T-cell receptor beta-chain expression: dependence on relatively few variable region genes

Fifteen independently isolated complementary DNA clones that contain T-cell receptor (TCR) V beta genes were sequenced and found to represent 11 different V beta genes. When compared with known sequences, 14 different V beta genes could be defined from a total of 25 complementary DNA's; 11 clones therefore involved repeated usage of previously identified V beta's. Based on these data, we calculate a maximum likelihood estimate of the number of expressed germline V beta genes to be 18 with an upper 95 percent confidence bound of 30 genes. Southern blot analysis has shown that most of these genes belong to single element subfamilies which show very limited interstrain polymorphism. The TCR beta-chain diversity appears to be generated from a limited V beta gene pool primarily by extensive variability at the variable-diversity-joining (V-D-J) junctional site, with no evidence for the involvement of somatic hypermutation.     

北京地区圆柏新分类群形态及化学分类的研究

本文系研究北京地区圆柏新分类群的形态分类,并用过氧化物同功酶谱及氨基酸组成含量进行化学分类认证。确定圆柏属新增四栽培变种的形态特征。亲缘关系、利用特点,为栽培圆柏分类和良种选育提供新见解和资料。     

A Silicon Single-Electron Transistor Memory Operating at Room Temperature

A single-electron memory, in which a bit of information is stored by one electron, is demonstrated at room temperature. The memory is a floating gate metal-oxide-semiconductor transistor in silicon with a channel width ( approximately 10 nanometers) smaller than the Debye screening length of a single electron and a nanoscale polysilicon dot ( approximately 7 nanometers by 7 nanometers) as the floating gate embedded between the channel and the control gate. Storing one electron on the floating gate screens the entire channel from the potential on the control gate and leads to (i) a discrete shift in the threshold voltage, (ii) a staircase relation between the charging voltage and the shift, and (iii) a self-limiting charging process. The structure and fabrication of the memory should be compatible with future ultralarge-scale integrated circuits.     

Cell corpse engulfment mediated by C. elegans phosphatidylserine receptor through CED-5 and CED-12

During apoptosis, phosphatidylserine, which is normally restricted to the inner leaflet of the plasma membrane, is exposed on the surface of apoptotic cells and has been suggested to act as an "eat-me" signal to trigger phagocytosis. It is unclear how phagocytes recognize phosphatidylserine. Recently, a putative phosphatidylserine receptor (PSR) was identified and proposed to mediate recognition of phosphatidylserine and phagocytosis. We report that psr-1, the Caenorhabditis elegans homolog of PSR, is important for cell corpse engulfment. In vitro PSR-1 binds preferentially phosphatidylserine or cells with exposed phosphatidylserine. In C. elegans, PSR-1 acts in the same cell corpse engulfment pathway mediated by intracellular signaling molecules CED-2 (homologous to the human CrkII protein), CED-5 (DOCK180), CED-10 (Rac GTPase), and CED-12 (ELMO), possibly through direct interaction with CED-5 and CED-12. Our findings suggest that PSR-1 is likely an upstream receptor for the signaling pathway containing CED-2, CED-5, CED-10, and CED-12 proteins and plays an important role in recognizing phosphatidylserine during phagocytosis.     

Impacts on soil quality from long-term irrigation with treated greywater

Drought condition in many places leads to the imperative use of greywater for irrigation. There is a serious concern on the impact of such prolonged uses on soil sustainability. The objective of this study was to evaluate the long-term impacts of greywater irrigation on soil electrical conductivity (EC) and other soil quality parameters in field conditions. Six locations were monitored in this study where home gardens have been irrigated with treated greywater for 2 years. Results showed a general reduction in EC levels of soil samples along all depth intervals at all locations. The average soil EC before greywater irrigation was 0.97 dS/m and decreased to 0.41 dS/m, which may be due to the use of greywater as well as the rainwater effect. The reduction in soil EC and irrigation water quantity shows positive correlation (correlation coefficient r = 0.64). Calcium precipitation might also have a major role in soil EC reduction. Soil calcium content was 81 mg L^?1 before using treated greywater and decreased to 43 mg L^?1 after 2 years of treated greywater usage, which might have been caused by calcium carbonates (CaCO₃) precipitation. The results of other soil chemical analyses clearly show that using treated greywater for irrigation has reduced the concentration of organic matters, K, Cd, Pb, P, Mg, Cl, Na, exchangeable sodium percentage, and sodium adsorption ratio after 2 years of application. Zn concentration increased from 11 to 15 mg L^?1, and soil pH became slightly higher from 7.6 to 7.8.     

Using a weft-knitting technique to make elastic degradable vascular stents

This study aims to develop reticular, tubular polyvinyl alcohol (PVA) vascular stents, and then examines their structure and properties. PVA fibers are knitted, followed by being immersed in a polycaprolactone (PCL) solution and thermally treated in order to form vascular stents. The test results indicate that the combination of a loop structure of knits and the PCL film that is adhered to fibers can effectively form elastic, compression-resistant PVA vascular stents. The vascular stents retain a stabilized path after an in vitro degradation, and thus this study successfully creates the desired elastic PVA vascular stents.     

Natural product chemistry of gorgonian corals of genus Junceella--part II

The structures, names, bioactivities, and references of 81 new secondary metabolites obtained from gorgonian corals belonging to the genus Junceella are described in this review. All compounds mentioned in this review were obtained from sea whip gorgonian corals Junceella fragilis and Junceella juncea, collected from the tropical and subtropical Indo-Pacific Ocean.     

Particle size reduction effectively enhances the cholesterol-lowering activities of carrot insoluble fiber and cellulose

This study investigated and compared the effects of particle size reduction on the cholesterol-lowering activities of carrot insoluble fiber-rich fraction (IFF) and plant cellulose. Our results demonstrated that micronization treatment effectively pulverized the particle sizes of these insoluble fibers to different microsizes. Feeding the micronized insoluble fibers, particularly the micronized carrot IFF, significantly (p < 0.05) improved their abilities in lowering the concentrations of serum triglyceride (18.6-20.0%), serum total cholesterol (15.5-19.5%), and liver lipids (16.7-20.3%) to different extents by means of enhancing (p < 0.05) the excretion of lipids (124-131%), cholesterol (120-135%), and bile acids (130-141%) in feces. These results suggested that particle size was one of the crucial factors in affecting the characteristics and physiological functions of insoluble fibers. Therefore, particle size reduction by micronization might offer the industry an opportunity to improve the physiological functions of insoluble fibers, particularly the carrot IFF, in health food applications.     

Preliminary study of community development and scleractinian recruitment on fibreglass artificial reef units in the sedimented waters of Singapore

• 1. Fibreglass was used to make specially designed reef enhancement units (REUs) for three reef sites in Singapore. Units were established in areas measuring approximately 20 × 50 m.
• 2. The units are compact and light enough to be deployed from small boats by scuba divers, and are suitable for shallow reefs with limited visibility.
• 3. The design of the REUs precludes excessive sediment build‐up on the settlement surfaces, while allowing water currents to flow through the system.
• 4. The REUs were monitored monthly over two years to observe community development and scleractinian coral recruitment on the exterior surfaces. Recruitment was compared between REUs and rubble quadrats at one study site.
• 5. The REUs were colonized by turf algae within the first month, followed by crustose coralline algae, macroalgae, ascidians and hydroids. At the end of two years, the percentage cover of crustose coralline algae at all three sites was more than 50%.
• 6. The first incidence of coral recruitment was six months post deployment, and recruitment rates at the end of the monitoring period ranged from 0.10 to 4.75 recruits per square metre for the three sites. Recruits show better survival and growth on REUs compared to rubble areas.
• 7. The most abundant recruit was Pocillopora damicornis, followed by favids, acroporids and poritids.

Copyright © 2006 John Wiley & Sons, Ltd.