Tarsal chemoreceptors and oviposition behaviour of the cabbage root fly (Delia radicum) sensitive to fractions and new compounds of host-leaf surface extracts

Abstract. Contact chemoreception plays a decisive role in host selection and oviposition behaviour of the cabbage root fly, Delia radicum L. (Diptera, Anthomyiidae). Glucosinolates (mustard oil glucosides) are known to be perceived by the flies, and when sprayed on paper leaf-models induce oviposition. Recently it has become clear that other non-volatile types of compounds must also be involved in host selection.
A pair of ventro-medial C sensilla on die fifth tarsomere respond strongly to a novel compound called tentatively 'cabbage identification factor' (CIF), but not to sucrose, glucose, fructose and proline. CDF is a new non-glucosinolate oviposition stimulant. A single neurone in each sensillum is activated by this compound and the same is true for glucosinolates. In some flies a mixture of bom types of stimuli evoked an apparent mononeural spike train, whereas in odiers spikes of two separate cells were activated. The significance of this variability is not yet clear.
The new stimulant, CIF, does not evoke responses in glucosinolate receptors in the D sensilla. The involvement of the C₃ sensilla in the detection of host-specific compounds constitutes the first known function for C sensilla in D. radicum. CIF appears to be present in leaf surface extracts from the host-plant Brassica oleracea in quantities as low as 1 ng per gram leaf. In spite of this low level, it stimulates oviposition significantly better than glucobrassicin at higher concentrations, which up till now was known as the most powerful stimulant for D.radicum.     

WLADIMIR KOWALEVSKY'S SOURCES OF IDEAS AND THEIR IMPORTANCE FOR HIS WORK AND FOR RUSSIAN EVOLUTIONARY PALAEONTOLOGY

Studies of documents and data about W.O. Kowalevsky's life and work have shed new light on his scientific background. After graduating from the School of Jurisprudence in St. Petersburg, he was first engaged in book publishing, but in 1868 began studies at the Anatomical Institute of the Medical-Surgical Academy, founded by N.I. Pirogov, a famous surgeon and anatomist. Pirogov's ideas were adopted by P.F. Lesshaft (1837–1907), later a prominent anatomist and founder of functional anatomy in Russia. Another teacher was the famous physiologist I.M. Sechenov. Only with the background of this new functional anatomy was Kowalevsky able to link up various data to form his own theories and create classical palaeontological works in the space of two and a half years (1871–1873). His influence on the development of vertebrate palaeontology has been lasting. In Russia and the Soviet Union, Kowalevsky and Lesshaft had such successors as A.P. Pavlov (1854–1929), A.A. Borissiak (1872–1944), N.N. Yakovlev (1870–1966), and many other disciples in younger generations of palaeontologists.     

Binding of Lectins to Culture and Vector Forms of Trypanosoma rangeli Tejera, 1920 (Protozoa, Kinetoplastida) and to Structures of the Vector Gut

Culture forms of Trypanosoma rangeli could be agglutinated with Canavalia ensiformis (Con A) lectin and, less effectively with Pisum sativum agglutinin (PEA), at a concentration of 200 μg/ml. Ricinus communis agglutinin I (RCA I) agglutinated trypanosomes only if they were not previously washed with physiological Ringer's solution. Three other lectins did not react with the same parasite forms. Direct or indirect lectin-gold labeling techniques were applied to LR-White embedded thin sections of T. rangeli culture forms and to forms in the gut, hemolymph, and salivary glands of Rhodnius prolixus. Under these conditions, Con A was the only lectin out of 9 that bound to the surface of trypanosomes from culture and from the bug hemolymph. Con A did not react with any midgut or salivary gland forms. The preservation of the biological activity of the lectin-gold complexes that did not bind to the parasite surface was confirmed by reactions with structures of the invertebrate host.     

Determination of Affinity and Activity of Ligands at the Human Neuropeptide Y Y4 Receptor by Flow Cytometry and Aequorin Luminescence

Fluorescence-labeled neuropeptide Y (NPY) has been used in flow cytometric binding assays for the determination of affinity constants of NPY Y₁, Y₂, and Y₅ receptor ligands. Because the binding of fluorescent NPY is insufficient for competition studies at the human Y₄ receptor (hY₄R), we replaced Glu-4 in hPP with Lys for the derivatization with cyanine-5. Because cy5-[K⁴]hPP has high affinity (K_d 5.6 nM) to the hY₄R, it was used as a probe in a flow cytometric binding assay. Specific binding of cy5-[K⁴]hPP to hY₄R was visualized by confocal microscopy. The hY₄R, the chimeric G protein G_qi5 and mitochondrially targeted apoaequorin were stably coexpressed in CHO cells. Aequorin luminescence was quantified in a microplate reader and by a CCD camera. By application of these methods 3-cyclohexyl-N-[(3-1H-imidazol-4-ylpropylamino)(imino)methyl]propanamide (UR-AK49) was discovered as the first nonpeptidic Y₄R antagonist (pK_i 4.17), a lead to be optimized in terms of potency and selectivity.     

Relative air humidity influences the function of the tarsal chemoreceptor cells of the cherry fruit fly (Rhagoletis cerasi)

ABSTRACT. Electrophysiological recordings from the tarsal D-sensilla of mature, 5–7-day-old female European cherry fruit fly ( Rhagoletis cerasi L.) revealed that a large proportion of sensilla showed no sensory activity in response to stimulation with the oviposition deterring pheromone ('ODP') or sucrose. In contrast, good recordings were obtained from almost all sensilla in freshly emerged, 1-day-old flies. Ageing, nutritional state and contamination were excluded as possible major factors influencing the responsiveness of the D-sensilla. The study of the variability in responsiveness of the sensilla of 1-day-old flies among different tarsomers, among tarsi of the same individual and among individuals, revealed that the major source of variability was among individuals.
Individual flies were also affected by the humidity in the holding cages: relative air humidity of less then 75% for 4–6 days was shown to reduce the number of D-sensilla giving recordings with a good signal-to-noise ratio. The D-sensilla on the most distal tarsomers were affected most by the reduced (30–55% r. h.) air humidity. Flies which had contact with plant leaves showed less reduction in responsiveness at low air humidity (40% r. h.) then flies without leaf contact.     

Seed preference and energy intake of Goldfinches Carduelis carduelis in the breeding season

The food of a population of Europeans Goldfinches breeding in Orchards was studied. More than 5% of the total foodstuff consumed was met by the seeds of seven food plants. Water, lipid, carbohydrate and protein content was determined from 20 different plants which Goldfinches used during the breeding season in order to calculate energy content. The energy of fresh seeds varied from 1.88 kJ/g in Tussilago farfara to 12.14 kJ/g in Dactylis glomerata. The dependence of the rate of energy intake (profitability) on the pecking rate and the size (weight) of the seeds was calculated. The profitability of various seeds is in agreement with the relative number of birds using them. Calculation of the feeding time that a Goldfinch needs during daylight hours, if it feeds only on a particular plant, indicates that there are several foods that cannot fill the energy demands of the bird during the breeding season. These are eaten only if others with a high energy content are not available. Thus food selection in Goldfinches depends, apart from availability, on seed profitability. The oxygen consumption of a male Goldfinch was significantly higher when the animal was feeding on seed heads of Tussilago farfara and Taraxacum officinale than when it fed on loose dry seeds, and so, different feeding techniques have to be taken into account in calculating net energy gain.     

Tarsal contact chemoreceptor response to glucosinolates and cardenolides mediating oviposition in Pieris rape

Abstract. Water-soluble extracts of a host crucifer (Brassica oleracea L.) and non-host crucifer (Erysimum cheiranthoides L.) and isolated pure cardenolides and glucosinolates were tested on Pieris rapae L. (Lepidoptera: Pieridae) butterflies in oviposition assays and by electrophysiological recordings from the contact-chemoreceptor sensilla of the prothoracic tarsi. Ten different glucosinolates stimulated oviposition to varying degree when put on non-host plant leaves. The most active compounds were glucobrassiein and gluconasturtiin (methylindole and phenylethyl aglycone), whereas glucocapparin, sinalbin. glucotropaeolin, sinigrin and glucoalyssinin had intermediate activity. Glucocheirolin, glucoerucin and glucoiberin (sulphur-containing aglycone) were significantly less active. Of eight cardenolides applied to host-plant leaves (100 μg each), four glycosides deterred oviposition strongly (erysimoside, erychroside, cymarin and K-strophanthin-β). Erycordin, helveticoside, digitoxin and strophanthidin had little or no deterrent activity. Sensilla located laterally on the prothoracic tarsi of female butterflies contained one receptor cell sensitive to sucrose. None of the tested extracts or pure compounds stimulated any cell in these sensilla. In contrast, the cells in the medial sensilla showed little or no sensitivity to sucrose. One cell was found to be sensitive to cardenolide glycosides. The threshold for one of the most active compounds, erychroside, was about 0.1 μg/ml (1.5 times 10^-7 M). Two receptor cells, characterized by spikes of differing amplitude, were sensitive to glucosinolates. One of these, with larger amplitude spikes, seemed to be the same as the cell sensitive to cardenolides. The threshold for the most active glucosinolates, glucobrassicin and gluconasturtiin was estimated to be below 0.1 mg/ml (2 times 10^-4 M). The neural activity of both classes of compounds, cardenolides and glucosinolates, was significantly correlated with their behavioural activity as deterrents or stimulants.