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D F Shuey

Publications and source records attributed to D F Shuey.

8 recordsLinked to original sources
PubMed1993

Lipase in serum--the elusive enzyme: an overview.

Lipase is a glycoprotein with 420-449 amino acid residues and a M(r) of 46,000-56,000 for pancreatic lipase and 32,000-39,000 for serum lipase. Lipase is present in the pancreas, intestines, and a variety of other tissues. The concentration gradient between pancreatic tissue and serum lipase is approximately 20,000-fold. Serine, as part of an Asp-His-Ser triad, is the nucleophilic residue essential for catalysis. Lipase differs from other esterases by the presence of a hydrophobic recognition site. The optimal pH is between 7.5 and 10.0, depending on the reaction condition; the pI for the various forms of the enzyme has been reported as 5.80 and 5.85; 6.4, 6.8, and 7.0; and 7.4 for a purified fraction. Several authors report the presence of two molecular forms in the pancreas and three electrophoretic bands with lipolytic activity. In normal serum two bands have been observed; in pancreatitis as many as four bands have been seen. Lipolytic activity may not always be due to lipase. Assays specific for lipase require a triglyceride as substrate as well as the presence of colipase (a water-soluble and heat-stable protein, essential for lipase action), a secondary bile salt, and Ca2+. The clinical sensitivity of all modern assays is high because of selection of a low decision limit; the clinical specificity varies greatly but can be improved by increasing the cutoff point. Lipase determinations in pancreatitis are superior to amylase determinations. The reasons for the great variability of reports regarding the clinical utility of lipase are discussed, and the clinical utility of lipase determinations is summarized.

Chemical Phenomena↗
PubMed1992

Laboratory values in fit aging individuals--sexagenarians through centenarians.

We determined approximately 15,000 laboratory values in 236 individuals between the ages of 60 and 90 y, 22 individuals between 90 and 99 y, and 69 individuals greater than or equal to 100 y, and compared these with values in young adults. We tested 47 different analytes in the 60-90-y group and 93 analytes in the greater than or equal to 90-y group. Na, K, Cl, and CO2 values were either identical or showed minimal change with age; pH decreased slightly. Differences in Ca values were only minor, but ionized Ca increased slightly. Phosphate decreased in men, but changed only minimally in women; parathyroid hormone increased with age. Increases with age were also observed for glucose, insulin, and C-peptide. Among the enzymes, alkaline phosphatase increased in women, but in men only greater than 90 y; gamma-glutamyltransferase increased in both sexes. Creatine kinase (CK) decreased slightly in individuals greater than 70 y and markedly in those greater than 90 y of age, whereas CK-MB decreased markedly greater than 70 y, reaching the detection limit in individuals greater than 90 y. Lactate dehydrogenase isoenzyme 5 decreased slightly with age. Urea nitrogen increased gradually with age, but creatinine increased only in individuals greater than or equal to 90 y. The increase in urea is not paralleled by a loss of protein in urine, suggesting that the possible cause of azotemia may not always be renal pathology. Urate increased in women but not in men. Liver function, as measured by total bilirubin and liver enzymes, was exceedingly well maintained. Concentrations of most proteins show little change, except for slight decreases in prealbumin, albumin, and transferrin, proteins used as an index of nutritional status. IgA values increased, IgG ranges were wider, IgM and IgD decreased, and the range for IgE was narrower than in young adults. Cholesterol, high-density lipoprotein cholesterol, and triglyceride values increased with age, but decreased in individuals greater than or equal to 90 y. Among the trace elements, magnesium changed little, zinc and lead decreased, and copper values increased with age. Total triiodothyronine and thyroxine decreased, with concomitant increases in thyroid-stimulating hormone. More individuals had increased microsomal antibodies and thyroglobulin titers in the aging population than in the young. In men, the free, percent free, bioactive, and total testosterone values decreased, but luteinizing hormone (LH) and follicle-stimulating hormone (FSH) values increased. In women, estrone and estradiol values decreased, with concomitant increases in LH and FSH. Androstenedione and progesterone decreased in both sexes.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Lipase activity measured in serum by a continuous-monitoring pH-Stat technique--an update.

Using recent knowledge regarding the roles of colipase, bile acids, Ca2+, and emulsifiers, we optimized a previously published pH-Stat method for lipase (EC 3.1.1.3) activity measurements. The recommended assay conditions are: olive oil/triolein, 100 mL/L; sodium glycocholate, 35 mmol/L; Ca2+, 8.5 mmol/L; and colipase, 6.0 mg/L. The sample volume is 0.10 mL, the reaction pH 9.0, the temperature 30 degrees C, and the concentration of titrant 15 mmol/L. Hydroxypropyl methylcellulose, 20 g/L, replaces acacia as emulsifier to avoid inhibition by excess Ca2+. The standard curve is linear to greater than 4566 U/L. The reference interval with olive oil as substrate is 30-235 U/L. Lipase activities with triolein substrate are 9.9% greater than with olive oil. Interference by pancreatic carboxylesterase (EC 3.1.1.1) activity is inhibited by incubating the sample with diisopropylfluorophosphate. Results correlate well with those by the optimized SingleVial method of Boehringer Mannheim Diagnostics (r = 0.997) and the immunochemical assay of Beckman Instruments, Inc. (r = 0.995). Correlation with the aca method (E.I. DuPont de Nemours & Company) is less satisfactory (r = 0.892), probably owing to lack of colipase in the latter method.

Adult↗
PubMed1987

Turbidimetric measurement of lipase activity--problems and some solutions.

We optimized a commercial turbidimetric method for lipase (EC 3.1.1.3) activity (Boehringer Mannheim Diagnostics) and overcame some of its deficiencies. Increasing the bile salt concentration to 35 mmol/L and the colipase concentration to 6 mg/L and using a continuous recording of the reaction-rate curve greatly improved the reaction kinetics, eliminated false results from increases in absorbance, reduced the lag phase, and increased the analytical sensitivity and accuracy. Differentiation of pancreatitis from nonpancreatitis sera by adding NaCl, 140 mmol/L, to the assay mixture to observe the degree of enzyme activation has important limitations. Sera from patients with pancreatitis and only slight or modest increases in lipase behave like sera from healthy individuals or from patients with nonpancreatic disease. The assay shows no interference by lipoprotein lipase and carboxyl esterase. Results compare well by this optimized method and by an optimized "pH-Stat" titrimetric method.

Adult↗
PubMed1986

Laboratory tests in the differential diagnosis of hyperamylasemia.

We evaluated the clinical utility of some recently developed laboratory methods, including total amylase by three methods; isoamylase by inhibition and isoelectric focusing; lipase by pH-Stat and turbidimetry; and immunoreactive trypsin. All methods correlated highly positively with hyperamylasemia due to primary acute pancreatitis. Pancreatic-type isoamylase determinations have the greatest clinical usefulness, because total amylase, lipase, and immunoreactive trypsin are increased in a relatively high percentage of other abdominal diseases. Increases in the last-mentioned enzymes in nonpancreatic abdominal disease may be the result of injuries to the pancreas secondary to the primary disease, which are being detected with these highly sensitive methods. Because of the high clinical sensitivity of lipase and immunoreactive trypsin determinations, a normal result tends to exclude acute pancreatitis. Hyperamylasemia seen in lung carcinoma is due to increase in an amylase isoenzyme similar to the salivary-type amylase. The method for pancreatic-type isoamylase based on selective inhibition is satisfactory for routine clinical laboratory use.

Amylases↗
PubMed1984

A two-year longitudinal reference range study for selected serum enzymes in a population more than 60 years of age.

The reference ranges for alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatine kinase (CK) in a population greater than 60 years were studied using commercially available reagents. All ranges except those for AST and ALT in women were higher than the ranges found in 20-50-year-old adults. A two-year longitudinal study indicated that individuals who had values above those found in younger adults did not show a greater incidence of disease than did individuals who had values in the lower portion of the distribution curve. Comparison of enzyme values at the beginning and at the end of the two-year study showed that mean ALP, AST, ALT, and LDH values (except for ALT values in men) increased gradually. It was concluded from these two findings that the higher values observed for the aging population were a result of the normal aging process, and thus these values were included in the reference range for this population. The range for CK in individuals greater than 60 years was also higher than that found for younger adults, but the mean value of the group was lower, except in women aged 60-69 years, in whom the mean value showed a slight increase over that found for normal adult women. This was believed to be the result of two independent processes; an increase in enzyme activity due to aging and a decrease in enzyme activity due to reduction in muscle mass as a result of the decreased muscular activity of some volunteers during retirement.

Adult↗
PubMed1984

A commercially available S-type amylase inhibitor evaluated for determination of amylase isoenzymes in serum.

On evaluation, an S-type alpha-amylase inhibitor from Sigma shows essentially the same performance characteristics as the inhibitor from wheat germ prepared according to O'Donnell and McGeeney (Biochim Biophys Acta 422:159, 1976). This inhibitor is now commercially available; thus any clinical laboratory can perform isoamylase determinations with a simple, fast procedure that is also suitable for emergency situations.

Amylases↗