Effects of examiner strength on reliability of hip-strength testing using a handheld dynamometer.

CONTEXT: Hip-muscle impairments are associated with a variety of lower-extremity dysfunctions. Accurate assessment in the clinical setting can be challenging due to the strength of hip muscles relative to examiner strength. OBJECTIVE: To examine the influence of examiner strength and technique on manual hip-strength testing using a handheld dynamometer. DESIGN: Repeated measures. SETTING: Research laboratory. PARTICIPANTS: 30 active adults (age 24 ± 1.4 y). INTERVENTIONS: Three examiners of different strength performed manual muscle tests (MMT) in 2 different positions for hip extension, abduction, and external rotation using a MicroFet handheld dynamometer. Examiner strength was quantified via a 1-repetition-maximum leg press and chest press with a Keiser A420 pneumatic resistance machine. MAIN OUTCOME MEASURES: Intrarater reliability (ICC3,1), interrater reliability (ICC2,1), and measured torque values. RESULTS: Intrarater reliability for all measurements ranged from .82 to .97. Interrater reliability ranged from .81 to .98. Main effects for hip extension revealed a significant difference in torque values between examiners and between techniques. For the short-lever hipabduction and seated hip-external-rotation tests, there was a significant difference between examiners. There was no significant difference in measured torque values between examiners with the long-lever hip-abduction or the prone hip-external-rotation tests. CONCLUSIONS: MMT of the hip may be performed with high reliability by examiners of different strength. To obtain valid MMT measurements of hip muscles, examiners must consider their own strength and testing techniques employed. The authors recommend a long-lever technique for hip abduction and a prone position for testing hip external rotation to minimize the influence of examiner strength. Both positions appear to provide mechanical advantages to the examiner compared with the alternative techniques. The authors are unable to recommend a preferred hip-extension-testing technique to minimize the influence of examiner strength.

Efficacious fluorescence turn-on probe for high-contrast imaging of human cells overexpressing quinone reductase activity.

We report a new turn-on substrate probe whose intense fluorescent reporter signature is selectively provided upon probe activation by the cancer-associated oxidoreductase, hNQO1. The extremely high fluorescence turn-on of the probe was utilized to generate fluorescence microscope images of hNQO1-expressing, tumor-derived colorectal and ovarian cancer cells with unprecedented positive signal-to-negative background ratios (PNRs), a key step toward probe application in guided surgical removal of diseased tissues.

Environmentally Robust Rhodamine Reporters for Probe-based Cellular Detection of the Cancer-linked Oxidoreductase hNQO1.

We successfully synthesized a fluorescent probe capable of detecting the cancer-associated NAD(P)H: quinoneoxidoreductase isozyme-1 within human cells, based on results from an investigation of the stability of various rhodamines and seminaphthorhodamines toward the biological reductant NADH, present at ∼100-200 µM within cells. While rhodamines are generally known for their chemical stability, we observe that NADH causes significant and sometimes rapid modification of numerous rhodamine analogues, including those oftentimes used in imaging applications. Results from mechanistic studies lead us to rule out a radical-based reduction pathway, suggesting rhodamine reduction by NADH proceeds by a hydride transfer process to yield the reduced leuco form of the rhodamine and oxidized NAD(+). A relationship between the structural features of the rhodamines and their reactivity with NADH is observed. Rhodamines with increased alkylation on the N3- and N6-nitrogens, as well as the xanthene core, react the least with NADH; whereas, nonalkylated variants or analogues with electron-withdrawing substituents have the fastest rates of reaction. These outcomes allowed us to judiciously construct a seminaphthorhodamine-based, turn-on fluorescent probe that is capable of selectively detecting the cancer-associated, NADH-dependent enzyme NAD(P)H: quinoneoxidoreductase isozyme-1 in human cancer cells, without the issue of NADH-induced deactivation of the seminaphthorhodamine reporter.