Altered shoot/root Na+ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na+ transporter AtHKTI1

Sodium (Na+) is toxic to most plants, but the molecular mechanisms of plant Na+ uptake and distribution remain largely unknown. Here we analyze Arabidopsis lines disrupted in the Na+ transporter AtHKT1. AtHKT1 is expressed in the root stele and leaf vasculature. athkt1 null plants exhibit lower root Na+ levels and are more salt resistant than wild-type in short-term root growth assays. In shoot tissues, however, athkt1 disruption produces higher Na+ levels, and athkt1 and athktl/sos3 shoots are Na+-hypersensitive in long-term growth assays. Thus wild-type AtHKT1 controls root/shoot Na+ distribution and counteracts salt stress in leaves by reducing leaf Na+ accumulation. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

Structural ordering of coal char during heat treatment and its impact on reactivity

The effect of heat treatment on the structure of an Australian semi-anthracite char was studied in detail in the 850-1150degreesC temperature range using XRD, HRTEM, and electrical resistivity techniques. It was found that the carbon crystallite size in the char does not change significantly during heat treatment in the temperature range studied, for both the raw coal and its ash-free derivative obtained by acid treatment. However, the fraction of the organized carbon in the raw coal chars, determined by XRD, increased with increase of heat treatment time and temperature, while that for the ash-free coal chars remained almost unchanged. This suggests the occurrence of catalytic ordering during heat treatment, supported by the observation that the electrical resistivity of the raw coal chars decreased with heat treatment, while that of the ash-free coal chars did not vary significantly. Further confirmatory evidence was provided by high resolution transmission electron micrographs depicting well-organized carbon layers surrounding iron particles. It is also found that the fraction of organized carbon does not reach unity, but attains an apparent equilibrium value that increases with increase in temperature, providing an apparent heat of ordering of 71.7 kJ mol(-1) in the temperature range studied. Good temperature-independent correlation was found between the electrical resistivity and the organized carbon fraction, indicating that electrical resistivity is indeed structure sensitive. Good correlation was also found between the electrical resistivity and the reactivity of coal char. All these results strongly suggest that the thermal deactivation is the result of a crystallite-perfecting process, which is effectively catalyzed by the inorganic matter in the coal char. Based on kinetic interpretation of the data it is concluded that the process is diffusion controlled, most likely involving transport of iron in the inter-crystallite nanospaces in the temperature range studied. The activation energy of this transport process is found to be very low, at about 11.8 kJ mol(-1), which is corroborated by model-free correlation of the temporal variation of organized carbon fraction as well as electrical resistivity data using the superposition method, and is suggestive of surface transport of iron. (C) 2002 Elsevier Science Ltd. All rights reserved.

The R8-BC8 phases and crystal growth in monocrystalline silicon under microindentation with a spherical indenter

The morphology and distribution of high-pressure metastable phases BC8 and R8, formed in monocrystalline silicon under microindentation, were identified and assessed using transmission electron microscopy nanodiffraction analysis. It was discovered that the crystal growth inside the transformation zone was stress-dependent with large crystals in its central region. The crystal size could also be increased using higher maximum indentation loads. The BC8 and R8 phases distributed unevenly across the transformation zone, with BC8 crystals mainly in the center of the zone and smaller R8 fragments in the peripheral regions. Such phase distribution was in agreement with the theoretical residual stress analysis.

Ion-trapping, microsomal binding, and unbound drug distribution in the hepatic retention of basic drugs

This study investigated the relative contribution of ion-trapping, microsomal binding, and distribution of unbound drug as determinants in the hepatic retention of basic drugs in the isolated perfused rat liver. The ionophore monensin was used to abolish the vesicular proton gradient and thus allow an estimation of ion-trapping by acidic hepatic vesicles of cationic drugs. In vitro microsomal studies were used to independently estimate microsomal binding and metabolism. Hepatic vesicular ion-trapping, intrinsic elimination clearance, permeability-surface area product, and intracellular binding were derived using a physiologically based pharmacokinetic model. Modeling showed that the ion-trapping was significantly lower after monensin treatment for atenolol and propranolol, but not for antipyrine. However, no changes induced by monensin treatment were observed in intrinsic clearance, permeability, or binding for the three model drugs. Monensin did not affect binding or metabolic activity in vitro for the drugs. The observed ion-trapping was similar to theoretical values estimated using the pHs and fractional volumes of the acidic vesicles and the pK(a) values of drugs. Lipophilicity and pK(a) determined hepatic drug retention: a drug with low pK(a) and low lipophilicity (e.g., antipyrine) distributes as unbound drug, a drug with high pK(a) and low lipophilicity (e.g., atenolol) by ion-trapping, and a drug with a high pK(a) and high lipophilicity (e.g., propranolol) is retained by ion-trapping and intracellular binding. In conclusion, monensin inhibits the ion-trapping of high pK(a) basic drugs, leading to a reduction in hepatic retention but with no effect on hepatic drug extraction.

Protein contamination of the laryngeal mask airway and its relationship to re-use

The Laryngeal Mask Airway is a reusable device for maintaining the patency of a patient's airway during general anaesthesia. The device can be reused after it has been cleaned and sterilized. Protein contamination of medical instruments is a concern and has been found to occur despite standard sterilization techniques. The reason for the concern relates to the possibility of the transmission of prions and the risk of developing a neurodegenerative disorder such as Creutzveldt-Jacob disease. The purpose of this study was to quantify the amount of protein contamination that occurs, and to relate this to the number of times the Laryngeal Mask Airway has been used. Fifty previously used Classic Laryngeal Masks were collected after routine sterilization and packaging. The devices were immersed in protein detecting stain and then visual inspection performed to assess the degree and distribution of the staining. The researcher was blinded to the number of times the Laryngeal Mask Airway had been used. Linear regression analysis of the degrees of staining of the airway revealed that protein contamination occurs after the first use of the device and this increases with each subsequent use. This finding highlights the concern that the currently used cleaning and sterilization methods do not prevent the accumulation of proteinaceous material on Laryngeal Mask Airways. Consideration should be given to the search for more efficient cleaning and sterilization techniques or the use of disposable devices.

Genetic and Cultural Transmission of Smoking Initiation: An Extended Twin Kinship Model

Background Considerable evidence from twin and adoption studies indicates that genetic and shared environmental factors play a significant role in the initiation of smoking behavior. Although twin and adoption designs are powerful to detect genetic and environmental influences, they do not provide information on the processes of assortative mating and parent–offspring transmission and their contribution to the variability explained by genetic and/or environmental factors. Methods We examined the role of genetic and environmental factors for smoking initiation using an extended kinship design. This design allows the simultaneous testing of additive and non-additive genetic, shared and individual-specific environmental factors, as well as sex differences in the expression of genes and environment in the presence of assortative mating and combined genetic and cultural transmission. A dichotomous lifetime smoking measure was obtained from twins and relatives in the Virginia 30,000 sample. Results Results demonstrate that both genetic and environmental factors play a significant role in the liability to smoking initiation. Major influences on individual differences appeared to be additive genetic and unique environmental effects, with smaller contributions from assortative mating, shared sibling environment, twin environment, cultural transmission and resulting genotype–environment covariance. The finding of negative cultural transmission without dominance led us to investigate more closely two possible mechanisms for the lower parent–offspring correlations compared to the sibling and DZ twin correlations in subsets of the data: (i) age × gene interaction, and (ii) social homogamy. Neither mechanism provided a significantly better explanation of the data, although age regression was significant. Conclusions This study showed significant heritability, partly due to assortment, and significant effects of primarily non-parental shared environment on smoking initiation.

Determination of the orientational distribution and orientation factor for transfer between membrane-bound fluorophores using a confocal microscope

Orientational fluorophores have been a useful tool in physical chemistry, biochemistry, and more recently structural biology due to the polarized nature of the light they emit and that fact that energy can be transferred between them. We present a practical scheme in which measurements of the intensity of emitted fluorescence can be used to determine limits on the mean and distribution of orientation of the absorption transition moment of membrane-bound. uorophores. We demonstrate how information about the orientation of. uorophores can be used to calculate the orientation factor k(2) required for use in FRET spectroscopy. We illustrate the method using images of AlexaFluor probes bound to MscL mechanosensitive transmembrane channel proteins in spherical liposomes.

Facilitating soil-and plant-water research through the use of TDR

The development of TDR for measurement of soil water content and electrical conductivity has resulted in a large shift in measurement methods for a breadth of soil and hydrological characterization efforts. TDR has also opened new possibilities for soil and plant research. Five examples show how TDR has enhanced our ability to conduct our soil- and plant-water research. (i) Oxygen is necessary for healthy root growth and plant development but quantitative evaluation of the factors controlling oxygen supply in soil depends on knowledge of the soil water content by TDR. With water content information we have modeled successfully some impact of tillage methods on oxygen supply to roots and their growth response. (ii) For field assessment of soil mechanical properties influencing crop growth, water content capability was added to two portable soil strength measuring devices; (a) A TDT (Time Domain Transmittivity)-equipped soil cone penetrometer was used to evaluate seasonal soil strengthwater content relationships. In conventional tillage systems the relationships are dynamic and achieve the more stable no-tillage relationships only relatively late in each growing season; (b) A small TDR transmission line was added to a modified sheargraph that allowed shear strength and water content to be measured simultaneously on the same sample. In addition, the conventional graphing procedure for data acquisition was converted to datalogging using strain gauges. Data acquisition rate was improved by more than a factor of three with improved data quality. (iii) How do drought tolerant plants maintain leaf water content? Non-destructive measurement of TDR water content using a flat serpentine triple wire transmission line replaces more lengthy procedures of measuring relative water content. Two challenges remain: drought-stressed leaves alter salt content, changing electrical conductivity, and drought induced changes in leaf morphology affect TDR measurements. (iv) Remote radar signals are reflected from within the first 2 cm of soil. Appropriate calibration of radar imaging for soil water content can be achieved by a parallel pair of blades separated by 8 cm, reaching 1.7 cm into soil and forming a 20 cm TDR transmission line. The correlation between apparent relative permittivity from TDR and synthetic aperture radar (SAR) backscatter coefficient was 0.57 from an airborne flyover. These five examples highlight the diversity in the application of TDR in soil and plant research.

Long-term potentiation of synaptic transmission in the avian hippocampus

The avian hippocampus plays a pivotal role in memory required for spatial navigation and food storing. Here we have examined synaptic transmission and plasticity within the hippocampal formation of the domestic chicken using an in vitro slice preparation. With the use of sharp microelectrodes we have shown that excitatory synaptic inputs in this structure are glutamatergic and activate both NMDA-and AMPA-type receptors on the postsynaptic membrane. In response to tetanic stimulation, the EPSP displayed a robust long-term potentiation (LTP) lasting >1 hr. This LTP was unaffected by blockade of NMDA receptors or chelation of postsynaptic calcium. Application of forskolin increased the EPSP and reduced paired-pulse facilitation: (PPF), indicating an increase in release probability. In contrast, LTP was not associated with a change in the PPF ratio. Induction of LTP did not occlude the effects of forskolin. Thus, in contrast to NMDA receptor-independent LTP in the mammalian brain, LTP in the chicken hippocampus is not attributable to a change in the probability of transmitter release and does not require activation of adenylyl cyclase, These findings indicate that a novel form of synaptic plasticity might underlie learning in the avian hippocampus.

A numerical study of pore-fluid, thermal and mass flow iu fluid-saturated porous rock basins

We present a numerical methodology for the study of convective pore-fluid, thermal and mass flow in fluid-saturated porous rock basins. lit particular, we investigate the occurrence and distribution pattern of temperature gradient driven convective pore-fluid flow and hydrocarbon transport in the Australian North West Shelf basin. The related numerical results have demonstrated that: (1) The finite element method combined with the progressive asymptotic approach procedure is a useful tool for dealing with temperature gradient driven pore-fluid flow and mass transport in fluid-saturated hydrothermal basins; (2) Convective pore-fluid flow generally becomes focused in more permeable layers, especially when the layers are thick enough to accommodate the appropriate convective cells; (3) Large dislocation of strata has a significant influence off the distribution patterns of convective pore;fluid flow, thermal flow and hydrocarbon transport in the North West Shelf basin; (4) As a direct consequence of the formation of convective pore-fluid cells, the hydrocarbon concentration is highly localized in the range bounded by two major faults in the basin.

Structure of the tegument and ectocommensal microorganisms of Gyliauchen nahaensis (Digenea : Gyliauchenidae), an inhabitant of herbivorous fish of the Great Barrier Reef, Australia

The ultrastructure of the tegument and tegument-associated microorganisms of the gyliauchenid digenean Gyliauchen nahaensis is described by transmission and scanning electron microscopy. The tegument is devoid of surface spines and is characterized by a moderately folded apical membrane, abundant vesicles, basal mitochondria, a folded basal plasma membrane, and a thick basal matrix. Microorganisms form a dense biofilm on the tegument of the posterodorsal surface and the excretory papilla. At least 7 microbial morphotypes were identified, including eubacteria, spirochaetes, and nanobacteria.

Increasingly inequitable distribution of general practitioners in Australia, 1986-96

Objective: To document trends in the distribution of general practitioners (GPs) in Australia between 1986 and 1996, adjusted for community need. Methods: Data on the location of GPs, population size and crude mortality in statistical divisions (SD) were obtained from the Australian Bureau of Statistics Census of Population and Housing in 1986 and 1996. From these data, we calculated measures of distribution equality (number of people sharing each GP in each SD) and distribution equity (number of people sharing each GP divided by the crude mortality rate; the Robin Hood Index), and analysed temporal changes in the distribution of GPs. Results: Nationally the number of people sharing each GP fell 11% from 1,038 in 1986 to 921 in 1996. However, in 41 of 57 SDs (72%, p=0.01) the number of people sharing a GP actually increased over this time, and the average Robin Hood Index across SDs fell from 0.943 to 0.783 (p=0.004), indicating increasingly inequitable distribution. Comparing the Robin Hood index values of all SDs ranked in pairs, the value fell in 53 of 57 (93%, p<0.001) paired SDs over the decade. These patterns demonstrate increasing inequity over the decade. The number of people sharing each GP was consistently and substantially lower in the capital city SDs and the Robin Hood Index values were consistently and substantially higher (overserved) compared with country SDs. Conclusions: Despite there being more GPs per capita in Australia, their distribution became increasingly unequal and inequitable between 1986 and 1996, such that rural and remote areas became increasingly poorly served.

Impact of undergraduate and postgraduate rural training, and medical school entry criteria on rural practice among Australian general practitioners: national study of 2414 doctors

Objective To determine the association between rural undergraduate training, rural postgraduate training and medical school entry criteria favouring rural students, on likelihood of working in rural Australian general practice. Methods National case - control study of 2414 rural and urban general practitioners (GPs) sampled from the Health Insurance Commission database. Participants completed a questionnaire providing information on demographics, current practice location and rural undergraduate and postgraduate experience. Results Rural GPs were more likely to report having had any rural undergraduate training [ odds ratio ( OR) 1.61, 95% confidence interval (CI) 1.32 - 1.95] than were urban GPs. Rural GPs were much more likely to report having had rural postgraduate training ( OR 3.14, 95% CI 2.57 - 3.83). As the duration of rural postgraduate training increased so did the likelihood of working as a rural GP: those reporting that more than half their postgraduate training was rural were most likely to be rural GPs ( OR 10.52, 95% CI 5.39 - 20.51). South Australians whose final high school year was rural were more likely to be rural GPs ( OR 3.18, 95% CI 0.99 - 10.22). Conclusions Undergraduate rural training, postgraduate training and medical school entry criteria favouring rural students, all are associated with an increased likelihood of being a rural GP. Longer rural postgraduate training is more strongly associated with rural practice. These findings argue for continuation of rural undergraduate training opportunities and rural entry schemes, and an expansion in postgraduate training opportunities for GPs.

The secondary vascular system of Actinopterygii: interspecific variation in origins and investment

Vascular casts of 3 species of Chondrichthyes, 1 of Dipnoi, 1 of Chondrostei and 14 species of the Teleostei were examined by light and scanning electron microscopy in order to give a qualitative and quantitative analysis of interarterial anastomoses (iaas) that indicate the presence (or absence) of a secondary vascular system (SVS). Anastomoses were found to originate from a variety of different primary blood vessels, many of which have not been previously identified as giving rise to secondary vessels. Segmental arteries derived from the dorsal aorta and supplying body musculature were major sites of origin of the SVS, although there was considerable variation in where, in the hierarchy of arterial branching, the anastomoses occurred. The degree of investment in a SVS was species specific, with more active species having a higher degree of secondary vascularisation. This difference was quantified using an absolute count of iaas between Anguilla reinhardtii and Trachinotus baillonii. A range of general features of the SVS is also described. No evidence of iaas was found on the coeliac, mesenteric or renal circulation in any species. Evidence of iaas was lacking in the dipnoan and chondrichthyan species examined, suggesting that a SVS is restricted to Actinopterygii. The presence and distribution of a SVS does not appear to be exclusively linked to phylogenetic position, but rather to the physiological adaptation of the species.