First Direct Measurement of ^{22}Mg(α,p)^{25}Al and Implications for X-Ray Burst Model-Observation Comparisons

Type-I x-ray bursts can reveal the properties of an accreting neutron star system when compared with astrophysics model calculations. However, model results are sensitive to a handful of uncertain nuclear reaction rates, such as ^{22}Mg(α,p). We report the first direct measurement of ^{22}Mg(α,p), performed with the Active Target Time Projection Chamber. The corresponding astrophysical reaction rate is orders of magnitude larger than determined from a previous indirect measurement in a broad temperature range. Our new measurement suggests a less-compact neutron star in the source GS1826-24.

Erratum: Direct Observation of Proton Emission in ^{11}Be [Phys. Rev. Lett. 123, 082501 (2019)]

This corrects the article DOI: 10.1103/PhysRevLett.123.082501.

P1740Clinical impact of symptom onset-to-balloon time and door-to-balloon time on 1-year adverse event in patients with ST-segment elevation myocardial infarction

Background and objectives

The impact of treatment delays to reperfusion on patient mortality after primary percutaneous coronary intervention (PCI) for ST elevation myocardial infarction (STEMI) is controversial. we evaluated the relation between the delay in the time to reperfusion during primary PCI and the 1-year clinical outcome of patients with STEMI treated by primary angioplasty.

Methods

The study enrolled 6,676 patients (age, 62.5±12.6 years; 26.5% female) with STEMI who underwent primary angioplasty onset between November 2005 and March 2012 from the KAMIR and KorMI Registry. The patients were divided into three groups according to the symptom onset-to-balloon (STB) time: group I, II, III (≤180 minutes, >180 ∼ ≤360 minutes, >360 minutes), and divided into three groups according to the door-to-balloon (DTB) time: group A, B, C (≤90 minutes, >90 ∼ ≤120 minutes, >120 minutes). The 1-year cardiac death and major adverse cardiac event (MACE) rates were compared among the three groups of time variables

Results

The cardiac death rate was 7.9% and MACE rate was 16.9% at one year follow-up. The 1-year cardiac death rate among STB time groups were significantly higher in group II (95% CI=1.05–2.60:p=0.030) and group III (95% CI=1.14–2.74:p=0.011), while that among DTB time groups were not significantly different based on a multivariate Cox proportional analysis, which was adjusted by age, sex, diabetes mellitus, hypertension, systolic blood pressure, left ventricular ejection fraction, peak level of CK-MB, anterior myocardial infarction. The 1-year MACE rate were not significantly different among STB time groups and DTB time group A, B, but was significantly higher in group C (95% CI=1.08–1.58:p=0.006).

Conclusions

These results suggest that, in patient with STEMI treated by primary angioplasty, STB time rather than DTB time was related 1-year clinical outcome especially cardiac death after adjustment for baseline characteristics. Therefore, all efforts should be made to shorten the total ischemic time in patients with acute myocardial infarction

Direct Observation of Proton Emission in ^{11}Be

The elusive β^{-}p^{+} decay was observed in ^{11}Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber in an experiment performed at ISAC-TRIUMF. The measured β^{-}p^{+} branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in ^{11}B above the proton separation energy.

First Measurement of the g Factor in the Chiral Band: The Case of the ^{128}Cs Isomeric State

The g factor of the 56 ns half-life isomeric state in ^{128}Cs has been measured using the time-differential perturbed angular distribution method. This state is the bandhead of the positive-parity chiral rotational band, which emerges when an unpaired proton, an unpaired neutron hole, and an even-even core are coupled such that their angular momentum vectors are aplanar (chiral configuration). g-factor measurements can give important information on the relative orientation of the three angular momentum vectors. The measured g factor g=+0.59(1) shows that there is an important contribution of the core rotation in the total angular momentum of the isomeric state. Moreover, a quantitative theoretical analysis supports the conclusion that the three angular momentum vectors lie almost in one plane, which suggests that the chiral configuration in ^{128}Cs demonstrated in previous works by characteristic patterns of electromagnetic transitions appears only above some value of the total nuclear spin.

Mutual Caring of Elderly Korean Couples

The article described the experiences of elderly couples caring for each other using ethnographic methodology. Ten couples were interviewed in depth. The presence of a support system was found to be the primary requirement of elderly couples. Three taxonomies comprised the support system: (a) desire for respect in care, (b) desire for reliance, and (c) expectation. The close linkage and interaction of desire for care, desire for reliance, and expectations were confirmed. The findings suggested establishing a holistic support network for these elders.

Abstract P2-08-19: Prognostication of HER family gene expression collaborate with ESR1 expression in patients with triple negative breast cancer

Background: Triple-negative breast cancer (TNBC) consists of heterogeneous sub-population. Although many investigators made an effort to categorize and classify TNBCs using genetic expressions, it is still needed to be defined for prognostication Traditionally, HER family genes have been known to contribute mammalian glands formation and breast cancer generation as well as ESR gene. Moreover, target agents for HER family genes have been already developed. Accordingly, we investigated the expression profiles of HER family genes with ESR in patients with TNBC to categorize into sub-types and determine the prognostic value of HER family genes in search of clinical implications.

Methods : We investigated the results of the nCounter expression assay (NanoString®) for ERBB1, ERBB2, ERBB3, ERBB4 and ESR1 using mRNA extract from paraffin-embedded tumor tissues in 203 patients diagnosed as TNBC. We used the results of nCounter expression assay using 84 TNBC tissues for validation and 52 breast cancer tissues diagnosed as other subtypes to control the expression assay results of these five genes.

Results: Two-hundred and three patients were diagnosed as TNBC from 2000 to 2004 and received adjuvant chemotherapy after curative surgery. Eighty-four TNBC patients for validation set and 52 patients diagnosed as other subtypes for control set were selected from the patients diagnosed as breast cancer from 2005 to 2010 and received curative surgery. Through analyzing 5 genes using the nCounter expression profiles from 203 TNBC tissues, we found that increased expression of ERBB4 was associated with poor prognosis by survival analysis (5 year disease recurrence free survival (DRFS), low vs. high expression [cut-off: median]: 90.1% vs. 80.2%; p =.002). This trend was still remained in validation set composed of TNBC (5 year DRFS, low vs. high expression [cut-off : median]: 61.1% vs. 44.0%), whereas was not observed in other subtypes of breast cancer (44.4% vs. 80.8%). The Kaplan-Meier estimates of the rates of 5 year DRFS in the subgroups classified according to the level of 5 genes expression showed that the group of higher expression of all HER family genes and lower expression of ESR1 gene had dismal prognosis rather than other groups in patients with TNBC (5 year DRFS, this group vs. others: 50.0% vs. 88.2%; p <.001). In a multivariate Cox regression model, ERBB4 expression identified as a useful marker for predicting long-term prognosis in patients with TNBC although other HER family genes and ESR1 expressions did not predict prognosis of TNBC with statistical significance (Table 1).

Impact of the m RNA expression levels of ERBB family and ESR1 on DRFS Hazard Ratio95% CIP-valueStage  <.001I1.0NA IIA1.200.40-3.57 IIB3.751.20-11.74 IIIA5.461.55-9.24 IIIC59.9214.30-251.12 EGFR  .167Low1.0NA High1.690.80-3.55 ERBB2  .057Low1.0NA High0.430.18-1.03 ERBB3  .061Low1.0NA High2.200.96-5.04 ERBB4  .016Low1.0NA High2.681.20-5.95 ESR1  .113Low1.0NA High0.570.28-1.15 

Conclusions: The expression profile of HER family genes could be used as a prognostic marker in patients with TNBC. Further study is needed to identify the expression profiles of HER family gene as predictive marker of HER targeting treatment in patients with TNBC.

Citation Format: Kim J-Y, Ahn T, Jung HH, Park K, Do I-G, Kil WH, Kim SW, Lee JE, Nam SJ, Ahn JS, Park YH, Im Y-H. Prognostication of HER family gene expression collaborate with ESR1 expression in patients with triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-08-19.

Prenatal testosterone excess decreases neurokinin 3 receptor immunoreactivity within the arcuate nucleus KNDy cell population

Prenatal exposure of the female ovine foetus to excess testosterone leads to neuroendocrine disruptions in adulthood, as demonstrated by defects in responsiveness with respect to the ability of gonadal steroids to regulate gonadotrophin-releasing hormone (GnRH) secretion. In the ewe, neurones of the arcuate nucleus (ARC), which co-expresses kisspeptin, neurokinin B (NKB) and dynorphin (termed KNDy cells), play a key role in steroid feedback control of GnRH and show altered peptide expression after prenatal testosterone treatment. KNDy cells also co-localise NKB receptors (NK3R), and it has been proposed that NKB may act as an autoregulatory transmitter in KNDy cells where it participates in the mechanisms underlying steroid negative-feedback. In addition, recent evidence suggests that NKB/NK3R signalling may be involved in the positive-feedback actions of oestradiol leading to the GnRH/luteinising hormone (LH) surge in the ewe. Thus, we hypothesise that decreased expression of NK3R in KNDy cells may be present in the brains of prenatal testosterone-treated animals, potentially contributing to reproductive defects. Using single- and dual-label immunohistochemistry we found NK3R-positive cells in diverse areas of the hypothalamus; however, after prenatal testosterone treatment, decreased numbers of NK3R immunoreactive (-IR) cells were seen only in the ARC. Moreover, dual-label confocal analyses revealed a significant decrease in the percentage of KNDy cells (using kisspeptin as a marker) that co-localised NK3R. To investigate how NKB ultimately affects GnRH secretion in the ewe, we examined GnRH neurones in the preoptic area (POA) and mediobasal hypothalamus (MBH) for the presence of NK3R. Although, consistent with earlier findings, we found no instances of NK3R co-localisation in GnRH neurones in either the POA or MBH; in addition, > 70% GnRH neurones in both areas were contacted by NK3R-IR presynaptic terminals suggesting that, in addition to its role at KNDy cell bodies, NKB may regulate GnRH neurones by presynaptic actions. In summary, the finding of decreased NK3R within KNDy cells in prenatal testosterone-treated sheep complements previous observations of decreased NKB and dynorphin in the same population, and may contribute to deficits in the feedback control of GnRH/LH secretion in this animal model.

Astrocyte elevated gene-1 overexpression in hepatocellular carcinoma: an independent prognostic factor

PURPOSE

Astrocyte elevated gene-1 (AEG-1) plays important roles in tumorigenesis such as proliferation, invasion, metastasis, angiogenesis, and chemoresistance. We examined the expression of AEG-1 in patients with hepatocellular carcinoma (HCC).

METHODS

Eighty-five samples were collected from patients with HCC who underwent surgery and were histopathologically confirmed to have HCC. Two independent pathologists, experienced in evaluating immunohistochemistry and blinded to the clinical outcomes of the patients, reviewed all samples. They determined AEG-1 expression semiquantitatively by assessing the percentage of positively stained immunoreactive cells and staining intensity. Clinicopathological data were analyzed in association with prognosis.

RESULTS

The association was estimated by univariate and multivariate analyses with Cox regression. Tumor size (hazard ratio [HR], 2.285; 95% confidence interval [CI], 1.175-4.447; P = 0.015), microvascular invasion (HR, 6.754; 95% CI, 1.631-27.965; P = 0.008), and AEG-1 expression (HR, 4.756; 95% CI, 1.697-13.329; P = 0.003) were independent prognostic factors for overall survival. Those for disease-free survival rate were tumor size (HR, 2.245; 95% CI, 1.282-3.933; P = 0.005) and AEG-1 expression (HR, 1.916; 95% CI, 1.035-3.545; P = 0.038). The cumulative 5-year survival and recurrence rates were 89.2% and 50.0% in the low-expressing group and 24.5% and 82.4% in the high-expressing group, respectively.

CONCLUSION

The results suggest that AEG-1 overexpression could serve as a valuable prognostic marker in patients with HCC.

Incidental cholecystojejunal fistula treated with successful laparoscopic management

Internal biliary fistula (IBF) is occurred spontaneously due to the biliary disease in most cases. Bilioenteric, biliobiliary, bronchobiliary, and vasculobiliary type of IBF have been reported in the literature. We herein describe our experience with an incidental cholecystojejunal fistula, a very rare type of bilioenteric fistula in laparoscopic cholecystectomy. A 61-year-old woman with several years' history of intermittent right upper abdominal pain was admitted to Soonchunhyang University Cheonan Hospital. Abdominal CT scan showed the pneumobilia in gallbladder with common bile duct dilatation. Endoscopic retrograde cholangiopancreatography and endoscopic sphincterotomy were done. On operative findings, there was a cholecystojejunal fistula. We performed laparoscopic cholecystectomy and fistulectomy with jejunal partial resection. To our knowledge, this is the first report on incidental cholecystojejunal fistula uncombined with any other disease and was treated with laparoscopic procedure.

Adrenal lymphangioma masquerading as a pancreatic tail cyst

Cystic lymphangiomas of the adrenal gland are rare. A 79-year-old female presented in the emergency room with epigastric discomfort, and an immovable mass was palpated in her abdomen upon physical examination. Imaging studies revealed a large cystic lesion in the pancreatic tail. The radiologic impression ruled out the possibility of a mucinous cystic neoplasm, or a pseudocyst in the pancreas. The operative findings demonstrated that the cystic mass originated in the left adrenal gland. A laparoscopic excision of the cystic mass was performed, and immunohistochemistry confirmed that this mass was a lymphangioma of the adrenal gland. Several prior reports have suggested that lymphangioma can mimic renal or splenic cysts. However, lymphangioma cases mimicking pancreatic cysts are very rare.

Synthetic lethal screening reveals FGFR as one of the combinatorial targets to overcome resistance to Met-targeted therapy

Met is a receptor tyrosine kinase that promotes cancer progression. In addition, Met has been implicated in resistance of tumors to various targeted therapies such as epidermal growth factor receptor inhibitors in lung cancers, and has been prioritized as a key molecular target for cancer therapy. However, the underlying mechanism of resistance to Met-targeting drugs is poorly understood. Here, we describe screening of 1310 genes to search for key regulators related to drug resistance to an anti-Met therapeutic antibody (SAIT301) by using a small interfering RNA-based synthetic lethal screening method. We found that knockdown of 69 genes in Met-amplified MKN45 cells sensitized the antitumor activity of SAIT301. Pathway analysis of these 69 genes implicated fibroblast growth factor receptor (FGFR) as a key regulator for antiproliferative effects of Met-targeting drugs. Inhibition of FGFR3 increased target cell apoptosis through the suppression of Bcl-xL expression, followed by reduced cancer cell growth in the presence of Met-targeting drugs. Treatment of cells with the FGFR inhibitors substantially restored the efficacy of SAIT301 in SAIT301-resistant cells and enhanced the efficacy in SAIT301-sensitive cells. In addition to FGFR3, integrin β3 is another potential target for combination treatment with SAIT301. Suppression of integrin β3 decreased AKT phosphorylation in SAIT301-resistant cells and restored SAIT301 responsiveness in HCC1954 cells, which are resistant to SAIT301. Gene expression analysis using CCLE database shows that cancer cells with high levels of FGFR and integrin β3 are resistant to crizotinib treatment, suggesting that FGFR and integrin β3 could be used as predictive markers for Met-targeted therapy and provide a potential therapeutic option to overcome acquired and innate resistance for the Met-targeting drugs.

Assessing sources of inconsistencies in genotypes and their effects on genome-wide association studies with HapMap samples

The discordance in results of independent genome-wide association studies (GWAS) indicates the potential for Type I and Type II errors. We assessed the repeatibility of current Affymetrix technologies that support GWAS. Reasonable reproducibility was observed for both raw intensity and the genotypes/copy number variants. We also assessed consistencies between different SNP arrays and between genotype calling algorithms. We observed that the inconsistency in genotypes was generally small at the specimen level. To further examine whether the differences from genotyping and genotype calling are possible sources of variation in GWAS results, an association analysis was applied to compare the associated SNPs. We observed that the inconsistency in genotypes not only propagated to the association analysis, but was amplified in the associated SNPs. Our studies show that inconsistencies between SNP arrays and between genotype calling algorithms are potential sources for the lack of reproducibility in GWAS results.

Detection of heavy metal and hydrocarbon contamination using a miniature resistivity probe

The usefulness of the electrical resistivity method for characterization of contaminated sites has been studied in many ways. The most commonly used device is a cone penetrometer that utilizes two or four electrodes to measure electrical resistivity (or conductivity) during a cone penetration test (CPT) along a vertical or horizontal alignment. This paper introduces a new miniature resistivity probe (MRP) that can potentially be deployed from a sampling platform to detect contaminant plumes prior to collecting soil samples. Following bench-scale tests aimed at quantifying the sensitivity of the MRP to various operating and environmental parameters, the response of the MRP in sandy soil containing various concentrations of tour heavy metals (Cu, Zn, Pb and Ni) and two hydrocarbons (phenol and gasoline) is evaluated. The test data revealed that the MRP has the potential to serve as an indexing tool for rapidly delineating contaminant plumes where heavy metals are present. The results for hydrocarbons were less conclusive, ranging from moderate ability to differentiate contaminated and non-contaminated soils for phenol to poor differentiation ability for gasoline.

Stabilization of nuclear isovector valence-shell excitations

Excited states in 138Ce have been studied via the 12C(138Ce, 138Ce*) Coulomb excitation reaction at 480 MeV. Relative cross sections have been determined from the gamma-ray yields observed with Gammasphere. The E2 and M1 strength distributions between the lowest six 2+ states up to 2.7 MeV enables us to identify the 2(4)+ state in 138Ce as the dominant fragment of the one-phonon 2(1,ms)+ mixed-symmetry state. Mixing between this level and a nearby isoscalar state is observed and is more than 4 times larger than in the neighboring isotone 136Ba. This is direct evidence that the stability of mixed-symmetry states strongly depends on the underlying subshell structure.

New optical frequency domain differential mode delay measurement method for a multimode optical fiber

A novel mode analysis method and differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry has been proposed for the first time. We have used a conventional OFDR with a tunable external cavity laser and a Michelson interferometer. A few-mode optical multimode fiber was prepared to test our proposed measurement technique. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method.

Effects of lipids on the interaction of SecA with model membranes

The effects of nonlamellar-prone lipids, diacylglycerol and phosphatidylethanolamine (PE), on the kinetic association of SecA with model membranes were examined by measuring changes in the intrinsic emission fluorescence with a stopped-flow apparatus. Upon interaction with standard liposomes composed of 50 mol% dioleolyphosphatidylcholine (DOPC) and 50 mol% of dioleoylphosphatidylglycerol (DOPG), the intrinsic fluorescence intensity of SecA was decreased after a lapse of time with a rate constant of 0.0049 s(-1). When the DOPC of the standard vesicles was gradually replaced with either dioeloyl PE (DOPE) or Escherichia coli (E. coli) PE, the rate constant increased appreciably as a function of PE concentration, in the order DOPE > E. coli PE. In addition, when the PE of E. coli PE/DOPG (50/50) vesicles was replaced with more than 5 mol% dioleoylglycerol (DOG), the rate constant further increased by 40%. The incorporation of nonlamellar-prone lipids in the vesicles also enhanced the binding of SecA to model membranes in the order DOPE > or = E. coli PE/DOG > E. coli PE > DOPC. These results provide the first kinetic evidence for the importance of nonlamellar-prone phospholipids for the association rate of SecA with membranes.

ORE9, an F-box protein that regulates leaf senescence in Arabidopsis

Senescence is a sequence of biochemical and physiological events that constitute the final stage of development. The identification of genes that alter senescence has practical value and is helpful in revealing pathways that influence senescence. However, the genetic mechanisms of senescence are largely unknown. The leaf of the oresara9 (ore9) mutant of Arabidopsis exhibits increased longevity during age-dependent natural senescence by delaying the onset of various senescence symptoms. It also displays delayed senescence symptoms during hormone-modulated senescence. Map-based cloning of ORE9 identified a 693-amino acid polypeptide containing an F-box motif and 18 leucine-rich repeats. The F-box motif of ORE9 interacts with ASK1 (Arabidopsis Skp1-like 1), a component of the plant SCF complex. These results suggest that ORE9 functions to limit leaf longevity by removing, through ubiquitin-dependent proteolysis, target proteins that are required to delay the leaf senescence program in Arabidopsis.

Microscopic polyangiitis complicated with massive intestinal bleeding

Microscopic polyangiitis (MPA) is associated with renal dysfunction, in most cases, and occasionally with pulmonary hemorrhage. However, massive intestinal bleeding is a rare manifestation. We report a case of MPA in a man who developed arterial bleeding in the small intestine. A 74-year-old man was admitted after enduring a fever for 4 weeks. Laboratory examination revealed leucocytosis with neutrophil predominance, and renal dysfunction was noted. He did not respond to treatment with antibiotics, and the worsened renal function soon required hemodialysis. On the seventh hospital day, he suddenly developed massive melena. A colonoscopic examination suggested bleeding in the small intestine, and abdominal angiography demonstrated that the bleeding originated in a branch of the ileal artery. Hemostasis was achieved by transarterial embolization (TAE), but the patient suffered a massive pulmonary hemorrhage 2 days after the TAE. Although he responded well to a combination treatment with corticosteroid and cyclophosphamide, recurrence of pulmonary hemorrhage led to death, on the 87th hospital day. MPA in this patient was associated with three serious complications; deteriorating renal function, massive melena, and pulmonary hemorrhage. Of the various manifestations associated with MPA, arterial bleeding in the gastrointestinal tract, although rare, should be considered as one of the serious complications in MPA.

Effect of divalent cations on the ATPase activity of Escherichia coli SecA

It was found that Ca(2+) stimulates the intrinsic SecA ATPase activity in the absence as well as in the presence of liposome. On the other hand, Mg(2+), the general cofactor for ATPase, did not affect the intrinsic SecA ATPase but reduced the portion of ATPase activity enhanced by Ca(2+). The enhancement of SecA ATPase activity correlated well with the increase in 8-anilino-1-naphthalene-sulfonic acid binding of SecA, suggesting that increased exposure of hydrophobic residues stimulates the enzyme activity.

Influence of stent expansion states on platelet deposition in an extracorporeal porcine arteriovenous shunt model using a multichannel perfusion chamber

Limited data are available about incomplete stent expansion (SE) on platelet deposition (PD). We examined PD following different SE using an extracorporeal porcine arteriovenous shunt model to which a perfusion chamber with four parallel silastic tubes were connected. Blood flow was set at a 20 and 100 mL/min in 1.8 and 3.1 mm diameter tubes, respectively. P154 stents were deployed completely (Group A, n=15) or incompletely (Group B, n=15) in 1.8 mm (n=13) and 3.1 mm (n=17) tubes. 51Cr-labelled platelet autologous blood was injected 1 hr before the perfusion. After 15 min-perfusion, the testing tubes were assessed for radioactivity counts. In-stent cross sectional area was measured by intravascular ultrasound. There was a significant difference in PD between group A and B regardless of channel size (118+/-18.4 vs 261.4+/-52.1 pits x 10(6)/cm2, p<0.05). With adjusted shear rate and similar stenosis, PD was similar in both tubes. In smaller 1.8 mm tubes, a stenosis as subtle as 10% was associated with a significant PD difference (226.1+/-20 vs 112.9+/-20.5 plts x 10(6)/cm2, p<0.005). This model enabled a repetitive, simultaneous comparison of PD following different SE states. It seems that the quality of SE remains crucial in smaller channels.

Importance of phosphatidylethanolamine for the interaction of apocytochrome c with model membranes containing phosphatidylserine

The effect of phosphatidylethanolamine (PE) on the binding of apocytochrome c to model membranes was examined. When 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) of the standard vesicles composed of 80% of this lipid and 20% of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS) was gradually replaced with upward of 50% of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), the binding increased appreciably. Ca(2+), causing the phase separation of PS, also brought about increased binding of apocytochrome c in the PC/PS system, underlining the importance of PS properties in membranes for the protein binding. The resonance energy transfer between Trp-59 in apocytochrome c and pyrene-PS incorporated into bilayers showed that the replacement of PC with PE increased the extent of apocytochrome c penetration into membranes by a PE concentration-dependent manner. However, in the absence of PS, PE had no apparent effect on these functions of apocytochrome c, suggesting that PE-induced change(s) of acidic membrane properties is important to the association of apocytochrome c with vesicles. From the observations that the excimer to monomer fluorescence ratio of pyrene-PS increased and the fluorescence of NBD-PS was quenched with increasing concentration of PE, it was deduced that PE caused PS-enriched domains in PC/PE/PS membranes. The colocalization of pyrene-PS with BODIPY-PS by PE further supported the possibility. We suggest that PE-induced formation of PS-enriched domains acts as binding sites for apocytochrome c in membranes.

Phase properties of liquid-crystalline Phosphatidylcholine/Phosphatidylethanolamine bilayers revealed by fluorescent probes

The mixing properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were examined in liquid-crystalline phase using fluorescent probes incorporated into lipid bilayers. The excimer to monomer (E/M) fluorescence ratio of 1-hexadecanoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine (PPC) versus PPC concentration was higher for binary mixtures containing phosphatidylcholine (PC)/phosphatidylethanolamine (PE) (1:1) compared to PC matrix. When POPC was gradually replaced with POPE, the E/M ratio also increased suggesting the enhanced lateral mobility or the lateral enrichment of PPC into domains or both. Evidences for the PE-induced domain formation were further provided by resonance energy transfer between 2-(4, 4-difluoro-5-methyl-4-boro-3a, 4a-diaza-s-indacene-3-dodecanoyl)-1-hexadecanoyl-sn-glycero- 3-phospho choline and PPC, which was enhanced as a function of PE concentration, and by the polarization of 1,6-diphenyl-1,3, 5-hexatriene. In addition, PE reduced free volume and polarity of lipid bilayers as measured by the emission fluorescence of 1,2-bis PPC and 6-lauroyl-2-dimethylaminonaphthalene. When POPE analogs with a methylated head group instead of normal POPE were used, the diminished effect on the domain formation was shown in the order N-methyl PE > N,N-dimethyl PE. The results suggest that the mixing properties of POPE and POPC are not random but that lipid domains of phospholipids are formed.

Molecular interactions in ribose transport: the binding protein module symmetrically associates with the homodimeric membrane transporter

The Escherichia coli high-affinity ribose transporter is composed of the periplasmic ribose-binding protein (RBP or RbsB), the membrane component (RbsC) and the ATP-binding protein (RbsA). In order to dissect the molecular interactions initiating the transport process, RbsC suppressors for transport-defective rbsB mutations were isolated. These suppressors are localized in two regions of RbsC, which are allele-specific to N- or C-terminal domain mutations of RBP, suggesting that there are two distinct regions of RbsC, each interacting with one of the two domains of RBP. To demonstrate that these two regions provide a homodimeric binding surface for RBP we constructed a dimeric rbsC in which two genes are joined tandemly from head to tail with the addition of a linker. The dimeric RbsC protein is stable and functional in growth and ribose uptake. By exploiting the allele specificity between the domain-specific mutations and their suppressors, we generated all mutation-suppressor combinations in a single rbsB plus the dimeric rbsC genes. Their phenotypes are consistent with the proposal that the binding protein module interacts symmetrically with homodimeric RbsC. The mode of association proposed here for the ribose transport components could be extended to other ABC transporters with similar structural organizations.

Phospholipase D activity of cytochrome P450 in human liver endoplasmic reticulum

Phospholipase D (PLD) activity in mammalian liver endoplasmic reticulum (ER) has not been characterized. Purified human liver microsomal cytochromes P450 (P450)-P450 1A2 and P450 2E1-were shown to have appreciable PLD activity, hydrolyzing phosphatidylcholine but not other phospholipids, generating PA and choline. The activity was confirmed using recombinant and mutated human P450s expressed in bacteria. In human liver microsomes, immunoinhibition of PLD activity was observed with anti-P450 1A2 > anti-P450 2C > anti-P450 2E1. Thus, P450 may act as a significant PLD in human liver ER and exert its biological effects by several mechanisms, including signaling functions and change of membrane properties.