The complementary information provided by combined MRI-PET modalities promises to facilitate metabolic investigations of complex physiological processes. We developed a radio frequency (RF) coil array that can operate in close proximity (2-mm radial distance) to a miniaturized PET camera insert for simultaneous PET-MRI of a rat brain at high magnetic fields (4 Tesla). All ferromagnetic components in the PET instrument were replaced with non-ferromagnetic components to minimize susceptibility artefacts in MRI, and optical fibres were used to connect the electronics of the PET camera to the acquisition system located outside the MRI scanner room. A passive electromagnetic shielding was developed to minimize the interference between the PET-electronics and MRI RF coil array. MR images of water phantoms and "ex-vivo" rat brains were collected in two different conditions: with and without PET acquisition. Similarly, PET data was acquired in two different conditions: with and without MRI pulses (RF and gradients). The MR images showed good uniform sensitivity profiles for all cases and 66% decrease in SNR for the shielded case. The PET and MRI datasets demonstrated that the electromagnetic shielding successfully minimizes the RF interference between the instruments, minimizing MRI artefacts and protecting the delicate components of the PET electronics from MRI RF pulses.

Comunidades de fungos micorrízicos arbusculares (FMAs) foram estudadas em diferentes ecossistemas, no sul da Austrália. A extração dos esporos do solo foi efetuada pelo método de peneiramento úmido, para posterior quantificação e identificação das espécies de FMAs. A percentagem de raízes colonizadas também foi determinada. Associações micorrízicas foram comuns em todos os ecossistemas estudados. Os esporos foram mais abundantes no sistema de pastagem permanente e menor no sistema de plantio contínuo com trigo. Percebeu-se a incidência de associações micorrízicas nas diferentes espécies de planta e a ocorrência de Arum e Paris-tipo de colonização. Esporos de 17 espécies de FMAs foram identificados durante as variações sazonais de 1996 e 1997 no sistema de permanente pastagem e em quatro hospedeiros (Plantago lanceolata, Sorghum sp., Trifolium subterraneum, Lolium perenne) cultivados em casa de vegetação. Glomus mosseae foi a espécie dominante em todas as épocas de coleta e nos vasos de cultivo. A diversidade micorrízica não foi significativa nas diferentes épocas de amostragem no campo, mas esta foi significativa nas culturas armadilhas. P. lanceolata, Sorghum sp. e T. subterraneum como hospedeiras das culturas armadilhas não mostraram diferença no número e diversidade de esporos de FMAs associados ao sistema radicular. Entretanto, o número e a diversidade de espécies foram mais baixas com L. perenne (principalmente em dezembro de 1996). A identificação de esporos extraídos do solo do campo e de plantas armadilhas é essencial para o estudo das populações e diversidade dos FMAs. Este trabalho proprociona dados para monitoramento das populações usando técnicas convencionais e material para determinação da efetividade simbiótica de espécies chaves da comunidade de FMAs.

Communities of arbuscular mycorrhizal fungi (AMF) were surveyed in different South Australian ecosystems. The soil was wet-sieved for spore extraction, followed by the determination of presence and abundance of AMF species as well as the percentage of root colonization. Mycorrhizal associations were common and there was substantial fungal diversity in different ecosystems. Spores were most abundant in the permanent pasture system and less abundant under continuous wheat. The incidence of mycorrhizal associations in different plant species and the occurrence of Arum and Paris type colonization generally conformed with previous information. Spores of seventeen AMF were verified throughout seasonal changes in 1996 and 1997 in the permanent pasture and on four host species (Lolium perenne, Plantago lanceolata, Sorghum sp. and Trifolium subterraneum) , set up with the same soils under greenhouse conditions. Glomus mosseae was the dominant spore type at all sampling times and in all trap cultures. Mycorrhizal diversity was significantly affected by different sampling times in trap cultures but not in field-collected soil. P. lanceolata, Sorghum sp. and T. subterraneum as hosts for trap cultures showed no differences in richness and diversity of AMF spores that developed in association with their roots. Abundance and diversity were lowest, however, in association with L. perenne , particularly in December 1996. Results show that the combination of spore identification from field-collected soil and trap cultures is essential to study population and diversity of AMF. The study provides baseline data for ongoing monitoring of mycorrhizal populations using conventional methods and material for the determination of the symbiotic effectiveness of AMF key members.