Biomedical subjects

S E Wilson

Publications and source records attributed to S E Wilson.

At least 73 records · Page 4Linked to original sources

PubMed1999

Fas-activated apoptosis and apoptosis mediators in human trabecular meshwork cells.

A gradual loss of cells occurs within the human trabecular meshwork during normal aging and appears to be increased in patients with primary open-angle glaucoma. The exact mechanism by which cells are lost in either condition is not known, however phagocytosis, cell migration and cell death have been suggested. Apoptosis is one method by which cell death can occur. We have examined the modulators for apoptosis within the human trabecular meshwork using both cell lines and ex-vivo dissected trabecular meshwork tissues obtained from normal donors. Using RT-PCR it was shown that mRNA for several modulators of apoptosis (Fas, Bcl-2, Bcl-xl, Bax, and ICE) are expressed by both cell lines and ex-vivo tissues. Apoptosis was stimulated to occur by treating cell lines with a monoclonal antibody (IgM) to Fas. Apoptosis was verified via morphological changes to the cells, transferase-mediated dUTP nick-end labeling TUNEL Immunofluorescence, and DNA laddering. Control cells exposed to IgM did not undergo apoptosis. These results represent the first report of apoptosis modulators within the human trabecular meshwork and demonstrate that human trabecular meshwork cells can be stimulated to undergo apoptosis via the Fas/FasL pathway.

Aged↗

PubMed1999

Stimulus-specific and cell type-specific cascades: emerging principles relating to control of apoptosis in the eye.

Apoptosis has a critical role in development, homeostasis, wound healing, and the pathophysiology of disease in the organs of multicellular organisms. It has been implicated in these processes in retina, lens, cornea, trabecular meshwork, optic nerve, and the central nervous system pathways that contribute to vision. Considerable interest has been focused on inhibiting apoptosis to control disease and wound healing processes in which programmed cell death is thought to have a critical role. A simplified view led to the search for effective inhibitors of 'the final common pathway for apoptosis'. Recent studies have provided important insights into the modulators that participate in and regulate the apoptosis cascades which are activated in response to cytokines, ionizing radiation, chemotherapeutic agents, growth factor deprivation, and other stimulators of cell death. These studies lead to the inescapable conclusion that the apoptosis pathways are not only stimulus-specific, but also cell-type specific. These observations have important implications related to development of pharmacological strategies for controlling apoptosis-associated disease and apoptosis-initiated wound healing.

Apoptosis↗

PubMed1999

Keratocyte apoptosis associated with keratoconus.

Keratoconus is an ectatic corneal dystrophy associated with stromal thinning and disruption of Bowman's layer. The purpose of this study was to explore a possible association between keratocyte apoptosis and keratoconus. Keratocyte apoptosis was evaluated in corneas of patients with keratoconus, corneas of patients with stromal dystrophies, and normal donor corneas using the transferase-mediated dUTP-digoxigenin nick and labeling (TUNEL) assay. Keratocyte apoptosis was also studied in keratoconus and normal corneas using transmission electron microscopy. TUNEL-stained keratocytes were detected in 60% of corneas with keratoconus, but only 35% of corneas with stromal dystrophies (P =0.03). The number of TUNEL-positive keratocytes detected in the keratoconus, stromal dystrophy, and normal corneas was 7+/-1 (mean+/-standard error, range 0-20), 2+/-0. 8 (range 0-9), and 0+/-0 (range 0-0) TUNEL-positive cells per section, respectively. The differences between the keratoconus and the stromal dystrophy (P =0.0097) or the normal cornea (P =0.01) groups were statistically significant. The difference between the stromal dystrophy and normal cornea groups was not statistically significant (P =0.45). The stromal dystrophy group was included to account for surgery-associated keratocyte apoptosis. No TUNEL-stained keratocytes were detected in normal corneas. Cell morphologic changes consistent with apoptosis were detected by transmission electron microscopy (TEM) in keratocytes of keratoconus corneas, but not in keratocytes in normal corneas. Chronic keratocyte apoptosis associated with ongoing epithelial injury may link risk factors associated with keratoconus such as chronic eye rubbing, contact lens wear, or atopic eye disease. Similarly, increases that have been detected in several different degradative enzymes in keratoconus corneas could be associated with chronic keratocyte apoptosis and less than perfect control of release of intracellular contents.

Apoptosis↗

PubMed1999

Improved imaging of carotid artery bifurcation using helical computed tomographic angiography.

Although duplex scan and magnetic resonance angiography (MRA) provide reliable and noninvasive tests for detecting extracranial carotid artery disease, they sometimes fail to differentiate between high-grade stenosis and total carotid occlusion. Helical computed tomographic angiography (CTA) is a safe, noninvasive technique that allows the rapid acquisition of data that can be reconstructed into two- and three-dimensional images. Axial images can be magnified and provide a cross-sectional view of the carotid vessel and the atherosclerotic plaque. Maximal intensity projection technique allows data to be reconstructed into images that closely resemble conventional arteriograms. Helical CTA has previously been shown to have a diagnostic accuracy approaching 90%. We present two case reports demonstrating the utility of helical CTA in carotid artery imaging when duplex scan and MRA results are ambiguous. These cases illustrate improved carotid imaging with helical CTA. Duplex scan results are unreliable in the presence of thick calcified plaques, and severe stenoses can be misread as occlusion by duplex and MRA due to low blood flow. Thus, helical CT angiography should be considered as a confirmatory test, before arteriography, when duplex scan or MRA results are equivocal.

Carotid Artery, Internal↗

PubMed1999

A prospective evaluation of PTFE graft patency and surveillance techniques in hemodialysis access.

The purpose of this study was to perform a prospective multicenter evaluation of the patency, complications, and predictive factors of patency for 6-mm expanded polytetrafluoroethylene (ePTFE) grafts used in hemodialysis access. Eighty-six patients were evaluated; the mean age was 55.8 years (range 23-90), 46 patients were female. Patency and complications were assessed at the initial dialysis and 1, 3, 6, 9, and 12 months postoperatively. Kaplan-Meier survival curves were calculated to determine primary and secondary patency, and log-rank analysis was used to determine differences between curves. The Student's t-test was used to compare groups. Primary and secondary patency rates at 1 year were 43% and 64%. Venous line pressures tended to rise over time. Recirculation values and blood flow rates during dialysis showed no correlation to graft patency. These results show that ePTFE provides a suitable secondary choice for vascular access for end-stage renal disease patients in whom an autogenous fistula is not possible. Thrombosis and anastomotic stenosis are common and should be aggressively identified and treated to prolong overall graft survival.

Arteriovenous Shunt, Surgical↗

PubMed1999

Epithelial removal with the excimer laser (laser-scrape) in photorefractive keratectomy retreatment.

OBJECTIVES: To retrospectively evaluate refractive and topographic outcomes after excimer laser photorefractive keratectomy (PRK) retreatment using the laser-scrape technique for epithelial removal. DESIGN: Retrospective clinical study. PARTICIPANTS: Thirty eyes of patients who had PRK retreatment for undercorrection after primary PRK were examined. INTERVENTION: The PRK retreatment was performed using a laser-scrape technique in which the excimer laser was used to remove the majority of the epithelium overlying the anterior stromal surface before additional PRK ablation. MAIN OUTCOME MEASURES: Uncorrected visual acuity, best-corrected visual acuity (BCVA), surface regularity index (SRI), and surface asymmetry index were measured. RESULTS: Primary PRK was performed for myopia of -5.1 +/- 1.7 diopters (range, -1.1 to -7.5 diopters). Mean spherical equivalent (SE) was -1.3 +/- 0.4 diopters (range, -0.6 to -2.0 diopters) before retreatment. Mean SE 6 months after retreatment decreased to +0.1 +/- 0.4 diopter (range, +1.25 to -0.75 diopters; P < 0.0001). Four eyes (15%) were more than +0.5 diopter overcorrected at 6 months. Ninety-six percent of eyes achieved mean SE within +/- 1 diopter and 77% within +/- 0.5 diopter of emmetropia after retreatment. Visual acuity improved significantly 6 months after reablation (P < 0.0001) with 100% 20/40 or better and 73% 20/25 or better without correction. Final BCVA also improved compared with before retreatment (P = 0.02). Twelve eyes gained 1 line of BCVA and no eye lost more than 1 line of BCVA. The SRI before retreatment was 0.6 +/- 0.3 (range, 0.0-0.9) and remained the same 0.6 +/- 0.2 (range, 0.1-1.0; P = 0.8), 6 months after retreatment. CONCLUSION: Excimer laser PRK retreatment using the laser-scrape technique for epithelial removal is an accurate and safe procedure for treating undercorrection of eyes after PRK for low-to-moderate myopia.

Adult↗

PubMed1999

Binocular function and patient satisfaction after monovision induced by myopic photorefractive keratectomy.

PURPOSE: To measure binocular function and patient satisfaction with monovision induced by photorefractive keratectomy (PRK) in myopic presbyopic patients. SETTING: Refractive Department, Cleveland Clinic, Cleveland, Ohio, USA. METHODS: This study comprised 21 myopic presbyopic patients with monovision induced by PRK. Sixteen emmetropic patients who had PRK served as a control group. Monovision was induced by undercorrecting the nondominant eye by 1.25 diopters for near vision and correcting the dominant eye with emmetropia for distance vision. Monocular and binocular uncorrected Snellen visual acuities at 20 feet and 13 inches, manifest refraction, ocular dominance, stereopsis at 20 feet and 13 inches, monocular and binocular contrast sensitivities, Worth-4-Dot test at 20 feet and 1/3 of a meter, and fusional convergence amplitudes were examined in each patient. RESULTS: In the monovision group at near and distance, 20 patients (95.3%) had binocular visual acuity of 20/25 or better. No patient in the monovision group used reading glasses postoperatively; 4 of 16 patients (25.0%) in the control group used such glasses. All patients maintained binocular fusion and stereo acuity ranging from 40 to 800 seconds of arc. Mean patient satisfaction was 86% (range 40% to 100%). In the control group, 12 patients (75.0%) had binocular distance visual acuity of 20/25 or better and 11 (68.8%) had binocular near visual acuity of 20/25 or better. CONCLUSION: Monovision PRK patients had better near vision than control PRK patients, with minimal compromise in stereo acuity and overall high patient satisfaction.

Adult↗

PubMed1999

Carbapenems in clinical practice: a guide to their use in serious infection.

Meropenem and imipenem/cilastatin, currently the only available carbapenem agents in Europe and the United States, are characterised by a broad spectrum of antimicrobial activity and stability to beta-lactamase-mediated resistance mechanisms. A guide to the use of carbapenems in clinical practice is presented; the role of carbapenems in the treatment of several types of serious bacterial infection and an up-to-date account of their clinical efficacy and safety profiles are discussed. The good clinical efficacy and favourable safety profiles of the carbapenems make them valuable as initial empirical therapy in the treatment of ventilator-associated pneumonia, sepsis of unknown origin, post-operative peritonitis, paediatric meningitis, and febrile neutropenia. However, to maintain superior efficacy, the carbapenems should be used appropriately for definitive therapy.

Bacterial Infections↗

PubMed1999

Stromal-epithelial interactions in the cornea.

Stromal-epithelial interactions are key determinants of corneal function. Bi-directional communications occur in a highly coordinated manner between these corneal tissues during normal development, homeostasis, and wound healing. The best characterized stromal to epithelial interactions in the cornea are mediated by the classical paracrine mediators hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF). HGF and KGF are produced by the keratocytes to regulate proliferation, motility, differentiation, and possibly other functions, of epithelial cells. Other cytokines produced by keratocytes may also contribute to these interactions. Epithelial to stromal interactions are mediated by cytokines, such as interleukin-1 (IL-1) and soluble Fas ligand, that are released by corneal epithelial cells in response to injury. Other, yet to be identified, cytokine systems may be released from the unwounded corneal epithelium to regulate keratocyte viability and function. IL-1 appears to be a master regulator of corneal wound healing that modulates functions such as matrix metalloproteinase production, HGF and KGF production, and apoptosis of keratocyte cells following injury. The Fas/Fas ligand system has been shown to contribute to the immune privileged status of the cornea. However, this cytokine-receptor system probably also modulates corneal cell apoptosis following infection by viruses such as herpes simplex and wounding. Pharmacologic control of stromal-epithelial interactions appears to offer the potential to regulate corneal wound healing and, possibly, treat corneal diseases in which these interactions have a central role.

Corneal Stroma↗

PubMed1999

How HIV-1 lentivirus causes immune deficiency disease.

Human immunodeficiency virus (HIV-1) associated immune deficiency has the characteristics of chronic graft versus host disease (GVHD) caused by human leukocyte antigen (HLA) class 2 incompatibility. The envelope glycoprotein fragment TKAKRRVVEREKR mimics HLA class 1 C molecules serologically, and also mimics an immune regulatory T cell epitope, in the region of amino acids 67 to 71, within the HLA DR beta chain. This beta chain alloepitopic region (between amino acids 67 to 80) furnishes peptides predicted to bind optimally to HLA class 1 B alleles. The hypothesis predicts that viral parameters, such as viral load, and clinical parameters, such as rate of progress to acquired immune deficiency syndrome (AIDS) and severity of the associated immune deficient state, are linked to the HLA B and HLA DR beta chain haplotype in infected patients. Immune suppression is caused by HLA class 1 B restricted CD8+ T cells which normally regulate HLA class 2 DR restricted antigen specific responses. The hypothesis further predicts the severity of immune deficiency to be linked to those HLA DR beta chain allotypes which express the amino-acid glutamine (Q) in position 70.

Amino Acid Sequence↗

PubMed1999

Treatment of hospitalized patients with complicated gram-positive skin and skin structure infections: two randomized, multicentre studies of quinupristin/dalfopristin versus cefazolin, oxacillin or vancomycin. Synercid Skin and Skin Structure Infection Group.

Quinupristin/dalfopristin (Synercid), the first injectable streptogramin antibiotic available for the treatment of complicated gram-positive skin and skin structure infections, was compared with standard comparators (cefazolin, oxacillin or vancomycin) in one USA and one international trial. These two randomized, open-label trials of virtually identical design enrolled a total of 893 patients (450 quinupristin/dalfopristin, 443 comparator). The majority of patients had erysipelas, traumatic wound infection or clean surgical wound infection. Staphylococcus aureus was the most frequently isolated pathogen in both treatment groups and polymicrobial infection was more common in the quinupristin/dalfopristin group than in the comparator group. The clinical success rate (cure plus improvement) in the clinically evaluable population was equivalent between the two treatment groups (68.2% quinupristin/dalfopristin, 70.7% comparator; 95% CI, -10.1, 5.1) despite a shorter mean duration of treatment for quinupristin/dalfopristin patients. In the bacteriologically evaluable population, by-patient and by-pathogen bacteriological eradication rates were somewhat lower for quinupristin/dalfopristin (65.8% and 66.6%, respectively) than for the comparator regimens (72.7% and 77.7%, respectively). The lower bacteriological response rates in the quinupristin/dalfopristin group were, in part, due to a higher rate of polymicrobial infections and a higher incidence of patients classified as clinical failure, a category which included premature discontinuation of treatment because of local venous adverse events. The bacteriological eradication rate for quinupristin/dalfopristin was higher in monomicrobial infections than in polymicrobial infections (72.6% versus 63.3%, respectively), whereas the corresponding rate for the comparator regimens was lower for monomicrobial infections than polymicrobial infections (70.8% versus 83.1%). This finding was not unexpected, since the spectrum of quinupristin/dalfopristin is focused on gram-positive pathogens and additional antibiotics to treat gram-negative bacteria were not required per protocol. The systemic tolerability of both treatment regimens was qualitatively similar. A higher rate of drug-related venous adverse events was reported for quinupristin/dalfopristin (66.2%) than for the comparator regimen (28.4%). Premature discontinuation of study drug was primarily due to adverse clinical events for quinupristin/dalfopristin (19.1%), whereas the most common reason for discontinuation among those receiving the comparator regimens was treatment failure (11.5%). Quinupristin/dalfopristin is an effective alternative for the treatment of hospitalized patients with complicated skin and skin structure infections due to quinupristin/ dalfopristin-susceptible gram-positive organisms, including methicillin- and erythromycin-resistant S. aureus.

Adolescent↗

PubMed1999

Epithelial scrape for photorefractive keratectomy overcorrection associated with induced regression.

PURPOSE: To study the effect of combined corneal epithelial scrape and contact lens wear treatment on regression in eyes with symptomatic overcorrection after photorefractive keratectomy (PRK) or PRK retreatment. METHODS: Fifteen eyes had corneal epithelial scrape with a scalpel followed by soft contact lens wear for approximately 1 month. Eight of the eyes were treated 3-4 months after the laser procedure, and seven eyes were treated >4 months after laser treatment. Fifteen eyes that had the same level of PRK correction and monitored during the same interval after PRK were used as matched control eyes. RESULTS: Epithelial scrape was performed for mean spherical equivalent (SE) of +1.1+/-0.4 diopters (D) (range, +0.50 to +1.75 D) at mean 6.1+/-3.2 months after PRK or PRK retreatment. The SE in these eyes was +0.5+/-0.6 D (range, -0.25 to +1.25 D) 3 months after epithelial scrape and +0.4+/-0.5 D (range, -0.75 to +1.25 D) 6 months after scrape. The change in scraped eyes at 3 and 6 months compared to before scrape was statistically significant (p = 0.001 and p = 0.001, respectively). The change in mean SE at 6 months after scrape (-0.7+/-0.5 D) was significantly different than the change noted in matched control eyes that were not scraped (-0.1+/-0.2 D) over the same interval after the PRK or PRK retreatment procedure. The change in SE at 6 months after epithelial scrape was greater for the eyes scraped 4 months or less (mean, 3.6+/-0.5 months) after PRK (-0.9+/-0.3 D) than eyes scraped >4 months (9.0+/-2.6 months) after PRK (-0.4+/-0.5 D). This difference approached statistical significance (p = 0.06). CONCLUSIONS: Epithelial scrape and soft contact lens treatment for symptomatic overcorrection after PRK may induce regression and is more likely to be effective when performed <4 months after the primary PRK or PRK retreatment procedure.

Adult↗

PubMed1999

New advances in the use of antimicrobial agents in surgery: intra-abdominal infections.

Advances in both technical methods and antimicrobial therapy have significantly reduced morbidity and mortality for secondary (enterogenous) or community-acquired intra-abdominal infections. Presumptive antimicrobial therapy for most community-acquired intra-abdominal infection can be safely initiated with a single broad-spectrum antimicrobial effective against the expected Enterobacteriaceae and anaerobic flora. Beta-lactams and carbapenems are effective against gram-negative rods and anaerobes, achieve therapeutic levels rapidly, and have low toxicity in the absence of penicillin allergy. Second generation cephalosporins (e.g. cefoxitin and cefotetan) remain useful in surgical prophylaxis and treatment of mild community-acquired pneumonia, but limitations in their spectra and antimicrobial resistance restrict their utility in more serious infections. The fourth generation cephalosporins are also effective, but should be combined with other antimicrobials such as metronidazole for adequate anaerobic coverage. Preliminary data on new fluoroquinolones are scant, but promising results were obtained in one clinical trial. We predict the current trend toward the use of broad-spectrum single agent antimicrobials for therapy of intra-abdominal infection will continue.

Abdomen↗

PubMed1999

Effect of PDGF, IL-1alpha, and BMP2/4 on corneal fibroblast chemotaxis: expression of the platelet-derived growth factor system in the cornea.

PURPOSE: The purpose of this study was to examine expression of platelet-derived growth factor (PDGF) and PDGF receptors in the human cornea and to study the effects of the PDGF isotypes on proliferation and chemotaxis of human corneal fibroblasts. The effects of interleukin (IL)-1alpha, bone morphogenic protein (BMP)2, and BMP4 on chemotaxis of human corneal fibroblasts were also studied. METHODS: mRNA expression was monitored with reverse transcription-polymerase chain reaction (RT-PCR) in primary cultured cells. Protein expression in fresh-frozen human corneal sections was studied with immunocytology. Chemotaxis was measured using a modified Boyden chamber, and proliferation was quantitated by cell counting. RESULTS: PDGF A, PDGF B, PDGF receptor alpha, and PDGF receptor beta mRNAs were detected in corneal epithelial cells, fibroblasts, and endothelial cells in culture. The proteins were expressed in each major cell type in human corneal sections, with PDGF A and PDGF B detected at high levels in the epithelial basement membrane. PDGF, BMP2, and BMP4 had attractive chemotactic effects on corneal fibroblasts, with the PDGF BB dimer having a significantly greater positive chemotactic effect than the other PDGF isotypes. Interleukin-1alpha had a repulsive chemotactic effect on corneal fibroblasts. PDGF AA, AB, and BB stimulated proliferation of human corneal fibroblasts. CONCLUSIONS: The PDGF growth factor receptor system is expressed in the human cornea. PDGF, BMP2, BMP4, and IL-1alpha may modulate keratocyte chemotaxis and proliferation during homeostasis and wound healing.

Bone Morphogenetic Protein 2↗

PubMed1999

Lacrimal gland HGF, KGF, and EGF mRNA levels increase after corneal epithelial wounding.

PURPOSE: To evaluate the effect of corneal epithelial wounding on lacrimal gland expression of hepatocyte growth factor (HGF), keratinocyte growth factor (KGF), and epidermal growth factor (EGF) in the rabbit model. METHODS: Rabbits had corneal epithelial scrape injuries, and the lacrimal gland was removed at different times after wounding. HGF, KGF, and EGF mRNA expression was examined by quantitative RNase protection assay. HGF, KGF, and EGF proteins were detected in rabbit lacrimal tissue using immunoprecipitation and western blot analysis. RESULTS: HGF mRNA and EGF mRNA were significantly increased in rabbit lacrimal gland tissue within 8 hours after corneal epithelial injury. The increase in KGF mRNA expression was small and reached significance I clay after corneal injury. Lacrimal gland expression peaked at 3 days after wounding for each growth factor mRNA, the same day, on average, that the epithelial defect healed. After the peak increase in expression, there was a progressive decline in expression of each growth factor mRNA, but production was still increased compared with prewound levels. HGF protein, KGF protein, and EGF proteins were detected in rabbit lacrimal gland tissue. CONCLUSIONS: Levels of HGF, KGF, and EGF mRNAs increase in rabbit lacrimal gland tissue in response to corneal epithelial wounding. The results of this study are consistent with the existence of a cornea-nervous system-lacrimal gland regulatory loop modulating expression of these growth factor mRNAs. The lacrimal gland is a likely source of increased HGF and EGF proteins detected in tears in previous studies.

Animals↗

PubMed1999

Nosocomial infections in the surgical intensive care unit: a difference between trauma and surgical patients.

In 1970, the Centers for Disease Control and Prevention (CDC) established the National Nosocomial Infection Surveillance System to assist institutions with infection surveillance, data collection, and processing. This facilitates interinstitutional comparison for nosocomial infection rates. Nosocomial infection rates in the surgical intensive care unit have been shown to be different from the medical intensive care unit. Whether there exists a difference in infection rates between trauma and surgical patients in the intensive care unit has not been established. Our objective was to determine whether there is a difference in rates of nosocomial infections between trauma and surgical patients in the surgical intensive care unit. From January 1995 through December 1997, we reviewed 3715 admissions to the surgical intensive care unit and separated them into trauma (1272) or surgical (2443) cases. We documented all nosocomial pneumonias, urinary tract infections, bloodstream infections, and surgical site infections. From these data we determined infection rates per 100 admissions. We also identified all device-related nosocomial infections and calculated infection rate by current CDC standards using number of device infections divided by number of device-days times 1000. We found that the overall trauma patient infection rate was 11.64 per cent compared with 6.43 per cent for surgical patients (P<.001). Using conventional infection rate criteria, trauma patients had higher frequency in the rate of ventilator-associated pneumonia (6.13% vs. 2.50%; P<0.001), urinary tract infection (2.36 versus 1.76; P<0.2), and bloodstream infection (2.52% versus 1.27%; P<0.01). However, when using the CDC guidelines, which correct for the number of device-days for infections, only the difference in rate of pneumonia between the two groups reached statistical significance (23.9 rate for trauma patients vs. 16.7 for the surgery group; P<0.005). We conclude that trauma patients are at higher risk for nosocomial infections than routine surgical patients. Because of this difference, centers should collect and report data separately for trauma and surgical patients in the intensive care unit. Specific attention should be focused on the causes and prevention of increased rates of nosocomial pneumonia in trauma patients.

Bacteremia↗

PubMed1999

Changes in corneal morphology associated with chronic epithelial injury.

PURPOSE: The purpose of this study was to evaluate the effect of chronic epithelial scrape injury on corneal morphology. METHODS: The corneal epithelia in one eye of 8-week-old New Zealand White rabbits were scraped at weekly intervals. Central corneal thickness was measured by ultrasonic pachymetry before epithelial scrape each week. Control never wounded (C), chronic wounded with scrape the last week (W), and chronic wounded without scrape the last week (WW) corneas were processed for histologic analysis and transmission electron microscopy (TEM). The time intervals for histologic analysis were 4 (4 C, 2 W, 2 WW), 8 (4 C, 2 W, 2 WW), and 16 (7 C, 2 W, 5 WW) weeks. Histologic findings were monitored using hematoxylin and eosin staining, the TdT-dUTP terminal nick-end labeling (TUNEL) assay, and TEM. RESULTS: Chronic wounded corneas developed marked epithelial hyperplasia and a subepithelial acellular zone. Keratocytes undergoing apoptosis were primarily detected adjacent to the acellular zone by TUNEL assay and TEM. Total central corneal thickness measured by ultrasonic pachymetry (n=7) was significantly thinner in chronically scraped eyes compared with control eyes after 8, 12, and 16 weeks (P < 0.05). Control corneas increased in total thickness over the 16 weeks of the study, but there was no significant change in total thickness of the corneas that had chronic epithelial scrape injury over this time interval. Two scraped corneas had marked decreases in total corneal thickness relative to the corneal thickness at the beginning of the study. Epithelial hyperplasia developed in all scraped corneas examined histologically after 4, 8, or 16 weeks of scraping. When central epithelial thickness measured on hematoxylin and eosin-stained sections was subtracted from the total pachymetric corneal thickness to give approximate stromal thickness, the stromal thickness was 23% lower in the chronic wounded (277+/-15 microm) compared with the unwounded (356+/-6 microm) corneas (P=0.0008) after 16 weeks of wounding. CONCLUSIONS: Chronic epithelial injury induces stromal thinning and epithelial hyperplasia. These changes in cornea structure associated with chronic epithelial injury may have relevance to the pathophysiology of keratoconus.

Animals↗

PubMed1999

Expression of alternatively spliced growth factor receptor isoforms in the human trabecular meshwork.

PURPOSE: Growth factors act through high-affinity cell surface receptors expressed by target cells and are critical modulators of cell function. Because aqueous humor is known to contain growth factors, these molecules may play a key role in maintaining the normal function of the human trabecular meshwork (HTM). Alternate mRNA splicing is an important mechanism used by cells to generate diverse isoforms of growth factor receptors. Although previous investigators have suggested that HTM cells may express alternative isoforms of several growth factor receptors, there have been no studies to verify these preliminary findings. The objective of this study was to determine whether cultured and ex vivo HTM cells express alternate isoforms of hepatocyte, keratinocyte, and transforming growth factor beta (TGFbeta)-II receptors and to characterize the isoform molecular sequences. METHODS: To determine whether cells within the HTM express mRNA for alternate isoforms of growth factor receptors, total RNA was isolated from several well-characterized HTM cell lines that were established from donors of various ages and from fresh ex vivo HTM tissues from healthy donors. After cDNA synthesis, polymerase chain reaction was initiated using specific primers for alternate forms of the following receptors: hepatocyte growth factor (HGFR), keratinocyte growth factor (KGFR), and transforming growth factor beta receptor II (TGFbetaR-II). Specificity and characterization of the polymerase chain reaction amplification products were determined by nucleic acid sequencing. RESULTS: Amplification products of the expected size for the growth factor isoforms were expressed in cell lines and in ex vivo tissues. Nucleic acid sequencing showed that cultured HTM cells and fresh ex vivo trabecular meshwork tissues expressed specific mRNA for alternatively spliced isoforms of HGFR, KGFR, and TGFbetaR-II The HGFR alternate isoform contained a 96-bp insert in the C-terminal coding region of the cytoplasmic tyrosine kinase domain. The KGFR alternate isoform is a soluble, truncated form, because it has no transmembrane or cytoplasmic domain as does the normal membrane-associated form. The TGFbetaR-II alternate isoform contained a 75-bp insert in the N-terminal coding region of the extracellular domain. CONCLUSIONS: In vitro and ex vivo HTM cells express mRNA for alternatively spliced isoforms of HGFR, KGFR, and TGFbetaR-II. These alternatively spliced receptor isoforms may be functional within the HTM and may play a critical role in maintaining the normal microenvironment of this important tissue.

Aged↗