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Biomedical subjects

D A Lee

Publications and source records attributed to D A Lee.

At least 91 records · Page 5Linked to original sources
PubMed1996

The use of bioerodible polymers and daunorubicin in glaucoma filtration surgery.

PURPOSE: Glaucoma filtering surgery usually fails from postoperative fibroblast proliferation, collagen deposition, and subsequent sclerostomy or bleb scarring. Daunorubicin inhibits fibroblast proliferation in vivo and in vitro. The authors studied the effect of a sustained subconjunctival release of daunorubicin by way of a bioerodible polymer on the success of glaucoma filtration surgery in a rabbit model. METHODS: Daunorubicin was incorporated into the copolymer by compression molding. The resultant implant measured 3.0 mm in diameter, 1.0 mm in thickness, and 8.0 mg in weight. A posterior lip sclerectomy was performed in both eyes of 23 rabbits by the same surgeon. One eye was randomized to receive the disc with daunorubicin, whereas the fellow eye received a blank disk as a control. The appropriate polymer disk then was placed on the scleral surface immediately posterior to the sclerostomy site and the conjunctiva was closed. Intraocular pressures and slit-lamp biomicroscopy were recorded preoperatively, then every other day after surgery for 31 days. Intraocular pressure, bleb survival, and complications were evaluated. RESULTS: The decrease in intraocular pressure from baseline was significantly greater in the daunorubicin eyes than in the control eyes during postoperative days 5 through 25. Bleb survival was significantly longer in the daunorubicin eyes than in the control eyes (bleb failure in 91% of control eyes versus 22% of treatment eyes by day 13). There were no statistically significant differences between the daunorubicin-treated and control eyes regarding corneal clouding, lens clarity, cataract formation, or conjunctival injection. However, conjunctival erosions occurred in four daunorubicin-treated eyes. Histopathologic examination was performed 2 weeks after surgery on the eyes of three randomly selected rabbits. CONCLUSION: Daunorubicin in a bioerodible delivery system may potentially be a useful adjunct to glaucoma filtering surgery and requires further evaluation.

Animals↗
PubMed1996

Localization and expression of ciliary neurotrophic factor (CNTF) in postmortem sciatic nerve from patients with motor neuron disease and diabetic neuropathy.

Ciliary neurotrophic factor (CNTF) is thought to play an important role in the maintenance of the mature motor system. The factor is found most abundantly in myelinating Schwann cells in the adult sciatic nerve. Lack of neuronal growth factors has been proposed as one possible etiology of amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). Growth factor replacement therapies are currently being evaluated as a treatment for motor neuron disease. In this report we determined whether the expression of CNTF in sciatic nerve differed in patients with motor neuron disease compared to controls or patients with another form of axonopathy. We identified 8 patients (7 with ALS and 1 with SMA) with motor neuron disease and 6 patients with diabetic motor neuropathy who had autopsy material available. Immunoperoxidase staining showed reduced CNTF expression in nerves of patients with motor neuron disease but not in patients with diabetic motor neuropathy. Decreased CNTF appears be associated with primary motor neuron disease rather than a generalized process of axon loss. This result supports suggestions that CNTF deficiency may be an important factor in the development of motor neuron disease.

Adult↗
PubMed1996

Generation and mapping of human chromosome 2 microdissection clone-derived STSs.

Twenty-nine new sequence-tagged sites (STSs) were derived from DNA sequences of clones from two human chromosome 2 microdissection libraries. The specificity of the STSs for human chromosome 2 was first demonstrated by PCR amplification of DNA from genomic human and hamster cells and a human chromosome 2-containing human x hamster hybrid cell line. The STSs were then mapped to chromosome 2 by two different approaches. In the first attempt, 12 of the STSs were shown to PCR amplify YAC clones associated with genetic markers on the chromosome. In the second approach, 27 of the STSs were localized to chromosome bands by FISH using cosmid or PAC clones encoding the STSs. The specific STSs mapped to chromosome 2 by these two approaches tie together the genetic and cytogenetic maps of the chromosome at the two termini. The distribution of these STSs further defines the region of the chromosome present in the two microdissection libraries.

Chromosome Banding↗
PubMed1996

The effects of growth factors on Tenon's capsule fibroblasts in serum-free culture.

This study was performed to develop and improve a completely defined in vitro ocular wound-healing model of fibroblast proliferation for glaucoma filtration surgery. This model is essential for the investigation of protein-sensitive drugs and cytokines. Tenon's capsule fibroblasts in their third passage were incubated overnight, washed free of serum, and fed defined media, Aim V or Clonetics FBM serum-free medium containing platelet-derived growth factor, basic fibroblast growth factor, epidermal growth factor, or fibronectin at various dilutions and in combinations at optimum concentrations. Proliferation was measured by 3H-thymidine incorporation at 1, 3, and 7 days. Morphology was compared to controls fed Minimum Essential Medium + 10% serum. Single factors stimulated the greatest amount of thymidine uptake on day 3. Optimum concentrations were epidermal growth factor at 5 ng/ml, basic fibroblast growth factor at 10 ng/ml and platelet-derived growth factor at 20 ng/ml. Identical combinations of factors stimulated nearly twice the thymidine uptake in Clonetics medium as in Aim V. Epidermal growth factor activity was inhibited by either basic fibroblast growth factor or platelet-derived growth factor. Basic fibroblast growth factor and platelet-derived growth factor together produced a less than additive effect. The performance of either serum-free medium may be improved by the addition of basic fibroblast growth factor or platelet-derived growth factor. The optimum serum-free medium (Clonetics FBM) with growth factors was unable to stimulate proliferation as much as Minimum Essential Medium + 10% NBS, but was successful in maintaining viability during the 7 day test period.

Cell Division↗
PubMed1996

Contact and noncontact transscleral neodymium:YAG laser cyclophotocoagulation in a rabbit model.

PURPOSE: Contact versus noncontact transscleral neodymium:YAG laser cyclophotocoagulation was compared in a rabbit model with respect to the effects on intraocular pressure and pathologic findings. METHODS: Thirty-two rabbits received comparable energy levels (2 joules) of contact and noncontact cyclophotocoagulation. Pneumotonometry was performed every other day following treatment. RESULTS: For both the 2-week and 8-week periods following treatment, intraocular pressure was significantly lower in eyes receiving contact cyclophotocoagulation than in eyes receiving noncontact cyclophotocoagulation (for the 2-week period, mean difference in intraocular pressure was 5.3 mm Hg, n = 22, p < 0.001; for the 8-week period, mean difference in intraocular pressure was 4.3 mm Hg, n = 17, p < 0.013). Pathologic findings include acute ciliary body hemorrhage and inflammation (1 day), chronic inflammation (1 week), granulation tissue within laser lesions (2 weeks), and marked ciliary body atrophy (8 weeks). CONCLUSIONS: In our rabbit model, contact cyclophotocoagulation was more effective in lowering intraocular pressure than noncontact cyclophotocoagulation. Both contact and noncontact cyclophotocoagulation produced a variety of pathologic lesions in the rabbit eye, including cataract, phthisis bulbi, and anterior synechiae.

Animals↗
PubMed1996

Prevalence of ocular disorders among 6- and 7-year-olds in Santa Monica, California.

BACKGROUND: Undetected ocular disorders can cause serious problems in a child's mental and social development. METHODS: To investigate relationships between ocular disease, gender and ethnicity in children, vision screening examination data was analyzed from the UCLA Mobile Eye Clinic (MEC), collected from 1985 to 1990 on first graders (69.9 percent 6- and 30.1 percent 7-year-olds) in Santa Monica, California. RESULTS: The sample consisted of 1,469 individuals, of whom 48.1 percent were female and 51.9 percent were male. Ethnicity data was available from 1988 to 1990 on 834 individuals, of whom 46.9 percent were Hispanic, 27.9 percent were White. 11.5 percent were Black, 4.4 percent were Asian, and 9.2 percent were of other races. Significantly more females than males had refractive errors, specifically hyperopia and astigmatism, and uncorrected visual acuity of 20/50 or worse in at least one eye. There were no significant associations of ethnicity or sex with any other disease category. The overall prevalences of other diseases were less than 4 percent. Of the 6- and 7-year-olds studied in Santa Monica, California, 18.5 percent had refractive errors. CONCLUSIONS: Screening for ocular disorders at an early age allows for detection of problems, especially refractive errors, that might affect school performance if uncorrected.

California↗
PubMed1995

Further validation of a quadruplex STR DNA typing system: a collaborative effort to identify victims of a mass disaster.

The relatively new, PCR-based technique of Short Tandem Repeat (STR) profiling has been used in the identification of the victims of a mass disaster. The analysis relied upon a recently developed multiplex reaction and the use of automated fluorescence technology to simulataneously analyse four tetrameric STR loci. The performance of the 'quadruplex' test was assessed by use of a collaborative study incorporating a blind trial and was demonstrated to be accurate, reliable and robust. Furthermore, the system proved to be highly successful despite the fact that many of the samples from the mass disaster scene were extremely degraded. The high success rate coupled with the discrimination power of the system enabled many severely decomposed human remains to be positively identified.

DNA↗
PubMed1995

A 30-Mb metric fluorescence in situ hybridization map of human chromosome 19q.

A high-resolution metric physical map of chromosome 19q has been constructed by fluorescence in situ hybridization. The map locates 136 cosmid reference points that span 30 Mb. The reference points are sequentially ordered from centromere to telomere, and the distance between neighboring cosmids is known from 240 partially overlapping, redundant estimates of genomic distances in kilobases separating pairs of cosmids. The average spacing between cosmid reference points is 220 kb, with over 75% of intervals less than 300 kb. Eighty-four genes and polymorphic markers have been assigned to mapped cosmids. The information on order and genomic distances separating pairs of cosmids, both key elements for building physical maps, has furthered the construction and integration of the genetic and physical maps of chromosome 19.

Chromosome Mapping↗
PubMed1995

The development and characterization of an in vitro system to study strain-induced cell deformation in isolated chondrocytes.

A model system has been developed to investigate cell deformation of chondrocytes in vitro. Chondrocytes were isolated from bovine articular cartilage by enzymatic digestion and seeded in agarose (type VII) at a final concentration of 2 x 10(6) cells.ml-1 in 3% agarose. Mechanical evaluation of the system showed no change in the tangent modulus of agarose/chondrocyte cultures over a 6-d culture period. The resulting agarose/chondrocyte cultures were subjected to compressive strains ranging from 5-20%. Cell shape was assessed by measuring the dimensions of the cell both perpendicular (x) and parallel (y) to the axis of compression and deformation indices (I = y/x) calculated. Cell deformation increased with the level of strain applied for freshly isolated chondrocytes. The cultures were maintained in medium that inhibits or stimulates matrix production (DMEM and DMEM + 20% FCS, respectively) in order to assess the effect of cartilaginous matrix on chondrocyte deformation. Matrix elaborated by the cells markedly influenced levels of cell deformation, an increase in matrix leading to a decrease in cell deformation. Freshly isolated deep zone chondrocytes were found to deform significantly more than surface zone chondrocytes, although this effect was lost after 6 d in culture. The elaborated matrix also altered the recovery characteristics of the chondrocytes following constant compressive strain of 15% for 24 h. Cells that had elaborated matrix took several hours to return to unloaded shape, while cells without matrix returned to the unloaded shape instantly.

Animals↗
PubMed1995

The effects of age and lifestyle factors on the accumulation of cytogenetic damage as measured by chromosome painting.

Individual responses to the aging process are variable and are affected by genetic as well as environmental factors. Fluorescent in situ hybridization with whole chromosome probes ('chromosome painting') provides an efficient approach for detecting structural chromosome aberrations in human lymphocytes. This rapid and sensitive technique is an effective tool for quantifying chronic exposure to environmental agents which may result in an accumulation of cytogenetic damage with age. We have applied this technology to a normal, putatively unexposed, population to document the relationship between age and the accumulation of cytogenetic damage, as well as to establish a baseline frequency of stable aberrations. Using probes for chromosomes 1, 2 and 4 simultaneously, the equivalent of 1000 metaphases was scored for stable and unstable aberrations from each of 91 subjects ranging in age from newborns (umbilical cord bloods; n = 14) to adults aged 19 to 79 years. Each subject (or one parent of each newborn) completed an extensive questionnaire to identify possible lifestyle factors that may influence the frequency of cytogenetic damage. Our findings show a significant increase in stable aberrations (translocations and insertions) with age (p < 0.0001). We also observed age-related increases with dicentrics (p < 0.0001) and acentric fragments (p < 0.0001). Relative to the frequencies observed in cord bloods, the frequencies of stable aberrations, dicentrics, and acentric fragments in adults aged 50 and over were elevated 10.6-fold, 3.3-fold, and 2.9-fold, respectively. Nine variables other than age are significantly associated with the frequency of stable aberrations; these are: smoking (two variables), consumption of diet drinks and/or diet sweeteners (4 variables), exposure to asbestos or coal products (1 variable each), and having a previous major illness (1 variable). Newborns whose mothers smoked during pregnancy had a 1.5-fold increase in stable aberrations (p = 0.029). Repeat samples from a subset of the adults indicate that for most subjects there is little change in individual translocation frequencies over a period of two to three years. These results support the hypothesis that stable chromosome aberrations show a greater accumulation with age than do unstable aberrations and suggest that lifestyle factors contribute to the accumulation of cytogenetic damage.

Adolescent↗
PubMed1995

Single-dose compared with fractionated-dose radiation of the OM431 choroidal melanoma cell line.

PURPOSE: To compare single-dose and fractionated-dose radiotherapeutic effects on choroidal melanoma cells. METHODS: We determined the effects of gamma radiation on OM431 cell survival by exposing cells to either a single 9-Gy dose or two 4.5-Gy fractionated doses at intervals of 20 minutes to eight hours. The effects of single dosing and fractionated dosing at six hours were compared at doses of 2 to 12 Gy. RESULTS: Tumor cell repair was most rapid during the first two hours. Maximum repair had occurred by six hours after radiation. Cell survival curves showed doses greater than 3 Gy of single-dose gamma radiation resulted in a greater number of cells killed than did equivalent fractionated doses. CONCLUSIONS: Ocular melanoma in vitro is relatively radioresistant to low-dose fractionated radiotherapy. High single-dose radiotherapy would be more effective but would also result in more damage to normal tissue unless more focused modalities of radiotherapy are used.

Cell Survival↗
PubMed1995

Effects of gamma radiation on the OM431 human ocular melanoma cell line.

In order to determine the dose responsiveness to radiation of ocular melanoma, we conducted an in vitro dose-response study on a monolayer cell culture using a clonogenic assay. The effects on cell survival were determined relative to unirradiated controls. A human epithelioid ocular melanoma cell line, OM431, was maintained in tissue culture and serial dilutions of viable cells were plated in flasks, allowed to settle and attach for 48 h, and subsequently irradiated with 1-10 Gy in single fractions. After 2 weeks, the number of reproducing clones (forming colonies with greater than 32 cells or five generations) were counted. The surviving fractions of cells were plotted on a cell survival curve using the linear quadratic model. The survival curve showed a large initial shoulder followed by an exponential decline in growth. Our data suggest that the OM431 ocular melanoma cell line responds to irradiation in a manner similar to other melanoma cell lines and is relatively radioresistant especially at lower doses.

Cell Survival↗
PubMed1995

Comparative efficacy of antiviral drugs on human ocular fibroblasts.

The effects of several antiviral drugs on fibroblast attachment and proliferation from human Tenon's capsule were investigated. These drugs included purine nucleoside analogs, vidarabine and acyclovir (ACV); pyrimidine nucleoside analog, AZT; and a synthetic cyclic primary amine, amantadine. Fibroblast attachment and proliferation inhibition were determined by Coulter counter, a colorimetric assay of the enzyme hexosaminidase, and a 3H-thymidine uptake assay. Amantadine and AZT inhibited fibroblast attachment at concentrations higher than 6.61 x 10(-4)M and 3.73 x 10(-4) M, respectively. Amantadine and AZT had inhibitory effects on fibroblast proliferation as early as day 1, whereas vidarabine and ACV manifested their inhibitory effects after day three by Coulter counter and hexosaminidase assays. For amantadine, AZT, ACV and vidarabine, the 50% inhibitory dose (ID50) were 4.94 x 10(-5) M, 1.26 x 10(-5) M, 4.60 x 10(-4) M, and 1.52 x 10(-5) M at day 9, respectively, as measured by 3H-thymidine uptake assay. All four antiviral agents tested had inhibitory effects on human ocular fibroblast proliferation and their inhibitory potential decreased in the order of amantadine > or = vidarabine > AZT > or = ACV.

Acyclovir↗
PubMed1995

Reducing blood donor exposures in low birth weight infants by the use of older, unwashed packed red blood cells.

We performed a prospective, randomized masked trial to determine whether the use of dedicated units of packed red blood cells equipped with seven satellite bags would reduce donor exposures in infants with birth weights < 1500 gm. We also examined the use of unwashed and older red blood cells. Red blood cells given to the study group were used without washing and until their expiration date (35 to 42 days). Changes in blood pH, potassium, ionized calcium, and hemoglobin were determined with each transfusion and compared with data collected from a control group that received washed, younger red blood cells. There was a 64% reduction in donor exposures in the study group. Changes in infants' blood pH and calcium levels with transfusion were the same in the two groups. There was a clinically unimportant difference in potassium levels. A greater rise in hemoglobin values occurred when washed cells were used. There was no correlation between changes in the blood levels measured and the age of unwashed cells infused. We conclude that the use of red blood cells from satellite bag-equipped dedicated units decreases donor exposures, and that the practices of using only younger red blood cells and of saline washing of red blood cells before infusion, are unwarranted.

Blood Donors↗
PubMed1995

Ciliary neurotrophic factor expression in Schwann cells is induced by axonal contact.

In the PNS, ciliary neurotrophic factor (CNTF) is found in significant amounts in the adult sciatic nerve, localized to myelin-related Schwann cells (SCs). Levels are undetectable in newborn but high in adult animals. After crush injury, CNTF production is reduced, recovering only as the nerve regenerates; if regeneration does not occur, CNTF levels remain low. We have examined the coupling of CNTF expression to myelination in vitro and in vivo to determine if axon-SC contact without myelination is sufficient to induce CNTF expression. Embryonic day 15 (E15) rat dorsal root ganglion (DRG) neuron and SCs were cocultured. CNTF was not detected in the DRGs either at E15 or after 2 days in vitro (div) by western blotting. However, after 10 div, CNTF could be identified and remained at constant levels up to 30 div. Depriving the cultures of ascorbic acid prevents myelination but not axon-SC contact. This did not affect CNTF protein production. Using reverse transcriptase-linked PCR (RT-PCR) techniques, no CNTF message was present in DRG from day 14 or 15 fetal rats; but by 6 days in culture, message was detected in both myelinating and nonmyelinating cultures. Isolated SC cultures, without axonal contact, failed to express CNTF protein; however, mRNA was detected by RT-PCR. Embryonic SC can be induced to synthesize CNTF in culture by axonal contact. Active myelination is not required.

Animals↗
PubMed1995

Validation of chromosome painting. II. A detailed analysis of aberrations following high doses of ionizing radiation in vitro.

Fluorescence in situ hybridization with chromosome-specific composite DNA probes ('chromosome painting') is useful for quantifying radiation-induced cytogenetic damage. Recently we showed that the frequency of aberrations observed with painting is similar to that seen with conventional cytogenetic methods, at least at doses of < or = 2 Gy. Above this dose, however, the agreement was not as good. We describe here the results of additional work designed to clarify our earlier findings, and provide a detailed analysis of the type and frequency of aberrations induced in human peripheral lymphocytes following acute exposure to 137Cs at doses of 0 (unexposed control), 1, 2, 3 and 4 Gy. The newly-developed nomenclature for chromosome aberrations detected by painting (Protocol for Aberration Identification and Nomenclature Terminology, 'PAINT') was used to classify all aberrations. Our results indicate that if the guidelines of the PAINT system are followed, chromosome painting can provide meaningful biodosimetry at high doses, and that the observation of complicated rearrangements not only does not interfere with dose estimation, but also the information provided by these exchanges can be easily broken down into the component aberrations and included in the dose estimate. We also show that the inequality between translocations and dicentrics that we previously observed can be explained by an excess of one class of translocated chromosomes, specifically those in which the centromere is from an unpainted chromosome. Translocated chromosomes in which the centromere is painted were found to occur at a frequency equal to dicentrics. These results should help clarify the use of painting for radiation biodosimetry by improving our understanding of the frequencies of various types of stable aberrations observed shortly after exposure. This will improve our ability to perform meaningful biodosimetry long after the frequencies of unstable aberrations have ceased to be informative.

Adult↗
PubMed1995

Ocular toxicity of iontophoretic foscarnet in rabbits.

Transscleral iontophoresis of foscarnet is a noninvasive drug delivery system for the local treatment of cytomegalovirus (CMV) retinopathy. We determined the retinotoxic effects of transscleral iontophoresis of foscarnet. Slit-lamp biomicroscopy revealed no toxic effects for any of the treated eyes. Indirect ophthalmoscopy showed retinal and choroidal burns 1-3 mm in diameter at the site of iontophoresis in both foscarnet-treated eyes and saline-treated control eyes. Light and electron microscopy revealed focal retinal, retinal pigment epithelial, and choroidal necrosis at the site of iontophoresis but no abnormalities elsewhere. Ganzfeld electroretinographic studies revealed no response differences between foscarnet-treated eyes vs. controls.

Animals↗