Risk Factors Associated with Plantar Necrosis following Tarsal Arthrodesis in Dogs.

OBJECTIVES: The aim of this study was to define landmarks of the intermetatarsal channel of the dorsal pedal artery and to assess whether damage to the dorsal pedal artery during metatarsal screw placement in dogs undergoing pan- and partial-tarsal arthrodesis (PanTA/ParTA) could be a mechanism in the development of plantar necrosis. STUDY DESIGN: This study was divided in to two parts: (1) ex-vivo anatomical study: 19 canine cadavers, (2) retrospective clinical study: 39 dogs. Cadaveric dissection documented the mean intermetatarsal channel position. Metatarsal screw position was evaluated on postoperative radiographs of dogs after PanTA or ParTA. Screw position, arthrodesis type and surgical approach were assessed for their impact on complications, including plantar necrosis. RESULTS: The mean proximal and distal extent of the intermetatarsal channel lies between 4.3% ± 1.9 and 22.8% ± 2.9 the length of metatarsal III (MTIII) respectively. The intermetatarsal channel lies within the most proximal 25% of MTIII in 95% of cases. At least one screw risked damaging the mean intermetatarsal channel position in 92% of dogs; 8% of these dogs went on to develop plantar necrosis. The mean screw position did not differ between ParTA cases with or without plantar necrosis (p > 0.05). CONCLUSION: Violation of the intermetatarsal channel is possible during metatarsal screw placement. Care should be taken when placing screws in the proximal 25% of the metatarsals, specifically avoiding exiting dorsally between MTII and MTIII and across the distal region of the intermetatarsal channel, where the perforating metatarsal artery passes interosseously, as damage may contribute to the aetiology of plantar necrosis.

Kinetics modeling predicts bioaugmentation with Sphingomonad cultures as a viable technology for enhanced pharmaceutical and personal care products removal during wastewater treatment.

Pharmaceutical and personal care products (PPCPs) discharged with wastewater treatment effluents are a surface water quality concern. PPCPs are partially removed during wastewater treatment and biological transformation is an important removal mechanism. To investigate the potential for enhanced PPCP removal using bioaugmentation, bacteria were previously isolated from activated sludge capable of degrading PPCPs to ng/L concentrations. This study examined the degradation kinetics of triclosan and bisphenol A by five of these bacteria, both in pure culture and when augmented to activated sludge. Sorption coefficients were determined to account for the influence of partitioning during bioremoval. When the bacteria were added to activated sludge, degradation increased. Experimentally determined kinetic parameters were used to model a full-scale continuous treatment process, showing that low biomass could achieve reduced effluent PPCP concentrations. These results demonstrated that bioaugmentation may improve PPCP removal using established wastewater infrastructure under conditions of high solids partitioning.

Characterization of persistent virus-like particles in two acetate-fed methanogenic reactors.

The objective of this study was to characterize the morphology, size-distribution, concentration and genome size of virus-like particles (VLPs) in two acetate-fed Methanosaeta-dominated reactors to better understand the possible correlation between viruses and archaeal hosts. The study reactors were dominated by a single genus of acetoclastic methanogen, Methanosaeta, which was present at 6 to 13 times higher than the combined bacterial populations consisting of Proteobacteria, Firmicutes, and Bacteroidetes. Epifluorescent microscopy showed VLPs concentration of 7.1 ± 1.5 × 10(7) VLPs/ml and 8.4 ± 4.3 × 10(7) VLPs/ml in the two laboratory reactors. Observations of no detectable import of VLPs with the reactor feed combined long operational time since the last inocula were introduced suggests that the VLP populations were actively propagating in the reactors. Transmission electron microscopy images showed VLPs with morphology consistent with Siphoviridae in both reactors, and VLPs with morphologies consistent with Myoviridae in one of the reactors. The morphology, size-distribution and genome size of VLPs were distinct between reactors suggesting that unique viral populations inhabited each reactor, though the hosts of these VLPs remain unclear.

Effects of chloride, sulfate and natural organic matter (NOM) on the accumulation and release of trace-level inorganic contaminants from corroding iron.

This study examined effects of varying levels of anions (chloride and sulfate) and natural organic matter (NOM) on iron release from and accumulation of inorganic contaminants in corrosion scales formed on iron coupons exposed to drinking water. Changes of concentrations of sulfate and chloride were observed to affect iron release and, in lesser extent, the retention of representative inorganic contaminants (vanadium, chromium, nickel, copper, zinc, arsenic, cadmium, lead and uranium); but, effects of NOM were more pronounced. DOC concentration of 1 mg/L caused iron release to increase, with average soluble and total iron concentrations being four and two times, respectively, higher than those in the absence of NOM. In the presence of NOM, the retention of inorganic contaminants by corrosion scales was reduced. This was especially prominent for lead, vanadium, chromium and copper whose retention by the scales decreased from >80% in the absence of NOM to <30% in its presence. Some of the contaminants, notably copper, chromium, zinc and nickel retained on the surface of iron coupons in the presence of DOC largely retained their mobility and were released readily when ambient water chemistry changed. Vanadium, arsenic, cadmium, lead and uranium retained by the scales were largely unsusceptible to changes of NOM and chloride levels. Modeling indicated that the observed effects were associated with the formation of metal-NOM complexes and effects of NOM on the sorption of the inorganic contaminants on solid phases that are typical for iron corrosion in drinking water.

Effects of blending of desalinated and conventionally treated surface water on iron corrosion and its release from corroding surfaces and pre-existing scales.

This study examined effects of blending desalinated water with conventionally treated surface water on iron corrosion and release from corroding metal surfaces and pre-existing scales exposed to waters having varying fractions of desalinated water, alkalinities, pH values and orthophosphate levels. The presence of desalinated water resulted in markedly decreased 0.45 µm-filtered soluble iron concentrations. However, higher fractions of desalinated water in the blends were also associated with more fragile corroding surfaces, lower retention of iron oxidation products and release of larger iron particles in the bulk water. SEM, XRD and XANES data showed that in surface water, a dense layer of amorphous ferrihydrite phase predominated in the corrosion products. More crystalline surface phases developed in the presence of desalinated water. These solid phases transformed from goethite to lepidocrocite with increased fraction of desalinated water. These effects are likely to result from a combination of chemical parameters, notably variations of the concentrations of natural organic matter, calcium, chloride and sulfate when desalinated and conventionally treated waters are blended.

Cultivation and characterization of bacterial isolates capable of degrading pharmaceutical and personal care products for improved removal in activated sludge wastewater treatment.

Pharmaceutical and personal care products (PPCPs) discharged with wastewater treatment plant (WWTP) effluents are an emerging surface water quality concern. Biological transformation has been identified as an important removal mechanism during wastewater treatment. The aim of this research was the identification of bacteria with characteristics for potential bioaugmentation to enhance PPCP removal. We report here the cultivation and characterization of bacteria capable of degrading PPCPs to ng/L concentrations. An isolation approach was developed using serial enrichment in mineral medium containing 1 mg/L of an individual PPCP as the sole organic carbon source available to heterotrophs until the original activated sludge inocula was diluted to ~10(-8) of its initial concentration, followed by colony growth on solid R2A agar. Eleven bacteria were isolated, eight that could remove triclosan, bisphenol A, ibuprofen, or 17ß-estradiol to below 10 ng/L, one that could remove gemfibrozil to below 60 ng/L, and two that could remove triclosan or E2, but not to ng/L concentrations. Most bacterial isolates degraded contaminants during early growth when grown utilizing rich carbon sources and were only able to degrade the PPCPs on which they were isolated. Seven of the bacterial isolates were sphingomonads, including all the triclosan and bisphenol A degraders and the ibuprofen degrader. The study results indicate that the isolated bacteria may have a positive influence on removal in WWTPs if present at sufficient concentrations and may be useful for bioaugmentation.

Formation of Pb(III) intermediates in the electrochemically controlled Pb(II)/PbO2 system.

The formation of lead dioxide PbO(2), an important corrosion product in drinking water distribution systems with lead-bearing plumbing materials, has been hypothesized to involve Pb(III) intermediates, but their nature and formation mechanisms remain unexplored. This study employed the electrochemical (EC) method of rotating ring disk electrode (RRDE) and quantum chemical (QC) simulations to examine the generation of intermediates produced during the oxidation of Pb(II) to PbO(2). RRDE data demonstrate that PbO(2) deposition and reduction involves at least two intermediates. One of them is a soluble Pb(III) species that undergoes further transformations to yield immobilized PbO(2) nanoparticles. The formation of this intermediate in EC system is mediated by hydroxyl radicals (OH(•)), as was evidenced by the suppression of intermediates formation in the presence of the OH(•) scavenger para-chlorobenzoic acid. QC simulations confirmed that the oxidation of Pb(II) by OH(•) proceeds via Pb(III) species. These results show that Pb(III) intermediates play an important role in the reactions determining transitions between Pb(II) and Pb(IV) species and could impact lead release in drinking water.

Effects of blending of desalinated water with treated surface drinking water on copper and lead release.

This study examined effects of desalinated water on the corrosion of and metal release from copper and lead-containing materials. A jar test protocol was employed to examine metal release from copper and lead-tin coupons exposed to water chemistries with varying blending ratios of desalinated water, alkalinities, pHs and orthophosphate levels. Increasing fractions of desalinated water in the blends resulted in non-monotonic changes of copper and lead release, with generally lower metal concentrations in the presence of desalinated water, especially when its contribution increased from 80% to 100%. SEM examination showed that the increased fractions of desalinated water were associated with pronounced changes of the morphology of the corrosion scales, likely due to the influence of natural organic matter. This hypothesis was corroborated by the existence of correlations between changes of the zeta-potential of representative minerals (malachite and hydrocerussite) and metal release. For practical applications, maintaining pH at 7.8 and adding 1 mg/L orthophosphate as PO(4) were concluded to be adequate to decrease copper and lead release. Lower alkalinity of desalinated water was beneficial for blends containing 50% or more desalinated water.

A candidate gene study of canine joint diseases.

Canine osteoarthritis (OA) commonly occurs in association with articular diseases, such as hip dysplasia (HD), elbow dysplasia (ED), or cranial cruciate ligament rupture (CCLR). We hypothesized that a common genomic risk for the development of canine joint disease and canine OA would be identified by evaluating the allele frequencies of candidate gene single nucleotide polymorphisms (SNPs) in dogs with OA associated with different articular diseases when compared with a general population of breed-matched dogs. DNA was extracted from blood samples obtained from Labrador Retrievers and Golden Retrievers surgically treated for ED, HD, and CCLR and confirmed to have radiographic evidence of OA. One hundred and thirteen SNPs in 20 candidate genes were genotyped. No significant associations were identified for SNPs or haplotypes in the candidate genes for the diseases evaluated. The candidate gene approach for the study of genetic association is unlikely to be successful for complex canine diseases such as OA without prior trait mapping evaluation.

Clinical evaluation of pancarpal arthrodesis using a CastLess plate in 11 dogs.

OBJECTIVE: To describe the use of a 3.5/2.7 mm CastLess Plate (CLP) for pancarpal arthrodesis (PCA) in dogs. STUDY DESIGN: Case series. ANIMALS: Dogs with traumatic/degenerative carpal disease (n=11). METHODS: Records (September 2006-July 2007) of dogs that had PCA using a 3.5/2.7 mm CLP were reviewed to determine intra- and postoperative complications and use of external coaptation. Follow-up (> or =12 months) was obtained by telephone interview of owners. RESULTS: Thirteen PCA procedures were performed; 5 intraoperative complications occurred in 4 procedures and included iatrogenic metacarpal fissure fracture (2), inability to remove an alignment pin (1), and poor distal plate position (2). External coaptation was used in 4 dogs: concomitant or iatrogenic injuries (3), bilateral PCA (1), for 3-6 weeks. Clinical evaluation 6-24 weeks postoperatively revealed iatrogenic metacarpal fractures to have healed and that 1 postoperative complication (infection) developed. Telephone follow-up for 10 dogs (mean, 14 months; range, 12-20 months) revealed no further problems. CONCLUSION: PCA using a 3.5/2.7 mm CLP reduces the need for external coaptation and seemingly reduces postoperative morbidity associated with other internal fixation techniques. CLINICAL RELEVANCE: PCA can be performed safely and successfully using a 3.5/2.7 mm CLP, with low postoperative morbidity compared with other PCA techniques. Particular attention should be taken when applying the distal component of the plate.

Interactions of Pb(II)/Pb(IV) solid phases with chlorine and their effects on lead release.

This study examined changes of colloidal properties and lead release from representative solid phases of lead (IV) (PbO2) and lead (II) (hydrocerussite, cerussite) and during the oxidation of the lead (II) solids by chlorine. Chlorine is determined to cause the zeta-potential of lead (II) solids to undergo significant changes apparently associated with the generation of Pb(lll) intermediates that are formed before the PbO2 phase becomes abundant enough to be morphologically distinct. Simultaneouslywith the changes of the zeta-potential, a pronounced decrease of lead release from hydrocerussite takes place. In contrast with that, lead release from cerussite undergoes a transient increase during the oxidation of that solid by chlorine. The existence of differences in processes governing lead release from these Pb(ll) solids is supported by SEM data showing different patterns of morphological changes of the cerussite and hydrocerussite crystal surfaces.

Investigation of the kinetics and mechanisms of the oxidation of cerussite and hydrocerussite by chlorine.

Reactions of representative lead (II) solid phases (hydrocerussite, cerussite) with chlorine were examined in this study. Chlorine consumption profiles for these solids exhibited a lag phase, during which little consumption of chlorine occurred, and an ensuing rapid reaction phase. The durations of these phases were affected by the pH, carbonate, and chlorine concentrations. SEM and XRD data showed that hydrocerussite started to be transformed into cerussite during the lag phase. Kinetic analysis indicated that only the protonated form of HClO drives the autocatalytic oxidation step, which is mediated by dispersed PbO2 crystals. The rate of the noncatalytic oxidation decreased with the increase of carbonate due to the formation of unreactive surface carbonate Pb(II) complexes.

Structural study of the incorporation of heavy metals into solid phase formed during the oxidation of EDTA by permanganate at high pH.

Properties of solid phases formed during the oxidation of EDTA by permanganate in a high-pH, high-ionic strength solution, and the retention of Cu2+, Ni2+, and Zn2+ by them were examined. Morphologically, the solids were agglomerates of particles with sizes <100 nm. X-ray absorption spectroscopy (XAS) analysis indicated that these particles were birnessite. Its precipitation was accompanied by the removal of Zn2+ and Cu2+ released as a result of the breakdown of their complexes with EDTA. However, Ni2+ was not removed from the supernatant. Cu2+ was strongly bound by birnessite and exhibited little mobility in the pH range from 3 to 14. Zn2+ was more mobile, especially at pH > 12. XAS showed that Cu2+ binding sites were located within MnO6 octahedra-comprised sheets that constitute birnessite while Zn2+ was positioned between them.

Investigation of mechanisms of oxidation of EDTA and NTA by permanganate at high pH.

Permanganate has been used for oxidation of nuclear wastes containing chelating agents such as ethylenediaminetetraacetic and nitrilotriacetic acids (EDTA and NTA) to improve separation of radionuclides and heavy metals from the wastes, butthe mechanisms of degradation of these and related organic ligands at high pHs have not been studied. EDTA, NTA, and the model compound ethylenediamine (EN) were found to be readily oxidized by permanganate at pH 12-14. The reduction of permangante was accompanied by formation of unstable manganate and dispersed MnO2 particles, which constituted the final product of permanganate reduction. The yields and speciation of EDTA, NTA, and EN breakdown products were affected by the pH and permanganate dose. Iminodiacetic acid (IDA), oxalate, formate, and ammonia were the predominant EDTA and NTA oxidation products. Mineralization of EDTA, NTA, and EN to CO2 was more significant at pH 12. At pH 14 formation of oxalate and deamination to NH3 were the most important reactions. IDA was released upon the oxidation of both EDTA and NTA, but EDTA oxidation yielded no ethylenediaminediacetic acid (EDDA). The speciation of the reaction products indicated that the ethylene group in EDTA was the preferred attack site in oxidations by alkaline permanganate.

Influence of natural organic matter on the morphology of corroding lead surfaces and behavior of lead-containing particles.

Influence of natural organic matter (NOM) on the morphology of lead surfaces exposed to drinking water and on the properties of lead-containing colloidal particles was explored based on the data of scanning electron microscopy, sequential filtrations, measurements of particle size distributions and electrophoretic potential. It was demonstrated that NOM prevented the formation of cerussite and hindered the growth of hydrocerussite crystals. Measurements of zeta-potential showed that the surface activity was highest for unaltered NOM, while ozonation and chlorination decreased it. The concentrations of soluble lead and tin increased several fold in the presence of NOM, while large colloidal particles of lead and solder corrosion products tended to break down to form smaller fragments. It is suggested that these phenomena are important for understanding of lead release mechanisms in drinking water.

Effect of solids retention time on the performance of thermophilic and mesophilic digestion of combined municipal wastewater sludges.

The steady-state performance of thermophilic (55 degrees C) and mesophilic (35 degrees C) anaerobic digestion as a function of solids retention time (SRT) was evaluated in laboratory digesters at SRTs ranging from 4 to 15 days, and in pilot-plant digesters at a 20-day SRT. All of the digesters were fed the same source of municipal combined primary and secondary waste sludge. The destruction efficiency of volatile solids increased from 53% to 66% as the SRT was increased from 6 days to 20 days. The average destruction efficiency of volatile solids was 3 percentage points higher for the thermophilic digester at the 6-day SRT and approximately 1 percentage point higher for the higher SRTs, but the difference was only statistically significant at the 15-day SRT. Based on volatile suspended solids measurements, the thermophilic solids destruction efficiency was approximately 4 percentage points higher at the 10- and 15-day SRTs. At a 4-day SRT, methanogenic activity could only be maintained in the thermophilic digester. The pH, alkalinity, ammonia, volatile fatty acid, and soluble chemical oxygen demand concentrations were higher for the thermophilic digester at each SRT. At SRTs of 10 days and less, the thermophilic digester had a much higher propionate and slightly higher butyrate concentration. Carbohydrates were readily degraded by both digesters, protein was the major component in the sludge at the long SRTs, and lipid degradation increased with increasing SRT.