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Yicheng Ni

Publications and source records attributed to Yicheng Ni.

28 records · Page 2Linked to original sources
PubMed2004

Microplasmin reduces ischemic brain damage and improves neurological function in a rat stroke model monitored with MRI.

BACKGROUND AND PURPOSE: Microplasmin (microPli), a derivative of plasmin lacking the 5 "kringle" domains, was studied in a rat thrombotic stroke model with MRI monitoring. METHODS: Brain ischemia was induced by middle cerebral artery (MCA) occlusion with photochemically induced thrombosis. Brain tissue damage was assessed at 1 hour and 24 hours after MCA occlusion by MRI and 2,3,5-triphenyl tetrazolium chloride (TTC) staining. Neurological symptoms were scored at 24 hours. Animals with insufficient evidence of significant jeopardized brain tissue on perfusion-weighted imaging (PWI) at 1 hour were excluded before randomization. Included animals were randomized (blinded) to controls (solvent), 7.5 or 10 mg/kg microPli, administered as an intravenous bolus 90 minutes after MCA occlusion (n=8 per dose group). RESULTS: microPli treatment reduced cerebral damage measured by TTC staining at 24 hours, from 250+/-69 mm3 (mean+/-SD) in controls to 150+/-30 and 170+/-62 mm3 with 7.5 and 10 mg/kg microPli, respectively; it reduced the expansion of the PWI positive area between 1 and 24 hours, and it reduced neurological deficits from a Bederson score of 7 (6 to 9) in controls to 4.5 (3 to 8) and 4 (3 to 6), with 7.5 and 10 mg/kg microPli, respectively (median and rangeP<0.05 for each dose versus controls for all parameters). CONCLUSIONS: Bolus intravenous microPli given 90 minutes after thrombotic MCA occlusion in rats reduces cerebral ischemic damage and improves neurological dysfunction, suggesting that microPli could be beneficial in ischemic stroke patients.

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PubMed2003

Potentiation of photodynamic therapy with hypericin by mitomycin C in the radiation-induced fibrosarcoma-1 mouse tumor model.

Hypericin, a polycyclic quinone obtained from plants of the genus Hypericum, has been shown to be a promising photosensitizer. We investigated the combination of hypericin-photodynamic therapy (PDT) and a bioreductive drug mitomycin C (MMC) in the present study. The radiation-induced fibrosarcoma-1 tumors were exposed to laser light (120 J/cm2 at 595 nm) 24 h after an intravenous injection of hypericin (1 mg/kg). Hypericin-PDT alone significantly decreased tumor perfusion and oxygen tension as demonstrated by India ink staining technique and OxyLite pO2 measurement, respectively. The in vivo-in vitro cell-survival assay revealed about 60% direct tumor cell killing immediately after PDT. No significant delayed tumor cell death was observed after PDT, which suggests that vascular damage does not contribute significantly to the overall tumor cell death. Injection of a 2.5 mg/kg dose of MMC 20 min before light application significantly decreased tumor cell survival and delayed tumor growth compared with PDT or MMC alone. No greater skin reaction was observed after the combination of MMC and PDT than after PDT alone. Our study demonstrates that combining hypericin-PDT with MMC can be effective in enhancing tumor response with little side effect.

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PubMed2002

Evaluation of radiofrequency ablation as an alternative for the treatment of brain tumor in rabbits.

Radiofrequency ablation (RFA) has emerged recently as a promising therapy for extracranial malignancies. This experiment was conducted to explore the potential of RFA for the treatment of brain tumor in a rabbit model with imaging-histological assessment. Eighteen rabbits with intracranially implanted VX2 tumors of 0.9+/-0.2 cm in diameter were divided into two groups. Group A (n = 12) was treated with a cooled-tip RFA technique at 30 watts for 30-60 s. Group B (n = 6) received sham operation. The therapeutic efficacy was evaluated by comparing survival rate, magnetic resonance imaging (MRI) and histological findings. All animals in Group B died within one month after tumor implantation (19+/-2.6 days). Tumor eradication was achieved in 6/12 rabbits (50.0%) in Group A, of which three rabbits survived longer than three months, another three rabbits were found free of viable tumor when sacrificed. Five rabbits suffered from local tumor relapse. One rabbit developed intracranial metastasis to the brain stem despite a complete ablation of the original tumor. Three-month survival rate of RFA treated rabbits was significantly higher (p < 0.05) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of three characteristic concentric zones, which corresponded to central coagulative tissues (Zone A), peripheral hemorrhagic rim (Zone B) and interstitial edema (Zone C) on histology. This study suggests that RFA may become a promising alternative therapy for the treatment of brain tumor. The recognized characters of thermal lesion on MRI and histology may prove valuable in delimitating the ablation range and understanding the biological response of the RFA.

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PubMed2002

Value of t2-weighted magnetic resonance imaging early after myocardial infarction in dogs: comparison with bis-gadolinium-mesoporphyrin enhanced T1-weighted magnetic resonance imaging and functional data from cine magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Magnetic Resonance Imaging (MRI) has proved to provide noninvasive methods to investigate the functional repercussion of myocardial infarction and to measure infarct size with specific contrast agents. In this study, we evaluate whether the combination of T2-weighted and contrast-enhanced T1-weighted MRI could detect and discern necrotic and ischemic, but salvageable, myocardium. METHODS: Reperfused myocardial infarction was surgically induced in 14 dogs. T1- and T2-weighted MRI was performed 6 hours after administration of the necrosis avid contrast agent Gadophrin-2 at 0.05 mmol/kg. Gradient-echo cine MRI series were performed at baseline and at 6 hours. Quantification of myocardial infarction was performed with triphenyltetrazolium chloride staining. RESULTS: There was a strong correlation between of postcontrast T1-weighted MRI and histomorphometry (r2 = 0.98, P < 0.01). T2-weighted MRI overestimated the infarct size by 10.5% +/- 4.3% of left ventricular area. A good correlation was found between hyperintense areas on T2-weighted images and the percentage of dysfunctional areas on cine MRI (r2 = 0.84, P < 0.01). In regions with increased signal intensity on T2-weighted MRI, a decreased maximal systolic thickening (11.8% +/- 4.9%, P = 0.043) was found. CONCLUSION: In this study, the difference between the hyperintense areas on T2-weighted and enhanced T1-weighted images after myocardial infarction likely represents viable myocardium.

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PubMedDate not supplied

Pharmacokinetic and in vivo evaluation of a self-assembled gadolinium(III)-iron(II) contrast agent with high relaxivity.

A high-molecular weight tetrametallic supramolecular complex [(Ln-DTPA-phen)3Fe]- (Ln = Gd, Eu, La) has been obtained upon self-assembly around one iron(II) ion of three 1,10-phenantroline-based molecules substituted in 5'-position with the polyaminocarboxylate diethylenetriamine-N,N,N',N',N'-pentaacetate, DTPA-phen(4-). The ICP-MS measurements indicated that the lanthanide:iron ratio is 3:1. Photoluminescence spectra of [Eu-DTPA-phen](-) and of [(Eu-DTPA-phen)3Fe]- are nearly identical, implying that the first coordination sphere of the lanthanide(III) ion has not been changed upon coordination of phenantroline unit to iron(II) ion. NMRD measurements revealed that at 20 MHz and 310 K the relaxivity of the [(Gd-DTPA-phen)3Fe]- is equal to 9.5 +/- 0.3 s(-1) mM(-1) of Gd (28.5 s(-1) per millimole per liter of complex) which is significantly higher than that for Gd-DTPA (3.9 s(-1) mM(-1)). The pharmacokinetic parameters of [(Gd-DTPA-phen)3Fe]- in rats indicate that the elimination of [(Gd-DTPA-phen)3Fe]- is significantly slower than that of Gd-DTPA and is correlated with a reduced volume of distribution. The low volume of distribution and the longer elimination time (T(e1/2)) suggest that the agent is confined to the blood compartment, so it could have an important potential as a blood pool contrast agent. The biodistribution profile of [(Gd-DTPA-phen)3Fe]- 2 h after injection indicates significantly higher concentrations of [(Gd-DTPA-phen)3Fe]- as compared with Gd-DTPA in kidney, liver, lungs, heart and spleen. The images obtained on rats by MR angiography show the enhancement of the abdominal blood vessels. The signal intensity reaches a maximum of 55% at 7 min post-contrast and remains around 25% after 90 min. MRI-histomorphological correlation studies of [Gd-DTPA-phen]- and [(Gd-DTPA-phen)3Fe]- showed that both agents displayed potent contrast enhancement in organs including the liver. The necrosis avidity tests indicated that, in contrast to the [Gd-DTPA-phen](-) precursor complex, the supramolecular complex [(Gd-DTPA-phen)3Fe]- exhibits necrosis avidity.

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PubMedDate not supplied

Magnetic resonance imaging of acute reperfused myocardial infarction: intraindividual comparison of ECIII-60 and Gd-DTPA in a swine model.

PURPOSE: To compare a necrosis-avid contrast agent (NACA) bis-Gd-DTPA-pamoic acid derivative (ECIII-60) after intracoronary delivery with an extracellular agent Gd-DTPA after intravenous injection on magnetic resonance imaging (MRI) in a swine model of acute reperfused myocardial infarction (MI). METHODS: Eight pigs underwent 90 min of transcatheter coronary balloon occlusion and 60 min of reperfusion. After intravenous injection of Gd-DTPA at a dose of 0.2 mmol/kg, all pigs were scanned with T1-weighted MRI until the delayed enhancement of MI disappeared. Then they were intracoronarily infused with ECIII-60 at 0.0025 mmol/kg and imaged for 5 hr. Signal intensity, infarct-over-normal contrast ratio and relative infarct size were quantified, compared, and correlated with the results of postmortem MRI and triphenyltetrazolium chloride (TTC) histochemical staining. RESULTS: A contrast ratio over 3.0 was induced by both Gd-DTPA and ECIII-60. However, while the delayed enhancement with Gd-DTPA virtually vanished in 1 hr, ECIII-60 at an 80x smaller dose depicted the MI accurately over 5 hr as proven by ex vivo MRI and TTC staining. CONCLUSION: Both Gd-DTPA and ECIII-60 strongly enhanced acute MI. Comparing with fading contrast in a narrow time window with intravenous Gd-DTPA, intracoronary ECIII-60 persistently demarcated the acute MI, indicating a potential method for postprocedural assessment of myocardial viability after coronary interventions.

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