We investigated the cutaneous expression of genes and enzymes responsible for the multistep conversion of tryptophan to serotonin and further to melatonin. Samples tested were human skin, normal and pathologic (basal cell carcinoma and melanoma), cultured normal epidermal and follicular melanocytes, melanoma cell lines, normal neonatal and adult epidermal and follicular keratinocytes, squamous cell carcinoma cells, and fibroblasts from dermis and follicular papilla. The majority of the samples showed simultaneous expression of the genes for tryptophan hydroxylase, arylalkylamine N-acetyltransferase (AANAT), and hydroxyindole-O-methyltransferase (HIOMT). The products of AANAT activity were identified by RP-HPLC with fluorimetric detection in human skin and in cultured normal and malignant melanocytes and immortalized keratinocytes; HIOMT activity was detected in human skin, keratinocytes, and melanoma cells. N-acetylserotonin (NAS) was detected by RP-HPLC in human skin extracts. NAS identity was confirmed further by LC/MS in keratinocytes. In conclusion, we provide evidence that the human skin expresses intrinsic serotonin and melatonin biosynthetic pathways.

Web-based computer-aided instruction (CAI) has become increasingly important to medical curricula. This multi-year study investigated the effectiveness of CAI and the factors affecting level of individual use. Three CAI were tested that differed in specificity of applicability to the curriculum and in the level of student interaction with the CAI. Student personality preferences and learning styles were measured using the Meyers Briggs Type Indicator (MBTI) and Kolb's Learning Style Inventory (LSI). Information on ''computer literacy'' and use of CAI was collected from student surveys. Server logs were used to quantify individual use of respective CAI. There was considerable variability in the level of utilization of each CAI by individual students. Individual use of each CAI differed and was associated with gender, MBTI preferences and learning style, but not with ''computer literacy.'' The majority of students found the CAI useful for learning and used the CAI by themselves. Students who accessed the CAI resources most frequently scored significantly higher on exams compared with students who never accessed the resources. Our results show that medical students do not uniformly use CAI developed for their curriculum and this variability is associated with various attributes of individual students. Our data also provide evidence of the importance of understanding student preferences and learning styles when implementing CAI into the curriculum.

Background: Increasing numbers of medical schools are providing videos of lectures to their students. This study sought to analyze utilization of lecture videos by medical students in their basic science courses and to determine if student utilization was associated with performance on exams.

Interstitial cells in the pineal gland of the rat were characterized immunocytochemically using the monoclonal antibodies MRC OX-42 and ED1 for macrophages/microglia, and MRC OX-6, which recognizes major histocompatibility complex (MHC) class II antigen. A polyclonal antibody against GFAP was used to identify astrocytes. Cells immunopositive for OX-42 and/or ED1 were distributed throughout the gland; they extended processes primarily along the perivascular spaces and occasionally within the parenchyma of the gland. Ultrastructurally, these OX-42-positive cells were characterized by a nucleus with sparse heterochromatin and cytoplasmic vacuoles/lysosomes. Cells expressing MHC class II antigen had a distribution and morphology similar to OX-42-immunopositive cells, suggesting that pineal macrophages/microglia play a role as antigen-presenting cells. GFAP-positive astrocytes were concentrated at the proximal end of the pineal where the pineal stalk enters the gland. The occurrence of antigen-presenting cells in this circumventricular neuroendocrine gland has important functional implications as these cells may be mediators of neuroimmunomodulatory mechanisms, and involved in certain disease states such as autoimmune pinealitis.

This study demonstrates an important advantage of web-based applications to collect and evaluate CAI utilization efficiently and objectively at both the level of the class and the level of the individual student.