.e. the distal portion of the Capillary bed, VC) endothelium with different colors. While the Geometry of the Capillary bed sets the surface area for diffusion of oxygen, the pattern of perfusion within the Capillary bed under in vivo conditions provides information as to regional conditions for oxygen diffusion. Accordingly, we used a highly concentrated colloidal gold solution as a plasma label, to identify capillaries perfused with plasma under controlled conditions. While gold particles may be directly visualized on electron micrographs, they require enhancement with silver to make them visible at the light microscopic level. To our knowledge, this is the first study where these methods have been combined within the same histological section, i.e. enzymatic labeling of the Capillary endothelium as well as delineation of Capillary perfusion with silver enhanced colloidal gold particles.
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Geometry of Capillary networks in volume overloaded rat heart
Microvascular Research, 1991Co-Authors: Sanjay Batra, Karel RakusanAbstract:Volume overload cardiac hypertrophy was induced in male Sprague-Dawley rats by experimental aortocaval fistula. This procedure resulted in considerable increases in left ventricular mass (70%) by 21–23 days. Our objective was to study the effect of volume overload on the Geometry of coronary capillaries in the left ventricular midmyocardium. Tissue sections were stained according to a protocol that distinguished arteriolar (AC) and venular (VC) Capillary regions by color. Morphometric data were then collected and compared between AC and VC regions. In sham-operated controls (CON; n = 8), the tissue area (Capillary domain) supplied by a single Capillary decreased from AC to VC regions (AC = 505 ± 5 μm2; VC = 452 ± 7 μm2; P < 0.01; mean ± SE). In volume overloaded hearts (VOL; n = 8), only VC domain areas were reduced from control values (P < 0.01) and the differences between AC and VC regions were preserved (AC = 480 ± 5 μm2; VC = 395 ± 6 μm2; P < 0.01). Minimal Capillary length was significantly longer in volume overloaded hearts (VOL = 723 ± 18; CON = 581 ± 20 μm; P < 0.01). In the control group, AC segment length was longer than VC segment length (AC = 93 ± 2 μm; VC = 74 ± 2 μm; P < 0.01). In volume overload, AC segment length was also longer than VC segment length, but the divergence between AC and VC regions was increased (AC = 108 ± 3 μm; VC = 71 ± 2 μm; P < 0.01). These changes in Capillary Geometry may be secondary to specific changes in the arrangement and dimension of myocytes in the left ventricular wall following volume overload hypertrophy.
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Geometry of Capillary networks in hypertrophied rat heart
Microvascular Research, 1991Co-Authors: Sanjay Batra, Karel Rakusan, Scott E CampbellAbstract:Capillary Geometry was examined in normal and hypertrophic myocardium. Hypertrophy was induced by aortic constriction in neonatal rats. Morphometric data were obtained from tissue sections exposed to a staining technique that distinguished the arteriolar and venular portions of capillaries by color. In sham-operated controls, the theoretical tissue region supplied by a single Capillary decreased from the arteriolar to venular side (499 +/- 3 microns 2 and 456 +/- 5 microns 2, P less than 0.05; mean +/- SE) of capillaries. In hypertrophy, only arteriolar Capillary tissue regions increased in size, thus enlarging the difference between arteriolar and venular ends (547 +/- 6 microns 2 and 464 +/- 5 microns 2, P less than 0.01). InterCapillary distances, measured at various levels along the Capillary path length, decreased in a stepwise manner in both normal and hypertrophic hearts. In hypertrophic hearts, mean Capillary path length was significantly longer than in controls, but the total length of the individual Capillary nets was reduced. In both groups, arteriolar Capillary segment length was longer (P less than 0.01) than venular Capillary segment length. Given that PO2 values are lower on the venular side of capillaries, this spatially distinctive Geometry in normal myocardium: smaller domains, shorter interCapillary distances and segment lengths, would provide favorable geometric conditions for oxygen diffusion. In hypertrophy, average interCapillary distance increased, and the distinction between arteriolar and venular portions of capillaries was further exacerbated.
David C Poole - One of the best experts on this subject based on the ideXlab platform.
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effects of aging on Capillary Geometry and hemodynamics in rat spinotrapezius muscle
American Journal of Physiology-heart and Circulatory Physiology, 2003Co-Authors: John A Russell, David C Poole, Casey A Kindig, Brad J Behnke, Timothy I MuschAbstract:The effects of aging on muscle microvascular structure and function may play a key role in performance deficits and impairment of O2 exchange within skeletal muscle of senescent individuals. To det...
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effect of heart failure on muscle Capillary Geometry implications for 02 exchange
Medicine and Science in Sports and Exercise, 1998Co-Authors: David C Poole, Timothy I MuschAbstract:UNLABELLED There is strong evidence that chronic heart chronic heart failure (CHF) impairs skeletal muscle function independent of blood flow and bulk O2 delivery. PURPOSE This investigation sought to determine whether alterations in muscle Capillary Geometry and surface area that are thought to be primary determinants of the efficacy for blood-tissue 02 exchange might be altered in CHF and contribute to these changes. METHODS Plantaris (fast twitch) and soleus (slow twitch) muscles from control (C) and 6- to 7-wk post myocardial infarcted (CHF) rates were perfusion-fixed in situ. These muscles were analyzed using morphometric techniques that facilitated determination of muscle sarcomere length fiber cross-sectional area, Capillary tortuosity and branching coefficient (c(K,0)), Capillary length, volume, and surface area. RESULTS Normalized to a sarcomere length of 2.1 microns, plantaris fiber cross-sectional area decreased by 21% (P < 0.05), and Capillary-to-fiber ratio decreased from 2.05 +2- 0.07 in C to 1.79 +2- 0.04 (P < 0.05) in CHF, but these variables were unchanged in soleus. These was no change in c(K,0) or Capillary diameter in either muscle, and thus Capillary length and surface area per fiber volume remained unchanged. From the measured fiber atrophy and Capillary involution in plantaris reductions of total muscle Capillary length, volume, and surface area of 11%, 9% and 17%, respectively, are estimated. CONCLUSION These changes, coupled with reduced blood flow may impair the effective matching of muscle fiber 02 delivery to 02 requirement during repeated muscle contractions (i.e. exercise). The scenario is expected to reduce intramyocyte 02 partial pressure and thereby contribute to the greater fatigability characteristic of the CHF condition.
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effect of pulmonary emphysema on diaphragm Capillary Geometry
Journal of Applied Physiology, 1997Co-Authors: David C Poole, Odile MathieucostelloAbstract:Poole, David C., and Odile Mathieu-Costello. Effect of pulmonary emphysema on diaphragm Capillary Geometry.J. Appl. Physiol. 82(2): 599–606, 1997.—In emphysema, the diaphragm shortens by losing sar...
Odile Mathieucostello - One of the best experts on this subject based on the ideXlab platform.
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effect of pulmonary emphysema on diaphragm Capillary Geometry
Journal of Applied Physiology, 1997Co-Authors: David C Poole, Odile MathieucostelloAbstract:Poole, David C., and Odile Mathieu-Costello. Effect of pulmonary emphysema on diaphragm Capillary Geometry.J. Appl. Physiol. 82(2): 599–606, 1997.—In emphysema, the diaphragm shortens by losing sar...
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Capillary fiber Geometry in pectoralis muscles of one of the smallest bats
Respiration Physiology, 1994Co-Authors: Odile Mathieucostello, P.j. Agey, Joseph M SzewczakAbstract:Abstract We previously reported striking similarities in the structural capacity for O 2 flux in the highly aerobic flight muscles of a hummingbird and bat despite their significant differences in Capillary-fiber Geometry and number, and fiber size. However, the bats of that study ( Eptesicus fuscus , BW 15–16 g) were about 5 times larger than the hummingbirds ( Selasphorus rufus ; BW 3–4 g). In this study, ww examined the flight muscle in a bat of approximately the same size as the hummingbird to determine whether features found in the big brown bat would be accentuated or if there would be additional similarities with the hummingbird. The pectoralis muscle of pipistrelle bats Pipistrellus hesperus (BW 3–5 g) was perfusion-fixed in situ, processed for electron microscopy and analyzed by morphometry. Fiber size (group mean ±SE, 314±22 μ m 2 at 2.1 μm sarcomere length) and Capillary Geometry (high degree of tortuosity and branching) were remarkably similar to those in pectoralis muscle of the big brown bat. Thus distances from capillaries to the center of the fibers were not reduced in pipistrelle flight muscle (as in hummingbird) nor was Capillary tortuosity and branching further increased (compared with big brown bat). Capillary-fiber surface ratio at a given mitochondrial volume/μm length of fiber was high and similar to that in big brown bat and hummingbird, consistent with the idea that the size of the Capillary-fiber interface plays an important role in providing the great O 2 flux potential in these muscles. In addition, Capillary-fiber number at a given fiber mitochondrial volume per μm length of fiber was similar to that in other muscles including big brown bat and hummingbird flight muscle, bat hindlimb and rat M. soleus. This supports the notion of a close relationship between Capillary number and mitochondrial volume on an individual fiber basis in aerobic muscles.
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morphometric analysis of Capillary Geometry in pigeon pectoralis muscle
American Journal of Anatomy, 1991Co-Authors: Odile MathieucostelloAbstract:The objective of the study was to examine the relationship(s) between the size and the Geometry of the Capillary network in the flight muscle of pigeon (Columbia livia). To this end, we used morphometry to analyze the degree of anisotropy (i.e., orientation) of capillaries with respect to the axis of the muscle fibers in perfusion-fixed samples of pigeon pectoralis muscles with large difference in Capillary density. Capillary number per fiber cross-sectional area (range, 1,491-5,680 mm-2) depended on fiber size (aerobic fibers, 304-782 microns 2; glycolytic, 1,785-2,444 microns 2), as well as sarcomere length (1.69-2.20 microns), and the relative sectional area of aerobic and glycolytic fibers (aerobic, 42-84% of total fiber area). The degree of tortuosity of capillaries, i.e., their bending or sinuosity relative to the muscle fiber axis, was primarily a function of sarcomere length. In spite of large differences in Capillary density, Capillary orientation at a given sarcomere length was remarkably similar among samples. In addition to capillaries running parallel to the muscle fiber axis, a unique arrangement of branches running perpendicular to the muscle fiber axis was found in all samples. This arrangement yielded a large circumferential distribution of Capillary surface around the muscle fibers. Compared to mammalian limb muscles examined over a 10-fold range of Capillary density (range, 450-4,670 mm-2), the degree of anisotropy of capillaries was greater in all samples of pigeon M. pectoralis. In the pigeon, there was no increase in the amount of Capillary surface area available for exchange per microvessel as a result of a greater degree of Capillary tortuosity in samples with larger Capillary density (Capillary number per fiber cross-sectional area greater than 4,000 mm-2), as compared to samples with a Capillary density less than 4,000 mm-2.
