Identification and characterization of a novel siglec, siglec-7, expressed by human natural killer cells and monocytes

We describe the characterization of sialic acid-binding Ig-like lectin-7 (siglec-7), a novel member of the siglec subgroup of the immunoglobulin superfamily. A full-length cDNA encoding siglec-7 was isolated from a human primary dendritic cell cDNA library. Siglec-7 is predicted to contain three extracellular immunoglobulin-like domains that comprise an N-terminal V-set domain and two C2-set domains, a transmembrane region and a cytoplasmic tail containing two tyrosine residues embodied in immunoreceptor tyrosine-based inhibition motif-like motifs. Overall, siglec-7 exhibited a high degree of sequence similarity to genes encoding CD33 (siglec-3), siglec-5, OBBP1/siglec-6, and OBBP-like protein and mapped to the same region on chromosome 19q13.3. When siglec-7 was expressed on COS or Chinese hamster ovary cells, it was able to mediate high levels of sialic acid-dependent binding to human erythrocytes and soluble sialoglycoconjugates, suggesting that it may be involved in cell-cell interactions. Among human peripheral blood leukocytes, siglec-7 was found to be present at low levels on granulocytes, intermediate levels on monocytes, and relatively high levels on a major subset of natural killer cells and a minor subset of CD8(+) T cells. Immunoprecipitation experiments indicated that siglec-7 is expressed as a monomer of approximately 65 kDa.     

Male Grey squirrel (Sciurus carolinensis) reproductive cycles in Britain

A synchronized seasonal cycle of sexual regression and development is described for the male Grey squirrel in Britain. Sexual development is maximal in December and May and minimal in August. The seasonal cycle can be overriden, but this is exceptional. Comparisons with previous work and the suggestion that the synchronized seasonal sexual cycle is general for Grey squirrels in Britain, and probably America, are made.     

Methods of age determination in Grey squirrels (Sciurus carolinensis) in Britain

Using X-ray and lens weight techniques on wild and known age captive animals age criteria have been established for Grey squirrels in Britain. Adults have fused epiphyses of the radius and ulna and a paired dried lens weight above 76.0 mg. The longevity of Grey squirrels in Britain is considered. Comparisons with similar data from the USA are made.