RESUMEN

Carcasses of South Polar Skuas (Catharacta maccormicki) and Kelp gulls (Larus dominicanus) were opportunistically collected around of Rothera Research station (67°35'8″S and 68°7'59″W) during the 2016/2017 austral summer. Samples of their tissues (muscle, liver and subcutaneous fat) were analysed for Persistent Organic Pollutants (POPs). Organochlorine pesticides (OCPs) showed the highest concentrations, notably for pp'-DDE and HCB. The Polychlorinated biphenyls (PCBs)-profiles demonstrated a clear dominance of hexa- and hepta-CBs, while concentrations of polybrominated diphenyl ethers (PBDEs) remained low. The concentrations of some POPs (e.g. HCB) were lower than in past studies on similar species, however others were within the previous range (PCBs) or even higher than previous reported values (DDE). Although no major interspecific differences in the absolute concentrations of POPs were detected, their profiles varied, being likely related to feeding and migration patterns of each species. The current study provides important baseline data for future monitoring of POPs in Antarctica.

Asunto(s)

RESUMEN

Heparan sulfate proteoglycans (HSPGs) are essential to respiratory morphogenesis in species as diverse as Drosophila and mice; they play a role in the regulation of numerous HS-binding growth factors, e.g. fibroblast growth factors. Moreover, an HS analogue, heparin, modulates lung growth in vitro. However, it has been difficult to assess the roles of specific HS structures in lung development due to technical barriers to their spatial localisation. Lungs from Sprague-Dawley rats were harvested between E15.5 and E19.5 and immediately fixed in 4 % (w/v) paraformaldehyde (in 0.1 M phosphate-buffered saline (PBS), pH 7.4). Lungs were washed in PBS, cryoprotected with 20% (w/v) sucrose (in PBS), gelatin embedded [7.5% (w/v) gelatin, 15% (w/v) sucrose in PBS], before being covered in Cryo-M-Bed (Bright, Huntingdon, UK) and snap frozen at -40 degrees C. Cryosections were cut at 8 microm and stained with the HSPG core protein specific antibody 3G10 and a HS 'phage display antibody, EW4G2V. 3G10 and EW4G2V immunohistochemistry highlighted the presence of specific HS structures in lungs at all gestational ages examined. 3G10 strongly labelled airway basement membranes and the surrounding mesenchyme and showed weak staining of airway epithelial cells. EW4G2V, however, was far more selective, labelling the airway basement membranes only. Mesenchymal and epithelial cells did not appear to possess the HS epitope recognised by EW4G2V at these gestational ages. Novel 'phage display antibodies allow the spatial distribution of tissue HS to be analysed, and demonstrate in situ that distinct cellular compartments of a tissue possess different HS structures, possibly on the same proteoglycan core protein. These probes offer a new opportunity to determine the role of HS in the pathogenesis of congenital defects such as congenital diaphragmatic hernia (CDH), where lung development is aberrant, and the resulting pulmonary hypoplasia and hypertension are a primary cause of mortality.

Asunto(s)

Asunto(s)

RESUMEN

CD45 is a transmembrane glycoprotein possessing tyrosine phosphatase activity, which is involved in cell signaling. CD45 is expressed on the surface of most leukocytes and can be alternatively spliced by the inclusion or skipping of three variable exons (4, 5, and 6 or A, B, and C) to produce up to eight isoforms. In T cells, the splicing pattern of CD45 isoforms changes after activation; naive cells express high m.w. isoforms of CD45 which predominantly express exon A (CD45RA), whereas activated cells lose expression of exon A to form low m.w. isoforms of CD45 including CD45RO. Little is known about the specific factors controlling the switch in CD45 splicing which occurs on activation. In this study, we examined the influence of the SR family of splicing factors, which, like CD45, are expressed in tissue-specific patterns and have been shown to modulate the alternative splicing of a variety of transcripts. We show that specific SR proteins have antagonistic effects on CD45 splicing, leading either to exon inclusion or skipping. Furthermore, we were able to demonstrate specific changes in the SR protein expression pattern during T cell activation.

Asunto(s)

RESUMEN

The leucocyte common antigen (LCA or CD45) consists of various isoforms generated by alternative splicing of variable exons 4, 5 and 6 (or A, B and C). To follow splicing behaviour in different cell types we developed a human CD45 mini-gene and analysed its expression in transfected cell lines and transgenic mouse tissues. In Cos-1, HeLa and 3T3 cells we found distinct expression patterns which could only be modulated slightly by protein synthesis inhibitors but not by variation in culture conditions like pH, serum concentration and cell density, or by stimulation with phorbol ester (TPA). In all non-lymphoid transgenic tissues the default splicing pattern (CD45R0) was found, while the expression profile in lymphoid cells, where all eight isoforms are present, mimics that of the endogenous mouse LCA gene products. Next, to examine the factors involved in alternative exon use we analysed the expression pattern of members of the family of SR proteins, well known splicing regulators with arginine/serine-rich (R/S) domains. Cell lines expressed variable levels of SRp75, SRp30 and SRp20 and constant amounts of SRp40. Mouse tissues expressed large amounts of SRp75, SRp55 and SRp40, additional expression of SRp30s and SRp20 was restricted to lymphoid tissues. Therefore, SRp30 and SRp20 may contribute to forming the appropriate cellular conditions for alternative use of CD45 exons 4-6 in the haematopoietic compartment.

Asunto(s)

RESUMEN

We have designed a new cell surface expression plasmid to study the structural and membrane-topological requirements for functioning of different isoforms of CD45, a leucocyte specific member of the protein tyrosine phosphatase (PTPase) family of proteins. Use of this vector in cell transfection experiments enabled us to produce multiple CD45 isoforms (ABC, B, Null), with their extracellular segment intact, and the entire membrane spanning and intracellular C-terminal domain replaced by a GPI-membrane-anchor and VSV-tag. Our strategy facilitated the identification and analysis of chimeric proteins and selection of cell clones from low transfection efficiency experiments. We demonstrate here that simple expression of GPI-anchored CD45 isoforms on transfected Cos-1 cells does not facilitate binding to CD22+ lymphoid cells. This suggests that not only the mere presence of CD45 extracellular domains but also their assembly into higher order structures at the cell surface, is necessary in order to engage in the recognition and/or signalling processes normally used by B- and T-cells.

Asunto(s)

RESUMEN

Two MoAbs, independently raised against ovarian carcinoma cells and referred to as OV-TL3 and OV-TL16, display an identical reaction pattern with a membrane-associated protein in both normal and malignant ovarian cells. Also, a similar binding affinity constant and a similar number of binding sites per cell indicate that both MoAbs bind to the same antigen. Competition assays reveal that OV-TL16 is able to compete with OV-TL3 for binding to OVCAR-3 cells. Epitope mapping using a filamentous phage hexapeptide epitope library showed that both MoAbs are able to select identical phages, suggesting that their epitopes are identical or at least overlapping. However, purified polyclonal and monoclonal anti-idiotypic antibodies directed against OV-TL3 failed to recognize the OV-TL16 idiotype, indicating that the structure of the antigen-binding regions of both antibodies is distinct. This was corroborated by molecular cloning and sequencing of the variable heavy (VH) and light (VL) chain immunoglobulin regions of both MoAbs. The VH regions of both antibodies were found to be distinct, whereas the VL regions are almost identical. Computer modelling of the idiotypes suggests that the complementarity determining regions (CDR), with the exception of VHCDR3, have (almost) identical spatial configurations. Our data indicate that, although structurally different in their VH regions, OV-TL3 and OV-TL16 are able to bind to identical epitopic regions on the antigen, because differences in primary structure do not exclude the formation of sufficient and similar spatial structures for the interaction with an epitope.

Asunto(s)

Asunto(s)

RESUMEN

The overall tuberculosis situation in the world in 1990 and its recent trends are reviewed by an analysis of the case notifications to WHO and tuberculosis mortality reports. Estimates of the prevalence of tuberculosis infection and the incidence of tuberculosis disease and deaths predicted in 1990 were carried out with simple epidemiological models. Approximately one third of the world's population is infected with Mycobacterium tuberculosis. In the past decade, an average of 2.5 to 3.2 million cases were notified every year globally, the small decrease in notification rates in recent years being offset by population growth. In 1990, an estimated 8 million people developed tuberculosis worldwide and 2.6 to 2.9 million died. The majority of these cases and deaths occurred in Asia, with an increasing number among HIV-infected individuals, especially in Africa where an upward trend is clearly detectable. Data on tuberculosis cases notified by WHO Member States demonstrate the magnitude of the problem but must be interpreted with caution. Being less than the expected incidence, they reflect the inadequacies of tuberculosis control programmes. This review confirms the very high global magnitude of the tuberculosis problem and calls for an urgent revitalization of tuberculosis control programmes throughout the world.

Asunto(s)