A P Atkinson | PubMed Health

PubMed1998

Developmental variation in stem-cell markers from human fetal liver and umbilical cord blood leukocytes.

Fetal tissues containing haematopoietic stem cells (HSC) are of potential value for allogeneic transplantation and gene therapy. Flow cytometry was used to investigate CD34+ cells from human fetal livers and umbilical cord (placental) blood (UCB). CD34+ cells, expressed as a proportion of CD45-positive leukocytes, were much more abundant in fetal livers (mean 38%) than in UCB (mean 0.3%), but fetal liver cells had lower proportions of CD34+HLA-DR+ and CD34+ CD38+ subsets. In fetal liver, there was a strong and highly significant inverse correlation between CD34+ cells (as a proportion of total leukocytes) and gestational age; no such relationship was found for subsets of CD34+ cells coexpressing CD38 or CDw90 (Thy-1), but CD34+HLA-DR+ cells were less abundant in first-compared to second-trimester livers. In UCB, a trend towards decreasing CD34+ cells (as a proportion of total leukocytes) with increasing gestational age in late pregnancy was also observed. The composition of fetal leukocytes changes during development, and therefore the timing of fetal HSC harvesting could be of relevance to transplantation outcome.

Antigens, CD↗

PubMed1993

What's lost in inverted faces?

Disproportionate inversion decrements for recognizing faces and other homogeneous stimuli are often interpreted as evidence that experts use relational features to recognize stimuli that share a configuration. However, it has never directly been shown that inversion disrupts the coding of relational features more than isolated features. Here we report three studies that compare inversion decrements for detecting changes that span the isolated-relational features continuum. Relatively large inversion decrements occurred for relational features (Thatcher illusion changes, internal feature spacing), with smaller decrements for isolated features (presence/absence of facial hair or glasses). The one discrepancy was a relatively large inversion decrement for detecting changes to the eyes and mouth, which we had classified as an isolated feature change. However, this decrement disappeared when the features were presented out of the face context (Experiments 2 and 3), suggesting that it occurs because subjects spontaneously code relations between the features and the rest of the face. Although the results support the interpretation of disproportionate inversion effects as evidence of relational coding, the difficulty of classifying changes as isolated or relational highlights an undesirable ambiguity in the isolated-relational feature distinction. We therefore consider alternative construals of the configural coding notion.

Facial Expression↗