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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 76 (1977), S. 259-266 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography A 123 (1976), S. 231-236 
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron Letters 17 (1976), S. 4501-4504 
    ISSN: 0040-4039
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-9702
    Keywords: Male ticks ; Rhipicephalus evertsi mimeticus ; Hyalomma truncatum ; foveal glands ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ultrastructure of the foveae dorsales and foveal glands in unfed and attached male Hyalomma truncatum and Rhipicephalus evertsi mimeticus ticks was studied. Both species are provided with a paired foveal gland system, which is similar in unfed as well as in attached ticks. This gland system consists of the fovea dorsalis with pores and pore tubes as the external part, the foveal neck zone as a link between the fovea dorsalis and the lobes of the gland and the bulbous lobes as the innermost part. The fovea dorsalis is located on either side of the dorsal midline in the midsection of the body and appears as a roundish plate containing 15±6.5 and 21±7 slit-like pores in R. evertsi mimeticus (n=210) and H. truncatum (n=210), respectively. Each pore leads into a cuticular lined channel containing a pore tube. Below each fovea, the foveal neck zone is located within a groove of the cuticle and consists of the termini of the pore tubes which enlarge basally to form a cup-shaped ampulla each. Furthermore, secretory lobes are located below the foveal neck zone. Each lobe consists of secretory cells and a central excretory duct which leads into the ampulla. The ducts are lined with microvilli. The secretory cells contain numerous vesicles of varying size with one or more granules. In male ticks of both species the secretory lobe cells remained unchanged in size, structure and granule content irrespective of whether they were unfed or attached for up to 30 days. Axons occur in the fascicles between the secretory lobe cells containing numerous neurosecretory vesicles. A possible role of the foveal glands in the production of pheromones is hypothesized.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental and applied acarology 21 (1997), S. 21-39 
    ISSN: 1572-9702
    Keywords: Adult ticks ; Hyalomma truncatum ; eyes ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The eyes of Hyalomma truncatum ticks are morphologically similar in both sexes. They appear aspaired hemispherical structures situated dorsally between the first and second pair of legs on thelateral scutal margin. Each eye consists of a lens and photoreceptor cells, which are separated by afine fibrillar layer and the hypodermis. The lens contains numerous channels which open beneaththe epicuticle, converge uninterruptedly to the interior of the lens and end below the fine fibrillarlayer. The inner closure of the lens is formed as an oval plateau with a cone-like projectionsituated caudolaterally and eccentrically to the longitudinal axis of the lens. The hypodermis is asingle layer of cells, situated immediately below the fine fibrillar layer. Beneath the hypodermis,directly below the cone-like projection of the inner lens are the photoreceptor cells localized in arosette-like arrangement. Facing the hypodermis, each photoreceptor cell is provided withnumerous microvilli. The microvilli consistently border the microvilli regions of other cells atdifferent angles but are always oriented at a right angle to the lenticular channels. Thephotoreceptor cells are unipolar neurons, whose axons arise from the basal portion of the cell andjoin to nerve fibre bundles forming the optic nerve. It is concluded that the eyes in adult H.truncatum ticks possess all the structures necessary to perceive and conduct light stimuli andvisual signals.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental and applied acarology 21 (1997), S. 307-315 
    ISSN: 1572-9702
    Keywords: Ticks ; Hyalomma truncatum ; visual signals ; perception ; eyes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adult Hyalomma truncatum ticks with uncovered and foil-covered eyes were exposed to an upright-positioned rectangle as a target giving a luminance contrast ratio of 5:1 at a sun-simulating radiation. The transmission rate of the foil was less than 0.003%. Significantly (p≤0.05) more locomotorally active ticks with uncovered eyes (36.6%) responded to the target than ticks with foil-covered eyes (7.3%). When the rectangle was illuminated by monochromatic light at wavelengths ranging between 420 and 648 nm, the target induced a positive scototaxis in ticks with uncovered eyes regardless of the wavelength range. In contrast, ticks with covered eyes did not exhibita positive scototaxis at wavelength ranges of 553–585 and 608–648 nm and very few ticks responded only to other wavelength ranges. The results indicate that the eyes are the only or at least the most essential sense organs in the visual system of adult H. truncatum ticks.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental and applied acarology 24 (2000), S. 63-76 
    ISSN: 1572-9702
    Keywords: Acari ; Ixodoidae ; Dermacentor reticulatus ; oviposition ; modus operandi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The process of oviposition in D. reticulatus was observed and found to be a sequence of exactly coordinated, interlocking events independent of the phase of oviposition. The average period of oviposition in the investigated ticks was 31.6 days at 20 °C and 95% relative humidity. The number of eggs deposited on each day increased until reaching a maximum on the fifth day of oviposition and then decreased continuously. As a result, most of the eggs were deposited during the initial phase of oviposition. The total number of eggs was proportional to the ticks' weight replenishment. Egg-laying commenced with the lowering of the capitulum and the simultaneous spread of the pedipalps which were lowered to the body wall embracing the genital aperture on both sides. Immediately afterwards the cuticular sac of Gene's organ was pushed out and retracted several times. At the cuticular sac's maximum extension, the vestibulum vaginae prolapsed, forming the ovipositor as an extended tube which handed over an egg to the two horns of the cuticular sac after a brief, but intensive, contact with the cuticular sac. Then the vestibulum vaginae invaginated, the pedipalps closed, and the cuticular sac was retracted. Finally, the egg was transported onto the dorsal area of the tick by means of a vigorous rising of the capitulum. During the course of oviposition most of the events, especially the period of egg embracement by the cuticular sac, were prolonged, as was the total time for laying one egg. Similarly, the intervals between successive egg-laying processes increased continuously. The number of eggs deposited was not dependent on the functional ability of Gene's organ, as shown by similar numbers of deposited eggs from ticks with and without mechanical blocking of the cuticular sac. But the participation of the organ in the process of oviposition proved to be a prerequisite for the viability of the eggs. Larvae developed and hatched only from those eggs which were deposited from ticks with an undisturbed Gene's organ. In comparison, eggs without contact to the cuticular sac of Gene's organ dried up and shrivelled immediately after being deposited and did not hatch. Consequently, it strongly suggests, together with the results from other studies, that Gene's organ covers the eggs with a secretion that prevents the loss of water.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1572-9702
    Keywords: Complex formation ; immuno-affinity chromatography ; low molecular mass neurotoxin ; synaptosomes ; tick paralysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study describes the isolation of a 11 kDa paralysis toxin from crude larval extracts of Argas (Persicargas) walkerae by exploiting the cross-reactivity of a monoclonal antibody (4B12), directed against the paralysis toxin of Rhipicephalus evertsi evertsi. This low molecular mass is in contrast to previous findings of a 60–70 kDa toxin for A. (P.) walkerae but is similar to neurotoxins isolated from venomous forms of the class Arachnida, which comprise the orders Araneae (spiders), Scorpionida (Scorpions) and Acari (ticks and mites). Since numerous antigenic bands, ranging between 11 and 115 kDa, were detected by the monoclonal antibody 4B12, the possibility of toxin-complex formation and the effect of pH on the latter were investigated by means of HPLC and ammonium sulphate precipitation. The results suggest that physiological conditions, with respect to pH and ionic strength, promote the formation of heterogeneous toxin-complexes while an acidic pH favours the formation of a more homogeneous toxin-containing complex. Furthermore, the effect of partially purified toxin on neurotransmitter release from crude rat brain synaptosomes was investigated, since tick paralysis toxins are hypothesised to inhibit neurotransmitter release from the presynaptic terminal. Both calcium-dependent, as well as calcium-independent release was inhibited by the toxin-containing sample.
    Type of Medium: Electronic Resource
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