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Biomedical subjects

C Fischer

Publications and source records attributed to C Fischer.

At least 361 records · Page 20Linked to original sources
PubMed1975

A direct ligand-binding radioassay for the measurement of methotrexate in tissues and biological fluids.

A direct ligand-banding radioassay for methotrexate (MTX) has been developed using dihydrofolate reductase, contained in the lysate of L1210 leukemia cells, as the binding determinant. The procedure is a two-phase reaction system where standard MTX concentrations or the sample being assayed in incubated with the reagent lysate in the first phase, and [3H]MTX is then added in the second phase to titrate the remaining unoccupied binding sites on the enzyme. This method eliminates the need for measuring the residual catalytic activity of the enzyme. The sensitivity of the radioassay is limited only by the specific activity of the [3H]MTX and how approximates 10 pg of the drug. Folic acid, methyltetrahydrofolate, formyltetrahydrofolate, and dehydrofolate in concentrations that are physiological do not interfere in the radioassay. Both mercaptoethanol and reduced nicotinamide andnine dinucleotide phosphate increase the binding capacity of the lysate for MTX; but the reduced nucleotide also increases the affinity of the enzyme for the inhibitor. MTX added to serum can be assayed without extraction if the concentration is greater than 500 pg/ml and recovery of the drug added to serum is about 92%. MTX has been assayed in serum, spinal fluid, and urine of patients who were treated with this drug. It has also been assayed in the lysates of L1210 cells from C57BL X DBA/2 F1 mice treated with MTX. The procedure is simple, rapid, and accurate and should permit better correlation of the therapeutic and toxic effects of MTX with blood concentrations over long-term treatment periods.

Animals↗
PubMedDate not supplied

A genetic study of the human low-voltage electroencephalogram.

The studied phenotype, the low-voltage electroencephalogram (LVEEG), is characterized by the absence of an alpha rhythm from the resting EEG. In previous studies, evidence was found for a simple autosomal-dominant mode of inheritance of the LVEEG. Such a polymorphism in brain function can be used as a research model for the stepwise elucidation of the molecular mechanism involved in those aspects of neuronal activity that are reflected in the EEG. Linkage with the variable number of tandem repeats (VNTR) marker CMM6 (D20S19) and localization of an LVEEG (EEGV1) gene on 20q have previously been reported, and genetic heterogeneity has been demonstrated. This latter result has been corroborated by studying new marker (MS214). The phenotype of the LVEEG is described here in greater detail. Its main characteristic is the absence of rhythmic alpha activity, especially in occipital leads, whereas other wave forms such as beta or theta waves may be present. Analysis of 17 new families (some of them large), together with 60 previously described nuclear families, supports the genetic hypothesis of an autosomal-dominant mode of inheritance. Problems connected with the analysis of linkage heterogeneity, exclusion mapping, and the study of multipoint linkage are discussed. A possible explanation of the localization of LVEEG in the close vicinity of another gene influencing synchronization of the normal EEG, the gene for benign neonatal epilepsie, is given.

Aging↗
PubMedDate not supplied

Evaluation of a bayesian pharmacokinetic program for phenytoin concentration predictions in outpatient population.

The present work evaluates the performances of a Bayesian program (PKS) for phenytoin concentration predictions in an outpatient population. The retrospective study involved 19 epileptic adults receiving oral phenytoin. The program was used to predict estimated serum concentrations from 0, 1, 2 or 3 feedback concentrations. Measurements of prediction bias (ME) decreased as soon as one steady-state concentration (Css) was used for estimations. Precision (MAE) was significantly improved with 1 Css and was even better and stable with 2 and 3 Css. Likewise, RMSE (composite of bias and precision) regularly decreased when the number of Css used increased. On a clinical way, 12% of the estimations were unacceptable (prediction error > 5 mg/l) with 1 Css and less than 3% with 2 or 3 Css. This number of rejected estimations increased to 45% when no feedback concentration was used. Besides, the program was able to predict important rises of serum levels in spite of relative low increase of the dose when 1 Css at least was known. Thus, the phenytoin dosing program has acceptable performances when at least 1 Css is known, and represents a potential tool to assist the clinician in the particular condition of outpatient population.

Adolescent↗
PubMedDate not supplied

Sequential mapping favours the hypothesis of distinct generators for Na and Pa middle latency auditory evoked potentials.

The temporo-spatial organization of Na and Pa middle latency auditory components evoked by monaural clicks delivered separately to right and left ears was assessed by sequential mapping of scalp potentials. The potential field distribution was found to be different for the two components and was assessed by calculating the maximal potential differences in the Na/Pa time period. These data are compatible with the hypothesis that distinct generators are responsible for the two components. Scalp potential field configuration observed for Na suggests a deep generator, which could be situated at the mesencephalic or diencephalic level. Bilateral cortical generators tangentially orientated satisfactorily account for the distribution of the Pa potential field, which could be related to simultaneous activation of both supratemporal auditory cortices in response to monaural stimulation.

Adult↗
PubMedDate not supplied

An alternative method of three-dimensional reconstruction from two-dimensional CT and MR data sets.

Cross-sectional images for medical diagnosis and therapy are obtained by sonography, CT or MRI. We propose an alternative solution to the problem of constructing a set of cross-sectional contours from two-dimensional (2D) CT or MR data sets. The method reduces the problem of constructing a shape over the cross-sections to one of constructing a sequence of partial shapes, each of them connecting two cross-sections lying on adjacent planes. The solution makes use of a spatial mathematical formalism (Delaunay triangulation). MR investigations were carried out on different objects (hips, livers) to illustrate the two-dimensional MR data sets by the reconstruction method. The resulting images represent the original image data in a way that is more suitable for observation of 3D relationships than the conventional cross-sectional viewing model.

Aorta↗
PubMedDate not supplied

Pediatric patients experiencing postoperative nausea and vomiting after burn reconstruction surgery: an analysis.

Nausea and vomiting after a surgical procedure has a significant impact on a patient's hospital course. A perceived increased incidence of postoperative nausea and vomiting (PONV) in pediatric patients undergoing reconstructive scalp surgery had been clinically observed. A chart review to determine if a relationship existed between the surgical procedure and the incidence of PONV was conducted by selecting patients who were 5 to 12 years old and whose surgery fell between April 1995 and August 1995. Thirty-eight patients were evaluated for 46 procedures; 8 patients were evaluated for both insertion and removal of scalp expanders. No differences were identified between groups for previous history of PONV, length of anesthesia, or position during surgery. Data from the retrospective review suggested that pediatric patients with reconstructive surgeries of the scalp experienced PONV at 100% (24 procedures), whereas only 45% (10 procedures) of patients whose surgeries did not involve the scalp experienced PONV. In addition, despite significant earlier return of bowel sounds, episodes of PONV and time to oral intake were also increased in the group of patients whose operations involved the scalp. On the basis of these findings, a prospective study has been initiated to determine if changes in the perioperative protocol will improve patient outcomes and reduce the incidence of PONV.

Burns↗