Limited recovery following a massive seagrass decline in subarctic eastern Canada.

Over the last few decades, there has been an increasing recognition for seagrasses' contribution to the functioning of nearshore ecosystems and climate change mitigation. Nevertheless, seagrass ecosystems have been deteriorating globally at an accelerating rate during recent decades. In 2017, research into the condition of eelgrass (Zostera marina) along the eastern coast of James Bay, Canada, was initiated in response to reports of eelgrass decline by the Cree First Nations of Eeyou Istchee. As part of this research, we compiled and analyzed two decades of eelgrass cover data and three decades of eelgrass monitoring data (biomass and density) to detect changes and assess possible environmental drivers. We detected a major decline in eelgrass condition between 1995 and 1999, which encompassed the entire east coast of James Bay. Surveys conducted in 2019 and 2020 indicated limited changes post-decline, for example, low eelgrass cover (<25%), low aboveground biomass, smaller shoots than before 1995, and marginally low densities persisted at most sites. Overall, the synthesized datasets show a 40% loss of eelgrass meadows with >50% cover in eastern James Bay since 1995, representing the largest scale eelgrass decline documented in eastern Canada since the massive die-off event that occurred in the 1930s along the North Atlantic coast. Using biomass data collected since 1982, but geographically limited to the sector of the coast near the regulated La Grande River, generalized additive modeling revealed eelgrass meadows are affected by local sea surface temperature, early ice breakup, and higher summer freshwater discharge. Our results caution against assuming subarctic seagrass ecosystems have avoided recent global declines or will benefit from ongoing climate warming.

Long non-coding RNA MALAT1 is up-regulated in ovarian cancer tissue and promotes SK-OV-3 cell proliferation and invasion.

Ovarian cancer is a gynecological malignancy worldwide. Long non-coding RNAs (lncRNAs) research is an emerging area in cancer studies, but little is known about lncRNA metastasis associated lung adenocarcinoma transcript 1 (MALAT1) in ovarian cancer. This study aims to investigate expression and roles of MALAT1 in ovarian cancer. MALAT1 level was detected in 20 ovarian cancer patients. MALAT1 expression was promoted by transforming growth factor ß1 (TGFB1) treatment and inhibited by siRNA transfection in human ovarian cancer cell line SK-OV-3, after which changes in cell viability, proliferation, migration and invasion were analyzed by MTT, colony formation and Transwell assays. Protein levels of mitogen-activated protein kinase factors, including MAPK kinase 1 (MEK1), extracellular signal-regulated kinase (ERK1), p38 and c-Jun N-terminal kinase 1 (JNK1), were detected by western blot. Results showed that MALAT1 was significantly up-regulated in ovarian cancer tissues compared to adjacent normal tissues (P < 0.001), and its expression was correlated to tumor size (r2 = 0.7770, P < 0.0001) and metastasis. TGFB1 and siRNA successfully altered MALAT1 levels in SK-OV-3 cells. Knockdown of MALAT1 suppressed SK-OV-3 cell viability, proliferation, migration and invasion (P < 0.05), and inhibited phosphorylation of MEK1, ERK1, p38 and JNK1, which suggested that MALAT1 promoted ovarian cancer cell proliferation, migration and invasion, and that MAPK pathways might be one of the regulatory mechanisms of MALAT1. This study reveals that MALAT1 is a potential biomarker for tumor growth and metastasis, as well as a promising therapeutic target in ovarian cancer, facilitating further ovarian cancer research.

Meta-analysis of IL-6 -174G/C polymorphism and psoriasis risk.

Previous studies examining the association between interleukin-6 (IL-6) -174G/C polymorphism and psoriasis risk have produced inconsistent results. The aim of this study was to offer a comprehensive review of the association between IL-6 -174G/C polymorphism and psoriasis risk through a meta-analysis. Literature search of PubMed and Embase databases was conducted to identify all eligible studies published before October 29, 2015. Four case-control studies involving 651 psoriasis cases and 552 controls were included in this meta-analysis. Data were extracted, and pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the associations. Combined analysis revealed a significant association between this polymorphism and psoriasis risk under the recessive model (OR = 1.69, 95%CI = 1.12-2.55, P = 0.013 for GG vs GC + CC), and the heterozygous comparison model (OR = 1.70, 95%CI = 1.29-2.23, P < 0.001 for GG vs GC). However, no significant association was observed under the allelic model (OR = 1.37, 95%CI = 0.99-1.89, P = 0.060 for G vs C), the dominant model (OR = 1.25, 95%CI = 0.92-1.71, P = 0.152 for GG + GC vs CC), and the homozygote comparison model (OR = 1.62, 95%CI = 0.79-3.32, P = 0.186 for GG vs CC). We conclude that the IL-6 -174G/C polymorphism contributes to psoriasis risk. However, further studies should be performed to validate our results.

Effect of RNAi-mediated silencing of Livin gene on biological properties of colon cancer cell line LoVo.

This study aimed to investigate the effect of RNAi-mediated silencing of the Livin gene on biological properties of the colon cancer cell line LoVo. Interference vectors pSilencer4.1-Ll and pSilencer4.1-L2 targeting the Livin gene were constructed and transfected into LoVo cells. The expression of the Livin gene was determined by RT-PCR and Western blotting. The apoptosis, cell cycle, colony formation, proliferation of LoVo cells, as well as their sensitivity to cisplatin, were detected by flow cytometry, colony formation assay and MTT. Livin mRNA and protein expression in LoVo cells could be effectively silenced by pSilencer4.1-Ll but not pSilencer4.1-L2. In the pSilencer4.1-Ll transfection group, the apoptosis rate of LoVo cells was significantly higher than in the control group (24.2 ± 3.2 vs 8.1 ± 1.4%, P < 0.01), and after 72 h, cell proliferation was clearly decreased (about 70% inhibition). Compared with the control group, the colony formation rate in pSilencer4.1-Ll transfection group was obviously decreased (15 ± 4.6 vs 85 ± 5.8%, P < 0.01), with increased proportion of S phase cells (45.7 ± 4.9 vs 28.0 ± 3.0%, P < 0.01), decreased proportion of G1 phase cells (43.0 ± 5.2 vs 62.8 ± 5.1%, P < 0.01), and increased sensitivity to cisplatin (apoptosis rate increased from 43.4 ± 6.9 to 65.3 ± 6.2%, P < 0.01). pSilencer4.1-Ll can effectively silence Livin gene expression in LoVo colon cancer cells, inhibit cell proliferation and colony formation, induce apoptosis, and enhance sensitivity to cisplatin.

[Diagnostic value of physical examination tests for supraspinatus tendon tears].

OBJECTIVE: To investigate the diagnostic value of 6 conventional physical examination tests for the diagnosis of supraspinatus tendon tears, and how well they could tell the difference between partial-and full-thickness tears. METHODS: A total of 91 patients with different shoulder symptoms who received shoulder arthroscopic procedure were enrolled in the study from June 2017 to September 2020. The intraoperative findings were compared with the results of the preoperative physical examination of 6 clinical tests, including the Hug-up test, the Jobe test, the 0°abduction test, the drop arm test, the Neer test, and the Hawkins test, to determine the sensitivity, specificity, positive and negative predictive value, accuracy, positive and negative likelihood ratio of each test. RESULTS: By arthroscopy, a total of 44 full-thickness tears, 34 partial-thickness tears, and 13 intact supraspinatus tendons were found in all 91 cases. The Hug-up and the Jobe tests significantly correlated with the intraoperative findings. The sensitivity of the Hug-up test, the Jobe test, the 0° abduction test, the drop arm test, the Neer test, and the Hawkins test was 0.90, 0.79, 0.64, 0.42, 0.49, 0.24 respectively;the specificity was 0.61, 0.69, 0.54, 0.38, 0.31, 0.77;the positive predictive value was 0.93, 0.94, 0.89, 0.80, 0.81, 0.86;the negative predictive value was 0.50, 0.36, 0.20, 0.10, 0.09, 0.14;the accuracy was 0.86, 0.78, 0.63, 0.42, 0.46, 0.32;the positive likelihood ratio was 2.30, 2.58, 1.39, 0.69, 0.71, 1.06;and the negative likelihood ratio was 0.16, 0.30, 0.67, 1.50, 1.65, 0.98. CONCLUSION: The Jobe test and the Hug-up test are both effective at accurately diagnosing supraspinatus tendon tears, the Hug-up test detects supraspinatus tears with a high sensitivity, and similar specificity. The tests assessed in this study are not capable of distinguish between partial-and full thickness supraspinatus tendon tears.

Natural and anthropogenic mercury distribution in marine sediments from Hudson Bay, Canada.

Twelve marine sediment cores from Hudson Bay, Canada, were collected to investigate the response of sub-Arctic marine sediments to atmospherically transported anthropogenic mercury (Hg). Modeling by a two-layer sediment mixing model suggests that the historical Hg deposition to most of the sediment cores reflects the known history of atmospheric Hg deposition in North America, with an onset of increasing anthropogenic Hg emissions in the late 1800s and early 1900s and a reduction of Hg deposition in the mid- to late-1900s. However, although anthropogenic Hg has contributed to a ubiquitous increase in Hg concentrations in sediments over the industrial era, the most elevated industrial-era sedimentary Hg concentrations only marginally exceed the upper preindustrial sedimentary Hg concentrations. Analysis of delta13C and relationship between Hg and organic matter capture suggests that the response of Hudson Bay sediments to changes in atmospheric Hg emissions is largely controlled by the particle flux in the system and that natural changes in organic matter composition and dynamics can cause variation in sedimentary Hg concentrations at least to the same extent as those caused by increasing anthropogenic Hg emissions.

Correlations of CYP11B2 gene polymorphisms with eclampsia.

OBJECTIVE: The aim of this study was to explore the relationship between CYP11B2 gene polymorphisms and eclampsia. PATIENTS AND METHODS: A total of 400 pregnant women treated in our hospital were enrolled in this study, including 200 normal pregnant women (pregnancy group) and 200 pregnant women with eclampsia (eclampsia group). Peripheral blood was collected from subjects of the two groups. Subsequently, genomic deoxyribonucleic acids (DNAs) were extracted and amplified via polymerase chain reaction (PCR) for detection of CYP11B2 rs4543, rs3802228 and rs104894072 polymorphisms. The expression level of CYP11B2 gene was measured as well. Additionally, the correlations of CYP11B2 gene polymorphisms with blood pressure and coagulation and renal function indexes were analyzed. RESULTS: The distribution of alleles of rs4543 locus in CYP11B2 gene was significantly different between eclampsia group and pregnancy group (p=0.027). The frequency of the allele C was significantly lower in eclampsia group than that of pregnancy group (p<0.05). There was a statistically significant difference in the genotype distribution of CYP11B2 rs3802228 (p=0.000) and rs104894072 (p=0.000) between eclampsia group and pregnancy group (p<0.05). Meanwhile, the frequency of AA genotype of rs3802228 and TG genotype of rs104894072 was remarkably higher in eclampsia group than that in pregnancy group (p<0.05). The distribution of the locus rs104894072 (p=0.044) in dominant model and rs3802228 (p=0.002) in recessive model in eclampsia group was different from that in pregnancy group (p<0.05). Eclampsia group showed remarkably elevated frequency of TT + TG of the locus rs104894072 in dominant model and lowered frequency of AG + GG of the locus rs3802228 in recessive model (p<0.05). Similarly, a significant difference was observed in the distribution of the haplotypes CGG (p=0.001) and TGT (p=0.048) in CYP11B2 gene between eclampsia group and pregnancy group (p<0.05). The linkage disequilibrium of the loci rs3802228 and rs104894072 was relatively high (D'=0.382). The polymorphism of the locus rs104894072 in CYP11B2 gene had an evident relation to CYP11B2 gene expression (p<0.05). Meanwhile, the expression of CYP11B2 gene was markedly higher in patients with GG genotype in eclampsia group (p<0.05). The polymorphism of CYP11B2 rs4543 was notably associated with PT level of patients in eclampsia group (p=0.000). Conversely, rs3802228 polymorphism was correlated with 24 h urine protein level (p=0.000). Besides, the proportion of patients with CGG haplotype was significantly larger among patients with systolic blood pressure of 140-160 mmHg (p<0.05). In addition, the proportion of patients with TGT haplotype was evidently greater among patients with systolic blood pressure >180 mmHg in eclampsia group (p<0.05). CONCLUSIONS: CYP11B2 gene polymorphisms are significantly correlated with the development and progression of eclampsia.

MiR-222-5p promotes the growth and migration of trophoblasts by targeting AHNAK.

OBJECTIVE: The purpose of this study was to detect microRNA-222-5p (miR-222-5p) levels in placental tissues of preeclampsia (PE) pregnancies, and to explore the role of miR-222-5p in the proliferative and migratory potentials of trophoblast cell line HTR-8/SVneo. PATIENTS AND METHODS: Expression levels of miR-222-5p and AHNAK in placental tissues of PE pregnancies (n=24) and healthy pregnancies (n=24) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Potential influences of miR-222-5p and AHNAK on proliferative, migratory and apoptotic potentials in HTR-8/SVneo cells were examined. At last, Luciferase assay was conducted to illustrate the interaction between miR-222-5p and AHNAK in trophoblasts. RESULTS: It was found that miR-222-5p was downregulated in placental tissues of PE pregnancies. Overexpression of miR-222-5p stimulated proliferative and migratory potentials, and inhibited apoptosis in HTR-8/SVneo cells. Moreover, AHNAK was the target gene binding to miR-222-5p, and overexpression of AHNAK inhibited proliferative and migratory potentials and promoted apoptosis in HTR-8/SVneo cells. CONCLUSIONS: MiR-222-5p stimulates proliferative and migratory potentials and inhibits apoptosis in HTR-8/SVneo cells by negatively regulating AHNAK.

MiR-134 inhibits infiltration of trophoblast cells in placenta of patients with preeclampsia by decreasing ITGB1 expression.

OBJECTIVE: Preeclampsia (PE) is an idiopathic disorder of pregnancy. The specific regulatory mechanisms of microRNAs (miRs) in the placenta of PE patients have not yet been completely revealed. This study mainly explored the mechanism of miR-134 in preeclampsia. PATIENTS AND METHODS: Real-time PCR and Western blot were used to detect the expression of miR-134 and ITGB1 in the placenta of patients with preeclampsia and normal pregnant women. Dual luciferase reporter assay was performed to detect luciferase activity in miR-134 and NC groups, respectively. Cell proliferation ability after transfection was evaluated by MTS colorimetric assay, and the effect of miR-134 on the infiltration of trophoblast cells was explored by cell invasion experiment. In addition, co-transfection of miR-134 and ITGB1 expression plasmids was carried out, and then changes in the cell invasiveness were also detected by cell invasion experiment. RESULTS: Compared with placenta of normal pregnant women, miR-134 was significantly up-regulated in the placenta of patients with preeclampsia and negatively correlated with the expression of ITGB1. MiR-134 suppressed the infiltration of trophoblast cells by targeting ITGB1. When ITGB1 was overexpressed, the suppression of invasiveness of trophoblast cells by miR-134 was almost abolished. Meanwhile, we found that miR-134 inhibitor could promote the invasiveness of trophoblast cells. In addition, tumor necrosis factor-α (TNF-α) was found to enhance miR-134 expression as well as inhibit ITGB1 expression. CONCLUSIONS: MiR-134 inhibited the infiltration of trophoblast cells in preeclampsia by down-regulating ITGB1 expression.

A deconvolutional Bayesian mixing model approach for river basin sediment source apportionment.

Increasing complexity in human-environment interactions at multiple watershed scales presents major challenges to sediment source apportionment data acquisition and analysis. Herein, we present a step-change in the application of Bayesian mixing models: Deconvolutional-MixSIAR (D-MIXSIAR) to underpin sustainable management of soil and sediment. This new mixing model approach allows users to directly account for the 'structural hierarchy' of a river basin in terms of sub-watershed distribution. It works by deconvoluting apportionment data derived for multiple nodes along the stream-river network where sources are stratified by sub-watershed. Source and mixture samples were collected from two watersheds that represented (i) a longitudinal mixed agricultural watershed in the south west of England which had a distinct upper and lower zone related to topography and (ii) a distributed mixed agricultural and forested watershed in the mid-hills of Nepal with two distinct sub-watersheds. In the former, geochemical fingerprints were based upon weathering profiles and anthropogenic soil amendments. In the latter compound-specific stable isotope markers based on soil vegetation cover were applied. Mixing model posterior distributions of proportional sediment source contributions differed when sources were pooled across the watersheds (pooled-MixSIAR) compared to those where source terms were stratified by sub-watershed and the outputs deconvoluted (D-MixSIAR). In the first example, the stratified source data and the deconvolutional approach provided greater distinction between pasture and cultivated topsoil source signatures resulting in a different posterior distribution to non-deconvolutional model (conventional approaches over-estimated the contribution of cultivated land to downstream sediment by 2 to 5 times). In the second example, the deconvolutional model elucidated a large input of sediment delivered from a small tributary resulting in differences in the reported contribution of a discrete mixed forest source. Overall D-MixSIAR model posterior distributions had lower (by ca 25-50%) uncertainty and quicker model run times. In both cases, the structured, deconvoluted output cohered more closely with field observations and local knowledge underpinning the need for closer attention to hierarchy in source and mixture terms in river basin source apportionment. Soil erosion and siltation challenge the energy-food-water-environment nexus. This new tool for source apportionment offers wider application across complex environmental systems affected by natural and human-induced change and the lessons learned are relevant to source apportionment applications in other disciplines.

Re-engineering adenovirus regulatory pathways to enhance oncolytic specificity and efficacy.

Replicating adenoviruses may prove to be effective anticancer agents if they can be engineered to selectively destroy tumor cells. We have constructed a virus (01/PEME) containing a novel regulatory circuit in which p53-dependent expression of an antagonist of the E2F transcription factor inhibits viral replication in normal cells. In tumor cells, however, the combination of p53 pathway defects and deregulated E2F allows replication of 01/PEME at near wild-type levels. The re-engineered virus also showed significantly enhanced efficacy compared with extensively studied E1b-deleted viruses such as dl1520 in human xenograft tumor models.

Ceramide reduces endothelium-dependent vasodilation by increasing superoxide production in small bovine coronary arteries.

Ceramide serves as a second messenger in a variety of mammalian cells. Little is known regarding the role of ceramide in the regulation of vascular endothelial function. The present study was designed to determine whether ceramide affects endothelium-dependent vasodilation in coronary arteries and to explore the mechanism of action of ceramide. In isolated and pressurized small bovine coronary arteries, cell-permeable C(2)-ceramide (10(-)(5) mol/L) markedly attenuated vasodilator responses to bradykinin and A23187 (by 40% and 60%, respectively). In the presence of K(G)-nitro-L-arginine methyl ester, ceramide produced no further inhibition on the vasodilation induced by these vasodilators. Ceramide had no effect on DETA NONOate-induced vasodilation. By use of a fluorescence NO indicator (4,5-diaminofluorescein diacetate), intracellular NO was measured in the endothelium of freshly isolated small coronary arteries. It was found that ceramide significantly inhibited bradykinin-induced NO increase within endothelial cells. However, it had no effect on the activity of arterial or endothelial NO synthase. Pretreatment of the arteries with sodium dihydroxybenzene disulfonate (Tiron, 10(-)(3) mol/L), a cell-permeable superoxide scavenger, or polyethylene glycol superoxide dismutase (100 U/mL) largely restored the inhibitory effects of ceramide on the vasodilation and NO increase induced by bradykinin or A23187. Moreover, ceramide time-dependently increased intracellular superoxide (O(2)(-. )) in the endothelium, as measured by a fluorescent O(2)(-. )indicator, dihydroethidium. These results demonstrate that ceramide inhibits endothelium-dependent vasodilation in small coronary arteries by decreasing NO in vascular endothelial cells and that this decrease in NO is associated with increased O(2)(-. ) but not with the inhibition of NO synthase activity within these cells.

Characteristics and superoxide-induced activation of reconstituted myocardial mitochondrial ATP-sensitive potassium channels.

Mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels have been suggested as triggers and end effectors in myocardial ischemic preconditioning. However, the intracellular mechanism regulating mitoK(ATP) channels remains unclear. In the present study, mitoK(ATP) channels from bovine ventricular myocardium were reconstituted using planar lipid bilayers, and the effect of superoxide (O(2-.)) on the activity of these reconstituted channels was examined. After incorporation, a potassium-selective current was recorded. The mean conductance of this current was 56 pS at 150 mmol/L KCl, which was substantially inhibited by 1 mmol/L MgATP. 5-Hydroxydecanoate (5-HD, 10 to 100 micromol/L), a selective mitoK(ATP) antagonist, reduced the open state probability (NPo) of these channels in a concentration-dependent manner, whereas diazoxide (10 micromol/L), a selective mitoK(ATP) agonist, significantly increased channel activity. HMR-1098 (100 micromol/L), a selective sarcolemmal K(ATP) antagonist, had no effect on the activity of reconstituted channels. Addition of xanthine/xanthine oxidase (100 micromol/L per 0.038 U/mL), an O(2-.)-generating system, resulted in a marked activation of mitoK(ATP) channels; the NPo of the channels was increased from 0.60+/-0.10 to 1.94+/-0.02. This O(2)(-.)-induced channel activation was completely abolished by pretreatment with 5-HD (100 micromol/L) or a sulfhydryl alkylating compound, N-ethylmaleimide (2 mmol/L). It is concluded that myocardial mitoK(ATP) channels can be reconstituted into lipid bilayers and that O(2-.) activates these channels. The effect of O(2-.) may be associated with its direct action on the sulfhydryl groups of the channel protein.

PCR-DGGE test for direct identification of intestinal bacterial flora in blood feeding ticks in China.

Ticks are vectors of diseases that affect humans and animals worldwide. In current study, the intestinal bacterial flora associated with the blood feeding ticks (Haemaphysalis flava, Haemaphysalis longicornis, Rhipicephalus haemaphysaloides, Boophilus microplus and Dermacentor sinicus) were analyzed using polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) and then sequenced. The five ticks were collected from cattle, dog, hedgehog and goats in Fujian, Shandong, Henan, Jiangxi, Hunan, Shanxi and Guangxi provinces, China. Our results show that nine distinct DGGE bands were found using PCR-DGGE method. Sequences analyses indicated that they belonged to Rickettsia peacockii, Rickettsia raoultii, Rickettsia helvetica, Rickettsia slovaca, Rickettsia tarasevichiae, Coxiella sp., Erwinia sp., Klebsiella pneumoniae and Pseudomonas aeruginos. The present results indicate that zoonotic pathogens are present in ticks in many provinces of China. This useful information will aid in the epidemiology of tick-borne zoonotic diseases in China as well as in raising awareness to avoid tick bites is an important measure to prevent the infection and transmission of zoonotic pathogens.

[Relationships between electrophysiological characteristic of speech evoked auditory brainstem response and Mandarin monosyllable discriminative ability at different hearing impairment].

OBJECTIVE: To investigate the relationships between electrophysiological characteristic of speech evoked auditory brainstem response(s-ABR) and Mandarin phonetically balanced maximum(PBmax) at different hearing impairment, so as to provide more clues for the mechanism of speech cognitive behavior. METHOD: Forty-one ears in 41 normal hearing adults(NH), thirty ears in 30 conductive hearing loss patients(CHL) and twenty-seven ears in 27 sensorineural hearing loss patients(SNHL) were included in present study. The speech discrimination scores were obtained by Mandarin phonemic-balanced monosyllable lists via speech audiometric software. Their s-ABRs were recorded with speech syllables /da/ with the intensity of phonetically balanced maximum(PBmax). The electrophysiological characteristic of s-ABR, as well as the relationships between PBmax and s-ABR parameters including latency in time domain, fundamental frequency(F0) and first formant(F1) in frequency domain were analyzed statistically. RESULTS: All subjects completed good speech perception tests and PBmax of CHL and SNHL had no significant difference (P>0.05), but both significantly less than that of NH (P<0.05). While divided the subjects into three groups by 90%

cDNA cloning of a novel G protein-coupled receptor with a large extracellular loop structure.

A cDNA designated as AZ3B has been isolated from a differentiated HL-6 0 cell cDNA library with a probe derived from the N-formyl peptide receptor gene. The 1.97-kb cDNA encodes a novel G protein-coupled receptor (GPCR) with 482 amino acids. In addition to the predicted 7 transmembrane domains common to all GPCRs, the protein encoded by AZ3B contains a large extracellular loop of approximately 172 amino acids between the fourth and the fifth transmembrane domains, a feature unique among the hundreds of GPCRs identified to date. High sequence homology exists between the AZ3B protein and a number of chemoattractant receptors in the amino-terminal 170 residues and the carboxyl-terminal 150 residues. Northern and flow cytometric analyses suggested that the AZ3B message and protein are widely expressed in several differentiated hematopoietic cell lines, in the lung, placenta, heart, and endothelial cells. We postulate that the AZ3B protein defines a distinct group of receptors within the GPCR superfamily.

Fast inactivation causes rectification of the IKr channel.

The mechanism of rectification of HERG, the human cardiac delayed rectifier K+ channel, was studied after heterologous expression in Xenopus oocytes. Currents were measured using two-microelectrode and macropatch voltage clamp techniques. The fully activated current-voltage (I-V) relationship for HERG inwardly rectified. Rectification was not altered by exposing the cytoplasmic side of a macropatch to a divalent-free solution, indicating this property was not caused by voltage-dependent block of outward current by Mg2+ or other soluble cytosolic molecules. The instantaneous I-V relationship for HERG was linear after removal of fast inactivation by a brief hyperpolarization. The time constants for the onset of and recovery from inactivation were a bell-shaped function of membrane potential. The time constants of inactivation varied from 1.8 ms at +50 mV to 16 ms at -20 mV; recovery from inactivation varied from 4.7 ms at -120 mV to 15 ms at -50 mV. Truncation of the NH2-terminal region of HERG shifted the voltage dependence of activation and inactivation by +20 to +30 mV. In addition, the rate of deactivation of the truncated channel was much faster than wild-type HERG. The mechanism of HERG rectification is voltage-gated fast inactivation. Inactivation of channels proceeds at a much faster rate than activation, such that no outward current is observed upon depolarization to very high membrane potentials. Fast inactivation of HERG and the resulting rectification are partly responsible for the prolonged plateau phase typical of ventricular action potentials.