In vivo assessment of microcystin-LR-induced hepatotoxicity in the rat using proton nuclear magnetic resonance (1H-NMR) imaging.

Microcystin-LR (MCLR)-induced hepatotoxicity was assessed in vivo in male Sprague-Dawley rats (150-350 g) using magnetic resonance imaging (MRI). Following the intraperitoneal administration of MCLR (LD(50)), a region of damage, characterised by increased signal intensity on T(2)-weighted images, was seen proximal to the hepatic portal vein in the liver. Similarly, increased signal intensity was seen in the chemical-shift selective images (CSSI) of water frequency, proximal to the hepatic portal vein in the liver. This indicates that the increased signal intensity observed in the T(2)-weighted images was due to an increased amount of magnetic resonance (MR) visible protons in the tissue which represents an oedematous response. Image analysis of regions of apparent damage around the hepatic portal vein indicated a statistically significant increase in signal intensity in this region. Mitochondrial swelling and lipid inclusions were observed by transmission electron microscopy (TEM) in samples obtained from the oedematous regions of the liver using spatial coordinates from the magnetic resonance (MR) images. Massive haemorrhagic necrosis and nuclear swelling were observed by light microscopy in the centrilobular regions of the lobules.     

Protective effect of L-carnitine on experimental lead toxicity in rats: a clinical,histopathological and immunohistochemical study

Abstract

Female Wistar-albino rats were given lead acetate (PbAc) for 60 days to investigate the protective effects of L-carnitine (CA) clinically and histopathologically on PbAc-induced tissue damage. Blood samples were obtained from the jugular vein for hemoglobin (HB), hematocrit (HCT), red blood cells (RBC), white blood cells (WBC), platelets (PLT), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatinine. PbAc treatment caused a significant decrease in HB, HCT and RBC, a significant increase in WBC, AST, ALT and creatinine compared to controls. Although administration of CA did not reverse HB and HCT values, it reversed both the decrease in RBC and the increase in WBC, AST, ALT and creatinine. After the experimental period, all rats were weighed, then decapitated for pathological examination. Control rat liver, kidney and brain showed normal histological architecture. Lead-induced nephropathic kidneys; degenerative changes, inflammation and portal edema of the liver; and brain neuropil vacuolation, neuronal vacuolation, satellitosis and neuronophagia were observed in experimental groups. All changes were reduced in the PbAc group treated with CA (PbAc + CA). PbAc caused copper/zinc superoxide dismutase (Cu/Zn-SOD) expression in both the hepatocytes and tubular epithelium of the kidney. PbAc + CA exposure caused moderate Cu/Zn-SOD immunoreactivity. While in the brain sections of the PbAc group the degenerative neurons were stained intensely with anti-ubiquitin antibody, PbAc + CA rats showed moderate staining in neurons with anti-ubiquitin antibody. These results show that CA as a food additive reduced the severity of tissue damage caused by PbAc.     

Sulfonamide derivatives of bridgehead substituted bicyclo[4.2.1]nonanes as gamma-secretase inhibitors

Bridgehead substituted derivatives of bicyclo[4.2.1]nonanes were synthesized and shown to be potent inhibitors of gamma-secretase. Two related series were synthesized to explore the SARs. More potent compounds were found in the non-benzofused series compared with the benzofused series. One compound from each series showed good exposure in the hepatic portal vein (HPV) following oral dosing to rats.     

Protection of salvia miltiorrhiza against aflatoxin-B1-induced hepatocarcinogenesis in Fischer 344 rats dual mechanisms involved.

Extract of Salvia Miltiorrhiza (SM) has been widely used in traditional Chinese medicine for treating liver diseases. Recent experimental evidence indicates that it has anti-tumor potential. In this study, the effect of SM on alfatoxin B1 (AFB1)-induced hepatocarcinogenesis was investigated in male Fischer 344 rats. AFB1 (40 microg/100 g body wt, by gavage) was administered once a week for 24 weeks. In SM treatment group, rats were given SM (0.25g/100g body wt, 5 days/week by gavage) for a total of 28 weeks, including 4 weeks before and 24 weeks during AFB1 exposure. Results showed that the elevation of serum alanine aminotransferase and aspartate aminotransferase activities due to AFB1 dosing was almost completely abolished by the treatment of SM, indicating that SM could prevent AFB1-induced liver cell injury. It was further observed that SM substantially reduced glutathione S-transferase placenta form (GST-P) positive foci formation and GST-P mRNA expression caused by AFB1, which clearly suggests that SM is effective in preventing AFB1-induced hepatocarcinogenesis. Furthermore, the inhibition on AFB1 hepatocarcinigenesis was associated with a corresponding decrease in AFB1-DNA adducts formation as well as AFB1-induced oxidative DNA damage (8-hydroxydeoxyguanosine) in rat liver. Our results also indicate that the protective effect of SM might be mediated through dual mechanisms: (i) the enhancement of AFB1 detoxification pathway, especially the induction of GST-Yc2 mRNA expression, and (ii) the antioxidant property of SM.     

饲喂不同浓度黄曲霉毒素B1饲料对异育银鲫成鱼的生长和毒素积累的影响

以含不同浓度黄曲霉毒素B1(AFB1)的配合饲料饲喂异育银鲫(Carassius auratus gibelio)成鱼56d,研究异育银鲫成鱼[(122.3±0.7)g]生长、生理反应、肝脏组织学变化、卵巢发育以及鱼体各组织中的AFB1的毒素积累状况。实验分为5个实验组,不同实验组饲料中AFB1含量分别为0、5、20、50、500μg/kg饲料(实测值分别为2.59、4.12、12.39、46.23、454.07μg/kg饲料),每个处理3个平行。在整个实验过程中各实验组均未表现出外部形态和行为异常,各组存活率均达到100%。各实验组异育银鲫成鱼终末体重、摄食率(FR)、特定生长率(SGR)和饲料效率(FE)均无显著差异。饲料AFB1水平对异育银鲫血清总胆固醇(TC)含量、血清谷丙转氨酶(GPT)、谷草转氨酶(GOT)和碱性磷酸酶(AKP)活性均无显著影响。各毒素组血清超氧化物岐化酶(SOD)活性与对照无显著差异。各毒素组肝脏和卵巢均未见明显的组织学病理变化。肌肉和性腺中的AFB1积累量低于FDA食品安全限定标准(5μg/kg)。肝胰脏中的AFB1积累和饲料中的AFB1水平呈对数关系。饲喂AFB1≥50μg/kg饲料使异育银鲫成鱼肝脏AFB1积累超过安全限量标准。结果表明,异育银鲫成鱼至少可耐受AFB1含量达500μg/kg饲料(实测值:454.07μg/kg饲料)56d。     

Identification of cholesteryl esters in human carotid atherosclerosis by ex vivo image-guided proton MRS

Vulnerable atherosclerotic plaques may be identified by their large lipid component, particularly liquid cholesteryl ester (CE), covered by a fibrous cap. We hypothesized that image-guided 1H proton magnetic resonance spectroscopy (MRS) would identify mobile CE in discrete, preselected regions of atherosclerotic plaque. Human carotid endarterectomy specimens (n = 10) were imaged ex vivo by magnetic resonance imaging (MRI) at high field (11.7 T) utilizing standard T1- and T2-weighted spin echo protocols. MRS spectra were acquired from 1 mm3 voxels, localized to plaque regions that we judged by MRI to be lipid rich or lipid poor. The spectra revealed methyl and methylene resonances of fatty acyl chains with relative intensities and linewidths characteristic of pure CE, by comparison with lipid standards. Regions judged to be lipid rich by MRI showed much more intense CE resonances than did lipid-poor regions. The integrated intensities of lipid peaks were 5.5 +/- 2.0% (lipid-rich regions) versus 0.9 +/- 0.6% (lipid-poor regions) of the unsuppressed water peak (P < 0.0001). Lipid distribution by histology, MRS, and MRI showed strong correlation. Image-guided proton MRS accurately identified CE in selected regions of atherosclerotic plaque as small as 1 mm3 in an ex vivo setting. This procedure may permit the noninvasive detection and quantification of CE in atherosclerotic plaque in vivo.     

Altered DNA mutation spectrum in aflatoxin b1-treated transgenic mice that express the hepatitis B virus x protein

Humans chronically infected with hepatitis B virus (HBV) are at further risk of liver cancer upon exposure to dietary aflatoxin B1 (AFB1), a carcinogenic product of the mold Aspergillus flavus. For the present study, we utilized double-transgenic mice (ATX mice) that express the HBV X protein (HBx) and possess a bacteriophage lambda transgene to evaluate the in vivo effect of HBx expression on AFB1-induced DNA mutations. The expression of HBx correlated with a 24% increase in mutation frequency overall and an approximately twofold increase in the incidence of G/C-to-T/A transversion mutations following AFB1 exposure. These results are consistent with a model in which expression of HBx during chronic HBV infection may contribute to the development of hepatocellular carcinoma following exposure to environmental carcinogens.     

In vivo assessment of nodularin-induced hepatotoxicity in the rat using magnetic resonance techniques (MRI, MRS and EPR oximetry)

Acute nodularin-induced hepatotoxicity was assessed in vivo, in rats using magnetic resonance (MR) techniques, including MR imaging (MRI), MR spectroscopy (MRS), and electron paramagnetic resonance (EPR) oximetry. Nodularin is a cyclic hepatotoxin isolated from the cyanobacterium Nodularia spumigena. Three hours following the intraperitoneal (i.p.) administration of nodularin (LD50), a region of 'damage', characterized by an increase in signal intensity, was observed proximal to the porta hepatis (PH) region in T2-weighted MR images of rat liver. Image analysis of these regions of apparent 'damage' indicated a statistically significant increase in signal intensity around the PH region following nodularin administration, in comparison with controls and regions peripheral to the PH region. An increase in signal intensity was also observed proximal to the PH region in water chemical shift selective images (CSSI) of nodularin-treated rat livers, indicating that the increased signal observed by MRI is an oedematous response to the toxin. Microscopic assessment (histology and electron microscopy) and serum liver enzyme function tests (aminotransferase (ALT) and aspartate ALT (AST)) confirmed the nodularin-induced tissue injury observed by MRI. In vivo and in vitro MRS was used to detect alterations in metabolites, such as lipids, Glu+Gln, and choline, during the hepatotoxic response (2-3 h post-exposure). Biochemical assessment of perchloric acid extracts of nodularin-treated rat livers were used to confirm the MRS results. In vivo EPR oximetry was used to monitor decreasing hepatic pO2 (approximately 2-fold from controls) 2-3 h following nodularin exposure. In vivo MR techniques (MRI, MRS and EPR oximetry) are able to highlight effects that may not have been evident in single end point studies, and are ideal methods to follow tissue injury progression in longitudinally, increasing the power of a study through repeated measures, and decreasing the number of animals to perform a similar study using histological or biochemical techniques.     

Histological alterations and biochemical changes in the liver of sheep following Echis coloratus envenomation

Snake envenoming is a major problem in Al-Jouf Province of Saudi Arabia where most of these envenoming are caused by Echis coloratus which is the highest risk to human and animals in this Province. Little, if any, has been carried out on the histological alterations and biochemical changes in the liver of sheep following snake envenomation. Healthy adult male Ovis orientalis sheep were subjected to E. coloratus envenomation in an attempt to evaluate the histological alterations and biochemical changes in the liver. E. coloratus venom elevated glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride and total bilirubin while cholesterol was reduced. The histological alterations were mainly pyknosis, karyorrhexis, cytoplasmic vacuolation, necrosis, fatty changes and hepatocytes atrophy. Sinusoidal dilatation, Kupffer cell activation, amyloidosis, portal vein thrombosis, partial glycogen depletion and hepatic architecture distortion were also detected. The findings revealed that E. coloratus venom produced biochemical changes and histological alterations in the liver of the envenomated sheep that might affect the functions of this organ severely.     

Effect of transplantation route on stem cell migration to fibrotic liver of rats via cellular magnetic resonance imaging

Background aimsAssessing mesenchymal stromal cells (MSCs) after grafting is essential for understanding their migration and differentiation processes. The present study sought to evaluate via cellular magnetic resonance imaging (MRI) if transplantation route may have an effect on MSCs engrafting to fibrotic liver of rats.MethodsRat MSCs were prepared, labeled with superparamagnetic iron oxide and scanned with MRI. Labeled MSCs were transplanted via the portal vein or vena caudalis to rats with hepatic fibrosis. MRI was performed in vitro before and after transplantation. Histologic examination was performed. MRI scan and imaging parameter optimization in vitro and migration under in vivo conditions were demonstrated.ResultsStrong MRI susceptibility effects could be found on gradient echo-weighted, or T21-weighted, imaging sequences from 24 h after labeling to passage 4 of labeled MSCs in vitro. In vivo, MRI findings of the portal vein group indicated lower signal in liver on single shot fast spin echo-weighted, or T2-weighted, imaging and T21-weighted imaging sequences. The low liver MRI signal increased gradually from 0–3 h and decreased gradually from 3 h to 14 days post-transplantation. The distribution pattern of labeled MSCs in liver histologic sections was identical to that of MRI signal. It was difficult to find MSCs in tissues near the portal area on day 14 after transplantation; labeled MSCs appeared in fibrous tuberculum at the edge of the liver. No MRI signal change and a positive histologic examination were observed in the vena caudalis group.ConclusionsThe portal vein route seemed to be more beneficial than the vena caudalis on MSC migration to fibrotic liver of rats via MRI.     

80%门静脉结扎后肝脏组织中MMP-9 的表达与肝再生作用 的相关性研究

目的:探讨基质金属蛋白酶-9(MMP-9)在大鼠80%门静脉分支结扎模型中大鼠增生肝脏组织中的表达及其与肝再生作用的关系。方法:健康SD雄性大鼠48只,随机平均分成假手术对照组(Sham)和门静脉结扎实验组(PVL)。观察术后1、3、7和14d保留侧肝叶重量/体重比值;下腔静脉采血后检测血清谷丙转氨酶(ALT)、谷草转氨酶(AST)值的变化;光镜下观察保留侧肝脏组织的病理形态变化;用免疫组化法检测增殖细胞核抗原(Proliferating cell nuclear antigen,PCNA)的表达,用免疫印记法检测MMP-9的表达,并进行统计分析。结果:80%门静脉分支结扎后,结扎侧肝叶呈进行性萎缩,保留侧肝叶重量/体重比值逐渐增加,7d达"平台期";与对照组明显不同,PVL组的ALT、AST的值在1h达到高峰,7d后回到正常水平;保留侧肝脏组织中PCNA阳性细胞计数与对照组比较,3d开始表达增强(P<0.05),7d以后逐渐恢复至正常水平(P>0.05);保留侧肝叶MMP-9蛋白的表达在术后3d开始增加,术后7d达到高峰。结论:MMP-9蛋白的表达在80%门静脉结扎后大鼠肝再生过程中发挥重要作用。     

Radiation exposure in supersonic transport by solar flares

Summary The following discourse presents the result of a theoretical analysis of the radiation exposure for solar proton beams and their secondaries in the altitude region of SST (supersonic transport) and pole regions. A statistical analysis of forms and intensities of measured solar flares has been made. The radiation dosage is calculated as a function of atmospheric depth for several characteristic flares. The dosage in rems from secondary neutrons exceeds the dosage in rems from protons in the altitude region of SST for flare events with low characteristic slopeparameterG, In general the radiation is — without some rare extreme events — beyond of dangerous limits and the rare extreme exposure values will be of some hundred mrem/h.     

Aflatoxin-albumin adduct formation after single and multiple doses of aflatoxin B(1) in rats treated with Thai medicinal plants.

The objective was to conduct an assessment of the ability of two Thai medicinal plants, Cymbopogon citratus Stapf and Murdannia loriformis, to modulate levels of serum aflatoxin-albumin (AF-albumin) adducts following aflatoxin B(1) (AFB(1)) exposure in rats. The influence of the plant extracts on AF-albumin adduct formation after a single exposure to 250 microg/kg body weight (bw) AFB(1) was measured over a 48-h period. Rats received M. loriformis extract (3 g/kg bw) or C. citratus Stapf extract (5 g/kg bw) daily for the week prior to the AFB(1) administration. In control rats, maximum adduct levels were observed 12 h post-AFB(1) treatment but in the animals receiving Murdannia extract, maximum levels occurred earlier, at 4 h post-treatment. No such effect was observed with the Cymbopogon extract. Daily treatment of rats with AFB(1) at 250 microg/kg bw for 3 weeks caused serum AF-albumin adduct levels to accumulate over a 10-14 day period and reach plateau levels 4.4-fold higher than observed after a single dose. Treatment with Murdannia extract for 1 week before and then throughout the AFB(1) exposure period resulted in a slight decrease in the AF-albumin adduct levels in the first week of the intervention. After that time, however, the reduction in adduct levels in the Murdannia extract group did not differ significantly from controls. No significant alteration in the biomarker levels was seen with the Cymbopogon extract treatments compared to control rats.     

不同入肝血流阻断方式对荷瘤小鼠肝功能影响的实验研究

目的:探讨不同血流阻断方式对荷瘤小鼠肝细胞功能的影响。方法:选择昆明小鼠24只随机分为三组,正常对照组(Suspe-nded operation,SO)、肝门阻断组(Occlusion of the portal triad,OPT)、保留肝动脉持续阻断门静脉(Occlusion of portal vein,OPV)各8只。采用门静脉注射肿瘤的方法建立肝癌模型,建模后3天采用阻断范围为左外叶和中叶、阻断时间为60分钟的入肝血流阻断方式,复流后5天后,通过测量3组对肝脏的缺血再灌注损伤程度以及病理学变化来评价不同血流阻断方式对肝细胞功能影响的程度。结果:门静脉注射小鼠肝癌细胞8天后,对照组测量小鼠正常丙氨酸氨基转移酶(ALT)值为66.5±22.3 IU/L,OPT组值为276.3±80.5 IU/L,OPV组值为89.6±28.4 IU/L,两组比较有统计学差异(P0.01);对照组测量小鼠正常天冬氨酸氨基转移酶(AST)值为301.3±126.7 IU/L,OPT组值为1126.4±285.5 IU/L,OPV组值为438.6±150.7 IU/L,两组比较有统计学差异(P0.01),病理组织学OPV组肝细胞损伤程度明显较OPT组轻。结论:保留肝动脉持续阻断门静脉可以减轻荷瘤小鼠肝脏的缺血再灌注损伤。     

Genome-Wide and Differential Proteomic Analysis of Hepatitis B Virus and Aflatoxin B1 Related Hepatocellular Carcinoma in Guangxi,China

Both hepatitis B virus (HBV) and aflatoxin B1 (AFB1) exposure can cause liver damage as well as increase the probability of hepatocellular carcinoma (HCC). To investigate the underlying genetic changes that may influence development of HCC associated with HBV infection and AFB1 exposure, HCC patients were subdivided into 4 groups depending upon HBV and AFB1 exposure status: (HBV(+)/AFB1(+), HBV(+)/AFB1(-), HBV(-)/AFB1(+), HBV(-)/AFB1(-)). Genetic abnormalities and protein expression profiles were analyzed by array-based comparative genomic hybridization and isobaric tagging for quantitation. A total of 573 chromosomal aberrations (CNAs) including 184 increased and 389 decreased were detected in our study population. Twenty-five recurrently altered regions (RARs; chromosomal alterations observed in ≥10 patients) in chromosomes were identified. Loss of 4q13.3-q35.2, 13q12.1-q21.2 and gain of 7q11.2-q35 were observed with a higher frequency in the HBV(+)/AFB1(+), HBV(+)/AFB1(-) and HBV(-)/AFB1(+) groups compared to the HBV(-)/AFB(-) group. Loss of 8p12-p23.2 was associated with high TNM stage tumors (P = 0.038) and was an unfavorable prognostic factor for tumor-free survival (P =0.045). A total of 133 differentially expressed proteins were identified in iTRAQ proteomics analysis, 69 (51.8%) of which mapped within identified RARs. The most common biological processes affected by HBV and AFB1 status in HCC tumorigenesis were detoxification and drug metabolism pathways, antigen processing and anti-apoptosis pathways. Expression of AKR1B10 was increased significantly in the HBV(+)/AFB1(+) and HBV(-)/AFB1(+) groups. A significant correlation between the expression of AKR1B10 mRNA and protein levels as well as AKR1B10 copy number was observered, which suggest that AKR1B10 may play a role in AFB1-related hepatocarcinogenesis. In summary, a number of genetic and gene expression alterations were found to be associated with HBV and AFB1- related HCC. The possible synergistic effects of HBV and AFB1 in hepatocarcinogenesis warrant further investigations.     

Intrahepatic ramification of the portal vein in the right and caudate lobes of the liver

We defined the subsegmental divisions and the ramification patterns of the portal vein in the right and caudate lobes using 25 human liver casts. The ramifications of the portal vein and the subdivisions of the liver were classified based on the major portal veins with the largest diameter and those having a diameter of not less than two thirds of the largest vein in each subsegment. The following results were obtained. (1) The portal trunk showed three ramification patterns and the basic pattern was bifurcation (80%). (2) The anterior portal vein first ramified into several anterior-inferior portal veins (P5) and ran toward the superior direction to bifurcate into 2 major portal veins in the anterior-superior subsegment (S8). (3) There were three types of ramification patterns of the portal veins in S8: bifurcation (84%), trifurcation and one-pedicle type. (4) There were also three branching types of the largest vein (P5-max) in P5: ramification from the anterior portal vein, P8-anterior vein supplying the anterior region of S8 and P8-posterior vein supplying the posterior region of S8. (5) The posterior portal vein showed two ramification patterns of the bifurcation (36%) and nonbifurcation type. (6) The major portal veins in the caudate subsegment ramified at various sites such as the portal trunk, left, right and/or other portal veins.     

Paramagnetic water-soluble metallofullerenes having the highest relaxivity for MRI contrast agents.

Water-soluble gadolinium (Gd) endohedral metallofullerenes have been synthesized as polyhydroxyl forms (Gd@C(82)(OH)(n)(), Gd-fullerenols) and their paramagnetic properties were evaluated by in vivo as well as in vitro for the novel magnetic resonance imaging (MRI) contrast agents for next generation. The in vitro water proton relaxivity, R(1) (the effect on 1/T(1)), of Gd-fullerenols is significantly higher (20-folds) than that of the commercial MRI contrast agent, Magnevist (gadolinium-diethylenetriaminepentaacetic acid, Gd-DTPA) at 1.0 T close to the common field of clinical MRI. This unusually high proton relaxivity of Gd-fullerenols leads to the highest signal enhancement at extremely lower Gd concentration in MRI studies. The strong signal was confirmed in vivo MRI at lung, liver, spleen, and kidney of CDF1 mice after i.v. administration of Gd-fullerenols at a dose of 5 micromol Gd/kg, which was 1/20 of the typical clinical dose (100 micromol Gd/kg) of Gd-DTPA.     

Bacterial-based systems for expression and purification of recombinant Lassa virus proteins of immunological relevance

This paper aimed at studying the transplacental transmission of HPV and looking at the epidemiological factors involved in maternal viral infection. The following sampling methods were used: (1) in the pregnant woman, (a) genital; (b) peripheral blood; (2) in the newborn, (a) oral cavity, axillary and inguinal regions; (b) nasopharyngeal aspirate, and (c) cord blood; (3) in the placenta. The HPV DNA was identified using two methods: multiplex PCR of human β-globin and of HPV using the PGMY09 and PGMY11 primers; and nested-PCR, which combines degenerated primers of the E6/E7 regions of the HPV virus, that allowed the identification of genotypes 6/11, 16, 18, 31, 33, 42, 52 and 58. Transplacental transmission was considered when type-specific HPV concordance was found between the mother, the placenta and the newborn or the mother and cord blood. The study included 49 HPV DNA-positive pregnant women at delivery. Twelve placentas (24.5%, n = 12/49) had a positive result for HPV DNA. Eleven newborn were HPV DNA positive in samples from the nasopharyngeal or buccal and body or cord blood. In 5 cases (10.2%, n = 5/49) there was HPV type-specific agreement between genital/placenta/newborn samples. In one case (2%, n = 1/49) there was type specific HPV concordance between genital/cord blood and also suggested transplacental transmission. A positive and significant correlation was observed between transplacental transmission of HPV infection and the maternal variables of immunodepression history (HIV, p = 0.011). In conclusion the study suggests placental infection in 23.3% of the cases studied and transplacental transmission in 12.2%. It is suggested that in future HPV DNA be researched in the normal endometrium of women of reproductive age. The possible consequence of fetal exposure to HPV should be observed.     

Discrimination between red blood cell and platelet components of blood clots by MR microscopy

Magnetic resonance imaging (MRI) of pulmonary emboli obtained ex vivo, verified by immunohistochemistry, showed that platelet layers display brighter signal intensity than areas containing predominantly red blood cells (RBC) in T (1)-weighted MRI. These results were surprising since platelets do not contain paramagnetic haemoglobin that would enhance magnetic relaxation. Our assumption was that the fibrin meshwork areas with entrapped RBC retain abundant extracellular space filled with serum, whereas platelets regroup into tight aggregates lacking serum, essentially mimicking solid tissue structure, rich with cellular proteins that enhance T (1)-relaxation. Our hypothesis was examined by MRI and NMR relaxometry of in vitro RBC suspensions and sedimented platelets, as well as by MRI of model clots and pulmonary emboli obtained ex vivo. Pure sedimented platelets exhibited shorter proton spin lattice relaxation times (T (1) = 874 +/- 310 ms) than those of venous blood of a healthy male with 40% haematocrit (T (1) = 1277 +/- 66 ms). T (1)-values of RBC samples containing high haematocrit (>/=80%) resembled T (1) of platelet samples. In T (1)-weighted spin-echo MRI echo time and repetition time (TE/TR = 10/120 ms) the ratio of signal intensities between a non-retracted whole blood clot (with a haematocrit of 35%) and a pure platelet clot was 3.0, and the ratio between a retracted whole blood clot with an estimated haematocrit of about 58% and a pure platelet clot was 2.6. We conclude that T (1)-weighted MRI can discriminate between platelet layers of thrombi and RBC-rich areas of thrombi that are not compacted to a haematocrit level of >/=80%.     

Using the amide proton signals of intracellular proteins and peptides to detect pH effects in MRI

In the past decade, it has become possible to use the nuclear (proton, 1H) signal of the hydrogen atoms in water for noninvasive assessment of functional and physiological parameters with magnetic resonance imaging (MRI). Here we show that it is possible to produce pH-sensitive MRI contrast by exploiting the exchange between the hydrogen atoms of water and the amide hydrogen atoms of endogenous mobile cellular proteins and peptides. Although amide proton concentrations are in the millimolar range, we achieved a detection sensitivity of several percent on the water signal (molar concentration). The pH dependence of the signal was calibrated in situ, using phosphorus spectroscopy to determine pH, and proton exchange spectroscopy to measure the amide proton transfer rate. To show the potential of amide proton transfer (APT) contrast for detecting acute stroke, pH effects were noninvasively imaged in ischemic rat brain. This observation opens the possibility of using intrinsic pH contrast, as well as protein- and/or peptide-content contrast, as diagnostic tools in clinical imaging.