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PubMed2003

Bone mineral density reference standards in adult baboons (Papio hamadryas) by sex and age.

Osteoporosis is a progressive condition involving structural deterioration of bone tissue, leading to skeletal fragility and an increased susceptibility to fractures due to low bone mass and high rates of bone turnover. Areal bone mineral density (aBMD) serves as the most reliable predictor of susceptibility to osteoporotic fracture. The development of animal models, including Old World Monkeys, has been essential to studies of bone mineral density. These animals, including the baboon, exhibit many biological similarities with our own species relevant to the variation in age-related changes and pathology in bone that may make them an excellent model for studies of skeletal structure and maintenance in humans. The baboon has been shown to exhibit extensive biological similarities to humans regarding skeletal biology, but little is known about the range of normal variation in skeletal traits, such as bone mineral density, in this species. Our data, collected on baboons (Papio hamadryas) that are part of a large breeding colony at the Southwest Foundation for Biomedical Research and the Southwest National Primate Research Center (San Antonio, TX), involve 466 females and 210 males, ranging in age from 5.5 to 30 years. Student's t tests, bivariate correlations, and likelihood ratio tests show sex and age effects at all spinal sites. Age effects are minimal or absent in the forearm sites. This study is the first to characterize normal variation in aBMD in baboons, to assess the effect of age and sex on this variation, and to compare this variation to those data currently available from experimental control animals. As such, it provides much-needed reference standards that will allow researchers to evaluate the status of their animals in cross-sectional studies and more fully assess the meaning of aBMD changes in longitudinal studies.

Absorptiometry, Photon↗
PubMed2003

New HLA haplotype frequency reference standards: high-resolution and large sample typing of HLA DR-DQ haplotypes in a sample of European Americans.

A collaborative study involving a large sample of European Americans was typed for the histocompatibility loci of the HLA DR-DQ region and subjected to intensive typing validation measures in order to accurately determine haplotype composition and frequency. The resulting tables have immediate application to HLA typing and allogeneic transplantation. The loci within the DR-DQ region are especially valuable for such an undertaking because of their tight linkage and high linkage disequilibrium. The 3798 haplotypes, derived from 1899 unrelated individuals, had a total of 75 distinct DRB1-DQA1-DQB1 haplotypes. The frequency distribution of the haplotypes was right skewed with haplotypes occurring at a frequency of less than 1% numbering 59 and yet constituting less than 12% of the total sample. Given DRB1 typing, it was possible to infer the exact DQA1 and DQB1 composition of a haplotype with high confidence (>90% likelihood) in 21 of the 35 high-resolution DRB1 alleles present in the sample. Of the DRB1 alleles without high reliability for DQ haplotype inference, only *0401, *0701 and *1302 were common, the remaining 11 DRB1 alleles constituting less than 5% of the total sample. This approach failed for the 13 serologically equivalent DR alleles in which only 33% of DQ haplotypes could be reliably inferred. The 36 DQA1-DQB1 haplotypes present in the total sample conformed to the known pattern of permissible heterodimers. Four DQA1-DQB1 haplotypes, all rare, are reported here for the first time. The haplotype frequency tables are suitable as a reference standard for HLA typing of the DR and DQ loci in European Americans.

Gene Frequency↗
PubMed2001

Exclusive breastfeeding and infant growth studies: reference standards for head circumference, length and mid-arm circumference/head circumference ratio for the first 6 months of life.

This paper presents the development of reference standards for head circumference (HC), length and mid-arm circumference/head circumference (MAC/HC) ratio for the evaluation of exclusively breastfed infants. A total of 219 exclusively breastfed term appropriate-for-gestational age (AGA) infants were studied and analysed from 1 June 1995 to 31 May 1997 at the Neonatal Follow-up Clinic, University Teaching Hospital, Benin City, Nigeria. Head circumference and length measurements were recorded for the infants at each postnatal completed month. MAC/HC ratios were also computed for each infant at each completed postnatal month. There was a progressive increase in the mean measurements at the completed months with increasing postnatal age and the differences between the mean measurements of length and head circumference at the 4th and 6th completed months were significant (p < 0.001). The head circumference, length and MAC/HC ratio had significant correlations with postnatal age. The standards represent the regression lines of the anthropometric measurements and MAC/HC ratio on postnatal age with the corresponding 95 per cent confidence limits. The standards identified 95 per cent (for head circumference), 93 per cent (for length) and 94 per cent (for MAC/HC ratio) of exclusively breastfed healthy infants as having normal infant growth for age.

Anthropometry↗
PubMed1989

[Studies on the identification of psychotropic substances. VI. Preparation and various analytical data of reference standards of some hallucinogens, 2,5-dimethoxy-4-methylamphetamine (STP), 2,5-dimethoxy-4-bromoamphetamine (DOB) and 2,5-dimethoxy-4-ethylamphetamine (DOET)].

The Reference Standards of 2,5-dimethoxy-4-methylamphetamine (STP), 2,5-dimethoxy-4-bromoamphetamine (DOB) and 2,5-dimethoxy-4-ethylamphetamine (DOET) were prepared. Their purities measured by HPLC were 99.5% for STP hydrochloride, 99.8% for DOB hydrobromide and 99.5% for DOET hydrochloride. For the identification and determination, various analytical data of the three drugs were obtained by using UV, IR, HPLC, GC/MS and NMR, and the discrimination were discussed.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1995

[The human chorionic gonadotrophin reference standard (Control 941) of the National Institute of Health Sciences].

Raw human chorionic gonadotrophin material was examined for preparation of the "Human Chorionic Gonadotrophin Reference Standard (Control 941)". The candidate material was assayed against the 3rd International Standard by the rat ovarian weight method. The potency of the new standard was defined as 1180 international units per ampoule as the result of 18 assays in four collaborative laboratories.

Chorionic Gonadotropin↗
PubMed2003

Determination of polybrominated diphenyl ethers in environmental standard reference materials.

The total concentrations (sigmaPBDE) of 15 polybrominated diphenyl ethers, BDEs 17, 28, 47, 49, 66, 71, 85, 99, 100, 138, 153, 154, 183, 190, and 209, and a predominant polybrominated biphenyl (PBB) congener, 2,2',4,4',5,5'-polybrominated biphenyl (PBB-153) were determined in six natural matrix Standard Reference Materials (SRM) provided by the National Institute of Standards and Technology (NIST). The sigmaPBDE concentrations (+/- one standard deviation) in SRM 1945 (whale blubber), SRM 1946 (fish tissue), SRM 1947 (fish tissue), and SRM 1974b (mussel tissue) were 126 +/- 7, 79 +/- 3, 134 +/- 5, and 7.9 +/- 0.2 ng/g of wet wt, respectively. The sigmaPBDE concentrations were 54 +/- 2 and 163 +/- 4 ng/g of dry wt for SRM 2977 (mussel tissue) and SRM 2978 (mussel tissue), respectively. Among the three kinds of marine animals, mussel tissue had the lowest total concentration of PBDEs. These values can provide an informal reference or benchmark to laboratories who measure these compounds.

Journal Article↗
PubMed1989

Reference standards for implantable materials: problems and needs.

Medical implant materials that come in contact with tissues, body fluids (including blood) constitute an area in medical devices where reliability and clinical performance limitations are vital. Polymeric implant materials differ in important aspects from metals and alloys, and ceramics (including glasses and carbons) with respect to their atomic and molecular structures and morphology. It is suggested that four categories of 'standards' be developed: (1) certified primary reference materials to be used for calibration purposes, (2) reference materials to be used for the comparative evaluation of physico-chemical and biological properties, (3) 'fabrication-grade' reference materials for intercomparative evaluation of processing conditions, and (4) reference implants aimed at the intercomparative evaluation of possible synergistic effects of additives, processing aids, and fabrication processes on in vivo service life, including biological and mechanical performance.

Biocompatible Materials↗
PubMed1994

A study on reference standard for cytotoxicity assay of biomaterials.

The objective of the present study was to find a standard substance for use as a reference in the cytotoxicity assay of biomaterials, as an alternative to animal experiments in recent years. Eight kinds of rubber were made in a plate shape to keep their surface area at 1 cm2 against 10 ml of extract volume. They were extracted by the following three extraction methods (a) dynamic extraction at 200 rpm gyration on alumina balls at 37 degrees C for 24 h; (b) static extraction at 37 degrees C for 24 h and (c) extraction by heating in an autoclave at 121 degrees C for 60 min. At the end of each period each extract was examined for cell viability based on an evaluation by neutral red uptake. These methods were repeated up to seven times. Two kinds of chemicals were also tested. The extracts obtained were used to treat human gingival fibroblasts that have been cultured with DMEM supplemented with 5% fetal bovine serum into a 96 well tissue culture plate by 1 x 10(5) cells/ml, in an incubator aerated with 5% CO2, and 95% humidified air at 37 degrees C for 48 h. The extracts of ethylene-propylene, butyl, nitrile rubbers, and two kinds of chemicals yielded strong cytotoxicity in all three kinds of extraction methods, while chloroprene, fluorine-contained, isoprene, India, and silicone rubbers showed little cytotoxicity. The results obtained by the three kinds of extraction methods revealed no differences in the order of cytotoxicity of the materials tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Testing Alternatives↗
PubMed1989

Rheumatoid arthritis of the temporomandibular joint: radiologic evaluation based on standard reference films.

A radiologic scoring system that uses tomography and panoramic radiography to evaluate severity of rheumatoid arthritis in the temporomandibular joint of adults is presented. The scoring system is based on six verbally described grades illustrated by standard reference films. The interobserver agreement was significantly higher for the grading with reference films than for that without reference films. Intraobserver performance was similar for grading with and without reference films. The grading system with reference films is recommended in epidemiologic studies of rheumatoid arthritis localized to the temporomandibular joint or other studies in which multiple observers are involved.

Arthritis, Rheumatoid↗
PubMed1996

Studies of critical factors in the determination of arsenic in Standard Reference Materials of Marine origin by ETAAS:;NMKL(*) interlaboratory study.

A study to determine factors which are known to influence the electrothermal atomic absorption (ETAAS) determination of As has been performed. The study has been carried out using five sample solutions of marine Standard Reference Materials distributed to four participating laboratories. Uncoated and pyrolytically coated graphite tubes with L'vov platform and Ni and Pd/Mg as chemical modifiers have been tested. No differences in results have been obtained between AAS instruments equipped with Zeeman correction or deuterium arc background correction. Small differences in concentration levels of arsenic as well as in characteristic mass were found when chemical modifiers were compared. Pd/Mg will be recommended in order to avoid a contamination of the graphite furnace with nickel. The characteristic mass was improved by using pyrolytically coated graphite tubes with the L'vov platform compared with uncoated graphite tubes with the L'vov platform. In the interlaboratory study, the standard addition procedure will be recommended.

Journal Article↗
PubMed1968

The maximum oxygen intake. An international reference standard of cardiorespiratory fitness.

Lack of cardiorespiratory fitness may well contribute to the increasing prevalence of degenerative cardiovascular disease throughout the world. As a first step towards co-ordinated and internationally comparable investigation of this problem, methods of measuring the reference standard of cardiorespiratory fitness-the maximum oxygen intake, (Vo(2))(max)-were compared by an international working party that met in Toronto in the summer of 1967.Repeated testing of 24 subjects showed that the (Vo(2))(max) was greatest on the treadmill, 3.4% smaller in a stepping test, and 6.6% smaller during use of a bicycle ergometer. There were also parallel differences in cardiac stroke volume. Uphill treadmill running was recommended for the laboratory measurement of (Vo(2))(max), and stepping or bicycle exercise for field studies. A discontinuous series of maximum tests caused some improvement in the fitness of subjects, and a "continuous" test (with small increases in load at 2-min intervals) was preferred.

Adult↗
PubMed2006

A reference standard for the measurement of macular oedema.

Macular oedema is associated with several conditions that lead to blindness. Accurate measurement of macular thickness is important in order to follow disease progression and evaluate treatments. Four techniques are examined to determine the best reference standard for the detection and quantification of macular oedema: ultrasound, optical coherence tomography, the retinal thickness analyser, and the scanning laser ophthalmoscope. The three optical techniques have the highest resolution and sensitivity, in particular optical coherence tomography. Ultrasound can be useful where dense opacities preclude optical imaging.

Humans↗
PubMed2004

Development of a new reference standard for microarray experiments.

Often microarray studies require a reference to indirectly compare the samples under observation. References based on pooled RNA from different cell lines have already been described (here referred to as RNA-R), but they usually do not exhaustively represent the set of genes printed on a chip, thus requiring many adjustments during the analyses. A reference could also be generated in vitro transcribing the collection of cDNA clones printed on the microarray in use (here referred to as T3-R). Here we describe an alternative and simpler PCR-based methodology to construct a similar reference (Chip-R), and we extensively test and compare it to both RNA-R and T3-R. The use of both Chip-R and T3-R dramatically increases the number of signals on the slides and gives more reproducible results than RNA-R. Each reference preparation is also evaluated in a simple microarray experiment comparing two different RNA populations. Our results show that the introduction of a reference always interferes with the analysis. Indeed, the direct comparison is able to identify more up- or down-regulated genes than any reference-mediated analysis. However, if a reference has to be used, Chip-R and T3-R are able to guarantee more reliable results than RNA-R.

Calibration↗
PubMed2001

Assessment of the exercise electrocardiogram in women versus men using tomographic myocardial perfusion imaging as the reference standard.

The exercise electrocardiogram (ECG) is widely believed to be less accurate in women, primarily due to a high prevalence of false-positive tests. The purpose of this study was to examine the relative accuracy of the exercise ECG in women versus men in 8,671 patients (3,213 women, 5,458 men) using myocardial perfusion imaging as the reference standard. More women (14%) than men (10%) had a false-positive ECG (p <0.001), but the absolute difference was relatively small. The false-negative rate was considerably lower in women (17% vs 32%, p <0.001). Compared with men, women had lower test sensitivity (30% vs 42%, p <0.001) and positive predictive value (34% vs 70%, p <0.001) but higher specificity (82% vs 78%, p = 0.002), negative predictive value (78% vs 52%, p <0.001), and accuracy (69% vs 58%, p <0.001). In patients with a false-negative exercise ECG, "high-risk" scans were less prevalent in women (12% vs 19%, p <0.001). In the smaller subset of patients referred for coronary angiography (205 women, 838 men), the false-positive electrocardiographic rate was again higher in women (13% vs 7%, p = 0.003), but neither specificity (69% vs 74%, p = NS) nor accuracy (60% vs 66%, p = NS) was different between the sexes. Thus, the percentage of patients with a false-positive exercise ECG was higher in women than men but low in absolute terms (<15%) for both sexes. Test specificity was not lower in women. These results suggest that gender should not be a major determinant for selecting stress imaging over standard treadmill testing.

Coronary Artery Disease↗