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Biomedical subjects

A W Tuberville

Publications and source records attributed to A W Tuberville.

At least 19 recordsLinked to original sources
PubMed1990

Aqueous humor protein and complement in pseudophakic eyes.

Intraocular lens (IOL) insertion is now the standard method of aphakic correction in this country. Previous studies have shown that an IOL can activate the alternative complement system of normal human serum in vitro, thereby generating peptides capable of stimulating inflammation that can result in visual morbidity in pseudophakic eyes. The objective of the present study was to determine if human aqueous humor (AH) levels of total protein, total C3, and C3a cleavage products (activated C3) are influenced by an IOL in pseudophakic eyes as compared with phakic and aphakic eyes. AH from five diagnostic categories was examined: cataract, posterior capsulotomy-IOL, Fuchs' endothelial dystrophy with corneal edema, aphakic bullous keratopathy, and pseudophakic bullous keratopathy. The results of this study do not support the hypothesis that IOLs affect AH protein and complement levels. Statistically, there was no significant difference in AH protein levels when pseudophakic eyes were compared with phakic and aphakic eyes. No significant difference in C3a levels was demonstrated between pseudophakic and phakic eyes, whereas aphakic eyes had significant higher levels than those with pseudophakia. There were significantly greater levels of protein, C3, and C3a in eyes with edematous corneas versus those with clear corneas. Although these studies are difficult to interpret, AH levels of these substances appear to be more related to dysfunctional corneal endothelium and corneal edema than to the presence of an IOL.

Aphakia↗
PubMed1989

A correlative electron microscopic and freeze-fracture examination of cat corneal endothelial wound repair.

In an attempt to create a model for sustained corneal edema in humans, the present study has examined wounded cat corneal endothelium. Small central (7 mm) wounds or large 90 percent debridement wounds were created with an olive tipped cannula and corneas sampled from 1 to 75 days post-wounding were processed for light and transmission electron microscopy and freeze-fracture. In small wounds, wound closure was complete by 14 days and corneal edema was absent. During wound closure, leading edge cell membranes had decreased intramembrane particles, numerous vesicle fusion sites and lacked cell junctions. Endothelium behind the wound margin was multilayered with fragmented cell junctions. After wound closure, endothelium returned to the morphology of non-wounded endothelium except that an abnormal posterior collagenous layer (PCL) was present. Wound closure was greatly retarded in large wounds and corneas remained edematous at 75 days. The morphology of the endothelial cells was similar to that in small wounds except for the presence of large multinucleated cells and a thicker PCL. These large wound findings are similar to those observed in chronically stressed dysfunctional human corneal endothelium and in this animal model may represent a similar response to injury.

Animals↗
PubMed1987

Cytochrome oxidase activity of postsurgical bullous keratopathy endothelium.

Proper corneal hydration is normally maintained by a pump-leak mechanism located on the lateral cell membranes of the endothelium (1,2). When endothelial cells become sufficiently dysfunctional in response to trauma, the cornea becomes irreversibly edematous and opaque. Previous studies in our laboratory have shown that mitochondrial cytochrome oxidase (CO) activity, an enzyme important in respiratory activities, is correlated with endothelial cell functional activity in corneas with Fuchs' endothelial dystrophy. In this study we investigated cytochrome oxidase activity in corneas with postsurgical bullous keratopathy. Corneas with aphakic and pseudophakic bullous keratopathy (ABK, PBK) were incubated in diaminobenzidine-cytochrome C media. Results showed that the staining pattern of ABK and PBK corneas was uniformly low compared to keratoconus corneas, and in contrast to previous studies on Fuchs' dystrophy corneas which demonstrated a regional staining pattern. This suggests that CO staining patterns correlate with functional activity and may be a useful technique to detect dysfunctional cells in various disease categories.

Corneal Diseases↗
PubMed1986

Cytochrome oxidase activity of Fuchs' endothelial dystrophy.

The normal human corneal endothelial monolayer maintains stromal water equilibrium and thus, transparency, by means of a pump-leak mechanism. Water leaks into the stroma through non-tight lateral cell junctional complexes and is drawn out by an energy dependent cell membrane ion pump. We investigated the histochemical localization of cytochrome oxidase activity (CO), an important energy-deriving mitochondrial enzyme in dysfunctional corneas with Fuchs' endothelial dystrophy (ED), which is a regionally distributed disease. Keratoconus corneas were used as controls for functional control endothelium. In the central area of the corneal button, decreased CO activity was demonstrated which correlated clinically with central corneal edema. This reflects decreased metabolic activity and/or decreased numbers of mitochondria in the attenuated dysfunctional cells. In the mid-periphery, CO activity was increased in the cellular rosettes surrounding guttata, which may be related to increased synthesis of abnormal Descemet's membrane and guttata. Peripherally, the large polygonal cells resembled functional endothelium in their morphology and CO activity. We have, therefore, demonstrated regional differences in energy metabolism in endothelium from Fuchs' ED patients which may be related to decreased numbers of mitochondria in the dysfunctional cells, and/or to synthesis of abnormal Descemet's membrane material.

Cornea↗
PubMed1986

Freeze fracture study of human corneal endothelial dysfunction.

Intramembrane changes occurring in dysfunctional corneal endothelial cell membranes were examined using freeze-fracture and transmission electron microscopy techniques. Three categories of dysfunctional endothelium were examined: aphakic bullous keratopathy, pseudophakic bullous keratopathy and Fuchs' endothelial dystrophy. Keratoconus corneas and a donor eye bank eye were examined as normal controls. Four intramembrane changes were observed on replicas of freeze-fractured membranes in each category of dysfunctional endothelium. These were a marked reduction in intramembrane particle density on lateral membranes, altered apico-lateral junctional complexes, increased vesicle fusion sites on apical, lateral and basal membranes, and abnormal desmosome-like particle aggregates on the lateral endothelial cell membranes. The marked reduction in intramembrane particles on lateral membranes may be due to a change in the macromolecular components associated with pump dysfunction. The increase in membrane vesicle fusion sites and the breakdown in intercellular junctions may be associated with increased permeability during barrier dysfunction.

Cornea↗
PubMed1984

Aqueous humor cytology of pseudophakic bullous keratopathy.

The long-term effects of the interaction between an IOL and the immune system of the implanted patient are not yet clear. This study presents the results of aqueous humor (AH) cytological analysis of 51 patients undergoing intraocular surgery for cataract, and aphakic (ABK) or pseudophakic bullous keratopathy (PBK). Cataract AH was acellular (N = 8). The mean ABK AH cell count was 8.5 +/- 6.4 cells per high power field (hpf) of cytologically filtered specimens; mean PBK cell count was 30.2 +/- 13.0. If inflamed eyes are defined as those with more than one cell/hpf, a statistically significant greater number of PBK eyes than ABK eyes were inflamed (93% versus 44%, P less than 0.003 chi square). More than 99% of the nucleated cells were mononuclear histiocytes. One PBK patient had many multinucleated giant cells in the AH.

Aphakia, Postcataract↗
PubMed1984

Timolol and postoperative intraocular pressure.

We studied the effect of timolol instillation at surgery on the acute postoperative pressure rise following extracapsular cataract extraction (ECCE) and posterior chamber lens implantation. The intraocular pressure (IOP) was measured daily during the first week following surgery in 85 eyes. Timolol was instilled immediately following surgery in 34 eyes; the remaining 51 served as controls. The mean preoperative IOP was 18.7 mm Hg in the treated and control groups. The mean IOP on the first day following surgery was 20.0 mm Hg in the timolol group and 20.7 mm Hg in the control group. Twenty-six percent of the timolol group had a pressure greater than 23.0 mm Hg (mean 35.6 mm Hg); 33% of the control group had a pressure greater than 23.0 mm Hg (mean 31.0 mm Hg). The IOP in all treated and untreated patients with ocular hypertension on the first day following surgery returned to normal within three days. Timolol, therefore, had no effect on acute postoperative pressure elevation following ECCE and posterior chamber lens implantation.

Cataract Extraction↗
PubMed1983

The effect of donor cornea epithelium removal on the incidence of allograft rejection reactions.

The most frequent cause of human corneal transplant failure is immunologic rejection. Surface antigenic determinants on nucleated cells are thought to prime the host's immune system for rejection. Greater than 90% of the nucleated cells of the cornea reside in the epithelium; therefore, one might expect that host sensitization and subsequent graft rejection could be modified by epithelium removal prior to transplantation. The major objective of this two-institution combined prospective and retrospective clinical study was to determine the effect of epithelium removal on the incidence of human corneal allograft rejection reaction. A retrospective study of 152 patients showed an incidence of 24.7% rejection reactions in patients with epithelium transplanted compared to 7.2% in the epithelium-removed group (P = 0.008). In the prospective study of 55 patients, there was a rejection incidence of 30% in the epithelium-on group versus 8.0% with epithelium removed (P = 0.04). The decision to remove graft epithelium, however, must be tempered by anticipation of postoperative healing problems.

Cornea↗
PubMed1982

Punctal occlusion in tear deficiency syndromes.

Punctal occlusion was carried out in 32 eyes with tear deficiency syndromes regardless of the preoperative Schirmer tear test values. Diagnoses included: keratoconjunctivitis sicca, Stevens-Johnson syndrome, congenital alacremia, and post-traumatic tear deficiency. Subjective symptomatic improvement was recorded in 97% of the eyes. Objective improvement was recorded as resolution or improvement of corneal ulceration, filamentary keratitis, and superficial punctate keratitis. All patients (100%) experienced improvement in one or more of these diagnostic signs. A tarsorrhaphy was required as adjunctive therapy to punctal occlusion in three eyes with Stevens-Johnson syndrome. Epiphora did not occur after surgery even though 16 eyes (50%) had preoperative Schirmer tear test values greater than 2 mm (range 0-15 mm). Artificial tears were discontinued or reduced to occasional use in 85% of eyes postocclusion of puncta. Eight puncta reopened; five of the eight required reocclusion. In this series, punctal occlusion was a safe and effective method of managing severe tear deficiency syndromes and should be considered more frequently in patients with the appropriate criteria.

Humans↗
PubMed1982

The long term effect of an iris-supported lens on the endothelium.

A retrospective study of 104 eyes that had iris-supported Sputnik intraocular lenses implanted and no surgery in the fellow eye and a separate series of 30 implanted eyes whose second eyes underwent surgery but did not receive implants disclosed that endothelial cell densities in the eyes with implants decreased immediately after surgery and then continued to decrease at the same rate as those of the control eyes. There was no sudden decrease in the endothelial cell counts during follow-up periods ranging from three to seven years. The main cause of large cell losses immediately after surgery, and possibly long-term corneal decompensation, was surgical manipulation rather than the presence of this style of intraocular lens.

Cell Count↗
PubMed1982

Complement activation by nylon- and polypropylene-looped prosthetic intraocular lenses.

Uncomplicated placement of an intraocular lens at the time of routine cataract extraction is associated with a greater inflammatory response than simple lens extraction. We have shown that certain components of prosthetic intraocular lenses are capable of activating the complement system in human serum in such a fashion as to generate peptides capable of mediating acute inflammatory reactions. Normal human serum was incubated with intraocular lenses in vitro and then examined for cleavage products of C3 and C5 and for C5-derived chemotactic activity for human polymorphonuclear leukocytes. Polymethylmethacrylate lenses with nylon and polypropylene loops were found to be capable of causing cleavage of C3 (detected by crossed immunoelectrophoresis) and C5 (detected by single-dimension radioimmunoelectrophoresis) as well as generation of C5-derived chemotactic activity in human serum. Serum incubated with polymethylmethacrylate lenses without loop supports exhibited no such activity. Results of our studies indicate that certain nylon- and polypropylene-looped intraocular lenses are not "inert" biologically and may elicit acute inflammatory reactions.

Autoradiography↗
PubMed1981

Corneal ulcers in corneal transplants.

Twenty-nine eyes, representing an infection rate of 4.9%, developed corneal ulcers following corneal transplant surgery; 26 with available data are presented. All occurred in the graft or at the wound margin. The median postoperative time to ulcer development was 5.5 months. All eyes were on topical steroids when the ulcer developed. Other associated factors were: loose sutures, bandage lenses and eyes grafted for herpes simplex keratitis. Ninety percent of the ulcers had one or more of these factors. Positive cultures for organisms were obtained in 75% and positive gram stain in 68% of the ulcers. Nine genera of bacteria were cultured; S. epidermidis, S. pneumoniae, P. aeruginosa and Corynebacterium were the most common organisms. Ninety-five percent of the bacteria tested were sensitive to gentamicin. Visual reduction occurred in 46% of the cases overall; herpetic corneas had an 88% incidence of visual loss.

Bacterial Infections↗
PubMed1981

Why do implants fail?

Nylon 66 and polypropylene are chemotactic in human serum while PMMA from intraocular lenses is not. Chemotactic activity is unaltered by Ridley, 5 per cent NaOH, or ethylene oxide sterilization. Chemotaxis is but one manifestation of an overall inflammatory process that may be involved in implant-induced corneal and retinal dysfunction.

Adult↗
PubMed1981

Chemical effects of alkali on polymethylmethacrylate intraocular lenses.

Polymethylmethacrylate intraocular lenses were left in 10% NaOH or 10% KOH for various periods of time. Contact angles were unaltered and electron spectroscopy for chemical analysis was unchanged. This concentration of alkali does not appear to chemically change the lens surface during the study period.

Alkalies↗
PubMed1980

Mechanism of implant inflammation.

Polymethylmethacrylate lenses with nylon-6 loops can activate the complement system. Such activation occurs primarily at the loops. This activation may be one pathway of implant-caused inflammation.

Complement Activation↗