Biomedical subjects

D M Klaus

Publications and source records attributed to D M Klaus.

10 recordsLinked to original sources

PubMed2002

The effect of space flight on the production of actinomycin D by Streptomyces plicatus.

The effect of space flight on production of the antibiotic actinomycin D by Streptomyces plicatus WC56452 was examined onboard the US Space Shuttle mission STS-80. Paired space flight and ground control samples were similarly prepared using identical hardware, media, and inoculum. The cultures were grown in defined and complex media under dark, anaerobic, thermally controlled (20 degrees C) conditions with samples fixed after 7 and 12 days in orbit, and viable residuals maintained through landing at 17 days, 15 h. Postflight analyses indicated that space flight had reduced the colony-forming unit (CFU) per milliliter count of S. plicatus and increased the specific productivity (pg CFU(-1)) of actinomycin D. The antibiotic compound itself was not affected, but its production time course was altered in space. Viable flight samples also maintained their sporulation ability when plated on agar medium postflight, while the residual ground controls did not sporulate.

Dactinomycin↗

PubMed2001

Clinostats and bioreactors.

The environment created on Earth within a clinostat or Rotating Wall Vessel (RWV) bioreactor is often referred to as "simulated microgravity". Both devices utilize constant reorientation to effectively nullify cumulative sedimentation of particles. Neither, however, can fully reproduce the concurrent lack of structural deformation, displacement of intercellular components and/or reduced mass transfer in the extracellular fluid that occur in actual weightlessness. Parameters including density, viscosity, and even container geometry must each be considered to determine the overall gravity-dependent effects produced by either a clinostat or the RWV bioreactor; in addition, the intended application of these two devices differs considerably. A state of particle "motionlessness" relative to the surrounding bulk fluid, which is nearly analogous to the extracellular environment encountered under weightless conditions, can theoretically be achieved through clinorotation. The RWV bioreactor, on the other hand, while similarly maintaining cells in suspension as they continually "fall" through the medium under 1 g conditions, can also purposefully induce a perfusion of nutrients to and waste from the culture. A clinostat, therefore, is typically used in an attempt to reproduce the quiescent, unstirred fluid conditions achievable on orbit; while the RWV bioreactor ideally creates a low shear, but necessarily mixed, fluid environment that is optimized for suspension culture and tissue growth. Other techniques for exploring altered inertial environments, such as freefall, neutral buoyancy and electromagnetic levitation, can also provide unique insight into how gravity affects biological systems. Ultimately, all underlying biophysical principles thought to give rise to gravity-dependent physiological responses must be identified and thoroughly examined in order to accurately interpret data from flight experiments or ground-based microgravity analogs.

Acceleration↗

PubMed1999

Bacterial growth in space flight: logistic growth curve parameters for Escherichia coli and Bacillus subtilis.

Previous investigations have reported that bacterial suspension cultures grow to higher stationary concentrations in space flight than on Earth; however, none of these investigations included extensive ground controls under varied inertial conditions. This study includes extensive controls and cell-growth data taken at several times during lag phase, log phase, and stationary phase of Escherichia coli and Bacillus subtilis. The Marquardt-Levenberg, least-squares fitting algorithm was used to calculate kinetic growth parameters from the logistic bacterial growth equations for space-flight and control growth curves. Space-flight cultures grew to higher stationary-phase concentrations and had shorter lag-phase durations. Also, evidence was found for increased exponential growth rate in space.

Bacillus subtilis↗

PubMed1998

The effects of space flight on the production of monorden by Humicola fuscoatra WC5157 in solid-state fermentation.

The effect of space flight on the production of the antibiotic monorden on two types of agar media, T8 and PG, by Humicola fuscoatra WC5157 was examined on board the US Space Shuttle mission STS-77 in May 1996. Paired space-flight and ground control samples were prepared using identical hardware, protocol, media, and inoculum. Inoculation occurred simultaneously for both groups 2.5 after launch. The flight and ground samples were allowed to grow for the entire 10-day mission in a dark, thermally controlled (22 degrees C) environment. Post-flight HPLC analysis of the flight and ground sample extracts indicated that the production of monorden by H. fuscoatra WC5157 in the flight samples was higher than in the ground samples in both agar media. In the T8 medium, the production of monorden in the flight and ground samples was 11.6 +/- 3.5 micrograms and 8.9 +/- 1.1 micrograms respectively (30% increase). In the PG medium, the production of monorden in the flight and ground samples was 23.8 +/- 3.3 micrograms and 8.2 +/- 2.2 micrograms respectively (190% increase). The production of monorden in the flight and ground control samples was confirmed by HPLC-MS analysis.

Antifungal Agents↗

PubMed1998

Microgravity and its implication for fermentation biotechnology.

Fermentation processes are highly dependent upon physical and chemical environmental parameters, many of which are influenced by gravity. Extending biotechnology into the realm of space flight provides researchers with an opportunity to investigate the role that gravity plays in natural growth processes. Physical factors governing cell sedimentation, nutrient mixing and byproduct dispersion are altered in the absence of the constant sedimenting force of gravity. In addition, space flight has also been shown to give rise to a wide variety of indirect consequences associated with the physiology of the organisms themselves.

Bacterial Physiological Phenomena↗

PubMed1998

Cellular responses to gravity: extracellular, intracellular and in-between.

Our understanding of gravitational effects (inertial effects in the vicinity of 1 x g) on cells has matured to a stage at which it is possible to define, on the basis of experimental evidence, extracellular effects on small cells and intracellular effects on eukaryotic gravisensing cells. Yet undetermined is the nature of response, if any, of those classes of cells that are not governed solely by extracellular physical events (as are prokaryotes) and are devoid of obvious mechanical devices for sensing inertial forces (such as those possessed by certain plant cells and sensory cells of animals). This "in-between" class of cells needs to be understood on the basis of the combination of intracellular and extracellular gravity-dependent processes that govern experimentally-measurable variables that are relevant to the cell's responses to modified inertial forces. The forces that certain cell types generate or respond to are therefore compared to those imposed by approximately 1 x g in the context of cytoskeletal action and symmetry-breaking pathways.

Animals↗

PubMed1998

Functional weightlessness during clinorotation of cell suspensions.

A clinostat is a device often used in gravitational biology studies. Selecting an appropriate speed of rotation, however, is a frequently debated topic, particularly for suspended cells. In an attempt to define the necessary criteria for determining an acceptable revolution speed, the primary forces governing particle behavior during clinorotation--gravity, diffusion and centrifugation--were mathematically assessed. In support of the theoretical exercise, bacterial growth experiments indicated that results obtained using a clinostat followed trends resembling previous space flight results. It is suspected that this is due, in part at least, to similarly altered external transport processes in each environment.

Bacterial Physiological Phenomena↗

PubMed1998

Autonomous Biological System (ABS) experiments.

Three space flight experiments have been conducted to test and demonstrate the use of a passively controlled, materially closed, bioregenerative life support system in space. The Autonomous Biological System (ABS) provides an experimental environment for long term growth and breeding of aquatic plants and animals. The ABS is completely materially closed, isolated from human life support systems and cabin atmosphere contaminants, and requires little need for astronaut intervention. Testing of the ABS marked several firsts: the first aquatic angiosperms to be grown in space; the first higher organisms (aquatic invertebrate animals) to complete their life cycles in space; the first completely bioregenerative life support system in space; and, among the first gravitational ecology experiments. As an introduction this paper describes the ABS, its flight performance, advantages and disadvantages.

Animals↗

PubMed1996

Theories and models on the biology of cells in space.

A wide variety of observations on cells in space, admittedly made under constraining and unnatural conditions in many cases, have led to experimental results that were surprising or unexpected. Reproducibility, freedom from artifacts, and plausibility must be considered in all cases, even when results are not surprising. The papers in the symposium on "Theories and Models on the Biology of Cells in Space" are dedicated to the subject of the plausibility of cellular responses to gravity--inertial accelerations between 0 and 9.8 m/s2 and higher. The mechanical phenomena inside the cell, the gravitactic locomotion of single eukaryotic and prokaryotic cells, and the effects of inertial unloading on cellular physiology are addressed in theoretical and experimental studies.

Bacteria↗

PubMed1994

Four educational programs in Space Life Sciences.

Four different educational programs impacting Space Life Sciences are described: the NASA/USRA Advanced Design Program, the NASA Specialized Center of Research and Training (NSCORT) Program, the Centers for the Commercial Development of Space (CCDS) Program, and the NASA Graduate Research Fellow Program. Each program makes somewhat different demands on the students engaged in them. Each program, at the University of Colorado, involves Space Life Sciences training. While the Graduate Student Research Fellow and NSCORT Programs are discipline oriented, the Advanced Design and CCDS Programs are focused on design, technologies and applications. Clearly, the "training paradigms" differ for these educational endeavors. But, these paradigms can be made to mutually facilitate enthusiasm and motivation. Discipline-oriented academic programs, ideally, must be flexible enough to accommodate the emergent cross-disciplinary needs of Space Life Sciences students. Models for such flexibility and resultant student performance levels are discussed based upon actual academic and professional records.

Biological Science Disciplines↗