bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal
Authors: Cox Daniel N. , Chao Anna , Baker Jeff , Chang Lisa , Qiao Dan , Lin Haifan
Published: February 2008

Germ-line stem cells (GSCs) serve as the source for gametogenesis in diverse organisms. We cloned and characterized the Drosophila piwi gene and showed that it is required for the asymmetric division of GSCs to produce and maintain a daughter GSC but is not essential for the further differentiation of the committed daughter cell. Genetic mosaic and RNA in situ analyses suggest that piwiexpression in adjacent somatic cells regulates GSC division.piwi encodes a highly basic novel protein, well conserved during evolution. We isolated piwi homologs inCaenorhabditis elegans and humans and also identifiedArabidopsis piwi-like genes known to be required for meristem cell maintenance. Decreasing C. elegans piwi expression reduces the proliferation of GSC-equivalent cells. Thus, piwi represents a novel class of genes required for GSC division in diverse organisms.
The bHLH protein PTF1-p48 is essential for the formation of the exocrine and the correct spatial organization of the endocrine pancreas
Authors: Krapp Andrea , Knöfler Martin , Ledermann Birgit , Bürki Kurt , Berney Catherine , Zoerkler Nicole , Hagenbüchle Otto , Wellauer Peter K.
Published: February 2008

We have generated a mouse bearing a null allele of the gene encoding basic helix–loop–helix (bHLH) protein p48, the cell-specific DNA-binding subunit of hetero-oligomeric transcription factor PTF1 that directs the expression of genes in the exocrine pancreas. The null mutation, which establishes a lethal condition shortly after birth, leads to a complete absence of exocrine pancreatic tissue and its specific products, indicating that p48 is required for differentiation and/or proliferation of the exocrine cell lineage. p48 is so far the only developmental regulator known to be required exclusively for committing cells to an exocrine fate. The hormone secreting cells of all four endocrine lineages are present in the mesentery that normally harbors the pancreatic organ until day 16 of gestation. Toward the end of embryonic life, cells expressing endocrine functions are no longer detected at their original location but are now found to colonize the spleen, where they persist in a functional state until postnatal death of the organism occurs. These findings suggest that the presence of the exocrine pancreas is required for the correct spatial assembly of the endocrine pancreas and that, in its absence, endocrine cells are directed by default to the spleen, a site that, in some reptiles, harbors part of this particular cellular compartment.
BMP4 is essential for lens induction in the mouse embryo
Authors: Furuta Yasuhide , Hogan Brigid L.M.
Published: February 2008

Vertebrate lens development is a classical model system for studying embryonic tissue interactions. Little is known, however, about the molecules mediating such inductive events. Here, we show thatBmp4, which is expressed strongly in the optic vesicle and weakly in the surrounding mesenchyme and surface ectoderm, has crucial roles during lens induction. In Bmp4tm1 homozygous null mutant embryos, lens induction is absent, but the process can be rescued by exogenous BMP4 protein applied into the optic vesicle in explant cultures. This is associated with rescue of ectodermal expression of Sox2, an early lens placode marker. Substituting the optic vesicle in explant cultures with BMP4-carrying beads, however, does not lead to lens induction, indicating that other factors produced by the optic vesicle are involved. BMP4 appears to regulate expression of a putative downstream gene, Msx2, in the optic vesicle. No change in Pax6 expression is seen inBmp4tm1 mutant eyes, and Bmp4 expression appears unaffected in the eyes of homozygousPax6Sey-1Neu, suggesting that PAX6 and BMP4 function independently. Based on these results we propose that BMP4 is required for the optic vesicle to manifest its lens-inducing activity, by regulating downstream genes and/or serving as one component of multiple inductive signals.
Transactivation-defective c-MycS retains the ability to regulate proliferation and apoptosis
Authors: Xiao Qiurong , Claassen Gisela , Shi Jingyu , Adachi Susumu , Sedivy John , Hann Stephen R.
Published: February 2008

Transcriptional activation by c-Myc through specific E box elements is thought to be essential for its biological role. However, c-MycS is unable to activate transcription through these elements and yet retains the ability to stimulate proliferation, induce anchorage-independent growth, and induce apoptosis. In addition, c-MycS retains the ability to repress transcription of several specific promoters. Furthermore, c-MycS can rescue the c-myc null phenotype in fibroblasts with homozygous deletion of c-myc. Taken together, our data argue against the paradigm that all of the biological functions of c-Myc are mediated by transcriptional activation of specific target genes through E box elements.
Double-strand break repair by interchromosomal recombination: suppression of chromosomal translocations
Authors: Richardson Christine , Moynahan Mary Ellen , Jasin Maria
Published: February 2008

To directly determine whether recombinational repair of double-strand breaks (DSBs) can occur between heterologous chromosomes and lead to chromosomal rearrangements in mammalian cells, we employed an ES cell system to analyze recombination between repeats on heterologous chromosomes. We found that recombination is induced at least 1000-fold following the introduction of a DSB in one repeat. Most (98%) recombinants repaired the DSB by gene conversion in which a small amount of sequence information was transferred from the unbroken chromosome onto the broken chromosome. The remaining recombinants transferred a larger amount of information, but still no chromosomal aberrations were apparent. Thus, mammalian cells are capable of searching genome-wide for sequences that are suitable for DSB repair. The lack of crossover events that would have led to translocations supports a model in which recombination is coupled to replication.
Maintenance of sister-chromatid cohesion at the centromere by the Drosophila MEI-S332 protein
Authors: Tang Tracy Tzu-Ling , Bickel Sharon E. , Young Lynn M. , Orr-Weaver Terry L.
Published: February 2008

Sister-chromatid cohesion is essential for the faithful segregation of chromosomes during cell division. Recently biochemical analysis withXenopus extracts suggests that cohesion is established during S phase by a cohesion complex but that other proteins must maintain it in mitosis. The Drosophila melanogaster MEI-S332 protein is present on centromeres in mitosis and meiosis and is essential for cohesion at the centromeres in meiosis II. Here, we analyze the timing of MEI-S332 assembly onto centromeres and the functional domains of the MEI-S332 protein. We find that MEI-S332 is first detectable on chromosomes during prometaphase, and this localization is independent of microtubules. MEI-S332 contains two separable functional domains, as mutations within these domains show intragenic complementation. The carboxy-terminal basic region is required for chromosomal localization. The amino-terminal coiled-coil domain may facilitate protein–protein interactions between MEI-S332 and male meiotic proteins. MEI-S332 interacts with itself in the yeast two-hybrid assay and in immunoprecipitates from Drosophila oocyte and embryo extracts. Thus it appears that MEI-S332 assembles into a multimeric protein complex that localizes to centromeric regions during prometaphase and is required for the maintenance of sister-chromatid cohesion until anaphase, rather than its establishment in S phase.
Combinatorial signaling codes for the progressive determination of cell fates in the Drosophila embryonic mesoderm
Authors: Carmena Ana , Gisselbrecht Stephen , Harrison Jacob , Jiménez Fernando , Michelson Alan M.
Published: February 2008

Mesodermal progenitors arise in the Drosophila embryo from discrete clusters of lethal of scute (l’sc)-expressing cells. Using both genetic loss-of-function and targeted ectopic expression approaches, we demonstrate here that individual progenitors are specified by the sequential deployment of unique combinations of intercellular signals. Initially, the intersection between the Wingless (Wg) and Decapentaplegic (Dpp) expression domains demarcate an ectodermal prepattern that is imprinted on the adjacent mesoderm in the form of a L’sc precluster. All mesodermal cells within this precluster are competent to respond to a subsequent instructive signal mediated by two receptor tyrosine kinases (RTKs), the Drosophila epidermal growth factor receptor (DER) and the Heartless (Htl) fibroblast growth factor receptor. By monitoring the expression of the diphosphorylated form of mitogen-associated protein kinase (MAPK), we found that these RTKs are activated in small clusters of cells within the original competence domain. Each cluster represents an equivalence group because all members initially resemble progenitors in their expression of both L’sc and mesodermal identity genes. Thus, localized RTK activity induces the formation of mesodermal equivalence groups. The RTKs remain active in the single progenitor that emerges from each cluster under the subsequent inhibitory influence of the neurogenic genes. Moreover, DER and Htl are differentially involved in the specification of particular progenitors. We conclude that distinct cellular identity codes are generated by the combinatorial activities of Wg, Dpp, EGF, and FGF signals in the progressive determination of embryonic mesodermal cells.
Cytosine methylation and mammalian development
Authors: Walsh Colum P. , Bestor Timothy H.
Published: February 2008

Programmed methylation and demethylation of regulatory sequences has been proposed to play a central role in vertebrate development. We report here that the methylation status of the 5′ regions of a panel of tissue-specific genes could not be correlated with expression in tissues of fetal and newborn mice. Genes reported to be regulated by reversible methylation were not expressed ectopically or precociously in Dnmt1-deficient mouse embryos under conditions where demethylation caused biallelic expression of imprinted genes and activated transcription of endogenous retroviruses of the IAP class. These and other data suggest that the numerous published expression–methylation correlations may have described not a cause but a consequence of transcriptional activation. A model is proposed under which cytosine methylation represents a biochemical specialization of large genomes that participates in specialized biological functions such as allele-specific gene expression and the heritable transcriptional silencing of parasitic sequence elements, whereas cellular differentiation is controlled by conserved regulatory networks that do not depend on covalent modification of the genome.
Keap1 represses nuclear activation of antioxidant responsive elements by Nrf2 through binding to the amino-terminal Neh2 domain
Authors: Itoh Ken , Wakabayashi Nobunao , Katoh Yasutake , Ishii Tetsuro , Igarashi Kazuhiko , Engel James Douglas , Yamamoto Masayuki
Published: February 2008

Transcription factor Nrf2 is essential for the antioxidant responsive element (ARE)-mediated induction of phase II detoxifying and oxidative stress enzyme genes. Detailed analysis of differential Nrf2 activity displayed in transfected cell lines ultimately led to the identification of a new protein, which we named Keap1, that suppresses Nrf2 transcriptional activity by specific binding to its evolutionarily conserved amino-terminal regulatory domain. The closest homolog of Keap1 is a Drosophila actin-binding protein called Kelch, implying that Keap1 might be a Nrf2 cytoplasmic effector. We then showed that electrophilic agents antagonize Keap1 inhibition of Nrf2 activity in vivo, allowing Nrf2 to traverse from the cytoplasm to the nucleus and potentiate the ARE response. We postulate that Keap1 and Nrf2 constitute a crucial cellular sensor for oxidative stress, and together mediate a key step in the signaling pathway that leads to transcriptional activation by this novel Nrf2 nuclear shuttling mechanism. The activation of Nrf2 leads in turn to the induction of phase II enzyme and antioxidative stress genes in response to electrophiles and reactive oxygen species.
The type 2C Ser/Thr phosphatase PP2Cγ is a pre-mRNA splicing factor
Authors: Murray Michael V. , Kobayashi Ryuji , Krainer Adrian R.
Published: February 2008

To identify activities involved in human pre-mRNA splicing, we have developed a procedure to separate HeLa cell nuclear extract into five complementing fractions. An activity called SCF1 was purified from one of these fractions by assaying for reconstitution of splicing in the presence of the remaining four fractions. A component of SCF1 is shown to be PP2Cγ, a type 2C Ser/Thr phosphatase of previously unknown function. Previous work suggested that dephosphorylation of splicing factors may be important for catalysis after spliceosome assembly, although the identities of the specific phosphatases involved remain unclear. Here we show that human PP2Cγ is physically associated with the spliceosome in vitro throughout the splicing reaction, but is first required during the early stages of spliceosome assembly for efficient formation of the A complex. The phosphatase activity is required for the splicing function of PP2Cγ, as an active site mutant does not support spliceosome assembly. The requirement for PP2Cγ is highly specific, as the closely related phosphatase PP2Cα cannot substitute for PP2Cγ. Consistent with a role in splicing, PP2Cγ localizes to the nucleus in vivo. We conclude that at least one specific dephosphorylation event catalyzed by PP2Cγ is required for formation of the spliceosome.
Prediction of reversibly oxidized protein cysteine thiols using protein structure properties
Authors: Sanchez Ricardo , Riddle Megan , Woo Jongwook , Momand Jamil
Published: February 2008

Protein cysteine thiols can be divided into four groups based on their reactivities: those that form permanent structural disulfide bonds, those that coordinate with metals, those that remain in the reduced state, and those that are susceptible to reversible oxidation. Physicochemical parameters of oxidation‐susceptible protein thiols were organized into a database named the Balanced Oxidation Susceptible Cysteine Thiol Database (BALOSCTdb). BALOSCTdb contains 161 cysteine thiols that undergo reversible oxidation and 161 cysteine thiols that are not susceptible to oxidation. Each cysteine was represented by a set of 12 parameters, one of which was a label (1/0) to indicate whether its thiol moiety is susceptible to oxidation. A computer program (the C4.5 decision tree classifier re‐implemented as the J48 classifier) segregated cysteines into oxidation‐susceptible and oxidation‐non‐susceptible classes. The classifier selected three parameters critical for prediction of thiol oxidation susceptibility: (1) distance to the nearest cysteine sulfur atom, (2) solvent accessibility, and (3) pKa. The classifier was optimized to correctly predict 136 of the 161 cysteine thiols susceptible to oxidation. Leave‐one‐out cross‐validation analysis showed that the percent of correctly classified cysteines was 80.1% and that 16.1% of the oxidation‐susceptible cysteine thiols were incorrectly classified. The algorithm developed from these parameters, named the Cysteine Oxidation Prediction Algorithm (COPA), is presented here. COPA prediction of oxidation‐susceptible sites can be utilized to locate protein cysteines susceptible to redox‐mediated regulation and identify possible enzyme catalytic sites with reactive cysteine thiols.
The solution structure of ZNF593 from Homo sapiens reveals a zinc finger in a predominately unstructured protein
Authors: Hayes Paulette L. , Lytle Betsy L. , Volkman Brian F. , Peterson Francis C.
Published: February 2008

Here, we report the solution structure of ZNF593, a protein identified in a functional study as a negative modulator of the DNA‐binding activity of the Oct‐2 transcription factor. ZNF593 contains a classic C2H2 zinc finger domain flanked by about 40 disordered residues on each terminus. Although the protein contains a high degree of intrinsic disorder, the structure of the zinc finger domain was resolved by NMR spectroscopy without a need for N‐ or C‐terminal truncations. The tertiary structure of the zinc finger domain is composed of a β‐hairpin that positions the cysteine side chains for zinc coordination, followed by an atypical kinked α‐helix containing the two histidine side chain ligands. The structural topology of ZNF593 is similar to a fragment of the double‐stranded RNA‐binding protein Zfa and the C‐terminal zinc finger of MBP‐1, a human enhancer binding protein. The structure presented here will provide a guide for future functional studies of how ZNF593 negatively modulates the DNA‐binding activity of Oct‐2, a POU domain‐containing transcription factor. Our work illustrates the unique capacity of NMR spectroscopy for structural analysis of folded domains in a predominantly disordered protein.
An intramolecular FRET system monitors fingers subdomain opening in Klentaq1
Authors: Allen William J. , Rothwell Paul J. , Waksman Gabriel
Published: February 2008

A major goal of polymerase research is to determine the mechanism through which a nucleotide complementary to a templating DNA base is selected and delivered to the polymerase active site. Structural evidence suggests a large open‐to‐closed conformational change affecting the fingers subdomain as being crucial to the process. We previously designed a FRET system capable of measuring the rate of fingers subdomain closure in the presence of correct nucleotide. However, this FRET system was limited in that it could not directly measure the rate of fingers subdomain opening by FRET after polymerization or in the absence of DNA. Here we report the development of a new system capable of measuring both fingers subdomain closure and reopening by FRET, and show that the rate of fingers subdomain opening is limited only by the rate of polymerization. We anticipate that this system will scale down to the single molecule level, allowing measurement of fingers subdomain movements in the presence of incorrect nucleotide and in the absence of DNA.
Integrin alphavbeta6 mediates the potential for colon cancer cells to colonize in and metastasize to the liver
Authors: Yang Guang‐Yun , Xu Ke‐Sen , Pan Zhong‐Qing , Zhang Zhao‐Yang , Mi Yue‐Tang , Wang Jin‐Shen , Chen Rong , Niu Jun
Published: February 2008

Integrin alphavbeta6 (αvβ6) is correlated with colon cancer progression. To detect the effects of αvβ6 on liver metastasis, the specificity of αvβ6 against the monoclonal antibody (mAb) 2G2 was examined by immunoprecipitation. Integrin αvβ6‐immunoreactivity (IR) in liver metastasis tissues (63 cases) and colon carcinoma (358 cases) were examined. These results showed that αvβ6 was specifically recognized by the mAb 2G2, and that rates of αvβ6 positivity in liver metastatic tissues (71.4%, 45/63) were higher than that for primary colon cancer (34.0%, 122/358) (P < 0.01). Patients who were αvβ6‐positive had higher liver metastasis rates (17%, 21/122) than those who were αvβ6‐negative (only 3%, 7/236) (P < 0.01). To examine the underlying mechanisms associated with αvβ6 regulating colonic metastasis in the liver, experimental liver metastasis (intrasplenic injection of HT29 transfectants) and liver colonization assays (direct injection of WiDr transfectants into the liver) in nude mice were performed; these demonstrated that αvβ6 contributed to the promotion of the metastatic potential and the survival of cancer cells in the liver. Matrix metalloproteinase‐9 (MMP‐9) levels in the cultures of both HT29 and WiDr cells were detected by the Biotrak MMP‐9 activity assay system and gelatin zymography assay, and showed that suppression of αvβ6‐IR inhibited MMP‐9 activity and secretion. Transwell migration assay in vitro also showed that αvβ6 promoted migration on fibronectin for HT29/WiDr mock compared with HT29/WiDr antisense β6 transfects (P < 0.01). We concluded that αvβ6 may mediate the potential for colon cancer cells to colonize in and metastasize to the liver. The mechanisms that αvβ6 may be involved in include the promotion of MMP‐9 secretion, the enhancement of migration on fibronectin, and the survival of cancer cells in the liver. (Cancer Sci 2008; 99: 879–887)
Phase I study of dexamethasone, methotrexate, ifosfamide, l‐asparaginase, and etoposide (SMILE) chemotherapy for advanced‐stage, relapsed or refractory extranodal natural killer (NK)/T‐cell lymphoma and leukemia
Authors: Yamaguchi Motoko , Suzuki Ritsuro , Kwong Yok‐Lam , Kim Won Seog , Hasegawa Yuichi , Izutsu Koji , Suzumiya Junji , Okamura Takayuki , Nakamura Shigeo , Kawa Keisei , Oshimi Kazuo
Published: February 2008

Extranodal natural killer (NK)/T‐cell lymphoma, nasal type, and aggressive NK‐cell leukemia are rare, and their standard therapy has not been established. They are Epstein–Barr virus‐associated lymphoid malignancies, and tumor cells express P‐glycoprotein leading to multidrug resistance of the disease. Patients with stage IV, relapsed or refractory diseases have a dismal prognosis, with survival measured in months only. To develop an efficacious chemotherapeutic regimen, we conducted a dose‐escalation feasibility study of a new chemotherapeutic regimen, SMILE, comprising the steroid dexamethasone, methotrexate, ifosfamide, l‐asparaginase, and etoposide. The components of SMILE are multidrug resistance‐unrelated agents and etoposide. Etoposide shows both in vitro and in vivo efficacy for Epstein–Barr virus‐associated lymphoproliferative disorders. Eligible patients had newly diagnosed stage IV, relapsed or refractory diseases after first‐line chemotherapy, were 15–69 years of age, and had satisfactory performance scores (0–2). Four dose levels of methotrexate and etoposide were originally planned to be evaluated. At level 1, six patients with extranodal NK/T‐cell lymphoma, nasal type, were enrolled. Their disease status was newly diagnosed stage IV (n = 3), first relapse (n = 2), and primary refractory (n = 1). All of the first three patients developed dose‐limiting toxicities, and one of them died of sepsis with grade 4 neutropenia. A protocol revision stipulating early granulocyte colony‐stimulating factor administration was made. Two out of three additional patients developed dose‐limiting toxicities that were all manageable and transient. For the six enrolled patients, the overall response rate was 67% and the complete response rate was 50%. Although its safety and efficacy require further evaluation, we recommend a SMILE chemotherapy dose level of 1 for further clinical studies. (Cancer Sci 2008; 99: 1016–1020)
Pharmacokinetic considerations regarding non‐viral cancer gene therapy
Authors: Nishikawa Makiya , Takakura Yoshinobu , Hashida Mitsuru
Published: February 2008

Cancer gene therapy, in which pharmacologically active compounds are administered to cancer patients in a genetic form, has been examined not only in animals but also in cancer patients. Viral vector‐induced severe side effects in patients have greatly underscored the importance of non‐viral gene transfer methods. Even though the importance of pharmacokinetics is undoubtedly understood in the development of anticancer therapies, its importance has been less well recognized in non‐viral cancer gene therapy. When transgene products express their activity within transduced cells, such as herpes simplex virus type 1 thymidine kinase and short hairpin RNA, the pharmacokinetics of the vectors and the expression profiles of the transgenes will determine the efficacy of gene transfer. The percentage of cells transduced is highly important if few by‐stander effects are expected. If transgene products are secreted from cells into the blood circulation, such as interferons and interleukins, the pharmacokinetics of transgenes becomes a matter of significant importance. Then, any approach to increasing the level and duration of transgene expression will increase the therapeutic effects of cancer gene therapy. Here we review the pharmacokinetics of both non‐viral vectors and transgene products, and discuss what should be done to achieve safer and more effective non‐viral cancer gene therapy. (Cancer Sci2008; 99: 856–862)
Papaya ringspot virus‐P: characteristics, pathogenicity, sequence variability and control
Authors: TRIPATHI SAVARNI , SUZUKI JON Y. , FERREIRA STEPHEN A. , GONSALVES DENNIS
Published: February 2008

Taxonomy:  Papaya ringspot virus (PRSV) is an aphid‐transmitted plant virus belonging to the genus Potyvirus, family Potyviridae, with a positive sense RNA genome. PRSV isolates belong to either one of two major strains, P or W. The P strains infect both papaya and cucurbits whereas the W strains infect only cucurbits.

Geographical distribution:  PRSV‐P is found in all major papaya‐growing areas.

Physical properties:  Virions are filamentous, non‐enveloped and flexuous measuring 760–800 × 12 nm. Virus particles contain 94.5% protein and 5.5% nucleic acid. The protein component consists of the virus coat protein (CP), which has a molecular weight of about 36 kDa as estimated by Western blot analysis. Density of the sedimenting component in purified PRSV preparations is 1.32 g/cm3 in CsCl.

Genome:  The PRSV genome consists of a unipartite linear single‐stranded positive sense RNA of 10 326 nucleotides with a 5′ terminus, genome‐linked protein, VPg.

Transmission:  The virus is naturally transmitted via aphids in a non‐persistent manner. Both the CP and helper component (HC‐Pro) are required for vector transmission. This virus can also be transmitted mechanically, and is typically not seed‐transmitted.

Hosts:  PRSV has a limited number of hosts belonging to the families Caricaceae, Chenopodiaceae and Cucurbitaceae. Propagation hosts are: Carica papaya, Cucurbita pepo and Cucumis metuliferus cv. accession 2459. Local lesion assay hosts are: Chenopodium quinoa and Chenopodium amaranticolor.

Control:  Two transgenic papaya varieties, Rainbow and SunUp, with engineered resistance to PRSV have been commercially grown in Hawaii since 1998. Besides transgenic resistance, tolerant varieties, cross‐protection and other cultural practices such as isolation and rogueing of infected plants are used to manage the disease.

Virus code:  00.057.0.01.045.

Virus accession number:  57010045.

Useful link:  http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/57010045.htm
Population pharmacokinetics of chloroquine and sulfadoxine and treatment response in children with malaria: suggestions for an improved dose regimen
Authors: Obua Celestino , Hellgren Urban , Ntale Muhammed , Gustafsson Lars L. , Ogwal‐Okeng Jasper W. , Gordi Toufigh , Jerling Markus
Published: February 2008

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Both chloroquine (CQ) and sulfadoxine/ pyrimethamine (SDx/PYR) remain important drugs in the control of malaria.

• The available data on CQ, SDx and PYR are summary pharmacokinetic parameters based on classical/traditional methods, mostly in adults.

• No study has described the population pharmacokinetics of a fixed‐dose CQ + SDx/PYR combination in children with falciparum malaria.

WHAT THIS STUDY ADDS

• This study presents population pharmacokinetic data on CQ and SDx in children with uncomplicated falciparum malaria.

• The study demonstrates that in age‐based fixed‐dose regimens with CQ and SDx, drug exposures and outcomes may be correctly predicted, although correlation with body weight is poor.

• The study proposes dose modification to improve response with the CQ + SDx/PYR combination.

AIMS

To describe the pharmacokinetics of chloroquine (CQ) and sulfadoxine (SDx), and to identify predictors of treatment response in children with malaria given the CQ + SDx and pyrimethamine (PYR) combination.

METHODS

Eighty‐six Ugandan children with uncomplicated falciparum malaria, 6 months to 5 years old, were randomly treated with prepacked fixed‐dose CQ + SDx/PYR. The youngest children (<24 months) received half strength and the older (>24 months) full strength treatment. The reported day 14 failure rates were 48% and 18%, respectively. Capillary blood (100 μl) applied on to filter paper was collected on eight occasions during 28 days of follow up. Concentrations of CQ and SDx were determined. A population approach was used for the pharmacokinetic analysis.

RESULTS

A two‐compartment model adequately described the data for both CQ and SDx. For CQ, the typical apparent clearance (CL/F) and volume of distribution (VC/F) values were estimated to be 2.84 l h−1 and 230 l. The typical CL/F for SDx was 0.023 l h−1, while the factor relating its VC/F to normalized body weight was 1.6 l kg−1. Post hoc parameter estimates for both drugs showed lower maximum concentrations (Cmax) and concentration‐time curve areas (AUC(0,336 h)) in younger children. The AUC(0,336 h) for SDx and CQ were independently significant factors for prediction of cure. Simulations suggest that giving the higher dose to the youngest children would result in higher CQ and SDx concentrations and improved outcome.

CONCLUSIONS

The study results suggest that full‐strength combination to all children would improve the cure rate.
Prescription drug use among fathers and mothers before and during pregnancy. A population‐based cohort study of 106 000 pregnancies in Norway 2004–2006
Authors: Engeland Anders , Bramness Jørgen G. , Daltveit Anne Kjersti , Rønning Marit , Skurtveit Svetlana , Furu Kari
Published: February 2008

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Mothers are using medicines during pregnancies; the extent varies across the world and is generally difficult to compare.

• In this registry‐based study, we examined more than 100 000 Norwegian pregnancies and described the drug prescription pattern of both fathers and mothers around conception and during pregnancy (mothers).

WHAT THIS STUDY ADDS

• In every trimester of pregnancy, about 30% of the mothers was dispensed a drug.

• The total drug exposure did not seem to diminish throughout pregnancy.

• One‐quarter of the fathers was dispensed drugs during the last 3 months prior to conception.

AIMS

The primary aim of this study was to describe the use of prescribed drugs in both mothers and fathers before and during pregnancy in Norway.

METHODS

This population‐based cohort study was based on data retrieved from the Medical Birth Registry of Norway and the Norwegian Prescription Database. These registries cover the entire population of Norway. Information on >100 000 births during 2004–2006 in the birth registry was linked to prescription data. Prescriptions issued to mothers just prior to, during and after the pregnancies as well as prescriptions to fathers just prior to conception were identified.

RESULTS

Among mothers, 83% were prescribed drugs during the period 3 months prior to estimated conception until 3 months after giving birth. The mothers who received drugs were prescribed on average 3.3 different Anatomical Therapeutic Chemical (ATC) codes (range 1–38). During pregnancy, 57% were prescribed drugs. In the first trimester, 33% of mothers were dispensed drugs, while the figure was 29% for mothers in the last trimester. Among fathers, 25% used prescribed drugs during the 3 months prior to conception, with on average 1.9 different ATC codes (range 1–22).

CONCLUSION

Large proportions of both fathers and mothers were dispensed drugs prior to conception or during pregnancy. While there is a high awareness of the issues involved in maternal drug use in pregnancy, possible teratogenic effects of drug use in fathers shortly before conception should be further explored.
Increased omeprazole metabolism in carriers of the CYP2C19*17 allele; a pharmacokinetic study in healthy volunteers
Authors: Baldwin R. Michael , Ohlsson Staffan , Pedersen Rasmus Steen , Mwinyi Jessica , Ingelman‐Sundberg Magnus , Eliasson Erik , Bertilsson Leif
Published: February 2008

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• The only existing study of CYP2C19*17‐associated alterations in drug pharmacokinetics was retrospective and compared probe drug metabolic ratios.

• The CYP2C19*17 allele had been associated with a two‐ and fourfold decrease in omeprazole and S/R‐mephenytoin metabolic ratios.

WHAT THIS STUDY ADDS

• This study characterized the single‐dose pharmacokinetics of omeprazole, along with the 5‐hydroxy and sulphone metabolites, in CYP2C19*17/*17 and CYP2C19*1/*1 subjects.

• The observed differences in omeprazole AUC∞ suggest that the CYP2C19*17 allele is an important explanatory factor behind individual cases of therapeutic failure.

AIMS

To investigate the influence of the CYP2C19*17 allele on the pharmacokinetics of omeprazole, a commonly used CYP2C19 probe drug, in healthy volunteers.

METHODS

In a single‐dose pharmacokinetic study, 17 healthy White volunteers genotyped as either CYP2C19*17/*17 or CYP2C19*1/*1 received an oral dose of 40 mg of omeprazole. Plasma was sampled for up to 10 h postdose, followed by quantification of omeprazole, 5‐hydroxy omeprazole and omeprazole sulphone by high‐performance liquid chromatography.

RESULTS

The mean omeprazole AUC∞ of 1973 h nmol l−1 in CYP2C19*17/*17 subjects was 2.1‐fold lower [95% confidence interval (CI) 1.1, 3.3] than in CYP2C19*1/*1 subjects (4151 h nmol l−1, P = 0.04). A similar trend was observed for the sulphone metabolite with the CYP2C19*17/*17 group having a mean AUC∞ of 1083 h nmol l−1, 3.1‐fold lower (95% CI 1.2, 5.5) than the CYP2C19*1/*1 group (3343 h nmol l−1, P = 0.03). A pronounced correlation (r2 = 0.95, P < 0.0001) was seen in the intraindividual omeprazole AUC∞ and omeprazole sulphone AUC∞ values.

CONCLUSIONS

The pharmacokinetics of omeprazole and omeprazole sulphone differ significantly between homozygous CYP2C19*17 and CYP2C19*1 subjects. For clinically important drugs that are metabolized predominantly by CYP2C19, the CYP2C19*17 allele might be associated with subtherapeutic drug exposure.
Interleukin‐12 is necessary for the priming of CD4+ T cells required during the elicitation of HIV‐1 gp120‐specific cytotoxic T‐lymphocyte function
Authors: Gupta Shalini , Boppana Ramanamurthy , Mishra Gyan C. , Saha Bhaskar , Mitra Debashis
Published: February 2008

The mechanism of the T‐cell response and cytokine induction to restrict human immunodeficiency virus 1 (HIV‐1) infection is not clear. During early infection, HIV‐infected individuals have a high frequency of virus‐specific cytotoxic T lymphocytes (CTLs) that effectively reduces the viral load. However, the CTLs are unable to clear the virus at later stages of infection, leading to disease progression. Dysregulation of cytokines like interleukin‐12 (IL‐12) and interferon‐γ (IFN‐γ) as a result of the interaction of HIV‐1‐specific T cells with antigen‐presenting cells is one of the possible causes of CTL dysfunction. Secretion of IL‐12 is reduced with the progression of HIV infection, correlating with impaired CTL function; however, the role of IL‐12 in CTL regulation awaits elucidation. Here, we have studied the role of IL‐12 in CTL dysfunction by using DNA immunization of wild‐type (WT) and IL‐12‐deficient mice with HIV‐1 gp120 complementary DNA. It was observed that the CTL response in IL‐12‐deficient mice was significantly less than that in WT mice. Our results further demonstrated that coimmunization with IL‐12 vector restored the impaired CTL response in IL‐12‐deficient mice. However, immunization with IL‐12 vector failed to rescue the CTL response in IFN‐γ deficient mice, suggesting that the CTL‐promoting function of IL‐12 is IFN‐γ‐mediated. Our data suggest a phase‐specific role of IL‐12 in the CTL response, specifically in the priming of CD4+ T cells that provide help to CD8+ T cells. Our results also suggest that IL‐12 is vital for the priming of antigen‐specific T cells and plays an essential role in IFN‐γ induction in T cells.
Comparison of operative procedure variables on pulpal viability in an ex vivo model
Authors: Murray P. E. , Smith A. J. , Garcia‐Godoy F. , Lumley P. J.
Published: February 2008

Aim  To measure and compare the responses of pulp tissue to cavity preparation and restoration variables using a novel tooth slice culture model.

Methodology  Experimental cavities (265) were continuously cut, under carefully controlled conditions, into the dentine of the labial aspect of 28‐day‐old Wistar rat incisors, and slices of these teeth maintained in organ culture for up to 2 weeks. The experimental variables examined were: the preparation method, remaining dentine thickness, coolant, drill speed, conditioning with EDTA and filling materials. The reactions of the dentine–pulp complex to the experimental variables were measured using pathohistometric analysis and the correlations between variables were determined using analysis of variance statistical tests.

Results  In rank order of surgically induced restorative pulpal injury, from the most to the least injurious were: remaining dentine thickness, absence of coolant during cavity preparation, bur speed, cavity conditioning treatments and the filling material.

Conclusions  To reduce pulp injury and to promote pulpal repair activity, the correct use of appropriate materials are important. However, of relatively greater importance is the operative technique adopted, the need to avoid the excess removal of dentine and to minimize trauma during preparation.
In vitro fluoride uptake by bovine enamel from aesthetic restorative materials
Authors: AHIROPOULOS VASILIS , HELVATJOGLU‐ANTONIADES MARIA , PAPADOGIANNIS YANNIS
Published: February 2008

Objectives.  The purposes of this in vitro study were to determine whether different types of fluoride‐containing restoratives produce differing levels of fluoride uptake by bovine enamel, and to determine the effect of time on this uptake.

Methods.  Seven aesthetic restorative materials were evaluated. Forty bovine enamel slabs were prepared for each tested material, five of which were used to determine baseline fluoride concentrations. Each slab was attached to a disc of the tested material and suspended in synthetic saliva for up to 64 days. After removal, the specimens were acid etched with perchloric acid, and the dissolved enamel was analysed for fluoride and calcium. Fluoride was determined by direct potensiometric analysis, whereas the amount of calcium was evaluated by means of atomic absorption spectrophotometry.

Results.  Higher values of fluoride uptake, not significantly different, were recorded in the first two groups. A statistically significant difference was found in fluoride uptake between Fuji II LC and the three compomers in all test intervals. No significant differences were found in the amounts of fluoride uptake between the three compomers. The highest fluoride uptake from all compomers was recorded by F2000.

Conclusion.  Enamel acquired significant amounts of fluoride from all materials with variations during the test intervals.
Correlation of bone age, dental age, and chronological age in survivors of childhood acute lymphoblastic leukaemia
Authors: MARTIN MARY BETH , LI CHIN‐SHANG , ROWLAND CHRISTOPHER C. , HOWARD SCOTT C. , KASTE SUE C.
Published: February 2008

Background. There is little information about oncotherapy‐related dental development in childhood acute lymphoblastic leukaemia (ALL).

Objective.  The objective of this study was to compare bone age (BA) and dental age (DA) to chronological age (CA) in childhood ALL survivors.

Methods.  We retrospectively reviewed hand–wrist and panoramic radiographs of patients treated on contemporary single institution protocols for ALL between 1991 and 2004. We recorded patient demographics, therapeutic protocol, CA, DA, and BA. The cohort was divided into three categories based on age at diagnosis (< 6 years, 6–9 years, > 9 years).

Results.  Of 73 patients, 39 (53.4%) were boys; 55 (75.3%) were Caucasian. Median CA at diagnosis was 4.5 years (range: 0.1–11.0 years); time to study was 4.1 years (range: 0.3–11.4 years). BA was normal in 61 (83.6%), delayed in 10 (13.7%), and advanced in 2 (2.7%). DA was normal in 41 (56.9%), delayed in 8 (11.1%), and advanced in 23 (31.9%). Abnormal BA, abnormal DA, and discrepancy between BA and DA are not statistically significantly associated with investigated patient or treatment factors.

Conclusions.  DA may be altered in 43.1% of patients treated for ALL. A large prospective study is warranted to better define our observations and to determine their impact on dental and orthodontic management.
A clinical and histological study of dental defects in a 10‐year‐old girl with pseudoxanthoma elasticum and amelogenesis imperfecta
Authors: MORRIER JEAN‐JACQUES , ROMEAS ANNICK , LACAN EMILIE , FARGES JEAN‐CHRISTOPHE
Published: February 2008

Background.  The prominent dental feature of a 10‐year‐old girl was severely hypoplastic enamel in permanent teeth.

Case report.  Severe dental defects were detected in a 10‐year‐old female patient affected by pseudoxanthoma elasticum and amelogenesis imperfecta. An orthopantomographic examination revealed a reduction of enamel thickness on the crown of all erupted and unerupted teeth, agenesis of the maxillary right second premolar, delayed eruption of mandibular first premolars, and the presence of large calcifications in all tooth pulp chambers. A detailed histological analysis of permanent mandibular first molars showed that pulp calcifications presented a concentric laminate organization and merged to almost completely obliterate the pulp chamber. Osteodentine was visible all along the pulpal surface of the radicular dentine. Broad resorption areas were present in the outermost dentine at both coronal and radicular levels. Radicular resorption areas presented a typical rectangular form and were filled with acellular cementum. Cementum thickness was highly increased on the root surface. Apposition of cellular cementum‐like tissue was also observed on the coronal dentine surface.

Conclusion.  Before treating patients affected by amelogenesis imperfecta and/or pseudoxanthoma elasticum, paediatric dentists should be aware of the presence of pulp calcifications that add to the complexity of endodontic procedures.
Heat‐treated glass ionomer cement fissure sealants: retention after 1 year follow‐up
Authors: SKRINJARIC KRISTINA , VRANIC DUBRAVKA NEGOVETIC , GLAVINA DOMAGOJ , SKRINJARIC ILIJA
Published: February 2008

Objective.  The aim of this study was to assess the retention rate of glass ionomer cement (GIC) fissure sealants heated during setting time.

Methods.  One hundred and twelve teeth with well‐delineated fissure morphology were sealed with composite resin and GIC. Composite resin (Helioseal F, Vivadent) was used in control group A (56 teeth). GIC (Fuji VII, GC) was applied using split‐mouth design with conditioning in group B (26 teeth) and without surface conditioning in group C (30 teeth). GIC was heated with external heat source (Elipar Trilight, Espe) for 40 s during the setting time according to the manufacturer's instructions. Fissure sealants were evaluated 1 year after clinical service.

Results.  Retention rate in group A was 80.4% after 1 year of clinical service. Group B showed retention rate of 30.8%, and group C of 26.7%. Two new caries lesions were detected in groups B and C. Significant differences in retention between the composite group and GIC groups were obtained by Kruskal–Wallis and Mann–Whitney tests.

Conclusion.  It could be concluded that retention rate of GIC sealing treated with heat during setting time was significantly lower than retention of conventional composite resin. The heating procedure during setting of GIC sealants cannot be recommended as routine treatment in clinical practice.
Ghrelin Induces Growth Hormone Secretion Via a Nitric Oxide /cGMP Signalling Pathway
Authors: Rodríguez‐Pacheco F. , Luque R. M. , Tena‐Sempere M. , Malagón M. M. , Castaño J. P.
Published: February 2008

The presence of ghrelin and its receptor, growth hormone (GH) secretagogue receptor, in the hypothalamus and pituitary, and its ability to stimulate GH release in vivo and in vitro, strongly support a significant role for this peptide in the control of somatotroph function. We previously demonstrated that ghrelin elicits GH secretion directly in somatotrophs by activating two major signalling cascades, which involve inositol phosphate and cAMP. In as much as nitric oxide (NO) and its mediator cGMP have been recently shown to contribute substantially to the response of somatotrophs to key regulatory hormones, including GH‐releasing hormone, somatostatin and leptin, we investigated the possible role of this signalling pathway in ghrelin‐induced GH release in vitro. Accordingly, cultures of pituitary cells from prepuberal female pigs were challenged with ghrelin (10−8 m, 30 min) in the absence or presence of activators or blockers of key steps of the NO synthase (NOS)/NO/guanylate cyclase (GC)/cGMP route and GH secretion was measured. Two distinct activators of the NO route, S‐nitroso‐N‐acetylpenicillamine (SNAP) (5 × 10−4 m) and l‐arginine methyl ester hydrochloride (l‐AME) (10−3 m), comparably stimulated GH secretion when applied alone. The presence of l‐AME enhanced ghrelin‐stimulated GH secretion, whereas SNAP did not alter its effect. Conversely, two different NOS/NO pathway inhibitors, Nw‐nitro‐l‐arginine methyl ester hydrochloride (10−5 m) or haemoglobin (20 μg/ml), similarly blocked ghrelin‐induced (but not basal) GH release, thus indicating that NO contributes critically to ghrelin action in somatotrophs. Moreover, incubation with a permeable cGMP analogue, 8‐Br‐cGMP (10−8 m) stimulated GH secretion, but did not modify the stimulatory action of ghrelin, suggesting that cGMP could mediate the action of NO. Indeed, inhibition of GC by 10 μm LY‐53,583 did not alter basal GH secretion but abolished the GH‐releasing action of ghrelin. Taken together, our results provide novel evidence indicating that ghrelin requires activation of the NOS/NO route, and its subsequent GC/cGMP signal transduction pathway, as necessary steps to induce GH secretion from somatotrophs.
Type 1 Angiotensin Receptor (AT1‐R)‐Mediated Decrease in Type 2 Angiotensin Receptor mRNA Level is Dependent on Gq and Extracellular Signal‐Regulated Kinase 1//2 in AT1‐R‐Transfected PC12 Cells
Authors: Saito M. , Shinohara Y. , Sasaki H. , Netsu Y. , Yoshida M. , Nakahata N.
Published: February 2008

Angiotensin II (Ang II) functions through two major Ang II receptor subtypes, type 1 (AT1‐R) and type 2 (AT2‐R), both of which are classified to be G protein‐coupled receptors. AT2‐R is highly expressed at the fetal stage, and in heart remodelling and brain ischaemia; therefore, it is important to clarify the regulatory mechanisms of AT2‐R expression. Although AT1‐R is generally believed to modulate AT2‐R expression in some tissues or cells, the exact mechanism remains to be clarified. In the present study, we examined the effect of AT1‐R stimulation on expression of endogenous rat AT2‐R (rAT2‐R) in AT1‐R‐transfected PC12 cells. rAT2‐R mRNA and protein expression were decreased by Ang II in PC12 cells transfected with rAT1A‐R in a time‐dependent manner, mediated through a decline in mRNA stability. The C‐terminus of G protein‐coupled receptor (GPCR) is important for GPCR‐mediated signal transduction. Therefore, we used C‐terminus‐deleted human AT1‐R (hAT1‐327STOP), which is thought to be a nondesensitised mutant of hAT1‐R. As a result, Ang II decreased rAT2‐R mRNA expression to a greater extent in cells transfected with hAT1‐327STOP than with wild‐type hAT1‐R. The decrease was completely reversed by AT1‐R antagonist candesartan, Gq inhibitor YM254980, and mitogen‐activated protein kinase (MAPK) kinase 1/2 inhibitor U0126, but not by pertussis toxin, which uncouples the receptor with Gi, or p38 MAPK inhibitor SB203580. We suggest, possibly for the first time, that the hAT1‐R/Gq/extracellular signal‐regulated kinase 1/2 pathway is involved in the down‐regulation of AT2‐R using PC12 cells transfected with AT1‐R.