Molecular-level Differences Research Articles

In vitro, induction of salt tolerant potato (solanum tuberosum l.) Plants with gamma irradiation and characterization of genetic variations through sds-page and issr-pcr analysis

Salt tolerant mutants of potato (Solanum tuberosum L. ‘Sponta’) were obtained via gamma irradiation. bud explants of two strains of potato (Sponta and lady rosetta were treated with various dosages of gamma irradiation, and the clonal generations were developed. Selection of salt-tolerant mutants was accomplished by in vitro selection media containing 30, 60, 90 and 120 mM NaCl. Molecular-level differences between the control and mutant plants were elucidated using ISSR technique, and the polymorphism rate according to the selected primers was calculated as 89.66%. Genetic distances between the controls and mutants were also calculated, and related dendrograms were produced. On average the mutants were genetically 27.5% different from the control plants. The greatest difference encountered between the control and mutants was 47%, which was detected in mutant plants produced by 20 or 30 Gy gamma irradiation and regenerated in selection medium containing 100 mM NaCl.

Mechanisms of noncovalent β subunit regulation of NaV channel gating.

Voltage-gated Na+ (NaV) channels comprise a macromolecular complex whose components tailor channel function. Key components are the non-covalently bound β1 and β3 subunits that regulate channel gating, expression, and pharmacology. Here, we probe the molecular basis of this regulation by applying voltage clamp fluorometry to measure how the β subunits affect the conformational dynamics of the cardiac NaV channel (NaV1.5) voltage-sensing domains (VSDs). The pore-forming NaV1.5 α subunit contains four domains (DI-DIV), each with a VSD. Our results show that β1 regulates NaV1.5 by modulating the DIV-VSD, whereas β3 alters channel kinetics mainly through DIII-VSD interaction. Introduction of a quenching tryptophan into the extracellular region of the β3 transmembrane segment inverted the DIII-VSD fluorescence. Additionally, a fluorophore tethered to β3 at the same position produced voltage-dependent fluorescence dynamics strongly resembling those of the DIII-VSD. Together, these results provide compelling evidence that β3 binds proximally to the DIII-VSD. Molecular-level differences in β1 and β3 interaction with the α subunit lead to distinct activation and inactivation recovery kinetics, significantly affecting NaV channel regulation of cell excitability.

Abstract 3432: microRNA expression reflects site specificity of metastatic colorectal cancer

Abstract Colorectal Cancer (CRC) is one of the leading causes of cancer related deaths in the western world, and metastatic progression is the dominating cause of mortality. The primary site of CRC metastasis is the liver, followed by the lungs and peritoneal cavity, and prognosis for patients with metastatic CRC (mCRC) is poor, with only 10 % five-year survival. Although much is known about progression and metastasis of CRC; how primary CRC (pCRC) differs from mCRC on the molecular level and potential differences between metastases located in different organs are incompletely understood. This is important for our understanding of the disease, but also could have significant implications with respect to treatment. MicroRNAs have been shown to be key elements in cancer progression, but recent reports on CRC failed to consistently identify microRNA signatures of metastatic progression. We have addressed this using a smallRNA sequencing approach to analyze primary tumors and a set of liver, lung and peritoneal metastases, including corresponding adjacent tissue (colon, liver, lung, peritoneum). Further, we use the highly curated and updated microRNA reference MirGeneDB.org, the novel pipeline MirAthon - including a correction-algorithm of benign tissue microRNA signatures for tumor or metastatic samples, and we compare pCRC and site specific metastases separately. We are able to show that microRNA profiles of mCRC are distinct to pCRC in a site-specific manner. We identify a small panel of differentially expressed microRNAs including isoforms (isomiRs) hidden under a layer of benign signatures that we confirmed in other available datasets, too. Our findings will help better understand metastatic progression and site-specificity in CRC and could be potential biomarkers for mCRC. Our work identifies microRNA signatures of mCRC and suggest that microRNA signatures reflect mCRC site specificity. Furthermore, the results underline the importance of using a curated reference for microRNA studies, and to differentiate metastases based on their localization ab initio. Citation Format: Bastian Fromm, Eirik Høye, Diana Domanska, Christin Lund-Andersen, Annette Torgrund Kristensen, Vegar J. Dagenborg, Paul H. Boettger, Torveig W. Abrahamsen, Steinar Solberg, Stein G. Larsen, Bjørn Edwin, Eivind Hovig, Susanne Lorenz, Kjersti Flatmark. microRNA expression reflects site specificity of metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3432. doi:10.1158/1538-7445.AM2017-3432

Models for Predicting Stage in Head and Neck Squamous Cell Carcinoma Using Proteomic and Transcriptomic Data.

Late diagnosis is one of the reasons that head and neck squamous cell carcinoma (HNSCC) patients experience relative five-year survival rates ranging from 40%-66%. The molecular-level differences between early and advanced stage HNSCC may provide insight into therapeutic targets and strategies. Previous bioinformatics studies have shown mixed or limited results in identifying gene and protein markers and in developing models for discriminating between early and advanced stage HNSCC. Thus, we have investigated models for HNSCC stage prediction using RNAseq and reverse phase protein array data from The Cancer Genome Atlas and The Cancer Proteome Atlas. We systematically assessed individual and ensemble binary classifiers, using filter and wrapper feature selection methods, to develop several well-performing models. In particular, integrated models harnessing both data types consistently resulted in better performance. This study identifies informative protein and gene feature sets which may increase understanding of HNSCC progression.

Molecular insights into the dynamics of pharmacogenetically important N-terminal variants of the human β2-adrenergic receptor.

The human β2-adrenergic receptor (β2AR), a member of the G-protein coupled receptor (GPCR) family, is expressed in bronchial smooth muscle cells. Upon activation by agonists, β2AR causes bronchodilation and relief in asthma patients. The N-terminal polymorphism of β2AR at the 16th position, Arg16Gly, has warranted a lot of attention since it is linked to variations in response to albuterol (agonist) treatment. Although the β2AR is one of the well-studied GPCRs, the N-terminus which harbors this mutation, is absent in all available experimental structures. The goal of this work was to study the molecular level differences between the N-terminal variants using structural modeling and atomistic molecular dynamics simulations. Our simulations reveal that the N-terminal region of the Arg variant shows greater dynamics than the Gly variant, leading to differential placement. Further, the position and dynamics of the N-terminal region, further, affects the ligand binding-site accessibility. Interestingly, long-range effects are also seen at the ligand binding site, which is marginally larger in the Gly as compared to the Arg variant resulting in the preferential docking of albuterol to the Gly variant. This study thus reveals key differences between the variants providing a molecular framework towards understanding the variable drug response in asthma patients.

Modulation of Epidermal Transcription Circuits in Psoriasis: New Links between Inflammation and Hyperproliferation

BackgroundWhole-genome expression profiling has been used to characterize molecular-level differences between psoriasis lesions and normal skin. Pathway analysis, however, is complicated by the fact that expression profiles have been derived from bulk skin biopsies with RNA derived from multiple cell types.ResultsWe analyzed gene expression across a large sample of psoriatic (PP) and uninvolved/normal (PN) skin biopsies (n = 215 patients). We identified 1975 differentially expressed genes, including 8 associated with psoriasis susceptibility loci. To facilitate pathway analysis, PP versus PN differences in gene expression were analyzed with respect to 235 gene modules, each containing genes with a similar expression pattern in keratinocytes and epidermis. We identified 30 differentially expressed modules (DEMs) biased towards PP-increased or PP-decreased expression. These DEMs were associated with regulatory axes involving cytokines (e.g., IFN-γ, IL-17A, TNF-α), transcription factors (e.g., STAT1, NF-κB, E2F, RUNX1) and chromatin modifiers (SETDB1). We identified an interferon-induced DEM with genes encoding anti-viral proteins (designated “STAT1-57”), which was activated in psoriatic epidermis but repressed following biologic therapy. Genes within this DEM shared a motif near the transcription start site resembling the interferon-stimulated response element (ISRE).ConclusionsWe analyzed a large patient cohort and developed a new approach for delineating epidermis-specific pathways and regulatory mechanisms that underlie altered gene expression in psoriasis. Our findings highlight previously unrecognized “transcription circuits” that can provide targets for development of non-systemic therapies.

Silver in geological fluids from in situ X-ray absorption spectroscopy and first-principles molecular dynamics

The molecular structure and stability of species formed by silver in aqueous saline solutions typical of hydrothermal settings were quantified using in situ X-ray absorption spectroscopy (XAS) measurements, quantum-chemical modeling of near-edge absorption spectra (XANES) and extended fine structure spectra (EXAFS), and first-principles molecular dynamics (FPMD). Results show that in nitrate-bearing acidic solutions to at least 200°C, silver speciation is dominated by the hydrated Ag+ cation surrounded by 4–6 water molecules in its nearest coordination shell with mean Ag–O distances of 2.32±0.02Å. In NaCl-bearing acidic aqueous solutions of total Cl concentration from 0.7 to 5.9mol/kg H2O (m) at temperatures from 200 to 450°C and pressures to 750bar, the dominant species are the di-chloride complex AgCl2− with Ag–Cl distances of 2.40±0.02Å and Cl–Ag–Cl angle of 160±10°, and the tri-chloride complex AgCl32− of a triangular structure and mean Ag–Cl distances of 2.60±0.05Å. With increasing temperature, the contribution of the tri-chloride species decreases from ∼50% of total dissolved Ag in the most concentrated solution (5.9m Cl) at 200°C to less than 10–20% at supercritical temperatures for all investigated solutions, so that AgCl2− becomes by far the dominant Ag-bearing species at conditions typical of hydrothermal–magmatic fluids. Both di- and tri-chloride species exhibit outer-sphere interactions with the solvent as shown by the detection, using FPMD modeling, of H2O, Cl−, and Na+ at distances of 3–4Å from the silver atom. The species fractions derived from XAS and FPMD analyses, and total AgCl(s) solubilities, measured in situ in this work from the absorption edge height of XAS spectra, are in accord with thermodynamic predictions using the stability constants of AgCl2− and AgCl32− from Akinfiev and Zotov (2001) and Zotov et al. (1995), respectively, which are based on extensive previous AgCl(s) solubility measurements. These data are thus recommended for chemical equilibrium calculations in mineral–fluid systems above 200°C. In contrast, our data disagree with SUPCRT-based datasets for Ag–Cl species, which predict large fractions of high-order chloride species, AgCl32− and AgCl43− in high-temperature saline fluids. Comparisons of the structural and stability data of Ag–Cl species derived in this study with those of their Au and Cu analogs suggest that molecular-level differences amongst the chloride complexes such as geometry, dipole moment, distances, and resulting outer-sphere interactions with the solvent may account, at least partly, for the observed partitioning of Au, Ag and Cu in vapor–brine and fluid–melt systems. In hydrothermal environments dominated by fluid–rock interactions, the contrasting affinity of these metals for sulfur ligands and the differences both in chemistry and stability of their main solid phases (Ag sulfides, Cu–Fe sulfides, and native Au) largely control the concentration and distribution of these metals in their economic deposits.

Comparative proteomic analysis of endothelial cells progenitor cells derived from cord blood- and peripheral blood for cell therapy

Vasculopathy due to ischemia in damaged tissues is a major cause of morbidity and mortality. To treat these conditions, endothelial progenitor cells (EPCs) from various sources, such as umbilical cord or peripheral blood, have been the focus of the regenerative medicine field due to their proliferative and vasculogenic activities. However, the fundamental, molecular-level differences between EPCs obtained from different cellular sources have rarely been studied. In this study, we established endothelial progenitor cells derived from cord blood- and peripheral blood (CB- and PB-EPCs) and investigated their fundamental differences at the cellular and molecular levels through a combination of stem cell biology techniques and proteomic analysis. Our results suggest that specifically up-regulated factors such as STMIN 1, CFL 1, PARK 7, NME 1, GLO 1, HSP 27 and PRDX 2 in CB-EPCs as key elements that could be functionally active in ischemic regions. We also discussed functional behaviors important for inducing and maintaining long-lasting blood vessels under ischemic conditions. As a result, CB-EPCs retained a higher anti-oxidant and migration ability than PB-EPCs in vitro. Furthermore, CB-EPCs retained a higher therapeutic efficacy than PB-EPCs in a hindlimb ischemic disease model. The up-regulated expression pattern of STMIN 1, CFL 1, PARK 7, NME 1, GLO 1, HSP 27 and PRDX 2 was confirmed under several conditions in vitro and in vivo, indicating that the up-regulation of these molecules in CB-EPCs may be critical to the mechanism of healing in ischemic conditions and that CB-EPCs may be more appropriate for inducing neo-vessels. Thus, these results may aid in predetermining which cell sources will be of value for cell-based therapies of pathological conditions and identify several candidate molecules that may be involved in the therapeutic mechanism for ischemia.

The interaction between the surfactant and the co-structure directing agent in anionic surfactant-templated mesoporous silicas

Anionic surfactant-templated mesoporous silicas (AMS) are synthesized with a co-structure directing agent (CSDA) that interacts with both the organic and inorganic components of the system. The AMS materials structure is controlled by pH. We investigated the formation of AMS cubic and hexagonal phases, prepared under the same conditions, except pH, by EPR spectroscopic measurements. We used silica-like and surfactant-like spin probes added to the reaction mixtures in minute amounts. Through the spin probes we resolved the specific interactions of the CSDA (N-trimethoxylsilylpropyl-N,N,N-trimethyl ammonium chloride (TMAPS)) with the surfactant (sodium myristate (C14AS)) and the polymerizing silica. We observed for both phases a fast formation of a mesophase upon addition of the silica precursor (TEOS, tetraethoxysilane) and the CSDA into the surfactant solution, attributed to the strong attraction between the CSDA and the anionic surfactant. This is then followed by a slow condensation of the silica. Electron spin echo envelope modulation (ESEEM) spectra of both spin probes in the as-synthesized materials indicated the presence of two types of CSDA molecules; one interacting with the surfactant and the other with the silica wall. Continuous wave EPR spectra showed different spin probe motilities in the two as-synthesized materials that indicated that the relative populations of the two CSDA types are different in the two phases. We attribute this difference to the pH differences in the reaction mixtures. A soft extraction of the surfactant from the pores did not alter the structure of the final materials, but it abolished the observed molecular level differences between them. The extraction allowed the pending ammonium groups to acquire a high degree of freedom and accessibility to water molecules.

Induction of salt-tolerant potato (Solanum tuberosum L.) mutants with gamma irradiation and characterization of genetic variations via RAPD-PCR analysis

Salt-tolerant mutants of potato (Solanum tuberosum L. 'Marfona') were obtained via gamma irradiation. Node explants of the Marfona potato plant were treated with various dosages of gamma irradiation, and the M_1V_2 and M_1V_3 clonal generations were developed. Selection of salt-tolerant mutants was accomplished by in vitro selection media containing 50, 100, and 125 mM NaCl. Molecular-level differences between the control and mutant plants were elucidated using RAPD-PCR method, and the polymorphism rate according to the selected primers was calculated as 89.66%. Genetic distances between the controls and mutants were also calculated, and related dendrograms were produced. On average the mutants were genetically 27.5% different from the control plants. The greatest difference encountered between the control and mutants was 47%, which was detected in mutant plants produced by 20 or 30 Gy gamma irradiation and regenerated in selection medium containing 100 mM NaCl.

Molecular basis for identification of species/isolates of gastrointestinal nematode parasites

Gastrointestinal (GI) parasitism is the most serious constraint throughout the world in small ruminants which causes significant production loss in animals. GI parasites are major contributor to reduce productivity in terms of meat, milk and wool in animals. Control of GI parasite is done primarily by anthelmintic treatment where choice and schedule of treatment is done after identification and quantitation of individual parasite. Identification of GI parasites is done through microscopic method by identifying specific morphological characteristics of egg and larva (L 3). Since most of parasite eggs are having similar morphological characteristics, identification up to species level through microscopy is not possible in most of cases. To address this issue, molecular techniques are the viable alternative for identification of species as well as molecular level differences within a species (isolates) of parasites. Different DNA based molecular techniques viz. PCR, AFLP, RAPD, RFLP, PCR-SSCP, real time PCR, DNA microarray etc. have been used for identification and to assess the genetic diversity among parasite population. For identification of species, the characteristic sequence of genomic DNA of different species should differ to allow the delineation of species, but at the same time, no/minor variation within the species should exist. In contrast, for purpose of identifying population variants (strains/isolates), a considerable degree of variation in the sequence should exist within a species. Various target regions, including nuclear ribosomal DNA (rDNA), mitochondrial DNA (mtDNA) or repetitive DNA elements (microsatellite loci), which show considerable variation in the number of repeats within individuals have been employed to achieve the identification of parasites species or strain.

Impact of fat type (dairy or soy) on postprandial plasma and chylomicron responses with special emphasis on molecular level differences during the postprandial state

School of Exercise and Nutrition Sciences, Deakin University, Australia (MB, AD, AL, PG, DCS), School of Medicine,Deakin University, Australia (AJS), Baker Heart Research Institute, Melbourne, Victoria, Australia (PM, JW), andDepartment of Biochemistry and Food Chemistry, University of Turku, Finland (KL, HK, ML)

Bio science: genetic genealogy testing and the pursuit of African ancestry.

This paper considers the extent to which the geneticization of 'race' and ethnicity is the prevailing outcome of genetic testing for genealogical purposes. The decoding of the human genome precipitated a change of paradigms in genetics research, from an emphasis on genetic similarity to a focus on molecular-level differences among individuals and groups. This shift from lumping to splitting spurred ongoing disagreements among scholars about the significance of 'race' and ethnicity in the genetics era. I characterize these divergent perspectives as 'pragmatism' and 'naturalism'. Drawing upon ethnographic fieldwork and interviews, I argue that neither position fully accounts for how understandings of 'race' and ethnicity are being transformed with genetic genealogy testing. While there is some acquiescence to genetic thinking about ancestry, and by implication, 'race', among African-American and black British consumers of genetic genealogy testing, test-takers also adjudicate between sources of genealogical information and from these construct meaningful biographical narratives. Consumers engage in highly situated 'objective' and 'affiliative' self-fashioning, interpreting genetic test results in the context of their 'genealogical aspirations'. I conclude that issues of site, scale, and subjectification must be attended to if scholars are to understand whether and to what extent social identities are being transformed by recent developments in genetic science.

Adsorption of Organic Acids on TiO2 Nanoparticles: Effects of pH, Nanoparticle Size, and Nanoparticle Aggregation

In this study, the adsorption of two organic acids, oxalic acid and adipic acid, on TiO2 nanoparticles was investigated at room temperature, 298 K. Solution-phase measurements were used to quantify the extent and reversibility of oxalic acid and adipic acid adsorption on anatase nanoparticles with primary particle sizes of 5 and 32 nm. At all pH values considered, there were minimal differences in measured Langmuir adsorption constants, K ads, or surface-area-normalized maximum adsorbate-surface coverages, Gamma max, between 5 and 32 nm particles. Although macroscopic differences in the reactivity of these organic acids as a function of nanoparticle size were not observed, ATR-FTIR spectroscopy showed some distinct differences in the absorption bands present for oxalic acid adsorbed on 5 nm particles compared to 32 nm particles, suggesting different adsorption sites or a different distribution of adsorption sites for oxalic acid on the 5 nm particles. These results illustrate that molecular-level differences in nanoparticle reactivity can still exist even when macroscopic differences are not observed from solution phase measurements. Our results also allowed the impact of nanoparticle aggregation on acid uptake to be assessed. It is clear that particle aggregation occurs at all pH values and that organic acids can destabilize nanoparticle suspensions. Furthermore, 5 nm particles can form larger aggregates compared to 32 nm particles under the same conditions of pH and solid concentrations. The relative reactivity of 5 and 32 nm particles as determined from Langmuir adsorption parameters did not appear to vary greatly despite differences that occur in nanoparticle aggregation for these two different size nanoparticles. Although this potentially suggests that aggregation does not impact organic acid uptake on anatase particles, these data clearly show that challenges remain in assessing the available surface area for adsorption in nanoparticle aqueous suspensions because of aggregation.

Interfacial Depth Profiling of the Orientation and Bonding of Water Molecules across Liquid−Liquid Interfaces

Molecular interactions that create the interfacial properties present at a junction between water and several hydrophobic liquids are the focus of this paper. This study employs molecular dynamics simulations to generate vibrational sum frequency (VSF) spectral profiles of water across the interfacial depth of three systems: the carbon tetrachloride−water, chloroform−water, and dichloromethane−water interfaces. These spectral profiles are calculated as functions of both frequency and interfacial depth, providing a visual description of interfacial water structure that can be difficult to elucidate from density profiles and sum frequency spectral intensities, or spectra that vary only as functions of frequency. VSF spectral intensities calculated for the OH stretch region that are integrated over the entire interfacial region are shown to compare well with the experimental VSF data for these systems. VSF spectral depth profiles show how the widths of the interfaces vary with the density and polarity of the organic phase and where different types of water species reside in the interfacial region. Furthermore they highlight the major molecular level differences found in these three interfacial regions and, in particular, identify oriented water monomers deeply immersed within the dichloromethane phase far removed from the Gibbs dividing surface. The penetration of water has important implications for how we view transport across water−hydrophobic liquid interfaces.

Screening for differences in the amorphous state of indomethacin using multivariate visualization

The aim of this study was to examine molecular-level differences in the amorphous state of indomethacin prepared from both α- and γ-polymorphs using various preparative techniques: milling, quench cooling of a melt, slow cooling of a melt and spray drying. X-ray powder diffraction (XRPD), polarizing light microscopy (PLM), differential scanning calorimetry, as well as mid-infrared (MIR), near infrared (NIR) and Raman spectroscopy were used to analyze the samples after preparation. Principal component analysis (PCA) was used to visualize the differences in the spectroscopic data. According to the XRPD and PLM measurements, all samples except the spray dried indomethacin were amorphous after preparation. Spray dried indomethacin had some remaining residual crystallinity. Differences in the amorphous samples could be found on molecular level: the milled samples clustered separately from the other amorphous samples in the PCA of MIR, NIR and Raman spectra. This could be due to either small degrees of undetected crystallinity remaining in the samples after milling or differences in the hydrogen bonding in the different amorphous samples of indomethacin. The spectroscopic techniques revealed different information about the samples. Raman spectroscopy was most sensitive to differences caused by the preparation techniques and degradation products. Multivariate methods, such as PCA, offer an efficient tool to screen for these differences in the amorphous state.

Identifying sequence similarities between DNA molecules

An atomic force microscope (AFM) imaging technique is described to compare sequences between two different DNA molecules and precisely locate nonhomologies in DNA strands. Sequence comparisons are made by forming heteroduplexes between the two molecules and, by AFM imaging the intact molecules formed, identifying both homologous and nonhomologous regions. By forming heteroduplexes between linearized wildtype pSV- β-galactosidase plasmid (6821 bp) and a series of deletion mutants we have identified nonhomologies (deletions) as small as 22 bp and as large as 418 bp. Furthermore, by incorporating our technique for AFM-mediated restriction mapping of DNA these mutations can be positioned relative to E coRI restriction sites. These results suggest AFM can be useful in identifying molecular level similarities and differences in DNA.

Molecular-level variations in particulate organic matter subclasses along the Mid-Atlantic Bight

Abstract A significant portion of oceanic primary productivity occurs on continental margins. As the fate of this primary production has not been clearly determined, continental margins have been the focus of increased research over the past two decades. In the present study, molecular-level characteristics of particulate organic matter (POM) subclasses from the Mid-Atlantic Bight (MAB) were explored in an attempt to further our understanding of organic matter cycling in productive continental shelf and slope waters. Small-particle POM (2→53 μm), large-particle POM (>53 μm), “phytoplankton” (2→53 μm) and “detritus” (2→53 μm) were isolated from surface waters collected from different regimes (mid-shelf, shelf-edge, and slope) along the MAB in March 1996. Broad-band molecular-level variations within these subclasses were explored using direct temperature-resolved mass spectrometry (DT–MS) and multivariate analysis techniques. Correlations between molecular-level compositional differences and external environmental and biological variables such as salinity, temperature, and chlorophyll a concentrations were also examined. Both large-particle and small-particle POM exhibited molecular-level variations related to regime. Large-particle POM from the continental shelf exhibited chemical characteristics consistent with a greater zooplankton biomass component, as indicated by an enhanced chitin, protein, and cholesterol signature. In contrast, large-particle POM from slope waters appeared to contain a greater phytodetrital component, as indicated by enrichment in molecular-level characteristics similar to those of phytoplankton. A higher relative proportion of phytoplankton biomass was present in small-particle POM from the shelf-edge than from the mid-shelf or the slope. In addition, there was also an alongshelf (roughly north–south) trend in the composition of 2→53 μm POM, with samples farther south exhibiting enrichment in polysaccharides, fatty acids, chlorophyll, and diglycerides (the latter may result from triglycerides, phospholipids, or diglycerides within the samples). The molecular-level composition of “phytoplankton” also appeared to vary as a function of location, while the composition of “detritus” illustrated no easily interpretable variations with either location or external variables.

The compositional heterogeneity of particulate organic matter from the surface ocean: an investigation using flow cytometry and DT-MS

In this study the morphological and chemical heterogeneity of particulate organic matter (POM) in the surface ocean was investigated by the application of flow cytometry, direct temperature-resolved mass spectrometry (DT-MS), and multivariate statistics. In order to obtain a diverse collection of surface-ocean POM samples, POM was collected from a station in Great Harbor, Woods Hole, MA, U.S.A. (on a monthly basis) and on transects across the Mid-Atlantic Bight (in March 1996). Small-particle (<53 μm) POM was separated from large-particle (>53 μm) POM by filtration through a nylon screen. Aliquots of the small-particle POM were then further separated, via flow cytometric sorting, into phytoplankton and detrital pools. Broad-band molecular-level characteristics of these POM subclasses were obtained through DT-MS (16 eV, EI +) and were explored via principal component and discriminant analyses. For both the Woods Hole (WHTS) and the Mid-Atlantic Bight (MAB) data sets, the statistical treatments separated POM samples primarily according to their class and subclass distinctions; therefore, this paper focuses on the molecular-level differences among large-particle and small-particle POM, phytoplankton and detritus. Small-particle POM is found to be more enriched in protein, phytosterols, diglycerides and chlorophyll than large-particle POM, which is more enriched in pentose polysaccharide fragments, C 16:0 fatty acid, and cholesterol. At the WHTS site, large-particle POM is also enriched in chitin and appears to contain a significant grazer biomass component. In the MAB, the corresponding POM fraction appears more phytodetrital. Phytoplankton particles are enriched in protein, chlorophyll and lipids relative to detritus. Detritus is enriched in selected polysaccharides and appears to be composed of phytodetritus and/or fecal material.

Molecular and surgical advances in pediatric tumors.

Before the 1950s, less than a third of children with Wilms’ tumor, rhabdomyosarcoma (RMS), or neuroblastoma survived. Because of the rarity of these tumors, no single institution could collect enough patients for randomized trials. In the United States, the pediatric cancer study groups joined forces to create the National Wilms’ Tumor Study Group (NWTS) in 1969 and the Intergroup Rhabdomyosarcoma Study Committee (IRS) in 1972. Protocols to treat neuroblastoma have been developed by both the Children’s Cancer Group (CCG) and the Pediatric Oncology Group (POG). The multinational Societe Internationale d’Oncologie Pediatrique (SIOP) studies form a European counterpart to these groups. The protocols used by these groups that employ multimodality therapy including multiagent chemotherapy, have led to the current long-term survival approaching 40% in neuroblastoma [1], 70% in RMS [2], and 95% in Wilms’ tumor [3]. Each group continues to modify risk-adapted therapy based on identified prognostic factors. Recent identifications of molecular level differences may allow for further stratification of risk and adaptation of therapy to maximize survival while minimizing therapy.