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At least 91 records · Page 5Linked to original sources

PubMed2000

Histochemical correlates of (15)O-water-perfusable tissue fraction in experimental canine studies of old myocardial infarction.

UNLABELLED: A method has been proposed to quantitate the myocardial water-perfusable tissue fraction (PTF) in the area of hypoperfused asynergic segments using (15)O-water (H2(15)O) and PET. This study investigated the histochemical correlates of PTF (and perfusable tissue index, PTI) in a canine model of old myocardial infarction. METHODS: Myocardial infarction was produced in 12 mongrel dogs, and PET was performed 1 mo later, providing quantitative parametric images of PTF, regional myocardial blood flow (MBF), and extravascular density from H2(15)O, (15)O-carbon monoxide, and transmission datasets. At the end of scanning, the myocardium was sectioned, and the PET images were compared directly with the corresponding myocardial sections. RESULTS: The distribution of tissue necrosis identified by histochemical staining corresponded well with the defect in PTF but not in MBF. PTF agreed with the equilibrium images of myocardial H2(15)O distribution, obtained after injection of a large bolus of H2(15)O. The defect surface area identified on PTF agreed well quantitatively with the morphometric estimates of the surface area of myocardial infarction. PTI agreed with the absolute proportion of histochemically defined normal myocardium (0.87 +/- 0.09 and 0.83 +/- 0.08, respectively; P < 0.01). Both PTF and PTI decreased significantly in segments of myocardial infarction and showed a significant difference between the transmural and nontransmural myocardial infarction. CONCLUSION: The absolute mass and proportion of histochemically defined noninfarcted tissue may be quantitated with PTF and PTI in the area of myocardial infarction segments.

Animals↗

PubMedDate not supplied

Observations of thermal gradients in perfused tissues during water bath heating.

Actual thermal gradients in perfused tissues are difficult to observe using thermocouples because of thermal conduction along the probes. We have used fine type-K (chromel-alumel) probes, which have a much lower thermal conductivity than equivalent-sized type-T (copper-constantan) thermocouples, to examine thermal gradients in two mouse tumour systems during water bath heating. The results indicate substantial heterogeneity in temperature distribution even in tumours transplanted in the foot and immersed to a depth of 2 cm in a 44 degrees C water bath for 20 min, i.e. thermal gradients greater than 1 degree C/mm were observed in KHT fibrosarcomas. The temperature heterogeneity for water bath heating is primarily a result of blood flow and appears to be tumour-specific. Temperature measurements using an excised perfused canine kidney demonstrate that increased perfusate volume flow increases the range of tissue temperatures. Consistent with theory, an artifactual improvement in temperature homogeneity resulted when temperature was measured using type-T thermocouples instead of type-K probes. These results emphasize the difficulties in obtaining accurate temperature measurements during experimental and clinical hyperthermia. Even extensive measurements of temperature in tissues may underestimate the true range of heterogeneity unless factors such as thermal smearing are controlled.

Animals↗

PubMed1993

Experimental study of the relationship between alterations in tissue perfusion and anastomotic patency.

It is generally believed that alterations in perfusion which endanger a free flap or replant are directly related to thrombus formation and obstruction of blood flow at the anastomotic site. Recent experimental work in our laboratory suggests that the presence of platelet emboli downstream in the microcirculation might be responsible at least in part for postoperative perturbations in perfusion. To determine whether changes in tissue perfusion can occur in the absence of corresponding changes in anastomotic patency we studied microvascular blood flow in the exposed rat cremaster flap model. We made continuous measurements of both anastomotic patency and downstream microcirculatory perfusion following small vessel repair. Using this approach we found that during one hour after clamp release and reperfusion in the 10 animals studied, pedicle artery blood pressure, which indicates pedicle patency in this model, was functionally normal 97% +/- 2 of the time while blood flow in the downstream tissue (cremaster) remained normal an average of only 65% +/- 7 of the time. In most cases these flow alterations were associated with the presence of visible platelet emboli in the microcirculation. From these studies we conclude that when flap perfusion failure temporarily occurs, a microsurgeon must consider not only the anastomosis but also the downstream microcirculation when searching for a possible cause.

Anastomosis, Surgical↗

PubMedDate not supplied

Skeletal muscle PO2: indicator of peripheral tissue perfusion in haemorrhagic shock.

The following conclusions can be made on the basis of this work: 1) Measurements of skeletal muscle oxygen tension provide an excellent index of tissue perfusion in haemorrhagic shock. 2) Correction of cardiac output and arterial blood oxygen tension in haemorrhagic shock does not necessarily ensure normal tissue oxygenation. 3) In haemorrhagic shock adequate replacement of blood loss using a balanced salt solution in addition to blood replacement is an integral part of the fluid management. 4) Correction of hypovolemia with an equivalent volume of a plasma expander and subsequent reinfusion of shed blood also returns tissue perfusion to normal. However, this treatment results in marked haemodilution and correction of extracellular fluid loss remains inadequate.

Abdominal Muscles↗

PubMed2002

Catalytic activity of phospholipase A2 in blood plasma and pancreatic tissue perfusion in early experimental acute pancreatitis.

BACKGROUND: To investigate the sequence of changes in the catalytic activity of phospholipase A2 in plasma and pancreatic tissue perfusion and oxygenation in mild and severe acute pancreatitis in pigs. METHODS: Twenty-four pigs were randomized into the groups of severe acute pancreatitis, mild acute pancreatitis, and controls. The pancreatic duct of eight anesthetized and mechanically ventilated pigs was cannulated, and taurocholic acid was infused into the pancreatic duct to induce severe acute pancreatitis. Eight animals received intraductal saline and developed mild acute pancreatitis. Eight pigs were cannulated only and served as controls. RESULTS: Central hemodynamics, arterial blood gases, and acid-base balance were stable throughout the study period in all three groups. Pancreatic tissue oxygenation decreased in pigs with severe acute pancreatitis and increased in animals with mild acute pancreatitis. The catalytic activity of phospholipase A2 in plasma remained stable, and there was no difference between the groups. Similarly, C-reactive protein values remained within the normal range during the study period in all groups. CONCLUSION: Plasma phospholipase A2 levels do not react to the changes in pancreatic tissue perfusion in the early phase of mild and severe acute pancreatitis.

Acute Disease↗

PubMed2000

Quantification of pressure relief using interface pressure and tissue perfusion in alternating pressure air mattresses.

OBJECTIVE: To examine whether the interface pressure (IP) relief provided by alternating pressure air mattresses (APAMs) is matched with maintenance of tissue perfusion over the points of contact by measuring transcutaneous oxygen and carbon dioxide (tcPO2, tcPCO2). DESIGN: Comparative analysis of 2 APAMs with a 2-parameter continuous time-based method for quantifying pressure relief (PR) and transcutaneous gas measurement for assessing tissue perfusion. SETTING: Rehabilitation research facility in a university hospital. PARTICIPANTS: Eleven able-bodied adult postgraduate student volunteers. MAIN OUTCOME MEASURES: Two full-replacement APAM systems were used. For each mattress the mean maximum and minimum interface pressures; mean peak air pressures in the mattresses; interface pressure durations below 30, 20, and 10 mmHg over a 60-minute period; mean maximum tcPCO2 and minimum tcPO2; and mean area under the tcPO2 and tcPCO2 curves were measured for each subject. RESULTS: IP on the sacrum was held below thresholds of 30, 20, and 10 mmHg longer on a 2-cell, low pressure system than on a 3-cell, high pressure system (p < .001). Integrated over time, tcPO2 levels also indicated that the 2-cell system retained oxygen levels closer to the unloaded baseline than did the 3-cell system (p < .01). tcPCO2 levels did not rise significantly (p > 0.1) compared with the baseline measurement in both mattresses. CONCLUSIONS: PR was sensitive to the design of the APAM, especially its inflation pressure, cycle time, and inflation sequence. If future trials demonstrate that PR values and transcutaneous blood gas measurements correlate significantly with the clinical incidence of pressure sore formation, then this technique may prove useful in assessing the effectiveness of alternating pressure support surfaces.

Adult↗

PubMed2004

Indocyanine-green fluorescence video angiography used clinically to evaluate tissue perfusion in microsurgery.

BACKGROUND: Laser-induced fluorescence angiography with indocyanine-green (ICG-FA) is a new diagnostic approach that allows quantitative evaluation of tissue perfusion in microsurgery as well as an analysis of the uptake, distribution, and clearance of dye-marked blood. METHODS: The ICG-FA technique was evaluated for its sensitivity and prognostic value in comparison with clinical parameters (turgor, temperature, reperfusion time, bleeding after puncture) during and after different surgical procedures. Altogether, 91 measurements were made in cases of microvascular repair (n = 43) and free-flap surgery (n = 48). RESULTS: Because of discrepancies between ICG-FA results and clinical findings, the planned postoperative management was changed 43 times (47.2%). In cases of microvascular repair that subsequently resulted in tissue necrosis, ICG fluorescence had a significantly higher prognostic value than any of the clinical parameters (p = 0.03). During free-flap surgery, intraoperative ICG-FA had better sensitivity for flap loss than clinical parameters, but postoperative ICG-FA did not. CONCLUSIONS: Fluorescence angiography with ICG is a sensitive diagnostic tool for detecting compromised tissue perfusion in trauma surgery and microsurgery. Its use may improve perioperative management and thereby lead to better clinical results.

Adolescent↗

PubMed2001

Splanchnic perfusion during hemodialysis: evidence for marginal tissue perfusion.

OBJECTIVE: Splanchnic perfusion may be compromised during hemodialysis because of hypovolemia, inflammatory response, and blood flow redistribution. The aim of this study was to assess the response of splanchnic blood flow and oxygen transport to hemodialysis. DESIGN: A prospective clinical study. SETTING: A mixed medical-surgical intensive care unit in a university hospital. PATIENTS: Nine patients with acute renal failure. INTERVENTIONS: A 4-hr period of hemodialysis. MEASUREMENTS AND MAIN RESULTS: Systemic (via a pulmonary artery catheter), hepatosplanchnic, and femoral (via dye dilution) blood flow and gastric mucosal Pco2 were measured before, during, and 2 hrs after hemodialysis. During hemodialysis, despite unchanged arterial blood pressure, cardiac output and stroke volume decreased from 3.0 +/- 1.0 L/m2/min (mean +/- sd) to 2.3 +/- 0.7 L/m2/min (p =.02), and from 38 +/- 16 mL/m2/min to 28 +/- 12 mL/m2/min (p =.01), respectively. Splanchnic but not femoral blood flow decreased from 0.9 +/- 0.3 L/m2/min to 0.7 +/- 0.2 L/m2/min (p =.02). The blood flows returned to baseline values after dialysis without need for therapeutic interventions. Gastric mucosal-arterial Pco2 gradients were high before dialysis (35 +/- 23 torr [4.6 +/- 3.1 kPa]) and did not change. Renin but not atrial natriuretic peptide concentration increased during hemodialysis from 13 +/- 13 microg/L to 35 +/- 40 microg/L and decreased afterward to baseline values (13 +/- 13 microg/L; p =.01). Whereas interleukin 6 tended to decrease, tumor necrosis factor alpha increased during hemodialysis from 74 +/- 24 pg/mL to 86 +/- 31 pg/mL and continued to increase after hemodialysis to 108 +/- 66 pg/mL (p =.022). CONCLUSION: Hemodialysis and fluid removal in normotensive patients with acute renal failure may result in a reduction of systemic and splanchnic blood flow that is undetectable using traditional clinical signs. In contrast to what is observed in hypovolemia, the changes in regional blood flow are rapidly reversible after hemodialysis.

Acute Kidney Injury↗

PubMed1994

Recent developments in modeling heat transfer in blood perfused tissues.

Successful hyperthermia treatment of tumors requires understanding the attendant thermal processes in both diseased and healthy tissue. Accordingly, it is essential for developers and users of hyperthermia equipment to predict, measure and interpret correctly the tissue thermal and vascular response to heating. Modeling of heat transfer in living tissues is a means towards this end. Due to the complex morphology of living tissues, such modeling is a difficult task and some simplifying assumptions are needed. Some investigators have recently argued that Pennes' interpretation of the vascular contribution to heat transfer in perfused tissues fails to account for the actual thermal equilibration process between the flowing blood and the surrounding tissue and proposed new models, presumably based on a more realistic anatomy of the perfused tissue. The present review compares and contrasts several of the new bio-heat transfer models, emphasizing the problematics of their experimental validation, in the absence of measuring equipment capable of reliable evaluation of tissue properties and their variations that occur in the spatial scale of blood vessels with diameters less than about .2 mm. For the most part, the new models still lack sound experimental grounding, and in view of their inherent complexity, the best practical approach for modeling bio-heat transfer during hyperthermia may still be the Pennes model, providing its use is based on some insights gained from the studies described here. In such cases, these models should yield a more realistic description of tissue locations and/or thermal conditions for which the Pennes' model might not apply.

Blood Physiological Phenomena↗

PubMed1981

Influence of ketamine anesthesia on cardiac output and tissue perfusion in rats subjected to hemorrhage.

Ketamine anesthesia has been considered suitable for use in patients suffering from acute hypovolemia. Using a microsphere technique, fractional distribution of cardiac output and tissue perfusion were determined in rats subjected to moderate (10 ml/kg), or severe (bled to 60 torr systolic arterial pressure) hemorrhage. In the moderate bleeding bleeding experiments, rats under ketamine anesthesia were compared to awake rats as well as to awake normovolemic rats. In the severe bleeding experiments, rats under ketamine anesthesia were compared to rats under barbiturate anesthesia. Following moderate bleeding the ketamine group had a significantly large cardiac output and higher arterial pressure than the unanesthetized group. There were no major differences in the fractional distribution of cardiac output, although tissue perfusion in the ketamine group was significantly larger in heart, kidneys, skin, and small intestine. The shed blood volume necessary to reach 60 torr in systolic arterial pressure was 36 per cent of normal blood volume in the ketamine group, and 23 per cent in the barbiturate group. In spite of the greater blood loss, rats under ketamine anesthesia displayed significantly larger cardiac output and a higher elevation of arterial pressure 20 min after the hemorrhage. In the ketamine group, fractional distribution of cardiac output favored the internal organs as opposed to an increase in the carcass in the barbiturate group. The ketamine anesthetized rats had a significantly larger perfusion to most organs, including heart, kidneys, and brain. It is concluded from this study that in rats experiencing acute hypovolemia blood flow to vital organs and cardiac output are well maintained under ketamine anesthesia.

Anesthesia, General↗

PubMed2001

Pancreatic tissue perfusion in experimental acute pancreatitis.

OBJECTIVE: To investigate pancreatic tissue perfusion and oxygenation in severe and mild experimental acute pancreatitis in pigs. DESIGN: Randomised controlled experiment. SETTING: Animal laboratory, Finland. ANIMALS: 24 domestic pigs weighing 21-27 kg. INTERVENTIONS: 24 pigs were randomised into severe acute pancreatitis, mild acute pancreatitis and control groups (n = 8 in each). The pancreatic duct of eight anaesthetised and mechanically ventilated pigs was cannulated and taurocholic acid was infused into the pancreatic duct to induce severe acute pancreatitis. Eight animals received intraductally infused saline and developed mild acute pancreatitis. Eight pigs had their ducts cannulated alone, and served as controls. MAIN OUTCOME MEASURES: Pancreatic tissue oxygenation, laser Doppler red cell flux, central haemodynamics. RESULTS: Intraductally infused taurocholic acid rapidly induced macroscopically and histologically proven severe necrotising acute pancreatitis. Histological changes characterising mild acute pancreatitis were seen in animals after intraductal saline infusion. Pancreatic tissue oxygen tension decreased in the severe group and increased in the mild group during the six-hour study period. Laser Doppler red cell flux decreased in the severe group. Central haemodynamics, arterial blood gases, and acid base balances were stable throughout the study period in all groups. CONCLUSION: The present model of severe acute pancreatitis significantly impairs pancreatic oxygenation in the early phase. In mild acute pancreatitis, pancreatic oxygenation increases.

Acute Disease↗

PubMed2004

Perfusable tissue index as a potential marker of fibrosis in patients with idiopathic dilated cardiomyopathy.

UNLABELLED: A varying degree of interstitial and perivascular fibrosis is a common finding in idiopathic dilated cardiomyopathy (DCM). The perfusable tissue index (PTI), obtained with PET, is a noninvasive tool for assessing myocardial fibrosis on a regional level. Measurements of the PTI in DCM, however, have not been performed yet. This study was undertaken to test the hypothesis that the PTI is reduced in patients with DCM. METHODS: Fifteen patients with an advanced stage of DCM (New York Heart Association class III or IV and left ventricular ejection fraction [LVEF] < 35%) and 11 healthy control subjects were studied. PET was performed using H(2)(15)O and C(15)O to obtain the perfusable tissue fraction (PTF) and the anatomic tissue fraction (ATF), respectively. RESULTS: The PTI (=PTF/ATF) was reduced in DCM compared with control subjects (0.91 +/- 0.12 vs. 1.12 +/- 0.10; P < 0.01). Heterogeneity of the PTI, expressed as the coefficient of variation, was increased in DCM versus that of healthy control subjects (0.18 +/- 0.07 vs. 0.13 +/- 0.06; P < 0.05). There was no correlation between the PTI and echocardiographically derived LVEF in both groups. CONCLUSION: The PTI was reduced in patients with an advanced stage of DCM. Interstitial and perivascular fibrosis may be responsible for this reduction. Furthermore, the degree of the PTI reduction was variable in DCM patients, both on a regional level and between patients. Noninvasive assessment of fibrosis with the PTI offers the opportunity to evaluate the effects of fibrosis on regional myocardial function, correlate fibrosis with prognosis, and monitor pharmaceutical intervention.

Adult↗

PubMedDate not supplied

[Evaluation of tissue perfusion by simultaneous non-invasive monitoring of the hemodynamic profile and capnography].

OBJECTIVES: To assess the simultaneous variations in blood gases and CO2 tele-expiratory pressure (ETCO2) produced by changes in tissue perfusion in anesthetized patients with stable lung perfusion, alveolar ventilation and metabolic states. MATERIAL AND METHODS: Forty patients were divided into two groups. Group 1 included 20 ASA I patients undergoing orthopedic surgery on the lower extremities. Group 2 included 20 ASA I-III patients undergoing peripheral vascular surgery during which myocardial depression developed after isoflurane administration. The decrease in minute volume was measured in the descending aorta by esophageal ultrasound in both groups. Other hemodynamic parameters were measured by digital plethysmography. ETCO2 was measured by lateral aspiration capnography, and central venous pressure was measured in group 2 by subclavian venous catheter. Measurements were taken before and after release of the tourniquet in group 1, and before and after the decrease in minute volume (> 30%) in group 2. RESULTS: Release of the tourniquet after a mean compression time of 51 +/- 07 minutes produced an increase of 52% (p < 0.001) in minute volume in all patients in group 1; an increase of 23% (p < 0.001) in ETCO2; and a decrease of 60% (p < 0.001) in total vascular resistance. In group 2 a 15% decrease in ETCO2 (p < 0.01) was observed, coinciding with a 35% decrease in minute volume (p < 0.01). CONCLUSIONS: An increase in minute volume produces an increase in ETCO2 while a decrease in minute volume results in a decrease in ETCO2. This means that sharp changes in ETCO2 may be useful in judging the degree of change in tissue perfusion when other parameters like alveolar ventilation, lung perfusion and metabolic rate remain constant.

Adult↗

PubMed2002

Perfusable tissue index obtained by positron emission tomography as a marker of myocardial viability in patients with ischemic ventricular dysfunction.

In areas of severe asynergy, the clinically important task is to identify functionally recoverable myocardium. Fourteen patients with asynergy were investigated by H2(15O) dynamic positron emission tomography imaging before revascularization. Regional myocardial blood flow (MBF) was determined and the water-perfusable tissue fraction (PTF) for each region of interest and the total anatomical tissue fraction (ATF) were estimated. The PTF/ATF was analyzed as the water perfusable tissue index (PTI). Asynergy was defined as segments with wall motion more than 2SD below than that of a normal population. An increase of >0.8SD in anterior wall segments with asynergy and an increase of >0.6 SD in inferior wall asynergy were defined as significant improvements of wall motion indicative of viable myocardium. Fifteen segments with wall motion abnormalities less than -2SD and 10 control segments were identified; 7 segments recovered and 8 segments did not. MBF was similar in both groups of segments before revascularization (0.78 +/- 0.27 vs 0.73 +/- 0.18 ml min-(-1) x g(-1), NS). The PTI in the recovered segments was significantly higher than that in the unimproved segments (0.734 +/- 0.058 vs 0.592 +/- 0.038, p<0.0001) and was similar to that of the control segments. After revascularization, the PTI correlated with the SD of wall motion (p<0.05, r=0.58). PTI may be a good predictor of contractile recovery after revascularization.

Aged↗

PubMed1990

Experimental verification of bioheat transfer theories: measurement of temperature profiles around large artificial vessels in perfused tissue.

The verification of thermal models for use in hyperthermia treatment planning is essential. We investigated the heat transfer between a single vessel and the surrounding vascularised tissue, comparing the conventional bioheat transfer theory and the recently developed keff model using analytical and numerical methods. A plastic tube inserted into the tissue of an isolated perfused organ served as an artificial vessel. This enabled us to vary the blood flow in the vessel and in the tissue independently. The organ used was a bovine kidney, turned into a perfused tissue phantom using an alcohol fixation technique. The temperature profile within the tissue was mapped with constantan-manganin thermocouple wire sensors with a total diameter of 50 microns. The temperature profile relative to the temperature difference between the vessel and organ was measured; increased perfusion caused a reduction of the vessel wall temperature but did not affect the width of the profile. Studying the transient tissue temperature after a step-wise change of the blood temperature in the vessel revealed a faster diffusion of heat at higher perfusion rates. These facts are in accordance with the keff model, but not with the conventional heat-sink theory.

Animals↗

PubMed1999

A novel approach to monitor tissue perfusion: bladder mucosal PCO2, PO2, and pHi during ischemia and reperfusion.

PURPOSE: The purpose of this study is to determine if monitoring urinary bladder PCO2, PO2, and calculated intramucosal pH would be a reliable index of tissue perfusion. MATERIALS AND METHODS: This nonrandomized controlled study was conducted in a laboratory at a university medical center. Eight immature female Yorkshire pigs were studied with T-9 aortic cross-clamping for 30 minutes followed by a 60-minute period of reperfusion. Cystotomy was performed for placement of a Foley catheter and Paratrend 7 O2/CO2 sensor. RESULTS: Baseline hemodynamic and metabolic measurements were obtained along with measurements of bladder mucosal PO2 and PCO2 (mean+/-SEM). Blood flow measured with microspheres confirmed absence of blood flow during occlusion and hyperemia during reperfusion. Bladder mucosal PO2 decreased from 42+/-14.0 mm Hg (5.6 kPa) to 1.3+/-1.3 mm Hg (1.4 kPa) during the 30-minute interval of ischemia. This was followed by an increase of bladder PO2 to greater than baseline values at the end of the reperfusion period. Bladder mucosal Pco2 increased from 57+/-4.7 mm Hg (7.6 kPa) to 117+/-7.1 mm Hg (15.6 kPa) (P < .05) during ischemia. During reperfusion the Pco2 returned to baseline levels (55+/-4.0 mm Hg [7.3 kPa]). Calculated bladder mucosal pHi declined from 7.31+/-0.04 to 7.08+/-0.05 (P < .05) during the ischemic period and after reperfusion pHi was 7.17+/-0.03. CONCLUSIONS: Monitoring urinary bladder PO2, PCO2, or calculating pHi may provide a simple and reliable means of monitoring tissue perfusion.

Animals↗

PubMedDate not supplied

[Correction of disorders of tissue perfusion in surgical patients in critical conditions and their evaluation by changes in the indices of the acid-soluble fractions of blood plasma].

Rheopolyglucin infusion and vasodilation therapy with droperidol have been performed in 16 critically ill surgical patients with low O2 tissue utilization with the aim in view to assess tissue perfusion disturbances and normalize peripheral blood flow. Basic central hemodynamic parameters and oxygen transport system parameters have been determined. Using gel filtration, acid-soluble blood plasma fractions have been studied spectrophotometrically. Despite the fact that rheopolyglucin infusion caused an increase in oxygen flow index (OFI) at the expense of cardiac index (CI) growth, O2 extraction remained practically unchanged. Vasodilation therapy, with slight changes of CI and OFI, caused an increase in O2 consumption and arterio venous difference, as well as a reduction of mixed venous blood pO2, this accompanied by an increase in acid-soluble blood plasma fractions, especially second fraction at 255 nm. A direct correlation has been established between basic oxygen transport system parameters, characterizing O2 tissue utilization and changes of acid-soluble blood plasma fractions parameters. The changes in acid-soluble blood plasma fractions parameters may serve one of the criteria characterizing the efficacy of procedures aimed at the improvement of tissue perfusion.

Adult↗

PubMedDate not supplied

RPE in perfusion tissue culture and its response to laser application. Preliminary report.

PURPOSE: To study the effects of conventional laser application on the retinal pigment epithelium (RPE) in a perfusion tissue culture model of porcine retinal pigment epithelium without overlying neurosensory retina. METHODS: RPE with underlying choroid was prepared from enucleated porcine eyes and fixed in a holding ring (Minusheet). Specimens were then placed in two-compartment tissue culture containers (MinuCell & Minutissue, Bad Abbach, Germany) and were cultured during continuous perfusion with culture medium at both sides of the entire specimen, the upper RPE and the lower choroid (12 specimens out of 6 eyes). Cultures were kept for 1, 3, 7 and 14 days and were examined histologically. Laser treatment was performed on each tissue ring by application of 3 x 3 laser burns one day after culture began (argon ion laser, wavelength: 514 nm, pulse duration: 100 ms; spot size: 200 microm) using different energy levels (400-1,000 mW); (16 specimens out of 8 eyes). RESULTS: During laser treatment a marked lightening of the RPE with centrifugal spreading was observed. Using higher levels of energy, a contraction of the RPE towards the center of the laser spot was noticed. One day after laser photocoagulation histology revealed destruction of RPE; within 3-7 days of culture, migration and proliferation of neighboring cells was observed in several lesions. After 7 days the initial defect of the irradiated area was covered with dome shaped RPE cells and after 14 days multilayered RPE cells were showing ongoing proliferation. However, there were also cases without proliferation after laser treatment. The non-treated, continuously perfused RPE showed regular appearance in histological sections: during the first 7 days of culture, light microscopy revealed a normal matrix with a well-differentiated RPE monolayer. Subsequently proliferation even without treatment was observed and after 14 days the RPE became multilayered. CONCLUSION: It was possible to study the early healing response to the effect of laser treatment using the permanently perfused tissue culture system. A marked proliferation and repair of the laser defect could be observed in several but not all lesions. After 14 days even without laser treatment a proliferative multilayered RPE was present. Although this limits the use of the system for longer than 7 days, it seems to be useful for investigation of RPE-related disorders.

Animals↗