Localization of the ribosomal protection protein Tet(O) on the ribosome and the mechanism of tetracycline resistance.

Tet(O) belongs to a class of ribosomal protection proteins that mediate tetracycline resistance. It is a G protein that shows significant sequence similarity to elongation factor EF-G. Here we present a cryo-electron microscopic reconstruction, at 16 A resolution, of its complex with the E. coli 70S ribosome. Tet(O) was bound in the presence of a noncleavable GTP analog to programmed ribosomal complexes carrying fMet-tRNA in the P site. Tet(O) is directly visible as a mass close to the A-site region, similar in shape and binding position to EF-G. However, there are important differences. One of them is the different location of the tip of domain IV, which in the Tet(O) case, does not overlap with the ribosomal A site but is directly adjacent to the primary tetracycline binding site. Our findings give insights into the mechanism of tetracycline resistance.

The surgical management of hypotony.

OBJECTIVE: To study the effect of dissecting epiciliary proliferative tissue in eyes that are hypotonous. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Eight patients (nine eyes). MAIN OUTCOME MEASURES: Normalization of intraocular pressure and preservation of vision. METHODS: A chart review was conducted to locate all surgical procedures performed primarily for hypotony. Nine procedures on eight eyes of eight patients seen in the vitreoretinal service of the Wilmer Ophthalmological Institute were identified and included in this study. Six of these eyes had undergone prior surgery for retinal detachment in association with proliferative vitreoretinopathy, one had undergone surgery for retinal detachment in the setting of a ruptured globe, and two had undergone cataract surgery and coined the diagnoses of uveitis (juvenile rheumatoid arthritis and sarcoid). Dissection and removal of the epiciliary proliferative tissue and lens capsule was undertaken by two surgeons (EdJ and MSH) using either a pars plana or limbal approach. The main outcome measures were intraocular pressure (IOP) and visual acuity after an average follow-up of 26 months (range, 9-48 months). RESULTS: In the immediate postoperative period, all patients showed an increase in IOP (average increase of 6.3 mm Hg; range, 3-14 mmHg). This average increase in IOP decreased to 5.2 mmHg at 6 months and 4.2 mm Hg at 12 or more months of follow-up. The rate of the IOP decrease appeared to lessen with time, suggesting long-term stabilization. Visual acuity remained stable in all patients, although the final level of vision was low. CONCLUSIONS: Surgical intervention for hypotony with greater than 1 year follow-up continues to show elevated IOP in some patients, despite the fact that the large initial increase in IOP is not sustained. No eye had phthisis develop or became painful. However, no eye had marked improvement in vision. Further study is needed to uncover the main contributing factors that result in hypotony before IOP can be maintained for prolonged periods in more hypotonous eyes and before these eyes can regain more vision.

Evaluating persistent and recurrent choroidal neovascularization. The role of indocyanine green angiography.

OBJECTIVE: To evaluate the clinical utility of routinely using indocyanine green angiography (ICGA) with fluorescein angiography (FA) in detecting persistent or recurrent choroidal neovascularization (CNV). DESIGN: Prospective, consecutive case series. PARTICIPANTS: Twenty-four eyes of 21 patients with exudative age-related macular degeneration (AMD) that had conventional laser treatment for CNV were examined. INTERVENTION: Fluorescein angiography and ICGA were performed together on all eligible eyes at the first post-treatment visit and all subsequent follow-up visits in which persistent or recurrent CNV was suspected clinically. MAIN OUTCOME MEASURES: Choroidal neovascularization detection and delineation by each angiographic technique were measured. RESULTS: Of the 54 FA-ICGA study pairs performed over a 20-month investigation period, FA showed well-defined, ill-defined, and no CNV in 10 (19%), 19 (35%), and 25 (46%) eyes, respectively. Indocyanine green angiography had a high concordance rate at 70% and 88% when persistent or recurrent CNV was well-defined and absent, respectively, on FA and rarely added additional, clinically useful information in these settings, particularly in the former presentation. Of the 29 eyes that showed some evidence of CNV by FA, the neovascular complex was ill-defined in 19 (66%) eyes. When CNV was ill-defined by FA, the corresponding ICGA showed well-defined CNV in 9 (47%) of 19 eyes, in 5 of which the CNV was nonsubfoveal in location. CONCLUSIONS: Persistent or recurrent CNV in AMD was frequently ill-defined by FA. Indocyanine green angiography was a valuable adjunct to FA by better delineating CNV in this specific setting. However, ICGA was not useful when the post-treatment FA showed well-defined CNV. Furthermore, ICGA was not helpful when the first post-treatment FA was negative and there were no ophthalmoscopic signs of exudation.

Comparison of bifocal and progressive addition lenses on aviator target detection performance.

The objective of this project was to determine if the type of presbyopic correction worn by aviators, conventional bifocal versus progressive addition lenses (PAL's), differentially affects aviator visual search performance. Experienced aviators, most with tactical fighter aircraft experience, searched for high-contrast targets under simulated dawn/dust (mesopic) lighting conditions (approximately 3.0 cd/m2) while wearing either a standard bifocal (ST-25) or PAL spectacle correction. Latency of locating high-contrast targets under these viewing conditions was differentially affected by the type of presbyopic correction used. Specifically, compared to a standard bifocal (ST-25), a PAL correction (Varilux Infinity) significantly lowered the time needed to locate static targets at a cockpit instrument viewing distance (83 cm). Accuracy of target location responses was not affected by the type of correction used. In addition, 7 months post-experiment, 7 of the 12 participants (58%) indicated that they used their PAL correction exclusively when flying the T-39 Sabre Liner. Three subjects (25%) used their PAL correction intermittently (primarily at night) when flying and two subjects preferred not to use the PAL's. These results suggest that relative to bifocals, speed of responding to static targets at intermediate viewing distances may be improved by wearing PAL's, and that subjects were able to adapt to PAL lenses quickly in a laboratory setting, using them later in a functional aviation environment.

The fate of eyewear in aircraft ejections.

Ejection from jet aircraft has been exhaustively studied from many perspectives; e.g., causes of ejection, types and causes of ejection injuries, etc. Curiously, no reports exist describing the fate of eyewear in ejections. Many pilots wear required corrective lenses during flight operations, and many wear tinted lenses. What happens to these during ejection? What injuries are a result of the eyewear? What factors can be identified that influence retention of the eyewear and severity of related injury? Do contact lenses provide significant advantages? There were 48 ejections occurring between 1977 and 1990 that involved corrective or tinted lens use that were retrospectively examined using Naval Safety Center records and personal questionnaires. There were five contact lens wearers included. Retention rates were calculated as functions of several variables. Although 37 of 46 lost all lenses, each instance of retention occurred with visor down, oxygen mask on, helmet properly secured, and at lower ejection speeds. Related injuries were minor and occurred in only 20%. The utility and need for enforcement of standard operating procedures (i.e., mask on, helmet secured, and visor down) was clearly demonstrated. Only 19 of 46 clearly met all 3 criteria. Contact lens users were too few to allow meaningful conclusions.

Recreation therapy: reducing the effects of isolation for the patient in a protected environment.

The psychological effect of extended isolation in a protected environment is of concern to health care professionals on the Pediatric Oncology Unit at the National Institutes of Health. Problems such as increased anxiety, depression, boredom, passivity, and time-space disorientation have been noted in similarly isolated patients. The development of a comprehensive therapeutic recreation program designed to address these issues, as well as to meet the individual leisure needs of the isolated patient, is seen as an essential component of patient care. This article outlines the rationale and format of such a program.