Pregnancy-induced changes to the gut microbiota drive macrophage pyroptosis and exacerbate septic inflammation.

The physiological and immune changes that occur during pregnancy are associated with worsened disease outcomes during infection and sepsis. How these perturbations exacerbate inflammation has not been explored. Here, using antibiotic treatment and fecal microbial transfers, we showed that sepsis susceptibility is driven by pregnancy-induced changes to gut microbiome in mice and humans. Integrative multiomics and genetically engineered bacteria revealed that reduced Parabacteroides merdae (P. merdae) abundance during pregnancy led to decreased formononetin (FMN) and increased macrophage death. Mechanistically, FMN inhibited macrophage pyroptosis by suppressing nuclear accumulation of hnRNPUL2 and subsequent binding to the Nlrp3 promoter. Treatment with FMN or deletion of murine hnRNPUL2 protected against septic inflammation. Intestinal abundances of P. merdae and FMN inversely correlated with the progression of septic patients. Our data reveal a microbe-immune axis that is disrupted in pregnant septic hosts, highlighting the potential of the FMN-hnRNPUL2-NLRP3 axis in providing promising therapeutic strategies for sepsis.

Erythrocyte ENT1-AMPD3 Axis is an Essential Purinergic Hypoxia Sensor and Energy Regulator Combating CKD in a Mouse Model.

SIGNIFICANCE STATEMENT: Hypoxia drives kidney damage and progression of CKD. Although erythrocytes respond rapidly to hypoxia, their role and the specific molecules sensing and responding to hypoxia in CKD remain unclear. In this study, we demonstrated in a mouse model that erythrocyte ENT1-AMPD3 is a master energy regulator of the intracellular purinergic hypoxic compensatory response that promotes rapid energy supply from extracellular adenosine, eAMPK-dependent metabolic reprogramming, and O 2 delivery, which combat renal hypoxia and progression of CKD. ENT1-AMPD3-AMPK-BPGM comprise a group of circulating erythroid-specific biomarkers, providing early diagnostic and novel therapeutic targets for CKD. BACKGROUND: Hypoxia drives kidney damage and progression of CKD. Although erythrocytes respond rapidly to hypoxia, their role and the specific molecules sensing and responding to hypoxia in CKD remain unclear. METHODS: Mice with an erythrocyte-specific deficiency in equilibrative nucleoside transporter 1 ( eEnt1-/- ) and a global deficiency in AMP deaminase 3 ( Ampd3-/- ) were generated to define their function in two independent CKD models, including angiotensin II (Ang II) infusion and unilateral ureteral obstruction (UUO). Unbiased metabolomics, isotopic adenosine flux, and various biochemical and cell culture analyses coupled with genetic studies were performed. Translational studies in patients with CKD and cultured human erythrocytes examined the role of ENT1 and AMPD3 in erythrocyte function and metabolism. RESULTS: eEnt1-/- mice display severe renal hypoxia, kidney damage, and fibrosis in both CKD models. The loss of eENT1-mediated adenosine uptake reduces intracellular AMP and thus abolishes the activation of AMPK α and bisphosphoglycerate mutase (BPGM). This results in reduced 2,3-bisphosphoglycerate and glutathione, leading to overwhelming oxidative stress in eEnt1-/- mice. Excess reactive oxygen species (ROS) activates AMPD3, resulting in metabolic reprogramming and reduced O 2 delivery, leading to severe renal hypoxia in eEnt1-/- mice. By contrast, genetic ablation of AMPD3 preserves the erythrocyte adenine nucleotide pool, inducing AMPK-BPGM activation, O 2 delivery, and antioxidative stress capacity, which protect against Ang II-induced renal hypoxia, damage, and CKD progression. Translational studies recapitulated the findings in mice. CONCLUSION: eENT1-AMPD3, two highly enriched erythrocyte purinergic components that sense hypoxia, promote eAMPK-BPGM-dependent metabolic reprogramming, O 2 delivery, energy supply, and antioxidative stress capacity, which mitigates renal hypoxia and CKD progression.

Biological Control of Avocado Branch Blight Caused by Lasiodiplodia theobromae Using Bacillus velezensis.

In recent years, avocado branch blight has gradually become one of the major diseases causing mortality of avocado trees, which seriously affects the economic development of avocado planting regions. In order to investigate the cause of the disease, the pathogens were isolated from the interroot of avocado trees with the onset of the disease and identified as Lasiodiplodia theobromae. At the same time, three Bacillus velezensis strains, YK194, YK201, and YK268, with better antagonistic effects and high stability against L. theobromae, were isolated from the rhizospheric soil of healthy avocado plants. The results of branch experiments and field trials showed that the avocado leaves as well as branches treated with the strains YK194, YK201, and YK268 did not develop disease, and the incidence of avocado trees was significantly reduced. In the branch experiments, the biological control effect of the strains YK194, YK201, and YK268 reached 62.07, 52.70, and 72.45%, respectively. In the field experiments, it reached 63.85, 63.43, and 73.86%, respectively, which indicated that all these three strains possessed good biological control effects on avocado branch blight. Further investigation on the mechanism of action of antagonistic strains revealed that B. velezensis YK268 could produce lipopeptides, namely, surfactin, fengycin, and iturin, which could significantly inhibit the spore germination of L. theobromae. Consequently, these three isolates have potential as biocontrol agents against L. theobromae.

Effect and Mechanism of Apple Polyphenols in Regulating Intestinal Flora and Inhibiting the TLR4/NF-κB/TGF-ß Signaling Pathway to Alleviate Alcoholic Liver Fibrosis.

Apple polyphenols (APs) have gained attention for their various bioactivities, while no studies on anti-liver fibrosis activity are reported. This study evaluated the protective effect of APs on liver fibrosis using LPS-treated activated HSC-T6 cells and alcohol-treated liver fibrosis (ALF) mice. The results indicated that APs inhibited HSC-T6 cells activation in vitro and reduced the level of serum hyaluronic acid (HA) (p < 0.05), decreased fibrogenesis marker expression (p < 0.05), thereby alleviating ALF. In addition, APs (800 mg/kg b.w.) decreased the Firmicutes/Bacteroidetes ratio (p < 0.05) in ALF mice, inhibited LPS accumulation in the liver tissue and serum (p < 0.05), and significantly inhibited the TLR4/NF-κB/TGF-ß signaling in mice liver. In conclusion, APs markedly ameliorated ALF, possibly by improving gut microbiota homeostasis, decreasing the translocation of bacterial endotoxins to the blood, and suppressing the TLR4/NF-κB/TGF-ß signaling pathway, indicating its potential as lead compounds for functional foods and/or drugs against ALF.

Amino Acid Derivatives of Ginsenoside AD-2 Induce HepG2 Cell Apoptosis by Affecting the Cytoskeleton.

AD-2 (20(R)-dammarane-3ß, 12ß, 20, 25-tetrol, 25-OH-PPD) was structurally modified to introduce additional amino groups, which can better exert its anti-tumor effects in MCF-7, A549, LoVo, HCT-116, HT -29, and U-87 cell lines. We investigated the cellular activity of 15 different AD-2 amino acid derivatives on HepG2 cells and the possible mechanism of action of the superior derivative 6b. An MTT assay was used to detect the cytotoxicity of the derivatives. Western blotting was used to study the signaling pathways. Flow cytometry was used to detect cell apoptosis and ghost pen peptide staining was used to identify the changes in the cytoskeleton. The AD-2 amino acid derivatives have a better cytotoxic effect on the HepG2 cells than AD-2, which may be achieved by promoting the apoptosis of HepG2 cells and influencing the cytoskeleton. The derivative 6b shows obvious anti-HepG2 cells activity through affecting the expression of apoptotic proteins such as MDM2, P-p53, Bcl-2, Bax, Caspase 3, Cleaved Caspase 3, Caspase 8, and NSD2. According to the above findings, the amino acid derivatives of AD-2 may be developed as HepG2 cytotoxic therapeutic drugs.

Lymph node ratio-based the ypTNrM staging system for gastric cancer after neoadjuvant therapy: a large population-based study.

PURPOSES: The lymph node ratio (LNR) has been considered a better prognostic factor than traditional N staging in patients with gastric cancer (GC), but its accuracy is unclear for those who receive neoadjuvant therapy (NAT). We aimed to compare the node ratio (Nr) staging with the ypN staging and to thereby develop a modified staging system incorporating Nr staging. METHODS: A total of 1791 patients who underwent gastrectomy after NAT in the Surveillance, Epidemiology, and End Results database were retrospectively analyzed. ypTNrM staging was established based on the overall survival (OS). RESULTS: The Nr staging was generated using 0.2 and 0.5 as the cutoff values of LNR and represented patients with more homogeneous OS compared with ypN staging. The 5-year OS rates for ypTNrM stages IA, IB, II, IIIA, and IIIB were 70.2%, 54.2%, 36.0%, 21.2%, and 6.6%, respectively, compared with 58.8%, 39.1%, and 21.6% for ypTNM stages I, II, and III, respectively. Compared with the ypTNM staging system, the ypTNrM staging system had a lower misclassification rate (3.0% vs. 50.9%) and better prognostic predictive power (C-index: 0.645 vs. 0.589, P < 0.001). CONCLUSIONS: The ypTNrM staging system incorporating Nr staging may provide a more accurate assessment in the clinical decision-making process for GC after NAT.

APA scoring system: a novel predictive model based on risk factors of pregnancy loss for recurrent spontaneous abortion patients.

The aim of this study was to analyse the risk factors of pregnancy loss of patients with recurrent spontaneous abortion (RSA) and develop a scoring system to predict RSA. Clinical data of 242 cases, with RSA who were treated at Fujian Provincial Maternity and Children's Hospital, were selected. The factors of pregnancy loss for RSA patients were evaluated by univariate and multivariate analyses. There were 242 RSA patients, of whom 34 (14.0%) developed pregnancy loss. A multivariate analysis showed the following adverse risk factors for RSA: antinuclear antibody spectrum, protein s deficiency and antiphospholipid antibodies. The pregnancy loss rates of antinuclear antibody spectrum group, protein S deficiency group and antiphospholipid antibodies group were 25.0%, 22.5% and 19.4%, respectively. Each of these factors contributed 1 point to the risk score. The pregnancy loss rates were 6.3%, 24.6%, 50% for the low-, intermediate- and high-risk categories, respectively (p < .001). The area under the receiver operating characteristic curve for the score of RSA was .733. Our findings suggest that this validated and simple scoring system could accurately predict the risk of pregnancy loss of RSA patients. The score might be helpful in the selection of risk-adapted interventions to decrease the incidence. Impact StatementWhat is already known on this subject? The live birth rate increases to 80%-90% after anticoagulant and/or immunosuppressive treatment in patients with RSA. However, there is still a high rate of re-abortion even after active treatment.What do the results of this study add? Antinuclear antibody spectrum, protein s deficiency and antiphospholipid antibodies were independent risk factors for pregnancy loss. A novel predictive model based on these factors was then established and validated.What are the implications of these findings for clinical practice and/or further research? The newly developed score might be helpful in the selection of risk-adapted interventions to decrease the incidence. For patients in the intermediate-risk and high-risk groups, we should conduct more targeted studies and formulate corresponding therapies to improve the success rate of treatment.

Oxidative stress contributes to vascular calcification in patients with chronic kidney disease.

Vascular calcification (VC) is a major cause of mortality in patients with chronic kidney disease (CKD). While elevations in serum phosphorus contribute to VC, we provide evidence here for a major role of oxidative stress (OS) in VC pathogenesis without an apparent increase in serum phosphorus in early CKD. In a rat model for stage 5 CKD (CKD5), we observed 1) robust increases of VC and OS, 2) significant reductions of smooth muscle 22 alpha (SM22α) and calponin, and 3) upregulations in Runt-related transcription factor 2 (RUNX2) and collagen I in vascular smooth muscle cells (VSMCs). Inhibition of OS using MnTMPyP dramatically reduced these events without normalization of hyperphosphatemia. In CKD5 patients with VC (n = 11) but not in those without VC (n = 13), OS was significantly elevated. While the serum levels of calcium and phosphate were not altered in the animal model for early stage CKD (ECKD), OS, VC, SM22α, calponin, RUNX2, collagen I and NADPH oxidase 1 (NOX1) in VSMCs were all significantly changed. More importantly, serum (5%) derived from patients with ECKD (n = 30) or CKD5 (n = 30) induced SM22α and calponin downregulation, and RUNX2, collagen I, NOX1 upregulation along with a robust elevation of OS and calcium deposition in primary rat VSMCs. These alterations were all reduced by MnTMPyP, ML171 (a NOX1 inhibitor), and U0126 (an inhibitor of Erk signaling). Collectively, we provide a comprehensive set of evidence supporting an important role of OS in promoting VC development in CKD patients (particularly in those with ECKD); this was at least in part through induction of osteoblastic transition in VSMCs which may involve the Erk singling. Our research thus suggests that reductions in OS may prevent VC in CKD patients.

Efficacy of corticosteroids in immunoglobulin A nephropathy with less than 25% crescents.

BACKGROUND: Crescent formation in immunoglobulin A nephropathy (IgAN) has been demonstrated to be a risk factor for worse outcomes. For IgAN patients with 0-25% crescentic glomeruli (C1), whether corticosteroids (CS) can improve the prognosis remains unclear. We tried to investigate the need for using CS in IgAN patients with C1 in different proteinuria levels. METHODS: A total of 120 eligible IgAN patients with C1 from two academic medical centers were retrospectively studied, and 57 (47.5%) received CS. Patients were grouped according to with or without CS. The outcomes were the rate of estimated glomerular filtration rate (eGFR) decline (ml/min per 1.73 m2/year) and a composite outcome (50% decrease in eGFR, end stage renal disease (ESRD) or death due to kidney disease). The progression of adverse outcome among them were analyzed in Kaplan-Meier curve. The independent significance of CS on renal outcome or eGFR decline rate were analyzed by multivariable Cox regression or linear regression. RESULTS: Unadjusted Kaplan-Meier showed that the outcome of treated patients was better than that of the untreated patients. Multiple Cox regression and linear regression analysis found that CS independently protected the renal outcome and decreased the eGFR decline rate. In the subgroup analysis, multivariate linear regression showed that CS decreased the eGFR decline rate both in proteinuria ≥ 1 g/day and < 1 g/day. CONCLUSIONS: CS protected the renal outcome and slowed the eGFR decline rate of IgAN patients with C1, it also decreased the eGFR decline rate even in those with initial proteinuria < 1 g/day.

Retrospective Analysis of Clinical Outcomes in Patients with Immunoglobulin A Nephropathy and Persistent Hematuria Following Renin-Angiotensin System Blockade.

BACKGROUND Recent guidelines recommend that patients with immunoglobulin A nephropathy (IgAN) and proteinuria 0.5-1 g/d and >1 g/d be treated with long-term renin-angiotensin system blockade (RASB). This study investigated whether patients with IgAN and persistent hematuria, but without proteinuria, can benefit from RASB. MATERIAL AND METHODS IgAN patients with persistent hematuria at four centers were recruited from January 2013 to December 2018. Patients were divided into those who did and did not receive long-term RASB. The primary outcome was the appearance of proteinuria, and the secondary outcomes were the decreased percentage of hematuria, rate of decline in estimated glomerular filtration rate (eGFR) and final blood pressure. The effects of RASB on these outcomes were assessed by multivariate Cox regression models and propensity score matching. RESULTS Of the 110 eligible patients, 44 (40.0%) received RASB and 66 (60.0%) did not. Treated patients had higher diastolic pressure. The unadjusted primary outcome, the appearance of proteinuria, was significantly less frequent in individuals who were than who were not treated with RASB. Multivariate Cox regression showed that RASB reduced the risk of the primary outcome and the levels of hematuria. The rate of eGFR decline and final blood pressure did not differ in the two groups. CONCLUSIONS RASB reduced the risk of proteinuria development and increased the remission of hematuria in patients with IgAN who presented with persistent hematuria alone. RASB, however, did not affect blood pressure in patients without hypertension and did not affect the rate of eGFR decline.

Rosmarinic acid protects on rat bone marrow mesenchymal stem cells from hydrogen peroxide-induced apoptosis.

To investigate the anti-oxidant activities and mechanism of rosmarinic acid (RA) on rat bone marrow mesenchymal stem cells (rBMSCs) from ischemia-induced apoptosis in vitro, which was established using H2O2-damage and analyzed for cell viability, cell apoptosis, ROS, morphological changes, and levels of apoptosis proteins. Pretreatment with RA significantly suppressed the generation of ROS, protected the morphological changes of cells, decrease the ratio of cell apoptosis, down-regulated the level of caspase-3, caspase-9, Bax/Bcl-2, and up-regulated the level of p-PI3K. These findings suggest that RA may protect rBMSCs from H2O2-induced apoptosis by partly regulating PI3K/Akt signaling pathway and can be developed as a potential anti-apoptotic agent for therapy in cardiovascular diseases.

Flexible link functions in nonparametric binary regression with Gaussian process priors.

In many scientific fields, it is a common practice to collect a sequence of 0-1 binary responses from a subject across time, space, or a collection of covariates. Researchers are interested in finding out how the expected binary outcome is related to covariates, and aim at better prediction in the future 0-1 outcomes. Gaussian processes have been widely used to model nonlinear systems; in particular to model the latent structure in a binary regression model allowing nonlinear functional relationship between covariates and the expectation of binary outcomes. A critical issue in modeling binary response data is the appropriate choice of link functions. Commonly adopted link functions such as probit or logit links have fixed skewness and lack the flexibility to allow the data to determine the degree of the skewness. To address this limitation, we propose a flexible binary regression model which combines a generalized extreme value link function with a Gaussian process prior on the latent structure. Bayesian computation is employed in model estimation. Posterior consistency of the resulting posterior distribution is demonstrated. The flexibility and gains of the proposed model are illustrated through detailed simulation studies and two real data examples. Empirical results show that the proposed model outperforms a set of alternative models, which only have either a Gaussian process prior on the latent regression function or a Dirichlet prior on the link function.

[Identification of Moghania philippinensis and Moghania macrophylla].

OBJECTIVE: To study the identification methods of Moghania philippinensis and Moghania macrophylla, and to establish a comprehensive precise discrimination method. METHODS: TLC and HPLC were applied to analyze genistein in the root of Moghania philippinensis and Moghania macrophylla. DNA barcoding establishment was based on ITS2 sequcence. RESULTS: A comprehensive differentiation method for Moghania philippinensis and Moghania macrophylla based on TLC was proposed, which was combined with HPLC for determination of genistein. The plants of Moghania philippinensis and Moghania macrophylla and their related species could be distinguished by DNA barcoding effectively. CONCLUSION: TLC and HPLC profiles of Flemingia Radix provide alternative methods of identification using chemical approach. This integrated chemical and molecular approach allows accurate comprehensive fast identification of Moghania philippinensis and Moghania macrophylla, which avoids the methods limitations on the accuracy of identification. The differentiation methods based on TLC, HPLC and DNA barcoding are simple,which provide a new scientific evidence for the identification of authenticity of Flemingia Radix.

Benchmark Dose Analysis via Nonparametric Regression Modeling.

Estimation of benchmark doses (BMDs) in quantitative risk assessment traditionally is based upon parametric dose-response modeling. It is a well-known concern, however, that if the chosen parametric model is uncertain and/or misspecified, inaccurate and possibly unsafe low-dose inferences can result. We describe a nonparametric approach for estimating BMDs with quantal-response data based on an isotonic regression method, and also study use of corresponding, nonparametric, bootstrap-based confidence limits for the BMD. We explore the confidence limits' small-sample properties via a simulation study, and illustrate the calculations with an example from cancer risk assessment. It is seen that this nonparametric approach can provide a useful alternative for BMD estimation when faced with the problem of parametric model uncertainty.

[Identification of Smilax glabra and its related species based on psbA-trnH sequence].

OBJECTIVE: To identify Smilax glabra and its related species using DNA barcoding technique and psbA-trnH sequence. METHODS: Total genomic DNA was isolated as template and the chloroplast gene psbA-trnH region was amplified by PCR technology and sequenced bidirectionally. The sequences and the related data were analyzed using the software CodonCode Aligner and MEGA 6.0; The intra- and inter-specific Kimura-2-Parameter(K2P) distances were calculated and the phylogenetic tree was constructed using the Neighbor-joining method. RESULTS: The maximum K2P genetic distance of the plants of Smilax glabra was lower than the minimum K2P genetic distance of its related species. In the cluster dendrogram, the plants of Smilax glabra from various sources showed the monophyletic and simultaneously distinguished from the closely relative species. CONCLUSION: psbA-trnH barcoding could be used to distinguish Smilax glabra and its related species effectively, and provide important molecular evidence for identification of original plant of Smilacis Glabrae Rhizoma and clinic safety in medicinal use.

Research waste among randomized controlled trials in ovarian cancer: A cross-sectional study.

OBJECTIVE: To examine the association between trial characteristics and research waste in randomized controlled trials (RCTs) on ovarian cancer over the past two decades. METHODS: ClinicalTrials.gov was searched for RCTs registered between 2000 and 2020 using the keyword ovarian cancer. Publication status of RCTs was determined through systematic searches of the PubMed and Google Scholar databases. Reporting adequacy was evaluated using the CONSORT checklist. Design limitations were assessed based on the risk of bias and whether a relevant systematic review was cited in the manuscript. The primary outcome was research waste, defined as an RCT that was unpublished, inadequately reported, or had avoidable design limitations. RESULTS: Among the 117 RCTs evaluated, 89 (76.1 %) were published as of February 14, 2024. Published RCTs were more likely to be pharmacological, conducted in North America or Europe, have a multicenter or multinational design, have a larger sample size (over 200 participants), and receive external funding (P < 0.05). Among the published RCTs, 73 (82.0 %) and 24 (27.0 %) were considered adequately reported and free from design limitations, respectively. Overall, 96 of the 117 RCTs (82.1 %) were associated with research waste. Factors independently associated with research waste were an open-label design and smaller sample size (P < 0.05). CONCLUSION: Over 80 % of the RCTs on ovarian cancer demonstrated at least one feature of research waste. Future efforts should focus on minimizing the potential waste in unblinded small-scale RCTs.

PTK6: An emerging biomarker for prognosis and immunotherapeutic response in clear cell renal carcinoma (KIRC).

Kidney renal clear cell carcinoma (KIRC), one of the most prevalent form of kidney carcinoma, is highly aggressive cancer known for significant immune infiltration and high mortality rates. The absence of sensitivity to traditional therapy has spurred the search for new treatments. Protein Tyrosine Kinase 6 (PTK6) is implicated in promoting cancer growth, spread, and metastasis. Our review of The Cancer Genome Atlas database revealed PTK6 overexpression in KIRC, though its specific role in this cancer type was unclear. We investigated PTK6's cancer-promoting roles in KIRC using the database and confirmed our findings with patient-derived tissues. Our analysis showed that elevated PTK6 expression is linked to worse outcomes and higher levels of immune infiltration. It also correlates positively with neo-antigens (NEO) and DNA ploidy changes in KIRC. This research delves into PTK6's role in KIRC development, suggesting PTK6 as a possible biomarker for prognosis and treatment in KIRC.

A pedigree analysis of Rotor hyperbilirubinemia combined with hepatitis B virus infection in a SLCO1B1 and SLCO1B3 gene mutations patient.

Background: Rotor syndrome (RS, OMIM#237450) is an extremely rare autosomal digenic recessive disorder characterized by mild non-hemolytic hereditary conjugated hyperbilirubinemia, caused by biallelic variation of SLCO1B1 and SLCO1B3 genes that resulted in OATP1B1/B3 dysfunction in the sinusoidal membrane leading to impaired bilirubin reuptake ability of hepatocytes. Methods: One RS pedigree was recruited and clinical features were documented. Whole genome second-generation sequencing was used to screen candidate genes and mutations, Sanger sequencing confirmed predicted mutations. Results: This study detected a homozygous nonsense variant c.1738C > T (p.R580*) in the coding region of the SLCO1B1 (NM006446) gene in a family with RS and hepatitis B virus infection by Variants analysis and Sanger sequencing, and confirmed by Copy Number Variation (CNV) analysis and Long Range PCR that there was a homozygous insertion of intron 5 of the SLCO1B3 gene into intron 5 of long-interspersed element 1 (LINE1). A few cases of such haplotypes have been reported in East Asian populations. A hepatitis B virus infection with fatty liver disease was indicated by pathology, which revealed mild-moderate lobular inflammation, moderate lobular inflammation, moderate hepatocellular steatosis, and fibrosis stage 1-2 (NAS score: 4 points/S1-2) alterations. Heterozygotes carrying p.R580* and LINE1 insertions were also detected in family members (I1, I2, III2, III3), but they did not develop conjugated hyperbilirubinemia. Conclusion: The mutations may be the molecular genetic foundation for the presence of SLCO1B1 c.1738C > T(p.R580*) and SLCO1B3 (LINE1) in this RS pedigree.

RECENT PROGRESS IN THE NONPARAMETRIC ESTIMATION OF MONOTONE CURVES -WITH APPLICATIONS TO BIOASSAY AND ENVIRONMENTAL RISK ASSESSMENT.

Three recent nonparametric methodologies for estimating a monotone regression function F and its inverse F-1 are (1) the inverse kernel method DNP (Dette et al. (2005), Dette and Scheder (2010)), (2) the monotone spline (Kong and Eubank (2006)) and (3) the data adaptive method NAM (Bhattacharya and Lin (2010), (2011)), with roots in isotonic regression (Ayer et al. (1955), Bhattacharya and Kong (2007)). All three have asymptotically optimal error rates. In this article their finite sample performances are compared using extensive simulation from diverse models of interest, and by analysis of real data. Let there be m distinct values of the independent variable x among N observations y. The results show that if m is relatively small compared to N then generally the NAM performs best, while the DNP outperforms the other methods when m is O(N) unless there is a substantial clustering of the values of the independent variable x.