Biomedical subjects

Brigitte Vollmar

Publications and source records attributed to Brigitte Vollmar.

62 records · Page 4Linked to original sources

PubMed2002

In vivo quantification of ageing changes in the rat liver from early juvenile to senescent life.

AIMS/METHOD: Using high resolution multifluorescence in vivo microscopy, the present study was undertaken to determine the changes in rat hepatic tissue architecture and microvasculature during the growth associated with juvenile maturation and adult senescence, i.e. the age of 1, 3, 12 and 24 months. RESULTS: By 1 month of age the liver attained its full size and functional capacity, as assessed by relative organ weight and hepatic bile flow. Survey of liver architecture revealed a progressive growth of lobular area with postsinusoidal venules exhibiting a proportional increase in length, diameter and inter-vascular distance up to the age of 12-24 months. In regard to the 3.5-4-fold average increase of lobular units, a minor reduction of sinusoidal density to 87% over life strongly implies the recruitment or formation of new sinusoidal microvessels as contributing mechanism to meet oxygen demand due to overall tissue enlargement. The sinusoidal perfusion rate remained above 98% over the whole lifespan. Leukocytic interaction with the hepatic microvascular endothelium was found within the physiological range in all age groups. Moreover, kinetics of clearance of latex beads as well as lobular distribution of Kupffer cells did not differ between animals of different age. Hepatic stellate cell-associated area of ultraviolet vitamin A-autofluorescence increased with age and significantly correlated with increasing tissue concentrations of vitamin A metabolites. Biochemical parameters serving as measures of tissue integrity did not indicate age-associated tissue alterations. CONCLUSION: These age-associated physiological changes should be carefully taken into account as a relevant variable in experimental research.

Aging↗

PubMed2002

High, but not low, dietary retinoids aggravate manifestation of rat liver fibrosis.

BACKGROUND: Although there is strong implication that retinoids regulate Ito cell proliferation and collagen synthesis, results from in vivo studies on the relationship between vitamin A and liver fibrosis are conflicting. The present study focuses on the role of vitamin A in carbon tetrachloride (CCl4)-induced fibrosis by chronic feeding of rats with either a vitamin A-supplemented or -depleted diet. METHODS AND RESULTS: In animals with high dietary hepatic retinoid levels, liver fibrosis was more pronounced and was associated with an increased CCl4-toxicity resulting in high mortality (73%). Enhanced liver fibrosis was confirmed by in vivo fluorescence microscopic determination of both collagen deposits (7.4 +/- 1.1 vs 3.9 +/- 0.3% in high vitamin A diet-fed and standard diet-fed fibrotic animals, respectively; P < 0.05) and rarefication of sinusoids (1.5 +/- 0.2 vs 2.4 +/- 0.2 sinusoids/200 microm in high vitamin A diet-fed and standard diet-fed fibrotic animals, respectively; P < 0.05). It was further associated with decreased bile flow and increased parenchymal cell damage. CCl4 reduced hepatic retinoid levels in high vitamin A diet-fed animals, but restored hepatic retinoid levels in animals fed with a vitamin A-deficient diet, implying major interference of vitamin A metabolism with hepatotoxic agents such as CCl4. Low vitamin A feeding did not modulate liver fibrogenesis and caused no mortality. CONCLUSIONS: These results show that the vitamin A status of the liver plays an important role in liver fibrogenesis. While dietary vitamin A shortage does not promote liver fibrogenesis, high levels of vitamin A have the potential to increase systemic and hepatic toxicity of CCl4. Thus, the narrow therapeutic window for nutritional vitamin A substitution must take into account that liver fibrotic patients may display enhanced susceptibility to the adverse effects of vitamin A.

Animals↗

PubMed2002

Hydroxyethyl starch (130 kD), but not crystalloid volume support, improves microcirculation during normotensive endotoxemia.

BACKGROUND: Increased leukocyte-endothelial cell interaction (LE) and deterioration of capillary perfusion represent key mechanisms of septic organ dysfunction. The type of volume support, however, which may be used during septic disorders, remains controversial. Using intravital microscopy, the authors studied the effect of different regimens of clinically relevant volume support on endotoxin-induced microcirculatory disorders, including the synthetic colloid hydroxyethyl starch (HES, 130 kD) and a crystalloid regimen with isotonic saline solution (NaCl). METHODS: In Syrian Golden hamsters, normotensive endotoxemia was induced by intravenous application of Escherichia coli lipopolysaccharide (LPS, 2 mg/kg). The microcirculation was analyzed in striated muscle of skinfold preparations. HES 130 kD (Voluven(R), 16 ml/kg, n = 7) or isotonic saline (NaCl, 66 ml/kg, n = 6) were infused 3 h after LPS exposure over a 1-h period (posttreatment mode). Animals receiving LPS without volume therapy served as control subjects (n = 8, control). LE, functional capillary density (FCD), and macromolecular leakage were repeatedly analyzed in the awake animals during a 24-h period using intravital fluorescence microscopy. RESULTS: HES 130 kD significantly reduced LPS-induced arteriolar and venular leukocyte adherence (P < 0.05), whereas NaCl resuscitation had no effect when compared with nontreated control animals. The LPS-induced decrease in FCD and increase in macromolecular leakage were also significantly attenuated by HES 130 kD but not by NaCl. Improvement of LPS-induced microcirculatory disorders by HES was unlikely the result of macro- and microhemodynamic changes because arterial blood pressure, heart rate, and venular wall shear rate did not differ between HES- and NaCl-treated animals. CONCLUSIONS: Thus, our study provides microhemodynamic and cellular mechanisms of HES 130 kD-mediated protection on microcirculation during endotoxemia, even when used in a clinically relevant posttreatment mode during normotensive conditions.

Animals↗

PubMed2002

Antithrombin effects on endotoxin-induced microcirculatory disorders are mediated mainly by its interaction with microvascular endothelium.

OBJECTIVE: To investigate whether the protective effect of antithrombin III, which has been shown to exert beneficial effects during septic disorders, including reduction of endotoxin-associated leukocyte/endothelial cell interaction and capillary perfusion failure, is mainly based on its anticoagulant capacity or direct effects on the microvascular endothelium. DESIGN: Animal study with three treatment groups. SETTING: Animal research facility. SUBJECTS: Syrian golden hamsters, 6-8 wks old with a body weight of 60-80 g. INTERVENTIONS: In skinfold preparations of hamsters, normotensive endotoxemia was induced by intravenous administration of 2 mg/kg endotoxin (lipopolysaccharide, 2 mg/kg). Antithrombin III (n = 7 animals; 250 units/kg) or tryptophan49-blocked antithrombin III (n = 6; 250 units/kg) was substituted intravenously 5 mins before lipopolysaccharide administration. Saline-treated animals (n = 11), receiving only lipopolysaccharide, served as controls. Tryptophan49-blocked antithrombin III binds to glycosaminoglycans at the endothelial surface to a significantly lower extent while retaining its progressive anticoagulant effects. MEASUREMENTS AND MAIN RESULTS: Compared with controls, antithrombin III significantly reduced lipopolysaccharide-induced arteriolar and venular leukocyte adherence (p < .01) and prevented depression of functional capillary density (p < .01), whereas tryptophan49-blocked antithrombin III failed to significantly improve both variables. As measured in vivo by a monoclonal fluorescein isothiocyanate-labeled anti-antithrombin III antibody and intravital microscopy, the lack of effect of tryptophan49-blocked antithrombin III was associated with significantly lower antithrombin III/endothelium binding coefficients after 1 hr, 3 hrs, and 24 hrs of endotoxemia (p < .01). CONCLUSIONS: We conclude that specific antithrombin III interactions with cell-surface glycosaminoglycans on the endothelium rather than anticoagulant properties are the mechanism of antithrombin III-mediated attenuation of leukocyte/endothelial cell interaction and capillary perfusion failure.

Animals↗

PubMed2002

n-3 Polyunsaturated fatty acid-enriched diet does not protect from liver injury but attenuates mortality rate in a rat model of systemic endotoxemia.

OBJECTIVE: We investigated the potential of dietary fish oil containing n-3 polyunsaturated fatty acids to attenuate hepatic injury and mortality rate of rats in response to systemic endotoxemia. DESIGN: Prospective, randomized, controlled animal study. SETTING: University laboratory. SUBJECTS: A total of 43 male Sprague Dawley rats. INTERVENTIONS: Rats were fed either fish oil supplement or regular standard lab chow. After 8 wks of feeding, each diet group was subjected to a single exposure of lipopolysaccharide (Escherichia coli, 10 mg/kg intravenously) or saline. Hepatic microvascular response and liver injury were assessed by in vivo analysis of Kupffer cell phagocytic activity, leukocyte-endothelial cell interaction, nutritive sinusoidal perfusion failure, and parenchymal cell apoptosis (intravital fluorescence epi-illumination technique) as well as bile flow, serum liver enzyme activities, and tissue histomorphology. MEASUREMENTS AND MAIN RESULTS: In animals fed a standard diet, livers at 16 hrs after lipopolysaccharide-exposure exhibited depressed Kupffer cell phagocytic activity, enhanced hepatic microvascular leukocyte activation, leukocytic tissue infiltration, sinusoidal perfusion failure, and parenchymal cell apoptosis. Hepatic microvascular injury was further accompanied by reduced bile flow and enhanced liver enzyme release. The fish oil enriched diet did not significantly change the multiple features of endotoxemia-associated liver injury; however, it maintained arterial blood pressure, systemic leukocyte count, and acid base balance and showed a tendency toward improved survival on lipopolysaccharide exposure with a 16 hr-survival rate of 80% (p =.06 vs. survival rate of 40% in animals fed a regular diet). Moreover, slightly increased serum concentrations of interleukin-10 coincided with enhanced concentrations of interleukin-6 in fish oil fed endotoxemic animals. Healthy, non-lipopolysaccharide-exposed, fish oil fed animals did not differ from those fed with the regular diet, except for dampened Kupffer cell phagocytic activity. CONCLUSIONS: Fish oil feeding does not protect from local endotoxemia-induced hepatic microvascular dysfunction. However, dietary modulation of inflammatory mediator response by macrophages, constituting an appropriate immune response, could add to the survival advantage seen in fish oil-fed animals on exposure to lipopolysaccharide.

Acid-Base Equilibrium↗

PubMed2002

Age-associated loss of immunomodulatory protection by granulocyte-colony stimulating factor in endotoxic rats.

Elderly patients have a higher incidence of morbidity and mortality due to infectious diseases. Because most immune functions in the elderly differ compared with those in younger subjects, we studied the effect of the immunomodulating agent G-CSF on endotoxic liver injury and cytokine release in an aging animal model of acute sepsis. Young (3-month-old), mature (12-month-old), and senescent (24-month-old) male Sprague-Dawley rats (n = 6 each) were treated with bacterial endotoxin for 6 h. Age-matched groups of animals (n = 6 each) received G-CSF (200 microg/kg i.v.) 1 h prior to endotoxin. LPS-induced hepatic toxicity, as assessed in vivo by nutritive perfusion failure, intravascular leukocyte accumulation, biliary excretion dysfunction, and liver enzyme release, was significantly more pronounced in mature and old animals when compared with young animals. Concomitantly, mature but, in particular, senescent endotoxic animals exhibited 2- to 14-fold higher plasma levels of TNF-alpha, IL-1beta, IL-6, IL-10, and Rantes than young endotoxic rats. The percentage of G-CSF receptor surface expression on neutrophils did not significantly differ between young, mature, and senescent animals (36%-46%) and was found comparably down-regulated at 6 h after LPS exposure (15%-19%). Kupffer cell activation, i.e., clearance of intravascularly applied fluorescent latex beads, did not differ between the LPS-exposed age groups. G-CSF dampened LPS-induced Kupffer cell activation, and significantly reduced plasma cytokine levels in young and mature, but not in senescent animals. Thereby, G-CSF caused attenuation of hepatic tissue injury in all except the senescent endotoxic animals. In summary, our results show an age-dependent increase in hepatic LPS toxicity. Because flow cytometric analysis of G-CSF receptor expression disproved that cytokinemia-induced down-regulation of G-CSF receptors might account for the unresponsiveness to G-CSF in the senescent animals, other homeostatic regulatory mechanisms appear to undergo changes with age that bring out a disrupted balance between inflammatory cytokines with unresponsiveness to G-CSF and, thus, compromised host defense mechanisms in the elderly.

Aging↗

PubMed2002

Adverse effect of heparin on antithrombin action during endotoxemia: microhemodynamic and cellular mechanisms.

A recent clinical sepsis trial reported a significant reduction in 90-day mortality by antithrombin (AT) exclusively in the subgroup of patients without simultaneous heparin prophylaxis. Patients additionally receiving heparin did not benefit from AT treatment. Herein, we studied the microhemodynamic and cellular mechanisms of this adverse effect of heparin on AT actions by the use of intravital microscopy and granulocyte culturing. In Syrian golden hamsters normotensive endotoxemia was induced by 2 mg/kg endotoxin (LPS, E. coli) i.v. In a first group of animals, AT (AT, 250 IU/kg i.v., n = 6) was given 5 min before LPS administration. A second group of animals (Heparin + AT, n = 5) received AT (250 IU/kg i.v.) combined with unfractionated heparin (sodium heparin, 100 IU/kg/24 h, i.v.). Additional animals (LMWH + AT, n = 5) received AT (250 IU/kg i.v.) combined with LMWH (nadroparin 47.5 IU anti-Xa/kg, s.c., 2 h before LPS). LPS-treated animals, which received only saline, served as controls (control, n = 6). Using dorsal skinfold fold preparations, LPS-induced microvascular leukocyte-endothelial cell interaction (LE) and alteration of functional capillary density (FCD) were studied by intravital video fluorescence microscopy. In controls, LPS induced a massive increase in LE with a maximum at 8 h and an impressive decrease in FCD over a 24-hour period. Both LPS effects were effectively prevented by AT treatment (p < 0.01), whereas Heparin + AT and LMWH + AT animals showed microcirculatory alterations comparable to that in controls. In additional in vitro chemotaxis assays. AT blocked neutrophil chemotaxis, an effect reversed by both unfractionated heparin and LMWH. Thus, our study elucidates a relevant in vivo and in vitro unfractionated heparin and LMWH adverse effect in the microcirculatory actions of AT during endotoxemia. These results indicate that heparin should be avoided to permit AT to modulate LPS-induced inflammatory responses.

Animals↗

PubMedDate not supplied

Viewing the microcirculation through the window: some twenty years experience with the hamster dorsal skinfold chamber.

Intravital microscopy represents a sophisticated technique to study the microcirculation in health and disease. While most preparations used for those studies are acute in nature, the use of chamber preparations in the skinfold bear the advantage to allow for chronic studies with repeated analysis of the microcirculation over a prolonged period of time. The skinfold chamber model for microcirculatory analysis has been adapted to mice, rats and hamsters. Although the use of rats and, in particular, the use of mice has the advantage of the availability of species-specific tools, the use of the hamster as the experimental animal may be preferred due to anatomical reasons, which facilitate the microsurgical preparation and improve the quality of microscopic imaging. The use of the hamster dorsal skinfold chamber, firstly described by Endrich and coworkers in 1980, has brought out during the last two decades a considerable number of experimental studies within the fields of microcirculation physiology, inflammation and sepsis, ischemia-reperfusion, angiogenesis, and transplantation, indicating that the model has to be considered a versatile tool to study the microcirculation in health and disease.

Animals↗