Browsing by Subject "Morphologie"

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Geschlechtsspezifische Unterschiede in der Fötalentwicklung beim Schwein
(2007) Häußler, Susanne; Claus, Rolf
Basic mechanisms of sexual differentiation in higher mammals are well established. The development of the testes is controlled by genetic mechanisms and initiated by the Y-chromosome. Further differentiation of the ?Anlagen? is performed by the presence of testicular androgens but requires no specific signal in females (basic femaleness). Speculation exists during the fetal development of pigs, because androgens are also measurable in female fetuses. In addition, the male gonad is able to synthesize remarkably high levels of estrogens. The aim of the present study was to follow up concentrations of steroids in peripheral plasma throughout fetal development, starting with week 6, and in particular to analyze changes in testicular cell populations (spermatogonia, Leydig cells) and to correlate them with testicular androgens, estrogens, 19-nortestosterone and cortisol. The expression of steroid converting enzymes such as 11beta-HSD 2 and aromatase as well as receptors were determined by immunocytochemistry and quantitative PCR. Altogether each of the stages of gestation (weeks 6, 10, 13, and 15 of pregnancy) was represented by 4 sows, so that a total of 158 fetuses were collected. Testicular steroid synthesis (testosterone, estradiol) could be demonstrated as early as week 6, but was independant of gonadotropine. 19-nortestosterone, which is formed during estrogen synthesis, was detected in amniotic fluid using a new established enzymeimmunoassay in this study. Aromatase activity clearly correlated with a wave-like pattern of cell development. Therefore the activity was elevated both during an alternating rise of Leydig cells or spermatogonia mitosis. During the rise of spermatogonia development Leydig cells remained quiescent and during the Leydig cell mitosis spermatogonia remained inactive. An increased aromatase activity was observed both during the rise of spermatogonia and Leydig cell mitosis, and in consequence an elevated concentration of estradiol was found. But during an increased Leydig cell formation aromatase expression and thus estradiol synthesis was taken over by spermatogonia. It is therefore reasonable to resume that estrogens are important mitogenic signals as it was also found earlier in mature boars. The expression of glucocorticoid receptors by spermatogonia could be demonstrated for the first time in fetal pig testes. As also shown for other tissues, its likely role in testes is the differentiation of new cells. This important role also explains the expression of the enzyme 11beta-HSD 2 both by Leydig cells and spermatogonia. This enzyme is a well known fine-tuning mechanism which indicates cortisol and thus the ligand for the glucocorticoid receptor. Its expression in parallel to the rise of estrogens suggests a dependancy on estrogens. Investigating this was, however, not the topic of the present study. The demonstration of androgens both in blood plasma and amniotic fluid in female fetuses seems to contradict the principle of basic femaleness. It was shown however, that concentrations of testosterone in males increase up to 2.01 ng/ml plasma during the main period of sexual differentiation whereas female levels remain at 0.2 ng/ml so that it is simply the concentration which decides where the male differentiation does occur. It can not be ruled out, however, that low concentrations in female fetuses may have an effect on follicular differentiation, as was also demonstrated in mature sows. At the same time androgens could have a mitotic effect caused by insulin-like growth factors (IGF I + II). Thus the present investigation was able to clarify of several new mechanisms and basic data of fetal pig development. Further confirmation of the mechanisms suspected in this study may be served by an aromatase inhibitor.
Leg attachment and egg adhesion of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) to different surfaces.
(2014) Al Bitar, Loris; Zebitz, Claus P. W.
Adults of Cydia pomonella live on host plant surfaces, differing considerably in their structural, chemical, and physicochemical characteristics according to host plant species, cultivar, plant organ, phenological stage, environmental conditions, and orchard management practices. This variable world provided by plant surfaces can profoundly affect many aspects of insect–plant interactions, such as attachment, locomotion, oviposition site selection, egg adhesion, and also survival of adults and their offsprings. Despite their importance, little attention has been given to the structural and wetting properties of the codling moth’s host plant surface and their effect on insect–plant interactions of this important pest. Therefore, studies in this thesis were undertaken to investigate the effect of structural and physicochemical characteristics of the substrate on two main codling moth-plant interactions: (1) the attachment ability of adults, and (2) the adhesion of their eggs. The first part of this thesis was performed to (1) analyze tarsal morphology of male and female C. pomonella to know more about their pretarsal attachment devices, and (2) to investigate their attachment ability on a variety of smooth and rough substrates, using a centrifugal force device. On all smooth artificial substrates tested, both sexes of C. pomonella adults achieved excellent attachment ability, by means of their smooth, flexible and well developed arolia. Hydrophobicity of the substrate had no considerable effect on friction forces. Cydia pomonella females showed a very good attachment ability to the smooth Plexiglas substrate in both horizontal and vertical positions. Thus, it can be concluded that the attachment system of C. pomonella is rather robust against physicochemical properties of the substrate and is able to achieve a very good attachment on vertical and horizontal plant surfaces. Results on the epoxy resin substrates, differing only in surface asperity size ranging from 0-12 µm revealed that the attachment ability of both sexes was significantly affected by surface roughness. Maximal friction force was measured on the smooth substrate whereas minimal friction force was assessed on microrough substrates with 0.3 µm and 1.0 µm size of asperities. On the remaining rough substrates, friction forces were significantly higher but still lower than on the smooth substrate. Both sexes generated similar friction forces on the same substrate, in spite of the considerable difference in their body mass, suggesting that both sexes attach effectively to variable rough plant surfaces in their habitat. However, since smooth surfaces have been reported previously to be the most favorable substrates for ovipositing females of C. pomonella, it is possible that they use their attachment system to sense the substrate texture and prefer those substrates to which their arolia attach the best. A better survival of the codling moth offspring is assumed to be ensured by the selection of suitable oviposition sites by females, as well as by a proper adhesion of deposited eggs to these sites. In apple orchards, eggs of the first generation of the codling moth are laid on leaf surfaces in the vicinity to small fruits, later in the growing season, most eggs are deposited directly on fruits. In the second part of this thesis, egg adhesion of the codling moth to different leaf and fruit surfaces of the domestic apple was investigated by measuring the pull-off force required to detach the eggs from the plant surface. Morphology, wettability, and free surface energy of the tested plant surfaces were analyzed to evaluate their role in egg adhesion. Furthermore, eggs and their adhesives covering leaf or fruit surfaces were visualized. Eggs on the smooth upper leaf sides of the tested cultivars were easily detached, requiring similar pull-off forces (total average of 6.0 mN). Up to 2-3 times stronger pull-off forces had to be applied to detach eggs from the trichome-covered lower leaf side, and these forces differed significantly between cultivars, owing mainly to different trichome covered areas. Whereas on the waxy fruit surface of all apple cultivars tested, eggs were very tightly adhered, and required 4-10 fold stronger pull-off forces than those previously measured on upper and lower leaf surfaces of the identical apple cultivars. Cydia pomonella eggs adhered stronger on the upper and middle fruit sections of all cultivars tested, than on the lower section. The influence of plant surface properties on egg adhesion, as well as the mechanisms used by the moth to overcome the presumable anti-adhesive properties of apple fruit surfaces, were discussed. Additionally, the results were debated in the context of the oviposition site selection, female attachment, as well as offspring survival of the codling moth.