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.

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.

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.

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.

Selective targeting and photodynamic destruction of intimal hyperplasia by scavenger-receptor mediated protein-chlorin e6 conjugates

BACKGROUND

Photosensitizers, such as Photofrin II or Chloroaluminum-sulfonated phthalocyanine accumulate at sites of arterial injury. We have exploited this property to develop a model of photodynamic therapy (PDT) for intimal hyperplasia. The fluorescent probe [maleylated-bovine serum albumin (mal-BSA) conjugated with Texas-red] can be selectively targeted to intimal macrophages and smooth muscle cells recruited during formation of hyperplasia via a receptor-mediated mechanism.

METHODS

In this study, the photosensitizer chlorin e6 (Cle6) was conjugated to mal-BSA in a rat model of intimal hyperplasia, then tested the efficacy of the ligand conjugation to photosensitizer (mal-BSA/Cle6) in PDT of intimal hyperplasia. Arterial wall injury was produced by a balloon catheter pulled through the abdominal aorta of the rat to create a model of intimal hyperplasia. Fluorescent compounds were injected two weeks after injury.

RESULTS

Four hours after injection, the intensity of fluorescence achieved with injection of mal-BSA/Cle6 was higher for intimal hyperplastic lesions as compared to control areas. BSA-Cle6 unconjugated did not demonstrate such delivery. Two weeks after balloon injury, the injured aorta was irradiated externally with an argon pumped dye laser four hours following the photosensitizer injection. We employed two total radiant exposures: 20 J/cm2 and 40 J/cm2. Forty-eight hours after PDT, the arteries were examined histologically. Intimal hyperplastic cells were significantly reduced by PDT in the mal-BSA/Cle6 injected group (40-100%) versus the Cle6 group (0-20%).

CONCLUSIONS

Mal-BSA/Cle6 is taken up efficiently by a scavenger pathway, localizes in areas of intimal hyperplasia, and functions as a photosensitizer for PDT.

Characterization of a soluble KGF receptor cDNA from human corneal and breast epithelial cells

PURPOSE

Keratinocyte growth factor (KGF) is a member of the fibroblast growth factor (FGF) family FGF-7. It exhibits potent mitogenic activity for epithelial cells, including corneal and mammary epithelial cells. A messenger RNA has been reported that is generated by alternative splicing of bek that putatively codes only for the extracellular ligand-binding domain of KGF receptor (soluble KGF receptor). In the present study, the expression of the mRNA coding for this alternative bek transcript was examined and the corresponding protein characterized.

METHODS

Alternative messenger RNA transcripts were detected in various cell lines or tissues using reverse transcription-polymerase chain reaction (RT-PCR) and RNase protection assay. NIH/3T3 fibroblast cells and 293 kidney embryonic epithelial cells were stably transfected with soluble KGF receptor cDNA and transmembrane KGF receptor cDNA. Soluble KGF receptor protein was produced using a baculovirus-insect expression system. Soluble KGF receptor protein was detected using western and dot blot analyses. Binding assays and cross-linking labeling were used to determine the affinity and specificity of soluble KGF receptor. A mitogenic assay was performed to examine the function of the soluble KGF receptor.

RESULTS

The soluble KGF receptor mRNA was primarily expressed in epithelial cells, including cells from the cornea and breast. Cross-linking labeling and affinity-binding assays with 125I-KGF showed that the soluble KGF receptor bound KGF (FGF-7) but not FGF-1 or FGF-2. Soluble KGF receptor was detected in the culture medium of cells stably transfected with soluble KGF receptor cDNA but not with transmembrane KGF receptor cDNA, suggesting that the soluble receptor was generated by mRNA splicing and probably not by proteolysis or posttranslational processing. Soluble KGF receptor inhibited KGF binding to transmembrane KGF receptor and DNA synthesis in BALB/MK epidermal keratinocytes in response to KGF, suggesting that soluble KGF receptor expression could provide a mechanism for the cell to downregulate responses to KGF.

CONCLUSIONS

A truncated soluble KGF receptor expressed in corneal and other epithelial cells probably functions to downregulate the response of the cell to KGF.

Bone morphogenic proteins 2 and 4 and their receptors in the adult human cornea

PURPOSE

To examine the expression of transforming growth factor family members bone morphogenic proteins 2 and 4 (BMP2, BMP4), their receptor mRNAs, and BMP2 and BMP4 proteins in the cells of the human cornea. The effects of BMP2 and BMP4 on corneal fibroblast proliferation and apoptosis were also examined.

METHODS

Reverse transcription-polymerase chain reaction, immunoprecipitation, and western blot analysis were used to examine mRNA and protein expression in cultured human corneal cells. Immunocytochemistry was applied to examine protein localization in fresh frozen human cornea cells. Stimulation and inhibition of nuclear factor-kappaB (NF-kappaB) activation was evaluated by gel shift assay. Apoptosis was examined using trypan blue exclusion, laddering of DNA, CPP32 assay, and transmission electron microscopy. Proliferation was monitored by counting cells.

RESULTS

BMP2 and BMP4 mRNAs and proteins were expressed in cultured human corneal epithelial cells, keratocytes, and corneal endothelial cells. BMP2 and BMP4 were detected in each major corneal cell type in fresh frozen human cornea. BMP receptor IA, IB, and II mRNAs were also detected in cultured human corneal epithelial cells, keratocytes, and endothelial cells. BMP2 and BMP4 stimulated activation of NF-kappaB. Actinomycin D and SN50 peptide, but not SN50M control peptide, inhibited NF-kappaB activation in response to BMP2 or BMP4. BMP2 and BMP4 stimulated apoptosis of corneal fibroblast cells when NF-kappaB activation was inhibited with the nonselective inhibitor actinomycin D or selective inhibitor SN50. The nonsteroidal anti-inflammatory agents ketorolac tromethamine and diclofenac sodium augmented the effect of BMP2 on corneal fibroblast apoptosis. BMP2 and BMP4 both stimulated proliferation of corneal fibroblast cells in the absence of inhibitors of NF-kappaB activation.

CONCLUSIONS

BMP2, BMP4, and their receptors are expressed in the cells of the adult human cornea. The functions regulated by these cytokines may include keratocyte proliferation and apoptosis.

Transepithelial photorefractive keratectomy for treatment of thin flaps or caps after complicated laser in situ keratomileusis

PURPOSE

To report transepithelial photorefractive keratectomy treatment of corneal irregularities produced during laser in situ keratomileusis (LASIK) in which there is a thin flap or cap associated with central corneal scarring or epithelial ingrowth that threatens vision.

METHODS

Case reports. The thickness of the abnormal corneal flap or cap and associated scarring or epithelial ingrowth is estimated at the slit lamp or measured with an optical pachymeter. If residual myopia is sufficiently high to allow complete ablation of the flap or cap in the central cornea, a transepithelial photorefractive keratectomy is performed in which the epithelium is completely ablated with the excimer laser in phototherapeutic keratectomy mode; residual myopia is corrected using photorefractive keratectomy.

RESULTS

This method was used successfully in two eyes of two patients in which a thin cap was associated with a transverse cut through the central cornea or a donut-shaped flap associated with epithelial ingrowth in the central cornea. In both cases, the abnormal cap or flap was ablated, central corneal clarity restored, and visual function improved.

CONCLUSION

Transepithelial photorefractive keratectomy may be effective in treating central corneal thin cap or flap abnormalities associated with LASIK.

Novel human malignancy-associated gene (MAG) expressed in various tumors and in some tumor preexisting conditions

We have identified a novel human malignancy-associated gene (MAG) expressed in various malignant tumors including glioblastomas and hepatocellular carcinomas (HCCs) and in tumor preexisting conditions such as hepatitis C virus- and hepatitis B virus-induced liver cirrhosis. The expression of MAG was characterized using reverse transcription-PCR (RT-PCR), rapid amplification of cDNA ends PCR, RNA dot blotting, RNase protection assay, and Northern blot analysis. Rapid amplification of cDNA ends PCR yielded a 536-bp MAG fragment in HCC, macroregenerative liver nodules with dysplasia, and liver cirrhosis but not in normal liver or placenta. By RT-PCR, MAG expression was not found in 12 different normal tissues but found in 46 of 51 (90%) premalignant and malignant tissues of various sites. Embryonic liver and brain were positive for MAG expression together with tumors from the same organs, but the corresponding normal adult tissues were negative. By RNase protection assay, MAG mRNA was expressed in the HepG2 liver tumor cell line and in an ovarian carcinoma but not in normal liver. The estimated transcript size from Northern blot analysis was 8.8 kb. This novel gene may play a role in the progression of premalignant conditions and in the development of HCC and other cancers.

Elder abuse and neglect: the emergency medicine perspective

The diagnosis of elder abuse and neglect is difficult to accomplish, making intervention elusive, primarily because to date there is no set definition of either abuse or neglect. This paper, written primarily from the American viewpoint, addresses definitions; assessment and diagnosis; aetiology of abuse; intervention; prevention and management; ethical and legal considerations; elder abuse and the emergency physician; and future goals.

Differences in Keratocyte Apoptosis Following Transepithelial and Laser-scrape Photorefractive Keratectomy in Rabbits

BACKGROUND

Anterior stromal keratocyte cells undergo programmed cell death (apoptosis) in response to corneal epithelial injury. Keratocyte apoptosis may be an initiator of the corneal wound healing response that includes keratocyte proliferation and activation, as well as changes to the overlying epithelium, occurring following refractive surgical procedures such as photorefractive keratectomy (PRK). This study compared the effect of laser-scrape and transepithelial PRK on keratocyte apoptosis.

METHODS

Photorefractive keratectomy was performed in both eyes of 10 New Zealand white rabbits using the Summit Apex excimer laser. Surgery was performed using transepithelial PRK in one eye and laser-scrape PRK in the other. The central cornea was analyzed at 4 hours after surgery using a quantitative TUNEL assay that detects fragmented DNA characteristic of apoptosis. Hepatocyte growth factor (HGF) production by keratocytes was detected by immunocytochemistry.

RESULTS

Average apoptotic cells per 400X microscopic field determined by 2 independent masked observers were 0.9 +/- 0.5 (scanning electron microscopy) and 0.2 +/- 0.2 in the transepithelial PRK group compared with 5.1 +/- 2.9 and 4.1 +/- 3.2 in the laser-scrape group. The difference between the two groups was statistically significant for both observers (P < .05, ANOVA). HGF was detected within keratocytes throughout the corneal stroma. Less HGF was detected in the anterior stroma in the laser-scrape group at 4 hours after surgery, consistent with more anterior keratocyte apoptosis in this group.

CONCLUSIONS

Transepithelial PRK induced less anterior keratocyte apoptosis in rabbits than laser-scrape PRK. This suggests that transepithelial PRK could be useful in preventing or minimizing refractive regression and subepithelial scarring.

Photorefractive keratectomy using the summit SVS Apex laser with or without astigmatic keratotomy

PURPOSE

The purpose of this study was to evaluate the results of myopic photorefractive keratectomy (PRK) with or without astigmatic keratotomy (AK) for different levels of intended correction by using the SVS Apex laser.

METHODS

This is a retrospective cohort study of 226 eyes that had PRK for myopia ranging from -1.0 to -7.6 diopters and 6 months of follow-up. In addition, 64 of these eyes had AK for naturally occurring or laser-induced astigmatism. Uncorrected visual acuity, spectacle-corrected visual acuity, and corneal topography with quantitative descriptors of surface regularity (SRI) and surface asymmetry (SAI) were used to monitor the results of PRK with or without AK.

RESULTS

At 6 months, 95.6% eyes had an uncorrected visual acuity of 20/40 or better, 90% eyes were within +/-1.0 diopter of emmetropia, and 3.1% eyes lost two lines of best-corrected vision. No eyes lost more than two lines of best-corrected vision. Mean refractive astigmatism was reduced, but mean SAI and SRI were increased, 6 months after PRK. Uncorrected vision, best-corrected vision, and predictability decreased, whereas SAI and SRI increased, with increasing attempted correction.

CONCLUSION

PRK, with or without AK, effectively reduced myopia in all eyes by 6 months after surgery. Predictability tended to decrease with increasing attempted correction, even for eyes with relatively low to moderate myopia. PRK may induce surface asymmetry and irregularity at 6 months, and these alterations tend to be greater as the attempted correction increases.

The management of skin and skin structure infections in children, adolescents and adults: a review of empiric antimicrobial therapy

This article reviews the diagnosis and management of mild-to-moderate skin and skin structure infections in children, adolescents and adults in a general practice setting. Therapies reviewed are those in current use: penicillins; beta-lactamase stable penicillins, including flucloxacillin, oxacillin, and amoxicillin-clavulanate; oral quinolones; macrolides; and oral cephalosporins. Consideration is given to duration of therapy, side-effect profile and compliance.

Application of coacervated alpha-elastin to arterial prostheses for inhibition of anastomotic intimal hyperplasia

Prevention of anastomotic intimal hyperplasia (AIH) requires inhibition of the migration of smooth muscle cells (SMCs) and promotion of endothelial cell (ECs) growth from the native arterial wall. We investigated the effect of coacervated alpha-elastin on migration of SMCs and ECs in vitro. SMCs and ECs were prepared from porcine aortic media and endothelium. Coacervated alpha-elastin was coated and cross-linked around the perimeter of each 1 cm diameter center of a well in a 12 well plate. SMCs and ECs were placed and cultured within the center of each well. The migration of SMCs and ECs on coacervated alpha-elastin was assayed on the second, third (10 mg/ml), or fourth day (0.1, 1.0, 10.0 mg/ml) of cultivation by measuring the area of migration from the 1 cm diameter center. Coacervated alpha-elastin was then coated and cross-linked on a Dacron graft using 1% glycerol polyglycidyl ether (GPGE) and examined with scanning electron microscopy to determine the feasibility of graft coating. SMC migration was significantly inhibited dose dependently over time (p < 0.005), e.g., 0.1 mg/ml (45.4% +/- 2.7%: % of MES [pH 5] and 1% GPGE without alpha-elastin), 1.0 mg/ml (32.0% +/- 1.4%), 10.0 mg/ml (8.3% +/- 2.9%). EC migration (90.7% +/- 6.2%: p = ns) was not inhibited by 0.1 mg/ml of coacervated alpha-elastin. Cross-linked coacervated alpha-elastin was coated on a dacron graft uniformly. Incorporation of coacervated alpha-elastin into the structure of arterial prostheses offers the possibility of inhibition of SMC hyperplasia without inhibition of EC formation.

LASIK: management of common complications. Laser in situ keratomileusis

PURPOSE

To review common complications noted with LASIK.

METHODS

Review of personal experience of the author with the procedure and work published in the literature.

RESULTS

The most common complications of the LASIK procedure include flap irregularities, epithelium and other materials within the lamellar interface, irregular astigmatism, regular astigmatism, regression, and overcorrection. Infection is a rare but potentially serious complication.

CONCLUSIONS

LASIK has impressive potential for the correction of myopia and hyperopia. Surgeons who perform the procedure must be familiar with recognition and treatment of potential complications of LASIK.

Cultured human trabecular meshwork cells express functional growth factor receptors

PURPOSE

To compare the mRNA expression of growth factor receptors in cultured human trabecular meshwork (HTM) cells with ex vivo HTM tissues and to determine whether HTM cells generate a physiologic response after exposure to exogenous growth factors.

METHODS

The reverse transcription-polymerase chain reaction (RT-PCR) method was used to detect the expression of various growth factor receptor mRNAs using early passaged, cultured HTM cells from donors of several ages. RT-PCR on ex vivo HTM tissues from healthy donors and donors with glaucoma were also used to compare and contrast mRNA expression with cell culture results. After the exogenous administration of growth factors, cell proliferation and extracellular acidification rate studies were used to measure the functional responses of HTM cells to growth factors.

RESULTS

Amplification products of the expected size for 15 growth factor receptors were detected in cultured HTM cells and in ex vivo HTM tissues. The administration of exogenous growth factors showed that (a) hepatocyte growth factor (HGF), epidermal growth factor (EGF), insulinlike growth factor (IGF)-1, tumor necrosis factor (TNF) alpha, platelet-derived growth factor (PDGF)-AA, PDGF-BB, PDGF-AB, and basic fibroblast growth factor (FGF-2) stimulated cell proliferation, whereas FGF-1 (acidic), transforming growth factor (TGF) alpha, interleukin (IL)-1alpha, nerve growth factor (NGF), and FGF-7 (keratinocyte growth factor [KGF]) had no significant influence on cell proliferation; (b) TGF-beta isoforms significantly inhibited EGF-stimulated trabecular meshwork cell proliferation; and (c) FGF-1 (acidic), TGF-alpha, EGF, IL-1alpha, IL-1beta, HGF, TNF-alpha, PDGF-AA, and IGF-1 significantly stimulated extracellular acidification, whereas FGF-2 (basic), FGF-7 (KGF), TGF-beta1-beta3 and NGF had no significant influence on extracellular acidification.

CONCLUSIONS

These studies show that mRNA for numerous growth factor receptors can be detected in cultured HTM cells and in ex vivo HTM tissues. They also show that many of the receptors are functional, because exogenous growth factor administration elicits a physiologic response. In vivo, these receptors may be activated by growth factors present within the aqueous humor (aquecrine/paracrine) or by growth factors synthesized and released locally by trabecular meshwork cells themselves (autocrine). Specific growth factors acting through high-affinity receptors may be involved in maintaining the normal microenvironment of the HTM and also may be involved in the pathogenesis of primary open-angle glaucoma.

Helical CT angiography in the preoperative evaluation of carotid artery stenosis

PURPOSE

To determine the utility and accuracy of helical CT angiography (CTA) in the evaluation of carotid artery stenosis.

METHODS

A comparison of CTA and conventional arteriogram was performed in 53 patients undergoing evaluation for carotid artery stenosis. Ninety-six carotid systems were evaluable. CTA stenosis was determined by the percent of area reduction seen on axial images through the level of greatest narrowing. MIP images were used to identify the point of maximal stenosis and to visualize overall vascular anatomy. The percent diameter stenosis was measured on conventional arteriograms using strict North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST) criteria.

RESULTS

Significant correlation was found between CTA and arteriography (NASCET method R=0.87, ECST method R=0.87, p < 0.001). Using NASCET >60% as an indicator for disease, CTA had a sensitivity of 87%, specificity of 90%, accuracy of 89%, negative predictive value of 88%, and positive predictive value of 89%. CTA identified plaque characteristics such as ulcerations (8), occlusion (10), fatty plaques (22), calcifications (48), and fibrosis (2). CTA underestimated 2 cases of short segment stenoses because of volume averaging, but this discrepancy was detected by duplex scan. No complications or renal dysfunction occurred with CTA; 1 patient became symptomatic during arteriography, necessitating termination of the procedure.

CONCLUSION

CTA is a safe, non-invasive technique that precisely measures carotid artery area reduction and highly correlates to conventional arteriography. With this new technology, the current standards for carotid artery imaging may need to be reevaluated, and the precise role for helical CTA more clearly defined.

Effect of surgical panel composition on patient outcome at a level I trauma center

OBJECTIVE

To compare the effect of staffing with general surgeons vs trauma specialists on patient outcome at a trauma center.

DESIGN

The care of injured patients at a level I urban trauma center serving a population of 2.5 million was the responsibility of 12 surgeons (10 general surgeons and 2 trauma specialists) between January 1 and June 30, 1996 (group 1). Between July 1 and December 31, 1996 (group 2), trauma was the responsibility solely of 4 trauma specialists. An additional comparison was made with those patients in group 1 who were admitted to the general surgeons (group 1A). The outcomes and quality of care for these periods, as determined by the quality assurance screens, were retrospectively analyzed and compared.

SETTING

Urban, tertiary care, level I trauma center.

PARTICIPANTS

Each trauma and burn patient admitted during the study periods is included in this study. Upon the patient's discharge from the hospital, specially trained nurses completed a review of the patient's stay and entered it into the TraumaOne database (Lancet Technology Inc, Cambridge, Mass). There were 693 trauma patients in group 1 (472 in group 1A) and 734 patients in group 2.

MAIN OUTCOME MEASURES

Mortality, length of stay, and 16 quality assurance screens were quantified and compared using chi(2) analyses and t tests.

RESULTS

The age and sex of the 2 groups were similar. The mortality rate was 6.2% (43/693) in group 1, 6.1% (29/472) in group 1A, and 6.5% (48/734) in group 2 (P = .80 and P = .78, respectively). When stratified by injury severity score (ISS), lengths of stay were statistically similar, except for patients with an ISS of 0 to 7. Patients with an ISS of 0 to 7 in groups 1 and 1A stayed a mean of 2.6 days, compared with 3.2 days for group 2 (P = .01 and P = .02, respectively). The results of quality assurance screens (missed injury, wound infection, readmission, and 13 others) were similar in the 2 groups.

CONCLUSIONS

Transitions in staffing afforded the opportunity to examine patient outcomes by surgeon specialization and frequency of call. In our sample, 12 well-trained surgeons taking call less frequently managed a trauma service as efficiently as a group of 4 trauma specialists, without any differences in morbidity and mortality.

Cross-clade envelope glycoprotein 160-specific CD8+ cytotoxic T lymphocyte responses in early HIV type 1 clade B infection

A major objective of current HIV-1 vaccination strategies is the induction of HIV-1-specific CD8+ MHC class I-restricted CTL responses, which are suggested to play a pivotal role in viral clearance and protection against HIV-1 disease progression. However, the marked genetic diversity of HIV-1 and existence of distinct viral subtypes or clades could potentially hinder the development of a universally efficacious HIV-1 vaccine. In this study we examined HIV-1 intraclade (B(LAI) versus B(MN)) Env gp160-specific CTL reactivity in recently HIV-1 clade B-infected individuals. We further evaluated the extent of interclade CTL cross-recognition of the divergent A and C Env gp160 subtypes, that are highly prevalent in the global pandemic. Freshly isolated PBMCs were stimulated in vitro with autologous PBMCs infected with recombinant vaccinia vectors expressing HIV-1 env, gag, pol, and nef genes derived from HIV-1 clade B. All 13 of the 19 HIV-1-seropositive subjects who elicited significant clade B Env gp160LAI CD8+ CTL responses also demonstrated comparable levels of CTL cross-reactivity against clade C92BR025 Env gp160. Nine of these individuals also showed extensive interclade CTL cross-recognition of clade A92UG037 Env gp160. Two HLA class I B7 donors had nondetectable intraclade CTL response against B Env gp160MN, while generating significant intraclade B(LAI) and interclade (A and C) Env gp160 CTL cross-reactivity. These observations serve to underscore the central importance of the HLA background of individuals in determining the pattern of immune reactivity to natural HIV-1 infection and presumably vaccines. Five donors studied also demonstrated broad CTL cross-reactivity against clade A92UG037 Gag p55, Pol, and/or Nef antigens. In conclusion, this present study indicates that there is a considerable degree of CD8+ CTL cross-recognition of the highly divergent HIV-1 Env gp160 subtypes during early phases of HIV-1 infection. Such findings suggest that HIV-1 vaccines based on a single clade that can induce extensive cross-clade immunity may demonstrate utility in diverse geographical regions.

Signaling by HGF and KGF in corneal epithelial cells: Ras/MAP kinase and Jak-STAT pathways

PURPOSE

To characterize the signaling pathways used by hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) in human corneal epithelial cells.

METHODS

Cultures of SV40 large T antigen-transfected human corneal epithelial cells were treated with recombinant human HGF or KGF at 50 ng/ml to 100 ng/ml for 5 to 30 minutes and harvested for protein isolation. Immunoprecipitation was performed with antisera to signal transducers and activators of transcription 1 (STAT1), STAT3, Janus kinase 1 (Jak1), Shc, Grb2, Sos1, and HGF receptor (met). Immunoprecipitated proteins were analyzed by western blot analysis. Gel retardation experiments were carried out with first-passage human corneal epithelial cells to detect binding of STATs to the high affinity c-sis (platelet-derived growth factor) inducible DNA element (hSIE). Effects of HGF, KGF, and kinase inhibitors on mitogen-activated protein kinase (MAPK) activation were evaluated by western blot analysis and enzymatic assays.

RESULTS

In human corneal epithelial cells, the phosphorylation of adapter protein Shc (52- and 66-kDa isoforms) was enhanced by HGF, but not by KGF. Phosphorylated HGF receptor coimmunoprecipitated with Shc, Grb2, and Sos1. Hepatocyte growth factor or KGF rapidly activated MAPK in corneal epithelial cells. The activation of MAPK (p42 and p44) by HGF or KGF was transient and decreased gradually within 1 hour. MAPK kinase 1 (MEK1) inhibitor PD098059 or the protein tyrosine kinase inhibitor genistein blocked MAPK activation. Activation of MAPK induced by HGF was partially inhibited by protein kinase C inhibitor calphostin C. Hepatocyte growth factor and KGF had no effect on the activation of Jak-STAT cascade components that are activated by epidermal growth factor.

CONCLUSIONS

Hepatocyte growth factor and KGF activate Ras-MAPK pathways in human corneal epithelial cells. There may be at least two routes used by HGF in transmitting signals from its receptor to the MAPK cascade. One is the receptor-Grb2/Sos complex to the Ras pathway, and the other is through protein kinase C. Hepatocyte growth factor and KGF did not activate the Jak-STAT cascade components STAT1, STAT3, or Jak1 in corneal epithelial cells.

Everett Kinsey Lecture. Keratocyte apoptosis in refractive surgery

PURPOSE

The purpose of this paper is to review the relevance of keratocyte programmed cell death (apoptosis) in response to epithelial injury to corneal wound healing following refractive surgery and the pathogenesis of corneal diseases such as keratoconus.

METHODS

The TUNEL assay (to detect DNA fragmentation in situ) DNA laddering assay, and transmission electron microscopy have been used to detect apoptosis in human and animal corneas and cultured corneal cells. Molecular and cell biologic techniques have been used to study the cytokine-receptor systems that are involved in modulating apoptosis in the cornea.

RESULTS

Keratocyte apoptosis, mediated through the release of cytokines such as soluble Fas ligand and interleukin-1 from the injured epithelium, occurs following refractive surgical procedures like photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Keratocytes that die in the anterior stroma following PRK or along the lamellar cut following LASIK are replenished in 2 to 4 days by proliferation and migration. The replenishing cells are activated myofibroblastic keratocytes that produce collagen, hyaluronic acid, growth factors modulating epithelial healing, and other components of the wound healing response. Keratocyte apoptosis can be inhibited by transepithelial PRK (probably by photodisruption of the apoptotic cytokines in the epithelium) or pharmacologic agents.

CONCLUSIONS

Keratocyte apoptosis may be an initiator of the wound healing response in the cornea. Control of this response has the potential to regulate wound healing in the cornea in response to PRK or LASIK. Recent evidence suggests that keratocyte apoptosis mediated by chronic epithelial injury could have a role in the pathogenesis of keratoconus.

Oligomeric properties and DNA binding specificities of repressor isoforms from the Streptomyces bacteriophage phiC31

Three protein isoforms (74, 54 and 42 kDa) are expressed from repressor gene c in the Streptomyces temperate bacteriophage phiC31. Because expression of the two smaller isoforms, 54 and 42 kDa, is sufficient for superinfection immunity, the interaction between these isoforms was studied. The native 42 kDa repressor (Nat42) and an N-terminally 6x histidine-tagged 54 kDa isoform (His54) were shown by co-purification on a Ni-NTA column to interact in Streptomyces lividans . In vitro three repressor preparations, containing Nat42, His54 and the native 54 and 42 kDa isoforms expressed together (Nat54&42), were subjected to chemical crosslinking and gel filtration analysis. Homo- and hetero-tetramers were observed. Previous work showed that the smallest isoform bound to 17 bp operators containing aconservedinvertedrepeat (CIR) and that the CIRs were located at 16 loci throughout the phiC31 genome. One of the CIRs (CIR6) is believed to be critical for regulating the lytic pathway. The DNA binding activities of the three repressor preparations were studied using fragments containing CIRs (CIR3-CIR6) from the essential early region as templates for DNase I footprinting. Whereas Nat42 bound to CIR6, poorly to CIR5 but undetectably to CIR3 or CIR4, the Nat54&42 preparation could bind to all CIRs tested, albeit poorly to CIR3 and CIR4. The His54 isoform bound all CIRs tested. Isoforms expressed from the phiC31 repressor gene, like those which are expressed from many eukaryotic transcription factor genes, apparently have different binding specificities.