Long-term maintenance of hematopoietic stem cells does not require contact with embryo-derived stromal cells in cocultures

We recently established that two midgestation-derived stromal clones--UG26-1B6, urogenital ridge-derived, and EL08-1D2, embryonic liver-derived--support the maintenance of murine adult bone marrow and human cord blood hematopoietic repopulating stem cells (HSCs). In this study, we investigate whether direct HSC-stroma contact is required for this stem cell maintenance. Adult bone marrow ckit+ Ly-6C- side population (K6-SP) cells and stromal cells were cocultured under contact or noncontact conditions. These experiments showed that HSCs were maintained for at least 4 weeks in culture and that direct contact between HSCs and stromal cells was not required. To find out which factors might be involved in HSC maintenance, we compared the gene expression profile of EL08-1D2 and UG26-1B6 with four HSC-nonsupportive clones. We found that EL08-1D2 and UG26-1B6 both expressed 21 genes at a higher level, including the putative secreted factors fibroblast growth factor-7, insulin-like growth factor-binding proteins 3 and 4, pleiotrophin, pentaxin-related, and thrombospondin 2, whereas 11 genes, including GPX-3 and HSP27, were expressed at a lower level. In summary, we show for the first time long-term maintenance of adult bone marrow HSCs in stroma noncontact cultures and identify some secreted molecules that may be involved in this support.     

Location of immunodominant antigenic determinants on fragments of the tick-borne encephalitis virus glycoprotein: Evidence for two different mechanisms by which antibodies mediate neutralization and hemagglutination inhibition

A model showing the topological distribution, functions, and serological specifities of eight distinct, monoclonal antibody-defined epitopes on the tick-borne encephalitis (TBE) virus glycoprotein has been presented in a previous publication [Heinz et al., 1983]. Virology 126, 525–537.) In the present report the influence of conformational change, chemical modification, and fragmentation on the antigenic reactivity of each epitope has been analyzed by the use of blocking enzyme immunoassays and “Western blotting.” One of the two major antigenic domains (A), composed of three different epitopes, completely lost its antigenicity upon incubation at pH 5.0 or by treatment with guanidine-HCl/urea, SDS, reduction and carboxymethylation, as well as by proteolytic (trypsin, α-chymotrypsin, thermolysin) and chemical (CNBr) fragmentation. The second major antigenic domain (B), however, defined by four distinct monoclonal antibodies, three of which are hemagglutination (HA)-inhibiting, neutralizing, and protective, was shown to be resistant to low pH, guanidine-HCl/urea treatment, and proteolytic cleavage of the native protein. Also, polyclonal immune sera from mice and rabbits contained antibody populations reactive with antigenic determinants which are resistant and others which are sensitive to conformational change and fragmentation. Glycoprotein fragments with molecular weights of about 9000, generated by proteolysis of the native protein, were immunoreactive with neutralizing and protective monoclonal antibodies (defining domain B) as well as with a polyclonal mouse immune serum. Thus, these fragments appear to contain antigenic determinants which are immunodominant on the native protein and play an important role in the induction of a protective immune response against TBE virus. In addition, these results show that antibody binding to antigenic domains which are topologically and structurally completely unrelated may result in neutralization and/or HA inhibition. As the presence of two receptor-binding sites is unlikely, different effector mechanisms may account for the effects of these antibodies. The antigenic reactivity of domain A is sensitive to the same treatments which also inactivate HA activity of TBE virus, whereas domain B is resistant. These treatments include a change of domain A induced by incubation at slightly acidic pH which also results in inactivation of virus infectivity. Antibodies to domain A therefore presumably block viral activities by direct binding at or near the putative receptor-binding site whereas antibodies to domain B may cause loss of biological activities by inducing a conformational change of the receptor-binding site.     

Association analysis of a polymorphism in the G‐protein stimulatory α subunit in patients with major depression*

Growing evidence suggests that G‐proteins may be involved in pathogenesis and treatment of affective disorders. Several studies have reported altered levels and/or activities of stimulatory G‐proteins in depression. The aim of this study was to investigate whether a polymorphism in the stimulatory α subunit of G‐proteins (T/C point mutation in exon 5; ATT → ATC at codon 131) is associated with major depression or response to antidepressant treatment. Therefore, we performed a case‐control association study with 212 depressive patients and 137 healthy, unrelated controls. There was no evidence for an association between the investigated polymorphism in the Gα_s gene and major depression, as well as to treatment response. The results of our study are in concordance with recently published findings which do not support the hypothesis that the gene for the stimulatory α subunit of G‐proteins is a major susceptibility factor in the pathophysiology of major depression. © 2002 Wiley‐Liss, Inc.     

Quantitative aspects of enhanced liver tumour formation in CF-1 mice by dieldrin

The dose-response characteristics of dieldrin-mediated enhancementof liver tumour formation in CF-1 mice were analysed, usingexisting tumour data from chronic feeding studies at six levelsof continuous exposure, involving a total of > 1500 animals.The dose-response relationship can be expressed as: D_x x T_x= D₀ x T₀ = constant, where T₀ = the median liver tumour inductionperiod in control CF-1 mice, T_x = the median liver tumour inductionperiod in dieldrin-treated mice at a dose level D_x, D₀ = thebackground dose equivalent for the induction of ‘spontaneous’liver tumours, D_x = the sum of background dose (D₀) and actualdieldrin dose (_x). The relationship, which is a Druckrey equation(D x Tⁿ = constant) where n = 1, indicates that: (i) the velocityof liver tumour development is proportional to the daily doselevel (D_x), (ii) the total tumourigenic dose is constant acrossall doses, (iii) the effects of dieldrin on the neo-plasticprocess in mouse liver are essentially irreversible and cumulative,and (iv) there is no evidence for a threshold level. However,when _x «D₀, the actual contribution of dieldrin to tumourformation is expected to be negligible.     

Colored neon flanks and line gap enhancement

When a colored line connects two black (or differently colored) lines across a gap, colored neon flanks are seen on either side of it. These flanks extend over gap sizes of 50 min arc foveally and are not explained by Bezold-type assimilation. They may be elicited by black lines as short as 6 min arc adjoining the colored line at each end. To maximize these flanks, the black and colored lines must appear linearly continuous. Nonaligned junctions weaken the effect and an angular tilt of more than 40 dog destroys it. In this and other respects, (local) neon flanks are similar to van Tuijl's (global) neon color spreading (1975). Both phenomena have analogs in brightness perception. We propose that neon spreading is a lateral extension of neon flanks across the empty space between them, and discuss similarities of these effects with other brightness illusions (Schumann, Prandtl, Ehrenstein). For this group of illusions the term "line gap enhancement" is introduced to imply perceptual enhancement of changes in brightness and/or color along lines. Correspondences between the psychophysical properties and structural prerequisites for line gap enhancement on one hand and neuronal response properties of end-zone inhibited (hypercomplex) cortical cells on the other are discussed.     

Determinants and Inequities in Sexual and Reproductive Health (SRH) Care Access Among Im/Migrant Women in Canada: Findings of a Comprehensive Review (2008–2018)

Given growing concerns of im/migrant women’s access to sexual and reproductive health (SRH) services, we aimed to (1) describe inequities and determinants of their engagement with SRH services in Canada; and (2) understand their lived experiences of barriers and facilitators to healthcare. Using a comprehensive review methodology, we searched the quantitative and qualitative peer-reviewed literature of im/migrant women’s access to SRH care in Canada from 2008 to 2018. Of 782 studies, 38 met inclusion criteria. Ontario (n?=?18), British Columbia (n?=?6), and Alberta (n?=?6) were primary settings represented. Studies focused primarily on maternity care (n?=?20) and sexual health screenings (n?=?12). Determinants included health system navigation and service information; experiences with health personnel; culturally safe and language-specific care; social isolation and support; immigration-specific factors; discrimination and racialization; and gender and power relations. There is a need for research that compares experiences across diverse groups of racialized im/migrants and a broader range of SRH services to inform responsive, equity-focused programs and policies.

     

Time-resolved fluorometric assay for the detection of endostatin in chromatographically separated extracts of natural peptides

We present a heterogeneous non-competitive immunological detection assay for peptide and protein antigens from crude extracts of biological sources. This time-resolved fluoroimmunoassay (TR-FIA) has been designed in a solid-phase mode using 96-well microtiter plates. Using the rare-earth metal europium as a fluorescent marker, a highly sensitive, selective and efficient procedure was developed. This technique prevents from interferences of intrinsic protein fluorescence which is highly important for antigen measurement in complex matrices. The TR-FIA has been applied for the detection of circulating forms of the potential anti-tumor agent endostatin, a C-terminal fragment of collagen XVIII, and its close homolog collagen XV (restin) from hemofiltrate. Endostatin was detected with a limit of detection of 3 ng (150 fmol/well) and a broad dynamic range from 10-1000 ng/well.