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Biomedical subjects

E W Gunter

Publications and source records attributed to E W Gunter.

At least 73 records · Page 4Linked to original sources
PubMed1991

The effect of glucocorticosteroids on serum, liver, and lung vitamin A and retinyl ester concentrations.

Vitamin A and its active metabolites are important factors in promoting normal respiratory epithelial differentiation and growth. Glucocorticoids, often used to treat chronic lung diseases in infancy and childhood, are known to increase serum retinol concentrations. To determine the effects of exogenous steroids on serum retinol and retinol-binding protein concentrations (as well as on liver and lung total vitamin A, retinol, and retinyl ester concentrations), 32 weanling Sprague-Dawley rats were divided into four equal experimental groups. Eight animals were vitamin A sufficient and received 7 days of intraperitoneal dexamethasone at 0.5 mg/kg/day (group SD), 8 were vitamin A sufficient and received placebo (group SP), 8 were made vitamin A deficient and subsequently received dexamethasone (group DD), and 8 were vitamin A deficient and received placebo (group DP). Dexamethasone increased serum retinol concentrations in the SD group (2.27 +/- 0.20 mumol/L) when compared with control (SP, 1.64 +/- 0.46 mumol/L, p less than 0.001) as well as with pretreatment baseline values (1.21 +/- 0.23 mumol/L, p less than 0.001). Lung total vitamin A, retinol, and individual retinyl esters were depleted by 56 +/- 19% in the SD group, whereas liver values were depleted by 36 +/- 23%. In the vitamin A-sufficient groups the relative percentages of four major retinyl esters (palmitate, stearate, oleate, and linoleate) did not change in either tissue after steroid exposure. The vitamin A-deficient groups had no detectable tissue vitamin A, and dexamethasone did not increase serum retinol concentrations in the DD group. Serum retinol-binding protein concentrations were significantly higher in both steroid-treated groups when compared with control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Comparing serum ferritin values from different population surveys.

This report compares serum ferritin data collected in recently conducted Health and Nutrition Examination Surveys by age, sex, and ethnic group. Serum ferritin assays and selected confounding variables are examined to explore the basis of the difference in serum ferritin values obtained from the different surveys.

Confounding Factors, Epidemiologic↗
PubMed1990

Within-person variance in biochemical indicators of iron status: effects on prevalence estimates.

The effect of within-person variance on prevalence estimates from population distributions based on a single measurement was examined for hematologic and iron-status indicators collected in the Hispanic Health and Nutrition Examination Survey (HHANES). Within-person to between-person variance ratios (W:Bs) were estimated for 11 indicators by using data from 80 persons who provided blood twice in HHANES. Distributions of selected iron-status indicators from 20-44-y-old Mexican American females from HHANES were adjusted for within-person variance by using the W:B estimates, and prevalences of low values based on the original and adjusted distributions were compared. W:B were less than 1 for the majority of the indicators. Nonetheless, prevalences of low values from the original distributions were inflated when commonly used cutoff values were applied. Within-person variance in serum analytes needs to be controlled when the prevalence of a condition in populations is assessed.

Adult↗
PubMed1990

Field issues for the plan and operation of the laboratory component of the Third National Health and Nutrition Examination Survey.

The design of the laboratory component of a mobile examination survey such as the National Health and Nutrition Examination Survey requires that the physical limitation of the mobile examination center be balanced against the requirements of the laboratory analyses needed to fulfill the goals of the survey. In order to include an analysis in the survey, the scientific merit of the laboratory test must be established and a consensus must be reached on the appropriateness of the technology for the six years of the survey. The public health importance of the analysis and the subsequent results are also evaluated before inclusion into the laboratory protocol. Finally, the feasibility of incorporating the analysis into the protocol is reviewed. The laboratory component of NHANES III is discussed, addressing these points with descriptions of the reasons for inclusion and exclusion of key analytes.

Blood Cells↗
PubMed1990

Quality control in planning and operating the laboratory component for the Third National Health and Nutrition Examination Survey.

Successfully acquiring high-quality laboratory data for a long-term nutrition survey such as the Third National Health and Nutrition Examination Survey (NHANES III) requires rigorous quality-control procedures throughout the entire design and implementation of the laboratory component. We discuss selection of nutritional biochemistry analyses, proper specimen collection, and the critical need for continuity of protocol during the entire survey. The NHANES III laboratory procedures are described, including specimen collection, processing, shipment to laboratories, and analyses.

Blood Chemical Analysis↗
PubMed1990

Blood lead and zinc protoporphyrin levels in donkeys and mules near a secondary lead smelter in Jamaica, 1987-88.

During the course of an investigation into community lead poisoning near a secondary lead smelter in Jamaica, blood lead and zinc protoporphyrin levels were measured in 8 exposed and 6 (3 Jamaican, 3 US) unexposed donkeys and mules. The blood lead levels of 6 animals in the contaminated area ranged from 7.5 to 33 micrograms/dl (mean = 17.6 micrograms/dl), compared to 1.8 and 2.4 in unexposed Jamaican animals. More striking was the difference in zinc protoporphyrin levels; all 8 exposed donkeys and mules had values between 900 and 1890 micrograms/dl, compared with a range of 34-46 micrograms/dl for 3 Jamaican control donkeys. These findings suggest that zinc protoporphyrin may be a useful method of screening for subclinical lead toxicity in equines.

Animals↗
PubMed1989

Age dependence of metals in hair in a selected U.S. population.

Concentrations of 28 metals were determined in hair samples from 199 children (age less than or equal to 12 years) and 322 adults (age 13-73) years. Levels of calcium, barium, magnesium zinc, and strontium all show a similar age-dependent increase up to about 12-14 years; levels of aluminum show a decrease with age. Relationships of elemental concentrations with age were examined by using correlation, linear regression, t tests, and discriminant analysis. Statistically significant differences in mean concentration values between children and adults were shown for these metals. Discriminant analysis gave about 95% accuracy in classifying a test data set into the categories of children and adults. A hypothesis suggested by the data is that there is an age-dependent excretion in hair of alkali metals during skeletal growth and development. The observed decrease in aluminum is largely unexplained at this time.

Adolescent↗
PubMed1989

Investigation of protoporphyrin IX standard materials used in acid-extraction methods, and a proposed correction for the millimolar absorptivity of protoporphyrin IX.

Erythrocyte protoporphyrin (EP) has been used for more than 30 years as an indicator of lead intoxication, iron deficiency, and porphyrias. Recently, numerous analytical problems associated with various EP methods have been reported, including a lack of consensus among investigators regarding the best calibration material or analytical procedure. We investigated commercially available protoporphyrin IX (PPIX) standard materials and measured the millimolar absorptivity (m epsilon) of these materials, focusing on variables affecting the determination of their absorptivities. Among the five forms of PPIX available, PPIX dimethyl ester, when hydrolyzed to PPIX free acid, gave the most consistent and reproducible results. This work confirmed our earlier observations, made on more than 600 separate occasions during 12 years, that the m epsilon of PPIX free acid in 1.5 mol/L HCl at the Soret maximum is 297 +/- 1.3 L.mmol-1.cm-1, 19% higher than the arbitrary value of 241 L.mmol-1.cm-1 generally accepted by most investigators but based on unpublished data. We propose that the m epsilon of 297 L.mmol-1.cm-1 for PPIX be adopted and that PPIX dimethyl ester be used for the calibration of acid-extraction methods. A detailed protocol for the preparation and verification of PPIX from the dimethyl ester is available upon request.

Chromatography, High Pressure Liquid↗
PubMed1989

An interlaboratory comparison of control materials for use with hematofluorometers.

This interlaboratory study was conducted to examine four erythrocyte protoporphyrin control materials from Aviv Biomedical, Helena Laboratories, Kaulson Laboratories, and the New York State Department of Health for use with hematofluorometers. Our principal aims were to monitor the stability of these materials at three different storage temperatures (room, refrigerator, freezer) and, where appropriate, to validate the manufacturer's target values. Measurements for the study were generated in three reference laboratories that used a total of five hematofluorometers, three from Environmental Science Associates and two from Aviv Biomedical. Each instrument was calibrated against a consensus acetic acid-ethyl acetate extraction procedure. We found the materials from Aviv to be the most stable, followed by the New York State material. However, the target values assigned by Aviv were not within the acceptable range determined by consensus. The target values assigned by Kaulson Laboratories for their materials did fall within the acceptable consensus range, but they were the least stable of the materials evaluated. The materials from Helena Laboratories were originally designed for use as calibrators with Helena's "ProtoFluor Z" hematofluorometer, which reports in different units. They were deemed unsuitable for use as control materials with the Aviv or Environmental Science Associates hematofluorometers because of the narrow range of values and the wide scatter of results.

Acetates↗
PubMed1989

Empirically determined lead-poisoning screening cutoff for the Protofluor-Z hematofluorometer.

A recently introduced hematofluorometer, the "Protofluor-Z" (Helena Laboratories, Beaumont, TX), has several novel features, most notably reporting units expressed as the molar ratio of zinc protoporphyrin (ZPP) to heme, i.e., micromoles of ZPP per mole of heme. We analyzed human blood specimens on the Protofluor-Z and by an ethyl acetate/acetic acid extraction procedure. Data from three laboratories were pooled and used to provide a comparison of the two methods. Results indicate that, with the Protofluor-Z, a value of 70 mumol of ZPP per mole of heme is approximately equivalent to the recommended screening cutoff of 35 micrograms of erythrocyte protoporphyrin per 100 mL of whole blood used in programs for pediatric lead-poisoning prevention. This empirically determined value is slightly lower than either that recommended by the manufacturer or a theoretical cutoff value that was determined mathematically.

Erythrocytes↗
PubMed1989

An improved radioimmunoassay of C-peptide and its application in a multiyear study.

A commercial radioimmunoassay (RIA) for human proinsulin C-peptide was modified to improve its ruggedness and specificity, to decrease the influence of specimen matrix, and to shorten "hands-on" time. In the new protocol, we prepare calibrators in a C-peptide-free serum pool, prepared by treatment with activated charcoal (biological matrix), instead of in a defined matrix. This yielded essentially 100% analytical recoveries for C-peptide concentrations up to 300 pmol/L, a broader analytical range. We also corrected calibrators and unknown samples for nonspecific binding (NSB). Decreasing the concentration of ethanol (from 950 to 880 mL/L) for differential precipitation of the antigen-antibody complex resulted in an NSB of less than 10%, while maintaining high bound/total count percentages for samples and calibrators. C-peptide is thermally unstable without aprotinin at -20 degrees C and with or without aprotinin at 4 degrees C or above, but multiple freeze-thaw cycles do not affect C-peptide in serum. The modified C-peptide assay was applied to plasma from a multiyear study (fasting and post-carbohydrate-challenge subjects). During the four years of the study CVs ranged from 1.9% to 8.6% for replicate analyses of C-peptide in samples with concentrations less than or equal to 500 pmol/L. Between-run CVs were 3.8% to 8.2%, total CVs 3.8% to 10.7%.

Buffers↗
PubMedDate not supplied

Serum carotenoids are associated with increased lung cancer risk among alcohol drinkers, but not among non-drinkers in a cohort of tin miners.

To examine the association between pre-diagnostic serum carotenoid levels and lung cancer risk and the effects of alcohol intake on the carotenoid-lung cancer relationship, we conducted a case-control study in an occupational cohort from the Yunnan Tin Corporation in China. During 6 years of follow-up, 339 cases of confirmed lung cancer were diagnosed. Among these cases, those who donated pre-diagnostic blood (n = 108) were eligible for this study. For each case, two individuals alive and free of cancer at the time of case diagnosis, matched on age, sex, and date of blood collection, were selected as controls. Serum beta-carotene (odds ratios (ORs) for tertiles: 1, 1.3, 2.0) and beta-cryptoxanthin (ORs for tertiles: 1, 1.8, 2.9) levels were positively associated with lung cancer risk after adjustment for tobacco use and radon exposure. Among alcohol drinkers, higher serum carotenoid levels were significantly associated with increased lung cancer risk (alpha-carotene OR 2.2, 95% confidence interval (CI) 1.1-4.4, beta-carotene OR 7.6, 95% CI 3.1-18.6, lutein/zeaxanthin OR 2.3, 95% CI 1.2-6.6 and beta-cryptoxanthin OR 7.6, 95% CI 2.7-21.5). Conversely, risk estimates among non-drinkers suggest a possible protective association for higher carotenoid levels.

Adult↗
PubMedDate not supplied

The effect of antenatal betamethasone on cord blood concentrations of retinol-binding protein, transthyretin, transferrin, retinol, and vitamin E.

We assessed the effect of short-term (less than or equal to 1 week) and prolonged (greater than 1 week) exposure to antenatal betamethasone on umbilical cord serum concentrations of retinol-binding protein (serum t 1/2 = 12 h), transthyretin (t 1/2 = 2 days), transferrin (t 1/2 = 8 days), retinol (vitamin A), and vitamin E in appropriate-for-gestational-age preterm newborn infants of less than 36 weeks' gestation. A group of 30 infants whose mothers received a single course of betamethasone less than or equal to 1 week prior to delivery had significantly elevated mean retinol-binding protein and transthyretin but not transferrin concentrations when compared with a group of 30 gestational age- and birth weight-matched infants with no exposure to antenatal betamethasone. A group of eight infants whose mothers received multiple (more than two) weekly courses of betamethasone prior to delivery had significantly elevated mean serum concentrations of all three proteins when compared with eight gestational age- and weight-matched control infants with no betamethasone exposure. Serum retinol and vitamin E concentrations were measured in a group of 21 infants exposed to short-term prenatal betamethasone and were significantly greater than in a group of 21 control infants without steroid exposure. We conclude that antenatal steroids increase the umbilical cord serum concentrations of retinol-binding protein, transthyretin, transferrin, retinol, and vitamin E. The effect on the various serum proteins is dependent on the duration of exposure to steroids.

Betamethasone↗