Honeydew amino acids in relation to sugars and their role in the establishment of ant-attendance hierarchy in eight species of aphids feeding on tansy (Tanacetum vulgare)

Abstract. The ratio of the concentration of honeydew total amino acids to total sugars in the honeydew of eight species of aphids, all feeding on tansy, Tanacetum vulgare (L.), was determined and correlated with honeydew production and ant‐attendance. The honeydew of the five ant‐attended aphid species [Metopeurum fuscoviride (Stroyan), Trama troglodytes (v. Hayd), Aphis vandergooti (Börner), Brachycardus cardui (L.), Aphis fabae (Scopoli)] was rich in total amino acids, ranging from 12.9 to 20.8 nmol µL^?1 compared with the unattended aphid Macrosiphoniella tanacetaria (Kalt.) with only 3 nmol µL^?1. Asparagine, glutamine, glutamic acid and serine (all nonessential amino acids) were the predominant amino acids in the honeydew of all species. The total concentration of amino acids in the phloem sap of tansy was much higher (78.7 nmol µL^?1) then in the honeydew samples, and the predominant amino acids were glutamate (34.3%) and threonine (17.7%). A somewhat unexpected result was the finding that those aphid species with the highest total amino acid concentration in the honeydew always had the highest concentration of sugars. The lowest amino acid–sugar combined value was 104–28.8 nmol µL^?1 in the non ant‐attended species M. tanacetaria, and the highest value was an average of 270–89.9 nmol µL^?1 for the three most intensely attended aphid species M. fuscoviride, A. vandergooti and T. troglodytes. There is no evidence that any single amino acid or group of amino acids in the honeydew acted as an attractant for ant‐attendance in these eight aphid species. The richness of the honeydew (rate of secretion × total concentration of sugars), along with the presence of the attractant sugar melezitose, comprised the critical factors determining the extent of ant‐attendance of the aphids feeding on T. vulgare. The high total amino acid concentration in sugar‐rich honeydews can be explained by the high flow‐through of nutrients in aphids that are particularly well attended by ants.     

6(5)CARBOXYFLUORESCEIN AS A TRACER OF PHLOEM SAP TRANSLOCATION

6(5)carboxyfluorescein (6(5)CF), a polar fluorescein with an apparent pK of 6.3, was introduced, as a pH 6.3 solution, into the apoplast of lamina or petioles of mature soybean leaves. Freehand sections were prepared at various times and immediately observed with a fluorescence microscope. 6(5)CF-associated fluorescence appeared in all sink organs, from shoot apex to roots. It was strictly confined to the phloem regions, even after 4 days. Its transport into young leaves ceased at approximately the time they underwent sink-to-source transition. It was never transported between two leaflets of the same leaf. Its transport was interrupted by phloem destruction. All these transport characteristics were highly reproducible, and were paralleled by those of ¹⁴C transport after application of (¹⁴C)sucrose to leaf surfaces. In contrast with 6(5)CF, fluorescein was transported between mature leaves, and between leaflets of the same leaf. It was not restricted to phloem, and often appeared in the xylem region. These results indicate that 6(5)CF can be used to monitor phloem sap translocation in real time, in short- and long-term experiments.     

Specific Antisera Against the Catecholamines: L-3,4-Dihydroxyphenylalanine, Dopamine, Noradrenaline, and Octopamine Tested by an Enzyme-Linked Immunosorbent Assay

Antisera were raised against L-3,4-dihydroxyphenylalanine (L-DOPA), dopamine (DA), noradrenaline (NA), and octopamine (OA). This was achieved by coupling each molecule to bovine serum albumin or human serum albumin using glutaraldehyde. The conjugated aromatic amines were kept in a reducing medium containing sodium metabisulfite. Antiserum specificity was tested using an enzyme-linked immunosorbent assay method for catecholamines. Competition experiments were done between the immunogen coated on the well plates and each catecholamine, either in the free state or in conjugated form, previously incubated with an antiserum. In each case, the nonconjugated compound was poorly recognized. The nonreduced conjugates of L-DOPA and DA were well recognized, whereas those of NA and OA were poorly immunoreactive. The cross-reactivity ratios established in the competition experiments allowed the specificity of the immune response to be defined. In each case, it was found to be high. The results suggest that the antibodies of L-DOPA and DA antisera recognize preferentially the catechol moiety, whereas for the anti-NA and anti-OA antibodies, the lateral chain is important.     

Cloning and sequencing of a rat CuZn superoxide dismutase cDNA. Correlation between CuZn superoxide dismutase mRNA level and enzyme activity in rat and mouse tissues

The molecular cloning and nucleotide sequence of a cDNA clone (pR SOD) for rat CuZn superoxide dismutase (CuZnSOD) is reported. Nucleotide sequence homology with human superoxide dismutase is 86% for the coding region and 71% for the 3' untranslated region. The deduced amino acid sequence is given and the homologies with the sequences reported for other species are presented. Northern blot analysis of total RNA from various rat and mouse tissues and from two mouse cell lines show that pR SOD hybridizes with one mRNA species of about 0.7 kb. The amount of CuZnSOD mRNA in each tissue, measured by densitometry of the Northern blot autoradiograms, correlates with the enzymatic activity based on protein content. These results indicate that the control of CuZnSOD activity in mammalian tissues is largely dependent on the regulation of CuZnSOD mRNA levels. In human liver, fibroblasts and FG2 hepatoma cells, two CuZnSOD mRNAs (0.7 kb and 0.9 kb) are observed. The level of CuZnSOD mRNA in FG2 is 25% that of the liver and four times more abundant than in fibroblasts.     

In situ accumulation of 3 beta-hydroxylanost-8-en-32-aldehyde in hepatocyte cultures. A putative regulator of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity

Biphasic modulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) has been demonstrated in primary hepatocyte cultures treated with the lanosterol 14 alpha-methyl demethylase inhibitor miconazole. At concentrations of the drug which lead to suppressed levels of reductase activity, the appearance of a polar, mevalonate-derived sterol is noted. Cochromatography of the identified sterol with 3 beta-hydroxylanost-8-en-32-aldehyde tentatively identified the metabolite as a lanosterol 14 alpha-methyl demethylation intermediate. Subsequent isolation and characterization of the metabolite by gas chromatography/mass spectroscopy confirmed this structural assignment. When the lanosterol 14 alpha-methyl demethylase-deficient mutant, AR45, was treated with authentic metabolite, a suppression of HMG-CoA reductase was observed. These results demonstrate that metabolism of the oxygenated biosynthetic intermediate is not required to suppress reductase activity. The results also strongly support the hypothesis that oxygenated 14 alpha-methyl demethylase intermediates are endogenously generated modulators of HMG-CoA reductase activity.