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M D Menger

Publications and source records attributed to M D Menger.

At least 199 records · Page 11Linked to original sources
PubMed1995

Microcirculatory models of ischaemia-reperfusion in skin and striated muscle.

Intravital microscopy is used for analysis of the microcirculation in various organs, e.g. mesentery, intestine, heart, liver and lung, requiring either exteriorization or in situ visualization techniques in anaesthetized animals. In contrast, the implantation of transparent chambers has been employed to allow chronic observation of the microcirculation in intact, non-anaesthetized animals. This paper reports results with two transparent chamber models: the skin-fold chamber model in the hamster and the mouse. An overview is provided of the technical development of the chamber technique and of the various experimental studies that have been performed using these models in ischaemia-reperfusion of striated muscle. Particular emphasis is given to a description of the methods used to induce ischaemia and reperfusion, namely pressure-induced or tourniquet-induced ischaemia. While the former allows simulation of the pathophysiological situation in compartment syndromes, the latter provides an appropriate simulation of the clinical situation in vascular, transplantation and reconstructive surgery. Future possibilities for these microcirculation models in research into the pathophysiology of ischemia-reperfusion are outlined, and potential therapeutic measures to preserve postischaemic tissue are discussed.

Animals↗
PubMed1995

Histogenesis and ultrastructure of pancreatic islet graft microvasculature. Evidence for graft revascularization by endothelial cells of host origin.

In previous studies we have demonstrated that syngeneic and xenogeneic pancreatic islet grafts are revascularized within a 10 to 14-day period after transplantation. With the combined use of intravital and electron microscopy, as well as immunohistochemistry using a set of species-specific or -crossreacting antibodies to endothelial cell antigens, we investigated 1) the origin of the endothelium of the newly formed capillaries in free pancreatic islet isografts (hamster-->hamster) and xenografts (rat-->hamster), and 2) the ultrastructural characteristics of these microvessels. Intravital microscopy demonstrated that newly formed microvessels grow from the vascular bed of the host muscle tissue into the islet grafts. Immunohistochemical analysis of host tissue and transplanted islets with antibodies against factor VIII (recognizing both hamster and rat factor VIII), bovine PECAM-1 (CD31; endoCAM, crossreacting with hamster but not rat PECAM-1), and rat ICAM-1 (CD54, non-crossreacting with hamster ICAM-1) showed that the transplanted rat islets were revascularized by endothelium of hamster (host) origin. At an ultrastructural level, the endothelial lining of the newly formed microvessels showed diaphragmatic fenestration, a characteristic feature of endothelial cells of pancreatic islets in situ. On the basis of these findings we suggest that pancreatic islet transplantation may take a unique position in the field of organ transplantation, since the generally proposed mechanisms of endothelial cell-dependent antigen recognition as a trigger of graft rejection may not be transferred to islet grafts, containing microvessels lined by endothelial cells of host origin.

Animals↗
PubMed1994

In vivo fluorescence microscopy for the assessment of microvascular reperfusion injury in small bowel transplants in rats.

With the use of in vivo fluorescence microscopy we have analyzed microvascular reperfusion injury of small bowel isograft transplants in rats. Following 1 hr cold storage in University of Wisconsin solution, the small bowel was transplanted heterotopically, and the intestinal microcirculation was quantitatively analyzed 20-60 min after onset of reperfusion. The intestinal grafts' capillary perfusion of both the mucosa and the circular and longitudinal muscles was not found altered when compared with the intestinal capillary perfusion of sham-operated controls. In contrast, leukocyte-endothelial cell interaction, including leukocyte rolling (40 +/- 5%) and sticking (280 +/- 100 mm-2) in submucosal postcapillary venules, was significantly increased when compared with nontransplanted controls (12 +/- 8% and 20 +/- 10 mm-2, P < 0.01 and P < 0.05, respectively). Leukocyte-endothelial cell interaction was associated with a marked alteration of lymphatic capillary drainage, as indicated by the low functional density of lymphatic microvessels of 10.2 +/- 6.1 cm-1 (P < 0.01 vs. sham-operated controls (39.2 +/- 6.1 cm-1)). From these results we propose that leukocyte-endothelial cell interaction, not capillary "no-reflow," is the primary step in the manifestation of microvascular reperfusion injury following a short period of cold ischemia in small bowel grafts.

Animals↗
PubMed1994

In vivo analysis of microvascular reperfusion injury in striated muscle and skin.

The use of intravital fluorescence microscopy in the models of the hamster dorsal skin fold chamber and the ear of the hairless mouse allows for the quantitative analysis of post-ischemic microvascular reperfusion injury in striated muscle and skin. Prolonged periods of ischemia (4 hours in striated muscle and 6 hours in skin) are associated with 1) perfusion failure of nutritive capillaries at the onset of reperfusion (no-reflow) and 2) activation, accumulation and microvascular adherence of white blood cells, formation of reactive oxygen metabolites and release of potent mediators (leukotrienes, platelet-activating factor) with the consequence of increased microvascular permeability due to the loss of endothelial integrity, interstitial edema and cell damage (reflow-paradox). Prophylactic and/or therapeutic regimens may, therefore, include improvement of capillary perfusion by hemodilution, and inhibition of leukocyte adherence, radical formation and mediator release by appropriate counteracting compounds, including anti-oxidants, antibodies directed against adhesion molecules, leukotriene synthesis inhibitors and platelet-activating factor receptor antagonists.

Animals↗
PubMed1994

Depressed phagocytic activity of Kupffer cells after warm ischemia-reperfusion of the liver.

Phagocytic activity of Kupffer cells following hepatic ischemia/reperfusion was studied in 39 livers of male Sprague-Dawley rats by in vivo fluorescence microscopy. Animals were subjected to either 20 min (group B, n = 9) and 60 min left hepatic lobar ischemia (group C, n = 9) or to 20 min of global hepatic ischemia (group D, n = 11). Sham-operated animals without ischemia served as controls (group A, n = 10). After 60 min postischemic reperfusion, fluorescent latex beads (3 x 10(8).kg body wt-1; diameter: 1.1 microns) were injected intra-arterially. The zonal distribution and kinetics of adherence of latex beads were quantified by off-line video analysis. After 20 min of left hepatic lobar ischemia, 50%, 38% and 12% of injected latex beads adhered in zones 1, 2 and 3, respectively, and did not significantly differ from control livers (group A: 57%, 32% and 11%). In contrast, after 60 min of left hepatic lobar ischemia (group C) as well as after 20 min of global hepatic ischemia (group D), a more homogeneous distribution of latex beads adherent in zones 1, 2 and 3 was observed (group C: 48%, 36% and 16%; group D: 48%, 36% and 16%). Kinetic analysis of phagocytosis (% adherence of visible latex beads 1 min and 3 min after injection) showed no significant difference between 20 min left hepatic lobar ischemia (group B: 84% and 95%) and control (group A: 81% and 95%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Timing of arterialization in liver transplantation.

OBJECTIVE: This study analyzed the pathophysiologic sequela of different modes of graft reperfusion in liver transplantation. SUMMARY BACKGROUND DATA: The grafted liver may be reperfused either immediately after completion of portal anastomosis followed by delayed arterial reconstruction or simultaneously by portal and arterial blood if all vascular anastomoses are completed during the anhepatic period. METHODS: Delayed arterialization, that is, arterial reperfusion 8 minutes after portal revascularization (n = 12), was compared with simultaneous arterialization (n = 8) using the model of syngeneic orthotopic liver transplantation in male Lewis rats. After cold storage for 24 hours in University of Wisconsin (UW) solution, intravital fluorescence microscopy was employed 30 to 90 minutes after reperfusion to assess hepatic microvascular perfusion, leukocyte accumulation, and phagocytic activity of Kupffer cells. RESULTS: Compared with delayed arterialization, the number of both nonperfused acini and nonperfused sinusoids was reduced after simultaneous reperfusion by 71% (p = 0.008) and 78% (p < 0.001), respectively. Leukocyte accumulation in sinusoids and postsinusoidal venules after simultaneous arterialization decreased by 17% (p = 0.01) and 64% (P < 0.001), respectively. In addition, simultaneous revascularization was able to attenuate Kupffer cell activation, indicated by significantly slower adherence of latex beads injected 80 minutes after reperfusion. Improved hepatocellular excretory function after simultaneous arterialization was demonstrated by increased bile flow during the observation period of 90 minutes after reperfusion (2.24 +/- 0.7 vs. 0.95 +/- 0.4 mL/100 g liver [mean +/- SEM], p < 0.05). CONCLUSIONS: Timing of arterial reperfusion in liver transplantation may be of critical importance in the prevention of various manifestations of reperfusion injury.

Animals↗
PubMed1994

Effects of warm Carolina rinse on microvascular reperfusion injury in rat liver transplantation.

Recently, it has been demonstrated that the use of both cold Carolina rinse (CR, 4 degrees C) as well as warm Ringer's lactate (RL, 37 degrees C) attenuates microvascular perfusion failure and leukocyte (WBC) accumulation in liver grafts. The aim of this study was to analyse in vivo whether warming of CR can also lead to a reduction in microvascular reperfusion injury in rat liver transplantation. Syngeneic orthotopic liver transplantation, including arterial reconstruction, was performed in male Lewis rats (180-300 g). Livers were stored in University of Wisconsin (UW) solution for 24 h and rinsed with 15 ml CR which was either cold 4 degrees C (n = 7) or warm 37 degrees C (n = 8) prior to reperfusion. Hepatic microcirculation and WBC accumulation were assessed by intravital fluorescence microscopy, and graft function was determined by analysis of bile flow during the 90-min reperfusion period. Warm CR yielded significantly (P < 0.01) improved sinusoidal perfusion when compared with cold CR; however, the extent of WBC adherence in both sinusoids and postsinusoidal venules did not vary between the groups. In addition, bile flow was slightly increased after warm CR. We conclude that after 24 h of cold storage in UW solution, warming of CR may offer additional benefit in the prevention of microcirculatory reperfusion injury without affecting WBC accumulation.

Adenosine↗
PubMed1994

Impact of leukocyte-endothelial cell interaction in hepatic ischemia-reperfusion injury.

To clarify the in vivo relevance of leukocyte-endothelial cell interactions in the manifestation of hepatic ischemia-reperfusion (I/R) injury, we studied leukocyte flow behavior in sinusoids and postsinusoidal venules of postischemic hepatic tissue in rats using intravital microscopy. Reperfusion following either 20 min (n = 9) or 60 min (n = 9) of left hepatic lobar ischemia resulted in a significant increase of the number of stagnant leukocytes in sinusoids and adherent cells in postsinusoidal venules compared with sham-operated controls (n = 10). Transmission electron microscopy revealed the extravasation of leukocytes from both sinusoids (into the space of Disse) and postsinusoidal venules. In parallel, hepatic I/R was associated with increased serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and reduced bile flow. Linear regression estimates revealed significant (P < 0.01) correlations between serum ALT (r = 0.76) and AST (r = 0.65) activities, bile flow (r = -0.62), and the number of adherent leukocytes in postsinusoidal venules. In contrast, parameters of hepatocellular integrity and function did not directly correlate with the number of stagnant leukocytes in liver sinusoids. We conclude that hepatic I/R induces accumulation, adherence, and extravasation of leukocytes in both hepatic sinusoids and postsinusoidal venules. However, the adherence of leukocytes to the endothelial lining of venules, rather than of sinusoids, may determine the manifestation of hepatocellular damage and liver dysfunction.

Alanine Transaminase↗
PubMed1994

Hypertonic hydroxyethyl starch restores hepatic microvascular perfusion in hemorrhagic shock.

The influence of small-volume resuscitation (hypertonic saline-10% hydroxyethyl starch, HS/HES) on liver microcirculation (intravital fluorescence microscopy) was studied in a nonheparinized hemorrhagic shock model [mean arterial pressure (MAP) 40 mmHg for 1 h] in rats. Resuscitation was performed with Ringer lactate (RL, 4-fold shed volume/20 min; n = 7), 10% hydroxyethyl starch 200/0.6 (HES, shed volume/5 min; n = 6), or 7.2% NaCl-10% hydroxyethyl starch 200/0.6 (HS/HES, 10% shed volume/2 min; n = 7). One hour after resuscitation, MAP increased in all groups, but it did not return to preshock values (P < 0.05). HES (16 +/- 2% nonperfused sinusoids) and HS/HES (14 +/- 2% nonperfused sinusoids), but not RL (24 +/- 2% nonperfused sinusoids), reduced (P < 0.05) shock-induced sinusoidal perfusion failure (28 +/- 3%) with restoration of leukocyte velocity in sinusoids (S) and postsinusoidal venules (V). Shock-induced stasis/adherence of leukocytes was further increased (P < 0.05) after resuscitation with RL (S, 38 +/- 6%; V, 55 +/- 20%) and HES (S, 31 +/- 8%; V, 23 +/- 14%). In contrast, resuscitation with HS/HES prevented increased leukocyte stasis in sinusoids (-4 +/- 4%) as well as adherence to endothelial lining of postsinusoidal venules (-5 +/- 10%). We conclude that replacement of only 10% of actual blood loss by means of small-volume resuscitation (HS/HES) can restore hepatic microvascular perfusion and prevent reperfusion-induced leukocyte stasis/adherence.

Animals↗
PubMed1994

Heparin-released superoxide dismutase inhibits postischemic leukocyte adhesion to venular endothelium.

Superoxide radicals formed during reperfusion of ischemic tissues have been identified as a key mediator in the microvascular manifestations of postischemic tissue damage. This understanding is based on studies in laboratory animals in which high doses of superoxide dismutase (SOD; 2.0-25.0 mg/kg body wt iv) were found to inhibit postischemic leukocyte adhesion and the leakage of fluid and macromolecules. Using a dorsal skinfold chamber model in hamsters, we demonstrate now that protection from reperfusion-induced leukocyte adhesion to venular endothelium after 4 h of ischemia to striated muscle can be attained by pretreatment of the animals with a significantly lower dose of exogenous CuZn-SOD (0.25 mg/kg body wt) or with heparin (2,000 IU/kg body wt), which induces a comparable increase in SOD plasma activity through the release of endogenous extracellular SOD from endothelial cell binding sites. This protective effect was maintained until 24 h after reperfusion. In contrast, CuZn-SOD or heparin failed to attenuate the postischemic shutdown of nutritional capillary perfusion, a phenomenon that is due to ischemia-induced endothelial cell swelling, rather than due to reperfusion-associated events, and hence is not susceptible to strategies directed against oxygen radicals generated during the reperfusion phase. The results of this study 1) imply that postischemic leukocyte/endothelium interaction can be attenuated by a low and clinically more relevant dose of SOD, and 2) caveat the administration of heparin in laboratory animals (i.e., to keep catheters patent) in studies of experimental ischemia/reperfusion injury or other oxygen radical-dependent pathomechanisms.

Animals↗
PubMed1994

Role of Mac-1 and ICAM-1 in ischemia-reperfusion injury in a microcirculation model of BALB/C mice.

The leukocyte beta 2-integrin Mac-1 (CD11b/CD18) and its endothelial ligand intercellular adhesion molecule 1 (ICAM-1) are involved in leukocyte adhesion to and macromolecular leakage from postcapillary venules during inflammatory reactions. Both events are also encountered after ischemia-reperfusion of striated muscle, suggesting a central role of both adhesion proteins in reperfusion injury. Using intravital fluorescence microscopy and a microcirculation model in awake BALB/C mice, we investigated the effects of monoclonal antibodies (MAb) and Fab fragments to Mac-1 and MAb to ICAM-1 on leukocyte-endothelium interaction and macromolecular leakage of fluorescein isothiocyanate-dextran (1.5 x 10(5) mol wt) in striated skin muscle after 3 h of ischemia followed by reperfusion. We demonstrated that administration of MAb and Fab to Mac-1 before reperfusion was as effective as administration of MAb to ICAM-1, which was found to be significantly upregulated in the postischemic tissue by immunohistochemical analysis, in preventing postischemic leukocyte adhesion to and macromolecular leakage from postcapillary venules, whereas postischemic leukocyte rolling was not affected after MAb administration. Postischemic capillary perfusion was efficiently preserved in animals treated with anti-Mac-1 and anti-ICAM-1 MAb compared with animals receiving the isotype-matched control antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Hemorrhagic hypotension induces arteriolar vasomotion and intermittent capillary perfusion in rat pancreas.

Hemorrhage-induced intermittent capillary perfusion and its relation to arteriolar vasomotion was studied in rat pancreatic acinar tissue using intravital fluorescence microscopy. During prehemorrhage conditions, microscopic analysis of the pancreatic microcirculation displayed neither arteriolar vasomotion nor intermittency of capillary perfusion (n = 22 animals). Hemorrhage-induced hypotension of 40 mmHg provoked arteriolar vasomotion in 18 of 22 animals and 59 of 115 arterioles studied. The maximum relative amplitude of arteriolar vasomotion was 44 +/- 8% (range 12-81%), and vasomotion frequency averaged 4.73 +/- 0.11 cycles/min. Hemorrhagic hypotension was further accompanied by 1) a decrease of functional capillary density [length of red blood cell-perfused capillaries per area of tissue under investigation (cm/cm2)] from 515 +/- 3 cm-1 at baseline to 386 +/- 3 cm-1 (P < 0.05) and 2) the instantaneous occurrence of intermittency of capillary perfusion in all observation areas (N = 220) of the 22 animals studied. The frequency of intermittency of capillary perfusion (4.72 +/- 0.14 cycles/min) did not differ from the frequency of arteriolar vasomotion, which implies a causal relationship between these two hemorrhage-induced microvascular mechanisms with the probable aim to counteract the decrease of functional capillary density.

Animals↗
PubMed1994

Orientation of microvascular blood flow in pancreatic islet isografts.

There is evidence that intraislet cellular communication and hormone delivery within the islets of Langerhans is controlled via capillary perfusion directed from the B cell core to the A/D cell mantle (intraislet portal system). To determine whether vascularization of freely transplanted islets repeats this "core-to-mantle" capillary perfusion, hamster islets were isolated by collagenase digestion and transplanted into a skinfold chamber of syngeneic animals (n = 12). 14 d after transplantation, the microvasculature of the islet grafts was analyzed by in vivo fluorescence microscopy. The capillary glomerulum-like network of the islet grafts (n = 109) was found supplied by individual arterioles, which regularly pierced the islet and broke into capillaries within the graft (96/109 [88.1%]), resulting in capillary flow directed from the core to the islet's periphery. Only in 13 of 109 islets (11.9%) arterioles broke into capillaries at the outside margin of the islet and capillary flow was directed simultaneously to vessels located within the core, as well as the periphery of the graft. The islet's capillary network was drained by individual venules and intercapillary anastomoses between the newly formed islet capillaries and the preexisting capillaries of the host muscle tissue. Immunohistochemical staining revealed B cells located within the core, and A and D cells scattered in the periphery of the islets, indicating reestablishment of sequential B-->A/D cellular perfusion of the grafts. Thus, freely transplanted islets develop an intra-islet portal system, similarly to that of pancreatic islets in situ.

Animals↗
PubMed1994

Diaspirin crosslinked hemoglobin: evaluation of effects on the microcirculation of striated muscle.

Hemoglobin-based oxygen carriers such as diaspirin-crosslinked hemoglobin (DCLHb) have been proposed for blood substitution due to their plasma expansion and oxygen transport capacity. This study investigates the effects of DCLHb on the microcirculation of striated muscle after moderate topload infusion and isovolemic exchange transfusion in awake hamsters. The skinfold chamber model in hamsters and intravital fluorescence microscopy were used for analysis of vessel diameter, red blood cell velocity (RBCV), leukocyte sticking to the microvascular endothelium, and macromolecular leakage in striated skin muscle. In each animal, arteriolar and postcapillary vessel segments were chosen and sequentially recorded on videotape (baseline). Animals were subjected to either topload infusion (10% of blood volume) or isovolemic exchange transfusion (hct 30%) of DCLHb followed by measurements at 10, 30, and 60 min thereafter. In vivo visualization of plasma and leukocytes was performed using FITC-dextran 150,000 and rhodamine 6G, respectively. No significant changes of vessel diameter and RBCV were observed after topload infusion or isovolemic exchange transfusion with DCLHb, either in postcapillary venules or in arterioles when compared with baseline values. Leukocyte sticking and macromolecular leakage were not found enhanced after administration of DCLHb. We conclude that the introduction of DCLHb-bound oxygen into the tissue does neither stimulate leukocyte adhesion nor impair endothelial integrity.

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