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981.
982.
A photoacoustic study of water infiltrated leaves 总被引:5,自引:0,他引:5
Photoacoustic measurements of photosynthetic energy storage were conducted on water infiltrated pea and sugar maple leaves. The samples were vacuum infiltrated with pure water or with a suitable buffer. The use of such methodology permitted an accurate determination of the energy storage parameter at low modulation frequencies, where in non-infiltrated leaves oxygen evolution dominates the photoacoustic signal and does not allow energy storage measurements. Differences between infiltration media were not essential, however the use of pure water as infiltration medium sometimes caused instability of the measured energy storage, particularly at longer experimental time. Values of energy storage in individual samples ranged mostly between 0.2 to 0.35. Measured as a function of the modulation frequency, energy storage was found to be constant from about 10 to 200 Hz for pea leaves. In sugar maple leaves, the energy storage slightly increased between 100 and 500 Hz. Obtaining an accurate value for energy storage also allowed an accurate estimation of the O2 evolution contribution to the photoacoustic signal of an unfiltrated leaf. In a maple leaf its frequency dependence showed only the effect of diffusion in the entire frequency range (10–500 Hz). Energy storage transients were observed after long periods (ca. 1/4-2 hrs) of dark adaptation upon the transition to light. In this case the initial energy storage was roughly about 1/2 that of the steady state value indicating strong PS I activity, while PS II was transiently incompetent. Energy-storage increased during illumination in a way to correspond to photosynthetic induction events as previously measured by fluorescence and O2 evolution. Transients in energy storage were also found following high light to low light transitions (i.e., switch off of the saturating background light), that paralleled similar transients in oxygen evolution, showing initial transient inactivation followed by progressive reactivation of PS II.Abbreviations ES
energy storage
- PA
photoacoustic(s)
- PTR
photothermal radiometry 相似文献
983.
Annette Tennstaedt Alfonso Mastropietro Melanie Nelles Andreas Beyrau Mathias Hoehn 《PloS one》2015,10(12)
We generated transgenic human neural stem cells (hNSCs) stably expressing the reporter genes Luciferase for bioluminescence imaging (BLI) and GFP for fluorescence imaging, for multimodal imaging investigations. These transgenic hNSCs were further labeled with a clinically approved perfluoropolyether to perform parallel 19F MRI studies. In vitro validation demonstrated normal cell proliferation and differentiation of the transgenic and additionally labeled hNSCs, closely the same as the wild type cell line, making them suitable for in vivo application. Labeled and unlabeled transgenic hNSCs were implanted into the striatum of mouse brain. The time profile of their cell fate after intracerebral grafting was monitored during nine days following implantation with our multimodal imaging approach, assessing both functional and anatomical condition. The 19F MRI demarcated the graft location and permitted to estimate the cell number in the graft. BLI showed a pronounce cell loss during this monitoring period, indicated by the decrease of the viability signal. The in vivo obtained cell fate results were further validated and confirmed by immunohistochemistry. We could show that the surviving cells of the graft continued to differentiate into early neurons, while the severe cell loss could be explained by an inflammatory reaction to the graft, showing the graft being surrounded by activated microglia and macrophages. These results are different from earlier cell survival studies of our group where we had implanted the identical cells into the same mouse strain but in the cortex and not in the striatum. The cortical transplanted cells did not show any loss in viability but only pronounced and continuous neuronal differentiation. 相似文献
984.
985.
Very Low Ethanol Concentrations Affect the Viability and Growth Recovery in Post-Stationary-Phase Staphylococcus aureus Populations
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Indranil Chatterjee Greg A. Somerville Christine Heilmann Hans-Georg Sahl Hans H. Maurer Mathias Herrmann 《Applied microbiology》2006,72(4):2627-2636
Pharmaceuticals, culture media used for in vitro diagnostics and research, human body fluids, and environments can retain very low ethanol concentrations (VLEC) (≤0.1%, vol/vol). In contrast to the well-established effects of elevated ethanol concentrations on bacteria, little is known about the consequences of exposure to VLEC. We supplemented growth media for Staphylococcus aureus strain DSM20231 with VLEC (VLEC+ conditions) and determined ultramorphology, growth, and viability compared to those with unsupplemented media (VLEC− conditions) for prolonged culture times (up to 8 days). VLEC+-grown late-stationary-phase S. aureus displayed extensive alterations of cell integrity as shown by scanning electron microscopy. Surprisingly, while ethanol in the medium was completely metabolized during exponential phase, a profound delay of S. aureus post-stationary-phase recovery (>48 h) was observed. Concomitantly, under VLEC+ conditions, the concentration of acetate in the culture medium remained elevated while that of ammonia was reduced, contributing to an acidic culture medium and suggesting decreased amino acid catabolism. Interestingly, amino acid depletion was not uniformly affected: under VLEC+ conditions, glutamic acid, ornithine, and proline remained in the culture medium while the uptake of other amino acids was not affected. Supplementation with arginine, but not with other amino acids, was able to restore post-stationary-phase growth and viability. Taken together, these data demonstrate that VLEC have profound effects on the recovery of S. aureus even after ethanol depletion and delay the transition from primary to secondary metabolite catabolism. These data also suggest that the concentration of ethanol needed for bacteriostatic control of S. aureus is lower than that previously reported. 相似文献
986.
987.
Simon Garnier Tucker Murphy Matthew Lutz Edward Hurme Simon Leblanc Iain D. Couzin 《PLoS computational biology》2013,9(3)
Robustness and adaptability are central to the functioning of biological systems, from gene networks to animal societies. Yet the mechanisms by which living organisms achieve both stability to perturbations and sensitivity to input are poorly understood. Here, we present an integrated study of a living architecture in which army ants interconnect their bodies to span gaps. We demonstrate that these self-assembled bridges are a highly effective means of maintaining traffic flow over unpredictable terrain. The individual-level rules responsible depend only on locally-estimated traffic intensity and the number of neighbours to which ants are attached within the structure. We employ a parameterized computational model to reveal that bridges are tuned to be maximally stable in the face of regular, periodic fluctuations in traffic. However analysis of the model also suggests that interactions among ants give rise to feedback processes that result in bridges being highly responsive to sudden interruptions in traffic. Subsequent field experiments confirm this prediction and thus the dual nature of stability and flexibility in living bridges. Our study demonstrates the importance of robust and adaptive modular architecture to efficient traffic organisation and reveals general principles regarding the regulation of form in biological self-assemblies. 相似文献
988.
Halldis Hellebust Mathias Uhlén Sven-Olof Enfors 《Applied microbiology and biotechnology》1988,28(3):258-262
Summary Fermentation of the fused protein staphylococcal protein A-human insulin-like growth factor I (SpA-IGF-I) was investigated. The fused protein was expressed in Staphylococcus aureus and secreted to the culture medium. The production of SpA-IGF-I was growth related and started after a short lag phase. Examination of the product quality by SDS-PAGE after IgG affinity purification showed that the product was partially degraded. Exoproteases appeared later than SpA-IGF-I and were responsible for some, but probably not all, of the degradation of the product. It was possible to influence the exoprotease activity and thereby the product degradation by varying the cultivation conditions. 相似文献
989.
Kristen L. Hollands Trudy A. Pelton Andrew Wimperis Diane Whitham Wei Tan Sue Jowett Catherine M. Sackley Alan M. Wing Sarah F. Tyson Jonathan Mathias Marianne Hensman Paulette M. van Vliet 《PloS one》2015,10(10)
Objectives
Given the importance of vision in the control of walking and evidence indicating varied practice of walking improves mobility outcomes, this study sought to examine the feasibility and preliminary efficacy of varied walking practice in response to visual cues, for the rehabilitation of walking following stroke.Design
This 3 arm parallel, multi-centre, assessor blind, randomised control trial was conducted within outpatient neurorehabilitation servicesParticipants
Community dwelling stroke survivors with walking speed <0.8m/s, lower limb paresis and no severe visual impairmentsIntervention
Over-ground visual cue training (O-VCT), Treadmill based visual cue training (T-VCT), and Usual care (UC) delivered by physiotherapists twice weekly for 8 weeks.Main outcome measures: Participants were randomised using computer generated random permutated balanced blocks of randomly varying size. Recruitment, retention, adherence, adverse events and mobility and balance were measured before randomisation, post-intervention and at four weeks follow-up.Results
Fifty-six participants participated (18 T-VCT, 19 O-VCT, 19 UC). Thirty-four completed treatment and follow-up assessments. Of the participants that completed, adherence was good with 16 treatments provided over (median of) 8.4, 7.5 and 9 weeks for T-VCT, O-VCT and UC respectively. No adverse events were reported. Post-treatment improvements in walking speed, symmetry, balance and functional mobility were seen in all treatment arms.Conclusions
Outpatient based treadmill and over-ground walking adaptability practice using visual cues are feasible and may improve mobility and balance. Future studies should continue a carefully phased approach using identified methods to improve retention.Trial Registration
Clinicaltrials.gov NCT01600391 相似文献990.
Annet Nanvubya Julius Ssempiira Juliet Mpendo Ali Ssetaala Annet Nalutaaya Mathias Wambuzi Paul Kitandwe Bernard S. Bagaya Sabrina Welsh Stephen Asiimwe Leslie Nielsen Fredrick Makumbi Noah Kiwanuka 《PloS one》2015,10(10)