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Capillary Diameter (capillary + diameter)
Selected AbstractsAngiogenesis in the Caprine Caruncles in Non-Pregnant and Pregnant Normal and Swainsonine-Treated DoesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 7 2007S.A. Hafez Abstract Microvascular corrosion casts of caruncles from non-pregnant and pregnant doe goats at 4, 7, 10, 13, 16, and 18 weeks were examined with scanning electron microscopy. The internal convex surface of the caruncles of non-pregnant does was covered with capillary meshes of regular diameter and form, without crypts. As pregnancy advanced the complexity of the vasculature increased: at 4 weeks the surface showed a pattern of ridges separated by troughs. At later stages, branches of radial arteries penetrated the periphery forming an extensive mesh of capillaries on the concave surface. Capillary diameters increased significantly during pregnancy, especially after 4 weeks, when large flattened sinusoids formed. These sinusoids had a great deal of surface area for potential contact with the fetal component. The caprine placenta is usually considered to have increased interhemal distance compared with endotheliochorial and hemochorial types: our results suggest that the very extensive development of sinusoids and crypts may compensate for any negative consequences of the placental architecture. Placental angiogenesis, which is physiologically normal, may serve as a general model of this process in other circumstances, such as tumor. The effect of swainsonine (active compound of locoweed and a potential anticancer drug) on vascular development showed no differences in sinusoidal diameters at 7 weeks, but a decrease in capillary density was noted. Swainsonine caused a great distortion to the vasculature at 18 weeks. The effects of this compound on the vascular development lend credibility to its potential as an anticancer agent. Anat Rec, 2007. © 2007 Wiley-Liss, Inc. [source] Experimental analysis of capillary tubes behaviour with some HCFC-22 alternative refrigerantsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2001Samuel M. Sami Abstract In this paper, an experimental study is presented to enhance our understanding of the capillary tube behaviour using some new alternative refrigerants to HCFC-22. An experimental setup fully instrumented was used to gather the behaviour of three different capillary tube geometries with R-410B, R-407C, and R-410A under various conditions; saturated, sub-cooled and two-phase. Experimental data showed that R-410B has the highest pressure drop along the capillary tubes compared to the alternatives under question and also has the highest temperature drop along the capillary tube. The data also showed that R-407C has similar capillary behaviour to that of R-22. The results clearly demonstrated that the pressure drop is significantly influenced by the diameter of the capillary tube, the type of refrigerant and inlet conditions to the capillary tube. The data also showed that the capillary pressure drop decreases with the increase of the capillary diameter. There is clear evidence that the component concentration of the refrigerant mixture significantly affects the capillary tube behaviour and particularly the pressure drop along the capillary tube length. Copyright © 2001 John Wiley & Sons, Ltd. [source] A direct comparison of pulsed dye, alexandrite, KTP and Nd:YAG lasers and IPL in patients with previously treated capillary malformations,LASERS IN SURGERY AND MEDICINE, Issue 6 2008David J. McGill MRCS(Ed) Abstract Introduction Several studies have reported laser treatment of Capillary Malformations (CMs) using systems other than pulsed dye lasers (PDL). Few, however, have compared different systems in the same patients. This study aimed to directly compare CM fading using five different systems. Methods Eighteen previously PDL-treated patients were test-patched using the alexandrite, KTP, and Nd:YAG lasers and intense pulsed light (IPL) with additional PDL patches as a control. Pre- and post-treatment videomicroscopy, and colour measurements using Munsell colour charts were carried out. Results Four patients failed to respond to any test patches. The alexandrite laser test patches had the largest mean improvement in Munsell colour following treatment (P,=,0.023) and resulted in CM fading in 10 patients, although 4 patients developed hyperpigmentation, and 1 patient scarring, following treatment. In addition, the alexandrite laser caused a significant decrease in mean post-treatment capillary diameter (P,=,0.007), which was not mirrored by the other systems. The KTP and Nd:YAG lasers were least effective, with fading seen in two patients for both systems, whilst IPL patches resulted in CM fading in six patients. In addition, five patients had further CM fading using double-passed PDL treatment. Mean pre-treatment capillary diameter measurements were predictive of those patients likely to respond to laser treatment. Conclusions Alexandrite laser treatment was the most effective, but resulted in hyperpigmentation and scarring in four patients, probably due to its deeper penetration and lower specificity for oxyhaemoglobin causing non-specific dermal damage. Double passing of the PDL can result in further CM fading even in previously treated patients. Videomicroscopy measurements of capillary diameter before treatment may be predictive of the likelihood for patient's to respond to laser treatment. Lesers Surg. Med. 40:390,398, 2008. © 2008 Wiley-Liss, Inc. [source] Morphology Modification of Polyethylene/Clay Nanocomposite Samples under Convergent FlowMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2009Francesco Paolo La Mantia Abstract The morphology of PE/CL nanocomposite samples subjected to convergent flows is studied. Elongational flow , the typical flow involved in spinning and film-blowing processing operations , significantly increases with the reduction of the capillary diameter. The values of the convergent extensional stress (calculated by Cogswell's formula) for the PE/CL systems, for all the adopted capillary geometries, are greater than the calculated values for pure polyethylene. The applied convergent flow, at the entrance of the capillary, is able to change the clay morphology and consequently the final material properties on the PE/CL system with limited affinity between the matrix and organo-modified clay particles. [source] Static Magnetic Fields Affect Capillary Flow of Red Blood Cells in Striated Skin MuscleMICROCIRCULATION, Issue 1 2008Gunnar Brix ABSTRACT Blood flowing in microvessels is one possible site of action of static magnetic fields (SMFs). We evaluated SMF effects on capillary flow of red blood cells (RBCs) in unanesthetized hamsters, using a skinfold chamber technique for intravital fluorescence microscopy. By this approach, capillary RBC velocities (vRBC), capillary diameters (D), arteriolar diameters (Dart), and functional vessel densities (FVD) were measured in striated skin muscle at different magnetic flux densities. Exposure above a threshold level of about 500 mT resulted in a significant (P < 0.001) reduction of vRBC in capillaries as compared to the baseline value. At the maximum field strength of 587 mT, vRBC was reduced by more than 40%. Flow reduction was reversible when the field strength was decreased below the threshold level. In contrast, mean values determined at different exposure levels for the parameters D, Dart, and FVD did not vary by more than 5%. Blood flow through capillary networks is affected by strong SMFs directed perpendicular to the vessels. Since the influence of SMFs on blood flow in microvessels directed parallel to the field as well as on collateral blood supply could not be studied, our findings should be carefully interpreted with respect to the setting of safety guidelines. [source] Local heat-shock priming-induced improvement in microvascular perfusion in osteomyocutaneous flaps is mediated by heat-shock protein 32BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 3 2001Dr M. Rücker Background: Stress conditioning is thought to improve microvascular free flap survival but the mechanisms of protection are not clear. The aim of this study was to determine whether local induction of heat-shock protein (HSP) 32 improves microvascular perfusion in transferred osteomyocutaneous flaps. Methods: The hindlimb harvest region of osteomyocutaneous flaps in Wistar rats was subjected to stress conditioning by local heating (30 min, 42·5°C) 24 h before microvascular flap transfer. In a second group of animals, after heat-shock priming, the action of HSP-32 was inhibited by tin protoporphyrin IX. Animals with unconditioned flaps served as controls. After transfer, the microcirculation of the muscle, cutaneous, subcutaneous and periosteal tissue of the flap was analysed quantitatively for 6 h using intravital fluorescence microscopy. Results: Immunohistochemistry revealed that HSP-32 was detectable only after priming and not in unconditioned flaps. Priming did not alter functional capillary density or capillary red blood cell velocity compared with that in unconditioned flaps. However, heat-shock priming induced significant capillary dilatation (P < 0·05) and thus a substantial increase in capillary blood flow volume (P < 0·05) in all tissues of the transferred flaps. Inhibition of HSP-32 by tin protoporphyrin IX completely abolished the priming-induced improvement in capillary perfusion, as indicated by the lack of increased capillary diameters and volumetric blood flow. Conclusion: The present study demonstrated that stress conditioning by local heat-shock priming improves nutritive perfusion in osteomyocutaneous flaps by capillary dilatation, probably mediated through the vasoactive action of HSP-32. © 2001 British Journal of Surgery Society Ltd [source] | ||||||||||