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B Vollmar

Publications and source records attributed to B Vollmar.

At least 91 records · Page 5Linked to original sources
PubMed1999

Microvascular response to compartment syndrome-like external pressure elevation: an in vivo fluorescence microscopic study in the hamster striated muscle.

OBJECTIVE: To quantitatively assess the nature and the magnitude of the microvascular response of striated muscle tissue upon elevation of external pressure, as in compartment syndrome. METHODS: Using the skinfold chamber model in Syrian golden hamsters and intravital fluorescence microscopy, we studied the individual response of the different segments of the microcirculation, i.e., the arterioles, capillaries, and postcapillary venules, in terms of vasomotor control (change of vessel diameter) and cessation of blood flow upon defined changes in external tissue pressure. RESULTS: The unique findings of our study are that (1) arteriolar flow ceased at mean external pressures of 25.6+/-2.4, 28.3+/-2.8, 34.5+/-4.6, and 44.4+/-6.8 mm Hg in vessels with diameters of less than 20, 20 to 40, 40 to 60, and greater than 60 microm, respectively, without signs of spasm or collapse even at a pressure maximum of 70 mm Hg, whereas (2) in venules the increase of external pressure was associated with a diameter reduction ranging from 5 to 25% with cessation of blood flow at mean external pressures between 27 and 33 mm Hg. Blood flow ceased in 50% of the muscle capillaries already at an external pressure of 12 mm Hg. Thus, at distinct external pressure levels venous and capillary blood flow ceased, but arterioles were still capable of carrying flow, which was directed along arteriolo-arteriolar "thoroughfare" channels. To restart blood flow, external pressure had to be decreased by 9, 11, 15, and 17 mm Hg in arterioles with diameters of less than 20, 20 to 40, 40 to 60, and greater than 60 microm, and by approximately 9 mm Hg in venules regardless of vessel diameter. Capillary blood flow was found to be restored at a mean reduction of external tissue pressure of approximately 4 mm Hg. CONCLUSION: Our study disproves the critical closing theory but complies-in particular because of the supposed constriction-induced increase of venular resistance-with the hypothesis of reduced arteriovenous pressure gradients as the cause of flow cessation in compartment syndrome. The necessity of a substantially increased perfusion pressure gradient to restart blood flow in arterioles, capillaries, and venules confirms the existence of yield stress in these microvessels. The high susceptibility of capillaries to elevated external pressure indicates the necessity of early fasciotomy to restore impaired nutritive circulation in cases of compartment syndrome.

Animals↗
PubMed1999

A chronic model for intravital microscopic study of microcirculatory disorders and leukocyte/endothelial cell interaction during normotensive endotoxemia.

Sepsis-induced microvascular leukocyte/endothelial cell interaction may result in a deterioration of capillary perfusion that finally leads to septic organ dysfunction. The aim of the present study was to characterize a novel, sublethal, two-hit model of chronic systemic sepsis that allows the repeated analysis of microcirculation by intravital microscopy. In Syrian golden hamsters the effect of a single i.v. endotoxin (LPS, 2 mg/kg, E. coli) injection (SH-LPS group, n = 5 animals) vs. a double LPS injection (DH-LPS group, n = 6 animals) was analyzed. After monitoring baseline parameters (t1), measurements were performed at 30 min (t2), 3 h (t3), 8 h (t4), 24 h (t5), 48 h (t6), 56 h (t7) and 72 h (t8) (both groups) after initial LPS exposure. In DH-LPS animals, a second LPS injection (2 mg/kg) was given at t6 (48 h). Intravital fluorescence microscopy was performed in a dorsal skin fold chamber preparation and allowed determination of leukocyte-endothelial cell interaction (leukocyte rolling and sticking), and measurement of functional capillary density (FCD), which served as a measure of capillary perfusion. The first LPS injection comparably altered leukocyte/endothelial cell interaction and capillary perfusion in both groups (t1-t6, P > 0.05, MANOVA). Between t6 and t8 leukocyte adherence decreased in SH-LPS animals, whereas in DH-LPS animals adherence remained constantly elevated (SH-LPS: -53.0 +/- 6.2% between t6 and t8 vs. DH-LPS: -3 +/- 5; P < 0.05). The ongoing inflammatory response in DH-LPS animals was associated with a progressive deterioration of FCD, whereas FCD remained constant in SH-LPS animals (DH-LPS: -71.5 +/- 17% between t6 and t8 vs. SH-LPS: 3.0 +/- 13%; P < 0.05). In parallel, coagulatory parameters were found significantly altered only in DH-LPS animals but not in SH-LPS animals. We conclude that "double hit" LPS exposure is an appropriate model (i) to analyze repeatedly over time microcirculatory disorders under conditions of persistent endotoxemia-induced inflammatory response, and (ii) to prove the effectiveness of novel anti-inflammatory strategies.

Animals↗
PubMed1999

Role of TNF-alpha in local surgical trauma-induced microvascular dysfunction.

BACKGROUND/AIM: The aim of this study was to gain insight into the mechanisms of microvascular dysfunction after local surgical trauma. METHODS: The effect of anti-tumor necrosis factor (TNF)-alpha antibody (Ab) on microvascular function, including arteriolar diameter response, nutritive perfusion, leukocyte-endothelial cell interaction and endothelial integrity disruption, was studied in hamster skinfold chamber preparations using intravital fluorescence microscopy. RESULTS: Directly after the surgical procedure, arteriolar diameters were found to be markedly (p < 0.05) reduced, but recovered significantly at 8 h and reached plateau levels after 24 h. Surgical trauma further induced a strong inflammatory response characterized by a significant (p < 0.05) increase in leukocyte adherence to the endothelium of postcapillary venules. This inflammatory response was associated with an increase in microvascular permeability, indicating endothelial integrity disruption. Anti-TNF-alpha Ab had no significant effect on the surgical trauma-induced arteriolar vasomotor dysfunction; however, it effectively (p < 0.05) reduced venular leukocyte adherence and attenuated the increase in microvascular permeability. CONCLUSION: Our study indicates that arteriolar constriction, leukocyte-endothelial cell interaction and endothelial macromolecular leakage have to be considered as the characteristic microvascular response after local surgical trauma. It is conceivable that TNF-alpha plays a role in mediating the inflammatory response, but not the dysfunction of vasomotor control.

Animals↗
PubMed1999

[Laparoscopic-transperitoneal and lumboscopic-retroperitoneal surgery of the spine. Developments from animal experiments for use in clinical practice].

With the use of an in vivo porcine training model we established the transperitoneal laparoscopic approach for the instrumentation of anterior lumbar spine fusion with Bagby-and-Kuslich (BAK) interbody implants as well as "Brantigan" cages. The transperitoneal laparoscopic approach caudally from the aortic bifurcation allows the spine fusion procedure of the caudal but not of the cranial part of the lumbar spine. Because ventral stabilization of the upper lumbar spine is frequently necessary, in particular in trauma patients with spine body fractures, an additional retroperitoneal minimal-invasive (lumboscopic) approach was established using again the in vivo porcine training model. We demonstrate that via this approach spine fusion can easily be performed including the Th12 segment after fenestration of the diaphragm. With the experience from the in vivo experiments, both techniques could safely and successfully be transferred to clinical practice with the advantage of markedly reducing the extent of operative trauma compared with the corresponding open approaches.

Animals↗
PubMed1999

Role of microcirculation in hepatic ischemia/reperfusion injury.

There is a large body of evidence that the liver microcirculation has to be considered as a major target in hepatic ischemia/reperfusion injury. The nature of microvascular injury, which precedes manifestation of hepatic parenchymal tissue damage, includes both hypoxia due to lack of microvascular perfusion (i.e. no-reflow), and a reperfusion-associated inflammatory response, which includes the activation and dysfunction of leukocytes and Kupffer cells (the reflow paradox). No-reflow in sinusoids is thought to be caused by endothelial cell swelling and intravascular hemoconcentration, and involves also a deterioration of the balance between ET and NO. The reflow paradox is associated with: (i) the release and action of proinflammatory cytokines (TNF-alpha, IL-1) and oxygen radicals; (ii) the up-regulation of endothelial and leukocytic adhesion molecules (selectins, beta-integrins, ICAM-1); and (iii) the interaction of leukocytes with the endothelial lining of the hepatic microvasculature.

Animals↗
PubMed1999

Intravital microscopy for the study of the microcirculation in various disease states.

The study of the microcirculation by intravital microscopy represents a sophisticated research tool to analyse complex biological interactions and disease mechanisms as well as to develop and test novel prophylactic and therapeutic approaches aimed at the prevention or attenuation of manifestation of disease-associated microvascular disorders and cellular dysfunction. This may include pathogenesis of atherosclerosis and thrombosis, fibrosis and cirrhosis as well as hypertension, diabetes and tumorogenesis. In addition, using the microscopic technique, circulatory and cellular disorders in surgical diseases and procedures, such as shock and resuscitation, ischaemia/reperfusion and transplantation, trauma, sepsis and inflammation, as well as burn injury and wound healing, may be analysed. With the background of the increasing knowledge of molecular and cellular mechanisms of disease evaluated in vitro, the technique of intravital microscopy ideally allows to bridge over from those in vitro observations to test their potential relevance in vivo.

Animals↗
PubMed1999

Surface cooling inhibits tumor necrosis factor-alpha-induced microvascular perfusion failure, leukocyte adhesion, and apoptosis in the striated muscle.

BACKGROUND: Surface cooling is frequently used in a number of conditions, especially traumatic, ischemic, burn, and neurologic injury to reduce the tissue damage. However, the protective mechanisms of cold therapy on traumatized tissues remain unclear. Tumor necrosis factor-alpha (TNF-alpha) is a fundamental mediator in inflammatory reactions and trauma-induced tissue injury. In the present study, we examined the microvascular response to TNF-alpha challenge and the effects of local cooling on the TNF-alpha-induced changes in the striated muscle of hamsters. METHODS: By the use of the dorsal skinfold chamber preparation and in vivo fluorescence microscopy in combination with computer-based image analysis, we determined TNF-alpha-induced leukocyte rolling and adhesion to microvascular endothelium, capillary perfusion, venular leakage, and cellular apoptosis with and without surface cooling. RESULTS: We found that topical administration of 2000 units TNF-alpha caused a progressive impairment of microvascular perfusion and increased leukocyte recruitment and vascular macromolecular leakage. Local cooling to 10 degrees C for 60 minutes markedly (P < .05) inhibited the TNF-alpha-induced capillary perfusion failure and leukocyte response and slightly attenuated the increase of microvascular permeability after 180 minutes of stimulation. Furthermore, it was observed that 24 hours of TNF-alpha stimulation increased the number of apoptotic cells (i.e., nuclear condensation and fragmentation) by 10-fold. This TNF-alpha-mediated effect was almost abolished by treatment with local hypothermia. CONCLUSION: These data suggest that the protective effect of surface cooling of traumatized tissue is due to its attenuation of the microvascular inflammatory response associated with the inhibition of the process of apoptosis.

Animals↗
PubMed1998

An intravital fluorescence microscopic study of hepatic microvascular and cellular derangements in developing cirrhosis in rats.

Quantitative data defining the relationship between the hepatic microcirculation and the development of liver pathological changes could provide a basis for a better understanding of fibrogenic processes, such as cirrhosis. Therefore, we established the technique of intravital fluorescence microscopy and computer-assisted microcirculation analysis systems in developing cirrhosis in rats with the aim of quantitatively assessing the association of hepatic microvascular morphology with its disordered acinar architecture, and nonparenchymal cell transformation with collagen deposition, parenchymal cell loss, and liver dysfunction. In animals chronically exposed to carbon tetrachloride (CCl4), the most significant microvascular changes progressively observed in vivo were the concomitant appearance of 1) sinusoid-free space around dilated postsinusoidal venules with 2) substituting occurrence of yellow-green autofluorescent collagen deposition, 3) reduction in sinusoidal density, but 4) increase of vascular lumen caused by the formation of shunting vessels bypassing the sinusoids. Present on-line analysis further indicated the local coincidence of changed spatial distribution of Ito cells (accumulation of vitamin A ultraviolet autofluorescence in zone 3) with fibrotic autofluorescent septa, causing significant collapse of parenchymal tissue (hepatocellular bis-benzamide fluorescence) and diminution of hepatocellular excretory function (bile flow). Regression analysis revealed strong correlations between loss of parenchymal tissue and both collagen deposition and sinusoidal rarefication, as well as between sinusoidal rarefication and collagen deposition. Thus, sequential in vivo analysis presented herein provides the new information on the concomitant onset of cellular, fibrotic, and microvascular changes in developing fibrosis/cirrhosis, excluding that distinct cellular or fibrotic alterations are a prerequisite for the manifestation of microcirculatory and vascular derangements or vice versa.

Animals↗
PubMed1998

Microscopic analysis of NADH fluorescence during aerobic and anaerobic liver preservation conditions: A noninvasive technique for assessment of hepatic metabolism.

Gaseous insufflation of oxygen via the venous vascular system is thought to be an useful tool for preventing anoxic tissue injury during extended time periods of ischemic preservation and for allowing for an improved recovery of organ function after transplantation. The present study aimed at the application of a noninvasive technique for monitoring effectiveness and homogeneity of gaseous areation by using an epiillumination microscopic technique for assessment of tissue nicotinamide adenine dinucleotide (NADH) fluorescence. Rat livers were flushed with and stored in University of Wisconsin solution at 4 degrees C for 48 h (n = 20). In half of the experiments (n = 10) gaseous oxygen was applied subsequent to organ harvest. Using ultraviolet-excitation high-resolution microscopy and computer-assisted image analysis liver surfaces were scanned for NADH intensity and spatial heterogeneity at 1, 24, and 48 h preservation time. Livers simply stored without aeration served as controls (n = 10). NADH intensity data were compared with corresponding data of tissue adenosine triphosphate (ATP) concentrations determined enzymatically. NADH fluorescence already differed at 1 h preservation between the two groups with significantly lower values in the aerobically stored livers. NADH fluorescence further decreased between 1 and 24 h preservation and remained low until 48 h, whereas in the anaerobically stored livers NADH fluorescence was found to be constantly high over the entire observation period. Aerobic storage resulted in rather homogeneous tissue oxygenation with an intrahepatic variation of NADH fluorescence <20%. In parallel, oxygen persufflation appropriately restored tissue ATP content within 1 to 24 h of preservation, while the simply stored livers exhibited pronounced depletion of ATP. We demonstrate for the first time that by means of retrograde gaseous oxygenation, ischemic livers can be readily and effectively oxygenated. Our study further indicates that the noninvasive microscopic analysis of tissue NADH fluorescence may be an useful tool for estimating efficiency of strategies in organ preservation.

Adenosine↗
PubMed1998

In vivo analysis of microvascular injury after myocardial cryothermia.

We studied microvascular injury after myocardial cryothermia in rats using intravital fluorescence microscopic techniques. Cryolesions were induced to the right ventricle by freezing with -160 degrees C (probe diameter: 5 mm) for a total of 5 min. Fluorescence microscopy was performed at 15, 30, 60, 90, and 120 min as well as at 3 and 7 days after cryothermia. Analysis of the epicardial microvasculature 15 min after cryothermia revealed an area of 24.6 +/- 3.8 mm2 of nonperfused tissue, which was reduced to 5.3 +/- 1.5 mm2 (P < 0.05) after the initial 2-h observation period. Vital microscopic images of reperfused tissue characteristically demonstrated extravasation of the macromolecular fluorescent tracer FITC-dextran (21.7 +/- 3.4 mm2), suggesting substantial loss of endothelial integrity. In vivo propidium iodide staining confirmed membrane damage of microvascular endothelial cells. Three days after cryoinjury the area of nonperfused tissue was reduced further to 1.1 +/- 0.4 mm2 in the center of the lesion, while the area of perfused tissue with disruption of endothelial integrity was found significantly increased to 47.4 +/- 5.9 mm2 (P < 0.05) toward the periphery. Analysis at 7 days revealed endothelial repair at the periphery of the cryolesion, but now a central necrotic area was found demarcated (nonperfused), presenting with a size (26.0 +/- 3.5 mm2) similar to that shown during the very early (15 min) reperfusion period. Our study demonstrates recovery of microvascular perfusion during the first hours and days after myocardial cryothermia. This is, however, associated with endothelial injury, i.e., damage of plasma membrane and loss of barrier function. Infarction with capillary perfusion failure is evident at 7 days with a size which strikingly corresponds to the sizeof nonperfused tissue observed immediately after cryointervention.

Animals↗
PubMed1998

A novel approach for comparative study of periosteum, muscle, subcutis, and skin microcirculation by intravital fluorescence microscopy.

Herein, we report a new model, which allows comparative study of the microcirculation of different peripheral tissues, i.e., periosteum, skeletal muscle, subcutis, and skin. Using dextran-insensitive Wistar rats gracilis and semitendinosus muscles of the left hindlimb were prepared in association with their appertaining tibial fragments, subcutis, and skin. Blood supply was guaranteed by the femoral artery via the saphenous vessels. High-resolution intravital epi-illumination microscopy of the two muscles displayed the typical microvascular architecture with the capillaries running in parallel to each other (capillary density (CD) 128.4 +/- 4.5 cm-1). In subcutis and skin, capillaries were found arranged as interconnecting mesh-like networks with a density, which was significantly higher (P < 0.05) in subcutis (191.0 +/- 5.5 cm-1) compared with skin (108.9 +/- 3.3 cm-1). Analysis of periosteal tissue revealed two distinct types of arrangements of microvascular architecture. Adjacent to the major feeding and draining vessels of the periosteum, capillaries were organized in densely meshed shunt-like networks, revealing the highest capillary density (242.7 +/- 13.2 cm-1; P < 0.05) of all tissues studied. Periosteal capillaries distant from the major feeding and draining vessels were arranged in parallel to the longitudinal axis of the tibial bone and presented with a density similar to that of the skeletal muscle (128. 6 +/- 9.4 cm-1). Topical application of acetylcholine for analysis of physiological reactivity of the microvasculature showed dose-dependent arteriolar dilation. Moreover, a 3-min upstream femoral artery occlusion demonstrated an appropriate hyperemic response in all tissues studied, indicating intact myogenic control. A prolonged period of ischemia (120 min) followed by reperfusion (60 min) caused massive (P < 0.05) leukocyte-endothelial cell interaction in postcapillary venules, similarly as reported in other microvascular tissue preparations. We propose that the model presented provides a good approach to all peripheral tissues for both the analysis of the physiology of tissue-confined microvascular control and the development of novel therapeutic strategies to counteract manifestation of nutritional dysfunction and inflammatory response in disease.

Acetylcholine↗
PubMed1998

Cold preservation of the small intestine with the new Celsior-solution. First experimental results.

The aim of the present study was to evaluate the potential of Celsior, a recently developed cardioplegic and heart storage solution, to protect the small bowel during ischemic storage. Small bowel segments were isolated from rats, flushed with either UW or Celsior solution, and cold-stored for 18 h at 4 degrees C in the respective solution. After ischemic storage, some preparations were freeze-clamped for analysis of tissue metabolites while other preparations were tested for structural and functional integrity by isolated perfusion in vitro using a previously validated model. After 18 h of ischemic storage no significant differences were seen between Celsior and UW with regard to the development of edema, energy charge, or creatine phosphate, but lactate accumulation was significantly reduced in the Celsior group, although glucose catabolism was not inhibited. Histological evaluation of the cold-stored organs showed no differences with regard to structural integrity between the two groups. Total vascular resistance upon reperfusion was significantly lower in the Celsior group (666 +/- 126 vs 827 +/- 88 MPa s m-3*), as was the intestinal release of LDH (9.7 +/- 4.4 vs 18.2 +/- 4.6 U/l*). Carbohydrate absorption from the intestinal lumen amounted to venous effluent concentrations of 0.58 +/- 0.24 vs 0.18 +/- 0.15 mg% * of galactose in the Celsior and UW groups, respectively. Within the limits of this in vitro pilot study, Celsior provided better postischemic recovery of the small bowel than UW in terms of vascular perfusion characteristics, enzyme release, and carbohydrate absorption and may, thus, be considered a suitable alternative for intestinal organ preservation.

Adenosine↗
PubMed1998

Failure of Kupffer cell blockade to prevent disseminated intravascular coagulation in endotoxemic rats despite improved survival.

OBJECTIVE: Studies were conducted to evaluate the impact of gadolinium chloride (GdCl3), an agent which blocks the phagocytosis of liver macrophages (Kupffer cells, KC), on the coagulation system and on mortality in a model of rats subjected to a lethal dose of Escherichia coli lipopolysaccharide (LPS) (10 mg/kg body weight, intravenously). METHODS: Rats were either pretreated with GdCl3 (10 mg/kg, i.v., 48 h and 24 h prior to LPS exposure) or saline vehicle. A variety of coagulation parameters such as activated partial prothrombin time (aPTT), fibrinogen, systemic platelet count, antithrombin III (AT III), and activities of factors V, VII, and XII were monitored in the early (1 h) and late time course (16 h) following administration of E.coli LPS. RESULTS: The administration of LPS resulted in the development of disseminated intravascular coagulation (DIC) and was associated with a mortality rate of 47% within 16 h. Blockade of KC by GdCl3 completely abolished LPS-related mortality (0%). However, despite improved survival, GdCl3 failed to prevent laboratory and clinical signs of DIC. GdCl3 per se even contributed to coagulatory and fibrinolytic disorders. CONCLUSION: These results confirm reports on the protective potential of GdCl3 pretreatment in experimental endotoxemia. However, the present study does not support the concept of DIC as a strong prognostic criterion for the outcome of sepsis and septic shock. Furthermore, the results presented suggest a minor role for KC in LPS-mediated activation of coagulation and indicate an involvement of KC in LPS-associated lethality independent of the coagulation system.

Animals↗
PubMed1998

The use of intravital microscopy in surgical research. 26-years of experience analyzed by studies presented at the Surgical Forum of the Annual Congress of the German Society of Surgery.

Recent developments in intravital microscopy make this technique an attractive approach to studying microvascular, cellular, and molecular mechanisms of distinct surgical diseases. We investigated the value of this technique in surgical research laboratories by analyzing the studies presented during the past 26 years (1972-1997) at the Surgical Forum of the Annual Congress of the German Society of Surgery. From a total of 2279 papers 188 contributions (8.3%) presented data which derived from the analysis of the microcirculation using techniques, such as H2 and 133Xe clearance, autoradiography, thermodiffusion, laser Doppler fluxmetry, laser speckle, radioactive and fluorescent microspheres, polarographic oximetry, and intravital microscopy. There were 72 presentations (3.2% of all contributions) reporting the use of intravital microscopy, thus reflecting 38.3% of all microcirculatory analyses. Although these numbers may be considered quite small, analysis over time revealed a significant (P<0.05) increase in the number of microcirculatory studies (11.4%) and in particular of those using intravital microscopy (6.3%) in the 1990s when compared to the 1970s (5.3%; 0.1%) and 80th (7.1 %; 1.3%). In 1997, 27 of 165 contributions (16.4%) included microcirculatory analyses, and 18 of the 165 contributions (10.9%) reported results analyzed by intravital microscopy. Thus our analysis reflects an increasing interest of surgical researchers to study in vivo the microcirculation, and by doing so to use intravital microscopy for the elucidation of mechanisms of surgical disease.

Germany↗
PubMed1998

Cell surface and nuclear changes during TNF-alpha-induced apoptosis in WEHI 164 murine fibrosarcoma cells. A correlative light, scanning, and transmission electron microscopical study.

Tumour necrosis factor (TNF)-alpha-induced apoptosis is associated with several nuclear and cell surface alterations, in particular with the condensation of chromatin and the fragmentation of the cell nucleus, formation of blebs on the cell surface and breakdown of the plasma membrane. However, there is little information about the relationship between the cell surface alterations and the nuclear changes during apoptosis. To study this, cultured WEHI cells were exposed to TNF-alpha over different time periods. The cytological changes were studied using a correlative approach, which allowed observation of the same cell consecutively under light, scanning and transmission electron microscopy. The earliest sign of cell alteration was a reduction of the number of microvilli after 15 min of TNF-alpha exposure. This reaction was reversible (reappearance of microvilli) and took place during the first hour, in which neither nuclear alterations nor plasma membrane breakdown were observed. The changes in the nucleus began with condensation of chromatin after approximately 1 h of TNF-alpha-exposure. After 4-5 h the microvilli disappeared again, particularly in areas where the formation of blebs (blebbing) was observed. Strikingly, cell surface alterations (bleb formation) were detected only in those cells that presented with condensed chromatin, and not in cells with a normal chromatin pattern, proving at least a close correlation between nuclear and cell surface changes during the process of apoptosis.

Animals↗