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At least 217 records · Page 12Linked to original sources
PubMed1983

Increased left ventricular ejection fraction after a meal: potential source of error in performance of radionuclide angiography.

The effect of a standardized meal on left ventricular (LV) ejection fraction (EF) was determined by equilibrium radionuclide angiography in 16 patients with stable congestive heart failure but without pulmonary or valvular heart disease. LVEF was determined in the fasting state and 15, 30, and 45 minutes after a meal. Patients with moderately depressed fasting LVEF (30 to 50%), Group I, had a mean increase of 6.9 +/- 2.9% (p less than 0.005) in the LVEF at 45 minutes after the meal. Patients with severely depressed fasting LVEF (less than 30%), Group II, had no change after the meal. It is concluded that significant increases in LVEF may occur after meals in patients with moderate but not severe left ventricular dysfunction. Equilibrium radionuclide angiography studies that are not standardized for patients' mealtimes may introduce an important unmeasured variable that will affect the validity of data in serial studies of left ventricular function.

Adult↗
PubMed1978

Measurement of polyadenylic acid by hybridization with polyuridylic acid: a source of error due to the lability of tritiated polyuridylic acid in trichloroacetic acid.

During brief exposure to trichloroacetic acid at 0 degree C, significant amounts of tritiated polyuridylic acid are converted to acid-soluble products. The loss of polymeric radioactivity is dependent on both acid concentration and the time of exposure to acid. When trichloroacetic acid precipitation is used to recover the tritiated polyuridylic acid present in a hybrid with polyadenylic acid, significant underestimates of the hybridized radioactivity can occur because of the lability of tritiated polyuridylic acid. Conditions are given which minimize the lability and permit quantitative recovery of tritiated polyuridylic acid by trichloroacetic acid precipitation.

Chemical Precipitation↗
PubMed1978

Sources of error in the channels ratio method for efficiency determination in liquid scintillation counting.

The reliability of the channels ratio method for determining counting efficiency in liquid scintillation counting was investigated. It was found that the efficiency of counting gels, cloudy samples, two-phase samples, samples in which the radioactive material was precipitating, and samples on solid supports could not be reliably determined from a normal quench correction curve. A curve constructed from external standard channels ratios was unreliable when mixing different vial sizes and sample volumes, but one constructed from sample channels ratios was not. It was also found that variation in instrument performance can result in large errors unless samples and standards are counted together. Statistical error changed relatively little within the range of ratios 0.3 to 0.8.

Carbon Radioisotopes↗
PubMed1984

Cysteine: a potential source of error in amino acid analysis of mercaptoethane sulfonic or hydrochloric acid hydrolysates of proteins and peptides.

Hydrolysis of proteins and peptides with mercaptoethane sulfonic acid is liable to produce overestimation of the proline content owing to the production of ninhydrin-positive material (probably cysteine) which coelutes with proline on many ion-exchange analytical systems. A similar error occurs with HCl hydrolysis (especially in the presence of mercaptoethanol or thioglycollic acid) if care is not taken to oxidize cysteine during reconstitution of the hydrolysate before amino acid analysis.

Amino Acids↗
PubMed1984

Sources of error in estimating radioactivity in protein from cell cultures by liquid scintillation counting.

In this study, several common sample preparation techniques for liquid scintillation counting were critically reviewed. It has been shown that techniques such as NaOH or formic acid solubilization of trichloroacetic acid (TCA)-precipitated proteins led to underestimation of the radioactivity by 20-40%; this loss was not corrected by either internal or external standardization. Hydrolysis of the proteins with 6 N HCl or Pronase significantly increased the recovery of the labeled proteins. Also, 10% of the labeled cell proteins remained on the dish when cells were scraped into buffer; these labelled proteins could be recovered either by in situ hydrolysis with Pronase or by solubilization and scraping in 0.3 N NaOH. These techniques increased the recovered radioactivity by 50-60%, allowing quantitative measurements to be made over a 3-day chase period. A possible mechanism and the implications of this observation were discussed.

Animals↗