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Biomedical subjects

C Schmidt

Publications and source records attributed to C Schmidt.

At least 469 records · Page 26Linked to original sources
PubMed1982

The effect of derivatives of folic acid on the fluorodeoxyuridylate-thymidylate synthetase covalent complex in human colon xenografts.

This study was designed to examine the endogenous concentrations of 5,10-methylenetetrahydrofolate (CH2FH4) in human colorectal adenocarcinoma xenografts, and to determine the ability of other folate derivatives to increase the formation of the ternary covalent complex between CH2FH4, [6-3H]-5-fluorodeoxyuridylate (FdUMP) and thymidylate synthetase (TS, EC 2.1.1.45). Levels of CH2FH4 were determined by measuring the release of [3H]2O from [5-3H]-dUMP using TS from Lactobacillus casei. The reaction was linear from 1.9 X 10(-13) to 2.4 X 10(-11) mol of CH2FH4 assayed. Concentrations of CH2FH4 were low, ranging from 66 to 233 nM in cell water. Tetrahydrofolate (FH4) and dihydrofolate (FH2) increased complex formation, while 5-formyltetrahydrofolate (5-CHOFH4) and 5-methyltetrahydrofolate (5-CH3FH4) decreased the covalent binding of [6-3H]-FdUMP in vitro. Administration of FH4 or FH2 to tumor-bearing mice reduced subsequent formation of the covalent complex in vitro. Since 5-CH3FH4 is a major derivative of folate in mammalian tissues, its effect on the covalent binding of [6-3H]-FdUMP was examined further; even in the presence of homocysteine and cyanocobalamin (B12), the formation of the covalent complex was not increased. The fate of [5-14CH3]-FH4 was subsequently examined in vivo. In tumors at 1 hr after injection, 72% of the radiolabel remained as [5-14CH3]-FH4, while 17% had been converted to [14C]-methionine or incorporated into protein. By contrast, however, the incorporation of radiolabel into the protein fraction of liver was almost 30-fold greater at this time. At 4 hr, radioactivity in tumors (dpm/g) and in the fraction associated with [5-14CH3]-FH4 was decreased by over 60%, while metabolism was increased by only 13%. No polyglutamate forms of [5-14CH3]-FH4 were detected in tumors at 4 hr after treatment.

Adenocarcinoma↗
PubMed1982

[Clinico-histologic-morphometric correlations in pulmonary arteries among patients with heart malformations ].

To improve the evaluation of grades of pulmonary vascular lesions in congenital heart malformations, we studied the extent to which there is a measurable relationship between pressure conditions in the pulmonary circulation and the area of the media in small and medium-sized pulmonary arteries, and the possibility of a correlation between the subjective evaluation of grades of hypertensive pulmonary vascular lesions according to Heath and Edwards (1958). Material and methods. The lungs in 68 children (mean age, 22.7 months) with congenital malformations of the heart or great vessels resulting in pulmonary hypertension were examined. The lungs were fixed in a 4% formalin solution passed via the trachea under a constant filling pressure of 150 cm H2O. Peripheral as well as central tissue was removed from all lobes of the lungs; the specimens were stained with Elastica-van Gieson. The extent of hypertensive pulmonary vasculopathy was staged, without knowledge of the pressure conditions, according to the grading system developed by Heath and Edwards. The diameter and the area of all muscular arteries with diameters smaller or larger than 100 micron were measured using a semiautomatic measurement device for quantitative morphometric analysis (MOP/AM 01). Cardiac catheter values were available for all cases. The quotient of systolic pressures in the pulmonary artery and the aorta was taken as the measure of hemodynamic conditions in the pulmonary circulation. The Pearson-Bravais correlation coefficient (r) was computed from the respective area quotient and the corresponding pressure values. In addition, the coefficient of determination (r2) and regression functions were determined. Results. A linear correlation (r = 0.70) exists between the pressure quotient (Psyst. pulm. art./ Psyst. aorta) and the vessel area quotient (media area/total area). The correlation is expressed by the following functions: x = 1.89 y - 0.08 y = 0.26 x + 0.24 Using the Heath and Edwards grading, the following frequencies were obtained: Grade 0: 21, Grade I: 7, Grade II: 16, Grade III: 15, Grade IV: 6, and 3 children were undeterminable. No relationship exists between the grades and certain heart malformations. In spite of the fact that hypertensive vasculopathy becomes progressively more severe as the child grows older, we found four cases of Grade IV in children under the age of one. On the whole, a comparison of the measured area quotients and the Heath and Edwards grading showed a good correlation. Although we considered only pressure quotients and no other hemodynamic parameters, conclusions can be drawn about the operability of congenital heart malformations based on these findings. Using measured pressure values, the morphologic state of the pulmonary arteries can be approximately evaluated.

Aorta↗
PubMed1981

Fabricating moisture chamber spectacles with a sectional facial moulage.

A technique for the construction of acrylic resin moisture chambers has been presented. The utilization of a sectional facial moulage allows for the construction of the chambers to be carried out in the laboratory saving valuable patient contact time. The necessary materials are readily available, and the techniques are common to dental practice.

Eyeglasses↗
PubMed1981

Social rank and darwinian fitness in a multimale group of Barbary macaques (Macaca sylvana Linnaeus, 1758). Dominance reversals and male reproductive success.

In a 5-year study data were compared on rank and reproductive success of 3 mature males in a group of barbary macaques who had sired 32 infants on 14 females. The results indicate that the absolute number of offspring as well as the proportion of offspring from higher-ranking females is a function of the male's rank. Asymmetrical access to receptive females was produced by either a high basic rank or by the formation of a coalition, or both of these, which resulted in at least partial exclusion of competitors from reproduction. Rank reversals in basic rank was preceded by severe fights between the opponents involving deep wounds or loss of canine teeth. When such fights occurred they reaped benefits in each case for the challenger, which were measurable in terms of reproductive success.

Animals↗
PubMed1980

Antitumor structure-activity relations. Nitrosoureas vs. L-1210 leukemia.

A quantitative structure-activity relationship (QSAR) for 90 nitrosoureas acting against L-1210 leukemia in mice has been formulated. This QSAR is compared with one correlating the LD10 of 96 nitrosoureas. The results indicate that neutral nitrosoureas with octanol/water partition coefficients in the range of -1.5 to -2.5 might have better therapeutic indices than those currently in use.

Animals↗
PubMed1980

[Peripheral haemodynamic disturbances of the limbs in Raynaud's phenomenon (author's transl)].

Study of 36 cases of Raynaud's phenomenon by Doppler effect (radial artery and digital pulp at rest and during hyperhaemia) showed that measurement of peripheral resistance is an excellent method for differentiating idiopathic Raynaud's disease (index higher than 5) from syndromes to obliterative disease of the digital arteries or scleroderma (index less than 4). Capillaroscopy offers additional information concerning the validity of the distal bed, stasis and sludging phenomena and is a diagnostic aid in early scleroderma.

Adult↗
PubMed1979

Lead determination in blood by atomic absorption spectroscopy.

This paper describes a one-tube sample preparation method for blood lead determination which is relatively simple to perform and which does not require background correction for matrix effects. The red cells are lysed with a dilute potassium cyanide solution and heat. A citrate buffer is added, and the solution is then extracted with ammonium pyrrolidine dithiocarbamate and methyl isobutyl ketone. An aliquot of the MIBK layer is applied to a carbon rod atomizer and the peak at 217.0 nm is measured. The method demonstrates an overall in-run reproducibility of 1.39 microgram/100 mL blood standard deviation, a between-run standard deviation of 2.27 microgram/100 mL blood and a sensitivity of 0.012 microgram/mL/1% nm.

Humans↗