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W H Porter

Publications and source records attributed to W H Porter.

32 records · Page 2Linked to original sources
PubMed1986

Measurement of alpha-glucosidase activity in serum from patients with cystic fibrosis or pancreatitis.

We measured the activity of a non-lysosomal alpha-glucosidase with pH optimum near 6.0 in serum from a wide variety of patients, using the fluorogenic substrate, 4-methylumbelliferyl-alpha-D-glucopyranoside. Acutely ill patients with cystic fibrosis (CF) demonstrated significant increases in alpha-glucosidase compared with CF outpatients. The former group of CF patients experienced far more severe chronic pulmonary disease than did the latter, whereas both groups had similar degrees of gastrointestinal impairment. Patients with pancreatitis associated with trauma or complicated by severe necrosis, hemorrhage, or abscess also displayed greater increases in alpha-glucosidase than did patients with uncomplicated (edematous) pancreatitis. For CF outpatients and patients with either edematous pancreatitis or pancreatic cancer, the alpha-glucosidase activity was similar to that for the general hospital-patient population. Corresponding changes were not observed for other measured serum glycosidases (alpha-fucosidase, alpha-mannosidase, beta-glucuronidase, beta-N-acetylglucosaminidase). Measurement of serum alpha-glucosidase may be of value in assessing the clinical course in CF and in differentiating necrotizing from edematous pancreatitis.

Adolescent↗
PubMed1984

Effect of protein concentration on the determination of digoxin in serum by fluorescence polarization immunoassay.

Determination of digoxin by fluorescence polarization immunoassay (FPIA) with the Abbott "TDx" is significantly influenced by the concentration of total serum protein. Each 10 g/L increase in serum protein results in an 8% decrease in measured digoxin. Studies with [3H]digoxin confirmed that digoxin binds to the protein pellet during the trichloroacetic acid precipitation step before the immunoassay. Serum protein, or equal concentrations of albumin or gamma-globulin, exert an equivalent effect on the apparent digoxin value. Because the total protein concentration of the assay calibrators is low (50 g/L) compared with its reference interval in serum (60-80 g/L), results by FPIA may be expected to be low by an average of 16% (range, 8-24%). Digoxin results by FPIA will be most nearly accurate when the calibrators include a total protein concentration of about 70 g/L. Patients' specimens with abnormally high or low protein content will give falsely high or low results for digoxin.

Blood Proteins↗
PubMed1982

Gas-chromatographic determination of ethylene glycol in serum.

We describe a new gas-chromatographic procedure for ethylene glycol in serum, determined as the cyclic phenylboronate ester. The method is rapid, requires only 100 microL of serum, and either an OV-1 or an OV-17 column is used. The linear dynamic range extends to at least 5000 mg/L, with a lower limit of detection of 10 mg/L. Analytical recovery of ethylene glycol from serum averaged 97% (95-101%) over the concentration range of 250-5000 mg/L. The method demonstrates good precision, with CVs less than 2.5%, over the concentration range 500-2000 mg/L.

Chromatography, Gas↗
PubMed1978

Enzyme-coupled ultraviolet determination of alpha-amylase activity with the GEMSAEC centrifugal analyzer.

We evaluated the Harleco alpha-glucosidase/hexokinase/glucose-6-phosphate dehydrogenase-coupled alpha-amylase method, bu use of the GEMSAEC centrifugal analyzer. Performance evaluation included kinetic studies of substrate and maltose hydrolysis as well as effects of endogenous glucose and fructose. The reagent was found to give a linear response with alpha-amylase activity to greater than 1200 U/liter. Within-run precision resulted in coefficients of variation (CV) of 0.9 to 3.2% over the range studied. Day-to-day precision corresponded to CV's of 2.4 to 4.4% over the same range of alpha-amylase procedure was found to be good (r = 0.997) for patients' sera examined.

Amylases↗
PubMed1977

Hemoglobin interference with Du Pont Automatic Clinical Analyzer procedure for calcium.

Hemoglobin in concentrations of approximately 2.5 g/liter or greater significantly increases values for apparent calcium in serum as determined with the Du Pont aca, an interference attributable to the 575-nm absorption band of oxyhemoglobin being uncompensated by the 577--600 nm differential absorption reading of the calcium o-cresolphthalein complexone complex.

Autoanalysis↗
PubMedDate not supplied

High-resolution proton nuclear magnetic resonance spectroscopy in the detection and quantitation of ethanol in human serum.

A precise, accurate, and nondestructive method for the detection and quantitation of serum ethanol in humans using proton (1H) nuclear magnetic resonance spectroscopy (MRS) was developed. The 1H MRS method was linear within the range of 30-1500 mg/L. The lowest detectable ethanol concentration was 15 mg/L, with 30 mg/L being the lowest level reproducibly quantitated. Within-run and day-to-day coefficients of variation (CV) ranged from 0.6 to 2.7% and 0.5 to 3.5%, respectively. The excellent day-to-day CVs indicate a negligible loss of ethanol due to volatilization during analysis. Fifteen human serum samples found to be negative for ethanol by headspace gas chromatography (HSGC) had no ethanol as detected by 1H MRS. Twenty-eight human serum samples with ethanol concentrations (determined by HSGC) ranging from 370 to 4440 mg/L were accurately reproduced by 1H MRS. The 1H MRS method required no pretreatment and was nondestructive, thereby allowing for further analysis by confirmatory methods.

Ethanol↗
PubMedDate not supplied

Simultaneous determination of ethylene glycol and glycolic acid in serum by gas chromatography-mass spectrometry.

We describe a gas chromatographic-mass spectrometric (GC-MS) procedure for the simultaneous determination of ethylene glycol (EG) and its major toxic metabolite, glycolic acid (GA), in serum. In this method, serum (50 microL) is treated with 150 microL of glacial acetic acid/acetonitrile (1:10, v/v; contains internal standard, 1,3-propanediol, 15 mg/dL) to precipitate protein. After centrifugation, 10 microL of supernate is treated with 500 microL of 2,2-dimethoxypropane/dimethylformamide (80:20, v/v) to convert water to methanol, and the volume is then reduced to < 100 microL of dimethylformamide (but not to dryness). After formation of tertbutyldimethylsilyl derivatives, analysis is performed by capillary column GC-MS in selected ion mode. The method gives a linear response to 1000 mg/L each EG and GA (16.1 mmol/L and 13.2 mmol/L, respectively) and has a lower limit of detection and a lower limit of quantitation of 10 mg/L each EG and GA (0.16 mmol/L and 0.13 mmol/L, respectively). Total assay imprecision is CV < or = 6.4% (200 and 800 mg/L EG and GA [3.2 and 12.9 mmol/L EG; 2.6 and 10.5 mmol/L GA, respectively]). Absolute recovery from human serum was 91.1% for EG and 77.6% for GA. The procedure is free from any known interference. A complete analysis set (three calibrators, patient serum neat, patient serum diluted 1:5 (v/v), and two controls) may be completed in about 2 h. A preliminary result, based on a single calibrator and patient serum diluted 1:5 (v/v), is complete in about 1 h. The method has been used to aid the diagnosis and management in 34 cases of EG intoxication. Selected cases are briefly reviewed.

Ethylene Glycol↗
PubMedDate not supplied

Severe phenytoin intoxication as a result of altered protein binding in AIDS.

Alterations in plasma protein binding may alter patient response to pharmaceutical agents because only free drug is considered to be pharmacologically active. Such alterations appear to be more significant with highly bound agents such as phenytoin. Traditionally, most drug assays monitor total drug concentrations and do not quantitate free drug. When binding alterations are present, total drug concentrations may mislead clinicians in evaluating patient response. We describe a case in which profound hypoalbuminemia (0.2 g/dL), associated with focal segmental glomerulosclerosis, produced toxic free phenytoin concentrations (4.9 micrograms/mL) in an HIV-positive 25-year-old black woman. At such a high serum concentration of free phenytoin, the patient exhibited seizure-like effects. Renal abnormalities and hypoalbuminemia associated with acquired immunodeficiency syndrome (AIDS) may place patients at risk for elevated free fractions of phenytoin and subsequent toxicity.

Acquired Immunodeficiency Syndrome↗