Subcutaneous and gut tissue perfusion and oxygenation changes as related to oxygen transport in experimental peritonitis

Peritonitis and septic shock may lead to tissue hypoxia, but this risk is not identical in all organ systems. This study was undertaken to measure changes in tissue oxygenation and perfusion in the gut wall and subcutaneous tissue, respectively, and to examine their relation to oxygen delivery and consumption. Twelve pigs were anesthesized and mechanically ventilated. An ultrasonic flow probe was placed around the superior mesenteric artery for registration of blood flow. A mesenteric vein was cannulated for blood sampling. For calculation of gut intramural pH (pHi), a Silastic balloon (Tonomitor) was placed in the lumen of the midileum. pHi was calculated from tonometrically measured PCO2 and arterial bicarbonate concentration. The subcutaneous PO2 was measured by means of an oxygen-permeable Silastic tube implanted in the subcutis of the abdominal wall. Oxygen delivery (DO2) and consumption (VO2) were determined for the gut as well as for the whole body. In six randomly allocated animals, peritonitis was induced after a stabilization period of at least 1 hr, by instillation of autologous faeces into the abdominal cavity, while the other six animals served as controls. The animals were then followed for 5 hr. pHi remained stable in the control group, whereas a drop from 7.37 to 7.02 took place in the peritonitis group. In the test group, subcutaneous oxygen tension (PscO2) already began to fall 1 hr after the induction of peritonitis, and gained the minimum at the end of the study. In peritonitis, a moderate correlation was seen between pHi and DO2 (r = 0.51 +/- 0.16); no statistical difference was noted if pHi was correlated to gut DO2 (r = 0.56 +/- 0.18).(ABSTRACT TRUNCATED AT 250 WORDS)     

Theoretical analysis of complex oscillations in multibranched microvascular networks

A mathematical model was used to study the origin of complex self-sustained diameter oscillations in multibranched microvascular networks. The model includes three branching levels (order 3, 2, and 1 arterioles) of a microvascular network derived from in vivo observation in the hamster dorsal cutaneous muscle. The main biomechanical aspects covered by the model are (1) the dependence of the elastic and active wall stress on the inner radius and (2) the static and dynamic myogenic response. Simulations on isolated arterioles indicate that self-sustained periodic diameter oscillations may occur at constant transmural pressure. Conversely, simulations on the entire network reveal different oscillatory patterns, including periodic, quasiperiodic, and chaotic fluctuations. Chaos in the model is revealed by the presence of a broad noise-like component in the frequency spectrum and by the sensitivity dependence of model results on small perturbations. Our results suggest that, owing to the intrinsic nonlinearity of the system, a contracting mechanism, such as the myogenic response, may induce different oscillatory patterns. The change from periodic to chaotic oscillations may be a consequence of a modest variation in a parameter (systemic pressure or arterial resistance) not necessarily related to pathophysiological conditions. Accordingly, our in vivo observations in the skeletal muscle showed that in some instances arteriolar vasomotion is converted from regular to highly irregular patterns in basal conditions. Vasomotion is found to affect mean blood flow compared with the nonoscillatory steady state. Chaotic oscillations tend to maintain a constant ratio of blood flows entering into bifurcation vessels, whereas periodic vasomotion determines a different flow distribution at branches.     

Role of oxygen extraction from coronary blood in the regulation of oxygen transport to the myocardium

Experiments on anesthetized dogs were made to examine oxygen extraction from coronary blood during increase and decrease in cardiac rhythm frequency under varying conditions of vasomotor regulation. With an initially high tone of the coronary vessels both increase and reduction of myocardial oxygen supply occurred at the expense of vasomotor reactions. Under these conditions the coronary blood flow velocity and systolic rhythm correlated well. At the same time the oxygen level in coronary blood did not experience noticeable changes. As the initial tone of the coronary vessels dropped, vasomotor reactions were attenuated and oxygen extraction from coronary blood underwent alterations which had occurred prior to depletion of the coronary expanding reserves. The data obtained suggest that reduction of the initial tone of the coronary vessels proceeds non-uniformly, leading to a decrease in vascular sensitivity to the tissue oxygen level.     

Prediction of microcirculatory oxygen transport by erythrocyte/hemoglobin solution mixtures

Vaccination with naked DNA may be an alternative to conventional vaccines because it combines the efficacy of attenuated vaccines with the biological safety of inactivated vaccines. We recently showed that the vaccination with naked DNA coding for the immunorelevant glycoprotein D (gD) of pseudorabies virus (PRV) induced both antibody and cell-mediated immunity in pigs and provided protection against challenge infection. To determine whether the efficacy of the naked DNA vaccination against PRV could be improved, we compared three sets of variables. First, the efficacy of the naked DNA vaccine coding only for the immunorelevant gD was compared with a cocktail vaccine containing additional plasmids coding for two other immunorelevant glycoproteins, gB and gC. Second, the intramuscular route of vaccination was compared with the intradermal route. Third, the commonly used needle method of inoculation was compared with the needleless Pigjet injector method. Five groups of five pigs were vaccinated three times at 4-weeks intervals and challenged with the virulent NIA-3 strain of PRV 6 weeks after the last vaccination. Results showed that although the cocktail vaccine induced stronger cell-mediated immune responses than the vaccine containing only gD plasmid, both vaccines protected pigs equally well against challenge infection. Intradermal inoculation with a needle induced significantly stronger antibody and cell-mediated immune responses and better protection against challenge infection than intramuscular inoculation. Our data show that the route of administering DNA vaccines in pigs is important for an optimal induction of protective immunity.     

Physiological transport properties of cultured retinal microvascular endothelial cell monolayers

PURPOSE: To characterize baseline transport properties: hydraulic conductivity (Lp), albumin permeability (Pe), and transendothelial electrical resistance (TER) of bovine retinal microvascular endothelial cells (RMEC) in the development of an in vitro model of the blood-retinal barrier (BRB). METHODS: RMEC were grown on porous, polycarbonate filters for determination of the number of days required to achieve minimal transport rates. Lp, Pe, and TER were measured by utilizing a bubble tracking spectrophotometer, by quantifying the diffusional movement of fluorescein isothiocyanate-labeled albumin, and by utilizing a Millipore electrical resistance meter, respectively. RESULTS: Lp decreased significantly from 7.82 +/- 0.85 x 10(-7) (mean +/- SEM) cm/sec/cm H2O at post-plating Day 5 to 1.44 +/- 0.26 x 10(-7) cm/sec/cm H2O at Day 9. Pe of the monolayer also decreased progressively with days post-plating from 3.44 +/- 0.53 x 10(-6) cm/sec at Day 7 to a minimum of 1.95 +/- 0.29 x 10(-6) cm/sec at Day II. Peak TER fluctuated until Day 7, when it began to steadily increase from 17.14 ohm-cm2 to a peak value of 25.42 ohm-cm2 at Day 10, decreasing from then on to 22.24 ohm.cm2 on Day 12. Known disrupters of the BRB, NECA and VEGF, elicited significant increase in RMEC Lp showing the sensitivity of this model to pharmacological alterations. CONCLUSIONS: Our data indicate that RMEC grown on polycarbonate filters form a restrictive monolayer of cells, which exhibit dynamic alterations in response to pharmacological agents, thus demonstrating an in vitro model of the BRB. Future studies with the model may offer insights into the pathogenesis of retinal vascular diseases and allow convenient testing of pharmacological interventions.     

Sensitivity of Ca2+ transport of mitochondria to reactive oxygen species

To determine the association between specific structural changes in the hemagglutinin gene and pathogenicity of avian influenza viruses (AIVs), groups of 4-week-old White Plymouth Rock chickens were inoculated intravenously or intranasally with AIVs of varying pathogenicities isolated from chickens in central Mexico during 1994-1995. Mildly pathogenic (MP) viruses had a common hemagglutinin-connecting peptide sequence of Pro-Gln-Arg-Glu-Thr-Arg decreases Gly and had restricted capability for replication and production of lesions in tissues. The principle targets for virus replication or lesion production were the lungs, lymphoid organs, and visceral organs containing epithelial cells, such as kidney and pancreas. Death was associated with respiratory and/or renal failure. By contrast, highly pathogenic (HP) AIVs had one substitution and the addition of two basic amino acids in the hemagglutinin connecting peptide, for a sequence of Pro-Gln-Arg-Lys-Arg-Lys-Thr-Arg decreases Gly. The HP AIVs were pantropic in virus replication and lesion production ability. However, the most severe histologic lesions were produced in the brain, heart, adrenal glands, and pancreas, and failure of multiple critical organs was responsible for disease pathogenesis and death. No differences in lesion distribution patterns or in sites of AIV replication were evident to explain the variation in mortality rates for different HP AIVs, but HP AIVs that produced the highest mortality rates had more severe necrosis in heart and pancreas. The ability of individual HP AIVs to produce low or high mortality rates could not be explained by changes in sequence of the hemagglutinin-connecting peptide alone, but probably required the addition of other undetermined genomic changes.     

Infarction of solid Hodgkin's tumors in mice by antibody-directed targeting of tissue factor to tumor vasculature

We demonstrated previously that selective thrombosis of the blood vessels of solid tumors in mice can be achieved by targeting the extracellular domain of tissue factor by means of an antibody to an experimentally induced marker on tumor vascular endothelium. In the present study, we extend this finding to a naturally occurring marker of tumor vascular endothelium, vascular cell adhesion molecule-1 (VCAM-1). VCAM-1 is expressed by vascular endothelial cells in Hodgkin's disease and various solid tumors in mice and humans. It is absent from vascular endothelial cells in normal tissues in mice, with the exception of the heart and lungs, where it is present on venules. A monoclonal antibody to murine VCAM-1 was covalently linked to the extracellular domain of human tissue factor to create a "coaguligand." After i.v. administration to severe combined immunodeficient mice bearing human Hodgkin's tumors, the coaguligand localized selectively to VCAM-1-expressing vessels, caused thrombosis of those vessels, and retarded tumor growth. The coaguligand also localized to VCAM-1-expressing vessels in the heart and lungs of the mice but did not induce thrombosis in these sites. An immunohistochemical evaluation of the distribution of a monoclonal anti-phosphatidylserine (PS) antibody in the mice showed that the VCAM-1-expressing vessels in the tumor expressed PS, whereas the VCAM-1-expressing vessels in the heart and lungs lacked PS. The lack of thrombotic effect of the coaguligand on heart and lung vessels may be because PS is needed to provide the procoagulant surface upon which coagulation complexes can assemble. The requirement for coincident expression of the targeted marker and PS on tumor endothelium probably contributes to the selectivity of thrombotic action and the safety of coaguligands.     

Capillary oxygen transport during severe hypoxia: role of hemoglobin oxygen affinity

The efficacy of an increased hemoglobin oxygen affinity [decreased oxygen half-saturation pressure of hemoglobin (P50)] on capillary oxygen transport was evaluated in the hamster retractor muscle under conditions of a severely limited oxygen supply resulting from the combined effects of a 40% reduction in systemic hematocrit and hypoxic ventilation (inspired oxygen fraction 0.1). Two groups of hamsters were utilized: one with a normal oxygen affinity (untreated; P50 = 26.1 +/- 2.4 Torr) and one with an increased oxygen affinity (treated; P50 = 15.7 +/- 1.4 Torr) induced by the chronic short-term administration of sodium cyanate. Using in vivo video microscopy and image analysis techniques, we determined oxygen saturation and associated hemodynamics at both ends of the capillary network. During hypoxic ventilation, the decrease in oxygen saturation across the network was 3.6% for untreated animals compared with 9.9% for treated animals. During hypoxia, estimated end-capillary PO2 was significantly higher in the untreated animals. These data indicate that, at the capillary level, a decreased P50 is advantageous for tissue oxygenation when oxygen supply is severely compromised, because normal oxygen losses in capillaries are maintained in treated but not in untreated animals. The data are consistent with the presence of a diffusion limitation for oxygen during severe hypoxia in animals with a normal hemoglobin oxygen affinity.     

Mathematical model of oxygen transport in the cerebral cortex

To estimate the magnitude of hyperemia necessary to support oxidative metabolism in the cerebral cortex during functional activation, a mathematical model of O2 transport from capillary to tissue was developed. Radial and axial gradients of O2 pressure in tissue surrounding a single capillary were calculated at normal and increased cerebral metabolic rates for O2. Cone-shaped tissue geometry and nonlinear oxyhemoglobin dissociation were assumed. Local O2 consumption was assumed to be supported with local tissue pO2 greater than 1 mmHg. The distribution of tissue pO2 was also calculated during moderate hypoxemia (paO2=42 mmHg), using experimental values of red blood cell velocity measured in individual capillaries of the rat cerebral cortex using intravital video-microscopy. The model predicted that moderate increases (相似文献   

Recognition of tissue oxygen debt in clinical settings

Despite intensive treatment, a great proportion of ICU patients is resuscitated incompletely. Presence of tissue oxygen debt is the crucial pathophysiologic element of multiple organ failure development and death in these patients. Parameters of oxygen metabolism, monitored in time, except prognostic value give us the possibility of therapeutic intervention, oriented to the prevention of multiple organ failure. In addition to parameters of global oxygen transport and utilization, gastric tonometry has been used in recent years, as a method for organ specific identification of tissue oxygen debt. In the article are considered acceptable and available options of solving this problem in everyday clinical work.     

Inhibition of tumor growth and microvascular angiogenesis by the potent angiogenesis inhibitor, TNP-470, in rats

OBJECTIVE: To analyse the longitudinal relationships between body mass index (BMI)/sum of skinfolds (SSF) and biological and lifestyle risk factors for coronary heart disease (CHD). DESIGN: An observational longitudinal study; that is, the Amsterdam Growth and Health Study. SUBJECTS: 181 males and females, initially aged 13 y. Over a period of 15 y, six repeated measurements were carried out. MEASUREMENTS: BMI and SSF, biological CHD risk factors; that is, total cholesterol (TC), high density lipoprotein (HDL), TC:HDL ratio, systolic/diastolic blood pressure (SBP/DBP) and cardiopulmonary fitness (VO2-max) and lifestyle CHD risk factors (that is, daily physical activity, dietary parameters, smoking, and alcohol consumption). The longitudinal relationships were analysed by an autoregressive model, in which the value of the outcome variable at time-point t is not only related to the value of the predictor variable at t, but also to the value of the outcome variable at t-1. RESULTS: Both BMI and SSF were positively related to TC and the TC:HDL ratio. Only BMI was positively related to SBP and only SSF was negatively related to VO2-max. Physical activity was negatively related to SSF. None of the other lifestyle parameters were related to SSF and/or BMI. CONCLUSIONS: Both BMI and SSF were related to a high risk profile regarding CHD. Different relationships for SSF and BMI are found, because BMI not only reflects body fatness, but also lean body mass. Analyses with BMI as an indicator for body fatness should therefore be interpreted cautiously.     

Estimation of S-phase fraction in tumor tissue sections by immunohistochemical staining of PCNA

We describe a method for measuring the size of the S-phase fraction in human tumor tissue sections using an antibody to PCNA (PC10). Although treatment with Triton X-100 before fixation extracted a large amount of PCNA from the cells even in frozen tissue sections, PCNA remained exclusively in S-phase cells. Immunohistochemical staining of PCNA after the detergent treatment allowed estimation of the S-phase fraction in solid tumors. The validity of the method was directly proven by double staining of bromodeoxyuridine (BrdU) and PCNA in HeLa cells. The PCNA-positive cells were identical with BrdUrd-positive cells after the detergent treatment. In contrast, almost all HeLa cells in the exponentially growing phase were positive for PC10 without treatment with Triton X-100.     

Antibody to tumor necrosis factor attenuates endotoxin-stimulated amino acid transport in rat liver

BACKGROUND: Endotoxemia stimulates amino acid consumption by the liver, but the regulation of this response is poorly understood. We studied the effect of Escherichia coli endotoxin (lipopolysaccharide) on hepatic carrier-mediated plasma membrane amino acid transport and the role of the cytokine tumor necrosis factor-alpha (TNF) in regulating this transport activity. METHODS: We investigated the activities of the Na(+)-dependent amino acid transport systems A, ASC, and N in hepatic plasma membrane vesicles prepared from rats treated with endotoxin in vivo. Vesicle purity and functionality were evaluated by assaying marker enzymes and by the presence of classic overshoots. RESULTS: Endotoxin treatment did not alter sodium transport but resulted in time- and dose-dependent 6-fold (system A), 3.5-fold (system N), and 3-fold (system ASC) increases in transport activity secondary to an increase in carrier maximum velocity. Lipopolysaccharide treatment did not alter transporter affinity or plasma membrane sodium transport. Transport activity increased within 2 hours of endotoxin administration, peaked at 4 hours after exposure to lipopolysaccharide, and returned to basal levels within 24 hours. Pretreatment of animals with an anti-TNF monoclonal antibody diminished the endotoxin-induced enhancement in transport activity by 50% to 75% by decreasing carrier maximum velocity. In contrast, when the antibody was given after endotoxin challenge, transport activity was not attenuated. CONCLUSIONS: The marked acceleration in hepatic amino acid uptake that occurs during endotoxemia is secondary to an increased Na(+)-dependent hepatocyte plasma membrane transport activity and is mediated, in large part, by the cytokine TNF.     

Regulation of transport pathways in tumor vessels: role of tumor type and microenvironment

Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite large (approximately 100-300 nm in diameter). An understanding of the functional size and physiological regulation of transvascular pathways is necessary to optimize delivery of these agents. Here we analyze the functional limits of transvascular transport and its modulation by the microenvironment. One human and five murine tumors including mammary and colorectal carcinomas, hepatoma, glioma, and sarcoma were implanted in the dorsal skin-fold chamber or cranial window, and the pore cutoff size, a functional measure of transvascular gap size, was determined. The microenvironment was modulated: (i) spatially, by growing tumors in subcutaneous or cranial locations and (ii) temporally, by inducing vascular regression in hormone-dependent tumors. Tumors grown subcutaneously exhibited a characteristic pore cutoff size ranging from 200 nm to 1.2 microm. This pore cutoff size was reduced in tumors grown in the cranium or in regressing tumors after hormone withdrawal. Vessels induced in basic fibroblast growth factor-containing gels had a pore cutoff size of 200 nm. Albumin permeability was independent of pore cutoff size. These results have three major implications for the delivery of therapeutic agents: (i) delivery may be less efficient in cranial tumors than in subcutaneous tumors, (ii) delivery may be reduced during tumor regression induced by hormonal ablation, and (iii) permeability to a molecule is independent of pore cutoff size as long as the diameter of the molecule is much less than the pore diameter.     

The effect of an implantable Doppler probe on the salvage of microvascular tissue transplants

One hundred forty-seven flaps in 135 consecutive patients undergoing microvascular transplantation were monitored using a miniature Doppler ultrasonic probe. Using a modification of a technique described previously by Swartz, the probes were secured to the outflow vein of the flap with Vicryl mesh. Twenty instances of thrombosis or spasm were detected in 16 patients, and all flaps were salvaged (100 percent). There were four false positive and no false negative results. This probe allows for safe, continuous monitoring of flap blood flow, which permits the rapid detection and hence rapid treatment of postoperative complications. Our experience suggests that a significant improvement in the salvage rate of microvascular transplants may be attainable with the use of this device.     

Magnitude and time course of microvascular obstruction and tissue injury after acute myocardial infarction

BACKGROUND: Microvascular obstruction within an area of myocardial infarction indicates worse functional recovery and a higher risk of postinfarction complications. After prolonged coronary occlusion, contrast-enhanced MRI identifies myocardial infarction as a hyperenhanced region containing a hypoenhanced core. Because the time course of microvascular obstruction after infarction/reperfusion is unknown, we examined whether microvascular obstruction reaches its full extent shortly after reperfusion or shows significant progression over the following 2 days. METHODS AND RESULTS: Seven dogs underwent 90-minute balloon occlusion of the left anterior descending coronary artery (LAD) followed by reflow. Gadolinium-DTPA-enhanced MRI performed at 2, 6, and 48 hours after reperfusion was compared with radioactive microsphere blood flow (MBF) measurements and myocardial staining to define microvascular obstruction (thioflavin S) and infarct size (triphenyltetrazolium chloride, TTC). The MRI hypoenhanced region increased 3-fold during 48 hours after reperfusion (3.2+/-1.8%, 6.7+/-4.4%, and 9.9+/-3.2% of left ventricular mass at 2, 6, and 48 hours, respectively, P<0.03) and correlated well with microvascular obstruction (MBF <50% of remote region, r=0.99 and thioflavin S, r=0.93). MRI hyperenhancement also increased (21.7+/-4.0%, 24.3+/-4.6%, and 28.8+/-5.1% at 2, 6, and 48 hours, P<0.006) and correlated well with infarct size by TTC (r=0.92). The microvascular obstruction/infarct size ratio increased from 13.0+/-4.8% to 22.6+/-8.9% and to 30.4+/-4.2% over 48 hours (P=0.024). CONCLUSION: The extent of microvascular obstruction and the infarct size increase significantly over the first 48 hours after myocardial infarction. These results are consistent with progressive microvascular and myocardial injury well beyond coronary occlusion and reflow.