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.     

Host selection by winged colonisers within the Myzus persicae group: a contribution towards understanding host specialisation

Abstract.  1.  Myzus persicae sensu lato demonstrates considerable genetic variation in respect to adaptation to host plants. The subspecies M. persicae nicotianae shows a preference for tobacco, while M. persicae sensu stricto ( s. str. ) for other herbaceous plants. Given that winged colonisers of several aphid species play an important role in selecting host plants, here their role in the host specialisation observed in M. persicae was examined in choice and no-choice tests conducted outdoors, in performance studies, and in DC Electrical Penetration Graph (DC-EPG) studies.
2. In outdoor choice tests, 77% of spring migrants of M. persicae nicotianae chose tobacco, whereas equal proportions of M. persicae s. str. selected tobacco and pepper. In no-choice tests, spring migrants settled more quickly after alighting on host rather than on non host plants, and significantly more alate M. persicae s. str. (27%) than M. persicae nicotianae (2%) left tobacco after walking briefly on the leaf surface, whilst no significant differences were found on pepper. Cross-host transfers significantly reduced the fecundity of both summer and spring migrants of the two subspecies. Finally, the results of no-choice tests and DC-EPG studies showed that winged aphids distinguished their host through cues located on the plant surface or in subcutaneous tissues perceived prior to the initiation of feeding.
3. This study demonstrates the important role of winged colonisers in the evolution of host specialisation in M. persicae . The multifarious divergent selection that the two host forms experience, i.e. the selection against cross-migrants and their subsequent generations, is a crucial factor involved in the development and maintenance of host specialisation and promotes the parallel evolution of improved host-recognition ability.     

The effects of Eleutherococcus senticosus and Panax ginseng on steroidal hormone indices of stress and lymphocyte subset numbers in endurance athletes.

A clinical trial was undertaken to investigate the effects of Eleutherococcus senticosus (ES) and Panax ginseng (PG) on competitive club-level endurance athletes engaged in their normal in-season training. Participants were matched for training stress and received a 33% ethanolic extract (8 mL/day) containing either ES, PG (equivalent to 4 g and 2 g/day of dried root, respectively), or a placebo. A pre-test and post-test were used to evaluate the effects of six weeks of supplementation on cortisol, testosterone, and testosterone to cortisol ratio (TCR) as well as circulating numbers of total T-cells, T-helper cells (CD4), T-suppressor cells (CD8), CD4 to CD8 ratio, natural killer cells, and B lymphocytes. None of the immune system variables changed significantly nor showed any clear trend from pre to post test in any of the treatment groups. No significant change in testosterone, cortisol or TCR was observed in the PG group. In the ES group, however, TCR decreased by 28.7% from 0.0464 to 0.0331 (P=0.03). The main contribution to this decrease appeared to be a non-significant (P= 0.07) 31% trend towards increased cortisol rather than a very small non-significant (P = 0.36) 7% decrease in the calculated mean for testosterone. This result suggested that contrary to initial expectation, ES increased rather than decreased hormonal indices of stress, which may be consistent with animal research suggesting a threshold of stress below which ES increases the stress response and above which ES decreases the stress response.     

Visual cues during the alarm reaction of Gymnocharacinus bergi (Pisces, Characidae)

Gymnocharacinus bergi (Pisces, Characidae), an endemic fish in the headwaters of the Valcheta stream in northern Patagonia, displays a fright reaction. As this species inhabits a rapid stream, we hypothesized that the alarm reaction might be socially transmitted through visual information, because the detection of alarm pheromone would be restricted to those fish located downstream from the releaser. Alarm substances elicited a decrease in the swimming activity and a tendency to remain at the bottom of the aquarium. Individuals that observed the fright reaction, but were not exposed to the pheromone, spent significantly more time at the bottom of the aquarium imitating the alarm response, and tended to approach the others. Gregarious behaviour was observed; however, interactions (number of approaches) were stronger between those fish held prior to testing in the same aquarium; smaller fish in particular tended to get closer to bigger ones. Greater group cohesion was found between individuals that were exposed to the alarm pheromone.     

Presence of haemocyte-like cells in coccinellid reflex blood

Abstract.  Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction.     

Different receptor subtypes are involved in the serotonin-induced modulation of epileptiform activity in rat frontal cortex in vitro.

The frontal cortex is innervated by serotonergic terminals from the raphe nuclei and it expresses diverse 5-HT receptor subtypes. We investigated the effects of 5-HT and different 5-HT receptor subtype-selective agonists on spontaneous discharges which had developed in rat cortical slices perfused with a Mg2+-free medium and the GABA(A) receptor antagonist picrotoxin. The frequency of synchronous discharges, recorded extracellularly in superficial layers (II/III) of the frontal cortex, was dose-dependently enhanced by 5-HT (2.5-40 microM). That excitatory effect was blocked by the 5-HT2 receptor selective antagonist ketanserin. The 5-HT2A/2C receptor-selective agonist DOI and the 5-HT4 receptor agonist zacopride also increased the frequency of spontaneous discharges. In the presence of ketanserin, 5-HT decreased the discharge rate; a similar effect was observed when the 5-HT1A receptor agonist 8-OH-DPAT or the 5-HT1B receptor agonist CGS-12066B was applied. The 5-HT3 receptor agonist m-CPBG was ineffective. In conclusion, 5-HT produces multiple effects on epileptiform activity in the frontal cortex via activation of various 5-HT receptor subtypes. The excitatory action of 5-HT, which predominates, is mediated mainly by 5-HT2 receptors. The inhibitory effects can be attributed to activation of 5-HT1A and 5-HT1B receptors.     

Ischemic heart disease as deficiency disease.

Four classes of agents capable of producing human illness have been identified: toxicity, heredity, infection and deficiency. The leading paradigm for the etiology and pathophysiology of ischemic heart disease in the 20th century was that of intoxication by too much of the wrong kind of dietary fat. This overemphasis on lipid metabolism persists because important data are neglected and because of inattention to details. For example, heart disease risk does not correlate with fat intake within nations in contrast to between nations. Also development of ischemic heart disease involves inter alia arterial spasm, cardiac rhythm, metabolism of connective tissue, glucose and homocysteine, plus paraoxonase activity and thrombus formation which generally are unaffected by dietary fat. Homocysteine thiolactone accumulates when homocysteine is high. This lactone specifically inhibits lysyl oxidase which depends on copper to catalyze cross linking of collagen and elastin in arteries and bone. The lactone is hydrolyzed by paraoxonase, activity of which can be decreased by copper deficiency. Just as cholesterol was an important focus for heart disease as intoxication, homocysteine can become an excellent focus for a paradigm shift to heart disease as deficiency because supplementation with several nutrients can alter homocysteine metabolism and decrease its plasma concentration. These supplements include betaine, copper, folate, pyridoxine and vitamin B-12. Opportunities for research on ischemic heart disease as deficiency disease are plentiful.