Medial Smooth Muscle Cell Proliferation in the Balloon Injured Rabbit Aorta: Effect of a Thiazole Compound with Platelet Inhibitory Activity

Twenty-seven adult male New Zealand rabbits (3–4 kgs) were used in this study. Six rabbits received vehicle, 3 groups of 6 each received doses of 4,5-bis(p-methoxyphenyl)-2-(trifluoromethyl)- thiazole, (U-53,059), at 0.3 mg/kg, 3.0 mg/kg and 30.0 mg/kg/day respectively. Drug and vehicle doses were given orally each day starting 3 days before balloon injury and continuing for the entire 2 week time period. Three rabbits were used as nontreated sham controls. In the vehicle and U-53,059 treated groups aortae were denuded of endothelial cells by balloon catheter injury. Two weeks after injury platelet aggregation to collagen was measured and the aortae removed for analysis of surface characteristics by scanning electron microscopy and lesion size by morphometry. All doses of U-53,059 inhibited platelet aggregation. The 3.0 and 30.0 mg/kg groups had the greatest inhibitory effect. All balloon injured aortae had the same morphologic characteristics. All vessels had similar extent and intensity of Evan’s blue staining, similar areas of leukocyte/platelet adhesion, and a myointimal cell cover of transformed smooth muscle cells. The myointimal proliferative response was not inhibited at any of the drug doses studied.

A Systematic Review of Part C Early Identification Studies

Authors conducted a systematic literature review on early identification steps leading at-risk young children to connect with Part C services. Authors classified data collection settings as primary (settings for general population) or specialized (settings for children at risk of developmental delay) and according to the phases of early identification in the study: (a) original population of children aged 0 to 6 years who had received Part C services, (b) screening and/or referral and/or developmental assessment from 0 through age 2 years, and (c) were deemed eligible and/or received Part C services. Authors identified 43 articles including at least two phases of the early identification process. The literature about connecting children to Part C early intervention (EI) is sparse and fragmented; few studies document the full process from community monitoring to service receipt. Results indicate opportunities for development of systems to better track and improve the identification of young children in need of EI.

Immunomodulatory polymeric scaffold enhances extracellular matrix production in cell co-cultures under dynamic mechanical stimulation

Despite the importance of immune cells in regulating the wound healing process following injury, there are few examples of synthetic biomaterials that have the capacity to push the body's immune cells toward pro-regeneration phenotypes, and fewer still that are designed with the intention of achieving this immunomodulatory character. While monocytes and their derived macrophages have been recognized as important contributors to tissue remodeling in vivo, this is primarily believed to be due to their ability to regulate other cell types. The ability of monocytes and macrophages to generate tissue products themselves, however, is currently not well appreciated within the field of tissue regeneration. Furthermore, while monocytes/macrophages are found in remodeling tissue that is subjected to mechanical loading, the effect this biomechanical strain on monocytes/macrophages and their ability to regulate tissue-specific cellular activity has not been understood due to the complexity of the many factors involved in the in vivo setting, hence necessitating the use of controlled in vitro culture platforms to investigate this phenomenon. In this study, human monocytes were co-cultured with human coronary artery smooth muscle cells (VSMCs) on a tubular (3mm ID) degradable polyurethane scaffold, with a unique combination of non-ionic polar, hydrophobic and ionic chemistry (D-PHI). The goal was to determine if such a synthetic matrix could be used in a co-culture system along with dynamic biomechanical stimulus (10% circumferential strain, 1Hz) conditions in order to direct monocytes to enhance tissue generation, and to better comprehend the different ways in which monocytes/macrophages may contribute to new tissue production. Mechanical strain and monocyte co-culture had a complementary and non-mitigating effect on VSMC growth. Co-culture samples demonstrated increased deposition of sulphated glycosaminoglycans (GAGs) and elastin, as well as increases in the release of FGF-2, a growth factor that can stimulate VSMC growth, while dynamic culture supported increases in collagen I and III as well as increased mechanical properties (elastic modulus, tensile strength) vs. static controls. Macrophage polarization toward an M1 state was not promoted by the biomaterial or culture conditions tested. Monocytes/macrophages cultured on D-PHI were also shown to produce vascular extracellular matrix components, including collagen I, collagen III, elastin, and GAGs. This study highlights the use of synthetic biomaterials having immunomodulatory character in order to promote cell and tissue growth when used in tissue engineering strategies, and identifies ECM deposition by monocytes/macrophages as an unexpected source of this new tissue.

STATEMENT OF SIGNIFICANCE

The ability of biomaterials to regulate macrophage activation towards a wound healing phenotype has recently been shown to support positive tissue regeneration. However, the ability of immunomodulatory biomaterials to harness monocyte/macrophage activity to support tissue engineering strategies in vitro holds enormous potential that has yet to be investigated. This study used a monocyte co-culture on a degradable polyurethane (D-PHI) to regulate the response of VSMCs in combination with biomechanical strain in a vascular tissue engineering context. Results demonstrate that immunomodulatory biomaterials, such as D-PHI, that support a desirable macrophage activation state can be combined with biomechanical strain to augment vascular tissue production in vitro, in part due to the novel and unexpected contribution of monocytes/macrophages themselves producing vascular ECM proteins.

Bone regeneration via a mineral substrate and induced angiogenesis

Angiogenesis and biomineral substrates play major roles in bone development and regeneration. We hypothesized that macroporous scaffolds of biomineralized 85:15 poly(lactide-co-glycolide), which locally release vascular endothelial growth factor-165 (VEGF), would direct simultaneous regeneration of bone and vascular tissue. The presence of a bone-like biomineral substrate significantly increased regeneration of osteoid matrix (32 +/- 7% of total tissue area; mean +/- SD; p < 0.05) and mineralized tissue (14 +/- 2%; P < 0.05) within a rat cranium critical defect compared with a non-mineralized polymer scaffold (19 +/- 8% osteoid and 10 +/- 2% mineralized tissue). Further, the addition of VEGF to a mineralized substrate significantly increased the generation of mineralized tissue (19 +/- 4%; P < 0.05) compared with mineralized substrate alone. This appeared to be due to a significant increase in vascularization throughout VEGF-releasing scaffolds (52 +/- 9 vessels/mm(2); P < 0.05) compared with mineralized scaffolds without VEGF (34 +/- 4 vessels/mm(2)). Surprisingly, there was no significant difference in total osteoid between the two samples, suggesting that increased vascularization enhances mineralized tissue generation, but not necessarily osteoid formation. These results indicate that induced angiogenesis can enhance tissue regeneration, supporting the concept of therapeutic angiogenesis in tissue-engineering strategies.

Identifying substrates for endothelium-specific Tie-2 receptor tyrosine kinase from phage-displayed peptide libraries for high throughput screening

The peptide substrate specificity of Tie-2 was probed using the phage display method in order to identify efficient substrate for high throughput screening. Two random peptide libraries, pGWX3YX4 and pGWX4YX4, were constructed, in which all twenty amino acid residues were represented at the X positions flanking the fixed tyrosine residue Y. A fusion protein of GST and the catalytic domain of human Tie-2 was used to perform the phage phosphorylation. The phosphorylated phage particles were enriched by panning over immobilized anti-phosphotyrosine antibody pY20 for a total of 5 rounds. Four phage clones (3T61, 3T68, C1-90 and D1-15) that express a peptide sequence that can be phosphorylated by the recombinant catalytic domain of human Tie-2 were identified. Synthetic peptides made according to the sequences of the 4 selected clones from the two libraries, which had widely different sequences, were active substrates of Tie-2. Kinetic analysis revealed that D1-15 had the best catalytic efficiency with a k(cat)/K(m) of 5.9x10(4) M(-1) s(-1). Three high throughput screening assay formats, dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA), radioactive plate binding (RPB) and time-resolved fluorescent resonance energy transfer (TR-FRET) were developed to assess the suitability of these phage display selected peptides in screening Tie-2 inhibitors. Three out of four peptides were functional in the DELFIA assay and D1-15 was functional in the TR-FRET assay.

Mechanical regulation of localized and appositional bone formation around bone-interfacing implants

The local mechanical environment around bone-interfacing implants determines, in large part, whether bone formation leading to functional osseointegration will occur. Previous attempts to relate local peri-implant tissue strains to tissue formation have not accounted for implant surface geometry, which has been shown to influence early tissue healing in vivo. Furthermore, the process by which mechanically regulated peri-implant bone formation occurs has not been considered previously. In the current study, we used a unit cell approach and the finite element method to predict the local tissue strains around porous-surfaced and plasma-sprayed implants, and compared the predictions to patterns of bone formation reported in earlier in vivo experiments. Based on the finite element predictions, we determined that appositional bone formation occurred when the magnitudes of the strain components at the tissue-host bone interface were <8%. Localized, de novo bone formation occurred when the distortional tissue strains were less than approximately 3%. Based on these threshold tissue strains, we propose a mechanoregulatory model to relate local tissue strains to the process of peri-implant bone formation. The mechanoregulatory model is novel in that it predicts both appositional and localized bone formation and its predictions are dependent on implant surface geometry. The model provides initial criteria with which the osseointegration potential of bone-interfacing implants may be evaluated, particularly under conditions of immediate or early loading.

Differences in osseointegration rate due to implant surface geometry can be explained by local tissue strains

Experimental evidence indicates that the surface geometry of bone-interfacing implants influences the nature and rate of tissues formed around implants. In a previously reported animal model study, we showed that non-functional, press-fitted porous-surfaced implants placed in rabbit femoral condyle sites osseointegrated more rapidly than plasma-sprayed implants. We hypothesized that the accelerated osseointegration observed with the porous-surfaced design was the result of this design providing a local mechanical environment that was more favourable for bone formation. In the present study, we tested this hypothesis using finite element analysis and homogenization methods to predict the local strains in the pre-mineralized tissues formed around porous-surfaced and plasma-sprayed implants. We found that, for loading perpendicular to the implant interface, the porous surface structure provided a large region that experienced low distortional and volumetric strains, whereas the plasma-sprayed implant provided little local strain protection to the healing tissue. The strain protected region, which was within the pores of the sintered porous surface layer. corresponded to the region where the difference in the amount of mineralization between the two implant designs was the greatest. Low distortional and volumetric strains are believed to favour osteogenesis, and therefore the model results provide initial support for the hypothesis that the porous-surfaced geometry provides a local mechanical environment that favours more rapid bone formation in certain situations.

Osseointegration of sintered porous-surfaced and plasma spray-coated implants: An animal model study of early postimplantation healing response and mechanical stability

The osseointegration and long-term success of bone-interfacing implants are dependent on mechanical stability of the implant relative to host bone during the early healing period. The geometric design of an implant surface may play an important role in affecting early implant stabilization, possibly by influencing tissue healing dynamics. In this study, we compared the early tissue healing response and resulting implant stability for two surface designs by characterizing the histological and mechanical properties of the healing tissue around Ti6Al4V sintered porous-surfaced and Ti plasma-sprayed implants. The implants were inserted transversely in rabbit femoral condyles and evaluated at 0, 4, 8, and 16 days postimplantation. At 4 and 8 days after implantation, the early healing tissue (fibrin and collagenous matrix) was more extensively integrated with the three-dimensional interconnected structure of the sintered porous surface than with the irregular geometry of the plasma-sprayed coating. In addition, histological examination indicated that initial matrix mineralization leading to osseointegration occurred more rapidly with the porous-surfaced implants. The more extensive tissue integration and more rapid matrix mineralization with the porous-surfaced implants were reflected in the mechanical test data, which demonstrated greater attachment strength and interfacial stiffness for the porous-surfaced implants 4 and 8 days postimplantation (p <.05). Sixteen days after implantation, both implant designs were osseointegrated and had comparable attachment characteristics. These data demonstrate that appropriate surface design selection can improve early implant stability and induce an accelerated healing response, thereby improving the potential for implant osseointegration.

Automation of yeast two-hybrid screening

We have developed an automated format for screening yeast two-hybrid libraries for protein-protein interactions. The format consists of a liquid array in which pooled library subsets of yeast, expressing up to 1000 different cDNAs, are mated to a yeast strain of the opposite mating type, expressing a protein of interest. Interactors are detected by a liquid assay for beta-galacsidase following prototrophic selection. The method is demonstrated by the detection of interactions between two encoded yeast RNA polymerase subunits in simulated libraries of varied complexity. To demonstrate its utility for large scale screening of complex cDNA libraries, two nuclear receptor ligand-binding domains were screened through two cDNA libraries arrayed in pooled subsets. Screening these libraries yielded clones which had previously been identified in traditional yeast two hybrid screens, as well as several new putative interacting proteins. The formatting of the cDNA library into pooled subsets lends itself to functional subtraction of the promiscuous positive class of interactor from the library. Also, the liquid arrayed format enables electronic handling of the data derived from interaction screening, which, together with the automated handling of samples, should promote large-scale proteome analysis.

Inhibition of Fas receptor (CD95)-induced hepatic caspase activation and apoptosis by acetaminophen in mice

The mechanism of liver cell injury induced by an overdose of the analgesic acetaminophen (AAP) remains controversial. Recently, it was hypothesized that a significant number of hepatocytes die by apoptosis. Since caspases have been implicated as critical signal and effector proteases in apoptosis, we investigated their potential role in the pathophysiology of AAP-induced liver injury. Male C3Heb/FeJ mice were fasted overnight and then treated with 500 mg/kg AAP. Liver injury became apparent at 4 h and was more severe at 6 h (plasma ALT activities: 4110 +/- 320 U/liter; centrilobular necrosis). DNA fragmentation increased parallel to the increase of plasma ALT values. At 6 h there was a 420% increase of DNA fragmentation and a 74-fold increase of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells located predominantly around central veins. However, the activity of the proapoptotic caspase-3 was not increased at any time after AAP. In contrast, injection of the anti-Fas antibody Jo-2 (positive control) caused a 28-fold increase of caspase-3 activity and severe DNA fragmentation before significant ALT release. Treatment with the caspase inhibitor ZVAD-CHF2 had no effect on AAP toxicity but completely prevented Jo-mediated apoptosis. In contrast, Jo-induced caspase activation and apoptosis could be inhibited by AAP treatment in a time- and dose-dependent manner. We conclude that AAP-induced DNA fragmentation does not involve caspases, suggesting a direct activation of endonucleases through elevated Ca2+ levels. In addition, electrophilic metabolites of AAP may inactivate caspases or their activation pathway. This indicates that AAP metabolism has the potential to inhibit signal transduction mechanisms of receptor-mediated apoptosis.

Parenchymal cell apoptosis as a signal for sinusoidal sequestration and transendothelial migration of neutrophils in murine models of endotoxin and Fas-antibody-induced liver injury

Endotoxin (ET) induces neutrophil sequestration in hepatic sinusoids, the activation of proinflammatory transcription factors (nuclear factor KB [NF-kappaB]) with up-regulation of adhesion molecules on sinusoidal endothelial cells and hepatocytes. However, if galactosamine (Gal) is co-administered with ET, neutrophils transmigrate and attack parenchymal cells. This suggests that a signal from parenchymal cells triggers neutrophil transmigration. In this study, we tested the hypothesis that parenchymal cell apoptosis may induce neutrophil transendothelial migration in the Gal/ET model. Treatment of C3Heb/FeJ mice with 700 mg/kg Gal and 100 microg/kg ET induced tumor necrosis factor alpha (TNF-alpha) formation (13.25 +/- 0.75 ng/mL) and hepatic NF-kappaB activation at 90 minutes; the generation of the C-X-C chemokine KC (2.86 +/- 0.30 ng/mL at 5 hours); sinusoidal neutrophil sequestration (380 +/- 21 polymorphonuclear leukocytes/50 high-power fields) and apoptosis (925% +/- 29% increase of DNA fragmentation; and a 45-fold increase of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells) at 6 hours, followed by transmigration of neutrophils and development of substantial necrosis (38% +/- 3% of hepatocytes; alanine transaminase [ALT]: 1,500 +/- 300 U/L) at 7 hours. Administration of uridine (1,000 mg/kg) did not reduce plasma levels of TNF-alpha and KC, NF-kappaB activation, or polymorphonuclear leukocyte sequestration, but attenuated apoptosis by 90% to 94%. In these livers, neutrophils did not transmigrate and liver injury was prevented (necrosis: < 5%; ALT: 40 +/- 3 U/L). However, massive apoptosis and liver injury initiated by the anti-Fas antibody, Jo2, did not recruit neutrophils into the liver. We conclude that excessive parenchymal cell apoptosis represents an important signal for transmigration of primed neutrophils sequestered in sinusoids during endotoxemia in vivo. However, apoptosis per se does not cause neutrophil sequestration in the liver vasculature.

Activation of caspase 3 (CPP32)-like proteases is essential for TNF-alpha-induced hepatic parenchymal cell apoptosis and neutrophil-mediated necrosis in a murine endotoxin shock model

Endotoxin (ET)-induced liver failure is characterized by parenchymal cell apoptosis and inflammation leading to liver cell necrosis. Members of the caspase family have been implicated in the signal transduction pathway of apoptosis. The aim of this study was to characterize ET-induced hepatic caspase activation and apoptosis and to investigate their effect on neutrophil-mediated liver injury. Treatment of C3Heb/FeJ mice with 700 mg/kg galactosamine (Gal) and 100 microg/kg Salmonella abortus equi ET increased caspase 3-like protease activity (Asp-Val-Glu-Asp-substrate) by 1730 +/- 140% at 6 h. There was a parallel enhancement of apoptosis (assessed by DNA fragmentation ELISA and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay). In contrast, activity of caspase 1 (IL-1beta-converting enzyme)-like proteases (Tyr-Val-Ala-Asp-substrate) did not change throughout the experiment. Caspase 3-like protease activity and apoptosis was not induced by Gal/ET in ET-resistant mice (C3H/HeJ). Furthermore, only murine TNF-alpha but not IL-1alphabeta increased caspase activity and apoptosis. Gal/ET caused neutrophil-dependent hepatocellular necrosis at 7 h (area of necrosis, 45 +/- 3%). Delayed treatment with the caspase 3-like protease inhibitor Z-Val-Ala-Asp-CH2F (Z-VAD) (10 mg/kg at 3 h) attenuated apoptosis by 81 to 88% and prevented liver cell necrosis (< or = 5%). Z-VAD had no effect on the initial inflammatory response, including the sequestration of neutrophils in sinusoids. However, Z-VAD prevented neutrophil transmigration and necrosis. Our data indicate that activation of the caspase 3 subfamily of cysteine proteases is critical for the development of parenchymal cell apoptosis. In addition, excessive hepatocellular apoptosis can be an important signal for transmigration of primed neutrophils sequestered in sinusoids.

Increased P-selectin gene expression in the liver vasculature and its role in the pathophysiology of neutrophil-induced liver injury in murine endotoxin shock

We studied the role of P-selectin, an adhesion molecule known to be important for neutrophil localization to sites of inflammation, in a model of inflammatory liver injury. Male C3Heb/FeJ (ET-sensitive) mice treated with 700 mg/kg galactosamine and 100 microg/kg Salmonella abortus equi endotoxin (Gal/ET), murine tumor necrosis factor alpha (TNF-alpha, 15 microg/kg), or interleukin-1 (IL-1, 13-23 microg/kg), showed increased P-selectin mRNA levels in the liver. In contrast, C3H/HeJ (ET-resistant) mice responded only to cytokines with P-selectin mRNA formation. Whereas no P-selectin expression was detectable in control livers, there was temporary staining of endothelium in large blood vessels but not in sinusoids between 3 and 5 h after ET, TNF-alpha, or IL-1 treatment. Severe liver injury induced by Gal/ET at 7 h was not inhibited by an anti-P-selectin antibody in C3Heb/FeJ mice or in P-selectin-deficient animals. Sequestration of neutrophils in sinusoids, i.e. those neutrophils that have been identified as critical for the injury, was not affected by the antibody or in P-selectin-deficient mice. However, the temporary margination in portal and post-sinusoidal venules was reduced by 75% in anti-P-selectin antibody-treated animals and by 51% in P-selectin-deficient mice. We conclude that hepatic P-selectin gene transcription in vivo involves cytokines. However, blocking P-selectin neither attenuated sinusoidal neutrophil sequestration nor prevented neutrophil-induced liver injury during endotoxin shock but attenuated neutrophil margination in larger vessels. Thus, our data demonstrate similarities and fundamental differences in the requirement for adhesion molecules to localize neutrophils in the liver vasculature compared to other organs during an inflammatory response.

Remodeling and neointimal formation in the carotid artery of normal and P-selectin-deficient mice

BACKGROUND

Inflammatory reactions such as leukocyte activation with platelet adherence and release of inflammatory mediators occur after percutaneous transluminal coronary angioplasty and may play a role in restenosis. Vascular remodeling with neointimal formation was studied in normal C57Bl/J6 and P-selectin-deficient mice.

METHODS AND RESULTS

The left common carotid artery was ligated just proximal to the carotid bifurcation. Four weeks later, left carotids and contralateral controls were snap-frozen. Computer-aided morphometry was performed to measure ratios of neointimal to medial area (NI/M) in 10 sections per animal as a measure of the thickness of the neointimal lesion. For normal mice, NI/M was 1.13+/-0.2 (n=20), whereas NI/M was reduced by 76% to 0.27+/-0.1 (n= 19) in P-selectin knockout mice. Vascular constriction (as measured by the length of external elastic lamina) was the same in both groups, but the circumference of the lumen in knockout mice was 26% larger. Also, normal and P-selectin-deficient mice were killed at 3 and 7 days after ligation (n=6 for each group per time point). Histological staining and immunostaining for CD45 showed no inflammatory cell presence in P-selectin knockout mice. However, in normal mice, leukocyte infiltration was observed in the adventitia, media, and developing neointima. Also, P-selectin immunostaining was observed in media and developing neointima of normal mice.

CONCLUSIONS

These data suggest that P-selectin is involved in processes leading to cell migration and proliferation associated with vascular remodeling, presumably by mediating leukocyte recruitment and the interaction between platelets and leukocytes.

Method-based differences in the automated analysis of the three-dimensional morphology of trabecular bone

The three-dimensional (3D) morphology of trabecular bone is frequently quantified using computer programs. However, there are no standardized implementations of morphology programs and many variations are possible. Even though programs may use the same basic method, results can be significantly different because of differences in implementation. Morphology data from different laboratories therefore may not be comparable. The method of directed secants, with parallel plate assumptions, is commonly used to quantify 3D morphology. We examined the effect of several variations in the implementation of this method on measurements of trabecular plate number (Tb.N), trabecular thickness, and trabecular spacing. Three-dimensional micromagnetic resonance images of 10 bovine trabecular bone specimens were analyzed using several variations of the directed secant method. An analysis of covariance with repeated measures suggested that variations in the algorithm used to count test line intersections, variations in the criteria used to classify a test coordinate as bone or marrow, and variations in the number of test grid rotations had significant effects on Tb.N (p < 0.0001). The largest difference in Tb.N (52%) was due to the method used to count test line intersections with the bone-marrow interface. Variations in the classification algorithm and variations in the number of test line grid rotations resulted in a 6% difference in Tb.N. The spacing of the test line grids did not affect Tb.N (p = 0.28), and all differences were independent of volume fraction (p = 0.67). These data show that there can be significant differences in trabecular bone morphology measurements due only to the method used for the measurements. To facilitate comparisons between laboratories, we have made validated computer programs to measure trabecular bone morphology available over the Internet.

Temporal expression of c-fos mRNA following balloon injury in the rat common carotid artery

OBJECTIVE

Restenosis is a common problem which limits the effectiveness of percutaneous transluminal coronary angioplasty (PTCA). The cellular mechanisms of restenosis appear to involve smooth muscle cell (SMC) migration to the neointima in response to mitogens and growth factors, resulting in proliferation and deposition of cells in the lumen of the vessel. An antibody directed against PDGF attenuates this response in the rat. Thus, signaling cascades induced by growth factors including PDGF may be important targets for therapeutic intervention.

METHODS

Since a number of growth factors activate c-fos via the p21-ras signaling pathway, we examined c-fos expression in a time course experiment involving restenotic lesions in rat carotid arteries. Sections of arteries collected at 1, 3, 7, 14 and 28 days following balloon injury were hybridized using a fluorescein-labeled RNA probe to c-fos. Immunohistochemistry was performed with antibodies to proliferating cell nuclear antigen (PCNA) and alpha-smc actin to characterize cellular constituents of the neointima, and detect any correlation between fos expression and PCNA localization.

RESULTS

Expression of c-fos was low at day 1. By day 3, the media and adventitia were positively stained. At days 7 and 14, most cells in the neointima were labeled. By day 28, c-fos was expressed mainly in scattered cells along the luminal surface. Control sections revealed little labeling and confirmed specific staining by the antisense strand, PCNA localization and c-fos expression were similar at days 1, 3, 7 and 28, but at day 14 c-fos was expressed throughout the lesion, with PCNA localized mainly along the luminal edge. The majority of the cells making up the neointima stained rather intensely for alpha-smc actin, identifying them as SMCs.

CONCLUSIONS

Results of these experiments indicate that, while c-fos expression correlates with lesion formation, it may be associated with a cellular process distinct from proliferation in this model.

Estimation of ozone with total ozone portable spectroradiometer instruments. II. Practical operation and comparisons

We used a microcomputer-controlled total ozone portable spectroradiometer instrument #21 (MTOPS21) to measure solar radiation at 298, 304 and 310 nm in Greenbelt, Md., during 1995. One day's ozone measurements from a Brewer instrument (B105) were used to calibrate the 304- and 310-nm channel ratios to a theoretical model. Total ozone estimates were then determined for the entire MTOPS21 data set. Differences between individual B105 and MTOPS21 ozone estimates show a 1% drop as solar zenith angles increase and depend on atmospheric attenuation and SO(2) variation at the ±2% level. Daily average values agree well (<0.5% average offset, 2% standard deviation).

Trabecular bone morphology from micro-magnetic resonance imaging

Micro-magnetic resonance imaging (micro-MRI) is potentially a widely available tool to image and quantify the three-dimensional structure of trabecular bone. However, it has not been demonstrated that the same quantitative measurements can be obtained using micro-MRI as would be obtained from conventional light microscope images. Bovine trabecular bone from several anatomic sites was imaged with both optical and micro-MRI methods. The six faces of approximately cubic trabecular bone specimens were examined with the light microscope, and the volume of bone internal to these faces was then imaged using an 8.6 T 25 mm bore magnet. Three-dimensional measures of bone morphology were calculated from both the optical and micro-MR images using the method of directed secants. Quantitative measures from the two imaging methods were compared by paired t-tests. Volume fractions (BV/TV) measured by micro-MRI were linearly related to (r2 = 0.81) and did not differ statistically from (p = 0.96) similar measurements from optical images. The trabecular plate number (Tb.N) measured by micro-MRI also was linearly related to (r2 = 0.53) and did not differ statistically from (p = 0.17) similar measurements from optical images. The orientation of trabeculae predicted from micro-MRI was within 6 degrees of that calculated from optical images in 10 out of 16 specimens. The micro-MRI morphology measurements are relatively easy to perform, and since several hundred small-bore high-field strength MRI systems are available, this technique could be used widely to quantify the morphology of trabecular bone.

In vitro and in vivo inhibition of rat vascular smooth muscle cell migration and proliferation by a 2-aminochromone U-86983

Vascular smooth muscle cell migration and proliferation are the primary events that govern neointimal thickening and thus they determine the extent to which delayed restenosis occurs after percutaneous transluminal coronary angioplasty. In this study, the in vitro and in vivo smooth muscle cell antichemotactic and antiproliferative properties of a 2-aminochromone, 2-(4-morpholinyl)-8-(3-pyridinylmethoxy)-4H-1-benzopyran-4-one (U-86983), were examined. Migration and proliferation of early-passage rat vascular smooth muscle cells were inhibited by U-86983 in a concentration-dependent manner (IC50S, approximately 10 microM and 3.5 microM, respectively). Longer-term studies showed that the proliferation of smooth muscle cells was inhibited by U-86983 for at least 7 days and was fully reversible on removal of the drug. In addition, the effect of U-86983 on neointimal formation was examined in rats subjected to left common carotid artery balloon dilatation injury. Continual (2-week) i.v. administration of U-86983 (216 mg kg-1 day-1) resulted in a mean plasma drug concentration of 2.39 micrograms/ml (blood level, approximately 3.5 microM) and a 42% (P = .003) reduction in the neointima/media ratio of the injured artery. In agreement with the in vitro reversibility results, administration of U-86983 for only 2, 4 or 7 days did not affect significantly the neointimal thickness measured at 14 days, which indicated that the stimuli for smooth muscle cell migration and/or proliferation were still present 1 week after injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of neointimal hyperplasia by coronary angioplasty balloon overinflation: comparison of feeder pigs to Yucatan minipigs

We evaluated the use of simple balloon overinflation to induce neointimal hyperplasia in a porcine model of coronary artery restenosis. By using standard percutaneous transluminal coronary angioplasty techniques, left anterior descending (LAD) and/or left circumflex (LCX) coronary arteries of either juvenile feeder pigs or adult Yucatan minipigs were intentionally overinflated. Four weeks later, resultant neointimal hyperplastic responses (neointima/media area; NI/M) were quantitated morphometrically. At all ballooned sites neointimal hyperplasia occurred only when the internal elastic lamina (IEL) was ruptured; the degree of hyperplasia correlated directly with the injury index, that is, the percentage of IEL circumference that fractured (r = 0.74; n = 25; p < 0.05). Despite similar injury indexes in the LAD bed, there was a trend (p = 0.07; analysis of variance) toward greater NI/M ratios in the Yucatan minipig versus the feeder pig group (1.14 +/- 0.21 vs 0.73 +/- 0.09, n = 7/group). We found no such trend in the LCX bed, where the injury index (25.7% +/- 3.5%) was significantly greater than that of the LAD (18.2% +/- 1.2%, p < 0.05). If variations in balloon-induced vascular injury are accounted for, the technique of balloon overinflation of coronary arteries should prove useful in testing potential antirestenotic agents in either adult or juvenile pigs.

Prevalence of uveitis: a retrospective study

BACKGROUND

Uveitis is commonly seen in optometric practice, and anterior uveitis accounts for more than 75% of all uveitis. Uveitis may be the initial manifestation of an associated systemic disease process; and, with proper testing and diagnosis, the patient's ocular and systemic condition may be more effectively treated.

METHODS

Retrospectively, 194 charts from a referral practice with a general diagnosis of uveitis, retinitis, or chorioretinal scar were reviewed to determine medical history, clinical findings, tests performed, and specific diagnoses obtained.

RESULTS

The majority of cases, 87.6%, were anterior uveitis with more than half, 54.7%, presenting with undetermined etiology. Trauma was the cause of the next most common group of anterior uveitis patients, 21.8%, and accounted for 19.1% of all uveitis cases. Glaucomatocyclitic crisis was seen in 8 cases, 4.1%, while there were 7 patients with sarcoid disease, and 5 with ankylosing spondylitis or systemic lupus erythematosus. Posterior uveitis was the principle finding in 12.4% of cases with ocular histoplasmosis being most common. There were 4 cases of toxoplasmosis and 3 cases of pars planitis.

CONCLUSIONS

Utilization of laboratory testing proved to be most valuable in the treatment and management of uveitis. Although there were fewer cases of pars planitis reported in our study in comparison to previous reports, the mix of cases of uveitis in our study was comparable to the work of others in the field. Accurate diagnosis of these cases is quite important since the treatment and prognosis for recovery is variable and different with its associated diseases.

1,4-Dihydronaphthoquinones as water-soluble inhibitors of 5-lipoxygenase

The acetate derivatives of 1,4-dihydronaphthoquinones showed significant inhibition of 5-lipoxygenase. Among them, 1-acetyl-2-n-butyl-4-methoxy-naphthalene and 1-acetyl-2, 3-diethyl- 4- methoxy-naphthalene were found to be the best inhibitors. A series of HCl salts of the amino acid esters and other derivatives of the two parent molecules, 1-hydroxy-2-n-butyl-4-methoxy-naphthalene and 1-hydroxy-2, 3-diethyl-4-methoxynaphthalene, were synthesized as water-soluble potential inhibitors of 5-lipoxygenase to improve the formulation characteristics of this class of compounds. The derivatives were evaluated for leukotriene (LT) C4/D4 and LTB4 inhibitory activity. The HCl salts of the L-valine esters from the two parent molecules exhibited the best potency for inhibition of LTC4/D4 (IC50 0.11-0.90 microM) in ionophore A23187-stimulated rat mononuclear cells and of LTB4 in A23187-stimulated rat blood (55.5-79.2% inhibition) following a single oral dose of 50 mg/kg.

Heparin inhibits fibrin, but not leukocytes, in a model of deep-vein thrombosis

Previous studies with models of deep-vein thrombosis (DVT) have demonstrated that leukocyte (PMN)-mediated vein injury may be an initiating event in DVT (14, 17). Since heparin (H) can prevent DVT, we studied its effect on vascular injury and thrombosis in our model. Three groups of rabbits were treated with H either sc (73 and 147 U/kg) or iv (662 U/kg). Scanning electron microscopy revealed that the 73 U/kg sc dose was ineffective. All veins had PMN accumulation, fibrin deposition and complex thrombus formation. There was no increase in anti-Xa activity; activated partial thromboplastin times (APTT) and whole blood clotting times were normal. The 147 U/kg sc and the intravenous dose did not inhibit PMN-mediated vein injury. The endothelium was sloughed by migrating PMNs, basement membrane was exposed, and platelets adhered to it. Thrombosis was completely absent in the iv dose group. This correlated with increased anti-Xa activity and prolonged APTT and whole blood clotting times. Our results indicate that heparin does not inhibit the PMN adhesion and migration which produces vascular injury. However, the anticoagulant activity of heparin effectively reduces fibrin deposition and complex thrombus formation.

Eicosanoid regulation of oosporogenesis by Lagenidium giganteum

Cell proliferation is inhibited in many biological systems by lipid peroxides and related products derived from polyunsaturated fatty acids. Using developmentally synchronized cultures of Lagenidium giganteum (Oomycetes: Lagenidiales), a facultative parasite of mosquito larvae, it has been documented that oxidative lipid metabolism is necessary for the induction and subsequent maturation of its sexual stage, the oospore. Addition of lipoxygenase inhibitors to liquid cultures of the fungus results in the stage-specific disruption of antheridial induction, gametangial fusion, induction of meiosis and spore cell wall formation. Oosporogenesis is inhibited by these compounds at concentrations which have no discernible effect on mycelial viability or asexual reproduction. Cyclooxygenase inhibition had comparable effects using ibuprofen and to a lesser extent with indomethacin. Phenylbutazone and the salicylates affected oosporogenesis only at concentrations which decreased asexual reproduction or mycelial viability. The inhibitory effects of NDGA on oosporogenesis could be reversed using partly purified eicosanoid extracts from growth media.

Smooth muscle proliferation in chronically injured canine pulmonary arteries is reduced by a potent platelet aggregation inhibitor U-53,059

Dirofilaria immitis (DI) infection chronically injures canine pulmonary arteries. This injury produces endothelial cell loss, platelet/leukocyte adhesion, and smooth muscle proliferation. In the present study we assessed the effect of the cyclooxygenase inhibitor, U-53,059, on platelet function, platelet kinetics, coagulation, and smooth muscle proliferation in DI infected dogs. Platelet aggregation to the combination of arachidonic acid/ADP was significantly inhibited by U-53,059. Coagulation and hematologic parameters were not effected by either DI infection or U-53,059 treatment. Platelet survival and the number of platelet dense granules were reduced in DI infection. Quantification of the lesions demonstrated that U-53,059 reduced both severity and density compared to non-treated dogs. U-53,059 is a potent and effective inhibitor of platelet aggregation which modifies smooth muscle proliferation produced by chronic vascular injury.

Early events in the formation of a venous thrombus following local trauma and stasis

A jugular vein was exposed in 20 cats divided into four groups of five cats each. In group 1 the vein was removed immediately after exposure. In group 2 the vein was removed after three 5-minute periods of stasis and reflow. Groups 3 and 4 had the jugular vein occluded for 24 and 72 hours, respectively. In all groups, veins were perfused under physiologic pressure by heparinized saline to remove blood and immersed in 2.5% glutaraldehyde for fixation. All vessels were prepared for scanning and transmission electron microscopy. Group 1 cats had a normal-appearing luminal surface. Group 2 cats had deposition of leukocytes with few erythrocytes or platelets. Groups 3 and 4 had deposition of leukocytes, platelets, and erythrocytes. Leukocytes were found in all areas and associated with all cell types. Platelets and erythrocytes were seldom found in the absence of leukocytes. Thrombi were found on normal-appearing and damaged endothelium. The majority of thrombi were found at side branches and valve pockets. Our results suggest that leukocytes play a primary role in the initiation of deep vein thrombosis. Platelets may have only a secondary role.

Medial smooth muscle cell proliferation in the balloon injured rabbit aorta: effect of a thiazole compound with platelet inhibitory activity

Twenty-seven adult male New Zealand rabbits (3-4 kgs) were used in this study. Six rabbits received vehicle, 3 groups of 6 each received doses of 4,5-bis(p-methoxyphenyl)-2-(trifluoromethyl)-thiazole, (U-53,059), at 0.3 mg/kg, 3.0 mg/kg and 30.0 mg/kg/day respectively. Drug and vehicle doses were given orally each day starting 3 days before balloon injury and continuing for the entire 2 week time period. Three rabbits were used as nontreated sham controls. In the vehicle and U-53,059 treated groups aortae were denuded of endothelial cells by balloon catheter injury. Two weeks after injury platelet aggregation to collagen was measured and the aortae removed for analysis of surface characteristics by scanning electron microscopy and lesion size by morphometry. All doses of U-53,059 inhibited platelet aggregation. The 3.0 and 30.0 mg/kg groups had the greatest inhibitory effect. All balloon injured aortae had the same morphologic characteristics. All vessels had similar extent and intensity of Evan's blue staining, similar areas of leukocyte/platelet adhesion, and a myointimal cell cover of transformed smooth muscle cells. The myointimal proliferative response was not inhibited at any of the drug doses studied.