BIOECONOMIC MODELLING OF ENDANGERED SPECIES CONSERVATION

Resource /Energy Economics and Policy,

USING LAND AS A CONTROL VARIABLE IN DENSITY-DEPENDENT BIOECONOMIC MODELS

The bioeconomic analysis of endangered species without consumptive values can be problematic when analysed with density-dependent models that assume a fixed environment size. Most bioeconomic models use harvest as a control variable, yet when modelling non-harvestable species, frequently the only variable under control of conservationists is the quantity of habitat to be made available. The authors explore the implications of this in a model developed to analyse the potential population recovery of New Zealand's yellow-eyed penguin. The penguin faces severe competition with man for the terrestrial resources required for breeding and has declined in population to perilously low levels. The model was developed to estimate the land use required for recovery and preservation of the species and to compare the results to current tourism-driven conservation efforts. It is demonstrated that land may serve as a useful control variable in bioeconomic models and that such a model may be useful for determining whether sufficient incentives exist to preserve a species. However, the model may generate less useful results for providing a specific estimate of the optimal allocation of land to such a species.Land Economics/Use,

Small-Diameter PTFE Portosystemic Shunts: Portocaval vs Mesocaval

Fifty-seven patients with failed sclerotherapy received a mesocaval interposition shunt with an externally supported, ringed polytetrafluoroethylene prosthesis of either 10 or 12 mm diameter. Thirty-one patients had Child-Pugh gradeA disease and 26 grade B; all had a liver volume of 1000– 2500 ml. Follow-up ranged from 16 months to 6 years 3 months. Three patients (5 per cent) died in the postoperative period. There were two postoperative recurrences of variceal haemorrhage and one recurrent bleed in the second year after surgery. The cumulative shunt patency rate was 95 per cent and the incidence of encephalopathy 9 per cent; the latter was successfully managed by protein restriction and/or lactulose therapy. The actuarial survival rate for the whole group at 6 years was 78 per cent, for those with Child-Pugh grade A 88 per cent and for grade B 67 per cent. Small-lumen mesocaval interposition shunting achieves portal decompression, preserves hepatopetal flow, has a low incidence of shunt thrombosis, prevents recurrent variceal bleeding and is not associated with significant postoperative encephalopathy

Extracellular DNA in head and neck biofilms

PhD ThesisExtracellular DNA (eDNA) is a ubiquitous component of the extracellular matrix of microbial biofilms. It has a number of functions that include a role as an adhesin during biofilm attachment, and facilitating matrix stability in mature biofilms. Increasingly, deoxyribonuclease (DNase) enzymes have been shown to reduce the colonisation of many microbial biofilms, both bacterial and fungal. Biofilms are estimated to be responsible for around 60% of bacterial infections, including many chronic diseases. The aim of this work was to determine the role of eDNA in chronic mixed-species biofilm infections, and to explore the potential of DNase enzymes for biofilm control. This included three major areas of research, focusing on chronic rhinosinusitis, tracheoesophageal speech valves (TESVs), and dental plaque. An important aspect was to test the efficacy of a novel bacterial nuclease, NucB, isolated from a seaweed-associated strain of Bacillus licheniformis, against microbial biofilms. The colonisation of speech valves by micro-organisms was studied using scanning electron microscopy (SEM). In keeping with previous observations, these biofilms were co-aggregations of fungal and bacterial species. Using confocal laser scanning microscopy, eDNA was observed in the biofilm matrix. Extracellular DNA was extracted and quantified from TESV biofilms. All six biofilms studied had detectable nucleic acids, as measured by NanoDrop spectrophotometry. The eDNA was apparently heavily degraded, and produced smears by agarose gel electrophoresis. Nevertheless, eDNA appeared to be providing biofilm stability since micro-organisms were liberated from the surface of the valves following treatment with NucB in over 60% of the TESVs tested. To assess the role of eDNA in biofilms associated with chronic rhinosinusitis, ‘obstructive mucin’ and sinus mucosa biopsy samples collected during functional endoscopic sinus surgery at the Freeman Hospital, Newcastle, were analysed for the presence of biofilms and biofilm-forming micro-organisms. An average of 3.75 bacterial species per patient were cultured from obstructive mucin. The most commonly isolated micro-organisms were Staphylococcus aureus, coagulase-negative staphylococci and α-haemolytic streptococci. Micro-organisms were not detected by transmission electron microscopy of the obstructive mucin and this material appeared to originate through a host inflammatory response. However, bacteria were visualised on the surface of sinus mucosa using a peptide nucleic acid fluorescence in situ hybridization (PNA-FISH) universal bacteria probe. Twenty-four bacterial isolates were iv assessed for their ability to form biofilms in a microtitre plate model. All micro-organisms tested formed biofilms, and 14 of 22 were susceptible to NucB. In total, 15 of 24 microbial species produced eDNA that was detectable by agarose gel electrophoresis. By SEM, cellular colonisation was lower in treated samples and, in the case of Streptococcus constellatus FH20 stringy, matrix-like material was not present after DNase treatment. The role of eDNA in matrix stability and initial biofilm attachment was also studied in oral bacteria. Streptococcus gordonii DL1, Streptococcus mutans GS-5, Fusobacterium nucleatum 25586 and Actinomyces oris MG1 were examined using DNase treatment, CLSM, and eDNA extraction. Of these species, all except S. gordonii appeared to rely on high molecular weight (HMW) eDNA for biofilm attachment and biofilm stability. Although S. gordonii did not produce detectable HMW eDNA, nucleic acids were detectable by NanoDrop spectrophotometry. Furthermore, this species produces an extracellular nuclease which may degrade the HMW eDNA in the conditions used to culture biofilms. Interestingly, four S. mutans strains differed in their sensitivity to DNase treatment. Oral biofilms were also modelled in a BioFlux microfluidics device using flowing human saliva. Mixed-species biofilms and single species biofilms of S. mutans UA159 and S. gordonii DL1 were cultured using this technique, to determine whether this model would allow more realistic experiments for DNase testing. Finally, the extracellular nuclease, SsnA, of S. gordonii DL1 was characterised. A nuclease-deficient mutant did not produce extracellular nuclease activity on DNase Test agar or during a Forster Resonance Energy Transfer (FRET) assay. Nuclease activity was cell-wall-associated as predicted from the predicted amino acid sequence of SsnA. Allelic exchange mutagenesis determined that ssnA expression was regulated by CcpA in response to repressing sugars. However, in planktonic culture non-repressing carbon sources also inhibited enzyme activity during a FRET assay. Further experiments using acidic buffers replicated the inhibition of SsnA without the presence of sugars. SsnA was purified as a GST-tagged fusion protein in an Escherichia coli protein expression system, and had anti-biofilm activity against S. mutans GS-5. However, this species is strongly acidogenic and therefore it is hypothesised that although SsnA may be a competition biofilm factor, acid production by S. mutans may reduce its efficacy in vivo. In conclusion, this thesis has provided strong evidence for the role of eDNA in facilitating biofilm formation and mature biofilm stability of clinically relevant v biofilms. Nucleic acids were present in biofilms associated with a chronic infection, medical implant biofouling and dental plaque. A variety of DNase enzymes (NucB, DNase I, and SsnA) were capable of reducing biofilm colonisation. Given the adhesive function of eDNA in biofilm matrices it is proposed that DNase enzymes may be beneficial for controlling healthcare-related biofilms

MAXIMUM PRICES WITH RESPECT TO AGRICULTURAL COMMODITIES

As we all know, prices of agricultural commodities during this war have been directly and substantially affected by Government controls and will probably continue to be so affected in the immediate future. These controls take two forms: First, there are those relating to price floors, that is, minimum support prices with respect to agricultural commodities; and, second, there are those relating to price ceilings, that is, maximum prices with respect to agricultural commodities

Preparing Teacher Interns for International Teaching: A Case Study of a Chinese Practicum Program

Acadia University, a small liberal arts institution, has for 15 years, offered a unique practicum experience for its teacher interns enrolled in the preservice Bachelor of Education. Students travel to Shanghai, China for a period of four months to teach English as a Second Language in school classrooms ranging from grades kindergarten to six. This paper describes the preparation of interns and the inherent challenges they face as pedagogues in a distinctly different teaching context. This action research account seeks to used mixed methods to identify areas of improvement in the process of preparing beginning teachers for a career in international teaching

Consequences of Dust in Metal-Rich HII Regions

Dust and associated depletion of heavy elements from the gas phase can modify the thermal properties of HII regions from the dust-free case, with significant consequences for the emergent optical spectrum. We present the results of theoretical calculations illustrating the effects of grains on the spectra of giant, extragalactic HII regions, with emphasis on high metallicity systems (i.e. solar and higher Z). Dust provides a simple explanation for the observational absence of pure Balmer-line spectra that are expected on theoretical grounds for dust-free, chemically enriched nebulae. Grains may also play a role in enhancements of forbidden-line emission observed in HII regions in the enriched nuclei of normal galaxies. In most cases, depletion introduces the strongest perturbations to the optical spectrum. Selective absorption of the ionizing continuum as well as heating by grain photoelectrons are important in some instances, however, and grain heating can be particularly important for enhancing emission in high-ionization lines. Allowing for depletion, the presence of dust is unlikely to introduce large errors in global metallicity indicators, although uncertainties in depletion factors coupled with the sensitivity of infrared cooling to electron density will make accurate calibrations difficult at high Z. The present calculations establish further that previous relative abundance analyses that fail to take into account dust effects in a self-consistent way (grain heating as well as depletion) may overestimate temperature gradients in high-Z nebulae, resulting in errors in relative abundances for different elements.Comment: 21 pages (AASTeX), plus 9 figures (uuencoded, gzipped, tar), to appear in ApJ, December 199

Atlas of Lobster Anatomy and Histology

This is a histological atlas of the most common organs and tissues found in the American lobster, Homarus americanus. The atlas contains photomicrographs from histological sections of healthy tissues. The atlas contains pictures of tissues that are readily observed in dissection and several that are commonly affected by diseases. It is not a complete atlas. Several organs are not covered, notably the brain, ventral nerve ganglion, sensory organs, and organs associated with molting