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41.
Lisa M. Vogler Sumner W. Jones Glen E. Jensen R. Gary Brewer Karen J. Brewer 《Inorganica chimica acta》1996,250(1-2):155-162
A number of osmium and ruthenium complexes of the tridentate ligands 2,2′:6′,2″-terpyridine (tpy) and 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tpp) have been prepared and characterized by our laboratory. All these complexes possess metal based oxidations and ligand based reductions localized on each polyazine ligand. Polymetallic complexes bridged by the tpp ligand exhibit two sequential tpp based reductions prior to the reduction of other polyazine ligands in these complexes. The spectroscopy of these complexes is dominated by ligand based π-π* transitions in the ultraviolet and MLCT (metal-to-ligand charge transfer) bands terminating on each polyzine ligand in the visible. For the complexes reported herein the lowest lying optical transitionis a M → BL CT band. For most of the complexes reported, occupation of this excited state gives rise to an observable emission at room temperature. For ruthenium complexes of these tridentate ligands, the presence of a low-lying LF state shortens the excited state lifetimes of these chromophores. This gives rise to ruthenium complexes that display shorter excited state lifetimes than the analogous osmium based systems. Incorporation of tpp based chromophores into polymetallic frameworks leads to the production of bimetallic species with long-lived excited states, 100 ns at room temperature. This makes these chromophores good candidates for the development of stereochemically defined supramolecular complexes. It is possible to measure an electrochemical HOMO-LUMO energy gap and a correlation between this electrochemically measured energy gap and the spectroscopic energy associated with this HOMO→LUMO transition are reported herein (HOMO== highest occupied molecular orbital, LUMO = lowest unoccupied molecular orbital). 相似文献
42.
Hydroperoxide inactivation of enzymes within spores of Bacillus megaterium ATCC19213 总被引:2,自引:0,他引:2
Abstract Hydroperoxide inactivation of the protoplast enzymes enolase, aldolase and glucose-6-phosphate dehydrogenase in intact spores of Bacillus megaterium ATCC19213 was assessed by first treating the cells with lethal levels of H2 O2 , then germinating them in the presence of chloramphenicol prior to permeabilization and enzyme assays. Glucose-6-phosphate dehydrogenase proved to be more sensitive to H2 O2 than enolase or aldolase, in agreement with findings for isolated enzymes. Average D values (time for 90% inactivation) for spores treated with 0.50% H2 O2 were 173 min for enolase, 67 min for aldolase and 32 min for glucose-6-phosphate dehydrogenase, compared with a D value of 34 min for spore killing. H2 O2 killing of spores was found to be conditional in that recoveries of survivors were greater on complex medium than on minimal medium. Overall, it appeared that oxidative inactivation of enzymes may be important for hydroperoxide killing of spores. 相似文献
43.
44.
The stable isotopes 2H and 18O were used to determine the water sources of Eucalyptus camaldulensis at three sites with varying exposure to stream water, all underlain by moderately saline groundwater. Water uptake patterns were a function of the long-term availability of surface water. Trees with permanent access to a stream used some stream water at all times. However, water from soils or the water table commonly made up 50% of these trees' water. Trees beside an ephemeral stream had access to the stream 40–50% of the time (depending on the level of the stream). No more than 30% of the water they used was stream water when it was available. However, stream water use did not vary greatly whether the trees had access to the stream for 2 weeks or 10 months prior to sampling. Trees at the third site only had access to surface water during a flood. These trees did not change their uptake patterns during 2 months inundation compared with dry times, so were not utilising the low-salinity flood water. Pre-dawn leaf water potentials and leaf 13C measurements showed that the trees with permanent access to the stream experienced lower water stress and had lower water use efficiencies than trees at the least frequently flooded site. The trees beside the ephemeral stream appeared to change their water use efficiency in response to the availability of surface water; it was similar to the perennial-stream trees when stream water was available and higher at other times. Despite causing water stress, uptake of soil water and groundwater would be advantageous to E. camaldulensis in this semi-arid area, as it would provide the trees with a supply of nutrients and a reliable source of water. E. camaldulensis at the study site may not be as vulnerable to changes in stream flow and water quality as previously thought. 相似文献
45.
Lymphocytes protect against and are not required for reovirus-induced myocarditis. 总被引:11,自引:10,他引:1 下载免费PDF全文
Many studies suggest that host lymphocytes are damaging, rather than protective, in virally induced myocarditis. We have investigated the role of lymphocyte-based immunity in murine myocarditis by using a myocarditic reovirus (reovirus serotype 3 8B), nonmyocarditic reoviruses, adoptive transfer experiments, and mice with severe combined immunodeficiency (SCID mice). Prior to infection, passive transfer of monoclonal antibodies specific for 8B capsid proteins protected neonatal mice against 8B-induced myocarditis, indicating that humoral immunity can protect against myocarditis. Some monoclonal antibodies acted by blocking viral spread to and/or replication in the heart. Passive transfer of reovirus-immune, but not naive, spleen cells prior to infection protected neonatal mice from 8B-induced myocarditis. Depletion of either CD4 or CD8 T cells resulted in increased viral titer in the heart but did not abrogate immune cell-mediated protection against myocardial injury. This shows that both CD4 and CD8 T cells can act independently to protect myocardial tissue from reovirus infection. In addition, reovirus 8B caused extensive myocarditis in SCID mice. This confirms a prior report (B. Sherry, F. J. Schoen, E. Wenske, and B. N. Fields, J. Virol. 63:4840-4849, 1989) that T cells are not required for reovirus-induced myocarditis and demonstrates for the first time that B cells are not required for reovirus-induced myocarditis. We used SCID mice and a panel of reoviruses to assess (i) the relationship between growth in the heart and myocardial damage and (ii) the possibility that nonmyocarditic reoviruses exhibit a myocarditic phenotype in the absence of functional lymphocytes. Growth in the heart was not the sole determinant of myocarditic potential in SCID mice. Although 8B induced myocarditis in SCID mice, no or minimal myocarditis was found in SCID mice infected with four reovirus strains previously shown (B. Sherry and B. N. Fields, J. Virol. 63:4850-4856, 1989) to be nonmyocarditic or poorly myocarditic in normal neonatal mice. We conclude that (i) humoral immunity and cellular immunity are protective against, and not required for, reovirus-induced myocarditis and (ii) the potential to induce cardiac damage is a property of the virus independent of lymphocyte-based immunity. 相似文献
46.
Several di-, tri-, and oligopeptides were incubated individually in vitro with rumen fluid from two sheep receiving a mixed grass hay/concentrate diet and with washed cells ofPrevotella (formerlyBacteroides)ruminicola M384 andP. ruminicola B14. The rates of breakdown of most peptides were similar in the rumen fluid from the two sheep. Acidic and proline-containing peptides tended to be more slowly degraded than neutral or basic peptides. The dipeptide at the N-terminus of higher peptides was observed as an early product of hydrolysis, confirming that a dipeptidyl aminopeptidase type of activity was present. The relative rates of breakdown of dipeptides byP. ruminicola were different from that of rumen fluid, but the hydrolysis of higher peptides followed a similar pattern, and dipeptides from the N-terminus were detected as early products. 相似文献
47.
A nematode, Phasmarhabditis hermaphrodita, known to be associated with slugs but not previously thought to be parasitic, was shown to be a parasite capable of killing the pest slug Deroceras reticulatum. The parasite infects slugs in the area beneath the mantle surrounding the shell, causing a disease with characteristic symptoms, particularly swelling of the mantle. Infection leads to death of the slug, usually between seven and 21 days afterwards. The nematode then spreads and multiplies in the cadaver. In an experiment where individual D. reticulatum were exposed to different numbers of P. hermaphrodita, a significant positive relationship was found between nematode dose and slug mortality. In two experiments on host range, the nematode was found to infect and kill all pest slug species tested: Deroceras caruanae, Arion distinctus, Arion silvaticus, Arion intermedius, Arion ater, Tandonia sowerbyi and T. budapestensis, in addition to D. reticulatum. 相似文献
48.
R. Ashton Lavoie Jeffrey T. Zugates Andrew T. Cheeseman Matt A. Teten Srivatsan Ramesh Julia M. Freeman Summer Swango Jeremy Fitzpatrick Amod Joshi Bradley Hollers Zufan Debebe Tyler K. Lindgren Amber N. Kozak Vinay K. Kondeti Mary K. Bright Eric J. Yearley Alexander Tracy Jacob A. Irwin Michael Guerrero 《Biotechnology and bioengineering》2023,120(10):2953-2968
Adeno-associated virus-based gene therapies have demonstrated substantial therapeutic benefit for the treatment of genetic disorders. In manufacturing processes, viral capsids are produced with and without the encapsidated gene of interest. Capsids devoid of the gene of interest, or “empty” capsids, represent a product-related impurity. As a result, a robust and scalable method to enrich full capsids is crucial to provide patients with as much potentially active product as possible. Anion exchange chromatography has emerged as a highly utilized method for full capsid enrichment across many serotypes due to its ease of use, robustness, and scalability. However, achieving sufficient resolution between the full and empty capsids is not trivial. In this work, anion exchange chromatography was used to achieve empty and full capsid resolution for adeno-associated virus serotype 5. A salt gradient screen of multiple salts with varied valency and Hofmeister series properties was performed to determine optimal peak resolution and aggregate reduction. Dual salt effects were evaluated on the same product and process attributes to identify any synergies with the use of mixed ion gradients. The modified process provided as high as ≥75% AAV5 full capsids (≥3-fold enrichment based on the percent full in the feed stream) with near baseline separation of empty capsids and achieved an overall vector genome step yield of >65%. 相似文献
49.
Glen P Kenny Julien Periard W Shane Journeay Ronald J Sigal Francis D Reardon 《Journal of applied physiology》2003,95(6):2355-2360
The hypothesis that the magnitude of the postexercise onset threshold for sweating is increased by the intensity of exercise was tested in eight subjects. Esophageal temperature was monitored as an index of core temperature while sweat rate was measured by using a ventilated capsule placed on the upper back. Subjects remained seated resting for 15 min (no exercise) or performed 15 min of treadmill running at either 55, 70, or 85% of peak oxygen consumption (V(o2 peak)) followed by a 20-min seated recovery. Subjects then donned a liquid-conditioned suit used to regulate mean skin temperature. The suit was first perfused with 20 degrees C water to control and stabilize skin and core temperature before whole body heating. Subsequently, the skin was heated ( approximately 4.0 degrees C/h) until sweating occurred. Exercise resulted in an increase in the onset threshold for sweating of 0.11 +/- 0.02, 0.23 +/- 0.01, and 0.33 +/- 0.02 degrees C above that measured for the no-exercise resting values (P < 0.05) for the 55, 70, and 85% of V(o2 peak) exercise conditions, respectively. We did note that there was a greater postexercise hypotension as a function of exercise intensity as measured at the end of the 20-min exercise recovery. Thus it is plausible that the increase in postexercise threshold may be related to postexercise hypotension. It is concluded that the sweating response during upright recovery is significantly modified by exercise intensity and may likely be influenced by the nonthermal baroreceptor reflex adjustments postexercise. 相似文献
50.
Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses 总被引:2,自引:0,他引:2
Tyler Catherine M.; Golland Lorraine C.; Evans David L.; Hodgson David R.; Rose Reuben J. 《Journal of applied physiology》1996,81(5):2244-2249
Tyler, Catherine M., Lorraine C. Golland, David L. Evans,David R. Hodgson, and Reuben J. Rose. Changes in maximum oxygenuptake during prolonged training, overtraining, and detraining inhorses. J. Appl. Physiol. 81(5):2244-2249, 1996.Thirteen standardbred horses were trained asfollows: phase 1 (endurance training, 7 wk),phase 2 (high-intensity training, 9 wk),phase 3 (overload training, 18 wk), andphase 4 (detraining, 12 wk). Inphase 3, the horses were divided intotwo groups: overload training (OLT) and control (C). The OLT groupexercised at greater intensities, frequencies, and durations than groupC. Overtraining occurred after 31 wk of training and was defined as asignificant decrease in treadmill run time in response to astandardized exercise test. In the OLT group, there was a significantdecrease in body weight (P < 0.05).From pretraining values of 117 ± 2 (SE)ml · kg1 · min1,maximal O2 uptake(O2 max) increased by15% at the end of phase 1, and when signs of overtraining werefirst seen in the OLT group,O2 max was 29%higher (151 ± 2 ml · kg1 · min1in both C and OLT groups) than pretraining values. There was nosignificant reduction inO2 max until after 6 wk detraining whenO2 max was 137 ± 2 ml · kg1 · min1.By 12 wk detraining, meanO2 max was134 ± 2 ml · kg1 · min1,still 15% above pretraining values. When overtraining developed, O2 max was notdifferent between C and OLT groups, but maximal values forCO2 production (147 vs. 159 ml · kg1 · min1)and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLTgroup. Overtraining was not associated with a decrease inO2 max and, afterprolonged training, decreases inO2 max occurredslowly during detraining. 相似文献