Am Miller

Aqueous humor sCD44 concentration and visual field loss in primary open-angle glaucoma

PurposeTo correlate aqueous humor soluble CD44 (sCD44) concentration, visual field loss, and glaucoma risk factors in primary open-angle glaucoma (POAG) patients. MethodsAqueous samples were obtained by paracentesis from normal and glaucoma patients who were undergoing elective surgery and analyzed for sCD44 concentration by enzyme-linked immunosorbent assay. ResultsIn normal aqueous (n=124) the sCD44 concentration was 5.88±0.27 ng/mL, whereas in POAG aqueous (n=90) the sCD44 concentration was 12.76±0.66 ng/mL, a 2.2-fold increase (P<0.000001). In POAG patients with prior successful filtration surgery (n=13), the sCD44 concentration was decreased by 43% to 7.32±1.44 (P=0.001) in comparison with POAG patients without filtration surgery; however, the sCD44 concentration in the prior successful filtration subgroup with no medications and normal intraocular pressure was 12.62±3.81 (P=0.05) compared with normal. The sCD44 concentration of normal pressure glaucoma patients was 9.19±1.75 ng/mL, a 1.6-fold increase compared with normal (P=0.02). Race and intraocular pressure pulse amplitude were significant POAG risk factors in this cohort of patients. In both normal and POAG patients with mild and moderate visual field loss, sCD44 concentration was greater in African Americans than in whites (P=0.04) ConclusionssCD44 concentration in the aqueous of POAG patients correlated with the severity of visual field loss in all stages in white patients and in mild to moderate stages in African American patients. sCD44 concentration in aqueous is a possible protein biomarker of visual field loss in POAG.

Reconstitution of trabecular meshwork GAGs: Influence of hyaluronic acid and chondroitin sulfate on flow rates

Purpose:This study was undertaken to determine whether the concentration of hyaluronic acid (HA) and of chondroitin sulfate (CS) occurring in the normal and the primary open-angle glaucoma (POAG) trabecular meshwork (TM) influences flow rates in vitro as a function of pressure. Methods:We tested 100, 500, and 4000 kDa molecular weight HA, CS, reconstituted normal and POAG TM HA-CS and juxtacanalicular connective tissue (JCT) HA-CS in a micro test chamber to determine initial and steady-state flow rates. The resistance and permeability (Ko) were calculated; Linear Newtonian mechanics were used to determine the possible contributions of the hydrophobic interactions of HA. Results:Initial flow rates increased in the pressure range of 5 to 20 mm Hg for the three HA preparations and the flow rates declined in the pressure range of 20 to 40 mm Hg. Flow rates of reconstituted normal TM and JCT were optimum at 10 mm Hg and then declined with increasing pressure. Flow rates of reconstituted POAG TM and JCT were optimum only at 5 mm Hg and then declined. The steady-state rate of POAG JCT HA-CS at 10 mm Hg was slow: the transition time (ie, the time required to start an increase in flow rate) was 29 hours and the lag time (ie, the time required to obtain steady-state flow rate) was 17 hours. The maximum flow rate in POAG JCT HA-CS decreased by 37.2% from the normal JCT HA-CS. The calculated resistance of reconstituted POAG JCT HA-CS was approximately 18% of the total resistance of the human JCT compared with 10% in the normal JCT. Conclusions:Hyaluronic acid and CS contribute to flow resistance and influence flow rate in vitro. The influence of HA is particularly sensitive to an increase in the pressure gradient, which may be caused by unfolding of the hydrophobic interactions of HA polymers that further entangles the HA polymer. The POAG JCT HA-CS concentrations represent a significant factor in outflow resistance in POAG, particularly at higher pressures.

Interstellar Iron and Silicon Depletions in Translucent Sight Lines

We report interstellar Fe II and Si II column densities toward six translucent sight lines (AV 1) observed with the Space Telescope Imaging Spectrograph (STIS). The abundances were determined from the absorption of Si II] at 2335 A, and several weak Fe transitions including the first reported detections of the λ2234 line. We derive an empirical f-value for the Fe II λ2234 transition of log(fλ) = -1.54 ± 0.05. The observed sight lines sample a variety of extinction characteristics as indicated by their RV values, which range from 2.6 to 5.8. The dust-phase abundances of both Si and Fe are positively correlated with the small-grain population (effective radii smaller than a few hundred μm) toward the targets. The physical conditions along the sight lines suggest that this relationship may be due to differences in the survival of small particles in some interstellar environments. The chemical composition of the small grains could either resemble dust mantles or be silicate-rich.