Five-hydroxytryptamine antagonists and feline aortic embolism

Clinically, feline aortic embolism is manifested by paresis or paralysis of the hind legs. Mere occlusion of the terminal aorta will not cause these signs to develop, i.e. a clot must be present. The clinical condition was duplicated if the aorta was ligated in a manner which formed a cul-de-sac into which autologous blood mixed with glass beads was injected.
In three different groups of cats 5-hydroxytryptamine (5-HT) antagonists were administered intravenously before the creation of a blood clot in the cul-de-sac. The antagonists used were methysergide, cyproheptadine and phenoxybenzamine. The results obtained indicate that cyproheptadine has promise as an effective agent for preventing paresis or paralysis in feline aortic embolism. The active role of 5-HT in the production of paresis or paralysis in feline aortic embolism is more clearly implicated by the work done in this investigation. This knowledge adds to the basic understanding of the pathophysiology involved in this disease.     

Evaluation of risk factors for luxation after total hip replacement in dogs

OBJECTIVE: To identify risk factors for luxation after canine total hip replacement (THR). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: 256 client-owned dogs that underwent THR. METHODS: Patient data surveyed included signalment, body weight, diagnosis, prior hip surgery, implant size, intraoperative complications, and angle of lateral opening of the acetabular component. RESULTS: Postoperative complications were recorded in 20 cases (7.8%). The most common complication was dorsal luxation which occurred in 12 dogs (4.7%). The interval between joint replacement and luxation ranged from 1 to 116 days (mean, 44 days). In 1 case, luxation was attributable to failure of the repair of an intraoperative fracture of the greater trochanter. Excluding this case, the mean angle of lateral opening in those dogs that sustained luxation was 62 degrees (range, 46 degrees - 75 degrees). The mean angle of lateral opening overall was 48 degrees (range, 18 degrees - 76 degrees). The angle of lateral opening was the only factor that had a statistically significant effect on whether luxation occurred (P = .035). Acetabular revision, performed primarily to reduce the angle of lateral opening, was performed in 8 dogs and successfully prevented subsequent luxation. CONCLUSION: Luxation of the prosthesis is substantially under the control of the surgeon. It is recommended that the acetabular cup be inserted at an angle of lateral opening of 35 degrees to 45 degrees. In those cases of THR luxation in which an inappropriate angle of lateral opening is identified, acetabular revision arthroplasty generally results in a good clinical outcome.     

The agricultural mechanization controversy

Attorneys of California Rural Legal Assistance are suing the University of California on behalf of 19 farm workers, alleging that publicly funded mechanization research displaces farm workers, eliminates small farmers, hurts consumers, impairs the quality of rural life, and impedes collective bargaining. This article reviews the evidence and finds that it does not support the charges. The mechanization lawsuit is important because applied research by universities is often authorized by legislation stipulating multiple goals, leaving researchers and universities vulnerable to lawsuits alleging that only some of the legislative goals are being pursued.     

A cost-benefit analysis to select the most effective method for positional cloning: genotyping by sequencing versus allele-specific PCR

Next-generation sequencing technologies have enabled the rapid generation of high-resolution genetic maps to enable the identification of genomic regions associated with traits of interest. In certain cases these regions of interest need to be narrowed down via fine mapping to increase resolution to the level of the individual gene. In those cases, there is a choice of genotyping options, whereby cost, time, and information content need to be considered. We developed detailed, customizable models to compare the cost of genotyping by sequencing and allele-specific PCR for fine-mapping genomic regions of interest. The models were validated experimentally with data from a fine-mapping experiment designed to identify candidate genes within a 3.2-Mb disease resistance locus in the cereal crop sorghum (Sorghum bicolor (L.). Moench), which has a sequenced genome. The size of the mapping population, genetic diversity of the parental lines, choice of reagents, and labor cost were shown to influence the overall cost of the two methods, and, consequently, which method would be most cost-effective for a given experiment. The model can be easily customized to reflect experiments with different species, genetic populations, experimental and personnel costs to determine the most cost-effective procedure for a new positional cloning project.     

In vitro evaluation of antibiotic elution from polymethylmethacrylate (PMMA) and mechanical assessment of antibiotic-PMMA composites

OBJECTIVE: To determine whether different methods of sterilization of antibiotic vials or the heat of polymerization altered the antimicrobial activity or mechanical properties of antibiotic/polymethylmethacrylate (PMMA) composites when compared to antibiotic-free PMMA. STUDY DESIGN: In vitro study. METHODS: Steam-sterilized, gas-sterilized, and non-sterilized 1 gram vials of cefazolin and injectable gentamicin sulfate (high and low doses) were mixed with PMMA to prepare composites for antibiotic elution evaluation, compression, and elongation testing. Blocks of PMMA that contained antibiotic were assayed for antibacterial activity using an agar gel diffusion method or were placed in phosphate buffered saline (PBS) to assess elution of antibiotic. Phosphate buffered saline samples from steam-sterilized cefazolin and high-dose gentamicin groups were assayed on days 1, 2, 5, and 9 for cefazolin or gentamicin concentration by high-pressure liquid chromatography or fluorescent polarization immunoassay, respectively. RESULTS: PMMA blocks containing antibiotic inhibited bacterial growth of Staphylococcus aureus 25923 for an average of 9 days. Cefazolin and gentamicin concentration in PBS decreased dramatically after the first 24 hours, but remained above minimum inhibitory concentration (MIC) throughout the experiment for all groups except low-dose gentamicin. Compressive strength of plugs made from plain cement and plugs made from PMMA mixed with untreated and steam-sterilized cefazolin was similar, but was significantly different from the other groups. There appeared to be an inverse relationship between compressive strength and elongation. CONCLUSION: PMMA/antibiotic composites inhibited bacterial growth for 7 to 10 days. Compressive strength was affected by different additions of antibiotic. CLINICAL RELEVANCE: Bacteria introduced during a surgical procedure may be inhibited by elution of antibiotic from PMMA at the time of contamination.     

RADIOGRAPHIC EVALUATION OF TOTAL HIP REPLACEMENT IN THE DOG

The radiographic signs associated with implanted canine total hip prostheses include: (1) a 1 mm-or-less wide static lucent zone at the acetabular and femoral bone-cement interfaces, and (2) periosteal bone proliferation surrounding the stem of the femoral prosthesis. The radiographic signs associated with total hip replacement complications are dislocation of the femoral component, bone changes suggestive of infection involving the acetabular and femoral components, and loosening of the acetabular component. Arthrography is beneficial in determining the presence of a loose prosthesis with or without infection.     

Measurement of tissue oxygen saturation levels using portable near‐infrared spectroscopy in clinically healthy dogs

Objective – To establish a reference interval for tissue oxygen saturation (StO₂) levels measured by a portable near‐infrared spectroscope and determine site(s) for reproducibly measuring StO₂ levels in dogs. Design – Prospective experimental study. Setting – Veterinary teaching hospital. Animals – Seventy‐eight healthy dogs. Measurements and Main Results – A portable device that quantitatively measures StO₂ levels directly in muscle tissue using near‐infrared spectroscopy (NIRS) was topically applied to shaved sites over 4 muscle bodies. Readings from the sartorius muscle were obtained 100% of the time. The digital extensors and biceps femoris muscles provided similar readings, but less consistently obtained StO₂ values (70% and 67%, respectively). Mean StO₂ levels measured over these 3 sites were not statistically different from one another. When readings from these 3 sites were combined, a mean ±1 SD of 92.9±7.4% was obtained. The epaxial muscles produced a significantly lower mean ±1 SD (68.5±22.4%), and readings were obtained only 60% of the time. Conclusions – In dogs, a mean ±1 SD of 92.9±7.4% can be used to investigate clinical applications of NIRS. The sartorius muscle most consistently allows for detection of StO₂ levels (100%). The epaxial muscles are not consistent or reliable for obtaining StO₂ readings and are not recommended for clinical application of near‐infrared spectroscope. Sex does not significantly affect StO₂ readings at any site. Body condition score only affects readings obtained from the sartorius muscle.     

Removal of infected canine cemented total hip prostheses using a femoral window technique

OBJECTIVE: To evaluate a femoral window technique for retrieval of cemented total hip prostheses. STUDY DESIGN: Retrospective clinical study. ANIMALS: Twelve dogs with infection of a cemented modular total hip prosthesis. METHODS: Implant removal was performed by an extended craniolateral approach to the hip and proximal femur without trochanteric osteotomy. The femoral cement mantle was fragmented and removed with simple orthopedic instrumentation by a lateral femoral window that was repaired using cerclage wires. Surgical technique, intraoperative and postoperative complications, bacterial culture results, histopathologic findings, and completeness of cement removal were recorded. Follow-up radiographs were taken 5 to 9 weeks postoperatively. Long-term follow-up information was obtained by client questionnaire. Functional outcome was assessed by scoring ability to stand, sit, walk, run, play, climb stairs, and get into a car. RESULTS: Prosthesis retrieval was performed 2 to 41 months after implantation (median, 14 months). Complete removal of femoral cement was achieved in 10 dogs. A nondisplaced femoral fissure, extending proximally from the window, was an intraoperative complication in 2 dogs. Staphylococcus spp was most commonly isolated (6 dogs) from interfacial membrane samples. Systemic antibiotic therapy, dependent on susceptibility testing, was administered for 3 to 10 weeks postoperatively. There was radiographic evidence of osteotomy healing at 5- to 9-week reassessment. Recurrence of osteomyelitis was not observed. Long-term functional outcome was considered mildly abnormal. CONCLUSIONS: The lateral window was an effective technique for retrieval of retained femoral cement. CLINICAL RELEVANCE: Removal of an infected prosthesis using this technique generally resulted in a clinical outcome comparable to that with ab initio femoral head and neck excision.