Psychological Research with Pediatric Conditions: If We Specialize, Can We Generalize?

Considered threats to validity and generalizability of psychologicalresearch with pediatric populations and proposed ways to betterunderstand and manage these problems. Variation due to characteristicsof acute and chronic conditions (e.g., duration, severity, illnesscourse), settings and referral patterns, family environmentalcharacteristics, as well as investigators' decisions concerningcriteria and recruitment limit inferences concerning the impactof pediatric conditions on psychological development and generalizabilityof findings. These problems call for an expanded use of replication,cross-center, population-based, and theory-driven research.Scientific progress will be made by increasing dialogues andcollaboration among researchers concerning generalizabilityproblems and improving research training in epidemiologicalmethods, analysis of large-scale data sets, and meta-analysis.     

Does hyperimmunoglobulinemia-E protect tropical populations from allergic disease?

The Waorani Indians of eastern Ecuador have the highest blood concentration of IgE reported in a human population. Evidence obtained by medical history, physical examination, and immediate hypersensitivity skin tests suggests that pollen allergy and other atopic diseases are rare among the Waorani. A similar association between parasite-induced hyperimmunoglobulinemia-E and a low prevalence of conventional atopic disease has been reported in numerous other tropical populations. Saturation of mast cell IgE receptors with antibodies directed to the parasite and/or other antigens and competitive inhibition of passive binding of pollen allergen-specific IgE is one hypothetical cause of this association. We have tested this interesting conjecture by passively sensitizing the skin of Waorani Indians with serum containing pollen allergen-specific IgE antibodies. Waorani Indians with hyperimmunoglobulinemia-E can be adoptively sensitized with human ragweed or rye grass hyperimmune IgE antisera. This suggests that the cutaneous mast cells of healthy Waorani have active IgE receptors. The high circulating plasma concentrations of IgE in the Waorani do not prevent adoptive cutaneous sensitization with pollen-specific IgE antibodies.     

Translocation (6;9)(p23;q34) in acute nonlymphocytic leukemia: Three new cases

Several recent reports have described cases of acute nonlymphocytic leukemia with a unique chromosome translocation, t(6;9)(p23;q34). We have studied three additional patients who have acute nonlymphocytic leukemia and t(6;9)(p23;q34). Our findings provide additional support for the suggestion that this translocation is yet another distinct cytogenetic abnormality associated with myeloproliferative disorders.     

Assessment of biomaterials as components of a reciprocating dialyser during canine dialysis

A recently reported device, the sorbent suspension reciprocating dialyser (SSRD), was investigated for use as a test system for biocompatibility of dialyser components. The device is easy to assemble and operate, and allows minimal blood contact with foreign material outside of dialyser components. Its constant pressure/ variable flow rate operation allows quantification of degree of clotting of dialyser versus time. The effect of heparinization of the blood distribution gaskets (BDG) of the device on performance and dialyser lifetime was investigated. Heparin was bound to the surface of polyethylene gaskets by immersion in a solution of tridodecylmethylammonium chloride (TDMAC)-heparin complex for several hours. Gaskets were then assembled in an SSRD which was then used for experimental dialysis in dogs with AV shunts. Dialysers assembled using non-heparinized gaskets were used as controls. Blood coagulation tendency was quantified by the activated clotting time (ACT) and partial thromboplastin time (PTT), and these values correlated with the rate of clotting of the device. Heparinization of the gaskets resulted in the prevention of clotting in the dialyser until the final minutes of dialysis in all cases, in contrast to the constant decay of blood fill volume and evidence of clotting in the non-heparinized cases. However, dialyser lifetime was not significantly increased by gasket heparinization. At normal initial values of ACT (80–95 s) dialyser clotting occurred in 10–15 mia In tests with non-heparinized gaskets and systemically heparinized dogs, values obtained in the ACT test were observed to decrease during dialysis, indicating the disappearance of heparin from the blood. Both ACT and PTT tests show promise as predictors of dialyser lifetime.     

Different specificities of an HLA-DRw6 haplotype detected by alloreactive T lymphocytes

DRw6 has been difficult to define serologically. In the present experiments we have developed T cell lines in order to characterize the components of a DRw6 haplotype. This was accomplished by priming T cells with allogeneic mononuclear cells mismatched for DRw6, Dw6, and MT2. Subsequently, three sublines with distinct reactivity patterns were derived by limiting dilution. The specificities detected by these sublines included: (a) a specificity found on a subset of cells positive for DRw6 which was inhibited by monoclonal antibodies against DS(DC), the human homologue of the murine IA-encoded molecules, (b) another DRw6-associated specificity blocked by an MT2-like antibody, and (c) an MT2-like specificity blocked by monoclonal antibodies reactive with a different MT2-associated determinant. These results show that more than one IE-like, as well as the DS/DC (IA-like) molecules, carry distinctive antigenic epitopes that can be recognized by allogeneic T cells. Primed T cell lines may be useful for a better definition of certain haplotypes which are at present difficult to characterize with serological reagents alone.