Activated protein C attenuates microvascular injury during systemic hypoxia

In response to hypoxia, an inflammatory cascade is initiated and microvascular injury ensues. Specifically, within 10 min, leukocyte adherence to the endothelium begins, and leukocyte emigration and vascular leak soon follow. Activated protein C (APC) has been reported to have both anticoagulant and anti-inflammatory properties. Activated protein C is best described in its role as a treatment for sepsis. However, it has been used, with some success, in experimental models of hypoxic injury. We hypothesized that APC would be protective against microvascular injury during systemic hypoxia. Randomized prospective animal study. Adult male Sprague-Dawley rats. To characterize the microvascular response to APC exposure during hypoxia, four rat groups were used: saline control, APC infusion alone (100 mg/kg bolus), hypoxia alone (10% O2), and simultaneous hypoxia + APC infusion. Measurements of leukocyte adherence (no. per 100-microm venule), leukocyte emigration (no. per 4,000 microm(2)), and venular leak by fluorescein isothiacyanate-labeled albumin (Fo/Fi) were performed during intravital microscopy of the intact venular bed. Leukocyte adherence decreased from 14.5 (+/-1.2) cells/100-microm venule in hypoxic rats to 4.4 (+/-1.5) cells/100-microm venule in those treated with both hypoxic gas and APC infusion (P < 0.001). Similarly, leukocyte emigration in hypoxic rats reached 12.3 (+/- 2.2) cells/4,000-microm(2) venule, but was reduced to 3.5 (+/-0.3) cells/4,000-microm(2) venule (P <.001). Venular permeability to protein was also significantly decreased in the APC-treated group from 0.82 (+/-0.14) to 0.25 (+/-0.14) (P < 0.001). The infusion of APC attenuates the inflammatory response during systemic hypoxia at the microvascular level, as evidenced by measurements of leukocyte adherence, emigration, and venular permeability. Further investigation is needed to examine the potential role of APC in the treatment of hypoxic injury.

Clinical and radiographic features of peritumoral infarction following resection of glioblastoma

Focal areas of restricted diffusion adjacent to high-grade glioma resection cavities were detected in 70% of patients on immediate postoperative MRI studies. Follow-up studies demonstrated cystic encephalomalacia in 91% of these foci, suggesting the presence of infarction, and the infarcted tissue demonstrated enhancement in 43% of cases. New postoperative deficits correlated well with the anatomic region of infarction in six patients. Enhancement in perioperative infarcts can mimic tumor progression on follow-up imaging studies.

Morphological study of endothelial cells during freezing

Microvascular injury is recognized as a major tissue damage mechanism of ablative cryosurgery. Endothelial cells lining the vessel wall are thought to be the initial target of freezing. However, details of this injury mechanism are not yet completely understood. In this study, ECMatrix 625 was used to mimic the tumour environment and to allow the endothelial cells cultured in vitro to form the tube-like structure of the vasculature. The influence of water dehydration on the integrity of this structure was investigated. It was found that the initial cell shape change was mainly controlled by water dehydration, dependent on the cooling rate, resulting in the shrinkage of cells in the direction normal to the free surface. As the cooling was prolonged and temperature was lowered, further cell shape change could be induced by the chilling effects on intracellular proteins, and focal adhesions to the basement membrane. Quantitative analysis showed that the freezing induced dehydration greatly enhanced the cell surface stresses, especially in the axial direction. This could be one of the major causes of the final breaking of the cell junction and cell detachment.

Oscillatory interaction between bubbles and confining microvessels and its implications on clinical vascular injuries of shock-wave lithotripsy

This paper presents a detailed study of the oscillation characteristics of a bubble confined inside a deformable microvessel, whose size is comparable with the bubble size. The vessel's compliance is characterized by a nonlinear relation between the intraluminal pressure and the expansion ratio of the vessel radius, which represents the variation of the vessel stiffness with the pressure of the filling liquid. In this analysis, an initially spherical bubble evolves into an ellipsoid, and the asymmetric oscillation appears immediately after the driving pressure is applied and magnifies with oscillation cycles. Compared with the symmetric oscillation in an unconstrained environment, the vessel constraint makes the bubble contract significantly more and subsequently expand in a more violent rebound, inducing substantially larger peaks of the intraluminal pressure exerted on the vessel wall. A larger initial bubble/vessel radius ratio leads to not only a larger peak but also a higher oscillation frequency of the intraluminal pressure, which are the two most dominating parameters in determining the vessel's failure under cyclic loading. The numerical results have further shown that an increase of the vessel wall stiffness strengthens the asymmetric effect, i.e., a larger peak of the intraluminal pressure with a higher oscillation frequency, and so does a larger pre-existing pressure in the liquid filling the vessel. These findings imply that the asymmetric effect is one of the primary mechanisms for clinical injuries of capillary and small blood vessels and for the higher risk of pediatric and hypertension patients in shock wave lithotripsy.

Bacterial Translocation, Microcirculation Injury and Sepsis

Sepsis is the result from a complex bacterial-host interaction, which is an often-fatal response when host protective molecular mechanisms designed to fight invading bacteria surpass the beneficial intensity to the point of causing injury to the host. Increasing evidences have implicated the bacterial translocation (BT) as the main source for the induction of sepsis, although the beneficial effect of BT process has been related to the development of the intestinal immune response by physiological interaction between bacteria and host. In this article, we examined evolving concepts concerning to BT and discussed about its potential role in the promotion of microcirculation injury, moreover, its possible participation in the sepsis induction. According to our data obtained from in-vivo BT animal-model, both bacterial overgrowth and bacterial pathogenic determinants seem to be major predisposing factors for the induction of BT. Besides, translocation of luminal bacteria through the lymphatic via elicits the activation of the GALT inflammatory response contributing to microcirculation injuries, and the haematological via of BT was responsible to the systemic bacterial spread. On other hand, the combination of BT process to the pre-existing host systemic infection played a crucial role in the worsening of the clinical outcome. In our understanding, studies concerning to intestinal immune response and the pathophysiology of bacterial-host interaction, under normal and disease conditions, seems to be the key elements to the development of therapeutic approaches towards sepsis.

Differential responses of pulmonary endothelial phenotypes to cyclical stretch

Endothelial phenotypes derived from different pulmonary vascular segments have markedly different permeability response to inflammatory agonists, but their responses to mechanical strain have not been characterized. Therefore, we evaluated the effect of cyclical stretch on cell shape, cell membrane wounding, and junctional beta-catenin in rat pulmonary artery (RPAEC) and microvascular (RPMVEC) endothelial cell monolayers. After 24 h of 24% uniaxial strain at 40 cycles/min, RPAEC but not RPMVEC reoriented transverse to the axis of strain. Total beta-catenin increased in RPAEC but decreased in RPMVEC. Transient plasma membrane wounding was produced by cyclical biaxial strain of 34% or by scratching of monolayers with a needle and was indicated by retention of lysine fixable fluorescent 70 kDa dextran. Junctional beta-catenin was quantified by fluorescence intensity and image analysis. beta-catenin fluorescence was significantly lower in wounded cells than in adjacent uninjured cells in both phenotypes, and the decrease was significantly greater in RPAEC compared to RPMVEC in both scratched (57% vs. 30%) and stretched (55% vs. 37%) cells. Using immunoprecipitation, VE-cadherin-associated beta-catenin decreased significantly in RPAEC (61%) but E-cadherin-associated beta-catenin was not significantly decreased in RPMVEC after 34% biaxial cyclical strain. These data suggest that RPAEC more readily remodel cell-cell adhesions during cyclical stretch than RPMVEC and that a reduced intercellular adhesion adjacent to wounded cells could serve as transvascular leak sites in both phenotypes.

Factor XIII Val34Leu polymorphism and gamma-chain cross-linking at the site of microvascular injury in healthy and coumadin-treated subjects

Fibrin (Fn) cross-linking by activated factor (F) XIII is essential for clot stability. In vitro, a common Leu34 polymorphism of the FXIIIA-subunit increases the rate of thrombin-mediated FXIII activation, but not cross-linking activity upon complete FXIII activation. The effect of FXIII Val34Leu polymorphism on fibrin(ogen) cross-linking in vivo when vascular injury triggers the blood coagulation has not been studied yet. Using quantitative immunoblotting with antibodies raised against FXIIIA-subunits, fibrinogen, and gamma-gamma-dimers, the rates of FXIIIA cleavage and fibrin(ogen) cross-link formation in the fluid phase of 30-s blood samples collected at the site of microvascular injury were compared in the Leu34-positive and -negative healthy individuals and patients on long-term oral anticoagulation. In addition to accelerated FXIII activation, in healthy subjects the presence of FXIII Leu34 allele was associated with increased soluble gamma-gamma-dimer formation by 40% (1355 +/- 17 microg L(-1) for Leu34 carriers vs. 804.3 +/- 17 microg L(-1) for Leu34 non-carriers; P = 0.028) at the site of microvascular injury. This solution phase effect was abolished in coumadin-treated patients (369.4 +/- 75.9 microg L(-1) for Leu34 carriers vs. 290.5 +/- 35.9 microg L(-1) for Leu34 non-carriers; P > 0.05). The present study indicates that the Leu34 allele affects soluble gamma-gamma-dimer formation in untreated individuals, but not in those receiving acenocoumarol. Our data may help elucidate the impact of the FXIII Val34Leu polymorphism on Fn cross-linking in vivo and its modulation by oral anticoagulants.

Vascular changes of the hand in professional baseball players with emphasis on digital ischemia in catchers

BACKGROUND

Repetitive trauma to the hand is a concern for baseball players. The present study investigated the effects of repetitive trauma and the prevalence of microvascular pathological changes in the hands of minor league professional baseball players. In contrast to previous investigators, we documented the presence of abnormalities in younger, asymptomatic individuals.

METHODS

Thirty-six baseball players on active minor league rosters underwent a history and physical examination of both hands as well as additional specialized tests, including Doppler ultrasound, a timed Allen test, determination of digital brachial pressure indices, and ring sizing of fingers. Data were compared between gloved hands and throwing hands, hitters and nonhitters, and players at four different positions (catcher [nine subjects], outfielder [seven subjects], infielder [five subjects], and pitcher [fifteen subjects]).

RESULTS

Digital brachial indices in the ring fingers of the gloved (p < 0.05) and throwing hands (p < 0.02) of catchers were significantly diminished compared with those in all other players. Doppler testing showed a significantly greater prevalence of abnormal flow in the ulnar artery at Guyon's canal when catchers were compared with other position players (p < 0.01). Doppler abnormalities were significantly more common in the gloved hand compared with the throwing hand (p < 0.05). Seven of nine catchers (and only catchers) were found to have index finger hypertrophy (average change, two ring sizes; p < 0.01); the hypertrophy occurred at the proximal phalanx and the proximal interphalangeal joint of the gloved hand. Catchers had a significantly higher prevalence of subjective hand symptoms (specifically, weakness in the gloved hand) compared with pitchers and infielders/outfielders (44% compared with 7% and 17%, respectively; p < 0.05).

CONCLUSIONS

Microvascular changes are present in the hands of otherwise healthy professional baseball players in all positions, with a significantly higher prevalence in catchers, prior to the development of clinically important ischemia. Repetitive trauma resulting from the impact of the baseball also leads to digital hypertrophy in the index finger of the gloved hand of catchers. Gloves currently used by professional catchers do not adequately protect the hand from repetitive trauma.

ANCA-induced neutrophil F-actin polymerization: implications for microvascular inflammation

BACKGROUND

The antineutrophil cytoplasmic antibody (ANCA)-positive vasculitides are characterized by a necrotizing vasculitis of small vessels with neutrophil infiltration. The reasons behind the selectivity for small vessels remain unclear, but may relate to the necessity for neutrophils to deform in order to pass through capillaries. The resistance to deformation of neutrophils largely arises from their actin cytoskeleton. It is hypothesized that ANCA, by inducing actin polymerization, increases neutrophil rigidity and contributes to their sequestration in capillaries.

METHODS

To test this hypothesis, neutrophils were treated with IgG-ANCA and the following characterizations: formation of filamentous F-actin (by flow cytometry); changes in morphology (by fluorescence and electron microscopy); and the potential to obstruct microvessels (by measuring entry times into micropipettes with comparable diameters to capillaries). The neutrophil signaling mechanisms activated by IgG-ANCA were investigated using blocking antibodies to Fcgamma receptors and inhibitors of tyrosine phosphorylation. Protein tyrosine phosphorylation was examined by immunoblotting of cell lysates, and calcium fluxes were measured by spectrofluorimetry of Fura-2 pentakis (acetoxymethyl) ester (Fura 2-AM) labeled neutrophils.

RESULTS

IgG-ANCA led to a significant dose-dependent actin polymerization over about 10 minutes. Over the same period, neutrophils became distorted in shape and more resistant to micropipette aspiration. Treatment with normal IgG caused less marked and delayed changes in these parameters. Actin polymerization required engagement of FcgammaRIIa receptor, tyrosine phosphorylation, and calcium fluxes.

CONCLUSION

These novel findings reveal signaling mechanisms that underlie ANCA-induced actin polymerization and might explain the predilection for small vessels in IgG-ANCA-associated vasculitis.

Application of lower fluence rate for less microvasculature damage and greater cell-killing during photodynamic therapy

During the process of photodynamic therapy (PDT), problems arise such as stasis or occlusion of microvasculature, tumor oxygen depletion, and photosensitizer bleaching. This study shows that the first problem could be reduced by using a lower fluence rate light source in PDT. Microvasculature damage was studied experimentally in hematoporphyrin derivative-mediated PDT against light fluence rate, and, to some extent, less microvasculature damage was induced under 75 mW/cm2 illumination than under 150 mW/cm2. Histology of vessels at the end of PDT showed that vessel damage could be observed in both groups, indicating that the microvasculature would eventually be damaged as long as the administration of light fluence was sufficient and regardless of the illuminating fluence rates. Thus microvasculature damage induced by low fluence rate illumination could also be effective in tumor control after PDT. The cell-killing experiment was performed in vitro and designed so that cell-killing rate was influenced only by light characteristics. The higher cell-killing rate caused by 75 mW/cm2 illumination indicated that lower fluence rate light could enhance the light absorbency or decrease the bleaching of photosensitizer.

Application of lower fluence rate for less microvasculature damage and greater cell-killing during photodynamic therapy

During the process of photodynamic therapy (PDT), problems arise such as stasis or occlusion of microvasculature, tumor oxygen depletion, and photosensitizer bleaching. This study shows that the first problem could be reduced by using a lower fluence rate light source in PDT. Microvasculature damage was studied experimentally in hematoporphyrin derivative-mediated PDT against light fluence rate, and, to some extent, less microvasculature damage was induced under 75 mW/cm(2) illumination than under 150 mW/cm(2). Histology of vessels at the end of PDT showed that vessel damage could be observed in both groups, indicating that the microvasculature would eventually be damaged as long as the administration of light fluence was sufficient and regardless of the illuminating fluence rates. Thus microvasculature damage induced by low fluence rate illumination could also be effective in tumor control after PDT. The cell-killing experiment was performed in vitro and designed so that cell-killing rate was influenced only by light characteristics. The higher cell-killing rate caused by 75 mW/cm(2) illumination indicated that lower fluence rate light could enhance the light absorbency or decrease the bleaching of photosensitizer.

Detection of microvascular injury by evaluating epicardial blood flow in early reperfusion following primary angioplasty

BACKGROUND

In a significant proportion of patients with acute myocardial infarction (AMI), successful opening of the infarct related artery (IRA) does not translate into adequate perfusion at the tissue level. We hypothesised that deterioration of epicardial blood flow in early reperfusion may identify early signs of coronary microvascular injury.

METHODS

In 272 consecutive patients (age 56.9+/-10.4 years) with AMI treated by primary angioplasty (PCI), coronary blood flow (Trombolysis in Myocardial Infarction (TIMI) scale and corrected TIMI frame count (cTFC)) was evaluated before [B], immediately after [O] and 15 min after [O15] opening of the IRA. The sum of ST-segment elevation in standard ECG leads (sigmaST) was measured at [B], at [O15] and 24 h after [C24]. Microvascular injury was assessed by indexes STi(O15)=sigmaST(O15)/sigmaST(B), STi(C24)=sigmaST(C24)/sigmaST(B), and by peak CK-MB release. Coronary flow deterioration (cTFC(DET)) was defined as the difference between cTFC(O15) and cTFC(O).

RESULTS

TIMI-3 flow was achieved in 236 (90.8%) patients at [O]. In the early phase of reperfusion (between [O] and [O15]), TIMI flow deteriorated by >/=1 point in 19 (7.3%) patients despite angiographic optimisation of the PCI result. At [O15] 224 (86.2%) patients had TIMI-3 flow (reflow), 36 (13.8%) patients had TIMI</=2 flow (no-reflow). cTFC(DET) was 30.2+/-16.5 in the no-reflow group but only 7.5+/-4.0 in the reflow group (p<0.001). cTFC(DET) showed a significant correlation with STi(O15) (r=0.63; p<0.001), STi(C24) (r=0.62; p<0.001) and peak CK-MB (r=0.36; p=0.001). In conclusion, we found that an increase in corrected TIMI frame count following successful IRA opening in AMI is an early angiographic indicator of coronary microvascular injury.

Early hepatic microvascular injury in response to acetaminophen toxicity

OBJECTIVE

The hepatic toxic response to acetaminophen (APAP) is characterized by centrilobular (CL) necrosis preceded by hepatic microvascular injury and congestion. The present study was conducted to examine changes in liver microcirculation after APAP dosing.

METHODS

Male C57Bl/6 mice were treated with APAP (600 mg/kg body weight) by oral gavage. The livers of anesthetized mice were examined using established in vivo microscopic methods at 0, 0.5, 1, 2, 4, 6, 12 hours after APAP.

RESULTS

The levels of hepatic transaminases (i.e., alanine aminotransferase [ALT] and aspartate transaminase) increased minimally for up to 2 hours. Thereafter, their levels were significantly and progressively increased. The numbers of swollen sinusoidal endothelial cells (SECs) in periportal regions were increased (3.5-fold) from 0.5 to 6 hours, and those in CL regions were increased (4.0-fold) at 0.5 and 1 hour. The intensity of in vivo staining for formaldehyde-treated serum albumin, which is a specific ligand for SECs, was reduced from 2 to 12 hours. Erythrocytes infiltrated into the space of Disse as early as 2 hours, and the area occupied by these cells was markedly increased at 6 hours. Sinusoidal perfusion was reduced from 1 through 12 hours, with a nadir (35% decrease) at 4 and 6 hours. Phagocytic Kupffer cell activity was significantly elevated from 0.5 through 12 hours. Although gadolinium chloride minimized the changes in sinusoidal blood flow and reduced ALT levels 6 hours after APAP, it failed to inhibit endothelial swelling, extravasation of erythrocytes, and CL parenchymal necrosis.

CONCLUSIONS

These results confirm that APAP-induced SEC injury precedes hepatocellular injury, supporting the hypothesis that SECs are an early and direct target for APAP toxicity. These findings also suggest that reduced sinusoidal perfusion and increased Kupffer cell activity contribute to the development of APAP-induced liver injury.

Combined photodynamic and photothermal induced injury enhances damage to in vivo model blood vessels

BACKGROUND AND OBJECTIVES

The degree of port wine stain (PWS) blanching following pulsed dye laser (PDL) therapy remains variable and unpredictable. Because of the limitations of current PDL therapy, alternative treatment approaches should be explored. The objective was to evaluate a novel methodology for selective vascular damage, combined photodynamic (PDT) and photothermal (PDL) treatment, using the in vivo chick chorioallantoic membrane (CAM) model.

STUDY DESIGN/MATERIALS AND METHODS

Thirty microliters of benzoporphyrin derivative monoacid ring A (BPD) solution was administered intraperitoneally into chick embryos at day 12 of development. Study groups were: (1) control (no BPD, no light); (2) BPD alone; (3) continuous wave irradiation (CW) alone (576 nm, 60 mW/cm2, 125 seconds); (4) CW + PDL; (5) BPD+PDL; (6) PDT (BPD+CW); (7) PDL alone (585 nm, 4 J/cm(2)); and (8) PDT+PDL (BPD + CW followed immediately by PDL). Vessels were videotaped prior to, and at 1 hour post-intervention and then assessed for damage based on the following scale: 0, no damage; 1, coagulation; 1.5, vasoconstriction; 2.0, coagulation+vasoconstriction; 2.5, angiostasis; 3.0, hemorrhage. Damage scores were weighted by vessel "order."

RESULTS

PDT + PDL resulted in significantly (P < 0.01) more severe vascular damage than was observed in any other study group: 127% more than PDT, 47% more than PDL alone.

CONCLUSIONS

PDT + PDL is a novel and promising approach for selective vascular damage and may offer a more effective method for treatment of PWS and other vascular skin lesions.

In vivo visualization of reactive oxidants and leukocyte-endothelial adherence following hemorrhagic shock

The generation of oxygen radicals during leukocyte-endothelial cell interaction is considered to represent one of the fundamental steps of microvascular injury following ischemia and reperfusion. Indirect evidence also suggests that this relationship may be important following hemorrhagic shock. The purpose of this study was to characterize the temporal changes of reactive oxygen species (ROS) in the mesenteric microvascular endothelium, in vivo, as a consequence of hemorrhagic shock and reperfusion, and to correlate this ROS production to leukocyte adherence. Following a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mmHg for 1 h in urethane-anesthetized rats. Mesenteric venules in a transilluminated segment of small intestine were examined to quantitate changes in ROS generation and leukocyte adherence. Sprague-Dawley rats were injected with dihydrorhodamine 123, a hydroperoxide-sensitive fluorescent probe that is trapped within viable cells as a nonfluorescent form and then converted to the mitochondrion-selective form rhodamine 123 by hydroperoxides. The fluorescent light emission from rhodamine 123 was recorded with digital microscopy and downloaded to a computerized image analysis program. Our results demonstrated an 80% increase in ROS generation beginning within 5 min into resuscitation and a 10-fold increase in leukocyte adherence that occurred at 10 min after resuscitation. Both ROS generation and leukocyte adherence were attenuated with pre-shock administration of platelet activating factor (PAF) antagonist, WEB 2086, and the CD11/CD18a antibody, anti-LFA-1beta. Our findings suggest that ROS production in endothelial cells is increased during reperfusion following hemorrhagic shock and that the mechanism of expression is mediated in part by both PAF expression and subsequent leukocyte adherence.

Assessing the microcirculation in a burn wound by use of OPS imaging

We report on the use of OPS imaging to visualize the microcirculation in a burn wound. This novel technique produces high quality images of the microcirculation and quantitative analysis of functional capillary density (FCD) was possible. FCD measured at day 3 following the injury was 11.2 +/- 4.6 (n/mm superset2; mean +/- SEM). During the initial phase of healing microcirculatory changes were characterized by a moderate but steady increase of FCD, which showed marked increase beginning from day 12 following the burn (16.6 +/- 6.9). Maximal FCD measured at day 23 (48.2 +/- 19.7) decreased from this point in time to finally reach 25.2 +/- 10.3 n/mm superset2 at the end of observation. OPS imaging allows for direct in vivo visualization and quantification of the microcirculation in burned skin. Our results of the use of OPS imaging in assessing the microcirculation in a burn wound 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.

In vivo mapping of the vascular changes in skin burns of anaesthetised mice by fibre optic confocal imaging (FOCI)

Burns (3 mm in diameter, 50 degrees C, 20 s duration) were induced on the skin of anaesthetised hairless mice. Anaesthesia was maintained throughout all experiments. Subsurface changes in the microvasculature at the burn site were imaged confocally following i. v. injection of fluorescently labelled (FITC) dextran. Blood cells moving through dermal blood vessels were seen and recorded on video tape. Multiple adjacent 2-D confocal images of the burn site and surrounding areas were assembled and enabled microscopic vascular imaging of the whole burn area (including zones of coagulation, stasis and hyperaemia) and the surrounding normal vessels. This mapping of the burn area by fibre optic confocal imaging (FOCI) in vivo demonstrated good congruence with vascular casts (Microfil MV-120, Flow tech, USA) made at 4 h post burn. This study demonstrates the usefulness of FOCI for in vivo vascular imaging in burns.

Early effects of ionizing radiation on the microvascular networks in normal tissue

Microvascular networks, which control the delivery of oxygen and nutrients and the removal of metabolic waste, are the most sensitive part of the vascular system to ionizing radiation. Structural and functional changes in microvascular networks were studied in locally irradiated (single 10-Gy dose) hamster cremaster muscles observed 3, 7 and 30 days post-irradiation. Networks were selected in reference to a well-defined location in the tissue to reduce heterogeneity due to spatial variations. Intravital microscopy was used to measure structural and functional parameters in vivo. A factorial design was used to examine the effects of radiation status, time postirradiation, and network vessel type on the structure and function of microvascular networks. While the diameter of microvessels in control animals increased significantly with age, vessel diameter in irradiated vessels decreased significantly with age. Red blood cell velocity in irradiated networks at 3 and 30 days postirradiation was significantly lower than in control networks. There was a significant decrease in capillary surface area and a significant increase in vessel hematocrit in irradiated animals. Blood flow in irradiated vessels was significantly lower than in control vessels. Changes in functional parameters were evident at 3 days postirradiation while changes in structural parameters occurred later. All vessel types were not damaged equally by radiation at every time examined.

[The histological changes and pathogenesis of an infarct of a long bone in soft-tissue trauma to an extremity with damage to the feeding artery]

Acute disturbances in diaphysial intraosseous circulation secondary to the major nutrient artery intersection are not fully compensated from the potential intraosseous collaterals early in their course, which fact leads to bone infarction, as evidenced by histological and angiomorphological investigations in the experiment in rats. Recovery of ischemic tissues occurs in different time periods, necrotized myelokaryocytes undergo lysis, the bone marrow ischemic necrosis focus gets revascularized, with the reduced blood supply foci being intact, immature hemocytes scanty; necrotized osseous tissue undergoes revascularization and revitalization during the course of long-continued reorganization.

Contusion of skeletal muscle increases leukocyte-endothelial cell interactions: an intravital-microscopy study in rats

OBJECTIVE

To investigate the relationship between secondary muscle damage after contusion and the interactions between leukocytes and endothelial cells, which are essential steps in secondary inflammatory response.

METHODS

In a randomized animal study, rats were chronically instrumented with dorsal skinfold microvascular chambers and exposed to standardized contusion or sham contusion. Leukocyte rolling and adherence in postcapillary venules before and after muscle contusion or sham contusion were quantitated using in vivo microscopy.

RESULTS

The number of rolling leukocytes in the postcapillary venules before contusion was low. At 300 minutes after contusion, the number of rolling and adherent leukocytes in the striated muscle microvasculature was increased significantly (p < or = 0.05) compared with either the baseline precontusion condition or the control group at the same time.

CONCLUSION

In the mid-term to long-term stages of skeletal muscle injury associated with contusion, a significant portion of tissue damage is secondary to leukocyte-endothelial cell interactions.

Focal microcirculation disorder induced by photochemical reaction in the guinea pig cochlea

A small region of microcirculation disorder in the cochlea of the guinea pig could be induced by a photochemical reaction. Photoillumination to the cochlea was done after systemic infusion of Rose Bengal (RB). The lateral wall of the second or third turn of the cochlea was illuminated for 10 min with a 1 mm diameter focused green light supplied by a xenon lamp. Degeneration of the stria vascularis (SV) was observed by a scanning electron microscope at 60-300 min after illumination. The range of length of degenerated area in the SV was from 111 to 1800 microns, with a mean of 760 microns. The organ of Corti along the illuminated lesion of the SV was well preserved in all animals at 60-300 min. In contrast, degeneration of sensory hair cells and scar formation in the SV were observed in the focal lesions of the three animals killed 1 week after illumination. The increase of diameter in the vessel of the SV from the radiating arteriole, the vessel of basilar membrane (VSBM) and limbus vessel (LVS) were observed in the illuminated area with diaminobenzidine (DAB) staining. These findings suggest that segmental microcirculation damage occurred in the SV and modiolus. In physiological studies, compound action potentials (CAP) were evaluated. Endocochlear potentials (EP) were also measured at the second turn under three different situations (groups A, B and C). A photochemically induced lesion was created at the site of EP measurement (group A), a site in the second turn 1 mm from the EP measurement site (group B) and a site in the third turn adjacent to the EP measurement site (group C). Threshold shift of CAP (up to 5.6 +/- 1.8 dB SPL) and reduction of EP (down to 11.4 +/- 10.7 mV) in the photochemically injured location were detected during about 15 min. EP did not recover to the predamaged level (79.9 +/- 3.7 mV) during 20 min. The morphological and physiological changes were not observed in the control group with illumination only. There were no significant decreases in EP values at the sites 1 mm from the lesion (group B) and at the inferior turn adjacent to the lesion (group C) compared to the marked decrease at the site of the photochemically induced lesion (group A). These findings suggest that CAP and EP are significantly affected by the interruption of segmental blood supply in the cochlea and remarkable decrease of EP occurs in the focal region of the guinea pig cochlea. We conclude that a localized blood circulation disorder induced by the photochemical reaction can make a focal lesion in guinea pig cochlea morphologically and physiologically.

Assessment of ischemia and reperfusion injury

Direct videomicroscopy of the rat cremaster muscle microcirculation supplemented by animal models of replantation, vascular crushing, and muscle function after injury and recovery were used to investigate the occurrence of reperfusion failure. It is evident that failure of blood reflow may be induced by multiple factors that can be grouped into categories of ischemia, intimal damage, and systemic or local responses, which are referred to as the no reflow triad. The components comprising the 3 sides of the no reflow triad can interact with one another in an intricate manner, and any single factor or combination of factors is capable of triggering the events leading to reperfusion failure. The pronounced regional nature of reperfusion injury and the direct relationship between the severity of the observed vascular alterations and increasing duration of ischemia have been documented. The dynamic changes and histopathology of the microcirculation included constriction of the arteries, swelling of endothelial and leukocytes, and erythrocyte rouleaux formation during ischemia. As ischemia duration was lengthened, the degree of these changes increased correspondingly. The changes on reperfusion were disruption of blood flow patterns, vortex formation, regional stasis, adhesion and migration of leukocytes, focal hemorrhage, edema, vasospasm, and platelet aggregation. The deleterious effects of systemic acidosis, interstitial hemorrhage, denervation, and prolonged venous occlusion were subsequently documented. The application of information gained from this series of laboratory experiments has resulted in continued improvement in the success rate in clinical microvascular surgery.

A new simple method for isolation of microvascular endothelial cells avoiding both chemical and mechanical injuries

Our study indicates that when small pieces of lung or muscles of chest wall are cultured, erythrocytes and leukocytes (PMNs) leave the tissues first, followed by vascular endothelial cells (ECs). Fibroblasts and other mixed cells grow after 72 hr culture. The ECs can then be isolated avoiding mechanical and chemical injuries. The lung tissue is obtained from the peripheral surface and muscles from the chest. It is then cut into pieces and cultured with DMEM containing 20% fetal bovine serum. After 60 hr culture, the tissues are discarded. The flask contains only ECs and blood cells. Blood cells can be cleared out after the cells are subcultured once or twice. The primary cells and the subcultured cells cultured on gelatinized culture dish give the capillary-like structure. Cells cultured on untreated dishes have regular cobblestone morphology and junctional contacts. The isolated cells were not mesothelial cells because the cells did not react to antibody against cytokeratin 18, while mesothelial cells reacted strongly to the antibody. The cells can be isolated from the lung tissue without pleura. The primary microvascular ECs are also cultured on microcarriers (cytodex 3). Because both mechanical and proteolytic injuries are avoided, the cells may be more similar to cells in the in vivo state. There are no significant differences in PMN-endothelium adherence and monolayer responses to second messengers, platelet activating factor, and phospholipase A2 when pulmonary and muscular microvascular endothelial cells are compared.

Light/dye microvascular injury eliminates pial arteriolar dilation in hypotensive piglets

Cerebral vasodilation in response to hypotension is necessary to maintain adequate cerebral blood flow. This study in newborn pigs examines the hypothesis that endothelial injury in vivo inhibits cerebral vasodilation in response to hypotension in newborn pigs, thus suggesting that this response is endothelium dependent. Chloralose-anesthetized piglets with closed cranial windows were studied before and after injury caused by light/dye or before and after dye only sham control. Light/dye injury was produced by injecting sodium fluorescein i.v. and passing filtered light from a mercury arc lamp through the cranial window. Measurements of pial arteries and arterioles were made during normotensive and hypotensive periods. Hemorrhagic hypotension (to 50% of the mean arterial control value) caused pial arterial and arteriolar diameters to increase 49 +/- 8% and 66 +/- 8%, respectively. After the light/dye injury, dilation in response to hypotension was absent, whereas dilations in response to isoproterenol and constriction in response to hypertension (3.33 to 4.0 kPa increase in arterial pressure) and hypocapnia were retained. These findings are consistent with the hypothesis that hypotension-induced cerebral arteriolar vasodilation is dependent on endothelial signals influencing adjacent smooth muscle.

Effects of intraoperative hyperthermia on canine sciatic nerve: histopathologic and morphometric studies

Failure to achieve local control in the treatment of pelvic and retroperitoneal tumours results in a high rate of recurrences. The objective of intraoperative hyperthermia (IOHT) is to enhance the effect of intraoperative radiation therapy and to increase local tumour control. The tolerance of peripheral nerves to heat may limit the heat dose that can be applied to tumours. Histopathologic and histomorphometric changes of canine sciatic nerve after 60-min IOHT were studied in three groups of five dogs each for temperatures of 43, 44 and 45 degrees C. IOHT was performed using a water-circulating hyperthermia device with a multichannel thermometry system on surgically exposed sciatic nerve. Histopathologic and histomorphometric studies were done immediately, 3 weeks and 12 months after IOHT. Histologic changes observed immediately after treatment were minimal but at 3 weeks following 60-min 45 degrees C IOHT both axon and myelin loss and an increase in endoneurial fibrous tissue were observed. Twelve months after treatment a statistically significant decrease in axon, myelin and small vessel percentages as well as an increase in endoneurial and epineural connective tissue were observed for dog treated to 45 degrees C. Dog treated to 44 degrees C for 60 min had similar statistically significant but less severe changes. Twelve months after 43 degrees C IOHT for 60 min, nerve fibres appeared normal and endoneurial connective tissue was only increased mildly around small and medium-sized vessels. These results suggest that temperatures to the peripheral nerve > 44 degrees C for 60 min are likely to cause significant histopathologic changes that can be found 12 months after treatment. A hypothesis of the mechanism of heat injury to peripheral nerves was developed.

Endothelial cells and hyperthermia

Most radiation oncologists are aware of the effects of clinical hyperthermia on neoplastic cells. Its effects on blood vessels, however, are not as well recognized. Yet, since the 1960s a number of investigators have described and categorized the effects of hyperthermia on microvessels (in vivo), and on cultured endothelial cells (EC) (in vitro). Both EC and microvessels can be lethally damaged by the hyperthermia doses used as antineoplastic therapy. In vitro data indicate that capillary EC are moderately sensitive to hyperthermia. Proliferating EC are more thermosensitive suggesting that microvessels of malignant neoplasms (which contain many proliferating EC) are more affected than microvessels of normal tissues. This differential sensitivity of microvessels has also been observed in blood flow studies. Furthermore, hyperthermia inhibits angiogenesis. Thus, some of the antineoplastic effects of heat are caused by ischaemia due to obstruction or destruction of the tumour vessels or to inability to form new vessels. Sublethal EC damage can also be demonstrated, resulting in decreased synthesis of most proteins including adhesion molecules (as well as increased expression of a few such as heat shock proteins) and producing reversible loss of cytoskeletal elements. The therapeutic advantage provided by the higher thermal sensitivity of neoplastic vessels should be exploited further, perhaps by developing strategies specifically aimed to the tumour microvasculature.

[Three dimensional architecture of the microvascular systems of the skin in wound healing processes of normal and streptozotocin-induced diabetic rats]

Fine vascular architectures in the wound healing process of streptozotocin (STZ)-induced diabetic rat skin were studied by scanning electron microscope with newly designed high pressure resin injection method. In the normal rat skin, the new method successfully demonstrated the hitherto unknown subepidermal fine capillary network which continuously surrounded the pillosebaceous tissues. In wound healing processes after combined resection of skin and fascia, vascular regeneration occurred from both the border and the base of the lesion. The new vasculatures from the border of dermis demonstrated concentric array of loops extending toward the center of the lesion. The direct budding emerged from the capillary network of the exposed muscle surface. Subepidermal vasculatures of the intact back skin of STZ-induced diabetic rats showed coarse and poorer network pattern. Increased number of anastomoses between arterioles and venules, insufficiently dilated arterioles distal to the A-V shunt were the other findings which may imply the increased shunt blood flow and consequent poor peripheral dermal circulation.

Effect of activation on neutrophil-induced hepatic microvascular injury in isolated rat liver

Polymorphonuclear neutrophils (PMNs) have been implicated in microvascular injury following ischemia and reperfusion (I/R) but the relative contribution of obstruction versus toxic mediators is not well defined. Therefore, the present study was performed to determine the contribution of exogenous or endogenous activation on PMN-induced microvascular and hepatocyte injury. Rat livers were isolated and perfused at constant pressure with Krebs buffer with red cells (Hct-10%) and monitored for perfused sinusoids (PS) and dead hepatocytes (propidium iodide-stained, DH) by intravital microscopy. PMNs isolated from the peritoneum after oyster glycogen injection were added to the perfusate either without or with activation by phorbol myristate acetate (PMA, 160 nM). Unactivated PMNs stuck in the liver but had no significant effect on either perfused sinusoids (11.1 +/- .4/field, unactivated PMNs versus 11.9 +/- .5/field, the time-matched control) or dead hepatocytes (1.2 +/- .4/field, unactivated PMNs versus 1 +/- .3/field, the time-matched control). Infusion of PMA-activated PMNs resulted in significant decrease in perfused sinusoids and increase in DH (9.5 +/- .3/field for PS and 3.2 +/- .6/field for DH, respectively). In contrast, when PMNs were "activated" by infusion into a liver previously made ischemic for 30 min, DH were significantly increased after 60 min (26.2 +/- 4.5/field, I/R plus PMNs versus 12.4 +/- 2/field, I/R only) but perfused sinusoids were not different from ischemia alone. These results demonstrate that oxidatively quiescent PMNs do not cause cellular or microvascular injury in spite of microvascular accumulation. Activated PMNs damage microcirculation or hepatocytes depending on the nature of the activation.

Inverse relation between plasma concentration of von Willebrand factor and CrEDTA clearance in systemic sclerosis

OBJECTIVE

Microvascular abnormalities involving endothelial cell dysfunction occur as an early event in systemic sclerosis. We studied plasma concentrations of von Willebrand factor (vWf), a substance released from injured endothelial cells, and its relation to pulmonary and renal dysfunction.

METHODS

vWf was determined by immunoelectrophoresis. Renal function was assessed by CrEDTA clearance, an accurate measure of glomerular filtration rate and pulmonary function by spirometry and carbon monoxide diffusing capacity. Pulmonary pressure was measured by Doppler cardiography.

RESULTS

In 22 patients with scleroderma, vWf concentrations related inversely to CrEDTA clearance. In contrast, no relationship between plasma vWf and pulmonary function was found; 9/10 patients with pulmonary hypertension and 9/12 patients with normal pulmonary pressure showed elevated levels of vWf. However in 5 patients with pulmonary hypertension without radiographic evidence of pulmonary fibrosis there was a strong correlation between plasma vWf and pulmonary pressure (rho = 0.90) which fell short of statistical significance due most likely to small population size.

CONCLUSION

Renal but not pulmonary dysfunction was associated with elevated plasma levels of vWf.

Microvascular injury induced by intravascular platelet aggregation. An experimental study

Microvascular injury due to platelet aggregation was studied in cats for an hour after 1-hour intraaortic infusion of a suspension of collagen fibrils. Haematocrit and numbers of circulating platelets and leukocytes were repeatedly measured in arterial blood and a major cutaneous lymph vessel in the thigh was cannulated for measurement of lymph flow and erythrocyte counts in peripheral lymph. There were seven groups, each of eight cats, viz. normal cats infused with collagen (I) or vehicle (II) and collagen-infused cats which were platelet-depleted--by antiserum (III), or neutrophil-depleted--by anti-serum (IV), or decomplemented--by cobra venom (V), or pretreated with indomethacin--10 mg/kg (VI), or treated with nonimmunized serum (VII). Induced intravascular platelet aggregation reduced the numbers of circulating platelets and leukocytes, and increased haematocrit, lymph flow and numbers of red cells in peripheral lymph. These effects were inhibited by platelet depletion and indomethacin and attenuated by decomplementation and neutrophil depletion. Platelet aggregation was thus shown to induce microvascular injury and increase microvascular permeability, which is partly dependent on complement and neutrophils.

Differential thermal sensitivity of tumour and normal tissue microvascular response during hyperthermia

The goal of this study was to investigate the heat sensitivity of the microcirculation in normal C3H murine leg muscle and a variety of transplanted tumour lines (KHT, SCC-VII, RIF-1, C3H mouse mammary carcinoma, two human mammary carcinomas MDA-468 and S5). Clearance rate of a radioactive tracer monitored following an intra-tissue injection was used as a measurement of microvascular integrity during heat treatment. Clearance rate in all tumours studied was significantly lower after 1 h of heating at 44 degrees C than the initial pretreatment clearance rate. Response of normal muscle differed from that of tumours in that the clearance rate after 1 h of heating at 44 degrees C was similar to the initial clearance rate. Vasculature in the KHT fibrosarcoma was more sensitive to heat treatment than that in other tumours. In response to a heat treatment at 43, 44, 45 and 46 degrees C the same level of microvascular damage occurred in half the time in KHT fibrosarcoma than in normal muscle. Furthermore, vascular damage in both muscle and KHT tumour followed the same relative isoeffect relationship, a 1 degree C change in temperature was equivalent to a change in heating time by a factor of two.

Changes in the microvasculature after mechanical pressure on the hamster cheek pouch

The reaction of the microvasculature in the periodontal ligament to mechanical pressure is considered a very important phenomenon with respect to the biological background to orthodontic tooth movement. For clarification of the microvascular reaction to mechanical pressure, an experimental model that incorporated a hamster cheek pouch was established. This in vivo model solves some of the problems of other experimental models of the microvasculature of the periodontal ligament. Blood plasma permeation in this model was examined by means of a blue dye (pontamine sky blue), and histological observation was performed by light and transmission electron microscopy. Increased vascular permeability was observed within 30 min after removal of the mechanical stimulation. The threshold weight resulting in dye leakage was between 1 and 5 g applied for 60 min. From the histological observations, some large gaps between the endothelial cells in venules were found, while most basement membranes remained undisturbed. These observations suggest that the plasma leakage was due to mild traumatic injury to the endothelial cells. Both leukocytes and platelets were observed in the gaps between the endothelial cells in the venule. These types of microvascular reactions to mechanical pressure could initiate tissue changes in the periodontal ligament during orthodontic tooth movement.

Mechanisms of extracellular reactive oxygen species injury to the pulmonary microvasculature

We investigated the effect of xanthine (X) plus xanthine oxidase (XO) on pulmonary microvascular endothelial permeability in isolated rabbit lungs perfused with Krebs buffer containing bovine serum albumin (5 g/100 ml). Addition of five mU/ml XO and 500 microM X to the perfusate caused a twofold increase in the pulmonary capillary filtration coefficient (Kf,c) 30 min later without increasing the pulmonary capillary pressure. This increase was prevented by allopurinol or catalase but not by superoxide dismutase or dimethyl sulfoxide. Because these data implicated hydrogen peroxide (H2O2) as the injurious agent, we measured its concentration in the perfusate after the addition of X and XO for a 60-min interval. In the absence of lung tissue and albumin, H2O2 increased with time, reaching a concentration of approximately 250 microM by 60 min. If albumin (5 g/100 ml) was added to the perfusate, or in the presence of lung tissue, the corresponding values were 100 microM and less than 10 microM, respectively. To understand the mechanisms of H2O2 scavenging by lung tissue, we added a 250 microM bolus of H2O2 to the lung perfusate. We found that H2O2 was removed rapidly, with a half-life of 0.31 +/- 0.04 (SE) min. This variable was not increased significantly by inhibition of lung catalase activity with sodium azide or inhibition of the lung glutathione redox cycle with 1-chloro-2,4-dinitrobenzene. However, inhibition of both enzymatic systems increased the half-life of H2O2 removal to 0.71 +/- 0.09 (SE) min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

PGE1 inhibited PMN attachment to air emboli in vivo during infusion of ZAP without preventing lung injury

Prostaglandin E1 (PGE1) treatment of neutrophils inhibits their adherence to substrates in vitro, including endothelial cell monolayers. Demonstration that PGE1 inhibits neutrophil adherence in vivo in the lung, however, is complicated by PGE1 effects on cells other than neutrophils, such as endothelial cells. To determine whether PGE1 inhibits neutrophil adherence properties in vivo, we used air emboli as intravascular targets for neutrophil attachment. Four experimental conditions were studied in anesthetized and awake sheep that were treated with 1) PGE1 and air emboli, 2) saline and air emboli, 3) PGE1 and zymosan-activated plasma (ZAP) + air emboli, and 4) saline and ZAP + air emboli. PGE1 (30 ng.kg-1.min-1) or saline was infused continuously 1 h before and 1 h during the infusion of air emboli (group 1; n = 13 sheep) or ZAP + air emboli (group 2; n = 13 sheep). The number of neutrophils (PMNs) attached to air emboli in four anesthetized sheep per condition was significantly less in sheep given PGE1 and ZAP + air emboli [8 +/- 3 (SD) PMNs/mm of embolus perimeter] than in the other three conditions (14-21 PMNs/mm; P less than 0.05). Repeated experiments in five awake sheep per group showed that PGE1 treatment did not prevent increased lung lymph protein clearance in either group compared with saline treatment. We conclude that PGE1 specifically inhibited attachment of ZAP-activated neutrophils to air emboli in vivo. The lack of pathophysiological protection suggests that PGE1-induced alterations in neutrophil attachment properties were independent of other cellular activation responses.

Cooling to heat of fusion (HOF), followed by rapid rewarming, does not reduce the integrity of microvascular corrosion casts

This study utilized microvascular corrosion casting techniques to evaluate changes in the microvascular patency of rat hindpaws cooled to four different subzero temperatures. Left hindpaws of anesthetized rats in group 1 were cooled to -5 degrees C, in group 2 to -15 degrees C, in group 3 to heat of fusion (HOF), and in group 4 to HOF and then to -15 degrees C. Although freezing did not take place in the hindpaws of groups 1 and 2, initiation of freezing in the tissues, as indicated by HOF, did occur in groups 3 and 4. Cooled hindpaws were rapidly rewarmed. Right hindpaws served as controls. Microvascular corrosion casts were made from the left and right hindpaws of all animals. There was no significant difference when the mean cast weights of cooled hindpaws from groups 1, 2, and 3 were compared to the mean cast weights of their respective control hindpaws. In group 4, there was a significant difference (P less than 0.05) when the mean cast weight of the cooled hindpaws (47.69 +/- 9.05, mg +/- SEM) was compared to that of the control hindpaws (80.63 +/- 12.23). Since, in this acute experiment, a loss of vascular integrity occurred when the hindpaws in group 4 were cooled to -15 degrees C after reaching HOF, the initiation of freezing alone was not sufficient to reduce mean cast weight.

Activated neutrophils increase microvascular permeability in skeletal muscle: role of xanthine oxidase

To determine the role of xanthine oxidase in the microvascular dysfunction produced by activated granulocytes, we examined the effect of xanthine oxidase depletion or inhibition on the increase in microvascular permeability produced by infusion of the neutrophil activator phorbol myristate acetate (PMA). Changes in vascular permeability were assessed by measurement of the solvent drag reflection coefficient for total plasma proteins (sigma) in rat hindquarters subjected to PMA infusion in xanthine oxidase-replete and -depleted animals, in animals pretreated with the xanthine oxidase inhibitor oxypurinol, and in animals depleted of circulating neutrophils by pretreatment with antineutrophil serum (ANS). Xanthine oxidase depletion was accomplished by administration of a tungsten-supplemented (0.7 g/kg diet) molybdenum-deficient diet. In animals fed the tungsten diet, muscle total xanthine dehydrogenase plus xanthine oxidase activity was decreased to less than 10% of control values. Estimates of sigma averaged 0.84 +/- 0.04 in control hindquarters, whereas PMA infusion was associated with a marked increase in microvascular permeability (decrease in sigma to 0.68 +/- 0.03). PMA infusion also caused an increase in the amount of the radical-producing oxidase form of xanthine oxidase (from 3.9 +/- 0.05 to 5.6 +/- 0.4 mU/g wet wt). ANS pretreatment attenuated this permeability increase (sigma = 0.77 +/- 0.04) and diminished the rise in xanthine oxidase activity (4.9 +/- 0.5 mU/g wet wt). Xanthine oxidase depletion with the tungsten diet or pretreatment with oxypurinol had no effect on this neutrophil-mediated microvascular injury (sigma = 0.69 +/- 0.06 and 0.67 +/- 0.03, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Functional state of blood vessels of the skin--a criterion after exposure to laser irradiation]

The status of the microcirculatory skin channel under laser irradiation with wave length 10.6 mkm of different energetic exposures has been studied. Higher density of vessels per unit of area, longer diameter of the vessels, disturbances in the blood flow have been observed in the dynamics of exposure, which can be used as a criterion of harmful skin effect of irradiation.

Microvascular injury after ischemia and reperfusion in skeletal muscle of exercise-trained rats

Ischemia and reperfusion in skeletal muscle is associated with increases in total vascular resistance (Rt) and the microvascular permeability to plasma proteins. To determine whether exercise training can attenuate ischemia and reperfusion-induced microvascular injury in skeletal muscle, intact (with skin) and skinned, maximally vasodilated (papaverine), isolated hindquarters of control (C) and exercise-trained (ET) rats were subjected to ischemia (intact 120 min; skinned 60 min) followed by 60 min of reperfusion. ET rats ran on a motorized treadmill at 32 m/min (8% grade), 2 h/day for 12 wk, whereas the C rats were cage confined. Before ischemia, ET hindquarters had higher isogravimetric flow, lower Rt, and similar solvent drag reflection coefficients (sigma f) compared with C. During reperfusion in intact hindquarters, flow was higher (P less than 0.05) and Rt tended to be lower (15 +/- 2 vs. 25 +/- 5 mmHg.ml-1.min.100 g; P less than 0.1) in ET compared with C; however, in skinned hindquarters flow and Rt (14 +/- 2 vs. 13 +/- 2 mmHg.ml-1.min.100 g) were not different between C and ET. During reperfusion, sigma f was reduced (P less than 0.05) in both intact (C 0.68 +/- 0.03; ET 0.68 +/- 0.02) and skinned (C 0.66 +/- 0.03; ET 0.68 +/- 0.03) hindquarters, indicative of an increased microvascular permeability to plasma proteins. These results indicate that exercise training did not attenuate the microvascular injury (increased Rt and decreased sigma f) associated with ischemia and reperfusion in rat skeletal muscle.

PO2 modulation of paraquat-induced microvascular injury in isolated dog lungs

We determined the effects of paraquat (PQ) concentrations ranging from 10(-3) to 10(-2) M and three levels of venous PO2 [hypoxia (41 +/- 3 Torr), normoxia (147 +/- 8 Torr), and hyperoxia (444 +/- 17 Torr)] in the presence of 4 x 10(-3) M PQ on microvascular permeability in isolated blood-perfused dog lungs. Capillary filtration coefficient (Kf,c) increased and isogravimetric capillary pressure (Pc,i) decreased 3 h after perfusion with 10(-2) M PQ (n = 7) and 5 h after perfusion with 4 x 10(-3) M PQ (n = 6) but not with 10(-3) M PQ (n = 4). In hyperoxic lungs perfused with 4 x 10(-3) M PQ, Kf,c increased to nine times the base-line value 5 h after PQ [0.15 +/- 0.01 to 1.35 +/- 0.25 (SE) ml.min-1.cmH2O-1.100 g-1]. Pc,i significantly decreased from a base-line value of 9.4 +/- 0.2 to 7.1 +/- 0.4 cmH2O at 3 h. In hypoxic lungs perfused with 4 x 10(-3) M PQ (n = 5), Pc,i and Kf,c changes were not significantly different from those in normoxic lungs treated with PQ. Thus both hyperoxia and an increased dose of PQ shortened the latent period and increased the severity of the PQ-induced microvascular permeability lesion, but hypoxia failed to prevent the PQ damage.

Susceptibility of hepatic microcirculation to reperfusion injury: a comparison of adult and suckling rats

Primary graft failure and vascular thromboses are frequent complications of liver transplantation, yet the mechanisms responsible remain unclear. Previous work from our laboratory has shown that hepatic reperfusion injury results in damage at the microvessel level. The present study was performed to determine whether an increased susceptibility of immature animals to microvascular injury during reperfusion might be a contributing factor in these complications. Suckling (35 to 50 g) or adult (250 to 400 g) rats were subjected to 30 or 60 minutes of hepatic ischemia to the left and median lobes followed by 90 minutes of reperfusion. Control animals were sham-operated, time-matched rats. At the end of reperfusion, fluorescein-labeled albumin was injected systemically to mark perfused sinusoids. Frozen sections of liver biopsies were viewed under fluorescence microscopy. The perfused sinusoid density was determined by point count analysis and expressed as the number of intersections of perfused sinusoids with 25 randomly oriented points superimposed on the sinusoid field. In sham-operated rats, at both 30 and 60 minutes, there were no differences between sucklings and adults. After 30 minutes of ischemia and 90 minutes of reperfusion, adults showed a significantly decreased density of perfused sinusoids (4.5 +/- 0.1 intersections per field) when compared with suckling rats (6.0 +/- 0.3 intersections per field, P less than .001). However, in rats subjected to 60 minutes of ischemia followed by 90 minutes of reperfusion, the microvascular injury was more severe in suckling rats (2.7 +/- 0.2 intersections per field) than in adults (4.7 +/- 0.2 intersections per field, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

PAF/cytokine auto-generated feedback networks in microvascular immune injury: consequences in shock, ischemia and graft rejection

The catastrophe theory evolved by Thom and Zeeman proposes a mathematical definition for the abrupt or 'catastrophic' changes that can suddenly occur in normally well-ordered and smooth-running systems. We have integrated this theory with our own PAF/cytokine feedback network hypothesis to explain the control and dysfunction of the inflammatory response. This process involves the activation of cells and factors such as proteases, and is coordinated by mediators such as PAF, cytokines and growth factors, minute amounts of which can prime cells to respond in an enhanced manner to subsequent agonistic stimuli. PAF and certain cytokines also possess the unique property of being able to induce the release of each other and their own generation in vivo. This 'singularity' may enable a self-generating feedback network to become established. The priming ability of these mediators indicates the extreme sensitivity of the inflammatory process and importance of a homeostatic equilibrium between the vectors involved in the priming and feedback processes and internal suppressive mechanisms. In pathological conditions, one can consider the phenomenon of PAF and cytokine autogeneration as a 'fold' in the feedback network and an expression of the singularity characteristic of the catastrophe hypothesis. This may lead to systemic toxicity and microcirculatory collapse, a characteristic feature of shock, sepsis, asthma, ischemia and graft rejection. A combination of drugs antagonizing the various feedback components may inhibit this catastrophic process and thus provide more successful therapy of these conditions.

A modified rabbit ear chamber and an example of its application for intravital-microscopic study on acute effects of topical thermal stimulation

A pre-existing plastic rabbit ear chamber was modified to be applicable for intravital-microscopic observations in pharmacological as well as pathophysiological studies on inflammation. The chamber consists of a base disk, a mica (or glass) cover-slip and a holder ring. The base disk has a round-table with a central protrusion in which a heat conductor of platinum wire is so implanted near the protrusion that thermal stimulation can be given to the regenerated tissue between the table and the coverslip.

Temporal effects of 5.0 Gy radiation in healing subcutaneous microvasculature of a dorsal flap window chamber

The temporal effects of 5.0 Gy of radiation on healing subcutaneous microvasculature were studied using a window chamber in the dorsal flap of the Fischer-344 rat. Microvascular function was assessed by morphometric and dynamic flow measurements which were made prior to and at 24 and 72 h after exposure. A comparison was made between chamber preps that were 3 and 14 days postsurgery. The hypothesis of the study was that the older preparation would be more refractory to damage by radiation. Both unirradiated preparations showed an increase in capillary numbers over the period of observation, while irradiated preps had a reduction, especially in vessels less than 50 microns in diameter. Red cells velocities increased by 20-100% in those vessels which survived the radiation exposure, indicating that tissue oxygen tensions might be preserved in spite of a loss of vasculature. These results explain the need for both morphologic and dynamic flow measurements when assessing the effect of therapeutic intervention on microcirculatory function. Further studies are underway to identify a fully mature capillary bed in this model, since it is apparent that capillary growth is continuing in the 14-day preparation.

Injury of brain microvessels with a helium-neon laser and Evans blue can elicit local platelet aggregation without endothelial denudation

A helium-neon laser was used to produce endothelial lesions and local platelet aggregation in brain microvessels (pial arterioles and venules) sensitized by intravascular Evans blue. Electron microscopy showed that the aggregates formed in the absence of endothelial denudation or exposure of basal lamina. Initial lesions consisted only of endothelial lucencies, vacuoles, and distended rough or smooth endoplasmic reticulum. Aggregates consisted not only of degranulating platelets, rounded platelets, and platelets with pseudopods, but also of masses of discoid platelets. Red blood cells were uninjured and did not form the nidus of these collections. The possibility that aggregation occurred as a result of direct injury to the platelet, and independently of the endothelial damage, is discussed and considered unlikely. Rather, the data are consonant with the hypothesis that in the microcirculation, endothelial injury can produce aggregation prior to exposure of basal lamina.