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Marrow stromal cells from wild-type mice were infused into transgenic mice that had a phenotype of fragile bones resembling osteogenesis imperfecta because they expressed a human minigene for type I collagen. In mice that were irradiated with potentially lethal levels (700 cGy) or sublethal levels (350 cGy), DNA from the donor marrow stromal cells was detected consistently in marrow, bone, cartilage, and lung either 1 or 2.5 mo after the infusions. The DNA also was detected but less frequently in the spleen, brain, and skin. There was a small but statistically significant increase in both collagen content and mineral content of bone 1 mo after the infusion. Similar results were obtained with infusion of relatively large amounts of wild-type whole marrow cells into the transgenic mice. In experiments in which male marrow stromal cells were infused into a female osteogenesis imperfecta-transgenic mouse, fluorescense in situ hybridization assays for the Y chromosome indicated that, after 2.5 mo, donor male cells accounted for 4-19% of the fibroblasts or fibroblast-like cells obtained in primary cultures of the lung, calvaria, cartilage, long bone, tail, and skin. In a parallel experiment in which whole marrow cells from a male mouse were infused into a female immunodeficient rag-2 mouse, donor male cells accounted for 4-6% of the fibroblasts or fibroblast-like cells in primary cultures. The results support previous suggestions that marrow stromal cells or related cells in marrow serve as a source for continual renewal of cells in a number of nonhematopoietic tissues.

Facial expressions of pain and emotions provide powerful social signals, which impart information about a person's state. Unfortunately, research on pain and emotion expression has been conducted largely in parallel with few bridges allowing for direct comparison of the expressive displays and their impact on observers. Moreover, although facial expressions are highly dynamic, previous research has relied mainly on static photographs. Here we directly compare the recognition and discrimination of dynamic facial expressions of pain and basic emotions by naive observers. One-second film clips were recorded in eight actors displaying neutral facial expressions and expressions of pain and the basic emotions of anger, disgust, fear, happiness, sadness and surprise. Results based on the Facial Action Coding System (FACS) confirmed the distinct (and prototypical) configuration of pain and basic emotion expressions reported in previous studies. Volunteers' evaluations of those dynamic expressions on intensity, arousal and valence demonstrate the high sensitivity and specificity of the observers' judgement. Additional rating data further suggest that, for comparable expression intensity, pain is perceived as more arousing and more unpleasant. This study strongly supports the claim that the facial expression of pain is distinct from the expression of basic emotions. This set of dynamic facial expressions provides unique material to explore the psychological and neurobiological processes underlying the perception of pain expression, its impact on the observer, and its role in the regulation of social behaviour.