In host-parasitoid systems, there is a continuous coevolutionary arms race where each species imposes a strong selection pressure on the other. The host needs to develop defence strategies in order to escape parasitism and the parasitoid must evolve counter-defence strategies in order to overcome the host’s immune defence and successfully reproduce. This makes host-parasitoid systems excellent model systems for understanding evolutionary processes underlying host race formation and speciation. In order to gain a better understanding of the complexity of host-parasitoid interactions several aspects must be considered, such as search behaviour and host selection in the parasitoid, the development of immune responses in the host and counter-defence strategies in the parasitoid. In this thesis, I investigate interactions and coevolution in a natural host-parasitoid system, consisting of five species of Galerucella leaf beetles and three species of Asecodes parasitoids, by combining behavioural ecology with chemical ecology and immunology. In the studies performed, I found that pheromone production and responses in the beetles are connected to the phylogenetic relatedness between the Galerucella species (Paper I). I found no evidence that Asecodes exploits the adult pheromone to locate host larvae, but observed an ability in the parasitoids to distinguish a better host from a less suitable one based on larval odors (Paper II). The studies also revealed large differences in immune competence between the Galerucella species, which were linked to differences in hemocyte composition in the beetle larvae (Paper III, IV). Further, the results suggest that parasitism success in polyphagous Asecodes is strongly affected by former host species of the parasitoid (Paper IV). In conclusion, the results of this thesis suggest an on-going evolution in both parasitoid virulence and host immune responses in the Asecodes-Galerucella system.

The uptake and distribution of radioactivity in vascular adrenergic nerves in the mouse pancreas following the injection of tritiated 5-hydroxytryptophan was studied by means of electron microscopic autoradiography. Autoradiographic silver grains were found selectively accumulated over axonal profiles. Quantitative analysis revealed a characteristic intraneuronal distribution of the silver grains, most of which probably represent 5-hydroxytryptamine formed by decarboxylation from the labeled precursor. Thus, the grain density over adrenergic nerve terminals, containing a mixed population of vesicles and granules, was about 5 times higher than the grain density recorded over non-terminal axonal parts and at least 20 times higher than the grain density found over surrounding adventitial tissue and smooth muscle cells. This was interpreted as an evidence that 5-hydroxytryptamine was taken up and stored in adrenergic terminals.

The protothyroid region in the endostyles of four species of tunicates was examined by means of autoradiography and cytochemistry, at both the light and electron-microscopic levels. To reveal the primary binding site for iodine, autoradiography was carried out on endostylar tissue from animals that had been incubated with high activity 125I over a short period of time. The specific iodine binding enzyme, a peroxidase, was traced by its reaction with DAB. In accordance with previous findings, the iodine-binding cells proved to be the same as those containing the peroxidase. There were also strong indications of a secondary uptake of iodinated compounds and subsequent release into the body fluid. Together with the ultrastructural features, the data provided strong evidence indicating that these cells constitute a protothyroid region, which partly functions as an endocrine organ, possibly homologous with the vertebrate thyroid gland. Since the number of zones varied between the species, the numeration of the protothyroid region also varied. However, in all the examined endostyles, the protothyroid region was seen to be situated dorsolaterally to the glandular regions of the endostyle concerned with food capture.

Clusters of luminal dense bodies, limited by a triple-layered membrane, were found in all follicle lumina in thyroid glands of mice. After thyroxine treatment the number of luminal dense bodies increased, especially in the periphery of the lumen, where the intraluminal bodies often displayed a striking resemblance to microvilli. In hyperplastic goiters, obtained by feeding mice with propylthiouracil, luminal dense bodies were replaced by intraluminal vesicles. During goiter involution the vesicles were gradually replaced by luminal dense bodies; the presence of intermediate forms suggests that vesicles and dense bodies are basically the same formations. Luminal dense bodies were observed in colloid droplets indicating their removal by endocytosis. As demonstrated by electron-microscopic cytochemistry, luminal dense bodies contain a membranebound peroxidase, and electron-microscopic autoradiography after administration of 125I indicate that they possess an iodinating capacity.

In the Marviken Full-Scale Critical Flow Test Program, a multinational project, 27 tests were conducted to obtain critical mass flow data for short nozzle geometries (200 to 509 mm in diameter with length-to-diameter ratios from 0.3 to 3.7) comparable to pipe sizes present in world nuclear reactor stations. The nozzle inlet pressures ranged from 5.2 to 2.6 MPa with the fluid subcooled as much as 50/sup 0/C to low-quality saturation. A maximum nozzle mass flow rate of 14 Mg/s was measured. Typical data are presented and discussed in this article. These data provide an important link between the previously available small-scale critical mass flow rate data and existing operational hardware.

The effect of vinblastine on the intracellular transport of newly synthesized protein in the mouse exocrine pancreas in vivo was studied by electron microscopic autoradiography after administration of 3H-leucine. Vinblastine (1.1 mumole/mouse; i.v. injection) was in general given 1 h before radioleucine and 2-4 h before fixation of the pancreas by perfusion with glutaraldehyde. Vinblastine causes the disappearance of microtubules, mainly present in controls in the apical portion of the acinar cell. After injection of vinblastine, zymogen granules from clusters located throughout the cell but often associated with Golgi areas. The latter are enlarged mainly due to the accumulation of small vesicles. In addition, Golgi areas are displaced, most often in an apical direction. Electron microscopic autoradiography demonstrated that vinblastine delays the appearance of labeled protein in zymogen granules; even 2 h after injection of radioleucine the majority of silver grains is located over the rough endoplasmic reticulum while very few grains are related to zymogen granules. This finding might be related to the structural changes of the Golgi areas observed. Although intracellular migration of protein is retarded, zymogen granules are formed. However, many of the labeled granules are found in peculiar locations, often distant from the acinar lumen. The present study suggests that vinblastine, possibly due to its effect on microtubules, influences both the formation and the translocation of zymogen granules.

The article reviews three multinational projects concerning full-scale nuclear safety experiments at the Marviken power station in Sweden. Experiments in the first project, carried out in 1972 and 1973, were related to the response of the pressure-suppression containment to simulated ruptures in pipe systems connected to the pressure vessel. Experiments in the second project, currently under way, are related to pressure oscillations in the containment system following simulated ruptures in the pipe system. The third project concerns a proposed program for the experimental investigation of critical mass flow through simulated ruptures in a full-scale piping system.

The cellular and subcellular distribution of radioactivity in the mouse thyroid gland different times (20 min — 8 hours) after intravenous administration of 3H-L-DOPA was studied by means of quantitative electron microscopic autoradiography.

Thyroid parafollicular cells of normocalcemic and vitamin D2-treated rats were investigated by electron microscopy and with the histochemical fluorescence technique of Hillarp and Falck.