Nitric oxide extends the oocyte temporal window for optimal fertilization

Deteriorating oocyte quality is a critical hurdle in the management of infertility, especially one associated with advancing age. In this study, we explore the role of nitric oxide (NO) on the sustenance of oocyte quality postovulation. Sibling oocytes from superovulated mice were subjected to intracytoplasmic sperm injection (ICSI) with cauda-epididymal spermatozoa following exposure to either the NO donor, S-nitroso-N-acetylpenicillamine (SNAP, 0.23 microM/min), an NO synthase (NOS) inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME, 1 mM), or an inhibitor of soluble guanylyl cyclase (sGC), 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ, 100 microM); while their sibling oocytes were subjected to ICSI either before (young) or after culture for the corresponding period of time (old). Outcomes of normal fertilization, cleavage, and development to the morula and blastocyst stages were compared. Embryos from each subgroup were also subjected to TUNEL assay for apoptosis. A significant deterioration in the ability of the oocytes to undergo normal fertilization and development to morula and blastocyst stages occurred among oocytes aged in culture medium compared to their sibling cohorts subjected to ICSI immediately after ovulation (P<0.05). This deterioration was prevented in oocytes exposed to SNAP. In contrast, exposure to L-NAME or ODQ resulted in a significant compromise in fertilization and development to the morula and blastocyst stages (P<0.05). Finally, apoptosis was noted in embryos derived from aged oocytes and those exposed to L-NAME or ODQ, but not in embryos derived from young oocytes or oocytes exposed to SNAP. Thus, NO is essential for sustenance of oocyte quality postovulation.     

Infection Process of Plectosporium tabacinum on False Cleavers (Galium spurium)

A native fungus, Plectosporium tabacinum (van Beyma) M. E. Palm, W. Gams et Nirenberg, has potential as a bioherbicide for the control of both herbicide-resistant and herbicide-susceptible false cleavers. Limited information is available on the infection process of P. tabacinum. P. tabacinum spore distribution pattern, germination, penetration, and colonization on false cleavers leaves were examined using confocal, light, and scanning electron microscopy. The results demonstrated that conidia were distributed over the entire surface of leaves and cotyledons. More than 90% of the conidia germinated on the leaf surface 6-8 h after inoculation. Penetration of the leaf epidermis by conidia started 8-10 h after inoculation. Histological observation showed that no appressoria were formed by P. tabacinum, but its hyphae produced appressed club-like structures that penetrated the cuticle and epidermal layers. No stomata or other natural openings were observed on the upper leaf surface of false cleavers seedlings. Penetration occurs directly on epidermal cells with more frequent intercellular penetrations. Hyphal penetration was visualized at a depth of 30 and 40 üm after 8 and 16 h of incubation, respectively. Secondary hyphae colonized mesophyll cells 16 h after inoculation. Even spore distribution, short spore germination time, club-like infection structure formation, direct penetration, quick colonization, and mucous secretion on false cleavers leaves may contribute to the kill of false cleavers by P. tabacinum. Slow spore germination and germ tube growth, low spore germination numbers, and no infection structure formation on Brassica napus leaves may be factors affecting the host selectivity of P. tabacinum.     

Control of Polymorphs on the Crystallization of Glycine Using a WWDJ Batch Crystallizer

The control of crystal polymorphs was investigated using a WWDJ batch crystallizer and glycine as a model compound. The WWDJ batch crystallizer is a newly developed crystallizer, which is equipped with a slurry sprinkler named Wall Wetter fixed on the shaft of an impeller and a double‐deck jacket. When a conventional crystallizer was used, the unstable α‐form crystals were always obtained. However, when the WWDJ batch crystallizer was used, the stable γ‐form crystals were obtained. The appearance of different polymorphs depends on the cooling rate during the crystallization. The γ‐form crystals were obtained by slow cooling, while the α‐form was obtained by rapid cooling. It means that the solvent‐mediated transformation of glycine crystal polymorphs can be controlled by changing the cooling rate in the WWDJ crystallizer. These results were obtained due to the fact that the WWDJ batch crystallizer accelerates the dissolution of metastable crystals and the growth of stable crystals.     

The contribution of PAS 2050 to the evolution of international greenhouse gas emission standards

Background, aim, and scope  The assessment of greenhouse gas (GHG) emissions arising from products (goods and services) is emerging as a high profile application of life cycle assessment (LCA), with an increasing desire from retailers and other supply chain organizations to better understand, and in some cases communicate, the carbon footprint of products. Publicly Available Specification 2050:2008, Specification for the assessment of the life cycle greenhouse gas emissions of goods and services, addresses the single-impact category of global warming to provide a standardized and simplified implementation of process LCA methods for assessing GHG emissions from products. This paper briefly reviews the development process followed for PAS 2050, before examining the treatment of GHG-specific contribution of PAS 2050 to product carbon footprinting. Materials and methods  PAS 2050 was jointly sponsored by the Carbon Trust and the UK Department for Environment, Food and Rural Affairs and was published by the British Standards Institution on 29 October 2008. An independent steering group oversaw the development of the specification, including the establishment of an expert workgroup program, comprehensive international consultation, and expert input on the requirements of the specification. Results  The development process for PAS 2050 resulted in a specification that includes specific requirements that limit the interpretation of the underlying LCA approach to product carbon footprinting. These requirements, including goal setting and life cycle inventory assessment, aspects of system boundary identification and temporal aspects of GHG emissions, clarify the approach to be taken by organizations implementing product carbon footprinting, and simplify the application of LCA procedures in relation to product carbon footprinting. Discussion  Assessment of the emissions arising from the life cycle of products has a clear international component, and delivering consistent results across the supply chain requires the application of consistent methods. There is an emerging recognition that further standardization of methods for product carbon footprinting is needed, and the specific requirements resulting from the PAS 2050 development process make a valuable contribution across a range of GHG assessment issues. Conclusions  The widespread interest in PAS 2050 from individuals and organizations, together with the development of similar guidance by other organizations, confirmed that there is a need for clarification, certainty, and requirements in the field of product carbon footprint analysis. The use of PAS 2050 to refine, clarify, and simplify existing LCA methods and standards has resulted in specific approaches to key GHG assessment issues being developed; it is important that future standards development work considers the impact of these approaches and their further refinement. Recommendations and perspectives  It is the consumption of goods and services by individuals around the world that drives global GHG emission, and PAS 2050 is a first attempt to provide integrated, consistent approaches that directly address the role of consumption at the product level in contributing to GHG emissions. Climate science and GHG assessment techniques are both evolving areas and it will be necessary to review the approach taken by PAS 2050 in the future: a formal review process for PAS 2050 will commence towards the end of 2009 and practitioners are encouraged to participate in this review process.

Strategy for a protein purification design using C-phycocyanin extract

A variety of techniques have been developed for the separation and recovery of proteins. The cost of purifying the product is frequently determined by the desired quality of the final product, which is evaluated by measuring the purity. In this work the design of a protein purification process for C-phycocyanin, a phycobiliprotein that can be used in the food and medical industries, was established. The study evaluated the use of ammonium sulfate precipitation, ion exchange chromatography and gel filtration to purify C-phycocyanin in a variety of sequences. The final design included the C-phycocyanin extraction step, precipitation with ammonium sulfate and ion exchange chromatography. When the elution step was studied, the kind of elution and pH were considered in order to obtain a product with a final purity of 4.0 with a purification factor of 6.35, so that, at the end of the strategy, C-phycocyanin of analytical grade would be obtained.     

Exploring the role of the immune response in preventing antibiotic resistance

For many bacterial infections, drug resistant mutants are likely present by the time antibiotic treatment starts. Nevertheless, such infections are often successfully cleared. It is commonly assumed that this is due to the combined action of drug and immune response, the latter facilitating clearance of the resistant population. However, most studies of drug resistance emergence during antibiotic treatment focus almost exclusively on the dynamics of bacteria and the drug and neglect the contribution of immune defenses. Here, we develop and analyze several mathematical models that explicitly include an immune response. We consider different types of immune responses and investigate how each impacts the emergence of resistance. We show that an immune response that retains its strength despite a strong drug-induced decline of bacteria numbers considerably reduces the emergence of resistance, narrows the mutant selection window, and mitigates the effects of non-adherence to treatment. Additionally, we show that compared to an immune response that kills bacteria at a constant rate, one that trades reduced killing at high bacterial load for increased killing at low bacterial load is sometimes preferable. We discuss the predictions and hypotheses derived from this study and how they can be tested experimentally.     

蛋白质特征曲线的研究

提出一种新颖的方案使蛋白质结构信息可视化。在滑动窗口方法基础上,每一个天然氨基酸采用从氨基酸索引数据库中挑选的48种特性参数描述,在某一特定窗口下的所有氨基酸残基的参数就组成一个矩阵,通过矩阵变换得到一个方矩阵,再经过窗口的滑动就得到基于整个蛋白质的所有这些窗口矩阵的本征值矩阵。对本征值矩阵元素作图得到一系列的本征值曲线,这种曲线的轮廓不随窗口的变化而变化,这些曲线被称为蛋白质的特征曲线。为选择合适的窗口宽度、对同一类型蛋白质不同窗口宽度及不同类型蛋白质相同窗口宽度下的本征值矩阵进行了比较研究,对其潜在的用途进行了讨论。     

LTD windows of the STDP learning rule and synaptic connections having a large transmission delay enable robust sequence learning amid background noise

Spike-timing-dependent synaptic plasticity (STDP) is a simple and effective learning rule for sequence learning. However, synapses being subject to STDP rules are readily influenced in noisy circumstances because synaptic conductances are modified by pre- and postsynaptic spikes elicited within a few tens of milliseconds, regardless of whether those spikes convey information or not. Noisy firing existing everywhere in the brain may induce irrelevant enhancement of synaptic connections through STDP rules and would result in uncertain memory encoding and obscure memory patterns. We will here show that the LTD windows of the STDP rules enable robust sequence learning amid background noise in cooperation with a large signal transmission delay between neurons and a theta rhythm, using a network model of the entorhinal cortex layer II with entorhinal-hippocampal loop connections. The important element of the present model for robust sequence learning amid background noise is the symmetric STDP rule having LTD windows on both sides of the LTP window, in addition to the loop connections having a large signal transmission delay and the theta rhythm pacing activities of stellate cells. Above all, the LTD window in the range of positive spike-timing is important to prevent influences of noise with the progress of sequence learning.     

How to evaluate the risk-benefit ratio of the low-dose hormone replacement therapy?

Since the results of the women health initiative study showing an overall negative risk-benefit ratio with 0.625 mg of conjugated estrogens plus 2.5 mg of medroxyprogesterone acetate, the use of the lowest effective dose of steroids in hormone replacement therapy (HRT) is recommended.

A low-dose regimen appears to induce less side effects such as breast tenderness or leg pain than do higher dose preparations.

The decrease in hot flashes with low-dose estrogens, range 60–70%, is less than the 80–90% reduction with standard dosing. But this mean that 60–70% of menopausal women do not need higher doses.

The same applies to bone preservation which is dose dependent: the number of non-respondant women will be higher than with standard doses. However, randomized double-blind, placebo controls trials have defined positive effects on bone of low doses of HRT with adequate calcium and Vitamin D in elderly women. The use of bone densitometry and of biochemical markers of bone turnover is mandatory in women using low or ultra-low-dose preparations.

In spite of the lack of trials conducted with low-dose HRT, this treatment seems to be safer:

• the plasma levels of estradiol are lower; as far as breast cancer risk is concerned, the decrease of this subrogate marker is considered as favourable;

• the increase in breast density is less pronounced;

• the nurses's health study found a dose relationship for stroke, with no increase in risk with low-dose of estrogens;

• the effects on subrogate markers of cardiovascular risk seem to be more favourable.

Beside the low-dose HRT, one must consider some other facts:

• the “critical window” theory: it is biologically plausible that HRT, if started early after the menopause can slow the progression of coronary atherosclerosis;

• the way of administration of HRT: some observational studies have shown no increase in the risk of venous thromboembolism risk among women treated with transdermal estrogens;

• the progestogen used: a French cohort study recently performed found no increase in breast cancer risk with the use of micronized progesterone meanwhile the increase in risk observed with other progestogens was similar to the findings of the WHI study.

In the future, it is conceivable that more comprehensive pharmacogenomic studies will lead to effective algorithms for individualizing the right dose of steroids to be used in HRT.