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31.
When Lactococcus lactis was grown in various complex or synthetic media, the fermentation of glucose remained homolactic whatever the medium used, with a global carbon balance of about 87%. Moreover, the nitrogen balance was not equilibrated, indicating that some amino acids led to the production of unknown nitrogen-containing carbon compounds while part of the glucose might contribute to anabolic pathways. In minimal medium containing six amino acids, a high concentration of serine was deaminated to pyruvate. This did not occur in more complete media, suggesting the presence of a regulation of this phenomenon by an amino acid. Ammonia produced during serine consumption was partly reconsumed after serine exhaustion. The values for biomass yield and biomass yield relative to ATP (Y(infATP)), the maximal growth rate, the specific rate of glucose consumption, and the corresponding rate of ATP synthesis all increased with the complexity of the medium, amino acid composition having the most pronounced effect. The Y(infATP) values were shown to range from 6.6 to 17.6 g of biomass(middot)mol of ATP(sup-1) on minimal and complex media.  相似文献   
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Traumatic brain injury (TBI) is a common cause of morbidity and mortality in people of all ages. Following the acute mechanical insult, TBI evolves over the ensuing minutes and days. Understanding the secondary factors that contribute to TBI might suggest therapeutic strategies to reduce the long-term consequences of brain trauma. To assess secondary factors that contribute to TBI, we studied a lateral fluid percussion injury (FPI) model in mice. Following FPI, the brain cortex became acidic, consistent with data from humans following brain trauma. Administering HCO3 after FPI prevented the acidosis and reduced the extent of neurodegeneration. Because acidosis can activate acid sensing ion channels (ASICs), we also studied ASIC1a−/− mice and found reduced neurodegeneration after FPI. Both HCO3 administration and loss of ASIC1a also reduced functional deficits caused by FPI. These results suggest that FPI induces cerebral acidosis that activates ASIC channels and contributes to secondary injury in TBI. They also suggest a therapeutic strategy to attenuate the adverse consequences of TBI.  相似文献   
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采用缩微实验法,初步系统研究了杉木叶凋落物分别与火力楠、红栲和木荷3个阔叶树种之一的叶凋落物两两混合分解的动态变化,以探明凋落物混合分解过程中可能存在的相互作用.结果表明,杉木叶凋落物与3种阔叶树种叶凋落物两两混合分解时所表现出不同的相互作用形式:杉木与木荷表现出抑制作用,杉木与红栲或火力楠表现为较弱的促进作用.  相似文献   
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A temperature-jump technique for single nodes of Ranvier has been developed using a pulsed laser system. The temperature perturbation was accomplished by firing the laser beam obtained from a neodymium rod through the solution surrounding a single node. The temperature step was achieved within 1 msec using the laser in the normal mode of operation. During the voltage-clamped steady-state current a temperature jump from 4°C increased the current to a new steady-state value within the time course of the T-jump. This finding suggests that the maximum potassium permeability PK has a rapid relaxation time and that the steady-state value of n (the value of potassium permeability divided by its maximum value) is relatively independent of temperature. T-jumps applied during the voltage-clamped sodium currents showed that the sodium permeability changed with a relaxation time that was also shorter than the duration of the normal mode laser output. T-jumps observed during a hyperpolarization or at the resting potential showed no detectable conductance change. When a T-jump immediately preceded a voltage clamp pulse the technique was then used to investigate the effect of changes in the steady-state temperature on the ionic conductances. It was found that the magnitude of the change in membrane current due to a T-clamp was directly related to the level of cathodal polarization.  相似文献   
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Dysregulation in central nervous system (CNS) signaling that results in chronic sympathetic hyperactivity is now recognized to play a critical role in the pathogenesis of heart failure (HF) following myocardial infarction (MI). We recently demonstrated that adenovirus-mediated gene transfer of cytoplasmic superoxide dismutase (Ad-Cu/ZnSOD) to forebrain circumventricular organs, unique sensory structures that lack a blood-brain barrier and link peripheral blood-borne signals to central nervous system cardiovascular circuits, inhibits both the MI-induced activation of these central signaling pathways and the accompanying sympathoexcitation. Here, we tested the hypothesis that this forebrain-targeted reduction in oxidative stress translates into amelioration of the post-MI decline in myocardial function and increase in mortality. Adult C57BL/6 mice underwent left coronary artery ligation or sham surgery along with forebrain-targeted gene transfer of Ad-Cu/ZnSOD or a control vector. The results demonstrate marked MI-induced increases in superoxide radical formation in one of these forebrain regions, the subfornical organ (SFO). Ad-Cu/ZnSOD targeted to this region abolished the increased superoxide levels and led to significantly improved myocardial function compared with control vector-treated mice. This was accompanied by diminished levels of cardiomyocyte apoptosis in the Ad-Cu/ZnSOD but not the control vector-treated group. These effects of superoxide scavenging with Ad-Cu/ZnSOD in the forebrain paralleled increased post-MI survival rates compared with controls. This suggests that oxidative stress in the SFO plays a critical role in the deterioration of cardiac function following MI and underscores the promise of CNS-targeted antioxidant therapy for the treatment of MI-induced HF.  相似文献   
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Aims:  To determine the effects of carbohydrates on Bacillus cereus ATCC14579T anaerobic metabolism and enterotoxin production in amino acids rich medium.
Methods and Results:  Bacillus cereus anaerobic growth on different carbohydrates (glucose, fructose, sucrose or glucose–fructose mixture) was examined in synthetic mMOD medium under continuous cultures (μ = 0·2 h−1). Fermentation end-products, flux partitioning at each key branch points of the mixed acid pathway and consumption or production of amino acids were determined. On both fructose and sucrose, ATP production was favoured via acetate production from acetyl-CoA. In addition, amino acids present in the growth medium showed significant variations with high consumption of serine and net production of glutamate and alanine on some or all sugars. Enterotoxins Hbl and Nhe production was high during growth on fructose (or mixtures involving a fructose moiety).
Conclusions:  Fructose was identified as a key sugar influencing anaerobic metabolism and toxin production of B. cereus .
Significance and Impact of the Study:  The physiological differences associated with the fermentation of the various carbohydrates clearly modify toxinogenesis indicating that the risk of foodborne pathogens is to some extent dependent upon the prevailing nutritional environment.  相似文献   
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