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At least 73 records · Page 4Linked to original sources
PubMed1986

Endogenous thymidine and hypoxanthine are a source of error in evaluating methotrexate cytotoxicity by clonogenic assays using undialyzed fetal bovine serum.

None of 13 fresh human tumor samples of various histology cloned in a two-layer agar culture system with 20% undialyzed fetal bovine serum (FBS) showed sensitivity to three antifolates, methotrexate (MTX), trimetrexate and 5,8-dideazaisofolic acid (IAHQ), even after continuous exposure to the highest concentrations (100 microM) for 21 days. In order to investigate this lack of antifolate drug effect, we compared the toxicity of continuous MTX exposure in the human colon carcinoma cell line HCT-8, cloned in a thymidineless medium (RPMI 1640) supplemented with 10% horse serum (HS), 10% fetal bovine serum (FBS), 20% FBS or 20% dialyzed FBS. In the presence of native FBS, when the minimum clone size was set at 30 cells/colony, the survival of HCT-8 cells reached a plateau at approximately 60% of untreated control after exposure to MTX concentrations between 0.1 microM and 100 microM. Only when the minimum clone size was set at 2 X 10(3) cells/colony was the sensitivity of HCT-8 cells to the antimetabolite comparable to that obtained in HS or dialyzed FBS (ED50 values in the range of 0.01 microM). MTX protection experiments indicated that even very small concentrations of thymidine and hypoxanthine together were sufficient to reproduce the pattern of sensitivity to MTX observed under culture conditions with undialyzed FBS. We conclude that for a proper evaluation of MTX cytotoxicity in clonogenic assays, dialyzed FBS and thymidine-less media should be employed; if native FBS is an absolute requirement for growth, only very large colonies (at least 10 cell divisions) should be scored.

Adenocarcinoma↗
PubMed1985

Storage of irradiated human blood; a source of error in quantitative chromosome analysis.

Human whole blood was irradiated with 2.5 Gy of 220 k Vp X-rays and stored before culture with 9.7 microM BrdU and 19.4 or 38.7 microM BrdU for 0, 24, 48 and 72 h. The frequency of dicentrics and ring chromosomes was determined in cells staining as first division (M1) metaphases with the fluorescence plus Giemsa technique. Storage had no influence on the observed aberration yields in 44 h cultures containing 9.7 microM BrdU. In 66 h cultures at 19.4 microM BrdU the observed yields after 2 and 3 days' storage were significantly lower as compared to cultures from fresh blood. No storage effect was revealed in 66 h cultures containing 38.7 microM BrdU. In cases where cytogenetic radiation dosimetry has to be carried out using blood samples which have been in transit for 2-3 days, the findings are of relevance for a correct determination of the chromosome damage in M1 cells.

Blood Preservation↗
PubMed1990

Major pitfalls in Doppler investigations with particular reference to the cerebral vascular system. Part I. Sources of error, resulting pitfalls and measures to prevent errors.

Major pitfalls in Doppler investigations are presented based on 340 evaluated cerebral Doppler examinations in infants. Substantial pitfalls may result from: A. Physics of sound waves and Doppler instruments (errors due to high pass filter cut off, aliasing, rapid image update). B. Quality and adjustment of the Doppler instrument (errors due to low sensitivity, inappropriate adjustment of Doppler controls, inadequate wall filter). C. Examination technique (errors due to an unfavourable angle of incidence or due to transducer-induced pressure: decrease predominantly in diastolic flow velocity-increase in maximum flow velocity in the straight sinus). D. Hemodynamics (errors due to spatial or temporal variations of the flow profile, pulsatility, non-uniform distribution of cerebral blood flow/CBF). E. Cerebral vascular anatomy (errors due to an unfavourable probe position as related to the three-dimensional arrangement of vessels, inadequate separation of closely adjacent vessels). F. Interpretation (flow velocity or Resistance Index/RI is taken to equal CBF, RI is taken to equal peripheral vascular resistance, one artery is taken to represent the cerebral circulation). Pitfalls may be avoided by using adequate means (low wall filter adjustment, high Doppler frequency, critical assessment of velocity spectra) to reduce the likelihood of errors occurring.

Adolescent↗
PubMed1976

A potential source of error in the enzymatic diagnosis of the neurolipidoses when radiolabelled sphinogolipids are used as substrates.

High specific activity 3H-labelled glucocerebroside, galactocerebroside and sphingomyelin but not 3H-labelled ceramide, have been found to bind to the wall of glass scintillation vials thereby greatly decreasing the counting efficiency. The binding of the lipids was largely eliminated by counting samples in scintillation fluid containing methanol (6-10%, v/v). To avoid possible errors in the enzymatic diagnosis of the neurolipidoses, it is suggested that the latter solvent should be routinely incorporated into scintillation fluid used for counting labelled sphingolipids.

Ceramides↗
PubMed1978

Pericellular glycosaminoglycans in cultured human cells. A possible source of error in prenatal diagnosis of mucopolysaccharidoses.

Normal fibroblasts and amniotic fluid cells, and cells from patients with Mucopolysaccharidosis type I and II, were cultured in the presence of 35SO4. After harvesting by trypsinization, the radioactivity was recovered from the intracellular and pericellular pool of glycosaminoglycans. The amount of incorporated radioactivity in these respective pools was 1 : 2.3 in normal fibroblasts and 1 : 7.2 in control amniotic fluid cells. Incorporation in the pericellular pool was not elevated in cells from patients with Mucopolysaccharidosis type I and II, in contrast to incorporation in the intracellular pool. Studies on different methods of harvesting showed that reliable prenatal analysis can be performed only if the pericellular pool is removed by trypsinization. Amniotic fluid cells from a pregnancy carrying a fetus affected with Hurler's disease revealed the expected increased level of 35SO4 incorporation if the cells were trypsinized, but the intracellular accumulation of glycosaminoglycans was obscured by the pericellular pool if the cells were harvested by scraping.

Amniotic Fluid↗