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Dihydroxyacetone, the browning ingredient in sunless tanning formulations, reacts with amino acids in the outer stratum corneum to form a mixture of high molecular weight pigments. Our initial observations indicated that high hydration of dihydroxyacetone-treated skin completely inhibited development of pigmentation. To investigate the mechanism underlying this effect, studies were carried out in isolated murine epidermis, polyvinyl alcohol/lysine films, and lysine in glycerol/water solvent. Murine epidermis treated with dihydroxyacetone showed a biphasic dependence on relative humidity: maximum pigmentation developed at 84% relative humidity and minimum pigmentation at 0% and 100% relative humidity. Filaggrin proteolysis, which shows a similar dependence on relative humidity and provides free amino acids in the outer stratum corneum, did not account for the relative humidity dependence of dihydroxyacetone pigmentation. A similar biphasic pigmentation response was obtained when polyvinyl alcohol film containing lysine was treated with dihydroxyacetone and incubated at various relative humidities, indicating that the structure of the stratum corneum was not a major factor. To remove the influence of the matrix, the reaction of dihydroxyacetone with lysine was followed at varying concentrations of water in mixed glycerol/buffer solvent. Again, greater pigment formation was found at an intermediate level of water (6% vol/vol) and little pigmentation at 0% and 100% water content. These results are consistent with a requirement for water at low relative humidity, which facilitates formation of free amine groups needed for the initial reaction with dihydroxyacetone, and with inhibition of the dehydration reactions by water through the law of mass action at high relative humidity.

Objective: evaluation of comedone lesions, especially in vivo, remains a challenge. We have used the rhino mouse model in combination with topical application of all-trans retinoic acid as a comedolytic agent, to investigate the potential of fluorescence spectroscopy as a noninvasive technique in the assessment of noninflammatory acne. The results indicate that there is a strong correlation between the fluorescence excitation spectral features assessed in vivo, and the histologic changes identified, particularly the size of the utriculi as well as the dermal and epidermal thickness. We conclude that fluorescence excitation spectroscopy represents a promising novel and useful tool in the quantitative evaluation of the pseudocomedones and could also be used for the rapid and noninvasive assessment of comedolysis induced by the application of pharmacologic agents such as retinoids.

The purpose of this study was to evaluate the clinical efficacy of ultrasmall superparamagnetic iron oxide particles as a magnetic resonance (MR) contrast agent in differentiating metastatic from benign lymph nodes. Eighteen patients with primary lung malignancy and suspected regional lymph node metastases underwent MR imaging before and after Combidex(R) infusion in a multi-institutional study. All MR sequences were interpreted by one or more board-certified radiologists experienced in imaging thoracic malignancy. Each patient was evaluated for the number and location of lymph nodes, homogeneity of nodal signal, and possible change of MR signal post contrast. All patients underwent resection or sampling of the MR-identified lymph node(s) 1-35 day(s) post contrast MR imaging. In all, 27 lymph nodes or nodal groups were available for histopathologic correlation. Combidex had a sensitivity of 92% and a specificity of 80% in identifying pathologically confirmed metastatic mediastinal lymph nodes. Based on our preliminary data, Combidex MR imaging may provide additional functional information useful in the staging of mediastinal lymph nodes.

Rationale and Objectives: The authors performed a baseline analysis of the information needs and information-seeking behaviors of on-call radiology residents to learn how to better serve their on-call information needs in the future., Materials and Methods: Print, electronic, and human information resources were made conveniently available to on-call radiology residents. A prospective, descriptive study was performed by using a modification of the critical incident technique to gather data from the residents every morning after being on call. Residents were asked to recall questions that arose, whether they sought answers to the questions, where they searched for answers, whether their search was successful, and whether they believed that patient care was affected., Results: The residents had 182 questions that encompassed all organ systems, imaging modalities, and aspects of radiologic practice. Residents sought answers to 138 of the 182 questions (76%) by using a wide variety of resources, with staff members and textbooks being the most common. They found answers to 114 of 138 questions (83%); 100 of the 114 (88%) answered questions affected patient care., Conclusion: The ideal way to meet the information needs of on-call radiology residents is to devise an authoritative information resource that is compatible with their information-seeking behaviors.

Atmospheric samples collected during rice straw burning at four different locations in Viet-Nam during the dry (March 1992, February 1993) and wet season (August 1992) were analysed for CO2, CO, and CH4. The emission ratios relative to CO2 for CO and CH4 for rice straw burning during the dry season were comparable to those observed on samples collected during burning of savanna in Africa or forest in the USA. During the wet season, however the emission ratios for CO and CH4 relative to CO2 were 3 to 10 times higher. With these emission ratios and estimates of rice production from Southeastern Asia, we estimated that burning of rice straw emits annually about 2.2 Tmol of CO (26 TgC) and 0.2 Tmol of CH4 (2.4 TgC) to the atmosphere. Taking into account these new results, CO and CH4 fluxes from biomass burning could be reevaluated by 5-21% and 5-24%, respectively, in respect with previous estimates of these gas emissions from all biomass burning activities.

We have studied in rats fed hypercholesterolemic diet the action of calcic and magnesic sulphurous water from Capvern on the modification of the lipoproteins metabolism caused by hypercholesterolemia. The rats subjected to a hypercholesterolemic diet with thermal water of Capvern was found to have a plasma level of cholesterol significantly less increased (P less than 0.01) compared to those subjected to the same diet with ordinary drinking water (25%). We demonstrated after 105 days of experimentation on tested rats that thermal water may affect the cholesterol catabolism by increased level of cholesterol HDL (52%) and stabilizing level of cholesterol LDL comparatively to the controls. These data suggest that the thermal water from Capvern enhanced the transformation of cholesterol to biliary acids and their biliary secretion. A possible relationship between the influence of the thermal water and the metabolism of lipoproteins would be explained by a possible increase of hepatic receptors which identify apolipoproteins B (LDL) and E (HDLc) on cholesterol fed rats, suggesting a great synthesis of nascent apolipoproteins HDL which are antiatherogenic.