A simple and reproducible method to reliably assess platelet activation.
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Adenosine Diphosphate↗
Biomedical subjects
B Vollmar
Publications and source records attributed to B Vollmar.
A peritoneal cavity chamber for intravital microscopy of the liver under conditions of pneumoperitoneum.
BACKGROUND: Intravital microscopy allows direct visualization of the hepatic microvasculature. We report on a novel application of this technique using a chamber model that simulates the conditions of pneumoperitoneum. METHODS: For this purpose, we designed a peritoneal cavity chamber for rats. In the present study, we evaluated the technical procedure without any induction of increased intraabdominal pressure to assess undisturbed hepatic microcirculation. Intravital microscopy of the liver was performed in 12 rats. Animals that underwent the same operative procedure without the chamber served as controls (n = 12). RESULTS: Hepatic sinusoidal perfusion rate, leukocyte-endothelial cell interaction, and bile flow showed no significant differences between the groups. Operating time was longer in the chamber group. CONCLUSION: The peritoneal cavity chamber is an attractive approach for the study of hepatic microvascular, cellular, and molecular mechanisms that are important to our understanding of the potential harmful effects of laparoscopy on hepatic circulation and liver function.
Animals↗
Noninvasive analysis of conjunctival microcirculation during carotid artery surgery reveals microvascular evidence of collateral compensation and stenosis-dependent adaptation.
OBJECTIVE: Hemodynamically relevant internal carotid artery (ICA) stenosis is a major cause of ischemic stroke. Despite its long-term benefit, carotid endarterectomy may also be associated with severe neurologic deficits. Intraoperative and early recognition of ischemia in the region of the ICA may reduce this risk. To date, direct imaging and quantitative analysis of microvascular structures and function in the human ICA region have not been possible. We purposed to visualize and quantify ischemia/reperfusion-induced microcirculatory changes in the terminal vascular bed of the ICA in patients undergoing unilateral ICA endarterectomy. METHODS: Sequential analysis of the ipsilateral and contralateral conjunctival microcirculation was performed with orthogonal polarized spectral imaging in 33 patients undergoing unilateral ICA endarterectomy because of moderate or severe ICA stenosis (North American Symptomatic Carotid Endarterectomy Trial score, 75% +/- 13%), before clamping the ICA (baseline), during clamping of the external carotid artery and ICA, during reperfusion of the ICA (intraluminal shunt), during the second clamping of the ICA (shunt removal), after declamping (reperfusion) of the external carotid artery and ICA, and 15 to 20 minutes after the second ICA reperfusion. RESULTS: During ICA clamping for shunt placement, ipsilateral and contralateral conjunctival capillary perfusion was significantly decreased, but it was completely restored after reperfusion with carotid shunting. Reclamping of the ICA for shunt removal caused microvascular dysfunction, which was significantly less pronounced than that observed during the first clamping. The individual degree of ICA stenosis was inversely correlated with the ipsilateral and contralateral decrease in conjunctival functional capillary density during the first ICA clamping. CONCLUSIONS: These results suggest adaptive mechanisms of capillary perfusion with increasing stenosis and development of collateral compensatory circulation in the vascular region of the human ICA. Conjunctival orthogonal polarized spectral imaging during unilateral ICA reconstruction enables continuous noninvasive analysis of bilateral conjunctival microcirculation in the terminal region of the ICA and enables monitoring for efficient carotid shunt perfusion during and after endarterectomy.
Adaptation, Physiological↗
Inhibition of p53 protects liver tissue against endotoxin-induced apoptotic and necrotic cell death.
There is increasing evidence that apoptotic and necrotic hepatocyte death following endotoxin-induced liver injury act as signals for leukocyte sequestration in the liver vasculature. p53 has been implicated to promote apoptosis through trans-activation and down-regulation of specific pro- and anti-apoptotic genes. Here, we report that inhibition of p53 decreases apoptotic and necrotic tissue injury as well as inflammatory cell response. Sprague-Dawley rats were injected intraperitoneally with 2.2 mg/kg pifithrin-alpha (PFT), a p53-inactivating agent, or the vehicle DMSO 30 min before intravenous exposure to lipopolysaccharide (LPS). In vehicle-pretreated animals, LPS induced significant apoptosis and necrosis of hepatocytes, which was associated with intrahepatic leukocyte recruitment, microvascular dysfunction, and enzyme release. Inhibition of p53 effectively attenuated (P<0.05) hepatocellular apoptosis and necrosis, but also reduced leukocyte recruitment and microvascular dysfunction. Western blot analysis revealed that PFT lowered the nuclear-to-cytoplasmic p53 ratio and reduced both activation of NF-kappaB and cleavage of procaspase 3 (P<0.05). In parallel, immunohistochemistry of PFT-pretreated, but not vehicle-pretreated, endotoxic animals exhibited nuclear p53 exclusion and reduced NF-kappaB p65 staining. This indicates that p53 mediates, at least in part, LPS-associated apoptosis and contributes to inflammatory endotoxic tissue injury through leukocyte activation and intraorgan sequestration.
Animals↗
Small volume hypertonic hydroxyethyl starch reduces acute microvascular dysfunction after closed soft-tissue trauma.
A major pathway of closed soft-tissue injury is failure of microvascular perfusion combined with a persistently enhanced inflammatory response. We therefore tested the hypothesis that hypertonic hydroxyethyl starch (HS/HES) effectively restores microcirculation and reduces leukocyte adherence after closed soft-tissue injury. We induced closed soft-tissue injury in the hindlimbs of 14 male isoflurane-anaesthetised rats. Seven traumatised animals received 7.5% sodium chloride-6% HS/HES and seven isovolaemic 0.9% saline (NS). Six non-injured animals did not receive any additional fluid and acted as a control group. The microcirculation of the extensor digitorum longus muscle (EDL) was quantitatively analysed two hours after trauma using intravital microscopy and laser Doppler flowmetry, i.e. erythrocyte flux. Oedema was assessed by the wet-to-dry-weight ratio of the EDL. In NS-treated animals closed soft-tissue injury resulted in massive reduction of functional capillary density (FCD) and a marked increase in microvascular permeability and leukocyte-endothelial cell interaction as compared with the control group. By contrast, HS/HES was effective in restoring the FCD to 94% of values found in the control group. In addition, leukocyte rolling decreased almost to control levels and leukocyte adherence was found to be reduced by approximately 50%. Erythrocyte flux in NS-treated animals decreased to 90 +/- 8% (mean SEM), whereas values in the HS/HES group significantly increased to 137 +/- 3% compared with the baseline flux. Oedema in the HS/HES group (1.06 +/- 0.02) was significantly decreased compared with the NS-group (1.12 +/- 0.01). HS/HES effectively restores nutritive perfusion, decreases leukocyte adherence, improves endothelial integrity and attenuates oedema, thereby restricting tissue damage evolving secondary to closed soft-tissue injury. It appears to be an effective intervention, supporting nutritional blood flow by reducing trauma-induced microvascular dysfunction.
Acute Disease↗
Comparison of surgical stress between laparoscopic and open colonic resections.
BACKGROUND: The magnitude of surgical trauma after laparoscopic and open colonic resection was evaluated by examining postoperative serum values of interleukin-6 (IL-6), IL-10, C-reactive protein (CRP), and granulocyte elastase (GE) for further evidence of the benefit realized with minimally invasive approaches in colonic surgery. METHODS: Altogether, 42 patients with Crohn's disease (n = 20) or colon carcinomas/adenomas (n = 22) were matched by age, gender, body mass index (BMI), and Crohn's Disease Activity Index for either a laparoscopic (n = 21) or an open colonic resection (n = 21). In both groups the postoperative serum levels of IL-6, IL-10, C-RP, and granulocyte elastase were determined, as indicators of surgical stress. RESULTS: Laparoscopic and open colonic resection caused a significant increase in serum IL-6, IL-10, CRP, and granulocyte elastase levels. The comparison between laparoscopic and open colonic resections, however, showed significantly lower serum IL-6, IL-10, CRP, and granulocyte elastase levels after laparoscopic colonic resection, which was most evident for IL-6 and granulocyte elastase. CONCLUSIONS: Our study demonstrated that IL-6 and granulocyte elastase may be appropriated particularly to monitor surgical stress. By using these parameters, we found a significant reduction in surgical trauma after laparoscopic surgery, was compared with the open procedure. This supports the clinical findings of a clear benefit for patients undergoing laparoscopic colonic surgery.
Adult↗
New model for in vivo quantification of microvascular embolization, thrombus formation, and recanalization in composite flaps.
BACKGROUND: Microthrombi are suggested to be involved in the pathogenesis of composite flap failure. Due to the lack of appropriate experimental models, however, the significance of microvascular thrombus formation and microthromboembolization in free flap failure remains poorly understood. The purpose of this study was therefore to develop a rat hindlimb model that allows tissue-confined in vivo analysis of thrombus formation, thromboembolization, and recanalization within the microcirculation of osteomyocutaneous flaps using intravital fluorescence microscopy. MATERIALS AND METHODS: Thrombus formation was induced photochemically in individual arterioles and venules of muscle, subcutis, and periosteum. To study thromboembolization, autologous arterial thrombi (40 microm) were preformed in vitro and were injected into the femoral artery supplying the osteomyocutaneous flap. RESULTS: First platelet deposition was found independent from microvascular red blood cell velocity, while the subsequent growth of thrombus correlated inversely with red blood cell flow measured in the respective microvessel. Time required for complete thrombotic arteriolar occlusion exceeded 700 s, whereas thrombus growth in venules was found to be significantly accelerated ( approximately 300 s) without differences between the individual tissues analyzed. The embolization resulted in a complete shutdown of capillary perfusion in muscle, subcutis, skin, and periosteum. During subsequent spontaneous recanalization, capillary perfusion increased in all tissues to approximately half of baseline, however, without further recovery during the 4-h postembolization period. CONCLUSIONS: The model presented is suitable to quantitatively study the pathophysiology of microvascular thrombus formation, thromboembolization, and recanalization in composite flaps, and may thus be used to evaluate the effectiveness of novel therapeutic strategies to prevent flap failure.
Animals↗
Microvascular transfer-related abrogation of capillary flow motion in critically reperfused composite flaps.
Capillary flow motion is defined as rhythmic fluctuations of blood flow in the capillaries. Although critical perfusion has been demonstrated to induce capillary flow motion, little is known about the role of capillary flow motion in microvascular free flaps. The aim of this study was to elucidate the tissue-confined incidence and consequence of capillary flow motion in microvascularly transferred composite flaps, using intravital fluorescence microscopy. In Wistar rats, transferred osteomyocutaneous flaps (n = 7), which were exposed to 1 h of ischaemia during the anastomotic procedure followed by 1 h of reperfusion, were subjected to critical perfusion by stepwise reduction of the femoral-artery blood flow to 0.15 ml min(-1), 0.10 ml min(-1) and 0.05 ml min(-1). Pedicled osteomyocutaneous flaps that were not subjected to ischaemia (n=8) served as controls. In pedicled flaps critical perfusion induced capillary flow motion in the muscle, but not in the skin, subcutis and periosteum. In these flaps, the functional capillary density was preserved in all tissues analysed, including the skeletal muscle. Additional sympathetic denervation of the pedicled flaps did not change the incidence or pattern of capillary flow motion. In contrast, after flap transfer capillary flow motion in muscle tissue did not occur during critical perfusion. As a consequence, a shutdown of perfusion of individual capillaries was observed, resulting in a significant reduction (P<0.05) in functional capillary density, not only in the subcutis, skin and periosteum but also in the muscle itself. Thus, our data suggest that the microcirculatory control of pedicled osteomyocutaneous flaps is preserved during critical perfusion by skeletal-muscle capillary flow motion, whereas this protective regulatory mechanism is lost during the initial reperfusion period after flap transfer, probably not because of denervation but because of surgery- and/or ischaemia-reperfusion-associated injury.
Animals↗
Acceleration of cutaneous wound healing by transient p53 inhibition.
The increase of cell proliferation during early wound healing is thought to be regulated by a decrease of apoptosis. In contrast, the reduction of cellularity during final wound maturation may be controlled by an increase of apoptotic cell death. Herein we studied whether p53 is involved in wound healing-associated apoptosis and whether transient inhibition of p53 is effective to improve the early healing process of cutaneous wounds. Using intravital microscopic and immunohistochemical techniques in hairless mice, we demonstrated that in vivo inhibition of p53 by pifithrin-alpha (PFT-alpha; 2.2 mg/kg ip) accelerates early epithelialization and neovascularization of cutaneous wounds by (i) promoting leukocyte recruitment, (ii) increasing cell proliferation, and (iii) reducing apoptotic cell death. We further show that final wound closure with down-regulation of cell proliferation is not inhibited by PFT-alpha treatment, indicating that transient blockade of p53 function does not affect the process of wound maturation. Western blot analysis revealed that PFT-alpha lowered nuclear but not cytoplasmic p53, implying that cytoplasmic retention of p53 mediates the antiapoptotic effects of PFT-alpha. Furthermore, PFT-alpha significantly increased expression of proliferating cell nuclear antigen protein in whole extracts of cutaneous tissue and caused a rise in proliferation of wild-type, but not mutant, p53-expressing keratinocytes. From our study we conclude that transient inhibition of p53 supports the early cell proliferation required for rapid tissue repair and that this may represent an attractive approach in the treatment of delayed wound healing.
Animals↗
Ovariectomy improves neovascularization and microcirculation of freely transplanted ovarian follicles.
To investigate the influence of ovariectomy on the physiological process of neovascularization of ovarian follicles, we harvested follicles with a theca interna at 48 h after pregnant mare's serum gonadotropin (PMSG) treatment of Syrian golden hamsters, for subsequent transplantation onto striated muscle tissue of chronically implanted skinfold chambers of non-ovariectomized PMSG-synchronized hamsters and bilaterally ovariectomized hamsters. Non-ovariectomized non-PMSG-treated animals served as controls. During a 2 week period after transplantation, neovascularization of these freely transplanted grafts was quantified in vivo by assessment of the newly developed microvascular follicular network, its microvessel density, the diameter of microvessels and their volumetric blood flow using fluorescence microscopic techniques. At day 3 after transplantation, capillary sprouts could be observed in all groups studied, finally developing a complete glomerulum-like microvascular network within 5-10 days. In ovariectomized animals, however, vascularization of follicular tissue was found to be accelerated and enhanced when compared with the follicles in both groups of non-ovariectomized animals. This was associated with significantly higher capillary blood perfusion, which may in part represent the graft's adaptive response to pro-angiogenic stimuli due to elevated gonadotropin levels, but might in particular be mediated by gonadotropin-induced release of vasoactive substances. Interestingly, small preantral follicles lacking a theca interna failed to vascularize in either of the groups. In conclusion, the study demonstrates that ovariectomy improves neovascularization and microcirculation of freely transplanted ovarian follicles.
Analysis of Variance↗
Effects of hematocrit on cerebral microcirculation and tissue oxygenation during deep hypothermic bypass.
BACKGROUND: One rationale for hemodilution during hypothermic cardiopulmonary bypass (CPB) has been improved microcirculation. However, the optimal degree of hemodilution remains unclear. We therefore studied cerebral microcirculation and tissue oxygenation in a new intravital microscopic model at 3 different hematocrit (Hct) values. METHODS AND RESULTS: Three groups of 5 piglets with a cranial window over the parietal cortex underwent cooling at Hct of 10%, 20%, or 30%, followed by 1-hour deep hypothermic circulatory arrest (DHCA) and rewarming on CPB. For assessment of functional capillary density (FCD), plasma was labeled with fluorescein-isothiocyanate-dextran. Rhodamine-stained leukocytes were observed in postcapillary venules with analysis for adhesion and rolling. NADH, a natural intracellular fluorophore that increases during ischemia, was measured densitometrically during bypass and DHCA. FCD did not significantly differ from baseline during cooling in any group. However, during early reperfusion (5 minutes) after DHCA, the FCD was significantly higher in the Hct 30% group than in the Hct 10% group. Leukocyte adherence decreased in all groups during CPB and was only moderately increased at the end of the experiment. However, severe hemodilution (Hct 10%) was associated with a significantly greater number of rolling leukocytes relative to Hct 30%. CONCLUSIONS: Higher Hct does not impair cerebral microcirculation and reduces white cell/endothelial activation after deep hypothermic bypass and circulatory arrest. Severe hemodilution (Hct 10%) results in evidence of inadequate cerebral tissue oxygenation during the cooling phase of CPB. This study suggests that Hct of 30% is preferable relative to lower Hct values during hypothermic CPB, particularly if DHCA is used.
Animals↗
Revascularization and microcirculation of freely grafted islets of Langerhans.
A considerable number of experimental studies have demonstrated that the reestablishment of an appropriate microvascular supply is an essential prerequisite for successful pancreatic islet transplantation. Freely transplanted islets show the first signs of angiogenesis (i.e., capillary sprout formation and protrusion) as early as 2 days after transplantation, and the entire vascularization process is completed after 10 to 14 days. Cryopreservation and culture of the isolated islets before transplantation and hyperglycemia of the transplant recipient seem not to affect the vascularization process essentially. In addition, immunosuppressive drugs, such as cyclosporin A and 15-deoxyspergualin, do not or only slightly inhibit revascularization of syngeneic islets; however, they are not able to prevent completely xenograft-induced microvascular perfusion failure. In contrast, novel immunosuppressants (e.g., RS-61443) or dietary supplementation of the antioxidant vitamin E were shown to prevent microvascular graft rejection almost completely, including leukocyte recruitment and capillary perfusion failure. Thus the development of novel strategies to improve posttransplant islet function should include concepts that accelerate the vascularization process and protect the newly formed microvasculature from rejection-mediated injury. The improvement of islet graft vascularization and the maintenance of adequate microvascular perfusion will contribute to the increased success of pancreatic islet transplantation.
Animals↗
Hepatic arteriolo-portal venular shunting guarantees maintenance of nutritional microvascular supply in hepatic arterial buffer response of rat livers.
To elucidate the hepatic microvascular response upon the hepatic arterial buffer response (HABR), we analysed blood flow (ultrasonic flowprobes) of the hepatic artery (HA) and portal vein (PV), microcirculation (intravital microscopy), and tissue oxygenation (polarography) in anaesthetized Sprague-Dawley rats and re-evaluated the role of adenosine in mediating the HABR by using 8-phenyltheophylline as a competitive antagonist. 2. Upon restriction of PV blood flow to 11 +/- 3 % of baseline values, HA blood flow increased by a factor of 1.77 (P < 0.05), thus confirming HABR. Strikingly, red blood cell velocity and volumetric blood flow in terminal hepatic arterioles (THAs) did not increase but were even found to be slightly decreased, by 8 and 13 %, respectively. In contrast, red blood cell velocity and volumetric blood flow in terminal portal venules (TPVs) decreased to only 66 % (P < 0.05), indicating upstream hepatic arteriolo-portal venular shunting. As a consequence, red blood cell velocity and volumetric blood flow in sinusoids were found to be reduced to only 66-68 % compared with baseline (P < 0.05). Diameters of neither of those microvessels changed, thus excluding THA-, TPV-, and sinusoid-associated mechanisms of vasomotor control in HABR. 3. Tissue PO2 and hepatocellular NADH fluorescence remained unchanged, indicating HABR-mediated maintenance of adequate oxygen delivery, despite the marked reduction of total liver blood flow. Further, hepatic arteriolo-portal venular shunting guaranteed homogeneity of nutritive blood flow upon HABR, as given by an unchanged intra-acinar coefficient of variance of sinusoidal perfusion. 4. Pretreatment of animals with the adenosine antagonist 8-phenyltheophylline completely blocked the hepatic arterial buffer response with the consequence of decreased tissue oxygenation and increased heterogeneity of sinusoidal perfusion. 5. In conclusion, hepatic microhaemodynamics, in particular unchanged diameters of THAs, TPVs and sinusoids, during HABR indicate that reduction in resistance to HA flow is located upstream and functions via hepatic arteriolo-portal venular shunts resulting in equal distribution of microvascular blood flow and oxygen delivery under conditions of restricted PV blood supply.
Adenosine↗
Microvascularization and ventricular function after local alginate-encapsulated angiogenic growth factor treatment in a rat cryothermia-induced myocardial infarction model.
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Alginates↗
Microcirculatory derangements in acute pancreatitis.
During the past decade, a considerable number of experimental studies have confirmed the hypothesis that microcirculatory derangements play a pivotal role in the pathogenesis of acute pancreatitis, including the process of conversion from edematous to necrotizing injury. Predominant microcirculatory disorders are nutritive capillary perfusion failure, with the consequence of prolonged focal hypoxia or anoxia, and inflammation-associated microvascular leukocyte recruitment, CD11b- and intercellular adhesion molecule (ICAM)-1-mediated leukocyte-endothelial cell interaction and loss of endothelial integrity, which may result in both edema formation and necrosis. A variety of proinflammatory mediators, such as oxygen radicals, leukotrienes, platelet-activating factor, and interleukins, but also bradykinin and endothelins, seem to be involved in triggering the manifestations of these microcirculatory disorders. In contrast, the anti-inflammatory interleukin-10, as well as nitric oxide, are thought to be capable of protecting from these pancreatitis-associated microvascular injuries. This knowledge may be encouraging for the development of novel therapeutic strategies, aiming at the attenuation of microcirculatory disorders, and, thus, preventing tissue injury in acute pancreatitis.
Animals↗
In vivo imaging of physiological angiogenesis from immature to preovulatory ovarian follicles.
To develop a model for the study of physiological angiogenesis, we transplanted ovarian follicles onto striated muscle tissue and analyzed the process of microvascularization in vivo using repeated fluorescence microscopy. Follicles were mechanically isolated from unstimulated as well as pregnant mare's serum gonadotropin (PMSG)- or PMSG/luteinizing hormone (LH)-stimulated Syrian golden hamster ovaries and were transplanted as free grafts into dorsal skinfold chambers of untreated or synchronized hamsters. Follicles lacking thecal cell layers did not vascularize regardless whether harvested from unstimulated or PMSG-stimulated animals, but underwent granulosa cell apoptosis, as indicated in vivo by nuclear condensation and fragmentation of bisbenzimide-stained follicular tissue. In contrast, all follicles at 48 hours after PMSG treatment with a multilayered thecal shell exhibited initial signs of angiogenesis within 3 days. Vascularization was completed within 7 to 10 days, comprising a dense glomerulum-like microvascular network. Nature and extent of vascularization of follicles harvested at 72 hours after either PMSG or PMSG/LH treatment did not notably differ from each other when transplanted into the respective synchronized animals. However, follicles with PMSG/LH treatment revealed significantly larger microvessel diameters and higher capillary blood perfusion compared to follicles with sole PMSG treatment, probably reflecting the adaptation to the increased functional demand upon the LH surge. Using the unique experimental approach of ovarian follicle transplantation in the dorsal skinfold chamber of Syrian golden hamsters, we could show in vivo the developmental stage-dependent vascularization of follicular grafts with sustained potential to meet their metabolic demand by increased blood perfusion.
Animals↗
Heparin and the nonanticoagulant N-acetyl heparin attenuate capillary no-reflow after normothermic ischemia of the lung.
BACKGROUND: Ischemia-reperfusion injury of the lung frequently occurs after cardiopulmonary bypass, after pulmonary thromboendarterectomy, and especially after lung transplantation. Heparin is known to be protective in ischemia-reperfusion injury, but the risk for bleeding disorders may restrict its use in a variety of diseased conditions. Therefore, we tested the efficiency of nonanticoagulant N-acetyl (NA) heparin to protect from postischemic reperfusion injury of the lung. METHODS: Pentobarbital-anesthetized, mechanically ventilated Lewis rats were heparinized (100 IU/kg) before insertion of catheters. Additionally, animals received either heparin (200 IU/kg; n = 7), NA heparin (1.1 mg/kg; n = 7), or saline (control, n = 7) before ischemia. After normothermic ischemia for 50 minutes, the left lung was reperfused for 120 minutes, or until the death of the animal. The nonischemic right lung was excluded after 10 minutes of reperfusion. RESULTS: Survival rate at 120 minutes of reperfusion was 7 of 7 and 6 of 7 in the heparin and the NA-heparin group, but 0 in 7 in the control group (p < 0.01). At 30 minutes of reperfusion, PaO2, blood flow through the ascending aorta and mean systemic blood pressure were also significantly higher in the heparin and the NA-heparin group when compared with the control group (p < 0.05). Pulmonary vascular resistance was significantly lower in the heparin and the NA-heparin groups, and histologic examination of the lungs from these groups confirmed reperfusion of nutritive alveolar capillaries by the presence of red blood cells. Lack of red blood cells in the alveolar capillaries of lung specimens from the control group indicated failure of capillary reperfusion. CONCLUSIONS: Heparin and NA heparin exert similar protection against capillary no-reflow after normothermic ischemia of the lung. This implies that the protective effect of heparin is mediated by properties different from its anticoagulant activity. Thus the nonanticoagulant N-acetyl heparin may pose a safe new therapeutic approach in lung ischemia-reperfusion injury without increasing the risk of hemorrhagic complications.
Animals↗
Preparation and investigation of tumor affinity, uptake kinetic and transport mechanism of iodine-123-labelled amino acid derivatives in human pancreatic carcinoma and glioblastoma cells.
In developing radioiodinated agents for pancreatic and brain tumor imaging by single photon emission tomography (SPET), we prepared p-amino-3-[123I]iodo-l-phenylalanine (IAPA), p-[123I]iodo-l-phenylalanine (IPA), L-8-[123I]iodo-1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid (ITIC) and L-3-[123I]iodo-alpha-methyl-tyrosine (IMT) in radiochemical yields up to 95%, and we investigated their uptake in human pancreatic carcinoma and glioblastoma cells as well as the mechanisms promoting the tumor uptake. The radiopharmaceutical uptake into tumor cells was rapid (t(1/2) < or = 5 min) and temperature- and pH-dependent. The radioactivity concentration in tumor cells varied from 10 to 33% of the total activity (105-310 cpm/1000 cells) following a 30-min incubation at 37 degrees C (pH 7.4). In comparison, accumulation of the radiopharmaceuticals into normal brain and pancreatic tissue remained relatively low. Depolarizing the plasma membrane potential in high K+ buffer significantly altered the radioactivity concentration in the tumor cells, suggesting that membrane potential plays a certain role in the cellular uptake. Competitive inhibition experiments with specific amino acid transport inhibitors indicated that the uptake of IAPA, IPA and IMT into human pancreatic carcinoma and glioblastoma cells is predominantly mediated by the L and ASC transport systems, while no substantial involvement of the transport system A in their tumor uptake could be demonstrated. In contrast, results of the present investigation indicated that ITIC is not taken up into tumor cells via the common neutral amino acid carrier systems, including the A, L and ASC system. Furthermore, preloading with naturally occurring L-amino acids failed to stimulate the cellular uptake of the radiopharmaceuticals. These data indicate that the investigated radiopharmaceuticals exhibit interesting characteristics with promise for in vivo tumor investigations to ascertain their potential as radioligands for glioma and pancreatic carcinoma imaging by SPET.
Amino Acids↗