Sulfur assimilation by Oxyrrhis marina feeding on a 35S‐DMSP‐labelled prey

A laboratory grazing experiment was conducted with the aim of quantifying the sulfur assimilation by a herbivore protist feeding on a dimethylsulfoniopropionate (DMSP)‐containing phytoplankter. When supplied with dissolved ³⁵S‐DMSP, cultures of an axenic strain of the diatom Thalassiosira pseudonana took up 60–95% of the added radioisotope and accumulated it untransformed in the cytoplasm. Radiolabelled diatom cells were offered as prey to the heterotrophic dinoflagellate Oxyrrhis marina. After 32 h in the dark, all the prey had been grazed and digested, leaving only radiolabelled O. marina in the grazing bottles and thus providing an estimate of the percentage of DMSP‐sulfur retained by the predator. Subsequent precipitation with cold trichloroacetic acid (TCA) provided the fraction of retained DMSP‐S that had been assimilated into the micrograzer macromolecules. In parallel incubations with predator and dissolved ³⁵S‐DMSP only (no prey), O. marina (and their closely associated bacteria) took up the radiolabelled substrate osmotrophically to an activity of 0.04 dpm cell^?1 and assimilated it all into macromolecules. By correcting grazing ³⁵S‐DMSP assimilation for osmotrophic ³⁵S‐DMSP assimilation, and comparing it with the ingested radioisotope, the percentage of ingested DMSP‐sulfur retained and assimilated by the predator was determined to be 32 ± 4%. This is the first study that provides direct evidence that ingestion of a DMSP‐containing prey supplies structural sulfur to a herbivore protist and that quantifies this assimilative supply at one‐third of ingested DMSP.     

Effects of gestational exposure to 1.95‐GHz W‐CDMA signals for IMT‐2000 cellular phones: Lack of embryotoxicity and teratogenicity in rats

The present study was designed to evaluate whether gestational exposure to an EMF targeting the head region, similar to that from cellular phones, might affect embryogenesis in rats. A 1.95‐GHz wide‐band code division multiple access (W‐CDMA) signal, which is one applied for the International Mobile Telecommunication 2000 (IMT‐2000) system and used for the freedom of mobile multimedia access (FOMA), was employed for exposure to the heads of four groups of pregnant CD(SD) IGS rats (20 per group) for gestational days 7–17. The exposure was performed for 90 min/day in the morning. The spatial average specific absorption rate (SAR) for individual brains was designed to be 0.67 and 2.0 W/kg with peak brain SARs of 3.1 and 7.0 W/kg for low (group 3) and high (group 4) exposures, respectively, and a whole‐body average SAR less than 0.4 W/kg so as not to cause thermal effects due to temperature elevation. Control and sham exposure groups were also included. At gestational day 20, all dams were killed and fetuses were taken out by cesarean section. There were no differences in maternal body weight gain. No adverse effects of EMF exposure were observed on any reproductive and embryotoxic parameters such as number of live (243–271 fetuses), dead or resorbed embryos, placental weights, sex ratios, weights or external, visceral or skeletal abnormalities of live fetuses. Bioelectromagnetics 30:205–212, 2009. © 2008 Wiley‐Liss, Inc.     

Hypoxia and stem cell‐based engineering of mesenchymal tissues

Stem cells have the ability for prolonged self‐renewal and differentiation into mature cells of various lineages, which makes them important cell sources for tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the “stem cell niche or microenvironment,” provides signals conducive to the maintenance of definitive stem cell properties. Physiological condition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulating both embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an environmental parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context of the need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Specific PCR product primer design using memetic algorithm

To provide feasible primer sets for performing a polymerase chain reaction (PCR) experiment, many primer design methods have been proposed. However, the majority of these methods require a relatively long time to obtain an optimal solution since large quantities of template DNA need to be analyzed. Furthermore, the designed primer sets usually do not provide a specific PCR product size. In recent years, evolutionary computation has been applied to PCR primer design and yielded promising results. In this article, a memetic algorithm (MA) is proposed to solve primer design problems associated with providing a specific product size for PCR experiments. The MA is compared with a genetic algorithm (GA) using an accuracy formula to estimate the quality of the primer design and test the running time. Overall, 50 accession nucleotide sequences were sampled for the comparison of the accuracy of the GA and MA for primer design. Five hundred runs of the GA and MA primer design were performed with PCR product lengths of 150–300 bps and 500–800 bps, and two different methods of calculating T_m for each accession nucleotide sequence were tested. A comparison of the accuracy results for the GA and MA primer design showed that the MA primer design yielded better results than the GA primer design. The results further indicate that the proposed method finds optimal or near‐optimal primer sets and effective PCR products in a dry dock experiment. Related materials are available online at http://bio.kuas.edu.tw/ma‐pd/ . © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Effect of Somatostatin Analog on Postprandial Satiation in Obesity

Objective: Altered satiation may impact postprandial symptoms and potentially change food intake in obesity. Our aim was to compare effects of octreotide and placebo on postprandial symptoms, satiation, and gastric volumes in obesity. Research Methods and Procedures: In a randomized, parallel‐group, double‐blind, placebo‐controlled study, 26 obese but otherwise healthy participants received 100 μg of octreotide or placebo subcutaneously 30 minutes before each study. Studies were performed on 2 separate days and included validated non‐invasive techniques: ^99mTc‐single photon emission computed tomography imaging to measure fasting stomach volume and gastric volume changes after 90 mL of water and 240 mL of Ensure and a standardized nutrient drink test to measure the maximum tolerated volume and postprandial symptoms. Results: Relative to placebo, octreotide increased gastric volume after 90 mL of water; however, fasting and gastric volume change post‐Ensure and maximum tolerated volume of Ensure were not different. Octreotide decreased sensations of fullness (p = 0.035) and bloating (p = 0.05) and tended to reduce aggregate symptoms (p = 0.07) after the fully satiating meal. Discussion: In obese individuals, somatostatin analog significantly reduced postprandial sensations after a satiating meal without altering maximum tolerated meal volume or postnutrient gastric volume, suggesting an effect on upper gut sensation. The role of somatostatin as a permissive factor in the development of obesity by reducing postprandial sensations deserves further study.     

A kinetic model of sugar metabolism in peach fruit reveals a functional hypothesis of a markedly low fructose‐to‐glucose ratio phenotype

The concentrations of sugars in fruit vary with fruit development, environment and genotype. In general, there were weak correlations between the variations in sugar concentrations and the activities of enzymes directly related with the synthesis or degradation of sugars. This finding suggests that the relationships between enzyme activities and metabolites are often non‐linear and are difficult to assess. To simulate the concentrations of sucrose, glucose, fructose and sorbitol during the development of peach fruit, a kinetic model of sugar metabolism was developed by taking advantage of recent profiling data. Cell compartmentation (cytosol and vacuole) was described explicitly, and data‐driven enzyme activities were used to parameterize equations. The model correctly accounts for both annual and genotypic variations, which were observed in 10 genotypes derived from an interspecific cross. They provided important information on the mechanisms underlying the specification of phenotypic differences. In particular, the model supports the hypothesis that a difference in fructokinase affinity could be responsible for a low fructose‐to‐glucose ratio phenotype, which was observed in the studied population.     

Helicobacter pylori antimicrobial resistance in a pediatric population

Background

The increasing prevalence of Helicobacter pylori (H. pylori) antimicrobial resistance, primarily for clarithromycin decreases the success of treatment. The aim of this study is to determine the local pattern of first‐line antimicrobials resistance and the eradication rate.

Material and Methods

Prospective cohort study of H. pylori infected patients (positive histological or cultural exams) treated at Centro Materno‐Infantil do Norte from January of 2013 to October of 2017. Susceptibility to 4 antibiotics: amoxicilin, metronidazole, clarithromycin, and levofloxacin were analyzed by E‐test (phenotypic resistance). The E‐test was chosen because it is simple and cost‐effective for routine susceptibility testing. Point mutations that confer clarithromycin resistance were surveyed (genotypic resistance). Eradication of H. pylori infection was defined by a negative urea breath test or fecal antigen 6‐8 weeks after the end of treatment.

Results

Of a total of 74 H. pylori infected patients, 16 were excluded because they had previous H. pylori treatment or severe systemic disease. Median age of infection cases was 15 years (3‐17 years). Eradication regimen used in all patients combined the use of 3 antibiotics (amoxicillin and metronidazole or clarithromycin) and proton pump inibhitor for 14 days and was tailored according antimicrobial susceptibility. 79.5% of the patients completed the treatment. The resistance rate for metronidazole and clarithromycin was 3.3% and 23.3%, respectively. There was no resistance for amoxicilin and levofloxacin. The rate of genotypic resistance to clarithromycin was 37.2%. The eradication rate was 97.8%.

Conclusions

The authors found a high resistance rate of H. pylori for clarithromycin in this northern portuguese pediatric center. This factor should determine a change in local current treatment, contraindicating the use of clarithromycin as a first‐line treatment for H. pylori infection in children. The high eradication rate maybe explained for the eradication treatment tailored according antimicrobial susceptibility.