Oxygen participation in the in vivo and in vitro aging of collagen fibres

We have examined, as a function of oxygen concentration, the in vivo and in vitro aging rates of tendon from animal species with widely differing life-spans. The results suggest that concomitant with the genetically determined aldimine type cross-linking reactions which probably are complete by the time the animal has reached physiological maturity, there is an on-going oxygen-mediated system of reactions which also effectively cross-link the structure. These reactions appear to proceed with their own intrinsic rate dependent only upon oxygen concentration, and independent of the particular species involved. They may not be required by connective tissues, but are an unavoidable consequence of the presence of free oxygen in tissues with a low rate of turnover.     

Melampolides from Enhydra fluctuans var. Fluctuans

The investigation of the aerial parts of a variety of Enhydra fluctuans afforded in addition to 4-hydroxyfarnesyl acetate and fluctuadin five new melampolides elucidated by high field ¹H NMR spectroscopy. The chemotaxonomic situation is discussed briefly.     

A dimeric germacranolide and other sesquiterpene lactones from Mikania species

The investigation of two Mikania species, both previously placed in the genus Kanimia, afforded in addition to known compounds several new germ     

Comparison of the alpha-mannosidases in fibroblast cultures from patients with mannosidosis and mucolipidosis II and from controls.

Normal human spleen contains two forms of membrane-bound beta-glucosidase, distinguishable by their thermostability and kinetic properties. The spleen from a patient with adult Gaucher's disease was deficient in the major, thermolabile, form of the enzyme.     

Polyploidy in the Australian leptodactylid frog genus Neobatrachus

Karyotypic analysis of six species of the Australian leptodactylid frog genus Neobatrachus showed that N. pictus, N. centralis, N. pelobatoides and N. wilsmorei are diploid (2n=24) while N. sudelli and N. sutor are tetraploid (4n=48). Polyploidy has not been reported previously among Australian anurans. Idiograms of the six species indicate that they are similar to the other Australian leptodactylids so far discribed. DNA values of the tetraploids are approximately double the values for diploids. Tetraploid nuclear and cell sizes are greater compared with diploids but total body size shows no increase. At diakinesis in primary spermatocytes of tetraploids, mainly tetravalents together with a few bivalents are present. Silver staining of metaphase spreads clearly demonstrates the location of NORs at the secondary constrictions and their frequent association in the tetraploid N. sutor. Nucleolar number in interphase nuclei provides a reliable guide for distinguishing tetraploid from diploid frogs in the absence of chromosome analysis and can be determined for both living and preserved specimens. The possible origins and relationships of the tetraploid species are discussed.     

Isolation and characterization of a Saccharomyces cerevisiae mutant disrupted for the succinate dehydrogenase flavoprotein subunit

A partial genomic clone of the flavoprotein subunit of the mitochondrial enzyme, succinate dehydrogenase (EC 1.3.99.1) from Saccharomyces cerevisiae has been isolated. The partial clone was used to construct, by targeted gene disruption, a yeast mutant with a defective flavoprotein subunit gene. Submitochondrial membranes from the mutant are defective in activities requiring a functional succinate dehydrogenase but not in other respiratory chain activities. In addition, the mutant contains significantly lower levels of covalently attached flavin adenine dinucleotide cofactor than does the wild type. Disruption of the flavoprotein subunit gene results in the simultaneous loss of both the iron-sulfur and the flavoprotein subunits from mitochondrial membranes.     

Detection and quantification of triazine herbicides using algal cell fluorescence

Summary A continuous-flow system is described which, by measuring fluorescence of the unicellular alga Chlorella, is capable of measuring concentrations of the triazine herbicide, simazine, as low as 60nM (approx 12g l^-1) within 5 minutes. Further developments are suggested to achieve the desired detection limit of 0.5nM. The use of such an instrument in environmental analysis is discussed.