A Local Area Network for Medical Research; Planning, Realization and Experience

This report focusses on the planning and realization of an interdisciplinary local area network (LAN) for medical research at the University of Heidelberg. After a detailed requirements analysis, several networks were evaluated by means of a test installation, and a cost-performance analysis was carried out. At present, the LAN connects 45 (IBM-compatible) PCs, several heterogeneous mainframes (IBM, DEC and Siemens) and provides access to the public X.25 network and to wide-area networks for research (EARN, BITNET). The network supports application software that is frequently needed in medical research (word processing, statistics, graphics, literature databases and services, etc.). Compliance with existing “official” (e.g., IEEE 802.3) and “de facto” standards (e.g., PostScript) was considered to be extremely important for the selection of both hardware and software. Customized programs were developed to improve access control, user interface and on-line help. Wide acceptance of the LAN was achieved through extensive education and maintenance facilities, e.g., teaching courses, customized manuals and a hotline service. Since requirements of clinical routine differ substantially from medical research needs, two separate networks (with a gateway in between) are proposed as a solution to optimally satisfy the users’ demands.

Effect of Intensive Walking Exercise on Skeletal Muscle Blood Flow in Intermittent Claudication

Walking exercise is generally accepted as a valid therapeutic regimen in the treatment of peripheral arterial occlusive disease (PAOD) of Fontaine stage II. In order to quantify the effect of walking exercise and/or drug therapy on regional muscular blood flow, PAOD Fontaine stage II was induced by multiple ligations of the femoral artery and of all side branches in one hindlimb of mongrel dogs; the contralateral extremity served as control.

The animals underwent walking exercise with increasing intensities on a tread mill five days per week over one year; one group received 600 mg buflomedil (BF) per day orally in addition. At the end of the training period, the regional blood flow in all skeletal muscles of both hindlimbs was quantified by means of 15 μm radioactively labeled microspheres at resting conditions, after treadmill exercise (ten minutes) with or without preinjection of BF (3 mg/kg body weight) into the abdominal aorta.

At resting condition and at the end of treadmill exercise the regional muscular blood flow did not differ significantly between the diseased and control extremity Supplementary oral treatment with BF over one year had no significant effect; the increase in muscular blood flow during treadmill exercise was not enhanced after intra- aortic injection of BE

Consequently walking exercise has the potential to increase the functional capacity of collaterals in intermittent claudication and to restore blood supply to skeletal muscle.

The hairless mouse ear: an in vivo model for studying wound neovascularization

Microvascular ingrowth into damaged tissue is an essential component of the normal healing process. In fact, wound therapy is often aimed at promoting neovascularization. However, little is known about the mechanisms that regulate microvascular ingrowth into a healing wound. This limited knowledge is largely due to the lack of adequate models in which microvascular ingrowth can be quantitatively analyzed throughout the healing process. To address this deficiency, we developed a model in which a wound was created on the ear of the hairless mouse-a well established model for directly viewing and measuring skin microcirculation. While the animals were under ketamine and xylazine anesthesia, 2.25 mm diameter full-thickness wounds were created on the dorsum of hairless mouse ears down to but not including the cartilage (0.125 mm depth). With the use of video microscopy and computer-assisted digitized planimetry, the precise epithelial and neovascular wound edge was viewed and measured regularly throughout healing. Therefore, this model can provide objective data on wound epithelialization and neovascularization throughout healing. This model was used to examine the effect of topical wound agents on epithelialization and neovascularization. Differential effects by these anti-microbial agents on these two processes were observed, which suggests clinical implications for their use.

Ischemic preconditioning attenuates portal venous plasma concentrations of purines following warm liver ischemia in man

BACKGROUND/AIMS

Degradation of adenine nucleotides to adenosine has been suggested to play a critical role in ischemic preconditioning (IPC). Thus, we questioned in patients undergoing partial hepatectomy whether (i) IPC will increase plasma purine catabolites and whether (ii) formation of purines in response to vascular clamping (Pringle maneuver) can be attenuated by prior IPC.

METHODS

75 patients were randomly assigned to three groups: group I underwent hepatectomy without vascular clamping; group II was subjected to the Pringle maneuver during resection, and group III was preconditioned (10 min ischemia and 10 min reperfusion) prior to the Pringle maneuver for resection. Central, portal venous and arterial plasma concentrations of adenosine, inosine, hypoxanthine and xanthine were determined by high-performance liquid chromatography.

RESULTS

Duration of the Pringle maneuver did not differ between patients with or without IPC. Surgery without vascular clamping had only a minor effect on plasma purine concentrations. After IPC, plasma concentrations of purines transiently increased. After the Pringle maneuver alone, purine plasma concentrations were most increased. This strong rise in plasma purines caused by the Pringle maneuver, however, was significantly attenuated by IPC. When portal venous minus arterial concentration difference was calculated for inosine or hypoxanthine, the respective differences became positive in patients subjected to the Pringle maneuver and were completely prevented by preconditioning.

CONCLUSION

These data demonstrate that (i) IPC increases formation of adenosine, and that (ii) the unwanted degradation of adenine nucleotides to purines caused by the Pringle maneuver can be attenuated by IPC. Because IPC also induces a decrease of portal venous minus arterial purine plasma concentration differences, IPC might possibly decrease disturbances in the energy metabolism in the intestine as well.

Particles of all sizes provoke inflammatory responses in vivo

The aim of this study was to investigate whether all sizes of wear particles are capable of provoking inflammatory responses and whether there are different responses among different particle sizes. The knees of 40 female Balb/c mice were injected with polystyrene particles of three different diameters, 0.5 microm, 2.0 microm, and 75 microm, using a 0.1% vol/vol concentration. Seven days after particle injection, assessment of the synovial microcirculation using intravital microscopy, and histologic examination, were done. All the mice injected with polystyrene particles had enhanced leukocyte-endothelial cell interactions and histologic scores regardless of particle size when compared with control animals injected with sterile phosphate buffered saline. Polystyrene particles 0.5 microm in size provoked stronger membrane thickening and increased leukocyte-endothelial cell interactions than 75-microm particles. The fraction of rolling leukocytes was enhanced in the 2.0-microm particle group when compared with the 75-microm particle group. These results indicate that polystyrene particles of all sizes (0.5 microm, 2.0 microm, and 75 microm) are capable of inducing an inflammatory response. Small particles (0.5 microm, 2.0 microm) seem to provoke a stronger inflammatory response than larger particles (75 microm) in conditions with equal particle volume.

Can we continue research in splenectomized dogs? Mycoplasma haemocanis: old problem--new insight

We report the appearance of a Mycoplasma haemocanis infection in laboratory dogs, which has been reported previously, yet, never before in Europe. Outbreak of the disease was triggered by a splenectomy intended to prepare the dogs for a hemorrhagic shock study. The clinical course of the dogs was dramatic including anorexia and hemolytic anemia. Treatment included allogeneic transfusion, prednisone, and oxytetracycline. Systematic follow-up (n = 12, blood smears, antibody testing and specific polymerase chain reaction) gives clear evidence that persistent eradication of M. haemocanis is unlikely. We, therefore, had to abandon the intended shock study. In the absence of effective surveillance and screening for M. haemocanis, the question arises whether it is prudent to continue shock research in splenectomized dogs.

The effects of Celecoxib on inflammation and synovial microcirculation in murine antigen-induced arthritis

OBJECTIVE

There is controversy about the effects of cyclooxygenase-2 (COX-2) on adhesion molecules and the microvasculature in inflamed tissue. Thus, the aim of this study was to assess COX-2-expression in Antigen-induced Arthritis (AiA) and to investigate the effects of selective COX-2 inhibition by Celecoxib (4-[5-(4-methylphenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl] benzenesulfonamide) (CXB), on synovial microcirculation and adhesion molecule expression in arthritic as well as healthy mice.

METHODS

Balb/c mice were allocated to 4 groups; 2 control groups with saline or CXB and 2 groups with AiA which also received saline or CXB (30 mg/kg BW in 0.3 ml solution). The severity of arthritis was assessed by changes in the transverse joint diameter On day 14 after AiA-induction, the patella tendon of the left knee joint was microsurgically resected and intravital fluorescence microscopy on synovial tissue was performed. Finally, the knee joint was removed for histology and immunohistochmistry.

RESULTS

COX-2-expression in the inflamed synovium was demonstrated by immunohistochemistry. Application of Celecoxib resulted in a significant reduction in the rolling leukocyte fraction as well as in the number of leukocytes adherent to the endothelium (0.25 +/- 0. 1 and 96 +/- 34 cells/mm2 respectively) in comparison to the untreated animals with AiA (0.44 +/- 0.03 and 206 +/- 22 cells/mm2 respectively). Additionally, CXB-treated arthritic animals showed significantly less knee joint swelling and reduced adhesion molecule expression.

CONCLUSION

In the present study, COX-2 expression in the synovial tissue of mice with AiA could be demonstrated. Selective COX-2 inhibition with CXB resulted in reduced leucocyte-endothelial cell interactions and decreased adhesion molecule expression. Evidence for a protective role of COX-2 in mouse AiA was not found.

Attenuation of Leukocyte Sequestration by Selective Blockade of PECAM-1 or VCAM-1 in Murine Endotoxemia

BACKGROUND

Molecular mechanisms regulating leukocyte sequestration into the tissue during endotoxemia and/or sepsis are still poorly understood. This in vivo study investigates the biological role of murine PECAM-1 and VCAM-1 for leukocyte sequestration into the lung, liver and striated skin muscle.

METHODS

Male BALB/c mice were injected intravenously with murine PECAM-1 IgG chimera or monoclonal antibody (mAb) to VCAM-1 (3 mg/kg body weight); controls received equivalent doses of IgG2a (n = 6 per group). Fifteen minutes thereafter, 2 mg/kg body weight of Salmonella abortus equi endotoxin was injected intravenously. At 24 h after the endotoxin challenge, lungs, livers and striated muscle of skin were analyzed for their myeloperoxidase activity. To monitor intravital leukocyte-endothelial cell interactions, fluorescence videomicroscopy was performed in the skin fold chamber model of the BALB/c mouse at 3, 8 and 24 h after injection of endotoxin.

RESULTS

Myeloperoxidase activity at 24 h after the endotoxin challenge in lungs (12,171 +/- 2,357 mU/g tissue), livers (2,204 +/- 238 mU/g) and striated muscle of the skin (1,161 +/- 110 mU/g) was significantly reduced in both treatment groups as compared to controls, with strongest attenuation in the PECAM-1 IgG treatment group. Arteriolar leukocyte sticking at 3 h after endotoxin (230 +/- 46 cells x mm(-2)) was significantly reduced in both treatment groups. Leukocyte sticking in postcapillary venules at 8 h after endotoxin (343 +/- 69 cells/mm2) was found reduced only in the VCAM-1-mAb-treated animals (215 +/- 53 cells/mm2), while it was enhanced in animals treated with PECAM-1 IgG (572 +/- 126 cells/mm2).

CONCLUSION

These data show that both PECAM-1 and VCAM-1 are involved in endotoxin-induced leukocyte sequestration in the lung, liver and muscle, presumably through interference with arteriolar and/or venular leukocyte sticking.

Fluorescent microspheres are reliable for serial bone blood flow measurements

The fluorescent microsphere method is one of the current techniques to determine regional blood flow in various organs. The purpose of this study was to examine the suitability of fluorescent microspheres for serial measurement of regional bone blood flow. Six anesthetized female New Zealand rabbits received five left ventricular injections of fluorescent microspheres in 20-minute intervals. To test the precision of the measurement two types of fluorescent microspheres were injected simultaneously at the first and last injections. Blood flow was calculated in the kidneys, lungs, brain, femurs, and tibias after measuring the fluorescence intensity in each reference blood and tissue sample. Comparison of blood-flow values obtained by simultaneously injected microspheres showed an excellent correlation and a minimal percentage difference at the first and last injections, indicating valid measurements of regional bone blood flow. No significant differences were observed when comparing blood flow in the corresponding regions of bones on the right side and left side. Mean blood flow in the femur and tibia significantly increased at the fourth injection whereas flow distribution within the femur and tibia essentially remained unchanged throughout the experiment. Comparison of blood flow values obtained by simultaneously injected microspheres showed moderate agreement for the kidneys and lungs at the last injections. Because this finding might be attributable to disturbances of microcirculation caused by accumulation of spheres in high-flow organs, the increase in regional bone blood flow observed in our experiments has to be interpreted carefully. This study showed that bone blood flow can be determined reliably in anesthetized rabbits by as many as three serial injections of fluorescent microspheres.

G209A mutant alpha synuclein expression specifically enhances dopamine induced oxidative damage

Alpha synuclein protein may play an important role in familial and sporadic Parkinson's disease pathology. We have induced G209A mutant or wild-type alpha-synuclein expression in stable HEK293 cell models to determine if this influences markers of oxidative stress and damage under normal conditions or in the presence of dopamine or paraquat. Induced wild-type or mutant alpha-synuclein expression alone had no effect upon levels of oxidative stress or damage, as measured by glutathione levels or aconitase activity. Both wild-type and mutant alpha-synuclein expression decreased the oxidative damage induced by paraquat, although the protection was less marked with mutant alpha-synuclein expression. This suggests that alpha-synuclein expression may either have anti-oxidant properties or may upregulate cellular antioxidant levels, a function that was diminished by the G209A mutation. However, mutant but not wild-type alpha-synuclein expression specifically enhanced dopamine associated oxidative damage. Non-expressing cells treated with reserpine to inhibit the vesicular monoamine compartmentalisation produced similar results. However, consistent with the hypothesis that mutant alpha-synuclein disrupts vesicular dopamine compartmentalization, this effect was diminished in cells expressing mutant alpha-synuclein. This may result in increased dopamine metabolism and cause selective oxidative damage to dopaminergic cells.

Microspheres accurately predict regional bone blood flow

Even though the microsphere method frequently is used to determinate bone blood flow, validation of this technique for bone blood flow measurement is incomplete. The method is based on the principle that injected microspheres are distributed with the arterial blood and trapped in the capillaries because of their diameter (15 microm). The number of spheres lodged in an organ is proportional to its blood flow. The number of radioactive or fluorescent microspheres in a specific organ is determined indirectly by measuring radioactivity or fluorescence intensity in the organ. In this study the reliability and precision of the microsphere method for determining bone blood flow was established using radioactive and fluorescent microspheres. Six female, anesthetized New Zealand rabbits received left ventricular injections of pairs of fluorescent and/or radioactive microspheres. The humerus, femur, and tibia were dissected in a standardized manner and blood flow was determined in each sample. Comparison of relative blood flow values showed an excellent correlation between radioactive and fluorescent microspheres. The percentage difference and variation between two simultaneously injected sets of microspheres was minimal for radioactive microspheres (0.8% +/- 9.6%) and for fluorescent microspheres (0.2% +/- 11.4%). Regional bone blood flow in different regions of the femur, tibia, or humerus ranged from 2.2-28.1 mL/minute/100 g, but there was no significant difference between right and left bone samples of the same region after repeated measurement. Radioactive and fluorescent microspheres allow precise determination of regional bone blood flow.

Soluble complement receptor 1 preserves endothelial barrier function and microcirculation in postischemic pancreatitis in the rat

Components of the activated complement cascade are considered to play a pivotal role in ischemia-reperfusion-induced organ injury. With the use of intravital epifluorescence microscopy, we investigated the effect of complement inhibition by the recombinant soluble complement receptor 1 (sCR1; TP10) on the effect of macromolecular microvascular permeability, functional capillary perfusion, and leukocyte endothelium interaction in postischemic pancreatitis. Anaesthetized Sprague-Dawley rats were subjected to 60 min of normothermic pancreatic ischemia induced by microclipping of the blood-supplying arteries of the organ. Rats who received sCR1 (15 mg/kg body wt iv; n = 7) during reperfusion showed a significant reduction of permeability (1.77 +/- 1.34 x 10(-8) cm/s; n = 7) of tetramethylrhodamine isothiocyanate-labeled albumin injected 90 min after the onset of reperfusion compared with vehicle-treated animals (6.95 +/- 1.56 x 10(-8) cm/s; n = 7). At 120 min after the onset of reperfusion, the length of red blood cell-perfused capillaries (functional capillary density) was significantly improved (from 279 +/- 15.7 to 330 +/- 3.7 cm(-1); n = 7) and the number of leukocytes adherent to postcapillary venules was significantly reduced (from 314 +/- 87 to 163 +/- 71 mm(-2); n = 7) by sCR1 compared with vehicle treatment. Complement inhibition by sCR1 effectively ameliorates pancreatic ischemia-reperfusion-induced microcirculatory disturbances and might be considered for treatment of postischemic pancreatitis.

Fluorescent microsphere method is suitable for chronic bone blood flow measurement: a long-term study after meniscectomy in rabbits

The fluorescent microsphere (FM) method is considered a reliable technique to determine regional bone blood flow (RBBF) in acute experiments. In this study, we verified the accuracy and validity of this technique for measurement of RBBF in a long-term experiment and examined RBBF after meniscectomy. Twenty-four anesthetized female New Zealand white rabbits (3 groups, each n = 8) received consecutive left ventricular injections of FM in defined time intervals after meniscectomy: group 1 from preoperation to 3 wk postoperation; group 2 from 3 to 7 wk postoperation; and group 3 from 7 to 11 wk postoperation. To test the precision of the FM method, two FM species were injected simultaneously at the first and last measurement. After the experiment, humeri, femora, tibiae, and reference organs (kidney, lung, brain) were removed and dissected according to standardized protocols. Fluorescence was determined in each reference blood and tissue sample, and blood flow values were calculated. Blood flow in kidney, lung, and brain revealed no significant difference between right and left side and remained unchanged during the observation period, thus excluding errors due to shunting and dislodging of spheres in our experiments. Comparison of relative bone blood flow values obtained by simultaneously injected FM showed an excellent correlation at the first and last injection, indicating valid RBBF measurements in long-term experiments. We found a significant increase in RBBF 3 wk after meniscectomy in the right tibial condyles compared with the nonoperated left side. Similar changes were found in the femoral condyles. RBBF in other regions of tibia, femur, and humerus revealed no significant differences between right- and left-sided bone samples of the same region. Our results demonstrate that the FM method is valid for measuring RBBF in long-term experiments. In addition, we were able to demonstrate that meniscectomy leads to an increase in RBBF in the tibial condyles at a very early stage. This increase might be caused by stress-induced alterations of the subchondral bone.

Direct assessment and distribution of regional portal blood flow in the pig by means of fluorescent microspheres

Measurement of regional organ blood flow by means of fluorescent microspheres (FM) is an accepted method. However, determination of regional portal blood flow (RPBF) cannot be performed by microspheres owing to the entrapment of the spheres in the upstream capillary bed of the splanchnic organs. We hypothesized that an adequate experimental setting would enable us to measure RPBF by means of FM and to analyze its distribution within the pig liver. A mixing chamber for the injection of FM was developed, and its capability to distribute FM homogeneously in the blood was evaluated in vitro. The chamber was implanted into the portal vein of six anesthetized pigs (23.5 +/- 2.9 kg body wt). Three consecutive, simultaneous injections of FM of two different colors into the chamber were performed. Reference portal blood samples were collected by means of a Harvard pump. At the end of the experiment, the liver was explanted and fixed in formalin before dissection. FM were isolated from the tissue samples by an automated process, and fluorescence intensity was determined. Comparison of 5,458 single RPBF values, determined by simultaneously injected FM, revealed good agreement (bias 2.5%, precision 12.7%) and high correlation (r = 0.97, r2 = 0,95, slope = 1.04, intercept = 0.05). Median RPBF was 1.07 +/- 0.78 ml x min(-1) x g(-1). Allocation of the blood flow values to the anatomic regions of the liver revealed a significantly higher RPBF (P = 0.01) in the liver tissue located close to the diaphragm compared with the rest of the organ and a significantly lower RPBF (P = 0.01) in the left liver lobe compared with the median and right lobes. The results show that the model presented makes it possible to measure RPBF by means of FM reliably and that RPBF is distributed heterogeneously in the porcine liver.

Quantitative Assessment of Angiogenesis in Murine Antigen-Induced Arthritis by Intravital Fluorescence Microscopy

Inhibition of angiogenesis might be a therapeutic approach to prevent joint destruction caused by the overgrowing synovial tissue during chronic joint inflammation. The aim of this study was to investigate angiogenesis in the knee joint of mice with antigen-induced arthritis (AIA) by means of intravital microscopy. In 14 mice (C57BL6/129Sv) intravital microscopic assessment was performed on day 8 after AIA induction in two groups (controls, AIA). Synovial tissue was investigated by intravital fluorescence microscopy using FITC-dextran (150 kD). Quantitative assessment of vessel density was performed according to the following categories: functional capillary density (FCD, vessels <10 microm in diameter), functional vessel density (FVD, vessels >10 microm) and FVD of vessels with angiogenic criteria (convoluted vessels, abrupt changes of diameter, vessels which are generated by sprouting and progressively pruned and remodelled). Microvessel count was performed using immunohistochemistry. There was no significant difference in FCD between the control group (337 +/- 9 cm/cm2; mean +/- SEM) and the AIA group (359 +/- 13 cm/cm2). The density of vessels larger than 10 microm diameter was significantly increased in animals with AIA (135 +/- 10 vs. 61 +/- 5 cm/cm2 in control). The density of blood vessels with angiogenic criteria was enhanced in arthritic animals (79 +/- 17 vs. 12 +/- 2 cm/cm2 in control). There was a significant increase in the microvessel count in arthritic animals (297 +/- 25 vs. 133 +/- 16 mm(-2) in control). These findings demonstrate that angiogenesis in murine AIA can be assessed quantitatively using intravital microscopy. Further studies will address antiangiogenic strategies in AIA.

Inhaled nitric oxide induces cerebrovascular effects in anesthetized pigs

Although inhaled nitric oxide (NO(i)) is considered to act selectively on pulmonary vessels, EEG abnormalities and even occasional neurotoxic effects of NO(i) have been proposed. Here, we investigated cerebrovascular effects of increasing concentrations of 5, 10 and 50 ppm NO(i) in seven anesthetized pigs. Cerebral hemodynamics were assessed non-invasively by use of near-infared spectroscopy and indicator dilution techniques. NO(i) increased cerebral blood volume significantly and reversibly. This effect was not attributable to changes of macrohemodynamic parameters or arterial blood gases. Simultaneously, cerebral transit time increased while cerebral blood flow remained unchanged. These data demonstrate a vasodilatory action of NO(i) in the cerebral vasculature, which may occur preferentially in the venous compartment.

Validity of fluorescent microspheres method for bone blood flow measurement during intentional arterial hypotension

In this study, we compared bone blood flow values obtained by simultaneously injected fluorescent (FM) and radiolabeled microspheres (RM) at stepwise reduced arterial blood pressure. Ten anesthetized female New Zealand White rabbits received simultaneous left ventricular injections of FM and RM at 90, 70, and 50 mmHg mean arterial blood pressure (MAP). After the experiments, both kidneys and long bones of all four limbs were removed and dissected in a standardized manner. Radioactivity (corrected for decay, background, and spillover) and fluorescence were determined, and blood flow values were calculated. Relative blood flow values estimated for each bone sample by RM and FM were significantly correlated (r = 0.98, slope = 0.99, and intercept = 0.04 for 90 mmHg; r = 0.98, slope = 0.94, and intercept = 0.09 for 70 mmHg; r = 0.98, slope = 0.96, and intercept = 0.07 for 50 mmHg). Blood flow values (ml x min-1 x 100 g-1) of right and left bone samples determined at the different arterial blood pressures were identical. During moderate hypotension (70 mmHg MAP), blood flow in all bone samples remained unchanged compared with 90 mmHg MAP, whereas a significant decrease of bone blood flow was observed at severe hypotension (50 mmHg MAP). Our results demonstrate that the FM technique is valid for measuring bone blood flow. Differences in bone blood flow during altered hemodynamic conditions can be detected reliably. In addition, changes in bone blood flow during hypotension indicate that vasomotor control mechanisms, as well as cardiac output, play a role in setting bone blood flow.

Evaluation of murine liver transmission electron micrographs by an innovative object-based quantitative image analysis system (Cellenger)

BACKGROUND

Transmission electron micrographs are widely used to demonstrate tissue damage. However, the results are qualitative and dependent on the experience of the investigator. Recently, a new multiscale object-based quantitative image analyzing systems (Cellenger) has been introduced to study highly textured black-and-white images. It is unknown, whether this system permits the quantitative image analysis of electron micrographs of parenchymal tissue. Therefore, we analyzed whether the Cellenge system permits the quantitative evaluation of electron micrographs of murine liver under normal conditions and after ischemia-reperfusion injury. The results were compared with those obtained by conventional qualitative classification. -

METHOD

Transmission electron micrographs from murine liver that had been exposed to isolated reversible ischemia at hypothermic conditions of 4 degrees C, 15 degrees C, 26 degrees C and 37 degrees C, and of sham-operated animals, which served as controls (2 images per animal, n = 3 in each group), were analyzed qualitatively by an investigator with experience in electron microscopy. For quantitative analysis, the Cellenger was used and the following damage parameters were studied: ratio of area of endothelial cell nucleus to area of endothelial cell (N/C ratio), ratio of area of hepatocellular vacuoles to area of total hepatocyte cytoplasm (V/C ratio) and ratio of area of microvilli in the space of Disse to area of the sinusoids (M/S ratio). All values were sampled within one group (n=6) and the data given in [%] (MW +/- SEM). P-values were accepted as significant below 0.05.

RESULTS

After normothermic ischemia, all quantitative damage parameter were significantly altered as compared to sham-operated animals (N/C 15 +/- 9% vs. 37 +/- 7%, V/C 18 +/- 4% vs. 0, and M/S 0 vs. 10 +/- 1%) and all hypothermia groups. The qualitative electron micrograph section analysis corresponded very well with these results.

CONCLUSION

We demonstrate that an multiscale object-based quantitative analysis of transmission electron micrographs from mouse liver under control conditions and after I/R provide accurate classification of relevant tissue damage parameter. The system is now ready to use for further applications within the field of highly textured electron micrographs.

Determination of regional bone blood flow by means of fluorescent microspheres using an automated sample-processing procedure

The determination of regional blood flow utilizing fluorescent microspheres (FMs) is an established method for numerous organs. Recent progress, in particular the automation of sample processing, has further improved this method. However, the FM method (reference sample technique), which allows repetitive measurement of regional organ blood flow, has so far not been used for the determination of blood flow in bone. The aim of the present study was to establish FM for the quantification of regional bone blood flow (RBBF). Female, anesthetized New Zealand rabbits (n = 6) received left ventricular injections of different amounts of FM at six subsequent time points. In order to examine the precision of RBBF determination, two different FM species were injected simultaneously at the sixth injection. At the end of the experiments the femoral and tibial condyles of each hind limb were removed and the fluorescence intensity in the tissue samples was measured by an automated procedure. In an in vitro study we have shown that acid digestion of the crystalline matrix has no effect on the fluorescence characteristics of FM. The determination of the number of spheres per tissue sample revealed that depending on the tissue sample size up to 3 x 10(6) spheres/injection were necessary to obtain about 400 microspheres in the individual bone samples. RBBF values of the tibial and femoral condyles did not differ at various injection intervals. The tibial blood flow values varied between 6.6 +/- 1.1 and 8.5 +/- 1.4 ml/min/100 g and were significantly higher than those of the femur (4.3 +/- 1.1 to 6.0 +/- 1.8 ml/min/100 g). The bone blood flow values obtained by simultaneous injection of two FM species correlated significantly (r = 0.96, slope = 1.06, intercept = 0.05), the mean difference was 0.39 +/- 1.11 ml/min/100 g. Our data demonstrate that the measurement of RBBF by means of FM allows a valid determination of RBBF.

[Direct visualization of microcirculation in burn wounds with OPS imaging--is determination of depth of burns possible?]

Adjunct diagnostic techniques might help surgeons to accurately analyse the depth of a burn. However, despite all technical innovations an ideal device for such an application has not been established for routine use as yet. OPS imaging implemented into the CYTOSCAN A/R is a new, recently introduced technique which allows to obtain high contrast images of the microcirculation without the necessity for fluorescent dyes. The aim of the study was to validate OPS imaging as a tool to study microcirculation in skin after burn injury. OPS imaging was applied by no-touch technique and capillary blood flow was videotaped. Subsequent measurements of the microcirculation were performed at the identical site of the burn. Quantitative analysis of the microcirculation was performed off-line using CapImage. OPS imaging produces high quality images of the microcirculation in a burn wound. Data is given as the number of perfused capillaries per observation area (functional capillary density; FCD) [n/cm2]. OPS imaging allows for direct in vivo visualization and quantification of the microcirculation in burned skin. Our preliminary results of the use of OPS imaging in assessing the microcirculation in burns appear promising, and we hope that this novel technique will allow to improve the knowledge of the dynamics of the microcirculation in the pathophysiology of thermal injury.

Effects of ibandronate on inflammation in mouse antigen-induced arthritis

OBJECTIVE

To investigate the effects of ibandronate, a novel aminobisphosphonate, on inflammation as well as leukocyte-endothelial cell interaction in mouse antigen-induced arthritis (AiA).

MATERIAL AND TREATMENT

36 Balb/c mice were subcutaneously injected with 160 microg/kg of ibandronate once per day beginning at day 7 until day 13 after induction of AiA.

METHODS

The severity of arthritis was assessed by changes of the transverse knee joint diameter. For the intravital fluorescence microscopy measurements on day 14 after AiA induction, the patella tendon was partly resected to visualize the intraarticular synovial tissue of the knee joint. The number of rolling and adherent leukocytes as well as red blood cell (RBC) velocity and functional capillary density (FCD) were quantified in synovial microvessels. Furthermore, leukocyte infiltration in the synovium was determined in histological sections with an established score.

RESULTS

Both fractions of rolling leukocytes (p = 0.016) as well as number of extravasated leukocytes (p = 0.004) were enhanced in control animals treated with ibandronate in comparison to animals which received saline. Arthritic animals with and without ibandronate treatment revealed an increased FCD (p = 0.006, p = 0.008), enhanced number of rolling ( p = 0.002, p = 0.001) and adherent leukocytes (p = 0.009, p = 0.007) and greater swelling of the left knee joint (p = 0.002, p = 0.001) when compared to control animals. No significant differences between arthritic animals and arthritic animals treated with ibandronate were found in any of the parameters assessed including leukocyte adherence, FCD, histology, and knee joint swelling.

CONCLUSION

Ibandronate treatment of healthy mice was associated with an enhanced fraction of rolling leukocytes and increased numbers of extravasated leukocytes indicating a proinflammatory effect on the synovial microcirculation. In animals with a preexisting antigen-induced arthritis, however, ibandronate did not induce an exacerbation of joint inflammation and leukocyte adherence.

[Inflammatory responses to wear particles in vivo: a novel model in the murine knee joint]

Although it is now widely recognized that the inflammatory response to implant wear particles plays an important role in aseptic loosening of total joint replacements, the precise mechanisms of this process remain unclear. The aim of this study was to establish an animal model for the study of the adverse response to particulate wear debris and the effects on the synovial microcirculation as well as the leukocyte-endothelial cell interaction in the murine knee joint in vivo. Balb/c mice were injected with 50 microl of a 0.5-microm polystyrene particle suspension (0.1% v/v) into the knee joint. The severity of the inflammatory response was evaluated at days 1, 2, 3, 5, 7 (acute), 21 (intermediate), and 63 (chronic) after particle injection. Histological examination as well as assessment of the synovial microcirculation using intravital microscopy was performed. For the intravital microscopy measurements, the patella tendon was partially resected for visualization of the synovial tissue of the knee joint and the fluorescent markers FITC-dextran and rhodamine 6G were injected intravenously. There was a significantly enhanced leukocyte-endothelial cell interaction beginning at day 3 after particle injection with a maximum in the acute phase (days 5-7) and a subsequent decline in the intermediate (day 21) and chronic (day 63) phases. Functional capillary density was significantly increased from day 3 until day 21 after particle application. The histological examination showed an inflammatory reaction that complied widely with the temporal course of the microvascular parameters and resembled the histological appearance of the synovial-like membrane around loose joint prostheses. A novel model was established for the qualitative and quantitative investigation of the particle-induced inflammatory response in the joint environment. It was shown for the first time that there is a significantly enhanced leukocyte-endothelial cell interaction in the synovial tissue after intra-articular particle injection. This model seems to be suitable for further investigations, e.g., dealing with the biocompatibility of different particle materials.

Noninvasive in vivo assessment of the pancreatic microcirculation: orthogonal polarization spectral imaging

INTRODUCTION

Capillary perfusion failure of the pancreatic microcirculation is characteristic in the pathogenesis of acute pancreatitis and ischemia-reperfusion damage after pancreas transplantation. Up to now, no logistic suitable method for analyzing pancreatic capillary perfusion during operations in humans has been established without the use of fluorescent dyes.

AIM

To compare the well-established technique of intravital epifluorescence microscopy with the novel noninvasive method of orthogonal polarization spectral (OPS) imaging for measurement of the pancreatic functional capillary density.

METHODOLOGY

In eight anesthetized rats, six identical capillary regions of interest per animal were measured by both methods, and the results were compared.

RESULTS

Absolute values from the capillary perfusion data were not significantly different between the two methods (fluorescence microscopy: 394 +/- 44 cm/cm2; OPS imaging: 385 +/- 45 cm/cm2). Correlation parameters were significant, and Bland-Altman analyses showed good agreement with a mean difference (bias) between the two methods of 6.9 cm/cm2, indicating that slightly smaller values are measured with OPS imaging.

CONCLUSION

OPS imaging is a valid noninvasive method that analyzes the pancreatic microcirculation as accurately as the established intravital microscopy technique and therefore could be useful for clinical research and diagnosis during transplantation and operations.

New mathematical model for the correct prediction of the exchangeable blood volume during acute normovolemic hemodilution

BACKGROUND

The blood volume that has to be exchanged for crystalloids and/or colloids during acute normovolemic hemodilution (ANH) in order to reach a preset target hemoglobin concentration (hb) is usually predicted by the Bourke and Smith formula developed in 1974. This formula systematically overestimates the 'true' exchangeable blood volume (EBV), a fact that may potentially endanger patients because the target hb will be missed and the normovolemic anemia might turn out to be more severe than a priori intended. Our objective was to develop a more accurate mathematical model of hemodilution kinetics and to validate this new model in animals and in patients undergoing ANH.

METHODS

Twenty-two anesthetized beagle dogs and 18 patients under balanced anesthesia underwent isovolemic hemodilution with hydroxyethyl starch (HAES 6%, 200 000) to a target hb of 7 g dl-1 or 9 g dl-1, respectively. Exchangeable blood volume predicted by use of the different mathematical models was compared with the blood volume actually exchanged to meet the preset target hb.

RESULTS

Calculation of EBV by the Bourke and Smith formula (EBVB + S) systematically overestimated the volume actually exchanged (overestimation: dogs 15%, patients 20%), whereas our new iterative model predicted EBV (EBViterative) more reliably (overestimation: dogs 1%, patients 8%). In both cases EBVB + S differed significantly from the EBViterative.

CONCLUSION

Exchangeable blood volume is predicted more accurately by the new iterative model than by the Bourke and Smith formula. The iterative model leads to an improvement in patient safety and provides a physiologically adequate basis for future studies investigating the efficacy of ANH in reducing allogenic blood transfusions.

Effect of C-peptide on wound healing and microcirculation in diabetic mice

AIM

Recent studies have demonstrated that C-peptide is biologically active and might have a beneficial effect on late complications in diabetes mellitus. The aim of this study was to investigate the effects of systemically given C-peptide on dermal wound healing in diabetic mice.

METHODS

Experiments were carried out in male SKH-1 hr hairless mice. Dermal wounds were created (diameter 2.5mm) in streptozotozin-diabetic and normal control mice. Mice were randomized into three treatment groups (n = 10 each): Normal controls, diabetic mice with PBS or C-peptide injection twice daily. At various time points (prior wounding as well as days 4, 7, 10 and 15) microcirculation was quantitatively analyzed by intravital fluorescent microscopy to determine wound surface area, vessel diameter, red blood cell velocity, plasma leakage, functional capillary density. In addition, leukocyte/endothelium interaction was quantified by in vivo visualization of leukocytes.

RESULTS

Systemic administration of C-peptide showed no influence on wound healing or standard microcirculatory parameters. The leukocyte/ endothelium interaction revealed a significant (p<0.05) increase in the number of adherent leukocytes 15 days after wound creation in C-peptide treated diabetic mice.

CONCLUSION

Except for the significantly increased number of leukocytes adherent to venular endothelium in the C-peptide group no alteration was observed in wound healing and microcirculation. Neutrophil recruitment after C-peptide injection is of interest because it may reduce the risk of infection in diabetes mellitus.

Initial reperfusion with magnesium after cardioplegic arrest attenuates myocardial reperfusion injury

BACKGROUND

Magnesium's effect on calcium ion concentrations may attenuate myocardial reperfusion injury. The aim of this study was therefore to investigate the effects on the recovery of myocardial function of initial reperfusion with varying Mg(2+) concentrations following cardioplegic arrest.

METHODS

Isolated guinea pig hearts underwent 3.5 hours of cardioplegic arrest in St. Thomas Hospital II solution (STH) or Bretschneider HTK solution (HTK) at 24 degrees C. Control hearts were reperfused with normal Krebs-Henseleit solution (KHS). In the therapy groups, hearts were initially reperfused with 5, 10, or 20 mM Mg(2+) for 15 minutes, followed by 30 minutes of perfusion with KHS.

RESULTS

During initial reperfusion, elevated Mg(2+) concentrations markedly reduced rate-pressure product, dP/dt and O 2 demand. Release of LDH and CK was reduced in the therapy groups pretreated with Bretschneider HTK. After Mg(2+) washout, left ventricular function recovery and compliance was improved after HTK but not after STH cardioplegia. Following both STH and HTK cardioplegia, Mg(2+) reperfusion reduced reperfusion arrhythmias.

CONCLUSIONS

The combination of HTK cardioplegia with 15 min initial Mg(2+) (5 and 10 mM, but not 20 mM) reperfusion was clearly superior to HTK followed by immediate Krebs-Henseleit reperfusion as well as STH cardioplegia with or without initial Mg(2+) reperfusion. The high Mg(2+) concentrations in the STH solution might mask beneficial effects of Mg(2+) reperfusion.

Characterization of microcirculatory disturbance in a novel model of pancreatic ischemia-reperfusion using intravital fluorescence-microscopy

INTRODUCTION

Microcirculatory disturbances caused by ischemia-reperfusion injury (IRI) are the crucial hallmarks of pancreatitis following pancreas transplantation.

AIMS

To develop a novel rodent model of normothermic in situ ischemia of a pancreatic tail-segment that simulates the clinical situation of pancreas transplantation by flushing the organ via an inserted microcatheter and thus enables selective treatment of the organ via this access.

METHODOLOGY

Four experimental groups were investigated (n = 7 Wistar rats/group): sham animals without ischemia and dissection of the pancreas; control animals with dissection of a pancreatic tail segment pedunculated on the splenic vessels and flushing od this segment with saline via a microcatheter; and two groups of animals treated like controls with a pancreatic ischemia time of 1 hour or 2 hours. With use of intravital epifluorescence microscopy, the microcirculatory damage was characterized by investigation of functional capillary density (FCD) and leukocyte adherence in postcapillary venules (LAV) before ischemia and during a reperfusion time of 2 hours. Dry:wet ratio determinations, light microscopy, and electron microscopic investigations were performed to characterize the histologic organ damage.

RESULTS

FCD decreased significantly (p < 0.05) 2 hours after reperfusion in the groups of 1-hour (-29.21%) and 2-hour ischemia (-42.73%), in comparison with baseline values. LAV increased significantly (p < 0.05), 4.3- and 5.8-fold, after 1-hour and 2-hour ischemia during the observation time. The histologic damage was similar to posttransplantation pancreatitis in humans 1 hour after reperfusion. In sham and control animals these alterations were not significant.

CONCLUSIONS

The rodent in situ model of pancreatic IRI showed standardized microcirculatory damage dependent on the ischemia time. Offering the possibility of selective treatment by the direct artery access to the ischemic pancreatic area, the model enables investigations of questions related to human pancreas transplantation.

Small-volume resuscitation: from experimental evidence to clinical routine. Advantages and disadvantages of hypertonic solutions

BACKGROUND

The concept of small-volume resuscitation (SVR) using hypertonic solutions encompasses the rapid infusion of a small dose (4 ml per kg body weight, i.e. approximately 250 ml in an adult patient) of 7.2-7.5% NaCl/colloid solution. Originally, SVR was aimed for initial therapy of severe hypovolemia and shock associated with trauma.

METHODS

The present review focuses on the findings concerning the working mechanisms responsible for the rapid onset of the circulatory effect, the impact of the colloid component on microcirculatory resuscitation, and describes the indications for its application in the preclinical scenario as well as perioperatively and in intensive care medicine.

RESULTS

With respect to the actual data base of clinical trials SVR seems to be superior to conventional volume therapy with regard to faster normalization of microvascular perfusion during shock phases and early resumption of organ function. Particularly patients with head trauma in association with systemic hypotension appear to benefit. Besides, potential indications for this concept include cardiac and cardiovascular surgery (attenuation of reperfusion injury during declamping phase) and burn injury. The review also describes disadvantages and potential adverse effects of SVR:

CONCLUSION

Small-volume resuscitation by means of hypertonic NaCl/colloid solutions stands for one of the most innovative concepts for primary resuscitation from trauma and shock established in the past decade. Today the spectrum of potential indications involves not only prehospital trauma care, but also perioperative and intensive care therapy.