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F Van Lente

Publications and source records attributed to F Van Lente.

At least 37 records · Page 2Linked to original sources
PubMed1994

Alteration of hydroxylapatite coatings exposed to chemicals used in histological fixation.

Histological evaluation of retrieved devices allows for assessment of the biological response to the implants. Interaction between the biomaterial and the fluids used in the processing may alter the appearance or composition of the device. This may result in artifacts due to processing which are misinterpreted as being caused by the biological response. Alteration by the fluids used in fixation may be particularly important with materials that have a propensity to interact with aqueous environments, as in the case of calcium phosphate ceramics. Therefore, we examined the effects of various standard histological fixation techniques on hydroxylapatite coated metal implants. Of the techniques examined, fixation with ethanol appeared to affect the surface morphology the least, whereas fixation in unbuffered formalin appeared to affect the bulk composition of these samples the least. Fixation in buffered formalin resulted in marked changes in both surface morphology and bulk composition.

Adhesiveness↗
PubMed1994

Characterization of calcium phosphate powders by ESCA and EDXA.

Calcium phosphate (CaP) materials can be well characterized by traditional methods such as wet chemistry and X-ray diffraction (XRD). These methods, however, offer limitations when non-destructive evaluation of CaP coatings on curved surfaces is required. Since the source powders for these coatings are generally commercially available CaP powders, careful characterization of the source powders may allow inferences to be made regarding the effects of plasma spraying on coating composition. Nine commercially available CaP powders were characterized by scanning electron microscopy, wet chemistry and XRD. These techniques showed that major differences exist between individual powders claiming to be hydroxyapatite. Analysis of these nine powders by electron spectroscopy for chemical analysis (ESCA) and energy dispersive X-ray analysis (EDXA) suggest that these techniques can provide the chemical composition of CaP in a non-destructive manner and thus may be of use in determining the composition of CaP in configurations (such as coatings on metal surfaces) not readily amenable to traditional methods. A calibration curve is required, however, to relate this surface chemical composition result to the material's bulk composition as determined by wet chemistry analysis. Errors of less than 10% can be obtained using ESCA and EDXA. These studies suggest that non-destructive chemical composition evaluation by EDXA and ESCA may also be applicable to CaP coatings.

Calcium Phosphates↗
PubMed1994

Serum lipid changes associated with modified protein diets: results from the feasibility phase of the Modification of Diet in Renal Disease Study.

The use of low-protein diets for the management of progressive renal insufficiency may require increases in dietary fats to maintain caloric balance. This raises the concern that such diets might exacerbate the lipid problems already prevalent in chronic renal insufficiency. We present a study in which protein-restricted diets were followed by a group of patients with renal insufficiency without a compensatory increase in fat calories and without adverse effects on serum lipids. Ninety-six patients with renal insufficiency were enrolled in the feasibility phase of the Modification of Diet in Renal Disease Study and were assigned to dietary protein intakes of 1.3, 0.575, or 0.28 g/kg body weight/d. The last diet was supplemented with amino acids or their keto analogs. Of this group, 25 participants were excluded from the present study of lipids because of changes in their intake of medications with known effects on serum lipids, three were excluded because of proteinuria increasing by more than 2 g/d, and seven were excluded because of incomplete measurements. For the remaining 61 participants, median serum total cholesterol at baseline was 215 mg/dL. In 72% of participants it exceeded the age- and sex-adjusted median of the Lipid Research Clinics Prevalence Study. Glomerular filtration rates varied from 8 to 56 mL/min/1.73 m2. The patients' serum lipid levels were stable by 6 months on assigned diets. Serum total and low-density lipoprotein cholesterol levels tended to decrease with reduced protein intake. The baseline to follow-up change in protein intake calculated from urinary urea measurements was significantly correlated with the change in serum total cholesterol (Spearman r = 0.31, P < 0.05) and also with change in low-density lipoprotein cholesterol (r = 0.34, P < 0.01). Surprisingly, correlations between change in serum cholesterol and intake of fats were small in magnitude and did not approach statistical significance. Protein intake did correlate, however, with intake of cholesterol. We conclude that the use of low-protein diets for patients with renal insufficiency did not adversely affect serum lipids.

Adolescent↗
PubMed1994

Vitamin E compared with other potential risk factor concentrations in patients with and without coronary artery disease: a case-matched study.

Thirty six individuals with angiographic evidence of coronary atherosclerosis and thirty six individuals without coronary disease, matched for a variety of cardiovascular risk factors including age, sex, smoking, hypertension, diabetes and family history, were evaluated for their serum concentrations of vitamin E, total cholesterol, triacylglycerols, high density lipoprotein-cholesterol, low density lipoprotein-cholesterol, apolipoprotein A-I, and apolipoprotein B. Apolipoprotein B, low density lipoprotein-cholesterol and total cholesterol concentrations were unequivocally higher in patients with coronary artery disease. Triacylglycerols were marginally higher in patients with disease. The antioxidant vitamin E (alpha-tocopherol) was significantly higher in patients with atherosclerosis when compared with controls (35.1 +/- 17.0 mumol/l vs. 29.0 +/- 13.2 mumol/l, p = 0.017). However, alpha-tocopherol concentrations were strongly associated with lipid concentrations and normalization to the total cholesterol concentrations produced ratios which were not significantly different in the two groups. Logistic regression analysis revealed that the association of lipid risk factors with coronary stenosis was determined primarily by the difference in total cholesterol values. This study demonstrated that in this group of patients referred for angiography and matched for other risk factors, higher alpha-tocopherol concentrations were associated with patients with coronary disease and were not useful for assessing risk of coronary artery disease.

Adult↗
PubMed1994

Concanavalin A-bound selenoprotein in human serum analyzed by graphite furnace atomic absorption spectrometry.

We developed an assay for the direct determination of selenium in serum with a Perkin-Elmer Model 4100ZL Zeeman atomic absorption spectrometer and Ag-Cu-Mg modifier. We used this assay to analyze concanavalin A-bound selenoprotein (CABSP) in human serum after concanavalin A (ConA) affinity chromatography. The CABSP was identified as a single-chain glycoprotein of 57.3 kDa. Carbohydrate units were N- and O-linked to the protein. The selenium moiety was selenocysteine. Total selenium, glutathione peroxidase (GPX; EC 1.11.1.9), ConA-bound selenium (CABS), and alpha 1-acid glycoprotein (AAG) were determined in normal subjects and patients with various pathological conditions. CABS accounted for 44.1% +/- 6.3% of total selenium in sera from normal subjects and 46.5% +/- 3.9% to 55.1% +/- 8.1% in sera from patients with a variety of diseases. Total selenium in serum was well correlated with serum CABS (r = 0.860), but not with serum GPX activity (r = 0.117), for all patients studied. Serum CABS increased in normal subjects after selenium supplementation. Serum CABSP did not behave as an acute-phase reactant, compared with AAG.

Adult↗
PubMed1993

Free radicals.

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Free Radicals↗
PubMed1993

Diagnostic accuracy of pancreatic enzymes evaluated by use of multivariate data analysis.

We analyzed pancreatic enzyme data from 508 patients with suspected pancreatitis by neural network analysis, by an Expert multirule generation protocol, and by receiver-operator characteristic (ROC) curve analysis of a single test result. Neural network analysis showed that use of lipase provided the best means for diagnosing pancreatitis. Diagnostic accuracies achieved by using amylase only, lipase only, and amylase and lipase in combination were 76%, 82%, and 84%, respectively. Use of the Expert rule generation protocol provided a diagnostic accuracy of 92% when rules for single and multiple samplings were combined. ROC curve analysis for initial enzyme activities showed the maximal diagnostic accuracy to be 82% and 85% for amylase and lipase, respectively; use of peak enzyme activities yielded accuracies of 81% and 88%, respectively. The evaluation of laboratory test data should include analysis of the diagnostic accuracy of laboratory tests by multivariate techniques such as neural network analysis or an Expert systems approach. Multivariate analysis should allow for a more realistic assessment of the diagnosis accuracy of laboratory tests because all the available data are included in the evaluation.

Amylases↗
PubMed1993

Measuring alveolar lavage fluid surfactant by fluorescence polarization.

We describe a procedure by which surfactant/albumin ratios in bronchoalveolar fluid (BALF) may be quantified with the Abbott Laboratories TDx fluorescence polarization analyzer and fetal lung maturity reagents. Adding albumin to BALF samples shifted the surfactant/albumin ratios to within the analytical range of the method. The analytical CV for assay of modified BALF samples was 2.9%. Ratios obtained for modified samples from normal individuals (n = 10), transplanted lungs (n = 23), and contralateral native lungs of the transplant recipients (n = 23) were significantly different (P = 0.006). The ratio obtained for these modified samples can be converted, if needed, to the ratio in the original sample by using a simple mathematical relationship and the albumin concentration of the sample. We propose that this ratio will be useful in evaluating the surfactant status of BALF, particularly in lung allografts.

Adult↗
PubMed1992

Characterization of selenocysteine lyase in human tissues and its relationship to tissue selenium concentrations.

The characterization of human selenocysteine lyase, an enzyme that specifically catalyzes the decomposition of L-selenocysteine to L-alanine and hydrogen selenide, is described. The enzyme is the first described that acts exclusively on a selenium compound. The enzyme from human tissues, analogous to that from pig tissues and bacteria, requires pyridoxal 5-phosphate as a cofactor. L-selenocysteine is the sole substrate with a Km = 0.50 mM. L-cysteine is a noncompetitive inhibitor of the enzyme with a Ki = 5.85 mM. The following amino acids and purines are inert: L-cysteine, selenocystamine, seleno-DL-methionine, 6-selenopurine, and 6-selenoguanosine. The enzyme was found in liver, kidney, heart, adrenal and muscle in decreasing order of specific activity. The enzyme activity in liver was found not to be related to tissue selenium concentration or glutathione peroxidase activity.

Glutathione Peroxidase↗
PubMed1992

Plasma selenium concentrations in patients with euthyroid sick syndrome.

We evaluated plasma selenium concentrations in patients with euthyroid sick syndrome express by low serum triiodothyronine (T3) concentrations. Selenium status in these patients was compared with that found in patients with both untreated and treated hypothyroidism. Selenium concentrations in plasma were significantly lower in hospitalized patients with either euthyroid sick syndrome (0.99 +/- 0.37 mumol/L) or treated hypothyroidism (1.09 +/- 0.25 mumol/L) than in patients with untreated hypothyroidism (1.39 +/- 0.28 mumol/L). However, there was no significant, independent relationship between selenium and the thyroid function indices determined in this study. The strongest association was between serum albumin concentration and either selenium (r = 0.65), T3 (r = 0.58), or the molar ratio of T3 to thyroxine (r = 0.64). The decreased average selenium concentration appears to be associated with the hypercatabolic state of severely ill patients, as indicated by the serum albumin concentration; these patients should be considered for selenium supplementation and their selenium status should be monitored.

Euthyroid Sick Syndromes↗
PubMed1991

Clinical chemistry.

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Chemistry, Clinical↗
PubMed1991

Serum enzyme alterations in chronic muscle disease. A biopsy-based diagnostic assessment.

The results of interpretation of muscle biopsies were compared retrospectively to activities of serum enzymes and isoenzymes. A total of 137 patients seen at the Cleveland Clinic Foundation in 1986 and 1987 were included in this study. Serum enzymes evaluated were CK, AST, LD, and aldolase (ALS), as well as the percentage CK-MB isoenzyme. The units of CK-MB and the ratios of CK to AST, LD, and ALS were calculated. Descriptive statistics, Kruskal-Wallis one-way analysis of variance, and stepwise logistic regression were performed. A diagnostic algorithm was constructed using a computer-assisted rule generation program. Myopathic diseases yielded a greater mean increase in serum enzyme activity than atrophic diseases. By multivariate stepwise logistic regression, increases in serum AST and CK activity were independently associated with the presence of inflammation in a muscle biopsy specimen. The diagnostic algorithm allowed for the separation of myopathies from atrophies and could identify cases of Duchenne's muscular dystrophy and polymyositis.

Algorithms↗
PubMed1991

Diagnostic and prognostic utility of phospholipase A activity in patients with acute pancreatitis: comparison with amylase and lipase.

We compared the diagnostic and prognostic utility of phospholipase A (PLA; EC 3.1.1.4) for acute pancreatitis with that of amylase and lipase by analysis of sera from 151 consecutive patients presenting with abdominal pain in whom assays of serum amylase and (or) lipase had been ordered. We determined the diagnostic accuracy for both the initial and the peak enzyme activities. Maximal diagnostic accuracy obtained for the initial activities of amylase, lipase, and PLA was 0.83, 0.83, and 0.76 at cutoff values of 650, 650, and 41 U/L, respectively. Use of peak enzyme activities showed maximal diagnostic accuracy of 0.85, 0.86, and 0.73 at cutoff values of 650, 1050, and 42 U/L, respectively. Receiver-operator characteristic curve analysis revealed the diagnostic performance of amylase and lipase to be similar, whereas that of PLA was almost random and not incremental. As with amylase and lipase, PLA activities in sera showed no relation to patients' survival; three patients who died after an attack of acute pancreatitis failed to demonstrate the dramatic increases in PLA activity previously described. We conclude that assessing the severity of acute pancreatitis by using enzyme activities still remains problematical. Measurements of amylase or lipase activities provide similar diagnostic discrimination when appropriate cutoff values are used and remain the methods of choice for diagnosis of acute pancreatitis.

Acute Disease↗
PubMed1990

Effect of reticulocytosis on lactate dehydrogenase isoenzyme distribution in serum: in vivo and in vitro studies.

We investigated the effect of reticulocytosis on the lactate dehydrogenase (LD; EC 1.1.1.27) isoenzyme LD1/LD2 ratio in patients with and without evidence of hemolytic disease. Analysis of sera from patients with reticulocytosis and in vivo hemolysis showed a mean LD1/LD2 ratio of 0.92 compared with a ratio of 0.69 in patients with in vivo hemolysis and normal reticulocyte counts. Determination of LD isoenzymes in erythrocyte lysate revealed significantly increased LD1/LD2 ratios for patients with marked reticulocytosis compared with those for patients with normal-to-minimal increases in reticulocytes. Finally, separation of mature erythrocytes and reticulocytes by flow cytometry revealed marked differences in the LD1/LD2 isoenzyme distribution between these two cell types. The ability of hemolysis to cause a "flipped" LD1/LD2 ratio is dependent on the proportion of the hemolyzed cells that are reticulocytes.

Cells, Cultured↗
PubMed1990

Financial impact of a rapid CK-MB-specific immunoassay on the diagnosis of myocardial infarction.

The purpose of this study was twofold. First, we evaluated the financial impact of a rapid, monoclonal antibody-based CK-MB mass assay (Stratus, Dade Division, Baxter Laboratories, Miami, Fla) for the direct measurement of CK-MB in serum samples from 65 patients admitted to the coronary care unit with the possible diagnosis of acute myocardial infarction. Second, we evaluated retrospectively the Stratus assay and an activity assay (electrophoresis) for CK-MB in the following patient categories: acute myocardial infarction treated with and without thrombolytic therapy, angina, congestive heart failure, skeletal muscle trauma, and the acutely ill without acute myocardial infarction. The advantageous features of the Stratus mass assay were as follows. First, the laboratory was able to perform the assay more frequently because of the short assay time per specimen (less than 10 minutes) without additional personnel. This had a substantial impact on the clinician's ability to diagnose acute myocardial infarction and to move patients out of an intensive care unit at substantial financial savings to the patient, the hospital, or the third-party payer. Second, the Stratus assay was able to detect low levels of CK-MB (1 to 2 micrograms/L) in the presence of low total creatine kinase activity (less than 100 U/L). Third, the Stratus assay showed no interference due to very-high-total creatine kinase activities (greater than 100,000 U/L), CK-BB, macro-creatine kinase, and mitochondrial creatine kinase.

Blood Protein Electrophoresis↗