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Biomedical subjects

M D Menger

Publications and source records attributed to M D Menger.

At least 217 records · Page 12Linked to original sources
PubMed1994

[Microcirculation of gastric mucosa in pathogenesis of stomach ulcer].

During the last decade, evidence increased that microcirculatory disorders play a pivotal role in the development of mucosal injury, and, hence, formation of gastric ulcer. Mucosal microcirculation is altered at least by two distinct mechanisms: Stimulation of acid secretion leads to a rise of blood flow in the acid-secreting areas, and, concomitantly, due to a steal-phenomenon to a decrease of mucosal capillary perfusion of the antrum, which results in temporary ischemia. In addition, surface noxae-induced release of potent mediators, such as histamine, leukotrienes, thromboxane, platelet-activating factor and reactive oxygen metabolites cause vasoconstriction, capillary stasis and increase of microvascular permeability (loss of endothelial integrity), which aggravate mucosal injury. Therefore, therapeutic strategies should consider leukotriene-synthesis inhibitors, histamine-, thromboxane- and platelet-activating factor receptor antagonists, oxygen radical scavengers, as well as counteracting mediators and hormones, such as prostaglandins and somatostatin, inasmuch as these compounds have been shown to additionally prevent mucosal microvascular injury, in particular capillary perfusion failure and loss of endothelial integrity, during gastric ulcer formation.

Acute-Phase Proteins↗
PubMed1994

Hepatic microcirculatory perfusion failure is a determinant of liver dysfunction in warm ischemia-reperfusion.

Hepatic ischemia-reperfusion (I/R) is characterized by circulatory and metabolic derangements, liver dysfunction, and tissue damage. However, little is known about the causative role of I/R-induced microcirculatory disturbance on the manifestation of postischemic reperfusion injury. Therefore, the intention of the study was to assess changes of hepatic microvascular perfusion (intravital fluorescence microscopy) as related to hepatic morphology (light/electron microscopy), hepatocellular integrity (serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities), and excretory function (bile flow). Sprague-Dawley rats were subjected to 20 minutes (group B, n = 9) and 60 minutes (group C, n = 9) of left hepatic lobar ischemia followed by 60 minutes of reperfusion. Sham-operated animals without ischemia served as controls (group A, n = 10). Lobar ischemia for 20 minutes followed by reperfusion resulted in a significant reduction of sinusoidal perfusion rate (93.9 +/- 1.4%; P < 0.05) and a decrease in erythrocyte flux (90.0 +/- 5.6%) when compared with controls (99.4 +/- 0.2 and 97.9 +/- 2.7%). This was accompanied by a significant increase of serum AST and ALT activities (P < 0.05) and a reduction of bile flow (P < 0.05). Prolongation of lobar ischemia (group C, 60 minutes) aggravated postischemic reperfusion injury (sinusoidal perfusion rate: 87.4 +/- 2.9%; erythrocyte flux: 62.1 +/- 8.4%) and was paralleled by severed hepatocellular damage. Electron microscopy of postischemic tissue demonstrated alteration of nonparenchymal cells (swelling of sinusoidal lining cells and widening of Disse's space) and substantial parenchymal cell damage (swelling of mitochondria, disarrangement of rough endoplasmatic reticulum, vacuolization, complete cytoplasmic degeneration). Initial postischemic increase in serum AST and ALT activities and reduction of bile flow directly correlated with the extent of microcirculatory failure (P < 0.01), ie, impairment of sinusoidal perfusion and decrease of erythrocyte flux, indicating the decisive role of microvascular perfusion failure for the manifestation of hepatic tissue damage and liver dysfunction.

Alanine Transaminase↗
PubMed1993

Cigarette smoke elicits leukocyte adhesion to endothelium in hamsters: inhibition by CuZn-SOD.

Although cigarette smoking has been identified as a major risk factor for cardiovascular diseases, the underlying pathomechanism is largely unknown. Using a dorsal skinfold chamber model in Syrian golden hamsters for intravital microscopy on striated muscle microcirculation, we investigated whether cigarette smoke (CS) affects the adhesion of circulating leukocytes to the endothelium, a constant feature of early atherogenesis and a hallmark of ischemia-reperfusion injury. Awake hamsters were exposed for 5 min to the mainstream smoke of one cigarette (2R1 research cigarette), inducing nicotine, cotinine, and carboxyhemoglobin plasma levels comparable to levels found in human smokers. In control animals (n = 7), CS exposure elicited the rolling and subsequent adhesion of fluorescently stained leukocytes to the endothelium of arterioles and postcapillary venules. Leukocyte/endothelium interaction was preceded by an early rise in xanthine oxidase activity and intravascular hemolysis. Leukocyte adhesion and xanthine oxidase (XO) activation were significantly attenuated in hamsters pretreated with superoxide dismutase (5 mg/kg, 10 min prior to CS, n = 7), suggesting a key role of superoxide in this event. These in vivo results suggest a novel pathomechanism of CS-induced cardiovascular pathology.

Animals↗
PubMed1993

Effects of Carolina rinse and adenosine rinse on microvascular perfusion and intrahepatic leukocyte-endothelium interaction after liver transplantation in the rat.

Flushing hepatic grafts immediately before revascularization with a specially designed rinse solution such as "Carolina rinse" has been reported to improve survival after liver transplantation in the rat. This study investigated the influence of Carolina rinse and adenosine rinse on early graft function, microcirculation, and leukocyte (WBC)-endothelial cell interaction of arterialized syngeneic orthotopic liver transplants in Lewis rats. Livers were preserved for 24 hr in University of Wisconsin solution and flushed immediately before reperfusion with either Ringer's lactate (group A: n = 7), Ringer's lactate + 0.2 mmol/liter adenosine (group B: n = 6), or Carolina rinse (group C: n = 7). Microvascular perfusion and WBC accumulation were assessed by intravital fluorescence microscopy. In group C, acinar perfusion was significantly improved, accompanied by a lower percentage of nonperfused sinusoids 1 hr after reperfusion (mean +/- SEM: 26 +/- 2% [group A], 21 +/- 2% [B], 11 +/- 1% [C], P < 0.01 for C vs. A or B). In addition, Carolina rinse and, to a lesser extent, adenosine rinse reduced the number of WBC sticking in sinusoids and postsinusoidal venules. Better graft function in group C was indicated by increased bile flow during the observation period of 90 min after reperfusion (0.5 +/- 0.3 ml/100 g liver [group A], 1.5 +/- 0.7 [B], 3.7 +/- 0.6 [C], P < 0.01 for C vs. A or B). We conclude that Carolina rinse is able to improve early excretory hepatocellular function, microvascular perfusion, and intrahepatic WBC accumulation after prolonged cold ischemia and reperfusion, but adenosine is unlikely to be the key component of this rinse solution.

Adenosine↗
PubMed1993

Oxidized LDL-induced leukocyte/endothelium interaction in vivo involves the receptor for platelet-activating factor.

Leukocyte adhesion and subendothelial emigration, constant hallmarks of early atherogenesis, have been ascribed to the action of oxidized low-density lipoprotein (oxLDL). Using intravital fluorescence microscopy in the skinfold-chamber model in hamsters, we have previously shown that systemic administration of oxLDL stimulates leukocyte adhesion in vivo through a mechanism that depends on the generation and/or action of both leukotrienes and superoxide radicals. On the basis of the fact that oxygen radical-catalyzed peroxidation of phospholipids results in the generation of fragments with short sn2 residues, which besides authentic platelet-activating factor (PAF), activate the receptor for PAF on leukocytes and thereby induce leukocyte adhesion, we asked whether pretreatment of hamsters with a specific PAF receptor antagonist (WEB2170; 1 mg/kg of body weight IV, 10 minutes before oxLDL) attenuates leukocyte adhesion after injection of oxLDL (4 mg/kg of body weight IV, oxidized by 7.5 mumol/L Cu2+ for 18 hours at 37 degrees C). We demonstrate herein that in contrast to untreated control animals in which oxLDL elicited rolling and adhesion of circulating leukocytes to the endothelium of venules and arterioles, oxLDL-induced leukocyte adhesion was significantly attenuated in WEB2170-pretreated animals. These changes cannot be ascribed to alterations of microhemodynamic parameters and, hence, wall shear conditions. This finding indicates that oxLDL-induced leukocyte/endothelium interaction involves the PAF receptor, which may function both as a receptor for authentic PAF or for PAF-like lipids that are generated in a free radical-catalyzed peroxidation of phospholipids.

Animals↗
PubMed1993

Dextran vs. hydroxyethylstarch in inhibition of postischemic leukocyte adherence in striated muscle.

Microvascular injury associated with ischemia/reperfusion (I/R) is characterized by both "no reflow" and "reflow paradox." Prophylactic isovolemic hemodilution with dextran 60 to a hematocrit of 30% has been shown to prevent I/R-induced capillary no reflow in striated muscle. The objective of the present study was to analyze whether hemodilution prior to ischemia has the potential to reduce postischemic leukocyte-endothelium interaction, which is known to be one of the major components of I/R-induced reflow paradox. Syrian golden hamsters (n = 21) were fitted with a dorsal skinfold chamber, which contains striated muscle and subcutaneous tissue and allows for repetitive analyses of the microcirculation by means of intravital fluorescence microscopy. Four hr of pressure-induced ischemia and 30 min of subsequent reperfusion (controls, n = 7) resulted in a significant (P < 0.05) increase of microvascular leukocyte accumulation (40,630 +/- 12,731 mm-3) and adherence to the endothelial lining of postcapillary venules (74.2% +/- 11.5%) when compared to preischemic baseline (7,502 +/- 1,700 mm-3 and 3.4% +/- 1.0%, respectively). Recovery was not complete after an observation period of 24 hr reperfusion [13,735 +/- 2,666 mm-3 (P < 0.05) and 18.5% +/- 6.0% (P < 0.05)]. Prophylactic isovolemic hemodilution with 6% dextran 60 (Dx60) to a hematocrit of 30% (Dx60, n = 7) significantly attenuated postischemic leukocyte accumulation (23,402 +/- 13,837 mm-3; P < 0.05 vs. controls) and adherence (22.6% +/- 6.4%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Dorsal skinfold chamber technique for intravital microscopy in nude mice.

For many years, observation chambers, implanted in various animal species and in man, have been used for intravital microscopy of the microcirculation in granulation tissue, preformed tissue, or of the microvascularization of tissue implants. We describe herein a skinfold chamber model for the intravital microscopic investigation of striated skin muscle in immunoincompetent, nude mice over a minimum period of 2 weeks. Using fluorescent markers for contrast enhancement of plasma (fluorescein isothiocyanate-dextran) and leukocytes (acridine orange), the presented model allows the quantitative analysis of 1) the microhemodynamic parameters microvessel diameter and red blood cell velocity in arterioles (16 to 50 mu diameter), capillaries (4 to 9 mu diameter), and post-capillary venules (19 to 60 mu diameter), 2) leukocyte/endothelium interaction in these vessel segments, 3) functional capillary density and intercapillary distance, and 4) endothelial cell integrity. These parameters can be assessed in the microcirculation of the striated muscle tissue under normal or pathological conditions, as well as in the microcirculation of transplanted xenogeneic (human) neoplastic and non-neoplastic tissue grafts.

Animals↗
PubMed1993

Stimulation of leukocyte/endothelium interaction by oxidized low-density lipoprotein in hairless mice. Involvement of CD11b/CD18 adhesion receptor complex.

BACKGROUND: The adhesion of leukocytes to the vascular endothelium has been identified as a constant, early feature of atherogenesis. Using a skinfold chamber model in hamsters for intravital microscopy, we have recently demonstrated the chemotactic and adhesion-promoting action of oxidatively modified low density lipoprotein (oxLDL) in vivo. EXPERIMENTAL DESIGN: In order to rule out a species specificity of the experimental approach, and to investigate the involvement of leukocyte adhesion receptors in oxLDL-induced leukocyte/endothelium interaction, we have adapted the skinfold chamber model to hairless mice. Using intravital fluorescence microscopy, leukocyte/endothelium interaction in a fine striated skin muscle was assessed during the time course after intravenous injection of native human LDL (4 mg/kg body weight) and oxLDL (oxidized in vitro by 7.5 microM Cu2+, 6 hours, 37 degrees C) into control mice and into mice pretreated with either the selective inhibitor of leukotriene biosynthesis MK-886 (20 mumol/kg body weight, intravenously, 10 minutes before oxLDL) or with a monoclonal antibody directed towards the CD11b subunit of the CD11b/CD18 adhesion receptor complex on leukocytes (monoclonal antibody anti-Mac1, 0.5 mg/kg, iv, 10 minutes before oxLDL). RESULTS: We demonstrate in this study that injection of oxLDL (4 mg LDL-cholesterol/kg, intravenously, oxidized by 7.5 microM Cu2+, 6 hours, 37 degrees C), but not of native LDL or LDL-free Cu(2+)-solution, elicits the adhesion of fluorescently stained leukocytes to the endothelium of postcapillary venules (173 +/- 75 cells/mm2 at 20 minutes after oxLDL, mean +/- SD) and arterioles (119 +/- 74 cells/mm2 at 20 minutes after oxLDL, mean +/- SD) in the mice. OxLDL-induced leukocyte adhesion was entirely prevented by pretreatment of the animals with the inhibitor of leukotriene biosynthesis or with monoclonal antibody anti-Mac-1. CONCLUSIONS: These results demonstrate the involvement of leukotrienes and of the CD11b/CD18 adhesion receptor complex in oxLDL-induced leukocyte adhesion in vivo and rule out a species specificity of this pathophysiologic event.

Animals↗
PubMed1993

Differential impact of Carolina rinse and University of Wisconsin solutions on microcirculation, leukocyte adhesion, Kupffer cell activity and biliary excretion after liver transplantation.

This quantitative in vivo fluorescence microscopy study investigated the relative impact of an optimized rinse solution (warm Carolina rinse) and that of an established storage solution (University of Wisconsin solution) on various pathomechanisms of hepatic reperfusion injury after cold storage. Syngeneic orthotopic, arterialized liver transplantation was performed in male Lewis rats after 24 hr of cold ischemia (n = 24). The four experimental groups differed according to the type of preservation/rinse solution used: University of Wisconsin solution/albumin rinse (group 1), autologous blood (just external cooling)/albumin rinse (group 2), blood/Carolina rinse (group 3) and University of Wisconsin solution/Carolina rinse (group 4). Hepatic microvascular perfusion, leukocyte accumulation and phagocytic activity of Kupffer cells were assessed by means of intravital fluorescence microscopy 30 to 90 min after reperfusion. Disturbances of microvascular perfusion were most pronounced in group 2, markedly reduced by University of Wisconsin solution (group 1) and Carolina rinse (group 3) and minimized by combined use of University of Wisconsin solution and Carolina rinse in group 4. Intrahepatic leukocyte-endothelium interaction in sinusoids and postsinusoidal venules was found to depend on the application of Carolina rinse before reperfusion rather than the use of University of Wisconsin solution during cold storage. Activation of phagocytosis by Kupffer cells was most pronounced in group 1, intermediate in groups 2 and 3 and not noticeable in group 4. Hepatocellular excretory function as assessed on the basis of total bile flow and excretion of bile acids during the first 90 min after reperfusion was found to be improved by application of Carolina rinse, both after storage in blood or in University of Wisconsin solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1993

Role of leukocytes in the initial hepatic microvascular response to endotoxemia.

INTRODUCTION: Accumulation and adherence of leukocytes within the hepatic microvasculature have been emphasized to play a major role in the pathogenesis of endotoxin/lipopolysaccharide (LPS)-induced liver injury. However, there is no information on their interrelation with hepatic microvascular perfusion failure, hepatocellular damage and liver dysfunction following LPS exposure. AIM AND METHODS: Therefore, we quantitatively assessed the initial LPS-induced hepatic microvascular response, including leukocyte-endothelium interaction and their interrelation with sinusoidal perfusion, hepatocellular integrity (serum AST/ALT activity) and excretory function (bile flow). After infusion of LPS (E. coli 0128:B12; 10 mg.kg-1 i.v.) intravital fluorescence microscopy was applied to livers of Sprague-Dawley rats. RESULTS: 1 h after LPS exposure deterioration of hepatic microcirculation was hallmarked by significant accumulation of leukocytes, stagnant within sinusoids and adherent to the endothelial lining of postsinusoidal venules. This was accompanied by a progressive increase of the number of non-perfused sinusoids (20 +/- 4%). During the 1 h period after LPS exposure, bile flow was found significantly (p < 0.05) reduced, while serum AST/ALT activities remained unchanged. Leukocytes appear to contribute to sinusoidal perfusion failure, since the number of non-perfused sinusoids significantly (p < 0.01) correlated with the number of leukocytes stagnant within the sinusoids. In addition, the inverse correlation (p < 0.01) of bile flow with the number of both, leukocytes stagnant within the sinusoids and non-perfused sinusoids indicates that microvascular injury initiates hepatic dysfunction. CONCLUSION: Inasmuch as LPS exposure initially induces only microcirculatory disturbances without substantial loss of hepatocellular integrity, we propose that therapeutic strategies during early endotoxemia should focus on attenuation of microvascular injury to prevent manifestation of hepatocellular damage.

Animals↗