Changes In Capillary Blood Flow Research Articles

Modeling the response of homogeneous and heterogeneous cerebral capillary networks to local changes in vessel diameters

While microvascular cerebral capillary networks are known to be highly heterogeneous, previous computational models have predicted that heterogeneous cerebral capillary flow patterns result in lower brain tissue partial oxygen pressures. Moreover, as blood flow increases, the flux among capillaries homogenizes. This homogenization of flow is expected to improve the efficiency of oxygenation extraction from the blood. In this work, we use mathematical modeling to explore a possible functional role for the high degree of heterogeneity observed in cerebral capillary networks. Our results suggest that heterogeneity allows for a greater response of tissue oxygen levels to local changes in vessel diameters due to neuronal activation. This result is confirmed for a full 3-dimensional model of capillary networks that includes oxygen diffusion within the tissue region and a reduced model that accounts for changes in capillary blood flow.

Application of a multicomponent model of convectional reaction-diffusion to description of glucose gradients in a neurovascular unit.

A supply of glucose to a nervous tissue is fulfilled by a cerebrovascular network, and further diffusion is known to occur at both an arteriolar and a microvascular level. Despite a direct relation, a blood flow dynamic and reaction-diffusion of metabolites are usually considered separately in the mathematical models. In the present study they are coupled in a multiphysical approach which allows to evaluate the effects of capillary blood flow changes on near-vessels nutrient concentration gradients evidently. Cerebral blood flow (CBF) was described by the non-steady-state Navier-Stokes equations for a non-Newtonian fluid whose constitutive law is given by the Carreau model. A three-level organization of blood–brain barrier (BBB) is modelled by the flux dysconnectivity functions including densities and kinetic properties of glucose transporters. The velocity of a fluid flow in brain extracellular space (ECS) was estimated using Darcy’s law. The equations of reaction-diffusion with convection based on a generated flow field for continues and porous media were used to describe spatial-time gradients of glucose in the capillary lumen and brain parenchyma of a neurovascular unit (NVU), respectively. Changes in CBF were directly simulated using smoothing step-like functions altering the difference of intracapillary pressure in time. The changes of CBF cover both the decrease (on 70%) and the increase (on 50%) in a capillary flow velocity. Analyzing the dynamics of glucose gradients, it was shown that a rapid decrease of a capillary blood flow yields an enhanced level of glucose in a near-capillary nervous tissue if the contacts between astrocytes end-feet are not tight. Under the increased CBF velocities the amplitude of glucose concentration gradients is always enhanced. The introduced approach can be used for estimation of blood flow changes influence not only on glucose but also on other nutrients concentration gradients and for the modelling of distributions of their concentrations near blood vessels in other tissues as well.

Tissue temperature, flux and oxygen of sacral and trochanteric area under pressure of healthy subjects: A quasi-experimental study

AimTo evaluate the changes that take place in the perfusion, oxygenation and local temperature of the skin of the sacrum and trochanter when subjected to direct pressure for 2 h. MethodsQuasi-experimental study in the preclinical phase with healthy subjects acting as their own controls (intrasubject control). The outcome variables were measured with a laser Doppler system (local temperature and oxygenation) and by near-infrared spectroscopy (perfusion). The pressure exerted was measured with a capacitive pressure sensor. No more than one week elapsed between the sacrum and trochanter measurements. ResultsThe study sample consisted of 18 persons. The comparative analysis of the fluctuations in the parameters measured on the skin of the trochanters and sacrum, according to the time elapsed, revealed a statistically significant increase in temperature and in the pressure exerted. On the other hand, the changes in capillary blood flow and in SaO2 were not statistically significant. ConclusionOur study results show that changes found in terms of temperature and pressure should be taking into account when planning personalised repositioning to patients according to biomechanical and biological situations that vary between anatomical areas. In future research, the changes reported could be evaluated in patients with risk factors for the development of pressure ulcers, thus facilitating the introduction of more personalised planning in the care and prevention of these injuries.

Bulbar capillaroscopy and plethysmography for assessment of blood microcirculation and endothelium properties in type 1 diabetes

To evaluate the properties of the microvasculature of bulbar conjunctiva and to assess the function of endothelium of the main arteries in type 1 diabetes mellitus (T1DM). The study included 35 patients with T1DM and initial nonproliferative diabetic retinopathy (NPDR). The control group consisted of 30 subjects. In addition to standard ophthalmic examination, all participants underwent digital bulbar capillaroscopy (DBC), pulse wave velocity (PWV) test, and plethysmography for assessment of endothelium function. According to DBC, in comparison to the control group, diabetic patients with even initial NPDR had disturbances of blood microcirculation manifested as increased average venous vessel width (p=0.04), reduced arterial capillary blood flow (p=0.02), increased blood sludging (p=0.001), and increased duration of blood stasis (p=0.03). Evaluation of vessel endothelium in T1DM patients with NPDR showed increased PWV (p=0.03). Diabetic patients with NPDR showed marked changes of capillary blood flow alongside signs of endothelial dysfunction. The most significant change was increased venous vessel width.

Профілактика та лікування реперфузійного пошкодження тканин при реконструкції артеріального русла аорто-стегно-підколінного сегмента в умовах хронічної критичної ішемії

Мета роботи: покращити результати реконструктивних операцій на аорті та магістральних артеріях в умовах хронічної критичної ішемії нижніх кінцівок.
 Матеріали і методи. В роботу включено 56 пацієнтів з облітеруючими ураженнями аорти та артерій нижніх кінцівок із ІІ, ІІІА, ІІІВ, IV ст. хронічної артеріальної недостатності.
 Для профілактики і лікування феноменів no-reflow і reflow-paradox на доопераційному періоді здійснювали комплекс запропонованих заходів.
 Для діагностики характеру ураження артеріального русла й особливостей гемодинамічних порушень застосовували показники ультразвукової доплерографії, дуплексного сканування, рентгеноконтрастної цифрової ангіографії. Для одержання інформації про зміни капілярного кровотоку і артеріо-венулярного шунтування крові застосовували метод лазерної доплерівської флоурометрії.
 Результати дослідження та їх обговорення. За об’ємом реваскуляризації аорто(клубово)-стегно-підколінного сегмента пацієнтів розділили на дві групи. Оперативне втручання в першій групі пацієнтів включало одномоментне аорто-біфеморальне алошунтування (14 спостережень) і однобічне аорто(клубово)-стегнове алошунтування (8 спостережень). Другу групу склали 34 пацієнти, у яких, крім атеросклеротичної оклюзії аорто(клубово)-стегнового, сегмента виявлено стенотично-оклюзивний процес стегно-підколінного сегмента. Динамічний ультразвуковий моніторинг стану гемодинаміки стегно-підколінного сегмента в післяопераційному періоді у хворих другої групи дозволив виявити зниження пікової систолічної швидкості та індексу резистентності, що було показанням до проведення додаткової реконструкції стегно-підколінного сегмента.

Патофізіологічно обґрунтована профілактика та лікування реперфузійно- реоксигенаційного синдрому при реваскуляризації нижніх кінцівок в умовах хронічної критичної ішемії

Introduction. One of the causes of the adverse effects of reconstruction of the aorto-femoral-popliteal segment is the development of reperfusion-reoxygenative syndrome.The aim. Improve the results of reconstructive operations on the aorta and major arteries under conditions of chronic critical ischemia of the lower extremities.Materials and methods. The work includes 56 patients with obliterating lesions of the aorta and arteries of the lower extremities of II, IIIA, IIIB, IV stages chronic arterial insufficiency. For the prevention and treatment of the phenomena of no-reflow and reflow-paradox in the pre-operative period, a complex of proposed measures was implemented. To diagnose the nature of the lesion of the arterial bed and the features of hemodynamic disturbances, indicators of ultrasound dopplerography, duplex scanning, X-ray contrast digital angiography were used. To obtain information on changes in capillary blood flow and arteriovenular blood flow, the method of laser doppler fluorometry was used.Results. By volume of revascularization patients are divided into two groups. Operative intervention in the 1st group of patients included single-stage aorto-bifermal bypass (14 observations) and one-sided aorto(ileo)-femoral bypass (8 observations). The second group included 34 patients who in addition to atherosclerotic occlusion aorto/ilia-femoral segment revealed stenotic-occlusive process femoral-popliteal segment. Dynamic ultrasound monitoring of hemodynamic femoral-popliteal segment postoperative patients II gr. revealed a decrease in peak systolic velocity and resistive index, which was an additional indication for reconstruction of the femoral-popliteal segment.Conclusions Pathophysiologically grounded preoperative prevention and treatment of reperfusion-reoxygenative syndrome in revascularisation of the lower extremities under conditions of chronic critical ischemia, make it possible to prevent the development of postoperative complications

Comparison of CCD-equipped laser speckle flowgraphy with hydrogen gas clearance method in the measurement of optic nerve head microcirculation in rabbits

The aim of this study was to verify the correlation between mean blur rate (MBR) obtained with CCD-equipped laser speckle flowgraphy (LSFG) and capillary blood flow (CBF) obtained by the hydrogen gas clearance method in rabbit optic nerve head (ONH). Using Japanese white rabbits under systemic anesthesia, a hydrogen electrode was inserted an area of the ONH free from superficial capillaries. MBR was measured with LSFG near the hydrogen electrode. CBF and MBR were measured in the range of 32.4–83.5 mL/min/100 g and 3.5–6.0, respectively. MBR and CBF were significantly correlated (r = 0.73, P < 0.01, n = 14). After inhalation of carbon dioxide (CO2) or intravenous administration of endothelin-1 (ET-1), MBR and CBF were changed in the relative range of 0.74–1.27 and 0.76–1.35, respectively. The relative changes in MBR and CBF induced by CO2 and ET-1 were also significantly correlated (r = 0.67, P < 0.01). The current results suggest that MBR may correlate with CBF and also change with CBF, as an index of blood flow in the ONH, linearly.

Motion Artifact Compensation for Wristwatch Type Photoplethysmography Sensor

Heart beat measurement is useful not just for medical use but also for daily healthcare monitoring and for sports. Photoplethysmography is an optical pulse measurement method that measures the variation of light absorption of the blood flow in capillary. Fingertip and earlobe, which are suitable places for this method, are not suitable for wearing sensors in daily life. Measurement at wrist will be more favorable. Technical difficulties of applying photoplethysmography measurement on wrist are: a) blood flow variation and change of sensor orientation caused by body motions, and b) low sensitivity compared to measurement at fingertips or earlobes because of the low capillary density in the tissue. We derived a transfer function that expresses the relationship between body acceleration and change in capillary blood flow based on a simple fluid dynamics model of artery and capillary. Preliminary experiments have shown that motion the artifacts can be reduced by subtracting the change of blood flow estimated from body acceleration. This method is different from conventional frequency filtering methods that do not consider the relationship between the body motion and the changes in the capillary blood flow. Furthermore, sensor head suspension mechanism has been employed in order to stabilize the sensor orientation with respect to the skin as well as the applied force on the skin.

Gender and eccentric training in Achilles mid-portion tendinopathy

The role of gender in Achilles tendinopathy is yet to be determined. We hypothesized that female patients respond the same as males to 12 weeks of painful eccentric training. A total number of 75 consecutive mid-portion patients with Achilles tendinopathy (25 females, 38 males) were enrolled in a cohort study with 63 being analyzed after 12 weeks according to their gender for tendon and paratendon microcirculatory mapping. Outcome was determined by pain on visual analogue scale, VISA-A score, Foot Ankle Outcome Score (FAOS), tendon and paratendon capillary blood flow, oxygen saturation, and postcapillary venous filling pressures. Eccentric training resulted in a morning resting pain reduction by 44% in males (P = 0.001) and by 27% in females (P = 0.08). VISA-A score improved in males by 27% from 63 +/- 12 to 86 +/- 13 (P = 0.036) and by 20% in females from 60 +/- 14 to 75 +/- 11 (P = 0.043, P < 0.05 for gender difference). Among females, only one out of five FAOS items was increased (sport 72 +/- 21 to 82 +/- 15, P = 0.045), while in males, four out of five items were increased (symptoms, pain, all-day-life, and sport, all P < 0.01). The microcirculatory gender-specific response to eccentric training revealed a greater postcapillary venous filling pressure reduction among symptomatic females and inconclusive capillary blood flow changes. No change in tendon oxygenation was noted in both genders. Symptomatic females suffering Achilles tendinopathy do not benefit as much as symptomatic males from 12 weeks of eccentric training. The pain reduction is significantly lower among symptomatic females in contrast to males, and the improvement in the FAOS and VISA-A scores is significantly lower among females in contrast to males. Additional treatment options warrant scrutiny to symptomatic females suffering Achilles tendinopathy beyond eccentric training.

Microcirculatory effects of topical glyceryl trinitrate on the Achilles tendon microcirculation in patients with previous Achilles tendon rupture

Topical glyceryl trinitrate treatment has demonstrated short- to mid-term efficacy in chronic noninsertional Achilles tendinopathy. However, the underlying mechanisms are far from being understood. We hypothetized that Achilles tendon capillary blood flow changes immediately after topical glyceryl trinitrate treatment. Fifteen patients (55 + or - 15 years, VAS 5.8 + or - 2.3) with current mid-portion Achilles tendon pain 36 months after open surgical Achilles tendon repair for tendon rupture were included. On the Achilles mid-portion, 1.2 mg topical glyceryl trinitrate was sprayed. Microcirculatory monitoring included capillary blood flow, tendon oxygen saturation and postcapillary venous filling pressures at the insertion and 2, 4 and 6 cm above the insertion using a combined laser Doppler and spectrophotometry system. Baseline capillary blood-flows of the painful versus the uninjured tendon were increased [108 + or - 46 vs. 81 + or - 20 (2 cm above the insertion), 104 + or - 40 vs. 76 + or - 20 (4 cm above the insertion), 111 + or - 53 vs. 90 + or - 21 (6 cm above the insertion, P < 0.05)]. However, topical glyceryl trinitrate did not change capillary blood-flow at 2 and 8-mm tissue depths at the painful Achilles tendon or the healthy tendon. Tendon oxygenation was not changed at the painful or the healthy Achilles tendon. Postcapillary venous filling pressure was reduced at 8 mm at the mid-portion in the painful Achilles tendon only (113 + or - 37 vs. 95 + or - 31, P = 0.030). Acute topical glyceryl trinitrate facilitates capillary venous outflow in painful Achilles tendons. However, capillary blood-flow and tendon oxygenation remain unchanged following acute topical glyceryl trinitrate application. Elevated capillary blood-flow at the entire mid-portion is encountered at baseline in previously ruptured painful Achilles tendons even 3 years after surgical repair of the Achilles tendon indicating an altered microcirculatory flow pattern.

Evaluation of Laser Doppler Flowmetry for Measurement of Capillary Blood Flow in the Stomach Wall of Dogs During Gastric Dilatation‐Volvulus

To validate laser doppler flowmetry (LDF) for measurement of blood flow in the stomach wall of dogs with gastric dilatation-volvulus (GDV). Six purpose-bred dogs and 24 dogs with naturally occurring GDV. Experimental and clinical. Capillary blood flow in the body of the stomach and pyloric antrum was measured with LDF (tissue perfusion unit (TPU) before and after induction of portal hypertension (PH) and after PH plus gastric ischemia (GI; PH + GI) and compared with flow measured by colored microsphere technique. Capillary flow was measured by LDF in the stomach wall of dogs with GDV. PH and PH+GI induced a significant reduction in blood flow in the body of the stomach (P = .019). A significant positive correlation was present between percent changes in capillary blood flow measured by LDF and colored microspheres after induction of PH + GI in the body of the stomach (r = 0.94, P = .014) and in the pyloric antrum (r = 0.95, P = .049). Capillary blood flow measured in the body of the stomach of 6 dogs that required partial gastrectomy (5.00+/-3.30 TPU) was significantly lower than in dogs that did not (28.00+/-14.40 TPU, P = .013). LDF can detect variations in blood flow in the stomach wall of dogs. LDF may have application for evaluation of stomach wall viability during surgery in dogs with GDV.

Characterization of a “Blanch-Blush” Mechano-Response in Palmar Skin

Palmar finger skin reacts to extension under mechanical load -- blanching over proximal (intercrease skin, ICS) and middle phalanges, while blushing in crease skin (CS), which we have called the Blanch-Blush Reaction (BBR). The idea that the BBR is a result of surface capillary blood flow changes that relate to predictable deformation of aligned collagen matrices under applied uniaxial loads was tested. Nondestructive techniques, digital image analysis (DIA), laser Doppler scanning, and elastic scatter spectroscopy (ESS) were used to measure color and blood flow changes in healthy fingers when at rest and extended. Skin strain increased directly with applied load and DIA identified blanching (loss of redness) in the ICS, reflected by a decrease in hemoglobin (by ESS). Laser Doppler flowmetry identified an increase in blood flow in the CS zone on extension, with a minor increase in blood flow in the ICS zone, apparently due to diversion of flow to deeper vessels, when monitored by this technique. These changes correlated with the BBR, owing to altered capillary flow in the ICS and CS. The histology of orientation of collagen fibers and vessels in the two zones was consistent with this mechanism. This study demonstrates the interdependence between matrix orientation, applied load, and flow. It represents an elegant demonstration of collagenous tissue function through an everyday tissue reaction, which has not been described previously.

Anterior Optic Nerve Capillary Blood Flow Response to Diurnal Variation of Mean Ocular Perfusion Pressure in Early Untreated Primary Open-Angle Glaucoma

To examine the impact of diurnal variation in intraocular pressure (IOP) and mean ocular perfusion pressure (MOPP) on the variation in anterior optic nerve capillary blood flow (BF) in patients with untreated early primary open-angle glaucoma (uPOAG) and healthy volunteers. Fourteen patients with uPOAG (age, 56.3 +/- 12 years [SD]; seven men) and 14 normal subjects (age, 57.6 +/- 9.9 years; five men) were examined. Diurnal IOP, systolic (SBP) and diastolic (DBP) blood pressures, and optic nerve head (ONH) topography were measured every hour; and diurnal BF was measured by flowmeter every 2 hours between 0700 and 2200 hours. A perfusion image analyzer was used to calculate the mean BF within the rim (mean rim flow, MRF). The local flow (LF) was calculated using the median and mean flow rates within a 10 x 10-pixel window placed on the rim in the area of maximum topography fluctuation (MTF). The MOPP was then calculated. Mixed-effect linear models were used to analyze the repeated measures data in which both fixed and random effects were included. IOP, BP, and MOPP had significant diurnal variation (P < 0.040). LF measured at the sector of MTF significantly changed in patients with uPOAG (P = 0.006) but not in normal subjects (P = 0.660). MRF did not show significant diurnal change in either group (P = 0.130, P = 0.770). LF increased significantly after lunch in the uPOAG group (P = 0.001). SBP had a significant effect on LF over the course of the day in the uPOAG group (P = 0.043). The diurnal change in IOP, BP, and MOPP did not have a significant effect on MTF in either group. In uPOAG, the local flow, in areas of greatest topographical change, correlated inversely with IOP at 0700 hours (P < or = 0.002). The mean rim flow did not change during the day, implying that the anterior optic nerve capillary blood flow was autoregulated in both normal subjects and in patients with uPOAG, despite significant changes in IOP and MOPP. However, the regions of greatest diurnal change in rim topography (MTF) had significant diurnal change in capillary blood flow in patients with uPOAG but not in normal subjects.

The effect of promontorial bone on laser light transmission in measuring capillary blood flow in vivo.

Use of laser Doppler flowmetry (LDF) to assess cochlear blood flow (CBF) in experimental animals has elucidated the complex mechanisms in CBF regulation. Some attempts have been made to measure CBF in humans, although earlier studies produced confusing data about the physical possibility of LDF penetrating the human tympanic cavity promontory. In this study, we used LDF in an attempt to observe capillary blood flow in vivo through the intact human promontory in order to develop a method for measuring CBF in human patients. Temporal bones from six human cadavers were removed and the promontory overlying the basal turn of the cochlea was drilled off and fixed in 10% formalin. Perpendicular bone thickness was measured at the site of the stria vascularis. Seven young rats were anesthetized and the carotid artery was cannulated for blood pressure recording. Capillary flow was registered with LDF from two sites, the kidney and the plantar area of a hind limb, using a custom-designed probe with 632.8 nm and 780 nm wavelengths. Intravenous epinephrine was used to evoke blood flow changes. The same measurements were repeated through the promontorial bone. The light attenuation induced by the promontorial bone was 79+/-28% for the 632.8 nm wavelength, and 22+/-15 to 65+/-13% for the 780 nm wavelength, depending on the thickness of the bone. The sensitivity in detecting minute changes was 78% and 91-96%, respectively, for the 632.8 nm and 780 nm wavelengths. This study indicates that it is possible to detect minute changes in capillary blood flow through the intact human promontory at the site of the stria vascularis.

Intestinal microcirculation and gut permeability in acute pancreatitis: early changes and therapeutic implications

Translocation of bacteria from the intestine causes local and systemic infection in severe acute pancreatitis. Increased intestinal permeability is considered a promoter of bacterial translocation. The mechanism leading to increased gut permeability may involve impaired intestinal capillary blood flow. The aim of this study was to evaluate and correlate early changes in capillary blood flow and permeability of the colon in acute rodent pancreatitis of graded severity. Edematous pancreatitis was induced by intravenous cerulein; necrotizing pancreatitis by intravenous cerulein and intraductal glycodeoxycholic acid. Six hours after induction of pancreatitis, the permeability of the ascending colon was assessed by the Ussing chamber technique; capillary perfusion of the pancreas and colon (mucosal and subserosal) was determined by intravital microscopy. In mild pancreatitis, pancreatic capillary perfusion remained unchanged (2.13 ± 0.06 vs. 1.98 ± 0.04 nl·min −1·cap −1 [control]; P = NS), whereas mucosal (1.59 ± 0.03 vs. 2.28 ± 0.03 nl·min −1·cap −1 [control]; P <0.01) and subserosal (2.47 ± 0.04 vs. 3.74 ± 0.05 nl·min −1·cap −1 [control]; P <0.01) colonic capillary blood flow was significantly reduced. Severe pancreatitis was associated with a marked reduction in both pancreatic (1.06 ± 0.03 vs. 1.98 ± 0.04 nl·min −1·cap −1 [control]; P <0.01) and colonic (mucosal: 0.59 ± 0.01 vs. 2.28 ± 0.03 nl·min −1·cap −1 [control], P <0.01; subserosal: 1.96 ± 0.05 vs. 3.74 ± 0.05 nl·min −1·cap −1 [control], P <0.01) capillary perfusion. Colon permeability tended to increase with the severity of the disease (control: 147 ± 19 nmol·hr −1·cm −2; mild pancreatitis: 158 ± 23 nmol·hr −1·cm −2; severe pancreatitis: 181 ± 33 nmol·hr −1·cm −2; P = NS). Impairment of colonic capillary perfusion correlates with the severity of pancreatitis. A decrease in capillary blood flow in the colon, even in mild pancreatitis not associated with significant protease activation and acinar cell necrosis or impairment of pancreatic capillary perfusion, suggests that colonic microcirculation is especially susceptible to inflammatory injury. There was no significant change in intestinal permeability in the early stage of pancreatitis, suggesting a window of opportunity for therapeutic interventions to prevent the later-observed increase in gut permeability, which could result in improved intestinal microcirculation.

Somatostatin attenuates microcirculatory impairment in acute sodium taurocholate-induced pancreatitis.

Using in vivo microscopy, red blood cell (RBC) velocities, functional capillary density (FCD), and overall changes in capillary blood flow (PI) were estimated following intraductal infusion of sodium taurocholate (0.8 ml; 4%) alone or in combination with systemic administration of somstostatin (single bolus SMS 100 microg/100 g body wt). Sodium taurocholate mediated a significant transient decrease in RBC velocities and a sustained decrease in FCD, which were paralleled by dramatic flow heterogeneity. Therefore, a significant reduction in overall capillary blood flow was calculated. Additional SMS treatment reduced microcirculatory impairment as expressed by reduction of blood flow heterogeneity, a less rarified functional capillary density, and a recovery of RBC velocities and acinar capillary overall perfusion to control values. As a result of this microcirculatory improvement, pancreas histology revealed slightly less severe tissue damage compared to the non-SMS-treated pancreatitis group. These findings demonstrate that exogenous SMS infusion can improve microcirculatory failure in acute biliary pancreatitis, which should have a beneficial effect on the course of the disease.

Acute pancreatitis in rats: effects of sodium taurocholate, CCK-8, and Sec on pancreatic microcirculation.

With use of in vivo microscopy, pancreatic duct permeability, red blood cell (RBC) velocities, functional capillary density (FCD), and overall changes in capillary blood flow (perfusion index) were estimated after intraductal infusion of sodium taurocholate (0.8 ml, 4%) alone or in combination with systemic administration of cholecystokinin (CCK, 0.3 microg/100 g body wt) or secretin (Sec, 10 microg/100 g body wt). Sodium taurocholate mediated a significant increase in pancreatic duct and capillary permeability within 105 +/- 26 s followed by a transient decrease in RBC velocities and a sustained decrease in FCD, which were paralleled by dramatic flow heterogeneity. Therefore, a significant reduction in overall capillary blood flow was calculated. CCK stimulation aggravated the microcirculatory failure due to a decrease in RBC velocities, which was accompanied by an increase in acinar cellular necrosis. Sec stimulation attenuated microcirculatory failure due to a more moderate reduction of FCD. The enhanced pancreatic duct and capillary permeability, which enables free diffusion of pancreatic digestive enzymes into the parenchyma, is the initiating event in acute biliary pancreatitis, causing microcirculatory failure and tissue damage. The microcirculatory changes are secondary and a propagating factor for the development of acini necrosis. Stimulation with CCK worsened the course of acute biliary pancreatitis.

Dermal blood flow after local challenges with allergen, histamine, bradykinin and compound 48/80

Blood flow was determined in weal and flare reactions and in late dermal reactions after skin-prick tests with allergen, histamine, bradykinin and compound 48/80 in pollen-allergic subjects. Local blood flow was measured with laser Doppler flowmetry intermittently for up to 48 hr at three distances from the prick centre (2 mm; weal, 15 mm; flare and 30 mm). Continuous recordings were also made in the weal area after challenge with bradykinn and compound 48/80. The size of the induced weal and flare area of all the substances and the late phase after allergen was determined using digitized planimetry. Furthermore, simultaneous determinations of local dermal temperature and blood flow in the weal and flare site were performed intermittently for 6 hr after allergen and histamine challenges. There was a dose-dependent and distance-related increase in blood flow for all the substances tested. The blood flow in the 2-mm registrations had normalized 20 min after bradykinin, 1.5-2 hr after histamine and 3 hr after compound 48/80, while allergen induced a continuous increase in blood flow for more than 24 hr. The area of the weal and flare reaction was dose related for all substances, and a similar dose-dependent increase was noted for the observed dermal late-phase reactions present after allergen. The local temperature after challenge with allergen and histamine was also increased in a distance-dependent manner. These studies suggest that laser Doppler flowmetry is a sensitive and reproducible method to quantify blood flow changes occurring after skin-prick tests. Different putative mediators or mast cell stimulating substances produce various response profiles, all of which differ from those observed after allergen. Temperature measurements after skin-prick tests seem to follow the observed changes in blood flow as measured with laser Doppler flowmetry, which may be why both techniques might reflect changes in capillary blood flow.

Maximal diffusion-distance within skeletal muscle can be estimated from mitochondrial distributions

Mitochondrial volume density (V v[mit]) distribution were measured with a test pattern of concentric rings centered upon randomly chosen capillaries in oxidative skeletal muscel cells of two Antarctic fishes, Trematomus newnesi and Notothenia gibberifrons. V v(mit) in both species was highest in the ring closet to the capillary, minimal further from the capillary (at a distance that was characteristic for each species), and rose in the annuli furthest from the capillary. Plots of V v(mit) against total area between each ring and the central capillary fit the form of a second-order polynomial ( r 2>0.9). If P O2 or blood-borne metabolite concentration predicates the pattern of V v(mit) distribution, minimal V v(mit) is at the same position as the minimum in concentration or gaseous partial pressure of capipllary-supplied commodities. This minimum is the boundary between cylinders of tissue being supplied by adjacent capillaries, and thus delineates the maximal diffusion-distance for capillary-supplied commodities. Maxima diffusion-distance (μm) for T. newnesi = 26.23 ± 1.64; N. gibberifrons = 21.45 ± 0.51. For O 2, maximal diffusion-distance conventionally is referred to as Krogh's radius, R. With an easily obtained estimate of numerical capillary density, these R values can be used to calculate a capillary tortuosity constant (c[k,0]) and capillary length density (J v[c,f]). c(k,0) values were also determined using an established method, and R and J v(c,f) values calculated from these values did not significantly differ from values determined from mitochondriol distributions. Mitochondriol distribution analysis may more accurately reflect changes in capillary blood flow and heterogeneity of diffusion and solubility constants within muscle than currently existing techniques. Similar distributions of V v(mit) reported for several species of vertebrates suggest wide applicability of the method.

Local hydrogen clearance as a method for the measurement of capillary blood flow

A hydrogen clearance technique for the measurement of capillary blood flow in skeletal muscle (both resting and working) and the beating heart in experimental animals is described. Various methods for introducing the hydrogen into the region of measurement are compared, together with the appropriate methods for evaluating the resultant curves. All methods yielded results which were proportional to each other signifying that this is a reliable method for measuring changes in capillary blood flow. Reproducible results were obtained, and physiological changes in flow could be easily detected. An approach towards obtaining absolute flow values is proposed by simultaneous measurement of the arterial input function together with the independent use of other indicators.