Involvement of hydrogen peroxide in the regulation of senescence in pear

Endogenous peroxide levels in pear fruit (Pyrus communis) were measured using a titanium assay method, and were found to increase during senescence in both Bartlett and Bosc varieties. Application of glycolic acid or xanthine, serving as substrates for the formation of H₂O₂, increased the peroxide content of the tissue and accelerated the onset of ripening, as measured by increased softening and ethylene evolution. Application of ethylene also induced increased peroxide levels. Ripening processes were similarly promoted when peroxides were conserved by inhibiting the activity of catalase with hydroxylamine or potassium cyanide. By comparison, the inhibition of glycolate oxidase with alphahydroxy-2-pyridinemethanesulfonic acid decreased the peroxide content of the tissue and delayed the onset of ripening. These results indicate that the onset of ripening correlates with the peroxide content of fruit tissues as occurring under normal conditions or as influenced by the treatments. Hydrogen peroxide may be involved in oxidative processes required in the initiation and the promotion of ripening.     

Studies on the ultrastructure and histochemistry of the lymph system of Gastrodiscoides hominis (Paramphistoma: Digenea).

The lymphatic system of the paramphistome, Gastrodiscoides hominis consists of numerous fluid-filled branches embedded in parenchyma and surrounded by extracellular material and is closely associated with the major organ systems of the fluke. The lymph matrix consists of a cytoplasmic syncytium within which nuclei, mitochondria and various sized granules and membranous structures occur. The granules found throughout the lymph system morphologically resemble autophagosomes and lysosomes. The lymph system provides a storage site for proteins which can be broken down to amino acids via autophagy, for subsequent mobilization and transport to tissues undergoing active protein synthesis. Many branches of the lymph system are surrounded by specialized parenchymal cells referred to as juxta-lymphatic cells. These cells are apparently associated with autophagic degradation of sequestered lymph cytoplasm, which may serve as an additional mechanism for the mobilization and transport of precursor molecules throughout the fluke via the parenchymal network.     

Evidence for the presence of a phosphatidylinositol anchor on the lipoarabinomannan and lipomannan of Mycobacterium tuberculosis

The recent availability (Hunter, S.W., Gaylord, H., and Brennan, P.J. (1986) J. Biol. Chem. 261, 12345-12351) of the well known arabinomannan of Mycobacterium leprae and Mycobacterium tuberculosis as the pure native lipoarabinomannan has resulted in its implication in key aspects of the immunopathogenesis of leprosy and tuberculosis. We had indicated that the lipid moiety of lipoarabinomannan is probably based on a diacylglycerol unit in that glycerol and the two fatty acids, hexadecanoate and 10-methyloctadecanoate, were identified. In addition, lipoarabinomannan was also shown to contain myo-inositol 1-phosphate. Evidence is now presented, based on selective radiolabeling and analysis of various cleavage fragments, that the inositol phosphate exists as both an alkalilable phosphodiester and as part of a phosphatidylinositol "membrane anchor." The mannan of M. tuberculosis was also isolated as the native lipomannan. It also apparently contains a phosphatidylinositol unit but is devoid of the alkali-labile inositol phosphate residues. These lipopolysaccharides are apparently multiglycosylated versions of the well known myocobacterial mannosyl phosphatidylinositols and are prokaryotic versions of the growing list of phosphatidylinositol-anchored macromolecules. Immunogold labeling demonstrates that lipoarabinomannan is a true antigenic capsular or extracellular product of M. tuberculosis. The presence of a phosphatidylinositol residue on lipoarabinomannan may explain its interaction with macrophage membranes and role in mycobacterial pathogenesis.     

200 injuries caused by playground equipment.

Two-hundred children with injuries caused by playground equipment were studied. Whereas only about 9% of the total casualty attendances are for fractures, 26-5% (53) of these children had fractures. The climbing frame and the slide seemed to be associated with more severe injuries than the swing or other equipment, but more cases need to be studied to confirm this. The youngest children were at particular risk on equipment such as the wooden rocking horse or roundabout, when the speed of operation could be controlled by older children. Many of the injuries to the very youngest children occurred when they were walking behind a moving swing. Faulty equipment did not seem to be a major factor in causing accidents, but the use by older children of apparatus designed for young ones led to accidents. There was supervision, either at home, in a school playground, or in a park, in 62% of the cases. Many of the accidents were the result of the normal desire of children for experimentation and adventure.     

Evidence for novel mechanisms of polychlorinated biphenyl metabolism in Alcaligenes eutrophus H850

Previous studies indicated that Alcaligenes eutrophus H850 attacks a different spectrum of polychlorinated biphenyl (PCB) congeners than do most PCB-degrading bacteria and that novel mechanisms of PCB degradation might be involved. To delineate this, we have investigated the differences in congener selectivity and metabolite production between H850 and Corynebacterium sp. strain MB1, an organism that apparently degrades PCBs via a 2,3-dioxygenase. H850 exhibited a superior ability to degrade congeners via attack on 2-, 2,4-, 2,5-, or 2,4,5-chlorophenyl rings in PCBs but an inferior ability to degrade congeners via attack on a 4-chlorophenyl ring. Reactivity preferences were also reflected in the products formed from unsymmetrical PCBs; thus MB1 attacked the 2,3-chlorophenyl ring of 2,3,2',5'-tetrachlorobiphenyl to yield 2,5-dichlorobenzoic acid, while H850 attacked the 2,5-chlorophenyl ring to yield 2,3-dichlorobenzoic acid and a novel metabolite, 2',3'-dichloroacetophenone. Furthermore, H850 oxidized 2,4,5,2',4',5'-hexachlorobiphenyl, a congener with no adjacent unsubstituted carbons, to 2',4',5'-trichloroacetophenone. The atypical congener selectivity pattern and novel metabolites produced suggest that A. eutrophus H850 may degrade certain PCB congeners by a new route beginning with attack by some enzyme other than the usual 2,3-dioxygenase.     

Sterile host yeasts (SHY): a eukaryotic system of biological containment for recombinant DNA experiments.

A system of biological containment for recombinant DNA experiments in Saccharomyces cerevisiae (Brewer's/Baker's yeast) is described. The principle of containment is sterility: the haploid host strains all contain a mating-type-non-specific sterile mutation. The hosts also contain four auxotrophic mutations suitable for selection for the various kinds of vectors used. All vectors are derivatives of pBR322 which can be selected and maintained in both yeast and Escherichia coli. The system has recently been certified at the HV2 level by the National Institutes of Health.     

Horizontal and vertical gradients in sediment nutrients on mudflats in the Shannon estuary,Ireland

Spatial variability in nutrient concentrations in the intertidal sediments and pore waters has been studied along downshore transects and in core profiles at three locations in the Shannon estuary on the west coast of Ireland. The parameters measured were N, as Kjeldahl N, NO₃, NO₂, and NH₃, and P as total P and PO₄ along with a range of other environmental variables such as salinity and sediment organic content. The concentrations of all nutrients varied with season, but winter values were generally low in comparison with polluted mainland european estuaries. There was a great deal of variation in nutrient concentrations along the transects, and coefficients of variability of up to 153% (NH₃), 173% (NO₃), 129% (NO₂) and 117% (PO₄) were found. Overall, there was little evidence of any trends in concentration in any of the nutrients from the top to the bottom of the transects, although it was occasionally possible to link particular instances to local conditions such as the presence of the channel or a stream. Sediment core profiles showed typical patterns, with NO₃ concentrations for example being highest in surface sediments, while NH₃ and PO₄ concentrations increased with depth. Rather surprisingly perhaps, NO₃ could still be detected on occasion at depths of up to 20 cm, well below the Redox Potential Discontinuity (RPD) and the limit of oxygen penetration which oxygen microelectrodes had measured as being within a few mm of the surface. This was ascribed to the activities of the macrofauna, in that the oxidised sediment which lined the burrows could clearly be seen in some cores. This study not only shows that nutrient distributions along estuarine gradients are linked to physicochemical factors such as oxygenation and freshwater/marine influence, but also that sediment instability, through random physical events such as storms, and macrofaunal activity play an important role and that these latter factors deserve closer attention.