Role of antioxidant enzymes on ionizing radiation resistance

Exposure of cells to ionizing radiation leads to formation of reactive oxygen species (ROS) that are associated with radiation-induced cytotoxicity. The antioxidant enzymes manganese superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), and glutathione peroxidase (GPx), are key intracellular antioxidants in the metabolism of ROS. We investigated the potential role of the three antioxidant enzymes in radioresistance by analyzing cell morphology, cell viability, and cellular radioresistance in stably transfected CHO cell lines overexpressing MnSOD, CuZnSOD, and GPx, respectively. We found that overexpression of human MnSOD substantially protected cells from ionizing radiation injury. Relative to MnSOD, GPx could slightly reduce the radiation sensitivity while the radioresistance in CuZnSOD expressing cells did not change significantly. The results suggested that MnSOD may play a central role in protecting cells against reactive oxygen species injury during ionizing radiation exposure among MnSOD, CuZnSOD, and GPx.

Cloning and sequence analysis of two copies of a 23S rRNA gene from Helicobacter pylori and association of clarithromycin resistance with 23S rRNA mutations

In this study, two identical copies of a 23S-5S gene cluster, which are separately situated within the Helicobacter pylori UA802 chromosome, were cloned and sequenced. Comparison of the DNA sequence of the H. pylori 23S rRNA gene with known sequences of other bacterial 23S rRNA genes indicated that the H. pylori UA802 23S rRNA genes are closely related to those of Campylobacter spp. and therefore belong in the proposed Proteobacteria subdivision. The 5'-terminal nucleotide T or A of the 23S rRNA is close to a Pribnow box which could be a -10 region of the transcription promoter for the 23S rRNA gene, suggesting that a posttranscriptional process is likely not involved in the maturation of the H. pylori 23S rRNA. Clinical isolates of H. pylori resistant to clarithromycin were examined by using natural transformation and pulsed-field gel electrophoresis. Cross-resistance to clarithromycin and erythromycin, which was transferred by natural transformation from the Cla(r) Ery(r) donor strain H. pylori E to the Cla(s) Ery(s) recipient strain H. pylori UA802, was associated with an single A-to-G transition mutation at position 2142 of both copies of the 23S rRNA in UA802 Cla(r) Ery(r) mutants. The transformation frequency for Cla(r) and Ery(r) was found to be approximately 2 x 10(-6) transformants per viable cell, and the MICs of both clarithromycin and erythromycin for the Cla(r) Ery(r) mutants were equal to those for the donor isolate. Our results confirmed the previous findings that mutations at positions 2142 and 2143 of the H. pylori 23S rRNA gene are responsible for clarithromycin resistance and suggest that acquisition of clarithromycin resistance in H. pylori could also result from horizontal transfer.

Helicobacter hepaticus infection in mice: models for understanding lower bowel inflammation and cancer

Pioneering work in the 1990s first linked a novel microaerobic bacterium, Helicobacter hepaticus, with chronic active hepatitis and inflammatory bowel disease in several murine models. Targeted H. hepaticus infection experiments subsequently demonstrated its ability to induce colitis, colorectal cancer, and extraintestinal diseases in a number of mouse strains with defects in immune function and/or regulation. H. hepaticus is now widely utilized as a model system to dissect how intestinal microbiota interact with the host to produce both inflammatory and tolerogenic responses. This model has been used to make important advances in understanding factors that regulate both acquired and innate immune response within the intestine. Further, it has been an effective tool to help define the function of regulatory T cells, including their ability to directly inhibit the innate inflammatory response to gut microbiota. The complete genomic sequence of H. hepaticus has advanced the identification of several virulence factors and aided in the elucidation of H. hepaticus pathogenesis. Delineating targets of H. hepaticus virulence factors could facilitate novel approaches to treating microbially induced lower bowel inflammatory diseases.

Changes of microstructure and mineralized tissue in the middle and late phase of osteoporotic fracture healing in rats

BACKGROUND

With osteoporosis emerged as one of the most important health issues, more and more investigations are focusing on osteoporotic fracture healing. However, there are few studies on the changes of microstructure and mineralized tissue of newly formed callus.

OBJECTIVE

We established an osteoporotic fracture rat model to evaluate the changes of microstructure and mineralized tissue during osteoporotic fracture healing.

MATERIALS AND METHODS

A mid-shaft femur fracture model was established 12 weeks after ovariectomy as an osteoporotic fracture group (OPF group). Femurs were then harvested at 4 weeks, 8 weeks and 12 weeks after fracture for peripheral quantitative computed tomography (pQCT), micro-computed tomography (MicroCT), histology and biomechanical test. A sham-operated group was used for comparison, i.e. the normal fracture group (NF group).

RESULTS

The pQCT-derived total external callus area in the OPF group was smaller than that in the NF group at 4 weeks after fracture (P<0.05), whereas it was 21% larger in the OPF group than that in the NF group at 12 weeks after fracture (P<0.01). The pQCT-derived bone mineral density in the OPF group was significantly inferior to the NF group at all the time points (P<0.05 for all the time points, respectively). MicroCT data, at 12 weeks after fracture, showed the total callus, bony callus, and newly formed bone was approximately 20% lower in the OPF group than that in the NP group, and the total connectivity was 56% lower in the OPF group as compared to the NF group. Biomechanical test data, at 12 weeks after fracture, showed that the failure load of the left femur of OPF group was 17% less compared to that of the NF group (P<0.01), and 15% lower bending stiffness (P<0.05), 20% lower bending stress (P<0.01), and 28% lower energy at failure (P<0.01) were observed in the OPF group as compared to the NF group.

CONCLUSION

The decrease in mineralized tissue and the not well connected microstructure in newly formed callus may explain the decline of mechanical impairment of fracture healing in the ovariectomized rats.

Interaction between retroviral U5 RNA and the T psi C loop of the tRNA(Trp) primer is required for efficient initiation of reverse transcription

The 5' end of avian sarcoma and leukosis virus RNA near the primer binding site forms two RNA secondary structures, U5-inverted repeat (U5-IR) and U5-leader stems, which are required for efficient initiation of reverse transcription. Lying between these two secondary structures is a 7-base sequence that can anneal to the T psi C loop of the tRNA(Trp) primer. Base substitutions in U5 RNA which disrupt this potential interaction result in a defect in the initiation of reverse transcription both in vivo and in vitro. The defect can be complemented in vitro by base substitutions in the primer. The U5 RNA-T psi C interaction is also dependent upon the presence of both the U5-IR and the U5-leader structures. These RNA secondary structures and primer interactions are conserved in other type C and D retroviruses, suggesting that there is a common mechanism for the initiation of reverse transcription in all of these retroviruses.

Lewis antigens in Helicobacter pylori: biosynthesis and phase variation

The lipopolysaccharides (LPS) of most Helicobacter pylori strains contain complex carbohydrates known as Lewis antigens that are structurally related to the human blood group antigens. Investigations on the genetic determinants involved in the biosynthesis of Lewis antigens have led to the identification of the fucosyltransferases of H. pylori, which have substrate specificities distinct from the mammalian fucosyltransferases. Compared with its human host, H. pylori utilizes a different pathway to synthesize the difucosylated Lewis antigens, Lewis y. and Lewis b. Unique features in the H. pylori fucosyltransferase genes, including homopolymeric tracts mediating slipped-strand mispairing and the elements regulating translational frameshifting, enable H. pylori to produce variable LPS epitopes on its surface. These new findings have provided us with a basis to further examine the roles of molecular mimicry and phase variation of H. pylori Lewis antigen expression in both persistent infection and pathogenesis of this important human gastric pathogen.

Cloning and heterologous expression of an alpha1,3-fucosyltransferase gene from the gastric pathogen Helicobacter pylori

Helicobacter pylori is an important human pathogen which causes both gastric and duodenal ulcers and is also associated with gastric cancer and lymphoma. This microorganism has been shown to express cell surface glycoconjugates including Lewis X (Lex) and Lewis Y. These bacterial oligosaccharides are structurally similar to tumor-associated carbohydrate antigens found in mammals. In this study, we report the cloning of a novel alpha1,3-fucosyltransferase gene (HpfucT) involved in the biosynthesis of Lex within H. pylori. The deduced amino acid sequence of HpfucT consists of 478 residues with the calculated molecular mass of 56,194 daltons, which is approximately 100 amino acids longer than known mammalian alpha1,3/1,4-fucosyltransferases. The approximately 52-kDa protein encoded by HpfucT was expressed in Escherichia coli CSRDE3 cells and gave rise to alpha1,3-fucosyltransferase activity but neither alpha1,4-fucosyltransferase nor alpha1,2-fucosyltransferase activity as characterized by radiochemical assays and capillary zone electrophoresis. Truncation of the C-terminal 100 amino acids of HpFuc-T abolished the enzyme activity. An approximately 72-amino acid region of HpFuc-T exhibits significant sequence identity (40-45%) with the highly conserved C-terminal catalytic domain among known mammalian and chicken alpha1,3-fucosyltransferases. These lines of evidence indicate that the HpFuc-T represents the bacterial alpha1,3-fucosyltransferase. In addition, several structural features unique to HpFuc-T, including 10 direct repeats of seven amino acids and the lack of the transmembrane segment typical for known eukaryotic alpha1,3-fucosyltransferases, were revealed. Notably, the repeat region contains a leucine zipper motif previously demonstrated to be responsible for dimerization of various basic region-leucine zipper proteins, suggesting that the HpFuc-T protein could form dimers.

Overlapping retrovirus U5 sequence elements are required for efficient integration and initiation of reverse transcription

A secondary structure in the 5' noncoding region of avian retrovirus RNA, called the U5-leader stem, was shown previously to have a role in initiation of reverse transcription (D. Cobrinik, L. Soskey, and J. Leis, J. Virol. 62:3622-3630, 1988). We now show that an additional RNA secondary structure near the U5 terminus, called the U5-IR stem, is also important for reverse transcription. Mutations that disrupt the U5-IR stem cause a replication defect associated with both a decrease in synthesis of viral DNA in infected cells and a decrease in initiation of reverse transcription in melittin-permeabilized virions. Structure-compensating base substitutions in the U5-IR restore reverse transcription efficiency. In viral DNA, U5-IR sequences are included in the U5 terminal region that functions as a viral integration donor site. When base substitutions are introduced into these sequences, a reduced efficiency of integration in vitro and in vivo is observed. These observations indicate that U5-IR sequences have a structural role in reverse transcription of viral RNA and a sequence-specific role in the integration of viral DNA.

Nucleotide sequence and mutational analysis indicate that two Helicobacter pylori genes encode a P-type ATPase and a cation-binding protein associated with copper transport

A 2.7 kb fragment of Helicobacter pylori UA802 chromosomal DNA was cloned and sequenced. Three open reading frames (designated ORF1, ORF2 and ORF3, respectively) were predicted from the DNA sequence, of which ORF1 and ORF2 appeared to be located within the same operon. The deduced 611-amino-acid sequence of ORF1, a P-type ATPase (designated hpCopA), had striking homology (29-38%) with several bacterial P-type ATPase and contained the potential functional domains conserved in P-type ATPases from various sources ranging from bacterial to human. A protein of 66 amino acids (designated hpCopP) encoded by ORF2 shared extensive sequence similarity with MerP, a periplasmic mercuric ion-transporting protein, and contains the heavy metal-binding motif. Disruption of ORF1 with a chloramphenicol-resistance cassette (CAT) rendered the H. pylori mutants more susceptible to cupric ion than their parental strains, whereas there is no significant alteration of susceptibility to Ni2+, Cd2d+ and Hg2+ between the mutants and the parental strains. The results obtained indicate that ORF1 and ORF2 comprise a cation-transporting system which is associated with copper export out of the H. pylori cells.

A novel urease-negative Helicobacter species associated with colitis and typhlitis in IL-10-deficient mice

A spiral-shaped bacterium with bipolar, single-sheathed flagella was isolated from the intestines of IL-10 (interleukin-10)-deficient (IL-10(-/-)) mice with inflammatory bowel disease. The organism was microaerobic, grew at 37 and 42 degrees C, and was oxidase and catalase positive but urease negative. On the basis of 16S rRNA gene sequence analysis and biochemical and phenotypic criteria, the organism is classified as a novel helicobacter. Cesarean section-rederived IL-10(-/-) mice without helicobacter infection did not have histological evidence of intestinal inflammation. However, helicobacter-free IL-10(-/-), SCID/NCr, and A/JNCr mice experimentally inoculated with the novel urease-negative Helicobacter sp. developed variable degrees of inflammation in the lower intestine, and in immunocompetent mice, the experimental infection was accompanied by a corresponding elevated immunoglobulin G antibody response to the novel Helicobacter sp. antigen. These data support other recent studies which demonstrate that multiple Helicobacter spp. in both naturally and experimentally infected mice can induce inflammatory bowel disease. The mouse model of helicobacter-associated intestinal inflammation should prove valuable in understanding how specific microbial antigens influence a complex disease process.

The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model

We have observed that low soil phosphorus availability alters the gravitropic response of basal roots in common bean (Phaseolus vulgaris L.), resulting in a shallower root system. In this study we use a geometric model to test the hypotheses that a shallower root system is a positive adaptive response to low soil P availability by (1) concentrating root foraging in surface soil horizons, which generally have the highest P availability, and (2) reducing spatial competition for P among roots of the same plant. The growth of nine root systems contrasting in gravitropic response over 320 h was simulated in SimRoot, a dynamic three-dimensional geometric model of root growth and architecture. Phosphorus acquisition and inter-root competition were estimated with Depzone, a program that dynamically models nutrient diffusion to roots. Shallower root systems had greater P acquisition per unit carbon cost than deeper root systems, especially in older root systems. This was due to greater inter-root competition in deeper root systems, as measured by the volume of overlapping P depletion zones. Inter-root competition for P was a significant fraction of total soil P depletion, and increased with increasing values of the P diffusion coefficient (De), with root age, and with increasing root gravitropism. In heterogenous soil having greater P availability in surface horizons, shallower root systems had greater P acquisition than deeper root systems, because of less inter-root competition as well as increased root foraging in the topsoil. Root P acquisition predicted by SimRoot was validated against values for bean P uptake in the field, with an r2 between observed and predicted values of 0.75. Our results support the hypothesis that altered gravitropic sensitivity in P-stressed roots, resulting in a shallower root system, is a positive adaptive response to low P availability by reducing inter-root competition within the same plant and by concentrating root activity in soil domains with the greatest P availability.

Predictive role of capsule endoscopy on the insertion route of double-balloon enteroscopy

BACKGROUND AND STUDY AIMS

Double-balloon enteroscopy (DBE) has been suggested to be more efficient if based on the results of screening video capsule endoscopy (VCE). We evaluated the utility of VCE for predicting the best insertion route of DBE for the evaluation and treatment of small-bowel lesions.

PATIENTS AND METHODS

Results of studies of patients with complete VCE examination of the small bowel and with findings confirmed by DBE are reported. A location index of lesions found on VCE was defined as the time from the pylorus to the lesion as a percentage of the time from the pylorus to the ileocecal valve. Based on our previous retrospective evaluation, a cut-off value of 0.6 was adopted, and the oral or anal approach was selected when the index was < or = 0.6 or > 0.6, respectively.

RESULTS

Data from 60 patients who underwent both VCE and DBE examinations and in whom the capsule reached the cecum were evaluated. Lesions shown on VCE were all reached by the first DBE procedures (41 orally and 19 anally). Based on the time index cut-off value of 0.6, the accuracy of selecting the insertion route of DBE was 100 %.

CONCLUSION

DBE is an effective approach for confirming VCE results. In patients with complete small-bowel investigation by VCE, the best insertion route for DBE can be reliably indicated using a time index based on the VCE records.

A specific orientation of RNA secondary structures is required for initiation of reverse transcription

The 5' end of avian retrovirus RNA near the primer-binding site (PBS) forms two secondary structures, the U5-inverted repeat (U5-IR) and the U5-leader stems, and contains a 7-nucleotide sequence that anneals to the T psi C loop of the tRNA(Trp) primer. Mutations that disrupt any of these base pair interactions cause defects in initiation of reverse transcription both in vivo and in vitro (D. Cobrinik, A. Aiyar, Z. Ge, M. Katzman, H. Huang, and J. Leis, J. Virol. 65:3864-3872, 1991; A. Aiyar, D. Cobrinik, Z. Ge, H.-J. Kung, and J. Leis, J. Virol. 66:2464-2472, 1992). We have now examined the effect of perturbing the non-base-paired intervening "spacer" sequences between these secondary-structure elements. Small deletions or insertions in these intervening sequences decreased initiation of reverse transcription in vitro. In contrast, base substitutions, which maintain the spacing distances between the structures, had no detectable effect. Additionally, a small deletion at the 3' end of the PBS caused a significant decrease in initiation of reverse transcription whereas substitution mutations again had no effect. Together, these results indicate that reverse transcriptase forms a complex in which the different structural elements are maintained in a specific orientation that is required for efficient initiation of reverse transcription. Specific sequence recognition of the duplex structures by reverse transcriptase is also required since mosaic RNAs that combine the human immunodeficiency virus type 1 PBS with avian sequences is not efficiently utilized for reverse transcription even though the primer used can anneal to the substituted PBS.

Comparison of osteogenesis of human embryonic stem cells within 2D and 3D culture systems

The objective of this study was to compare the osteogenic potential of human embryonic stem cells (hESCs) within two- and three-dimensional (2D and 3D) culture systems. hESCs of the H1 line (Wicell Inc., Madison, Wisc., USA) were induced to form embryoid bodies (EBs) through 5 days of suspension culture within non-adherent culture dishes. Following enzymatic dissociation, the EB-derived single cells were seeded on either novel 3D porous PLGA scaffolds or 2D culture dishes with the same total cell number. Osteogenic differentiation was induced through culture media supplemented with dexamethasone, L-ascorbic acid and beta-glycerophosphate. After 3 weeks of in vitro culture, quantitative and qualitative assays of osteogenic differentiation were conducted. Osteocalcin secretion and alkaline phosphatase (AP) activities were detected at significantly higher levels within 3D culture compared with the 2D system. Subsequently, the cell-scaffold constructs were implanted in iliac crest defects of immunosuppressed rabbits. After 4 weeks, the constructs were subsequently explanted and characterized by histology and X-ray analysis. Formation of new bone was detected within and around the implanted scaffolds. The results demonstrate that the osteogenic differentiation of human embryonic stem cells is enhanced in a 3D culture system compared to a 2D culture environment. Upon implantation in situ, the differentiating human embryonic stem cells can contribute positively to the repair and regeneration of bone defects.

Fluorogenic PCR-based quantitative detection of a murine pathogen, Helicobacter hepaticus

Helicobacter hepaticus infection in mice is being used as an animal model for elucidating the pathogenesis of gastrointestinal and biliary diseases in humans. H. hepaticus, which forms a spreading film on selective agar, is not amenable to routine quantitative counts of organisms in tissues using a CFU method. In this study, a fluorogenic PCR-based assay was developed to quantitatively detect H. hepaticus in mouse ceca and feces using the ABI Prism 7700 sequence detection system. A pair of primers and a probe for this assay were generated from the H. hepaticus cdtB gene (encoding subunit B of the H. hepaticus cytolethal distending toxin). Using this assay, the sensitivity for detection of H. hepaticus chromosomal DNA prepared from pure culture was 20 fg, which is equivalent to approximately 14 copies of the H. hepaticus genome based on an estimated genome size of approximately 1.3 Mb determined by pulsed-field gel electrophoresis. H. hepaticus present in feces and cecal samples from H. hepaticus-infected mice was readily quantified. The selected PCR primers and probe did not generate fluorescent signals from eight other helicobacters (H. canis, H. cineadi, H. felis, H. mustelae, H. nemestrinae, H. pullorum, H. pylori, and H. rodentium). A fluorescent signal was detected from 20 ng of H. bilis DNA but with much lower sensitivity (10(6)-fold) than from H. hepaticus DNA. Therefore, this assay can be used with high sensitivity and specificity to quantify H. hepaticus in experimentally infected mouse models as well as in naturally infected mice.

Fumarate reductase is essential for Helicobacter pylori colonization of the mouse stomach

Fumarate reductase (FRD) is the key enzyme in fumarate respiration induced by anaerobic growth of bacteria. In Helicobacter pylori, this enzyme appears to be constitutively expressed under microaerobic conditions and is not essential for its survival in vitro. In this study, the role of FRD in the colonization of H. pylori was investigated using a mouse model. The frdA gene coding for subunit A of FRD, and two control genes, copA and copP associated with the export of copper out of H. pylori, were inactivated by insertion of the chloramphenicol acetyltransferase cassette into these individual genes. The isogenic mutants of H. pylori strain AH244 were obtained by natural transformation. Seventy-five ICR mice (15 mice/group) were orogastrically dosed with either the wild type H. pylori strain AH244, its isogenic mutants, or Brucella broth (negative control). Five mice from each group were killed at 2, 4 and 8 weeks post-inoculation (WPI), respectively. H. pylori colonization was not detected in mouse gastric mucosa infected with the frdA mutant at any time point in the study by both quantitative culture and PCR. In contrast, the mice inoculated with either wild type AH244, copA or copPH. pylori mutants became readily infected. These data indicate that FRD plays a crucial role in H. pylori survival in the gastric mucosa of mice. Given that FRD, present in all H. pylori strains, is immunogenic in H. pylori -infected patients and H. pylori growth in vitro can be inhibited by three anthelmintics (morantel, oxantel and thiabendazole), this enzyme could potentially be used both as a novel drug target as well as in the development of vaccines for H. pylori prevention and eradication.

Dose-dependent protective effect of propofol against mitochondrial dysfunction in ischaemic/reperfused rat heart: role of cardiolipin

BACKGROUND AND PURPOSE

Ischaemia damages to the cardiac mitochondria by increasing generation of reactive oxygen species (ROS) and peroxidation of cardiolipin. The inhibited mitochondrial function leads to the cardiac injury during reperfusion. Propofol (2, 6-diisopropylphenol), an intravenous anaesthetic, has been shown to decrease cardiac ischaemia and reperfusion injury. In the present study, we propose that propofol protects mitochondrial function and decreases cardiac injury by prevention of cardiolipin peroxidation during ischaemia and reperfusion.

EXPERIMENTAL APPROACH

After isolation of mitochondria from isolated rat heart perfused on a Langendorff model, various mitochondrial bioenergetic parameters were evaluated such as rates of mitochondrial oxygen consumption, H(2)O(2) production, complex I and III activity as well as the degree of lipid peroxidation and cardiolipin content. The action of propofol was also explored in isolated mitochondria. And the effect of cardiolipin was evaluated by fusing cardiolipin liposome with mitochondria.

KEY RESULTS

Propofol treatment had strong dose-dependent protection attenuating these parameters alterations in reperfused rat heart and isolated mitochondria. Additionally, cardiolipin treatment had the same protective effect, compared with propofol treatment at high concentration.

CONCLUSIONS AND IMPLICATIONS

The protective effect of propofol appears to be due, at least in part, as a chemical uncoupler, to the interruption of the vicious circle of ROS-cardiolipin-complexes of the respiratory chain-ROS through preserving the content and integrity of cardiolipin molecules by ROS attack. These findings may provide an explanation for some of the factors responsible for cardioprotection and one approach exploring an available antioxidant.

Multiple-dose safety and pharmacokinetics of oral garenoxacin in healthy subjects

Garenoxacin (T-3811ME, BMS-284756) is a novel des-F(6) quinolone that has been shown to be effective in vitro against a wide range of clinically important pathogens, including gram-positive and gram-negative aerobes and anaerobes. This study was conducted to evaluate the safety and tolerability of multiple oral doses (100 to 1200 mg/day) of garenoxacin in healthy subjects and to determine its multiple-dose pharmacokinetics. Forty healthy male and female subjects (18 to 45 years of age) were enrolled in this randomized, double-blind, placebo-controlled, sequential, multiple- and ascending-dose study. Each subject received a once-daily oral dose of garenoxacin (100, 200, 400, 800, or 1200 mg) or a placebo for 14 days. Blood and urine samples were collected for measurements of garenoxacin by validated liquid chromatography with dual mass spectrometry, and plasma garenoxacin concentration-time data were analyzed by noncompartmental methods. The effects of garenoxacin on Helicobacter pylori, psychometric test performance, and electrocardiograms were assessed, as was drug safety. Over the 14 days of dosing, geometric mean peak concentrations of garenoxacin in plasma (C(max)) at the 100- and 1200-mg doses were within the ranges of 1.2 to 1.6 and 16.3 to 24 microg/ml, respectively. The corresponding values for the geometric mean area under the concentration-time curve over the dosing interval (AUC(tau)) for garenoxacin in plasma at the 100- and 1200-mg doses were within the ranges of 11.5 to 15.7 and 180 to 307 microg. h/ml, respectively. Increases in systemic exposure to garenoxacin in terms of AUC and C(max) were approximately dose proportional over the 100- to 400-mg dose range but demonstrated increases that were somewhat greater than the dose increments at the 800- and 1200-mg doses. Median values for the time to achieve C(max) were in the range of 1.13 to 2.50 h for all doses. The mean elimination half-life for garenoxacin in plasma appeared to be independent of dose and ranged from 13.3 to 17.8 h (day 14). Approximately 30 to 50% of an administered garenoxacin dose was excreted unchanged in the urine. At doses of 100 to 400 mg, steady-state concentrations of garenoxacin in plasma appeared to be attained by the fourth dose. Multiple oral doses of garenoxacin were well tolerated and did not demonstrate clinically significant effects on QT(c) or psychometric test results. Garenoxacin administered alone for 14 days at doses of >or=400 mg demonstrated activity against H. pylori. These results suggest that multiple once-daily oral doses of garenoxacin of up to 1200 mg are safe and well tolerated and that the pharmacokinetics of garenoxacin support once-daily administration.

Contributions of genome sequencing to understanding the biology of Helicobacter pylori

About half of the world's population carries Helicobacter pylori, a gram-negative, spiral bacterium that colonizes the human stomach. The link between H. pylori and, ulceration as well as its association with the development of both gastric cancer and mucosa-associated lymphoid tissue lymphoma in humans is a serious public health concern. The publication of the genome sequences of two stains of H. pylori gives rise to direct evidence on the genetic diversity reported previously with respect to gene organization and nucleotide variability from strain to strain. The genome size of H. pylori strain 26695 is 1,6697,867 bp and is 1,643,831 bp for strain J99. Approximately 89% of the predicted open reading frames are common to both of the strains, confirming H. pylori as a single species. A region containing approximately 45% of H. pylori strain-specific open reading frames, termed the plasticity zone, is present on the chromosomes, verifying that some strain variability exists. Frequent alteration of nucleotides in the third position of the triplet codons and various copies of insertion elements on the individual chromosomes appear to contribute to distinct polymorphic fingerprints among strains analyzed by restriction fragment length polymorphisms, random amplified polymorphic DNA method, and repetitive element-polymerase chain reaction. Disordered chromosomal locations of some genes seen by pulsed-field gel electrophoresis are likely caused by rearrangement or inversion of certain segments in the genomes. Cloning and functional characterization of the genes involved in acidic survival, vacuolating toxin, cag-pathogenicity island, motility, attachment to epithelial cells, natural transformation, and the biosynthesis of lipopolysaccharides have considerably increased our understanding of the molecular genetic basis for the pathogenesis of H. pylori. The homopolymeric nucleotide tracts and dinucleotide repeats, which potentially regulate the on- and off-status of the target genes by the strand-slipped mispairing mechanism, are often found in the genes encoding the outer-membrane proteins, in enzymes for lipopolysaccharide synthesis, and within DNA modification/restriction systems. Therefore, these genes may be involved in the H. pylori-host interaction.

Rapid onset of ulcerative typhlocolitis in B6.129P2-IL10tm1Cgn (IL-10-/-) mice infected with Helicobacter trogontum is associated with decreased colonization by altered Schaedler's flora

Infection with Helicobacter trogontum, a urease-positive helicobacter isolated from subclinically infected rats, was evaluated in B6.129P2-IL10(tm1Cgn) (interleukin-10(-/-) [IL-10(-/-)]) and C57BL/6 (B6) mice. In a first experiment, IL-10(-/-) mice naturally infected with Helicobacter rodentium had subclinical typhlocolitis but developed severe diarrhea and loss of body condition with erosive to ulcerative typhlocolitis within 1 to 3 weeks of experimental infection with H. trogontum. A second experiment demonstrated that helicobacter-free IL-10(-/-) mice dosed with H. trogontum also developed severe clinical signs and typhlocolitis within 2 to 4 weeks, whereas B6 mice colonized with H. trogontum were resistant to disease. In a third experiment, using helicobacter-free IL-10(-/-) mice, dosing with H. trogontum resulted in acute morbidity and typhlocolitis within 8 days. Acute typhlocolitis was accompanied by signs of sepsis supported by degenerative hemograms and recovery of Escherichia coli and Proteus spp. from the livers of infected mice. Quantitative PCR data revealed that H. rodentium and H. trogontum may compete for colonization of the lower bowel, as H. trogontum established higher colonization levels in the absence of H. rodentium (P < 0.003). H. trogontum-induced typhlocolitis was also associated with a significant decrease in the levels of colonization by five of eight anaerobes that comprise altered Schaedler's flora (P < 0.002). These results demonstrate for the first time that H. rodentium infection in IL-10(-/-) mice causes subclinical typhlocolitis and that infection with H. trogontum (with or without H. rodentium) induces a rapid-onset, erosive to ulcerative typhlocolitis which impacts the normal anaerobic flora of the colon and increases the risk of sepsis.

Characterization of knitted polymeric scaffolds for potential use in ligament tissue engineering

Different scaffolds have been designed for ligament tissue engineering. Knitted scaffolds of poly-L-lactic acid (PLLA) yarns and co-polymeric yarns of PLLA and poly(glycolic acid) (PLGA) were characterized in the current study. The knitted scaffolds were immersed in medium for 20 weeks, before mass loss, molecular weight, pH value change in medium were tested; changes in mechanical properties were evaluated at different time points. Results showed that the knitted scaffolds had 44% porosity. There was no significant pH value change during degradation, while there was obvious mass loss at initial 4 week, as well as smooth molecular weight drop of PLLA. PLGA degraded more quickly, while PLLA kept its integrity for at least 20 weeks. Young's modulus increased while tensile strength and strain at break decreased with degradation time; however, all of them could maintain the basic requirements for ACL reconstruction. It showed that the knitted polymeric structures could serve as potential scaffolds for tissue-engineered ligaments.

H. pylori DNA Transformation by Natural Competence and Electroporation

Helicobacter pylori is an important etiological pathogen of human stomach diseases, such as gastritis, peptic ulcer, and gastric carcinoma (1). In the past few years, great progress has been made in the cloning and characterization of H. pylori genes. Success of these studies stems in part from the finding that chromosomal and recombinant plasmid DNA are able to be efficiently transformed into H. pylori cells by natural competence (2-4) and electroporation (3,5). Such techniques allow the transfer of cloned H. pylori genes, manipulated in vitro, which can then shed light on the structural and functional relationships of the genes of interest. In this chapter, we describe the protocols for the isolation of H. pylori chromosomal and plasmid DNA, natural transformation, and electroporation.