Occupational cancer: experience in Ontario.

This paper reviews the experience of the Workmen''s Compensation Board of Ontario in identifying cases of cancer that could be attributed to occupational hazards. Worker''s claims for compensation are allowed if there is reasonable medical evidence that their cancer was caused by exposure to risk factors associated with their occupation. Details of the types of cancer associated with specific carcinogens or fields of employment are discussed. About 50% of the cases were related to exposure in particular industrial operations that functioned for relatively brief periods. The number of deaths from cancer identified as being caused by occupational factors is compared with the total for cancer from all causes in Ontario during the period 1971 through 1975. Although all workers eligible for compensation may not have been identified, the data suggest that less than 1% of cancer is presently caused by occupational factors.     

Assessing nursery habitat quality for native smelts (Osmeridae) in the low-salinity zone of the San Francisco estuary

Habitat quality was assessed for two native osmerids, delta smelt Hypomesus transpacificus and longfin smelt Spirinchus thaleichthys , between two distinct nursery areas located in the low-salinity zone of the San Francisco estuary. The relationship between several variables was investigated including fish density, fish size, feeding success and the general condition of larvae as well as juveniles for both species. The nursery habitats that were evaluated included the North and South Channels of Suisun Bay. The results showed higher densities of zooplankton and decreased water velocities for the North Channel when compared to the South Channel. The dominant prey item was calanoid copepod Pseudodiaptomus forbesi for both species although longfin smelt residing in the North Channel also included another copepod in their diets, Acanthocyclops spp. In both locations, delta smelt fed predominantly during daytime flood tides, while longfin smelt feeding appeared to continue into the night hours. When both locations were compared, delta smelt in the North Channel exhibited higher densities, larger sizes, increased somatic condition and larvae <15 mm standard length demonstrated greater feeding success. Longfin smelt, exhibited similar densities, feeding success and size distributions between both channels, but generally showed poorer somatic condition for the South Channel, potentially due to energetic costs associated with documented vertical migration behaviour. Overall, the physical conditions of the North Channel provided superior habitat for both species, while the South Channel afforded only marginal habitat for longfin smelt and very poor habitat for delta smelt. Therefore, the North Channel of Suisun Bay acts as critical nursery habitat by providing better feeding and growing conditions leading to increased health and survival for both species.     

Amplified immunohistochemical detection of PrPsc in animal transmissible spongiform encephalopathies using streptomycin.

Due to its sensitivity, immunohistochemistry (IHC) of abnormal prion protein (PrPsc) is used to study experimental and natural cases of transmissible spongiform encephalopathies (TSEs) such as Creutzfeldt-Jakob disease in humans or scrapie and bovine spongiform encephalopathy (BSE) in animals. The limits of detection are particularly critical when PrPsc IHC is used for diagnostic purposes. In this article, we describe for the first time the use of streptomycin sulfate in IHC, providing a novel original and easy way to amplify specifically PrPsc immunohistochemical detection in natural cases of BSE and scrapie, as well as in experimental TSEs in mice models using two different PrP antibodies.     

Crystal structure of the S.cerevisiae exocyst component Exo70p

The exocyst is an evolutionarily conserved multiprotein complex required for the targeting and docking of post-Golgi vesicles to the plasma membrane. Through its interactions with a variety of proteins, including small GTPases, the exocyst is thought to integrate signals from the cell and signal that vesicles arriving at the plasma membrane are ready for fusion. Here we describe the three-dimensional crystal structure of one of the components of the exocyst, Exo70p, from Saccharomyces cerevisiae at 3.5A resolution. Exo70p binds the small GTPase Rho3p in a GTP-dependent manner with an equilibrium dissociation constant of approximately 70 microM. Exo70p is an extended rod approximately 155 angstroms in length composed principally of alpha helices, and is a novel fold. The structure provides a first view of the Exo70 protein family and provides a framework to study the molecular function of this exocyst component.     

Palmitoyl-protein thioesterase 1 deficiency in Drosophila melanogaster causes accumulation of abnormal storage material and reduced life span

Human neuronal ceroid lipofuscinoses (NCLs) are a group of genetic neurodegenerative diseases characterized by progressive death of neurons in the central nervous system (CNS) and accumulation of abnormal lysosomal storage material. Infantile NCL (INCL), the most severe form of NCL, is caused by mutations in the Ppt1 gene, which encodes the lysosomal enzyme palmitoyl-protein thioesterase 1 (Ppt1). We generated mutations in the Ppt1 ortholog of Drosophila melanogaster to characterize phenotypes caused by Ppt1 deficiency in flies. Ppt1-deficient flies accumulate abnormal autofluorescent storage material predominantly in the adult CNS and have a life span 30% shorter than wild type, phenotypes that generally recapitulate disease-associated phenotypes common to all forms of NCL. In contrast, some phenotypes of Ppt1-deficient flies differed from those observed in human INCL. Storage material in flies appeared as highly laminar spherical deposits in cells of the brain and as curvilinear profiles in cells of the thoracic ganglion. This contrasts with the granular deposits characteristic of human INCL. In addition, the reduced life span of Ppt1-deficient flies is not caused by progressive death of CNS neurons. No changes in brain morphology or increases in apoptotic cell death of CNS neurons were detected in Ppt1-deficient flies, even at advanced ages. Thus, Ppt1-deficient flies accumulate abnormal storage material and have a shortened life span without evidence of concomitant neurodegeneration.     

Indexes to the reassociation and stability of solution DNA hybrids

Summary The computation, assumptions, and properties of DNA-hybrid stability and reassociation indexes were reviewed. Different methods of computing the same index typically yielded similar values. However, because dissociation curves change from asymmetric to symmetric as increasingly divergent DNAs are compared, adequate determination of mode required fitting a complex function. Delta Tm, delta mode, and delta T50H correlated well up to ca. 12, and all were found to be useful indexes of genomic similarity in that range. They also exhibited similar levels of error, even though T50H comprises a percent reassociation component with relatively large variance. At greater distances, the delta Tm scale became markedly compressed because of the boundary imposed by the temperature of hybrid formation (incubation temperature). Though not compressed or technically limited by it, delta mode and delta T50H could not be extrapolated with certainty below the incubation temperature. Among theoretical problems discussed: Tm and mode index an increasingly small percentage of the genome as the extent of reassociation decreases, and they may compare different genomic segments as DNAs become highly diverged. T50H relies upon the assumptions that all sequences evolve at a constant rate and that reassociation behavior is the same among all sequences regardless of their extent of divergence. Tm and T50H may be biased by selfhybridization of repetitive elements or cross-hybridization of paralogous sequences. Delta mode is free of such biases as long as the genomes under comparison are not too diverged. No index was found to be best in all circumstances.