M-ary Rank Classifier Combination: A Binary Linear Programming Problem

The goal of classifier combination can be briefly stated as combining the decisions of individual classifiers to obtain a better classifier. In this paper, we propose a method based on the combination of weak rank classifiers because rankings contain more information than unique choices for a many-class problem. The problem of combining the decisions of more than one classifier with raw outputs in the form of candidate class rankings is considered and formulated as a general discrete optimization problem with an objective function based on the distance between the data and the consensus decision. This formulation uses certain performance statistics about the joint behavior of the ensemble of classifiers. Assuming that each classifier produces a ranking list of classes, an initial approach leads to a binary linear programming problem with a simple and global optimum solution. The consensus function can be considered as a mapping from a set of individual rankings to a combined ranking, leading to the most relevant decision. We also propose an information measure that quantifies the degree of consensus between the classifiers to assess the strength of the combination rule that is used. It is easy to implement and does not require any training. The main conclusion is that the classification rate is strongly improved by combining rank classifiers globally. The proposed algorithm is tested on real cytology image data to detect cervical cancer.

Balancing contest competition, scramble competition, and social tolerance at feeding sites in wild common marmosets (Callithrix jacchus)

Models of primate sociality focus on the costs and benefits of group living and how factors such as rank, feeding competition, alliance formation, and cooperative behavior shape within-group social relationships. We conducted a series of controlled field experiments designed to investigate how resource distribution (one or three of four reward platforms) and amount of food on a reward platform affected foraging strategies and individual feeding success in four groups of wild common marmosets (Callithrix jacchus) living in the Caatinga of northeastern Brazil. At our field site, common marmoset groups are characterized by a single breeding female who can produce twin litters twice per year, strong social cohesion, and cooperative infant care provided principally by several adult male helpers. We found that except for the dominant breeding female, rank (based on aggression) was not a strong predictor of feeding success. Although the breeding female in each group occupied the highest rank position and obtained the greatest daily feeding success, all other group members, including adults and juveniles experienced relatively equal feeding success across most experimental conditions. This was accomplished using a balance of behavioral strategies related to contest competition, scramble competition (associated with a finder's advantage), and social tolerance (sharing the same feeding platform). Based on these results, the social structure of common marmosets is best described as "single female dominance," with the breeding female maximizing food intake needed to offset the energetic costs associated with reproductive twinning and the ability to produce two litters per year. Cooperative infant caregiving, in which the number of helpers is positively correlated with offspring survivorship, requires a set of behavioral strategies that serve to reduce contest competition and promote prosocial behaviors at feeding sites.

First-line chemotherapy regimens for locally advanced and metastatic pancreatic adenocarcinoma: a Bayesian analysis

Background

Systemic chemotherapy is the standard treatment for locally advanced and metastatic pancreatic cancer, but there is no consensus on the optimum regimen. We aimed to compare and rank the locally advanced and metastatic pancreatic adenocarcinoma chemotherapy regimens evaluated in randomized controlled trials (RCTs) in the past 15 years.

Materials and methods

PubMed, Embase, Cochrane Collaboration database, and ClinicalTrials.gov were searched for RCTs comparing chemotherapy regimens as first-line treatment for locally advanced and metastatic pancreatic adenocarcinomas. By using Bayesian network meta-analysis, we compared and ranked all included chemotherapy regimens in terms of overall survival, progression-free survival, response rate, and hematological toxicity.

Results

The analysis included 68 RCTs, with 14,908 patients and 63 treatment strategies. For overall survival, NSC-631570 (hazard ratio [HR] vs gemcitabine monotherapy 0.44, 95% credible interval: 0.24–0.76) and gemcitabine+NSC-631570 (HR 0.45, 0.24–0.86) were the two top-ranked chemotherapy regimens. For progression-free survival, PEFG (cisplatin + epirubicin + fluorouracil + gemcitabine) ranked first (HR 0.51, 0.34–0.77). PG (gemcitabine + pemetrexed) (odds ratio [OR] 4.68, 2.24–9.64) and FLEC (fluorouracil + leucovorin + epirubicin + carboplatin) (OR 4.52, 1.14–24.00) were ranked the most hematologically toxic, with gastrazole having the least toxicity (OR 0.03, 0.00–0.46).

Conclusion

The chemotherapy regimens NSC-631570 and gemcitabine+NSC-631570 were ranked the most efficacious for locally advanced and metastatic pancreatic adenocarcinomas in terms of overall survival, which warrants further confirmation in large-scale RCTs.

Systemic Chemotherapy as First-line Treatment for Metastatic Pancreatic Adenocarcinoma: A Bayesian Analysis

Objective The preferred chemotherapy regimen for metastatic pancreatic cancer remains a matter of controversy. In the present study, we aimed to assess and rank the effectiveness and toxicity of all of the available chemotherapy regimens included in the last 15 years' randomized controlled trials (RCTs) for metastatic pancreatic adenocarcinomas objectively. Methods PubMed, Embase, Cochrane Collaboration database, and ClinicalTrials.gov were searched for RCTs comparing chemotherapy regimens as first-line treatment for metastatic pancreatic adenocarcinomas. Using a Bayesian network meta-analysis, we compared and ranked all included chemotherapy regimens in terms of the overall survival, progression-free survival, response rate, and hematological toxicity. Results We identified 2,206 articles and included in the analysis 46 eligible articles reporting 44 RCTs with a total of 9,133 patients and 48 first-line intravenous systemic chemotherapy regimens. The models showed a good fit to the data. The top-ranked chemotherapy regimen for the overall survival was FP (simplified leucovorin + fluorouracil + nab-paclitaxel), with a hazard ratio (HR) of 0.45 versus gemcitabine monotherapy (95% credible interval 0.28-0.71). The regimen ranked first for the progression-free survival was gemcitabine + erlotinib + bevacizumab (HR 0.39, 0.23-0.62). GS (gemcitabine + S-1) had the highest overall response rate [odds ratio (OR) versus gemcitabine monotherapy 7.06, 1.15-51.15]. GemCape (gemcitabine + capecitabine) + erlotinib was ranked the most hematologically toxic (OR 7.78, 0.75-95.60). Conclusion The available evidence suggests that FP ranked first for metastatic pancreatic cancer in terms of the overall survival. GemCape + erlotinib ranked the most toxic.

Effects of group size and rank on mother-infant relationships and reproductive success in rhesus macaques (Macaca mulatta)

In the present study, we compared mother-infant relationships in 57 mother-infant dyads residing in two wild, semi-provisioned (22 mother-infant dyads in 2014, 35 dyads in 2015) groups of rhesus macaques (Macaca mulatta) in the Nanwan Nature Reserve for Rhesus Macaques, Hainan, China. We also compared reproductive success between these two groups. The ecology and provisioning regime for each group was similar. These groups differed however, in size. Group 1 contained ∼35 individuals and Group 2 contained ∼120 individuals. Data were collected over a 2-year period (2014-2015). We found that during the birth season, mother-infant relationships in the larger group were characterized by less time in contact and more time separated than in the smaller group. Mothers in the smaller group initiated more contact and proximity with their infants. During the mating season when infants were approximately 6 months old, mother-infant relationships in the smaller group were more rejecting. We also found that birth rates were significantly higher but infant survivorship (to 1-year-old) was significantly lower in the smaller group. Moreover, higher-ranking mothers in the larger group were characterized by a higher reproductive output than females of lower rank. In the smaller group, female rank did not affect reproductive output. There was, however, no clear relationship between infant survivorship and maternal rank. We hypothesize that differences in reproductive success and changes in mother-infant relationships between the birth and mating seasons reflect differences in the costs and benefits of group size: females in the larger group faced (i) higher intragroup feeding competition leading to a reduction in birth rate but also (ii) lower predation risk, resulting in higher infant survival rate compared to females in the smaller group. The results of this study point to the tradeoffs that primate females face in living in smaller and larger social groups.

Genetic parameter estimation for long endurance trials in the Uruguayan Criollo horse

The aim of this study was to estimate the genetic parameters of performance in a 750-km, 15-day ride in Criollo horses. Heritability (h² ) and maternal lineage effects (mt² ) were obtained for rank, a relative placing measure of performance. Additive genetic and maternal lineage (rmt) correlations among five medium-to-high intensity phase ranks (pRK) and final rank (RK) were also estimated. Individual records from 1,236 Criollo horses from 1979 to 2012 were used. A multivariate threshold animal model was applied to the pRK and RK. Heritability was moderate to low (0.156-0.275). Estimates of mt² were consistently low (0.04-0.06). Additive genetic correlations between individual pRK and RK were high (0.801-0.924), and the genetic correlations between individual pRKs ranged from 0.763 to 0.847. The pRK heritabilities revealed that some phases were explained by a greater additive component, whereas others showed stronger genetic relationships with RK. Thus, not all pRK may be considered as similar measures of performance in competition.

The lower bounds for the rank of matrices and some sufficient conditions for nonsingular matrices

The paper mainly discusses the lower bounds for the rank of matrices and sufficient conditions for nonsingular matrices. We first present a new estimation for [Formula: see text] ([Formula: see text] is an eigenvalue of a matrix) by using the partitioned matrices. By using this estimation and inequality theory, the new and more accurate estimations for the lower bounds for the rank are deduced. Furthermore, based on the estimation for the rank, some sufficient conditions for nonsingular matrices are obtained.

Space Allowance of the Littered Area Affects Lying Behavior in Group-Housed Horses

Horses can sleep while standing; however, recumbency is required for rapid eye movement (REM) sleep and therefore essential. Previous research indicated a minimal duration of recumbency of 30 min per 24 h to perform a minimal duration of REM sleep. For group-housed horses, suitable lying area represents a potentially limited resource. In Switzerland, minimal dimensions for the space allowance of the littered area are therefore legally required. To assess the effect of different space allowances of the littered area on lying behavior, 38 horses in 8 groups were exposed to 4 treatments for 11 days each; T0: no litter provided, T0.5: 0.5× minimal dimensions, T1: minimal dimensions, and T1.5: 1.5× minimal dimensions. Non-littered areas were covered with hard rubber mats. Lying behavior was observed during the last 72 h of each treatment. The total number of lying bouts per 24 h was similar in treatments providing litter, whereas in treatment T0, recumbency occurred only rarely (F_1,93 = 14.74, p = 0.0002) with the majority of horses lying down for less than 30 min per 24 h (χ12=11.82, p = 0.0006). Overall, the total duration of recumbency per 24 h increased with increasing dimensions of the littered area, whereby the effect attenuated between treatment T1 and T1.5 in high-ranking horses but continued in low-ranking horses (F_1,91 = 3.22, p = 0.076). Furthermore, low-ranking horses showed considerably more forcedly terminated lying bouts in treatments T0.5 and T1, but were similar to high-ranking horses in T1.5 (F_1,76 = 8.43, p = 0.005). Nonetheless, a number of individuals showed durations of recumbency of less than 30 min per 24 h even in treatment T1.5. The lying behavior was dependent on the availability of a soft and deformable surface for recumbency. A beneficial effect of enlarged dimensions of the littered area was shown by increased durations of recumbency and decreased proportion of forcedly terminated lying bouts in low-ranking horses. Taking this into account, it became evident that the minimal dimensions for the littered area as implemented in the Swiss animal welfare legislation do not ensure undisturbed lying behavior for all members of a given group.

Socially transmitted diffusion of a novel behavior from subordinate chimpanzees

Chimpanzees (Pan troglodytes) demonstrate much cultural diversity in the wild, yet a majority of novel behaviors do not become group-wide traditions. Since many such novel behaviors are introduced by low-ranking individuals, a bias toward copying dominant individuals ("rank-bias") has been proposed as an explanation for their limited diffusion. Previous experimental work showed that chimpanzees (Pan troglodytes) preferentially copy dominant over low-rank models. We investigated whether low ranking individuals may nevertheless successfully seed a beneficial behavior as a tradition if there are no "competing" models. In each of four captive groups, either a single high-rank (HR, n = 2) or a low-rank (LR, n = 2) chimpanzee model was trained on one method of opening a two-action puzzle-box, before demonstrating the trained method in a group context. This was followed by 8 hr of group-wide, open-access to the puzzle-box. Successful manipulations and observers of each manipulation were recorded. Barnard's exact tests showed that individuals in the LR groups used the seeded method as their first-choice option at significantly above chance levels, whereas those in the HR groups did not. Furthermore, individuals in the LR condition used the seeded method on their first attempt significantly more often than those in the HR condition. A network-based diffusion analysis (NBDA) revealed that the best supported statistical models were those in which social transmission occurred only in groups with subordinate models. Finally, we report an innovation by a subordinate individual that built cumulatively on existing methods of opening the puzzle-box and was subsequently copied by a dominant observer. These findings illustrate that chimpanzees are motivated to copy rewarding novel behaviors that are demonstrated by subordinate individuals and that, in some cases, social transmission may be constrained by high-rank demonstrators.

A novel rank-based non-parametric method for longitudinal ordinal data

Longitudinal ordinal data are common in biomedical research. Although various methods for the analysis of such data have been proposed in the past few decades, they are limited in several ways. For instance, the constraints on parameters in the proportional odds model may result in convergence problems; the rank-based aligned rank transform method imposes constraints on other parameters and the distributional assumptions with parametric model. We propose a novel rank-based non-parametric method that models the profile rather than the distribution of the data to make an effective statistical inference without the constraint conditions. We construct the test statistic of the interaction first, and then construct the test statistics of the main effects separately with or without the interaction, while "adjusted coefficient" for the case of ties is derived. A simulation study is conducted for comparison between rank-based non-parametric and rank-transformed analysis of variance. The results show that type I errors of the two methods are both maintained closer to the priori level, but the statistical power of rank-based non-parametric is greater than that of rank-transformed analysis of variance, suggesting higher efficiency of the former. We then apply rank-based non-parametric to two real studies on acne and osteoporosis, and the results also illustrate the effectiveness of rank-based non-parametric, particularly when the distribution is skewed.

A semi-parametric statistical model for integrating gene expression profiles across different platforms

BACKGROUND

Determining differentially expressed genes (DEGs) between biological samples is the key to understand how genotype gives rise to phenotype. RNA-seq and microarray are two main technologies for profiling gene expression levels. However, considerable discrepancy has been found between DEGs detected using the two technologies. Integration data across these two platforms has the potential to improve the power and reliability of DEG detection.

METHODS

We propose a rank-based semi-parametric model to determine DEGs using information across different sources and apply it to the integration of RNA-seq and microarray data. By incorporating both the significance of differential expression and the consistency across platforms, our method effectively detects DEGs with moderate but consistent signals. We demonstrate the effectiveness of our method using simulation studies, MAQC/SEQC data and a synthetic microRNA dataset.

CONCLUSIONS

Our integration method is not only robust to noise and heterogeneity in the data, but also adaptive to the structure of data. In our simulations and real data studies, our approach shows a higher discriminate power and identifies more biologically relevant DEGs than eBayes, DEseq and some commonly used meta-analysis methods.

High rank elliptic curves with torsion ℤ/4ℤ

Working over the field ℚ(t), Kihara constructed an elliptic curve with torsion group ℤ/4ℤ and five independent rational points, showing the rank is at least five. Following his approach, we give a new infinite family of elliptic curves with torsion group ℤ/4ℤ and rank at least five. This matches the current record for such curves. In addition, we give specific examples of these curves with high ranks 10 and 11.

Social ranking effects on tooth-brushing behaviour

OBJECTIVE

A tooth-brushing social rank hypothesis is tested suggesting tooth-brushing duration is influenced when individuals position their behaviour in a rank when comparing their behaviour with other individuals.

DESIGN

Study 1 used a correlation design, Study 2 used a semi-experimental design, and Study 3 used a randomized intervention design to examine the tooth-brushing social rank hypothesis in terms of self-reported attitudes, cognitions, and behaviour towards tooth-brushing duration.

METHODS

Study 1 surveyed participants to examine whether the perceived health benefits of tooth-brushing duration could be predicted from the ranking of each person's tooth-brushing duration. Study 2 tested whether manipulating the rank position of the tooth-brushing duration influenced participant-perceived health benefits of tooth-brushing duration. Study 3 used a longitudinal intervention method to examine whether messages relating to the rank positions of tooth-brushing durations causally influenced the self-report tooth-brushing duration.

RESULTS

Study 1 demonstrates that perceptions of the health benefits from tooth-brushing duration are predicted by the perceptions of how that behaviour ranks in comparison to other people's behaviour. Study 2 demonstrates that the perceptions of the health benefits of tooth-brushing duration can be manipulated experimentally by changing the ranked position of a person's tooth-brushing duration. Study 3 experimentally demonstrates the possibility of increasing the length of time for which individuals clean their teeth by focusing on how they rank among their peers in terms of tooth-brushing duration.

CONCLUSIONS

The effectiveness of interventions using social-ranking methods relative to those that emphasize comparisons made against group averages or normative guidelines are discussed.

STATEMENT OF CONTRIBUTION

What is already known on this subject? Individual make judgements based on social rank information. Social rank information has been shown to influence positive health behaviours such as exercise. What does this study add? The health benefits of tooth-brushing are predicted by how tooth-brushing duration ranks within a distribution. Focussing on how teeth-cleaning duration ranks among others produces longer teeth-cleaning durations.

Modeling Area-Level Health Rankings

OBJECTIVE

Rank county health using a Bayesian factor analysis model.

DATA SOURCES

Secondary county data from the National Center for Health Statistics (through 2007) and Behavioral Risk Factor Surveillance System (through 2009).

STUDY DESIGN

Our model builds on the existing county health rankings (CHRs) by using data-derived weights to compute ranks from mortality and morbidity variables, and by quantifying uncertainty based on population, spatial correlation, and missing data. We apply our model to Wisconsin, which has comprehensive data, and Texas, which has substantial missing information.

DATA COLLECTION METHODS

The data were downloaded from www.countyhealthrankings.org.

PRINCIPAL FINDINGS

Our estimated rankings are more similar to the CHRs for Wisconsin than Texas, as the data-derived factor weights are closer to the assigned weights for Wisconsin. The correlations between the CHRs and our ranks are 0.89 for Wisconsin and 0.65 for Texas. Uncertainty is especially severe for Texas given the state's substantial missing data.

CONCLUSIONS

The reliability of comprehensive CHRs varies from state to state. We advise focusing on the counties that remain among the least healthy after incorporating alternate weighting methods and accounting for uncertainty. Our results also highlight the need for broader geographic coverage in health data.

Nursing in the 8th Evacuation Hospital, 1942-1945

This article describes the experiences of Army nurses in the University of Virginia sponsored 8th Evacuation Hospital during World War II. In addition, it examines gender and role differences within the Army Medical Department, and how nurses' contributions helped shape the profession. This research used traditional historical methods of inquiry to include both primary and secondary sources of information. Primary sources include newspaper clippings, letters, citations, and photographs from the archival collections of the 8th Evacuation Hospital located in the University of Virginia Historical Collections and Services, Charlottesville, VA, and journal articles from that period. Secondary sources consisted of bibliographical and historical texts. Evidence suggests that advances in the chain-of-evacuation, antibiotics, dissemination of blood products, and nurses' expanded roles all contributed to increased survival of the wounded. Nurses' performance garnered an enduring respect from combatants who received care, as well as the medical officers and enlisted personnel with whom they worked on a daily basis. Collaboration, mutual respect, and coordinated teamwork were critical for mission success. Army nurses demonstrated that they had the mettle to go into a war zone and perform in an exemplary manner.

A novel method to identify pathways associated with renal cell carcinoma based on a gene co-expression network

The aim of the present study was to develop a novel method for identifying pathways associated with renal cell carcinoma (RCC) based on a gene co-expression network. A framework was established where a co-expression network was derived from the database as well as various co-expression approaches. First, the backbone of the network based on differentially expressed (DE) genes between RCC patients and normal controls was constructed by the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. The differentially co-expressed links were detected by Pearson's correlation, the empirical Bayesian (EB) approach and Weighted Gene Co-expression Network Analysis (WGCNA). The co-expressed gene pairs were merged by a rank-based algorithm. We obtained 842; 371; 2,883 and 1,595 co-expressed gene pairs from the co-expression networks of the STRING database, Pearson's correlation EB method and WGCNA, respectively. Two hundred and eighty-one differentially co-expressed (DC) gene pairs were obtained from the merged network using this novel method. Pathway enrichment analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and the network enrichment analysis (NEA) method were performed to verify feasibility of the merged method. Results of the KEGG and NEA pathway analyses showed that the network was associated with RCC. The suggested method was computationally efficient to identify pathways associated with RCC and has been identified as a useful complement to traditional co-expression analysis.

RANK/RANKL/OPG signaling pathways in necrotic jaw bone from bisphosphonate-treated subjects

Osteonecrosis of the jaw (ONJ) is a chronic complication affecting long-term bisphosphonate-treated subjects, recognized by non-healing exposed bone in the maxillofacial region. The pathophysiological mechanism underlying ONJ has not been fully elucidated. The aim of the present study was to investigate the role of RANK/RANKL/OPG signaling pathway and, in parallel, to evaluate angiogenic and matrix mineralization processes in jaw bone necrotic samples obtained from bisphosphonate-treated subjects with established ONJ. Necrotic bone samples and native bone samples were processed for Light and Field Emission in Lens Scanning Electron Microscope (FEISEM) analyses, for Real-Time RT-PCR to evaluate the gene expression of TNFRSF11A (RANK), TNFSF11 (RANKL), and TNFSF11B (OPG) and for immunohistochemical analyses of VEGF and BSP expression. Morphological analyses performed by Light microscope and FEISEM show empty osteocytic lacunae and alteration of lamellar organization with degradation of the mineralized bone matrix in necrotic bone samples. A significant increase in TNFRSF11A, TNFSF11, TRAF6 and NFAT2 gene expression, and a reduction of TNFSF11B gene transcription level compared is also showed in necrotic bone compared to control samples. No significant difference of VEGF expression is evidenced, while lower BSP expression in necrotic bone compared to healthy samples is found. Even if the pathogenesis of bisphosphonate-associated ONJ remains unknown, a link between oral pathogens and its development seems to exist. We suppose lipopolysaccharide produced by bacteria colonizing and infecting necrotic bone and the surrounding viable area could trigger RANK/RANKL/OPG signaling pathway and, in this context, osteoclasts activation could be considered as a protective strategy carried out by the host bone tissue to delimitate the necrotic area and to counteract infection.

Rank-based tests for identifying multiple genetic variants associated with quantitative traits

We consider the analysis of multiple genetic variants within a gene or a region that are expected to confer risks to human complex diseases with quantitative traits, where the trait values do not follow the normal distribution even after some transformations. We rank the phenotypic values, calculate a score to measure the trend effect of a particular allele for each marker, and then construct three statistics based on the quadratic frameworks of methods Hotelling T(2) , the summation of squared univariate statistic and the inverse of the square root weighted statistics to combine the scores for different marker loci. Simulation results show that the above three test statistics can control the type I error rate well and are more robust than standard tests constructed based on linear regression. Application to GAW16 data for rheumatoid arthritis successfully detects the association between the HLA-DRB1 gene and anticyclic citrullinated protein measure, while the standard methods based on normal assumption cannot detect this association.

Egalitarian despots: hierarchy steepness, reciprocity and the grooming-trade model in wild chimpanzees, Pan troglodytes

Biological market theory models the action of natural selection as a marketplace in which animals are viewed as traders with commodities to offer and exchange. Studies of female Old World monkeys have suggested that grooming might be employed as a commodity to be reciprocated or traded for alternative services, yet previous tests of this grooming-trade model in wild adult male chimpanzees have yielded mixed results. Here we provide the strongest test of the model to date for male chimpanzees: we use data drawn from two social groups (communities) of chimpanzees from different populations and give explicit consideration to variation in dominance hierarchy steepness, as such variation results in differing conditions for biological markets. First, analysis of data from published accounts of other chimpanzee communities, together with our own data, showed that hierarchy steepness varied considerably within and across communities and that the number of adult males in a community aged 20-30 years predicted hierarchy steepness. The two communities in which we tested predictions of the grooming-trade model lay at opposite extremes of this distribution. Second, in accord with the grooming-trade model, we found evidence that male chimpanzees trade grooming for agonistic support where hierarchies are steep (despotic) and consequent effective support is a rank-related commodity, but not where hierarchies are shallow (egalitarian). However, we also found that grooming was reciprocated regardless of hierarchy steepness. Our findings also hint at the possibility of agonistic competition, or at least exclusion, in relation to grooming opportunities compromising the free market envisioned by biological market theory. Our results build on previous findings across chimpanzee communities to emphasize the importance of reciprocal grooming exchanges among adult male chimpanzees, which can be understood in a biological markets framework if grooming by or with particular individuals is a valuable commodity.

The role of calcium and nicotinic acid adenine dinucleotide phosphate (NAADP) in human osteoclast formation and resorption

Osteoclasts are specialised bone resorbing cells which form by fusion of circulating mononuclear phagocyte precursors. Bone resorption results in the release of large amounts of calcium into the extracellular fluid (ECF), but it is not certain whether changes in extracellular calcium concentration [Ca(2+)]e influence osteoclast formation and resorption. In this study, we sought to determine the effect of [Ca(2+)]e and NAADP, a potent calcium mobilising messenger that induces calcium uptake, on human osteoclast formation and resorption. CD14+ human monocytes were cultured with M-CSF and RANKL in the presence of different concentrations of calcium and NAADP and the effect on osteoclast formation and resorption evaluated. We found that the number of TRAP+ multinucleated cells and the extent of lacunar resorption were reduced when there was an increase in extracellular calcium and NAADP. This was associated with a decrease in RANK mRNA expression by CD14+ cells. At high concentrations (20 mM) of [Ca(2+)]e mature osteoclast resorption activity remained unaltered relative to control cultures. Our findings indicate that osteoclast formation is inhibited by a rise in [Ca(2+)]e and that RANK expression by mononuclear phagocyte osteoclast precursors is also [Ca(2+)]e dependent. Changes in NAADP also influence osteoclast formation, suggesting a role for this molecule in calcium handling. Osteoclasts remained capable of lacunar resorption, even at high ECF [Ca(2+)]e, in keeping with their role in physiological and pathological bone resorption.

Bibliometric evaluation of pediatric neurosurgery in North America

OBJECT

The application of bibliometric techniques to academic neurosurgery has been the focus of several recent publications. The authors provide here a detailed analysis of all active pediatric neurosurgeons in North America and their respective departments.

METHODS

Using Scopus and Google Scholar, a bibliometric profile for every known active pediatric neurosurgeon in North America was created using the following citation metrics: h-, contemporary h-, g-, and e-indices and the m-quotient. Various subgroups were compared. Departmental productivity from 2008 through 2013 was measured, and departments were ranked on the basis of cumulative h- and e-indices and the total number of publications and citations. Lorenz curves were created, and Gini coefficients were calculated for all departments with 4 or more members.

RESULTS

Three hundred twelve pediatric neurosurgeons (260 male, 52 female) were included for analysis. For the entire group, the median h-index, m-quotient, contemporary h-, g-, and e-indices, and the corrected g- and e-indices were 10, 0.59, 7, 18, 17, 1.14, and 1.01, respectively; the range for each index varied widely. Academic pediatric neurosurgeons associated with fellowship programs (compared with unassociated neurosurgeons), academic practitioners (compared with private practitioners), and men (compared with women) had superior measurements. There was no significant difference between American and Canadian pediatric neurosurgeons. The mean Gini coefficient for publications was 0.45 (range 0.18-0.70) and for citations was 0.53 (range 0.25-0.80).

CONCLUSIONS

This study represents the most exhaustive evaluation of academic productivity for pediatric neurosurgeons in North America to date. These results should serve as benchmarks for future studies.

Confidence intervals for ranks of age-adjusted rates across states or counties

Health indices provide information to the general public on the health condition of the community. They can also be used to inform the government's policy making, to evaluate the effect of a current policy or healthcare program, or for program planning and priority setting. It is a common practice that the health indices across different geographic units are ranked and the ranks are reported as fixed values. We argue that the ranks should be viewed as random and hence should be accompanied by an indication of precision (i.e., the confidence intervals). A technical difficulty in doing so is how to account for the dependence among the ranks in the construction of confidence intervals. In this paper, we propose a novel Monte Carlo method for constructing the individual and simultaneous confidence intervals of ranks for age-adjusted rates. The proposed method uses as input age-specific counts (of cases of disease or deaths) and their associated populations. We have further extended it to the case in which only the age-adjusted rates and confidence intervals are available. Finally, we demonstrate the proposed method to analyze US age-adjusted cancer incidence rates and mortality rates for cancer and other diseases by states and counties within a state using a website that will be publicly available. The results show that for rare or relatively rare disease (especially at the county level), ranks are essentially meaningless because of their large variability, while for more common disease in larger geographic units, ranks can be effectively utilized.

Quantitative summaries of treatment effect estimates obtained with network meta-analysis of survival curves to inform decision-making

BACKGROUND

Increasingly, network meta-analysis (NMA) of published survival data are based on parametric survival curves as opposed to reported hazard ratios to avoid relying on the proportional hazards assumption. If a Bayesian framework is used for the NMA, rank probabilities associated with the alternative treatments can be obtained, which directly support decision-making. In the context of survival analysis multiple treatment effect measures are available to inform the rank probabilities.

METHODS

A fractional polynomial NMA of overall survival in advanced melanoma was performed as an illustrative example. Rank probabilities were calculated and presented for the following effect measures: 1) median survival; 2) expected survival; 3) mean survival at the follow-up time point of the trial with the shortest follow-up; 4) hazard or hazard ratio over time; 5) cumulative hazard or survival proportions over time; and 6) mean survival at subsequent time points. The advantages and disadvantages of the alternative measures were discussed.

RESULTS

Since hazard and survival estimates may vary over time for the compared interventions, calculations of rank probabilities for an NMA of survival curves may depend on the effect measure. With methods 1-3 rank probabilities do not vary over time, which are easier to understand and communicate than rank probabilities that vary over time as obtained with methods 4-6. However, rank probabilities based on methods 4-6 provide useful information regarding the relative treatment effects over time.

CONCLUSIONS

Different approaches to summarize results of a NMA of survival curves with rank probabilities have pros and cons. Rank probabilities of treatment effects over time provide a more transparent and informative approach to help guide decision-making than single rank probabilities based on collapsed measures, such as median survival or expected survival. Rank probabilities based on survival proportions are the most intuitive and straightforward to communicate, but alternatives based on the hazard function or mean survival over time may also be useful.

RANK/RANK-L/OPG in patients with bone metastases treated with anticancer agents and zoledronic acid: a prospective study

Patients with solid cancer frequently develop bone metastases (BM). Zoledronic acid (Zometa®, ZA), routinely used to treat patients with BM, acts on osteoclasts and also has antitumor properties. We aimed to assess the effect of ZA over time in novel bone turnover markers (RANK/receptor activator of nuclear factor-k B ligand (RANK-L)/ Osteoprotegerin (OPG)) and to correlate these with serum N-terminal telopeptide (NTX). The study prospectively evaluated levels of RANK, RANK-L and OPG transcripts by real-time PCR and NTX expression by ELISA in the peripheral blood of 49 consecutive patients with advanced breast, lung or prostate cancer. All patients received the standard ZA schedule and were monitored for 12 months. Median baseline values of RANK, RANK-L and OPG were 78.28 (range 7.34-620.64), 319.06 (21.42-1884.41) and 1.52 (0.10-58.02), respectively. At 12 months, the median RANK-L value had decreased by 22% with respect to the baseline, whereas median OPG levels had increased by about 96%. Consequently, the RANK-L/OPG ratio decreased by 56% from the baseline. Median serum NTX levels decreased over the 12-month period, reaching statistical significance (p < 0.0001). Our results would seem to indicate that ZA modulates RANK, RANK-L and OPG expression, thus decreasing osteoclast activity.

Accelerated MRI by SPEED with generalized sampling schemes

PURPOSE

To enhance the fast imaging technique of skipped phase encoding (PE) and edge deghosting (SPEED) for more general sampling options, and thus more flexibility in implementations and applications.

METHODS

SPEED uses skipped PE steps to accelerate MRI scan. Previously, the PE skip size was chosen from prime numbers only. This restriction has been relaxed in this study to allow choice of any integers rather than merely prime numbers. Various sampling patterns were studied under all possible combinations of PE skip size and PE shifts. A criterion based on the rank values of ghost phasor matrices was introduced to evaluate SPEED reconstruction.

RESULTS

The reconstruction quality was found to correlate with the rank value of the ghost phasor matrix and the skipped PE size N. A low-rank value indicates a singular matrix that causes failure of the SPEED reconstruction. Composite numbers combined with appropriately chosen PE shifts yielded satisfactory reconstruction results.

CONCLUSION

With properly chosen PE shifts, it was found that any integers, including both prime numbers and composite numbers, could be used as PE skip size for SPEED. This finding allows much more flexible data acquisition options that may lead to more freedom in practical implementations and applications.