Functional genomics: expression analysis of Escherichia coli growing on minimal and rich media

DNA arrays of the entire set of Escherichia coli genes were used to measure the genomic expression patterns of cells growing in late logarithmic phase on minimal glucose medium and on Luria broth containing glucose. Ratios of the transcript levels for all 4,290 E. coli protein-encoding genes (cds) were obtained, and analysis of the expression ratio data indicated that the physiological state of the cells under the two growth conditions could be ascertained. The cells in the rich medium grew faster, and expression of the majority of the translation apparatus genes was significantly elevated under this growth condition, consistent with known patterns of growth rate-dependent regulation and increased rate of protein synthesis in rapidly growing cells. The cells grown on minimal medium showed significantly elevated expression of many genes involved in biosynthesis of building blocks, most notably the amino acid biosynthetic pathways. Nearly half of the known RpoS-dependent genes were expressed at significantly higher levels in minimal medium than in rich medium, and rpoS expression was similarly elevated. The role of RpoS regulation in these logarithmic phase cells was suggested by the functions of the RpoS dependent genes that were induced. The hallmark features of E. coli cells growing on glucose minimal medium appeared to be the formation and excretion of acetate, metabolism of the acetate, and protection of the cells from acid stress. A hypothesis invoking RpoS and UspA (universal stress protein, also significantly elevated in minimal glucose medium) as playing a role in coordinating these various aspects and consequences of glucose and acetate metabolism was generated. This experiment demonstrates that genomic expression assays can be applied in a meaningful way to the study of whole-bacterial-cell physiology for the generation of hypotheses and as a guide for more detailed studies of particular genes of interest.

Niclosamide ethanolamine-induced mild mitochondrial uncoupling improves diabetic symptoms in mice

Type 2 diabetes (T2D) has reached an epidemic level globally. Most current treatments ameliorate the hyperglycemic symptom of the disease but are not effective in correcting its underlying cause. One important causal factor of T2D is ectopic accumulation of lipids in metabolically sensitive organs such as liver and muscle. Mitochondrial uncoupling, which reduces cellular energy efficiency and increases lipid oxidation, is an appealing therapeutic strategy. The challenge, however, is to discover safe mitochondrial uncouplers for practical use. Niclosamide is an anthelmintic drug approved by the US Food and Drug Administration that uncouples the mitochondria of parasitic worms. Here we show that niclosamide ethanolamine salt (NEN) uncouples mammalian mitochondria at upper nanomolar concentrations. Oral NEN increases energy expenditure and lipid metabolism in mice. It is also efficacious in preventing and treating hepatic steatosis and insulin resistance induced by a high-fat diet. Moreover, it improves glycemic control and delays disease progression in db/db mice. Given the well-documented safety profile of NEN, our study provides a potentially new and practical pharmacological approach for treating T2D.

Intestinal mast cell progenitors require CD49dbeta7 (alpha4beta7 integrin) for tissue-specific homing

Mast cells (MCs) are centrally important in allergic inflammation of the airways, as well as in the intestinal immune response to helminth infection. A single lineage of bone marrow (BM)-derived progenitors emigrates from the circulation and matures into phenotypically distinct MCs in different tissues. Because the mechanisms of MC progenitor (MCp) homing to peripheral tissues have not been evaluated, we used limiting dilution analysis to measure the concentration of MCp in various tissues of mice deficient for candidate homing molecules. MCp were almost completely absent in the small intestine but were present in the lung, spleen, BM, and large intestine of beta7 integrin-deficient mice (on the C57BL/6 background), indicating that a beta7 integrin is critical for homing of these cells to the small intestine. MCp concentrations were not altered in the tissues of mice deficient in the alphaE integrin (CD103), the beta2 integrin (CD18), or the recombination activating gene (RAG)-2 gene either alone or in combination with the interleukin (IL)-receptor common gamma chain. Therefore, it is the alpha4beta7 integrin and not the alphaEbeta7 integrin that is critical, and lymphocytes and natural killer cells play no role in directing MCp migration under basal conditions. When MCp in BALB/c mice were eliminated with sublethal doses of gamma-radiation and then reconstituted with syngeneic BM, the administration of anti-alpha4beta7 integrin, anti-alpha4 integrin, anti-beta7 integrin, or anti-MAdCAM-1 monoclonal antibodies (mAbs) blocked the recovery of MCp in the small intestine. The blocking mAbs could be administered as late as 4 d after BM reconstitution with optimal inhibition, implying that the MCp must arise first in the BM, circulate in the vasculature, and then translocate into the intestine. Inasmuch as MCp are preserved in the lungs of beta7 integrin-deficient and anti-alpha4beta7 integrin-treated mice but not in the small intestine, alpha4beta7 integrin is critical for tissue specific extravasation for localization of MCp in the small intestine, but not the lungs.

Warfarin use leads to larger intracerebral hematomas

BACKGROUND

Among patients with intracerebral hemorrhage (ICH), warfarin use before onset leads to greater mortality. In a retrospective study, we sought to determine whether warfarin use is associated with larger initial hematoma volume, one determinant of mortality after ICH.

METHODS

We identified all patients hospitalized with ICH in the Greater Cincinnati region from January through December 2005. ICH volumes were measured on the first available brain scan by using the abc/2 method. Univariable analyses and a multivariable generalized linear model were used to determine whether international normalized ratio (INR) influenced initial ICH volume after adjusting for other factors, including age, race, sex, antiplatelet use, hemorrhage location, and time from stroke onset to scan.

RESULTS

There were 258 patients with ICH, including 51 patients taking warfarin. In univariable comparison, when INR was stratified, there was a trend toward a difference in hematoma volume by INR category (INR <1.2, 13.4 mL; INR 1.2-2.0, 9.3 mL; INR 2.1-3.0, 14.0 mL; INR >3.0, 33.2 mL; p = 0.10). In the model, compared with patients with INR <1.2, there was no difference in hematoma size for patients with INR 1.2-2.0 (p = 0.25) or INR 2.1-3.0 (p = 0.36), but patients with INR >3.0 had greater hematoma volume (p = 0.02). Other predictors of larger hematoma size were ICH location (lobar compared with deep cerebral, p = 0.02) and shorter time from stroke onset to scan (p < 0.001).

CONCLUSION

Warfarin use was associated with larger initial intracerebral hemorrhage (ICH) volume, but this effect was only observed for INR values >3.0. Larger ICH volume among warfarin users likely accounts for part of the excess mortality in this group.

Conserved and sexually dimorphic behavioral responses to biogenic amines in decapitated Drosophila

A preparation of decapitated Drosophila melanogaster has been used for direct application of drugs to the nerve cord. Serotonin, dopamine, and octopamine stimulate locomotion and grooming, showing distinguishable effects that often are potentiated by addition of the vertebrate monoamine oxidase-inhibitor hydrazaline. Many of the hydrazaline-induced effects are sexually dimorphic, with males showing greater responses than females. Behaviors similar to those induced by dopamine can be induced by application of the vertebrate dopamine D2-like receptor agonist quinpirole, whose effects are also sexually dimorphic. In contrast, vertebrate D2-like and D1-like dopamine antagonists result in akinesic states, and D1-like agonists selectively stimulate grooming. These data indicate that Drosophila nerve cord amine receptors are coupled to reflexive behaviors similar to those stimulated by brain dopamine receptors in vertebrates.

Ultrafast internal conversion in ethylene. I. The excited state lifetime

Using a combined theoretical and experimental approach, we investigate the non-adiabatic dynamics of the prototypical ethylene (C(2)H(4)) molecule upon π → π∗ excitation. In this first part of a two part series, we focus on the lifetime of the excited electronic state. The femtosecond time-resolved photoelectron spectrum (TRPES) of ethylene is simulated based on our recent molecular dynamics simulation using the ab initio multiple spawning method with multi-state second order perturbation theory [H. Tao, B. G. Levine, and T. J. Martinez, J. Phys. Chem. A 113, 13656 (2009)]. We find excellent agreement between the TRPES calculation and the photoion signal observed in a pump-probe experiment using femtosecond vacuum ultraviolet (hν = 7.7 eV) pulses for both pump and probe. These results explain the apparent discrepancy over the excited state lifetime between theory and experiment that has existed for ten years, with experiments [e.g., P. Farmanara, V. Stert, and W. Radloff, Chem. Phys. Lett. 288, 518 (1998) and K. Kosma, S. A. Trushin, W. Fuss, and W. E. Schmid, J. Phys. Chem. A 112, 7514 (2008)] reporting much shorter lifetimes than predicted by theory. Investigation of the TRPES indicates that the fast decay of the photoion yield originates from both energetic and electronic factors, with the energetic factor playing a larger role in shaping the signal.

Effects of Lactobacillus GG on genes expression pattern in small bowel mucosa

BACKGROUND AND AIMS

Probiotics have been used for cure and prevention of several clinical conditions. However, further insights into the mechanism of action are needed to understand the rationale of their use. The aim of this study was to investigate the influence of Lactobacillus GG on the genetic expression patterns in the small bowel mucosa.

METHODS

Six male patients (38+/-5 years) with endoscopically proven oesophagitis were enrolled. All patients were treated for 1 month with esomeprazole and randomised to receive Lactobacillus GG or placebo. After 1 month of treatment, upper endoscopy was repeated. Biopsies of the duodenal mucosa were taken prior to and after the treatment, and the genes expression patterns were assessed using GeneChip Human U133A array. Genes with significant expression changes were selected and analysed to identify specific cellular pathways modified by Lactobacillus GG. To support the array data, 10 target genes were studied using Syber-Green PCR.

RESULTS

Microarray analysis showed that Lactobacillus GG administration determined the up- and down-regulation of 334 and 92 genes, respectively. Real-time PCR confirmed the reliability of the analysis. Lactobacillus GG mainly affected the expression of genes involved in immune response and inflammation (TGF-beta and TNF family members, cytokines, nitric oxide synthase 1, defensin alpha 1), apoptosis, cell growth and cell differentiation (cyclins and caspases, oncogenes), cell-cell signalling (ICAMs and integrins), cell adhesion (cadherins), signal transcription and transduction.

CONCLUSIONS

These data indicate that administration of Lactobacillus GG is associated with a complex genetic response of the duodenal mucosa, reflected by the up- and down-regulation of several genes involved in specific cellular pathways.

Prevention of Obesity and Type 2 Diabetes with Aged Citrus Peel (Chenpi) Extract

Chenpi is the dry peel of the plant Citrus reticulata Blanco after an aging processing. It has been used as an antidigestive and anti-inflammatory traditional medicine, as well as culinary seasoning and dietary supplement, in China. However, its efficacy and underlying scientific mechanism have not been sufficiently investigated. Chenpi is uniquely enriched with a high content of 5-demethylated polymethoxyflavones (5-OH PMFs). The effect of chenpi extract on improving metabolic features was examined using high-fat diet (HFD)-induced obesity/diabetes mouse model. Oral administration of 0.25 and 0.5% chenpi extract in food over 15 weeks markedly prevented HFD-induced obesity, hepatic steatosis, and diabetic symptoms. The beneficial effect is associated with 5'-adenosine monophosphate-activated protein kinase (AMPK) activation in adipose tissue. Our results indicate that 5-OH PMFs-enriched chenpi extract is effective in preventing obesity and type 2 diabetes, and its effect might be related to improvement in lipid metabolism associated with activation of the AMPK pathway.

Engineering a homo-ethanol pathway in Escherichia coli: increased glycolytic flux and levels of expression of glycolytic genes during xylose fermentation

Replacement of the native fermentation pathway in Escherichia coli B with a homo-ethanol pathway from Zymomonas mobilis (pdc and adhB genes) resulted in a 30 to 50% increase in growth rate and glycolytic flux during the anaerobic fermentation of xylose. Gene array analysis was used as a tool to investigate differences in expression levels for the 30 genes involved in xylose catabolism in the parent (strain B) and the engineered strain (KO11). Of the 4,290 total open reading frames, only 8% were expressed at a significantly higher level in KO11 (P < 0.05). In contrast, over half of the 30 genes involved in the catabolism of xylose to pyruvate were expressed at 1.5-fold- to 8-fold-higher levels in KO11. For 14 of the 30 genes, higher expression was statistically significant at the 95% confidence level (xylAB, xylE, xylFG, xylR, rpiA, rpiB, pfkA, fbaA, tpiA, gapA, pgk, and pykA) during active fermentation (6, 12, and 24 h). Values at single time points for only four of these genes (eno, fbaA, fbaB, and talA) were higher in strain B than in KO11. The relationship between changes in mRNA (cDNA) levels and changes in specific activities was verified for two genes (xylA and xylB) with good agreement. In KO11, expression levels and activities were threefold higher than in strain B for xylose isomerase (xylA) and twofold higher for xylulokinase (xylB). Increased expression of genes involved in xylose catabolism is proposed as the basis for the increase in growth rate and glycolytic flux in ethanologenic KO11.

Repetitive transcranial magnetic stimulation enhances spatial learning and synaptic plasticity via the VEGF and BDNF-NMDAR pathways in a rat model of vascular dementia

This study aimed to evaluate the effects of repetitive transcranial magnetic stimulation (rTMS) on learning and memory in a rat model of vascular dementia (VaD) and to analyze the associated mechanisms. Bilateral carotid artery occlusion (2-VO) was used to establish a rat model of VaD. High-frequency (5Hz) rTMS was performed on rats for four weeks. Spatial learning and memory abilities were evaluated using the Morris water maze (MWM), and synaptic plasticity in the hippocampus was assessed via long-term potentiation (LTP). Hippocampal expression of vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF) and three subunits of the N-methyl-D-aspartic acid receptor (NMDAR), NR1, NR2A and NR2B, was analyzed by Western blotting. Compared with the VaD group, escape latency was decreased (P<0.05) and the time spent in the target quadrant and the percentage of swimming distance within that quadrant were increased (P<0.05) in the rTMS group. LTP at hippocampal CA3-CA1 synapses was enhanced by rTMS (P<0.05). VEGF expression was up-regulated following 2-VO and was further increased by rTMS (P<0.05). BDNF, NR1 and NR2B expression was decreased in the VaD group and increased by rTMS (P<0.05). There were no significant differences in NR2A expression among the three groups. These results suggest that rTMS improved learning and memory in the VaD model rats via the up-regulation of VEGF, BDNF and NMDARs. In addition, NR2B may be more important than NR2A for LTP induction in the hippocampus during rTMS treatment of VaD.

Rhizobium leguminosarum CFN42 lipopolysaccharide antigenic changes induced by environmental conditions

Four monoclonal antibodies were raised against the lipopolysaccharide of Rhizobium leguminosarum bv. phaseoli CFN42 grown in tryptone and yeast extract. Two of these antibodies reacted relatively weakly with the lipopolysaccharide of bacteroids of this strain isolated from bean nodules. Growth ex planta of strain CFN42 at low pH, high temperature, low phosphate, or low oxygen concentration also eliminated binding of one or both of these antibodies. Lipopolysaccharide mobility on gel electrophoresis and reaction with other monoclonal antibodies and polyclonal antiserum indicated that the antigenic changes detected by these two antibodies did not represent major changes in lipopolysaccharide structure. The antigenic changes at low pH were dependent on growth of the bacteria but were independent of nitrogen and carbon sources and the rich or minimal quality of the medium. The Sym plasmid of this strain was not required for the changes induced ex planta. Analysis of bacterial mutants inferred to have truncated O-polysaccharides indicated that part, but not all, of the lipopolysaccharide O-polysaccharide portion was required for binding of these two antibodies. In addition, this analysis suggested that O-polysaccharide structures more distal to lipid A than the epitopes themselves were required for the modifications at low pH that prevented antibody binding. Two mutants were antigenically abnormal, even though they had abundant lipopolysaccharides of apparently normal size. One of these two mutants was constitutively unreactive toward three of the antibodies but indistinguishable from the wild type in symbiotic behavior. The other, whose bacteroids retained an epitope normally greatly diminished in bacteroids, was somewhat impaired in nodulation frequency and nodule development.

Screening of gene expression profiles in gastric epithelial cells induced by Helicobacter pylori using microarray analysis

BACKGROUND

H. pylori infection is a major risk factor in gastric cancer development. The availability of cDNA microarrays creates the unprecedented opportunity to examine simultaneously dynamic changes of multiple pathways affected by H. pylori infection.

AIM

In this study we examined broad patterns of gene expression induced by H. pylori in the gastric cancer cell line 1739-CRL AGS cells in culture using the U95A microarray.

METHODS

H. pylori were cocultured with AGS cells for 4, 12, 24 and 48 h. Total RNA was extracted and after labelling was used for detection of genes represented in the human U95A microarray set. Data analyses were performed using GeneChip and CLUSFAVOR software.

RESULTS

Nearly 6000 genes present in the array were expressed by AGS cells. We report approximately 200 genes that showed the most marked changes. Our studies confirm the up-regulation of c-jun, jun-B, c-fos and cyclin D1 by H. pylori. We report for the first time the induction of the serine threonine kinase pim-1 and ATF3 by H. pylori infection of AGS cells.

CONCLUSIONS

In this microarray analysis of gene expression induced by H. pylori in gastric epithelial cells, we identified a large number of unsuspected genes affected by H. pylori. Further, we show that unsupervised hierarchical cluster analysis can provide useful insight into the possible contribution of genes in specific pathways, based on their profile of expression.

Gene therapy in allergic encephalomyelitis using myelin basic protein-specific T cells engineered to express latent transforming growth factor-beta1

A myelin basic protein (MBP)-specific BALB/c T helper 1 (Th1) clone was transduced with cDNA for murine latent transforming growth factor-beta1 (TGF-beta1) by coculture with fibroblasts producing a genetically engineered retrovirus. When SJL x BALB/c F1 mice, immunized 12-15 days earlier with proteolipid protein in complete Freund's adjuvant, were injected with 3 x 10(6) cells from MBP-activated untransduced cloned Th1 cells, the severity of experimental allergic encephalomyelitis (EAE) was slightly increased. In contrast, MBP-activated (but not resting) latent TGF-beta1-transduced T cells significantly delayed and ameliorated EAE development. This protective effect was negated by simultaneously injected anti-TGF-beta1. The transduced cells secreted 2-4 ng/ml of latent TGF-beta1 into their culture medium, whereas control cells secreted barely detectable amounts. mRNA profiles for tumor necrosis factor, lymphotoxin, and interferon-gamma were similar before and after transduction; interleukin-4 and -10 were absent. TGF-beta1-transduced and antigen-activated BALB/c Th1 clones, specific for hemocyanin or ovalbumin, did not ameliorate EAE. Spinal cords from mice, taken 12 days after receiving TGF-beta1-transduced, antigen-activated cells, contained detectable amounts of TGF-beta1 cDNA. We conclude that latent TGF-beta1-transduced, self-reactive T cell clones may be useful in the therapy of autoimmune diseases.

Effect of mitochondrial uncouplers niclosamide ethanolamine (NEN) and oxyclozanide on hepatic metastasis of colon cancer

Metabolism of cancer cells is characterized by aerobic glycolysis, or the Warburg effect. Aerobic glycolysis reduces pyruvate flux into mitochondria, preventing a complete oxidation of glucose and shunting glucose to anabolic pathways essential for cell proliferation. Here we tested a new strategy, mitochondrial uncoupling, for its potential of antagonizing the anabolic effect of aerobic glycolysis and for its potential anticancer activities. Mitochondrial uncoupling is a process that facilitates proton influx across the mitochondrial inner membrane without generating ATP, stimulating a futile cycle of acetyl- CoA oxidation. We tested two safe mitochondrial uncouplers, NEN (niclosamide ethanolamine) and oxyclozanide, on their metabolic effects and anti-cancer activities. We used metabolomic NMR to examine the effect of mitochondrial uncoupling on glucose metabolism in colon cancer MC38 cells. We further tested the anti-cancer effect of NEN and oxyclozanide in cultured cell models, APCmin/+ mouse model, and a metastatic colon cancer mouse model. Using a metabolomic NMR approach, we demonstrated that mitochondrial uncoupling promotes pyruvate influx to mitochondria and reduces various anabolic pathway activities. Moreover, mitochondrial uncoupling inhibits cell proliferation and reduces clonogenicity of cultured colon cancer cells. Furthermore, oral treatment with mitochondrial uncouplers reduces intestinal polyp formation in APCmin/+ mice, and diminishes hepatic metastasis of colon cancer cells transplanted intrasplenically. Our data highlight a unique approach for targeting cancer cell metabolism for cancer prevention and treatment, identified two prototype compounds, and shed light on the anti-cancer mechanism of niclosamide.

A fast estimate of electrostatic group contributions to the free energy of protein-inhibitor binding

Dissecting ligand-protein binding free energies in individual contributions of protein residues (which are referred to here as 'group contributions') is of significant importance. For example, such contributions could help in estimating the corresponding mutational effects and in studies of drug resistance problems. However, the meaning of group contributions is not always uniquely defined and the approximations for rapid estimates of such contributions are not well developed. In this paper, the nature of group contributions to binding free energy is examined, focusing particularly on electrostatic contributions which are expected to be well behaved. This analysis examines different definitions of group contributions; the 'relaxed' group contributions that represent the change in binding energy upon mutation of the given residue to glycine, and the 'non-relaxed' group contributions that represent the scaled Coulomb interaction between the given residue and the ligand. Both contributions are defined and evaluated by the linear response approximation (LRA) of the PDLD/ S method. The present analysis considers the binding of pepstatin to endothiapepsin and 23 of its mutants as a test case for a neutral ligand. The 'non-relaxed' group contributions of 15 endothiapepsin residues show significant peaks in the 'electrostatic fingerprint'. The residues that contribute to the electrostatic fingerprint are located in the binding site of endothiapepsin. They include the aspartic dyad (Asp32, Asp215) with adjacent residues and the flap region. Twelve of these 15 residues have a heavy atom distance of <3.75 A to pepstatin. The contributions of 8 (10) of these 12 residues can be reconciled with the calculated 'relaxed' group contributions where one allows the protein and solvent (solvent only) to relax upon mutation of the given residue to glycine. On the other hand, it was found that residues at the second 'solvation shell' can have relaxed contributions that are not captured by the non-relaxed approach. Hence, whereas residues with significant non-relaxed electrostatic contributions are likely to contribute to binding, residues with small non-relaxed contributions may still affect the binding energy. At any rate, it is established here that even in the case of uncharged inhibitors it is possible to use the non-relaxed electrostatic fingerprint to detect 'hot' residues that are responsible for binding. This is significant since some versions of the non-relaxed approximation are faster by several orders of magnitude than more rigorous approaches. The general applicability of this approach is outlined, emphasizing its potential in studies of drug resistance where it is crucial to have a rapid way of anticipating the effect of mutation on both drug binding and catalysis.

Sera from patients with chronic Lyme disease protect mice from Lyme borreliosis

Sera from selected patients with Lyme disease in different stages were used to passively immunize mice against Borrelia burgdorferi challenge to determine if human antibodies could protect the animals from infection. Sera from 2 patients with late-stage Lyme disease that contained strong antibody reactivity to proteins in B. burgdorferi lysates, including antibodies to the outer surface proteins (Osps) A and B, partly protected mice from infection after challenge with a small inoculum (10(2)) of B. burgdorferi. Mice immunized with sera from either of these 2 patients developed significantly fewer infections from the borreliae (patient 1 serum, 5%; patient 2 serum, 25%) relative to control mice (patient 1 serum, 90%; patient 2 serum, 74%). In contrast, sera from 2 patients with early or late Lyme disease that lacked antibodies reactive to OspA and OspB did not confer protection. Immunity appeared to be related, at least in part, to the presence of a strong humoral response to the Osps. These results suggest that during prolonged infection, some patients develop an immune response that may be partly protective against reinfection with B. burgdorferi. Therefore, although most patients do not mount a strong humoral response to the Osps during natural infection, vaccination with an Osp may elicit protective immunity.

Evasion of protective immunity by Borrelia burgdorferi by truncation of outer surface protein B

We analyzed variability in outer surface protein B (OspB) from Borrelia burgdorferi (Bb), the causative agent of Lyme disease, to determine how Bb escapes immune destruction. We have shown that vaccination with OspB from Bb strain B31 protected mice from infection with Bb B31 but not against Bb N40. The present study demonstrates that Bb N40 spirochetes which evade vaccination immunity to OspB have a truncated form of OspB, due to a TAA stop codon at nucleotide 577. In contrast, Bb N40 spirochetes that express full-length OspB are unable to infect mice immunized with OspB, analogous to our previous studies with Bb B31. Mapping of the OspB antibody response shows that epitopes in the C terminus of OspB are surface-exposed and bind protective monoclonal and polyclonal antibodies. This suggests that the C terminus of OspB is important for eliciting a protective immune response to OspB. Truncation or modification of outer surface proteins that do not bind protective antibody may be a means by which Bb evades host defenses.

Tin speciation in the femtogram range in open ocean seawater by gas chromatography/inductively coupled plasma mass spectrometry using a shield torch at normal plasma conditions

A sensitive method for the determination of ultratrace organotin species in seawater is described. The merits and demerits of derivatization methods using Grignard reagent or sodium tetraethylborate (NaBEt4) were evaluated in terms of derivatization efficiency, applicability to the programmed temperature vaporization (PTV) method, and procedural blanks. The sensitivity of the gas chromatography/inductively coupled plasma mass spectrometry (GC/ICPMS) was improved by more than 100-fold by operating the shield torch at normal plasma conditions, compared with that obtained without using it. The absolute detection limit as tin reached subfemtogram (fg) levels. Furthermore, the detection limit in terms of relative concentration was improved 100-fold by using the PTV method, which enabled the injection of a large sample volume of as much as 100 microL without loss of analyte. When the organotin species in seawater were extracted into hexane with a preconcentration factor of 1000 after ethylation with NaBEt4 and a 100 microL aliquot of the extract was injected into the GC, the instrumental detection limit in relative concentration reached 0.01 pg/L in original seawater. Sources of contamination of organotin species during the sample preparation were examined, and a purification method of NaBEt4 was developed. Finally, the method was successfully applied to open ocean seawater samples containing organotin species at the level of 1-100 pg/L.

Antigenic characterization and ELISA detection of adult diarrhea rotaviruses

Recently, severe epidemics of diarrhea among both adults and children in China have been associated with an agent called adult diarrhea rotavirus (ADRV). We have studied ADRV from two areas of China (Jinzhou and Guangxi) and compared them with prototype group A, B, and C rotaviruses. The viral genomes were compared by electrophoresis of the RNA genome segments in polyacrylamide gels, and the antigenic relatedness of these viruses was examined by immune electron microscopic studies using virus preparations of either double- or single-capsid particles. Hyperimmune antisera (guinea pig and rabbit) to one strain of ADRV reacted with high titers with other strains of ADRV and with single-shelled capsids of a porcine group B rotavirus. The antisera to ADRV did not react with either group A or group C rotaviruses. Antisera to either bovine or porcine group B rotaviruses reacted with ADRV but not with the group A or group C viruses. Antisera to group A or group C virus reacted only with their respective homologous virus. These results and those of immunofluorescence studies place the human ADRV rotaviruses from China among the group B rotaviruses. We also report the development of an ELISA to detect ADRV; this ELISA should be useful for defining the epidemiology of these recently described rotaviruses.

Cord blood is better than bone marrow for generating megakaryocytic progenitor cells

Thrombocytopenia remains an important problem for patients post high-dose chemotherapy and hematopoietic stem cell transplantation. The study of megakaryocytes, the direct precursors of platelets, has been hampered by their relatively low frequency in hematopoietic tissues. In an attempt to obtain a large number of functional megakaryocytic cells, we established a serum-free culture system to grow megakaryocytic progenitor cells derived from normal human bone marrow (BM) and cord blood (CB). Highly purified (purity >95%) CD34+ cells were obtained using magnetic cell sorting (MACS) followed by fluorescence activated cell sorting (FACS). The cells were cultured in a serum-free culture system for 3 weeks in the presence of a single dose of MGDF (50 ng/mL). On days 0, 5, 8, 12, 14, 18, and 21 of culture, the cellularity and morphology were examined. Megakaryocytic cells were monitored by detecting the expression of GPIIIa (CD61), GPIIb/IIIa (CD41) and GPIb (CD42b), and the distribution of megakaryocyte (MK) ploidy was analyzed by two-color flow cytometry. MGDF alone induced maximal nucleated cell expansion at day 14, resulting in a 38.20+/-10.47-fold increase in cell number for CB and a 5.08+/-1.30-fold increase in cell number for BM. On day 14 of the culture, the percentage of CD41-/CD14- cells derived from CB reached 73.54%+/-6.01% giving an absolute number of CD41+/CD14- cells of 27.25+/-2.23 x 10(4)/mL (27,250-fold increase), whilst the percentage of CD41+/CD14- cells derived from BM was only 29.21%+/-5.63% with an absolute number of 1.36+/-0.26 x 10(4)/mL (680-fold increase). Increased expression of GPIIIa occurred the earliest in culture, followed by GPIIb/IIIa, and then GPIb. The majority (81.6%-92.6%) of megakaryocytes (CD41+ cells) on day 14 of culture were 2N, although we did detect some 4N, 8N and greater ploidy cells. In conclusion, CD34+ cells stimulated by MGDF alone generated highly enriched MK progenitor cells at day 14 of serum-free culture. CB stem and progenitor cells have a greater proliferative response to MGDF alone than those derived from BM and may, therefore, prove to be a better source of cells for MK expansion.

An estimation method for the semiparametric mixed effects model

A semiparametric mixed effects regression model is proposed for the analysis of clustered or longitudinal data with continuous, ordinal, or binary outcome. The common assumption of Gaussian random effects is relaxed by using a predictive recursion method (Newton and Zhang, 1999) to provide a nonparametric smooth density estimate. A new strategy is introduced to accelerate the algorithm. Parameter estimates are obtained by maximizing the marginal profile likelihood by Powell's conjugate direction search method. Monte Carlo results are presented to show that the method can improve the mean squared error of the fixed effects estimators when the random effects distribution is not Gaussian. The usefulness of visualizing the random effects density itself is illustrated in the analysis of data from the Wisconsin Sleep Survey. The proposed estimation procedure is computationally feasible for quite large data sets.

A quantitative extraction method for the determination of trace amounts of both butyl- and phenyltin compounds in sediments by gas chromatography-inductively coupled plasma mass spectrometry

A simple and reliable extraction method was developed for quantitative determination of both butyl- and phenyltin compounds in sediments by capillary gas chromatography combined with inductively coupled plasma mass spectrometry (GC-ICP-MS). Both types of organotin compounds were extracted quantitatively from sediment by mechanical shaking into tropolone-toluene and HCl-methanol. After phase separation and pH adjustment, these organotins were ethylated with sodium tetraethylborate. The method was evaluated by analyzing PACS-2 and NIES No. 12 sediment certified reference materials. The dibutyltin (DBT; 1.14 +/- 0.02 micrograms g-1) and tributyltin (TBT; 1.01 +/- 0.04 micrograms g-1) values observed in PACS-2 sediment closely matched the certified values (DBT, 1.09 +/- 0.15; TBT, 0.98 +/- 0.13 microgram g-1 as tin). The monobutyltin (MBT) value was higher (0.62 +/- 0.02 microgram g-1) by more than two fold over the reference value (0.3 microgram g-1 as tin). The concentrations of TBT (0.18 +/- 0.04 microgram g-1) and triphenyltin (TPhT; 0.0099 +/- 0.002 microgram g-1) in the NIES No. 12 sediment were also in good agreement with the certified and reference values of TBT (0.19 +/- 0.03 microgram g-1 as compound) and TPhT (0.008 microgram g-1 as compound), respectively. Recoveries of TBT, tripentyltin (TPeT) and TPhT from spiked sediments were satisfactory (TBT, 102 +/- 3.4%; TPrT, 96 +/- 3.4%; TPhT, 99 +/- 8.5%). The detection limits as tin were in the range 0.23-0.48 ng g-1 for a 0.5 g sample size. It is also noteworthy that clean-up of the extract is not necessary because of the superior selectivity of ICP-MS detection. The present method was successfully applied to marine sediment samples.

Does uncomplicated diverticular disease produce symptoms?

A questionnaire dealing with bowel symptoms was administered to 97 outpatients referred for air-contrast barium enema. Subsequently, the barium enema was interpreted by a radiologist who did not know the results of the questionnaire. Forty-nine had normal x-rays, and 27 had uncomplicated diverticular disease. Weight loss, rectal bleeding, abdominal pain, and pain at night were as common in those with a normal examination as in those with diverticula. Symptoms of colon dysfunction included abdominal pain relieved by defecation, altered stool frequency and consistency with pain onset, abdominal distension, feeling of incomplete evacuation after defecation, and mucus in the stool. These were equally prevalent in both groups. Therefore, no symptoms could be ascribed to the presence of diverticula.