No abstract

IntroductionSevere hyperkalemia, with potassium (K+) levels ≥ 6.5 mEq/L, is a potentially life-threatening electrolyte imbalance. For prompt and effective treatment, it is important to know its risk factors, clinical manifestations, and predictors of mortality.MethodsAn observational cohort study was performed at 2 medical centers. A total of 923 consecutive Korean patients were analyzed. All were 19 years of age or older and were hospitalized with severe hyperkalemia between August 2007 and July 2010; the diagnosis of severe hyperkalemia was made either at the time of admission to the hospital or during the period of hospitalization. Demographic and baseline clinical characteristics at the time of hyperkalemia diagnosis were assessed, and clinical outcomes such as in-hospital mortality were reviewed, using the institutions' electronic medical record systems.ResultsChronic kidney disease (CKD) was the most common underlying medical condition, and the most common precipitating factor of hyperkalemia was metabolic acidosis. Emergent admission was indicated in 68.6% of patients, 36.7% had electrocardiogram findings typical of hyperkalemia, 24.5% had multi-organ failure (MOF) at the time of hyperkalemia diagnosis, and 20.3% were diagnosed with severe hyperkalemia at the time of cardiac arrest. The in-hospital mortality rate was 30.7%; the rate was strongly correlated with the difference between serum K+ levels at admission and at their highest point, and with severe medical conditions such as malignancy, infection, and bleeding. Furthermore, a higher in-hospital mortality rate was significantly associated with the presence of cardiac arrest and/or MOF at the time of diagnosis, emergent admission, and intensive care unit treatment during hospitalization. More importantly, acute kidney injury (AKI) in patients with normal baseline renal function was a strong predictor of mortality, compared with AKI superimposed on CKD.ConclusionsSevere hyperkalemia occurs in various medical conditions; the precipitating factors are similarly diverse. The mortality rate is especially high in patients with severe underlying disease, coexisting medical conditions, and those with normal baseline renal function.

Mdm2 is a cellular antagonist of p53 that keeps a balanced cellular level of p53. The two proteins are linked by a negative regulatory feedback loop and physically bind to each other via a putative helix formed by residues 18 -26 of p53 transactivation domain (TAD) and its binding pocket located within the N-terminal 100-residue domain of mdm2 (Kussie, P. H., Gorina, S., Marechal, V., Elenbaas, B., Moreau, J., Levine, A. J., and Pavletich, N. P. (1996) Science 274, 948 -953). In a previous report we demonstrated that p53 TAD in the mdm2-freee state is mostly unstructured but contains two nascent turns in addition to a "preformed" helix that is the same as the putative helix mediating p53-mdm2 binding. Here, using heteronuclear multidimensional NMR methods, we show that the two nascent turn motifs in p53 TAD, turn I (residues 40 -45) and turn II (residues 49 -54), are also capable of binding to mdm2. In particular, the turn II motif has a higher mdm2 binding affinity (ϳ20 M) than the turn I and targets the same site in mdm2 as the helix. Upon mdm2 binding this motif becomes a well defined full helix turn whose hydrophobic face formed by the side chains of Ile-50, Trp-53, and Phe-54 inserts deeply into the helix binding pocket. Our results suggest that p53-mdm2 binding is subtler than previously thought and involves global contacts such as multiple "non-contiguous" minimally structured motifs instead of being localized to one small helix mini-domain in p53 TAD.p53 is known to be implicated in more than 50% of all human cancers and probably represents one of the proteins that is most critically associated with cancer (1, 2). Understanding how this "hub" in the cancer protein network interacts with other members of the network is not only important for gaining insights into fundamental principles underlying tumorigenesis but also for efficient development of anticancer agents (3-6). Ironically, establishing a structure-function relationship for p53 has been possible only for ϳ30% of its amino acid residues; namely, for those forming globular domains, a DNA binding domain (7) and an oligomerization domain (8, 9). This fact can be attributed to a rather interesting finding that a large fraction (ϳ70%) of amino acid residues in p53 does not participate in forming a well defined tertiary structure, a common feature shared by many intrinsically unstructured proteins (IUPs) 2 (10 -16).IUPs are an interesting class of proteins that maintain their function despite the lack of a well defined globular structure. Structurally, IUPs are in a similar state as folding intermediates but are distinct from the latter in that they are not in an artificially denatured state. Although some IUPs totally lack any structural elements, others have minimal secondary structural elements (12,16,(17)(18)(19). One subgroup of IUPs consists of unstructured or flexible domains consisting of more than ϳ50 amino acid residues within large mother proteins (12,20,21). Because of their flexible nature, structural features of IUPs can be characterized ...

Dopamine (DA) modulates central neuronal activity through both phasic (second to second) and tonic (minutes to hours) terminal release. Conventional fast-scan cyclic voltammetry (FSCV), in combination with carbon fiber microelectrodes, has been used to measure phasic DA release in vivo by adopting a background subtraction procedure to remove background capacitive currents. However, measuring tonic changes in DA concentrations using conventional FSCV has been difficult because background capacitive currents are inherently unstable over long recording periods. To measure tonic changes in DA concentrations over several hours, we applied a novel charge-balancing multiple waveform FSCV (CBM-FSCV), combined with a dual background subtraction technique, to minimize temporal variations in background capacitive currents. Using this method, in vitro, charge variations from a reference time point were nearly zero for 48 h, whereas with conventional background subtraction, charge variations progressively increased. CBM-FSCV also demonstrated a high selectivity against 3,4-dihydroxyphenylacetic acid and ascorbic acid, two major chemical interferents in the brain, yielding a sensitivity of 85.40 ± 14.30 nA/μM and limit of detection of 5.8 ± 0.9 nM for DA while maintaining selectivity. Recorded in vivo by CBM-FSCV, pharmacological inhibition of DA reuptake (nomifensine) resulted in a 235 ± 60 nM increase in tonic extracellular DA concentrations, while inhibition of DA synthesis (α-methyl-dl-tyrosine) resulted in a 72.5 ± 4.8 nM decrease in DA concentrations over a 2 h period. This study showed that CBM-FSCV may serve as a unique voltammetric technique to monitor relatively slow changes in tonic extracellular DA concentrations in vivo over a prolonged time period.

No abstract

The preS1 surface antigen of hepatitis B virus (HBV) is known to play an important role in the initial attachment of HBV to hepatocytes. We have characterized structural features of the full-length preS1 using heteronuclear NMR methods and discovered that this 119-residue protein is inherently unstructured without a unique tertiary structure under a nondenaturing condition. Yet, combination of various NMR parameters shows that the preS1 contains ''pre-structured'' domains broadly covering its functional domains. The most prominent domain is formed by residues 27-45 and overlaps with the putative hepatocyte-binding domain (HBD) encompassing residues 21-47, within which two welldefined pre-structured motifs, formed by Pro 32 -Ala 36 and Pro 41 -Phe 45 are found. Additional, somewhat less prominent, pre-structured motifs are also formed by residues 11-18, 22-25, 37-40, and 46-50. Overall results suggest that the preS1 is a natively unstructured protein (NUP) whose N-terminal 50 residues, populated with multiple pre-structured motifs, contribute critically to hepatocyte binding.Keywords: hepatitis B virus; preS1; NMR; natively unstructured protein; pre-structured motif Supplemental material: see www.proteinscience.org Hepatitis B virus (HBV) is a member of the hepadnaviridae family (Ganem and Varmus 1987;Chisari et al. 1989) that poses a significant health threat to millions of people worldwide, particularly in Africa, Asia, and certain parts of Europe (Fung and Lok 2004;Wright 2006). Whereas HBV infection itself may not appear so fatal as AIDS or SARS chronic hepatitis B infection often develops into more serious symptoms such as cirrhosis, liver failure, and hepatocelluar carcinoma (Blumberg et al. 1989). While successful administration of HBV vaccines led to a significant reduction of HBV-related casualties (Stephenne 1990;Mahoney et al. 1993;Jilg 1998;Poland and Jacobson 2004), emergence of escape mutants or nonresponders to current vaccines argues for attempts to develop vaccines with better efficacy. In addition, more specific anti-HBV therapeutics are needed in order to completely eradicate HBV infection, since nucleoside drugs currently in use for HBV-related symptoms are not HBV specific, often causing side effects or inducing drug resistance. Efforts to discover anit-HBVspecific agents based upon natural products or siRNAs have been met with only partial success (Saag 2006;Shin et al. 2006).Even though it is generally accepted that HBV infection begins with an attachment of HBV surface antigens to a HBV-specific hepatocyte receptor, followed by subsequent entry of viral DNA into hepatocyte (Neurath 3 These authors contributed equally to this work. Reprint requests to: Kyou-Hoon Han, Molecular Cancer Research Center, Division of Molecular Therapeutics, KRIBB, Daejeon 305-806, Korea; e-mail: khhan600@kribb.re.kr; fax: 82-42-860-4259.Abbreviations: HBV, hepatitis B virus; NMR, nuclear magnetic resonance; NUP, natively unstructured protein; CSI, chemical-shift index.Article published online ahead of pr...

The timing of referral to a nephrologist may influence the outcome of chronic kidney disease patients, but its impact has not been evaluated thoroughly. The results of a recent study showing an association between early referral and patient survival are still being debated. A total of 1028 patients newly diagnosed as end-stage renal disease (ESRD) from July 2008 to October 2011 were enrolled. Early referral (ER) was defined as patients meeting with a nephrologist more than a year before dialysis and dialysis education were provided, and all others were considered late referral (LR). The relationship of referral pattern with mortality in ESRD patients was explored using a Cox proportional hazards regression models. Time from referral to dialysis was significantly longer in 599 ER patients than in 429 LR patients (62.3±58.9 versus 2.9±3.4 months, P<0.001). Emergency HD using a temporary vascular catheter was required in 485 (47.2%) out of all patients and in 262 (43.7%) of ER compared with 223 (52.0%) of LR (P = 0.009). After 2 years of follow-up, the survival rate in ER was better than that in LR (hazard ratio [HR] 2.38, 95% confidence interval [CI] 1.27–4.45, P = 0.007). In patients with diabetes nephropathy, patient survival was also significantly higher in ER than in LR (HR 4.74, 95% CI 1.73–13.00, P = 0.002). With increasing age, HR also increased. Timely referral to a nephrologist in the predialytic stage is associated with reduced mortality.

Aged population with comorbidities demonstrated high mortality rate and severe clinical outcome in the patients with coronavirus disease 2019 (COVID-19). However, whether age-adjusted Charlson comorbidity index score (CCIS) predict fatal outcomes remains uncertain. This retrospective, nationwide cohort study was performed to evaluate patient mortality and clinical outcome according to CCIS among the hospitalized patients with COVID-19 infection. We included 5621 patients who had been discharged from isolation or had died from COVID-19 by April 30, 2020. The primary outcome was composites of death, admission to intensive care unit, use of mechanical ventilator or extracorporeal membrane oxygenation. The secondary outcome was mortality. Multivariate Cox proportional hazard model was used to evaluate CCIS as the independent risk factor for death. Among 5621 patients, the high CCIS (≥ 3) group showed higher proportion of elderly population and lower plasma hemoglobin and lower lymphocyte and platelet counts. The high CCIS group was an independent risk factor for composite outcome (HR 3.63, 95% CI 2.45–5.37, P < .001) and patient mortality (HR 22.96, 95% CI 7.20–73.24, P < .001). The nomogram showed that CCIS was the most important factor contributing to the prognosis followed by the presence of dyspnea (hazard ratio [HR] 2.88, 95% confidence interval [CI] 2.16–3.83), low body mass index < 18.5 kg/m 2 (HR 2.36, CI 1.49–3.75), lymphopenia (<0.8 x10 9 /L) (HR 2.15, CI 1.59–2.91), thrombocytopenia (<150.0 x10 9 /L) (HR 1.29, CI 0.94–1.78), anemia (<12.0 g/dL) (HR 1.80, CI 1.33–2.43), and male sex (HR 1.76, CI 1.32–2.34). The nomogram demonstrated that the CCIS was the most potent predictive factor for patient mortality. The predictive nomogram using CCIS for the hospitalized patients with COVID-19 may help clinicians to triage the high-risk population and to concentrate limited resources to manage them.