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E Benes

Publications and source records attributed to E Benes.

9 recordsLinked to original sources
PubMed2000

Mechanical culture conditions effect gene expression: gravity-induced changes on the space shuttle.

Three-dimensional suspension culture is a gravity-limited phenomenon. The balancing forces necessary to keep the aggregates in suspension increase directly with aggregate size. This leads to a self-propagating cycle of cell damage by balancing forces. Cell culture in microgravity avoids this trade-off. We determined which genes mediate three-dimensional culture of cell and tissue aggregates in the low-shear stress, low-turbulent environment of actual microgravity. Primary cultures of human renal cortical cells were flown on the space shuttle. Cells grown in microgravity and ground-based controls were grown for 6 days and fixed. RNA was extracted, and automated gene array analysis of the expression of 10, 000 genes was performed. A select group of genes were regulated in microgravity. These 1,632 genes were independent of known shear stress response element-dependent genes and heat shock proteins. Specific transcription factors underwent large changes in microgravity including the Wilms' tumor zinc finger protein, and the vitamin D receptor. A specific group of genes, under the control of defined transcription factors, mediate three-dimensional suspension culture under microgravity conditions.

Animals↗
PubMed2000

Viability of plant cell suspensions exposed to homogeneous ultrasonic fields of different energy density and wave type.

Exposure of Petunia hybrida cell suspensions to ultrasound at a frequency of 2.43 MHz in a standing wave field at an energy density of 70 Jm-3 (pressure amplitude of 0.78 MPa) decreased their mean viability to 35% after 20 min of sonication. A comparison of propagating wave and standing wave treatments at equal frequency (2.15 MHz) and energy density (8.5 Jm-3) showed, in the first case, a rapid decline in mean viability of cells (to 30% after 10 min of sonication) and, in the second case, a retaining of the initial viability (95%), respectively. Cells sonicated 4 days after subculture were more sensitive than cells sonicated 2 or 6 days after transfer to new culture medium. It was concluded that cellular viability depends primarily on the acoustic energy density, the exposure time, and the mechanical properties of the cells determined by age. As a consequence of the trapping of cells in the anti-node planes of the standing wave, propagating wave fields reduced cellular viability compared with standing wave fields at equal energy density.

Cell Survival↗
PubMed2000

Viability of yeast cells in well controlled propagating and standing ultrasonic plane waves.

Recent studies have shown that there is no loss of cell viability when the cells are subjected to ultrasonic standing wave fields in acoustic cell retention systems. These systems are characterised by waves that spatially vary in pressure amplitude in the direction of sound propagation. In this work an anechoic 'one-dimensional' sonication chamber has been developed that produces propagating waves, which differ from standing waves in that the pressure amplitude remains constant as the wave travels in a medium with negligible attenuation. The viability of yeast cell suspensions as a function of treatment time was investigated during exposure to both standing and propagating wave fields with frequencies slightly above 2 MHz. The influence of 12% (vol/vol) of ethanol in water on the spatial arrangement of the cells in suspension was also studied. Changes in yeast cell morphology caused by the different types of suspension media and the ultrasonic treatment were examined by transmission electron microscopy (TEM). The agglomeration of yeast cells within the pressure nodal planes appears to minimise damaging effects due to ultrasonic fields.

Cell Survival↗
PubMed2000

Breakdown of immobilisation/separation and morphology changes of yeast suspended in water-rich ethanol mixtures exposed to ultrasonic plane standing waves.

Some physiological/morphological changes have been reported before, when suspended yeasts have been irradiated with well-defined ultrasonic standing, as well as propagating, plane waves around 2.2 MHz, as used in ultrasonic coagulation, e.g., for cell filtering. Thus we used yeast as a biological model to explore the reasons for both those morphology changes and some unusual macroscopic behaviour in the case of water-rich ethanol mixtures when used as carrier liquid. When the cells were suspended in 12% (v/v) ethanol-water mixture separation was greatly reduced; the yeast cells were not retained in the pressure nodal planes of the standing wave, but mixed turbulently through the separation system. How this behaviour alters the efficiency of retention/immobilisation was measured. As the viability of the yeast was decreased as well the morphology of the cells was examined using transmission electron microscopy. Two effects, according to the type of assessment, were evident; a disruption of the cells vacuole and also damage to the cell wall/membrane complex. The extent of the alterations in vacuole structure with sonication time, utilising a fluorescent vacuole membrane dye, was measured. Transient cavitation was not detected and thus could be excluded as being responsible for the observed effects. Other possible reasons for the disruption of the intracellular compartments may be acoustic pressure, displacement or other, secondary effects like (sub) harmonic cavitation. The investigations contribute to a better understanding of the physical conditions experienced when a cell is stressed in a high-frequency ultrasonic wave in the MHz range.

Ethanol↗
PubMed1993

Rapid agglutination testing in an ultrasonic standing wave.

The time taken to perform diagnostic agglutination tests can be significantly reduced by applying an ultrasonic standing wave field to a droplet of reactants held in a capillary tube. Avian erythrocytes, bacteria and latex particles from commercially available test kits were agglutinated in 15 s, 5 min, and 1 min respectively. These times compare favourably with the times of 30 min, 4 h, and 8 min required for agglutination by the methods prescribed for the respective kits. No loss in sensitivity or specificity was observed with the ultrasonic method. A multi-test procedure is also described whereby a series of five droplets loaded in a single capillary can be tested in less than 4 min by drawing the capillary along the axis of the ultrasonic field of a ring transducer.

Agglutination↗
PubMedDate not supplied

A novel ultrasonic resonance field device for the retention of animal cells.

This article describes two types of flow-through cell retention devices based on the concept of layered piezoelectric resonators. A single-chamber device is compared to a novel optimized steam-sterilizable prototype ultrasonic cell separator with improved acoustic design and an integrated cooling circuit, eliminating the problem of local temperature increase caused by the high amplitudes necessary to achieve the separation of animal cells with low acoustic contrast. This setup yields highly reproducible results and is ideal for studying the long-term effects of ultrasonic sound fields and separation efficiency. The novel two-chamber system has the potential for scaleability due to the reduction in thermal and acoustic flow, increased field stability, and separation efficiency. Finally, the effect of power input on separation and cell viability is reported. Such flow-through cell retention systems could be used as systems to retain biomass within the fermentor or as a substitute for centrifugation, with the major advantage of eliminating high-speed rotational motion.

Animals↗
PubMedDate not supplied

Selective retention of viable cells in ultrasonic resonance field devices.

A double-chamber ultrasonic resonance field device was used for the separation and retention of animal cells. By controlling operational parameters such as flow and power input, the device can retain viable cells more efficiently, allowing for selective removal of nonviable cells and cell debris. A simple model describing the forces acting on spherical particles in a sound field (primary radiation force, Bernoulli force, secondary radiation force) is presented. Field stability increases with decreasing average flow rates and increasing power input. At very high field stability, as achieved with low flow rates and high power input, the selectivity for viable cells is reduced, due to the efficient retention of all types of particles. At high flow rates and resulting low field stability, selectivity is also reduced, due to poor separation efficiency, resulting in equally low retention of viable cells, nonviable cells, and cell debris.

Animals↗