A comparison of two methods for testing defined formulations of PVC for resistance to fungal colonisation with two methods for the assessment of their biodegradation

Using plasticised PVC of defined formulation containing a biocide, a comparison has been made of two methods used to assess resistance to fungal colonisation (inhibition of fungal spore germination and use as a carbon source by test fungi) with two physical methods used to assess biodegradation (changes in tensile strength and in extension under load). The results of the first two methods were easier to interpret, but there was general agreement with the results of the measurements of physical characteristics. There are however problems with the choice of methods for the assessment of bioresistance and biodegradation and these are discussed.     

Nutrient-mediated germination of Beauveria bassiana conidia on the integument of the bark beetle Dendroctonus ponderosae (Coleoptera:Scolytidae)

Field-collected adult mountain pine beetles, Dendroctonus ponderosae, were inoculated with the white muscardine fungus, Beauveria bassiana, and thoroughly examined externally with a scanning electron microscope. Germinating conidia were found at a very low incidence, and only on antennal clubs. However, mortality of inoculated controls was high, and B. bassiana was confirmed as the causative agent. Germination on the cuticle was greatly increased by sonication of adult beetles. The hypothesis that hemolymph released through sonication-damaged membranes provided a nutrient stimulus that enhanced conidial germination was tested by placing hemolymph or yeast-malt extract broth on the cuticle of otherwise nontreated beetles, which were then inoculated with conidia. Significant germination occurred on the cuticle of these beetles. Therefore, a limiting factor for conidial germination on the sclerotized cuticle of D. ponderosae is probably a lack of sufficient nutrients.     

Resolution of the isoenzymes of soybean lipoxygenase using isoelectric focusing and chromatofocusing

Isoelectric focusing in thin-layer polyacrylamide gels has been applied to the analysis of the enzymes involved in the formation and destruction of peroxides in soybeans [Glycine max (L.)], lipoxygenases and peroxidases, respectively. As a result of differences in pH optima for catalytic activity, lipoxygenases were selectively detected by adjusting the pH employed for activity-specific staining. Type-1 lipoxygenase was revealed not only by staining based on the conversion of linoleic acid to hydroperoxide but also by two stains based on the reduction of the hydroperoxide. These methods were found to be suitable for the analysis and characterization of isoenzyme patterns in different soybean cultivars. A substantial difference in the distribution of lipoxygenases maximally active near pH 7 was observed for cultivars Provar and Vickery. A similar degree of separation of the isoenzymes was achieved on a larger scale using chromato-focusing in the pH range 7.4-5.0.     

Comparative Biochemistry of a Cytosolic Artiodactyl Glycosidase

Artiodactyls possess abundant neutral glycosidase activity in liver, kidney and intestine. This enzyme is cytosolic and displays a more neutral pH optimum, more acidic isoelectric point and broader substrate range than the corresponding acidic β-galactosidases. The neutral glycosidases were more thermolabile than the respective acidic β-galactosidases and displayed a relative molecular mass approximating 60 kDa. This isozyme appeared to be a minor species in both rat and dog liver. The porcine enzyme was studied in more detail. Porcine neutral glycosidase activity was detected in 45-day gestational fetuses in both liver and kidney but not brain. Fetal kidney activities were about half those observed in adult kidney extracts. Porcine neutral glycosidase was immunologically distinct from acidic β-galactosidase and was immunologically similar to the corresponding isozymes from deer, ovine and bovine liver. Porcine neutral glycosidase was moderately inhibited by d-galactonic acid γ-lactone and strongly inhibited by d-gluconic acid δ-lactone; however, acidic β-galactosidase was not inhibited by the δ-lactone. Inhibition by the γ-lactone was competitive for both enzymes. 4-Methylumbelliferyl-β-d-galactoside, -glucoside and -xyloside competed for the same active site. A polymorphism for fast- and slow-migrating isozymes of porcine neutral glycosidase was observed, which appeared to be under genetic control.     

Relationship between large and small tumor-binding cells in the spleen and bone marrow.

By employing a distinctive feature of natural killer (NK) cells, i.e., spontaneous target cell binding, the present study aimed to follow a relatively large cohort of target-binding cells (TBC), subdivided according to size and the presence of the radioautographically labelled nucleotide, tritiated thymidine, incorporated during a 1- or 6-hour exposure period. Labelling among all TBC in the spleen was 5% by 1 h after a single injection of the isotope and this value did not change significantly after 6 h of isotope exposure. There was an insignificant increase in the labelling index of spleen-localized, labelled, large TBC throughout and beyond the isotope exposure period for at least 48 h, concomitant with a significant increase in the labelling index of spleen-localized, small TBC during the same period. In the bone marrow, small TBC showed only 2% labelling by 1 h after a single injection of isotope, while 21% of large TBC in that organ were synthesizing DNA during the same period. The results are consistent with a precursor-product relationship between large and small TBC within the bone marrow but not the spleen, and with a bone marrow-to-spleen migration of small (+/- large) TBC. Moreover, a minor population of large TBC was detected in the spleen with kinetic characteristics distinct from those of the bone marrow.