ALBERT

Description: Successional theory predicts that opportunistic species with high investment of energy in reproduction and wide niche width will be replaced by equilibrium species with relatively higher investment of energy in maintenance and narrower niche width as communities develop. Since the ability to rapidly grow into a detectable colony on nonselective agar medium could be considered as characteristic of opportunistic types of bacteria, the percentage of culturable cells may be an indicator of successional state in microbial communities. The ratios of culturable cells (colony forming units on R2A agar) to total cells (acridine orange direct microscopic counts) and culturable cells to active cells (reduction of 5-cyano-2,3-ditolyl tetrazolium chloride) were measured over time in two types of laboratory microcosms (the rhizosphere of hydroponically grown wheat and aerobic, continuously stirred tank reactors containing plant biomass) to determine the effectiveness of culturabilty as an index of successional state. The culturable cell:total cell ratio in the rhizosphere decreased from approximately 0.25 to less than 0.05 during the first 30-50 days of plant growth, and from 0.65 to 0.14 during the first 7 days of operation of the bioreactor. The culturable cell:active cell ratio followed similar trends, but the values were consistently greater than the culturable cell:total cell ratio, and even exceeded I in early samples. Follow-up studies used a cultivation-independent method, terminal restriction fragment length polymorphisms (TRFLP) from whole community DNA, to assess community structure. The number of TRFLP peaks increased with time, while the number of culturable types did not, indicating that the general decrease in culturability is associated with a shift in community structure. The ratio of respired to assimilated C-14-labeled amino acids increased with the age of rhizosphere communities, supporting the hypothesis that a shift in resource allocation from growth to maintenance occurs with time. Results from this work indicate that the percentage of culturable cells may be a useful method for assessing the successional state of microbial communities.

Description: To further validate the Pellet Gastric Emptying Test (PGET) as a marker of gastric emptying, a randomized, four-way crossover study was conducted with 12 healthy subjects. The study consisted of oral co-administration of enteric coated caffeine (CAFF) and acetaminophen (APAP) pellets in four treatment phases: Same Size (100 kcal), Fasted, Small Liquid Meal (100 kcal), and Standard Meal (847 kcal). The time of first appearance of measurable drug marker in plasma, t(initial), was taken as the emptying time for the markers. Co-administration of same size enteric coated pellets of CAFF and APAP (0.7 mm in diameter) revealed no statistically significant differences in t(initial) values indicating that emptying was dependent only on size and not on chemical make-up of the pellets. Co-administration of different size pellets indicated that the smaller 0.7-mm diameter (CAFF) pellets were emptied and absorbed significantly earlier than the larger 3.6-mm diameter (APAP) pellets with both the Small Liquid Meal (by 35 min) and the Standard Meal (by 33 min) (P〈0.05). The differences in emptying of the pellets were not significant in the Fasted Phase. The results suggest that the pellet gastric emptying test could prove useful in monitoring changes in transit times in the fasted and fed states and their impact on drug absorption.

Description: Although humans hold great advantages over other species as subjects for biomedical research, they also bring major disadvantages. One is that among the many rhythmic physiological signals that can be recorded, there is no sure way to know which individual change precedes another, or which change represents cause and which represents effect. In an attempt to deal with the inherent complexity of research conducted in intact human subjects, we developed and used a structural equation model to analyse responses of healthy young men to pharmacological changes of arterial pressure and graded inspiratory resistance, before and after vagomimetic atropine. Our model yielded a good fit of the experimental data, with a system weighted R2 of 0.77, and suggested that our treatments exerted both direct and indirect influences on the variables we measured. Thus, infusions of nitroprusside and phenylephrine exerted all of their direct effects by lowering and raising arterial pressure; the changes of R-R intervals, respiratory sinus arrhythmia and arterial pressure fluctuations that these drugs provoked, were indirect consequences of arterial pressure changes. The only direct effect of increased inspiratory resistance was augmentation of arterial pressure fluctuations. These results may provide a new way to disentangle and understand responses of intact human subjects to experimental forcings. The principal new insight we derived from our modelling is that respiratory gating of vagal-cardiac motor neurone firing is nearly maximal at usual levels of arterial pressure and inspiratory motor neurone activity.

Description: ALTEA-MICE will supplement the ALTEA project on astronauts and provide information on the functional visual impairment possibly induced by heavy ions during prolonged operations in microgravity. Goals of ALTEA-MICE are: (1) to investigate the effects of heavy ions on the visual system of normal and mutant mice with retinal defects; (2) to define reliable experimental conditions for space research; and (3) to develop animal models to study the physiological consequences of space travels on humans. Remotely controlled mouse setup, applied electrophysiological recording methods, remote particle monitoring, and experimental procedures were developed and tested. The project has proved feasible under laboratory-controlled conditions comparable in important aspects to those of astronauts' exposure to particle in space. Experiments are performed at the Brookhaven National Laboratories [BNL] (Upton, NY, USA) and the Gesellschaft fur Schwerionenforschung mbH [GSI]/Biophysik (Darmstadt, FRG) to identify possible electrophysiological changes and/or activation of protective mechanisms in response to pulsed radiation. Offline data analyses are in progress and observations are still anecdotal. Electrophysiological changes after pulsed radiation are within the limits of spontaneous variability under anesthesia, with only indirect evidence of possible retinal/cortical responses. Immunostaining showed changes (e.g. increased expression of FGF2 protein in the outer nuclear layer) suggesting a retinal stress reaction to high-energy particles of potential relevance in space. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Description: Using a maskless photolithography method, we produced DNA oligonucleotide microarrays with probe sequences tiled throughout the genome of the plant Arabidopsis thaliana. RNA expression was determined for the complete nuclear, mitochondrial, and chloroplast genomes by tiling 5 million 36-mer probes. These probes were hybridized to labeled mRNA isolated from liquid grown T87 cells, an undifferentiated Arabidopsis cell culture line. Transcripts were detected from at least 60% of the nearly 26,330 annotated genes, which included 151 predicted genes that were not identified previously by a similar genome-wide hybridization study on four different cell lines. In comparison with previously published results with 25-mer tiling arrays produced by chromium masking-based photolithography technique, 36-mer oligonucleotide probes were found to be more useful in identifying intron-exon boundaries. Using two-dimensional HPLC tandem mass spectrometry, a small-scale proteomic analysis was performed with the same cells. A large amount of strongly hybridizing RNA was found in regions "antisense" to known genes. Similarity of antisense activities between the 25-mer and 36-mer data sets suggests that it is a reproducible and inherent property of the experiments. Transcription activities were also detected for many of the intergenic regions and the small RNAs, including tRNA, small nuclear RNA, small nucleolar RNA, and microRNA. Expression of tRNAs correlates with genome-wide amino acid usage.

Description: We hypothesized that vestibular otolith organ stimulation contributes to human orthostatic responses. Twelve subjects underwent three 60 degrees upright tilts: (1) with the neck flexed from 0 degrees to 30 degrees relative to the body during 60 degrees tilt, such that the head moved from horizontal to 90 degrees above horizontal (0 to 1 Gz otolith stimulation); (2) with the head and body aligned, such that they tilted together to 60 degrees (0 to 0.87 Gz otolith stimulation); and (3) with the neck flexed 30 degrees relative to the body during supine conditions, and the neck then extended to -30 degrees during 60 degrees body tilting, such that the head remained at 30 degrees above horizontal throughout body tilting (constant 0.5 Gz otolith stimulation). All three tilt procedures increased thoracic impedance, sympathetic nerve activity (N = 8 of 12), arterial pressure, and heart rate relative to supine conditions (all P 〈 0.04). Within the first 20 s of tilt, arterial pressure increased most obviously in the 0 to 1 Gz otolith condition. Thoracic impedance tended to increase more in otolith-constant conditions, but no dependent variable differed significantly between tilt conditions, and no significant time x tilt interactions emerged. Otolith inputs may contribute to early transient adjustments to orthostasis. However, lack of significant main effects of tilt condition and time x tilt interactions suggests that potential otolith effects on the variables we studied are relatively subtle and ephemeral, or that other mechanisms compensate for a lack of change in otolith input with orthostasis.

Description: Deep-space manned flight as a reality depends on a viable solution to the radiation problem. Both acute and chronic radiation health threats are known to exist, with solar particle events as an example of the former and galactic cosmic rays (GCR) of the latter. In this experiment Iron ions of 1A GeV are used to simulate GCR and to determine the secondary radiation field created as the GCR-like particles interact with a thick target. A NASA prepared food pantry locker was subjected to the iron beam and the secondary fluence recorded. A modified version of the Monte Carlo heavy ion transport code developed by Zeitlin at LBNL is compared with experimental fluence. The foodstuff is modeled as mixed nuts as defined by the 71st edition of the Chemical Rubber Company (CRC) Handbook of Physics and Chemistry. The results indicate a good agreement between the experimental data and the model. The agreement between model and experiment is determined using a linear fit to ordered pairs of data. The intercept is forced to zero. The slope fit is 0.825 and the R2 value is 0.429 over the resolved fluence region. The removal of an outlier, Z=14, gives values of 0.888 and 0.705 for slope and R2 respectively. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Description: Two configurations of a continuous wave quantum cascade distributed feedback laser-based gas sensor for the detection of NO at a parts per billion (ppb) concentration level, typical of biomedical applications, have been investigated. The laser was operated at liquid nitrogen temperature near lambda = 5.2 microns. In the first configuration, a 100 m optical path length multi-pass cell was employed to enhance the NO absorption. In the second configuration, a technique based on cavity-enhanced spectroscopy (CES) was utilized, with an effective path length of 670 m. Both sensors enabled simultaneous analysis of NO and CO2 concentrations in exhaled air. The minimum detectable NO concentration was found to be 3 ppb with a multi-pass cell and 16 ppb when using CES. The two techniques are compared, and potential future developments are discussed.

Description: Adequate nutrition is critical during long-term spaceflight, as is the ability to easily monitor dietary intake. A comprehensive nutritional status assessment profile was designed for use before, during and after flight. It included assessment of both dietary intake and biochemical markers of nutritional status. A spaceflight food-frequency questionnaire (FFQ) was developed to evaluate intake of key nutrients during spaceflight. The nutritional status assessment protocol was evaluated during two ground-based closed-chamber studies (60 and 91 d; n = 4/study), and was implemented for two astronauts during 4-mo stays on the Mir space station. Ground-based studies indicated that the FFQ, administered daily or weekly, adequately estimated intake of key nutrients. Chamber subjects maintained prechamber energy intake and body weight. Astronauts tended to eat 40--50% of WHO-predicted energy requirements, and lost 〉10% of preflight body mass. Serum ferritin levels were lower after the chamber stays, despite adequate iron intake. Red blood cell folate concentrations were increased after the chamber studies. Vitamin D stores were decreased by 〉 40% on chamber egress and after spaceflight. Mir crew members had decreased levels of most nutritional indices, but these are difficult to interpret given the insufficient energy intake and loss of body mass. Spaceflight food systems can provide adequate intake of macronutrients, although, as expected, micronutrient intake is a concern for any closed or semiclosed food system. These data demonstrate the utility and importance of nutritional status assessment during spaceflight and of the FFQ during extended-duration spaceflight.

Description: Articular cartilage is a heterogeneous tissue, with cell density and organization varying with depth from the surface. The objectives of the present study were to establish a method for localizing individual cells in three-dimensional (3D) images of cartilage and quantifying depth-associated variation in cellularity and cell organization at different stages of growth. Accuracy of nucleus localization was high, with 99% sensitivity relative to manual localization. Cellularity (million cells per cm3) decreased from 290, 310, and 150 near the articular surface in fetal, calf, and adult samples, respectively, to 120, 110, and 50 at a depth of 1.0 mm. The distance/angle to the nearest neighboring cell was 7.9 microm/31 degrees , 7.1 microm/31 degrees , and 9.1 microm/31 degrees for cells at the articular surface of fetal, calf, and adult samples, respectively, and increased/decreased to 11.6 microm/31 degrees , 12.0 microm/30 degrees , and 19.2 microm/25 degrees at a depth of 0.7 mm. The methodologies described here may be useful for analyzing the 3D cellular organization of cartilage during growth, maturation, aging, degeneration, and regeneration.