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Biomedical subjects

G Kraft

Publications and source records attributed to G Kraft.

104 records · Page 6Linked to original sources
PubMed1983

Heavy ion action on yeast cells: inhibition of ribosomal-RNA synthesis, loss of colony forming ability and induction of mutants.

The action of heavy ions (Ar to U) accelerated to specific energies up to about 10 MeV/u (u=atomic mass unit) on different functions of yeast cells was studied. Ribosomal-RNA synthesis is inhibited according to a single-hit mechanism. Inactivation cross-sections were linearly related to the ratio of the squares of the effective charge Z* and the velocity of the ions. It is concluded from the analysis that the range of the most energetic delta-electrons is larger than previously assumed. There is no such dependence for survival and induction of mutants. In both cases cross-sections increase with the ion's specific-energy indicating an important contribution of long-range delta-electrons. The analysis shows that diploid yeast is not killed by a single-hit mechanism even by very heavy ions if the track width is too small. The relative importance of the penumbral region is even more pronounced with the more sensitive strains.

Argon↗
PubMed1983

Inactivation of Ehrlich ascites tumor cells by heavy ions.

Exponentially growing and plateau-phase cultures of Ehrlich ascites tumor cells were irradiated with heavy ions (Z greater than or equal to 20) and assayed for loss of reproductive capacity either immediately or at delayed times after irradiation. The results indicated no modification of the exponential dose response due to conditions which usually favor the repair of potentially lethal damage at low ionization density. Postirradiation treatment of the cells with beta-arabinofuranosyladenine, a DNA synthesis inhibitor known to act on PLD repair, resulted in effects similar to those observed without this drug and confirmed the hypothesis that at such high values of ionization density only lethal, unmodifiable damage can be expressed. The inactivation cross-section values calculated from the slope of the measured survival curves showed no significant correlations with commonly used parameters of radiation quality such as LET or z2/beta 2. Instead, a functional dependence on the primary ion energy was indicated, being smaller by a factor of two at low energies (less than or equal to 2 MeV/amu) compared with values at energies above 4 MeV/amu, where agreement with the morphological nuclear cross section of the culture was found. This suggests that at higher specific ion energies energetic secondary electrons contribute to the induction of lethal damage, and that interaction of damaged sites between the primary track and the track ends of delta electrons may occur. The data are therefore also discussed in terms of the "penumbra model" which emphasizes the role of delta electrons in cell killing when radiations with very high ionization density are applied.

Animals↗
PubMed1982

Heavy ion effects on yeast cells: induction of canavanine-resistant mutants.

The induction of forward mutations (resistance to canavanine) by heavy ion bombardment was investigated in wild type haploid yeast Saccharomyces cerevisiae. Accelerated ions of argon, titanium, nickel, krypton, xenon, lead and uranium with specific energies between 1.7 and 9.25 MeV/u were obtained from the UNILAC machine at the Gesellschaft für Schwerionenforschung, Darmstadt/Germany. LET-values ranged from 1200 to about 15 000 keV/microns. There was no unequivocal dependence of mutation induction cross section on either LET or Z*2/beta 2, but also a prominent influence of ion specific energy. This is explained by the action of long-ranging delta-electrons.

Canavanine↗
PubMed1975

[Lipid islands in the gastric mucosa].

Circumscribed lipoid deposition in the gastric mucosa ("lipid island") can macroscopically be mistaken for "early cancer" of the stomach. The aetiology of the lipid islands is not quite clear. Precise diagnosis is possible only with selective biopsy and special staining. Such lipid islands were found in five patients among 1 200 gastrocopies.

Biopsy↗
PubMedDate not supplied

Radiotherapy with heavy ions: radiobiology, clinical indications and experience at GSI, Darmstadt.

In the history of external beam radiotherapy, the trend for a better conformation as well as for a higher biological efficiency has been the driving force for the improvement of clinical results. However, these two goals had to be followed with separate types of radiation, i.e. photons and neutrons, and could not be combined. For the first time being, beams of heavy ions like carbon offer the possibility to combine both advantageous properties: better targeting and higher biological efficiency. Particle beams have an inverse depth dose profile, with a maximum dose in the deep seated tumor, a finite range, small lateral scattering, and a drastically increased biological efficiency in the tumor. These properties maximize the deletion effects on tumor cells. In addition, particle beams can be directed precisely in the limit of one or two millimeters, and can be monitored using positron emission tomography (PET) with the same precision. In the following paper the conditions are given that are necessary to translate these properties into clinical routine.

Carbon↗
PubMedDate not supplied

The Italian Heart Transplant Project: organization of a multicenter program.

The Italian Heart Transplant Project is a national program coordinated by the Health Ministry and involves eight cardiac surgery centers, two coordination centers for organ procurement, and one national registry. An intercenter network for the solution of logistic problems regarding organ procurement and assignment has been built up. Preintervention and clinical follow-up data are recorded in each center and in a national registry by the implementation of a computerized data base. This is realized by employing low cost and diffuse software and hardware. The complex goal of common data collection and standardization is also being pursued for collateral areas such as cardiac pathology and immunologic surveillance. Data collection is useful for clinical monitoring and also for costs and/or requirements analysis.

Data Collection↗