Heavy Ion Irradiation Reduces Vulnerability to Atrial Tachyarrhythmias　- Gap Junction and Sympathetic Neural Remodeling.

BACKGROUND: Low-invasive stereotactic body radiation therapy is a novel anti-arrhythmic strategy. The mechanisms underlying its effects against ventricular tachycardia/fibrillation (VT/VF) are gradually becoming clear, whereas those underlying atrial tachycardia/fibrillation (AT/AF) remain unknown. This study investigated the effects of carbon ion beam on gap junction expression and sympathetic innervation.Methods and Results: Atrial and ventricular tachyarrhythmia models was established in 26 hypercholesterolemic (HC) 3-year-old New Zealand white rabbits; 12 rabbits were irradiated with a single 15-Gy carbon ion beam (targeted heavy ion irradiation [THIR]) and 14 were not (HC group). Eight 3-month-old rabbits (Young) were used as a reference group. In vivo induction frequencies in the Young, HC, and HC+THIR groups were 0%, 9.9%, and 1.2%, respectively, for AT/AF and 0%, 7.8%, and 1.2%, respectively, for VT/VF (P<0.01). The conduction velocity of the atria and ventricles on optical mapping was significantly reduced in the HC group; this was reversed in the HC+THIR group. Connexin-40 immunolabelling in the atria was 66.1-78.7% lower in the HC than Young group; this downregulation was less pronounced in the HC+THIR group (by 23.1-44.4%; P<0.01). Similar results were obtained for ventricular connexin-43. Sympathetic nerve densities in the atria and ventricles increased by 41.9-65.3% in the HC vs. Young group; this increase was reversed in the HC+THIR group. CONCLUSIONS: Heavy ion radiation reduced vulnerability to AT/AF and VT/VF in HC elderly rabbits and improved cardiac conductivity. The results suggest involvement of connexin-40/43 upregulation and suppression of sympathetic nerve sprouting.

Revisitation of imaging features of skull base chondrosarcoma in comparison to chordoma.

PURPOSE: Pre-surgical diagnosis of skull base chondrosarcoma (SBC) is often challenging due to the resemblance to chordoma. The goal of this study was to develop an optimal method for predicting SBC diagnosis. METHODS: This retrospective study included patients with histologically diagnosed SBC and skull base chordoma. Their clinical and radiologic features were compared, and the predictive factors of SBC were examined. RESULTS: Forty-one patients with SBC and 41 with chordoma were included. Most SBCs exhibited hypointensity (25, 64.1%) or isointensity (12, 30.8%) on T1-weighted images, and hyperintensity (34, 87.1%) or mixed intensity (5, 12.8%) on T2-weighted images. MRI contrast enhancement was usually avid or fair (89.7%) with "arabesque"-like pattern (41.0%). The lateral/paramidline location was more common in SBC than in chordoma (85.4% vs. 9.8%; P < 0.01), while midline SBCs (14.6%) were also possible. Multivariate analysis demonstrated that higher apparent diffusion coefficient (ADC) value (unit odds ratio 1.01; 95% confidence interval 1.00-1.02; P < 0.01) was associated with an SBC diagnosis. An ADC value of ≥ 1750 × 10-6 mm2/s demonstrated a strong association with an SBC diagnosis (odds ratio 5.89 × 102; 95% confidence interval 51.0-6.80 × 103; P < 0.01) and yielded a sensitivity of 93.9%, specificity of 97.4%, positive predictive value of 96.9%, and negative predictive value of 95.0%. CONCLUSION: The ADC-based method is helpful in distinguishing SBC from chordoma and readily applicable in clinical practice. The prediction accuracy increases when other characteristics of SBC, such as non-midline location and arabesque-like enhancement, are considered together.

Occipital artery-anterior cerebral artery bypass with posterior auricular artery-middle cerebral artery bypass for stenosis of the internal carotid artery bifurcation.

Superficial temporal artery (STA)-middle cerebral artery (MCA) bypass, and STA-anterior cerebral artery (ACA) bypass, are options for direct revascularisation of anterior circulation. However, some patients don't have a suitable STA to use as a donor, so an alternative procedure must be performed. A 59-year-old, right-handed man presented with dysphasia and right-sided hemiparesis due to a transient ischaemic attack. Imaging studies revealed severe stenosis of the left internal carotid artery bifurcation. Iodoamphetamine single photon emission computed tomography demonstrated reduced cerebrovascular reserve capacity in the left hemisphere. The patient was started on antiplatelet therapy, but the ischaemic attacks persisted after one month. Thus, revascularisation of the ACA and MCA territories was considered. Digital subtraction angiography revealed prominence in the left occipital artery (OA) and posterior auricular artery (PAA), while the left STA was hypoplastic, terminating at the squamous suture level. Therefore, anastomoses were performed between both the OA and ACA and the PAA and MCA. Revascularisation was successful, and the ischaemic attacks disappeared. OA-ACA bypass, together with PAA-MCA bypass, may be effective for wide cerebral revascularisation when the STA is not available.

Partial IK1 blockade destabilizes spiral wave rotation center without inducing wave breakup and facilitates termination of reentrant arrhythmias in ventricles.

It has been reported that blockade of the inward rectifier K(+) current (IK1) facilitates termination of ventricular fibrillation. We hypothesized that partial IK1 blockade destabilizes spiral wave (SW) re-entry, leading to its termination. Optical action potential (AP) signals were recorded from left ventricles of Langendorff-perfused rabbit hearts with endocardial cryoablation. The dynamics of SW re-entry were analyzed during ventricular tachycardia (VT), induced by cross-field stimulation. Intercellular electrical coupling in the myocardial tissue was evaluated by the space constant. In separate experiments, AP recordings were made using the microelectrode technique from right ventricular papillary muscles of rabbit hearts. Ba(2+) (10-50 µM) caused a dose-dependent prolongation of VT cycle length and facilitated termination of VT in perfused hearts. Baseline VT was maintained by a stable rotor, where an SW rotated around an I-shaped functional block line (FBL). Ba(2+) at 10 µM prolonged I-shaped FBL and phase-singularity trajectory, whereas Ba(2+) at 50 µM transformed the SW rotation dynamics from a stable linear pattern to unstable circular/cycloidal meandering. The SW destabilization was not accompanied by SW breakup. Under constant pacing, Ba(2+) caused a dose-dependent prolongation of APs, and Ba(2+) at 50 µM decreased conduction velocity. In papillary muscles, Ba(2+) at 50 µM depolarized the resting membrane potential. The space constant was increased by 50 µM Ba(2+) Partial IK1 blockade destabilizes SW rotation dynamics through a combination of prolongation of the wave length, reduction of excitability, and enhancement of electrotonic interactions, which facilitates termination of ventricular tachyarrhythmias.

A Case of Multiple Coronary Artery-Left Ventricular Micro Fistulae Complicated With Hepatic Arteriovenous Fistulae.

We present the first case of multiple coronary artery-left ventricular micro fistulae complicated with hepatic arteriovenous fistulae (AVF) in an adult patient. Multiple coronary artery fistulae originated from the left anterior descending coronary artery with aneurysmal change. Multiple coronary artery-left ventricular micro fistulae presented on the left ventricular wall and showed significant localized hypertrophic change. Stress and enhanced cardiac magnetic resonance imaging (CMR) revealed myocardial ischemia that could not be detected by stress Tl-201 cardiac scintigraphy, and late patchy gadolinium enhancement (LGE) in the mid-ventricular wall apex. This LGE pattern did not match the typical pattern observed in patients with apical hypertrophic cardiomyopathy. These observations may help distinguish multiple coronary artery-associated myocardial ischemia and hypertrophy from apical cardiomyopathy.

Invention of an Online Interactive Virtual Neurosurgery Simulator With Audiovisual Capture for Tactile Feedback.

BACKGROUND: Present neurosurgical simulators are not portable. OBJECTIVE: To maximize portability of a virtual surgical simulator by providing online learning and to validate a unique psychometric method ("audiovisual capture") to provide tactile information without force feedback probes. METHODS: An online interactive neurosurgical simulator of a posterior petrosectomy was developed. The difference in the hardness of compact vs cancellous bone was presented with audiovisual effects as inclinations of the drilling speed and sound based on engineering perspectives. Three training methods (the developed simulator, lectures and review of slides, and dissection of a 3-dimensional printed temporal bone model [D3DPM]) were evaluated by 10 neurosurgical residents. They all first attended a lecture and were randomly allocated to 2 groups by the training D3DPM (A: simulator; B: review of slides, no simulator). In D3DPM, objective measures (required time, quality of completion, injury scores of important structures, and the number of instructions provided) were compared between groups. Finally, the residents answered questionnaires. RESULTS: The objective measures were not significantly different between groups despite a younger tendency in group A (graduate year -2.4 years, 95% confidence interval -5.3 to 0.5, P = .081). The mean perceived hardness of cancellous bone on the simulator was 70% of that of compact bone, matching the intended profile. The simulator was superior to lectures and review of slides in feedback and repeated practices and to D3DPM in adaptability to multiple learning environments. CONCLUSION: A novel online interactive neurosurgical simulator was developed, and satisfactory validity was shown. Audiovisual capture successfully transmitted the tactile information.

De-Identification Technique with Facial Deformation in Head CT Images.

Head CT, which includes the facial region, can visualize faces using 3D reconstruction, raising concern that individuals may be identified. We developed a new de-identification technique that distorts the faces of head CT images. Head CT images that were distorted were labeled as "original images" and the others as "reference images." Reconstructed face models of both were created, with 400 control points on the facial surfaces. All voxel positions in the original image were moved and deformed according to the deformation vectors required to move to corresponding control points on the reference image. Three face detection and identification programs were used to determine face detection rates and match confidence scores. Intracranial volume equivalence tests were performed before and after deformation, and correlation coefficients between intracranial pixel value histograms were calculated. Output accuracy of the deep learning model for intracranial segmentation was determined using Dice Similarity Coefficient before and after deformation. The face detection rate was 100%, and match confidence scores were < 90. Equivalence testing of the intracranial volume revealed statistical equivalence before and after deformation. The median correlation coefficient between intracranial pixel value histograms before and after deformation was 0.9965, indicating high similarity. Dice Similarity Coefficient values of original and deformed images were statistically equivalent. We developed a technique to de-identify head CT images while maintaining the accuracy of deep-learning models. The technique involves deforming images to prevent face identification, with minimal changes to the original information.

Reproducibility of Facial Information in Three-Dimensional Reconstructed Head Images: An Exploratory Study.

BACKGROUND: Facial information acquired via three-dimensional reconstruction of head computed tomography (CT) data may be considered personal information, which can be problematic for neuroimaging studies. However, no study has verified the relationship between slice thickness and face reproducibility. This study determined the relationship and match rate between image slice thickness and face detection accuracy of face-recognition software in facial reconstructed models. METHODS: Head CT data of 60 cases comprising entire faces obtained under conditions of non-contrast and 1-mm slice thickness were resampled to obtain 2-10-mm slice-thickness data. Facial models, reconstructed by image thresholding, were acquired from the data. We performed face detection tests per slice thickness on the models and calculated the face detection rate. The reconstructed facial models created from 1-mm slice-thickness data and other slice thicknesses were used as training and test data, respectively. Match confidence scores were obtained via three programs, match rates were calculated per slice thickness, and generalized estimating equations were used to evaluate the match rate trend. RESULTS: In general, the face detection rates for the 1-10-mm slice thicknesses were 100, 100, 98.3, 98.3, 95.0, 91.7, 86.7, 78.3, 68.3, and 61.7 %, respectively. The match rates for the 2-10-mm slice thicknesses were 100, 98.3, 98.3, 95.0, 85.0, 71.7, 53.3, 28.3, and 16.7 %, respectively. CONCLUSION: The reconstructed models tended to have higher match rates as the slice thickness decreased. Thus, thin-slice head CT imaging data may increase the possibility of the information becoming personally identifiable health information.

Symptomatic Change of an Intracranial Neuroepithelial Cyst 7 Years After Its Incidental Finding.

A natural course of asymptomatic neuroepithelial cysts (NECs) is poorly understood due to its rarity. Herein we report a 23-year-old female patient of an asymptomatic NEC which grew in size from 1 cm to 5 cm and caused progressive symptoms seven years after its incidental finding. Partial resection of the cyst was performed for decompression and pathological examination and effectively achieved symptoms alleviation and regression of the cyst. Our case showed the importance of regular follow-up because NECs may show symptomatic change even in the late phase.

Hypofractionated Stereotactic Radiotherapy with CyberKnife for Large Arteriovenous Malformations and Arteriovenous Malformations Located in Eloquent Areas.

Literature has yet to establish an appropriate treatment strategy for large arteriovenous malformations (AVMs) and AVMs located in eloquent areas. In this study, the treatment outcomes of hypofractionated stereotactic radiotherapy (HSRT) with CyberKnife (CK) for large AVMs and AVMs in eloquent areas were evaluated. This study retrospectively evaluated 38 consecutive patients with AVMs treated with HSRT in the Japanese Red Cross Medical Center between August 2010 and July 2015. Obliteration rates and hemorrhage rates at 3- and 5-years of follow-up were calculated. Factors for hemorrhage and obliteration were analyzed with logistic regression analysis. Fourteen (36.8%) patients had a history of hemorrhage. Twenty (52.6%) AVMs were larger than 10 mL, and 34 (89.5%) AVMs were located in eloquent areas. The majority of the AVMs (84.2%) were classified into high grades (grades 3, 4, and 5) using the Spetzler-Martin grading scale. The median modified radiosurgery-based AVM score was 2.05, and the median Virginia Radiosurgery AVM Score was 3. The mean marginal dose was 24.5 ± 2.5 Gy. Twenty-three and 15 patients received three- and five-fraction stereotactic radiotherapy, respectively. At 3 and 5 years posttreatment, two (2.0%/year) and six (6.7%/year) patients had hemorrhage with obliteration rates of 15.2% and 16.7%, respectively. AVM localization in eloquent areas was a risk factor for obliteration failure. This study revealed that HSRT with CK for large AVMs and AVMs located in eloquent areas contributed to hemorrhage risk reduction and obliteration, at least in the early stages.

A Case of Enigmatic Stroke Caused by Severe Systemic Sepsis: The Importance of Careful Assessment of Insidious Systemic Infection.

Severe sepsis is a dreaded disease with high mortality, especially in the case of delayed detection. Early diagnosis and treatment initiation is critical for patient survival. However, the septic conditions might be masked by other clinical conditions such as stroke, which may result in a serious delay in diagnosis and treatment. We report a case of iliopsoas abscess that initially presented with cerebellar infarction and subarachnoid hemorrhage. Although severe neurological symptoms were prominent, some signs indicating systemic infection, such as "psoas position", prompted us to investigate the existence of systemic infection. Consequently, severe sepsis with multiple infectious foci, such as iliopsoas abscess, purulent spondylitis, mitral valve valvulitis, and brain abscess, was revealed and was detected as the cause of stroke. The timely and accurate diagnosis of sepsis minimized the delay of the initiation of antibiotic treatment. Approximately five months of intensive care, including two heart valve surgeries, cured the patient, and she was discharged with no neurological deficit. This case demonstrates the importance of careful assessment of the insidious systemic infection as a covert cause of stroke.

Rotors anchored by refractory islands drive torsades de pointes in an experimental model of electrical storm.

BACKGROUND: Electrical storm (ES) is a life-threatening emergency in patients at high risk of ventricular tachycardia/ventricular fibrillation (VF), but the pathophysiology and molecular basis are poorly understood. OBJECTIVE: The purpose of this study was to explore the electrophysiological substrate for experimental ES. METHODS: A model was created by inducing chronic complete atrioventricular block in defibrillator-implanted rabbits, which recapitulates QT prolongation, torsades des pointes (TdP), and VF episodes. RESULTS: Optical mapping revealed island-like regions with action potential duration (APD) prolongation in the left ventricle, leading to increased spatial APD dispersion, in rabbits with ES (defined as ≥3 VF episodes/24 h). The maximum APD and its dispersion correlated with the total number of VF episodes in vivo. TdP was initiated by an ectopic beat that failed to enter the island and formed a reentrant wave and perpetuated by rotors whose centers swirled in the periphery of the island. Epinephrine exacerbated the island by prolonging APD and enhancing APD dispersion, which was less evident after late Na+ current blockade with 10 µM ranolazine. Nonsustained ventricular tachycardia in a non-ES rabbit heart with homogeneous APD prolongation resulted from multiple foci with an electrocardiographic morphology different from TdP driven by drifting rotors in ES rabbit hearts. The neuronal Na+-channel subunit NaV1.8 was upregulated in ES rabbit left ventricular tissues and expressed within the myocardium corresponding to the island location in optically mapped ES rabbit hearts. The NaV1.8 blocker A-803467 (10 mg/kg, intravenously) attenuated QT prolongation and suppressed epinephrine-evoked TdP. CONCLUSION: A tissue island with enhanced refractoriness contributes to the generation of drifting rotors that underlies ES in this model. NaV1.8-mediated late Na+ current merits further investigation as a contributor to the substrate for ES.

Accurate Preoperative Identification of Motor Speech Area as Termination of Arcuate Fasciculus Depicted by Q-Ball Imaging Tractography.

BACKGROUND: Tractography is one way to predict the distribution of cortical functional domains preoperatively. Diffusion tensor tractography (DTT) is commonly used in clinical practice, but is known to have limitations in delineating crossed fibers, which can be overcome by Q-ball imaging tractography (QBT). We aimed to compare the reliability of these 2 methods based on the spatial correlation between the arcuate fasciculus depicted by tractography and direct cortical stimulation during awake surgery. METHODS: In this study, 15 patients with glioma underwent awake surgery with direct cortical stimulation. Tractography was depicted in a three-dimensional computer graphic model preoperatively, which was integrated with a photograph of the actual brain cortex using our novel mixed-reality technology. The termination of the arcuate fasciculus depicted by either DTT or QBT and the results of direct cortical stimulation were compared, and sensitivity and specificity were calculated in speech-associated brain gyri: pars triangularis, pars opercularis, ventral precentral gyrus, and middle frontal gyrus. RESULTS: QBT had significantly better sensitivity and lower false-positive rate than DTT in the pars opercularis. The same trend was noted for the other gyri. CONCLUSIONS: QBT is more reliable than DTT in identification of the motor speech area and may be clinically useful in brain tumor surgery.

Nonrheumatoid Retro-Odontoid Pseudotumors: Characteristics, Surgical Outcomes, and Time-Dependent Regression After Posterior Fixation.

OBJECTIVE: Although a retro-odontoid pseudotumor associated with rheumatoid arthritis is a well-known clinical entity, little is known about retro-odontoid pseudotumors not associated with rheumatoid arthritis due to their rarity. METHODS: Between 2006 and 2019, consecutive patients with nonrheumatoid pseudotumors were included and retrospectively compared with patients with rheumatoid pseudotumors. RESULTS: Nineteen patients had nonrheumatoid pseudotumors (mean age, 73 ± 6 years; male, 53%). All had cervical lesions including ossified anterior and posterior longitudinal ligaments with a history of cervical surgery in 5. The mean thickness of the pseudotumors at diagnosis was 8.1 mm (range, 4.2-17.2 mm). Pseudotumor thickness had a significant negative correlation with the atlantodental interval (p = 0.008) and the subaxial range of motion (p = 0.049). In comparison with 7 rheumatoid pseudotumor patients, nonrheumatoid pseudotumor patients were older (p = 0.042), had a higher proportion of males (p = 0.023), had a smaller atlantodental interval (p = 0.007), and had larger pseudotumors at diagnosis (p = 0.030). Of the 19 patients, 18 received posterior fixation with or without C1 laminectomy, while the other received C1 laminectomy alone. The percent pseudotumor thickness at follow-up to those at diagnosis was 91%, 77%, 68%, 46%, 58%, and 49% at 1, 3, 6, 12, 24, and 36 months after surgery, respectively. CONCLUSION: This study revealed markedly clinical and radiological differences between nonrheumatoid and rheumatoid pseudotumors. The main etiology for nonrheumatoid pseudotumors was subaxial cervical degeneration and ossified lesions. There were good outcomes following posterior fixation and time-dependent pseudotumor regression within 12 months.

Differential action of chlorinated polycyclic aromatic hydrocarbons on aryl hydrocarbon receptor-mediated signaling in breast cancer cells.

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs), which are a series of halogenated aromatic hydrocarbons, have been found in the environment. The primary step in their metabolic activation seems to be associated with aryl hydrocarbon receptor (AhR)-mediated induction of the cytochrome P450 (CYP) 1 family, although the evidence remains unclear. In this study, we first investigated the effects of five ClPAHs with three to five rings and the corresponding parent PAHs on the expression of CYP1A1 and 1B1 in human breast cancer MCF-7 cells. For the targeted ClPAHs, Western blot analysis of ClPAH-induced CYP1A1 and 1B1 showed an enhancement in activities in comparison with induction by the corresponding parent PAHs, and the effects of chlorination were especially prominent in phenanthrene. In a further study, using 6-chlorobenzo[a]pyrene (6-ClBaP), cotreatment with 17beta-estradiol showed an increase in the expression of CYP1B1 mRNA but not CYP1A1 mRNA. Since the AhR ligand has been reported to induce formation of an AhR-estrogen receptor (ER) complex, which stimulates transcription of ER target genes, the effects of ClPAHs in MCF-7 cells transfected with estrogen response elements-regulated green fluorescent protein (GFP) reporter genes were also investigated in this study. 6-ClBaP induced a dose-dependent increase in GFP expression related to ER signaling through AhR activation in the cells, but 3,9,10-trichlorophenanthrene (3,9,10-Cl(3)ClPhe) did not, despite its ability to activate AhR. Furthermore, we investigated the effect of ClPAHs on the expression of the endogenous ER-responsive genes, cathepsin D, in MCF-7 cells. 6-ClBaP stimulated expression of the ER-responsive genes but 3,9,10-Cl(3)ClPhe did not, as in the GFP expression system. These results suggest that estrogenic action mediated ER signaling through AhR activation does not necessarily occur for every ligand that can activate AhR.

Measurement of bisphenol A concentrations in human colostrum.

Bisphenol A (BPA), an estrogenic endocrine disrupting chemical, has been reported to affect embryos and alter their postnatal development. In the present study, we measured the concentrations of BPA in human colostrum by a competitive enzyme-linked immunosorbent assay (ELISA) with the aim of understanding the present status of BPA burden in human breast milk in Shizuoka, Japan. Human colostral samples were collected from 101 healthy mothers within three days after delivery. The BPA concentrations of colostral samples were estimated by ELISA after the acetonitrile extraction and solid phase extraction column purification. BPA in 101 samples was detected in the concentration range of 1-7 ng ml(-1). The mean concentration of BPA was 3.41+/-0.13 (mean+/-SD) ng ml(-1). This is the first demonstration as to what BPA concentrations are in human colostrum. The BPA concentrations in colostrum were higher than those in blood sera samples obtained from healthy women in a previous study. In our study, there was no significant correlation between the concentrations of BPA in colostrum and the age and parity of mothers.

Formation of chlorinated estrones via hypochlorous disinfection of wastewater effluent containing estrone.

Chlorinated derivatives of estrone (E1) in the effluent of a municipal sewage treatment plant located in Shizuoka prefecture, Japan were detected by gas chromatography/mass spectrometry using electron impact in selected ion monitoring (GC/MS-EI-SIM) analysis. The concentrations of E1, 2-chloroestrone, 4-chloroestrone and 2,4-dichloroestrone in the effluent sample collected in December 2005 were 60.0 ng l(-1), 4.0 ng l(-1), 14.5 ng l(-1), and 9.8 ng l(-1), respectively. In the effluent sample taken in June 2005, 2,4-dichloroestrone was detected at 5.6 ng l(-1) along with 17.6 ng l(-1) of E1. However, only E1 was detected at 5.9 ng l(-1) in the sample in May 2005. To elucidate the behavior of E1 during the disinfection process with sodium hypochlorite in the sewage treatment plant, we carried out a reaction of E1 with sodium hypochlorite in buffer solutions at pH 7 and 9. As E1 was consumed rapidly, chlorinated estrones were produced and relatively fast formation of 2-chloroestrone, 4-chloroestrone, and 2,4-dichloroestrone was observed. Furthermore, 1,4-estradiene-3,17-dione derivatives were formed from the reaction between 2,4-dichloroestrone and sodium hypochlorite.

Estrogenic activity of the chlorinated derivatives of estrogens and flavonoids using a GFP expression system.

Estrogenic chemicals are widely reported to be present in the environment. Their chlorinated derivatives are considered to be produced through the chlorination process in water purification and sewage treatment plants. In this study, several chlorinated derivatives of estrogens and flavonoids, including phytoestrogens, were synthesized by the reaction with hypochlorous acid, and their estrogenic activities were investigated using a devised GFP expression system in human breast carcinoma MCF7 cells. The chlorinated derivatives were less estrogenic than the parent compounds. The EC(50) ranking of estrogen-related compounds was 17ß-estradiol (E2)>4-ClE2>estrone (E1)>4-ClE1>10-Cl-1,4-estradiene-3,17-dione (10-Cl-3,17-dione)>2-ClE2>2-ClE1. 2,4-diClE2, 2,4-diClE1, and 2,4,16,16-tetraClE1 showed lower or no estrogenic activity. Genistein and daidzein are well known as phytoestrogens. 6,8-diCl-genistein, 3',8-diCl-daidzein, (+)-6,8-diCl-naringenin, and 6,8-diCl-apigenin showed lower estrogenic activity than their parent compounds. 3',5',8-triCl-daidzein exhibited no estrogenic activity. No activity was detected in chrysin, (+)-catechin, and their chlorinated derivatives. Similar results were obtained in a cell proliferation assay using MCF7 cells.

Extended atrial conduction system characterised by the expression of the HCN4 channel and connexin45.

OBJECTIVE: In the heart, there are multiple supraventricular pacemakers involved in normal pacemaking as well as arrhythmias and the objective was to determine the distribution of HCN4 (major isoform underlying the pacemaker current, I(f)) in the atria. METHODS: In the atria of the rat, the localisation of HCN4 and connexins was determined using immunohistochemistry, and electrical activity was recorded using extracellular electrodes. RESULTS: As expected, HCN4 and Cx45 (but not Cx43) were expressed in the sinoatrial node extending from the superior vena cava down the crista terminalis. The same pattern of expression of HCN4 and connexins was observed in a novel tract of nodal-like cells extending from the superior vena cava down the interatrial groove. Although the sinoatrial node was usually the leading pacemaker site, the novel tract of HCN4-expressing cells was capable of pacemaking and could act as the leading pacemaker site; there was evidence of a hierarchy of pacemakers. The same pattern of expression of HCN4 and connexins was also observed in the atrioventricular ring bundle (including the atrioventricular node) encircling the tricuspid valve, but not in the atrioventricular ring bundle encircling the mitral valve. HCN4 was not expressed in the pulmonary veins. CONCLUSIONS: The widespread distribution of HCN4 can explain the widespread location of the leading pacemaker site during sinus rhythm, the extensive region of tissue that has to be ablated to stop sinus rhythm, and the widespread distribution of ectopic foci responsible for atrial tachycardia.