Asbestos disease in Australia: looking forward and looking back.

This article provides an overview and analysis of recent developments in policy and practice in relation to asbestos disease in Australia. It complements three other concurrent publications in this issue representing important contributions of people and organizations toward addressing the health and social impacts of Australia's asbestos disease epidemic. The campaign to "Make James Hardie Pay" as well as the efforts of workers and advocates are profiled in this article as well as in this issue's Documents and Voices sections. Discussion of recent developments in asbestos-related disease research and mesothelioma surveillance is followed by articulation of the comprehensive public and social health response that is needed to fully engage and address the asbestos disease legacy and to apply lessons learned to help revive the currently waning societal commitment to occupational health and safety in Australia and elsewhere.

The retinoid anticancer signal: mechanisms of target gene regulation.

Retinoids induce growth arrest, differentiation, and cell death in many cancer cell types. One factor determining the sensitivity or resistance to the retinoid anticancer signal is the transcriptional response of retinoid-regulated target genes in cancer cells. We used cDNA microarray to identify 31 retinoid-regulated target genes shared by two retinoid-sensitive neuroblastoma cell lines, and then sought to determine the relevance of the target gene responses to the retinoid anticancer signal. The pattern of retinoid responsiveness for six of 13 target genes (RARbeta2, CYP26A1, CRBP1, RGS16, DUSP6, EGR1) correlated with phenotypic retinoid sensitivity, across a panel of retinoid-sensitive or -resistant lung and breast cancer cell lines. Retinoid treatment of MYCN transgenic mice bearing neuroblastoma altered the expression of five of nine target genes examined (RARbeta2, CYP26A1, CRBP1, DUSP6, PLAT) in neuroblastoma tumour tissue in vivo. In retinoid-sensitive neuroblastoma, lung and breast cancer cell lines, direct inhibition of retinoid-induced RARbeta2 expression blocked induction of only one of eight retinoid target genes (CYP26A1). DNA demethylation, histone acetylation, and exogenous overexpression of RARbeta2 partially restored retinoid-responsive CYP26A1 expression in RA-resistant MDA-MB-231 breast, but not SK-MES-1 lung, cancer cells. Combined, rather than individual, inhibition of DUSP6 and RGS16 was required to block retinoid-induced growth inhibition in neuroblastoma cells, through phosphorylation of extracellular-signal-regulated kinase. In conclusion, sensitivity to the retinoid anticancer signal is determined in part by the transcriptional response of key retinoid-regulated target genes, such as RARbeta2, DUSP6, and RGS16.

A specific GFP expression assay, penetrance estimate, and histological assessment for a putative splice site mutation in BRCA1.

Genetic testing for cancer predisposing mutations in BRCA1 and BRCA2 has been of benefit to many individuals from breast and ovarian cancer-prone kindreds. However, a function has not been assigned to many of the domains that make up these complex proteins and hence, the significance of many sequence variants, including missense mutations, splice-site mutations, and in-frame deletions/insertions, remains unclear. We identified a putative splice site mutation (IVS6-2delA) in BRCA1 in a family attending a Familial Cancer Centre that had a significant history of both breast and ovarian cancer. This sequence variant was not novel but the exact effect on mRNA splicing and hence the biological impact of this sequence variation was unclear and therefore the finding was unable to be used in genetic counseling of the family. Via the construction of novel GFP-based expression fusion constructs, we demonstrated that this sequence variation prevented normal splicing of the BRCA1 transcript. By combining these data with an assessment of the histopathological features of the breast carcinomas in this family and mutation penetrance estimate we were able to conclude that this BRCA1 variant conveyed an increased risk of breast cancer.

Chromosomal mapping of five highly conserved murine homologues of the Drosophila RING finger gene seven-in-absentia.

Seven-in-absentia (sina) is epistatic to all other known genes in the sevenless-ras signaling pathway, which mediates R7 photoreceptor formation in the Drosophila eye. The murine genome contains several closely related sina homologues (Siah1A-D, Siah2) that are also likely to participate in ras signaling. As part of a genetic and biochemical analysis of the mammalian Siah genes, we have used gene-specific probes to map the chromosomal positions of each family member. Here we report their chromosomal positions in relation to a number of known mouse mutations and also describe an analysis of the human Siah genes. By comparing the complexity of the Siah genes in these two mammalian species we have gained further insight into which members of this murine multigene family are likely to be functional.

A combined genetic and biochemical approach to mammalian signal transduction.

The last five years have seen a rapid increase in interest and understanding of signal transduction pathways. While the description of such pathways has become more detailed and complex, a number of consistent findings have emerged. Modular domains, such as SH2 and SH3 domains, are present on a wide variety of proteins and mediate specific protein-protein interactions. By defining the interaction mediated by such domains, a 'language' of interaction between proteins in signalling pathways is emerging. As more signalling proteins are identified it has become apparent that most oncogenes and tumour suppressor genes are components of major signalling pathways. Therefore, studies on the basic biology of signal transduction are having a direct impact on our understanding of cell transformation. With the characterisation of signalling pathways in a range of organisms, it has also become obvious that signalling pathways are ancient and have been highly conserved over the last billion years of evolution. A practical result of this finding has been the ability to exploit results obtained in genetically tractable invertebrate species such as C. elegans and Drosophila melanogaster to investigate signal transduction in mammals. This is an approach we have emphasized in our investigation of signal transduction by tyrosine kinase receptors in human and mouse cells. Results obtained in these studies with the Sos and Siah proteins are reviewed.

The use of in vitro fertilization to detect reductions in the fertility of male rats exposed to 1,3-dinitrobenzene.

1,3-Dinitrobenzene (DNB) is an intermediate chemical in the manufacture of dyes and explosives and its toxic effects include specific damage to the Sertoli cells of the testis. This investigation determined the effect a toxic insult to Sertoli cells had on the functional capacity of developing germ cells as assessed by in vitro fertilization. Male rats were given a single, oral dose of 5, 15, or 25 mg DNB/kg. At selected times after treatment, spermatozoa recovered from the cauda epididymidis were tested for fertilizing capacity using in vitro fertilization techniques and the testicular response to DNB was determined by histological examination. Treatment with 15 and 25 mg DNB/kg resulted in substantial exfoliation of germ cells between 0.5 and 3.5 weeks after exposure and again after 4.5 weeks; seminiferous tubules which were not depleted showed signs of disrupted spermatogenesis. Reduced sperm fertilizing capacity in vitro was observed from 1.5 to 5 weeks and between 7.5 and 8.5 weeks after treatment with 15 and 25 mg DNB/kg. There were slight, but significant, reductions in fertility at 3, 5.5, 7.5, and 8.5 weeks after dosing with 5 mg DNB/kg. These data suggested that DNB did not affect all Sertoli cells equally, but acted in a stage-specific manner. Stages III, IV, XII, and XIV were most vulnerable to the toxicant. Germ cells associated with an affected Sertoli cell were usually sloughed off, resulting in lowered fertility at the time when these cells should have reached maturity in the epididymis. The extent of the testicular lesions and the loss of fertility were dose dependent. This investigation confirmed the use of in vitro fertilization to detect the effects of testicular toxicants.

The use of rat in vitro fertilization to detect reductions in the fertility of spermatozoa from males exposed to ethylene glycol monomethyl ether.

An in vitro fertilization (IVF) assay sensitive enough to detect changes in the fertilizing capacity of spermatozoa would be a useful tool with which to investigate the action of testicular toxicants. A known testicular toxicant, ethylene glycol monomethyl ether (EGME), was used to induce specific lesions in the germinal epithelium so that the ability of a rat IVF system to detect changes in fertility could be tested. Male rats were given single, oral doses of 50, 100, and 200 mg EGME/kg. Spermatozoa were recovered from the cauda epididymides of these males at intervals after treatment; their fertility was assessed using IVF, and the testes were processed for histologic examination. The fertility of the control males was consistently greater than 65%. Spermatozoa from males treated with EGME had reduced fertility at specific times after dosing. Thus, after 50 mg EGME/kg there was reduced fertility at 5 weeks; after 100 mg EGME/kg there was reduced fertility at 3.5, 4.5, 5, 6, and 6.5 weeks, and after 200 mg EGME/kg there was reduced fertility at 2 and 3 weeks, between 4.5 and 6 weeks, and at 7 weeks. This corresponded to damage to the elongated spermatids (2, 3, and 3.5 weeks), pachytene spermatocytes (4.5 to 6 weeks), and leptotene and preleptotene spermatocytes (7 weeks). This accords well with the data from serial breeding trials and reports of histologic damage after exposure to EGME. Therefore, using IVF it was possible to detect EGME-induced changes in fertilizing capacity which correlated closely with observations of testicular damage. It was also possible to demonstrate a clear dose response to EGME.

Differential phase quadrature surface profiling interferometer.

This paper describes an optical surface profiling system based on phase quadrature differential interferometry. The optical path difference between two adjacent optical probe beams is measured. Interference phase calculation and sample scanning is controlled by a PC computer. Height sensitivity is of the order of 1 nm and lateral resolution is ~10 microm. Results are given which demonstrate the reproducibility and stability of the system.