Loss of Histochemical Identity in Mast Cells Lacking Carboxypeptidase A

Mast cell carboxypeptidase A (Mc-cpa) is a highly conserved secretory granule protease. The onset of expression in mast cell progenitors and lineage specificity suggest an important role for Mc-cpa in mast cells. To address the function of Mc-cpa, we generated Mc-cpa-null mice. Mc-cpa(−)(/)(−) mast cells lacked carboxypeptidase activity, revealing that Mc-cpa is a nonredundant enzyme. While Mc-cpa(−)(/)(−) peritoneal mast cells were ultrastructurally normal and synthesized normal amounts of heparin, they displayed striking histochemical and biochemical hallmarks of immature mast cells. Wild-type peritoneal mast cells had a mature phenotype characterized by differential histochemical staining with proteoglycan-reactive dyes (cells do not stain with alcian blue but stain with safranin and with berberine) and a high side scatter to forward scatter ratio by flow cytometry and were detergent resistant. In contrast, Mc-cpa(−)(/)(−) peritoneal mast cells, like immature bone marrow-derived cultured mast cells, stained with alcian blue normally or weakly and either did not stain with safranin and berberine or stained weakly, had a low side scatter to forward scatter ratio, and were detergent sensitive. This phenotype was partially ameliorated with age. Thus, histochemistry and flow cytometry, commonly used to measure mast cell maturation, deviated from morphology in Mc-cpa(−)(/)(−) mice. The Mc-cpa(−)(/)(−) mast cell phenotype was not associated with defects in degranulation in vitro or passive cutaneous anaphylaxis in vivo. Collectively, Mc-cpa plays a crucial role for the generation of phenotypically mature mast cells

Swedish preschool teachers’ ideas of the ideal preschool group

In Sweden, preschool has been noted as being of a high quality compared to many other countries. However, dramatic changes in the preschool sector are taking place. A recent law states that it is a child’s right to get a preschool place within a few months. As a consequence, the number of children in preschool has increased, which could influence group sizes since there is no state regulation of the number of children in a group. This article based on the project The impact of group size on children’s affordances in preschool aims to describe and analyse preschool teachers’ ideas of what an ideal preschool group is. It is a qualitative study based on a questionnaire with mainly open-ended questions, answered by preschool teachers. The results show that preschool teachers define a well-functioning group as having a balance between gender, age and ethnicity. The preschool teachers stress that they prefer a group with fewer children than they have today. A key aspect of having a well-functioning group is also the preschool teachers’ competence and the preschool environment. Preschool teachers’ ideas of what constitute an ideal group of children may contribute to why they perceive the group size too large