The marginal zone (MZ) of the mouse spleen contains macrophages that express receptors that trap pathogens, including the scavenger receptor macrophage receptor with a collagenous structure and the C-type lectin specific intracellular adhesion molecule-grabbing nonintegrin receptor 1 (SIGN-R1). We previously reported that expression of SIGN-R1 was decreased in CD19-deficient mice. In this study, we demonstrate that SIGN-R1 is expressed on a subset of macrophage receptor with a collagenous structure (MARCO)+ macrophages. This subset is diminished when MZ B cells are absent due to either genetic developmental defects or following transient migration of B cells out of the MZ. When B cells return to the MZ, there is a delay in recovery of SIGN-R1–expressing macrophages. During this period, capture of Ficoll, which for the macrophages requires SIGN-R1, remains defective not only by the macrophages, but also by the B cells. Thus, MZ B cells regulate expression of molecules on macrophages that are important for trapping Ag, which, in turn, is required for Ag capture by the B cells.

To evaluate the relationship between folate and zinc, and its effect on pregnancy outcome, maternal serum folate and zinc concentrations were determined at 18 and 30 wk gestation in a defined population of 285 pregnant women as part of a large-scale study to identify risk factors for fetal growth retardation (FGR). These results were correlated with birth weight and Apgar scores of newborn infants and with maternal infections during the perinatal period. A weak linear relationship was observed between maternal serum folate and zinc concentrations at 30 wk gestation. Folic acid supplementation had favorable effects on birth weight and Apgar scores of newborns, and reduced prevalence of FGR and maternal infections. No significant correlation was found between serum zinc concentration and birth weight of infants. The concept that folic acid supplementation has an adverse effect on maternal zinc nutriture and pregnancy outcome was not supported.

The objective of the study was to document the existence of localized deficiency of folate in a tissue exposed to cigarette smoke, by analysis of oral and circulatory levels of this vitamin in smokers and non-smokers. Buccal mucosal cells and blood samples were collected from 25 smokers and 34 non-smokers. The Health Habits and History Questionnaire was completed by each subject. A 96-well plate L. casei assay, along with preincubation with a folate-free chick pancreas pteroyl-gamma-glutamyl hydrolase, was used to quantitate total buccal mucosal cell folates. The reproducibility (CV 5 to 7%) and recovery (95 to 106%) of the folate assay were satisfactory. Smokers had significantly lower buccal mucosal cell folate levels than did non-smokers. The mean plasma folate level of smokers although within normal limits, was also significantly lower than that of non-smokers. There were no significant differences in mean dietary folate intake or in alcohol consumption between the 2 groups. The strength of the positive association between smoking and plasma and buccal mucosal cell folate deficiency (by any definition) was moderate to strong and statistically significant. Our results indicate that cigarette smoking may result in a localized folate deficiency in buccal mucosal cells, independent of the plasma folate levels.

Juvenile channel catfish, Ictalurus punctatus, were fed semipurified basal diets containing 0, 0.2, 0.5, 1.0, 4.0 or 10.0 mg/kg of folic acid or 10 g/kg of succinylsulfathiazole in aquaria for 15 wk. Fish fed the sulfonamide showed higher mortality, lower weight gain, lower thrombocyte counts, higher hemocytoblast and neutrophil counts, and lower liver folate concentrations than did control fish (0 folic acid), indicating that significant intestinal bacterial synthesis of folate occurs in channel catfish. There were positive quadratic regressions of weight gain, hematocrit, erythrocyte and leukocyte numbers, and positive linear regressions of plasma and liver folate on dietary folic acid concentrations. Broken-line analysis showed that the dietary requirements for folic acid for optimum weight gain, hematocrit, and erythrocyte and leukocyte numbers were 1.01, 1.17, 1.12 and 1.15 mg/kg, respectively. Plasma and liver concentrations of folate associated with normal growth and hematopoiesis were 22.9 nmol/L and 20.0 nmol/g, respectively. Ratios of leukocytes and lymphocytes to erythrocytes were maximal in fish fed 4.0 mg folic acid/kg, indicating that immunocompetence may increase as the dietary dose exceeds that required for normal growth. Anemia in folate-deficient channel catfish was characterized by pale livers, spleens, gills and kidneys, and by poikilocytosis, anisocytosis, pyknosis, cytoplasmic clearing, increased numbers of hemocytoblasts, macrocytosis, and binucleated erythrocytes or "spectacle" cells.

An evaluation of refrigeration (7 degrees C) to prevent falsely high plasma or serum zinc concentrations owing to elapsed time between blood collection and centrifugation was performed. At room temperature (23 degrees C), both plasma and serum zinc concentrations increased significantly, if blood samples were stored uncentrifuged. Plasma zinc concentrations increased 6.3% at 1 h and 40.7% at 24 h, whereas serum zinc concentrations increased only 0.9% at 1 h and 12.5% at 24 h at room temperature. When blood samples were stored uncentrifuged in the refrigerator for up to 24 h, there were no significant increases in zinc concentrations in either plasma or serum. These findings suggest that plasma or serum separation should be performed immediately after blood drawing to obtain accurate zinc concentrations, and if this is not feasible, the samples should be immediately refrigerated and separation performed within eight hours.

No abstract

CD19 is required for the development of B1 and marginal zone B cells, for Ab responses, and for B cell memory. CD19 immunoprecipitates contain a complex of cytoplasmic proteins, including Lyn, Vav, phospholipase Cγ2 (PLCγ2), Grb2, and the p85 subunit of phosphatidylinositol 3-kinase. Which of these bind directly to CD19 and the strengths of the interactions are unknown. These issues are important in understanding the signaling functions of CD19, which are crucial for normal B cell physiology. Using purified, recombinant proteins, we now show that each of these signaling proteins contains at least one Src homology 2 (SH2) domain that interacts directly with the phosphorylated CD19 cytoplasmic domain. The affinities of binding of the SH2 domains of Vav, p85, and Grb2 to CD19 are each in the nanomolar range by surface plasmon resonance (Biacore) analysis. Binding of Lyn and PLCγ2 do not fit 1:1 modeling. However, analyses of binding data (Lyn) and competition experiments (PLCγ2) suggest that these bind with comparable affinity. Competition experiments demonstrate that SH2 domains whose binding is dependent on the same CD19 tyrosine(s) compete for binding, but these SH2 domains do not impede binding of different SH2 domains to other CD19 tyrosines. We conclude that binding to the CD19 cytoplasmic domain is multimeric, high affinity, and competitive. The high affinity of the interactions also suggests that tyrosines that were nonessential in vivo are nevertheless functional. A preliminary structural model suggests that CD19 forms a signaling complex containing multiple cytoplasmic proteins in close proximity to each other and to the plasma membrane.

Erythorbic acid, an epimer of L-ascorbic acid, is used in the United States as a food additive. Studies were conducted to determine whether the ingestion of erythorbic acid in the diet had any beneficial or adverse effects on the human requirement for vitamin C. Young women were fed diets that contained controlled amounts of erythorbic acid and ascorbic acid. In pharmacokinetic evaluations, erythorbic acid and ascorbic acid were rapidly absorbed with little interaction. Erythorbic acid cleared from the body more rapidly than ascorbic acid. Some subjects received diets deficient in vitamin C for periods < or = 30 d. Increasing intakes of erythorbic acid or prolonged intakes of < or = 1 g erythorbic acid/d did not indicate any interactions with ascorbic acid. Consumption of erythorbic acid resulted in the presence of erythorbic acid in mononuclear leukocytes. Ascorbic acid concentrations in these cells were not affected by the presence of erythorbic acid. Erythorbic acid disappeared quickly from these cells with cessation of erythorbic acid supplements. Prolonged ingestion of erythrobic acid by young women neither antagonized nor spared their vitamin C status.