Flexible Distribution-Based Regression Models for Count Data: Application to Medical Diagnosis

Abstract

Data mining techniques have been successfully utilized in different applications of significant fields, including medical research. With the wealth of data available within the health-care systems, there is a lack of practical analysis tools to discover hidden relationships and trends in data. The complexity of medical data that is unfavorable for most models is a considerable challenge in prediction. The ability of a model to perform accurately and efficiently in disease diagnosis is extremely significant. Thus, the model must be selected to fit the data better, such that the learning from previous data is most efficient, and the diagnosis of the disease is highly accurate. This work is motivated by the limited number of regression analysis tools for multivariate counts in the literature. We propose two regression models for count data based on flexible distributions, namely, the multinomial Beta-Liouville and multinomial scaled Dirichlet, and evaluated the proposed models in the problem of disease diagnosis. The performance is evaluated based on the accuracy of the prediction which depends on the nature and complexity of the dataset. Our results show the efficiency of the two proposed regression models where the prediction performance of both models is competitive to other previously used regression models for count data and to the best results in the literature.     

Diversity of lactic acid bacteria from Hussuwa, a traditional African fermented sorghum food

The diversity of lactic acid bacteria associated with Hussuwa fermentation, a Sudanese fermented sorghum food, was studied using a polyphasic taxonomical approach. Predominant strains could be well characterised based on a combination of phenotypic tests and genotypic methods such as ARDRA, rep-PCR and RAPD-PCR, as well as 16S rRNA gene sequencing of representative strains. Thus, the majority (128 of 220, 58.3%) of strains exhibited phenotypic properties typical of heterofermentative lactobacilli and of these, 100 strains were characterised more closely using the genotyping methods. The majority (97/100) strains could be characterised as Lactobacillus fermentum strains. Seventy-two of 220 strains (32.7%) showed phenotypic properties that are characteristic of pediococci. Of 41 selected strains investigated by genotyping techniques, 38 (92.7%) could be characterised as Pediococcus acidilactici strains, while three (7.3%) could be characterised as Pediococcus pentosaceus strains. The Hussuwa fermentation thus appears to be dominated by L. fermentum strains and P. acidilactici strains. For this reason, we selected representative and predominant strains as potential starter cultures for Hussuwa fermentation. These strains, L. fermentum strains BFE 2442 and BFE 2282 and P. acidilactici strain BFE 2300, were shown on the basis of RAPD-PCR fingerprinting to predominate in a model fermentation when used as starter cultures inoculated at 1 × 10⁶ CFU/g and to lower the pH of the fermentation to below pH 4.0 within 48 h. These cultures should be studied for further development as starter preparations in pilot scale studies in actual field fermentations.     

Cloning of the bile salt hydrolase (bsh) gene from Enterococcus faecium FAIR-E 345 and chromosomal location of bsh genes in food enterococci

Enterococcus faecium strain FAIR-E 345 isolated from food was shown to possess bile salt hydrolase (Bsh) activity in a plate screening assay and by high-performance liquid chromatography analysis. The bsh gene was cloned and sequenced. DNA sequence analysis revealed that it encoded a protein of 324 amino acids, with pI 4.877. A bsh gene probe was prepared from the cloned bsh gene and was used for probing plasmid and total genomic DNA of Bsh-positive enterococci isolated from food to determine the genomic location of their bsh genes. This probe was able to detect the bsh gene among total genomic DNA preparations but not from plasmid preparations of 10 plasmid-bearing Enterococcus strains. However, the probe could detect the bsh gene from total genomic DNA preparations of 12 Enterococcus strains that did not contain detectable plasmid DNA. In no cases did the probe hybridize with plasmid DNA preparations, suggesting that the bsh gene among enterococci is probably generally chromosomally encoded. This presumptive chromosomal location of bsh genes among food enterococci suggests that transfer of this trait by conjugative plasmids is unlikely.     

Silver nanowire as an efficient filler for high conductive polyurethane composites

Composites of silver nanowires (AgNWs) and polyurethane (PU) were prepared and their properties evaluated for potential applications as electrically conducting materials. Polyurethanes were chosen as the base substrate because of their inherent biocompatibility, biostability, excellent processability and good mechanical properties. The composites were prepared with varying content of AgNW by a solvent casting method. The electrical conductivity of the resulting composites was assessed using a 4-probe conductivity method and a maximum conductivity of 352.6?S?cm^–1 was achieved with 25% AgNW loading. The composite films were then characterised by various techniques to investigate the structure–property relationships. The above-mentioned analyses showed that the composite films retained the tensile and thermal properties of the parent PU while showing excellent conductivity.     

Polymer-layered silicate nanocomposites prepared through in situ reversible addition-fragmentation chain transfer (RAFT) polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerizations were performed in the presence of organically modified clays and successfully prepared polystyrene-, poly(methyl methacrylate)-, and poly(n-butyl acrylate)-layered silicate nanocomposites. The polymers had well-defined molecular weights and low polydispersities, as expected from RAFT polymerizations. The morphology of polystyrene-, and poly(n-butyl acrylate)-nanocomposites were found to be exfoliated using montmorillonite modified with N,N-dimethyl-n-hexadecyl-(4-vinylbenzyl) ammonium (MMT-VB16). In the case of PMMA nanocomposite, the structure was a mixture of intercalated and exfoliated when MMT-VB16 was used, while the use of montmorillonite modified with 2-methacryloyloxyethyl-hexadecyldimethyl ammonium (MMT-MA16) resulted in exfoliation.     

Cytotoxic,hematologic and histologic effects of niobium pentoxide in Swiss mice

The use of metal devices in medical application is increasing but it remains incompletely understood the physiological effects of component degradation. Niobium (Nb) alloys have already been investigated in the 1980’s and recent studies demonstrated the potential of Nb as an implant material. The purpose of this study was to determine cytotoxic, hematologic and histologic effects of niobium in Swiss mice. Animals were treated with a single dose of 3 % niobium oxide (Nb₂O₅) diluted in PBS, i.p. Cytotoxic assay, hematologic and histologic evaluation were done 3, 7 and 12 days after niobium treatment. Data have shown increased number of cells after niobium treatment, but there was no difference in cell viability. Furthermore, it was not observed hematological modification 3, 7 or 12 days after niobium treatment. Despite the fact that animals treated with niobium for 3 and 7 days showed mild degeneration in hepatocytes, mice kept alive for 12 days showed liver cells regeneration. Our results suggested that niobium cytotoxicity was not progressive because 12 days after treatment there was an evident liver regeneration. Data obtained indicated that niobium may be promising alternatives to biomedical applications.     

The apoptosis-necrosis paradox. Apoptogenic proteases activated after mitochondrial permeability transition determine the mode of cell death

Mitochondrial alterations including permeability transition (PT) constitute critical events of the apoptotic cascade and are under the control of Bcl-2 related gene products. Here we show that induction of PT is sufficient to activate CPP32-like proteases with DEVDase activity and the associated cleavage of the nuclear DEVDase substrate poly(ADP-ribose) polymerase (PARP). Thus, direct intervention on mitochondria using a ligand of the mitochondrial benzodiazepin receptor or a protonophore causes DEVDase activation. In addition, the DEVDase activation triggered by conventional apoptosis inducers (glucocorticoids or topoisomerase inhibitors) is prevented by inhibitors of PT. The protease inhibitor N-benzyloxycabonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD.fmk) completely prevents the activation of DEVDase and PARP cleavage, as well as the manifestation of nuclear apoptosis (chromatin condensation, DNA fragmentation, hypoploidy). In addition, Z-VAD.fmk delays the manifestation of apoptosis-associated changes in cellular redox potentials (hypergeneration of superoxide anion, oxidation of compounds of the inner mitochondrial membrane, depletion of non-oxidized glutathione), as well as the exposure of phosphatidylserine residues in the outer plasma membrane leaflet. Although Z-VAD.fmk retards cytolysis, it is incapable of preventing disruption of the plasma membrane during protracted cell culture (12-24 h), even in conditions in which it completely blocks nuclear apoptosis (chromatin condensation and DNA fragmentation). Electron microscopic analysis confirms that cells treated with PT inducers alone undergo apoptosis, whereas cells kept in identical conditions in the presence of Z-VAD.fmk die from necrosis. These observations are compatible with the hypothesis that PT would be a rate limiting step in both the apoptotic and the necrotic modes of cell death. In contrast, it would be the availability of apoptogenic proteases that would determine the choice between the two death modalities.     

Urolithin A and B Alter Cellular Metabolism and Induce Metabolites Associated with Apoptosis in Leukemic Cells

Leukemia is persistently a significant cause of illness and mortality worldwide. Urolithins, metabolites of ellagic acid and ellagitannins produced by gut microbiota, showed better bioactive compounds liable for the health benefits exerted by ellagic acid and ellagitannins containing pomegranate and walnuts. Here, we assessed the potential antileukemic activities of both urolithin A and urolithin B. Results showed that both urolithin A and B significantly inhibited the proliferation of leukemic cell lines Jurkat and K562, among which urolithin A showed the more prominent antiproliferative capability. Further, urolithin treatment alters leukemic cell metabolism, as evidenced by increased metabolic rate and notable changes in glutamine metabolism, one-carbon metabolism, and lipid metabolism. Next, we evidenced that both urolithins equally promoted apoptosis in leukemic cell lines. Based on these observations, we concluded that both urolithin A and B alter leukemic cell metabolome, resulting in a halt of proliferation, followed by apoptosis. The data can be used for designing new combinational therapies to eradicate leukemic cells.     

Measurements and Analysis of Fingerprinting Structures for WLAN Localization Systems

Channel‐based radio‐frequency fingerprinting such as a channel impulse response (CIR), channel transfer function (CTF), and frequency coherence function (FCF) have been recently proposed to improve the accuracy at the physical layer; however, their empirical performance, advantages, and limitations have not been well reported. This paper provides a comprehensive empirical performance evaluation of RF location fingerprinting, focusing on a comparison of received‐signal strength, CIR‐, CTF‐, and FCF‐based fingerprinting using the weighted k‐nearest neighbor pattern recognition technique. Frequency domain channel measurements in the IEEE 802.11 band taken on a university campus were used to evaluate the accuracy of the fingerprinting types and their robustness to human‐induced motion perturbations of the channel. The localization performance was analyzed, and the results are described using the spatial and temporal radio propagation characteristics. In particular, we introduce the coherence region to explain the spatial properties and investigate the impact of the Doppler spread in time‐varying channels on the time coherence of RF fingerprint structures.