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  • Life Sciences (General)  (1,190)
  • Aircraft Stability and Control
  • Analytical Chemistry and Spectroscopy
  • GENERAL
  • Inorganic Chemistry
  • 2000-2004  (635)
  • 1995-1999  (822)
  • 1955-1959  (48)
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  • 1
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    Culturability as an indicator of succession in microbial communities (2001)
    In:  Other Sources
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    Publication Date: 2011-08-24
    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.
    Keywords: Life Sciences (General)
    Type: Microbial ecology (ISSN 0095-3628); Volume 42; 2; 150-8
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  • 2
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    Novel method to assess gastric emptying in humans: the Pellet Gastric Emptying Test (2001)
    In:  Other Sources
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    Publication Date: 2019-07-13
    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.
    Keywords: Life Sciences (General)
    Type: European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences (ISSN 0928-0987); 14; 4; 347-53
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  • 3
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    Drug marker absorption in relation to pellet size, gastric motility and viscous meals in humans (1998)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: PURPOSE: The objective of this study was to evaluate drug marker absorption in relation to the gastric emptying (GE) of 0.7 mm and 3.6 mm enteric coated pellets as a function of viscosity and the underlying gastric motility. METHODS: Twelve subjects were evaluated in a 3-way crossover study. 0.7 mm caffeine and 3.6 mm acetaminophen enteric coated pellets were concurrently administered with a viscous caloric meal at the levels of 4000, 6000 and 8000 cP. Gastric motility was simultaneously measured with antral manometry and compared to time events in the plasma profiles of the drug markers. RESULTS: Caffeine, from the 0.7 mm pellets, was observed significantly earlier in the plasma than acetaminophen, from the 3.6 mm pellets, at all levels of viscosity. Motility related size differentiated GE was consistently observed at all viscosity levels, however, less variability was observed with the 4000 cP meal. Specifically, the onset of absorption from the of 3.6 mm pellets correlated with the onset of Phase II fasted state contractions (r = 0.929, p 〈 0.01). CONCLUSIONS: The timeframe of drug marker absorption and the onset of motility events were not altered within the range of viscosities evaluated. Rather, the differences in drug marker profiles from the non-digestible solids were most likely the result of the interaction between viscosity and motility influencing antral flow dynamics. The administration of the two sizes of pellets and a viscous caloric meal with subsequent monitoring of drug marker profiles is useful as a reference to assess the influence of motility patterns on the absorption profile of orally administered agents.
    Keywords: Life Sciences (General)
    Type: Pharmaceutical research (ISSN 0724-8741); 15; 2; 233-8
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  • 4
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    Influence of respiratory motor neurone activity on human autonomic and haemodynamic rhythms (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    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.
    Keywords: Life Sciences (General)
    Type: Clinical physiology (Oxford, England) (ISSN 0144-5979); 21; 3; 323-34
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  • 5
    Electronic Resource
    Electronic Resource
    GC-MS determination of catechin and epicatechin levels in human plasma (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 621-623 
    Details
    ISSN: 0935-6304
    Keywords: GC-MS ; Catechin ; Epicatechin ; Flavonoids ; Plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240201111
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  • 6
    Electronic Resource
    Electronic Resource
    Conformational and configurational study of 1,3-dioxolanes by proton and carbon NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 167-173 
    Details
    ISSN: 0749-1581
    Keywords: 1,3-dioxolanes ; NOE ; vicinal proton-proton coupling ; configurational analysis ; conformational analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational and conformational properties of six 4-trimethylammoniummethyl 2,2-disubstituted 1,3-dioxolanes were studied using NOE experiments and vicinal coupling constants. Selective 1D NOE experiments proved to be effective tools in the configurational assignment of C-2 relative to C-4. The preferred conformation of the dioxolane ring and the exocyclic group at C-4 was obtained by employing vicinal coupling constants and NOE results. The 1H and 13C NMR chemical shifts show stereochemically dependent trends. Quantitative analysis of conformer populations was performed using Haasnoot et al's equation. The —N+(CH3)3 group was found to be synclinal with respect to the heterocyclic O-3 atom and points outside the ring. When a phenyl group is present at C-2, the 4-CH2N+ -  group in a trans relationship to the 2-phenyl ring was found to occur prevalently in a pseudo-axial orientation, whereas it was established to be prevalently pseudo-equatorial when cis with respect to the phenyl ring.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330303
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  • 7
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    Spaceflight alters microtubules and increases apoptosis in human lymphocytes (Jurkat) (1998)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Alteration in cytoskeletal organization appears to underlie mechanisms of gravity sensitivity in space-flown cells. Human T lymphoblastoid cells (Jurkat) were flown on the Space Shuttle to test the hypothesis that growth responsiveness is associated with microtubule anomalies and mediated by apoptosis. Cell growth was stimulated in microgravity by increasing serum concentration. After 4 and 48 h, cells filtered from medium were fixed with formalin. Post-flight, confocal microscopy revealed diffuse, shortened microtubules extending from poorly defined microtubule organizing centers (MTOCs). In comparable ground controls, discrete microtubule filaments radiated from organized MTOCs and branched toward the cell membrane. At 4 h, 30% of flown, compared to 17% of ground, cells showed DNA condensation characteristic of apoptosis. Time-dependent increase of the apoptosis-associated Fas/ APO-1 protein in static flown, but not the in-flight 1 g centrifuged or ground controls, confirmed microgravity-associated apoptosis. By 48 h, ground cultures had increased by 40%. Flown populations did not increase, though some cells were cycling and actively metabolizing glucose. We conclude that cytoskeletal alteration, growth retardation, and metabolic changes in space-flown lymphocytes are concomitant with increased apoptosis and time-dependent elevation of Fas/APO-1 protein. We suggest that reduced growth response in lymphocytes during spaceflight is linked to apoptosis.
    Keywords: Life Sciences (General)
    Type: The FASEB journal : official publication of the Federation of American Societies for Experimental Biology (ISSN 0892-6638); Volume 12; 11; 1007-18
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  • 8
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    Effects of heavy ions on visual function and electrophysiology of rodents: the ALTEA-MICE project (2004)
    In:  Other Sources
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    Publication Date: 2011-08-24
    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.
    Keywords: Life Sciences (General)
    Type: Advances in space research : the official journal of the Committee on Space Research (COSPAR); Volume 33; 8; 1347-51
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  • 9
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    Transport proteins of the plant plasma membrane (1996)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Recently developed molecular and genetic approaches have enabled the identification and functional characterization of novel genes encoding ion channels, ion carriers, and water channels of the plant plasma membrane.
    Keywords: Life Sciences (General)
    Type: Current opinion in cell biology (ISSN 0955-0674); Volume 8; 4; 458-67
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  • 10
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    A model for the kinetics of homotypic cellular aggregation under static conditions (1997)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We present the formulation and testing of a mathematical model for the kinetics of homotypic cellular aggregation. The model considers cellular aggregation under no-flow conditions as a two-step process. Individual cells and cell aggregates 1) move on the tissue culture surface and 2) collide with other cells (or aggregates). These collisions lead to the formation of intercellular bonds. The aggregation kinetics are described by a system of coupled, nonlinear ordinary differential equations, and the collision frequency kernel is derived by extending Smoluchowski's colloidal flocculation theory to cell migration and aggregation on a two-dimensional surface. Our results indicate that aggregation rates strongly depend upon the motility of cells and cell aggregates, the frequency of cell-cell collisions, and the strength of intercellular bonds. Model predictions agree well with data from homotypic lymphocyte aggregation experiments using Jurkat cells activated by 33B6, an antibody to the beta 1 integrin. Since cell migration speeds and all the other model parameters can be independently measured, the aggregation model provides a quantitative methodology by which we can accurately evaluate the adhesivity and aggregation behavior of cells.
    Keywords: Life Sciences (General)
    Type: Biophysical journal (ISSN 0006-3495); Volume 72; 1; 51-64
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