Repression of Farnesoid X receptor contributes to biliary injuries of liver grafts through disturbing cholangiocyte bile acid transport

Biliary epithelial damage is the critical point in the development of nonanastomotic strictures, a serious biliary complication after liver transplantation (LT). Current study focuses on the roles and mechanisms of unbalanced bile acid (BA) transporting of cholangiocytes in biliary epithelial damages following LT. Using rat LT models, we observed that biliary transit time (BTT) of BA was prolonged, and the degree and duration of BTT prolongation were related to the cold ischemia time of donor liver. Moreover, prolonged BTT was correlated with bile duct injury severity. The expression of Farnesoid X receptor (FXR) underwent a dramatic decrease after transplantation, and the decrease in FXR was related to cold ischemic time of donor liver. Negative correlation was observed between FXR expression and BTT. With in vitro cultured human biliary epithelial cells, it was observed that FXR expressions and DNA binding activities were repressed under hypoxic conditions. FXR repression by hypoxia mediated unparallel expressions of BA transporters and intracellular accumulation of BAs, which induced higher cell apoptosis rates and enhanced profibrotic factor expression in cholangiocytes. These findings indicated that FXR repression under ischemic/hypoxic conditions contributed to biliary epithelial damages by disturbing BA transporting of cholangiocytes after LT.

Abstract 77: MicroRNA-34a Accelerates Aging in Vascular Smooth Muscle Cells (SMCs) Isolated from Transgenic Mice Overexpressing Nox1 in SMCs

Background: Aging increases cardiovascular morbidity. Aging in vascular smooth muscle cells (VSMC) induces cell senescence, leading to impaired vasodilation with decreased vascular compliance, increased inflammation and oxidative stress. MicroRNA-34a (miR-34a) has been reported as a biomarker of aging.

Methods and Results: After screening for a group of miRs, there was a > 2 fold of miR-34a in aortic SMCs isolated from transgenic mice overexpressing Nox1 in SMCs (Nox-1 SMCs). Therefore, we hypothesized that miR34 contributes to VSMC aging. TaqMan miR assay confirmed an increased miR-34a by 2.1 fold in young NOX-1 SMCs (passage 3-7) with an increase by 5.25 fold in activity of senescence-associated β-galactosidase (SA-β-Gal ) compared to WT. miR-34a in old NOX-1 and WT SMCs (passage 14-16) was increased by 3.8 fold and 2.1 fold, respectively, compared to young SMCs (both P< 0.01 ). There was 1.8 fold more miR-34a detected in old NOX-1 vs. old WT SMCs. SA-β-Gal positive cells accounted for 0.8±1% and 4±1.3% in young WT and NOX-1 SMCs (P<0.01), and 5±1.5% and 32±5% in old WT and NOX-1 SMCs (P <0.005). After transfection with miR-34a inhibitor, mature miR-34a was decreased by 75% and SA-β-Gal activity by 58% in old NOX-1 cells with parallel changes in the protein expression for Gamma-H2AX( a DNA damage marker) and p21( an activator for cell senescence). Moreover, phosphatase nuclear targeting subunit (PNUTS, a recently identified anti-age protein and direct miR-34a target) was not changed in young NOX-1 SMCs but reduced by 78% in old NOX-1 SMCs. Interestingly, nuclear factor (erythroid-derived 2)-like 2 (Nrf2, a key transcription factor for antioxidant genes) mRNA and protein were decreased by 55% and 32% in old NOX-1 SMCs (P<0.01 and 0.05). Nrf2 activator tert-butylhydroquinone (tBHQ) reduced miR-34a from 2.9±0.4 to 1.8±0.2 fold in those cells.

Conclusion: Increased NOX-1 in SMCs induces miR-34a that accelerates SMC senescence. The pathway may involve downregulation of Nrf2 and increased P21 through P53 pathway. This provides potential targets for protecting against vascular aging.

Galectin-7 in cardiac allografts in mice: increased expression compared with isografts and localization in infiltrating lymphocytes and vascular endothelial cells

We sought to identify elevated expression of galectin-7, a T-cell-binding protein, in renal allograft recipients undergoing acute rejection episodes. Allografts and isografts were examined immunohistologically and using quantitative Western blot analysis for galectin-7 protein. The expression of galectin-7 in T lymphocytes from draining lymph nodes in the recipient mice was examined using flow cytometry. We observed galectin-7 to gradually increase with time in the allografts to be significantly higher than that in isografts at days 3, 5, and 7 postoperative: 0.85 ± 0.03 versus 0.69 ± 0.05; 1.15 ± 0.11 versus 0.81 ± 0.02; and 2.02 ± 0.12 versus 0.81 ± 0.05 (P < .05). The majority of galectin-7 was located in the infiltrating lymphocytes and vascular endothelial cells. Furthermore, the percentage of CD4+galectin-7+ and CD8+galectin-7+ T cells from draining lymph nodes in the allograft group was higher than that in the isograft group: 28.0 ± 1.0% versus 1.2 ± 0.2%; and 12.4 ± 0.8% versus 0.4 ± 0.1% (P < .01). In conclusion, galectin-7 relates to acute allograft rejection and T-cell responses possibly as an accelerant.

A synthetic oxygen carrier in fibrin matrices promotes sciatic nerve regeneration in rats

Tissue-engineering nerve conduits have been studied for a long time in bridging large nerve defects. However, the low oxygen availability within the nerve conduits, which results in death of migratory Schwann cells (SC) or loss of the newly formed tissue's function, is still an obstacle for axonal regeneration. Thus, it was hypothesized that an oxygen-enriched conduit would enhance axonal regeneration and functional recovery in vivo. To address this issue, perfluorotributylamine (PFTBA) enriched fibrin hydrogel was prepared and injected into collagen-chitosan conduits. The conduit containing PFTBA-enriched fibrin hydrogel was then used to bridge a 12-mm sciatic nerve defect in rats. The control rats were bridged with collagen-chitosan conduits filled with fibrin matrices without PFTBA. It was found that axonal regeneration and functional recovery in the combined PFTBA group were significantly higher than those in the control group without PFTBA. Further investigations showed that the mRNA and protein levels of S-100, brain-derived neurotrophic factor and nerve growth factor were enhanced by PFTBA at 1 and 3weeks after surgery. However, the mRNA and protein levels of vascular endothelial growth factor were in a similar range between the combined PFTBA group and the control group without PFTBA. In addition, immunohistochemical results showed that the morphological appearances of regenerated nerve and survival of SC were enhanced by PFTBA at 4 and 12weeks after surgery. In conclusion, PFTBA-enriched nerve conduit is capable of enhancing axonal regeneration, which provides a new avenue for achieving better functional recovery in the treatment of nerve defect.

Influence of predispositions on post-traumatic stress disorder: does it vary by trauma severity?

BACKGROUND

Only a minority of trauma victims (<10%) develops post-traumatic stress disorder (PTSD), suggesting that victims vary in predispositions to the PTSD response to traumas. It is assumed that the influence of predispositions is inversely related to trauma severity: when trauma is extreme predispositions are assumed to play a secondary role. This assumption has not been tested. We estimate the influence of key predispositions on PTSD induced by an extreme trauma - associated with a high percentage of PTSD - (sexual assault), relative to events of lower magnitude (accidents, disaster, and unexpected death of someone close).

METHOD

The National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) is representative of the adult population of the USA. A total of 34 653 respondents completed the second wave in which lifetime PTSD was assessed. We conducted three series of multinomial logistic regressions, comparing the influence of six predispositions on the PTSD effect of sexual assault with each comparison event. Three pre-existing disorders and three parental history variables were examined.

RESULTS

Predispositions predicted elevated PTSD risk among victims of sexual assault as they did among victims of comparison events. We detected no evidence that the influence of predispositions on PTSD risk was significantly lower when the event was sexual assault, relative to accidents, disasters and unexpected death of someone close.

CONCLUSIONS

Important predispositions increase the risk of PTSD following sexual assault as much as they do following accidents, disaster, and unexpected death of someone close. Research on other predispositions and alternative classifications of event severity would be illuminating.

Effects of waterborne acephate exposure on antioxidant responses and acetylcholinesterase activities in Synechogobius hasta

The present study was conducted to determine the 24, 48, 72, and 96-h median lethal concentration (LC50) of acephate and investigate the antioxidant response and acetylcholinesterase (AChE) activities in liver, gill, and spleen of Synechogobius hasta exposed to 0 (control), 5, and 10 mg/L acephate, at the fixed interval time of 24, 48, 72, and 96 h, respectively. LC50 value was 60.83 mg/L at 24 h, 51.36 mg/L at 48 h, 47.07 mg/L at 72 h and 40.13 mg/L at 96 h, respectively. Dismutase (SOD), catalase (CAT), AChE activities, and malondialdehyde (MDA) levels in these tissues for the control remained stable over the exposure period. However, for the two tested groups, tissue-, dose-, and time-dependent responses of these parameters were observed in S. hasta. In general, hepatic SOD and CAT activities were significantly inhibited at 24 h, activated, and increased at 48 h, but again inhibited from 48 to 96 h in fish exposed to the two tested concentrations. Hepatic MDA levels of fish for the two tested concentration peaked at 48 h, significantly higher than the control. Hepatic AChE activity was inhibited at 24 h, peaked at 48 h, and then declined at 72 h for the two tested groups. For gills, the highest SOD and CAT activities for the two tested groups were observed at 48 h, higher than the control. AChE activities for the two tested groups were significantly inhibited at 24 h, but activated at 48 h. At 96 h, AChE activities among the treatments showed no significant differences. Gill MDA levels at 48 h for the tested groups were significantly higher than the control, but showed no significant differences at 24 and 72 h among the treatments. In spleen, SOD and CAT activities at 48 h for the two tested groups were significantly higher than those in the control, but at 96 h the vice versa was true. Spleenic AChE activities and MDA levels for the two tested groups were inhibited at 24 h, activated at 48 h, and then were again inhibited at 72 h. Based on these observations earlier, the results obtained in our study will have important toxicological implications for waterborne acephate pollution and, meantime, provide the basis for the effective risk assessment of acephate in water environment and appropriate safety recommendations for fish.

Gonadotrophin-releasing hormone signalling downstream of calmodulin

Gonadotrophin-releasing hormone (GnRH) regulates reproduction via binding a G-protein coupled receptor on the surface of the gonadotroph, through which it transmits signals, mostly via the mitogen-activated protein (MAPK) cascade, to increase synthesis of the gonadotrophin hormones: luteinising hormone (LH) and follicle-stimulating hormone (FSH). Activation of the MAPK cascade requires an elevation in cytosolic Ca(2+) levels, which is a result of both calcium influx and mobilisation from intracellular stores. However, Ca(2+) also transmits signals via an MAPK-independent pathway, through binding calmodulin (CaM), which is then able to bind a number of proteins to impart diverse downstream effects. Although the ability of GnRH to activate CaM was recognised over 20 years ago, only recently have some of the downstream effects been elucidated. GnRH was shown to activate the CaM-dependent phosphatase, calcineurin, which targets gonadotrophin gene expression both directly and indirectly via transcription factors such as nuclear factor of activated T-cells and Nur77, the Transducer of Regulated CREB (TORC) co-activators and also the prolyl isomerase, Pin1. Gonadotrophin gene expression is also regulated by GnRH-induced CaM-dependent kinases (CaMKs); CaMKI is able to derepress the histone deacetylase-inhibition of β-subunit gene expression, whereas CaMKII appears to be essential for the GnRH-activation of all three subunit genes. Asides from activating gonadotrophin gene expression, GnRH also exerts additional effects on gonadotroph function, some of which clearly occur via CaM, including the proliferation of immature gonadotrophs, which is dependent on calcineurin. In this review, we summarise these pathways, and discuss the additional functions that have been proposed for CaM with respect to modifying GnRH-induced signalling pathways via the regulation of the small GTP-binding protein, Gem, and/or the regulator of G-protein signalling protein 2.

Hypertonic saline reduces lipopolysaccharide-induced mouse brain edema through inhibiting aquaporin 4 expression

INTRODUCTION

Three percent sodium chloride (NaCl) treatment has been shown to reduce brain edema and inhibited brain aquaporin 4 (AQP4) expression in bacterial meningitis induced by Escherichia coli. Lipopolysaccharide (LPS) is the main pathogenic component of E. coli. We aimed to explore the effect of 3% NaCl in mouse brain edema induced by LPS, as well as to elucidate the potential mechanisms of action.

METHODS

Three percent NaCl was used to treat cerebral edema induced by LPS in mice in vivo. Brain water content, IL-1β, TNFα, immunoglobulin G (IgG), AQP4 mRNA and protein were measured in brain tissues. IL-1β, 3% NaCl and calphostin C (a specific inhibitor of protein kinase C) were used to treat the primary astrocytes in vitro. AQP4 mRNA and protein were measured in astrocytes. Differences in various groups were determined by one-way analysis of variance.

RESULTS

Three percent NaCl attenuated the increase of brain water content, IL-1β, TNFα, IgG, AQP4 mRNA and protein in brain tissues induced by LPS. Three percent NaCl inhibited the increase of AQP4 mRNA and protein in astrocytes induced by IL-1β in vitro. Calphostin C blocked the decrease of AQP4 mRNA and protein in astrocytes induced by 3% NaCl in vitro.

CONCLUSIONS

Osmotherapy with 3% NaCl ameliorated LPS-induced cerebral edema in vivo. In addition to its osmotic force, 3% NaCl exerted anti-edema effects possibly through down-regulating the expression of proinflammatory cytokines (IL-1β and TNFα) and inhibiting the expression of AQP4 induced by proinflammatory cytokines. Three percent NaCl attenuated the expression of AQP4 through activation of protein kinase C in astrocytes.

One-way transmission of linearly polarized light in plasmonic subwavelength metallic grating cascaded with dielectric grating

We show that optical transmission of linearly polarized light through a plasmonic subwavelength metallic grating cascaded with a dielectric grating at a 45° angle to each other is asymmetric in opposite directions. A key characteristic of this asymmetric transmission is that the polarization of the transmitted light is changed. Simulation results reveal that transmission of 0.92 in one direction and 10(-5) in the opposite direction can be obtained at normal incidence at a wavelength of 1550 nm. Because of their high optical performance and loose fabrication requirements, the structures may provide practical applications in the control of light transmission.

Induction of autophagy and senescence by knockdown of ROC1 E3 ubiquitin ligase to suppress the growth of liver cancer cells

Regulator of Cullins-1 (ROC1) or RING box protein-1 (RBX1) is an essential RING component of Cullin-RING ligase (CRL). Our previous studies showed that ROC1 is required for the growth of several cancer cell lines while ROC1 siRNA silencing inactivates CRL, leading to cell cycle arrest, cell senescence and/or apoptosis. However, it is completely unknown whether ROC1 knockdown triggers autophagic response by inactivating CRL. Moreover, the role of ROC1 in liver cancer remains elusive. In this study, we reported that ROC1 knockdown significantly inhibited the growth of liver cancer cells by sequentially and independently inducing autophagy and p21-dependent cell senescence. Mechanism analysis revealed that ROC1 silencing triggered autophagy by inhibition of mammalian target of rapamycin (mTOR) activity due to accumulation of mTOR-inhibitory protein Deptor, a substrate of CRL. Consistently, Deptor knockdown significantly blocked autophagy response upon ROC1 silencing. Biologically, autophagy response upon ROC1 silencing was a survival signal, and blockage of autophagy pathway sensitized cancer cells to apoptosis. Finally, we demonstrated that ROC1 was overexpressed in hepatocellular carcinomas, which is associated with poor prognosis of liver cancer patients. These findings suggest that ROC1 is an appealing drug target for liver cancer and provide a proof-of-concept evidence for a novel drug combination of ROC1 inhibitor and an autophagy inhibitor for effective treatment of liver cancer by enhancing apoptosis.

Effects of the antioxidant drug tempol on renal oxygenation in mice with reduced renal mass

We tested the hypothesis that reactive oxygen species (ROS) contributed to renal hypoxia in C57BL/6 mice with &frac56; surgical reduction of renal mass (RRM). ROS can activate the mitochondrial uncoupling protein 2 (UCP-2) and increase O(2) usage. However, UCP-2 can be inactivated by glutathionylation. Mice were fed normal (NS)- or high-salt (HS) diets, and HS mice received the antioxidant drug tempol or vehicle for 3 mo. Since salt intake did not affect the tubular Na(+) transport per O(2) consumed (T(Na/)Q(O2)), further studies were confined to HS mice. RRM mice had increased excretion of 8-isoprostane F(2α) and H(2)O(2), renal expression of UCP-2 and renal O(2) extraction, and reduced T(Na/)Q(O2) (sham: 20 ± 2 vs. RRM: 10 ± 1 μmol/μmol; P < 0.05) and cortical Po(2) (sham: 43 ± 2, RRM: 29 ± 2 mmHg; P < 0.02). Tempol normalized all these parameters while further increasing compensatory renal growth and glomerular volume. RRM mice had preserved blood pressure, glomeruli, and patchy tubulointerstitial fibrosis. The patterns of protein expression in the renal cortex suggested that RRM kidneys had increased ROS from upregulated p22(phox), NOX-2, and -4 and that ROS-dependent increases in UCP-2 led to hypoxia that activated transforming growth factor-β whereas erythroid-related factor 2 (Nrf-2), glutathione peroxidase-1, and glutathione-S-transferase mu-1 were upregulated independently of ROS. We conclude that RRM activated distinct processes: a ROS-dependent activation of UCP-2 leading to inefficient renal O(2) usage and cortical hypoxia that was offset by Nrf-2-dependent glutathionylation. Thus hypoxia in RRM may be the outcome of NADPH oxidase-initiated ROS generation, leading to mitochondrial uncoupling counteracted by defense pathways coordinated by Nrf-2.

Protective effects of calcium on copper toxicity in Pelteobagrus fulvidraco: copper accumulation, enzymatic activities, histology

The present study was conducted to determine interactive effects of waterborne co-exposure of copper (Cu) and calcium (Ca) on Cu accumulation, enzymatic activities and histology in yellow catfish Pelteobagrus fulvidraco and test the prediction that Ca could protect against Cu--induced toxicity in the fish species. Yellow catfish were exposed to 0, 1.0, 2.0 mg Cu/l, in combination with 0 and 50 mg Ca/l. Waterborne Cu and Ca co-exposure influenced the majority of tested enzymatic activities (succinate dehydrogenase, malic dehydrogenase, lactate dehydrogenase, lipoprotein lipase and hepatic lipase), and changed Cu contents in several organs (gill, liver, kidney, gastrointestine and muscle). For histological observations, at the same Ca level, waterborne Cu exposure induced injuries in gills and liver. However, Ca addition seemed to mitigate the severity of Cu--induced injuries. Thus, our study demonstrated that Ca had the capacity to reduce Cu toxicity in P. fulvidraco.

p47(phox) is required for afferent arteriolar contractile responses to angiotensin II and perfusion pressure in mice

Myogenic and angiotensin contractions of afferent arterioles generate reactive oxygen species. Resistance vessels express neutrophil oxidase-2 and -4. Angiotensin II activates p47(phox)/neutrophil oxidase-2, whereas it downregulates NOX-4. Therefore, we tested the hypothesis that p47(phox) enhances afferent arteriolar angiotensin contractions. Angiotensin II infusion in p47(phox) +/+ but not -/- mice increased renal cortical NADPH oxidase activity (7±1-12±1 [P<0.01] versus 5±1-7±1 10(3) · RLU · min(-1) · μg protein(-1) [P value not significant]), mean arterial pressure (77±2-91±2 [P<0.005] versus 74±2-77±1 mm Hg [P value not significant]), and renal vascular resistance (7.5±0.4-10.1±0.7 [P<0.01] versus 7.9±0.4-8.3±0.4 mm Hg/mL · min(-1) · gram kidney weight(-1) [P value not significant]). Afferent arterioles from p47(phox) -/- mice had a lesser myogenic response (3.1±0.4 versus 1.4±0.2 dynes · cm(-1) · mm Hg(-1); P<0.02) and a lesser (P<0.05) contraction to 10(-6) M angiotensin II (diameter change +/+: 9.3±0.2-3.4±0.6 μm versus -/-: 9.9±0.6-7.5±0.4 μm). Angiotensin and increased perfusion pressure generated significantly (P<0.05) more reactive oxygen species in p47(phox) +/+ than -/- arterioles. Angiotensin II infusion increased the maximum responsiveness of afferent arterioles from p47(phox) +/+ mice to 10(-6) M angiotensin II yet decreased the response in p47(phox) -/- mice. The angiotensin infusion increased the sensitivity to angiotensin II only in p47(phox) +/+ mice. We conclude that p47(phox) is required to enhance renal NADPH oxidase activity and basal afferent arteriolar myogenic and angiotensin II contractions and to switch afferent arteriolar tachyphylaxis to sensitization to angiotensin during a prolonged angiotensin infusion. These effects likely contribute to hypertension and renal vasoconstriction during infusion of angiotensin II.

Tranilast prevents the progression of chronic cyclosporine nephrotoxicity through regulation of transforming growth factor β/Smad pathways

PURPOSE

Our aim was to investigate the role of tranilast in transforming growth factor (TGF) β/Smad pathways using a rat model of chronic cyclosporine (CsA) nephrotoxicity.

METHODS

Thirty Sprague-Dawley (SD) rats were equally randomized in to 5 groups for gavage treatments daily for 4 weeks: normal control (N), olive oil; CsA (25 mg/kg), (M) CsA plus low-dose tranilast group (T1; CsA 25 mg/kg and tranilast 100 mg/kg); CsA plus medium-dose tranilast group (T2; CsA 25 mg/kg and tranilast 200 mg/kg); and CsA plus high-dose tranilast group (T4; CsA 25 mg/kg and tranilast 400 mg/kg). Kidneys were harvested at the end of the fourth week. TGF-β1 as well as Smad3 and Smad7 were detected by reverse-transcription polymerase chain reaction and immunohistochemistry.

RESULTS

The administration of tranilast decreased the expression of TGF-β1 and Smad3 by CsA-treated rats, whereas it increased both mRNA and protein levels of Smad7. Semiquantitative analysis of mRNA production revealed these treatments to markedly reduce the amount of TGF-β1: T1: 0.8452 ± 0.0825 vs 0.8529 ± 0.0606 (P < .05); T2: 0.8414 ± 0.0696 vs 0.8529 ± 0.0606 (P < .05); T4: 0.8336 ± 0.0592 vs 0.8529 ± 0.0606 (P < .05). For Smad3: T1: 0.8581 ± 0.0328 vs 0.8613 ± 0.0542 (P < .05); T2: 0.8528 ± 0.0599 vs 0.8613 ± 0.0542 (P < .05); T4: 0.8436 ± 0.0185 vs 0.8613 ± 0.0542 (P < .05). The significantly elevated dose-dependent amounts of Smad7 were: T1: 0.9026 ± 0.0522 vs 0.8678 ± 0.0246, (P < .05); T2: 0.9087 ± 0.0506 vs 0.8678 ± 0.0246 (P < .05); T4: 0.9151 ± 0.0793 vs 0.8678 ± 0.0246 (P < .05).

CONCLUSION

Regulation of TGF-β/Smad pathways is one of the mechanisims by which tranilast mitigates the progression of chronic CsA nephrotoxicity in rats.

Effect of waterborne zinc exposure on metal accumulation, enzymatic activities and histology of Synechogobius hasta

The present study was conducted to determine the metal accumulation, antioxidant enzymatic response, hepatic intermediary metabolism and histological changes in Synechogobius hasta exposed to 0.35 (control), 9.7 and 19.2mg/L Zn, respectively, on the 0, 4th, 8th and 12th day. Waterborne Zn exposure significantly reduced hepatosomatic index, hepatic lipid contents and fatty liver occurrence rate, increased Zn, Fe and Mn contents and reduced the contents of Cu and Ca in liver, and increased muscle Zn content. Waterborne Zn exposure also significantly influenced enzymatic activities involved in antioxidant responses (superoxide dismutase, catalase, glutathione-S-transferase, malondialdehyde) in liver and spleen, and changed hepatic intermediary enzymatic activities (succinate dehydrogenase, malic dehydrogenase, lactate dehydrogenase, lipoprotein lipase, hepatic lipase), impaired the histological structure of the gill and spleen, and reduced vacuolated hepatocytes. Thus, our study demonstrated for the first time that waterborne Zn exposure could reduce fatty liver syndrome in S. hasta.

Radiation dose in coronary artery angiography with 320-detector row CT and its diagnostic accuracy: comparison with 64-detector row CT

AIM

The aim of this study was the comparison of image quality, diagnostic accuracy and radiation dose of ECG-gated volume scan mode of 320-detector row CT with 64-detector row CT.

METHODS

A hundred and twenty patients receiving coronary artery CT angiography (CTA) were divided into two groups. Sixty patients in Group A underwent 64-detector row CTA; for the remainder, Group B, 320-detector row CT was used. Conventional coronary angiography was then performed in all patients. In Group B, patients with a pulse <65 beat/min underwent a prospective ECG-gated volume scan using a 70-80% R-R phase window and 1-beat, whereas a 30-80% R-R phase window, 2-beat CT was performed in patients with a pulse >65 beat/min.

RESULTS

In Group A, 247 vessels and 920 segments were assessed; in Group B, 242 and 906. In 320-detector row CTA, the coronary stenosis diagnosis' specificities were 98%, 96%, and 95% at the segmental, vessel, and patient levels, respectively (98%, 94%, and 92% in 64-detector row CTA); the negative predictive values were 99%, 98%, and 100% (98%, 97%, and 95% in 64-detector row CTA). There was no significant difference in specificity or negative predictive values between the groups. The average effective radiation dose in Group B was lower than in Group A (P<0.001). In Group B, the dose for 48 patients with 70-80% R-R phase window, 1-beat scan, was lower than for the remaining 12 patients (30-80% R-R phase window, 2-beat) (P<0.001).

CONCLUSION

The 320-detector CT reduces the radiation exposure by approximately 80% compared with 64-detector CT, with similar diagnostic accuracy and image quality.