Fluorescence Lifetime Imaging of Human Sub-RPE Calcification In Vitro Following Chlortetracycline Infusion.

We have shown that all sub-retinal pigment epithelial (sub-RPE) deposits examined contain calcium phosphate minerals: hydroxyapatite (HAP), whitlockite (Wht), or both. These typically take the form of ca. 1 µm diameter spherules or >10 µm nodules and appear to be involved in the development and progression of age-related macular degeneration (AMD). Thus, these minerals may serve as useful biomarkers the for early detection and monitoring of sub-RPE changes in AMD. We demonstrated that HAP deposits could be imaged in vitro by fluorescence lifetime imaging microscopy (FLIM) in flat-mounted retinas using legacy tetracycline antibiotics as selective sensors for HAP. As the contrast on a FLIM image is based on the difference in fluorescence lifetime and not intensity of the tetracycline-stained HAP, distinguishing tissue autofluorescence from the background is significantly improved. The focus of the present pilot study was to assess whether vascular perfusion of the well tolerated and characterized chlortetracycline (widely used as an orally bioavailable antibiotic) can fluorescently label retinal HAP using human cadavers. We found that the tetracycline delivered through the peripheral circulation can indeed selectively label sub-RPE deposits opening the possibility for its use for ophthalmic monitoring of a range of diseases in which deposit formation is reported, such as AMD and Alzheimer disease (AD).

Quantitative analysis of intermuscular septa in the leg: implications for trauma surgery.

BACKGROUND: Compartment syndrome is the excess swelling within an inelastic compartment leading to excessive compartment pressure. Lower limb trauma has a high risk of compartment syndrome, which is typically mitigated using a two-incision fasciotomy. Our previous findings showed surgeons sometimes perform incomplete fasciotomies due to misidentifying the septum between the lateral and superficial posterior compartments as the septum between the anterior and lateral compartments. We conjectured this may be due to variability in the septal position between individuals leading to misinterpretation of the septal identity. METHODS: A retrospective analysis was performed using CT angiograms to analyze septal position between the anterior and lateral compartments of the leg of 100 patients randomly selected from the University of Maryland Shock Trauma Center database. RESULTS: Analysis of septal position showed that (1) as the septum progresses distally down the leg, the relative septum position shifts anteriorly; and that (2) there was considerable variability in the intermuscular septum position between individuals even when accounting for the anterior to posterior progression of septal position. DISCUSSION: This variability could lead to erroneous septal identification in individuals with a very anteriorly located septum during a leg fasciotomy with the classic initial incision being insufficiently anterior. We propose making the lateral initial incision 'two finger breadths posterior the tibia' rather than the traditional 'one finger breadth anterior' to the fibula. This moves the initial incision slightly anteriorly, uses the more readily palpable tibia, and makes the medial and lateral incisions symmetrical at 'two finger breadths' from the tibia, simplifying the procedure. LEVEL OF EVIDENCE: Level 3.