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Biomedical subjects

K Messmer

Publications and source records attributed to K Messmer.

At least 559 records · Page 31Linked to original sources
PubMedDate not supplied

Open chest and open pericardium affect the distribution of myocardial blood flow in the right ventricle.

We have investigated the effects of open chest and open pericardium on the distribution of myocardial blood flow assessed with the radioactive microsphere technique (15 microns). Five dogs with intact thorax served as controls (group I) and six dogs were studied after a right-sided thoracotomy and pericardiotomy (group II). Global myocardial blood flow (mean +/- S.D.) was 0.73 +/- 0.17 ml.min-1.g-1 in group I and 1.22 +/- 0.09 ml.min-1.g-1 in group II (p less than 0.05). Analysis of transmural blood flow distribution revealed that flow was 44% higher in the right and 60% higher in the left ventricular endocardial layers in the open-chest animals, whereas epicardial flow increased by 105% and 90%, respectively. As a result of the preferential blood flow to the epicardial layers of the right ventricle, the endo/epi ratio was reduced from 1.30 +/- 0.26 in group I to 0.86 +/- 0.11 in the open-chest group (p less than 0.05). Left ventricular endo/epi ratio was 1.27 +/- 0.16 and 1.06 +/- 0.11 (n.s.), respectively. External work and diastolic filling pressure of the right ventricle did not differ between the two groups and therefore cannot account for the redistribution of myocardial blood flow. It is concluded that the distribution of myocardial blood flow, particularly in the RV, is severely disturbed by thoracotomy and pericardiotomy. This is an important aspect for the planning and evaluation of studies under open-chest/open-pericardium conditions.

Animals↗
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Hemodilution in clinical surgery: state of the art 1996.

Acute normovolemic hemodilution entails removal of blood from a patient either immediately before or shortly after induction of anesthesia and simultaneous replacement with cell-free fluid. Nowadays, because of their predictable volume effects, the synthetic colloids (6% dextran 60/70, 6% hydroxyethyl starch 200,000) are preferred as volume substitutes; albumin should be avoided because of its high cost. Hemodilution has experienced a renaissance in recent years, mainly due to the evolving discussion of legal aspects, immunologic changes, viral infections, and a potentially higher cancer recurrence rate associated with the transfusion of homologous blood. Hemodilution should be considered for elective surgical patients free of contraindications and presenting with an initial hemoglobin concentration >/= 12 g/dl and an anticipated blood loss of >/= 1500 ml. The efficacy of this method (judged by the need to give homologous blood transfusion) depends on the preoperative (initial) hematocrit, the target hematocrit (to which hemodilution is performed), and the preset intra- and postoperative transfusion trigger. In the past, data from clinical trials showed that in healthy subjects a target hematocrit of 20% to 25% (hemoglobin 7.0-8. 0 g/dl) is feasible and safe for the patient. The lower the target hematocrit accepted, the more extensive is the monitoring required: Intraoperative target hemoglobin concentrations of 5.0 g/dl and less have been tolerated by surgical patients without adverse effects. The safety and efficacy of acute normovolemic hemodilution in terms of reducing homologous blood transfusion requirements has been demonstrated in various clinical studies. Hemodilution therefore is regarded an integral part of programs aimed at reducing the need for homologous blood and can thus be successfully combined with preoperative autologous blood deposition, intraoperative blood salvage, and carefully adjusted surgical techniques. Hemodilution is feasible and relatively cost-effective, and it minimizes adverse effects associated with transfusion of homologous blood, particularly transmission of viral diseases, immunosuppression, and infectious complications.

Blood Transfusion↗
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Comparative analysis of tissue fluorescence as related to capillary perfusion in random pattern skin flaps.

In random pattern skin flaps of mice, tissue fluorescence measured by means of videodensitometry at 24 h after flap elevation significantly correlates with intravital microscopically measured functional vessel density and viability of skin tissue as assessed by transmission light and electron microscopy. The correlation was found reproducible in non-ischaemic flaps (r = 0.86) and flaps being rendered ischaemic for 6 h after elevation (r = 0.98), indicating that increased microvascular permeability as a result of ischaemia/reperfusion does neither affect tissue fluorescence nor the accuracy of the fluorescein dye test. In addition, tissue fluorescence at 24 h after flap elevation accurately predicts ultimate flap survival on the 7th postoperative day with a sensitivity of 0.89 and a specificity of 0.85. These results suggest that in non-ischaemic as well as in ischaemic random pattern skin flaps tissue fluorescence can be used for assessment of nutritive blood flow, viability of skin tissue and ultimate tissue survival in these flaps.

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Pseudocolor display of regional organ blood flow determined by means of the radioactive microsphere technique.

The measurement of regional blood flow (RBF) by means of the radioactive microsphere method yields large sets of raw data. In order to display this large volume of data, we have developed a program which provides the user with a graphical illustration of RBF in different organs (e.g., heart, kidney, brain) using various projections and sections. RBF is visualized by a pseudocolor representation. This set-up enables the user to perform a semiquantitative analysis of RBF and provides a tool for the compact representation of the spatial distribution of RBF values in different parts and layers of the organs being studied. The program runs on a standard microcomputer.

Animals↗
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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.

Journal Article↗
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Phenotypic and functional differences between rat alveolar, pleural, and peritoneal macrophages.

Tissue macrophages (M phi) play a central and essential role in modulating the initiation and perpetuation of the inflammatory response. Phenotypical and functional differences among alveolar M phi (AM) and peritoneal M phi (PM) have been reported, but less is known about pleural M phi (PLM) and their ability and capacity to release biologically active substances. Therefore, the aim of this study was to determine the production of superoxide anion, nitric oxide (NO), and tumor necrosis factor alpha (TNF-alpha) by PLM in comparison to AM and PM in vitro. M phi from rats were isolated by lavage of the respective body compartment and characterized by evaluating the expression of the surface antigens MHC class II molecules, CD11b, and ED2-like antigen. Upon activation, AM produced significantly higher amounts of superoxide anion, NO, and TNF-alpha compared to PM and PLM. Taken together, the findings of this study demonstrate that rat PLM resemble PM more than AM in terms of production of key inflammatory mediators.

Animals↗
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Effects of NO synthase inhibitors on the synovial microcirculation in the mouse knee joint.

Production of nitric oxide by the inducible NO synthase (iNOS) is known to be enhanced in chronic joint inflammation and osteoarthritis as well as aseptic loosening of joint prostheses. Initial studies yielded promising results after inhibition of the nitric oxide synthase (NOS). However, the effect of NOS inhibition has not been studied at the site of the primary function of NO, the microcirculation of the synovium in vivo. Using our recently developed model for the in vivo study of synovial microcirculation in the mouse knee joint, the effects of selective versus nonselective inhibition of iNOS were investigated by means of intravital fluorescence microscopy. After resection of the patella tendon, the synovial fatty tissue was exposed for intravital microscopy. Diameter of arterioles, functional capillary density (FCD), diameter of venules, venular red blood cell velocity and leukocyte-endothelial cell interaction were quantitatively analyzed before, and 10 and 60 min after intravenous injection of NOS inhibitors [selective iNOS inhibitor N-iminoethyl-L-lysine (L-NIL), and nonselective NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME)]. Our results demonstrate that L-NAME causes a significant decrease in the arteriolar diameter and FCD associated with an increase in the leukocyte accumulation in the synovium in vivo. In contrast, L-NIL neither altered the microhemodynamics nor the leukocyte-endothelial cell interaction in the synovium, indicating its potential use for selective inhibition of iNOS in joint inflammation. Using our method, further studies will provide new insights into the unknown effect of NOS inhibition on the synovial microvasculature in inflammatory joint disease in vivo.

Animals↗
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The Cytoscan Model E-II, a new reflectance microscope for intravital microscopy: comparison with the standard fluorescence method.

The Cytoscan Model E-II (Cytometrics Inc., Philadelphia, Pa., USA) is a newly developed instrument which functions as an intravital microscope and is small and easily portable. Through the use of orthogonal polarization spectral (OPS) imaging, the Cytoscan Model E-II delivers images of the microcirculation which are comparable to those achieved with intravital fluorescence videomicroscopy (IFM), but without the use of fluorescent dyes. The purpose of this study was to validate the Cytoscan Model E-II instrument against IFM. The experiments were carried out on striated muscle in the dorsal skinfold chamber of the awake Syrian hamster. The following parameters were measured in identical regions of interest in the same animal under baseline conditions and 0.5 and 2 h after a 4-hour period of pressure-induced ischemia: arteriolar diameter, venular diameter and venular red blood cell velocity. Bland-Altman plots showed good agreement between the two techniques for venular red blood cell velocity. As expected, arteriolar and venular diameters as measured by the Cytoscan were on average 5 microm smaller than the values from IFM, since the Cytoscan measures the red blood cell column width and IFM measures luminal diameter. Thus, OPS imaging can be used to make valid measurements of microvascular diameter and red blood cell velocity in tissues.

Animals↗
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Comparison of regional blood flow values measured by radioactive and fluorescent microspheres.

Fluorescent microspheres (FM) have become an attractive alternative to radioactive microspheres (RM) for the measurement of regional blood flow (RBF). The aim of the present study was to investigate the comparability of both methods by measuring RBF with FM and RM. Eight anaesthetised pigs received simultaneous, left atrial injections of FM and RM with a diameter of 15 microm at six different time points. Blood reference samples were collected from the descending aorta. RBF was determined in tissue samples of the myocardium, spleen and kidneys of all 8 animals. After radioactivity of the tissue samples was determined, the samples were processed automatically for measuring fluorescence using a recently developed filter device (SPU). RBF was calculated with both the isotope and spectrometric data of both methods for each sample resulting in a total of 10,512 blood flow values. The comparison of the RBF values yielded high linear correlation (mean r(2) = 0.95 +/- 0.03 to 0.97 +/- 0.02) and excellent agreement (bias 5.4-6.7%, precision 9.9- 16.5%) of both methods. Our results indicate the validity of MS and of the automated tissue processing technique by means of the SPU.

Animals↗
PubMedDate not supplied

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.

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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.

Animals↗
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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.

Animals↗
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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.

Adenosine↗
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Impact of ischemia on tissue oxygenation and wound healing: intravital microscopic studies on the hairless mouse ear model.

To determine the effect of ischemia on tissue oxygenation and the healing of experimental wounds, chronic ischemia was induced in the ears of hairless mice by ligating 2 of the 3 main nutritional arteries. Tissue ischemia was verified by measurement of transcutaneous pO2 (tcpO2) prior to and on days 3, 6, 9, 12 and 15 after vessel ligation. TcpO2 values decreased from 24 to 6 mm Hg at day 2 after ligation, and slowly recovered to 12 mm Hg at day 12 after vessel ligation. In animals treated with the vasoactive drug buflomedil (3 mg/kg BW i.v., startling 2 days after vessel ligation) tcpO2 values were significantly higher on days 6 and 9 when compared to saline-treated control animals. In order to find out whether the enhanced tissue oxygenation resulted in enhancement of healing of wounds, we created circular wounds (diameter = 2.5 mm, depth 0.1 mm) on ischemic ears 2 days after vessel ligation. The wound surface area was measured by means of intravital fluorescence microscopy and digital planimetry at 3-day intervals until the time of wound closure. These experiments were performed on buflomedil-treated and control animals receiving equivalent amounts of saline. The reduction of wound surface area was accelerated and wound closure time was reduced from 15 days in control animals to 12 days in buflomedil-treated animals (p < 0.01). Functional capillary density as well as the microhemodynamic parameters microvessel diameter and red blood cell velocity were not different between buflomedil-treated and control animals.

Animals↗
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Buflomedil hydrochloride attenuates tourniquet-induced microvascular reperfusion injury in striated muscle.

With the use of intravital fluorescence microscopy and the dorsal skinfold chamber model we studied the effect of buflomedil hydrochloride on microvascular reperfusion injury after 4 h of tourniquet-induced ischemia in hamster striated muscle. Animals (n = 15) received 3 mg/kg buflomedil (i.v. bolus) 5 min before onset of reperfusion, and 3 mg/kg buflomedil (continuous i.v. infusion) during the first 20 min of reperfusion. Animals (n = 13) receiving equivalent volumes of saline served as controls. Tourniquet-induced ischemia resulted in (a) a marked decrease of functional capillary density and (b) accumulation and adherence of leukocytes in postcapillary venules after 30 min and 2 h of reperfusion. This was associated with an increased microvascular permeability (leakage of macromolecules), reflecting the alteration of endothelial cell integrity. Treatment with buflomedil significantly reduced both post-ischemic capillary perfusion failure and leukocyte adherence in venules. Concomitantly, the increase of microvascular permeability in postcapillary venules was almost prevented, indicating the beneficial effect of buflomedil on the manifestation of microvascular reperfusion injury following tourniquet ischemia in striated muscle.

Animals↗
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Prevalence of cyclic changes in limb volume (volumotion) of male patients with knee injury and the effects of ischemia/reperfusion due to tourniquet.

During surgery of limbs tourniquet up to a maximum of 2 h is frequently applied which may cause ischemia/reperfusion injury (IRI). During this condition the presence of vasomotion may have consequences for the perfusion and nutritive state of the tissues. We used a noninvasive plethysmographic method to investigate periodic changes in limb circumference (volumotion) in healthy male patients (n = 24) undergoing surgery for knee injury. To facilitate surgery a tourniquet was applied to the thigh, which caused an IRI of the leg. Results are given as mean of all values +/- SEM. Immediately after tourniquet release (duration 57.75 +/- 5.19 min) blood lactate levels in the femoral vein increased significantly from 1.40 +/- 0.08 to 2.59 +/- 0.20 mmol/l (p < 0.001) and pH fell from 7.39 +/- 0.01 to 7.32 +/- 0.01 (p < 0.001). Preoperatively 10 out of 24 patients (42%) showed signs of volumotion on the injured leg with a periodicity ranging from 0.8 to 6.9 cycles/min, whereas none showed volumotion in the control leg (p < 0.001). In the second measurement, taken after surgery and reperfusion while peripheral sympathetic nerves were blocked, 7 out of 18 patients (39%) showed volumotion on the injured leg and 0 on the control leg (p < 0.004). 6 h after IRI, volumotion was observed in 11 out of 17 patients (65%) on the injured leg and in 1 patient (6%) on the control leg (p < 0.001). The mean volume change in the patients with volumotion on the injured leg was 0.057 +/- 0.007 ml/100 ml tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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Functional capillary density: an indicator of tissue perfusion?

Functional capillary density (FCD) is one of the parameters obtained by intravital microscopy using epi-illumination of the tissue surface or trans-illumination of thin tissue layers. FCD, defined as the length of red cell-perfused capillaries per observation area (cm-1), has been used as an indicator of the quality of tissue perfusion in various animal models. Quantitative analysis of FCD in randomly selected regions of the tissue is performed by means of a computer-assisted video analysis system which allows calculation of the length of RBC-perfused capillaries. Basically, two different mathematical approaches can be employed: the first approach is based on the addition of the distances between two neighboring points (pixels) on the video screen (Pythagorean principle). The second approach uses the superimposition of a grid system that allows estimation of the capillary length by counting the number of intersections between the capillaries and the grid lines (stereological approach). The immanent error has been calculated in our laboratory to be +/- 1% with the Pythagorean and +/- 5% with the stereological method. Beside these systematic errors of computerized measurement, the individual (user-dependent) errors occurring during recognition and redrawing of the capillaries on the video image with use of a digitizing tablet are in the range of +/- 10% (intraindividual) and +/- 70% (interindividual) for the recognition and +/- 3% (interindividual) for the redrawing procedure. Our studies indicate that the errors resulting from the use of a computer-assisted calculation (Pythagorean or stereological approach) or the user-assisted redrawing of the capillaries are negligible when compared to the errors made during recognition of the capillaries on the video screen. The methods are applied for assessment of FCD in two different microcirculation models of skin muscle and pancreas yielding highly reproducible, user-independent results under physiologic conditions and the pathophysiologic conditions of ischemia-reperfusion.

Animals↗