Studies on the ultrastructure, histochemistry and cytochemistry of the uninfected digestive gland of Bithynia tentaculata (Mollusca: Gastropoda) and on the ultrastructure of this host organ in snails infected with larval digeneans

The structure and function of the digestive gland of the gastropod mollusc, Bithynia tentaculata, was investigated using ultrastructural, histochemical, and cytochemical techniques. The digestive gland was shown to be composed of two main cell types, the "digestive" cells and "secretory" cells. The digestive cells appeared to be concerned with the absorption and digestion of nutrients, while secretory cells produced digestive enzymes and calcareous concretions. Undifferentiated cells were scattered between these two main cell types. The pathological effects of larval digeneans on the digestive gland were also investigated, at the ultrastructural level. In such infected snails the digestive gland appeared to be degenerating. The significance of this tissue destruction was briefly discussed.     

PDF417二维条码肖像图片压缩编码的优化算法研究

针对PDF417二维条码存储空间有限的问题，提出了一种基于小波变换的有损图像压缩算法，通过这个算法，可以将静态图片信息加入PDF417条码中，并能够满足在指定字节数情况下保证高质量地压缩图像，该文在分析小波变换等算法理论的基础上，详细介绍了PDF417二维条码肖像图片压缩编码的优化算法及该算法的实验结果与美国Symbol公司的PC2VQ算法结果对比。     

The Limehouse Link: the architectural and cultural history of a monumental road tunnel in London's Docklands

In the Docklands area of London lies the ‘Limehouse Link’, a dual-bore road tunnel used by around 80,000 cars each day. A monumental and highly expensive piece of construction, the Limehouse Link has nonetheless received almost no attention from architectural historians or others concerned with the history of construction, engineering or urban development.

This article provides an introduction to the Limehouse Link, explaining some of the fundamental characteristics of its construction and position in London's urban landscape. More importantly, the article then considers how one might understand an everyday yet monumental construction such as this: a tunnel without obvious aesthetic form, design intent or symbolic meaning, but which nonetheless has an undeniable presence in the city. The Limehouse Link is therefore interpreted in terms of the car driver's immersive experience of the tunnel, more active constructions of this experience through sensory qualities of sound, representations of the tunnel in different media and art, ways of knowing the history of Limehouse, and, in particular, as a kind of aesthetic experience. The article concludes that driving through the Limehouse Link is to engage in a different way of knowing the postmodern city.     

化学合成制药综合废水的处理

本文介绍了化学合成制药废水的处理工艺、原理和运行效果,该工艺处理后的污水完全达到国家规定的污水排放标准。     

精炼工艺对椰子油品质的影响

研究了精炼工艺对椰子油品质的影响。分析了毛椰油、碱炼油、脱色油、脱臭油的理化指标、脂肪酸、甘油酯组成和脂肪伴随物(甾醇、生育酚、多酚)的变化情况。结果表明:精炼工艺使椰子油的酸值、过氧化值显著降低,脂肪酸和甘油酯组成无显著变化;总甾醇、总生育酚和多酚含量显著降低,损失率分别为63.77%、68.03%、71.20%。综上表明,精炼能够显著影响油脂品质,需注重油脂适度加工技术的应用。     

General method for plasmid construction using homologous recombination

We describe a general method for plasmid assembly that uses yeast and extends beyond yeast-specific research applications. This technology exploits the homologous recombination, double-stranded break repair pathway in Saccharomyces cerevisiae to join DNA fragments. Synthetic, double-stranded "recombination linkers" were used to "subclone" a DNA fragment into a plasmid with > 80% efficiency. Quantitative data on the influence of DNA concentration and overlap length on the efficiency of recombination are presented. Using a simple procedure, plasmids were shuttled from yeast into E. coli for subsequent screening and large-scale plasmid preps. This simple method for plasmid construction has several advantages. (i) It bypasses the need for extensive PCR amplification and for purification, modification and/or ligation techniques routinely used for plasmid constructions. (ii) The method does not rely on available restriction sites, thus fragment and vector DNA can be joined within any DNA sequence. This enables the use of multifunctional cloning vectors for protein expression in mammalian cells, other yeast species, E. coli and other expression systems as discussed. (iii) Finally, the technology exploits yeast strains, plasmids and microbial techniques that are inexpensive and readily available.     

Rapid detection of epidemic strains of methicillin-resistant Staphylococcus aureus

Fifty methicillin-resistant Staphylococcus aureus (MRSA) initial isolates obtained from patients hospitalized in the orthopedic clinic of the Frankfurt University Hospital and 150 methicillin-sensitive Staphylococcus aureus (MSSA) isolates were investigated in this study to determine whether the Slidex Staph-Kit is capable of differentiating between MRSA and MSSA owing to its unique performance characteristics. The Slidex Staph-Kit is a combined latex hemagglutination test designed to detect clumping factor, protein A, and a specific surface immunogen for S. aureus. Clumping factor-positive strains cause erythrocytes sensitized with fibrinogen to hemagglutinate, thereby resulting in visible red clumps. S. aureus strains deficient in clumping factor agglutinate latex particles sensitized with specific antibodies against surface proteins of S. aureus, thereby resulting in visible white clumps. Our results demonstrate that white clumping has a 99% specificity as well as a 98% positive predictive value for MRSA. Clumping factor-negative MRSA, which have been reported to occur in several countries, are epidemic in the Frankfurt area and account for 80% of all MRSA initial isolates in the orthopedic clinic of the Frankfurt University Hospital. Genotyping of all MRSA isolates by macrorestriction analysis of chromosomal DNA revealed that 83% of clumping factor-negative MRSA are closely related to the "southern-German" epidemic strain. This is the first study demonstrating the Slidex Staph-Kit's capability for identifying epidemic clumping factor-negative S. aureus strains as methicillin resistant even prior to antimicrobial susceptibility testing.     

Protein kinase C regulates a vesicular class of calcium channels in the bag cell neurons of aplysia

Protein kinase C (PKC) acutely increases calcium currents in Aplysia bag cell neurons by recruiting calcium channels different from those constitutively active in the plasma membrane. To study the mechanism of PKC regulation we previously identified two calcium channel alpha1-subunits expressed in bag cell neurons. One of these, BC-alpha1A, is localized to vesicles concentrated primarily in somata and growth cones. We used antibodies to BC-alpha1A to analyze its expression in the bag cell neurons of juvenile Aplysia at a developmental stage at which PKC-sensitive calcium currents have previously been shown to be low. We find that vesicular BC-alpha1A staining is generally reduced in juvenile bag cell neurons but that its expression level can vary among juvenile animals. In 17 bag cell clusters examined, the percentage of neurons that displayed punctate alphaBC-alpha1A staining ranged from 0 to 85%. Sampling of calcium currents from cells of the same clusters by whole cell patch-clamp techniques revealed that the PKC-sensitive calcium current density is significantly correlated with the degree of vesicular staining. In contrast, no correlation of basal calcium current levels with aBC-alpha1A staining was found. These results strongly suggest that BC-alpha1A, a member of the ABE-subfamily of calcium channels, carries the PKC-sensitive calcium current in bag cell neurons. They are consistent with a model in which PKC recruits channels from the vesicular pool to the plasma membrane.     

Immune response to an intercalated enhanced inactivated polio vaccine/oral polio vaccine programme in Israel: impact on the control of poliomyelitis

A combined enhanced inactivated polio vaccine (EIPV) and oral polio vaccine (OPV) programme was introduced in Israel in 1990, with the purpose of providing a solution to the persistent polio morbidity in spite of a 30 year long OPV programme. The schedule comprised two doses of EIPV administered at the age of 2 and 4 months, intercalated with two doses of OPV at 4 and 6 months, followed by a reinforcing dose with the two vaccines simultaneously administered at 12 months. The 5-year evaluation of the programme included: the assessment of clinical suspicions of polio, early immune response in successive cohorts administered the new schedule, dynamics of the immune profile in a cohort followed up to the age of 5, and monitoring of wild poliovirus excretion in sewage specimens collected in 25 permanent sites throughout Israel as well as from the Palestinian Authority. No paralytic polio cases associated with a wild or vaccinal poliovirus strain were detected since the introduction of the programme. At the age of 4 months, one week after administration of the second EIPV and first OPV dose, 100% seropositivity and high geometric mean titres (GMTs) of neutralizing antibody (NA) to the three vaccinal and to the wild poliovirus type 1, responsible for the 1988 polio outbreak, were observed. No change in percent of seropositivity occurred between the age of 6 and 12 months. Thirty days after the IPV and OPV reinforcing doses, GMTs to each of the four poliovirus strains were > or = 3037. Up to the age of 5, the seropositivity was unchanged. After a 2.5-10-fold decline in the first year following the completion of the programme, GMTs to the three vaccinal and the wild poliovirus strain levelled off at rather high values, considered protective. Between 1990 and 1995, 16 wild poliovirus type 1 strains were isolated in three separate episodes in Gaza Strip sewage and once only in one Israeli site very close to Gaza City. The rapidly established, high and persistent NA titre to the vaccinal and wild poliovirus strains and the presence of immunological memory are indicative of high individual protection throughout the first 5 years of life. The only one-time introduction, without circulation, of a wild poliovirus strain in a single Israeli settlement suggests community protection. The intercalated programme offers a contribution to polio eradication by providing a solution to the primary and secondary failure associated with OPV, as well as to the control of vaccine-associated paralytic poliomyelitis.