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Biomedical subjects

J H Lass

Publications and source records attributed to J H Lass.

At least 55 records · Page 3Linked to original sources
PubMed1991

Topical fluoroquinolones: antimicrobial activity and in vitro corneal epithelial toxicity.

To assess the potential of fluoroquinolones as topical antimicrobial agents, we evaluated in vitro the antimicrobial activity of five fluoroquinolones (ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, and temafloxacin), as well as gentamicin, tobramycin, and cefazolin against 96 isolates of common bacterial corneal pathogens. Ciprofloxacin and temafloxacin were the most active quinolones [minimal inhibitory concentration inhibiting 90% of stains (MIC90) of 1 microgram/ml], followed by ofloxacin (MIC90 2 micrograms/ml), and norfloxacin and pefloxacin (MIC90s 4 micrograms/ml). In contrast, gentamicin and tobramycin MIC90s were 32 and 64 micrograms/ml, respectively; cefazolin MIC90 was greater than 2048 micrograms/ml. The corneal epithelial cytotoxicity of the fluoroquinolones also was evaluated utilizing an in vitro assay of 3H-thymidine uptake of rabbit corneal epithelial cell cultures. The least to greatest toxicity of the fluoroquinolones were as follows: ciprofloxacin and temafloxacin less than norfloxacin less than ofloxacin less than pefloxacin. Our study suggests that the fluoroquinolones, especially ciprofloxacin and temafloxacin, possess excellent in vitro activity against common bacterial corneal pathogens and are less toxic to the corneal epithelium than the aminoglycosides.

4-Quinolones↗
PubMed1991

Human crystalline lens phospholipid analysis with age.

Paired human crystalline lenses (n = 21, patient ages 20-79 years) were extracted for lipids with chloroform-methanol 2:1, using the Folch method. The extracted crude lipids were analyzed at 202.4 MHz by phosphorus-31 magnetic resonance spectroscopy (31P NMR). Fourteen membrane phospholipids were detected including phosphatidylcholine (PC), lysophosphatidylcholine (LPC), phosphatidylcholine plasmalogen (PC plas), phosphatidylethanolamine (PE), phosphatidylethanolamine plasmalogen, lysophosphatidylethanolamine (PA), phosphatidylglycerol (PG), lysophosphatidylglycerol, phosphatidylserine (PS), phosphatidic acid, phosphatidylinositol, sphingomyelin (SPH), and two uncharacterized phospholipids. The uncharacterized phospholipid at 0.13 was the predominant phospholipid, comprising 43.20% of the lens phospholipid profile. A decrease in mole percent of phosphorus concentrations of PE, PC plas, and PC and an increase in SPH correlated with age. The following computed indices decreased with age: PC/PG and PE/PS; PC + PE; (PC + PC plas); and PC/PS. The following computed indices increased with age: (PC + SPH)/(PE + PS), SPH/PG, (PC + SPH)/(PE + PS), LPC/PC, LPE/PE, SPH/PE, and SPH/PC. Changes in membrane phospholipids of the crystalline lens with age as detected by 31P NMR can be used to fingerprint lens maturation.

Adult↗
PubMed1990

Clinical and morphometric results of penetrating keratoplasty with one-piece anterior-chamber or suture-fixated posterior-chamber lenses in the absence of lens capsule.

The clinical records and serial corneal endothelial images of 25 acapsular, pseudophakic eyes with Kelman-style, one-piece, anterior-chamber intraocular lenses and 24 acapsular, pseudophakic eyes with suture-fixated, posterior-chamber intraocular lenses following penetrating keratoplasty were reviewed to determine clinical success and endothelial survival after 1 year. Twenty-two (88%) of 25 grafts in the anterior-chamber intraocular lens group and 23 (96%) of 24 grafts in the sutured posterior-chamber intraocular lens group were clear after 1 year; best corrected visual acuity of 20/40 or better was noted in 25% of the eyes in the anterior-chamber intraocular lens group and 29% of the eyes in the sutured posterior-chamber intraocular lens group. The mean intraocular pressure for the anterior-chamber intraocular lens group was significantly lower than for the sutured posterior-chamber intraocular lens group at 3 months (17 +/- 4 vs 21 +/- 7 mm Hg) and at 6 months (17 +/- 3 vs 20 +/- 5 mm Hg); but did not differ at 1 year. The mean percent of endothelial cell loss after 1 year did not differ between the anterior-chamber intraocular lens group (32% +/- 26%) and the sutured posterior-chamber intraocular lens group (27% +/- 26%). No clinical or endothelial morphometric advantages were noted after 1 year for the suture-fixated, posterior-chamber intraocular lens over the Kelman-style, one-piece anterior chamber, intraocular lens following pseudophakic penetrating keratoplasty; however, a long-term, prospective, randomized study of these two intraocular lens types is recommended.

Aged↗
PubMed1990

Clinical management of keratoconus. A multicenter analysis.

The clinical management of 746 eyes in 417 patients referred for keratoconus from January 1984 through January 1988 was retrospectively analyzed. In 357 patients, 554 eyes (74%) did not require surgery and were managed with contact lenses or spectacles, 156 eyes (21%) in 137 patients either underwent penetrating keratoplasty (PK) (140 eyes) or surgery was recommended (16 eyes), and 36 eyes (4%) in 34 patients underwent epikeratoplasty. Comparing baseline and final examination findings, the nonsurgical group showed a significant improvement in average best-corrected visual acuity from 20/30 to 20/25, the PK group from 20/70 to 20/25, and the epikeratoplasty group from 20/40 to 20/30. Average keratometry was unchanged in the nonsurgical group, but decreased by 10.7 diopters (D) for the PK group and 6.5 D for the epikeratoplasty group. Corneal cylinder was unchanged in the nonsurgical group, whereas there was a reduction of the percentage of eyes with indeterminant cylinder from 55 to 2% in the PK group and from 36 to 0% in the epikeratoplasty group. Previous contact lens history, best-corrected visual acuity of 20/50 or worse, and average keratometry of 55 D or greater at baseline were associated with a significant risk for PK. No baseline variables were associated with significant risk for epikeratoplasty, suggesting that this group was similar to the nonsurgical group, except for contact lens intolerance. The nonsurgical management of keratoconus continues to play a predominant role in the management of this disorder in a referral population.

Adolescent↗
PubMed1990

An in vitro and clinical comparison of corneal storage with chondroitin sulfate corneal storage medium with and without dextran.

The safety and efficacy of 1% dextran in Chondroitin Sulfate Corneal Storage Medium (CSM) in reducing corneal swelling after 4 degrees C storage was assessed in a corneal endothelial cell culture system. No difference was found in 3H-thymidine incorporation by cells incubated in either CSM-dextran medium or CSM medium alone. Subsequently, 21 pairs of corneas, stored in either CSM or CSM-dextran from 30 to 112 hours, were transplanted into 42 eyes of 42 patients, paired by diagnostic group and procedure. All CSM grafts and 19 of 21 CSM-dextran grafts were clear at 4 months with no primary donor failures in either group. Intraoperative corneal thickness was significantly greater in the CSM group (0.82 +/- 0.07 mm) than the CSM-dextran group (0.76 +/- 0.06 mm); however, the two groups did not differ thereafter. No differences in all endothelial morphometric parameters were noted between the two groups pre- and postoperatively. Average endothelial cell loss by 4 months was 13.0 +/- 16.4% for the CSM group and 16.4 +/- 15.5% for the CSM-dextran group. The addition of dextran to CSM medium results in significant intraoperative corneal thinning without adversely affecting endothelial DNA synthesis in vitro and endothelial survival in vivo.

Adult↗
PubMed1990

P-31 NMR analysis of phospholipids from cultured human corneal epithelial, fibroblast and endothelial cells.

Corneal epithelial, fibroblast and endothelial cells, cultured from human donors, were analyzed to determine their characteristic phospholipid profiles by 31P NMR. Tissue phospholipid profiles from epithelial, fibroblast and endothelial cell cultures were evaluated to differentiate the individual cell types and to identify resonances that typically appear in high-resolution phospholipid profiles of whole corneas. Phosphatidylcholine, phosphatidylethanolamine plasmalogen, an uncharacterized phospholipid at 0.13 delta, phosphatidylinositol, phosphatidylserine and sphingomyelin were determined to be, in decreasing order of concentration, the major phospholipids detected in these three cultured corneal cell types. Indices of phospholipid metabolism representing total plasmalogen content, total choline-containing lipids and the total choline-containing lipids less those synthesized through the plasmalogen pathway were found to differentiate the three cell types. Minor phospholipids cardiolipin, lysophosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine (LPC) and LPC plasmalogen not usually reported in studies of corneal phospholipids using other techniques, were useful in discriminating between cell types. Phospholipid profiles of the whole cornea provide important information concerning the biochemistry and pathology of the tissue, however, phospholipid analysis of individual components of the cornea, such as the epithelial, fibroblast and endothelial cells, makes it possible to understand the contribution of specific cellular constituents to the spectral information obtained from the whole cornea.

Cells, Cultured↗
PubMed1990

Expression of two molecular forms of the complement decay-accelerating factor in the eye and lacrimal gland.

Complement is present in ocular fluids, but the molecular mechanism(s) restricting its activation to exogenous targets and not to autologous ocular cells are currently unknown. To clarify how this control is achieved, monoclonal antibody (mAb)-based techniques were used to examine the eye, the lacrimal gland, and ocular fluids for the decay-accelerating factor (DAF), a membrane regulatory protein which protects blood cells from autologous complement activation on their surfaces. Immunohistochemical staining of tissue sections revealed DAF antigen on corneal and conjunctival epithelia, corneal endothelium, trabecular meshwork, and retina, as well as on lacrimal gland acinar cells and in adjacent lumens. By flow cytometry, cultures of conjunctival epithelium exhibited the highest DAF levels and levels on corneal epithelium greater than corneal endothelium greater than conjunctival fibroblasts. Biosynthetic labeling of corneal endothelium yielded de novo DAF protein with an apparent molecular weight (Mr) of 75 kD, approximating that of blood cell DAF protein, and digestions of conjunctival epithelium with phosphatidylinositol-specific phospholipase C (PI-PLC), an enzyme which cleaves glycoinositolphospholipid membrane anchors, released approximately 70% of the ocular surface DAF protein similar to leukocyte surface DAF protein. Quantitations of DAF by radioimmunometric assay employing mAbs against two DAF epitopes revealed 325 ng/ml (n = 12), 4.8 ng/ml (n = 10), and 22.0 ng/ml (n = 8) of soluble DAF antigen in tears, aqueous humor, and vitreous humor, respectively. Western blot analyses of the tear DAF antigen revealed two DAF forms, one with an apparent Mr of 72 kD resembling membrane DAF forms in other sites, and a second with an apparent Mr of 100 kD, which is previously undescribed. Since DAF activity is essential physiologically in protecting blood cells from autologous complement attack, the identification of DAF on the ocular surface, intraocularly, in the lacrimal gland, and in tears suggests that DAF-mediated control of complement activation is also required in these locations.

Antibodies, Monoclonal↗
PubMed1990

Severe anterior segment inflammation following corneal surgery for keratoconus.

We present three keratoconus patients who experienced severe anterior segment inflammation, two following penetrating keratoplasty, and one following epikeratoplasty. A favorable response to indomethacin therapy in the second eyes of these patients suggests that the inflammation in the first ones was prostaglandin mediated.

Adult↗
PubMed1990

Infectious crystalline keratopathy associated with topical anesthetic abuse.

Two patients with infectious crystalline keratopathy associated with topical anesthetic abuse are described. No previously reported predisposing factors existed, including topical corticosteroid use during active Herpes simplex or Acanthamoeba keratitis, or following penetrating keratoplasty. Cultures from corneal biopsies of both patients grew Streptococcus viridans. Both infections resulted in corneal scarring with vascularization. Ultimately, corneal transplantation was performed in one case.

Adult↗
PubMed1989

The use of contact lenses after keratoconic epikeratoplasty.

Thirty-three epikeratoplasties were performed on 31 keratoconic contact lens intolerant patients. Thirty-two of these procedures were anatomically successful with clear lenticules and flattening of the postoperative keratometric measurements in all but one eye. One patient's lenticule developed a persistent epithelial defect that eventually required its removal at 42 days. This patient subsequently underwent a successful penetrating keratoplasty. Of the 32 eyes that were anatomically successful, 20 eyes in 19 patients were able to achieve satisfactory visual improvement requiring either no correction or spectacle lenses. Twelve eyes in 11 patients were successfully refit with contact lenses for anisometropic refractive errors (11 eyes) and residual irregular astigmatism (one eye). Three patients (two in the non-contact lens group and one in the contact lens group) have subsequently undergone penetrating keratoplasty for further visual improvement. Our data suggest that the majority of keratoconic epikeratoplasties achieve a satisfactory visual result either unaided or with spectacles; however, those patients who wish to resume contact lens wear may do so successfully.

Adult↗
PubMed1989

Noninvasive metabolic analysis of eye bank corneas: a magnetic resonance spectroscopic study.

Nondestructive, noninvasive metabolic analysis of corneal donor tissue preserved in modified McCarey-Kaufman medium was achieved using phosphorus-31 magnetic resonance spectroscopy (31 P MRS). Clear corneas (n = 10) with minimal Descemet's folds and an endothelial cell density of 2990 +/- 166 cells/mm2 from donors aged 26 to 89 years were used. Relative amounts of low- and high-energy phosphatic metabolites were quantitated during a 1-h period using the integral of the 31P spectrum. The following indicators of the tissue's energy status were determined: (1) 31P spectral energy modulus (ratio of high- to low-energy metabolites, average 0.95 +/- 0.14); (2) adenosine triphosphate/inorganic orthophosphate (ATP/Pi) ratio, 1.97 +/- 0.55; (3) sugar phosphate/inorganic orthophosphate (SP/Pi) ratio, average 1.07 +/- 0.12; and (4) intracorneal pH, calculated from the resonance shift position of inorganic orthophosphate, average 7.28 +/- 0.05. The 31P MRS technique measures key corneal metabolic processes (maintenance of the high-energy phosphate complement, interrelationship of inorganic orthophosphate and its bioesters, and pH). This study provides baseline data for eventually determining optimal parameters of eye bank corneal tissues and for evaluating the metabolic status, or health, of the cornea.

Adenosine Triphosphate↗
PubMed1989

Phosphatic metabolites in keratoconus.

Sixteen corneal buttons were obtained from 16 patients with keratoconus at the time of penetrating keratoplasty (mean age, 34 +/- 3.2 yr) and prepared for phosphorus-31 nuclear magnetic resonance spectroscopy following perchloric acid extraction. The corneas were compared with age-matched corneas from fresh eye-bank eyes with normal slit-lamp biomicroscopic appearance. Higher levels (P less than 0.05) of nucleoside monophosphates and choline phosphate and lower levels (P less than 0.05) of adenosine diphosphate were detected in keratoconus than in eye-bank corneas. The level of an unidentified metabolite at 3.96 delta, present in eye-bank corneas, was ninefold higher in keratoconus corneas. Another unidentified metabolite at 3.31 delta, accounting for 1.5% of the total detected phosphatic metabolites, appeared in keratoconus but not in eye-bank cornea spectra. These findings of altered phosphatic metabolites are consistent with altered corneal metabolism. The unidentified, unknown metabolites in the spectral profile uniquely distinguish keratoconus from eye-bank corneas.

Adenine Nucleotides↗
PubMed1989

Interspecies analysis of corneal phosphate metabolites.

Phosphate metabolite profiles of corneas were determined for human, baboon, monkey, cat, guinea-pig, pig, dog, rabbit, and cow using 31P-nuclear magnetic resonance (NMR) spectroscopy. Metabolites quantitatively measured included the low-energy metabolites: hexose 6-phosphates, alpha-glycerophosphate, unassigned phosphorus compound(s) at 4.26-3.91 delta, ethanolamine phosphate, nucleoside monophosphates, choline phosphate, inorganic orthophosphate, phosphodiesters (glycerol 3-phosphoethanolamine and glycerol 3-phosphocholine), and the high-energy metabolites: phosphocreatine, adenosine triphosphate (ATP), adenosine diphosphate (ADP), nucleoside diphosphosugars and dinucleotides. The number of significant differences in metabolites among the species studied, relative to humans, increased in the following order: baboon less than monkey approximately pig approximately cow less than cat approximately guinea-pig less than rabbit less than dog. The 31P energy modulus (human, 1.3 +/- 0.20 S.D.). ATP:Pi ratio (human, 0.5 +/- 0.05 S.D.). ATP:ADP ratio (human, 0.38 +/- 0.34 S.D.). ATP:ADP plus Pi ratio (human, 0.43 +/- 0.04 S.D.) and SP:Pi ratio (human, 0.37 +/- 0.04 S.D.) were determined for each species. All these ratios are indicators of corneal metabolic status, and their values suggest that, of the common laboratory research animals examined, the baboon and monkey are the most like man, and the rabbit and cow the least like man.

Animals↗
PubMed1989

Comparison of corneal storage in K-Sol and chondroitin sulfate corneal storage medium in human corneal transplantation.

Fifty-one pairs of corneas, stored in either K-Sol or CSM (chondroitin sulfate corneal storage medium) from 8 to 97 hours (mean +/- standard deviation, 58 +/- 21 and 57 +/- 21 hours, respectively), were transplanted in a prospective, randomized manner into 99 patients (n = 102 eyes), paired by diagnostic group and procedure. Ninety-six percent of K-Sol grafts (n = 51) and 94% of the CSM grafts (n = 51) were clear at 6 months; 92% of both the K-Sol (n = 38) and CSM (n = 35) grafts were clear at 12 months. One primary donor failure occurred, a K-Sol cornea stored for 76 hours. The CSM group experienced a greater number of persistent epithelial defects beyond 2 weeks (7 versus 4 defects) and graft reaction episodes (7 versus 3 episodes) than the K-Sol group; however, an equal number of late graft failures (3) occurred in both groups. No significant differences by paired t test analyses were found in endothelial cell density, area, coefficient of variation, or figure coefficient at 3 (n = 37 pairs), 6 (n = 36 pairs), and 12 (n = 26 pairs) months between the two groups. Mean endothelial cell density significantly decreased by 11% +/- 22 by 3 months in the K-Sol group, whereas the 7% +/- 24 decrease in the CSM group was insignificant. By 12 months, both groups experienced a significant decrease: K-Sol, 27% +/- 22; CSM, 17% +/- 26. A significant decrease in the mean coefficient of variation (polymegathism) was noted after 3 months in the K-Sol group which returned to the preoperative mean by 1 year, whereas this parameter remained unchanged in the CSM group. Both chondroitin sulfate-based media result in successful corneal transplantation with storage up to 4 days; however, endothelial survival with both media are comparable with previous studies with McCarey-Kaufman (M-K) medium.

Adolescent↗
PubMed1989

An in vitro analysis of aminoglycoside corneal epithelial toxicity.

We evaluated the cytotoxicity of four aminoglycoside agents (neomycin, gentamicin, tobramycin, and amikacin) using an in vitro confluent rabbit corneal epithelial cell culture model. Primary corneal epithelial cell cultures were established and cells replated at 2 x 10(4) cells/2 cm2 well. After 48 hours either vehicle or an antibiotic was added at varying concentrations, each for 5, 30, or 60 minutes. 3H-thymidine was added immediately after drug removal and incorporation was measured 8 hours after drug or vehicle exposure. Comparisons of each drug to vehicle were expressed as % inhibition of control culture values. At the 5-minute exposure time tobramycin and amikacin showed no significant inhibition at any concentration, whereas neomycin and gentamicin showed significant inhibition at 6 mg/ml and 3.5 mg/ml or greater concentrations, respectively (p less than 0.05). At 30- and 60-minute exposure times all agents demonstrated significant inhibition at all tested concentrations in a non-dose dependent fashion (p less than 0.05). These in vitro data corroborate the animal and limited clinical data available for the aminoglycosides. Based on these toxicity profiles, tobramycin appears to be the topical agent of choice in the treatment of susceptible bacterial keratitis.

Aminoglycosides↗
PubMed1989

An in vitro method which assesses corneal epithelial toxicity due to antineoplastic, preservative and antimicrobial agents.

We developed an in vitro model for studying the cytotoxicity of pharmacologic agents on corneal epithelium employing 3H-thymidine incorporation. Primary rabbit corneal epithelial cell cultures were established, and the cells plated prior to each experiment. 3H-thymidine incorporation was measured after the addition of drug or vehicle to these confluent cells, and dose-response curves were generated. Marked inhibition of 3H-thymidine incorporation was reached at chemotherapeutic concentrations achieved clinically for cytosine arabinoside (10(-7) M), methotrexate (10(-3) M), and 5-fluorouracil (10(-6) M). A 10(-4) M concentration of 2-deoxycytidine, a naturally occurring competitive inhibitor of cytosine arabinoside, protected cells up to a concentration of 10(-5) M. We utilized these data to undertake an in vivo prophylaxis study in 13 leukemia patients receiving high-dose iv cytosine arabinoside. Topical deoxycytidine 10(-4) M and 1% prednisolone phosphate, given 12 hours prior to the start of antileukemic therapy, were effective in reducing symptoms and signs of keratitis; both were better than historical placebo-treated eyes. Ophthalmic preservatives were studied in vitro at concentrations used clinically: benzalkonium chloride (BAC) (0.004-0.02%) was the most toxic, thimerosal (TMS) (0.001-0.004%) intermediate, and chlorobutanol (CHB) (0.2-0.5%) the least toxic. Antiviral agents (final concentration) included: trifluridine (TFT) (1.0%), ethyldeoxuridine (EDU) (2.0%), and idoxuridine (IDU) (0.1%). Dose but not time-dependent concentrations of these 3 agents were noted to cause toxicity; however, (E)-5(2-bromovinyl)-2'-deoxyuridine (BVDU) (0.1%) was non-toxic. Similarly, tobramycin and amikacin were significantly less toxic than gentamicin and neomycin in this system. These in vitro cytotoxicity data correlate well with previous in vivo and pre-clinical corneal epithelial toxicity studies. Our model may be useful in the toxicologic study of future topical ophthalmic agents.

Adult↗
PubMed1988

Experimental interstitial keratitis induced by Onchocerca volvulus antigens.

To elucidate the pathogenic mechanisms involved in onchocercal sclerosing keratitis in humans, we developed a model of onchocercal interstitial keratitis in guinea pigs. Onchocerca volvulus antigens injected intrastromally into corneas of preimmunized Hartley guinea pigs induced an intense stromal keratitis with corneal edema, neovascularization, and infiltration with acute and chronic inflammatory cells. This reaction subsided after two weeks. Repeated intrastromal injection resulted in an exacerbation of the keratitis and ultimately in residual scarring. These findings are consistent clinically and histopathologically with the chronic interstitial keratitis observed in humans. To define which antigens induce the corneal reaction, O volvulus antigens were separated by molecular sieve chromatography and injected intrastromally. The highest activity was shown to reside in the fraction containing molecules of intermediate molecular weight. This model will be useful in defining O volvulus antigens and their role in sclerosing keratitis as well as in elucidating the immune mechanisms involved.

Animals↗