Biomedical subjects

G Vétek

Publications and source records attributed to G Vétek.

3 recordsLinked to original sources

PubMed2006

Interrelationship between the raspberry cane midge, Resseliella theobaldi (Diptera: Cecidomyiidae) and its parasitoid, Aprostocetus epicharmus (Hymenoptera: Eulophidae).

The raspberry cane midge Resseliella theobaldi (Barnes) is one of the most important pests of cultivated red raspberry Rubus idaeus L. throughout Europe. For the last 50 years several studies have been made on the biology, life cycle and control of the pest. Some data can also be found on its natural enemies, but among these species only the chalcidoid Tetrastichus inunctus Nees turned out to be important in controlling raspberry cane midge populations. However, this species name is now ambiguous as the type is lost. In the present study, Aprostocetus epicharmus Walker was the chalcidoid species that parasitized the larvae of the raspberry cane midge, and its biology seems to be very similar to that of T. inunctus. It is therefore probable that the eulophid species earlier referred to as T. inunctus in the literature is A. epicharmus. Besides discussing this problem, particular consideration and detailed data are given on the biology and life cycle of A. epicharmus in relation to R. theobaldi. Different factors having effect on the population dynamics of both species are also discussed as results of a survey on several red raspberry cultivars, carried out in Hungary between 2002 and 2005.

Animals↗

PubMed2000

Determination of the MRI contrast agent concentration time course in vivo following bolus injection: effect of equilibrium transcytolemmal water exchange.

For bolus-tracking studies, it is commonly assumed that CR concentration bears a linear relationship with the measured (usually longitudinal) (1)H(2)O relaxation rate constant, R*(1) identical with(T(1) *)(-1). This requires that equilibrium transcytolemmal water exchange be in the fast exchange limit (FXL). However, though systems remain in fast exchange, the FXL will not usually obtain. Here, the consequences are considered: 1) the measurement of R(1) * itself can be affected, 2) the resultant non-linear [CR]-dependence causes significant error by assuming FXL, 3) the thermodynamic [CR] (based on the space in which CR is actually distributed) can be determined, 4) transcytolemmal water permeability may be estimated, and 5) the pharmacokinetic parameters can be factored. For a 30-sec, 0.17 mmol/kg dose of GdDTPA(2-), the FXL assumption underestimates the [CR] maximum in rat thigh muscle by a factor of almost two. Similar results are obtained for a rat brain GS-9L gliosarcoma tumor model.

Animals↗

PubMed1994

Relaxographic imaging.

A fundamental extension of NMR imaging is described. The distribution of relaxation times, the relaxogram, is considered as the third (or fourth) dimension of a set of 2D (or 3D) image data. There is a relaxographic dimension for each type of relaxation: longitudinal, transverse, rotating frame, etc. It is the formal inverse Laplace transform of the relaxation decay data set. Thus, combined relaxography and imaging (CRI) approaches are defined. CRI data can be displayed in two fundamental ways: localized relaxograms (relaxograms from any part of an image) or relaxographic images (images produced from discrete portions of a relaxogram). Relaxographic images are elemental components of the true spin-density image. The CRI concept is demonstrated with longitudinal relaxation data from samples of yeast cells suspended in media containing the contrast agent (CR) GdDTPA2-. This allows the discrimination of subvoxel intra- and extracellular 1H2O signals in the relaxograms from very small image voxels (about 400 nl). It is possible to isolate the intracellular 1H2O resonance from as few as a million cells. Relaxographic images are shown of the extracellular space (i.e., the distribution space of the CR) and the cytoplasmic space of a cell suspension with a cytocrit gradient. These have important potential applications in the in vivo situation. Also, the extent of equilibrium transcytolemmal water exchange can be detected and quantified.

Body Water↗