Assessing in vitro dermal absorption of dry residues of agrochemical sprays using human skin within OECD TG 428.

We describe a novel experimental method that mimics exposure to dried agrochemical residues on contact surfaces during re-entry into crops. It includes the creation of dry dislodgeable residues and subsequent transfer to human skin for in vitro measurement of dermal absorption within a standard Organisation for Economic Co-operation and Development test guideline (OECD TG) 428 study. A pre-determined volume of spray containing 14C-labelled active substance is transferred onto a polytetrafluorethylene-coated septum and air-dried. The septum is then gently placed onto the pre-wetted skin mounted in a flow-through Franz diffusion chamber. The septum is gently rotated thrice to transfer the dose. Preliminary tests determined transfer efficiency to ensure the appropriate test concentration on the skin. Then, a standard dermal absorption study is performed according to OECD TG 428. Results from 10 compounds indicate that the methodology can be robustly incorporated into a standard TG study. These data show that the dermal absorption from a dry dislodgeable residue is lower than that from the equivalent dose of the aqueous spray, regardless of formulation type or active substance. Studies following the scenario described above can be a suitable tool to better estimate dermal absorption from dry residues in re-entry worker and resident exposure assessment for agrochemicals.

Water Fluoridation and Dental Caries in U.S. Children and Adolescents.

Fluoridation of America's drinking water was among the great public health achievements of the 20th century. Yet there is a paucity of studies from the past 3 decades investigating its dental health benefits in the U.S. POPULATION: This cross-sectional study sought to evaluate associations between availability of community water fluoridation (CWF) and dental caries experience in the U.S. child and adolescent population. County-level estimates of the percentage of population served by CWF (% CWF) from the Centers for Disease Control and Prevention's Water Fluoridation Reporting System were merged with dental examination data from 10 y of National Health and Nutrition Examination Surveys (1999 to 2004 and 2011 to 2014). Dental caries experience in the primary dentition (decayed and filled tooth surfaces [dfs]) was calculated for 7,000 children aged 2 to 8 y and in the permanent dentition (decayed, missing, and filled tooth surfaces [DMFS]) for 12,604 children and adolescents aged 6 to 17 y. Linear regression models estimated associations between % CWF and dental caries experience with adjustment for sociodemographic characteristics: age, sex, race/ethnicity, rural-urban location, head-of-household education, and period since last dental visit. Sensitivity analysis excluded counties fluoridated after 1998. In unadjusted analysis, caries experience in the primary dentition was lower in counties with ≥75% CWF (mean dfs = 3.3; 95% confidence limit [CL] = 2.8, 3.7) than in counties with <75% CWF (mean dfs = 4.6; 95% CL = 3.9, 5.4), a prevented fraction of 30% (95% CL = 11, 48). The difference was also statistically significant, although less pronounced, in the permanent dentition: mean DMFS (95% CL) was 2.2 (2.0, 2.4) and 1.9 (1.8, 2.1), respectively, representing a prevented fraction of 12% (95% CL = 1, 23). Statistically significant associations likewise were seen when % CWF was modeled as a continuum, and differences tended to increase in covariate-adjusted analysis and in sensitivity analysis. These findings confirm a substantial caries-preventive benefit of CWF for U.S. children and that the benefit is most pronounced in primary teeth.

Towards single egg toxicity screening using microcoil NMR.

Planar microcoils with diameter ranging from 20 to 1000 µm I.D. (130-1130 µm O.D.) are evaluated for their applications in NMR spectroscopy. The coils are first overfilled with a standard sucrose solution and compared against each other. Coils with smaller I.D. (≤100 µm) perform extremely well. One hypothesis is that as the coils get smaller the volume occupied by the copper turns increases relative to the open I.D.; as such a large proportion of the sample is brought in close proximity to the coil turns and likely gives rise to strong sample-coil magnetic coupling, which increases the signal. The applications of the planar microcoils are demonstrated on Cypselurus poecilopterus (fish) and Daphnia magna (water flea) eggs. A single D. magna egg on a 50 µm coil yielded at least 3000 times the mass sensitivity (∼9,000,000 time saving) when compared to a 5 mm probe. This value could be at least 4 times higher if the B1 homogeneity of the coils could be improved. With the current design, 80% of the signal is lost in multiple pulse experiments that rely on phase inversion and signal cancellation between scans. The data were extrapolated to predict that biological samples as small as ∼4 µm may become accessible via planar microcoil designs. To fulfill their potential for in situ metabolic screening, specialized magnetic susceptibility matched sample holders that restrict the sample to the homogeneous B1 field region (i.e. within the 90% RF field) of the coil and advanced experiments that narrow spectral lines, suppress lipids and disperse signals into multiple dimensions will be required.

Evidence-based Update of Pediatric Dental Restorative Procedures: Preventive Strategies.

BACKGROUND: There has been significant advances in the understanding of preventive restorative procedures regarding the advantages and disadvantages for restorative procedures; the evidence for conservative techniques for deep carious lesions; the effectiveness of pit and fissure sealants; and the evidence for use of resin infiltration techniques. AIM: The intent of this review is to help practitioners use evidence to make decisions regarding preventive restorative dentistry in children and young adolescents. STUDY DESIGN: This evidence-based review appraises the literature, primarily between the years 1995-2013, on preventive restorative strategies. The evidence was graded as to strong evidence, evidence in favor, or expert opinion by consensus of authors Results: The preventive strategy for dental caries includes individualized assessment of disease progression and management with appropriate preventive and restorative therapy. There is strong evidence that restoration of teeth with incomplete caries excavation results in fewer signs and symptoms of pulpal disease than complete excavation. There is strong evidence that sealants should be placed on pit and fissure surfaces judged to be at risk for dental caries, and surfaces that already exhibit incipient, non-cavitated carious lesions. There is evidence in favor for resin infiltration to improve the clinical appearance of white spot lesions. CONCLUSIONS: Substantial evidence exists in the literature regarding the value of preventive dental restorative procedures.

Overhauser effects in insulating solids.

We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The (1)H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d21-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a (1)H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields.

[Safety in intensive care medicine. Can we learn from aviation?]. / Sicherheit in der Intensivmedizin : Können wir von der Luftfahrtindustrie lernen?

Safety is of extraordinary value in commercial aviation. Therefore, sophisticated and complex systems have been developed to ensure safe operation. Within this system, the pilots are of specific concern: they form the human-machine interface and have a special responsibility in controlling and monitoring all aircraft systems. In order to prepare pilots for their challenging task, specific selection of suitable candidates is crucial. In addition, for every commercial pilot regulatory requirements demand a certain number of simulator training sessions and check flights to be completed at prespecified intervals. In contrast, career choice for intensive care medicine most likely depends on personal reasons rather than eligibility or aptitude. In intensive care medicine, auditing, licensing, or mandatory training are largely nonexistent. Although knowledge of risk management and safety culture in aviation can be transferred to the intensive care unit, the diversity of corporate culture and tradition of leadership and training will represent a barrier for the direct transfer of standards or procedures. To accomplish this challenging task, the analysis of appropriate fields of action with regard to structural requirements and the process of change are essential.

A sandwich-cultured rat hepatocyte system with increased metabolic competence evaluated by gene expression profiling.

A rapid decline of cytochrome P450 (CYP450) enzyme activities remains a drawback of rat hepatocyte-based in vitro cultures. Consequently, judgment of the toxic potential of compounds that need bioactivation by CYP450s may not be adequate using this model. In the present study, an improved hepatocyte-based in vitro system was developed with special focus on metabolic competence. Therefore, a mixture of CYP450 inducers, phenobarbital, dexamethasone and beta-naphthoflavone, was added to culture medium of sandwich-cultured rat hepatocytes. The resulting modified model was evaluated by comparing its genome-wide expression profiles with liver and a standard model without the inducer mixture. Metabolic capacity for CYP450 enzymes showed that the modified model resembled more closely the in vivo situation. Gene expression results revealed large differences between in vivo and both in vitro models. The slight differences between the two sandwich models were predominantly represented by gene expression changes in CYP450s. Importantly, in the modified model, expression ratios of the phase I and the majority of phase II genes more closely resembled liver in vivo. The CYP450 enzyme activities corresponded with gene expression data. In conclusion, for toxicological applications using sandwich-cultured hepatocytes, the modified model may be preferred.

In vitro predictions of skin absorption of caffeine, testosterone, and benzoic acid: a multi-centre comparison study.

To obtain better insight into the robustness of in vitro percutaneous absorption methodology, the intra- and inter-laboratory variation in this type of study was investigated in 10 European laboratories. To this purpose, the in vitro absorption of three compounds through human skin (9 laboratories) and rat skin (1 laboratory) was determined. The test materials were benzoic acid, caffeine, and testosterone, representing a range of different physico-chemical properties. All laboratories performed their studies according to a detailed protocol in which all experimental details were described and each laboratory performed at least three independent experiments for each test chemical. All laboratories assigned the absorption of benzoic acid through human skin, the highest ranking of the three compounds (overall mean flux of 16.54+/-11.87 microg/cm(2)/h). The absorption of caffeine and testosterone through human skin was similar, having overall mean maximum absorption rates of 2.24+/-1.43 microg/cm(2)/h and 1.63+/-1.94 microg/cm(2)/h, respectively. In 7 out of 9 laboratories, the maximum absorption rates of caffeine were ranked higher than testosterone. No differences were observed between the mean absorption through human skin and the one rat study for benzoic acid and testosterone. For caffeine the maximum absorption rate and the total penetration through rat skin were clearly higher than the mean value for human skin. When evaluating all data, it appeared that no consistent relation existed between the diffusion cell type and the absorption of the test compounds. Skin thickness only slightly influenced the absorption of benzoic acid and caffeine. In contrast, the maximum absorption rate of testosterone was clearly higher in the laboratories using thin, dermatomed skin membranes. Testosterone is the most lipophilic compound and showed also a higher presence in the skin membrane after 24 h than the two other compounds. The results of this study indicate that the in vitro methodology for assessing skin absorption is relatively robust. A major effort was made to standardize the study performance, but, unlike in a formal validation study, not all variables were controlled. The variation observed may be largely attributed to human variability in dermal absorption and the skin source. For the most lipophilic compound, testosterone, skin thickness proved to be a critical variable.

Advancing NMR sensitivity for LC-NMR-MS using a cryoflow probe: application to the analysis of acetaminophen metabolites in urine.

Cryogenic cooling of the NMR radio frequency coils and electronics to give greatly enhanced sensitivity is arguably the most significant recent advance in NMR spectroscopy. Here we report the first cryogenic probe built in flow configuration and demonstrate the application to LC-NMR-MS studies. This probe provides superior sensitivity over conventional noncryogenic flow NMR probes, allowing the use of 100 microL of untreated urine (40% less material than previous studies that required preconcentration) and yet revealing drug metabolites hitherto undetected by LC-NMR-MS at 500 MHz. Besides the known sulfate and glucuronide metabolites, previously undetected metabolites of acetaminophen were directly observable in a 15-min on-flow experiment. Simultaneous MS data also provided knowledge on the NMR-silent functional moieties. Further, stop-flow LC-NMR-MS experiments were conducted for greater signal-to-noise ratios on minor metabolites. The cryoflow probe enables the NMR analysis of lower concentrations of metabolites than was previously possible for untreated biofluids. This strategy is generally applicable for samples containing mass-limited analytes, such as those from drug metabolism studies, biomarker and toxicity profiling, impurity analysis, and natural product analysis.

Dental services. An analysis of utilization over 20 years.

BACKGROUND: Utilization studies serve as an important tool for oral health policy decision-making. A number of important reports have been published that help to characterize the dental utilization patterns of most Americans. For the most part, these studies have focused on utilization estimates for a particular survey period or year. Fewer studies have examined changing utilization patterns over time. METHODS: This article focuses on dental utilization and the changes in utilization for the civilian, community-based U.S. population during 1977, 1987 and 1996. Using data from the National Medical Care Expenditure Survey, National Medical Expenditure Survey and Medical Expenditure Panel Survey, the authors provide national estimates of dental visits for each of several socioeconomic and demographic categories during 1977, 1987 and 1996. RESULTS: Although the dental use rates for children between 6 and 18 years of age were the highest of any age group in each of the three years studied, the use rate for children and the elderly increased during this same 20-year period. Data also showed that the gap in use rates between lower- and higher-income people widened during the 20-year period. Generally, use rates according to sex and race/ethnicity were unchanged in each of the survey years, except for a narrowing of the gap between whites and nonwhites by 1996. CONCLUSION: These data are unique and comparable and establish a mechanism by which dental visits can be compared during a 20-year period. While aggregate utilization rates generally were stable during this 20-year period, some differences within socioeconomic and demographic groups are notable. For instance, the use rate increased during the 20-year period for people 65 years of age and older and for children younger than 6 years of age. PRACTICE IMPLICATIONS: By understanding these analyses, U.S. dentists will be better positioned to provide care and meet the needs of all Americans.

EPR spectral determination of electronic substituent effects on the D values of hydrocarbon polyradicals (Quintet and septet spin states) composed of localized 1,3-cyclopentanediyl spin-carrying units linked by 1,3-Di- and 1,3,5-trimethylenebenzene ferromagnetic couplers

The parent and p-nitrophenyl-substituted diradicals D-3a,b (triplets), tetraradicals T-3a,b (quintets), and hexaradicals H-3a,b (septets) were photochemically generated in matrix-isolated form (toluene, 77 K) by successive denitrogenation of the trisazoalkanes 3a,b and EPR spectrally characterized. In these high-spin polyradicals the spin-spin interaction within the localized spin-carrying 1,3-cyclopentanediyl diradical unit is much stronger than within the cross-conjugated ferromagnetic coupling unit. Accordingly, a change of the electronic properties in the cyclopentanediyl unit affects decisively the D value of the whole polyradical. Therefore, the spin-accepting p-nitro group reduces the D value of the tetra- and hexaradical in the same amount as that of the diradical. Thus, irrespective of the spin multiplicity, the substituent stabilizes electronically the triplet (D-3a,b), quintet (T-3a,b), and septet (H-3a,b) species with equal efficacy.

Cryopreservation of precision-cut rat liver slices using a computer-controlled freezer.

Precision-cut liver slices are frequently used to study hepatic toxicity and metabolism of xenobiotics in vitro. Successful cryopreservation techniques will enhance an efficient and economic use of scarcely available (human) liver tissue. For primary hepatocytes, slow freezing has been accepted as the best approach towards successful cryopreservation. For slices, however, no agreement exists on the optimal way of cryopreservation and both slow and fast freezing techniques have been reported. The aim of the present study was to determine the applicability of a computer-controlled slow freezing technique for the cryopreservation of (rat) liver slices. Thus far, this technique has not been described in detail. Our studies confirmed that slow freezing was most successful in the cryopreservation of primary rat hepatocytes. Based on this observation, the slow freezing technique was applied to the cryopreservation of rat liver slices. Directly after thawing, slice viability was between 60 and 100% of fresh values, depending on the parameter determined. However, after additional culturing, slice viability was reduced. This decrease in slice viability was more pronounced in comparison to primary hepatocytes. In conclusion, the slow freezing technique was confirmed to be a successful approach for the cryopreservation of primary rat hepatocytes, and was found to be of limited use for the cryopreservation of rat liver slices.

Perceived unmet need for oral treatment among a national population of HIV-positive medical patients: social and clinical correlates.

OBJECTIVES: This study examines social, behavioral, and clinical correlates of perceived unmet need for oral health care for people with HIV infection. METHODS: Baseline in-person interviews with 2864 individuals were conducted with the HIV Cost and Services Utilization Study cohort, a nationally representative probability sample of HIV-infected persons in medical care. Bivariate and logistic regression analyses were conducted, with unmet need in the last 6 months as the dependent variable and demographic, social, behavioral, and disease characteristics as independent variables. RESULTS: We estimate that 19.3% of HIV-infected medical patients (n = 44,550) had a perceived unmet need for dental care in the last 6 months. The odds of having unmet dental needs were highest for those on Medicaid in states without dental benefits (odds ratio [OR] = 2.21), for others with no dental insurance (OR = 2.26), for those with incomes under $5000 (OR = 2.20), and for those with less than a high school education (OR = 1.83). Low CD4 count was not significant. CONCLUSIONS: Perceived unmet need was related more to social and economic factors than to stage of infection. An expansion of dental benefits for those on Medicaid might reduce unmet need for dental care.

Use of dental care by HIV-infected medical patients.

Although increasing attention has been paid to the use of dental care by HIV patients, the existing studies do not use probability samples, and no accurate population estimates of use can be made from this work. The intent of the present study was to establish accurate population estimates of the use of dental services by patients under medical care. The study, part of the HIV Cost and Services Utilization Study (HCSUS), created a representative national probability sample, the first of its kind, of HIV-infected adults in medical care. Both bivariate and logistic regressions were conducted, with use of dental care in the preceding 6 months as the dependent variable and demographic, social, behavioral, and disease characteristics as independent variables. Forty-two percent of the sample had seen a dental health professional in the preceding 6 months. The bivariate logits for use of dental care show that African-Americans, those whose exposure to HIV was caused by hemophilia or blood transfusions, persons with less education, and those who were employed were less likely to use dental care (p < 0.05). Sixty-five percent of those with a usual source of care had used dental care in the preceding 6 months. Use was greatest among those obtaining dental care from an AIDS clinic (74%) and lowest among those without a usual source of dental care (12%). We conclude that, in spite of the high rate of oral disease in persons with HIV, many do not use dental care regularly, and that use varies by patient characteristics and availability of a regular source of dental care.

Assessment of some critical factors in the freezing technique for the cryopreservation of precision-cut rat liver slices.

A number of studies on the cryopreservation of precision-cut liver slices using various techniques have been reported. However, the identification of important factors that determine cell viability following cryopreservation is difficult because of large differences between the various methods published. The aim of this study was to evaluate some important factors in the freezing process in an effort to find an optimized approach to the cryopreservation of precision-cut liver slices. A comparative study of a slow and a fast freezing technique was carried out to establish any differences in tissue viability for a number of endpoints. Both freezing techniques aim at the prevention of intracellular ice formation, which is thought to be the main cause of cell death after cryopreservation. Subsequently, critical variables in the freezing process were studied more closely in order to explain the differences in viability found in the two methods in the first study. For this purpose, a full factorial experimental design was used with 16 experimental groups, allowing a number of variables to be studied at different levels in one single experiment. It is demonstrated that ATP and K(+) content and histomorphology are sensitive parameters for evaluating slice viability after cryopreservation. Subsequently, it is shown that freezing rate and the cryopreservation medium largely determine the residual viability of liver slices after cryopreservation and subsequent culturing. It is concluded that a cryopreservation protocol with a fast freezing step and using William's Medium E as cryopreservation medium was the most promising approach to successful freezing of rat liver slices of those tested in this study.

Early detection of speech and language delays in the Netherlands. The case for integrating primary and secondary prevention.

The early detection of speech and language delays has been an important feature of the child health services in the Netherlands for some 15 years. During this period ideas about both the purpose of screening and the methods themselves have changed considerably. There are four key outstanding issues: What is the best age to identify children? What screening measures are available? How can we detect speech and language delays in multilingual children? Which groups are best able to detect speech and language difficulties: parents, teachers, playgroup leaders, doctors, nurses, or speech and language therapists? These questions are influenced by social, demographic developments and an increase in the understanding of language delay. This article examines the Dutch solutions to these problems. The conclusion reached is that early language screening can only be part of the answer to early detection both because the available measures are not yet sufficiently accurate and because the growing group of multilingual children (e.g. in Amsterdam more than 50% of the children under the age of 4 years are multilingual) makes the application of specific measures at a population level unworkable. An alternative method is suggested, namely primary prevention by giving information and support to parents, playgroup leaders, doctors, etc.

Wavelength-selective photodenitrogenation of azoalkanes to high-spin polyradicals with cyclopentane-1,3-diyl spin-carrying units and their photobleaching: EPR/UV spectroscopy and product studies of the matrix-isolated species.

The photolysis of the mono-, bis-, and trisazoalkanes 1, 2, and 3 in a toluene matrix at 77 K has been studied by EPR and UV spectroscopy. The purpose was to find the optimal conditions for the generation of the corresponding organic high-spin polyradicals (the triplet diradicals D-1, D-2, and D-3, the tetraradicals T-2 and T-3, and the hexaradical H-3) all with localized cyclopentane-1,3-diyl spin-carrying units, connected by m-phenylene (except D-1) as ferromagnetic coupler. Irradiation of these azoalkanes at 333, 351, or 364 nm gave different polyradical compositions. This observed wavelength dependence is due to the secondary photoreaction (photobleaching) of the polyradical intermediate. The photobleaching process has been examined in detail for the triplet diradical D-1, for which pi,pi excitation affords the cyclopentenes 5 instead of the housane 4 (the usual product of the diradical D-1 on warm-up of the matrix). The pi,pi-excited diradical D-1 fragments into a pair of allyl and methyl radicals (the latter was observed by EPR spectroscopy of a photobleached sample), and recombination affords the cyclopentene. Similar photochemical events are proposed for the photobleaching of the tetraradical T-2 and hexaradical H-3, derived from the respective azoalkanes 2 and 3. Thus, photobleaching of the polyradicals competes effectively with their photogeneration from the azoalkane. This unavoidable event is the consequence of spectral overlap between the cumyl-radical pi,pi chromophore of the polyradical and the n,pi chromophore of the azoalkane at the wavelength (364 nm), at which the latter is photoactive for the required extrusion of molecular nitrogen.

Magnetic field gradients in solid state magic angle spinning NMR.

Magnetic field gradients have proven useful in NMR for coherence pathway selection, diffusion studies, and imaging. Recently they have been combined with magic angle spinning to permit high-resolution measurements of semi-solids, where magic angle spinning averages any residual dipolar couplings and local variations in the bulk magnetic susceptibility. Here we show the first examples of coherence pathway selection by gradients in dipolar coupled solids. When the gradient evolution competes with dipolar evolution the experiment design must take into account both the strength of the dipolar couplings and the means to refocus it. Examples of both homonuclear and heteronuclear experiments are shown in which gradients have been used to eliminate the need for phase cycling.

A comparison of dental care expenditures and office-based medical care expenditures, 1987.

BACKGROUND: This article compares national estimates of utilization of and expenditures for dental care and office-based medical care. The comparison includes respondents in several socioeconomic and demographic categories. METHODS: The focus of the analyses is on dental care and office-based medical care utilization during 1987. Specifically, the authors provide national estimates for numbers of dental and office-based medical visits made, expenditures for and sources of payment for each of several socioeconomic and demographic categories using household survey data from the 1987 National Medical Expenditure Survey, or NMES. RESULTS: Data show that out-of-pocket expenditures are greater for dental care than for office-based medical care; that few Medicaid dollars are spent on dental care; that insurance is an important component of dental and office-based medical care; and that dentists provide greater amounts of unreimbursed care than do their office-based physician counterparts. CONCLUSIONS: NMES data show that dental care expenditures are considerable, almost as large as expenditures for office-based medical care, and are a significant component of all nonhospital health care expenditures for noninstitutionalized Americans. PRACTICE IMPLICATIONS: U.S. dentists provide a significant amount of care. By understanding these analyses, practitioners will be better positioned to provide care and to better meet the dental needs of all Americans.