PRIMARY IRRADIATION OF CANINE INTRACRANIAL MASSES

Twenty-nine dogs received primary radiation therapy for intracranial lesions and clinical signs suggestive of neoplasia. Presumptive diagnosis and tumor categorization was based on computed tomographic or magnetic resonance images. Meningioma was the most likely tumor type in 22 dogs and glioma or choroid plexus tumors were tentatively identified in 4 and 3 dogs, respectively. Cobalt-60 radiation was delivered in 3 Gy fractions on a daily, Monday-through-Friday basis for a total dose of 48 Gy (16 fractions) in 28 dogs; one dog received 54 Gy. Two of 29 dogs died during treatment of signs suggestive of progressive tumor growth but were included in the overall evaluation of response to treatment. Median overall survival was 250 days (range 21-804). Mild acute radiation effects on normal tissue developed and did not influence outcome in any dog. Late radiation effects could not be evaluated in this study. No significant predictive indicators were identified from the clinical or imaging data. Radiation therapy is superior to medical treatment of brain tumors in dogs with steroids, is useful for tumors that are not currently operable and may be preferable to surgical resection in dogs if the mass appears infiltrative. However, 22/29 (76%) dogs died of recurrent progressive neuropathy suggestive of tumor regrowth or progression. Thus, alternative methods for delivery of radiation to dogs with brain tumors or novel combinations of therapy should continue to undergo evaluation.     

Measures of self-efficacy and norms for low-fat milk consumption are reliable and related to beverage consumption among 5th graders at school lunch

OBJECTIVE: To determine the reliability and validity of scales measuring low-fat milk consumption self-efficacy and norms during school lunch among a cohort of 5th graders. DESIGN: Two hundred and seventy-five students completed lunch food records and a psychosocial questionnaire measuring self-efficacy and norms for school lunch low-fat milk consumption during the fall and spring semesters of the 1998-1999 academic year. Test-retest reliability was assessed in participants who also completed the questionnaire in the spring semester (n = 262). Principal component analyses identified and confirmatory factor analyses confirmed latent variables. Bivariate correlations measured construct validity. SETTING: Houston-area middle school. SUBJECTS: Fifth graders (n = 275) from one middle school in southeast Texas. RESULTS: Two scales measuring psychosocial influences of low-fat milk consumption were identified and proved reliable in this population: milk self-efficacy and milk norms. Milk self-efficacy and norms were positively correlated with milk consumption and negatively correlated with consumption of sweetened beverages. CONCLUSIONS: These questionnaires can be used in similar interventions to measure the impact of self-efficacy and norms for drinking low-fat milk during school lunch.     

Influence of storage on soil microbial biomass estimated by three biochemical procedures

The effects of 28 and 56 days' storage at 25°, 4° and ?20°C on the microbial biomass content of four soils from tussock grasslands were studied by three biochemical procedures. Two of the procedures involved measurement of CO₂ and mineral-N (Min-N) production by chloroform-fumigated and unfumigated soil, and consequent estimation of biomass C and Min-N flush respectively. In the third, adenosine 5'-triphosphate (ATP) content was determined.Patterns of CO₂ production were often influenced by storage treatment. The use of fixed incubation periods for estimating the CO₂ flush of fumigated soil and the steady rate of CO₂ production by unfumigated soil did, however, give biomass C estimates that were generally similar to those calculated from individually determined incubation periods for each treatment and soil.Biomass C values could change significantly at all storage temperatures, but generally least at ?20°C. Storage at ?20°C was also the most suitable for retaining ATP contents, whereas 4°C was best for values of Min-N flush. Values of Min-N flush after storage of soil at ?20°C decreased significantly in two of the soils but increased in another. No storage temperature was thus satisfactory for all three indices of microbial biomass. Generally, however, 4°C was adequate for short periods, and 25°C the least suitable.     

Residue chemistry and microbial community structure during decomposition of eucalypt, wheat and vetch residues

Previous studies have shown that residue chemistry and microbial community structure change during decomposition, however little is known about the relationship between C-chemistry and microbial community structure. To address this knowledge gap, we studied C-chemistry and microbial community structure during the decomposition of eucalypt, wheat and vetch residues with and without additional inorganic N. Bags containing ground residues of eucalypt, wheat, and vetch were buried in sand microcosms after inoculation with a diverse microbial community. Respiration was measured over an incubation period of 150 days. At different times during incubation, total C and N of the residues were analysed and residue carbon chemistry was determined by ¹³C-NMR (nuclear magnetic resonance) spectroscopy. Microbial communities were assessed by phospholipid fatty acid (PLFA) analyses.Results indicated that during decomposition, residue C-chemistry and microbial community composition changed over time and differed between residue types. Changes in microbial community structure were associated with changes in residue C-chemistry, mainly the relative content of aryl-C and O-alkyl-C. Addition of N increased cumulative respiration, altered C-chemistry during decomposition, particularly in high C/N residues (wheat and eucalypt), and changed microbial succession leading to an earlier establishment of a stable microbial community structure. N addition to eucalypt and wheat reduced the decomposition of aryl-C compounds.     

Characterisation of agricultural drainage ditch sediments along the phosphorus transfer continuum in two contrasting headwater catchments

Purpose

This study investigated the phosphorus (P) source, mobilisation and transport potential of ditch bed sediments as well as surrounding field and bank soils in two agricultural headwater catchments with contrasting soil drainage capacities. This information is important for discerning the potential for ditches to attenuate or augment transfers of P from upstream sources and thus for developing appropriate management strategies for these features.

Materials and methods

Phosphorus sources were characterised using the Mehlich3-P, water-soluble P and total P tests. Phosphorus mobilisation potential was characterised using the Mehlich3-AL/P, Mehlich3-Ca/P and DESPRAL P tests. Phosphorus transport potential was characterised using data collected on the presence/absence of surface water in ditches during field surveys and downstream turbidity data.

Results and discussion

Ditch sediments had similar P source contents (Mehlich3-P, water-soluble P and total P) to the surrounding field soils and higher P contents than bank soils. However, calcium contents of sediments in the poorly drained catchment reflected the deep sub-soils rather than the surrounding field and bank soils. Mehlich3-Al/P and Mehlich3-Ca/P contents of ditch sediments in the well (non-calcareous) and poorly (calcareous) drained catchments respectively indicated potential for P retention (above thresholds of 11.7 and 74, respectively). However, sediments were less aggregated than field soils and may mobilise more particulate P (PP) during rain events. Nevertheless, the majority of surveyed ditches dried out from March to September 2011; thus, their potential to mobilise PP may be less important than their capacity to attenuate soluble and PP during this time.

Conclusions

In these and similar catchments, soluble P attenuation and particulate P mobilisation should be maximised and minimised, respectively, for example, by cleaning out the sediments before they become saturated with P and encouraging vegetation growth on ditch beds. This study also highlighted the influence of deep sub-soils on soluble P retention in ditches and thus the utility of characterising soils below depths normally included in soil classifications.

     

Loading of VO2+ and Cu2+ to partially oxidized charcoal fines rejected from Brazilian metallurgical industry

Purpose

Charcoal is utilized in Brazil for the metallurgical industry. Small size pieces, called charcoal fines, are rejected and sometimes are used to produce energy by burning. This charcoal can be used as soil conditioner to improve retention of metal ions in soil. However, changing the charcoal's surface chemistry via oxidation may increase retention of metal ions.

Materials and methods

Two kinds of oxidants were employed, nitric acid and selenium dioxide/hydrogen peroxide. Vanadyl ion (VO²⁺) and copper ion (Cu²⁺) were utilized as probe to study the metal ion complexation by the partially oxidized charcoal obtained. FTIR and EPR spectroscopy were used to characterize the materials.

Results and discussion

Oxidation with nitric acid increased nitrogen content, while oxidation with SeO₂/H₂O₂ elevated carbon content of treated charcoals. Organic free radicals (OFRs) with the unpaired electron in p orbitals of aromatic structures were confirmed by the EPR g-factors that ranged from 2.0038 to 2.0031. The oxidation with selenium dioxide/hydrogen peroxide formed charcoal with largest quantity of OFR. Loading charcoal with VO²⁺ and Cu²⁺ resulted in formation of complexes were oxygen acted as coordination atom. The formed complexes were of axial symmetry. The configurations around the Cu²⁺ ions were: CUNCu²⁺ complex (more stable square planar symmetry) and CFNCu²⁺ complex (less stable distorted tetrahedral configuration). Both complexes had oxygen as coordinating atoms. CFNVO²⁺ and CFSeVO²⁺ complexes presented complexation sites of axial symmetry, C_4v, with oxygen as coordinating atoms.

Conclusions

The oxidative treatment of charcoal with SeO₂/H₂O₂ is more appropriate to produce soil organic conditioner for complexation of metal ions.     

Evidence of indirect impacts of introduced trout on native amphibians via facilitation of a shared predator

Hyperpredation occurs when non-native prey facilitate invasive predators, which then suppress native prey. Direct impacts of introduced fish on amphibians are well studied, but the role of fish in supporting shared predators has not been considered. We present evidence for indirect effects of trout on amphibians through snake predation. Analyses of the diet, distribution and density of the Pacific coast aquatic garter snake (Thamnophis atratus) relative to the sympatric common garter snake (Thamnophis sirtalis) in the Klamath Mountains of California suggest that trout introductions facilitated expansion of T. atratus by providing alternative prey. T. atratus diet included trout and amphibians whereas T. sirtalis preyed solely upon amphibians. The distribution and density of T. atratus matched that of introduced trout instead of native amphibians. Populations of T. atratus could reach high densities in the absence of high densities of amphibians. When the snakes opportunistically prey upon amphibians whose numbers are already directly impacted by trout, they can cause significant additional declines. When T. atratus was present in lake basins, native Cascades frogs (Rana cascadae) were rarer than in basins without T. atratus. This case differs from other hyperpredation studies because the two prey species also interact via intraguild predation. Given the worldwide practice of stocking fish into aquatic habitats, it is important to understand the consequences of the practice on food-web structure and ecosystem functioning. Bottom-up impacts of introduced predators should be considered as well as top-down so that managers can incorporate the range of ecosystem-level effects into conservation goals and decisions.