How to avoid common errors in clinical photography

This paper demonstrates some of the errors commonly seen in both conventional and digital photography when used for clinical purposes, and details how some of these mistakes may be avoided.     

Keratinocyte cell-mediated mutagenesis assay: correlation with in vivo tumor studies

A murine keratinocyte cell-mediated mutagenesis assay was characterizedand examined as an in vitro model system for studying the biotransformationof promutagens/procarcinogens by mouse skin. The assay usedliving cultured newborn SENCAR keratinocytes for the metabolicactivation of promutagens and Chinese hamster lung V-79 fibroblastsfor detection of resulting mutagens. Mutations at, or affecting,the hypoxanthine-guanine phosphoribosyltransferase locus werescored by resisistance to 6-thioguanine. The relative mutagenicitiesof several polycyclic aromatic hydrocarbons (PAHs) in the cell-mediatedassay correlated with the in vivo skin tumongenicity of thePAHs determined in a two-stage carcinogenesis protocol. Metabolicactivation of the promutagenic PAHs to ultimate mutagens wasdependent upon the presence of the cultured keratinocyte feederlayer. 7,8-Benzoflavone, a potent inhibitor of 7, 12-dimethylbenz-[a]anthracene (DMBA)-dependent initiation in mouse skin, inhibitedDMBA-dependent mutagenesis in the cell-mediated assay in a concentrationresponsive manner. The non-PAH promutagens, dimethylnitrosamine(DMN) and sterigmatocystin (STC) were both activated by culturedkeratinocytes to cytotoxic derivatives. DMN was neither mutagenicin the cell-mediated assay nor tumorigenic in mouse skin whentested in a two-stage carcinogenesis protocol. STC was weaklymutagenic and tumorigenic in mouse skin.     

Linking hemodynamic and electrophysiological measures of brain activity: evidence from functional MRI and intracranial field potentials

We investigated the relation between electrophysiological and hemodynamic measures of brain activity through comparison of intracranially recorded event-related local field potentials (ERPs) and blood-oxygenation level dependent functional magnetic resonance imaging (BOLD fMRI). We manipulated the duration of visual checkerboard stimuli across trials and measured stimulus-duration-related changes in ERP and BOLD activity in three brain regions: peri-calcarine cortex, the fusiform gyrus and lateral temporal-occipital (LTO) cortex. ERPs were recorded from patients who had indwelling subdural electrodes as part of presurgical testing, while BOLD responses were measured in similar brain regions in a second set of subjects. Similar BOLD responses were measured in peri-calcarine and fusiform regions, with both showing monotonic but non-linear increases in hemodynamic amplitude with stimulus duration. In sharp contrast, very different ERP responses were observed in these same regions, such that calcarine electrodes exhibited onset potentials, sustained activity over the course of stimulus duration and prominent offset potentials, while fusiform electrodes only exhibited onset potentials that did not vary with stimulus duration. No duration-related ERP or BOLD changes were observed in LTO. Additional analyses revealed no consistent changes in the EEG spectrum across different brain sites that correlated with duration-related changes in the BOLD response. We conclude that the relation between ERPs and fMRI differs across brain regions.