Development of gold standard ion-selective electrode-based methods for fluoride analysis

BACKGROUND/AIMS

Currently available techniques for fluoride analysis are not standardized. Therefore, this study was designed to develop standardized methods for analyzing fluoride in biological and nonbiological samples used for dental research.

METHODS

A group of nine laboratories analyzed a set of standardized samples for fluoride concentration using their own methods. The group then reviewed existing analytical techniques for fluoride analysis, identified inconsistencies in the use of these techniques and conducted testing to resolve differences. Based on the results of the testing undertaken to define the best approaches for the analysis, the group developed recommendations for direct and microdiffusion methods using the fluoride ion-selective electrode.

RESULTS

Initial results demonstrated that there was no consensus regarding the choice of analytical techniques for different types of samples. Although for several types of samples, the results of the fluoride analyses were similar among some laboratories, greater differences were observed for saliva, food and beverage samples. In spite of these initial differences, precise and true values of fluoride concentration, as well as smaller differences between laboratories, were obtained once the standardized methodologies were used. Intraclass correlation coefficients ranged from 0.90 to 0.93, for the analysis of a certified reference material, using the standardized methodologies.

CONCLUSION

The results of this study demonstrate that the development and use of standardized protocols for F analysis significantly decreased differences among laboratories and resulted in more precise and true values.

Pyrimidine and halogenated pyrimidines near edge x-ray absorption fine structure spectra at C and N K-edges: experiment and theory

The inner shell excitation of pyrimidine and some halogenated pyrimidines near the C and N K-edges has been investigated experimentally by near edge x-ray absorption fine structure spectroscopy and theoretically by density functional theory calculations. The selected targets, 5-Br-pyrimidine, 2-Br-pyrimidine, 2-Cl-pyrimidine, and 5-Br-2-Cl-pyrimidine, allow the effects of the functionalization of the pyrimidine ring to be studied either as a function of different halogen atoms bound to the same molecular site or as a function of the same halogen atom bound to different molecular sites. The results show that the individual characteristics of the different spectra of the substituted pyrimidines can be rationalized in terms of variations in electronic and geometrical structures of the molecule depending on the localization and the electronegativity of the substituent.

Feeding-based RNA interference of a trehalose phosphate synthase gene in the brown planthopper, Nilaparvata lugens

The brown planthopper, Nilaparvata lugens, is the most devastating rice insect pest to have given rise to an outbreak in recent years. RNA interference (RNAi) is a technological breakthrough that has been developed as a powerful tool for studying gene function and for the highly targeted control of insect pests. Here, we examined the effects of using a feeding-based RNAi technique to target the gene trehalose phosphate synthase (TPS) in N. lugens. The full-length cDNA of N. lugens TPS (NlTPS) is 3235 bp and has an open reading frame of 2424 bp, encoding a protein of 807 amino acids. NlTPS was expressed in the fat body, midgut and ovary. Quantitative real-time PCR (qRT-PCR) analysis revealed that NlTPS mRNA is expressed continuously with little change during the life of the insect. Efficient silencing of the TPS gene through double-stranded RNA (dsRNA) feeding led to rapid and significant reduction levels of TPS mRNA and enzymatic activity. Additionally, the development of N. lugens larvae that had been fed with the dsRNA was disturbed, resulting in lethality, and the cumulative survival rates dropped to 75.56, 64.44, 55.56 and 40.00% after continuous ingestion of 0.5 µg/µl dsRNA for 2, 4, 7 and 10 days, respectively. These values were significantly lower than those of the insects in the control group, suggesting that NlTPS dsRNA may be useful as a means of insect pest control.

Genetic diversity and differentiation among laboratory and field populations of the soybean aphid, Aphis glycines

The soybean aphid, Aphis glycines Matsumura, is a recent invasive pest of soybean in North America. Currently, much research is focused on developing and characterizing soybean cultivars expressing host-plant resistance. During the initial phases of host-plant resistance screening, many of these studies use soybean aphid laboratory populations. Previous studies in other systems have documented substantial differences among laboratory and field populations. Whether or not this pattern exists in A. glycines is unknown, but it is extremely important when estimating the level of selection and virulence to host-plant resistant soybeans. In this study, we used seven microsatellite markers to estimate and compare genetic diversity and differentiation among five laboratory and 12 field populations. Our results indicate that soybean aphid laboratory populations are severely lacking in genotypic diversity and show extreme genetic differentiation among each other and to field populations. Continued use of laboratory populations for initial soybean aphid resistance screening could lead to erroneous estimations of the potential success for host-plant resistance.

An Effective Algorithm for and Phase Transitions of the Directed Hamiltonian Cycle Problem

The Hamiltonian cycle problem (HCP) is an important combinatorial problem with applications in many areas. It is among the first problems used for studying intrinsic properties, including phase transitions, of combinatorial problems. While thorough theoretical and experimental analyses have been made on the HCP in undirected graphs, a limited amount of work has been done for the HCP in directed graphs (DHCP). The main contribution of this work is an effective algorithm for the DHCP. Our algorithm explores and exploits the close relationship between the DHCP and the Assignment Problem (AP) and utilizes a technique based on Boolean satisfiability (SAT). By combining effective algorithms for the AP and SAT, our algorithm significantly outperforms previous exact DHCP algorithms, including an algorithm based on the award-winning Concorde TSP algorithm. The second result of the current study is an experimental analysis of phase transitions of the DHCP, verifying and refining a known phase transition of the DHCP.

In vitro Ad5F35-mediated CTLA4-Ig gene transfer prolongs pig skin xenotransplant survival

Wound closure and coverage are the biggest challenges faced by medical practitioners in treating severe burns. Fresh cadaver allografts are still considered to be the gold standard skin substitute. Unfortunately, their use is severely impeded by inadequate availability. In this report we endeavored to solve this problem by using gene-modified pig skin as a substitute for human skin. We report that adenovirus (Ad)-mediated transfer of human cytotoxic T-lymphocyte-associated antigen 4 immunoglobin (CTLA4-Ig) into pig skin in vitro is a useful approach to lower immunostimulatory ability and improve the take of pig skin for wound coverage. To optimize gene transfer efficiency, we also compared exogenous gene transfer efficiency in pig skin by Ad5F35 vector with that of the widely used Ad5. The uptake efficiency of Ad5F35 was about 1.3 times more than that of Ad5, and the survival time on rat burn wounds was prolonged by about 3 days. Our results demonstrate that CTLA4Ig gene-modified pig skin is a promising biologic dressing for wound coverage and Ad5F35 an effective viral carrier for delivery.

A psychopharmacological treatment algorithm for generalised anxiety disorder (GAD)

Generalised anxiety disorder (GAD) is defined as excessive and uncontrollable worry and anxiety about everyday life situations. It is a chronic disorder, and is associated with substantial somatisation, high rates of comorbid depression and other anxiety disorders, and significant disability. The evidence base for pharmacotherapy and psychotherapy has continued to grow, and a wide range of drug choices for GAD now exists. Current guidelines for GAD generally restrict themselves to presentation of the evidence for various treatments, which, as a result, generally do not offer detailed discussion or recommendation of strategies beyond the first level of treatment, or take into account the individual circumstances of the patient. Thus, there is a lack of algorithm-based treatment guidelines for GAD. Our aim is, therefore, to present an algorithm for the psychopharmacologic management of GAD, intended for all clinicians who treat patients with GAD, where issues of pharmacotherapy are under consideration. We also hope that these GAD algorithms and other guidelines can help to identify high-priority areas that need further study. In this algorithm, we provide a sequenced approach to the pharmacotherapy of GAD, taking into account salient symptomatology and comorbidity, levels of evidence and extent of response. Special issues, including comorbidity, insomnia, suicidality, substance abuse, treatment adherence, pregnancy and lactation, cross-cultural issues, use of medication in the elderly, psychosocial treatment and dosing issues are also addressed.

Fast reciprocating probe system on the EAST superconducting tokamak

A new fast reciprocating probe system (FRPS) has been built and installed on the outer midplane of the EAST tokamak to investigate the profiles of the boundary plasma parameters such as electron density and temperature. The system consists of a two-stage motion drive mechanism: slow motion and fast motion. The fast motion is powered by a servo motor, which drives the probe horizontally up to 50 cm to scan the edge region of the EAST tokamak. The maximum velocity achieved is 2 m/s. High velocity and flexible control of the fast motion are the remarkable features of this FRPS. A specially designed connector installed at the front end of the probe shaft makes it easy to install or replace the probe head on FRPS. During the latest experimental campaign in the spring of 2010, a probe head with seven tips, including two tips for a Mach probe, has been used. An example is given for simultaneous profile measurements of the plasma temperature, plasma density, and the plasma flow velocity.

Cardiovascular diseases in the cohort of workers first employed at Mayak PA in 1948-1958

Incidence of and mortality from cardiovascular diseases have been studied in a cohort of 12,210 workers first employed at one of the main plants of the Mayak nuclear facility during 1948-1958 and followed up to 31 December 2000. Information on external gamma-ray doses is available for virtually all of these workers (99.9%); the mean total gamma-ray dose (+/-SD) was 0.91 +/- 0.95 Gy (99% percentile 3.9 Gy) for men and 0.65 +/- 0.75 Gy (99% percentile 2.99 Gy) for women. In contrast, plutonium body burden was measured for only 30.0% of workers; among those monitored, the mean cumulative liver dose from plutonium alpha exposure (+/- SD) was 0.40 +/- 1.15 Gy (99% percentile 5.88 Gy) for men and 0.81 +/- 4.60 Gy (99% percentile 15.95 Gy) for women. A total of 3751 cases of ischemic heart disease (IHD), including 683 cases of acute myocardial infarction (AMI), and 1495 IHD deaths, including 338 AMI deaths, were identified in the study cohort during the follow-up period. Having adjusted for non-radiation factors, there were statistically significant increasing trends with both total external gamma-ray dose and internal liver dose in IHD incidence. The trend with internal dose was weaker and was not statistically significant after adjusting for external dose, whereas the external dose trend was little changed after adjusting for internal dose. The trend with external dose in IHD mortality was not statistically significantly greater than zero but was consistent with the corresponding trend in IHD incidence. The estimated trend in IHD mortality with internal dose was lower and was not statistically significant once adjustment was made for external dose. There was a statistically significantly increasing trend in AMI incidence but not AMI incidence with external dose. The risk estimates for IHD in relation to external radiation are generally compatible with those from other large occupational studies and the Japanese A-bomb survivors.

A comparative study of two hazard handling training methods for novice drivers

OBJECTIVES

The effectiveness of two hazard perception training methods, simulation-based error training (SET) and video-based guided error training (VGET), for novice drivers' hazard handling performance was tested, compared, and analyzed.

METHODS

Thirty-two novice drivers participated in the hazard perception training. Half of the participants were trained using SET by making errors and/or experiencing accidents while driving with a desktop simulator. The other half were trained using VGET by watching prerecorded video clips of errors and accidents that were made by other people. The two groups had exposure to equal numbers of errors for each training scenario. All the participants were tested and evaluated for hazard handling on a full cockpit driving simulator one week after training. Hazard handling performance and hazard response were measured in this transfer test.

RESULTS

Both hazard handling performance scores and hazard response distances were significantly better for the SET group than the VGET group. Furthermore, the SET group had more metacognitive activities and intrinsic motivation. SET also seemed more effective in changing participants' confidence, but the result did not reach the significance level.

CONCLUSIONS

SET exhibited a higher training effectiveness of hazard response and handling than VGET in the simulated transfer test. The superiority of SET might benefit from the higher levels of metacognition and intrinsic motivation during training, which was observed in the experiment. Future research should be conducted to assess whether the advantages of error training are still effective under real road conditions.

Involvement of cysteinyl leukotriene receptors in angiogenesis in rat thoracic aortic rings

Cysteinyl leukotrienes (CysLTs) are potent inflammatory mediators that induce inflammation through the activation of CysLT1 and CysLT2 receptors. It has been reported that inflammatory mediators, such as prostaglandins, play an important role in angiogenesis. However, whether CysLTs and the receptor subtypes are involved in angiogenesis is not clarified. Here, we determined the effects of CysLT receptor agonist leukotriene D4 (LTD4) and antagonists on angiogenesis by rat thoracic aortic ring assay. We found that the microvessel growth in 25% serum-containing cultures was significantly inhibited by the CysLT1 receptor antagonist montelukast (0.1-1 microM), but not by the CysLT2 receptor antagonist BAY cyslt2 (0.1-1 microM). The microvessel growth in serum-free culture was affected neither by montelukast (0.01-1 microM) nor by BAY cyslt2 (0.1-1 microM). Furthermore, LTD4 at 100 nM significantly enhanced the microvessel growth in serum-free culture and LTD4 at 10-100 nM significantly enhanced the microvessel growth in 25% serum-containing cultures. The enhancement was abrogated by both montelukast and BAY cyslt2. Thus, CysLT1 receptors may mediate endogenously regulated microvessel growth in normal culture; whereas the exogenous agonist LTD4 induces angiogenesis through the activation of both CysLT1 and CysLT2 receptors. The CysLT receptor antagonists can be developed as angiogenesis inhibitors.