Discordant Observations Research Articles

Salmonella actively modulates TFEB in murine macrophages in a growth-phase and time-dependent manner.

Activation of the host transcription factor TFEB helps mammalian cells adapt to stresses such as starvation and infection by upregulating lysosome, autophagy, and immuno-protective gene expression. Thus, TFEB is generally thought to protect host cells. However, it may also be that pathogenic bacteria like Salmonella orchestrate TFEB in a spatio-temporal manner to harness its functions to grow intracellularly. Indeed, the relationship between Salmonella and TFEB is controversial since some studies showed that Salmonella actively promotes TFEB, while others have observed that Salmonella degrades TFEB and that compounds that promote TFEB restrict bacterial growth. Our work provides a path to resolve these apparent discordant observations since we showed that stationary-grown Salmonella actively delays TFEB after infection, while late-log Salmonella is permissive of TFEB activation. Nevertheless, the exact function of this manipulation remains unclear, but conditions that erase the conditional control of TFEB by Salmonella may be detrimental to the microbe.

Outlier detection in a few catchments of the Godavari river basin: A case study

The efficiency of the Grubbs-Beck test and the multiple Grubbs-Beck tests to detect discordant observations are compared in this research using a few catchment areas of the Godavari river basin in Maharashtra, India. The Multiple Grubbs-Beck tests are proven to be more effective than the original Grubbs-Beck tests when applied to the Weibull distribution. When using the Grubbs test, only one lower discordant observation was identified in all of the river stations, and no lower discordant observation was found in the Somanpally river station when using the Multiple Grubbs Beck test (MGBT) five survey catchments.

Emergency activations for chest pain and ventricular arrhythmias related to regional COVID-19 across the US

Evidence that patients may avoid healthcare facilities for fear of COVID-19 infection has heightened the concern that true rates of myocardial infarctions have been under-ascertained and left untreated. We analyzed data from the National Emergency Medical Services Information System (NEMSIS) and incident COVID-19 infections across the United States (US) between January 1, 2020 and April 30, 2020. Grouping events by US Census Division, multivariable adjusted negative binomial regression models were utilized to estimate the relationship between COVID-19 and EMS cardiovascular activations. After multivariable adjustment, increasing COVID-19 rates were associated with less activations for chest pain and non-ST-elevation myocardial infarctions. Simultaneously, increasing COVID-19 rates were associated with more activations for cardiac arrests, ventricular fibrillation, and ventricular tachycardia. Although direct effects of COVID-19 infections may explain these discordant observations, these findings may also arise from patients delaying or avoiding care for myocardial infarction, leading to potentially lethal consequences.

Evolutionary course of the femoral head osteonecrosis: Histopathological - radiologic characteristics and clinical staging systems.

Osteonecrosis of the femoral head (ONFH) is a recalcitrant ischemic disorder, which could be classified into two major categories: traumatic and nontraumatic. Regardless of different risk factors, it has been testified that ONFH results from primitive vascular problems, leading to temporary or permanent loss of blood supply to bone tissue. Histopathological and microarchitectural alterations ensues, which is a gradual evolutionary process involving bone marrow and osteocyte necrosis, progressive destruction of subchondral bone, unsuccessful reparative process, and eventual articular collapse and degenerative arthritis. Based on the imaging features of ONFH, different classification systems have been developed to evaluate the severity and prognosis of the disease, which is pivotal for implementation of treatment strategy, especially the joint-preserving surgery. However, patients classified with the same severity stage, especially in the peri-collapse stage, sometimes responded differently after similar joint-preserving surgery. The unusual phenomenon may be attributed to the limitation of the current imaging classification systems, which might underestimate the disease severity, especially when referring to the early stages. In this review, we briefly summarize the etiology and pathogenesis of ONFH. The imaging features and staging classification systems of ONFH are also described. More importantly, we focus on histopathological and microstructural alterations of the femoral head, and provide an overview of their essential contribution to ONFH progression. Given the observation of discordance between imaging characteristics and histopathological alterations, a substantial amount of research on the relationship between imaging and histopathological features is required to further modify and revise the current wide-accepted classification systems.

Canadian contributions to research on neglected tropical diseases.

BackgroundThe World Health Organization’s (WHO) Neglected Tropical Disease (NTD) Road Map for 2021–2030 was recently endorsed by all member states at the World Health Assembly in November 2020. Although only 3 of the 20 NTDs are endemic in Canada (i.e., echinococcosis, rabies, and scabies), the Canadian research community has contributed to advancing the knowledge base of all 20 NTDs. Previous research comprehensively detailed Canadian research on 11 NTDs between 1950 and 2010 using a network analysis approach. The specific objective of the present analysis was to update the publication record over the last decade (2010–2019) to include all 20 NTDs.Materials and methodsA bibliometric analysis was conducted in Scopus and Web of Science databases (for English or French articles published between January 1, 2010 and December 31, 2019) using appropriate search terms for each of the 20 NTDs and where at least 1 of the authors had a Canadian institution address. A 21st search was added to include publications including multiple NTDs or a discussion of NTDs in general. Following assessment of inclusion and exclusion criteria, 2 reviewers independently screened all abstracts, with discordant observations rereviewed to arrive at an agreement. Duplicates were removed.ResultsA total of 1,790 publications were retrieved (1,738 with a disease–specific NTD focus and 52 with a general NTD focus, resulting in 1,659 unique publications), giving an average of over 160 articles per year. Over 80% were classified as full–length research articles. The top 3 journals in terms of frequency were PLOS Neglected Tropical Diseases, PLOS ONE, and the American Journal of Tropical Medicine and Hygiene. Authors’ institutions were from all Canadian provinces. While all 20 NTDs were addressed in these publications, the 5 most commonly studied were leishmaniasis, dengue fever and chikungunya, Chagas disease, soil–transmitted helminthiases, and rabies.ConclusionsCanadian researchers across the country have contributed to the evidence base of all 20 NTDs, publishing an average of over 160 publications per year between 2010 and 2019. As WHO NTD Road Map 2021–2030 rolls out globally, the Canadian research community, in collaboration with its partners and in solidarity with people living in vulnerable circumstances in endemic regions worldwide, is well positioned to meet future research challenges so that the goal of eliminating the disease burden attributable to NTDs can be achieved.

HIF-1α and HIF-2α redundantly promote retinal neovascularization in patients with ischemic retinal disease.

Therapies targeting VEGF have proven only modestly effective for the treatment of proliferative sickle cell retinopathy (PSR), the leading cause of blindness in patients with sickle cell disease. Here, we shift our attention upstream from the genes that promote retinal neovascularization (NV) to the transcription factors that regulate their expression. We demonstrated increased expression of HIF-1α and HIF-2α in the ischemic inner retina of PSR eyes. Although both HIFs participated in promoting VEGF expression by hypoxic retinal Müller cells, HIF-1 alone was sufficient to promote retinal NV in mice, suggesting that therapies targeting only HIF-2 would not be adequate to prevent PSR. Nonetheless, administration of a HIF-2-specific inhibitor currently in clinical trials (PT2385) inhibited NV in the oxygen-induced retinopathy (OIR) mouse model. To unravel these discordant observations, we examined the expression of HIFs in OIR mice and demonstrated rapid but transient accumulation of HIF-1α but delayed and sustained accumulation of HIF-2α; simultaneous expression of HIF-1α and HIF-2α was not observed. Staggered HIF expression was corroborated in hypoxic adult mouse retinal explants but not in human retinal organoids, suggesting that this phenomenon may be unique to mice. Using pharmacological inhibition or an in vivo nanoparticle-mediated RNAi approach, we demonstrated that inhibiting either HIF was effective for preventing NV in OIR mice. Collectively, these results explain why inhibition of either HIF-1α or HIF-2α is equally effective for preventing retinal NV in mice but suggest that therapies targeting both HIFs will be necessary to prevent NV in patients with PSR.

Prevalence of Genetically Complex Leishmania Strains With Hybrid and Mito-Nuclear Discordance.

Approximately 20 Leishmania species are known to cause cutaneous, mucocutaneous, and visceral disorders in humans. Identification of the causative species in infected individuals is important for appropriate treatment and a favorable prognosis because infecting species are known to be the major determinant of clinical manifestations and may affect treatments for leishmaniasis. Although Leishmania species have been conventionally identified by multilocus enzyme electrophoresis, genetic analysis targeting kinetoplast and nuclear DNA (kDNA and nDNA, respectively) is now widely used for this purpose. Recently, we conducted countrywide epidemiological studies of leishmaniasis in Ecuador and Peru to reveal prevalent species using PCR-RFLP targeting nDNA, and identified unknown hybrid parasites in these countries together with species reported previously. Furthermore, comparative analyses of kDNA and nDNA revealed the distribution of parasites with mismatches between these genes, representing the first report of mito-nuclear discordance in protozoa. The prevalence of an unexpectedly high rate (~10%) of genetically complex strains including hybrid strains, in conjunction with the observation of mito-nuclear discordance, suggests that genetic exchange may occur more frequently than previously thought in natural Leishmania populations. Hybrid Leishmania strains resulting from genetic exchanges are suggested to cause more severe clinical symptoms when compared with parental strains, and to have increased transmissibility by vectors of the parental parasite species. Therefore, it is important to clarify how such genetic exchange influences disease progression and transmissibility by sand flies in nature. In addition, our aim was to identify where and how the genetic exchange resulting in the formation of hybrid and mito-nuclear discordance occurs.

The relationship between released soluble FceRI-alpha and its cell surface density on human basophils.

BackgroundThe IgE-mediated activation of mast cells and basophils results in the secretion of many substances, including the release of FceRI-alpha subunit. This released alpha subunit can bind IgE and it may act as a down-regulator of subsequent IgE-dependent reactions. However, previous studies do not observe loss of the mass of FceRI-alpha associated with the cells, at least not for human basophils. This study was designed to understand the basis for the discordant observations.MethodsPurified human basophils were stimulated with multiple activating secretagogues and supernatants were examined for histamine and released FceRI-alpha. In addition, cell surface IgE densities (occupied and unoccupied) were measured by flow cytometry and total cellular content of mature and immature FceRI-alpha determined with Western blots.ResultsReleased FceRI-alpha, on average, represented 7% of the total surface FceRI before the reaction. The molecular weight of the soluble FceRI-alpha was approximately 54 kD, larger than immature subunit and somewhat smaller than surface subunit. In addition, 1) release ceased long before internalized FceRI-alpha was processed, 2) release was insensitive to Bafilomycin A, 3) release was independent of the starting density of FceRI and 4) release occurred more effectively with non-IgE-dependent stimuli, FMLP or C5a.ConclusionsThere appears to be relatively constant amount of nearly mature FceRI-alpha that is susceptible to secretion events induced by any form of stimulation. The amount, on average, represents about 7% of the mature form of FceRI-alpha.

A Retrospective Study to Evaluate the Impact of In-Patient Dermatological Consultations on Diagnostic Accuracy in a Tertiary Care Setting.

Background:Dermatology is primarily an outpatient specialty. However, dermatology consultations play an important role in care of inpatients. Data on inpatient dermatological consultations in tertiary care settings is limited.Objectives:To evaluate clinical characteristics of inpatient dermatological consultations and effect on clinical outcomes in a tertiary care setting.Methods:This was a single-center retrospective study where the records of all dermatological consultations for patients admitted under various specialties, emergency services, and intensive care units (ICU) at our tertiary care institute over 2 years period were reviewed. The details of patients, primary care unit, dermatological complaints, diagnosis, investigations performed, treatment given, and follow-up were recorded and analyzed.Results:Total of 1717 dermatologic consultations (1000 males) were recorded, with mean age of study population being 33.6 ± 21.6 years (median - 32 years). Out of total 1717 patients, 136 (7.9%), 321 (18.7%), 1135 (66.1%), and 125 (7.3%) patients were infants, children, adolescents, adults, and elderly, respectively. The most frequent diagnostic group was infective diseases (586; 34.1%) followed by inflammatory diseases (442; 25.7%), mucocutaneous adverse drug reactions (160; 9.3%), and autoimmune diseases (65; 3.8%). Primary team's diagnosis was concordant with the dermatology consultation in 1112 (64.8%) patients and discordant observations were recorded in 605 patients (35.2%). Most discordant dermatological diagnoses included inflammatory disorders such as lichen planus, atopic dermatitis, bullous pemphigoid; mechanical disorders; nutritional deficiency disorders, and benign neoplasms.Conclusion:Common skin conditions account for a large majority of dermatologic consultations in a hospital setting. Inpatient dermatology consultations improve the diagnostic accuracy.

Coherent Effects in Charge Transport in Molecular Wires: Toward a Unifying Picture of Long-Range Hole Transfer in DNA.

In the framework of a multistep mechanism in which environmental motion triggers comparatively faster elementary electron-transfer steps and stabilizes hole-transfer products, microscopic coherence is crucial for rationalizing the observed yield ratios of oxidative damage to DNA. Interference among probability amplitudes of indistinguishable electron-transfer paths is able to drastically change the final outcome of charge transport, even in DNA oligomers constituted by similar building blocks, and allows for reconciling apparently discordant experimental observations. Properly tailored DNA oligomers appear to be a promising workbench for studying tunneling in the presence of dissipation at the macroscopic level.

Lead Impairs the Development of Innate Lymphoid Cells by Impeding the Differentiation of Their Progenitors.

Lead (Pb) is a heavy metal toxic to the immune system, yet the influence of Pb on innate lymphoid cells (ILC) remains to be defined. In this study, we found that occupationally relevant level of Pb exposure impaired ILC development at the progenitor level by activating Janus Kinase1. C57BL/6 mice treated with 1250 ppm, but not 125 ppm Pb acetic via drinking water for 8 weeks had reduced number of mature ILC, which was not caused by increased apoptosis or suppressed proliferation. Conversely, Pb increased the number of innate lymphoid cell progenitors (ILCP) in the bone marrow. The discordant observation indicated that an obstruction of ILCP differentiation into mature ILC during Pb exposure existed. Pb directly acted on ILCP to suppress their proliferation, indicating that ILCP were less activated during Pb exposure. Reciprocal ILCP transplantation assay confirmed that Pb impeded the differentiation of ILCP into mature ILC, as ILCP gave rise to fewer mature ILC in Pb-treated recipients compared with control recipients. In vitro assays suggested that the obstruction of ILCP differentiation by Pb exposure was due to increased activation of Janus Kinase1. Thus, Pb impeded ILCP differentiation into mature ILC to result in an accumulation of ILCP in the bone marrow and the resultant decreased number of mature ILC in lymphoid and nonlymphoid tissues in mice. Moreover, by analyses of ILC and ILCP in peripheral blood mononuclear cells of human subjects occupationally exposed to Pb, we revealed that Pb might also impede the development of ILC in human.

Automatic recognition of anomalous patterns in discharges by recurrent neural networks

Anomaly detection refers to the problem of finding patterns in data that do not conform to expected behavior. These off-normal patterns are often referred to as anomalies, outliers, discordant observations, or exceptions in different application domains. The importance of anomaly detection is due to the fact that anomalies in data frequently involve significant and critical information in many application domains. In the particular case of nuclear fusion, there are a wide variety of anomalies that could be related to particular plasma behaviors, such as disruptions or L-H transitions. In the case of unknown anomalies, they probably represent the major proportion with respect to the total anomalies that can be found in fusion. Whether the anomaly is known or not, all the anomalies in a nuclear fusion device should be detected by using the same approach, i.e. the physical state of the plasma during a shot should be reflected in some of the thousands acquired signals. In this article, we study the application of Deep Learning and a particular recurrent neural network called LSTM to detect anomalies by forecasting in a discharge.

Routine lung ultrasound to detect postoperative pulmonary complications following major abdominal surgery: a prospective observational feasibility study

BackgroundPostoperative pulmonary complications after major abdominal surgery are associated with adverse outcome. The diagnostic accuracy of chest X-rays (CXR) to detect pulmonary disorders is limited. Alternatively, lung ultrasound (LUS) is an established evidence-based point-of-care diagnostic modality which outperforms CXR in critical care. However, its feasibility and diagnostic ability for postoperative pulmonary complications following abdominal surgery are unknown. In this prospective observational feasibility study, we included consecutive patients undergoing major abdominal surgery with an intermediate or high risk developing postoperative pulmonary complications according to the Assess Respiratory risk In Surgical patients in CATalonia (ARISCAT) score. LUS was routinely performed on postoperative days 0–3 by a researcher blinded for CXR or other clinical findings. Then, reports were drawn up for LUS concerning feasibility and detection rates of postoperative pulmonary complications. CXRs were performed on demand according to daily clinical practice. Subsequently, we compared LUS and CXR findings.ResultsA total of 98 consecutive patients with an ARISCAT score of 41 (34–49) were included in the study. LUS was feasible in all patients. In 94 (95%) patients, LUS detected one or more postoperative pulmonary complications during the first four postoperative days. On day 0, LUS detected 31 out of 43 patients (72.1%) with one or more postoperative pulmonary complications, compared to 13 out of 36 patients (36.1%) with 1 or more postoperative pulmonary complications detected with CXR RR 2.0 (95 CI [1.24–3.20]) (p = 0.004). The number of discordant observations between both modalities was high for atelectasis 23 (43%) and pleural effusion 29 (54%), but not for pneumothorax, respiratory infection and pulmonary edema 8 (15%), 3 (5%), and 5 (9%), respectively.ConclusionsThis study shows that LUS is highly feasible and frequently detects postoperative pulmonary complications after major abdominal surgery. Discordant observations in atelectasis and pleural effusions for LUS and CXR can be explained by a superior diagnostic ability of LUS in detecting these conditions. The effects of LUS as primary imaging modality on patient outcome should be evaluated in future studies.

Diagnostics for repeated measurements in nonlinear mixed effects models

This paper introduces a new non-deletion method which identifies discordant subjects in nonlinear mixed effects models under a self-modeling framework. The new method decomposes the population level residuals into two parts and suggests two-dimensional plots to identify discordant subjects. An observation-wise investigation for alleged discordant subjects is also presented. The performances of the new methods are illustrated with simulation data and two real data examples. The new methods successfully identify the intended or important discordant subjects and observations. In a comparison with the local influence method, the new method reaches a consistent conclusion in a simpler and more efficient manner.

Diagnostics for repeated measurements in generalized linear mixed effects models

ABSTRACTAs there is an extensive body of research on diagnostics in regression models, various outlier detection methods have been developed. These methods have been extended to mixed effects models and generalized linear models, but there exist intrinsic drawbacks and limitations. This paper presents two-dimensional plots to identify discordant subjects and observations in generalized linear mixed effects models, displaying discordance in two directions. The sTudentized Residual Sum of Squares is not an extension of any regression tools but a new approach designed to efficiently reflect the characteristics of repeated measures. And this noteworthy clustering of outliers is identified in the plot. Applications to real-life examples are presented to illustrate the favorable/beneficial performance of the new tool.

Norcorrole as a Delocalized, Antiaromatic System

Nickel norcorrole provides an unusual example of a molecule that is strongly antiaromatic according to the magnetic criterion, but which exhibits, according to high-quality DFT calculations, a symmetric, delocalized structure with no difference in bond length between adjacent Cmeso-Cα bonds. A fragment molecular orbital analysis suggests that these discordant observations are a manifestation of the high stability of the dipyrrin fragments, which retain their electronic and structural integrity even as part of the norcorrole ring system.

Cytarabine Crystals in CSF

Distinguish the discordant microscopic observations between hemocytometer and Wright-stained concentrated CSF slide of patients with cytarabine crystals. The method incorporated in this study is a careful review of patient history and comparison of microscopic elements on the patient’s cerebrospinal fluid. CSF from a 16-year-old male. AML, FLT3 positive. A bone marrow aspirate, flow cytometry on bone marrow, and spinal tap were performed on the same day. The aspirate showed a hypocellular/hemodilute sample with trilineage hematopoiesis and 11% myeloblasts. Flow cytometry results included 21% atypical myeloid blasts and 44% atypical/immature monocytes. Eight fresh RBCs and 0 WBCs were observed on the hemacytometer. Eleven WBCs were noted on the cytospin slide; 100% were normal lymphocytes. Thirty-none variably sized, round cells (some with small inclusions) were seen on the hemacytometer but could not be recovered on the cytospin, despite using various stains. After much discussion with pathologists and microbiologists, it was discovered that the cells were cytarabine crystals. The patient had two recent doses of 50 mg cytarabine 2 weeks and 1 week prior to the lumbar puncture and bone marrow procedures. Cytarabine crystals can be an interfering microscopic examination that would show discordant results of cellular elements counted in hemocytometer vs concentrated Wright-stained smears.

Trends in Adult Alcohol Use and Binge Drinking in the Early 21st-Century United States: A Meta-Analysis of 6 National Survey Series.

Recent trends in alcoholic liver disease, alcohol-related emergency room admissions, and alcohol use disorder prevalence as measured by general-population surveys have raised concerns about rising alcohol-related morbidity and mortality in the United States. In contrast, upward trends in per capita alcohol consumption have been comparatively modest. To resolve these discordant observations, we sought to examine trends in the prevalence of alcohol use and binge drinking from 6 regularly or periodically administered national surveys using a meta-analytic approach. Annual or periodic prevalence estimates for past-12-month or past-30-day alcohol use and binge drinking were estimated for available time points between the years 2000 and 2016. Estimates were combined in a random-effects regression model in which prevalence was modeled as a log-linear function of time to obtain meta-analytic trend estimates for the full population and by sex, race, age, and educational attainment. Meta-analysis-derived estimates of average annual percentage increase in the prevalence of alcohol use and binge drinking were 0.30% per year (95% CI: 0.22%, 0.38%) and 0.72% per year (95% CI: 0.46%, 0.98%), respectively. There was substantial between-survey heterogeneity among trend estimates, although there was notable consistency in the degree to which trends have impacted various demographic groups. For example, most surveys found that the changes in prevalence for alcohol use and binge drinking were large and positive for ages 50 to 64 and 65 and up, and smaller, negative, or nonsignificant for ages 18 to 29. Significant increases in the prevalence of alcohol use and of binge drinking over the past 10 to 15years were observed, but not for all demographic groups. However, the increase in binge drinking among middle-aged and older adults is substantial and may be driving increasing rates of alcohol-related morbidity and mortality.

Evidence that TLR4 Is Not a Receptor for Saturated Fatty Acids but Mediates Lipid-Induced Inflammation by Reprogramming Macrophage Metabolism

Chronic inflammation is a hallmark of obesity and is linked to the development of numerous diseases. The activation of toll-like receptor 4 (TLR4) by long-chain saturated fatty acids (lcSFAs) is an important process in understanding how obesity initiates inflammation. While experimental evidence supports an important role for TLR4 in obesity-induced inflammation invivo, via a mechanism thought to involve direct binding to and activation of TLR4 by lcSFAs, several lines of evidence argue against lcSFAs being direct TLR4 agonists. Using multiple orthogonal approaches, we herein provide evidence that while loss-of-function models confirm that TLR4 does, indeed, regulate lcSFA-induced inflammation, TLR4 is not a receptor for lcSFAs. Rather, we show that TLR4-dependent priming alters cellular metabolism, gene expression, lipid metabolic pathways, and membrane lipid composition, changes that are necessary for lcSFA-induced inflammation. These results reconcile previous discordant observations and challenge the prevailing view of TLR4's role in initiating obesity-induced inflammation.

Phosphorylation Weakens but Does Not Inhibit Membrane Binding and Clustering of K-Ras4B.

K-Ras4B is one of the most frequently mutated Ras isoforms in cancer. The signaling activity of K-Ras4B depends on its localization to the plasma membrane (PM), which is mainly mediated by its polybasic farnesylated C-terminus. On top of the constitutive cycles that maintain the PM enrichment of K-Ras4B, conditional phosphorylation at Ser181 located within this motif has been found to be involved in regulating K-Ras4B's cell distribution and signaling activity. However, discordant observations have undermined our understanding of the role this phosphorylation plays. Here, we report an efficient strategy for producing K-Ras4B simultaneously bearing phosphate, farnesyl, and methyl modifications on a preparative scale, a very useful in vitro system when used in concert with model biomembranes. By using this system, we determined that phosphorylation at Ser181 does not fully inhibit membrane binding and clustering of K-Ras4B but reduces its membrane binding affinity, depending on membrane fluidity. In addition, phosphorylated K-Ras4B maintains tight association with its cytosolic shuttle protein PDEδ. After delivering K-Ras4B containing nonhydrolyzable phosphoserine mimetic into cells, the protein displayed a decreasing PM distribution compared with nonphosphorylable K-Ras4B, implying that phosphorylation might facilitate the dissociation of K-Ras4B from the PM. In addition, phosphorylation does not alter the localization of K-Ras4B in the liquid-disordered lipid subdomains of the membrane but slightly alters the thermotropic properties of K-Ras4B-incorporated membranes probably due to minor differences in membrane partitioning and dynamics. These results provide novel mechanistic insights into the role that phosphorylation at Ser181 plays in regulating K-Ras4B's distribution and activity.