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Results for “Radioactive Tracers”

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At least 199 records · Page 11Linked to original sources
PubMed1981

In vitro assay of erythropoietin in fetal mouse liver cultures. I. Comparison of radioactive tracers and evidence of assay specificity.

In a 13 d fetal mouse liver tissue culture system for assay of erythropoietin, stimulation of incorporation of 3H-thymidine and of 125I-iodo-2'-deoxy uridine into DNA and of 59Fe iron into haem were compared as metameters of erythropoietin effect. With both DNA and haem tracers, log-dose response curves given by two preparations of human urinary erythopoietin purified to different extents (respectively 2 and 1300 IU, by bioassay in vivo, per mg of protein) were essentially identical at low dose levels although at high dose levels the less pure preparation decreased stimulation of both DNA and haem synthesis. Pre-incubation of erythropoietin with an antiserum to human erythropoietin abolished the effects of the hormones on both DNA and haem synthesis.

Animals↗
PubMed2006

L-glutamate and glutamine improve haemodynamic function and restore myocardial glycogen content during postischaemic reperfusion: A radioactive tracer study in the rat isolated heart.

1. L-Glutamate and glutamine have been suggested to have cardioprotective effects. However, the issue is controversial and the metabolic mechanisms underlying a beneficial effect are not well understood. 2. In the present study we investigated the effects of L-glutamate and glutamine on haemodynamic recovery, the rate of de novo glycogen synthesis and myocardial glucose uptake during postischaemic reperfusion. 3. Hearts from male Wistar rats (250-300 g) were divided into three groups as follows: (i) control (n = 12); (ii) L-glutamate (n = 12); and (iii) glutamine (n = 12). Hearts were mounted in a Langendorff preparation and perfused with oxygenated Krebs'-Henseleit solution at 80 mmHg and 37C. Global ischaemia for 20 min was followed by 15 min reperfusion, during which L-glutamate (50 mmol/L) or glutamine (20 mmol/L) were administered. Left ventricular developed pressure (LVDP), de novo synthesis of glycogen using [14C]-glucose and myocardial glucose uptake using D-[2-3H]-glucose were measured. 4. L-Glutamate and glutamine increased postischaemic LVDP (P < 0.01 vs control hearts for both). L-Glutamate and glutamine increased de novo glycogen synthesis by 78% (P < 0.001) and 55% (P < 0.01), respectively. At the end of reperfusion, total myocardial glycogen content was increased by both L-glutamate and glutamine (5.7 +/- 0.3 and 6.2 +/- 0.7 micromol/g wet weight, respectively; P < 0.05 and 0.01, respectively) compared with that in control hearts (3.6 +/- 0.4 micromol/g wet weight). Neither L-glutamate nor glutamine affected myocardial glucose uptake during reperfusion. 5. Improved postischaemic haemodynamic recovery after L-glutamate and glutamine supplementation during reperfusion is associated with increased de novo glycogen synthesis, suggesting a favourable modulation of intracellular myocardial carbohydrate metabolism.

Animals↗
PubMed1977

Methodological aspects of tear flow determination by means of a radioactive tracer.

Theoretical considerations on a simplified biological system representing the tear pathways lead to the assumption of an exponential pattern of elimination of tracer substances from the conjunctival sac. The tracer used in the present study was technetium, Tc99m, as sodium pertechnetate. The detection system consisted of a gamma camera coupled to a digital system, a minicomputer and a magnetic tape unit. After instillation of 10 microliter normal saline solution containing Tc99m the decay of activity was followed by means of an activity-time function curve to which exponential curves were approximated by the computer. As a parameter for tear flow the fractional turnover rate was calculated from 7 to 15 min after instillation. An initial faster elimination was found in the first 7 min following instillation. Corrections for background radiation, evaporation of water and transconjunctival transport of Tc99m were estimated.

Animals↗
PubMed1968

Occupancy principle for radioactive tracers in steady-state biological systems.

Bergner's theoretical analysis of tracer dynamics has important ap plications in biology, not only for the measurement of exchangeable mass (as he demonstrated) but also for elicitation of otherwise inaccessible information on total masses of particular elements in body organs or systems-as well as in Chemical engineering and geophysics.

Biological Transport↗
PubMed1984

Measurement of skin and total blood flow to the rabbit lower limb by washout of freely diffusible radioactive tracers introduced intra-arterially.

Good agreement was obtained when measuring total (capillary) blood flow in 9 rabbit thighs using two different techniques. The 133Xenon washout technique yielded a mean value of 8.0 cm3 X min-1 X 100 g tissue-1 whilst the microsphere technique gave a mean value of 7.8 cm3 X min-1 X 100 g tissue-1. There was a significant correlation (r = 0.83, p less than 0.006). In a further 14 rabbit thighs an attempt was made to measure skin blood flow by washout of 85Kr and to compare it with the microsphere technique. 133Xe promises to be a useful tracer for measuring lower limb flow when introduced intra-arterially. Because 85Kr tends to underestimate skin blood flow, and because of problems of diffusion of the tracer between compartments, which are discussed, this tracer is not satisfactory as a technique for measuring skin blood flow.

Animals↗
PubMed1980

[Study of the regional distribution of inspired gas with radioactive tracers (author's transl)].

Two different techniques are utilized: aerosol with 198Au particles (size 0.5-15 micron) and different gaz mixtures (air; O2 20% + He 80+; O2 60% + N2 40%; O2 60% + He 40%) with 133Xe and registration of the regional distribution along a wash-in (upper, middle and basal) of every lung (gamma camer, computer, Polaroid photographs, scans), performed in three groups of subjects (normal: 5, bronchogenic carcinoma: 11 and chronic bronchitis: 5). Modifications of the airway distribution and blood gas data according to the technical approach (particularly, variations of densities and viscosities) are compared with results in normal subjects.

Adult↗