Spread of cobalt from a cortical epileptic lesion induced by a cobalt-gelatine implant into the frontal cortex of the rat

Summary The spread of cobalt ions from cobalt induced epileptic foci in rats has been investigated. Atomic absorption spectrophotometry and heavy-metal histochemistry reveal cobalt ions spread very widely from the focus. Biochemical and physiological consequences for this model of epilepsy are discussed.     

大连市银杏叶斑病病原菌鉴定

银杏(Ginkgo biloba L.)是常见的城市园林观赏绿化树种,并具有极高的材用、食用和药用价值.近年来,大连市银杏树发生了一种不明病因且较为严重的叶斑病,查明病因、为病害防治提供理论依据迫在眉睫.从病害发生严重区域采集叶斑病病叶样本,采用感病叶片单斑分离法,对分离菌株进行致病性测定、形态学鉴定及分子生物学鉴定等,对大连市银杏树发生的叶斑病进行了病原菌鉴定.结果表明,大连银杏叶斑病致病菌有2种,分别为链格孢属细极链格孢(Alternaria tenuissima)和链格孢(Alternaria alternata).迄今为止,细极链格孢(Alternaria tenuissima)侵染银杏导致其发生叶斑病鲜有报道.     

Localization of type 1 diabetes susceptibility to the MHC class I genes HLA-B and HLA-A

The major histocompatibility complex (MHC) on chromosome 6 is associated with susceptibility to more common diseases than any other region of the human genome, including almost all disorders classified as autoimmune. In type 1 diabetes the major genetic susceptibility determinants have been mapped to the MHC class II genes HLA-DQB1 and HLA-DRB1 (refs 1-3), but these genes cannot completely explain the association between type 1 diabetes and the MHC region. Owing to the region's extreme gene density, the multiplicity of disease-associated alleles, strong associations between alleles, limited genotyping capability, and inadequate statistical approaches and sample sizes, which, and how many, loci within the MHC determine susceptibility remains unclear. Here, in several large type 1 diabetes data sets, we analyse a combined total of 1,729 polymorphisms, and apply statistical methods-recursive partitioning and regression-to pinpoint disease susceptibility to the MHC class I genes HLA-B and HLA-A (risk ratios >1.5; P(combined) = 2.01 x 10(-19) and 2.35 x 10(-13), respectively) in addition to the established associations of the MHC class II genes. Other loci with smaller and/or rarer effects might also be involved, but to find these, future searches must take into account both the HLA class II and class I genes and use even larger samples. Taken together with previous studies, we conclude that MHC-class-I-mediated events, principally involving HLA-B*39, contribute to the aetiology of type 1 diabetes.     

A single type of progenitor cell maintains normal epidermis

According to the current model of adult epidermal homeostasis, skin tissue is maintained by two discrete populations of progenitor cells: self-renewing stem cells; and their progeny, known as transit amplifying cells, which differentiate after several rounds of cell division. By making use of inducible genetic labelling, we have tracked the fate of a representative sample of progenitor cells in mouse tail epidermis at single-cell resolution in vivo at time intervals up to one year. Here we show that clone-size distributions are consistent with a new model of homeostasis involving only one type of progenitor cell. These cells are found to undergo both symmetric and asymmetric division at rates that ensure epidermal homeostasis. The results raise important questions about the potential role of stem cells on tissue maintenance in vivo.     

Planning for the future by western scrub-jays

Knowledge of and planning for the future is a complex skill that is considered by many to be uniquely human. We are not born with it; children develop a sense of the future at around the age of two and some planning ability by only the age of four to five. According to the Bischof-K?hler hypothesis, only humans can dissociate themselves from their current motivation and take action for future needs: other animals are incapable of anticipating future needs, and any future-oriented behaviours they exhibit are either fixed action patterns or cued by their current motivational state. The experiments described here test whether a member of the corvid family, the western scrub-jay (Aphelocoma californica), plans for the future. We show that the jays make provision for a future need, both by preferentially caching food in a place in which they have learned that they will be hungry the following morning and by differentially storing a particular food in a place in which that type of food will not be available the next morning. Previous studies have shown that, in accord with the Bischof-K?hler hypothesis, rats and pigeons may solve tasks by encoding the future but only over very short time scales. Although some primates and corvids take actions now that are based on their future consequences, these have not been shown to be selected with reference to future motivational states, or without extensive reinforcement of the anticipatory act. The results described here suggest that the jays can spontaneously plan for tomorrow without reference to their current motivational state, thereby challenging the idea that this is a uniquely human ability.     

Explosive nucleosynthesis in stars

Recent calculations provide convincing evidence that the naturally occurring nuclei were produced in explosions. The required temperature, density and expansion rate strongly suggest that before the explosion the objects were ordinary evolved massive stars. We review these new developments and present a new table indicating our hypothesis concerning the origin of the nuclei in the mass range 20 < or = A < or = 62.