The use of expanded polytetrafluoroethylene as an interpositional membrane after lumbar laminectomy.

STUDY DESIGN: Prevention of post-laminectomy membrane formation was evaluated in a canine model. Fat graft, Silastic sheeting and expanded polytetrafluoroethylene were compared with nonimplanted control sites. OBJECTIVES: The development of an effective barrier to peridural scar invasion is of major importance in optimizing results after lumbar laminectomy. SUMMARY OF BACKGROUND DATA: Postoperative peridural fibrosis represents a normal biologic response after lumbar spinal surgery. A variety of biologic and nonbiologic interpositional materials have been studied. Expanded polytetrafluoroethylene has been shown to limit scar adhesion in the pericardium and peritoneum and has not been studied previously as a postlaminectomy interpositional membrane. METHODS: Eleven adult female cross-bred hounds underwent multilevel standardized laminotomies. Three materials--fat graft, Silastic sheeting, and expanded polytetrafluoroethylene--were compared with nonimplanted controls. The animals were killed 12 weeks after surgery and were evaluated histologically and using gadolinium-enhanced magnetic resonance imaging. RESULT: The magnetic resonance imaging studies were inconclusive in assessing peridural scar extension or identifying the implanted membranes. Histology revealed dense scar tissue at all control sites and replacement of all fat grafts by scar. Scar density was significantly less for the expanded polytetrafluoroethylene membrane surgical sites than for the control, fat graft, and Silastic sheeting sites. CONCLUSIONS: Expanded polytetrafluoroethylene membrane is biocompatible, maintains its structural integrity, and is impervious to fibrous ingrowth. These findings support further investigation of expanded polytetrafluoroethylene membrane as an interpositional material to prevent post-laminectomy peridural fibrosis.

Quinolone antibacterial agents. Synthesis and structure-activity relationships of 8-substituted quinoline-3-carboxylic acids and 1,8-naphthyridine-3-carboxylic acids.

A series of 7,8-disubstituted 1-cyclopropyl-6-fluoroquinoline-3-carboxylic acids, 7-substituted 1-cyclopropyl-6-fluoro-1,8-naphthyridine-3-carboxylic acids, and 10-substituted 9-fluoropyridobenzoxazine-6-carboxylic acids has been prepared and evaluated for antibacterial activity. The side chains examined at the 7-position (benzoxazine 10-position) included piperazinyl (g), 3-aminopyrrolidinyl (a), 3-(aminomethyl)pyrrolidinyl (b), and alkylated 3-(aminomethyl)pyrrolidinyl (c-f). Variations at C-8 of the quinolone ring system included hydrogen, nitro, amino, fluorine, and chlorine. The relative enhancement of in vitro activities by the side chains on the 8-hydrogen quinolone and 1,8-naphthyridine against Gram-negative organisms was a greater than b greater than g greater than c-f. The activity imparted to the substituted quinolone nucleus by the 8-substituent was in the order F greater than Cl greater than naphthyridine greater than H greater than benzoxazine greater than NH2 greater than NO2. These trends were retained in vivo.

1-Substituted 7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6,8- difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acids. New quantitative structure-activity relationships at N1 for the quinolone antibacterials.

A series of 18 1-substituted 7-[3-[(ethylamino)methyl]-1- pyrrolidinyl]-6,8-difluoro-1,4-dihydro-4-oxo-3-quinoline- carboxylic acids (N1 analogues of CI-934) were synthesized and evaluated for antibacterial activity and DNA-gyrase inhibition. Correlations between the inhibition of DNA gyrase and antibacterial potency were established. A quantitative structure-activity relationship (QSAR) was derived by using the antibacterial potency for each of 11 strains of bacteria and the Gram-negative mean. The equations indicated that antibacterial potency was strongly dependent on STERIMOL length and width and the level of unsaturation of the N1 substituent. Some strains also showed a dependence on the presence of heteroatoms (O, N, S) in the N1 group. No significant correlations between gyrase inhibition and combinations of these parameters were found. These QSAR results are discussed in conjunction with the conformational analyses from molecular modeling studies. The substituent that most enhanced the activity of the quinolone in all regards was the cyclopropyl group. This analogue, 1-cyclopropyl-7-[3-[(ethylamino)-methyl]-1-pyrrolidinyl]-6, 8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (PD 117558), demonstrated outstanding broad spectrum activity both in vitro and in vivo when compared to relevant standards.

Natural history of the obstructed rabbit appendix: observations with radiography, sonography, and CT.

Chronic (1-3 months' duration) appendiceal obstruction was induced in 11 rabbits to assess the pathologic consequences and to study the associated radiologic, sonographic, and CT findings. Three pathologic/radiologic groups resulted with approximately equal frequency. In group A, the abscess was characterized by inflammatory cells in the lumen and wall of the appendix without mucin production. Calcification was shown radiographically, and sonography showed an anechoic or complex pattern. Group B, the "mixed response," was characterized by an intact hyperplastic mucosa, mucin secretion, and inflammatory debris in the lumen. Occasional calcification was present radiographically, and sonography showed a complex or hypoechoic pattern. In group C, true mucoceles had an intact hyperplastic mucosa, a mucin-filled lumen, and minimal inflammation. These were anechoic on sonography except for mobile foci of inflammatory debris. Chronic obstruction of the appendix results in a spectrum of pathologic responses with varying degrees of either inflammation and mucosal destruction or mucosal hyperplasia and mucin secretion. An abscess results when infection overwhelms the host's inflammatory responses. If the bacteria are destroyed by these defenses, a mucocele forms. An intermediate situation occurs when there is a mixed response with chronic inflammatory changes and an intact mucosa. This finding supports the existence of chronic appendicitis in humans.

Ocular trauma modelling.

Non-ophthalmologists must know how to detect, diagnose, and initially manage acute eye and ocular adnexal injuries in order to minimize their morbidity. Such instruction can be provided medical students in part from dog eyes and lids injured so as to produce models of common forms of ocular trauma. We describe the generation of such models and the format of instruction employed at the Uniformed Services University of the Health Sciences.

Spinal decompression in a black bear.

A 17-year-old black bear was examined because of posterior paralysis. Radiography revealed a narrowed disk space at T10-11, indicating a ruptured intervertebral disk. Subsequently, a dorsolateral hemilaminectomy was performed. Recovery from paralysis was slow because of the size of the animal (127 kg) and lack of appropriate physical therapy. When evaluated more than 1 year later, however, the bear had no signs of neurologic deficits.

Aortic interruption in a dog.

A 3-month-old English Bulldog was found to have a discontinuity between the ascending and descending aorta. There were no signs of illness associated with the interruption. The descending aorta was supplied with blood by collateral circulation. An aortic graft of woven synthetic material was surgically implanted to connect the ascending and descending aorta. Without any restrictions on the dog's activity, the dog has lived for over 1 year and continues to do well.