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We have analyzed the cell wall of the radio-resistant bacterium Deinococcus radiodurans. Unexpectedly, the bacterial envelope appears to be organized in different complexes of high molecular weight. Each complex is composed of several proteins, most of which are coded by genes of unknown function and the majority are constituents of the inner/outer membrane system. One of the most abundant complexes is constituted by the gene DR_0774. This protein is a type of secretin which is a known subunit of the homo-oligomeric channel that represents the main bulk of the type IV piliation family. Finally, a minor component of the pink envelope consists of several inner-membrane proteins. The implications of these findings are discussed.  相似文献   
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Recent investigations have demonstrated that taurine and phosphoethanolamine (PEA) are the amino acids most sensitive to microdialysis-perfusion with reduced concentrations of NaCl. The aim of the present work was to assess the importance of Na+ deficiency in evoking this response. Further, the previously described selectivity of replacement of Cl- with acetate with respect to amino acid release was reinvestigated. The hippocampus of urethane-anesthetized rats was dialyzed with Krebs-Ringer bicarbonate buffer, and amino acid concentrations of the perfusate were determined. Choline chloride was then stepwise substituted for NaCl, and, in some cases, mannitol (122 mM) was included in low sodium-containing media. In other experiments, NaCl was replaced with sodium acetate. The dialysate levels of taurine increased selectively in response to Na+ substitution. The elevation of taurine was linearly related to the increase in choline chloride, and maximal levels amounted to 335% of basal levels. The increase in extracellular taurine was not inhibited by perfusion with medium made hyperosmotic with mannitol. Replacement of Cl- with acetate stimulated the release of taurine to 652% of resting levels. In addition, PEA levels increased to 250% of control concentration. Other amino acids were unaffected by Cl- substitution. The results show that taurine transport is considerably more sensitive to Na+ depletion than glutamate transport, which also is known to be Na+ dependent. The taurine increase evoked by low Na+ is not caused by cellular swelling as it was unaffected by hyperosmolar medium. Finally, substitution of acetate for Cl- causes a specific elevation of extracellular taurine and PEA, possibly as a result of cytotoxic edema.  相似文献   
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Summary The plasma levels of four osmoregulatory hormones and their target ion-transport systems in the lower intestines of the domestic fowl were determined in order to elucidate their interrelationship and their setpoints in relation to NaCl intake. White Plymouth Rock hens were adapted to six intake levels of NaCl (0.20±0.02–24.7±1.9 mmoles Na+·kg bw–1·day–1) for 6 weeks. The Na+ absorption and the Cl secretion of colon and coprodeum were characterized in vitro by the effects of hexoses, amino acids, amiloride, and theophylline on the short-circuit current (SCC) and electrical potential difference (PD). The NaCl-conserving system of the adult chicken is set at low intake levels of NaCl as the 80% range (quantitized by non-linear, logistic regression analyses) of the change in the plasma [ALDO], the amiloride-inhibitable Na+ absorption of coprodeum and colon ( SCC), occurred from 0.18 to 2.3, from 0.9 to 4.3, and from 1.2 to 7.3 mmoles Na+·kg bw–1·day–1, respectively. These results demonstrate that the amiloride-inhibitable Na+ absorption of coprodcum is more closely linked to plasma [ALDO] than that of colon. The aminoacid-Na+ coabsorption of colon increased over exactly the same range of Na+ intake as the colonic amiloride-inhibitable Na+ absorption decreased, whereas the hexose-Na+ coabsorption increased at higher levels of Na+ intake, from 2 to 11 mmoles Na+·kg bw–1·day–1. Both these Na+ absorption types had reached their maximums at 24.7 mmoles Na+·kg bw–1·day–1, whereas the plasma [AVT] and plasma [PRL], although significantly increased, apparently had not; their 80% range of change occurred from 9.9 to 99 mmoles Na+·kg bw–1·day–1, and the main changes in plasma osmolity were predicted to occur from 5.4 to 107 mmoles Na+·kg bw–1·day–1. These results suggest that these colonic and hormonal variables conserve osmotically-free water and operate at high NaCl intake. The theophylline-induced colonic Cl secretion did not change with NaCl intake, whereas the stimulation of SCC in coprodeum decreased with increasing NaCl intake: The main change occurred between 0 and 3.2 mmoles Na+·kg bw–1·day–1. Thus, all ion-transport capacity disappears in coprodeum with increased dietary NaCl intake, whereas colon maintains its ion-transport capacity (although the nature of the Na+ transport changes). It is suggested that hormones defending the extracellular volume and composition are regulated close to zero input and output of both NaCl and water, regardless of whether they are NaCl conserving or free-water conserving. Therefore, changes in their stable plasma concentrations occur at the extremes of tolerable range of NaCl intake.Abbreviation AA aminoacids - ALDO aldosterone - AMI amiloride - AVT arginine vasotocin - bw body weight - CS corticosterone - HEX hexoses - INDO indomethacin - PD potential difference - PRL prolactin - R resistance - SCC short-circuit current - SD standard deviation - SEM standard error of mean - THEO theophylline  相似文献   
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目的:探讨滑膜炎颗粒联合玻璃酸钠治疗创伤性膝关节滑膜炎的疗效及对患者血清炎症因子水平的影响。方法:选取2015年2月~2017年12月期间我院收治的创伤性膝关节滑膜炎患者216例为研究对象。根据随机数字表法将患者分为对照组(n=108)与研究组(n=108)。对照组患者给予玻璃酸钠治疗,研究组则在此基础上联合滑膜炎颗粒进行治疗,两组均治疗5周。比较两组治疗5周后(治疗后)的临床疗效及治疗前后血清白介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)、白介素-1β(IL-1β)水平,采用视觉模拟量表(VAS)评价患者治疗前后膝关节疼痛程度,美国特种外科医院量表(HSS)评价患者治疗前后膝关节功能,同时观察两组治疗期间不良反应发生情况。结果:研究组患者总有效率为92.59%(100/108),高于对照组患者的78.70%(85/108)(P0.05)。两组患者治疗后IL-6、TNF-α以及IL-1β水平均较治疗前降低,且研究组低于对照组(P0.05)。两组患者治疗后VAS评分较治疗前降低,且研究组低于对照组,HSS评分较治疗前升高,且研究组高于对照组(P0.05)。两组患者不良反应发生率对比差异无统计学意义(P0.05)。结论:滑膜炎颗粒联合玻璃酸钠治疗创伤性膝关节滑膜炎安全有效,可显著改善患者血清炎症因子水平以及膝关节功能,并减轻患者疼痛程度,具有一定的临床应用价值。  相似文献   
7.
23Na nuclear magnetic resonance (NMR) has previously been used to monitor Na+ translocation across membranes in gram-negative bacteria and in various other organelles and liposomes using a membrane-impermeable shift reagent to resolve the signals resulting from internal and external Na+. In this work, the 23Na NMR method was adapted for measurements of internal Na+ concentration in the gram-positive bacterium Bacillus subtilis, with the aim of assessing the Na+ translocation activity of the Mrp (multiple resistance and pH) antiporter complex, a member of the cation proton antiporter-3 (CPA-3) family. The sodium-sensitive growth phenotype observed in a B. subtilis strain with the gene encoding MrpA deleted could indeed be correlated to the inability of this strain to maintain a lower internal Na+ concentration than an external one.  相似文献   
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Abstract: The mechanism of unidirectional transport of sodium from blood to brain in pentobarbital-anesthetized rats was examined using in situ perfusion. Sodium transport followed Michaelis-Menten saturation kinetics with a V max of 50.1 nmol/g/min and a K m of 17.7 m M in the left frontal cortex. The kinetic analysis indicated that, at a physiologic sodium concentration, ∼26% of sodium transport at the blood-brain barrier (BBB) was carrier mediated. Dimethylamiloride (25 µ M ), an inhibitor of Na+/H+ exchange, reduced sodium transport by 28%, whereas phenamil (25 µ M ), a sodium channel inhibitor, reduced the transfer constant for sodium by 22%. Bumetanide (250 µ M ) and hydrochlorothiazide (1.5 m M ), inhibitors of Na+-K+-2Cl/NaCl symport, were ineffective in reducing blood to brain sodium transport. Acetazolamide (0.25 m M ), an inhibitor of carbonic anhydrase, did not change sodium transport at the BBB. Finally, a perfusate pH of 7.0 or 7.8 or a perfusate P co 2 of 86 mm Hg failed to change sodium transport. These results indicate that 50% of transcellular transport of sodium from blood to brain occurs through Na+/H+ exchange and a sodium channel in the luminal membrane of the BBB. We propose that the sodium transport systems at the luminal membrane of the BBB, in conjunction with Cl/HCO3 exchange, lead to net NaCl secretion and obligate water transport into the brain.  相似文献   
10.
Patch clamp techniques were used to record whole cell and single channel Na+ currents from NB41A3 neuroblastoma cells grown in culture. Cells were grown for two weeks in control medium or medium supplemented with 30 mm d-glucose of 30 mm l-fucose.Cells exposed to glucose or l-fucose had smaller whole cell Na+ currents than cells grown in unsupplemented medium, consistent with earlier studies (Yorek, Stefani & Wachtel, 1994). Whole cell macroscopic currents showed no change in activation or inactivation kinetics. Single channel current properties and opening probability were also unchanged.The number of [3H]saxitoxin binding sites, and therefore the total number of Na+ channels, was not reduced in cells grown in glucose or l-fucose (Yorek et al., 1994). Therefore, we conclude that some of the channels must have been rendered nonfunctional by the conditioning media. The finding that single channel properties are not altered suggests that channels become nonfunctional in an all-or-none manner.This work was supported by Merit Review Awards to M.A. Yorek and R.E. Wachtel from the Department of Veterans Affairs and by National Institutes of Health grant DK45453 to M.A. Yorek.  相似文献   
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