- Email: [email protected]
Environmental adaptations as windows on molecular evolution
$84
Abstracts / Comparative Biochemistry and Physiology, Part B 126 (2000) SI-S108
E N V I R O N M E N T A L A D A P T A T I O N S AS W I N D O W S ON M O L E C U L A R E V O L U T I O N Patricia M. Schulte Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
Changes in gene regulation may play an important role in adaptive evolution, and changes in gene regulation must be particularly important in the process of adaptation to a changing environment. However, little is known about the molecular mechanisms underlying adaptively significant variation in gene regulation. In principle, there are two major approaches that can be applied to study this problem: experimental evolution, and comparative molecular biology. From the limited data derived from experimental studies, it is clear that changes in the regulation of a very large number of different genes generally accompany adaptation to a novel environment in the laboratory. However, the mechanisms that cause these changes remain largely unknown. Comparative studies of the mechanisms and significance of changes in gene regulation are also rare. We have been using a comparative approach to investigate the molecular basis of changes in gene expression between populations of a fish, Fundulus hetero¢litus. Populations of F. heteroclitus are distributed along the East Coast of North America, along a steep thermal gradient. At the extremes of the species range, populations have undergone local adaptation to their respective habitat temperatures. A variety of genes differ in their regulation between these populations. We have recently determined the mechanism responsible for changes in the regulation of the lactate dehydrogenase-B gene (Ldh-B). A limited number of mutations in the regulatory sequence of this gene result in changes in its expression. These results demonstrate that even a single mutation within important regulatory sequences can have important impacts on environmental adaptation.
SURFACE ACTIVITY INSITU, IN VIVO AND IN THE CAPTIVE BUBBLE ~ l , H a n s Bachofen 2 and Fred Possmayer3 1Respiratory Research Group, Univ. of Calgary, Calgary, Canada; 2Dept. of Medicine, Univ. of Berne. Switzerland;3Depts. of Ob/Gyn and Biochern., Univ. of Western Ontario, London, Canada For studies of the mechanical effects of lung surfactants, the captive bubble surfactometer (CBS) combines the advantages of the continuous film of Pattle's bubbles with the feasibility of the Langmuir-Wilhelmy balance to produce surface tension-area hysteresis loop. In accordance with direct measurements of alveolar surface tensions using the microdroplet spreading technique, the CBS allows the compression of films to very low and stable surface tensions, i.e., the surface tension increases only about 1-2 mN/m in 20 min. Such low and stable surface tensions are in line with results obtained from pressure-volume studies on excised lungs. In addition, the CBS is useful to test other physical proporties of the surfactant system which are essential for normal lung function, including (!) rapid film formation (within seconds) through adsorption from the hypophase, (2) low film compressibility with a fall in surface tension to very low (< 2 mN/m) values during surface compression, and (3) effective replenishment of the surface film on expansion by the incorporation of surfactant material from material associated with the surface. Depletion of the subphase in captive bubble experiments have demonstrated the presence of'surplus" material (the surface associated reservoir) in the air-liquid interface upon de n o v o adsorption of surfactants derived from natural sources or of phospholipid mixtures with added SP-B or SP-C. In addition to the reservoir formed by de novo adsorption, an additional reservoir is formed during film compression, especially if the films are compressed beyond the point where minimum surface tension is obtained regardless of the level of minimum surface tension. Morphological observations of films fixed in situ or in vitro reveal frequently their muitilayered structure. The deviation of the bubbles from a Laplacian shape at very low surface tension and the morphological observations suggest that the surfactant film cannot be considered a simple monolayer. The mechanical stability of the surfactant layer on expiration appears to be related to the structure of the interfacial region that is the surfactant film and its associated material. (Supported by the MRC, Canada and the NSF, Switzerland)
Abstracts / Comparative Biochemistry and Physiology, Part B 126 (2000) SI-S108
E N V I R O N M E N T A L A D A P T A T I O N S AS W I N D O W S ON M O L E C U L A R E V O L U T I O N Patricia M. Schulte Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
Changes in gene regulation may play an important role in adaptive evolution, and changes in gene regulation must be particularly important in the process of adaptation to a changing environment. However, little is known about the molecular mechanisms underlying adaptively significant variation in gene regulation. In principle, there are two major approaches that can be applied to study this problem: experimental evolution, and comparative molecular biology. From the limited data derived from experimental studies, it is clear that changes in the regulation of a very large number of different genes generally accompany adaptation to a novel environment in the laboratory. However, the mechanisms that cause these changes remain largely unknown. Comparative studies of the mechanisms and significance of changes in gene regulation are also rare. We have been using a comparative approach to investigate the molecular basis of changes in gene expression between populations of a fish, Fundulus hetero¢litus. Populations of F. heteroclitus are distributed along the East Coast of North America, along a steep thermal gradient. At the extremes of the species range, populations have undergone local adaptation to their respective habitat temperatures. A variety of genes differ in their regulation between these populations. We have recently determined the mechanism responsible for changes in the regulation of the lactate dehydrogenase-B gene (Ldh-B). A limited number of mutations in the regulatory sequence of this gene result in changes in its expression. These results demonstrate that even a single mutation within important regulatory sequences can have important impacts on environmental adaptation.
SURFACE ACTIVITY INSITU, IN VIVO AND IN THE CAPTIVE BUBBLE ~ l , H a n s Bachofen 2 and Fred Possmayer3 1Respiratory Research Group, Univ. of Calgary, Calgary, Canada; 2Dept. of Medicine, Univ. of Berne. Switzerland;3Depts. of Ob/Gyn and Biochern., Univ. of Western Ontario, London, Canada For studies of the mechanical effects of lung surfactants, the captive bubble surfactometer (CBS) combines the advantages of the continuous film of Pattle's bubbles with the feasibility of the Langmuir-Wilhelmy balance to produce surface tension-area hysteresis loop. In accordance with direct measurements of alveolar surface tensions using the microdroplet spreading technique, the CBS allows the compression of films to very low and stable surface tensions, i.e., the surface tension increases only about 1-2 mN/m in 20 min. Such low and stable surface tensions are in line with results obtained from pressure-volume studies on excised lungs. In addition, the CBS is useful to test other physical proporties of the surfactant system which are essential for normal lung function, including (!) rapid film formation (within seconds) through adsorption from the hypophase, (2) low film compressibility with a fall in surface tension to very low (< 2 mN/m) values during surface compression, and (3) effective replenishment of the surface film on expansion by the incorporation of surfactant material from material associated with the surface. Depletion of the subphase in captive bubble experiments have demonstrated the presence of'surplus" material (the surface associated reservoir) in the air-liquid interface upon de n o v o adsorption of surfactants derived from natural sources or of phospholipid mixtures with added SP-B or SP-C. In addition to the reservoir formed by de novo adsorption, an additional reservoir is formed during film compression, especially if the films are compressed beyond the point where minimum surface tension is obtained regardless of the level of minimum surface tension. Morphological observations of films fixed in situ or in vitro reveal frequently their muitilayered structure. The deviation of the bubbles from a Laplacian shape at very low surface tension and the morphological observations suggest that the surfactant film cannot be considered a simple monolayer. The mechanical stability of the surfactant layer on expiration appears to be related to the structure of the interfacial region that is the surfactant film and its associated material. (Supported by the MRC, Canada and the NSF, Switzerland)