The influence of oxygen concentrations on denitrification in soil

Summary The influence of different O₂ concentrations on denitrification was studied in an agricultural soil. In both nitrate and nitrite amended soil, denitrification was not observed until the O₂ concentration decreased to 0.20 and 0.21 mol/ml, respectively. Denitrification was not observed in soil samples with O₂ concentrations above 0.28 mol/ml in the gas phase. These findings suggest that a completely anoxic environment is not required for denitrification to occur in soil.     

经阴道宫腔镜手术与腹腔镜手术对输卵管妊娠的疗效比较

目的:比较经阴道宫腔镜手术与腹腔镜手术对输卵管妊娠的临床疗效和安全性。方法:选取2013年3月至2015年3月在我院接受治疗的输卵管妊娠患者95例,按照手术方式的不同分为对照组48例和观察组47例。对照组患者给予腹腔镜手术治疗,观察组患者给予经阴道宫腔镜手术治疗。比较两组手术时间、术中出血量、排气时间、住院时间、症状消失时间以及手术结果,炎性因子包括血清C反应蛋白(CRP)、白细胞介素2(IL-2)、白细胞介素6(IL-6)、白细胞介素8(IL-8)水平的变化。结果:两组的手术时间、术中出血量、住院时间以及症状消失时间比较差异无统计学意义(P0.05);而观察组的排气时间显著短于对照组(P0.05);术后,观察组的学期CRP、IL-2、IL-6、IL-8水平显著低于对照组,差异具有统计学意义(P0.05)。两组的手术成功率、患侧输卵管通畅率比较差异无统计学意义(P0.05);而观察组的再次宫内妊娠率显著高于对照组,不良反应发生率显著低于对照组,差异具有统计学意义(P0.05)。结论:经阴道宫腔镜手术和腹腔镜手术治疗输卵管妊娠均效果良好,而经阴道宫腔镜手术在抑制炎症和提高再次宫内妊娠率的效果更优,且安全性更高。     

实时三维超声输卵管造影与X线造影诊断不孕症患者输卵管病变的价值比较

目的:比较实时三维超声输卵管造影与X线造影检查诊断女性不孕症患者输卵管病变的临床应用价值。方法:选择2014年3月至2016年12月我院诊治的不孕症患者60例作为研究对象,所有患者都于月经干净后3-7 d同时随机实施实时三维超声输卵管造影与X线造影检查,观察并记录造影图像质量与诊断结果,比较两种方法的诊断效果。结果:实时三维超声输卵管造影与X线造影的图像质量优良率分别为98.3%和86.7%,实时三维超声输卵管造影的图像质量明显高于X线造影(P0.05)。实时三维超声输卵管造影与X线造影诊断不孕症患者输卵管不通畅率分别为56.7%和46.7%,实时三维超声输卵管造影组显著高于X线造影组(P0.05)。输卵管通畅性评价金标准腹腔镜下通液术诊断发现输卵管不通畅35例,在此基础上实时三维超声输卵管造影与X线造影检查不孕症的敏感性分别为97.1%和80.0%,特异性均为100.0%,超声诊断的敏感性明显高于X线(P0.05)。结论:相对于X线造影,实时三维超声输卵管造影检查不孕症患者输卵管病变的图像质量更好,有利于疾病的判断,对输卵管通畅度判断更精确,利于后期治疗及疾病预防,还可提高诊断敏感性。     

Rapid cooling triggers forisome dispersion just before phloem transport stops

Phloem transport stops transiently within dicot stems that are cooled rapidly, but the cause remains unknown. Now it is known that (1) rapid cooling depolarizes cell membranes giving a transient increase in cytoplasmic Ca²⁺, and (2) a rise of free calcium triggers dispersion of forisomes, which then occlude sieve elements (SEs) of fabacean plants. Therefore, we compared the effects of rapid chilling on SE electrophysiology, phloem transport and forisomes in Vicia faba. Forisomes dispersed after rapid cooling with a delay that was longer for slower cooling rates. Phloem transport stopped about 20 s after forisome dispersion, and then transport resumed and forisomes re‐condensed within similar time frames. Transport interruption and forisome dispersion showed parallel behaviour – a cooling rate‐dependent response, transience and desensitization. Chilling induced both a fast and a slow depolarization of SE membranes, the electrical signature suggesting strongly that the cause of forisome dispersion was the transient promotion of SE free calcium. This apparent block of SEs by dispersed forisomes may be assisted by other Ca²⁺‐dependent sealing proteins that are present in all dicots.     

Replication protein A and gamma-H2AX foci assembly is triggered by cellular response to DNA double-strand breaks

Human replication protein A (RPA p34), a crucial component of diverse DNA excision repair pathways, is implicated in DNA double-strand break (DSB) repair. To evaluate its role in DSB repair, the intranuclear dynamics of RPA was investigated after DNA damage and replication blockage in human cells. Using two different agents [ionizing radiation (IR) and hydroxyurea (HU)] to generate DSBs, we found that RPA relocated into distinct nuclear foci and colocalized with a well-known DSB binding factor, gamma-H2AX, at the sites of DNA damage in a time-dependent manner. Colocalization of RPA and gamma-H2AX foci peaked at 2 h after IR treatment and subsequently declined with increasing postrecovery times. The time course of RPA and gamma-H2AX foci association correlated well with the DSB repair activity detected by a neutral comet assay. A phosphatidylinositol-3 (PI-3) kinase inhibitor, wortmannin, completely abolished both RPA and gamma-H2AX foci formation triggered by IR. Additionally, radiosensitive ataxia telangiectasia (AT) cells harboring mutations in ATM gene product were found to be deficient in RPA and gamma-H2AX colocalization after IR. Transfection of AT cells with ATM cDNA fully restored the association of RPA foci with gamma-H2AX illustrating the requirement of ATM gene product for this process. The exact coincidence of RPA and gamma-H2AX in response to HU specifically in S-phase cells supports their role in DNA replication checkpoint control. Depletion of RPA by small interfering RNA (SiRNA) substantially elevated the frequencies of IR-induced micronuclei (MN) and apoptosis in human cells suggestive of a role for RPA in DSB repair. We propose that RPA in association with gamma-H2AX contributes to both DNA damage checkpoint control and repair in response to strand breaks and stalled replication forks in human cells.     

Evaluation of the factors affecting avicel reactivity using multi-stage enzymatic hydrolysis

Multi-stage and single-stage enzymatic hydrolysis of cellulose (Avicel PH-101) were conducted to investigate individual factors that affect the rate-reducing kinetics of enzymatic hydrolysis. Understanding factors affecting enzymatic hydrolysis of Avicel will help improve hydrolysis of various biomasses. Product inhibition, enzyme deactivation, and the changes of substrate are potential factors that can affect the hydrolysis efficiency of Avicel. Multi-stage enzymatic hydrolysis resulted in 36.9% and 25.4% higher carbohydrate conversion as compared to a single-stage enzymatic hydrolysis with an enzyme loading of 5 and 20 FPU/g in a 96 h reaction. However, a decline in carbohydrate conversion of 1.6% and 2.6% was observed through each stage with 5 and 20 FPU/g, respectively. This indicated that the substrate became more recalcitrant as hydrolysis progressed. The decreased reactivity was not due to crystallinity because no significant change in crystallinity was detected by X-ray diffraction. Product inhibition was significant at low enzyme loading, while it was marginal at high enzyme loading. Therefore, product inhibition can only partially explain this decreased conversion. Another important factor, enzyme deactivation, contributed to 20.3% and 25.4% decrease in the total carbohydrate conversion of 96 h hydrolysis with 5 and 20 FPU/g, respectively. This work shows that an important reason for the decreased Avicel digestibility is the effect of enzyme blockage, which refers to the enzymes that irreversibly adsorb on accessible sites of substrate. About 45.3% and 63.2% of the total decreased conversion at the end of the 8th stage with 5 and 20 FPU/g, respectively, was due to the presence of irreversibly adsorbed enzymes. This blockage of active sites by enzymes has been speculated by other researchers, but this article shows further evidence of this effect.     

Blockage errors in studies of the effect of wind on thermoregulatory responses

1. 1.The presence of an animal in a wind tunnel increases the effective wind velocity, and so increases heat transfer rates.

2. 2.Potentially significant errors in thermal conductance and thermoregulatory metabolism measurements may result.

3. 3.In a given wind tunnel metabolism chamber, these errors are size dependent and thus may lead to invalid allometric or adaptive interpretations of data.

4. 4.The errors are also sensitive to the shape, orientation, and characteristics of the fur or feather insulation of the animal. Thus, only approximate guidelines can be given for choosing correction factors.

Decrease of the hydraulic conductivity of sand columns by Methanosarcina barkeri

The extent to which a methanogen can clog sand columns was examined: two permeameters packed with clean quartz sand were sterilized, saturated with water, inoculated with Methanosarcina barkeri and percolated under upward flow conditions. After approx. 5 months, the hydraulic conductivity of the sand had decreased to 3% and 25% of the highest values measured earlier. At that point, gas-filled regions in the sand were clearly visible through the transparent walls of the permeameters, and methane bubbles were continuously released from the columns into the effluent. Scanning electron microscopy observations and biomass assays indicated that cell mass accumulation did not contribute significantly to the observed decrease of the hydraulic conductivity. This decrease was therefore attributed to pore blocking due to the entrapment of methane bubbles.D. Sanchez de Lozada and P. Baveye are with the Department of Soil, Crop and Atmospheric Sciences, Bradfield Hall, Cornell University, Ithaca, NY 13853, USA; P. Vandevivere is with the College of Marine Studies, University of Delaware, Lewes, DE 19958, USA. S. Zinder is with the Department of Microbiology, Rice Hall, Cornell University, Ithaca, NY 14853, USA.     

Ultrastructure of pig tubal ova

Summary The unfertilized ova of the pig are characterized by the first polar body situated in the perivitelline space. The metaphase chromosomes of the ova are found free in a cortical area, predominantly inhabited by the spindle fibers. Mitochondria show morphological changes in the form of swelling of their matrices. Frequently, the membranes of the individual cristae mitochondriales meet each other, forming meeting points, at regular intervals. The endoplasmic reticulum increases in quantity when compared with that of the pig follicular oocytes (Norberg, 1972b). The Golgi complexes are sparse and scattered. Occasionally, remnants of the end bulbs of the corona radiata cell processes occur below the surface membrane of the ova.Usually, the sperm-penetrated ova contain the first and the second polar body within the perivitelline space. Intranuclear annulate lamellae are observed within the male and female pronucleoplasm, and of particular interest are extended linear structures in one of the pronuclei. These structures may be considered as precursor stage in the formation of the intranuclear annulate lamellae. The parapronuclear cytoplasm is rich in organelles, especially the cytoplasmic annulate lamellae. In contrast to the scarcity of Golgi complexes in the unfertilized ova, many newly formed Golgi vesicles and lamellae reappear in the pronuclear stage. The zona pellucida displays ultrastructural changes following sperm penetration of the ova.This work was supported by the Agricultural Research Council of Norway.     

Blocking gap junctional intercellular communication in myoblasts inhibits myogenin and MRF4 expression

Cells rely heavily on cues from their extracellular environment and other cells to coordinate normal physiological processes, and the exchange of molecules via gap junctions has been suggested as an important avenue for cell-cell communication. Gap junctions are found in virtually all mammalian tissues with the notable exception of adult skeletal muscle. However, since functional gap junctions have been detected during the early stages of muscle development, gap junctional intercellular communication (GJIC) may play an important role in myogenesis. In this study, GJIC in normal L6 myoblasts was inhibited using the known blockers 1-octanal and β-glycyrrhetinic acid (β-GA). Under differentiation promoting conditions, L6 cells fused to form multinucleated myotubes, but when treated with either octanol or β-GA, no fusion was observed. The expression of two muscle regulatory factors (MRFs), myogenin and MRF4, was examined in both the blocked and control cells. As expected, the activation of both the myogenin and MRF4 genes coincided with the onset of differentiation in the control L6 cells. Neither of these genes were turned on in the blocked cells, even when grown under low serum conditions. This inhibition of differentiation by octanol and β-GA was reversible, since the activation of both MRF genes as well as myoblast fusion were observed when the blocking medium was replaced with normal differentiating medium. These results suggest that intercellular communication via gap junctions plays an important role in skeletal muscle development and perhaps in the cell signaling events that trigger the activation of muscle-specific MRF genes. Dev. Genet. 20:133–144. 1997. © 1997 Wiley-Liss, Inc.