Isolation and Analysis of Somatic Hybrids Derived from Two Human Diploid Cells

Lesch-Nyhan fibroblasts and normal human leukocytes with different glucose-6-phosphate dehydrogenase genotypes were fused by Sendai virus. Clones were isolated on the basis of their resistance to a medium containing hypoxanthine, amethopterin, and thymidine and ability to proliferate in monolayer culture. These mononuclear cells (1) incorporated [³H]hypoxanthine, (2) expressed the glucose-6-phosphate dehydrogenase heteropolymer, and (3) were polyploid. Therefore, hybrids can originate from the fusion of two diploid human cells. X chromosome inactivation did not occur in these hybrid cells of male origin. The hybrids expressed both parental genomes and exhibited the senescence and contact feeding characteristic of the human skin fibroblast.     

Multilevel Analysis of Women's Empowerment and HIV Prevention: Quantitative Survey Results from a Preliminary Study in Botswana

This preliminary study explored relationships between women's empowerment and HIV prevention on the national and individual level with a focus on Botswana. Among sub-Saharan Africa countries, HIV prevalence was positively correlated with indirect indicators of women's empowerment relating to their education (female enrollment in secondary education and ratio of female to male secondary school enrollment), but not to their economic status (female share of paid employment in industry and services) or political status (women's share of seats in national parliament), while controlling for gross national income, percentage of births attended, and percentage of roads paved. Condom use at last sexual encounter was positively and significantly correlated with both indicators of women's educational empowerment, but was not significantly related to the other two indices. Empowerment at the individual level was explored through a preliminary quantitative survey of 71 sexually active women in Gaborone, Botswana, that was conducted in February 2001. Regression analyses showed that women's negotiating power and economic independence were the factors most strongly related to condom use, and did not show that education was a crucial factor. Economic independence was the factor most strongly related to negotiating power. These results suggest that in Botswana, HIV prevention efforts may need to improve women's negotiating skills and access to income-generating activities.     

Role of extracellular matrix in insulin-like growth factor (IGF) binding protein-2 regulation of IGF-II action in normal human osteoblasts

Insulin-like growth factor binding protein-2 (IGFBP-2) in its native form had little affinity for extracellular matrix (ECM) derived from human or rat osteoblastic cells. However, in the presence of IGFs, IGFBP-2 binding to ECM was markedly enhanced, with IGF-II being more effective than IGF-I. IGF-II-enhanced binding of IGFBP-2 to ECM was specific for IGFBP-2 of the six known IGFBPs. In the presence of IGF-II, IGFBP-2 bound with high affinity to heparin-Sepharose, but not to type I collagen, fibronectin, or laminin. Furthermore, heparin and heparan sulfate, but not chondroitin sulfate, inhibited IGFBP-2/IGF-II binding to ECM. High salt (100 mM NaCl) inhibited, while CaCl(2) enhanced binding of IGFBP-2/IGF-II to ECM. In the presence of ECM, IGFBP-2/IGF-II was as effective as IGF-II alone in stimulating [3H]thymidine and [3H]proline incorporation and in inhibiting apoptosis in cultured human osteoblasts. On the other hand, IGFBP-2 was a potent inhibitor of IGF-II action in human breast and ovarian carcinoma cells. There was no difference between soluble and ECM-associated IGFBP-2 in affinity for IGF-I and IGF-II. These data suggest a unique mechanism for targeting an anabolic IGFBP-2/IGF-II complex in bone.     

Blood leukocytes recapitulate diabetogenic peptide–MHC-II complexes displayed in the pancreatic islets

Assessing the self-peptides presented by susceptible major histocompatibility complex (MHC) molecules is crucial for evaluating the pathogenesis and therapeutics of tissue-specific autoimmune diseases. However, direct examination of such MHC-bound peptides displayed in the target organ remains largely impractical. Here, we demonstrate that the blood leukocytes from the nonobese diabetic (NOD) mice presented peptide epitopes to autoreactive CD4 T cells. These peptides were bound to the autoimmune class II MHC molecule (MHC-II) I-A^g7 and originated from insulin B-chain and C-peptide. The presentation required a glucose challenge, which stimulated the release of the insulin peptides from the pancreatic islets. The circulating leukocytes, especially the B cells, promptly captured and presented these peptides. Mass spectrometry analysis of the leukocyte MHC-II peptidome revealed a series of β cell–derived peptides, with identical sequences to those previously identified in the islet MHC-II peptidome. Thus, the blood leukocyte peptidome echoes that found in islets and serves to identify immunogenic peptides in an otherwise inaccessible tissue.