Parasites of fishes from Laurel Creek, Ontario

Two-hundred and nine fish of 13 species from Laurel Creek, Ontario, were examined for parasites between May and October 1973. Eighty-four species of parasites (22 of Protozoa, 24 of Monogenea, 17 of Digenea, 11 of Cestoda, 4 of Nematoda, 1 of Hirudinea, 1 of glochidia, and 4 of Crustacea) were collected and are listed and discussed.     

Ultrastructural investigation of the mechanism of muscle attachment to the gastropod shell

The ultrastructure of the muscle-shell attachment was investigated in the land pulmonate snails Helix aspersa, Anguispira altemata, in the freshwater pulmonate Laevipex sp., and in the freshwater prosobranch Pomacea paludosa. In all cases, a collagenous intercellular matrix and a specialized epithelium (tendon cells) intervene between the columellar muscle and the shell. These tendon cells are characterized by hemidesmosomes at both apical and basal ends, connected by thick bundles of microfilaments. The tendon cells do not insert into the shell directly by microvilli, as formerly thought, but by an extensive network of extracellular organic fibers.     

Does Intrinsic Disorder in Proteins Favor Their Interaction with Lipids?

Intrinsically disordered proteins (IDPs) are implicated in a range of human diseases, some of which are associated with the ability to bind to lipids. Although the presence of solvent‐exposed hydrophobic regions in IDPs should favor their interactions with low‐molecular‐weight hydrophobic/amphiphilic compounds, this hypothesis has not been systematically explored as of yet. In this study, the analysis of the DisProt database with regard to the presence of lipid‐binding IDPs (LBIDPs) reveals that they comprise, at least, 15% of DisProt entries. LBIDPs are classified into four groups by ligand type, functional categories, domain structure, and conformational state. 57% of LBIDPs are classified as ordered according to the CH‐CDF analysis, and 70% of LBIDPs possess lengths of disordered regions below 50%. To investigate the lipid‐binding properties of IDPs for which lipid binding is not reported, three proteins from different conformational groups are rationally selected. They all are shown to bind linoleic (LA) and oleic (OA) acids with capacities ranging from 9 to 34 LA/OA molecules per protein molecule. The association with LA/OA causes the formation of high‐molecular‐weight lipid–protein complexes. These findings suggest that lipid binding is common among IDPs, which can favor their involvement in lipid metabolism.     

Photoelectric monitoring of single beating heart cells in culture

This paper characterizes a photoelectric recording system which monitors individual beating heart cells in vitro. A culture procedure which supports continued beating for up to three months without confluent overgrowth or aggregation is described.     

Quantitation of o-, m- and p-cresol and deuterated analogs in human urine by gas chromatography with electron capture detection

A gas chromatographic method for the analysis of cresol metabolites of toluene and [²H₈]toluene in urine was developed. Cresol glucuronides and sulfates in urine were hydrolyzed with β-glucuronidase and arylsulfatase. Following extraction with tert.-butyl methyl ether and solvent exchange into benzene, the cresols were derivatized with heptafluorobutyric anhydride to form the heptafluorobutyrate esters. The derivatives were analyzed by gas chromatography with electron capture detection. Chromatographic resolution was achieved between all cresol isomers and their ²H₇ analogs. Calibration ranged from 0.001 to 500 μg/ml. Recoveries were 55–97% and showed no trend with respect to analyte concentration. Within-day precision of analyses of benchmark urine samples had a coefficient of variation of less than 4%. The assay sensitivity was limited by chromatographic background but was sufficient for quantification of the unlabeled cresols in urine from men with only environmental exposure to toluene. Average levels in urine samples from 45 men were 0.023, 0.054 and 37 μg/ml for o-, m- and p-cresol, respectively.     

Detection of 6-thioguanine resistance in human peripheral blood lymphocytes (PBL) of industrial workers and lung cancer patients

Human peripheral blood lymphocytes (PBL) were selected for 6-thioguanine (6-TG) resistance in short-term (42-h) cultures in 110 high-cancer-risk industrial workers, 131 primary lung cancer patients and 96 low-risk controls. The lymphocytes were cultured and stimulated by phytohemagglutinin (PHA). A labeling index (LI) was scored using light microscope autoradiography, based on the lymphocyte's ability to incorporate tritiated thymidine with or without selective agent 6-TG. The number of 6-TG-resistant cells increased in the high-occupational-cancer-risk group of vinyl chloride- and mixed organic industrial dust (MOID)-exposed workers as well as in primary lung cancer patients. The results were compared with the low-occupational-cancer-risk groups and with samples taken from the 70 healthy individuals and 26 hospitalized, non-cancerous controls. In both risk-exposed groups the frequency of 6-TG-resistant lymphocytes was significantly higher (P < 0.01) than in the controls. These results suggest that the original Strauss and Albertini (1977, 1979) method can be used to study qualitative risk assessment in carcinogen- or mutagen-exposed occupational groups.