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Biomedical subjects

J C Standefer

Publications and source records attributed to J C Standefer.

16 recordsLinked to original sources
PubMed1991

Thyroid function in a healthy elderly population: implications for clinical evaluation.

Evaluation of thyroid function in elderly people is complex and has generated some controversy about what is normal. This study analyzed thyroid function assays in an identified healthy elderly population of 216 subjects. Thyroxine, free thyroxine, triiodothyronine, T3 uptake, "supersensitive" thyrotropin, and thyroid antibody titers were performed. Histories of treatment for thyroid conditions were present in 13.9% (n = 30) of the population, and test results for an additional 4.3% (n = 8) revealed some hypothyroidism. These subjects were excluded from statistical analysis. Test results revealed significant differences from younger controls as well as skewed distributions for T4, FT4, and TSH. There were no significant correlations with increasing age or gender within the elderly population. 11.8% (n = 21) of the population exhibited elevated TSF levels with normal T4 values, and 23.0% (n = 41) exhibited a titer of one or both thyroid antibodies. Current reference ranges for thyroid tests are broad enough to include the range of values seen in the healthy elderly, but some cautions are discussed.

Adult↗
PubMed1991

Drug screening with EMIT reagents: a quantitative approach to quality control.

We investigated the precision, linearity, accuracy, and stability of quantitative results for five drugs of abuse [amphetamines, benzoylecgonine, opiates, phencyclidine, and the cannabinoid-tetrahydrocannabinol (THC)-9-acid metabolite], analyzed in control specimens by using EMIT d.a.u. reagents (Syva Co.) with a Monarch 2000 analyzer with a nonlinear interpolation curve-fitting algorithm. The within-day and between-days coefficients of variation (CVs) were less than 5% for all drugs except THC-9-acid, which had a CV between 10% and 20%. The drift of control values during a 30-day stability study was less than 10% from target values for three weeks after a single calibration, except for THC-9-acid control values, which were stable for only two to three days. Daily calibration reduced the drift away from target values during the 30-day stability study and produced optimum precision of all drug assays. Mean control values near the National Institute on Drug Abuse cutoff limits were within 10% of their target values.

Antidepressive Agents↗
PubMed1990

Failure of single dose methotrexate followed by citrovorum factor in nonmetastatic gestational trophoblastic neoplasia.

With increasing cost of medical care, newer methods of administering chemotherapy on an outpatient basis are being sought to reduce the need for hospitalization and protracted losses of valuable time for patients with nonmetastatic gestational trophoblastic neoplasia (NMGTN). To achieve this end, two NMGTN patients were treated with a single course of one dose of methotrexate (MTX) followed by multidose Citrovorum Factor (CF) without observing the expected response. Failure to respond appeared to be due to the schedule of administration. Although the dose and plasma concentrations of MTX were considered to be adequate for cell kill, fractionation--as established by conventional schedules of MTX administration--appeared necessary for response by exposing the maximum number of trophoblastic cells to inhibitory levels of MTX during the S-phase of the cell cycle.

Adult↗
PubMed1989

Depletion of guanine nucleotides with mycophenolic acid suppresses IgE receptor-mediated degranulation in rat basophilic leukemia cells.

In RBL-2H3 rat basophilic leukemia cells, Ag that crosslink IgE-receptor complexes stimulate the turnover of inositol phospholipids, the mobilization of Ca2+ from intra- and extracellular sources, the release of serotonin and other substances from granules and the transformation of the cell surface from a microvillous to a lamellar architecture. This study explores the role of GTP-binding proteins (G proteins) in the control of these biochemical and functional responses. We report that incubating RBL-2H3 cells for 4 h with 10 microM mycophenolic acid (MPA), an inhibitor of de novo GTP synthesis, reduces GTP levels by over 60% and causes an average reduction of 50% in Ag-stimulated serotonin release. This inhibition of secretion is associated with a 50% decrease in the rate of 45Ca2+ influx in MPA-treated cells. In contrast, Ag-stimulated inositol trisphosphate production is only slightly reduced, indicating that the phosphatidylinositol-specific phospholipase C can be activated by Ag in GTP-depleted cells. The membrane responses to IgE receptor cross-linking are unaffected by incubating cells with MPA. Exogenous guanine or guanosine protects the GTP pools in MPA-treated cells and permits normal ion transport and secretory responses to Ag; adenine does not. These results implicate a guanine nucleotide-binding protein in the control of IgE receptor-dependent signal transduction in RBL-2H3 cells. This protein may particularly control the Ca2+ influx pathway that is essential for secretion.

Animals↗
PubMed1988

Serum methotrexate and human chorionic gonadotropin concentrations during five-day chemotherapy for low-risk metastatic gestational trophoblastic neoplasia.

A recent report of serum methotrexate (MTX) levels measured during treatment of gestational trophoblastic neoplasia (GTN) led us to determine MTX and human chorionic gonadotropin (beta-hCG) levels in a patient with low-risk metastatic GTN with a pulmonary metastasis. Peak MTX concentrations exceeded 10(-6) mol/l considered by many investigators to be within the therapeutic range against many human tumors. Serum beta-hCG levels did not decline during MTX administration; however, after 5 days of MTX a steep dose-response curve was observed which continued during 5 courses of chemotherapy.

Adult↗
PubMed1979

Reverse tri-iodothyronine to tri-iodothyronine ratio and gestational age.

The biologic significance of reverse tri-iodothyronine is not yet identified. Cord blood values reflect the fetal thyroid state, with rT3 excess and tri-iodothyronine deficiency. In an attempt to correlate thyroid function and gestational age, T3 and rT3 concentrations were measured by radioimmunoassay on 64 cord blood samples. Infant gestational ages ranged from 29 to 42 weeks; birth weights from 650 to 3,870 gm. The results show a significant positive correlation between gestational age and T3 and a significant negative correlation between gestational age and rT3. The rT3/T3 offers the best correlation.

Female↗
PubMed1979

Solid-phase enzyme immunoassay for serum ferritin.

We describe a solid-phase enzyme immunoassay for ferritin in human serum, with use of a horseradish peroxidase-labeled antibody and a highly sensitive chromogen, 2,2'-azino-di(3-ethyl-benzthiazoline-6-sulfonate). The assay requires only 10 microL of serum per assay, relatively less time and labor than other assys for ferritin, and as little as 10 pg of ferritin can be measured. We believe this assay offers a reliable alternative to radioimmunoassay for serum ferritin.

Ferritins↗
PubMed1979

Death associated with nitrite ingestion: report of a case.

The tissue concentrations of nitrite and nitrate found at autopsy of a case of intentional ingestion of nitrite salts have been reported. The percentage of methemoglobin and the serum nitrite concentrations are consistent with those reported for acute overdoses. We conclude that noth nitrite and nitrate salts may be identified in tissues from persons ingesting only nitrite salts and that a significant conversion to nitrate may result from oxidation of nitrite during the conversion of heme iron to Fe3+.

Adult↗
PubMed1979

Enzymic assay for lecithin in amniotic fluid.

We describe an enzymic method for determining lecithin in amniotic fluid. Phospholipase D from savoy cabbage is used to liberate choline from lecithin, and the liberated choline is oxidized to betaine and hydrogen peroxide by choline oxidase from Arthrobacter globiformis. The hydrogen peroxide forms a colored complex with phenol and 4-aminoantipyrene in the presence of horseradish peroxidase, and this color is measured spectrophotometrically. The method is relatively easy, precise, and accurate, requires less time and sample than other methods, and offers a reliable alternative to the lecithin/sphingomyelin ratio techniques for assessing fetal lung maturity.

Alcohol Oxidoreductases↗
PubMed1978

Enzyme immunoassay for gentamicin.

We describe a gentamicin assay in which a peroxidase-gentamicin conjugate competes with gentamicin for binding to a gentamicin antibody adsorbed to a polystyrene solid phase. The assay can be completed in 30 min and requires 50 microliter of diluted serum. The precision and accuracy are equivalent to that of a radioimmunoassay technique and the reagents are stable for several months.

Gentamicins↗
PubMed1977

Use of tetramethylbenzidine in plasma hemoglobin assay.

Plasma hemoglobin can be assayed by substituting 3,3',5,5'-tetramethylbenzidine for benzidine (a carcinogen) as the chromogenic reducing substance. Sensitivity, precision, and accuracy compare well with methods in which benzidine is used. Plasma inhibition can be accommodated by preincubation with hydrogen peroxide.

Benzidines↗
PubMed1975

Death associated with fluorocarbon inhalation: report of a case.

This case documents postmortem tissue concentrations of fluorocarbons in an individual whose inhalation of cooking spray vapors was well documented. The data presented here should contribute to the information base which will assist the pathologist in determining the cause of death in cases related to inhalation of these fluorocarbons.

Adolescent↗