Implications of Seedling Emergence to Site Restoration following Bauxite Mining in Western Australia

Seedling emergence of 12 selected northern jarrah (Eucalyptus marginata Donn ex Smith) forest species were investigated to assist Alcoa of Australia Ltd. in maximizing the establishment of topsoil species in rehabilitated bauxite mining sites. The species, which encompassed a range of seed weights (0.024 mg to 87 mg), plant families, seed-storage types, life forms, and germination requirements, were placed on the soil surface and at depths of 1, 2, 5, 10, and 15 cm under controlled conditions in a glasshouse. Ability to emerge from deep burial was found to depend on seed size for species that annually release their seed to the topsoil but not for species that store their seed on the plant. All selected species were capable of emerging from 2 cm depth of burial, but eight of the 12 species were either unable to emerge from 5 cm or showed a significant reduction in emergence from 5 cm depth of burial compared to optimally buried seed. This group included two small-seeded species, Stylidium calcaratum and Chamaescilla corymbosa; the major forest dominant, Eucalyptus marginata; the serotinous canopy-borne seed of Hakea amplexicaulis; and the wind-dispersed seed of Xanthorrhoea gracilis. A few seeds of the legume species Kennedia coccinea, Acacia pulchella, and Bossiaea aquifolium established seedlings from depths of 15 cm. Currently, Alcoa removes the upper 15 cm of topsoil separately from the underlying soil prior to the commencement of mining. This topsoil is respread at a similar depth following mining as part of the rehabilitation procedure. It is recommended that Alcoa continue to strip topsoil to a depth of 15 cm but investigate the option of re-spreading topsoil onto rehabilitated pits at a shallower depth to maximize establishment via the soil seed bank.     

Nerve Growth Factor Administration Attenuates Cognitive but Not Neurobehavioral Motor Dysfunction or Hippocampal Cell Loss Following Fluid-Percussion Brain Injury in Rats

Abstract: Lateral fluid-percussion brain injury in rats results in cognitive deficits, motor dysfunction, and selective hippocampal cell loss. Neurotrophic factors have been shown to have potential therapeutic applications in neurodegenerative diseases, and nerve growth factor (NGF) has been shown to be neuroprotective in models of excitotoxicity. This study evaluated the neuroprotective efficacy of intracerebral NGF infusion after traumatic brain injury. Male Sprague-Dawley rats received lateral fluid-percussion brain injury of moderate severity (2.1–2.3 atm). A miniosmotic pump was implanted 24 h after injury to infuse NGF (n = 34) or vehicle (n = 16) directly into the region of maximal cortical injury. Infusions of NGF continued until the animal was killed at 72 h, 1 week, or 2 weeks after injury. Animals were evaluated for cognitive dysfunction (Morris Water Maze) and regional neuronal cell loss (Nissl staining) at each of the three time points. Animals surviving for 1 or 2 weeks were also evaluated for neurobehavioral motor function. Although an improvement in memory scores was not observed at 72 h after injury, animals receiving NGF infusions showed significantly improved memory scores when tested at 1 or 2 weeks after injury compared with injured animals receiving vehicle infusions ( p < 0.05). Motor scores and CA3 hippocampal cell loss were not significantly different in any group of NGF-treated animals when compared with controls. These data suggest that NGF administration, in the acute, posttraumatic period following fluid-percussion brain injury, may have potential in improving post-traumatic cognitive deficits.     

Isolation,culture and regeneration of protoplasts from birdsfoot trefoil (Lotus corniculatus)

A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus L. cv. Leo). Green cotyledons from in vitro grown seedlings were preplasmolyzed in CPW salts containing 13% mannitol (CPW 13 M) for 1 h prior to the enzyme treatment. The enzyme formula consisted of 2% (w/v) Onozuka Cellulase R-10, 1% (w/v) Macerase and 0.1% (w/v) Pectolyase Y-23 in CPW 13 M. This method produced high yields of viable protoplasts after purification. The procedure is reproducible and takes approximately 2.5 months from protoplast isolation to plantlet establishment in a greenhouse. More than 100 plantlets were grown in soil. Two somaclonal variants, a chimeric plant for chlorophyll production and an albino cell line, have been obtained by this procedure.     

Predator Avoidance and Alarm-response Behaviour in Kin-discriminating Tadpoles (Rana cascadae)

When captured by predators, the tadpoles of some species of frogs and toads may release an alarm substance that alters the behaviour of conspecifics. Such ‘alarm response’ behaviour has been proposed as a potential mechanism whereby related conspecifics may ‘warn’ relatives of a predator's presence and thus, improve their inclusive fitness. We examined predator avoidance and alarm response behaviour in tadpoles of the Cascades frog (Rana cascadae) and tested whether such behaviour is influenced by kinship factors. Tadpoles reduced activity when in the presence of a predatory newt (Taricha granulosa). Individuals in sibling groups were more active than both solitary tadpoles and individuals in mixed groups of siblings and nonsiblings. However, we found no evidence of an alarm response in R. cascadae. Behaviour of tadpoles in groups exposed only to predators was not different from that of tadpoles in groups exposed to predators plus crushed conspecifics. Tadpoles in groups exposed to crushed tadpoles were as active as tadpoles in groups exposed to water controls, and some test individuals fed upon the dead tadpoles. Thus, while R. cascadae tadpoles reduce activity in response to newt predators, crushed tadpoles appear to initiate a feeding response rather than an alarm response as has been previously proposed.     

THE FOUNDING OF A NEW POPULATION OF DARWIN'S FINCHES

We report the natural colonization of the small Galápagos island Daphne Major by the large ground finch (Geospiza magnirostris). Immigrants of this species were present in every year of a 22-yr study, 1973–1994. Typically they arrived after a breeding season and left at the beginning of the next one. Geospiza magnirostris bred on the island for the first time in the exceptionally wet El Niño year of 1982–1983, and bred in all subsequent years except drought years. In agreement with theoretical expectations the frequency of inbreeding was unusually high. Pronounced fluctuating asymmetry in tarsus length, together with slightly reduced breeding success of inbreeding pairs, suggests a low level of inbreeding depression. Despite this, the population increased from 5 breeding individuals in 1983 to 20 breeding individuals in 1992, and probably more than twice that number in 1993, largely through recruitment of locally born birds.     

Catalytic components of proteasomes and the regulation of proteinase activity

The proteasome (multicatalytic proteinase complex) is a large multimeric complex which is found in the nucleus and cytoplasm of eukaryotic cells. It plays a major role in both ubiquitin-dependent and ubiquitin-independent nonlysosomal pathways of protein degradation. Proteasome subunits are encoded by members of the same gene family and can be divided into two groups based on their similarity to the and subunits of the simpler proteasome isolated fromThermoplasma acidophilum. Proteasomes have a cylindrical structure composed of four rings of seven subunits. The 26S form of the proteasome, which is responsible for ubiquitin-dependent proteolysis, contains additional regulatory complexes. Eukaryotic proteasomes have multiple catalytic activities which are catalysed at distinct sites. Since proteasomes are unrelated to other known proteases, there are no clues as to which are the catalytic components from sequence alignments. It has been assumed from studies with yeast mutants that -type subunits play a catalytic role. Using a radiolabelled peptidyl chloromethane inhibitor of rat liver proteasomes we have directly identified RC7 as a catalytic component. Interestingly, mutants in Prel, the yeast homologue of RC7, have already been reported to have defective chymotrypsin-like activity. These results taken together confirm a direct catalytic role for these -type subunits. Proteasome activities are sensitive to conformational changes and there are several ways in which proteasome function may be modulatedin vivo. Our recent studies have shown that in animal cells at least two proteasome subunits can undergo phosphorylation, the level of which is likely to be important for determining proteasome localization, activity or ability to form larger complexes. In addition, we have isolated two isoforms of the 26S proteinase.