Comparison of the novel Medtentia double helix mitral annuloplasty system with the Carpentier-Edwards Physio annuloplasty ring: morphological and functional long-term outcome in a mitral valve insufficiency sheep model

Background

The prevalence of mitral regurgitation in cardiac diseases requires annuloplasty systems that can be implanted without excessive patient burden. This study was designed to examine the morphological and functional outcome of a new double helix mitral annuloplasty ring in an ovine model in comparison to the classical Carpentier-Edwards (CE) annuloplasty ring as measured by reduction of mitral regurgitation and tissue integration. The Medtentia annuloplasty ring (MAR) is a helical device that is rotated into the annulus self-restoring the valve geometry, enabling a faster fixation without the need of elaborate repair of the valve geometry. The ventricular part of the helical ring encircles the valve chords.

Methods

Twenty adult sheep were overpaced until 2+ level mitral valve regurgitation was achieved. Seven animals per group received either the MAR or the CE ring. Implantation was performed on-pump in a beating heart through the left atrial appendix. The animals were sacrificed 3.6 ± 0.3 months after surgery following an echocardiography for assessing mitral regurgitation as primary endpoint. The annuloplasty rings with surrounding tissue were harvested for histological analyses as secondary endpoints. The remaining six sheep received the MAR system and were sampled seven, nine or 12 months after surgery.

Results

Implantation time (p < 0.01) and perfusion time (p < 0.001) as clinical secondary endpoints were significantly shorter in the MAR group. Echocardiography follow-ups showed sufficient valve function repair in nearly all animals with a normalization of the ventricle diameters in both groups (group difference: p = 0.147). The weights of the hearts did not differ significantly. Histology revealed adequately covered atrial annuloplasty rings with functional endothelium and lack of excessive granulation tissue or fibrosis in all specimens. The ventricular projections of the MAR systems encircling the chordae tendineae were not completely covered with neointimal tissue, although in no case were microthrombi detected and no thromboembolic events were recorded.

Conclusions

The new MAR system is an easy to use annuloplasty system with a functional outcome comparable to that of the well–proven CE ring. Mitral valve regurgitation is effectively stopped both by restricting the pathological expansion of the annulus and by gathering the chords without thrombus formation.

Alveolar epithelial dynamics in postpneumonectomy lung growth

The intimate anatomic and functional relationship between epithelial cells and endothelial cells within the alveolus suggests the likelihood of a coordinated response during postpneumonectomy lung growth. To define the population dynamics and potential contribution of alveolar epithelial cells to alveolar angiogenesis, we studied alveolar Type II and I cells during the 21 days after pneumonectomy. Alveolar Type II cells were defined and isolated by flow cytometry using a CD45(-) , MHC class II(+) , phosphine(+) phenotype. These phenotypically defined alveolar Type II cells demonstrated an increase in cell number after pneumonectomy; the increase in cell number preceded the increase in Type I (T1α(+) ) cells. Using a parabiotic wild type/GFP pneumonectomy model, <3% of the Type II cells and 1% of the Type I cells were positive for GFP-a finding consistent with the absence of a blood-borne contribution to alveolar epithelial cells. The CD45(-) , MHC class II(+) , phosphine(+) Type II cells demonstrated the active transcription of angiogenesis-related genes both before and after pneumonectomy. When the Type II cells on Day 7 after pneumonectomy were compared to nonsurgical controls, 10 genes demonstrated significantly increased expression (P<0.05). In contrast to the normal adult Type II cells, there was notable expression of inflammation-associated genes (Ccl2, Cxcl2, Ifng) as well as genes associated with epithelial growth (Ereg, Lep). Together, the data suggest an active contribution of local alveolar Type II cells to alveolar growth.

Intussusceptive remodeling of vascular branch angles in chemically-induced murine colitis

Intussusceptive angiogenesis is a developmental process linked to both blood vessel replication and remodeling in development. To investigate the prediction that the process of intussusceptive angiogenesis is associated with vessel angle remodeling in adult mice, we systematically evaluated corrosion casts of the mucosal plexus in mice with trinitrobenzesulfonic acid (TNBS)-induced and dextran sodium sulfate (DSS)-induced colitis. The mice demonstrated a significant decrease in vessel angles in both TNBS-induced and DSS-induced colitis within 4 weeks of the onset of colitis (p<.001). Corrosion casts 28-30 days after DSS treatment were studied for a variety of detailed morphometric changes. The vessel diameter and interbranch distance were significantly increased in the descending colon (p<.05). Also consistent with vessel growth, intervascular distance was decreased in the descending colon (p<.05). In contrast, no statistically significant morphometric changes were noted in the ascending colon. The morphometry of the corrosion casts also demonstrated 1) a similar orientation of the remodeled angles within the XY coordinate plane of the mucosal plexus, and 2) alternating periodicity of remodeled and unremodeled vessel angles. We conclude that inflammation-associated intussusceptive angiogenesis in adult mice is associated with vessel angle remodeling. Further, the morphometry of the vessel angles suggests the influence of blood flow on the location and orientation of remodeled vessels.

Mechanostructural adaptations preceding postpneumonectomy lung growth

In many species, pneumonectomy results in compensatory growth in the remaining lung. Although the late mechanical consequences of murine pneumonectomy are known, little is known about the anatomic adaptations and respiratory mechanics during compensatory lung growth. To investigate the structural and mechanical changes during compensatory growth, mice were studied for 21 days after left pneumonectomy using microCT and respiratory system impedance (FlexiVent). Anatomic changes after left pneumonectomy included minimal mediastinal shift or chestwall remodeling, but significant displacement of the heart and cardiac lobe. Mean displacement of the cardiac lobe centroid was 5.2 ± 0.8 mm. Lung impedance measurements were used to investigate the associated changes in respiratory mechanics. Quasi-static pressure-volume loops demonstrated progressive increase in volumes with decreased distensibility. Measures of quasi-static compliance and elastance were increased at all time points postpneumonectomy (P < .01). Oscillatory mechanics demonstrated a significant change in tissue impedance on the third day after pneumonectomy. The input impedance on day 3 after pneumonectomy demonstrated a significant increase in tissue damping (5.8 versus 4.3 cm H(2)O/mL) and elastance (36.7 versus 26.6 cm H(2)O/mL) when compared to controls. At all points, hysteresivity was unchanged (0.17). We conclude that the timing and duration of the mechanical changes was consistent with a mechanical signal for compensatory growth.

Detection of murine post-pneumonectomy lung regeneration by 18FDG PET imaging

BACKGROUND

An intriguing biologic process in most adult mammals is post-pneumonectomy lung regeneration, that is, the removal of one lung (pneumonectomy) results in the rapid compensatory growth of the remaining lung. The spatial dependence and metabolic activity of the rodent lung during compensatory lung regeneration is largely unknown.

METHODS

To determine if murine lung regeneration could be detected in vivo, we studied inbred mice 3, 7, 14, and 21 days after left pneumonectomy. The remaining lung was imaged using microCT as well as the glucose tracer 2-deoxy-2-[18 F]fluoro-d-glucose (18FDG) and positron-emission tomography (PET). Because of the compliance of the murine chest wall, reproducible imaging required orotracheal intubation and pressure-controlled ventilation during scanning.

RESULTS

After left pneumonectomy, the right lung progressively enlarged over the first 3 weeks. The cardiac lobe demonstrated the greatest percentage increase in size. Dry weights of the individual lobes largely mirrored the increase in lung volume. PET/CT imaging was used to identify enhanced metabolic activity within the individual lobes. In the cardiac lobe, 18FDG uptake was significantly increased in the day 14 cardiac lobe relative to preoperative values (p < .05). In contrast, the 18FDG uptake in the other three lobes was not statistically significant at any time point.

CONCLUSIONS

We conclude that the cardiac lobe is the dominant contributor to compensatory growth after murine pneumonectomy. Further, PET/CT scanning can detect both the volumetric increase and the metabolic changes associated with the regenerative growth in the murine cardiac lobe.

Computational analysis of lung deformation after murine pneumonectomy. [corrected]

In many mammalian species, the removal of one lung (pneumonectomy) is associated with the compensatory growth of the remaining lung. To investigate the hypothesis that parenchymal deformation may trigger lung regeneration, we used microCT scanning to create 3D finite element geometric models of the murine lung pre- and post-pneumonectomy (24 h). The structural correspondence between models was established using anatomic landmarks and an iterative computational algorithm. When compared with the pre-pneumonectomy lung, the post-pneumonectomy models demonstrated significant translation and rotation of the cardiac lobe into the post-pneumonectomy pleural space. 2D maps of lung deformation demonstrated significant heterogeneity; the areas of greatest deformation were present in the subpleural regions of the lobe. Consistent with the previously identified growth patterns, subpleural regions of enhanced deformation are compatible with a mechanical signal - likely involving parenchymal stretch - triggering lung growth.

Alveolar macrophage dynamics in murine lung regeneration

In most mammalian species, the removal of one lung results in dramatic compensatory growth of the remaining lung. To investigate the contribution of alveolar macrophages (AMs) to murine post-pneumonectomy lung growth, we studied bronchoalveolar lavage (BAL)-derived AM on 3, 7, 14 and 21 days after left pneumonectomy. BAL demonstrated a 3.0-fold increase in AM (CD45(+), CD11b(-), CD11c(+), F4/80(+), Gr-1(-)) by 14 days after pneumonectomy. Cell cycle flow cytometry of the BAL-derived cells demonstrated an increase in S + G2 phase cells on days 3 (11.3 ± 2.7%) and 7 (12.1 ± 1.8%) after pneumonectomy. Correspondingly, AM demonstrated increased expression of VEGFR1 and MHC class II between days 3 and 14 after pneumonectomy. To investigate the potential contribution of peripheral blood cells to this AM population, parabiotic mice (wild-type/GFP) underwent left pneumonectomy. Analysis of GFP(+) cells in the post-pneumonectomy lung demonstrated that by day 14, less than 1% of the AM population were derived from the peripheral blood. Finally, AM gene transcription demonstrated a significant shift from decreased transcription of angiogenesis-related genes on day 3 to increased transcription on day 7 after pneumonectomy. The increased number of locally proliferating AM, combined with their growth-related gene transcription, suggests that AM actively participate in compensatory lung growth.

Finger injuries caused by power-operated windows of motor vehicles: an experimental cadaver study

The aim of this experimental cadaver study was to investigate which kinds of lesions could occur in jam events between the glass and seal entry of power-operated motor vehicle side door windows at two different closing forces. Ten hands of fresh cadaver specimens were used. Three different hand positions chosen to simulate real events in which a finger is jammed between the glass and seal entry of the window of a current motor vehicle were examined. The index, middle, ring, and little finger of each hand were separately jammed both at the proximal and distal interphalangeal joint at closing forces of 300 and 500 N with a constant window glass closing speed of 10 cm/s. Macroscopically visible injuries were documented and radiographs of all fingers were obtained in two standard planes. At a closing force of 300 N, contusion marks of the skin, palmar joint instabilities and superficial skin lesions occurred, whilst at 500 N superficial skin lesions, superficial and deep open crush injuries, and fractures were observed. The results of this study experimentally demonstrate the kinds of finger injuries that could be expected in real jam events between the glass and seal entry in automatic power-operated windows.

Spatial dependence of alveolar angiogenesis in post-pneumonectomy lung growth

Growth of the remaining lung after pneumonectomy has been observed in many mammalian species; nonetheless, the pattern and morphology of alveolar angiogenesis during compensatory growth is unknown. Here, we investigated alveolar angiogenesis in a murine model of post-pneumonectomy lung growth. As expected, the volume and weight of the remaining lung returned to near-baseline levels within 21 days of pneumonectomy. The percentage increase in lobar weight was greatest in the cardiac lobe (P < 0.001). Cell cycle flow cytometry demonstrated a peak of lung cell proliferation (12.02 ± 1.48%) 6 days after pneumonectomy. Spatial autocorrelation analysis of the cardiac lobe demonstrated clustering of similar vascular densities (positive autocorrelation) that consistently mapped to subpleural regions of the cardiac lobe. Immunohistochemical staining demonstrated increased cell density and enhanced expression of angiogenesis-related factors VEGFA, and GLUT1 in these subpleural regions. Corrosion casting and scanning electron microscopy 3-6 days after pneumonectomy demonstrated subpleural vessels with angiogenic sprouts. The monopodial sprouts appeared to be randomly oriented along the vessel axis with interbranch distances of 11.4 ± 4.8 μm in the regions of active angiogenesis. Also present within the regions of increased vascular density were frequent "holes" or "pillars" consistent with active intussusceptive angiogenesis. The mean pillar diameter was 4.2 ± 3.8 μm, and the pillars were observed in all regions of active angiogenesis. These findings indicate that the process of alveolar construction involves discrete regions of regenerative growth, particularly in the subpleural regions of the cardiac lobe, characterized by both sprouting and intussusceptive angiogenesis.

Cross-circulation and cell distribution kinetics in parabiotic mice

Blood-borne nucleated cells participate not only in inflammation, but in tissue repair and regeneration. Because progenitor and stem cell populations have a low concentration in the blood, the circulation kinetics and tissue distribution of these cells is largely unknown. An important approach to tracking cell lineage is the use of fluorescent tracers and parabiotic models of cross-circulation. Here, we investigated the cross-circulation and cell distribution kinetics of C57/B6 GFP(+)/wild-type parabionts. Flow cytometry analysis of the peripheral blood after parabiosis demonstrated no evidence for a "parabiotic barrier" based on cell size or surface characterstics; all peripheral blood cell subpopulations in this study reached equilibrium within 14 days. Whole blood fluorescence analysis indicated that the mean exchange flow rate was 16 µl/h or 0.66% of the circulating blood volume per hour. Studies of peripheral lymphoid organs indicated differential cell distribution kinetics. Some subpopulations, such as CD8(+) and CD11c(+), equilibrated in both lymph nodes and spleen indicating a residence time <28 days; in contrast, other lymphocyte subpopulations, such as B220(+) and CD4(+) cells, had not yet reached equilibrium at 28 days. We conclude that parabiosis can provide important insights into defining tissue distribution, residence times, and recirculating pools using fluorochrome markers of cell lineage.

CD34+ progenitor to endothelial cell transition in post-pneumonectomy angiogenesis

In many species, pneumonectomy triggers compensatory lung growth that results in an increase not only in lung volume, but also in alveolar number. Whether the associated alveolar angiogenesis involves the contribution of blood-borne progenitor cells is unknown. To identify and characterize blood-borne progenitor cells contributing to lung growth after pneumonectomy in mice, we studied wild-type and wild-type/green fluorescence protein (GFP) parabiotic mice after left pneumonectomy. Within 21 days of pneumonectomy, a 3.2-fold increase occurred in the number of lung endothelial cells. This increase in total endothelial cells was temporally associated with a 7.3-fold increase in the number of CD34(+) endothelial cells. Seventeen percent of the CD34(+) endothelial cells were actively proliferating, compared with only 4.2% of CD34(-) endothelial cells. Using wild-type/GFP parabiotic mice, we demonstrated that 73.4% of CD34(+) cells were derived from the peripheral blood. Furthermore, lectin perfusion studies demonstrated that CD34(+) cells derived from peripheral blood were almost uniformly incorporated into the lung vasculature. Finally, CD34(+) endothelial cells demonstrated a similar profile, but had enhanced transcriptional activity relative to CD34(-) endothelial cells. We conclude that blood-borne CD34(+) endothelial progenitor cells, characterized by active cell division and an amplified transcriptional signature, transition into resident endothelial cells during compensatory lung growth.

Entrapment of adult fingers between window glass and seal entry of a motor vehicle side door: an experimental study for investigation of the force at the subjective pain threshold

In modern motor vehicles with automatic power windows, a potential hazard exists for jam events of fingers between the window glass and seal entry. This study determined entrapment forces acting on adult fingers at the subjective maximum pain threshold during entrapment in such windows. The length and the girth of the proximal and distal interphalangeal joints of the triphalangeal fingers of the right hands of 109 participants (60 men, 49 women) were measured; the diameter was calculated from girth, which was assumed to be circular. The automatic power window system of a motor vehicle side door was changed to a mechanical system. During entrapment the force distributed across the four proximal interphalangeal joints (PIPs), and separately on the proximal interphalangeal (iPIP) and then the distal interphalangeal (iDIP) joints of the index finger was measured using a customized force sensor. The maximum bearable entrapment force was 97.2 ± 51.8 N for the PIPs, 43.4 ± 19.9 N for the iPIP, and 36.9 ± 17.8 N for the iDIP. The positive correlation between finger diameter and maximum entrapment force was significant. Particularly with regard to the risk to children's fingers, the 100 N statutory boundary value for closing force of electronic power windows should be reduced.

Dynamic determination of oxygenation and lung compliance in murine pneumonectomy

Thoracic surgical procedures in mice have been applied to a wide range of investigations, but little is known about the murine physiologic response to pulmonary surgery. Using continuous arterial oximetry monitoring and the FlexiVent murine ventilator, the authors investigated the effect of anesthesia and pneumonectomy on mouse oxygen saturation and lung mechanics. Sedation resulted in a dose-dependent decline of oxygen saturation that ranged from 55% to 82%. Oxygen saturation was restored by mechanical ventilation with increased rate and tidal volumes. In the mouse strain studied, optimal ventilatory rates were a rate of 200/minute and a tidal volume of 10 mL/kg. Sustained inflation pressures, referred to as a "recruitment maneuver," improved lung volumes, lung compliance, and arterial oxygenation. In contrast, positive end-expiratory pressure (PEEP) had a detrimental effect on oxygenation; an effect that was ameliorated after pneumonectomy. These results confirm that lung volumes in the mouse are dynamically determined and suggest a threshold level of mechanical ventilation to maintain perioperative oxygen saturation.

Submicron scale-structured hydrophilic titanium surfaces promote early osteogenic gene response for cell adhesion and cell differentiation

BACKGROUND AND PURPOSE

Titanium (Ti) surface roughness and surface hydrophilicity are key factors to regulate osteogenic cell responses during dental implant healing. In detail, specific integrin-mediated interactions with the extracellular environment trigger relevant osteogenic cell responses like differentiation and matrix synthesis via transcriptions factors. Aim of this study was to monitor surface-dependent osteogenic cell adhesion dynamics, proliferation, and specific osteogenic cell differentiation over a period of 7 days.

MATERIALS AND METHODS

Ti disks were manufactured to present smooth pretreatment (PT) surfaces and rough sandblasted/acid-etched (SLA) surfaces. Further processing to isolate the uncontaminated TiO(2) surface from contact with atmosphere provided a highly hydrophilic surface without alteration of the surface topography (modSLA). Tissue culture polystyrene (TCPS) served as control. Human osteogenic cells were cultivated on the respective substrates. After 24 hours, 48 hours, 72 hours, and 7 days, cell morphology on the Ti substrates was visualized by scanning transmission electron microscopy. As a marker of cellular proliferation, cell count was assessed. For the analysis of cell adhesion and differentiation, specific gene expression levels of the integrin subunits β1 and αv, runx-2, collagen type Iα (COL), alkaline phosphatase (AP), and osteocalcin (OC) were obtained by real-time RT-PCR for the respective time points. Data were normalized to internal controls.

RESULTS

TCPS and PT surfaces preserved a rather immature, dividing osteogenic phenotype (high proliferation rates, low integrin levels, and low specific osteogenic cell differentiation). SLA and especially modSLA surfaces promoted both cell adhesion as well as the maturation of osteogenic precursors into post-mitotic osteoblasts. In detail, during the first 48 hours, modSLA resulted in lowest cell proliferation rates but exhibited highest levels of the investigated integrins, runx-2, COL, AP, and OC.

CONCLUSION

Our results revealed a strong synergistic effect between submicron-scale roughness and surface hydrophilicity on early osteogenic cell adhesion and maturation.

Intravascular pillars and pruning in the extraembryonic vessels of chick embryos

To investigate the local mechanical forces associated with intravascular pillars and vessel pruning, we studied the conducting vessels in the extraembryonic circulation of the chick embryo. During the development days 13-17, intravascular pillars and blood flow parameters were identified using fluorescent vascular tracers and digital time-series video reconstructions. The geometry of selected vessels was confirmed by corrosion casting and scanning electron microscopy. Computational simulations of pruning vessels suggested that serial pillars form along pre-existing velocity streamlines; blood pressure demonstrated no obvious spatial relationship with the intravascular pillars. Modeling a Reynolds number of 0.03 produced 4 pillars at approximately 20-μm intervals matching the observed periodicity. In contrast, a Reynolds number of 0.06 produced only 2 pillars at approximately 63-μm intervals. Our modeling data indicated that the combination of wall shear stress and gradient of shear predicted the location, direction, and periodicity of developing pillars.

Priming with a combination of proangiogenic growth factors improves wound healing in normoglycemic mice

Growth factors and/or angiogenic factors are supposed to improve wound healing. The aim of our study was to evaluate the effects of subcutaneous pretreatment with combinatory proangiogenic factors on wound closure, mechanical properties, vessel density and morphology. Twenty-eight Balb/c mice were divided equally into two groups. A mixture of VEGF (35.0 µg), bFGF (2.5 µg) and PDGF (3.5 µg) was administered subcutaneously 3, 5 and 7 days to 14 mice before full thickness skin punch biopsy wounding, whereas 14 control animals received three injections of 0.2 ml saline solution. Wound sizes were assessed daily and the repaired tissues were harvested 7 days after complete wound closure. Complete closure (≥ 95% healing of initial wound area) was reached in all proangiogenic pretreated animals on day 10, whereas controls needed 13 days for complete closure. Tensile strengths were nearly twofold higher compared to the controls (p ≤ 0.01). The punch biopsy material revealed 4.2-fold higher vessel densities in the proangiogenic pretreated group. On day 17, the vessel densities in the proangiogenic pretreated wounds were also 3.2-fold higher compared to the untreated controls. No significant differences were seen in the collagen ratio. Pretreatment with proangiogenic factors revealed several significant effects on wound healing: faster time to closure, a higher vessel density and a better functional outcome. These results suggest a beneficial effect of pretreatment with combinatory growth factors in mouse skin wounds without impaired wound healing. This might be exploited in further investigations in diabetic healing as a therapeutic approach for elective surgery.

Adnectin CT-322 inhibits tumor growth and affects microvascular architecture and function in Colo205 tumor xenografts

Antiangiogenesis has become a promising pillar in modern cancer therapy. This study investigates the antiangiogenic effects of the PEGylated Adnectin™, CT-322, in a murine Colo-205 xenograft tumor model. CT-322 specifically binds to and blocks vascular endothelial growth factor receptor (VEGFR-2). Adnectins are a novel class of targeted biologics engineered from the 10th domain of human fibronectin. CT-322 treated tumors exhibited a significant reduction in tumor growth of 69%, a 2.8 times lower tumor surface area and fewer necrotic areas. Control tumors showed a 2.36-fold higher microvessel density (MVD) and a 2.42 times higher vessel volume in corrosion casts. The vascular architecture in CT-322-treated tumors was characterized by a strong normalization of vasculature. This was quantified in corrosion casts of CT-322 treated tumors in which the intervascular distance (a reciprocal parameter indicative of vessel density) and the distance between two consecutive branchings were assessed, with these distances being 2.21 times and 2.37 times greater than in controls, respectively. Fluorescence molecular tomography (FMT) equally affirmed the inhibitory effects of CT-322 on tumor vasculature as indicated by a 60% reduction of the vascular probe, AngioSense, accumulating in tumor tissue, as a measurement of vascular permeability. Moreover, AngioSense accumulation was reduced as early as 24 h after starting treatment. The sum of these effects on tumor vasculature illustrates the anti-angiogenic mechanism underlying the antitumor activity of CT-322 and provides support for further evaluation of this Adnectin in combinatorial strategies with standard of care therapies.

Antitumor effect of the vascular-disrupting agent ZD6126 in a murine renal cell carcinoma model

ZD6126 is a vascular-disrupting agent that affects the endothelial tubulin cytoskeleton causing selective occlusion of tumor vasculature and extensive tumor cell necrosis. The present study evaluated the antitumor and antivascular activities of ZD6126 in the clinically relevant murine renal cell carcinoma (RENCA) model and also evaluated biological response to therapy using color Doppler imaging as biomarker. Mice were implanted with RENCA tumor cells (day 0) and established tumors were treated with ZD6126 (100 mg/kg i.p.) or vehicle with repeated intermittent doses on day 10, 14 and 18. ZD6126 treatment led to a significant reduction in tumor size and was associated with extensive tumor necrosis and a reduction in tumor blood flow versus controls. MVD increased with intermittent treatment (day 10, 14 and 18). In an additional study, animals were treated at day 19 and quantitative three-dimensional microvascular corrosion casting was performed to enable detailed assessment of the tumor vascular architecture. Corrosion casting showed that tumor vessel architecture is affected by treatment, whereas pre-existing vessels in control tissues are practically not affected. Inter-vessel and inter-branch distances as well as vessel diameters are influenced by treatment. In conclusion, ZD6126 showed potent antitumor efficacy in the RENCA model and our data suggest that decrease in tumor blood flow may be a useful surrogate marker of treatment effect.

Forces and deformations of the abdominal wall--a mechanical and geometrical approach to the linea alba

Force-elongation responses of the human abdominal wall in the linea alba region were determined by tensile tests in which the linea alba was seen to exhibit a nonlinear elastic, anisotropic behavior as is frequently observed in soft biological tissues. In addition, the geometry of the abdominal wall was determined, based on MRI data. The geometry can be specified by principal radii of curvature in longitudinal of approximately 470 mm and in the transverse direction of about 200 mm. The determined radii agree with values found in other studies. Mechanical stresses, deformations and abdominal pressures for load cases above 6% elongation can be related using Laplace's formula and our constitutive and geometrical findings. Results from uni- and biaxial tensile tests can thus be compared using this model. Calculations confirm that abdominal pressures of approximately 20 kPa correspond to related biaxial forces of about 3.4N/mm in the transverse and 1.5 N/mm in the longitudinal direction. Young's moduli can be calculated with respect to the uniaxial as well as the biaxial loading. At these physiological loadings, a compliance ratio of about 2:1 between the longitudinal and transversal directions is found. Young's moduli of about 50 kPa occur in transversal direction and of about 20 kPa in longitudinal direction at transverse and longitudinal strains both in the order of 6%. These findings coincide with results from other investigations in which the properties of the abdominal wall have been examined.

Endoscopic transventricular third ventriculostomy through the lamina terminalis

Object

Endoscopic third ventriculostomy (ETV) has become a well-accepted option for obstructive hydrocephalus. However, standard ventriculostomy at the floor of the third ventricle might not be feasible under certain conditions. Here, the authors report in detail on their initial experience with an alternative option of endoscopic ventriculostomy through the lamina terminalis via a transventricular route.

Methods

Endoscopic third ventriculostomy through the lamina terminalis from a transventricular transforaminal route was evaluated in 4 cadaveric human heads and in 4 clinical cases.

Results

In all 4 human cadavers, an opening of the lamina terminalis via a transventricular approach could be achieved without injury to either the optic chiasm or the anterior cerebral arteries. In the 4 clinical cases, an accurate and reliable ventriculostomy was performed at the lamina terminalis. The bur hole was placed directly at the coronal suture 2 cm lateral from the midline. After identifying the optic chiasm and the anterior cerebral arteries, a blunt perforation was made just anterior to the optic chiasm by using perforation forceps and a balloon catheter. After the opening, the stoma was inspected with a 0° and 30° rod lens endoscope, and its patency as well as the preservation of vessels and optic nerves was checked. No complications occurred, although all patients suffered from a clinically silent fornical contusion at the foramen of Monro.

Conclusions

Endoscopic opening of the lamina terminalis via a transventricular transforaminal route appears to be feasible. No complications were observed. Although no conclusions on the clinical success rate can be drawn, the reliable anatomical opening and known success rate for anterior subfrontal approaches suggest that the technique represents an alternative in a small subgroup of patients in whom a standard ETV cannot be performed.

Dextran sulfate sodium leads to chronic colitis and pathological angiogenesis in Endoglin heterozygous mice

BACKGROUND

Pathological angiogenesis is an intrinsic component of chronic intestinal inflammation, which results in remodeling and expansion of the gut microvascular bed. Endoglin is essential for endothelial cell function and physiological angiogenesis. In this study we investigated its potential role in the regulation of inflammation by testing the response of Endoglin heterozygous (Eng(+/-)) mice to experimental colitis.

METHODS

C57BL/6 Eng(+/-) and littermate control mice drank water supplemented with 3% dextran sulfate sodium (DSS) for 5 days and were monitored for up to 26 days for clinical signs of colitis. Inflammation, crypt damage, and angiogenic index were scored on histological sections of distal colon. Levels of the vascular endothelial growth factor (VEGF) and angiopoietins were measured by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and/or Western blots. Vascular permeability was assessed using Evans Blue.

RESULTS

Eng(+/-) and control mice developed acute colitis, which peaked at day 9. While control mice recovered by days 19-26, Eng(+/-) mice progressed to chronic colitis and showed numerous vascular protrusions penetrating into the serosa of the inflamed distal colon. Prior to DSS induction, VEGF levels and vascular permeability were higher in the distal colon of Eng(+/-) mice, while angiopoietin 1 and 2 levels were unchanged. In the chronic phase of colitis, VEGF levels were increased in both groups of mice and remained significantly higher in the Eng(+/-) mice.

CONCLUSIONS

Higher VEGF levels and increased vascular permeability in the distal colon may predispose Eng(+/-) mice to progress to chronic and persistent bowel inflammation, associated with pathological angiogenesis.

Inflammation-induced intussusceptive angiogenesis in murine colitis

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.

Blood flow shapes intravascular pillar geometry in the chick chorioallantoic membrane

The relative contribution of blood flow to vessel structure remains a fundamental question in biology. To define the influence of intravascular flow fields, we studied tissue islands--here defined as intravascular pillars--in the chick chorioallantoic membrane. Pillars comprised 0.02 to 0.5% of the vascular system in 2-dimensional projection and were predominantly observed at vessel bifurcations. The bifurcation angle was generally inversely related to the length of the pillar (R = -0.47, P < .001). The pillar orientation closely mirrored the axis of the dominant vessel with an average variance of 5.62 ± 6.96 degrees (p = .02). In contrast, the variance of pillar orientation relative to nondominant vessels was 36.78 ± 21.33 degrees (p > .05). 3-dimensional computational flow simulations indicated that the intravascular pillars were located in regions of low shear stress. Both wide-angle and acute-angle models mapped the pillars to regions with shear less than 1 dyn/cm². Further, flow modeling indicated that the pillars were spatially constrained by regions of higher wall shear stress. Finally, the shear maps indicated that the development of new pillars was limited to regions of low shear stress. We conclude that mechanical forces produced by blood flow have both a limiting and permissive influence on pillar development in the chick chorioallantoic membrane.