Cellular transformation, tyrosine kinase oncogenes, and the cellular adhesion plaque

The study of adhesion plaques in normal and transformed cells provides a series of phenotypic markers by which the process of transformation can be followed. Several proteins which are concentrated in adhesion plaques have now been identified; a few of these can act as targets for tyrosine kinase. In an attempt to characterize the relationship between tyrosine phosphorylation and cell transformation, the reactions of three such proteins – vinculin, talin and integrin – with a range of tyrosine kinase oncogene products have been studied in detail.     

Interaction of tumour promoters with epithelial cells in culture : An immunofluorescence study

12-O-tetradecanoyl phorbol-13-acetate (TPA) has a profound and rapid influence on the cytoskeleton of Madin-Darby Canine Kidney (MDCK) cells. Within 10 min, TPA induces a rapid change in morphology, from a flat, cuboidal state to a rounded or elongated morphology in which the cell membranes become convoluted. Concomitant with this morphological change is a rapid dissolution of stress fibres and a redistribution of F-actin from microfilament bundles to a membrane or sub-membranous location. The rearrangement of actin is paralleled by a rearrangement of alpha-actinin and a reduction in the number of vinculin-containing adhesion plaques. Unusual F-actin configurations are often found emanating from a perinuclear location, usually containing alpha-actinin and terminating in a vinculin-containing adhesion plaque. The cytoskeletal rearrangements occur in the presence of inhibitors of protein synthesis or oxidative phosphorylation, but do not occur if glycolysis is also inhibited. The rearrangements are partly abrogated by the presence of cytochalasin B (CB). Despite these dramatic changes in microfilaments the polymerization state of actin remained unaltered after TPA treatment. Furthermore, although changes in the movement of membrane lipids have been reported, no obvious differences in the ability of glycoproteins to redistribute in the plane of the membrane were found as judged by FITC-concanavalin A (conA) induced patching. The rapidity of the morphological response of MDCK cells to TPA indicates that the cytoskeleton is one of the primary targets of TPA, but that tumour promoters differ from RNA tumour viruses in their effect on the state of actin polymerization.     

The gas–liquid chromatography of carboxylic acid esters of the urinary 11-deoxy-17-oxo steroids: Determination as n-butyrates

1. The gas-liquid-chromatographic separations of the acetate, propionate, n-butyrate, isobutyrate and n-valerate esters of androsterone, aetiocholanolone and dehydroepiandrosterone were studied on a 1% neopentyl glycol sebacate column. The n-butyrate, isobutyrate and n-valerate esters were well resolved. 2. The three steroids derived from hydrolysed urinary 17-oxo steroid conjugate extracts were analysed by gas-liquid chromatography after conversion into their n-butyrate esters. The results were compared with independent determinations involving chromatography on alumina.     

Investigating genetic discrimination in Australia: opportunities and challenges in the early stages

Genetic discrimination, defined as the differential treatment of individuals or their relatives on the basis of actual or presumed genetic differences, is an emerging issue of interest in academic, clinical, social and legal contexts. While its potential significance has been discussed widely, verified empirical data are scarce. Genetic discrimination is a complex phenomenon to describe and investigate, as evidenced by the recent Australian Law Reform Commission inquiry in Australia. The authors research project, which commenced in 2002, aims to document the multiple perspectives and experiences regarding genetic discrimination in Australia and inform future policy development and law reform. Data are being collected from consumers, employers, insurers and the legal system. Attempted verification of alleged accounts of genetic discrimination will be a novel feature of the research. This paper overviews the early stages of the research, including conceptual challenges and their methodological implications.     

Risk,parental autonomy and the epistemic divide: preimplantation genetic diagnosis in the Australian print news media, 1990–2007

Preimplantation genetic diagnosis (PGD) is a reproductive/genetic technology which has become the subject of public and scholarly debate because it involves the evaluation and consequent selection (and implantation) or destruction of human embryos. This research investigates the way PGD is constituted in the Australian print news media. Foucauldian discourse analysis reveals that proponents draw on their direct knowledge and experience of PGD to support their claims. There is an epistemic divide between consumers and others claiming direct knowledge, and critics and others drawing on indirect or abstract understandings of PGD. This divide characterizes the discourses present in the data and is directly linked to changes in these over the period under analysis.     

Eotaxin selectively binds heparin. An interaction that protects eotaxin from proteolysis and potentiates chemotactic activity in vivo

An important feature of chemokines is their ability to bind to the glycosaminoglycan (GAG) side chains of proteoglycans, predominately heparin and heparan sulfate. To date, all chemokines tested bind to immobilized heparin in vitro, as well as cell surface heparan sulfate in vitro and in vivo. These interactions play an important role in modulating the action of chemokines by facilitating the formation of stable chemokine gradients within the vascular endothelium and directing leukocyte migration, by protecting chemokines from proteolysis, by inducing chemokine oligomerization, and by facilitating transcytosis. Despite the importance of eotaxin in eosinophil differentiation and recruitment being well established, little is known about the interaction between eotaxin and GAGs and the functional consequences of such an interaction. Here we report that eotaxin binds selectively to immobilized heparin with high affinity (K(d) = 1.23 x 10(-8) M), but not to heparan sulfate or a range of other GAGs. The interaction of eotaxin with heparin does not promote eotaxin oligomerization but protects eotaxin from proteolysis directly by plasmin and indirectly by cathepsin G and elastase. In vivo, co-administration of eotaxin and heparin is able to significantly enhance eotaxin-mediated eosinophil recruitment in a mouse air-pouch model. Furthermore, when heparin is co-administered with eotaxin at a concentration that does not normally result in eosinophil infiltration, eosinophil recruitment occurs. In contrast, heparin does not enhance eotaxin-mediated eosinophil chemotaxis in vitro, suggesting protease protection or haptotactic gradient formation as the mechanism by which heparin enhances eotaxin action in vivo. These results suggest a role for mast cell-derived heparin in the recruitment of eosinophils, reinforcing Th2 polarization of inflammatory responses.     

Alterations in habituation of the tail flip response in epigean and troglobitic crayfish

We demonstrate that the probability of the crayfish, P. clarkii, to tail flip in response to a touch on the dorsal tail fan is dependent on both the size and the behavioral state of the animal. Alterations in the animal's internal physical state, such as when the animal autotomizes its chelipeds, will cause larger-sized animals to tail flip; if they were not autotomized, then no tail flip response would occur. Altering the external environment by removal of water causes small crayfish, which normally habituate slowly, to rapidly habituate. Observation of large adult crayfish in a species, O. australis packardi, one that evolved to live in total cave darkness, revealed that they are more likely to tail flip than are the sighted, adult P. clarkii. Results indicate that the behavioral state of the crayfish can result in rapid and long-term alterations in the tail flip response and in habituation rates to repetitive stimuli. This ability to show plasticity in gain setting may be regulated by neuromodulators and can occur in large adults of the sighted crayfish. Differences between the two species indicate that size may not be the sole contributing factor to account for tail flip behaviors. J. Exp. Zool. 290:163-176, 2001.     

Ultraviolet properties of Australian mammal urine

The exploitation of predator signals by potential prey is well researched, but relatively little is known about how predators exploit chemical cues (either deliberate signals or waste by-products) produced by their prey. In Finland, the urine of some small rodents (Microtus spp. and Clethrionomys spp.) is reflective in the ultraviolet range of wavelengths, and diurnal raptors with ultraviolet vision use these urine marks to track their rodent prey. This study examines the potential for such a phenomenon in Australian systems by studying the ultraviolet properties of urine from 13 native and introduced mammal species that are variously preyed upon by raptors. Urine from all 13 species displayed various levels of ultraviolet absorbance in their urine and fluorescence in the ultraviolet range. However, no signs of ultraviolet hyper-reflectance were detected, suggesting that the urine of European voles have unique ultraviolet properties. Ultraviolet-sensitive predators in Australia may be able to distinguish between species based on variation in the ultraviolet absorbance of their urine, but ultraviolet properties did not differ between prey and non-prey species, nor marsupial and placental groups. Moreover, because many natural surfaces are ultraviolet absorbing, it is unlikely that raptors could rely upon the ultraviolet properties of urine to target key prey species.