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Biomedical subjects

R Schaffer

Publications and source records attributed to R Schaffer.

At least 37 records · Page 2Linked to original sources
PubMed1983

Sonography of tuberculous kidney.

Sonography of 8 patients with renal tuberculosis is reported and collated with 3 additional cases reported in the literature. The patterns of hydronephrosis versus granuloma formation are presented and the differential diagnoses at sonography reviewed.

Diagnosis, Differential↗
PubMed1983

Sonography of vesical and perivesical abnormalities in children.

Pelvic sonograms of 40 children who had abnormalities related to the bladder and perivesical region were reviewed. The lesions detected were categorized into three groups, intramural, intravesical, and perivesical; in each category, conditions not related to vesical or perivesical anomalies that could mimic such anomalies were encountered. Real-time ultrasonography was most helpful in identifying ectopic ureteroceles. Aperistaltic loops of bowel were found to mimic perivesical cysts.

Adolescent↗
PubMed1982

The accurate determination of serum glucose by isotope dilution mass spectrometry--two methods.

Two isotope dilution mass spectrometric methods have been developed for the determination of D-glucose in human serum. Each uses a uniformly labeled (13C)glucose as the internal standard. The first method involves conversion of glucose into 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose and an extensive clean-up, followed by quantitation using packed column gas chromatography mass spectrometry. In the second method, glucose is converted into alpha-D-glucofuranose cyclic 1,2:3,5-bis(butylboronate)-6-acetate. The wet chemistry work-up is simpler, but analysis by capillary gas chromatography mass spectrometry is required. Both methods exhibit excellent precision (coefficients of variation less than 0.3%) and provided mean values that agree within 1% for all serum pools tested.

Blood Glucose↗
PubMed1982

Comparison of two isotope dilution/mass spectrometric methods for determination of total serum cholesterol.

Isotope dilution/mass spectrometric methods for total serum cholesterol, developed separately at the Karolinska Institutet (KI) and the National Bureau of Standards (NBS), were compared by applying them to a common set of serum pools. A search for the cause of a systematic difference of a few percent in results from the two methods revealed that the KI cholesterol standard contained lathosterol, which interfered with the calibration of the method. With NBS Standard Reference Material cholesterol used for new analyses at the KI, the average difference in mean values dropped to 0.2%. The NBS results are more precise. This is attributed to the protocols NBS used for sample preparation and mass spectrometry. However, these protocols make the NBS method more complex and time-consuming. A recent critical article on the use of this technique for total cholesterol is also examined.

Cholesterol↗
PubMed1982

A candidate reference method for uric acid in serum. II. Interlaboratory testing.

We describe the interlaboratory testing of a candidate Reference Method (Part I) for uric acid in serum. The method is based on the ultrasound spectrophotometric quantitation of uric acid before and after incubation with uricase. A comprehensive investigation involving 12 laboratories was organized to document the transferability, intra- and interlaboratory precision, and general reliability of the candidate Reference Method. The interlaboratory CV with this method was about 2 to 6% for uric acid concentrations ranging from 0.12 to 0.60 mmol/L. The results detailed here demonstrate that the method can be successfully duplicated among different laboratories.

Evaluation Studies as Topic↗
PubMed1981

A candidate reference method for determination of total protein in serum. I. Development and validation.

We developed a candidate Reference Method for measuring total serum protein by use of the biuret reaction. The method involves a previously described biuret reagent (Clin. Chem. 21: 1159, 1975) and Standard Reference Material (SRM) 927 bovine albumin (National Bureau of Standards) as the standard. At 25 degrees C, color development for 30 or 60 min provides identical serum protein values. Glucose (up to 10 g/L) and bilirubin (up to 300 mg/L) do not interfere. Hemoglobin, at 3 g/L, increases apparent serum protein by 0.4 g/L. The presence of dextran in serum causes easily detected turbidity, but this interference can be eliminated by centrifuging the reaction mixture. Therapeutic concentrations of ampicillin, carbenicillin, penicillin, oxacillin, nafcillin, chloramphenicol, cephalothin, and methicillin in blood do not interfere, nor do triglycerides up to 10 g/L. Within-run and day-to-day standard deviations of the method are 0.1 and 0.4 g/L, respectively.

Bilirubin↗
PubMed1981

A candidate reference method for determination of total protein in serum. II. Test for transferability.

The transferability of the candidate Reference Method for total serum protein was tested in eight laboratories in the United States and Europe. National Bureau of Standards SRM 927 (bovine serum albumin) was used in each analytical run as the calibration standard. The mean absorptivity value obtained for this material was 0.2983 L g-1 cm-1. Four serum pools prepared at the Centers for Disease Control were analyzed on each of 15 days. Within-run variation of the protein values (expressed as CV) in the eight laboratories ranged from 0.1 to 2.5% and day-to-day (total) variation in six of the laboratories ranged from 0.4 to 1%.

Biuret Reaction↗
PubMed1981

A multilaboratory-evaluated reference method for the determination of serum sodium.

We carried out a statistically designed, multilaboratory study to evaluate a flame atomic emission spectroscopic (FAES) method for serum sodium as a Reference Method. definitive values for the serum pools for the study, with sodium in the 110-160 mmol/L range, were determined at the National Bureau of Standards by an ion-exchange/gravimetry method. The multilaboratory FAES results were judged against the preselected performance criteria for the Reference Method: maximum imprecision 1.5 mmol/L, maximum bias 2.0 mmol/L. The standard error of a single laboratory's performance of the method varied with concentration from 0.46 to 0.86 mmol/L with a maximum bias of 1.0 mmol/L; thus, the criteria were satisfied. The cooperating laboratories performed the method with either manual or semi-automated pipetting. Although both modes of pipetting satisfied our acceptability criteria, only the method with semi-automated pipetting is described here as the Reference Method. The statistical results indicate that the precision criterion can be fulfilled with fewer than four replicate analyses.

Humans↗
PubMed1980

Total serum cholesterol by isotope dilution/mass spectrometry: a candidate definitive method.

We describe a highly accurate and precise method for determination of total cholesterol in serum by isotope dilution/mass spectrometry. The method was developed for a Study Group of the Committee on Standards of the American Association for Clinical Chemistry, for use in establishing the accuracy of a candidate reference method for total cholesterol, and fulfills their criteria for a definitive method. Cholesterol-d7 is added to serum, with the weight ratio of cholesterol-d7 to total serum cholesterol kept near to 1:1. The esters are hydrolyzed and the cholesterol is separated and converted into the trimethylsilyl ether derivative for measurement by combined gas chromatography/mass spectrometry. The intensity ratio of the molecular ions at m/z 465 and 458 is measured for each sample and for two calibration mixtures, according to a prescribed bracketing protocol. A weight ratio for the sample is obtained by linear interpolation of the ion-intensity ratios, and the total cholesterol is then calculated. The method was applied four times over several weeks to each of five serum pools. Statistical analysis involving consideration of both replication error and variability between weeks gave a coefficient of variation for a single measurement of 0.36%. The absence of interferences in the method was demonstrated by measurements at several other masses.

Carbon Radioisotopes↗
PubMed1980

High-purity 4-nitrophenol: purification, characterization, and specifications for use as a spectrophotometric reference material.

We describe specifications for high-purity 4-nitrophenol, which is suitable for spectrophotometric standardization. Such a reference material is needed in clinical enzymology to establish the proper molar absorptivity of 4-nitrophenol under final reaction conditions, particularly for measuring alkaline phosphatase activity in human serum. Some lots of 4-nitrophenol available commercially met these specifications, but several did not. The latter can be purified to meet our specifications by recrystallization or sublimation. The molar absorptivity of 4-nitrophenol (35 mumol/L) IN 10 mmol/L NaOH at 25 degrees C at 401 nm is 18380 +/- 90 L.mol-1.cm-1.

Alkaline Phosphatase↗
PubMed1979

Lactate-to-pyruvate or pyruvate-to-lactate assay for lactate dehydrogenase: a re-examination.

The pyruvate-to-lactate assay for determining lactate dehydrogenase (EC 1.1.1.27) can now yield linearity equal to or better than that obtained by the lactate-to-pyruvate assay. In addition, there are significant advantages to the pyruvate-to-lactate reaction: (a) a greater change in absorbance per unit time, which allows more accurate spectrophotometric readout; (b) lower reactant concentrations are required, which substantially reduces the cost per assay; (c) solid reagents are used to prepare the assay solution; and (d) reagent solutions are more stable. However, impurities present in commercial NADH preparations may substantially affect measured lactated dehydrogenase activities; therefore, a Standard Reference Material for NADH is being developed for issuance by the National Bureau of Standards.

L-Lactate Dehydrogenase↗
PubMed1978

Treatment of experimental cerebral infarction in rats with levodopa or with glycerol.

Administration of large amounts of levodopa did not improve survival rates of rats after acute cerebral infarction induced by injection of carbon microspheres. However, when 10% glycerol was used, the number of rats that survived after cerebral infarction was significantly greater than in the control or in the levodopa-treated rats. Combination of levodopa and glycerol therapy also significantly improved the survival rate of beneficial effect. Pathological findings (gross or microscopic) indicate striking changes in brain tissue after embolization. Development of brain edema of the infarcted left hemisphere corresponded to the type of treatment and to the length of animal survival. Brain-tissue histology indicates that glycerol-treated animals developed less severe edema and had less tissue disruption than control animals. The results suggest that treatment of edema should be one of the primary steps in therapy after acute cerebral infarction.

Animals↗