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Biomedical subjects

P B Williams

Publications and source records attributed to P B Williams.

At least 19 recordsLinked to original sources
PubMed2005

Chronic topical administration of WIN-55-212-2 maintains a reduction in IOP in a rat glaucoma model without adverse effects.

Glaucoma, one of the leading causes of blindness, is associated with high intraocular pressure (IOP) as a risk factor. The aim of this study was to examine both local and systemic effects of chronic topical administration of the synthetic CB1/CB2 agonist, WIN-55-212-2 and its potential to sustain ocular hypotension. WIN-55-212-2 (0.5%) or Tocrisolve, the vehicle, was administered topically three times daily to rats with surgically created glaucoma for 4 weeks, followed by a 1-week washout period. IOP, blood pressure and heart rate were measured weekly along with confocal microscopy and slit lamp biomicroscopy to detect ocular toxicity. IOP decreased rapidly by up to 47% in the WIN-55-212-2 treated group from 14.1+/-0.7 to 6.6+/-0.2 mmHg. The decrease was maintained during the treatment period. After the washout period, IOP (12.3+/-0.2 mmHg) was not different from baseline. In the contralateral eye, IOP showed a downward trend. Tocrisolve alone had no effect on IOP. No changes in blood pressure, heart rate or indicators of ocular toxicity were noted within either group. Topical application of WIN-55-212-2 significantly deceased IOP for duration of treatment. The decrease was sustained without the development of tolerance. Following cessation of therapy, IOP rapidly returned to baseline. No significant cardiovascular effects or ocular toxicity were noted during chronic topical therapy with either drug or vehicle.

Animals↗
PubMed2004

Comparison of topical steroids for acute anterior uveitis.

This study objectively compares efficacy of dexamethasone Na phosphate 0.1%, fluorometholone 0.1% (FML), loteprednol etabonate 0.5% (Lotemax [LE]; Bausch & Lomb Pharmaceuticals, Inc., Tampa, FL), prednisolone acetate 1% (Pred Forte [PRED F]; Allergan Pharmaceuticals, Irvine, CA), and generic prednisolone acetate 1% (PRED A). These steroids were administered for 24 hours or 72 hours to New Zealand white rabbits with endotoxin-induced uveitis. Intraocular pressure (IOP), slit-lamp examination, and confocal microscopy were performed daily. Internalization of the glucocorticoid receptor (GC) was assayed in iris tissue by Western blot, and protein in aqueous humor by Bradford assay. Only LE and PRED F treatments significantly internalized GC receptor after 72 hours of treatment. Only LE and PRED A reduced protein concentration between 24 hours and 72 hours of treatment. All drugs improved clinical signs after 24 hours of treatment. None of the steroids promoted return of the inflammation-induced corneal thickness to baseline. While none returned IOP to baseline, LE was most effective. Confocal microscopy indicated that only treatment with LE reverted the abnormal endothelial-cell shape to normal. In conclusion, all steroid treatments reduced uveitis to some degree but LE was consistently effective. A longer observation period may be required to document the return of IOP and corneal thickness to baseline values.

Acute Disease↗
PubMed2001

Precision and accuracy of commercial laboratories' ability to classify positive and/or negative allergen-specific IgE results.

BACKGROUND: Accurate and reliable evaluation of the presence or absence of allergen-specific IgE is important in the differential diagnosis of allergic disease. A variety of different commercial tests are available for this purpose. There are few data available to judge how the results of these different tests compare with one another in everyday use. OBJECTIVE: To examine prospectively the extent of comparability among specific IgE results from different laboratories. METHODS: Six diagnostic laboratories employing five different methods to assay specific IgE were selected. Aliquots from 26 serum samples that contained variable levels of IgE specific to 17 common aeroallergens were sent in triplicate to each study laboratory during a 6-week time period. Results were reported numerically and by class scores and then compared by examining their concordance using Kendall's W nonparametric statistical test. In addition, cut-off values were compared by a best agreement analysis using reported results. Reproducibility was determined using precision profiles based upon the coefficient of variation among triplicates for each allergen across the range of reported results. RESULTS: In all, 7,813 tests were analyzed. Concordance among different assays in commercial use with one exception was not good. This was particularly true around the cut-off region where most assays demonstrated high imprecision. The Pharmacia CAP System used by two different laboratories demonstrated highly comparable results with good precision. Some assays were reproducible but not accurate. Others were neither reproducible nor accurate. CONCLUSIONS: The results of this study indicate that not all commercial laboratories/assays for specific IgE provide reproducible and accurate data. Significant potential for misdiagnosis was detected for some reported results. Methods were identified that do give sensitive, accurate, and reproducible results.

Allergens↗
PubMed2001

Efficacy of a single diagnostic test for sensitization to common inhalant allergens.

BACKGROUND: UniCAP Phadiatop is a single laboratory test designed to determine the presence or absence of specific IgE to a variety of common inhalants. Its purpose is to aid in the differentiation of patients with symptoms attributable to allergic disease from other common causes. METHODS: Consecutive children and adolescent patients (n = 145) at two centers were examined by having their history and physical examination performed by two board certified allergists. Their conclusions along with skin prick tests and specific IgE measurements regarding seven common inhalants (mite, oak, ragweed, grass, dog, cat, Alternaria) were compared with UniCAP Phadiatop test results. This was done using concordance of all test results. Attempts to resolve test discrepancies, when found, included specific RAST inhibitions, total IgE values, and physicians' judgment after testing. RESULTS: All patients with resolved diagnoses (143 of 145, 103 positive and 40 negative) were identified correctly by the UniCAP Phadiatop test. Skin test results and specific IgE measurements correlated well, but neither correlated well with the history by itself, suggesting a minimal false-positive component of the history of 23%. UniCAP Phadiatop results demonstrated a quantitative relationship between the patient's score and the amount of IgE specific to these individual allergens. CONCLUSIONS: The UniCAP Phadiatop test was shown to be highly sensitive and specific in differentiating individuals who are sensitized to common inhalants from those who are not. This test is recommended to all physicians as an aid in diagnostic and referral decisions for patients suspected of having an inhalant allergic diathesis.

Administration, Inhalation↗
PubMed2001

Study of distribution and factors affecting syphilis epidemic among inner-city minorities of Baltimore.

Disparities in health and medical conditions among ethnic and racial groups have been repeatedly documented. These inequalities, which have been noted in the recent past, include health outcomes such as quality of life and mortality, process, accessibility and appropriateness of care, and the prevalence of certain degenerative conditions and infectious diseases. Syphilis, a sexually transmitted disease (STD) which seemed to have disappeared or had been controlled over the years, has now re-emerged as a major public health problem in many rural, urban and suburban communities. Progression of the current rate of syphilis, which erupted in Baltimore during the later part of 1994, has continued unabated, most especially among the ethnic minorities, despite efforts of the Baltimore City Health Department and Maryland Department of Health and Mental Hygiene to control the epidemic. With the current incidence rates of 270 per 100 000 live births for congenital syphilis and 99.3 per 100 000 population for primary, secondary and latent syphilis (96% of the cases being in the non-white population), Baltimore becomes the city with the highest number of syphilis cases in the nation, surpassing the national average of 2.6 cases per 100 000 population. This study, which utilizes a combination of retrospective and questionnaire-oriented approach, was designed to assess factors that influenced the high incidence of syphilis among Baltimore inner-city dwellers between 1994 and 1998. Data for the study included syphilis reports from private physicians, the Baltimore City Health Department, STD clinics, the Center for Disease Control (CDC), and ethnographic interviews. Factors favoring the distribution and infectivity of the disease among the inner-city dwellers include greater poverty, high level of communication gaps between providers and a cross-section of minority inner-city dwellers, exchange of sex for crack cocaine, lower educational background, and inadequate and inappropriate health education/health promotion programs for the ethnic minorities.The paper calls for, among other things, culturally-sensitive and competent syphilis elimination/prevention health education and health promotion programs for the ethnic minority inner-city dwellers of Baltimore.

Adolescent↗
PubMed2001

Evaluation of student achievement and educational outcomes.

Development of problem-solving skills is vital to professional education as is factual recall. Student mastery must be measured to document student achievement requiredfor completion of educational requirements and professional certification. These measurements also help determine if the educational process is meeting its goal of helping students develop critical cognitive skills for therapeutic problem solving. Testing student growth in the ability to solve problems is less understood. Stressing integration of information across disciplines to derive answers is also important. Test items should resemble the real-world task that students are expected to master. Thatisreallythe essence of content validity, which means faculty should be biased toward presenting information that way. This article is based on a symposium presented at the annual meeting of the American College of Clinical Pharmacology in September 1996. Symposium goals were to define purposes and uses of student evaluations by type and format, including application of techniques that improve evaluation, precision, and validity. Technical applications of computer-based learning and evaluation of problem-solving skills are described. Actual experience with evaluation of problem solving in the curriculum is discussed. The process by which a medical school developed and implemented an evaluation system for a new problem-based curriculum is presented, followed by a critique of the successes and problems encountered during the first year of implementation. Criteria that a well-constructed evaluation program must meet are explored. The approach and philosophy of national standardized testing centers are explained.

Educational Status↗
PubMed2000

Structural characterization of a methionine-rich, emulsifying protein from sunflower seed.

The 2 S seed storage protein, sunflower albumin 8, contains an unusually high proportion of hydrophobic residues including 16 methionines in a mature protein of 103 amino acids. A structural model, based on the known structure of a related protein, has been constructed as a four-helix bundle cross-linked by four disulphide bonds. This model structure is consistent with data from circular dichroism and nuclear magnetic resonance experiments. Analysis of the model's surface shows the presence of a large hydrophobic face that may be responsible for the highly stable emulsions this protein is known to form with oil/water mixtures.

2S Albumins, Plant↗
PubMed2000

A blinded, multi-center evaluation of two commercial in vitro tests for latex-specific IgE antibodies.

PURPOSE: To compare the diagnostic value of two commercial in vitro tests for the detection of latex-specific IgE antibodies. METHODS: Serum samples were collected from latex-allergic and nonlatex-allergic individuals. Persons were classified as latex allergic if they had a positive clinical history and a positive skin prick test with a latex extract. Persons with no latex-related symptoms and negative skin tests were classified as nonlatex allergic. The serum samples were tested in a blinded fashion by a laboratory using the CAP (Pharmacia-Upjohn) and AlaSTAT (Diagnostic Products Company) assays. Values of 0.35 kA U/L or greater were considered positive in both tests. RESULTS: The 143 sera studied came from 83-latex allergic and 60 nonallergic persons. The in vitro tests were found to have sensitivities of 79.5% and 73.8%, and specificities of 90.2% and 91.7%, for CAP and AlaSTAT, respectively. The positive predictive values were 91.7% and 92.5%, while the negative predictive values were 76.4% and 71.4% for the CAP and AlaSTAT, respectively. CONCLUSION: In individuals classified by the combination of clinical history and skin test results, both the Pharmacia CAP and the DPC AlaSTAT demonstrated acceptable sensitivities, specificities, and predictive values for detection of antilatex IgE antibodies. These findings suggest that both assays can be useful adjuncts to the diagnosis of latex allergy.

Adolescent↗
PubMed2000

Analytic precision and accuracy of commercial immunoassays for specific IgE: establishing a standard.

BACKGROUND: Different laboratory assays are used to detect and measure specific IgE antibodies. No standard exists to assess their analytic performance. OBJECTIVE: We sought to analyze reported specific IgE results from different laboratories on the same serum samples for their accuracy and precision. METHODS: Blinded serum samples (26) containing variable levels of specific IgE to 17 common aeroallergens were sent on 3 different occasions through normal channels to 6 laboratories that used 5 different test procedures. Six samples were presented as a dilution series. Laboratory-assay performance was assessed by analyzing the reported results (n = 12, 708) by using ordinary least squares regression with slope coefficients, the t statistic, SEs, confidence intervals, and R (2) values. These were compared with a theoretic ideal assay as the reference. RESULTS: Analysis revealed that one system used in two different laboratories performed nearly as well as the ideal standard, with an overall average slope (0.97; range, 0.91-1.01), SE (0.05; range, 0.02-0.16), R (2) value (93%; range, 0.64-0.99), and coefficient of variation (10.3%; range, 6%-14%). Extensive variability was observed in the other 4 laboratory-assay systems with respect to overall average slope (0.76; range, 0.11-1.24), SE (0.19; range, 0.03-0.95), R (2) value (53%; range, 0.00-0.98), and coefficient of variation (19%; range, 5%-49%). For some specific allergens, some laboratories-assays were not able to detect serial dilutions of the same sample. CONCLUSIONS: One commercial system used in two different laboratories performed nearly as well as the ideal standard. Four of the laboratories-assays for specific IgE antibodies demonstrated substandard overall performance with multiple instances of poor precision and accuracy, particularly for certain allergens, such as weeds and molds.

Air Pollutants↗
PubMed2000

Quantitative IgE antibody assays in allergic diseases.

During the past several years, immunoassays for specific IgE antibodies have been refined to permit reporting results in mass units. Thus quantitative immunoassays for IgE antibodies may be an adjunct to skin tests. In cases of food allergy among children with atopic dermatitis, cutoff values for IgE antibody concentrations to egg, milk, peanut, and fish have been derived to provide 95% positive and 90% negative predictive values. Food-specific IgE antibody determinations can also be used to predict which food allergies are resolving spontaneously. Elevated egg-specific IgE antibody levels in infancy are associated with significantly increased risk for development of inhalant allergies later in childhood. In cases of inhalant allergy, specific IgE antibody levels correlate closely with results of inhalation challenge studies in cat-sensitive persons. Also, mite-specific IgE antibody levels correlate significantly with the mite allergen contents of reservoir dust in the homes of mite-sensitive persons. Immunoassays for quantitation of specific IgE antibodies may be used to document allergen sensitization over time and to evaluate the risk of reaction on allergen exposure. However, immunoassays and skin tests are not entirely interchangeable, and neither will replace the other in appropriate circumstances.

Antibodies, Anti-Idiotypic↗
PubMed2000

The birth of ocular pharmacology in the 20th century.

Nineteenth century ophthalmology, characterized by significant gains in diagnostic techniques, provided the basis for great advancements in treatment during the 20th century. Drug therapy at the turn of the century was empiric, palliative, and often toxic. The development of ocular pharmacology during the 20th century provided the basis for a rational therapeutic approach to ocular disease. Foremost among the therapeutic developments were antibiotics, due to their potential to cure conditions that frequently resulted in blindness. Second, other therapeutic classes provided palliative therapy for chronic diseases, and thus decreased morbidity. For example, drugs specifically targeting many different aspects of glaucoma have had remarkable success controlling intraocular pressure and forestalling development of blindness. In addition, other new approaches provided palliative therapy for nonblinding conditions and effective adjuncts to surgical procedures. Antiallergy and anti-inflammatory drugs greatly increased patient comfort and facilitated treatment of allergic and inflammatory reactions. Local anesthetics and analgesia reduced patient discomfort during surgery. Other adjunct drugs improved surgical outcomes by reducing inflammation and infectious complications. The 21st century will undoubtedly provide novel approaches to address many of today's therapeutic dilemmas. Photodynamic therapy, growth factors, antisense technology, and genetic-based therapies all show great promise. Many of the conditions that are only treated palliatively today will be curable in the next century using many of these pharmacological advances.

Anti-Allergic Agents↗
PubMed1999

Direct kinetic evidence for folding via a highly compact, misfolded state.

The 2 S seed storage protein, sunflower albumin 8 (SFA-8), contains an unusually high proportion of hydrophobic residues including 16 methionines (some of which may form a surface hydrophobic patch) in a disulfide cross-linked, alpha-helical structure. Circular dichroism and fluorescence spectroscopy show that SFA-8 is highly stable to denaturation by heating or chaotropic agents, the latter resulting in a reversible two-state unfolding transition. The small m(U) (-4.7 M(-1) at 10 degrees C) and DeltaC(p) (-0.95 kcal mol(-1) K(-1)) values indicate that relatively little nonpolar surface of the protein is exposed during unfolding. Commensurate with the unusual distribution of hydrophobic residues, stopped-flow fluorescence data show that the folding pathway of SFA-8 is highly atypical, in that the initial product of the rapid collapse phase of folding is a compact nonnative state (or collection of nonnative states) that must unfold before acquiring the native conformation. The inhibited folding reaction of SFA-8, in which the misfolded state (m(M) = -0.95 M(-1) at 10 degrees C) is more compact than the transition state for folding (m(T) = -2.5 M(-1) at 10 degrees C), provides direct kinetic evidence for the transient misfolding of a protein.

2S Albumins, Plant↗
PubMed1999

Topical aminocaproic acid facilitates reepithelialization of persistent epithelial defects.

PURPOSE: After corneal injury, persistent epithelial defects (PED's) may occur due to the chronic failure of the regenerating epithelium to adhere to the underlying stroma. The aim of this study was to examine the potential of epsilonaminocaproic acid (EACA) as a topical treatment for PED's. EACA inhibits the activation of plasmin, which metabolizes fibronectin. Fibronectin, a glycoprotein, anchors corneal epithelium to the basement membrane and the underlying stroma. METHODS: In anesthetized rabbits, PED's were induced with sodium hydroxide (1 N). Seven days later, during the late healing phase, treatment began with administration of EACA (30%) to the right eye and administration of vehicle alone to the left eye three times daily. A control group received neither EACA nor vehicle. Rabbits were treated for 19 days. PED's were visualized by fluorescein staining. Their size was mapped using digital planimetry. RESULTS: After 11 days of treatment with EACA, treated PED's were 50% smaller than in corneas treated with vehicle alone. Following treatment for 15 days, corneas treated with EACA had significantly greater re-epithelialization than vehicle-treated or control corneas. Frozen sections stained immunofluorescently for fibronectin appeared to qualitatively contain more adherent fibronectin in treated corneas. Transmission and scanning electron microscopy indicated that the epithelium was more polymorphic, thinner and vacuolated in untreated controls compared to EACA treated eyes. Light microscopy demonstrated more continuous adherent epithelium after EACA treatment. CONCLUSIONS: Topically administered EACA decreases both the severity and incidence of persistent epithelial defects produced by alkali bums to the cornea. EACA appears to promote adherence of the regenerating epithelium to the underlying stroma. Thus, topically administered EACA may be an effective treatment for this chronic condition.

Administration, Topical↗
PubMed1998

Aminocaproic acid and tranexamic acid increase the rate of acute corneal reepithelialization in Sprague Dawley rats.

Antifibrinolytic agents, epsilon-aminocaproic acid (EACA) and tranexamic acid (TXA), have been reported to be efficacious in the treatment of chronic persistent epithelial defects. Within the regulatory mechanism of corneal reepithelialization, fibronectin serves as a primary adhesive component in the healing process and anchors regenerating epithelial cells to underlying stroma. EACA and TXA inhibit the activation of plasmin thereby decreasing plasmin-induced catabolism of fibronectin. In this study, acute reepithelialization following treatment with EACA and TXA was evaluated in the cultured rat cornea model. Sprague Dawley rat corneal explants with 3 mm corneal defects, induced with 1 N NaOH, were cultured with either EACA or TXA. After 12 or 24 hr incubation periods, corneal explants were stained with bromodeoxyuridine stain for measuring cellular division and migration or Trypan Blue for measuring the extent of dead cells. Both EACA and TXA increased the rate of reepithelialization in comparison to an untreated control. EACA was up to 35% more efficacious than TXA. Thus, this study demonstrated an acute effect for EACA and TXA versus the previously reported efficacy of chronic therapy required for persistent epithelial defects. Broad applications may prove beneficial in the clinical treatment of corneal abrasions, persistent corneal epithelial defects, or alkali burns.

Aminocaproic Acid↗
PubMed1998

Topical versus intravenous administration of tranexamic acid: a comparison of intraocular and serum concentrations in the rabbit.

BACKGROUND: Tranexamic acid has been shown to greatly reduce the incidence of secondary hemorrhage when administered orally or intravenously. Topical administration of the drug should result in much lower serum concentrations, with fewer adverse effects. We performed a study to determine whether topical application of tranexamic acid would yield higher intraocular concentrations and lower serum concentrations of drug than intravenous administration. METHODS: Ten New Zealand white rabbits received 25 mg/kg of tranexamic acid intravenously every 8 hours for 3 days. Another group of 10 rabbits received one drop (0.05 mL) of commercially available tranexamic acid solution (100 mg/mL) every 8 hours for 3 days to one eye. Tranexamic acid levels in the aqueous humour, vitreous humour and serum 1 hour after administration of the last dose of drug were determined. RESULTS: Analysis of variance showed that aqueous concentrations of tranexamic acid were significantly higher with topical delivery than with intravenous administration (15 vs. 9 micrograms/mL)(p < 0.05). Serum concentrations were significantly lower following topical administration (9 vs. 19 micrograms/mL)(p < 0.01). The drug was not detected in the vitreous humour in either group. INTERPRETATION: Topical delivery of tranexamic acid may prove to be valuable in yielding therapeutic intraocular concentrations of drug in patients with hyphema while minimizing systemic toxicity.

Administration, Topical↗
PubMed1997

Topical aminocaproic acid in the treatment of traumatic hyphema.

OBJECTIVES: To determine whether topically applied aminocaproic acid, like systemic aminocaproic acid, effectively reduces secondary hemorrhage after hyphemas and to compare the safety and effectiveness of topical application with those of systemic use and a control group. DESIGN: A prospective, randomized, double-masked, multicenter study. PATIENTS: Sixty-four patients with traumatic hyphema treated with topical or systemic aminocaproic acid and compared with 54 control patients with hyphema. Daily slitlamp examinations for hyphema grading and corneal clarity, initial and final visual acuity, applanation tonometry, and fundus indirect ophthalmoscopy were studied. Follow-up was 6 months to 5 1/2 years (mean, 2.96 years). RESULTS: Compared with the control group, topical and systemic aminocaproic acid was statistically significant in preventing secondary hemorrhage. Only 3% (2/64) of the patients who received topical or systemic aminocaproic acid had secondary hemorrhage compared with 22% (12/54) of the control group (P = .002). Final visual acuity was 20/40 or better in 30 patients (86%) in the topical group compared with 23 patients (43%) in the control group (P < .001). Final visual acuity was 20/40 or better in 20 patients (69%) in the systemic aminocaproic acid group compared with 23 patients (43%) in the control group (P = .04). The topical aminocaproic acid group had a final visual acuity of 20/40 or better in 86% of patients, compared with 69% of patients in the systemic group. CONCLUSIONS: Topical aminocaproic acid appears to be a safe, effective treatment to prevent secondary hemorrhage in traumatic hyphema. It is as effective as systemic aminocaproic acid in reducing secondary hemorrhage. No systemic side effects were observed with topical use. Topical aminocaproic acid provides an effective out-patient treatment for traumatic hyphemas.

Administration, Topical↗