Microvascular consequences of Kupffer cell modulation in rat liver fibrogenesis

The process of Ito cell activation, which is thought to be the central pathogenic mechanism in liver fibrogenesis, may involve distinct interactions with Kupffer cells (KCs) mediated by various cytokines and growth factors. The aim of this study was to determine whether targeting KC function using gadolinium chloride (GdCl(3)) interferes with the manifestation of carbon tetrachloride (CCl(4))-induced hepatic fibrosis, placing special emphasis on the process of microvascular remodelling. Using in vivo fluorescence microscopy, characteristic microvascular features of CCl(4)-induced liver fibrosis, progressively observed within the 8-week period of toxin exposure, were the significant reduction in sinusoidal density; the increase of venular vascular space; the perivenular accumulation of Ito cells, with concomitant collagen deposition; and the collapse of parenchymal tissue. GdCl(3) effectively attenuated sinusoidal rarefaction and delayed, but did not prevent, the process of Ito cell activation-associated collagen deposition. Strikingly, the 8-week modulation of KC function by GdCl(3) exhibited sustained hepatocellular fatty vacuolation with organ weight increase, liver enzyme release, and bile flow reduction. Thus, GdCl(3) treatment attenuates the hepatic microvascular response, but favours fatty change and only delays the development of liver fibrosis following CCl(4)-exposure.

Glioma cell migration is associated with glioma-induced angiogenesis in vivo

To simultaneously assess glioma cell invasion and glioma angiogenesis in vivo by non-invasive and quantitative means, DiI-labeled C6 glioma spheroids were implanted into the dorsal skinfold chamber preparation of nude mice (n = 6). Heat-inactivated spheroids served as controls to distinguish between active and passive cell spread. Using multi-fluorescent intravital videomicroscopy, glioma cell migration was analyzed on days 1-4, 6, and 10 and spheroid vascularization was analyzed on days 3, 6, and 10 after implantation. Additionally, C6 glioma spheroids were implanted into the chronic cranial window of nude mice as an orthotopic implantation site (n = 4). In the dorsal skinfold chamber, spheroids were vascularized within 10 days and revealed a tumor-specific microvasculature. In parallel, individual glioma cells detached from the spheroid edge and migrated centrifugally demonstrating an affinity to tumor and host vessels. Glioma cells demonstrated a heterogeneous pattern of their regional migratory activity (0.2-9.6 microm/h) which correlated well with regional glioma angiogenesis (r = 0.733). Using the cranial window, glioma cells spread similarly demonstrating an affinity to the perivascular space of pial/subpial vessels with preference to the arteriolar segments. Intravital fluorescence microscopy represents a versatile technique to assess the complex relationship between glioma-driven angiogenesis and glioma cell invasion.

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.

Secondary ischaemia in experimental free flaps--treatment by long acting prostacyclin analogues

Secondary postoperative ischaemia due to venous occlusion is the most detrimental insult to free microvascular flaps. In an experimental rat free flap model the efficacy of long acting prostacyclin analogues iloprost (Ilomedin) and cicaprost in venous occlusion induced postoperative ischaemia was studied. Free, microvascular groin flaps were transplanted to the neck and the draining veins were temporarily occluded on the first postoperative day for a total of 20 min. In the untreated control group, haemorrhagic flap necrosis occurred. Intravital microscopy after secondary ischaemia revealed flap areas without reperfusion. The functional vessel density was significantly reduced. Reperfused capillaries were tortuous and significantly dilated. After reperfusion the interstitial leakage of macromolecular dextran increased, indicating loss of microvascular endothelial integrity. Intraarterial and intravenous applications of iloprost were able to diminish the ischaemic effects, giving a flap survival rate of 83%. Similar results were obtained by intravenous and enteral administration of cicaprost. Transcutaneous oxygen partial pressure measurements confirmed the viability of the surviving flaps. We conclude that both iloprost and cicaprost are effective in preventing venous occlusion induced failure of free microvascular groin flaps.

[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.

Differential effect of anti-TNF-alpha antibody on proinflammatory cytokine release by Kupffer cells following liver ischemia and reperfusion

To study the role of tumor necrosis factor-alpha (TNF-alpha) for induction of the proinflammatory cytokine cascade after liver ischemia and reperfusion (I/R), rats were injected intraperitoneally with anti-TNF-alpha monoclonal antibodies (mAb) or placebo (IgG1) 30 min prior to global hepatic ischemia. Blood levels of TNF-alpha, interleukin (IL)-1alpha and -6 were determined. In addition, Kupffer cells (KC) were harvested after 60 min of reperfusion and spontaneous cytokine release was measured. Sham-operated animals were used as controls. Levels of proinflammatory cytokines in serum and KC supernatants were detected using specific bioassays and ELISA. Liver I/R resulted in increased (p < .01) serum levels of TNF-alpha, IL-1alpha, and IL-6, which was associated with an enhanced (p < .05) release of these cytokines by KC. In vivo pretreatment with anti-TNF-alpha mAb led to complete neutralization of TNF-alpha serum levels and decreased (p < .01) IL-6 levels (-62%). Moreover, anti-TNF-alpha mAb markedly (p < .05) decreased the release of TNF-alpha (-69%) and IL-6 (-56%) by KC, while IL-1alpha was not affected. These data indicate that TNF-alpha produced early after liver I/R triggers both its own secretion as well as IL-6 release by KC during reperfusion while the release of IL-1alpha occurs independent from TNF-alpha.

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.

Cardiopulmonary dysfunction during minimally invasive thoraco-lumboendoscopic spine surgery

The endoscopic retroperitoneal approach to thoracolumbar anterior spine fusion is associated with CO2 insufflation into the thoracic space. We studied the cardiopulmonary effects of this CO2 thoraco-retroperitoneal insufflation compared with the conventional open surgical procedure using thoraco-phreno-lumbotomy in 12 pigs under balanced anesthesia, paralysis, and mechanical ventilation. During open surgery of the thoracolumbar spine, animals exhibited unchanged systemic and pulmonary hemodynamics, as well as ventilation and oxygenation variables. Animals retroperitoneally insufflated with CO2 (12 mm Hg) exhibited a significant increase of PaCO2 and a moderate decrease of PaO2, SaO2, and pH, with insignificant changes of central venous filling pressures and systemic hemodynamics. Endoscopic phrenotomy with thoracic CO2 insufflation instantaneously and drastically affected hemodynamic status and pulmonary gas exchange with marked hypoxia, hypercapnia, systemic hypotension, tachycardia, and pulmonary hypertension within minutes. An increase of minute ventilation, inspiratory oxygen fraction, and positive end-expiratory pressure promptly reversed these cardiopulmonary effects. CO2 evacuation allowed the animals to completely recover and regain almost baseline cardiopulmonary status, except for a reduced arterial blood pressure. Appropriate monitoring and immediate CO2 desufflation may be beneficial in cases of therapy-resistant hemodynamic, oxygenation, and ventilation difficulties.

IMPLICATIONS

For endoscopic thoraco-lumbar spine fusion, CO2 thoraco-retroperitoneum-induced cardiopulmonary dysfunction must be of concern, especially in patients with cardiopulmonary compromise. Appropriate monitoring and immediate CO2 desufflation may be beneficial in cases of therapy-resistant hemodynamic, oxygenation, and ventilation difficulties.

Attenuation of microvascular reperfusion injury in rat pancreas transplantation by L-arginine

BACKGROUND

Despite improving results, exocrine complications remain a major challenge in clinical pancreas transplantation. The etiology of posttransplantation pancreatitis relates almost certainly to cold ischemia/reperfusion-induced microvascular injury with an imbalance of vasoconstricting and vasodilating mediators due to endothelial dysfunction. We therefore studied the effectiveness of a nitric oxide donor on postischemic microvascular reperfusion injury after pancreas transplantation.

METHODS

Heterotopic isogeneic pancreaticoduodenal transplantation was performed in spontaneously breathing, chloralhydrate-anesthetized Sprague Dawley rats after 16 hr (n=5) of cold storage of the graft in 4 degrees C histidine-tryptophane-ketoglutarate solution. An additional five animals received L-arginine immediately before (50 mg/kg i.v.) and during the first 30 min of reperfusion (100 mg/kg i.v.). Five animals that did not undergo transplantation served as controls. Intravital fluorescence microscopy was used for analysis of functional capillary density, capillary diameters, and capillary red blood cell velocity in exocrine pancreatic tissue during 120 min of reperfusion. Histology served for quantitative assessment of inflammatory response (leukocytic tissue infiltration) and endothelial disintegration (edema formation).

RESULTS

In L-arginine-treated animals, functional capillary density of exocrine tissue of pancreatic grafts was found slightly higher after 30 and 60 min, and significantly higher after 120 min of postischemic reperfusion compared with untreated pancreatic grafts. This was accompanied by a significant increase of capillary diameters. In parallel, pancreatic histology revealed significant attenuation of both leukocytic tissue infiltration and edema formation in the L-arginine-treated animals when compared with the nontreated controls.

CONCLUSIONS

Besides reduction of leukocyte-dependent microvascular injury, L-arginine improves postischemic microvascular reperfusion, supposedly by capillary dilatation. Thus, our results suggest that supplement of nitric oxide during reperfusion is effective in attenuating exocrine microvascular reperfusion injury.

Angiogenesis and microvascularization after cryothermia-induced myocardial infarction: a quantitative fluorescence microscopic study in rats

OBJECTIVE

Microvascularization of infarcted myocardial tissue may be a prerequisite for successful therapeutic interventions, including cardiomyoblast or satellite cell transplantation. Because little is known on microvascular restitution within infarcted tissue, we studied angiogenesis and microvascularization after cryothermia-induced myocardial infarction using intravital fluorescence microscopic techniques.

METHODS

In anesthetized, orally intubated and ventilated Sprague-Dawley rats (n = 20), a sternotomy was performed and a standardized cryolesion was induced to the right ventricle by freezing for 5 min to -160 degrees C. Myocardial angiogenesis and microvascularization were analyzed quantitatively after rethoracotomy on days 7 (n = 6) or 28 (n = 8). Sham-operated animals (n = 6) served as controls.

RESULTS

Seven days after cryothermia, the central tissue area of the injured myocardium (28.4 +/- 9.2 mm2) was characterized by complete lack of capillary perfusion, while the periphery of the cryolesion (27.6 +/- 5.7 mm2) revealed a heterogeneous capillary perfusion pattern with a density of 300.9 +/- 38.9 cm-1. Adjacent myocardial tissue showed intact capillary perfusion (density: 563.0 +/- 44.4 cm-1) comparable with that of sham-operated controls. After 28 d the area with lack of capillary perfusion was found significantly reduced to 7.3 +/- 3.7 mm2 (P < 0.05); however, it was still surrounded by a heterogeneously perfused area of myocardial tissue of 57.7 +/- 19.2 mm2 (density: 271.1 +/- 52.7 cm-1), indicating partial restitution of capillary perfusion. Although at day 7 within the central zone of the cryolesions, capillary perfusion was completely shut down, perfusion of microvessels larger than capillaries, i.e., arterioles and venules, were found maintained, however, with a density markedly lower (1.96 +/- 1.04 mm-1) when compared with that of sham-controls (4.28 +/- 1.52 mm-1). After 28 d the number of these larger-sized microvessels increased significantly with values of density even higher compared with those observed in controls (6.89 +/- 1.71 mm-1; P < 0.05), indicating new vessel formation.

CONCLUSIONS

Our study indicates partial restitution and function of the microvascular network within infarcted myocardial tissue, which may serve as an appropriate prerequisite for successful application of novel therapeutic strategies to improve myocardial function.

Differential gene expression of CINC, NOS II, and ICAM-1 in endotoxemic liver cells by rG-CSF

INTRODUCTION

We have recently demonstrated that recombinant granulocyte colony-stimulating factor (rG-CSF) modulates lipopolysaccharide (LPS)-induced Kupffer cell activation with subsequent reduction in hepatic leukocyte-endothelial cell interaction, thereby achieving protection against microcirculatory perfusion failure and hepatic dysfunction. To further clarify the underlying mechanisms, rG-CSF treated liver cells were tested for the LPS-induced gene expression of cytokine-induced neutrophil chemoattractant (CINC) and intercellular adhesion molecule-1 (ICAM-1) as potential chemotactic and leukocyte-recruiting factors and for the gene expression of inducible nitric oxide synthase (NOS II) as potential modulator of leukocyte adherence.

METHODS

Using a collagenase, DNAse/pronase digestion technique, hepatic parenchymal and nonparenchymal cell fractions were obtained from livers of in vivo rG-CSF pretreated Sprague-Dawley rats 2 h after LPS exposure. mRNA transcripts were assessed using northern blot analysis.

RESULTS

In control livers only ICAM-1 mRNA was found constitutively expressed in hepatic nonparenchymal cells. rG-CSF per se did not affect NOS II, CINC, or ICAM-1 expression in hepatic liver cells, while LPS induced a marked expression of NOS II, CINC, and ICAM-1 in nonparenchymal cells and, to a lesser extent, in hepatocytes. Administration of rG-CSF prior to LPS exposure tended to increase NOS II, CINC, and ICAM-1 mRNA transcripts in hepatocytes. In nonparenchymal cells, however, NOS II and CINC were found reduced in rG-CSF pretreated animals upon LPS exposure.

CONCLUSIONS

The present data show a strikingly different cell type specific pattern of inflammatory response genes in rG-CSF-modulated hepatic endotoxemia. Reduced expression of NOS II, in particular of CINC, in the nonparenchymal cell fraction may contribute to the reduced leukocyte adherence and thus attenuation of cell-dependent tissue injury in rG-CSF pretreated endotoxemic animals.

Inhibition of tumor growth, angiogenesis, and microcirculation by the novel Flk-1 inhibitor SU5416 as assessed by intravital multi-fluorescence videomicroscopy

Vascular endothelial growth factor (VEGF) plays a fundamental role in mediating tumor angiogenesis and tumor growth. Here we investigate the direct effect of a novel small molecule inhibitor of the Flk-1-mediated signal transduction pathway of VEGF, SU5416, on tumor angiogenesis and microhemodynamics of an experimental glioblastoma by using intravital multifluorescence videomicroscopy. SU5416 treatment significantly suppressed tumor growth. In parallel, SU5416 demonstrated a potent antiangiogenic activity, resulting in a significant reduction of both the total and functional vascular density of the tumor microvasculature, which indicates an impaired vascularization as well as significant perfusion failure in treated tumors. This malperfusion was not compensated for by changes in vessel diameter or recruitment of nonperfused vessels. Analyses of the tumor microcirculation revealed significant microhemodynamic changes after angiogenesis blockage such as a higher red blood cell velocity and blood flow in remnant tumor vessels when compared with controls. Our results demonstrate that the novel antiangiogenic concept of targeting the tyrosine kinase of Flk-1/KDR by means of a small molecule inhibitor represents an efficient strategy to control growth and progression of angiogenesis-dependent tumors. This study provides insight into microvascular consequences of Flk-1/KDR targeting in vivo and may have important implications for the future treatment of angiogenesis-dependent neoplasms.

Exocrine, but not endocrine, tissue is susceptible to microvascular ischemia/reperfusion injury following pancreas transplantation in the rat

While post-transplant pancreatitis is still a frequently occurring complication of whole pancreas transplantation, dysfunction of the endocrine tissue is rarely observed. Given that microcirculatory disorders play a major role in the pathogenesis of pancreatitis, we hypothesized a dissociation of endocrine and exocrine microvascular control in pancreas transplantation (cold ischemia-reperfusion) and studied this dissociation quantitatively, analyzing the pancreatic microcirculation after heterotopic isogeneic pancreaticoduodenal transplantation in rats by means of fluorescence microscopy. Functional capillary density (FCD) of both exocrine and endocrine tissue of pancreatic grafts after 1 h of cold storage in HTK solution did not differ when compared to sham-operated, time-matched controls. Intermittent capillary perfusion, which is absent under sham control conditions and which is proposed to be operative as a compensatory mechanism to counteract malperfusion, was observed in 52% of the exocrine, but in only 8% of the endocrine, tissue studied (p < 0.05). In contrast, cold storage of pancreatic grafts for 6 h in HTK resulted in a complete loss of intermittent capillary perfusion in exocrine tissue and, consequently, marked exocrine perfusion failure (decrease in FCD), while FCD of pancreatic endocrine tissue was preserved without any significant change in the incidence of intermittent capillary perfusion. Thus, our results indicate a higher susceptibility of the exocrine pancreas to cold ischemia/reperfusion events that is associated with significant alterations in nutritive perfusion and, thus, with limitations of the oxygen supply to the tissue. This may lead to inflammatory tissue reactions in the clinical setting of pancreas transplantation.

Epi-illumination fluorescent light microscopy for the in vivo study of rat hepatic microvascular response to cryothermia

To elucidate the hepatic microvascular response to cryothermia, we studied the liver microcirculation of Sprague-Dawley rats after one and two 4-minute freeze-thaw cycles using intravital fluorescence microscopy. Irrespective of the number of freeze-thaw cycles applied, the nature of hepatic microvascular injury was characterized by complete stasis of sinusoidal blood flow within the central part of the cryolesions and heterogeneous sinusoidal perfusion in a critically perfused border zone located at the periphery of the lesions. Analysis over time (2 hours) revealed a successive shutdown of sinusoidal perfusion within this critically perfused border zone, which was caused by intravascularly lodging cell aggregates, blocking the lumen of individual sinusoids. The aggregates consisted of parenchymal cells and cell fragments, but did not include leukocytes or platelets. Strikingly, microvascular perfusion failure was associated with Ito cell disintegration and marked dilation of sinusoids (15.6 +/- 0.8 microm vs. 8.8 +/- 0.8 microm; P <.05). This excludes sinusoidal constriction as the cause of nutritive perfusion failure, and may indicate dysfunction of Ito cell-regulated vasomotor control by cryothermia. However, because circulating cell aggregates were frequently observed plugging individual microvessels, dilation of sinusoids may just be the result of passive distension caused by outflow blockade. Analysis of hepatic tissue at 8 weeks after cryothermia did not reveal regeneration and microvascular remodeling, but loss of hepatic tissue, which corresponded well with the tissue area presenting with sinusoidal perfusion failure during the initial observation period after cryothermia. The fact that there was no recovery of sinusoidal perfusion over the initial 2-hour observation period, but loss of tissue after 8 weeks, supports the view that cryothermia induces injury not only by direct low-temperature-mediated action, but also through ischemia caused by irreversible deterioration of the microcirculation.

Mixed agonistic-antagonistic cytokine response in whole blood from patients undergoing abdominal aortic aneurysm repair

OBJECTIVE

To characterize the impact of abdominal aortic aneurysm repair (AAAR) on spontaneous as well as lipopolysaccharide (LPS)-induced gene expression of pro- and anti-inflammatory cytokines.

DESIGN

Prospective, controlled in vivo/ex vivo study.

SETTING

University hospital.

PATIENTS AND INTERVENTIONS

Whole blood from 14 consecutive patients undergoing AAAR withdrawn prior to surgery (T1), at the end of ischemia (T2), 90 min after declamping (T3) and on the first postoperative day (T4) was cultured in the absence or presence of LPS. Five patients undergoing elective inguinal hernia repair served as controls.

MEASUREMENTS AND RESULTS

While tumor necrosis factor (TNF), Interleukin (IL)-1 and IL-10 plasma concentrations did not increase significantly, IL-6 was elevated at each time point, as compared with T1. Despite the spontaneous release of trace amounts of IL-6, the ability of cultured whole blood to mount a cytokine response in vitro to LPS was impaired for all cytokines studied at T2 (TNF-62%, IL-1-51%, IL-6 -20%, IL-10-51%). The stimulated IL-6 response was restored early after declamping (T3: +56 %) and enhanced 1 day after operation (T4: +144%). In contrast, stimulated TNF and IL-1 responses remained depressed at T3 (TNF -48%, IL-1-64%) and T4 (TNF-40%, IL-1-24%). A biphasic pattern was observed for IL-10 with initial depression at T3 (-51%) and restoration at T4 (+40%). Among the different cytokines monitored, only impaired TNF responsiveness at early reperfusion (T3) correlated with the postoperative course, as reflected by APACHE II. Cytokine response to LPS was maintained or even increased during and after surgery in the whole blood from patients undergoing hernia repair.

CONCLUSIONS

Despite consistent development of clinical signs of systemic inflammatory response syndrome (SIRS) and spontaneous release of IL-6 abdominal aortic aneurysm repair produces a state of impaired pro-inflammatory cytokine response upon a subsequent in vitro Gram-negative stimulus. This early impairment of TNF responsiveness seems to correlate with an unfavorable postoperative course.

Effectiveness of a hands-on training course for laparoscopic spine surgery in a porcine model

BACKGROUND

Although it is widely proposed that surgeons, before introducing a novel laparoscopic technique in man, should practice in an appropriate animal model for acquisition of the necessary technical skills, the effectiveness of those hands-on training courses are rarely documented.

METHODS

In 1995 we have organized eight hands-on training courses for laparoscopic anterior interbody spine fusion in an in vivo porcine model. A total of 72 colleagues from 50 different centers of 12 countries participated, including orthopedic, trauma, visceral, neuro-, and vascular surgeons. Quality and effectiveness of the course were evaluated by a questionnaire after a 1.5- to 2.5-year period.

RESULTS

During this time, 42.2% of the participating centers had applied the new technique successfully in man. Centers which participated in the course with a team that included a skilled laparoscopic surgeon and an orthopedic or trauma surgeon introduced the technique more frequently to clinical practice (57.9%) than those represented by only one participant (30. 8%). Moreover, there was a tendency toward a more frequent introduction of the technique to clinical practice in centers associated with university hospitals (57.1% vs. 29.2%), indicating the requirement of a particular infrastructure for this complex interdisciplinary procedure. Almost all participants (98.3%) agreed that for novel surgical techniques requiring advanced technical skills, there should first be training in a large animal model before the technique is applied in man.

CONCLUSIONS

Complex laparoscopic procedures (i.e., laparoscopic spine surgery) can be successfully learned by in vivo hands-on training courses. We propose that for refinements and modifications of the technique (e.g. , the lumboscopic approach), there should also first be training in a large animal model before these are applied in man.

Do vitamin E supplements in diets for laboratory animals jeopardize findings in animal models of disease?

Vitamin E has been supplemented to the diets of farm animals to improve fertility, health, growth rates and quality of animal products. Because of the positive experience obtained in farm animals, vitamin E has been added in increasing amounts to the diets of laboratory animals. Today, vitamin E levels in standard rodent maintenance diets range from 30 mg/kg (France, United States), 90-120 mg/kg (Netherlands, United Kingdom) to as much as 200 mg/kg (Germany). While increasing fertility and health of laboratory animals, these vitamin E supplements affect diverse pathophysiological conditions and thus the outcome of animal models of disease. Because of the large variability of vitamin E levels between laboratories within and between different countries, results obtained in established animal models may no longer be comparable and/or reproducible. Researchers should be aware of these vitamin E supplements and carefully control for potential effects in their respective animal models that involve--or may involve--the generation of reactive oxygen species.

In vivo analysis of hepatic NADH fluorescence. Methodological approach to exclude Ito-cell vitamin A-derived autofluorescence

Assessment of hepatic surface NADH fluorescence is complicated by questions concerning the relative contribution of Ito cell-associated vitamin A autofluorescence, which cannot be distinguished from each other using ultraviolet epi-illuminated microfluorographs. However, as presented herein, vitamin A autofluorescence can easily be eliminated due to its rapid photobleaching property. In line with in vitro studies on liver perfusion reported by Suematsu and coworkers (1993b), we assessed NADH fluorescence in liver surface regions, which were epi-illuminated for elimination of vitamin A autofluorescence and were allowed to recover for 20 min prior to onset of the experiment. To assess whether this procedure is stringent for accurate estimation of NADH fluorescence, we studied NADH fluorescence in non prebleached surface regions after a 30 sec and 60 sec epi-illumination period. Epi-illumination of these hepatic surface regions for more than 20 sec guaranteed also complete elimination of vitamin A autofluorescence (Vollmar et al., 1996) and further allowed to calculate the subsequent loss of NADH fluorescence due to a potential photobleaching effect after 30 sec and 60 sec of continuous light exposure. Corresponding data of the present study reveal a constant loss of NADH fluorescence of approximately 20% due to its photobleaching property over the time period from 20-60 sec of epi-illumination. Linear regression analysis of the kinetics of NADH fluorescence upon continuous light exposure allowed the calculation of the initial NADH fluorescence, excluding the interference with the Ito cell vitamin A-derived autofluorescence. The concurrency of this mathematically assessed value for the initial (non-bleached) NADH fluorescence within normal hepatic livers with the recovered value of NADH fluorescence allows the conclusion that the procedure for elimination of vitamin A autofluorescence, including ultraviolet epi-illumination with a subsequent NADH recovery period of at least 20 min, is not a prerequisite for the reliable assessment of intraindividual changes of hepatic NADH fluorescence in vivo. Thus, valid assessment of hepatic NADH fluorescence in vivo can be performed by analyzing initial NADH fluorescence bleaching kinetics, and does not necessarily require the 20 min recovery period after bleaching of the Ito cell vitamin A-derived autofluorescence.