Toxicity of mono-, di- and tri-chlorophenols to lux marked terrestrial bacteria, Burkholderia species Rasc c2 and Pseudomonas fluorescens.

Burkholderia species RASC and Pseudomonas fluorescens were marked with lux genes, encoding for bioluminescence and used to assess the toxicity of mono-, di- and tri-chlorophenols by determining the decline in bioluminescence following exposure to the compounds in aqueous solution. Toxicity was expressed as a 50% effective concentration value (EC50, equating to the concentration of compound which caused a 50% decline in bioluminescence. Comparing the toxicity values of the compounds showed that, in general, increasing the degree of chlorination, increased toxicity. By carrying out forward multiple linear regressions with log10 EC50 values and physio-chemical descriptors, it was shown that molecular parameters describing the hydrogen bonding nature of a chlorophenol provided a better fit than regressions between toxicity data and log10 Kow alone. Utilising these descriptor variables in equations, it was shown that the toxicity of chlorophenols to the lux marked bacteria could be predicted from the compounds physio-chemical characteristics. By correlating lux marked RASC c2 and P. fluorescens EC50 values with toxicity values using Pimephales promelas (fathead minnow), Tetrahymena pyriformis (ciliate) and marine bacterium Vibriofischeri, it was apparent that lux marked RASC c2 correlated well with the freshwater aquatic species (P. promelas and T. pyriformis). This implied that for predictions of toxicity of organic xenobiotic compounds to higher organisms, lux marked RASC c2 could be utilised as a rapid surrogate.

Benefits of stereolithography in orbital reconstruction.

OBJECTIVE: To describe the benefits of the stereolithography (SLA) modeling system in the evaluation and surgical planning of selected bony orbital pathology. DESIGN: Two case reports. PARTICIPANTS: One patient presented with a displaced left orbital roof fracture into his orbit causing globe compression and binocular vertical diplopia. A second patient underwent removal of his right orbital floor, medial wall, and inferior portion of his lateral wall during excision of a cylindrical cell papilloma of the paranasal sinuses. Postoperatively, he suffered from globe ptosis and binocular oblique diplopia. INTERVENTION: Stereolithographic models of the patients' orbits were obtained from computed tomography data to better assess the bony orbital pathology. In the second patient, the model was used as a template to create a temporary custom fit prosthesis to repair the defect of his orbital walls. RESULTS: The SLA models were useful in evaluating the dimensions of the bony defects and in preoperative surgical planning. Intraoperatively, the SLA models facilitated orbital surgical rehabilitation. Postoperatively, both patients noted resolution of their diplopia after reconstruction of more normal bony anatomy. CONCLUSIONS: In selected cases, SLA offers highly accurate models of the bony orbit for preoperative evaluation, surgical planning, and teaching and can act as a template for custom prosthesis manufacturing. This technology increases the orbital surgeon's options in managing complex orbital pathology.

Squamous cell carcinoma arising in the epithelial lining of a dentigerous cyst.

The dentigerous cyst is a common oral lesion arising as a developmental anomaly during amelogenesis. In rare instances, the epithelial lining of these cysts may give rise to squamous cell carcinoma (SCC). Fewer than 50 cases of this rare entity have been reported in the world literature to date. We present an additional case of SCC arising in a dentigerous cyst with a rationale for our treatment approach. In addition, we offer a review of the literature and a review of the clinical, histologic, and radiographic findings associated with this finding. We discuss epidemiologic data and treatment options.

Quantitative structure-toxicity relationships for chlorophenols to bioluminescent lux-marked bacteria using atom-based semi-empirical molecular-orbital descriptors.

Literature data on the toxicity of chlorophenols for three luminescent bacteria (Vibrio fischeri, and the lux-marked Pseudomonas fluorescens 10586s pUCD607 and Burkholderia spp. RASC c2 (Tn4431)) have been analyzed in relation to a set of computed molecular physico-chemical properties. The quantitative structure-toxicity relationships of the compounds in each species showed marked differences when based upon semi-empirical molecular-orbital molecular and atom based properties. For mono-, di- and tri-chlorophenols multiple linear regression analysis of V. fischeri toxicity showed a good correlation with the solvent accessible surface area and the charge on the oxygen atom. This correlation successfully predicted the toxicity of the heavily chlorinated phenols, suggesting in V. fischeri only one overall mechanism is present for all chlorophenols. Good correlations were also found for RASC c2 with molecular properties, such as the surface area and the nucleophilic super-delocalizability of the oxygen. In contrast the best QSTR for P. fluorescens contained the 2nd order connectivity index and ELUMO suggesting a different, more reactive mechanism. Cross-species correlations were examined, and between V. fischeri and RASC c2 the inclusion of the minimum value of the nucleophilic susceptibility on the ring carbons produced good results. Poorer correlations were found with P. fluorescens highlighting the relative similarity of V. fischeri and RASC c2, in contrast to that of P. fluorescens.

Long-term follow-up of aviators after functional endoscopic sinus surgery for sinus barotrauma.

Prior to endonasal endoscopic advances for the treatment of sinus disease, surgical results for aviators with recurrent sinus barotrauma (RSB) were inconsistent. Between 1988 and 1992, 54 aviators, who were permanently or temporarily grounded, underwent functional endoscopic sinus (FES) surgery in an attempt to return them to active flying status. Follow-up in the immediate postoperative period revealed that 98% of these aviators returned to active flight duty. A questionnaire was mailed to each of these aviators to compare their preoperative and long-term postoperative symptoms and determine their current flying status. Long-term follow-up time ranged from 20 to 72 mo with average of 48 mo. Of the aviators who responded to the survey, 92% have continued their flying duties and do not report difficulties with RSB. We conclude that FES surgery is effective in the short- and long-term management RSB in aviators.

Toxicity assessment of xenobiotic contaminated groundwater using lux modified Pseudomonas fluorescens.

A bacterial bioassay, suitable for rapid screening to assess the relative toxicity of xenobiotic contaminated groundwater has been developed. The quantitative bioassay utilizes a decline in luminescence of the lux marked soil bacterium Pseudomonas fluorescens on exposure to contaminated groundwaters from which effective concentration (EC) values can be assessed and compared. P. fluorescens was most sensitive to semivolatile organics in groundwaters but there was no correlation between EC value and chemical content. The sensitivity and reproducibility of the P. fluorescens bioassay was compared with that of Microtox and results showed that mean EC50 values for diluted ground water replicate samples were 20% and 18% respectively. This suggested that the P. fluorescens bioassay was as applicable to groundwater screening as the widely used Microtox bioassay.

Rehabilitation of lower cranial nerve deficits.

Lower cranial nerve deficits following skull base surgery can be accompanied by significant morbidity, especially if the vagus nerve has been sacrificed or injured. Loss of pharyngeal function and glottic closure can result in dysphagia and aspiration. Left untreated, these can result in the major morbidity for the patient following skull base surgery. The authors discuss the management of lower cranial nerve deficits, with emphasis on rehabilitation of swallowing function and prevention of aspiration following vagal injury.

Pediatric sphenoidotomy.

The posterior ethmoid air cells and the sphenoid sinuses have a complex anatomy that is surrounded by vital structures. To more easily protect these structures, three approaches are presented that make pediatric sphenoidotomy a safer procedure. The approaches include measuring the distance from the anterior nasal spine to the anterior and surgical posterior faces of the sphenoid sinus intraoperatively and comparing these to the patient's height and age, the use of the "ridge" to ensure a safe entry into the sphenoid, and, in patients where isolated sphenoid disease is present, the use of a powered instrument to enlarge the sphenoid ostium. The availability of measurements relating the height of the patient to the location of the sphenoid sinus, the use of the "ridge," and the use of powered instrumentation, should help the surgeon enter the sphenoid with greater confidence and achieve a more effective result.

Contract learning.

The learning contract format can be used to provide a learning situation that encourages individuality, flexibility, and mutuality. General components of the learning contract are formats, roles, climate setting, goal setting, resources, timing, and evaluation. Suggestions are made for applying the learning contract to self-directed continuing education for physical therapist educators, clinical physical therapists, and individual physical therapists.