Preclinical Development and Validation of Translational Temperature Sensitive Iodized Oil Emulsion Mediated Transcatheter Arterial Chemo-Immuno-Embolization for the Treatment of Hepatocellular Carcinoma

Herein a practical strategy for augmenting immune activation in transcatheter arterial chemoembolization (TACE) of hepatocellular carcinoma (HCC) is presented. Pluronic F127 (PF127) is incorporated with Lipiodol (LPD) to achieve safe and effective delivery of therapeutic agents during transcatheter intra-arterial (IA) local delivery. Enhanced emulsion stability, IA infusion, embolic effect, safety, pharmacokinetics, and tumor response of Doxorubicin loaded PF127-LPD (Dox-PF127-LPD) for TACE in both in vitro and in vivo preclinical VX2 liver cancer rabbit model and N1S1 HCC rat model are demonstrated. Then, transcatheter arterial chemo-immuno-embolization (TACIE) combining TACE and local delivery of immune adjuvant (TLR9 agonist CpG oligodeoxynucleotide) is successfully performed using CpG-loaded Dox-PF127-LPD. Concurrent and safe local delivery of CpG and TACE during TACIE demonstrate leveraged TACE-induced immunogenic tumor microenvironment and augment systemic anti-tumor immunity in syngeneic N1S1 HCC rat model. Finally, the broad utility and enhanced therapeutic efficacy of TACIE are validated in the diethylnitrosamine-induced rat HCC model. TACIE using clinically established protocols and materials shall be a convenient and powerful therapeutic approach that can be translated to patients with HCC. The robust anti-cancer immunity and tumor regression of TACIE, along with its favorable safety profile, indicate its potential as a novel localized combination immunotherapy for HCC treatment.

Yttrium-90 Radioembolization in the VX2 Rabbit Model: Radiation Safety and Factors Influencing Delivery Efficiency

The purpose of this study was to define the optimal infusion parameters and operator radiation exposure for yttrium-90 (⁹⁰Y) radioembolization in the VX2 rabbit model of liver cancer. Forty-one rabbits with VX2 were treated with glass microspheres with vial sizes of 1, 3, and 5 GBq. The mean administered activity was 51.5 MBq (95% CI, 39.1-63.9). Delivery efficiency improved with 1 GBq versus with 3 GBq (residual 11.0% vs 46.4%, respectively; P = .0013) and improved with 1 GBq versus with 5 GBq (residual 11.0% vs 33.8%, respectively; P = .0060). The mean operator extremity exposure was 41.7 μSv/infusion. The optimal minimum infusion volume and rate was 49 mL and 21 mL/min, respectively. Fecal elimination occurred with microsphere uptake in the gallbladder at 1 and 2 weeks. ⁹⁰Y radioembolization can be safely and efficiently performed in the VX2 rabbit model. Methodological considerations as a "how-to" for the setup of a preclinical ⁹⁰Y laboratory are included to support future translational research.

Yttrium-90 Radioembolization and Tumor Hypoxia: Gas-challenge BOLD Imaging in the VX2 Rabbit Model of Hepatocellular Carcinoma

RATIONALE AND OBJECTIVES

To use a rapid gas-challenge blood oxygen-level dependent magnetic resonance imaging exam to evaluate changes in tumor hypoxia after ⁹⁰Y radioembolization (Y90) in the VX2 rabbit model.

MATERIALS AND METHODS

White New Zealand rabbits (n = 11) provided a Y90 group (n = 6 rabbits) and untreated control group (n = 5 rabbits). R2* maps were generated with gas-challenges (O₂/room air) at baseline, 1 week, and 2 weeks post-Y90. Laboratory toxicity was evaluated at baseline, 24 hours, 72 hours, 1 hours, and 2 weeks. Histology was used to evaluate tumor necrosis on hematoxylin and eosin and immunofluorescence imaging was used to assess microvessel density (CD31) and proliferative index (Ki67).

RESULTS

At baseline, median tumor volumes and time to imaging were similar between groups (p = 1.000 and p = 0.4512, respectively). The median administered dose was 50.4 Gy (95% confidence interval:44.8-55.9). At week 2, mean tumor volumes were 5769.8 versus 643.7 mm³ for control versus Y90 rabbits, respectively (p = 0.0246). At two weeks, ΔR2* increased for control tumors to 12.37 ± 12.36sec^-1 and decreased to 4.48 ± 9.00sec^-1 after Y90. The Pearson correlation coefficient for ΔR2* at baseline and percent increase in tumor size by two weeks was 0.798 for the Y90 group (p = 0.002). There was no difference in mean microvessel density for control versus Y90 treated tumors (p = 0.6682). The mean proliferative index was reduced in Y90 treated tumors at 30.5% versus 47.5% for controls (p = 0.0071).

CONCLUSION

The baseline ΔR2* of tumors prior to Y90 may be a predictive imaging biomarker of tumor response and treatment of these tumors with Y90 may influence tumor oxygenation over time.

Feasibility of Combination Intra-arterial Yttrium-90 and Irinotecan Microspheres in the VX2 Rabbit Model

PURPOSE

To evaluate the combination of 90Y radioembolization (Y90) and drug-eluting bead irinotecan (DEBIRI) microspheres in the VX2 rabbit model.

MATERIALS AND METHODS

An initial dose finding study was performed in 6 White New Zealand rabbits to identify a therapeutic but subcurative dose of Y90. In total, 29 rabbits were used in four groups: Y90 treatment (n = 8), DEBIRI treatment (n = 6), Y90 + DEBIRI treatment (n = 7), and an untreated control group (n = 8). Hepatic toxicity was evaluated at baseline, 24 h, 72 h, 1 week, and 2 weeks. MRI tumor volume (TV) and enhancing tumor volume were assessed baseline and 2 weeks. Tumor area and necrosis were evaluated on H&E for pathology.

RESULTS

Infused activities of 84.0-94.4 MBq (corresponding to 55.1-72.7 Gy) were selected based on the initial dose finding study. Infusion of DEBIRI after Y90 was technically feasible in all cases (7/7). Overall, 21/29 animals survived to 2 weeks, and the remaining animals had extrahepatic disease on necropsy. Liver transaminases were elevated with Y90, DEBIRI, and Y90 + DEBIRI compared to control at 24 h, 72 h, and 1 week post-treatment and returned to baseline by 2 weeks. By TV, Y90 + DEBIRI was the only treatment to show statistically significant reduction at 2 weeks compared to the control group (p = 0.012). The change in tumor volume (week 2-baseline) for both Y90 + DEBIRI versus control (p = 0.002) and Y90 versus control (p = 0.014) was significantly decreased. There were no statistically significant differences among groups on pathology.

CONCLUSION

Intra-arterial Y90 + DEBIRI was safe and demonstrated enhanced antitumor activity in rabbit VX2 tumors. This combined approach warrants further investigation.

On-demand degradable embolic microspheres for immediate restoration of blood flow during image-guided embolization procedures

Degradable embolic agents that provide transient arterial occlusion during embolization procedures have been of interest for many years. Ideally, embolic agents are visible with standard imaging modalities and offer on-demand degradability, permitting physicians to achieve desired arterial occlusion tailored to patient and procedure indication. Subsequent arterial recanalization potentially enhances the overall safety and efficacy of embolization procedures. Here, we report on-demand degradable and MRI-visible microspheres for embolotherapy. Embolic microspheres composed of calcium alginate and USPIO nanoclusters were synthesized with an air spray atomization and coagulation reservoir equipped with a vacuum suction. An optimized distance between spray nozzle and reservoir allowed uniform size and narrow size distribution of microspheres. The fabricated alginate embolic microspheres crosslinked with Ca²⁺ demonstrated highly responsive on-demand degradation properties in vitro and in vivo. Finally, the feasibility of using the microspheres for clinical embolization and recanalization procedures was evaluated with interventional radiologists in rabbits. Digital subtraction angiography (DSA) guided embolization of hepatic arteries with these embolic microspheres was successfully performed and the occlusion of artery was confirmed with DSA images and contrast enhanced MRI. T2 MRI visibility of the microspheres allowed to monitor the distribution of intra-arterial (IA) infused embolic microspheres. Subsequent on-demand image-guided recanalization procedures were also successfully performed with rapid degradation of microspheres upon intra-arterial infusion of an ion chelating agent. These instant degradable embolic microspheres will permit effective on-demand embolization/recanalization procedures offering great promise to overcome limitations of currently available permanent and biodegradable embolic agents.

Yttrium-90 Portal Vein Radioembolization in Sprague-Dawley Rats: Dose-Dependent Imaging and Pathological Changes in Normal Liver

PURPOSE

Portal vein embolization (PVE) is an established neoadjuvant method to induce future liver remnant hypertrophy prior to surgical resection of hepatic tumors. The purpose of our study was to examine the feasibility of PVE with glass ⁹⁰Y microspheres (Y90 PVE) in Sprague-Dawley rats. We tested the hypothesis that increased doses of Y90 PVE would increase target lobe fibrosis and atrophy.

METHODS

Twenty-two rats were assigned to four groups for Y90 PVE to the right median lobe: very high- (273.8 MBq; n = 2), high- (99.9 MBq; n = 10), medium- (48.1 MBq; n = 5), and low-dose (14.8 MBq; n = 5). An untreated control group included seven rats. ⁹⁰Y PET/CT of ⁹⁰Y distributions confirmed lobar targeting. MRI volumes were measured at baseline, 2-, 4-, 8- and 12-weeks. Explanted hepatic lobes were weighed, sectioned, and stained for H&E and immunohistochemistry. Digitized slides allowed quantitative measurements of fibrosis (20 foci/slide).

RESULTS

Ex vivo measurements confirmed 91-97% activity was localized to the target lobe (n = 4). The percent growth of the target lobe relative to baseline was - 5.0% (95% CI - 17.0-6.9%) for high-, medium dose rats compared to + 18.6% (95% CI + 7.6-29.7%) in the low-dose group at 12-weeks (p = 0.0043). Radiation fibrosis increased in a dose-dependent fashion. Fibrotic area/microsphere was 22,893.5, 14,946.2 ± 2253.3, 15,304.5 ± 4716.6, and 5268.8 ± 2297.2 μm² for very high- (n = 1), high- (n = 4), medium- (n = 3), and low-dose groups (n = 5), respectively.

CONCLUSION

Y90 PVE was feasible in the rat model, resulted in target lobe atrophy, and dose-dependent increases in hepatic fibrosis at 12 weeks. The onset of imaging-based volumetric changes was 8-12 weeks.

Pickering-Emulsion for Liver Trans-Arterial Chemo-Embolization with Oxaliplatin

PURPOSE

Biodegradable polylactic-co-glycolic acid (PLGA) nanoparticles can adsorb at the water/oil interface to stabilize the emulsion (forming Pickering-emulsion). The purpose of this study was to compare the release profiles of oxaliplatin from Pickering-emulsion and Lipiodol-emulsion.

MATERIALS/METHODS

Pickering-emulsions and Lipiodol-emulsions were both formulated with oxaliplatin (5 mg/mL) and Lipiodol (water/oil ratio: 1/3). For Pickering-emulsion only, PLGA nanoparticles (15 mg/mL) were dissolved into oxaliplatin before formulation. In vitro release of oxaliplatin from both emulsions was evaluated. Then, oxaliplatin was selectively injected into left hepatic arteries of 18 rabbits bearing VX2 liver tumors using either 0.5 mL Pickering-emulsion (n = 10) or 0.5 mL Lipiodol-emulsion (n = 8). In each group, half of the rabbits were killed at 1 h and half at 24 h. Mass spectrometry was used to quantify drug pharmacokinetics in blood and resulting tissue (tumors, right, and left livers) oxaliplatin concentrations.

RESULTS

Pickering-emulsion demonstrated a slow oxaliplatin release compared to Lipiodol-emulsion (1.5 ± 0.2 vs. 12.0 ± 6% at 1 h and 15.8 ± 3.0 vs. 85.3 ± 3.3% at 24 h) during in vitro comparison studies. For animal model studies, the plasmatic peak (C_max) and the area under the curve (AUC) were significantly lower with Pickering-emulsion compared to Lipiodol-emulsion (C_max = 0.49 ± 0.14 vs. 1.08 ± 0.41 ng/mL, p = 0.01 and AUC = 19.8 ± 5.9 vs. 31.8 ± 14.9, p = 0.03). This resulted in significantly lower oxaliplatin concentrations in tissues at 1 h with Pickering-emulsion but higher ratio between tumor and left liver at 24 h (43.4 vs. 14.5, p = 0.04).

CONCLUSION

Slow release of oxaliplatin from Pickering-emulsion results in a significant decrease in systemic drug exposure and higher ratio between tumor and left liver oxaliplatin concentration at 24 h.

Immunomodulatory Magnetic Microspheres for Augmenting Tumor-Specific Infiltration of Natural Killer (NK) Cells

The purpose of this research is to develop magnetic resonance imaging (MRI) visible immunomodulatory microspheres (IMM-MS) for efficient image guided cancer immunotherapy. IMM-MS composed of recombinant interferon gamma (IFN-γ), iron oxide nanocubes (IONC), and biodegradable poly(lactide-co-glycolide) (PLGA) were successfully prepared via a double-emulsion method. The prepared IMM-MS exhibited a sustained IFN-γ release and highly sensitive MR T₂ contrast effects. Finally, in an orthotopic liver tumor VX2 rabbit model, successful hepatic intra-arterial (IA) transcatheter delivery of IMM-MS to liver tumors was confirmed with MR images. The deposition of IMM-MS significantly increased NK-cell infiltration into the liver tumor site.

An empirical method for reducing variability and complexity of myocardial perfusion quantification by dual bolus cardiac MRI

PURPOSE

Myocardial perfusion can be quantified using the "dual bolus" technique, which uses two separate contrast boluses to avoid signal nonlinearity in the blood pool. This technique relies on knowing the precise ratio of contrast concentrations between the two boluses. In this study, we investigated the variability found in these ratios, as well as the error it introduces, and developed a method for correction.

METHODS

Five dogs received dual bolus myocardial perfusion MRI scans. Perfusion was calculated separately using assumed contrast dilution ratios and empirically determined contrast ratios. Perfusion was compared with reference standard fluorescent microspheres. The same technique was then applied to a cohort of six patients with no significant coronary artery stenosis by cardiac catheterization.

RESULTS

Assumed contrast dilution ratios were 10:1 for all animal and patient scans. Empirically derived contrast ratios were significantly different for animal (8.51:1 ± 1.53:1, P < 0.001) and patient scans (7.32:1 ± 2.27:1, P < 0.01). Incorporating empirically derived ratios for animal scans improved correlation with microspheres from 0.84 to 0.90 (P < 0.05).

CONCLUSION

Variability in dual bolus contrast concentration ratios is an important source of experimental error, especially outside of a carefully controlled laboratory setting. Empirically deriving the correct ratio is feasible and improves the accuracy of quantitative perfusion measurements. Magn Reson Med 77:2347-2355, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Poly(lactide-co-glycolide) microspheres for MRI-monitored delivery of sorafenib in a rabbit VX2 model

Transcatheter arterial embolization and chemoembolization are standard locoregional therapies for hepatocellular carcinoma (HCC). However, these can result in tumor hypoxia, thus promoting tumor angiogenesis. The anti-angiogenic agent sorafenib is hypothesized to improve outcomes; however, oral administration limits patient tolerance. Therefore, the purpose of this study was to fabricate poly(lactide-co-glycolide) microspheres for local sorafenib delivery to tumors during liver-directed embolotherapies. Iron oxide nanoparticles (IONP) were co-encapsulated for magnetic resonance imaging (MRI) of microsphere delivery. Microspheres were fabricated using a double emulsion/solvent evaporation method and characterized for size, sorafenib and IONP content, and MRI properties. MRI was performed before and after intra-arterial microsphere infusions in a rabbit VX2 liver tumor model. The microspheres were 13 microns in diameter with 8.8% and 0.89% (w/w) sorafenib and IONP, respectively. 21% and 28% of the loaded sorafenib and IONP, respectively, released within 72 h. Rabbit VX2 studies demonstrated that sorafenib microspheres normalized VEGFR 2 activity and decreased microvessel density. Quantitative MRI enabled in vivo visualization of intra-hepatic microsphere distributions. These methods should avoid systemic toxicities, with MRI permitting follow-up confirmation of microsphere delivery to the targeted liver tumors.

Percutaneous ultrasound guided implantation of VX2 for creation of a rabbit hepatic tumor model

Creation of a VX2 tumor model has traditionally required a laparotomy and surgical implantation of tumor fragments. Open surgical procedures are invasive and require long procedure times and recovery that can result in post-operative morbidity and mortality. The purpose of this study is to report the results of a percutaneous ultrasound guided method for creation of a VX2 model in rabbit livers. A total of 27 New Zealand white rabbits underwent a percutaneous ultrasound guided approach, where a VX2 tumor fragment was implanted in the liver. Magnetic resonance imaging was used to assess for tumor growth and necropsy was performed to determine rates of tract seeding and metastatic disease. Ultrasound guided tumor implantation was successful in all 27 rabbits. One rabbit died 2 days following the implantation procedure. Two rabbits had no tumors seen on follow-up imaging. Therefore, tumor development was seen in 24/26 (92%) rabbits. During the follow-up period, tract seeding was seen in 8% of rabbits and 38% had extra-hepatic metastatic disease. Therefore, percutaneous ultrasound guided tumor implantation safely provides reliable tumor growth for establishing hepatic VX2 tumors in a rabbit model with decreased rates of tract seeding, compared to previously reported methods.

Leakage and water exchange characterization of gadofosveset in the myocardium

PURPOSE

To determine the compartmentalization of the blood pool agent gadofosveset and the effect of its transient binding to albumin on the quantification of steady-state fractional myocardial blood volume (fMBV).

METHODS

Myocardial vascular fraction measurements were simulated assuming the limiting cases (slow or fast) of two-compartment water exchange for different contrast agent injection concentrations, binding fractions, bound and free relaxivities, and true cardiac vascular fractions. fMBV was measured in five healthy volunteers (4 males, 1 female, average age 33) at 1.5T after administration of five injections of gadofosveset. The measurements in the volunteers were retrospectively compared to measurements of fMBV after three serial injections of the ultra-small, paramagnetic iron oxide (USPIO) blood pool agent ferumoxytol in an experimental animal. The true fMBV and exchange rate of water protons in both human and animal data sets was determined by chi square minimization.

RESULTS

Simulations showed an error in the measurement of fMBV due to partial binding of gadofosveset of less than 30%. Measured fMBV values over-estimate simulation predictions, and approach cardiac extracellular volume (22%), which suggests that the intravascular assumption may not be appropriate for the myocardium, although it may apply to more distal perfusion beds. In comparison, fMBV measured with ferumoxytol (5%, with slow water proton exchange across vascular wall) agree with published values of myocardial vascular fraction. Further comparison between myocardium relaxation rates induced by gadofosveset and by other extracellular and intravascular contrast agents showed that gadofosveset behaves like an extracellular contrast agent.

CONCLUSIONS

The distribution of the volunteer data indicates that a three-compartment model, with slow water exchange of gadofosveset and water protons between the vascular and interstitial compartments, and fast water exchange between the interstitium and the myocytes, is appropriate. The ferumoxytol measurements indicate that this USPIO is an intravascular contrast agent that can be used to quantify myocardial blood volume, with the appropriate correction for water exchange using a two-compartment water exchange model.

The study of in vivo acute effect of two different delivery modalities of iron oxide core with titanium dioxide shell nanoparticles in rabbits liver tumor

e22204

Background: To compare intravenous (IV) versus fluoroscopy-guided transarterial intra-catheter (IC) delivery of iron oxide core with titanium dioxide shell nanoparticles (NPs) in vivo in VX2 model of liver cancer in rabbits and detect the NPs distribution and effect of NPs presence on the target tumor and other rabbit’s organs. Methods: After obtaining the IACUC approval, liver tumors were obtained by implantation of tumor tissue obtained from a hind limb VX2 tumor of donor rabbits. NPs were delivered either IV or IC. After rabbit termination, 2 hours post NPs injection, tumor, liver, kidney, lung and spleen were harvested, split in half and a part of it was frozen while the remainder was formalin fixed and paraffin embedded. To assess the NPs distribution in 2D we stained 5um thick paraffin tissue sections using Dopamine-Biotin-DHS histochemical (HC) staining followed by Nanozoomer microscopy analysis. H and E staining, TUNEL assay and Ki67 immunohistochemistry were also done. X-ray Fluorescence Microscopy (XFM) was used to quantify the NPs. Frozen tissue was used for bulk NPs concentration analysis using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results: This study included ten rabbits; 3 rabbits had IV NPs injections, 3 had IC NPs injection, 2 control and 2 donors. ICP-MS analysis showed statistically significant higher NPs concentration in tumors of IC arm vs. IV arm (p= 0.0356), while there was higher concentration of NPs in liver (p=0.00077) and spleen (p = 0.01356) of IV vs. IC arms but no difference in kidneys or lungs. These findings were consistent with results from HC and XFM analyses. HC 2D analysis of NPs distribution showed that the RES have taken up the NPs non-specifically. There were no statistically significant differences between the treatment groups regarding the Ki67 proliferation or the TUNEL apoptosis indices or when control rabbits were compared to NPs treated rabbits. Conclusions: Both IV and IC NPs injection are feasible modalities for delivering NPs to tumors with acceptable acute systemic effects and comparable tumor effect. IV delivery increased sequestration of the NPs by RES and their accumulation in spleen and liver.

Absolute quantification of myocardial blood flow with constrained estimation of the arterial input function

PURPOSE

To evaluate the performance of the constrained alternating minimization with model (CAMM) method for estimating the input function from the myocardial tissue curves.

MATERIALS AND METHODS

Myocardial perfusion imaging was performed on seven canine models of coronary artery disease in 15 imaging sessions. In each session, stress was induced with intravenous infusion of adenosine and a variable occluder created coronary artery stenosis. A dual bolus protocol was used for each acquisition, and input functions were then estimated using the CAMM method with data acquired from the high dose scan following each imaging session. For each acquisition, myocardial blood flow was measured by injected microspheres.

RESULTS

The dual bolus and CAMM-derived flows were not significantly different (P = 0.18), and the correlation between the two methods was high (r = 0.97). The correlation between the dual bolus and CAMM methods and microsphere measurements was lower than that for the two MR methods (r = 0.53; r = 0.43, respectively).

CONCLUSION

The CAMM method presented here shows promise in estimating myocardial blood flow in patients with coronary artery disease at stress with a single injection and without any specialized acquisitions. Further work is needed to validate the approach in a clinical setting.

Rabbit VX2 tumors as an animal model of uterine fibroids and for uterine artery embolization

PURPOSE

To determine the suitability of the rabbit VX2 tumor animal model for uterine fibroids and uterine artery embolization (UAE).

MATERIALS AND METHODS

The authors implanted and grew one uterine VX2 tumor per rabbit in six rabbits. UAE was performed by using 100-300 microm embolic particles and confirmed with x-ray digital subtraction angiography, magnetic resonance (MR) imaging, and necropsy. Unenhanced and contrast medium-enhanced MR images of VX2 tumors were obtained before and after UAE. Relative MR signal-to noise-ratio (SNR) was measured in the uterine VX2 tumor and in normal uterine tissue before and after UAE and compared by using a paired t-test (P = .05).

RESULTS

VX2 uterine tumors were successfully grown, and both VX2 tumor presence in the uterus and UAE were seen angiographically and confirmed with necropsy in all six rabbits. Statistically significant reductions in relative SNRs were measured in tumors (SNR before UAE, 15.3 +/- 5.15; SNR after UAE, 3.84 +/- 3.94; P < .0001). No statistically significant decrease in SNR was measured in normal uterine tissue before and after UAE (P = .63 for the right uterine horn and P = .93 for the left uterine horn).

CONCLUSION

Rabbit VX2 uterine tumors may be a suitable animal model of uterine fibroids and UAE.

Off-resonance positive contrast imaging of a passive endomyocardial catheter in swine

The use of off-resonance methods in interventional MRI may be valuable since active devices that provide positive signal enhancements are currently not approved for human use. This study investigated the capacity of a low flip angle steady-state free precession (FLAPS) method for generating off-resonance positive contrast surrounding a susceptibility-shifted endomyocardial Stiletto catheter in excised swine hearts and in live swine. Consistent with theory, discernable positive contrast surrounding the interventional device was visualized under ex-vivo (CNR of 24 +/- 2.1 in the left ventricular (LV) chamber and 18 +/- 2.7 in LV myocardium) and in-vivo conditions (CNR of 22 +/- 3.9 in aorta, 16 +/- 4.1 in the LV chamber and 13 +/- 0.9 in LV myocardium). The findings show that off-resonance imaging with the FLAPS method may be used for passive device visualization with positive contrast. Further studies are necessary prior to clinical translation.

Comparison of two different methods for inoculating VX2 tumors in rabbit livers and hind limbs

PURPOSE

To compare two methods to (a) propagate VX2 cell strain in rabbit hind limbs and (b) inoculate liver parenchymal tumors in rabbits.

MATERIALS AND METHODS

One hundred forty-two New Zealand white rabbits were used for this study (60 with hind limb tumor [donors] and 82 with liver tumors [recipients]). In the donor group, nine rabbits received frozen VX2 cell suspension and 51 were injected with freshly prepared VX2 cell suspension. In the recipient group, 32 rabbits were injected with VX2 tumor cells and 50 were implanted with a small tumor fragment in the liver parenchyma. Success rates in terms of tumor growth were compared by using chi(2) or Fisher exact tests, with alpha = .05.

RESULTS

Hind limb and liver tumors were successfully grown in 48 of the 60 rabbits in the donor group (80%) and 57 of the 82 rabbits in the recipient group (70%). The success rate of growing hind limb tumors increased from 33% (three of nine rabbits) to 88% (45 of 51 rabbits) when fresh VX2 cells instead of frozen were injected percutaneously (P < .0011). Similarly, the success rate for VX2 liver tumors almost doubled from 47% (15 of 32 rabbits) to 84% (42 of 50 rabbits) when a tumor fragment instead of VX2 cell suspension was used (P < .00036). This also significantly reduced the frequency of metastasis (P < .005).

CONCLUSIONS

The authors recommend (a) the use of fresh VX2 cell suspension for percutaneous injection in the hind limbs of rabbits to maintain the VX2 cell strain and (b) the surgical implantation of freshly harvested VX2 tumor fragment into the liver parenchyma to establish liver tumors.

Comparison of transcatheter intraarterial perfusion MR imaging and fluorescent microsphere perfusion measurements during transcatheter arterial embolization of rabbit liver tumors

PURPOSE

Transcatheter intraarterial perfusion (TRIP) magnetic resonance (MR) imaging is clinically used in the interventional MR imaging setting to verify distribution of injected embolic or chemoembolic material during liver-directed transcatheter therapies and to monitor reductions in perfusion. The accuracy of this technique remains unknown. In the present study, rabbit VX2 liver tumors were used to test the hypothesis that TRIP MR imaging accurately measures changes in tumor perfusion during transcatheter arterial embolization (TAE), with injection of fluorescent microspheres used as the gold-standard technique.

MATERIALS AND METHODS

Five New Zealand White rabbits were used for this study (two donor rabbits and three with VX2 liver tumors). In three rabbits with implanted VX2 liver tumors, catheters were superselectively placed under digital subtraction angiographic guidance into the left hepatic artery supplying the targeted tumor. Fluorescent microspheres were injected into each rabbit's left ventricle before and after TAE. TRIP MR images were obtained at baseline and after embolizations for all rabbits with intraarterial injections of 2.5% gadopentetate dimeglumine solution. Linear regression was used to compare relative reductions in tumor perfusion between TRIP MR imaging and fluorescent microspheres. Results were considered statistically significant at a P value less than .05.

RESULTS

There was good correlation between TRIP MR imaging and fluorescent microsphere measurements of reduction in tumor perfusion (r = 0.722, P < .012).

CONCLUSIONS

TRIP MR imaging provides accurate semiquantitative measurement of perfusion reduction during TAE in rabbit liver tumors.

Gadofluorine-enhanced magnetic resonance imaging of carotid atherosclerosis in Yucatan miniswine

OBJECTIVE

The aim of this study was to determine whether gadofluorine, a paramagnetic magnetic resonance imaging (MRI) contrast agent, selectively enhances carotid atherosclerotic plaques in Yucatan miniswine.

METHODS

Atherosclerotic plaques were induced in the left carotid arteries (LCA) of Yucatan miniswine (n=3) by balloon denudation and high cholesterol diet. T1-weighted MRI was performed before and 24 hours after gadofluorine injection (at a dose of 100 micromol/kg) to assess the enhancement of the balloon-injured LCA wall relative to healthy, uninjured right carotid artery (RCA) wall. Histopathology was performed to verify the presence and composition of the atherosclerotic plaques imaged with MRI.

RESULTS

Gadofluorine was found to enhance LCA atherosclerotic lesions relative to RCA wall by 21% (P<0.025) 24 hours after contrast injection. Enhancement of healthy LCA wall relative to healthy RCA wall was not observed.

CONCLUSION

Gadofluorine selectively enhances carotid atherosclerotic plaques in Yucatan miniswine. Gadofluorine appears to be a promising MR contrast agent for detection of atherosclerotic plaques in vivo.

Magnetic resonance imaging of myocardial infarction using a manganese-based contrast agent (EVP 1001-1): preliminary results in a dog model

PURPOSE

To investigate the MRI characteristics of an intracellular manganese-based contrast agent, EVP 1001-1 (Eagle Vision Pharmaceutical Corp.), in a canine model of myocardial infarction.

MATERIALS AND METHODS

Three dogs were imaged 14-37 days following permanent ligation of the left anterior descending coronary artery (LAD). Measurements of the longitudinal relaxation rate R(1) were made prior to EVP 1001-1 administration (20 micromol/kg i.v.) and for one hour thereafter. Triphenyl tetrazolium chloride (TTC) staining was used to document infarction.

RESULTS

In normal myocardium, EVP 1001-1 produced a substantial increase in the longitudinal relaxation rate, which remained fairly constant over the postcontrast imaging period (DeltaR1= 1.47 +/- 0.58 sec(-1) (mean +/- SD) at 35 minutes, P < 0.05). In the infarct, the response to EVP 1001-1 was small or negligible (DeltaR1= 0.27 +/- 0.28 sec(-1)). This resulted in a significant postcontrast difference in relaxation rate between normal and infarcted tissue (R1(normal) - R1(infarct) = 1.08 +/- 0.26 sec(-1), P < 0.05). The infarct remained clearly delineated in all animals throughout the steady-state imaging period, and qualitatively matched TTC results.

CONCLUSION

The persistent enhancement pattern revealed by MRI following EVP 1001-1 administration may be beneficial for identifying and characterizing myocardial infarction.

Myocardial Perfusion Imaging Based on the Blood Oxygen Level–Dependent Effect Using T 2 -Prepared Steady-State Free-Precession Magnetic Resonance Imaging

Background— The decision to perform coronary revascularization procedures may hinge on assessment of myocardial perfusion reserve. Blood oxygen level–dependent (BOLD) MRI is a potential method to detect the effects of regional variations in myocardial blood flow during vasodilation.

Methods and Results— We imaged dogs (n=13) on a 1.5-T whole-body MRI scanner using a new T 2 -prepared steady-state free-precession (SSFP) MRI pulse sequence sensitive to BOLD contrast. Images (in-plane resolution ≈1 mm 2 ) of 5 short-axis and 2 long-axis slices of the heart were acquired during graded levels of adenosine infusion via a surgically placed left circumflex (LCx) catheter (n=11) or via a right atrial catheter in animals with an LCx occluder (n=2). Relative myocardial perfusion was measured with the use of fluorescent microspheres. Signal intensity changes in myocardium subtended by the left anterior descending coronary artery were compared with those in the LCx region. Unprocessed T 2 -weighted images revealed changes in signal intensity corresponding to areas of regional vasodilation or reduced myocardial perfusion reserve during systemic vasodilation. At maximal vasodilation, the signal intensity ratio in the LCx versus left anterior descending territories increased by 33±4% compared with baseline, corresponding to a 3.8±0.3-fold increase in relative perfusion ( P <0.01). MR intensity at progressive levels of vasodilation demonstrated good agreement with microsphere flow ( R =0.80, P <0.01).

Conclusions— T 2 -prepared SSFP BOLD imaging is a promising method to determine an index of myocardial perfusion reserve in this animal model.

Magnetic resonance versus radionuclide pharmacological stress perfusion imaging for flow-limiting stenoses of varying severity

BACKGROUND

Although magnetic resonance first-pass imaging (MRFP) has potential advantages in pharmacological stress perfusion imaging, direct comparisons of current MRFP and established radionuclide techniques are not available.

METHODS AND RESULTS

Graded regional differences in coronary flow were produced during global coronary vasodilation in chronically instrumented dogs by partially occluding the left circumflex artery. Regional differences in full-thickness flow quantified using microspheres were compared with regional differences obtained with MRFP and radionuclide SPECT imaging (99mTc-sestamibi and 201Tl). Relative regional flows (RRFs) derived from the initial areas under MRFP signal intensity-time curves were linearly related to reference microsphere RRFs over the full range of vasodilation (y=0.93x+4.3; r2=0.77). Relationships between 99mTc-sestamibi and 201Tl RRFs and microsphere RRFs were curvilinear, plateauing as flows increased. The high spatial resolution of the MRI enabled transmural flow to be evaluated in 3 to 5 layers across the myocardial wall. Reductions in subendocardial flow were visually apparent in MRFP images for > or =50% reductions in full-thickness flow. Endocardial-to-epicardial gradients in MRFP flow increased progressively with stenosis severity, whereas transmural flow patterns in remote normally perfused myocardium remained normal. Flow reductions of > or =50% not identified by radionuclide imaging were apparent in MRFP full-thickness and transmural analyses.

CONCLUSIONS

High-resolution MRFP can identify regional reductions in full-thickness myocardial blood flow during global coronary vasodilation over a wider range than current SPECT imaging. Transmural flow gradients can also be identified; their magnitude increases progressively as flow limitations become more severe and endocardial flow is compromised increasingly.

Infarct resorption, compensatory hypertrophy, and differing patterns of ventricular remodeling following myocardial infarctions of varying size

OBJECTIVES

We sought to identify advantages of contrast-enhanced magnetic resonance imaging (MRI) in studying postinfarction ventricular remodeling.

BACKGROUND

Although sequential measurements of ventricular volumes, internal dimensions, and total ventricular mass have provided important insights into postinfarction left ventricular remodeling, it has not been possible to define serial, directionally opposite changes in resorption of infarcted tissue and hypertrophy of viable myocardium and effects of these changes on commonly used indices of remodeling.

METHODS

Using gadolinium-enhanced MRI, the time course and geometry of changes in infarcted and noninfarcted regions were assessed serially in dogs subjected to coronary occlusion for 45 min, 90 min, or permanently.

RESULTS

Infarct mass decreased progressively between three days and four to eight weeks following coronary occlusion; terminal values averaged 24 +/- 3% of those at three days. Radial infarct thickness also decreased progressively, whereas changes in circumferential and longitudinal extent of infarction were variable. The ability to define the circumferential endocardial and epicardial extents of infarction allowed radial thinning without epicardial expansion to be distinguished from true infarct expansion. The mass of noninfarcted myocardium increased by 15 +/- 2% following 90-min or permanent occlusion. However, the time course of growth of noninfarcted myocardium differed systematically from that of infarct resorption. Measurements of total ventricular mass frequently failed to reflect concurrent changes in infarcted and noninfarcted regions. Reperfusion accelerated infarct resorption. Histologic reductions in nucleus-to-cytoplasm ratios corresponded with increases in noninfarcted ventricular mass.

CONCLUSIONS

Concurrent directionally opposite changes in infarcted and noninfarcted myocardium can be defined serially, noninvasively, and with high spatial resolution and full ventricular coverage following myocardial infarction.

Antirestenotic Effects of a Locally Delivered Caspase Inhibitor in a Balloon Injury Model

BACKGROUND

The precise role of arterial barotrauma-mediated apoptosis in causing restenosis is unclear. The purpose of this study was to determine if a link exists between angioplasty-mediated medial smooth muscle cell apoptosis and subsequent neointimal hyperplasia.

METHODS AND RESULTS

Bilateral iliac artery angioplasty was performed in 25 male New Zealand White rabbits. Simultaneous with balloon injury, each artery was treated locally with either the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp(Ome)-fluoromethylketone (ZVAD-fmk) or control. In the acute cohort that was survived to 4 hours (n=10, 7 high dose and 3 low dose), an apoptotic index was calculated using the terminal deoxynucleotidyl TUNEL method. In the intermediate cohort that was survived to 2 weeks (n=5), luminal reendothelialization was measured via CD-31 staining. In the chronic cohort that was survived to 4 weeks (n=10), neointimal area was measured. In the acute cohort, there was a 40% reduction in the apoptotic index with high-dose ZVAD-fmk (P=0.008) and a 33% reduction with low-dose ZVAD-fmk (P=0.08). At 2 weeks, there was no significant difference in the degree of luminal reendothelialization. However, at 4 weeks, there was a 33% (0.33+/-0.23 versus 0.22+/-0.20 mm2) (P<0.005) reduction in neointimal area in ZVAD-fmk-treated arteries.

CONCLUSIONS

The local delivery of ZVAD-fmk during balloon injury inhibits smooth muscle cell apoptosis. This corresponds to a significant reduction in neointimal proliferation seen at 4 weeks without a significant change in the degree of reendothelialization at 2 weeks.

Prevalence of fetal alcohol syndrome in the Top End of the Northern Territory

OBJECTIVE

To establish the prevalence of fetal alcohol syndrome (FAS) in the Top End of the Northern Territory (NT), Australia, in both the indigenous and non-indigenous populations. Fetal alcohol syndrome is a preventable disease that is a major cause of intellectual handicap worldwide. The prevalence of FAS in the NT, and in Australia as a whole, is unknown.

METHODOLOGY

Cases were identified through retrospective review of medical records and outpatient letters of children seen by Royal Darwin Hospital paediatric staff. Cases were also identified by tracing potentially affected siblings, or incidentally during clinical work. All children were born between 1990 and 2000, and lived in the Top End of the NT.

RESULTS

Seventeen children were identified with definite FAS. Twenty-six children with partial FAS or alcohol-related neurodevelopmental disorder (ARND) were also identified. The prevalence of FAS in the Top End of the NT was calculated to be 0.68 per 1000 live births. The prevalence might be as high as 1.7 per 1000 live births, if cases identified as partial FAS or ARND because of insufficient records, were assumed to have full FAS. In indigenous children, the corresponding prevalence was calculated to be between 1.87 and 4.7 per 1000 live births. The difference between indigenous and non-indigenous rates of FAS was significant (P < 0.0001).

CONCLUSIONS

The prevalence of FAS in indigenous children of the Top End of the NT is comparable to the high rates in indigenous populations worldwide.

HSC73-tubulin complex formation during low-flow ischemia in the canine myocardium

Canine myocardium was exposed to bouts of low-flow ischemia to identify the interactions that develop between the microtubule-based cytoskeleton and the heat shock protein 70 (HSP70) family of heat shock proteins in viable cardiomyocytes. "Moderate" or "severe" low-flow ischemia was produced in chronically instrumented dogs by reducing circumflex coronary flow by 50% for 2 h or by 75% for 5 h followed by reperfusion for 2 and 24 h, respectively. Electron and immunofluorescence microscopy demonstrated either partial or nearly complete depolymerization of the intermyofibrillar microtubules in areas of myofibril disruption and partial dissolution of the perinuclear microtubule girdle. In contrast, centrosomal tubulin arrays appeared to remain intact following low-flow ischemia. In cardiomyocytes displaying myofibril disruption, constitutively expressed HSP73 (HSC73) colocalized with intact but not disrupted microtubules and with perinuclear and centrosomal tubulin following moderate ischemia. Microtubule depolymerization and high molecular weight tubulin-HSC73 complexes were present in more severely ischemic tissue. These results suggest that HSC73 directly interacts with tubulin and may protect selected elements of the microtubule network and limit myofibril disruption during reversible low-flow ischemia.

Electrical stimulation of abdominal muscles for control of blood pressure and augmentation of cough in a C3/4 level tetraplegic

OBJECTIVES

Evaluation of a FES (Functional Electrical Stimulation) device for the relief of postural hypertension and augmentation of cough in a C3 ventilator-dependent tetraplegic.

STUDY DESIGN

A single case study.

SETTING

A supra regional spinal unit in the UK.

METHOD

A dual channel stimulator was designed that allowed selection and initiation of two predetermined stimulation intensities using a chin controlled joystick. Two sets of 70 mm diameter electrodes were placed either side of the abdomen. Approximately 80 mA, 300 micros, 40 Hz was required for assisted cough while about 40 mA was required for maintenance of blood pressure. After eating, the lower level stimulus is self-administered every 3 to 5 min gradually increasing the time between groups of burst to once every hour after 90 min.

RESULTS

Following eating, a blood pressure of 60/45 mmHg was recorded. After five 1 s bursts of stimulation in quick repetition, this was increased to 133/92 mmHg. After 2 min blood pressure had fallen to 124/86 mmHg and to 93/66 after a further 4 min. The electrical stimulation was then repeated, returning the blood pressure to the previous higher level. Measurement of peak expiratory flow showed an increase from 275 l/min for an unassisted cough to 425 l/min when using the device.

CONCLUSION

The device is used every day. The user is now independent in coughing function and no longer requires suction or manual assistance. Maintenance of blood pressure has significantly improved his quality of life.

Limits of detection of regional differences in vasodilated flow in viable myocardium by first-pass magnetic resonance perfusion imaging

BACKGROUND

Perfusion imaging techniques intended to identify regional limitations in coronary flow reserve in viable myocardium need to identify 2-fold differences in regional flow during coronary vasodilation consistently. This study evaluated the suitability of current first-pass magnetic resonance approaches for evaluating such differences, which are 1 to 2 orders of magnitude less than in myocardial infarction.

METHODS AND RESULTS

Graded regional differences in vasodilated flow were produced in chronically instrumented dogs with either left circumflex (LCx) infusion of adenosine or partial LCx occlusion during global coronary vasodilation. First-pass myocardial signal intensity-time curves were obtained after right atrial injection of gadoteridol (0.025 mmol/kg) with an MRI inversion recovery true-FISP sequence. The area under the initial portion of the LCx curve was compared with that of a curve from a remote area of the ventricle. Relative LCx and remote flows were assessed simultaneously with microspheres. The ratio of LCx and remote MRI curve areas and the ratio of LCx and remote microsphere concentrations were highly correlated and linearly related over a 5-fold range of flow differences (y=0.96 x+/-0.07, P<0.0001, r(2)=0.87). The 95% confidence limits for individual MRI measurements were +/-35%. Regional differences of >/=2-fold were consistently apparent in unprocessed MR images.

CONCLUSIONS

Clinically relevant regional reductions in vasodilated flow in viable myocardium can be detected with 95% confidence over the range of 1 to 5 times resting flow. This suggests that MRI can identify and quantify limitations in perfusion reserve that are expected to be produced by stenoses of >/=70%.

Assessment of regional differences in myocardial blood flow using T2-weighted 3D BOLD imaging

The feasibility of detecting regional differences in myocardial blood flow based on the blood oxygen level-dependent (BOLD) effect was evaluated in vivo in dogs (N = 9) using a 3D T2-prepared segmented gradient-echo sequence at 1.5 T. Regional differences in myocardial blood flow were created by administering adenosine through a catheter placed in the left circumflex coronary artery (LCX). The difference in the R2 (1/T2) relaxation rate between the left ventricular myocardial region supplied by the LCX and regions supplied by the left anterior descending coronary artery (LAD) or septal artery during adenosine administration was correlated to the corresponding regional myocardial blood flow difference determined using fluorescent microspheres. A correlation coefficient of 0.80 was found between the MR BOLD measurements and the myocardial flow assessment. Our results show that the sequence used in this study allows fast 3D BOLD imaging of the heart, and is a promising technique for detecting regional myocardial perfusion differences.

Myofibrillar disruption in hypocontractile myocardium showing perfusion-contraction matches and mismatches

Chronically instrumented dogs underwent 2- or 5-h regional reductions in coronary flow that were followed, respectively, by balanced reductions in myocardial contraction and O(2) consumption ("hibernation") and persistently reduced contraction despite normal myocardial O(2) consumption ("stunning"). Previously unidentified myofibrillar disruption developed during flow reduction in both experimental models and persisted throughout the duration of reperfusion (2-24 h). Aberrant perinuclear aggregates that resembled thick filaments and stained positively with a monoclonal myosin antibody were present in 34 +/- 3.8% (SE) and 68 +/- 5.9% of "hibernating" and "stunned" subendocardial myocytes in areas subjected to flow reduction and in 16 +/- 2.5% and 44 +/- 7.4% of subendocardial myocytes in remote areas of the same ventricles. Areas of myofibrillar disruption also showed glycogen accretion and unusual heterochromatin clumping adjacent to the inner nuclear envelope. The degrees of flow reduction employed were sufficient to reduce regional myofibrillar creatine kinase activity by 25-35%, but troponin I degradation was not evident. The observed changes may reflect an early, possibly reversible, phase of the myofibrillar loss characteristic of hypocontractile myocardium in patients undergoing revascularization.

Immunoexpression of villin in neuroendocrine tumors and its diagnostic implications

BACKGROUND

Villin, a 95-kd cytoskeletal protein associated with axial microfilament bundles of brush border microvilli, is mostly restricted to intestinal glandular tumors. Villin immunoexpression was recently observed in a small number of carcinoids of the intestinal tract and lung, but its significance in a broad category of neuroendocrine tumors has not been evaluated.

DESIGN

A total of 114 neuroendocrine tumors of different origins were tested for villin expression. They included gastrointestinal carcinoids (n = 30), lung carcinoids (n = 15), small cell carcinomas of the lung (n = 24), small cell carcinomas of other sites (n = 15), islet cell tumors (n = 8), Merkel cell carcinomas (n = 6), paragangliomas (n = 6), and others (n = 10). Nine round cell sarcomas were tested as well.

RESULTS

Villin immunoreactivity was present in 85% of gastrointestinal carcinoids and small cell carcinomas, but was found in only 40% of lung carcinoids. Other tumors tested were virtually negative for villin. In general, while cytoplasmic reactivity was most common, a characteristic apical membranous pattern simulating brush border was seen in 76% of the gastrointestinal carcinoids and in 50% of the lung carcinoids.

CONCLUSIONS

We found that villin was predominantly restricted to gastrointestinal neuroendocrine tumors (excluding islet cell tumors), although a small number of bronchial carcinoids may be positive as well. These results suggest a role for villin in the differential diagnosis of neuroendocrine tumors.

Coronary vascular responsiveness to adenosine is impaired additively by blockade of nitric oxide synthesis and a sulfonylurea

OBJECTIVES

We sought to define effects of glibenclamide, a sulfonylurea known to block ATP-dependent potassium (KATP) channels, and Nomega-nitro-L-arginine methyl ester (L-NAME), an L-arginine analog known to block nitric oxide (NO) synthesis, on coronary vascular responsiveness to adenosine.

BACKGROUND

The role of adenosine in coronary flow regulation becomes increasingly important when KATP channel function or NO synthesis is impaired. Both variables are potentially altered in patients with coronary artery disease taking a sulfonylurea.

METHODS

Dose-response curves relating coronary conductance to plasma adenosine concentration were obtained by using intracoronary infusions of adenosine (10 to 1,000 microg/min) in chronically instrumented dogs.

RESULTS

ED50, the plasma concentration of adenosine needed to produce 50% of the maximal increase in conductance under baseline conditions, increased threefold after either 1 or 10 mg/kg of L-NAME. ED50 also increased in response to glibenclamide in a dose-related fashion (5.7-fold increase per 1 mg/kg body weight of glibenclamide). Effects of combined blockade of KATP channels and NO synthesis were additive, with increases in ED50 as high as 15-fold. Both L-NAME and glibenclamide increased systemic pressure and reduced coronary conductance, confirming the roles of NO and KATP channels in regulating coronary and systemic vascular tone under rest conditions as well as during stress.

CONCLUSIONS

Coronary vascular responsiveness to adenosine is blunted in vivo by both L-NAME and glibenclamide. Effects of the sulfonylurea and blockade of NO synthesis are additive and can limit coronary vasodilation as well as other responses involving KATP channels and NO.

Proportionate reversible decreases in systolic function and myocardial oxygen consumption after modest reductions in coronary flow: hibernation versus stunning

OBJECTIVES

This study sought to determine whether modest short-term reductions in coronary flow can produce subsequent proportionate reductions in myocardial function and O2 consumption compatible with myocardial hibernation.

BACKGROUND

Acute studies indicate that myocardial energy utilization can be downregulated during moderate flow reduction. Whether this apparently beneficial adjustment persists into the reperfusion period is unsettled because most postischemic contractile dysfunction has been presumed to represent stunned or irreversibly injured myocardium.

METHODS

Responses of regional myocardial function and O2 consumption were assessed in chronically instrumented dogs after approximately 50% reductions in flow for 2 h (n = 8) or repeated 2-min total coronary occlusions (n = 6).

RESULTS

When unrestricted perfusion was restored after sustained partial occlusions, regional function and O2 consumption stabilized at proportionate, systematically decreased levels ([mean +/- SEM] 80 +/- 3.1% and 81 +/- 5.1% of control values, both p < 0.05) and then returned to control values within 24 h. Similar proportionate reductions occurred after as few as five cycles of brief total occlusion (79 +/- 5.1% and 83 +/- 1.6% of control values, both again p < 0.05); these persisted with additional occlusions and then returned to baseline values within 3 h. The absence of irreversible injury was documented histologically in both series. Sham animals (n = 5) showed no changes in regional function or O2 consumption throughout similar experimental periods.

CONCLUSIONS

Moderate decreases in coronary flow or repeated brief coronary occlusions can be followed by proportionate reversible reductions in regional systolic function and O2 consumption compatible with the traditional definition of myocardial hibernation. These findings emphasize the complexity of myocardial responses to flow restriction and call attention to limitations in characterizing reversibly hypocontractile myocardium as simply hibernating or stunned.

Blockade of nitric oxide synthesis reduces myocardial oxygen consumption in vivo

BACKGROUND

Although cardiac myocytes and coronary vascular endothelium are known to express a constitutive form of NO synthase, the in vivo effects of tonic endogenous production of NO on myocardial O2 consumption and contractile performance remain unclear.

METHODS AND RESULTS

The effects of blockade of NO synthase were determined in intact dogs. Myocardial O2 consumption decreased systematically over a wide range of hemodynamic demand after the systemic administration of N omega-nitro-L-arginine methyl ester (L-NAME) or N omega-nitro-L-arginine. Decreases after doses of 1 and 10 mg/kg L-NAME averaged 23 +/- 3.8% and 34 +/- 7.2% at a heart rate of 90 bpm in open-chest animals. Similar reductions occurred after the administration of L-NAME and N omega-nitro-L-arginine in chronically instrumented animals and were unaffected by beta-adrenergic blockade. Intracoronary infusion of L-NAME in chronically instrumented animals reduced both myocardial O2 consumption and regional segment shortening, even at a dose that did not increase systemic arterial pressure.

CONCLUSIONS

The blockade of NO synthesis reduces myocardial O2 consumption in vivo. The decrease in O2 consumption is accompanied by a decrease in segment shortening. It involves a direct myocardial action of NO, is unaffected by beta-blockade, and is consistent with in vitro studies indicating that low levels of NO augment contractile performance by inhibition of a cGMP-dependent phosphodiesterase.

The effects of goal setting and self-instruction on learning a reading comprehension strategy: a study of students with learning disabilities

This study examined the contributions of instruction in goal setting and self-instruction, separately and combined, on the acquisition, maintenance, and generalization of a reading comprehension strategy by fourth-through sixth-grade students with learning disabilities. A previously validated strategy involving the use of story structure to analyze and remember story content was taught to 47 students with learning disabilities using the self-regulated strategy development (SRSD) model. Comparisons were made among students with learning disabilities in four conditions (strategy instruction, strategy instruction plus goal setting, strategy instruction plus self-instruction, and strategy instruction plus goal setting and self-instruction). Result indicated that instruction in the reading strategy produced meaningful, lasting, and generalizable effects on students' story comprehension skills. Furthermore, the comprehension performance of the students with learning disabilities after strategy instruction was indistinguishable from that of a social comparison group of normally achieving students. Explicit instruction in goal setting and self-instruction, however, did not augment the comprehension performance of students with learning disabilities.

A comparison between Mohs micrographic surgery and wide surgical excision for the treatment of dermatofibrosarcoma protuberans

BACKGROUND

There is growing evidence that Mohs micrographic surgery (MMS) is the treatment of choice for dermatofibrosarcoma protuberans (DFSP).

OBJECTIVE

This study retrospectively compared the recurrence rates of DFSP after MMS with those after wide surgical excision; results at the Mayo Clinic and in the world literature were evaluated. In addition, preoperative tumor sizes and postoperative defect sizes after MMS were compared to determine whether MMS conserved more normal tissue than wide surgical excision.

METHODS

The medical records of 84 patients with DFSP who had been treated at the Mayo Clinic were reviewed. They were categorized into two treatment groups: MMS and surgical excision.

RESULTS

Fifteen patients with DFSP who underwent MMS had follow-up data available; one of these patients had local recurrence (recurrence rate, 6.6%; average duration of follow-up, 40 months). Thirty-nine patients had wide excision; four of these patients had local recurrences and one had pulmonary metastases (recurrence rate, 10%; average duration of follow-up, 36 months). A review of the world literature revealed neither local recurrences nor metastases in the 11 studies in which DFSP was treated with MMS. Overall, including our results, the average recurrence rate of DFSP after MMS was 0.6% (range, 0% to 6.6%) and the total recurrence rate was 1.6% (1 of 64). Including our series, DFSP was treated with wide excision in 15 studies; the average recurrence rate was 18% (range, 0% to 60%) and the total recurrence rate was 20% (100 of 489). In eight published studies, DFSP was surgically resected with undefined or conservative excisional margins; the average recurrence rate was 43% (range, 26% to 60%) and the total recurrence rate was 44% (140 of 317). A surgical margin of 2.5 cm to deep fascia was required for complete clearance of all tumors treated with MMS. Twenty-two percent of tumors were removed with a 0.5 cm margin, 50% with a 1.0 cm margin, 67% with a 1.5 cm margin, and 89% with a 2.0 cm margin.

CONCLUSION

On the basis of our results and data compiled from the literature, MMS may be the treatment of choice for DFSP because of its high cure rate and maximal conservation of tissue.

Serum C-reactive protein. A useful and economical marker of immune activation in renal transplantation

This study investigated whether serial daily measurements of serum C-reactive protein (sCRP) in 187 renal allograft recipients could help discriminate episodes of renal dysfunction due to rejection or cyclosporine (CsA) nephrotoxicity and help adjust immunosuppression in the early posttransplant period. Excellent primary graft function was associated with an initial peak of sCRP on day 2 after transplant (median, 29 microg/ml; range, 4 to >200 microg/ml) with a return to <20 microg/ml in all patients by day 5 (median, 7 microg/ml; range, 2-19 microg/ml). Stable graft function (mean creatinine, 155 microg/ml) was accompanied by a median sCRP of 4 microg/ml (range, 1-19 microg/ml). In 30 episodes of rejection responsive to methylprednisolone, sCRP was initially significantly raised to a median of 49 microg/ml (P<0.001) but fell rapidly in response to treatment to a median of 11 microg/ml and continued to fall. In 19 episodes of rejection unresponsive to methylprednisolone, median initial sCRP levels were significantly higher (P<0.001) at 119 microg/ml and were still at a median of 77 microg/ml at the end of the treatment. Twenty-four patients in whom renal dysfunction was associated with CsA nephrotoxicity showed no increase in sCRP concentrations; median sCRP concentrations remained at <5 microg/ml throughout the episodes. A similar pattern was seen in patients with acute tubular necrosis. Serial sCRP measurements provide economical and reproducible evidence of immune activation, help discriminate renal dysfunction due to CsA nephrotoxicity or rejection, and allow appropriate modification of immunosuppressive therapy.

Endothelium-derived relaxing factor (nitric oxide) has a tonic vasodilating action on coronary collateral vessels

OBJECTIVES

We sought to determine whether endothelium-derived relaxing factor (nitric oxide) exerts a tonic vasodilating effect on coronary collateral channels developed in response to myocardial ischemia.

BACKGROUND

Although the coronary collateral circulation is known to react to several vasoactive agents, the role of endogenously produced nitric oxide is unclear.

METHODS

Coronary collateral channels were induced in the left circumflex artery bed of 12 chronically instrumented dogs by either ameroid implantation or repeated occlusion of the left circumflex coronary artery. With the native circumflex artery occluded, aortic and circumflex pressures and microsphere flows were measured before and after systemic administration of NG-nitro-L-arginine methyl ester, an arginine analogue known to block the synthesis of nitric oxide.

RESULTS

NG-nitro-L-arginine methyl ester increased mean aortic pressure from a mean +/- SEM of 92 +/- 4 to 114 +/- 4 mm Hg, whereas pressure in the occluded circumflex artery decreased from 61 +/- 4 to 55 +/- 4 mm Hg. The increase in aortic-circumflex pressure gradient (from 31 +/- 4 to 59 +/- 5 mm Hg) was accompanied by a decrease in flow in the circumflex bed (from 1.31 to +/- 0.14 to 1.09 +/- 0.15 ml/min per g), resulting in an increase in coronary collateral resistance averaging 173 +/- 37% (from 26 +/- 4 to 64 +/- 9 mm Hg/ml per min per g, p < 0.01). The increase in collateral resistance could be partially reversed by administration of L-arginine.

CONCLUSIONS

We conclude that nitric oxide normally exerts a substantial tonic dilating effect in coronary collateral vessels. Disease-induced alterations in endothelial function may limit collateral perfusion importantly.

The spelling for writing list

Four different vocabulary lists based on the study of children's writing were used to generate a basic spelling list for students with learning disabilities and other poor spellers. For each vocabulary list, the smallest number of different words that accounted for 80% of the words children used in their writing were identified. Words that were common to only one or two of the lists or not normally used by children until fourth grade or later were eliminated. Each word was assigned a grade placement based on difficulty, pattern of occurrence in children's writing, and placement on current vocabulary lists and spelling materials. The resulting spelling list of 335 words is provided.

Lack of correlation between IgG T-lymphocyte flow cytometric crossmatches with primary renal allograft outcome

The flow cytometric crossmatch (FCXM) has been reported to be more sensitive and capable of detecting very low levels of antibodies than the normally used complement dependent cytotoxicity test. We studied both the two colour IgG T cell FCXM and CDC-XM in 146 renal allograft recipients, 111 primary and 35 regrafts, of which 26% (29/111) of 1st and 20% (7/35) of regrafts had a positive FCXM. There was no overall correlation between the FCXM results and early graft outcome in primary renal allografts. The FCXM did not appear to have any advantage over the CDC-XM in predicting graft outcome in unsensitized first grafts. In the small number of regrafts studied, a positive FCXM was associated with a higher degree of graft failure. FCXM can exhibit false negative results if sera are used solely neat although these prozone phenomena do not influence subsequent graft outcome.

The effects of cognitive-behavior modification on private speech and task performance during problem solving among learning-disabled and normally achieving children

Recent research has supported the hypothesis that poor performance among learning-disabled (LD) children is frequently the result of deficits in self-regulation of strategic behaviors, rather than structural or ability deficits. As a result, cognitive-behavior modification (CBM) techniques that emphasize development of self-regulation through self-verbalizations (private speech) have been strongly recommended. The present study examined the natural occurrence of regulatory private speech among LD and normally achieving children during problem solving, as well as the effects of CBM training on private speech and task performance. Results indicated significant deficiencies in private speech and task performance among LD children; CBM training resulted in significant improvements. These results provide further verification of deficits in self-regulation of cognitive activity among LD children and import implications for intervention.

Self-monitoring of attentional behavior versus self-monitoring of productivity: effects on on-task behavior and academic response rate among learning disabled children

I investigated the differential effects of self-monitoring of attentional behavior and self-monitoring of productivity on on-task behavior and academic response rate. Subjects were four learning disabled children with significant attentional problems. Results indicated relatively equivalent increases in on-task behavior over baseline during all treatment phases. Academic response rate also improved under both interventions, with self-monitoring of productivity showing a superior effect for one subject, an equivalent effect for one subject, and less clear results for two subjects.