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Biomedical subjects

L Keay

Publications and source records attributed to L Keay.

At least 19 recordsLinked to original sources
PubMed2006

The effect of short term contact lens wear on the tear film and ocular surface characteristics of tolerant and intolerant wearers.

The purpose of this study was to determine the effect of contact lens wear on the tear film and ocular surface of people tolerant or intolerant to contact lens wear. Twenty subjects participated; 11 tolerants and nine intolerants. Their baseline tear film (no lens wear) was analysed with a range of clinical measurements and protein analyses (lactoferrin, sIgA and lysozyme). The tests were then repeated at the end of 6h of contact lens wear during the day and while lenses were worn. Both tolerants and intolerants showed statistically significant increases in bulbar and overall conjunctival redness after 6h of lens wear. For tolerants only, there was a statistically significant increase in the tear film meniscus area (0.08 mm(2) +/- 0.04 compared to 0.14 mm(2) +/- 0.06 (p = 0.023)) and a statistically significant decrease in the non-invasive tear film break-up time (NI-TBUT; 21.3 s +/- 5.7 compared to 3.7 s +/- 4.3 (p = 0.003)) after 6h of lens wear. There were no changes in other tear film or ocular surface parameters. The protein concentration and lipid layer appearance did not change during lens wear for either population. Prior to lens wear, tolerant subjects had a statistically longer NI-TBUT, higher phenol red thread test and higher tear flow rate. After 6h of lens wear and while wearing lenses, all but NI-TBUT remained statistically different. Lens wear affected only a small number of clinical variables and 6h wear did not effect the concentration of those proteins measured in tears in this study.

Adult↗
PubMed2001

Short term wear of high Dk soft contact lenses does not alter corneal epithelial cell size or viability.

BACKGROUND/AIMS: Current contact lenses (CLs) when worn on an extended wear basis cause corneal epithelial alterations. The aim of this study was to evaluate changes in corneal epithelial cell morphology and physiology following short term (3 months) wear of highly oxygen permeable CLs and to compare this with disposable CLs. METHODS: Subjects were wearers of highly oxygen permeable CLs (n=11, wearing CLs on a 30 night schedule), disposable CL users (n=6, wearing CLs on a 6 night schedule), and non-CL wearers (n=20). Mean CL wear experience was 3 months. Epithelial cells were harvested using corneal cytology and were stained using acridine orange and ethidium bromide. Epithelial cell size and viability were determined. RESULTS: The majority of epithelial cells recovered were non-viable (71%), and the mean longest cell diameter was 38 (SD 8) microm. Disposable CLs caused an increase in cell size (42 (7) microm) compared with both non-wear (39 (7) microm, p=0.01) and wear of highly oxygen permeable CLs (37 (10) microm, p=0.0049). There was no difference in cell viability between groups. CONCLUSIONS: Extended wear of disposable CLs caused an 8% increase in cell diameter in harvested corneal epithelial cells following 3 months of CL wear. Cells harvested following 3 months' wear of highly oxygen permeable CLs were indistinguishable from those recovered from non-CL wearers.

Adult↗
PubMed2001

Bacterial populations on 30-night extended wear silicone hydrogel lenses.

PURPOSE: Ocular infection and inflammation during hydrogel lens extended wear is often associated with colonization of the lenses with bacteria. This study compares colonization of a high Dk silicone hydrogel contact lens (lotrafilcon A) worn on a 30-night extended wear basis to a low Dk HEMA-based lens (etafilcon A) worn on a 6-night extended wear schedule. METHODS: The group wearing the low Dk/t soft contact lens (n = 63) replaced their lenses weekly and the group wearing high Dk/t soft contact lenses replaced their lenses monthly (n = 64). Lens allocation was assigned randomly at enrollment. Worn lenses, from one eye only, were collected aseptically and placed in sterile vials. Microbial growth on various media was enumerated and the number of colony forming units (cfu) per lens was calculated in categories of normal ocular microbiota (such as coagulase-negative staphylococci and Propionibacterium spp.) and known ocular pathogens (such as Staphylococcus aureus and gram-negative bacteria). The proportion of samples colonized with these bacteria and the extent of colonization were compared between the two groups. The proportion of sterile lenses was calculated, and the types of bacteria on each lens group were compared. RESULTS: No differences between the low and high Dk/t Soft contact lens groups were observed in the proportion of lenses colonized by Propionibacterium spp. (48% vs 43%, P = 0.4) or coagulase-negative staphylococci (47% vs 54%, P = 0.2). Similarly, no differences were found for lenses colonized by S. aureus (0% vs 2%, P = 0.1) or gram-negative bacteria (3% vs 2%, P = 0.8). The types of bacteria isolated from the high and low Dk/t lenses were similar. There were no differences in the number of sterile samples (28% vs 27%, P = 0.8) from each group. CONCLUSIONS: These findings suggest that high Dk/t silicone hydrogel materials are colonized by similar numbers and types of microorganisms during extended wear compared to HEMA-based material. Most lenses were colonized by commensal bacteria during 30-night extended wear with high Dk/t lenses and during 6-night extended wear with low Dk/t lenses. The incidence of sterile samples was the same between the high and low Dk/t soft contact lens groups.

Adult↗
PubMed2001

Microcysts: clinical significance and differential diagnosis.

BACKGROUND: Microcysts are the most-distinctive and easily detectable indicator of contact lens-induced hypoxia. They should not be confused with cyst-like inclusions that occur in conditions such as Meesmann's dystrophy, bullous keratopathy, and Cogan's microcystic dystrophy, or with mucin balls, vacuoles, microcystic edema, and infiltrates. METHODS: Data from published literature and recent data from The Cornea and Contact Lens Research Unit (CCLRU) clinical trials involving low Dk and prototype high Dk soft contact lenses (SCLs) were examined. RESULTS: Extended wear with low Dk SCLs induces significant numbers of microcysts, whereas extended wear with high Dk SCLs does not. Subjects who transfer from low Dk to high Dk lenses have an initial increase in the number of microcysts after seven days that declines to normal levels over 1 to 3 months. Microcysts can be differentiated from other ocular conditions as they show reversed illumination, are 10- to 50-microm irregularly shaped dots, and are often associated with lens-induced hypoxia. CONCLUSIONS: Microcysts are easily observed and differentiated from other conditions in clinical practice. On average, fewer than ten microcysts per eye occur in nonhypoxic lens wear and, on average, more than 20 microcysts per eye are an indication of chronic hypoxia. The increase in microcyst numbers after transfer from low to high Dk lens wear is transitory and does not necessitate a period of no lens wear.

Contact Lenses, Extended-Wear↗
PubMed2001

Tear exchange under hydrogel contact lenses: methodological considerations.

PURPOSE: To characterize hydrogel lens tear exchange and to apply an optimized method to compare tear exchange of a marketed hydrogel lens to that measured with a prototype silicone hydrogel lens. METHODS: Fluorophotometry and a nonpenetrating tracer (70-kDa FITC-dextran) were used with a single extended-wear soft contact lens (EWSCL) material on 11 subjects to characterize tear-exchange kinetics. Twenty to 30 measurements were obtained over a 30-minute period to allow accurate modeling and estimation of the several tear-exchange parameters. Calculated values included tear-replenishment rate (TRR), elimination rate (ER), and the time for 95% of the signal to be eliminated (T(95)). Major experiments were (1) comparison of ER under controlled and physiological conditions, (2) comparison of right and left eyes, (3) repeatability of ER and T(95) on five occasions, and (4) comparison of a marketed lens (oxygen permeability [Dk] 28 x 10(-9) [cm/sec][ml O(2)/ml mm Hg]) to a prototype silicone hydrogel lens (Dk 140 x 10(-9) [cm/sec][ml O(2)/ml mm Hg]). RESULTS: Tracer elimination behind a hydrogel contact lens (CL), up to 30 minutes after insertion, was optimally described by double-exponential kinetics. Physiological ER (5-30 minutes after CL insertion) was optimally described by single-exponential kinetics. Overall, physiological ER was 8.8% +/- 3.8% per minute, and T(95) was 31.0 +/- 16.1 minutes (n = 76 and 72 determinations, respectively). Differences between right and left eyes in ER and T(95) were not significant at the 0.05 level. No difference in ER or T(95) was found between habitual and controlled blinking. Mean TRR was 0.67% +/- 0.26% per blink (n = 11 determinations). No differences were shown between ER or T(95) measurements over time. A prototype highly oxygen-permeable silicone hydrogel lens showed higher ER than did a marketed hydrogel lens (P < 0.01). CONCLUSIONS: Estimates of postlens tear exchange using a slit lamp fluorophotometer are similar to previously reported rates using similar fluorophotometric techniques. Fluorescent decay behind a hydrogel lens is most precisely described using a double-exponential curve equation and tear exchange may be described using ER, TRR and T(95), although the T(95) may be the least reliable of these measures. The technique appears capable of discriminating between lens types.

Adult↗
PubMed2000

Infiltrative keratitis associated with extended wear of hydrogel lenses and Abiotrophia defectiva.

PURPOSE: Infiltrative keratitis is a common complication associated with extended wear of hydrogel lenses. Causative bacteria are often isolated from the lens at the time of an event. We report a case where three repeated occurrences of infiltrative keratitis were associated with contamination of the contact lenses by Abiotrophia defectiva. METHODS: A 34-year-old man participating in a clinical trial of extended wear hydrogel contact lenses experienced three episodes of infiltrative keratitis. The clinical presentation was observed using a biomicroscope. At the time of each event, the contact lenses were removed aseptically and ocular swabs were taken for bacterial identification and enumeration. The condition was monitored until full resolution. RESULTS: The condition was characterized by irritation, marked bulbar and limbal injection, and multiple focal subepithelial infiltrates. Many of the infiltrates also showed overlying staining with fluorescein. In each of the three events of infiltrative keratitis, A. defectiva was cultured from the contact lens and ocular swabs. CONCLUSION: This is the first reported occurrence of infiltrative keratitis associated with A. defectiva contamination of contact lenses.

Adult↗
PubMed2000

Microcyst response to high Dk/t silicone hydrogel contact lenses.

PURPOSE: To investigate the microcyst response to extended wear (EW) with high oxygen transmissible (Dk/t) silicone hydrogel lenses. METHODS: Microcysts were monitored for 12 months in subjects wearing low Dk/t hydrogel lenses on a 6-night EW schedule or high Dk/t hydrogel lenses on a 30-night EW schedule. Subjects wearing low Dk/t lenses transferred to the high Dk/t EW lenses and schedule after 12 months and were monitored for a further 6 months. RESULTS: The mean number of microcysts did not deviate from baseline in the high Dk/t group. Microcysts in the low Dk/t group increased over 12 months, and more microcysts were observed in low Dk/t lens wearers compared with high Dk/t lens wearers after 3 months. Microcysts increased in 50% of subjects 1 week after transfer to high Dk/t lenses and returned to baseline levels seen with high Dk/t lens wear within 3 months. CONCLUSIONS: EW with high Dk/t silicone hydrogel lenses did not cause an increase in microcyst numbers. It is not necessary to discontinue lens wear with patients who transfer from low to high Dk/t lenses because the increase in microcysts is transitory. This result has implications for practitioners when fitting and assessing the success of high Dk/t hydrogel lenses.

Adult↗
PubMed1990

Production of recombinant human erythropoietin in Bowes melanoma cells in suspension culture.

Recombinant DNA technology was used to insert a fetal liver genomic library ApaI fragment encoding for human erythropoietin (Epo) into Bowes melanoma cells. The cells expressed the erythropoietin gene, and Epo was secreted into the culture medium together with the normally-secreted tissue plasminogen activator. Attempts to grow the cells in glass spinners in Dulbecco's medium supplemented with fetal bovine serum produced cell aggregates growing in suspension. When calcium-free suspension culture media (Joklik, DME-S, McCoy 5A-S) were used, single cell suspension cultures were obtained and high Epo production observed. When attempts were made to scale up the small glass spinners, poor growth or Epo production occurred unless the vessels were aerated. This was shown to be because of the drop in pH, possibly due to CO2 accumulation, rather than due to oxygen depletion. It was shown that a semi-continuous operation could be achieved in aerated 8-1 spinners fitted with either a conventional stirrer or a vibromixer agitator. The system was scaled up to a 100-1 stainless steel vessel fitted with a vibromixer agitator. This system was operated for over 4 months with weekly harvests producing over 100 million units of Epo in about 1000-1 of culture fluid. Interference by the serum proteins with downstream purification of the hormone from the culture fluid made the use of serum-free media highly desirable. Studies showed that the Epo was produced in serum-free systems containing peptones.

DNA, Recombinant↗
PubMed1990

Development of a new radioimmunoassay for erythropoietin using recombinant erythropoietin.

The development of a 24 hour radioimmunoassay for erythropoietin (EPO) using EPO derived from recombinant DNA as both immunogen and ligand is described in the present paper. Mixed breed rabbits immunized with 10 micrograms/kg of EPO derived from a stably transfected cell line (Elanex Pharmaceuticals Inc., Bothel, Washington, USA, through McDonnell Douglas Corp., St. Louis, Missouri, USA; "MD") produced antibodies to EPO with high titer (up to 1:896,000 final dilution in the tube), high affinity (8.4 x 10(11) liter/M), and good specificity. Purified EPO from the above source or from AmGen Biologicals (Thousand Oaks, California, USA; "AG") were successfully radioiodinated with the chloramine-T method and used as ligand in the radioimmunoassay. Standard dose-response curves prepared with EPO from both commercial sources were not significantly different and showed a sensitivity of 0.75 to 0.96 mU/tube. The dose-response curves in both systems also showed parallelism with serially diluted serum from a patient with aplastic anemia. Within-assay and between-assay precision were determined by assaying multiple replicates of a serum pool. Recovery of exogenous EPO added to a serum pool averaged 97% for both systems. The range of normal human serum EPO was determined by assaying the sera of 153 hematologically-normal adult subjects and was found to be 1.1 to 27.3 mU/ml for MD EPO and 0.5 to 16.7 mU/ml for AG EPO. Sera from several patients with hematologic abnormalities were also assayed, including those of 36 patients with anemia of end-stage renal disease (mean +/- SEM, 29.5 +/- 4.0 mU/ml; P less than 0.01). In conclusion, this new, more rapid and sensitive radioimmunoassay system can be used to measure EPO levels in sera from normal human subjects and patients with several types of anemia, and should also be very useful in therapeutic drug monitoring of patients receiving EPO from various commercial sources.

Anemia↗
PubMed1977

The growth of L-cells and Vero cells on an autoclavable MEM-peptone medium.

The growth of L-60TM cells (a suspension culture adapted L-cell) on media composed of MEM (minimum essential medium (Eagle)) and bactopeptone autoclaved together or separately under a variety of conditions has veen determined. It has been found that MEM autoclaved with 0.5% bactopeptone at 15 psi for 20 min, cooled and then neutralized with NaHCO3, consistently supported good cell growth of L-60TM and L-929 cells. Similar results were obtained when the MEM and bactopeptone were autoclaved separately. The cells grew initially as a monolayer, subsequently becoming a stationary suspension. Some experiments were carried out with agitated suspension culture of L-60TM cells in the autoclaved MEM-bactopeptone combination with and without added methylcellulose and results were obtained which indicate that large scale suspension culture is possible in this system. Other peptones were also found to support cell growth. The autoclaved MEM-bactopeptone combination also supported the growth of Chang liver and Vero cells. The Chang liver cells rapidly dissociated from the plastic surface but the Vero cells remained sufficiently securely attached so that it was possible to grow them near to confluency in roller bottles.

Animals↗
PubMed1976

Autoclavable low cost serum-free cell culture media: the growth of established cell lines and production of viruses.

Five cell lines (BSC-1, CHO, Balb/c 3T3, HeLa, and KB) have been grown in serum-free media for several months with regular schedules of media changing and subculturing. The medium found to be successful in all cases was MEM-alpha (without the ribosides and deoxyribosides) supplemented with 1% bacteropeptone, although simple MEM (minimum essental medium (Eagle) with bacteropeptone (BP) gave fairly good growth in the case of BSC-1 and 3T3 cells. The addition of insulin was necessary for CHO, 3T3, HeLa, and KB cells. Only the BSC-1 cells grew exclusively as a stationary suspensions and the 3T3 cells growing as a combination of monalayer and suspension depending on the age of the culture and the nature of the growth surface. SV40 was produced in BSC-1 cells grown and infected in the MEM-alpha, bactopeptone medium and adenovirus-2 was produced in spinners of HeLa and KB cells grown in MEM-alpha, bactopeptone, PVP-360, and insulin. The yield of virus and infectivity of the viruses produced were about the same as those produced in conventional serum-containing systems.

Cells, Cultured↗