ABSTRACT
The dermal absorption potential of a nanocrystalline magnesium oxide (MgO) and titanium dioxide (TiO(2)) mixture in dermatomed human skin was assessed in vitro using Bronaugh-type flow-through diffusion cells. Nanocrystalline material was applied to the skin surface at a dose rate of 50 mg/cm(2) as a dry powder, as a water suspension, and as a water/surfactant (sodium lauryl sulfate) suspension, for 8 hours. Dermal absorption of nanocrystalline MgO and TiO(2) through human skin with intact, functional stratum corneum was not detectable under the conditions of this experiment.
Subject(s)
Magnesium Oxide/pharmacokinetics , Nanoparticles , Skin Absorption , Skin/drug effects , Titanium/pharmacokinetics , Administration, Topical , Adult , Diffusion Chambers, Culture , Humans , In Vitro Techniques , Magnesium Oxide/administration & dosage , Magnesium Oxide/blood , Magnesium Oxide/chemistry , Magnesium Oxide/toxicity , Microscopy, Electron, Transmission , Models, Biological , Skin/metabolism , Skin/ultrastructure , Titanium/administration & dosage , Titanium/blood , Titanium/chemistry , Titanium/toxicityABSTRACT
In responding to Drs Calabrese and Baldwin's question, 'At what point, if ever, should hormesis be employed as the principal dose response default assumption in risk assessment?', we examined the benefits of replacing traditional dose-response with hormesis. In general, hormesis provides more complete useful information for risk assessment than does traditional dose-response. A major limitation of using hormesis as a default assumption in risk estimation is the difficulty of differentiating complex low-level hormetic responses from the placebo effect. A second limitation is that hormesis merely further defines one response. Most toxicoses have many responses. The most complete information takes all responses and their connections into account.
Subject(s)
Carbon/toxicity , Dose-Response Relationship, Drug , Risk Assessment/methods , Animals , Carbon/administration & dosage , Child , Female , Humans , Indoles/toxicity , Lead/adverse effects , Lead/therapeutic use , No-Observed-Adverse-Effect Level , Skatole/metabolismABSTRACT
OBJECTIVE AND METHODS: Insecticide use, grower preferences regarding genetically engineered (GE) corn resistant to corn rootworm (CRW), and the health effects of using various CRW insecticides (organophosphates, pyrethroids, fipronil and carbamates) are reviewed for current and future farm practices. RESULTS: Pest damage to corn has been reduced only one-third by insecticide applications. Health costs from insecticide use appear significant, but costs attributable to CRW control are not quantifiable from available data. Methods reducing health-related costs of insecticide-based CRW control should be evaluated. As a first step, organophosphate insecticide use has been reduced as they have high acute toxicity and risk of long-term neurological consequences. A second step is to use agents which more specifically target the CRW. CONCLUSION: Whereas current insecticides may be poisonous to many species of insects, birds, mammals and humans, a protein derived from Bacillus thurigiensis and produced in plants via genetic modification can target the specific insect of CRW (Coleoptra), sparing other insect and non-insect species from injury.
Subject(s)
Food, Genetically Modified , Insecta , Insecticides/adverse effects , Pest Control, Biological , Plants, Genetically Modified , Zea mays/genetics , Animals , Consumer Product Safety , Insecticide Resistance , Pest Control, Biological/economics , Pest Control, Biological/methods , Plant Roots , Zea mays/growth & developmentABSTRACT
INTRODUCTION: Group learning has become important to professional students in the healing sciences. Groups share factual and procedural resources to enhance their performances. METHODOLOGY: We investigated the extent to which students analyzing case-based evaluations as teams acquired an immediate performance advantage relative to those analyzing them as individuals and the extent to which group work on one problem led to better performance by individual students on related problems. We blinded written evaluations by randomly assigning numbers to groups of students and using removable tracers. Differences between groups and individuals were evaluated using Student's t statistic. Similar comparisons were evaluated by meta-analysis to determine overall trends. RESULTS: Students who analyzed evaluations as a group had an 8.5% performance advantage over those who analyzed them as individuals. When evaluations were divided into those asking questions related to treatment, differential diagnosis, and prognosis, specific performance advantages for groups relative to individuals were 8.9%, 5.9%, and 6.1% respectively. Students who had previously been trained by group evaluations had a 1.5% advantage relative to those who received their training as individuals. CONCLUSIONS: Answers by students analyzing evaluations as groups suggested a deeper understanding, in large part because of their improved ability to explain treatment and to conduct differential diagnosis. These improvements suggested limited abilities to use previous experience to improve present performance.
