Cigarette smoke: protection of alveolar macrophages by glutathione and cysteine

Phagocytosis of bacteria by rabbit alveolar macrophages is inhibited quantitatively by cigarette smoke in vitro. This phagocytoxic effect was abolished by addition of 0.2 to 0.4 micromole of glutathione or cysteine per milliliter of cigarette smoke. Serum protein was required to obtain both the toxic effect of the smoke and the protective action of the sulfhydryl compounds. The protective role of the sulfhydryl agents suggests an oxidant action of the cigarette smoke on these pulmonary cells.     

Inhibition of bacterial adherence by secretory immunoglobulin A: a mechanism of antigen disposal

Preparations of secretory iminunoglobuilin A (S-IgA) isolated from human parotid fluid specifically inhibited the adherence of Streptococcus strains to epithelial cells. Since bacterial adherence is a prerequisite for colonization of mucous surfaces. S-IgA-mediated inhibition of adherence would limit bacterial colonization. This mechanism can explain how secretory immunoglobulins function in the disposal of bacterial antigens.     

Inhibition of protein synthesis: a mechanism for the production of impaired iron absorption

Treatment of rats with cycloheximide results in a defect in intestinal iron transport. A similar defect occurs after the parenteral administration of iron. Under both conditions there is impaired uptake of iron into the mucosal cells as well as defective transfer from the intestinal mucosa. It is suggested that the interference in iron transport may be due to a deficiency of an unidenti-fild carrier Substance.     

Inhibition of biogenic amine uptake by hydrogen peroxide: a mechanism for toxic effects of 6-hydroxydopamine

Hydrogen peroxide, dialuric acid, or 6-hydroxydopamine inhibited the uptake of dopamine, norepinephrine, and serotonin into rat brain synaptosomal preparations. The addition of catalase protected all systems, but catalase was only partially protective for 6-hydroxydopamine acting upon catecholamine uptake. The data show that 6-hydroxydopamine generates hydrogen peroxide and that hydrogen peroxide can damage the biogenic amine uptake systems. Part of the damage caused by the 6-hydroxydopamine that accumulates in the catecholamine nerve terminals in vivo may be attributed to the hydrogen peroxide.     

锰对外生菌根真菌生长、养分吸收及有机酸分泌的影响

在液体培养条件下,研究了不同质量浓度锰对外生菌根真菌Pt 715、Sl 13和Cg 04菌丝生长、草酸和乙酸分泌,以及氮、磷、钾吸收的影响。结果表明:Pt 715的生物量最高, Sl 13次之,Cg 04最低。锰显著抑制菌丝生长,菌丝生物量（y）与培养基中的锰质量浓度（0～800 mg/L）呈y=ax+b的关系（a0）;但锰对Pt 715和Sl 13生长的抑制作用较小,说明这2株外生菌根真菌抗锰能力较强,其原因可能是它们长期生存于活性锰含量较高的酸性土壤中,产生了环境适应性,逐渐进化出对锰的抗性。此外,Cg 04和Pt 715不分泌乙酸,但分泌草酸的速率随锰质量浓度的增加而提高;Sl 13能分泌乙酸,在锰质量浓度较高时,分泌草酸的速率显著降低,说明分泌草酸络合锰可能不是外生菌根真菌抗锰的唯一生化途径。Pt 715和Sl 13的氮、磷、钾吸收量显著高于Cg 04。在培养基中添加锰尤其是较高质量浓度的锰（800 mg/L）,Pt 715和Sl 13吸收养分的降幅显著低于Cg 04（除氮外）,降幅比Cg 04低20.28%～15.44%（磷）和51.20%～27.27%（钾）。在锰胁迫条件下,菌丝保持较强的养分吸收能力有益于细胞的健康,增强其抗锰能力,对于提高寄主植物的抗锰能力也可能有积极意义。      

隐绿原酸对H9N2-AIV致小鼠肺损伤的免疫调节和抗氧化效果

为探讨隐绿原酸(4-CQA)对感染H9N2亚型禽流感(H9N2-AIV)病毒的小鼠造成肺损伤的修复作用,将90只6～8周龄健康昆明系小鼠随机分为病毒(H9N2)感染组、H9N2+4-CQA组、空白对照组、4-CQA对照组,用H9N2-AIV滴鼻复制小鼠肺损伤模型并灌胃4-CQA干预.观察各组小鼠肺组织病理学变化;测定肺...     

Amino acid acylation: a mechanism of nitrogen excretion in inborn errors of urea synthesis

Treatment of a patient deficient in carbamyl phosphate synthetase with benzoate or phenylacetic acid resulted in an increase in urinary nitrogen, which could be accounted for by the respective amino acid acylation product, hippurate or phenylacetylgultamine. Benzoate treatment of four hyperammonemic comatose patients led to clinical improvement and a return of plasma ammonium levels toward normal.     

5-Hydroxyindoleacetic acid in the lumbar fluid: a specific indicator of spinal cord injury

In cats, 19 days after the lower thoracic cord was injllred, the concentrations of 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid in the lumbosacral cord and that of 5-hydroxyindoleacetic acid in the lumbar fluid decreased. At the same time the concentrations of these substances in the cord above the lesion and that of 5-hydroxyindoleacetic acid in the cisternal fluid was not significantly altered. Since high concentrations of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid are present in the human lumbosacral cord, it appears that the concentration of 5-hydroxyincdoleacetic acid in the lumbar fluid of animals and man reflects the biochemical changes of 5-hydroxytryptamine in the spinal cord.     

人工湿地对低污染水中氮去除的研究进展：效果、机制和影响因素

低污染水类型多样,水体性质复杂,主要包括低污染河水、污水厂尾水、城镇地表径流、农田径流排水（含农村分散性生活污水）4类,具有量大面广、可生化性差、部分水碳氮比（C/N）低等特点。人工湿地是净化低污染水的有效手段,不同类型湿地对低污染水的污染物净化效果不同。本文探讨了不同类型人工湿地净化低污染水中氮的效果,并总结了人工湿地处理低污染水的微生物机制,分析了不同因素（pH、溶解氧、温度、C/N、植物、基质）对人工湿地低污染水水质净化的影响及优化方法,以期为人工湿地净化低污染水的工程实践提供理论参考。     

日光温室不同温光环境下番茄对氮磷钾吸收规律的研究

为探明环境对番茄养分吸收的影响，以中杂9号番茄为试材，研究日光温室秋冬、冬春2个栽培茬口不同温光环境下番茄对氮磷钾的吸收规律。结果表明：温光环境对番茄吸收氮磷钾总量的变化产生影响。以果实膨大期为例，秋冬茬番茄对全N、P和K吸收的绝对量只相当于冬春茬的85．41％、70．51％和82．4％；但2个茬口番茄全生育期对全N、P和K的吸收比例基本相同，为1：(0．14～0．17)：(1．68～1．73)，与温光环境无关。秋冬茬和冬春茬番茄对全N、P和K的吸收量均呈单峰曲线，果实膨大期达到最大值。果实膨大和采收初期是营养吸收最旺盛时期，吸收量均占到全生育期总量的60％以上，生产上应根据番茄生长环境及生育时期进行科学施肥。     

Indole-2-carboxylic acid: a competitive antagonist of potentiation by glycine at the NMDA receptor

The N-methyl-D-aspartate (NMDA) class of excitatory amino acid receptors regulates the strength and stability of excitatory synapses and appears to play a major role in excitotoxic neuronal death associated with stroke and epilepsy. The conductance increase gated by NMDA is potentiated by the amino acid glycine, which acts at an allosteric site tightly coupled to the NMDA receptor. Indole-2-carboxylic acid (I2CA) specifically and competitively inhibits the potentiation by glycine of NMDA-gated current. In solutions containing low levels of glycine, I2CA completely blocks the response to NMDA, suggesting that NMDA alone is not sufficient for channel activation. I2CA will be useful for defining the interaction of glycine with NMDA receptors and for determining the in vivo role of glycine in excitotoxicity and synapse stabilization.     

Synthesis of methylphosphonic acid by marine microbes: a source for methane in the aerobic ocean

Relative to the atmosphere, much of the aerobic ocean is supersaturated with methane; however, the source of this important greenhouse gas remains enigmatic. Catabolism of methylphosphonic acid by phosphorus-starved marine microbes, with concomitant release of methane, has been suggested to explain this phenomenon, yet methylphosphonate is not a known natural product, nor has it been detected in natural systems. Further, its synthesis from known natural products would require unknown biochemistry. Here we show that the marine archaeon Nitrosopumilus maritimus encodes a pathway for methylphosphonate biosynthesis and that it produces cell-associated methylphosphonate esters. The abundance of a key gene in this pathway in metagenomic data sets suggests that methylphosphonate biosynthesis is relatively common in marine microbes, providing a plausible explanation for the methane paradox.     

模拟酸雨对羟基磷灰石稳定化土壤镉的分布、可浸出性及生物可给性的影响

通过室内土柱淋溶实验,以0.5%的质量比向镉污染土壤中添加羟基磷灰石(HAP),以不施HAP土壤为对照,考察p H 3.5、4.5和5.6的模拟酸雨对土壤镉的分布、可浸出性、生物可给性及其健康风险的影响。结果表明:酸雨淋溶显著降低了对照处理表层土壤p H,添加HAP增加了土壤对酸雨淋洗的缓冲能力,土壤p H较对照高约1个单位。对照处理酸雨p H的降低加剧了Cd在土柱内的下移,但HAP处理各土层全Cd分别较对照0~5 cm和5~10 cm土壤高出8.54~10.0、3.13~3.29 mg·kg-1。对照处理土壤在酸雨作用下可浸出性Cd含量从0~5 cm的0.17~0.23 mg·L-1增加到10~20 cm的0.61~0.68 mg·L-1,但HAP处理各土层可浸出性Cd维持在0.45~0.50 mg·L-1。总体上,对照和HAP处理土壤胃液和肠液阶段溶解态Cd含量及胃液阶段Cd的生物可给性均随酸雨p H的降低而降低。与对照相比,HAP处理土壤增加了胃液和肠液阶段溶解态Cd含量及胃液阶段Cd的生物可给性,但显著降低了肠液阶段Cd的生物可给性。对照和HAP处理土壤胃液和肠液阶段无意摄入土壤中Cd对儿童的每月允许摄入量PTMI(Provisional tolerable monthly intake)贡献率均随酸雨p H的降低而降低,且HAP处理显著高于对照。以上结果表明高强度酸雨淋溶下,HAP能够有效提高土壤对酸雨的缓冲能力,降低土壤Cd的淋失,但增加了表层土壤Cd的生物可给性及人体健康风险,需要引起特别关注。     

苏子油对瘤胃体外发酵模式、脂肪酸组成及甲烷生成的影响

为探讨苏子油对瘤胃体外发酵的影响,采用人工瘤胃技术分析不同添加水平的苏子油对瘤胃发酵模式、发酵参数和瘤胃脂肪酸代谢的影响.结果表明:添加不同剂量苏子油对发酵液pH值和氨氮(NH3-N)含量无显著影响(P0.05);与对照相比较,随着苏子油添加量的增加干物质降解率、中性洗涤纤维降解率、酸性洗涤纤维降解率、发酵底物单位产气量显著降低(P0.05),甲烷产量呈下降趋势(P0.05);对TVFA无显著影响(P0.05),丙酸含量显著增加(P0.05),乙酸含量和乙酸丙酸比例显著降低(P0.05);C18:1、c9,t11-CLA和总的长链脂肪酸浓度均明显升高(P0.01).表明在粮中添加一定量的苏子油,可改变瘤胃发酵类型、降低甲烷产量、调节瘤胃液脂肪酸组成.     

A pulsar, the heliosphere, and pioneer 10: probable mimicking of a planet of PSR B1257+12 by solar rotation

Doppler data generated with the Pioneer 10 spacecraft's radio carrier wave between 1987 and 1995 show a 25.3-day periodicity which is related to the solar rotation. The timing data of the pulsar PSR B1257+12 also show a periodicity of 25.34 days, which has been explained as a signature of the pulsar's barycentric motion in response to the existence of a small moon-like object. However, because PSR B1257+12 is located close to the ecliptic and because the timing variations are in the range of microseconds, it is likely that the pulsar signal is affected by the same mechanism acting on the Pioneer 10 Doppler data. Hence, the hypothesized inner planet around PSR B1257+12 is probably an artifact of the heliosphere.