The oral medicine of tooth wear

This review illustrates, through a series of case histories, how oral medicine insights aid the diagnosis and management of patients with excessive tooth wear. The cases reviewed are drawn from the records of 500 southeast Queensland patients referred to the author over a 12 year period. Patients most at risk of dental erosion have work and sports dehydration, caffeine addiction, gastro-oesophageal reflux, asthma, diabetes mellitus, hypertension or other systemic diseases or syndromes that predispose to xerostomia. Saliva protects the teeth from the extrinsic and intrinsic acids which cause dental erosion. Erosion, exacerbated by attrition and abrasion, is the main cause of tooth wear. These cases illustrate that teeth, oral mucosa, salivary glands, skin and eyes should be examined for evidence of salivary hypofunction and attendant medical conditions. Based on comprehensive oral medicine, dietary analyses and advice, it would seem patients need self-management plans to deal with incipient chronic tooth wear. The alternative is the expensive treatment of pain, occlusal damage and pulp death required to repair the effects of acute severe tooth wear.

Developments in the understanding of South African style SAG mills

The South African style SAG (RoM) mills operate in a window that is almost exclusive from the operation of the Australian and North American mills that have been used for the development of SAG mill models. Combining good quality, test data from the RoM mills is extending and improving these models, and assisting in a practical manner in improving our understanding of SAG/AG milling. Data from high mill loads, both in absolute filling and ball loading, have been used to extend and improve the JK SAG mill model. This improved understanding has been successfully applied to increasing the throughput of a mill by 8%. Data is presented on relationships between power and load for high mill loading. Slurry pooling is common in closed-circuit RoM mills, and the detrimental effect of this has been dramatically demonstrated at ALCOA with a mill throughput increase of over 20%. Techniques for calculating the effects of slurry pooling have been developed and a new pulp lifter system designed to give optimal slurry discharge. The influence of mill speed in shifting the product size distribution has also been measured. (C) 2001 Elsevier Science Ltd. All rights reserved.

Chemistry, properties, and phylogenetic implications of the methylated carrageenans from red algae of the genus Areschougia (Areschougiaceae, Gigartinales, Rhodophyta)

The three Australian-endemic species comprising the genus Aresehougia have been examined to determine the structure of their nonfibrillar wall components. The polysaccharide extracted from the most widely distributed species, A. congesta (Turner) J. Agardh, was shown by compositional analyses, Fourier transform infrared (FTIR) spectroscopy, linkage analysis, and C-13-NMR spectroscopy to be a carrageenan composed predominantly of the repeating disaccharides 6'-O-methylcarrabiose 2,4'-disulfate, carrabiose 2,4-disulfate (the repeating unit of L-carrageenan), 4',6'-O-(1-carboxyethylidene)carrabiose 2-sulfate, and 6'-O-methylcarrabiose 2-sulfate. The carrageenan also contained small amounts of 4-linked Galp residues, some bearing methyl ether substitution at O-3 and some possibly bearing sulfate ester and/or glycosyl substitutions at O-3. The A. congesta carrageenan had unique rheological properties, its gels having some similarities to those of commercial iota -carrageenan but with the viscosity of commercial lambda -carrageenan. Polysaccharides from A. ligulata Harvey ex J. Agardh and A. stuartii Harvey were shown by constituent sugar and FTIR analyses to be sulfated galactans rich in mono-O-methylgalactose. The carrageenan structures of Areschougia spp. were consistent with those of the genera Rhabdonia, Erythroclonium, and Austroclonium, the other genera constituting the family Areschougiaceae.

Liveweight gains of steers at different stocking rates on monospecific Gatton panic and Estrella grass pastures in the Chaco Central region of Paraguay

A grazing trial to study the effect of stocking rate on animal production and botanical composition of Gallon panic (Panicum maximum) and Estrella grass (Cynodon nlemfuensis) was conducted in the central region of the Paraguayan Chaco between 1992 and 1998. The experiment included 6 stocking rates (0.5, 0.8. 1.1, 1.4. 1.7 and 2.0 AU/ha) on individual 4-ha paddocks. The pasture treatments were continuously grazed by yearling steers. replaced annually, over a 4-year grazing period. No fertiliser was used. Botanical composition was recorded annually in autumn from 1992 to 1998 while animal production data were recorded monthly from 1992 to 1996. Relationships between animal productivity and stocking rates were determined by regression analysis. Gallon panic produced greater liveweight gains per head than Estrella grass at low and intermediate stocking rates. However, the slope of the linear relationship between liveweight gain per head and stocking rate increased each year in Gallon panic indicating that the productivity of this grass progressively declined at higher stocking rates over the period of observation. Estrella grass showed less sensitivity to stocking rate but was affected severely by periods of low rainfall.

A multifunctional polyketide-peptide synthetase essential for albicidin biosynthesis in Xanthomonas albilineans

Albicidins, a family of potent antibiotics and phytotoxins produced by the sugarcane leaf scald pathogen Xanthomonas albilineans, inhibit DNA replication in bacteria and plastids. A gene located by Tn5-tagging was confirmed by complementation to participate in albicidin biosynthesis. The gene (xabB) encodes a large protein (predicted Mr 525695), with a modular architecture indicative of a multifunctional polyketide synthase (PKS) linked to a non-ribosomal peptide synthetase (NRPS). At 4801 amino acids in length, XabB is the largest reported PKS–NRPS. Twelve catalytic domains in this multifunctional enzyme are arranged in the order N terminus–acyl-CoA ligase (AL)–acyl carrier protein (ACP)–ß-ketoacyl synthase (KS)–ß-ketoacyl reductase (KR)–ACP–ACP–KS–peptidyl carrier protein (PCP)–condensation (C)–adenylation–PCP–C. The modular architecture of XabB indicates likely steps in albicidin biosynthesis and approaches to enhance antibiotic yield. The novel pattern of domains, in comparison with known PKS–NRPS enzymes for antibiotic production, also contributes to the knowledge base for rational design of enzymes producing novel antibiotics.

Differentiation of peanut seedborne potyviruses and curcumoviruses by RT-PCR

Seedborne peanut viruses pose important constraints to peanut production and safe movement of germ plasm. They also pose a risk of accidental introduction into previously disease-free regions. We have developed reverse transcription-polymerase chain reaction (RT-PCR) assays based on identical cycling parameters which identified peanut stripe, Peanut mottle, Peanut stunt, and Cucumber mosaic viruses through production of specific DNA fragments of 234 bp, 327 bp, 390 bp, and 133 bp, respectively. Assay sensitivity in the picogram range was achieved. The two potyviruses and two cucumoviruses could be differentiated using duplex RT-PCR assays. These assays should be useful for testing peanut leaves or seeds for virus identification in epidemiological studies, seed testing or in post-entry quarantine.

Stenotherms at sub-zero temperatures: thermal dependence of swimming performance in Antarctic fish

We examined the burst swimming performance of two Antarctic fishes, Trematomus bernacchii and T. centronotus, at five temperatures between -1 degreesC and 10 degreesC. As Antarctic fishes are considered one of the most cold specialised and stenothermal of all ectotherms, we predicted they would possess a narrow thermal performance breadth for burst swimming and a correlative decrease in performance at high temperatures. Burst swimming was assessed by videotaping swimming sequences with a 50-Hz video camera and analysing the sequences frame-by-frame to determine maximum velocity, the distance moved throughout the initial 200 ms, and the time taken to reach maximum velocity. In contrast to our prediction, we found both species possessed a wide thermal performance breadth for burst swimming. Although maximum swimming velocity for both T. bernacchii and T. centronotus was significantly highest at 6 degreesC, maximum velocity at ah other test temperatures was less than 20% lower. Thus, it appears that specialisation to a highly stable and cold environment is not necessarily associated with a narrow thermal performance breadth for burst swimming in Antarctic fish. We also examined the ability of the Antarctic fish Pagothenia borchgrevinki to acclimate their burst-swimming performance to different temperatures. We exposed P, borchgrevinki to either -1 degreesC or 4 degreesC for 4 weeks and tested their burst-swimming performance at four temperatures between -1 degreesC and 10 degreesC. Burst-swimming performance of Pagothenia borchgrevinki was unaffected by exposure to either -1 degreesC or 4 degreesC for 4 weeks. Maximum swimming velocity of both acclimation groups was thermally independent over the total temperature range of -1 degreesC to 10 degreesC. Therefore, the loss of any capacity to restructure the phenotype and an inability to thermally acclimate swimming performance appears to be associated with inhabiting a highly stable thermal environment.

A survey of dental and oral trauma in south-east Queensland during 1998

Background: This project investigated the aetiology of dental and oral trauma in a population in southeast Queensland. The literature shows there is a lack of dental trauma studies which are representative of the general Australian population. Method: Twelve suburbs in the south-east district of Queensland were randomly selected according to population density in these suburbs for each 25th percentile. All dental clinics in these suburbs were eligible to participate. Patients presenting with dental and oral trauma were eligible to participate. Results: A total of 197 patients presented with dental/oral trauma over a 12 month period. The age of patients ranged from 1-64 years whilst the most frequently presenting age group was 6-10 years. There was a total of 363 injured teeth with an average of 1.8 injured teeth per patient. Males significantly outnumbered females in the incidence of trauma. Conclusions: The highest frequency of trauma occurred in the 6-10 year age group. Most injuries in this group occurred while playing or riding bicycles. In the next most prevalent trauma group, 16-20 years, trauma occurred as a result of fighting and playing sport. Overall, males significantly outnumbered females by approximately 1.8:1.0. The majority of injuries in the deciduous dentition were to periodontal tissues. In the secondary dentition most injuries were to hard dental tissue and pulp.

Pulpal heat changes with newly developed resin photopolymerisation systems

Composite resin is a widely-used direct tooth coloured restorative material. Photoactivation of the polymerisation reaction can be achieved by visible blue light from a range of light sources, including halogen lamps, metal halide lamps, plasma arc lamps, and Light Emitting Diode (LED) lights. Concerns have been raised that curing lights may induce a temperature rise that could be detrimental to the vitality of the dental pulp during the act of photoactivation. The present study examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds. The independent effects of type of light source, resin shade and remaining tooth thickness were assessed using a matrix experimental design. When a conventional halogen lamp, a metal halide lamp and two different LED lights were compared, it was found that both LED lamps elicited minimal thermal changes at the level of the dental pulp, whereas the halogen lamp induced greater changes and the metal halide lamp caused the greatest thermal insult of all the light sources. These thermal changes were influenced by resin shade, with different patterns for LED versus halogen or halide sources. Thermal stress reduced as the remaining thickness of tooth structure between the pulp and the cavity floor increased. From these results, it is concluded that LED lights produce the least thermal insult during photopolymerisation of composite resins.

Constitutive expression of a phenylalanine ammonia-lyase gene from Stylosanthes humilis in transgenic tobacco leads to enhanced disease resistance but impaired plant growth

Transgenic tobacco plants expressing a phenylalanine ammonia-lyase cDNA (ShPAL), isolated from Stylosanthes humilis, under the control of the 35S promoter of the cauliflower mosaic virus were produced to test the effect of high level PAL expression on disease resistance. The transgenic plants showed up to eightfold PAL activity and were slowed in growth and flowering relative to non-transgenic controls which have segregated out the transgene. The expression of the ShPAL transgene and elevated PAL levels were correlated and stably inherited. In T-1 and T-2 tobacco plants with increased PAL activity, lesion expansion was significantly reduced by up to 55% on stems inoculated with the Oomycete pathogen Phytophthora parasitica pv. nicotianae, Lesion area was significantly reduced by up to 50% on leaves inoculated with the fungal pathogen Cercospora nicotianae. This study provides further evidence that PAL has a role in plant defence. (C) 2002 Elsevier Science Ltd. All rights reserved.

beta-strand mimicking macrocyclic amino acids: Templates for protease inhibitors with antiviral activity

New amino acids are reported in which component macrocycles are constrained to mimic tripeptides locked in a beta-strand conformation. The novel amino acids involve macrocycles functionalized with both an N- and a C-terminus enabling addition of appendages at either end to modify receptor affinity, selectivity, or membrane permeability. We show that the cycles herein are effective templates within inhibitors of HIV-1 protease. Eleven compounds originating from such bifunctionalized cyclic templates are potent inhibitors of HIV-1 protease (Ki 0.3-50 nM; pH 6.5, I = 0.1 M). Unlike normal peptides comprising amino acids, five of these macrocycle-containing compounds are potent antiviral agents with sub-micromolar potencies (IC50 170-900 nM) against HIV-1 replication in human MT2 cells. The most active antiviral agents are the most lipophilic, with calculated values of LogD(6.5) greater than or equal to 4. All molecules have a conformationally constrained 17-membered macrocyclic ring that has been shown to structurally mimic a tripeptide segment (Xaa)-(Val/Ile)-(Phe/Tyr) of a peptide substrate in the extended conformation. The presence of two trans amide bonds and a para-substituted aromatic ring prevents intramolecular hydrogen bonds and fixes the macrocycle in the extended conformation. Similarly constrained macrocycles may be useful templates for the creation of inhibitors for the many other proteins and proteases that recognize peptide beta-strands.

Transformation and transposon mutagenesis of Leifsonia xyli subsp. Xyli, causal organism of Ratoon Stunting Discease of sugarcane

Conditions have been developed for genetic transformation and insertional mutagenesis in Leifsonia xyli subsp. xyli (Lxx), the causal organism of ratoon stunting disease (RSD), one of the most damaging and intractable diseases of sugarcane internationally. Transformation frequencies ranged from 1 to 10 colony forming units (CFU)/mug of plasmid DNA using Clavibacter/Escherichia coli shuttle vectors pCG188, pDM302, and pDM306 and ranged from 50 to 500 CFU/mug using cosmid cloning vectors pLAFR3 and pLAFR5-km. The transformation/transposition frequency was 0 to 70 CFU/mug of DNA, using suicide vectors pUCD623 and pSLTP2021 containing transposable elements Tn4431 and Tn5, respectively. It was necessary to grow Lxx in media containing 0.1% glycine for electroporation and to amplify large plasmids in a dam(-)/dcm(-) E. coli strain and purify the DNA by anion exchange. To keep selection pressure at an optimum, the transformants were grown on nitrocellulose filters (0.2-mum pore size) on media containing the appropriate antibiotics. Transposon Tn4431 containing a promoterless lux operon from Vibrio fischeri and a tetracycline-resistance gene was introduced on the suicide vector pUCD623. All but 1% of the putative transposon mutants produce light, indicating transposition into functional Lxx genes. Southern blot analysis of these transformants indicates predominantly single transposon insertions at unique sites. The cosmid cloning vector pLAFR5-km was stably maintained in Lxx. The development of a transformation and transposon mutagenesis system opens the way for molecular analysis of pathogenicity determinants in Lxx.