Three-dimensional structure of interleukin-2

Interleukin-2 is an effector protein that participates in modulating the immune response; it has become a focal point for the study of lymphokine structure and function. The three-dimensional structure of the interleukin molecule has been solved to 3.0 angstrom resolution. Interleukin-2 has a novel alpha-helical tertiary structure that suggests one portion of the molecule forms a structural scaffold, which underlies the receptor binding facets of the molecule.     

Surface molecules identify groups of growing axons

Studies on vertebrate and invertebrate species have established that, during development, axons have the ability to choose particular paths over others. The chemical basis of this pathfinding is not clear but biochemical differences between neurons have long been postulated to account for the specificity of neuronal connections. Such subtle molecular differences between different cells in a single tissue are difficult to study with standard biochemical techniques but hybridoma technology has offered a potential solution to this type of problem. This technique has made possible the production of monoclonal antibodies for identifying and characterizing a family of glycoproteins which are expressed on the surface of specific axon bundles during the development of the leech nervous system. The results show that groups of growing axons do indeed carry chemically distinct surface molecules.     

Differentiation of embryonic stem cells to insulin-secreting structures similar to pancreatic islets

Although the source of embryonic stem (ES) cells presents ethical concerns, their use may lead to many clinical benefits if differentiated cell types can be derived from them and used to assemble functional organs. In pancreas, insulin is produced and secreted by specialized structures, islets of Langerhans. Diabetes, which affects 16 million people in the United States, results from abnormal function of pancreatic islets. We have generated cells expressing insulin and other pancreatic endocrine hormones from mouse ES cells. The cells self-assemble to form three-dimensional clusters similar in topology to normal pancreatic islets where pancreatic cell types are in close association with neurons. Glucose triggers insulin release from these cell clusters by mechanisms similar to those employed in vivo. When injected into diabetic mice, the insulin-producing cells undergo rapid vascularization and maintain a clustered, islet-like organization.     

小麦D~2型细胞质光敏雄性不育性的研究

D2型细胞质与有些普通小麦材料的细胞核互作,可产生特异核质互作不育现象,其中有的表现为长光照敏感型雄性不育。文章研究了具有D2型细胞质的光敏不育系Ae.crassa—Norin26、核质杂种NC2134及克引11、克引12在黑龙江省克山地区自然条件下的育性表现,并以NC2134为细胞质供体,与20个小麦品种(系)杂交,获得一些核质代换系材料,对其育性及主要性状进行观察研究。结果表明:(1)在自然条件下,播种期对育性有影响,随着播种期推迟,Ae.crassa—Norin26不育度增加,1 999年4月22日播种达到全不育,Norin26则在所设播种条件下表现正常可育;(2)NC2134表现可育,这与其可能携带雄性不育的恢复基因有关,克引11、克引12在正常播种情况下表现高度不育甚至全不育;(3)不育系的不育性表现为不同程度的雄蕊心皮化;(4)不同普通小麦材料其核质杂种育性表现不同,有些材料其核质代换低世代分离出一定比例的高不育、半不育及可育株,通过进一步的核置换,可转育成相应的D2型细胞质不育系。     

Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.     

The Incidence and Significance of Clostridia Isolated from Ready-to-eat Meats and Rendered Products

Approximately 26% of rendered and 10% of ready-to-eat products contained species of the genus Clostridium.

Eleven species of clostridia were isolated from a total of 524 products tested. Some products harboured more than one species.

C. sporogenes, one of the most heat resistant organisms, was the most common type isolated.

C. sordellii produced a transient illness in guinea pigs while all other species were innocuous.

     

The influence of photoperiod and plant density on yield of winter-grown gladioli in Queensland

The yields of inflorescences, corms and cormlets, and the inflorescence quality of winter-grown gladioli in south-east Queensland, were studied under 2 daylength regimes, 3 plant densities (150 000, 300 000 and 450 000 corms ha^?1) and 3 plant arrangements (bed, double row and single row). The daylength treatments were the natural daylength (12.3–14.5 hours) and a 24-hour photoperiod treatment in which natural daylengths were extended using incandescent light of an intensity of 150 lux. Two cultivars were used.Extending the photoperiod to 24 hours delayed flowering by approximately 15 days, and increased the number of inflorescences harvested from low, medium and high density treatments by 20, 91 and 169%, respectively, when compared to the inflorescence yield from these density treatments under natural daylengths. The quality of the inflorescences from the high-density treatment receiving the 24-hour photoperiod was similar or superior in all quality characteristics to that of inflorescences grown under the most favourable density treatment under natural daylengths (150 000 corm ha^?1). Plant arrangement had little effect on the number of days to flowering or inflorescence yield but inflorescence quality was improved when plants were grown in a double-row arrangement compared to those from the bed or single-row arrangements. Extension of the photoperiod had no effect on the number of new corms per plot. However, the average weight of new corms and the weight of cormlets per plot and per corm were reduced by approximately 32, 71 and 63%, respectively, when compared to the results obtained from plants grown under natural daylengths. These results suggest that flowers compete for available photosynthates with corms and cormlet development.The economic feasibility of extending photoperiod for the commercial production of winter-grown gladioli in south-east Queensland is discussed.     

Genetic correlation between boars, barrows and gilts for various carcass traits

Data from 11 generations of a selection study were analyzed to estimate genetic correlations between boars and gilts, boars and barrows, and gilts and barrows for carcass traits in the Lacombe and Yorkshire breeds of swine. Genetic correlations were estimated to determine if genotype X sex interactions existed and to assess the need for separate genetic parameters for boars and gilts in selection response equations. Genotype X sex interactions were found for total carcass fat/kg of cold carcass weight, area of lean in the ham face/kg of cold carcass weight and percent lean in the ham face/kg of cold carcass weight. Carcass length, longissimus muscle area/kg of cold carcass weight percent ham of side and percent lean in the ham face did not have genotype X sex interactions. Selection based on pooled genetic parameters over sex were favored over selection based on separate genetic parameters regardless of the presence or absence of genotype X sex interactions.     

First Report of Post‐Weaning Multisystemic Wasting Syndrome and Porcine Dermatitis and Nephropathy Syndrome in Pigs in Greece

Post‐weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) are two recently described conditions of pigs at the late nursery and fattening stages. The aim of this short communication was to describe the first reported occurrence of these conditions and of porcine circovirus type 2 (PCV2) infection in Greece. The clinical signs, gross post‐mortem changes and histopathological changes observed in affected pigs, were similar to those previously described for both PDNS and PMWS. As in previous reports, the lesions were associated with PCV2 infection, which was demonstrated by immunohistochemical and in situ hybridization methods.