Sediment transport in an inland river in North Queensland

Rivers in northern Queensland are ephemeral and carry water mainly as a direct response to heavy rainfall. Sediment is transported downstream with the runoff and sediment deposition may be a major problem in many proposed reservoirs. Hence information about sediment transport, particularly under high flow conditions, is required for planning and design of water storage reservoirs. In this region, bed material samples can be obtained during low flow periods and suspended sediment sampling during floods is possible but only with difficulty. Little reliable data is available.This paper outlines a possible approach to predicting sediment loads in such rivers. Suspended sediment samples have been analysed to give both particulate concentrations and their grain size distributions. The latter have been compared with bed material size distributions, and the concentrations of suspended bed material and wash load components have been estimated.After investigations of a number of methods for predicting bed material transport, those which treat bed load and suspended load independently have been selected. Field data have been used to determine the wash load and the suspended bed material load. The bed load was then computed so that the total sediment load could be determined.This approach has been applied to the Flinders River at Glendower, based on field data obtained by the Queensland Water Resources Commission in 1982/83.     

Compartmentation of glutamate metabolism in brain. Evidence for the existence of two different tricarboxylic acid cycles in brain

1. (14)C from [1-(14)C]glucose injected intraperitoneally into mice is incorporated into glutamate, aspartate and glutamine in the brain to a much greater extent than (14)C from [2-(14)C]glucose. This difference for [1-(14)C]glucose and [2-(14)C]glucose increases with time. The amount of (14)C in C-1 of glutamate increases steadily with time with both precursors. It is suggested that a large part of the glutamate and aspartate pools in brain are in close contact with intermediates of a fast-turning tricarboxylic acid cycle. 2. (14)C from [1-(14)C]acetate and [2-(14)C]acetate is incorporated to a much larger extent into glutamine than into glutamate. An examination of the time-course of (14)C incorporated into glutamine and glutamate reveals that glutamine is not formed from the glutamate pool, labelled extensively by glucose, but from a small glutamate pool. This small glutamate pool is not derived from an intermediate of a fast-turning tricarboxylic acid cycle. 3. It is proposed that two different tricarboxylic acid cycles exist in brain.     

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The findings in and experiences with 19 consecutive patients subjected to open mitral valve surgery are described. All patients underwent a right-heart catheterization. In order to exclude multivalvular heart disease, a left-heart catheterization was performed in 10 patients and angiographic studies of the aortic valve area in 12. Pulmonary function studies were performed on 11 patients. The FEV (0.75 sec.) and the MMFR were found to correlate well with existing pulmonary reserves.Fourteen of the 19 patients subjected to open mitral valve surgery survived the operation and have been followed up for three months to 2½ years. Four patients had a mitral valvuloplasty. Three of these four have deteriorated and will require a valvular replacement. Ten of 15 patients subjected to a mitral valve replacement are alive; five of these 10 have had signs and symptoms indicating peripheral embolization. Mitral valvuloplasty is preferable to a valvular replacement as far as embolic complications are concerned, while valvular replacements result in a more perfect and lasting hemodynamic repair. The high incidence of peripheral embolization following valvular replacements focuses attention on the need for improved mitral valve prostheses.     

Structure-function analysis of recombinant substrate protein 22 kDa (SP-22). A mitochondrial 2-CYS peroxiredoxin organized as a decameric toroid

Bovine mitochondrial SP-22 is a member of the peroxiredoxin family of peroxidases. It belongs to the peroxiredoxin 2-Cys subgroup containing three cysteines at positions 47, 66, and 168. The cloning and overexpression in Escherichia coli of recombinant wild type SP-22 and its three cysteine mutants (C47S, C66S, and C168S) are reported. Purified His-tagged SP-22 was fully active with Cys-47 being confirmed as the catalytic residue. The enzyme forms a stable decameric toroid consisting of five basic dimeric units containing intermolecular disulfide bonds linking the catalytically active Cys-47 of one subunit and Cys-168 of the adjacent monomer. The disulfide bonds are not required for overall structural integrity. The toroidal units have average external and internal diameters of 15 and 7 nm, respectively, and can form stacks in a lateral arrangement of two or three rings. C47S had a pronounced tendency to stack in long tubular structures containing up to 60 rings. Further unusual structural features are the presence of radial spikes projecting from the external surface and ordered electron-dense material within the central cavity of the toroid.     

Probing the active site of the sugar isomerase domain from E. coli arabinose-5-phosphate isomerase via X-ray crystallography

Lipopolysaccharide (LPS) biosynthesis represents an underexploited target pathway for novel antimicrobial development to combat the emergence of multidrug‐resistant bacteria. A key player in LPS synthesis is the enzyme D ‐arabinose‐5‐phosphate isomerase (API), which catalyzes the reversible isomerization of D ‐ribulose‐5‐phosphate to D ‐arabinose‐5‐phosphate, a precursor of 3‐deoxy‐D ‐manno‐octulosonate that is an essential residue of the LPS inner core. API is composed of two main domains: an N‐terminal sugar isomerase domain (SIS) and a pair of cystathionine‐β‐synthase domains of unknown function. As the three‐dimensional structure of an enzyme is a prerequisite for the rational development of novel inhibitors, we present here the crystal structure of the SIS domain of a catalytic mutant (K59A) of E. coli D ‐arabinose‐5‐phosphate isomerase at 2.6‐Å resolution. Our structural analyses and comparisons made with other SIS domains highlight several potentially important active site residues. In particular, the crystal structure allowed us to identify a previously unpredicted His residue (H88) located at the mouth of the active site cavity as a possible catalytic residue. On the basis of such structural data, subsequently supported by biochemical and mutational experiments, we confirm the catalytic role of H88, which appears to be a generally conserved residue among two‐domain isomerases.     

<Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> inhibits <Emphasis Type="Italic">in-vitro Candida</Emphasis> biofilm development

Background  

Elucidation of the communal behavior of microbes in mixed species biofilms may have a major impact on understanding infectious diseases and for the therapeutics. Although, the structure and the properties of monospecies biofilms and their role in disease have been extensively studied during the last decade, the interactions within mixed biofilms consisting of bacteria and fungi such as Candida spp. have not been illustrated in depth. Hence, the aim of this study was to evaluate the interspecies interactions of Pseudomonas aeruginosa and six different species of Candida comprising C. albicans, C. glabrata, C. krusei, C. tropicalis, C. parapsilosis, and C. dubliniensis in dual species biofilm development.