In vitro phagocytosis of Giardia duodenalis cysts by hemocytes of the Asian freshwater clam Corbicula fluminea

Hemocytes of the Asian freshwater clam Corbicula fluminea, phagocytosed in vitro infectious Giardia duodenalis cysts. After 15, 30, 60, 90, and 120 min of incubation an average of 22%, 32%, 43%, 54%, and 72% of the cysts were phagocytosed by 22%, 55%, 63%, 81%, and 86% of the hemocytes, respectively. The number of hemocytes showing phagocytosis and the mean number of cysts ingested per hemocyte increased significantly over time (P < 0.01); the numbers of nonphagocytosed cysts significantly decreased (P < 0.02). Extrapolation reveals that C. fluminea can retain by phagocytosis an average of 1.6 x 10(6) G. duodenalis cysts/ml hemolymph. The phagocytic capacity of C. fluminea hemocytes indicates the applicability of this freshwater benthic bivalve for bioindication of contamination of waste waters and agricultural drainage with Giardia cysts.     

V-D-J rearrangements at the T cell receptor delta locus in mouse thymocytes of the alpha beta lineage

The T cell receptor (TCR) delta locus lies within the TCR alpha locus and is excised from the chromosome by V alpha-J alpha rearrangement. We show here that delta sequences persist in a large fraction of the DNA from mature CD4+CD8- alpha beta+ mouse thymocytes. Virtually all delta loci in these cells are rearranged and present in extrachromosomal DNA. In immature alpha beta lineage thymocytes (CD3-/loCD4+CD8+) and in CD4+CD8- alpha beta+ thymocytes expressing a transgene-encoded alpha beta receptor, rearranged delta genes are present both in chromosomal and extrachromosomal DNA. Thus, contrary to earlier proposals, commitment to the alpha beta lineage does not require recombinational silencing of the delta locus or its deletion by a site-specific mechanism prior to V alpha-J alpha rearrangement.     

What is remembered about early childhood events?

Almost 100 years ago, Freud identified infantile or childhood amnesia, the difficulty that most adults have remembering events from their first years of life. Recent research in cognitive psychology has in fact demonstrated a paucity of verbal memories of early life experiences. Although Freud believed that childhood memories are repressed, modern explanations for childhood amnesia focus instead on cognitive and social developmental advances of the early preschool years. According to the social interaction hypothesis, a narrative sense of self emerges as a result of parent-child conversations about the past. Implications of autobiographical memory research for models of adult attachment and psychotherapy are discussed.     

Defining an antigenic epitope on platelet factor 4 associated with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a potentially serious complication of heparin therapy. Antibodies to platelet factor 4 (PF4)/heparin complexes have been implicated in the pathogenesis of this disorder, but the antigenic epitope(s) on the protein have not been defined. To address this issue, we studied the binding of HIT antibodies to a series of recombinant proteins containing either point mutations in PF4 or chimeras containing various domains of PF4 and the related protein, neutrophil activating peptide-2 (NAP-2). Serum samples from 50 patients with a positive 14C-serotonin release assay (14C-SRA) and a clinical diagnosis of HIT and 20 normal controls were studied. HIT antibodies reacted strongly with wild-type (WT) PF4/heparin complexes, but reacted little, if at all, with NAP-2/heparin complexes (optical density [OD]405 = 2.5 and 0.2, respectively). Alanine substitutions at three of the four lysine residues implicated in heparin binding, K62, K65, and K66, had little effect on recognition by HIT antibodies (OD405 = 2.2, 2.8, and 2.0, respectively), whereas an alanine substitution at position K61 led to reduced, but still significant binding (OD405 = 1.0). Similar studies involving chimeras between PF4 and NAP-2 localized a major antigenic site to the region between the third and fourth cysteine residues for more than half of the sera tested. This site appears to involve a series of amino acids immediately after the third cysteine residue beginning with P37. Thus our studies suggest that whereas the C-terminal lysine residues of PF4 are important for heparin binding, they do not comprise a critical antigenic site for most HIT antibodies. Rather, we propose that maintaining a region near the third cysteine residue of PF4, distal from the proposed heparin-binding domain, is required to form the epitope recognized by many HIT antibodies.     

Patient satisfaction after limb-sparing surgery and amputation for pediatric malignant bone tumors

We surveyed 65 patients age 13 years or older who had been treated for malignant bone tumors and were in remission at least 1 year after limb-sparing surgery (LS) or amputation (AMP) to assess general satisfaction with the surgical outcome and its impact on various areas of functioning. Of 130 eligible patients, 65 responded (61 treated for osteosarcoma, 3 for Ewing's sarcoma, and 1 for mesenchymoma). The median current age of the cohort was 25.8 years (range, 14.2 to 47.5 years). The median time from surgery was 14.2 years (range, 4.0 to 30.4 years) for the AMP group, and 5.5 years (range, 2.0 to 13.8 years) for the LS patients. Questionnaire responses of patients treated with AMP compared to those who had LS surgery showed no significant differences in the impact of the surgical procedure on educational and occupational status, functional limitations, pain intensity and degree of pain interference, emotional distress, interpersonal/social interactions and self-image, rehabilitation experience, and overall satisfaction with the surgical procedure. Functional limitation was significantly related to pain interference, as well as emotional distress, self-image, and interpersonal difficulties for the entire cohort. Our findings highlight procedure-related advantages and difficulties that may potentially enhance decision making regarding the selection of the surgical procedure for individual patients with malignant bone tumors of an extremity.