Role of PGF(2 alpha) and oxytocin in parturition in the brushtail possum (Trichosurus vulpecula)

Maturation of the fetal pituitary and adrenal glands allows the secretion of cortisol, which in turn leads to an increase in prostaglandin and mesotocin production. The production of prostaglandin and mesotocin results in an increase in uterine contractions and initiates birth in marsupials. The major metabolite of PGF(2alpha), 13,14-dihydro-15-keto-prostaglandin F-2alpha (PGFM), has been found in the plasma of the possum at the time of birth and administration of PGF(2alpha) to female possums induced the adoption of the birth position. Evidence that mesotocin is an integral hormone of birth in the tammar wallaby indicates that both PGF(2alpha) and mesotocin or oxytocin are required for marsupial birth. The presence of PGF(2alpha) receptors in the uterus and corpus luteum of the possum, and the in vitro uterine responsiveness to PGF(2alpha) or oxytocin, were examined. PGF(2alpha) receptors were not observed in possum uteri and the inability of PGF(2alpha) to cause contractions indicates that PGF(2alpha) is not involved directly in contraction of the uterus at parturition. The presence of oxytocin and mesotocin receptors in the uterus of possoms and the ability of oxytocin to induce uterine contraction in vitro supports the view that mesotocin is required for expulsion of the young from the uterus. Low numbers of PGF(2alpha) receptors were found in the possum corpus luteum at birth, indicating an involvement of PGF(2alpha) in regression of the corpus luteum.

Effects of the herbicide diuron on the early life history stages of coral

The effects of the herbicide diuron on the early life history stages of broadcast spawning and brooding corals were examined in laboratory experiments. Fertilisation of Acropora millepora and Montipora aequituberculata oocytes were not inhibited at diuron concentrations of up to 1000 mu gl(-1). Metamorphosis of symbiont-free A. millepora larvae was only significantly inhibited at 300 mu gl(-1) diuron. Pocillopora damicornis larvae, which contain symbiotic dinoflagellates, were able to undergo metamorphosis after 24h exposure to diuron at 1000 mu gl(-1). Two-week old P. damicornis recruits on the other hand were as susceptible to diuron as adult colonies, with expulsion of symbiotic dinoflagellates (bleaching) evident at 10 mu gl(-1) diuron after 96 h exposure. Reversible metamorphosis was observed at high diuron concentrations, with fully bleached polyps escaping from their skeletons. Pulse amplitude modulation (PAM) chlorophyll fluorescence techniques demonstrated a reduction in photosynthetic efficiency (Delta F/F'(m)) in illuminated P. dami- cornis recruits after a 2h exposure to 1 mu gl(-1) diuron. The dark-adapted quantum yields (F-v/F-m also declined, indicating chronic photoinhibition and damage to photosystem H. Crown Copyright (c) 2004 Published by Elsevier Ltd. All rights reserved.

Liquid distribution as a means to describing the granule growth mechanism

Copper concentrate (chalcopyrite) was granulated in a rotating drum with a diameter of 0.3 m and a length of 0.2 m. Water was used as the binder and it was sprayed onto the powder bed with a nozzle. This material exhibited induction type behaviour, which was defined by Iveson and Litster [AIChE J. 44 (1998) 1510]. Induction type behaviour is characterized by the occurrence of an induction stage, during which the granules are gradually being compacted and little or no growth occurs. At the end of this induction stage, binder liquid is squeezed from the interior of the granules onto the granule surface and the granules are then surface-wet. This results in a rapid growth rate of the granules. Different types of experiments were conducted. The influence of the nozzle pressure and the distance from the nozzle to the powder bed on the growth behaviour of the granules as well as on the binder distribution was examined. The results of these experiments led to the postulation of a modified mechanism for induction type behaviour: it was found that after the binder was delivered, there were large granules containing a high amount of binder and small granules containing less binder. During the induction stage, the granules are compacted and binder liquid continuously appears at the surface of the large granules. These wet spots that are continuously being formed pick up the dry and small granules. When all the small granules have been picked up, further expulsion of binder liquid onto the granules' surface results in granules that remain surface-wet. This phenomenon marks the end of the induction stage and it coincides with the disappearance of the small granules. The hypothesis was tested by selectively removing the smaller granules during an experiment. As expected, this resulted in a shorter induction time.

The investigation of optimal bombardment parameters for transient and stable transgene expression in sorghum

This report outlines the development of optimized particle inflow gun (PIG) parameters for producing transgenic sorghum (Sorghum bicolor (L.) Moench). Both transient and stable expression were examined when determining these parameters. The uidA reporter gene (GUS) encoding beta -glucuronidase was used in transient experiments and the green fluorescent protein (GFP) used to monitor stable expression. Initially, optimization was conducted using leaf segments, as the generation of sorghum callus in sufficiently large quantities is time-consuming. Following leaf optimization, experiments were conducted using callus, identifying a high similarity between the two tissue types (r(s) = 0.83). High levels of GUS expression were observed in both leaf and callus material when most distant from the DNA expulsion point, and using a pressure greater than 1800 kPa. A higher level of expression was also observed when the aperture of the helium inlet valve was constricted. Using the optimized conditions (pressure of 2200 kPa, distance to target tissue of 15 cm from the expulsion point, and the aperture of the helium inlet valve at one full turn), three promoters (Ubiquitin, Actin1 and CaMV 35S) were evaluated over a 72-h period using GUS as the reporter gene. A significantly higher number of GUS foci were counted with the Ubiquitin construct over this period, compared to the Actin1 and CaMV 35S constructs. Stable callus sectors (on 2 mg l(-1) bialaphos) with GFP expression were visualized for as long as 6 wk post-bombardment. Using this optimized protocol, several plants were regenerated after having been bombarded with the pAHC20 construct (containing the bar gene), with molecular evidence confirming integration.

Tolerance of endolithic algae to elevated temperature and light in the coral Montipora monasteriata from the southern Great Barrier Reef

Photosynthetic endolithic algae and cyanobacteria live within the skeletons of many scleractinians. Under normal conditions, less than 5% of the photosynthetically active radiation (PAR) reaches the green endolithic algae because of the absorbance of light by the endosymbiotic dinoflagellates and the carbonate skeleton. When corals bleach (loose dinoflagellate symbionts), however, the tissue of the corals become highly transparent and photosynthetic microendoliths may be exposed to high levels of both thermal and solar stress. This study explores the consequence of these combined stresses on the phototrophic endoliths inhabiting the skeleton of Montipora monasteriata, growing at Heron Island, on the southern Great Barrier Reef. Endoliths that were exposed to sun after tissue removal were by far more susceptible to thermal photoinhibition and photo-damage than endoliths under coral tissue that contained high concentrations of brown dinoflagellate symbionts. While temperature or light alone did not result in decreased photosynthetic efficiency of the endoliths, combined thermal and solar stress caused a major decrease and delayed recovery. Endoliths protected under intact tissue recovered rapidly and photoacclimated soon after exposure to elevated sea temperatures. Endoliths under naturally occurring bleached tissue of M. monasteriata colonies (bleaching event in March 2004 at Heron Island) acclimated to increased irradiance as the brown symbionts disappeared. We suggest that two major factors determine the outcome of thermal bleaching to the endolith community. The first is the microhabitat and light levels under which a coral grows, and the second is the susceptibility of the coral-dinoflagellates symbiosis to thermal stress. More resistant corals may take longer to bleach allowing endoliths time to acclimate to a new light environment. This in turn may have implications for coral survival.