Chemical and immunological characterisation of glycophospholipid and phospho-oligosaccharide from mycobacteria

Following ligand binding by a wide variety of cytokines and growth factors, a glycosylphosphatidyl inositol phospholipase D (GPI-PLD) cleaves free membrane glycosylphosphatidyl inositol (GPI) to liberate water-soluble inositol phosphoglycan (IPG) second messengers. IPG are released outside cells and mediate many of the immediate metabolic effects of insulin. Many other cytokines and growth factors use IPG to signal, including IL-2, NGF, IGF-1 and ACTH. The composite structure of IPG molecules is known and they consist of hexose, hexosamine, inositol, phosphate and divalent cations. The development of clinical tuberculosis in a susceptible host appears to involve a highly complex interaction between the infecting organism and the host immune system, with much or indeed all the tissue damage characteristic of the disease being immune mediated. Many Mycobacterium tuberculosis colonised individuals do not develop active disease, and there are demonstrable immunological differences between the asymptomatic immune carrier state and the state of active disease in both humans and animal models. Mycobacterium tuberculosis contains PLD activity and contains phosphatidyl inositol linked glycans that could theoretically give rise to IPG like structures. Such glycolipids include lipoarabinomannan (LAM), lipomannan (LM) and phosphoinositol mannoside (PIM). Previously it has been shown in our laboratory and that of our collaborators that two strains of the pathogen M. tuberculosis and a non-pathogen, M. vaccae, contain IPG- like biological activity. This mycobacteria derived material has been provisionally named phospho-oligosaccharide (POS). The aim of this study was to examine the hypothesis that mycobacteria may contain a homologous system to the mammalian GPI/IPG signalling mechanism. Using an established protocol for the purification of mammalian GPI a glycophospholipid (GPL) was isolated from M. tuberculosis and M. vaccae that showed similar characteristics to mammalian GPI. This GPL was a substrate for (glycosyl) phosphatidylinositol phospholipase C (GPI-PLC), contained phosphate, sugar residues and did not contain amino groups. GPL was biologically active in a cell free pyruvate dehydrogenase (PDH) phosphatase activation assay and induced inflammatory mediator release from monocyte/macrophage cells. GPL is distinct from LAM, LM and PIM because it was sensitive to GPI-PLC and incorporated radioactive galactose. POS fractions were isolated from mycobacteria that were biologically active in PDH phosphatase, lipogenesis, cell proliferation and nitric oxide production assays, contained carbohydrate, phosphate (except for one fraction) and amino groups. On the basis of amino group analysis, which revealed that POS contained amino groups and GPL did not, POS is not a cleavage product of mycobacterial GPL, as is the case with GPI and IPG in mammalian cells. However, there were interesting similarities in biological activity between GPL and POS. Serological studies were undertaken to characterise mycobacterial POS both structurally and immunologically. Although POS exhibit biological activity in systems where mammalian IPG are also active, there are clearly structural differences between POS and IPG because some antibodies that bind IPG do not bind POS. POS are immunogenic: administration of complete Freund's adjuvant induced an anti-POS antibody response in rabbits (but not in mice) and sera from tuberculosis patients contained significantly higher levels of anti-POS antibody than healthy controls. POS is proliferogenic for human peripheral blood mononuclear cells in vitro, in particular, POS activates human B cells in vitro causing a greater increase in B cell CD25 expression than T cell CD25 expression. Thus the material described has some interesting immunological properties, although its role in the pathogenesis of tuberculosis remains to be determined. The growth factors IL-2 and insulin have both been shown to signal using IPG cleaved from GPI, it is therefore intriguing that mycobacteria appear to contain a homologue of an immunologically relevant mammalian second messenger

The effects of ultraviolet radiation, highway contamination, and synergism of the two on spotted salamander embryos

In this study, I examined the effects of ultraviolet radiation, highway contamination and a synergism of both factors on the spotted salamander, Ambystoma maculatum embryos in field and laboratory experiments. There are numerous reports of amphibian population declines from around the world. There are several possible factors causing the decline, including, habitat loss, environmental pollution, disease, and ultraviolet B radiation (UVB, 290--320 nm). Results of studies conducted to date seem to indicate that the impacts of these factors vary greatly among species and across geography. Amphibians have unique characteristics and life histories that make them more vulnerable to changes in their environment then many other organisms. In particular, A. maculatum breeds in temporary wetlands in which embryos and larvae must metamorphose before the wetland dries. Factors that prolong development may reach increase mortality due to pool desiccation. Therefore, habitat degradation may be more harmful for amphibians that breed in this temporary environment. I conducted field and laboratory experiments to test the effects of roadside runoff on A. maculatum embryos. Results indicate that embryo survival is very low roadside vernal pools contaminated with highway runoff. I also tested the effects of UVB on embryos using three radiation treatments. There was no statistically significant effect of UVB radiation on embryo size at hatching, melanin concentration, or DNA damage in field experiments. Vernal pool water was so darkly colored with dissolved organic material that UVB was quickly attenuated, therefore UVB exposure was very low for the embryos. I also tested the effects of UVB radiation, highway contamination, and the impact of a synergism between these factors in the laboratory. The impact of highway contamination was much clearer than that of UVB radiation. Highway contamination significantly affected membrane diameter, embryo length at hatching and DNA damage. UVB significantly affected embryo wet mass at hatching. Results suggested that the two factors may act synergistically to negatively affect embryos but the trends were not significant

Roe v. Wade: The Religious Response

No abstrac

Forest Schools and environmental attitudes: a case study of children aged 8–11 years

There is growing evidence that children in the UK are suffering from a lack of engagement with nature and the outdoor environment. This paper investigates the attitudes of children towards the natural environment and focuses on Forest School programmes as a mechanism to promote a “pro-environmental” attitude. The study identified that there was a statistically significant difference in environmental attitude between groups of children that had participated in a Forest Schools programme and those that had not participated, with children who have taken part in Forest Schools demonstrating a more pro-environmental attitude. Whilst it is recognised that Forest Schools may not be the only factor influencing these attitudes, this is still an important finding that adds to the overall benefits of participation in Forest Schools programmes

Intelligent search for distributed information sources using heterogeneous neural networks

As the number and diversity of distributed information sources on the Internet exponentially increase, various search services are developed to help the users to locate relevant information. But they still exist some drawbacks such as the difficulty of mathematically modeling retrieval process, the lack of adaptivity and the indiscrimination of search. This paper shows how heteroge-neous neural networks can be used in the design of an intelligent distributed in-formation retrieval (DIR) system. In particular, three typical neural network models - Kohoren's SOFM Network, Hopfield Network, and Feed Forward Network with Back Propagation algorithm are introduced to overcome the above drawbacks in current research of DIR by using their unique properties. This preliminary investigation suggests that Neural Networks are useful tools for intelligent search for distributed information sources

Loggerheadlines 2019

This issue of Loggerheadlines features articles on citizen stewardship, tagging, nesting news, regional news, research and other announcements