Dino J Ravnic

Publications (12)32.93 Total impact

• Article: Inflammation-induced intussusceptive angiogenesis in murine colitis.

  Moritz A Konerding, Aslihan Turhan, Dino J Ravnic, Miao Lin, Christine Fuchs, Timothy W Secomb, Akira Tsuda, Steven J Mentzer
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  ABSTRACT: Intussusceptive angiogenesis is a morphogenetic process that forms new blood vessels by the division of a single blood vessel into two lumens. Here, we show that this process of intraluminal division participates in the inflammation-induced neovascularization associated with chemically induced murine colitis. In studies of both acute (4-7 days) and chronic (28-31 days) colitis, intravital microscopy of intravascular tracers demonstrated a twofold reduction in blood flow velocity. In the acute colitis model, the decreased velocity was associated with marked dilatation of the mucosal plexus. In contrast, chronic inflammation was associated with normal caliber vessels and duplication (and triplication) of the quasi-polygonal mucosal plexus. Scanning electron microscopy (SEM) of intravascular corrosion casts suggested that pillar formation and septation, previously linked to the morphogenetic process of intussusceptive angiogenesis, were present within days of the onset of inflammation. Four weeks after the onset of inflammation, SEM of vascular corrosion casts demonstrated replication of the mucosal plexus without significant evidence of sprouting angiogenesis. These data suggest that mucosal capillaries have comparable aggregate cross-sectional area in acute and chronic colitis; however, there is a significant increase in functional capillary density in chronic colitis. We conclude that intussusceptive angiogenesis is a fundamental mechanism of microvascular adaptation to prolonged inflammation.
  The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 03/2010; 293(5):849-57. · 1.47 Impact Factor
• Article: Bridging mucosal vessels associated with rhythmically oscillating blood flow in murine colitis.

  Aslihan Turhan, Moritz A Konerding, Akira Tsuda, Dino J Ravnic, Dusan Hanidziar, Miao Lin, Steven J Mentzer
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  ABSTRACT: Oscillatory blood flow in the microcirculation is generally considered to be the result of cardiopulmonary influences or active vasomotion. In this report, we describe rhythmically oscillating blood flow in the bridging vessels of the mouse colon that appeared to be independent of known biological control mechanisms. Corrosion casting and scanning electron microscopy of the mouse colon demonstrated highly branched bridging vessels that connected the submucosal vessels with the mucosal plexus. Because of similar morphometric characteristics (19 +/- 11 microm vs. 28 +/- 16 microm), bridging arterioles and venules were distinguished by tracking fluorescent nanoparticles through the microcirculation using intravital fluorescence videomicroscopy. In control mice, the blood flow through the bridging vessels was typically continuous and unidirectional. In contrast, two models of chemically induced inflammation (trinitrobenzenesulfonic acid and dextran sodium sulfate) were associated with a twofold reduction in flow velocity and the prominence of rhythmically oscillating blood flow. The blood oscillation was characterized by tracking the bidirectional displacement of fluorescent nanoparticles. Space-time plots and particle tracking of the oscillating segments demonstrated an oscillation frequency between 0.2 and 5.1 cycles per second. Discrete Fourier transforms demonstrated a power spectrum composed of several base frequencies. These observations suggest that inflammation-inducible changes in blood flow patterns in the murine colon resulted in both reduced blood flow velocity and rhythmic oscillations within the bridging vessels of the mouse colon.
  The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 02/2008; 291(1):74-82. · 1.47 Impact Factor
• Article: Biological and optical properties of fluorescent nanoparticles developed for intravascular imaging.

  Dino J Ravnic, Yu-Zhong Zhang, Aslihan Turhan, Akira Tsuda, Juan P Pratt, Harold T Huss, Steven J Mentzer
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  ABSTRACT: Intravascular tracers in the blood circulation can provide a description of the flow field over time and space. To address the limitations of existing intravascular tracers, we have developed fluorescent nanoparticles capable of providing detailed information regarding the intravascular flow field. The nanoparticles were designed to maximize plasma half-life as well as minimize interactions with other blood components. The bioavailability of the particles in the blood circulation required nanoscale size and low surface charge density. Intravital imaging of nanoparticles in the microcirculation demonstrated that the fluorescence intensity of the nanoparticles was a major determinant of both temporal and spatial resolution of the flow field. We conclude that nanoparticles prepared with these physical and optical properties can provide an accurate description of the localized intravascular flow field.
  Microscopy Research and Technique 10/2007; 70(9):776-81. · 1.79 Impact Factor
• Article: Murine microvideo endoscopy of the colonic microcirculation.

  Dino J Ravnic, Moritz A Konerding, Harold T Huss, Tanja Wolloscheck, Juan P Pratt, Steven J Mentzer
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  ABSTRACT: Natural orifice endoscopy in small animal models has been limited in the past by instrument size and optical performance. In this report, we investigate the feasibility of using a recently developed microvideo endoscopy system to evaluate the colon microcirculation. Using a murine model of acute colitis, microvideo endoscopy was useful in mapping the topography of inflammation as well as identifying relevant structures in the microcirculation. We conclude that natural orifice endoscopy is a useful method for the minimally invasive longitudinal assessment of the colonic mucosal microcirculation.
  Journal of Surgical Research 10/2007; 142(1):97-103. · 2.25 Impact Factor
• Article: Structural adaptations in the murine colon microcirculation associated with hapten-induced inflammation.

  Dino J Ravnic, Moritz A Konerding, Akira Tsuda, Harold T Huss, Tanja Wolloscheck, Juan P Pratt, Steven J Mentzer
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  ABSTRACT: Blood flowing across the vascular endothelium creates wall shear stress, dependent on velocity of flow and vessel geometry, that tends to disrupt lymphocyte-endothelial cell adhesion. The microcirculation in a murine model of acute colitis was investigated to identify structural adaptations during acute colitis that may facilitate transmigration. In 2,4,6-trinitrobenzenesulphonic acid-induced acute colitis, the infiltrating cells and colonic microcirculation was investigated by cellular topographic mapping, corrosion casting and three-dimensional scanning electron microscopy (SEM). Colonic blood velocimetry was performed using intravital microscopy. Clinical and histological parameters suggested a peak inflammatory response at 96 h (p<0.001). The infiltrating cells were spatially related to the mucosal capillary plexus by three-dimensional topographic mapping (p<0.001). In normal mice, corrosion casting and three-dimensional SEM showed a polygonal mucosal plexus supplied by ascending arteries and descending veins. After 2,4,6-trinitrobenzenesulphonic acid stimulation, three-dimensional SEM showed preserved branch angles (p = 0.52) and nominal vessel lengths (p = 0.93), but a significantly dilated mucosal capillary plexus (p<0.001). Intravital microscopy of the mucosal plexus showed a greater than twofold decrease in the velocity of flow (p<0.001). The demonstrable slowing of the velocity of flow despite an increase in volumetric flow suggests that these microvascular adaptations create conditions suitable for leucocyte adhesion and transmigration.
  Gut 05/2007; 56(4):518-23. · 10.11 Impact Factor
• Article: The murine bronchopulmonary microcirculation in hapten-induced inflammation.

  Dino J Ravnic, Moritz A Konerding, Juan P Pratt, Tanja Wolloscheck, Harold T Huss, Steven J Mentzer
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  ABSTRACT: The clinical observation of central bronchial artery hypertrophy in chronic lung inflammation suggests the possibility that the bronchial circulation may also participate in adaptive responses in peripheral lung inflammation. To investigate the potential role of the bronchial microcirculation in peripheral lung inflammation, we developed a murine model of lung inflammation using the intratracheal instillation of the peptide-hapten trinitrophenol in presensitized mice. Clinical parameters indicated a peak inflammatory response at 96 hours. Similarly, gross and microscopic evidence of inflammation was observed 96 hours after antigen instillation. Using a forced oscillation technique to probe peripheral lung mechanics at 96 hours, we detected no change in central airway resistance (P > .05), but a significant increase in peripheral tissue resistance (P < .05). The structure of the bronchial circulation was investigated by microsphere occlusion of the pulmonary circulation and corrosion casting of the bronchial circulation. SEM of the bronchial artery casts demonstrated (1) the presence of the peripheral bronchial circulation in mice, (2) interconnections of the two systems in the distal bronchial arteries and at the level of alveolar capillaries, and (3) functional evidence of increased bronchial perfusion of alveolar capillaries during mononuclear inflammation. These results suggest an important adaptive role of the bronchial circulation in pulmonary inflammation.
  The Journal of thoracic and cardiovascular surgery 02/2007; 133(1):97-103. · 3.41 Impact Factor
• Source

  Available from: Harold Huss

  Article: Multiframe particle tracking in intravital imaging: defining Lagrangian coordinates in the microcirculation.

  Dino J Ravnic, Akira Tsuda, Aslihan Turhan, Juan P Pratt, Harold T Huss, Yu-Zhong Zhang, Steven J Mentzer
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  ABSTRACT: The cellular composition of the microcirculation creates blood flow that can be unsteady and nonuniform. To obtain information about nonuniform cellular trajectories, we describe in vivo imaging techniques that provide both detailed tracking of individual particles as well as an approach to simultaneous multicolor particle tracking. Particularly relevant to biologic systems, Lagrangian methods provide information about the fate of individual particles and flow in the system.
  BioTechniques 12/2006; 41(5):597-601. · 2.67 Impact Factor
• Article: Inflammation-responsive focal constrictors in the mouse ear microcirculation.

  Dino J Ravnic, Moritz Konerding, Juan P Pratt, Tanja Wolloscheck, Harold T Huss, Steven J Mentzer
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  ABSTRACT: In many capillary exchange beds, blood flow is locally regulated by precapillary sphincter-like activity. In this study, we used intravascular tracers and scanning electron microscopy to investigate precapillary blood flow regulation in the mouse ear. Gelatin ink injections of the normal mouse ear demonstrated 6.8 +/- 2.3 axial vessels with a cutoff of detectable tracer in the early branches: 19 +/- 11 focal constrictions were observed along the 1st to 5th order branches of the axial vessels. A perfusion tracer consisting of biotinylated anti-endothelial lectins (Ricinus Communis Agglutin, Lycopersicon Esculentum and Griffonia Simplicifolia) was circulated for 30 min under physiological conditions. Subsequent enzyme histochemistry demonstrated no significant change in distal perfusion or in the number of focal constrictions (P > 0.05). Furthermore, the focal constrictions were unresponsive to vasodilators such as organic nitrates and prostaglandin E1. By contrast, the presence of oxazolone-induced inflammation resulted in significant and sustained vasodilatation for more than 96 h (P > 0.001). Scanning electron microscopy demonstrated discrete constricting bands morphologically distinct from known precapillary sphincters. These results suggest that these previously unappreciated inflammation-responsive precapillary constrictors regulate capillary recruitment in the mouse ear microcirculation.
  Journal of Anatomy 12/2006; 209(6):807-16. · 2.37 Impact Factor
• Source

  Available from: Harold Huss

  Article: Structural mapping of immunoglobulin subclasses using multiplexed bead flow cytometry.

  Xiaoqun Jiang, Juan Pablo Pratt, Harold O Huss, Dino J Ravnic, Steven J Mentzer
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  ABSTRACT: Monoclonal hybridomas secrete immunoglobulin molecules with a single specificity and distinct class/subclass structure. The determination of immunoglobulin structure can be used to facilitate hybridoma colony management and predict monoclonality. In this report, we used multiplexed bead flow cytometry to define hybridoma class/subclass. The assay was sufficiently sensitive to detect 50 ng/mL of antibody. The multiplexed bead assay efficiently defined traditional class/subclass determinants as well as more subtle patterns of crossreactivity. Further, the assay was combined with Poisson statistics to provide a numerical estimate of hybridoma monoclonality. The sensitivity and flexibility of this approach suggests the utility of multiplexed bead flow cytometry in the early management of immunoglobulin-secreting hybridomas.
  Hybridoma (2005) 07/2006; 25(3):133-8. · 0.42 Impact Factor
• Article: Vessel painting of the microcirculation using fluorescent lipophilic tracers.

  Dino J Ravnic, Xiaoqun Jiang, Tanja Wolloscheck, Juan P Pratt, Harold Huss, Steven J Mentzer, Moritz A Konerding
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  ABSTRACT: Flexible approaches to defining microvessel morphometry are useful in the study of both acute and chronic structural changes of the microcirculation. In this report, we examined the utility of the intravascular infusion of lipophilic carbocyanine tracers in the structural assessment of the retina, skin, lung, and colon microcirculation. The microvessel labeling technique, here termed fluorescent vessel painting, involved the intravascular injection of sulfonated lipophilic carbocyanine tracers. The utility of vessel painting in morphometry was assessed using morphometric comparisons with corrosion casting and 2-dimensional and 3-dimensional scanning electron microscopy. The comparisons demonstrated that fluorescent vessel painting modestly overestimated the interbranch angles, interbranch distances, and vessel diameters of the 2D mucosal plexus of the colon. These differences were narrowed with the application of confocal microscopy. The advantages of fluorescence vessel painting included (1) the filling of all tissues including the relatively high resistance microvessels of the mouse skin, (2) the ability to use tissue counterstains such as DAPI, and (3) the prolonged stability of the lipophilic tracer after aldehyde fixation. These studies suggest the utility of fluorescent vessel painting as a complementary technique to corrosion casting in the morphometric study of the microcirculation.
  Microvascular Research 08/2005; 70(1-2):90-6. · 2.83 Impact Factor
• Article: Multi-image particle tracking velocimetry of the microcirculation using fluorescent nanoparticles.

  Dino J Ravnic, Yu-Zhong Zhang, Akira Tsuda, Juan P Pratt, Harold T Huss, Steven J Mentzer
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  ABSTRACT: Particle tracking velocimetry provides a Lagrangian description of flow properties in the microcirculation. To determine the utility of fluorescent nanoparticles to provide Lagrangian coordinates, we tracked these particles both in vitro and in vivo. The particles had a neutral charge and fluorescence intensity greater than 1,000 times the PKH26-labeled red blood cells. At image acquisition rates of 60 frames per second, particles were tracked at velocities up to 4,000 microm/s. Morphometric changes reflecting streaking artifact were significant at velocities of 4,000 microm/s (P < 0.05), but not at lower velocities (P > 0.05). Intravital microscopy monitoring after intravenous injection of the particles demonstrated a circulation half-life that was inversely related to particle size: 500 nm nanoparticles demonstrated a smaller change in plasma concentration than larger particles. Regardless of the size of the particles, more than 50% of the recovered fluorescence was located in the liver. These results suggest that fluorescent nanoparticles provide a convenient and practical Lagrangian description of flow velocity in the microcirculation.
  Microvascular Research 72(1-2):27-33. · 2.83 Impact Factor
• Article: Melittin-induced membrane permeability: a nonosmotic mechanism of cell death.

  Juan Pablo Pratt, Dino J Ravnic, Harold T Huss, Xiaoqun Jiang, Benjamin S Orozco, Steven J Mentzer
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  ABSTRACT: Derived from honeybees, melittin is a 26-amino acid, alpha-helical, membrane-attack protein that efficiently kills mammalian cells. To investigate the contribution of colloid-osmotic effects to the mechanism of cell death, we studied the effect of melittin on lymphocyte membrane permeability and cell volumes. Melittin concentrations of 0.5 to 2.0 microM induced release of membrane permeability markers without total disruption of the cell membrane. At these melittin concentrations, electrical-impedance cytometry demonstrated melittin-induced changes in red blood cell volumes (P<0.01), but no change in lymphocyte cell volumes (P>0.05). Streaming video microscopy, obtaining images of melittin-treated lymphocytes at 80-ms intervals, demonstrated a loss of optical density (P<0.001) suggesting a flattening of the cell but no significant increase in cell perimeter (P>0.05). Real-time multiparameter flow cytometry of melittin-treated lymphocytes confirmed simultaneous loss of the cytoplasmic marker, calcein, and uptake of the DNA dye, ethidium homodimer, but demonstrated no increase in forward light scatter. Transmission-electron microscopy of melittin-treated lymphocytes showed normal cell volumes but discontinuities in the cell membrane suggesting direct membrane toxicity. We conclude that melittin causes lymphocyte death by a "leaky patch" mechanism that is independent of colloid-osmotic effects.
  In Vitro Cellular & Developmental Biology - Animal 41(10):349-55. · 1.31 Impact Factor