Complexity of enzymatic inhibition by cigarette smoke

Zusammenfassung Die Hemmung der Alkoholdehydrogenase aus Hefe durch Zigarettenrauch beruht auf verschiedenen Inaktivierungsmechanismen. Die Gasphase zeigt eine kompetitive Hemmung, die Partikelphase und der ganze Rauch eine gemischte Hemmung. Da die Hemmung durch den ganzen Rauch nicht der Summe der Hemmungen beider Phasen entspricht, ist anzunehmen, dass Wechselwirkungen zwischen den Inhibitoren und Antagonisten vorliegen.     

The mdx mouse diaphragm reproduces the degenerative changes of Duchenne muscular dystrophy

Although murine X-linked muscular dystrophy (mdx) and Duchenne muscular dystrophy (DMD) are genetically homologous and both characterized by a complete absence of dystrophin, the limb muscles of adult mdx mice suffer neither the detectable weakness nor the progressive degeneration that are features of DMD. Here we show that the mdx mouse diaphragm exhibits a pattern of degeneration, fibrosis and severe functional deficit comparable to that of DMD limb muscle, although adult mice show no overt respiratory impairment. Progressive functional changes include reductions in strength (to 13.5% of control by two years of age), elasticity, twitch speed and fibre length. The collagen density rises to at least seven times that of control diaphragm and ten times that of mdx hind-limb muscle. By 1.5 years of age, similar but less severe histological changes emerge in the accessory muscles of respiration. On the basis of these findings, we propose that dystrophin deficiency alters the threshold for work-induced injury. Our data provide a quantitative framework for studying the pathogenesis of dystrophy and extend the application of the mdx mouse as an animal model.     

Myosin gene mutation correlates with anatomical changes in the human lineage

Powerful masticatory muscles are found in most primates, including chimpanzees and gorillas, and were part of a prominent adaptation of Australopithecus and Paranthropus, extinct genera of the family Hominidae. In contrast, masticatory muscles are considerably smaller in both modern and fossil members of Homo. The evolving hominid masticatory apparatus--traceable to a Late Miocene, chimpanzee-like morphology--shifted towards a pattern of gracilization nearly simultaneously with accelerated encephalization in early Homo. Here, we show that the gene encoding the predominant myosin heavy chain (MYH) expressed in these muscles was inactivated by a frameshifting mutation after the lineages leading to humans and chimpanzees diverged. Loss of this protein isoform is associated with marked size reductions in individual muscle fibres and entire masticatory muscles. Using the coding sequence for the myosin rod domains as a molecular clock, we estimate that this mutation appeared approximately 2.4 million years ago, predating the appearance of modern human body size and emigration of Homo from Africa. This represents the first proteomic distinction between humans and chimpanzees that can be correlated with a traceable anatomic imprint in the fossil record.     

上市公司经营活动状况对金融资产规模影响探究

越来越多的非金融业上市公司开始参与金融投资.通过实证研究来探索非金融业上市公司经营状况对其金融资产投资规模的影响,发现上市公司的金融资产有显著规模效应,同一行业内经营活动状况较好的上市公司有较少的金融投资,经营活动收入稳定增长的上市公司有较少的金融投资.