Planning for children whose parents are dying of HIV/AIDS. American Academy of Pediatrics. Committee on Pediatric AIDS, 1998-1999

Although the character of acquired immunodeficiency syndrome is changing into a chronic illness, it is estimated that by the end of this century, 80 000 children and adolescents in the United States will be orphaned by parental death caused by human immunodeficiency virus infection. Plans for these children need to be made to ensure not only a stable, consistent environment that provides love and nurturing, but also the medical and social interventions necessary to cope with the tragic loss. Pediatricians should become aware of local laws and community resources and initiate discussion early in the course of parental illness to facilitate planning for the future care and custody of the children. States need to adopt laws and regulations that provide flexible approaches to guardianship and placement of children orphaned by acquired immunodeficiency syndrome.     

Structure of the antithrombin-binding site in heparin.

Heparin preparations from pig intestinal mucosa and from bovine lung were separated by chromatography on antithrombin-Sepharose into a high-affinity fraction (with high anticoagulant activity) and a low-affinity fraction (with low anticoagulant). Antithrombin-binding heparin fragments (12-16 monosaccharide units) were prepared, either by digesting a high-affinity heparin-antithrombin complex with bacterial heparinase or by partial deaminative cleavage of the unfractionated polysaccharide with nitrous acid followed by affinity chromatography on immobilized antithrombin. Compositional analysis based on separation and identification of deamination products reduced with sodium boro[3H]hydride showed that nonsulfated L-iduronic acid occurred in larger amounts in high-affinity heparin than in low-affinity heparin; furthermore, this component was concentrated in the antithrombin-binding regions of the high-affinity heparin molecules, amounting to approximately one residue per binding site. It is suggested that nonsulfated L-iduronic acid is essential for the anticoagulant activity of heparin. The location of the non-sulfated uronic acid in the antithrombin-binding site was determined by periodate oxidation of antithrombin-binding fragments containing a terminal 2,5-anhydro-D-[1-3H]mannitol unit. Tentative structures for antithrombin-binding sequences in heparin are proposed, including some structural variants believed to be compatible with, but not required for, activity.     

Polar/apolar interfaces modulate the conformational behavior of cyclic peptides with impact on their passive membrane permeability

Cyclic peptides have the potential to vastly extend the scope of druggable proteins and lead to new therapeutics for currently untreatable diseases. However, cyclic peptides often suffer from poor bioavailability. To uncover design principles for permeable cyclic peptides, a promising strategy is to analyze the conformational dynamics of the peptides using molecular dynamics (MD) and Markov state models (MSMs). Previous MD studies have focused on the conformational dynamics in pure aqueous or apolar environments to rationalize membrane permeability. However, during the key steps of the permeation through the membrane, cyclic peptides are exposed to interfaces between polar and apolar regions. Recent studies revealed that these interfaces constitute the free energy minima of the permeation process. Thus, a deeper understanding of the behavior of cyclic peptides at polar/apolar interfaces is desired. Here, we investigate the conformational and kinetic behavior of cyclic decapeptides at a water/chloroform interface using unbiased MD simulations and MSMs. The distinct environments at the interface alter the conformational equilibrium as well as the interconversion kinetics of cyclic peptide conformations. For peptides with low population of the permeable conformation in aqueous solution, the polar/apolar interface facilitates the interconversion to the closed conformation, which is required for membrane permeation. Comparison to unbiased MD simulations with a POPC bilayer reveals that not only the conformations but also the orientations are relevant in a membrane system. These findings allow us to propose a permeability model that includes both ‘prefolding’ and ‘non-prefolding’ cyclic peptides – an extension that can lead to new design considerations for permeable cyclic peptides.

This study uses molecular dynamics and Markov state models to analyse how interfaces interact with cyclic decapeptides and modulate their dynamic and equilibrium properties.     

Modulation of megakaryocytopoiesis by human basic fibroblast growth factor

Basic fibroblast growth factor (bFGF) may act to modulate hematopoiesis in addition to its effects on mesenchymal cells. We studied the effects of bFGF on human and murine primary marrow megakaryocytes. bFGF modestly enhanced the size of the human megakaryocyte colony-forming unit (CFU-MK) and cell numbers per colony, in combination with interleukin-3 (IL-3) or granulocyte-macrophage colony stimulating factor (GM-CSF). Adhesion of human megakaryocytes to bone marrow (BM) stromal fibroblasts was enhanced when either stromal fibroblasts or megakaryocytes were treated with bFGF. This resulted in significantly increased proliferation of megakaryocytes. In addition, bFGF augmented secretion of the cytokines tumor necrosis factor alpha and IL-6 by human primary BM megakaryocytes. Immature murine megakaryocytes showed a significant growth response to bFGF as measured by the single cell growth assay. This effect was abrogated by specific antibodies for bFGF and combination of anti-IL-6 and anti-IL-1 beta antibodies. bFGF has no effect on murine CFU-MK formation, but significantly potentiated CFU-MK formation in the presence of IL-3 or GM-CSF. These results indicate that the effect of bFGF on various megakaryocyte populations is different and that bFGF may affect megakaryocytopoiesis via modulation of megakaryocyte-stromal interactions and via augmentation of cytokine secretion from megakaryocytes.     

Interleukin-10 is an autocrine growth factor for acquired immunodeficiency syndrome-related B-cell lymphoma [see comments]

Interleukin-10 (IL-10) is an acid-sensitive protein of 35 kD that has pleiotropic effects including inhibition of cytotoxic T-cell response, induction of major histocompatibility complex type II in B lymphocytes, induction of B-cell growth and differentiation, and autocrine growth factor activity in monocytes. We and others have shown that IL-10 is produced spontaneously by blood mononuclear cells from human immunodeficiency virus-seropositive patients. In an attempt to ascertain the potential role of IL-10 in acquired immunodeficiency syndrome (AIDS)-related B-cell lymphoma, we evaluated the expression of human IL-10 in both tumor-derived B-cell lines and primary tumor cells. Expression of human IL-10 (hIL-10) mRNA and protein was detected in four of five cell lines examined. An IL-10 antisense oligonucleotide inhibited IL-10 mRNA expression and IL-10 protein production. The proliferation of all B-cell lines was inhibited by an antisense oligonucleotide in a dose-dependent manner that was abrogated by the addition of recombinant hIL-10 protein. No effect of antisense oligonucleotide was observed in the B-cell line not producing hIL-10. Evaluation of primary tumor cells from patients with AIDS-lymphoma cells showed similar production and response to IL-10. These data suggest an autocrine growth mechanism for IL-10 in AIDS-related lymphoma cells and that IL-10 may be important in its pathogenesis.     

Autologous stem cell transplantation for acute myeloid leukemia

Autologous bone marrow transplant (ABMT) and stem cell transplantation (ASCT) are important treatment modalities for acute myeloid leukemia (AML). The role of ASCT in first remission patients remains controversial. Phase II and phase III studies demonstrate that patients with favorable-risk cytogenetics benefit from ASCT, with reduction in relapse and improvement in leukemia-free survival (LFS). Patients with poor-risk cytogenetics do not appear to benefit significantly from ASCT and should preferentially be treated with allogeneic transplant. The role of ASCT for patients with intermediate risk disease is uncertain. It appears that ASCT in first remission will improve disease-free survival compared to standard chemotherapy. Sufficient patients who relapse after chemotherapy treatment can be salvaged with ASCT in second remission such that the beneficial effect on overall survival is blunted. ASCT produces equivalent results to ABMT but with reduced morbidity. The collection of stem cells during recovery from intensive dose consolidation therapy appears to be an attractive strategy that can increase the percentage of patients who are able to receive their intended transplant. Consolidation therapy prior to stem cell collection and transplant has been shown to decrease the relapse rate and improve outcomes, but the optimal nature of this consolidation therapy is unknown. For patients with AML in second remission, ABMT/ASCT offers a substantial salvage rate, and is particularly effective for patients with acute promyelocytic leukemia.     

Multiple sclerosis in families: risk factors beyond known genetic polymorphisms

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system that predominantly affects young adults. The genetic contributions to this multifactorial disease were underscored by genome wide association studies and independent replication studies. A weighted genetic risk score (wGRS) was recently established using the identified MS risk loci in order to predict MS outcome including clinical and paraclinical features. Here, we present the results on a family with several affected siblings including a monozygotic triplet. The individuals were genotyped for 57 non-MHC risk loci as well as the HLA DRB1*1501 tagging SNP rs3135388 with subsequent calculation of the wGRS. Additionally, SNP array based analyses for aberrant chromosomal regions were performed for all individuals.