Another look at: fuel + O2 --> CO2 + H2O. Developing a water-oriented perspective.

Water plays many vital roles which must be maintained despite constant threat of water stress from the environment. Mechanisms to maintain these roles over the long-term involve intermediates of many metabolic pathways, such as glycerol, sucrose, free amino acids and their derivatives. In addition to viewing metabolic products as intermediates along energy-related pathways, nutrition researchers and epidemiologists should consider them as determinants of intracellular fluid maintenance. Satiety processes, oxidative-fuel selection, hormonal control, and intracellular-signaling processes can all be interpreted in terms of water-oriented metabolism. Water intake and hydration status can vary considerably, and may be inadequate for a sizeable proportion of Western adults. Due to the metabolic adaptations required to compensate for perpetually inadequate water, chronic sub-optimal water intakes may be highly relevant to chronic disease etiology. Preliminary evidence links water-oriented metabolism to obesity, diabetes, cardiovascular disease, hypertension and cancer. Development of a water-oriented perspective may reveal an important new area of research in human nutrition and epidemiology.     

H2O2 enhances Ca2+ release from osteoblast internal stores

The physiological activity of osteoblasts is known to be closely related to increased intracellular Ca2+ activity ([Ca2+]i) in osteoblasts. The cellular regulation of [Ca2+]i in osteoblasts is mediated by Ca2+ movements associated with Ca2+ release from intracellular Ca2+ stores, and transmembrane Ca2+ influx via Na+-Ca2+ exchanger, and Ca2+ ATPase. Reactive oxygen species, such as H2O2, play an important role in the regulation of cellular functions, and act as signaling molecules or toxins in cells. In this study, we investigated the effects of H2O2 on cellular Ca2+ regulation in osteoblasts by measuring intracellular Ca2+ activities using cellular calcium imaging techniques. Osteoblasts were isolated from the femurs and tibias of neonatal rats, and cultured for 7 days. The cultured osteoblasts were loaded with a Ca2+-sensitive fluorescent dye, Fura-2, and fluorescence images were monitored using a cooled CCD camera, and subsequently analyzed using image analyzing software. The results obtained are as follows: (1) The osteoblasts with lower basal Ca2+ activities yielded a transient Ca2+ increase, a Ca2+ spike, while osteoblasts with higher basal Ca2+ activities showed a continuous increase in [Ca2+]i leading to cell death. (2) Ca2+ spikes, generated after removing Na+ from superfusing solutions, were blocked by H2O2 and this was followed by a sustained increase in Ca2+ activity. (3) ATP- induced Ca2+ spikes were inhibited by pretreating with H2O2 and this was followed by a continuous increase of [Ca2+]i. When cells were pretreated with the exogenous nitric oxide (NO) donor S-Nitroso-N-acetylpenicilance (SNAP, 50 microM), treatments of ATP (1 mM) induced a Ca2+ spike-like increase, but [Ca2+]i did not return to the basal level. (4) The expression of inositol- 1,4,5-triphosphate receptor (IP3R) was enhanced by H2O2. Our results suggest that H2O2 modulates intracellular Ca2+ activity in osteoblasts by increasing Ca2+ release from the intracellular Ca2+ stores.     

人阴道乳酸杆菌的体外拮抗作用

目的初步探讨阴道内产H2O2能力不同的乳酸杆菌对大肠杆菌的拮抗作用及拮抗机制,以期筛选菌株用于治疗女性泌尿生殖道感染。方法从阴道分泌物中分离筛选出产H2O2的乳酸杆菌,通过比浊法判断各菌产H2O2的能力,采用打孔法测量各菌对大肠杆菌产生的抑菌圈直径。结果从阴道共分离出4株产H2O2菌株,其中L.paracasei3和L.acidophilus1产生H2O2的能力较强;L.acidophilus1产生的抑菌作用最大,L.crispatus次之。结论不同乳酸杆菌产H2O2能力不同,对大肠杆菌的体外拮抗作用亦不同,L.acidophilus1和L.crispatus的拮抗作用较强,此拮抗作用不完全依赖细菌产生的H2O2和乳酸。     

Ca2+与NO在过氧化氢所致正常成年大鼠肠系膜微血管通透性增高中的作用

 目的 观察内皮细胞Ca2+浓度及NO生成在过氧化氢所致正常成年大鼠肠系膜微血管通透性增高中的作用。方法 通过测定在体大鼠肠系膜微血管静水传导性观察微血管通透性变化。采用钙荧光指示剂(Fura 2-AM)、NO荧光指示剂(DAF-2 DA)标记在体微血管内皮细胞,并应用荧光显微镜检测细胞内钙或NO的荧光信号,观察H2O2作用下内皮细胞内钙离子浓度([Ca2+]i)、NO的变化。结果 H2O2可增加正常成年大鼠微血管通透性（正常对照的6.13±0.87倍,P<0.01）,同时增加微血管内皮细胞[Ca2+]i（714.58±144.70 nmol/L,P<0.01）,并促进内皮细胞NO的生成（正常对照荧光强度的1034.3%±44.3%,P<0.01）。Ca2+通道阻滞剂氯化镧可抑制H2O2所引起的微血管通透性增加（P<0.01）及内皮细胞[Ca2+]i升高（P<0.01）。NOS抑制剂AP-Cav-1可抑制H2O2所引起的微血管通透性增加（P<0.01）,但对H2O2的Ca2+增加作用无影响。结论 H2O2所致的通透性增加与细胞内Ca2+增加、NO的产生增多有关。     

HA(+ZrO2+Y2O3)/Ti6A14V复合涂层的微结构与生物活性

采用射频磁控溅射法成功制备了HA(+ZrO2+Y3O3)/Ti6A14V生物复合涂层.借助于XRD、SEM、FTIR及AFM等对溅射涂层的相组成、微观形貌和界面结合进行了研究,并以模拟体液试验探讨了涂层的生物活性.实验结果表明磁控溅射的复合涂层呈非晶态,经过退火处理,可以使其完全转化为晶态;复合涂层的微观表面凹凸不平,并呈现网状结构和较多的孔隙,其孔隙直径约为0.5 μm～2 μm;涂层的生长模式为层状加岛状生长;复合涂层在模拟体液中浸泡一段时间后,表面覆盖一层新生物质--含有CO32-的类骨磷灰石,其晶粒非常小,它与自然骨中无机相的结构成份相似,因此复合涂层具有良好生物相容性和生物活性.     

H2O2-stimulated Ca2+ influx via TRPM2 is not the sole determinant of subsequent cell death

Activation of transient receptor potential melastatin 2 (TRPM2), a non-selective, Ca²⁺-permeable cation channel, is implicated in cell death. Channel opening is stimulated by oxidative stress, a feature of numerous disease states. The wide expression profile of TRPM2 renders it a potentially significant therapeutic target in a variety of pathological settings including cardiovascular and neurodegenerative diseases. HEK293 cells transfected with human TRPM2 (HEK293/hTRPM2) were more vulnerable to H₂O₂-mediated cell death than untransfected controls in which H₂O₂-stimulated Ca²⁺ influx was absent. Flufenamic acid partially reduced Ca²⁺ influx in response to H₂O₂ but had no effect on viability. N-(p-Amylcinnamoyl) anthranilic acid substantially attenuated Ca²⁺ influx but did not alter viability. Poly(adenosine diphosphate ribose) polymerase inhibitors (N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylacetamide, 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone and nicotinamide) reduced Ca²⁺ influx and provided a degree of protection but also had some protective effects in untransfected controls. These data suggest H₂O₂ triggers cell death in HEK293/hTRPM2 cells by a mechanism that is in part Ca²⁺ independent, as blockade of channel opening (evidenced by suppression of Ca²⁺ influx) did not correlate well with protection from cell death. Determining the underlying mechanisms of TRPM2 activation is pertinent in elucidating the relevance of this channel as a therapeutic target in neurodegenerative diseases and other pathologies associated with Ca²⁺ dysregulation and oxidative stress.     

Surface modification of A12O3 bioceramic by NH2+ ion implantation

Ion implantation technique was applied to graft the -NH2 amidogen radicals onto the surface of Al2O3 bioceramic. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of the implanted radicals on the Al2O3 ceramic surface. It was found that the amount of grafted amidogen radicals was proportional to the dosage of NH2+ ions used during the ion implantation. Furthermore, when implantation energy of 100 keV was used, maximum amount of -NH2 radicals would be grafted on the Al2O3 ceramic surface. The biocompatibility of the implanted Al2O3 ceramic was also investigated, and the results indicate that the implanted surface has better biocompatibility with animal bone tissue than the plain ceramic surface.     

Effects of dantrolene and D2O on K+-stimulated respiration of skeletal muscle

We have examined the effects of dantrolene and D2O on the K+-stimulated respiration in frog skeletal muscle. The threshold for K+ stimulation was around 10 mM extracellular potassium concentration ([K+]o). A further marked increase in respiration to levels about ten times the resting level was noted when [K+]o was between 15 and 20 mM. The increase was sustained for hours when [K+]o was less than 20 mM; however, with higher concentrations the stimulation consisted of an initial burst followed by a decline. Dantrolene shifted the relationship between [K+]o and peak increase in respiration toward higher [K+]o by about 10 mM; in addition it nearly completely blocked the sustained component of the increase. D2O, nearly abolished the K+-induced respiration. Neither agent shifted the relationship between [K+]o and membrane potential nor abolished the stimulation of respiration caused by caffeine. Dantrolene did not block the stimulation of Na+ efflux caused by 15 mM K+. The results with these agents are consistent with the proposal that K+-stimulated respiration is due to Ca2+ release into the cytoplasm. In addition, they provide evidence that the stimulated rate of Ca2+ release into the cytoplasm can remain at a persistently high level for hours provided [K+]o does not exceed 20 mM. We calculated that the level of this constant Ca2+ release is about 3.4 X 10(16) ions/(s.cm3).     

Ca2+-dependent inactivation of Ca2+-induced Ca2+ release in bullfrog sympathetic neurons

We studied inactivation of Ca(2+)-induced Ca(2+) release (CICR) via ryanodine receptors (RyRs) in bullfrog sympathetic neurons. The rate of rise in [Ca(2+)](i) due to CICR evoked by a depolarizing pulse decreased markedly within 10-20 ms to a much slower rate despite persistent Ca(2+) entry and little depletion of Ca(2+) stores. The Ca(2+) entry elicited by the subsequent pulse within 50 ms, during which the [Ca(2+)](i) level remained unchanged, did not generate a distinct [Ca(2+)](i) rise. This mode of [Ca(2+)](i) rise was unaffected by a mitochondrial uncoupler, carbonyl cyanide p-trifluromethoxy-phenylhydrazone (FCCP, 1 microm). Paired pulses of varying interval and duration revealed that recovery from inactivation became distinct >or= 50 ms after depolarization and depended on [Ca(2+)](i). The inactivation was prevented by BAPTA (>or= 100 microm) but not by EGTA (相似文献   

O2 sensing by recombinant TWIK-related halothane-inhibitable K+ channel-1 background K+ channels heterologously expressed in human embryonic kidney cells

Hypoxic inhibition of K+ channels provides a link between low O2 and cell function, and in glossopharyngeal neurons hypoxic inhibition of a TWIK-related halothane-inhibitable K+ channel-1 (THIK-1)-like background K+ channel regulates neuronal function. In the present study, we examined directly the O2 sensitivity of recombinant THIK-1 channels, expressed in human embryonic kidney (HE293) cells. THIK-1 expression conferred a moderately outwardly rectifying halothane-inhibited and arachidonic acid-potentiated K+ current and invoked a strongly hyperpolarized resting membrane potential. Endogenous K+ currents in untransfected cells were unaffected by either agent. Hypoxia (P(O2), 20 mmHg) reversibly inhibited THIK-1 currents and caused membrane depolarization, effects that were occluded by halothane. Neither the mitochondrial complex I inhibitors rotenone, myxothiazol and sodium cyanide, nor the NADPH oxidase inhibitors diphenylene iodonium and phenylarsine oxide, were effective in inhibiting the O2-sensitivity of THIK-1. Thus, hypoxic inhibition of THIK-1 occurs by a mechanism dissimilar to that which regulates the activity of other members of the background K+ channel family. Given the O2 sensitivity of THIK-1 channels and their abundant expression in the CNS, we raise for the first time the possibility of a physiological and/or pathological role for these channels during brain ischemia.     

长春新碱诱导的自噬性凋亡与细胞内游离Ca^2＋浓度的相关性研究

目的 研究长春新碱（ＶＣＲ）诱导的Ｌ－０２细胞自噬性凋亡细胞内游离钙离子浓度（［Ｃａ＾２＋］ｉ）的变化,以及自噬特异性抑制剂３－ｍｅｔｈｙｌａｄｅｎｉｎｅ（３ＭＡ）对此自噬性凋亡和［Ｃａ＾２＋］ｉ的影响。方法 应用已建立的ＶＣＲ诱导的Ｌ－０２细胞自噬性凋亡模型,使用电镜、流式细胞术检测细胞;用Ｆｌｕｏ－３／ＡＭ荧光探针经流式细胞仪测定Ｌ－０２细胞平均［Ｃａ＾２＋］ｉ。结果 电镜及流式细胞术检测证实     

Interaction of O2 diffusion and O2 metabolism in cat urinary bladder tissue.

We measured oxygen exchange across the inside surface of excised urinary bladders that were inflated with gas mixtures. By using a range of Po2 differences between the two sides of the tissue and relatively simple mathematical models, we could infer the exchanges across the outside surface and the total O2 economy of the tissue so that we could evaluate the interaction between diffusion and metabolic O2 consumption. The estimate of the Krogh diffusion constant or permeation coefficient with this preparation avoids errors due to O2 consumption and unstirred layers. At 37 degrees C, the value of bladder tissue O2 consumption was 4.4 times 10(-3) min-1 and the value of the Krogh constant for O2 was 2.22 times 10(-5)cm2min-1atm-1.     

Ca2+ channels that activate Ca2+-dependent K+ currents in neostriatal neurons

It is demonstrated that not all voltage-gated calcium channel types expressed in neostriatal projection neurons (L, N, P, Q and R) contribute equally to the activation of calcium-dependent potassium currents. Previous work made clear that different calcium channel types contribute with a similar amount of current to whole-cell calcium current in neostriatal neurons. It has also been shown that spiny neurons posses both “big” and “small” types of calcium-dependent potassium currents and that activation of such currents relies on calcium entry through voltage-gated calcium channels. In the present work it was investigated whether all calcium channel types equally activate calcium-dependent potassium currents. Thus, the action of organic calcium channel antagonists was investigated on the calcium-activated outward current. Transient potassium currents were reduced by 4-aminopyridine and sodium currents were blocked by tetrodotoxin. It was found that neither 30 nM ω-Agatoxin-TK, a blocker of P-type channels, nor 200 nM calciseptine or 5 μM nitrendipine, blockers of L-type channels, were able to significantly reduce the outward current. In contrast, 400 nM ω-Agatoxin-TK, which at this concentration is able to block Q-type channels, and 1 μM ω-Conotoxin GVIA, a blocker of N-type channels, both reduced outward current by about 50%. These antagonists given together, or 500 nM ω-Conotoxin MVIIC, a blocker of N- and P/Q-type channels, reduced outward current by 70%. In addition, the N- and P/Q-type channel blockers preferentially reduce the afterhyperpolarization recorded intracellularly.The results show that calcium-dependent potassium channels in neostriatal neurons are preferentially activated by calcium entry through N- and Q-type channels in these conditions.     

Ca2+ signaling by T-type Ca2+ channels in neurons

Among the major families of voltage-gated Ca²⁺ channels, the low-voltage-activated channels formed by the Ca_v3 subunits, referred to as T-type Ca²⁺ channels, have recently gained increased interest in terms of the intracellular Ca²⁺ signals generated upon their activation. Here, we provide an overview of recent reports documenting that T-type Ca²⁺ channels act as an important Ca²⁺ source in a wide range of neuronal cell types. The work is focused on T-type Ca²⁺ channels in neurons, but refers to non-neuronal cells in cases where exemplary functions for Ca²⁺ entering through T-type Ca²⁺ channels have been described. Notably, Ca²⁺ influx through T-type Ca²⁺ channels is the predominant Ca²⁺ source in several neuronal cell types and carries out specific signaling roles. We also emphasize that Ca²⁺ signaling through T-type Ca²⁺ channels occurs often in select subcellular compartments, is mediated through strategically co-localized targets, and is exploited for unique physiological functions. Lucius Cueni and Marco Canepari contributed equally to this review.     

K2O-B2O3-Al2O3-SiO2-MgO-F系统可切削生物微晶玻璃

目的 可切削微晶玻璃的制备温度高达1500 ℃以上,此特性严重制约其产业化发展.本文设计制备了K2O-B2O3-Al2O3-SiO2-MgO-F系统低温云母生物微晶玻璃,并探讨制备工艺对材料结构和性能的影响.方法 采用1300 ℃熔化工艺与600～750 ℃晶化热处理工艺制备微晶玻璃,通过X射线衍射分析方法研究微晶玻璃的晶相组成,利用扫描电子显微镜观察微晶玻璃的形貌,并通过显微硬度分析、高速砂轮切削实验考察微晶玻璃的可切削性能.结果 分别经过600 ℃、650 ℃、700 ℃、750 ℃晶化热处理2 h、4 h、8 h后,玻璃中均形成了主晶相为氟金云母的微晶玻璃,微晶玻璃的显微硬度为3～8 GPa.且随着晶化温度的升高,微晶玻璃层状结构逐渐明晰,但硬度不断下降,其可切削性持续提高.结论 低温下熔化K2O-B2O3-Al2O3-SiO2-MgO系统玻璃工艺降低了可切削微晶玻璃的制备温度和成本,利于产业化生产和推广应用.     

Effect of prolonged O2 deprivation on Na+ channels: differential regulation in adult versus fetal rat brain

Neuronal Na+ channels are functionally inhibited in the adult in response to acute O2 deprivation. Since prolonged hypoxia may not only affect channel function, but also its expression, we hypothesized that long-term hypoxia alters Na+ channel density. This alteration may depend on age, because we have found major differences in neuronal responses to hypoxia between the immature and adult. In the present work, we used northern blots, slot blots, saxitoxin binding and autoradiography to ask whether: (i) prolonged hypoxia alters Na+ channel messenger RNA and protein levels in the brain; (ii) there is a difference between the adult and prenatal brains regarding Na+ channel expression with hypoxic exposure; and (iii) regional differences in Na+ channel expression occur in hypoxia-exposed brains. Our results show the following. (1) Na+ channel messenger RNA and saxitoxin binding density decreased after prolonged hypoxia in adult brain homogenates; this is in sharp contrast to the changes observed in fetal brains, which tended to increase Na+ channel messenger RNA and protein after hypoxia. (2) Changes in saxitoxin binding density are related to alterations in the number of saxitoxin binding sites and not to binding affinity, since there was no major change in Kd values between the hypoxia and naive groups. (3) The hypoxia-induced Na+ channel expression was heterogeneous, with major differences between rostral regions (e.g., the cortex) and caudal regions (e.g., the medulla and pons). We speculate that down-regulation of Na+ channels during long-term hypoxia in mature brains is an adaptive cellular response, aimed at minimizing the mismatch between energy supply and demand, since maintenance of Na+ gradients is a major energy-requiring process. However, the prenatal brain does not depend on this adaptive mechanism in response to hypoxic stress.