Measurement Of Mucosal Blood Flow Research Articles

Mucosal blood flow measurements using laser Doppler perfusion monitoring

Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insufficiency of perfusion, is a common mechanism for tissue death or degeneration, and at a lower threshold, a mechanism for the generation of sensory signalling including pain. It is of considerable interest to study perfusion of peripheral abdominal tissues in a variety of circumstances. Microvascular disease of the abdominal organs has been implicated in the pathogenesis of a variety of disorders, including peptic ulcer disease, inflammatory bowel disease and chest pain. The basic principle of laser Doppler perfusion monitoring (LDPM) is to analyze changes in the spectrum of light reflected from tissues as a response to a beam of monochromatic laser light emitted. It reflects the total local microcirculatory blood perfusion, including perfusion in capillaries, arterioles, venules and shunts. During the last 20-25 years, numerous studies have been performed in different parts of the gastrointestinal (GI) tract using LDPM. In recent years we have developed a multi-modal catheter device which includes a laser Doppler probe, with the intent primarily to investigate patients suffering from functional chest pain of presumed oesophageal origin. Preliminary studies show the feasibility of incorporating LDPM into such catheters for performing physiological studies in the GI tract. LDPM has emerged as a research and clinical tool in preference to other methods; but, it is important to be aware of its limitations and account for them when reporting results.

New method of evaluating gastric mucosal blood flow by ultrasound

Objective. Evaluation of gastrointestinal blood flow is important. However, a non-invasive measurement method has not yet been established. The aim of this study was to compare measurement of normal gastric mucosal blood flow by advanced dynamic flow (ADF) flash echo imaging (FEI) with intravenous Levovist with measurement by laser Doppler flowmetry (LDF) to clarify the usefulness of ADF-FEI and thereby consider its feasibility as a non-invasive gastric mucosal blood flow measurement method. Material and methods. Measurements were obtained in 25 beagle dogs (8-month-old males, body-weight, 10.6±1.3 kg, mean±SD). After insertion of a gastrointestinal endoscope, gastric mucosal blood flow at the greater curvature of the corpus was measured by LDF, and images of gastric mucosal blood flow were obtained by ADF-FEI (frequency; 4.7 MHz) with intravenous injection of Levovist (30 mg/kg). ADF-FEI images were transferred to a personal computer. A region of interest was set on the mucosa of the greater curvature of the corpus, and a time intensity curve (TIC) was plotted from the measured echo intensities. The area under the curve (AUC) calculated from the TIC and the median flow determined by LDF were analyzed and compared. Results. Evaluation of normal gastric mucosal blood flow by ADF-FEI was possible in all animals. There was a strong, significant correlation between gastric mucosal blood flow measured by LDF and the AUC obtained by ADF-FEI (r=0.869, p<0.0001). Conclusions. Gastric mucosal blood flow can be accurately measured by ADF-FEI with intravenous Levovist injection.

Laser Doppler flowmetry as a measure of extrinsic colonic innervation in functional bowel disease

BACKGROUNDIn functional disorders it is unknown whether disturbed function is due to an intrinsic gut abnormality or altered extrinsic innervation.AIMSTo study whether measurement of mucosal blood flow could be used...

Laser Doppler measurement of rectal mucosal blood flow

BACKGROUNDGut mucosal blood flow measurement is used to study a variety of disorders and possibly extrinsic neural function.AIMSTo determine optimal measurement criteria and validate this technique as a measure of...

Significance of Measurement of Mucosal Blood Flow in Experimental Colonic Ischemia in Rats

Significance of Measurement of Mucosal Blood Flow in Experimental Colonic Ischemia in Rats

Tracheal transplantation for carinal reconstruction in dogs

Background: Experimental carinal allotransplantation has been performed with tracheocarinal Y-shaped allografts in dogs. In this study we tried canine carinal reconstruction with cylindrical allografts. Material and methods: Carinal reconstruction was performed with allotransplantation of cylindrical trachea in dogs, and graft healing was evaluated by bronchoscopic observation, mucosal blood flow measurement, and histologic examination. A section of the recipient carina containing five tracheal rings and two main stem bronchi was removed, and a donor trachea seven rings long was inserted between the recipient trachea and the left main stem bronchus; then side-to-end anastomosis was performed between the graft midportion and recipient right main stem bronchus (new carina). The grafts were wrapped with pedicled omentum. Fresh grafts were transplanted into one group of dogs ( n = 8 ), and grafts cryopreserved for 1 week were transplanted into another group ( n = 7). Results: No anastomotic leakage occurred in any dog. Excellent healing of grafts and graft anastomoses was observed by fiberoptic bronchoscopy in six dogs (75%) in the fresh graft group and in four dogs (57%) in the cryopreserved graft group. The mucosal blood flow in the new carina decreased remarkably and, although it recovered, mucosal blood flow remained under the preoperative level on day 28 after the operation. Conclusion: Cylindrical tracheal allotransplantation is useful for carinal reconstruction, and the method of side-to-end anastomosis between the donor trachea and recipient bronchus is a feasible and accessible procedure in dogs. (J Thorac Cardiovasc Surg 1998;116:397-401)

Gastric Blood Flow and Acid Secretion: Problems of the Methodology and Regulatory Mechanisms

Methods for proper measurement of gastric mucosal blood flow (MBF) in animal experiments or in clinical studies are critically reviewed. It can be stated that none of the techniques hitherto published fulfil all the criteria for proper measurement of the mucosal blood flow and concomitant acid production in the stomach. Some give an estimate of local blood flow changes (e.g. H 2 gas clearance, laser Doppler flowmetry) in man without the possibility of simultaneous acid measurement. The 99m Tc-MAP clearance technique developed by the authors reflects changes in both parameters and may also be used in clinical studies, when limitations of the method are taken into consideration. As a rule we assume that acid production and mucosal blood flow may change independently. The effects of various bioactive substances and drugs on both parameters are analysed. It seems that many contradictory findings have arisen because of differences in technique and experimental animals used.

Dobutamine improves gastrointestinal mucosal blood flow in a porcine model of endotoxic shock.

To test the hypothesis that saline solution plus dobutamine increases gastrointestinal mucosal perfusion better than saline solution alone in a model of endotoxic shock. Prospective, randomized, unblinded study. Animal research laboratory affiliated with a university teaching hospital. Twelve female pigs, weighing 30 to 32 kg. Animals were anesthetized, and their lungs were mechanically ventilated. Catheters were inserted into the right atrium, pulmonary artery, and carotid artery for blood sampling and blood pressure and cardiac output measurements. A tonometer and a laser Doppler probe were placed in the lumen of the stomach and the ileum for determination of mucosal acid-base status and measurement of mucosal blood flow. Group 1 animals (n = 6) received an infusion (T = 0 min) of 150 mcirog/kg Escherichia coli endotoxin and normal saline solution (0.3 mL/kg/min). Group 2 animals (n = 6) received an infusion of endotoxin and were resuscitated with the same method as used in group 1, but an infusion of dobutamine (5 microg/kg/min) was begun at T = 60 mins, and continued for the duration of the experiment. Both experimental regimens produced shock, with decreased mean arterial pressure and systemic vascular resistance, without change in cardiac output and oxygen delivery. Endotoxin plus saline infusion decreased gastrointestinal mucosal blood flow to <60% of baseline and decreased gastrointestinal pH. In contrast, gastrointestinal mucosal blood flow returned to baseline values, and intramucosal pH tended to normalize by the end of the saline solution plus dobutamine resuscitative protocol. Compared with saline solution alone, saline solution plus dobutamine increased blood flow to the gastrointestinal mucosa, and may have partially improved oxygenation.

L-arginine and endogenous nitric oxide protect the gastric mucosa from endothelin-1-induced gastric ulcers in rats.

We have reported that endothelin-1 induces gastric ulcer characterized by a potent long-lasting vasoconstriction of the regional microvasculature. Nitric oxide synthesized from L-arginine has been shown to regulated gastric mucosal blood flow, and inhibition of its synthesis has been shown to delay the healing of gastric ulcers. We examined the effect of exogenous L-arginine and the inhibition of nitric oxide synthesis on the development of endothelin-1-induced gastric ulcers. In rats anesthetized with urethane, a continuous intravenous infusion of L- or D-arginine (10 mg.kg-1.min-1) was followed, 15 min later, by a submucosal injection of endothelin-1 (200 pmol/kg) in the anterior wall of the gastric body. In another group, rats were intravenously pretreated with N omega-nitro-L-arginine-methyl ester (1-10 mg/kg), a nitric oxide synthesis inhibitor, and then injected with endothelin-1 (40 pmol/kg). Twenty-four h later, L-arginine, but not D-arginine, had significantly reduced the extent and the severity of the endothelin-1-induced ulcer (mucosal wall damage, 18.11 +/- 4.79% and 88.14 +/- 7.06%, respectively; mean +/- SD, P < 0.001), and the nitric oxide synthesis inhibitor (10 mg/kg) had increased the endothelin-1-induced mucosal damage (ulcer length, 3.8 +/- 1.2 mm and 1.1 +/- 0.2 mm, respectively, P < 0.01). Continuous gastric mucosal blood flow measurements showed that L-arginine antagonized the endothelin-1-induced vasoconstriction. L-arginine protected the gastric mucosa from the ulcerogenic action of endothelin-1 and antagonized its vasoconstrictive action. The inhibition of endogenous nitric oxide potentiated the ulcerogenic effect of endothelin-1 on rat gastric mucosa.

Dissociated effect of nicotine on pentagastrin-stimulated acid secretion and blood flow in the rat stomach.

Knowledge of the effect of parenteral nicotine on physiologic gastric hyperemia is limited. This study examined the effect of intravenous nicotine on gastric hyperemia and and secretion induced by pentagastrin. In starved, urethane-anesthetized rats, gastric corpus blood flow was monitored continuously in a localized area of the mucosa, using laser Doppler flowmetry. The tip of the laser Doppler flow probe was positioned against the mid-gastric corpus mucosa along the greater curvature. Intravenous nicotine (4 or 40 micrograms/kg/min) or vehicle was infused. The gastric acid secretion stimulated by intravenous pentagastrin, 20 micrograms/kg/min, was completely inhibited by both doses of nicotine. In contrast to previous reports based on the clearance of weak bases for gastric mucosal blood flow measurement, neither dose of nicotine altered the hyperemia induced by pentagastrin. A dissociated effect of intravenous nicotine on pentagastrin-stimulated gastric acid secretion and hyperemia is documented.

The immunosuppressive effect of FK 506 on canine lung transplantation

The immunosuppressive potency of FK 506 was studied after left lung transplantation in adult mongrel dogs in comparison with cyclosporine. Fiberoptic bronchoscopy, bronchial mucosal blood flow measurement with laser Doppler velocimetry, and chest x-ray and pathologic examinations were performed. Group A had no immunosuppression (n = 5); group B received FK 506 (0.10 mg/kg/day intramuscularly (n = 5); group C received cyclosporine (20 mg/kg/day orally) (n = 5). In group A four dogs died of rejection on the seventh to the twenty-first postoperative days. Another one was killed on the fourteenth postoperative day because bronchial dehiscence occurred at the anastomosis. In group B one died of alveolar rejection on the seventh postoperative day. The remaining four survived 28 days and were put to death. In group C all five dogs survived 28 days and were put to death. In group A bronchial stenosis or dehiscence at the anastomosis was found in every one during the early postoperative period. In group B stenosis did not develop in any of the dogs, including the one that died on the seventh postoperative day. In group C slight stenosis was seen in one dog, severe narrowing in another, and good healing in the remaining three. The transplanted lungs were almost normal histologically in four animals of group B, and one showed alveolar phase rejection. In all animals of group A severe rejection was observed, and in group C two of five animals showed vascular phase rejection, two latent phase, and one fibrosis. Histologic examination of the bronchial anastomosis in group B showed almost normal bronchial epithelium and slight submucosal infiltration of mononuclear cells. In group A there was desquamation of epithelium and mild to moderate mononuclear cell infiltration. In group C hyperplasia of the epithelium was observed in two animals, an abscess at the site of anastomosis in one, and mild to moderate mononuclear cell infiltration in all five. With use of laser Doppler velocimetry, bronchial blood flow in group B was found to be the same as in group C. Laser Doppler velocimetry values reached preoperative levels by the twenty-eighth postoperative day in both groups. Although diarrhea developed in two dogs of group B, no other significant side effect of FK 506 was seen.

耳鼻咽喉科領域における粘膜血流量 文献的考察

The measurement of mucosal blood flow is important for assessing condition in the nose, pharynx, larynx and middle ear. Recently the measurement of mucosal blood flow has been made very accurate by the development of new methods of measurement (e. g. Laser-Doppler flowmeter, RI clearance method, spectrophotometric analyzer).Earlier works on the assessment of mucosal blood flow in the nose, pharynx, larynx and middle ear are reviewed.

Measurement of nasal mucosal blood flow by a thermal clearance method.

A new method for nasal mucosal blood flow measurement is described. The orifice of the nasal cavity is closed by a probe which includes a thermocouple. The temperature of the mucosa is increased, since cooling by airflow is now impossible. The temperature increase is due to blood flow. The rate of temperature increase depends both on blood flow and the heat capacity of the probe. A method to obtain mucosal blood flow from a temperature versus time curve is presented. Experimental results are compared to those obtained by other methods.

Regional gastric mucosal blood flow measurements by hydrogen gas clearance in the anesthetized rat and rabbit

Hydrogen gas clearance using 3% hydrogen in air and platinum contact electrodes was employed for measuring antral and corpus mucosal Wood flow in anesthetized animals. Significantly greater antral than corpus mucosal blood flow was consistently demonstrated. Corpus but not antral mucosal blood flow showed a significant dose-related increase with intravenous pentagastrin. Vasopressin induced a significant dose-related decrease in both antral and corpus mucosal blood flow. Simultaneous measurement of basal corpus mucosal blood flow by hydrogen gas clearance and of gastric mucosal blood flow by aminopyrine clearance gave similar values, but the changes with intravenous pentagastrin or vasopressin measured by aminopyrine clearance were of a much higher order of magnitude. Hydrogen gas clearance, however, reflected changes in left gastric artery blood flow much more closely than did aminopyrine clearance. Therefore, we conclude that the hydrogen gas clearance technique as described is valid for measuring regional gastric mucosal blood flow. It is safe and has potential application in human studies.

Measurement of mucosal blood flow in the canine intestine with laser doppler velocimetry

Laser Doppler velocimetry is a technique for continuous estimation of changing blood flow in the surface of a tissue and does not require invasion of the circulation. This technique is based upon the Doppler principle that a shift in the frequency of an electromagnetic wave emitted or reflected from a moving object is proportional to the velocity of the object. The capacity of Laser Doppler velocimetry to estimate changes in intestinal mucosal blood flow was tested in a canine free flow preparation. In anesthetized dogs in which a segment of ileum was isolated, simultaneous measurements of instantaneous changes in total blood flow (measured with the electromagnetic blood flow meter) and instantaneous changes in presumed mucosal blood flow (using laser Doppler velocimetry) were obtained. Determinations were made during conditions of rest, prostacyclin induced vasodilation and norepinephrine induced vasoconstriction. Changes in laser Doppler velocimeter readings were qualitatively similar to and temporally related to changes in total blood flow to the gut segment during administration of the vasoactive drugs. The magnitude and direction of changes with the two measurements were significantly correlated. Stabilizing the laser probe on the mucosal surface to ensure reproducible readings proved technically difficult. Pharmacologically induced changes in laser Doppler velocimeter estimated changes in flow were more readily correlated with changes in electromagnetic flow meter readings than were control values obtained with the two methods.

Effect of nicotine on gastric mucosal blood flow and acid secretion.

The effects of an intravenous infusion of nicotine at a dose of 2 . 5, 5 . 0, 7 . 5, or 10 . 0 micrograms kg-1h-1 on pentagastrin-stimulated gastric mucosal blood flow and acid secretion were investigated in eight healthy male non-smokers. Each dose was tested in two males. Gastric neutral red clearance served as a measure of mucosal blood flow. Nicotine reduced volume secretion, acid secretion, and neutral red clearance in a dose dependent manner. In five healthy male smokers smoking of five cigarettes per two hours induced similar changes to the intravenous infusion of 5 micrograms kg-1h-1 nicotine. As volume secretion was inhibited more than neutral red clearance, it is concluded that nicotine increases blood supply to the gastric mucosa relatively to the reduced gastric secretion. Nicotine is either not associated with the development of peptic ulcers, or it exerts its ulcerogenic action via other mechanisms than change of acid secretion and gastric mucosal blood flow.

Measurement of mucosal blood flow by assay of absorption of 125I from the intestinal lumen

A method which utilized the absorption of 125I as a measure of intestinal mucosal blood flow was developed. In the pentobarbital anesthetized dog a segment of mid-jejunum was isolated from adjacent vasculature and perfused with 125I solution. Superior mesenteric artery flow, blood flow to the isolated segment of intestine and 125I absorption were measured. Changes in 125I absorption were found to correlate closely with changes in blood flow ( r = 0.95). Using an autoradiographic technique 125I absorption was found to be localized to the intestinal mucosa.

Effect of 16, 16-dimethyl PGE2 on resting and histamine-stimulated gastric mucosal blood flow.

Using [14C]aminopyrine clearance as a measure of mucosal blood flow, 16,16-dimethyl PGE2 was administered orally as a single bolus and its effects on resting and histamine-stimulated gastricmucosal blood flow assessed in conscious dogs with vagally denervated gastric pouches. No effect on resting mucosal flow was observed with any of the doses (ie, 2, 10, and 50 microgram/kg) of prostaglandin given. In histamine-stimulated experiments, intravenous infusion of histamine dihydrochloride (1 mg/hr) elicited a significant (P < 0.0005) increase from basal in gastric acid production, volume output, and gastric mucosal blood flow which remained unchanged for the duration of the study. Prostaglandin (50 microgram/kg) significantly decreased (P < 0.0005) these secretory responses and markedly inhibited (P < 0.005) mucosal blood flow without altering the ratio (R) of flow to the volume rate of secretion. The observation that R was unchanged suggests that this inhibitory action of 16,16-dimethyl PGE2 on gastric secretion and blood flow was mediated through direct effects on gastric parietal cells rather than any primary alteration in the gastric microcirculation. We conclude that 16,16-dimethyl PGE2 given orally has no effect on the resting gastric mucosal circulation and that any reduction in mucosal flow during histamine stimulation is secondary to its inhibitory effects on gastric acid secretion.

Influence of hydrogen ion concentration on bile acid induced acute gastric mucosal ulcerogenesis.

Aggressive treatment with H(2) receptor blocking agents and/or antacids has been advocated as effective prophylaxis against and treatment for "stress ulcer," based on the logical but infrequently tested assumption that the severity of the disease is critically determined by the concentration of intraluminal acid. The present study investigated this assumption in a model which employed topical acid, topical bile acid and mucosal ischemia to induce ulcerogenesis. With vascularized, chambered ex vivo wedges of canine proximal gastric wall, groups of animals were studied during three sequential periods using topical test solutions (TS) containing either 0 mM, 100 mM or 160 mM HCI. During period 1, mucosae were exposed to TS alone; during period 2, either to TS containing 1 mM sodium taurocholate (TC) or to TS and concomitant vasopressin infusion (VP); and during period 3, to TS + TC + VP. Parameters evaluated included net H(+) flux ( big up tri, openH(+)), aminopyrine clearance (AC), a measure of mucosal blood flow, net TC flux ( big up tri, openTC) and the lesion index, graded 0-5. The data indicate that in nonischemic mucosa exposed to constant [TC], AC was significantly increased, big up tri, openH(+) ("back-diffusion") increased as a linear function of [H(+)] and no lesions were observed. Under the same circumstances in ischemic mucosa, big up tri, openH(+) increased as linear function of [H(+)]. As a consequence, lesion severity was also a linear function of [H(+)]. big up tri, openTC was enhanced at low pH but bore no relation to the degree of mucosal damage induced. Assuming applicability of the model, these studies provide support for the use of H(2) receptor blocking agents and/or antacids to prevent or ameliorate "stress ulcer" disease.

Measurement of 42K concentration in the mucosal portion of the intestine without tissue samples: an approach to the measurement of mucosal blood flow in the dog.

1. The concentration of 42K within the jejunal mucosa was measured by intraluminal miniatrue Geiger-Müller tubes shieleded with platinum foil. 2. Isotope concentration measured by tissue assay of jejunal mucosa gave similar results to that obtained by the Geiger-Müller tubes. 3. Isotope measurement by shielded Geiger-Müller tubes obviates the need for tissue samples and permits repeat measurement in the same animal. This should find physiological application in measuring the mucosal portion of total intestinal blood flow by the indicator fractionation technique.