Influence of selected plant amines on probing behaviour of bird cherry-oat aphid (Rhopalosiphum padi L.).

The study aimed to quantify the influence of common plant polyamines and tyramine on probing behaviour in the bird cherry-oat aphid (Rhopalosiphum padi L.). Electrical penetration graphs (DC) were used to monitor the probing and feeding behaviour of R. padi exposed to the amines agmatine, cadaverine, putrescine, spermidine, spermine and tyramine. The study results showed that the analyzed amines tended to shorten the stylet activity of aphids in the gels (as indicated by the g-C pattern), prolong the duration of non-probing behaviour (g-np pattern) and decrease salivation into the gels (g-E1pattern) and ingestion from the gels (g-G pattern). The 10 mM concentration of the studied amines, especially cadaverine, reduced or completely inhibited aphid ingestion. The obtained results demonstrate that plant amines participate in plant defence responses to R. padi through disturbance of its probing behaviour and the intensity of such effects is concentration dependent.

Three dimensional visualisation and morphometry of bone samples studied in microcomputed tomography (micro-CT).

This article highlights the utility of micro-computed tomography (micro-CT) for characterisingmicroscale bone morphology. For this purpose we tested selected samplesof the human bones (Wormian bone, rib, lumbar vertebra) to reconstruct externaland internal morphological features. Selected bony samples were investigatedusing a micro-CT scanner (Skyscan 1172, N.V., Aartselaar, Belgium). The imageresolution of scans varied from 5 to 27 µm/pixel depending on the bone sample.We used CTvox software (by Skyscan) to perform volume rendering of the samples.Further, 3-dimensional geometrical models were reconstructed using theCTvol application. Such models enabled graphical distinction between osseouscomponents of various morphology and were used to visualise the Haversian canalsystem inside the compact bone of the rib. Applying a modified transfer functionfor volume rendering we presented the overall morphology of the Wormian boneand small vascular channels penetrating its interior. As an example of quantitativeanalysis based on micro-CT scans we compared the trabecular structure of thelumbar vertebrae with CTAn software. Significant differences in percent bonevolume (BV/TV) were determined. Micro-CT was found to be a very accurate andhelpful method to study small anatomical structures of the bones in micro scale.

Topography and morphometry of the subarcuate canal.

The current study shows in a close-up view anatomical relationship between the subarcuate canal and the osseous labyrinth. For this purpose we used micro-computed tomography which allowed performing three-dimensional reconstruction of the subarcuate canal and gave adequate data for estimation its diameter across its course. The diameter of the middle part (the most uniform) of the subarcuate canal varied from 0.28 mm to 0.46 mm. Hence, we calculated the centre of mass for each cross-section of the separated subarcuate canal. This procedure helped us to visualise trajectory of the subarcuate canal and its spatial orientation within the petrous bone. From our data we concluded that subarcuate canals revealed not well defined trajectories and their spatial orientation varied across the studied temporal bones.

Induced proteolysis within the bird cherry leaves evoked by Rhopalosiphum padi L. (Hemiptera, Aphidoidea).

The objectives of this study were to elucidate the impact of bird cherry-oat aphid (Rhopalosiphum padi L.) feeding on functioning of the proteolytic machinery in bird cherry leaves. Biochemical analyses proved that R. padi feeding in tissues of primary host stimulated activity of the two major fractions of proteinases (extracted at the optimal pH values: 5.0 and 7.0). Additionally, it has been demonstrated that aphids' feeding on bird cherry led to a decline in levels of albumins and globulins (main protein fractions in P. padus leaves). The opposite tendency, regarding the amounts of these protein fractions was ascertained at the phase of disappearance of R. padi population on tested shoots. Furthermore, it is reported that an increase in activity of the analysed enzymes and a decline in the content of tested protein fractions, were proportional to density of aphid individuals developing on P. padus side shoots. It is hypothesized that long-term R. padi feeding may lead to intensifying the catabolic processing of proteins by the activated proteolytic machinery in bird cherry leaves. The multi-level biological functions of endogenous plant proteinases and their significance in triggering the defense reactions in aphid-infested plant tissues are discussed.

Changes in activity of lysine decarboxylase in winter triticale in response to grain aphid feeding.

Changes in lysine decarboxylase (LDC) activity caused by Sitobion avenae (F.) feeding on two winter triticale cultivars (cvs) were studied. The aphid fecundity and values of intrinsic rate of natural increase showed that cv Witon was less susceptible to S. avenae than cv Tornado. The grain aphid feeding on more susceptible triticale caused a decrease in the LDC activity, with exceptions of root tissues after two weeks of the feeding. In case of less susceptible cv Witon reduction of the LDC activity was observed only during initial period of S. avenae feeding. Later the aphid infestation induced activity of the LDC within tissues of cv Witon.

Biochemical markers of oxidative stress within tissues of cereal aphids.

Effects of some dietary o-dihydroxyphenols on biochemical markers of oxidative stress within tissues of Sitobion avenae (Fabricius), (Homoptera, Aphididae) and Rhopalosiphum padi (Linnaeus), (Homoptera, Aphididae) has been studied. Among the studied aphid morphs the highest concentration of total thiols, hydrogen peroxide and lipid peroxidation products (TBARS) was noted for winged adults (alatae). Higher content of H2O2 was observed within tissues of the oligophagous species R. padi while the monophagous species S. avenae had higher TBARS and total thiols concentration. Aphids exposed the dietary pro-oxidative o-dihydroxyphenols (quercetin, caffeic acid, chlorogenic acid) demonstrated significantly lower concentration of total sulfhydryls and higher level of TBARS and H2O2 than the control ones. Among the studied compounds, chlorogenic acid showed the strongest effect on the level of thiols and TBARS while caffeic acid caused the highest accumulation of the hydrogen peroxide within the aphid tissues.

Activity of glutathione transferase and reductase in tissues of bird cherry-oat aphid during its host-plant alternation.

Changes in activity of detoxifying enzymes, involved in metabolism of glutathione in bird cherry-oat aphid during its host alternation have been investigated. Glutathione transferase (GST) and glutathione reductase (GR) activity was found in homogenates from tissues of the bird cherry-oat aphid, Rhopalosiphum padi (L.). The highest activity of the enzymes was recorded in winged migrants that fly from bird cherry (Prunus padus L.), the winter host onto cereals a summer host. Before the migration an increase in activity of the glutathione transferase and glutathione reductase within tissues of winged migrants was observed. When the migrants started to feed on cereals, GST activity further increased and GR activity decreased. The significance of the R. padi glutathione transferase and reductase in detoxification of plant allelochemicals while the aphid host-plants alternation is discussed.

Detoxification of cereal plant allelochemicals by aphids: Activity and molecular weights of glutathioneS-transferase in three species of cereal aphids.

The activity and molecular weights of glutathioneS-transferase were studied in three species of cereal aphid:Metopolophium dirhodum, Sitobion avenae, andRhopalosiphum padi. The highest level of glutathioneS-transferase activity was recorded in extracts fromM. dirhodum and the lowest fromS. avenae, and extracts of larvae were more active than those from adults. The activity of this enzyme was higher in extracts ofS. avenae andR. padi previously fed on a moderately resistant wheat variety than on a susceptible variety. Gel filtration followed by SDS-PAGE revealed three protein bands in the active fractions. The first had a molecular weight of 28,500 and the second of 27,500 and were present in all three species of aphid. The third protein differed in the three species, having a molecular weight of 26,000 inS. avenae, 25,500 inM. dirhodum, and 24,000 inR. padi.

Resistance of cereals to aphids: The interaction between hydroxamic acids and UDP-glucose transferases in the aphidSitobion avenue (Homoptera: Aphididae).

UPD-glucose transferases are found in the cytosolic and microsomal fractions of the grain aphidSitobion avenae F. Gel filtration and SDSPAGE revealed that the microsomal fraction contained several forms of the enzyme. The molecular weights of the three most active fractions might be 68,000, 66,000, and 36,500. There was a negative correlation between the enzymes' activity in extracts of aphids and the concentration of DIMBOAaglucone in the winter wheat variety fed on by the aphid. A strong inhibition of the activity of the UPD-glucose transferases was observedin vitro at a concentration of DIMBOA as low as 0.01 mM. There was a greater activity of the enzymes in aphids fed on seedlings of susceptible than on moderately resistant wheat cultivars. Prolonged feeding on resistant cultivars resulted in a further reduction in the activity of the aphid's enzymes. The significance for cereal aphids of the role of their UDP-glucose tranferases in the detoxification of plant allelochemicals and adaptation to resistant varieties of cereals is discussed.