Age-dependent changes in porcine alveolar macrophage function during the postnatal period of alveolarization

During early postnatal ontogeny in most mammals, the lung is structurally and functionally immature. In some species with relatively altricial lung morphology, there is evidence of a coupling between functional maturity of the pulmonary cellular immune system and alveolar maturation. Herein, we examine changes in alveolar macrophage (AM) number and function occurring during alveolarization in a more precocial species, the pig, to determine if heightened oxidative metabolism and phagocytic ability is similarly delayed until completion of lung morphogenesis. We assessed cell differential in lavage fluid and evaluated two main functional parameters of AM phagocytic response, the generation of reactive oxygen species (ROS), and particle internalization. AM functional maturation occurred mainly during the first postnatal week: the proportion of AMs, ROS generation, and phagocytosis all increased significantly. These results suggest maturational improvement of the impaired AM-based pulmonary immune system of the neonate piglet occurs during the postnatal period of rapid alveolarization.

Hamiltonian Chaos in a Model Alveolus

In the pulmonary acinus, the airflow Reynolds number is usually much less than unity and hence the flow might be expected to be reversible. However, this does not appear to be the case as a significant portion of the fine particles that reach the acinus remains there after exhalation. We believe that this irreversibility is at large a result of chaotic mixing in the alveoli of the acinar airways. To test this hypothesis, we solved numerically the equations for incompressible, pulsatile, flow in a rigid alveolated duct and tracked numerous fluid particles over many breathing cycles. The resulting Poincaré sections exhibit chains of islands on which particles travel. In the region between these chains of islands, some particles move chaotically. The presence of chaos is supported by the results of an estimate of the maximal Lyapunov exponent. It is shown that the streamfunction equation for this flow may be written in the form of a Hamiltonian system and that an expansion of this equation captures all the essential features of the Poincaré sections. Elements of Kolmogorov–Arnol’d–Moser theory, the Poincaré–Birkhoff fixed-point theorem, and associated Hamiltonian dynamics theory are then employed to confirm the existence of chaos in the flow in a rigid alveolated duct.

Modelling thrombosis using dissipative particle dynamics method

AIM

Arterial occlusion is a leading cause of cardiovascular disease. The main mechanism causing vessel occlusion is thrombus formation, which may be initiated by the activation of platelets. The focus of this study is on the mechanical aspects of platelet-mediated thrombosis which includes the motion, collision, adhesion and aggregation of activated platelets in the blood. A review of the existing continuum-based models is given. A mechanical model of platelet accumulation onto the vessel wall is developed using the dissipative particle dynamics (DPD) method in which the blood (i.e. colloidal-composed medium) is treated as a group of mesoscale particles interacting through conservative, dissipative, attractive and random forces.

METHODS

Colloidal fluid components (plasma and platelets) are discretized by mesoscopic (micrometre-size) particles that move according to Newton's law. The size of each mesoscopic particle is small enough to allow tracking of each constituent of the colloidal fluid, but significantly larger than the size of atoms such that, in contrast to the molecular dynamics approach, detailed atomic level analysis is not required.

RESULTS

To test this model, we simulated the deposition of platelets onto the wall of an expanded tube and compared our computed results with the experimental data of Karino et al. (Miscrovasc. Res. 17, 238-269, 1977). By matching our simulations to the experimental results, the platelet aggregation/adhesion binding force (characterized by an effective spring constant) was determined and found to be within a physiologically reasonable range.

CONCLUSION

Our results suggest that the DPD method offers a promising new approach to the modelling of platelet-mediated thrombosis. The DPD model includes interaction forces between platelets both when they are in the resting state (non-activated) and when they are activated, and therefore it can be extended to the analysis of kinetics of binding and other phenomena relevant to thrombosis.

Finite element 3D reconstruction of the pulmonary acinus imaged by synchrotron X-ray tomography

The alveolated structure of the pulmonary acinus plays a vital role in gas exchange function. Three-dimensional (3D) analysis of the parenchymal region is fundamental to understanding this structure-function relationship, but only a limited number of attempts have been conducted in the past because of technical limitations. In this study, we developed a new image processing methodology based on finite element (FE) analysis for accurate 3D structural reconstruction of the gas exchange regions of the lung. Stereologically well characterized rat lung samples (Pediatr Res 53: 72-80, 2003) were imaged using high-resolution synchrotron radiation-based X-ray tomographic microscopy. A stack of 1,024 images (each slice: 1024 x 1024 pixels) with resolution of 1.4 mum(3) per voxel were generated. For the development of FE algorithm, regions of interest (ROI), containing approximately 7.5 million voxels, were further extracted as a working subunit. 3D FEs were created overlaying the voxel map using a grid-based hexahedral algorithm. A proper threshold value for appropriate segmentation was iteratively determined to match the calculated volume density of tissue to the stereologically determined value (Pediatr Res 53: 72-80, 2003). The resulting 3D FEs are ready to be used for 3D structural analysis as well as for subsequent FE computational analyses like fluid dynamics and skeletonization.

Emerging lupus-like manifestations in acute parvovirus B19 infection

We encountered an adult patient with acute parvovirus B19 infection who presented with transient lupus-like symptoms (i.e., polyarthritis, fever, myalgia, pancytopenia, hypocomplementemia, and nephritis). Our case is characterized by the demonstration of acute nephritis as a complication of this infection, making it difficult to distinguish between a viral infection and the first episode of systemic lupus erythematosus.

Mesoscale Iron Enrichment Experiments 1993-2005: Synthesis and Future Directions

Since the mid-1980s, our understanding of nutrient limitation of oceanic primary production has radically changed. Mesoscale iron addition experiments (FeAXs) have unequivocally shown that iron supply limits production in one-third of the world ocean, where surface macronutrient concentrations are perennially high. The findings of these 12 FeAXs also reveal that iron supply exerts controls on the dynamics of plankton blooms, which in turn affect the biogeochemical cycles of carbon, nitrogen, silicon, and sulfur and ultimately influence the Earth climate system. However, extrapolation of the key results of FeAXs to regional and seasonal scales in some cases is limited because of differing modes of iron supply in FeAXs and in the modern and paleo-oceans. New research directions include quantification of the coupling of oceanic iron and carbon biogeochemistry.

IL-8 Response of Cyclically Stretching Alveolar Epithelial Cells Exposed to Non-fibrous Particles

Using a cell stretcher device, we have previously shown that A549 cells exposed to asbestos fibers gave significantly increased cytokine responses (IL-8) when they were cyclically stretched [Tsuda, A., B. K. Stringer, S. M. Mijailovich, R. A. Rogers, K. Hamada, and M. L. Gray. Am. J. Respir. Cell Mol. Biol. 21(4):455-462, 1999]. In the present study, cell stretching experiments were performed using non-fibrous riebeckite particles, instead of fibrous particles. Riebeckite particles are ground asbestos fibers with the size of a few microns and non-fibrous shape, and are often used as "non-toxic" control particles in the studies of fibrous particle-induced pathogenesis. Although it is generally assumed that riebeckite particles do not elicit strong biological responses, in our studies in cyclically stretched cell cultures, the riebeckite particles coated with adhesion proteins induced significant IL-8 responses, but in static cell cultures the treatment with adhesion protein-coated riebeckite did not induce comparable cytokine responses. To interpret these data, we have developed a simple mathematical model of adhesive interactions between a cell layer and rigid fibrous/non-fibrous particles that were subjected to external tensile forces. The analysis showed that because of considerable dissimilarity in deformations (i.e., strain mismatch) between the cells and particles during breathing, the attachment of particles as small as 1 micro in size could induce significant mechanical forces on the cell surface receptors, which may trigger subsequent adverse cell response under dynamic stretching conditions.

Dissipative particle dynamics simulation of flow generated by two rotating concentric cylinders: boundary conditions

The dissipative particle dynamics (DPD) method was used to simulate the flow in a system comprised of a fluid occupying the space between two cylinders rotating with equal angular velocities. The fluid, initially at rest, ultimately reaches a steady, linear velocity distribution (a rigid-body rotation). Since the induced flow field is solely associated with the no-slip boundary condition at the walls, we employed this system as a benchmark to examine the effect of bounce-back reflections, specular reflections, and Pivkin-Karniadakis no-slip boundary conditions, upon the steady-state velocity, density, and temperature distributions. An additional advantage of the foregoing system is that the fluid occupies inherently a finite bounded domain so that the results are affected by the prescribed no-slip boundary conditions only. Past benchmark systems such as Couette flow between two infinite parallel plates or Poiseuille flow in an infinitely long cylinder must employ artificial periodic boundary conditions at arbitrary upstream and downstream locations, a possible source of spurious effects. In addition, the effect of the foregoing boundary conditions on the time evolution of the simulated velocity profile was compared with that of the known, time-dependent analytical solution. It was shown that bounce-back reflection yields the best results for the velocity distributions with small fluctuations in density and temperature at the inner fluid domain and larger deviations near the walls. For the unsteady solutions a good fit is obtained if the DPD friction coefficient is proportional to the kinematic viscosity. Based on dimensional analysis and the numerical results a universal correlation is suggested between the friction coefficient and the kinematic viscosity.

Acquired resistance to berenil in a cloned isolate of Trypanosoma evansi is associated with upregulation of a novel gene, TeDR40

Drug resistance is now a severe and increasing problem in trypanosomes, but molecular details of mechanisms of resistance are only beginning to unveil. There is urgent need to clearly elucidate the different mechanisms of drug resistance in trypanosomes in order to circumvent existing resistance problems and avoid emergence of resistance to the next generation drugs. In this study, we cloned and characterized a novel gene, TeDR40, whose expression is associated with resistance to berenil in Trypanosoma evansi. Expression analysis showed that the gene was at least 1000-fold upregulated in resistant parasites and the encoded protein appeared to have a ubiquitous cellular localization. To investigate the association of TeDR40 with berenil-resistance, we genetically modified wild-type berenil-sensitive T. evansi for inducible over-expression of the TeDR40 gene. Induction of over-expression of TeDR40 in T. evansi led to decreased (P < 0.01) sensitivity to berenil. Our findings indicate a possible correlation between over-expression of a novel gene, TeDR40, and reduced sensitivity to berenil in an in vitro-cultured clonal line of T. evansi.

In vitro effects of antihypertensive drugs on thromboxane agonist (U46619)-induced vasoconstriction in human internal mammary artery

BACKGROUND

Hypertension is a major problem in the perioperative period of cardiac and non-cardiac surgery. The vascular endothelium plays a crucial role in modulating vascular tone by producing vasodilators as well as vasoconstrictors. Thromboxane A2 (TxA2), a prototypical vasoconstrictor produced by endothelium and platelets, may play an important role in the pathogenesis of hypertension and subsequent ischaemic events. Although multiple drugs are currently available to treat perioperative hypertension, there is a paucity of data comparing these agents. Therefore, we examined the in vitro vascular effects of commonly used antihypertensive drugs on human internal mammary artery (IMA) segments.

METHODS

Relaxation responses to adenosine (a nucleoside), enalaprilat (a competitive inhibitor of angiotensin-converting enzyme), fenoldopam (a D1-dopamine receptor agonist), hydralazine, labetalol (an alpha- and beta-adrenergic blocker), nicardipine (a calcium channel blocker), nicorandil (K(+)-ATP channel opener), nitroglycerin (GTN, a nitrosovasodilator), and sodium nitroprusside (SNP, a nitrosovasodilator) were studied in IMA segments pre-contracted with the TxA2 analogue (U46619, 1.0 x 10(-8) M). Effects of labetalol were also studied in IMA segments pre-contracted with norepinephrine (1.0 x 10(-6) M). All drugs were added in a cumulative fashion (range 10(-10) to 10(-3) M).

RESULTS

All agents in the current study, with the exception of enalaprilat, dilated the IMA segments pre-contracted with U46619. Only GTN and SNP induced a complete (90-100%) relaxation. The order of efficacy of the in vitro relaxation was as follows: SNP, GTN, nicardipine, nicorandil, fenoldopam, hydralazine, adenosine, and labetalol. The potency was in the order of GTN, SNP, fenoldopam, nicorandil, hydralazine, adenosine, and nicardipine.

CONCLUSIONS

Various antihypertensive agents are effective in attenuating U46619-induced IMA vasoconstriction, but the efficacy and potency differ. The in vitro vasodilation may not be simply extrapolated to the clinical efficacy or outcome of each antihypertensive therapy; however, our data provide additional grounds for the choice of antihypertensive medication. Further clinical studies are needed to help to fully elucidate the use of different antihypertensive agents and clinical outcomes.

Gravitational deposition in a rhythmically expanding and contracting alveolus

In a previous simulation, our laboratory demonstrated that the flow induced by a rhythmically expanding and contracting alveolus is highly complex (Haber S, Butler JP, Brenner H, Emanuel I, and Tsuda A, J Fluid Mech 405: 243-268, 2000). Based on these earlier findings, we hypothesize that the trajectories and deposition of aerosols inside the alveoli differ substantially from those previously predicted. To test this hypothesis, trajectories of fine particles (0.5-2.5 microm in diameter) moving in the foregoing alveolar flow field and simultaneously subjected to the gravity field were simulated. The results show that alveolar wall motion is crucial in determining the enhancement of aerosol deposition inside the alveoli. In particular, 0.5- to 1-microm-diameter particles are sensitive to the detailed alveolar flow structure (e.g., recirculating flow), as they undergo gravity-induced convective mixing and deposition. Accordingly, deposition concentrations within each alveolus are nonuniform, with preferentially higher densities near the alveolar entrance ring, consistent with physiological observations. Deposition patterns along the acinar tree are also nonuniform, with higher deposition in the first half of the acinar generations. This is a result of the combined effects of enhanced alveolar deposition in the proximal region of the acinus due to alveoli expansion and contraction and reduction in the number of particles remaining in the gas phase down the acinar tree. We conclude that the cyclically expanding and contracting motion of alveoli plays an important role in determining gravitational deposition in the pulmonary acinus.

Four serine proteinase inhibitors (serpin) from the brown ear tick, Rhiphicephalus appendiculatus; cDNA cloning and preliminary characterization

While development of an anti-Boophilus microplus vaccine is advanced and practical, work on other economically important ticks such as Rhipicephalus appendiculatus is still in its infancy. Guess PCR primers, designed from a consensus amino acid sequence (NAVYKFG) motif were used with rapid amplification of cDNA ends (RACE) to clone four cDNAs encoding serine proteinase inhibitors (serpin) from the brown ear tick Rhipicephalus appendiculatus. The four genes designated as R. appendiculatus serpin (RAS) -1 to -4 encode polypeptides of 378, 380, 398 and 486 amino acids long, respectively. Sequence comparison of RAS-1 to -4 predicted amino acid sequences to the serpin-like hypothetical protein from Ixodes ricinus (Leboulle et al., 2002) revealed closer structural similarities among tick serpins. Expression analysis by RT-PCR showed that RAS-1 to -4 are expressed in other tick organs in addition to salivary glands and midguts. Except for RAS-3 whose expression level appears to be equivalent in all tick organs, RAS-1, -2 and -4 are predominantly expressed in the salivary glands. We have discussed our findings with reference to development of vaccines against R. appendiculatus.

Kinematically irreversible acinar flow: a departure from classical dispersive aerosol transport theories

Current theories describe aerosol transport in the lung as a dispersive (diffusion-like) process, characterized by an effective diffusion coefficient in the context of reversible alveolar flow. Our recent experimental data, however, question the validity of these basic assumptions. In this study, we describe the behavior of fluid particles (or bolus) in a realistic, numerical, alveolated duct model with rhythmically expanding walls. We found acinar flow exhibiting multiple saddle points, characteristic of chaotic flow, resulting in substantial flow irreversibility. Computations of axial variance of bolus spreading indicate that the growth of the variance with respect to time is faster than linear, a finding inconsistent with dispersion theory. Lateral behavior of the bolus shows fine-scale, stretch-and-fold striations, exhibiting fractal-like patterns with a fractal dimension of 1.2, which compares well with the fractal dimension of 1.1 observed in our experimental studies performed with rat lungs. We conclude that kinematic irreversibility of acinar flow due to chaotic flow may be the dominant mechanism of aerosol transport deep in the lungs.

The in vitro reversal of histamine-induced vasodilation in the human internal mammary artery

Anaphylactic shock therapy includes the use of catecholamines but they may not always be effective. Because vasodilation during anaphylaxis is a result of the endothelial release of multiple mediators, we investigated the effects of epinephrine, vasopressin, and inhibitors of nitric oxide and prostanoid pathways on histamine-induced relaxation in human internal mammary artery. The vessel segments were obtained intraoperatively and were suspended in organ chambers to record isometric tension. Norepinephrine (10(-6) M) was used to precontract the rings followed by histamine (10(-6.5) M) to relax the vessels and mimic vascular collapse. Epinephrine, vasopressin, methylene blue, N(G)-monomethyl-L-arginine (L-NMA) and indomethacin were added in a cumulative fashion to reverse the histamine-induced vasodilation. The internal mammary artery segments exhibited greater contraction in the presence of the epinephrine (4.9 +/- 0.7 g) compared with vasopressin (2.6 +/- 0.7 g). Vasopressin (10(-11) to 10(-7) M), methylene blue (10(-7) to 10(-5) M), L-NMA (10(-6) to 10(-4) M), and indomethacin (10(-7) to 10(-5) M) were only partially effective. These findings suggest that vasopressin and methylene blue may offer a potential therapeutic option in the treatment of histamine-induced vasodilatory shock.

IMPLICATIONS

Epinephrine only partially reverses histamine-induced vasodilation in human internal mammary arteries, whereas vasopressin, methylene blue, and drugs involved in the inhibition of nitric oxide and prostaglandin generation lead to a complete reversal of the vascular relaxation.

Syntheses, structural characterizations, and optical and electrochemical properties of directly fused diporphyrins

Directly fused diporphyrins display the extensive pi conjugation as evinced by highly perturbed electronic absorption spectra as well as lowered and largely split first oxidation potentials. Such diporphyrins prepared include meso-beta doubly linked diporphyrins 7, meso-meso beta-beta beta-beta triply linked diporphyrins 8, and meso-meso beta-beta doubly linked diporphyrins 9. Oxidation of 5,15-diaryl-substituted and 5,10,15-triaryl-substituted Ni(II)-, Cu(II)-, and Pd(II)-porphyrins with tris(4-bromophenyl)aminium hexachloroantimonate (BAHA) in CHCl(3) afforded 7, and triply linked Cu(II)-diporphyrins 8a and 8g were respectively prepared by the oxidation of meso-meso singly linked Cu(II)-diporphyrins 5c and 5f with BAHA. Meso-meso beta-beta doubly linked Ni(II)-diporphyrin 9a was isolated along with triply linked Ni(II)-diporphyrin 8e from the similar oxidation of meso-meso singly linked Ni(II)-diporphyrin 5a. Doubly linked diporphyrins 7 and 9a both exhibit significantly perturbed electronic absorption spectra, in which the Soret-like bands are largely split at around 405-418 and 500-616 nm and the Q-bandlike absorption bands are substantially intensified and red-shifted at 748-820 nm, probably as a consequence of symmetry lowering. Triply linked diporphyrins 8 display more strongly perturbed electronic absorption spectra with split Soret-like bands at 408-419 and 567-582 nm and Q-bandlike absorption bands reaching far-infrared region. Structures of three types of fused diporphyrins 7b and 7c, 8g and 8j, and 9a have been unambiguously determined by X-ray crystallography to be nearly coplanar. Both the triply linked diporphyrins 8g and 8j exhibit very flat structures, whereas the doubly linked diporphyrins 7b and 7c exhibit ruffled structures. The doubly linked diporphyrin 9a shows a helically twisted conformation with larger ruffling toward the opposite directions and has been actually separated into two enantiomers, which display strong Cotton effects in the CD spectra. The first oxidation potentials (E(OX1)) decrease in the order of 5 > 7 > or = 9 > 8, indicating lift-up of HOMO orbital in this order, and split potential differences DeltaE = E(OX1) - E(OX2), in turn, increase in the reverse order of 5 < 7< or = 9 < 8. The (1)H NMR spectra have indicated that the aromatic porphyrin ring current becomes weakened in the order of 5 > 7 > 8. Collectively, the electronic interactions between the diporphyrins have been concluded to increase in the other of 5 << 7 < or = 9 < 8.