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Biomedical subjects

C D Leahy

Publications and source records attributed to C D Leahy.

14 recordsLinked to original sources
PubMed1999

Effects of eyelid scrubbing on the lid margin.

PURPOSE: To compare the effects of eyelid scrubbing with an eyelid cleansing solution (ECS) to eyelid scrubbing with ECS and the addition of antibacterial or anti-inflammatory pharmaceuticals on the clinical appearance, microbial status, tissue histology, and the inflammatory cell profile of the normal eyelid margin. METHODS: Eyelid scrubbing was performed twice daily using ECS; ECS with the antibacterial sulfacetamide (ECS+); and ECS with sulfacetamide and prednisolone acetate (ECS++) over a 21 day period on three groups of 16 rabbits with clinically normal eyelids. RESULTS: Significant hyperemia of the margin occurred in all three groups over the 3 week period; however, the degree of hyperemia was less with ECS+ (P<0.05) and ECS++ (P<0.05). Chemosis, tearing, mucus discharge, and the microbial status were not significantly different than controls. There were no marked histologic differences in the tissues, except for increased red blood cell packing in the small vessels near the lid margins in scrubbed eyelids, consistent with hyperemia. The inflammatory cell profile showed minimal changes that were not statistically significant in any of the three groups, except that >50% of mast cells showed evidence of degranulation. CONCLUSIONS: Use of ECS with an antibiotic, or an antibiotic and steroid solution, resulted in less inflammation than scrubbing with ECS alone.

Administration, Topical↗
PubMed1997

Histopathology of the ocular surface after eye rubbing.

PURPOSE: This study demonstrates the effects of eye rubbing on ocular surface tissue. METHODS: Rabbits (3-4 kg; n = 24) were killed at 0, 4-h, 8-h, and 12-h intervals after a 5-min period of eye rubbing. Ocular surface tissues were studied by light and scanning electron microscopy. Contralateral eyes served as controls. Eye rubbing was accomplished by using digital pressure over the closed eyelid with a force sufficient to appreciate by palpation the orbital rim. Biomicroscopic examination revealed marked vascular injection of the conjunctiva. Ocular surface tissues studied included the lid margins, the upper and lower tarsal conjunctivae, the bulbar conjunctiva, and the cornea. RESULTS: Changes in the ocular surface included dramatic alteration in the upper tarsal conjunctiva when compared with controls. The cornea and bulbar and lower tarsal conjunctiva were not altered when compared with control tissues, except for some increase in exfoliating cells in the cornea. The surface epithelial cells of the upper tarsal conjunctiva had a spheroidal structure and were markedly elevated, the microprojections were altered, and there was evidence of increased cellular exfoliation. These changes were most pronounced at the 0 and 4-h time points, less noticeable at 8 h, and no appreciable changes were observed when compared with control tissues at 12 h. CONCLUSION: This study demonstrates that eye rubbing causes surface alterations in the stratified cuboidal to columnar epithelial surface of the upper tarsal conjunctiva while sparing the stratified squamous epithelial surface of the distal lid margins and cornea.

Animals↗
PubMed1996

Phospholipids in meibomian gland secretion.

The bulk of the lipid layer overlying the aqueous portion of the precorneal tear film is composed of polar and nonpolar components. The nonpolar lipids have been the subject of numerous studies; however, the polar lipids have remained relatively uncharacterized. The polar lipids are thought to contain surfactant phospholipids that are critical to the spreading of a lipid film over the aqueous layer, by providing an interface between this layer and the nonpolar lipids. The purpose of the present study is to identify and quantitate the phospholipid complement of meibomian gland secretion which provides the tear film with phospholipids. Meibomian gland secretion was collected from rabbits and phospholipids identified and quantitated by 31P nuclear magnetic resonance spectroscopy. Ten phospholipids were detected from meibomian gland secretion: diphosphatidylglycerol, dihydrosphingomyelin, ethanolamine plasmalogen, phosphatidylethanolamine (PE), phosphatidylserine, sphingomyelin, lysophosphatidylcholine, phosphatidylinositol, alkylacylphosphatidylcholine, and phosphatidylcholine (PC). The two major phospholipids were PC and PE, together comprising nearly 60% of the total phospholipid profile. The nature and relative concentrations of the meibomian gland secretion phospholipids are congruous with a surfactant role at the aqueous-lipid interface and, considering the physical chemistry of the tear film, suggest that the phospholipids should be organized in a very flat or planar configuration.

Animals↗
PubMed1996

Meibomian gland phospholipids.

The content of the meibomian gland lipid exprimate is known, but little is known about the phospholipids that comprise the glandular cells. The purpose of the present study is to identify and quantitate the phospholipid complement of the meibomian gland cells that produce the lipid secretion of meibomian oil and which is vital to tear film stability. Eyelids (n = 50) were excised from rabbits, and after surgical removal of surrounding tissues, the tarsal plates with and without expressing meibomian oil were extracted and phospholipids of the plates quantified by 31P nuclear magnetic resonance (NMR). Seventeen phospholipids were quantified from tarsal plates expressed of oil and tarsal plates containing meibomian oil: alkylacylphosphatidylcholine (AAPC), dihydrosphingomyelin (DHSM), dimethylphosphatidylethanolamine, diphosphatidylglycerol (cardiolipin), ethanolamine plasmalogen (EPLAS), lysoethanolamine plasmalogen, lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylserine, phosphatidic acid, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol, phosphatidylinositol, phosphatidylserine, sphingomyelin (SM), sphingosylphosphorylcholine. The six zwitterionic and neutral phospholipids, DHSM, EPLAS, PE, SM, AAPC, and PC together comprise 79.5% of the total meibomian gland phospholipid profile (in meibomian oil this value is 84.2%). The zwitterionic and neutral phospholipids dominate meibomian gland phospholipid profiles. Since the meibomian gland cells undergo holocrine secretion and form the meibomian glad secretion, such a composition is consistent with the hypothesis that a chemically stable lamellar surfactant layer phospholipids bind non-polar meibomian oil to the aqueous layer of the tear film.

Animals↗
PubMed1995

Distribution of membrane phospholipids in the rabbit neural retina, optic nerve head and optic nerve.

Since diseases of the neural retina and optic nerve can result in alteration of biological membranes, this study determines similarities and differences in the membrane phospholipid content of the neural retina, optic nerve head, and optic nerve to serve as baseline data. Neural retina, optic nerve head, and optic nerve were dissected, isolated as 5 sets from 20 rabbits and frozen in liquid N2. Separate pooled-tissue extracts were prepared for each set of tissues and phosphorus-31 nuclear magnetic resonance (31P NMR) analyses performed. Ten phospholipids were quantified (respective neural retina, optic nerve head, and optic nerve mole % are given for the 5 major phospholipids detected): phosphatidylcholine (PC), 44.61, 27.67, 26.40; PC plasmalogen or alkylacyl PC (CPLIP); phosphatidylinositol (PI); sphingomyelin (SM); phosphatidylserine (PS), 12.63, 14.77, 15.09; phosphatidylethanolamine (PE), 21.21, 9.59, 8.69; PE plasmalogen (EPLAS), 11.07, 30.96, 33.93; an unidentified (unknown) phospholipid (U) at the chemical-shift value of 0.13 ppm; diphosphatidylglycerol (DPG); and phosphatidic acid (PA), 0.46, 2.92, 1.57. Significant differences between the various tissues were determined by the one-way analysis of variance, using a Scheffé range value of P < 0.05. The neural retina in all phospholipids detected except for the uncharacterized (unknown) phospholipid was significantly different from the optic nerve head tissue. The optic nerve head was significantly different from the optic nerve in PC, CPLIP, PE, EPLAS, U, DPG, and PA. The data provide a baseline for studies on pathologically changed neural retina, optic nerve head, and optic nerve.

Animals↗
PubMed1995

Distribution of membrane phospholipids in the rabbit uvea.

BACKGROUND AND AIMS: Since the uveal tract becomes involved in inflammatory disorders, which are known to affect lipid metabolism, we studied normal membrane phospholipids (PLs) in order to (1) determine baseline PL profiles of the iris, ciliary body, and choroid, and (2) compare and contrast PL profiles of the uveal tissues. METHODS: Iris, ciliary body and choroid tissues were isolated from rabbit eyes (n = 30) and extracted with chloroform-methanol using a modified Folch procedure. Quantitative tissue PL profiles were obtained using 31P nuclear magnetic resonance. RESULTS: Fourteen PLs were detected and quantitated in all three uveal tissues among which was one unidentified PL at -0.17 ppm. The five major PLs in the iris, ciliary body and choroid, respectively, have the following PL composition (mole percent of total phosphorus): ethanolamine plasmalogen 14.58, 15.07, 16.52; phosphatidylethanolamine 13.10, 12.40, 9.23; phosphatidylserine 11.24, 10.27, 12.13; sphingomyelin (SM) 11.10, 11.97, 18.21; and phosphatidylcholine (PC) 36.61, 36.70, 29.88. Additionally, lysophosphatidic acid, phosphatidic acid, lysophosphatidylcholine, phosphatidylinositol, and PC plasmalogen or alkacyl PC were detected in all tissues. Sphingosylphosphorylcholine also was detected in the ciliary body and choroid. Lysophosphatidylethanolamine was detected in the choroid. In addition, 42 PL metabolic indexes were calculated from these data, which permitted pathway-specific lipid analyses. CONCLUSION: This study establishes baseline PL profiles of the uveal tract tissues and will permit comparisons with tissues from eyes with inflammatory disorders. The PL concentrations in conjunction with the indexes demonstrate that overall the choroid has membranes that are less permeable to ion translocation than either the iris or the ciliary body, although there are compensatory concentration changes between the SM and PC components among these three tissues.

Animals↗
PubMed1994

Tear film lipid layer thickness as a function of blinking.

Alterations in the tear film lipid layer as a function of blinking were investigated using a custom-designed specular reflection monitoring system. The tear film lipid layer of 104 subjects under conditions of normal ("baseline") blinking and "forceful" blinking was quantitated on the basis of specific interference colors. Deliberate, forceful blinking was found to significantly increase the lipid layer thickness (LLT) of the tear film. The magnitude of increase was found to be correlated with the baseline LLT values; individuals with baseline LLT values of 75-150 nm demonstrated a mean increase in LLT of 33 nm following forceful blinking, whereas subjects with baseline LLT values < or = 60 nm experienced a mean increase of 19 nm. The difference in the magnitude of increase between the groups was highly significant (p = 0.0001). The data suggest that, in addition to playing a role in the spreading of lipid across the tear film, the blinking mechanism may be important in the maintenance of the lipid layer by augmenting the expression of lipids from the meibomian glands.

Adolescent↗
PubMed1994

Distribution of membrane phospholipids in the crystalline lens.

PURPOSE: To determine the phospholipid content of specific anatomic regions within the crystalline lens. METHODS: Phospholipid extracts of tissues dissected from 5 sets of 10 rabbit lenses were analyzed by 31P nuclear magnetic resonance spectroscopy. Twenty-nine pathway-specific metabolic indexes were calculated from groups of phospholipids and ratios of phospholipids. RESULTS: Phospholipid levels (mole percent) were determined from the capsule with attached epithelium, the cortex, and the nucleus. Eleven phospholipids were detected with significant regional differences in the lens phospholipid profiles. The levels of phosphatidylcholine (PC), PC plasmalogen-alkylacyl PC, phosphatidylinositol (PI), phosphatidylethanolamine (PE), and diphosphatidylglycerol (DPG), and of the lyso derivatives (lyso PC and lyso PE) were greater in the capsule plus epithelium than in the cortex or the nucleus. Levels of sphingomyelin, phosphatidylserine, and PE plasmalogen (EPLAS) were less in the capsule plus epithelium than in the cortex or the nucleus. PC, PC plasmalogen-alkylacyl PC, EPLAS, and lyso PE had nearly equal amounts in the cortex and the nucleus. PI, lyso PC, and DPG could not be detected in the nucleus. DPG was only detected in the capsule plus epithelium. An unidentified phospholipid at 0.13 ppm was approximately equal in the cortex and the nucleus, but it could not be detected in the capsule plus epithelium. CONCLUSIONS: These differences demonstrate a significant heterogeneity among these anatomic regions of the lens, and differences in the nucleus relative to other regions studied are consistent with those in membranes that less readily undergo transitions from the relatively impermeable lamellar phase to the more permeable hexagonal HII phase.

Animals↗
PubMed1991

Protein accumulation on disposable extended wear lenses.

We investigated protein accumulation on disposable extended wear contact lenses. Fifteen volunteers were fit with one low water content, non-ionic lens (Bausch & Lomb's SeeQuence) randomly assigned to one eye and a high water content ionic lens (Vistakon's Acuvue) assigned to the fellow eye. During the first 7 weeks of extended wear the lenses were removed weekly for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of protein deposition, and replacement lenses were inserted. Four subjects completed additional test sessions of 1 minute, 15 minutes, 24 hours, and 1 week extended wear. Lysozyme accumulation, as measured by SDS-PAGE, increased with wearing times up to one week on all Acuvue lenses, but after 24 hours wear lysozyme accumulation did not increase on the SeeQuence lens. Proteins falling into the reported molecular weight ranges of albumin, PMFA, IgG, IgA (sec), lactoferrin and subunits of protein G were evident on all gels at 1 minute of wear, but these protein groups did not have a detectable increase in deposition after 24 hours wear for either the SeeQuence or the Acuvue lenses. In most cases, the protein accumulation evident from SDS-PAGE analysis was not observable by biomicroscopy using standard clinical methods. A few patients reported preference for the initial comfort and vision achieved by the Acuvue lens, but no preference was found after adaptation.

Adult↗
PubMed1990

Initial in vivo tear protein deposition on individual hydrogel contact lenses.

We investigated and compared the initial composition, morphology, and time course of deposits on individual soft contact lenses of different water contents and surface charges in order to evaluate the potential for antigenic reactions and to predict the optimal frequency of lens replacement. Newly manufactured lenses were worn for graduated periods of time from 1 min to 8 h by subjects who were first adapted to daily wear soft lenses. The morphology and composition of the deposits were analyzed by histological staining, light microscopy, scanning electron microscopy (SEM), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with silver nitrate staining, and immunofluorescence microscopy. The protein bands of the acrylamide gels were divided according to their molecular weights into six groups which have been defined in the literature from tear analyses by electrophoretic techniques and include lysozyme, proteins migrating faster than albumin (PMFA), protein G, albumin, lactoferrin, and other proteins heavier than albumin such as Ig-G and secretory Ig-A. Specific proteins (lysozyme, PMFA, and protein G) were detected on individual lenses after as little as 1 min of wear. There was an increasing amount of protein deposited as the wearing time increased. Differences in the rates and amounts of deposition were more dependent on lens water content and ionic characteristics than on intersubject differences. Such early significant protein deposition may occur in wearers of disposable lenses as well as in those subject to complications due to accumulation of protein.

Adolescent↗
PubMed1989

The effect of time, patching, and lens flexibility on RGP lens adherence.

The effects of time, eye patching, and lens flexibility on rigid lens adherence was evaluated in five overnight, in-laboratory test sessions. Patching was investigated with a group of 11 subjects in two overnight test sessions. Sleep time and lens flexibility were investigated in three separate overnight test sessions with two groups of subjects wearing two lens types of fluorosilicone materials (Dk 92 and 60). Adherence occurred in a significant portion of eyes within a 2-hour time period, and the incidence increased throughout the night. There was no significant difference between the incidence of adherence for lenses of a flexible material compared to lenses of a more rigid material (p greater than 0.6, X2 test), nor did patching have a significant influence on the incidence of adherence. The mechanism of lens adherence may be related to several factors including arbitrary lens movement to a peripheral corneal position, the creation of a geometric spacing between the lens and the eye, lid forces producing a negative pressure, and an increase in tear viscosity throughout the night.

Adhesiveness↗