Changing attentional demands in left hemispatial neglect.

Seven variations of a letter cancellation test were used to examine how varying attentional demands affect hemispatial neglect in patients with right hemisphere lesions. While the 14 targets always remained in the same location, the number of distractors (zero, nine, 28, or 82) as well as their complexity (one letter or nine different letters) were varied. The percentage of targets canceled in the left hemispace was linearly related to the number of distractors. There were no differences between the complexity conditions. In a second study, the same 14 targets were presented but the distractors (zero, 14, or 41) were all placed on the right. Increasing the number of distractors on the right increased neglect on both sides of the space. Taken together, these results suggest that, while the limited attentional resources of the left hemisphere are biased toward the right hemispace, the absence of contralateral attentional demands allows these resources to be directed ipsilaterally.     

Recommendations for the evaluation and treatment of neonatal autoimmune and alloimmune thrombocytopenia. The Working Party on Neonatal Immune Thrombocytopenia of the Neonatal Hemostasis Subcommittee of the Scientific and Standardization Committee of the ISTH

The following recommendations of the Neonatal Hemostasis Subcommittee of the Scientific and Standardization Committee of the ISTH for the management of neonatal immune thrombocytopenia were prepared by the working party on neonatal immune thrombocytopenia. Evaluation, diagnosis, and treatment of the mother and neonate with alloimmune and autoimmune thrombocytopenia are discussed and current recommendations provided. This document is likely to require frequent future revision(s).     

Immunogenicity of four Haemophilus influenzae type b conjugate vaccines in 17- to 19-month-old children

OBJECTIVE: To compare the immunogenicity of four Haemophilus influenzae type b (Hib) conjugate vaccines in different populations of 17- to 19-month-old children in the United States. DESIGN: Four immunogenicity trials with sera were assayed in one laboratory. Trials 1 and 2 each compared one vaccine in two regions, and trials 3 and 4 were randomized comparisons of multiple vaccines within a region. SUBJECTS: A convenience sample of 313 healthy children recruited from pediatric practices in Minneapolis, Minn., Dallas and Houston, Tex., and Sellersville, Pa. MEASUREMENTS AND RESULTS: Children with prevaccination antibody greater than 0.15 microgram/ml showed higher antibody responses to vaccination than children with less than or equal to 0.15 microgram/ml (p less than 0.001). Among the former, there were no significant differences in antibody response to vaccination with the different conjugates within any of the trials. Among children with less than or equal to 0.15 microgram/ml of antibody before vaccination, there were no significant differences in the geometric mean antibody responses of children in trial 1 vaccinated with polyribosylribitol phosphate-diphtheria toxoid (PRP-D) in Dallas or in Minneapolis, or of children in trial 3 in Dallas randomly assigned to receive Hib oligosaccharide-CRM197 (HbOC) or PRP-D. In contrast, in trial 2, children given PRP-tetanus toxoid (PRP-T) in Pennsylvania had a significantly higher geometric mean antibody response than children given PRP-T in Houston (13.5 vs 3.0 micrograms/ml; p = 0.005). In trial 4 in Minneapolis, the geometric mean antibody response was highest in children randomly assigned to receive PRP-outer membrane protein (OMP) (9.3 micrograms/ml), followed by PRP-D (5.0 micrograms/ml) and HbOC (2.3 micrograms/ml) (PRP-OMP vs HbOC; p = 0.005). In all four trials, IgG1 responses predominated compared with IgG2 responses. CONCLUSIONS: All four conjugate vaccines are immunogenic in children 17 to 19 months of age. However, the magnitude of the anticapsular antibody response varied by vaccine type, the level of antibody in prevaccination sera, and geographic location.     

Regulation of B Cell:T Cell Interactions: Potential Involvement of an Endogenous B Cell Sialidase

In light of the ability of B cells treated with neuraminidase to interact more effectively with T cells, the increased capacity of activated, but not small resting B cells, to interact with T cells could be associated with the level of sialylation on certain B cell surface molecules which influences the effectiveness of the physical interaction between B and T cells. The purpose of this study was to determine if activation of B cells altered sialylation via an endogenous sialidase which affected both the initial interaction between T and B cells and subsequent B cell-induced T cell proliferation. The competitive neuraminidase inhibitor, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (NeuAc2en), inhibited LPS-mediated enhancement of B cell conjugate formation with Ia-specific T cell clones as well as enhancement of their capacity to stimulate a mixed lymphocyte reaction. The addition of NeuAc2en during LPS stimulation did not affect the surface expression of Ia, LFA-1, ICAM-1 or mB7, suggesting that inhibition of LPS-mediated enhancement by the sialidase inhibitor was not due to changes in the level of expression of the major B cell adhesion or co-stimulatory molecules. Short term stimulation with phorbol myristate acetate (PMA) and ionomycin also enhanced the ability of resting B cells to form antigen specific T:B conjugates. However, activation of B cells with PMA and ionomycin or with LPS did not change the capacity of a sialic acid specific lectin to bind to the B cells, suggesting that activation was not associated with global changes in surface sialic acid content. B cell stimulation did not appear to increase the activity of the most prevalent B cell sialidase activity as measured in an in vitro assay system, suggesting that the major B cell sialidase may not be responsible for the alteration of B cell sialylation levels or the ability of activated B cells to interact more effectively with T cells. The possibility of intracellular compartmentalization of sialidase activity or that a minor B cell sialidase may play a role in the regulation of a B cells ability to interact with T cells are discussed.     

Axial diffusion of retinol in isolated frog rod outer segments following substantial bleaches of visual pigment

Partial bleaches of rhodopsin were made in either the proximal or distal halves of isolated Rana pipiens rod outer segments. The fluorescence of all-trans retinol was recorded 15, 60 and 120 min following 17% and 63% bleaches. Some of the retinol that formed remained immobilized in the bleached halves of the outer segments, while another portion was slowly mobilized and diffused along the cell axis.