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Biodiversity and Conservation - Understanding community structure together with regeneration and disturbance provides a holistic purview of forest health and the necessary management implications...  相似文献   
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Heat loss from airway smooth muscle is a potent stimulus which causes substantial, but poorly understood, alterations in muscle tension. This study considered the involvement of endogenous mediators in cooling-induced tension changes in incubated guinea pig trachea. Smooth muscle tension was monitored in tracheal cylinders which were carefully cooled from 37 to 30 degrees C in the presence or absence of various inotropic mediators. In our study, cooling alone, at a rate of 1 degree C/min, was associated with an average loss of smooth muscle tension of 88.2 mg. Cooling tracheal tissue that had been previously exposed to 3 X 10(-6) M histamine, however, caused an additional increase in tracheal tension of 133 mg, over and above that caused by histamine alone. In the presence of 10(-5) M prostaglandin F2 alpha, or 10(-5) M thromboxane B2, cooling was associated with respective losses of smooth muscle tension of 211.4 and 211.2 mg, as compared to the tension associated with these mediators when they were used alone under control conditions. When the speed of tracheal cooling was increased to 40 degrees C/min, there was a slight increase in tension for 20 sec followed by a pronounced and sustained relaxation. The mechanisms involved in the response of airway smooth muscle to cooling are complex. The results of our study, however, suggest that mediators may play a role in the cooling-induced alterations of airway smooth muscle tension.  相似文献   
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Microdissected arm specific paints (ASPs) for human (HSA) chromosomes (Chrs) 2, 5, 6, 16, and 19 were used as probes on pig (SSC) and horse (ECA) metaphase chromosomes. Regions homologous to individual human arms were delineated in the two species studied. Of the ten ASPs used, HSA6 and 16 ASPs showed complete synteny conservation of individual arms as single blocks/arms both in pig and horse. A similar trend was, in general, also observed for HSA19 ASPs. However, contrary to these observations, synteny conservation of individual arms of HSA2 and HSA5 was not observed in pig and horse. The arm specific painting data, coupled with the available gene mapping data, showed that, although HSA2 corresponded to two arms/chromosomes each in pig and horse, the breakpoint of this synteny in humans was not located at the centromere, but at HSA2q13 band. Similarly, arm specific paints for HSA5 showed that of the two blocks/chromosomes painted in pig and horse, one corresponded to HSA5q13-pter, the other to HSA5q13-qter. The findings suggest that 5q13 band may also be an evolutionary break point, similar to the one detected on HSA2q13. The microdissected human arm specific painting probes used in the present work provide more accurate and refined comparative information on pig and horse chromosomes than that available through the use of human whole chromosome specific paints. Received: 1 June 1997 / Accepted: 5 September 1997  相似文献   
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The present study focusses on the effects of pH, temperature, intensity of white, red far-red light on zygospore germination in the filamentous green algaSpirogyra hyalina. Maximum germination of zygospores occurred at pH 8.0 and 25°C. Germination of zygospores was favored by white light at an intensity of 3–4 klx. Red light resulted in higher germination when applied at the beginning or in the middle of the dark period, while far-red light decreased zygospore germination. Red light in the middle of the dark period was found to be most effective for germination. These observations suggest a possible presence of the phytochrome system in the test alga contributing to its morphogenetic response.  相似文献   
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Microbial cells have extensively been utilized to produce value-added bioactive compounds. Based on advancement in protein engineering, DNA recombinant technology, genome engineering, and metabolic remodeling, the microbes can be re-engineered to produce industrially and medicinally important platform chemicals. The emergence of co-culture system which reduces the metabolic burden and allows parallel optimization of the engineered pathway in a modular fashion restricting the formation of undesired byproducts has become an alternative way to synthesize and produce bioactive compounds. In this study, we present genetically engineered E. coli-based co-culture system to the de novo synthesis of apigetrin (APG), an apigenin-7-O-β-d-glucopyranoside of apigenin. The culture system consists of an upstream module including 4-coumarate: CoA ligase (4CL), chalcone synthase, chalcone flavanone isomerase (CHS, CHI), and flavone synthase I (FNSI) to synthesize apigenin (API) from p-coumaric acid (PCA). Whereas, the downstream system contains a metabolizing module to enhance the production of UDP-glucose and expression of glycosyltransferase (PaGT3) to convert API into APG. To accomplish this improvement in titer, the initial inoculum ratio of strains for making the co-culture system, temperature, and media component was optimized. Following large-scale production, a yield of 38.5 µM (16.6 mg/L) of APG was achieved. In overall, this study provided an efficient tool to synthesize bioactive compounds in microbial cells.  相似文献   
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