Independent transfer of mitochondrial chromosomes and plasmids during unstable vegetative fusion in Neurospora

The sporadic distribution of similar introns in organelle, nuclear ribosomal RNA and bacteriophage genes suggests that at least some of these introns are mobile genetic elements. Some plasmids in fungal mitochondria contain intron-like sequences and, like introns, they have scattered distributions within and among species. The occurrence and evolutionary importance of such horizontal transfer of DNA, not only between fungi, but among a wide range of organisms have been matters of much discussion. Here, we report experimental evidence for transfer of Neurospora mitochondrial plasmids from one mitochondrial genotype to another at high frequency during unstable vegetative cell fusion. Exchange of mitochondrial and nuclear genomes can also occur. These observations suggest that vegetative fusion may have a more important role in the mitochondrial genetic structure of natural populations than is generally thought, and may provide an explanation for the distribution of certain plasmids and possibly other mobile genetic elements.     

Control of enzyme secretion by non-cholinergic, non-adrenergic nerves in guinea pig pancreas

Depolarization of pancreatic cells by exposure to high potassium solutions is associated with release of amylase. In the guinea pig, but not the mouse or cat, this Ca-dependent amylase secretion is resistant to atropine blockade, thus Scheele and Haymovits concluded that the enzyme secretion evoked by K depolarization does not involve release of transmitter from intrapancreatic nerves but is a consequence of Ca uptake into acinar cells mediated by the membrane depolarization. This hypothesis is inconsistent with current concepts of stimulus--secretion coupling in electrically non-excitable cells. The observation of Scheele and Haymovits could, however, also be explained by the release of a non-cholinergic, secretomotor transmitter as a consequence of the depolarization of intrapancreatic nerves. By adapting the technique of electrical field stimulation of isolated pancreatic segments to our studies of amylase secretion, we have now been able to demonstrate both cholinergic and non-cholinergic, non-adrenergic secretomotor nerves in the guinea pig pancreas. Excitation of the non-cholinergic nerves stimulates amylase secretion by a different intracellular coupling mechanism from that activated by cholinergic nerves or by peptides belonging to the cholecystokinin, gastrin or bombesin families.     

甘肃民勤盆地人类活动对生态环境的影响及其生态环境变化对人类的反作用研究--民勤盆地社会调查结果分析

主要根据民勤盆地的社会调查资料分析了甘肃省河西地区石羊河流域下游民勤盆地近50年来人类活动对生态环境的影响以及生态环境变化对人类的反作用,并着重分析了当地人对当地生态环境变化及其原因的理解与认识.认为民勤盆地存在环境恶化趋势.该地区地下水位迅速下降,沙漠化、土壤盐渍化、植被衰退过程加快,这些生态环境变化对人类的生产、生活造成了重大而深刻的影响,并对人类身体健康造成了持久的危害.     

Discovery of single-molecule electret properties in the endohedral fullerene Gd@C82

The recent history of nanocarbon materials has been dominated by the spectacular rise of graphene and its myriad applications [1].in this phase of rapid develop...     

Initial sequencing and comparative analysis of the mouse genome

The sequence of the mouse genome is a key informational tool for understanding the contents of the human genome and a key experimental tool for biomedical research. Here, we report the results of an international collaboration to produce a high-quality draft sequence of the mouse genome. We also present an initial comparative analysis of the mouse and human genomes, describing some of the insights that can be gleaned from the two sequences. We discuss topics including the analysis of the evolutionary forces shaping the size, structure and sequence of the genomes; the conservation of large-scale synteny across most of the genomes; the much lower extent of sequence orthology covering less than half of the genomes; the proportions of the genomes under selection; the number of protein-coding genes; the expansion of gene families related to reproduction and immunity; the evolution of proteins; and the identification of intraspecies polymorphism.