Diagnostic accuracy of contrast-enhanced computed tomography for assessment of mandibular and medial retropharyngeal lymph node metastasis in dogs with oral and nasal cancer.

The diagnostic accuracy of contrast-enhanced CT for detection of cervical lymph node metastasis in dogs is unknown. The purpose of this retrospective, observational, diagnostic accuracy study was to assess the efficacy of CT for detection of mandibular and medial retropharyngeal lymph node metastasis in dogs. Histopathology of dogs with cancer of the head, CT and bilateral mandibular and medial retropharyngeal lymphadenectomy was reviewed. A single radiologist measured lymph nodes to derive short axis width and long-short axis ratios. Two blinded radiologists separately assessed lymph node margins, attenuation and contrast enhancement and each provided a final subjective interpretation of each node site as benign or neoplastic. Where radiologists' opinions differed, a consensus was reached. Sensitivity, specificity and accuracy were calculated for mandibular and medial retropharyngeal sites. Agreement between radiologists was assessed. Fisher's exact test and the Kruskal-Wallis H-test were used to assess associations between variables. Forty-one primary tumours were recorded in 40 dogs. Metastasis to mandibular or retropharyngeal lymph nodes occurred in 16 out of 40 dogs (43/160 nodes). Agreement between radiologists was almost perfect for margination, attenuation and enhancement, strong for interpretation of mandibular lymph node metastasis, and weak for interpretation of medial retropharyngeal lymph node metastasis. Sensitivity of CT was 12.5% and 10.5%, specificity was 91.1% and 96.7%, and accuracy was 67.5% and 76.3% for mandibular and medial retropharyngeal lymph nodes respectively. No individual CT findings were predictive of nodal metastasis. Given the low sensitivity of CT, this modality cannot be relied upon alone for assessment of cervical lymph node metastasis in dogs.

Hinged circular fixator construct for correction of congenital metatarsal deformity in a foal.

A five-week-old American Quarter Horse colt was presented for evaluation of a left hindlimb deformity and lameness. Radiographs of the left hindlimb revealed a varus deformity with recurvatum originating in the mid-diaphysis of the third metatarsal bone. Surgical correction was undertaken by performing an osteotomy through the centre of rotation of angulation located within the mid-diaphysis of the third metatarsal bone, and a four-ring hinged circular external fixator construct was applied. Distraction of the osteotomy site was performed over an 11 day period. Notable complications included failure of a fixation pin, infection of the surgical site, and temporary laxity of the supporting tendons and ligaments of the contralateral metatarsophalangeal joint. The fixator was maintained until there was sufficient bone formation to allow frame removal, 152 days after the initial surgery. Use of a hinged circular construct allowed for partial correction of the deformity with resultant lengthening and resolution of the lameness in this colt.

Birth control discontinuance as a diffusion process.

This paper applies the diffusion of innovations model to the study of the birth control discontinuance of first-time users in the Dominican Republic. Two sets of factors are examined: social characteristics of the adopters are used to test Rogers's and Shoemaker's contention that discontinuers have more traditional values than continuers; and the adoption decision process is analyzed to identify the relationship of communication factors to discontinuance. Although number of children and experience of method problems were the major determinants of discontinuance, unfavorable information from friends and other birth control users was a significant factor. Rumor was found to have little effect on a women's decision to continue or discontinue.

PIP: The diffusion of innovations model provides a general framework for describing the rate of growth of acceptance for a new idea or pattern of behavior within a social system. It is here applied to the study of birth control discontinuance among a sample of 1st-time users in the Dominican Republic. Social characteristics and communication variables are examined as explanatory factors for discontinuance. The 1st set, namely socioeconomic status, education and rural-urban residence, are used to test Rogers' and Shoemaker's contention that discontinuers have more traditional values than continuers. The multivariate effect of these factors is tested by a stepwise logistic regression analysis. The communication variables are intended to measure the effect of unfavorable information from unidentified sources compared to that channelled through identified social networks. A short follow-up period of 4 months permits an examination of the way the women communicated after adopting birth control. To test the strength of the relationships between social and communication variables, each set is tested against the effect of adding the variable number of children to the model. The effect of this factor alone on discontinuance is significant; yet, even when it is removed, it appears that the interaction between place of residence and socioeconomic status is most significant in explaining discontinuance. The data provide only weak support for Roger's and Shoemaker's thesis, as number of children and experience of method problems, not underlying cultural values, emerge as the major determinants of discontinuance in this study. Moreover, unfavorable information from friends and other birth control users carry greater weight in encouraging a woman to discontinue her use of a contraceptive method than does favorable information in persuading her to continue. Such findings establish the importance of communication credibility for effective conveyance of an unfavorable message. It is concluded that more attention should be paid to the interpersonal networks that channel such information.

The solubility of anesthetic gases in lipid bilayers.

We have measured the lipid/gas partition coefficients at various temperatures of eight anesthetic agents in two sonicated lipid bilayers containing either 96% egg phosphatidylcholine/4% phosphatidic acid or 64% egg phosphatidylcholine/3% phosphatidic acid/33% cholesterol. The Bunsen lipid/gas partition coefficients in the pure phospholipid bilayer at 25 degrees C were: methoxyflurane 820 (interpolated), halothane 150, isoflurane 140, fluroxene 52, xenon 1.4, sulfur hexafluoride 0.24, carbon tetrafluoride 0.056 and hexafluoroethane 0.34. These partition coefficients were close to those in a bulk hydrophobic solvent (olive oil) but were reduced by about 20% in the cholesterol-containing bilayer preparation. In biomembranes the partition coefficient for halothane was lower than in lipid bilayers by about half an order of magnitude. As in olive oil, the partition coefficients mostly increased with decreasing temperature. The enthalpy, entropy and free energy associated with transfer of 1 mol of these agents from the gas phase at 1 atmosphere partial pressure and 25 degrees C into the lipid bilayers under the same conditions were calculated from the temperature variation of the partition coefficients. All of these compounds, with the exception of methoxyflurane, fit the Barclay Butler relationship between entropy and enthalpy of partitioning. The Bunsen partition coefficients were correlated with the anesthetic potencies of seven of these agents in mice and in dogs. Comparisons were made between the different bilayers and olive oil and between hypotheses of anesthesia based on concentration of anesthetic at the active site (Meyer-Overton) and based on the product of concentration and molar volume of anesthetic at the active site (Mullins). Excellent correlations between anesthetic potency and lipid bilayer partition were obtained in all cases. The most consistent fits to the predicted slopes were achieved when both molar volume and partitioning of the anesthetic into the cholesterol-containing bilayer were taken into account, but the differences between the models were small.