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At least 109 records · Page 6Linked to original sources
PubMed2003

Prevention of immunosuppression by sunscreens in humans is unrelated to protection from erythema and dependent on protection from ultraviolet a in the face of constant ultraviolet B protection.

Sunscreens have been advocated as an important means of preventing skin cancer. Ultraviolet radiation induced immunosuppression is recognized as an important event in skin cancer development, yet the effectiveness of sunscreens in protecting the human immune system from ultraviolet radiation (i.e. ultraviolet radiation) is still unclear. The only currently accepted method of sunscreen rating is the sun protection factor system based on the prevention of erythema. We determined immune protection factors for six commercially available sunscreens using a nickel contact hypersensitivity model in humans. Both sun protection factor and immune protection factor testing was performed using the same solar simulated ultraviolet radiation source and dose-responses were used to determine endpoints both with and without sunscreens. We found that the immune protection factor did not correlate with the sun protection factor; however, immune protection factor was significantly correlated to the ultraviolet A protective capability of the sunscreens, indicating that sunscreen protection from ultraviolet A is important for the prevention of ultraviolet immunosuppression, when there is constant ultraviolet B protection. We recommend that sunscreens should be rated against their immune protective capability to provide a better indication of their ability to protect against skin cancer.

Adolescent↗
PubMed2004

Egg:embryo weight ratio as an indicator of dwarfism induced by infectious bronchitis virus.

A simple objective method to quantify embryo dwarfism induced by infectious bronchitis virus in embryonated chicken eggs has been used to determine endpoints in virus titration and neutralization assays. The eggs and the respective embryos were weighed and embryo:egg weight (EE) ratios were calculated. The EE ratios were compared with the uninoculated control eggs and endpoints could be calculated objectively. EE indices were also calculated by dividing the EE ratios of inoculated embryonated chicken eggs by the mean EE ratio of uninoculated controls, or in the case of virus neutralization tests by the mean EE ratio of eggs inoculated with virus alone. Although this mean EE index did not reflect the dwarfing (or lack of it) in individual eggs, it served as a group indicator. This method would be useful to observe embryo lesions especially in field (non-egg adapted) infectious bronchitis virus isolates, which does not cause observable dwarfing until several embryo passages.

Animals↗
PubMed1990

International collaborative study to compare assays for antibodies that neutralize human immunodeficiency virus.

A variety of techniques are currently in use to measure antibodies that neutralize human immunodeficiency virus (HIV), and standardization of these assays is needed. Eleven laboratories participated in this comparison study of 14 methods for detection of HIV neutralizing antibodies (NA). A panel of 10 coded sera and a positive and a negative control serum were tested in each assay. The 10 coded samples included aliquots of the same sera that were distributed as positive and negative control sera, an aliquot of the WHO reference human anti-HIV-1 serum, and seven other sera from people with HIV-1 infection. Each laboratory reported features of its test methods and results. The results demonstrated excellent within laboratory and between laboratory consistency. The most important variable appeared to be the virus strain used. Cell line, conditions of neutralization or culture, method of endpoint determination, or use of VSV pseudotypes did not appear to be important variables. The results indicate that standardization of HIV-1 NA assays should be readily achievable.

Blotting, Western↗
PubMed2001

Protective role of probiotics and prebiotics in colon cancer.

Ingestion of viable probiotics or prebiotics is associated with anticarcinogenic effects, one mechanism of which is the detoxification of genotoxins in the gut. This mechanism was shown experimentally in animals with use of the rat colon carcinogen 1,2-dimethylhydrazine and by determining endpoints that range from tumorigenesis to induction of DNA damage. Because of the complexity of cancer initiation, cancer progression, and the exposure of cancer in the gut, many types of interactions may be envisaged. Notably, some of our newer studies showed that short-lived metabolite mixtures isolated from milk that was fermented with strains of Lactobacillus bulgaricus and Streptococcus thermophilus are more effective in deactivating etiologic risk factors of colon carcinogenesis than are cellular components of microorganisms. Ingestion of prebiotics results in a different spectrum of fermentation products, including the production of high concentrations of short-chain fatty acids. Gut flora, especially after the ingestion of resistant starch, induces the chemopreventive enzyme glutathione transferase pi in the colon of the rat. Together, these factors lead to a reduced load of genotoxic agents in the gut and to an increased production of agents that deactivate toxic components. Butyrate is one such protective agent and is associated with lowering cancer risk. It was recently shown that buytrate may inhibit the genotoxic activity of nitrosamides and hydrogen peroxide in human colon cells. In humans, the ingestion of probiotics leads to the excretion of urine with low concentrations of components that are genotoxic in human colon cells and high concentrations of components that induce oxidized DNA bases.

Animals↗
PubMed1995

Reproducibility of the signal-averaged electrocardiogram using individual lead analysis.

The aim of the study was to evaluate the immediate reproducibility of time domain parameters in the signal averaged electrocardiogram using a new method for endpoint determination in individual Frank leads. The method is based on a statistical model of the electrocardiogram (ECG) in which maximum likelihood (ML) estimation is employed. The reproducibility of the ML method was compared to that of conventional time domain analysis using the vector magnitude (VM) of Frank leads. Fifty-nine patients were included in the study and two consecutive ECGs were recorded for signal averaging. The results showed that the mean of the absolute difference of the filtered QRS duration (QRSD) between two consecutive recordings was significantly lower for the ML method than the conventional method when employing 60 Hz highpass filtering (2.1 +/- 2.2 ms vs 5.9 +/- 10.2 ms, P < 0.05). Moreover, the ML method resulted in a significantly longer QRSD compared to the VM-based method (P < 0.05). The terminal amplitude of the QRS complex (RMS40) showed a greater variability than the QRSD for both methods, although the ML method was associated with a higher reproducibility than the VM method for the 60 Hz filter. These findings may contribute to a better identification of patients at high risk of ventricular arrhythmias. A reduction in the number of measurement errors has important implications when QRS changes are analysed over time.

Adult↗
PubMed1999

The efficacy and tolerance of one or two daily doses of eprosartan in essential hypertension. The Eprosartan Multinational Study Group.

OBJECTIVE: The primary objective of this double-blind, parallel-group, placebo-controlled, multicentre study was to compare the antihypertensive efficacy of one versus two daily doses of eprosartan, a novel nonbiphenyl, nontetrazole angiotensin II receptor antagonist, in 243 patients with mild to moderate hypertension (sitting diastolic blood pressure > or = 95 to < or = 114 mmHg). PATIENTS AND METHODS: The patients were randomized to titrated doses of eprosartan at 400-800 mg once a day, eprosartan at 200-400 mg twice a day, or placebo, with the incremental dose titrated over a 9-week period. Patients reaching target blood pressure (sitting diastolic blood pressure of < or = 90 mmHg) continued the fixed-dose treatment for 4 weeks. The primary efficacy measure was the mean change in trough sitting diastolic blood pressure from baseline to the study endpoint, determined on an intent-to-treat basis. RESULTS: By the end of the study, eprosartan had significantly reduced mean trough sitting systolic and diastolic blood pressure relative to baseline and to placebo. The mean +/- SD change from baseline in diastolic pressure was -9 +/- 8.4 mmHg for the single daily dose, -9 +/- 8.5 mmHg for two doses a day and -4 +/- 8.1 mmHg for placebo (P < 0.0001 versus placebo for both eprosartan regimens). Similarly, both eprosartan regimens significantly reduced mean trough standing systolic and diastolic blood pressure. At the end of the study, the response rate in the single daily dose group (46.8%) was significantly higher than in the placebo group (25.6%). There were no significant differences between the treatment groups in the number of patients whose blood pressure responded to treatment; 41.7% of those taking eprosartan once a day and 44.4% of those taking eprosartan twice a day, and who responded to treatment, were maintained on their original starting doses. The total daily dose required to achieve target blood pressure was comparable, whether eprosartan was administered once or twice a day. Both eprosartan regimens were well tolerated and the incidence of adverse events with eprosartan was similar to that of placebo. CONCLUSIONS: These results demonstrate that there was no significant difference in antihypertensive efficacy or tolerance between eprosartan taken in one or in two daily doses. Both dosing regimens provided significant and clinically meaningful reductions in blood pressure that were superior to placebo. Eprosartan in a single daily dose was shown to be an effective antihypertensive agent. Because of the good adverse-effect profile and the simplicity of a single daily dose, eprosartan has the potential to improve patient compliance.

Acrylates↗
PubMed1996

Maximum likelihood analysis of cardiac late potentials.

This study presents a new time-domain method for the detection of late potentials in individual leads. Basic statistical properties of the ECG samples are modeled in order to estimate the amplitude and duration of late potentials. The signal model accounts for correlation in both time and across the ensemble of beats. Late potentials are modeled as a colored process with unknown amplitude which is disturbed by white, Gaussian noise. Maximum likelihood estimation is applied to the model for estimating the amplitude of the late potentials. The resulting estimator consists of an eigenvector-based filter followed by a nonlinear operation. The performance of the maximum likelihood procedure was compared to that obtained by traditional time-domain analysis based on the vector magnitude. It was found that the new technique yielded a substantial improvement of the signal-to-noise ratio in the function used for endpoint determination. This improvement leads to a prolongation of the filtered QRS duration in cases with late potentials.

Action Potentials↗
PubMed1982

Detection of class-specific antibodies of pemphigus vulgaris using a solid phase radioimmunoassay.

A sensitive solid phase radioimmunoassay was developed to detect class-specific pemphigus antibodies. COLO-16, a cell line derived from a human squamous cell carcinoma of the skin, was used as the substrate, since this cell line has been shown by indirect immunofluorescence to bind IgG antibodies in sera from patients with pemphigus vulgaris, but not from those with bullous pemphigoid. IgG antibodies to COLO-16 were significantly greater in sera from 17/24 patients (p less than 0.05) with pemphigus vulgaris than in sera obtained from a control population consisting of normal volunteers and patients with other dermatologic diseases. The relative binding of the positive sera correlated well (p less than 0.05, by Spearman's rank correlation test), with the endpoint determined by indirect immunofluorescence against monkey esophagus. This technique is 10-100 times more sensitive than immunofluorescence for the detection of pemphigus antibodies and will be useful in studying the cellular mechanisms controlling the synthesis of pemphigus antibody in vitro.

Antibody Specificity↗
PubMed1983

A new technique in quantitative immunohematology: solid-phase kinetic enzyme-linked immunosorbent assay.

A solid-phase kinetic enzyme-linked immunosorbent assay has been developed to measure binding of antibodies to purified or synthetic blood group antigens and tested in the Lewis blood group system. Chemically synthesized Lewis a antigen is used as the target for the binding of serum antibody in this sandwich-type assay. Kinetic, rather than endpoint, determinations are used to calculate the amount of specific antibody. Data are presented showing the assay to be quantitative, sensitive, and specific. It can separately quantitate the amount of IgG or IgM anti-Lewis a present in patient sera. The assay uses commercially available reagents and is semiautomated. Thus, it will be useful for studies in quantitative immunohematology as other blood group antigens become available in purified form.

Antibody Specificity↗
PubMed2001

Present status of the detection of antifungal resistance: the perspective from both sides of the ocean.

The NCCLS reference methodology for antifungal susceptibility testing is a new milestone of the evolution of medical mycology. The use of this methodology however, is not problem-free. At present, major limitations are a trailing phenomenon with azoles, unreliable detection of resistance to amphotericin B, poor growth of some organisms and unpractical procedures for the clinical laboratory. Herein a overview of NCCLS guidelines for yeasts and filamentous fungi is presented. Likewise, a review of studies conducted trying to overcome the limitations of reference procedures is also included. Several alternative approaches are reviewed as alternative media, inoculum size and incubation time. Modifications of reading procedure and endpoint determination are also evaluated. Agar diffusion methods and other methods for susceptibility testing are cited. Finally, we discuss the data on correlation of the in vitro results with the in vivo activity.

Antifungal Agents↗
PubMed1995

Tissue dosimetry, pharmacokinetic modeling, and interspecies scaling factors.

Interspecies scaling factors (ISFs) are numbers used to adjust the potency factor (for example, the q1* for carcinogens or reference doses for compounds eliciting other toxic endpoints) determined in experimental animals to account for expected differences in potency between test animals and people. ISFs have been developed for both cancer and non-cancer risk assessments in response to a common issue: toxicologists often determine adverse effects of chemicals in test animals and then they, or more commonly risk assessors and risk managers, have to draw inferences about what these observations mean for the human population. This perspective briefly reviews the development of ISFs and their applications in health risk assessments over the past 20 years, examining the impact of pharmacokinetic principles in altering current perceptions of the ISFs applied in these health risk assessments, and assessing future directions in applying both pharmacokinetic and pharmacodynamic principles for developing ISFs.

Animals↗
PubMed1987

Broth dilution testing of Candida albicans susceptibility to ketoconazole.

We performed a detailed investigation of the kinetics of ketoconazole activity in the setting of broth dilution testing of Candida albicans susceptibility. Turbidimetric readings reflected parallel quantitative colony counts. The method of endpoint determination markedly affected the results. Determinations of 50% inhibitory concentrations clearly separated the ketoconazole-resistant strains from the susceptible strains.

Candida albicans↗
PubMed1969

Simple method for rapid determination of antibiotic blood levels.

A simple method for the rapid determination of antibiotic blood levels is described. Results are readily obtainable within 4 to 6 hr. The reported procedure is based upon determination of the highest dilution of a patient's serum capable of inhibiting dextrose fermentation by a standardized inoculum of a staphylococcus strain or of an Escherichia coli strain, when colymycin or polymyxin are involved, as compared to previously determined endpoints in this regard of defined concentrations of the different antibiotics dissolved in normal human serum. Excellent correlation was observed with 36 serum specimens that contained different antimicrobial agents in varied concentrations when simultaneously assayed by the standard method and the subject procedure of this report.

Anti-Bacterial Agents↗
PubMed1984

Latex immunoassay for rapid detection of rotavirus.

A latex agglutination (LA) test was evaluated for the detection of human rotaviruses in stool specimens. Both antiserum and immunoglobulin G (IgG)-sensitized latex particles were used, with IgG-coated beads being more sensitive for human rotavirus antigen detection. Latex beads sensitized with anti-simian-SA-11 IgG were stable for at least 8 months when stored at 4 degrees C. The sensitivity of the test was compared with that of the Rotazyme (Abbott Laboratories, Diagnostics Div., North Chicago, Ill.) test. The least number of particles detected was 9.0 X 10(5) particles by the LA test versus 4.5 X 10(5) particles by the Rotazyme test. When 10 stool specimens were serially diluted for antigen endpoint determinations, the geometric mean titer by the LA test was 592 versus 1,280 by the Rotazyme test. Forty-three stool samples positive by the Rotazyme test were all positive by the LA test, and no false negative results were detected. Unconfirmed false positive reactions ranged between 8 and 24%. The LA test for rotavirus antigen detection is direct, easy to perform, sensitive, quick, and may have application for use in diagnostic laboratories, emergency rooms, and physician's offices.

Antigens, Viral↗
PubMed1989

Characterization of instrumentation and calibrators for quantitative microfluorometry for immunofluorescence tests.

The current method for measuring reagents for immunofluorescence microscopy involves a subjective evaluation of the endpoint (titer) with a negative or positive (1+ to 4+) scale. Variability is due to the biological constituents of the reagent, the observer, and the instrumentation. To have reliable methods for evaluation of performance of these products, we are developing a quantitative method that uses photometric measurements of microscopically observed epifluorescence of slide preparations. A computer-controlled microscope-photometer converts the light intensity into a voltage measurement. Our goal is to replace the subjective endpoint determination with an objective, quantitative method. The instrumentation and its operating characteristics are presented in this paper. Selected commercially available fluorescent materials were evaluated as calibrators for the instrumentation. These materials showed consistency in measurement and thus demonstrated their suitability for various levels of calibration. It is possible that they will prove useful as a reference standard for interlaboratory comparisons.

Cytophotometry↗
PubMed1989

Application of quantitative immunofluorescence to clinical serology: antibody levels of Toxoplasma gondii.

Methods currently used for immunofluorescent reagent standardization require subjective visual comparison of reagents with control materials. Reactivities of reagents in immunofluorescence test kits vary from manufacturer to manufacturer. To solve these problems, a quantitative immunofluorescence (QIF) method which uses a calibrated photometric system and incorporates reducing agents into the mounting medium to reduce fading was developed to replace the visual method of endpoint determination. A uranyl glass slide was used to calibrate the instrument's voltage measurements, permitting daily comparisons and measurement of the instrument reading fluctuations. The QIF method was initially tailored to the determination of serum antibodies to Toxoplasma gondii by measuring the fluorescence intensity of individual tagged organisms. The nonspecific fluorescence intensity resulting from the counterstain was eliminated by use of a red-suppressing filter. The dilution-correlated polar fluorescence component was removed by subtraction of the intensity for the matching negative control dilution from each sample dilution intensity. The QIF method showed a 94% correlation with the visual comparison method for 62 clinical specimens.

Animals↗
PubMed1992

Application of quantitative immunofluorescence to clinical serology: antibody levels of Treponema pallidum.

A previously reported method of quantitative immunofluorescence, employing a calibrated photometric system and chemically stabilized fluorescence intensity, was used to replace the subjective, visual method of endpoint determination with a quantitative, calibrated measurement of antibodies to Treponema pallidum in serum. The results of the quantitative immunofluorescence method showed a 90% correlation with the subjective determinations of the visual method.

Antibodies, Bacterial↗