PubMed Health⌕ Search

Biomedical subjects

K W Ryder

Publications and source records attributed to K W Ryder.

34 records · Page 2Linked to original sources
PubMed1985

Radioimmunoassay for arylsulfatase A in urine.

Purified arylsulfatase A (EC 3.1.6.1) from human urine was radioiodinated under conditions that caused no significant loss of antigenic activity. We used this labeled arylsulfatase A (specific radioactivity 4-7.5 Ci/g) together with nonlabeled enzyme and rabbit antiserum produced against homogeneous enzyme to develop a radioimmunoassay for arylsulfatase A in urine. A solid-phase, second-antibody technique (Immunobead Second Antibody; Bio-Rad Laboratories) was used to separate free enzyme from antigen-antibody complexes. The working range of the assay was 0.1-4.0 ng of enzyme; within- and between-assay CVs were around 10%, and the analytical recovery was 105.5% (SD 7.7%). The lower limit of detection was 0.08 ng of arysulfatase A per assay, substantially less than that of typical activity-based assays. Over a wide range of urinary arylsulfatase A activities, results by this method agreed well (r = 0.99) with those obtained by activity assays. We measured the enzyme in urines of 59 healthy volunteers and 92 patients with different diseases, including a group of colorectal cancer cases, to determine whether this could serve as a reliable marker for cancer of the colon; however, urinary excretion of arylsulfatase A by most patients with colon cancer was within normal limits.

Binding, Competitive↗
PubMed1984

A radioassay for angiotensin converting enzyme.

Current methods for measuring angiotensin converting enzyme activity (EC 3.4.15.1, ACE) are somewhat cumbersome and have limited the general availability of the test. We describe here a simple four-step radioassay for ACE which uses the substrate 14C-Hippurate-L-Histidyl-L-Leucine and measures the product, 14C-Hippurate. We found that incubation at pH 7.0 (Hepes buffer) increased the sensitivity of the test by 50 percent when compared to results obtained with the pH 8.0 buffer normally used for ACE assays. A split sample comparison study between the radioassay and the spectrophotometric method showed good correlation (n = 47; mean, spectrophotometric, 26.0 U/mL; mean, radioassay, 26.1 U/mL; m = 0.86; b = 3.9; r = 0.868). We found that there was no significant difference between the spectrophotometric, kinetic and radioassay (Newman-Keuls multiple range test), but the liquid chromatographic method gave results significantly different from the other methods. The assay for ACE described here combines enhanced technical ease with the sensitivity of a radioassay.

Carbon Radioisotopes↗
PubMed1984

Hyperammonemia after transurethral resection of the prostate: a report of 2 cases.

We report on 2 patients who became deeply comatose after transurethral resection of the prostate. Both patients were severely hyponatremic and hyperammonemic but the course of the comas followed serum ammonia concentrations more closely than serum sodium concentrations. The genitourinary irrigant used in both procedures was a 1.5 per cent glycine solution. Serum amino acid analyses in 1 patient suggested that the postoperative hyperammonemia was due to catabolism of glycine absorbed during surgery. The inadequate activation of normal pathways of ammonia metabolism in this patient may have been caused by a partial deficiency of the urea cycle enzyme argininosuccinate synthetase. We believe that hyperammonemia should be considered as a cause of encephalopathy after transurethral resection of the prostate. The 1.5 per cent glycine genitourinary irrigating solution may not be as nontoxic as generally believed.

Aged↗
PubMed1984

Particle-enhanced turbidimetric inhibition immunoassay for theophylline evaluated with the Du Pont aca.

We evaluated the Du Pont Particle-Enhanced Turbidimetric Inhibition Immunoassay (PETINIA) for theophylline. The imprecision (CV) of the assay was less than 4.7% between-run and less than 3.6% within-run for theophylline concentrations between 5 and 30 mg/L. Standard curves for the assay were linear for theophylline concentrations from 0 to 46 mg/L and were stable throughout the study (i.e., for at least three months). The monoclonal antibody against theophylline used in this assay increases specificity; of the possibly interfering drugs, metabolites, and anticoagulants tested, only 1,3-dimethyluric acid and EDTA showed measurable effects. Bilirubin (less than 300 mg/L), hemoglobin (less than 6 g/L), or lipemia (triglycerides less than 6 g/L) does affect the quality of the assay. Analytical recovery of theophylline added to serum (5 to 40 mg/L) averaged 98% (range 93% to 112%). Comparison of results for patients' sera by the PETINIA method with those by enzyme immunoassay (EMIT) and by "high-performance" liquid chromatography yielded slopes and intercepts not significantly different from 1.0 and 0.0, respectively, and correlation coefficients ranging from 0.986 to 0.995.

Autoanalysis↗
PubMed1984

Inhibition of cholesterol oxidase in a patient with Cushing's syndrome.

Serum from a patient with Cushing's syndrome who was being treated with mitotane contained components that interfered with determination of cholesterol in the Du Pont aca. A measured concentration of cholesterol of 4.19 g/L in the undiluted serum increased to a calculated concentration of 9.50 g/L in diluted serum. Adding additional cholesterol oxidase (EC 1.1.3.6) overcame the reaction inhibition in the undiluted sample; adding additional cholesterol esterase (EC 3.1.1.13) had no effect. There is the potential for clinically significant underestimation of cholesterol with the aca in such patients, because the interference may remain undetected. On the other hand, the aca accurately quantified undiluted specimens containing as much as 10 g of cholesterol per liter when mitotane was not present.

3-Hydroxysteroid Dehydrogenases↗
PubMed1983

Serum angiotensin converting enzyme activity in patients with histoplasmosis.

The association between increased serum angiotensin converting enzyme (ACE) activity and active sarcoidosis is well documented. During a recent outbreak of acute histoplasmosis, a disease that shares many of the clinical and roentgenographic features of sarcoidosis, we examined serum ACE activity. Twenty-one (25%) of 86 patients with histoplasmosis had increased serum ACE activity. There were neither roentgenographic nor other substantive clinical differences between the groups of patients with increased and normal ACE values. Therefore, an increase in serum ACE activity must not be assumed to be caused by sarcoidosis unless histoplasmosis had been excluded.

Acute Disease↗
PubMed1983

An evaluation of four serum tests for pregnancy.

We evaluated four pregnancy tests (Biocept-G, Beta-CG, Preg/Stat, and HCG-Beta Screen), using sera from 59 nonpregnant subjects and 77 patients with serum human choriogonadotropin beta-subunit (beta-hCG) concentrations ranging from 4 to 100 000 int. units/L. The results obtained for each test were compared with the results predicted on the basis of the sample's beta-hCG concentration and the beta-hCG concentration the manufacturer claimed necessary for a positive result (the test's analytical sensitivity). Biocept-G had the best sensitivity (100%), specificity (98.9%), and accuracy (99.2%). Beta-CG had the poorest sensitivity (86.4%), Preg/Stat the poorest specificity (87.5%), and accuracy (92.6%). We confirmed the manufacturer's claimed analytical sensitivity (200 int. units/L) for the Biocept-G procedure, but our calculated analytical sensitivity for the other tests was significantly different from that claimed by their manufacturers. Best results were obtained with Biocept-G, but with its analytical sensitivity of 200 int. units/L, samples from early pregnancy will give negative results. None of the pregnancy tests evaluated here will establish the presence or absence of early pregnancy with certainty.

Chorionic Gonadotropin↗
PubMed1983

Five recent urinary tests for early pregnancy evaluated.

We evaluate five tests developed for the earlier detection of pregnancy, either in the clinical laboratory or by the patient in her home. These tests offer no advantage over other urinary pregnancy tests, and the results are distinctly inferior to those reported (Clin. Chem. 29: 561-563, 1983) for some serum tests for pregnancy.

Chorionic Gonadotropin↗
PubMed1981

Characterization of a spectrophotometric assay for angiotensin converting enzyme.

Although serum angiotensin converting enzyme (EC 3.4.15.1) activity has generally been shown to be increased in patients with sarcoidosis, considerable variation in the diagnostic usefulness of this test has been reported. We investigated the possibility that this variation may be the result of inhibition of the widely used spectrophotometric assay by various substances. We also prospectively examined the predictive value of measurements of this enzyme in serum from 100 patients being evaluated for sarcoidosis. The following did not significantly affect the results: storage at 4 or 25 degrees C for one week, hemoglobin, lipoproteins, or corticosteroid medications. Bilirubin, at concentrations of 20 mg/L of serum or move, significantly inhibited the assay. Sera with increased activity showed nonlinear reaction rates during the usual 60-min reaction interval, This was corrected by shortening the reaction time to 30 min. We found a predictive value of 88% when the serum angiotensin converting enzyme test was applied to the diagnosis of active sarcoidosis.

Acetylcholinesterase↗
PubMed1975

Serum calcium and hepatic Kupffer cell phagocytosis.

Serum calcium can markedly influence the phagocytic activity of the hepatic Kupffer cell. Specifically, depletion of calcium by chelator induced impairment of phagocytosis but elevation of serum calcium levels above normal leads to a progressive inhibition of phagocytosis. The findings suggest that alterations of serum calcium may induce significant R.E.S. functional changes which may produce a state of altered host resistance. The relationship of these observation to disturbances of the macrophage system during mealignancy, which is known for its ability to alter dramatically the serum calcium concentration warrants further investigation.

Animals↗