Distal end of the atrioventricular nodal artery predicts the risk of atrioventricular block during slow pathway catheter ablation of atrioventricular nodal re-entrant tachycardia

OBJECTIVE

To search for a reliable anatomical landmark within Koch's triangle to predict the risk of atrioventricular (AV) block during radiofrequency slow pathway catheter ablation of AV nodal re-entrant tachycardia (AVNRT).

PATIENTS AND METHODS

To test the hypothesis that the distal end of the AV nodal artery represents the anatomical location of the AV node, and thus could be a useful landmark for predicting the risk of AV block, 128 consecutive patients with AVNRT receiving slow pathway catheter ablation were prospectively studied in two phases. In phase I (77 patients), angiographic demonstration of the AV nodal artery and its ending was performed at the end of the ablation procedure, whereas in the subsequent phase II study (51 patients), the angiography was performed immediately before catheter ablation to assess the value of identifying this new landmark in reducing the risk of AV block. Multiple electrophysiologic and anatomical parameters were analysed. The former included the atrial activation sequence between the His bundle recording site (HBE) and the coronary sinus orifice or the catheter ablation site, either during AVNRT or during sinus rhythm. The latter included the spatial distances between the distal end of the AV nodal artery and the HBE and the final catheter ablation site, and the distance between the HBE and the tricuspid border at the coronary sinus orifice floor.

RESULTS

In phase I, nine of the 77 patients had complications of transient (seven patients) or permanent (two patients) complete AV block during stepwise, anatomy guided slow pathway catheter ablation. These nine patients had a wider distance between the HBE and the distal end of the AV nodal artery, and a closer approximation of the catheter ablation site to the distal end of the AV nodal artery, which independently predicted the risk of AV block. In contrast, none of the available electrophysiologic parameters were shown to be reliable. When the distance between the distal end of the AV nodal artery and the ablation target site was more than 2 mm, the complication of AV block virtually never occurred. In phase II, all 51 patients had successful elimination of the slow pathways without complication when the ablation procedure was guided by preceding angiography with identification of the distal end of the AV nodal artery.

CONCLUSIONS

The distal end of the AV nodal artery shown by angiography serves as a useful landmark for the prediction of the risk of AV block during slow pathway catheter ablation of AVNRT.

Metal complexes of N-tosylamidoporphyrin: cis-acetato-N-tosylimido-meso-tetraphenylporphyrinatothallium(III) and trans-acetato-N-tosylimido-meso-tetraphenylporphyrinatogallium(III)

The crystal structures of acetato-N-tosylimido-meso-tetraphenylporphyrinatothallium(III), Tl(N-NTs-tpp)(OAc) (1), and acetato-N-tosylimido-meso-tetraphenylporphyrinatogallium(III), Ga(N-NTs-tpp)(OAc) (2), were determined. The coordination sphere around the Tl3+ ion is a distorted square-based pyramid in which the apical site is occupied by a chelating bidentate OAc- group, whereas for the Ga3+ ion, it is a distorted trigonal bipyramid with O(3), N(3), and N(5) lying in the equatorial plane. The porphyrin ring in the two complexes is distorted to a large extent. For the Tl3+ complex, the pyrrole ring bonded to the NTs ligand lies in a plane with a dihedral angle of 50.8 degrees with respect to the 3N plane, which contains the three pyrrole nitrogens bonded to Tl3+, but for the Ga3+ complex, this angle is found to be only 24.5 degrees. In the former complex, Tl3+ and N(5) are located on the same side at 1.18 and 1.29 A from its 3N plane, but in the latter one, Ga3+ and N(5) are located on different sides at -0.15 and 1.31 A from its 3N plane. The free energy of activation at the coalescence temperature Tc for the intermolecular acetate exchange process in 1 in CD2Cl2 solvent is found to be delta G++171 = 36.0 kJ/mol through 1H NMR temperature-dependent measurements. In the slow-exchange region, the methyl and carbonyl (CO) carbons of the OAc- group in 1 are separately located at delta 18.5 [3J(Tl-13C) = 220 Hz] and 176.3 [2J(Tl-13C) = 205 Hz] at -110 degrees C.

Surgical results in patients with hepatitis B-related hepatocellular carcinoma and positive hepatitis B early antigen

Hepatitis B virus (HBV) infection is the major risk factor in the pathogenesis of hepatocellular carcinoma (HCC). Patients who are positive for hepatitis B early antigen (HBeAg) have active liver disease. The present study aimed to evaluate the possible role of HBeAg in patients with resectable HCC. A series of 249 HCC patients with complete preoperative hepatitis marker who had undergone potentially curative resection were enrolled. Patients with hepatitis C virus infection were excluded. Of these patients, 27 were positive for hepatitis B surface antigen (HBsAg) and HBeAg (group I), 171 were positive for HBsAg and negative for HBeAg (group II), and 51 were negative for hepatitis B markers (group III). The clinicopathologic features and postoperative survivals were compared among the three groups. The prevalence of HBeAg was 10.8%. Group I patients were significantly younger and had worse liver function, smaller tumors, and a higher incidence of liver cirrhosis and chronic active hepatitis than those in groups II and III. No increase in tumor invasiveness was noted in group I patients. The operative morbidity, mortality, and postresection survival were comparable among the three groups. Our findings indicated that HBeAg positivity is not a negative factor for resection in HCC patients and has no significant influence on postresection survival.

Home telecare system using cable television plants--an experimental field trial

To solve the inconvenience of routine transportation of chronically ill and handicapped patients, this paper proposes a platform based on a hybrid fiber coaxial (HFC) network in Taiwan designed to make a home telecare system feasible. The aim of this home telecare system is to combine biomedical data, including three-channel electrocardiogram (ECG) and blood pressure (BP), video, and audio into a National Television Standard Committee (NTSC) channel for communication between the patient and healthcare provider. Digitized biomedical data and output from medical devices can be further modulated to a second audio program (SAP) subchannel which can be used for second-language audio in NTSC television signals. For long-distance transmission, we translate the digital biomedical data into the frequency domain using frequency shift key (FSK) technology and insert this signal into an SAP band. The whole system has been implemented and tested. The results obtained using this system clearly demonstrated that real-time video, audio, and biomedical data transmission are very clear with a carrier-to-noise ratio up to 43 dB.

The role of bcl-2, p53, and ki-67 index in predicting tumor recurrence for low grade superficial transitional cell bladder carcinoma

PURPOSE

We assess the prognostic significance of bcl-2 expression, p53 mutation and ki-67 index for low grade, superficial transitional cell bladder carcinoma.

MATERIALS AND METHODS

The medical records of 93 cases of primary, low grade (24 G1, 69 G2), superficial (70 pTa, 23 pT1) transitional cell carcinoma of the bladder were reviewed. Association of bcl-2, p53 and ki-67 index immunoreactivity with tumor grade and stage was examined. Prognostic significance of tumor grade, pathological stage, bcl-2 expression, p53 mutation and ki-67 index in predicting tumor recurrence was assessed.

RESULTS

Of the tumors 60 (70%) had p53 mutation and 9 (10.5%) expressed bcl-2. These 2 markers did not relate to tumor grade or pathological stage. Median ki-67 index was 10.9% and positively correlated with tumor grade. Recurrence was noted in 34.9% of patients with a median followup of 26 months (range 1 to 84). The ki-67 index was the only significant prognostic indicator in univariate and multivariate analyses. This marker can further distinguish grade 2 tumors with a favorable prognosis from those with an unfavorable outcome.

CONCLUSIONS

The ki-67 labeling index is an independent predictor of tumor recurrence for patients with primary superficial, low grade bladder cancers.

Modulation of ciliary activity by tumor necrosis factor-alpha in cultured sinus epithelial cells. Possible roles of nitric oxide

The primary function of well-differentiated ciliated epithelium in the paranasal sinus is to eliminate harmful agents through the beating action of cilia. Respiratory epithelium also contributes to local inflammatory processes through the release of various proinflammatory cytokines. Recently, considerable attention has been focused on the intimate relationship between the cytokine-dependent regulation of the ciliary beat frequency (CBF) and intra-cellular production of nitric oxide (NO) in ciliated epithelial cells. The aims of this study are to examine the effect of tumor necrosis factor-alpha (TNF-alpha), one of the major proinflammatory cytokines, on the ciliary activity of human sinus epithelial cells and to assess the hypothesis that NO is involved in this regulatory mechanism. Human maxillary or ethmoidal sinus mucosa (n = 23) were cultured by the explant-outgrowth method. CBF of the outgrowth ciliated cells was measured by the photoelectrical method before and after being treated with TNF-alpha (0.1, 1 and 10 ng/ml) or dexamethasone (10(-6) M and 10(-7) M). We also investigated the expression of nitric oxide synthase (NOS) isoforms, enzymes responsible for NO synthesis, by fluorescent immunohistochemistry. TNF-alpha increased CBF at relatively low concentrations (0.1 and 1 ng/ml) and decreased CBF at a high concentration (10 ng/ml). Dexamethasone decreased CBF at a concentration of 10(-6) M. Fluorescent immunohistochemistry demonstrated that the expression of inducible NOS was augmented by TNF-alpha and attenuated by dexamethasone, whereas that of endothelial NOS remained unchanged. We conclude that human sinus epithelial cells potentially contribute to the inflammatory process by regulating their ciliary motility through an NO-dependent pathway. Proinflammatory cytokines and steroids are able to modulate this mechanism by the induction or inhibition of expression of different NOS isoforms.

Effects of Welsh onion extracts on human platelet function in vitro

Welsh onion has been consumed for prevention of cardiovascular disorders. However, its underlying mechanisms are still unclear. This study investigated whether Welsh onion extracts can alter human platelet function (ie, platelet adhesion, aggregation, and thromboxane release). To clarify the underlying mechanisms, we also measured the intracellular calcium ([Ca2+]i) and cyclic nucleotide levels in platelets. Our results showed that 1) boiled extracts directly induced platelet aggregation in a dose-dependent manner; 2) raw extracts inhibited platelet adhesion and ADP-evoked platelet aggregation, while boiled extracts enhanced them; 3) raw green extract suppressed ADP-stimulated platelet [Ca2+]i elevation and thromboxane production, whereas boiled green extract enhanced them; 4) raw green extract elevated platelet cAMP level, whereas boiled green extract had no effect on cAMP level. Furthermore, the boiled green extract, but not the raw extract, induced pronounced platelet morphological changes. In conclusion, raw extracts of Welsh onion inhibit platelet function in vitro while boiled extracts activate platelets.

Prediction of common secondary structures of RNAs: a genetic algorithm approach

In this study we apply a genetic algorithm to a set of RNA sequences to find common RNA secondary structures. Our method is a three-step procedure. At the first stage of the procedure for each sequence, a genetic algorithm is used to optimize the structures in a population to a certain degree of stability. In this step, the free energy of a structure is the fitness criterion for the algorithm. Next, for each structure, we define a measure of structural conservation with respect to those in other sequences. We use this measure in a genetic algorithm to improve the structural similarity among sequences for the structures in the population of a sequence. Finally, we select those structures satisfying certain conditions of structural stability and similarity as predicted common structures for a set of RNA sequences. We have obtained satisfactory results from a set of tRNA, 5S rRNA, rev response elements (RRE) of HIV-1 and RRE of HIV-2/SIV, respectively.

Association of follow-up change of left atrial appendage blood flow velocity with spontaneous echo contrast in nonrheumatic atrial fibrillation

STUDY OBJECTIVES

To evaluate the time-related change of left atrial (LA) appendage flow velocity in chronic atrial fibrillation (AF) by follow-up transesophageal echocardiography (TEE) and to investigate its association with the occurrence of LA spontaneous echo contrast.

DESIGN

Prospective follow-up study.

SETTING

University-based, tertiary referral medical center.

PATIENTS

Forty-seven patients with chronic nonrheumatic AF.

INTERVENTIONS

All studied patients underwent both a baseline and follow-up TEE during a mean period of 13 +/- 7 months.

MEASUREMENTS AND RESULTS

Baseline TEE revealed that LA spontaneous echo contrast was present in 28 patients (group 1) and was absent in 19 patients (group 2). The LA appendage flow velocity profiles at baseline were significantly lower in group 1 than in group 2; on follow-up, the appendage flow velocities decreased significantly in group 2, but were not significantly changed in group 1. Follow-up TEE revealed that spontaneous echo contrast was persistent in all group 1 patients. In group 2, LA spontaneous echo contrast was newly observed in 9 patients (group 2A) but was persistently absent in 10 patients (group 2B). In group 2A, all of the LA appendage flow velocity profiles decreased significantly at the follow-up study. In group 2B, however, only LA appendage inflow velocity integral showed significant decrease on follow-up; there were no significant changes in LA appendage outflow velocity indexes and peak inflow velocity.

CONCLUSIONS

LA appendage flow velocity may decrease with time in some patients with AF, and this change is associated with a new occurrence of LA spontaneous echo contrast. For patients without LA spontaneous echo contrast, serial follow-up of the LA appendage flow velocity profiles may be useful for predicting future development of spontaneous echo contrast. Once LA spontaneous echo contrast occurs in AF patients, it tends to persist with time and the LA appendage is usually under a persistently low flow state.

Chronic consumption of raw but not boiled Welsh onion juice inhibits rat platelet function

Welsh onion has been consumed for prevention of cardiovascular disorders. To study if it has antithrombotic effects, 9-wk-old male Sprague-Dawley rats were studied. Some rats were fed raw or boiled Welsh onion juice (2 g. kg(-1). d(-1)) for 4 wk, and the remaining acted as the control. Before and after feeding, their systolic blood pressure was measured by a tail-cuff method. Two days after the treatment period, tail bleeding time, platelet function (including platelet aggregation and adhesion), plasma levels of prostaglandins, and platelet cyclic nucleotide levels were determined. In comparison to the control, raw Welsh onion juice consumption significantly (1) lowered resting systolic blood pressure; (2) prolonged the bleeding time; (3) diminished platelet adhesion on a fibrinogen-coated surface, ADP-evoked platelet aggregation and ADP-stimulated thromboxane release; (4) elevated the concentration of cyclic AMP, but not cyclic GMP, in platelets; (5) increased the plasma level of 6-keto-prostaglandin F(1alpha), the stable prostacyclin metabolite, but not the plasma nitrite level. On the contrary, boiled Welsh onion juice consumption was totally ineffective. In conclusion, consuming raw Welsh onion juice, but not boiled juice, has blood pressure lowering and antithrombotic effects in rats. These effects may be mediated by PGI(2)-cAMP pathway.

G-33A mutation in the promoter region of thrombomodulin gene and its association with coronary artery disease and plasma soluble thrombomodulin levels

Thrombomodulin is an endothelial glycoprotein that decreases thrombin activity and activates protein C. A recent study has shown that G-33A promoter mutation of the thrombomodulin gene occurs particularly in Asians. In this study, we analyzed the distribution of G-33A mutation in the promoter region of the thrombomodulin gene in the Chinese population and determined whether the mutation might be a risk for coronary artery disease (CAD). In addition, the influence of this mutation on plasma soluble thrombomodulin levels in patients with CAD was also examined. We studied 320 consecutive patients (mean age 63 years; 73% men) with CAD and 200 age- and sex-matched control subjects. Screening for thrombomodulin G-33A promoter mutation was conducted using polymerase chain reaction, single-strand conformation polymorphism, and direct deoxyribonucleic acid sequencing. The frequency of the G-33A mutation (GA+AA genotypes) was significantly higher in the CAD group (23.8% vs 15.5%, odds ratio [OR] 1.70, p = 0.031). Multiple logistic regression analysis showed that the mutation was an independent risk factor (OR 1.81, p = 0.016) for CAD, as was hypertension (OR 1.44, p = 0.040), diabetes mellitus (OR 2.50, p <0.001), and smoking (OR 2.15, p <0.001). In CAD patients with GG genotype, the soluble thrombomodulin level increased with the extent of CAD (36 +/- 15 vs 47 +/- 18 vs 55 +/- 36 ng/ml in 1-, 2-, or 3-vessel CAD, p <0.001). However, in CAD patients with G-33A mutation, there was no difference between the levels of soluble thrombomodulin (39 +/- 17 vs 37 +/- 15 vs 42 +/- 18 ng/ml, p = NS) in 1-, 2-, or 3-vessel CAD. Our observations suggest that there is a significant association of the G-33A mutation in thrombomodulin gene with CAD, and this mutation may influence the soluble thrombomodulin levels in patients with CAD.

Correlation of homocytsteine levels with the extent of coronary atherosclerosis in patients with low cardiovascular risk profiles

Elevation of homocysteine is now known as an independent risk factor for vascular diseases. However, influences of homocysteine to the extent of coronary atherosclerosis in patients with different coronary risk profiles have not been studied. In this study, we used angiographic "diffuse score" and "clinical vessel score" to evaluate the extent of coronary atherosclerosis, and examined the correlation between levels of serum total homocysteine and angiographic scores among patients with high- and low-risk profiles. Seventy consecutive patients (58 men and 12 women, mean age 50 years) undergoing selective coronary angiography for the first time were recruited for this study. Patients were divided into high-risk (risk factor > or =3, n = 35) and low-risk (risk factor <3, n = 35) groups. Linear regression analysis revealed that levels of serum homocysteine were only significantly correlated with diffuse (r = 0.217, p = 0.007) and clinical vessel (r = 0.078, p = 0.037) scores in low-risk patients. These correlations could not be observed in diffuse (r = 0.070, p = 0.319) and clinical vessel (r = -0.001, p = 0.970) scores in the high-risk group. In conclusion, levels of homocysteine correlated with the extent of coronary atherosclerosis only among patients with low cardiovascular risk profiles.

Quantitative spectral/spatial analysis of phased array coil in magnetic resonance imaging based on method of moment

A new approach for analysis of RF coils in magnetic resonance (MR) experiments is reported. Instead of assuming current distribution in conventional quasi-static algorithm, this approach transforms the coil geometry into an equivalent circuit for complex current calculation. Self and mutual inductance are taken into consideration. Frequency responses of RF coils and transverse magnetic field (B1) maps can be simulated. This approach is especially efficient for phased array coil design for its small matrix size when implemented on computers. Experiments on both single surface coil and phased array coils are consistent with simulation results. Index Terms-Magnetic resonance, method of moment, phased array coil, RF coil.

Model-free functional MRI analysis using Kohonen clustering neural network and fuzzy C-means

Conventional model-based or statistical analysis methods for functional MRI (fMRI) suffer from the limitation of the assumed paradigm and biased results. Temporal clustering methods, such as fuzzy clustering, can eliminate these problems but are difficult to find activation occupying a small area, sensitive to noise and initial values, and computationally demanding. To overcome these adversities, a cascade clustering method combining a Kohonen clustering network and fuzzy, means is developed. Receiver operating characteristic (ROC) analysis is used to compare this method with correlation coefficient analysis and t test on a series of testing phantoms. Results shown that this method can efficiently and stably identify the actual functional response with typical signal change to noise ratio, from a small activation area occupying only 0.2% of head size, with phase delay, and from other noise sources such as head motion. With the ability of finding activities of small sizes stably this method can not only identify the functional responses and the active regions more precisely, but also discriminate responses from different signal sources, such as large venous vessels or different types of activation patterns in human studies involving motor cortex activation. Even when the experimental paradigm is unknown in a blind test such that model-based methods are inapplicable, this method can identify the activation patterns and regions correctly.

Impact of magnetic resonance imaging on the advancement of medicine

Magnetic resonance (MR) imaging has had a significant impact in many areas of modern medicine. Because of its good image resolution, tissue characterization, and functional assessment of various organs and systems, MR imaging has become an important modern technology in clinical practice and medical research. MR imaging has great flexibility in viewing anatomic structures in arbitrary imaging planes. With ultrafast MR imaging techniques, images of areas of interest can be obtained in a very short time, with elimination of physiologic motion artifacts. MR angiography obviates the need for catheterization and provides highly detailed images of the vascular anatomy, even of structures as small as the coronary artery. MR cholangiopancreatography provides results comparable to those of endoscopic retrograde cholangiopancreatography in many hepatobiliary diseases. Functional MR imaging is a new tool to evaluate physiologic function. MR spectroscopy has been used to explore the metabolic activity of normal and diseased organs and structures. The applications of MR imaging in clinical medicine and biomedical research are expanding.

Recent advances in telemedicine

With continuing advances in information technology, the applications of computers in medicine are increasing rapidly. Modern information technology not only affects the delivery of health care, but also significantly influences the doctor-patient relationship. Since the 1990s, technologic developments in high-bandwidth telecommunications systems and digitizing devices have led to a surge of interest in telemedicine. In recent years, the Internet, with its powerful penetration and scalability, has become an increasingly popular medical information resource and a new platform for telemedicine. The impact of modern technology on the advancement of telemedicine in Taiwan started with the 1995 National Information Infrastructure project, which uses networks of different bandwidths for teleconsultation and distance education programs. In 1998, National Taiwan University and Taipei Medical College in Taiwan, and the University of Pittsburgh and the University of Iowa in the USA, began cooperation on a new Cyber Medical Center (CMC) project that integrates the technologies of multimedia, database management, a multiple-site videoconferencing system, and the World Wide Web. The aim of the CMC is to create a multimedia network system for the management of electronic patient records, teleconsultation, online continuing medical education, and information services on the Web. In the future, telemedicine systems in Taiwan are expected to combine the Internet and cable television to connect clinics, hospitals, insurance organizations, and public health administrations; and, finally, to extend health services to every household.

46,XY gonadal dysgenesis associated with congenital nephrotic syndrome and sepsis

The occurrence of nephrosis in the first 3 months of life is rare and is termed 'congenital nephrotic syndrome.' The congenital nephrotic syndrome is a group of heterogeneous diseases with a clinical course that differs markedly from the childhood nephrotic syndrome. The coexistence of a congenital nephrotic syndrome and gonadal dysgenesis in a 46,XY karyotype with normal female external genitalia is extremely rare. Frequent severe infections are often seen in the Finnish type, but sepsis leading to death is rare in the neonatal onset of gonadal dysgenesis. This report describes an unusual case of complete XY gonadal dysgenesis in a 46,XY female neonate with the congenital nephrotic syndrome and overwhelming sepsis.

Novel role of the Ca(2+)-ATPase in NMDA-induced intracellular acidification

The mechanism involved in N-methyl-D-glucamine (NMDA)-induced Ca(2+)-dependent intracellular acidosis is not clear. In this study, we investigated in detail several possible mechanisms using cultured rat cerebellar granule cells and microfluorometry [fura 2-AM or 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein-AM]. When 100 microM NMDA or 40 mM KCl was added, a marked increase in the intracellular Ca(2+) concentration ([Ca(2+)](i)) and a decrease in the intracellular pH were seen. Acidosis was completely prevented by the use of Ca(2+)-free medium or 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid-AM, suggesting that it resulted from an influx of extracellular Ca(2+). The following four mechanisms that could conceivably have been involved were excluded: 1) Ca(2+) displacement of intracellular H(+) from common binding sites; 2) activation of an acid loader or inhibition of acid extruders; 3) overproduction of CO(2) or lactate; and 4) collapse of the mitochondrial membrane potential due to Ca(2+) uptake, resulting in inhibition of cytosolic H(+) uptake. However, NMDA/KCl-induced acidosis was largely prevented by glycolytic inhibitors (iodoacetate or deoxyglucose in glucose-free medium) or by inhibitors of the Ca(2+)-ATPase (i.e., Ca(2+)/H(+) exchanger), including La(3+), orthovanadate, eosin B, or an extracellular pH of 8.5. Our results therefore suggest that Ca(2+)-ATPase is involved in NMDA-induced intracellular acidosis in granule cells. We also provide new evidence that NMDA-evoked intracellular acidosis probably serves as a negative feedback signal, probably with the acidification itself inhibiting the NMDA-induced [Ca(2+)](i) increase.

Prenatal diagnosis of trisomy 20 mosaicism by maternal serum screening for Down syndrome

We report two cases of prenatally diagnosed trisomy 20 mosaicism associated with positive Down syndrome screening at 16 weeks' gestation. Both infants exhibited normal growth and mental development. These cases suggest that the multiple-marker screening test may play an important role in prenatal detection and diagnosis of chromosomal anomalies in addition to Down syndrome.

Magnetization transfer contrast imaging of liver cirrhosis

BACKGROUND/AIMS

To test the feasibility of magnetization transfer contrast (MTC) imaging in the evaluation of liver cirrhosis.

METHODOLOGY

Three normal volunteers and 22 cirrhotic liver patients (13 of them harbored hepatoma) were prospectively studied with on-resonance binomial pulsed MTC imaging using a 1.0 Tesla MR scanner. Both MTC and non-MTC images were acquired. The magnetization transfer (MT) effect (defined as: 1-signal intensity of MTC/signal intensity of non-MTC), was used as an indicator and was correlated with different disease status. Lesion-to-liver contrast of non-MTC versus MTC imaging was also compared.

RESULTS

Chronic hepatitis and early fibrosis had a MT effect similar to that of the normal group. Frank cirrhosis had the strongest MT effect. Cirrhosis, when infiltrated by diffuse hepatoma, showed a significantly weaker MT effect than that of the normal group (p<0.05), early cirrhosis (P<0.005), and frank cirrhosis (p<0.05). Overall, the MT effects in these 22 patients were widely variable. There was no significant improvement in lesion contrast of MTC imaging when compared to that of non-MTC imaging due to complex signal attenuation behavior of either the background liver tissue or the tumor itself.

CONCLUSIONS

The complex pathological change of the cirrhotic liver tissue may account for the wide variation of the MT effect and the compromised lesion contrast in cirrhotic patients. Caution should be taken when cirrhotic tissue has an unusually weak MT effect. Then, the possibility of a mixed disease process such as fatty metamorphosis or diffuse hepatoma should be highly suspected. Our experience shows that MTC imaging plays a potential role in the evaluation of the multi-facets of cirrhotic tissue change.

The mouse SLIT family: secreted ligands for ROBO expressed in patterns that suggest a role in morphogenesis and axon guidance

The Slit gene encodes a secreted molecule essential for neural development in Drosophila embryos. Here we report the identification of three Slit homologues in the mouse. We demonstrate that the mouse SLIT1 protein can bind ROBO1, a transmembrane receptor implicated in axon guidance. Both whole-mount and section in situ hybridization studies reveal unique and complementary patterns of expression of the three mouse Slit genes and of Robo1, both within the central nervous system and in other developing tissues. The complementary expression patterns of Slit and Robo1 and their in vitro interaction suggest a ligand-receptor relationship. The expression of all three Slit genes in the floor plate suggests that they are likely to share the same functional properties with their Drosophila homologue in midline neural development and axon guidance. The complementary expression of Slit and Robo1 in different subdivisions of the somites suggests their possible function in axon pathfinding and neural crest cell migration. The unique expression pattern in limb and other organs indicates additional potential functions of the Slit gene family.