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BACKGROUND: The goal of this study was to examine the impact of subjective and physiological stress responses on medical students' diagnostic reasoning and communication skills. METHOD: A prospective randomized quantitative study was undertaken, looking at ambulatory consultations in internal medicine. On the first day (baseline day), volunteer year 6 students (n = 41) participated in a simulated ambulatory consultation with standardized patients (SPs). On the second day (study day), one week later, they were randomly assigned to two groups: a low stress (n = 20) and a high stress (n = 21) simulated ambulatory consultation. Stress was measured using validated questionnaires and salivary cortisol. The SPs assessed the students' reasoning and communication. The students completed assessments of their clinical reasoning after the consultations. RESULTS: Although stress measures were all significantly higher in the high-stress condition (all p < 0.05), no differences were found in diagnostic accuracy and justification scores. However, correlational analyses revealed a negative correlation between multiple-stress measures and the students' ability to generate arguments for differential diagnoses. CONCLUSION: Stress was associated with impairments in clinical reasoning, of a nature typically suggestive of premature closure.

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YKL-40 (cartilage gp-39), is a mammalian glycoprotein related in sequence to chitinases. Its function is unknown, but it is thought to be involved in tissue remodeling. Immunocytochemical staining of YKL-40 in guinea pig chondrocytes (GPC), rabbit chondrocytes (RC), and rabbit synoviocytes (RS) was higher in dividing cells than in confluent cells, suggesting a participation of YKL-40 in cell cycle events. As assessed by the MTT assay, YKL-40 at 1.9-7.6 nM had dose-dependent mitogenic activity toward the three cell types. At 7.6 nM, YKL-40 increased the number of cells of 42% in GPC, 75% in RC, and 86% in RS after 72 h. YKL-40 also stimulated total proteoglycan synthesis by chondrocytes in a dose-dependent manner as assessed by Na[35SO4] incorporation and cetylpyridinium chloride precipitation. At 9.4 nM, YKL-40 increased proteoglycan synthesis of 42% in GPC and 58% in RC after 24 h. The growth factor properties of YKL-40 may explain the increased tissue remodeling associated with high levels of YKL-40 in joint diseases, and possibly, in malignant pathologies such as breast cancer or colorectal cancer.

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In the albinos rat, at day 20 in utero, the outer epithelial layer of the first molar is depressed by numerous capillaries. The mesenchymal cells of the follicle present cytoplasmic extensions which are in close relationship with the basement lamina of the external epithelial layer with fibrillar material adherent to the basement lamina. The endothelial cells of the capillaries also present cytoplasmic extensions in contact with the basement lamina. At day 21 in utero, the capillaries penetrate deeply into the stellate reticulum. The fact that the epithelium which surrounds the capillaries is separated from the latter by a basement membrane indicates that the vascular penetration induces a very deep invagination of the epithelium and the basement membrane. This vascular penetration could play a role in the transport of precursors towards the secretory ameloblasts. The mesenchymal and endothelial tissues of the capillaries could have an inductive role on the external epithelial layer through the basement membrane, leading to a disorganization of the enamel organ.

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The oral nerve endings of the palate, the buccal mucosa and the periodontal ligament of the cat canine were characterized by the presence of a cellular envelope which is the final form of the Henle sheath. The structures described as end-rings in the periodontal ligament are more probably subterminal nervous structures rather then receptors. They are not specific to the ligament. They can be observed in the palate and in the buccal mucosa where, as in the periodontal ligament, mechano-receptors of the Vater-Pacini type can be seen.

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In the albino rat, at the 21th day of gestation, the capillaries entered the stellate reticulum of the molar and came into contact with the stratum intermedium. This vascular penetration was followed on the 10th day of age by a connective penetration. The stellate reticulum was thus disorganized and was built up by small epithelial islands surrounded by collagen and reticulin fibrils. Finally, the reduced enamel epithelium fused with the oral epithelium and formed the epithelial attachment. After a trophic role, the vascularization, with the help of the connective tissue penetration, had a destructive function. Both vascularization and connective tissue invasion contribute to the enamel organ involution.

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