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At least 1,171 records · Page 65Linked to original sources
PubMed1994

Age-related reference values for urinary organic acids in a healthy Turkish pediatric population.

Organic acid concentrations were quantified by gas chromatography and the individual acids identified by mass spectrometry in urine specimens from a healthy Turkish pediatric population of ages 2 days to 16 years, subdivided into five age groups. We quantified 69 organic acids (32 major and 37 minor components) and report here the median values and percentiles for each compound, adjusted for creatinine content, for the five groups. Concentrations of most of the organic acids tend to decrease with age but display substantial differences between age groups. This emphasizes the importance of comparing patients' data with age-matched reference data. Correlations between the excretion of organic acids and protein or caloric intake were significant for several compounds.

Aging↗
PubMed2007

Identification of multixenobiotic defence mechanism (MXR) background activities in the freshwater bivalve Dreissena polymorpha as reference values for its use as biomarker in contaminated ecosystems.

The biological defence mechanism called MXR or MXD for multixenobiotic resistance or defence protects cells against the entry and the accumulation of xenobiotics. As the defence is modulated by man made chemicals, MXR is used as a biomarker of organisms' exposure to environmental contamination. However, to reliably assess and evidence MXR induction, the use of a reference level is required. In this context, we focused on MXR background level in a freshwater bivalve, the zebra mussel Dreissena polymorpha, in order to propose its use as a reference during MXR evaluation. We monitored the MXR transport activity in mussels collected either in a natural population or in a caged population and then transplanted to clean water in the laboratory. The results showed that MXR activity was decreased to its baseline level after an eight to nine day depuration period (13.1+/-3.1; 7+/-2.6; 13.7+/-3.9 pmol RB min(-1)org(-1) after three experiments of laboratory depurations). Moreover, significant MXR induction was measured in depurated zebra mussels exposed to contaminated sites (39.6+/-3.7; 59.2+/-20.3 pmol RB min(-1)org(-1) after two experiments of field exposure), showing that the laboratory depuration did not affect the induction potential. The MXR responses (decrease as well as increase) occurred in few days and were highly significant, highlighting its reactivity in zebra mussels. Finally, this paper confirms the usefulness of MXR as a tool in biomonitoring studies and provides a protocol for field experiments that enables to establish and use the background level of MXR activity as a reference.

Animals↗
PubMed1989

[Computer-assisted tissue analysis for cancer detection in breast ultrasound--significance of reference values].

Due to the inhomogeneous and very variable structure of healthy tissue of the female breast it is often very difficult to detect a carcinoma via computer-aided sonography. The present study based on preoperative measurements in 29 woman patients with carcinoma of the breast aimed at finding out to what extent it would be possible to circumvent this problem by means of additional reference measurements in healthy tissue. For this purpose, relative image parameters were determined besides absolute ones from measurements in tumorous and healthy reference tissue. These relative image parameters are much more suitable for subsequent decision analysis on account of their narrower range of variation. The results obtained in this manner could be improved further by additional optimization or extension (such as analysis of other combinations of parameters, by enlarging the field of measurement and hence the data available per tissue sample, use of higher or even different ultrasound frequencies).

Adipose Tissue↗
PubMed1988

Reference values for nucleosides and nucleobases in cerebrospinal fluid of children.

Disturbances in the metabolism of purines and pyrimidines in neurologically affected patients can be reflected by aberrant concentrations of nucleosides and nucleobases in cerebrospinal fluid (CSF). However, normal values, especially for children at different ages, are lacking. We collected 1000 specimens of CSF from subjects ranging in age from newborn to 18 years, who were undergoing a diagnostic lumbar puncture for several clinical indications. Of these, 78 samples could be used retrospectively as a reference according to our criteria. The analyses were performed with a modified HPLC procedure. None of the substances shows age-dependency except uridine and uric acid. Uridine increases with age, and uric acid increases with age in boys older than 12 years.

Adolescent↗
PubMed2004

Reference values for bone mineral density in 12- to 18-year-old girls categorized by weight, race, and age.

BACKGROUND: Normative bone mineral density (BMD) values for adults do not apply to the pediatric population because of dramatic and variable rates of bone mineral acquisition that take place throughout adolescence. OBJECTIVE: This study was designed to provide normative BMD values for the lumbar spine and femoral neck by age, weight, and race in female adolescents for use by clinicians. MATERIALS AND METHODS: The study population comprised 422 healthy adolescent girls aged 12-18 years recruited from four primary-care clinics. BMD measurements were performed with dual-energy X-ray absorptiometry (DEXA). RESULTS: The major statistical predictors of lumbar spine BMD and femoral neck BMD were race, chronological age, and weight. There was an increase in both lumbar spine and femoral neck BMD that paralleled an increase in age and weight. In addition, the lumbar spine BMD and the femoral neck BMD were higher in the black participants than in the non-black participants with mean BMD values in grams per centimeter squared of 1.02 and 0.98, respectively, for blacks and 0.96 and 0.89, respectively, for non-blacks ( P<0.001). CONCLUSION: Our study produced the largest set of lumbar spine and femoral neck BMD normative values for female adolescents and confirms the importance of both demographic and anthropomorphic variables in determining normative BMD values.

Absorptiometry, Photon↗