Morphology of the thyroid in coastal and noncoastal populations of the koala (Phascolarctos cinereus) in Queensland

The gross morphology, histology, and ultrastructure of the thyroid gland of the koala, Phascolarctos cinereus, is described. Generally, the glands were found to contain large-diameter follicles in association with an epithelium of low height. Morphometric analysis demonstrated a high relative thyroid weight (0.3 +/- 0.2 g/kg) for koalas compared with the 0.07-0.24 g/kg typical of eutherian mammals and 0.03-0.1 g/kg found in other marsupials. The relative thyroid weight of glands (0.33 +/- 0.21 g/kg) from the coastal population (less than 28 km from the coastline) was found to be significantly higher (ANOVA: P = 0.007, significant at the 1% level) than that for glands (0.21 +/- 0.11 g/kg) of noncoastal koalas (greater than 28 km from the coastline). Follicle size was positively correlated (at the 0.1% level) with relative thyroid weight in the overall koala sample. The presence of C cells, occurring singly in the epithelial layer, was demonstrated in electron micrographs. Structural features such as low epithelial height, large follicle length and width, and large intercellular spaces in association with low concentrations of free TS (3.3 +/- 2.1 pM) and free T-3 (1.4 +/- 0.9 pM) as reported previously (Lawson et al., 1996) are consistent with an unusually low level of glandular activity in the koala thyroid even though iodine concentrations in the thyroid gland [4.7 +/- 1.6 mg/g (dry weight)] as well as leaf [0.8 +/- 0.3 mu g (dry weight)] and soil samples [3.8 mu g/g (dry weight)] from the koalas' habitat appear unremarkable. (C) 1998 Academic Press.

The impact of prolonged fasting during aestivation on the structure of the small intestine in the green-striped burrowing frog, Cyclorana alboguttata

The effects of short-term fasting and prolonged fasting during aestivation on the morphology of the proximal small intestine and associated organs were investigated in the green-striped burrowing frog, Cyclorana alboguttata (Anura: Hylidae). Animals were fasted for 1 week while active or for 3-9 months during aestivation. Short-duration fasting (1 week) had little effect on the morphology of the small intestine, whilst prolonged fasting during aestivation induced marked enteropathy including reductions in intestinal mass, length and diameter, longitudinal fold height and tunica muscularis thickness. Enterocyte morphology was also affected markedly by prolonged fasting: enterocyte cross-sectional area and microvillous height were reduced during aestivation, intercellular spaces were visibly reduced and the prevalence of lymphocytes amongst enterocytes was increased. Mitochondria and nuclei were also affected by 9 months of aestivation with major disruptions to mitochondrial cristae and increased clumping of nuclear material and increased infolding of the nuclear envelope. The present study demonstrates that the intestine of an aestivating frog responds to prolonged food deprivation during aestivation by reducing in size, presumably to reduce the energy expenditure of the organ.

Localization and movement of mineral oil in plants by fluorescence and confocal microscopy

Fluorescence and confocal laser scanning microscopy were explored to investigate the movement and localization of mineral oils in citrus. In a laboratory experiment, fluorescence microscopy observation indicated that when a 'narrow' distillation fraction of an nC23 horticultural mineral oil was applied to adaxial and opposing abaxial leaf surfaces of potted orange [Citrus x aurantium L. (Sapindales: Rutaceae)] trees, oil penetrated steadily into treated leaves and, subsequently, moved to untreated petioles of the leaves and adjacent untreated stems. In another experiment, confocal laser scanning microscopy was used to visualize the penetration into, and the subsequent cellular distribution of, an nC24 agricultural mineral oil in C. trifoliata L. seedlings. Oil droplets penetrated or diffused into plants via both stomata and the cuticle of leaves and stems, and then moved within intercellular spaces and into various cells including phloem and xylem. Oil accumulated in droplets in intercellular spaces and within cells near the cell membrane. Oil entered cells without visibly damaging membranes or causing cell death. In a field experiment with mature orange trees, droplets of an nC23 horticultural mineral oil were observed, by fluorescence microscopy, in phloem sieve elements in spring flush growth produced 4-5 months and 16-17 months after the trees were sprayed with oil. These results suggest that movement of mineral oil in plants is both apoplastic via intercellular spaces and symplastic via plasmodesmata. The putative pattern of the translocation of mineral oil in plants and its relevance to oil-induced chronic phytotoxicity are discussed.

Investigation into the ability of Gluconacetobacter sacchari to live as an endophyte in sugarcane

The relatively low numbers and sporadic pattern of incidence of the acetic acid bacterium Gluconacetobacter sacchari with the pink sugarcane mealybug (PSMB) Saccharicoccus sacchari Cockerell (Homoptera: Pseudococcidae) over time and from different sugarcane-growing regions do not indicate that Glac. sacchari is a significant commensal of the PSMB, as has been previously proposed. This study was conducted to investigate the hypothesis that Glac. sacchari is, like its closest relative Glac. diazotrophicus, an endophyte of sugarcane (Saccharum officinarium L.). In this study, both Glac. sacchari and Glac. diazotrophicus were isolated from internal sugarcane tissue, although the detection of both species was sporadic in all sugarcane-growing regions of Queensland tested. To confirm the ability of Glac. sacchari to live endophytically, an experiment was conducted in which the roots of micropropagated sugarcane plantlets were inoculated with Glac. sacchari, and the plantlets were subsequently examined for the presence of the bacterium in the stem cells. Pure cultures of Glac. sacchari were grown from homogenized surface sterilized sugarcane stems inoculated with Glac. sacchari. Electron microscopy was used to provide further conclusive evidence that Glac. sacchari lives as an endophyte in sugarcane. Scanning electron microscopy of (SEM) sugarcane plantlet stems revealed rod-shaped cells of Glac. sacchari within a transverse section of the plantlet stem cells. The numbers of bacterial cells inside the plant cell indicated a successful infection and colonization of the plant tissue. Using transmission electron microscopy, (TEM) bacterial cells were more difficult to find, due to their spatial separation. In our study, bacteria were mostly found singularly, or in groups of up to four cells inside intercellular spaces, although bacterial cells were occasionally found inside other cells.

Hamiltonian mappings and circle packing phase spaces.

We introduce three area preserving maps with phase space structures which resemble circle packings. Each mapping is derived from a kicked Hamiltonian system with one of the three different phase space geometries (planar, hyperbolic or spherical) and exhibits an infinite number of coexisting stable periodic orbits which appear to ‘pack’ the phase space with circular resonances.