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K O Ash

Publications and source records attributed to K O Ash.

At least 73 records · Page 4Linked to original sources
PubMed1982

A reproducible sodium-lithium countertransport assay: the outcome of changing key laboratory parameters.

This paper describes experimental conditions for reproducible measurement of sodium-lithium countertransport in red blood cells. The assay is sensitive to temperature (10% per degree C) and the condition of the red cells; it is affected little by changes in intracellular lithium over the range 2-7 mmol/1 or by red cell concentrations with laboratory hematocrits of 0.03 to 0.07. Repeated measurements of the same subjects give day-to-day coefficients of variation of 10% or less. The mean difference for interlaboratory comparisons is 11%.

Biological Transport↗
PubMed1982

A kinetic expression for sodium-lithium countertransport in human red cells.

Sodium-lithium counter-transport in human red blood cells may be a potentially useful measurement in studies of hypertension. A kinetic expression describing this counter-transport was derived and evaluated using red cells from nine subjects at various concentrations of intracellular and extracellular Li+ and Na+. The countertransport is dependent upon all four concentrations, intracellular Li+ and Na+ as well as extracellular Li+ and Na+. We confirm that the maximum Na+-Li+ counter-transport (Vmax) is a property of the individual cells while the half-maximal saturating concentrations (K 1/2) for Li+ and Na+ are the same for all subjects. This expression permits a more thorough understanding of conditions affecting Na+-Li+ countertransport measurement.

Biological Transport↗
PubMed1980

Reserve bilirubin binding capacity assessed by difference spectroscopy: assay statistics and results on newborn sera.

Bilirubin binding properties of newborn sera and assay parameters have been investigated using a difference spectroscopy procedure [9]. Reserve bilirubin binding capacity, serum bilirubin and the total bilirubin binding capacity can be determined using only 40 microliters of serum. The measured total binding capacities agreed with the theoretical binding capacities calculated from serum albumin concentrations assuming a 1 : 1 molar binding ratio of bilirubin to albumin; in 102 assays on newborn sera, the ratio of experimental to theoretical total binding capacity was 1.04. Bilirubin binding capacity measurements were linear over the range 0--600 mg/l. Day to day precision of binding capacity determinations on 6 albumin controls yielded coefficients of variation between 4.1 and 7.2%. Recovery for the reserve bilirubin binding capacity determinations was 99.6%. In a study of 22 newborns, reserve bilirubin binding capacities showed an inverse relationship with the changes in serum bilirubin concentrations. None of the newborns included in our study appeared to be in dange of bilirubin encephalopathy.

Bilirubin↗
PubMed1980

Reference intervals (normal ranges): a challenge to laboratorians.

Interpretation of laboratory data depends on comparison of individual patient results with reference information from three sources: literature reports, previous results from the patient, and studies conducted in one's own laboratory. Reference data are commonly generated by analyzing specimens from readily available "healthy" subjects, and the results are often used to derive reference intervals which are then given the confusing designation "normal ranges". This paper includes: a review of current practices, recommendations for immediate improvements, and suggestions of future improvements. As acceptable accuracy and precision are established, it will be possible to develop an interlaboratory reference data base. With the developing potential for computer communications, each laboratory could provide reference information relevant to the individual patient, ie, age, sex, body weight, posture, race, diet, physical activity, etc. Not only will reference data be available on "healthy" subjects, but it will be possible to compare patient data with reference intervals associated with specific diseases.

Age Factors↗
PubMed1979

Manual fluorometry of phenylalanine from blood specimens collected on filter paper: a modified procedure.

In this manual fluorometric method, blood samples are used that have been impregnated on the filter paper, a convenient collection technique that is widely used to screen newborns for phenylketonuria. The modified procedure, based on the method of McCaman and Robins [J. Lab Clin. Med. 59, 885 (1962)], includes elution of phenylalanine from specimens on filter paper, removal of proteins by precipitation with trichloroacetic acid at 0 degrees C, and then reaction with ninhydrin-peptide reagent for color development. The standard curve is linear to at least 200 mg/L and the CV is 6.3% for a phenylalanine concentration of 27 mg/L. The modified procedure is suitable both for early screening for phenylketonuria and for monitoring blood phenylalanine of phenylketonurics during dietary therapy.

Blood Specimen Collection↗
PubMed1978

High-density lipoproteins estimated by an enzymatic cholesterol procedure, with a centrifugal analyzer.

We describe an assay for high-density lipoprotein cholesterol, adapted to a centrifugal analyzer, the GEMSAEC System 3, which includes use of an increased Mn2+concentration (91 mmol/liter) [J. Lipid Res. 19, 65 (1978)] and ethylenediaminetetraacetate [Clin. Chem. 22, 98 (1976)]. Modifications to the GEMSAEC system include reducing the mixing burst and preconditioning the sample tip. Accuracy of this procedure, as assessed by analysis of a control pool from the Center for Disease Control, was 99.2%. Day-to-day precision for two control pools was 320 +/- 13 and 506 +/- 17 mg/liter. Serum sample volume was decreased to 0.5 ml. In blanks with heparin/Mn2+ present, the pseudocholesterol concentrations resulting from a reaction of the enzymatic cholesterol reagent and the heparin/Mn2+ precipitating reagent depend on the source of the enzymatic reagent and appear to be enhanced slightly by the use of ethylenediaminetetraacetate. Pseudocholesterol concentrations reach a maximum at heparin/Mn2+ concentrations well below those needed to completely precipitate the low-density and very-low-density lipoprotein fractions. Population reference values were obtained from analyses done on 224 local physicians (mean: male, 500 mg/liter; female, 620 mg/liter) and 156 ambulatory patients (mean: male, 463 mg/liter; female, 553 mg/liter).

Autoanalysis↗
PubMed1978

A protocol for the adoption of analytical methods in the clinical chemistry laboratory.

The demand on the clinical chemistry service laboratory to continually adopt more precise and accurate methodologies makes it mandatory for the service laboratory to have a systematic protocol for evaluating and adopting new assay methods. A protocol is presented for adopting clinical chemistry methods in the service laboratory, with emphasis on spectrophotometric determinations. The recommended protocol may be used to evaluate alternate procedures to those currently in use as well as procedures for additional analytes. We present those critical points to be considered in method adoption and instruction for the resolution of each point.

Chemistry Techniques, Analytical↗
PubMed1978

Effect of evaporation from sample cups on urea nitrogen assay.

The effects of evaporation from sample cups for urea nitrogen assays were determined. Thirty replicate analyses were performed on each of five groups of pooled human serum subjected to controlled evaporation in our laboratory. We found a mean increase in urea nitrogen concentration of one percent per hour due to evaporation. We urge laboratory personnel to take the action necessary to minimize errors due to evaporation. Specimens should always be capped while awaiting analysis in the laboratory.

Blood Urea Nitrogen↗
PubMed1978

Gas-chromatographic method for plasma acetate analysis in acetate-intolerance studies.

We describe a modified gas-chromatographic method for acetate in serum or plasma, intended for use in the investigation of acetate intolerance in hemodialysis patients. The assay may be adapted for use with a single-column gas chromatograph equipped with a flame ionization detector. The analysis, made isothermally, requires only 0.5 ml of plasma or serum. Only one deproteinizing step is required to prepare the sample for analysis. Additionally, we present preliminary findings of an ongoing acetate-intolerance study.

Acetates↗
PubMed1978

Bilirubin-protein interactions monitored by difference spectroscopy.

Difference spectroscopy is used to monitor bilirubin-protein interactions, to assess the residual binding capacity of proteins for bilirubin. A change in the difference spectra monitored at 482 nm is directly proportional to bound bilirubin up to a molar ratio of bilirubin to albumin of approximately 1; increasing bilirubin beyond the 1:1 molar ratio does not further change the difference spectra. After excess free bilirubin is added, the change in the difference spectrum is proportional to the residual binding capacity of the serum for bilirubin. The risk of kernicterus among neonates may be assessed by monitoring the residual bilirubin binding capacity of serum. This report summarizes our research effort leading to an assay method which requires only 40 microliter of serum and can be completed in less than 10 min.

Adult↗
PubMed1978

Modified micro-scale enzymatic method for plasma ammonia in newborn and pediatric patients; comparison with a modified cation-exchange procedure.

We modified two "kit" procedures for plasma ammonia to make them suitable for use with newborn and pediatric patients. Available methods either require too large a specimen, are insufficiently sensitive in the normal range, or are too cumbersome. One was an enzymatic (Sigma Chemical Co., St. Louis, Mo. 63178), the other a cation-exchange (Hyland, Costa Mesa, Calif. 92626) method. The modified micro-scale enzymatic method requires 100 microliter of plasma (CV at 38 micronmol/liter, 8%). Reagent costs per patient assay, including controls and standards, are currently $0.53. An assay run can be completed in 30 min. The modified cation-exchange method requires 200 microliter of plasma; the within-run CV is 12% for a concentration of 34.2 micronmol/liter. Reagents currently cost $0.74 per assay and each run requires less than 2 h to complete. The correlation coefficient for the two methods was 0.98.

Ammonia↗
PubMed1969

Ascorbic acid: cofactor in rabbit olfactory preparations.

A stimulant-induced decrease in absorbance at 267 nanometers in preparations from rabbit olfactory epithelium requires ascorbic acid as a cofactor. Vitamin C is bound to proteins in the olfactory mucosa in vivo. When the stimulant. 3,7-dimethyl-6-octen-3-ol interacts with olfactory proteins, it triggers a change in protein conformation which renders ascorbic acid available for oxidation. The specific decrease in absorbance at 267 nanometers is produced when the "freed" ascorbic acid is oxidized.

Animals↗