Stem cell factor enhances the survival but not the self-renewal of murine hematopoietic long-term repopulating cells

The effects of stem cell factor (SCF) have been tested on a murine bone marrow subpopulation (RH123lo, Lin-, Ly6A/E+) that is highly enriched for long-term hematopoietic repopulating cells. SCF maintained cells from this population with long-term repopulating ability for up to 10 days in vitro. However, compared with freshly isolated cells, the level of engraftment in vivo by the cultured cells declined during the in vitro culture period, suggesting that SCF alone was unable to stimulate the self-renewal of long-term repopulating cells. By direct visualization of cultures, only small numbers of cells survived and rarely underwent cell division. However, SCF did directly stimulate proliferation of a population (Rh123med/hi,Lin-,Ly6A/E+) enriched for short-term repopulating cells. These data suggest that stem cell differentiation is associated with the development of mitogenic activity by SCF at least in some progenitor cell populations.     

Time dependent EC′, ECE and EC2E mechanisms at microdisc electrodes: simulations using adaptive finite element methods

In this paper we extend the work in [Electrochem. Commun. 5 (2003) 519] to more complex reaction mechanisms. We use the adaptive finite element algorithm described there to simulate the chronoamperometric current for EC^′ reaction mechanisms (catalytic reaction mechanisms) at inlaid and recessed microdisc electrodes and for ECE and EC₂E reaction mechanisms at microdisc electrodes.     

High titer anti-HIV antibody reactivity associated with a paraprotein spike in a homosexual male with AIDS related complex

We observed a human immunodeficiency virus (HIV)-infected homosexual male with AIDS related complex (ARC) who had a serum globulin level of 80 g/L. Serum protein electrophoresis revealed a gamma globulin fraction of 40 g/L, of which 50% (20 g/L) was contained within a paraprotein spike, comprised predominantly of IgG kappa. This patient also had high titer anti-HIV antibodies in his serum, which were Western blot reactive at a final dilution of 1:500,000, and recognized gp120env, p66pol, p55gag, p53pol, p41gag, and p24gag. Because paraproteins in the past have been shown to be directed against specific antigens, we purified this patient's paraprotein using a modified high performance liquid chromatography (HPLC)-hydroxylapatite procedure and tested the purified paraprotein for anti-HIV antibody activity. The purified paraprotein retained anti-HIV antibody activity to a final dilution of 1:100,000, and recognized p66pol, p55gag, p53pol, p41gag, and p24gag. The recognition of both "gag" and "pol" gene products suggested that the purified paraprotein might not be monoclonal in origin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the purified paraprotein contained at least two immunoglobulin light chain species (Mol wt 30 to 33 Kd). Affinity chromatography of the purified paraprotein using a p24- Sepharose 4B matrix separated the "gag" and "pol" antibody activities. Immunoglobulin gene rearrangement analysis of a bone marrow aspirate (which contained 15% plasma cells) failed to reveal a clonal population of immunoglobulin producing cells. We conclude that this patient's paraprotein accounted for most of the anti-HIV activity present in whole serum, and that this paraprotein was not monoclonal in origin.     

Heterogeneity in human neutrophil, macrophage and eosinophil progenitor cells demonstrated by velocity sedimentation separation

Progenitor cells of neutrophils, monocyte-macrophages, and eosinophils in human marrow were enumerated in agar cultures stimulated by placental conditioned medium or white cell underlayers. Fractionation of marrow populations by velocity sedimentation showed that the profiles of neutrophil and macrophage colony-forming cells shifted from a peak of 8-9 mm/hr in 7-day cultures to a peak of 6-7 mm/hr in 14-day cultures. This shift was due to degeneration of some early colonies formed by rapidly sedimenting cells and the delayed formation of colonies by slowly sedimenting cells. Eosinophil colony formation was delayed until the second week of incubation. Further evidence of heterogeneity was the observation that rapidly sedimenting colony forming cells were more responsive to stimulation than more slowly sedimenting cells. In the macrophage and eosinophil populations, cluster-forming cells were partially segregatable form colony-forming cells. The observed heterogeneity was similar to the described previously in the mouse and suggests that separate subpopulations of progenitor cells may exist within each hemopoietic family that could possibly give rise to functionally different progeny.     

Meniscal injuries: detection using MR imaging

Both retrospective and blinded analyses of thin-section, high-resolution magnetic resonance (MR) images of the knee joint, produced using a solenoid surface coil, indicate that MR imaging is an effective technique for evaluating meniscal injuries. Images of 49 patients were evaluated, and the results were correlated with those of subsequent arthroscopy. A grading scale was developed to rate the index of suspicion of a meniscal tear based on the MR images. Overall, approximately 80% of menisci rated grade 4 (definite tear) or 3 (probable tear) were found to have corresponding tears at arthroscopy. In many other patients with a grade 4 or 3 meniscus in whom a corresponding tear was not found arthroscopically, meniscal tears at other sites or other abnormalities were correctly diagnosed using MR. A majority of the false-positive MR images involved the posterior horns of the menisci, the sites of most false-negative arthroscopic diagnoses. The predictive value of a negative MR image was almost 100%. Even in patients with moderate-to-large effusions, the menisci were accurately evaluated. The results imply that MR imaging is useful in the preoperative evaluation of suspected meniscal tears.     

祛白酊质量标准的实验研究

目的：建立祛白酊的质量标准。方法：采用薄层色谱法鉴别其中的补骨脂素,异补骨脂素,栀子苷;导数分光光度法测定其中醋酸氢化可的松的含量。结果;薄层色谱鉴别方法有良好的重现性,专属性;醋酸氢化可的松在11－19ug.ml^-1呈良好的线性关系（r=0.9996)其含量测定平均回收率100．9％,RSD＝0．9％（n=5)。结论：制定的质量标准可以保证祛白酊的质量。     

Biofortification of UK food crops with selenium

Se is an essential element for animals. In man low dietary Se intakes are associated with health disorders including oxidative stress-related conditions, reduced fertility and immune functions and an increased risk of cancers. Although the reference nutrient intakes for adult females and males in the UK are 60 and 75 microg Se/d respectively, dietary Se intakes in the UK have declined from >60 microg Se/d in the 1970s to 35 microg Se/d in the 1990s, with a concomitant decline in human Se status. This decline in Se intake and status has been attributed primarily to the replacement of milling wheat having high levels of grain Se and grown on high-Se soils in North America with UK-sourced wheat having low levels of grain Se and grown on low-Se soils. An immediate solution to low dietary Se intake and status is to enrich UK-grown food crops using Se fertilisers (agronomic biofortification). Such a strategy has been adopted with success in Finland. It may also be possible to enrich food crops in the longer term by selecting or breeding crop varieties with enhanced Se-accumulation characteristics (genetic biofortification). The present paper will review the potential for biofortification of UK food crops with Se.